TITLE

PRODUCTION OF THREE DIMENSIONAL BODIES BY PHOTOPOLYMERIZATION

DEFINITIONS

As used herein, and in the appended claims, unless the contrary is indicated, the terms "percent" and "parts'¹ refer to percent and parts by weight, and the following terms have the meanings stated: "nm" means nanometer or nanometers; "g" means gram or grams; "kg" means kilogram or kilograms; ¥ray", as applied to activating radiation for a photoinitiator refers to such radiation which has negligible dimensions at right angles to its direction of travel; "cm" means centimeter or centimeters; "μm" means micrometer or micrometers; "mm" means millimeter or millimeters; "L" means liter or liters; Ml means milliliter or milliliters; "m" means mole or moles; ^nm/₀ ⁿ means mole percent, and equals 100 times the number of moles of the constituent designated in a composition divided by the total number of moles in the composition; "m sec" means millisecond or milliseconds; "mW" means milliwatt or milliwatts; "psi" means pounds per square inch; and "MPa" means 10⁶ Pascals.

BACKGROUND OF THE INVENTION

FIELD OF THE INVENTION

This invention relates to a new composition comprising a fluid monomer and a photoinitiator system for the monomer, and to a method for producing three dimensional bodies by photopolymerization of the fluid monomer and, more particularly, to such a method in which a laser is used to provide activating radiation for the photoinitiator system for the monomer. THE PRIOR ART

Broadly speaking, a body of a composition comprising a photopolymerizable monomer, usually an acrylate or an acrylate derivative, and a photoinitiator system therefor can be caused to undergo photopolymerization by subjecting it to activating radiation of a suitable wave length. The photoinitiator system includes a compound, called a "photoinitiator", and, usually, an "accelerator". Activating radiation causes the photoinitiator to undergo a reaction, producing an intermediate which includes a free radical chain and, as a consequence, causes the monomer to polymerize. The accelerator, usually a tertiary amine, acts by ameliorating the effect of oxygen, which is to terminate the free radical chains that are produced by the reaction of the photoinitiator and, as a consequence, to quench the free radical polymerization.

Most photopolymerizations are carried out to polymerize monomers in relatively thin films, for example, to "dry" printing ink after it has been applied to paper, or to cure solventless varnishes, adhesives and photoresists. Indeed, U.S. patent No. 4,575,330 granted March 11, 1986, "The 3-D Patent", discloses a method for producing three dimensional articles by a process which involves a plurality of photopolymerizations, one to form each of a large number of thin films which ultimately make up the desired article.

Most photoinitiators that have been used commercially are activated by ultraviolet radiation, i.e., radiation having a wavelength shorter than 400nm, and usually from mercury lamps, for example mercury resonance lamps with output at 313nm and 364nm. An ultraviolet laser is used in the process disclosed by the 3-D Patent, but such a laser, at the present time, is not reliable, has a short lifetime, is expensive and has a high power requirement. Recently, photoinitiators that are activated by visible light have also been used, notably in a colored copying process that is available under the trade designation "CYCOLOR". Benzoin ethers and related acetals, Hammond's initiators, diaryliodonium and triaryl sulfonium salts and various photosensitive peroxides and peresters are examples of known photoinitiators that are activated by ultraviolet radiation (see, for example, U.S. patent No. 4,561,951, "Neckers", granted December 31, 1985 to one of the present inventors) . Cyanine dye, borate- so-called (+,-) ion pair initiators, xanthene dye, and onium salt (-,+) ion pair photoinitiators are examples of known photoinitiators that are activated by radiation in the visible spectrum.

BRIEF DESCRIPTION OF THE INSTANT INVENTION The instant invention is based upon the discovery of composition that is comprised of a photopolymerizable monome and a photoinitiator system therefor. The system is one wherein a ray of activating radiation which enters the body through a surface thereof activates the photoinitiator system and causes polymerization at each of a succession of points, the first such point being immediately adjacent the surface and subsequent points being successively farther from the surface in the direction of travel of the ray of activating radiation; the distance from the surface to the point of the succession farthest therefrom varies as a function of at least one of (a) the intensity of the activating radiation and

(b) the time during which the activating radiation enters the body through the surface. Trimethylolpropane triacrylate with 0.06g eosin lactone and 15g triethanolamine per kg triacrylate dissolved therein is an example of such a composition. When a beam of visible light from an argon ion laser having a wavelength of 514nm passes through the composition, the eosin undergoes a reaction with the triethanol-amine, producing two moieties, one of which is a free radical which serves as an activator for the polymerization of the trimethylolpropane triacrylate. Loss of the dye color also occurs as a consequence of the eosin reaction with th triethanol amine, enabling subsequent radiation from the argo ion laser to penetrate farther into the composition and to caus reaction of eosin with triethanol amine and activation of th trimethylolpropane triacrylate at the level of greate penetration, and still greater penetration by subsequen radiation with consequent reaction and activation at the leve of the still greater penetration. The invention is also based upon the discovery that suc photoinitiators as eosin lactone, methylene violet, methylen blue, methylene green, ethyl eosin ester, RB lactone, ethyl RB, RB peroxide and erythrosin Bd, usually in the presence of a accelerator such as triethanolamine, can be used i comparatively high concentrations with a photopolymerizabl monomer to produce a composition wherein a high intensity ra of activating radiation in the visible or infra red spectru will cause polymerization to a desired extend in a short perio of time. The invention, in one aspect, is a method which comprises the steps of directing a ray of activating radiation for the photoinitiator system to and through a point in a given plane and into a body of the foregoing trimethylolpropane triacrylate composition, or an equivalent, and controlling at least one of

(c) the intensity of the activating radiation of the ray and

(d) the time during which the ray entering the body is directed through the point to determine the distance from a surface through which the ray of activating radiation enters the body to the point of the succession of points to which the ray activates the photoinitiator system that is farthest from the surface.

In another aspect, the invention involves a method for polymerizing a body of a composition comprised of a photopolymerizable monomer and a photoinitiator system for the monomer which system includes any one of a number of dyes which are broadly classified as xanthene, thionine, cyanine, stryllium ion, pyrrilium salt, oxazone, azinium ion, and triphenylmethane dyes. The photoinitiator system for the monomer includes one of the following, for example: eosin lactone, methylene violet, methylene blue, methylene green, ethyl eosin ester, eosin ester, RB lactone, ethyl RB, RB peroxide, eosin peroxide or erythrosin Bd. The photopolymerization is carried out by directing visible or infra red spectrum ray of activating radiation fo the photoinitiator system into the body, and controlling th intensity of the activating radiation so that the desired exten of polymerization occurs in an acceptable time. The visible o infra red spectrum ray has a wavelength of from 400 to lOOOn . The ray of activating radiation preferably has a wavelength fro 600 to lOOOnm because available lasers which emit radiatio having such a wavelength are markedly less expensive than laser which emit radiation having shorter wavelengths.

In still another aspect, the invention is a photochemica method for applying a polymeric coating to a metal, glass, o other substrate, or for welding, laminating or sealing tw bodies, at least one of which is transparent, to one another.

In yet another aspect, the invention is a method fo initiating photopolymerization with an inexpensive diode laser,

SUBSTITUTE SHEET for example one which emits radiation having a frequency of 682 nm.

In a still further aspect, the invention is a photo¬ polymerizable which contains a xanthene dye derivative having a Y2•substituent which makes the derivative more soluble than the dye in the composition. Preferably, the xanthene dye derivative has the structure of Fig. 1 of the attached drawing. In still another aspect the invention is a method for photo- polymerizing which involves the use, as an activator, of a xanthene dye derivative having a Y2' substituent which makes the derivative more soluble than the dye in the composition. Preferably, the xanthene dye derivative has the structure of Fig. 1 of the attached drawing.

In yet another aspect, the invention is a photopolymerizable composition which contains one of a family of dyes o derivatives which have the structure of Fig. 2, 3 or 4 of th attached drawing.

In still another aspect the invention is a method fo photopolymerizing which involves the use of a dye or dy derivative having the structure of Fig. 1, 2 or 3 of th attached drawing as an initiator.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a structural formula for a family of xanthene dy derivatives which are initiators in photopolymerizabl compositions according to the invention.

Fig. 2 is a structural formula for a family of derivative of 7-hydroxy-3H-phenoxazin-3one, sodiumsalt ("resorutim") whic are initiators in photopolymerizable compositions according t the invention. Fig. 3 is a structural formula for another family o resorutim derivatives which are initiators in photopolymerizabl compositions according to the invention.

Fig. 4 is a structural formula for still another family o resorutimderivatives which are initiators inphotopolymerizabl compositions according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following examples are presented solely for the purpos of further illustrating and disclosing the invention and are no to be construed as limiting. EXAMPLE 1

A photopolymerizable composition prepared by mixing trimethylolpropane triacrylate with 0.0669g eosin lactone and

16g triethanolamine, per kg triacrylate, was placed in a glass vessel that was square in horizontal cross section, each side of the square being substantially 1 cm in length. A shutter was then positioned closely adjacent one of the walls of the vessel, and a beam of light having a wavelength of 514nm was directed from an argon ion laser toward the shutter and one of the walls of the vessel. The shutter was so positioned that, when closed, it prevented light from the laser from impinging on the vessel and, when open, a beam of light that was circular in cross section and had a radius substantially less than 1mm traveled through one of the glass walls of the vessel, at substantially a right angle thereto, and into the photopolymerizable composition.

In a first series of photopolymerizations, the shutter was opened for 125 m sec while the laser was set to deliver a light beam which had a power varying from 25 to 250 W, and the position of the glass vessel was changed after each shutter opening, so that different parts of the photopolymerizable composition were activated by light having a wavelength of 514 nm and of diverging intensities. The depth to which photopolymerization occurred at each of four intensities is shown in the following table:

Power, mW Depth of photopolymerization, mm

250 5.40

100 2.06

50 1.25 25 0.60

In a second series of photopolymerizations, a similar procedure was used, except that the shutter was opened for 66.7 m sec. The depth to which photopolymerization occurred at each of four intensities is shown in the following table: Power, mW Depth of photopolymerization, mm

250 3.60

100 1.01

50 0.66

25 thin film In a third series of photopolymerizations, a simila procedure was used, except that the power was kept constant, th shutter was opened for different periods of time, and th photopolymerizable composition was composed of trimethylol propane triacrylate containing 0.0596g eosin lactone and 7.38 triethanolamine, per kg triacrylate. The depth to whic photopolymerization occurred at a power of 250 mW and at eac of eight different exposure times is shown in the followin table: Exposure time, m sec Depth of photopolymerization, mm 8 0.61

16.7 1.2

33.3 1.76

66.7 3.06 125 5.24

250 6.67

500 8.05

1000 >10.0

It will be appreciated that the foregoing data show depth o polymerization to be a direct function of exposure time when th power is constant, and of power when exposure time is constant This phenomenon is sometimes called "reciprocity".

The trimethylolpropane triacrylate used as described abov in Example 1 (hereafter "Monomer 1") is one that is availabl commercially under the trade designation "Sun Printing Ink 1622

53-1". It contains about 94 percent of trimethylolpropan triacrylate and minor amounts of various modifiers.

The laser used as described above in Example 1 was one tha is commercially available under the trade designation "Spectr Physics argon ion laser Model 2016-05". As indicated above, i was tuned to emit light having a wavelength of 514 nm. EXAMPLE 2

A photopolymerizable composition composed of Monomer 1, 0.26 methylene violet and 16.4g triethanolamine, per kg of t monomer, was photopolymerized as described in Example 1, usi a helium/neon laser which emitted light at 632nm and of 15.8 mW power, and various activating times. The depth to whi photopolymerization occurred at each of three different exposu times is shown in the following table: Exposure time, m sec Depth of photopolymerization, mm

500 4.27

250 1.85

125 0.25 Distortion was observed in the polymer when an activating time of 1000 sec was used.

In a second series of photopolymerizations, a similar procedure was used, except that the photopolymerizable composition was composed of Monomer 1 containing 0.27g methylene violet and 40.1g triethanolamine, per kg of the monomer. The depth to which photopolymerization occurred at each of seven different exposure times is shown in the following table:

Exposure time, m sec Depth of photopolymerization, mm 8 thin film 16.7 0.38

33.0 0.37

125 1.61

250 2.85

500 6.55 1000 6.55

The helium/neon laser (hereafter "Laser 2") used as described above in Example 2 is commercially available under the trade designation "Nelles-Griot He/Ne Laser". As used in the present

Examples it emits light having a wavelength of 632nm, 15.83 mW. EXAMPLE 3

A photopolymerizable composition composed of Monomer 1, 0.037g methylene blue and 38.839g triethanolamine, per kg of the monomer, was photopolymerized as described in Example 1, usin Laser 2, and various activating times. The depth to which photopolymerization occurred at each of thre different exposure times is shown in the following table:

Exposure time, m sec Depth of photopolymerization, nm 1000 >10

500 7.74 250 4.57

125 2.36

The data were divergent and not reliable when an activating tim of 66.7 m sec or less was used. In a second series of photopolymerizations, a simila procedure was used, except that the photopolymerizabl composition was composed of Monomer 1 containing 0.03689 methylene blue and 14.38g triethanolamine, per kg of th monomer. The depth to which photopolymerization occurred at eac of four different exposure times is shown in the followin table:

Exposure time, m sec Depth of photopolymerization, mm 125 1.44 250 2.81

500 5.68

1000 >7.6

Activating times shorter than 125 sec did not produce reliabl results. EXAMPLE 4

A photopolymerizable composition composed of Monomer 1 0.358g methylene green and 36.47g triethanolamine, per kg of th monomer, was photopolymerized as described in Example 1, usin Laser 2, and various activating times. The depth to whic photopolymerization occurred at each of six different exposur times is shown in the following table:

Exposure time, m sec Depth of photopolymerization, mm 16.66 0.189

33.33 0.640 66.67 0.643

125 1.132

250 2.459

500 2.980

Activating times shorter than 66.67 m sec did not always giv reproducible results.

In a second series of photopolymerizations, a simila procedure was used, except that the photopolymerizabl composition was composed of Monomer 1 containing 0.36g methylen green and 17.9g triethanolamine, per kg of the monomer. Th depth to which photopolymerization occurred at each of fou different exposure times is shown in the following table: Exposure time, m sec Depth of photopolymerization, mm 33.33 0.758

66.67 0.801

125 1.147 250 2.642

Activating times shorter than 66.67 m sec did not always give reproducible results.

A photopolymerizable composition composed of Monomer 1 containing 0.036g methylene green and 17.9g triethanolamine, per kg of the monomer, was found to have a long induction period, polymerization being initiated only at flash periods greater than 500 m sec. Examples 5-22

Several photopolymerizations have been carried out usin various photoinitiator systems in a monomer system composed of lg vinyl 2-pyrollidone and 9g dipentaerythritol hydroxy penta- acrylate and activating radiation from an argon ion laser which had a wavelength of 514 nm. Typical photoinitiators that were used (the amount of each ingredient being given parenthetically following its name) and the depth to which the composition was polymerized by a 1 second exposure at 500mW are given in th following table:

Example Photoinitiator System

Initiator (g/kg monomer) Accelerator (g/kg mono

5 Eosin lactone (0.080) triethanolamine (1

6 Ethyl eosin ester (0.084) triethanolamine (1

7 RB Lactone (0.104) triethanolamine (1

8 Ethyl RB (0.103) triethanolamine (1

9 RB Peroxide (0.12)

10 Eosin lactone (0.080) Naphthalene peroxi

11 Erythrosin B (0.084) triethanolamine (1

12 Methylene violet (0.045) triethanolamine (1

13 Methylene violet (0.25) triethanolamine (1 4 Eosin lactone (0.08) triethanolamine (1 5 Eosin lactone (0.084) triethanolamine (1 6 Rose Bengal lactone (0.104) triethanolamine (1 7 Rose Bengal ethyl ester (0.103) triethanolamine (1 8 RB peroxide (0.12) none 9 Eosin lactone (0.08) naphthyl peroxide 0 Erythrosin B (0.084) triethanolamine (1 1 Methylene violet (0.04) triethanolamine (1 2 Methylene violet (0.25) triethanolamine (1

this composition required a long exposure time at 500mW

The monomer system composed of vinyl 2-pyrollidone and dipentaerythritol hydroxypenta acrylate (hereafter "Monomer 2") which was used as described above in connection with Examples 5-22 is available from Mead Imaging under the trade designation "DPHPA". Examples 23-29

Several photopolymerizations have been carried out using various photoinitiator systems in lOg Monomer 2 and activating radiation from a helium/neon laser which emitted light at 632nm. Typical photoinitiators that were used (the amount of each ingredient being given parenthetically following its name) and the depth to which the composition was polymerized by a 1 second exposure at 500mW are given in the following table:

Example Photoinitiator System Depth of Polymerization

Initiator (g/kg monomer) Accelerator (g/kg monomer)

23 Methylene violet (0.046) triethanolamine (19) >1 second inductio

24 Methylene violet (0.27) triethanolamine (19) 7.94

25 Methylene blue (0.38) triethanolamine (19) >1 second inductio

26 Methylene blue (0.44) triethanolamine (19) 5.94

27 Thionin triethanolamine (19) does not work

28 Methylene green (0.038) triethanolamine (18) long induction time

29 Methylene green (0.337) triethanolamine (18) 3.76

It has been found that the depth of polymerization, when photopolymerizable compositions according to the instant invention are subjected to photon initiation of suitable, constant intensity, is directly proportional to log T, where T is the time of exposure, which is conveniently measured in seconds. As a consequence, the exposure time necessary to polymerize to any given depth, using any given intensity of photon initiation, can be calculated if the depth to which photon initiation of that intensity causes polymerization in a given time and the slope (S) of the straight line relationship between log time and depth are known. In fact, the equation is simple if depth (I) of polymerization at one second (log T = zero) is determined; the depth of polymerization (L) in mm then equals S times log T plus I. In the data for Examples 5-29 which is set forth in the foregoing tables, depth of polymerization is I; S is given in the following table for Examples 5-13 when the intensity of the activating radiation is 500mW and for Examples 14-29 when the intensity is lOOmW (omitting data concerning inoperable compositions in both cases) :

Example No. Slope

5 3.653

6 5. 639

7 5.473

8 4 .600

9 5.821

10 4.297

11 5.093

13 7.535

14 3. 653

15 5.639

16 5.473

17 4. 60

18 5.821

19 4.297

20 5.093

22 7.535

24 7.831

26 4.830

29 2.98

EXAMPLE 30

Several photopolymerizations have also been carried out usin a monomer system composed of 12.Ig diacrylate of an ethoxylated bisphenol and 12.Ig acrylic monomer, using an Ar(+) laser wavelength 514nm, intensity SOOirfW. In one series o photopolymerizations the monomer composition also containe 0.02g eosin Y lactone dissolved in 0.48g 2-hydroxyethyl methacrylate and 0.8g triethanolamine. I was found to be 0.480m and S was found to be 3.26.

In a second series of photopolymerizations the monome composition also contained O.lg eosin Y lactone dissolved i 0.4g 2-hydroxyethylmethacrylate and 0.8g triethanolamine. I wa found to be 0.450mm and S was found to be 1.90. The ethoxylatedbisphenol diacrylate used as described abo in Example 30 is available from Sartomer Company under the tra designation SR349. The acrylic monomer used as described above in Example 30 is available under the trade designation "NOVACURE C3700" from Radcure Company. Examples 31 and 32 Several photopolymerizations have also been carried out using various photoinitiator systems in lOg Monomer 1 and activating radiation from an inexpensive diode laser which emitted light at 682nm, 5mW. Two of the photoinitiators that were used were methylene violet (0.13 g/kg monomer) and methylene blue (0.13 g/kg monomer) and, in each case, triethanolamine (1.25g/kg monomer) . The beam of the laser was unfocused, but a spot of polymer 2mm wide by 5mm deep at the center was formed in 0.5 second. The spot of polymer was progressively larger when the exposure time was increased to 2 seconds, 10 seconds and 25 seconds, demonstrating that the 682nm, 5mW laser can be used according to the method of the instant invention to initiate three dimensional photopolymerization. Example 33

A xanthate dye derivative for use according to the invention as an initiator in a polymerizable composition was produced from 42.00 g rose bengal (structure of Fig. 1 where X2, X4, X5 and X7 are iodo, Y2'is COONa, Y3', Y4', Yδ'and Y6' are chloro, and R is Na) which was dissolved in 350 mL dimethyl formamide. The solution was refluxed under an argon blanket for about 16 hours, with stirring, and was then concentrated to 80 mL by distillation of dimethyl formamide. An addition of 200 mL 2M hydrochloric acid was then made to the concentrated solution, after which a pasty red solid was recovered by vacuum filtration. The red solid was washed with 500 mL of water and then with 300 mL of hexanes, and was then dried for 48 hours under vacuum. The yield was 31.72 g decarboxylated rose bengal (structure of Fig. 1 where X2, X4, X5 and X7 are iodo, Y2' is H, Y3', Y4¹, Y5'and Y6' are chloro and R is Na) , 82.63 percent of theory. The compound was identified by NMR and IR. A 3.20 g portion of the decarboxylated rose bengal was dissolved in 20 L acetyl chloride, and the solution was refluxed, with stirring, under an argon blanket for 36 hours, after which time the solution was ound to be almost completel free of the starting dye. The solution was then concentrate under vacuum, leaving a dark red solid. A part of the solid wa used in photopolymerization studies which are subsequentl described herein, while another part was purified and identifie by NMR as O-acetyl decarboxylated rose bengal (structure of Fig. 1 where X2, X4, X5 and X7 are iodo, Y2' is H, Y3' , Y4' , Y5' an Y6' are chloro, and R is acetyl). EXAMPLE 34

O-trichloroaσetyl decarboxylated rose bengal (structure o Fig. 2 where X2, X4, X5 and X7 are iodo, Y2'is H, Y3' , Y4' , Y5^f and Y6'are chloro, and R is trichloroacetyl) was produced fro 5.24 g decaraboxylated rose bengal prepared as described i Example 33, and dissolved in 20 mL trichloroacetyl chloride. Th solution was refluxed under an argon blanket, with stirring, fo forty hours, after which time the solution was found to b almost completely free of the starting dye. The solution wa then concentrated under vacuum at about 80^*, leaving a dark re solid. A part of the solid was used in photopolymerizatio studies which are subsequently described herein, while anothe part was identified by NMR as O-trichloroacetyl decarboxylate rose bengal. EXAMPLE 35

O-methyl decarboxylated rose bengal (structure of Fig. where X2, X4, X5 and X7 are iodo, Y2• is H, Y3' , Y4', Y5¹ an Y6* are chloro, and R is methyl) was produced from 1.17 decarboxylated rose bengal produced as described in Example 33 2.0 mL dimethyl sulfate, and 4.0 g sodium carbonate dissolve in 30 mL 1,2-dimethoxyethane. The solution was refluxed, wit stirring, under an argon blanket for 5 hours and was cooled t room temperature of about 22^*. Solids which formed wer separated from the liquid by filtration and washed with 50 dichloromethane. The wash was combined with the filtrate and th resulting solution was concentrated under vacuum. The residu was placed on a 4 inch alumina column and eluted with 500 m hexanes (fractions 1 and 2) and with 1,750 mL dichloromethan (fractions 3 through 9) . The dichloromethane fractions wer combined, and the resulting solution was concentrated unde vacuum, leaving 9.19 g O-methyl decarboxylated rose bengal which was identified by NMR and IR. EXAMPLE 36

0-(3,5-dinitrobenzoyl) decarboxylated rose bengal (structure of Fig. 1 where X2, X4, X5 and X7 are iodo, Y2' is H, Y3' , Y4', R5* and Y6* are chloro, and R is 3,5-dinitrobenzoyl) was produced from 3.00 g decarboxylated rose bengal produced as described in Example 33 and 0.88 g 3,5-dinitrobenzoyl chloride dissolved in 40 L toluene. The solution was refluxed, with stirring, under a nitrogen atmosphere for 48 hours. 0-(3,5- dinitrobenzoyl) decarboxylated rose bengal, whichwas identified by NMR, was recovered by concentrating the reaction mixture under vacuum. EXAMPLE 37

O-acetyl ethyl eosin (structure of Fig. 1 where X2, X4, X5 and X7 are bromo, Y2'is -COOCH₂CH₃, Y3', Y4', Y5' and Y6' are H, and R is acetyl) was produced from a solution of 5.00 g ethyl eosin (structure of Fig. 1 where X2, X4, X5 and X7 are bromo, Y2'is -COOCH₂CH₃, Y3', Y4' , Y5' and Y6' are H and R is Na) in 30 mL acetyl chloride by refluxing the solution, with stirring, under an argon blanket for 36 hours and removing the excess acetyl chloride under vacuum. The product, an orange solid, was dried under vacuum at about 80^* for 48 hours, and was identified by NMR. EXAMPLE 38

Several polymerizations were carried out using O-acetyl decarboxylated rose bengal produced as described above as a initiator for the polymerization of dipentaerythritol hydrox penta-acrylate, triethanolamine as an accelerator, an activating radiation from an argon ion laser which had wavelength of 514 nm. The composition polymerized was a solutio which contained 20 percent of tetrahydrofuran in the dipenta erythritol hydroxy penta-acrylate, and, per 1000 g of th solution, 0.0087 g O-acetyl decarboxylated rose bengal and 0.1 g triethanolamine. The composition was placed in a quart cuvette which had a square base 1 cm on a side and four side at right angles to the base, each, 1 cm by 4 cm, and severa portions of the composition were exposed to light from the argo laser at a power of lOOmW in the manner described in Example 1. The unreacted solution was then decanted from the cuvette, an the lengths of spikes attached to the interior of the cuvett which had been formed by polymerization of the solution wer measured. The lengths of the spikes at various exposure time are given in the following table:

Spike Length (mm) Time (Seconds) 9.100 0.5000

8.006 0.2500

7.630 0.1250

4.340 0.0667 no spike 0.0333 2.980 0.0167

The procedure described above in Example 38 was repeated t polymerize a solution which contained 20 percent o tetrahydrofuran in the dipenta-erythritol hydroxy penta acrylate, and, per 1000 g of the solution, 0.0090 g O-acety decarboxylated rose bengal and 0.08 g triethanolamine. Th lengths of the spikes at various exposure times are given in th following table:

Spike Length (mm) Time (Seconds)

9.000 0.5000 7.590 0.2500

5.930 0.1250

4.050 0.0667

0.700 0.0333 no spike 0.0167 The procedure described above in Example 38 was also repeate to polymerize a solution which contained 20 percent o tetrahydrofuran in the dipenta-erythritol hydroxy penta acrylate, and, per 1000 g of the solution, 0.0876 g O-acety decarboxylated rose bengal and 0.16 g triethanolamine. Th lengths of the spikes at various exposure times are given in th following table:

Spike Length (mm) Time (Seconds)

2.204 0.5000

1.934 0.2500 1.476 0.1250

1.244 0.0667

1.140 0.0333

1.096 0.0167 The procedure described above in Example 38 was repeated, except that the wavelength of the radiation was 488 nm, t polymerize a solution which contained 20 percent o tetrahydrofuran in the dipenta-erythritol hydroxy penta acrylate, and, per 1000 g of the solution, 0.07650 g O-acetyl decarboxylated rose bengal and 0.09 g triethanolamine. Th lengths of the spikes at various exposure times are given in th following table:

Spike Length (mm) Time (Seconds) (Distorted) 0.500

2.400 0.250

1.260 0.130

1.000 0.060

0.670 0.030 Diffuse spike 0.0167

Finally, the procedure described above in Example 38 wa repeated to polymerize a solution which contained 20 percent o tetrahydrofuran in the dipenta-erythritol hydroxy penta acrylate, and, per 1000 g of the solution, 0.04900 g O-acety decarboxylated rose bengal and 0.40 g tetramethylammonium n butyl borate. The lengths of the spikes at various exposur times are given in the following table:

Spike Length (mm) Time (Seconds)

1.088 0.5000 0.943 0.2500

0.883 0.1250

0.745 0.0667

0.617 0.0333 no spike 0.0167 Examples 33 through 36 describe the decarboxylation of ros bengal to produce decarboxylated rose bengal and the production from the latter, of O-acetyl decarboxylated rose bengal, 0 trichloroacetyl decaraboxylated rose bengal, O-methy decarboxylated rose bengal and 0-(3,5-dinitrobenzoyl decarboxylated rose bengal. It will be appreciated that thes reactions are general in the sense that equivalent amounts o other xanthene dyes, all compounds having the structure of Fig

1 where Y2' is COONa, COOK, or the like and R is Na, K or th like, can be substituted for the rose bengal and decarboxylate by the method of the first paragraph of Example 33 to produc xanthene dye derivatives which are more soluble in polymerizabl compositions than the parent dye. Examples of known xanthen dyes include rose bengal (the starting material in Example 33) , fluorescein, eosin, phloxin, erythrosin, dichloro eosin (tw compounds, one where Y3• and Y6• are Cl and one where X2 and X are Cl) , dibromo flourescein (two compounds, one where X4 an X5 are Br, and one where X2 and X4 are Br) and diiodofluoroes cein. Many other xanthene dyes are disclosed in the literature commencing with Baeyer, A. (Chemische Berichte. 1871, 4, 555 an 1875, 8, 146 and Anna1en. 1880, 202) and continuing to th present (Hon, D.N.S. et al.. Wood Sci. Techno. 1982, 16, 193 this paper is reference number 109 in a study that is about t be published) . Accordingly, it will be appreciated that each o 2, X4, X5, X7, Y3• , Y4• , Y5• , and Y6• in Fig. 1 can be H, Br Cl, I, N0₂ or NR, where R has the meaning set forth below, tha R can be an alkyl group having from 1 to 22 carbon atoms, a alkaryl group having from 7 to 22 carbon atoms, an aryl grou having from 6 to 20 carbon atoms, an aralkyl group having fro 7 to 22 carbon atoms, a 2 to 10 membered carbocyclic o heterocyclic group, an olefinically unsaturated hydrocarbo group having from 2 to 10 carbon atoms, an acyl group havin from 2 to 22 carbon atoms, or a halogenated acyl group havin from 2 to 22 carbon atoms. Preferably, R is an alkyl group othe than t-butyl having from 1 to 4 carbon atoms, an acyl grou having from 1 to 4 carbon atoms or a halogenated acyl grou having from 1 to 4 carbon atoms. In Fig. 1, Y2• can be a grou having the formula -C00R' , where R' can be an alkyl group havin from 1 to 22 carbon atoms, an alkaryl group having from 7 to 2 carbon atoms, an aryl group having from 6 to 20 carbon atoms an aralkyl group having from 7 to 22 carbon atoms, a 2 to 1 membered carbocyclic or heterocyclic group, or an olefinicall unsaturated hydrocarbon group having from 2 to 10 carbon atoms Preferably, R' is an alkyl group other than t-butyl having fro 1 to 4 carbon atoms. Similarly, in Fig. 1, M can be oxygen sulfur, selenium, tellurium, S0₂, SO or NR' , where R' has th meaning set forth above. Each of the foregoing compounds i either known or can be produced from known compounds by know chemical processes that will be apparent to one skilled in the art if requested to prepare that compound. EXAMPLE 39

The sodium salt of tetraiodoresorufim, a compound having the structure of Fig. 2 of the drawings where XI, X2, X3, and X4 are I, and R is Na was produced from a mixture of 1.0 g resorufim, 70 mL water, 21 L saturated aqueous sodium carbonate and 4.84 g iodine. The iodine was added slowly to a mixture of the resorufim, water, and sodium carbonate solution, and the reaction mixture which resulted was stirred for about 16 hours at about 20^*. The final reaction mixture, which contained the sodium salt of tetraiodoresorufim, was then acidified with concentrated hydrochloric acid; the precipitate which formed was recovered by filtration, washed with dilute hydrochloric acid, and dried under reduced pressure, yielding 1.2 g tetraiodoresorufim, which was identified by IR and NMR.

Tetraiodoresorufim acetate (the acetate of a compound having the structure of Fig. 2 of the drawings where XI, X2, X3, and X4 are I, and R is H) was then produced by stirring a mixture of 500 mg tetraiodoresorufim produced as described in the preceding paragraph, 20 mg 4-dimethylaminopyridine, and 3 ml acetic anhydride in 40 ml dry tetrahydrofuran at about 20^* for about 16 hours. The solvent was then removed from the reaction mixture under reduced pressure, and the residue which remained was dissolved in 100 mL diethyl ether. The ether solution was washed three times with 20 mL portions of dilute hydrochloric acid, three times with 20 mL portions of a 5 percent aqueous sodium bicarbonate solution and twice with 30 mL portions distilled water. The washed solution was then dried with magnesium sulfate and, after separation of the magnesium sulfate by filtration, concentrated, yielding 480 mg tetraiodoresorufim acetate. EXAMPLE 40

Polymerizations were carried out using tetraiodoresorufi acetate produced as described above as an initiator for the polymerization of Monomer 1, cetylpyridinium triphenyl butyl borate as an accelerator, and activating radiation from an argon ion laser which had a wavelength of 514 nm. The composition polymerized was a solution of 8.7 mg tetraiodoreserufim acetate and 60.7 mg cetylpyridinium triphenyl butyl borate in 10 m Monomer 1. The polymerizations were carried out as described i Example 38. The weight of the polymer spike that was formed whe the composition was exposed to light from the argon laser at power of HOmW are given in the following table. Exposure, seconds 4 2 1 h k Vi mg Polymer 60.68 25.47 12.21 5.71 2.52 1.19 The weight of the polymer spike that was formed when th composition was exposed to light from the argon laser at a powe of lOOmW are given in the following table. Exposure, seconds 4 2 1 i mg Polymer 61.66 32.30 15.03 1.30

Tetrabromoresorufim, tetrachlororesorufim and tetrafluoro resorufim can be produced by bubbling bromine, ejilorine o fluorine through a stirred reaction mixture composed o resorufim, water and sodium carbonate, and other compound having the structure of Fig. 2 can be produced by the method o Example 39 by substituting other starting materials for th resorufim. Lacmoid, a compound having the structure of Fig. where X4, X5, and X7 are hydrogen and M is oxygen, is an exampl of another starting material that can be substituted fo resorufim, as is a known compound having the structure of Fig 3 where X4, X5 and X7 are hydrogen and M is oxygen. Compound having the structures of Fig. 2, Fig. 3 or Fig. 4 where each o X2, X4, X5 and X7 H, Br, Cl, I, F, N0₂ or NR, where R has th meaning set forth below, M is oxygen, sulfur, selenium tellurium, S0₂, SO or NR¹ , where R is an alkyl group having fro 1 to 22 carbon atoms, an alkaryl group having from 7 to 2 carbon atoms, an aryl group having from 6 to 20 carbon atoms an aralkyl group having from 7 to 22 carbon atoms, a 2 to 1 membered carbocyclic or heterocyclic group, an olefinicall unsaturated hydrocarbon group having from 2 to 10 carbon atoms an acyl group having from 2 to 22 carbon atoms, or a halogenate acyl group having from 2 to 22 carbon atoms can be produced fro known compounds by known chemical processes that will b apparent to one skilled in the art if requested to prepare tha compound, and can be used as photoinitiators in compositions an methods of the invention. Preferably, X2, X4, X5 and X7 are H F, Cl, Br or I. As has been explained above, when the photopolymerizable composition is composed of trimethylolpropane triacrylate, eosin lactone and triethanolamine, a beam of activating radiation, for example, from an argon ion laser having a wavelength of 514nm, entering the composition causes the eosin to react with the triethanolamine, with the result that the dye color is lost, and two moieties are formed, one of which serves as an activator fo the trimethylolpropane triacrylate; as a consequence of the loss of the dye color, subsequent radiation can penetrate deeper in the photopolymerizable composition. A similar mechanism is involved when the other photopolymerizable compositions specifically disclosed above are suitably activated. It will be appreciated, however, that other photopolymerizabl compositions, in addition to those specifically disclosed, will react in a similar manner, and that such compositions can b used in practicing the method of the instant invention, as ca still other compositions, so long as they are ones in which a entering ray of activating radiation activates th photoinitiator system thereof at each of a succession of points, the first such point being immediately adjacent the surfac through which the ray enters and subsequent points bein successively farther from the surface in the direction of trave of the ray of activating radiation, the distance from th surface to the point of the succession farthest therefro varying as a function of at least one of

(a) the intensity of the activating radiation and

(b) the time during which the activating radiation enters the body through the surface. When the invention is practiced using a visible ligh photoinitiator such as eosin and its derivatives and visibl light for activation, it is not necessary that th photoinitiator have a peak absorbance at the wavelength of th activating light; all that is required is that there b sufficient absorbance at the wavelength of the activating ligh to cause the reactions which form the activator and cause th dye to lose its color at the required rates. If bleaching occur too rapidly, by comparison with the rate at which polyme forming radical formation occurs, radical reactions which do no cause polymerization, e.g., radical coupling, can be expected. On the other hand, if polymerization occurs too rapidly, b comparison with the rate at which bleaching occurs, activatin light can not penetrate the monomer/photoinitiator mixture t a sufficient depth, and polymerization stops on or near th surface through which the light enters. This balance is achieve in the foregoing examples by selection of certain dyes a photoinitiators, using triethanolamine as an accelerator, an controlling the proportions of the two. In general, th photoinitiators are used at extremely low concentrations, b comparison with those which have previously been suggested an used, most frequently in curing thin films, for example o printing ink, solventless varnishes, adhesive or photoresists. The concentrations in which photoinitiators are used for thi film photopolymerizations are so high that activating light ca not penetrate the monomer/photoinitiator mixture to a sufficien depth, and polymerization stops on or near the surface throug which the light enters. On the other hand, as is shown by th data set forth above, the concentration of the photoinitiato must be sufficiently high that the induction period is no excessive, and the concentration of the activator and the photo density must both be sufficiently high that the rates o bleaching and polymerization are appropriately matched t achieve polymerization to a desired depth in photopolymerizable composition.

The foregoing examples disclose several photopolymerizabl compositions composed of a trimethylolpropane triacrylat monomer, a vinyl 2-pyrollidone and dipentaerythritol hydrox penta acrylate monomer system, and a monomer system composed o a diacrylate of an ethoxylated-bisphenol and an acrylic monomer one of several dyes which are photoinitiators an triethanolamine or another accelerator. Othet monomers photoinitiators and accelerators that can be used will b apparent to one skilled in the art from the foregoin disclosure. In general, the monomer should be one which has a electron starved double bond that is subject to additio polymerization, acrylic monomers, generally, being suitable Similarly, other accelerators can be used, tertiary amines bein preferred when visible light is used for activation and th photoinitiator is eosin lactone, methylene violet, methylene blue, methylene green or another photoinitiator which is a dye in the conventional sense. However, the invention can also be practiced with activating radiation that is outside the visible spectrum and a suitable activator, for example, one that, prior to activation is opaque to the activating radiation but, upon activation, undergoes a reaction which causes it to be transparent to the activating radiation. So far as the eye is concerned, bleaching is not associated with activation, but it does occur so far as the activating radiation is concerned. Indeed, all that is necessary is that the photopolymerizable composition be one wherein a ray of activating radiation which enters a body of the composition through a surface thereof activates the photoinitiator system and causes polymerization at each of a succession of points, the first such point being immediately adjacent the surface and subsequent points being successively farther from the surface in the direction of travel of the ray of activating radiation, and the distance from the surface to the point of the succession farthest therefrom varies as a function of at least one of

(a) the intensity of the activating radiation and

(b) the time during which the activating radiation enters the body through the surface. The method of the invention can also be used to produce a colored body. For example, a dye or pigment which imparts a color to a polymer produced from a body of the polymerizable composition can be to the body, and a polymer can be produced as previously described. The polymer can then be immersed in a body of another polymerizable composition containing another dye or pigment which imparts a different color to a polymer produced therefrom, and a second polymer can be produced. Finally, the composite polymer can be immersed in a body of a third polymerizable composition containing a dye or pigment which imparts a third color to a polymer produced therefrom, and a third polymer can be produced. It will be appreciated that the colors of the three polymers of the final composite can complement one another as colored printing inks complement one another in producing colored images. The method of the invention can also be used in surgical procedures, for example to reconstruct a bone or to construct a hip. A photopolymerizable composition according to the invention can be positioned in any suitable way in the region where construction or reconstruction is required, and photopolymerization can be initiated by light of a suitable wavelength conducted to the polymer through optical fibers, the depth of polymerization being controlled by the duration of the activating light, the intensity, or both. Indeed, data concerning the reconstruction or construction can be input to a computer remote from the surgery, and the output from the computer can be used to control the activating light.

Three dimensional objects can be made according to the method of the invention by positioning an appropriate laser and moving a body of the composition to be photopolymerized appropriately relative to the fixed laser. Indeed, the body of the composition to be polymerized can be moved either vertically or horizontally and then translated in the other direction; by repeating these movements radiation from the laser can be caused to enter the body in a complete two dimensional grid. The depth of polymerization can then be controlled by varying the rate of movement of the body, slower movement causing deeper polymerization, and vice versa. A similar result can be achieved by moving the laser rather than the body of the photopolymerizable composition.

By way of example, a relief map can be made by the method of the instant invention by directing a suitable laser upwardl through a bottom of a container and into a body of a appropriate photopolymerizable composition, moving the body o the polymerizable composition so that the laser enters the bod in a complete two-dimensional grid, as described, and varyin the rate of movement so that the depth of polymerizatio corresponds with the height to be represented at all points o the grid. The bottom of the container can be a material to whic the polymer adheres, so that the relief map, when completed, i mounted on the bottom of the container as a base.

The method can also be used to weld two pieces, one of whic is transparent to the radiation from the laser used, b confining a body of a photopolymerizable material in a regio which includes that where the weld is desired, and then initiating photopolymerization with a laser to form the weld. Similarly, a spacer can be formed between two sheets, one of which is transparent to the radiation, by confining the body of the photopolymerizable material between the sheets, and then initiating photopolymerization with the laser to form the spacer. In a like manner, the edges of two sheets, one of which is transparent to the radiation, can be sealed and supported relative to one another by confining the body of the photopolymerizable material between the sheets, and then initiating photopolymerization with the laser to seal the edges and support them relative to one another.

It will be apparent that various changes and modifications can be made from the specific details of the invention as disclosed herein without departing from the spirit and scope thereof as defined in the appended claims.