US 3867169 A
In a non-carbon copying paper comprising upper paper, lower paper and/or at least one intermediates paper, smoothness of coating surface of the upper or intermediate paper can be improved and smudge formation on the paper and changes in compositions of coating material during application can be prevented by incorporating microspheres, e.g., vinylidene chloride-acrylic acid ester copolymer microspheres in the coating layer of microcapsules on the upper or intermediate paper.
Description (OCR text may contain errors)
v  Filed:
llnited States Patent [191 Shimizu NON-CARBON COPYING UPPER PAPER  Inventor: Hideo Shimizu, Takasago, Japan  Assignee: Mitsubishi Paper Mills, Ltd., Tokyo,
Japan Aug. 14, 1972  Appl. No.: 280,163
 Foreign Application Priority Data Feb. 18, 1975 3,265,524 8/1966 Echeagaray 117/368 3,554,932 l/197l Overcashier 117/100 C 3,615,972 10/1971 Morehouse et a1. 156/79 3,625,736 12/1971 Matsukawa et al 1 17/362 3,726,755 4/1973 Shannon 161/D1G. 5
Primary Examiner-Thomas J. Herbert, Jr. Attorney, Agent, or FirmCushman, Darby & Cushman 1 ABSTRACT In a non-carbon copying paper comprising upper paper, lower paper and/or at least one intermediates paper, smoothness of coating surface of the upper or intermediate paper can be improved and smudge formation on the paper and changes in compositions of coating material during application can be prevented by incorporating microspheres, e.g., vinyliclene chloride-acrylic acid ester copolymer microspheres in the coating layer of microcapsules on the upper or intermediate paper.
10 Claims, 4 Drawing Figures Pmzmmrzm a ma FIG. 2
I NON-CARBON COPYING UPPER PAPER The present invention relates to an improved noncarbon copying paper.
A non-carbon copying paper generally comprises an upper paper the back face of which is coated with microcapsules in which an oil in which an electron donating organic color former, e.g., a triphenylmethane dye such as crystal violet lactone, a leuco dye such as benzoil leucomethylene blue is dissolved is contained by coacervation method disclosed in US. Pat. No. 2,800,457, a lower paper the top face of which is coated with a solid acid such as attapulgite, montmorillonite, bentonite, Japanese acid clay, kaolin or an oil soluble phenol resin and at least one intermediate papers, the top face of which is coated with a solid acid and the back face of which is coated with microcapsules. The coated face of the upper paper and that of the lower paper are allowed to contact with each other of the intermediate paper or papers are put therebetween and writing pressure is applied to the top face of the upper paper to form a coloredimage corresponding to said pressure applied image on the lower paper or the intermediate paper,
One of the important requirements for such noncarbon copying paper is that no color formation or smudge occurs on the surface of the intermediate or lower paper in the superposed state before using. If the smudge occurs before using, not only the copying paper becomes unattractive, but the written and pressured parts become indistinct and practical difficulties are caused. The mechanism of smudge formation is as follows: the microcapsules (fine spheres of 320 ,1 in diameter) containing dye-oil which are applied to paper surface tend to be partially ruptured even by low writing pressure and when the microcapsules are ruptured, the contents thereof are transferred to the surface of the intermediate or lower paper to cause color formation.
In order to prevent rupture of microcapsules under a pressure of lower than the writing pressure, methods by which the microcapsules are mixed with materials somewhat greater than the microcapsules have been proposed. Examples of such materials are cellulose fibers proposed in US. Pat. No. 2,711,375 and starch particles in British Pat. No. l,232,347. As the cellulose fibers (flocks), mechanically cut pulp is used and therefore the particle size is not uniform and considerably coarse particles are also included. Therefore, the coated face of the upper paper becomes very rough and is inferior to the lower paper. Furthermore, when an aqueous coating material is prepared by mixing the microcapsules with flocks including such coarse particles whose size is not uniform, the viscosity'of the coating material is high and the fluidity thereof is extremely damaged. Moreover, in continuing of coating of the coating material, the proportion of the flocks in the coating material increases with lapse of time and hence the characteristics of the upper paper (amount of coating material applied, smoothness, etc.) change.
In case of using starch particles, the kind of starch can be suitably selected and moreover since the particle size is relatively uniform, the smoothness of the coated face of the upper paper can be considerably improved. Furthermore, the aqueous coating material prepared by mixing the starch particles and the microcapsules is considerably improved in stability and the degree of increase of viscosity is low. However, with progress of the coating of the coating material, the compositions of the coating material change because the specific gravity (about 1.6) and average particle size (about 30p) of the starch particles are considerably greater than the specific gravity (about 1.0) and the particle size (3-20 1.) of the microcapsules. That is, accumulation of precipitate of the starch particles in the coating material or increase of proportion of the starch particles in the coating material are caused and the characteristics of the upper paper (amount of coating material, smoothness, color formation, smudge, etc.) change.
In an attempt of removing the above mentioned defects, the inventors have succeeded in producing copying paper which can prevent formation of smudge and is improved in smoothness and stability of the coating material and which shows no precipitation and no change in compositions during coating of the coating material by incorporating microspheres asa smudge preventing agent in place of said conventionally used cellulose fibers and starch particles.
FIG. 1 shows a rough cross section of micro-capsule,
FIG. 2 shows a rough cross section of micro-sphere expanded after heating,
FIG. 3 shows a rough cross section of an upper paper of immediately after coating of an aqueous coating material containing microcapsules, microspheres, etc. to a support (before drying and FIG. 4 shows a rough cross section of an upper paper in usable state as non-carbon copying paper after drymg.
The term microsphere used herein means, as shown in FIG. I, a fine sphere comprising wall 1 of vinylidene chloride-acrylic acid ester copolymer and foaming hydrocarbon 2 contained therein, which has a specific gravity of about 1.3 and an average particle size of about 5,u and which is converted into particles of about 30 .t (l0 a, preferably 20 50 in average particle size by expansion of wall 1 caused by foaming of the hydrocarbon at a temperature of 120C as shown in FIG. 2 (In this respect, see microsphere XD 7059.] of Dow Chemical Company).
A suitable amount of said microspheres can be well mixed with microcapsules and substantially no precipitation occurs because the particle size of the microspheres is extremely smaller than that of cellulose fibers and starch particles and is nearly comparable to that of the microcapsules and moreover, the microspheres have a low specific gravity. Furthermore, addition of only a small amount of the microspheres can accomplish the purpose. The mixing ratio of the microcapsules to the microspheres is 1 20 prefera bly 100:2 l0
When such aqueous mixed liquid is applied to a paper, microsphere 1 is in the state of fine sphere immediately after coating as shown in FIG. 3. At the heat drying step, the microsphere is expanded and as shown in FIG. 4, microsphere 1 becomes larger than microcapsule 2. Moreover, even after expansion, the microsphere maintains spherical shape and hence it has an excellent smoothness.
The size of the microsphere can be optionally adjusted by controlling the drying conditions of the coat ing material such as heating temperature, heating time, etc. Therefore, use of the micros'pherescan provide characteristics of upper paper in accordance with the incorporated in the microcapsules layer on the back face of the intermediate paper to obtain the same effects.
purpose of use regardless of particle size of the microcapsules as compared with cellulose fibers and starch particle whose shape and size are originally fixed. The microspheres used in the present invention are not limited to vinylidene chloride-acrylic acid ester copolymer 5 microspheres of Dow Chemical Company, but any microspheres which can foam and expand by heating can 'be used.
It is a matter of course that said microspheres can be The present invention will be illustrated in the following Examples.
EXAMPLE '1 An oil obtained by dissolving 2 parts of Crystal Violet Lactone and 1 part of Benzoil Leuco Methylene Blue in 100 parts of tripropylnaphthalene was encapsulated by the coacervation method disclosed in US. Pat. No. 2,800,457. The average particle size of thus obtained microcapsules was 10p and solid matter was 18.0
Microcapsules (net amount) 100 parts Microsphere XD7059.1 (net amount) 2 parts MS-3800 (20 7: aqueous solution of Japan Food oxidized starch) 50 parts (Adhesive) The above components were mixed and stirred in a tank with stirrer.
The obtained aqueous coating material (solid matter 4O Said upper paper was superposed'on a lower paper and degree of smudge formed was examined to find that the smudge formation was very little. The application of the coating material was continued for further several hours to find that the compositions of the coating material were substantially the same as those at the beginning of the application.
EXAMPLE 2 Using the microcapsules of Example 1, a coating ma- 50 terial comprising the following components was prepared. V V a Thus obtained coating liquid (solid matter 19 was coated in a net amount of 7 g/m on one face ofa base paper of 40 g/m with an air knife coater and was dried with a hot air drier of an internal temperature of 100C to obtain an upper paper. The microspheres were expanded to an average particle size of 30p. (20 The smoothness of the coating surface of thus obtained upper paper was excellent. Said upper paper was superposed on a lower paper and smudge formation was observed to find that the smudge was caused with extreme difficulty. The application was continued for further several hours to find that the compositions of the coating material were substantially the same as those at beginning.
Reference Example 1 Using the microcapsules of Example I, a coating material comprising the following components was prepared.
Microcapsules (net amount) 100 parts K.C. Flock (pulp fine powders manufactured by Kokusaku Pulp K.K., net amount) 20 parts MS-3800 (20 aqueous solution) i 80 parts Thus obtained coating material was coated in a net amount of 9 g/m on one face of a base paper of 40 g/m with an air knife coater and was dried with a hot air drier of an internal temperature of 120C to obtain an upper paper. The smoothness of the coating surface of the upper paper was very low. Said upper paper was superposed on a lower paper and degree of smudge formation was observed to find that somewhat smudge was formed. After application of several hours, the compositions of the coating material were examined to find that the proportion of the K.C. Flock increased and viscosity was increased.
Reference Example 2 Reference Example 1 was repeated except that 20 parts ofwheat flour (particle size 2535;t) was substituted for the KC. Flock to produce an upper paper. The smoothness of the coating surface of said upper paper was excellent. The upper paper was superposed on a lower paper and degree of smudge formation was examined to find thatthe smudge occurred with difficulty.
After application of the coating material for several hours, the compositions of the coating material were examined to find that the proportion of wheat starch increased and the wheat starch was deposited at the bottom of the coating material and the viscosity was Microcapsules (net amount) [00 parts Microsphere M37059, (net amount) 5 parts somewhat increased. The results of Examples 1 and 2 MS-3800 20 aqueous solution of and Reference Examples 1 and 2 are shown in the fol- Japan food oxidized starch) P [Owing Table.
Table Example 1 Example 2 Reference Reference Example l Example 2 Smudge preventing Microsphere Microsphere KC Flock W-Zlll) Wheat starch agent XD 7059.1 XD 7059.1
Amount of the agent added based on 2 7! 5 VI 20 '71 20 X microcapsules smoothness of 50 sec. 35 sec. 7 sec.
upper paper* 30 sec.
Table Continued Example l Example 2 Reference Reference Example I Example 2 Smudge caused by upper paper Little Little Great Little (remarkable) Change in compositions of coating Almost none Almost none Extremely Great material great (remarkable) (remarkable) Initial viscosity** 55 op 55 cp I cp 65 cp Viscosity after coating of 3 I 58 cp 56 cp 350 cp 9() cp hours Increase of viscosity of +3 cp +l cp +250 cp +25 cp coating material** Bekk smoothness. The viscosity was measured with Brookfield viscometer,
What is claimed is: I
1. A method of producing non-carbon paper comprising coating a paper substrate with a mixture containing therein microcapsules containing an encapsulated dye-oil and microspheres containing a foaming hydrocarbon, said microspheres having a particle size of about microns, and heating said coated paper thus expanding said microspheres to a particle size of 10-70 microns.
2. A process according to claim 1 wherein the microspheres are vinylidene chlorideacryli c acid ester copolymer microspheres.
3. A process according to claim 1 wherein there is employed an aqueous mixture of the encapsulated dyeoil and microspheres containing the foaming hydrocarbon.
4. A process according to claim 3 wherein the coating also contains starch particles.
5. A process according to claim 4 wherein the microcapsules have a size of 3-20 microns and the ratio of microcapsules to microspheres -is 100.0-20.
6. A process according to claim 5 wherein the microspheres are of a vinylidene chloride-acrylic acid ester copolymer.
7. A process according to claim 1 wherein the noncarbon paper comprises an-upper paper and a lower paper and a coating is applied to the back face of the upper paper. v
9. A process according to claim 1 wherein the heating is at a temperature of about -120C,
l0. A process according to claim 9 wherein there is employed an aqueous mixture of the encapsulated dyeoil and microspheres containing the foaming hydrocar