WO2007137889A2

WO2007137889A2 - Method for producing a coloured thermoplastic plastic film, film and use thereof

Info

Publication number: WO2007137889A2
Application number: PCT/EP2007/052406
Authority: WO
Inventors: Herbert Groothues; Claude Guenanten; Günther DICKHAUT-BAYER; Christoph Steinfels; Berthold SCHÖNIG; Christoph Krohmer
Original assignee: Evonik Röhm Gmbh
Priority date: 2006-05-30
Filing date: 2007-03-14
Publication date: 2007-12-06
Also published as: DE102006025481A1; TW200811857A; WO2007137889A3

Abstract

The invention relates to a method for producing a coloured thermoplastic plastic film. According to said method, the thermoplastic plastic is melted and transported in an extrusion installation comprising an extruder, an extrusion nozzle with a wide-slot outlet and a chill roll which is fixed to a roll frame, and then leaves the outlet of the extrusion nozzle in the form of a flat, coloured melted web. Said coloured melted web is then applied to the chill roll and is cooled. The invention is characterised in that the chill roll has a rotational accuracy of +/- 10 μm or less and that the average distance between the outlet of the extrusion nozzle and the chill roll does not vary by more than +/- 25 μm during operation. The invention also relates to the coloured film of this type and to the uses thereof as a coloured film for optical data carriers.

Description

Process for the preparation of a colored film of thermoplastics, film and use of the film

The invention relates to a process for the preparation of a colored, optically isotropic film made of thermoplastic materials, the film itself and the use of the film as a cover film in optical data carriers, such as the Blu-ray Disc ^® and the data carrier equipped therewith.

State of the art

EP 1 117 731 B1 describes optically virtually isotropic polycarbonate films and a chill-roll process for their preparation. The films consist of linear or branched polycarbonate having an average molecular weight M _w of 10,000 to 40,000. Inventive films can, for. B. have a shrinkage of <1% / <1% (190 ⁰ C / 30 min machine-direction (MD) / Traverse-direction (TD)). The film according to the invention preferably does not have a deflection of linearly polarized light of greater than 2 angular minutes in any area of the surface. The path difference can z. B. 31 nm, the birefringence delta n 4 x 10 ^-4 . In the tensile test z. B. an elongation at break according to ISO 527-3 MD / TD of 39 and 35% measured. In order to avoid nozzle lines or extrusion strips, it is recommended to use an extrusion die whose inner surface has a roughness depth in the die lip area according to DIN 4768 of 0.025 to 0.002. This can be achieved by chrome plating and polishing. EP 1 285 742 A2 describes films for optical applications in the thickness range below 100 μm with a low phase difference of not more than 10 nm, an "optical axis deviation" of +/- 10 angular minutes and small thickness fluctuations in the range of maximum 2.4 μm per 2 cm in width The films are produced by means of a chill-roll process The favorable material properties are to be achieved in particular by the temperature of the polymer melt after exiting the extrusion die to the contact with the chill-roll roll at at least 30 ^° C. above the glass transition temperature of the plastic For this purpose, the path from the exit from the extrusion nozzle and the contact point on the chill roll can be relatively short, for example in the range of, for example, 30 to 150 The exiting melt film can also be thermally shielded or additionally heated by means of an enclosure Variety of plastics, especially for norbornene plastics.

US Pat. No. 5,476,134 describes chromium nitride-coated extruders for the production of parts from aluminum-iron alloys. These are particularly suitable for reducing the erosion of the extruded parts in the production of aluminum alloys with low iron content below 0.3

%.

EP 351 886 (Bayer AG) describes a casting or extrusion process for producing optically uniaxial, birefringent polycarbonate films, which are heated by means of a quartz heater. This achieves a reduction of the unwanted birefringence to no longer disturbing values.

JP 8336883 describes a process for the extrusion of films of thermoplastic material, wherein an extrusion die is used, at the edges of the exit opening have a radius of 30 μm or less with an unevenness of not more than +/- 20%. The nozzle geometry described counteracts in particular the formation of undesirable deposits.

JP 6335949 describes a process for the extrusion of films of thermoplastic material, preferably z. As polyethersulfones, polyphenylene oxides or polyether ketones, wherein an extrusion die is used, wherein the edges of the outlet opening have a radius of 30 microns or less at a non-uniformity of not more than +/- 20%. The extrusion die can be made of steel or ceramic. Coatings with chromium, nickel, titanium, copper, zinc, etc. can counteract possible interactions of the nozzle material with the extruded plastic materials. The nozzle geometry described counteracts in particular the formation of nozzle lines.

JP 2002-028941 describes a process for producing films of polyvinyl alcohol which can be used as polarizing films. Films with reduced thickness variations can be obtained by using an extrusion die in which the edges of the exit orifice have a radius of 200 μm or less.

JP 2003-267758 describes a process for coating optical fibers with a plastic coating. In this case, an extrusion die is used, in which the edges of the outlet opening have a radius of 10 to 30 microns. The nozzle geometry described counteracts in particular the formation of plastic deposit in the region of the nozzle edge, so that the method now over a longer production period can be operated trouble-free. Another advantage is that the plastic coating has lower thickness variations.

EP 0 547 562 A1 describes a method for coating a non-descript planar web, which is transported deflected via a roller, wherein in the deflection region an extrudate is applied from a slot extrusion nozzle. In order to advantageously influence the reproducibility and accuracy of the method, a distance measurement is installed to the right and left of the extrusion nozzle with a control loop. If the distance between the outlet opening of the extrusion nozzle and the roller deviates from a desired value, the position of the extrusion nozzle is correspondingly corrected by means of a servomotor.

Among others, the vertical birefringence of commercially available, extruded, chill-rolled polycarbonate films and commercial cast polycarbonate films is compared. The extruded films have vertical birefringence values of 0.00029, the cast films values of 0.00066.

EP 1 327 978 (Lintec, Sony) describes a transparent cover film for optical data carriers, which is weather-resistant. The cover film consists of a binder layer of acrylic polymers and the actual protective layer of polyolefins or polycarbonates.

DE 102 0050 204 24 describes a process for producing a thermoplastic film, the film and the use of the film. The film consists of transparent polycarbonates with a thickness of 10 .mu.m to 150 .mu.m and an in-plane birefringence, which causes an optical retardation of at most 25 nm when irradiated vertically, thereby characterized in that the film in any area of the surface, based on a circular area with a diameter of 12 cm, a deflection of a perpendicularly incident light beam of greater than 0.8 angular minutes and a vertical birefringence of at most 0.0004. The film has a thickness tolerance, based on a circular area with a diameter of 12 cm, of not more than +/- 1%.

The "White Paper Blu-Ray Disc", 4th Edition published in November 2005, describes the physical requirements for the Blu-ray ^Disc® . The reflectance of the BD-ROM is set to 35% to 70% for the recording layer of a single layer BD.

Task and solution

A number of application fields for plastic films, in particular in the field of films for use as cover sheets for optical data carriers, in addition to low optical birefringence and in addition to improved surface quality of the films and lower thickness tolerances also increasingly attractive features (optical eye-catcher effects) for Markets such as film industry and video game industry.

EP 1 117 731 B1 and EP 1 285 742 A2 disclose remarkable solutions for the production of films with extremely low birefringence properties in the range of a few nanometers, which meet high requirements in the optical field. According to the teaching of EP 1 117 731 B1, it is possible with the surface properties to produce films which have no deflection of linearly polarized light of greater than 2 angular minutes in any area of the surface. According to EP 1 285 742 A2, thickness tolerances in the range be implemented by about 2.4 microns per 2 cm in width. The European patent applications describe transparent, undyed films, colorations are not described.

It was seen as an object to provide a film of plastic which has an extremely good birefringence properties in the field of EP 1 117 731 B1 or EP 1 285 742 A2 and, secondly, a further improved surface quality and, in particular, even lower thickness tolerances over the entire film range and which moreover can be dyed without impairing the excellent optical properties. The thickness tolerances should in particular meet high requirements for optical data carriers and should therefore refer to a specification within a circular area with a diameter of 12 cm. The use of dyes must under no circumstances impair the good optical properties.

The task is solved by a

A process for producing a film of colored thermoplastic material, wherein the thermoplastic material is melted and conveyed on an extrusion line comprising an extruder, an extrusion die with an outlet opening in slot shape and a tempered roll (chill roll roll) and in the form of a flat Melt web emerges from the outlet opening of the extrusion die, the melt web is applied to the tempered roll (chill-roll roll) and cooled,

characterized in that the tempered roller (chill-roll roller) has a concentricity of +/- 10 microns or less and the mean distance between the outlet opening extrusion die and the tempered roller (chill-roll roller) in the operating state by no more than +/- 25 μm varies over time.

The process of the invention is a colored film of a thermoplastic material having a thickness of 10 .mu.m to 150 .mu.m and an in-plane birefringence, which causes a vertical optical path difference of at most 15 nm when viewed vertically, and a vertical birefringence of at most 0, 0004, manufacturable or obtainable, characterized in that the film in no area of the surface, a deflection of a vertically incident light greater than an angular minute and a thickness tolerance based on a circular area with a diameter of 12 cm of not more than +/- 1%.

An advantage of the film according to the invention is that with it small lot sizes compared to the spin coating process when applying thin, transparent layers are easier to realize on disk.

A further advantage of the film according to the invention is that it is possible to provide a certificate of authenticity and origin for an exclusive coloration with a specific color mixture of the film according to the invention for certain customers. This proof of authenticity can be easily seen by anyone without additional aids for everyone, by measuring the spectrum you can analyze the film at any time more precisely, if circumstances require it. The function of exclusive coloring is comparable to that of a hologram. The advantage of this proof of authenticity is that the colored film extends over the entire data carrier and not like a sticker that the Hologram bears, must be applied in a separate operation. The foil can not be detached from the data carrier without destruction.

Embodiment of the invention

method

Essential to the invention is the use of the chill-roll melt casting process, as has long been known (see, for example, EP 1 117 731 B1 or EP 1 285 742 A2). In this case, a melt film emerging from an extrusion die is applied to a single cooling roll, the chill-roll roll, and cooled. Particularly preferably, the melt film should not or only slightly, not more than a factor of 5 be stretched in the extrusion direction and be exposed to any active cooling before it impinges on the chill-roll roll. This has the advantage that hardly any molecular orientations occur and the resulting film has a high degree of optical isotropy. The chill-roll process differs in particular from the so-called calendering processes, in which the melt film passes through a nip formed by two opposing rolls.

The invention relates to a process for the preparation of the colored film of the invention.

The thermoplastic dyed plastic is melted on an extrusion line with an extruder, a melt pump and an extrusion die with an outlet opening in a slot shape, conveyed and in the form of a flat melt web ejected from the outlet opening of the extrusion die.

The coloring of the thermoplastic material can be done by any conventional method. Preferred is the use of a masterbatch, i. a premix of the plastic to be extruded with the dye to be used, wherein the dye concentration in the master batch is higher than in the finally colored plastic film.

Preferably, a melt filter is provided between the melt pump and the extrusion die, which retains impurities. The mesh size of the filter insert can, for. B. 5 microns to 50 microns, preferably z. B. 10 microns to 30 microns.

The extrusion die can furthermore be provided in the nozzle exit region in a manner known per se with a profile tool. The profile tool is used for fine adjustment of the exiting colored melt profile by a thin-walled designed exit area under pressure of actuators, eg. As bolts, expansion bolts or piezotranslators, is deformed accordingly. Suitable is z. Example, the execution of the nozzle exit area as a flexible lip or as a so-called "superflex lip" (see, for example, EP-A 367 022) or as a membrane (see, Gross et al., Plastics 84 (1994) 10, pp 1352-1358).

The dyed melt web is applied to a single cooled roll, called a chill roll roll, and cooled. The chill roll can be z. B. have a temperature of 100 ⁰ C to 200 ⁰ C, preferably from 100 ° C to 130 ⁰ C. Avoidance of vibration transmission

The advantages of the chill-roll process in the production of a low-oriented colored film contrast with a significant disadvantage that the achievable thickness tolerances both in and transverse to the extrusion direction are significantly worse than in the calendering process. In the calendering process, a small melt supply is formed in the process upstream of the nip. This supply and the pressure in the nip lead to a homogenization of the film thickness in all directions. Due to the principle, the thickness tolerances that are usually achievable in the chill-roll process are much worse.

The invention is based on the finding that vibrations can be transmitted to the extrusion nozzle from the area of the extruder and in particular the melt pump. These vibrations result in varying operating distances between the outlet opening of the extrusion die and the chill-roll roll. The varying distances in turn lead to compressions or elongations of the colored melt web, which in turn leads to an increase in thickness tolerances.

The invention is further based on the finding that the chill-roll roll contributes to its own imbalance at varying distances between the outlet opening of the extrusion die and the chill-roll roll. The varying distances in turn lead to compressions or elongations of the colored melt web, which in turn leads to an increase in thickness tolerances.

It is therefore used or used according to the invention, an extrusion plant, in which the cooled roll (chill-roll roll) a Concentricity of +/- 10 microns or less, preferably of +/- 5 microns or less, and the mean distance between the outlet opening of the extrusion die and the cooled roll (chill-roll roll) in the operating state by not more than + / - 25 microns, preferably by not more than +/- 15 microns, more preferably not changed by more than +/- 10 microns. These measures lead to reduced thickness tolerances and improved surface quality of the resulting colored films.

For the purposes of the invention, suitable temperature-controllable rollers (chill roll) with a concentricity of +/- 10 microns or less, preferably from +/- 5 microns can be manufactured in this accuracy and are available from manufacturers of parts for extrusion equipment. The specified runout accuracy refers to the installed state or to the operating state. The roller must therefore be both accurately manufactured and positioned and centered with high accuracy in the extrusion line.

The average distance or the respective minimum distance between the outlet opening of the extrusion die and the cooled roll can, for. B. be determined by means of optical measuring sensors or by Laserwegemessung practically between any selected measuring points. It does not depend on the distance itself, but on the temporal variation of the distance. Advantageously, the average distance is measured by two temperature-independent distance sensors, which are respectively positioned to the right and left of the outlet opening of the extrusion die, so that they can capture from there, preferably the shortest distance or the shortest distances to tempered roller.

The limitation of the temporal variation or change of the mean distance between the outlet orifice and the tempered Roller (chill-roll roller) in the operating state can be achieved in different ways.

A technical measure may be, the roll mill holding the tempered roll (chill-roll roll), at one or more points z. B. via braces, z. As steel, fixed to the extrusion die, z. B. by screwing or riveting to connect. By this simple measure, the average distance between the outlet opening extrusion nozzle and the cooled roller negative impacting vibrations are already significantly reduced.

A further technical measure may be to connect the roll mill holding the cooled roll (chill-roll roll) to the extrusion die via at least two actuators, the actuators being controlled via a control loop so as to actively change the distance between the exit orifice Counteract the extrusion die and the tempered roll. By this measure, the mean distance between the outlet opening of the extrusion die and the tempered roller negatively influencing vibrations are further reduced further. The actuators, z. B. piezo actuators, z. B. be installed right and left of the tempered roller and connected at points right and left of the outlet opening of the extrusion die with this. If necessary, additional fixed braces can also be attached between the roll mill and the extrusion die.

melt pump

A certain effect, although not in the scope of the measures described above, can additionally be achieved if the extrusion line has a melt pump between the extruder and the extrusion die. The melt pump brings about a leveling of the otherwise fluctuating melt pressure from the extruder into the extrusion nozzle and thus likewise contributes to the reduction of vibration transmissions.

Preferably, an extrusion plant is used in which the melt pump is decoupled from the extrusion die to avoid vibration transmission. The decoupling can be accomplished mechanically, z. B. over flexible, high temperature resistant lines for the colored melt.

A reduction or avoidance of the vibration transmission from the melt pump to the extrusion die has the advantage that dyed films can be obtained with further reduced thickness tolerances and improved surface quality.

Edge radius of the outlet opening of the extrusion die

Another feature that may contribute to low thickness tolerances of the films of the invention in a preferred embodiment, the radius of the edges of the outlet opening of the extrusion die of at most 50 .mu.m, preferably of at most or less than 30 .mu.m, in particular of at most or less than 25 microns. The radii of the edges of the outlet opening of the extrusion nozzle preferably have an unevenness of at most or less +/- 5% over the width of the outlet opening. The comparatively sharp and very uniform edges probably lead to a particularly good detachment of the melt web, which can contribute to the preservation of films with low thickness tolerances. Preferably, the edge or both edges of the outlet opening at an angle of 45 to 100 °, usually of 90 °. The roughness of the inner surface of the die lip area can affect the surface quality of the films produced. The inner surface of the die lip area is the area behind the distribution channel and an optional jam island. Depending on the nature of the extrusion nozzle, the inner surface of the die lip region extends approximately 0.5 cm to 5 cm from the outlet opening into the interior of the extrusion die. The inner surface of the die lip region should preferably have roughness R ₃ to DIN 4768 of 0.01 .mu.m to 0.002 .mu.m or less, R _z of 0.08 .mu.m to 0.015 .mu.m and R _max 0.10 .mu.m to 0.025 .mu.m.

Friction reducing coatings

Preferably, the inner surface of the die lip portion of the extrusion die is provided with a friction reducing coating. This has the advantage that the process reliability, especially in long-term operation is increased. After prolonged operation of the extrusion plant, z. B. after 20 to 60 hours of continuous operation, undesirable deposits can form in the die lip area, which can cause nozzle lines on the film surface. These can be significantly reduced or even avoided altogether if the inner surface of the nozzle lip area of the extrusion nozzle is provided with a friction-reducing coating. In order not to affect the elasticity of the die lip area, the coating should not be too thick. Favorable coatings are having a total thickness in the range of 10 .mu.m to 30 .mu.m, preferably from 15 .mu.m to 25 .mu.m.

The lip region of the nozzle is preferably subdivided into separable elements, thus allowing better accessibility in the processing of the inner surface. The preferred roughness depth range can be achieved by polishing or by coating the inner surface of the die lip area. According to EP 1 117 731 B1, the inner surface of the nozzle lip region z. B. be equipped with a chrome plating, which can be additionally polished.

The coating may preferably consist of Ni, CrN, TiCN, TiC, TiAIN, DLC (diamond-like carbon) or another diamond-like carbon coating. These coatings have the advantage of higher, up to ten times longer service life compared to a chromium coating as described in EP 1 117 731 B1. Corresponding coatings and their application to steel surfaces are known in the art in principle, for. From US 5,476,134 or US 4,637,477.

A suitable method for applying a corresponding coating to the inner surface of the die lip area is z. For example, the "physical vapor deposition" method (PVD method, see, for example, US Pat. No. 5,476,134 or US Pat. No. 4,637,477) The coating can be single-layer or preferably multi-layered In the multilayer coating, the comparatively soft steel or steel alloy Preferably, a hard layer, eg a 10 μm to 20 μm thick layer of nickel, which is then coated with an even harder layer, eg a 2 μm to 5 μm thick layer of TiN, CrN or DLC, is preferably applied to the extrusion die A multilayer coating of the inner surface of the inner nickel layer and a layer of TiN, CrN or DLC coated thereon is particularly advantageous for the extrusion of polycarbonate films, and the inner surface of the extrusion die in the extrusion die lip region can be metallurgically or chemically altered or be doped. The inner surface of the extrusion die in the extrusion die lip region may be provided with a single or multi-layer coating of a fluorine compound.

Heating of the exiting colored melt film

Preferably, the inked melt web is heated on the way between the exit from the extrusion die and the touchdown point on the chill-roll roll. This has the advantage that internal molecular stresses occur only reduced. It is advantageous to heat the dyed melt web so that it at or shortly before the touchdown on the chill roll a temperature of at least 30 ⁰ C, at least 40 ⁰ C, at least 50 ⁰ C, at least 60 ° C or at least Having 80 ° C above the glass transition temperature of the extruded plastic.

By glass temperature is meant in particular the midpoint temperature T _mg according to ISO 11357-2, point 3.3.3. The measurement is carried out without addition of plasticizer, with residual monomer contents (REMO) of less than 100 ppm, at a heating rate of 10 ° C / min and under a nitrogen atmosphere.

Housing / Inertgasatmosphäre

An extrusion line is preferably used or used in which the colored melt web is surrounded by an enclosure between the exit from the extrusion die and the touchdown point on the chill roll roll. On the one hand, this enables effective heating of the colored melt web and at the same time opens up the possibility of the inked melt web on the way between the exit from the extrusion die and the landing point on the chill-roll roll with an inert gas, e.g. As nitrogen, to surround. The latter has the advantage that oxidation processes in the plastic material and in the dye, which can lead to undesired discolorations or turbidity, are reduced or avoided.

The dyed foil

The invention relates to a colored film of a thermoplastic material having a thickness of 10 .mu.m to 150 .mu.m, preferably 20 .mu.m to 120 .mu.m, in particular 30 .mu.m to 100 .mu.m.

In-plane birefringence

The in-plane birefringence of the inked film is calculated from the optical retardation. The optical path difference due to the birefringence of a, with respect to the film surface perpendicular incident light beam z. B. according to the principle of polarization microscopy (polarimeter) can be determined. The methodology is familiar to the person skilled in the art (see, for example, ISO 11455).

The colored film has a birefringence (in-plane birefringence), the vertical transmission a optical retardation of at most 15 nm, preferably at most 5 nm, it can, for. B. 2 nm to 10 nm or 2 nm to 5 nm. Colored films with these values are called optically and mechanically isotropic or nearly isotropic and are suitable for optical applications with high requirements. Vertical birefringence

The colored extruded film according to the invention differs, among other things, from cast films (see, for example, EP 351 886), by a significantly lower vertical birefringence (see, for example, EP 1 202 261 A1). The vertical birefringence of the colored film according to the invention is at most 0.0004, preferably at most 0.0003. A suitable measurement method for determining the vertical birefringence is z. In detail in EP 1 202 261 A1, p. 11, line 44 - p. 12, line 24. In contrast to the in-plane birefringence measurement, the principle is based on a light incidence angle of 45 °.

A low value in the vertical birefringence is particularly advantageous when the colored film according to the invention is used in optical data carriers. The higher the numerical aperture of the laser optics for scanning the data carrier, the greater the proportion of obliquely incident laser radiation. Especially with high numerical aperture optics, the signal-to-noise ratio degrades with increasing vertical birefringence.

surface quality

The colored film does not have a deflection of a vertically incident light beam of greater than in any area of the surface, based on a circular area with a diameter of 12 cm, preferably based on an area of 1 m ² , more preferably based on an area of 10 m ² as an angular minute, preferably not more than 0.5 angular minutes. The measurement is carried out by means of the registration of the deflection angle, which is experienced by a laser beam of about 200 μm diameter, which penetrates the colored foil. For this purpose, the so-called laser deflection method is used. Over the entire extrusion width, the angular deviation is measured by means of a displacement table operated with a stepper motor, which is experienced by a laser beam of about 100 μm in diameter when the colored foil is irradiated vertically. In order to verify the required surface quality of the colored film according to the invention, punched pieces with a circular area with a diameter of 12 cm or sections or sections of the film web of 1 or 10 m ^{2 can be} measured.

thickness tolerance

In particular, the inked film has a thickness tolerance or difference in the thickness of the film, based on a circular area with a diameter of 12 cm, of not more than +/- 1%, preferably not more than +/- 0.5% , The percentage deviation refers to the mean of the maximum and the minimum thickness value within the circular area with a diameter of 12 cm. This specification ensures that the film z. B. for the production of optical data storage with high storage density of z. B. 25 gigabytes (GB) or more is suitable. Based on a 100 μm thick colored film, the thickness deviation from the mean value is accordingly no more than +/- 1 μm within a circular area with a diameter of 12 cm.

The determination of the thickness tolerance can be determined by interferometric layer thickness measurement, which is known to the person skilled in the art. For the interferometric layer thickness measurement z. B. an achromatic measuring head can be used. The layer thickness measurement is based on the superimposition of the light reflected at both boundary surfaces of the colored film. With a known refractive index of the material, the layer thickness can be determined from the spectrum of the reflected light.

plastics

The colored film consists of a thermoplastic, preferably of transparent thermoplastic material. Preferably, the non-colored film has a light transmittance for daylight (standard illuminant D65) T _D65 SZB DIN 5033/5036 in the range of at least 60%, preferably from 65 to 92%.

The colored film can, for. B. from polymethyl methacrylate plastic, impact modified polymethylmethacrylate, polycarbonate plastic, polystyrene plastic, styrene-acrylonitrile plastic, polyethylene terephthalate plastic, glycol-modified polyethylene terephthalate plastic, polyvinyl chloride plastic, polyolefin plastic, cycloolefinic copolymers (COC), P PS plastic or PPSU plastic, acrylonitrile-butadiene-styrene (ABS) plastic or mixtures (blends) of various thermoplastic materials.

The inked film preferably consists of a linear or branched polycarbonate having an average molecular weight Mw (weight average) of from 10,000 to 45,000, preferably from 12,000 to 25,000, particularly preferably from 15,000 to 20,000. The molecular weight M _w (weight average) can be determined, for example, by gel permeation chromatography or by scattered light method (see, for example, BHF Mark et al., Encyclopaedia of Polymer Science and Engineering, 2nd Edition, Vol , 1989).

The dyes

Dyes which can be used are all dyes which are compatible with polycarbonates and can be dispersed very well.

Particular preference is given, for example, to dyes from Clariant (Sandoplast dyes such as Orange 3G, Red PFS, Red Violet R, Blue 2B, Green G) or, for example, equivalent dyes from Ciba.

Particular preference is given to using dyes from Clariant (Sandoplast).

uses

The colored film of the invention may, for. B. for the construction of transparent, colored layers in optical media, as a colored cover of optical media, as a colored cover for scratch protection of optical media, as a colored carrier material for the information layer of optical media or as a colored functional film in liquid crystal displays. Furthermore, the film can be used as proof of authenticity or origin. For this purpose, it is colored individually. EXAMPLES

Process for the preparation of the colored film

Production of a dyed film according to the invention by chill-roll extrusion of a dyed polycarbonate molding composition having an average molecular weight Mw (weight average) of about 20,000 (daltons).

The extrusion plant consists of a single-screw extruder, a melt pump and a slot-type extrusion die with an outlet opening of 680 mm x 0.4 mm. The slot-type extrusion die is designed as a superflex lip (see EP-A 367 022).

The inner surface of the extrusion nozzle in the lip area is polished, so that a roughness Ra of 0.002 μm, Rz of 0.015 μm and Rmax of 0.025 μm is achieved. The inner surface of the extrusion die is provided with a duplex coating of 15 μm nickel and 5 μm CrN.

The radius of the die lip in the exit region is between approximately 100 and 200 μm and has a radius uniformity of +/- 50 μm across the width.

At a distance of 25 mm from the outlet opening of the slot extrusion die, a chill-roll roll is positioned in the center. The roller has a diameter of 400 mm and a width of 700 mm. The roll surface has a roughness Ra <= 0.003 μm, and Rmax <0.25 μm measured according to DIN 4768. The roller has a concentricity <= 3μm. The extrusion die is firmly connected to the roll mill at two points on the right and left of the outlet opening of the extrusion die via steel profile beams with a cross section of 5 cm × 1 cm.

The temperature of the chill-roll roller is set between 100 ⁰ C and 130 ⁰ C, preferably 110 ° C to 120 ⁰ C.

The temperature of the colored melt stream is about 240 ⁰ C. The colored melt film places approximately tangentially to the roll surface and wraps around the roller at approximately 180 ° C.

The distance between the outlet of the colored melt from the nozzle and the contact point to the chill-roll roll is housed, the internal temperature is about 120 ⁰ C. This enclosure can be heated or under a protective gas atmosphere, eg heated and filtered (clean room class 100 ) Nitrogen, be filled.

After wrapping other rolls, the thickness of the inked film web is determined by a traversierend arranged, non-contact measuring system and regulated by means of electronically processed information, the melt distribution of the nozzle by means of a Dehnbolzensystems across the width.

Example 1 Reference samples of polycarbonates without coloring

Examples 2, 3 and 4 were made with Clariant Sandoplast Blue 2B Examples 5 and 6 were made with Clariant Sandoplast Green G Examples 7 and 8 were made with Clariant Sandoplast Red PFS The relevant measured quantities of the dyed films obtained in Examples 1 to 8 are determined by means of punched-out circular colored surface pieces with a diameter of 12 cm and are summarized in the following table.

Claims

claims

1. Colored film of a thermoplastic material with a thickness of 10 to 150 .mu.m as a colored cover sheet in optical data carriers, as a colored cover for scratch protection of optical data carriers or as a colored carrier material for the information layer of optical data carriers,

characterized in that

the film has a coloring and the light transmission (in the wavelength range of 385nm to 425nm) after double penetration of the film thickness between 35% and 90%.

2. Colored foil according to claim 1,

characterized in that

Light transmission (in the wavelength range of 385nm to 425nm) after double penetration of the film thickness between 50% and 90%.

3. Colored foil according to claim 1,

characterized in that

Light transmission (in the wavelength range of 385nm to 425nm) after double penetration of the film thickness between 70% and 90%.

4. Colored foil according to claim 1,

characterized in that

the colored film of an in-plane birefringence, which when viewed vertically causes an optical retardation of at most 25 nm.

5. inked film according to claim 4,

characterized in that

the colored film of an in-plane birefringence, which when viewed vertically causes an optical retardation of at most 15 nm

6. Colored foil according to claim 4,

characterized in that

the colored film of an in-plane birefringence, which when viewed vertically causes an optical retardation of at most 10 nm

7. inked film according to claim 1, characterized in that

the inked film has a thickness tolerance, based on a circular area with a diameter of 12 cm, of not more than +/- 2%.

8. inked film according to claim 1,

characterized in that

the inked film has a thickness tolerance, based on a circular area with a diameter of 12 cm, of not more than +/- 1%.

9. inked film according to claim 1,

characterized in that

the inked film has a thickness tolerance, based on a circular area with a diameter of 12 cm, of not more than +/- 0.5%.

10. inked film according to claim 1,

characterized in that in no area of the surface of the inked film, based on a circular area with a diameter of 12 cm, a deflection of a perpendicularly incident light beam of greater than 0.8 angular minutes and a vertical birefringence of at most 0.0004.

11. inked film according to claim 1,

characterized in that

they are made of polymethyl methacrylate plastic, impact-modified polymethyl methacrylate, polycarbonate plastic, polystyrene plastic, styrene-acrylonitrile plastic, polyethylene terephthalate plastic, glycol-modified polyethylene terephthalate plastic, polyvinyl chloride plastic, polyolefin plastic, cycloolefinic copolymers (COC), PPS - Plastic or PPSU plastic, acrylonitrile-butadiene-styrene (ABS) - plastic or mixtures (blends) of various thermoplastics.

12. inked film according to one or more of claims 1 to 12,

characterized in that

it consists of a linear or branched polycarbonate having an average molecular weight M _w of 10,000 to 45,000.

13. Use of the colored film according to one of the preceding claims as a cover film in optical data carriers.

H.Use of the colored film according to claims 1 to 12 as a cover for scratch protection of optical data carriers.

15. Use of the film dyed according to claims 1 to 12 as a carrier material for the information layer of optical data carriers.

16. Process for producing a colored film,

characterized in that

In a first step, a colored granulate is produced from a dyed masterbatch and the plastic or the plastic mixture and then extruded.

17. A process for the preparation of a colored film of thermoplastic material, wherein the colored thermoplastic on an extrusion line, comprising an extruder, an extrusion die with an outlet opening in slot shape and a tempered roll (chill-roll roll), which is fixed to a roll mill , is melted and conveyed and exits in the form of a flat melt web from the outlet opening of the extrusion die, the melt web is applied to the tempered roll (chill-roll roll) and cooled, characterized in that

the tempered roller (chill-roll roller) has a concentricity of +/- 10 microns or less and the average distance between the outlet opening extrusion die and the tempered roller (chill-roll roller) in the operating state by not more than +/- 25 μm varies over time.

18. The method according to claim 16,

characterized in that

the tempered roller (chill-roll roller) is attached to a roller mill, which is firmly connected to the extrusion die.

19. The method according to claim 16 or 17,

characterized in that

the tempered roller (chill-roll roller) is attached to a roller mill, which is connected to the extrusion nozzle via at least two actuators, wherein the actuators are controlled via a control loop, so that they active distance changes between the outlet opening of the extrusion die and the cooled roller counteract.

20. The method according to one or more of claims 16 to 19,

characterized in that

the edges of the outlet opening of the extrusion nozzle have a radius of at most 50 μm with an unevenness of not more than +/- 5%.

21. The method according to one or more of claims 16 to 21,

characterized in that

the extrusion line between the extruder and the extrusion die has a melt pump.

22. The method according to one or more of claims 16 to 21,

characterized in that

the inner surface of the die lip portion of the extrusion die is provided with a friction reducing coating.

23. The method according to claim 22,

characterized in that the coating consists of a single- or multi-layer, optionally modified coating of Ni, CrN, TiCN, TiC, TiAIN, DLC or a diamond-like carbon coating.

24. The method according to claim 22 or 23,

characterized in that

the inner surface of the extrusion nozzle is metallurgically or chemically altered or doped in the extrusion die lip region.

25. The method according to claim 24,

characterized in that

the inner surface of the extrusion nozzle is provided in the extrusion die lip region with a single or multi-layer coating of a fluorine compound.

26. The method according to one or more of claims 16 to 25,

characterized in that

the inked melt web is heated on the way between the exit from the extrusion die and the touchdown point on the chill roll roll.

27. The method according to one or more of claims 16 to 26,

characterized in that

an extrusion plant is used in which the colored melt web is surrounded by an enclosure between the exit from the extrusion die and the touchdown point on the chill roll roll.

28. The method according to claim 27,

characterized in that

the colored melt web is surrounded on the way between the exit from the extrusion die and the touchdown point on the chill roll roll with an inert gas.

29. The method according to one or more of claims 16 to 29,

characterized in that

the inner surface of the die lip region has roughness R ₃ according to DIN 4768 of 0.01 μm to 0.002 μm or less, R _z of 0.08 μm to 0.015 μm and R _{max of} 0.10 μm to 0.025 μm.

30. data carriers,

characterized in that

it is associated with a film according to any one of the preceding claims.

31. data carriers,

characterized in that

he is associated with a film with an individual coloring.