HK1125700A - Light-scattering moulded body with a high level of light transmission - Google Patents

Description

Light-scattering shaped body with high light transmission

The invention relates to a multilayer solid plate, the base material of which consists of a combination of free-flowing transparent polycarbonate and transparent polymer particles having an optical density different from that of the base material, and optionally also having one or more back-coating layers applied to one or both sides of the solid plate in a coextrusion process.

A key point when using diffuser plates in so-called backlight units (BLUs) for flat panel displays is that the optical density of the system is very high, so that the picture brightness of the flat panel display is as high as possible. The backlight unit (directional light system) basically has a structure as described below. It is generally constituted by a case provided with different numbers of light emitting tubes, so-called CCFLs (cold cathode fluorescent lamps), depending on the size of the backlight unit. A light reflecting surface is provided on the inner face of the housing. A diffuser plate having a thickness of 1 to 3mm, preferably 2mm, is arranged on the illumination system. On the diffuser plate is a set of films that have the following functions: light scattering (scattering films), circular polarizers, focusing light in the forward direction by means of so-called BEF (brightness enhancement film), and linear polarizers. The linear polarizing film is directly under the LCD display screen placed thereon.

Light-scattering translucent products obtained from polycarbonates with different light-scattering additives and shaped parts made therefrom are known from the prior art.

For example, light scattering is disclosed in EP-A634445Injectable composition containing vinyl acrylate-based polymer having a core/shell morphology and incorporating TiO₂The polymer particles of (1).

US2004/0066645 describes the use of light scattering polycarbonate films in flat panel displays. As light-scattering components, mention may be made here of polyacrylates, PMMA, polytetrafluoroethylene, polyalkyltrialkoxysiloxanes and mixtures composed of these components.

JP03078701 describes a light scattering PC board having calcium carbonate and titanium dioxide as scattering pigments and a light transmission of about 40%.

JP05257002 describes an astigmatic PC board with scattering pigments made of silica.

JP10046022 describes PC boards with scattering pigments consisting of polyorganosiloxanes.

JP2004/029091 describes PC scatter plates containing 0.3 to 20% of scattering pigments and 0.0005 to 0.1% of optical brighteners (aufhellers).

However, the molecular weight of the polycarbonates is generally not further defined in these documents.

PC boards containing 0.01 to 1% of crosslinked spherical polyacrylate are described in JP 10046018.

In order to evaluate the suitability of the diffuser plate for so-called backlight units for LCD flat panel displays, special attention must be paid to the brightness (brightness) of the entire system, i.e., the entire BLU, rather than just the diffuser plate itself. The diffuser plates disclosed in the prior art, while having a very high brightness (brightness), have a unsatisfactory color consistency.

In the present invention it has now been found that the viscosity of the polycarbonate base resin used can critically influence the properties of the diffuser plate. The polycarbonate resin having a lower viscosity (low molar mass) when used as a diffuser plate is superior to the polycarbonate resin having a higher viscosity (higher molar mass),surprisingly, significantly higher optical densities were exhibited, and the optical properties of the base resins used in the examples were the same in terms of light transmission of the base resins. It is particularly advantageous here for the polycarbonate resin to have M_wA molar mass of 16000 to 21000g/mol or an MFR of 50 to 80cm³/(10min)(300℃；1.2kg)。

A first subject of the invention is therefore a solid sheet made of a composition comprising:

80 to 99.99% by weight of a molar mass M_w15000 to 21000g/mol, preferably 15000 to 21000 and 18000 excluded and particularly preferably 18100 to 21000, very preferably 18500 to 20000g/mol or an MFR of 50 to 80cm³/(10min) (300 ℃ C.; 1.2kg) of a transparent polycarbonate, and

0.01 to 20% by weight of transparent polymer particles having an optical density different from polycarbonate.

The solid plates according to the invention have a high light transmission while simultaneously having a high light scattering rate and can be used, for example, in the illumination system of flat-panel displays (LCD-screens). Here, it is important that high light transmittance be combined with high light scattering property. The illumination regime of such flat panel displays can be achieved with side light injection (side light regime) or, if the display screen is larger in size and where side light injection is already not satisfactory, via a backlight unit (BLU) where the directional illumination behind the diffuser plate has to be distributed as uniformly as possible through it.

In addition, the (optionally multi-layered) solid panels described herein are also characterized by a high color consistency over a long period of time without a reduction in optical density (brightness) during operation of the flat panel display.

Another subject of the invention is the use of the solid plate according to the invention as a diffuser plate for flat panel displays, in particular for backlighting LCD displays.

Suitable polycarbonates for the preparation of the solid sheets according to the invention are all known polycarbonates. They are homopolycarbonates, copolycarbonates and thermoplastic polyester carbonates.

Average molecular weight M of suitable polycarbonates_wFrom 15000 to 21000, which are calculated by measuring the relative solution viscosity in methylene chloride or in a mixture of equal weights of phenol/o-dichlorobenzene and calibrating by light scattering. The average molecular weight is preferably from 15000 to 21000 and excludes 18000, particularly preferably from 18100 to 21000 and very particularly preferably from 18500 to 20000.

For the preparation of Polycarbonates, reference may be made, for example, to "Schnell, Chemistry and Physics of Polycarbonates, Polymer Reviews, volume 9, Interscience Publishers, New York, London, Sydney 1964" and to "D.C. PREVORSEK, B.T. DEBONA and Y.KESTEN, Corporation Research Center, Allied Chemical Corporation, Moristown, New Jersey 07960, Polymer Science journal, the" Synthesis of Polymer Science in the Chemical edition of Polymer, volume 19, volume 75-90(1980) ", and to" D.G., U.G., P.R.M. Lever, N.Noutverne, AG, Encyclopedia of cellulose, cell Corporation, and filtration of molecular dynamics, U.G., Grigo, P.R.M. Hold, cell Corporation, cell dynamics, cell pages 11, Polymer Science, cell dynamics, cell pages 21, cell pages 11, cell pages 21, cell industries, cell 2, cell industries, cell 2, cell industries, cell 2, cell industries, cell 2, cell industries.

The polycarbonates are preferably prepared according to the phase interface process or the melt transesterification process and are described below, for example, in the phase interface process.

The compounds preferably used as starting compounds are bisphenols of the general formula

HO-Z-OH

Wherein

Z represents a divalent organic group having 6 to 30 carbon atoms and which contains one or more aromatic groups.

Examples of such compounds are bisphenols, including dihydroxybiphenyl, bis (hydroxyphenyl) alkanes, indane bisphenols, bis (hydroxyphenyl) ethers, bis (hydroxyphenyl) sulfones, bis (hydroxyphenyl) ketones, and α, α' -bis (hydroxyphenyl) -diisopropylbenzenes.

Particularly preferred diphenols belonging to the aforementioned group of compounds are bisphenol A, tetraalkylbisphenol A, 4- (M-phenylenediisopropyl) diphenol (bisphenol M), 4- (p-phenylenediisopropyl) diphenol, 1-bis- (4-hydroxyphenyl) -3, 3, 5-trimethylcyclohexane (bisphenol TMC) and mixtures thereof.

The bisphenol compounds used according to the invention are preferably reacted with carbonic acid compounds, in particular phosgene, or diphenyl carbonate or dimethyl carbonate in the melt transesterification process.

Polyestercarbonates are preferably obtained by reacting the above-mentioned bisphenols, at least one aromatic dicarboxylic acid and optionally carbonic acid equivalents. Suitable aromatic dicarboxylic acids are, for example, phthalic acid, terephthalic acid, isophthalic acid, 3 '-or 4, 4' -diphenyldicarboxylic acid and benzophenonedicarboxylic acids. In part, not more than 80 Mol%, preferably from 20 to 50 Mol%, of the carbonate groups in the polycarbonate may be replaced by aromatic dicarboxylic acid ester groups.

Inert organic solvents used in the interfacial polymerization are, for example, dichloromethane, the various dichloroethanes and chloropropane compounds, tetrachloromethane, trichloromethane, chlorobenzene and chlorotoluene, preference being given to using chlorobenzene or dichloromethane or mixtures of dichloromethane and chlorobenzene.

The phase interface reaction can be promoted by catalysts such as tertiary amines, in particular N-alkylpiperidines or onium salts. Tributylamine, triethylamine and N-ethylpiperidine are preferably used. In the case of the melt transesterification process, preference is given to using those catalysts which are mentioned in DE-A4238123.

The polycarbonates can be branched consciously and controllably by using small amounts of branching agents. Some suitable branching agents are: phloroglucinol, 4, 6-dimethyl-2, 4, 6-tris- (4-hydroxyphenyl) -hepten-2; 4, 6-dimethyl-2, 4, 6-tris- (4-hydroxyphenyl) -heptane; 1, 3, 5-tris- (4-hydroxyphenyl) -benzene; 1, 1, 1-tris- (4-hydroxyphenyl) -ethane; tris- (4-hydroxyphenyl) -phenylmethane; 2, 2-bis- [4, 4-bis- (4-hydroxyphenyl) -cyclohexyl ] -propane; 2, 4-bis- (4-hydroxyphenyl-isopropyl) -phenol; 2, 6-bis- (2-hydroxy-5' -methyl-benzyl) -4-methylphenol; 2- (4-hydroxyphenyl) -2- (2, 4-dihydroxyphenyl) -propane; hexa- (4- (4-hydroxyphenyl-isopropyl) -phenyl) -ortho-phthalate; tetrakis- (4-hydroxyphenyl) -methane; tetrakis- (4- (4-hydroxyphenyl-isopropyl) -phenoxy) -methane; α, α', α "-tris- (4-hydroxyphenyl) -1, 3, 5-triisopropylbenzene; 2, 4-dihydroxybenzoic acid; trimesic acid; cyanuric chloride; 3, 3-bis- (3-methyl-4-hydroxyphenyl) -2-oxo-2, 3-indoline; 1, 4-bis- (4 ', 4' -dihydroxytriphenyl) -methyl) -benzene and is particularly preferably: 1, 1, 1-tris- (4-hydroxyphenyl) -ethane and bis- (3-methyl-4-hydroxyphenyl) -2-oxo-2, 3-indoline.

Optionally, 0.05 to 2 Mol%, based on the diphenols used, of branching agents or branching agent mixtures used together may be used in combination with the diphenols, but may also be added in a subsequent synthesis stage.

As chain terminators there are preferably used phenols, such as phenol, alkylphenols, such as cresol and 4-tert-butylphenol, chlorophenol, bromophenol, cumylphenol or mixtures thereof, in amounts of 1 to 20 Mol%, preferably 2 to 10 Mol%, per Mol of bisphenol. Preference is given to phenol, 4-tert-butylphenol or cumylphenol.

Chain terminators and branching agents may be added separately or together with the bisphenols in the synthesis.

The preparation of polycarbonates according to the melt transesterification process is described, for example, in DE-A4238123.

Preferred polycarbonates according to the invention are homopolycarbonates based on bisphenol A, homopolycarbonates based on 1, 1-bis- (4-hydroxyphenyl) -3, 3, 5-trimethylcyclohexane and copolycarbonates based on the two monomers bisphenol A and 4, 4' -dihydroxybiphenyl (DOD).

Particular preference is given to homopolycarbonates based on bisphenol A.

Suitable transparent polymer particles having an optical density different from polycarbonate are, for example, those based on acrylates having a core-shell morphology, preferably those disclosed in EP-A634445.

These polymer particles have a core composed of a rubber-based vinyl polymer. The rubbery vinyl polymer may be a homopolymer or copolymer of any of the monomers described hereinafter, i.e., monomers having at least one ethylenically unsaturated group and which are subjected to addition polymerization under aqueous emulsion polymerization conditions well known to those skilled in the art. These monomers are listed in column 3, lines 40-62 of US 4226752.

The rubbery vinyl polymer contains preferably at least 15%, more preferably at least 25%, most preferably at least 40% of polymerized acrylate, methacrylate, monovinylarene or optionally substituted butadiene and from 0 to 85%, more preferably from 0 to 75%, most preferably from 0 to 60% of one or more copolymerized vinyl monomers, based on the total weight of the rubbery vinyl polymer.

Preferred acrylates and methacrylates are alkyl acrylates or methacrylates having preferably from 1 to 18, particularly preferably from 1 to 8, most preferably from 2 to 8, carbon atoms in the alkyl radical, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl or tert-butyl or hexyl, heptyl or octyl. The alkyl group may be branched or straight chain. Preferred alkyl acrylates are ethyl acrylate, n-butyl acrylate, isobutyl acrylate or 2-ethylhexyl acrylate. The most preferred alkyl acrylate is butyl acrylate.

Other suitable acrylates are, for example, 1, 6-hexanediol diacrylate, ethylthioethyl methacrylate, isobornyl acrylate, 2-hydroxyethyl acrylate, 2-phenoxyethyl acrylate, glycidyl acrylate, neopentyl glycol diacrylate, 2-ethoxyethyl acrylate, tert-butylaminoethyl methacrylate, 2-methoxyethyl acrylate, glycidyl methacrylate or benzyl methacrylate.

Preferred monovinylarenes are styrene or alpha-methylstyrene and are optionally substituted on the aromatic ring with alkyl groups such as methyl, ethyl or tert-butyl or with halogens, such as chlorostyrene.

If substituted, it is preferred that the butadiene is substituted with one or more alkyl groups containing from 1 to 6 carbon atoms, or with one or more halogens, most preferably with one or more methyl groups and/or one or more chlorine atoms. Preferred butadienes are 1, 3-butadiene, isoprene, chlorobutadiene or 2, 3-dimethyl-1, 3-butadiene.

The rubbery vinyl polymer may contain one or more (co) polymerized acrylates, methacrylates, monovinylarenes, and/or optionally substituted butadienes. These monomers may be copolymerized with one or more other copolymerizable vinyl polymers, such as diacetone acrylamide, vinyl naphthalene, 4-vinyl benzyl alcohol, vinyl benzoate, vinyl propionate, vinyl hexanoate, vinyl chloride, vinyl oleate, dimethyl maleate, maleic anhydride, dimethyl fumarate, vinyl sulfonic acid, vinyl sulfonamide, methyl vinyl sulfonate, N-vinyl pyrrolidone, vinyl pyridine, divinyl benzene, vinyl acetate, vinyl versatate, acrylic acid, methacrylic acid, N-methyl acrylamide, acrylonitrile, methacrylonitrile, acrylamide, or N- (isobutoxymethyl) -acrylamide.

One or more of the aforementioned monomers are optionally reacted with 0 to 10%, preferably with 0 to 5%, of a copolymerizable multifunctional crosslinking agent and/or with 0 to 10%, preferably 0 to 5%, of a copolymerizable multifunctional graft crosslinking agent, relative to the total weight of the core. If a crosslinking monomer is used, it is preferred to use a content of 0.05 to 5%, more preferably 0.1 to 1%, relative to the total weight of the core monomers. Crosslinking monomers are widely known in the art and generally have a degree of unsaturation similar to polyethylene, where the ethylenically (ethyleneartig) unsaturated groups have a reactivity similar to those of the latter, such as divinylbenzene, trivinylbenzene, 1, 3-or-1, 4-triol acrylate-or methacrylate, diol di-or trimethacrylate-or acrylate, such as ethylene glycol dimethacrylate or diacrylate, propylene glycol dimethacrylate or diacrylate, 1, 3-or 1, 4-butanediol dimethacrylate or, most preferably, 1, 3-or 1, 4-butanediol diacrylate. If graft-crosslinking monomers are used, they are preferably used in a content of 0.1 to 5%, more preferably 0.5 to 2.5%, relative to the total weight of the core monomers. Graft-crosslinking monomers are widely known in the art and are generally polyethylenically unsaturated monomers having sufficiently low reactivity of the unsaturated groups to enable significant amounts of unsaturation to remain in the core in subsequent polymerization reactions. Preferred graft crosslinkers are the copolymerizable allyl-, methallyl-or crotyl-esters of alpha, beta-ethylenically unsaturated carboxylic or dicarboxylic acids, such as allyl methacrylate, allyl acrylate, diallyl maleate and allyl acryloxypropionate esters, with allyl methacrylate being most preferred.

The polymer particles most preferably contain a core derived from a rubbery alkyl acrylate polymer having an alkyl group of 2 to 8 carbon atoms optionally copolymerized with 0 to 5% of a crosslinking agent and 0 to 5% of a graft crosslinking agent, relative to the total weight of the core. The rubbery alkyl acrylate is preferably copolymerized with up to 50% of one or more copolymerizable vinyl monomers as previously described. Suitable crosslinking and graft-crosslinking monomers are well known to the person skilled in the art and are preferably those described in EP-A0269324.

The core of the polymer particles may contain residual oligomeric material used in the polymerization process to swell the polymer particles, but such oligomeric material also has sufficient molecular weight to inhibit diffusion thereof or to inhibit extraction upon processing or wetting.

The polymer particles contain one or more shells. The shell or shells are preferably made from vinyl homopolymers or copolymers. Suitable monomers for preparing one or more shells are listed in column 4, lines 20-46 of US patent 4226752, which is incorporated herein. The shell or shells are preferably polymers from the group consisting of methacrylates, acrylates, vinylaromatics, vinyl carboxylates, acrylic acid and/or methacrylic acid.

Preferred acrylates and methacrylates are alkyl acrylates or methacrylates having preferably 1 to 18, more preferably 1 to 8, most preferably 2 to 8 carbon atoms in the alkyl group, such as methyl, ethyl, n-propyl, isopropyl, n-, sec-or tert-butyl, 2-ethylhexyl or hexyl, heptyl or octyl. The alkyl group may be branched or straight chain. The preferred alkyl acrylate is ethyl acrylate. Other useful acrylates and methacrylates are those described above for the core, preferably 3-hydroxypropyl methacrylate. The most preferred alkyl methacrylate is methyl methacrylate.

Preferred vinyl aromatic hydrocarbons are styrene or alpha-methylstyrene and are optionally substituted on the aromatic ring by an alkyl group, for example methyl, ethyl or tert-butyl, or by a halogen, such as chlorostyrene.

The preferred vinyl carboxylate is vinyl acetate.

The shell or shells contain preferably at least 15%, more preferably at least 25%, most preferably at least 40% polymerized methacrylate, acrylate or monovinylarene and from 0 to 85%, more preferably from 0 to 75%, most preferably from 0 to 60% of one or more vinyl monomers, such as other alkyl methacrylates, aryl methacrylates, alkyl acrylates, aryl acrylates, alkyl and aryl acrylamides, acrylonitrile, methacrylonitrile, maleimide and/or alkyl and aryl acrylates and methacrylates, and which are substituted with one or more substituents, such as halogen, alkoxy, alkylthio, cyanoalkyl or amino.

Examples of suitable vinyl comonomers are as described above. Two or more monomers may be copolymerized.

The shell polymer may contain a crosslinking agent and/or graft crosslinking agent of the kind previously described in the context of the core polymer.

The shell polymer preferably constitutes from 5 to 40%, more preferably from 15 to 35% by weight of the total particle.

The polymer particles contain at least 15%, preferably 20 to 80%, more preferably 25 to 60%, most preferably 30 to 50% polymerized alkyl esters of acrylic or methacrylic acid, based on the total weight of the polymer. Preferred alkyl acrylates and methacrylates are as previously described. The alkyl acrylate or methacrylate component may be present in the core and/or one or more shells of the polymer particle. Homopolymers of alkyl acrylates or methacrylates in the core and/or one or more shells may be used, but it is preferred to copolymerize the alkyl (meth) acrylates with one or more other types of alkyl (meth) acrylates and/or one or more other vinyl polymers, the preferred materials listed above. Most preferably, the polymer particles comprise a core comprised of poly (butyl acrylate) and one or more shells comprised of poly (methyl methacrylate).

The polymer particles are used to impart light scattering properties to the polycarbonate. The refractive index n of the core and the shell of the polymer particles is preferably within +/-0.25 units, more preferably within +/-0.18 units, most preferably within +/-0.12 units of the refractive index of the polycarbonate. The refractive index n of the core and the shell or shells is preferably no closer than +/-0.003 units, more preferably no closer than +/-0.01 units, most preferably no closer than +/-0.05 units of the refractive index of the polycarbonate. The refractive index is determined according to ASTM D542-50 and/or DIN 53400.

Typically, the polymer particles have an average particle diameter of at least 0.5 microns, preferably at least 2 microns, more preferably from 2 to 50 microns, most preferably from 2 to 15 microns. By "average particle diameter" is understood a number average. Preferably at least 90%, most preferably at least 95% of the polymer particles have a diameter of more than 2 microns. The polymer particles are preferably free-flowing powders.

The polymer particles can be prepared in a known manner. Typically, at least one of the monomer components of the core polymer is subjected to an emulsion polymerization reaction to form emulsion polymer particles. The emulsion polymer particles are swollen with the same or one or more other monomer components of the core polymer and one or more monomers are polymerized within the emulsion polymer particles. The swelling and polymerization stages are repeated until the particles grow to the desired particle size. The core polymer particles are suspended in a second aqueous monomer emulsion and the polymer shell is polymerized from the monomers on the polymer particles in the second emulsion. The shell or shells may be polymerized on the core polymer. The preparation of core/shell polymer particles is described in EP-A0269324 and in U.S. Pat. Nos. 3793402 and 3808180.

It has also surprisingly been found that brightness can be further improved by using smaller amounts of optical brighteners.

As optical brighteners the following types of compounds can be used:

a) a bis-benzoxazole having the structure:

wherein R is¹，R²，R⁵And R⁶Independently of one another, represents H, alkyl, aryl, heteroaryl or halogen and X may represent the following groups:

stilbene, which is:

thiophene:

naphthalene:

and R is¹And R²Independently of one another, H, alkyl, aryl, heteroaryl or halogen.

For example Ciba having the formulaOf a companyOB

Or Hostalux KCB of Clariant GmbH having the formula

b) A phenylcoumarin having the structure:

c) wherein R is¹And R²May independently represent H, alkyl, aryl, heteroaryl or halogen.

For example of the formula Clariant GmbHEGM：

d) Bis-styryl-biphenyl having the structure:

wherein R is¹And R²May independently represent H, alkyl, aryl, heteroaryl or halogen.

A preferred embodiment of the present invention is therefore a solid panel according to the present invention which additionally contains from 0.001 to 0.2% by weight, preferably about 1000ppm, of an optical brightener from the group of bisbenzoxazoles, phenylcoumarins or bis-styrylbiphenyls. A particularly preferred optical brightener is CibaUvitex OB of Inc.

The solid sheets of the invention can be made by casting or by extrusion. In the case of large-area solid plates, the production process by casting is very uneconomical for technical reasons. In this case extrusion is preferred. For extrusion, the polycarbonate pellets are introduced into an extruder and melted in the plasticizing system of the extruder. The plastic melt is pressed and deformed by a wide slot nozzle, made into the desired final shape in the nip of a calender and set by alternating side cooling and ambient air on smooth rolls. Polycarbonates with high melt viscosities for extrusion are generally processed at melt temperatures of 230 to 320 ℃ and the barrel temperature of the plasticizing cylinder and the nozzle temperature are correspondingly adjusted.

The solid sheets of the invention may also have one or more layers produced by coextrusion (coextruded layers). By using one or more auxiliary extruders (Seitenextruder) and using suitable melt adapters before the wide-slot nozzle, polycarbonate melts of various compositions can be superimposed and thus multilayer solid sheets can be produced (see, for example, EP-A0110221 and EP-A0110238).

The base layer and optionally the coextruded layer or layers of the solid sheet according to the invention may also contain additives such as UV absorbers and other conventional processing aids, in particular mould release agents and flow aids and stabilizers generally used for polycarbonates, in particular heat stabilizers and antistatic agents, optical brighteners. Different additives or additive concentrations may be present in each layer. In particular, the co-extruded layer may contain a UV absorber and a release agent.

In a preferred embodiment, the composition of the solid sheet also contains 0 to 0.5% by weight of a UV absorber of the benzotriazole derivative, dimeric benzotriazole derivative, triazine derivative, dimeric triazine derivative, diaryl cyanoacrylate type.

The UV-protective layer preferably consists of at least one coextruded layer which has at least one UV absorber and is present in an amount of from 0.1 to 20% by weight, based on the coextruded layer.

The solid sheets according to the invention preferably have a thickness of 0.1 to 4.0mm, particularly preferably 1.0 to 2.0mm, in particular about 2 mm.

The optionally present coextruded layers preferably have a thickness of from 10 to 100 μm, particularly preferably from 20 to 60 μm.

Suitable stabilizers are, for example, phosphines, phosphites or Si-containing stabilizers and other compounds described in EP-A0500496. Examples are triphenyl phosphite, diphenylalkyl phosphite, phenyldialkyl phosphite, tris- (nonylphenyl) phosphite, tetrakis- (2, 4-di-tert. -butylphenyl) -4, 4' -biphenylene-diphosphonite, bis (2, 4-dicumylphenyl) pentaerythritol diphosphite and triaryl phosphite. Particular preference is given to triphenylphosphine and tris- (2, 4-di-tert. -butylphenyl) phosphite.

Suitable mould release agents are, for example, esters or partial esters of monohydric to hexahydric alcohols, in particular glycerol, pentaerythritol or guerbet alcohols.

Monohydric alcohols are, for example, stearyl alcohol, palmityl alcohol and guerbet alcohols, dihydric alcohols are, for example, ethylene glycol, trihydric alcohols are, for example, glycerol, tetrahydric alcohols are, for example, pentaerythritol and mesoerythritol, pentahydric alcohols are, for example, arabitol, ribitol and xylitol, and hexahydric alcohols are, for example, mannitol, sorbitol and dulcitol.

The esters are preferably monoesters, diesters, triesters, tetraesters, pentaesters and hexaesters or mixtures thereof, in particular from saturated aliphatic C₁₀To C₃₆And optionally hydroxy-monocarboxylic acids, more preferably from saturated aliphatic C₁₄To C₃₂And optionally a hydroxy-monocarboxylic acid.

Commercially available fatty acid esters, in particular pentaerythritol and glycerol, may contain < 60% of different partial esters due to the preparation conditions.

Saturated aliphatic monocarboxylic acids having 10 to 36C atoms are, for example, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, hydroxystearic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid and montanic acid.

Preferred saturated aliphatic monocarboxylic acids having 14 to 22C atoms are, for example, myristic acid, palmitic acid, stearic acid, hydroxystearic acid, arachidic acid and behenic acid.

Particularly preferred are saturated aliphatic monocarboxylic acids such as palmitic acid, stearic acid and hydroxystearic acid.

Saturated aliphatic C₁₀To C₃₆The carboxylic acids and fatty acid esters are known per se from the literature or can be prepared according to methods disclosed in the literature. Examples of pentaerythritol fatty acid esters are particularly preferred esters of the aforementioned monocarboxylic acids.

Especially preferred are esters of pentaerythritol and glycerol with stearic acid and palmitic acid.

Also particularly preferred are esters of Guerbet alcohol and glycerol with stearic and palmitic acid and optionally hydroxystearic acid.

Examples of suitable antistatic agents are cationic active compounds, for example quaternary ammonium salts, onium salts or sulfonium salts, anionic active compounds, for example alkylsulfonates, alkylsulfates, alkylphosphates, carboxylates in the form of alkali metal or alkaline earth metal salts, nonionic compounds, for example polyethylene glycol esters, polyethylene glycol ethers, fatty acid esters, ethoxylated aliphatic amines. Preferred antistatic agents are nonionic compounds.

Suitable UV absorbers are, for example

a) Benzotriazole derivatives having the following formula (I):

in formula (I), R and X are the same or different and represent H or an alkyl or alkylaryl group.

Preferred is Tinuvin 329, where X ═ 1, 1, 3, 3-tetramethylbutyl and R ═ H

Tinuvin 350, wherein X ═ tert-butyl and R ═ 2-butyl

Tinuvin 234, wherein X ═ R ═ 1, 1-dimethyl-1-phenyl

b) A dimeric benzotriazole derivative having the following formula (II):

in the formula (II), R¹And R²Identical or different and denotes H, halogen, C₁-C₁₀Alkyl radical, C₅-C₁₀-cycloalkyl, C₇-C₁₃-aralkyl group, C₆-C₁₄-aryl, -OR⁵Or- (CO) -O-R⁵And R is⁵H or C₁-C₄-an alkyl group.

In the formula (II), R³And R⁴Are identical or different and are denoted H, C₁-C₄Alkyl radical, C₅-C₆-cycloalkyl, benzyl or C₆-C₁₄-an aryl group.

In formula (II), m represents 1, 2 or 3 and n is 1, 2, 3 or 4.

Preferred is Tinuvin 360 wherein R¹＝R³＝R⁴＝H；n＝4；R²1, 1, 3, 3-tetramethylbutyl; m is 1

b1) Dimeric benzotriazole derivatives having the formula (III):

wherein the bridge bond represents

R¹，R²M and n have the meanings indicated in formula (II),

and wherein p is an integer of 0 to 3,

q is an integer of 1 to 10,

y is equal to-CH₂-CH₂-，-(CH₂)₃-，-(CH₂)₄-，-(CH₂)₅-，-(CH₂)₆-, or CH (CH)₃)-CH₂-and

R³and R⁴Have the meaning indicated in formula (II).

Preferred Tinuvin 840 and R¹＝H；n＝4；R²Tert-butyl; m is 1; r²Placed in ortho position to the OH group; r³＝R⁴＝H；p＝2；Y＝-(CH₂)₅-；q＝1

c) Triazine derivatives having the formula (IV):

wherein R in formula (IV)¹，R²，R³，R⁴Identical or different and denotes H or aryl or alkyl or CN or halogen and X is equal to alkyl.

Preferred are Tinuvin 1577 and R¹＝R²＝R³＝R⁴H; x is hexyl and

cyasorb UV-1164 and R¹＝R²＝R³＝R⁴Methyl group; x ═ octyl

d) Triazine derivatives having the following formula (IVa)

Wherein

R¹Is represented by C₁-alkyl to C₁₇-an alkyl group,

R²represents H or C₁-alkyl to C₄-alkyl, and

n represents 0 to 20.

e) Dimeric triazine derivatives having the formula (V):

wherein

R in the formula (V)¹，R²，R³，R⁴，R⁵，R⁶，R⁷，R⁸May be the same or different and represents H or alkyl or CN or halogen and

x is equal to alkyl or- (CH)₂CH₂-O-)n-C(＝O)-。

f) A diaryl cyanoacrylate having the following formula (VI):

wherein R is¹To R⁴⁰May be the same or different and represents H, alkyl, CN or halogen.

Preferred is Uvinul 3030 and R¹To R⁴⁰＝H

The abovementioned UV absorbers are generally known to the skilled worker and are partly commercially available or can be prepared according to known methods.

The following examples are intended to illustrate the invention without limiting it.

Examples

Solid 2mm plates as described in examples 1 to 6 were prepared as follows:

1. the compounds were prepared using a conventional twin-screw compounding extruder (e.g., ZSK 32) at temperatures of 250 to 330 ℃ which are conventional for polycarbonates.

2. The machinery and equipment used for the preparation of the optionally co-extruded 2mm solid sheets comprises:

main extruder with degassing, with screw length 33D (diameter) and diameter 70mm

Co-extruder with a screw length of 25D and a diameter of 35mm for applying the coating

Special coextrusion wide slot nozzle with a width of 450mm

Calender

-roller table

-extraction device

Length control device (cutting)

-a stockpiling table

The polycarbonate pellets of the base material were introduced into the feed hopper of the main extruder. The individual materials are melted and conveyed within the plasticizing system barrel/screw. Other devices play a role in transporting, fixing the length and placing the extruded sheet.

For the examples to be described next, the following types of polycarbonates were used:

from Bayer MaterialScience3100(Mw about 32000, light transmission 89.8% at 4mm according to DIN 5036-1, yellowness index 1.94 according to ASTM E313).

From Bayer MaterialScience2800(Mw about 29000, light transmission 89.8% at 4mm according to DIN 5036-1, yellowness index 1.65 according to ASTM E313).

Makrolon CD from Bayer MaterialScience(Mw about 19000, light transmittance of 89.9% at 4mm according to DIN 5036-1, yellowness index of 1.19 according to ASTM E313)

Example 1

A compound having the following composition was prepared:

polycarbonate Makrolon 3100, content 97.5% by weight

Core-shell particles having a butadiene/styrene core and a shell of methyl methacrylate, Paraloid EXL 5137 from Rohm & Haas, having a particle size of from 2 to 15 μm and an average particle size of 8 μm and a content of 2.4% by weight.

Thermal stabilizers: triphenylphosphine, content 0.1% by weight.

A2 mm solid sheet without coextruded layers was extruded from the compound.

Example 2

A compound having the following composition was prepared:

makrolon 3100, 96.9%

Core-shell particles having a butadiene/styrene core and a shell of methyl methacrylate, Paraloid EXL 5137 from Rohm & Haas, having a particle size of from 2 to 15 μm and an average particle size of 8 μm and a content of 3.0% by weight.

Thermal stabilizers: triphenylphosphine and contained in an amount of 0.1 wt.%.

A2 mm solid sheet without coextruded layers was extruded from the compound.

Example 3

A compound having the following composition was prepared:

polycarbonate Makrolon 2800 in an amount of 97.5% by weight

Core-shell particles having a butadiene/styrene core and a shell of methyl methacrylate, Paraloid EXL 5137 from Rohm & Haas, having a particle size of from 2 to 15 μm and an average particle size of 8 μm and a content of 2.4% by weight.

Thermal stabilizers: triphenylphosphine and contained in an amount of 0.1 wt.%.

A2 mm solid sheet without coextruded layers was extruded from the compound.

Example 4

A compound having the following composition was prepared:

the polycarbonate Makrolon 3100 content was 96.9% by weight

Core-shell particles having a butadiene/styrene core and a shell of methyl methacrylate, Paraloid EXL 5137 from Rohm & Haas, having a particle size of from 2 to 15 μm and an average particle size of 8 μm and a content of 3.0% by weight.

Thermal stabilizers: triphenylphosphine and contained in an amount of 0.1 wt.%.

A2 mm solid sheet without coextruded layers was extruded from the compound.

Example 5 (according to the invention)

A compound having the following composition was prepared:

polycarbonate Makrolon CD2005, content 97.5% by weight

Core-shell particles having a butadiene/styrene core and a shell of methyl methacrylate, Paraloid EXL 5137 from Rohm & Haas, having a particle size of from 2 to 15 μm and an average particle size of 8 μm and a content of 2.4% by weight.

Thermal stabilizers: triphenylphosphine and contained in an amount of 0.1 wt.%.

A2 mm solid sheet without coextruded layers was extruded from the compound.

Example 6 (according to the invention)

A compound having the following composition was prepared:

polycarbonate Makrolon CD2005, content 96.9% by weight

Core-shell particles having a butadiene/styrene core and a shell of methyl methacrylate, Paraloid EXL 5137 from Rohm & Haas, having a particle size of from 2 to 15 μm and an average particle size of 8 μm and a content of 3.0% by weight.

Thermal stabilizers: triphenylphosphine and contained in an amount of 0.1 wt.%.

A2 mm solid sheet without coextruded layers was extruded from the compound.

The optical properties of the 2mm solid plates described in examples 1 to 6 were measured according to the following criteria and using the following measuring instrument:

to determine the light transmission (Ty (D6510 ℃)) and light reflection (Ry (D6510 ℃) on a white background, an Ultra Scan XE from Hunter Associates Laboratory, Inc. was used. In addition, measurements were carried out with the apparatus to determine the yellowness values (yellowness index YI (D65, C2 ℃), ASTME313), the x, y color values (D65, C2 ℃, CIE-standard color palette) and the L, a, b color values (D65, C2 ℃, CIELAB-color system, DIN 6174). Hazegard Plus from Byk-Gardner was used for determining the haze (according to ASTM D1003).

Optical density measurements (Luminance measurements) were carried out on a backlight unit (BLU) of the DS LCD company (LTA170WP, 17 "LCD TV Panel) using the luminescence Meter LS100 of Minolta. For this purpose, the diffuser plate of the batch product was removed and replaced by the 2mm solid plate produced in examples 1 to 6, respectively. The BLU contained four membranes and was constructed in the following order: light source-diffuser plate-film (circular polarizer, diffuser film, prism film/BEF, linear polarizer) -LCD-display.

The measurement results are shown in table 1 below.

Table 1:optical data for 2mm solid plate

	Example 1	Example 2	Example 3	Example 4	Example 5	Example 6
							Ty[％](C2°)HunterUltra Scan	56.39	56.21	58.38	55.10	58.94	59.04

Ry[％](C2°)HunterUltra Scan	82.75	85.06	85.77	85.55	80.83	79.47
							YI(C2°)	-13.24	-5.72	-16.66	-7.46	-0.55	-9.70
L*(C2°)	79.84	79.73	80.95	79.10	81.26	81.31
							a*(C2°)	-1.11	-1.71	-0.74	-1.42	0.78	-1.25
b*(C2°)	-5.29	-1.85	-6.93	-2.69	-0.56	-3.81
							Haze [% ]]	100	100	100	100	100	100
Luminance [ cd/m2]Without film	5550	5550	5600	5500	5550	5550
							Luminance [ cd/m2]With a membrane	5700	5800	6000	5800	6700	6750

In examples 1 to 6, sheets made of base resins having the same additive composition but different viscosities were described, and they showed that their properties significantly depend on the viscosity of the base resin when used as a diffuser sheet for a backlight unit.

The optical properties or light transmission measured in accordance with DIN 5036-1 at 4mm are all equal to Ty 89.8 to 89.9% for the three polycarbonate viscosities used. For example, in both examples 1 and 2, polycarbonate of higher molar mass (Makrolon 3100) was used, while the scattering additive components were 2.4 and 3.0% by weight. It is clear here that the key value of the brightness is not dependent on the amount of scattering additive. The optical density in the forward direction is increased by the cover film system (see table 1, last and penultimate rows). The difference between examples 1 and 3 is within the measurement accuracy of the optical density measurement.

For examples 3 and 4, which differ from examples 1 and 2 only in the base material used, more precisely Makrolon 2800 in both examples the optical properties of the base material are equal to those of Makrolon 3100 and the optical density measurements of examples 3 and 4 are likewise equal to those in examples 1 and 2.

However, the optical density measurements in examples 5 and 6 are surprising. Although the optical density without film is still equal to that of the previous example in the first place, there is a clear jump in the optical density when using the film kit, i.e. in the finished BLU. The optical density is about 15 to 18% higher than in the previous examples, which is unexpected given that the base material used is equal to the CD2005 optical data.

Claims (13)

1. A solid plate consisting of a solid material containing 80 to 99.99% by weight of molar mass M_w15000 to 21000g/mol of transparent polycarbonate and 0.01 to 20% by weight of transparent polymer particles having an optical density different from that of the polycarbonate.

2. The solid panel of claim 1 wherein said transparent polycarbonate has M_w(iii) a molar mass of 18500 to 20000 g/mol.

3. The solid panel according to claim 1 or 2, wherein the transparent polymer particles having an optical density different from polycarbonate are based on acrylates having a core-shell morphology and have a particle size between 1 and 100 μm.

4. The solid sheet according to claims 1 to 3, further comprising at least one coextruded layer.

5. The solid sheet of claim 4 wherein at least one of the coextruded layers contains a UV absorber.

6. The solid sheet according to claim 4 or 5 wherein at least one of the coextruded layers contains a lubricant.

7. The solid sheet according to any one of claims 4 to 6 having coextruded layers on both sides.

8. The solid sheet according to claims 5 to 8, wherein each coextruded layer has a thickness of 10 to 100 μm.

9. The solid plate according to claims 1 to 8, characterized in that it has a thickness of 0.1 to 4.0 mm.

10. Use of a solid plate according to any one of claims 1 to 9 as a diffuser plate in a flat panel display screen.

11. The solid panel of claim 1 wherein the light transmission is less than 70%.

12. The solid panel of claim 1 wherein the particles are organic.

13. The solid plate of claim 1 wherein the molar mass is from 15000 to 18000 g/mol.