TW201500455A - Black composite film having a low coefficient of thermal expansion - Google Patents

Abstract

The invention relates to a black composite composition and film which has a very low coefficient of thermal expansion, a good flexibility, a high thermal stability and a good chemical resistance, and a method to produce the same. This composite, upon being cured and fabricated into films or sheets, can be used to replace glass panels for applications as the substrates in electroluminescent devices, organic light emitting diode displays, electrophoretic displays, lenses in electronics devices, and solar cells, etc.

Description

Black composite film with low coefficient of thermal expansion

The present invention relates to a black composite composition and film having a very low coefficient of thermal expansion, good flexibility, high thermal stability and good chemical resistance, and a method for producing the black composite composition and film . The composite composition, when cured and formed into a film or sheet, can be used as a flexible top-emitting OLED (organic light-emitting diode) flexible reflective display TFT (thin film transistor) backplane (backplanes) ) The substrate produced.

Glass panels have been widely used in displays as substrates for thin film transistor (TFT) deposition. The TFT-deposited glass panel is a back sheet for liquid crystal displays, electrophoretic displays, and organic light emitting diode displays. In addition, glass panels are also used to manufacture color filters, touch panels, and solar cell substrates.

In recent years, there has been considerable interest in the use of polymeric substrates in place of glass panels for flat panel displays because of their advantages of being thin, light, robust and flexible. Furthermore, the polymer substrate provides the possibility of reducing manufacturing costs due to compatibility with the roll-to-roll process. There are several commercially available polymer substrates such as polycarbonate and co-polycarbonate (PC), polyether oxime (PES), polyethylene terephthalate (PEN), polyimine (PI), etc. .

However, in order to replace the glass plate as a substrate, the polymer film must meet some of the properties required for display applications, including high penetration, low haze and birefringence, good thermal and chemical resistance, And a low coefficient of thermal expansion (CTE). There is no optical requirement for a polymer film to be fabricated on a TFT backsheet for top-emitting OLED and reflective display applications, i.e., the polymer need not be transparent. In contrast, black is a better choice when black is improved. Therefore, this low CTE requirement is the biggest challenge when most amorphous polymer materials exhibit high CTE. In the fabrication of the backsheet, the TFT layer, typically an inorganic material having a low CTE, is deposited directly on the substrate at elevated temperatures.

A mismatched CTE between the inorganic TFT layer body and the substrate will result in severe stress and even cracking of the TFT layer. Several approaches have been taken to reduce the CTE of the polymeric material, including the addition of inorganic particles and fibers. However, the addition of these particles generally reduces the impact resistance of the polymeric material.

For the fabrication of low CTE glass fiber reinforced transparent composite films, some studies have documented the development of specific matrix resins for the composite film. Typical substrates for the production of transparent composite films having a low CTE include cycloaliphatic epoxides as described in WO20/1024911, WO2011/062290, US2010/0216912, US2010/0009149, US7132154B2, etc., as described Acrylates in US 2007/0219309, US Pat. No. 7,250,209, etc., sol-gel as embodied in US 2010/0178478 A1 and US 2011/0052890 A1, and half as claimed in TW201041945 A1 et al. Silesquioxane.

However, epoxide and acrylate matrices generally exhibit coloration. At the same time, the composite film based on the sol-gel matrix is easily cleaved due to post cure at room temperature and exhibits low penetration (US2011/0052890 A1). Therefore, the black composite film made of the combination of the fiberglass and the above substrate still needs improvement in crack resistance, low coefficient of thermal expansion, high temperature resistance, and black.

The present invention has the object of overcoming at least some of the disadvantages of this technical field. In particular, the present invention has the object of providing an improved composite membrane for photovoltaic applications.

This object is achieved by a composite film comprising a matrix, a black material and a glass filler at least partially embedded in the matrix, wherein the matrix comprises a crosslinked polyurethane polymer having a thermal expansion coefficient of less than 20 ppm/K. And the film has a thickness of less than 500 μm.

The composite film according to the present invention has a black color, good crack resistance and flexibility, and a low coloring effect. The resulting black composite film thus meets the substrate requirements for TFT deposition. The TFT deposited backplane can be used for an organic light emitting diode display, an electrophoretic display, a lens in an electronic device, a solar cell, and, in particular, as a flexible top emitting OLED (organic light emitting diode) A substrate for the fabrication of a TFT (Thin Film Transistor) backsheet of a flexible reflective display.

The composite film can be in the form of a layer comprising a crosslinked polyurethane substrate and a glass filler. Alternatively, the composite film may comprise several layers of a crosslinked polyurethane matrix comprising a glass filler, if desired.

In its broadest form, the composite film according to the present invention is formed from a crosslinked polyurethane polymer matrix and a glass filler.

A "crosslinked polyurethane polymer" is understood to mean a polymer comprising a polyurethane chain forming a three dimensional network. This can be, for example, by using a starting material (NCO compound and/or NCO-reactive compound) having an average functionality greater than 2 or by using an (average) functionality of greater than 2 for the prepolymer chain. A chain extender is achieved. Another example is the use of reactive crosslinking groups in the polymer chain, such as (meth) acrylate groups. The term "aminoformate (meth) acrylate" will then be used.

At the isocyanate end, aliphatic isocyanates are preferred due to their photostability. except In addition, it is also possible to use uretdione, isocyanurate, urethane, allophanate, biuret, imido oxadiazinedione and/or oxalate in proportion. Modified diisocyanates of diazinone structure and unmodified polyisocyanates containing more than 2 NCO groups per molecule, such as 4-isocyanatomethyloctane 1,8-diisocyanate ( Decane triisocyanate) or triphenylmethane 4,4',4"-triisocyanate.

These are preferably polyisocyanates or the above-mentioned polyisocyanate mixtures of the type containing only aliphatic and/or cycloaliphatic bound isocyanate groups, and having an average NCO functionality of from 2 to 4 in the mixture.

Polyols suitable for the polyurethane formation reaction include polyester polyols, polyacrylate polyols, polyurethane polyalcohols, polycarbonate polyols, polyether polyols, Polyester-polyacrylate polyols, polyurethane polyacrylate polyols, polyurethane polyester polyols, polyurethane polyether polyols, polyurethane polycondensates Carbonate polyols and polyester polycarbonate polyols are known per se in polyurethane technology.

With regard to the nature of the polyol, it is advantageous that the -OH content is quite high, especially 10 weight-%, better 12 weight-% to 18 weight-% and best 13 weight-% to 16 weight-%. It has been found that when a polyol having a lower OH content is used, the matrix material becomes too soft. The hydroxyl content is related to the number of hydroxyl groups, which can be obtained from the titration known to those skilled in the art of polyols, according to the following equation: OH number = (56100/1700) * OH content

Procedures for the determination of OH numbers can be found in the corresponding specifications and standards, such as DIN 53240.

Special consideration is given to having a hydroxyl content of 10%, better 12% to 18% and best 13 weight-% to 16% by weight of polyester polyol.

A typical resin composition for producing a matrix of a composite film according to the present invention comprises 45 to 70 wt.% of a polyisocyanate, preferably an aliphatic isocyanate such as HDI, THDI, H-MDI and IPDI. And their dimers and trimers of from 25 to 45 wt.% of the polyol compound, preferably polyester polyols.

The term "glass" according to the invention encompasses glass fibers. Glass fibers are used in the art and are preferably used in the form of weavings, monofilaments and chopped staple fibers.

The most commonly used types of glass materials in this field are E-glass (alumino-borate glass containing less than 1% w/w basic oxide, mainly used for glass-reinforced plastics) And A-glass (alkali-lime glass with little or no boron oxide), E-CR-glass (aluminum-calcium sodium containing less than 1% w/w basic oxide) Alumino-lime silicate with high acid resistance, C-glass (soda lime glass with high boron oxide content, for example, glass staple fiber), D-glass (with High dielectric constant borosilicate glass), R-glass (high-mechanical aluminum silicate glass without MgO and CaO), and S-glass (high tensile strength without CaO but high MgO content) Aluminum silicate glass). T-glass is a variant of North American C-glass.

In the present invention, the glass filler is preferably E-glass, S-glass, and/or T-glass.

Regarding the black material, generally, any black pigment, carbon black, organic or inorganic black dye can be used. However, in order to obtain a stable composite film, it is preferred that the black material is chemically stable, chemically inert, compatible with the polyurethane substrate, heat resistant, and stable to UV-light. Non-bleeding and non-migratory. Black materials that meet these requirements are well known to those skilled in the art and are generally commercially available. In particular, the black pigment may be a carbon black, inorganic black pigment with or without a dispersant.

The composite film of the present invention has a coefficient of thermal expansion (CTE) of less than 40 ppm/K and preferably a CTE of less than 20 ppm/K, preferably 1ppm/K to 15ppm/K.

The coefficient of thermal expansion has the general meaning used in the art, that is, the linear thermal expansion Expansion coefficient. It is measured according to ASTM E831. Preferably, it can be measured according to ASTM E831 using a Thermal Mechanical Analyzer (TMA) in a nitrogen atmosphere at a heating rate of 10 ° C/min and a temperature range of 30 to 200 ° C. The tension applied to the sample during the CTE measurement can be 0.1 N.

While the total thickness of the composite film according to the present invention is less than 500 μm (preferably 10 to 200 μm), its shape itself is not limited. For example, both planar and non-planar shapes are equally feasible. When using the composite film according to the present invention, the product designer has a great degree of freedom in his design.

Specific embodiments and fields of the invention will be described in more detail below. They can be freely combined unless otherwise clearly indicated herein.

In one embodiment of the composite film according to the invention, the glass filler is in the form of a glass fabric, non-woven clothes, glass monofilament or chopped glass fibers.

If a glass or glass cloth is used, the thickness of the fabric or cloth plays an important role in defining the preferred properties of the composite film. The thickness of the glass fabric is preferably in the range of 10 to 200 μm, and preferably 20 to 100 μm. If the thickness is in a preferred range, a composite film having excellent CTE and exhibiting superior flexibility, crack resistance and transparency can be obtained. If the thickness of the fabric or cloth used is too thin, crack resistance is observed to decrease. The use of larger thickness fabrics and fabrics results in a lower flexibility composite film. In addition, transparency will be affected.

Accordingly, in another embodiment of the composite film according to the present invention, the glass filler has a thickness of 20 to 200 μm, preferably 30 to It is in the form of a glass fabric having a thickness of 100 μm.

In another embodiment of the composite film according to the invention, the polyurethane polymer has been prepared from a mixture comprising at least one aliphatic polyisocyanate and at least one polyester polyol.

In particular, the polyurethane may be prepared from a mixture comprising at least one of the following polyisocyanate compounds 1) and at least one of the following polyols 2):

1) tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), 2-methyl pentamethylene Diisocyanate, 2,2,4-trimethyl-hexamethylene diisocyanate (THDI), dodecyl methylene diisocyanate, 1,4-diisocyanatocyclohexane, 3-isocyanate Methyl-3,3,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate=IPDI), 4,4'-diisocyanatodicyclohexylmethane (Desmodur® W), 4,4' -Diisocyanato-3,3'-dimethyldicyclohexylmethane, 4,4'-diisocyanato-2,2-dicyclohexylpropane. For the purpose of upgrading, other terpolymers, carbamates, biurets, allophanates or uretdiones of the above diisocyanates may be used.

2) Di- and optionally poly-condensates of tri- and tetraols with di- and optionally tri- and tetracarboxylic acids or hydroxycarboxylic acids or lactones (known per se). Instead of the free polycarboxylic acid, it is also possible to use corresponding polycarboxylates for the preparation of polyesters corresponding to polycarboxylic anhydrides or lower alcohols.

Examples of suitable diols are ethylene glycol, butylene glycol, diethylene glycol, triethylene glycol, polyalkylene glycols such as polyethylene glycol, and 1,2-propanediol, 1, 3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol and isomers, neopentyl glycol or neopentyl glycol hydroxyvalerate Among them, preferred are 1,6-hexanediol and isomers, neopentyl glycol and neopentyl glycol hydroxyvalerate. In addition, polyols such as trimethylolpropane, glycerol, erythritol, pentaerythritol, trimethylolbenzene or trishydroxyethyl isocyanurate may also be used.

Dicarboxylic acids which can be used are phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, cyclohexanedicarboxylic acid, adipic acid, azelaic acid. , azelaic acid, glutaric acid, tetrachlorophthalic acid, maleic acid, fumaric acid, isaconic acid, malonic acid, suberic acid, 2-methylsuccinic acid, 3, 3-diethylglutaric acid and / or 2,2-dimethylsuccinic acid. The corresponding anhydride can also be used as the acid source.

Preferred acids are aliphatic or aromatic acids of the above type. Particularly suitable are adipic acid, isophthalic acid and optionally trimellitic acid.

Other monomers such as thiols and amines which can react with aliphatic isocyanates to form transparent matrices can also be used.

In another embodiment of the composite film according to the present invention, the polyurethane polymer has been prepared from an unsaturated polyurethane resin. Unsaturated polyurethane-based resins generally comprise acrylate-modified polyurethanes. These lines are known, for example, from WO-A-2008125200. Such unsaturated polyurethane-based resins can, for example, utilize polymerization from A) polyisocyanates, B) isocyanate-reactive block copolymers, and C) with ethylene under exposure to actinic radiation. It is obtained by reacting a compound of a reactive group (radiation-curing group) of a reactive compound.

As component C), α,β-unsaturated carboxylic acid derivatives such as acrylates, methyl-acrylates, maleic esters, fumarates, maleic acid can be used. Terpenoids, acrylamides, and vinyl ethers, propylene ethers, allyl ethers, and compounds containing dicyclopentadienyl units and olefinically unsaturated compounds, such as Styrene, α-methylstyrene, vinyltoluene, vinylcarbazole, olefins such as, for example, 1-octene and/or 1-decene, vinyl esters such as, for example, (methyl) Acrylonitrile, (meth) acrylamide, methacrylic acid, acrylic acid and the desired mixtures thereof. Preferred are acrylates and methacrylates, and particularly preferred are acrylates.

The esters of acrylic or methacrylic generally refer to acrylates or methacrylates. Examples of acrylates and methacrylates that can be used are methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, ethoxyethyl acrylate, ethoxyethyl methacrylate, N-butyl acrylate, n-butyl methacrylate, tertiary butyl acrylate, tertiary butyl methacrylate, hexyl acrylate, hexyl methacrylate, 2-ethylhexyl acrylate, methyl 2-ethylhexyl acrylate, butoxyethyl acrylate, butoxyethyl methacrylate, lauryl acrylate, lauryl methacrylate, isobornyl acrylate, isobornyl methacrylate, phenyl acrylate, Phenyl methacrylate, p-chlorophenyl acrylate, p-chlorophenyl methacrylate, p-bromophenyl acrylate, p-bromophenyl methacrylate, trichlorophenyl acrylate, A Trichlorophenyl acrylate, tribromophenyl acrylate, tribromophenyl methacrylate, pentachloro acrylate Phenyl ester, pentachlorophenyl methacrylate, pentabromophenyl acrylate, pentabromophenyl methacrylate, pentabromobenzyl acrylate, pentabromobenzyl methacrylate, phenoxyethyl acrylate , phenoxyethyl methacrylate, phenoxyethoxyethyl acrylate, phenoxyethoxyethyl methacrylate, 2-naphthyl acrylate, 2-naphthyl methacrylate, 1,4-double acrylic acid -(2-thionaphthyl)-2-butyl ester, 1,4-bis-(2-thionaphthyl)-2-butyl methacrylate, bisphenol A diacrylate, bisphenol A dimethacrylate Ester, tetrabromobisphenol A diacrylate, tetrabromobisphenol A dimethacrylate, 2,2,2-trifluoroethyl acrylate, 2,2,2-trifluoroethyl methacrylate, 1,1,1,3,3,3-hexafluoroisopropyl acrylate, 1,1,1,3,3,3-hexafluoroisopropyl methacrylate, acrylic acid 2,2,3,3,3 - pentafluoropropyl ester and / or 2,2,3,3,3-pentafluoropropyl methacrylate.

As mentioned above, the black material needs to meet specific criteria regarding chemical stability and UV-light resistance. Particularly suitable black materials are carbon nanotubes, carbon black, inorganic black pigments, black organic dyes or black polymer pigments. Thus, in a preferred embodiment of the invention, the black material is selected from the group consisting of these compounds.

When a composite film of particularly smooth surface is desired, it is advantageous to provide a film that does not contain any coating layer of glass filler. The coating is the same crosslinked polyurethane as the crosslinked polyurethane matrix of the corresponding composite film, but does not contain the glass filler. Thus, in another embodiment of the film according to the invention, the film may additionally comprise at least one coating. This coating is not included in the calculation of the film thickness. Any planarized material can be used as a coating. Based on chemical compatibility factors, it is preferred that the coating comprises a polyurethane polymer of the matrix material. The coating may or may not contain black material. In particular, when the composite film according to the invention comprises at least one coating, the black material is preferably a black dye. If no coating is applied to the composite film, it is preferred that the black material be carbon black, an inorganic black pigment, and/or a carbon nanotube.

Another field of the invention is a method of making a composite film comprising the steps of: - preparing a resin composition for crosslinking a polyurethane substrate, the resin composition comprising a polyisocyanate (preferably, an aliphatic isocyanate), a polyhydric alcohol and optionally an antifoaming agent, a heat stabilizer and a wetting agent; - providing a glass fabric or a non-woven glass cloth The glass fabric or the glass non-woven fabric is brought into contact with the resin composition; - the resin composition is cured; wherein the obtained film has a thermal expansion coefficient of less than 20 ppm/K and a thickness of less than 500 μm.

The discussion relating to the details of the polyurethane material, the glass type, and the like in connection with the composite film according to the present invention is also applicable herein. Based on the concise factors, the narrative is not repeated.

Application of the resin composition can be carried out, for example, by means of a doctor blade or by extrusion. Additionally, several layers can be laminated together to form a composite film. The individual layer body may be a layer body without a glass filler and a layer body containing a glass filler.

In one embodiment of the method according to the invention, the glass or glass cloth has a thickness in the range from 10 to 200 μm.

With regard to this curing step, in one embodiment of the method according to the invention, the curing step comprises thermal curing and/or radiation curing. For example, a "dual cure" system can be used in which a prepreg is heat treated to make it easier to process and then hardened by radiation to give a final product.

When the glass material is contacted with the resin composition, a support or substrate can be used. In another embodiment of the method according to the invention, the glass fabric or glass non-woven fabric is contacted with the resin composition on a support and the support is a release film. This represents a very efficient means for making a composite film according to the invention. The release film can be a PTFE- or anthrone-impregnated fabric or paper.

In another embodiment of the process according to the invention, the resin comprises at least one aliphatic isocyanate and at least one polyester polyol.

In a particularly preferred embodiment of the present invention, the method comprises preparing a resin composition comprising 55 to 70 wt.% of an aliphatic polyisocyanate (such as HDI and IPDI), 25 to 40 wt.% of a polyester polyol, 5 to 15 wt.% of the black material and 0.01 to 0.05 wt.% of the antifoaming agent, and a glass fabric or glass having a thickness of 15 to 45 μm is disposed on a substrate (preferably a PTFE coated release fabric). The glass fabric or glass cloth is coated with the resin composition and the composition is cured, whereby a composite film having a black, a thermal expansion coefficient of less than 20 ppm/K and a thickness of less than 200 μm is obtained.

The invention also relates to an assembly comprising a support and an optical element supported by the support, wherein the support comprises a composite film comprising a substrate and a glass filler at least partially embedded in the substrate, wherein the substrate A crosslinked polyurethane polymer and a black material are included, and wherein the composite film has a thermal expansion coefficient of less than 20 ppm/K and a thickness of less than 500 μm.

With regard to the assembly according to the invention, it is preferred that the composite membrane is a composite membrane according to the invention.

In another embodiment of the assembly according to the invention, the optical element is an electroluminescent element, a light emitting diode, an organic light emitting diode, an electrophoretic display element, a thin film transistor, a lens element or a photovoltaic element, preferably flexible Sex-emitting organic light-emitting diodes.

Finally, the invention relates to an electronic device comprising an assembly according to the invention.

Figures 1 to 8 depict the measurement of the coefficient of thermal expansion, on which the dL/μm is on the x-axis and the temperature (°C).

Figure 9 shows the TGA results for the black composite film of Example 1 (wt% on the x-axis, temperature (°C) on the y-axis).

Example :

In the following, the invention will be explained in more detail with reference to examples, without however limiting the invention.

Figures 1 to 8 depict the measurement of the coefficient of thermal expansion, dL/μm on the x-axis and temperature (°C on the y-axis).

Figure 9 shows the TGA results for the black composite film of Example 1 (wt% on the x-axis, temperature (°C) on the y-axis).

measuring: 1. Linear thermal expansion coefficient (CTE)

The CTE was measured according to ASTM E831 using a Thermal Mechanical Analyzer (TMA) in a nitrogen atmosphere at a heating rate of 10 ° C/min and a temperature range of 30 to 200 ° C. The tension applied to the sample during the CTE measurement was 0.1N.

2. Measurement of color scale L.a.b.

The measurement of the color scale L.a.b. was carried out using an Ultrascan Pro manufactured by Hunterlab.

3. Thermal stability

The thermal stability of the black composite film was measured using a thermogravimeter analyzer (TGA) in an air environment at a heating rate of 10 ° C/min and a temperature ranging from 100 to 800 ° C.

Example 1

A glass cloth made of E-glass (thickness 40 μm, refractive index 1.56, HP-Textile HP-P48E, plain, 48 g/m ² ) was used for the impregnation. This glass cloth was impregnated with a resin composition consisting of 50.87% by weight of Desmodur N3900 (polyisocyanate based on hexamethylene diisocyanate (HDI), having an NCO content of 23.5% and a viscosity of 730 mPa at 23 ° C. ̇s, Bayer AG, Leverkusen, Germany), 31.93 wt% Desmophen VPLS 2249/1 (polyester polyol, OH content 15.5 wt-%, viscosity at 23 ° C 1900 mPa ̇s, Bayer AG, Leverkusen, Germany) It is composed of 10% by weight of black pigment (30C965, Shepherd). The impregnation is carried out at a high temperature of 55 °C. The resin-impregnated glass cloth was placed on a release liner. The curing was carried out at 80 ° C for 1 hr, at 120 ° C for 30 min and at 150 ° C for 1 hr. The cured black composite film had a linear thermal expansion coefficient of 13.5 ppm/K, a thickness of 74 μm, and a Lab color scale of L = 25.74, a = -0.09, and b = -0.95. Further, when the black composite film was rolled on a cylinder having a diameter of 10 cm, no cracks and any whitening were observed, and the film was extremely flexible.

The measurement curve of the coefficient of thermal expansion is shown in Fig. 1.

Example 2

A sample film having a thickness of 107 μm was prepared in the same manner as in Example 1 except that an E-glass cloth (thickness 40 μm, refractive index 1.56, HP-Textile, HP-P50EF, plane, 48 g/m ² ) was used. The black composite film had a linear thermal expansion coefficient of 15.3 ppm/K, and a Lab color scale of L = 25.55, a = -0.08, and b = -0.97.

The measurement curve of the coefficient of thermal expansion is shown in Fig. 2.

Example 3

A sample film having a thickness of 146 μm was prepared in the same manner as in Example 1 except that 30 C933 black pigment (Shepherd) was used. The black composite film had a thermal expansion coefficient of 14.4 ppm/K, and an L.a.b. color scale of L = 27.22, a = 0.44, and b = -0.24.

The measurement curve of the coefficient of thermal expansion is shown in Fig. 3.

Example 4

A sample film having a thickness of 207 μm was prepared in the same manner as in Example 1, except that an E-glass cloth (thickness 40 μm, refractive index 1.56, HP-Textile, HP-50EF, plane, 48 g/m ² ) and black pigment 30C933 (using a thickness of 40 μm) were used. Shepherd). The black composite film had a linear thermal expansion coefficient of 18.0 ppm/K, and a Lab color scale of L = 26.10, a = 0.41, and b = -0.27.

The measurement curve of the coefficient of thermal expansion is shown in Fig. 4.

Example 5

A sample film having a thickness of 101 μm was prepared in the same manner as in Example 1, except that BLA-PH046 carbon black (Chemtura) was used. The black composite film has a linear thermal expansion coefficient of 15.2 ppm/K, and an L.a.b. color scale of L = 24.66, a = -0.14, and b = -0.44.

The measurement curve of the coefficient of thermal expansion is shown in Fig. 5.

Example 6

A sample film having a thickness of 123 μm was prepared in the same manner as in Example 5 except that E-glass (thickness 40 μm, refractive index 1.56, HP-Textile, HP-50EF, plane, 48 g/m ² ) was used. The black composite film has a linear thermal expansion coefficient of 9.5 ppm/K, and a Lab color scale of L = 24.30, a = -0.17, and b = -0.55.

The measurement curve of the coefficient of thermal expansion is shown in Fig. 6.

Example 7

A sample film having a thickness of 55 μm was prepared in the same manner as in Example 1 except that NS550 black dye (Nova Speciality Chemical) was used. The black composite film has 9.4 ppm/K The linear thermal expansion coefficient, and L = 23.34, a = 0.51, b = -0.69 L. a. b. color scale.

The measurement curve of the coefficient of thermal expansion is shown in Fig. 7.

Example 8

A sample film having a thickness of 42 μm was prepared in the same manner as in Example 7, except that E-glass (thickness 40 μm, refractive index 1.56, HP-Textile, HP-50EF, plane, 48 g/m ² ) was used. The black composite film had a linear thermal expansion coefficient of 10.7 ppm/K, and a Lab color scale of L = 23.45, a = 0.78, and b = -0.85.

The measurement curve of the coefficient of thermal expansion is shown in Fig. 8.

Claims (15)

A composite film comprising a substrate, a glass filler at least partially embedded in the substrate, and a black material, wherein the matrix comprises a crosslinked polyurethane polymer characterized in that the composite film has less than 20 ppm/K The coefficient of thermal expansion and the thickness of less than 500 μm. The film according to claim 1, wherein the glass filler is in the form of a glass fabric, a non-woven fabric, a glass monofilament or a chopped glass fiber. The film according to claim 1 or 2, wherein the glass filler is present in the form of a glass fabric having a thickness of 10 to 200 μm, preferably 20 to 100 μm. The film according to any one of claims 1 to 3, wherein the polyurethane polymer has been prepared from a mixture comprising at least one aliphatic polyisocyanate and at least one polyol. The film according to any one of claims 1 to 3, wherein the polyurethane polymer has been prepared from an unsaturated polyurethane resin. The film according to any one of claims 1 to 5, wherein the black material is selected from the group consisting of carbon black, inorganic black pigment, black organic dye, carbon nanotube, graphite, graphene, fullerene or black polymer color. material. The film according to any one of claims 1 to 6, wherein the film further comprises at least one coating. A method of producing a black composite film comprising the steps of: - preparing a resin composition for crosslinking a polyurethane substrate, the resin composition comprising a polyisocyanate (preferably an aliphatic isocyanate), a polyol and optionally an antifoaming agent, a heat stabilizer and a wetting agent; - providing a glass fabric or a glass nonwoven fabric; - contacting the glass fabric or glass nonwoven fabric with the resin composition; - curing the resin composition; wherein the composite film has a coefficient of thermal expansion of less than 20 ppm/K and a thickness of less than 500 μm. The method of claim 8, wherein the glass fabric or the glass non-woven fabric has a thickness in the range of 10 to 200 μm. The method of claim 8 or 9, wherein the curing step comprises heat curing and/or radiation curing. The method of any one of clauses 8 to 10 wherein the substrate is a release film. The method of any one of clauses 8 to 11, wherein the resin comprises at least one aliphatic isocyanate and at least one polyester polyol. An assembly comprising a support and an optical element supported by the support, wherein the support comprises a composite film comprising a substrate and a glass filler at least partially embedded in the substrate, wherein the substrate comprises a cross The polyurethane resin is combined with a black material having a coefficient of thermal expansion of less than 20 ppm/K and a thickness of less than 500 μm. The assembly of claim 13, wherein the optical element is an electroluminescent element, a light emitting diode, an organic light emitting diode, an electrophoretic display element, a thin film transistor, a lens element, or a photovoltaic element. An electronic device comprising an assembly according to item 13 of the patent application or item 14 of the patent application.