JP2011093966A - Transparent film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transparent film which has a high transparency and is excellent in a heat resistance. <P>SOLUTION: In the transparent film which comprises a substrate of glass fiber and a transparent resin held thereon, a resin composition for forming the transparent resin contains a thermosetting solvent-soluble imide resin. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a transparent film, and more particularly to a transparent film comprising a transparent resin and a glass fiber substrate.

  Conventionally, flat panel displays such as liquid crystal displays, plasma displays, and EL displays have been made thinner and lighter. However, replacement of glass substrates with plastic films has been studied as a means for further progress. By replacing the glass substrate with a plastic film, it can be made thinner and lighter, and properties such as resistance to cracking and flexibility can be imparted.

  Recently, a transparent film made of a transparent resin and a glass fiber substrate has been proposed (see Patent Documents 1 and 2).

  When producing this transparent film, a high refractive index resin having a higher refractive index than that of glass fiber and a low refractive index resin having a lower refractive index than that of glass fiber are mixed, and the refractive index is that of the glass fiber. The resin composition is prepared so as to approximate Then, a glass fiber base material is impregnated with the resin composition, dried and semi-cured to prepare a prepreg, and the prepreg is heated and pressed to produce a transparent film. An epoxy resin or the like is used as the high refractive index resin and the low refractive index resin.

  Thus, by combining the glass fiber of the base material and the refractive index of the matrix resin (resin composition), the refraction of light in the transparent film can be suppressed and used as a transparent film of a display having excellent visibility. .

  In addition to the general physical properties required for liquid crystal displays and the like, this transparent film can also provide performance such as adhesion to a conductive film such as an ITO film, surface smoothness, and gas barrier properties. It is attracting attention as a material.

JP 2004-307851 A JP 2009-066931 A

  However, the transparent film composed of the transparent resin and the glass fiber substrate has room for further improvement in heat resistance. That is, conventionally, a transparent film using an epoxy resin as a high refractive index resin and a low refractive index resin has been proposed, but a transparent film using this epoxy resin usually has an upper limit of heat resistance of about 200 ° C., There is concern that heat resistance may be a problem depending on the application.

  The present invention has been made in view of the circumstances as described above, and an object thereof is to provide a transparent film having high transparency and excellent heat resistance.

  The present invention is characterized by the following in order to solve the above problems.

  1stly, the transparent film of this invention WHEREIN: In the transparent film by which transparent resin is hold | maintained at the base material of glass fiber, the resin composition for transparent resin formation contains a thermosetting solvent-soluble imide resin.

  Second, in the first transparent film, the thermosetting solvent-soluble imide resin has the following formula (A):

(In the formula, each R ₁ independently represents a divalent aromatic group or alicyclic group, each R ₂ independently represents a trivalent aromatic group or alicyclic group, and n represents a positive integer. It is expressed by.)

  Thirdly, in the second transparent film, the resin composition for forming a transparent resin contains an epoxy resin.

  Fourth, in any of the first to third transparent films, the resin composition for forming a transparent resin has the following formula (I):

(In the formula, R ¹ represents a hydrogen atom or a methyl group, R ² represents a divalent organic group, and R ^{3 to} R ¹⁰ each independently represent a hydrogen atom, a substituent, or an epoxy group-containing molecular chain. .) Containing a polyfunctional epoxy resin.

  Fifth, in any of the first to fourth transparent films, the resin composition for forming a transparent resin contains an alicyclic epoxy resin having a 3,4-epoxycyclohexenyl skeleton.

  Sixth, in any one of the first to fifth transparent films, the resin composition for forming a transparent resin has the following formula (II):

(In the formula, R represents an m-valent organic group, and m and n represent positive integers).

  Seventhly, in any of the first to sixth transparent films, the resin composition for forming a transparent resin contains a cyanate resin.

  According to the first and second inventions described above, by adding a thermosetting solvent-soluble imide resin to a resin composition for forming a transparent resin, a transparent film having high transparency and excellent heat resistance can be obtained. Obtainable.

  According to said 3rd thru | or 7th invention, by using said specific epoxy resin etc. in combination with a thermosetting type solvent-soluble imide resin, while maintaining high transparency, the transparent film excellent in heat resistance especially Can be obtained.

  Hereinafter, the present invention will be described in detail.

  The transparent film of the present invention is a transparent film in which a transparent resin is held on a glass fiber substrate, a high refractive index resin having a higher refractive index than glass fiber, and a low refractive index having a lower refractive index than glass fiber. It is formed by impregnating a glass fiber substrate such as a glass cloth and curing a resin composition prepared by mixing a resin and having a refractive index close to that of the glass fiber.

  In the present invention, the resin composition is characterized by containing a thermosetting solvent-soluble imide resin as at least one of the high refractive index resin and the low refractive index resin.

  In general, polyimide resins are used in various fields such as the electronics field because they are excellent in heat resistance, electrical characteristics, and mechanical strength, and products are provided as films and precursor solutions thereof. However, since the film is difficult to mold, process, and coat, and the precursor solution requires high temperature for imidization, a transparent film is prepared by combining with a glass fiber substrate as in the present invention. It is difficult.

  In contrast, in the present invention, by using a thermosetting solvent-soluble imide resin that is soluble in a solvent, a glass fiber base material is impregnated with a resin composition containing this and cured to make a transparent film. A transparent film having high heat resistance and high transparency is obtained by the imide group.

  As the thermosetting solvent-soluble imide resin, for example, one represented by the above formula (A) can be used.

In the formula (A), each R ₁ independently represents a divalent aromatic group or alicyclic group, and each R ₂ independently represents a trivalent aromatic group or alicyclic group.

The aromatic group of R ₁ is preferably a group having 6 to 20 carbon atoms containing an aromatic ring, and is a residue of the raw material aromatic diamine or aromatic diisocyanate. Examples of the aromatic diamine include m-phenylenediamine, p-phenylenediamine, tolylenediamine, xylylenediamine, 4,4′-diaminodiphenylmethane, 4,4′-diaminobiphenyl, 3,3′-diaminobiphenyl, 3,4′-diaminobiphenyl, 4,4′-diamino-3,3′-dimethylbiphenyl, 4,4′-diamino-2,2′-dimethylbiphenyl, 4,4′-diamino-3,3′- Diethylbiphenyl, 4,4′-diamino-2,2′-diethylbiphenyl, 4,4′-diamino-3,3′-dimethoxybiphenyl, 4,4′-diamino-2,2′-dimethoxybiphenyl, 5- Diaminonaphthalene, 2,6-diaminonaphthalene, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, 4,4'-diamino Examples include diphenylsulfone and 2,2-bis [4- (4′-aminophenoxy) phenyl] propane. As aromatic diisocyanate, what substituted the amino group of these aromatic diamine by the isocyanate group etc. are mentioned, for example.

The alicyclic group of R ₁ is preferably a group having 6 to 20 carbon atoms containing an aliphatic ring, and is a residue of a starting alicyclic diamine or alicyclic diisocyanate. Examples of the alicyclic diamine include 4,4′-diamino-dicyclohexylmethane, 3,3′-dimethyl-4,4′-diamino-dicyclohexylmethane, 3,3′-diethyl-4,4′-diamino- Dicyclohexylmethane, 3,3 ′, 5,5′-tetramethyl-4,4′-diamino-dicyclohexylmethane, 3,3 ′, 5,5′-tetraethyl-4,4′-diamino-dicyclohexylmethane, 3, 5-diethyl-3 ′, 5′-dimethyl-4,4′-diaminodicyclohexylmethane, 1,4-cyclohexanediamine, 1,3-cyclohexanediamine, isophoronediamine, 2,2-bis [4- (4-amino Cyclohexyloxy) cyclohexyl] propane, bis [4- (3-aminocyclohexyloxy) cyclohexyl] sulfone, bis [4- ( -Aminocyclohexyloxy) cyclohexyl] sulfone, 2,2-bis [4- (4-aminocyclohexyloxy) cyclohexyl] hexafluoropropane, bis [4- (4-aminocyclohexyloxy) cyclohexyl] methane, 4,4'- Bis (4-aminocyclohexyloxy) dicyclohexyl, bis [4- (4-aminocyclohexyloxy) cyclohexyl] ether, bis [4- (4-aminocyclohexyloxy) cyclohexyl] ketone, 1,3-bis (4-aminocyclohexyl) Oxy) benzene, 1,4-bis (4-aminocyclohexyloxy) benzene, (4,4′-diamino) dicyclohexyl ether, (4,4′-diamino) dicyclohexylsulfone, (4,4′-diaminocyclohexyl) ketone (3,3′-diamino) benzophenone, 2,2′-dimethylbicyclohexyl-4,4′-diamine, 2,2′-bis (trifluoromethyl) dicyclohexyl-4,4′-diamine, 5,5 ′ -Dimethyl-2,2'-sulfonyldicyclohexyl-4,4'-diamine, 3,3'-dihydroxydicyclohexyl-4,4'-diamine, (4,4'-diamino) dicyclohexylmethane, (4,4'- And diamino) dicyclohexyl ether, (3,3′-diamino) dicyclohexyl ether, 2,2-bis (4-aminocyclohexyl) propane, and the like. As alicyclic diisocyanate, what substituted the amino group of these alicyclic diamine with the isocyanate group etc. are mentioned, for example.

The aromatic group of R ₂ is preferably a group having 6 to 20 carbon atoms containing an aromatic ring, and is a residue of a raw material aromatic tricarboxylic acid or its anhydride. Examples of the aromatic tricarboxylic acid include benzene-1,2,4-tricarboxylic acid, naphthalene-1,2,4-tricarboxylic acid, 2,5,7-naphthalene tricarboxylic acid, diphenyl ether-3,3 ′, 4 ′. -Tricarboxylic acid, diphenylsulfone-3,3 ', 4'-tricarboxylic acid, benzophenone-3,3', 4'-tricarboxylic acid, 5-methylbenzene-1,2,4-tricarboxylic acid, 6-methylbenzene- Examples include 1,2,4-tricarboxylic acid and 3-methylbenzene-1,2,4-tricarboxylic acid.

The alicyclic group represented by R ₂ is preferably a group having 6 to 20 carbon atoms containing an aliphatic ring, and is a residue of a starting alicyclic tricarboxylic acid or anhydride. Examples of the alicyclic tricarboxylic acid include cyclohexane-1,2,3-tricarboxylic acid, cyclohexane-1,2,4-tricarboxylic acid, cyclohexane-1,3,5-tricarboxylic acid, 5-methylcyclohexane-1, Examples include 2,4-tricarboxylic acid, 6-methylcyclohexane-1,2,4-tricarboxylic acid, and 3-methylcyclohexane-1,2,4-tricarboxylic acid.

When a thermosetting solvent-soluble imide resin is used as a high refractive index resin, a wholly aromatic resin using an aromatic group as R ₁ and R ₂ can be preferably used. Alternatively, an alicyclic group using an alicyclic group as R ₁ or R ₂ can also be used.

When a thermosetting solvent-soluble imide resin is used as the low refractive index resin, an alicyclic type resin using an alicyclic group as R ₁ or R ₂ can be preferably used.

  The acid value of the thermosetting solvent-soluble imide resin represented by the formula (A) is preferably 30 to 80 mgKOH / g, more preferably 40 in terms of solid content in consideration of solubility in organic solvents and curing characteristics. -70 mg KOH / g.

  The thermosetting solvent-soluble imide resin of the formula (A) can be used as a solution by dissolving in a solvent such as ethers, esters, ketones, and aromatic hydrocarbons.

  Examples of ethers include ethylene glycol dialkyl ether, polyethylene glycol dialkyl ether, ethylene glycol monoalkyl ether acetate, polyethylene glycol monoalkyl ether acetate, propylene glycol dialkyl ether, polypropylene glycol dialkyl ether, propylene glycol monoalkyl ether acetate, polypropylene glycol Examples include monoalkyl ether acetate, dialkyl ether of copolymerized polyether glycol, monoacetate monoalkyl ether of copolymerized polyether glycol, alkyl ester of copolymerized polyether glycol, monoalkyl ester monoalkyl ether of copolymerized polyether glycol, etc. It is done.

  Examples of the esters include γ-butyrolactone, ethyl acetate, butyl acetate and the like.

  Examples of ketones include acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone.

  Examples of aromatic hydrocarbons include toluene, xylene and the like.

  In addition, a solvent such as dimethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, or sulfolane may be used in combination with the above solvent.

  The thermosetting solvent-soluble imide resin of the formula (A) can be dissolved in the above solvent and used as a solution having a viscosity of 0.1 to 100 Pa · s (25 ° C.), for example.

  Such a thermosetting solvent-soluble imide resin can be combined with an epoxy resin or a cyanate ester resin to obtain a transparent cured product having high heat resistance.

  As the high refractive index resin blended in the resin composition together with the thermosetting solvent-soluble imide resin, polyfunctional epoxy resins and cyanate ester resins represented by the above formula (I) are preferably used.

  By using this polyfunctional epoxy resin represented by formula (I), while maintaining high transparency, the glass transition temperature is high, the heat resistance of the cured product can be increased, and further, discoloration due to heat is also possible. Can be suppressed.

Examples of the divalent organic group represented by R ² in the formula (I) include a substituted or unsubstituted arylene group such as a phenylene group, or a structure in which a substituted or unsubstituted arylene group is bonded to a carbon atom or a carbon chain. Groups and the like. Examples of the carbon atom or carbon chain include an alkylene group such as a methylmethylene group and a dimethylmethylene group, and a carbonyl group.

As the divalent organic group represented by R ^2, a group that forms a glycidyloxyphenyl group by bonding a phenylene group to the glycidyloxy group on the right side of the formula (I) is preferably used. Further, from the viewpoint of suppressing discoloration of the transparent film due to heat, a carbon atom or carbon chain interposed between arylene groups preferably does not contain a methylene group (—CH ₂ —).

Examples of the divalent organic group represented by R ² include the following structures (inside square brackets).

Examples of the substituent of R ³ to R ¹⁰ in the formula (I), is not particularly limited, for example, hydrocarbon groups such as lower alkyl groups, such as other organic groups. Examples of the molecular chain containing an epoxy group of R ^{3 to} R ¹⁰ include the following structures (inside square brackets).

(In the formula, p represents a positive integer.)
As the polyfunctional epoxy resin represented by the formula (I), for example, polyfunctional epoxy resins represented by the following formulas (Ia), (Ib), and (Ic) can be used.

(In the formula, q represents a positive integer.)

  Examples of cyanate ester resins include 2,2-bis (4-cyanatephenyl) propane, bis (3,5-dimethyl-4-cyanatephenyl) methane, 2,2-bis (4-cyanatephenyl) ethane, and the like. Or an aromatic cyanate ester compound can be used. These may be used alone or in combination of two or more.

  Cyanate ester resin generates a triazine ring or an oxazoline ring by causing a curing reaction together with the epoxy resin, increases the crosslink density of the epoxy resin, and forms a rigid structure to give the cured product a high glass transition temperature. Can do. In addition, since the cyanate ester resin is solid at room temperature, when preparing a prepreg by impregnating the resin composition into a glass fiber base material and drying it as described later, it becomes easy to dry by touch. The handleability of the prepreg is improved.

  The refractive index of the high refractive index resin is preferably 1.58 to 1.63. For example, when the refractive index of the glass fiber is 1.563 (E glass fiber), the high refractive index resin preferably has a refractive index of around 1.6, and n + 0.03, where n is the refractive index of the glass fiber. The thing of the range of -n + 0.06 is preferable.

  In the present invention, the refractive index of the resin means the refractive index in the state of the cured resin (cured resin), and is a value tested according to ASTM D542.

  As a low refractive index resin blended in a resin composition together with a thermosetting solvent-soluble imide resin, an alicyclic epoxy resin having a 3,4-epoxycyclohexenyl skeleton, and a structure represented by the above formula (II) The polyfunctional epoxy resin which has is used preferably.

  By using this alicyclic epoxy resin having a 3,4-epoxycyclohexenyl skeleton, the glass transition temperature is high while maintaining high transparency, and the heat resistance of the cured product can be increased.

  As the alicyclic epoxy resin having a 3,4-epoxycyclohexenyl skeleton, for example, a liquid resin at room temperature having a plurality of 3,4-epoxycyclohexenyl skeletons in one molecule can be used. Specifically, for example, 3,4-epoxycyclohexenylmethyl-3 ', 4'-epoxycyclohexene carboxylate can be used. In addition, the following structure:

(Wherein n represents a positive integer), ε-caprolactone modified 3,4-epoxycyclohexenylmethyl-3 ', 4'-epoxycyclohexanecarboxylate, and the following compound comprising adipic acid:

Etc. can be used.

  By using the polyfunctional epoxy resin having the structure represented by the formula (II), the glass transition temperature is high and the heat resistance of the cured product can be enhanced while maintaining high transparency.

  In the formula (II), the organic group R may be arbitrary as long as the effect of the present invention based on the alicyclic epoxy structure in the square brackets is not impaired. Examples include branched hydrocarbon groups. M in the formula (II) is not particularly limited, but is, for example, 1 to 5, and n is not particularly limited, but is preferably in a range that loses fluidity at normal temperature (25 ° C.) and becomes solid. Production of a transparent film can be facilitated by being solid at room temperature.

  As a polyfunctional epoxy resin having a structure represented by the formula (II), for example, 1,2-epoxy-4- (2-oxiranyl) cyclohexane is added to 2,2-bis (hydroxymethyl) -1-butanol. What is obtained can be used. Specifically, for example, those represented by the following formula (II-a) can be used.

(In the formula, three n's each independently represent a positive integer.)
For example, the polyfunctional epoxy resin has a melting point of about 85 ° C. and the molecular weight is not particularly limited, but is, for example, about 2000 to 3000 in terms of weight average molecular weight.

  Further, as the low refractive index resin, for example, a hydrogenated bisphenol type epoxy resin can be used. As the hydrogenated bisphenol type epoxy resin, for example, bisphenol A type, bisphenol F type, bisphenol S type and the like can be used. Preferably, a hydrogenated bisphenol type epoxy resin that is solid at room temperature is used. Although hydrogenated bisphenol-type epoxy resin that is liquid at room temperature can be used, when preparing a prepreg by impregnating the resin composition into a glass fiber base material and drying it, it becomes sticky to the touch. However, in many cases, the prepreg cannot be dried, and the handling property of the prepreg may be deteriorated.

  In the present invention, the refractive index of the low refractive index resin is preferably 1.47 to 1.53. For example, when the refractive index of the glass fiber is 1.563, the low refractive index resin preferably has a refractive index of around 1.5. When the refractive index of the glass fiber is n, n−0.04 to n−. The thing of the range of 0.08 is preferable.

  In the present invention, a high refractive index resin and a low refractive index resin as exemplified above are mixed, and the resin composition is prepared so that the refractive index approximates the refractive index of the glass fiber. The resin composition is prepared such that the glass transition temperature (Tg) of the cured resin is preferably 200 ° C. or higher, more preferably 220 ° C. or higher, and further preferably 230 ° C. or higher. Due to the high glass transition temperature of the cured resin, the heat resistance of the transparent film can be increased. The upper limit of the glass transition temperature is not particularly limited, but about 280 ° C. is practically the upper limit.

  In the present invention, the glass transition temperature is a value measured according to the JIS C6481 TMA method.

  In the present invention, a curing initiator (curing agent) can be blended in the resin composition. Examples of the curing initiator include tertiary amines such as triphenylphosphine, triethylamine, and triethanolamine, and curing catalysts such as 2-ethyl-4-imidazole, 4-methylimidazole, and 2-ethyl-4-methylimidazole. Can be used. The blending amount of the curing catalyst in the resin composition is preferably in the range of 0.5 to 5.0 PHR.

  Moreover, a cationic hardening | curing agent can be used as a hardening initiator. By using a cationic curing agent, the transparency of the cured resin can be increased. Examples of the cationic curing agent include aromatic sulfonium salts, aromatic iodonium salts, aromatic ammonium salts, aluminum chelates, and boron trifluoride amine complexes. The blending amount of the cationic curing agent in the resin composition is preferably in the range of 0.2 to 3.0 PHR.

  An organic metal salt can be used as a curing initiator. Examples of the organic metal salts include salts of organic acids such as octanoic acid, stearic acid, acetylacetonate, naphthenic acid, and salicylic acid with metals such as Zn, Cu, and Fe. These may be used alone or in combination of two or more. Of these, zinc octoate is preferable. By using zinc octoate as the curing initiator, the glass transition temperature of the cured resin can be increased. The amount of the organic metal salt such as zinc octoate in the resin composition is preferably in the range of 0.01 to 0.1 PHR.

  The resin composition can be prepared by blending the high refractive index resin, the low refractive index resin, and a curing initiator as necessary. This resin composition can be prepared as a varnish by diluting with a solvent as necessary. Examples of the solvent include benzene, toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, acetone, methanol, ethanol, isopropyl alcohol, 2-butanol, ethyl acetate, butyl acetate, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, diacetone. Alcohol, N, N′-dimethylacetamide and the like can be mentioned.

  As the glass fiber constituting the glass fiber base material, fiber of E glass or NE glass is preferably used from the viewpoint of enhancing the impact resistance of the transparent film and being inexpensive and stable in supply quality. The E glass fiber is also called an alkali-free glass fiber, and is a glass fiber that is widely used as a glass fiber for resin reinforcement. NE glass is NewE glass. T glass fibers can also be used. T glass has better mechanical and thermal properties than general-purpose E glass.

  Moreover, it is preferable to surface-treat glass fiber with the silane coupling agent normally used as a glass fiber processing agent in order to improve impact resistance. The refractive index of the glass fiber is preferably 1.55 to 1.57, more preferably 1.555 to 1.565. If the refractive index of glass fiber is this range, the transparent film excellent in visibility can be obtained. As the glass fiber substrate, a glass fiber woven fabric or non-woven fabric can be used.

  And a prepreg can be prepared by impregnating the glass fiber base material with the varnish of the resin composition, heating and drying. The drying conditions are not particularly limited, but a drying temperature of 100 to 160 ° C. and a drying time of 1 to 10 minutes are preferable.

  Next, one or a plurality of the prepregs are stacked and heated and pressed to cure the resin composition to obtain a transparent film. The conditions for the heat and pressure molding are not particularly limited, but a temperature of 150 to 200 ° C., a pressure of 1 to 4 MPa, and a time of 10 to 120 minutes are preferable.

  In the transparent film obtained as described above, a resin matrix formed by polymerizing a high refractive index resin and a low refractive index resin has a high glass transition temperature, and a transparent film excellent in heat resistance is obtained. be able to.

  Moreover, the high refractive index resin and the low refractive index resin as exemplified above are excellent in transparency, and a transparent film ensuring high transparency can be obtained. In this transparent film, the content of the glass fiber substrate is preferably in the range of 25 to 65 mass%, more preferably in the range of 35 to 60 mass%. If it is this range, while being able to obtain high impact resistance with the reinforcement effect by glass fiber, sufficient transparency can be obtained. Moreover, when there are too many glass fibers, the surface unevenness | corrugation will become large and transparency will also fall. On the other hand, when there are too few glass fibers, the thermal expansion coefficient of a transparent film may become large.

  Note that a plurality of thin glass fiber substrates can be used in order to obtain high transparency. Specifically, a glass fiber substrate having a thickness of 50 μm or less can be used, and two or more of them can be used in an overlapping manner. The thickness of the glass fiber substrate is not particularly limited, but about 10 μm is a practical lower limit. The number of glass fiber substrates is not particularly limited, but about 20 is the practical upper limit. Thus, when manufacturing a transparent film using a plurality of glass fiber base materials, each glass fiber base material is impregnated with a resin composition and dried to prepare a prepreg, and a plurality of the prepregs are stacked. A transparent film can be obtained by heat and pressure molding, but the resin composition is impregnated and dried in a state where a plurality of glass fiber substrates are stacked, and a prepreg is produced by heating and pressure molding the prepreg. Thus, a transparent film may be obtained.

  The transparent film of the present invention thus obtained is excellent in transparency and heat resistance, and can impart conductivity to the surface of the transparent film with ITO, and is suitable for a liquid crystal display or the like.

  In addition, the transparent film of the present invention has high dimensional stability, and particularly has a low coefficient of thermal expansion (CTE) in the plane direction (XY direction). For example, the thermal expansion coefficient in the plane direction at 50 to 150 ° C. can be set to 30 ppm / ° C. or less.

  Moreover, the surface of a transparent film is smooth, for example, surface roughness (Rz) can be 1 micrometer or less. Furthermore, the smoothness can be further improved by providing a hard coat layer and a gas barrier layer.

  The transparent film of the present invention is an LED illumination, LED backlight by a flat panel display such as a liquid crystal display, plasma display, EL display, etc., organic EL illumination, flexible solar cell, etc., or a laminate of a transparent film and a metal layer. It is suitable for reflective substrates such as organic EL lighting and organic EL displays, and electrophoretic electronic paper.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples at all.

The followings were used as the blending components of Examples and Comparative Examples.
High refractive index resin / Unidic V-8001, manufactured by DIC Corporation, thermosetting solvent-soluble imide resin, wholly aromatic, solvent γ-butyrolactone, viscosity 0.1 to 10 Pa · s (25 ° C.), nonvolatile content 30-50 mass%, acid value 40-70 mgKOH / g, refractive index 1.75
・ Unidic V-8002, manufactured by DIC Corporation, thermosetting solvent-soluble imide resin, alicyclic, solvent ethyl diglycol acetate, viscosity 50 to 150 Pa · s (25 ° C.), nonvolatile content 35 to 45 mass% , Acid value 45-65 mgKOH / g, Refractive index 1.53
-Techmore VG3101, manufactured by Printec Co., Ltd., trifunctional epoxy resin having a molecular structure represented by the above formula (Ia), refractive index 1.59
-JER1003, manufactured by Japan Epoxy Resin Co., Ltd., solid bisphenol type epoxy resin, epoxy equivalent 670-770, softening point 89 ° C., refractive index 1.60
Low refractive index resin / Unidic V-8002, manufactured by DIC Corporation, Celoxide 2021P, manufactured by Daicel Chemical Industries, Ltd., 3,4-epoxycyclohexenylmethyl-3 ′, 4′-epoxycyclohexene carboxylate, refractive index 1.50
EHPE3150, manufactured by Daicel Chemical Industries, Ltd., 2,2-bis (hydroxymethyl) -1-butanol 1,2-epoxy-4- (2-oxiranyl) cyclohexane adduct, epoxy equivalent 185, molecular weight 2234, refraction Rate 1.51
YL7170, manufactured by Japan Epoxy Resin Co., Ltd., hydrogenated bisphenol A type epoxy resin, epoxy equivalent 1200, refractive index 1.51)
Curing initiator · SI-150L, available from Sanshin Chemical Industry Co., Ltd., cationic curing agent (SbF ₆ ^- sulfonium salt)
Triphenylphosphine The above-described high refractive index resin and low refractive index resin are blended in the amounts shown in Table 1, and further a curing initiator is blended, to which 50 parts by mass of toluene and 50 parts by mass of methyl ethyl ketone are added, and the temperature The resin composition varnish was prepared by stirring and dissolving at 70 ° C.

  Next, a glass fiber cloth with a thickness of 25 μm (Asahi Kasei Electronics Co., Ltd., product number “1037”, E glass fiber, refractive index 1.56, or Nittobo Co., Ltd., product number “1037”, T glass fiber, refraction A prepreg was prepared by impregnating the varnish of the above resin composition at a rate of 1.53) and heating at 150 ° C. for 5 minutes to remove the solvent and to semi-cur the resin.

  Then, two prepregs were stacked, set in a press machine, and heat-press molded under conditions of 170 ° C., 2 MPa, 15 minutes to obtain a transparent film having a resin content of 63 mass% and a thickness of 70 μm. .

The following measurements and evaluations were performed on the transparent films of Examples and Comparative Examples thus obtained.
[transparency]
Using a haze meter NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd., the haze value of the transparent film was measured according to JISK7136.
[Glass-transition temperature]
The resin component was scraped off from the prepared prepreg, and a resin plate obtained by direct pressure molding under the same conditions as the molding conditions of the transparent film was used as a test sample and measured according to the JIS C6481 TMA method.

  The results of these measurements and evaluations are shown in Table 1.

  From Table 1, in Examples 1-7, when a thermosetting solvent-soluble imide resin was used as at least one of the high refractive index resin and the low refractive index resin, the transparent film had a high glass transition temperature and excellent heat resistance. there were. Furthermore, high transparency was maintained.

  On the other hand, in Comparative Example 1, when an epoxy resin was used as the high refractive index resin and the low refractive index resin, sufficient heat resistance was not obtained as compared with Examples 1-7.

Claims (7)

  A transparent film in which a transparent resin is held on a glass fiber substrate, wherein the transparent resin-forming resin composition contains a thermosetting solvent-soluble imide resin. The thermosetting solvent-soluble imide resin has the following formula (A):

(In the formula, each R ₁ independently represents a divalent aromatic group or alicyclic group, each R ₂ independently represents a trivalent aromatic group or alicyclic group, and n represents a positive integer. The transparent film according to claim 1, wherein the transparent film is represented by:   The transparent film according to claim 1 or 2, wherein the resin composition for forming a transparent resin contains an epoxy resin. The resin composition for forming the transparent resin has the following formula (I):

(In the formula, R ¹ represents a hydrogen atom or a methyl group, R ² represents a divalent organic group, and R ^{3 to} R ¹⁰ each independently represent a hydrogen atom, a substituent, or an epoxy group-containing molecular chain. The transparent film according to claim 1, comprising a polyfunctional epoxy resin represented by the formula:   The transparent film according to any one of claims 1 to 4, wherein the resin composition for forming a transparent resin contains an alicyclic epoxy resin having a 3,4-epoxycyclohexenyl skeleton. The resin composition for forming the transparent resin has the following formula (II):

6. A polyfunctional epoxy resin having a structure represented by the formula: wherein R represents an m-valent organic group, and m and n represent positive integers. The transparent film according to claim 1.   The transparent film according to claim 1, wherein the resin composition for forming a transparent resin contains a cyanate resin.