Optical film, method for manufacturing optical film, transparent conductive film, and gas barrier film

Abstract

Provided is an optical film that is thin, has superior heat resistance, and readily forms a functional layer such as a transparent conductive layer or a gas barrier layer. This optical film comprises a process film and a cured resin layer, wherein the cured resin layer is a layer comprising the cured product of a curable resin composition that includes a polymer component (A) and a curable monomer (B), and [a] regarding characteristic values that are obtained through a dynamic viscoelasticity measurement from 25°C to 280°C at a temperature increase speed of 3°C / second, (I) at least one loss tangent peak is present on a curve expressing the change in loss tangent relative to temperature, and the peak temperature of each loss tangent peak is 150°C or greater, and (II) the storage elastic modulus decrease percentage, which is the percentage of decrease in the storage elastic modulus, from 25°C to 150°C is 40% or less, or [b] the glass transition temperature of the polymer component (A) is 250°C or greater, at least one loss tangent peak is present on the aforementioned curve, and the peak temperature of each loss tangent peak is 150°C or greater.

Description

[Technical Field]

[0001] The present invention relates to an optical film, a method for producing an optical film, a transparent conductive film, and a gas barrier film. [Background technology]

[0002] Transparent conductive films, which have a transparent conductive layer formed on the surface of a base film, are used in liquid crystal displays, EL (electroluminescence) displays, EC (electrochromic) displays, solar cells, electromagnetic shielding films for electromagnetic shielding, film sensors such as transparent touch panels, etc. In the manufacturing process of transparent conductive films, processing is often carried out under harsh conditions involving heating, such as sputtering of metal compounds and subsequent annealing treatment. For this reason, high heat resistance is required for the optical film that serves as the substrate on which the transparent conductive layer is formed. Therefore, it is thought that this problem can be solved by using a heat-resistant optical film formed from a highly heat-resistant resin such as a polyimide resin (for example, a resin with a glass transition temperature of 250°C or higher).

[0003] Gas barrier films are widely used as substrate materials and sealing materials. Gas barrier films are required to have high gas barrier properties that can suppress the transmission of water vapor, oxygen, etc. In addition, for example, they are required to have high light transmittance so as not to impair the visibility of the object to which the gas barrier film is attached, such as an electronic device, and to avoid impairing the lightweight of the object to which the gas barrier film is attached. From the above viewpoint, it is known to prepare an optical film by applying a curable composition containing a curable compound onto a support, curing the curable compound contained in the obtained coating layer to form a thin cured resin layer, and then forming a gas barrier layer made of an inorganic film or the like on the cured resin layer of this optical film directly or via another layer. Hereinafter, the property of inhibiting the transmission of water vapor and oxygen will be referred to as "gas barrier property," a layer having gas barrier property will be referred to as a gas barrier layer, and a film having a gas barrier layer will be referred to as a "gas barrier film." For example, Patent Document 1 describes a method of forming a cured resin layer on a process sheet using a curable resin composition containing a resin such as a polysulfone resin and a curable monomer, and then forming a gas barrier layer on the cured resin layer. This production method results in a gas barrier film having a cured resin layer on one surface and a gas barrier layer on the other surface.

[0004] In recent years, there has been a demand for thinner optical films in order to further improve the transparency and flexibility of transparent conductive films and gas barrier films, and to further reduce their weight. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2013 / 065812 Summary of the Invention [Problem to be solved by the invention]

[0006] Conventional optical films having a curable resin layer have the following problems. First, the cured resin layer is required to have solvent resistance so as to avoid damage caused by solvents when coated with a liquid such as a polysilazane-based coating liquid for a gas barrier layer or a silver nanowire dispersion liquid for a transparent conductive layer. In addition, when the optical film is exposed to high temperatures, the cured resin layer is required to withstand the thermal load when forming the transparent conductive layer, the gas barrier layer, etc. by suppressing a significant decrease in storage modulus or an increase in linear expansion coefficient. These properties are becoming increasingly desirable as the need for thinner optical films increases for transparency and weight reduction, and further improvement is required.

[0007] In view of the above problems, an object of the present invention is to provide an optical film that is thin, has excellent heat resistance, and is easy to form functional layers such as a transparent conductive layer and a gas barrier layer, and a method for producing the same. Another object of the present invention is to provide a transparent conductive film and a gas barrier film that are easy to produce, are thin, and have excellent heat resistance. [Means for solving the problem]

[0008] As a result of extensive research into solving the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by providing an optical film comprising a process film and a cured resin layer, in which the cured resin layer is a layer made of a cured product of a curable resin composition, and in which, in a measurement curve obtained by measuring the dynamic viscoelasticity of the cured resin layer, the peak temperatures of all loss tangent peaks are equal to or higher than a predetermined temperature, and further the cured resin layer has predetermined physical properties, thereby completing the present invention. That is, the present invention provides the following [1] to [6]. [1] An optical film comprising a cast film and a cured resin layer, wherein the cured resin layer is a layer made of a cured product of a curable resin composition containing a polymer component (A) and a curable monomer (B), and wherein the optical film satisfies the following (I) and (II) in terms of characteristic values obtained by dynamic viscoelasticity measurement at a heating rate of 3°C / sec from 25°C to 280°C. (I) In the curve showing the change in loss tangent with respect to temperature, there is one or more loss tangent peaks, and the peak temperatures of all loss tangent peaks are 150°C or higher. (II) The storage modulus decrease rate, which is the rate of decrease in storage modulus from 25° C. to 150° C., calculated by the following formula (1) is 40% or less. Storage modulus reduction rate = (storage modulus at 25°C - storage modulus at 150°C) ÷ storage modulus at 25°C × 100 (%) Formula (1) [2] An optical film comprising a cast film and a cured resin layer, wherein the cured resin layer is a layer made of a cured product of a curable resin composition containing a polymer component (A) and a curable monomer (B), wherein the glass transition temperature of the polymer component (A) is 250°C or higher, and a curve showing the change in loss tangent with temperature obtained by dynamic viscoelasticity measurement from 25°C to 280°C at a heating rate of 3°C / sec has one or more loss tangent peaks, and the peak temperatures of all loss tangent peaks are 150°C or higher. [3] The optical film according to the above [1] or [2], wherein the thickness of the cured resin layer is 20 μm or less. [4] A first step of forming a curable resin layer composed of a curable resin composition containing a polymer component (A) and a curable monomer (B) on a processing film; a second step of irradiating the curable resin layer with at least one of an energy ray and an electron beam to at least partially cure the curable resin layer; and The method for producing an optical film includes, after the start of the second step, a third step of performing a heat treatment of heating the curable resin layer to 150°C or higher to obtain a cured resin layer. [5] A transparent conductive film comprising: an optical film according to any one of the above [1] to [3]; and a transparent conductive layer provided on the cured resin layer of the optical film. [6] A gas barrier film comprising: an optical film according to any one of the above [1] to [3]; and a gas barrier layer provided on the cured resin layer of the optical film. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an optical film that is thin, has excellent heat resistance, and is easy to form functional layers such as a transparent conductive layer, a gas barrier layer, etc., and a method for producing the same. Furthermore, according to the present invention, it is possible to provide a transparent conductive film and a gas barrier film that are easy to produce, are thin, and have excellent heat resistance. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view schematically illustrating an example of the configuration of an optical film according to an embodiment of the present invention. [Figure 2] 1 is a cross-sectional view schematically illustrating an example of the configuration of a transparent conductive film and a gas barrier film according to an embodiment of the present invention. [Figure 3] 1A to 1C are process diagrams illustrating an example of a method for producing an optical film. DETAILED DESCRIPTION OF THE INVENTION

[0011] In this specification, the expression "XX to YY" means "XX or more and YY or less." In this specification, for example, "(meth)acrylic acid" refers to both "acrylic acid" and "methacrylic acid," and the same applies to other similar terms. Hereinafter, each optical film according to an embodiment of the present invention will be described.

[0012] 1. Optical films An optical film according to one embodiment of the present invention comprises a casting film and a cured resin layer, wherein the cured resin layer is a layer made of a cured product of a curable resin composition containing a polymer component (A) and a curable monomer (B), and the optical film satisfies the following (I) and (II) in terms of characteristic values obtained by dynamic viscoelasticity measurement at a heating rate of 3°C / sec from 25°C to 280°C: (I) In the curve showing the change in loss tangent with respect to temperature, there is one or more loss tangent peaks, and the peak temperatures of all loss tangent peaks are 150°C or higher. (II) The storage modulus decrease rate, which is the rate of decrease in storage modulus from 25° C. to 150° C., calculated by the following formula (1) is 40% or less. Storage modulus reduction rate = (storage modulus at 25°C - storage modulus at 150°C) ÷ storage modulus at 25°C × 100 (%) Formula (1)

[0013] As a result of extensive investigations, the present inventors have found the following. (i) By forming the cured resin layer from a cured product of a curable resin composition containing a polymer component (A) and a curable monomer (B), effects such as improved solvent resistance and removability from the casting film can be achieved. (ii) In addition, regarding the characteristic values obtained by dynamic viscoelasticity measurement at a heating rate of 3°C / sec from 25°C to 280°C, (I) if there is at least one loss tangent peak in the curve showing the change in loss tangent with temperature, and all of the loss tangent peaks have peak temperatures of 150°C or higher, the cured resin layer can exhibit small changes in storage modulus and linear expansion coefficient at high temperatures. Furthermore, (II) if the storage modulus decrease rate, which is the rate of decrease in storage modulus from 25°C to 150°C calculated using the above formula (1), is 40% or less, the cured resin layer can withstand the thermal loads encountered when forming functional layers such as a transparent conductive layer or a gas barrier layer. (iii) Furthermore, the inclusion of a curable monomer in the curable resin composition can suppress curling after peeling the casting film and facilitate peeling the casting film.

[0014] Another embodiment of the optical film of the present invention includes a casting film and a cured resin layer. The cured resin layer is a layer made of a cured product of a curable resin composition containing a polymer component (A) and a curable monomer (B), wherein the polymer component (A) has a glass transition temperature of 250°C or higher, and a curve showing the change in loss tangent with temperature obtained by dynamic viscoelasticity measurement from 25°C to 280°C at a heating rate of 3°C / sec has one or more loss tangent peaks, and all of the loss tangent peaks have peak temperatures of 150°C or higher.

[0015] As a result of extensive investigations, the present inventors have found the following. In addition to the above items (i) and (iii), (iv) if the glass transition temperature of polymer component (A) is 250°C or higher, and a curve showing the change in loss tangent with temperature obtained by dynamic viscoelasticity measurement at a heating rate of 3°C / sec from 25°C to 280°C has one or more loss tangent peaks, and the peak temperatures of all loss tangent peaks are 150°C or higher, then the change in storage modulus and linear expansion coefficient of the cured resin layer at high temperatures can be reduced.

[0016] The loss tangent peak is obtained by peak separation of a curve showing the change in loss tangent with temperature obtained by dynamic viscoelasticity measurement at a heating rate of 3°C / sec from 25°C to 280°C, using a Gaussian function as a fitting function. The temperature at the apex of each peak is defined as the peak temperature. The peak temperature of the loss tangent peak is specifically measured by the method described in the Examples.

[0017] By ensuring that the peak temperatures of all loss tangent peaks are 150°C or higher, no loss tangent peaks exist in the temperature range below 150°C. Therefore, even if the heating temperature during, for example, the formation of a transparent conductive material layer by sputtering, the annealing of a transparent conductive material layer containing a silver nanofiller, or the formation of a gas barrier layer reaches approximately 150°C, the optical film is less likely to deform due to heating, making it easier to form a transparent conductive layer or a gas barrier layer. This also makes it easier to obtain a transparent conductive film or a gas barrier film that has the required electrical conductivity and gas barrier properties. From this perspective, it is more preferable that the peak temperatures of all loss tangent peaks be 200°C or higher.

[0018] In the measurement curve of loss tangent obtained by the dynamic viscoelasticity measurement, a method for making the peak temperatures of all loss tangent peaks of the optical film 150°C or higher includes carrying out the third step in the manufacturing method of the optical film described below.

[0019] In an optical film according to one embodiment of the present invention, as defined in (II) above, the storage modulus decrease rate, which is the rate of decrease in storage modulus from 25°C to 150°C, calculated by the above formula (1) is 40% or less. The storage modulus decrease rate is preferably 35% or less, more preferably 30% or less. Specifically, the storage modulus decrease rate is measured by the method described in the examples. When the storage modulus reduction rate is within the above range, the optical film can withstand the heat load that occurs when functional layers such as a transparent conductive layer and a gas barrier layer are formed. As a method for adjusting the storage modulus reduction rate within the above range, for example, a resin having a high glass transition temperature, as described below, may be used as the polymer component (A).

[0020] For ease of understanding, the following description will be made with reference to the drawings and with the use of the symbols shown in the drawings to explain the structure of each layer and film, but the present invention is not limited to the illustrated embodiments.

[0021] FIG. 1 shows a specific example of the configuration of the optical film according to an embodiment of the present invention. 1(a) has a processing film 1 on one side of a cured resin layer 2. As will be described later, a functional layer such as a transparent conductive layer or a gas barrier layer is provided on the side of the cured resin layer 2 opposite to the side on which the processing film 1 is provided, and the optical film 10A is used as a transparent conductive film or a gas barrier film. The optical film 10B shown in FIG. 1(b) has casting films 1A and 1B on both sides of the cured resin layer 2. When a functional layer such as a transparent conductive layer or a gas barrier layer is to be provided, one of the casting films 1A and 1B is peeled off and removed. Then, the functional layer such as a transparent conductive layer or a gas barrier layer is provided on the exposed surface.

[0022] 1-1. Cured resin layer The cured resin layer of the optical film according to the embodiment of the present invention is made of a cured product of a curable resin composition containing a polymer component (A) and a curable monomer (B). The cured resin layer may be a single layer or may include multiple laminated layers.

[0023] [Polymer component (A)] In an optical film according to one embodiment of the present invention, the glass transition temperature (Tg) of the polymer component (A) is 250°C or higher. The Tg of the polymer component (A) is preferably 290°C or higher, more preferably 320°C or higher. When the Tg of the polymer component (A) is 250°C or higher, it is easier to avoid a decrease in heat resistance due to the influence of a polymer produced when a curable composition is prepared together with the curable monomer (B) described below and the cured composition is cured. As a result, the change in storage modulus and linear expansion coefficient of the cured resin layer at high temperatures can be reduced, and when a functional layer such as a transparent conductive layer or a gas barrier layer is formed, it is easier to prevent the cured resin layer from being affected by heating during film formation or heating during annealing treatment, etc., and causing deformation or the like. Here, Tg refers to the temperature at the maximum point of the loss tangent (tanδ) obtained by viscoelasticity measurement (measurement in tension mode at a frequency of 11 Hz, a heating rate of 3°C / min in the range of 0 to 250°C), expressed as loss modulus / storage modulus.

[0024] The weight average molecular weight (Mw) of the polymer component (A) is preferably 100,000 or more, more preferably 200,000 or more, and is preferably 1,000,000 or less, more preferably 800,000 or less, and even more preferably 500,000 or less. The molecular weight distribution (Mw / Mn) of the polymer component (A) is preferably in the range of 1.0 to 5.0, more preferably 2.0 to 4.5. The weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) are values measured by gel permeation chromatography (GPC) in terms of polystyrene. By setting Mw to 100,000 or more, the breaking elongation of the cured resin layer can be easily increased.

[0025] As the polymer component (A), a thermoplastic resin is preferred, and an amorphous thermoplastic resin is more preferred. The use of an amorphous thermoplastic resin makes it easier to obtain a cured resin layer with excellent optical isotropy and an optical film with excellent transparency. Furthermore, since amorphous thermoplastic resins are generally easily soluble in organic solvents, a cured resin layer can be efficiently formed using a solution casting method, as described below. Here, the term "amorphous thermoplastic resin" refers to a thermoplastic resin whose melting point is not observed in differential scanning calorimetry.

[0026] The polymer component (A) is preferably soluble in a general-purpose organic solvent having a low boiling point, such as ethyl acetate or methyl ethyl ketone (MEK), etc. If the polymer component (A) is soluble in a general-purpose organic solvent, it becomes easy to form a cured resin layer by coating.

[0027] Particularly preferred polymer component (A) is an amorphous thermoplastic resin having a Tg of 250° C. or higher, which is soluble in a general-purpose organic solvent having a low boiling point, such as ethyl acetate or methyl ethyl ketone.

[0028] From the viewpoint of heat resistance, the polymer component (A) is preferably a thermoplastic resin having a ring structure such as an aromatic ring structure or an alicyclic structure, and more preferably a thermoplastic resin having an aromatic ring structure.

[0029] Specific examples of the polymer component (A) include polyimide resins and polyarylate resins having a Tg of 250°C or higher. These resins generally have a high Tg and excellent heat resistance, and because they are amorphous thermoplastic resins, they can be used to form coating films by solution casting. Among these, polyimide resins are preferred because they have a high Tg and excellent heat resistance, and are easily obtained as resins that are soluble in general-purpose organic solvents while exhibiting good heat resistance.

[0030] The polyimide resin is not particularly limited as long as it does not impair the effects of the present invention, and examples thereof include aromatic polyimide resins, aromatic (carboxylic acid component)-aliphatic cyclic (diamine component) polyimide resins, aliphatic cyclic (carboxylic acid component)-aromatic (diamine component) polyimide resins, aliphatic cyclic polyimide resins, and fluorinated aromatic polyimide resins. In particular, polyimide resins having a fluoro group in the molecule are preferred.

[0031] Specifically, a polyimide resin obtained by using an aromatic diamine compound and a tetracarboxylic dianhydride, polymerizing the polyamic acid, and then chemically imidizing the polyamic acid is preferred.

[0032] Any aromatic diamine compound can be used as long as it is soluble in a common solvent (e.g., N,N-dimethylacetamide (DMAC)) and gives a polyimide having a predetermined transparency upon reaction with the tetracarboxylic dianhydride used in combination. Specifically, m-phenylenediamine, p-phenylenediamine, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminobenzophenone, 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 2,2-bis(4-aminophenyl)propane, 2,2-bis(3-aminophenyl)propane, 2-(3-aminophenyl)propane, 2,2-bis(4-aminophenyl)-2-(4-aminophenyl)propane, 2,2-bis(4-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 2,2-bis(3-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 2-(3-aminophenyl)-2-(4-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(3-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, 3,3'-bis(4-aminophenoxy)biphenyl, 3,4'-bis(3-aminophenoxy)biphenyl, bis[4-(4-aminophenoxy)phenyl]sulfide, bis[3-(4-aminophenoxy)phenyl]sulfide, bis[4-(3-aminophenoxy)phenyl]sulfide, bis[3-(4-aminophenoxy)phenyl]sulfide, bis[3-(3-aminophenoxy)phenyl]sulfide, bis[3-(4-aminophenoxy)phenyl]sulfide, bis[3-(4-aminophenoxy)phenyl]sulfone, bis[4-(4-aminophenyl)]sulfone, bis[3-(3-aminophenoxy)phenyl]sulfone, bis[ 4-(3-aminophenyl) sulfone, bis[4-(3-aminophenoxy)phenyl] ether, bis[4-(4-aminophenoxy)phenyl] ether, bis[3-(3-aminophenoxy)phenyl] ether, bis[4-(3-aminophenoxy)phenyl]methane, bis[4-(4-aminophenoxy)phenyl]methane, bis[3-(3-aminophenoxy)phenyl]methane, bis[3-(4-aminophenoxy)phenyl]methane, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2-bis[4 -(4-aminophenoxy)phenyl]propane, 2,2-bis[3-(3-aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 2,2-bis[3-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 2,2-bis[3-(4-aminophenoxy)phenyl]-1,1,1,3,3 ,3-hexafluoropropane, 1,3-bis[4-(4-amino-6-trifluoromethylphenoxy)-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-amino-6-fluoromethylphenoxy)-α,α-dimethylbenzyl]benzene, 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 3,3'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, and the like.

[0033] These aromatic diamine compounds may be used alone or in combination of two or more kinds thereof. From the viewpoint of transparency and heat resistance, preferred aromatic diamine compounds include 2,2-bis(4-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 2,2-bis(3-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 2-(3-aminophenyl)-2-(4-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 2,2-bis[4-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, and 2,2-bis[3-(3-aminophenoxy)phenyl]-1,1,1,3,3 Examples of aromatic diamine compounds having a fluoro group include 1,3-hexafluoropropane, 2,2-bis[3-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 1,3-bis[4-(4-amino-6-trifluoromethylphenoxy)-α,α-dimethylbenzyl]benzene, 3,3'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, and 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl. It is preferred that at least one of the aromatic diamine compounds used be an aromatic diamine compound having a fluoro group, with 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl being particularly preferred. Using an aromatic diamine compound having a fluoro group makes it easier to achieve transparency, heat resistance, and solubility in solvents.

[0034] As with the aromatic diamine compounds, any tetracarboxylic acid dianhydride can be used as long as it is soluble in common solvents (e.g., N,N-dimethylacetamide (DMAC)) and provides a polyimide having a predetermined transparency. Specific examples include 4,4'-(1,1,1,3,3,3-hexafluoropropane-2,2-diyl)diphthalic dianhydride, pyromellitic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 1,4-hydroquinone dibenzoate-3,3',4,4'-tetracarboxylic dianhydride, 3,3',4,4'-biphenyl tetracarboxylic dianhydride, and 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride. These tetracarboxylic acid dianhydrides may be used alone, or two or more types of tetracarboxylic acid dianhydrides may be used together. From the viewpoints of transparency, heat resistance, and solubility in solvents, it is preferable to use a tetracarboxylic acid dianhydride having at least one type of fluoro group, such as 4,4'-(1,1,1,3,3,3-hexafluoropropane-2,2-diyl)diphthalic dianhydride.

[0035] The polymerization to form polyamic acid can be carried out by reacting the aromatic diamine compound and tetracarboxylic dianhydride while dissolving the resulting polyamic acid in a solvent that the polyamic acid is soluble in. Examples of the solvent that can be used for the polymerization to form polyamic acid include N,N-dimethylacetamide, N,N-dimethylformamide, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, and dimethyl sulfoxide.

[0036] The polymerization reaction to form polyamic acid is preferably carried out in a reaction vessel equipped with a stirrer while stirring. For example, there may be mentioned a method of dissolving a predetermined amount of aromatic diamine compound in the solvent, adding tetracarboxylic dianhydride while stirring, and carrying out a reaction to obtain polyamic acid, a method of dissolving tetracarboxylic dianhydride in a solvent, adding aromatic diamine compound while stirring, and carrying out a reaction to obtain polyamic acid, and a method of alternately adding aromatic diamine compound and tetracarboxylic dianhydride and carrying out a reaction to obtain polyamic acid.

[0037] There are no particular restrictions on the temperature of the polymerization reaction to form polyamic acid, but it is preferably carried out at a temperature of 0 to 70° C., more preferably 10 to 60° C., and even more preferably 20 to 50° C. By carrying out the polymerization reaction within the above range, it is possible to obtain a high-molecular-weight polyamic acid that is less colored and has excellent transparency.

[0038] The aromatic diamine compound and tetracarboxylic dianhydride used in the polymerization to form polyamic acid are generally used in roughly equimolar amounts, but the molar ratio of tetracarboxylic dianhydride to aromatic diamine compound (molar ratio) can be varied within a range of 0.95 to 1.05 to control the degree of polymerization of the resulting polyamic acid. The molar ratio of tetracarboxylic dianhydride to aromatic diamine compound is preferably within a range of 1.001 to 1.02, more preferably 1.001 to 1.01. By using a slight excess of tetracarboxylic dianhydride relative to the aromatic diamine compound, the degree of polymerization of the resulting polyamic acid can be stabilized and units derived from the tetracarboxylic dianhydride can be positioned at the polymer terminals, resulting in a polyimide with little coloration and excellent transparency.

[0039] The concentration of the resulting polyamic acid solution is preferably adjusted to an appropriate concentration (for example, about 10 to 30% by mass) so that the viscosity of the solution is kept appropriate and handling in the subsequent steps is easy.

[0040] An imidizing agent is added to the resulting polyamic acid solution to carry out a chemical imidization reaction. As the imidizing agent, carboxylic acid anhydrides such as acetic anhydride, propionic anhydride, succinic anhydride, phthalic anhydride, and benzoic anhydride can be used. Acetic anhydride is preferred from the viewpoints of cost and ease of removal after the reaction. The equivalent weight of the imidizing agent used is equal to or greater than the equivalent weight of the amide bond in the polyamic acid to be subjected to the chemical imidization reaction, and is preferably 1.1 to 5 times, and more preferably 1.5 to 4 times, the equivalent weight of the amide bond. By using a slight excess of the imidizing agent relative to the amide bond in this way, the imidization reaction can be carried out efficiently even at a relatively low temperature.

[0041] In the chemical imidization reaction, an aliphatic, aromatic, or heterocyclic tertiary amine such as pyridine, picoline, quinoline, isoquinoline, trimethylamine, triethylamine, etc. can be used as an imidization accelerator. By using such amines, the imidization reaction can be carried out efficiently at a low temperature, and as a result, coloration during the imidization reaction can be suppressed, making it easier to obtain a more transparent polyimide.

[0042] There are no particular restrictions on the temperature for the chemical imidization reaction, but it is preferably carried out at a temperature of 10° C. or higher but lower than 50° C., and more preferably at a temperature of 15° C. or higher but lower than 45° C. By carrying out the chemical imidization reaction at a temperature of 10° C. or higher but lower than 50° C., coloration during the imidization reaction is suppressed, and a polyimide with excellent transparency can be obtained.

[0043] Thereafter, if necessary, a poor solvent for polyimide is added to the polyimide solution obtained by the chemical imidization reaction to precipitate the polyimide into powder, followed by drying.

[0044] The polyimide resin is preferably soluble in a low-boiling organic solvent such as benzene or methyl ethyl ketone. In particular, it is preferably soluble in methyl ethyl ketone. When the polyimide resin is soluble in methyl ethyl ketone, a layer of the curable resin composition can be easily formed by coating and drying.

[0045] Polyimide resins containing fluoro groups are particularly preferred from the viewpoint that they are easily soluble in general-purpose organic solvents with low boiling points such as methyl ethyl ketone, and can be easily used to form a cured resin layer by coating. The polyimide resin having a fluoro group is preferably an aromatic polyimide resin having a fluoro group in the molecule, and preferably has a skeleton represented by the following chemical formula in the molecule. [ka]

[0046] Polyimide resins having a skeleton represented by the above chemical formula have an extremely high Tg exceeding 300°C due to the high rigidity of the skeleton. This can significantly improve the heat resistance of the cured resin layer. Furthermore, the skeleton is linear and relatively flexible, making it easier to increase the breaking elongation of the cured resin layer. Furthermore, the polyimide resins having the above skeleton contain fluoro groups, making them soluble in low-boiling point, general-purpose organic solvents such as methyl ethyl ketone. Therefore, they can be applied using a solution casting method to form a cured resin layer as a coating film, and the solvent can be easily removed by drying. Polyimide resins having a skeleton represented by the above chemical formula can be obtained by polymerization and imidization of the above-mentioned polyamic acid using 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl and 4,4'-(1,1,1,3,3,3-hexafluoropropane-2,2-diyl)diphthalic dianhydride.

[0047] Polyarylate resin is a resin made of a polymer compound obtained by reacting an aromatic diol with an aromatic dicarboxylic acid or its chloride. Polyarylate resin also has a relatively high Tg and relatively good elongation properties. There are no particular limitations on the polyarylate resin, and known polyarylate resins can be used.

[0048] Examples of aromatic diols include bis(hydroxyphenyl)alkanes such as bis(4-hydroxyphenyl)methane (bisphenol F), bis(3-methyl-4-hydroxyphenyl)methane, 1,1-bis(4'-hydroxyphenyl)ethane, 1,1-bis(3'-methyl-4'-hydroxyphenyl)ethane, 2,2-bis(4'-hydroxyphenyl)propane (bisphenol A), 2,2-bis(3'-methyl-4'-hydroxyphenyl)propane, 2,2-bis(4'-hydroxyphenyl)butane, and 2,2-bis(4'-hydroxyphenyl)octane; and bis(hydroxyphenyl)cycloalkanes such as 1,1-bis(4'-hydroxyphenyl)cyclopentane, 1,1-bis(4'-hydroxyphenyl)cyclohexane (bisphenol Z), and 1,1-bis(4'-hydroxyphenyl)-3,3,5-trimethylcyclohexane.Bis(4-hydroxyphenyl)phenylmethane, bis(3-methyl-4-hydroxyphenyl)phenylmethane, bis(2,6-dimethyl-4-hydroxyphenyl)phenylmethane, bis(2,3,6-trimethyl-4-hydroxyphenyl)phenylmethane, bis(3-t-butyl-4-hydroxyphenyl)phenylmethane, bis(3-phenyl-4-hydroxyphenyl)phenylmethane, bis(3-fluoro-4-hydroxyphenyl)phenylmethane, bis(3-bromo-4-hydroxyphenyl)phenyl Methane, bis(4-hydroxyphenyl)-4-fluorophenylmethane, bis(3-fluoro-4-hydroxyphenyl)-4-fluorophenylmethane, bis(4-hydroxyphenyl)-4-chlorophenylmethane, bis(4-hydroxyphenyl)-4-bromophenylmethane, bis(3,5-dimethyl-4-hydroxyphenyl)-4-fluorophenylmethane, 1,1-bis(4'-hydroxyphenyl)-1-phenylethane [bisphenol P], 1,1-bis(3'-methyl-4'-hydroxyphenyl) )-1-phenylethane, 1,1-bis(3'-t-butyl-4'-hydroxyphenyl)-1-phenylethane, 1,1-bis(3'-phenyl-4'-hydroxyphenyl)-1-phenylethane, 1,1-bis(4'-hydroxyphenyl)-1-(4'-nitrophenyl)ethane, 1,1-bis(3'-bromo-4'-hydroxyphenyl)-1-phenylethane, 1,1-bis(4'-hydroxyphenyl)-1-phenylpropane, bis(4-hydroxyphenyl)diphenylmethane, bis(4-hydroxyphenyl)diphenylmethane bis(hydroxyphenyl)phenylalkanes such as bis(4-hydroxyphenyl)dibenzylmethane; bis(hydroxyphenyl)ethers such as bis(4-hydroxyphenyl)ether and bis(3-methyl-4-hydroxyphenyl)ether; bis(hydroxyphenyl)ketones such as bis(4-hydroxyphenyl)ketone and bis(3-methyl-4-hydroxyphenyl)ketone; bis(hydroxyphenyl)sulfides such as bis(4-hydroxyphenyl)sulfide and bis(3-methyl-4-hydroxyphenyl)sulfide;Examples of suitable bis(hydroxyphenyl)sulfoxides include bis(4-hydroxyphenyl)sulfoxide and bis(3-methyl-4-hydroxyphenyl)sulfoxide; bis(hydroxyphenyl)sulfones such as bis(4-hydroxyphenyl)sulfone [bisphenol S] and bis(3-methyl-4-hydroxyphenyl)sulfone; and bis(hydroxyphenyl)fluorenes such as 9,9-bis(4'-hydroxyphenyl)fluorene and 9,9-bis(3'-methyl-4'-hydroxyphenyl)fluorene.

[0049] Examples of aromatic dicarboxylic acids or chlorides thereof include phthalic acid, isophthalic acid, terephthalic acid, 4,4'-biphenyldicarboxylic acid, diphenoxyethanedicarboxylic acid, diphenyl ether 4,4'-dicarboxylic acid, 4,4'-diphenylsulfonedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and chlorides thereof. The polyarylate resin used may be a modified polyarylate resin. Among these, a resin made of a polymer compound obtained by reacting 2,2-bis(4'-hydroxyphenyl)propane with isophthalic acid is preferred.

[0050] The polymer component (A) may be used alone or in combination of two or more. Alternatively, the polymer component (A) may be a combination of a polymer component (A') having a Tg of 250°C or higher and a polymer component (A") having a Tg of less than 250°C. Examples of the polymer component (A") include polyamide resins and polyarylate resins having a Tg of less than 250°C, with polyamide resins being preferred.

[0051] The polyamide resin is preferably one that is soluble in an organic solvent, and is preferably a rubber-modified polyamide resin, such as that described in JP-A-2004-035638.

[0052] As the polymer component (A) and the polymer component (A"), those using a single type of polyimide resin, those using a plurality of different types of polyimide resins, and those in which at least one of a polyamide resin and a polyarylate resin is added to a polyimide resin are preferred from the viewpoint of being able to adjust elongation properties and solvent resistance.

[0053] When a polyamide resin or a polyarylate resin having a Tg of less than 250°C is added to a polyimide resin, the amount of the resin added is, from the viewpoint of imparting appropriate flexibility while maintaining a high Tg, preferably 100 parts by mass or less, more preferably 70 parts by mass or less, even more preferably 50 parts by mass or less, and even more preferably 30 parts by mass or less, relative to 100 parts by mass of the polyimide resin, and is preferably 1 part by mass or more, more preferably 3 parts by mass or more.

[0054] [Curable monomer (B)] The curable monomer (B) is a monomer having a polymerizable unsaturated bond, and is a monomer that can participate in a polymerization reaction or a polymerization reaction. The use of the curable monomer (B) improves the drying efficiency when a cured resin layer is obtained by coating and drying, and also makes it easier to peel the cured resin layer from the casting film. Furthermore, an optical film with excellent solvent resistance can be obtained. By forming the cured resin layer from a cured product of the curable resin composition containing the polymer component (A) and the curable monomer (B), it becomes easy to form a thin cured resin layer with excellent heat resistance. Furthermore, the use of such a material does not cause optical problems caused by materials with anisotropic molecular orientation, such as polyester films commonly used as substrates for optical films.

[0055] The molecular weight of the curable monomer (B) is usually 3,000 or less, preferably 200 to 2,000, and more preferably 200 to 1,000. When the molecular weight of the curable monomer (B) is within this range, the skinning phenomenon described below can be more efficiently suppressed when a coating film of the curable resin composition is formed.

[0056] Examples of the curable monomer (B) include monofunctional (meth)acrylic acid derivatives and polyfunctional (meth)acrylic acid derivatives. Polyfunctional (meth)acrylic acid derivatives are preferred because they can provide a cured resin layer with superior heat resistance and solvent resistance. As the polyfunctional (meth)acrylic acid derivative, bifunctional (meth)acrylic acid derivatives are preferred because they are easily mixed with the polymer component (A), are less likely to cause shrinkage during curing of the polymer, and can suppress curling of the cured product. The monofunctional (meth)acrylic acid derivative is not particularly limited, and known compounds can be used, such as monofunctional (meth)acrylic acid derivatives having a nitrogen atom, monofunctional (meth)acrylic acid derivatives having an alicyclic structure, and monofunctional (meth)acrylic acid derivatives having a polyether structure.

[0057] Examples of the monofunctional (meth)acrylic acid derivative having a nitrogen atom include compounds represented by the following formula:

[0058] [ka]

[0059] In the formula, R 1 represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R 2 and R 3 each independently represents a hydrogen atom or an organic group having 1 to 12 carbon atoms; R 2 and R 3 may be bonded to form a ring structure, R 4 represents a divalent organic group. R 1 Examples of the alkyl group having 1 to 6 carbon atoms represented by the formula include a methyl group, an ethyl group, and a propyl group, with a methyl group being preferred. R 2 and R 3Examples of the organic group having 1 to 12 carbon atoms represented by the formula (I) include alkyl groups having 1 to 12 carbon atoms, such as methyl, ethyl, and propyl; cycloalkyl groups having 3 to 12 carbon atoms, such as cyclopentyl and cyclohexyl; and aromatic groups having 6 to 12 carbon atoms, such as phenyl, biphenyl, and naphthyl. These groups may have a substituent at any position. In addition, R 2 and R 3 may be joined together to form a ring, and the ring may further have a nitrogen atom or an oxygen atom in the skeleton. R 4 The divalent organic group represented by -(CH2) m -, -NH-(CH2) m In this case, m is an integer of 1 to 10.

[0060] Among these, (meth)acryloylmorpholine represented by the following formula is preferred as the monofunctional (meth)acrylic acid derivative having a nitrogen atom.

[0061] [ka]

[0062] By using a monofunctional (meth)acrylic acid derivative having a nitrogen atom as the curable monomer (B), a cured resin layer having better heat resistance can be formed.

[0063] Examples of the monofunctional (meth)acrylic acid derivative having an alicyclic structure include compounds represented by the following formula:

[0064] [ka]

[0065] In the formula, R 1 has the same meaning as above, and R 5 is a group having an alicyclic structure. R 5Examples of the group having an alicyclic structure represented by the formula (I) include a cyclohexyl group, an isobornyl group, a 1-adamantyl group, a 2-adamantyl group, and a tricyclodecanyl group.

[0066] Specific examples of monofunctional (meth)acrylic acid derivatives having an alicyclic structure include isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, 1-adamantyl (meth)acrylate, and 2-adamantyl (meth)acrylate.

[0067] By using a monofunctional (meth)acrylic acid derivative having an alicyclic structure as the curable monomer (B), a cured resin layer with more excellent optical properties can be formed.

[0068] Examples of the monofunctional (meth)acrylic acid derivative having a polyether structure include compounds represented by the following formula:

[0069] [ka]

[0070] In the formula, R 1 has the same meaning as above, and R 6 represents an organic group having 1 to 12 carbon atoms. 6 Examples of the organic group having 1 to 12 carbon atoms represented by the formula (I) include alkyl groups having 1 to 12 carbon atoms such as methyl, ethyl, and propyl groups; cycloalkyl groups having 3 to 12 carbon atoms such as cyclohexyl groups; and aromatic groups having 6 to 12 carbon atoms such as phenyl, biphenyl, and naphthyl groups. j represents an integer of 2 to 20.

[0071] Specific examples of monofunctional (meth)acrylic acid derivatives having a polyether structure include ethoxylated o-phenylphenol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, and phenoxypolyethylene glycol (meth)acrylate.

[0072] By using a monofunctional (meth)acrylic acid derivative having a polyether structure as the curable monomer (B), a cured resin layer with excellent toughness can be formed.

[0073] The polyfunctional (meth)acrylic acid derivative is not particularly limited, and known compounds can be used. For example, difunctional to hexafunctional (meth)acrylic acid derivatives can be mentioned, and as mentioned above, difunctional (meth)acrylic acid derivatives are preferred. Examples of the bifunctional (meth)acrylic acid derivative include compounds represented by the following formula:

[0074] [ka]

[0075] In the formula, R 1 means the same as above, and R 7 represents a divalent organic group. 7 Examples of the divalent organic group represented by the formula include groups represented by the following formula:

[0076] [ka]

[0077] (In the formula, s represents an integer of 1 to 20, t represents an integer of 1 to 30, u and v each independently represent an integer of 1 to 30, and "-" at both ends represents a bond.)

[0078] Specific examples of the bifunctional (meth)acrylic acid derivatives represented by the above formula include tricyclodecane dimethanol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propoxylated ethoxylated bisphenol A di(meth)acrylate, ethoxylated bisphenol A di(meth)acrylate, 1,10-decanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene, etc. Among these, from the viewpoint of heat resistance and toughness, tricyclodecane dimethanol di(meth)acrylate and the like, which have R 7 and propoxylated ethoxylated bisphenol A di(meth)acrylate, ethoxylated bisphenol A di(meth)acrylate, etc., in which R 7 and 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene, etc., in which R 7 Preferably, the divalent organic group represented by the following formula has a 9,9-bisphenylfluorene skeleton.

[0079] Other examples of bifunctional (meth)acrylic acid derivatives include neopentyl glycol adipate di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, caprolactone-modified dicyclopentenyl di(meth)acrylate, ethylene oxide-modified phosphate di(meth)acrylate, di(acryloxyethyl) isocyanurate, and allylated cyclohexyl di(meth)acrylate.

[0080] Examples of trifunctional (meth)acrylic acid derivatives include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propionic acid-modified dipentaerythritol tri(meth)acrylate, propylene oxide-modified trimethylolpropane tri(meth)acrylate, and tris(acryloxyethyl)isocyanurate. Examples of tetrafunctional (meth)acrylic acid derivatives include pentaerythritol tetra(meth)acrylate. Examples of the pentafunctional (meth)acrylic acid derivatives include propionic acid-modified dipentaerythritol penta(meth)acrylate. Examples of the hexafunctional (meth)acrylic acid derivative include dipentaerythritol hexa(meth)acrylate and caprolactone-modified dipentaerythritol hexa(meth)acrylate.

[0081] A cyclopolymerizable monomer may be used as the curable monomer (B). The cyclopolymerizable monomer is a monomer that has the property of undergoing radical polymerization while undergoing cyclization. Examples of the cyclopolymerizable monomer include non-conjugated dienes, and for example, an α-allyloxymethylacrylic acid-based monomer can be used. C1-4 alkyl esters of 2-allyloxymethylacrylic acid and cyclohexyl 2-(allyloxymethyl)acrylate are preferred, C1-4 alkyl esters of 2-allyloxymethylacrylic acid are more preferred, and methyl 2-(allyloxymethyl)acrylate is even more preferred. Cyclopolymerizable monomers such as dimethyl-2,2'-[oxybis(methylene)]bis-2-propenoate, diethyl-2,2'-[oxybis(methylene)]bis-2-propenoate, di(n-propyl)-2,2'-[oxybis(methylene)]bis-2-propenoate, di(i-propyl)-2,2'-[oxybis(methylene)]bis-2-propenoate, di(n-butyl)-2,2'-[oxybis(methylene)]bis-2-propenoate, di(n-hexyl)-2,2'-[oxybis(methylene)]bis-2-propenoate, and dicyclohexyl-2,2'-[oxybis(methylene)]bis-2-propenoate can also be used.

[0082] The curable monomer (B) can be used alone or in combination of two or more. The curable monomer (B) preferably includes a polyfunctional (meth)acrylic acid derivative and a cyclopolymerizable monomer, which can appropriately adjust the heat resistance of the cured resin layer while facilitating the adjustment of the breaking elongation of the cured resin layer to a predetermined range. When the curable monomer (B) contains a polyfunctional (meth)acrylic acid derivative, the content thereof is preferably 40 mass % or more, more preferably 50 to 100 mass %, of the total amount of the curable monomer (B).

[0083] [Curable resin composition] The curable resin composition used to form the cured resin layer according to an embodiment of the present invention can be prepared by mixing the polymer component (A), the curable monomer (B), and, if desired, a polymerization initiator and other components described below, and dissolving or dispersing the mixture in a suitable solvent.

[0084] The total content of the polymer component (A) and the curable monomer (B) in the curable resin composition is preferably 40 to 99.5 mass%, more preferably 60 to 99 mass%, and even more preferably 80 to 98 mass%, based on the total mass of the curable resin composition excluding the solvent.

[0085] The content of the polymer component (A) and the curable monomer (B) in the curable resin composition is, in terms of the mass ratio of the polymer component (A) to the curable monomer (B), preferably polymer component (A):curable monomer (B)=30:70 to 90:10, more preferably 35:65 to 80:20. In the curable resin composition, when the mass ratio of polymer component (A):curable monomer (B) is within this range, the flexibility of the obtained cured resin layer tends to be more improved, and the solvent resistance of the cured resin layer and its releasability from the casting film tend to be more easily maintained.

[0086] Furthermore, if the content of the curable monomer (B) in the curable resin composition is within the above range, for example, when a cured resin layer is obtained by a solution casting method or the like, the solvent can be removed efficiently, thereby solving the problem of deformation such as curling and undulation caused by a long drying process.

[0087] When a combination of multiple resins with different solvent solubilities is used as the polymer component (A), such as a combination of the above-mentioned polyimide resin with a polyamide resin or a polyarylate resin, it is preferable to first dissolve the resins in solvents suitable for each resin, and then add a solution of the other resin to the low-boiling organic solvent in which the resin has been dissolved.

[0088] The curable resin composition may contain a polymerization initiator if desired. The polymerization initiator is not particularly limited as long as it initiates a curing reaction, and examples thereof include photopolymerization initiators.

[0089] Photopolymerization initiators include 2,2-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxy-cyclohexyl-phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-[4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl]-2-methyl-propan-1-one, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamine, and the like. Alkylphenone-based photopolymerization initiators such as 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, ethyl (2,4,6-trimethylbenzoyl)-phenylphosphine phosphate, and bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide; bis(η 5Titanocene photopolymerization initiators such as (2,4-cyclopentadien-1-yl)-bis[2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl]titanium; oxime ester photopolymerization initiators such as 1,2-octanedione-1-[4-(phenylthio)-2-(O-benzoyloxime)] and ethanone-1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-1-(O-acetyloxime); benzophenone, p-chlorobenzophenone, benzoylbenzoic acid, methyl o-benzoylbenzoate, 4-methylbenzophenone, 4-phenylbenzophenone, hydroxybenzophenone, acrylated benzophenone, 4-benzoyl benzophenone-based photopolymerization initiators such as 13-acryloyl-4'-methyl-diphenyl sulfide, 3,3'-dimethyl-4-methoxybenzophenone, 2,4,6-trimethylbenzophenone, and 4-(13-acryloyl-1,4,7,10,13-pentaoxatridecyl)-benzophenone; and thioxanthone-based photopolymerization initiators such as thioxanthone, 2-chlorothioxanthone, 3-methylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diisopropylthioxanthone, 2,4-dichlorothioxanthone, 1-chloro-4-propoxythioxanthone, 2-methylthioxanthone, 2-isopropylthioxanthone, and 4-isopropylthioxanthone.

[0090] Among the above photopolymerization initiators, phosphorus-based photopolymerization initiators such as 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, ethyl(2,4,6-trimethylbenzoyl)-phenylphosphineate, and bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl-pentylphosphine oxide are preferred. When the polymer component (A) is a thermoplastic resin having an aromatic ring, the polymer component (A) may absorb ultraviolet light, making it difficult for the curing reaction to occur. However, by using the phosphorus-based photopolymerization initiator, the curing reaction can be efficiently promoted by utilizing light of a wavelength that is not absorbed by the polymer component (A). The polymerization initiators can be used alone or in combination of two or more.

[0091] The content of the polymerization initiator is preferably from 0.05 to 15 mass %, more preferably from 0.05 to 10 mass %, and even more preferably from 0.05 to 5 mass %, based on the total amount of the curable resin composition.

[0092] Furthermore, the curable resin composition may contain a photopolymerization initiation aid such as triisopropanolamine or 4,4'-diethylaminobenzophenone in addition to the polymer component (A), the curable monomer (B), and the polymerization initiator.

[0093] The solvent used in preparing the curable resin composition is not particularly limited, and examples thereof include aliphatic hydrocarbon solvents such as n-hexane and n-heptane; aromatic hydrocarbon solvents such as toluene and xylene; halogenated hydrocarbon solvents such as dichloromethane, ethylene chloride, chloroform, carbon tetrachloride, 1,2-dichloroethane, and monochlorobenzene; alcohol solvents such as methanol, ethanol, propanol, butanol, and propylene glycol monomethyl ether; ketone solvents such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone; ester solvents such as ethyl acetate and butyl acetate; cellosolve solvents such as ethyl cellosolve; and ether solvents such as 1,3-dioxolane.

[0094] The content of the solvent in the curable resin composition is not particularly limited, but is usually 0.1 to 1,000 g, preferably 1 to 100 g, per 1 g of the polymer component (A). By appropriately adjusting the amount of the solvent, the viscosity of the curable resin composition can be adjusted appropriately.

[0095] The curable resin composition may further contain known additives such as plasticizers, antioxidants, and ultraviolet absorbers, within the scope of not impairing the objects and effects of the present invention.

[0096] The method for curing the curable resin composition can be appropriately determined depending on the type of polymerization initiator and curable monomer used, and details will be described later in the section on the method for producing an optical film.

[0097] [Properties of the cured resin layer] As described above, the cured resin layer has one or more loss tangent peaks in a curve showing the change in loss tangent with temperature obtained by dynamic viscoelasticity measurement at a heating rate of 3°C / sec from 25°C to 280°C, and all of the loss tangent peaks have peak temperatures of 150°C or higher. Furthermore, as described above, the cured resin layer of the optical film according to one embodiment of the present invention has a storage modulus reduction rate of 40% or less. In addition to these characteristics, the cured resin layer has the following properties.

[0098] The thickness of the cured resin layer is preferably 20 μm or less, more preferably 15 μm or less, even more preferably 12 μm or less, and even more preferably 10 μm or less. There is no particular lower limit to the thickness of the cured resin layer, but it is usually 0.1 μm or more, preferably 0.2 μm or more. When the cured resin layer includes a plurality of laminated layers, the thickness of the cured resin layer is the total thickness including the plurality of layers. When the thickness of the cured resin layer is 20 μm or less, a thin and lightweight optical film can be easily obtained, and an optical film with excellent handleability can be obtained. Furthermore, because the cured resin layer is thin, it is possible to obtain a transparent conductive film or gas barrier film that is highly transparent and is thin and lightweight. Therefore, in applications such as organic EL displays, which require thinness, the transparent conductive film or gas barrier film is preferable because it does not increase the overall thickness of the applied device. Furthermore, a thin transparent conductive film or gas barrier film can improve the flexibility and bending resistance of the transparent conductive film or gas barrier film after mounting.

[0099] The absolute value of the thermal deformation rate of the cured resin layer of the optical film according to an embodiment of the present invention due to a temperature rise of 150°C is preferably 1.2% or less, more preferably 1.1% or less, and even more preferably 1.0% or less. By setting the absolute value of the thermal deformation rate of the cured resin layer due to a temperature rise of 150°C within the above numerical range, the cured resin layer is likely to exhibit good heat resistance, and when a transparent conductive layer or a gas barrier layer is formed by heating the conductive material layer, deterioration in the performance of the transparent conductive layer or the gas barrier layer due to deformation of the cured resin layer due to heating can be more easily suppressed. In particular, even when a transparent conductive film or a gas barrier film is produced through a process involving heating after the formation of a cured resin layer, such as forming a conductive material layer on a cured resin layer by sputtering, vapor deposition, coating, or the like, and then heating the conductive material layer to form a transparent conductive layer, or applying a coating liquid for forming a gas barrier layer and heating it to form a gas barrier layer, the high heat resistance of the cured resin layer prevents deformation of the cured resin layer, which can make it difficult to form a transparent conductive layer or a gas barrier layer. Furthermore, it prevents the transparent conductive layer from failing to exhibit sufficient electrical properties, and the gas barrier layer from failing to exhibit sufficient gas barrier properties. From the same perspective, it is preferable that the absolute value of the thermal deformation rate of the cured resin layer when heated to 150°C is 0.8% or less.

[0100] The thermal deformation rate of the cured resin layer is a characteristic value measured by the following method. The thickness of the cured resin layer is adjusted to 20 μm for measurement in order to avoid the problem of the cured resin layer stretching when attached to the jig of the thermomechanical analyzer due to its thinness. After peeling and removing the process film, four cured resin layers were stacked to form a 20 μm-thick laminate. Next, the laminate was cut into 5 mm x 30 mm test pieces and clamped using a thermomechanical analyzer (TMA4000SE, manufactured by Netsch Japan Co., Ltd.) with a chuck distance of 20 mm. The cured resin layer laminate was then heated from 25°C to 150°C at a rate of 5°C / min and then cooled to 25°C at a rate of 5°C / min. The rate of change in longitudinal displacement before and after heating (the percentage of the amount of displacement relative to a chuck distance of 20 mm) was taken as the thermal deformation rate of the cured resin layer. Contraction of the cured resin layer laminate was considered a negative value, and expansion was considered a positive value.

[0101] The cured resin layer also has excellent solvent resistance. Because of its excellent solvent resistance, the surface of the cured resin layer is hardly dissolved, even when an organic solvent is used to form another layer on the surface of the cured resin layer. Therefore, even when a transparent conductive layer is formed on the surface of the cured resin layer by a coating method using a resin solution containing an organic solvent, or when a gas barrier layer is formed using a polysilazane-based gas barrier layer coating liquid, components of the cured resin layer are unlikely to be mixed into the transparent conductive layer or the gas barrier layer. Therefore, the electrical properties of the transparent conductive layer and the gas barrier properties of the gas barrier layer are unlikely to be deteriorated.

[0102] From this viewpoint, the gel fraction of the cured resin layer is preferably 94% or more, and more preferably 97% or more. A cured resin layer having a gel fraction of 94% or more has a small amount of the curable monomer (B) remaining after curing, and it is easy to obtain a cured resin layer that satisfies the above-mentioned requirement (I).

[0103] Here, the gel fraction is calculated by wrapping a cured resin layer cut to a size of 100 mm x 100 mm in a 150 mm x 150 mm nylon mesh (#120) whose mass has been measured in advance, immersing it in toluene (100 mL) for 3 days, removing it, drying it at 120°C for 1 hour, and then leaving it to stand for 3 hours under conditions of 23°C and a relative humidity of 50% to condition the humidity, measuring the mass, and then calculating the gel fraction from the following formula (2):

[0104] Gel fraction (%) = [(mass of remaining resin after immersion) / (mass of resin before immersion)] × 100 Equation (2)

[0105] The cured resin layer has excellent interlayer adhesion with functional layers such as a transparent conductive layer and a gas barrier layer, that is, functional layers such as a transparent conductive layer and a gas barrier layer can be formed on the cured resin layer without providing an anchor coat layer.

[0106] The cured resin layer is preferably colorless and transparent. The colorless and transparent cured resin layer allows the optical film according to the embodiment of the present invention to be preferably used for optical applications. Specifically, the total light transmittance of the optical film according to the embodiment of the present invention is preferably 85% or more, and more preferably 90% or more. The total light transmittance is a characteristic value measured by the method described in the examples.

[0107] The cured resin layer has low birefringence and excellent optical isotropy. The in-plane retardation of the cured resin layer is usually 20 nm or less, preferably 15 nm or less. The thickness direction retardation is usually −500 nm or less, preferably −450 nm or less. The value obtained by dividing the in-plane retardation by the thickness of the cured resin layer (birefringence) is usually 100×10 -5 or less, preferably 20 × 10 -5 The following is the result. When the in-plane retardation, thickness direction retardation, and birefringence of the cured resin layer are within the above-mentioned ranges, an optical film having low birefringence and excellent optical isotropy can be obtained, and transparent conductive films and gas barrier films produced using this optical film can be preferably used for optical applications.

[0108] The breaking elongation of the cured resin layer is preferably 2.5% or more, more preferably 2.6% or more, and even more preferably 2.7% or more. If the breaking elongation of the cured resin layer is 2.5% or more, it becomes easy to adjust the breaking elongation of the optical film to about 2% or more, and as a result, it becomes easy to obtain an optical film with excellent flexibility. The breaking elongation can be measured according to JIS K7127:1999.

[0109] 1-2.Processing film The processing film has the role of protecting the cured resin layer and other layers that are optionally provided as described later when storing, transporting, etc. the optical film, the transparent conductive film, and the gas barrier film described later, and is peeled off in a predetermined process. The casting film has, for example, a base layer. The casting film may have other layers in addition to the base layer, and the other layers may include a release layer. The cured resin layer is a cured product of a curable resin composition containing the curable monomer (B), and therefore can be easily peeled from the casting film even if the casting film does not have a release layer.

[0110] By including a processing film in the optical film, the optical film can be made easy to handle while protecting the cured resin layer. The optical film may have a processing film on one side of the cured resin layer as shown in Fig. 1(a) above, or may have a processing film on both sides of the cured resin layer as shown in Fig. 1(b) above. In the latter case, it is preferable to use two types of processing films, making the processing film to be peeled first easier to peel than the other processing film.

[0111] The process film is preferably in the form of a sheet or film. Here, the term "sheet or film" does not limit to long films, but also includes short flat films.

[0112] Examples of the substrate layer of the process film include paper substrates such as glassine paper, coated paper, and fine paper; laminated paper obtained by laminating these paper substrates with a thermoplastic resin such as polyethylene or polypropylene; the above paper substrates that have been sealed with cellulose, starch, polyvinyl alcohol, acrylic-styrene resin, or the like; plastic films such as polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, and polyolefin films such as polyethylene and polypropylene; and glass.

[0113] The release layer can be formed using a conventionally known release agent such as a silicone-based release agent, a fluorine-based release agent, an alkyd-based release agent, or an olefin-based release agent. The thickness of the release layer is not particularly limited, but is usually 0.02 to 2.0 μm, more preferably 0.05 to 1.5 μm.

[0114] The thickness of the casting film is preferably 1 to 500 μm, more preferably 5 to 300 μm, from the viewpoint of ease of handling.

[0115] The average surface roughness (arithmetic mean roughness Ra) of the surface of the casting film on which the cured resin layer is formed is preferably 10 nm or less, more preferably 8.0 nm or less, and even more preferably 5.0 nm or less. The maximum surface roughness (maximum cross-sectional height Rt) of the surface of the casting film on which the cured resin layer is formed is preferably 100 nm or less, more preferably 70 nm or less, and even more preferably 50 nm or less. While there are no particular lower limits for the average surface roughness and maximum surface roughness, the average surface roughness is typically 0.3 nm or more, and the maximum surface roughness is typically 10 nm or more. By setting the average surface roughness of the surface of the base layer of the process film on which the cured resin layer is provided to 10 nm or less and the maximum surface roughness to 100 nm or less, an increase in haze of the cured resin layer can be suppressed. In this specification, "maximum surface roughness" refers to the maximum cross-sectional height Rt, and "average surface roughness" refers to the arithmetic mean roughness Ra. Both are values obtained by optical interferometry in a measurement area of 100 μm × 100 μm.

[0116] 1-3.Other layers The casting film may have layers other than the release layer, such as an easy-adhesion layer and an antistatic layer.

[0117] Among the layers constituting the optical film, the portion (separation layer) that is peeled off from the processing film in a predetermined process contains a cured resin layer. The cured resin layer is laminated on the processing film without any other layers in between, and is therefore located on one outermost surface of the separation layer. An easy-adhesion layer, an antistatic layer, etc. other than the cured resin layer may be provided on the other surface side of the separation layer. However, since the separation layer is a layer that constitutes the transparent conductive film or gas barrier film after the processing film is removed, it is preferably thin, and the number and thickness of layers other than the cured resin layer are preferably minimized.

[0118] 2. Transparent conductive film The transparent conductive film according to an embodiment of the present invention has a transparent conductive layer on the cured resin layer of the optical film. In other words, the transparent conductive film comprises a processing film, a cured resin layer, and a transparent conductive layer, in this order. When the transparent conductive film is actually used, the processing film is peeled off from the transparent conductive film and incorporated into a display or solar panel, or attached to the substrate of a touch sensor for a touch panel. For example, when the transparent conductive film has an adhesive layer as described below, the transparent conductive film can be attached to the application portion via the adhesive layer, and after attachment, the processing film is peeled off and removed.

[0119] Specific examples of the configuration of the transparent conductive film according to the embodiment of the present invention are shown in FIGS. 2(a) and 2(b). The transparent conductive film 20 shown in Figure 2(a) has a transparent conductive layer 3 on one side of a cured resin layer 2, and a processing film 1 on the side of the cured resin layer 2 opposite the transparent conductive layer 3. The transparent conductive layer 3 is formed, for example, so as to cover the entire surface of the cured resin layer 2. The transparent conductive layer 3 can be patterned into a desired shape by an appropriate method such as etching. The transparent conductive film 21 shown in FIG. 2(b) has a patterned transparent conductive layer 31 on one side of the cured resin layer 2. Note that by selectively disposing a transparent conductive material on the cured resin layer 2, the transparent conductive layer 31 having a desired pattern shape may be formed on the cured resin layer 2 without undergoing a process such as etching. If the process film 1 is peeled off from the transparent conductive film in the state shown in Figures 2(a) and 2(b), handling tends to become difficult. Therefore, it is preferable to peel off and remove the process film 1 after applying the transparent conductive film to the application part such as an adherend.

[0120] The thickness of the transparent conductive film can be appropriately determined depending on the intended use, etc. From the viewpoint of handleability, the substantial thickness of the transparent conductive film according to the embodiment of the present invention is preferably 0.3 to 50 μm, more preferably 0.5 to 25 μm, and more preferably 0.7 to 12 μm. The term "substantial thickness" refers to the thickness in use. That is, although the transparent conductive film has a processing film, the thickness of the portion (such as the processing film) that is removed during use is not included in the "substantial thickness."

[0121] In this specification, the term "transparent" in the context of a transparent conductive film means that the light transmittance at a wavelength of 450 nm is 80% or more.

[0122] Examples of conductive materials constituting the transparent conductive layer include metals, alloys, metal oxides, electrically conductive compounds, and mixtures thereof. Specific examples include antimony-doped tin oxide (ATO), fluorine-doped tin oxide (FTO), semiconductive metal oxides such as tin oxide, germanium-doped zinc oxide (GZO), zinc oxide, indium oxide, indium tin oxide (ITO), and indium zinc oxide (IZO); metals such as gold, silver, chromium, and nickel; mixtures of these metals with conductive metal oxides; inorganic conductive materials such as copper iodide and copper sulfide; and organic conductive materials such as polyaniline, polythiophene, and polypyrrole. Metals such as silver may be aggregated in particulate form, such as nanofillers, nanorods, and nanofibers, to form the transparent conductive layer.

[0123] The method for forming the transparent conductive layer is not particularly limited, and examples thereof include vapor deposition, sputtering, ion plating, thermal CVD, and plasma CVD. Alternatively, for example, a coating material containing particulate metal may be applied to an optical film to obtain a transparent conductive layer from the coating film. More specifically, it is preferable to form a conductive material layer by the above-mentioned PVD method or CVD method, or by applying and drying a coating material, and then heating the conductive material layer to 140°C or higher using an electric furnace or the like to crystallize the conductive material to form a transparent conductive layer. When a cured resin layer with low heat resistance is used, the cured resin layer may be deformed by heating during such vapor deposition, sputtering, or post-coating heat treatment. Deformation of the cured resin layer may adversely affect the conductivity of the transparent conductive layer of the transparent conductive film. However, the cured resin layer of the transparent conductive film according to the embodiment of the present invention has excellent heat resistance, and is therefore less likely to deform even when heated in such processes. Therefore, a decrease in the conductivity of the transparent conductive film due to deformation of the cured resin layer can be avoided. After the transparent conductive film is obtained, an adhesive layer may be provided on the transparent conductive layer.

[0124] The thickness of the transparent conductive layer may be appropriately selected depending on the application, etc. It is usually 10 nm to 50 μm, preferably 20 nm to 20 μm.

[0125] The transparent conductive film according to the embodiment of the present invention is not limited to the configuration shown in Figures 2(a) and 2(b), and may further contain one or more other layers as long as the object of the present invention is not impaired. Examples of other layers include an adhesive layer, an impact absorbing layer, a hard coat layer, a refractive index adjusting layer (index matching layer), etc. Furthermore, there are no particular limitations on the locations of other layers.

[0126] The adhesive layer is a layer used when attaching the transparent conductive film to an adherend. The material for forming the adhesive layer is not particularly limited, and known adhesives or pressure-sensitive adhesives, such as acrylic, silicone, or rubber-based adhesives, heat-sealing materials, etc., can be used. In a transparent conductive film, when an adhesive layer is formed on the side of the cured resin layer opposite the surface facing the processing film, the transparent conductive film can be attached to the adherend using the adhesive layer, and then the processing film can be peeled off, thereby easily forming a thin coating having a cured resin layer and a transparent conductive layer on the adherend. In the transparent conductive film according to the embodiment of the present invention, the processing film is flexible, which facilitates such attachment and also facilitates peeling of the processing film. The transparent conductive film may have a release film for protecting the adhesive layer on the side of the adhesive layer opposite the side facing the cured resin layer. Adopting this configuration results in the transparent conductive film having a processing film and a release film on both outermost layers, making it easy to handle.

[0127] 3.Gas barrier film The gas barrier film includes a gas barrier layer and a cured resin layer. The gas barrier film includes a processing film, a cured resin layer, and a gas barrier layer in this order. The gas barrier film may include two or more gas barrier layers.

[0128] A specific example of the configuration of the gas barrier film according to an embodiment of the present invention is shown in FIG. 2(c). The gas barrier film 22 shown in FIG. 2( c ) has a gas barrier layer 4 on one side of the cured resin layer 2 , and a processing film 1 on the side of the cured resin layer 2 opposite to the gas barrier layer 4 . If the process film 1 is peeled off from the gas barrier film 22 in the state shown in Figure 2(c), handling is likely to become difficult. Therefore, it is preferable to peel off and remove the process film 1 after applying the gas barrier film 22 to the application part such as the adherend.

[0129] The gas barrier layer and the cured resin layer may be laminated directly to each other, or may be laminated via another layer therebetween, such as an adhesive layer or an impact absorbing layer. A plurality of pairs of a cured resin layer and a gas barrier layer may be laminated, and in this case, another layer may be present between at least one of the plurality of pairs of a cured resin layer and a gas barrier layer.

[0130] The water vapor permeability of gas barrier films at 40°C and 90% relative humidity is typically 1.0 x 10 -2 g / m 2 / day or less, preferably 8.0 × 10 -3 g / m 2 / day or less, preferably 6.0 × 10 -3 g / m 2 / day or less.

[0131] The gas barrier layer in the gas barrier film according to the embodiment of the present invention is not particularly limited in terms of material, etc., as long as it has gas barrier properties. Examples include a gas barrier layer made of an inorganic film, a gas barrier layer containing a gas barrier resin, and a gas barrier layer obtained by modifying a layer containing a polymer compound. Among these, a gas barrier layer made of an inorganic film and a gas barrier layer obtained by subjecting a layer containing a polymer compound to a modification treatment are preferred, as they allow for efficient formation of a thin layer having excellent gas barrier properties and solvent resistance.

[0132] The inorganic film is not particularly limited, and examples thereof include inorganic vapor deposition films. Examples of inorganic vapor-deposited films include vapor-deposited films of inorganic compounds and metals. Raw materials for the inorganic compound vapor deposition film include inorganic oxides such as silicon oxide, aluminum oxide, magnesium oxide, zinc oxide, indium oxide, and tin oxide; inorganic nitrides such as silicon nitride, aluminum nitride, and titanium nitride; inorganic carbides; inorganic sulfides; inorganic oxynitrides such as silicon oxynitride; inorganic oxycarbides; inorganic nitride carbides; and inorganic nitride oxycarbides. Examples of raw materials for the metal vapor deposition film include aluminum, magnesium, zinc, and tin. These may be used alone or in combination of two or more. The thickness of the inorganic vapor-deposited film is usually in the range of about 10 to 2,000 nm.

[0133] Methods for forming inorganic vapor-deposited films include PVD (physical vapor deposition) methods such as vacuum deposition, sputtering, and ion plating, and CVD methods such as thermal CVD (chemical vapor deposition), plasma CVD, and photo-CVD. When a cured resin layer with low heat resistance is used, the heating that occurs during such vapor deposition or sputtering may cause deformation of the cured resin layer. Deformation of the cured resin layer may adversely affect the gas barrier properties of the gas barrier layer of the gas barrier film. However, the cured resin layer of the gas barrier film according to the embodiment of the present invention has excellent heat resistance and is therefore less likely to deform even when heated during vapor deposition or sputtering. This avoids a decrease in the gas barrier properties of the gas barrier film due to deformation of the cured resin layer.

[0134] In the gas barrier layer obtained by modifying a layer containing a polymer compound (hereinafter sometimes referred to as a "polymer layer"), the polymer compound used is preferably a silicon-containing polymer compound. Examples of the silicon-containing polymer compound include polysilazane-based compounds, polycarbosilane-based compounds, polysilane-based compounds, and polyorganosiloxane-based compounds.

[0135] Among these, polysilazane-based compounds are preferred from the viewpoint of being able to form a gas barrier layer with excellent gas barrier properties. Examples of polysilazane-based compounds include inorganic polysilazanes and organic polysilazanes. Examples of inorganic polysilazanes include perhydropolysilazane, and examples of organic polysilazanes include compounds in which part or all of the hydrogen atoms of perhydropolysilazane have been substituted with organic groups such as alkyl groups. Among these, inorganic polysilazanes are more preferred from the viewpoint of easy availability and being able to form a gas barrier layer with excellent gas barrier properties. Furthermore, as the polysilazane compound, commercially available products available as glass coating materials and the like can also be used as they are. The polysilazane compounds can be used singly or in combination of two or more.

[0136] In addition to the polymer compound described above, the polymer layer may contain other components within the scope of not impairing the object of the present invention, such as a curing agent, other polymers, an antioxidant, a light stabilizer, and a flame retardant.

[0137] Examples of methods for forming the polymer layer include a method in which a layer-forming solution containing at least one polymer compound, optionally other components, and a solvent, etc., is applied onto a resin layer or, if desired, a primer layer formed on the resin layer using a spin coater, knife coater, gravure coater, etc., and the resulting coating film is appropriately dried to form the layer.

[0138] The resulting coating film is preferably dried or heated to improve the gas barrier properties of the gas barrier film. Heating and drying methods include conventionally known drying methods such as hot air drying, hot roll drying, and infrared irradiation. The heating temperature is typically 80 to 150°C, and the heating time is typically several tens of seconds to several tens of minutes.

[0139] When forming the gas barrier layer of the gas barrier film, for example, if a polysilazane-based compound such as those described above is used, a conversion reaction of the polysilazane occurs upon heating after coating, resulting in a coating film with excellent gas barrier properties. On the other hand, when a cured resin layer with low heat resistance is used, the heating during the formation of such a coating film may cause deformation of the cured resin layer. Deformation of the cured resin layer may adversely affect the gas barrier properties of the gas barrier layer of the gas barrier film. However, the resin layer of the gas barrier film according to the embodiment of the present invention has excellent heat resistance, and is therefore less likely to deform even when heated during and after coating. Therefore, deterioration of the gas barrier properties of the gas barrier film due to deformation of the cured resin layer can be avoided.

[0140] The thickness of the polymer layer is usually 20 to 1,000 nm, preferably 30 to 800 nm, and more preferably 40 to 400 nm. Even if the polymer layer has a thickness on the order of nanometers, a gas barrier film having sufficient gas barrier properties can be obtained by carrying out a modification treatment as described below.

[0141] Examples of modification treatments include ion implantation and vacuum ultraviolet light irradiation. Among these, ion implantation is preferred because it can provide high gas barrier performance. In the ion implantation, the amount of ions implanted into the polymer layer may be appropriately determined depending on the intended use of the gas barrier film to be formed (required gas barrier properties, transparency, etc.).

[0142] Examples of ions to be implanted include ions of rare gases such as argon, helium, neon, krypton, and xenon; ions of fluorocarbons, hydrogen, nitrogen, oxygen, carbon dioxide, chlorine, fluorine, and sulfur; ions of alkane gases such as methane, ethane, propane, butane, pentane, and hexane; ions of alkene gases such as ethylene, propylene, butene, and pentene; ions of alkadiene gases such as pentadiene and butadiene; ions of alkyne gases such as acetylene and methylacetylene; ions of aromatic hydrocarbon gases such as benzene, toluene, xylene, indene, naphthalene, and phenanthrene; ions of cycloalkane gases such as cyclopropane and cyclohexane; ions of cycloalkene gases such as cyclopentene and cyclohexene; ions of conductive metals such as gold, silver, copper, platinum, nickel, palladium, chromium, titanium, molybdenum, niobium, tantalum, tungsten, and aluminum; and ions of silane (SiH4) or organic silicon compounds. These ions may be used alone or in combination of two or more.

[0143] Among these, at least one ion selected from the group consisting of hydrogen, nitrogen, oxygen, argon, helium, neon, xenon, and krypton is preferred, as it can be more easily injected and results in a gas barrier layer with particularly excellent gas barrier properties.

[0144] The method of injecting ions is not particularly limited, but examples include a method of irradiating ions accelerated by an electric field (ion beam), a method of injecting ions in plasma, etc. Among these, the latter method of injecting plasma ions is preferred because it allows a gas barrier film to be easily obtained.

[0145] The ion species to be implanted by plasma ion implantation may be the same as the above-mentioned ions exemplified as the ions to be implanted.

[0146] The thickness of the portion into which ions are implanted can be controlled by the type of ion, the applied voltage, the treatment time, and other implantation conditions, and can be determined depending on the thickness of the polymer layer, the intended use of the gas barrier film, and other factors, but is typically 5 to 1,000 nm.

[0147] The implantation of ions can be confirmed by performing elemental analysis measurement at a depth of approximately 10 nm from the surface of the polymer layer using X-ray photoelectron spectroscopy (XPS).

[0148] 4. Optical film manufacturing method The method for producing an optical film according to an embodiment of the present invention includes the following first, second, and third steps using a processing film, and each optical film according to an embodiment of the present invention can be easily produced by such a production method. By using a production method including steps 1 to 3, it is possible to produce an optical film that is thin, has excellent heat resistance, and is easy to form functional layers such as a transparent conductive layer and a gas barrier layer on. Furthermore, by using a processing film, the optical film can be produced efficiently and easily. First step: A curable resin layer is formed on a processing film using a curable resin composition containing a polymer component (A) and a curable monomer (B). Second step: The curable resin layer obtained in the first step is irradiated with at least one of an energy ray and an electron beam, thereby curing at least a part of the curable resin layer. Third step: After the start of the second step, the curable resin layer is subjected to a heat treatment in which the layer is heated to 150° C. or higher to obtain a cured resin layer.

[0149] Fig. 3 is a process diagram showing an example of a manufacturing process of an optical film according to an embodiment of the present invention. Specifically, Fig. 3(a) is a cross-sectional schematic diagram corresponding to a state before the curable resin layer is formed, Fig. 3(b) is a state after the first step, Fig. 3(c) is a state after the second step, and Fig. 3(d) is a state after the third step.

[0150] (First step) First, a curable resin layer (2a in FIG. 3(b)) is formed on the surface of a casting film (1 in FIG. 3(a)) using a curable resin composition containing a polymer component (A) and a curable monomer (B). The curable resin layer is preferably formed by coating.

[0151] The method for applying the curable resin composition to the casting film is not particularly limited, and known application methods such as spin coating, spray coating, bar coating, knife coating, roll coating, blade coating, die coating, gravure coating, etc. Applying the curable resin composition to the surface of the casting film on which the cured resin layer is to be formed makes it easy to obtain a uniform coating film.

[0152] The method for drying the resulting coating film is not particularly limited, and conventionally known drying methods such as hot air drying, hot roll drying, and infrared irradiation can be used. When a resin layer is formed by dissolving the polymer component (A) alone in a solvent without using the curable monomer (B), the surface of the resin layer dries first, and the solvent tends to remain inside the resin layer (so-called "skinning"). As described above, the cured resin layer according to the embodiment of the present invention is preferably formed with a high Tg of the polymer component (A) contained in the curable resin composition. When the polymer component (A) has a high Tg, the skinning phenomenon is particularly likely to occur. However, since the curable resin composition contains the curable monomer (B), when a coating film obtained by solution casting is dried, the fluidity of the resin composition is maintained, and the solvent can be efficiently removed all the way to the inside of the resin layer.

[0153] The temperature for drying the coating is usually 30 to 150°C, and preferably 50 to 100°C. The thickness of the dried coating film (curable resin layer) is not particularly limited, but since there is almost no difference in thickness from the thickness after curing, it may be the same as the thickness of the curable resin layer described above.

[0154] (Second step) In the second step, the curable resin layer obtained in the first step is irradiated with at least one of an energy ray and an electron beam to at least partially cure the curable resin layer, whereby the curable resin layer 2a in Fig. 3(a) becomes the curable resin layer 2b after irradiation with an energy ray or an electron beam as shown in Fig. 3(b). It is desirable to irradiate the entire surface of the curable resin layer with the energy beam or electron beam.

[0155] The energy rays can be irradiated using a high-pressure mercury lamp, an electrodeless lamp, a xenon lamp, or the like. The wavelength of the energy ray is preferably 200 to 400 nm, more preferably 350 to 400 nm. The irradiation dose is usually an illuminance of 50 to 1,000 mW / cm. 2 , light intensity 50~5,000mJ / cm 2 , preferably 1,000 to 5,000 mJ / cm 2 The irradiation time is usually 0.1 to 1,000 seconds, preferably 1 to 500 seconds, and more preferably 10 to 100 seconds. In consideration of the heat load in the light irradiation step, irradiation may be carried out multiple times to satisfy the above-mentioned light amount.

[0156] In this case, to prevent deterioration of the polymer component (A) due to the energy ray irradiation and coloration of the cured resin layer, the curable resin composition may be irradiated with energy rays through a filter that absorbs light of wavelengths unnecessary for the curing reaction. According to this method, light of wavelengths unnecessary for the curing reaction and that deteriorate the polymer component (A) is absorbed by the filter, so deterioration of the polymer component (A) is suppressed and a colorless and transparent cured resin layer is easily obtained. A resin film such as a polyethylene terephthalate film can be used as the filter. When a resin film is used, it is preferable to provide a step between the first and second steps in which a resin film such as a polyethylene terephthalate film is laminated on the curable resin layer, separate from the processing film used in the first step. The resin film is usually peeled off after the second step. The resin film can also be considered a processing film, and by sandwiching the cured resin layer between the processing film used in the first step and a resin film (second processing film), an optical film 10B having the configuration shown in FIG. 1(b) can be obtained.

[0157] The curable resin layer can also be cured by irradiating it with an electron beam. When irradiating with an electron beam, the curable resin layer can usually be cured without using a photopolymerization initiator. When irradiating with an electron beam, an electron beam accelerator or the like can be used. The irradiation dose is usually in the range of 10 to 1,000 krad. The irradiation time is usually 0.1 to 1,000 seconds, preferably 1 to 500 seconds, and more preferably 10 to 100 seconds.

[0158] The curable resin layer may be cured in an inert gas atmosphere such as nitrogen gas, if necessary. By performing the curing in an inert gas atmosphere, it becomes easier to avoid oxygen, moisture, etc. from interfering with the curing.

[0159] (Third step) In the third step, after the start of the second step, the curable resin layer is subjected to a heat treatment in which the curable resin layer is heated to 150° C. or higher to obtain a cured resin layer (reference numeral 2 in FIG. 3(d)). By going through the third step, the curing of the curable resin layer is substantially completed, and a cured resin layer is formed.

[0160] In the third step, the temperature of the heat treatment is preferably 160° C. or higher, more preferably 170° C. or higher, and even more preferably 180° C. or higher, from the viewpoint of further accelerating the curing. Moreover, from the viewpoint of suppressing deterioration of the obtained cured resin layer, the temperature is preferably 210° C. or lower, more preferably 200° C. or lower, and even more preferably 190° C. or lower. The heat treatment time varies depending on the type of curable resin composition used and the heat treatment temperature, but from the viewpoint of sufficiently promoting curing, it is preferably 30 minutes or more, more preferably 45 minutes or more, and even more preferably 1 hour or more, and from the viewpoint of productivity, it is preferably 3 hours or less, more preferably 2.5 hours or less, and even more preferably 2 hours or less. The heat treatment may be started after the start of the second step, and may be carried out, for example, after the completion of the second step, or in parallel with the second step after a certain time has elapsed since the start of the second step. There are no particular limitations on the heat treatment method, and various methods can be used. For example, the heat treatment can be performed by heating the curable resin layer in air or an inert gas atmosphere using a heating oven or autoclave. [Example]

[0161] Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples in any way.

[0162] Measurement and evaluation of the physical properties of the cured resin layer and the optical film in each of the Examples and Comparative Examples were carried out according to the following procedures.

[0163] <Peak temperature of loss tangent and rate of decrease in storage modulus> Eight cured resin layers, each corresponding to a process film, were laminated to a thickness of 40 μm, after peeling off the polyethylene terephthalate (PET) films on both sides of the cured resin layer. These were then cut into 5 mm x 30 mm test pieces and clamped using a thermomechanical analyzer (DMA242, manufactured by Netsch Japan Co., Ltd.) with a chuck distance of 15 mm. The cured resin layer laminate was then heated from 25°C to 280°C at a rate of 3°C / min to measure the storage modulus and loss modulus. A loss tangent (loss modulus / storage modulus) curve was then plotted over the temperature range from 25°C to 280°C, and the curve was fitted with a Gaussian function to separate the peaks. The temperature at the apex of each peak was determined as the loss tangent peak temperature. The rate of decrease in storage modulus from 25° C. to 150° C. was calculated by the following formula (1) to obtain the rate of decrease in storage modulus. Storage modulus reduction rate = (storage modulus at 25°C - storage modulus at 150°C) ÷ storage modulus at 25°C × 100 (%) Formula (1)

[0164] <Total light transmittance> As an optical property of the optical film, the total light transmittance was measured by the following procedure. The polyethylene terephthalate (PET) films on both sides of the cured resin layer, which corresponded to the process film, were peeled off to form a test piece, and the transmittance of white light transmitted through the test piece was measured using a haze meter (NDH5000, manufactured by Nippon Denshoku Industries Co., Ltd.), and this was taken as the total light transmittance (%).

[0165] [Example 1] A curable resin composition E1 for forming a cured resin layer was prepared by the following procedure. As the polymer component (A), 100 parts by mass of polyimide resin (PI) pellets (Kawamura Sangyo Co., Ltd., product name KPI-MX300F, Tg = 354°C, weight average molecular weight 280,000) were dissolved in methyl ethyl ketone (MEK) to prepare a 15% by mass solution of PI. Next, 122 parts by mass of tricyclodecane dimethanol diacrylate (Shin-Nakamura Chemical Co., Ltd., A-DCP) as the curable monomer (B) and 5 parts by mass of bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (BASF, Irgacure 819) as the polymerization initiator were added to this solution and mixed to prepare curable resin composition E1. The curable monomer (B) and polymerization initiator used in this and other experimental examples did not contain solvent and were all 100% solids raw materials.

[0166] Next, a first PET film (Cosmoshine PET100A-4160, 100 μm thick, manufactured by Toyobo Co., Ltd.) having an easy-adhesion layer on one side was used as the first process film, and the curable resin composition E1 was applied to the side of this PET film opposite the easy-adhesion layer side, and the coating was dried by heating at 90°C for 3 minutes. Furthermore, a second PET film (Cosmoshine PET50A-4160, manufactured by Toyobo Co., Ltd., thickness 50 μm) having an easy-adhesion layer on one side was laminated as a second process film on the dried coating film so that the surface opposite the easy-adhesion surface faced the easy-adhesion surface. Then, using a belt conveyor type ultraviolet irradiation device (manufactured by iGraphics Co., Ltd., product name: ECS-401GX), ultraviolet light was irradiated from a high-pressure mercury lamp (manufactured by iGraphics Co., Ltd., product name: H04-L41) with an ultraviolet lamp height of 100 mm, an ultraviolet lamp output of 3 kW, and a light wavelength of 365 nm at an illuminance of 400 mW / cm. 2 , light intensity 800mJ / cm 2 The resin was irradiated with ultraviolet light through the second PET film under the conditions (measured with an ultraviolet actinometer UV-351 manufactured by ORC Manufacturing Co., Ltd.) to cause a curing reaction, thereby forming a cured resin layer with a thickness of 5 μm. Furthermore, this cured resin layer was subjected to a heat treatment by heating at 180° C. for 1 hour using a heating oven, thereby obtaining an optical film.

[0167] [Comparative Example 1] An optical film was obtained in the same manner as in Example 1, except that the cured resin layer was not subjected to the heat treatment of heating at 180° C. for 1 hour.

[0168] Comparative Example 2 An optical film was obtained in the same manner as in Example 1, except that pellets of a polysulfone resin (ULTRASON S3010, manufactured by BASF, Tg=180° C.) were used instead of pellets of a polyimide resin (PI).

[0169] The measurement results of the examples and comparative examples are shown in Table 1. In the heat treatment column of Table 1, "Y" indicates that heat treatment was performed, and "N" indicates that heat treatment was not performed.

[0170] [Table 1]

[0171] As is clear from Table 1, only a loss tangent peak with a peak temperature of 250° C. is observed in the optical film of Example 1. In other words, the optical film of Example 1 has one or more loss tangent peaks, and the peak temperatures of all of the loss tangent peaks are 150° C. or higher. Therefore, the optical film of Example 1 can have a small rate of decrease in storage modulus.

[0172] On the other hand, in the film of Comparative Example 1, loss tangent peaks are observed at peak temperatures of 130°C, 190°C, and 250°C, respectively. That is, the film of Comparative Example 1 has one or more loss tangent peaks, but not all of the loss tangent peaks have peak temperatures of 150°C or higher. Therefore, the storage modulus decrease rate is larger than that of the optical film of Example 1. Therefore, it can be understood that the film of Comparative Example 1 is subject to a large degree of thermal deformation, and there is room for improvement when used to form functional layers that require a formation process involving heating, such as transparent conductive layers and gas barrier layers. In Comparative Example 2, a polysulfone-based resin having a Tg of 180°C was used as the polymer component (A), and the rate of decrease in storage modulus was larger than that of the optical film of Example 1. Therefore, it can be seen that the film of Comparative Example 2 is highly deformed by heat, and there is room for improvement when used to form functional layers that require a formation process involving heating, such as transparent conductive layers and gas barrier layers. [Explanation of symbols]

[0173] 1, 1A, 1B: Processing film 2: Cured resin layer 2a: Curable resin layer 2b: Curable resin layer after irradiation with energy rays or electron beams 3: Transparent conductive layer 4: Gas barrier layer 10A, 10B: Optical film 20: Transparent conductive film 21: Transparent conductive film with a patterned transparent conductive layer 22: Gas barrier film 31: Patterned transparent conductive layer

Claims

1. An optical film comprising a process film and a cured resin layer, an optical film, wherein the cured resin layer is a layer made of a cured product of a curable resin composition containing a polymer component (A) and a curable monomer (B), the cured resin layer has a thickness of 15 μm or less, and characteristic values obtained by dynamic viscoelasticity measurement at a heating rate of 3°C / sec from 25°C to 280°C satisfy the following (I) and (II): (I) In a curve showing the change in loss tangent with respect to temperature, there is one or more loss tangent peaks, and the peak temperatures of all loss tangent peaks are 150°C or higher; (II) The storage modulus decrease rate, which is the rate of decrease in storage modulus from 25°C to 150°C, calculated by the following formula (1) is 40% or less. Storage modulus reduction rate = (storage modulus at 25°C - storage modulus at 150°C) ÷ storage modulus at 25°C × 100 (%) Formula (1)

2. An optical film comprising a process film and a cured resin layer, the cured resin layer is a layer made of a cured product of a curable resin composition containing a polymer component (A) and a curable monomer (B), the thickness of the cured resin layer is 15 μm or less, the glass transition temperature of the polymer component (A) is 250°C or higher, and a curve showing the change in loss tangent with temperature obtained by dynamic viscoelasticity measurement from 25°C to 280°C at a heating rate of 3°C / sec has one or more loss tangent peaks, and the peak temperatures of all of the loss tangent peaks are 150°C or higher.

3. 3. The optical film according to claim 1, wherein the cured resin layer has a thickness of 12 μm or less.

4. a first step of forming a curable resin layer on a cast film, the curable resin layer being made of a curable resin composition containing a polymer component (A) and a curable monomer (B); a second step of irradiating the curable resin layer with at least one of an energy ray and an electron beam to at least partially cure the curable resin layer; and a third step, after the start of the second step, of performing a heat treatment on the curable resin layer to 150°C or higher to obtain a cured resin layer having a thickness of 15 µm or less.

5. A transparent conductive film comprising: the optical film according to any one of claims 1 to 3; and a transparent conductive layer provided on the cured resin layer of the optical film.

6. A gas barrier film comprising: the optical film according to any one of claims 1 to 3; and a gas barrier layer provided on the cured resin layer of the optical film.

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