Epoxy film with release film, epoxy film and roll

Abstract

To provide an epoxy film with a release film, wherein the epoxy film does not easily peel from the release film, offers excellent productivity, and ensures excellent transparency of the epoxy film itself.SOLUTION: An epoxy film with a release film includes a release film and an epoxy resin layer. The epoxy resin layer includes an epoxy resin (A) and an isocyanate compound-derived unit (B). The surface of the release film that comes into contact with the epoxy resin layer has an average surface roughness (Sa) of 5 nm or more and 50 nm or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an epoxy film with a release film, an epoxy film, and a wound body. [Background technology]

[0002] Epoxy resins are used in a variety of fields, such as paints, civil engineering, adhesives, and electronic components, due to their excellent heat resistance, adhesive properties, water resistance, mechanical strength, and electrical properties.

[0003] For example, Patent Document 1 discloses a curable resin composition using a specific polymer polyether polyol resin, a tri- or higher functional epoxy resin, and an epoxy resin curing agent, and describes that the cured product obtained by curing the composition has excellent heat resistance and bending resistance, and is therefore applicable to foldable OLED displays. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2020 / 080292 Summary of the Invention [Problem to be solved by the invention]

[0005] Meanwhile, in order to apply a resin film to optical applications such as foldable OLED displays, the film is required to have high transparency.

[0006] However, when forming a cured product from the curable resin composition described in Patent Document 1, the curing time is long, 1 hour, and it has been found that, due to the long curing time at high temperature, the components of the release layer may be transferred to the epoxy layer, resulting in a loss of transparency.

[0007] Furthermore, the cure shrinkage that occurs when the thermosetting resin hardens creates stress during the cooling process after the film hardens, causing the epoxy layer to peel off from the release film, which can contaminate the drying oven and reduce productivity.

[0008] Therefore, an object of the present invention is to provide an epoxy film with a release film, which does not peel from the release film, has good productivity, and has excellent transparency. [Means for solving the problem]

[0009] The present inventors have discovered that when a coating liquid comprising an epoxy resin composition is applied to a release film to produce an epoxy film with a release film, the longer the time required for curing of the epoxy film, the more likely it is that the components of the release layer will be transferred.

[0010] Furthermore, the present inventors have discovered that by using a release film having a surface roughness within a specific range, not only is it less likely that the components of the release layer will be transferred during peeling, but peeling of the epoxy resin layer from the release film due to the cure shrinkage of the epoxy resin can also be suppressed, and that this makes it possible to solve the above-mentioned problems of productivity and transparency.

[0011] That is, the present invention has the following aspects.

[0012] [1] A first aspect of the present invention is an epoxy film with a release film, which comprises a release film and an epoxy resin layer, wherein the epoxy resin layer contains an epoxy resin (A) and an isocyanate compound-derived unit (B), and the average surface roughness (Sa) of the surface of the release film on the side in contact with the epoxy resin layer is 5 nm or more and 50 nm or less.

[0013] [2] A second aspect of the present invention is an epoxy film with a release film, wherein the release film in the first aspect has a substrate and a release layer, the epoxy resin layer is laminated on the release layer, and the average surface roughness (Sa) of the surface of the release layer on the side in contact with the epoxy resin layer is 5 nm or more and 50 nm or less.

[0014] [3] A third aspect of the present invention is an epoxy film with a release film according to the first or second aspect, wherein the epoxy resin (A) is a resin obtained by reacting an epoxy compound and a phenolic compound.

[0015] [4] A fourth aspect of the present invention is the epoxy film with a release film according to the third aspect, wherein the epoxy compound is a compound having two or more epoxy groups in the molecule.

[0016] [5] A fifth aspect of the present invention is an epoxy film with a release film according to the third or fourth aspect, wherein the phenolic compound is a compound having two or more hydroxyl groups bonded to an aromatic ring.

[0017] [6] A sixth aspect of the present invention is the epoxy film with a release film according to any one of the first to fifth aspects, wherein the molecular weight of the epoxy resin (A) before curing is 2,000 to 300,000.

[0018] [7] A seventh aspect of the present invention is an epoxy film with a release film, wherein in any one of the first to sixth aspects, the isocyanate compound-derived units (B) are units derived from a compound having an aliphatic isocyanate as the main skeleton.

[0019] [8] An eighth aspect of the present invention is the epoxy film with a release film according to any one of the first to seventh aspects, wherein the epoxy resin layer further contains a leveling agent.

[0020] [9] A ninth aspect of the present invention is the epoxy film with a release film according to any one of the first to eighth aspects, wherein the glass transition temperature of the epoxy resin layer is 100° C. or higher.

[0021]

[10] A tenth aspect of the present invention is an epoxy film having an epoxy resin layer containing an epoxy resin (A) and an isocyanate compound-derived unit (B), wherein the average surface roughness (Sa) of at least one surface of the epoxy resin layer is in the range of 5 nm to 50 nm.

[0022]

[11] An eleventh aspect of the present invention is the epoxy film according to the tenth aspect, further comprising a protective film.

[0023]

[12] A twelfth aspect of the present invention is the epoxy film according to the tenth or eleventh aspect, which has a functional layer on at least one side of the epoxy resin layer.

[0024]

[13] A thirteenth aspect of the present invention is a wound body obtained by winding the epoxy film with a release film according to any one of the first to ninth aspects or the epoxy film according to any one of the tenth to twelfth aspects around a core. [Effects of the Invention]

[0025] According to the present invention, an epoxy film with a release film can be obtained which does not peel from the release film, has good productivity, and has excellent transparency of the epoxy film. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 is a schematic diagram of a cross section of an epoxy film with a release film of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0027] An embodiment of the present invention will be described below. However, the present invention is not limited to the embodiment described below, and various modifications are possible without departing from the gist of the present invention. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​written before and after "to" as the lower and upper limits.

[0028] <<Epoxy film with release film>> The epoxy film with a release film of the present invention (hereinafter also referred to as "the epoxy film with the release film of this invention", and the release film in such a configuration will also be simply referred to as "the release film of this invention") has a configuration in which an epoxy resin layer is provided on the release layer side of the release film, and the average surface roughness (Sa) of the release layer surface on the side in contact with the epoxy resin layer is 5 nm or more and 50 nm or less.

[0029] By ensuring that the average surface roughness (Sa) of the release layer surface is within the above range, it is possible to uniformly apply an epoxy resin layer that can be cured in a short time without repelling, and the appropriate surface irregularities provide an anchoring effect, thereby preventing peeling of the epoxy resin layer from the release film due to cure shrinkage of the epoxy resin. Furthermore, by ensuring that the average surface roughness (Sa) of the release layer surface is within the above range, an excessive anchoring effect due to the surface irregularities is suppressed, preventing the transfer of the release component of the release layer of the release film. This allows for the production of a highly transparent epoxy film.

[0030] From this viewpoint, the average surface roughness (Sa) of the release layer surface is more preferably 5 nm or more and 50 nm or less, even more preferably 10 nm or more and 40 nm or less, and most preferably 15 nm or more and 30 nm or less.

[0031] Furthermore, the epoxy resin layer in this epoxy film with a release film contains an isocyanate compound to enable it to be cured in a short time and to increase the transparency of the film. When producing an epoxy film with a release film, the longer it takes to cure the epoxy film, the more the components of the release layer are transferred, reducing the transparency of the epoxy film. Therefore, by including an isocyanate compound in the epoxy resin layer, the transparency of the epoxy film can be more effectively increased.

[0032] As described above, in this epoxy film with release film, by setting the average surface roughness (Sa) of the release layer surface within a predetermined range and by incorporating an isocyanate compound into the epoxy resin layer, the epoxy film with release film does not peel off, has good productivity, and has succeeded in increasing the transparency of the resulting epoxy film.

[0033] The average surface roughness (Sa) of the release layer side of the present release film is an arithmetic mean height, and is a value measured in accordance with ISO 25178-2 (2012). More specifically, it is a value measured in accordance with the method described in the examples.

[0034] As shown in Figure 1, the present release film preferably has a release layer 2. Although the present release film may be a release film consisting of only the release layer 2, the present release film 5 preferably has a substrate 1 and a release layer 2. This release layer 2 is disposed on the epoxy resin layer 3 side. The average surface roughness (Sa) of the surface of the release layer 2 on the epoxy resin layer 3 side is preferably within the above range.

[0035] As shown in Figure 1, in the epoxy film 10 with a release film, it is preferable that the release layer 2 and the epoxy resin layer 3 in the release film 5 are directly laminated. It is preferable that the epoxy film with a release film has an epoxy resin layer formed on the release layer of the release film.

[0036] <Release film> This release film is a release film for laminating an epoxy resin layer containing an epoxy resin (A) and an isocyanate compound-derived unit (B), and the average surface roughness (Sa) of the release film surface on the side in contact with the epoxy resin layer is 5 nm or more and 50 nm or less.

[0037] The release film may be, for example, a thin sheet-like substrate made of paper, resin, metal or the like, on the surface of which a release layer is formed by applying a silicone resin release agent or the like. The substrate is preferably paper or resin from the viewpoints of low cost, ease of processing, and ease of disposal and recycling, and more preferably resin from the viewpoint of transparency.

[0038] Examples of the paper include fine paper, kraft paper, glassine paper, parchment paper, and supercalendered kraft paper whose surfaces have been silicone coated.

[0039] As the resin film, for example, a film containing as a main component polyolefin such as polyethylene or polypropylene, polyester such as polyethylene terephthalate or polyethylene naphthalate, polyimide, or polycarbonate can be used. Among the above, it is preferable to use a resin film containing polyester as a main component in terms of appearance, ease of processing, durability, heat resistance, cost, etc. The resin film may have a single layer structure or a multi-layer structure of two or more layers.

[0040] The term "main component resin" refers to the resin with the highest content among the resins constituting the base material, specifically a resin that accounts for 50% by mass or more, particularly 70% by mass or more, particularly 80% by mass or more, and particularly 90% by mass or more (including 100% by mass) of that.

[0041] The polyester is preferably one obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol. The polyester may be a polyester composed of one type of aromatic dicarboxylic acid and one type of aliphatic glycol, or a copolymer polyester in which one or more other components are further copolymerized. Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of the aliphatic glycol include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. On the other hand, examples of dicarboxylic acids used as other components of the copolymer polyester include isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, and sebacic acid, and examples of glycol components include ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, and neopentyl glycol. Further, oxycarboxylic acids such as p-oxybenzoic acid can also be used.

[0042] Typical examples of polyesters include polyethylene terephthalate obtained by polycondensation of terephthalic acid and ethylene glycol, and polyethylene naphthalate obtained by polycondensation of 2,6-naphthalenedicarboxylic acid and ethylene glycol. The polyester film may be either a non-stretched film or a stretched film, but from the viewpoint of mechanical strength, a stretched film is preferred, and a biaxially stretched film is more preferred. The polyester film may be previously subjected to a surface treatment such as a corona treatment or a plasma treatment.

[0043] Furthermore, the present release film preferably further comprises a release layer as the outermost layer on the side that comes into contact with the epoxy resin layer. When the present release film further comprises a release layer in addition to the substrate, the peelability between the epoxy resin layer and the release film is improved.

[0044] The components of the release layer are not particularly limited, and may contain silicone compounds, fluorine compounds, waxes, surfactants, etc. From the viewpoint of a good balance between cost and releasability, it is preferable to use silicone compounds. Furthermore, a release control agent may be used in combination to adjust the release properties of the release layer, or a surface treatment such as corona treatment or plasma treatment may be carried out. The release layer may be laminated directly onto the substrate, or may be laminated via another layer, such as an easy-adhesion layer or an antistatic layer.

[0045] As described above, in this release film, the average surface roughness (Sa) of the release layer surface on the side in contact with the epoxy resin layer is 5 nm or more and 50 nm or less. To adjust the average surface roughness (Sa) within this range, the thickness of the release film and the release layer can be controlled, or the particle size and content of the inorganic particles (so-called lubricant) contained in the release layer can be adjusted. Among these, from the viewpoint of reducing the average surface roughness (Sa), it is preferable that the substrate and / or the release layer does not substantially contain particles. In addition, "substantially free of particles" is defined as, for both the substrate and the release layer, for example, in the case of inorganic particles, being 50 ppm or less when elements derived from the particles are quantitatively analyzed by fluorescent X-ray analysis, preferably 10 ppm or less, and most preferably below the detection limit.

[0046] (Thickness of this release film) The thickness of the present release film is preferably 5 to 300 μm, and more preferably 20 to 150 μm. It is preferable that the thickness of the release film is equal to or greater than the above lower limit, since this improves the handling properties when applying the epoxy resin composition and when peeling the epoxy resin layer from the release film. In addition, when the thickness is equal to or less than the upper limit, the present release film is less likely to break, and material costs can be reduced, which is also preferable.

[0047] (Release layer thickness) When the release film has a release layer, the thickness of the release layer after curing is preferably 0.05 to 1 μm, and more preferably 0.1 to 0.5 μm. When the thickness of the release layer is equal to or greater than the lower limit, the release properties are good and the handling properties when peeling off the epoxy resin layer are improved, so that a film with good appearance can be obtained, which is preferable. Furthermore, when the thickness is equal to or less than the upper limit, there is no problem with the releasability, and the cost of the release layer can be reduced, which is preferable.

[0048] (Release film manufacturing method) When the release film has a substrate and a release layer, the method for forming the release layer of the release film is not particularly limited, and for example, a method is used in which a coating liquid in which a release agent is dissolved or dispersed is spread by coating or the like on one side of the substrate, the solvent and the like are removed by drying, and then the layer is cured. Furthermore, after the solvent has dried, it is also preferable to irradiate the composition with active energy rays to promote the curing reaction. The active energy rays used in this case can be ultraviolet rays, electron beams, X-rays, etc., but ultraviolet rays are preferred because they are easy to use. Furthermore, there are two methods for applying the coating liquid: an offline method in which the coating liquid is applied to a pre-stretched film, and an in-line method in which the substrate coated with the coating liquid is dried and stretched. However, the in-line method is preferred from the viewpoint of being able to reduce the average surface roughness (Sa) of the release layer surface. When applied by the in-line method, the coating film applied to the substrate is formed simultaneously with stretching due to the heat generated during stretching, and the particles dispersed in the coating liquid fuse together, thereby reducing the surface roughness parameter Sa.

[0049] The substrate can be produced by a known method such as coextrusion, extrusion lamination, dry lamination, or inflation.

[0050] <Epoxy resin layer> The epoxy film with a release film has an epoxy resin layer, which is obtained by curing an epoxy resin composition containing an epoxy resin (A) and an isocyanate compound (B). That is, the epoxy resin layer contains the epoxy resin (A) and units derived from an isocyanate compound (B). Because the epoxy resin composition contains an isocyanate compound (B) as a crosslinking agent, the time required for curing can be shortened, resulting in increased productivity. Furthermore, because the epoxy resin layer contains the isocyanate compound-derived unit (B), the transfer of the release component contained in the release layer of the release film can be prevented, thereby forming an epoxy resin layer with high transparency. Furthermore, because the epoxy resin layer contains the isocyanate compound-derived unit (B), the transfer of the release component contained in the release layer of the release film can be prevented, thereby suppressing problems such as poor adhesion between the epoxy resin layer and the release film.

[0051] (Epoxy resin composition) Each component constituting the epoxy resin composition will be described below.

[0052] 1. Epoxy resin (A) The epoxy resin composition contains an epoxy resin (A). Examples of the epoxy resin (A) include alcohol-type epoxy resins, bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, bisphenol C-type epoxy resins, bisphenol S-type epoxy resins, naphthalene-type epoxy resins, phenol novolac-type epoxy resins, cresol novolac-type epoxy resins, bisphenol A novolac-type epoxy resins, biphenyl-type epoxy resins, triphenylmethane-type epoxy resins, dicyclopentadiene-type epoxy resins, glycidyl ester-type epoxy resins, glycidyl amine-type epoxy resins, polyfunctional phenol-type epoxy resins, aliphatic epoxy resins, alicyclic epoxy resins, heterocyclic epoxy resins, and epoxy resins having any combination of these structures.

[0053] The epoxy resin (A) may be one of the epoxy resins exemplified above, or two or more of them may be used in any combination and ratio.

[0054] Among these, as the epoxy resin (A), it is preferable to use an epoxy resin having at least one skeleton selected from the group consisting of a phenyl skeleton (phenol skeleton), a naphthalene skeleton, a fluorene skeleton, a biphenyl skeleton, an anthracene skeleton, a pyrene skeleton, a xanthene skeleton, an adamantane skeleton, and a dicyclopentadiene skeleton; from the viewpoint of heat resistance, it is more preferable to use an epoxy resin having at least one skeleton selected from the group consisting of a phenyl skeleton, a fluorene skeleton, and a biphenyl skeleton; and from the viewpoints of ease of production and heat resistance, it is even more preferable to use an epoxy resin having at least one skeleton selected from the group consisting of a bisphenol A skeleton, a bisphenol F skeleton, and a biphenyl skeleton.

[0055] The type and skeleton of the epoxy resin (A) can be confirmed by NMR (nuclear magnetic resonance spectroscopy), IR (infrared spectroscopy), SEM (scanning electron microscope) analysis, IPC (inductively coupled plasma) optical emission spectroscopy, TGA (thermogravimetric analysis), DSC (differential scanning calorimetry), various types of chromatography, and the like.

[0056] The epoxy resin (A) is preferably the epoxy resin (α) shown below.

[0057] (Epoxy resin (α)) The epoxy resin (α) is preferably a resin obtained by reacting an epoxy compound with a phenolic compound, and can be obtained, for example, by a two-stage method in which a bifunctional epoxy resin is reacted with a divalent hydroxyl group-containing compound. Alternatively, it can be obtained by a one-stage method in which two or more divalent hydroxyl group-containing compounds are directly reacted with epichlorohydrin. However, the two-stage method is preferred because it allows for easier production of a variety of epoxy resins, from low to high molecular weight, than the one-stage method.

[0058] =Epoxy compounds= The epoxy compound is preferably a compound having two or more epoxy groups in the molecule, and examples of such compounds include bifunctional epoxy compounds and polyfunctional epoxy compounds (trifunctional or higher).

[0059] Examples of the bifunctional epoxy compound include bisphenols such as bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol E diglycidyl ether, bisphenol C diglycidyl ether, bisphenol Z diglycidyl ether, bisphenol S diglycidyl ether, bisphenol AD ​​diglycidyl ether, bisphenol acetophenone diglycidyl ether, bisphenol trimethylcyclohexane diglycidyl ether, bisphenol fluorene diglycidyl ether, tetramethyl bisphenol A diglycidyl ether, tetramethyl bisphenol F diglycidyl ether, tetra-t-butyl bisphenol A diglycidyl ether, and tetramethyl bisphenol S diglycidyl ether. biphenol diglycidyl ethers such as biphenol diglycidyl ether, tetramethylbiphenol diglycidyl ether, dimethylbiphenol diglycidyl ether, and tetra-t-butylbiphenol diglycidyl ether; benzenediol diglycidyl ethers such as hydroquinone diglycidyl ether, methylhydroquinone diglycidyl ether, dibutylhydroquinone diglycidyl ether, resorcinol diglycidyl ether, and methylresorcinol diglycidyl ether; dihydroanthrahydroquinone diglycidyl ether, dihydroxydiphenyl ether diglycidyl ether, thiodiphenol diglycidyl ether, and dihydroxynaphthalene diglycidyl ether.

[0060] Further, epoxy compounds in which hydrogen is added to the aromatic ring of the bifunctional epoxy compounds exemplified above; epoxy compounds produced from various carboxylic acids such as adipic acid, succinic acid, phthalic acid, tetrahydrophthalic acid, methylhexahydrophthalic acid, terephthalic acid, isophthalic acid, orthophthalic acid, biphenyldicarboxylic acid, and dimer acid, and epihalohydrin; epoxy compounds produced from various amine compounds such as diaminodiphenylmethane, aminophenol, and xylenediamine, and epihalohydrin; ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, polytetramethyl ether, and (poly)alkylene glycol diglycidyl ethers consisting only of a chain structure, such as 1,5-pentanediol diglycidyl ether, polypentamethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, polyhexamethylene glycol diglycidyl ether, 1,7-heptanediol diglycidyl ether, polyheptamethylene glycol diglycidyl ether, 1,8-octanediol diglycidyl ether, 1,10-decanediol diglycidyl ether, and 2,2-dimethyl-1,3-propanediol diglycidyl ether; and alkylene glycol diglycidyl ethers having a cyclic structure, such as 1,4-cyclohexanedimethanol diglycidyl ether.

[0061] Examples of the polyfunctional epoxy compound include phenol novolac epoxy resins, cresol novolac epoxy resins, bisphenol A novolac epoxy resins, naphthol novolac epoxy resins, phenol aralkyl epoxy resins, biphenyl aralkyl epoxy resins, dicyclopentadiene epoxy resins, phenol-modified xylene epoxy resins, trisphenolmethane epoxy resins, tetraphenolethane epoxy resins, polyhydric phenol resins obtained by condensation reaction of these various phenols with various aldehydes such as hydroxybenzaldehyde, crotonaldehyde, glyoxal, and epoxy resins using various phenolic compounds such as co-condensation resins of heavy oils or pitches with phenols and formaldehydes.

[0062] The epoxy compound may be used alone or in any combination of two or more of the epoxy compounds exemplified above in any ratio. Among these, bifunctional epoxy compounds are preferred from the viewpoint of obtaining a copolymer with a molecular weight suitable for film formation while suppressing gelation during the reaction, and bisphenol diglycidyl ethers are more preferred from the viewpoint of the transparency of the epoxy resin layer, and bisphenol A diglycidyl ether is even more preferred from the viewpoint of the transparency and heat resistance of the epoxy resin layer.

[0063] =Phenol compounds= The phenolic compound is preferably a compound having two or more hydroxyl groups bonded to an aromatic ring, and more preferably a compound having two hydroxyl groups bonded to an aromatic ring.

[0064] Examples of the phenolic compounds include bisphenols such as bisphenol A, bisphenol F, bisphenol E, bisphenol C, bisphenol Z, bisphenol S, bisphenol AD, bisphenolacetophenone, bisphenoltrimethylcyclohexane, bisphenolfluorene, tetramethylbisphenol A, tetramethylbisphenol F, tetra-t-butylbisphenol A, and tetramethylbisphenol S; biphenols such as biphenol, tetramethylbiphenol, dimethylbiphenol, and tetra-t-butylbiphenol; benzenediols such as hydroquinone, methylhydroquinone, dibutylhydroquinone, resorcin, and methylresorcin; dihydroanthrahydroquinones such as dihydroanthrahydroquinone; and dihydroxydiphenyl ether. dihydroxynaphthalenes such as dihydroxystilbenes; bisphenol-based novolac resins such as phenol novolac resins, cresol novolac resins, and bisphenol A novolac resins; various phenolic resins such as naphthol novolac resins, phenol aralkyl resins, terpene phenolic resins, dicyclopentadiene phenolic resins, phenol biphenylene resins, and phenol-modified xylene resins; polyhydric phenolic resins obtained by the condensation reaction of these various phenols with various aldehydes such as hydroxybenzaldehyde, crotonaldehyde, and glyoxal; and various phenolic compounds such as co-condensation resins of heavy oils or pitches, phenols, and formaldehydes.

[0065] The phenolic compound may be used alone or in any combination of two or more of the phenolic compounds listed above in any ratio. Among these, bisphenols are preferred from the viewpoints of obtaining a copolymer with a molecular weight suitable for film formation while suppressing gelation during reaction with the glycidyl ether, and from the viewpoints of the transparency and heat resistance of the epoxy resin layer.

[0066] =Amount of epoxy compound and phenolic compound used= When preparing the epoxy resin (α), the amount of the phenolic compound used is preferably 0.05 mol or more, more preferably 0.10 mol or more, even more preferably 0.15 mol or more, and even more preferably 0.20 mol or more, per 1.00 mol of the epoxy compound. On the other hand, the amount of the phenolic compound used is preferably 1.25 mol or less, more preferably 1.20 mol or less, even more preferably 1.15 mol or less, and even more preferably 1.10 mol or less, per 1.00 mol of the epoxy compound. It is preferable from the viewpoint of molecular weight elongation if the amount of the phenolic compound used is equal to or more than the above lower limit. In particular, within this range, the amount of the phenolic compound should be reduced when a low molecular weight epoxy compound is desired, and the amount of the phenolic compound should be increased when a high molecular weight epoxy compound is desired. On the other hand, if the content is equal to or less than the upper limit, an epoxy compound with good curability is easily obtained, which is preferable.

[0067] =Catalyst= In preparing the epoxy resin (α), a catalyst may be used in the reaction between the epoxy compound and the phenolic compound. The catalyst used in producing the epoxy resin (α) is not particularly limited as long as it is a compound with catalytic ability to promote the reaction between the epoxy group and the phenolic hydroxyl group, alcoholic hydroxyl group, or carboxyl group. Examples of the catalyst include alkali metal compounds, organic phosphorus compounds, tertiary amines, quaternary ammonium salts, cyclic amines, and imidazoles.

[0068] Specific examples of the alkali metal compound include alkali metal hydroxides such as sodium hydroxide, lithium hydroxide, and potassium hydroxide; alkali metal salts such as sodium carbonate, sodium bicarbonate, sodium chloride, lithium chloride, and potassium chloride; alkali metal alkoxides such as sodium methoxide and sodium ethoxide; alkali metal phenoxides; alkali metal hydrides such as sodium hydride and lithium hydride; and alkali metal salts of organic acids such as sodium acetate and sodium stearate.

[0069] Specific examples of the organic phosphorus compound include tri-n-propylphosphine, tri-n-butylphosphine, triphenylphosphine, tetramethylphosphonium bromide, tetramethylphosphonium iodide, tetramethylphosphonium hydroxide, trimethylcyclohexylphosphonium chloride, trimethylcyclohexylphosphonium bromide, trimethylbenzylphosphonium chloride, trimethylbenzylphosphonium bromide, tetraphenylphosphonium bromide, triphenylmethylphosphonium bromide, triphenylmethylphosphonium iodide, triphenylethylphosphonium chloride, triphenylethylphosphonium bromide, triphenylethylphosphonium iodide, triphenylbenzylphosphonium chloride, and triphenylbenzylphosphonium bromide.

[0070] Specific examples of tertiary amines include triethylamine, tri-n-propylamine, tri-n-butylamine, triethanolamine, and benzyldimethylamine.

[0071] Specific examples of quaternary ammonium salts include tetramethylammonium chloride, tetramethylammonium bromide, tetramethylammonium hydroxide, triethylmethylammonium chloride, tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium iodide, tetrapropylammonium bromide, tetrapropylammonium hydroxide, tetrabutylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium iodide, benzyltrimethylammonium chloride, benzyltrimethylammonium bromide, benzyltrimethylammonium hydroxide, benzyltributylammonium chloride, and phenyltrimethylammonium chloride.

[0072] Specific examples of imidazoles include 2-methylimidazole, 2-ethyl-4-methylimidazole, and 2-phenylimidazole.

[0073] Specific examples of cyclic amines include 1,8-diazabicyclo(5,4,0)7-undecene, 1,5-diazabicyclo(4,3,0)5-nonene, and the like. These catalysts may be used alone or in combination of two or more.

[0074] The amount of catalyst used is usually preferably 0.001 to 1% by mass of the reaction solid content. By using the catalyst in an amount equal to or greater than the above-mentioned lower limit, it becomes easier to increase the molecular weight, and by using the catalyst in an amount equal to or less than the above-mentioned upper limit, it becomes easier to suppress gelation. The reaction solid content refers to the total amount of reaction substrates other than the solvent in the reaction system.

[0075] =Solvent= In the preparation of the epoxy resin (α), a solvent may be used in the reaction step of the epoxy compound and the phenolic compound. The solvent is not particularly limited as long as it dissolves the epoxy compound, the phenolic compound, and other raw materials, but is usually an organic solvent, such as an aromatic solvent, a ketone solvent, an amide solvent, or a glycol ether solvent.

[0076] Examples of the aromatic solvent include benzene, toluene, and xylene. Examples of the ketone solvent include acetone, methyl ethyl ketone, methyl isobutyl ketone, 2-heptanone, 4-heptanone, 2-octanone, cyclopentanone, cyclohexanone, and acetylacetone. Examples of the amide solvent include formamide, N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, 2-pyrrolidone, and N-methylpyrrolidone. Examples of the glycol ether solvent include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol dimethyl ether, ethylene glycol monoethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol dimethyl ether, diethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether, propylene glycol mono-n-butyl ether, and propylene glycol monomethyl ether acetate.

[0077] The solvent may be one of the solvents exemplified above, or two or more of them may be used in any combination and ratio.

[0078] =Reaction conditions= The reaction between the epoxy compound and the phenolic compound may be carried out by a known method. The reaction system may be under normal pressure, elevated pressure or reduced pressure. The reaction temperature is usually 80 to 240°C, preferably 100 to 220°C, and more preferably 120 to 200°C. A reaction temperature equal to or higher than the lower limit is preferred because the reaction proceeds easily. A reaction temperature equal to or lower than the upper limit is preferred because side reactions are less likely to proceed and a high-purity epoxy compound can be obtained. The reaction time is not particularly limited, but is usually 0.5 to 24 hours, preferably 1 to 22 hours, and more preferably 1.5 to 20 hours. A reaction time of not more than the above upper limit is preferred from the viewpoint of improving production efficiency, and a reaction time of not less than the above lower limit is preferred from the viewpoint of reducing unreacted components.

[0079] (Molecular weight of epoxy resin (α)) The mass average molecular weight (mass average molecular weight before curing) of the epoxy resin (α) contained in the epoxy resin composition is preferably 2,000 to 300,000, and more preferably 10,000 to 100,000. When the mass average molecular weight is equal to or greater than the above lower limit, an epoxy resin layer having sufficient elasticity and elongation can be obtained. On the other hand, when the content is equal to or less than the upper limit, the type of solvent is not limited, and a coating liquid suitable for efficient film formation can be obtained.

[0080] (epoxy equivalent of epoxy resin (α)) The epoxy equivalent of the epoxy resin (α) is preferably 100 g / eq or more, more preferably 200 g / eq or more, even more preferably 300 g / eq or more, and even more preferably 500 g / eq or more.

[0081] On the other hand, the epoxy equivalent is preferably 200,000 g / eq or less, more preferably 150,000 g / eq or less, even more preferably 100,000 g / eq or less, and even more preferably 50,000 g / eq or less.

[0082] An epoxy equivalent of at least the above lower limit is preferred from the viewpoint of flexibility of the epoxy compound, whereas an epoxy equivalent of at most the above upper limit is preferred from the viewpoint of increasing the density between crosslinking points between epoxy groups and making it easier to obtain cured physical properties when curing an epoxy compound-containing composition described below. In the present invention, the term "epoxy equivalent" is defined as "the mass of an epoxy compound containing one equivalent of an epoxy group" and can be measured in accordance with JIS K7236:2009.

[0083] 2. Isocyanate Compound (B) The epoxy resin composition contains an isocyanate compound (B) as a crosslinking agent, which can increase the curing rate, resulting in improved optical properties, heat resistance, and solvent resistance of the resulting epoxy resin layer. In the present invention, the term "crosslinking agent" refers to a component that contributes to the crosslinking reaction and / or chain extension reaction between epoxy groups in the epoxy resin (A).

[0084] Examples of the isocyanate compound (B) include aliphatic isocyanates such as methylcyclohexane diisocyanate, hexamethylene diisocyanate, hydrogenated xylylene diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate, dimer acid diisocyanate, and trimethylhexamethylene diisocyanate; aromatic isocyanates such as tolylene diisocyanate, xylylene diisocyanate, and diphenylmethane diisocyanate; and lysine triisocyanate. Further examples include isocyanate compounds (e.g., adducts of isocyanate compounds, biurets of isocyanate compounds, etc.) obtained by reacting the isocyanate compounds exemplified above with compounds having an active hydrogen atom such as an amino group, a hydroxyl group, a carboxyl group, or water, and trimers to pentamers of the isocyanate compounds exemplified above (e.g., isocyanurates of isocyanate compounds, etc.).

[0085] The isocyanate compound (B) may be one of the isocyanate compounds exemplified above, or two or more of them may be used in any combination and ratio. Among these, compounds having an aliphatic isocyanate as the main skeleton are preferred from the viewpoint of film transparency and weather resistance, and compounds having hexamethylene diisocyanate as the main skeleton are more preferred.

[0086] The content of the isocyanate compound (B) is preferably 0.1 to 100 parts by mass, more preferably 1 to 80 parts by mass, and even more preferably 5 to 60 parts by mass, relative to 100 parts by mass of the epoxy resin (A).

[0087] 3. Other ingredients The epoxy resin composition may contain components other than the epoxy resin (A) and the isocyanate compound (B). Examples of the other components include crosslinking agents other than the isocyanate compound (B), leveling agents, solvents, curing accelerators (excluding those corresponding to the crosslinking agents), coupling agents, flame retardants, antioxidants, light stabilizers, plasticizers, reactive diluents, filler pigments, inorganic fillers, organic fillers, etc. The other components can be used in appropriate combinations depending on the desired physical properties of the epoxy resin composition.

[0088] (Crosslinking agent) Examples of the crosslinking agent other than the isocyanate compound (B) include polyfunctional phenols, amine compounds, acid anhydride compounds, imidazole compounds, amide compounds, cationic polymerization initiators, organic phosphines, etc. Among them, it is preferable to use an imidazole compound as the crosslinking agent other than the isocyanate compound (B), and it is preferable to use the isocyanate compound (B) and an imidazole compound in combination as the crosslinking agent.

[0089] Examples of the polyfunctional phenols include bisphenols such as bisphenol A, bisphenol F, bisphenol S, bisphenol B, bisphenol AD, bisphenol Z, and tetrabromobisphenol A; biphenols such as 4,4'-biphenol and 3,3',5,5'-tetramethyl-4,4'-biphenol; catechol, resorcinol, hydroquinone, and dihydroxynaphthalenes; and compounds in which the hydrogen atoms bonded to the aromatic rings of these compounds have been substituted with non-interfering substituents such as halogen groups, alkyl groups, aryl groups, ether groups, ester groups, and organic substituents containing hetero elements such as sulfur, phosphorus, and silicon. Further examples include the phenols exemplified above, and novolaks and resols which are polycondensates of monofunctional phenols such as phenol, cresol, and alkylphenols with aldehydes.

[0090] Examples of the amine compounds include aliphatic primary, secondary, and tertiary amines, aromatic primary, secondary, and tertiary amines, cyclic amines, guanidines, and urea derivatives. Specific examples include triethylenetetramine, diaminodiphenylmethane, diaminodiphenyl ether, metaxylenediamine, dicyandiamide, 1,8-diazabicyclo(5,4,0)-7-undecene, 1,5-diazabicyclo(4,3,0)-5-nonene, dimethylurea, and guanylurea.

[0091] Examples of the acid anhydride compounds include phthalic anhydride, hexahydrophthalic anhydride, trimellitic anhydride, and condensates of maleic anhydride and unsaturated compounds.

[0092] Examples of the imidazole compounds include 1-isobutyl-2-methylimidazole, 2-methylimidazole, 1-benzyl-2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, and benzimidazole.

[0093] Examples of the amide compounds include dicyandiamide and its derivatives, polyamide resins, and the like.

[0094] The cationic polymerization initiator generates cations when exposed to heat or active energy rays, and examples thereof include aromatic onium salts. Specifically, SbF6 - , BF4 - , AsF6 - , PF6 - , CF3SO3, B(C6F5) 4- and an aromatic cation component containing an atom such as iodine, sulfur, nitrogen, phosphorus, etc. Among these, diaryliodonium salts and triarylsulfonium salts are preferred.

[0095] Examples of the organic phosphines include tributylphosphine, methyldiphenylphosphine, triphenylphosphine, diphenylphosphine, and phenylphosphine. Examples of the phosphonium salts include tetraphenylphosphonium tetraphenylborate, tetraphenylphosphonium ethyltriphenylborate, and tetrabutylphosphonium tetrabutylborate. Examples of the tetraphenylboron salts include 2-ethyl-4-methylimidazole tetraphenylborate and N-methylmorpholine tetraphenylborate.

[0096] When polyfunctional phenols, amine compounds, or acid anhydride compounds are used, they are preferably used so that the equivalent ratio of functional groups in the crosslinking agent (hydroxyl groups of polyfunctional phenols, amino groups of amine compounds, or acid anhydride groups of acid anhydride compounds) to all epoxy groups in the epoxy resin composition is in the range of 0.01 to 1.5.

[0097] When an imidazole compound is used, it is preferably used in an amount of 0.001 to 10 parts by mass relative to 100 parts by mass of the total epoxy components.

[0098] When an amide compound is used, it is preferably used in an amount of 0.001 to 20% by mass in 100% by mass of the epoxy resin composition.

[0099] When a cationic polymerization initiator is used, it is preferably used in an amount of 0.001 to 15 parts by mass relative to 100 parts by mass of the total epoxy components.

[0100] When organic phosphines are used, they are preferably used in an amount of 0.001 to 20% by mass in 100% by mass of the epoxy resin composition.

[0101] (Leveling agent) The epoxy resin composition may contain a leveling agent to improve the surface appearance of the film formed therefrom. Adding a leveling agent to the epoxy resin composition also makes it possible to control the water droplet contact angle on the surface of the epoxy resin layer. Examples of the leveling agent include silicone-based leveling agents such as silane coupling agents, polyacrylate-based leveling agents, and perfluoroalkyl-based leveling agents. Only one of the leveling agents listed above may be used, or two or more may be used in any combination and ratio. Among these, it is preferable to use silicone macromer-modified acrylate, polyether macromer-modified acrylate, silicone, polyether macromer-modified acrylate, etc. as the leveling agent.

[0102] (solvent) The solid content concentration of the epoxy resin composition may be adjusted by adding a solvent to the epoxy resin composition. The solvent may generally be any solvent that dissolves the epoxy resin (A), the isocyanate compound (B), and other components, and the same solvents as those used in the preparation of the epoxy resin (α) above can be used. The solvent is used so that the solid content concentration of the epoxy resin composition is preferably 10 to 90 mass %, more preferably 20 to 80 mass %.

[0103] <Physical properties of the cured product (epoxy resin layer)> The epoxy resin layer of the present epoxy film with a release film is a cured product obtained by curing the above-mentioned epoxy resin composition. In the present invention, "curing" means intentionally curing an epoxy resin composition by heat and / or light, etc. The degree of curing may be selected depending on the desired physical properties and application, and may be in a completely cured state or a semi-cured state, but completely cured is preferred from the viewpoint that the physical properties of the cured product will not change even if a heat treatment is performed in a subsequent step.

[0104] Whether the epoxy resin layer is completely cured or not can be confirmed by the glass transition temperature measured during heating and reheating using a differential scanning calorimeter in accordance with JIS K7121: 2012. In the present invention, the epoxy resin layer is considered to be completely cured when the glass transition temperature during reheating does not increase by 3°C or more from that during heating.

[0105] The thickness of the epoxy resin layer is preferably from 1 to 1000 μm, more preferably from 5 to 500 μm, and even more preferably from 10 to 300 μm. When the thickness of the epoxy resin layer is within the above range, the layer has suitable handleability and bending resistance, making it suitable for use in electronic components.

[0106] The glass transition temperature of the epoxy resin layer is preferably 100°C or higher, more preferably 110°C or higher, even more preferably 115°C or higher, even more preferably 120°C or higher, and even more preferably 125°C or higher. When the glass transition temperature is within the above range, the heat resistance of the epoxy resin layer is good.

[0107] When the epoxy resin layer is used in electronic components such as displays, it is preferable that the epoxy resin layer has high transparency. From this viewpoint, the light transmittance at 400 nm of the epoxy resin layer is preferably 75% or more, more preferably 80% or more, even more preferably 85% or more, and even more preferably 88% or more. The light transmittance of the epoxy resin layer at 650 nm is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. The light transmittance of the epoxy resin layer is a value measured in accordance with JIS K7375:2008.

[0108] The haze of the epoxy resin layer is preferably 5% or less, more preferably 3% or less, and even more preferably 1% or less, as measured in accordance with JIS K 7136:2000.

[0109] The yellowness index (YI) of the epoxy resin layer is preferably not more than 5, more preferably not more than 3, and even more preferably not more than 1. The yellowness index (YI) of the epoxy resin layer is a value measured in accordance with JIS K7373:2006.

[0110] When the epoxy resin layer is used in electronic components such as flexible displays, it is preferable that the epoxy resin layer has bending resistance. The bending resistance is evaluated by the minimum bending radius R at which no cracks or creases occur when the epoxy resin layer is repeatedly bent, for example, 200,000 times. The radius R of the epoxy resin layer is preferably 3 mm or less, more preferably 2 mm or less, even more preferably 1.5 mm or less, and even more preferably 1 mm or less. When the maximum bending radius R is within the above range, the durability against bending is good when used in electronic components such as flexible displays.

[0111] <<Manufacturing method of epoxy film with release film>> The epoxy film with a release film of the present invention can be obtained by applying a coating liquid comprising the above-mentioned epoxy resin composition to a release film and curing it. The epoxy film can be obtained by peeling the release film from the epoxy film with a release film.

[0112] The coating liquid may be applied to the release film by a known method, such as comma coating, gravure coating, reverse coating, knife coating, dip coating, spray coating, air knife coating, spin coating, roll coating, printing, slide coating, curtain coating, die coating, casting, bar coating, and extrusion coating.

[0113] The curing conditions for the coating liquid may be adjusted as appropriate depending on the components and blending amounts in the epoxy resin composition, but the curing conditions for the epoxy resin composition are preferably heating conditions of 1 to 180 minutes at 80 to 200°C. Furthermore, when heating the epoxy resin composition, it is preferable to perform heating in a two-stage process, which involves primary heating at 80 to 160°C for 1 to 30 minutes and secondary heating at 120 to 200°C, which is 40 to 120°C higher than the primary heating temperature, for 1 to 150 minutes, in order to reduce curing defects.

[0114] <Epoxy film> The epoxy film of the present invention (hereinafter also referred to as "the present epoxy film") has an epoxy resin layer made of an epoxy resin composition containing an epoxy resin (A) and an isocyanate compound (B), and the average surface roughness (Sa) of at least one side of the epoxy resin layer is 5 nm or more and 50 nm or less. The present epoxy film is preferably obtained by peeling off the release film from the above-mentioned epoxy film with release film.

[0115] The present epoxy film can be obtained by applying a coating liquid comprising the above-mentioned epoxy resin composition to a release film having a specific surface roughness, and then curing the coating liquid. More specifically, the epoxy film is obtained by applying a coating liquid consisting of the epoxy resin composition to one side of the release film (for example, a side on which the average surface roughness (Sa) of the release layer is adjusted to a range of 5 nm to 50 nm), curing the coating, and then peeling the release film from the epoxy film with the release film attached. As a result, the surface roughness of the release layer is transferred to the epoxy resin layer of the obtained epoxy film, and its average surface roughness (Sa) becomes 5 nm to 50 nm. The epoxy film obtained in this way suppresses excessive anchoring effect due to surface irregularities, and transfer of release layer components is reduced. Furthermore, by having the surface roughness of the epoxy film in the above range, diffuse reflection is suppressed, resulting in an epoxy film with low haze and high transparency. Furthermore, by controlling the surface roughness of the epoxy film to fall within the above range, it is expected that blocking and squeak noise during winding can be suppressed, thereby making it possible to obtain an epoxy film with excellent handleability.

[0116] Furthermore, the epoxy film of the present invention may have a functional layer or a protective film in addition to the epoxy resin layer, as will be described later.

[0117] As described above, the present epoxy film is usually used with a functional layer provided on at least one side of the epoxy resin layer, and in this case, there may be a problem of poor adhesion between the epoxy resin layer and the functional layer. However, in the present epoxy film, as described above, by setting the average surface roughness (Sa) of at least one surface of the epoxy resin layer within a specific range, it is presumed that an anchoring effect due to the moderate surface unevenness is exerted, thereby enabling excellent adhesion to the functional layer. From the above viewpoints, the average surface roughness (Sa) of at least one surface of the epoxy resin layer is preferably 5 nm or more and 50 nm or less, more preferably 10 nm or more and 40 nm or less, and most preferably 15 nm or more and 30 nm or less.

[0118] <Functional layer> The epoxy film may have a functional layer on at least one surface. When a functional layer is provided on at least one surface of the present epoxy film, examples of the functional layer include a hard coat layer, an antistatic layer, an antiglare layer, a low reflection layer, an antireflection layer, and an antifouling layer. The functional layer may be a single layer having the above-mentioned multiple functions, or may be a laminate of two or more layers each having a different function.

[0119] (Hard coat layer) When the present epoxy film has a hard coat layer on at least one surface, scratch resistance, chemical resistance, etc. can be imparted to the surface of the present epoxy film. The hard coat layer is preferably formed from a curable resin composition. The curable resin composition is not particularly limited as long as it is cured by irradiation with energy rays such as electron beams, radioactive rays, or ultraviolet rays, or by heating. However, from the viewpoints of molding time and productivity, an ultraviolet-curable resin composition is preferred.

[0120] Preferred examples of the curable resin or curable compound constituting the curable resin composition include acrylate compounds, urethane acrylate compounds, epoxy acrylate compounds, carboxyl group-modified epoxy acrylate compounds, polyester acrylate compounds, copolymeric acrylates, alicyclic epoxy resins, glycidyl ether epoxy resins, vinyl ether compounds, and oxetane compounds. These curable resins or curable compounds can be used alone or in combination of two or more. In particular, in order to obtain a curable resin that imparts excellent surface hardness, it is preferable that the curable resin composition contains a radical polymerization type curable compound such as a polyfunctional acrylate compound, a polyfunctional urethane acrylate compound, or a polyfunctional epoxy acrylate compound, and a thermal polymerization type curable compound such as an alkoxysilane or an alkylalkoxysilane.

[0121] Furthermore, the curable resin composition may be an organic-inorganic hybrid curable resin composition in which the curable resin or curable compound contains an inorganic component. Examples of the organic-inorganic hybrid curable resin composition include a curable resin composition in which the curable resin or curable compound contains an inorganic component having a reactive functional group. By utilizing such an inorganic component having a reactive functional group, for example, the inorganic component copolymerizes and crosslinks with a radical polymerizable monomer, the composition is less likely to undergo cure shrinkage and exhibits high surface hardness compared to organic-inorganic hybrid curable resin compositions in which an inorganic component is simply contained in an organic binder. Furthermore, from the viewpoint of reducing cure shrinkage, it is also preferable to use an organic-inorganic hybrid curable resin composition containing ultraviolet-reactive colloidal silica as an inorganic component having a reactive functional group.

[0122] The curable resin composition for forming the hard coat layer may contain, in addition to the curable resin or curable compound, a leveling agent, a photopolymerization initiator, a refractive index adjusting component, a lubricant, an antioxidant, an ultraviolet absorber, an antistatic agent, a flame retardant, a filler, glass fiber, silica, and the like.

[0123] <Protective film> The epoxy film may have a protective film. The protective film is preferably one that can prevent damage or deformation of the epoxy resin layer. The structure of the epoxy film with a release film is not particularly limited, and examples thereof include a structure of protective film / functional layer / epoxy resin layer / release film. The protective film may consist of a single layer of substrate (protective film substrate), or may have a structure that further includes an adhesive layer as the outermost layer on the side that comes into contact with the epoxy resin layer in addition to the protective film substrate.

[0124] The protective film substrate is preferably a resin film, more specifically, a film mainly composed of a polyolefin such as polyethylene or polypropylene, a polyester such as polyethylene terephthalate or polyethylene naphthalate, a polyimide, or a polycarbonate. The specific configuration of the resin film may be the same as that described for the release film above. When the protective film substrate is used as a single layer, a film having self-adhesive properties is preferred.

[0125] The constituent components of the adhesive layer are not particularly limited, but examples thereof include rubber-based adhesives, acrylic-based adhesives, polyvinyl ether-based adhesives, urethane-based adhesives, silicone-based adhesives, etc. More specific examples thereof include acrylic resins, urethane-based resins, ethylene-vinyl acetate copolymer resins, polyolefin-based resins, etc.

[0126] <<Wound body>> The epoxy film with a release film or the epoxy film of the present invention may be wound around a core and taken up into a roll to form a wound body. The length of the epoxy film with a release film and the epoxy film is not particularly limited, but from the viewpoint of ease of handling, it is preferably 5 m or more, more preferably 10 m or more, and even more preferably 50 m or more. The length of the epoxy film with a release film and the epoxy film is preferably 10,000 m or less.

[0127] The core refers to a cylindrical core used for winding up the film. The material of the core is not particularly limited, but examples thereof include paper, resin-impregnated paper, acrylonitrile-butadiene-styrene copolymer (ABS resin), FRP, phenolic resin, and inorganic-containing resin. Among these, from the viewpoints of a small coefficient of thermal expansion, high rigidity, low swelling due to humidity, and excellent winding properties, it is preferable to use a resin such as acrylonitrile-butadiene-styrene copolymer (ABS resin), FRP, phenolic resin, or inorganic-containing resin. When the core material is paper, the desired properties can be easily obtained by coating the surface with a resin, etc. Furthermore, from the viewpoint of surface smoothness, it is also preferable that the core be a tube made of resin-impregnated paper.

[0128] When constructing a wound body, it is preferable to wind the epoxy film or the epoxy film with a base film around a core so that the epoxy resin layer of the epoxy film or the epoxy film with a base film is on the inside and the active energy ray-cured resin layer is on the outside.

[0129] <<Application>> The epoxy film with a release film and the epoxy film of the present invention have high transparency of the epoxy resin layer and excellent flex resistance, and therefore can be suitably used in electronic component applications such as displays and printed wiring boards. [Example]

[0130] Next, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the examples described below.

[0131] <<Materials>> The materials used in the examples and comparative examples are as follows.

[0132] <Epoxy resin> (A-1): An epoxy resin containing bisphenol A type epoxy resin as the main component ("YL7852BT40" manufactured by Mitsubishi Chemical Corporation) was used.

[0133] <Crosslinking agent> (B-1): A polyisocyanate containing hexamethylene diisocyanate as a main component ("Coronate 2715" manufactured by Tosoh Corporation) was used. (B-2): A polyisocyanate containing hexamethylene diisocyanate as the main component ("Takenate D-160N" manufactured by Mitsui Chemicals, Inc.) was used. (B-3): 1-benzyl-2-phenylimidazole ("Curezol 1B2PZ" manufactured by Shikoku Chemical Industries, Ltd.) was used.

[0134] <Additives> (C-1): A leveling agent (BYK-3566 manufactured by BYK Japan Co., Ltd., silicone and polyether macromer modified acrylate) was used.

[0135] <Solvent> (D-1): Toluene (D-2): Methyl ethyl ketone

[0136] <<Release film>> (F-1): Product name "SP-PET (registered trademark) O3-BU" (100 μm / release layer surface roughness Sa1 = 20 nm), manufactured by Mitsui Chemicals Tocello Co., Ltd. (F-2): Daicel Corporation, product name "N-5030C" (100 μm / release layer surface roughness Sa1 = 30 nm) (F-3): Daicel Corporation, product name "M-7011" (100 μm / release layer surface roughness Sa = 3 nm) (F-4): Manufactured by Aim Co., Ltd., product name "RF2PET75CSH40" (75 μm / release layer surface roughness Sa = 51 nm)

[0137] <<Preparation of epoxy film with release film>> [Example 1] Epoxy resin (A-1), crosslinking agents (B-1) and (B-2), additive (C-1), and solvents (D-1) and (D-2) were mixed in the proportions shown in Table 1 to prepare a coating liquid for forming an epoxy resin layer. The coating liquid was applied to a release film (F-1) using an applicator, and a curing treatment was performed using a constant temperature dryer by first heating at 80°C for 2 minutes and then second heating at 180°C for 5 minutes, followed by natural cooling to room temperature (25°C) to form an epoxy resin layer. In this way, an epoxy film with a release film of Example 1 was obtained. The obtained epoxy resin layer had a thickness of 25 μm. In addition, a wound body was produced by winding the epoxy film with the base film of Example 1 around a core (made of ABS resin) with the epoxy resin layer facing inward. The epoxy film (epoxy resin layer) was peeled off from the obtained epoxy film with release film, and the glass transition temperature was measured. The glass transition temperature of the epoxy resin layer was 129°C, and the glass transition temperature upon re-heating was also 129°C, confirming that the epoxy resin was completely cured.

[0138] [Example 2] An epoxy resin layer was formed under the same conditions as in Example 1, except that the composition of the coating liquid for forming an epoxy resin layer was changed as shown in Table 1, to obtain an epoxy film with a release film and a wound body of Example 2. The thickness of the obtained epoxy resin layer was 25 μm. The glass transition temperature of the obtained epoxy resin layer was 112°C, and the glass transition temperature upon re-heating was 110°C, confirming that it was completely cured.

[0139] [Example 3] An epoxy resin layer was formed under the same conditions as in Example 1, except that the composition of the coating liquid for forming an epoxy resin layer was changed as shown in Table 1, to obtain an epoxy film with a release film and a wound body of Example 3. The thickness of the obtained epoxy resin layer was 25 μm. The glass transition temperature of the obtained epoxy resin layer was 105°C, and the glass transition temperature upon re-heating was 107°C, confirming that it was completely cured.

[0140] [Example 4] An epoxy resin layer was formed under the same conditions as in Example 1, except that the composition of the coating liquid for forming an epoxy resin layer was changed as shown in Table 1, to obtain an epoxy film with a release film and a wound body of Example 4. The thickness of the obtained epoxy resin layer was 25 μm. The glass transition temperature of the obtained epoxy resin layer was 131°C, and the glass transition temperature upon reheating was 129°C, confirming that it was completely cured.

[0141] [Example 5] An epoxy resin layer was formed under the same conditions as in Example 1, except that a release film (F-2) was used, to obtain an epoxy film with a release film and a wound body of Example 5. The thickness of the obtained epoxy resin layer was 25 μm.

[0142] [Example 6] An epoxy resin layer was formed under the same conditions as in Example 2, except that a release film (F-2) was used, to obtain an epoxy film with a release film and a wound body of Example 6. The thickness of the obtained epoxy resin layer was 25 μm.

[0143] [Comparative Example 1] An epoxy resin layer was formed under the same conditions as in Example 1, except that a release film (F-3) was used, to obtain an epoxy film with a release film and a wound body of Comparative Example 1. The thickness of the obtained epoxy resin layer was 25 μm.

[0144] Comparative Example 2 An epoxy resin layer was formed under the same conditions as in Example 1, except that a release film (F-4) was used, to obtain an epoxy film with a release film and a wound body of Comparative Example 1. The thickness of the obtained epoxy resin layer was 25 μm.

[0145] <Evaluation items> (1) Glass transition temperature and degree of hardening The glass transition temperature and degree of cure of the epoxy resin layer were measured based on the "midpoint glass transition temperature (Tmg)" described in JIS K7121:2012 "Method for measuring transition temperature of plastics." Specifically, a differential scanning calorimeter "DSC8500" manufactured by PerkinElmer Japan Co., Ltd. was used to measure the glass transition temperature and degree of cure. The glass transition temperature was increased from 20 to 250°C at a rate of 10°C / min, then decreased to 0°C at a rate of 10°C / min, and then increased again from 0 to 250°C at a rate of 10°C / min. The glass transition temperature was considered to be fully cured when the glass transition temperature upon re-heating did not rise by more than 3°C from the glass transition temperature upon heating.

[0146] (2) Haze The release film was peeled off from the epoxy film with the release film attached, and the haze of the epoxy film (epoxy resin layer) at 400 nm to 650 nm was measured using a haze meter "NDH 7000II" manufactured by Nippon Denshoku Industries Co., Ltd. The measurement was carried out in accordance with JIS (haze: JIS K 7136:2000).

[0147] (3) Average surface roughness (Sa) The average surface roughness (Sa) of the release layer surface of the release film was measured using a non-contact surface / layer cross-section measurement system VertScan (registered trademark) 2.0 (manufactured by Ryoka Systems Co., Ltd.) to observe the surface of the release layer of the release film (observation field: 948.8 μm × 711.6 μm), and the average surface roughness (arithmetic mean roughness Sa) was calculated. In addition, the average surface roughness (Sa) of the surface of the epoxy resin layer exposed after peeling from the release film, which was in direct contact with the release layer, was also observed in the same manner as above (observation field: 948.8 μm × 711.6 μm), and the average surface roughness (arithmetic mean roughness Sa) was calculated. The analysis for calculating Sa was performed as follows. The data obtained from the above measurements was imported into VertScan® 2.0's image analysis software VS-Viewer, and the waviness of the curved surface was removed by performing a fourth-order polynomial approximation using the "surface correction" function. The arithmetic mean height (Sa), defined in ISO 25178-2 (2012), was then calculated using the "ISOPara" function.

[0148] (4) Peeling evaluation The peeling of the epoxy resin layer was evaluated by visually checking whether the epoxy resin layer and the release film peeled off naturally when the epoxy film was naturally cooled to room temperature (25°C) after the curing treatment during the production process of the epoxy film with release film. The evaluation criteria were as follows: Peelability evaluation A: The epoxy resin layer and the release film remain in close contact with each other and can be peeled off at will. Peeling evaluation B: The epoxy resin layer and the release film peeled off naturally.

[0149] (5) Flexibility (R) Using a bending tester (Yuasa System Co., Ltd., DLDMLH-FS), a bending test was carried out 200,000 times on the epoxy resin layer of the example, and the minimum bending radius R at which cracks and creases did not occur was evaluated. In addition, since the epoxy resin layer of the example did not develop cracks or creases even when R=1 mm, it is indicated as "≦1" in Table 1. In addition, "-" in Table 1 indicates that no evaluation was performed.

[0150] (6) Coating layer thickness The thickness of the epoxy resin layer was measured using a thickness gauge (Mitutoyo Corporation, ABS Digimatic Indicator ID-F125).

[0151] [Table 1]

[0152] By using a release film having an appropriate surface roughness as in the examples, peeling between the epoxy resin layer and the release film was suppressed. Furthermore, in the examples, an epoxy film having good transparency was obtained. On the other hand, when a release film with low surface roughness such as that in Comparative Example 1 was used, the optical properties (transparency) of the resulting epoxy film were good, but the epoxy resin layer peeled off from the release film, resulting in reduced productivity. Furthermore, when a release film with a high surface roughness such as that of Comparative Example 2 was used, the optical properties (transparency) of the resulting epoxy film were impaired. [Explanation of symbols]

[0153] 1 Base material 2 Release layer 3 Epoxy resin layer (epoxy film) 5 Release film 10 Epoxy film with release film

Claims

1. An epoxy film with a release film, comprising a release film and an epoxy resin layer, the epoxy resin layer includes a cured product obtained by curing an epoxy resin composition containing an epoxy resin (A), an isocyanate compound (B), and an imidazole-based compound, the average surface roughness (Sa) of the surface of the release film in contact with the epoxy resin layer is 15 nm or more and 50 nm or less; The epoxy film with a release film is used for a member of a flexible display by peeling off the release film from the epoxy film with a release film.

2. The release film has a substrate and a release layer, the epoxy resin layer is laminated on the release layer, 2. The epoxy film with a release film according to claim 1, wherein the average surface roughness (Sa) of the surface of the release layer on the side in contact with the epoxy resin layer is 15 nm or more and 50 nm or less.

3. 3. The epoxy film with a release film according to claim 1, wherein the epoxy resin (A) is a resin obtained by reacting an epoxy compound with a phenolic compound.

4. 4. The epoxy film with a release film according to claim 3, wherein the epoxy compound is a compound having two or more epoxy groups in the molecule.

5. 5. The epoxy film with a release film according to claim 3, wherein the phenolic compound is a compound having two or more hydroxyl groups bonded to an aromatic ring.

6. The epoxy film with a release film according to any one of claims 1 to 5, wherein the mass average molecular weight of the epoxy resin (A) before curing is 2,000 to 300,000.

7. 7. The epoxy film with a release film according to claim 1, wherein the isocyanate compound (B) is a compound having an aliphatic isocyanate as a main skeleton.

8. The epoxy film with a release film according to any one of claims 1 to 7, wherein the epoxy resin layer further contains a leveling agent.

9. The epoxy film with a release film according to any one of claims 1 to 8, wherein the glass transition temperature of the epoxy resin layer is 100°C or higher.

10. an epoxy resin layer including a cured product obtained by curing an epoxy resin composition containing an epoxy resin (A), an isocyanate compound (B), and an imidazole-based compound; An epoxy film for use as a member of a flexible display, wherein the average surface roughness (Sa) of at least one surface of the epoxy resin layer is 15 nm or more and 50 nm or less.

11. The epoxy film according to claim 10, further comprising a protective film on at least one side of the epoxy resin layer.

12. The epoxy film according to claim 10 or 11, further comprising a functional layer on at least one side of the epoxy resin layer.

13. A wound body obtained by winding the epoxy film with a release film according to any one of claims 1 to 9 or the epoxy film according to any one of claims 10 to 12 around a core.

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