JP7154738B2 - transparent laminate - Google Patents

Description

TECHNICAL FIELD The present invention relates to a transparent laminate that can be used for flexible displays.

In recent years, flexible OLED, flexible PV, lightweight displays, flexible encapsulants, color EPDs, plastic LCDs, TSPs, OPVs, etc. have been used to develop bendable and flexible displays. Conventional displays have used a glass substrate to protect the elements within the display, but in developing a flexible display, it is necessary to develop a flexible film to replace the glass substrate. Properties such as high hardness, low moisture permeability, high chemical resistance, and high light transmittance are required for such films, and polyimide films are attracting attention as films having these properties.

Conventionally used polyimide films have low total light transmittance values and high b* values in the L*a*b* color system. was there. In recent years, these problems have been overcome, and transparent polyimide films having heat resistance and low moisture permeability have been developed.

It has been proposed to provide a polyimide film for a flexible display with a hard coat layer for the protection of the film itself. For example, Patent Document 1 proposes providing a hard coat layer containing an acrylate group on a polyimide film.

JP 2016-501144 A

In the course of research, the present inventors found that when a hard coat layer containing an acrylate group was provided on a polyimide film, the problem of poor adhesion between the polyimide film and the hard coat layer and the occurrence of many interference fringes occurred. I found a problem. The problem of adhesion is thought to lead to peeling of the hard coat layer due to repeated flexing and bending when used as a film for flexible displays. Moreover, the problem of interference fringes leads to difficulty in seeing the displayed image when the film is used as a display film.

Therefore, the present invention provides a transparent laminate comprising a polyimide film and a hard coat layer, in which the adhesion between the polyimide film and the hard coat layer is better and the occurrence of interference fringes is further suppressed. Make it an issue.

The present inventor considered that the problem of adhesion was caused by relatively low-molecular-weight polyimide deposited on the surface of the polyimide film. Therefore, in order to suppress the deposition of these low-molecular-weight components, it was considered to sufficiently harden the polyimide film during its production as a countermeasure against the adhesion problem. However, this deteriorates the production efficiency of the polyimide film and, by extension, the production efficiency of the transparent laminate.

Regarding the problem of interference fringes, adding inorganic particles with a high refractive index to the hard coat layer brings the refractive index of the hard coat layer closer to that of the polyimide film, thereby suppressing the interference fringes. it was thought. However, there is a problem that the cleanliness of the production line may deteriorate, a problem that inorganic particles may precipitate when sintering is performed, and a problem that the hard coat layer is likely to deteriorate due to friction between the inorganic particles and the resin component. etc. can be considered.

As a result of intensive research under these circumstances, the present inventor adopted a hard coat layer containing a resin having a benzene ring content of 50% by mass or more and an epoxy resin as a hard coat layer laminated on a polyimide film. The inventors have found that the above problems can be solved by The present inventor has completed the present invention as a result of further research based on this finding.

That is, the present invention includes the following aspects:
Section 1. A resin (A) comprising a polyimide film and a hard coat layer, wherein the hard coat layer is disposed on at least one surface of the polyimide film, and the hard coat layer has a benzene ring content of 50% by mass or more; and an epoxy resin (B), a transparent laminate.
Section 2. Item 2. The transparent laminate according to Item 1, wherein the hard coat layer contains 5 to 50 parts by mass of the epoxy resin (B) with respect to 100 parts by mass of the resin (A) having a benzene ring content of 50% by mass or more.
Item 3. Item 3. The transparent laminate according to item 1 or 2, wherein the hard coat layer contains 10 to 30 parts by mass of the epoxy resin (B) with respect to 100 parts by mass of the resin (A) having a benzene ring content of 50% by mass or more. body.
Section 4. Item 4. The transparent laminate according to any one of Items 1 to 3, which is used for a flexible display.
Item 5. A flexible display comprising the transparent laminate according to any one of items 1 to 4.

According to the present invention, it is possible to provide a transparent laminate comprising a polyimide film and a hard coat layer, in which the adhesion between the polyimide film and the hard coat layer is better and the occurrence of interference fringes is further suppressed. can.

1 is a schematic cross-sectional view showing the structure of one embodiment of a laminate of the present invention; FIG.

As used herein, the expressions "contain" and "include" include the concepts "contain", "include", "consist essentially of" and "consist only of".

The present invention, as one aspect thereof, includes a polyimide film and a hard coat layer, wherein the hard coat layer is disposed on at least one surface of the polyimide film, and the hard coat layer has a benzene ring content of 50 The present invention relates to a transparent laminate (which may be referred to herein as the "transparent laminate of the present invention") containing a resin (A) and an epoxy resin (B) in an amount equal to or greater than mass %. These are described below.

<Polyimide film>
The polyimide film is a layer that functions as a substrate in the laminate of the present invention, and is not particularly limited as long as it contains a polyimide resin as the resin. The polyimide film is preferably a film containing a polyimide resin as a main component. The term "main component" means that the polyimide film contains a polyimide resin in terms of solid content of 50% by mass or more, preferably 70% by mass or more, more preferably 90% by mass or more, and still more preferably 95% by mass or more. , and more preferably 99% by mass or more.

The polyimide resin is not particularly limited, but for example general formula (1):

[In general formula (1), R ¹ represents a tetravalent organic group. ^R2 represents a divalent organic group. ]
A resin containing a repeating unit represented by is mentioned. The content (molar conversion) of the repeating unit in the polyimide resin is, for example, 70 mol % or more, preferably 90 mol % or more, and more preferably 95 mol % or more.

Examples of R ¹ include, but are not particularly limited to, a tetravalent group obtained by removing four hydrogen atoms from an optionally substituted aromatic hydrocarbon such as benzene and biphenyl.

R ² is not particularly limited. For example, optionally substituted aromatic hydrocarbons such as benzene and biphenyl; two or more optionally substituted aromatic hydrocarbons such as diphenyl ether through a linker organic compound;

Polyimide resins preferably include aromatic polyimide resins in which R ¹ and/or R ² contain groups derived from aromatic hydrocarbons.

The polyimide resin may be used singly or in combination of two or more.

The polyimide film may contain a resin other than the polyimide resin as a resin constituting the film, as long as the physical properties of the polyimide resin are not significantly impaired. Examples of resins other than polyimide resins include polyester resins, acetate resins, polyether resins, polycarbonate resins, polyacrylic resins, polymethacrylic resins, polystyrene resins, polyolefin resins, polyamide resins, polyvinyl chloride resins, polyacetal resins, poly vinylidene chloride resin, polyphenylene sulfide resin, and the like.

Resins other than the polyimide resin may be used singly or in combination of two or more.

The content of resins other than the polyimide resin is, for example, 0 to 20% by mass, preferably 0 to 10% by mass, and more preferably 0 to 5% by mass with respect to 100% by mass of the polyimide film.

Further, when the polyimide film contains a resin other than the polyimide resin, the content of the polyimide resin is, for example, 50% by mass or more, preferably 70% by mass, with respect to the total 100% by mass of the polyimide resin and the other resin. % or more, more preferably 90 mass % or more, still more preferably 95 mass % or more, still more preferably 99 mass % or more.

The polyimide film may contain components other than the resin constituting the film, as long as the effects of the present invention are not significantly impaired. Other components other than the resin constituting the film include, for example, antibacterial properties, antifouling properties, finger-sliding properties, antistatic properties, ultraviolet shielding properties, antiglare properties, hardness, and the like. Additives are included. Examples of additives for imparting antifouling properties include silicone-based antifouling agents and fluorine-based antifouling agents, and examples of additives for imparting finger-sliding properties include silicone-based lubricants and fluorine-based lubricants. Examples of additives for improving coatability include leveling agents, and examples of additives for imparting antistatic properties include metal oxide fine particles, antistatic resins, conductive polymers, Examples of additives for imparting UV shielding properties include metal oxide fine particles, UV absorbers, light stabilizers, etc. Additives for imparting antiglare properties and / or hardness Examples thereof include inorganic fine particles and organic fine particles. Inorganic fine particles, organic fine particles, and the like can also be contained in order to improve anti-blocking properties.

The other components in the polyimide film may be used singly or in combination of two or more.

The content of the other components in the polyimide film is, for example, 0 to 10% by mass, preferably 0 to 5% by mass, relative to 100% by mass of the polyimide film.

A polyimide film can be produced, for example, by applying a polyimide film-forming composition containing a polyimide resin, a polyimide resin precursor, or the like onto a coating substrate and, if necessary, curing the composition. The coating method is not particularly limited, and includes known methods capable of forming a film, such as spin coating, spray coating, bar coating, roll coating, extrusion through a slit nozzle, and the like. Curing conditions are also not particularly limited, and known conditions can be employed. Moreover, a commercially available polyimide film can also be used as a polyimide film.

The layer structure of the polyimide film is not particularly limited. The polyimide film may be a film consisting of one layer, or a film consisting of a plurality of layers (for example, 2 layers, 3 layers, 4 layers, 5 layers, etc.) having the same or different compositions.

The surface shape of the polyimide film may be flat or uneven.

The thickness of the polyimide film is not particularly limited. The thickness is preferably 5 to 200 μm, more preferably 10 to 100 μm, still more preferably 15 to 50 μm, still more preferably 15 to 30 μm.

The optical properties of the polyimide film are not particularly limited as long as the optical properties do not impair the transparency of the transparent laminate of the present invention.

The total light transmittance of the polyimide film is preferably 80% or higher, more preferably 83% or higher, still more preferably 85% or higher.

The haze value of the polyimide film is preferably 0 to 5%, more preferably 0 to 4%, still more preferably 0 to 3.5%.

The L* value of the polyimide film in the L*a*b* color system is preferably 80 or more, more preferably 85 or more, even more preferably 90 or more, and even more preferably 92 or more.

The absolute value of the a* value in the L*a*b* color system of the polyimide film is preferably 0 to 10, more preferably 0 to 8, more preferably 0 to 5, and even more preferably 0 to 2. . When the absolute value of the a* value is a value other than 0, the a* value is, for example, a negative value.

The absolute value of the b* value in the L*a*b* color system of the polyimide film is preferably 0-10, more preferably 0-8, still more preferably 0-5. When the absolute value of the b* value is a value other than 0, the b* value is, for example, a positive value.

<Hard coat layer>
The hard coat layer is a layer containing a resin (A) having a benzene ring content of 50% by mass or more and an epoxy resin (B), which is arranged to protect the polyimide film. The hard coat layer is preferably a film mainly composed of a resin (A) having a benzene ring content of 50% by mass or more and an epoxy resin (B). The term "mainly composed of" means that the hard coat layer contains a resin (A) having a benzene ring content of 50% by mass or more and an epoxy resin (B) of 50% by mass or more in terms of solid content, preferably The content is 70% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and even more preferably 99% by mass or more.

The resin (A) having a benzene ring content of 50% by mass or more is, in other words, a resin having a benzene ring content of 50% by mass or more in the resin structure, and is not particularly limited in this respect. The term "benzene ring" as used herein refers to a group in which 1, 2, 3, 4, 5, or 6 hydrogen atoms are removed from benzene, which exists as a partial structure in the resin structure. be. The benzene ring also includes a benzene ring existing as a partial structure within a condensed ring such as a naphthalene ring or an indole ring.

The benzene ring content is preferably 50 to 70% by mass, more preferably 50 to 60% by mass, based on 100% by mass of the resin (A) having a benzene ring content of 50% by mass or more.

The structure of the resin (A) having a benzene ring content of 50% by mass or more is not particularly limited. Examples of such resins include polyester urethane resins, polyester resins, acrylic resins, phenol resins, urea resins, diallyl phthalate resins, melamine resins, unsaturated polyester resins, polyurethane resins, epoxy resins, aminoalkyd resins, silicone resins, and polysiloxane resins. thermosetting resins such as; active energy ray-curable resins such as urethane acrylic resins, acrylic resins, polyester acrylic resins, and epoxy acrylic resins; In addition, the urethane acrylic resin shown here has a polyoxyalkylene segment, a saturated polyester segment, or both, which are linked via a urethane bond, and has acryloyl groups at both ends. The resin (A) is preferably a urethane acrylic resin.

The resin (A) having a benzene ring content of 50% by mass or more may be used singly or in combination of two or more.

The epoxy resin (B) is not particularly limited as long as it is a resin crosslinked via epoxy groups. Examples of the epoxy resin (B) include thermosetting epoxy resins and active energy ray-curable epoxy resins (epoxy acrylic resins).

The epoxy resin (B) may be used alone or in combination of two or more.

The blending ratio of the resin (A) having a benzene ring content of 50% by mass or more and the epoxy resin (B) is not particularly limited. From the viewpoint that the adhesion between the polyimide film and the hard coat layer can be improved, the hard coat layer is prepared by adding an epoxy resin ( B) is contained in an amount of, for example, 5 parts by mass or more, preferably 10 parts by mass or more. On the other hand, from the viewpoint that the generation of interference fringes can be further suppressed, the hard coat layer contains epoxy resin (B) with respect to 100 parts by mass of resin (A) having a benzene ring content of 50% by mass or more. For example, it contains 50 parts by mass or less, preferably 30 parts by mass or less. From the viewpoint of both the improvement of the adhesion and the suppression of the interference fringes, the hard coat layer contains 100 parts by mass of the resin (A) having a benzene ring content of 50% by mass or more, and an epoxy resin (B), for example 5 to 50 parts by mass, preferably 10 to 30 parts by mass.

The hard coat layer contains other resins other than the resin (A) having a benzene ring content of 50% by mass or more and the epoxy resin (B) as the resin constituting the layer, as long as the effects of the present invention are not significantly impaired. may contain. The other resins include resins other than epoxy resins having a benzene ring content of less than 50% by mass, specifically, polyester urethane resins, polyester resins, acrylic resins, phenol resins, urea resins, diallyl phthalate resins thermosetting resins such as melamine resins, unsaturated polyester resins, polyurethane resins, aminoalkyd resins, silicon resins, and polysiloxane resins; active energy ray-curable resins such as urethane acrylic resins, acrylic resins, and polyester acrylic resins; be done.

The content of the other resin is, for example, 0 to 20% by mass, preferably 0 to 10% by mass, more preferably 0 to 5% by mass, based on 100% by mass of the hard coat layer.

In addition, when the hard coat layer contains the above other resins, the total content of the resin (A) having a benzene ring content of 50% by mass or more and the epoxy resin (B) is For example, 50% by mass or more, preferably 70% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 99% by mass or more, relative to the total 100% by mass with the resin. .

The hard coat layer may contain components other than the resin constituting the layer, as long as the effects of the present invention are not significantly impaired. Other components other than the resin constituting the layer include, for example, residual components of additives used during polymerization of the resin (e.g., cross-linking agents, photoinitiators, photosensitizers, solvents, etc.); Known additives used for imparting stain resistance, finger sliding properties, antistatic properties, ultraviolet shielding properties, antiglare properties, hardness and the like can be mentioned.

Examples of cross-linking agents include isocyanate compounds, epoxy compounds, oxazoline compounds, aziridine compounds, metal chelate compounds, and butylated melamine compounds. Among these cross-linking agents, isocyanate compounds and epoxy compounds are preferred. Examples of isocyanate compounds include tolylene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and the like. Examples of epoxy compounds include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerin diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diol. glycidyl ether, tetraglycidylxylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, trimethylolpropane polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitol polyglycidyl ether, etc. mentioned.

Known photopolymerization initiators can be used, for example, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, 2,2-dimethoxy- 2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropane-1-one, 1-hydroxycyclohexylphenyl ketone, 2-methyl-1-[4-(methylthio)phenyl] -21 morpholinopropane-1-one, 4-(2-hydroxyethoxy)phenyl-2(hydroxy-2-propyl)ketone, benzophenone, p-phenylbenzophenone, 4,4'-diethylaminobenzophenone, propiophenone, dichlorobenzophenone , 2-methylanthraquinone, 2-ethylanthraquinone, 2-1-sharybutylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4- diethylthioxanthone, benzyl dimethyl ketal, acetophenone dimethyl ketal, p-dimethylamine benzoate and the like.

Examples of photosensitizers include n-butylamine, triethylamine, tri-n-butylphosphine and the like.

Examples of solvents include methanol, ethanol, isopropanol, acetone, methyl ethyl ketone, toluene, n-hexane, n-butyl alcohol, methyl isobutyl ketone, methyl butyl ketone, ethyl butyl ketone, cyclohexanone, ethyl acetate, butyl acetate, propylene glycol monomethyl. ether acetate, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, N-methyl-2-pyrrolidone and the like.

Examples of additives for imparting antifouling properties include silicone-based antifouling agents and fluorine-based antifouling agents, and examples of additives for imparting finger-sliding properties include silicone-based lubricants and fluorine-based lubricants. Examples of additives for improving coatability include leveling agents, and examples of additives for imparting antistatic properties include metal oxide fine particles, antistatic resins, conductive polymers, Examples of additives for imparting UV shielding properties include metal oxide fine particles, UV absorbers, light stabilizers, etc. Additives for imparting antiglare properties and / or hardness Examples thereof include inorganic fine particles and organic fine particles. Inorganic fine particles, organic fine particles, and the like can also be contained in order to improve anti-blocking properties.

The other components in the hard coat layer may be used singly or in combination of two or more.

The content of the other components in the hard coat layer is, for example, 0 to 10% by mass, preferably 0 to 5% by mass, based on 100% by mass of the polyimide film.

The hard coat layer is formed, for example, by applying a composition for forming a hard coat layer containing the above-described resin, a precursor of the resin, etc. onto a polyimide film, preferably drying, and then curing as necessary. can be manufactured. Alternatively, it can be obtained by disposing a hard coat film previously formed on another coating substrate by a similar method (for example, via an adhesive layer) on a polyimide film.

The drying process can be performed using a known heating device such as an air circulation type constant temperature oven, a heating furnace, an infrared lamp, or the like.

The drying temperature is, for example, 60-150°C, preferably 80-120°C.

The drying time varies depending on the drying temperature, but is, for example, 15 seconds to 5 minutes, preferably 30 seconds to 2 minutes.

An appropriate method can be adopted as the curing method depending on the curing conditions of the resin. For example, if a photocurable resin is used as the resin, it can be cured by light irradiation with a light irradiation device equipped with a known lamp such as a high-pressure mercury light, a black light, a chemical light, and an LED light. can.

The hard coat layer is arranged on at least one side of the polyimide film, preferably on one side. The hard coat layer may be arranged on the polyimide film through another layer such as an adhesive layer, or may be arranged directly on the polyimide film without interposing another layer. Preferably, the hard coat layer is directly arranged on the polyimide film without interposing other layers.

The layer structure of the hard coat layer is not particularly limited. The hard coat layer may be a hard coat layer consisting of one layer, or a hard coat layer consisting of a plurality of layers (for example, 2 layers, 3 layers, 4 layers, 5 layers, etc.) having the same or different compositions. may

The surface shape of the hard coat layer may be flat or uneven.

The thickness of the hard coat layer is not particularly limited. The thickness can be, for example, 0.5 μm or more, and can be selected within the range of 1.0 μm or more and 2.0 μm or more. Although the upper limit varies depending on the application, it can be selected within the range of, for example, 1 mm or less, 50 μm or less, or 20 μm or less.

<Transparent laminate>
FIG. 1 shows a schematic cross-sectional view showing the structure of one embodiment of the laminate of the present invention.

The thickness of the transparent laminate of the present invention is, for example, 1 to 100 μm, preferably 5 to 50 μm, more preferably 10 to 25 μm.

The total light transmittance of the transparent laminate of the present invention is preferably 80% or higher, more preferably 83% or higher, still more preferably 85% or higher.

The haze value of the transparent laminate of the invention is preferably 0 to 5%, more preferably 0 to 4%, still more preferably 0 to 3.5%.

The L* value of the transparent laminate of the present invention in the L*a*b* color system is preferably 80 or more, more preferably 85 or more, even more preferably 90 or more, and even more preferably 92 or more.

The absolute value of the a* value in the L*a*b* color system of the transparent laminate of the present invention is preferably 0 to 10, more preferably 0 to 8, still more preferably 0 to 5, and even more preferably 0. ~2. When the absolute value of the a* value is a value other than 0, the a* value is, for example, a negative value.

The absolute value of the b* value in the L*a*b* color system of the transparent laminate of the present invention is preferably 0-10, more preferably 0-8, still more preferably 0-5. When the absolute value of the b* value is a value other than 0, the b* value is, for example, a positive value.

The transparent laminate of the present invention can be used for various purposes, for example, as a hard coat film. Further, in the transparent laminate of the present invention, the essential layers (polyimide film and hard coat layer) are mainly composed of a resin, the adhesion between the polyimide film and the hard coat layer is better, and interference fringes is more suppressed, it can be suitably used for a flexible display. More specifically, for example, it can be suitably used as a cover sheet for the front or back surface of a flexible display or as a base material for wiring formation. The flexible display is not particularly limited as long as it can be bent or bent.

From the viewpoint of the above applications, one aspect of the present invention relates to a flexible display (which may be referred to herein as the "flexible display of the present invention") including the transparent laminate of the present invention. . In the flexible display of the present invention, the transparent laminate of the present invention is arranged, for example, as a cover sheet on the front surface or rear surface of the display. In this case, the hard coat layer may be arranged on the surface of the polyimide film outside the display, may be arranged on the surface inside the display, and may be arranged on both the surface outside the display and the surface inside the display. may be placed.

By using the transparent laminate of the present invention in a flexible display, it is possible to further suppress the occurrence of interference fringes, thereby making it possible to make the displayed image easier to see, and to bend or bend the display repeatedly. It is possible to further suppress peeling between the polyimide film and the hard coat layer that may occur in the process.

EXAMPLES The present invention will be described in detail below based on examples, but the present invention is not limited by these examples.

(1) Preparation of laminate
Example 1
100 parts by mass of a hard coating agent A (Z-819L, manufactured by Aica Kogyo Co., Ltd., benzene ring content in resin: 50 to 60% by mass) containing a benzene ring in the urethane acrylate resin skeleton and an acryloyl group at the end of the resin On the other hand, 5 parts by mass of a hard coating agent B having an epoxy-based skeleton (epoxy resin for polyimide (PI) manufactured by Aica Kogyo Co., Ltd.) was added, and a solution with a solid content concentration of 20% by mass with propylene glycol monomethyl ether (PGM) was prepared. and stirred for 30 minutes. Thus, a photocurable hard coat resin composition was prepared.

The benzene ring content in the resin of the hard coating agent A was measured using a pyrolysis gas chromatograph/mass spectrometer (pyrolysis device: JCI-22 type manufactured by Nippon Analytical Industry, gas chromatograph: 6890N manufactured by Agilent Technologies, mass spectrometer: 5973N manufactured by Agilent Technologies).

On one side of a transparent aromatic polyimide film (manufactured by I.S.T., Tormed #23, thickness 23 μm) having the same surface property on both sides, the photocurable hard coating resin composition prepared above was coated with a bar coater. (Matsuo Sangyo Co., Ltd., bar coater) was used to coat so that the coating thickness after UV irradiation was 1±0.5 μm. This was dried at 100° C. for 1 minute in an air circulating constant temperature oven. After drying, an antireflection plate is provided on the opposite side of the transparent polyimide film to the surface coated with the photocurable hard coat resin composition so that light is not reflected, and then a high-pressure mercury lamp (manufactured by Eye Graphics, H04- L41) equipped with a light irradiation device (ECS-301G1, manufactured by Eye Graphics Co., Ltd.) to irradiate light (accumulated light amount 400 mJ/cm ² , illuminance 100 mW/cm ² ), and thereby, on one surface of the transparent polyimide film A laminate having a hard coat layer was obtained.

The high-pressure mercury lamp used here is a quartz glass arc tube filled with high-purity mercury (Hg) and a small amount of rare gas. of ultraviolet rays can be efficiently radiated.

Example 2
A laminate was produced in the same manner as in Example 1, except that the hard coating agent B (epoxy resin for PI manufactured by Aica Kogyo Co., Ltd.) was changed to 10 parts by mass.

Example 3
A laminate was produced in the same manner as in Example 1, except that the hard coating agent B (epoxy resin for PI manufactured by Aica Kogyo Co., Ltd.) was changed to 20 parts by mass.

Example 4
A laminate was produced in the same manner as in Example 1, except that the hard coating agent B (epoxy resin for PI manufactured by Aica Kogyo Co., Ltd.) was changed to 30 parts by mass.

Example 5
A laminate was produced in the same manner as in Example 1, except that the hard coating agent B (epoxy resin for PI manufactured by Aica Kogyo Co., Ltd.) was changed to 35 parts by mass.

Example 6
A laminate was produced in the same manner as in Example 1, except that the hard coating agent B (epoxy resin for PI manufactured by Aica Kogyo Co., Ltd.) was changed to 40 parts by mass.

Example 7
A laminate was produced in the same manner as in Example 1, except that the hard coating agent B (epoxy resin for PI manufactured by Aica Kogyo Co., Ltd.) was changed to 50 parts by mass.

Comparative example 1
A laminate was produced in the same manner as in Example 1, except that the hard coating agent B (epoxy resin for PI manufactured by Aica Kogyo Co., Ltd.) was changed to 0 parts by mass.

Comparative example 2
A laminate was produced in the same manner as in Comparative Example 1, except that hard coating agent B (epoxy resin for PI, manufactured by Aica Kogyo Co., Ltd.) was used instead of hard coating agent A (Z-819L, manufactured by Aica Kogyo Co., Ltd.).

(2) Evaluation of Adhesion The adhesion between the hard coat layer and the transparent polyimide film in the laminate obtained in "(1) Production of the laminate" was evaluated using a grid according to JIS K 5600-5-6. It was measured and evaluated by an adhesion test. Specifically, it was carried out as follows. Cellophane tape (manufactured by Nichiban Co., Ltd., CT28) was adhered to the surface of the hard coat layer cut into 100 squares (10 rows x 10 columns) at intervals of 1 mm by pressing from above with a finger, and then peeled off. . Of the 100 squares, the case where the hard coat layer is not peeled off in all squares is 100/100, and the case where the hard coat layer is peeled off in all squares is 0/100. was counted, and the adhesion of the hard coat layer was evaluated according to the following evaluation criteria.

(Evaluation criteria)
○: 100/100
△: 50/100 to 99/100
×: 0/100 to 49/100.

(3) Evaluation of the degree of generation of interference fringes The degree of generation of interference fringes when using the laminate obtained in the above "(1) Production of laminate" was evaluated as follows. Peel off the release film on one side of an adhesive sheet (manufactured by 3M, 8146-4) provided with release films on both sides by hand, and apply the resulting adhesive sheet to the surface opposite to the hard coat layer of the laminate with a roller. to obtain a laminated sheet. The release film on the laminated sheet was peeled off by hand, and the resulting laminated sheet was attached to a black acrylic plate (manufactured by Mitsubishi Rayon Co., Ltd., Acrylite, size: 70 mm × 120 mm × thickness 2 mm) using a roller, and the test was performed. Got a sample. The surface appearance of the test sample was visually confirmed and evaluated according to the following criteria.

(Evaluation criteria)
◯: No interference fringes are observed Δ: Interference fringes are partially observed ×: Interference fringes are observed as a whole.

(4) Measurement of total light transmittance and haze value Using a haze meter "NDH4000" manufactured by Nippon Denshoku Co., Ltd., the total light transmittance and haze value were measured.

(5) Measurement of color difference Using a spectral color difference meter "Spectro Color Meter SE2000" manufactured by Nippon Denshoku Industries Co., Ltd., in the transmission measurement mode, the laminate obtained in the above "(1) Production of laminate", The L* value, a* value, and b* value in the L*a*b* color system were measured.

(6) Refractive index calculation method Using a digital Abbe refractometer "DR-A1" manufactured by ATAGO, methylene iodide was used to measure the refractive index value.

(7) Results of measurement and evaluation Table 1 shows the results of measurement and evaluation.

In Examples 1 to 7, the occurrence of interference fringes was relatively suppressed, and the adhesion between the hard coat layer and the transparent polyimide film was relatively good. Above all, as in Examples 2 to 4, when 10 to 30 parts by mass of epoxy resin is mixed with 100 parts by mass of resin having a benzene ring content of 50 to 60%, the occurrence of interference fringes is further suppressed. , and the adhesion was better.

1 laminate 10 hard coat layer 11 polyimide film

Claims (4)

including a polyimide film and a hard coat layer having a total light transmittance of 80% or more,
The hard coat layer is arranged on at least one surface of the polyimide film,
The hard coat layer contains a resin (A) having a benzene ring content of 50% by mass or more and an epoxy acrylic resin (B),
The hard coat layer contains 5 to 50 parts by mass of epoxy acrylic resin (B) with respect to 100 parts by mass of resin (A) having a benzene ring content of 50% by mass or more,
The resin (A) is a urethane acrylic resin, an acrylic resin, a polyester acrylic resin, or an epoxy acrylic resin,
The polyimide film has the general formula (1):

[In general formula (1), R ¹ represents an optionally substituted aromatic hydrocarbon. ^R2 represents an optionally substituted aromatic hydrocarbon or diphenyl ether. ] A polyimide film containing 90% by mass or more in terms of solid content of a polyimide resin containing 70 mol% or more of repeating units represented by
A laminate having a total light transmittance of 80% or more. The laminate according to claim 1 , wherein the hard coat layer contains 10 to 30 parts by mass of the epoxy acrylic resin (B) with respect to 100 parts by mass of the resin (A) having a benzene ring content of 50% by mass or more. . The laminate according to claim 1 or 2 , which is for a flexible display. A flexible display comprising the laminate according to any one of claims 1 to 3 .

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