WO2023008492A1

WO2023008492A1 - Hardcoat film, method for producing same, and display

Info

Publication number: WO2023008492A1
Application number: PCT/JP2022/028985
Authority: WO
Inventors: 文康石黒; 祐介田口; 寛人高麗; 聡子小松
Original assignee: 株式会社カネカ
Priority date: 2021-07-28
Filing date: 2022-07-27
Publication date: 2023-02-02
Also published as: JPWO2023008492A1

Abstract

A hardcoat film (11) is equipped with a hardcoat layer which contains a cured article of a silsesquioxane compound and is located on one or more main surfaces of a resin film (1). The silsesquioxane compound contains a structure represented by general formula (5) and a structure represented by general formula (6), the ratio of the structure represented by general formula (5) to the total amount of Si atoms is 0.2-0.95, and the ratio of the structure represented by general formula (5) to the total amount of the structure represented by general formula (5) and the structure represented by general formula (6) is greater than 0.4. Z represents an organic group containing an alicyclic epoxy group in general formula (5), and in general formula (6), R4 represents a divalent organic group, the main chain of which has a carbon number of 4-16, and Y represents a glycidyloxy group.　(5): [Z-Si]; (6): [Y-R4-Si]

Description

HARD COAT FILM, METHOD FOR MANUFACTURING SAME, AND DISPLAY

The present invention relates to a hard coat film and its manufacturing method. Furthermore, the present invention relates to a display comprising a hardcoat film.

Curved displays and foldable displays (flexible displays and foldable displays) are being developed, and studies are underway to replace the glass materials used for display cover windows and substrates with highly flexible plastic film materials. ing. Cover windows of flexible displays such as foldable displays are required to have various properties such as transparency, hardness, and bending resistance.

Patent Documents 1 to 3 disclose a polysiloxane-based hard coat material containing a silsesquioxane compound having an epoxy group as a curable resin component.

JP 2015-112599 A JP 2019-056106 A WO2016/098596

There are two types of foldable displays: the type that folds so that the display surface faces inside, and the type that folds so that the display surface faces outside. When the hard coat film is used as a cover window of a foldable display that is folded so that the display surface faces outward, the hard coat film is bent so that the hard coat layer-formed surface faces outward when the device is folded. be.

As disclosed in Patent Document 1, a hard coat film containing a polysiloxane compound having an alicyclic epoxy group as a curable resin component is bent so that the hard coat layer is on the outside. The layer is prone to cracking and does not have sufficient flex resistance.

In Patent Document 2, in addition to a hard coat material having a polysiloxane compound having an alicyclic epoxy group as a curable resin component, a hard coat material having a polysiloxane compound having a glycidyl group as a curable resin component was prepared. Examples are given. A cured film (hard coat layer) of a polysiloxane compound having a glycidyl group can exhibit superior flex resistance compared to a cured film of a polysiloxane compound having an alicyclic epoxy group. However, a cured film of a polysiloxane compound having a glycidyl group does not have sufficient surface hardness.

Patent Document 3 describes a hard coat film using a siloxane compound obtained by co-condensation of a silane compound having an alicyclic epoxy group and a silane compound having a glycidyl group. None of them can be said to have sufficient flex resistance.

In view of the above, an object of the present invention is to provide a hard coat film capable of achieving both excellent surface hardness and bending resistance.

A hard coat film of one embodiment of the present invention comprises a hard coat layer containing a cured product of a silsesquioxane compound on at least one main surface of a resin film. The resin film may be a transparent polyimide film.

In one embodiment of the present invention, a hard coat layer is formed by applying a hard coat composition containing a silsesquioxane compound onto a resin film and curing the hard coat layer by irradiating it with an active energy ray. A film is formed.

The hard coat film may have a top coat layer on the hard coat layer. The topcoat layer may contain a fluorine compound. For example, the hard coat layer is coated with a composition containing a compound having an alkoxysilyl group and a perfluoroalkyl group in the molecule, and the compound is condensed to form the top coat layer.

The silsesquioxane compound, which is the curable resin component of the hard coat material, includes a structure represented by general formula (5) and a structure represented by general formula (6).
[Z—Si] (5)
[YR ⁴ -Si] (6)

In general formula (5), Z is an organic group containing an alicyclic epoxy group. In general formula (6), R ⁴ is a divalent organic group having a main chain of 4 to 16 atoms, and Y is a glycidyloxy group.

In the silsesquioxane compound, the ratio of the structure represented by general formula (5) to the total amount of Si atoms is 0.2-0.95. In the silsesquioxane compound, the ratio of the structure represented by general formula (6) to the total amount of Si atoms is preferably 0.05 or more and less than 0.6.

In the silsesquioxane compound, the ratio of the structure represented by general formula (5) to the total of the structure represented by general formula (5) and the structure represented by general formula (6) is higher than 0.4. big. The ratio of the structure represented by general formula (5) to the sum of the structure represented by general formula (5) and the structure represented by general formula (6) is preferably 0.95 or less.

The hard coat film may have hard coat layers on both sides of the resin film. In the hard coat film having hard coat layers on both sides of the resin film, the hard coat layer on at least one side should contain the above cured silsesquioxane compound.

The hard coat film of the present invention can achieve both excellent surface hardness and bending resistance, and can be suitably used as a cover window material for a foldable display that is folded so that the display surface faces the outside.

1 is a cross-sectional view of a hard coat film of one embodiment; FIG. 1 is a cross-sectional view of a hard coat film of one embodiment; FIG. 1 is a cross-sectional view of a hard coat film of one embodiment; FIG. 1 is a cross-sectional view of a hard coat film of one embodiment; FIG.

FIG. 1 is a cross-sectional view of a hard coat film according to one embodiment of the present invention. The hard coat film 11 has a hard coat layer 3 on one main surface of the resin film 1 . The hard coat layer 3 is a cured polysiloxane resin layer containing a cured silsesquioxane compound. As shown in FIGS. 2 and 4, the hard coat film may have

hard coat layers

3 and 4 on both sides of the resin film 1 . As shown in FIGS. 3 and 4, the hard coat film may have a top coat layer 5 on the hard coat layer 3 .

[Resin film]
The resin film 1 is a resin substrate that serves as a base for forming the hard coat layer 3 . The resin film 1 is preferably transparent. The total light transmittance of the resin film 1 is preferably 80% or higher, more preferably 85% or higher, even more preferably 90% or higher. The haze of the resin film 1 is preferably 2% or less, more preferably 1% or less.

The thickness of the resin film 1 is, for example, about 1 to 1000 μm. The thickness of the resin film 1 is preferably 5 to 500 μm, more preferably 10 to 200 μm, even more preferably 15 to 150 μm. If the thickness is too small, the hardness tends to be insufficient, and if the thickness is too large, the flexibility tends to be poor.

The resin material constituting the resin film 1 includes polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), acrylic resins such as polymethyl methacrylate (PMMA), and cellulose resins such as triacetyl cellulose (TAC). , polycarbonate, polyamide, transparent polyimide, cyclic polyolefin, and the like.

Among them, polyesters such as PET, cellulosic resins such as TAC, and polyimides are preferable as resin materials because of their excellent transparency and mechanical strength. When the hard coat film is used for the cover window of a display, transparent polyimide is particularly preferable as the resin material for the resin film, since the film substrate is required to have excellent heat resistance and mechanical strength. General wholly aromatic polyimides are colored yellow or brown, but transparent polyimides with high visible light transmittance have been created by introducing alicyclic structures, bending structures, and fluorine substituents. can get.

The resin film 1 may contain two or more resin materials. The resin film may contain an ultraviolet absorber for the purpose of imparting weather resistance, a stabilizer such as a radical trapping agent, and a dye or pigment such as a bluing agent for the purpose of color tone adjustment.

The resin film 1 may have a single-layer structure or a multi-layer structure. For example, the resin film may be a laminate in which a plurality of films are bonded together, and the surface of the film (the surface on which the hard coat layer 3 is formed and/or the surface on which the hard coat layer is not formed) is provided with an easy-adhesion layer, an antistatic layer, and a reflective layer. A functional layer such as a prevention layer may be provided.

The thickness of the resin film 1 is not particularly limited, and can be appropriately selected, for example, from the range of 1 to 1000 μm, preferably 5 to 500 μm, more preferably 10 to 200 μm, and still more preferably 15 to 150 μm.

[Hard coat layer]
A hard coat layer 3 is formed by applying a hard coat composition onto the resin film 1 and curing the hard coat composition. The hard coat composition used for forming the hard coat layer 3 contains a silsesquioxane compound as a curable resin component.

<Silsesquioxane compound>
The silsesquioxane compound contained in the hard coat composition is a condensate of the silane compound represented by general formula (A).
R ^a -(Si(OR ² ) _x R ³ _3-x ) (A)

In general formula (A), ^R2 is a hydrogen atom or an alkyl group ^, R3 is a hydrogen atom or a monovalent hydrocarbon group selected from the group consisting of an alkyl group, an aryl group and an aralkyl group, R ^a is any monovalent organic group. x is an integer of 1-3.

The silsesquioxane compound contained in the hard coat composition is a condensate of a silane compound and includes a structure represented by general formula (5) and a structure represented by general formula (6).
[Z—Si] (5)
[YR ⁴ -Si] (6)

In general formula (5), Z is an organic group containing an alicyclic epoxy group. In general formula (6), R ⁴ is a divalent organic group having a main chain of 4 to 16 atoms, and Y is a glycidyloxy group represented by the following formula.

As the silane compound represented by the general formula (A), a mixture of the silane compound represented by the general formula (1) and the silane compound represented by the general formula (2) is condensed to obtain the silane compound represented by the general formula (5). A silsesquioxane compound containing the structure represented by and the structure represented by general formula (6) is obtained.
Z-(Si(OR ² ) _x R ³ _3-x ) (1)
YR ⁴ -(Si(OR ² ) _x R ³ _3-x ) (2)

R ² and R ³ in general formulas (1) and (2) are the same as R ² and R ³ in general formula (A). Z in general formula (1) is the same as Z in general formula (5), and Y and ^R4 in general formula (2) are the same as Y and ^R4 in general formula (6).

(Silane compound)
The silane compounds represented by general formula (A) and general formulas (1) and (2) have 1 to 3 (—OR ² ) in one molecule, and Si—OR ² is hydrolyzed. have sex. Therefore, a silsesquioxane compound is obtained by condensation of the silane compound.

R ² in general formula (A), general formula (1) and general formula (2) is preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. From the viewpoint of hydrolyzability, R ² is preferably an alkyl group having 3 or less carbon atoms, particularly preferably a methyl group.

R ³ in general formula (A), general formula (1) and general formula (2) is preferably a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 25 carbon atoms and 7 carbon atoms. A monovalent hydrocarbon group selected from the group consisting of 1 to 12 aralkyl groups. Specific examples of hydrocarbon groups include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, isopropyl, isobutyl, cyclohexyl, and ethylhexyl groups. , benzyl group, phenyl group, tolyl group, xylyl group, naphthyl group, phenethyl group and the like.

In general formula (A), general formula (1) and general formula (2), x is preferably 2 or 3. When x=3 (ie, when the Si atom has three alkoxy groups (or hydroxy groups) —OR ² attached), the silane compound does not have R ³ . From the viewpoints of improving the hardness by forming a network-like silsesquioxane compound and improving the curing speed by increasing the number of epoxy groups contained in the silsesquioxane compound, it is preferable that x=3. A silane compound with x=2 and a silane compound with x=3 may be used in combination. In addition to the silane compound in which x is 2 or 3, a silane compound in which x is 1 may be used for the purpose of adjusting the molecular weight of the silsesquioxane compound obtained by condensation.

Z in general formulas (1) and (5) is an organic group containing an alicyclic epoxy group, preferably an alkyl group having an alicyclic epoxy group as a substituent. The cycloaliphatic epoxy group is preferably 3,4-epoxycyclohexyl. When Z is an alkyl group having an alicyclic epoxy group as a substituent, the number of carbon atoms in the alkyl group is preferably 16 or less, more preferably 12 or less, even more preferably 10 or less, and particularly preferably 1 to 5.

A silsesquioxane compound obtained by condensation of a silane compound containing an alicyclic epoxy group retains its alicyclic structure even after curing by ring-opening polymerization of the epoxy group, so that its molecular volume is less reduced by curing. Rather, it tends to increase in volume due to curing. Therefore, cure shrinkage is less likely to occur, which can contribute to the suppression of curling of the hard coat film. Moreover, since the alicyclic structure is more rigid than the chain structure, the hardness of the hard coat layer tends to be improved. Therefore, the higher the ratio of the silane compound represented by the general formula (1) used in the synthesis of the silsesquioxane compound, the higher the hardness of the hard coat layer of the hard coat film, and the less the curl tends to be.

Specific examples of the silane compound represented by the general formula (1) include 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethylmethyldimethoxysilane, 3-( 3,4-epoxycyclohexyl)propyltrimethoxysilane, 3-(3,4-epoxycyclohexyl)propylmethyldimethoxysilane, 4-(3,4-epoxycyclohexyl)butyltrimethoxysilane, 4-(3,4-epoxy cyclohexyl)butylmethyldimethoxysilane, 5-(3,4-epoxycyclohexyl)pentyltrimethoxysilane, 5-(3,4-epoxycyclohexyl)pentylmethyldimethoxysilane and the like.

R ⁴ in general formulas (2) and (6) is a divalent organic group having a main chain of 4 to 16 atoms. ^R4 may be linear or branched. The number of atoms in the main chain is the number of atoms constituting the straight chain connecting the Si atom and the oxygen atom of the glycidyloxy group Y in general formulas (2) and (6). That is, the silane compound of general formula (2) is a compound in which a Si atom and a glycidyloxy group Y are bonded via 4 to 16 atoms between them.

R ⁴ may be a linear or branched alkylene group, and may contain atoms other than carbon in the main chain. For example, ^R4 may be a heteroalkylene group and may contain an ether bond, an ester bond, an amide bond, a carbonyl group, an imino group, and the like.

When ^R4 is a linear alkylene group, specific examples include tetramethylene, pentamethylene, hexamethylene, heptamethylene, octamethylene, decamethylene, dodecamethylene, tetradecamethylene, hexa A decamethylene group and the like can be mentioned. In R ⁴ , part or all of the hydrogen atoms of methylene (—CH ₂ —) constituting a linear alkylene may be substituted with a substituent. Specific examples of substituents include methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, cyclohexyl group, phenyl group, amino group, (meth)acrylic group, halogen, allyl group, vinyl group, mercapto group, carboxyl group, nitro group, sulfone group, hydroxy group and the like.

The silsesquioxane compound obtained by condensation of the silane compound represented by the general formula (2) has an organic group ^R4 having a specific chain length between the epoxy group, which is a polymerizable functional group, and the Si atom. Due to the presence of , the molecular structure has flexibility even after curing due to the reaction of epoxy groups. Therefore, the hard coat layer composed of the cured product of the silsesquioxane compound exhibits excellent flexibility (flexibility). The greater the distance between the Si atom and the epoxy group, that is, the greater the number of atoms constituting the main chain of the spacer organic group ^R4 and the longer the chain length, the more likely the bending resistance of the hard coat layer 3 will improve. be. As described above, the number of atoms in the main chain of ^R4 is 4 or more, preferably 6 or more, and may be 8 or more. On the other hand, when the number of atoms in the main chain of ^R4 is excessively large, the hardness of the hard coat layer tends to be insufficient. Therefore, the number of atoms in the main chain of R ⁴ is 16 or less, preferably 14 or less, more preferably 12 or less, and may be 10 or less.

Specific examples of the silane compound represented by formula (2) include 4-glycidyloxybutyltrimethoxysilane, 4-glycidyloxybutylmethyldimethoxysilane, 4-glycidyloxybutyltriethoxysilane, and 4-glycidyloxybutylmethyl. diethoxysilane, 5-glycidyloxypentyltrimethoxysilane, 5-glycidyloxypentylmethyldimethoxysilane, 5-glycidyloxypentyltriethoxysilane, 5-glycidyloxypentylmethyldiethoxysilane, 6-glycidyloxyhexyltrimethoxysilane, 6-glycidyloxyhexylmethyldimethoxysilane, 6-glycidyloxyhexyltriethoxysilane, 6-glycidyloxyhexylmethyldiethoxysilane, 7-glycidyloxyheptyltrimethoxysilane, 7-glycidyloxyheptylmethyldimethoxysilane, 7-glycidyloxy heptyltriethoxysilane, 7-glycidyloxyheptylmethyldiethoxysilane, 8-glycidyloxyoctyltrimethoxysilane, 8-glycidyloxyoctylmethyldimethoxysilane, 8-glycidyloxyoctyltriethoxysilane, 8-glycidyloxyoctylmethyldiethoxysilane Silane, 9-glycidyloxynonyltrimethoxysilane, 9-glycidyloxynonylmethyldimethoxysilane, 9-glycidyloxynonyltriethoxysilane, 9-glycidyloxynonylmethyldiethoxysilane, 10-glycidyloxydecyltrimethoxysilane, 10- glycidyloxydecylmethyldimethoxysilane, 10-glycidyloxydecyltriethoxysilane, 10-glycidyloxydecylmethyldiethoxysilane, 11-glycidyloxyundecyltrimethoxysilane, 11-glycidyloxyundecylmethyldimethoxysilane, 11-glycidyloxy undecyltriethoxysilane, 11-glycidyloxyundecylmethyldiethoxysilane, 12-glycidyloxydodecyltrimethoxysilane, 12-glycidyloxydodecylmethyldimethoxysilane, 12-glycidyloxydodecyltriethoxysilane, 12-glycidyloxydodecylmethyl Diethoxysilane, 13-glycidyloxytridecyltrimethoxysilane, 13-glycidyloxytridecylmethyldimethoxysilane, 13-glycidyloxytridecyl triethoxysilane, 13-glycidyloxytridecylmethyldiethoxysilane, 14-glycidyloxytetradecyltrimethoxysilane, 14-glycidyloxytetradecylmethyldimethoxysilane, 14-glycidyloxytetradecyltriethoxysilane, 14-glycidyloxytetra Decylmethyldiethoxysilane, 15-glycidyloxypentadecyltrimethoxysilane, 15-glycidyloxypentadecylmethyldimethoxysilane, 15-glycidyloxypentadecyltriethoxysilane, 15-glycidyloxypentadecylmethyldiethoxysilane, 16-glycidyl oxyhexadecyltrimethoxysilane, 16-glycidyloxyhexadecylmethyldimethoxysilane, 16-glycidyloxyhexadecyltriethoxysilane, 16-glycidyloxyhexadecylmethyldiethoxysilane, and the like.

As the silane compound, compounds other than the silane compound represented by the general formula (1) and the silane compound represented by the general formula (2) may be used. In such silane compounds, R ^a in general formula (A) is a group containing a substituted or unsubstituted double bond, a group containing a substituted or unsubstituted cycloalkyl group, or a substituted or unsubstituted aromatic ring. , a substituted or unsubstituted alkyl group, a group having a glycidyl group, or a group having an oxetanyl group. Specific examples of R ^a include vinyl group, allyl group, acryloyloxypropyl group, methacryloyloxypropyl group, cyclopentyl group, cyclohexyl group, benzyl group, phenyl group, tolyl group, xylyl group, naphthyl group, phenethyl group and methyl group. , ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, isopropyl group, isobutyl group, 3-glycidyloxypropyl group and the like.

(Hydrolysis and condensation of silane compound)
By reacting the above silane compound with water, the Si—OR ² portion of the silane compound is hydrolyzed, and the hydrolyzate is condensed to form a Si—O—Si bond, resulting in a condensate of the silane compound (sil sesquioxane compound) is produced. The amount of water required for hydrolysis and condensation reaction is preferably 0.3 to 10 equivalents, more preferably 0.5 to 5 equivalents, and 1 to 3 equivalents per equivalent of —OR ² groups bonded to Si atoms. is more preferred. When the amount of water is excessively small, the number of OR ² groups remaining without hydrolysis is large and the molecular weight of the silsesquioxane compound is small, so that the hardness of the hard coat layer tends to be insufficient. When the amount of water is excessively large, the reaction rate of hydrolysis and condensation reactions is high, resulting in the formation of high-molecular-weight condensates, which tends to reduce the transparency and flexibility of the hard coat layer.

From the viewpoint of increasing the hardness of the cured film (hard coat layer), the weight average molecular weight of the silsesquioxane compound is preferably 500 or more. Also from the viewpoint of suppressing volatilization, the weight average molecular weight of the silsesquioxane compound is preferably 500 or more. On the other hand, if the molecular weight is excessively high, cloudiness may occur due to a decrease in compatibility with other compositions or the like. Therefore, the weight average molecular weight of the silsesquioxane compound is preferably 20,000 or less. The molecular weight of the silsesquioxane compound can be controlled by selecting the amount of water used in the reaction and the type and amount of catalyst. For example, increasing the amount of water tends to increase the molecular weight.

From the viewpoint of improving the curing speed and hardness of the hard coat layer, the silsesquioxane compound preferably has a large content of epoxy groups. The residual rate of epoxy groups is preferably 40% or more, more preferably 60% or more, still more preferably 80% or more, and may be 90% or more or 95% or more. The residual rate of epoxy groups can be calculated by ¹ H-NMR measurement.

In the hydrolysis reaction and condensation reaction of the silane compound, it is preferable to carry out the reaction under neutral or basic conditions from the viewpoint of suppressing the ring opening of the epoxy group. In particular, from the viewpoint of reducing the T3/T2 ratio of the silsesquioxane compound obtained as a condensate of the silane compound, it is preferable to carry out the hydrolysis and condensation reaction in the presence of a neutral salt catalyst.

A silsesquioxane compound produced by hydrolysis and condensation of a silane compound is a silane compound having a T unit structure where x=3 in general formula (A) and general formulas (1) and (2). A structure in which all alkoxy groups (Si—OR ² ) undergo a condensation reaction to form Si—O—Si bonds (referred to as “SiO _3/2 form” or “T3 form”), and three It may include a structure in which two of the alkoxy groups are condensed to form a Si—O—Si bond (referred to as “SiO _2/2 form” or “T2 form”).

The silsesquioxane compound may preferably have a molar ratio of SiO _3/2 form (T3 form) to SiO _2/2 form (T2 form): T3/T2 ratio of less than 5 in some cases. The T3/T2 ratio may be 4 or less, 3.5 or less, 3 or less or 2.5 or less. The T3/T2 ratio is preferably 0.8 or more, and may be 1 or more, 1.5 or more, or 2 or more.

By carrying out the reaction in the presence of a neutral salt catalyst, the T3/T2 ratio tends to decrease. Neutral salt catalysts include salts composed of acids and bases, and salts composed of cations of alkali metals or alkaline earth metals and anions of halogens are preferred. Specific examples of neutral salts include lithium chloride, sodium chloride, potassium chloride, beryllium chloride, magnesium chloride, calcium chloride, lithium bromide, sodium bromide, potassium bromide, beryllium bromide, magnesium bromide, and calcium bromide. , lithium iodide, sodium iodide, potassium iodide, beryllium iodide, magnesium iodide, calcium iodide and the like.

When a neutral salt catalyst is used for hydrolysis and condensation of the silane compound, the neutral salt catalyst may remain in the silsesquioxane compound. The amount of neutral salts remaining in the silsesquioxane compound may be from 1 ppm to 10000 ppm, or from 50 ppm to 5000 ppm or from 100 ppm to 1000 ppm.

As described above, the silsesquioxane compound obtained by condensation of the silane compound includes the structure represented by general formula (5) and the structure represented by general formula (6).

From the viewpoint of increasing the hardness of the hard coat layer 3, the ratio of the structure represented by the general formula (5) to the total number of Si atoms in the silsesquioxane compound is preferably 0.2 or more, more preferably 0.3 or more. Preferably, 0.4 or more is more preferable. On the other hand, from the viewpoint of increasing the bending resistance of the hard coat layer when the hard coat film is bent with the surface on which the hard coat layer 3 is formed on the outside, general formula (5) for the total number of Si atoms in the silsesquioxane compound is preferably 0.95 or less, more preferably 0.9 or less, and even more preferably 0.8 or less.

From the viewpoint of increasing the bending resistance of the hard coat layer 3, the ratio of the structure represented by the general formula (6) to the total number of Si atoms in the silsesquioxane compound is preferably 0.05 or more, and 0.1 or more. is more preferable, and 0.2 or more is even more preferable. On the other hand, from the viewpoint of reducing curling of the hard coat film, the ratio of the structure represented by the general formula (6) to the total number of Si atoms in the silsesquioxane compound is preferably less than 0.6, and 0.55 or less. is more preferable, and 0.5 or less is even more preferable.

In the silsesquioxane compound, the total ratio of the structure represented by the general formula (5) and the structure represented by the general formula (6) to the total number of Si atoms is preferably 0.4 or more, and 0.6. more preferably 0.8 or more, and may be 0.9 or more, 0.95 or more, or 1.

In the silsesquioxane compound, the ratio of the structure represented by general formula (5) to the total of the structure represented by general formula (5) and the structure represented by general formula (6) is higher than 0.4. Large is preferred. The ratio of the structure of general formula (5) to the sum of the structure of general formula (5) and the structure of general formula (6) is more preferably 0.45 or more, more preferably 0.5 or more. As the ratio of the structure represented by formula (5) increases, the hardness of the hard coat layer 3 tends to increase, and curling of the hard coat film tends to be suppressed.

The inclusion of the structure of general formula (6) tends to improve the bending resistance of the hard coat layer 3 . From the viewpoint of increasing the bending resistance of the hard coat layer when the surface on which the hard coat layer 3 is formed is bent outward, the structure represented by the general formula (5) and the general formula (6) in the silsesquioxane compound The ratio of the structure represented by general formula (5) to the total number of structures represented is preferably 0.95 or less, more preferably 0.9 or less, and even more preferably 0.8 or less.

In hydrolysis and condensation reactions of silane compounds, —OR ² in general formula (A) and general formulas (1) and (2) participates in the reaction, but other functional groups bonded to Si atoms are epoxy It does not react except for side reactions such as ring-opening of groups. Therefore, in a silsesquioxane compound obtained by condensation of a silane compound, R ^a in general formula (A) (including Z in general formula (1) and R ⁴ and Z in general formula (5)) is the structure is retained.

Therefore, the ratio of the structure of general formula (5) to the total number of Si atoms contained in the silsesquioxane compound is the ratio of the silane compound of general formula (1) to the total amount of the silane compound represented by general formula (A). approximately equal to Similarly, the ratio of the structure of general formula (6) to the total number of Si atoms contained in the silsesquioxane compound is the ratio of the silane compound of general formula (2) to the total amount of the silane compound of general formula (A). Almost equal to the ratio. Further, in the silsesquioxane compound, the ratio of the structure represented by the general formula (5) to the total of the structure represented by the general formula (5) and the structure represented by the general formula (6) is the general formula ( It is substantially equal to the ratio of the silane compound of general formula (1) to the sum of the silane compound of general formula (1) and the silane compound of general formula (2).

That is, by adjusting the charging ratio of the silane compound when synthesizing the silsesquioxane compound, the structure represented by the general formula (5) and the structure represented by the general formula (6) have the above ratio. A silsesquioxane compound is obtained. The ratio of the silane compound represented by the general formula (1) to the total amount of the silane compound represented by the general formula (A) is preferably 0.2 to 0.95, more preferably 0.3 to 0.9, 0.4 to 0.8 is more preferred. The ratio of the silane compound represented by the general formula (2) to the total amount of the silane compound represented by the general formula (A) is preferably 0.05 or more and less than 0.6, more preferably 0.1 to 0.55. , 0.2 to 0.5 are more preferred.

The total ratio of the silane compound represented by the general formula (1) and the silane compound represented by the general formula (2) to the total amount of the silane compound represented by the general formula (A) is preferably 0.4 or more. , is more preferably 0.6 or more, more preferably 0.8 or more, and may be 0.9 or more, 0.95 or more, or 1.

The ratio of the silane compound represented by the general formula (1) to the total of the silane compound represented by the general formula (1) and the silane compound represented by the general formula (2) is greater than 0.4 and 0.95 or less. is preferred, 0.45 to 0.9 is more preferred, and 0.5 to 0.8 is even more preferred.

<Hard coat composition>
The hard coat composition contains the above silsesquioxane compound as a curable resin component, and further contains a photocationic polymerization initiator. The hardcoat composition may further include leveling agents, reactive diluents, photosensitizers, particles and other additives as solids (non-volatiles). From the viewpoint of forming a hard coat layer with excellent mechanical strength, the content of the silsesquioxane compound in the hard coat composition is preferably 40 parts by weight or more with respect to 100 parts by weight of the total solid content (non-volatile content). , more preferably 50 parts by weight or more, and more preferably 60 parts by weight or more.

(Photo cationic polymerization initiator)
A photocationic polymerization initiator is a compound (photoacid generator) that generates an acid upon irradiation with an active energy ray. The acid generated from the photoacid generator promotes the ring-opening and polymerization reaction of the epoxy groups of the silsesquioxane compound, forms intermolecular crosslinks, and cures the hard coat material.

Photocationic polymerization initiators include strong acids such as toluenesulfonic acid, antimony hexafluoride, boron tetrafluoride, phosphorus hexafluoride, fluoroalkyl phosphorus fluoride, and fluoroalkyl gallium fluoride; sulfonium salts, ammonium salts, and phosphonium salts. , iodonium salts, selenium salts and other onium salts; iron-allene complexes; silanol-metal chelate complexes; sulfonic acid derivatives of; and organic halogen compounds. Among these, aromatic sulfonium salts and aromatic iodonium salts are preferred because of their high stability in the hard coat composition.

The content of the photocationic polymerization initiator in the hard coat composition is preferably 0.05 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, relative to 100 parts by weight of the silsesquioxane compound. , more preferably 0.2 to 2 parts by weight.

(leveling agent)
The hard coat composition may contain a leveling agent. As the leveling agent, a silicone-based leveling agent and a fluorine-based leveling agent are preferred. Inclusion of a leveling agent is expected to reduce the surface tension of the hard coat composition and improve the surface smoothness.

The content of the leveling agent in the hard coat composition is preferably 0.001 to 10 parts by weight, more preferably 0.01 to 5 parts by weight, and 0.05 parts by weight, based on 100 parts by weight of the silsesquioxane compound. ~1 part by weight is more preferred.

(reactive diluent)
The hardcoat composition may contain a reactive diluent. Examples of reactive diluents include cationically polymerizable compounds other than the silsesquioxane compounds described above. A compound having a cationic polymerizable functional group is used as the reactive diluent for cationic photopolymerization. Cationically polymerizable functional groups of reactive diluents include epoxy groups, vinyl ether groups, oxetane groups, and alkoxysilyl groups. Among them, as the reactive diluent, one having an epoxy group is preferable because of its high reactivity with the epoxy group of the silsesquioxane compound.

The content of the reactive diluent in the hard coat composition is preferably 100 parts by weight or less, more preferably 50 parts by weight or less, relative to 100 parts by weight of the silsesquioxane compound.

(photosensitizer)
The hard coat composition may contain a photosensitizer for the purpose of improving the photosensitivity of the photocationic polymerization initiator (photoacid generator). As a photosensitizer, there is a type that improves the photosensitivity of the photocationic polymerization initiator by absorbing light in the wavelength range that the photocationic polymerization initiator cannot absorb, and a type that has a large absorption wavelength range with the photocationic polymerization initiator. Although there is no difference, any type that improves the photosensitivity of the photocationic polymerization initiator may be used. As the type of photosensitizer that absorbs light in a wavelength range that cannot be absorbed by the photocationic polymerization initiator, one having strong absorption in a wavelength range different from the absorption wavelength range of the photocationic polymerization initiator is preferred. Photosensitizers include anthracene derivatives, benzophenone derivatives, thioxanthone derivatives, anthraquinone derivatives, benzoin derivatives, naphthalene derivatives and the like.

The content of the photosensitizer in the hard coat composition is preferably 500 parts by weight or less, more preferably 100 parts by weight or less, and even more preferably 50 parts by weight or less with respect to 100 parts by weight of the photocationic polymerization initiator. .

(particle)
The hard coat composition may contain particles for the purpose of adjusting film properties such as surface hardness and bending resistance. As the particles, organic particles, inorganic particles, organic-inorganic composite particles, etc. may be appropriately selected and used. The particles may be surface-modified, and polymerizable functional groups may be introduced by surface modification.

The average particle diameter of the particles is, for example, about 5 nm to 10 μm. From the viewpoint of increasing the transparency of the hard coat layer, the average particle size is preferably 1000 nm or less, more preferably 500 nm or less, even more preferably 300 nm or less, and particularly preferably 100 nm or less. The particle size can be measured by a laser diffraction/scattering type particle size distribution analyzer, and the volume-based median size is taken as the average particle size.

The content of the particles in the hard coat composition is preferably 100 parts by weight or less, more preferably 50 parts by weight or less, relative to 100 parts by weight of the silsesquioxane compound.

(solvent)
The hard coat composition may be solventless or may contain a solvent. When the hard coat composition contains a solvent, it preferably does not dissolve the resin film 1 as the substrate. On the other hand, the adhesion between the resin film 1 and the hard coat layer 3 may be improved by using a solvent having sufficient solubility to swell the resin film. The content of the solvent is preferably 500 parts by weight or less, more preferably 300 parts by weight or less, and even more preferably 100 parts by weight or less with respect to 100 parts by weight of the silsesquioxane compound.

(other ingredients)
The hard coat composition may contain additives such as inorganic pigments, organic pigments, surface conditioners, surface modifiers, plasticizers, dispersants, wetting agents, thickeners, antifoaming agents, and UV stabilizers. good. The hard coat composition may also contain a thermoplastic, thermosetting or photocurable resin material other than the silsesquioxane compound described above. When the silsesquioxane compound and/or the resin material other than the silsesquioxane compound has radical polymerizability, the hard coat composition may contain a radical polymerization initiator in addition to the photocationic polymerization initiator.

<Formation of hard coat layer>
A hard coat layer 3 is formed on the resin film 1 by applying a hard coat composition onto the resin film 1, removing the solvent by drying if necessary, and then curing the hard coat composition by irradiating an active energy ray. is formed.

Examples of the method of applying the hard coat composition include roll coating such as bar coating, gravure coating and comma coating, die coating such as slot die coating and fountain die coating, spin coating, spray coating and dip coating. Before applying the hard coat composition, the surface of the resin film may be subjected to surface treatment such as corona treatment or plasma treatment. Also, an easy-adhesion layer or the like may be provided on the surface of the resin film 1 .

By irradiation with active energy rays or heat, an acid is generated from the cationic polymerization initiator, and the epoxy group of the silsesquioxane compound undergoes ring-opening and cationic polymerization, and curing proceeds. When additives such as reactive diluents and particles contained in the hard coat composition contain epoxy groups, in addition to the polymerization reaction between the silsesquioxane compounds, the reaction between the silsesquioxane compounds and the additives Polymerization reactions also occur.

Ultraviolet rays are preferable as active energy rays. The cumulative irradiation dose of active energy rays is, for example, about 50 to 10000 mJ/cm ² , and may be set according to the type and amount of the cationic photopolymerization initiator, the thickness of the film, and the like. Although the curing temperature is not particularly limited, it is usually 150° C. or lower, and may be 100° C. or lower or 90° C. or lower.

The thickness of the hard coat layer 3 is preferably 0.5 µm or more, more preferably 2 µm or more, still more preferably 3 µm or more, and particularly preferably 5 µm or more. The thickness of the hard coat layer 3 is preferably 100 μm or less, more preferably 80 μm or less. Mechanical properties such as surface hardness tend to improve as the thickness of the hard coat layer increases. On the other hand, when the thickness of the hard coat layer is excessively large, the flex resistance of the hard coat layer may decrease.

The total thickness of the resin film 1 and the hard coat layer 3 is preferably 10-500 μm, more preferably 15-250 μm, even more preferably 20-200 μm. If the thickness is too small, the mechanical strength may be insufficient, and if the thickness is too large, the transparency and flexibility may be insufficient. The ratio of the thickness D ₁ of the resin film 1 to the thickness D ₃ of the hard coat layer 3: D ₃ /D ₁ is about 0.01 to 10, for example.

As shown in FIGS. 2 and 4, the hard coat film may have the hard coat layer 3 on one side of the resin film 1 and the hard coat layer 4 on the other side. By providing the hard coat layers on both sides of the resin film 1, there is a tendency for the hardness of the hard coat films to further increase. Further, by forming hard coat layers on both sides of the resin film 1 to balance the stress at the interface between the front and back surfaces of the resin film, the curling of the hard coat film can be reduced in some cases.

When the hard coat film has hard coat layers on both sides, the hard coat layer 3 on one side may be a polysiloxane-based hard coat layer having the above composition, and the composition of the hard coat layer 4 on the other side is It is not particularly limited. The hard coat layer 4 may be a polysiloxane-based hard coat layer, or may be a cured composition containing a silsesquioxane compound having the structure of general formula (5).

When the hard coat film has hard coat layers on both sides, the ratio of the thickness D3 of the hard coat layer ₃ to the thickness D4 of the hard coat layer ₄ : _D3 / _D4 is, for example, 0.025 to 40. , 0.05-20 or 0.1-10. When D ₃ /D ₄ is excessively large or excessively small, the hard coat film may curl greatly and be inferior in handleability.

[Top coat layer]
As shown in FIGS. 3 and 4, a top coat layer 5 may be provided on the surface of the hard coat layer 3 . For example, by providing the top coat layer 5 containing a fluorine compound on the outermost surface of the hard coat film, the scratch resistance and antifouling properties are improved.

<Fluorine compound>
The fluorine compound that constitutes the topcoat layer contains one or more fluorine atoms in the molecule. The fluorine compound preferably contains a perfluoroalkyl group. Compounds containing a perfluoroalkyl group include perfluoroalkyl compounds, perfluoroalkyl ether compounds, perfluoroether compounds, perfluoropolyether compounds, and the like.

The fluorine compound constituting the topcoat layer is preferably a condensate of a compound having an alkoxysilyl group and a perfluoroalkyl group in the molecule, and the alkoxysilyl group is hydrolyzed and condensed to form a high molecular weight compound to form a film. be.

A perfluoroalkyl group is an alkyl group in which all hydrogen atoms are replaced with fluorine atoms, and is represented by CF ₃ (CF ₂ ) _n —. From the viewpoint of condensation reactivity, the alkoxysilyl group is preferably a trialkoxysilyl group, more preferably a triethoxysilyl group or a trimethoxysilyl group, and particularly preferably a trimethoxysilyl group.

A compound having an alkoxysilyl group and a perfluoroalkyl group in the molecule preferably has a fluoroalkyl ether structure, and is preferably an oligomer having a fluoroalkyl ether repeating unit.

Examples of the fluoroalkyl ether structure include -(OC ₄ F ₈ )-, -(OC ₃ F ₆ )-, -(OC ₂ F ₄ )-, -(OCF ₂ )- and the like. The perfluoroalkyl group of the fluoroalkyl ether may be linear or branched, but is preferably linear from the viewpoint of scratch resistance.

The number average molecular weight of the oligomer is preferably 1,000 to 50,000, more preferably 3,000 to 20,000, even more preferably 5,000 to 10,000. If the number average molecular weight is less than 1,000, the scratch resistance may be poor, and if it is more than 50,000, it may be difficult to apply the composition.

The perfluoroalkyl group-containing compound may contain substituents other than perfluoroalkyl groups and repeating units other than fluoroalkyl ethers. Examples of substituents include alkyl groups and fluoroalkyl groups obtained by substituting fluorine atoms for some of the hydrogen atoms of alkyl groups (that is, fluoroalkyl groups other than perfluoroalkyl groups). From the viewpoint of scratch resistance, the perfluoroalkyl group-containing compound preferably has a higher ratio of hydrogen atoms in the alkyl group substituted with fluorine.

<Formation of top coat layer>
The method of forming the topcoat layer 5 is not particularly limited, and includes roll coating such as bar coating, gravure coating and comma coating, die coating such as slot die coating and fountain die coating, wet methods such as spin coating, spray coating and dip coating; vacuum deposition. , sputtering, CVD, etc. can be used. When a compound having an alkoxysilyl group and a perfluoroalkyl group in the molecule is condensed to form a film, a wet method is preferred from the viewpoint of promoting hydrolysis.

Before forming the top coat layer 5 on the hard coat layer 3, surface treatments such as corona treatment, plasma treatment, and ion beam treatment may be performed. Alternatively, a primer layer may be provided on the hard coat layer 3 and the top coat layer 5 may be formed thereon. Materials for the primer layer include metal oxides such as silicon oxide, titanium oxide, aluminum oxide and zirconium oxide; and organic/inorganic hybrid materials, which are hydrolytic condensates of alkoxysilanes.

Surface treatment of the hard coat layer 3 generates hydroxyl groups, carboxyl groups, carbonyl groups, silanol groups, etc., and adhesion with compounds containing alkoxysilyl groups and perfluoroalkyl groups (components of the top coat layer 5) in the molecule. is improved, and scratch resistance and antifouling properties tend to be improved.

As the surface treatment, corona treatment is preferable because the treatment can be easily performed at atmospheric pressure. The corona treatment density is preferably 1 W·min/m ² or more, more preferably 10 W·min/m ² or more, 30 W·min/m ² or more, 100 W·min/m ² or more, or 500 W·min/m ² or more. 3000 W·min/m ² or less is preferable, and 600 W·min/m ² or less is more preferable. If the treatment density is too low, the effect of surface treatment on improving adhesion may be insufficient, and if the treatment density is too high, the hard coat layer may deteriorate.

When the scratch-resistant layer is formed by a wet method, it is preferable to use a composition obtained by diluting a compound (oligomer) having an alkoxysilyl group and a perfluoroalkyl group in the molecule with a solvent. Preferred solvents from the viewpoint of compound solubility and solvent volatility are perfluoroaliphatic hydrocarbons having 5 to 12 carbon atoms such as perfluorohexane, perfluoromethylcyclohexane and perfluoro-1,3-dimethylcyclohexane. polyfluoroaromatic hydrocarbons such as bis(trifluoromethyl)benzene; perfluoropropylmethyl ether ( _C3F7OCH3 ) _, _{perfluorobutylmethylether} ₍ _C4F9OCH3 ) _, perfluorobutylethylether (C ₄ F ₉ OC ₂ H ₅ ), perfluorohexylmethyl ether (C ₂ F ₅ CF(OCH ₃ )C ₃ F ₇ ) and other hydrofluoroethers (HFE). The perfluoroalkyl group and alkyl group of the hydrofluoroether may be linear or branched. As the solvent, hydrofluoroether is preferred, and perfluorobutyl methyl ether ₍ _C4F9OCH3 ) and _{perfluorobutylethyl} _ether ₍ _C4F9OC2H5 ) _are preferred. The solvent may be a mixed solvent of two or more.

In addition to the above perfluoro compounds, the composition contains perfluoroalkyl group-containing compounds typified by fluoroalkyl ether oligomers having no alkoxysilyl groups in the molecule, fluorine-based oils, and other additives such as silicone-based oils. may contain The inclusion of fluorine oil or silicone oil may improve scratch resistance and antifouling properties.

The composition may contain catalysts such as acids, bases, and metal organic compounds. Containing a catalyst promotes the reaction between the alkoxysilyl groups and the functional groups on the surface of the hard coat layer, and may improve the adhesion of the top coat layer 5 to the hard coat layer 3 . The composition may contain water. Since the presence of water hydrolyzes the alkoxysilyl groups, the reaction with the functional groups on the surface of the hard coat layer is promoted, and the adhesion of the top coat layer 5 to the hard coat layer 3 may be improved.

As the scratch resistant coating composition, commercially available products such as "OPTOOL UD509" and "OPTOOL DSX-E" manufactured by Daikin Industries may be used. Solvents and additives may be added to commercially available coating compositions.

The solid content concentration of the compound (oligomer) having an alkoxysilyl group and a perfluoroalkyl group in the molecule in the composition is not particularly limited, but from the viewpoint of coating properties, it is preferably 20% by weight or less, more preferably 10% by weight or less. , more preferably 5% by weight or less, and may be 1% by weight or less or 0.5% by weight or less. If the solid content concentration is excessively high, the coating film may become cloudy.

It is preferable to heat after applying the composition onto the hard coat layer 3 . Heating promotes condensation of the compound having an alkoxysilyl group and a perfluoroalkyl group in the alkoxysilyl group molecule. The heating temperature is preferably 30° C. or higher, more preferably 60° C. or higher, and may be 100° C. or higher or 130° C. or higher. The heating temperature is usually 170° C. or lower.

Although the thickness of the topcoat layer 5 is not particularly limited, it is preferably 1 nm or more, more preferably 5 nm or more, even more preferably 6 nm or more, and particularly preferably 10 nm or more. The thickness of the scratch resistant layer is preferably 1000 nm or less, more preferably 100 nm or less, and may be 50 nm or less, 45 nm or less, 40 nm or less, 35 nm or less, or 30 nm or less. If the thickness of the scratch-resistant layer is too small, the scratch resistance and antifouling property may be insufficient, and if the thickness is too large, the coating film may become cloudy and the transparency may be lowered.

In the scratch-resistant layer formed from a composition containing a compound having an alkoxysilyl group and a perfluoroalkyl group in the molecule, the alkoxysilyl group of the perfluoroalkyl compound is preferably hydrolyzed and condensed. If the hydrolysis and condensation are accelerated by heating or the like after application of the composition, the hydroxyl groups generated by hydrolysis of the alkoxysilyl groups are only the alkoxysilyl groups of other perfluoro compounds (hydroxyl groups generated by the hydrolysis thereof). It is possible to form a covalent bond through a condensation reaction with the functional group on the surface of the hard coat layer 3 . Therefore, it is considered that the perfluoroalkyl compound is firmly fixed to the hard coat layer 3 and the scratch resistance is improved.

In particular, a hard coat layer formed by curing a silsesquioxane compound having an epoxy group has a hydroxyl group (silanol group) generated by hydrolysis during condensation of a silane compound, and furthermore, an epoxy group during curing. has a hydroxyl group generated with the ring opening of These hydroxyl groups are capable of a condensation reaction with alkoxysilyl groups of perfluoroalkyl compounds. In addition, the silsesquioxane compound constituting the hard coat layer is an organic compound containing a Si atom, similar to the alkoxysilyl group of the perfluoro compound, and has a high affinity with each other, and the alkoxysilyl group of the silsesquioxane compound. , a silanol group or the like can be condensed with an alkoxysilyl group of the perfluoro compound.

[Characteristics of hard coat film]
A hard coat film in which a hard coat layer 3 containing a cured product of a silsesquioxane compound having a structure represented by the general formula (5) and a structure represented by the general formula (6) is provided on the resin film 1. has high surface hardness and excellent bending resistance.

The pencil hardness of the surface on which the hard coat layer 3 is formed is preferably HB or higher, more preferably H or higher, still more preferably 2H or higher, even more preferably 3H or higher, and may be 4H or higher. Surface hardness tends to increase as the ratio of the structure represented by general formula (5) in the silsesquioxane compound increases. Further, the surface hardness tends to increase as the thickness of the hard coat layer 3 increases.

It is preferable that the hard coat film has a small mandrel diameter φ at which cracks occur in the hard coat layer when a cylindrical mandrel test according to JIS-K5600 is performed with the surface on which the hard coat layer 3 is formed on the outside. φ is more preferably 4 mm or less, more preferably 3 mm or less, and may be 2 mm or less. When the silsesquioxane compound has the structure represented by the general formula (6), φ tends to decrease, and the larger the ratio of the structure represented by the general formula (6) in the silsesquioxane compound, φ tends to be small. In addition, φ tends to decrease as the thickness of the hard coat layer 3 decreases. In the silsesquioxane compound, the ratio of the structure represented by general formula (5) to the total of the structure represented by general formula (5) and the structure represented by general formula (6) is 0.95 or less. (the ratio of the structure represented by the general formula (6) is 0.05 or more), even when the thickness of the hard coat layer 3 is 40 μm or more, the hard coat layer 3 is bent on the outside. When the mandrel diameter φ is within the above range, a hard coat film having excellent bending resistance can be obtained.

From the viewpoint of handling, it is preferable that the hard coat film has a small curl. For example, when the hard coat film is cut into a 3 cm square, it is preferred that it does not form a cylinder. When a hard coat film cut into 3 cm squares is left standing on a horizontal table, the average value of the lifting amount of the four vertices of the hard coat film is preferably 10 mm or less, more preferably 8 mm or less.

A polysiloxane-based hard coat layer formed by curing a silsesquioxane compound having an alicyclic epoxy group has excellent hardness, but tends to be inferior in flex resistance. On the other hand, a hardener formed by curing a silsesquioxane compound having a glycidyloxy group and a spacer with a long chain length (having 4 or more atoms in the main chain) between the Si atom and the glycidyloxy group The coat layer has excellent bending resistance, but low surface hardness. Further, when a hard coat layer is formed by curing a silsesquioxane compound having a long-chain spacer between Si atoms and glycidyloxy groups, the hard coat film tends to curl more due to curing shrinkage.

On the other hand, a silsesquioxane compound having both the structure represented by the general formula (5) and the structure represented by the general formula (6) and having both structures in a specific ratio is cured. By forming a hard coat layer on the surface, both high surface hardness and flex resistance can be achieved, and the occurrence of curling tends to be suppressed.

By providing the hard coat film with a fluorine-based coating layer as the top coat layer 5 on the hard coat layer 3, the hard coat film tends to have improved antifouling properties and scratch resistance. The hard coat film including the top coat layer 5 preferably has a water contact angle of 100° or more on the surface (top coat layer 5). The water contact angle is more preferably 105° or more, more preferably 110° or more. A high water contact angle means high water repellency, and is also excellent in resistance to dirt such as finger oil (stain resistance).

The hard coat film has a water contact angle of 100° or more with a small change in water contact angle even after a scratch resistance test (steel wool test) and an abrasion resistance test (eraser test). is preferred. As described above, the fluorine-based top coat layer 5 formed of a predetermined material has high adhesion to the polysiloxane-based hard coat layer 3, and therefore has excellent scratch resistance and abrasion resistance. It is possible to maintain a high water contact angle even after the wear resistance test.

The total light transmittance of the hard coat film is preferably 80% or higher, more preferably 85% or higher, and even more preferably 88% or higher. The haze of the hard coat film is preferably 1.5% or less, more preferably 0.9% or less, still more preferably 0.7% or less, and particularly preferably 0.5% or less. The yellowness index (YI) of the hard coat film is preferably 5 or less, more preferably 4 or less, and particularly preferably 3 or less.

[Application of hard coat film]
The hard coat film may have various functional layers. Examples of functional layers include antireflection layers, antiglare layers, antistatic layers, transparent electrodes, and the like. A transparent adhesive layer may be attached to the surface of the resin film 1 on which the hard coat layer is not formed. Moreover, a transparent pressure-sensitive adhesive layer may be attached to the hard coat film.

The above hard coat film has high hardness, so it can be suitably used as a cover window material arranged on the outermost surface of the image display device. Since the hard coat film has excellent bending resistance, it can be suitably used as a cover window for a foldable display (foldable display). Applicable.

The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to the following examples.

[Preparation of polyimide film]
As diamines, 2,2′-bis(trifluoromethyl)benzidine (TFMB) and 3,3′-diaminodiphenylsulfone (3,3′-DDS) were dissolved in dimethylformamide (DMF) at a molar ratio of 90:10. and, as a tetracarboxylic dianhydride, bis(1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylic acid)-(2,2',3,3',5,5'-hexamethyl [ 1,1′-biphenyl]-4,4′-diyl)ester (TAHMBP), 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) and 4,4′-oxydiphthalic dianhydride ( ODPA) was added at a molar ratio of 50:30:20 and stirred for 12 hours under a nitrogen atmosphere to obtain a polyamic acid solution with a solid concentration of 18%.

Pyridine and acetic anhydride were added to this polyamic acid solution, and imidization was performed by stirring at 80°C for 4 hours. A mixture of 2-propyl alcohol (IPA) and DMF was added dropwise to this solution to precipitate a polyimide resin, followed by suction filtration, washing and vacuum drying to obtain a polyimide resin.

100 parts by weight of the above polyimide, 2 parts by weight of ADEKA's "ADEKA STAB LA-31RG" as a UV absorber, and 0.8 parts by weight of ADEKA's "ADEKA STAB LA-F70", and a blueing agent by Arimoto Chemical Industry Co., Ltd. 0.006 part by weight of "Plast Blue 8590" was dissolved in methylene chloride to obtain a polyimide solution with a solid concentration of 10% by weight. Using a bar coater, the polyimide solution is applied to a non-alkali glass plate, 40 ° C. for 60 minutes, 80 ° C. for 30 minutes, 150 ° C. for 30 minutes, 170 ° C. for 30 minutes, 200 ° C. for 60 minutes, in an air atmosphere. The solvent was removed by heating to obtain a polyimide film having a thickness of 50 μm.

[Synthesis of silsesquioxane compound]
<Synthesis Example 1>
A reaction vessel equipped with a thermometer, a stirrer and a reflux condenser was charged with 43.1 g (175 mmol) of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (“KBM-303” manufactured by Shin-Etsu Chemical Co., Ltd.), 8- 23.0 g (75 mmol) of glycidyloxyoctyltrimethoxysilane (“KBM-4803” manufactured by Shin-Etsu Chemical Co., Ltd.), propylene glycol monomethyl ether (15.8 g) and 5.6 g of methanol were charged and uniformly stirred. A solution prepared by dissolving 11.9 mg (0.125 mmol) of magnesium chloride as a catalyst in 13.5 g (750 mmol) of water was slowly added dropwise to this mixture, and the mixture was stirred until uniform. After that, the temperature was raised to 80° C., and the polycondensation reaction was carried out for 6 hours while stirring. After completion of the reaction, the solvent and water were distilled off using a rotary evaporator to obtain a silsesquioxane compound 1.

The percentage of residual methoxy groups and the percentage of residual epoxy groups calculated from ¹ H-NMR spectrum measured using a 400 MHz-NMR manufactured by Bruker and using deuterated acetone as a solvent was 4.5% and 98%, respectively. The residual amount of magnesium chloride calculated based on the charged weight was 211 ppm.

<Synthesis Example 2>
30.9 g (125 mmol) of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (KBM-303) and 38.4 g (125 mmol) of 8-glycidyloxyoctyltrimethoxysilane (KBM-4803) ) in the same manner as in Synthesis Example 1, to obtain a silsesquioxane compound 2. Silsesquioxane compound 2 had a residual methoxy group ratio of 4.5%, an epoxy group residual ratio of 98%, and a residual magnesium chloride amount (calculated value) of 211 ppm.

<Synthesis Example 3>
368 g (1200 mmol) of 8-glycidyloxyoctyltrimethoxysilane (KBM-4803) and 76.9 g of methanol were charged into a reaction vessel equipped with a thermometer, stirrer and reflux condenser, and stirred uniformly. A solution prepared by dissolving 57 mg (0.6 mmol) of magnesium chloride in 64.7 g (3600 mmol) of water was slowly added dropwise to this mixture, and the mixture was stirred until uniform. After that, the temperature was raised to 80° C., and the polycondensation reaction was carried out for 6 hours while stirring. The polycondensation reaction was carried out for 6 hours while stirring. After completion of the reaction, the solvent and water were distilled off using a rotary evaporator to obtain a silsesquioxane compound 3. Silsesquioxane compound 3 had a residual methoxy group ratio of 4.5%, an epoxy group residual ratio of 95% or more, and a residual magnesium chloride amount (calculated value) of 198 ppm.

<Synthesis Example 4>
A reaction vessel equipped with a thermometer, stirrer and reflux condenser was charged with 61.6 g (250 mmol) of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (KBM-303) and 1-methoxy-2-propanol. 15.3 g was charged and uniformly stirred. A solution prepared by dissolving 36 mg (0.375 mmol) of magnesium chloride in 9.0 g (499 mmol) of water was slowly added dropwise to this mixed solution, and the mixture was stirred until uniform. After that, the temperature was raised to 80° C., and the polycondensation reaction was carried out for 6 hours while stirring. After completion of the reaction, the solvent and water were distilled off using a rotary evaporator to obtain a silsesquioxane compound 4. Silsesquioxane compound 4 had a residual methoxy group ratio of 4.6%, an epoxy group residual ratio of 95% or more, and a residual magnesium chloride amount (calculated value) of 800 ppm.

[Preparation of hard coat film]
<Example 1>
(Preparation of hard coat composition)
Silsesquioxane Compound 1 was diluted to 50% with propylene glycol monomethyl ether. With respect to 100 parts by weight of the silsesquioxane compound, 2 parts by weight of a 50% propylene carbonate solution of a photocationic polymerization initiator (manufactured by San-Apro "CPI-310FG") as a solid content, a silicone leveling agent (manufactured by BYK "BYK -300") was blended as a solid content to obtain a hard coat composition 1.

(Formation of hard coat layer)
One surface of a transparent polyimide film with a thickness of 50 μm was subjected to corona treatment at a discharge output of 600 W min/m ² , and then the above hard coat composition was applied using a bar coater so that the dry film thickness was 40 μm. It was applied and heated at 120° C. for 10 minutes. After that, using a high-pressure mercury lamp, the hard coat composition was cured by irradiating with ultraviolet rays so that the integrated amount of light at a wavelength of 365 nm was 600 mJ/cm ² .

(Formation of topcoat layer)
After corona treatment was performed on the surface of the hard coat layer at a discharge output of 3000 W min/m ² , a fluorine-based coating agent ("OPTOOL UD509" manufactured by Daikin) was applied with hydrofluoroether ("NOVEC7200" manufactured by 3M) at a concentration of 0.1. The solution diluted to % by weight was applied using a bar coater so that the dry film thickness was 10 nm, heated at 150 ° C. for 30 minutes to form a topcoat layer, and on one side of the transparent polyimide film, A hard coat film comprising a hard coat layer and a top coat layer was obtained.

<Example 2, Comparative Examples 1 and 2>
Silsesquioxane compounds 2 to 4 were used instead of silsesquioxane compound 1 in the preparation of the hard coat composition. Other than that, in the same manner as in Example 1, a hard coat film having a hard coat layer and a top coat layer on one side of the transparent polyimide film was obtained.

[Evaluation of Hard Coat Film]

<Flexibility (cylindrical mandrel test)>
According to JIS K5600-5-1: 1999, using a type 1 testing machine, a cylindrical mandrel test is performed on the hard coat film with the hard coat layer forming surface facing outward, and the bending diameter φ at which cracks occur in the hard coat layer is determined. rice field.

<Surface hardness (pencil hardness)>
According to JIS K5600-5-4:1999, the pencil hardness of the hard coat layer forming surface (top coat layer surface) was measured with a load of 750 g.

<Water contact angle>
The contact angle of pure water (droplet volume: 2 μL) on the surface on which the hard coat layer was formed was measured using a contact angle meter (“PCA-11” manufactured by Kyowa Interface Science Co., Ltd.).

<Scratch resistance test (steel wool test)>
Steel wool #0000 is set in an indenter with a diameter of 27 mm, and a reciprocating abrasion tester (Shinto Kagaku TYPE: 30S) is used. A scratch resistance test (steel wool test) was carried out on the surface on which the coat layer was formed. Water contact angles were measured after the scratch resistance test.

<Abrasion resistance test (eraser test)>
An eraser with a diameter of 6 mm manufactured by Minoan was set on the indenter, and an abrasion resistance test (eraser test) of the hard coat layer formed surface was conducted using a reciprocating abrasion tester under the same conditions as the above abrasion resistance test. After the abrasion resistance test, the water contact angle was measured.

<Total light transmittance and haze>
Measured by the method described in JIS K7361-1:1999 and JIS K7136:2000 using a haze meter "HZ-V3" manufactured by Suga Test Instruments.

<Yellowness index (YI)>
Measured by the method described in JIS K7373-:2006 with a color meter “SC-P” manufactured by Suga Test Instruments.

[Evaluation results]
Table 1 shows the compositions of the hard coat layers (molar ratios of the silane compounds used in the synthesis of the silsesquioxane compounds) in the hard coat films of Examples and Comparative Examples, and the evaluation results.

The hard coat films of Examples 1 and 2 had both high surface hardness and excellent bending resistance. In addition, the change in water contact angle in the scratch resistance test and abrasion resistance test was small, and the scratch resistance and abrasion resistance of the topcoat layer were also excellent.

The hard coat of Comparative Example 1, in which the silsesquioxane compound 3 obtained by condensing only the silane compound (KBM-4803) having 8 atoms in the main chain between the Si atom and the glycidyloxy group is used as the curable resin component. Although the film exhibited excellent bending resistance, the surface hardness was insufficient as compared with Examples 1 and 2. The hard coat film of Comparative Example 2, in which the silsesquioxane compound 4 obtained by condensing only the silane compound (KBM-303) having an alicyclic epoxy group is used as the curable resin component, exhibited high surface hardness, but was resistant to heat. Flexibility was insufficient.

From the above results, silsesquioxane obtained by cocondensation of a silane compound having an alicyclic epoxy group and a silane compound having a spacer having a specific chain length between the Si atom and the glycidyloxy group at a specific ratio. It can be seen that a hard coat film containing a compound as a curable resin component can achieve both high surface hardness and bending resistance when the hard coat is bent outward.

1

resin film

3, 4 hard coat layer 5

top coat layer

11, 12, 13, 14 hard coat film

Claims

A hard coat film comprising a hard coat layer on the first main surface of a resin film having a first main surface and a second main surface,
The hard coat layer contains a cured product of a silsesquioxane compound,
The silsesquioxane compound is
including a structure represented by general formula (5) and a structure represented by general formula (6),
The ratio of the structure represented by general formula (5) to the total amount of Si atoms is 0.2 to 0.95,
the ratio of the structure represented by general formula (5) to the total of the structure represented by general formula (5) and the structure represented by general formula (6) is greater than 0.4;
Hard coat film:
[Z—Si] (5)
[YR 4 -Si] (6)
In general formula (5), Z is an organic group containing an alicyclic epoxy group,
In general formula (6), R 4 is a divalent organic group having a main chain of 4 to 16 atoms, and Y is a glycidyloxy group.
In the silsesquioxane compound, the ratio of the structure represented by general formula (5) to the total of the structure represented by general formula (5) and the structure represented by general formula (6) is 0.95 or less. The hard coat film according to claim 1, wherein
The hard coat film according to claim 1, wherein the silsesquioxane compound has a ratio of the structure represented by general formula (6) to the total amount of Si atoms of 0.05 or more and less than 0.6.
The hard coat film according to any one of claims 1 to 3, comprising a top coat layer containing a fluorine compound on the hard coat layer.
The hard coat film according to any one of claims 1 to 3, comprising a second hard coat layer on the second main surface of the resin film.
The hard coat film according to any one of claims 1 to 3, wherein the resin film is a transparent polyimide film.
A method for producing a hard coat film according to any one of claims 1 to 3,
A method for producing a hard coat film, comprising coating a resin film with a hard coat composition containing the silsesquioxane compound and curing the resin film by irradiating it with an active energy ray to form a hard coat layer.
After forming the hard coat layer, a composition containing a compound having an alkoxysilyl group and a perfluoroalkyl group in the molecule is applied onto the hard coat layer, and the compound is condensed to form a top coat layer. The method for producing a hard coat film according to claim 7.
A display comprising an image display panel and the hard coat film according to any one of claims 1 to 3.