CN112041707A - Optical film, optical laminate, and flexible image display device - Google Patents

Abstract

The purpose of the present invention is to provide an optical film having excellent visibility when suitably used as an optical film in an image display device. Which is an optical film comprising at least one selected from the group consisting of polyimide, polyamide, and polyamideimide, and satisfies formula (1): 1.1. ltoreq. transmission b-reflection (SCE) b. ltoreq. 15 … … (1) [ formula (1), transmission b represents light transmitted from the optical film b in a system denoted by la. abb. and reflection (SCE) b represents light reflected from the optical film b in a system denoted by la. abb. determined as SCE ].

Description

Optical film, optical laminate, and flexible image display device

Technical Field

The present invention relates to an optical film including at least one selected from the group consisting of polyimide, polyamide, and polyamideimide.

Background

In recent years, an optical film containing a polyimide resin has been used as a functional film for providing a function to an image display device such as a television, a personal computer, a smart phone, a tablet computer, and electronic paper. Since a user of such an image display apparatus visually recognizes a displayed image directly through an optical film used in the display apparatus, the optical film is required to have very high visibility. For example, patent document 1 describes an optical film containing a polyimide resin and silica particles.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2009-215412

Disclosure of Invention

Problems to be solved by the invention

However, according to the study of the inventors of the present application, it has been found that sufficient visibility may not be obtained even when such an optical film containing a polyimide-based resin is applied to an image display device.

Accordingly, an object of the present invention is to provide an optical film having excellent visibility, and an optical laminate and a flexible image display device each including the optical film.

Means for solving the problems

As a result of intensive studies to solve the above problems, the inventors of the present application have found that the above problems can be solved by adjusting transmission b-reflection (SCE) b to a predetermined range in an optical film containing at least one selected from the group consisting of polyimide, polyamide, and polyamideimide, and have completed the present invention. Namely, the present invention includes the following modes.

[1] An optical film comprising at least one selected from the group consisting of polyimide, polyamide, and polyamideimide, and satisfying formula (1):

1.1. ltoreq. transmission b x-reflection (SCE) b x 15 … … (1)

In formula (1), transmission b denotes light transmitted through the optical film in the L × a × b color system, and reflection (SCE) b denotes light reflected by the optical film in the L × a b color system, which is determined by SCE.

[2] The optical film according to [1], further satisfying formula (2):

transmission b reflection (SCI) b ≦ 4.5 … … (2)

[ in formula (2), transmission b denotes light transmitted through the optical film in L a b color system, and reflection (SCI) b denotes light reflected by the optical film in L a b color system, which is determined in SCI.

[3] The optical film according to [1] or [2], which has a haze of 1% or less and a total light transmittance Tt of 85% or more.

[4] The optical film according to any one of [1] to [3], further comprising silica particles.

[5] The optical film according to [4], wherein the silica particles are silica particles obtained by solvent substitution of a water-soluble alcohol-dispersed silica sol.

[6] The optical film according to any one of [1] to [5], further comprising an ultraviolet absorber.

[7] The optical film according to any one of [1] to [6], further comprising silica particles,

the three-dimensional distance Ra determined by the hansen lyosphere method satisfies formula (3):

Ra≤8.0……(3)

[ in formula (3), Ra represents a three-dimensional distance between the silica particles and at least one selected from the group consisting of the polyimide, the polyamide, and the polyamideimide in a solubility parameter space ].

[8] An optical laminate comprising: [1] the optical film according to any one of [1] to [7 ]; and a hard coat layer on at least one side of the optical film.

[9] A flexible image display device comprising the optical laminate according to [8 ].

[10] The flexible image display device according to [9], further comprising a polarizing plate.

[11] The flexible image display device according to [9] or [10], further comprising a touch sensor.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, an optical film having excellent visibility when used as an optical film in an image display device can be provided. In addition, according to the present invention, an optical laminate and a flexible image display device including an optical film having excellent visibility can be provided.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail. The scope of the present invention is not limited to the embodiments described herein, and various modifications can be made without departing from the scope of the present invention.

< optical film >

The optical film of the present invention is an optical film comprising at least one selected from the group consisting of polyimide, polyamide, and polyamideimide, and satisfies formula (1):

1.1. ltoreq. transmission b x-reflection (SCE) b x 15 … … (1)

In formula (1), transmission b represents light transmitted through the optical film in a system of L × a × b color, and reflection (SCE) b represents light reflected by the optical film in a system of L × a × b color, which is determined by SCE.

[1. formula (1) ]

When the optical film satisfies formula (1), the optical film is excellent in visibility. From the viewpoint of further improving the visibility of the optical film, the formula (1) is preferably 10 or less, more preferably 8 or less, further preferably 6 or less, and particularly preferably 4 or less. From the viewpoint of further improving the clarity of the optical film, the numerical value (transmission b — reflection (SCE) b) of formula (1) is preferably 1.3 or more, more preferably 1.4 or more, further preferably 1.45 or more, and particularly preferably 1.5 or more.

(transmission b)

The transmission b of the optical film is the value b of light transmitted from the optical film in the L a b color system, and in the present specification, the value b is the value b in the CIE1976L a b color system with respect to the transmission light of incident light (white light) having a wavelength in the range of 380 to 780nm incident from the direction perpendicular to the plane of the optical film. The transmission b is preferably 0.3 or more, more preferably 1.6 or less, and further preferably 1.5 or less. These plural upper limit values and lower limit values may be arbitrarily combined. The transmission b of the optical film can be measured using an ultraviolet-visible near-infrared spectrophotometer, for example, by the method described in examples.

(reflection (SCE) b)

The reflection (SCE) b of the optical film is b of light reflected by the optical film in the L a b color system obtained as SCE (Specular Component exposed: excluding Specular reflection light), and in the present specification, is b of diffuse reflection light excluding Specular reflection light in the CIE197 1976L a b color system, out of reflection light of incident light in a range of wavelengths from 380 to 780nm, the incident light being incident from a direction inclined at a predetermined angle from a perpendicular direction to a plane of the optical film. The reflection (SCE) b is preferably-2.5 or more, preferably-2.4 or more, and more preferably-2.3 or more. The reflection (SCE) b is preferably-0.02 or less, preferably-0.05 or less, more preferably-0.07 or less, and particularly preferably-0.1 or less. These plural upper limit values and lower limit values may be arbitrarily combined. The reflection (SCE) b of the optical film can be measured using a spectrocolorimeter, for example, by the method described in examples.

Examples of the means for adjusting the value of formula (1) to fall within the predetermined value range include means for reducing the interaction between white light and components in the optical film. Examples of means for reducing the interaction include means for adjusting the film thickness of the optical film, the addition of additives (more specifically, silica particles, an ultraviolet absorber, a whitening agent, and the like), and the properties of the additives (more specifically, particle diameter, surface modification, content, and the like) to predetermined ranges. However, when the particle size, surface modification, and content of the silica particles are adjusted to be within predetermined ranges, the silica particles are less likely to aggregate in the optical film and can exist in the form of primary particles, and therefore the silica particles are easily dispersed uniformly in the optical film. Further, it is considered that the interaction with white light due to the uneven shape is reduced on the surface of the optical film, and the interaction between the aggregates and white light is reduced in the optical film, thereby contributing to visibility.

[2. formula (2) ]

The optical film of the present invention preferably satisfies formula (2):

transmission b reflection (SCI) b ≦ 4.5 … … (2)

[ in the formula (2), the transmission b is the same as the formula (1), and the reflection (SCI) b represents the light reflected by the optical film in the L a b color system, which is determined by SCI.

When the optical film satisfies the formula (2), the visibility of the optical film is further improved. From the viewpoint of further improving the visibility of the optical film, the numerical value (transmission b — reflection (SCI) b) of formula (2) is preferably 4.1 or less, more preferably 4.0 or less, and further preferably 3.9 or less.

(reflection (SCI) b)

Reflection (SCI) b of the optical film is b of light reflected by the optical film in the L a b color system, which is determined as SCI (Specular Component Included), and in this specification, is b of light incident from a direction inclined at a predetermined angle from a direction perpendicular to the plane of the optical film and having a wavelength in a range of 380 to 780nm in CIE1976L a b color system, with respect to reflection light of incident light (reflection light including Specular reflection light) in the L a b color system. The reflection (SCI) b is preferably-2.9 or more, more preferably-2.7 or more, and still more preferably-2.5 or more. The reflection (SCI) b is preferably-1.2 or less, more preferably-1.4 or less, and still more preferably-1.6 or less. These plural upper limit values and lower limit values may be arbitrarily combined. The reflectance (SCI) b of the optical film can be measured using a spectrocolorimeter, for example, by the method described in the examples. Examples of the means for adjusting the numerical value of the formula (2) to fall within the predetermined numerical value range include means for adjusting the numerical value of the formula (1) to fall within the predetermined numerical value range.

[3. haze ]

From the viewpoint of further improving the visibility of the optical film, the haze of the optical film of the present invention is preferably 1% or less, more preferably 0.8% or less, still more preferably 0.5% or less, and particularly preferably 0.3% or less. The haze of the optical film can be measured according to JIS K7136: the measurement can be carried out by the method described in examples 2000. Since the haze of the optical film indicates the degree of dispersibility of the additive in the optical film, the optical film has excellent visibility when the haze of the optical film is within the above range.

[4. Total light transmittance ]

The optical film of the present invention has a total light transmittance of preferably 85% or more, more preferably 87% or more, and further preferably 89% or more. The total light transmittance of the optical film can be measured according to JIS K7361-1: 1997, the measurement can be carried out by the method described in the examples. When the total light transmittance of the optical film is within the above numerical range, sufficient visibility can be ensured when the optical film is incorporated into an image display device. Further, when the total light transmittance of the optical film is within the above numerical range, a certain luminance can be easily ensured, and therefore, for example, the light emission intensity of a display element or the like can be suppressed, and the power consumption of the image display device can be reduced.

[5. Yellow Index (YI) ]

The yellow index of the optical film of the present invention is preferably 3.0 or less, more preferably 2.7 or less, and further preferably 2.5 or less. The yellow index of the optical film may be measured according to JIS K7373: the measurement 2006 can be performed, for example, by the method described in the examples.

[6. film thickness ]

The thickness of the optical film of the present invention is preferably 10 μm or more, more preferably 20 μm or more, and still more preferably 25 μm or more. The film thickness is preferably 120 μm or less, more preferably 100 μm or less, still more preferably 90 μm or less, and particularly preferably 85 μm or less. If the film thickness is 30 μm or more, it is advantageous from the viewpoint of protecting the inside when the optical film is formed into a device, and if the film thickness is 120 μm or less, it is advantageous from the viewpoint of folding endurance, cost, transparency, and the like. The film thickness of the optical film can be measured, for example, by the method described in examples.

[7. solubility parameter ]

The inventors of the present application have found that the composition in an optical film is aggregated due to dispersion failure, and the visibility in a wide angle direction is lowered, and that a Hansen Solubility Parameter (hereinafter abbreviated as HSP in some cases) is introduced as an index for evaluating the affinity between a solute (for example, an additive, more specifically, an ultraviolet absorber, silica particles, a whitening agent, and the like) and a medium (for example, a resin, more specifically, at least one resin selected from the group consisting of polyimide, polyamide, and polyamideimide) in a solid system such as an optical film. The present inventors have conducted extensive studies and, as a result, have derived the following formulae (3) to (5). That is, from the viewpoint of further improving the visibility in the wide angle direction (particularly, from the viewpoint of suppressing the occurrence of a defect of white tinge in black display), the optical film of the present invention preferably satisfies formula (3) related to HSP:

Ra≤8.0……(3)

[ in formula (3), Ra represents a three-dimensional distance between the solute and the mediator in the HSP space ].

From the viewpoint of further improving the visibility in the wide angle direction, the optical film of the present invention more preferably satisfies formula (4) or formula (5) related to HSP in addition to formula (3):

Δ_t≤2.0……(4)

[ in the formula (4), [ Delta ]_tA total of a dispersion term, a polar term and a hydrogen bond term representing HSP between the solute and the mediator_tDifference of difference]

Δ_p≤4.5……(5)

[ in the formula (5), [ Delta ]_pA term indicating the polarity of HSP between the solute and the mediator_pDifference of difference]。

From the viewpoint of further improving the visibility in the wide angle direction, the optical film of the present invention preferably satisfies all of formulas (3) to (5).

(7-1. calculation method of HSP value)

The HSP value was calculated by the Hansen Solubility Sphere method (Hansen Solubility Sphere method). The details thereof will be described below. The target composition (the solute and the medium) is dissolved or dispersed in a solvent having a known HSP value, and the solubility or dispersibility of the composition in a specific solvent is evaluated. The solubility and dispersibility were evaluated in the following manner: whether or not the target composition was dissolved in the solvent and whether or not the target composition was dispersed in the solvent were determined by visual observation. This evaluation was performed for a variety of solvents. As the kind of the solvent, it is preferable to use_tWidely differing solvents, more particularlyPreferably 10 or more, more preferably 15 or more, and still more preferably 18 or more. Next, the obtained evaluation results of solubility or dispersibility are plotted as a dispersion term containing HSP_dPolar term_pAnd hydrogen bonding term_hThree-dimensional space (HSP space). A ball (Hansen ball) is prepared in which a solvent for dissolving or dispersing a target composition is contained inside, a solvent for not dissolving or dispersing a target composition is contained outside, and the radius is minimized. The obtained center coordinates of the Hansen ball (c) ((m))_d，_p，_h) HSP as a subject component.

(7-2._t、Δ_t、Δ_pAnd Ra calculating method

(HSP value in the case of using resin as component 1 and silica as component 2, for example, calculated by the HSP value calculation method 7-1: (_d1，_p1，_h1: HSP number of component 1;_d2，_p2，_h2: HSP value of component 2).

For the sum of the dispersion term, polar term and hydrogen bond term of HSP_tAnd the difference Δ of the sum of the components 1 and 2_tThe calculation is performed using the equations (6) and (7), respectively. Obtained_tHSP's corresponding to Hildebrand (Hildebrand).

_t ²＝_d ²+_p ²+_h ²……(6)

Δ_t＝|_t2-_t1|……(7)

From the viewpoint of further improving the visibility in the wide angle direction, Δ_tPreferably 3.5 or less, more preferably 3.0 or less, further preferably 2.0 or less, further preferably 1.0 or less, and particularly preferably 0.5 or less.

Difference Δ in polarity terms of HSP between component 1 and component 2_pCalculated by using equation (8).

Δ_p＝|_p2-_p1|……(8)

From the viewpoint of further improving the visibility in the wide angle direction, Δ_pPreferably 4.5 or less, more preferably 3.5 or less, further preferably 3.0 or less, further preferably 2.0 or less, and particularly preferably 1.0 or less.

The three-dimensional distance Ra (>0) between component 1 and component 2 in the HSP space is calculated using equation (9).

Ra²＝4(_d2-_d1)²+(_p2-_p1)²+(_h2-_h1)²……(9)

The smaller the Ra value, the better the affinity between component 1 and component 2. From the viewpoint of further improving the visibility in the wide angle direction, the Ra value is preferably 8.0 or less, more preferably 7.0 or less, further preferably 6.0 or less, further preferably 5.5 or less, and particularly preferably 5.0 or less.

[8] polyimide, Polyamide, polyamideimide ]

The optical film of the present invention contains at least one resin selected from the group consisting of polyimide-based resins and polyamide-based resins. The polyimide-based resin refers to at least one polymer selected from the group consisting of a polymer containing a repeating structural unit containing an imide group (hereinafter, sometimes referred to as polyimide) and a polymer containing a repeating structural unit containing both an imide group and an amide group (hereinafter, sometimes referred to as polyamideimide). The polyamide resin represents a polymer containing a repeating structural unit containing an amide group.

The polyimide resin preferably has a repeating structural unit represented by formula (10). Here, G is a tetravalent organic group, and a is a divalent organic group. The polyimide resin may contain two or more kinds of repeating structural units represented by the formula (10) in which G and/or a are different.

[ chemical formula 1]

The polyimide resin may contain 1 or more selected from the group consisting of the repeating structural units represented by the formulae (11), (12) and (13) within a range that does not impair various physical properties of the optical film.

[ chemical formula 2]

In formulas (10) and (11), G and G¹Each independently a tetravalent organic group, preferably an organic group which may be substituted by a hydrocarbyl or fluoro-substituted hydrocarbyl group. As G and G¹Examples of the group include a group represented by formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28), or formula (29), and a tetravalent chain hydrocarbon group having 6 or less carbon atoms. Among them, the group represented by formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26) or formula (27) is preferable in terms of easily suppressing the yellowness index (YI value) of the optical film.

[ chemical formula 3]

In the formulae (20) to (29),

the symbol represents a chemical bond,

z represents a single bond, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-Ar-、-SO₂-、-CO-、-O-Ar-O-、-Ar-O-Ar-、-Ar-CH₂-Ar-、-Ar-C(CH₃)₂-Ar-or-Ar-SO₂-Ar-. Ar represents an arylene group having 6 to 20 carbon atoms which may be substituted with a fluorine atom, and specific examples thereof include a phenylene group.

In formula (12), G²Is a trivalent organic group, preferably an organic group which may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. As G²Examples of the hydrogen atom-substituted group include a group in which 1 of the chemical bonds of the group represented by formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) or formula (29) is replaced by a hydrogen atom, and a carbon having a valence of 3Chain hydrocarbon groups having 6 or less atoms.

In formula (13), G³Is a divalent organic group, preferably an organic group which may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. As G³Examples of the chain hydrocarbon group include a group in which 2 nonadjacent groups among the chemical bonds of the group represented by formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) or formula (29) are replaced with a hydrogen atom, and a chain hydrocarbon group having 6 or less carbon atoms.

A, A in formulae (10) to (13)¹、A²And A³Each independently is a divalent organic group, preferably an organic group which may be substituted with a hydrocarbyl group or a fluoro-substituted hydrocarbyl group. As A, A¹、A²And A³Examples thereof include a group represented by formula (30), formula (31), formula (32), formula (33), formula (34), formula (35), formula (36), formula (37) or formula (38); a group in which the above-mentioned groups are substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and a chain hydrocarbon group having 6 or less carbon atoms.

[ chemical formula 4]

In the formulae (30) to (38),

the symbol represents a chemical bond,

Z¹、Z²and Z³Each independently represents a single bond, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-or-CO-.

As 1 example, Z¹And Z³is-O-, and Z²is-CH₂-、-C(CH₃)₂-、-C(CF₃)₂-or-SO₂-。Z¹And Z²Bonding position with respect to each ring, and Z²And Z³The bonding position to each ring is preferably meta or para, respectively, to each ring.

From the viewpoint of improving the visibility, the polyimide-based resin is preferably a polyamide imide having at least a repeating structural unit represented by formula (10) and a repeating structural unit represented by formula (13). The polyamide resin preferably has at least a repeating structural unit represented by formula (13).

In one embodiment of the present invention, the polyimide resin is a condensation-type polymer obtained by reacting (polycondensing) a diamine with a tetracarboxylic acid compound (e.g., an acid chloride compound or a tetracarboxylic acid dianhydride analog), and optionally a dicarboxylic acid compound (e.g., an acid chloride compound analog), a tricarboxylic acid compound (e.g., an acid chloride compound or a tricarboxylic acid anhydride analog), and the like. The repeating structural unit represented by formula (10) or formula (11) is generally derived from a diamine and a tetracarboxylic acid compound. The repeating structural unit represented by formula (12) is generally derived from diamine and tricarboxylic acid compounds. The repeating structural unit represented by formula (13) is usually derived from a diamine and a dicarboxylic acid compound.

In one embodiment of the present invention, the polyamide resin is a condensation-type polymer obtained by reacting (polycondensing) a diamine with a dicarboxylic acid compound. That is, the repeating structural unit represented by formula (13) is generally derived from a diamine and a dicarboxylic acid compound.

Examples of the tetracarboxylic acid compound include aromatic tetracarboxylic acid compounds such as aromatic tetracarboxylic dianhydride; and aliphatic tetracarboxylic acid compounds such as aliphatic tetracarboxylic dianhydride. The tetracarboxylic acid compound may be used alone or in combination of 2 or more. The tetracarboxylic acid compound may be a tetracarboxylic acid compound analog such as an acid chloride compound, in addition to a dianhydride.

Specific examples of the aromatic tetracarboxylic acid dianhydride include 4,4 '-oxydiphthalic dianhydride (4, 4' -oxydiphthalic dianhydride), 3,3 ', 4, 4' -benzophenonetetracarboxylic acid dianhydride, 2 ', 3, 3' -benzophenonetetracarboxylic acid dianhydride, 3,3 ', 4, 4' -biphenyltetracarboxylic acid dianhydride, 2 ', 3, 3' -biphenyltetracarboxylic acid dianhydride, 3,3 ', 4, 4' -diphenylsulfonetetracarboxylic acid dianhydride, 2-bis (3, 4-dicarboxyphenyl) propane dianhydride, 2-bis (2, 3-dicarboxyphenyl) propane dianhydride, 2-bis (3, 4-dicarboxyphenoxyphenyl) propane dianhydride, 4,4 '- (hexafluoroisopropylidene) diphthalic dianhydride (4, 4' - (hexafluoroiodopropyliden) diphenic dianhydride, 6FDA), 1, 2-bis (2, 3-dicarboxyphenyl) ethane dianhydride, 1-bis (2, 3-dicarboxyphenyl) ethane dianhydride, 1, 2-bis (3, 4-dicarboxyphenyl) ethane dianhydride, 1-bis (3, 4-dicarboxyphenyl) ethane dianhydride, bis (3, 4-dicarboxyphenyl) methane dianhydride, bis (2, 3-dicarboxyphenyl) methane dianhydride, and 4,4 '- (p-phenylenedioxy) diphthalic dianhydride and 4, 4' - (m-phenylenedioxy) diphthalic dianhydride. These may be used alone or in combination of 2 or more.

Examples of the aliphatic tetracarboxylic dianhydride include cyclic and acyclic aliphatic tetracarboxylic dianhydrides. The cyclic aliphatic tetracarboxylic dianhydride is a tetracarboxylic dianhydride having an alicyclic hydrocarbon structure, and specific examples thereof include cycloalkanetetracarboxylic dianhydrides such as 1,2,4, 5-cyclohexanetetracarboxylic dianhydride, 1,2,3, 4-cyclobutanetetracarboxylic dianhydride and 1,2,3, 4-cyclopentanetetracarboxylic dianhydride, bicyclo [2.2.2] oct-7-ene-2, 3,5, 6-tetracarboxylic dianhydride, dicyclohexyl-3, 3 ', 4, 4' -tetracarboxylic dianhydride and positional isomers thereof. These may be used alone or in combination of 2 or more. Specific examples of the acyclic aliphatic tetracarboxylic acid dianhydride include 1,2,3, 4-butanetetracarboxylic acid dianhydride, 1,2,3, 4-pentanetetracarboxylic acid dianhydride, and the like, and these can be used alone or in combination of 2 or more. In addition, cyclic aliphatic tetracarboxylic dianhydride and acyclic aliphatic tetracarboxylic dianhydride may be used in combination.

Among the tetracarboxylic dianhydrides, 1,2,4, 5-cyclohexane tetracarboxylic dianhydride, bicyclo [2.2.2] oct-7-ene-2, 3,5, 6-tetracarboxylic dianhydride, 4' - (hexafluoroisopropylidene) diphthalic dianhydride, and mixtures thereof are preferable from the viewpoint of high transparency and low coloring property. In addition, as the tetracarboxylic acid, an aqueous adduct of an anhydride of the above tetracarboxylic acid compound can be used.

Examples of the tricarboxylic acid compound include an aromatic tricarboxylic acid, an aliphatic tricarboxylic acid, and a chloride compound and an acid anhydride similar thereto, and 2 or more kinds thereof may be used in combination.

Specific examples thereof include 1,2, 4-benzenetricarboxylic acidAnhydride of (a); 2,3, 6-naphthalene tricarboxylic acid-2, 3-anhydride; phthalic anhydride and benzoic acid via single bond, -CH₂-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-or phenylene groups.

The dicarboxylic acid compound includes aromatic dicarboxylic acid, aliphatic dicarboxylic acid, and the like, and acid chloride compounds and acid anhydrides thereof, and 2 or more of these may be used in combination. Specific examples thereof include terephthaloyl chloride (TPC); isophthaloyl dichloride; naphthaloyl dichloride; 4, 4' -biphenylenedioyl dichloride; 3, 3' -biphenylene dicarboxylic acid dichloride; 4,4 '-oxybis (benzoyl chloride) (OBBC, 4, 4' -oxybis (benzoyl chloride)); a dicarboxylic acid compound of a chain hydrocarbon having 8 or less carbon atoms and 2 benzoic acids via a single bond, -CH₂-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-or phenylene groups.

Examples of the diamine include an aliphatic diamine, an aromatic diamine, and a mixture thereof. In the present embodiment, the "aromatic diamine" refers to a diamine in which an amino group is directly bonded to an aromatic ring, and a part of the structure of the diamine may include an aliphatic group or another substituent. The aromatic ring may be a monocyclic ring or a condensed ring, and examples thereof include a benzene ring, a naphthalene ring, an anthracene ring, and a fluorene ring, but are not limited thereto. Of these, the aromatic ring is preferably a benzene ring. The "aliphatic diamine" refers to a diamine in which an amino group is directly bonded to an aliphatic group, and a part of the structure of the diamine may contain an aromatic ring or other substituent.

Examples of the aliphatic diamine include acyclic aliphatic diamines such as 1, 6-hexamethylenediamine and cyclic aliphatic diamines such as 1, 3-bis (aminomethyl) cyclohexane, 1, 4-bis (aminomethyl) cyclohexane, norbornanediamine and 4, 4' -diaminodicyclohexylmethane. These may be used alone or in combination of 2 or more.

Examples of the aromatic diamine include aromatic diamines having 1 aromatic ring such as p-phenylenediamine, m-phenylenediamine, 2, 4-toluenediamine, m-xylylenediamine, p-xylylenediamine, 1, 5-diaminonaphthalene, and 2, 6-diaminonaphthalene; 4,4 ' -diaminodiphenylmethane, 4 ' -diaminodiphenylpropane, 4 ' -diaminodiphenyl ether, 3 ' -diaminodiphenyl ether, 4 ' -diaminodiphenyl sulfone, 3 ' -diaminodiphenyl sulfone, 1, 4-bis (4-aminophenoxy) benzene, 1, 3-bis (4-aminophenoxy) benzene, 4 ' -diaminodiphenyl sulfone, bis [4- (4-aminophenoxy) phenyl ] sulfone, bis [4- (3-aminophenoxy) phenyl ] sulfone, 2-bis [4- (4-aminophenoxy) phenyl ] propane, 2-bis [4- (3-aminophenoxy) phenyl ] propane, 2,4 ' -diaminodiphenyl sulfone, 3 ' -diaminodiphenyl sulfone, 1,4 ' -diaminodiphenyl sulfone, 1,3 ' -bis (4-aminophenoxy) phenyl ] sulfone, 2-bis (4- (3-aminophenoxy), Aromatic diamines having 2 or more aromatic rings, such as 2,2 '-dimethylbenzidine, 2' -bis (trifluoromethyl) benzidine (2,2 '-bis (trifluoromethyl) -4, 4' -diaminobiphenyl (TFMB)), 4 '-bis (4-aminophenoxy) biphenyl, 4' -diaminodiphenyl ether, 3,4 '-diaminodiphenyl ether, 4' -diaminodiphenylmethane, 9-bis (4-aminophenyl) fluorene, 9-bis (4-amino-3-methylphenyl) fluorene, 9-bis (4-amino-3-chlorophenyl) fluorene, and 9, 9-bis (4-amino-3-fluorophenyl) fluorene. These may be used alone or in combination of 2 or more.

Among the diamines, 1 or more selected from the group consisting of aromatic diamines having a biphenyl structure is preferably used from the viewpoint of high transparency and low coloring property. More preferably, 1 or more selected from the group consisting of 2,2 ' -dimethylbenzidine, 2 ' -bis (trifluoromethyl) benzidine, 4 ' -bis (4-aminophenoxy) biphenyl, and 4,4 ' -diaminodiphenyl ether is used, and still more preferably, 2 ' -bis (trifluoromethyl) benzidine is used.

The polyimide-based resin can be obtained by: the above-mentioned raw materials such as diamine, tetracarboxylic acid compound, tricarboxylic acid compound and dicarboxylic acid compound are mixed by a conventional method such as stirring, and the obtained intermediate is imidized in the presence of an imidization catalyst and, if necessary, a dehydrating agent. The polyamide resin can be obtained by: the above-mentioned diamine, dicarboxylic acid compound and other raw materials are mixed by a conventional method, for example, stirring.

As imidesThe imidization catalyst used in the formation step is not particularly limited, and examples thereof include aliphatic amines such as tripropylamine, dibutylpropylamine, and ethyldibutylamine; n-ethylpiperidine, N-propylpiperidine, N-butylpyrrolidine, N-butylpiperidine, and N-propylhexahydroazepino

Alicyclic amines (monocyclic); azabicyclo [2.2.1]Heptane, azabicyclo [3.2.1]Octane, azabicyclo [2.2.2]Octane, and azabicyclo [3.2.2]Alicyclic amines (polycyclic) such as nonane; and aromatic amines such as 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 2-ethylpyridine, 3-ethylpyridine, 4-ethylpyridine, 2, 4-dimethylpyridine, 2,4, 6-trimethylpyridine, 3, 4-cyclopentenopyridine, 5,6,7, 8-tetrahydroisoquinoline, and isoquinoline.

The dehydrating agent used in the imidization step is not particularly limited, and examples thereof include acetic anhydride, propionic anhydride, isobutyric anhydride, pivalic anhydride, butyric anhydride, and isovaleric anhydride.

In the mixing and imidizing step of the raw materials, the reaction temperature is not particularly limited, and is, for example, 15 to 350 ℃, preferably 20 to 100 ℃. The reaction time is also not particularly limited, and is, for example, about 10 minutes to 10 hours. If necessary, the reaction may be carried out in an inert atmosphere or under reduced pressure. The reaction may be carried out in a solvent, and examples of the solvent include solvents that can be used for the preparation of varnish. After the reaction, the polyimide-based resin or the polyamide-based resin is purified. Examples of the purification method include the following methods: a poor solvent is added to the reaction solution, a resin is precipitated by reprecipitation, and the precipitate is taken out by drying, and if necessary, the precipitate is washed with a solvent such as methanol and dried.

For example, the production method described in jp 2006-199945 a or 2008-163107 a can be referred to for the production of the polyimide resin. Further, as the polyimide resin, commercially available products can be used, and specific examples thereof include Neopulim (registered trademark) manufactured by Mitsubishi gas chemical corporation, KPI-MX300F manufactured by the Fumura industries, Ltd.

The weight average molecular weight of the polyimide-based resin or the polyamide-based resin is preferably 200,000 or more, more preferably 250,000 or more, further preferably 300,000 or more, preferably 600,000 or less, and more preferably 500,000 or less. The larger the weight average molecular weight of the polyimide-based resin or the polyamide-based resin is, the more easily the polyimide-based resin or the polyamide-based resin tends to exhibit high bending resistance in film formation. Therefore, the weight average molecular weight is preferably not less than the above-described lower limit from the viewpoint of improving the bending resistance of the optical film. On the other hand, as the weight average molecular weight of the polyimide-based resin or the polyamide-based resin is smaller, the viscosity of the varnish tends to be more easily reduced, and the processability tends to be more easily improved. Further, the stretchability of the polyimide-based resin or the polyamide-based resin tends to be easily improved. Therefore, the weight average molecular weight is preferably not more than the above upper limit from the viewpoint of processability and stretchability. In the present application, the weight average molecular weight can be determined by Gel Permeation Chromatography (GPC) measurement in terms of standard polystyrene, and can be calculated by the method described in examples, for example.

The imidization ratio of the polyimide resin is preferably 95 to 100%, more preferably 97 to 100%, still more preferably 98 to 100%, and particularly preferably 100%. The imidization ratio is preferably not less than the above-described lower limit from the viewpoint of the stability of the varnish and the mechanical properties of the optical film to be obtained. The imidization ratio can be determined by an IR method, an NMR method, or the like. From the above viewpoint, the imidization ratio of the polyimide resin contained in the varnish is preferably within the above range.

In a preferred embodiment of the present invention, the polyimide-based resin or the polyamide-based resin contained in the optical film of the present invention may contain a halogen atom such as a fluorine atom, which may be introduced through the above-mentioned fluorine-containing substituent or the like. When the polyimide-based resin or the polyamide-based resin contains a halogen atom, the elastic modulus of the optical film is easily increased, and the yellow index (YI value) is easily decreased. When the elastic modulus of the optical film is high, the generation of scratches, wrinkles, and the like in the film is easily suppressed, and when the yellow index of the optical film is low, the transparency of the film is easily improved. The halogen atom is preferably a fluorine atom. Examples of the fluorine-containing substituent which is preferable for the polyimide resin or the polyamide resin to contain a fluorine atom include a fluorine group and a trifluoromethyl group.

The content of the halogen atom in the polyimide-based resin or the polyamide-based resin is preferably 1 to 40% by mass, more preferably 5 to 40% by mass, and still more preferably 5 to 30% by mass, based on the mass of the polyimide-based resin or the polyamide-based resin. When the content of the halogen atom is 1% by mass or more, the elastic modulus at the time of forming a film is further increased, the water absorption is reduced, the yellow index (YI value) is further reduced, and the transparency is further improved. If the content of the halogen atom exceeds 40 mass%, synthesis may become difficult.

In one embodiment of the present invention, the content of the polyimide-based resin and/or the polyamide-based resin in the optical film is preferably 40% by mass or more, more preferably 50% by mass or more, and still more preferably 70% by mass or more, based on the total mass of the optical film. The content of the polyimide-based resin and/or the polyamide-based resin is preferably not less than the above-described lower limit from the viewpoint of easy improvement of the bending resistance. The content of the polyimide-based resin and/or the polyamide-based resin in the optical film is usually 100 mass% or less based on the total mass of the optical film.

[9. additive ]

The optical film of the present invention may further contain an additive. Examples of such additives include fillers (more specifically, silica particles and the like), ultraviolet absorbers, brighteners, silica dispersants, antioxidants, pH adjusters, and leveling agents.

(silica particles)

The optical film of the present invention may further contain silica particles as an additive. The content of the silica particles is preferably 1 mass% or more, more preferably 3 mass% or more, and further preferably 5 mass% or more, based on the total mass of the optical film. The content of the silica particles is preferably 60 mass% or less, more preferably 50 mass% or less, and still more preferably 45 mass% or less, based on the total mass of the optical film. The content of the silica particles may be selected from any of the upper limit and the lower limit, and may be combined with the upper limit. When the content of the silica particles is within the numerical range of the upper limit value and/or the lower limit value, the silica particles tend to be less likely to aggregate and to be uniformly dispersed in the state of primary particles in the optical film of the present invention, and therefore, the decrease in visibility of the optical film of the present invention can be suppressed.

The particle diameter of the silica particles is preferably 1nm or more, more preferably 3nm or more, further preferably 5nm or more, particularly preferably 8nm, preferably 30nm or less, more preferably 28nm or less, further preferably 25nm or less. The particle size of the silica particles can be obtained by selecting and combining any lower limit value and any upper limit value among these upper limit value and lower limit value. When the content of the silica particles is within the numerical range of the upper limit value and/or the lower limit value, the optical film of the present invention is less likely to interact with light of a specific wavelength in white light, and thus the decrease in visibility of the optical film of the present invention can be suppressed. In the present specification, the particle size of the silica particles means an average primary particle size. The particle diameter of the silica particles in the optical film can be measured by photographing using a Transmission Electron Microscope (TEM). The particle size of the silica particles before the optical film is produced (for example, before the addition to the varnish) can be measured by a laser diffraction particle size distribution meter. The method for measuring the particle diameter of the silica particles is described in detail in examples.

Examples of the form of the silica particles include silica sol in which silica particles are dispersed in an organic solvent or the like, and silica powder produced by a vapor phase method. Among these, silica sol is preferable from the viewpoint of handling properties.

The silica particles may be subjected to a surface treatment, and for example, may be silica particles obtained by solvent (more specifically, γ -butyrolactone or the like) substitution of a water-soluble alcohol-dispersed silica sol. The water-soluble alcohol has not more than 3 carbon atoms per 1 hydroxyl group in 1 molecule of the water-soluble alcohol, and examples thereof include methanol, ethanol, 1-propanol, and 2-propanol. Although it depends on the compatibility of the silica particles with the types of polyimide-based resin and polyamide-based resin, in general, when the silica particles are surface-treated, affinity with the polyimide-based resin and polyamide-based resin included in the optical film is improved, and dispersibility of the silica particles tends to be improved, so that a decrease in visibility of the present invention can be suppressed.

(ultraviolet absorber)

The optical film of the present invention may further contain an ultraviolet absorber. Examples thereof include triazine-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, benzoate-based ultraviolet absorbers, and cyanoacrylate-based ultraviolet absorbers. These may be used alone or in combination of two or more. Examples of preferable commercially available ultraviolet absorbers include Sumisorb (registered trademark) 340 manufactured by Sumika Chemtex (Co., Ltd.), (Adekastab (registered trademark) LA-31 manufactured by ADEKA (Co., Ltd.), and TINUVIN (registered trademark) 1577 manufactured by BASF JAPAN (Co., Ltd.)). The content of the ultraviolet absorber is preferably 1phr or more and 10phr or less, more preferably 3phr or more and 6phr or less, based on the mass of the optical film of the present invention.

(whitening agent)

The optical film of the present invention may further contain a whitening agent. As for the whitening agent, for example, in the case where an additive other than the whitening agent is added, the whitening agent may be added for the purpose of adjusting the color tone. Examples of the whitening agent include monoazo dyes, triarylmethane dyes, phthalocyanine dyes, and anthraquinone dyes. Among these, anthraquinone dyes are preferable. Examples of a preferable commercially available whitening agent include Macrolex (registered trademark) Violet B manufactured by Lanxess, Sumiplast (registered trademark) Violet B manufactured by Sumika Chemtex, and Diarsesin (registered trademark) Blue G manufactured by Mitsubishi chemical corporation. These may be used alone or in combination of two or more. The content of the whitening agent is preferably 5ppm or more and 40ppm or less based on the mass of the optical film of the present invention.

The use of the optical film of the present invention is not particularly limited, and the optical film can be used in various applications. The optical film of the present invention may be a single layer as described above, or may be a laminate, and the optical film of the present invention may be used as it is, or may be used in the form of a laminate with another film. The optical film of the present invention has excellent surface quality, and is therefore useful as an optical film in an image display device or the like.

The optical film of the present invention is useful as a front panel of an image display device, particularly a front panel (window film) of a flexible display. The flexible display includes, for example, a flexible functional layer and the polyimide film laminated on the flexible functional layer and functioning as a front panel. That is, the front panel of the flexible display is arranged on the viewing side on the flexible functional layer. The front panel has the function of protecting the flexible functional layer.

[10. method for producing optical film ]

The optical film of the present invention can be produced, for example, by a method including the following steps, but is not particularly limited:

(a) a step of preparing a liquid (hereinafter, sometimes referred to as a varnish) containing the resin and the filler (varnish preparation step);

(b) a step (coating step) of applying a varnish to a substrate to form a coating film; and

(c) and a step of drying the applied liquid (coating film) to form an optical film (optical film forming step).

In the varnish preparation step, the resin is dissolved in a solvent, and the filler and, if necessary, other additives are added thereto and stirred and mixed to prepare a varnish. When silica is used as the filler, a dispersion of silica sol containing silica may be substituted with a solvent capable of dissolving the resin, for example, a solvent used in the preparation of the varnish described below, and the silica sol thus obtained may be added to the resin.

The solvent that can be used in the preparation of the varnish is not particularly limited as long as the resin can be dissolved. Examples of the solvent include: amide solvents such as N, N-dimethylacetamide and N, N-dimethylformamide; lactone solvents such as γ -butyrolactone (GBL) and γ -valerolactone; sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide and sulfolane; carbonate solvents such as ethylene carbonate and propylene carbonate; and combinations thereof. Among these, an amide solvent or a lactone solvent is preferable. These solvents may be used alone or in combination of two or more. The varnish may contain water, an alcohol solvent, a ketone solvent, an acyclic ester solvent, an ether solvent, and the like. The solid content concentration of the varnish is preferably 1 to 25 mass%, more preferably 5 to 20 mass%.

In the coating step, a varnish is applied to a substrate by a known coating method to form a coating film. Examples of known coating methods include roll coating methods such as wire bar coating, reverse coating, and gravure coating, die coating, comma coating, lip coating, spin coating, screen coating, spray coating, dipping, spraying, and casting.

In the optical film forming step, the coating film is dried and peeled from the substrate, whereby an optical film can be formed. After the peeling, a drying step of drying the optical film may be further performed. The drying of the coating film can be carried out at a temperature of 50 to 350 ℃. If necessary, the coating film may be dried in an inert atmosphere or under reduced pressure.

Examples of the substrate include a metal-based substrate, a SUS plate, and a resin-based substrate, a PET film, a PEN film, another polyimide-based resin, a polyamide-based resin film, a cycloolefin-based polymer (COP) film, and an acrylic film. Among them, a PET film, a COP film, and the like are preferable from the viewpoint of excellent smoothness and heat resistance, and a PET film is more preferable from the viewpoint of adhesion to an optical film and cost.

< optical laminate >

The optical laminate of the present invention includes the optical film of the present invention and a hard coat layer (protective film) on at least one of the optical films. The optical stack may further have an adhesive layer. The optical laminate of the present invention may be configured, for example, by bonding the optical film of the present invention and the hard coat layer via an adhesive layer.

(hard coating)

The thickness of the hard coat layer is not particularly limited, and may be, for example, 2 to 100 μm. When the thickness of the hard coat layer is within the above range, sufficient scratch resistance can be secured, and the flex resistance is less likely to decrease, and the problem of curling due to curing shrinkage is less likely to occur.

The hard coat layer may be formed by curing a hard coat composition containing a reactive material capable of forming a crosslinked structure by irradiation with an active energy ray or application of thermal energy, and is preferably obtained by irradiation with an active energy ray. The active energy ray is defined as an energy ray that can decompose a compound that generates an active species to generate an active species, and examples thereof include visible light, ultraviolet light, infrared light, X-ray, α -ray, β -ray, γ -ray, and electron beam, and preferable examples thereof include ultraviolet light. The hard coat composition contains a polymer of at least one of a radical polymerizable compound and a cation polymerizable compound.

The radical polymerizable compound is a compound having a radical polymerizable group. The radical polymerizable group of the radical polymerizable compound may be a functional group capable of undergoing a radical polymerization reaction, and examples thereof include a group containing a carbon-carbon unsaturated double bond, specifically, a vinyl group and a (meth) acryloyl group. When the radical polymerizable compound has 2 or more radical polymerizable groups, the radical polymerizable groups may be the same or different. The number of radical polymerizable groups contained in 1 molecule of the radical polymerizable compound is preferably 2 or more in terms of increasing the hardness of the hard coat layer. The radical polymerizable compound preferably includes a compound having a (meth) acryloyl group in view of high reactivity, specifically, a compound called a multifunctional acrylate monomer having 2 to 6 (meth) acryloyl groups in 1 molecule, an oligomer called epoxy (meth) acrylate, urethane (meth) acrylate, and polyester (meth) acrylate having several (meth) acryloyl groups in a molecule and having a molecular weight of several hundred to several thousand, and preferably 1 or more selected from the group consisting of epoxy (meth) acrylate, urethane (meth) acrylate, and polyester (meth) acrylate.

The cationically polymerizable compound is a compound having a cationically polymerizable group such as an epoxy group, an oxetane group, or a vinyl ether group. The number of the cationically polymerizable groups contained in 1 molecule of the cationically polymerizable compound is preferably 2 or more, and more preferably 3 or more, from the viewpoint of improving the hardness of the hard coat layer.

Among the above cationically polymerizable compounds, preferred are compounds having at least 1 of an epoxy group and an oxetane group as a cationically polymerizable group. A cyclic ether group such as an epoxy group or an oxetane group is preferable in that shrinkage accompanying the polymerization reaction is small. Among cyclic ether groups, compounds having an epoxy group have the following advantages: it is easy to obtain compounds having various structures, to exert no adverse effect on the durability of the obtained hard coat layer, and to control the compatibility with the radical polymerizable compound. Among cyclic ether groups, an oxetanyl group has the following advantages over an epoxy group: the polymerization degree is easily increased, the formation speed of the network of the cationic polymerizable compound in the obtained hard coat layer is increased, and even in the region where the hard coat layer is mixed with the radical polymerizable compound, the unreacted monomer is not left in the film, and an independent network can be formed; and so on.

Examples of the cationically polymerizable compound having an epoxy group include polyglycidyl ethers of polyhydric alcohols having an alicyclic ring, and alicyclic epoxy resins obtained by epoxidizing compounds containing a cyclohexene ring or a cyclopentene ring with an appropriate oxidizing agent such as hydrogen peroxide or a peroxy acid; aliphatic epoxy resins such as polyglycidyl ethers of aliphatic polyols or alkylene oxide adducts thereof, polyglycidyl esters of aliphatic long-chain polybasic acids, homopolymers and copolymers of glycidyl (meth) acrylate; glycidyl ethers produced by the reaction of bisphenols such as bisphenol a, bisphenol F and hydrogenated bisphenol a, or derivatives thereof such as alkylene oxide adducts and caprolactone adducts with epichlorohydrin, and glycidyl ether type epoxy resins derived from bisphenols such as Novolac epoxy resins.

The above hard coating composition may further comprise a polymerization initiator. Examples of the polymerization initiator include a radical polymerization initiator, a cationic polymerization initiator, a radical and cationic polymerization initiator, and they can be appropriately selected and used. These polymerization initiators are decomposed by at least one of irradiation with active energy rays and heating to generate radicals or cations, and are subjected to radical polymerization and cationic polymerization.

The radical polymerization initiator may be one that can release a substance that initiates radical polymerization by at least one of irradiation with active energy rays and heating. Examples of the thermal radical polymerization initiator include organic peroxides such as hydrogen peroxide and perbenzoic acid, and azo compounds such as azobisisobutyronitrile.

The active energy ray radical polymerization initiator includes a Type1 radical polymerization initiator which generates radicals by decomposition of molecules and a Type2 radical polymerization initiator which generates radicals by a hydrogen abstraction-Type reaction in the coexistence of a tertiary amine, and these may be used alone or in combination.

The cationic polymerization initiator may be one which can release a substance for initiating cationic polymerization by at least one of irradiation with active energy rays and heating. As the cationic polymerization initiator, aromatic iodonium salts, aromatic sulfonium salts, cyclopentadienyl iron (II) complexes, and the like can be used. For them, cationic polymerization can be initiated by either or both of irradiation with active energy rays or heating, depending on the structural difference.

The polymerization initiator is preferably contained in an amount of 0.1 to 10% by mass based on 100% by mass of the entire hard coat composition. When the content of the polymerization initiator is within the above range, the curing can be sufficiently advanced, the mechanical properties and the adhesion force of the finally obtained coating film can be in a favorable range, and poor adhesion, a cracking phenomenon, and a curling phenomenon due to curing shrinkage tend to be less likely to occur.

The hard coating composition may further include one or more selected from the group consisting of a solvent and an additive.

The solvent is a solvent capable of dissolving or dispersing the polymerizable compound and the polymerization initiator, and may be used in a range not interfering with the effects of the present invention, as long as it is known as a solvent for a hard coat composition in the art.

The above additives may further contain inorganic particles, leveling agents, stabilizers, surfactants, antistatic agents, lubricants, antifouling agents, and the like.

The optical laminate of the present invention can be used, for example, in a flexible image display device, and among them, can be suitably used in a foldable display device or a rollable display device.

< Flexible image display device >

The flexible image display device of the present invention includes the optical laminate of the present invention. For example, a flexible image display device is formed of an optical laminate (laminate for flexible image display device) and an organic EL display panel, and the laminate for flexible image display device is disposed on the viewing side of the organic EL display panel and is configured to be bendable. The laminate for a flexible image display device may further include a window, a polarizing plate, and a touch sensor, and the order of lamination is arbitrary, and it is preferable that the window, the polarizing plate, the touch sensor, or the window, the touch sensor, and the polarizing plate are laminated in this order from the viewing side. The presence of the polarizing plate on the viewing side of the touch sensor is preferable because the pattern of the touch sensor is less likely to be observed and the visibility of the display image is good. The members may be laminated using an adhesive, or the like. Further, the light-shielding film may include a light-shielding pattern formed on at least one surface of any one of the window, the polarizing plate, and the touch sensor. The polarizing plate may be a circular polarizing plate.

(Window)

The window is disposed on the viewing side of the flexible image display device, and plays a role of protecting other components from external impact or environmental changes such as temperature and humidity. Conventionally, glass has been used as such a protective layer, but a window in a flexible image display device has a flexible characteristic rather than being rigid and hard as glass. The window is formed of a flexible transparent substrate, and may have a hard coat layer on at least one surface thereof. The window optionally contains a hard coat layer having the same meaning as the hard coat layer of the optical laminate described above.

(polarizing plate)

The circularly polarizing plate is a functional layer having a function of transmitting only a right-handed or left-handed circularly polarized light component by laminating a λ/4 phase difference plate on a linearly polarizing plate. For example, can be used for: the external light is converted into right-handed circularly polarized light, the external light which is reflected by the organic EL panel and becomes left-handed circularly polarized light is blocked, only the light-emitting component of the organic EL is transmitted, and therefore the influence of reflected light is inhibited, and the image can be easily viewed. In order to achieve the circularly polarized light function, the absorption axis of the linear polarizer and the slow axis of the λ/4 phase difference plate need to be 45 ° in theory, but in practical applications, 45 ± 10 °. The linear polarizing plate and the λ/4 phase difference plate do not necessarily have to be stacked adjacent to each other, and the relationship between the absorption axis and the slow axis may satisfy the above range. It is preferable to achieve completely circularly polarized light at all wavelengths, but this is not necessarily the case in practical applications, and therefore, the circularly polarizing plate in the present invention also includes an elliptically polarizing plate. It is also preferable to further laminate a λ/4 retardation film on the viewing side of the linear polarizing plate to convert the emitted light into circularly polarized light, thereby improving visibility in a state where the polarized sunglasses are worn.

The linear polarizing plate is a functional layer having the following functions: light vibrating in the direction of the transmission axis is passed through, and polarized light of a vibration component perpendicular to the light is blocked. The linear polarizing plate may be a single linear polarizer or a structure including a linear polarizer and a protective film attached to at least one surface of the linear polarizer. The thickness of the linearly polarizing plate may be 200 μm or less, and preferably 0.5 to 100 μm. When the thickness is within the above range, the flexibility tends not to be easily lowered.

The linear polarizer may be a film type polarizer manufactured by dyeing and stretching a polyvinyl alcohol (PVA) film. The polarizing performance can be exhibited by adsorbing a dichroic dye such as iodine to a PVA film that has been stretched to be oriented, or by stretching the PVA film in a state of being adsorbed to the dichroic dye to orient the dichroic dye. The film-type polarizer may be produced by steps such as swelling, crosslinking with boric acid, washing with an aqueous solution, and drying. The stretching and dyeing step may be performed as a PVA film alone or in a state of being laminated with another film such as polyethylene terephthalate. The thickness of the PVA film to be used is preferably 10 to 100 μm, and the stretch ratio is preferably 2 to 10 times.

In addition, as another example of the polarizer, a liquid crystal coating type polarizer formed by coating a liquid crystal polarizing composition may be used. The liquid crystal polarizing composition may include a liquid crystal compound and a dichroic dye compound. The liquid crystalline compound is preferably used because it has a property of exhibiting a liquid crystal state, and particularly, when it has a high-order alignment state such as smectic, it can exhibit high polarizing performance. The liquid crystalline compound preferably has a polymerizable functional group.

The dichroic dye may be a dye that exhibits dichroism by being aligned with the liquid crystal compound, and may have liquid crystallinity or a polymerizable functional group. Any of the compounds in the liquid crystal polarizing composition has a polymerizable functional group.

The liquid crystal polarizing composition may further include an initiator, a solvent, a dispersant, a leveling agent, a stabilizer, a surfactant, a crosslinking agent, a silane coupling agent, and the like.

The circular polarizing plate may be a liquid crystal polarizing layer. The liquid crystal polarizing layer is manufactured by applying a liquid crystal polarizing composition on an alignment film to form a liquid crystal polarizing layer.

The liquid crystal polarizing layer can be formed to a thinner thickness than the film type polarizer. The thickness of the liquid crystal polarizing layer may be preferably 0.5 to 10 μm, and more preferably 1 to 5 μm.

The above-described alignment film can be produced, for example, by: the alignment film-forming composition is applied to a substrate, and alignment properties are imparted by rubbing, polarized light irradiation, or the like. The above-mentioned alignment film forming composition may contain a solvent, a crosslinking agent, an initiator, a dispersant, a leveling agent, a silane coupling agent, and the like in addition to the alignment agent. Examples of the orientation agent include polyvinyl alcohols, polyacrylates, polyamide acids, and polyimides. In the case of applying photo-alignment, an alignment agent containing a cinnamate group (cinnamate group) is preferably used. The weight average molecular weight of the polymer that can be used as the orientation agent may be about 10,000 to 1,000,000. The thickness of the alignment film is preferably 5 to 10,000nm, more preferably 10 to 500nm, from the viewpoint of alignment regulating force. The liquid crystal polarizing layer may be laminated by being peeled off from the substrate and then transferred, or the substrate may be directly laminated. The substrate preferably functions as a protective film, a retardation plate, or a transparent substrate for a window.

The protective film may be a transparent polymer film, and a material and an additive that can be used for the transparent base material may be used. Cellulose-based films, olefin-based films, acrylic films, and polyester films are preferable. The protective film may be a coating type protective film obtained by coating and curing a cationically curable composition such as an epoxy resin or a radically curable composition such as an acrylate. If necessary, a plasticizer, an ultraviolet absorber, an infrared absorber, a pigment, a colorant such as a dye, a fluorescent brightener, a dispersant, a heat stabilizer, a light stabilizer, an antistatic agent, an antioxidant, a lubricant, a solvent, or the like may be included. The thickness of the protective film may be 200 μm or less, preferably 1 to 100 μm. When the thickness of the protective film is within the above range, the flexibility of the protective film is less likely to decrease. The protective film may also function as a transparent substrate for the window.

The λ/4 phase difference plate is a film that imparts a phase difference of λ/4 in a direction (in-plane direction of the film) orthogonal to the traveling direction of incident light. The λ/4 retardation plate may be a stretched retardation plate produced by stretching a polymer film such as a cellulose film, an olefin film, or a polycarbonate film. If necessary, a phase difference adjusting agent, a plasticizer, an ultraviolet absorber, an infrared absorber, a pigment, a colorant such as a dye, a fluorescent brightener, a dispersant, a heat stabilizer, a light stabilizer, an antistatic agent, an antioxidant, a lubricant, a solvent, and the like may be included. The thickness of the stretched retardation film may be 200 μm or less, preferably 1 to 100 μm. When the thickness is within the above range, the flexibility of the film tends not to be easily lowered.

Further, another example of the λ/4 retardation plate may be a liquid crystal coating type retardation plate formed by coating a liquid crystal composition. The liquid crystal composition contains a liquid crystalline compound having a property of exhibiting a liquid crystal state such as a nematic state, a cholesteric state, or a smectic state. Any compound including a liquid crystalline compound in the liquid crystal composition has a polymerizable functional group. The liquid crystal coating type retardation plate may further contain an initiator, a solvent, a dispersant, a leveling agent, a stabilizer, a surfactant, a crosslinking agent, a silane coupling agent, and the like. The liquid crystal coating type retardation plate can be produced by coating a liquid crystal composition on an alignment film and curing the coating to form a liquid crystal retardation layer, as described in the liquid crystal polarizing layer. The liquid crystal coating type retardation plate can be formed to a smaller thickness than the stretching type retardation plate. The thickness of the liquid crystal polarizing layer may be usually 0.5 to 10 μm, preferably 1 to 5 μm. The liquid crystal coated retardation film may be laminated by being peeled from a substrate and then transferred, or the substrate may be directly laminated. The substrate preferably functions as a protective film, a retardation plate, or a transparent substrate for a window.

In general, the birefringence is large as the wavelength is shorter, and the birefringence is small as the wavelength is longer. In this case, since it is not possible to achieve a retardation of λ/4 in all visible light regions, it is often designed so that an in-plane retardation of λ/4 is 100 to 180nm, preferably 130 to 150nm, in the vicinity of 560nm, which is high in visibility. The use of an inverse dispersion λ/4 phase difference plate using a material having a birefringence wavelength dispersion characteristic opposite to that of the usual one is preferable because it can improve visibility. As such a material, the material described in japanese patent application laid-open No. 2007-232873 and the like is preferably used also in the case of a stretched phase difference plate, and the material described in japanese patent application laid-open No. 2010-30979 is preferably used also in the case of a liquid crystal coated phase difference plate.

As another method, a technique of obtaining a wide-band λ/4 phase difference plate by combining with a λ/2 phase difference plate is also known (japanese patent application laid-open No. h 10-90521). The λ/2 phase difference plate can be manufactured by the same material method as the λ/4 phase difference plate. The combination of the stretching type retardation plate and the liquid crystal coating type retardation plate is arbitrary, and the use of the liquid crystal coating type retardation plate is preferable because the thickness can be reduced.

For the circularly polarizing plate, a method of laminating a positive C plate is also known in order to improve visibility in an oblique direction (japanese patent application laid-open No. 2014-224837). The positive C plate may be a liquid crystal coated retardation plate or a stretched retardation plate. The phase difference in the thickness direction is-200 to-20 nm, preferably-140 to-40 nm.

(method for manufacturing circular polarizing plate)

An example of a method for manufacturing a circularly polarizing plate will be described. In the case of manufacturing a circular polarizing plate having a polarizing layer/a retardation layer in this order, first, the polarizing layer and the retardation layer are separately formed. For example, an alignment layer, a polarizer, and a protective layer are sequentially stacked on a protective film as a base material to form a polarizing layer. Further, a λ/4 retardation plate and a positive C plate were bonded to each other with an adhesive to form a retardation layer.

Then, the formed polarizing layer and retardation layer were bonded to each other with an adhesive to produce a circularly polarizing plate. In the lamination of the polarizing layer and the retardation layer, the polarizing layer and the retardation layer are laminated so that the absorption axis of the polarizing layer is substantially 45 ° with respect to the slow axis (optical axis) of the retardation layer. In this manner, a circular polarizing plate in which an adhesive layer/a polarizing layer (protective film/alignment layer/polarizer/protective layer)/an adhesive layer/a retardation layer (λ/4 retardation plate/positive C plate) are sequentially stacked can be manufactured.

The laminate having a circularly polarizing plate (hereinafter, also referred to as an optical laminate) of the present invention includes the optical film of the present invention.

(formula (39))

The optical laminate having a circularly polarizing plate of the present invention satisfies formula (39):

transmission b reflection (SCE) b ≧ 4.0 … … (39)

In formula (39), transmission b represents light transmitted from the optical stack in the L × a × b color system, and reflection (SCE) b represents light reflected from the optical stack in the L × a b color system, which is determined by SCE.

When the optical laminate having a circularly polarizing plate of the present invention satisfies formula (39), the transmittance of light from a light source is increased, the reflection of external light is decreased, and the reflected b hue is decreased and approaches a neutral hue, thereby providing excellent visibility.

From the viewpoint of further improving the visibility of the optical laminate having a circularly polarizing plate, the numerical value (transmission b — reflection (SCE) b) of formula (39) is preferably 4.2 or more, more preferably 4.5 or more, further preferably 5.0 or more, and particularly preferably 6.5 or more.

(formula (40))

From the viewpoint of further improving visibility, the optical laminate having a circularly polarizing plate of the present invention preferably satisfies formula (40):

transmission b reflection (SCI) b ≧ 4.5 … … (40)

[ in formula (40), transmission b denotes light transmitted from the optical stack in the L.a.b.color system, and reflection (SCI) b denotes light reflected from the optical stack in the L.a.b.color system, which is determined in SCI.

When the optical laminate having a circularly polarizing plate of the present invention satisfies formula (40), the reflection b hue becomes small and approaches a neutral hue, and thus, the optical laminate has excellent visibility.

From the viewpoint of further improving the visibility of the optical laminate having the circularly polarizing plate, the numerical value (transmission b — reflection (SCI) b) of formula (40) is preferably 4.7 or more, more preferably 5.5 or more, and further preferably 6.0 or more.

(transmission b)

The transmission b of the optical laminate having the circular polarizing plate is b of light transmitted from the optical laminate in the L a b color system, and in the present specification, the value b of light transmitted from incident light (white light) in a wavelength range of 380 to 780nm incident from a direction perpendicular to the plane of the optical laminate having the circular polarizing plate in the CIE1976L a b color system is referred to as b of light transmitted from the optical laminate having the circular polarizing plate. The transmission b is preferably 4.0 or more, more preferably 5.0 or more, and further preferably 6.0 or more. The transmission b of the optical laminate having a circularly polarizing plate can be measured using an ultraviolet-visible near-infrared spectrophotometer, for example, by the method described in examples.

(reflection (SCE) b)

The reflection (SCE) b of an optical laminate having a circular polarizing plate is b of light reflected by the optical laminate in the L a b color system obtained by the SCE method, and in the present specification, is a b value of CIE197 1976L a b color system excluding diffuse reflection light other than specular reflection light among reflection light of incident light in a range of wavelengths from 380 to 780nm which is incident from a direction inclined at a predetermined angle from a direction perpendicular to a plane of the optical laminate having the circular polarizing plate. The reflection (SCE) b is preferably 1.5 or less, preferably 1.0 or less, more preferably 0 or less, and particularly preferably-1.5 or less. The reflection (SCE) b of the optical laminate having a circularly polarizing plate can be measured using a spectrocolorimeter, for example, by the method described in examples.

(reflection (SCI) b)

The reflection (SCI) b of the optical laminate having the circular polarizing plate is b of light reflected by the optical laminate in the L a b color system, which is determined in the SCI system, and in the present specification, is a b value in the CIE197 1976L a b color system with respect to reflected light (including specular reflected light) of incident light in a range of wavelengths from 380 to 780nm, which is incident from a direction inclined at a predetermined angle from a direction perpendicular to the plane of the optical laminate having the circular polarizing plate. The reflection (SCI) b of the optical laminate having a circularly polarizing plate can be measured using a spectrocolorimeter, for example, by the method described in examples.

Examples of the means for adjusting the transmission b-reflection (SCE) b in formula (39) to fall within a predetermined numerical range include means for adjusting the transmission b-reflection (SCE) b of the optical film to fall within the numerical range of formula (1), and color adjustment by composition change of the window.

Examples of the means for adjusting the transmission b-reflection (SCI) b in the formula (40) to fall within a predetermined numerical range include means for adjusting the transmission b-reflection (SCI) b of the optical film to fall within the numerical range of the formula (2), and adjustment of the hue by changing the composition of the window.

(touch sensor)

The touch sensor may be used as an input mechanism. As the touch sensor, various types such as a resistive film type, a surface acoustic wave type, an infrared ray type, an electromagnetic induction type, and a capacitance type have been proposed, and any type may be used. Among them, the electrostatic capacitance system is preferable. The capacitive touch sensor may be divided into an active region and an inactive region located at a peripheral portion of the active region. The active region is a region corresponding to a region (display portion) on the display panel where a screen is displayed, and is a region where a user's touch is sensed, and the inactive region is a region corresponding to a region (non-display portion) on the display device where a screen is not displayed. The touch sensor may include: a substrate having flexible properties; a sensing pattern formed in an active region of the substrate; and each sensing line formed in the inactive region of the substrate and used for connecting the sensing pattern with an external driving circuit through a pad (pad) portion. As the substrate having the flexible property, the same material as the transparent substrate of the window can be used. The substrate of the touch sensor preferably has a toughness of 2,000 MPa% or more in terms of suppressing cracks in the touch sensor. The toughness may be more preferably 2,000 to 30,000 MPa%. Here, the toughness is defined as the area of the lower part of a Stress (MPa) -strain (%) curve (Stress-strain curve) obtained by a tensile test of a polymer material up to a failure point.

The sensing pattern may include a 1 st pattern formed along a 1 st direction and a 2 nd pattern formed along a 2 nd direction. The 1 st pattern and the 2 nd pattern are arranged in mutually different directions. The 1 st pattern and the 2 nd pattern are formed in the same layer, and in order to sense a touched position, the patterns must be electrically connected. The 1 st pattern is a form in which the unit patterns are connected to each other via a terminal, and the 2 nd pattern is a structure in which the unit patterns are separated from each other into islands, and therefore, in order to electrically connect the 2 nd pattern, a separate bridge electrode is required. The sensing pattern may use a known transparent electrode material. Examples thereof include Indium Tin Oxide (ITO), Indium Zinc Oxide (IZO), zinc oxide (ZnO), Indium Zinc Tin Oxide (IZTO), Indium Gallium Zinc Oxide (IGZO), Cadmium Tin Oxide (CTO), PEDOT (poly (3, 4-ethylenedioxythiophene)), Carbon Nanotube (CNT), graphene, and a metal wire, and these may be used alone or in combination of 2 or more. Preferably, ITO can be used. The metal usable for the wire is not particularly limited, and examples thereof include silver, gold, aluminum, copper, iron, nickel, titanium, selenium, chromium, and the like. These can be used alone or in combination of 2 or more.

The bridge electrode may be formed on the insulating layer with an insulating layer interposed therebetween on the sensing pattern, the bridge electrode may be formed on the substrate, and the insulating layer and the sensing pattern may be formed thereon. The bridge electrode may be formed of the same material as the sensing pattern, or may be formed of a metal such as molybdenum, silver, aluminum, copper, palladium, gold, platinum, zinc, tin, titanium, or an alloy of 2 or more of these metals. The 1 st pattern and the 2 nd pattern must be electrically insulated, and thus, an insulating layer is formed between the sensing pattern and the bridge electrode. The insulating layer may be formed only between the tab of the 1 st pattern and the bridge electrode, or may be formed in a structure of a layer covering the sensing pattern. In the latter case, the 2 nd pattern may be connected to the bridge electrode through a contact hole formed in the insulating layer. In the touch sensor, as means for appropriately compensating for a difference in transmittance between a pattern region where a pattern is formed and a non-pattern region where no pattern is formed (specifically, a difference in transmittance due to a difference in refractive index in these regions), an optical adjustment layer may be further included between the substrate and the electrode, and the optical adjustment layer may include an inorganic insulating substance or an organic insulating substance. The optical adjustment layer can be formed by applying a photocurable composition containing a photocurable organic binder and a solvent onto a substrate. The above-mentioned photocurable composition may further comprise inorganic particles. The refractive index of the optical adjustment layer can be increased by the inorganic particles.

The photocurable organic binder may include, for example, a copolymer of monomers such as an acrylate monomer, a styrene monomer, and a carboxylic acid monomer. The photocurable organic binder may be, for example, a copolymer containing repeating units different from each other, such as repeating units containing an epoxy group, repeating units containing an acrylate, repeating units containing a carboxylic acid, and the like.

The inorganic particles may include, for example, zirconium dioxide particles, titanium dioxide particles, aluminum oxide particles, and the like. The photocurable composition may further contain various additives such as a photopolymerization initiator, a polymerizable monomer, and a curing assistant.

(adhesive layer)

The layers (window, polarizing plate, touch sensor) forming the laminate for a flexible image display device and the film members (linear polarizing plate, λ/4 phase difference plate, etc.) constituting the layers may be formed by an adhesive. As the adhesive, a commonly used adhesive such as an aqueous adhesive, an organic solvent adhesive, a solvent-free adhesive, a solid adhesive, a solvent-volatile adhesive, a moisture-curable adhesive, a heat-curable adhesive, an anaerobic curable adhesive, an active energy ray-curable adhesive, a curing agent-mixed adhesive, a hot-melt adhesive, a pressure-sensitive adhesive (pressure-sensitive adhesive), and a remoistenable adhesive can be used. Among them, water-based solvent-volatile adhesives, active energy ray-curable adhesives, and adhesives are generally used. The thickness of the adhesive layer can be adjusted to 0.01 to 500 μm, preferably 0.1 to 300 μm, as appropriate depending on the required adhesive strength, and the thickness of the adhesive layer and the type of the adhesive used may be the same or different, depending on the number of adhesive layers present in the laminate for a flexible image display device.

The aqueous solvent-based volatile adhesive may be a polyvinyl alcohol polymer, a water-soluble polymer such as starch, or a water-dispersed polymer such as an ethylene-vinyl acetate emulsion or a styrene-butadiene emulsion. In addition to water and the above-mentioned main agent polymer, a crosslinking agent, a silane compound, an ionic compound, a crosslinking catalyst, an antioxidant, a dye, a pigment, an inorganic filler, an organic solvent, and the like may be blended. In the case of bonding with the aqueous solvent volatile adhesive, the aqueous solvent volatile adhesive may be injected between the layers to be bonded, and the layers to be bonded may be bonded and then dried to impart adhesiveness. The thickness of the adhesive layer when the aqueous solvent volatile adhesive is used may be 0.01 to 10 μm, preferably 0.1 to 1 μm. When the aqueous solvent-volatile adhesive is used for forming a plurality of layers, the thickness of each layer and the type of the adhesive may be the same or different.

The active energy ray-curable adhesive can be formed by curing an active energy ray-curable composition containing a reactive material capable of forming an adhesive layer by irradiation with active energy rays. The active energy ray-curable composition may contain at least 1 polymer selected from the group consisting of radical polymerizable compounds and cationic polymerizable compounds, which are similar to the hard coat composition. The radical polymerizable compound may be the same type of radical polymerizable compound as used in the hard coat composition, as used in the hard coat composition. As the radical polymerizable compound that can be used in the adhesive layer, a compound having an acryloyl group is preferable. In order to reduce the viscosity of the adhesive composition, a monofunctional compound is preferably contained.

The cationic polymerizable compound may be the same kind of cationic polymerizable compound as used in the hard coat composition, similarly to the hard coat composition. As the cationically polymerizable compound which can be used in the active energy ray-curable composition, an epoxy compound is particularly preferable. In order to reduce the viscosity as an adhesive composition, it is also preferable to include a monofunctional compound as a reactive diluent.

In the active energy ray composition, a polymerization initiator may be further contained. The polymerization initiator may be selected from a radical polymerization initiator, a cationic polymerization initiator, a radical and cationic polymerization initiator, and the like. These polymerization initiators are those which can be decomposed by at least one of irradiation with active energy rays and heating to generate radicals or cations, thereby allowing radical polymerization and cationic polymerization to proceed. The initiator described in the description of the hard coating composition, which can initiate at least either of radical polymerization or cationic polymerization by irradiation with active energy rays, may be used.

The active energy ray-curable composition may further contain an ion scavenger, an antioxidant, a chain transfer agent, an adhesion-imparting agent, a thermoplastic resin, a filler, a flow viscosity modifier, a plasticizer, an antifoaming agent, an additive, and a solvent. When the bonding is performed by the active energy ray-curable adhesive, the bonding may be performed by: the active energy ray-curable composition is applied to one or both of the adhesive layers and then bonded thereto, and the adhesive layer or both of the adhesive layers is irradiated with an active energy ray through the adhesive layer or both of the adhesive layers to be cured. The thickness of the adhesive layer when the active energy ray-curable adhesive is used may be 0.01 to 20 μm, preferably 0.1 to 10 μm. When the active energy ray-curable adhesive is used for forming a plurality of layers, the thickness of each layer and the type of the adhesive used may be the same or different.

The adhesive may be classified into an acrylic adhesive, a urethane adhesive, a rubber adhesive, a silicone adhesive, and the like according to the base polymer, and may be used. The binder may contain a crosslinking agent, a silane compound, an ionic compound, a crosslinking catalyst, an antioxidant, an adhesion promoter, a plasticizer, a dye, a pigment, an inorganic filler, and the like in addition to the main polymer. The pressure-sensitive adhesive layer can be formed by dissolving and dispersing the components constituting the pressure-sensitive adhesive in a solvent to obtain a pressure-sensitive adhesive composition, applying the pressure-sensitive adhesive composition to a substrate, and drying the applied pressure-sensitive adhesive composition. The adhesive layer may be formed directly or by transferring an adhesive layer separately formed on the substrate. A release film is also preferably used to cover the pressure-sensitive adhesive surface before bonding. The thickness of the adhesive layer when the adhesive is used may be 1 to 500. mu.m, preferably 2 to 300. mu.m. When the above-mentioned adhesive is used for forming a plurality of layers, the thickness of each layer and the kind of the adhesive used may be the same or different.

(light-shielding pattern)

The light shielding pattern may be applied as at least a part of a bezel (bezel) or a housing of the flexible image display device. The wiring disposed at the edge of the flexible image display device is hidden by the light-shielding pattern and is not easily viewed, thereby improving visibility of an image. The light-shielding pattern may be in the form of a single layer or a plurality of layers. The color of the light-shielding pattern is not particularly limited, and may have various colors such as black, white, metallic color, and the like. The light-shielding pattern may be formed of a pigment for color, and polymers such as acrylic resin, ester resin, epoxy resin, polyurethane, silicone, and the like. They may be used alone or in the form of a mixture of 2 or more. The light-shielding pattern can be formed by various methods such as printing, photolithography, and inkjet. The thickness of the light-shielding pattern is usually 1 to 100 μm, preferably 2 to 50 μm. Further, it is preferable to provide a shape such as an inclination in the thickness direction of the light-shielding pattern.

Examples

The present invention will be described in more detail below with reference to examples. Unless otherwise specified, "%" and "parts" in the examples mean mass% and parts by mass. First, the evaluation method will be explained.

< 1. measurement method >

(reflection of optical film (SCE) b, and reflection (SCI) b)

The optical films obtained in examples and comparative examples were cut into 50X 50mm size, and then bonded to black PET ("Kukkiri Mieru" manufactured by Bachuan corporation) to obtain a sample for reflection optical measurement.

The color of the obtained evaluation sample was measured by the SCE method (specular reflection removal) and the SCI method (including specular reflection) using a spectrophotometer ("CM-3700A" manufactured by Konica Minolta corporation). The measurement diameter was set as LAV: diameter 8mm, and measurement conditions were di: 8 °, de: the measurement field of view was 2 ° at 8 ° (diffused illumination and light reception in the 8 ° direction), and the light source used was D65 light source, and the UV condition was 100% Full. Here, the hue refers to a and b in CIE1976L a b color space. The reflection (SCE) a and the reflection (SCI) a of the optical film were also measured under the same conditions as described above.

(reflection (SCE) b and reflection (SCI) b of optical stack with circularly polarizing plate)

The measurement was performed in the same manner as the optical film measurement method except that the reflection (SCE) b and the reflection (SCI) b of the optical laminate having the circularly polarizing plate were changed from the optical film to the optical laminate having the circularly polarizing plate. In addition, the reflection (SCE) a and the reflection (SCI) a were also measured in the same manner.

(visual transmittance Y of laminate with circularly polarizing plate)

The visual transmittance Y is a physical property value indicating lightness of a color of an object in the XYZ color system. The visual transmittance Y of SCE system of SCI system was measured using a spectrophotometer ("CM-2600 d" manufactured by Konica Minolta).

(Transmission of optical film b)

The optical films obtained in examples and comparative examples were cut into a size of 50mm × 50mm, and transmitted light was measured using a spectrophotometer ("CM-3700A" manufactured by Konica Minolta). The measurement diameter was set as LAV: the diameter was 25.4mm, and the measurement field was set to 2 °. The measurement light source used was a D65 light source, and the UV condition was 100% Full. Here, the hue refers to a and b in CIE1976L a b color space.

(Transmission of optical laminate with circularly polarizing plate b.)

The measurement was performed in the same manner as the optical film measurement method except that the transmission b of the optical laminate having the circularly polarizing plate was changed from the optical film to the optical laminate having the circularly polarizing plate. In addition, the transmission a of the optical laminate having the circularly polarizing plate was also measured in the same manner.

(thickness of optical film and pressure-sensitive adhesive layer)

The thickness of the optical film at 10 or more positions was measured using a micrometer ("ID-C112 XBS" manufactured by Mitutoyo Co., Ltd.), and the average value thereof was calculated. The thickness of the pressure-sensitive adhesive layer was measured in the same manner, and the average value thereof was calculated.

(Total luminous transmittance and haze of optical film)

The total light transmittance of the optical film was measured according to JIS K7361-1: 1997. haze was measured according to JIS K7136: 2000, measured by using a fully automatic direct reading haze computer HGM-2DP manufactured by Suga Test Instruments. The optical films of examples and comparative examples were cut into 30mm × 30mm to prepare measurement samples.

(yellow index of optical film)

The Yellow Index (YI value) of the optical film was measured using an ultraviolet-visible near-infrared spectrophotometer ("V-670" manufactured by Nippon Denshoku Co., Ltd.). After the background measurement was performed in the absence of the sample, the optical films obtained in examples and comparative examples were placed on a sample holder, and transmittance measurement was performed with respect to light of 300 to 800nm to obtain a tristimulus value (X, Y, Z). From the tristimulus values obtained, the YI value was calculated based on the following formula based on ASTM D1925.

YI＝100×(1.2769X-1.0592Z)/Y

(particle diameter of silica particles)

The particle size of the silica particles was calculated from the measurement value of the specific surface area by the BET adsorption method in accordance with JIS Z8830. The specific surface area of the powder obtained by drying the silica sol at 300 ℃ was measured using a specific surface area measuring apparatus ("MONOSORB (registered trademark) MS-16" manufactured by Yuasa-ionics corporation).

(weight average molecular weight)

Gel Permeation Chromatography (GPC) measurement

(1) Pretreatment method

The sample was dissolved in gamma-butyrolactone (GBL) to prepare a 20 mass% solution, which was then diluted 100-fold with DMF eluent, filtered through a 0.45 μm membrane filter, and the filtrate was used as a measurement solution.

(2) Measurement conditions

A chromatographic column: TSKgel SuperAWM-H.times.2 + SuperAW 2500X 1(6.0mm I.D.. times.150 mm. times.3)

Eluent: DMF (10 mmol of lithium bromide added)

Flow rate: 0.6 mL/min

A detector: RI detector

Column temperature: 40 deg.C

Sample introduction amount: 20 μ L

Molecular weight standard: standard polystyrene

(imidization ratio)

The imidization rate is determined by¹H-NMR measurement was carried out in the following manner.

(1) Pretreatment method

Dissolving an optical film comprising a polyimide resin in deuterated dimethyl sulfoxide (DMSO-d)₆) A2 mass% solution was prepared as a measurement sample.

(2) Measurement conditions

A measuring device: 400MHz NMR device JNM-ECZ400S/L1 manufactured by JEOL

Standard substance: DMSO-d₆(2.5ppm)

Temperature of the sample: at room temperature

Cumulative number of times: 256 times

Relaxation time: 5 seconds

(3) Method for analyzing imidization rate

(imidization ratio of polyimide resin)

Obtained for a measurement sample containing a polyimide resin¹Int represents the integral value of a benzene proton A derived from a structure unchanged before and after imidization, among benzene protons observed in an H-NMR spectrum_A. Int represents the integral value of amide protons observed from the amic acid structure remaining in the polyimide resin_B. From these integrated values, the imidization ratio of the polyimide resin was determined based on the following formula.

Imidization ratio (%) < 100 × (1-. alpha.Xint)_B/Int_A)

In the above formula, α represents the ratio of the number of benzene protons a to 1 amide proton in the case of polyamic acid (imidization ratio of 0%).

(imidization ratio of Polyamide-imide resin)

In the field of polyamide-containing acidObtained by measuring a sample of an imine resin¹Int represents the integral value of benzene proton C having a structure unchanged before and after imidization and not affected by the structure derived from the amic acid structure remaining in the polyamideimide resin, among the benzene protons observed in the H-NMR spectrum_C. Int represents the integral value of benzene proton D derived from a structure which does not change before and after imidization and which is affected by the structure derived from the amic acid structure remaining in the polyamideimide resin_D. According to the obtained Int_CAnd Int_DThe β value is obtained by the following equation.

β＝Int_D/Int_C

Next, the β value of the above formula and the imidization ratio of the polyimide resin of the above formula were obtained for a plurality of polyamide-imide resins, and based on these results, the following correlation formula was obtained.

Imidization ratio (%) ═ kxbeta +100

In the above correlation, k is a constant.

Substituting β into the correlation equation gives the imidization ratio (%) of the polyamide-imide resin.

(calculation of HSP value of resin)

The solubility of the polyamideimide resin 1(PAI-1) in a solvent was evaluated. A mixed solution was prepared by charging 10mL of a solvent (ex: Polymer handbook, 4 th edition) having known solubility parameters as shown in Table 1 and 0.1g of polyamideimide resin 1 into a transparent container. The obtained mixture was subjected to ultrasonic treatment for a total of 6 hours. The appearance of the liquid mixture after the ultrasonic treatment was visually observed, and from the obtained observation results, the solubility of the polyamideimide resin 1 in the solvent was evaluated based on the following evaluation criteria. The evaluation results are shown in table 1. Similarly, the solubility in a solvent was evaluated in the same manner except that the types of the polyamideimide resin 1 and the resin in the polyamideimide resin 1-solvent system were changed for the polyamideimide resin 2(PAI-2) and the polyimide resin 1 (PI).

(evaluation criteria)

1: the appearance of the mixed solution was white turbid.

0: the appearance of the mixed solution is transparent.

[ Table 1]

Hansen beads were produced by using the hansen bead method described above based on the evaluation result of the solubility of the obtained resin in the solvent. The obtained central coordinates of the hansen beads were used as HSP values. The results are shown in Table 2.

[ Table 2]

(calculation of HSP value of silica)

The solvent was removed from the silica sol 1, and silica 1 as a solid component was taken out. The dispersibility of the silica 1 in a solvent was evaluated. A mixed solution was prepared by charging 10mL of a solvent (ex: Polymer handbook, 4 th edition) having known solubility parameters as shown in Table 3 and 0.1g of silica 1 into a transparent container. The obtained mixture was subjected to ultrasonic treatment for a total of 6 hours. The appearance of the liquid mixture after the ultrasonic treatment was visually observed, and from the obtained observation results, the dispersibility of the silica 1 in the solvent was evaluated based on the following evaluation criteria. The evaluation results are shown in table 3. The dispersibility in a solvent was evaluated in the same manner except that the kind of silica sol as a raw material in the silica 1-solvent system was changed for the methanol-dispersed silica sol ("MA-ST-L" manufactured by nippon chemical industry, ltd., having a primary particle diameter of 20 to 25nm) and the methanol-dispersed silica sol ("silica sol 2" having a primary particle diameter of 10 to 12 nm).

(evaluation criteria)

1: the appearance of the mixed solution was white turbid.

0: the appearance of the mixed solution is transparent.

[ Table 3]

Hansen spheres were prepared by the hansen sphere dissolution method described above based on the evaluation results of dispersibility of each silica dispersed in silica sol in a solvent. The obtained central coordinates of the hansen beads were used as HSP values. The results are shown in Table 4.

[ Table 4]

(HSP value of resin-silica System)

From tables 2 and 4, HSP values of the resin-silica system were calculated using formulae (6) to (9). The results are shown in Table 5.

[ Table 5]

As shown in Table 5, Ra, Delta of the silica 1, 2-resin System_tAnd Δ p is less than Ra and Δ of the silica (MA-ST-L) -resin system, respectively_tAnd Δ p. Ra, Delta of silica 1, 2-resin System_tAnd Δ p satisfy formulas (3) to (5), respectively.

(modulus of elasticity)

The elastic modulus (tensile elastic modulus) G' of the pressure-sensitive adhesive layer was measured by a tensile test in accordance with JIS K7127 using an electromechanical universal tester (Instron). The measurement conditions were a test speed of 5 m/min and a load cell (load cell) of 5 kN.

< 2. evaluation method >

(evaluation of visibility of optical film)

A film is provided as a front panel on the surface of a liquid crystal display device, and white display or black display is performed, and a viewer visually observes the optical film by tilting the optical film at an angle of 45 ° from the perpendicular direction to the plane of the optical film. From the observation results, the visibility of the optical film was evaluated based on the following evaluation criteria. Excellent properties are expressed as excellent, good, Δ and × in this order.

(evaluation criteria for visibility of optical film)

Very good: both the white display and the black display have no yellow color at all.

Good: both the white display and the black display are slightly yellow.

And (delta): at least one of the white display and the black display is yellowish.

X: both white display and black display are yellowish. Further, it is whitish in black display.

(evaluation of visibility of optical laminate having circularly polarizing plate)

An optical laminate having a circularly polarizing plate was provided on the surface of a reflector (aluminum plate, reflectance 97%), and the optical laminate was observed by visual observation by an observer at an angle of 45 ° from the perpendicular direction to the plane of the optical laminate. From the observation results, the visibility of the optical laminate having a circularly polarizing plate was evaluated based on the following evaluation criteria. From the excellent condition, the values are represented by good, good.

(evaluation criteria for visibility of optical laminate having circularly polarizing plate)

Good: on the reflector, the hue of the front surface of the reflector was neutral with respect to the hue change on a 45 ° slope as compared with the vertical direction, and there was no hue change due to the viewing angle.

And (delta): on the reflector, the hue of the front surface of the reflector is neutral with respect to the hue change on a 45 ° slope, and the hue change due to the viewing angle is slightly larger than that in the vertical direction.

X: on the reflector, the hue of the front surface on the reflector is changed by 45 ° slope as compared with the vertical direction, and the hue change by the viewing angle is large.

< 3. production of optical film >

[3-1. production of polyimide resin ]

(production example 1: polyimide resin 1]

A reaction vessel having a separable flask equipped with a silicone tube, a stirrer, and a thermometer, and an oil bath were prepared. Into a reaction vessel placed in an oil bath were charged 75.52g of 4,4 ' - (hexafluoroisopropylidene) diphthalic dianhydride (6FDA) and 54.44g of 2,2 ' -bis (trifluoromethyl) -4,4 ' -diaminobiphenyl (TFMB). While the contents of the reaction vessel were stirred at 400rpm, 519.84g of N, N-dimethylacetamide (DMAc) was further charged into the reaction vessel, and the stirring was continued until the contents of the reaction vessel became a uniform solution. Then, the reaction was further continued for 20 hours while adjusting the temperature in the container to a range of 20 to 30 ℃ by using an oil bath, and a polyamic acid was produced.

After 30 minutes, the stirring speed was changed to 100 rpm. After stirring for 20 hours, the reaction system temperature was returned to room temperature (25 ℃ C.), and 649.8g of DMAc was further charged into the reaction vessel so that the polymer concentration was adjusted to 10 mass% (based on the total mass of the contents in the reaction vessel). Further, 32.27g of pyridine and 41.65g of acetic anhydride were put into the reaction vessel, and stirred at room temperature for 10 hours to effect imidization. The polyimide varnish was taken out of the reaction vessel. The obtained polyimide varnish was dropped into methanol and reprecipitated. The precipitate was taken out by filtration and dried to obtain a powder. The obtained powder was further heated and dried to remove the solvent, and a polyimide resin 1 was obtained as a solid component. The weight-average molecular weight of the obtained polyimide resin 1 was 320,000, and the imidization rate was 98.6%.

(production example 2: polyamide-imide resin 1]

A reaction vessel equipped with a stirring blade in a separable flask having a capacity of 1L and an oil bath were prepared under a nitrogen atmosphere. Into the reaction vessel placed in an oil bath were charged 45g of TFMB (140.52mmol) and 768.55g of DMAc. The contents of the reaction vessel were stirred at room temperature to dissolve TFMB in DMAc. Subsequently, 18.92g (42.58mmol) of 6FDA was further charged into the reaction vessel, and the contents of the reaction vessel were stirred at room temperature for 3 hours. Then, 4.19g (14.19mmol) of 4, 4' -oxybis (benzoyl chloride) (OBBC) was charged into the reaction vessel, and 17.29g (85.16mmol) of terephthaloyl chloride (TPC) was charged into the reaction vessel, and the contents of the reaction vessel were stirred at room temperature for 1 hour. Subsequently, 4.63g (49.68mmol) of 4-methylpyridine and 13.04g (127.75mmol) of acetic anhydride were further charged into the reaction vessel, and the contents of the reaction vessel were stirred at room temperature for 30 minutes. After the stirring, the temperature in the reaction vessel was raised to 70 ℃ by using an oil bath, and the contents in the reaction vessel were further stirred for 3 hours while maintaining the temperature at 70 ℃ to obtain a reaction solution.

The obtained reaction solution was cooled to room temperature, and put into a large amount of methanol in a linear form to precipitate a precipitate. The precipitated precipitate was taken out, immersed in methanol for 6 hours, and then washed with methanol. Then, the precipitate was dried under reduced pressure at 100 ℃ to obtain a polyamideimide resin. The polyamideimide resin had a weight average molecular weight of 400,000 and an imidization rate of 98.8%.

(production example 3: polyamide-imide resin 2)

A reaction vessel equipped with a stirring blade in a separable flask having a capacity of 1L and an oil bath were prepared under a nitrogen atmosphere. Into the reaction vessel placed in an oil bath were charged 45g (140.52mmol) of TFMB and 768.55g of DMAc. TFMB was dissolved in DMAc while the contents of the reaction vessel were stirred at room temperature. Then, 19.01g (42.79mmol) of 6FDA was further charged into the reaction vessel, and the contents of the reaction vessel were stirred at room temperature for 3 hours. Then, 4.21g (14.26mmol) of OBBC and 17.30g (85.59mmol) of TPC were put into the reaction vessel, and the contents of the reaction vessel were stirred at room temperature for 1 hour. Subsequently, 4.63g (49.68mmol) of 4-methylpyridine and 13.04g (127.75mmol) of acetic anhydride were further charged into the reaction vessel, and the contents of the reaction vessel were stirred at room temperature for 30 minutes. After stirring, the temperature in the vessel was raised to 70 ℃ by using an oil bath, and further stirred for 3 hours while maintaining the temperature at 70 ℃ to obtain a reaction solution.

The obtained reaction solution was cooled to room temperature, and put into a large amount of methanol in a linear form to precipitate a precipitate. The precipitated precipitate was taken out, immersed in methanol for 6 hours, and then washed with methanol. Then, the precipitate was dried under reduced pressure at 100 ℃ to obtain a polyamideimide resin. The weight-average molecular weight of the obtained polyamideimide resin was 365,000, and the imidization rate was 98.9%.

[3-2. production of silica particles ]

(production example 4: silica sol 1]

A flask having a capacity of 1L as a reaction vessel and a hot water bath were prepared. Into a reaction vessel placed in a hot water bath, 442.6g of methanol-dispersed silica sol (primary particle diameter of 25nm, silica solid content of 30.5%) and 301.6g of γ -butyrolactone were charged. The temperature in the reactor was set to 45 ℃ by using a hot water bath, the pressure in the reactor was set to 400hPa by using an evaporator, and the pressure in the reactor was maintained for 1 hour, and then the pressure in the reactor was set to 250hPa by using an evaporator, and methanol was evaporated. The pressure in the reaction vessel was further set to 250hPa, and the temperature in the reaction vessel was raised to 70 ℃ and heated for 30 minutes. As a result, a γ -butyrolactone dispersed silica sol (silica sol 1, SGS7#09) was obtained. The solid content of the obtained γ -butyrolactone dispersed silica sol was 28.9%.

[ production example 5 silica Sol 2]

A γ -butyrolactone-dispersed silica sol (silica sol 2) having a solid content of 20% was obtained by solvent substitution in the same manner as in production example 4, except that the primary particle diameter of the methanol-dispersed silica sol was changed to 10nm and the solid content of silica was changed to 22%.

[ production example 6 silica Sol 3]

Solvent substitution was carried out in the same manner as in production example 4 except that the methanol-dispersed silica sol (primary particle diameter of 25nm, silica solid content of 30.5%) was changed to a methanol-dispersed silica sol ("MA-ST-L" manufactured by nippon chemical industry co., ltd., primary particle diameter of 40 to 50nm), to obtain a γ -butyrolactone-dispersed silica sol (silica sol 3) having a solid content of 30.5% and a primary particle diameter of 50 nm.

[3-3. production of varnish ]

[ production example 7 varnish 1]

To γ -butyrolactone, polyamideimide resin 1, silica sol 1, sumirorb (registered trademark) 340 as an ultraviolet absorber, and Sumiplast (registered trademark) Violet B as a whitening agent were added in the composition shown in table 6, and varnish 1 was prepared so that the solid content became 10.2%.

In table 6, the unit wt% of the content in the columns of "resin" and "silica particles" represents the proportion (mass%) relative to the total mass of the resin and the silica particles. The unit phr of the content in the column of "ultraviolet absorber" represents the proportion (% by mass) relative to the total mass of the resin and the silica particles.

[ Table 6]

[ production examples 8 to 13: varnish 2-8 ]

Varnish 3 was prepared in the same manner as varnish 1 except that the composition (type and/or content of component) shown in table 6 was changed, the solvent to be replaced was changed from γ -butyrolactone to N, N-dimethylacetamide, and the solid content concentration of the resin was changed to 11.0%. Varnishes 2 and 4 to 8 were prepared in the same manner as the varnish 1 except that the compositions (types and/or contents of components) shown in table 6 were changed.

[ example 1]

[3-4. production of optical film ]

The varnish 1 thus obtained was cast on a PET film ("Cosmoshine (registered trademark) a 4100" manufactured by tokyo corporation) to form a coating film. The carrying speed of PET in casting was 0.3 m/min. Then, the coating film was dried by heating at 80 ℃ for 20 minutes and at 90 ℃ for 20 minutes, and the coating film was peeled off from the PET film. Then, the coating film was heated while being stretched transversely for 12 minutes at 200 ℃ by a tenter, thereby obtaining a polyamide-imide film 1 having a film thickness of 51 μm.

[ example 2]

A polyamideimide film 2 having a film thickness of 29 μm was obtained in the same manner as in example 1, except that the film thickness was changed.

[ example 3]

A polyamideimide film 3 having a film thickness of 50 μm was obtained in the same manner as in example 1, except that the varnish 1 was changed to the varnish 2.

[ example 4]

A polyamideimide film 4 having a film thickness of 49 μm was obtained in the same manner as in example 1, except that the varnish 1 was changed to the varnish 3.

[ example 5]

A48 μm thick polyamideimide film 5 was obtained in the same manner as in example 1, except that the varnish 1 was changed to the varnish 4.

[ example 6]

A48 μm thick polyamideimide film 6 was obtained in the same manner as in example 1, except that the varnish 1 was changed to the varnish 5.

[ example 7]

A polyimide film 7 having a film thickness of 78 μm was obtained in the same manner as in example 1, except that the varnish 1 was changed to the varnish 6.

[ comparative example 1]

A polyimide film 8 having a film thickness of 52 μm was obtained in the same manner as in example 1, except that the varnish 1 was changed to the varnish 7.

[ comparative example 2]

A polyamideimide film 9 having a film thickness of 50 μm was obtained in the same manner as in example 1, except that the varnish 1 was changed to the varnish 8.

[ Table 7]

The optical films of examples 1 to 7 satisfied formula (1), and the visibility thereof was evaluated as any one of very good, o, and Δ. The optical films of comparative examples 1 to 2 contain polyamideimide, do not satisfy formula (1), and their visibility evaluation results were x.

It is found that the optical films of examples 1 to 7 are superior in visibility to the optical films of comparative examples 1 to 2.

[ example 8]

[3-5. production of adhesive layer ]

(preparation of composition for Forming adhesive layer)

Based on the compositions described in table 8, adhesive layer-forming compositions were prepared.

Based on the compositions described in table 8, adhesive layer-forming compositions were prepared. In Table 8, BA means butyl acrylate. MMA denotes methyl methacrylate. HEA represents hydroxyethyl acrylate. AA represents acrylic acid. The amounts of the crosslinking agent and the SC agent added are mass per 100 parts by mass of the monomer.

[ Table 8]

(formation of adhesive layer 1)

On the release-treated surface of the release-treated substrate (polyethylene terephthalate film, thickness 38 μm), the adhesive layer-forming composition 1 was applied by an applicator to form a coating layer. The coating layer was dried at 100 ℃ for 1 minute to form the adhesive layer 1. The thickness of the adhesive layer 1 was 25 μm.

Then, another substrate (polyethylene terephthalate film, 38 μm thick) subjected to a release treatment was attached to the pressure-sensitive adhesive layer 1. Then, the mixture was aged at 23 ℃ and 50% RH relative humidity for 7 days. Thereby, a film having the pressure-sensitive adhesive layer 1 was obtained. The elastic modulus G' and the thickness of the obtained pressure-sensitive adhesive layer 1 were measured. The results are summarized in Table 9.

In the following description, when the pressure-sensitive adhesive layer is laminated, and then the release-treated substrate is peeled off.

(formation of adhesive layer 2)

The pressure-sensitive adhesive layer 2 was formed in the same manner as in the formation of the pressure-sensitive adhesive layer 1 except that the pressure-sensitive adhesive layer forming composition 1 was changed to the pressure-sensitive adhesive layer forming composition 2 and the pressure-sensitive adhesive layer forming composition was applied so that the thickness of the pressure-sensitive adhesive layer became 5 μm. The elastic modulus and thickness of the adhesive layer 2 are summarized in Table 9.

[ Table 9]

[3-6. production of polarizing plate ]

(preparation of composition for Forming alignment film)

The polymer 1 is a polymer having a photoreactive group, which comprises the following structural units.

The molecular weight of the obtained polymer 1 was 28,200 in terms of number average molecular weight, polydispersity (Mw/Mn) was 1.82 and the monomer content was 0.5% as determined by GPC. A solution obtained by dissolving polymer 1 in cyclopentanone at a concentration of 5 mass% was used as the alignment film forming composition.

(formation of alignment film)

The above composition for forming an alignment film was applied on a protective film (triacetyl cellulose: TAC) by a bar coating method to form a coating film. The coating film was dried at 80 ℃ for 1 minute. Next, an exposure amount was set to 100mJ/cm using a UV irradiation apparatus (SPOT CURE SP-7, manufactured by USHIO INC.) and a wire grid (UIS-27132 # #, manufactured by USHIO INC.)²The coating film was irradiated with polarized UV light (365nm basis). Thereby forming an alignment film on the protective film. The alignment film had an alignment property and a thickness of 100 nm.

(preparation of composition for Forming polarizing plate)

The composition for forming a polarizer includes a polymerizable liquid crystal compound and a dichroic dye.

(polymerizable liquid Crystal Compound)

As the polymerizable liquid crystal compound, a polymerizable liquid crystal compound represented by formula (5) [ hereinafter, also referred to as compound (5) ] and a polymerizable liquid crystal compound represented by formula (6) [ hereinafter, also referred to as compound (6) ] were used.

[ chemical formula 5]

[ chemical formula 6]

The compounds (5) and (6) were synthesized by the method described in Lub et al, Recl, Travv, Chim, Pays-Bas, 115, 321-328 (1996).

(dichroic pigment)

As the dichroic dye, azo dyes described in examples of Japanese patent application laid-open No. 2013-101328, represented by the following formulae (7), (8) and (9), are used.

[ chemical formula 7]

[ chemical formula 8]

[ chemical formula 9]

(preparation of composition for Forming polarizing plate)

The composition for forming a polarizer was prepared in the following manner: 75 parts by mass of the compound (5), 25 parts by mass of the compound (6), 2.5 parts by mass of each of the azo dyes represented by the above formulae (7), (8) and (9) as dichroic dyes, 6 parts by mass of 2-dimethylamino-2-benzyl-1- (4-morpholinophenyl) -1-butanone (Irgacure369, manufactured by BASF Japan) as a polymerization initiator, and 1.2 parts by mass of a polyacrylate compound (BYK-361N, manufactured by BYK-Chemie) as a leveling agent were mixed with 400 parts by mass of toluene, and the resulting mixture was stirred at 80 ℃ for 1 hour.

(production of polarizing plate)

The polarizing plate-forming composition was applied to the alignment film by a bar coating method to form a coating film. The coating film was dried by heating at 100 ℃ for 2 minutes. Then, the mixture was cooled to room temperature. Using the above UV irradiation apparatus, the cumulative light amount was 1200mJ/cm²The coating film was irradiated with ultraviolet rays (365nm basis). Thereby, a polarizer is formed on the alignment film. The thickness of the polarizer was 3 μm.

(formation of protective layer)

On the polarizer, a composition containing polyvinyl alcohol and water was applied to form a coating film. The coating film was dried at a temperature of 80 ℃ for 3 minutes. Thereby, a protective layer is formed on the polarizer. The thickness of the protective layer was 0.5 μm.

In this manner, a polarizing layer in which a protective film, an alignment film, a polarizer, and a protective layer are sequentially stacked was manufactured.

(formation of lambda/4 retardation plate and Positive C plate)

The λ/4 phase difference plate is formed in the following manner.

The following components were mixed, and the resulting mixture was stirred at 80 ℃ for 1 hour to obtain a λ/4 retardation layer-forming composition.

A compound b-1 represented by the following formula: 80 parts by mass

A compound b-2 of the formula: 20 parts by mass

Polymerization initiator (Irgacure369, 2-dimethylamino-2-benzyl-1- (4-morpholinophenyl) -1-butanone, manufactured by BASF Japan): 6 parts by mass

Leveling agent (BYK-361N, polyacrylate compound, BYK-Chemie Co., Ltd.): 0.1 part by mass

Cyclopentanone: 400 parts by mass

The above-mentioned composition for forming an alignment film was applied to a No. 1 substrate film (100 μm thick, polyethylene terephthalate film (PET)) by a bar coating method, and dried by heating in an oven at 80 ℃ for 1 minute. The obtained dried film was irradiated with polarized UV light to form a 2 nd alignment film. For the polarized UV light treatment, the above UV irradiation apparatus was used so that the cumulative light amount measured at a wavelength of 365nm was 100mJ/cm²The conditions of (1) are carried out. The polarization direction of the polarized UV light is set to 45 ° with respect to the absorption axis of the polarizing layer. In this manner, a laminate composed of "1 st substrate film/2 nd alignment film" was obtained. The thickness of the 2 nd alignment film was 100 nm.

On the 2 nd alignment film of the laminate formed of "1 st base material film/2 nd alignment film", a composition for forming a λ/4 retardation layer was applied by a bar coating method, dried by heating in a drying oven at 120 ℃ for 1 minute, and then cooled to room temperature. The obtained dried film was irradiated with a cumulative light amount of 1000mJ/cm using the UV irradiation apparatus described above²Ultraviolet rays (365nm basis), thereby forming a retardation layer. The thickness of the obtained retardation layer was measured by a laser microscope (OLS 3000 manufactured by Olympus corporation), and it was 2.0. mu.m. The phase difference layer is a λ/4 plate exhibiting a phase difference value of λ/4 in the in-plane direction. In this manner, a laminate composed of "1 st substrate film/2 nd alignment film/λ/4 retardation layer" was obtained.

The following components were mixed, and the resulting mixture was stirred at 80 ℃ for 1 hour to obtain a composition for forming a positive C retardation layer.

A compound represented by the following formula (LC242, manufactured by BASF Japan): 100 parts by mass

Polymerization initiator (Irgacure907, 2-methyl-4' - (methylthio) -2-morpholinopropiophenone, manufactured by BASF Japan): 2.6 parts by mass

Leveling agent (BYK-361N, polyacrylate compound, BYK-Chemie Co., Ltd.): 0.5 part by mass

Additive (LR9000, manufactured by BASF Japan): 5.7 parts by mass

Solvent (propylene glycol 1-monomethyl ether 2-acetate): 412 parts by mass

The above-mentioned composition for forming an alignment film was applied to a 2 nd base film (100 μm thick, polyethylene terephthalate film (PET)) by a bar coating method in the same manner as in the above-mentioned λ/4 retardation plate, and then heated and dried in a drying oven at 90 ℃ for 1 minute to form a 3 rd alignment film. Then, on the 3 rd alignment film, a composition for forming a positive C retardation layer was applied by a bar coating method, dried by heating in a drying oven at 90 ℃ for 1 minute, and then irradiated with a cumulative light amount of 1000mJ/cm in a nitrogen atmosphere using the above-mentioned UV irradiation apparatus²Ultraviolet light (365nm basis), thereby forming a positive C plate. The thickness of the positive C plate thus obtained was measured by a laser microscope (OLS 3000, manufactured by Olympus corporation), and found to be 1.8. mu.m.

Then, the surface of the positive C plate from which the 2 nd base film was peeled was bonded to the opposite side of the λ/4 retardation plate from the 1 st base film by using the adhesive layer 2, thereby producing a retardation layer.

Both the formed λ/4 retardation plate and the positive C plate include a layer obtained by curing a polymerizable liquid crystal compound in an aligned state.

[3-7. production of optical laminate having circularly polarizing plate ]

The optical laminate 1 was produced using the polyamideimide film 1, the polarizing layer, the pressure-sensitive adhesive layer 1, and the pressure-sensitive adhesive layer 2. The laminate 1 includes a polyamideimide film 1, a pressure-sensitive adhesive layer 1, a polarizing layer (protective film/alignment film/polarizer/protective layer)/a pressure-sensitive adhesive layer 2 in this order. The surface of the retardation layer from which the 1 st base film was peeled was bonded to the side of the polarizing layer opposite to the side of the protective film via the adhesive layer 2. The retardation layer is a layer obtained by laminating a λ/4 retardation plate (RWP) and a positive C plate (PosiC). Then, an adhesive layer 1 was provided on the side of the retardation layer opposite to the polarizing layer. Thereby, a laminate 1 including a circularly polarizing plate was produced. The laminate 1 comprises a polyamideimide film 1, an adhesive layer 1, a polarizing layer (protective film/alignment film/polarizer/protective layer)/an adhesive layer 2/a retardation layer (λ/4 retardation plate/positive C plate)/an adhesive layer 1 in this order. Here, the expression of the alignment film in the retardation layer is omitted.

In the bonding of the polarizing layer and the retardation layer, the polarizing layer and the retardation layer are bonded via the adhesive layer 2 so that the absorption axis of the polarizing layer is substantially 45 ° with respect to the slow axis (optical axis) of the retardation layer.

The optical characteristic values were measured and calculated for the optical laminate having the circularly polarizing plate. In detail, transmission b, transmission a, reflection (SCE) a, b, and Y, and reflection (SCI) a, b, and Y were measured. From the obtained transmission b and reflection (SCE) b, transmission b-reflection (SCE) b was calculated. The measurement results and calculation results are shown in Table 10.

[ example 9]

An optical laminate 2 having a circularly polarizing plate was produced in the same manner as in example 8, except that a polyamideimide film 5 was applied to the front panel instead of the polyamideimide film 1, and the optical characteristic values were measured and calculated.

[ example 10]

An optical laminate 3 having a circularly polarizing plate was produced in the same manner as in example 8, except that a polyimide film 7 was applied to the front panel instead of the polyamideimide film 1, and the optical characteristic values were measured and calculated.

[ comparative example 3]

An optical laminate 4 having a circularly polarizing plate was produced in the same manner as in example 8, except that a polyimide film 8 was applied to the front panel instead of the polyamideimide film 1, and the optical characteristic values were measured and calculated.

[ Table 10]

The optical laminates having circular polarizers of examples 8 to 10 satisfied formula (39), and their visibility was evaluated as either o or Δ. The optical layered bodies having circularly polarizing plates of examples 8 to 10 also satisfy formula (40).

The optical laminate having a circularly polarizing plate of comparative example 3 did not satisfy formula (39), and the visibility thereof was evaluated as x. The optical laminate having a circularly polarizing plate of comparative example 3 also does not satisfy formula (40).

It is found that the optical laminates having the circularly polarizing plates of examples 8 to 10 are superior in visibility to the optical laminate having the circularly polarizing plate of comparative example 3.

Claims (10)

1. An optical film comprising at least one selected from the group consisting of polyimide, polyamide, and polyamideimide, and satisfying formula (1):

1.1. ltoreq. transmission b x-reflection (SCE) b x 15 … … (1)

In formula (1), transmission b denotes light transmitted from the optical film in the L × a × b color system, and reflection (SCE) b denotes light reflected from the optical film in the L × a × b color system, which is determined by SCE.

2. The optical film according to claim 1, which further satisfies formula (2):

transmission b reflection (SCI) b ≦ 4.5 … … (2)

In formula (2), transmission b represents light transmitted from the optical film in the L a b color system, and reflection (SCI) b represents light reflected from the optical film in the L a b color system, which is determined in the SCI manner.

3. The optical film according to claim 1 or 2, wherein the haze is 1% or less and the total light transmittance Tt is 85% or more.

4. The optical film according to any one of claims 1 to 3, further comprising silica particles.

5. The optical film according to claim 4, wherein the silica particles are silica particles obtained by solvent substitution of a water-soluble alcohol-dispersed silica sol.

6. The optical film according to any one of claims 1 to 5, further comprising an ultraviolet absorber.

7. An optical laminate comprising: the optical film according to any one of claims 1 to 6; and a hard coat layer on at least one side of the optical film.

8. A flexible image display device comprising the optical laminate according to claim 7.

9. The flexible image display device according to claim 8, further comprising a polarizing plate.

10. The flexible image display device according to claim 8 or 9, further provided with a touch sensor.