KR102625083B1 - Optical film - Google Patents

Abstract

An optical film capable of suppressing deterioration of optical properties due to repeated object collisions is provided.
An optical film comprising at least one type of resin selected from the group consisting of polyimide resin and polyamide resin, and having a dent amount of 15 μm or less in an impact resistance test.

Description

Optical film {OPTICAL FILM}

The present invention relates to an optical film used as a front panel, etc. of an image display device, and a flexible image display device provided with the optical film.

Image display devices such as liquid crystal displays and organic EL displays are widely used in various applications such as mobile phones and smart watches. Glass has been used as a front panel for such image display devices, but because glass is very rigid and fragile, it is difficult to use it as a front panel material for, for example, flexible displays. As one of the materials that replace glass, there are polyimide resins and polyamide resins, and optical films using these resins are being studied (for example, patent document 1).

Japanese Patent Publication No. 2015-521687

However, according to the present inventor's examination, the optical film used as the front panel material of such an image display device is touched directly by the user or collided with surrounding objects, so if the contact or collision is repeated, the optical film is damaged on the surface. It was found that in some cases, optical properties deteriorated due to scratches such as dents.

Therefore, an object of the present invention is to provide an optical film capable of suppressing deterioration of optical properties due to repeated object collisions, and a flexible image display device including the optical film.

As a result of intensive studies in order to solve the above problems, the present inventor has found that an optical film containing at least one type of resin selected from the group consisting of polyimide resin and polyamide resin has no dents in an impact resistance test. It was discovered that the above object was achieved when the amount was 15 μm or less, and the present invention was completed. That is, the present invention includes the following aspects.

[1] An optical film containing at least one type of resin selected from the group consisting of polyimide resin and polyamide resin, and having a dent amount of 15 μm or less in an impact resistance test.

[2] The optical film according to [1], wherein the haze is 1% or less.

[3] The optical film according to [1] or [2], wherein the yellowness is 5 or less.

[4] The optical film according to any one of [1] to [3], comprising a filler having a primary particle diameter of 25 nm or less.

[5] The optical film according to any one of [1] to [4], wherein the film thickness is 25 to 100 μm.

[6] A flexible image display device comprising the optical film according to any one of [1] to [5].

[7] The flexible image display device according to [6], further comprising a polarizing plate.

[8] The flexible image display device according to [6] or [7], further comprising a touch sensor.

Since the optical film of the present invention can suppress deterioration of optical properties due to repeated object collisions, it can be used as a front panel material for an image display device.

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

[Optical film]

The optical film of the present invention contains at least one type of resin selected from the group consisting of polyimide resin and polyamide resin, and has a dent of 15 μm or less in an impact resistance test.

The amount of dents in the impact resistance test represents the average value of the dent depth when the impact resistance test was performed 5 times. The dent depth in the impact resistance test was determined by manufacturing a laminate in which glass, an adhesive layer, and an optical film were laminated in this order, and using a weight (4.6 g in mass, a sphere with a diameter of 0.75 mm at the impact point, made of stainless steel) at 10 cm. When dropped from a height on the optical film surface of a laminate, the depth of the largest dent obtained by observation using an optical interference film thickness meter (shortest distance from the film surface in the non-dented state before the test to the largest dent point) represents. The amount of dents in the impact resistance test can be measured, for example, by the method described in the section <Impact Resistance Test> of the Examples. Additionally, the impact resistance test may be performed using a drop tester or the like.

As described above, the amount of dents in the impact resistance test indicates the degree to which dents occur when a predetermined weight collides with the film surface. The smaller the amount of dents, the greater the impact resistance, that is, the greater the impact resistance when an object is hit on the surface of the optical film. It is easier to suppress the occurrence of dents or changes in the shape of the film surface in the event of a collision. Since the optical film of the present invention has a small dent of 15 μm or less in the impact resistance test and has excellent impact resistance, it can suppress degradation of optical properties due to objects repeatedly colliding with the film surface. Additionally, when the amount of depression exceeds 15 μm, the shape change of the film surface due to repeated collisions with objects becomes relatively large, and the optical properties tend to deteriorate significantly.

The amount of dent in the impact resistance test is preferably 10 μm or less, more preferably 5 μm or less. If the amount of depression is below the above upper limit, the change in shape of the film surface due to repeated object collisions can be effectively suppressed, and deterioration of optical properties can be effectively suppressed.

The optical film of the present invention also has excellent optical properties. In addition, in this specification, optical properties refer to, for example, reflection a* and reflection b*, total light transmittance, yellowness (YI value), and haze, etc., and excellent optical properties mean that It indicates that reflection a* and reflection b* are close to 0, haze and yellowness (YI value) are low, and total light transmittance is high. In addition, the optical film of the present invention exhibits excellent optical properties, especially high total light transmittance, so that, for example, in a flexible device, when obtaining the same brightness, the luminous intensity of the backlight, etc. can be lowered. It can contribute to energy saving.

The optical film of the present invention has excellent surface reflection properties. Here, as parameters representing surface reflection characteristics, for example, there are parameters representing reflection color such as reflection a*(SCE) and reflection b*(SCE). The closer the reflection a* is to 0, the greener the optical film. The smaller the color taste, such as red or red, and the closer the reflection b* is to 0, the less color taste, such as blue or yellow, in the optical film, indicating that the transparency is good. The reflection a*(SCE) and reflection b*(SCE) of the optical film are each determined by the SCE (Specular Component Excluded) method in the L*a*b* colorimetric system of the light reflected from the optical film. a* and b*, and in this specification, among the reflected light for incident light in the range of wavelength 380 to 780 nm, incident from a direction inclined at a predetermined angle from the vertical direction of the optical film plane, diffuse reflected light excluding regular reflection light. Refers to the a* and b* values of the CIE 1976 L*a*b* color space. The reflection a*(SCE) of the optical film of the present invention is preferably -1 to 1, more preferably -0.5 to 0.5, even more preferably -0.3 to 0.3, and reflection b*(SCE) is preferably. Preferably it is -5 to 5, more preferably -3 to 3, further preferably -2 to 3, especially preferably -2 to 2. If the reflection a*(SCE) and reflection b*(SCE) of the optical film are within the above range, transparency becomes good and high visibility can be achieved when used in the front panel of an image display device. Additionally, reflection a*(SCE) and reflection b*(SCE) of the optical film can be measured using a spectrophotometer, for example, by the method described in the Examples.

Since the optical film of the present invention can suppress changes in the shape of the film surface due to object collisions, deterioration of optical properties due to repeated collisions, such as changes in the reflection color of the film surface, such as reflection a* and Changes in both reflex b*(SCE) can be effectively suppressed. These film properties were obtained by repeating the operation of dropping a weight (mass 4.6 g, spherical with a diameter of 0.75 mm at the impact point, made of stainless steel) 20 times from a position of 10 cm in height within a range of 8 mm in diameter on the film surface, and spectroscopic measurements were performed. Using a colorimeter, the reflection color (reflection a* and b*) before and after the operation can be measured and evaluated, for example, by the method described in the <Impact Fatigue Test> section of the Examples. In the optical film of the present invention, the amount of change (absolute value) in reflection a*(SCE) before and after the impact fatigue test is preferably 0.16 or less, more preferably 0.10 or less, further preferably 0.05 or less, and even more preferably Preferably it is 0.03 or less, particularly preferably 0.01 or less, and the change (absolute value) of reflection b*(SCE) is preferably 0.35 or less, more preferably 0.30 or less, further preferably 0.25 or less, especially preferably It is less than 0.20. Additionally, the impact fatigue test may be performed using a drop tester or the like.

In the optical film of the present invention, the total light transmittance at a thickness of 50 μm is preferably 80% or more, more preferably 85% or more, and still more preferably 90% or more. If the total light transmittance is more than the above lower limit, transparency becomes good and can contribute to high visibility when used in the front panel of an image display device. Additionally, the upper limit of total light transmittance is usually 100% or less. In addition, the total light transmittance can be measured using a haze computer based on JIS K 7361-1:1997, and can be measured, for example, by the method described in the Examples.

The yellowness (YI value) of the optical film of the present invention is preferably 5 or less, more preferably 3 or less, and still more preferably 2.5 or less. If the yellowness of the optical film is below the above upper limit, transparency becomes good and can contribute to high visibility when used in the front panel of an image display device. Moreover, the yellowness is usually -5 or more, preferably -2 or more. In addition, the yellowness (YI value) is measured by measuring the transmittance for light of 300 to 800 nm using an ultraviolet, visible, and near-infrared spectrophotometer, and the three stimulation values (X, Y, Z) are obtained, and YI = 100 × (1.2769 × It can be calculated based on the formula -1.0592Z)/Y. Yellowness can be measured, for example, by the method described in the Examples.

The haze of the optical film of the present invention is preferably 1% or less, more preferably 0.5% or less, and still more preferably 0.2% or less. If the haze of the optical film is below the above upper limit, transparency becomes good and can contribute to high visibility when used in the front panel of an image display device. Additionally, the lower limit of haze is usually 0.01% or more. Additionally, haze can be measured using a haze computer based on JIS K 7136:2000, and can be measured, for example, by the method described in the Examples.

The film thickness of the optical film of the present invention is preferably 25 μm or more, more preferably 30 μm or more, preferably 100 μm or less, more preferably 80 μm or less, and still more preferably 60 μm or less. It may be a combination. If the thickness of the optical film is within the above range, it is easy to suppress deterioration of optical properties after repeated collisions with objects. In addition, the film thickness of the optical film can be measured using a micrometer, for example, by the method described in the Examples.

<Suzy>

The optical film of the present invention contains at least one type of resin selected from the group consisting of polyimide-based resin and polyamide-based resin.

Polyimide resin is a group consisting of a polymer containing a repeating structural unit containing an imide group and a polymer containing a repeating structural unit containing both an imide group and an amide group (sometimes called polyamidoimide). It represents at least one type of polymer selected from: In addition, polyamide-based resin refers to a polymer containing a repeating structural unit containing an amide group. In addition, in this specification, a repeating structural unit may be referred to as a structural unit.

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 types of repeating structural units represented by formula (10), where G and/or A are different.

The polyimide resin may contain one or more units selected from the group consisting of repeating structural units represented by Formula (11), Formula (12), and Formula (13), as long as they do not impair the various physical properties of the optical film. .

In formulas (10) and (11), G and G ¹ are each independently a tetravalent organic group, and are preferably organic groups that may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. As G and G ¹ , Equation (20), Equation (21), Equation (22), Equation (23), Equation (24), Equation (25), Equation (26), Equation (27), Equation (28) Alternatively, a group represented by formula (29) and a tetravalent chain hydrocarbon group having 6 or less carbon atoms are examples. Since it is easy to suppress the yellowness (YI value) of the optical film, among them, Equation (20), Equation (21), Equation (22), Equation (23), Equation (24), Equation (25), Equation (26) or a group represented by formula (27) is preferable.

In equations (20) to (29),

* represents the bonding hand,

Z is a single bond, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, - Ar-, -SO ₂ -, -CO-, -O-Ar-O-, -Ar-O-Ar-, -Ar-CH ₂ -Ar-, -Ar-C(CH ₃ ) ₂ -Ar- or -Ar-SO ₂ represents -Ar-. Ar represents an arylene group having 6 to 20 carbon atoms which may be substituted with a fluorine atom, and a phenylene group is a specific example.

In formula (12), G ² is a trivalent organic group, and is preferably an organic group that may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. As G ² , Equation (20), Equation (21), Equation (22), Equation (23), Equation (24), Equation (25), Equation (26), Equation (27), Equation (28) or Equation Examples include a group in which one of the bonding hands of the group represented by (29) is substituted with a hydrogen atom, and a trivalent chain hydrocarbon group having 6 or less carbon atoms.

In formula (13), G ³ is a divalent organic group, and is preferably an organic group that may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. As G ³ , Equation (20), Equation (21), Equation (22), Equation (23), Equation (24), Equation (25), Equation (26), Equation (27), Equation (28) or Equation Among the bonds of the group represented by (29), examples include a group in which two non-adjacent bonds are substituted with hydrogen atoms and a chain hydrocarbon group with 6 or less carbon atoms.

In formulas (10) to (13), A, A ¹ , A ² and A ³ are each independently a divalent organic group, and are preferably organic groups that may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. am. As A, A ¹ , A ² and A ³ , Equation (30), Equation (31), Equation (32), Equation (33), Equation (34), Equation (35), Equation (36), Equation (37) ) or a group represented by formula (38); groups in which they are substituted with a methyl group, fluoro group, chloro group or trifluoromethyl group; And a chain hydrocarbon group having 6 or less carbon atoms is exemplified.

In equations (30) to (38),

* represents the bonding hand,

Z ¹ , Z ² and Z ³ are each independently a single bond, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, - It represents C(CF ₃ ) ₂ -, -SO ₂ - or -CO-.

One example is where Z ¹ and Z ³ are -O- and Z ² is -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ - or -SO ₂ -. The bonding positions for each ring of Z ¹ and Z ² and the bonding positions for each ring of Z ² and Z ³ are preferably meta or para positions for each ring, respectively.

In one embodiment of the present invention, the polyimide resin is a polyamideimide having at least a repeating structural unit represented by formula (10) and a repeating structural unit represented by formula (13) from the viewpoint of easy improvement of impact resistance. It is desirable. Moreover, it is preferable that the polyamide-based resin has at least a repeating structural unit represented by formula (13).

In one embodiment of the present invention, the resin may contain multiple types of G ³ , and the multiple types of G ³ may be the same or different from each other. In particular, from the viewpoint of improving the surface hardness, impact resistance, and bending resistance of the obtained optical film, at least a part of G ³ is expressed in equation (3)

[In formula (3), R ¹ to R ⁸ each independently represent a hydrogen atom, an alkyl group with 1 to 6 carbon atoms, or an aryl group with 6 to 12 carbon atoms, and the hydrogen atoms contained in R ¹ to R ⁸ each independently represent halogen. It may be substituted with an atom.

B is a single bond, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, - It represents SO ₂ -, -S-, -CO- or -N(R ⁹ )-, and R ⁹ represents a hydrocarbon group of 1 to 12 carbon atoms which may be substituted with a hydrogen atom or a halogen atom.

n is an integer from 0 to 4,

* indicates a combined hand]

It is preferable that it is a structural unit expressed as .

In formula (3), B is each independently a single bond, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, - C(CF ₃ ) ₂ -, -SO ₂ -, -S-, -CO- or -N(R ⁹ )-, and from the viewpoint of improving the impact resistance and bending resistance of the optical film, preferably -O- Or -S-, and more preferably -O-. R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ each independently represent a hydrogen atom, an alkyl group with 1 to 6 carbon atoms, or an aryl group with 6 to 12 carbon atoms. Examples of alkyl groups having 1 to 6 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, and 2-methyl-butyl. , 3-methylbutyl group, 2-ethyl-propyl group, n-hexyl group, etc. Moreover, examples of the aryl group having 6 to 12 carbon atoms include phenyl group, tolyl group, xylyl group, naphthyl group, and biphenyl group. From the viewpoint of surface hardness, impact resistance, and flexibility of the optical film, R ¹ to R ⁸ each independently preferably represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and more preferably represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. represents an alkyl group, and more preferably represents a hydrogen atom. Here, the hydrogen atoms contained in R ¹ to R ⁸ may each independently be substituted with a halogen atom.

R ⁹ represents a hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a hydrogen atom or a halogen atom. Monovalent hydrocarbon groups having 1 to 12 carbon atoms include, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, n-pentyl group, 2- Methyl-butyl group, 3-methylbutyl group, 2-ethyl-propyl group, n-hexyl group, n-heptyl group, n-octyl group, tert-octyl group, n-nonyl group, n-decyl group, etc. and these may be substituted with halogen atoms. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

In Formula (3), n is an integer in the range of 0 to 4, and when n is within this range, the optical film has good impact resistance, bending resistance, and elastic modulus. Moreover, in formula (3), n is preferably an integer in the range of 0 to 3, more preferably an integer in the range of 0 to 2, and still more preferably 0 or 1. If n is within this range, , the optical film has good impact resistance, bending resistance, and elastic modulus, and the availability of raw materials is relatively good. In addition, G ³ may contain one or two or more types of structural units represented by formula (3), from the viewpoint of improving the impact resistance, elastic modulus and bending resistance of the optical film and reducing the yellowness (YI value). , In particular, it may contain two or more types of structural units with different n values, preferably two types of structural units with different n values. In that case, from the viewpoint that the optical film tends to exhibit high elastic modulus, impact resistance, bending resistance, and low yellowness (YI value), it is preferable that n contains both structural units of 0 and 1.

In a preferred embodiment of the present invention, formula (3) is a structural unit where n=0 and R ¹ to R ⁸ are hydrogen atoms, or formula (3'):

It is a structural unit represented by , and these can be used together. In this case, the optical film can exhibit high surface hardness and impact resistance, have high bending resistance, and can have a low yellowness.

In a preferred embodiment of the present invention, the sum of the structural units represented by formula (10) and the structural units represented by formula (13) of the polyimide resin is expressed by formula (3) when n is 0 to 4. The structural unit is preferably 20 mol% or more, more preferably 30 mol% or more, further preferably 40 mol% or more, particularly preferably 50 mol% or more, most preferably 60 mol% or more, and is preferred. Preferably it is 90 mol% or less, more preferably 85 mol% or less, and even more preferably 80 mol% or less. Regarding the sum of the structural units expressed by formula (10) and the structural units expressed by formula (13) in the polyimide resin, if the structural unit expressed by formula (3) when n is 0 to 4 is more than the above lower limit, Optical films can exhibit high surface hardness and impact resistance, and can also have excellent bending resistance and elastic modulus. Regarding the sum of the structural units expressed by formula (10) and the structural units expressed by formula (13) in the polyimide resin, if the structural unit expressed by formula (3) when n is 0 to 4 is less than or equal to the upper limit above, By suppressing thickening due to hydrogen bonding between amide bonds derived from formula (3), the viscosity of the polyimide resin varnish can be suppressed, and processing of the optical film can be facilitated.

In a preferred embodiment of the present invention, with respect to the sum of the structural units represented by formula (10) and the structural units represented by formula (13) of the polyimide resin, n in formula (3) is a structural unit represented by 1 to 4. is preferably 3 mol% or more, more preferably 5 mol% or more, further preferably 7 mol% or more, particularly preferably 9 mol% or more, preferably 90 mol% or less, more preferably It is 70 mol% or less, more preferably 50 mol% or less, and particularly preferably 30 mol% or less. With respect to the sum of the structural units represented by formula (10) and the structural units represented by formula (13) in the polyimide resin, if n in formula (3) is greater than the lower limit above, the optical film It can exhibit high surface hardness and impact resistance, and its bending resistance is further improved. Regarding the sum of the structural units represented by formula (10) and the structural units represented by formula (13) in the polyimide resin, if n in formula (3) is the structural unit represented by 1 to 4 or less than the upper limit above, the formula ( 3) By suppressing thickening due to hydrogen bonds between amide bonds, the viscosity of the polyimide resin varnish can be suppressed, making processing of the optical film easier. In addition, the content of the structural unit represented by formula (3) can be measured using, for example, ¹ H-NMR, or can also be calculated from the introduction ratio of the raw materials.

In a preferred embodiment of the present invention, the G ³ of the polyimide resin is preferably 5 mol% or more, more preferably 8 mol% or more, further preferably 10 mol% or more, particularly preferably 12 mol% or more. Mol% or more is expressed in equation (3) when n is 1 to 4. If G ³ of the polyimide resin is more than the above lower limit, expressed by equation (3) when n is 1 to 4, the optical film can exhibit high surface hardness and impact resistance, and have high bending resistance. there is. Moreover, G ³ in the polyimide resin is preferably 90 mol% or less, more preferably 70 mol% or less, further preferably 50 mol% or less, especially preferably 30 mol% or less, and n is 1. It is preferable to express it as equation (3) in the case of ~4. If the above upper limit or less of G ³ of the polyimide resin is expressed by equation (3) when n is 1 to 4, the viscosity of the resin varnish is increased by suppressing thickening due to hydrogen bonding between amide bonds derived from equation (3). can be suppressed, making processing of the optical film easy.

In a preferred embodiment of the present invention, G ³ in the polyimide resin is preferably 30 mol% or more, more preferably 50 mol% or more, particularly preferably 70 mol% or more, and n is 0 to 70 mol%. In the case of 4, it is expressed as equation (3). If the above lower limit of G ³ of the polyimide resin or more is expressed by equation (3) when n is 0 to 4, the optical film can exhibit high surface hardness and impact resistance, and at the same time have high bending resistance. there is. Moreover, it is preferable that G ³ in the polyimide resin, preferably 100 mol% or less, is represented by formula (3) when n is 0 to 4. If G ³ of the polyimide resin is below the above upper limit, expressed by equation (3) when n is 0 to 4, thickening due to hydrogen bonding between amide bonds derived from equation (3) is suppressed, and the resin varnish Viscosity can be suppressed, making processing of the optical film easy. In addition, the ratio of the structural unit represented by formula (3) in the polyimide resin can be measured using, for example, ¹ H-NMR, or can also be calculated from the introduction ratio of the raw materials.

In a preferred embodiment of the present invention, at least a portion of the plurality of A and A ³ in formulas (10) and (13) is expressed in formula (4):

[In formula (4), R ¹⁰ to R ¹⁷ each independently represent a hydrogen atom, an alkyl group with 1 to 6 carbon atoms, or an aryl group with 6 to 12 carbon atoms, and the hydrogen atoms contained in R ¹⁰ to R ¹⁷ each independently represent a halogen. It may be substituted with an atom, * indicates a bond]

It is a structural unit represented by . If at least a portion of A and A ³ in formulas (10) and (13) is a group represented by formula (4), the optical film can exhibit high surface hardness and impact resistance, and has high transparency. You can.

In formula (4), R ¹⁰ , R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ and R ¹⁷ are each independently a hydrogen atom, an alkyl group with 1 to 6 carbon atoms, or an aryl group with 6 to 12 carbon atoms. It represents energy. Examples of the alkyl group having 1 to 6 carbon atoms or the aryl group having 6 to 12 carbon atoms include those exemplified as the alkyl group having 1 to 6 carbon atoms or the aryl group having 6 to 12 carbon atoms in Formula (3). R ¹⁰ to R ¹⁷ each independently preferably represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and more preferably represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, wherein R ¹⁰ to R ¹⁷ are included. Each hydrogen atom may be independently substituted with a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. R ¹⁰ to R ¹⁷ are each independently independently a hydrogen atom, a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, from the viewpoint of the surface hardness, impact resistance, transparency and bending resistance of the optical film, and are particularly preferred. Specifically, R ¹⁰ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ and R ¹⁶ are hydrogen atoms, R ¹¹ and R ¹⁷ are hydrogen atoms, methyl groups, fluoro groups, chloro groups or trifluoromethyl groups, especially R ¹¹ and R ¹⁷ is preferably a methyl group or a trifluoromethyl group.

In a preferred embodiment of the present invention, the structural unit represented by formula (4) is expressed by formula (4'):

It is a structural unit represented by , that is, at least a part of a plurality of A and A ³ is a structural unit represented by formula (4'). In this case, the optical film exhibits high transparency, and at the same time, the solubility of the resin in the solvent is improved by the skeleton containing the fluorine element, the viscosity of the resin varnish can be suppressed low, and the optical film can be processed. It can be done easily.

In a preferred embodiment of the present invention, preferably 30 mol% or more, more preferably 50 mol% or more, and still more preferably 70 mol% or more of A and A ³ in the resin are represented by formula (4), especially It appears as equation (4'). When A and A ³ within the above range in the resin are expressed by formula (4), especially formula (4'), the optical film exhibits high transparency and at the same time, the resin has a skeleton containing a fluorine element. The solubility in the solvent can be improved, the viscosity of the resin varnish can be suppressed low, and the processing of the optical film can be facilitated. Also, preferably, 100 mol% or less of A and A ³ in the resin is represented by formula (4), especially formula (4'). A and A ³ in the above resin may be of formula (4), especially formula (4'). The ratio of the structural units represented by the formula (4) of A and A ³ in the resin can be measured, for example, using ¹ H-NMR, or calculated from the introduction ratio of the raw materials.

In a preferred embodiment of the present invention, at least a portion of the plurality of Gs in formula (10) is expressed in formula (5):

[In formula (5), R ¹⁸ to R ²⁵ each independently represent a hydrogen atom, an alkyl group with 1 to 6 carbon atoms, or an aryl group with 6 to 12 carbon atoms, and the hydrogen atoms contained in R ¹⁸ to R ²⁵ each independently represent a halogen. It may be substituted with an atom, * indicates a bond]

It is a structural unit represented by . When at least part of the plurality of Gs in the formula (10) is a group represented by the formula (5), the optical film exhibits high transparency, improves the solubility of the polyimide resin in the solvent, and reduces the viscosity of the resin varnish. can be suppressed to a low level, and processing of the optical film can be facilitated.

In formula (5), R ¹⁸ , R ¹⁹ , R ²⁰ , R ²¹ , R ²² , R ²³ , R ²⁴ and R ²⁵ are each independently a hydrogen atom, an alkyl group with 1 to 6 carbon atoms, or an aryl group with 6 to 12 carbon atoms. It represents energy. Examples of the alkyl group having 1 to 6 carbon atoms or the aryl group having 6 to 12 carbon atoms include those exemplified as the alkyl group having 1 to 6 carbon atoms or the aryl group having 6 to 12 carbon atoms in Formula (3). R ¹⁸ to R ²⁵ each independently preferably represent a hydrogen atom or an alkyl group with 1 to 6 carbon atoms, and more preferably represent a hydrogen atom or an alkyl group with 1 to 3 carbon atoms, wherein R ¹⁸ to R ²⁵ are included. Each hydrogen atom may be independently substituted with a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. R ¹⁸ to R ²⁵ each independently are more preferably a hydrogen atom, a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, from the viewpoint of easily improving the surface hardness, bending resistance and transparency of the optical film. More preferably, R ¹⁸ , R ¹⁹ , R ²⁰ , R ²³ , R ²⁴ and R ²⁵ are hydrogen atoms, and R ²¹ and R ²² are hydrogen atoms, methyl groups, fluoro groups, chloro groups or trifluoromethyl groups, especially R ²¹ and R ²² are preferably methyl or trifluoromethyl.

In a preferred embodiment of the present invention, the structural unit represented by formula (5) is expressed by formula (5'):

It is a structural unit represented by , that is, at least a part of the plurality of Gs is a structural unit represented by formula (5'). In this case, the optical film can have high transparency.

In a preferred embodiment of the present invention, G in the polyimide resin is preferably 50 mol% or more, more preferably 60 mol% or more, and still more preferably 70 mol% or more according to formula (5), especially It appears as equation (5'). When G within the above range in the polyimide-based resin is expressed by formula (5), especially formula (5'), the optical film can have high transparency, and the polyimide can further be formed by a skeleton containing a fluorine element. The solubility of the system resin in a solvent can be improved, the viscosity of the resin varnish can be suppressed low, and the production of an optical film is easy. Also, preferably, 100 mol% or less of G in the polyimide resin is represented by formula (5), especially formula (5'). G in the polyimide resin may be of the formula (5), particularly of the formula (5'). The ratio of the structural unit represented by the formula (5) of G in the polyimide resin can be measured using, for example, ¹ H-NMR, or can be calculated from the introduction ratio of the raw materials.

In one embodiment of the present invention, the polyimide resin includes diamine and tetracarboxylic acid compounds (tetracarboxylic acid compound analogs such as acid chloride compounds and tetracarboxylic dianhydride), If necessary, dicarboxylic acid compounds (dicarboxylic acid compound analogs such as acid chloride compounds), tricarboxylic acid compounds (tricarboxylic acid compound analogs such as acid chloride compounds and tricarboxylic acid anhydride), etc. It is a condensation type polymer obtained by reacting (polycondensation) with . The repeating structural unit represented by formula (10) or formula (11) is usually derived from diamine and tetracarboxylic acid compounds. The repeating structural unit represented by formula (12) is usually derived from diamine and tricarboxylic acid compounds. The repeating structural unit represented by formula (13) is usually derived from diamine and dicarboxylic acid compounds.

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

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 individually, or two or more types may be used together. 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 aromatic tetracarboxylic dianhydride include 4,4'-oxydiphthalic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 2,2',3,3'- Benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride (sometimes written as BPDA), 2,2',3,3'-biphenyltetra Carboxylic dianhydride, 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis( 2,3-dicarboxyphenyl)propane dianhydride, 2,2-bis(3,4-dicarboxyphenoxyphenyl)propane dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride ( 6FDA), 1,2-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,2-bis(3,4-di) Carboxyphenyl)ethane dianhydride, 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, 4,4'-(p-phenylenedioxy)diphthalic dianhydride, and 4,4'-(m-phenylenedioxy)diphthalic dianhydride (6FDA). These can be used individually or in combination of two or more types.

Examples of aliphatic tetracarboxylic dianhydride include cyclic or acyclic aliphatic tetracarboxylic dianhydride. Cyclic aliphatic tetracarboxylic dianhydride is tetracarboxylic dianhydride having an alicyclic hydrocarbon structure, and specific examples thereof include 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2, Cycloalkane tetracarboxylic dianhydrides such as 3,4-cyclobutane tetracarboxylic dianhydride and 1,2,3,4-cyclopentane tetracarboxylic dianhydride, bicyclo[2.2.2]oct-7 -N-2,3,5,6-tetracarboxylic dianhydride, dicyclohexyl-3,3'-4,4'-tetracarboxylic dianhydride, and positional isomers thereof. These can be used individually or in combination of two or more types. Specific examples of acyclic aliphatic tetracarboxylic dianhydride include 1,2,3,4-butanetetracarboxylic dianhydride, 1,2,3,4-pentanetetracarboxylic dianhydride, and these Can be used alone or in combination of two or more types. Additionally, cyclic aliphatic tetracarboxylic dianhydride and acyclic aliphatic tetracarboxylic dianhydride may be used in combination.

Among the tetracarboxylic dianhydrides, from the viewpoint of high transparency and low discoloration, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, bicyclo[2.2.2]oct-7-en-2, 3,5,6-tetracarboxylic dianhydride and 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride, and mixtures thereof are preferred. Moreover, as tetracarboxylic acid, you may use the water adduct of the anhydride of the said tetracarboxylic acid compound.

Examples of the tricarboxylic acid compound include aromatic tricarboxylic acid, aliphatic tricarboxylic acid, and their related acid chloride compounds and acid anhydrides. Two or more types may be used in combination. Specific examples include anhydride of 1,2,4-benzenetricarboxylic acid; 2,3,6-naphthalenetricarboxylic acid-2,3-anhydride; Examples include compounds in which phthalic anhydride and benzoic acid are linked by a single bond, -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ -, or a phenylene group.

Examples of the dicarboxylic acid compound include aromatic dicarboxylic acid, aliphatic dicarboxylic acid, and their related acid chloride compounds and acid anhydrides, and two or more types thereof may be used in combination. Specific examples thereof include terephthalic acid dichloride; isophthalic acid dichloride; naphthalenedicarboxylic acid chloride; 4,4'-biphenyldicarboxylic acid chloride; 3,3'-biphenyldicarboxylic acid chloride; 4,4'-oxybis(benzoylchloride) (OBBC); A dicarboxylic acid compound of a chain hydrocarbon having 8 or less carbon atoms and two benzoic acids bonded together, -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ -, or phenyl Examples include compounds linked to a ren group. Among these dicarboxylic acid compounds, terephthaloyl chloride and 4,4'-oxybis(benzoyl chloride) are more preferable. These dicarboxylic acids can be used individually or in combination of two or more types.

Examples of diamine include aliphatic diamine, aromatic diamine, and mixtures thereof. In addition, in this embodiment, “aromatic diamine” refers to a diamine in which an amino group is directly bonded to an aromatic ring, and a part of its structure may contain an aliphatic group or other substituent. The aromatic ring may be a single ring or a condensed ring, and examples include, but are not limited to, a benzene ring, a naphthalene ring, an anthracene ring, and a fluorene ring. Among these, it is preferable that the aromatic ring is a benzene ring. Additionally, “aliphatic diamine” refers to a diamine in which an amino group is directly bonded to an aliphatic group, and a part of its structure may contain an aromatic ring or other substituents.

Examples of aliphatic diamine include acyclic aliphatic diamine such as hexamethylenediamine, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, norbornanediamine, 4,4' -Cyclic aliphatic diamines such as diaminodicyclohexylmethane, etc. can be mentioned. These can be used individually or in combination of two or more types.

As aromatic diamine, for example, p-phenylenediamine, m-phenylenediamine, 2,4-toluenediamine, m-xylylenediamine, p-xylylenediamine, 1,5-diaminonaphthalene, 2,6 -Aromatic diamines having one aromatic ring, such as diaminonaphthalene; 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-dia Minodiphenyl ether, 4,4'-diaminodiphenylsulfone, 3,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, 1,4-bis(4-aminophenoxy) Benzene, 1,3-bis(4-aminophenoxy)benzene, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]sulfone, 2,2- Bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2'-dimethylbenzidine, 2,2'-bis(tri) Fluoromethyl)benzidine (2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl (TFMB)), 4,4'-bis(4-aminophenoxy)biphenyl, 9 ,9-bis(4-aminophenyl)fluorene, 9,9-bis(4-amino-3-methylphenyl)fluorene, 9,9-bis(4-amino-3-chlorophenyl)fluorene, 9, Aromatic diamines having two or more aromatic rings, such as 9-bis(4-amino-3-fluorophenyl)fluorene, can be mentioned. These can be used individually or in combination of two or more types.

Among the above diamines, from the viewpoint of high transparency and low discoloration, it is preferable to use at least one type selected from the group consisting of aromatic diamines having a biphenyl structure. Consisting of 2,2'-dimethylbenzidine, 2,2'-bis(trifluoromethyl)benzidine, 4,4'-bis(4-aminophenoxy)biphenyl, and 4,4'-diaminodiphenyl ether. It is more preferable to use one or more types selected from the group, and it is even more preferable to use 2,2'-bis(trifluoromethyl)benzidine.

The polyimide resin is obtained by mixing each raw material such as the diamine, tetracarboxylic acid compound, tricarboxylic acid compound, and dicarboxylic acid compound by a conventional method, for example, stirring. The intermediate can be obtained by imidizing the intermediate in the presence of an imidization catalyst and, if necessary, a dehydrating agent. Polyamide-based resin can be obtained by mixing each raw material such as the diamine and dicarboxylic acid compound using a conventional method, for example, stirring.

The imidization catalyst used in the imidization step is not particularly limited, and examples include aliphatic amines such as tripropylamine, dibutylpropylamine, and ethyldibutylamine; Alicyclic amines (monocyclic) such as N-ethylpiperidine, N-propylpiperidine, N-butylpyrrolidine, N-butylpiperidine, and N-propylhexahydroazepine; Alicyclic amines (polycyclic) such as azabicyclo[2.2.1]heptane, azabicyclo[3.2.1]octane, azabicyclo[2.2.2]octane, and azabicyclo[3.2.2]nonane; And 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 2-ethylpyridine, 3-ethylpyridine, 4-ethylpyridine, 2,4-dimethylpyridine, 2,4,6-trimethylpyridine, 3,4 -Aromatic amines such as cyclopentenopyridine, 5,6,7,8-tetrahydroisoquinoline, and isoquinoline can be mentioned.

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

In the mixing and imidization process of each raw material, the reaction temperature is not particularly limited, but is, for example, 15 to 350°C, preferably 20 to 100°C. The reaction time is also not particularly limited, but is, for example, about 10 minutes to 10 hours. If necessary, the reaction may be performed under inert atmosphere or reduced pressure conditions. Additionally, the reaction may be performed in a solvent, and examples of the solvent include those exemplified as solvents used in the preparation of varnish. After the reaction, the polyimide-based resin or polyamide-based resin is purified. As a purification method, for example, a poor solvent is added to the reaction solution, the resin is precipitated by reprecipitation, dried, the precipitate is taken out, and if necessary, the precipitate is washed with a solvent such as methanol and dried. there is.

In addition, for the production of polyimide-based resin, you may refer to the production method described in, for example, Japanese Patent Application Laid-Open No. 2006-199945 or Japanese Patent Application Publication No. 2008-163107. In addition, commercial products can also be used as the polyimide resin. Specific examples include Neoprem (registered trademark) manufactured by Mitsubishi Gas Chemical Company, Inc., Kawamura Sangyo Co., Ltd. Co., Ltd.) KPI-MX300F, etc. can be mentioned.

The weight average molecular weight of the polyimide resin or polyamide resin is preferably 100,000 or more, more preferably 150,000 or more, further preferably 200,000 or more, even more preferably 250,000 or more, especially preferably 300,000 or more. , preferably 600,000 or less, more preferably 500,000 or less. The larger the weight average molecular weight of the polyimide-based resin or polyamide-based resin, the easier it is to develop high impact resistance and bending resistance when formed into a film. For this reason, from the viewpoint of easily improving the impact resistance and bending resistance of the optical film, it is preferable that the weight average molecular weight is more than the above lower limit. On the other hand, the smaller the weight average molecular weight of the polyimide-based resin or polyamide-based resin, the easier it is to lower the viscosity of the varnish and the easier it is to improve processability. Additionally, the stretchability of polyimide-based resin or polyamide-based resin tends to be easily improved. For this reason, from the viewpoint of processability and stretchability, it is preferable that the weight average molecular weight is below the above upper limit. In addition, in this application, the weight average molecular weight can be determined by performing gel permeation chromatography (GPC) measurement and converted to standard polystyrene, and can be calculated, for example, by the method described in the Examples.

The imidization rate of the polyimide resin is preferably 95 to 100%, more preferably 97 to 100%, further preferably 98 to 100%, and particularly preferably 100%. From the viewpoint of the stability of the varnish and the mechanical properties of the resulting optical film, it is preferable that the imidization ratio is at least the above lower limit. Additionally, the imidization rate can be determined by IR method, NMR method, etc. From the above viewpoint, it is preferable that the imidation rate of the polyimide-based resin contained in the varnish is within the above range.

In a preferred embodiment of the present invention, the polyimide-based resin or polyamide-based resin contained in the optical film of the present invention contains, for example, a halogen atom such as a fluorine atom that can be introduced by the above-mentioned fluorine-containing substituent, etc. You may include . When the polyimide-based resin or polyamide-based resin contains a halogen atom, it is easy to improve the impact resistance and elastic modulus of the optical film and reduce the yellowness (YI value). When the impact resistance and elastic modulus of the optical film are high, it is easy to suppress the occurrence of scratches and wrinkles in the film, and when the yellowness of the optical film is low, it is easy to improve the transparency of the film. The halogen atom is preferably a fluorine atom. Preferred fluorine-containing substituents for making the polyimide resin or polyamide resin contain a fluorine atom include, for example, a fluoro group and a trifluoromethyl group.

The content of halogen atoms in the polyimide resin or polyamide resin is preferably 1 to 40% by mass, more preferably 5 to 40% by mass, based on the mass of the polyimide resin or polyamide resin. % by mass, and more preferably 5 to 30 % by mass. If the halogen atom content is 1% by mass or more, the impact resistance and elastic modulus when formed into a film are further improved, the water absorption is lowered, the yellowness (YI value) is further reduced, and transparency is easily improved. If the halogen atom content exceeds 40% by mass, synthesis may become difficult.

When the polyimide resin is polyamideimide, the content of the structural unit represented by formula (13) is preferably 0.1 mol or more, more preferably 0.5 mol or more, per 1 mole of the structural unit represented by formula (10). , more preferably 1.0 mol or more, particularly preferably 1.5 mol or more, preferably 6.0 mol or less, more preferably 5.0 mol or less, further preferably 4.5 mol or less. If the content of the structural unit represented by Formula (13) is more than the above lower limit, the optical film is likely to exhibit high surface hardness, impact resistance, and bending resistance. Additionally, if the content of the structural unit represented by formula (13) is below the above upper limit, thickening due to hydrogen bonding between amide bonds in formula (13) can be suppressed, and the viscosity of the resin varnish can be reduced, making it possible to manufacture an optical film. It's easy.

In one embodiment of the present invention, the content of polyimide resin and/or polyamide resin in the optical film is preferably 40% by mass or more, more preferably, based on the total mass of the optical film. is 50% by mass or more, more preferably 70% by mass or more. It is preferable that the content of polyimide-based resin and/or polyamide-based resin is more than the above lower limit from the viewpoint of easily improving impact resistance, bending resistance, etc. In addition, the content of polyimide-based resin and/or polyamide-based resin in the optical film is usually 100% by mass or less based on the total mass of the optical film.

<Filler>

The optical film of the present invention may contain a filler. Examples of fillers include organic particles and inorganic particles, and inorganic particles are particularly preferable. Inorganic particles include metal oxide particles such as silica, zirconia, alumina, titania, zinc oxide, germanium oxide, indium oxide, tin oxide, indium tin oxide (ITO), antimony oxide, and cerium oxide, magnesium fluoride, sodium fluoride, etc. Metal fluoride particles, etc. can be mentioned, and among these, silica particles, zirconia particles, and alumina particles are preferable, and silica particles are especially preferable, from the viewpoint of easily suppressing deterioration of optical properties due to repeated collisions with objects. These fillers can be used individually or in combination of two or more types.

The primary particle diameter of the filler, preferably silica particles, is preferably 1 nm or more, more preferably 3 nm or more, further preferably 5 nm or more, particularly preferably 7 nm or more, preferably 25 nm or less, more preferably It is 20 nm or less, more preferably 15 nm or less, even more preferably 12 nm or less, particularly preferably less than 12 nm, and a combination of these upper and lower limits may be used. If the primary particle diameter of the silica particles is more than the above lower limit, agglomeration of silica particles is easily suppressed and the optical properties of the optical film are easily improved, and if the primary particle size of the silica particles is less than the above upper limit, it is easy to suppress deterioration of optical properties due to repeated collisions with objects. . The primary particle size of the filler can be measured by the BET method. Additionally, the primary particle diameter (average primary particle diameter) of the filler may be measured by image analysis using a transmission electron microscope (TEM) or scanning electron microscope (SEM).

In a preferred embodiment of the present invention, the optical film contains a polyamide-based resin and a filler having a primary particle size of 1 to 25 nm. Additionally, in a preferred embodiment of the present invention, the optical film contains a polyimide resin and a filler having a primary particle size of 5 to 20 nm. The optical film in these preferred embodiments can effectively suppress degradation of optical properties due to repeated object collisions.

The content of the filler, preferably silica particles, is preferably 1% by mass or more, more preferably 5% by mass or more, further preferably 10% by mass or more, particularly preferably 20% by mass, relative to the mass of the optical film. % or more, preferably 60 mass% or less, more preferably 50 mass% or less, further preferably 45 mass% or less, especially preferably 40 mass% or less, and a combination of these upper and lower limits may be used. If the content of the filler is more than the above lower limit, it is easy to improve the impact resistance of the optical film, and if it is less than the above upper limit, it is easy to improve the optical properties of the optical film. In addition, by adjusting the composition of the optical film, for example, the type and composition ratio of the repeating structure of the resin contained in the optical film, and the type, primary particle size and content, etc. of fillers contained in the optical film, the impact resistance test is performed. The amount of indentation can be adjusted to 15μm or less.

The optical film of the present invention may contain additives other than the resin and the filler. Other additives include, for example, leveling agents, antioxidants, ultraviolet absorbers, bluing agents, plasticizers, surfactants, etc. These other additives can be used individually or in combination of two or more types. When the optical film contains other additives, the content of the other additives may be, for example, 0.01 to 20 parts by mass, preferably 0.1 to 10 parts by mass, relative to the mass of the optical film.

[Method for manufacturing optical film]

The optical film of the present invention is not particularly limited, but for example, the following processes:

(a) A process of preparing a liquid (sometimes called varnish) containing the above resin and, if necessary, the above filler and the above other additives (varnish preparation process),

(b) a process of applying varnish to a substrate to form a coating film (application process), and

(c) Process of drying the applied liquid (coat film) to form an optical film (optical film formation process)

It can be manufactured by a method comprising:

In the varnish preparation step, the varnish is prepared by dissolving the resin in a solvent, adding the filler and other additives as necessary, and stirring and mixing. In addition, when using silica particles as a filler, a silica sol dispersion of silica sol containing silica particles may be replaced with a solvent in which the resin can dissolve, for example, a solvent used in the preparation of the varnish below, and added to the resin. do.

The solvent used to prepare the varnish is not particularly limited as long as it can dissolve the resin. Examples of such solvents include amide-based solvents such as N,N-dimethylacetamide and N,N-dimethylformamide; Lactone-based solvents such as γ-butyrolactone and γ-valerolactone; Sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide, and sulfolane; Carbonate-based solvents such as ethylene carbonate and propylene carbonate; and combinations thereof. Among these, amide-based solvents or lactone-based solvents are preferable. These solvents can be used individually or in combination of two or more types. Additionally, the varnish may contain water, alcohol-based solvent, ketone-based solvent, non-cyclic ester-based solvent, ether-based solvent, etc. The solid content concentration of the varnish is preferably 1 to 25% by mass, more preferably 5 to 15% by mass.

In the application process, varnish is applied to the substrate using a known application method to form a coating film. Known application methods include, for example, roll coating methods such as wire bar coating method, reverse coating, and gravure coating, die coating method, comma coating method, lip coating method, spin coating method, screen coating method, fountain coating method, and di-coating method. Examples include the spraying method, spraying method, and soft forming method.

In the optical film formation process, the optical film can be formed by drying the coating film and peeling it from the substrate. After peeling, a drying process of additionally drying the optical film may be performed. Drying of the coating film can usually be performed at a temperature of 50 to 350°C. If necessary, the coating film may be dried in an inert atmosphere or under reduced pressure conditions.

Examples of the substrate include PET film, PEN film, other polyimide resins, or polyamide resin films. Among them, PET film, PEN film, etc. are preferable from the viewpoint of excellent heat resistance, and PET film is more preferable from the viewpoint of adhesion to the optical film and cost.

The use of the optical film of the present invention is not particularly limited, and it may be used for various purposes. As explained above, the optical film of the present invention may be a single layer or a laminated body. The optical film of the present invention may be used as is or may be used as a laminated body with another film. Additionally, when the optical film is a laminated body, all layers laminated on one or both sides of the optical film are referred to as the optical film.

When the optical film of the present invention is a laminate, it is preferable to have one or more functional layers on at least one side of the optical film. Examples of the functional layer include an ultraviolet absorbing layer, a primer layer, a gas barrier layer, an adhesive layer, a color adjustment layer, a refractive index adjustment layer, and a hard coating layer. The functional layer can be used alone or in combination of two or more types.

The ultraviolet absorbing layer is a layer that has the function of absorbing ultraviolet rays, and is composed, for example, of a base selected from ultraviolet curing transparent resin, electron beam curing transparent resin, and thermosetting transparent resin, and an ultraviolet absorber dispersed in this base. do.

The adhesive layer is a layer that has an adhesive function and has the function of adhering the optical film to another member. As a forming material for the adhesive layer, commonly known materials can be used. For example, a thermosetting resin composition or a photocurable resin composition can be used. In this case, the thermosetting resin composition or the photo-curable resin composition can be polymerized and cured by supplying energy afterwards.

The adhesive layer may be a layer that is adhered to an object by pressure, called a pressure sensitive adhesive (PSA). The pressure-sensitive adhesive may be an adhesive that is “a substance that has tackiness at room temperature and adheres to the adherend under light pressure” (JIS K 6800), or may be an adhesive that contains “specific ingredients in a protective film (microcapsule) and is applied by appropriate means (pressure). , heat, etc.) may be a capsule-type adhesive that is capable of maintaining stability until the film is destroyed (JIS K 6800).

The color adjustment layer is a layer that has a color adjustment function and is a layer that can adjust the optical film to the target color. The color adjustment layer is a layer containing, for example, a resin and a colorant. Examples of this colorant include inorganic pigments such as titanium oxide, zinc oxide, bengala, titanium oxide-based fired pigments, ultramarine blue, cobalt aluminate, and carbon black; Organic pigments such as azo-based compounds, quinacridone-based compounds, anthraquinone-based compounds, perylene-based compounds, isoindolinone-based compounds, phthalocyanine-based compounds, quinophthalone-based compounds, thyrene-based compounds, and diketopyrrolopyrrole-based compounds; extender pigments such as barium sulfate and calcium carbonate; and dyes such as basic dyes, acid dyes, and mordant dyes.

The refractive index adjustment layer is a layer that has the function of adjusting the refractive index. For example, it has a refractive index different from that of a single-layer optical film, and is a layer that can provide a predetermined refractive index to the optical film. The refractive index adjustment layer may be, for example, a resin layer containing an appropriately selected resin and, in some cases, a pigment further, or may be a thin film of metal. Pigments that adjust the refractive index include, for example, silicon oxide, aluminum oxide, antimony oxide, tin oxide, titanium oxide, zirconium oxide, and tantalum oxide. The average primary particle diameter of the pigment may be 0.1 μm or less. By setting the average primary particle diameter of the pigment to 0.1 μm or less, diffuse reflection of light passing through the refractive index adjustment layer can be prevented and a decrease in transparency can be prevented. Metals used in the refractive index adjustment layer include, for example, titanium oxide, tantalum oxide, zirconium oxide, zinc oxide, tin oxide, silicon oxide, indium oxide, titanium oxynitride, titanium nitride, silicon oxynitride, and silicon nitride. Metal oxides or metal nitrides may be mentioned.

The hard coating layer can be formed by curing a hard coating composition containing a reactive material capable of forming a crosslinked structure by irradiation of active energy rays or application of thermal energy, preferably by irradiation of active energy rays. Active energy rays are defined as energy rays that can generate active species by decomposing compounds that generate active species, and include visible light, ultraviolet rays, infrared rays, X-rays, α-rays, β-rays, γ-rays, and electron rays. and, preferably, ultraviolet rays. The hard coating composition contains at least one type of polymer of a radically polymerizable compound and a cationically polymerizable compound.

The radically polymerizable compound is a compound having a radically polymerizable group. The radical polymerizable group possessed by the radical polymerizable compound may be any functional group capable of generating a radical polymerization reaction, and may include a group containing a carbon-carbon unsaturated double bond, and specifically, vinyl group and (meth)acrylic group. Examples include Roilgi and the like. Additionally, when the radically polymerizable compound has two or more radically polymerizable groups, these radically polymerizable groups may be the same or different. The number of radically polymerizable groups that the radically polymerizable compound has in one molecule is preferably two or more from the viewpoint of improving the hardness of the hard coat layer. The radically polymerizable compound is preferably a compound having a (meth)acryloyl group because of its high reactivity, and specifically, it has 2 to 6 (meth)acryloyl groups per molecule. Compounds called functional acrylate monomers, epoxy (meth)acrylates, urethane (meth)acrylates, and polyester (meth)acrylates are oligomers with a molecular weight of hundreds to thousands of (meth)acryloyl groups within the molecule. and, preferably, at least one selected from 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, oxetanyl group, or vinyl ether group. The number of cationic polymerizable groups in one molecule of the cationically polymerizable compound is preferably 2 or more, more preferably 3 or more, from the viewpoint of improving the hardness of the hard coat layer.

Moreover, as the said cationically polymerizable compound, a compound which has at least 1 type of an epoxy group and an oxetanyl group as a cationic polymerizable group is especially preferable. Cyclic ether groups such as epoxy groups and oxetanyl groups are preferable because shrinkage accompanying the polymerization reaction is small. In addition, the compound having an epoxy group among the cyclic ether groups has the advantage that it is easy to obtain compounds of various structures, does not adversely affect the durability of the obtained hard coating layer, and is easy to control compatibility with radically polymerizable compounds. there is. In addition, the oxetanyl group among the cyclic ether groups tends to have a higher degree of polymerization compared to the epoxy group, has low toxicity, accelerates the rate of network formation from the cationically polymerizable compound in the obtained hard coating layer, and does not react even in the area where it is mixed with the radically polymerizable compound. There are advantages such as forming an independent network without leaving monomers in the film.

As a cationically polymerizable compound having an epoxy group, for example, a polyglycidyl ether of a polyhydric alcohol having an alicyclic ring or a cyclohexene ring- or cyclopentene ring-containing compound can be epoxidized with a suitable oxidizing agent such as hydrogen peroxide or peracid. a cycloaliphatic epoxy resin obtained by; Aliphatic epoxy resins such as polyglycidyl ethers of aliphatic polyhydric alcohols or their alkylene oxide adducts, polyglycidyl esters of aliphatic long-chain polybasic acids, and homopolymers and copolymers of glycidyl (meth)acrylate; Glycidyl ether produced by the reaction of bisphenols such as bisphenol A, bisphenol F, and hydrogenated bisphenol A, or their derivatives such as alkylene oxide adducts and caprolactone adducts, and epichlorohydrin, and Examples include rockfish epoxy resins and glycidyl ether type epoxy resins derived from bisphenols.

The hard coating composition may further include a polymerization initiator. Examples of the polymerization initiator include radical polymerization initiators, cationic polymerization initiators, radical and cationic polymerization initiators, and are appropriately selected and used. These polymerization initiators are decomposed by at least one of active energy ray irradiation and heating to generate radicals or cations to advance radical polymerization and cationic polymerization.

The radical polymerization initiator may be capable of releasing a substance that initiates radical polymerization by at least one of active energy ray irradiation and heating. For example, examples of the thermal radical polymerization initiator include organic peroxides such as hydrogen peroxide and perbenzoic acid, and azo compounds such as azobisbutyronitrile.

Active energy ray radical polymerization initiators include Type 1 radical polymerization initiators, which generate radicals by decomposition of molecules, and Type 2 radical polymerization initiators, which coexist with tertiary amines and generate radicals through hydrogen abstraction-type reactions. Or it is used in combination.

The cationic polymerization initiator may be capable of releasing a substance that initiates cationic polymerization by at least one of active energy ray irradiation and heating. As a cationic polymerization initiator, aromatic iodonium salt, aromatic sulfonium salt, cyclopentadienyl iron(II) complex, etc. can be used. Depending on the difference in structure, cationic polymerization can be initiated by either or both irradiation of active energy rays or heating.

The content of the polymerization initiator is preferably 0.1 to 10% by mass based on 100% by mass of the total hard coating composition. If the content of the polymerization initiator is within the above range, curing can be sufficiently progressed, and the mechanical properties and adhesion of the finally obtained coating film can be within a good range. In addition, poor adhesion, cracking, and curling phenomenon due to curing shrinkage can be prevented. This tends to become more difficult to occur.

The hard coating composition may further include one or more selected from the group consisting of solvents and additives.

The solvent can dissolve or disperse the polymerizable compound and the polymerization initiator, and can be used as long as it is known as a solvent for hard coating compositions in the present technical field, as long as it does not impair the effect of the present invention.

The additives may further include inorganic particles, leveling agents, stabilizers, surfactants, antistatic agents, lubricants, antifouling agents, etc.

The thickness of the hard coating layer is not particularly limited, and may be, for example, 2 to 100 μm. If the thickness of the hard coating layer is within the above range, sufficient scratch resistance can be secured, bending resistance is unlikely to decrease, and the problem of curling due to curing shrinkage tends to be unlikely to occur.

The optical film may further include a protective film. The protective film may be laminated on one side or both sides of the optical film. When the optical film has a functional layer on one side, the protective film may be laminated on the surface on the optical film side or the surface on the functional layer side, or may be laminated on both the optical film side and the functional layer side. When the optical film has functional layers on both surfaces, the protective film may be laminated on the surface on one functional layer side, or may be laminated on the surfaces on both functional layer sides. The protective film is a film for temporarily protecting the surface of the optical film or functional layer, and is not particularly limited as long as it is a peelable film that can protect the surface of the optical film or functional layer. Examples of the protective film include polyester resin films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; Examples include polyolefin-based resin films such as polyethylene and polypropylene films, and acrylic-based resin films, and are preferably selected from the group consisting of polyolefin-based resin films, polyethylene terephthalate-based resin films, and acrylic resin films. When the optical film has two protective films, each protective film may be the same or different.

The thickness of the protective film is not particularly limited, but is usually 10 to 100 μm, preferably 10 to 80 μm, and more preferably 10 to 50 μm. When the optical film has two protective films, the thickness of each protective film may be the same or different.

Since the optical film of the present invention can maintain excellent optical properties even when an object collides with the surface, it can be suitably used as an optical film in image display devices and the like. The optical film of the present invention is preferably useful as a front panel of an image display device, particularly a front panel (window film) of a flexible image display device (flexible display). A flexible display has, for example, a flexible functional layer and an optical film that is laminated on the flexible functional layer and functions as a front plate. That is, the front plate of the flexible display is disposed on the viewer side above the flexible functional layer. This front plate has the function of protecting the flexible functional layer.

Examples of image display devices include televisions, smart phones, mobile phones, car navigation systems, tablet PCs, portable game consoles, electronic papers, indicators, bulletin boards, watches, and wearable devices such as smart watches. Flexible displays are all image display devices that have flexible characteristics.

[Flexible image display device]

The present invention includes a flexible image display device comprising the optical film of the present invention. As described above, the optical film of the present invention is preferably used as a front plate in a flexible image display device, and the front plate may be called a window film. The flexible image display device is made of a flexible image display device laminate and an organic EL display panel. The flexible image display device laminate is disposed on the viewing side with respect to the organic EL display panel and is configured to be bendable. The laminate for a flexible image display device may contain a window film, a polarizer, and a touch sensor, and the order of stacking them is arbitrary; however, the order of the window film, polarizer, and touch sensor or the window film, touch sensor, and polarizer from the viewing side. It is preferable that they are laminated. The presence of a polarizing plate on the viewing side of the touch sensor is preferable because it makes it difficult for the pattern of the touch sensor to be recognized and visibility of the displayed image improves. Each member can be laminated using adhesives, adhesives, etc. Additionally, a light-shielding pattern may be formed on at least one surface of any one of the window film, polarizer, and touch sensor layers.

[Polarizer]

As described above, the flexible image display device of the present invention contains a polarizing plate, preferably a circularly polarizing plate. The circularly polarizing plate is a functional layer that transmits only right-handed or left-handed circularly polarized light components by laminating a λ/4 retardation plate on a linear polarizing plate. For example, it is used to convert external light into right-circularly polarized light, block left-circularly polarized external light reflected from the organic EL panel, and transmit only the organic EL luminescence component to suppress the influence of reflected light and make images easier to see. In order to achieve the circular polarization function, the absorption axis of the linear polarizer and the slow axis of the λ/4 retardation plate need to be 45° in theory, but in practice, they are 45±10°. The linear polarizer and the λ/4 retardation plate do not necessarily have to be stacked adjacently, and the relationship between the absorption axis and the slow axis just needs to satisfy the range described above. Although it is desirable to achieve complete circular polarization in the radio wave field, in practical terms it is not necessarily necessary, so the circular polarizer in the present invention also includes an elliptically polarizer. It is also preferable to further laminate a λ/4 phase difference film on the viewing side of the linear polarizer to change the emitted light into circularly polarized light to improve visibility when wearing polarized sunglasses.

A linear polarizer is a functional layer that allows light vibrating in the direction of the transmission axis to pass, but blocks polarization of a vibration component perpendicular to it. The linear polarizing plate may be comprised of a linear polarizer alone or a linear polarizer and a protective film attached to at least one surface thereof. The thickness of the linear polarizing plate may be 200 μm or less, and is preferably 0.5 to 100 μm. When the thickness is within the above range, flexibility tends to be difficult to deteriorate.

The linear polarizer may be a film-type polarizer manufactured by dyeing and stretching a polyvinyl alcohol (PVA)-based film. A dichroic dye such as iodine is adsorbed to a PVA-based film oriented by stretching, or is stretched while adsorbed on PVA, so that the dichroic dye is oriented and exhibits polarization performance. In the production of the film-type polarizer, other processes such as swelling, crosslinking with boric acid, washing with an aqueous solution, and drying may be performed. Stretching and dyeing processes may be performed on the PVA-based film alone or in a state where it is laminated with another film such as polyethylene terephthalate. The thickness of the PVA-based film used is preferably 10 to 100 μm, and the stretching ratio is preferably 2 to 10 times.

Additionally, another example of the polarizer may be a liquid crystal application-type polarizer formed by applying a liquid crystal polarizing composition. The liquid crystal polarizing composition may include a liquid crystal compound and a dichroic dye compound. The liquid crystalline compound just needs to have the property of showing a liquid crystal state, and in particular, if it has a high-order alignment state such as a smectic phase, it is preferable because it can exhibit high polarization performance. Moreover, it is preferable that the liquid crystalline compound also has a polymerizable functional group.

The dichroic dye is a dye that exhibits dichroism by aligning with the liquid crystal compound, and the dichroic dye itself may have liquid crystallinity or may have a polymerizable functional group. Some compounds in the liquid crystal polarizing composition have a polymerizable functional group.

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

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

The alignment film can be manufactured, for example, by applying an alignment film-forming composition onto a substrate and imparting orientation by rubbing, polarized light irradiation, etc. The alignment film forming composition may contain a solvent, crosslinking agent, initiator, dispersant, leveling agent, silane coupling agent, etc. in addition to the alignment agent. As the alignment agent, for example, polyvinyl alcohol, polyacrylate, polyamic acid, and polyimide can be used. When applying photo-alignment, it is preferable to use an alignment agent containing a cinnamate group. The weight average molecular weight of the polymer used as the alignment agent may be about 10,000 to 1,000,000. The thickness of the alignment film is preferably 5 to 10,000 nm, more preferably 10 to 500 nm, from the viewpoint of orientation regulation force. The liquid crystal polarizing layer may be peeled from the substrate and transferred and laminated, or may be laminated on the substrate as is. It is also preferable that the substrate serves as a transparent substrate for a protective film, retardation plate, or window.

As the protective film, any transparent polymer film can be used, and materials and additives used in the transparent substrate can be used. Cellulose-based films, olefin-based films, acrylic films, and polyester-based films are preferable. It may be a coating-type protective film obtained by applying and curing a cationic curing composition such as an epoxy resin or a radical curing composition such as an acrylate. If necessary, it may contain plasticizers, ultraviolet absorbers, infrared absorbers, colorants such as pigments and dyes, fluorescent whitening agents, dispersants, heat stabilizers, light stabilizers, antistatic agents, antioxidants, lubricants, solvents, etc. The thickness of the protective film may be 200 μm or less, and is preferably 1 to 100 μm. If the thickness of the protective film is within the above range, the flexibility of the protective film is unlikely to decrease. The protective film can also serve as a transparent substrate for the window.

The λ/4 retardation plate is a film that provides a λ/4 phase difference in a direction perpendicular to the direction of travel of incident light (in-plane direction of the film). The λ/4 retardation plate may be a stretched type retardation plate manufactured by stretching a polymer film such as a cellulose-based film, an olefin-based film, or a polycarbonate-based film. If necessary, it may contain a phase difference adjuster, plasticizer, ultraviolet absorber, infrared absorber, colorant such as pigment or dye, fluorescent whitening agent, dispersant, heat stabilizer, light stabilizer, antistatic agent, antioxidant, lubricant, solvent, etc. The thickness of the stretched phase difference plate may be 200 μm or less, and is preferably 1 to 100 μm. When the thickness is within the above range, the flexibility of the film tends to be difficult to deteriorate.

Additionally, another example of the above λ/4 retardation plate may be a liquid crystal-coated retardation plate formed by applying a liquid crystal composition. The liquid crystal composition includes a liquid crystal compound having properties that exhibit a liquid crystal state such as nematic, cholesteric, or smectic. Some compounds, including liquid crystal compounds in the liquid crystal composition, have a polymerizable functional group. The liquid crystal coated retardation plate may further include an initiator, solvent, dispersant, leveling agent, stabilizer, surfactant, crosslinking agent, silane coupling agent, etc. The liquid crystal coated retardation plate can be manufactured by applying and curing a liquid crystal composition on an alignment film to form a liquid crystal retardation layer, similar to the substrate for the liquid crystal polarizing layer. A liquid crystal-coated retardation plate can be formed to be thinner than a stretched type retardation plate. The thickness of the liquid crystal polarizing layer is usually 0.5 to 10 μm, preferably 1 to 5 μm. The liquid crystal-coated retardation plate may be peeled from the substrate and transferred and laminated, or may be laminated on the substrate as is. It is also preferable that the substrate serves as a transparent substrate for a protective film, retardation plate, or window.

In general, the shorter the wavelength, the greater the birefringence, and the longer the wavelength, the smaller the birefringence. In this case, since a phase difference of λ/4 cannot be achieved in the entire visible light region, it is often designed to have an in-plane phase difference of 100 to 180 nm, preferably 130 to 150 nm, which is λ/4 around 560 nm, where visibility is high. . It is preferable to use an inverse dispersion λ/4 retardation plate using a material with a birefringence wavelength dispersion characteristic opposite to that of usual because it can improve visibility. As such materials, it is also preferable to use those described in Japanese Patent Application Publication No. 2007-232873 for stretched type retardation plates, and those described in Japanese Patent Application Publication No. 2010-30979 for liquid crystal-coated retardation plates.

Additionally, as another method, a technique for obtaining a broadband λ/4 retardation plate by combining it with a λ/2 retardation plate is also known (Japanese Patent Publication No. Hei 10-90521). The λ/2 retardation plate is also manufactured using the same material method as the λ/4 retardation plate. The combination of the stretched retardation plate and the liquid crystal-coated retardation plate is arbitrary, but it is preferable to use the liquid crystal-coated retardation plate for both because the thickness can be reduced.

There is also a known method of laminating positive C plates on the circular polarizer plate to increase visibility in the oblique direction (Japanese Patent Publication No. 2014-224837). The positive C plate may also be a liquid crystal-coated retardation plate or a stretched type retardation plate. The phase difference in the thickness direction is -200 to -20 nm, preferably -140 to -40 nm.

[Touch sensor]

The flexible image display device of the present invention contains a touch sensor as described above. A touch sensor is used as an input means. As a touch sensor, various styles have been proposed, such as a resistive film type, surface acoustic wave type, infrared type, electromagnetic induction type, and capacitance type, and any type may be used. Among them, the electrostatic capacitance method is preferable. A capacitive touch sensor is divided into an active area and an inactive area located on the outside of the active area. The active area is the area corresponding to the area where the screen is displayed (display area) on the display panel, and is the area where the user's touch is detected, and the inactive area is the area corresponding to the area where the screen is not displayed (non-display area) on the display device. . The touch sensor includes a substrate having flexible characteristics; a sensing pattern formed in an active area of the substrate; It is formed in an inactive area of the substrate and may include each sensing line for connection to an external driving circuit through the sensing pattern and pad portion. As a substrate having flexible characteristics, 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 from the viewpoint of suppressing cracks in the touch sensor. More preferably, the toughness may be 2,000 to 30,000 MPa%. Here, toughness is defined as the area under the curve from the stress (MPa)-strain (%) curve to the breaking point obtained through tensile testing of polymer materials.

The sensing pattern may include a first pattern formed in a first direction and a second pattern formed in a second direction. The first pattern and the second pattern are arranged in different directions. The first pattern and the second pattern are formed on the same layer, and in order to detect a touched point, each pattern must be electrically connected. In the first pattern, each unit pattern is connected to each other through a seam, but in the second pattern, each unit pattern is separated from each other in the form of an island, so a separate bridge electrode is required to electrically connect the second pattern. need. The sensing pattern can be made of a known transparent electrode material. For example, 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 nanotubes (CNT), graphene, metal wire, etc., and these can be used alone or in a mixture of two or more types. Preferably, ITO can be used. The metal used in the metal wire is not particularly limited, and examples include silver, gold, aluminum, copper, iron, nickel, titanium, selenium, and chromium. These can be used individually or in combination of two or more types.

A bridge electrode can be formed on top of the insulating layer through an insulating layer on top of the sensing pattern. The bridge electrode can be formed on a substrate, and the insulating layer and sensing pattern can be formed on it. 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 two or more of these. there is. Since the first pattern and the second pattern must be electrically insulated, an insulating layer is formed between the sensing pattern and the bridge electrode. The insulating layer may be formed only between the seam of the first pattern and the bridge electrode, or may be formed as a layer covering the sensing pattern. In the latter case, the bridge electrode can connect the second pattern through a contact hole formed in the insulating layer. The touch sensor is used to properly compensate for the difference in transmittance between the patterned area and the non-patterned area, specifically, the difference in light transmittance caused by the difference in refractive index in these areas. As a means, an optical control layer may be further included between the substrate and the electrode, and the optical control layer may include an inorganic insulating material or an organic insulating material. The optical adjustment layer can be formed by coating a photocurable composition containing a photocurable organic binder and a solvent on a substrate. The photocurable composition may further include inorganic particles. The refractive index of the optical adjustment layer may be increased by the inorganic particles.

The photocurable organic binder may include, for example, a copolymer of each monomer, such as an acrylate-based monomer, a styrene-based monomer, and a carboxylic acid-based monomer. The photocurable organic binder may be, for example, a copolymer containing different repeating units such as an epoxy group-containing repeating unit, an acrylate repeating unit, and a carboxylic acid repeating unit.

The inorganic particles may include, for example, zirconia particles, titania particles, alumina particles, etc. The photocurable composition may further include additives such as a photopolymerization initiator, polymerizable monomer, and curing aid.

[Adhesive layer]

Each layer (window, circular polarizer, touch sensor) forming the laminate for the flexible image display device and the film member (linear polarizer, λ/4 retardation plate, etc.) constituting each layer can be formed with an adhesive. Adhesives include water-based adhesives, water-based solvent volatilizing adhesives, organic solvent-based adhesives, solvent-free adhesives, solid adhesives, solvent volatilizing adhesives, moisture-curing adhesives, heat-curing adhesives, anaerobic curing types, active energy ray-curing adhesives, hardener mixed adhesives, and heat-curing adhesives. General-purpose adhesives such as melt-type adhesives, pressure-sensitive adhesives (adhesives), and rewetting-type adhesives can be used. Among them, water-based solvent vaporizing adhesives, active energy ray curing adhesives, and adhesives are often used. The thickness of the adhesive layer can be appropriately adjusted depending on the required adhesive strength, etc., and is 0.01 to 500 μm, preferably 0.1 to 300 μm. There are multiple layers in the above laminate for a flexible image display device, but each thickness and the type of adhesive used are It can be the same or different.

As the water-based solvent vaporizing adhesive, water-soluble polymers such as polyvinyl alcohol-based polymers and starch, ethylene-vinyl acetate-based emulsions, and styrene-butadiene-based emulsions can be used as the main polymer. In addition to water and the above-described main polymer, cross-linking agents, silane compounds, ionic compounds, cross-linking catalysts, antioxidants, dyes, pigments, inorganic fillers, organic solvents, etc. may be added. In the case of bonding using the water-based solvent volatilizing adhesive, adhesiveness can be imparted by injecting the water-based solvent volatilizing adhesive between the bonded layers, bonding the bonded layers, and then drying them. When using the water-based solvent volatilizing adhesive, the thickness of the adhesive layer may be 0.01 to 10 μm, preferably 0.1 to 1 μm. When the water-based solvent volatilizing adhesive is used to form multiple 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 that forms an adhesive layer by irradiating active energy rays. The active energy ray curable composition may contain at least one type of polymer of a radically polymerizable compound and a cationically polymerizable compound similar to the hard coating composition. The radically polymerizable compound is the same as that of the hard coating composition, and the same type of compound as the hard coating composition can be used. As a radically polymerizable compound used in the adhesive layer, a compound having an acryloyl group is preferable. It is also preferable to include a monofunctional compound in order to lower the viscosity of the adhesive composition.

The cationically polymerizable compound is the same as that of the hard coating composition, and the same type of compound as the hard coating composition can be used. As a cationically polymerizable compound used in an active energy ray curable composition, an epoxy compound is particularly preferable. In order to lower the viscosity of the adhesive composition, it is also preferable to include a monofunctional compound as a reactive diluent.

The active energy ray composition may further include a polymerization initiator. Polymerization initiators include radical polymerization initiators, cationic polymerization initiators, radical and cationic polymerization initiators, and can be appropriately selected and used. These polymerization initiators are decomposed by at least one of active energy ray irradiation and heating to generate radicals or cations to advance radical polymerization and cationic polymerization. Among the base materials of the hard coating composition, an initiator capable of initiating at least one of radical polymerization or cationic polymerization by irradiation with active energy rays can be used.

The active energy ray cured composition may further include an ion trap, antioxidant, chain transfer agent, adhesion imparting agent, thermoplastic resin, filler, flow viscosity modifier, plasticizer, antifoam solvent, additive, and solvent. In the case of bonding with the active energy ray curable adhesive, the active energy ray curable composition is applied to one or both of the adhered layers and then bonded, and cured by irradiating active energy rays through one or both adhered layers. It can be bonded by doing so. When using the active energy ray curable adhesive, the thickness of the adhesive layer may be 0.01 to 20 μm, preferably 0.1 to 10 μm. When the active energy ray-curable adhesive is used to form multiple layers, the thickness of each layer and the type of adhesive used may be the same or different.

The adhesive is classified into acrylic adhesive, urethane adhesive, rubber adhesive, silicone adhesive, etc., depending on the main polymer, and any one can be used. In addition to the main polymer, the adhesive may contain a crosslinking agent, silane compound, ionic compound, crosslinking catalyst, antioxidant, tackifier, plasticizer, dye, pigment, inorganic filler, etc. Each component constituting the adhesive is dissolved and dispersed in a solvent to obtain an adhesive composition, and the adhesive composition is applied to a substrate and then dried to form an adhesive layer. The adhesive layer may be formed directly, or may be formed separately on a substrate and transferred thereto. It is also desirable to use a release film to cover the adhesive surface before adhesion. When using the adhesive, the thickness of the adhesive layer may be 1 to 500 μm, preferably 2 to 300 μm. When the adhesive is used to form multiple layers, the thickness of each layer and the type of adhesive used may be the same or different.

[Light blocking pattern]

The light blocking pattern can be applied as at least a part of the bezel or housing of the flexible image display device. The light-shielding pattern obscures the wiring disposed at the edge of the flexible image display device and makes it difficult to see, thereby improving image visibility. The light-shielding pattern may be in the form of a single layer or a double layer. The color of the light-shielding pattern is not particularly limited, and may have various colors such as black, white, and metallic color. The light-shielding pattern can be formed with pigments to implement color and polymers such as acrylic resin, ester resin, epoxy resin, polyurethane, and silicone. These may be used alone or in a mixture of two or more types. The light-shielding pattern can be formed by various methods such as printing, lithography, and inkjet. The thickness of the light-shielding pattern is usually 1 to 100 μm, preferably 2 to 50 μm. Additionally, it is also desirable to provide a shape such as an inclination in the thickness direction of the optical pattern.

Example

Hereinafter, the present invention will be described in more detail based on examples and comparative examples, but the present invention is not limited to the following examples. “%” and “part” in the examples mean mass% and mass part, unless otherwise specified. First, the measurement and evaluation methods are explained.

<Primary particle size of silica particles>

The primary particle diameter of the silica particles in the examples and comparative examples was measured and evaluated by the BET method.

<Haze>

In accordance with JIS K 7136:2000, the optical films obtained in Examples and Comparative Examples were cut to a size of 30 mm Haze (%) was measured using “-2DP”).

<Yellowness (YI value)>

The yellowness (Yellow Index: YI value) of the optical films obtained in the examples and comparative examples was measured using an ultraviolet, visible, and near-infrared spectrophotometer "V-670" manufactured by JASCO Corporation. After performing a background measurement in the absence of a sample, the optical film is set in the sample holder, the transmittance for light of 300 to 800 nm is measured, the three stimulus values (X, Y, Z) are obtained, and based on the formula below: YI values were calculated.

YI=100×(1.2769X-1.0592Z)/Y

<Total light transmittance (Tt)>

In accordance with JIS K 7361-1:1997, the optical films obtained in Examples and Comparative Examples were cut to a size of 30 mm × 30 mm, using a Haze computer (Suga Testing Machine Co., Ltd., “HGM-2DP”), The total light transmittance (%) at a thickness of 50 μm of the optical film was measured.

<Impact resistance test>

· Production of samples for impact resistance evaluation

In a reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping device, and nitrogen introduction tube, 97.0 parts by mass of n-butyl acrylate, 1.0 part by mass of acrylic acid, 0.5 part by mass of 2-hydroxyethyl acrylate, 200 parts by mass of ethyl acetate, and 0.08 parts by mass of 2,2'-azobisisobutyronitrile was introduced, and the air in the reaction vessel was replaced with nitrogen gas. While stirring in a nitrogen atmosphere, the reaction solution was heated to 60°C, reacted for 6 hours, and then cooled to room temperature. The weight average molecular weight of a portion of the obtained solution was measured, and the production of a (meth)acrylic acid ester polymer of 1,800,000 was confirmed.

100 parts by mass of the (meth)acrylic acid ester polymer obtained in the above process (solid content conversion value; the same below), and trimethylolpropane-modified tolylene diisocyanate (manufactured by Tosoh Corporation, brand name "Colonate ()) as an isocyanate-based crosslinking agent. Registered trademark) L") 0.30 parts by mass, and 3-glycidoxypropyltrimethoxysilane (Shin-Etsu Chemical Co., Ltd., brand name "KBM403") as a silane coupling agent. ) 0.30 parts by mass was mixed, sufficiently stirred, and diluted with ethyl acetate to obtain a coating solution of the adhesive composition.

The above coating solution was applied to the release surface (release layer surface) of the separator (LINTEC Corporation: SP-PLR382190) using an applicator so that the thickness after drying was 25 μm, and then applied at 100°C for 1 minute. After drying, another separator (SP-PLR381031, manufactured by Lintec Co., Ltd.) was bonded to the side opposite to the side of the adhesive layer to which the separator was bonded, to obtain an adhesive layer provided with a double-sided separator.

A pressure-sensitive adhesive layer is formed by transferring the pressure-sensitive adhesive layer to glass from the pressure-sensitive adhesive layer provided with a double-sided separator, and the optical films obtained in Examples and Comparative Examples are bonded on the pressure-sensitive adhesive layer to form glass, pressure-sensitive adhesive layer, and optical film. A laminate (sample for impact resistance evaluation) in which the films were laminated in this order was obtained.

·Impact resistance evaluation

Impact resistance was evaluated. Specifically, a weight was dropped from a height of 10 cm on the optical film surface of the laminate (sample for impact resistance evaluation) to create a dent. The weight has a mass of 4.6 g, the point where it impacts the optical film surface is a sphere with a diameter of 0.75 mm, and is made of stainless steel. Next, the shape of the depression on the surface of the optical film was observed using an optical interference film thickness meter (“Micromap (MM557N-M100 type)” manufactured by Ryoka Systems Inc.), and the page before the test was observed. The depth of the largest dent (the shortest distance from the undented film surface before the test to the largest dent) was measured based on the undented film surface. The measurement was repeated 5 times, and the average value of the dent depth was taken as the dent amount in the impact resistance test.

<Impact fatigue test>

An impact fatigue test was performed. Specifically, the optical films obtained in the examples and comparative examples were placed on a glass substrate, and the operation of dropping a weight from a position of 10 cm in height within a diameter of 8 mm on the film surface was repeated 20 times. The weight has a mass of 4.6 g, the point where it impacts the optical film surface is a sphere with a diameter of 0.75 mm, and is made of stainless steel.

The reflection color (reflection a* and b*) of the optical film before and after the test was evaluated using a spectrophotometer (CM3700A) manufactured by Konica Minolta, Inc. under the following conditions.

·Light source: D light source

Incident light: Irradiated at an angle of 2° from the normal direction to the optical film

·Detection mode: Reflection SCE

·Target mask: LAV mask (measurement range: 8mm diameter)

·Sample measurement conditions: Install an optical film at the reflection measurement location and measure by covering it with a dark box.

<Weight average molecular weight (Mw)>

Gel permeation chromatography (GPC) measurements

·Pretreatment method

DMF eluent (10mM lithium bromide solution) was added to the polyamideimide obtained in the example to a concentration of 2 mg/mL, heated with stirring at 80°C for 30 minutes, cooled, and filtered through a 0.45μm membrane filter to serve as the measurement solution. I did it.

·Measuring conditions

Column: TSKgel SuperAWM-H×2+SuperAW2500×1 (6.0mm I.D.×150mm×3)

Eluent: DMF (with addition of 10mM lithium bromide)

Flow rate: 1.0mL/min.

Detector: RI detector

Column temperature: 40℃

Injection volume: 100μL

Molecular Weight Standard: Standard Polystyrene

<Thickness of optical film>

The film thickness of the optical films obtained in the examples and comparative examples was measured using a micrometer manufactured by Mitutoyo Corporation.

[Example 1]

(Preparation of silica sol)

523.8 g of methanol-dispersed silica sol (primary particle diameter 11 nm, silica particle solid content 21.0%) and 440.0 g of γ-butyrolactone (GBL) were placed in a 1,000 mL flask, and placed in a water bath at 45°C using a vacuum evaporator. ), methanol was evaporated at 400 hPa for 1 hour and at 250 hPa for 1 hour. Additionally, the temperature was raised to 70°C at 250 hPa and heated for 30 minutes to obtain γ-butyrolactone dispersed silica sol 1 (GBL dispersed silica sol 1). The solid content concentration of the obtained GBL dispersed silica sol 1 was 19.3%.

(Preparation of polyamideimide)

In a 1 L separable flask equipped with a stirring blade under a nitrogen gas atmosphere, 45 g (140.52 mmol) of 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl (TFMB) and N,N -768.55 g of dimethylacetamide (DMAc) was added and TFMB was dissolved in DMAc while stirring at room temperature. Next, 18.92 g (42.58 mmol) of 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA) was added to the flask, and stirred at room temperature for 3 hours. After that, 4.19 g (14.19 mmol) of 4,4'-oxybis(benzoyl chloride) (OBBC), followed by 17.29 g (85.16 mmol) of terephthaloyl chloride (TPC) were added to the flask and stirred at room temperature for 1 hour. Next, 4.63 g (49.68 mmol) of 4-methylpyridine and 13.04 g (127.75 mmol) of acetic anhydride were added to the flask and stirred at room temperature for 30 minutes, then raised to 70°C using an oil bath and stirred for an additional 3 hours. A reaction solution was obtained.

The obtained reaction liquid was cooled to room temperature, poured into a large amount of methanol as a filament, and the precipitate was taken out, soaked in methanol for 6 hours, and then washed with methanol. Next, the precipitate was dried under reduced pressure at 100°C to obtain polyamidoimide 1. The weight average molecular weight of the obtained polyamidoimide 1 was 400,000.

(Manufacture of optical film)

Polyamidoimide 1 was dissolved in GBL, and the GBL dispersed silica sol 1 described above was added and thoroughly mixed to obtain a polyamidoimide 1/silica particle mixed varnish. The ratio of polyamidoimide 1 and silica particles was 70:30. Additionally, it was adjusted so that the polyamidoimide 1/silica particle concentration (total mass of resin and silica particles relative to the mass of varnish) was 10% by mass.

After filtering the obtained mixed varnish through a filter with a sieve size of 10 micrometers, the self-supporting film was spread on the smooth surface of a polyester base (manufactured by Toyobo Co., Ltd., brand name “A4100”) with a film thickness of 55 μm. was applied using an applicator, dried at 50°C for 30 minutes, then dried at 140°C for 15 minutes, and the polyester base material was peeled off to obtain a self-supporting film. The free-standing film was fixed to a metal frame and dried at 200°C to obtain optical film 1 with a film thickness of 50 μm.

[Example 2]

(Preparation of silica sol)

398.5 g of methanol-dispersed silica sol (primary particle size 12 nm, silica solid content 31.1%) and 272.2 g of γ-butyrolactone (GBL) were added to a 1,000 mL flask, and evaporated in a vacuum evaporator at 45°C for 1 hour at 400 hPa. , methanol was evaporated at 250 hPa for 1 hour. Additionally, the temperature was raised to 70°C at 250 hPa and heated for 30 minutes to obtain γ-butyrolactone dispersed silica sol 2 (GBL dispersed silica sol 2). The solid content concentration of the obtained GBL dispersed silica sol 2 was 30.9%.

(Preparation of polyamideimide and production of optical film)

An optical film was obtained in the same manner as in Example 1, except that GBL dispersed silica sol 2 was used as the GBL dispersed silica sol.

[Example 3]

(Preparation of silica sol)

398.1 g of methanol-dispersed silica sol (primary particle size 21 nm, silica solid content 30.9%) and 269.9 g of GBL were placed in a 1,000 mL flask, and methanol was added for 1 hour at 400 hPa and 1 hour at 250 hPa under a water bath at 45°C in a vacuum evaporator. evaporated. Additionally, the temperature was raised to 70°C at 250 hPa and heated for 30 minutes to obtain γ-butyrolactone dispersed silica sol 3 (GBL dispersed silica sol 3). The solid content concentration of the obtained GBL dispersed silica sol 3 was 30.3%.

(Preparation of polyamideimide and production of optical film)

An optical film was obtained in the same manner as in Example 1, except that GBL dispersed silica sol 3 was used as the GBL dispersed silica sol.

[Example 4]

(Preparation of polyamideimide)

Under a nitrogen gas atmosphere, 53.05 g (165.66 mmol) of TFMB and 670.91 g of DMAc were added to a 1L separable flask equipped with a stirring blade, and TFMB was dissolved in DMAc while stirring at room temperature. Next, 22.11 g (49.77 mmol) of 6FDA and 4.88 g (16.59 mmol) of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) were added to the flask, followed by 20.21 g of TPC. (99.54 mmol) was added and stirred at room temperature for 1 hour. Next, 10.53 g (133.08 mmol) of pyridine and 13.77 g (134.83 mmol) of acetic anhydride were added to the flask and stirred at room temperature for 30 minutes. Then, the temperature was raised to 70°C using an oil bath, and the reaction solution was stirred for an additional 3 hours. got it

The obtained reaction liquid was cooled to room temperature, poured into a large amount of methanol, and the precipitate was taken out, immersed in methanol for 6 hours, and then washed with methanol. Next, the precipitate was dried under reduced pressure at 100°C to obtain polyamidoimide 2. The weight average molecular weight of the obtained polyamidoimide 2 was 190,000.

(Manufacture of optical film)

An optical film was obtained in the same manner as in Example 1, except that polyamideimide 2 was used as the polyamideimide.

[Comparative Example 1]

(Preparation of silica sol)

Put 442.6 g of methanol-dispersed silica sol (primary particle diameter 27 nm, silica particle solid content 30.5%) and 301.6 g of GBL in a 1000 mL flask, and evaporate methanol for 1 hour at 400 hPa and 1 hour at 250 hPa under a water bath at 45°C in a vacuum evaporator. evaporated. Additionally, the temperature was raised to 70°C at 250 hPa and heated for 30 minutes to obtain γ-butyrolactone dispersed silica sol 4. The solid content concentration of the obtained γ-butyrolactone dispersed silica sol 4 was 28.9%.

(Preparation of polyamideimide and production of optical film)

An optical film was obtained in the same manner as in Example 1, except that the GBL dispersed silica sol 4 having a primary particle diameter of 27 nm was used as the GBL dispersed silica sol.

[Comparative Example 2]

An optical film was obtained in the same manner as in Example 1, except that methanol-dispersed silica was not used and the varnish was prepared so that the polyamideimide concentration (mass of polyamideimide relative to the mass of varnish) was 6% by mass.

[Comparative Example 3]

(Preparation of silica sol)

Put 502.5 g of methanol-dispersed silica sol (primary particle diameter 12 nm, silica particle solid content 20.7%) and 403.5 g of GBL in a 1000 mL flask, and evaporate methanol for 1 hour at 400 hPa and 1 hour at 250 hPa under a water bath at 45°C in a vacuum evaporator. evaporated. Additionally, the temperature was raised to 70°C at 250 hPa and heated for 30 minutes to obtain γ-butyrolactone dispersed silica sol 5. The solid content concentration of the obtained γ-butyrolactone dispersed silica sol 5 was 20.2%.

(Manufacture of optical film)

A polyimide-based polymer (“KPI-MX300F (100)” manufactured by Kawamura Sangyo Co., Ltd. was dissolved in GBL, and the GBL dispersed silica sol 5 described above was added and thoroughly mixed to obtain a polyimide/silica particle mixed varnish. The ratio of polyimide and silica particles was 70:30. In addition, the polyimide/silica particle concentration (total mass of resin and silica particles relative to the mass of varnish) was adjusted to 16% by mass. Other than that, Example 1 and An optical film was obtained similarly.

In the optical films obtained in Examples 1 to 4 and Comparative Examples 1 to 3, the type of resin, silica content, primary particle size of silica, amount of dents in the impact resistance test, total light transmittance, yellowness, haze, and impact fatigue test. Table 1 shows reflection a*, reflection b*, and their change amounts before and after. In Table 1, PAI(1) represents polyamideimide 1, PAI(2) represents polyamideimide 2, PI represents polyimide, and the silica content (% by mass) is the mass of the optical film (resin and It represents the mass of silica particles relative to the total mass of silica particles.

As shown in Table 1, the optical films of Examples 1 to 4 showed a small amount of change in both reflection a* and reflection b* before and after the impact fatigue test compared to the optical films of Comparative Examples 1 to 3, that is, It was confirmed that the change in reflected color was significantly small. That is, it was confirmed that the optical films of Examples 1 to 4 were able to suppress deterioration of optical properties due to repeated object collisions.

Claims (8)

It contains at least one kind of resin selected from the group consisting of polyimide resin and polyamide resin, and the amount of dent in the impact resistance test is 15 μm or less,
The amount of the indentation is determined by manufacturing a laminate in which glass, an adhesive layer, and an optical film are laminated in this order, the mass of which is 4.6 g, the collision point is a sphere with a diameter of 0.75 mm, and a weight made of stainless steel is placed on the laminate from a height of 10 cm. An optical film, which is the average value of five measurements of the depth of the largest depression obtained by observation using an optical interference film thickness meter when dropped on the optical film surface. According to paragraph 1,
An optical film with a haze of 1% or less. According to paragraph 1,
An optical film having a yellowness of 5 or less. According to paragraph 1,
An optical film containing a filler with a primary particle diameter of 25 nm or less. According to paragraph 1,
An optical film with a film thickness of 25 to 100 μm. A flexible image display device comprising the optical film according to any one of claims 1 to 5. According to clause 6,
A flexible image display device further comprising a polarizer. According to clause 6,
A flexible image display device further comprising a touch sensor.