KR20230017146A - Varnish, optical film, and method of producing optical film - Google Patents

Abstract

The present invention relates to a varnish containing at least a solvent and a polyimide resin, wherein the content of dicarboxylic acid in the varnish is 10 ppm or less.

Description

Varnish, optical film, and manufacturing method of optical film {VARNISH, OPTICAL FILM, AND METHOD OF PRODUCING OPTICAL FILM}

The present invention relates to a varnish containing a polyimide-based resin having a specific dicarboxylic acid content, an optical film formed from the varnish, and a method for producing the optical film.

BACKGROUND OF THE INVENTION Currently, image display devices such as liquid crystal display devices and organic EL display devices are widely used not only in televisions but also in various applications such as mobile phones and smart watches. Along with the expansion of these uses, an image display device (sometimes referred to as a flexible display) having flexible characteristics is in demand. BACKGROUND ART An image display device is composed of display elements such as a liquid crystal display element or an organic EL display element, as well as constituent members such as a polarizing plate, a retardation plate, and a front plate. In order to achieve a flexible display, all of these constituent members need to have flexibility.

Until now, glass has been used as the front plate. While glass has high transparency and can exhibit high hardness depending on the type of glass, it is very rigid and brittle, so it is difficult to use it as a front plate material for flexible displays. Therefore, as one of the materials that replace glass, there is a polyimide-based resin, and an optical film using the polyimide-based resin is being studied (for example, JP2017-203984A1). An optical film using a polyimide-based resin is usually manufactured using a varnish containing the polyimide-based resin, and long-term storage properties of the varnish are also studied (for example, JP2020-186369A1).

An optical film using a polyimide-based resin is used for a long period of time, for example, as a front plate of an image display device, but a conventional optical film may yellow over time. According to the present inventors, such yellowing over time is caused by decomposition of additives such as a polyimide-based resin included in the optical film, a bluing agent, and an ultraviolet absorber included in the optical film by exposure to external factors such as UV light irradiation. can be thought to occur.

Conventionally, optical films as shown in Patent Literature 1 and Patent Literature 2 have been studied, but a technique capable of further suppressing yellowing of the optical film with time as described above is desired.

Therefore, the present invention is to form an optical film in which the increase in yellowness (hereinafter sometimes referred to as YI value or simply YI) due to UV light irradiation is suppressed, that is, the YI value is relatively low even after UV light irradiation. It is an object to provide a possible varnish and an optical film formed from the varnish.

As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by setting the content of dicarboxylic acid contained in a varnish containing polyimide-based resin to a predetermined value or less. came to complete the invention.

That is, the present invention includes the following aspects.

[1] A varnish containing at least a solvent and a polyimide resin, wherein the content of dicarboxylic acid in the varnish is 10 ppm or less.

[2] The varnish according to [1], wherein the light transmittance of the solvent at a wavelength of 275 nm is 95% or more.

[3] The varnish according to [1] or [2], wherein the solvent is γ-butyrolactone.

[4] The varnish according to any one of [1] to [3], wherein the dicarboxylic acid is an aliphatic dicarboxylic acid having 4 to 10 carbon atoms.

[5] The varnish according to any one of [1] to [4], wherein the dicarboxylic acid is at least one type of dicarboxylic acid selected from the group consisting of maleic acid and succinic acid.

[6] The varnish according to any one of [1] to [5], further comprising at least one bluing agent.

[7] The varnish according to [6], wherein the half width of the absorption peak of the bluing agent is 70 nm or more and 200 nm or less.

[8] The varnish according to [6] or [7], wherein the bluing agent is an anthraquinone-based bluing agent.

[9] The varnish according to any one of [1] to [8], wherein the solvent content is 75 to 99% by mass based on the total amount of the varnish.

[10] The varnish according to any one of [1] to [9], wherein the content of the polyimide-based resin is 1 to 25% by mass based on the total amount of the varnish.

[11] The varnish according to any one of [1] to [10], wherein the polyimide resin is a polyamideimide resin.

[12] An optical film formed of the varnish according to any one of [1] to [11].

[13] (a) step of preparing a solvent having a dicarboxylic acid content of 10 ppm or less;

(b) a step of preparing a varnish having a dicarboxylic acid content of 10 ppm or less by mixing the solvent prepared in step (a) with a polyimide-based resin;

(c) a step of applying the obtained varnish on a support to form a coating film; and

(d) process of drying the coating film to obtain an optical film

A method for manufacturing an optical film comprising at least one.

ADVANTAGE OF THE INVENTION According to this invention, the varnish which can form the optical film in which the YI value increase of the optical film by irradiation with UV light was suppressed, and the optical film formed with this varnish can be provided.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described in detail. In addition, the scope of the present invention is not limited to the embodiment described here, and various changes can be made without departing from the gist of the present invention.

The varnish of the present invention is a varnish containing at least a solvent and a polyimide resin, and the content of dicarboxylic acid in the varnish is 10 ppm or less. When the content of the dicarboxylic acid contained in the varnish exceeds 10 ppm, the dicarboxylic acid is also included in the optical film made of the varnish, and as a result, the optical film tends to yellow over time. In addition, in this specification, yellowing with time of an optical film is evaluated by the accelerated test which irradiates an optical film with UV light. From the standpoint of easily suppressing yellowing of the optical film over time, the content of dicarboxylic acid contained in the varnish is preferably 9 ppm or less, more preferably 7 ppm or less, still more preferably 5 ppm or less.

In addition, in this specification, the content of the said dicarboxylic acid is shown by the concentration of a dicarboxylic acid, unless otherwise indicated.

The content of dicarboxylic acid in the varnish may be 1 ppm or more. In particular, in order to purify the amount of dicarboxylic acid in the solvent to less than 1 ppm, purification takes a long time, so if it is set to 1 ppm or more, it can be produced in a reasonable production time.

It is thought that the dicarboxylic acid contained in the varnish reacts with the polyimide-based resin and/or with additives such as a UV absorber and a bluing agent, which are included as the case may be, over time. In addition, the dicarboxylic acid included in the varnish is also included in the optical film made of the varnish, and the polyimide-based resin included in the optical film, and / or, in some cases, additives such as an ultraviolet absorber and a bluing agent, You can think of it as a temporary reaction. In addition, it is considered that exposure of the optical film to external factors such as UV promotes the reaction as described above, and as a result, yellowing is also promoted. It is conceivable that such a reaction over time can be suppressed and yellowing can be prevented by setting the amount of dicarboxylic acid contained in the varnish to a predetermined value or less.

Among the dicarboxylic acids, dicarboxylic acids are preferably aliphatic dicarboxylic acids, from the viewpoint of making the amount of dicarboxylic acids highly reactive with polyimide-based resins or the like less than or equal to a specific value to increase the effect of suppressing yellowing of the optical film. It is levonic acid, more preferably an aliphatic dicarboxylic acid having 4 to 10 carbon atoms, and still more preferably at least one dicarboxylic acid selected from the group consisting of maleic acid and succinic acid.

The solvent contained in the varnish is not particularly limited, and examples thereof include N,N-dimethylacetamide (hereinafter sometimes referred to as DMAc) and N,N-dimethylformamide (hereinafter referred to as DMF). amide solvents such as); lactone solvents such as γ-butyrolactone (hereinafter sometimes referred to as GBL) and γ-valerolactone; sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide, and sulfolane; carbonate solvents such as ethylene carbonate and propylene carbonate; and combinations thereof. Among these solvents, amide-based solvents or lactone-based solvents are preferred. In addition, water, an alcohol solvent, a ketone solvent, an acyclic ester solvent, an ether solvent, and the like may be contained in the varnish.

Although the cause of dicarboxylic acid being contained in varnish is not clear, it may be contained due to the manufacturing process of the raw material contained in varnish, for example, the said solvent, for example. In particular, dicarboxylic acid may be contained due to the solvent contained in the varnish.

For example, GBL can be mentioned as a solvent for varnish. GBL can be manufactured using maleic anhydride as a starting material. As GBL which uses maleic anhydride as a starting material, Mitsubishi Chemical Co., Ltd. GBL is mentioned. GBL can be manufactured by converting maleic anhydride into succinic anhydride by a hydrogenation reaction and further hydrogenating when maleic anhydride is used as a starting material. When GBL is produced by such a manufacturing method, maleic acid and/or succinic acid are contained as impurities in the GBL solvent due to the manufacturing process. In addition, GBL is sometimes produced by cyclization and dehydration using 1,4-butanediol as a starting material, but even in this case, due to the manufacturing process, maleic acid and/or succinic acid are It may be included as an impurity in the solvent. Therefore, when the solvent included in the varnish is GBL, in particular, maleic acid and/or succinic acid, which tends to cause yellowing of the optical film, is the solvent It becomes easy to be included in varnish via. Therefore, when the varnish contains GBL as a solvent, in particular when the varnish contains maleic anhydride or 1,4-butanediol, particularly maleic anhydride as a starting material, and GBL obtained by hydrogenation as a solvent, It is easy to obtain a more remarkable effect by making content of dicarboxylic acid into 10 ppm or less.

In addition, when N-methyl-2-pyrrolidone (hereinafter sometimes referred to as NMP) is used as a solvent for varnish, since NMP is sometimes produced using GBL as a raw material, similarly dicarboxylic acid is used as an impurity. may be included as

Even when a cyclic ester other than GBL is used as a varnish solvent, dicarboxylic acid may be contained as an impurity because the cyclic ester may be produced by a reaction pathway similar to that of GBL.

Since lactam solvents other than NMP are sometimes produced using the above cyclic ester solvent as a raw material, they may contain dicarboxylic acid as an impurity.

The method for measuring the content of dicarboxylic acid in the varnish is not particularly limited, but the type of dicarboxylic acid that can be contained in the varnish is specified, and the amount of the dicarboxylic acid is quantified by ion chromatography-mass spectrometry or the like. you can measure it. In addition, when raw materials such as polyimide-based resin and additives contained in the varnish are raw materials with high purity, the content of dicarboxylic acid in the solvent contained in the varnish is converted into the content in the entire varnish, and in the varnish It is good also as content of dicarboxylic acid of.

In addition, when dicarboxylic acid is also significantly contained in components other than the solvent, the amount of dicarboxylic acid may be measured using the varnish as a measurement sample, and after separating the components such as resin as necessary, You may measure the total amount of dicarboxylic acid contained.

As a method of making content of dicarboxylic acid in a varnish below the said upper limit, the method of using a raw material with high purity is mentioned. As a method of increasing the purity of the polyimide-based resin contained in the varnish, it is possible to use the synthesized resin reaction solution after purification without using it as it is. As the purification method, a poor solvent is added dropwise to a resin solution dissolved in a good solvent, or a resin solution is added dropwise into a poor solvent to precipitate a pure resin component, followed by filtering.

Examples of methods for increasing the purity of the solvent contained in the varnish include distillation, chemical treatment, adsorption, extraction, and recrystallization. Distillation is preferably carried out by combining a plurality of distillation columns, and purification is preferably repeated a plurality of times until dicarboxylic acid is sufficiently removed. In addition, it becomes possible to reliably reduce the amount of dicarboxylic acid by sampling a part after the purification step, quantifying the amount of dicarboxylic acid, and performing purification again when the amount exceeds a predetermined amount.

The light transmittance of the solvent contained in the varnish of the present invention at a wavelength of 275 nm is preferably 96% or more. Although it is considered that the component itself having absorption at a wavelength of 275 nm does not contribute to the yellowing of the optical film, when a high-purity solvent having a light transmittance of 96% or more at a wavelength of 275 nm is used, in the varnish obtained It is considered that the content of dicarboxylic acid in is also easily adjusted within the above range. Here, when the varnish of this invention contains one type of solvent, it is preferable that the light transmittance in the wavelength of 275 nm of this solvent is 96% or more preferably. Further, when the varnish of the present invention contains two or more types of solvents, the light transmittance at a wavelength of 275 nm measured for each of the two or more types of solvents may be preferably 96% or more, and the two or more types of solvents The light transmittance at a wavelength of 275 nm measured for the mixed solvent of is preferably 96% or more.

The content of dicarboxylic acid in the solvent contained in the varnish of the present invention is preferably 10 ppm or less, more preferably 7 ppm or less, from the viewpoint of making the content of dicarboxylic acid in the varnish easily within the above range, More preferably, it is 5 ppm or less. In addition, from the viewpoint of the production efficiency of the varnish, the content of dicarboxylic acid in the solvent contained in the varnish may be 1 ppm or more. Here, when the varnish of this invention contains one type of solvent, it is preferable that content of the dicarboxylic acid of the said solvent is within the said range. Further, when the varnish of the present invention contains two or more types of solvents, it is preferable that the amount of dicarboxylic acid in the mixed solvent of the two or more types of solvents is within the above range.

The light transmittance of the solvent contained in the varnish at a wavelength of 275 nm is preferably 96% or more, more preferably 97% or more, still more preferably 98%, from the viewpoint of easily suppressing yellowing of the optical film over time. More than that.

The content of the solvent in the varnish of the present invention is preferably 75 to 99% by mass, more preferably 78 to 95% by mass, and even more preferably 80 to 90% by mass with respect to the total amount of the varnish. If the content of the solvent is within the range described above, since the viscosity tends to be optimal for casting a varnish into a film, the visibility of the obtained optical film is easy to be improved while handling property is improved.

The content of the polyimide-based resin in the varnish of the present invention is preferably 1 to 25% by mass, more preferably 5 to 22% by mass, still more preferably 10 to 20% by mass based on the total amount of the varnish. am. When the content of the polyimide-based resin is within the above range, the content of dicarboxylic acid in the obtained optical film is easily kept within a predetermined range, and yellowing with time of the optical film is easily suppressed. Moreover, since it tends to become the optimum viscosity for casting a varnish into a film, it is easy to improve the visibility of the optical film obtained while handling property becomes favorable.

<Polyimide-based resin>

The polyimide resin contained in the varnish of the present invention is a polyimide resin, a polyamideimide resin, or a polyamic acid resin that is a precursor of a polyimide resin and a polyamideimide resin. The varnish of this invention may contain one type of polyimide-type resin, and may contain 2 or more types of polyimide-type resin. The polyimide-based resin is preferably a polyimide resin or a polyamide-imide resin, more preferably a polyamide-imide resin, from the viewpoint of film forming properties.

The polystyrene-reduced weight average molecular weight of the polyimide-based resin contained in the varnish of the present invention is preferably 200,000 or more, more preferably 250,000 or more, from the viewpoint of suppression of yellowing of the optical film over time and resistance to bending of the film. At least 300,000 or more. The polystyrene-reduced weight average molecular weight of the polyimide-based resin is preferably 800,000 or less, more preferably 600,000 or less, still more preferably 500,000 or less, from the viewpoint of the ease of production of varnish and the film formability when producing a polymer material. More preferably, it is 450,000 or less. The said weight average molecular weight is measured by gel permeation chromatography (GPC) measurement. As the measurement conditions, you may use the conditions described in the Example.

In one embodiment of the present invention, the polyimide-based resin is a polyimide resin having a structural unit represented by formula (1), or a structural unit represented by formula (1) and formula (2) It is preferable that it is a polyamide-imide resin which has a structural unit. The polyimide-based resin is a polyamide-imide resin having a structural unit represented by Formula (1) and a structural unit represented by Formula (2) from the viewpoints of transparency and flexibility and suppression of yellowing of the optical film over time. is more preferable. Formulas (1) and (2) will be described below, but the description of Formula (1) relates to both polyimide resins and polyamideimide resins, and the description of Formula (2) relates to polyimide resins. It relates to an amideimide resin.

The structural unit represented by formula (1) is a structural unit formed by the reaction of a tetracarboxylic acid compound and a diamine compound, and the structural unit represented by formula (2) is formed by the reaction of a dicarboxylic acid compound and a diamine compound. is a constituent unit.

The polyimide-based resin is a polyimide resin having a structural unit represented by formula (1) or a polyamideimide resin having a structural unit represented by formula (1) and a structural unit represented by formula (2). 1 aspect of this invention WHEREIN: Y in formula (1) represents a tetravalent organic group mutually independently, Preferably it represents a C4-C40 tetravalent organic group. The organic group is an organic group in which hydrogen atoms in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, and in that case, the hydrocarbon group and the fluorine-substituted hydrocarbon group preferably have 1 to 8 carbon atoms. The polyimide-based resin as an embodiment of the present invention may contain plural types of Y, and the plural types of Y may be the same as or different from each other. As Y, formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) or formula ( a group represented by 29); groups in which hydrogen atoms in groups represented by formulas (20) to (29) are substituted with methyl, fluoro, chloro or trifluoromethyl groups; and a tetravalent chain hydrocarbon group having 6 or less carbon atoms.

[In formula (20) to formula (29),

* represents a bonding hand,

W ¹ 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 -Ar-. Ar represents an arylene group having 6 to 20 carbon atoms in which hydrogen atoms may be substituted with fluorine atoms, and specific examples include phenylene groups.]

Equation (20), Equation (21), Equation (22), Equation (23), Equation (24), Equation (25), Equation (26), Equation (27), Equation (28) and Equation (29) Among the groups represented, from the viewpoint of the surface hardness and flexibility of the optical film made of the polyimide-based resin, groups represented by formula (26), formula (28) or formula (29) are preferable, and formula (26) The group represented by is more preferable. In addition, W ¹ is each independently a single bond, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, from the viewpoint of the surface hardness and flexibility of the optical film made of the polyimide resin. -CH(CH ₃ )-, -C(CH ₃ ) ₂ - or -C(CF ₃ ) ₂ - is preferable, and a single bond, -O-, -CH ₂ -, -CH(CH ₃ )-, It is more preferably -C(CH ₃ ) ₂ - or -C(CF ₃ ) ₂ -, and more preferably a single bond, -O-, -C(CH ₃ ) ₂ - or -C(CF ₃ ) ₂ - Preferred, -O- or -C(CF ₃ ) ₂ - is even more preferred.

In the above aspect, it is preferable that at least a part of the plurality of Ys in formula (1) is a structural unit represented by formula (5). When at least one part of Y in Formula (1) is a group represented by Formula (5), the obtained optical film tends to express high transparency. In addition, due to the highly flexible skeleton, the solubility of the polyimide-based resin in a solvent can be improved, the viscosity of a varnish containing the polyimide-based resin can be suppressed to a low level, and processing of an optical film can be facilitated. there is.

[In Formula (5), R ¹⁸ to R ²⁵ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, and the hydrogen atoms contained in R ¹⁸ to R ²⁵ are mutually Independently, it may be substituted with a halogen atom, and * represents a bond.]

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 having 1 to 6 carbon atoms, or an alkyl group having 6 to 12 carbon atoms. represents an aryl group, preferably represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. As the C1-C6 alkyl group, C1-C6 alkoxy group and C6-C12 aryl group, the C1-C6 alkyl group, C1-C6 alkoxy group, or C6-C12 aryl group in Formula (3) Examples of the aryl group include those described later. Here, the hydrogen atom contained in R ¹⁸ to R ²⁵ may be independently substituted with a halogen atom. R ¹⁸ to R ²⁵ are each independently a hydrogen atom, a methyl group, a fluoro group, a chloro group, or a trifluoro group, more preferably from the viewpoint of the surface hardness and flexibility of the optical film comprising the polyimide-based resin. It is a methyl group, and it is a hydrogen atom or a trifluoromethyl group especially preferably.

In a preferred embodiment of the present invention, the structural unit represented by formula (5) is a group represented by formula (5'), that is, at least a part of the plurality of Y's is represented by formula (5') is a unit In this case, the optical film made of the polyimide-based resin can have high transparency.

[In formula (5'), * represents a bond]

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

In one aspect of the present invention in which the polyimide-based resin is a polyamideimide resin having a structural unit represented by formula (1) and a structural unit represented by formula (2), Z in formula (2) is independently of each other , represents a divalent organic group. In one embodiment of the present invention, the polyamide-imide resin may contain plural types of Z, and the plural types of Z may be the same as or different from each other. The divalent organic group preferably represents a divalent organic group having 4 to 40 carbon atoms. The organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, and in that case, the hydrocarbon group and the fluorine-substituted hydrocarbon group preferably have 1 to 8 carbon atoms. As the organic group of Z, formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) Or among the bonds of the group represented by Formula (29), a group in which two non-adjacent ones are substituted with hydrogen atoms and a divalent chain hydrocarbon group having 6 or less carbon atoms are exemplified. From the viewpoint of improving the optical properties of the optical film, for example, reducing the YI value, formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), Among the bonds of groups represented by formula (26), formula (27), formula (28) or formula (29), groups represented by groups in which two non-adjacent hydrogen atoms are substituted are preferable. In one embodiment of the present invention, the polyamide-imide resin may contain one type of organic group as Z, or may contain two or more types of organic groups.

As the organic group of Z, formula (20'), formula (21'), formula (22'), formula (23'), formula (24'), formula (25'), formula (26'), formula ( 27'), Eq. (28') and Eq. (29'):

[In formulas (20') to formulas (29'), W ¹ and * are as defined in formulas (20) to (29)]

A divalent organic group represented by is more preferable. In addition, the cyclic hydrogen atom in formulas (20) to (29) and formulas (20') to (29') is a hydrocarbon group having 1 to 8 carbon atoms, or a fluorine-substituted carbon atom having 1 to 8 carbon atoms. It may be substituted with a hydrocarbon group of 8, an alkoxy group of 1 to 6 carbon atoms, or an alkoxy group of 1 to 6 carbon atoms substituted with fluorine.

When the polyamide-imide resin has a structural unit in which Z in formula (2) is represented by any of the above formulas (20') to (29'), the polyamide-imide resin is added to the structural unit as follows Equation (d1) of:

[In formula (d1), R ²⁴ independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and R ²⁵ is R ²⁴ or -C(=O)-*, where * represents a bonding hand]

It is preferable to further have a structural unit derived from carboxylic acid represented by from the viewpoint of easily lowering the viscosity of the varnish, increasing the film formability of the varnish, and increasing the uniformity of the obtained optical film.

Examples of the C1-C6 alkyl group, the C1-C6 alkoxy group, and the C6-C12 aryl group for R ²⁴ include those exemplified for R ¹ to R ⁸ in Formula (3) described below, respectively. there is. As the structural unit (d1), specifically, a structural unit in which both R ²⁴ and R ²⁵ are hydrogen atoms (structural units derived from dicarboxylic acid compounds), R ²⁴ are all hydrogen atoms, and R ²⁵ is -C (= structural units representing O)-* (structural units derived from tricarboxylic acid compounds); and the like.

In one embodiment of the present invention, the polyamide-imide resin may contain plural types of Z, and the plural types of Z may be the same as or different from each other. In particular, from the viewpoint of easily improving the surface hardness and optical properties of the resulting film, at least a part of Z is Formula (3a):

[In formula (3a), R ^g and R ^h each independently represent a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and R ^g and R The hydrogen atom contained in ^h may be independently substituted with a halogen atom, A, m and * are the same as A, m and * in formula (3), and t and u are independently of 0 to 4 is an integer]

It is preferably represented by Equation (3):

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

A is, independently of each other, 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 )-, R ⁹ represents a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a hydrogen atom or a halogen atom,

m is an integer from 0 to 4;

* represents a bonding hand]

It is more preferable to be represented by

In Formulas (3) and (3a), A is, independently of each other, 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 bending resistance of the resulting film, preferably Represents -O- or -S-, more preferably represents -O-.

R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a carbon atom 6 to 12 aryl groups. R ^g and R ^h each independently represent a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group 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. are mentioned. Examples of the alkoxy group having 1 to 6 carbon atoms include methoxy group, ethoxy group, propyloxy group, isopropyloxy group, butoxy group, isobutoxy group, tert-butoxy group, pentyloxy group, hexyloxy group, and cyclohexyloxy group. timing, etc. As a C6-C12 aryl group, a phenyl group, a tolyl group, a xylyl group, a naphthyl group, a biphenyl group etc. are mentioned, for example. From the viewpoint of the surface hardness and flexibility of the film obtained from the varnish, R ¹ to R ⁸ independently of each other preferably represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. represents an alkyl group of, more preferably represents a hydrogen atom. Here, the hydrogen atom contained in R ¹ to R ⁸ , R ^g and R ^h may be independently substituted with a halogen atom.

R ⁹ represents a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a hydrogen atom or a halogen atom. As a monovalent hydrocarbon group of 1 to 12 carbon atoms, 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 a halogen atom. As said halogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc. are mentioned. The polyimide-based resin may contain multiple types of A, and the multiple types of A may be mutually the same or different.

In Formula (3a), t and u are each independently an integer of 0 to 4, preferably an integer of 0 to 2, more preferably 0 or 1, still more preferably 0.

In formulas (3) and (3a), m is an integer in the range of 0 to 4, and when m is within this range, the stability of the varnish and the bending resistance and elastic modulus of the film obtained from the varnish become good. easy. In formulas (3) and (3a), m is preferably an integer in the range of 0 to 3, more preferably an integer in the range of 0 to 2, still more preferably 0 or 1, and more is preferably 0. When m is within this range, it is easy to improve the bending resistance and elastic modulus of the film. Furthermore, Z may contain one or two or more types of structural units represented by formula (3) or formula (3a), from the viewpoint of improving the elastic modulus and bending resistance of the optical film, reducing the YI value, and aging the optical film. From the viewpoint of effective yellowing suppression, in particular, two or more types of structural units having different values of m, preferably two or three types of structural units having different values of m may be included. In that case, the resin contains a structural unit represented by formula (3) or formula (3a) in which m is 0 in Z, from the viewpoint of easy expression of high elastic modulus, bending resistance and low YI value of the film obtained from the varnish. It is preferable to do it, and it is more preferable to further contain a structural unit represented by formula (3) or formula (3a) in which m is 1 in addition to the structural unit concerned. In addition to the structural unit represented by formula (2) having Z represented by formula (3) where m is 0, it is also preferable to further have a structural unit represented by the above formula (d1).

In one preferred embodiment of the present invention, the resin has, as a structural unit represented by formula (3), m=0, and R ⁵ to R ⁸ are hydrogen atoms. In a more preferable embodiment of the present invention, the resin is a structural unit represented by formula (3), m = 0, and R ⁵ to R ⁸ are hydrogen atoms, and formula (3'):

It has a constituent unit represented by In this case, it is easy to improve the surface hardness and bending resistance of the film obtained from the varnish, it is easy to reduce the YI value, and it is easy to suppress yellowing of the optical film over time.

In a preferred embodiment of the present invention, when the total of the structural unit represented by formula (1) and the structural unit represented by formula (2) of the polyamideimide resin is 100 mol%, formula (3) or formula The ratio of the structural unit represented by (3a) is preferably 20 mol% or more, more preferably 30 mol% or more, still more preferably 40 mol% or more, still more preferably 50 mol% or more, particularly preferably Preferably it is 60 mol% or more, preferably 90 mol% or less, more preferably 85 mol% or less, and still more preferably 80 mol% or less. When the ratio of the structural units represented by formula (3) or formula (3a) is equal to or greater than the lower limit above, the surface hardness of the film obtained from the varnish is easily increased, and the bending resistance and elastic modulus are easily increased. When the ratio of the constituent units represented by formula (3) or formula (3a) is less than or equal to the above upper limit, an increase in the viscosity of the resin-containing varnish due to hydrogen bonds between amide bonds derived from formula (3) or formula (3a) is suppressed, , it is easy to improve the workability of the film.

Further, when the polyamide-imide resin has a structural unit represented by formula (3) or formula (3a) where m = 1 to 4, the structural unit represented by formula (1) and formula (2) of the polyamide-imide resin are represented by When the total of the constituent units is 100 mol%, the ratio of the constituent units represented by formula (3) or formula (3a) in which m is 1 to 4 is preferably 2 mol% or more, more preferably 4 mol% or more, more preferably 6 mol% or more, still more preferably 8 mol% or more, preferably 70 mol% or less, more preferably 50 mol% or less, even more preferably 30 mol% or less, still more It is preferably 15 mol% or less, particularly preferably 12 mol% or less. When the proportion of structural units in formula (3) or formula (3a) in which m is 1 to 4 is equal to or greater than the lower limit above, the surface hardness and bending resistance of the film obtained from the varnish are likely to be improved. If the ratio of the constituent units of the formula (3) or formula (3a) in which m is 1 to 4 is equal to or less than the above upper limit, the viscosity of the resin-containing varnish due to hydrogen bonds between amide bonds derived from formula (3) or formula (3a) It is easy to suppress the rise and improve the processability of the film. In addition, the content of the structural unit represented by formula (1), formula (2), formula (3) or formula (3a) can be measured using ¹ H-NMR, for example, or from the introduction ratio of raw materials can also be calculated.

In one preferred embodiment of the present invention, the Z in the polyamideimide resin is preferably 30 mol% or more, more preferably 40 mol% or more, still more preferably 45 mol% or more, still more preferably 50 mol% or more, More preferably 70 mol% or more is a structural unit represented by formula (3) or formula (3a) in which m is 0 to 4. If the above lower limit or more of Z is a structural unit represented by formula (3) or formula (3a) in which m is 0 to 4, it is easy to increase the surface hardness of the film obtained from the varnish, and also to increase the bending resistance and elastic modulus. . In addition, 100 mol% or less of Z in the polyamideimide resin may be a structural unit represented by formula (3) or formula (3a) in which m is 0 to 4. In addition, the ratio of the structural unit represented by formula (3) or formula (3a) in which m is 0 to 4 in the resin can be measured using ¹ H-NMR, for example, or calculated from the introduction ratio of raw materials. You may.

In one preferred embodiment of the present invention, Z in the polyamideimide resin is preferably 5 mol% or more, more preferably 8 mol% or more, still more preferably 10 mol% or more, still more preferably 12 mol% or more is represented by formula (3) or formula (3a) in which m is 1 to 4. Z of the polyamide-imide resin is a ratio within the above range, and m is 1 to 4 when expressed by formula (3) or formula (3a), it is easy to increase the surface hardness of the film obtained from the varnish, and also to increase the bending resistance and elastic modulus. easy. In addition, Z is preferably 90 mol% or less, more preferably 70 mol% or less, still more preferably 50 mol% or less, still more preferably 30 mol% or less, and m is 1 to 4 in the formula ( 3) or what is represented by formula (3a) is preferable. Z is within the above upper limit range, and m is 1 to 4, when represented by formula (3) or formula (3a), m is 1 to 4, formula (3) or hydrogen bond between amide bonds derived from formula (3a) It is easy to suppress the increase in the viscosity of the resin-containing varnish due to and improve the workability of the film. In addition, the ratio of the structural unit represented by formula (3) or formula (3a) in which m is 1 to 4 in the resin can be measured, for example, using ¹ H-NMR, or can be calculated from the introduction ratio of raw materials. there is.

In the formulas (1) and (2), X independently represents a divalent organic group, preferably a divalent organic group having 4 to 40 carbon atoms, more preferably having a cyclic structure of 4 to 40 carbon atoms. represents a divalent organic group of As a cyclic structure, an alicyclic ring, an aromatic ring, and a heterocyclic structure are mentioned. The organic group may have a hydrogen atom in the organic group substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, and in that case, the hydrocarbon group and the fluorine-substituted hydrocarbon group preferably have 1 to 8 carbon atoms. In one embodiment of the present invention, the polyimide resin or the polyamideimide resin may contain plural types of X, and the plural types of X may be the same or different from each other. X is represented by formulas (10), (11), (12), (13), (14), (15), (16), (17) and (18). energy; groups in which hydrogen atoms in groups represented by formulas (10) to (18) are substituted with methyl, fluoro, chloro or trifluoromethyl groups; and a chain hydrocarbon group having 6 or less carbon atoms.

In formulas (10) to (18), * represents a bond,

V ¹ , V ² and V ³ are, independently of each other, a single bond, -O-, -S-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ -, -CO- or -N(Q)-. Here, Q represents a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom. Examples of the monovalent hydrocarbon group having 1 to 12 carbon atoms include the groups described above for R ⁹ .

In one example, V ¹ and V ³ are single bonds, -O- or -S-, and V ² is -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ - or -SO ₂ -. The binding position to each ring of V ¹ and V ² and the binding position to each ring of V ² and V ³ are independently of each other, preferably a meta position or a para position with respect to each ring, more preferably is the para position.

Among the groups represented by formulas (10) to (18), formula (13), formula (14), formula (15), and formula (16) from the viewpoint of increasing the surface hardness and bending resistance of the film obtained from the varnish And the group represented by Formula (17) is preferable, and the group represented by Formula (14), Formula (15), and Formula (16) is more preferable. In addition, V ¹ , V ² and V ³ are independently from each other, preferably a single bond, -O- or -S-, more preferably from the viewpoint of increasing the surface hardness and flexibility of the film obtained from the varnish of the present invention. It is preferably a single bond or -O-.

In a preferred embodiment of the present invention, at least some of the plurality of Xs in formulas (1) and (2) are formula (4):

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

It is a constituent unit represented by . When at least one part of X in Formula (1) and Formula (2) is a group represented by Formula (4), the surface hardness and transparency of the film obtained from the varnish are easily improved.

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 having 1 to 6 carbon atoms, or a carbon number 1 to 6 represents an alkoxy group or an aryl group having 6 to 12 carbon atoms. As a C1-C6 alkyl group, C1-C6 alkoxy group, or C6-C12 aryl group, the C1-C6 alkyl group, C1-C6 alkoxy group, or C6-C12 aryl group in Formula (3) What was illustrated as an aryl group of is mentioned. R ¹⁰ to R ¹⁷ independently of each other preferably represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, wherein R ¹⁰ to R ¹⁷ The contained hydrogen atoms may be independently substituted with halogen atoms. As a halogen atom, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom are mentioned, for example. R ¹⁰ to R ¹⁷ independently represent a hydrogen atom, a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, more preferably from the viewpoints of the surface hardness, transparency and bending resistance of the optical film, and Preferably R ¹⁰ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ and R ¹⁶ represent a hydrogen atom, R ¹¹ and R ¹⁷ represent a hydrogen atom, a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, in particular Preferably, R ¹¹ and R ¹⁷ represent a methyl group or a trifluoromethyl group.

In one preferred embodiment of the present invention, the constituent unit represented by formula (4) is formula (4'):

It is a structural unit represented by , that is, at least a part of a plurality of Xs among the plurality of structural units represented by formulas (1) and (2) is a structural unit represented by formula (4'). In this case, the solubility of the polyimide-based resin in a solvent is likely to be enhanced by the fluorine-containing skeleton. Moreover, it is easy to reduce the viscosity of a varnish, and it is easy to improve the workability of an optical film. In addition, the optical properties of the film obtained from the varnish are easily improved by the skeleton containing the elemental fluorine.

In one preferred embodiment of the present invention, preferably 30 mol% or more, more preferably 50 mol% or more, still more preferably 70 mol% or more of X in the polyimide-based resin is the formula (4); In particular, it is represented by formula (4'). When X within the above range in the polyimide resin is represented by formula (4), particularly formula (4'), the solubility of the polyimide resin in a solvent is easily improved by the fluorine element-containing skeleton. Moreover, it is easy to reduce the viscosity of a varnish, and it is easy to improve the processability of the film obtained from a varnish. In addition, the optical properties of the film obtained from the varnish are also easily improved by the skeleton containing the elemental fluorine. Further, preferably, 100 mol% or less of X in the polyimide resin is represented by formula (4), particularly formula (4'). X in the said polyamideimide resin may be Formula (4), especially Formula (4'). The ratio of the structural unit represented by formula (4) of X in the resin can be measured, for example, using ¹ H-NMR, or can be calculated from the introduction ratio of raw materials.

The polyimide-based resin may include a structural unit represented by formula (30) and/or a structural unit represented by formula (31), and in the structural units represented by formulas (1) and (2), the formula It may contain the structural unit represented by (30) and/or the structural unit represented by Formula (31).

In formula (30), Y ¹ is each independently a tetravalent organic group, and is preferably an organic group in which a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. As Y ¹ , formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) and formula Groups represented by (29), groups in which hydrogen atoms in groups represented by formulas (20) to (29) are substituted with methyl, fluoro, chloro or trifluoromethyl groups, and tetravalent carbon atoms of 6 or less A chain hydrocarbon group is exemplified. In one embodiment of the present invention, the polyimide-based resin may contain plural types of Y ^{1 , and the plural types of Y 1 may} be the same as or different from each other.

In formula (31), Y ² is a trivalent organic group, preferably an organic group in which a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. As Y ² , formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) and a group in which any one of the bonds of the group represented by formula (29) is substituted with a hydrogen atom, and a trivalent chain hydrocarbon group having 6 or less carbon atoms. In one embodiment of the present invention, the polyimide-based resin may contain plural types of Y ^{2 , and the plural types of Y 2 may} be the same as or different from each other.

In the formulas (30) and (31), X ¹ and X ² are each independently a divalent organic group, preferably a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. It is a device. As X ¹ and X ² , formulas (10), (11), (12), (13), (14), (15), (16), (17) and a group represented by (18); groups in which hydrogen atoms in groups represented by formulas (10) to (18) are substituted with methyl, fluoro, chloro or trifluoromethyl groups; and a chain hydrocarbon group having 6 or less carbon atoms.

In one embodiment of the present invention, the polyimide-based resin is a constituent unit represented by formula (1) and/or formula (2), and in some cases, formula (30) and/or formula (31) made up of constituent units. Further, from the viewpoint of the optical properties, surface hardness, and bending resistance of the film obtained from the varnish, in the polyimide-based resin, the structural units represented by formulas (1) and (2) are formulas (1) and ( 2), and optionally 80 mol% or more, more preferably 90 mol% or more, still more preferably 95 mol% based on the precursor units represented by formulas (30) and (31) More than that. Further, in the polyimide-based resin, the constituent units represented by formulas (1) and (2) are formulas (1) and (2), and in some cases, formulas (30) and/or (31) Based on the precursor unit represented by , it is usually 100% or less. In addition, the said ratio can be measured using ¹ H-NMR, for example, or it can also be calculated from the introduction ratio of a raw material.

In one embodiment of the present invention, the content of the polyimide-based resin in the film obtained from the varnish is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, with respect to 100 parts by mass of the film. It is preferably 50 parts by mass or more, preferably 99.5 parts by mass or less, and more preferably 95 parts by mass or less. When the content of the polyimide-based resin is within the above range, it is easy to improve the optical properties and elastic modulus of the film obtained from the varnish.

In the polyamideimide resin, the content of the structural unit represented by formula (2) is preferably 0.1 mol or more, more preferably 0.5 mol or more, with respect to 1 mol of the structural unit represented by formula (1). It is preferably 1.0 mol or more, still more preferably 1.5 mol or more, preferably 6.0 mol or less, more preferably 5.0 mol or less, still more preferably 4.5 mol or less. When content of the structural unit represented by Formula (2) is more than the lower limit described above, it is easy to increase the surface hardness of the film obtained from the varnish. In addition, when the content of the structural unit represented by formula (2) is equal to or less than the above upper limit, it is easy to suppress thickening due to hydrogen bonds between amide bonds in formula (2) and improve the workability of the optical film.

In one preferred embodiment of the present invention, the polyimide-based resin may also contain a halogen atom such as a fluorine atom that can be introduced by, for example, the fluorine-containing substituent described above. When polyimide-type resin contains a halogen atom, it is easy to improve the elastic modulus of the film containing this polyimide-type resin, and to reduce YI value. When the elastic modulus of the film is high, when the film is used in, for example, a flexible display device, it is easy to suppress occurrence of scratches, wrinkles, and the like in the film. Moreover, when the YI value of a film is low, it becomes easy to improve the transparency and visibility of the said film. A halogen atom is preferably a fluorine atom. Preferable examples of the fluorine-containing substituent for making the polyimide-based resin contain a fluorine atom include a fluoro group and a trifluoromethyl group.

The content of halogen atoms in the polyimide-based resin is preferably 1 to 40% by mass, more preferably 5 to 40% by mass, and still more preferably 5 to 30% by mass based on the mass of the polyimide-based resin. is mass %. When the content of halogen atoms is at least the above lower limit, the elastic modulus of the film made of the polyimide resin is further improved, the water absorption is lowered, the YI value is further reduced, and transparency and visibility are more likely to be improved. When the content of the halogen atom is equal to or less than the above upper limit, the synthesis of the resin becomes easy.

The imidation rate of the polyimide-based resin is preferably 90% or more, more preferably 93% or more, still more preferably 96% or more. It is preferable that the imidation ratio is more than the said lower limit from a viewpoint of being easy to improve the optical homogeneity of the film containing the said polyimide-type resin. In addition, the upper limit of the imidation ratio is 100% or less. The imidation rate represents the ratio of the molar amount of the imide bond in the polyimide-based resin to twice the molar amount of the structural unit derived from the tetracarboxylic acid compound in the polyimide-based resin. In addition, when the polyimide-based resin contains a tricarboxylic acid compound, the value of twice the molar amount of the structural unit derived from the tetracarboxylic acid compound in the polyimide-based resin and the structural unit derived from the tricarboxylic acid compound The ratio of the molar amount of the imide bond in the polyimide resin and the polyamideimide resin to the total molar amount is shown. In addition, the imidation rate can be obtained by IR method, NMR method or the like, and for example, in NMR method, it can be measured by the method described in Examples.

A commercial item may be used for polyimide-type resin. As a commercial item of polyimide resin, Mitsubishi Gas Chemical Co., Ltd. product Neoprim (registered trademark), Kawamura Sangyo Co., Ltd. product KPI-MX300F, etc. are mentioned, for example. In the case of using a commercially available polyimide-based resin, it is preferable to reduce the amount of dicarboxylic acid that may be contained in the polyimide-based resin raw material by purifying the resin.

<Method for producing polyimide resin>

The polyimide resin can be produced using, for example, a tetracarboxylic acid compound and a diamine compound as main raw materials, and the polyamideimide resin can use, for example, a tetracarboxylic acid compound, a dicarboxylic acid compound, and a diamine compound as main raw materials. can be manufactured as Here, it is preferable that the dicarboxylic acid compound contains at least a compound represented by formula (3'').

[In formula (3''), R ¹ to R ⁸ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and R ¹ The hydrogen atom contained in -R ⁸ may be independently substituted with a halogen atom;

A is a single bond, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, - represents SO ₂ -, -S-, -CO- or -N(R ⁹ )-;

R ⁹ represents a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a hydrogen atom or a halogen atom;

m is an integer from 0 to 4;

R ³¹ and R ³² , independently of each other, represent a hydroxyl group, a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, a sec-butoxy group, a tert-butoxy group, or a chlorine atom. indicate.]

Moreover, when using a dicarboxylic acid compound for manufacture of polyimide-type resin, it is preferable to refine polyimide-type resin sufficiently so that an unreacted dicarboxylic acid compound may not be included in polyimide-type resin. By using a polyimide-based resin having high purity, it becomes easy to adjust the content of dicarboxylic acid in the varnish containing the polyimide-based resin to 10 ppm or less.

In one preferred embodiment of the present invention, the dicarboxylic acid compound is a compound represented by formula (3'') in which m is 0. As the dicarboxylic acid compound, it is more preferable to use a compound represented by formula (3'') in which A is an oxygen atom in addition to a compound represented by formula (3'') in which m is 0. In another preferred embodiment, the dicarboxylic acid compound is a compound represented by formula (3'') in which R ³¹ and R ³² are chlorine atoms. Moreover, you may use a diisocyanate compound instead of the diamine compound.

As a diamine compound used for manufacture of resin, aliphatic diamine, aromatic diamine, and mixtures thereof are mentioned, for example. In the present embodiment, "aromatic diamine" refers to diamine in which an amino group is directly bonded to an aromatic ring, and may contain an aliphatic group or other substituent in a part of its structure. This aromatic ring may be a monocyclic ring or a condensed ring, and examples thereof include a benzene ring, a naphthalene ring, an anthracene ring and a fluorene ring, but are not limited thereto. Among these, a benzene ring is preferable. In addition, "aliphatic diamine" represents diamine in which an amino group is directly bonded to an aliphatic group, and may contain an aromatic ring or other substituents in a part of its structure.

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

As aromatic diamine, for example, p-phenylenediamine, m-phenylenediamine, 2,4-toluenediamine, m-xylylenediamine, p-xylylenediamine, 1,5-diaminonaphthalene, 2, Aromatic diamines having one aromatic ring such as 6-diaminonaphthalene, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 4,4'-diaminodiphenylsulfone, 3,4'-diaminodiphenylsulfone, 3,3'-dia Minodiphenylsulfone, 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(trifluoromethyl)-4,4'-diaminodiphenyl (sometimes described as 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- and aromatic diamines having two or more aromatic rings, such as chlorophenyl)fluorene and 9,9-bis(4-amino-3-fluorophenyl)fluorene. These can be used individually or in combination of 2 or more types.

Aromatic diamine is preferably 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether , 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, 1,4-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 (trifluoromethyl) -4,4'-diaminodiphenyl (TFMB), 4,4'-bis (4-aminophenone) C) biphenyl, more preferably 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl ether, 4,4'-diamino Diphenylsulfone, 1,4-bis(4-aminophenoxy)benzene, bis[4-(4-aminophenoxy)phenyl]sulfone, 2,2-bis[4-(4-aminophenoxy)phenyl] Propane, 2,2'-dimethylbenzidine, 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl (TFMB), 4,4'-bis(4-aminophenoxy) is phenyl. These can be used individually or in combination of 2 or more types.

Among the above diamine compounds, it is preferable to use at least one selected from the group consisting of aromatic diamines having a biphenyl structure from the viewpoint of high surface hardness, high transparency, high flexibility, high bending resistance and low colorability of the optical film. 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 at least one selected from the group, and it is even more preferable to use 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl (TFMB).

As a tetracarboxylic acid compound used for manufacture of resin, Aromatic tetracarboxylic acid compounds, such as aromatic tetracarboxylic dianhydride; and aliphatic tetracarboxylic acid compounds such as aliphatic tetracarboxylic dianhydride. A tetracarboxylic acid compound may be used independently or may be used in combination of 2 or more types. The tetracarboxylic acid compound may be a tetracarboxylic acid compound analog such as an acid chloride compound other than a dianhydride.

Specific examples of the aromatic tetracarboxylic dianhydride include non-condensed polycyclic aromatic tetracarboxylic dianhydride, monocyclic aromatic tetracarboxylic dianhydride, and condensed polycyclic aromatic tetracarboxylic dianhydride. Examples of the non-fused polycyclic aromatic tetracarboxylic acid dianhydride include 4,4'-oxydiphthalic acid dianhydride, 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride, 2,2', 3,3'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 3 ,3',4,4'-diphenylsulfotetracarboxylic acid 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 (sometimes listed as 6FDA) , 1,2-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,2-bis (3,4-dicarboxyphenyl) )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. Moreover, examples of the monocyclic aromatic tetracarboxylic acid dianhydride include 1,2,4,5-benzenetetracarboxylic acid dianhydride, and examples of the condensed polycyclic aromatic tetracarboxylic acid dianhydride include, for example, and 2,3,6,7-naphthalene tetracarboxylic dianhydride.

Among these, 4,4'-oxydiphthalic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, and 2,2',3,3'-benzophenone tetracarboxylic acid are preferred. Dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-di Phenylsulfonetetracarboxylic acid 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-dicarboxyphenyl)ethane dianhydride, 1,1-bis(3,4-di Carboxyphenyl)ethane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, 4,4'-(p-phenylenedioxy)diphthalic dianhydride water and 4,4'-(m-phenylenedioxy)diphthalic dianhydride, more preferably 4,4'-oxydiphthalic dianhydride and 3,3',4,4'-biphenyl Tetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA), bis(3,4 -dicarboxyphenyl)methane dianhydride and 4,4'-(p-phenylenedioxy)diphthalic dianhydride. These can be used individually or in combination of 2 or more types.

Examples of the aliphatic tetracarboxylic dianhydride include cyclic or acyclic aliphatic tetracarboxylic dianhydride. Cyclic aliphatic tetracarboxylic dianhydride is a tetracarboxylic dianhydride having an alicyclic hydrocarbon structure, and specific examples thereof include 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4- Cycloalkane tetracarboxylic dianhydrides such as cyclobutanetetracarboxylic dianhydride and 1,2,3,4-cyclopentanetetracarboxylic dianhydride, bicyclo[2.2.2]oct-7-en-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 2 or more types. Specific examples of the acyclic aliphatic tetracarboxylic dianhydride include 1,2,3,4-butanetetracarboxylic dianhydride and 1,2,3,4-pentanetetracarboxylic dianhydride. Or it can use in combination of 2 or more types. Moreover, you may use combining cyclic aliphatic tetracarboxylic dianhydride and acyclic aliphatic tetracarboxylic dianhydride.

Among the above tetracarboxylic dianhydrides, 4,4'-oxydiphthalic dianhydride, 3,3',4, 4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 3,3 ',4,4'-diphenylsulfotetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride Water, and mixtures thereof are preferred, 3,3',4,4'-biphenyltetracarboxylic dianhydride and 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride, and mixtures thereof This is more preferable, and 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA) is more preferable.

As the dicarboxylic acid compound used for production of the resin, terephthalic acid, 4,4'-oxybisbenzoic acid or acid chloride compounds thereof are preferably used. In addition to terephthalic acid, 4,4'-oxybisbenzoic acid or their acid chloride compounds, other dicarboxylic acid compounds may be used. As another dicarboxylic acid compound, aromatic dicarboxylic acid, aliphatic dicarboxylic acid, and their derivative acid chloride compound, acid anhydride, etc. are mentioned, You may use in combination of 2 or more type. As a specific example, isophthalic acid; naphthalenedicarboxylic acid; 4,4'-biphenyldicarboxylic acid; 3,3'-biphenyldicarboxylic acid; In a chain hydrocarbon having 8 or less carbon atoms, a dicarboxylic acid compound and two benzoic acids are formed by a single bond, -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ - or a phenylene group. linked compounds, and acid chloride compounds thereof. As a specific example, 4,4'-oxybis (benzoyl chloride) and terephthaloyl chloride are preferable, and it is more preferable to use a combination of 4,4'-oxybis (benzoyl chloride) and terephthaloyl chloride.

Further, the polyimide-based resin may be obtained by further reacting tetracarboxylic acid and tricarboxylic acid, anhydrides and derivatives thereof, in addition to the tetracarboxylic acid compound, within a range that does not impair various physical properties of the optical film.

As tetracarboxylic acid, the aqueous adduct of the anhydride of the said tetracarboxylic acid compound is mentioned.

As a tricarboxylic acid compound, aromatic tricarboxylic acid, aliphatic tricarboxylic acid, and their derivative acid chloride compounds, acid anhydrides, etc. are mentioned, You may use in combination of 2 or more type. Specific examples include anhydrides of 1,2,4-benzenetricarboxylic acid; acid chloride compounds of 1,3,5-benzenetricarboxylic acid; 2,3,6-naphthalene tricarboxylic acid-2,3-anhydride; and compounds in which phthalic anhydride and benzoic acid are linked by a single bond, -O-, -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ - or a phenylene group.

In the production of the resin, the amount of the diamine compound, the tetracarboxylic acid compound and/or the dicarboxylic acid compound used can be appropriately selected depending on the desired ratio of each constituent unit of the polyimide resin.

In the production of the resin, the reaction temperature of the diamine compound, the tetracarboxylic acid compound and the dicarboxylic acid compound is not particularly limited, but is, for example, 5 to 350°C, preferably 20 to 200°C, more preferably 25 to 25°C. It is 100°C. The reaction time is also not particularly limited, but is, for example, about 30 minutes to 10 hours. If necessary, the reaction may be performed under an inert atmosphere or reduced pressure. In a preferable aspect, the reaction is performed under normal pressure and/or an inert gas atmosphere with stirring. Further, the reaction is preferably carried out in a solvent inert to the reaction. The solvent is not particularly limited as long as it does not affect the reaction, and examples thereof include water, methanol, ethanol, ethylene glycol, isopropyl alcohol, propylene glycol, ethylene glycol methyl ether, ethylene glycol butyl ether, 1-methoxy- alcohol solvents such as 2-propanol, 2-butoxyethanol, and propylene glycol monomethyl ether; ester solvents such as ethyl acetate, butyl acetate, ethylene glycol methyl ether acetate, GBL, γ-valerolactone, propylene glycol methyl ether acetate, and ethyl lactate; ketone solvents such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, 2-heptanone, and methyl isobutyl ketone; aliphatic hydrocarbon solvents such as pentane, hexane, and heptane; alicyclic hydrocarbon solvents such as ethylcyclohexane; aromatic hydrocarbon solvents such as toluene and xylene; nitrile solvents such as acetonitrile; ether solvents such as tetrahydrofuran and dimethoxyethane; chlorine-containing solvents such as chloroform and chlorobenzene; amide solvents such as DMAc and DMF; sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide, and sulfolane; carbonate solvents such as ethylene carbonate and propylene carbonate; and combinations thereof. Among these, amide type solvents can be used suitably from a solubility viewpoint.

In the imidation process in manufacture of polyimide-type resin, imidation can be carried out in presence of an imidation catalyst. Examples of the imidation catalyst 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 pyridine, 2-methylpyridine (2-picoline), 3-methylpyridine (3-picoline), 4-methylpyridine (4-picoline), 2-ethylpyridine, 3-ethylpyridine, 4-ethylpyridine , aromatic amines such as 2,4-dimethylpyridine, 2,4,6-trimethylpyridine, 3,4-cyclopentenopyridine, 5,6,7,8-tetrahydroisoquinoline, and isoquinoline. . Moreover, it is preferable to use an acid anhydride with an imidation catalyst from a viewpoint which promotes an imidation reaction easily. Examples of the acid anhydride include common acid anhydrides used in the imidation reaction, and specific examples thereof include aliphatic acid anhydrides such as acetic anhydride, propionic anhydride and butyric anhydride, and aromatic acid anhydrides such as phthalic acid.

The polyimide-based resin may be isolated (separated and purified) by a common method, for example, a separation means such as filtration, concentration, extraction, crystallization, recrystallization, column chromatography, or a combination thereof, and a preferred embodiment In , it can be isolated by adding a large amount of alcohol such as methanol to a reaction solution containing a transparent polyamideimide resin to precipitate the resin, and concentrating, filtering, drying or the like.

(Bluingje)

The varnish of this invention may also contain 1 type, or 2 or more types of bluing agents. When the varnish contains a bluing agent, the optical film also contains a bluing agent. The bluing agent is used to adjust the YI value of the optical film, but when the optical film contains the bluing agent, yellowing of the optical film over time, which is considered to be caused by dicarboxylic acid contained in the varnish, may become remarkable. . Therefore, with respect to a varnish containing a bluing agent, the effect of setting the content of dicarboxylic acid within a predetermined range is more remarkable.

The bluing agent is an additive, such as a dye or a pigment, that absorbs light in a wavelength range such as orange to yellow in the visible light range and adjusts the hue, such as ultramarine blue and Prussian blue. , inorganic dyes and pigments such as cobalt blue, and organic dyes and pigments such as phthalocyanine-based bluing agents and condensed polycyclic bluing agents. The type of bluing agent is not particularly limited, but from the viewpoint of increasing the total light transmittance, the half width of the absorption peak is preferably 70 nm or more and 200 nm or less, more preferably 70 nm or more and 195 nm or less, still more preferably 70 nm or more. It is preferable to use a bluing agent of 190 nm or less.

The bluing agent is not particularly limited, but from the viewpoint of heat resistance, light resistance, and solubility, and easy to increase the transparency of the obtained optical film, condensed polycyclic bluing agents are preferred, and anthraquinone-based bluing agents are more preferred. Conventionally, when such a bluing agent is used, there is an advantage that it is easy to increase the transparency of the obtained optical film, but yellowing of the optical film with time, which is considered to be caused by dicarboxylic acid contained in varnish, sometimes becomes remarkable. According to the present invention, even in the case of using the above bluing agent, such yellowing can be effectively suppressed.

Examples of the condensed polycyclic bluing agent include an anthraquinone-based bluing agent, an indigo-based bluing agent, and a phthalocyanine-based bluing agent.

The anthraquinone-based bluing agent is formula (a):

It is a bluing agent containing an anthraquinone ring represented by As an anthraquinone-based bluing agent, preferably Formula (a1):

[In formula (a1), M ¹ represents OH, NHR ^a or NR ^a R ^b , M ² represents NHR ^c or NR ^c R ^d , and R ^a , R ^b , R ^c and R ^d are independent of each other represents a straight-chain or branched alkyl group having 1 to 6 carbon atoms or a phenyl group substituted with a straight-chain or branched alkyl group having 1 to 6 carbon atoms.]

A compound represented by and formula (a2):

[In formula (a2), M ³ and M ⁴ independently represent OH, NH ₂ , NHR ^a or NR ^a R ^b , preferably NH ₂ , and R ^a and R ^b are as defined above. As it is, R ^e is a C1-C6 linear or branched alkyl group, and at least one -C- of the alkyl group may be substituted with -O-, preferably a C1-C6 linear group. or a group in which one -C- of a branched alkyl group is substituted with -O-.]

The compound represented by is mentioned. In a preferred aspect of the present invention, the varnish of the present invention is preferably a compound represented by formula (a1) from the viewpoint of easily preventing yellowing due to UV irradiation and easily increasing the transparency of the optical film, and It contains a bluing agent that is at least one compound selected from the group consisting of compounds represented by formula (a2), more preferably at least one compound represented by formula (a2).

As the anthraquinone-based bluing agent, compounds represented by the following formulas (a3) to (a6) are more preferably used.

The anthraquinone-based bluing agent can also be obtained as a commercial item. Commercially available products include, for example, Plast Blue 8510, Plast Blue 8514, Plast Blue 8516, Plast Blue 8520, Plast Blue 8540, Plast Blue 8580, and Plast Blue 8590 (above, all manufactured by Arimoto Chemical Industry). For example, Macrorex Violet B, Macrorex Violet 3R, Macrorex Blue RR (above, all products from Bayer), etc., for example, Diaresin Blue B, Diaresin Violet D, Diaresin Blue J, Diaresin Blue N (above, all products) Mitsubishi Chemical Co., Ltd.), etc., for example, Smiplast Violet B, Smiplast Blue OA, Smiplast Blue GP, Smiplast Dark Green G, Smiplast Blue S, Smiplast Green G ( Above, all are Sumitomo Chemical Co., Ltd. product), PET BLUE 2000 (Mitsui Chemical Fine Co., Ltd. product), etc. are mentioned.

An indigo-based bluing agent is a bluing agent containing indoxyl or thioindoxyl. The indigo-based bluing agent can also be obtained as a commercial item. As a commercial item, Dystar Indigo 4B Coll Liq, DyStar Indigo Coat, Dystar Indigo Vat (above, all made by Dystar) etc. are mentioned, for example.

A phthalocyanine-based bluing agent is a bluing agent containing a cyclic structure in which four phthalic acid imides are crosslinked with nitrogen atoms. A phthalocyanine-type bluing agent can be obtained also as a commercial item. Commercially available products include, for example, Chromofine Blue, Chromofine Green (above, all made by Dai Nippon Chemical Industry Co., Ltd.), Pigment Blue 15, Pigment Blue 16 (above, all made by Tokyo Chemical Industry Co., Ltd.), etc. can

The varnish of the present invention preferably contains an anthraquinone-based bluing agent from the viewpoints of heat resistance, light resistance, and solubility, and from the viewpoint of facilitating the transparency of the obtained optical film, and has a structure represented by the formula (a). It is more preferable to contain at least one type of bluing agent, and it is more preferable to contain at least one type of bluing agent having a structure represented by the above formula (a1) or (a2), and the above formulas (a3) to ( It is particularly preferable to contain at least one bluing agent selected from the group consisting of compounds represented by a6). In addition, the compound represented by formula (a3) - (a6) can be obtained also as a commercial item. As commercially available products, Sumiplast Violet B (compound represented by formula (a3), half width of absorption peak: 117 nm), PET BLUE 2000 (compound represented by formula (a4), half width of absorption peak: 113 nm), Sumi Plast Blue OA (compound represented by formula (a5)) and Sumiplast Blue GP (compound represented by formula (a6)) are exemplified.

A bluing agent may be used individually by 1 type, and may use 2 or more types together. From the viewpoint of keeping the total light transmittance high, the total amount of the bluing agent used (mixing amount) is preferably relatively small, and the type of bluing agent used is also preferably small.

When the varnish of the present invention contains a bluing agent, the content of the bluing agent is preferably 5 ppm or more, more preferably 8 ppm or more, still more preferably 10 ppm or more based on the total mass of the polyimide film. . When content of a bluing agent is more than the said lower limit, since it is easy to fully reduce YI and improve visibility, it is preferable. Further, the content is preferably 150 ppm or less, more preferably 120 ppm or less, still more preferably 100 ppm or less. When content of a bluing agent is below the said upper limit, since a total light transmittance does not fall too much and visibility is easily improved, it is preferable.

(filler)

The varnish of the present invention may contain a filler. Examples of the filler include organic particles and inorganic particles, preferably inorganic particles. As inorganic particles, silica, zirconia, alumina, titania, zinc oxide, germanium oxide, indium oxide, tin oxide, indium tin oxide (sometimes described as ITO), antimony oxide, metal oxide particles such as cerium oxide, magnesium fluoride , metal fluoride particles such as sodium fluoride; Silica particles are exemplified. These fillers can be used alone or in combination of two or more.

The average primary particle diameter of the filler, preferably silica particles, is preferably 10 nm or more, more preferably 15 nm or more, even more preferably 20 nm or more, preferably 100 nm or less, more preferably 90 nm or less. nm or less, more preferably 80 nm or less, still more preferably 70 nm or less, particularly preferably 60 nm or less, particularly more preferably 50 nm or less, and still more preferably 40 nm or less. When the average primary particle diameter of the silica particles is within the above range, it is easy to suppress the aggregation of the silica particles and improve the optical properties of the obtained optical film. The average primary particle size of the filler can be measured by the BET method. Further, the primary particle size (also referred to as average primary particle size) may be measured by image analysis using a transmission electron microscope or a scanning electron microscope.

When the varnish of the present invention contains a filler, preferably silica particles, the content of the filler, preferably silica particles, is usually 0.1% by mass or more, preferably 1% by mass or more, more preferably 1% by mass or more, based on the solid content in the varnish. It is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 20% by mass or more, particularly preferably 30% by mass or more, and preferably 60% by mass or less. If content of a filler is more than the said lower limit, it is easy to improve the elastic modulus of the optical film obtained. Moreover, when content of a filler is below the said upper limit, the storage stability of a varnish improves and it is easy to improve the optical characteristic of the optical film obtained.

(ultraviolet ray absorbent)

The varnish of this invention may contain 1 type, or 2 or more types of ultraviolet absorbers. The ultraviolet absorber can be appropriately selected from those commonly used as ultraviolet absorbers in the field of resin materials. The ultraviolet absorber may contain a compound that absorbs light having a wavelength of 400 nm or less. Examples of the ultraviolet absorber include at least one compound selected from the group consisting of benzophenone-based compounds, salicylate-based compounds, benzotriazole-based compounds, and triazine-based compounds. Since deterioration of polyimide-type resin is suppressed when the optical film obtained from the varnish of this invention contains a ultraviolet absorber, the visibility of an optical film can be improved.

In addition, in this specification, "system compound" refers to the derivative of the compound to which the said "system compound" is attached. For example, "benzophenone compound" refers to a compound having benzophenone as a parent skeleton and a substituent bonded to benzophenone.

When the varnish of the present invention contains a UV absorber, the content of the UV absorber is preferably 1% by mass or more, more preferably 2% by mass or more, and still more preferably 3% by mass or more with respect to the solid content of the varnish. , Preferably it is 10 mass % or less, More preferably, it is 8 mass % or less, More preferably, it is 6 mass % or less. Although the preferable content rate differs depending on the ultraviolet absorber used, adjusting the content rate of the ultraviolet absorber so that the light transmittance of 400 nm is about 20 to 60% can improve the light resistance of the optical film and obtain an optical film with high transparency. can

(other additives)

The varnish of the present invention may further contain other additives. Examples of other components include antioxidants, release agents, stabilizers, flame retardants, pH adjusters, silica dispersants, lubricants, thickeners, and leveling agents.

When other additives are included, the content thereof is preferably 0.01% by mass or more and 20% by mass or less, more preferably 0.01% by mass or more and 10% by mass or less, based on the solid content of the varnish.

[optical film]

The present invention also provides an optical film formed from the varnish of the present invention. The optical film of the present invention can be produced by forming the varnish of the present invention into a film, for example, by a method described later. Since the optical film is excellent in flexibility, bending resistance and surface hardness, it is suitable as a front plate of an image display device, particularly a front plate (sometimes referred to as a window film) of a flexible display. A single layer or a multi-layer may be sufficient as an optical film. When an optical film is a multilayer, each layer may have the same composition or a different composition.

When obtaining an optical film by casting the varnish of the present invention, the content of the polyimide-based resin in the optical film is preferably 40% by mass or more, more preferably 50% by mass, relative to the total mass of the optical film. or more, more preferably 70% by mass or more, particularly preferably 80% by mass or more, and very preferably 90% by mass or more. When the content of the polyimide-based resin is equal to or greater than the above lower limit, the bending resistance of the optical film is good. Moreover, the content rate of polyimide-type resin in an optical film is 100 mass % or less normally with respect to the total mass of an optical film.

The thickness of the optical film obtained from the varnish of the present invention is appropriately adjusted depending on the application, but is usually 10 to 1,000 µm, preferably 15 to 500 µm, more preferably 20 to 400 µm, and still more preferably 25 to 300 µm. am. Further, in the present invention, the thickness can be measured by a contact type digimatic indicator.

The total light transmittance (Tt) of the optical film obtained from the varnish of the present invention is preferably 70% or more, more preferably 80% or more, even more preferably 85% or more, still more preferably 89% or more, particularly preferably It is more than 90%. When the total light transmittance (Tt) of the optical film is at least the lower limit described above, when the optical film is attached to an image display device, it is easy to ensure sufficient visibility. Moreover, the upper limit of the total light transmittance (Tt) of an optical film is 100% or less normally. The haze of the optical film is preferably 3.0% or less, more preferably 2.0% or less, still more preferably 1.0% or less, still more preferably 0.8% or less, particularly preferably 0.5% or less, particularly more preferably is less than 0.3%. When the haze of an optical film is below the said upper limit and attaches an optical part film to flexible electronic devices, such as an image display apparatus, it is easy to ensure sufficient visibility. In addition, the lower limit of the haze is not particularly limited, and may be 0% or more. In addition, the total light transmittance and haze can be measured using a haze computer based on JIS K 7105:1981.

The YI value of the optical film obtained from the varnish of the present invention is preferably 8 or less, more preferably 5 or less, still more preferably 3 or less, still more preferably 2.8 or less. Transparency becomes good as the YI value of an optical film is below the said upper limit, and it can contribute to high visibility, when used for the front plate of an image display apparatus, for example. In addition, the YI value is usually -5 or more, preferably -2 or more. In addition, the YI value is obtained by measuring the transmittance for light of 300 to 800 nm using a spectrophotometer for ultraviolet, visible, near-infrared, and obtaining tristimulus values (X, Y, Z), YI = 100 × (1.2769X-1.0592Z ) / Y can be calculated based on the formula. For example, you may measure by the method described in the Example. The optical film obtained from the varnish of the present invention preferably has a YI value within the above range even after 24 hours of UV irradiation, for example, 313 nm UV light at 40 W for 24 hours.

(Method of manufacturing optical film)

Using the varnish of the present invention, the above optical film can be produced. The manufacturing method of the optical film is not particularly limited, but, for example, the following steps:

(a) a step of preparing a solvent having a dicarboxylic acid content of 10 ppm or less (solvent preparation step);

(b) a step of preparing a varnish having a dicarboxylic acid content of 10 ppm or less by mixing the solvent prepared in step (a) with a polyimide resin (varnish preparation step);

(c) a step of applying the obtained varnish on a support to form a coating film (application step), and

(d) Process of drying the coating film to obtain an optical film (formation process)

It can be manufactured by the manufacturing method of the optical film containing at least. The present invention also provides an optical film formed from the varnish of the present invention, and a method for producing the above optical film.

In the solvent preparation step, for example, as a method of increasing the purity of the solvent contained in the varnish, it is preferable to prepare a solvent having a dicarboxylic acid content of 10 ppm or less by purifying the solvent by the method described above. The solvent preparation step may further include a step of confirming that the content of dicarboxylic acid contained in the solvent is 10 ppm or less.

In the above production method, raw materials with high purity are preferably used as components other than the solvent contained in the varnish, specifically the polyimide-based resin, and other additives optionally included. In that case, content of dicarboxylic acid contained in a varnish can be made 10 ppm or less by making content of dicarboxylic acid into 10 ppm or less with respect to the solvent contained in a varnish.

In the varnish preparation step, a varnish having a dicarboxylic acid content of 10 ppm or less is prepared by mixing the solvent prepared in step (a) and the polyimide-based resin along with other additives as the case may be. It is preferable that the said polyimide-type resin is a polyimide-type resin obtained by the purification process, such as washing|cleaning a polyimide-type resin with sufficient quantity of solvent after manufacture.

In the application step, the varnish obtained in the varnish preparation step is applied on the support to form a coating film. The coating film is formed on a support such as a resin substrate, a SUS belt, or a glass substrate by casting or the like by a known roll-to-roll or batch method, for example. You can do it by doing

In the forming step, the optical film can be formed by drying the coating film and peeling it from the base material. You may perform the drying process of drying an optical film further after peeling. Drying of the coating film can be normally 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.

You may perform the surface treatment process of giving surface treatment to at least one surface of an optical film. As surface treatment, UV ozone treatment, plasma treatment, and corona discharge treatment are mentioned, for example.

Examples of the resin base material include metal belts such as SUS, PET film, PEN film, polyimide film, and polyamideimide film. Among them, from the viewpoint of excellent heat resistance, a PET film, a PEN film, a polyimide film, and other polyamideimide films are preferable. Further, from the viewpoints of adhesion to the optical film and cost, a PET film is more preferable.

From the viewpoint of easy production of an optical film with reduced YI, a process of applying the varnish of the present invention on a support to form a coating film, and drying the coating film at a temperature of 100 ° C. or more and 240 ° C. or less to obtain an optical film It is preferable to manufacture an optical film by a manufacturing method including at least a process. The drying temperature of the coating film is preferably 100 to 240°C, more preferably 120 to 220°C, still more preferably 150 to 220°C.

An optical film that can be produced using the varnish of the present invention preferably has a high elastic modulus and flexibility. In a suitable embodiment of the present invention, the modulus of elasticity of the optical film is preferably 3.0 GPa or more, more preferably 4.0 GPa or more, still more preferably 5.0 GPa or more, particularly preferably 6.0 GPa or more, preferably is 10.0 GPa or less, more preferably 8.0 GPa or less, still more preferably 7.0 GPa or less. When the elastic modulus of an optical film is below the said upper limit, when a flexible display bends, damage to another member by the said optical film can be suppressed. The modulus of elasticity is determined by measuring the S-S curve of a test piece having a width of 10 mm under conditions of a distance between chucks of 50 mm and a tensile speed of 20 mm/min using, for example, Autograph AG-IS manufactured by Shimadzu Corporation. can be measured

The above optical film preferably has excellent bending resistance. In a preferred embodiment of the present invention, the optical film has a number of reciprocating bends until breaking when measured at 135° at R = 1 mm, a load of 0.75 kgf, and a speed of 175 cpm, preferably 10,000 times or more, more preferably It is preferably 20,000 times or more, more preferably 30,000 times or more, still more preferably 40,000 times or more, and particularly preferably 50,000 times or more.

When the number of times of reciprocating bending of the optical film is equal to or greater than the above lower limit, fold wrinkles that may occur when the optical film is bent can be further suppressed. In addition, although the number of reciprocal bending of the optical film is not limited, it is usually sufficiently practical if it can be bent 1,000,000 times. The number of times of reciprocating bending can be determined using a test piece (optical film) having a thickness of 50 μm and a width of 10 mm, for example, with an MIT internal bending fatigue tester (model 0530) manufactured by Toyo Seiki Seisakusho Co., Ltd.

The said optical film can express excellent transparency. Therefore, the said optical film is very useful as an image display apparatus, especially a window film. In a preferred embodiment of the present invention, the optical film has a YI value based on JIS K 7373:2006 of preferably 5 or less, more preferably 3 or less, still more preferably 2.5 or less, still more preferably 2.0 or less. The optical film whose YI value is below the said upper limit can contribute to high visibility, such as a display device. Also, the YI value of the optical film is preferably 0 or more.

[Optical laminate]

In the optical film of the present invention, an optical laminate may be formed by laminating one or more functional layers on at least one surface. Examples of the functional layer include a UV absorbing layer, a hard coat layer, a primer layer, a gas barrier layer, an adhesive layer, a hue adjusting layer, and a refractive index adjusting layer. A functional layer can be used individually or in combination of 2 or more types.

The ultraviolet absorbing layer is a layer having a function of absorbing ultraviolet rays, and includes, for example, a main material selected from ultraviolet curing type transparent resins, electron beam curing type transparent resins, and thermosetting type transparent resins, and dispersed in the main material. Composed of UV absorbers.

A hard coat layer may be provided on at least one surface of the optical film of the present invention. The thickness of the hard coat layer is not particularly limited, and may be, for example, 2 to 100 μm. If the thickness of the said hard-coat layer is in said range, it is easy to improve impact resistance. The hard coat layer can be formed by curing a hard coat composition containing a reactive material capable of forming a crosslinked structure by irradiation with active energy rays or application of thermal energy, and irradiation with active energy rays is preferable. An active energy ray is defined as an energy ray capable of generating active species by decomposing a compound generating active species, and includes visible light, ultraviolet rays, infrared rays, X-rays, α-rays, β-rays, γ-rays, and electron rays. and, preferably, ultraviolet rays. The said hard-coat composition contains at least 1 sort(s) of polymer of a radically polymerizable compound and a cationic polymerizable compound.

The radical polymerizable compound is a compound having a radical polymerizable group. The radical polymerizable group of the radical polymerizable compound may be a functional group capable of causing a radical polymerization reaction, and includes a group containing a carbon-carbon unsaturated double bond. Specifically, a vinyl group, (meta) An acryloyl group etc. are mentioned. In addition, when the said radically polymerizable compound has two or more radically polymerizable groups, these radically polymerizable groups may be the same or different, respectively. The number of radical polymerizable groups the radical polymerizable compound has in one molecule is preferably two or more from the viewpoint of improving the hardness of the hard coat layer. As said radical polymerizable compound, the compound which has a (meth)acryloyl group is mentioned preferably from the viewpoint of high reactivity, Specifically, the polyfunctional which has 2-6 (meth)acryloyl groups in 1 molecule. A compound called an acrylate monomer or an oligomer having a molecular weight of hundreds to thousands of (meth)acryloyl groups in a molecule called epoxy (meth)acrylate, urethane (meth)acrylate, or polyester (meth)acrylate and preferably at least one selected from epoxy (meth)acrylate, urethane (meth)acrylate and polyester (meth)acrylate.

The said cationically polymerizable compound is a compound which has cationically polymerizable groups, such as an epoxy group, an oxetanyl group, and a vinyl ether group. The number of cationically polymerizable groups the cationically polymerizable compound has in one molecule is preferably two or more, more preferably three or more, from the viewpoint of improving the hardness of the hard coat layer.

Moreover, as said cationically polymerizable compound, the compound which has at least 1 sort(s) of an epoxy group and oxetanyl group as a cationically polymerizable group is preferable especially. Cyclic ether groups, such as an epoxy group and an oxetanyl group, are preferable in terms of low shrinkage due to the polymerization reaction. In addition, compounds having an epoxy group among cyclic ether groups have advantages in that compounds having various structures are easily available, do not adversely affect durability of the obtained hard coat layer, and compatibility with radically polymerizable compounds is easily controlled. In addition, the oxetanyl group among the cyclic ether groups has a higher degree of polymerization than the epoxy group, has low toxicity, speeds up the network formation rate obtained from the cationically polymerizable compound of the obtained hard coat layer, and is mixed with the radical polymerizable compound. Also, there are advantages such as forming an independent network without leaving unreacted monomers in the film.

As the cationically polymerizable compound having an epoxy group, for example, polyglycidyl ether of a polyhydric alcohol having an alicyclic ring or a compound containing a cyclohexene ring or cyclopentene ring is epoxidized with an appropriate oxidizing agent such as hydrogen peroxide or peracid. an alicyclic epoxy resin obtained by doing; 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 reaction of bisphenols such as bisphenol A, bisphenol F, and hydrogenated bisphenol A, or derivatives thereof such as alkylene oxide adducts and caprolactone adducts, with epichlorohydrin , and novolac epoxy resins, and glycidyl ether type epoxy resins derived from bisphenols.

The hard coat 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 the like, and are appropriately selected and used. Such a polymerization initiator is decomposed by at least one type of active energy ray irradiation and heating to generate radicals or cations to advance radical polymerization and cationic polymerization.

The radical polymerization initiator should be capable of releasing a substance that initiates radical polymerization by at least one of active energy ray irradiation and heating. For example, as a thermal radical polymerization initiator, organic peroxides, such as hydrogen peroxide and perbenzoic acid, and azo compounds, such as azobis butyronitrile, etc. are mentioned.

As the active energy ray radical polymerization initiator, there are a Type 1 radical polymerization initiator in which radicals are generated by decomposition of molecules and a Type 2 radical polymerization initiator in which radicals are generated by a hydrogen withdrawal type reaction coexisting with tertiary amines. used together or in combination.

A cationic polymerization initiator should just be able to release the substance which initiates cationic polymerization by at least any of active energy ray irradiation and heating. As a cationic polymerization initiator, an aromatic iodonium salt, an aromatic sulfonium salt, a cyclopentadienyl iron (II) complex, etc. can be used. These can initiate cationic polymerization by any or any of active energy ray irradiation or heating depending on the difference in structure.

The polymerization initiator may preferably be included in an amount of 0.1 to 10% by mass based on 100% by mass of the entire hard coat composition. When the content of the polymerization initiator is within the above range, curing can be sufficiently progressed, and the mechanical properties and adhesion of the finally obtained coating film can be within a good range. The phenomenon tends to be less likely to occur.

The hard coat composition may further include at least one selected from the group consisting of solvents and additives.

The solvent is capable of dissolving or dispersing the polymerizable compound and the polymerization initiator, and any solvent known as a solvent for a hard coat composition in the art can be used within a range that does not impair the effects of the present invention.

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

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

The pressure-sensitive adhesive layer may be a layer called pressure sensitive adhesive (PSA), which adheres to the object by pressing. The pressure-sensitive adhesive may be an adhesive that is "a substance that has adhesiveness at room temperature and adheres to adherends with light pressure" (JIS K6800), and "specific components are incorporated into a protective film (microcapsule), and suitable means An adhesive capable of maintaining stability until the film is destroyed by (pressure, heat, etc.)” (JIS K6800) may be a capsule type adhesive.

A color adjustment layer is a layer which has a function of color adjustment and is a layer which can adjust an optical laminated body to a target color. A color adjusting layer is a layer containing resin and a coloring agent, for example. Examples of the coloring agent 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, threnic compounds, and diketopyrrolopyrrole-based compounds; extender pigments such as barium sulfate and calcium carbonate; and dyes such as alkaline dyes, acid dyes, and mordant dyes.

A refractive index adjustment layer is a layer which has a function of refractive index adjustment, has a refractive index different from that of an optical film, for example, and is a layer which can provide a predetermined refractive index to an optical laminated body. The refractive index adjusting layer may be, for example, a resin layer containing an appropriately selected resin and, in some cases, a pigment, or may be a metal thin film. As a pigment which adjusts a refractive index, silicon oxide, aluminum oxide, antimony oxide, a tin oxide, a titanium oxide, zirconium oxide, and tantalum oxide are mentioned, for example. The average primary particle size 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, irregular reflection of light passing through the refractive index adjusting layer can be prevented, and a decrease in transparency can be prevented. Examples of the metal used in the refractive index adjustment layer include metal oxides such as titanium oxide, tantalum oxide, zirconium oxide, zinc oxide, tin oxide, silicon oxide, indium oxide, titanium oxynitride, titanium nitride, silicon oxynitride, and silicon nitride; and metal nitrides.

The optical laminate may further contain 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 optical film side surface or the functional layer side surface, or may be laminated on both the optical film side and the functional layer side. In the case of having a functional layer on both surfaces of the optical film, the protective film may be laminated on the surface of one functional layer side, or may be laminated on the surface of both functional layers. 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 capable of protecting the surface of the optical film or functional layer. Examples of protective films include polyester resin films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; and polyolefin resin films such as polyethylene and polypropylene films, acrylic resin films, and the like, and those selected from the group consisting of polyolefin resin films, polyethylene terephthalate resin films, and acrylic resin films are preferred. When an optical layered body 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 layered body has two protective films, the thickness of each protective film may be the same or different.

In one embodiment of the present invention, the optical laminate may be wound around a core in a roll shape, and the form is referred to as a laminate film roll. As the material constituting the winding core, for example, polyethylene resin, polypropylene resin, polyvinyl chloride resin, polyester resin, epoxy resin, phenol resin, melamine resin, silicon resin, polyurethane resin, polycarbonate resin, ABS resin, etc. synthetic resin; metals such as aluminum; and fiber-reinforced plastics (FRP: a composite material in which fibers such as glass fibers are incorporated into plastics to improve strength). The winding core has a shape such as a cylindrical shape or a columnar shape, and its diameter is, for example, 80 to 170 mm. In addition, the diameter of the laminate film roll, that is, the diameter after winding is not particularly limited, but is usually 200 to 800 mm. In one embodiment of the present invention, in the laminate film roll, in the manufacturing process of the optical film, the laminate having the support, the optical film, and optionally the functional layer and the protective film is formed on the core without peeling the support from the optical film. You may have a form wound into a roll shape. Laminate film rolls are often stored once in the form of film rolls due to space and other constraints in continuous production, and in the form of laminate film rolls, since the laminate is more tightly wound and tightened, it causes cloudiness on the support. The material becomes easier to transfer onto the optical film. However, if a support having a predetermined logarithmic contact angle is used, it is difficult for cloudiness to be transferred from the support to the optical film, and even if it is wound into a laminate film roll and tightened, cloudiness is unlikely to occur.

The optical film described above may include a functional layer such as an ultraviolet absorbing layer, an adhesive layer, a color adjusting layer, and a refractive index adjusting layer, and a hard coat layer.

[Image display device]

Since the optical film of the present invention is formed from the varnish of the present invention and has excellent optical properties, it can be suitably used as a window film of an image display device. The optical film of the present invention can be disposed as a front plate on the visual side surface of an image display device, particularly a flexible display. The said front plate has a function of protecting the image display element in a flexible display. Since the image display device provided with the above optical film has high flexibility and bending resistance and can have high surface hardness, it does not damage other members when bent, and the optical film itself does not have fold wrinkles. It is unlikely to occur, and further surface scratches can be advantageously suppressed.

Examples of image display devices include televisions, smartphones, mobile phones, car navigation systems, tablet PCs, portable game consoles, electronic paper, indicators, bulletin boards, watches, and wearable devices such as smart watches. Examples of flexible displays include image display devices having flexible characteristics, such as televisions, smart phones, mobile phones, and smart watches.

In one embodiment of the present invention, the image display device may include the optical film of the present invention, and at least one selected from the group consisting of a polarizing plate, a touch sensor, and a display panel. For example, an image display device in which a polarizing plate, a touch sensor, and a display panel are laminated on one side of the optical film with or without a transparent adhesive or a transparent pressure-sensitive adhesive may be used. The image display device may be provided with a bezel or may have a light-shielding pattern described later. Further, the optical film of the present invention may be attached to an image display device as the optical laminate, and the optical film included in the image display device may be the optical laminate.

In one embodiment of the present invention, the image display device may include a colored light-shielding pattern printed around an edge on at least one surface of the optical film or the polarizing plate, and the light-shielding pattern is in the form of a single layer or a multi-layer. may be The polarizing plate may continuously extend over the non-display area or bezel portion, and includes a polyvinyl alcohol-based polarizer and a protective layer laminated or bonded to at least one surface of the polyvinyl alcohol-based polarizer. A polarizing plate may be sufficient.

In one embodiment of the present invention, in the structure in which the polarizing plate and the touch sensor are integrated on one surface of the optical film, the order of disposing the polarizing plate and the touch sensor is not limited, and the order of the optical film, the polarizing plate, the touch sensor, and the display panel Alternatively, the optical film, the touch sensor, the polarizer, and the display panel may be arranged in that order. When the optical film, the polarizing plate, the touch sensor, and the display panel are arranged in this order, the touch sensor exists below the polarizing plate when the image display device is viewed from the viewing side, so the pattern of the touch sensor is difficult to be visually recognized. There is an advantage. In this case, it is preferable that the front surface retardation of the substrate of the touch sensor is ±2.5 nm or less. The material of the substrate may be an unstretched film, for example, a film of at least one material selected from the group consisting of materials such as triacetyl cellulose, triacetyl cellulose, cycloolefin, cycloolefin copolymer, and polynorbornene copolymer. do. Meanwhile, a structure in which only a pattern is transferred to an optical film and a polarizing plate without a touch sensor substrate may be provided.

The polarizing plate and touch sensor may be disposed between the optical film and the display panel by a transparent adhesive layer or a transparent adhesive layer, but a transparent adhesive layer is preferred. When the optical film, the polarizing plate, the touch sensor, and the display panel are arranged in this order, a transparent adhesive layer may be positioned between the optical film and the polarizing plate and between the touch sensor and the display panel. When the optical film, the touch sensor, the polarizing plate, and the display panel are arranged in that order, a transparent adhesive layer may be disposed between the optical film and the touch sensor, between the touch sensor and the polarizing plate, and between the polarizing plate and the display panel.

The thickness of the transparent adhesive layer is not particularly limited, and may be, for example, 1 to 100 μm. In the transparent adhesive layer, it is preferable that the thickness of the transparent adhesive layer on the lower display panel side is equal to or greater than the thickness of the upper transparent adhesive layer on the optical film side, and the viscoelasticity at -20 to 80°C is 0.2 MPa or less. In this case, noise generated by interference between the touch sensor and the display panel can be reduced, and breakage of upper and lower members can be suppressed by relieving interface stress during bending. From the viewpoint of suppressing cohesive failure of the transparent adhesive and at the same time relieving interface stress, the viscoelasticity may be 0.01 to 0.15 MPa.

<Polarizer>

The said polarizing plate may contain, for example, a polarizer and, if necessary, at least one selected from a support body, an alignment film, a retardation coating layer, an adhesive layer, an adhesive layer, and a protective layer. The thickness of the polarizing plate is not particularly limited, and may be, for example, 100 μm or less. When the thickness is 100 μm or less, the flexibility is difficult to decrease. Within the above range, for example, 5 to 100 μm may be sufficient.

The polarizer may be a film-type polarizer commonly used in the art prepared by a process including steps of swelling, dyeing, crosslinking, stretching, washing, and drying a polyvinyl alcohol-based film, and polymerizable liquid crystal and dichromatic It may be an application-type polarizer (sometimes referred to as a polarization coating layer) formed by applying a polarizing coating layer-forming composition containing a sexual dye. The polarization coating layer (sometimes simply referred to as a polarization layer) is, for example, formed by applying an alignment film-forming composition on a support, imparting alignment properties to form an alignment film, and forming a polymerizable liquid crystal compound and a dichroic dye on the alignment film. It can be prepared by applying a polarizing coating layer-forming composition containing a to form a liquid crystal coating layer. Such a polarizing coating layer can be formed thinner than a polarizing plate including a protective layer attached to both surfaces of the film-type polarizer with an adhesive. The thickness of the polarizing coating layer may be 0.5 to 10 μm, preferably 2 to 4 μm. As the support, the polymer film exemplified above as a protective film can be used.

(alignment layer)

The alignment layer may be formed by applying an alignment layer forming composition. The composition for forming an alignment layer may include an alignment agent, a photopolymerization initiator, and a solvent commonly used in the related art. As the alignment agent, an alignment agent commonly used in the field may be used without particular limitation. For example, a polyacrylate-based polymer, a polyamic acid, a polyimide-based polymer, or a polymer containing a cinnamate group can be used as an alignment agent, and when photo-alignment is applied, it is preferable to use a polymer containing a cinnamate group. do. As the solvent, for example, methanol, ethanol, ethylene glycol, isopropyl alcohol, propylene glycol, methyl cellosolve, butyl cellosolve, alcohol solvents such as propylene glycol monomethyl ether, ethyl acetate, butyl acetate, ethylene glycol methyl ether Ester solvents such as acetate, GBL, propylene glycol methyl ether acetate and ethyl lactate, ketone solvents such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, methyl amyl ketone and methyl isobutyl ketone, pentane, hexane, heptane, etc. aliphatic hydrocarbon solvents, aromatic hydrocarbon solvents such as toluene and xylene, nitrile solvents such as acetonitrile, ether solvents such as tetrahydrofuran and dimethoxyethane, and chlorinated hydrocarbon solvents such as chloroform and chlorobenzene. A solvent can be used individually or in combination of 2 or more types.

The coating of the alignment layer forming composition may include, for example, spin coating, extrusion molding, dip coating, flow coating, spray coating, roll coating, gravure coating, micro gravure coating, etc., preferably using an in-line coating method. use. Alignment treatment is performed after the alignment film-forming composition is applied and, if necessary, dried. For the alignment treatment, various methods known in the art can be employed without limitation, and preferably, photo-alignment film formation can be used. The photo-alignment layer is usually obtained by applying a composition for forming a photo-alignment layer containing a polymer or monomer having a photoreactive group and a solvent to a support, and irradiating polarized light, preferably, polarized UV. The photo-alignment film is more preferable in that the direction of the alignment control force can be arbitrarily controlled by selecting the polarization direction of the irradiated polarized light.

The thickness of the photo-alignment layer is usually 10 to 10,000 nm, preferably 10 to 1,000 nm, and more preferably 10 to 500 nm. When the thickness of the photo-alignment film is within the above range, the orientation regulating force is sufficiently expressed.

(polarization coating layer)

The polarization coating layer may be formed by applying a composition for forming a polarization coating layer. Specifically, the composition for forming a polarizing coating layer includes a polymerizable liquid crystal composition (hereinafter referred to as polymerizable liquid crystal (B)) containing at least one polymerizable liquid crystal (hereinafter sometimes referred to as polymerizable liquid crystal (B)) serving as a host compound in addition to a dichroic dye. It is sometimes called liquid crystal composition B).

A "dichroic dye" means a dye having a property in which the absorbance in the direction of the major axis of the molecule is different from the absorbance in the direction of the minor axis of the molecule. As long as it has such properties, the dichroic dye is not limited, and may be a dye or a pigment. Two or more types of dyes may be used in combination, two or more types of pigments may be used in combination, or dyes and pigments may be used in combination.

The dichroic dye preferably has a maximum absorption wavelength (λ _MAX ) in the range of 300 to 700 nm. Examples of such dichroic dyes include acridine dyes, oxazine dyes, cyanine dyes, naphthalene dyes, azo dyes, and anthraquinone dyes, preferably azo dyes. Examples of the azo dye include monoazo dyes, bisazo dyes, trisazo dyes, tetrakisazo dyes, and stilbenazo dyes, and preferably include bisazo dyes and trisazo dyes.

The liquid crystal state represented by the polymerizable liquid crystal (B) is preferably a smectic phase, and is more preferably a high-order smectic phase from the viewpoint of being able to produce a polarizing layer having a higher degree of alignment order. A polymerizable liquid crystal (B) exhibiting a smectic phase is referred to as a polymerizable smectic liquid crystal compound. The polymerizable liquid crystal (B) can be used alone or in combination. Moreover, when combining 2 or more types of polymerizable liquid crystals, it is preferable that at least 1 type is polymerizable liquid crystal (B), and it is more preferable that 2 or more types are polymerizable liquid crystals (B). By combining these, liquid crystallinity can be temporarily maintained even at a temperature below the liquid crystal-crystal phase transition temperature in some cases. Polymerizable liquid crystal (B) is, for example, Lub et al. Recl. Trav. Chim. It is produced by a known method described in Pays-Bas, 115, 321-328 (1996) or Japanese Patent No. 4719156. The content of the dichroic dye in the polymerizable liquid crystal composition B can be appropriately adjusted according to the type of the dichroic dye, etc., but is preferably 0.1 to 50 parts by mass, more preferably 0.1 to 50 parts by mass, relative to 100 parts by mass of the polymerizable liquid crystal (B). It is preferably 0.1 to 20 parts by mass, more preferably 0.1 to 10 parts by mass. When the content of the dichroic dye is within the above range, it can be polymerized without disturbing the orientation of the polymerizable liquid crystal (B), and the tendency to inhibit the orientation of the polymerizable liquid crystal (B) is small.

The polymerizable liquid crystal composition B preferably contains a solvent. In general, since a smectic liquid crystal compound has a high viscosity, a polymerizable liquid crystal composition containing a solvent is easy to apply, and as a result, it is often easy to form a polarizing film. Examples of the solvent include solvents similar to those contained in the orientation polymer composition described above, and can be appropriately selected depending on the solubility of the polymerizable liquid crystal (B) and the dichroic dye. The content of the solvent is preferably 50 to 98% by mass relative to the total amount of the polymerizable liquid crystal composition B. In other words, the solid content in the polymerizable liquid crystal composition B is preferably 2 to 50% by mass relative to the total amount of the polymerizable liquid crystal composition B.

The polymerizable liquid crystal composition B preferably contains at least one leveling agent. The leveling agent has a function of adjusting the fluidity of the composition B and further flattening the coating film obtained by applying the polymerizable liquid crystal composition B, and specifically includes a surfactant. When the polymerizable liquid crystal composition B contains a leveling agent, the content is preferably 0.05 to 5 parts by mass, more preferably 0.05 to 3 parts by mass with respect to 100 parts by mass of the polymerizable liquid crystal. When the content of the leveling agent is within the above range, it is easy to horizontally align the polymerizable liquid crystal, and the obtained polarizing layer tends to be smoother. If the content of the leveling agent relative to the polymerizable liquid crystal is within the above range, there is a tendency that unevenness does not occur so much in the polarizing layer obtained.

The polymerizable liquid crystal composition B preferably contains at least one polymerization initiator. The polymerization initiator is a compound capable of initiating a polymerization reaction of the polymerizable liquid crystal (B), and a photopolymerization initiator is preferable in that it can initiate a polymerization reaction under a lower temperature condition. Specifically, photopolymerization initiators capable of generating active radicals or acids by the action of light are exemplified, and among these, photopolymerization initiators capable of generating radicals by the action of light are preferable. Examples of the polymerization initiator include benzoin compounds, benzophenone compounds, alkylphenone compounds, acylphosphine oxide compounds, triazine compounds, iodonium salts and sulfonium salts.

When the polymerizable liquid crystal composition B contains a polymerization initiator, the content thereof can be appropriately adjusted according to the type and amount of the polymerizable liquid crystal contained in the polymerizable liquid crystal composition, but preferably, with respect to 100 parts by mass of the polymerizable liquid crystal It is preferably 0.1 to 30 parts by mass, more preferably 0.5 to 10 parts by mass, and still more preferably 0.5 to 8 parts by mass. If the content of the polymerization initiator is within this range, it can be polymerized without disturbing the orientation of the polymerizable liquid crystal (B). When the polymerizable liquid crystal composition B contains a photopolymerization initiator, the polymerizable liquid crystal composition may further contain a photosensitizer. When the polymerizable liquid crystal composition B contains a photopolymerization initiator and a photosensitizer, the polymerization reaction of the polymerizable liquid crystal contained in the polymerizable liquid crystal composition can be further promoted. The amount of the photosensitizer used can be appropriately adjusted depending on the type and amount of the photopolymerization initiator and polymerizable liquid crystal, but is preferably 0.1 to 30 parts by mass, more preferably 0.5 to 10 parts by mass, based on 100 parts by mass of the polymerizable liquid crystal. part, more preferably 0.5 to 8 parts by mass.

In order to advance the polymerization reaction of the polymerizable liquid crystal more stably, the polymerizable liquid crystal composition B may contain an appropriate amount of a polymerization inhibitor, thereby making it easier to control the progress of the polymerization reaction of the polymerizable liquid crystal. When the polymerizable liquid crystal composition B contains a polymerization inhibitor, the content can be appropriately adjusted depending on the type and amount of the polymerizable liquid crystal and the amount of the photosensitizer, but preferably with respect to 100 parts by mass of the polymerizable liquid crystal It is preferably 0.1 to 30 parts by mass, more preferably 0.5 to 10 parts by mass, and still more preferably 0.5 to 8 parts by mass. If the content of the polymerization inhibitor is within this range, it can be polymerized without disturbing the alignment of the polymerizable liquid crystal.

The polarization coating layer is usually formed by applying a polarization coating layer-forming composition on a support that has been subjected to orientation treatment, and polymerizing the polymerizable liquid crystal in the obtained coating film. A method of applying the polarizing coating layer forming composition is not limited. As an orientation treatment, what was illustrated previously is mentioned. A dry film is formed by applying the composition for forming a polarizing coating layer and drying and removing the solvent under conditions in which the polymerizable liquid crystal contained in the obtained film does not polymerize. As a drying method, a natural drying method, an air drying method, a heat drying method, and a vacuum drying method are mentioned. When the polymerizable liquid crystal is a polymerizable smectic liquid crystal compound, it is preferable to change the liquid crystal state of the polymerizable smectic liquid crystal compound contained in the dry film to a nematic phase (ie, a nematic liquid crystal state) and then to transfer to the smectic phase. . In order to form a smectic phase via a nematic phase, for example, the dry film is heated above the temperature at which the polymerizable smectic liquid crystal compound contained in the dry film undergoes a phase transition to the liquid crystal state of the nematic phase, and then, A method of cooling to the temperature at which the smectic liquid crystal compound exhibits the liquid crystal state of the smectic phase is employed. Subsequently, after changing the liquid crystal state of the polymerizable liquid crystal in the dry film into a smectic phase, a method of photopolymerizing the polymerizable liquid crystal while maintaining the liquid crystal state of the smectic phase will be described. In photopolymerization, the light irradiated to the dry film can be appropriately selected according to the type of photopolymerization initiator contained in the dry film, the type of polymerizable liquid crystal (particularly, the type of photopolymerizer possessed by the polymerizable liquid crystal) and the amount thereof, , Specific examples thereof include active energy rays selected from the group consisting of visible light, ultraviolet light, and laser light. Among these, ultraviolet light is preferable in that it is easy to control the progress of the polymerization reaction and in that a photopolymerization apparatus widely used in the art can be used. By carrying out photopolymerization, the polymerizable liquid crystal is polymerized while maintaining a smectic phase, preferably a liquid crystal state of a higher order smectic phase, to form a polarizing layer.

(Phase difference coating layer)

The polarizing plate may include a retardation coating layer (sometimes simply referred to as a retardation layer). The retardation coating layer is collectively referred to as a λ/2 layer, a λ/4 layer, a positive C layer, or the like, depending on optical properties. The retardation coating layer is, for example, coated with a retardation coating layer forming composition containing a liquid crystal compound on the alignment film of a support having an alignment film formed on the surface to form a liquid crystal coating layer, and then attaching the liquid crystal coating layer to the polarizing layer via an adhesive layer. After that, it can be formed by peeling off the support, but it is not limited to this method. As the support, the polymer film exemplified above can be used as a protective film, and the surface of the support on the side where the alignment film and the retardation layer are formed may be subjected to surface treatment before forming the alignment film. The composition for forming the alignment layer and the coating and drying method thereof are the same as those described for the polarization coating layer. The composition of the composition for forming the retardation coating layer is the same as that described for the polarization coating layer, except that the dichroic dye is not included. In addition, the method of applying, drying, and curing the composition for forming the retardation coating layer is the same as that described for the polarizing coating layer.

The thickness of the retardation coating layer may be preferably 0.5 to 10 μm, more preferably 1 to 4 μm.

In one embodiment of the present invention, the optical properties of the retardation coating layer may be adjusted according to the thickness of the coating layer, the alignment state of the polymerizable liquid crystal compound, and the like. By adjusting the thickness of the retardation layer, it is possible to manufacture a retardation layer giving a desired in-plane retardation. An in-plane retardation value (in-plane retardation value, Re) is a value defined by formula (1), and in order to obtain a desired Re, Δn and thickness d may be adjusted.

Re=d×Δn(λ) Equation (1) (where Δn=nx-ny)

(In Equation (1), Re represents the in-plane retardation value, d represents the thickness of the coating layer, and Δn represents the birefringence. Considering the refractive index ellipsoid formed by orientation of the polymerizable liquid crystal compound, three directions The refractive indices of, that is, nx, ny, and nz are defined as follows: nx represents the principal refractive index of the refractive index ellipsoid formed by the retardation layer in a direction parallel to the plane of the retardation layer ny is the retardation layer formed represents the refractive index in a direction parallel to the plane of the retardation layer in the refractive index ellipsoid and orthogonal to the direction of nx nz is the direction perpendicular to the plane of the retardation layer in the refractive index ellipsoid formed by the retardation layer When the retardation layer is a λ/4 layer, the range of the in-plane retardation value (Re(550)) is usually 113 to 163 nm, preferably 130 to 150 nm. When the retardation layer is a λ/2 layer, The range of Re (550) is usually 250 to 300 nm, preferably 250 to 300 nm)

In addition, a retardation layer exhibiting a retardation in the thickness direction can be produced according to the alignment state of the polymerizable liquid crystal compound. Expression of the retardation in the thickness direction indicates the characteristic that the retardation value Rth in the thickness direction becomes negative in equation (2).

Rth=[(nx+ny)/2-nz]×d Equation (2)

(In Formula (2), nx, ny, nz, and d are the same as the above definitions)

The range of the in-plane retardation value (Re(550)) of the positive C layer is usually 0 to 10 nm, preferably 0 to 5 nm, and the range of the retardation value (Rth) in the thickness direction is usually -10 to -300 nm. , preferably -20 to -200 nm. The polarizing plate may have two or more retardation coating layers, and in the case of having two retardation coating layers, the first retardation coating layer is a λ / 4 layer for producing circularly polarized light, and the second retardation coating layer is a positive for improving color when viewed from an angle. C layer may be sufficient. In addition, the first retardation coating layer may be a positive C layer for improving color when viewed from an angle, and the second retardation coating layer may be a λ/4 layer for producing circularly polarized light.

(Adhesive layer and adhesive layer)

The said polarizing plate may contain an adhesive bond layer and/or an adhesive layer. In one embodiment of the present invention, the polarization coating layer and the first retardation coating layer, or the first retardation coating layer and the second retardation coating layer may be bonded through an adhesive or an adhesive. As the adhesive forming the adhesive layer, a water-based adhesive, an active energy ray-curable adhesive or a thermosetting adhesive can be used, and a water-based adhesive or an active energy ray-curable adhesive is preferable. As an adhesive layer, the thing mentioned later can be used.

Examples of water-based adhesives include adhesives made of a polyvinyl alcohol-based resin aqueous solution, water-based two-component urethane emulsion adhesives, and the like. Among them, a water-based adhesive composed of a polyvinyl alcohol-based resin aqueous solution is preferably used. Examples of the polyvinyl alcohol-based resin include a vinyl alcohol homopolymer obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, and a polyvinyl alcohol-based copolymer obtained by saponifying a copolymer of vinyl acetate and another monomer copolymerizable therewith Polymers or modified polyvinyl alcohol-based polymers obtained by partially modifying their hydroxyl groups can be used. The water-based adhesive may contain a crosslinking agent such as an aldehyde compound (eg glyoxal), an epoxy compound, a melamine compound, a methylol compound, an isocyanate compound, an amine compound, or a polyvalent metal salt.

In the case of using a water-based adhesive, it is preferable to perform a drying step for removing water contained in the water-based adhesive after bonding the coating layers together.

The active energy ray-curable adhesive is an adhesive containing a curable compound that is cured by irradiation with active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays, and is preferably an ultraviolet curable adhesive.

The curable compound may be a cationic curable compound or a radical polymerizable curable compound. Examples of the cationically polymerizable curable compound include an epoxy compound (a compound having one or two or more epoxy groups in a molecule), an oxetane compound (a compound having one or two or more oxetane rings in a molecule), or combinations thereof. Examples of the radically polymerizable curable compound include (meth)acrylic compounds (compounds having one or two or more (meth)acryloyloxy groups in the molecule) and other vinyl compounds having radically polymerizable double bonds. , or combinations thereof. A cationically polymerizable curable compound and a radically polymerizable curable compound may be used together. The active energy ray-curable adhesive usually further contains a cationic polymerization initiator and/or a radical polymerization initiator for initiating a curing reaction of the curable compound.

In bonding the coating layers, surface activation treatment may be applied to at least one of the surfaces to be bonded in order to improve adhesiveness. As the surface activation treatment, dry treatment such as corona treatment, plasma treatment, electric discharge treatment (glow discharge treatment, etc.), flame treatment, ozone treatment, UV ozone treatment, ionizing active ray treatment (ultraviolet ray treatment, electron beam treatment, etc.); Wet treatment such as ultrasonic treatment using a solvent such as water or acetone, saponification treatment, or anchor coat treatment may be used. These surface activation treatments may be performed alone or in combination of two or more.

The thickness of the adhesive layer can be adjusted according to its adhesive strength, and may be preferably 0.1 to 10 μm, more preferably 1 to 5 μm. In one embodiment of the present invention, in the case of a configuration in which a plurality of adhesive layers are used, they may be made of the same material or different materials, and may have the same thickness or different thicknesses.

The pressure-sensitive adhesive layer can be composed of a pressure-sensitive adhesive composition containing a resin such as (meth)acrylic resin, rubber resin, polyurethane resin, polyester resin, silicone resin, or polyvinyl ether resin as a main component. Among them, a pressure-sensitive adhesive composition having, as a base polymer, a polyester-based resin or a (meth)acrylic-based resin having excellent transparency, weather resistance, heat resistance, and the like is suitable. The pressure-sensitive adhesive composition may be of an active energy ray curing type or a thermosetting type.

As an adhesive resin used by this invention, the thing whose weight average molecular weight is 300,000-4 million is used normally. Considering durability and especially heat resistance, the weight average molecular weight is preferably 500,000 to 3,000,000, more preferably 650,000 to 2,000,000. When the weight average molecular weight is larger than 300,000, it is preferable from the viewpoint of heat resistance, and when the weight average molecular weight is smaller than 4,000,000, it is preferable also from the viewpoint of reducing adhesion and adhesive strength. In addition, a weight average molecular weight is measured by GPC (gel permeation chromatography) and says the value computed by polystyrene conversion.

Moreover, a crosslinking agent can be contained in an adhesive composition. As the crosslinking agent, an organic type crosslinking agent or a polyfunctional metal chelate can be used. As an organic type crosslinking agent, an isocyanate type crosslinking agent, a peroxide type crosslinking agent, an epoxy type crosslinking agent, an imine type crosslinking agent, etc. are mentioned. A polyfunctional metal chelate is one in which a multivalent metal is bonded covalently or coordinately to an organic compound. Examples of the multivalent metal atom include Al, Cr, Zr, Co, Cu, Fe, Ni, V, Zn, In, Ca, Mg, Mn, Y, Ce, Sr, Ba, Mo, La, Sn, Ti, and the like. there is. An oxygen atom etc. are mentioned as an atom in the organic compound which forms a covalent bond or coordinate bond, and an alkyl ester, an alcohol compound, a carboxylic acid compound, an ether compound, a ketone compound etc. are mentioned as an organic compound.

When a crosslinking agent is contained, the usage amount is preferably from 0.01 to 20 parts by mass, more preferably from 0.03 to 10 parts by mass with respect to 100 parts by mass of the pressure-sensitive adhesive resin. In addition, when the crosslinking agent exceeds 0.01 parts by mass, the cohesive force of the pressure-sensitive adhesive layer tends not to be insufficient, and there is little risk of foaming during heating, while when it is less than 20 parts by mass, the moisture resistance is sufficient and peeling in reliability tests or the like. becomes difficult to occur.

The pressure-sensitive adhesive composition preferably contains a silane coupling agent as an additive. Examples of the silane coupling agent include silicon having an epoxy structure such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane. compound; amino group-containing silicon compounds such as 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)3-aminopropylmethyldimethoxysilane; 3-chloropropyltrimethoxysilane; (meth)acrylic group-containing silane coupling agents such as acetoacetyl group-containing trimethoxysilane, 3-acryloxypropyltrimethoxysilane, and 3-methacryloxypropyltriethoxysilane; Isocyanate group containing silane coupling agents, such as 3-isocyanate propyl triethoxysilane, etc. are mentioned. A silane coupling agent can impart durability, especially the effect of suppressing exfoliation in a humid environment. The amount of the silane coupling agent used is preferably 1 part by mass or less, more preferably 0.01 to 1 part by mass, still more preferably 0.02 to 0.6 part by mass with respect to 100 parts by mass of the pressure-sensitive adhesive resin.

In addition, the pressure-sensitive adhesive composition may contain other known additives, for example, in the pressure-sensitive adhesive composition, powders such as colorants and pigments, dyes, surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, softeners , antioxidants, anti-aging agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, inorganic or organic fillers, metal powders, particulates, foils, and the like can be appropriately added depending on the use. Further, within a controllable range, a redox system to which a reducing agent is added may be employed.

The thickness of the pressure-sensitive adhesive layer is not particularly limited, and is, for example, about 1 to 100 μm, preferably 2 to 50 μm, and more preferably 3 to 30 μm.

(protective layer)

The said polarizing plate may contain the protective layer. In one embodiment of the present invention, the polarizing plate may have at least one protective layer, and is located on one side of the polarizer constituting the polarizing plate or, if the polarizer has a retardation layer, the retardation layer is located on the opposite side of the polarizer. can do.

The protective layer is not particularly limited as long as it is a film excellent in transparency, mechanical strength, thermal stability, moisture barrier properties, isotropy, and the like. Specifically, polyester-based films, such as polyethylene terephthalate, polyethylene isophthalate, and polybutylene terephthalate; cellulosic films such as diacetyl cellulose and triacetyl cellulose; polycarbonate-based film; acrylic films such as polymethyl (meth)acrylate and polyethyl (meth)acrylate; styrenic films such as polystyrene and acrylonitrile-styrene copolymer; polyolefin-based films such as cycloolefin, cycloolefin copolymer, polynorbornene, polypropylene, polyethylene, and ethylene-propylene copolymer; Vinyl chloride-based film; polyamide-based films such as nylon and aromatic polyamide; Imide-based film; sulfone-based film; polyether ketone-based films; Sulfurized polyphenylene-based film; vinyl alcohol-based film; Vinylidene chloride-based film; vinyl butyral-based films; arylate-based films; polyoxymethylene-based film; Urethane-based film; Epoxy-based film; A silicone type film etc. are mentioned. Among these, a cellulose-based film having a surface saponified by alkali or the like is particularly preferable considering polarization characteristics or durability. Further, the protective layer may also have an optical compensation function such as a retardation function.

The protective layer may have been subjected to an adhesion-facilitating treatment for improving adhesion to a surface to be adhered to the polarizer or the retardation coating layer. The adhesion-facilitating treatment is not particularly limited as long as it can improve the adhesive strength, and examples thereof include dry treatment such as primer treatment, plasma treatment, and corona treatment; chemical treatment such as alkali treatment and saponification treatment; Low pressure UV treatment etc. are mentioned.

<Touch sensor>

The image display device may include a touch sensor. The touch sensor has a support, a lower electrode provided on the support, an upper electrode opposed to the lower electrode, and an insulating layer sandwiched between the lower electrode and the upper electrode.

As the support, various materials can be employed as long as they are flexible resin films having light transmission properties. As a support body, the film illustrated above as a protective layer is mentioned, for example.

The lower electrode has, for example, a plurality of small electrodes having a square shape in plan view. A plurality of small electrodes are arranged in a matrix shape.

Further, the plurality of small electrodes are connected to each other adjacent to each other in a diagonal direction of one of the small electrodes to form a plurality of electrode strings. A plurality of electrode strings are connected to each other at the ends so that the electric capacitance between adjacent electrode strings can be detected.

The upper electrode has, for example, a plurality of small electrodes having a square shape in plan view. The plurality of small electrodes are complementaryly arranged in a matrix at positions where the lower electrode is not disposed when viewed from above. That is, the upper electrode and the lower electrode are arranged without a gap in plan view.

Further, the plurality of small electrodes are connected to each other adjacent to each other in the diagonal direction of the other small electrode to form a plurality of electrode strings. A plurality of electrode strings are connected to each other at the ends so that the electric capacitance between adjacent electrode strings can be detected.

The insulating layer insulates the lower electrode and the upper electrode. As the material for forming the insulating layer, a material commonly known as a material for the insulating layer of a touch sensor can be used.

Further, in the present embodiment, the touch sensor has been described as being a so-called projected capacitance type touch sensor, but within a range that does not impair the effect of the invention, a touch sensor of another type such as a film resistance type is employed. You may.

<Light blocking pattern>

The light blocking pattern may be an optical film or at least a part of a bezel or a housing of a display device to which the optical film is applied. For example, there is a case in which each wire of the display device is hidden by a light-shielding pattern and is not visually recognized by the user. The color and/or material of the light-shielding pattern is not particularly limited, and may be formed of a resin material having various colors such as black, white, and gold. For example, the light-shielding pattern may be formed of a resin material such as acrylic resin, ester-based resin, epoxy-based resin, polyurethane, or silicone in which pigments for realizing color are mixed. The material and thickness of the light blocking pattern may be determined in consideration of protection and flexibility characteristics of an optical film or display device. Moreover, these can also be used individually or in mixture of 2 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. In addition, it is also preferable to give a shape such as an inclination in the thickness direction of the light-shielding pattern.

[Example]

Hereinafter, the present invention will be described in more detail by examples. "%" and "part" in examples mean mass % and mass part unless otherwise specified.

[Measurement of weight average molecular weight in terms of polystyrene]

Gel permeation chromatography (GPC) measurements

(1) Pretreatment method

After dissolving the sample in GBL to obtain a 20% solution, it was diluted 100-fold with a DMF eluent and filtered through a 0.45 μm membrane filter to obtain a measurement solution.

(2) Measurement conditions

Column: TSKgel SuperAWM-H × 2 + SuperAW2500 × 1 (internal diameter 6.0 mm, length 150 mm, 3 connections)

Eluent: DMF solution containing 10 mmol/L lithium bromide

Flow rate: 0.6mL/min

Detector: RI detector

Column temperature: 40°C

Injection volume: 20μL

Molecular Weight Standard: Standard Polystyrene

[Production Example 1: Synthesis of polyamideimide resin (1)]

In a nitrogen gas atmosphere, 313.57 g of DMAc was added to a 1 L separable flask equipped with a stirring blade. 18.36 g (57.33 mmol) of TFMB was then added, and TFMB was dissolved in DMAc with stirring at room temperature. Next, 7.72 g (17.38 mmol) of 6FDA was added to the flask, cooled to 10°C, and stirred for 16 hours. Thereafter, 1.71 g (5.81 mmol) of 4,4'-oxybis(benzoyl chloride) (also referred to as "OBBC") and then 6.35 g (31.28 mmol) of terephthaloyl chloride (also referred to as "TPC") were added to the flask. was added and stirred at 10°C for 30 minutes. Then, 313.57 g of DMAc was added, and after stirring for 10 minutes, 0.71 g (3.48 mm °l) of TPC was further added to the flask and stirred for 2 hours. Next, 5.24 g (40.54 mmol) of diisopropylethylamine, 3.78 g (40.54 mmol) of 4-methylpyridine, and 12.42 g (121.65 mmol) of acetic anhydride were added to the flask, and the mixture was stirred at 10°C for 30 minutes. Thereafter, the temperature was raised stepwise from 10°C to 85°C over 1 hour using an oil bath, and further stirred at 85°C for 3 hours to obtain a reaction solution.

The obtained reaction liquid was cooled to room temperature, and it was fed into a large amount of methanol in a filamentous manner. The deposited precipitate was taken out and immersed in methanol for 6 hours. After that, it was washed with methanol and dried under reduced pressure to obtain polyamide-imide resin (1). The weight average molecular weight of the obtained polyamideimide resin (1) was 300000.

[Preparation Example 2: Purification of Solvent (GBL)]

Using Mitsubishi Chemical Co., Ltd. GBL as a raw material, purification was performed a plurality of times according to the distillation method described in Patent No. 2871841 until the dicarboxylic acid content was sufficiently reduced to obtain purified GBL (1).

Next, using the same GBL manufactured by Mitsubishi Chemical Co., Ltd. as the raw material, purification was performed according to the distillation method described in Patent No. 4154897 to obtain purified GBL (2).

Purified GBL (1) and purified GBL (2) were mixed in a ratio of 3:1 to obtain purified GBL (3).

Purified GBL (1) and purified GBL (2) were mixed in a ratio of 1:2 to obtain purified GBL (4).

Purified GBL (1) and purified GBL (2) were mixed at a ratio of 3:2 to obtain purified GBL (5).

5 ppm maleic acid was added to purified GBL (1) to obtain purified GBL (6).

In addition, in this Example, two types of GBLs having different degrees of purification were mixed as described above, but GBLs having different degrees of purification can be obtained by optimizing the distillation conditions.

[Content of Dicarboxylic Acid in Solvent]

GBL obtained as described above was diluted with pure water, and ion chromatograph-mass spectrometry was performed under the following measurement conditions to quantify succinic acid and maleic acid, which are dicarboxylic acids. The measurement was repeated twice, and the average was used as a quantitative value.

Separation column: IonPac AG11-HC (2 mm inner diameter) + AS11-HC (2 mm inner diameter) (both manufactured by Thermo Scientific)

Eluent, flow rate: 10 mmol/L KOH aqueous solution 0.3 mL/min

Column temperature: 35°C

Measurement mode: Selective ion monitoring (SIM) mode m/z=115 (equivalent to maleic acid), m/z=117 (equivalent to succinic acid)

The obtained results are shown in Table 1.

In addition, in this Example and this comparative example, dicarboxylic acid content is expressed by concentration.

(Light transmittance at a wavelength of 275 nm of the solvent)

The light transmittance of the GBL obtained as described above was measured using a spectrophotometer for ultraviolet, visible, near-infrared (Nippon Spectroscopy Co., Ltd., model V-670). First, a quartz cell having an optical path length of 1 cm was filled with Milli-Q water, and the quartz cell was set in a spectrophotometer for ultraviolet, visible, and near-infrared, and blank measurement was performed. Subsequently, GBL was filled in a quartz cell having an optical path length of 1 cm, and the quartz cell was set in the spectrophotometer. The light transmittance of each solvent at a wavelength of 275 nm was obtained by irradiating white light with a wavelength of 250 to 850 nm and measuring the transmittance. The obtained results are shown in Table 1. In Table 1, N.D. indicates that the dicarboxylic acid was not detected.

[Solvent Substitution of Silica Sol]

300 g of methanol-dispersed silica sol (average primary particle size: 27 nm, silica solid content: 30% by mass) and 210 g of purified GBL (1) were put in a 1 L flask, and using a vacuum evaporator, in a water bath at 45 ° C., at 400 hPa. 1 hour, then 1 hour at 250 hPa, methanol was evaporated. Furthermore, the temperature was raised to 70°C under 250 hPa and heated for 30 minutes to obtain GBL dispersed silica sol (1).

[Example 1]

GBL dispersed silica sol (1) and purified GBL (1) were mixed, and PET BLUE 2000 (manufactured by Mitsui Chemical Fine Co., Ltd., hereinafter referred to as "PB2000") was obtained as a bluing agent based on the total mass of the polyamideimide resin and silica solid content. After adding and dissolving 70 ppm), polyamideimide resin (1) was added and dissolved to obtain a varnish.

At this time, the mass ratio of the solid content of the polyamideimide resin (1) to silica is 8:2 (ie, the amount of silica relative to the total mass of the solid content of the polyamideimide resin and silica is 20% by mass), A varnish was prepared so that the concentration of the total solid content of the amide-imide resin (1) and the silica was 10.5% by mass.

[Example 2]

In Example 1, purified GBL (3) was used instead of purified GBL (1), and Sumisorb (registered trademark) 340 (manufactured by Sumica Chemtex Co., Ltd., hereinafter referred to as "SS340") as an ultraviolet absorber was used instead of 70 ppm of PB2000. may be described), 5.7 parts by mass based on 100 parts by mass of the total mass of polyamideimide resin and silica solid content, Sumiplast (registered trademark) Violet B as a bluing agent (manufactured by Sumika ChemteX Co., Ltd., hereinafter referred to as “Violet B”) was added in an amount of 35 ppm based on the total mass of the polyamideimide resin and silica solid content, and a varnish was prepared in the same manner as in Example 1.

[Examples 3 to 7, Comparative Examples 1 to 6]

A varnish was prepared in the same manner as in Example 1, except that the type of GBL, the amount of silica, and the type and amount of ultraviolet absorber and bluing agent were changed as shown in Table 3 below.

[Example 8]

In purified GBL (1), 3.5 parts by mass of Chiguard 5599 (manufactured by Chitec, hereinafter sometimes referred to as "CG5559"), an ultraviolet absorber, based on the mass of polyamide-imide resin, relative to 100 parts by mass of polyamide-imide resin, PB2000 After adding and dissolving 45 ppm based on the mass of the polyamide-imide resin, the polyamide-imide resin (1) was added and dissolved to obtain a varnish. At this time, the concentration of the polyamideimide resin (1) with respect to the entire varnish was set to 9% by mass.

[Measurement of absorption peak half height width of bluing agent]

PB2000 and Violet B, which are the bluing agents used in the above examples and comparative examples, were each dissolved in Mitsubishi Chemical Co., Ltd. GBL to prepare a 0.01% by mass bluing agent GBL solution. The absorption peak of the obtained solution was measured using an ultraviolet, visible, near infrared spectrophotometer ("V-670" manufactured by Nippon Spectroscopy Co., Ltd.). First, a quartz cell having an optical path length of 1 mm was filled with Milli-Q water, and the quartz cell was set to a spectrophotometer for ultraviolet, visible, and near-infrared, and blank measurement was performed. Subsequently, a quartz cell having an optical path length of 1 cm was filled with the GBL solution made from bluing, and the quartz cell was set in the spectrophotometer. Absorbance was measured by irradiation with white light having a wavelength of 250 to 850 nm, and the maximum wavelength of the absorption peak and the half width of the peak were determined. The obtained results are shown in Table 2.

[Manufacture of optical film]

The varnish obtained in Examples and Comparative Examples was coated on a smooth surface of a polyester base material (manufactured by Toyobo Co., Ltd., trade name “A4100”) using an applicator, and dried at 50° C. for 30 minutes and then at 140° C. for 15 minutes, A self-supporting membrane was obtained. The self-supporting film was fixed to a metal frame, heated to 200°C over 40 minutes, maintained at 200°C for 20 minutes, and dried to obtain an optical film. The average thickness of the obtained optical film was 50 micrometers.

[UV light irradiation test]

The obtained optical film was subjected to a QUV test using UVCON manufactured by Atras. The light source was UV-B 313 nm, the output was 40 W, the distance between the optical film and the light source was set to 5 cm, and the obtained optical film was irradiated with ultraviolet rays for 24 hours.

<YI value>

The YI value of the optical film after the UV light irradiation test was measured in accordance with JIS K 7373: 2006 using an ultraviolet-visible and near-infrared spectrophotometer "V-670" manufactured by Nihon Spectrosco. After performing the background measurement in the absence of the sample, the optical film is set in the sample holder, the transmittance for light of 300 to 800 nm is measured, and the tristimulus values (X, Y, Z) are obtained, based on the following formula to calculate the YI value.

YI=100×(1.2769X-1.0592Z)/Y

<Measurement of total light transmittance>

The total light transmittance (Tt) of the optical film after the UV light irradiation test was measured in accordance with JIS K 7105:1981 using a fully automatic direct reading haze computer HGM-2DP manufactured by Suga Test Instruments Co., Ltd.

[Calculation of dicarboxylic acid content]

Based on the content of dicarboxylic acid in the solvent contained in each varnish measured as described above and the mass of the solvent contained in each varnish, the content of dicarboxylic acid in the varnish was calculated. The obtained results are shown in Table 3.

Among the varnishes obtained in Examples and Comparative Examples, components other than the solvent were of high purity that did not contain dicarboxylic acid. Therefore, based on the content of dicarboxylic acid contained in each solvent shown in Table 1, the content of dicarboxylic acid in the varnish was calculated from the weight of each solvent contained in the varnish.

Table 3 shows the composition of the varnish and the measurement results of the optical film of each Example and each Comparative Example.

Examples 1 to 4 and Comparative Examples 1 to 4 are varnishes having the same composition but differing only in the solvent. Comparing these, when purified GBL (1) or (3) with a low content of dicarboxylic acid is used, compared to the case where purified GBL (4) or (5) with a high content of dicarboxylic acid is used, after UV irradiation A tendency for the YI value to decrease was confirmed.

From the comparison of Examples 1 and 3 and Comparative Examples 1, 3 and 5, it can be confirmed that there is a particularly remarkable effect when the content of dicarboxylic acid is small in order to reduce the YI value after UV irradiation. This tendency is the same also when an ultraviolet absorber is included (Example 2 and Comparative Examples 2 and 6). Further, when comparing the rate of change of YI before and after UV irradiation, it was also confirmed that the rate of change of YI can be remarkably reduced with the varnish of the present invention.

Claims (13)

A varnish containing at least a solvent and a polyimide resin, wherein the content of dicarboxylic acid in the varnish is 10 ppm or less. According to claim 1,
A varnish having a light transmittance of 96% or more at a wavelength of 275 nm of the solvent. According to claim 1,
A varnish wherein the solvent is γ-butyrolactone. According to claim 1,
A varnish in which dicarboxylic acid is an aliphatic dicarboxylic acid having 4 to 10 carbon atoms. According to claim 1,
The varnish, wherein the dicarboxylic acid is at least one type of dicarboxylic acid selected from the group consisting of maleic acid and succinic acid. According to claim 1,
A varnish further comprising at least one bluing agent. According to claim 6,
A varnish in which the half width of the absorption peak of the bluing agent is 70 nm or more and 200 nm or less. According to claim 6,
Blueing agent Anthraquinone-based blueing agent, varnish. According to claim 1,
The varnish in which the content of the solvent is 75 to 99% by mass based on the total amount of the varnish. According to claim 1,
A varnish in which the content of the polyimide-based resin is 1 to 25% by mass based on the total amount of the varnish. According to claim 1,
A varnish in which the polyimide-based resin is a polyamideimide resin. An optical film formed from the varnish according to any one of claims 1 to 11. (a) a step of preparing a solvent having a dicarboxylic acid content of 10 ppm or less;
(b) a step of preparing a varnish having a dicarboxylic acid content of 10 ppm or less by mixing the solvent prepared in step (a) with a polyimide-based resin;
(c) a step of applying the obtained varnish on a support to form a coating film; and
(d) process of drying the coating film to obtain an optical film
A method for manufacturing an optical film comprising at least one.