JP2006249116A - Polyimide and optical film using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical film excellent in optical properties on which various functional layers can be provided at elevated temperatures and which has excellent heat-resistance and low linear thermal expansibility. <P>SOLUTION: The optical film comprises a polyimide having a repeating unit represented by the formula of the drawing, wherein A denotes a 4-30C group having a monocyclic or condensed polycyclic aromatic group or a monocyclic or condensed polycyclic aliphatic group; X<SP>1</SP>and X<SP>2</SP>each denote a halogen atom, wherein at least one atom is selected from chlorine, bromine, and iodine; Y<SP>1</SP>, Y<SP>2</SP>, R<SP>1</SP>, and R<SP>2</SP>each denote a halogen atom, an alkyl group, an alkoxy group, or an aryl group; and j and k each denote 0, 1, or 2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polyimide and an optical film excellent in heat resistance, optical characteristics, and low linear thermal expansion.

In recent years, in the field of flat panel displays such as liquid crystal display elements and organic EL elements, it has been studied to replace a substrate from glass to plastic in order to improve breakage resistance, reduce the weight, and reduce the thickness. In particular, there is a strong demand for display devices for mobile information communication devices such as mobile phones, electronic notebooks, laptop computers, and other portable information terminals.
This plastic substrate requires electrical conductivity. Therefore, on a plastic film, a semiconductor film such as an oxide of indium oxide, tin oxide or tin-indium alloy, a metal film such as an oxide film of gold, silver or palladium alloy, the semiconductor film and the metal film The use of a transparent conductive substrate provided with a film formed in combination as a transparent conductive layer as an electrode substrate of a display element has been studied.

Plastics used for this purpose include heat-resistant amorphous polymers such as modified polycarbonates (see, for example, Patent Document 1), polyethersulfones (see, for example, Patent Document 2), and cycloolefin copolymers (for example, Patent Document 3). And a transparent conductive layer and a gas barrier layer are known.
However, even when such a heat-resistant plastic is used, sufficient heat resistance as a plastic substrate cannot be obtained. That is, when a conductive layer is formed on a plastic substrate using these heat-resistant plastics and then exposed to a temperature of 150 ° C. or higher for providing an alignment film or the like, there is a problem that the conductivity and gas barrier properties are greatly lowered. Further, when installing a TFT for manufacturing an active matrix image element, further heat resistance is required.

Patent Document 4 describes a method of forming a polycrystalline silicon film at a temperature of 300 ° C. or lower by plasma decomposition of a gas containing SiH ₄ . Patent Document 5 describes a method for forming a semiconductor layer in which amorphous silicon and polycrystalline silicon are mixed on a polymer substrate by irradiation with an energy beam. Patent Document 6 describes a method of providing a thermal buffer layer and irradiating a pulsed laser beam to form a polycrystalline silicon semiconductor layer on a plastic substrate. Various methods for forming a polycrystalline silicon film for TFTs at 300 ° C. or lower like these have been proposed, but the configuration and apparatus are complicated, and the manufacturing cost is high. For this reason, heat resistance of 300 ° C. to 350 ° C. or more is required for plastic substrates.

Patent Document 7 describes a thin film transistor substrate using a polyimide derived from an aliphatic tetracarboxylic acid anhydride. Although this polyimide film is good in terms of transparency, the linear thermal expansion is insufficient, and it cannot be said that the heat resistance is sufficient to form a high-quality polycrystalline silicon film for TFT. On the other hand, as a polyimide having excellent transparency and high heat resistance, there is a method using an aromatic diamine having fluorine as a substituent (see, for example, Patent Document 8). To increase the number of fluorine substituents, there is a problem that the polymerizability deteriorates.
JP 2000-227603 A (all pages) JP 2000-284717 A (all pages) JP 2001-150584 A (all pages) JP-A-7-81919 (all pages) Japanese National Patent Publication No. 10-512104 (all pages) Japanese Patent Laid-Open No. 11-102867 (all pages) JP 2003-168800 A (all pages) JP 11-35684 A (all pages)

  The problem to be solved by the present invention is to provide an optical film having excellent heat resistance and low linear thermal expansibility capable of installing various functional layers at high temperatures, and an optimal polyimide for it. It is to provide.

［一般式（１）中、Ａは、単環式もしくは縮合多環式の芳香族基、または、単環式もしくは縮合多環式の脂肪族基を含有する基であり、かつ構成する炭素原子数が４〜３０である基を表し、Ｘ¹およびＸ²はそれぞれ独立にハロゲン原子を表し、少なくとも１つは塩素、臭素、ヨウ素から選ばれる原子である。Ｙ¹、Ｙ²、Ｒ¹およびＲ²はそれぞれ独立にハロゲン原子、置換もしくは無置換のアルキル基、置換もしくは無置換のアルコキシ基、または置換もしくは無置換のアリール基を表し、jおよびkはそれぞれ独立に０、１または２を表す。］
［２］ 一般式（１）で表される繰り返し単位を有するポリイミドのガラス転移温度が３００℃以上である［１］に記載の光学フィルム。
［３］ 線熱膨張係数が５０ｐｐｍ／℃以下である［１］または［２］に記載の光学フィルム。
［４］ 厚さが５０μｍの場合における波長４２０ｎｍの光線透過率が３０％以上である［１］〜［３］のいずれか１項に記載の光学フィルム。
［５］ 一般式（１）のＡが単環式もしくは縮合多環式の芳香族基を含有する基であることを特徴とする［１］〜［４］のいずれか１項に記載の光学フィルム。
［６］ 一般式（２）で表される繰り返し単位を有するポリイミド。
一般式（２）

［一般式（２）中、Ａは、単環式もしくは縮合多環式の芳香族基、または、単環式もしくは縮合多環式の脂肪族基を含有する基であり、かつ構成する炭素原子数が４〜３０である基を表し、Ｙ¹、Ｙ²、Ｒ¹およびＲ²はそれぞれ独立にハロゲン原子、置換もしくは無置換のアルキル基、置換もしくは無置換のアルコキシ基、または置換もしくは無置換のアリール基を表し、jおよびkはそれぞれ独立に０、１または２を表す。］ The above problems have been achieved by the means described below.
[1] An optical film containing polyimide having a repeating unit represented by the general formula (1).
General formula (1)

[In General Formula (1), A is a monocyclic or condensed polycyclic aromatic group, or a group containing a monocyclic or condensed polycyclic aliphatic group, and constituting carbon atoms. A group having a number of 4 to 30 is represented, X ¹ and X ² each independently represent a halogen atom, and at least one is an atom selected from chlorine, bromine and iodine. Y ¹ , Y ² , R ¹ and R ² each independently represent a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, or a substituted or unsubstituted aryl group, and j and k are each Independently represents 0, 1 or 2. ]
[2] The optical film according to [1], wherein the glass transition temperature of the polyimide having the repeating unit represented by the general formula (1) is 300 ° C. or higher.
[3] The optical film according to [1] or [2], which has a linear thermal expansion coefficient of 50 ppm / ° C. or less.
[4] The optical film according to any one of [1] to [3], wherein the light transmittance at a wavelength of 420 nm when the thickness is 50 μm is 30% or more.
[5] The optical system according to any one of [1] to [4], wherein A in the general formula (1) is a group containing a monocyclic or condensed polycyclic aromatic group. the film.
[6] A polyimide having a repeating unit represented by the general formula (2).
General formula (2)

[In General Formula (2), A is a monocyclic or condensed polycyclic aromatic group, or a group containing a monocyclic or condensed polycyclic aliphatic group, and constituting carbon atoms. Represents a group having a number of 4 to 30, and Y ¹ , Y ² , R ¹ and R ² are each independently a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, or a substituted or unsubstituted group And j and k each independently represents 0, 1 or 2. ]

  The optical film of the present invention has excellent heat resistance and low linear thermal expansion, and is excellent in optical characteristics. For this reason, it is possible to install various functional layers at a high temperature and to manufacture an image display device having excellent display quality. The polyimide of this invention can be preferably used for manufacture of such an optical film.

BEST MODE FOR CARRYING OUT THE INVENTION

  Hereinafter, the optical film of the present invention will be described in detail. The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

  The optical film of this invention is an optical film containing the polyimide which has a repeating unit represented by General formula (1).

一般式（１）中、Ａは、単環式もしくは縮合多環式の芳香族基、または、単環式もしくは縮合多環式の脂肪族基を含有する基であり、かつ構成する炭素原子数が４〜３０である基を表す。 Below, the polyimide which has a repeating unit represented by General formula (1) used for this invention is demonstrated.
General formula (1)

In general formula (1), A is a monocyclic or condensed polycyclic aromatic group, or a group containing a monocyclic or condensed polycyclic aliphatic group, and the number of constituent carbon atoms Represents a group of 4 to 30.

Preferred A contains an aromatic group and comprises 6 to 28 carbon atoms, or a monocyclic or condensed polycyclic aliphatic group, and comprises 4 to 4 carbon atoms. And more preferably a group containing an aromatic group and comprising 7 to 28 carbon atoms, or a monocyclic aliphatic group and comprising 4 carbon atoms. Is a group having 10 to 10 carbon atoms, a condensed polycyclic aliphatic group and a group having 7 to 20 carbon atoms, particularly preferably 2 or more aromatic groups, and It is a group having 12 to 28 carbon atoms, in which four carbonyl groups serving as imide bonds are not bonded to one aromatic group.
Examples of the ring structure of the aromatic group include a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, etc. Among them, a benzene ring and a naphthalene ring are preferable, and a benzene ring is particularly preferable. Examples of the ring structure of the aliphatic group include a cyclobutane ring, a cyclohexane ring, a bicycloheptane ring, a bicyclooctane ring, an adamantane ring, and a diadamantane ring, and among them, a cyclobutane ring, a bicycloheptane ring, and a bicyclooctane ring are preferable.

  In order to reduce the coloration of the polyimide, it is desirable to reduce the CT interaction. The structure of A is preferably an aliphatic group because it has little influence on coloring even if it has any substituent. In the case of an aromatic group, it is preferably an electron donating group when there is no substituent other than the polymerizable group or when it has a substituent. Explaining using Hammett's substituent constant σ value, which is a measure of electron withdrawing and electron donating properties of substituents, by introducing substituents with small σ values such as alkyl groups, aryl groups, and alkoxy groups. It can be said that coloring can be reduced.

  When the specific structure of A is indicated by the name of tetracarboxylic acid, (trifluoromethyl) pyromellitic acid, di (trifluoromethyl) pyromellitic acid, di (phenyl) pyromellitic acid, pentafluoroethyl pyromellitic acid, Bis [3,5-di (trifluoromethyl) phenoxy] pyromellitic acid, 2,3,3 ′, 4′-biphenyltetracarboxylic acid, 3,3 ′, 4,4′-biphenyltetracarboxylic acid, 3, 3 ', 4,4'-tetracarboxydiphenyl ether, 2,3', 3,4'-tetracarboxydiphenyl ether, 3,3 ', 4,4'-benzophenone tetracarboxylic acid, 2,3,6,7-naphthalene Tetracarboxylic acid, 1,4,5,8-naphthalenetetracarboxylic acid, 1,2,5,6-naphthalenetetracarboxylic acid, 3,3 ′, 4 '-Tetracarboxydiphenylmethane, 3,3', 4,4'-tetracarboxydiphenylsulfone, 2,2-bis (3,4-dicarboxyphenyl) propane, 2,2-bis (3,4-dicarboxyphenyl) ) Hexafluoropropane, 5,5′-bis (trifluoromethyl) -3,3 ′, 4,4′-tetracarboxybiphenyl, 2,2 ′, 5,5′-tetrakis (trifluoromethyl) -3, 3 ', 4,4'-tetracarboxybiphenyl, 5,5'-bis (trifluoromethyl) -3,3', 4,4'-tetracarboxydiphenyl ether, 5,5'-bis (trifluoromethyl)- 3,3 ′, 4,4′-tetracarboxybenzophenone, bis (3,4-dicarboxyphenoxy) tetrakis (trifluoromethyl) benze 3,4,9,10-perylenetetracarboxylic acid, 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] propane, cyclobutanetetracarboxylic acid, cyclopentanetetracarboxylic acid, 2,2- Bis (4- (3,4-dicarboxyphenoxy) phenyl) hexafluoropropane, bis (3,4-dicarboxyphenyl) dimethylsilane, 1,3-bis (3,4-dicarboxyphenyl) tetramethyldisiloxane , Difluoropyromellitic acid, 1,4-bis (3,4-dicarboxytrifluorophenoxy) tetrafluorobenzene, 1,4-bis (3,4-dicarboxytrifluorophenoxy) octafluorobiphenyl, pyrazine-2, 3,5,6-tetracarboxylic acid, pyrrolidine-2,3,4,5-tetracarboxylic Acid, thiophene-2,3,4,5-tetracarboxylic acid, bicyclo [2.2.1] hepta-2,3,5,6-tetracarboxylic acid, bicyclo [2.2.2] octa-2, 3,5,6-tetracarboxylic acid and the like.

  The structure of the diamine to reduce the coloration of the polyimide is preferably an aliphatic group because it has little influence on the coloration even if it has any substituent, but because of its strong basicity, it forms a salt during the polymerization reaction However, there are problems such that it is generally necessary to use a silylating agent in combination, and it is difficult to obtain a strong film. In the case of an aromatic group, the polymerization reaction is easy to proceed and it is easy to obtain a film having an excellent strength, but the color derived from the CT interaction is large. In order to reduce the CT interaction, an electron withdrawing substituent may be introduced into the aromatic group of the diamine (if the Hammett's substituent constant σ value is used, one having a large σ value), and fluorine may be substituted. However, there are problems such as that the raw material becomes remarkably expensive and that the polymerizability deteriorates when the number of fluorine substituents is increased in order to increase transparency. As a result of intensive studies by the present inventors, by introducing at least one halogen atom other than fluorine at the ortho position of the biphenyl linking site, the electronic effect of the halogen atom and the twist angle between the benzene rings of the biphenyl structure are reduced. It has been found that a polyimide that is inexpensive and excellent in heat resistance, transparency, and low linear thermal expansion can be provided by the effect of increasing.

From the above viewpoint, X ¹ and X ² represent a halogen atom, and at least one is an atom selected from chlorine, bromine and iodine. Preferred X ¹ and X ² are chlorine atoms.
Y ¹ , Y ² , R ¹ and R ² each independently represent a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, or a substituted or unsubstituted aryl group.
The alkyl group is preferably a group having 1 to 8 carbon atoms, and more preferably a group having 1 to 3 carbon atoms. The alkoxy group is preferably a group having 1 to 8 carbon atoms, and more preferably a group having 1 to 3 carbon atoms. The aryl group is preferably a group having 6 to 12 carbon atoms, and more preferably a group having 6 carbon atoms.
Examples of the substituent include a halogen atom (for example, a chlorine atom, a bromine atom, a fluorine atom and an iodine atom, preferably a fluorine atom, a chlorine atom or a bromine atom), an alkoxycarbonyl group (for example, methoxycarbonyl). Group), an acyl group (for example, an acetyl group), an acyloxy group (for example, an acetyloxy group), an alkylaminocarbonyl group (for example, an aminocarbonyl group), and the like. And a halogen atom is particularly preferable.
Preferred Y ¹ , Y ² , R ¹ and R ² are fluorine atom, chlorine atom, methyl group, trifluoromethyl group, trichloromethyl group, methoxy group and trifluoromethoxy group, and more preferably fluorine atom, chlorine An atom, a methyl group, and a trifluoromethyl group.
j and k are 0, 1 or 2, 0 or 1 is preferable, and 0 is particularly preferable.

一般式（１−２）中、Ａ、Ｘ¹、Ｘ²、Ｙ¹、Ｙ²、Ｒ¹、Ｒ²、jおよびkは一般式（１）と同義であり、好ましい構造あるいは数値も同様である。 Among the general formula (1), a polyimide having a repeating unit represented by the following general formula (1-2) is more preferable, and a polyimide having a repeating unit represented by the following general formula (2) is more preferable.
Formula (1-2)

In general formula (1-2), A, X ¹ , X ² , Y ¹ , Y ² , R ¹ , R ² , j and k have the same meanings as in general formula (1), and the preferred structures or numerical values are also the same. is there.

一般式（２）中、Ａ、Ｙ¹、Ｙ²、Ｒ¹、Ｒ²、j、kは一般式（１）と同義であり、好ましい構造あるいは数値も同様である。 General formula (2)

In General Formula (2), A, Y ¹ , Y ² , R ¹ , R ² , j, and k have the same meanings as those in General Formula (1), and preferred structures and numerical values are also the same.

Although the specific example of the diamine part as described in General formula (1) and (2) below is given with the form of diamine, the diamine part which can be employ | adopted by this invention is not limited to these.
4,4′-diamino-2,2′-dichloro-6,6′-difluorobiphenyl, 4,4′-diamino-2,2 ′, 6,6′-tetrachlorobiphenyl, 4,4′-diamino- 2,2′-dichloro-6,6′-ditrifluoromethylbiphenyl, 4,4′-diamino-2,2′-dichloro-6,6′-dimethylbiphenyl, 4,4′-diamino-2,2 ′ -Dibromo-6,6'-dichlorobiphenyl, 4,4'-diamino-2,2'-dichloro-3,3 ', 5,5', 6,6'-hexafluorobiphenyl, 4,4'-diamino -2,2 ', 5,5'-tetrachloro-6,6'-dimethylbiphenyl, 4,4'-diamino-2,2', 6,6'-tetrachloro-3,3 ', 5,5 '-Tetrafluorobiphenyl, 3,4'-diamino-2,2'-dichloro-6,6'-difluorobiphenyl, , 4'-diamino-2,2'-dichloro-6,6'-difluorobiphenyl, 2,4'-diamino-4,2 ', 6,6'-tetrachlorobiphenyl, 3,3'-diamino-2 , 2 ′, 6,6′-tetrachlorobiphenyl, 4,4′-diamino-2-chloro-2 ′, 6,6′-trifluorobiphenyl, 4,4′-diamino-2,6,6′- And trichloro-2′-fluorobiphenyl.

A polyimide having a repeating unit represented by the general formula (1) suitable for the present invention includes a tetracarboxylic acid containing a skeleton of A, an acid anhydride, an acid chloride, an esterified product, etc. as a derivative thereof (hereinafter referred to as tetracarboxylic acid). (Referred to as acids) and an aromatic diamine. In order to adjust characteristics such as heat resistance and transparency, a plurality of tetracarboxylic acids and diamines may be used.
Furthermore, a structure other than the diamine represented by the general formula (1) (hereinafter referred to as other diamines) may be copolymerized as long as the effects of the present invention are not impaired. In the case of copolymerizing other diamines, 0 to 50 mol% is preferable, 0 to 30 mol% is more preferable, and 0 to 15 mol% is more preferable when the entire diamine is 100 mol%.

  Examples of other diamines include the following. p-phenylenediamine, benzidine, o-tolidine, m-tolidine, bis (trifluoromethyl) benzidine, octafluorobenzidine, 4,4 ″ -diamino-p-terphenyl, 4,4′-diamino-diphenylmethane, 4 , 4'-diamino-diphenyl sulfide, 3,3'-diamino-diphenyl sulfide, 4,4'-diamino-diphenyl sulfone, 4,4'-diamino-diphenyl ether, 3,3'-diamino-diphenyl ether, 3,3 '-Diamino-biphenyl, 3,3'-dimethyl-4,4'-diamino-biphenyl, 3,3'-dimethoxy-benzidine, 4,4'-diamino-p-terphenyl, bis (4-aminocyclohexyl) Methane, 1,5-diaminonaphthalene, 2,6-diamino-naphthalene, 2 6-diaminopyridine, 2,5-diamino-1,3,4-oxadiazole, 1,4-diaminocyclohexane, piperazine, methylene diamine, ethylene diamine, 2,2-dimethyl-propylene diamine, 9,9'-bis (4-aminophenyl) fluorene and the like.

The polyimide which has a repeating unit represented by General formula (1) is manufactured by the well-known method which passes through a polyimide precursor. That is,
1) A polyimide precursor is synthesized in an organic solvent, and the solvent is removed at a low temperature using a technique such as distillation under reduced pressure, or the polyimide precursor is simply removed by a method of discharging the obtained polyimide precursor solution into a poor solvent. After releasing, this is heated and imidized to obtain polyimide.
2) After preparing a polyimide precursor solution in the same manner as in 1), a dehydrating agent represented by acetic anhydride is added, and a catalyst is added if necessary to chemically imidize. A method of isolating the polyimide by washing and washing and drying as necessary.
3) A method in which a polyimide precursor solution is obtained in the same manner as in 1), and then the solvent is removed by decompression or heat treatment, and at the same time, thermal imidization is performed.
4) A method in which a raw material is charged into an organic solvent and then heated to simultaneously synthesize a polyimide precursor and imidization reaction, and allow a catalyst, an azeotropic agent, and a dehydrating agent to coexist as necessary.

  The polyimide precursor refers to an organic compound (for example, polyamic acid, polyisoimide, polyamic acid ester, etc.) that becomes a polyimide by ring closure by heating or chemical action. Here, ring closure means that an imide ring is formed. A polyimide precursor solution is a solution in which a polyimide precursor is dissolved in a solvent. Here, the solvent means a compound that is liquid at 25 ° C.

  The polyimide precursor solution can be produced by dissolving 0.95 to 1.05 mol of tetracarboxylic acid with respect to 1 mol of diamine after dissolving diamine in the solvent. Here, as a preferred example, a method using a tetracarboxylic acid anhydride as the tetracarboxylic acid will be described.

  First, after dissolving diamine in a solvent, tetracarboxylic anhydride is added to the obtained diamine solution. The reaction temperature is preferably -30 to 200 ° C, more preferably -20 to 150 ° C, particularly preferably 10 to 120 ° C. The time when the viscosity of the polyimide precursor becomes almost constant is taken as the reaction end point. Depending on the type of acid anhydride and diamine, it can usually be completed in 3-24 hours. The solute concentration is preferably 5 to 60%, more preferably 10 to 50%, and particularly preferably 15 to 40%.

  In the synthesis of the polyimide precursor or polyimide, dicarboxylic acids and monoamines can be used in combination for adjusting the molecular weight and preventing coloring, and it is preferable to add a dicarboxylic acid anhydride.

  Any solvent can be used as long as it dissolves the diamine, tetracarboxylic acids, and the resulting polyimide precursor. Specific examples of the solvent include N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, chlorophenol, anisole, diethylene glycol monomethyl ether, 1-methoxy-2-propanol and the like. A solvent can be used individually or in mixture of 2 or more types.

  The molecular weight of the polymer having the structure represented by the general formula (1) and the general formula (2) that can be used in the present invention is preferably 10,000 to 500,000 in terms of weight average molecular weight, more preferably 10,000 to 300,000, 20,000 to 200,000 is particularly preferable. When the molecular weight is too low, film formation is difficult or mechanical properties are deteriorated. If the molecular weight is too high, it is difficult to control the molecular weight in the synthesis, or the viscosity of the solution is too high and handling becomes difficult. The molecular weight can be based on the viscosity of the polyimide solution or the polyimide precursor solution. The viscosity of the solution is preferably 500 to 200,000, more preferably 2000 to 100,000, and particularly preferably 10,000 to 60,000 mPa · s.

  Although the preferable specific example of the polyimide which has a repeating unit represented by General formula (1) and General formula (2) below is given, the polyimide which can be used by this invention is not limited to these. The number in the lower right of the parenthesis represents the molar ratio in the case of the copolymer.

  Next, a method for producing the optical film of the present invention will be described. When the polyimide becomes a solution, the polyimide solution is applied onto the substrate and peeled to obtain a polyimide film. When the polyimide precursor solution is used, the polyimide precursor solution is applied onto the substrate and heated. When imidized, a polyimide coating film is obtained, and when the polyimide coating film is peeled from the substrate, a polyimide film is obtained. For example, the polyimide precursor solution can be exfoliated by removing the solvent to some extent by drying the polyimide precursor solution by applying it on a substrate by means of a conventionally known spin coating method, spray coating method or the like, by extruding from a slit nozzle, or by a bar coater. In this state, the film is peeled from the substrate and further heated to obtain a polyimide film. 200-400 degreeC is preferable and the maximum temperature of the heating conditions in this case has more preferable 250-350 degreeC. Outside the range of 200 to 400 ° C., imidization may be insufficient or the coating film may be deformed or deteriorated by heat.

  The concentration of the polyimide precursor in the polyimide precursor solution in the present invention is preferably 20% by mass or more, more preferably 30% by mass or more, and further preferably 40% by mass or more. If it is less than 20% by mass, the effect of increasing the productivity during coating may be diminished. The upper limit is preferably 70% by mass, and if it exceeds 80% by mass, dissolution may be insufficient. Further, the viscosity of the polyimide precursor solution is preferably 100 poise or less, more preferably 85 poise or less, and further preferably 60 poise or less. If it exceeds 100 poise, coating may be difficult.

The thickness of the optical film of the present invention is 10 μm to 700 μm, preferably 20 μm to 200 μm, more preferably 40 μm to 150 μm.
When the film has a thickness of 50 μm, the light transmittance at a wavelength of 420 nm is 30% or more, preferably 40% or more, more preferably 60% or more, and even more preferably 70% or more. The light transmittance at a wavelength of 550 nm is 70% or more, preferably 80% or more, more preferably 85% or more, and further preferably 90% or more. The haze is preferably 3% or less, more preferably 2% or less, and still more preferably 1% or less.

  The heat resistant temperature of the optical film of the present invention is preferably high, and the glass transition temperature obtained from DSC measurement or the thermal deformation start temperature of TMA can be used as a guide. In this case, a preferable glass transition temperature is 300 ° C. or higher, more preferably 350 ° C. or higher, and particularly preferably 380 ° C. or higher.

  The linear thermal expansion coefficient of the optical film of the present invention is preferably a small value, and in the case of a film having a thickness of 50 to 100 μm, the preferable linear thermal expansion coefficient when the linear thermal expansion measurement range is 100 to 200 ° C. is 50 ppm / ° C. In the following, it is more preferably 40 ppm / ° C. or less, further preferably 30 ppm / ° C. or less, and particularly preferably 20 ppm / ° C. or less.

  The surface of the optical film of the present invention is subjected to saponification, corona treatment, flame treatment, glow discharge treatment, etc. on the surface of the film substrate in order to enhance the adhesion with other layers or components depending on the application. Can do. Furthermore, an adhesive layer and an anchor layer may be provided on the film surface. Depending on the purpose, smoothing layer for surface smoothing, hard coat layer for imparting scratch resistance, ultraviolet absorbing layer for enhancing light resistance, surface roughening layer for improving film transportability, etc. Various known functional layers can be provided.

A transparent conductive layer can be installed in the optical film of the present invention. As the transparent conductive layer, known metal films, metal oxide films, and the like can be applied. Among these, metal oxide films are preferable from the viewpoint of transparency, conductivity, and mechanical properties. For example, metal oxide films such as indium oxide, cadmium oxide and tin oxide to which tin, tellurium, cadmium, molybdenum, tungsten, fluorine, zinc, germanium, etc. are added as impurities, zinc oxide, titanium oxide, etc. to which aluminum is added as impurities, Can be mentioned. Among them, an indium oxide thin film mainly composed of tin oxide and containing 2 to 15% by weight of zinc oxide is excellent in transparency and conductivity, and is preferably used.
These transparent conductive layers can be formed by any method as long as the target thin film can be formed. For example, the material can be formed from a gas phase such as sputtering, vacuum deposition, ion plating, and plasma CVD. A vapor phase deposition method in which a film is deposited to form a film is suitable, and a film can be formed by the methods described in Japanese Patent No. 3430344, Japanese Patent Application Laid-Open No. 2002-322561, and Japanese Patent Application Laid-Open No. 2002-361774.
Among these, the sputtering method is preferable from the viewpoint that particularly excellent conductivity and transparency can be obtained.

A preferable degree of vacuum of such a sputtering method, a vacuum deposition method, an ion plating method, and a plasma CVD method is 0.133 mPa to 6.65 Pa, more preferably 0.665 mPa to 1.33 Pa. Before providing such a transparent conductive layer, it is preferable to subject the base film to a surface treatment such as plasma treatment (reverse sputtering) or corona treatment. Moreover, you may heat up to 50 to 200 degreeC during providing the transparent conductive layer.
The film thickness of the transparent conductive layer thus obtained is preferably 20 nm to 500 nm, more preferably 30 nm to 400 nm, and further preferably 50 nm to 300 nm.
Further, the surface electrical resistance of the transparent conductive layer thus obtained, measured at 25 ° C. and 60% relative humidity, is preferably 0.1Ω / □ to 200Ω / □, more preferably 0.1Ω / □. -100Ω / □, more preferably 0.5Ω / □ -60Ω / □. Further, the light transmittance is 80% or more, more preferably 83% or more, and still more preferably 85% or more.

  The optical film of the present invention is preferably provided with a gas barrier layer in order to suppress gas permeability. Preferred gas barrier layers include, for example, metal oxides composed mainly of one or more metals selected from the group consisting of silicon, aluminum, magnesium, zinc, zirconium, titanium, yttrium, and tantalum, silicon, aluminum, boron Metal nitrides or mixtures thereof. Among these, the main component is silicon oxide having a ratio of the number of oxygen atoms to the number of silicon atoms of 1.5 to 2.0 in terms of gas barrier properties, transparency, surface smoothness, flexibility, film stress, cost, and the like. Metal oxide is good. These inorganic gas barrier layers can be produced by vapor deposition such as sputtering, vacuum deposition, ion plating, plasma CVD, etc., in which a material is deposited in the vapor phase to form a film. Of these, the sputtering method is preferred from the viewpoint that particularly excellent gas barrier properties can be obtained. Further, the temperature may be raised to 50 ° C. to 200 ° C. while the gas barrier layer is provided.

The film thickness of the inorganic gas barrier layer thus obtained is preferably 10 nm to 300 nm, more preferably 30 nm to 200 nm.
Such a gas barrier layer may be provided on either the same side or the opposite side as the transparent conductive layer, but it is more preferable to provide it on the opposite side.
The barrier property of the gas barrier film thus obtained is preferably 5 g / m ² · day or less, more preferably 1 g / m ² · day or less, further preferably 40 ° C. or 90% relative humidity. Is 0.5 g / m ² · day or less. The oxygen permeability measured at 40 ° C. and 90% relative humidity is preferably 1 ml / m ² · day or less, more preferably 0.7 ml / m ² · day or less, and even more preferably 0.5 ml / m ² · day. It is as follows.

For the purpose of improving the barrier property, it is particularly desirable to provide a defect compensation layer adjacent thereto. As the defect compensation layer, (1) a method using an inorganic oxide layer prepared by using a sol-gel method as described in US Pat. No. 6,171,663 and JP-A-2003-94572, (2) US Pat. A method using an organic material layer as described in each specification of 64136645, 64163645, and a method for applying these compensation layers by vacuum or vacuum curing as described, or curing with ultraviolet rays or electron beams, or coating Thereafter, it can be prepared by curing with heating, electron beam, ultraviolet rays or the like.
When the coating method is used, various conventionally used coating methods such as spray coating, spin coating, and bar coating can be used.

  The optical film of the present invention can be used as a substrate for a thin film transistor (TFT) display element. Examples of the method for producing the TFT array include the method described in JP-T-10-512104. Further, these substrates may have a color filter for color display. The color filter may be produced by any method, but a photolithography technique is preferable.

  The optical film of the present invention can be used in an image display device after providing various functional layers as necessary. Here, it does not specifically limit as an image display apparatus, A conventionally well-known thing can be used. Moreover, the flat panel display excellent in display quality can be created using the optical film of this invention. Flat panel displays include liquid crystals, plasma displays, electroluminescence (EL), fluorescent display tubes, light emitting diodes, etc. In addition to these, they should be used as substrates instead of display-type glass substrates that have conventionally used glass substrates. Can do. Furthermore, the optical film of the present invention can also be used for applications such as solar cells and touch panels. The touch panel can be applied to those described in JP-A-5-127822, JP-A-2002-48913, and the like.

  When the optical film of the present invention is used for liquid crystal display applications, it is preferably an amorphous polymer in order to achieve optical uniformity. The birefringence is preferably small, and in-plane retardation (Re) is preferably 50 nm or less, more preferably 30 nm or less, and still more preferably 15 nm or less.

When used in a reflection type liquid crystal display device, it is composed of a lower substrate, a reflective electrode, a lower alignment film, a liquid crystal layer, an upper alignment film, a transparent electrode, an upper substrate, a λ / 4 plate, and a polarizing film in order from the bottom. Of these, the optical film of the present invention may be used as a λ / 4 plate or a protective film for a polarizing film by adjusting optical properties, but is preferably used as a substrate from the viewpoint of heat resistance, and from the viewpoint of transparency. It is preferably used as an upper substrate with a transparent electrode and an alignment film. Moreover, a gas barrier layer, TFT, etc. can also be provided as needed. In the case of color display, it is preferable to further provide a color filter layer between the reflective electrode and the lower alignment film, or between the upper alignment film and the transparent electrode.
When used in a transmissive liquid crystal display device, the backlight, polarizing plate, λ / 4 plate, lower transparent electrode, lower alignment film, liquid crystal layer, upper alignment film, upper transparent electrode, upper substrate, λ / 4 are sequentially arranged from the bottom. It consists of a plate and a polarizing film. Of these, the optical film of the present invention may be used as a λ / 4 plate or a protective film for a polarizing film by adjusting the optical characteristics, but is preferably used as a substrate from the viewpoint of its heat resistance. It is preferable to use as. Moreover, a gas barrier layer, TFT, etc. can also be provided as needed. In the case of color display, it is preferable to further provide a color filter layer between the lower transparent electrode and the lower alignment film, or between the upper alignment film and the transparent electrode.

  The liquid crystal cell is not particularly limited. ), VA (Vertically Aligned) and HAN (Hybrid Aligned Nematic) have been proposed. In addition, a display mode in which the above display mode is oriented and divided has been proposed. The optical film of the present invention is effective in any display mode liquid crystal display device. Further, it is effective in any of a transmissive type, a reflective type, and a transflective liquid crystal display device.

  These are JP-A-2-176625, JP-B-7-69536, MVA (SID97, Digest of tech. Papers (Preliminary Collection) 28 (1997) 845), SID99, Digest of tech. Papers (Preliminary Collection) 30. (1999) 206, JP-A-11-258605, SURVAIVAL (Monthly Display, Vol. 6, No. 3 (1999) 14), PVA (Asia Display 98, Proc. Of the-18th-Inter. Display res. Conf. (Preliminary Collection (1998) 383), Para-A (LCD / PDP Iternational`99), DDVA (SID98, Digest of tech. Papers (Preliminary Collection) 29 (1998) 838), EOC (SID98, Digest of tech Papers 29 (1998) 319), PSHA (SID98, Digest of tech. Papers 29 (1998) 1081), RFFMH (Asia Display 98, Proc. Of the-18th-Inter.Display res Conf. (Preliminary Collection) (1998) 375), HMD (SID98, Digest of tech. Papers (Preliminary Collection) 29 (1998) 702), JP-A-10-123478, International Publication No. 98/48320 Pamphlet, Patent No. 3022477 and International Publication No. 00/65384 Pan It is described in the toilet or the like.

The optical film of the present invention is provided with a gas barrier layer and TFT as necessary, and can be used as a substrate with a transparent electrode for organic EL display applications.
As a specific layer structure as the organic EL display element, anode / light emitting layer / transparent cathode, anode / light emitting layer / electron transport layer / transparent cathode, anode / hole transport layer / light emitting layer / electron transport layer / transparent cathode , Anode / hole transport layer / light emitting layer / transparent cathode, anode / light emitting layer / electron transport layer / electron injection layer / transparent cathode, anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron Examples include injection layer / transparent cathode.

The organic EL element in which the optical film of the present invention can be used applies a direct current (which may contain an alternating current component as necessary) voltage (usually 2 to 40 volts) or a direct current between the anode and the cathode. By doing so, light emission can be obtained.
Regarding driving of these light emitting elements, JP-A-2-148687, JP-A-6-301355, JP-A-5-290080, JP-A-7-134558, JP-A-8-234485, and JP-A-8-214447, US Pat. No. 5,828,429. No. 6023308, Japanese Patent No. 2784615, etc. can be used.

  The features of the present invention will be described more specifically with reference to the following examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

<Example 1> Synthesis of polyimide (synthesis of polymer P-101)
Under nitrogen, 7.89 g of 4,4′-diamino-2,2 ′, 6,6′-tetrachlorobiphenyl was dissolved in 60.5 g of dimethylacetamide, and then at a temperature of 20 ° C., 3,3 ′, 7.21 g of 4,4′-biphenyltetracarboxylic dianhydride was gradually added. When the reaction was carried out at 40 ° C. for 2 hours, 60 ° C. for 10 hours, and 80 ° C. for 5 hours, a transparent solution was obtained. Further, this solution was applied on a glass plate with a bar coater, and imidized by heating in a nitrogen atmosphere at 100 ° C. for 1 hour, 150 ° C. for 30 minutes, 250 ° C. for 30 minutes, and 350 ° C. for 1 hour. The obtained polyimide coating film was peeled off from the glass plate to obtain polymer P-101. The IR spectrum of polymer P-101 is shown in FIG.
From FIG. 1, there is no peak in the vicinity of a wavelength 1650 cm ^-1 of the precursor, since the peak is observed in the vicinity of a wavelength of 1780 cm ^-1 of the polyimide, it is understood polymers P-101 is a polyimide.

(Synthesis of polymers P-105, 115, 116, 120)
Polymers P-105, 115, 116, and 120 were produced in the same manner as polymer P-101.

(Synthesis of polymer C-1)
Polyimide produced from 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 4,4′-diamino-2,2 ′, 6,6′-tetramethylbiphenyl (polymer C-1) Was prepared in the same manner as for polymer P-101.

(Synthesis of polymer C-2)
A polyimide (polymer C-2) produced from 1,2,4,5-cyclohexanetetracarboxylic dianhydride and 4,4′-diaminodiphenyl ether was prepared according to the example of JP-A-2003-168800. That is, a polyimide precursor was synthesized, and a polyimide precursor solution was coated on a glass plate with a spin coater, and was then subjected to a nitrogen atmosphere at 100 ° C. for 1 hour, 150 ° C. for 30 minutes, 250 ° C. for 30 minutes, and 350 ° C. for 1 hour. It heated and imidized. The obtained polyimide coating film was peeled off from the glass plate to obtain polymer C-2.

(Evaluation)
Table 1 shows the results of measuring the characteristic values of the prepared polymers by the following method.
1) Light transmittance The transmittance at a wavelength of 420 nm was measured with an ultraviolet-visible spectrophotometer (manufactured by Shimadzu Corporation, UV-3100PC). As a reference, assuming that the absorbance is proportional to the film thickness, a converted value of light transmittance when the film thickness is 50 μm is shown.
2) Glass transition temperature (Tg)
Measured by DSC (in nitrogen, temperature rising temperature 10 ° C./min) (Seiko Co., Ltd., DSC6200).
3) Linear thermal expansion coefficient (CTE)
It was measured by TMA (in nitrogen, temperature rising temperature 10 ° C./min) and obtained from expansion at 100 to 200 ° C. (manufactured by Shimadzu Corporation, TMA50).

P-101, P-115, P-116, and P-120 are all flexible films that are flexible and do not break even when bent, and all of transmittance, Tg, and CTE were excellent. Although aliphatic P-116 having an aliphatic tetracarboxylic acid moiety is excellent in transparency, the CTE is larger than that of aromatic P-101. Therefore, when importance is attached to the characteristics of low linear thermal expansion, tetracarboxylic acid is used. An aromatic moiety is preferred. In formula (1), X ¹ , X ² , Y ¹ , Y ² are chlorine, chlorine, methyl group, methyl group P-120 has the same tetracarboxylic acid structure, and diamine X ¹ , X ² , Y ¹ , Y ² is lower in light transmittance than P-101 in which all of chlorine is chlorine, and in the present invention, all of X ¹ , X ² , Y ¹ and Y ² in the general formula (1) are halogens. Things are preferred. On the other hand, C-1 had a good glass transition temperature and low linear thermal expansibility, but was extremely inferior in light transmittance. C-2 had a low glass transition temperature of 315 ° C. and a linear thermal expansion coefficient of 50 or more, which was a bad value. It can be seen from Table 1 that an optical film excellent in heat resistance, optical properties, and low linear thermal expansion can be obtained by the present invention.

<Example 2> Preparation of organic EL element sample F-1 (installation of gas barrier layer)
Oxygen was introduced into both surfaces of the optical film P-101 by DC magnetron sputtering under a vacuum of 500 Pa under an Ar atmosphere and a pressure of 0.1 Pa, and sputtering was performed at an output of 5 kW by a DC magnetron sputtering method. The film thickness of the obtained gas barrier layer was 60 nm. The optical film sample on which the gas barrier layer is formed has a water vapor permeability of 0.1 g / m ² · day or less at 40 ° C. and a relative humidity of 90%, and an oxygen permeability of 0.1 ml / m at 40 ° C. and a relative humidity of 90%. ² · day or less.

(Installation of transparent conductive layer)
While heating the optical film sample provided with the gas barrier layer to 100 ° C, ITO (In ₂ O ₃ 95% by mass, Sn0 ₂ 5% by mass) was used as a target by DC magnetron sputtering under a vacuum of 0.665 Pa, Ar A transparent conductive layer made of an ITO film having an output of 5 kW and a thickness of 140 nm was provided on one side in an atmosphere. The surface electrical resistance at 25 ° C. and 60% relative humidity of the optical film sample provided with the transparent conductive layer was 30Ω / □.

(Heat treatment of optical film with transparent conductive layer)
The optical film sample provided with the transparent conductive layer obtained above was subjected to heat treatment at 300 ° C. for 1 hour assuming TFT installation.

(Creation of organic EL elements)
From the transparent electrode layer of the optical film sample on which the transparent conductive layer subjected to the heat treatment was installed, an aluminum lead wire was connected to form a laminated structure.
The surface of the transparent electrode was spin-coated with an aqueous dispersion of polyethylene dioxythiophene / polystyrene sulfonic acid (BAYER, Baytron P: solid content: 1.3% by mass), and then vacuum-dried at 150 ° C. for 2 hours. A hole-transporting organic thin film layer having a thickness of 100 nm was formed. This is referred to as a substrate X.
On the other hand, a coating solution for a light-emitting organic thin film layer having the following composition was applied on one side of a temporary support made of 188 μm thick polyethersulfone (Sumilite FS-1300 manufactured by Sumitomo Bakelite Co., Ltd.) using a spin coater. The luminescent organic thin film layer having a thickness of 13 nm was formed on the temporary support by applying and drying at room temperature. This is designated as transfer material Y.

Polyvinylcarbazole (Mw = 63000, manufactured by Aldrich) 40 parts by mass Tris (2-phenylpyridine) iridium complex (orthometalated complex) 1 part by mass Dichloroethane 3200 parts by mass

  The luminescent organic thin film layer side of the transfer material Y is superimposed on the upper surface of the organic thin film layer of the substrate X, heated and pressurized at 160 ° C., 0.3 MPa, 0.05 m / min using a pair of heat rollers, and the temporary support is attached. By peeling off, a light-emitting organic thin film layer was formed on the upper surface of the substrate X. This was designated as substrate XY.

In addition, a patterned vapor deposition mask (a mask with a light emitting area of 5 mm × 5 mm) is installed on one side of a polyimide film (UPILEX-50S, manufactured by Ube Industries, Ltd.) having a thickness of 50 μm cut into 25 mm square, Al was evaporated in a reduced pressure atmosphere of about 0.1 mPa to form an electrode having a thickness of 0.3 μm. Using an Al ₂ O ₃ target by DC magnetron sputtering, the Al ₂ O ₃ was deposited in the same pattern as the Al layer and the thickness of 3 nm. An aluminum lead wire was connected from the Al electrode to form a laminated structure. A coating solution for an electron transporting organic thin film layer having the following composition is coated on the obtained laminated structure using a spin coater coating machine, and vacuum dried at 80 ° C. for 2 hours, thereby transporting an electron having a thickness of 15 nm. An organic thin film layer was formed. This was designated as substrate Z.

Polyvinyl butyral 2000L (Mw = 2000, manufactured by Denki Kagaku Kogyo) 10 parts by mass
1-butanol 3500 parts by mass An electron transporting compound having the following structure 20 parts by mass

  Using the substrates XY and Z, the electrodes are stacked so that the electrodes face each other with the light-emitting organic thin film layer interposed therebetween, and heated and pressurized at 160 ° C., 0.3 MPa, 0.05 m / min using a pair of heat rollers, The organic EL element sample F-1 was obtained by bonding.

  A direct voltage was applied to the organic EL element of the obtained organic EL element sample F-1 using a source measure unit type 2400 (manufactured by Toyo Technica Co., Ltd.). It was confirmed that Sample F-1 of the present invention emitted light.

  From the above examples, it was revealed that the optical film of the present invention does not contain fluorine, is inexpensive, and is excellent in heat resistance, transparency, and low linear thermal expansion. Further, it has been clarified that a gas barrier layer and a transparent conductive layer can be laminated and function as a substrate film for an organic EL element even if a heat treatment assuming a TFT process is performed.

  The optical film of the present invention has excellent heat resistance and low linear thermal expansibility, and is excellent in optical characteristics. Therefore, various functional layers at high temperatures can be installed, optical members having various functions can be provided, and an image display device having excellent display quality can also be provided. Therefore, the present invention has high industrial applicability.

It is IR spectrum of polymer P-101.

Claims (6)

An optical film containing a polyimide having a repeating unit represented by the general formula (1).
General formula (1)

[In General Formula (1), A is a monocyclic or condensed polycyclic aromatic group, or a group containing a monocyclic or condensed polycyclic aliphatic group, and constituting carbon atoms. A group having a number of 4 to 30 is represented, X ¹ and X ² each independently represent a halogen atom, and at least one is an atom selected from chlorine, bromine and iodine. Y ¹ , Y ² , R ¹ and R ² each independently represent a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, or a substituted or unsubstituted aryl group, and j and k are each Independently represents 0, 1 or 2. ]   The optical film according to claim 1, wherein the glass transition temperature of the polyimide having the repeating unit represented by the general formula (1) is 300 ° C. or higher.   The optical film according to claim 1, wherein the linear thermal expansion coefficient is 50 ppm / ° C. or less.   The optical film according to any one of claims 1 to 3, wherein the light transmittance at a wavelength of 420 nm when the thickness is 50 µm is 30% or more.   The optical film according to any one of claims 1 to 4, wherein A in the general formula (1) is a group containing a monocyclic or condensed polycyclic aromatic group. A polyimide having a repeating unit represented by the general formula (2).
General formula (2)

[In General Formula (2), A is a monocyclic or condensed polycyclic aromatic group, or a group containing a monocyclic or condensed polycyclic aliphatic group, and constituting carbon atoms. Represents a group having a number of 4 to 30, and Y ¹ , Y ² , R ¹ and R ² are each independently a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, or a substituted or unsubstituted group And j and k each independently represents 0, 1 or 2. ]

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