JP3815790B1 - Retardation film, optical film, liquid crystal panel, liquid crystal display device, and image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a modified polymer as a raw material for a new reverse dispersion retardation film which does not require selection of a plurality of monomers and polymers in order to realize reverse dispersion and has no problems such as glass transition temperature in a stretching process. provide.
A polymer having a polyol skeleton as a main chain is reacted with a modifying compound such as an aromatic carboxylic acid halide. By the reaction, a modified polymer in which a chemical group such as an aromatic carbonyl group is bonded to the oxygen atom of the side chain of the polyol skeleton can be prepared. For example, polyvinyl alcohol can be used as the polymer, benzoic acid chloride can be used as the modifying compound, and the chemical group includes a benzoyl group. Further, when this modified polymer is formed into a film and subjected to a stretching treatment, a retardation film showing reverse dispersion wavelength dispersion characteristics can be obtained.
[Selection] Figure 1

Description

  The present invention relates to a retardation film, an optical film having the retardation film, a liquid crystal panel, a liquid crystal display device, and an image display device.

  In an image display device such as a liquid crystal display device, a retardation film is generally widely used in order to improve the viewing angle characteristics of a display screen.

  As the retardation film, a λ / 2 plate or a λ / 4 plate is known, but many of these have a characteristic of absorbing on the short wavelength side and increasing the phase difference toward the short wavelength side. is doing. Such a characteristic is generally called a positive wavelength dispersion characteristic (hereinafter referred to as “positive dispersion”). However, the retardation film exhibiting positive dispersion has the following problems.

  The retardation of the retardation film is usually set to be 1/2 of the wavelength for a λ / 2 plate and 1/4 of the wavelength for a λ / 4 plate. Ideally, when the wavelength is on the horizontal axis and the phase difference is on the vertical axis, it is desired that the retardation film plot shows a straight line rising to the right. This is because, if such a plot is shown, the phase difference increases as the wavelength increases, so that a phase difference close to 1/4 or 1/2 of the wavelength can be obtained at any wavelength. However, since the retardation of a positive dispersion retardation film increases as it approaches the short wavelength side as described above, the plot actually shows a curve that rises to the left and behaves differently from the ideal straight line. . That is, although a desired phase difference is satisfied at a certain wavelength, a desired phase difference cannot be obtained in a wide wavelength band. For this reason, it is difficult to perform linear polarization in a wide wavelength band with a positive dispersion retardation film.

  Thus, in recent years, attention has been focused on retardation films that exhibit wavelength dispersion characteristics different from positive dispersion. The retardation film exhibits the property that the phase difference increases as the wavelength approaches the longer wavelength side, that is, the so-called reverse dispersion wavelength dispersion characteristic (hereinafter referred to as “reverse dispersion”). In such a phase difference film, the phase difference increases as the wavelength approaches the longer wavelength side. Therefore, the phase difference plot as described above shows an upward curve and approximates an ideal behavior. That is, for example, with a λ / 4 plate, a phase difference close to a quarter value of the wavelength can be obtained in the wide wavelength band, so that polarization conversion as a λ / 4 plate in the wide wavelength band is possible. In addition, if the retardation film exhibits a larger reverse dispersion, it can be used in a wide wavelength band as a λ / 2 plate having an ideal retardation of a half value of the wavelength. Note that “the magnitude of inverse dispersion” can be, for example, “large” as the slope is relatively large and “small” as the slope is relatively small in the plot as described above. Therefore, in the case of the λ / 2 plate, ½ of the wavelength is an ideal phase difference, so that the slope of the plot is larger than that of the λ / 4 plate (the phase difference at each wavelength is large), that is, A large inverse dispersion is required.

  The reverse dispersion characteristics as described above usually depend on the type of polymer that is the raw material of the retardation film. However, there are very few reports on polymers that can achieve reverse dispersion.

  Specifically, for example, a method of forming a reverse dispersion retardation film by forming a film from a polymer obtained by polymerizing two types of monomers and stretching the film to develop a retardation is reported. (Patent Document 1). In the two types of monomers in this method, one shows positive birefringence (monomer 1), the other shows negative birefringence (monomer 2), and the wavelength dispersion characteristics of both are such that monomer 1 <monomer 2 It is a combination. In addition, there has been reported a method of blending two types of polymers having different retardation and wavelength dispersion characteristics to form a reverse dispersion retardation film (Patent Document 2). Furthermore, a method for producing a reverse dispersion retardation film from a mixture of liquid crystal molecules and a polymer has been reported (Patent Document 3).

  However, the polycarbonate having a fluorene skeleton disclosed in Patent Document 1 has a very high glass transition point due to its structure. For this reason, in the extending | stretching process which expresses a phase difference, there exists a problem that extending | stretching temperature must be set to very high temperature. In addition, in order to increase the refractive index in the thickness direction, the following problems also arise when such a polycarbonate unstretched film is subjected to shrinkage treatment. The shrinkage treatment is a method in which an unstretched film is bonded to a film that shrinks by heating, and this laminate is heated and stretched (Patent Document 4). In this case, since the stretching temperature of the polycarbonate unstretched film is too high with respect to the shrinking temperature of the shrinkable film, it is difficult to industrially produce a retardation film having a high refractive index in the thickness direction.

Moreover, in the method described in Patent Document 2, it is difficult to maintain the transparency of the blend polymer obtained when two types of polymers are compatible, and there is a problem that choices of polymer combinations are limited. is there. Furthermore, even in the method described in Patent Document 3, it is difficult to select a combination in which the polymer and the liquid crystal molecules are compatible. For example, depending on the combination, the liquid crystal molecules dispersed in the polymer may be liquefied in the heat stretching treatment of the film, resulting in an increase in the haze of the resulting retardation film, which may reduce transparency.
JP 2002-221622 A JP 2002-14234 A JP 2002-48919 A Japanese Patent No. 2818983 (JP-A-5-157911)

Therefore, as described above, the present invention eliminates the need to select a plurality of monomers and polymers in order to achieve reverse dispersion, and can also avoid problems such as stretching temperature depending on the type of polymer. It aims at provision of the retardation film using this, and its use.

前記式（１）において、Ｒ^１、Ｒ^２、Ｒ^３、Ｒ^４およびＲ^５は、それぞれ同一であっても異なってもよく、水素原子、ハロゲン原子、水酸基、メチル基、エチル基、ハロゲン化メチル、ハロゲン化エチル基、またはニトロ基（−ＮＯ_２）であり、前記式（２）において、Ｒ^６、Ｒ^７、Ｒ^８、Ｒ^９、Ｒ^１０、Ｒ^１１およびＲ^１２は、それぞれ同一であっても異なってもよく、水素原子、ハロゲン原子、水酸基、メチル基、エチル基、ハロゲン化メチル基、ハロゲン化エチル基またはニトロ基（−ＮＯ_２）である。

前記式（５）〜（７）において、Ｒ^１３、Ｒ^１４およびＲ^１５は、水素原子、ハロゲン原子、水酸基、メチル基、エチル基、ハロゲン化メチル基、ハロゲン化エチル基またはニトロ基（−ＮＯ_２）である。
上記アリール置換低級アルキルカルボニル基としては、下記式（３）又は（４）で表されるものが挙げられる。

前記式（３）において、Ｒ^１、Ｒ^２、Ｒ^３、Ｒ^４およびＲ^５は、それぞれ同一であっても異なってもよく、水素原子、ハロゲン原子、水酸基、メチル基、エチル基、ハロゲン化メチル基、ハロゲン化エチル基、またはニトロ基（−ＮＯ_２）であり、前記式（４）において、Ｒ^６、Ｒ^７、Ｒ^８、Ｒ^９、Ｒ^１０、Ｒ^１１およびＲ^１２は、それぞれ同一であっても異なってもよく、水素原子、ハロゲン原子、水酸基、メチル基、エチル基、ハロゲン化メチル基、ハロゲン化エチル基またはニトロ基（−ＮＯ_２）であり、前記両式において、ｎは１〜２の整数である。 In order to achieve the above object, the retardation film of the present invention has a polyvinyl alcohol skeleton or a polyethylene vinyl alcohol skeleton as a main chain, and is represented by the following formula (1) or (2) on the oxygen atom of the skeleton side chain. An aromatic carbonyl group, an aryl-substituted lower alkylcarbonyl group represented by Ar— (CH ₂ ) _n —CO— (wherein Ar is an aromatic ring and n is an integer of 1 to 2), and the following formula (5) It is comprised with the film containing the modified polymer which has a part which at least 1 chemical group selected from the group which consists of unsaturated aliphatic carbonyl groups represented by (7) has couple | bonded. It is characterized by being.

In the formula (1), R ¹ , R ² , R ³ , R ⁴ and R ⁵ may be the same or different and each is a hydrogen atom, a halogen atom, a hydroxyl group, a methyl group, an ethyl group, or a halogenated group. Methyl, a halogenated ethyl group, or a nitro group (—NO ₂ ), and in the formula (2), R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ and R ¹² are the same. It may be either a hydrogen atom, a halogen atom, a hydroxyl group, a methyl group, an ethyl group, a halogenated methyl group, a halogenated ethyl group or a nitro group (—NO ₂ ).

In the above formulas (5) to (7), R ¹³ , R ¹⁴ and R ¹⁵ are each a hydrogen atom, a halogen atom, a hydroxyl group, a methyl group, an ethyl group, a halogenated methyl group, a halogenated ethyl group or a nitro group (—NO ₂ ).
Examples of the aryl-substituted lower alkylcarbonyl group include those represented by the following formula (3) or (4).

In the formula (3), R ¹ , R ² , R ³ , R ⁴ and R ⁵ may be the same or different, and each is a hydrogen atom, a halogen atom, a hydroxyl group, a methyl group, an ethyl group, or a halogenated group. A methyl group, an ethyl halide group, or a nitro group (—NO ₂ ). In the formula (4), R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ^11, and R ¹² are the same. Or a hydrogen atom, a halogen atom, a hydroxyl group, a methyl group, an ethyl group, a halogenated methyl group, a halogenated ethyl group, or a nitro group (—NO ₂ ), It is an integer of 1-2.

Moreover, the optical film of this invention has the said retardation film, It is characterized by the above-mentioned.
The liquid crystal panel of the present invention is characterized in that the retardation film is disposed on at least one surface of a liquid crystal cell.
The liquid crystal display device of the present invention comprises the above-mentioned liquid crystal panel.
The image display device of the present invention is characterized by comprising the above retardation film.

Since the retardation film of the present invention uses a modified polymer in which a chemical group such as an aromatic carbonyl group is bonded to an oxygen atom of a polyol skeleton side chain, it exhibits reverse dispersion and can realize a large retardation. Furthermore, since a modified polymer having a polyol skeleton is used, the glass transition temperature is suppressed, and the retardation film can be produced by stretching at a relatively low temperature.

As described above, the modified polymer used in the retardation film of the present invention has a polyol skeleton as a main chain, and a chemical group such as the aromatic carbonyl group is bonded to an oxygen atom in a side chain of the polyol skeleton. It is characterized by being. As will be described later, all the oxygen atoms in the side chain of the polyol skeleton need not be modified with the chemical group, and may be a polymer partially modified with the chemical group. Therefore, the modified polymer used in the present invention is a polymer having a moiety in which the side chain of the polyol skeleton is modified with the following chemical group.
This modified polymer exhibits a large phase difference although its wavelength dispersion is small due to the polyol skeleton as the main chain, and the chemical group is bonded to the oxygen atom of the polyol skeleton side chain, thereby providing reverse dispersion. Has been. Therefore, when the modified polymer is used, a retardation film that exhibits reverse dispersion and can realize a large retardation can be obtained. Thus, the present inventors have discovered for the first time that both reverse dispersion and a large phase difference can be realized by the bonding of the chemical group to the side chain of the polyol skeleton.
In addition, by changing the modification rate of the chemical group on the polyol skeleton, for example, it is possible to change the magnitude of wavelength dispersion or develop a large phase difference while maintaining transparency. . For this reason, in the formation of the retardation film, it is possible to adjust the retardation more easily than the conventional method only by changing the thickness, the conditions of the stretching treatment, and the like. Further, unlike the polycarbonate having a fluorene skeleton, the modified polymer has a polyol skeleton and the glass transition temperature is suppressed, so that the problem of the stretching temperature as described above in the formation of the retardation film can be avoided. . Furthermore, since a modified polymer that exhibits reverse dispersion and can exhibit a large retardation can be easily obtained by the following production method, the production of a reverse dispersion retardation film itself is also simple.

Examples of the polyol skeleton of the modified polymer include a polyvinyl alcohol (PVA) skeleton and a polyethylene vinyl alcohol (EVOH) skeleton, and a PVA skeleton is preferable. In addition to the chemical group, a lower alkylcarbonyl group may be partially bonded to the oxygen atom in the side chain of the polyol skeleton. Examples of the lower alkylcarbonyl group include an acetyl group (CH ₃ —CO—).

The aromatic carbonyl group which is the said chemical group is represented by following formula (1) or (2), for example. In the following formula (1), R ¹ , R ² , R ³ , R ⁴ and R ⁵ may be the same or different, and each is a hydrogen atom, a halogen atom, a hydroxyl group, a methyl group, an ethyl group, or a halogenated group. A methyl group, an ethyl halide group, or a nitro group (—NO ₂ ). In the following formula (2), R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ and R ¹² are the same. Or a hydrogen atom, a halogen atom, a hydroxyl group, a methyl group, an ethyl group, a halogenated methyl group, a halogenated ethyl group, or a nitro group (—NO ₂ ).

The aromatic carbonyl group represented by the formula (1), for ^example, R 1 to R ⁵ is a hydrogen atom, a benzoyl group _{(C 6} H 5 -CO-) are preferred.

The aryl-substituted lower alkylcarbonyl group is represented by, for example, Ar— (CH ₂ ) _n —CO—, wherein Ar is an aromatic ring, n is an integer of 1 to 2, and preferably n is 1 (aryl-substituted methylcarbonyl group: Ar—CH ₂ —CO—).

The aryl-substituted lower alkylcarbonyl group can be represented by the following formula (3) or (4) as a specific example. In the following formula (3), R ¹ , R ² , R ³ , R ⁴ and R ⁵ may be the same or different from each other, and may be a hydrogen atom, a halogen atom, a hydroxyl group, a methyl group, an ethyl group or a halogenated group. A methyl group, an ethyl halide group, or a nitro group (—NO ₂ ). In the following formula (4), R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ and R ¹² are the same. Or a hydrogen atom, a halogen atom, a hydroxyl group, a methyl group, an ethyl group, a halogenated methyl group, a halogenated ethyl group, or a nitro group (—NO ₂ ). In both the above formulas, n is an integer of 1 to 2, and preferably n is 1 (aryl-substituted methylcarbonyl group).

The chemical group preferably includes at least one of an aromatic carbonyl group and an aryl-substituted lower alkylcarbonyl group. The aryl-substituted lower alkylcarbonyl group includes an aryl-substituted methylcarbonyl group in which n is 1 in the above formulas ( Ar—CH ₂ —CO—) is preferable. Thus, when the chemical group is an aromatic carbonyl group or an aryl-substituted methylcarbonyl group, the number of carbon atoms between the main chain and the aromatic ring of the chemical group is 1 or 2. If the carbon number is 1 or 2, for example, a very rigid film can be obtained by forming a film using the modified polymer. In addition, since the degree of freedom of the side chain of the polymer is further limited, it is easier to realize reverse dispersion. This is presumed to be due to the following reason. When the film is stretched, the polymer main chain is usually oriented in the stretching direction, and the side chains are accordingly oriented in the same direction. However, if it has an aromatic ring as described above and the carbon number is set to 1 or 2, the degree of freedom of the side chain can be further limited. For this reason, it is sufficiently suppressed that the side chain is oriented in the stretching direction like the main chain, and the side chain is easily oriented in the direction perpendicular to the main chain. As a result, it is considered that the reverse dispersion property imparted by the bonded chemical group is sufficiently exhibited.

The unsaturated fatty acid carbonyl group preferably has, for example, at least one of a double bond and a triple bond. Specifically, the unsaturated fatty acid carbonyl group is represented by any one of the following formulas (5) to (7). Group. In the following formulas (5) to (7), R ¹³ , R ¹⁴ and R ¹⁵ are each a hydrogen atom, a halogen atom, a hydroxyl group, a methyl group, an ethyl group, a halogenated methyl group, a halogenated ethyl group or a nitro group (—NO ₂ ).

Among the unsaturated fatty acid carbonyl groups, a chemical group represented by the formula (5) is preferable, and a propioyl group (CH≡C—CO—) in which R ¹³ is a hydrogen atom is particularly preferable.

  The modification rate by the chemical group in the polyol skeleton is, for example, preferably in the range of 1 to 20% of the total number of carbons in the main chain of the polyol skeleton, more preferably in the range of 4 to 20%, particularly preferably in the range of 4 to 15%. Range.

  Unlike the polycarbonate having a fluorene skeleton as described above, the modified polymer of the present invention has a polyolefin skeleton, and therefore its glass transition temperature is usually in the range of 80 to 180 ° C.

  Next, the manufacturing method of the modified polymer of this invention is demonstrated. As described above, the method for producing the modified polymer of the present invention comprises a polymer having a polyol skeleton as a main chain (hereinafter also referred to as “raw polymer”), an aromatic carboxylic acid, an aromatic carboxylic acid halide, an aromatic carboxylic acid. Acid anhydride, aryl-substituted lower alkyl carboxylic acid, aryl-substituted lower alkyl carboxylic acid halide, aryl-substituted lower alkyl carboxylic acid anhydride, aromatic ketone, aromatic aldehyde, unsaturated aliphatic carboxylic acid, unsaturated aliphatic carboxylic acid It comprises a step of reacting at least one modifying compound selected from the group consisting of a halide, an unsaturated aliphatic carboxylic acid anhydride, an unsaturated aliphatic ketone and an unsaturated aliphatic aldehyde. According to this production method, for example, a reaction (for example, dehydration reaction, dehydrohalogenation) between a hydroxyl group of a raw material polymer and a functional group (carboxyl group, carbonyl halide group, carbonyl group, etc.) of the modifying compound. Reaction) occurs. By this reaction, the chemical group is bonded to the oxygen atom in the side chain of the raw material polymer (for example, an ester bond), and the modified polymer of the present invention is obtained. In addition, the manufacturing method of the modified polymer of this invention is not limited to this method.

The aromatic carboxylic acid is represented by, for example, RCOOH, the aromatic carboxylic acid halide is represented by, for example, RCOZ, and the aromatic carboxylic acid anhydride is represented by, for example, (RCO) ₂ O, In the formula, R is represented by the following formula (8) or (9), and Z is a halogen atom.

In the formula (8), R ¹ , R ² , R ³ , R ⁴ and R ⁵ may be the same or different and each is a hydrogen atom, a halogen atom, a hydroxyl group, a methyl group, an ethyl group or a halogenated group. A methyl group, an ethyl halide group or a nitro group (—NO ₂ ). In the formula (9), R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ and R ¹² are the same. It may be either a hydrogen atom, a halogen atom, a hydroxyl group, a methyl group, an ethyl group, a halogenated methyl group, a halogenated ethyl group or a nitro group (—NO ₂ ).

Aromatic acyl halide RCOZ preferably among the modifying compound, In particular, R is represented by the formula ^(8), R 1 ~R ⁵ is a hydrogen atom, Z is Cl acid chloride _(C 6 H ₅ COCl) is preferred.

The aryl-substituted lower alkyl carboxylic acid is represented by, for example, Ar— (CH ₂ ) _n —COOH, and the aryl-substituted lower alkyl carboxylic acid halide is represented by, for example, Ar— (CH ₂ ) _n —COZ, The aryl-substituted lower alkylcarboxylic acid anhydride is represented by (Ar— (CH ₂ ) _n —CO) ₂ O, for example. In the above formulas, Ar is an aromatic ring, Z is a halogen atom, n is an integer of 1 to 2, and preferably n is 1 (aryl-substituted methylcarboxylic acid, aryl-substituted methylcarboxylic acid halide) , Aryl substituted methylcarboxylic anhydrides).

Further, as specific examples, an aryl-substituted lower alkyl carboxylic acid is represented by R′COOH, an aryl-substituted lower alkyl carboxylic acid halide is represented by R′COZ, and an aryl-substituted lower alkyl carboxylic acid anhydride is represented by (R ′ CO) ₂ O, and in each of the above formulas, R ′ is represented by the following formula (10) or (11), and Z is a halogen atom.

In the formula (10), R ¹ , R ² , R ³ , R ⁴ and R ⁵ may be the same or different and each is a hydrogen atom, a halogen atom, a hydroxyl group, a methyl group, an ethyl group or a halogenated group. A methyl group, an ethyl halide group or a nitro group (—NO ₂ ). In the formula (11), R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ and R ¹² are the same. It may be either a hydrogen atom, a halogen atom, a hydroxyl group, a methyl group, an ethyl group, a halogenated methyl group, a halogenated ethyl group or a nitro group (—NO ₂ ). In both the above formulas, n is an integer of 1 to 2, and preferably n is 1.

  Examples of the modifying compound include the aromatic carboxylic acid, aromatic carboxylic acid halide and aromatic carboxylic acid anhydride, aryl-substituted lower alkyl carboxylic acid, aryl-substituted lower alkyl carboxylic acid halide, and aryl-substituted lower alkyl carboxylic acid. Preferably, the aryl-substituted lower alkyl carboxylic acid, the aryl-substituted lower alkyl carboxylic acid halide and the aryl-substituted lower alkyl carboxylic acid anhydride are each an aryl-substituted methyl carboxylic acid in which n is 1 in the above formulas, Aryl substituted methyl carboxylic acid halides and aryl substituted methyl carboxylic acid anhydrides are preferred. When these modifying compounds are used, the number of carbon atoms between the main chain and the aromatic ring of the chemical group is 1 or 2 in the modified polymer to be produced, and thus the above-described effects can be obtained.

The unsaturated aliphatic carboxylic acid, unsaturated aliphatic carboxylic acid halide, and unsaturated aliphatic carboxylic anhydride preferably have at least one of a double bond and a triple bond. The unsaturated aliphatic carboxylic acid is represented by, for example, R ″ COOH, the unsaturated aliphatic carboxylic acid halide is represented by, for example, R ″ COZ, and the unsaturated aliphatic carboxylic acid anhydride is, for example, ( R ″ CO) ₂ O. In the above formulas, R ″ is represented by any one of the following formulas (12) to (14), and Z is preferably a halogen atom.

In the formulas (12) to (14), R ¹³ , R ¹⁴ and R ¹⁵ are each a hydrogen atom, a halogen atom, a hydroxyl group, a methyl group, an ethyl group, a halogenated methyl group, an ethyl halide group or a nitro group (—NO ₂ ).

Among the unsaturated aliphatic carboxylic acids, unsaturated aliphatic carboxylic acid halides and unsaturated aliphatic carboxylic anhydrides, an unsaturated aliphatic carboxylic acid represented by R ″ COOH is preferable. Propiolic acid (HC≡C—COOH) represented by formula (12) and R ¹³ being hydrogen is preferred.

  Examples of the polymer having a polyol skeleton (raw polymer) include PVA and polyethylene vinyl alcohol (EVOH), and PVA is preferable. In general, PVA is produced by saponifying polyvinyl acetate, and EVOH is produced by saponifying ethylene-vinyl acetate copolymer (EVA). For example, it is in the range of 40 to 100%, preferably in the range of 60 to 100%, and more preferably in the range of 80 to 100%. The modification rate by the chemical group can be controlled by the degree of saponification of PVA or EVOH, which will be described later.

Since the degree of saponification of the raw material polymer is not particularly limited, the raw material polymer has a partial lower alkylcarbonyl group such as an acetyl group (CH ₃ —CO—) partially on the oxygen atom in the side chain of the polyol skeleton. It may be a bonded polymer.

  Each of the modifying compound and the raw material polymer may be used singly or in combination of two or more.

  In the present invention, it is preferable to adjust the introduction ratio (modification ratio by chemical group) of the modifying compound to the polyol skeleton of the raw material polymer in the range of 1 to 20% of the total carbon number of the main chain, more preferably 4 It is in the range of -20%, particularly preferably in the range of 4-15%. The adjustment method will be described later.

  Although an example of the manufacturing method of the modified polymer of this invention is shown below, it is not limited to this.

  First, a raw material polymer is dissolved in a solvent to prepare a polymer solution. The type of the solvent can be appropriately determined according to the type of the raw material polymer. For example, a chlorinated solvent such as pyridine, methylene chloride, trichloroethylene, and tetrachloroethane, a ketone solvent such as acetone, methyl ethyl ketone (MEK), and cyclohexanone, Examples thereof include aromatic solvents such as toluene, cyclic alkanes such as cycloheptane, amide solvents such as N-methylpyrrolidone, and ether solvents such as tetrahydrofuran. These may be used alone or in combination of two or more.

  The raw material polymer is preferably dissolved under dry conditions. For example, the raw material polymer itself may be dried in advance.

  Then, the modifying compound is further added to the polymer solution, and the raw material polymer and the modifying compound are reacted. In addition, although the introduction rate (modification rate by a chemical group) of the said compound for a modification to a raw material polymer can be controlled by the addition amount of the compound for a modification, this is mentioned later.

  The reaction is preferably performed under heating conditions. The reaction temperature is not particularly limited, but is usually in the range of 25-60 ° C., and the reaction time is usually in the range of 2-8 hours. When the reaction temperature is lower than the dissolution treatment temperature of the raw material polymer, for example, it is preferable to add the modifying compound after once lowering the temperature of the polymer solution to the reaction temperature. The reaction is preferably performed while stirring a reaction solution containing the raw material polymer and the modifying compound.

  The reaction may be performed in the presence of a catalyst, and a conventionally known catalyst such as an acid catalyst such as p-toluenesulfonic acid monohydrate can be used.

  And the modified polymer which is a reaction product is collect | recovered from this reaction liquid. The modified polymer can be recovered, for example, as follows.

  First, a solvent such as acetone is added to the reaction solution, and the filtrate is recovered. The modified polymer can be recovered by adding water to the filtrate to precipitate the modified polymer and filtering the precipitate. The recovered precipitate is usually white. The recovered modified polymer is preferably further washed by stirring in water. Then, after washing, the recovered modified polymer can be dried under reduced pressure to obtain a dried modified polymer.

  The introduction rate (modification rate by chemical group) of the modifying compound with respect to the raw material polymer can be controlled as follows, for example.

  As a first control method, there is a method of selecting a raw material polymer according to the degree of saponification. In other words, when the addition ratio of the raw material polymer and the modifying compound and the reaction conditions such as temperature are the same, for example, by using the raw material polymer having a relatively high degree of saponification, the introduction rate (modification rate) is set high. The introduction rate (modification rate) can be set low by using a raw material polymer having a relatively low saponification degree.

  As a second control method, there is a method of adjusting the addition ratio of the raw material polymer and the modifying compound. That is, the introduction rate (modification rate) is set high by relatively increasing the addition ratio of the modifying compound relative to the raw material polymer, and the introduction rate ( (Modification rate) can be set low.

  As a third control method, for example, a raw material polymer and a modifying compound are reacted to bond a chemical group to the polymer, and then a process such as hydrolysis is performed to remove the bonded chemical group. Can be given.

The modified polymer of the present invention can be produced by the method as described above. In addition, the modification rate by the chemical group in the modified polymer of the present invention can be detected by, for example, ¹ H-NMR.

  Next, the film of the present invention will be described. The film of this invention is a film containing the modified polymer of this invention, Comprising: For example, it is useful as a raw material film of retardation film which shows reverse dispersion.

  The method for producing this film is not particularly limited, and examples thereof include conventionally known film forming methods. For example, it can be produced by developing (coating) a polymer solution or polymer melt on a substrate and solidifying the coating film. The modified polymer of the present invention may be used alone or in combination of two or more. That is, a modified polymer having a different modification rate, a modified polymer having a different chemical group, a modified polymer having a different raw material polymer, or the like can be mixed and used.

  The polymer solution can be prepared by, for example, dissolving a modified polymer in a solvent. The solvent is not particularly limited, and examples thereof include halogenated hydrocarbons such as dimethyl sulfoxide (DMSO), chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene, chlorobenzene, and orthodichlorobenzene; Phenols such as chlorophenol; aromatic hydrocarbons such as benzene, toluene, xylene, methoxybenzene, and 1,2-dimethoxybenzene; acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, cyclopentanone, 2-pyrrolidone, N- Ketone solvents such as methyl-2-pyrrolidone; ester solvents such as ethyl acetate and butyl acetate; t-butyl alcohol, glycerin, ethylene glycol, triethyl Alcohol solvents such as glycol, ethylene glycol monomethyl ether, diethylene glycol dimethyl ether, propylene glycol, dipropylene glycol and 2-methyl-2,4-pentanediol; amide solvents such as dimethylformamide and dimethylacetamide; acetonitrile, butyronitrile and the like Nitrile solvents; ether solvents such as diethyl ether, dibutyl ether, and tetrahydrofuran; carbon disulfide, ethyl cellosolve, butyl cellosolve, and the like. These solvents may be used alone or in combination of two or more.

  Although the addition ratio of the polymer is not particularly limited, for example, the range of 5 to 50 parts by weight is preferable with respect to 100 parts by weight of the solvent, and more preferably 10 to 40 parts by weight. In addition, various additives such as stabilizers, plasticizers, and metals may be further added to the polymer solution as needed, and the range that does not affect the wavelength dispersion characteristics of the retardation film described later. Thus, another different resin may be added.

  The development method of the polymer solution is not particularly limited. For example, spin coating method, roll coating method, flow coating method, printing method, dip coating method, casting film forming method, bar coating method, gravure printing method, and die code method. Conventionally known methods such as curtain coating can be employed. Moreover, solidification of a coating film can be performed by natural drying or drying, for example. Although the conditions are not particularly limited, the temperature is usually 40 ° C to 300 ° C, preferably 50 ° C to 250 ° C, more preferably 60 ° C to 200 ° C. The coating film may be dried at a constant temperature or may be performed while increasing or decreasing the temperature stepwise. The drying time is not particularly limited, and is usually 10 seconds to 30 minutes, preferably 30 seconds to 25 minutes, and more preferably 1 minute to 20 minutes or less.

  In addition, examples of the method for producing the film of the present invention include a method of forming the film by heating and melting the modified polymer at a melting temperature or higher, and extrusion molding from a nozzle.

  Since the film of the present invention is useful as a material for forming a retardation film, it is preferably set to a size suitable for production of a retardation film described later. Generally as a material of retardation film, it is preferable that thickness is 5-500 micrometers, More preferably, it is 20-300 micrometers, Most preferably, it is 50-200 micrometers.

  Next, the optical film of the present invention includes a retardation film containing the modified polymer of the present invention (hereinafter referred to as “retardation film of the present invention”). Since the retardation film contains the modified polymer of the present invention, the retardation film exhibits reverse dispersion without performing complicated control when a conventional polymer is used, and can easily express a large retardation.

  As long as the optical film of this invention contains the retardation film of this invention as mentioned above, the structure is not restrict | limited at all. Therefore, the structure of the retardation film of this invention alone may be sufficient, and the structure which combined optical components, such as the said retardation film and a polarizer mentioned later, may be sufficient.

  The production method of the retardation film of the present invention is not particularly limited, and a conventionally known method can be adopted except that the modified polymer of the present invention is used, but it is preferable to use the above-described film of the present invention. . Specifically, for example, by subjecting the film of the present invention to a stretching treatment or a shrinking treatment, a retardation is developed, and a retardation film is obtained.

  In the stretching treatment, conditions such as the type of stretching (for example, uniaxial stretching, biaxial stretching, etc.) and the stretching ratio can be appropriately determined according to the desired phase difference. In addition, a shrinkable film that shrinks in the vicinity of the stretching temperature may be bonded in advance to the film of the present invention, and both may be uniaxially stretched (JP-A-5-157911). According to this method, for example, a retardation film in which the refractive index in the thickness direction is larger than the in-plane refractive index and Nz described below is less than 1 can be easily produced.

  The stretching of the film is preferably performed at a temperature higher than the glass transition temperature of the modified polymer of the present invention, for example. In general, stretching at a temperature 5 to 50 ° C. higher than the glass transition temperature is preferable, and a temperature 10 to 40 ° C. higher than the glass transition temperature is more preferable.

In the retardation film of the present invention, the in-plane retardation Δnd (450 nm) at a wavelength of 450 nm and the in-plane retardation Δnd (550 nm) at a wavelength of 550 nm satisfy the relationship of the following formula. This indicates that the in-plane retardation Δnd (Xnm) at each wavelength (Xnm) tends to increase as the wavelength approaches the long wavelength side, which is inverse dispersion. The wavelength (Xnm) is generally in the range of 400 to 700 nm.
Δnd (450 nm) / Δnd (550 nm) <1

  Δnd is represented by (nx−ny) · d, and nx and ny indicate refractive indexes in the X-axis direction and the Y-axis direction in the retardation film, respectively, and the X-axis direction is the surface of the retardation film. The Y axis direction is the axial direction perpendicular to the X axis in the plane, and d indicates the thickness of the retardation film.

  Δnd (450 nm) / Δnd (550 nm) is more preferably 0.6 ≦ Δnd (450 nm) / Δnd (550 nm) <1, and particularly preferably 0.7 ≦ Δnd (450 nm) / Δnd (550 nm) ≦ 0. .9 range.

  In the retardation film of the present invention, the in-plane retardation Δnd (650 nm) at a wavelength of 650 nm and the in-plane retardation Δnd (550 nm) at a wavelength of 550 nm have a relationship of 1 <Δnd (650 nm) / Δnd (550 nm). It is preferable to satisfy, more preferably 1 <Δnd (650 nm) / Δnd (550 nm) ≦ 2, and particularly preferably 1.1 ≦ Δnd (650 nm) / Δnd (550 nm) ≦ 1.3.

  The magnitude of reverse dispersion of the retardation film can be changed, for example, by controlling the modification rate of the chemical group in the modified polymer of the present invention. In addition to this, by preparing several types of modified polymers having different modification rates and mixing them at a predetermined ratio, desired reverse dispersion with varying wavelength dispersion characteristics can be obtained. Thus, when mixing a modified polymer, it is preferable that the modification rate as the whole mixture is 1 to 20% with respect to the total carbon number of a principal chain, for example.

  The retardation film of the present invention may exhibit in-plane retardation and exhibit reverse dispersion. For example, optical uniaxial “nx> ny = nz”, optical biaxial “nx> ny> It is preferable to show optical characteristics of “nz” and “nx> nz> ny”. Such uniaxial and biaxial optical characteristics can be set, for example, by a conventionally known method of adjusting the type and conditions of the stretching treatment as described above. Similarly, the in-plane retardation and thickness direction retardation at a predetermined wavelength can also be set by a conventionally known method that appropriately sets the type and conditions of the stretching treatment, the thickness of the film to be used, and the like.

  The retardation film in the present invention preferably has an in-plane retardation Δnd (550 nm) of 10 to 1000 nm. When used as a λ / 4 plate, a range of 100 to 170 nm is preferable, and a λ / 2 plate is used. When using, the range of 200-340 nm is preferable.

Further, the retardation film of the present invention has an Nz coefficient represented by the following formula showing the relationship between the thickness direction birefringence (nx-nz) and the in-plane birefringence (nx-ny), for example, 0 < It is preferable that Nz <1. Moreover, when using one retardation film of this invention for a liquid crystal cell, it is preferable that it is 0.3 <Nz <0.7, and when using two sheets, one retardation film is used. It is preferable to combine 0.3 <Nz <0.7 and the other retardation film as 0.1 <Nz <0.4.
Nz = (nx-nz) / (nx-ny)

  A normal retardation film (uniaxial retardation film) produced by uniaxial stretching has an Nz coefficient of 1 because its Y-axis direction refractive index (ny) and Z-axis direction refractive index (nz) are equal. When the retardation film is tilted with respect to the slow axis, the phase difference is generally increased with the tilt angle. However, if the Nz coefficient of the retardation film is in the range of 0 <Nz <1, as described above, the change in the retardation with respect to the change in the tilt angle is smaller than that of the normal uniaxial retardation film described above. In particular, when Nz is 0.5, for example, if the tilt angle is about 60 °, the phase difference hardly changes. Also in the case of the inclination with respect to the fast axis, the change in phase difference becomes smaller as the Nz coefficient approaches 0.5. That is, the change rate of the phase difference observed by the change in the tilt angle changes continuously with respect to the Nz coefficient, but particularly in the range “0 <Nz <1” as described above, the change due to the change in the tilt angle. The change in phase difference can be sufficiently suppressed.

  In addition, when a normal uniaxial retardation film (Nz = 1) is arranged so that its slow axis is 45 ° with respect to the tilt axis, the slow axis is tilted with the tilt angle. It changes so as to approach parallel to the axis. On the other hand, if the retardation film satisfies 0 <Nz <1, the amount of change in the shaft angle is smaller than that of a normal uniaxial retardation film. Specifically, if the retardation film has Nz = 0.5, it remains almost unchanged at 45 °.

  Although the thickness of the retardation film in this invention is not specifically limited, For example, 5-500 micrometers, Preferably it is 10-200 micrometers, Most preferably, it is 20-100 micrometers.

  The retardation film in the present invention is preferably, for example, a λ / 4 plate or a λ / 2 plate. As described above, when used as a λ / 4 plate, the wavelength becomes ¼ wavelength with respect to the target wavelength, and when used as a λ / 2 plate, with respect to the target wavelength. The phase difference is designed to be ½ wavelength. This design can be performed by a conventionally known method of adjusting the stretching method and conditions as described above. Since the retardation film of the present invention exhibits reverse dispersion as described above and can also realize a large retardation, functions as a λ / 4 plate, λ / 2 plate, etc. can be realized in a wide wavelength band. .

  Next, the optical film of the present invention will be described by taking as an example a polarizing plate further containing a polarizer in addition to the retardation film.

  For example, the retardation film and the polarizer may be disposed so that the slow axis of the retardation film and the absorption axis of the polarizer are perpendicular to each other, or may be disposed in parallel. In particular, when arranged so as to be parallel, a wide viewing angle broadband polarizing plate having excellent visual characteristics in a wide wavelength band of visible light is obtained.

  The polarizer is not particularly limited, and a conventionally known one can be used. Usually, a dichroic substance such as iodine or a dichroic dye is adsorbed on a polymer film, and further crosslinked, stretched and dried. Prepared by Among these, a polarizer excellent in light transmittance and polarization degree is preferable. The polymer film is not particularly limited, and examples thereof include hydrophilic polymer films such as PVA films, partially formalized PVA films, ethylene / vinyl acetate copolymer partially saponified films, and cellulose films. . In addition, polyene oriented films such as PVA dehydrated products and polyvinyl chloride dehydrochlorinated products can also be used. Among these, a PVA film is preferable. The thickness of the polarizer is usually in the range of 1 to 80 μm, but is not limited thereto.

  The laminate of the retardation film and the polarizer preferably further has a protective film disposed on one side or both sides thereof. The protective film is not particularly limited, and a conventionally known transparent protective film can be used. For example, a film having excellent transparency, mechanical strength, thermal stability, moisture barrier property, isotropy and the like is preferable. Examples of the material for the protective film include cellulose resins such as triacetyl cellulose (TAC); polyester, polynorbornene, polycarbonate, polyamide, polyimide, polyethersulfone, polysulfone, polystyrene, Examples thereof include polyolefin resins, acrylic resins, and acetate-based transparent resins. Further, examples thereof include thermosetting resins such as acrylic, urethane, acrylic urethane, epoxy, and silicone, or ultraviolet curable resins. These may be used alone or in combination of two or more. Among these, a TAC film, particularly a TAC film whose surface is saponified with an alkali or the like is preferable from the viewpoint of polarization characteristics and durability.

  Moreover, the polymer film as described in Unexamined-Japanese-Patent No. 2001-343529 (WO 01/37007) can also be used. As the polymer, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain, and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in the side chain can be used, Specific examples include a resin composition having an alternating copolymer composed of isobutene and N-methylmaleimide and an acrylonitrile / styrene copolymer. The polymer film may be, for example, an extruded product of the resin composition.

The thickness of the protective film is not particularly limited, but is usually 500 μm or less, preferably 5 to 300 μm, more preferably 5 to 100 μm, and even more preferably 5 to 60 μm. Although not particularly limited, for example, when used in a liquid crystal display device, birefringence characteristics can be set according to the mode. For example, in the in-plane switching (IPS) mode, a phase difference as small as possible is preferable. In the case of the vertical alignment (VA) mode, it is preferable that the phase difference in the front is as small as possible, and the phase difference in the oblique direction shows negative optical uniaxiality in which the slow axis appears horizontally with respect to vision. It is preferable.

  For example, the retardation film and the polarizer of the present invention may be laminated via a protective film as described above, or both may be laminated directly. This is because the retardation film of the present invention has a polyol skeleton, so that a polarizer can be used without using a protective film or the like as compared with conventional retardation films of polycarbonate, polyolefin, polynorbornene, etc. This is because (especially a PVA polarizer) is easily adhered. Further, when the retardation film and the polarizer are directly laminated without using a protective film or the like, negative uniaxiality (nx = ny> nz) such as a TAC film is formed on the other surface of the retardation film, for example. It is preferable to arrange a protective film showing The term “directly” means that the retardation film and the polarizer are laminated without using a member such as a protective film, and does not mean that, for example, an adhesive or a pressure-sensitive adhesive is excluded.

  The adhesion method between each member, such as between the retardation film and the polarizer, is not particularly limited, and conventionally known adhesives and pressure-sensitive adhesives can usually be used. Examples of the pressure-sensitive adhesive include transparent pressure-sensitive adhesives having excellent stress relaxation properties, such as acrylic polymers, silicone-based polymers, polyesters, polyurethanes, polyethers, and synthetic rubbers. In view of weather resistance, an acrylic pressure-sensitive adhesive is preferred.

  The optical film of this invention should just contain the retardation film of this invention as mentioned above, and the number of lamination | stacking of the member contained is not restrict | limited in particular. When two or more retardation films are included, the same retardation film or different retardation films may be used.

  In the case of producing a polarizing plate having a wide viewing angle and a wide band by combining the retardation film of the present invention and a polarizer, the optical properties of the retardation film of the present invention are preferably set as follows. In the case of a λ / 2 plate, the retardation of the retardation film is generally adjusted to ½ of the center wavelength, and the center wavelength is usually set in the range of 400 nm to 700 nm. For example, when the optical film of the present invention includes one layer of the retardation film of the present invention, the Nz of the retardation film is preferably set to 0.1 to 0.9, more preferably 0.8. It is in the range of 25 to 0.75, more preferably in the range of 0.4 to 0.6. With this setting, crossed Nicols can be realized with a very wide viewing angle when the polarizing plate of the present invention is viewed from the front.

  The polarizing plate of the present invention is preferably a circular polarizing plate. For the circularly polarizing plate, for example, the retardation film (λ / 4 plate) of the present invention and a polarizer may be arranged so that the respective optical axis angles are 45 °.

  When the retardation film to be used completely gives a quarter-wave retardation, the circularly polarizing plate can change the transmitted light to circularly polarized light. On the other hand, when the retardation film gives a retardation other than ¼ wavelength, the circularly polarizing plate changes the transmitted light to elliptically polarized light instead of circularly polarized light. For this reason, as a characteristic of the circularly polarizing plate, it is desired to provide circularly polarized light or elliptically polarized light close to it in the widest possible wavelength band.

  Furthermore, in an image display device or the like, polarized light that has passed through the circularly polarizing plate is reflected by a reflector that does not depolarize the polarized light. At this time, the conversion closer to the circularly polarized light is achieved, and if it is completely circularly polarized light, it is converted into circularly polarized light of completely opposite polarity. Then, the reflected circularly polarized light having the opposite polarity cannot be transmitted again through the circularly polarizing plate and is completely absorbed by the circularly polarizing plate. However, when the circular polarization property decreases, the conversion efficiency of reflected light decreases with the decrease, and the reflected light passes through the circularly polarizing plate. For this reason, the achromatic color is realized as the circularly polarized light can be achieved in a wider wavelength band.

  In particular, when a circularly polarizing plate is used for the purpose of preventing reflection, a material that gives circularly polarized light or elliptically polarized light close to it in the entire visible light region is a good circularly polarizing plate. However, with a positive dispersion λ / 4 plate, circular polarization can be achieved only in a part of the central wavelength band, and as the distance from the central wavelength increases, the circular polarization decreases and the ellipticity of the circular polarization is Get smaller. For this reason, the amount of reflected light transmitted through the circularly polarizing plate becomes zero at the center wavelength where the phase difference is ¼ wavelength, but increases as the distance from the center wavelength increases. As a result, the amount of transmitted light itself increases and the color appears to be further colored. Such a phenomenon is similarly seen even in the case of flat chromatic dispersion, that is, chromatic dispersion in which the phase difference does not change much with wavelength. In this case, coloring is reduced as compared with positive dispersion, but the amount of transmitted light is also increased in a wavelength band far from the center wavelength. On the other hand, since the circularly polarizing plate of the present invention uses the retardation film of the present invention that exhibits reverse dispersion as described above, it can achieve circular polarization of transmitted light in a wider wavelength band. For this reason, the transmitted light amount of the reflected light is suppressed, and the circularly polarizing plate transmittance of the reflected light is reduced even at a wavelength away from the center wavelength, thereby realizing an achromatic color.

  The optical film of the present invention can be used for, for example, a liquid crystal panel, a liquid crystal display device, and other image display devices, and the usage and arrangement thereof are the same as those of conventional liquid crystal panels and liquid crystal display devices. In the liquid crystal panel of the present invention, for example, the optical film of the present invention is preferably disposed on at least one surface of the liquid crystal cell, particularly on the display screen side. It only has to have a panel.

  The display method of the liquid crystal display device of the present invention is not particularly limited, but, for example, an IPS mode or a VA mode is preferable because a high contrast can be realized with an extremely wide viewing angle. This is because the crossed Nicols can be realized in a wide viewing angle range and a wide wavelength band by the optical film of the present invention. In addition, since the VA mode liquid crystal cell exhibits positive uniaxiality (nx = ny <nz), in particular, the retardation film of the present invention, a polarizer, and negative uniaxiality (nx = ny> nz) are protected. It is preferable to use an optical film including a film. By further including such a protective film, liquid crystal cells can be compensated in addition to the realization of crossed Nicols in a wide viewing angle range and a wide wavelength band. In addition, when the phase difference of a protective film is small, you may arrange | position the film which shows negative uniaxiality (nx = ny> nz) separately in a liquid crystal cell.

  The optical film of the present invention is not limited to the liquid crystal display device as described above. For example, self-luminous such as an organic electroluminescence (EL) display, a plasma display (PD), and an FED (Field Emission Display). It can also be used for type display devices. When the optical film of the present invention is used in these various image display devices, a circularly polarizing plate including the retardation film of the present invention and a polarizer as described above is preferable, and the circularly polarizing plate is disposed on the display screen side. It is preferable to arrange. Thereby, for example, the external light reflected by the electrode is removed, and the visibility can be improved even in a bright environment. In addition, it replaces with the conventional optical film and there is no restriction | limiting in particular except using the optical film of this invention, A conventionally well-known structure and arrangement | positioning are applicable.

  EXAMPLES Hereinafter, although this invention is demonstrated in more detail using an Example and a comparative example, this invention is not limited to a following example.

11 g of PVA having a saponification degree of 88% was suspended in 100 mL of pyridine and stirred overnight at 100 ° C. under dry conditions. After adding pyridine 100mL to this reaction liquid and cooling to 50 degreeC, the benzoic acid chloride 8.2g was added little by little, and it stirred at 50 degreeC for 6 hours. To this reaction solution, 800 mL of acetone was added and filtered, and the obtained filtrate was mixed with 7 L of distilled water for reprecipitation. The precipitated polymer (white precipitate) was separated by filtration, poured into distilled water at 50 ° C., and washed by stirring. Again, the precipitated polymer recovered by filtration was dried under reduced pressure to obtain 7.4 g of benzoyl-modified PVA. When this benzoyl-modified PVA was analyzed by ¹ H-NMR, the modification rate of the benzoyl group with respect to the total carbon of the PVA main chain was 13.5%.

  2 g of the obtained benzoyl-modified PVA and 0.2 g of glycerin were dissolved in 20 g of dimethyl sulfoxide (DMSO) to prepare a modified PVA solution. This modified PVA solution was applied onto a glass plate with an applicator and dried to form a benzoyl-modified PVA film on the glass plate. This film was peeled from the glass plate and stretched twice at 100 ° C. to prepare a retardation film.

  A retardation film was produced in the same manner as in Example 1 except that 13.4 g of benzoic acid chloride was used. The obtained benzoyl-modified PVA was 7.8 g, and the modification rate of the benzoyl group with respect to the total carbon of the PVA main chain was 19.5%.

  A retardation film was produced in the same manner as in Example 1 except that 2.5 g of benzoic acid chloride was used. The obtained benzoyl-modified PVA was 7.5 g, and the modification rate of the benzoyl group with respect to the total carbon of the PVA main chain was 1.5%.

11 g of PVA having a saponification degree of 88% was suspended in 100 mL of pyridine and stirred overnight at 100 ° C. under dry conditions. After adding 100 mL of pyridine to this reaction liquid and cooling to 50 ° C., 4.7 g of propiolic acid was added little by little and the mixture was stirred at 50 ° C. for 6 hours. 800 mL of acetone was added to this reaction liquid and filtered, and the obtained filtrate was mixed with 7 L of distilled water to perform reprecipitation. The precipitated polymer (white precipitate) was separated by filtration, poured into distilled water at 50 ° C., and washed by stirring. Again, the precipitated polymer recovered by filtration was dried under reduced pressure to obtain 6.7 g of propioyl-modified PVA. When this propioroyl-modified PVA was analyzed by ¹ H-NMR, the modification ratio of the propioroyl group with respect to the total carbon of the PVA main chain was 15%.

  2 g of the obtained propioyl-modified PVA and 0.2 g of glycerol were dissolved in 20 g of DMSO to prepare a propioroyl-modified PVA solution. And this solution was apply | coated with the applicator on the glass plate, and the propioroyl modified PVA film was formed on the said glass plate by drying. This film was peeled from the glass plate and stretched twice at 100 ° C. to prepare a retardation film.

  A retardation film was produced in the same manner as in Example 4 except that 6 g of propiolic acid was used. In addition, the obtained propioyl modified PVA was 7.2g, and the modification rate of the propioyl group with respect to all the carbons of the PVA main chain was 18%.

  A retardation film was produced in the same manner as in Example 4 except that 2 g of propiolic acid was used. The obtained propioyl-modified PVA was 6.4 g, and the modification ratio of the propioyl group with respect to the total carbon of the PVA main chain was 2.5%.

  A benzoyl-modified PVA film (unstretched) was prepared in the same manner as in Example 1, and a biaxially stretched polyolefin film was attached to both surfaces of this film with an adhesive. And after extending | stretching this laminated body twice at 100 degreeC, the said polyolefin film was peeled and the benzoyl modified PVA film to which the extending | stretching process was performed was obtained. This was used as a retardation film.

  The retardation film of Example 7 was bonded to one surface of a PVA iodine polarizer using a PVA adhesive. The retardation film and the polarizer were arranged so that the slow axis of the retardation film and the absorption axis of the polarizer were parallel. Furthermore, a TAC film (protective film, the same applies hereinafter) was bonded to the other surface of the polarizer to produce a polarizing plate.

(Comparative Example 1)
2 g of polycarbonate was dissolved in 20 g of methylene chloride, this solution was applied on a glass plate with an applicator, and a polycarbonate film was formed on the glass plate by drying. This film was stretched 1.5 times at 160 ° C. to prepare a retardation film.

(Comparative Example 2)
An unmodified PVA film was prepared in the same manner as in Example 1 except that benzoyl chloride was not added, and this was stretched to prepare a retardation film.

Each characteristic was evaluated about the retardation film of Examples 1-7 obtained as mentioned above and the retardation film of Comparative Examples 1-2. In addition, the relationship of the refractive index of each obtained retardation film was as follows, respectively.
Example 1 nx> ny≈nz
Example 2 nx> ny≈nz
Example 3 nx> ny≈nz
Example 4 nx> ny≈nz
Example 5 nx> ny≈nz
Example 6 nx> ny≈nz
Example 7 nx>nz> ny
Comparative Example 1 nx> ny≈nz
Comparative Example 2 nx> ny≈nz

(Chromatic dispersion characteristics)
Using a birefringence measuring apparatus (trade name KOBRA-21ADH: manufactured by Oji Scientific Instruments), in-plane retardation of each retardation film was measured for wavelength dispersion. These results are shown in the following Table 1 and the graphs of FIGS. In each figure, the horizontal axis represents wavelength, and the vertical axis represents in-plane retardation wavelength dispersion (Δnd (Xnm) / Δnd (550 nm)). FIG. 1 shows Examples 1-4, and FIG. 2 shows Examples 5-7. FIG. 3 shows the results of Comparative Examples 1 and 2, respectively. Each graph also shows ideal inverse dispersion (ideal dispersion).

  As shown in FIGS. 1 and 2, the retardation films of Examples 1 to 7 each exhibited reverse dispersion in which the in-plane retardation on the short wavelength side was smaller than the in-plane retardation on the long wavelength side. On the other hand, as shown in FIG. 3, the retardation film of Comparative Example 1 exhibited normal dispersion, and the retardation film of Comparative Example 2 was close to flat wavelength dispersion and did not reach reverse dispersion.

(Circular polarization)
Each retardation film was bonded to a polarizing plate (trade name SEG1425DU: manufactured by Nitto Denko Corporation) to prepare a circularly polarizing plate. In addition, both were arrange | positioned so that the absorption axis of retardation film and the slow axis of a polarizing plate might be 45 degrees. And this circularly-polarizing plate was arrange | positioned on the surface (aluminum vapor deposition film surface) of the reflecting plate which vapor-deposited aluminum on PET, and the reflective color was evaluated using the apparatus (brand name MCPD3000: Otsuka Electronics Co., Ltd. product). These results (a * value, b * value) are shown in Table 2 below. It can be determined that the larger the absolute value of the a * value, the more reddish, and the larger the absolute value of the b * value, the more yellowish.

  As shown in Table 2, when the retardation films of Examples 1 and 4 are used, the absolute values of a * and b * are both smaller than those of Comparative Examples 1 and 2, so that they are more achromatic. It can be said that there is little coloring. For this reason, according to the retardation film of an Example, the circular polarization property in a wider wavelength range can be achieved compared with a comparative example.

(Phase difference change)
Next, the retardation change of the retardation film of Example 7 was confirmed.

  For the retardation film of Example 7, the front retardation and the retardation in a state where the retardation film was inclined by 40 ° with respect to the slow axis were measured, and the change in retardation was confirmed. As a result, the retardation film of Example 7 hardly changed the retardation, and the result of calculation by extrapolation (result calculated from the measured birefringence) was Nz coefficient of about 0.55.

(Observation of transmitted light)
The polarizing plate of Example 8 and the linear polarizing plate in which a protective film (TAC film) was laminated on one surface of the PVA iodine-based polarizer were arranged so that the respective absorption axes were orthogonal to each other, and the transmitted light was observed. . The linear polarizing plate was disposed so that the protective film was located on the opposite side of the polarizing plate of Example 8. Then, the polarizing plate and the linear polarizing plate of Example 8 are arranged so that the respective absorption axes are 45 ° and −45 ° with respect to the 0 ° direction on the plane, and the normal line is 0 The transmitted light was observed in a state inclined at 45 ° in the ° direction. As a result, almost no light leakage occurred, which was almost the same as the result observed from the normal direction (inclination angle 0 °). At this time, when the linear polarizing plate was rotated, the amount of transmitted light increased. From this, it can be seen that in the polarizing plate of Example 8, the angle of the absorption axis hardly changes even when it is tilted. On the other hand, using the retardation films of Comparative Example 1 and Comparative Example 2, polarizing plates were produced in the same manner as in Example 8, and the same observation was performed. As a result, in the polarizing plates using the retardation films of Comparative Examples 1 and 2, light leaked as the inclination angle increased, and the transmitted light gradually decreased when the combined linear polarizing plates were rotated. From this, it is considered that the change in the angle of the absorption axis occurred in the polarizing plates using the retardation films of Comparative Examples 1 and 2.

  As described above, according to the present invention, it is possible to easily obtain a modified polymer exhibiting reverse dispersion without selecting a combination of a plurality of monomers and polymers as in the prior art. Further, by using the modified polymer of the present invention, it is possible to produce a reverse dispersion retardation film while avoiding problems such as the glass transition temperature in the conventional stretching treatment. For this reason, the modified polymer of this invention is very useful as a new raw material of the retardation film which shows reverse dispersion.

It is a graph which shows the wavelength dispersion of the retardation film of Examples 1-4. It is a graph which shows the wavelength dispersion of the retardation film of Examples 5-7. It is a graph which shows the wavelength dispersion of the retardation film of Comparative Examples 1-2.

Claims (14)

An aromatic carbonyl group represented by the following formula (1) or (2), Ar— (CH ₂ ) _n —CO, having a polyvinyl alcohol skeleton or a polyethylene vinyl alcohol skeleton as a main chain, and an oxygen atom of the skeleton side chain An aryl-substituted lower alkylcarbonyl group represented by-(wherein Ar is an aromatic ring and n is an integer of 1 to 2), and any one of the following represented by the following formulas (5) to (7): A retardation film comprising a film containing a modified polymer having a portion to which at least one chemical group selected from the group consisting of saturated aliphatic carbonyl groups is bonded.

In the formula (1), R ¹ , R ² , R ³ , R ⁴ and R ⁵ may be the same or different and each is a hydrogen atom, a halogen atom, a hydroxyl group, a methyl group, an ethyl group, or a halogenated group. Methyl, a halogenated ethyl group, or a nitro group (—NO ₂ ), and in the formula (2), R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ and R ¹² are the same. It may be either a hydrogen atom, a halogen atom, a hydroxyl group, a methyl group, an ethyl group, a halogenated methyl group, a halogenated ethyl group or a nitro group (—NO ₂ ).

In the above formulas (5) to (7), R ¹³ , R ¹⁴ and R ¹⁵ are each a hydrogen atom, a halogen atom, a hydroxyl group, a methyl group, an ethyl group, a halogenated methyl group, a halogenated ethyl group or a nitro group (—NO ₂ ). The retardation film according to claim 1, wherein the aryl-substituted lower alkylcarbonyl group is represented by the following formula (3) or (4).

In the formula (3), R ¹ , R ² , R ³ , R ⁴ and R ⁵ may be the same or different, and each is a hydrogen atom, a halogen atom, a hydroxyl group, a methyl group, an ethyl group, or a halogenated group. A methyl group, an ethyl halide group, or a nitro group (—NO ₂ ). In the formula (4), R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ^11, and R ¹² are the same. Or a hydrogen atom, a halogen atom, a hydroxyl group, a methyl group, an ethyl group, a halogenated methyl group, a halogenated ethyl group, or a nitro group (—NO ₂ ), It is an integer of 1-2.   The retardation film according to claim 1 or 2, wherein a modification rate of the chemical group in the skeleton is in a range of 1 to 20% of the total carbon number of the main chain.   The retardation film according to any one of claims 1 to 3, wherein the glass transition temperature of the modified polymer is 80 to 180 ° C. The retardation film according to any one of claims 1 to 4, wherein the in-plane retardation Δnd (450 nm) at a wavelength of 450 nm and the in-plane retardation Δnd (550 nm) at a wavelength of 550 nm satisfy the following relational expression.
Δnd (450 nm) / Δnd (550 nm) <1 The retardation film according to claim 1, wherein the in-plane retardation Δnd (650 nm) at a wavelength of 650 nm and the in-plane retardation Δnd (550 nm) at a wavelength of 550 nm satisfy the following relational expression.
Δnd (650 nm) / Δnd (550 nm)> 1 It is a film which satisfy | fills 0 <Nz <1 about the Nz coefficient represented by a following formula, The retardation film as described in any one of Claims 1-6.
Nz = (nx-nz) / (nx-ny)
In the above formula, nx and ny represent the refractive indexes in the X-axis direction and the Y-axis direction in the retardation film, respectively, nz represents the refractive index in the thickness direction (Z-axis direction) in the retardation film, and The X-axis direction is an axial direction showing the maximum refractive index in the plane of the retardation film, and the Y-axis direction is an axial direction perpendicular to the X-axis in the plane.   An optical film having the retardation film according to claim 1.   A liquid crystal panel comprising the optical film according to claim 8.   A liquid crystal panel, wherein the retardation film according to any one of claims 1 to 7 is disposed on at least one surface of a liquid crystal cell.   The liquid crystal panel according to claim 10, wherein the retardation film is disposed on a display screen side of the liquid crystal cell.   A liquid crystal display device provided with the liquid crystal panel as described in any one of Claims 9-11.   An image display apparatus provided with the retardation film as described in any one of Claims 1-7.   The image display device according to claim 13, wherein the image display device is at least one selected from the group consisting of an electroluminescence (EL) display, a plasma display (PD), and an FED (Field Emission Display).

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