JP2012025804A - Polymer film, polarizing plate and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polymer film, which can reduce a work load in film formation, is substantially optically isotropic with little optical anisotropy, and can inhibit optical unevenness in a liquid crystal display device.SOLUTION: The polymer film contains a thermoplastic polymer that can be formed into a film by a solution casting method and a polyester-based oligomer having a number-average molecular weight of 500 to 10,000 and having a repeating unit comprising a dicarboxylic acid and a diol. The polymer film is characterized in that: the dicarboxylic acid that constitutes the polyester oligomer is at least one dicarboxylic acid selected from an aliphatic dicarboxylic acid having 2 to 20 carbon atoms and an aromatic dicarboxylic acid having 8 to 20 carbon atoms; the diol is at least one diol selected from an aliphatic diol having 2 to 12 carbon atoms, an alkyl ether diol having 4 to 20 carbon atoms, and an aromatic ring-containing diol having 6 to 20 carbon atoms; and the polyester-based oligomer is included by 30 mass% or more with respect to the thermoplastic polymer.

Description

  The present invention relates to a polymer film, and a polarizing plate and a liquid crystal display device using the polymer film.

  In recent years, various polymer films have been used as optical films for liquid crystal display devices. For example, cellulose acylate film is excellent as an optical material for devices that handle polarized light such as liquid crystal display devices because of its high optical transparency and optical isotropy. It has been used as a support for a protective film for a polarizer and an optical compensation film capable of improving the display viewed from an oblique direction (viewing angle compensation).

In recent liquid crystal display devices, improvement in viewing angle characteristics is strongly demanded, and optical films such as polarizer protective films and optical compensation film supports are more optically isotropic. It is required to be. Optically isotropic means that the retardation value represented by the product of birefringence and thickness of the optical film is small. In particular, in order to improve the display from the oblique direction, it is necessary to reduce not only the in-plane retardation (Re) but also the absolute value of the retardation (Rth) in the film thickness direction. Specifically, when the optical properties of the optical transparent film are evaluated, the Re measured from the front of the film is small, and it is required that the Re does not change even if the angle is changed.
Patent Document 1 discloses a technique for containing 5% by mass or more of a polyester diol having hydroxyl groups at both ends with respect to cellulose acylate, with the purpose of reducing Re and Rth of the cellulose acylate film. Has been.

  As liquid crystal display devices are becoming slimmer, the occurrence of circular light unevenness on the display surface is becoming a problem in recent years. Although the generation mechanism of this light unevenness is still unclear, one reason is that the backlight member and the liquid crystal panel (particularly the backlight side polarizing plate) are in contact. Patent Document 2 discloses a method of preventing contact with a backlight member and preventing light unevenness by providing irregularities on the surface of a backlight side protective film of a backlight side polarizing plate.

  Further, as a method for producing a polymer film used for optical applications, a solution casting method having a good surface shape is known. In the case of the solution casting method, it is generally known that the drying load is large and very much energy is required. On the other hand, a plasticizer is also added for the purpose of imparting high-speed film-forming suitability to solution casting, but in a cellulose acylate film, it is dried at a high temperature exceeding 90 to 100 ° C. while being conveyed. The process to do was necessary. As polymer films containing a plasticizer, for example, Patent Documents 3 and 4 disclose polymer films to which polyester oligomers are added.

JP 2009-098764 A JP 2009-169393 A Japanese Patent No. 4192411 JP 2009-155454 A

In Patent Document 2, since a PET film is used as a protective film for a polarizing plate, there is difficulty in polarizing plate workability, and even when a cellulose acylate film having good polarizing plate workability is used, generation of light unevenness can be suppressed. Technology is desired.
Further, in improving the display quality of the liquid crystal display device, it is required to prevent light leakage when viewed from an oblique direction. When the cellulose acylate film containing a polyester diol described in Patent Document 1 is used in a liquid crystal display device, Rth becomes too large when the content of the polyester diol increases, and light leakage when viewed from an oblique direction occurs. It turns out that it gets worse.

The present invention can reduce the load during film formation, has a small optical anisotropy, is substantially optically isotropic, can suppress the occurrence of light unevenness in a liquid crystal display device, and can also emit light from an oblique direction. It is to provide a polymer film that can reduce leakage.
Another object of the present invention is to provide a polarizing plate using a polymer film having a small optical anisotropy and a substantially optical isotropic property. Still another object of the present invention is to provide a liquid crystal display device using these polymer film and polarizing plate and having improved light unevenness and light leakage.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by adding a specific polyester-based oligomer as a plasticizer to the polymer film in a specific amount in the polymer film. Furthermore, it discovered that the improvement effect of the drying process at the time of film forming was also seen. That is, it has been found that by including the specific amount of plasticizer, the drying property during film formation is improved, the drying proceeds sufficiently even at a low temperature of 70 ° C. or less, and the drying load during film formation can be reduced.
That is, the present invention can be achieved by the following means.

(1)
In a polymer film containing a thermoplastic polymer capable of film formation by a solution casting method and a polyester-based oligomer having a number average molecular weight of 500 to 10,000 and having a repeating unit consisting of a dicarboxylic acid and a diol,
The dicarboxylic acid forming the polyester-based oligomer is at least one dicarboxylic acid selected from aliphatic dicarboxylic acids having 2 to 20 carbon atoms and aromatic dicarboxylic acids having 8 to 20 carbon atoms, and the diol is At least one diol selected from an aliphatic diol having 2 to 12 carbon atoms, an alkyl ether diol having 4 to 20 carbon atoms, and an aromatic ring-containing diol having 6 to 20 carbon atoms,
A polymer film comprising the polyester-based oligomer in an amount of 30% by mass or more based on the thermoplastic polymer.
(2)
The aliphatic dicarboxylic acid is malonic acid, succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, azelaic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, 1,3-cyclobutane Dicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, or 1,4-cyclohexanedicarboxylic acid,
Aromatic dicarboxylic acids are phthalic acid, isophthalic acid, terephthalic acid, 1,4-xylidenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,8 -The polymer film as described in (1) above, which is naphthalenedicarboxylic acid or 2,6-naphthalenedicarboxylic acid.
(3)
The aliphatic diol is ethanediol, 3-oxapentane-1,5-diol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2-methyl- 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, 1,4-hexanediol, 1,5-hexanediol, 1, 6-hexanediol, 2-methyl-1,8-octanediol, 1,4-cyclohexanediol, or 1,4-cyclohexanedimethanol,
The polymer film as described in (1) or (2) above, wherein the aromatic ring-containing diol is bisphenol A, 1,4-dihydroxybenzene, or benzene-1,4-dimethanol.
(4)
In the polyester oligomer, at least one terminal is an aliphatic group having 1 to 22 carbon atoms, an aromatic ring-containing group having 6 to 20 carbon atoms, an aliphatic carbonyl group having 1 to 22 carbon atoms, and 6 to 20 carbon atoms. The polymer film as described in any one of (1) to (3) above, which is at least one selected from the aromatic carbonyl groups.
(5)
The film thickness of this polymer film is 20-200 micrometers, The polymer film of any one of said (1)-(4) characterized by the above-mentioned.
(6)
Re and Rth defined by the following formula (I) and the following formula (II) satisfy the following formula (III) and the following formula (IV) at a wavelength of 590 nm: (1) to (5) The cellulose acylate film according to any one of the above.
Formula (I) Re = (nx−ny) × d
Formula (II) Rth = {(nx + ny) / 2−nz} × d
Formula (III) 0 ≦ Re ≦ 10
Formula (IV) −25 ≦ Rth ≦ 25
In the formula, nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, nz is the refractive index in the thickness direction of the film, and d is the film (Nm).
(7)
The polymer film according to any one of (1) to (6), wherein the thermoplastic polymer is cellulose acylate.
(8)
A polarizing plate comprising at least one of the polymer films according to any one of (1) to (7) above.
(9)
A liquid crystal display device comprising at least one of the polymer film according to any one of (1) to (6) and the polarizing plate according to (8).

  The polymer film of the present invention can be used as a substantially optically isotropic film for polarizing plates and liquid crystal display devices. By using the polymer film of the present invention, it is possible to improve the occurrence of light unevenness and light leakage from an oblique direction in a liquid crystal display device. Furthermore, the load improvement effect of the drying process at the time of polymer film manufacture is acquired.

  Hereinafter, the present invention will be described in detail. In the present specification, when numerical values represent physical property values, characteristic values, etc., the descriptions “(numerical value 1) to (numerical value 2)” and “(numerical value 1) to (numerical value 2)” are “(numerical value 1). ) ”(Numerical value 2) or less”.

The polymer film of the present invention is a polymer film containing a thermoplastic polymer that can be formed by a solution casting method, and a polyester-based oligomer having a number average molecular weight of 500 to 10,000 and having a repeating unit composed of a dicarboxylic acid and a diol. Because
The dicarboxylic acid forming the polyester-based oligomer is at least one dicarboxylic acid selected from an aliphatic dicarboxylic acid having 2 to 20 carbon atoms and an aromatic dicarboxylic acid having 8 to 20 carbon atoms, and the diol has a carbon number. 2 to 12 aliphatic diols, 4 to 20 carbon alkyl diols, and 6 to 20 aromatic ring-containing diols selected from at least one diol,
The polyester-based oligomer is characterized by containing 30% by mass or more based on the thermoplastic polymer.

The polymer film of the present invention contains the specific amount of the specific polyester-based oligomer described above, thereby expressing desired optical isotropy and improving light unevenness and light leakage from the oblique direction of the liquid crystal display device. be able to. Furthermore, the load improvement effect of the drying process at the time of polymer film manufacture is acquired.
30 mass% or more and 80 mass% or less are preferable with respect to a thermoplastic polymer, and, as for content of a polyester-type oligomer, 35 mass% or more and 60 mass% or less are more preferable. If content is 80 mass% or less, it is easy to suppress the bleed out from a film, and it is preferable.
When two or more polyester oligomers are contained, the total content of the two or more polyester oligomers may be within the above range in the polymer film of the present invention.

[Polyester oligomer]
The polyester oligomer used in the present invention will be described.
The number average molecular weight (Mn) of the polyester-based oligomer in the present invention is 500 to 10000, preferably 600 to 2000, more preferably 600 to 1500, and still more preferably 600 to 1200. If the number average molecular weight of the polyester-based oligomer is 500 or more, the volatility is low, and film failure and process contamination due to volatilization under high temperature conditions during stretching of the polymer film are less likely to occur. Moreover, if it is 10,000 or less, compatibility with a thermoplastic polymer will become high, and it will become difficult to produce the bleed out at the time of film forming and at the time of heat-stretching.
The number average molecular weight of the polyester-based oligomer in the present invention can be measured and evaluated by gel permeation chromatography.

  The polyester oligomer used in the present invention includes at least one dicarboxylic acid selected from aliphatic dicarboxylic acids having 2 to 20 carbon atoms and aromatic dicarboxylic acids having 8 to 20 carbon atoms, and 2 to 12 carbon atoms. The diol is synthesized from at least one diol selected from aromatic ring-containing diols having 6 to 20 carbon atoms, and aliphatic diols having 4 to 20 carbon atoms. As a synthesis method, a known method such as a dehydration condensation reaction of a dicarboxylic acid and a diol, or addition of a dicarboxylic anhydride to a diol and a dehydration condensation reaction can be used.

From the viewpoint of improving light unevenness, it is preferable to contain two or more polyester oligomers.
From the viewpoint of improving light leakage from an oblique direction, when two or more polyester oligomers are contained, at least one is preferably a polyester oligomer containing an aromatic ring. Furthermore, it is more preferable that at least one is a polyester-based oligomer containing an aromatic ring, and at least one other is a polyester-based oligomer containing no aromatic ring.
Here, the polyester oligomer containing an aromatic ring is preferably a polyester oligomer obtained by synthesis of an aromatic dicarboxylic acid and a diol.
Hereinafter, dicarboxylic acids and diols that can be preferably used in the synthesis of the polyester-based oligomer in the present invention will be described.

(Dicarboxylic acid)
As the dicarboxylic acid, either an aliphatic dicarboxylic acid or an aromatic dicarboxylic acid can be used.
Examples of the aliphatic dicarboxylic acid include oxalic acid, malonic acid, succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, azelaic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid and Examples include 1,4-cyclohexanedicarboxylic acid. Of these, malonic acid, succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, azelaic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid are preferred. .
As aromatic dicarboxylic acids, phthalic acid, isophthalic acid, terephthalic acid, 1,4-xylidene dicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, Examples include 2,8-naphthalenedicarboxylic acid and 2,6-naphthalenedicarboxylic acid.
Among these, more preferred aliphatic dicarboxylic acids are malonic acid, succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, 1,4-cyclohexanedicarboxylic acid, and aromatic dicarboxylic acids include Phthalic acid, terephthalic acid, isophthalic acid, 1,5-naphthalenedicarboxylic acid and 1,4-naphthalenedicarboxylic acid are preferred. Particularly preferably, the aliphatic dicarboxylic acid is succinic acid, glutaric acid, or adipic acid, and the aromatic dicarboxylic acid is phthalic acid, terephthalic acid, or isophthalic acid.

The aliphatic dicarboxylic acid used in the present invention preferably has 3 to 12 carbon atoms, and more preferably 3 to 8 carbon atoms. The aromatic dicarboxylic acid preferably has 8 to 14 carbon atoms, and more preferably 8 carbon atoms.
In this invention, you may use the mixture of 2 or more types of dicarboxylic acid, In this case, it is preferable that the average carbon number of 2 or more types of dicarboxylic acid is 3-14, and it is more preferable that it is 3-8.
If the carbon number of the dicarboxylic acid is within the above range, it is preferable because in addition to improving light unevenness, it has excellent compatibility with a thermoplastic polymer, and bleed-out is unlikely to occur during film formation and heat stretching.
It is also preferable to use an aliphatic dicarboxylic acid and an aromatic dicarboxylic acid in combination. Specifically, a combination of adipic acid and phthalic acid, a combination of adipic acid and terephthalic acid, a combined use of succinic acid and phthalic acid, and a combined use of succinic acid and terephthalic acid are preferred. The combined use of succinic acid and terephthalic acid is more preferable. When aliphatic dicarboxylic acid and aromatic dicarboxylic acid are used in combination, the ratio (molar ratio) between them is preferably 95: 5 to 40:60, and more preferably 55:45 to 45:55.

(Diol)
The diol (glycol) is selected from aliphatic diols having 2 to 12 carbon atoms, alkyl ether diols having 4 to 20 carbon atoms, and aromatic ring-containing diols having 6 to 20 carbon atoms.
Examples of the aliphatic diol include alkyl diols and alicyclic diols. For example, ethane diol (ethylene glycol), 3-oxapentane-1,5-diol (diethylene glycol), 1,2-propanediol, 1, 3-propanediol, 1,2-butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl- 1,3-propanediol (neopentyl glycol), 2,2-diethyl-1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3,3-dimethylolheptane), 3-methyl-1,5-pentanediol, 1,4-hexanedio 1,5-hexanediol, 1,6-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2-methyl-1,8- There are octanediol, 1,9-nonanediol, 1,10-decanediol, 1,4-cyclohexanediol, or 1,4-cyclohexanedimethanol, and these glycols are used as one kind or a mixture of two or more kinds. used.
Preferred aliphatic diols include ethanediol, 3-oxapentane-1,5-diol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, and 2-methyl. -1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, 1,4-hexanediol, 1,5-hexanediol, 1 , 6-hexanediol, 2-methyl-1,8-octanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, particularly preferably ethanediol, 1,2-propanediol, 1,3 -Propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1, - pentanediol, 1,6-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol.

  Preferred examples of the alkyl ether diol having 4 to 20 carbon atoms include polytetramethylene ether glycol, polyethylene ether glycol, polypropylene ether glycol, and combinations thereof. Although the average degree of polymerization is not particularly limited, it is preferably 2 to 20, more preferably 2 to 10, further 2 to 5, and particularly preferably 2 to 4. As examples of these, commercially useful polyether glycols typically include Carbowax resin, Pluronics resin, and Niax resin.

  Examples of the aromatic diol having 6 to 20 carbon atoms include, but are not limited to, bisphenol A, 1,2-hydroxybenzene, 1,3-hydroxybenzene, 1,4-hydroxybenzene, and benzene-1,4-methanol. Of these, bisphenol A, 1,4-hydroxybenzene, and benzene-1,4-dimethanol are preferred.

The aromatic diol preferably has 6 to 12 carbon atoms.
When using 2 or more types of diol, it is preferable that the average carbon number of 2 or more types becomes 2-12.
If the carbon number of the diol is in the above range, in addition to improving the light unevenness, it is excellent in compatibility with the thermoplastic polymer, and it is preferable that bleeding out hardly occurs at the time of film formation and heat stretching of the polymer film.

(Sealing)
Both ends of the polyester oligomer of the present invention may be sealed or unsealed.
When both ends of the polyester oligomer are unsealed, the oligomer is preferably a polyester polyol.
In addition, at least one terminal is sealed, and the terminal is an aliphatic group having 1 to 22 carbon atoms, an aromatic ring-containing group having 6 to 20 carbon atoms, an aliphatic carbonyl group having 1 to 22 carbon atoms, and a carbon number. It is also preferable that it is at least one selected from 6 to 20 aromatic carbonyl groups.
Furthermore, when both ends of the polyester-based oligomer are sealed, it is more preferable to seal by reacting with a monoalcohol or monocarboxylic acid. At this time, both ends of the oligomer are monoalcohol residues or monocarboxylic acid residues. Here, the residue is a partial structure of the oligomer and represents a partial structure having the characteristics of the monomer forming the oligomer. For example, the monocarboxylic acid residue formed from monocarboxylic acid R—COOH is R—CO—.

As the monoalcohol residue, a substituted or unsubstituted monoalcohol residue having 1 to 30 carbon atoms is preferable. Methanol, ethanol, propanol, isopropanol, butanol, isobutanol, pentanol, isopentanol, hexanol, isohexanol, cyclohexyl Alcohol, octanol, isooctanol, 2-ethylhexyl alcohol, nonyl alcohol, isononyl alcohol, tert-nonyl alcohol, decanol, dodecanol, dodecahexanol, aliphatic alcohol such as dodecaoctanol, allyl alcohol, oleyl alcohol, benzyl alcohol, 3- Examples include substituted alcohols such as phenylpropanol.
The end-capping alcohol residues that can be preferably used are methanol, ethanol, propanol, isopropanol, butanol, isobutanol, isopentanol, hexanol, isohexanol, cyclohexyl alcohol, isooctanol, 2-ethylhexyl alcohol, isononyl alcohol, Oleyl alcohol and benzyl alcohol, especially methanol, ethanol, propanol, isobutanol, cyclohexyl alcohol, 2-ethylhexyl alcohol, isononyl alcohol and benzyl alcohol.

The monocarboxylic acid residue is preferably an aliphatic monocarboxylic acid residue having 2 to 22 carbon atoms, more preferably an aliphatic monocarboxylic acid residue having 2 to 3 carbon atoms, and 2 carbon atoms. Particularly preferred are aliphatic monocarboxylic acid residues.
If the number of carbon atoms of the monocarboxylic acid residues at both ends of the polyester-based oligomer is 3 or less, the volatility decreases, the weight loss due to heating of the oligomer does not increase, and process contamination and surface failure occur. Can be reduced. That is, aliphatic monocarboxylic acids are preferable as monocarboxylic acids used for sealing. The monocarboxylic acid is more preferably an aliphatic monocarboxylic acid having 2 to 22 carbon atoms, more preferably an aliphatic monocarboxylic acid having 2 to 3 carbon atoms, and an aliphatic monocarboxylic acid residue having 2 carbon atoms. Particularly preferred is a group.
Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butanoic acid, caprylic acid, caproic acid, decanoic acid, dodecanoic acid, stearic acid, and oleic acid. Examples of the aromatic ring-containing monocarboxylic acid include benzoic acid, p-tert-butylbenzoic acid, p-tert-amylbenzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethylbenzoic acid, ethylbenzoic acid, and normalpropyl benzoic acid. Acid, aminobenzoic acid, acetoxybenzoic acid, etc. are mentioned.
Among these, acetic acid, propionic acid, butanoic acid, benzoic acid and derivatives thereof are preferable, acetic acid or propionic acid is more preferable, and acetic acid (terminal is an acetyl group) is most preferable. Two or more monocarboxylic acids used for sealing may be mixed.

  When both ends are sealed, the state at normal temperature is unlikely to be in a solid form, the handling becomes good, and a polymer film excellent in humidity stability and polarizing plate durability can be obtained.

The thermoplastic polymer suitably used in the present invention is not particularly limited as long as it can be formed by a solution casting method and exhibits a thermoplastic property. Specific examples of the thermoplastic polymer include cellulose acylate, cycloolefin polymer, acrylic polymer, and the like. Hereinafter, the present invention will be described by taking cellulose acylate, which is one of suitable polymers, as an example.
[Cellulose acylate]
Next, the cellulose acylate in the present invention will be described.
Cellulose acylate raw material cellulose used in the present invention includes cotton linter and wood pulp (hardwood pulp, conifer pulp), and any cellulose acylate obtained from any raw material cellulose can be used. May be used. Detailed descriptions of these raw material celluloses can be found in, for example, Plastic Materials Course (17) Fibrous Resin (Maruzawa, Uda, Nikkan Kogyo Shimbun, published in 1970) and Invention Association Open Technical Report 2001-1745 (page 7). To page 8) can be used, and the cellulose acylate film of the present invention is not particularly limited.

The cellulose acylate according to the present invention produced from the above-described cellulose will be described.
Cellulose acylate is obtained by acylating a hydroxyl group of cellulose, and the substituent can be any acetyl group having 2 carbon atoms in the acyl group to those having 22 carbon atoms.

The acyl group having 2 to 22 carbon atoms to be substituted for the hydroxyl group of cellulose is not particularly limited and may be an aliphatic group or an aromatic group, and may be a single type or a mixture of two or more types. Cellulose acylates substituted with these groups are, for example, cellulose alkylcarbonyl esters, alkenylcarbonyl esters, aromatic carbonyl esters, aromatic alkylcarbonyl esters, and the like, and each may further have a substituted group.
Preferred acyl groups include acetyl, propionyl, butanoyl, heptanoyl, hexanoyl, octanoyl, decanoyl, dodecanoyl, tridecanoyl, tetradecanoyl, hexadecanoyl, octadecanoyl, iso-butanoyl, t-butanoyl, cyclohexanecarbonyl, oleoyl Benzoyl, naphthylcarbonyl, cinnamoyl group and the like. Among these, acetyl, propionyl, butanoyl, dodecanoyl, octadecanoyl, t-butanoyl, oleoyl, benzoyl, naphthylcarbonyl, cinnamoyl and the like are preferable, and acetyl, propionyl and butanoyl are more preferable.
Among these, an acetyl group and a propionyl group are preferable, and an acetyl group is particularly preferable from the viewpoints of ease of synthesis, cost, and ease of control of substituent distribution. When two or more acyl groups are substituted, an acetyl group and a propionyl group are preferred.

In the cellulose acylate of the present invention, the acyl substitution degree to the hydroxyl group of cellulose is not particularly limited, but when used for the application of a polarizing plate protective film and an optical film, the higher the acyl substitution degree, the moisture permeability and hygroscopicity of the film. It is preferable because it is excellent. For this reason, it is preferable that the acyl substitution degree (total substitution degree) to the hydroxyl group of a cellulose is 2.50-3.00. Furthermore, the acyl substitution degree is preferably 2.70 to 2.96, and more preferably 2.80 to 2.94. Moreover, when only an acetyl group substitutes, it is preferable that the substitution degree of this acetyl group is 2.70-2.96, and it is more preferable that it is 2.80-2.94. The substitution degree of the propionyl group is preferably 0.20 to 2.60.
In the cellulose acylate according to the present invention, the method for measuring the substitution degree (acyl substitution degree) of acetic acid and / or a fatty acid having 3 to 22 carbon atoms substituted on the hydroxyl group of cellulose is in accordance with ASTM D-817-91. And the NMR method.

  The degree of polymerization of cellulose acylate preferably used in the present invention is 180 to 700 in terms of viscosity average polymerization degree, and in cellulose acetate, 180 to 550 is more preferable, 180 to 400 is more preferable, and 180 to 350 is particularly preferable. . If the degree of polymerization is too high, the viscosity of the cellulose acylate dope solution tends to be high, and film production tends to be difficult due to casting. If the degree of polymerization is too low, the strength of the produced film tends to decrease. The average degree of polymerization can be measured by Uda et al.'S intrinsic viscosity method (Kazuo Uda, Hideo Saito, Journal of Textile Society, Vol. 18, No. 1, pages 105-120, 1962). This is described in detail in JP-A-9-95538.

  Further, the molecular weight distribution of cellulose acylate preferably used in the present invention is evaluated by gel permeation chromatography, and its polydispersity index Mw / Mn (Mw is mass average molecular weight, Mn is number average molecular weight) is small, and molecular weight distribution. Is preferably narrow. The specific value of Mw / Mn is preferably 1.0 to 4.0, more preferably 2.0 to 3.5, and most preferably 2.3 to 3.4. preferable.

  When the low molecular component is removed, the average molecular weight (degree of polymerization) increases, but the viscosity becomes lower than that of normal cellulose acylate, which is useful. Cellulose acylate having a small amount of low molecular components can be obtained by removing low molecular components from cellulose acylate synthesized by a usual method. The removal of the low molecular component can be carried out by washing the cellulose acylate with an appropriate organic solvent. In addition, when manufacturing a cellulose acylate with few low molecular components, it is preferable to adjust the sulfuric acid catalyst amount in an acetylation reaction to 0.5-25 mass parts with respect to 100 mass parts of cellulose. When the amount of the sulfuric acid catalyst is within the above range, cellulose acylate that is preferable in terms of molecular weight distribution (narrow molecular weight distribution) can be synthesized. When used in the production of the polymer film of the present invention, the moisture content of cellulose acylate is preferably 2% by mass or less, more preferably 1% by mass or less, and particularly preferably 0.7% by mass. It is as follows. In general, cellulose acylate contains water, and its water content is known to be 2.5 to 5% by mass. In order to obtain the moisture content of the cellulose acylate as described above in the present invention, it is necessary to dry, and the method is not particularly limited as long as the desired moisture content is obtained. Regarding these cellulose acylates of the present invention, the raw material cotton and the synthesis method thereof are disclosed on the 7th to 12th pages of the Japan Society for Invention and Innovation (public technical number 2001-1745, published on March 15, 2001, Japan Institute of Invention). It is described in detail.

  In the present invention, cellulose acylate can be used by mixing two or more different types of cellulose acylates from the viewpoint of substituents, substitution degree, polymerization degree, molecular weight distribution, and the like.

[Retardation adjuster]
The optical anisotropy of the polymer film of the present invention is controlled by the addition of the polyester oligomer described above, but a different optical anisotropy adjusting agent may be further added. Examples thereof include compounds that reduce Rth described in JP-A 2006-30937, pages 23 to 72.

[Retardation]
The polymer film of the present invention preferably has a small optical anisotropy. Specifically, Re and Rth (defined by the following formula (I) and formula (II)) measured at a wavelength of 590 nm should be made to satisfy both formula (III) and formula (IV). Is preferred. This value can be controlled by the degree of substitution of cellulose ester cotton, the amount of the polyester oligomer added, the film thickness of the film, and the like.
Formula (I) Re = (nx−ny) × d
Formula (II) Rth = {(nx + ny) / 2−nz} × d
Formula (III) 0 ≦ Re ≦ 10
Formula (IV) −25 ≦ Rth ≦ 25
In the formula, nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, nz is the refractive index in the thickness direction of the film, and d is the film (Nm).
Since the film satisfying the above formulas (III) and (IV) has small optical anisotropy, it can be suitably used as a protective film for a polarizing plate. Furthermore, another functional layer can be provided using a polymer film used as a protective film as a support. For example, an optically anisotropic layer or the like can be provided for the purpose of improving the contrast of the display screen of the liquid crystal display device or improving viewing angle characteristics and color.
Re is more preferably 0 nm to 5 nm. Rth is more preferably −15 to 5 nm, and further preferably −10 to 0 nm. When the polymer film of the present invention is used as a protective film on the liquid crystal cell side of a polarizing plate of a liquid crystal display device, if Re and Rth are in the above ranges, light leakage from an oblique direction is further improved and display quality is improved. Can do.
The absolute value ΔRth of the difference between the Rth value at 25 ° C. and 80% RH and the 25 ° C. and 10% RH value at a wavelength of 590 nm is preferably 0 to 15, more preferably 0 to 10, More preferably, it is -5. When ΔRth is within this range, the light unevenness from the oblique direction is further improved, and the display quality can be improved.

Re and Rth can be measured as follows.
Re is measured with KOBRA 21ADH (manufactured by Oji Scientific Instruments Co., Ltd.) by making light of wavelength λ nm incident in the normal direction of the film. Rth was measured by making light having a wavelength λ nm incident from a direction inclined + 40 ° with respect to the normal direction of the film with the slow axis in the plane (determined by KOBRA 21ADH) as the tilt axis (rotation axis). A retardation value and a retardation value measured by making light of wavelength λ nm incident from a direction inclined by −40 ° with respect to the film normal direction with the in-plane slow axis as the tilt axis (rotation axis). KOBRA 21ADH is calculated based on the retardation value measured in the direction. Here, as the assumed value of the average refractive index, values in the polymer handbook (John Wiley & Sons, Inc.) and catalogs of various optical films can be used. Those whose average refractive index is not known can be measured with an Abbe refractometer. The average refractive index values of main optical films are exemplified below: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), Polystyrene (1.59). The KOBRA 21ADH calculates nx, ny, and nz by inputting the assumed value of the average refractive index and the film thickness.

[Matting agent fine particles]
It is preferable to add fine particles as a matting agent to the polymer film of the present invention. The fine particles used in the present invention include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate and Mention may be made of calcium phosphate. Fine particles containing silicon are preferable in terms of low turbidity, and silicon dioxide is particularly preferable. The silicon dioxide fine particles preferably have a primary average particle size of 20 nm or less and an apparent specific gravity of 70 g / liter or more. Those having an average primary particle size as small as 5 to 16 nm are more preferred because they can reduce the haze of the film.
The apparent specific gravity is preferably 90 to 200 g / liter or more, and more preferably 100 to 200 g / liter or more. A larger apparent specific gravity is preferable because a high-concentration dispersion can be produced, and haze and aggregates are improved.

  These fine particles usually form secondary particles having an average particle diameter of 0.1 to 3.0 μm, and these fine particles are present as aggregates of primary particles in the film, and 0.1 to 0.1 μm on the film surface. An unevenness of 3.0 μm is formed. The secondary average particle size is preferably from 0.2 to 1.5 μm, more preferably from 0.4 to 1.2 μm, and most preferably from 0.6 to 1.1 μm. The primary and secondary particle sizes were determined by observing the particles in the film with a scanning electron microscope and determining the diameter of a circle circumscribing the particles as the particle size. In addition, 200 particles were observed at different locations, and the average value was taken as the average particle size.

  As the fine particles of silicon dioxide, for example, commercially available products such as Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (above Nippon Aerosil Co., Ltd.) can be used. Zirconium oxide fine particles are commercially available, for example, under the trade names Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.) and can be used.

  Among these, Aerosil 200V and Aerosil R972V are fine particles of silicon dioxide having a primary average particle diameter of 20 nm or less and an apparent specific gravity of 70 g / liter or more, and the coefficient of friction is maintained while keeping the turbidity of the optical film low. It is particularly preferable because it has a great effect of reducing the effect.

In order to obtain a polymer film having particles having a small secondary average particle size in the present invention, several methods are conceivable when preparing a dispersion of fine particles. For example, in the case of a film using cellulose acylate, a fine particle dispersion in which a solvent and fine particles are stirred and mixed is prepared in advance, and this fine particle dispersion is added to a separately prepared small amount of cellulose acylate solution and stirred and dissolved. There is a method of mixing with the cellulose acylate dope solution. This method is a preferred preparation method in that the dispersibility of the silicon dioxide fine particles is good and the silicon dioxide fine particles are more difficult to reaggregate. In addition, after adding a small amount of cellulose acylate to the solvent and dissolving with stirring, add fine particles to this and disperse with a disperser to make this fine particle additive solution, which is sufficiently mixed with the dope solution using an in-line mixer. There is also a method of mixing. The present invention is not limited to these methods, but the concentration of silicon dioxide when the silicon dioxide fine particles are mixed and dispersed with a solvent or the like is preferably 5 to 30% by mass, more preferably 10 to 25% by mass, and 15 to 20%. Mass% is most preferred. A higher dispersion concentration is preferable because the liquid turbidity with respect to the added amount is lowered, and haze and aggregates are improved.
The addition amount of the matting agent in the final cellulose acylate dope solution is preferably 0.01 to 1.0 g, more preferably 0.03 to 0.3 g, and 0.08 to 0.16 g per 1 m ^2. Most preferred. Further, when the cellulose acylate film is formed from multiple layers, it is preferably not added to the inner layer, but only to the surface layer side. In this case, the amount of the matting agent added to the surface layer is 0.001% by mass. The content is preferably 0.2% by mass or less and more preferably 0.01% by mass or more and 0.1% by mass or less.

  As the solvent used for dispersion, lower alcohols are preferable, and examples thereof include methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, and butyl alcohol. Although it does not specifically limit as solvents other than a lower alcohol, It is preferable to use the solvent used at the time of film formation of a cellulose acylate.

[Other additives]
In addition to the above-mentioned polyester-based oligomer, retardation adjusting agent, matte particles, the polymer film of the present invention has various additives (for example, plasticizer, ultraviolet absorber, deterioration inhibitor, release agent, infrared absorber, A wavelength dispersion adjusting agent, etc.) can be added, and they can be solid or oily. That is, the melting point and boiling point are not particularly limited. For example, mixing of ultraviolet absorbing material at 20 ° C. or lower and 20 ° C. or higher, and similarly mixing of a plasticizer is described in, for example, JP-A-2001-151901. Furthermore, infrared absorbing dyes are described in, for example, JP-A No. 2001-194522. Moreover, the addition time may be added at any time in the dope preparation step, but may be added by adding an additive to the final preparation step of the dope preparation step. Furthermore, the amount of each material added is not particularly limited as long as the function is manifested. Moreover, when a polymer film is formed from a multilayer, the kind and addition amount of the additive of each layer may differ. For example, it is described in Japanese Patent Application Laid-Open No. 2001-151902, and these are conventionally known techniques. For these details, materials described in detail on pages 16 to 22 in the Japan Institute of Invention Disclosure Technical Bulletin (Public Technical No. 2001-1745, published on March 15, 2001, Japan Institute of Invention) are preferably used.

[Additive amount of additive]
In the polymer film of the present invention, when these other additives are added in addition to the above-mentioned polyester oligomer, the total amount of the additives may be 30% by mass or more and 100% by mass or less with respect to the thermoplastic polymer. Preferably, it is 35 mass% or more and 60 mass% or less.

[Production method of polymer film]
The polymer film of the present invention can be formed by a solution casting method. Hereinafter, the method for producing a polymer film of the present invention will be described with reference to a film formed by using cellulose acylate as a thermoplastic polymer (referred to as “cellulose acylate film”).

(Organic solvent for cellulose acylate solution)
In the present invention, it is preferable to produce a cellulose acylate film by a solution casting method (solvent cast method), and the film is produced using a solution (dope) in which cellulose acylate is dissolved in an organic solvent. The organic solvent preferably used as the main solvent of the present invention is preferably a solvent selected from esters, ketones, ethers having 3 to 12 carbon atoms, and halogenated hydrocarbons having 1 to 7 carbon atoms. Esters, ketones and ethers may have a cyclic structure. A compound having two or more functional groups of esters, ketones and ethers (that is, —O—, —CO— and —COO—) can also be used as a main solvent. It may have a functional group of

  For the cellulose acylate film according to the present invention, a chlorinated halogenated hydrocarbon may be used as a main solvent, and as described in JIII Journal of Technical Disclosure 2001-1745 (pages 12 to 16), A non-chlorine solvent may be used as the main solvent, and is not particularly limited to the cellulose acylate film according to the present invention.

  In addition, the solvent for the cellulose acylate solution and the film according to the present invention is disclosed in the following patents, including its dissolution method, and is a preferred embodiment. They are, for example, JP 2000-95876, JP 12-95877, JP 10-324774, JP 8-152514, JP 10-330538, JP 9-95538, JP 9-95557, JP 10-10. -235664, JP-A-12-63534, JP-A-11-21379, JP-A-10-182853, JP-A-10-278056, JP-A-10-279702, JP-A-10-323853, JP-A-10-237186, JP-A-11-60807. JP-A-11-152342, JP-A-11-292988, JP-A-11-60752, JP-A-11-60752, and the like. According to these patents, not only the preferred solvent for the cellulose acylate according to the present invention but also the physical properties of the solution and the coexisting substances to be coexisted are described, which is also a preferred embodiment in the present invention.

(Dissolution process)
Preparation of the cellulose acylate solution (dope) according to the present invention is not particularly limited in its dissolution method, and may be performed at room temperature, and further, a cooling dissolution method or a high temperature dissolution method, and further a combination thereof. Regarding the preparation of the cellulose acylate solution in the present invention, and further on the steps of solution concentration and filtration accompanying the dissolving step, the technical report of the Japan Society of Invention (Publication No. 2001-1745, published on March 15, 2001, Japan Society of Invention) The manufacturing process described in detail on pages 22 to 25 is preferably used.

(Casting, drying, winding process)
Next, the method for producing a film using the cellulose acylate solution according to the present invention will be described more specifically. As a method and equipment for producing a cellulose acylate film according to the present invention, a solution casting film forming method and a solution casting film forming apparatus conventionally used for producing a cellulose triacetate film can be used. The dope (cellulose acylate solution) prepared from the dissolving machine (kettle) is temporarily stored in a storage kettle, and the foam contained in the dope is defoamed for final preparation. The dope is sent from the dope discharge port to the pressure die through a pressure metering gear pump capable of delivering a constant amount of liquid with high accuracy, for example, by the number of rotations, and the dope is run endlessly from the die (slit) of the pressure die. The dry-dried dope film (also referred to as a polymer web) is peeled off from the metal support at a peeling point which is uniformly cast on the metal support and substantially rounds the metal support. The both ends of the obtained web are sandwiched between clips, transported by a tenter while holding the width and dried, and then the obtained film is mechanically transported by a roll group of a drying device, dried, and then rolled by a winder Wind up to a predetermined length. The combination of the tenter and the roll group dryer varies depending on the purpose. As another embodiment, the metal support described above is a drum cooled to 0 ° C. or less, and the dope cast from the die is gelled on the drum and then peeled off after about one turn, and stretched with a pin-shaped tenter. Various methods for forming a film by a solvent cast method, such as a method of transporting and drying the solution, can be used.

Since the cellulose acylate film according to the present invention contains a specific polyester-based oligomer in an amount of more than 30 mass, the polymer web can be dried at 80 ° C. or less, and the load in the drying process can be reduced. it can. The temperature for drying (film surface temperature of the polymer web) is preferably 50 to 80 ° C, more preferably 60 to 75 ° C. The drying time is preferably 5 to 60 minutes, more preferably 10 to 30 minutes.
The amount of residual solvent in the polymer web after drying is preferably 0 to 1% by mass, more preferably 0 to 0.5% by mass.

  In the solution casting film-forming method used for the functional polarizing plate protective film and the silver halide photographic light-sensitive material, which are optical members for electronic displays, which is the main use of the cellulose acylate film according to the present invention, solution casting In addition to the film forming apparatus, a coating apparatus is often added for surface processing on films such as an undercoat layer, an antistatic layer, an antihalation layer, and a protective layer. These are described in detail on pages 25 to 30 in the Japan Society for Invention and Innovation Technical Report (Public Technical Number 2001-1745, published on March 15, 2001, Japan Society of Inventions). Including), metal support, drying, peeling and the like, and can be preferably used in the present invention.

[Film thickness]
The thickness of the polymer film of the present invention is preferably 20 to 200 μm, more preferably 20 to 120 μm, still more preferably 30 to 90 μm, and particularly preferably 35 to 80 μm. Moreover, when using as a polarizer protective film bonded to a liquid crystal panel, 30-80 micrometers is preferable and 35-65 micrometers is more preferable when improving light nonuniformity. Furthermore, if it is within this range, the warpage of the panel accompanying the change in temperature and humidity can be reduced.

[Haze of film]
The transparency of the film is important as an optical film, and the haze of the polymer film of the present invention is preferably as small as possible, preferably 0.01 to 2.0%. More preferably, it is 1.0% or less, More preferably, it is 0.5% or less. The haze can be measured according to JIS K-6714 using a polymer film sample 40 mm × 80 mm of the present invention at 25 ° C. and 60% RH using a haze meter (HGM-2DP, Suga Test Instruments).

[Spectral characteristics, Spectral transmittance]
A transmittance of a polymer film sample 13 mm × 40 mm at a wavelength of 300 to 450 nm can be measured with a spectrophotometer “U-3210” {Hitachi, Ltd.} at 25 ° C. and 60% RH. The inclination width can be obtained at a wavelength of 72% -5%. The limiting wavelength can be represented by a wavelength of (gradient width / 2) + 5%, and the absorption edge can be represented by a wavelength of transmittance of 0.4%. From this, the transmittances at 380 nm and 350 nm can be evaluated.
When the polymer film of the present invention is used on the opposite side of the protective film facing the liquid crystal cell of the polarizing plate, the spectral transmittance at a wavelength of 380 nm measured by the above method is 45% or more and 95% or less and a wavelength of 350 nm. The spectral transmittance at is preferably 10% or less.

[Glass-transition temperature]
The glass transition temperature of the polymer film of the present invention is preferably 120 ° C. or higher, more preferably 140 ° C. or higher.
The glass transition temperature is a temperature at which the base line derived from the glass transition of the film starts to change and a temperature at which it returns to the base line again when measured at a heating rate of 10 ° C./min using a differential scanning calorimeter (DSC). It can be calculated as an average value.
Moreover, the measurement of a glass transition temperature can also be calculated | required using the following dynamic viscoelasticity measuring apparatuses. After the cepolymer film sample (unstretched) 5 mm × 30 mm of the present invention was conditioned at 25 ° C. and 60% RH for 2 hours or more, a dynamic viscoelasticity measuring device (Vibron: DVA-225 (IT Measurement Control Co., Ltd.) )), The distance between the grips is 20 mm, the heating rate is 2 ° C./min, the measurement temperature range is 30 ° C. to 250 ° C., the frequency is 1 Hz, the logarithmic axis is the storage elastic modulus, the horizontal axis is the temperature (linear axis) When the storage elastic modulus shifts from the solid region to the glass transition region, a straight decrease in the storage elastic modulus is drawn in the solid region and a straight line 2 is drawn in the glass transition region. Is the temperature at which the storage elastic modulus suddenly decreases and the film begins to soften when the temperature rises, and the glass transition temperature Tg (dynamic viscosity) Elasticity).

[Equilibrium moisture content of film]
The water content (equilibrium water content) of the polymer film of the present invention is 25, regardless of the film thickness, so as not to impair the adhesion to a water-soluble polymer such as polyvinyl alcohol when used as a protective film for a polarizing plate. It is preferable that the water content in 0 degreeC and 80% RH is 0-4 mass%. More preferably, it is 0.1-3.5 mass%, and it is especially preferable that it is 1-3 mass%. When the equilibrium moisture content is 4% by mass or less, it is preferable that the dependency of retardation due to humidity change does not become too large when used as a support for an optical compensation film.
The moisture content was measured by the Karl Fischer method using a polymer film sample 7 mm × 35 mm of the present invention with a moisture measuring device, sample drying apparatus “CA-03” and “VA-05” (both manufactured by Mitsubishi Chemical Corporation). It was measured. It was calculated by dividing the amount of water (g) by the sample mass (g).

[Water permeability of film]
The moisture permeability of the film is measured under conditions of 60 ° C. and 95% RH based on JIS Z-0208.
The moisture permeability decreases as the thickness of the polymer film increases, and increases as the thickness of the polymer film decreases. Therefore, for samples having different film thicknesses, it is necessary to convert the reference to 80 μm. The film thickness can be converted according to the following mathematical formula.
Formula: Moisture permeability in terms of 80 μm = measured moisture permeability × measured film thickness (μm) / 80 (μm).
The measurement method of water vapor transmission rate is “Polymer Physical Properties II” (Polymer Experiment Course 4, Kyoritsu Shuppan), pages 285-294 “Measurement of vapor permeation amount (mass method, thermometer method, vapor pressure method, adsorption amount method) Can be applied.
The moisture permeability of the polymer film of the present invention is preferably 400 to 5000 g / m ² · 24 h. More preferably 400~4000g ^/ m 2 · 24h, and particularly preferably 400~3500g ^/ m 2 · 24h. If the water vapor transmission rate is 4000 g / m ² · 24 h or less, there is no inconvenience that the absolute value of the humidity dependence of the Re value and Rth value of the film exceeds 0.5 nm /% RH, which is preferable.

[Changes in film dimensions]
The dimensional stability of the polymer film of the present invention is 24% under the conditions of dimensional change when left standing at 60 ° C. and 90% RH for 24 hours (high humidity), and 90 ° C. and 5% RH. The dimensional change rate when left standing for a long time (high temperature) is preferably 0.5% or less. More preferably, it is 0.3% or less, More preferably, it is 0.15% or less.
ing.

[Elastic modulus of film]
The tensile modulus of the polymer film of the present invention is preferably less than 3.0 GPa, more preferably 1.0 to 3.0 GPa, still more preferably 1.2 to 2.8 GPa. As a specific measurement method, using a universal tensile tester “STM T50BP” manufactured by Toyo Baldwin Co., Ltd., the stress at 0.5% elongation was measured at 23 ° C. and 70 RH% atmosphere at a tensile rate of 10% / min. The elastic modulus was determined.

[Photoelastic coefficient]
When the polymer film of the present invention is used as a polarizing plate protective film, birefringence (Re, Rth) may change due to stress caused by the contraction of the polarizer. The change in birefringence due to such stress can be measured as a photoelastic coefficient, but the range is preferably 15 Br or less, more preferably −3 to 12 Br, and further preferably 0 to 11 Br. preferable.

[Contact angle of film surface by alkali saponification]
One effective means of surface treatment when the polymer film of the present invention is used as a polarizing plate protective film is alkali saponification treatment. In this case, the contact angle of the film surface after the alkali saponification treatment is preferably 55 ° or less. More preferably, it is 50 ° or less, and further preferably 45 ° or less.

[surface treatment]
The polymer film can achieve improved adhesion between the polymer film and each functional layer (for example, the undercoat layer and the back layer) by optionally performing a surface treatment. For example, glow discharge treatment, ultraviolet irradiation treatment, corona treatment, flame treatment, acid or alkali treatment can be used. The glow discharge treatment here may be low-temperature plasma that occurs under a low pressure gas of 10 ^{−3 to} 20 Torr, and plasma treatment under atmospheric pressure is also preferred. A plasma-excitable gas is a gas that is plasma-excited under the above conditions, and includes chlorofluorocarbons such as argon, helium, neon, krypton, xenon, nitrogen, carbon dioxide, tetrafluoromethane, and mixtures thereof. It is done. Details of these are described in detail in pages 30 to 32 in the Japan Institute of Invention Disclosure Technical Bulletin (Public Technical Number 2001-1745, published on March 15, 2001, Japan Institute of Invention), and are preferably used in the present invention. be able to.

[Functional layer]
The polymer film of the present invention is applied to, for example, optical applications and photographic light-sensitive materials. In particular, the optical application is preferably a liquid crystal display device, and the liquid crystal display device has a liquid crystal cell in which liquid crystal is supported between two electrode substrates, two polarizing elements disposed on both sides thereof, and the liquid crystal It is more preferable that at least one optical compensation sheet is disposed between the cell and the polarizer. As these liquid crystal display devices, TN, IPS, FLC, AFLC, OCB, STN, ECB, VA and HAN are preferable.
In that case, when using the polymer film of this invention for the above-mentioned optical use, providing various functional layers is implemented. These are, for example, an antistatic layer, a cured resin layer (transparent hard coat layer), an antireflection layer, an easy adhesion layer, an antiglare layer, an optical compensation layer, an alignment layer, a liquid crystal layer, and the like. Examples of these functional layers and materials thereof include surfactants, slip agents, matting agents, antistatic layers, hard coat layers, etc., and are disclosed by the Japan Institute of Technology (Technical Number 2001-1745, March 15, 2001). (Nippon Issuance, Invention Association), page 32 to page 45, and can be preferably used in the present invention.

[Polarizer]
The use of the polymer film of the present invention will be described.
When the polymer film of the present invention is used as an optical film, it is particularly useful for a polarizing plate protective film. When using as a polarizing plate protective film, the manufacturing method of a polarizing plate is not specifically limited, It can manufacture by a general method. There is a method in which the obtained polymer film is treated with an alkali and bonded to both surfaces of a polarizer prepared by immersing and stretching a polyvinyl alcohol film in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution. Instead of alkali treatment, easy adhesion processing as described in JP-A-6-94915 and JP-A-6-118232 may be performed.
Examples of the adhesive used to bond the protective film treated surface and the polarizer include polyvinyl alcohol adhesives such as polyvinyl alcohol and polyvinyl butyral, vinyl latexes such as butyl acrylate, and the like.
The polarizing plate is composed of a polarizer and a protective film that protects both surfaces of the polarizer, and further includes a protective film bonded to one surface of the polarizing plate and a separate film bonded to the other surface. The protective film and the separate film are used for the purpose of protecting the polarizing plate at the time of shipping the polarizing plate and at the time of product inspection. In this case, the protect film is bonded for the purpose of protecting the surface of the polarizing plate, and is used on the side opposite to the surface where the polarizing plate is bonded to the liquid crystal plate. Moreover, a separate film is used in order to cover the adhesive layer bonded to a liquid crystal plate, and is used for the surface side which bonds a polarizing plate to a liquid crystal plate.
In a liquid crystal display device, a substrate containing liquid crystal is usually disposed between two polarizing plates. However, the polarizing plate protective film to which the optical film of the present invention is applied can provide excellent display properties regardless of the location. . In particular, since the polarizing plate protective film on the outermost surface of the display side of the liquid crystal display device is provided with a transparent hard coat layer, an antiglare layer, an antireflection layer, and the like, the polarizing plate protective film is particularly preferably used in this portion.

[Optical compensation film]
The polymer film of the present invention can be used in various applications, and is particularly effective when used as an optical compensation film for liquid crystal display devices. The optical compensation film is generally used for a liquid crystal display device and refers to an optical material that compensates for a retardation, and is synonymous with a retardation plate, an optical compensation sheet, and the like. The optical compensation film has birefringence and is used for the purpose of removing the color of the display screen of the liquid crystal display device or improving the viewing angle characteristics.
When the polymer film of the present invention is produced with a small optical anisotropy such as Re and Rth of 0 ≦ Re ≦ 10 nm and | Rth | ≦ 25 nm, an optically anisotropic layer having a birefringence is used in combination. Only optical performance can be expressed mainly, and it can be used suitably.

Therefore, when the polymer film of the present invention is used as a support for an optical compensation film of a liquid crystal display device, any optically anisotropic layer may be used together.
The optical performance and driving method of the liquid crystal cell of the liquid crystal display device in which the polymer film of the present invention is used are not limited, and any optical anisotropic layer required as an optical compensation film can be used in combination. The optically anisotropic layer used in combination may be formed from a composition containing a liquid crystalline compound or may be formed from a polymer film having birefringence. The liquid crystal compound is preferably a discotic liquid crystal compound or a rod-like liquid crystal compound.

(General liquid crystal display device configuration)
When a polymer film is used as the optical compensation film, the transmission axis of the polarizer and the slow axis of the optical compensation film made of the polymer film may be arranged at any angle. The liquid crystal display device includes a liquid crystal cell having a liquid crystal supported between two electrode substrates, two polarizers disposed on both sides thereof, and at least one sheet between the liquid crystal cell and the polarizer. The optical compensation film is arranged.
The liquid crystal layer of the liquid crystal cell is usually formed by sealing liquid crystal in a space formed by sandwiching a spacer between two substrates. The transparent electrode layer is formed on the substrate as a transparent film containing a conductive substance. The liquid crystal cell may further be provided with a gas barrier layer, a hard coat layer, or an undercoat layer (undercoat layer) (used for adhesion of the transparent electrode layer). These layers are usually provided on the substrate. The substrate of the liquid crystal cell generally has a thickness of 50 μm to 2 mm.

(Types of liquid crystal display devices)
The polymer film of the present invention can be used for liquid crystal cells in various display modes. TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), AFLC (Anti-Ferroly Liquid Liquid Crystal), OCB (Optically Liquid BTS). ECB (Electrically Controlled Birefringenc
e) and various display modes such as 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 polymer film of the present invention is effective in any display mode liquid crystal display device. Further, it is effective in any of a transmissive, reflective, and transflective liquid crystal display device.

(IPS liquid crystal display device)
The polymer film of the present invention is also particularly advantageously used as a support for an optical compensation sheet of an IPS type liquid crystal display device having an IPS mode liquid crystal cell, or as a protective film for a polarizing plate. In these modes, the liquid crystal material is aligned substantially in parallel during black display, and black is displayed by aligning liquid crystal molecules in parallel with the substrate surface in the absence of applied voltage. In these embodiments, the polarizing plate using the polymer film of the present invention is effective in reducing changes in color and contrast depending on the viewing angle.
Further, although | Rth | ≦ 25 is preferable, in the region of 450 to 650 nm, it is particularly preferable that Rth is 0 nm or less because the change in color is small.

  In this embodiment, among the protective films for the polarizing plates above and below the liquid crystal cell, the polarizing film using the polymer film of the present invention for the protective film (the protective film on the cell side) disposed between the liquid crystal cell and the polarizing plate. It is preferable to use plates above and below the liquid crystal cell. More preferably, an optically anisotropic layer in which the retardation value of the optically anisotropic layer between the protective film of the polarizing plate and the liquid crystal cell is set to not more than twice the value of Δn · d of the liquid crystal layer is provided. It is preferable to arrange on one side.

(Hard coat film, antiglare film, antireflection film)
The polymer film of the present invention can be applied to a hard coat film, an antiglare film, and an antireflection film. For the purpose of improving the visibility of flat panel displays such as LCD, PDP, CRT, EL, etc., any or all of a hard coat layer, an antiglare layer and an antireflection layer are provided on one or both sides of the polymer film of the present invention. be able to. Preferred embodiments of such an antiglare film and antireflection film are described in detail in pages 54 to 57 of the Japan Institute of Invention and Technology (Publication No. 2001-1745, published on March 15, 2001, Japan Society of Invention). The sepolymer film of the present invention can be preferably used.

(Transparent substrate)
If the polyester-based oligomer in the present invention is used, the optical anisotropy of the polymer film can be made close to zero, and since it has excellent transparency, it is an alternative to the liquid crystal cell glass substrate of the liquid crystal display device, that is, It can also be used as a transparent substrate enclosing the driving liquid crystal.
Since the transparent substrate enclosing the liquid crystal needs to be excellent in gas barrier properties, a gas barrier layer may be provided on the surface of the polymer film of the present invention as necessary. The form and material of the gas barrier layer are not particularly limited, but a polymer having a relatively high gas barrier property such as SiO ₂ or the like is vapor-deposited on at least one side of the polymer film of the present invention, or a vinylidene chloride polymer or vinyl alcohol polymer. The method of providing the coating layer of this can be considered, and these can be used suitably.
In order to use as a transparent substrate for enclosing liquid crystal, a transparent electrode for driving the liquid crystal by applying a voltage may be provided. Although it does not specifically limit as a transparent electrode, A transparent electrode can be provided by laminating | stacking a metal film, a metal oxide film, etc. on the at least single side | surface of the polymer film of this invention. Among these, a metal oxide film is preferable from the viewpoint of transparency, conductivity, and mechanical properties, and an indium oxide thin film mainly containing 2 to 15% of zinc oxide can be preferably used. Details of these techniques are disclosed in, for example, Japanese Patent Application Laid-Open Nos. 2001-125079 and 2000-227603.

  Hereinafter, the present invention will be specifically described based on examples. However, the present invention is not limited to the following examples.

[Production of cellulose acylate film]
(Preparation of cellulose acylate dope)
The cellulose acylate having the degree of acetyl substitution shown in Table 1 below is prepared by adding sulfuric acid (7.8 parts by mass with respect to 100 parts by mass of cellulose) as a catalyst to cellulose and adding a carboxylic acid as a raw material for acyl substituents. The acylation reaction was carried out at 40 ° C. At this time, the substitution degree of the acyl group was adjusted by adjusting the amount of carboxylic acid. In addition, aging was performed at 40 ° C. after acylation. Further, the low molecular weight component of the cellulose acylate was removed by washing with acetone.
Subsequently, cellulose acylate and additives listed in Table 1 below, and further silica particles (Aerosol R972, manufactured by Nippon Aerosil Co., Ltd.) as solvents (methylene chloride, methanol, and 1-butanol (mass ratio 81: 18: 1) ) Was added to the mixing tank and stirred while heating to dissolve each component to prepare a dope. In any dope, the silica particles were added in an amount of 0.1% by mass relative to the cellulose acylate. Moreover, content (%) of the additive in Table 1 is the mass% with respect to a cellulose acylate. The amount of the solvent was adjusted so that the solid content concentration (total concentration of cellulose acylate, additive, and silica particles in the dope) was 25% by mass.

(Preparation of cellulose acylate film)
The cellulose acylate dope prepared as described above was cast from a casting port onto a drum cooled to −5 ° C. The film is peeled off in a state where the solvent content is approximately 70% by mass, and both ends in the width direction of the film are fixed with a pin tenter (a pin tenter described in FIG. 3 of JP-A-4-1009), and the solvent content is 3-5% by mass. In this state, the film was dried while maintaining an interval at which the stretching ratio in the transverse direction (direction perpendicular to the machine direction) was about 3%. Then, it dried further by conveying between the rolls of a heat processing apparatus, and produced the cellulose acylate film of Examples 1-22 and Comparative Examples 1-6 of the thickness of following Table 1.
The drying rate of the dope film of the produced cellulose acylate film was measured as follows. The measurement results are shown in Table 1 below. For the cellulose acylate films of Examples 1 and 2 and Comparative Examples 1 and 5, Re, Rth, ΔRth, photoelastic coefficient, elastic modulus and moisture content were measured as follows.

(Retardation value)
The prepared cellulose acylate film is conditioned at 25 ° C. and 60% RH for 2 hours or more, and is used at a wavelength of 25 ° C. and 60% RH using a birefringence measuring device (KOBRA 21ADH, manufactured by Oji Scientific Instruments). The Re value and Rth value at 590 nm were measured.
Further, an Rth value at 25 ° C. and 80% RH and a 25 ° C. and 10% RH value at a wavelength of 590 nm were measured, and the absolute value of the difference was obtained as ΔRth.
(Photoelastic coefficient)
A 2 cm × 10 cm sample was cut out from the produced cellulose acylate film, and a retardation value in the film plane was applied while applying a stress to the sample at 23 ° C. using a spectroscopic ellipsometer (M-220, manufactured by JASCO Corporation). Was calculated from the slope of the function of retardation value and stress.
(Elastic modulus)
Using an all-purpose tensile tester “STM T50BP” manufactured by Toyo Baldwin Co., Ltd., the stress at 0.5% elongation was measured in an atmosphere of 23 ° C. and 70 RH% at a tensile rate of 10% / min to obtain the elastic modulus.
(Moisture content)
A 7 mm × 35 mm sample was cut out from the produced cellulose acylate film, and the moisture content was measured by the Karl Fischer method with a moisture measuring device and a sample drying apparatus “CA-03” and “VA-05” (both manufactured by Mitsubishi Chemical Corporation). Was measured.
(Drying speed)
For each cellulose acylate film, the dope was cast on a drum and peeled off under the same conditions as described above. The removed dope film was dried at 70 ° C. (film surface temperature) for 20 minutes, and the amount of residual solvent after drying was measured by gas chromatography (gas chromatograph apparatus GC-2014 (manufactured by Shimadzu Corporation)). A smaller residual solvent amount means a faster drying rate.
Residual solvent amount (% by mass) = weight of solvent component detected by gas chromatography / film weight × 100

  Additives A to Q in Table 1 are polyester oligomers obtained by polycondensation reaction of dicarboxylic acids and diols shown in Table 2 below and having a number average molecular weight of 500 to 10,000. For B, C, E, F, H to M, O, and Q, both ends of the molecule are sealed (that is, they are not hydroxyl groups).

  In Table 2, the “ratio” column of each component represents the molar ratio in each component, and “100” represents that only one type in the right column was used as the corresponding component.

(Preparation of polarizing plate)
The cellulose acetate films of Examples 1 and 2 and Comparative Examples 1 and 5 prepared as described above were immersed in a 1.5 N aqueous sodium hydroxide solution at 55 ° C. for 2 minutes and washed in a room temperature water bath. The mixture was neutralized with 0.05N sulfuric acid at 30 ° C. Again, it was washed in a water bath at room temperature and further dried with hot air at 100 ° C.
A roll-shaped polyvinyl alcohol film having a thickness of 80 μm was continuously stretched 5 times in an aqueous iodine solution and dried to obtain a polarizing film. One cellulose acylate film of Example 1 subjected to alkali saponification treatment with a 3% aqueous solution of polyvinyl alcohol (Kuraray PVA-117H) as an adhesive, and a commercially available cellulose acetate film (Fujitac TD60UL) treated with alkali saponification as described above. Prepared by Fuji Film Co., Ltd.) and bonded together with a polarizing film in between to obtain a polarizing plate having both surfaces protected by a cellulose acylate film. At this time, the cellulose acylate films on both sides were pasted so that the slow axes of the cellulose acylate films were parallel to the transmission axis of the polarizing film. The cellulose acylate films of Example 2 and Comparative Examples 1 and 5 were similarly processed to produce polarizing plates. Both the cellulose acylate films of Examples 1 and 2 had sufficient bonding properties with the stretched polyvinyl alcohol, and had excellent polarizing plate processing suitability.
Further, instead of the cellulose acylate film of Example 1, a commercially available cellulose acylate film having a film thickness of 60 μm (Fujitac TD60UL; manufactured by Fuji Film Co., Ltd.) was used to make a polarizing plate having both sides of Fujitac TD60UL as described above. Made. Hereinafter, this polarizing plate is referred to as P-TD.

(Mounting on IPS liquid crystal display)
The commercially available polarizing plate of IPS-TV was carefully peeled off, and the polarizing plate produced as described above was placed on both sides of the IPS cell via an adhesive. Here, Examples 1 and 2 and Comparative Examples 1 and 5 cellulose acylate films were respectively installed between the IPS cell and the polarizer.

Light leakage and light unevenness of the liquid crystal display device produced as described above were evaluated. The evaluation results are shown in Table 3 below.
(Oblique light leakage)
The light leakage rate during black display in the azimuth direction 45 degrees and polar angle direction 70 degrees from the front of the apparatus was measured. Compared with the case where the polarizing plate P-TD was used, the evaluation was performed according to the following criteria.
○: Less than 1/30 when P-TD is used Δ: 1/30 or more and less than 1/10 when P-TD is used ×: 1/10 or more when P-TD is used (in the front direction) Light unevenness level)
When observed from the front of the apparatus, luminance unevenness during black display was observed and evaluated according to the following criteria.
○: Unevenness is hardly visually recognized in an environment with an illuminance of 100 lx. Δ: Light unevenness is visually recognized in an environment with an illuminance of 100 lx. Clearly sees unevenness (light unevenness level in an oblique direction)
Luminance unevenness and color unevenness during black display in an azimuth direction of 45 degrees and a polar angle direction of 70 degrees from the front of the apparatus were observed and evaluated according to the following criteria.
○: Unevenness is hardly visually recognized in an environment with an illuminance of 100 lx. Δ: Light unevenness is visually recognized in an environment with an illuminance of 100 lx. A clear unevenness is visible

  As shown in Tables 1 and 3, the cellulose acylate film of the present invention containing 30% by mass or more of a specific polyester-based oligomer with respect to cellulose acylate has a high drying speed and reduces the load in the drying process. Can do. Moreover, as shown in Table 3, Re and Rth are low and optically isotropic, and when used in a liquid crystal display device, light unevenness and oblique light leakage are improved.

Claims (9)

In a polymer film containing a thermoplastic polymer capable of film formation by a solution casting method and a polyester-based oligomer having a number average molecular weight of 500 to 10,000 and having a repeating unit consisting of a dicarboxylic acid and a diol,
The dicarboxylic acid forming the polyester-based oligomer is at least one dicarboxylic acid selected from aliphatic dicarboxylic acids having 2 to 20 carbon atoms and aromatic dicarboxylic acids having 8 to 20 carbon atoms, and the diol is At least one diol selected from an aliphatic diol having 2 to 12 carbon atoms, an alkyl ether diol having 4 to 20 carbon atoms, and an aromatic ring-containing diol having 6 to 20 carbon atoms,
A polymer film comprising the polyester-based oligomer in an amount of 30% by mass or more based on the thermoplastic polymer. The aliphatic dicarboxylic acid is malonic acid, succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, azelaic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, 1,3-cyclobutane Dicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, or 1,4-cyclohexanedicarboxylic acid,
Aromatic dicarboxylic acids are phthalic acid, isophthalic acid, terephthalic acid, 1,4-xylidenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,8 The polymer film according to claim 1, wherein the polymer film is naphthalenedicarboxylic acid or 2,6-naphthalenedicarboxylic acid. The aliphatic diol is ethanediol, 3-oxapentane-1,5-diol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2-methyl- 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, 1,4-hexanediol, 1,5-hexanediol, 1, 6-hexanediol, 2-methyl-1,8-octanediol, 1,4-cyclohexanediol, or 1,4-cyclohexanedimethanol,
The polymer film according to claim 1 or 2, wherein the aromatic ring-containing diol is bisphenol A, 1,4-dihydroxybenzene, or benzene-1,4-dimethanol.   In the polyester oligomer, at least one terminal is an aliphatic group having 1 to 22 carbon atoms, an aromatic ring-containing group having 6 to 20 carbon atoms, an aliphatic carbonyl group having 1 to 22 carbon atoms, and 6 to 20 carbon atoms. The polymer film according to claim 1, wherein the polymer film is at least one selected from the following aromatic carbonyl groups.   The film thickness of this polymer film is 20-200 micrometers, The polymer film of any one of Claims 1-4 characterized by the above-mentioned. The Re and Rth defined by the following formula (I) and the following formula (II) satisfy the following formula (III) and the following formula (IV) at a wavelength of 590 nm. 2. The cellulose acylate film according to item 1.
Formula (I) Re = (nx−ny) × d
Formula (II) Rth = {(nx + ny) / 2−nz} × d
Formula (III) 0 ≦ Re ≦ 10
Formula (IV) −25 ≦ Rth ≦ 25
In the formula, nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, nz is the refractive index in the thickness direction of the film, and d is the film (Nm).   The polymer film according to claim 1, wherein the thermoplastic polymer is cellulose acylate.   A polarizing plate comprising at least one polymer film according to claim 1.   A liquid crystal display device comprising at least one of the polymer film according to claim 1 and the polarizing plate according to claim 8.