JPWO2015060167A1 - Retardation film, polarizing plate and liquid crystal display device - Google Patents

Abstract

An object of the present invention is to reduce the occurrence of a color shift due to light leakage of blue light from an oblique direction of a liquid crystal display device equipped with a white LED backlight, and a horizontal stage due to deterioration of peelability on a web casting belt. It is providing the retardation film which improved generation | occurrence | production and improved visibility. The retardation film of the present invention includes cellulose acetate having an acetyl group substitution degree of 2.56 to 2.70, and at least one nitrogen-containing heterocyclic compound having a pyrrole ring, a pyrazole ring, a triazole ring, or an imidazole ring. And retardation in the film thickness direction exhibits wavelength dispersion satisfying the following formula 1. Formula 1 1.0 ≦ Rth (450) / Rth (650) ≦ 1.2 (where Rth (450) and Rth (650) are respectively at an optical wavelength of 450 nm and 650 nm in an environment of 23 ° C. and 55% RH, respectively. Represents the measured retardation value Rth (nm) in the film thickness direction.)

Description

  The present invention relates to a retardation film, a polarizing plate, and a liquid crystal display device. More specifically, the present invention relates to a retardation film, a polarizing plate, and a liquid crystal display device that reduce occurrence of a color shift due to light leakage of blue light from an oblique direction in a liquid crystal display device including a light emitting diode that emits white light as a backlight.

Conventionally, cold cathode fluorescent lamps used as backlights for liquid crystal televisions have disadvantages such as the harmful effects of containing mercury, poor temperature characteristics, high power consumption, and high-speed blinking. Replacement of light emitting diodes that emit light (for example, a combination of a light emitting diode that emits blue light and a yellow / green / red phosphor) is underway (see, for example, Patent Document 1).
The above disadvantage can be improved by using a light emitting diode (hereinafter also referred to as a white LED) that emits white light as a backlight. However, when a liquid crystal display device is placed in a high temperature and high humidity environment for a long period of time, an image is displayed. In particular, when the screen is enlarged to 50 inches or more, there is a problem that variations in brightness and color occur in various parts of the screen. Furthermore, this tendency tends to be prominent when a member such as liquid crystal cell glass is thinned.
According to the study by the present inventors, the cause of the problem is that the fluorescence efficiency of the phosphor (red to green) of the white LED backlight deteriorates, and as a result, only the blue light of the light source is emphasized, It was inferred that a color shift occurred due to a large amount of light leakage from an oblique direction.
In order to optically compensate for the retardation of the liquid crystal cell layer in a liquid crystal display device, a retardation film is used. However, a retardation having reverse wavelength dispersion, which has been considered to have excellent contrast performance, is conventionally used. It was revealed that the film cannot sufficiently suppress light leakage from an oblique direction of blue light having a light absorption peak on the short wavelength side.
Therefore, in the case of a liquid crystal display device using a white LED backlight, it is desirable to compensate for the retardation in the thickness direction of the liquid crystal cell layer using a retardation film having a forward wavelength dispersion.

  In order to impart forward wavelength dispersion to the retardation film, it is known to use cellulose acetate with the acetyl group substitution degree adjusted or to contain a retardation increasing agent in the retardation film (for example, , Refer to Patent Documents 2 to 4), depending on the type of cellulose acetate in which the degree of substitution of the acetyl group is adjusted, and by adding the retardation increasing agent to an amount that exhibits forward wavelength dispersibility. Since the hydrogen bonding property of the web becomes strong, the peelability of the web from the belt is deteriorated, and a horizontal step is likely to occur when peeling from the belt, and streaky irregularities are observed when observing a large-screen liquid crystal display panel. A new problem occurred.

JP 2010-241995 A Japanese Patent No. 4187593 JP 2012-214683 A JP 2003-344655 A

  The present invention has been made in view of the above problems and situations, and its solution is to reduce the occurrence of color shift due to light leakage of blue light from an oblique direction of a liquid crystal display device equipped with a white LED backlight. In addition, the present invention is to provide a retardation film having improved visibility by improving the occurrence of lateral steps due to deterioration of peelability on a web casting belt. Furthermore, it is providing the polarizing plate and liquid crystal display device which improved the visibility which comprise the said retardation film.

  In order to solve the above problems, the present inventor contains a cellulose acetate having a specific degree of acetyl group substitution and a nitrogen-containing heterocyclic compound having a specific ring structure in the course of examining the cause of the above problems, And it discovered that the subject of this invention could be solved by the retardation film which has forward wavelength dispersion.

  That is, the said subject which concerns on this invention is solved by the following means.

1. Cellulose acetate having an acetyl group substitution degree in the range of 2.56 to 2.70, and at least one nitrogen-containing heterocyclic compound having a pyrrole ring, a pyrazole ring, a triazole ring, or an imidazole ring, and A retardation film, wherein retardation in the film thickness direction exhibits wavelength dispersion satisfying the following formula 1.
Formula 1 1.0 ≦ Rth (450) / Rth (650) ≦ 1.2
(Where Rth (450) and Rth (650) are the film thickness directions represented by the following formula (ii) measured using light having wavelengths of 450 nm and 650 nm in an environment of 23 ° C. and 55% RH, respectively. Represents the retardation value Rth (nm).
Formula (ii) Rth = {(n _x + _ny ) / 2−n _z } × d
However, n _x represents a refractive index in the direction x in which the refractive index is maximized in the plane direction of the optical film. n _y in-plane direction of the optical film, the refractive index in the direction y perpendicular to the direction x. _nz represents the refractive index in the thickness direction z of the film. d represents the thickness (nm) of the optical film. )
2. 2. The retardation film according to item 1, wherein the nitrogen-containing heterocyclic compound is a compound having a pyrazole ring, a triazole ring, or an imidazole ring.

  3. The retardation film according to item 1 or 2, wherein the nitrogen-containing heterocyclic compound is a compound having a structure represented by the following general formula (3).

（式中Ａはピラゾール環を表す。Ａｒ_１及びＡｒ_２はそれぞれ芳香族炭化水素環又は芳香族複素環を表し、置換基を有してもよい。Ｒ_１は水素原子、アルキル基、アシル基、スルホニル基、アルキルオキシカルボニル基、又はアリールオキシカルボニル基を表す。ｑは１又は２を表し、ｎ及びｍは１〜３の整数を表す。）
４．さらに、糖エステル又は下記一般式（４）で表される構造を有する重縮合エステルを少なくとも１種含有することを特徴とする第１項から第３項までのいずれか一項に記載の位相差フィルム。

(In the formula, A represents a pyrazole ring. Ar ₁ and Ar ₂ each represent an aromatic hydrocarbon ring or an aromatic heterocyclic ring and may have a substituent. R ₁ represents a hydrogen atom, an alkyl group, or an acyl group. Represents a sulfonyl group, an alkyloxycarbonyl group, or an aryloxycarbonyl group, q represents 1 or 2, and n and m represent an integer of 1 to 3.)
4). The retardation according to any one of items 1 to 3, further comprising at least one sugar ester or polycondensation ester having a structure represented by the following general formula (4): the film.

Formula _{(4): B 3 - (} G 2 -A) n -G 2 -B 4
(In the formula, B ₃ and B ₄ each independently represent an aliphatic or aromatic monocarboxylic acid residue or a hydroxy group. G ₂ represents an alkylene glycol residue having 2 to 12 carbon atoms, or 6 to 6 carbon atoms. 12 represents an aryl glycol residue having 12 carbon atoms or an oxyalkylene glycol residue having 4 to 12 carbon atoms, and A represents an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms or an aryl dicarboxylic acid residue having 6 to 12 carbon atoms. N represents an integer of 1 or more.)
5). The retardation film according to any one of Items 1 to 4, wherein the film thickness is in a range of 20 to 40 μm.

  6). The retardation film according to any one of items 1 to 5, further comprising an ultraviolet absorber.

  7). A polarizing plate, wherein the retardation film according to any one of items 1 to 6 is bonded to a polarizer using water glue or an active energy ray-curable adhesive.

  8). A polyester film or an acrylic film is bonded to the polarizer using a water glue or an active energy ray-curable adhesive on the surface opposite to the surface on which the retardation film of the polarizer is bonded. 8. The polarizing plate according to item 7, wherein

  9. A liquid crystal display device comprising the polarizing plate according to item 7 or 8.

  10. Item 10. The liquid crystal display device according to item 9, wherein a light emitting diode that emits white light is provided as a backlight.

  By the above means of the present invention, the occurrence of a color shift due to the light leakage of blue light from an oblique direction of a liquid crystal display device equipped with a white LED backlight is reduced, and the laterality due to deterioration of the peelability on the web casting belt is reduced. It is possible to provide a retardation film with improved visibility by improving the generation of steps. Furthermore, a polarizing plate and a liquid crystal display device having the retardation film and improved visibility can be provided.

The expression mechanism or action mechanism of the effect of the present invention is not clear, but is presumed as follows.
According to the study by the present inventors, when a liquid crystal display device using a white LED as a backlight is placed in a high-temperature and high-humidity environment for a long period of time, there is a problem that variations in brightness and color occur in various places on the screen. However, the fluorescent efficiency (red to green) of the white LED backlight deteriorates. As a result, only the blue light of the light source is emphasized, and there is much light leakage from the oblique direction of the blue light. It was inferred that a shift would occur.
For light leakage, it is effective to use a retardation film that optically compensates for the retardation of the liquid crystal cell layer of the liquid crystal display device. However, the reverse wavelength dispersion, which has been considered to have excellent contrast performance, is conventionally used. Since the retardation film has a large retardation in the in-plane direction as the wavelength becomes longer, the optical compensation action cannot be effectively applied to a short wavelength, that is, blue light. The leak cannot be suppressed sufficiently.
Therefore, for blue light having a light absorption peak on the short wavelength side, a liquid crystal cell layer in the thickness direction of the liquid crystal cell layer is used by using a retardation film having a forward wavelength dispersion having a retardation larger on the short wavelength side than on the long wavelength side It is inferred that it is effective to compensate for the retardation. However, depending on the type of cellulose acetate constituting the retardation film, and by adding a retardation increasing agent known in the art up to an amount that exhibits forward wavelength dispersion, the hydrogen bonding properties of the film are all included. Since the strength of the web becomes stronger, the affinity of the web with the casting belt is increased, and a horizontal step is likely to occur due to the deterioration of the web peelability. The horizontal stage has a new visibility problem that it is observed as streaky irregularities during observation, particularly in a large-screen liquid crystal display panel.

  As a result of studying this hydrogen bondability, the present inventors have found that the affinity for the casting belt is increased by the CH / π interaction between a specific cellulose acetate having a weak hydrogen bondability and cellulose acetate described later. With a retardation film using a specific nitrogen-containing heterocyclic compound that can be lowered as a retardation increasing agent, while imparting forward wavelength dispersibility that can sufficiently suppress light leakage from an oblique direction of blue light, It is presumed that a retardation film having improved visibility and no streak-like unevenness was obtained.

The schematic diagram which shows an example of the dope preparation process of the preferable solution casting film forming method of the retardation film of this invention, a casting process, and a drying process.

  The retardation film of the present invention comprises at least a cellulose acetate having an acetyl group substitution degree in the range of 2.56 to 2.70 and a nitrogen-containing heterocyclic compound having a pyrrole ring, a pyrazole ring, a triazole ring, or an imidazole ring. 1 type is contained and the wavelength dispersion of the retardation of a film thickness direction satisfy | fills the said Formula 1. This feature is a technical feature common to the inventions according to claims 1 to 10.

  As an embodiment of the present invention, it is preferable that the nitrogen-containing heterocyclic compound is a compound having a pyrazole ring, a triazole ring, or an imidazole ring from the viewpoint of manifesting the effects of the present invention. Further, the compound having the structure represented by the general formula (3) gives forward wavelength dispersibility and is due to light leakage of blue light from an oblique direction of a liquid crystal display device provided with a white LED backlight. The effect of reducing the occurrence of color shift and improving the occurrence of lateral steps due to deterioration of the peelability of the web on the belt is also preferable.

  Furthermore, it is preferable to contain at least one sugar ester or a polycondensed ester having a structure represented by the general formula (4) from the viewpoint of adjusting the retardation and improving the stability of the retardation.

  The retardation film of the present invention has a film thickness in the range of 20 to 40 μm, and can reduce the distortion of the member with respect to the thinning of a member such as a liquid crystal cell glass of a thin film. This is preferable because light leakage can be reduced.

  The retardation film of the present invention preferably contains an ultraviolet absorber from the viewpoint of alleviating the influence of unnecessary ultraviolet rays on the liquid crystal cell layer when the retardation film is bonded to the viewing side. .

  The retardation film of the present invention is a polarizing film that is bonded to a polarizer using water glue or an active energy ray-curable adhesive, suppresses expansion and contraction of the film, and has a small retardation fluctuation due to environmental humidity fluctuations. A plate can be provided, and a polyester film or an acrylic film is preferably a water paste or an active energy ray-curable adhesive on the surface of the polarizer opposite to the surface on which the retardation film is bonded. From the viewpoint of providing a polarizing plate having higher durability against environmental fluctuations, it is preferable to be bonded to a polarizer.

  The retardation film and polarizing plate of the present invention are suitably provided in a liquid crystal display device. The liquid crystal display device preferably includes a light emitting diode that emits white light as a backlight.

  Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In addition, in this application, "-" is used in the meaning which includes the numerical value described before and behind that as a lower limit and an upper limit.

<< Outline of retardation film of the present invention >>
The retardation film of the present invention comprises at least a cellulose acetate having a degree of acetyl group substitution in the range of 2.56 to 2.70 and a nitrogen-containing heterocyclic compound having a pyrrole ring, a pyrazole ring, a triazole ring, or an imidazole ring. 1 type, and the retardation of a film thickness direction shows the wavelength dispersion which satisfy | fills following formula 1.

Formula 1 1.0 ≦ Rth (450) / Rth (650) ≦ 1.2
(Where Rth (450) and Rth (650) are the film thickness directions represented by the following formula (ii) measured using light having wavelengths of 450 nm and 650 nm in an environment of 23 ° C. and 55% RH, respectively. Retardation value Rth (nm).
Formula (ii) Rth = {(n _x + _ny ) / 2−n _z } × d
(Where Rth (450) and Rth (650) are the film thickness directions represented by the following formula (ii) measured using light having wavelengths of 450 nm and 650 nm in an environment of 23 ° C. and 55% RH, respectively. Represents the retardation value Rth (nm).
However, n _x represents a refractive index in the direction x in which the refractive index is maximized in the plane direction of the optical film. n _y in-plane direction of the optical film, the refractive index in the direction y perpendicular to the direction x. _nz represents the refractive index in the thickness direction z of the film. d represents the thickness (nm) of the optical film. )
The value of Rth (450) / Rth (650) needs to be in the range of 1.0 to 1.2 although it depends on the type of white LED. If it is less than 1.0, it becomes reverse wavelength dispersion and does not show the effect of the present invention for performing optical compensation for LED light on the short wavelength side. If it exceeds 1.2, it is necessary to add a large amount of a retardation increasing agent, so that the internal haze increases and the contrast decreases.

  The wavelength dispersibility of the retardation film of the present invention is in the range of 1.0 to 1.15, sufficiently expressing the optical compensation function, and at the same time, the retardation increasing agent bleeds out from the film, It can suppress that haze becomes high, and is a more preferable range.

  The retardation value Rth in the thickness direction is measured at 450 nm and 650 nm in an environment of 23 ° C. and 55% RH using an automatic birefringence meter Axoscan (Axo Scan Mueller Matrix Polarimeter: manufactured by Axometrics). It can be calculated from the obtained refractive indexes nx, ny, and nz by performing a three-dimensional refractive index measurement.

  The retardation film of the present invention comprises a cellulose acetate having a weak hydrogen bonding property and easily causing retardation, and a nitrogen-containing heterocyclic compound whose hydrogen bonding property is optimally controlled and functions as a retardation increasing agent. Reduces the occurrence of color shift due to light leakage of blue light from an oblique direction in a liquid crystal display device equipped with a white LED backlight, and improves the occurrence of horizontal steps due to deterioration of the peelability of the web casting belt Thus, a retardation film with improved visibility can be provided.

<< Configuration of retardation film of the present invention >>
<Cellulose acetate>
The cellulose acetate constituting the retardation film of the present invention is a cellulose acetate having an acetyl group substitution degree in the range of 2.56 to 2.70, and is characterized by being a cellulose acetate having a weak hydrogen bonding property. . In the case of cellulose acetate having an acetyl group substitution degree in the range of 2.0 to 2.55, the hydrogen bondability is strong and the peelability of the web from the casting belt is deteriorated. In addition, cellulose acetate having a degree of acetyl group substitution exceeding 2.70 has low retardation expression, requires a large amount of addition of a retardation increasing agent, tends to increase haze, and has poor bleedout resistance.

  Examples of the raw material cellulose include cotton linter and wood pulp (hardwood pulp, softwood pulp). Cellulose acetate obtained from any raw material cellulose can be used, and in some cases, it may be mixed and used. Detailed descriptions of these raw material celluloses can be found in, for example, Marusawa and Uda, “Plastic Materials Course (17) Fibrous Resin”, published by Nikkan Kogyo Shimbun (published in 1970), and the Japan Society of Invention and Innovation Technical Bulletin No. 2001. The cellulose described in No.-1745 (pages 7 to 8) can be used.

  The cellulose acetate is required to be a cellulose acetate having an acetyl group substitution degree in the range of 2.56 to 2.70 from the viewpoint of improving the peelability of the web from the belt and reducing the occurrence of lateral steps, Furthermore, it is excellent in retardation expression and forward wavelength dispersion. Among these, 2.60 to 2.65 is more preferable.

  In addition, the substitution degree of an acetyl group can be calculated | required by the method prescribed | regulated to ASTM-D817-96.

  The weight average molecular weight (Mw) of the cellulose acetate according to the present invention is preferably 75,000 or more, more preferably in the range of 75,000 to 300,000, still more preferably in the range of 100,000 to 240,000, and 160000 to 240000. Are particularly preferred. If the weight average molecular weight (Mw) of a cellulose acetate is 75000 or more, the self-film-forming property of a cellulose acetate layer itself and the improvement effect of adhesion | attachment are exhibited, and it is preferable. In the present invention, two or more cellulose acetates can be mixed and used.

  The average molecular weight (Mn, Mw) of the cellulose acetate can be measured by gel permeation chromatography under the following measurement conditions.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) A calibration curve with 13 samples in the range of Mw = 500 to 2800000 was used. The 13 samples are preferably used at approximately equal intervals.

<Nitrogen-containing heterocyclic compound>
The nitrogen-containing heterocyclic compound according to the present invention can control the hydrogen bondability by CH / π interaction with cellulose acetate, and can reduce the affinity with the casting belt. By improving the peelability of the web from the casting belt, it is possible to obtain a retardation film having excellent visibility without streaks.

  Here, the CH / π interaction is a phase of an additive such as a hydrogen bond donating site (for example, a hydrogen atom of a hydroxy group) or a hydrogen bond accepting site (for example, a carbonyl oxygen atom of an ester group) such as cellulose acetate. This is a bond interaction between the hydrogen bonding site present in the main chain or side chain of the resin and the π electron of the aromatic compound of the additive. Due to this CH / π interaction, the interaction between the additive and the resin is stronger than the interaction between the polar component of the casting belt and the hydrogen bonding site of the resin, and the hydrogen bonding site of the resin becomes the casting belt. As a result, the peelability of the web from the casting belt is improved.

  When the CH / π interaction is formed using the hydrogen bonding site of the resin (CH of the cellulose acetate resin) and π of the additive, it is naturally better that the π property of the additive is stronger. There is an index called a NICS (nucleus-independent chemical shift) value as an example that directly represents the strength of the π property.

  This NICS value is an index used for quantification of aromaticity by magnetic properties. If the ring is aromatic, the ring current effect strongly shields the center of the ring, and conversely if it is antiaromatic. Anti-shielding (J. Am. Chem. Soc. 1996, 118, 6317). Depending on the magnitude of the NICS value, it is possible to determine the strength of the ring current, that is, the degree of contribution of π electrons to the aromaticity of the ring. Specifically, it represents the chemical shift (calculated value) of a virtual lithium ion arranged directly in the center of the ring, and the larger the value, the stronger the π property.

  Several reports have been made regarding the measured NICS values. For example, Canadian Journal of Chemistry. , 2004, 82, 50-69 (Document A) and The Journal of Organic Chemistry. , 2000, 67, 1333-1338 (Document B).

  Specifically, a pyrrole ring (-14.87), a thiophene ring (-14.09) furan rather than an aromatic hydrocarbon such as a benzene ring (-7.98) or a naphthalene ring (-8.11). 5-membered aromatic heterocycles such as ring (-12.42), pyrazole ring (-13.82), or imidazole ring (-13.28), triazole ring (-13.18), oxadiazole ring ( -12.44) or 6-membered aromatic hydrocarbon rings such as thiazole ring (-12.82) have a larger NICS value, and such aromatic 5-membered rings or aromatic 6-membered rings It is predicted that the CH / π interaction can be strengthened by using the compound having the above (the NICS value is shown in parentheses).

  The nitrogen-containing heterocyclic compound according to the present invention is characterized by being a nitrogen-containing heterocyclic compound having a pyrrole ring, a pyrazole ring, a triazole ring, or an imidazole ring, and has a structure represented by the following general formula (1). Among the nitrogen-containing heterocyclic compounds having, it is preferably a nitrogen-containing heterocyclic compound having the specific ring structure. The compound having the structure represented by the following general formula (1) is used together with cellulose acetate, so that when a polarizing plate is used in a liquid crystal display device, the occurrence of retardation fluctuation due to environmental humidity fluctuation is suppressed, and contrast reduction or Occurrence of color unevenness can be suppressed, and furthermore, by appropriately adjusting the type and addition amount of the nitrogen-containing heterocyclic compound, it functions as a phase difference increasing agent exhibiting forward wavelength dispersion.

  The molecular weight is preferably in the range of 100 to 800, from the viewpoint of controlling the affinity with the casting belt, and more preferably in the range of 250 to 450.

<Compound having the structure represented by the general formula (1)>

In the general formula (1), A ₁ , A ₂ and B are each independently an alkyl group (methyl group, ethyl group, n-propyl group, isopropyl group, tert-butyl group, n-octyl group, 2- An ethenyl group), a cycloalkyl group (cyclohexyl group, cyclopentyl group, 4-n-dodecylcyclohexyl group, etc.), an aromatic hydrocarbon ring or an aromatic heterocycle. Among these, an aromatic hydrocarbon ring or an aromatic heterocyclic ring is preferable, and a 5-membered or 6-membered aromatic hydrocarbon ring or aromatic heterocyclic ring is particularly preferable.

  The structure of a 5-membered or 6-membered aromatic hydrocarbon ring or aromatic heterocycle includes, for example, a benzene ring, a pyrrole ring, a pyrazole ring, an imidazole ring, a 1,2,3-triazole ring, and a 1,2,4-triazole ring. , Tetrazole ring, furan ring, oxazole ring, isoxazole ring, oxadiazole ring, isoxadiazole ring, thiophene ring, thiazole ring, isothiazole ring, thiadiazole ring, and isothiadiazole ring.

The 5-membered or 6-membered aromatic hydrocarbon ring or aromatic heterocyclic ring represented by A ₁ , A ₂ and B may have a substituent. Examples of the substituent include a halogen atom ( Fluorine atom, chlorine atom, bromine atom, iodine atom, etc.), alkyl group (methyl group, ethyl group, n-propyl group, isopropyl group, tert-butyl group, n-octyl group, 2-ethylhexyl group, etc.), cycloalkyl Group (cyclohexyl group, cyclopentyl group, 4-n-dodecylcyclohexyl group, etc.), alkenyl group (vinyl group, allyl group, etc.), cycloalkenyl group (2-cyclopenten-1-yl, 2-cyclohexen-1-yl group, etc.) ), Alkynyl group (ethynyl group, propargyl group, etc.), aromatic hydrocarbon ring group (phenyl group, p-tolyl group, naphthyl group, etc.), aromatic heterocyclic group (2 Pyrrole group, 2-furyl group, 2-thienyl group, pyrrole group, imidazolyl group, oxazolyl group, thiazolyl group, benzimidazolyl group, benzoxazolyl group, 2-benzothiazolyl group, pyrazolinone group, pyridyl group, pyridinone group, 2- Pyrimidinyl group, triazine group, pyrazole group, 1,2,3-triazole group, 1,2,4-triazole group, oxazole group, isoxazole group, 1,2,4-oxadiazole group, 1,3,4 -Oxadiazole group, thiazole group, isothiazole group, 1,2,4-thiodiazole group, 1,3,4-thiadiazole group, etc.), cyano group, hydroxy group, nitro group, carboxy group, alkoxy group (methoxy group) Ethoxy group, isopropoxy group, tert-butoxy group, n-octyloxy group, 2-methyl Xyloxy group, etc.), aryloxy groups (phenoxy group, 2-methylphenoxy group, 4-tert-butylphenoxy group, 3-nitrophenoxy group, 2-tetradecanoylaminophenoxy group, etc.), acyloxy groups (formyloxy group, Acetyloxy group, pivaloyloxy group, stearoyloxy group, benzoyloxy group, p-methoxyphenylcarbonyloxy group, etc.), amino group (amino group, methylamino group, dimethylamino group, anilino group, N-methyl-anilino group, diphenyl) Amino groups, etc.), acylamino groups (formylamino group, acetylamino group, pivaloylamino group, lauroylamino group, benzoylamino group, etc.), alkyl and arylsulfonylamino groups (methylsulfonylamino group, butylsulfonylamino group, phenyl) Sulfonylamino group, 2,3,5-trichlorophenylsulfonylamino group, p-methylphenylsulfonylamino group, etc.), mercapto group, alkylthio group (methylthio group, ethylthio group, n-hexadecylthio group, etc.), arylthio group (phenylthio group) P-chlorophenylthio group, m-methoxyphenylthio group, etc.), sulfamoyl group (N-ethylsulfamoyl group, N- (3-dodecyloxypropyl) sulfamoyl group, N, N-dimethylsulfamoyl group, N -Acetylsulfamoyl group, N-benzoylsulfamoyl group, N- (N'-phenylcarbamoyl) sulfamoyl group, etc.), sulfo group, acyl group (acetyl group, pivaloylbenzoyl group, etc.), carbamoyl group (carbamoyl group) Group, N-methylcarbamoyl group, N, N-di Chi-carbamoyl, N, N-di -n- octylcarbamoyl group, and each group such as N- (methylsulfonyl) carbamoyl group).

In the general formula (1), A ₁ , A ₂ and B represent a benzene ring, a pyrrole ring, a pyrazole ring, an imidazole ring, a 1,2,3-triazole ring or a 1,2,4-triazole ring. It is preferable because a retardation film having excellent optical property variation effects and excellent durability can be obtained.

In the general formula (1), T ₁ and T ₂ each independently represent a pyrrole ring, a pyrazole ring, an imidazole ring, a 1,2,3-triazole ring or a 1,2,4-triazole ring. Among these, a pyrazole ring, a triazole ring, or an imidazole ring is preferable because a resin composition that is particularly excellent in retardation fluctuation suppressing effect against humidity fluctuation and excellent in durability is obtained. It is particularly preferred. The pyrazole ring, 1,2,3-triazole ring, 1,2,4-triazole ring and imidazole ring represented by T ₁ and T2 may be tautomers. Specific structures of the pyrrole ring, pyrazole ring, imidazole ring, 1,2,3-triazole ring or 1,2,4-triazole ring are shown below.

In the formula, * represents a bonding position with L ₁ , L ₂ , L ₃ or L ₄ in the general formula (1). R ⁵ represents a hydrogen atom or a non-aromatic substituent. Examples of the non-aromatic substituent represented by R ⁵ include the same groups as the non-aromatic substituent among the substituents that A ₁ in the general formula (1) may have. When the substituent represented by R ⁵ is a substituent having an aromatic group, A ₁ and T ₁ or B and T ₁ are easily twisted, and A ₁ , B and T ₁ form an interaction with cellulose acetate. Since it becomes impossible, it is difficult to suppress the fluctuation | variation of an optical characteristic. In order to enhance the effect of suppressing fluctuation in optical properties, R ⁵ is preferably a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or an acyl group having 1 to 5 carbon atoms, and particularly preferably a hydrogen atom. .

In the general formula (1), T ₁ and T ₂ may have a substituent, and examples of the substituent include a substituent that A ₁ and A ₂ in the general formula (1) may have Similar groups can be mentioned.

In the general formula (1), L ₁ , L ₂ , L ₃ and L ₄ each independently represent a single bond or a divalent linking group, and are 5 or 6 via 2 or less atoms. Membered aromatic hydrocarbon rings or aromatic heterocycles are linked. The term “via two or less atoms” refers to the minimum number of atoms existing between the connected substituents among the atoms constituting the linking group. The divalent linking group having 2 or less linking atoms is not particularly limited, but includes an alkylene group, an alkenylene group, an alkynylene group, O, (C═O), NR, S, and (O═S═O). It is a divalent linking group selected from the group consisting of or a linking group in which two of them are combined. R represents a hydrogen atom or a substituent. Examples of the substituent represented by R include an alkyl group (methyl group, ethyl group, n-propyl group, isopropyl group, tert-butyl group, n-octyl group, 2-ethylhexyl group, etc.), cycloalkyl group ( Cyclohexyl group, cyclopentyl group, 4-n-dodecylcyclohexyl group, etc.), aromatic hydrocarbon ring group (phenyl group, p-tolyl group, naphthyl group, etc.), aromatic heterocyclic group (2-furyl group, 2-thienyl group). Group, 2-pyrimidinyl group, 2-benzothiazolyl group, 2-pyridyl group, etc.), cyano group and the like. The divalent linking group represented by L ₁ , L ₂ , L ₃ and L ₄ may have a substituent, and the substituent is not particularly limited. For example, A in the general formula (1) and ₁ and a ₂ have include the same groups as also substituents.

In the general formula (1), L ₁ , L ₂ , L ₃ and L ₄ are a resin that adsorbs water by increasing the planarity of the compound having the structure represented by the general formula (1). Interaction is suppressed and fluctuations in optical properties are suppressed, so that a single bond, O, (C═O) —O, O— (C═O), (C═O) —NR or NR— (C═O) is preferable, and a single bond is more preferable.

In the said General formula (1), n represents the integer of 0-5. When n represents an integer of 2 or more, the plurality of A ₂ , T ₂ , L ₃ , and L ₄ in the general formula (1) may be the same or different. The larger n is, the stronger the interaction between the compound having the structure represented by the general formula (1) and the resin that adsorbs water is, so that the effect of suppressing fluctuations in optical properties is excellent. Excellent compatibility with resin that adsorbs. For this reason, n is preferably an integer of 1 to 3, and more preferably 1 or 2.

<Compound having a structure represented by the general formula (2)>
The compound having a structure represented by the general formula (1) is preferably a compound having a structure represented by the general formula (2).

(In the formula, A ₁ , A ₂ , T ₁ , T ₂ , L ₁ , L ₂ , L ₃ and L ₄ are respectively A ₁ , A ₂ , T ₁ , T ₂ , L in the general formula (1). _{1, L} 2, _{L 3} and .A ₃ and _{T 3 L 4} as synonymous, the .L ₅ and _{L 6} represent the same group as _{a 1} and _{T 1,} respectively, in the general formula (1), the general Represents the same group as L ₁ in formula (1), and m represents an integer of 0 to 4.)
Since the one where m is smaller is excellent in compatibility with cellulose acetate, m is preferably an integer of 0 to 2, and more preferably an integer of 0 to 1.

<Compound having structure represented by general formula (1.1)>
The compound having a structure represented by the general formula (1) is preferably a triazole compound having a structure represented by the following general formula (1.1).

_(Wherein, A 1, B, _{L 1} and _{L 2,} .k representing the _A 1, B, the same group as _{L 1} and _{L 2} in formula (1) represents an integer of 1 to 4 T ₁ represents a 1,2,4-triazole ring.)
Furthermore, the triazole compound having a structure represented by the general formula (1.1) is preferably a triazole compound having a structure represented by the following general formula (1.2).

(In the formula, Z represents the structure of the following general formula (1.2a). Q represents an integer of 2 to 3. At least two Z's represent at least one Z substituted on a benzene ring. Bonded to ortho or meta position.)

(In the formula, R ¹⁰ represents a hydrogen atom, an alkyl group or an alkoxy group. P represents an integer of 1 to 5. * represents a bonding position with a benzene ring. T ₁ represents a 1,2,4-triazole ring. Represents.)
The compound having the structure represented by the general formula (1), (2), (1.1) or (1.2) may form a hydrate, a solvate or a salt. In the present invention, the hydrate may contain an organic solvent, and the solvate may contain water. That is, “hydrate” and “solvate” include mixed solvates containing both water and organic solvents. Salts include acid addition salts formed with inorganic or organic acids. Examples of inorganic acids include, but are not limited to, hydrohalic acids (hydrochloric acid, hydrobromic acid, etc.), sulfuric acid, phosphoric acid, and the like. Examples of organic acids include acetic acid, trifluoroacetic acid, propionic acid, butyric acid, oxalic acid, citric acid, benzoic acid, alkyl sulfonic acid (such as methane sulfonic acid), allyl sulfonic acid (benzene sulfonic acid, 4-toluene) Sulfonic acid, 1,5-naphthalenedisulfonic acid, etc.) and the like. Of these, hydrochloride, acetate, propionate and butyrate are preferable.

  Examples of salts are those in which the acidic moiety present in the parent compound is a metal ion (eg, an alkali metal salt, such as sodium or potassium salt, an alkaline earth metal salt, such as calcium or magnesium salt, an ammonium salt, an alkali metal ion, alkaline earth And salts formed when substituted with organic bases (ethanolamine, diethanolamine, triethanolamine, morpholine, piperidine, etc.) It is not limited. Of these, sodium salts and potassium salts are preferred.

  Examples of the solvent included in the solvate include any common organic solvent. Specifically, alcohol (eg, methanol, ethanol, 2-propanol, 1-butanol, 1-methoxy-2-propanol, t-butanol), ester (eg, ethyl acetate), hydrocarbon (eg, toluene, hexane) , Heptane), ether (eg, tetrahydrofuran), nitrile (eg, acetonitrile), ketone (acetone) and the like. Preferably, it is a solvate of alcohol (eg, methanol, ethanol, 2-propanol, 1-butanol, 1-methoxy-2-propanol, t-butanol). These solvents may be a reaction solvent used at the time of synthesizing the compound, a solvent used at the time of crystallization purification after synthesis, or a mixture thereof.

  Two or more kinds of solvents may be included at the same time, or a form containing water and a solvent (for example, water and alcohol (for example, methanol, ethanol, t-butanol, etc.), etc.).

  Even if the compound having the structure represented by the general formula (1), (2), (1.1) or (1.2) is added in a form not containing water, solvent or salt, Hydrates, solvates or salts may be formed in the resin composition or retardation film of the invention.

  The molecular weight of the compound having the structure represented by the general formula (1), (2), (1.1) or (1.2) is not particularly limited, but the smaller the compound, the better the compatibility with the resin and the greater Since the effect of suppressing fluctuations in the optical value with respect to changes in environmental humidity is higher, it is preferably 150 to 2000, more preferably 200 to 1500, and more preferably 300 to 1000.

  Furthermore, the nitrogen-containing heterocyclic compound according to the present invention is particularly preferably a compound having a structure represented by the following general formula (3).

（式中Ａはピラゾール環を表す。Ａｒ_１及びＡｒ_２はそれぞれ芳香族炭化水素環又は芳香族複素環を表し、置換基を有してもよい。Ｒ_１は水素原子、アルキル基、アシル基、スルホニル基、アルキルオキシカルボニル基、又はアリールオキシカルボニル基を表す。ｑは１又は２を表し、ｎ及びｍは１〜３の整数を表す。）
Ａｒ_１及びＡｒ_２で表される芳香族炭化水素環又は芳香族複素環は、それぞれ一般式（１）で挙げた５員若しくは６員の芳香族炭化水素環又は芳香族複素環であることが好ましい。また、Ａｒ_１及びＡｒ_２の置換基としては、前記一般式（１）で表される構造を有する化合物で示したのと同様な置換基が挙げられる。

(In the formula, A represents a pyrazole ring. Ar ₁ and Ar ₂ each represent an aromatic hydrocarbon ring or an aromatic heterocyclic ring and may have a substituent. R ₁ represents a hydrogen atom, an alkyl group, or an acyl group. Represents a sulfonyl group, an alkyloxycarbonyl group, or an aryloxycarbonyl group, q represents 1 or 2, and n and m represent an integer of 1 to 3.)
The aromatic hydrocarbon ring or aromatic heterocyclic ring represented by Ar ₁ and Ar ₂ may be the 5-membered or 6-membered aromatic hydrocarbon ring or aromatic heterocyclic ring mentioned in the general formula (1), respectively. preferable. Examples of the substituent for Ar ₁ and Ar ₂ include the same substituents as those shown for the compound having the structure represented by the general formula (1).

Specific examples of R ₁ include halogen atoms (fluorine atom, chlorine atom, bromine atom, iodine atom, etc.), alkyl groups (methyl group, ethyl group, n-propyl group, isopropyl group, tert-butyl group, n-octyl group). Group, 2-ethylhexyl group, etc.), acyl group (acetyl group, pivaloylbenzoyl group, etc.), sulfonyl group (eg, methylsulfonyl group, ethylsulfonyl group, etc.), alkyloxycarbonyl group (eg, methoxycarbonyl group), An aryloxycarbonyl group (for example, phenoxycarbonyl group etc.) etc. are mentioned.

  q represents 1 or 2, and n and m represent an integer of 1 to 3.

  Below, the specific example of the compound which has a 5-membered or 6-membered aromatic hydrocarbon ring or aromatic heterocyclic ring used for this invention is illustrated. Among these, compounds having a structure represented by the general formulas (1), (2), (1.1), and (1.2) are preferable, and a compound having a structure represented by the general formula (3). It is preferable. The compound having a 5-membered or 6-membered aromatic hydrocarbon ring or aromatic heterocyclic ring that can be used in the present invention is not limited by the following specific examples. As described above, the following specific examples may be tautomers, and may form hydrates, solvates or salts.

  Next, a method for synthesizing the compound having the structure represented by the general formula (1) will be described.

  The compound having the structure represented by the general formula (1) can be synthesized by a known method. In the compound having the structure represented by the general formula (1), any raw material may be used as the compound having a 1,2,4-triazole ring, but a nitrile derivative or an imino ether derivative and a hydrazide derivative may be used. A reaction method is preferred. The solvent used for the reaction may be any solvent as long as it does not react with the raw material, but may be any ester type (eg, ethyl acetate, methyl acetate), amide type (dimethylformamide, dimethylacetamide, etc.), ether type (Ethylene glycol dimethyl ether, etc.), alcohols (eg, methanol, ethanol, propanol, isopropanol, n-butanol, 2-butanol, ethylene glycol, ethylene glycol monomethyl ether, etc.), aromatic hydrocarbons (eg, toluene, xylene, etc.) ), Water can be mentioned. As a solvent to be used, an alcohol solvent is preferable. These solvents may be used as a mixture.

  Although there is no restriction | limiting in particular in the usage-amount of a solvent, It is preferable to exist in the range of 0.5-30 times amount with respect to the mass of the hydrazide derivative to be used, More preferably, it is 1.0-25 times amount. Yes, particularly preferably within the range of 3.0 to 20 times the amount.

  When reacting a nitrile derivative and a hydrazide derivative, it is not necessary to use a catalyst, but it is preferable to use a catalyst in order to accelerate the reaction. As a catalyst to be used, an acid may be used and a base may be used. Examples of the acid include hydrochloric acid, sulfuric acid, nitric acid, acetic acid and the like, preferably hydrochloric acid. The acid may be added after diluted in water, or may be added by a method of blowing a gas into the system. Bases include inorganic bases (potassium carbonate, sodium carbonate, potassium bicarbonate, sodium bicarbonate, potassium hydroxide, sodium hydroxide, etc.) and organic bases (sodium methylate, sodium ethylate, potassium methylate, potassium ethylate, Sodium butyrate, potassium butyrate, diisopropylethylamine, N, N′-dimethylaminopyridine, 1,4-diazabicyclo [2.2.2] octane, N-methylmorpholine, imidazole, N-methylimidazole, pyridine, etc.) Any of them may be used, and the inorganic base is preferably potassium carbonate, and the organic base is preferably sodium ethylate, sodium ethylate or sodium butyrate. The inorganic base may be added as a powder or may be added in a state dispersed in a solvent. The organic base may be added in a state dissolved in a solvent (for example, a 28% methanol solution of sodium methylate).

  Although there will be no restriction | limiting in particular if the usage-amount of a catalyst is the quantity which reaction advances, The inside of the range of 1.0-5.0 times mole with respect to the triazole ring formed is preferable, and also 1.05-3. A range of 0-fold mole is preferable.

  When the imino ether derivative and the hydrazide derivative are reacted, it is not necessary to use a catalyst, and the target product can be obtained by heating in a solvent.

  The addition method of the raw material, solvent, and catalyst used for the reaction is not particularly limited, and the catalyst may be added last, or the solvent may be added last. Also preferred is a method of dispersing or dissolving a nitrile derivative in a solvent, adding a catalyst, and then adding a hydrazide derivative.

  The solution temperature during the reaction may be any temperature as long as the reaction proceeds, but is preferably in the range of 0 to 150 ° C, more preferably in the range of 20 to 140 ° C. Moreover, you may react, removing the water to produce | generate.

  Any means may be used as a method for treating the reaction solution, but when a base is used as a catalyst, a method of neutralizing the reaction solution by adding an acid is preferable. Examples of the acid used for neutralization include hydrochloric acid, sulfuric acid, nitric acid, and acetic acid. Acetic acid is particularly preferable. The amount of acid used for neutralization is not particularly limited as long as the pH of the reaction solution is in the range of 4 to 9, but is preferably 0.1 to 3 moles, particularly preferably, relative to the base used. , Within a range of 0.2 to 1.5 moles.

  As a method for treating the reaction solution, when extracting using a suitable organic solvent, a method of washing the organic solvent with water after extraction and then concentrating is preferable. The appropriate organic solvent here is a water-insoluble solvent such as ethyl acetate, toluene, dichloromethane, ether, or a mixed solvent of the water-insoluble solvent and tetrahydrofuran or an alcohol solvent, preferably Ethyl acetate.

  When the compound having the structure represented by the general formula (1) is crystallized, there is no particular limitation, but a method of crystallizing by adding water to the neutralized reaction solution or represented by the general formula (1) A method in which an aqueous solution in which a compound having a structure is dissolved is neutralized and crystallized is preferable.

  For example, Exemplary Compound 1 can be synthesized by the following scheme.

(Synthesis of Exemplified Compound 1)

  To 350 ml of n-butanol, 77.3 g (75.0 mmol) of benzonitrile, 34.0 g (25.0 mmol) of benzoylhydrazine and 107.0 g (77.4 mmol) of potassium carbonate were added and stirred at 120 ° C. for 24 hours under a nitrogen atmosphere. did. The reaction solution was cooled to room temperature, the precipitate was filtered, and the filtrate was concentrated under reduced pressure. 20 ml of isopropanol was added to the concentrate, and the precipitate was collected by filtration. The precipitate collected by filtration was dissolved in 80 ml of methanol, 300 ml of pure water was added, and acetic acid was added dropwise until the pH of the solution reached 7. The precipitated crystals were collected by filtration, washed with pure water, and blown and dried at 50 ° C. to obtain 38.6 g of Exemplified Compound 1. The yield was 70% based on benzoylhydrazine.

The ¹ H-NMR spectrum of the obtained exemplary compound 1 is as follows.

¹ H-NMR (400 MHz, solvent: heavy DMSO, standard: tetramethylsilane) δ (ppm): 7.56-7.48 (6H, m), 7.62-7.61 (4H, m)
(Synthesis of Exemplified Compound 6)
Exemplary compound 6 can be synthesized by the following scheme.

  To 40 ml of n-butanol, 2.5 g (19.5 mmol) of 1,3-dicyanobenzene, 7.9 g (58.5 mmol) of benzoylhydrazine and 9.0 g (68.3 mmol) of potassium carbonate were added, and the temperature was 120 ° C. under a nitrogen atmosphere. For 24 hours. After cooling the reaction solution, 40 ml of pure water was added and the mixture was stirred at room temperature for 3 hours, and then the precipitated solid was separated by filtration and washed with pure water. Water and ethyl acetate were added to the obtained solid for liquid separation, and the organic layer was washed with pure water. The organic layer was dried over magnesium sulfate, and the solvent was distilled off under reduced pressure. The resulting crude crystals were purified by silica gel chromatography (ethyl acetate / heptane) to obtain 5.5 g of exemplary compound 6. The yield was 77% based on 1,3-dicyanobenzene.

The ¹ H-NMR spectrum of the obtained Exemplified Compound 6 is as follows.

¹ H-NMR (400 MHz, solvent: heavy DMSO, standard: tetramethylsilane) δ (ppm): 8.83 (1H, s), 8.16-8.11 (6H, m), 7.67-7 .54 (7H, m)
(Synthesis of Exemplary Compound 176)
Exemplary compound 176 can be synthesized according to the following scheme.

  To 520 ml of dehydrated tetrahydrofuran was added 80 g (0.67 mol) of acetophenone and 52 g (0.27 mol) of dimethyl isophthalate. . After stirring for 3 hours under ice-water cooling, the mixture was stirred for 12 hours under water-cooling. Concentrated sulfuric acid was added to the reaction solution for neutralization, and then pure water and ethyl acetate were added for liquid separation, and the organic layer was washed with pure water. The organic layer was dried over magnesium sulfate, and the solvent was distilled off under reduced pressure. 55.2 g of intermediate A was obtained by adding methanol to the obtained crude crystal and suspending and washing it.

  Intermediate A 55 g (0.15 mol) was added to tetrahydrofuran 300 ml and ethanol 200 ml, and 18.6 g (0.37 mol) of hydrazine monohydrate was added dropwise little by little while stirring at room temperature. After completion of dropping, the mixture was heated to reflux for 12 hours. Pure water and ethyl acetate were added to the reaction solution for liquid separation, and the organic layer was washed with pure water. The organic layer was dried over magnesium sulfate, and the solvent was distilled off under reduced pressure. The obtained crude crystals were purified by silica gel chromatography (ethyl acetate / heptane) to obtain 27 g of Exemplified Compound 176.

The ¹ H-NMR spectrum of the obtained exemplary compound 176 is as follows. In order to avoid complication of chemical shift due to the presence of tautomers, the measurement was performed by adding a few drops of trifluoroacetic acid to the measurement solvent.

¹ H-NMR (400 MHz, solvent: heavy DMSO, standard: tetramethylsilane) δ (ppm): 8.34 (1H, s), 7.87-7.81 (6H, m), 7.55-7 .51 (1H, m), 7.48-7.44 (4H, m), 7.36-7.33 (2H, m), 7.29 (1H, s)
Other compounds can be synthesized by the same method.

<About the usage method of the compound which has a structure represented by General formula (1)-(3)>
The compound having the structure represented by the general formulas (1) to (3) according to the present invention can be appropriately adjusted and contained in the retardation film, but the addition amount is in the retardation film. 0.1 to 10% by mass, preferably 1 to 5% by mass, particularly preferably 2 to 5% by mass. The addition amount varies depending on the type of cellulose acetate and the type of the compound, but the retardation film of the present invention has a desired retardation value and determines the optimum value depending on the addition amount exhibiting forward wavelength dispersion. be able to. If it is in this range, the fluctuation | variation of the retardation depending on the change of environmental humidity can be reduced, without impairing the mechanical strength of the retardation film of this invention.

  In addition, as a method for adding the compound having the structure represented by the general formulas (1) to (3), it may be added as a powder to the resin forming the retardation film. You may add to resin which forms a phase difference film.

  In addition to the nitrogen-containing heterocyclic compound, the retardation film of the present invention preferably contains a sugar ester and a polycondensed ester as a retardation adjusting agent and a retardation stabilizer.

<Sugar ester>
The sugar ester according to the present invention is preferably a sugar ester in which at least one pyranose ring or furanose ring is 1 to 12 and all or part of the OH groups in the structure are esterified.

  The sugar ester according to the present invention is a compound containing at least one of a furanose ring and a pyranose ring, and may be a monosaccharide or a polysaccharide having 2 to 12 sugar structures linked together. The sugar ester is preferably a compound in which at least one OH group of the sugar structure is esterified. In the sugar ester according to the present invention, the average ester substitution degree is preferably within the range of 4.0 to 8.0, and more preferably within the range of 5.0 to 7.5.

  The sugar ester according to the present invention is not particularly limited, and examples thereof include sugar esters having a structure represented by the following general formula (A).

Formula (A)
_{(HO) m -G- (O-} C (= O) -R 2) n
In the general formula (A), G represents a monosaccharide or disaccharide residue, R ² represents an aliphatic group or an aromatic group, and m is directly bonded to the monosaccharide or disaccharide residue. N is the total number of — (O—C (═O) —R ² ) groups directly bonded to the monosaccharide or disaccharide residue, 3 ≦ m + n ≦ 8, and n ≠ 0.

The sugar ester having the structure represented by the general formula (A) is a single type in which the number (m) of hydroxy groups and the number (n) of-(O—C (═O) —R ² ) groups are fixed. It is difficult to isolate as a compound of the above, and it is known that a compound in which several components different in m and n in the formula are mixed is obtained. Therefore, the performance as a mixture in which the number (m) of hydroxy groups and the number (n) of — (O—C (═O) —R ² ) groups are changed is important. In the case of the retardation film of the present invention, A sugar ester having an average ester substitution degree in the range of 5.0 to 7.5 is preferable.

  In the general formula (A), G represents a monosaccharide or disaccharide residue. Specific examples of monosaccharides include allose, altrose, glucose, mannose, gulose, idose, galactose, talose, ribose, arabinose, xylose, lyxose, and the like.

  Specific examples of the compound having a monosaccharide residue of a sugar ester having a structure represented by the general formula (A) are shown below, but the present invention is not limited to these exemplified compounds.

  Specific examples of the disaccharide residue include trehalose, sucrose, maltose, cellobiose, gentiobiose, lactose, and isotrehalose.

  Specific examples of the compound having a disaccharide residue of a sugar ester having a structure represented by the general formula (A) are shown below, but the present invention is not limited to these exemplified compounds.

In the general formula (A), R ² represents an aliphatic group or an aromatic group. Here, the aliphatic group and the aromatic group may each independently have a substituent.

In general formula (A), m is the total number of hydroxy groups directly bonded to the monosaccharide or disaccharide residue, and n is directly bonded to the monosaccharide or disaccharide residue. The total number of — (O—C (═O) —R ² ) groups. Further, it is necessary that 3 ≦ m + n ≦ 8, and it is preferable that 4 ≦ m + n ≦ 8. Further, n ≠ 0. When n is 2 or more, the — (O—C (═O) —R ² ) groups may be the same as or different from each other.

The aliphatic group in the definition of R ² may be linear, branched or cyclic, and preferably has 1 to 25 carbon atoms, more preferably 1 to 20 carbon atoms. Those of ˜15 are particularly preferred. Specific examples of the aliphatic group include, for example, methyl, ethyl, n-propyl, iso-propyl, cyclopropyl, n-butyl, iso-butyl, tert-butyl, amyl, iso-amyl, tert-amyl, n- Examples include hexyl, cyclohexyl, n-heptyl, n-octyl, bicyclooctyl, adamantyl, n-decyl, tert-octyl, dodecyl, hexadecyl, octadecyl, didecyl and the like.

The aromatic group in the definition of R ² may be an aromatic hydrocarbon group or an aromatic heterocyclic group, and more preferably an aromatic hydrocarbon group. The aromatic hydrocarbon group preferably has 6 to 24 carbon atoms, and more preferably 6 to 12 carbon atoms. Specific examples of the aromatic hydrocarbon group include rings such as benzene, naphthalene, anthracene, biphenyl, and terphenyl. As the aromatic hydrocarbon group, a benzene ring, a naphthalene ring, and a biphenyl ring are particularly preferable. As the aromatic heterocyclic group, a ring containing at least one of an oxygen atom, a nitrogen atom or a sulfur atom is preferable. Specific examples of the heterocyclic ring include, for example, furan, pyrrole, thiophene, imidazole, pyrazole, pyridine, pyrazine, pyridazine, triazole, triazine, indole, indazole, purine, thiazoline, thiadiazole, oxazoline, oxazole, oxadiazole, quinoline, Examples of each ring include isoquinoline, phthalazine, naphthyridine, quinoxaline, quinazoline, cinnoline, pteridine, acridine, phenanthroline, phenazine, tetrazole, benzimidazole, benzoxazole, benzthiazole, benzotriazole, and tetrazaindene. As the aromatic heterocyclic group, a pyridine ring, a triazine ring, and a quinoline ring are particularly preferable.

  Next, although the preferable example of the sugar ester represented by general formula (A) is shown below, this invention is not limited to these illustrated compounds.

  A sugar ester may contain two or more different substituents in one molecule, contains an aromatic substituent and an aliphatic substituent in one molecule, and contains two or more different aromatic substituents. Two or more different aliphatic substituents contained in one molecule can be contained in one molecule.

  It is also preferable to contain a mixture of two or more sugar esters. It is also preferable to simultaneously contain a sugar ester containing an aromatic substituent and a sugar ester containing an aliphatic substituent.

<Synthesis Example: Synthesis Example of Sugar Ester Represented by Formula (A)>
Below, an example of the synthesis | combination of the sugar ester which can be used suitably for this invention is shown.

Four-headed Kolben equipped with a stirrer, reflux condenser, thermometer and nitrogen gas inlet tube, 34.2 g (0.1 mol) of sucrose, 180.8 g (0.8 mol) of benzoic anhydride, pyridine 379.7 g (4.8 mol) of each were charged, and the temperature was raised while bubbling nitrogen gas from a nitrogen gas inlet tube under stirring, and esterification was carried out at 70 ° C. for 5 hours. Next, the inside of the Kolben was depressurized to 4 × 10 ² Pa or less, and after excess pyridine was distilled off at 60 ° C., the inside of the Kolben was depressurized to 1.3 × 10 Pa or less and the temperature was raised to 120 ° C. Most of the acid and benzoic acid formed were distilled off. Then, 1 L of toluene and 300 g of a 0.5% by mass sodium carbonate aqueous solution were added, and the mixture was stirred at 50 ° C. for 30 minutes, and then allowed to stand to separate a toluene layer. Finally, 100 g of water was added to the separated toluene layer, and after washing with water at room temperature for 30 minutes, the toluene layer was separated, and toluene was distilled off at 60 ° C. under reduced pressure (4 × 10 ² Pa or less). A mixture of compounds A-1, A-2, A-3, A-4 and A-5 was obtained. When the obtained mixture was analyzed by HPLC and LC-MASS, A-1 was 7% by mass, A-2 was 58% by mass, A-3 was 23% by mass, A-4 was 9% by mass, A-5. Was 3% by mass, and the average ester substitution degree of the sugar ester was 6.57. A part of the obtained mixture was purified by silica gel column chromatography to obtain A-1, A-2, A-3, A-4 and A-5 having a purity of 100%, respectively.

  The addition amount of the sugar ester is preferably 0.1 to 20% by mass and more preferably 1 to 15% by mass with respect to cellulose acetate.

  Moreover, it is preferable that hue APHA in the 50 mass% toluene solution of sugar ester exists in the range of 10-300, and it is more preferable that it is the range of 10-40.

<Polycondensed ester>
In the retardation film of the present invention, it is preferable to use a polycondensed ester having a structure represented by the following general formula (4) because it functions as a retardation adjusting agent in addition to film properties.

  In the retardation film of the present invention, the polycondensation ester is preferably contained in the range of 1 to 30% by mass, more preferably in the range of 2 to 20% by mass, because of its plastic effect. More preferably, it is the range of 3-10 mass%.

General formula (4)
_{B 3 - (G 2 -A)} n -G 2 -B 4
In the general formula (4), B ₃ and B ₄ each independently represent an aliphatic or aromatic monocarboxylic acid residue or a hydroxy group. G ₂ represents an alkylene glycol residue having 2 to 12 carbon atoms, an aryl glycol residue having 6 to 12 carbon atoms, or an oxyalkylene glycol residue having 4 to 12 carbon atoms. A represents an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms or an aryl dicarboxylic acid residue having 6 to 12 carbon atoms. n represents an integer of 1 or more.

In the present invention, the polycondensed ester is a polycondensed ester containing a repeating unit obtained by reacting a dicarboxylic acid and a diol, A represents a carboxylic acid residue in the polycondensed ester, and G ₂ represents an alcohol residue. Represent.

  The dicarboxylic acid constituting the polycondensed ester is an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid or an alicyclic dicarboxylic acid, preferably an aromatic dicarboxylic acid. The dicarboxylic acid may be one type or a mixture of two or more types. In particular, it is preferable to mix aromatic and aliphatic.

  The diol constituting the polycondensed ester is an aromatic diol, an aliphatic diol or an alicyclic diol, preferably an aliphatic diol, and more preferably a diol having 1 to 4 carbon atoms. The diol may be one type or a mixture of two or more types.

  Among these, it is preferable to include a repeating unit obtained by reacting at least a dicarboxylic acid containing an aromatic dicarboxylic acid and a diol having 1 to 8 carbon atoms, and a dicarboxylic acid containing an aromatic dicarboxylic acid and an aliphatic dicarboxylic acid; More preferably, it contains a repeating unit obtained by reacting with a diol having 1 to 8 carbon atoms.

  Both ends of the polycondensed ester molecule may or may not be sealed.

  Specific examples of the alkylene dicarboxylic acid constituting A in the general formula (4) include 1,2-ethanedicarboxylic acid (succinic acid), 1,3-propanedicarboxylic acid (glutaric acid), and 1,4-butanedicarboxylic acid. Divalent groups derived from (adipic acid), 1,5-pentanedicarboxylic acid (pimelic acid), 1,8-octanedicarboxylic acid (sebacic acid) and the like are included. Specific examples of the alkenylene dicarboxylic acid constituting A include maleic acid and fumaric acid. Specific examples of the aryl dicarboxylic acid constituting A include 1,2-benzenedicarboxylic acid (phthalic acid), 1,3-benzenedicarboxylic acid, 1,4-benzenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, and the like. Can be mentioned.

  A may be one type or two or more types may be combined. Among these, A is preferably a combination of an alkylene dicarboxylic acid having 4 to 12 carbon atoms and an aryl dicarboxylic acid having 8 to 12 carbon atoms.

G ₂ in the general formula (4) is a divalent group derived from an alkylene glycol having 2 to 12 carbon atoms, a divalent group derived from an aryl glycol having 6 to 12 carbon atoms, or a carbon atom. It represents a divalent group derived from oxyalkylene glycols of 4 to 12.

Examples of the divalent group derived from an alkylene glycol having 2 to 12 carbon atoms in G ₂ include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, , 3-butanediol, 1,2-propanediol, 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-di) Methylol heptane), 3-methyl-1,5-pentanediol, 1,6-hexanediol, 2,2,4-trimethyl-1,3-pentanedio , 2-ethyl-1,3-hexanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, and the like. Divalent groups are included.

Examples of divalent groups derived from aryl glycols having 6 to 12 carbon atoms in G ₂ include 1,2-dihydroxybenzene (catechol), 1,3-dihydroxybenzene (resorcinol), 1,4-dihydroxy Divalent groups derived from benzene (hydroquinone) and the like are included. Examples of the divalent group derived from oxyalkylene glycol having 4 to 12 carbon atoms in G are derived from diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol and the like. Divalent groups are included.

G ₂ may be a single type or a combination of two or more types. Among these, G ₂ is preferably a divalent group derived from an alkylene glycol having 2 to 12 carbon atoms, more preferably 2 to 5, and most preferably 2 to 4.

B ₃ and B ₄ in the general formula (4) are each a monovalent group derived from an aromatic ring-containing monocarboxylic acid or an aliphatic monocarboxylic acid, or a hydroxy group.

  The aromatic ring-containing monocarboxylic acid in the monovalent group derived from the aromatic ring-containing monocarboxylic acid is a carboxylic acid containing an aromatic ring in the molecule, and not only those in which the aromatic ring is directly bonded to a carboxy group, Also included are those in which an aromatic ring is bonded to a carboxy group via an alkylene group. Examples of monovalent groups derived from aromatic ring-containing monocarboxylic acids include benzoic acid, para-tert-butyl benzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethyl benzoic acid, ethyl benzoic acid, and normal propyl benzoic acid. Monovalent groups derived from aminobenzoic acid, acetoxybenzoic acid, phenylacetic acid, 3-phenylpropionic acid, and the like. Of these, benzoic acid and p-toluic acid are preferable.

  Examples of monovalent groups derived from aliphatic monocarboxylic acids include monovalent groups derived from acetic acid, propionic acid, butanoic acid, caprylic acid, caproic acid, decanoic acid, dodecanoic acid, stearic acid, oleic acid and the like. Is included. Among these, a monovalent group derived from an alkyl monocarboxylic acid having 1 to 3 carbon atoms in the alkyl portion is preferable, and an acetyl group (a monovalent group derived from acetic acid) is more preferable.

  The weight average molecular weight of the polycondensed ester according to the present invention is preferably in the range of 500 to 3000, and more preferably in the range of 600 to 2000. The weight average molecular weight can be measured by the gel permeation chromatography (GPC).

  Hereinafter, although the specific example of the polycondensation ester which has a structure represented by General formula (4) is shown, it is not limited to this.

  Hereinafter, a specific synthesis example of the polycondensed ester described above will be described.

<Polycondensed ester P1>
180 g of ethylene glycol, 278 g of phthalic anhydride, 91 g of adipic acid, 610 g of benzoic acid, and 0.191 g of tetraisopropyl titanate as an esterification catalyst were charged into a 2 L four-necked flask equipped with a thermometer, a stirrer, and a quick cooling tube. The temperature is gradually raised with stirring until reaching 230 ° C. in a nitrogen stream. The dehydration condensation reaction was carried out while observing the degree of polymerization. After completion of the reaction, unreacted ethylene glycol was distilled off under reduced pressure at 200 ° C. to obtain a polycondensed ester P1. The acid value was 0.20 and the number average molecular weight was 450.

<Polycondensed ester P2>
251 g of 1,2-propylene glycol, 103 g of phthalic anhydride, 244 g of adipic acid, 610 g of benzoic acid, 0.191 g of tetraisopropyl titanate as an esterification catalyst, 2 L four-neck equipped with a thermometer, stirrer, and quick cooling tube The flask is charged and gradually heated with stirring until it reaches 230 ° C. in a nitrogen stream. The dehydration condensation reaction was carried out while observing the degree of polymerization. After completion of the reaction, unreacted 1,2-propylene glycol was distilled off at 200 ° C. under reduced pressure to obtain the following polycondensed ester P2. The acid value was 0.10 and the number average molecular weight was 450.

<Polycondensed ester P3>
330 g of 1,4-butanediol, 244 g of phthalic anhydride, 103 g of adipic acid, 610 g of benzoic acid, 0.191 g of tetraisopropyl titanate as an esterification catalyst, 4 L of 2 L equipped with a thermometer, a stirrer, and a slow cooling tube The flask is charged and gradually heated with stirring until it reaches 230 ° C. in a nitrogen stream. The dehydration condensation reaction was carried out while observing the degree of polymerization. After completion of the reaction, unreacted 1,4-butanediol was distilled off under reduced pressure at 200 ° C. to obtain a polycondensed ester P3. The acid value was 0.50 and the number average molecular weight was 2000.

<Polycondensed ester P4>
251 g of 1,2-propylene glycol, 354 g of terephthalic acid, 610 g of benzoic acid, and 0.191 g of tetraisopropyl titanate as an esterification catalyst were charged into a 2 L four-necked flask equipped with a thermometer, a stirrer, and a quick cooling tube, The temperature is gradually raised with stirring until it reaches 230 ° C. in an air stream. The dehydration condensation reaction was carried out while observing the degree of polymerization. After completion of the reaction, unreacted 1,2-propylene glycol was distilled off under reduced pressure at 200 ° C. to obtain a polycondensed ester P4. The acid value was 0.10 and the number average molecular weight was 400.

<Polycondensed ester P5>
251 g of 1,2-propylene glycol, 354 g of terephthalic acid, 680 g of p-troyl acid and 0.191 g of tetraisopropyl titanate as an esterification catalyst are charged into a 2 L four-necked flask equipped with a thermometer, a stirrer and a slow cooling tube. The temperature is gradually raised with stirring until it reaches 230 ° C. in a nitrogen stream. The dehydration condensation reaction was carried out while observing the degree of polymerization. After completion of the reaction, unreacted 1,2-propylene glycol was distilled off at 200 ° C. under reduced pressure to obtain the following polycondensed ester P5. The acid value was 0.30 and the number average molecular weight was 400.

<Polycondensed ester P6>
180 g of 1,2-propylene glycol, 292 g of adipic acid, and 0.191 g of tetraisopropyl titanate as an esterification catalyst were charged into a 2 L four-necked flask equipped with a thermometer, a stirrer, and a slow cooling tube, in a nitrogen stream. The temperature is gradually raised while stirring until 200 ° C is reached. The dehydration condensation reaction was carried out while observing the degree of polymerization. After completion of the reaction, unreacted 1,2-propylene glycol was distilled off under reduced pressure at 200 ° C. to obtain a polycondensed ester P6. The acid value was 0.10 and the number average molecular weight was 400.

<Polycondensed ester P7>
180 g of 1,2-propylene glycol, 244 g of phthalic anhydride, 103 g of adipic acid, and 0.191 g of tetraisopropyl titanate as an esterification catalyst are charged into a 2 L four-necked flask equipped with a thermometer, a stirrer, and a slow cooling tube. The temperature is gradually raised with stirring until it reaches 200 ° C. in a nitrogen stream. The dehydration condensation reaction was carried out while observing the degree of polymerization. After completion of the reaction, unreacted 1,2-propylene glycol was distilled off under reduced pressure at 200 ° C. to obtain a polycondensed ester P7. The acid value was 0.10 and the number average molecular weight was 320.

<Polycondensed ester P8>
251 g of ethylene glycol, 244 g of phthalic anhydride, 120 g of succinic acid, 150 g of acetic acid, and 0.191 g of tetraisopropyl titanate as an esterification catalyst were charged into a 2 L four-necked flask equipped with a thermometer, a stirrer, and a slow cooling tube, and nitrogen The temperature is gradually raised with stirring until it reaches 200 ° C. in an air stream. The dehydration condensation reaction was carried out while observing the degree of polymerization. After completion of the reaction, unreacted ethylene glycol was distilled off under reduced pressure at 200 ° C. to obtain a polycondensed ester P8. The acid value was 0.50 and the number average molecular weight was 1200.

<Polycondensed ester P9>
In the same production method as in the polycondensation ester P2, the reaction conditions were changed to obtain a polycondensation ester P9 having an acid value of 0.10 and a number average molecular weight of 315.

<Other additives>
The retardation film of the present invention preferably contains a plasticizer, an ultraviolet absorber, an antioxidant, a matting agent and the like in addition to the additives.

<Polyhydric alcohol ester>
The retardation film of the present invention preferably contains a polyhydric alcohol ester as a plasticizer.

  The polyhydric alcohol ester is a compound composed of an ester of a dihydric or higher aliphatic polyhydric alcohol and a monocarboxylic acid, and preferably has an aromatic ring or a cycloalkyl ring in the molecule. Preferably it is a 2-20 valent aliphatic polyhydric alcohol ester.

  The polyhydric alcohol preferably used in the present invention is represented by the following general formula (5).

Formula _{(5) R 11 - (OH} ) n
However, R ₁₁ represents an n-valent organic group, n represents a positive integer of 2 or more, and the OH group represents an alcoholic and / or phenolic hydroxy group.

  Examples of preferred polyhydric alcohols include the following, but the present invention is not limited to these.

  Adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3- Butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, galactitol, mannitol, 3-methylpentane- Examples include 1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, xylitol and the like.

  In particular, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, and xylitol are preferable.

  There is no restriction | limiting in particular as monocarboxylic acid used for polyhydric alcohol ester, Well-known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid, etc. can be used. Use of an alicyclic monocarboxylic acid or aromatic monocarboxylic acid is preferred in terms of improving moisture permeability and retention.

  Examples of preferred monocarboxylic acids include the following, but the present invention is not limited thereto.

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. The number of carbon atoms is more preferably 1-20, and particularly preferably 1-10. The inclusion of acetic acid is preferred because the compatibility with cellulose acetate increases, and it is also preferred to use a mixture of acetic acid and other monocarboxylic acids.

  Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanoic acid, undecylic acid, lauric acid, tridecylic acid, Saturated fatty acids such as myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, laccelic acid, undecylenic acid, olein Examples thereof include unsaturated fatty acids such as acid, sorbic acid, linoleic acid, linolenic acid, and arachidonic acid.

  Examples of preferred alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, or derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include those in which 1 to 3 alkoxy groups such as an alkyl group, a methoxy group or an ethoxy group are introduced into the benzene ring of benzoic acid such as benzoic acid or toluic acid, biphenylcarboxylic acid, Examples thereof include aromatic monocarboxylic acids having two or more benzene rings such as naphthalenecarboxylic acid and tetralincarboxylic acid, or derivatives thereof. Benzoic acid is particularly preferable.

  The molecular weight of the polyhydric alcohol ester is not particularly limited, but is preferably in the range of 300 to 1500, and more preferably in the range of 350 to 750. A higher molecular weight is preferred because it is less likely to volatilize, and a smaller one is preferred in terms of moisture permeability and compatibility with cellulose acetate.

  The carboxylic acid used for the polyhydric alcohol ester may be one kind or a mixture of two or more kinds. Moreover, all the OH groups in the polyhydric alcohol may be esterified, or a part of the OH groups may be left as they are.

  Below, the specific compound of a polyhydric alcohol ester is illustrated.

  The polyhydric alcohol ester used in the present invention is preferably contained in the range of 0.5 to 5% by mass, more preferably in the range of 1 to 3% by mass with respect to the retardation film. It is especially preferable to contain in the range of 2 mass%.

  The polyhydric alcohol ester used in the present invention can be synthesized according to a conventionally known general synthesis method.

<Phosphate ester>
The retardation film of the present invention can use a phosphate ester as a plasticizer. As phosphoric acid esters, triaryl phosphoric acid esters, diaryl phosphoric acid esters, monoaryl phosphoric acid esters, aryl phosphonic acid compounds, aryl phosphine oxide compounds, condensed aryl phosphoric acid esters, halogenated alkyl phosphoric acid esters, halogen-containing condensed phosphoric acid Examples thereof include esters, halogen-containing condensed phosphonic acid esters, and halogen-containing phosphorous acid esters.

  Specific phosphoric acid esters include triphenyl phosphate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, phenylphosphonic acid, tris (β-chloroethyl) phosphate, tris (dichloro) Propyl) phosphate, tris (tribromoneopentyl) phosphate, and the like.

<Esters of glycolic acid>
In the present invention, glycolic acid esters (glycolate compounds) can be used as one kind of polyhydric alcohol esters.

  The glycolate compound applicable to the present invention is not particularly limited, but alkylphthalylalkyl glycolates can be preferably used.

  Examples of alkyl phthalyl alkyl glycolates include methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate, methyl phthalyl Ethyl glycolate, ethyl phthalyl methyl glycolate, ethyl phthalyl propyl glycolate, methyl phthalyl butyl glycolate, ethyl phthalyl butyl glycolate, butyl phthalyl methyl glycolate, butyl phthalyl ethyl glycolate, propyl phthalyl butyl Glycolate, butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalyl octyl glycolate, octyl phthalyl methyl glycolate, octyl phthalate Ethyl glycolate and the like, preferably ethyl phthalyl ethyl glycolate.

<Ultraviolet absorber>
Since the retardation film of the present invention is preferably used on the viewing side or the backlight side of the polarizing plate, it preferably contains an ultraviolet absorber for the purpose of imparting an ultraviolet absorbing function.

  Although it does not specifically limit as a ultraviolet absorber, For example, ultraviolet absorbers, such as a benzotriazole type, 2-hydroxybenzophenone type, or a salicylic acid phenyl ester type, are mentioned. For example, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (3 Triazoles such as 5-di-t-butyl-2-hydroxyphenyl) benzotriazole, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone And benzophenones.

  Of the UV absorbers, UV absorbers having a molecular weight of 400 or more are not sublimated or are not easily volatilized at a high boiling point. From the viewpoint of improving weather resistance, it is preferable.

  Examples of the ultraviolet absorber having a molecular weight of 400 or more include 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole, 2,2-methylenebis [4- ( 1,1,3,3-tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol] and the like, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, Hindered amines such as bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and further 2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-n-butyl Bis (1,2,2,6,6-pentamethyl-4-piperidyl) malonate, 1- [2- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy Cis] ethyl] -4- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] -2,2,6,6-tetramethylpiperidine The hybrid type | system | group which has the structure of a hindered amine is mentioned, These can be used individually or in combination of 2 or more types. Among these, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole and 2,2-methylenebis [4- (1,1,3,3- Tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol] is particularly preferred.

  As these ultraviolet absorbers, commercially available products may be used, for example, Tinuvin 109, Tinuvin 171, Tinuvin 234, Tinuvin 326, Tinuvin 327, Tinuvin 328, Tinuvin 928, etc. manufactured by BASF Japan, or 2, 2'-methylenebis [6- (2H-benzotriazol-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol] (molecular weight 659; examples of commercially available products are manufactured by ADEKA Corporation LA31) can be preferably used.

  The said ultraviolet absorber can be used individually by 1 type or in combination of 2 or more types.

  The amount of the UV absorber used is not uniform depending on the type of UV absorber, usage conditions, etc., but generally 0.05 to 10% by weight, preferably 0.1 to 5% by weight, based on cellulose acetate. It is added in the range of.

  The method of adding the UV absorber can be added to the dope after dissolving the UV absorber in an alcohol such as methanol, ethanol or butanol, an organic solvent such as methylene chloride, methyl acetate, acetone or dioxolane or a mixed solvent thereof. Or you may add directly in dope composition.

  For an inorganic powder that does not dissolve in an organic solvent, a dissolver or a sand mill is used in the organic solvent and cellulose acetate to disperse and then added to the dope.

<Antioxidant>
Antioxidants are also referred to as deterioration inhibitors. When a liquid crystal display device or the like is placed in a high humidity and high temperature state, the retardation film may be deteriorated.

  The antioxidant has a role of delaying or preventing the retardation film from being decomposed by, for example, the residual solvent amount of halogen in the retardation film or phosphoric acid of the phosphoric acid plasticizer. It is preferable to make it contain in retardation film.

  As such an antioxidant, a hindered phenol compound is preferably used. For example, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di- -T-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3 -(3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino)- 1,3,5-triazine, 2,2-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octa Sil-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide) 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-t-butyl-4-hydroxy Benzyl) -isocyanurate and the like.

  In particular, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3 -(3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] is preferred. Further, for example, hydrazine-based metal deactivators such as N, N′-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine and tris (2,4-di- A phosphorus processing stabilizer such as t-butylphenyl) phosphite may be used in combination.

  The amount of these compounds added is preferably in the range of 1 ppm to 1.0% by mass relative to the retardation film, and more preferably in the range of 10 to 1000 ppm.

<Peeling accelerator>
The retardation film of the present invention preferably contains a release accelerator from the viewpoint of improving releasability. The peeling accelerator can be included at a ratio of 0.001 to 1% by mass, for example, and the addition of 0.5% by mass or less is preferable because separation of the release agent from the film hardly occurs. 005% by mass or more is preferable because a desired peeling reduction effect can be obtained. Therefore, it is preferably included at a rate of 0.005 to 0.5% by mass, and at a rate of 0.01 to 0.3% by mass. More preferably. As the peeling accelerator, known ones can be adopted, and organic and inorganic acidic compounds, surfactants, chelating agents and the like can be used. Among them, polyvalent carboxylic acids and esters thereof are effective, and in particular, ethyl esters of citric acid can be used effectively.

<Fine particles (matting agent)>
The retardation film may further contain fine particles (matting agent) as necessary in order to improve the slipperiness of the surface.

  The fine particles may be inorganic fine particles or organic fine particles. Examples of inorganic fine particles include silicon dioxide (silica), titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, Examples include magnesium silicate and calcium phosphate. Among these, silicon dioxide and zirconium oxide are preferable, and silicon dioxide is more preferable in order to reduce the increase in haze of the obtained film.

  Examples of the fine particles of silicon dioxide include Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600, NAX50 (manufactured by Nippon Aerosil Co., Ltd.), Seahoster KE-P10, KE-P30, KE-P50, KE-P100 (manufactured by Nippon Shokubai Co., Ltd.) and the like are included. Among them, Aerosil R972V, NAX50, Seahoster KE-P30 and the like are particularly preferable because the coefficient of friction is reduced while keeping the turbidity of the obtained film low.

  The primary particle diameter of the fine particles is preferably in the range of 5 to 50 nm, and more preferably in the range of 7 to 20 nm. A larger primary particle size has a larger effect of increasing the slipperiness of the resulting film, but the transparency tends to decrease. Therefore, the fine particles may be contained as secondary aggregates having a particle diameter in the range of 0.05 to 0.3 μm. The size of the primary particles or the secondary aggregates of the fine particles is as follows. The primary particles or secondary aggregates are observed with a transmission electron microscope at a magnification of 50 to 2 million times, and 100 primary particles or secondary aggregates are observed. It can obtain | require as an average value of a diameter.

  The content of the fine particles is preferably in the range of 0.05 to 1.0% by mass and more preferably in the range of 0.1 to 0.8% by mass with respect to the resin forming the retardation film. .

≪Method for producing retardation film≫
As a method for producing the retardation film of the present invention, the usual inflation method, T-die method, calendar method, cutting method, casting method, emulsion method, hot press method and the like can be used, but coloring suppression, From the viewpoint of suppression of foreign matter defects, suppression of optical defects such as die lines, etc., a film casting method can be selected from a solution casting film forming method and a melt casting film forming method, and in particular, a solution casting film forming method, It is preferable from the viewpoint that a uniform and smooth surface can be obtained.

(A) Solution Casting Film Production Method Hereinafter, production examples for producing the retardation film of the present invention by the solution casting method will be described.

  The production of the retardation film of the present invention comprises the steps of preparing a dope by dissolving cellulose acetate, a nitrogen-containing heterocyclic compound and other additives in a solvent, and casting the dope onto a belt-like or drum-like metal support. It is carried out by a step of drying, a step of drying the cast dope as a web, a step of peeling from the metal support, a step of stretching, a step of further drying, and a step of winding after cooling. The retardation film of the present invention preferably contains cellulose acetate in the range of 60 to 95% by mass in the solid content.

(1) Dissolution process In a dissolution vessel, the cellulose acetate, a nitrogen-containing heterocyclic compound according to the present invention, a sugar ester, a polycondensation ester, other plasticizers, etc. Is a main solution by mixing the other compound solution such as the nitrogen-containing heterocyclic compound, sugar ester, polycondensation ester and the like with the cellulose acetate solution in the step of dissolving with stirring to form a dope, or the cellulose acetate solution This is a step of forming a dope.

  When the retardation film of the present invention is produced by a solution casting method, an organic solvent useful for forming a dope can be used without limitation as long as it dissolves cellulose acetate and other compounds simultaneously.

  For example, as the chlorinated organic solvent, methylene chloride, as the non-chlorinated organic solvent, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro- Examples include 2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, and nitroethane. Methylene chloride, methyl acetate, ethyl acetate, and acetone can be preferably used.

  In addition to the organic solvent, the dope preferably contains a linear or branched aliphatic alcohol having 1 to 4 carbon atoms in the range of 1 to 40% by mass. When the proportion of alcohol in the dope increases, the web gels, and peeling from the metal support becomes easy. When the proportion of alcohol is small, cellulose acetate and other compounds dissolve in non-chlorine organic solvents. There is also a role to promote. In film formation of the retardation film of the present invention, a method of forming a film using a dope having an alcohol concentration in the range of 0.5 to 15.0 mass% from the viewpoint of enhancing the flatness of the obtained retardation film. Can be applied.

  In particular, a dope composition in which cellulose acetate and other compounds are dissolved in a total amount of 15 to 45% by mass in a solvent containing methylene chloride and a linear or branched aliphatic alcohol having 1 to 4 carbon atoms. It is preferable that it is a thing.

  Examples of the linear or branched aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Methanol and ethanol are preferred because of the stability, boiling point of these inner dopes, and good drying properties.

  For dissolving other compounds such as cellulose acetate, nitrogen-containing heterocyclic compounds, sugar esters, polycondensed esters, and polyhydric alcohol esters, a method performed at normal pressure, a method performed at a temperature lower than the boiling point of the main solvent, a boiling point of the main solvent The method of pressurizing as described above, the method of performing the cooling dissolution method as described in JP-A-9-95544, JP-A-9-95557, or JP-A-9-95538, JP-A-11-21379 Various dissolution methods such as the method performed at a high pressure described in the above can be used, but a method performed by pressurizing at a temperature equal to or higher than the boiling point of the main solvent is particularly preferable.

  The concentration of cellulose acetate in the dope is preferably in the range of 10 to 40% by mass. After the compound is added to the dope during or after dissolution and dissolved and dispersed, it is filtered through a filter medium, defoamed, and sent to the next step with a liquid feed pump.

  It is preferable to use a filter medium having a collected particle diameter of 0.5 to 5 μm and a drainage time of 10 to 25 sec / 100 ml.

  In this method, the aggregate remaining at the time of particle dispersion and the aggregate generated when the main dope is added are aggregated by using a filter medium having a collected particle diameter of 0.5 to 5 μm and a drainage time of 10 to 25 sec / 100 ml. Can only be removed. In the main dope, the concentration of particles is sufficiently thinner than that of the additive solution, so that aggregates do not stick together at the time of filtration and the filtration pressure does not increase suddenly.

  FIG. 1 is a diagram schematically showing an example of a dope preparation step, a casting step, and a drying step of a solution casting film forming method preferable for the present invention.

  Large agglomerates are removed from the charging kettle 41 by the filter 44 and fed to the stock kettle 42. Thereafter, various additive solutions are added from the stock kettle 42 to the main dope dissolving kettle 1.

  Thereafter, the main dope is filtered by the main filter 3, and an ultraviolet absorbent additive solution is added in-line from 16 to the main dope.

  In many cases, the main dope may contain about 10 to 50% by mass of the recycled material.

  Recycled material is a product obtained by finely pulverizing a retardation film, which is generated when a retardation film is formed, and is obtained by cutting off both sides of the film, or a retardation that exceeds the specified value of the film due to scratches, etc. Film stock is used.

  Moreover, as a raw material of resin used for dope preparation, what pelletized cellulose acetate and other compounds previously can be used preferably.

(2) Casting step (2-1) Casting of dope An endless metal support 31 that feeds the dope to the pressurizing die 30 through a feed pump (for example, a pressurization type metering gear pump) and transfers it infinitely, For example, a dope is cast from a pressure die slit at a casting position on a metal support such as a stainless steel belt or a rotating metal drum.

  The metal support in the casting (casting) step preferably has a mirror-finished surface, and a stainless steel belt or a drum whose surface is plated with a casting is preferably used as the metal support. The cast width can be in the range of 1 to 4 m, preferably in the range of 1.5 to 3 m, and more preferably in the range of 2 to 2.8 m. The surface temperature of the metal support in the casting step is set in the range of −50 ° C. to a temperature at which the solvent boils and does not foam, more preferably in the range of −30 to 0 ° C. A higher temperature is preferable because the web can be dried faster, but if it is too high, the web may foam or the flatness may deteriorate. A preferable support temperature is appropriately determined at 0 to 100 ° C, and more preferably 5 to 30 ° C. Alternatively, it is also a preferable method that the web is gelled by cooling and peeled from the drum in a state containing a large amount of residual solvent. The method for controlling the temperature of the metal support is not particularly limited, and there are a method of blowing warm air or cold air, and a method of contacting hot water with the back side of the metal support. It is preferable to use warm water because heat transfer is performed efficiently, so that the time until the temperature of the metal support becomes constant is short. When using warm air, considering the temperature drop of the web due to the latent heat of vaporization of the solvent, while using warm air above the boiling point of the solvent, there may be cases where wind at a temperature higher than the target temperature is used while preventing foaming. . In particular, it is preferable to perform drying efficiently by changing the temperature of the support and the temperature of the drying air during the period from casting to peeling.

  A pressure die that can adjust the slit shape of the die base portion and can easily make the film thickness uniform is preferable. Examples of the pressure die include a coat hanger die and a T die, and any of them is preferably used. The surface of the metal support is a mirror surface. In order to increase the film forming speed, two or more pressure dies may be provided on the metal support, and the dope amount may be divided and stacked.

(3) Solvent evaporation step The web (the dope is cast on the casting support and the formed dope film is referred to as a web) is heated on the casting support to evaporate the solvent.

  To evaporate the solvent, there are a method of blowing air from the web side, a method of transferring heat from the back side of the support, a method of transferring heat from the front and back by radiant heat, etc. Is preferable. A method of combining them is also preferably used. The web on the support after casting is preferably dried on the support in an atmosphere of 40 to 100 ° C. In order to maintain the atmosphere at 40 to 100 ° C., it is preferable to apply hot air at this temperature to the upper surface of the web or to heat by means such as infrared rays.

  From the viewpoint of surface quality, moisture permeability, and peelability, it is preferable to peel the web from the support within 30 to 120 seconds.

(4) Peeling process It is the process of peeling the web which the solvent evaporated on the metal support body in a peeling position. The peeled web is sent to the next process.

  The temperature at the peeling position on the metal support is preferably in the range of 10 to 40 ° C, more preferably in the range of 11 to 30 ° C.

  In addition, it is preferable that the residual solvent amount at the time of peeling of the web on the metal support at the time of peeling is peeled in the range of 50 to 120% by mass depending on the strength of drying conditions, the length of the metal support, and the like. When peeling at a higher residual solvent amount, if the web is too soft, the flatness at the time of peeling is impaired, and slippage and vertical stripes are likely to occur due to the peeling tension. The amount of solvent is determined.

  The residual solvent amount of the web is defined by the following formula (Z).

Formula (Z)
Residual solvent amount (%) = (mass before web heat treatment−mass after web heat treatment) / (mass after web heat treatment) × 100
Note that the heat treatment for measuring the residual solvent amount represents performing heat treatment at 115 ° C. for 1 hour.

  The peeling tension when peeling the metal support from the film is usually in the range of 196 to 245 N / m. However, when wrinkles are likely to occur during peeling, peeling with a tension of 190 N / m or less is preferable. .

  In the present invention, the temperature at the peeling position on the metal support is preferably in the range of −50 to 40 ° C., more preferably in the range of 10 to 40 ° C., and in the range of 15 to 30 ° C. Is most preferred.

(5) Drying and stretching step The drying step can be divided into a preliminary drying step and a main drying step.

<Preliminary drying process>
The web obtained by peeling from the metal support is dried. The web may be dried while being conveyed by a large number of rollers arranged above and below, or may be dried while being conveyed while fixing both ends of the web with clips like a tenter dryer. .

  The means for drying the web is not particularly limited and can be generally performed with hot air, infrared rays, a heating roller, microwaves, or the like, but it is preferably performed with hot air in terms of simplicity.

  The drying temperature in the web drying step is preferably a glass transition point of the film of −5 ° C. or less, and it is effective to perform a heat treatment at 100 ° C. or more and 10 minutes or more and 60 minutes or less. Drying is performed at a drying temperature in the range of 100 to 200 ° C, more preferably in the range of 110 to 160 ° C.

<Extension process>
The retardation film of the present invention is preferably stretched in the MD direction (also referred to as the longitudinal direction) and / or the TD direction (also referred to as the width direction), and at least tenter-stretched in order to impart desired retardation. It is preferable to produce by stretching in the TD direction with an apparatus.

  The stretching can be uniaxial stretching or biaxial stretching, and biaxial stretching includes a mode in which stretching is performed in one direction and the tension in the other direction is relaxed and contracted.

  The cellulose acetate film of the present invention has (Tg + 15) when the glass transition temperature of the film is defined as Tg in the MD direction and / or TD direction, preferably in the TD direction so that the film thickness after stretching is in a desired range. ) To (Tg + 50) It is preferable to stretch in the temperature range. If the stretching is performed within the above temperature range, the retardation can be easily adjusted, and the stretching stress can be reduced, so that the haze is lowered. Moreover, the generation | occurrence | production of a fracture | rupture is suppressed and the polarizing plate phase difference film excellent in the planarity and the coloring property of the film itself is obtained. The stretching temperature is preferably in the range of (Tg + 20) to (Tg + 40) ° C.

  In addition, the glass transition temperature Tg here is measured at a temperature rising rate of 20 ° C./min using a commercially available differential scanning calorimeter, and is determined at an intermediate glass transition temperature (Tmg) determined according to JIS K7121 (1987). It is.

  A specific method for measuring the glass transition temperature Tg of the retardation film is measured using a differential scanning calorimeter DSC220 manufactured by Seiko Instruments Inc. according to JIS K7121 (1987).

  The retardation film of the present invention preferably stretches the web at least 1.1 times in the TD direction. The range of stretching is preferably 1.1 to 1.5 times the original width, and more preferably 1.05 to 1.3 times. Within the above range, the movement of molecules in the film is large, and not only a desired retardation value can be obtained, but also the behavior of the dimensional change of the film can be controlled within the desired range.

  Furthermore, it is preferable to start stretching the film in the MD direction when the residual solvent amount is 40% by mass or more after film formation, and in the TD direction when the residual solvent amount is less than 40% by mass. It is preferable to stretch.

  In order to stretch in the MD direction, it is preferable to peel at a peeling tension of 130 N / m or more, and particularly preferably 150 to 170 N / m. Since the web after peeling is in a high residual solvent state, stretching in the MD direction can be performed by maintaining the same tension as the peeling tension. As the web dries and the residual solvent amount decreases, the stretch ratio in the MD direction decreases.

  The draw ratio in the MD direction can be calculated from the rotation speed of the belt support and the tenter operation speed.

  In order to stretch in the TD direction, for example, the entire drying process or a part of the process as disclosed in Japanese Patent Application Laid-Open No. 62-46625 is performed while holding the width at both ends of the web with clips or pins in the width direction. A drying method (referred to as a tenter method), among them, a tenter method using clips and a pin tenter method using pins are preferably used.

  The retardation film of the present invention inevitably has retardation by stretching, but the in-plane retardation value Ro and the retardation value Rth in the thickness direction are measured by an automatic birefringence meter Axoscan (Axo Scan Mueller Matrix Polarimeter). : Manufactured by Axometrics Co., Ltd.) under the environment of 23 ° C. and 55% RH at a wavelength of 590 nm, the three-dimensional refractive index measurement can be performed, and the obtained refractive indexes nx, ny and nz can be calculated.

  The retardation film of the present invention has an in-plane retardation value Ro defined by the following formula (i) in the range of 40 to 70 nm, and a retardation in the thickness direction defined by the following formula (ii). The value Rth is preferably in the range of 100 to 300 nm from the viewpoint of improving the visibility when the VA mode liquid crystal display device is provided. The retardation film of the present invention contains the cellulose acetate according to the present invention and a nitrogen-containing heterocyclic compound, and is adjusted within the above retardation value by stretching at least while adjusting the stretching ratio in the TD direction. be able to.

Formula _{(i): Ro = (n} x -n y) × d (nm)
Formula (ii): _Rth = In _{{(n x + n y)} / 2-n z} × d (nm) [formula (i) and Formula (ii), _{n x} is a refractive index in the plane direction of the film It represents the refractive index in the direction x that becomes maximum. n _y, in-plane direction of the film, the refractive index in the direction y perpendicular to the direction x. _nz represents the refractive index in the thickness direction z of the film. d represents the thickness (nm) of the film. ]
<Knurling>
After a predetermined heat treatment or cooling treatment, it is preferable to provide a slitter and cut off the end portion before winding to obtain a good winding shape. Furthermore, it is preferable to knurling both ends of the width.

  The knurling process can be formed by pressing a heated embossing roller. Fine embossing is formed on the embossing roller, and by pressing the embossing roller, unevenness can be formed on the film and the end can be made bulky.

  The height of the knurling at both ends of the width of the retardation film of the present invention is preferably 4 to 20 μm and a width of 5 to 20 mm.

  In the present invention, the knurling process is preferably provided after the drying in the film forming step and before the winding.

(6) Winding step This is a step of winding as a film after the residual solvent amount in the web is 2% by mass or less, and the film having good dimensional stability by making the residual solvent amount 0.4% by mass or less. Can be obtained.

  As a winding method, a generally used method may be used, and there are a constant torque method, a constant tension method, a taper tension method, a program tension control method with a constant internal stress, and the like.

(B) Melt Casting Method The method for producing the retardation film of the present invention by the melt casting method is as follows: B1) Step of producing molten pellet (pelletizing step), B2) Step of extruding after melt-kneading the molten pellet (Melt extrusion step), B3) a step of cooling and solidifying the molten resin to obtain a web (cooling solidification step), and B4) a step of stretching the web (stretching step).

B1) Pelletizing step The composition containing cellulose acetate, which is the main component of the retardation film, is preferably kneaded and pelletized in advance. Pelletization can be performed by a known method. For example, a resin composition containing the aforementioned cellulose acetate and, if necessary, an additive such as a plasticizer, is melt-kneaded in an extruder, and then from a die. Extrude into a strand. The molten resin extruded in a strand form can be cooled with water or air, and then cut to obtain pellets.

  The pellet raw material is preferably dried before being fed to the extruder in order to prevent decomposition.

  The mixture of the antioxidant and the thermoplastic resin may be mixed with each other, may be mixed by impregnating the thermoplastic resin with an antioxidant dissolved in a solvent, or the antioxidant may be thermoplastic. The resin may be sprayed and mixed. The atmosphere around the feeder portion of the extruder and the outlet portion of the die is preferably an atmosphere of dehumidified air or nitrogen gas in order to prevent deterioration of the raw material of the pellet.

  In an extruder, it is preferable to knead at a low shearing force or at a low temperature so as not to cause deterioration of the resin (decrease in molecular weight, coloring, gel formation, etc.). For example, when kneading with a twin-screw extruder, it is preferable to use a deep groove type screw so that the rotational directions of the two screws are the same. In order to knead uniformly, it is preferable that two screw shapes mesh with each other.

B2) Melt Extrusion Step The obtained molten pellets and other additives as necessary are supplied from the hopper to the extruder. The supply of pellets is preferably performed under vacuum, reduced pressure, or an inert gas atmosphere in order to prevent oxidative decomposition of the pellets. Then, in an extruder, melt pellets that are film materials and, if necessary, other additives are melt-kneaded.

  The melting temperature of the film material in the extruder is preferably in the range of Tg to (Tg + 100) ° C., more preferably when the glass transition temperature of the film is Tg (° C.), although it depends on the type of film material. Is within the range of (Tg + 10) to (Tg + 90) ° C.

  Furthermore, when additives such as plasticizers and fine particles are added in the middle of the extruder, a mixing device such as a static mixer is further arranged on the downstream side of the extruder to uniformly mix these components. May be.

  The molten resin extruded from the extruder is filtered through a leaf disk filter or the like as necessary, and further mixed with a static mixer or the like, and extruded from a die into a film.

  The extrusion flow rate is preferably stabilized using a gear pump. Moreover, it is preferable that the leaf disk filter used for removal of a foreign material is a stainless fiber sintered filter. A stainless steel fiber sintered filter is an integrated, intricately intertwined stainless steel fiber body that is compressed and sintered at the contact point. The density is changed according to the thickness of the fiber and the amount of compression, and the filtration accuracy is adjusted. it can.

  The melting temperature of the resin at the exit portion of the die can be in the range of about 200-300 ° C.

B3) Cooling and solidifying step The resin extruded from the die is nipped between the cooling roller and the elastic touch roller to make the film-like molten resin a predetermined thickness. Then, the film-like molten resin is cooled and solidified stepwise by a plurality of cooling rollers.

  The surface temperature of the cooling roller can be Tg (° C.) or lower when the glass transition temperature of the obtained film is Tg (° C.). The surface temperatures of the plurality of cooling rollers may be different.

  The elastic touch roller is also called a pinching rotary body. A commercially available elastic touch roller can also be used. The film surface temperature on the elastic touch roller side can be in the range of Tg to (Tg + 110) ° C. of the film.

  The film-like molten resin solidified from the cooling roller is peeled off by a peeling roller or the like to obtain a web. When peeling the film-like molten resin, it is preferable to adjust the tension in order to prevent deformation of the obtained web.

B4) Stretching step The obtained web is stretched with a stretching machine to obtain a film. Stretching is performed in any of the web width direction, the conveyance direction, or the oblique direction.

  The stretching method, stretching ratio, and stretching temperature of the web can be the same as described above.

<Physical properties of retardation film>
(Haze)
The retardation film of the present invention preferably has a haze of less than 1%, more preferably less than 0.5%. By setting the haze to less than 1%, there is an advantage that the transparency of the film becomes higher and it becomes easier to use as a film for optical applications. The haze can be measured using a haze meter (NDH2000 type, manufactured by Nippon Denshoku Industries Co., Ltd.) according to JIS K7136.

(Equilibrium moisture content)
In the retardation film of the present invention, the equilibrium water content at 25 ° C. and 60% relative humidity is preferably 4% or less, more preferably 3% or less. By setting the equilibrium moisture content to 4% or less, it is preferable to easily cope with a change in humidity and to hardly change the optical characteristics and dimensions. Equilibrium moisture content is determined by leaving the sample film in a room conditioned at 23 ° C. and 20% relative humidity for 4 hours or more and then leaving it in a room conditioned at 23 ° C. and 80% RH for 24 hours. Using a meter (for example, CA-20, manufactured by Mitsubishi Chemical Corporation), the moisture is dried and vaporized at a temperature of 150 ° C., and then quantified by the Karl Fischer method.

(Film length, width, film thickness)
The retardation film of the present invention is preferably long, specifically, preferably has a length of about 100 to 10000 m, and is wound into a roll. In addition, the width of the retardation film of the present invention is preferably 1 m or more, more preferably 1.4 m or more, and particularly preferably 1.4 to 4 m.

  The film thickness is preferably in the range of 10 to 100 μm from the viewpoint of thinning the display device and productivity. If the film thickness is 10 μm or more, a certain level of film strength and retardation can be exhibited. If the film thickness is 100 μm or less, the variation in retardation due to heat and humidity can be suppressed. Preferably, it exists in the range of 20-70 micrometers.

  The film thickness unevenness of the film is preferably in the range of 0 to 5 μm, more preferably in the range of 0 to 3 μm, and still more preferably in the range of 0 to 2 μm in both the thickness direction and the width direction.

<Polarizing plate>
In the polarizing plate of the present invention, it is preferable that the retardation film of the present invention is bonded to at least one surface of a polarizer using a water paste or an active energy ray-curable adhesive.

  Moreover, the polyester film or the acrylic film is bonded to the polarizer using a water paste or an active energy ray-curable adhesive on the surface of the polarizer opposite to the surface on which the retardation film is bonded. It is preferable that the variation of retardation with respect to humidity is further reduced.

  When the polarizing plate of the present invention is used as a viewing side polarizing plate, the viewing side film of the polarizing plate is provided with an antiglare layer or a clear hard coat layer, an antireflection layer, an antistatic layer, an antifouling layer, and the like. Is preferred.

[Polarizer]
The polarizer, which is the main component of the polarizing plate of the present invention, is an element that passes only light having a plane of polarization in a certain direction, and a typical known polarizer is a polyvinyl alcohol polarizing film. The polyvinyl alcohol polarizing film includes those obtained by dyeing iodine on a polyvinyl alcohol film and those obtained by dyeing a dichroic dye.

  As the polarizer, a polarizer obtained by forming a polyvinyl alcohol aqueous solution into a film and dyeing it by uniaxial stretching or dyeing and then uniaxially stretching and then preferably performing a durability treatment with a boron compound may be used. The film thickness of the polarizer is preferably 2 to 30 μm, particularly preferably 2 to 15 μm.

  Further, the ethylene unit content described in JP-A-2003-248123, JP-A-2003-342322, etc. is 1 to 4 mol%, the degree of polymerization is 2000 to 4000, and the degree of saponification is 99.0 to 99.99 mol%. The ethylene-modified polyvinyl alcohol is also preferably used. Among these, an ethylene-modified polyvinyl alcohol film having a hot water cutting temperature of 66 to 73 ° C. is preferably used. A polarizer using this ethylene-modified polyvinyl alcohol film is excellent in polarization performance and durability, and has little color unevenness, and is particularly preferably used for a large liquid crystal display device.

<Laminated film type polarizer>
In addition, the polarizing plate of the present invention is preferably a thin film, and the thickness of the polarizer is particularly preferably in the range of 2 to 15 μm from the viewpoint of achieving both the strength of the polarizing plate and the thinning.

  As such a thin film polarizer, a laminated film type polarizer is produced by the method described in JP2011-1000016, JP4691205, JP4751481, JP48080489. Is preferred.

  As an example, it is preferable to use a thin film laminated film type polarizer (polarizing laminated film) manufactured by the following steps from the viewpoint of reducing the overall thickness of the polarizing plate and reducing the weight.

(Production method of polarizing laminated film)
The manufacturing method of the light-polarizing laminated film used for this invention includes the following process.
(A) a laminating step of obtaining a laminated film by forming a polyvinyl alcohol-based resin layer on one surface of a base film in which a rubber component is dispersed in a thermoplastic resin;
(B) A stretching process for uniaxially stretching the laminated film to obtain a stretched film;
(C) a dyeing process of obtaining a dyed film by dyeing a polyvinyl alcohol resin layer of a stretched film with a dichroic dye;
(D) The polyvinyl alcohol resin layer of the dyed film is immersed in a solution containing a crosslinking agent to form a polarizer layer, and a crosslinking step for obtaining a crosslinked film; and (e) a drying step for drying the crosslinked film. Explaining the process,
(A) Laminating step In this step, a film obtained by dispersing (blending) a rubber component in a thermoplastic resin is used as a base film, and a polyvinyl alcohol resin layer is formed on one surface to obtain a laminated film. Is preferred.

(1) Base film The thermoplastic resin that is the base of the base film is preferably a thermoplastic resin that is excellent in transparency, mechanical strength, thermal stability, stretchability, and the like. Specific examples of such thermoplastic resins include, for example, chain polyolefin resins; cyclic polyolefin resins; (meth) acrylic resins; polyester resins; cellulose acylate resins; polycarbonate resins; Resin; Vinyl acetate resin; Polyarylate resin; Polystyrene resin; Polyethersulfone resin; Polysulfone resin; Polyamide resin; Polyimide resin; and mixtures or copolymers thereof.

  The rubber component dispersed in the thermoplastic resin is a resin component having rubber elasticity, and is usually uniformly dispersed in the thermoplastic resin as rubber particles. By mixing and dispersing the rubber component, it is possible to improve the tear strength of the base film and thus the stretched film. The rubber component is not particularly limited as long as it is a resin having rubber elasticity. However, from the viewpoint of compatibility with the thermoplastic resin, the rubber component is preferably composed of the same or similar resin as the thermoplastic resin to be used.

  For example, when the thermoplastic resin is a chain polyolefin-based resin, the rubber component can be a copolymer of two or more monomers selected from ethylene and α-olefin. In this case, the content (polymerization ratio) of each monomer constituting the copolymer is preferably less than 90% by mass, and more preferably less than 80% by mass.

  When the thermoplastic resin is a (meth) acrylic resin, it is preferable to contain an acrylic polymer having rubber elasticity as a rubber component from the viewpoint of compatibility. The acrylic polymer is preferably a polymer mainly composed of alkyl acrylate, and may be a homopolymer of alkyl acrylate, or 50% by mass or more of alkyl acrylate and 50% by mass or less of other monomers. And a copolymer thereof.

  The compounding amount of the rubber component is preferably 5 to 50% by mass of the thermoplastic resin, more preferably 10 to 45% by mass. When the blending amount of the rubber component is too small, it is difficult to obtain a sufficient effect of improving the tear strength, and when the blending amount of the rubber component is too large, the handleability of the base film tends to be lowered.

  The method for dispersing the rubber component in the thermoplastic resin is not particularly limited. For example, the thermoplastic resin and rubber component (rubber particles) produced separately are kneaded and dispersed with a plastmill or the like, or the same reaction when preparing the thermoplastic resin. Examples thereof include a reactor blend method in which a rubber component is also prepared in a container to obtain a thermoplastic resin in which the rubber component is dispersed. The reactor blending method is advantageous in improving the degree of dispersion of the rubber component.

(2) Polyvinyl alcohol-type resin layer As a polyvinyl alcohol-type resin which forms a polyvinyl alcohol-type resin layer, a polyvinyl alcohol resin and its derivative (s) are mentioned, for example. Derivatives of polyvinyl alcohol resin include polyvinyl formal, polyvinyl acetal, etc., olefins such as ethylene and propylene, unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid, and alkyl esters of unsaturated carboxylic acids. And those modified with acrylamide or the like. Among these, it is preferable to use a polyvinyl alcohol resin.

  The polyvinyl alcohol resin is preferably a completely saponified product. The range of the saponification degree is preferably in the range of 80.0 to 100.0 mol%, more preferably in the range of 90.0 to 99.5 mol%, still more preferably 94.0 to 99.0. It is in the range of mol%.

  If necessary, additives such as a plasticizer and a surfactant may be added to the polyvinyl alcohol-based resin described above. As the plasticizer, polyols and condensates thereof can be used, and examples thereof include glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, and polyethylene glycol. Although the compounding quantity of an additive is not restrict | limited in particular, It is suitable to set it as 20 mass% or less of a polyvinyl alcohol-type resin.

  As a method for coating a polyvinyl alcohol resin solution on a base film, a wire bar coating method, a roll coating method such as reverse coating or gravure coating, a spin coating method, a screen coating method, a fountain coating method, a dipping method, or a spray method. It can select suitably from well-known methods, such as. A drying temperature is the range of 50-200 degreeC, for example, Preferably it is the range of 60-150 degreeC. The drying time is, for example, in the range of 2 to 20 minutes.

  The thickness of the polyvinyl alcohol resin layer in the laminated film is preferably 3 μm or more and 50 μm or less, and more preferably 5 μm or more and 45 μm or less. If it is 3 μm or less, it becomes too thin after stretching and the dyeability is significantly deteriorated. If it exceeds 50 μm, the resulting polarizing laminate film becomes thick.

  The thickness of the polyvinyl alcohol-based resin layer as a polarizer used in the present invention is within the range of 2 to 15 μm as the film thickness after the following stretching treatment from the viewpoint of thinning, strength as a polarizer, and flexibility. Is preferred.

(B) Stretching step This step is a step of obtaining a stretched film by uniaxially stretching a laminated film including a base film and a polyvinyl alcohol-based resin layer. The draw ratio of the laminated film can be appropriately selected according to the desired polarization characteristics, but is preferably in the range of 5 to 17 times, more preferably 5 to 8 times the original length of the laminated film. Within range.

  The stretching is preferably longitudinal stretching in which stretching is performed in the longitudinal direction (film transport direction) of the laminated film. Examples of the longitudinal stretching method include an inter-roller stretching method, a compression stretching method, and a stretching method using a tenter. The uniaxial stretching is not limited to the longitudinal stretching process, and may be oblique stretching or the like.

(C) Dyeing step This step is a step of obtaining a dyed film by dyeing the polyvinyl alcohol resin layer of the stretched film with a dichroic dye. Examples of the dichroic dye include iodine and organic dyes. Examples of organic dyes include Red BR, Red LR, Red R, Pink LB, Rubin BL, Bordeaux GS, Sky Blue LG, Lemon Yellow, Blue BR, Blue 2R, Navy RY, Green LG, Violet LB, Violet B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Brilliant Violet BK, Spura Blue G, Spura Blue GL, Spura Orange GL, Direct Sky Blue, Direct First Orange S, First Black, etc. can be used. These dichroic substances may be used alone or in combination of two or more.

  When iodine is used as the dichroic dye, it is preferable to further add iodide to the dyeing solution containing iodine because the dyeing efficiency can be further improved. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and iodide. Examples include titanium.

(D) Crosslinking step In this step, the polyvinyl alcohol resin layer of the dyed film obtained by dyeing with a dichroic dye is subjected to a crosslinking treatment, and a crosslinked film using the polyvinyl alcohol resin layer as a polarizer layer is obtained. It is a process to obtain. The crosslinking step can be performed, for example, by immersing the dyed film in a solution containing a crosslinking agent (crosslinking solution). Conventionally known substances can be used as the crosslinking agent. Examples thereof include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. These may be used alone or in combination of two or more.

(E) Drying step The obtained crosslinked film is usually dried after washing. Thereby, a light-polarizing laminated film is obtained. Washing can be performed by immersing the crosslinked film in pure water such as ion exchange water or distilled water. The water washing temperature is usually in the range of 3 to 50 ° C, preferably in the range of 4 to 20 ° C. The immersion time is usually in the range of 2 to 300 seconds, preferably 5 to 240 seconds. The washing may be a combination of a washing treatment with an iodide solution and a water washing treatment, and a solution in which a liquid alcohol such as methanol, ethanol, isopropyl alcohol, butanol, propanol or the like is appropriately blended may be used.

  Any appropriate method (for example, natural drying, air drying, heat drying) can be adopted as the drying method. For example, the drying temperature in the case of heat drying is usually in the range of 20 to 95 ° C., and the drying time is usually about 1 to 15 minutes.

  The polarizing laminated film includes a polarizer layer composed of a polyvinyl alcohol-based resin layer in which a dichroic dye is adsorbed and oriented, and can itself be used as a polarizing plate. As a preferred embodiment of the present invention, after the polarizing laminated film is formed by the above-mentioned process, the polyvinyl alcohol layer of the polarizing laminated film is peeled from the substrate film, whereby the polyvinyl alcohol layer is related to the present invention. It is to be used as a polarizer. According to the method of the present invention, since the thickness of the polarizer layer can be 15 μm or less, a thin polarizer can be obtained. Moreover, the polarizer used in the present invention is excellent in polarization performance and durability.

[Preparation of polarizing plate]
The polarizing plate of the present invention can be produced by a general method. Using a completely saponified polyvinyl alcohol aqueous solution (water paste) on at least one surface of a polarizer prepared by subjecting the polarizer side of the retardation film of the present invention to alkali saponification treatment and immersion drawing in an iodine solution. It is preferable to bond them together. Another polarizing plate protective film can be bonded to the other surface. When the retardation film of the present invention is used as a liquid crystal display device, it is preferably provided on the liquid crystal cell side of the polarizer, and a conventional polarizing plate protective film can be used as the film outside the polarizer.

  For example, as a conventional polarizing plate protective film, a commercially available cellulose ester film (for example, Konica Minoltak KC8UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5, KC8UY, KC6UY, KC6UA, KC4UY, KC4UE, KC8UE, KC8UE, KC8UE, KC8UE, KC8UE, RHA, KC8UXW-RHA-C, KC8UXW-RHA-NC, KC4UXW-RHA-NC, manufactured by Konica Minolta, Inc.) are preferably used.

[Active energy ray curable adhesive]
Moreover, in the polarizing plate of this invention, it is also preferable that the phase difference film of this invention and a polarizer are bonded by the active energy ray hardening adhesive.

  As the active energy ray curable adhesive, the following ultraviolet curable adhesive is preferably used.

  In the present invention, by applying an ultraviolet curable adhesive to the lamination of the retardation film and the polarizer, a polarizing plate having high strength and excellent flatness can be obtained even in a thin film.

<Composition of UV curable adhesive>
As the UV curable adhesive composition for polarizing plates, a photo radical polymerization composition using photo radical polymerization, a photo cation polymerization composition using photo cation polymerization, and photo radical polymerization and photo cation polymerization are used in combination. Hybrid type compositions are known.

  As a radical photopolymerization type composition, a radical polymerizable compound containing a polar group such as a hydroxy group or a carboxy group described in JP-A-2008-009329 and a radical polymerizable compound not containing a polar group are contained in a specific ratio. Composition) and the like are known. In particular, the radical polymerizable compound is preferably a compound having a radical polymerizable ethylenically unsaturated bond. Preferable examples of the compound having an ethylenically unsaturated bond capable of radical polymerization include a compound having a (meth) acryloyl group. Examples of the compound having a (meth) acryloyl group include an N-substituted (meth) acrylamide compound and a (meth) acrylate compound. (Meth) acrylamide means acrylamide or methacrylamide.

  Moreover, as a photocationic polymerization type composition, as disclosed in JP 2011-08234 A, (α) a cationic polymerizable compound, (β) a photocationic polymerization initiator, and (γ) a wavelength longer than 380 nm. And an ultraviolet curable adhesive composition containing each component of a photosensitizer exhibiting maximum absorption in the light of (δ) and a naphthalene-based photosensitization aid. However, other ultraviolet curable adhesives may be used.

(1) Pre-processing process A pre-processing process is a process of performing an easily bonding process to the adhesive surface with the polarizer of retardation film. Examples of the easy adhesion treatment include corona treatment and plasma treatment.

(Application process of UV curable adhesive)
In the step of applying the ultraviolet curable adhesive, the ultraviolet curable adhesive is applied to at least one of the adhesive surfaces of the polarizer and the retardation film. When the ultraviolet curable adhesive is applied directly to the surface of the polarizer or the retardation film, the application method is not particularly limited. For example, various wet coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used. Moreover, after casting an ultraviolet curable adhesive between a polarizer and a phase difference film, the method of pressurizing with a roller etc. and spreading it uniformly can also be utilized.

(2) Bonding process After apply | coating an ultraviolet curable adhesive by said method, it processes by a bonding process. In this bonding step, for example, when an ultraviolet curable adhesive is applied to the surface of the polarizer in the previous application step, a retardation film is superimposed thereon. In the case of a method in which an ultraviolet curable adhesive is first applied to the surface of a retardation film, a polarizer is superimposed thereon. In addition, when an ultraviolet curable adhesive is cast between the polarizer and the retardation film, the polarizer and the retardation film are superposed in that state. Usually, in this state, the pressure is sandwiched between the pressure-difference films on both sides with a pressure roller or the like. Metal, rubber, or the like can be used as the material of the pressure roller. The pressure rollers arranged on both sides may be made of the same material or different materials.

(3) Curing step In the curing step, an uncured UV curable adhesive is irradiated with UV rays, and a cationic polymerizable compound (for example, an epoxy compound or an oxetane compound) or a radical polymerizable compound (for example, an acrylate compound, acrylamide). The ultraviolet curable adhesive layer containing the compound and the like is cured, and the polarizer and the retardation film are bonded to each other through the ultraviolet curable adhesive. When laminating a retardation film on one side of a polarizer, the active energy ray may be irradiated from either the polarizer side or the retardation film side. In addition, when laminating retardation films on both sides of a polarizer, both sides of the polarizer are irradiated with ultraviolet rays in a state where the retardation films are superimposed on each other via an ultraviolet curable adhesive, and both sides are cured with ultraviolet rays. It is advantageous to cure the adhesive simultaneously.

Any appropriate conditions can be adopted as the ultraviolet irradiation conditions as long as the ultraviolet curable adhesive applied to the present invention can be cured. Preferably the dose of ultraviolet rays in the range of 50~1500mJ / cm ² in accumulated light quantity, and even more preferably in the range of 100 to 500 mJ / cm ^2.

  When performing the manufacturing process of a polarizing plate by a continuous line, although line speed is based on the hardening time of an adhesive agent, Preferably it is the range of 1-500 m / min, More preferably, it is the range of 5-300 m / min, More preferably, it is 10- The range is 100 m / min. If the line speed is 1 m / min or more, productivity can be ensured, or damage to the retardation film can be suppressed, and a polarizing plate having excellent durability can be produced. If the line speed is 500 m / min or less, the ultraviolet curable adhesive is sufficiently cured, and an ultraviolet curable adhesive layer having a desired hardness and excellent adhesiveness can be formed.

[Polyester film and acrylic film]
A polyester film or an acrylic film is bonded to the polarizer using a water glue or an active energy ray-curable adhesive on the surface opposite to the surface on which the retardation film of the polarizer is bonded. It is a preferable embodiment from the viewpoint of obtaining a polarizing plate having high durability against humidity fluctuations. For the bonding, either the water glue or the ultraviolet curable adhesive which is an active energy ray curable adhesive can be used, but it is preferable to use an ultraviolet curable adhesive from the viewpoint of the effect of the present invention. .

  In the present invention, the outer film (polarizing plate protective film) is a polyester film or acrylic film having low moisture permeability, and the inner film (retardation film) is a retardation film with improved retardation variation with respect to the humidity variation of the present invention. With this configuration, it is possible to reduce the influence of moisture from the outside, and to easily release the moisture inside, and to obtain a polarizing plate with improved durability against the humidity fluctuation of the polarizing plate in a comprehensive manner. It is estimated to be.

(1) Polyester film The polyester resin that forms the polyester film is not particularly limited. For example, terephthalic acid, isophthalic acid, orthophthalic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalene. Dicarboxylic acid, 1,5-naphthalenedicarboxylic acid, diphenylcarboxylic acid, diphenoxyethanedicarboxylic acid, diphenylsulfonecarboxylic acid, anthracene dicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4 -Cyclohexanedicarboxylic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, malonic acid, dimethylmalonic acid, succinic acid, 3,3-diethylsuccinic acid, glutaric acid, 2,2-dimethylglutaric acid, adipic acid, 2-methyl Dicarboxylic acids such as tiladipic acid, trimethyladipic acid, pimelic acid, azelaic acid, dimer acid, sebacic acid, suberic acid, dodecadicarboxylic acid, ethylene glycol, propylene glycol, hexamethylene glycol, neopentyl glycol, 1,2-cyclohexane Dimethanol, 1,4-cyclohexanedimethanol, decamethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexadiol, 2,2-bis (4 -Hydroxyphenyl) propane, bis (4-hydroxyphenyl) sulfone and other diols, each of which is a homopolymer obtained by polycondensation, or a copolymerization obtained by polycondensation of one or more dicarboxylic acids and two or more diols Combined or two or more dicarboxylic acids Copolymer diol made by polycondensation of one or more of, and can include any of the polyester resin of the blend resin obtained by blending two or more of these homopolymers and copolymers. Of these, polyethylene terephthalate resin is preferably used. Further, the above resins can be mixed and used.

  The polyester film can be obtained, for example, by a method in which the above-described polyester resin is melt-extruded into a film and cooled and solidified with a casting drum to form a film. As the polyester film in the polarizing plate of the present invention, any of an unstretched film and a stretched film can be used. For example, when a film having a small birefringence is required, an unstretched film can be suitably used. In addition, when birefringence is used for optical compensation of a liquid crystal display device, a stretched film can be suitably used. A stretched film, particularly a biaxially stretched film, is also preferably used from the viewpoint of strength.

  Polyester films are more durable than TAC films, but unlike TAC films, they tend to have birefringence, so when used as a polarizing plate protective film, rainbow-like color unevenness occurs when observed from an oblique direction. , The image quality is degraded.

  For this reason, the polyester film is preferably a polyester film having a retardation value in the in-plane direction of 3000 to 30000 nm. At this time, the polarizing plate protective film on the emission light side of the polarizing plate disposed on the emission light side with respect to the liquid crystal cell is preferably a polyester film having a retardation value of 3000 to 30000 nm. The ratio value (Ro / Rth) of the retardation value Ro in the in-plane direction of the polyester film to the retardation value Rth in the thickness direction is preferably 0.200 or more. With such a configuration, it is possible to obtain a spectrum that approximates the light source at any observation angle, and it is possible to ensure good visibility without rainbow-like color unevenness. Moreover, the mechanical strength suitable for thin film formation can be provided.

  Such a polyester film can use polyethylene terephthalate or polyethylene naphthalate, but may contain other copolymerization components. These resins are excellent in transparency and excellent in thermal and mechanical properties, and the retardation value can be easily controlled by stretching. In particular, polyethylene terephthalate is the most suitable material because it has a large intrinsic birefringence and a relatively large retardation value can be obtained relatively easily even if the film is thin.

  The retardation value can be obtained by measuring the refractive index and thickness in the biaxial direction, and a commercially available automatic birefringence measuring device such as KOBRA-21ADH (Oji Scientific Instruments Co., Ltd.) or Axoscan from Axometrics. It can also be obtained using.

  The polyester film can be manufactured according to a general method for manufacturing a polyester film. For example, the polyester resin is melted and the non-oriented polyester extruded and formed into a sheet shape is stretched in the longitudinal direction by utilizing the speed difference of the roll at a temperature equal to or higher than the glass transition temperature, and then stretched in the transverse direction by a tenter. The method of performing heat processing is mentioned.

  The polyester film according to the present invention may be a uniaxially stretched film or a biaxially stretched film, but when the biaxially stretched film is used as a polarizing plate protective film, it is observed from directly above the film surface. Although no rainbow-like color unevenness is observed, rainbow-like color unevenness may be observed when observed from an oblique direction.

  This phenomenon is because the biaxially stretched film consists of refractive index ellipsoids having different refractive indexes in the running direction, width direction, and thickness direction, and the in-plane retardation is zero due to the light transmission direction inside the film. This is because there exists a direction in which the refractive index ellipsoid appears to be a perfect circle. Therefore, when the liquid crystal display screen is observed from a specific oblique direction, a point where the retardation value in the in-plane direction becomes zero may occur, and rainbow-like color unevenness occurs concentrically around that point. It becomes. When the angle from the position directly above the film surface (normal direction) to the position where the rainbow-like color unevenness can be seen is θ, this angle θ becomes larger as the birefringence in the film surface becomes larger. Unevenness is difficult to see. Since biaxially stretched film tends to reduce the angle θ, uniaxially stretched film is preferable because rainbow-like color unevenness is less visible.

  However, a perfect uniaxial (uniaxial symmetry) film is not preferable because the mechanical strength in the direction orthogonal to the orientation direction is significantly reduced. The polyester film according to the present invention has biaxiality (biaxial symmetry) within a range that does not substantially cause rainbow-like color unevenness or a range that does not cause rainbow-like color unevenness in a viewing angle range required for a liquid crystal display screen. ) Is preferable.

  As means for suppressing the occurrence of color unevenness while maintaining the mechanical strength of the polarizing plate protective film, the retardation (in-plane direction retardation) value and the thickness direction retardation (Rth) value of the polarizing plate protective film. It is preferable to control so that the value of the ratio falls within a specific range. The smaller the difference between the in-plane retardation and the retardation in the thickness direction, the more isotropic the birefringence action due to the observation angle, so the change in retardation due to the observation angle becomes smaller. For this reason, it is considered that rainbow-like color unevenness due to the observation angle hardly occurs.

  The ratio value (Ro / Rth) of the retardation value Ro in the in-plane direction and the retardation value Rth in the thickness direction of the polyester film according to the present invention is preferably 0.200 or more, more preferably 0.500 or more, More preferably, it is 0.600 or more. The larger the ratio (Ro / Rth) of the retardation value Ro in the in-plane direction to the retardation value Rth in the thickness direction, the more the birefringence action becomes more isotropic and the occurrence of rainbow-like color unevenness depending on the observation angle. Is less likely to occur. In a complete uniaxial (uniaxial symmetry) film, the ratio value (Ro / Rth) of the retardation value Ro in the in-plane direction to the retardation value Rth in the thickness direction is 2.0. However, as described above, the mechanical strength in the direction orthogonal to the orientation direction is significantly lowered as the film approaches a complete uniaxial (uniaxial symmetry) film.

  On the other hand, the ratio value (Ro / Rth) of the retardation value Ro in the in-plane direction and the retardation value Rth in the thickness direction of the polyester film according to the present invention is preferably 1.2 or less, more preferably 1.0. It is as follows. In order to completely suppress the occurrence of rainbow-like color unevenness due to the observation angle, the ratio value (Ro / Rth) of the in-plane retardation value Ro to the thickness direction retardation value Rth is 2.0. There is no need, and 1.2 or less is sufficient. Even if the ratio is 1.0 or less, it is possible to satisfy the viewing angle characteristics (180 degrees left and right, 120 degrees up and down) required for the liquid crystal display device.

Describing specifically the film forming conditions of the polyester film according to the present invention, the longitudinal stretching temperature and the transverse stretching temperature are preferably from 80 to 130 ° C, particularly preferably from 90 to 120 ° C. The longitudinal draw ratio is preferably from 1.0 to 3.5 times, particularly preferably from 1.0 to 3.0 times. Further, the transverse draw ratio is preferably 2.5 to 6.0 times, particularly preferably in the range of 3.0 to 5.5 times. In order to control the retardation within the above range, it is preferable to control the ratio of the longitudinal draw ratio and the transverse draw ratio. If the difference between the vertical and horizontal draw ratios is too small, it is difficult to increase the retardation, which is not preferable. Also, setting the stretching temperature low is a preferable measure for increasing the retardation. In the subsequent heat treatment, the treatment temperature is preferably from 100 to 250 ° C, particularly preferably from 180 to 245 ° C.
In order to suppress the fluctuation of the retardation, it is preferable that the thickness unevenness of the film is small. Since the stretching temperature and the stretching ratio greatly affect the thickness unevenness of the film, it is necessary to optimize the film forming conditions from the viewpoint of the thickness unevenness. In particular, when the longitudinal stretching ratio is lowered to increase the retardation, unevenness in the longitudinal thickness may be deteriorated. Since there is a region where the vertical thickness unevenness becomes extremely worse within a specific range of the draw ratio, it is desirable to set the film forming conditions outside this range.

  The thickness unevenness of the film is preferably 5.0% or less, more preferably 4.5% or less, still more preferably 4.0% or less, and 3.0% or less. Is particularly preferred.

  As described above, in order to control the retardation value of the film within a specific range, the stretching ratio, the stretching temperature, and the thickness of the film can be appropriately set. For example, the higher the stretching ratio, the lower the stretching temperature, and the thicker the film, the easier it is to obtain a higher retardation value. Conversely, the lower the stretching ratio, the higher the stretching temperature, and the thinner the film, the easier it is to obtain a lower retardation value. However, when the thickness of the film is increased, the retardation value in the thickness direction tends to increase. Therefore, it is desirable to set the film thickness appropriately in the range described later. In addition to controlling the retardation value, it is necessary to set final film forming conditions in consideration of physical properties necessary for processing.

  Although the thickness of the polyester film concerning this invention is arbitrary, the range of 15-300 micrometers is preferable, More preferably, it is the range of 15-200 micrometers. Even in the case of a film having a thickness of less than 15 μm, it is possible in principle to obtain a retardation value of 3000 nm or more. However, in that case, the anisotropy of the mechanical properties of the film becomes remarkable, and it becomes easy to cause tearing, tearing, etc., and the practicality as an industrial material is remarkably lowered. A particularly preferable lower limit of the thickness is 25 μm. On the other hand, if the upper limit of the thickness of the polyester film exceeds 300 μm, the thickness of the polarizing plate becomes too thick, which is not preferable. From the viewpoint of practicality as a polyester film, the upper limit of the thickness is preferably 200 μm. A particularly preferable upper limit of the thickness is 100 μm, which is about the same as a general TAC film. In order to control the retardation value within the range of the present invention even within the above thickness range, the polyester used as the film substrate is preferably polyethylene terephthalate.

  Various additives may be used in the polyester film according to the present invention. Examples of other additives include plasticizers, ultraviolet absorbers, fluorine-based surfactants, release agents, matting agents, deterioration preventing agents, optical anisotropy control agents, infrared absorbers, and the like. Can be used.

(2) Acrylic film The acrylic resin contained in an acrylic film (hereinafter also referred to as an acrylic resin film) means a (meth) acrylic resin and is a concept including both an acrylic resin and a methacrylic resin. Hereinafter, the acrylic resin will be described.

  As described above, the acrylic resin is a (meth) acrylic resin and means a polymer of acrylic acid ester or methacrylic acid ester. As the polymer of the methacrylic acid ester, for example, a polymer composed mainly of an alkyl methacrylate is preferable. The monomer composition of the alkyl methacrylate is preferably 70% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more, based on a total of 100% by mass of all monomers. And alkyl methacrylate is 99% by mass or less. The acrylic resin may be a homopolymer of alkyl methacrylate or a copolymer of 50% by mass or more of alkyl methacrylate and 50% by mass or less of a monomer other than alkyl methacrylate. Good. As the alkyl methacrylate, those having 1 to 4 carbon atoms of the alkyl group are usually used, and among them, methyl methacrylate is preferably used.

  The monomer other than alkyl methacrylate may be a monofunctional monomer having one polymerizable carbon-carbon double bond in the molecule, or two or more polymerizable carbons in the molecule. -A polyfunctional monomer having a carbon double bond may be used. In particular, monofunctional monomers are preferably used, and examples thereof include alkyl acrylates such as methyl acrylate and ethyl acrylate, and further, such as styrene and alkyl styrene as long as the effects of the present invention are not impaired. Examples include styrene monomers and unsaturated nitriles such as acrylonitrile and methacrylonitrile. When using alkyl acrylate as a copolymerization component, the carbon number is 1-8 normally.

  The acrylic resin preferably does not have a glutarimide derivative, a glutaric anhydride derivative, a lactone ring structure, or the like. These acrylic resins may not provide sufficient mechanical strength and heat-and-moisture resistance as an acrylic resin film.

  In the present invention, the weight average molecular weight (Mw) of the acrylic resin applied to the present invention can be reduced from the viewpoint that the content of the organic solvent in the dope can be reduced, the drying time can be shortened, and the surface shape of the film to be formed is excellent. ) Is preferably 80,000 or more. Further, from the viewpoint of further improving the film surface shape when laminated, the weight average molecular weight of the acrylic resin is in the range of 100,000 to 4000000. preferable.

  The upper limit of the weight average molecular weight of the acrylic resin can maintain the solution casting suitability without excessively increasing the viscosity, and can ensure compatibility with organic solvents and additives during dope preparation. The upper limit is preferably 4000000.

  The weight average molecular weight of the acrylic resin used in the present invention can be measured by the gel permeation chromatography.

  In order to improve the flexibility of the acrylic film and enhance the handling properties, it is preferable that rubber elastic particles are blended in the acrylic resin. The rubber elastic particles are particles containing a rubber elastic body, and may be particles composed only of a rubber elastic body, or may be particles having a multilayer structure having a rubber elastic body layer. Examples of rubber elastic bodies include olefin-based elastic polymers, diene-based elastic polymers, styrene-diene-based elastic copolymers, and acrylic-based elastic polymers. Among these, an acrylic elastic polymer is preferable from the viewpoint of surface hardness, light resistance, and transparency of the acrylic resin film.

  The acrylic elastic polymer is preferably a polymer mainly composed of alkyl acrylate, may be a homopolymer of alkyl acrylate, or may be a single polymer other than alkyl acrylate 50 mass% or more and alkyl acrylate. It may be a copolymer with 50% by mass or less of the monomer. As the alkyl acrylate, those having 4 to 8 carbon atoms in the alkyl group are usually used. Examples of monomers other than alkyl acrylate include alkyl methacrylates such as methyl methacrylate and ethyl methacrylate, styrene monomers such as styrene and alkyl styrene, acrylonitrile and methacrylonitrile. Monofunctional monomers such as unsaturated nitriles, alkenyl esters of unsaturated carboxylic acids such as allyl (meth) acrylate and methallyl (meth) acrylate, dialkenyl esters of dibasic acids such as diallyl maleate, And polyfunctional monomers such as unsaturated carboxylic acid diesters of glycols such as alkylene glycol di (meth) acrylate.

  The rubber elastic particle containing the acrylic elastic polymer is preferably a particle having a multilayer structure having an acrylic elastic polymer layer, and a polymer mainly composed of alkyl methacrylate outside the acrylic elastic polymer. It may be a two-layer structure having the above-mentioned layer, or a three-layer structure having a polymer layer mainly composed of alkyl methacrylate inside the acrylic elastic polymer. In addition, the example of the monomer composition of the polymer mainly composed of alkyl methacrylate constituting the layer formed on the outside or inside of the acrylic elastic polymer is the same as the alkyl methacrylate previously mentioned as an example of the acrylic resin. This is the same as the monomer composition example of the main polymer. Such acrylic rubber elastic particles having a multilayer structure can be produced, for example, by the method described in Japanese Patent Publication No. 55-27576.

  As the rubber elastic particles, those having a number average particle diameter of 10 to 300 nm of the rubber elastic bodies contained therein can be used. Thereby, when an acrylic resin film is laminated | stacked on a polarizing film using an adhesive agent, an acrylic resin film can be made hard to peel from an adhesive bond layer. The number average particle diameter of the rubber elastic body is preferably 50 nm or more and 250 nm or less.

  In the rubber elastic particle in which the outermost layer is a polymer mainly composed of methyl methacrylate and the acrylic elastic polymer is encapsulated in the polymer, when the rubber elastic particle is mixed with the base acrylic resin, the rubber elastic particle The outermost layer is mixed with the base acrylic resin. Therefore, in the cross section, when the acrylic elastic polymer is dyed with ruthenium oxide and observed with an electron microscope, the rubber elastic particles can be observed as particles excluding the outermost layer. Specifically, in the case of using rubber elastic particles having a two-layer structure in which the inner layer is an acrylic elastic polymer and the outer layer is a polymer mainly composed of methyl methacrylate, the inner layer is an acrylic elastic polymer. The portion is dyed and observed as particles having a single layer structure. Further, the rubber elastic particles having a three-layer structure in which the innermost layer is a polymer mainly composed of methyl methacrylate, the intermediate layer is an acrylic elastic polymer, and the outermost layer is a polymer mainly composed of methyl methacrylate. When is used, the center part of the innermost layer particle is not dyed, and only the acrylic elastic polymer part of the intermediate layer is dyed and observed as a two-layered particle.

  In the present specification, the number average particle diameter of the rubber elastic particles is, as described above, when the rubber elastic particles are mixed with the base resin and the cross section is dyed with ruthenium oxide, and is dyed in a substantially circular shape. It is the number average value of the diameters of the parts observed in FIG.

  In the acrylic film, the blending amount of the rubber elastic particles is not particularly limited. For example, 25 to 45% by mass of rubber elastic particles having a number average particle diameter of 10 to 300 nm are blended in a transparent acrylic resin. Those are preferred.

  The acrylic resin may be produced, for example, by obtaining rubber elastic particles and then polymerizing a monomer as a raw material of the acrylic resin in the presence thereof to produce a base acrylic resin, or rubber. After obtaining the elastic particles and the acrylic resin, they may be produced by mixing them by melt kneading or the like.

  The glass transition temperature Tg of the acrylic resin is preferably in the range of 80 to 120 ° C. Further, the acrylic resin preferably has a high surface hardness when formed into a film, specifically, a pencil hardness (load of 500 g, conforming to JIS K5600-5-4) of B or more.

  The acrylic resin film preferably has a flexural modulus (JIS K7171) of 1500 MPa or less from the viewpoint of the flexibility of the acrylic resin. The flexural modulus is more preferably 1300 MPa or less, and still more preferably 1200 MPa or less. This bending elastic modulus varies depending on the type and amount of acrylic resin and rubber elastic particles in the acrylic resin film. For example, the bending elastic modulus generally decreases as the content of rubber elastic particles increases. In addition, the flexural modulus is generally smaller when an acrylic resin is a copolymer of alkyl methacrylate and alkyl acrylate than a homopolymer of alkyl methacrylate.

  In addition, the elastic elastic polymer particles having the two-layer structure are generally used as the elastic rubber particles, rather than the acrylic elastic polymer particles having the two-layer structure. In general, the flexural modulus is smaller when the acrylic elastic polymer particles having a layer structure are used. Further, in the rubber elastic body particles, as the average particle diameter of the rubber elastic body is smaller or the amount of the rubber elastic body is larger, the bending elastic modulus is generally smaller. Therefore, it is preferable to adjust the kind and amount of acrylic resin and rubber elastic body particles within the predetermined range so that the flexural modulus is 1500 MPa or less.

  When the acrylic film has a multilayer structure, the layer that can exist other than the layer of the acrylic resin composition is not particularly limited in composition, for example, an acrylic resin that does not contain rubber elastic particles or a layer of the composition. Alternatively, it may be a layer made of an acrylic resin in which the content of the rubber elastic body particles and the average particle diameter of the rubber elastic body in the rubber elastic body particles are not specified above.

  Typically, it has a two-layer or three-layer structure, for example, a two-layer structure including an acrylic resin layer / an acrylic resin not containing rubber elastic particles or a layer of the composition thereof, or an acrylic resin. A three-layer structure comprising an acrylic resin not containing rubber elastic particles or a composition layer / acrylic resin composition layer may be employed. What is necessary is just to let the surface of the layer of an acrylic resin composition be a bonding surface with a polarizer in the multilayer acrylic film.

  Moreover, when making an acrylic film into a multilayer structure, you may mutually differ content of rubber elastic-body particle | grains or each layer of the said compounding agent. For example, a layer containing an ultraviolet absorber and / or an infrared absorber and a layer not containing an ultraviolet absorber and / or an infrared absorber may be laminated with this layer interposed therebetween. Further, the content of the ultraviolet absorber in the acrylic resin composition layer may be higher than the content of the ultraviolet absorber in the acrylic resin or the composition layer containing no rubber elastic particles, Specifically, the former is preferably 0.5 to 10% by mass, more preferably 1 to 5% by mass, and the latter is preferably 0 to 1% by mass, more preferably 0 to 0.5% by mass. Thus, ultraviolet rays can be efficiently blocked without deteriorating the color tone of the polarizing plate, and a decrease in the degree of polarization during long-term use can be prevented.

  The acrylic film may be non-oriented or unstretched, or may be stretched. When the stretching treatment is not performed, the total film thickness of the polarizing plate is likely to be increased because the film thickness is increased, but on the other hand, the handling property of the acrylic film is improved due to the thick film thickness. Such an acrylic film can be obtained from an unstretched film (raw film) obtained by forming an acrylic resin composition. On the other hand, when stretched, retardation is easily developed, but stretching has the advantage that the thickness of the acrylic film is reduced and the rigidity is improved. The stretched film can be produced by stretching an unstretched film by an arbitrary method.

  The acrylic resin can be formed into an unstretched film by any method. This unstretched film is preferably transparent and substantially free of in-plane retardation. Examples of the film forming method include an extrusion method in which a molten resin is extruded to form a film, and a solvent cast method in which a solvent dissolved in an organic solvent is cast on a flat plate and then the solvent is removed to form a film. Etc. can be adopted.

  As a specific example of the extrusion molding method, for example, there is a method of forming a film in a state where the acrylic resin composition is sandwiched between two rolls. At this time, by varying the rigidity of the roll surface, it is possible to make one surface of the acrylic resin film smooth and the other surface rough.

  As a specific example of the extrusion molding method, for example, there is a method of forming a film in a state where the acrylic resin composition is sandwiched between two metal rolls. In this case, the metal roll is preferably a mirror roll. Thereby, the unstretched film excellent in surface smoothness can be obtained. In addition, when obtaining the thing of multilayer structure as an acrylic film, what is necessary is just to film-form the said acrylic resin composition after multilayer extrusion with another acrylic resin composition. The thickness of the unstretched film thus obtained is preferably in the range of 5 to 200 μm, more preferably in the range of 10 μm to 85 μm.

≪Liquid crystal display device≫
By using the polarizing plate on which the retardation film of the present invention is bonded to a liquid crystal display device, the liquid crystal display device of the present invention excellent in various visibility can be produced.

  The polarizing plate of the present invention can be used for liquid crystal display devices of various drive systems such as STN, TN, OCB, HAN, VA (MVA, PVA), IPS, OCB and the like. A VA (MVA, PVA) type liquid crystal display device is preferable.

  In the liquid crystal display device, usually two polarizing plates, a polarizing plate on the viewing side and a polarizing plate on the backlight side, are used, but it is also preferable to use the polarizing plate of the present invention as both polarizing plates. It is also preferable to use as. In particular, the polarizing plate of the present invention is preferably used as a viewing-side polarizing plate that directly touches the external environment, and in this case, the retardation film of the present invention is preferably disposed on the liquid crystal cell side.

  Further, the polarizing plate on the backlight side may be a polarizing plate other than the present invention. In that case, both sides of the polarizer may be, for example, a commercially available cellulose ester film (for example, Konica Minoltack KC8UX, KC5UX, KC4UX, KC8UCR3, KC4SR, KC4BR, KC4CR, KC4DR, KC4FR, KC4KR, KC8UY, KC6UY, KC4UY, KC4UE, KC8UE, KC8UY-HA, KC2UA, KC4UA, KC6UA, KC4UAH, KC2UAH, KC4UAH, KC4UAH, KC4UAH, KC4UAH T60UZ, Fujitac T80UZ, Fujitac TD80UL, Fujitac TD60UL, Fujitac TD40UL, Fujitac R02, Fujitac R06, Fujifilm Corporation Polarizing plate stuck etc.) is preferably used.

  Moreover, as the polarizing plate on the backlight side, the retardation film of the present invention is used on the liquid crystal cell side of the polarizer, and the above-mentioned commercially available retardation film, polyester film, acrylic film, polycarbonate film, or cycloolefin is used on the opposite surface. A polarizing plate bonded with a polymer film can also be preferably used.

  By using the polarizing plate of the present invention, it is possible to obtain a liquid crystal display device excellent in visibility such as display unevenness and front contrast, even in the case of a large-screen liquid crystal display device having a screen size of 30 or more.

  The backlight of the liquid crystal display device of the present invention is preferably a flat type backlight, and either a flat type fluorescent lamp, a flat type light emitting diode (LED) lamp, or an organic EL element substrate is used. It is preferable. Among them, the polarizing plate using the retardation film of the present invention is suitably provided in a large-screen liquid crystal display device having a white light emitting LED backlight, and color due to light leakage of blue light from an oblique direction of the liquid crystal display device. It is possible to provide a liquid crystal display device in which the occurrence of shift is reduced and there is no stripe-shaped unevenness and visibility such as front contrast is improved.

  The LED lamp is an LED backlight for a color liquid crystal display device having a red (R) LED, a green (G) LED, and a blue (B) LED. For example, the peak wavelength of the red (R) LED is 610 nm. That is the above, and the peak wavelength of the green (G) LED is in the range of 530 ± 10 nm, and the peak wavelength of the blue (B) LED is preferably 480 nm or less. Examples of types of green (G) LEDs having a peak wavelength within the above range include DG1112H (manufactured by Stanley Electric Co., Ltd.), UG1112H (manufactured by Stanley Electric Co., Ltd.), and E1L51-3G (manufactured by Toyoda Gosei Co., Ltd.). E1L49-3G (manufactured by Toyoda Gosei Co., Ltd.), NSPG500S (manufactured by Nichia Chemical Co., Ltd.), and the like. The types of LEDs used as red (R) LEDs include, for example, FR1112H (manufactured by Stanley Electric Co., Ltd.), FR5366X (manufactured by Stanley Electric Co., Ltd.), NSTM515AS (manufactured by Nichia Corporation), GL3ZR2D1COS (Sharp) GM1JJ35200AE (manufactured by Sharp Corporation) and the like. As types of LEDs used as blue (B) LEDs, DB1112H (manufactured by Stanley Electric Co., Ltd.), DB5306X (manufactured by Stanley Electric Co., Ltd.), E1L51-3B (manufactured by Toyoda Gosei Co., Ltd.), E1L4E-SB1A (manufactured by Stanley Electric Co., Ltd.) Toyoda Gosei Co., Ltd.), NSPB630S (Nichia Chemical Co., Ltd.), NSPB310A (Nichia Chemical Co., Ltd.), and the like.

  A white backlight can be formed by combining the above-described three-color LEDs. Alternatively, an LED that emits white light can also be used directly. As an example of a configuration of a liquid crystal display device using an LED lamp, a configuration example described in FIG. 9 of JP-A-2006-148036 can be referred to.

  Moreover, as another white LED, a light-emitting device including a light-emitting light source and, for example, a β-type sialon phosphor is also preferable. In particular, by irradiating ultraviolet light or visible light containing a wavelength of 240 to 480 nm as an excitation source, the β-type sialon phosphor emits green narrow band light, so an ultraviolet LED or a blue LED and, if necessary, In combination with a red phosphor and / or a blue phosphor, white light can be easily obtained.

  Further, as an example of a white LED using a β-type sialon phosphor, an LED is manufactured by using a known method described in JP-A-5-152609, JP-A-7-99345, JP-A-2927279, or the like. can do. In this case, the light-emitting light source is preferably an ultraviolet LED or a blue LED that emits light having a wavelength of 240 to 480 nm, particularly preferably a blue LED that emits light having a wavelength of 440 to 470 nm. Examples of these light emitting elements include GaN and InGaN. The light emitting light source that emits light of a predetermined wavelength can be obtained by adjusting the composition.

In particular, a narrow-band green phosphor such as a β-sialon phosphor uses a blue LED as an excitation source and is combined with a red phosphor having an emission wavelength peak of 600 to 700 nm, such as CaAlSiN ₃ : Eu. It is suitable for a white LED for a backlight of an image display device excellent in color reproducibility.

  Since these white LEDs have little decrease in luminance at high temperature, the light emitting device using the white LED has small decrease in luminance and chromaticity deviation, does not deteriorate even when exposed to high temperature, and has excellent heat resistance and an oxidizing atmosphere. In addition, since it is excellent in long-term stability in a moisture environment, the light-emitting device has an excellent feature in that it has high brightness and a long life.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

Example 1
<Preparation of retardation film 101>
<Fine particle dispersion 1>
Fine particles (Aerosil R812 manufactured by Nippon Aerosil Co., Ltd.) 11 parts by weight Ethanol 89 parts by weight The above was stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin.

<Fine particle addition liquid 1>
The fine particle dispersion 1 was slowly added to the dissolution tank containing methylene chloride with sufficient stirring. Further, the particles were dispersed by an attritor so that the secondary particles had a predetermined particle size. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution 1.

Methylene chloride 99 parts by mass Fine particle dispersion 1 5 parts by mass A main dope having the following composition was prepared. First, methylene chloride and ethanol were added to the pressure dissolution tank. Cellulose acetate C1 having an acetyl group substitution degree of 2.41 was added to a pressure dissolution tank containing a solvent while stirring. This is completely dissolved with heating and stirring. This was designated as Azumi Filter Paper No. The main dope was prepared by filtration using 244.

<Composition of main dope>
Methylene chloride 365 parts by weight Ethanol 50 parts by weight Cellulose acetate (acetyl group substitution degree 2.56, number average molecular weight (Mn
) 65000) 100 parts by mass Nitrogen-containing heterocyclic compound Exemplified Compound No. 176 3 parts by mass Polycondensation ester P2 5 parts by mass Particulate additive liquid 1 1 part by mass The above was put into the sealed main dissolution vessel 1 and dissolved while stirring to prepare a dope.

  On the stainless steel belt support, the solvent was evaporated until the residual solvent amount in the cast (cast) film was 75%, and then peeled off from the stainless steel belt support with a peeling tension of 130 N / m. The peeled retardation film was stretched 30% in the width direction using a tenter while applying heat at 150 ° C. The residual solvent at the start of stretching was 15%.

  Next, drying was completed while the drying zone was conveyed by a number of rollers. The drying temperature was 130 ° C. and the transport tension was 100 N / m. As described above, a retardation film 101 having a dry film thickness of 40 μm was obtained.

<Preparation of retardation films 102 to 125>
In the retardation film 101, the same procedure was performed except that the type of cellulose acetate (acetyl group substitution degree: 2.42 to 2.85), the type of nitrogen-containing heterocyclic compound, and the addition amount were changed as shown in Table 1. The retardation films 102 to 125 were produced.

  In addition, the following H-1 and H-2 were used as a comparative example of a nitrogen-containing heterocyclic compound.

<Preparation of polarizing plates 101-125>
The surface of each retardation film produced above was subjected to alkali saponification treatment. It was immersed in a 1.5 N aqueous sodium hydroxide solution at 55 ° C. for 2 minutes, washed in a water bath at room temperature, and neutralized with 0.1 N 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. Subsequently, 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 polarizer 1 having a thickness of 20 μm. Prepare each of the above alkali saponified retardation films and the same alkali saponified Konica Minolta KC6UA (manufactured by Konica Minolta Co., Ltd.) using a 3% aqueous solution of polyvinyl alcohol (Kuraray PVA-117H) as an adhesive. Then, these saponified surfaces were bonded so that the polarizer was sandwiched therebetween, and polarizing plates were obtained in which the respective retardation films, the polarizer 1, and KC6UA were bonded in this order. Under the present circumstances, it affixed so that the MD direction of each retardation film and the slow axis of KC6UA might become parallel to the absorption axis of a polarizer.

<Production of liquid crystal display devices 101-125>
The polarizing plates on both surfaces of the Sony KDL-40HX720, which are liquid crystal display devices having white LEDs as a backlight, are peeled off in advance, and the prepared polarizing plates 101 to 125 are respectively attached to the glass surfaces of the liquid crystal cells. The both sides were bonded using an acrylic adhesive.

  At that time, the polarizing plate is bonded so that the surface of the retardation film is on the liquid crystal cell side and the absorption axis is directed in the same direction as the polarizing plate previously bonded. The liquid crystal display devices 101 to 125 corresponding to the polarizing plates 101 to 125 were respectively produced.

≪Evaluation≫
<Measurement of wavelength dispersion and retardation value>
The wavelength dispersion of the retardation film was measured by the following procedure.

  The retardation value Rth in the thickness direction of the retardation film was measured at 450 nm and 650 nm in an environment of 23 ° C. and 55% RH using an automatic birefringence meter Axoscan (Axo Scan Mueller Matrix Polarimeter: manufactured by Axometrics). At 10 wavelengths, 10 locations of the retardation film were sampled, each of which was subjected to three-dimensional refractive index measurement, and was calculated from the average values of the obtained refractive indexes nx, ny and nz using the following formula (ii). .

  When the obtained measured value satisfies the following formula 1, it is a retardation film having forward wavelength dispersion.

Formula 1 1.0 ≦ Rth (450) / Rth (650) ≦ 1.2
(Where Rth (450) and Rth (650) are the film thickness directions represented by the following formula (ii) measured using light having wavelengths of 450 nm and 650 nm in an environment of 23 ° C. and 55% RH, respectively. Retardation value Rth (nm).
In addition, the retardation value of the retardation film is an in-plane retardation value (Ro) defined by the following formula (i) at a wavelength of 590 nm in an environment of a temperature of 23 ° C. and a relative humidity of 55%, and the following formula: The retardation value (Rth) in the thickness direction defined by (ii) was measured using an Axoscan manufactured by Axometrics.

Specifically, the retardation film 23 ° C. was prepared, in an environment of 55% RH, subjected to refractive index measurement of the three-dimensional in 10 locations at a wavelength of 590 nm, the refractive indices _{n x,} n y, the _{n z} After obtaining the average value, the retardation value Ro in the in-plane direction and the retardation value Rth in the thickness direction were calculated according to the following formula.

Formula _{(i): Ro = (n} x -n y) × d (nm)
Formula (ii): Rth = {(n _x + n _y ) / 2−n _z } × d (nm)
In [Equation (i) and Formula (ii), n _x represents a refractive index in the direction x in which the refractive index is maximized in the plane direction of the film. n _y, in-plane direction of the film, the refractive index in the direction y perpendicular to the direction x. _nz represents the refractive index in the thickness direction z of the film. d represents the thickness (nm) of the film. ]
<Color change (color shift)>
During black display, changes in chromaticity Δxθ and Δyθ when the viewing angle is tilted from the normal direction of the liquid crystal cell to the center line direction of the transmission axis of the pair of polarizing plates (azimuth angle 45 degrees) are polar angles 0 to 80. Measured between degrees. Here, [Delta] x [theta] = x [theta] -x [theta] 0, [Delta] y [theta] = y [theta] -y [theta] 0, (x [theta] 0, y [theta] 0) is the chromaticity measured in the normal direction of the liquid crystal cell in black display, and (x [theta], y [theta]) is the liquid crystal cell in black display. It is chromaticity measured in a direction in which the viewing angle is tilted from the normal direction to the polar angle θ degree in the direction of the center line of the transmission axis of the pair of polarizing plates.

  The produced liquid crystal display device was allowed to stand for 3 days in an environment of 60 ° C. and 80% RH, then the chromaticity was measured, and the results were evaluated according to the following criteria. The smaller the value, the smaller the color shift.

A: Both Δxθ and Δyθ are 0.03 or less. ○: Both Δxθ and Δyθ exceed 0.03 and are 0.05 or less. Δ: Both Δxθ and Δyθ exceed 0.05 and 0.07 or less. Yes x: Both Δxθ and Δyθ exceed 0.07 <Front contrast>
Each of the manufactured liquid crystal display devices was continuously lit for 1 hour in an environment of 23 ° C. and 55% RH, and then the front contrast was measured.

  For measurement, EZ-Contrast 160D manufactured by ELDIM was used to measure the luminance from the normal direction of the display screen of white display and black display with a liquid crystal display device, and the ratio was defined as the front contrast.

Front contrast = (brightness of white display measured from normal direction of display device) / (brightness of black display measured from normal direction of display device)
The front contrast at any 10 points of the liquid crystal display device was measured and evaluated according to the following criteria.

A: Front contrast is 5000 or more. O: Front contrast is 4500 or more and less than 5000. Δ: Front contrast is 4000 or more and less than 4500. X: Front contrast is less than 4000.
If the peelability of the web from the casting belt is inferior when the retardation film is formed, horizontal streaks are generated in the film.
Each of the manufactured liquid crystal display devices was continuously lit for 1 hour in an environment of 23 ° C. and 55% RH, and then the screen was displayed in black so that the streak was visually evaluated.

◎: No streak is observed at all ○: Somewhat weak streak is observed at the edge of the screen △: Weak streak is observed at several places on the screen ×: Strong streak is clearly observed on the screen ○ In practice ○ The above is acceptable.

  The constitution of the retardation film and the above evaluation results are shown in Table 1 below.

  The retardation film No. of the present invention. 101 to 115 exhibit forward wavelength dispersion with respect to the retardation film of the comparative example, and are excellent in color change, color contrast, front contrast, and stripe generation rate when equipped in a liquid crystal display device of an LED light source. It can be seen that these characteristics are exhibited. In particular, for front contrast, retardation film No. using a compound having a pyrazole ring structure as a nitrogen-containing heterocyclic compound. 101-108 was excellent.

Example 2
The retardation film No. 1 of Example 1 was used. In the preparation of No. 102, retardation film No. was similarly changed except that the film thickness change of the film, the kind change of the nitrogen-containing heterocyclic compound and the comparative compound were added and the constitution shown in Table 2 was adopted. 201-210 were produced. Moreover, it carried out similarly to Example 1, and produced the polarizing plates 201-210 and the liquid crystal display devices 201-210, adding in-plane retardation value Ro, thickness direction retardation value Rth, and the following internal haze evaluation, and implemented. Evaluation similar to Example 1 was performed.

  In addition, the said H-2 and H-3 were used as a comparative example of a nitrogen-containing heterocyclic compound.

<Internal haze>
Cut the sample film into 6cm pieces, apply glycerin on both sides, and sandwich two glass plates (film with micro slide glass product number S9111, made by MATSANAMI) from the front and back, completely with two glass plates and film Was measured in accordance with JIS K7136, and the value obtained by subtracting the haze measured by sandwiching only glycerin between two separately measured glass plates was calculated as the internal haze value of the film. In addition, the measurement of haze was measured using the haze meter (NDH2000 type | mold, Nippon Denshoku Industries Co., Ltd. product).

  The internal haze is for evaluating the turbidity inside the film due to bleed-out of additives and the like after the film production process and film production, and the lower the value, the better.

  The constitution and evaluation results of the retardation film are shown in Table 2 below.

  The retardation film No. of the present invention. 201 to 208 are excellent in color change (color shift), front contrast, and streak generation rate. Moreover, the correlation with the NICS value of a nitrogen-containing heterocyclic compound is seen.

  Among them, as a nitrogen-containing heterocyclic compound, compound No. 1 having a pyrazole ring structure is used. 172, 176, and 185 using retardation film No. Nos. 201 to 203 were results in which the internal haze value was low, and the color change (color shift), the front contrast, and the stripe generation rate were more excellent.

Example 3
The retardation film No. 1 of Example 1 was used. 102, instead of the polycondensed ester P2, additive 1 (sugar ester B-2: benzyl sucrose (a mixture of the sugar residue is exemplified B-2 and the substituents are a1 to a4), average ester substitution degree = 5.5), additive 2 (polycondensation ester exemplified compound 1-15), additive 3 (ultraviolet absorber UV-1: 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) ) Phenyl] -2-benzotriazole) was added in the same manner as shown in Table 3 and the film thickness was changed in the same manner. 301-308 were produced.

  Using the produced retardation film, polarizing plates 301 to 308 and liquid crystal display devices 301 to 308 were produced in the same manner as in Example 1, and the same evaluation as in Example 2 was performed.

  The constitution and evaluation results of the retardation film are shown in Table 3 below.

As an additive, a sugar ester or a polycondensation ester is added, and the film thickness is in the range of 20 to 40 μm. No. 305, 306, and retardation film No. further added with an ultraviolet absorber. No. 308 was a result of better color change (color shift), front contrast, and streak generation rate.
Example 4
A polyester film and an acrylic film were prepared according to the following procedure.

<Polyester film>
(Production Example 1-Polyester A)
When the temperature of the esterification reactor was raised to 200 ° C., 86.4 parts by mass of terephthalic acid and 64.6 parts by mass of ethylene glycol were charged and 0.017 parts by mass of antimony trioxide as a catalyst while stirring. 0.064 parts by mass of magnesium acetate tetrahydrate and 0.16 parts by mass of triethylamine were charged. Next, the pressure was raised and the pressure esterification reaction was carried out under conditions of a gauge pressure of 0.34 MPa and 240 ° C., and then the esterification reaction vessel was returned to normal pressure, and 0.014 parts by mass of phosphoric acid was added. Furthermore, it heated up to 260 degreeC over 15 minutes, and 0.012 mass part of trimethyl phosphate was added. Then, after 15 minutes, dispersion treatment was performed with a high-pressure disperser, and after 15 minutes, the obtained esterification reaction product was transferred to a polycondensation reaction can and subjected to polycondensation reaction at 280 ° C. under reduced pressure.

After completion of the polycondensation reaction, it is filtered through a NASRON filter with a 95% cut diameter of 5 μm, extruded into a strand from a nozzle, and cooled and solidified using cooling water that has been filtered (pore diameter: 1 μm or less) in advance. And cut into pellets. The obtained polyethylene terephthalate resin (A) had an intrinsic viscosity of 0.62 dl / g and contained substantially no inert particles and internally precipitated particles. (Hereafter, abbreviated as PET (A).)
(Production Example 2-Polyester B)
Next, 10 parts by weight of a dried UV absorber (2,2 ′-(1,4-phenylene) bis (4H-3,1-benzoxazinon-4-one), PET (A) containing no particles 90 parts by mass (inherent viscosity is 0.62 dl / g) was mixed, and a polyethylene terephthalate resin (B) containing an ultraviolet absorber was obtained using a kneading extruder (hereinafter abbreviated as PET (B)).

(Production Example 3-Preparation of Adhesive Modified Coating Solution)
A transesterification reaction and a polycondensation reaction are performed by a conventional method, and as a dicarboxylic acid component (based on the whole dicarboxylic acid component) 46 mol% terephthalic acid, 46 mol% isophthalic acid, and 8 mol% sodium 5-sulfonatoisophthalate, A water-dispersible sulfonic acid metal group-containing copolymer polyester resin having a composition of 50 mol% ethylene glycol and 50 mol% neopentyl glycol (relative to the entire glycol component) was prepared as a glycol component. Next, 51.4 parts by mass of water, 38 parts by mass of isopropyl alcohol, 5 parts by mass of n-butyl cellosolve, 0.06 parts by mass of nonionic surfactant were mixed and then heated and stirred. After adding 5 parts by mass of a water-dispersible sulfonic acid metal base-containing copolymer polyester resin and continuing to stir until the resin is no longer agglomerated, the resin water dispersion is cooled to room temperature to obtain a solid content concentration of 5.0% by mass. A uniform water-dispersible copolymerized polyester resin liquid was obtained. Furthermore, after dispersing 3 parts by mass of aggregated silica particles (manufactured by Fuji Silysia Co., Ltd., Silicia 310) in 50 parts by mass of water, 99.46 parts by mass of the water-dispersible copolymerized polyester resin liquid was mixed with water of Silicia 310. 0.54 parts by mass of the dispersion was added, and 20 parts by mass of water was added with stirring to obtain an adhesive modified coating solution.

(Preparation of PET film)
After drying 90 parts by mass of PET (A) resin pellets containing no particles as a raw material for the base film intermediate layer and 10 parts by mass of PET (B) resin pellets containing an ultraviolet absorber at 135 ° C. for 6 hours under reduced pressure (1 Torr) , And supplied to the extruder 2 (for the intermediate layer II layer). Also, the PET (A) was dried by a conventional method and supplied to the extruder 1 (for the outer layer I layer and the outer layer III).
And dissolved. After filtering these two kinds of polymers with a filter medium made of a sintered stainless steel (nominal filtration accuracy of 10 μm particles 95% cut), laminating them in a two-kind / three-layer confluence block, and extruding them into a sheet form from a die, The film was wound around a casting drum having a surface temperature of 30 ° C. using an electrostatic application casting method, and then cooled and solidified to produce an unstretched film. At this time, the discharge amount of each extruder was adjusted so that the ratio of the thicknesses of the I layer, the II layer, and the III layer was 10:80:10.

Next, after applying the above-mentioned adhesiveness-modified coating solution on the both sides of this unstretched PET film by a reverse roll method so that the coating amount after drying becomes 0.096 g / m ² , the coating was dried at 80 ° C. for 20 seconds. .

  The unstretched film on which this coating layer was formed was guided to a tenter stretching machine, and the film was guided to a hot air zone at a temperature of 125 ° C. while being gripped by a clip, and stretched 4.0 times in the width direction. Next, while maintaining the width stretched in the width direction, the film was treated at a temperature of 225 ° C. for 30 seconds and further subjected to a relaxation treatment of 3% in the width direction to obtain a uniaxially oriented polyester film having a film thickness of 60 μm.

<Production of acrylic film>
(Acrylic resin and acrylic elastic polymer particles)
As the acrylic resin, a copolymer having a mass ratio of methyl methacrylate / methyl acrylate of 96/4 was used. Further, as the elastic rubber particles, acrylic elastic polymer particles having a three-layer structure including an innermost layer, an intermediate layer, and an outermost layer were used. In the acrylic elastic polymer particles, the innermost layer is a hard polymer obtained by polymerizing methyl methacrylate with a small amount of allyl methacrylate, the intermediate layer is mainly composed of butyl acrylate, styrene and a small amount of Soft elastic body polymerized using allyl methacrylate, outermost layer is made of a hard polymer polymerized with a small amount of ethyl acrylate in methyl methacrylate, and the average particle size up to the elastic body that is the intermediate layer The diameter is 240 nm.

(Production of acrylic film)
Pellets in which the above acrylic resin and the above acrylic elastic polymer particles were blended at a mass ratio of the former / the latter = 70/30 were melt-kneaded with a twin screw extruder to obtain an acrylic resin composition pellet. The pellets were put into a 65 mmφ single screw extruder, extruded through a T die having a set temperature of 275 ° C., and both sides of the extruded film-like molten resin were polished rolls (cooling rolls) having mirror surfaces set at 45 ° C. And an acrylic film having a thickness of 60 μm was prepared by sandwiching and cooling between a roll and a metal elastic roll (elastic roll) having a high elastic modulus whose surface was formed of a metal material and filled with fluid.

<Preparation of polarizing plate>
(Preparation of polarizer)
In order to form a thin film polarizer by the following steps, a polarizing laminated film was prepared, and the base film was peeled from the polarizing laminated film to obtain a thin film polarizer.

(1) Production of base film A thermoplastic resin and a rubber component were sequentially prepared in the same reaction vessel by a reactor blend method. Specifically, propylene monomer was fed in the gas phase as a first step using a Ziegler-Natta type catalyst to produce a propylene homopolymer as a thermoplastic resin. After stopping the reaction by stopping the propylene monomer feed, the ethylene monomer and the propylene monomer are fed into the reaction vessel as they are in the gas phase as the second step, and the ethylene-propylene copolymer as a rubber component is fed. Propylene homopolymer produced by dispersing ethylene-propylene copolymer, which is a rubber component, in the form of particles was obtained. The ethylene unit content in the copolymer was determined from the material balance during polymerization and found to be 35% by mass. Further, the content of ethylene units in the entire resin (total of thermoplastic resin and rubber component) is determined according to the method described on page 616 of the Polymer Handbook (published by Kinokuniya Shoten in 1995), and the resin is determined from this value. When the content of the ethylene-propylene copolymer in the whole was calculated, it was 29% by mass (that is, the content of the ethylene-propylene copolymer was 40.8% by mass of the thermoplastic resin).

  The obtained mixed resin was melt-kneaded at 250 ° C., and then melt-extruded at a temperature of 280 ° C. with a T die to obtain a base film having a thickness of 100 μm.

(2) Formation of primer layer Polyvinyl alcohol powder (“Z-200” manufactured by Nippon Synthetic Chemical Industry Co., Ltd., average polymerization degree 1100, average saponification degree 99.5 mol%) was dissolved in 95 ° C. hot water, A polyvinyl alcohol aqueous solution having a concentration of 3% by mass was prepared. The resulting aqueous solution was mixed with 5 parts by mass of a crosslinking agent (“SUMIREZ RESIN 650” manufactured by Sumitomo Chemical Co., Ltd.) with respect to 6 parts by mass of the polyvinyl alcohol powder. The obtained mixed aqueous solution is coated on the corona-treated surface of the base film subjected to the corona treatment using a micro gravure coater and dried at 80 ° C. for 10 minutes, whereby a primer layer having a thickness of 0.2 μm. Formed.

(3) Formation of polyvinyl alcohol resin layer Polyvinyl alcohol powder (“PVA124” manufactured by Kuraray Co., Ltd., average polymerization degree 2400, average saponification degree 98.0-99.0 mol%) is dissolved in hot water at 95 ° C. An aqueous polyvinyl alcohol solution having a concentration of 8% by mass was prepared. The obtained aqueous solution was coated on the primer layer using a lip coater, and dried under conditions of 80 ° C. for 2 minutes, 70 ° C. for 2 minutes, and then 60 ° C. for 4 minutes, whereby a base film A laminated film having a polyvinyl alcohol resin layer laminated thereon with a primer layer interposed therebetween was produced. The thickness of the polyvinyl alcohol-based resin layer was 9.8 μm.

(4) Production of stretched film The laminated film was uniaxially stretched 5.8 times at a stretching temperature of 160 ° C. to obtain a stretched film. The obtained stretched film had a thickness of 28.5 μm, and the polyvinyl alcohol-based resin layer had a thickness of 5.0 μm.

(5) Preparation of polarizing laminated film The stretched film was immersed in a 60 ° C. warm bath for 60 seconds, and then immersed in a dyeing solution at 30 ° C., which is an aqueous solution containing iodine and potassium iodide, for about 150 seconds. The system resin layer was dyed, and then the excess iodine solution was washed away with pure water at 10 ° C. Next, it was immersed for 600 seconds in the 76 degreeC bridge | crosslinking solution which is the aqueous solution containing a boric acid and potassium iodide. Thereafter, the film was washed with pure water at 10 ° C. for 4 seconds, and finally dried at 50 ° C. for 300 seconds to obtain a polarizing laminated film. The polyvinyl alcohol resin layer of this polarizing laminate film was peeled from the base film, and the polyvinyl alcohol resin layer was used as the polarizer 2.

(Preparation of UV curable adhesive solution 1)
After mixing the following components, defoaming was performed to prepare an ultraviolet curable adhesive liquid 1. Triarylsulfonium hexafluorophosphate was blended as a 50% propylene carbonate solution, and the solid content of triarylsulfonium hexafluorophosphate was shown below.

3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate 45 parts by mass Epolide GT-301 (alicyclic epoxy resin manufactured by Daicel Chemical Industries)
40 parts by mass 1,4-butanediol diglycidyl ether 15 parts by mass Triarylsulfonium hexafluorophosphate 2.3 parts by mass 9,10-dibutoxyanthracene 0.1 parts by mass 1,4-diethoxynaphthalene 2.0 parts by mass (Preparation of polarizing plate)
Polarizing plates 401 and 402 were prepared according to the following method.

  First, the retardation film No. 1 prepared in Example 3 was used. The surface of 305 was subjected to corona discharge treatment. The corona discharge treatment was performed at a corona output intensity of 2.0 kW and a line speed of 18 m / min. Subsequently, the retardation film No. The prepared ultraviolet curable adhesive liquid 1 was applied to the corona discharge treated surface of 305 with a bar coater so that the film thickness after curing was about 3 μm to form an ultraviolet curable adhesive layer. The polarizer 2 (thickness 5 μm) side of the produced polarizing laminated film was bonded to the obtained ultraviolet curable adhesive layer, and then the base film was peeled off.

  Next, the produced polyester film and acrylic film were each subjected to corona discharge treatment. The conditions of the corona discharge treatment were a corona output intensity of 2.0 kW and a speed of 18 m / min.

  Next, the prepared UV curable adhesive liquid 1 is applied to the corona discharge treated surface of the polyester film and acrylic film with a bar coater so that the film thickness after curing is about 3 μm, and UV curable adhesive is applied. An agent layer was formed.

  A polarizer 2 bonded to one side of the retardation film is bonded to the ultraviolet curable adhesive layer, and the retardation film No. 2 is bonded. A laminate in which 305 / ultraviolet curable adhesive layer / polarizer 2 / ultraviolet curable adhesive layer / polyester film or acrylic film was laminated was obtained. At that time, the retardation film and the acrylic film were bonded so that the slow axis of the acrylic film and the absorption axis of the polarizer were orthogonal to each other.

From both sides of this laminate, using a UV irradiation device with a belt conveyor (the lamp uses a D bulb manufactured by Heraeus, Noblelight, Fusion, and Ubui Systems), so that the integrated light quantity becomes 750 mJ / cm ^2. Were irradiated with ultraviolet rays to cure the respective ultraviolet curable adhesive layers, and polarizing plates 401 and 402 having a total film thickness of 91 μm described in Table 4 were produced.

(Production of liquid crystal display devices 401, 402, and 403)
The polarizing plates on both surfaces of SONY KDL-40HX720 that had been bonded in advance were peeled off, and the prepared polarizing plate 401 was bonded to both surfaces of the glass surface of the liquid crystal cell using an acrylic pressure-sensitive adhesive.

  At that time, the direction of bonding of the polarizing plate was determined as retardation film No. The liquid crystal display device 401 corresponding to the polarizing plates 401 and 402 is arranged so that the surface of 305 is on the liquid crystal cell side and the absorption axis is directed in the same direction as the polarizing plate bonded in advance. And 402 were produced.

  Next, using the polarizing plate 305 produced in Example 3, using the KDL-52W5 made by a liquid crystal display device SONY using a cold cathode tube as the backlight, the polarizing plates on both sides that were bonded in advance were peeled off. The polarizing plate 305 was similarly bonded to both surfaces of the glass surface of the liquid crystal cell.

  At that time, the direction of bonding of the polarizing plate was determined as retardation film No. A liquid crystal display device 403 was manufactured in such a manner that the surface of 305 was on the liquid crystal cell side and the absorption axis was directed in the same direction as the polarizing plate bonded in advance.

  For each of the liquid crystal display devices 401, 402, and 403 produced as described above, each evaluation of color change (color shift) and front contrast was performed in the same manner as in Example 3.

  Table 4 shows configurations of the polarizing plate and the liquid crystal display device and the evaluation results.

  From the results in Table 4, the retardation film of the present invention is provided in a liquid crystal display device using a white LED backlight, whereby a polarizing plate excellent in color change (color shift) and front contrast, and a liquid crystal display device It can be seen that can be provided.

  Moreover, the liquid crystal display device 401,402 which comprised the polarizing plate 401 and 402 using the retardation film of this invention and the thin film polarizer which used the polyester film or the acrylic film for the protective film used the white LED backlight. When provided in a liquid crystal display device, the color change (color shift) and front contrast were superior. Further, even when the liquid crystal display devices 401 and 402 were placed in a high temperature and high humidity environment such as 60 ° C. and 80% RH for 3 days, the temporal change of the front contrast was smaller than that of the liquid crystal display device 305.

  The retardation film of the present invention can reduce the occurrence of color shift due to light leakage of blue light from an oblique direction of a liquid crystal display device equipped with a white LED backlight, and due to deterioration of peelability on a web belt. Since it has an effect of improving visibility by improving the occurrence of horizontal rows, it is suitably used as an optical film for polarizing plates and liquid crystal display devices.

DESCRIPTION OF SYMBOLS 1 Melting pot 3, 6, 12, 15 Filter 4, 13 Stock pot 5, 14 Liquid feed pump 8, 16 Conduit 10 Ultraviolet absorber preparation pot 20 Merge pipe 21 Mixer 30 Pressure die 31 Metal belt 32 Web 33 Peeling Position 34 Tenter stretching device 35 Drying device 41 Feeding pot 42 Stock pot 43 Pump 44 Filter

Claims (10)

Cellulose acetate having an acetyl group substitution degree in the range of 2.56 to 2.70, and at least one nitrogen-containing heterocyclic compound having a pyrrole ring, a pyrazole ring, a triazole ring, or an imidazole ring, and A retardation film, wherein retardation in the film thickness direction exhibits wavelength dispersion satisfying the following formula 1.
Formula 1 1.0 ≦ Rth (450) / Rth (650) ≦ 1.2
(Where Rth (450) and Rth (650) are the film thickness directions represented by the following formula (ii) measured using light having wavelengths of 450 nm and 650 nm in an environment of 23 ° C. and 55% RH, respectively. Represents the retardation value Rth (nm).
Formula (ii) Rth = {(n _x + _ny ) / 2−n _z } × d
However, n _x represents a refractive index in the direction x in which the refractive index is maximized in the plane direction of the optical film. n _y in-plane direction of the optical film, the refractive index in the direction y perpendicular to the direction x. _nz represents the refractive index in the thickness direction z of the film. d represents the thickness (nm) of the optical film. )   The retardation film according to claim 1, wherein the nitrogen-containing heterocyclic compound is a compound having a pyrazole ring, a triazole ring, or an imidazole ring. The retardation film according to claim 1, wherein the nitrogen-containing heterocyclic compound is a compound having a structure represented by the following general formula (3).

(In the formula, A represents a pyrazole ring. Ar ₁ and Ar ₂ each represent an aromatic hydrocarbon ring or an aromatic heterocyclic ring and may have a substituent. R ₁ represents a hydrogen atom, an alkyl group, or an acyl group. Represents a sulfonyl group, an alkyloxycarbonyl group, or an aryloxycarbonyl group, q represents 1 or 2, and n and m represent an integer of 1 to 3.) Furthermore, it contains at least 1 sort (s) of sugar ester or the polycondensation ester which has a structure represented by following General formula (4), The phase difference as described in any one of Claim 1- Claim 3 characterized by the above-mentioned. the film.
Formula _{(4): B 3 - (} G 2 -A) n -G 2 -B 4
(In the formula, B ₃ and B ₄ each independently represent an aliphatic or aromatic monocarboxylic acid residue or a hydroxy group. G ₂ represents an alkylene glycol residue having 2 to 12 carbon atoms, or 6 to 6 carbon atoms. 12 represents an aryl glycol residue having 12 carbon atoms or an oxyalkylene glycol residue having 4 to 12 carbon atoms, and A represents an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms or an aryl dicarboxylic acid residue having 6 to 12 carbon atoms. N represents an integer of 1 or more.)   The retardation film according to any one of claims 1 to 4, wherein the film thickness is in a range of 20 to 40 µm.   The retardation film according to any one of claims 1 to 5, further comprising an ultraviolet absorber.   The retardation film as described in any one of Claim 1- Claim 6 is bonded with the polarizer using the water paste or the active energy ray hardening adhesive, The polarizing plate characterized by the above-mentioned.   A polyester film or an acrylic film is bonded to the polarizer using a water glue or an active energy ray-curable adhesive on the surface opposite to the surface on which the retardation film of the polarizer is bonded. The polarizing plate according to claim 7, wherein:   A liquid crystal display device comprising the polarizing plate according to claim 7 or 8.   The liquid crystal display device according to claim 9, further comprising a light emitting diode that emits white light as a backlight.

Images