JP2017072775A - Phase difference film, polarizing plate, and liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a phase difference film that has good brittleness and good saponification suitability, and can suppress a variation in retardation due to a variation in humidity and temperature.SOLUTION: An optical film 13 as a phase difference film is a lamination type phase difference film having skin layers 22 and 23 provided on both sides of a core layer 21. The core layer 21 includes an acetyl cellulose resin having an acetyl group substitution degree of 2.4 or more and 2.6 or less, and a nitrogen-containing heterocyclic compound as a retardation enhancer. The skin layers 22 and 23 include an acetyl cellulose resin having an acetyl group substitution degree of larger than 2.6 and 2.9 or less. The above-mentioned nitrogen-containing heterocyclic compound includes a pyrazole compound.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a retardation film applicable to, for example, a vertical alignment (VA) liquid crystal display device, a polarizing plate using the retardation film, and a liquid crystal display device using the polarizing plate. Is.

  In recent years, in the transportation of liquid crystal display devices, simplification of packaging has been promoted from the viewpoint of cost reduction. For this reason, condensation is likely to occur during conveyance. When dew condensation occurs during conveyance, the retardation film used for the polarizing plate of the liquid crystal display device absorbs moisture, thereby changing the retardation (retardation Ro in the in-plane direction and retardation Rth in the thickness direction). Since retardation variation causes display unevenness, a retardation film with little retardation variation due to moisture has been demanded.

  In this regard, for example, in Patent Document 1, a retardation film (polymer film) is formed by adding a pyrimidine-based compound to an acetyl cellulose resin (diacetyl cellulose resin) having an acetyl group substitution degree of about 2.4. In addition, the retardation fluctuation accompanying the humidity fluctuation is suppressed. Patent Document 1 also discloses that retardation may be adjusted by laminating a plurality of polymer films.

Japanese Patent Laying-Open No. 2015-134938 (see paragraphs [0005], [0006], [0216], [0274], etc.)

  The diacetyl cellulose resin has good brittleness and can be made into a thin film. However, since it is a hydrophilic resin, it has low saponification suitability. Here, brittleness refers to the property of breaking an object when it is subjected to external force before it deforms so much that the better the brittleness, the less brittle and the better the mechanical strength. The saponification suitability refers to suitability for alkali saponification treatment when producing a polarizing plate. For example, in alkali saponification treatment, when a part of the retardation film elutes into the saponification solution and causes contamination of the saponification solution, the saponification suitability is low. When contamination of the liquid can be suppressed, saponification suitability is high.

  When a diacetyl cellulose resin is used for the retardation film, a device for increasing the saponification suitability is required. However, Patent Document 1 does not make any study to improve the saponification suitability. Further, as in Patent Document 1, it has been found that when a pyrimidine compound is added to a diacetyl cellulose resin, retardation variation occurs when not only humidity but also temperature varies.

  The present invention has been made in order to solve the above-described problems, and the purpose thereof is a retardation film that has good brittleness, good saponification suitability, and can suppress retardation fluctuation due to wet heat fluctuation. It is providing the polarizing plate using a phase difference film, and the liquid crystal display device using the polarizing plate.

  The above object of the present invention is achieved by the following configurations.

（式中、Ａはピラゾール環を表し、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し、ｑは１〜２の整数を表し、ｎ及びｍは１〜３の整数を表す。） 1. A laminated type retardation film in which skin layers are provided on both sides of a core layer,
The core layer includes an acetyl cellulose resin having an acetyl group substitution degree of 2.4 or more and 2.6 or less, and a nitrogen-containing heterocyclic compound as a retardation increasing agent,
The skin layer includes an acetyl cellulose resin having an acetyl group substitution degree of greater than 2.6 and 2.9 or less,
The said nitrogen-containing heterocyclic compound contains the pyrazole type compound which has a structure represented with the following general formula, The retardation film characterized by the above-mentioned.

(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. A group, a sulfonyl group, an alkyloxycarbonyl group, or an aryloxycarbonyl group, q represents an integer of 1 to 2, and n and m represent an integer of 1 to 3).

  2. 2. The retardation film as described in 1 above, wherein the pyrazole compound is 5,5 ′-(1,3-phenylene) bis (3-phenyl-1H-pyrazole).

  3. 3. The retardation film as described in 1 or 2 above, wherein the total film thickness is from 20 μm to 40 μm.

  4). 4. The retardation film as described in any one of 1 to 3 above, which comprises a sugar ester compound.

  5. 5. A polarizing plate comprising the retardation film according to any one of 1 to 4 and a polarizer.

  6). 6. A liquid crystal display device comprising the polarizing plate according to 5 and a liquid crystal cell.

7). The polarizing plate is located on the viewing side with respect to the liquid crystal cell,
7. The liquid crystal display device according to 6, wherein the retardation film of the polarizing plate is located on the liquid crystal cell side with respect to the polarizer.

  According to the configuration of the retardation film, the brittleness is good, the saponification suitability is good, and the retardation fluctuation due to wet heat fluctuation can be suppressed.

1 is a cross-sectional view illustrating a schematic configuration of a liquid crystal display device according to an embodiment of the present invention. It is sectional drawing which shows the detailed structure of the optical film as a phase difference film used for the polarizing plate of the said liquid crystal display device. It is explanatory drawing which shows typically an example of the apparatus which manufactures the said retardation film.

  An embodiment of the present invention will be described below with reference to the drawings. In the present specification, when the numerical range is expressed as A to B, the numerical value range includes the values of the lower limit A and the upper limit B. The present invention is not limited to the following contents.

[Liquid Crystal Display]
FIG. 1 is a cross-sectional view showing a schematic configuration of a vertical alignment type (VA type) liquid crystal display device 1 according to the present embodiment. The liquid crystal display device 1 includes a liquid crystal display panel 2 and a backlight 3. The backlight 3 is a light source for illuminating the liquid crystal display panel 2.

  The liquid crystal display panel 2 is configured by disposing a polarizing plate 5 on the viewing side of a liquid crystal cell 4 driven by the VA method and disposing a polarizing plate 6 on the backlight 3 side. The liquid crystal cell 4 is formed by sandwiching a liquid crystal layer between a pair of transparent substrates (not shown). The liquid crystal cell 4 has a so-called color filter on array (COA) structure in which a color filter is disposed on a transparent substrate on the backlight 3 side with respect to the liquid crystal layer, that is, on a substrate on the TFT (Thin Film Transistor) formation side. However, a liquid crystal cell in which a color filter is arranged on a transparent substrate on the viewing side with respect to the liquid crystal layer may be used.

  The polarizing plate 5 includes a polarizer 11 and optical films 12 and 13. The polarizer 11 transmits predetermined linearly polarized light. The optical film 12 is a protective film disposed on the viewing side of the polarizer 11. The optical film 13 is a protective film / retardation film disposed on the backlight 3 side (liquid crystal cell 4 side) of the polarizer 11. The polarizing plate 5 is attached to the viewing side of the liquid crystal cell 4 via an adhesive layer 7. That is, the polarizing plate 5 is bonded to the liquid crystal cell 4 so that the polarizing film 5 is positioned on the viewing side with respect to the liquid crystal cell 4 and the optical film 13 is positioned on the liquid crystal cell 4 side with respect to the polarizer 11.

  The polarizing plate 6 includes a polarizer 14 and optical films 15 and 16. The polarizer 14 transmits predetermined linearly polarized light. The optical film 15 is a protective film disposed on the viewing side of the polarizer 14 and can also function as a retardation film. The optical film 16 is a protective film disposed on the backlight 3 side of the polarizer 14. Such a polarizing plate 6 is attached to the backlight 3 side of the liquid crystal cell 4 via an adhesive layer 8. Note that the viewing-side optical film 15 may be omitted, and the polarizer 14 may be in direct contact with the adhesive layer 8. The polarizer 11 and the polarizer 14 are arranged so as to be in a crossed Nicols state.

  The retardation film of this embodiment can be used, for example, as the optical film 13 of the polarizing plate 5 or the optical film 15 of the polarizing plate 6.

  FIG. 2 is a cross-sectional view showing a detailed configuration of the optical film 13 as the retardation film of the present embodiment. The optical film 13 is a so-called laminated type retardation film in which skin layers 22 and 23 are provided on both sides (front side and back side) of the core layer 21. Any one of the skin layers 22 and 23 may be bonded to the polarizer 11 (see FIG. 1).

（式中、Ａはピラゾール環を表し、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し、ｑは１〜２の整数を表し、ｎ及びｍは１〜３の整数を表す。） The core layer 21 includes an acetyl cellulose resin (diacetyl cellulose resin) having an acetyl group substitution degree of 2.4 or more and 2.6 or less, and a nitrogen-containing heterocyclic compound as a retardation increasing agent. The skin layers 22 and 23 each include an acetyl cellulose resin (triacetyl cellulose resin) having an acetyl group substitution degree of greater than 2.6 and less than or equal to 2.9. The nitrogen-containing heterocyclic compound includes a pyrazole compound having a structure represented by the following general formula.

(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. A group, a sulfonyl group, an alkyloxycarbonyl group, or an aryloxycarbonyl group, q represents an integer of 1 to 2, and n and m represent an integer of 1 to 3).

  The triacetyl cellulose resin contained in the skin layers 22 and 23 has a higher degree of acetyl group substitution than the diacetyl cellulose resin (because the number of OH groups exhibiting hydrophilicity is small), and therefore is less hydrophilic than the diacetyl cellulose resin. For this reason, the triacetyl cellulose resin has higher saponification suitability than diacetyl cellulose. That is, in the alkali saponification treatment when producing the polarizing plate, a part of the triacetyl cellulose resin is not easily eluted into the saponification solution.

  On the other hand, the diacetyl cellulose resin contained in the core layer 21 has a higher hydrophilicity than the triacetyl cellulose resin and thus has low saponification suitability, but the core layer 21 is sandwiched between the skin layers 22 and 23 from both sides. There is no direct contact with the saponification solution, and a part of the diacetylcellulose resin is not easily eluted into the saponification solution.

  Therefore, as described above, the core layer 21 containing the diacetyl cellulose resin is sandwiched between the skin layers 22 and 23 containing the triacetyl cellulose resin, so that the saponification suitability of the entire film is improved and the contamination of the saponification solution is reduced. Can be suppressed.

  Moreover, the diacetyl cellulose resin has good brittleness and excellent mechanical strength. Therefore, when the optical film 13 as the retardation film contains the diacetyl cellulose resin (core layer 21), the brittleness of the entire film becomes good, and the overall film thickness can be reduced and the productivity of the thin film can be improved. it can.

  The core layer 21 contains a nitrogen-containing heterocyclic compound as a retardation increasing agent, and the nitrogen-containing heterocyclic compound contains the pyrazole compound described above. The pyrazole-based compound is a compound having a function as a retardation increasing agent. However, since the core layer 21 includes the pyrazole-based compound, the retardation due to wet heat fluctuation (the retardation Ro in the in-plane direction and the retardation Rth in the thickness direction). It was found from the results of Examples described later that there is an effect of suppressing the fluctuation.

  Therefore, according to the above configuration, it is possible to realize a retardation film that has good brittleness, can be thinned, can improve saponification suitability, and can suppress retardation fluctuation due to wet heat fluctuation.

  Further, since the triacetyl cellulose resin has a large retardation fluctuation due to moisture absorption, if the core layer 21 and the skin layers 22 and 23 all contain the triacetyl cellulose resin, the retardation film due to moisture absorption becomes large as a whole retardation film. . For this reason, when the retardation film is applied to a liquid crystal display device, display unevenness (water unevenness) due to retardation fluctuation due to moisture absorption occurs. Since a part of the retardation film (core layer 21) contains a diacetyl cellulose resin that is a resin having a different degree of substitution from the triacetyl cellulose resin of the skin layers 22 and 23, the retardation film as a whole absorbs moisture. Retardation fluctuation due to can be suppressed. As a result, the occurrence of water unevenness can be suppressed.

  The above-mentioned pyrazole compound may be 5,5 '-(1,3-phenylene) bis (3-phenyl-1H-pyrazole). The above compound is a representative example of a pyrazole compound, and the above-described effects can be obtained in a configuration using this compound.

  The optical film 13 as the retardation film of this embodiment desirably has a total film thickness of 20 μm or more and 40 μm or less. When the optical film 13 becomes a thin film, the skin layers 22 and 23 containing a triacetyl cellulose resin also become a thin film. The triacetyl cellulose resin has a large retardation fluctuation due to moisture absorption, so that the skin layers 22 and 23 become thin, so that the retardation fluctuation due to moisture absorption of the entire film can be further suppressed. Unevenness can be further suppressed. In addition, since the optical film 13 is a thin film, a thin polarizing plate 5 can be realized, which can contribute to the thinning of the liquid crystal display device 1.

  The optical film 13 as the retardation film of this embodiment desirably contains a sugar ester compound. The sugar ester compound may be contained in the core layer 21 or in the skin layers 22 and 23. Since the sugar ester compound is a water-resistant additive, the hydrophilicity of the entire film is lowered, thereby further improving the saponification suitability.

  Of course, the configuration of the optical film 13 described above can also be applied to the optical film 15 as a retardation film.

  The polarizing plate (for example, polarizing plate 5) of the present embodiment is configured to include the above-described retardation film (for example, optical film 13) and a polarizer (for example, polarizer 11). The retardation film is located on one surface side of the polarizer, and is bonded to the polarizer with, for example, water glue. Since the retardation film of this embodiment is brittle and can be thinned, a thin polarizing plate can be easily realized.

  The liquid crystal display device 1 of the present embodiment includes the above polarizing plate (for example, polarizing plate 5) and the liquid crystal cell 4. The polarizing plate is located on one surface side of the liquid crystal cell 4 and is bonded to the liquid crystal cell 4 via an adhesive layer. Since the retardation film of this embodiment can suppress the retardation fluctuation due to moisture absorption as described above, the liquid crystal display device 1 can suppress the display unevenness due to the retardation fluctuation.

  The polarizing plate may be located on the viewing side with respect to the liquid crystal cell 4, and the retardation film of the polarizing plate may be located on the liquid crystal cell 4 side with respect to the polarizer 11. In the liquid crystal display device 1 in which the polarizing plates are arranged as described above, display unevenness due to the retardation variation can be suppressed.

  Hereinafter, the retardation film of the present embodiment will be described in more detail.

[Cellulose ester resin]
Examples of the cellulose ester resin used in the core layer of the laminated retardation film include acetyl cellulose resins (diacetyl cellulose resins) having an acetyl group substitution degree of 2.4 or more and 2.6 or less. Examples of the cellulose ester resin used for the skin layer of the retardation film include acetyl cellulose resins (triacetyl cellulose resins) having an acetyl group substitution degree of greater than 2.6 and 2.9 or less. In addition, the substitution degree of an acetyl group can be measured according to the provisions of ASTM-D817-96, which is one of the standards formulated and issued by ASTM (American Society for Testing and Materials).

  Examples of cellulose as a raw material for cellulose ester include cotton linter, wood pulp, kenaf and the like, but are not particularly limited thereto. Moreover, the cellulose ester obtained from them can be mixed and used for each arbitrary ratio.

  The weight average molecular weight (Mw) of the cellulose ester-based resin 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 from 160000 to 240,000. Is particularly preferred. If the weight average molecular weight (Mw) of the cellulose ester-based resin is 75000 or more, the self-film-forming property and the adhesion improving effect of the layer containing the cellulose ester-based resin are exhibited, which is preferable.

  The average molecular weight (Mn, Mw) of the cellulose ester-based resin 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.

[Retardation raising agent]
The core layer of the retardation film contains a nitrogen-containing heterocyclic compound. This nitrogen-containing heterocyclic compound is a compound that functions as a retardation increasing agent. The retardation increasing agent refers to a compound having a function of increasing the retardation of the film at the measurement wavelength of 590 nm (particularly the retardation Rth in the thickness direction) as compared with the case where the retardation increasing agent is not added.

When the retardation film contains a retardation increasing agent, a retardation film in which the retardation Ro in the in-plane direction and the retardation Rth in the thickness direction of the retardation film are in the following ranges can be realized.
30 nm <Ro <70 nm
100 nm <Rth <300 nm

The above Ro and Rth are, for example, third order at a measurement wavelength of 590 nm under an environment of a temperature of 23 ° C. and a relative humidity of 55% using an automatic birefringence meter Axoscan (Axo Scan Mueller Matrix Polarimeter: manufactured by Axometrics). From the refractive indexes _nx , _ny , and _nz obtained by performing the original refractive index measurement, it can be calculated based on the following formula.
_{Ro = (n x -n y)} × d (nm)
Rth = {(n _x + _ny ) / 2−n _z } × d (nm)
(Wherein, n _x is .n _y representing the refractive index in the direction x in which the refractive index is maximized in the plane direction of the film represents the refractive index in the direction y perpendicular to the direction x in the plane direction of the film. _nz represents the refractive index in the thickness direction z of the film, and d represents the thickness (nm) of the film.)

  In the present embodiment, a nitrogen-containing heterocyclic compound having a molecular weight in the range of 100 to 800 can be used as a retardation increasing agent. Especially, it is preferable that a nitrogen-containing heterocyclic compound is a compound (pyrazole type compound) of the structure represented by following General formula (1). By using the above compound together with a resin, it is possible to realize a retardation film having Ro and Rth in the above ranges, and it is possible to suppress retardation fluctuation due to wet heat fluctuation.

（式中、Ａはピラゾール環を表し、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し、ｑは１〜２の整数を表し、ｎ及びｍは１〜３の整数を表す。）

(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. A group, a sulfonyl group, an alkyloxycarbonyl group, or an aryloxycarbonyl group, q represents an integer of 1 to 2, and n and m represent an integer of 1 to 3).

The structure of the aromatic hydrocarbon ring or aromatic heterocyclic ring represented by Ar ₁ and Ar ₂ is not limited. For example, a benzene ring, a pyrrole ring, a pyrazole ring, an imidazole ring, a 1,2,3-triazole ring, 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, isothiadiazole ring, etc. Is mentioned.

  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-cyclopentene-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, ben Imidazolyl 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-methoxyethoxy group, etc. ), Aryloxy group (phenoxy group, 2-methylphenoxy group, 4-tert-butylphenoxy) Group, 3-nitrophenoxy group, 2-tetradecanoylaminophenoxy group, etc.), acyloxy group (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, diphenylamino group, etc.), acylamino group (formylamino group, acetylamino group, pivaloylamino group, lauroylamino group, benzoyl) Amino group, alkyl and arylsulfonylamino groups (methylsulfonylamino group, butylsulfonylamino group, phenylsulfonylamino 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-ethylsulfuryl group) Famoyl 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, N-methylcarbamoyl group, N, N-dimethylcarbamoyl group, N, N-di-n) -Octylcarbamoyl group, N- (methylsulfonyl) carbamoyl group, etc.) Each group.

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.

Specific examples of the pyrazole-based compound as the nitrogen-containing heterocyclic compound include compounds having a pyrazole ring among the compounds described in paragraphs [0140] to [0214] of International Publication No. WO2014 / 109350A1, for example. it can. Among them, a compound having the following structure, that is, 5,5 ′-(1,3-phenylene) bis (3-phenyl-1H-pyrazole) is given as a representative example of the pyrazole-based compound. Hereinafter, this compound is also called Exemplified Compound 1.

  The compound having the structure represented by the general formula (1) can be contained in the retardation film by appropriately adjusting the amount. The amount of the compound added is preferably 0.1 to 10% by mass, and particularly preferably 0.5 to 5% by mass with respect to the resin constituting the retardation film. Within this range, retardation fluctuations due to wet heat fluctuations can be suppressed without impairing the mechanical strength of the retardation film.

  In addition, as a method for adding the compound having the structure represented by the general formula (1), it may be added as a powder to a resin forming a retardation film, and after being dissolved in a solvent, the retardation film is formed. It may be added to the resin.

(Synthesis of Exemplified Compound 1)
The exemplified compound 1 described above can be synthesized by the following scheme.

  To 520 ml of dehydrated tetrahydrofuran, 80 g (0.67 mol) of acetophenone and 52 g (0.27 mol) of dimethyl isophthalate were added, and 52.3 g (1.34 mol) of sodium amide was added dropwise little by little with stirring under ice water cooling in a nitrogen atmosphere. did. 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 1.

The ¹ H-NMR spectrum of the obtained exemplary compound 1 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)

[Organic ester]
The retardation film of the present embodiment preferably contains at least one selected from sugar esters (sugar ester compounds), polycondensed esters, and polyhydric alcohol esters as organic esters, and the polycondensed ester has a structure. It is preferable that nitrogen atoms are not contained therein, because when it is cooled in the production line, it liquefies and adheres to the filter, and the bulk of the nitrogen-containing heterocyclic compound filter collection can be reduced. Among these, sugar esters and polycondensed esters are preferable because they function as plasticizers, and thus can reduce film thickness non-uniformity in the film plane during film formation and reduce variations in retardation Rth.

(Sugar ester)
The sugar ester 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. The average ester substitution degree in the sugar ester 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 is not particularly limited, and examples thereof include sugar esters 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 kind of hydroxy group (m) and-(O—C (═O) —R ² ) group in which the number (n) is fixed. It is difficult to isolate as a compound, and it is known that a compound in which several components different in m and n in the formula are mixed is obtained. Accordingly, the number of hydroxy groups (m), - (O- C (= O) -R 2) is important performance as a mixture in the number (n) has changed each group, the retardation film of the present embodiment In this case, 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.

  Although the specific example of the compound which has the monosaccharide residue of the sugar ester represented by general formula (A) below is shown, it is not limited to these illustrated compounds.

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

  Although the specific example of the compound which has the disaccharide residue of the sugar ester represented with general formula (A) below is shown, it is not limited to these illustrated 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.

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

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

<Synthesis Example: Synthesis Example of Sugar Ester Represented by Formula (A)>
Below, the synthesis example of sugar ester 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 in the range of 0.1 to 20% by mass, and in the range of 1 to 15% by mass with respect to the resin (for example, cellulose acylate) constituting the optical film. Is more preferable.

  As the sugar ester, those having a hue of 10 to 300 are preferred, and those having 10 to 40 are preferred.

(Polycondensed ester)
In the retardation film of this embodiment, it is preferable to use a polycondensation ester having a structure represented by the following general formula (2) as the organic ester. The polycondensed ester is preferably contained in the range of 1 to 30% by mass, more preferably in the range of 5 to 20% by mass with respect to the resin constituting the retardation film because of its plastic effect. .

General formula (2)
_{B 3 - (G 2 -A)} n -G 2 -B 4
In the general formula (2), 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.

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.

  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 (2) 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 (2) 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 (2) 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.

  In the present embodiment, the weight average molecular weight of the polycondensed ester 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 (2) is shown, it is not limited to this.

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

  The polyhydric alcohol ester is a compound comprising an ester of a divalent 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 embodiment is represented by the following general formula (3).

Formula _{(3) 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 hydroxyl group.

  Examples of preferred polyhydric alcohols include, but are not limited to, the following.

  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 are 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 preferable because it is less likely to volatilize, and a lower molecular weight is preferable in terms of moisture permeability and compatibility with cellulose acylate.

  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 is preferably contained in the range of 0.5 to 5% by mass relative to the retardation film, more preferably in the range of 1 to 3% by mass, and in the range of 1 to 2% by mass. It is particularly preferable to contain.

  The polyhydric alcohol ester can be synthesized according to a conventionally known general synthesis method.

[Other additives]
<Phosphate ester>
The retardation film of this embodiment can also contain a phosphate ester. 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 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>
Further, glycolic acid esters (glycolate compounds) can be used as one kind of polyhydric alcohol esters. Although it does not specifically limit as a glycolate compound, Alkyl phthalyl alkyl glycolates can be used preferably.

  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.

<Fine particles (matting agent)>
The retardation film of this embodiment 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. .

<Phase difference control agent>
In order to improve the display quality of an image display device such as a liquid crystal display device, a retardation control agent is added to the retardation film or an alignment film is formed to provide a liquid crystal layer. By combining the retardation, optical compensation ability can be imparted to the retardation film.

  Examples of the retardation control agent include aromatic compounds having two or more aromatic rings as described in the specification of European Patent 911,656A2, rod-shaped compounds described in JP-A-2006-2025, and the like. It is done. Two or more aromatic compounds may be used in combination. The aromatic ring of the aromatic compound is preferably an aromatic heterocyclic ring including an aromatic heterocyclic ring in addition to the aromatic hydrocarbon ring. The aromatic heterocycle is generally an unsaturated heterocycle.

  In addition, the pyrazole type compound which has a structure represented by General formula (1) functions also as a phase difference controlling agent.

  The addition amount of the retardation control agent is preferably in the range of 0.5 to 20% by mass, and preferably in the range of 1 to 10% by mass with respect to 100% by mass of the resin used as the film substrate. Is more preferable.

[Method for producing retardation film]
In general, the retardation film can be produced by, for example, a solution casting film forming method or a melt casting film forming method. However, when a thin film retardation film is produced, it is necessary to increase the amount of the nitrogen-containing heterocyclic compound as a retardation increasing agent in order to suppress a decrease in the retardation Rth. When the amount of nitrogen-containing heterocyclic compound added is large, the melt-casting film formation method does not melt the nitrogen-containing heterocyclic compound, and scorching occurs during the film-forming process. It is desirable to do. Details of the solution casting film forming method will be described below.

(Solution casting film forming method)
FIG. 3 schematically shows an example of an apparatus for producing a retardation film by a solution casting film forming method. In the solution casting film forming method, (1) a dope is prepared by dissolving at least an additive such as a cellulose ester resin, a retardation increasing agent (for example, a nitrogen-containing heterocyclic compound) and an organic ester (for example, a sugar ester) in a solvent. A step, (2) a step of casting the dope on a belt-like or drum-like metal support, (3) a step of evaporating a solvent of the dope cast on the metal support to obtain a web, and (4) a web (5) A step of stretching and drying the peeled web (film), and (6) a step of winding the film after cooling it.

(1) Dope preparation step In this step, the cellulose ester resin, optionally a nitrogen-containing heterocyclic compound, a sugar ester, a polycondensation in an organic solvent mainly composed of a good solvent for the cellulose ester resin in the dissolution vessel 31. An ester, polyhydric alcohol ester, or other compound is dissolved with stirring to form a dope. Alternatively, the cellulose ester resin solution is mixed with a nitrogen-containing heterocyclic compound, sugar ester, polycondensed ester, polyhydric alcohol ester, or other compound solution to form a dope that is a main solution.

  When the retardation film is produced by the solution casting method, any organic solvent useful for forming the dope can be used without limitation as long as it dissolves the cellulose ester resin 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 ester resins and other compounds in a non-chlorine organic solvent system There is also a role of promoting dissolution of the. In forming the retardation film, a method of forming a film using a dope having an alcohol concentration in the range of 0.5 to 15.0% by mass is applied in order to improve the flatness of the obtained retardation film. be able to.

  In particular, a dope in which cellulose acylate and other compounds are dissolved in a total range 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. A composition is preferred.

  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.

  Cellulose ester-based resin, nitrogen-containing heterocyclic compound, sugar ester, polycondensation ester, polyhydric alcohol ester, or other compounds are dissolved at normal pressure, below the boiling point of the main solvent, main solvent A method of pressurizing at a boiling point or higher, a method of performing a 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 publication can be used, but the 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 the cellulose ester resin 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.

(2) Casting step In this step, the dope in the melting pot 31 is fed to the pressurizing die 32 through a liquid feed pump (for example, a pressurization type metering gear pump) and transferred onto the endless metal support 33. The dope is cast from the pressure die 32 at the casting position. The pressure die 32 is preferable in that it can adjust the slit shape of the die portion of the die and can easily make the film thickness uniform. The pressure die 32 includes a coat hanger die and a T die, and any of them is preferably used. In order to increase the film forming speed, two or more pressure dies 32 may be provided on the metal support 33, and the dope amount may be divided and stacked.

  The metal support 33 is composed of a stainless steel belt stretched around two rollers 34. The metal support 33 preferably has a mirror-finished surface. In addition to the stainless steel belt, a metal drum having a surface plated with a casting can be used.

  The width of casting (casting) 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 33 in the casting step is set in a range of −50 ° C. to a temperature at which the solvent boils and does not foam, more preferably −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 support in a state containing a large amount of residual solvent.

  The method for controlling the temperature of the metal support 33 is not particularly limited, and there are a method of blowing hot air or cold air, and a method of contacting hot water with the back side of the metal support 33. It is preferable to use warm water because heat transfer is performed efficiently, so that the time until the temperature of the metal support 33 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 is a case where wind at a temperature higher than the target temperature is used while preventing foaming. is there. 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.

(3) Solvent evaporation step In this step, the film (web) formed by the dope cast on the metal support 33 is heated to evaporate the solvent. In order to evaporate the solvent, a method of blowing air from the surface of the web (opposite side of the metal support 33), a method of transferring heat by liquid from the back side of the metal support 33 (opposite side of the web), Although there is a method of transferring heat from the front and back by radiant heat, the backside liquid heat transfer method is preferable because of good drying efficiency. A method of combining them is also preferably used. The web on the metal support 33 after casting is preferably dried on the metal support 33 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 metal support 33 within 30 to 120 seconds.

(4) Peeling Step In this step, the web from which the solvent has evaporated on the metal support 33 is peeled off at a predetermined peeling position by the peeling roller 35. Hereinafter, the web after peeling is referred to as a web 36. The web 36 is sent to the next process.

  The temperature at the peeling position on the metal support 33 is preferably in the range of 10 to 40 ° C, more preferably in the range of 11 to 30 ° C.

  The residual solvent amount of the web on the metal support 33 at the time of peeling is preferably peeled in the range of 50 to 120% by mass depending on the strength of drying conditions, the length of the metal support 33, and the like. When peeling at a time when the amount of residual solvent is larger, if the web is too soft, the flatness at the time of peeling is impaired, and slippage and vertical stripes due to peeling tension are likely to occur, so the residual solvent at the time of peeling due to the balance between economic speed and quality The amount is decided. The residual solvent amount of the web is defined by the following formula.

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

  The peeling tension at the time of peeling the web from the metal support 33 is usually within a range of 196 to 245 N / m. However, when wrinkles are easily generated at the time of peeling, the web may be peeled with a tension of 190 N / m or less. preferable.

  In the present embodiment, the temperature at the peeling position on the metal support 33 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 preferable.

(5) Stretching and drying step In this step, a preliminary drying step, a stretching step, and a main drying step are sequentially performed. The preliminary drying may be performed as necessary.

<Preliminary drying process>
The web 36 obtained by peeling from the metal support 33 is dried. The web 36 may be dried while being transported by a large number of rollers arranged above and below, or may be dried while being transported while fixing both ends of the web 36 with clips like a tenter dryer. May be.

  The means for drying the web 36 is not particularly limited, and can be generally performed by hot air, infrared rays, a heating roller, microwaves, or the like, but it is preferably performed by hot air from the viewpoint of simplicity.

  The drying temperature in the drying step of the web 36 is preferably a glass transition point of the film of −5 ° C. or lower and 100 ° C. or higher, and it is effective to perform heat treatment for 10 minutes or longer and 60 minutes or shorter. The drying temperature is preferably in the range of 100 to 200 ° C, more preferably in the range of 110 to 160 ° C.

<Extension process>
In this step, the web 36 peeled off from the metal support 33 and preliminarily dried as necessary is directed to the MD direction (Machine Direction) and / or the TD direction (Transverse Direction). Stretching is performed. At this time, it is preferable to stretch at least by the tenter stretching device 37 in the TD direction.

  Stretching in the stretching step can be uniaxial stretching or biaxial stretching. Biaxial stretching also includes a mode in which stretching is performed in one direction and the tension in the other direction is relaxed and contracted.

  In the stretching step, it is preferable to stretch in the temperature range of (Tg + 15) to (Tg + 50) ° C. 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. . Tg is the glass transition temperature (° C.) of the film. When 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, generation | occurrence | production of a fracture | rupture is suppressed and the retardation film for polarizing plates excellent in 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.

  The glass transition temperature Tg referred to here is the midpoint glass transition temperature (Tmg) determined according to JIS K7121 (1987) using a commercially available differential scanning calorimeter with a temperature increase rate of 20 ° C./min. is there. 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).

  In the stretching step, it is preferable to stretch the web 36 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 the molecules in the film is large and a desired retardation value can be obtained, and the dimensional change behavior of the film can be controlled within the desired range.

  Further, in the stretching step, it is preferable to start stretching in the MD direction with respect to the web 36 when the residual solvent amount is 40% by mass or more, and when the residual solvent amount is less than 40% by mass, stretching is performed in the TD direction. It is preferable to do.

  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 36 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 36 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 formed by stretching necessarily has retardation, but each value of in-plane retardation Ro and retardation Rt in the thickness direction is determined by an automatic birefringence meter Axoscan (Axo Scan Mueller Matrix Polarimeter: Axometrics Co., Ltd.) can be used to measure the three-dimensional refractive index at a wavelength of 590 nm in an environment of 23 ° C. and 55% RH, and the refractive index can be calculated from the obtained refractive indexes nx, ny, and nz.

In the retardation film of the present embodiment, the in-plane direction retardation Ro defined by the following formula (i) and the thickness direction retardation Rth defined by the following formula (ii) are in the following ranges. When it is provided in a VA liquid crystal display device, it is preferable from the viewpoint of improving the visibility of a display image.
30 nm <Ro <70 nm
100 nm <Rth <300 nm

Formula (i): Ro = (nx−ny) × d (nm)
Formula (ii): Rt = {(nx + ny) / 2−nz} × d (nm)
[In Formula (i) and Formula (ii), nx represents the refractive index in the direction x in which the refractive index is maximum in the in-plane direction of the film. ny represents the refractive index in the direction y orthogonal to the direction x in the in-plane direction of the film. nz represents the refractive index in the thickness direction z of the film. d represents the thickness (nm) of the film. ]

  The retardation film can be stretched while adjusting the stretching ratio at least in the TD direction, whereby the retardations Ro and Rth can be adjusted within the above ranges.

<Main drying process>
The stretched web 36 is conveyed as a film F to a drying device 38, where drying is performed in the same manner as the preliminary drying described above. Note that the drying conditions in the main drying step may be different from those in the preliminary drying step.

<Knurling>
After the completion of the main drying, it is preferable to provide a slitter and cut off the end of the film F before winding the film F in order to obtain a good winding shape. Furthermore, it is preferable to give a knurling process to both ends of the film 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 widthwise ends of the film F is preferably 4 to 20 μm and a width of 5 to 20 mm.

(6) Winding step This step is a step of winding the film F by the winding device 39 after the residual solvent amount becomes 2 mass% or less. By setting the residual solvent amount to 0.4% by mass or less, a film having good dimensional stability can be obtained.

  As a method for winding the film F, a commonly 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. .

(Method for producing laminated type retardation film)
In producing a laminated type retardation film as in this embodiment, it is preferable to use a laminated casting method such as a co-casting method (multi-layer simultaneous casting method), a sequential casting method, a coating method, etc. It is preferable to use the co-casting method from the viewpoint of stable production and production cost reduction.

  In the co-casting method and the sequential casting method, a retardation film can be produced using the above-described solution casting film forming method. That is, first, a dope for forming each layer is prepared. In the co-casting method, a casting dope corresponding to each layer is cast on a casting support (band or drum). At this time, each dope for casting is simultaneously extruded from separate slits of a pressure die (casting die) and cast on the casting support at the same time. Then, the cast film is peeled off from the support at an appropriate time and dried to produce a film.

  On the other hand, in the sequential casting method, the casting dope for the first layer is first extruded from the pressure die on the casting support, cast, dried, or without drying. On top, the casting dope for the second layer is extruded from a pressure die. Thereafter, the above steps are repeated to sequentially cast the casting dope for the required number of layers, and the casting film is peeled off from the support and dried at an appropriate time to produce a film.

  In the coating method, a core layer film is generally produced by a solution casting film forming method. And the coating liquid apply | coated to a surface layer is prepared, a coating liquid is apply | coated on a film one side at a time or simultaneously on both surfaces using an appropriate coating machine, and it is made to dry, and the film of laminated structure is produced.

[Physical properties of retardation film]
(Haze)
The retardation film of the present embodiment preferably has a haze of less than 1%, and 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.

(Equilibrium moisture content)
In the retardation film of this embodiment, the equilibrium moisture content at 25 ° C. and 60% relative humidity is preferably 4% or less, and 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.

(Film length, width, film thickness)
The retardation film of the present embodiment is preferably long, specifically, preferably has a length of about 100 to 10,000 m, and is wound into a roll. The width of the retardation film of the present embodiment is preferably 1 m or more, more preferably 1.4 m or more, and particularly preferably 1.4 to 4 m.

  The thickness of the retardation film is preferably in the range of 10 to 100 μm, more preferably 20 to 40 μm, from the viewpoints of thinning the display device and productivity.

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

[Polarizing plate and liquid crystal display]
The polarizing plate having the retardation film described above can be produced by a general method. That is, an optical film (for example, a retardation film) is subjected to alkali saponification treatment, and the treated optical film is immersed and stretched in an iodine solution on one surface of a polarizing film (polarizer). It is preferable to use (water glue, water-based adhesive) for bonding. An optical film (for example, a surface protective film) can be bonded to the other surface of the polarizer in the same manner as described above. Note that the polarizer and the optical films on both sides thereof may be bonded together using an active energy ray-curable adhesive or the like.

  A polarizing film, which is a main component of the polarizing plate, is an element that transmits only light having a polarization plane in a certain direction, and a typical polarizing film that is currently known is a polyvinyl alcohol polarizing film. The polarizing film includes a polyvinyl alcohol film dyed with iodine and a dichroic dye dyed, but is not limited thereto.

  As the polarizing film, a film obtained by uniaxially stretching and dyeing a polyvinyl alcohol film, or uniaxially stretching after dyeing is preferably used after being subjected to a durability treatment with a boron compound. The thickness of the polarizing film is 5 to 30 μm, preferably 8 to 15 μm.

  A transparent substrate of a VA driving type liquid crystal cell and the above polarizing plate are bonded together with an adhesive layer, thereby forming a VA liquid crystal display device. Here, the polarizing plate is bonded to the liquid crystal cell via an adhesive layer such that the polarizing film is positioned on the viewing side and the retardation film is positioned on the liquid crystal cell side with respect to the polarizer. It is desirable.

  The pressure-sensitive adhesive layer is preferably optically transparent and exhibits moderate viscoelasticity and pressure-sensitive adhesive properties. Specific examples of the adhesive layer include adhesives or adhesives such as acrylic copolymers, epoxy resins, polyurethane, silicone polymers, polyethers, butyral resins, polyamide resins, polyvinyl alcohol resins, and synthetic rubbers. A film such as a drying method, a chemical curing method, a thermal curing method, a thermal melting method, a photocuring method, or the like can be formed and cured using a polymer such as the above. Among them, the acrylic copolymer can be preferably used because it is most easy to control the physical properties of the adhesive and is excellent in transparency, weather resistance, durability and the like.

〔Example〕
Examples of the present invention will be specifically described below, but the present invention is not limited to these examples.

(Preparation of dope 1)
The following composition was put into a mixing tank and stirred to dissolve each component to prepare a dope 1 for forming a core layer.
Diacetylcellulose resin (acetyl group substitution degree 2.5) 100.0 parts by mass Retardation increasing agent (Exemplary Compound 1) 2.0 parts by mass Methylene chloride 365.5 parts by mass Methanol 54.6 parts by mass

  Illustrative compound 1 is 5,5 ′-(1,3-phenylene) bis (3-phenyl-1H-pyrazole), which is a typical example of a pyrazole compound (see Chemical Formula 2).

(Preparation of dope 2)
The following composition was put into a mixing tank and stirred to dissolve each component to prepare a dope 2 for forming a skin layer.
Triacetyl cellulose resin (acetyl group substitution degree 2.9) 100.0 parts by mass Silica fine particles R972 (manufactured by Nippon Aerosil Co., Ltd.) 0.15 parts by mass Methylene chloride 395.0 parts by mass Methanol 59.0 parts by mass

(Preparation of retardation film F-1)
Using the manufacturing apparatus in FIG. 3, each dope is metal from a pressure die by a co-casting method so that a laminated structure of skin layer / core layer / skin layer is formed using dope 1 and dope 2 produced as described above. Cast on a support. Then, the solvent was evaporated on the metal support until the amount of residual solvent in the web as a cast film reached 75% by mass, and then the web was peeled off from the metal support with a peeling tension of 130 N / m. Thereafter, the peeled web was stretched 30% in the width direction using a tenter. The residual solvent at the start of stretching was 15%. The stretching temperature in the tenter was 160 ° C.

  Next, drying was completed while the drying zone was conveyed by a number of rollers. The drying temperature after stretching was 100 ° C., and the drying time was 5 minutes. As described above, a retardation film F-1 having a dry film thickness of 50 μm was obtained.

(Production of retardation films F-2 to F-12)
Except that the acetyl cellulose resin (core layer resin) contained in the dope 1 and the acetyl cellulose resin (skin layer resin) contained in the dope 2 and the types and addition amounts of the retardation increasing agents were changed as shown in Table 1, Retardation films F-2 to F-12 were produced in the same manner as the production of the retardation film F-1. In the table, “Ac substitution degree” refers to acetyl group substitution degree, and “Pr substitution degree” refers to propionyl group substitution degree.

  Here, as exemplary compound 2 of the retardation increasing agent, a pyrimidine-based compound having the following structure was used.

  As an example compound 3 of the retardation increasing agent, a triazole compound having the following structure was used.

  As the exemplary compound 4 of the retardation increasing agent, an imidazole compound having the following structure was used.

≪Evaluation≫
(Measurement of retardation value)
Ten sample films were arbitrarily cut out from the prepared retardation film, and using an automatic birefringence meter Axoscan (Axo Scan Mueller Matrix Polarimeter: manufactured by Axometrics) under an environment of 23 ° C. and 55% RH, 590 nm At the wavelength, three-dimensional refractive index measurement is performed, and the obtained average refractive indexes nx, ny, and nz are substituted into the following formulas (i) and (ii) to obtain in-plane retardation Ro and thickness direction retardation Rth. Asked.
Formula (i): Ro = (nx−ny) × d (nm)
Formula (ii): Rth = {(nx + ny) / 2−nz} × d (nm)
[In Formula (i) and Formula (ii), nx represents the refractive index in the direction x in which the refractive index is maximum in the in-plane direction of the film. ny represents the refractive index in the direction y orthogonal to the direction x in the in-plane direction of the film. nz represents the refractive index in the thickness direction z of the film. d represents the thickness (nm) of the film. ]

(Evaluation of retardation fluctuation by wet heat durability test)
About the produced retardation film, the fluctuation | variation of the retardation by a wet heat endurance test was investigated as follows.

  1. As the values of Ro and Rth of the retardation film, the above values (values measured before the wet heat durability test) measured in an environment of 23 ° C. and 55% RH were respectively Ro1 and Rth1.

  2. Next, the retardation film was stored in an environment of 60 degrees and 90% RH for 120 hours, and then conditioned for 24 hours in an environment of 23 ° C. and 55% RH. Thereafter, Ro and Rth of the retardation film were measured to be Ro2 and Rth2, respectively.

3. From the values of Ro1, Rth1, Ro2, and Rth2 obtained in 1 and 2 above, the amount of change in Ro ΔRo and the amount of change in Rth ΔRth were calculated based on the following equations.
ΔRo = | Ro1-Ro2 |
ΔRth = | Rth1-Rth2 |

4). From the obtained ΔRo and ΔRth, the retardation fluctuation by the wet heat durability test was evaluated based on the following evaluation criteria.
"Evaluation criteria"
A: ΔRo and ΔRth are both less than 4 nm (the wet heat durability is the best).
○: Both ΔRo and ΔRth are 4 nm or more and less than 7 nm (wet heat resistance is good).
Δ: ΔRo and ΔRth are both 7 nm or more and less than 10 nm (wet heat resistance is poor).
X: ΔRo and ΔRth are both 10 nm or more (the wet heat durability is the worst).

(Evaluation by water unevenness test)
<Preparation of polarizing plate>
Using the retardation films F-1 to F-12 produced above, polarizing plates were produced as follows.

  A 70 μm thick polyvinyl alcohol film was swollen with water at 35 ° C. The obtained film was immersed in an aqueous solution consisting of 0.075 g of iodine, 5 g of potassium iodide and 100 g of water for 60 seconds, and further immersed in an aqueous solution at 45 ° C. consisting of 3 g of potassium iodide, 7.5 g of boric acid and 100 g of water. . The obtained film was uniaxially stretched under conditions of a stretching temperature of 55 ° C. and a stretching ratio of 5 times. The uniaxially stretched film was washed with water and dried to obtain a polarizer having a thickness of 15 μm.

  Next, Konica Minolta KC6UA with a thickness of 60 μm, which is a commercially available polarizing plate protective film, was prepared as a cellulose acylate film to be bonded to one of the polarizers. And the polarizing plate was produced through the following processes.

  Step 1: Retardation film and KC6UA were each immersed in a 2 mol / L sodium hydroxide solution at 60 ° C. for 90 seconds, then washed with water and dried, and subjected to saponification treatment on the side to be bonded to the polarizer. .

  Process 2: The polarizer was immersed in a polyvinyl alcohol adhesive tank having a solid content of 2% by mass for 1 to 2 seconds.

  Step 3: Excess adhesive adhered to the polarizer in Step 2 was lightly wiped off, and the retardation film treated in Step 1 was placed on one side of the polarizer and KC6UA was placed on the opposite side.

Step 4: The retardation film, polarizer, and KC6UA laminated in Step 3 were bonded at a pressure of 20 to 30 N / cm ² and a conveyance speed of about 2 m / min.

  Process 5: The laminated body bonded at the process 4 was dried for 2 minutes in the 80 degreeC dryer, and the polarizing plate was produced.

  The above process was performed for each of the produced retardation films F-1 to F-12, and two polarizing plates having the same configuration were produced. One polarizing plate is a polarizing plate for the viewing side with respect to the liquid crystal cell, and the other polarizing plate is a polarizing plate for the backlight side with respect to the liquid crystal cell.

<Panel evaluation>
SAMSUNG's VA liquid crystal display device (model number: UN55HU-8500) was peeled off the two polarizing plates that had been pasted together, and the two polarizing plates prepared above were applied to both sides of the glass surface of the liquid crystal cell. Bonding was performed using an acrylic adhesive. At this time, polarizing plates were attached to both surfaces of the liquid crystal cell so that the produced retardation film was on the liquid crystal cell side with respect to the polarizer. And the wet cloth was affixed on the surface of the produced liquid crystal display device, and it was left to stand for 3 days. Thereafter, the cloth was peeled off to display the screen in black, and the degree of display unevenness (water unevenness) due to moisture absorption was visually observed. And the water nonuniformity was evaluated based on the following evaluation criteria.
"Evaluation criteria"
A: No unevenness was observed at all.
○: Slightly weak unevenness was observed depending on the accuracy of visual observation, but it is a level with no problem in actual use.
(Triangle | delta): Although weak nonuniformity was observed irrespective of the visual angle, it is a level which does not have a problem on actual use.
X: Strong unevenness is clearly observed on the screen, and there is a problem in actual use.

(Evaluation by brittleness test)
The retardation film was torn using a light load tear tester (manufactured by Toyo Seiki Co., Ltd.), the tear surface was visually observed, and the brittleness of the retardation film was evaluated based on the following criteria.
"Evaluation criteria"
(Double-circle): The tear surface is very smooth and is torn straight (the brittleness is the best).
○: There is a slight burr (ragged irregularities) on the tear surface, but it is torn straight (brittleness is quite good).
Δ: There are burrs on the tear surface, but it is torn straight (good brittleness).
X: There are considerable burrs on the tear surface, and it is not torn straight (brittleness is poor).

(Saponification suitability)
The retardation film produced above was subjected to alkali saponification treatment for 120 hours continuously under the following conditions.
<Saponification process>
Saponification process 2M-KOH 55 ° C. 30 seconds Water washing process Water 30 ° C. 45 seconds Neutralization process 10% HCl 30 ° C. 45 seconds Water washing process Water 30 ° C. 45 seconds

Thereafter, the saponification solution was sampled and visually confirmed. When white foreign matter was confirmed, the film was also visually confirmed after saponification. Based on the following evaluation criteria, the saponification suitability of the retardation film was evaluated.
"Evaluation criteria"
(Double-circle): The white foreign material was not confirmed in the saponification liquid, and coloring of the saponification liquid was not confirmed (the saponification suitability is the best).
○: White foreign matter was slightly confirmed in the saponification solution, and coloring of the saponification solution was also confirmed slightly, but re-adhesion of the white foreign matter to the film was not confirmed (good saponification suitability).
(Triangle | delta): Although the white foreign material was confirmed in the saponification liquid and coloring of the saponification liquid was confirmed, the reattachment of the white foreign material to the film was not confirmed (saponification ability is bad).
X: A large amount of white foreign matter was confirmed in the saponification solution, and reattachment of the white foreign matter to the film was also confirmed (saponification suitability is the worst).

  Table 1 summarizes the parameters and evaluation results of the retardation films F-1 to F-12 produced as described above.

  From Table 1, about retardation film F-1 to F-3, a core layer has a diacetyl cellulose resin and a pyrazole type compound (especially 5,5 '-(1,3-phenylene) bis (3-phenyl- 1H-pyrazole)), and the skin layer contains a triacetyl cellulose resin. As a result, there are few fluctuations in Ro and Rth due to wet heat changes, little display unevenness due to moisture absorption, good brittleness, and good saponification suitability.

  In contrast, the retardation film F-4 has poor saponification suitability. This is presumably because the acetyl group substitution degree of the acetyl cellulose resin of the core layer was as low as 2.3 and the hydrophilicity of the film as a whole became high, so that part of the film was eluted in the saponification solution.

  In the retardation film F-5, display unevenness due to moisture absorption occurs. This is considered to be because the acetyl cellulose resin contained in the core layer is composed of a triacetyl cellulose resin having an acetyl group substitution degree of 2.7. That is, since the core layer and the skin layer all contain a triacetyl cellulose resin that has a large retardation fluctuation due to moisture absorption, the retardation film as a whole has a large retardation fluctuation due to moisture absorption, and display unevenness occurs in the liquid crystal display device. it is conceivable that.

  In the retardation film F-6, the saponification suitability is the worst. This is presumably because a part of the skin layer was eluted in the saponification solution because the outermost skin layer contained diacetylcellulose resin having a high hydrophilicity and an acetyl group substitution degree of 2.5.

  In the retardation films F-7 and F-8, brittleness is poor. This is probably because the acetyl cellulose resin contained in the core layer is a cellulose acetate propionate resin, and this resin is brittle.

  In the retardation films F-9 to F-12, the saponification suitability is the worst. This is because the retardation films F-9 to F-12 are composed of a single layer containing a diacetyl cellulose resin, and the hydrophilicity of the diacetyl cellulose resin is high, so that a part of the resin is eluted in the saponification solution. It is considered a thing.

  Moreover, in the retardation film F-9, the fluctuation | variation of the retardation by fluctuation | variation of wet heat cannot be suppressed, and the wet heat durability is quite lacking. This is because, in the retardation film F-9, a pyrimidine compound is added to the diacetyl cellulose resin as in Patent Document 1, but this pyrimidine compound exhibits retardation fluctuations due to fluctuations in both humidity and temperature. This is probably because it does not have a function to suppress.

  In the retardation films F-10 and F-11, the fluctuation of the retardation due to the wet heat fluctuation occurs, and the wet heat durability is lacking. This is because the retardation films F-10 and F-11 contain a triazole compound or an imidazole compound as a retardation increasing agent in the diacetyl cellulose resin. This is considered to be because there is almost no effect of suppressing the above.

(Preparation of retardation films F-13 to F-17)
Next, as the acetyl cellulose resin contained in the dope 1 and the acetyl cellulose resin contained in the dope 2, the resin used in the production of the retardation film F-1 was used, and the retardation increasing agent was also used as the retardation film F-1. Except for using Exemplified Compound 1 (pyrazole compound) used in the preparation of the above, changing the total film thickness of the film and the amount of addition of the retardation increasing agent as shown in Table 2, and adding additives as necessary In the same manner as in the production of the retardation film F-1, retardation films F-13 to F-17 were produced. As the additive, sugar ester compound a3 of Chemical formula 6 was used. The sugar ester compound a3 is a compound in which the sugar residue is B-2 (see Chemical Formula 5), the substitution degree of the substituent 1 is 6, and the substitution degree of the substituent 2 is 2.

  And evaluation similar to the above was performed about produced retardation film F-13-F-17. Table 2 summarizes the parameters and evaluation results of the produced retardation films F-13 to F-17. In Table 2, the sugar ester compound a3 is described as sugar ester A.

  From Table 2, in the retardation films F-13 to F-15, display unevenness due to moisture absorption is not observed at all. This is considered to be due to the following reasons. That is, when the total film thickness of the retardation films F-13 to F-15 is in the range of 20 μm or more and 40 μm or less, the skin layer containing the triacetyl cellulose resin is thinner than the retardation film F-1 or the like. Become. Since the triacetyl cellulose resin has a large retardation fluctuation due to moisture absorption, when the skin layer becomes a thin film, the retardation fluctuation due to moisture absorption of the entire film is further suppressed, and display unevenness is further suppressed.

  Moreover, in the retardation films F-16 to F-17, the saponification suitability is the best. This is because the sugar ester compound contained in the retardation films F-16 to F-17 is a water-resistant additive, so the hydrophilicity of the entire film is lowered, and this causes part of the resin to elute into the saponification solution. It is thought that it is difficult to do.

  The retardation film of the present invention can be used for polarizing plates and VA liquid crystal display devices.

DESCRIPTION OF SYMBOLS 1 Liquid crystal display device 4 Liquid crystal cell 5 Polarizing plate 11 Polarizer 13 Optical film (retardation film)
21 Core layer 22 Skin layer 23 Skin layer

Claims (7)

A laminated type retardation film in which skin layers are provided on both sides of a core layer,
The core layer includes an acetyl cellulose resin having an acetyl group substitution degree of 2.4 or more and 2.6 or less, and a nitrogen-containing heterocyclic compound as a retardation increasing agent,
The skin layer includes an acetyl cellulose resin having an acetyl group substitution degree of greater than 2.6 and 2.9 or less,
The said nitrogen-containing heterocyclic compound contains the pyrazole type compound which has a structure represented with the following general formula, The retardation film characterized by the above-mentioned.

(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. A group, a sulfonyl group, an alkyloxycarbonyl group, or an aryloxycarbonyl group, q represents an integer of 1 to 2, and n and m represent an integer of 1 to 3).   The retardation film according to claim 1, wherein the pyrazole-based compound is 5,5 ′-(1,3-phenylene) bis (3-phenyl-1H-pyrazole).   The retardation film according to claim 1, wherein the total film thickness is 20 μm or more and 40 μm or less.   The retardation film according to claim 1, comprising a sugar ester compound.   A polarizing plate comprising the retardation film according to claim 1 and a polarizer.   A liquid crystal display device comprising the polarizing plate according to claim 5 and a liquid crystal cell. The polarizing plate is located on the viewing side with respect to the liquid crystal cell,
The liquid crystal display device according to claim 6, wherein the retardation film of the polarizing plate is positioned on the liquid crystal cell side with respect to the polarizer.

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