TW201708352A - Phase-difference film, polarizing plate, and vertical-alignment liquid-crystal display device - Google Patents

Abstract

In the present invention, a phase-difference film contains a sugar ester, a retardation-elevating agent, and a cellulose ester resin that has acetyl groups and butyryl groups. The relationships 50 nm ≤ |Ro| ≤ 80 nm and 200 nm ≤ |Rth| ≤ 300 nm hold, where Ro (nm) is the in-plane retardation of the film, and Rth (nm) is the thickness-direction retardation of the film.

Description

Phase difference film, polarizing plate and vertical alignment type liquid crystal display device

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

In recent years, there has been an increasing demand for thinner, lighter, and lower cost of informational devices (especially display devices). In particular, in a VA type liquid crystal display device (LCD) of a display device, thin film formation of a retardation film for improving the viewing angle of the LCD or improving the contrast (phase difference) is produced, and the liquid crystal cell is on the visible side. And the backlight side is required to be made of one retardation film of two pieces.

In the VA type LCD, if the number of retardation films to be used is one, the retardation Ro in the in-plane direction and the retardation Rth in the thickness direction of the retardation film are used to form two retardation films. The situation is still higher than necessary. For example, in the case of using two retardation films (two retardation films), Ro and Rth of each retardation film are Ro=50 nm and Rth=120 nm, and only one retardation film is used. In one mode (one phase difference film), the phase difference must be Ro and Rth of the film were such that Ro = 65 nm and Rth = 250 nm. Thus, a VA type LCD system using only one retardation film has been disclosed in, for example, Patent Document 1.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] JP-A-2005-241794 (refer to claim 1, paragraphs [0204] to [0209], [0215], [0221], etc.)

However, the film thickness of the phase difference film of Patent Document 1 is set to be thick (for example, about 100 μm). When the film thickness is thick, it is difficult to peel the film (cast film) from the support in the film formation by the solution casting film formation method, and the grain is formed on the film at the time of peeling to cause a defect rate. When the temperature is increased, the drying after stretching requires a long time and the like, and the film productivity is lowered. Further, when the film thickness is thick, the fluctuation range of the film thickness (the difference between the maximum value and the minimum value of the film thickness) tends to be large, and the film thickness variation (non-uniformity) in the film surface is likely to increase. When the deviation of the film thickness is large, the variation in the retardation Rth in the thickness direction in the film surface becomes large, and there is a concern that the LCD display unevenness occurs.

The present invention has been made to solve the above problems, and an object of the invention is to provide a retardation film which can improve the productivity of a retardation film used as one, and can reduce the in-plane due to retardation Rth. The display is uneven due to the deviation, and a polarizing plate using the retardation film and a vertical alignment type liquid crystal display device using the polarizing plate are provided.

The above object of the present invention is achieved by the following constitution. That is, the retardation film of one aspect of the present invention comprises a cellulose ester resin having an ethyl fluorenyl group and a butyl group, a retardation enhancer, and a sugar ester, and the retardation of the in-plane direction of the film is set to Ro (nm). When the retardation in the thickness direction of the film is set to Rth (nm), it is 50 nm ≦ | Ro | ≦ 80 nm

200 nm ≦ | Rth | ≦ 300 nm.

The retardation film can still achieve high retardation (Ro and Rth) by including a retardation enhancer, that is, a film thickness of the thinned film. Therefore, it is possible to realize thin film formation of a retardation film used as one. Further, the film containing the cellulose ester-based resin having an acetyl group and a butyl group is more likely to be peeled off from the support in the film formation under the solution casting film forming method than in the case of containing another cellulose ester-based resin. Therefore, by thinning the retardation film and using a specific cellulose ester-based resin, the peeling property of the retardation film from the support at the time of film formation can be surely improved, whereby the productivity of the retardation film can be improved.

Further, by thinning the retardation film, since the variation range of the film thickness (the difference between the maximum value and the minimum value of the film thickness) becomes small, the thinning can be reduced. Film thickness deviation (non-uniformity) in the film surface. Further, since the retardation film contains a sugar ester, since the film becomes soft (because the sugar ester has a function as a plasticizer), the retardation enhancer is more uniformly mixed in the film (due to the sugar ester having a function as a plasticizer) The function of the compatibilizing agent) can further reduce the film thickness deviation in the film surface during film formation. Therefore, by the thinning of the retardation film and the use of the sugar ester, the variation in the retardation Rth in the in-plane of the film can be surely reduced, and the display unevenness when the film-formed retardation film is applied to the liquid crystal display device can be reduced.

1‧‧‧Liquid crystal display device (vertical alignment type liquid crystal display device)

2‧‧‧LCD panel

3‧‧‧ Backlight

4‧‧‧Liquid Crystal Unit

5‧‧‧Polar plate

6‧‧‧Polar plate

7‧‧‧Adhesive layer

8‧‧‧Adhesive layer

11‧‧‧Polarizer

12‧‧‧Optical film

13‧‧‧Optical film (phase difference film)

14‧‧‧Polarizer

15‧‧‧Optical film

16‧‧‧Optical film

31‧‧‧Solution kettle

32‧‧‧Pressure mould

33‧‧‧Metal support

34‧‧‧ Roll

35‧‧‧ peeling roller

36‧‧‧ net model

37‧‧‧Zoom extension

38‧‧‧Drying device

39‧‧‧Winding device

F‧‧‧film

Fig. 1 is a cross-sectional view showing a schematic configuration of a vertical alignment type liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is an explanatory view showing an example of an apparatus for manufacturing a retardation film to which a polarizing plate of the liquid crystal display device is applied.

One embodiment of the present invention will be described below based on the drawings. Further, in the present specification, when the numerical range is indicated as A to B, it is considered that the values of the lower limit A and the upper limit B are included in the numerical range. Further, the present invention is not limited by the following contents.

[Vertical alignment type liquid crystal display device]

1 is a view showing a vertical alignment type (VA type) liquid crystal of this embodiment. A cross-sectional view showing a schematic configuration of the display device 1. The liquid crystal display device 1 has 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.

In the liquid crystal display panel 2, the polarizing plate 5 is disposed on the visible side of the liquid crystal cell 4 driven by the VA method, and the polarizing plate 6 is disposed on the side of the backlight 3. The liquid crystal cell 4 is formed by sandwiching a liquid crystal layer with a pair of transparent substrates (not shown). The liquid crystal cell 4 can be a transparent substrate disposed on the side of the backlight 3 with respect to the liquid crystal layer, that is, a substrate disposed on the substrate on the side of the TFT (Thin Film Transistor), which is called an array filter (color filter on array). The liquid crystal cell of the COA structure may be a liquid crystal cell in which the color filter is disposed on the visible side transparent substrate with respect to the liquid crystal layer.

The polarizing plate 5 is provided with a polarizer 11 and an optical film 12‧13. The polarizer 11 penetrates a predetermined linearly polarized light. The optical film 12 is a protective film disposed on the visible side of the polarizer 11. The optical film 13 is a protective film and a retardation film which are disposed on the backlight 3 side (the liquid crystal cell 4 side) of the polarizer 11. The polarizing plate 5 is attached to the visible side of the liquid crystal cell 4 via the adhesive layer 7. In other words, the polarizing plate 5 is on the visible side with respect to the liquid crystal cell 4, and the optical film 13 is bonded to the liquid crystal cell 4 so as to become the liquid crystal cell 4 side with respect to the polarizer 11.

The polarizing plate 6 is provided with a polarizer 14 and an optical film 15‧16. The polarizer 14 penetrates the prescribed linearly polarized light. The optical film 15 is a protective film disposed on the visible 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. The polarizing plate 6 is attached to the liquid crystal single layer via the adhesive layer 8 The backlight 3 side of the element 4. Further, the optical film 15 on the visible side may be omitted, and the polarizer 14 may be directly in contact with the adhesive layer 8. The polarizer 11 and the polarizer 14 are arranged in a crossed nicol state.

In the retardation film of the present embodiment, an optical film 15 which is, for example, the optical film 13 of the polarizing plate 5 or the polarizing plate 6 can be used. However, in the retardation film of the present embodiment, as described below, the retardation Ro in the in-plane direction and the retardation Rth in the thickness direction are higher than those of the retardation film when two retardation films are used. The so-called one. Therefore, any one of the optical film 13 and the optical film 15 uses the retardation film of the present embodiment, and the other uses a simple protective film or a zero retardation film which hardly imparts a phase difference to the transmitted light. Hereinafter, the retardation film will be described in detail.

[Retardation film]

The retardation film of the present embodiment comprises a cellulose ester resin having an acetamidine group and a butyl group, a retardation enhancer, and a sugar ester, and the retardation in the in-plane direction of the film is set to Ro (nm), and the thickness direction of the film is When the retardation is set to Rth (nm), it is 50 nm ≦ | Ro | ≦ 80 nm

200 nm ≦ | Rth | ≦ 300 nm.

In addition, the retardation film may contain a cellulose ester-based resin (for example, cellulose diacetate or cellulose triacetate) other than the cellulose ester-based resin having an ethylene group and a butyl group, or may not be contained.

The phase difference film of the embodiment is improved by including delay The agent can achieve high retardation even if the film thickness of the retardation film is thinned. Specifically, even if the film thickness of the retardation film is reduced to, for example, 80 μm or less, the Ro and Rth systems can achieve the above-mentioned higher value (range). Therefore, the retardation film can be formed into one having a high retardation Ro and Rth, and simultaneously thinned. Further, by thinning the retardation film, the material cost of the retardation film can be reduced.

Further, when a film comprising a cellulose ester resin (cellulose acetate butyrate) having an acetyl group and a butyl group is formed by a solution casting film forming method, it is easily peeled off from the support (metal support). The reason is presumed to be as follows. When the polarity of the substituent of the cellulose ester-based resin is strong, the interaction with the surface of the metal support becomes large, and the adhesion between the matrix (resin) flowing through the metal support and the metal support becomes high. As a result, the film becomes less likely to be peeled off from the metal support. Compared with an ethyl hydrazide or a propyl fluorenyl group, the butyl fluorenyl group is a more hydrophobic substituent, and the adhesion of the film containing the cellulose ester resin (cellulose acetate butyrate) substituted with butyl fluorenyl group to the metal support is weak due to the weak polarity. It becomes lower and becomes easy to peel off from the metal support.

Therefore, by the thinning of the retardation film and the use of a specific cellulose ester-based resin, the peeling property of the retardation film from the support at the time of film formation can be surely improved. As a result, in the film formation, it is possible to avoid the occurrence of a grain on the film at the time of peeling, resulting in a high defect rate or a long drying time after stretching, and the film can be produced at a high speed and stably. That is, the productivity of the film can be improved.

Further, when the film thickness of the retardation film is thicker, the range in which the film thickness varies (the difference between the maximum value and the minimum value of the film thickness, and the amount of variation) becomes large. Therefore, the film thickness unevenness in the film surface also becomes large. That is, as the film thickness of the retardation film is thicker, the film thickness variation in the film surface becomes larger. However, in the present embodiment, in addition to the above-mentioned thin filmable retardation film, the retardation film also contains a sugar ester. The sugar ester function serves as a plasticizer for softening the film, and a compatibilizing agent for more uniformly mixing the retardation enhancer in the film. Therefore, by including a sugar ester, the retardation film can further reduce variations in film thickness in the film surface during film formation. Thereby, it is possible to reduce the film thickness variation (film thickness unevenness) in the film surface at the time of film formation, and to reduce the variation in the in-plane retardation Rth. As a result, in the liquid crystal display device including the retardation film of the present embodiment, occurrence of display unevenness can be reduced.

In particular, the retardation film of the present embodiment preferably has a film thickness of 40 μm or more and 70 μm or less. Since the retardation film is a film, it is possible to surely obtain the above-described effects of reducing variations in film thickness in the film surface and variations in retardation Rth and reducing display unevenness.

Moreover, it is preferable that the cellulose ester-based resin contained in the retardation film of the present embodiment satisfies the following formulas (1) and (2) at the same time.

1.8≦X+Y≦2.9‧‧‧(1)

0.03≦Y≦0.8‧‧‧(2)

However, X represents the degree of substitution of the ethyl group and Y represents the degree of substitution of the group.

Further, the degree of substitution of the ethyl sulfhydryl group and the butyl sulfhydryl group can be measured in accordance with ASTM-D817-96, which is one of the specifications issued by ASTM (American Society for Testing and Materials).

The cellulose ester-based resin satisfying the formulas (1) and (2) is cellulose acetate butyrate. By including such cellulose acetate butyrate, the retardation film can surely improve the peelability of the film from the support in the film formation under the solution casting film formation method, and can surely improve the productivity of the film. Further, the more desirable range of total thiol substitution (X+Y) is 2.4≦X+Y≦2.9‧‧‧(1').

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

[Cellulose ester resin]

Examples of the cellulose raw material of the cellulose ester include cotton linters, wood pulp, and kenaf, but are not particularly limited by these. Further, the cellulose esters obtained from them can also be used in combination at any arbitrary ratio.

The cellulose ester resin is selected from the group consisting of cellulose acetate (cellulose diacetate, cellulose triacetate), cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate benzoate, cellulose propionate, butyric acid fiber. At least one of them is preferable, and among these, the cellulose ester-based resin is preferably cellulose acetate butyrate from the viewpoint of improving the peelability from the support and improving the film productivity. That is, the cellulose ester-based resin may be composed only of cellulose acetate butyrate, or may be formed by mixing other components (for example, cellulose diacetate or cellulose triacetate) with cellulose acetate butyrate. Resin. From the viewpoint of the improvement of the film productivity, it is preferable that 80% or more of the cellulose ester-based resin is cellulose acetate butyrate, and the cellulose acetate butyrate is the most preferable.

The weight average molecular weight (Mw) of the cellulose ester-based resin is preferably 75,000 or more, preferably 75,000 to 300,000, more preferably 100,000 to 240,000, and particularly preferably 160,000 to 20,000. When the weight average molecular weight (Mw) is at least 75,000, the effect of improving the self-filming property or adhesion of the cellulose ester-based resin itself 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, respectively.

Solvent: dichloromethane

Pipe column: Shodex K806, K805, K803G (connected to Showa Denko (share) system)

Column temperature: 25 ° C

Sample concentration: 0.1% by mass

Detector: RI Model 504 (manufactured by GL Scientific Co., Ltd.)

Pump: L6000 (Hitachi Manufacturing Co., Ltd.)

Flow rate: 1.0ml/min

Calibration curve: A calibration curve obtained from 13 samples in the range of Mw = 500 to 2800000 in standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) was used. It is preferred that the 13 samples are used at almost equal intervals.

[delay lifter]

The retardation enhancer means that the film can be delayed at a measurement wavelength of 590 nm (especially in the thickness direction) compared to the case where no retardation enhancer is added. A compound that extends the function of Rth).

The phase difference film can realize a retardation film in which the retardation Ro in the in-plane direction of the retardation film and the retardation Rth in the thickness direction become the retardation film in the following range by including the retardation promoting agent.

50nm≦|Ro|≦80nm

200nm≦|Rth|≦300nm

For the above-mentioned Ro and Rth systems, for example, an automatic birefringence meter AxoScan (Axo Scan Mueller Matrix Polarimeter: manufactured by Axometrics Co., Ltd.) can be used to perform a three-dimensional refractive index in an environment of a temperature of 23 ° C and a relative humidity of 55% RH at a measurement wavelength of 590 nm. The measured refractive indices n _x , n _y , and n _{z were} calculated according to the following formula.

Ro=(n _x -n _y )×d(nm)

Rth={(n _x +n _y )/2-n _z }×d(nm) (wherein n _x represents a refractive index in a direction x in which the refractive index in the in-plane direction of the film is the largest. n _y represents The refractive index in the direction y orthogonal to the aforementioned direction x in the in-plane direction of the film. n _z 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 of from 100 to 800 can be used as the retardation enhancer. Among them, the nitrogen-containing heterocyclic compound is preferably a compound having a structure represented by the following general formula (1). By using a compound having a structure represented by the following general formula (1) together with a resin, in addition to the retardation film in which Ro and Rth are in the above range, variation in retardation due to environmental humidity fluctuation can be suppressed.

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

In the above general formula (1), A ₁ , A ₂ and B each independently represent an alkyl group (methyl, ethyl, n-propyl, isopropyl, tert-butyl, n-octyl, 2-B). A hexyl group or the like, a cycloalkyl group (cyclohexyl group, cyclopentyl group, 4-n-dodecylcyclohexyl group, etc.), an aromatic hydrocarbon ring or an aromatic hetero ring. Among them, an aromatic hydrocarbon ring or an aromatic heterocyclic ring is preferred, and an aromatic hydrocarbon ring or an aromatic heterocyclic ring of five or six members is particularly preferred.

The structure of the aromatic hydrocarbon ring or the aromatic heterocyclic ring of five or six members is not limited, and examples thereof include a benzene ring, a pyrrole ring, a pyrazole ring, an imidazole ring, and a 1,2,3-triazole ring. 2,4-triazole ring, tetrazole ring, furan ring, oxazole ring, isoxazole ring, oxadiazole ring, isoxazole ring, thiophene ring, thiazole ring, isothiazole ring, thiadiazole ring, Isothiadiazole ring, carbazole ring, quinoxaline ring, benzoxazole ring and the like. The nitrogen-containing heterocyclic compound is preferably one of at least one selected from the group consisting of a compound having an indazole ring, a quinoxaline ring, a benzoxazole ring, an oxadiazole ring, an oxazole ring, a triazole ring, and a pyrazole ring. .

The aromatic hydrocarbon ring or the aromatic heterocyclic ring of five or six members represented by A ₁ , A ₂ and B may have a substituent. The substituent may, for example, be a halogen atom (such as a fluorine atom, a chlorine atom, a bromine atom or an iodine atom) or an alkyl group (methyl, ethyl, n-propyl, isopropyl, tert-butyl, n). -octyl, 2-ethylhexyl, etc.), cycloalkyl (cyclohexyl, cyclopentyl, 4-n-dodecylcyclohexyl, etc.), alkenyl (vinyl, allyl, etc.), cycloalkenyl (2-cyclopenten-1-yl, 2-cyclohexen-1-yl, etc.), alkynyl (ethynyl, propargyl, etc.), aromatic hydrocarbon ring (phenyl, p-tolyl, naphthalene) Alkyl, etc., an aromatic heterocyclic group (2-pyrrolyl, 2-furyl, 2-thienyl, pyrrolyl, imidazolyl, oxazolyl, thiazolyl, benzimidazolyl, benzoxazolyl, 2 -benzothiazolyl, pyrazolone, pyridyl, pyridinyl, 2-pyrimidinyl, triazinyl, pyrazolyl, 1,2,3-triazolyl, 1,2,4-triazole Base, oxazolyl, isoxazolyl, 1,2,4-oxadiazolyl, 1,3,4-oxadiazolyl, thiazolyl, isothiazolyl, 1,2,4-thiadiazolyl , 1,3,4-thiadiazolyl, etc.), cyano, hydroxy, nitro, carboxy, alkoxy (methoxy, ethoxy, isopropoxy, tert-butoxy, n-octyl Oxyl, 2-methoxyethoxy Ethyloxy (phenoxy, 2-methylphenoxy, 4-tert-butylphenoxy, 3-nitrophenoxy, 2-tetradecylaminophenoxy, etc.) , anthraceneoxy (methyloxy, ethoxycarbonyl, trimethylacetoxy, stearyloxy, benzyloxy, p-methoxyphenylcarbonyloxy, etc.), amine group ( Amino group, methylamino group, dimethylamino group, anilino group, N-methyl-anilino group, diphenylamino group, etc.), mercaptoamino group (formylamino group, etidylamino group, Trimethylethenylamine, laurylamine, benzhydrylamine, etc., alkyl and arylsulfonylamino (methylsulfonylamino, butylsulfonylamino, Phenylsulfonylamino, 2,3,5-trichlorophenylsulfonylamino, p-methylphenylsulfonylamino, etc., mercapto, alkylthio (methylthio, ethylsulfide) Base, n-hexadecylthio, etc.), arylthio (phenylthio, p-chlorophenylthio, m-methoxyphenylthio, etc.), aminesulfonyl (N-ethylaminesulfonate) , N-(3-dodecyloxy)amine sulfonyl, N,N-dimethylamine sulfonyl, N-acetyl sulfonyl sulfonyl, N-benzyl hydrazinyl sulfonyl , N-(N'-phenylamine-mercapto)aminesulfonyl, etc., sulfonic acid group Anthracenyl (ethenyl, trimethylethylbenzylbenzyl, etc.), amine carbaryl (amine methyl sulfhydryl, N-methylamine carbhydryl, N,N-dimethylamine carbhydryl, Each group such as N,N-di-n-octylaminecarbamyl, N-(methylsulfonyl)aminomethane, etc.).

In order to obtain a cellulose acylate film which is excellent in the effect of changing optical characteristics and excellent in durability, in the above general formula (1), A ₁ , A ₂ and B represent a benzene ring, a pyrrole ring, and a pyrene. The azole ring, the imidazole ring, the 1,2,3-triazole ring or the 1,2,4-triazole ring is preferred.

In the above general formula (1), it is preferred that the T ₁ and T ₂ systems each independently represent a pyrrole ring, a pyrazole ring, an imidazole ring, a 1,2,3-triazole ring or a 1,2,4-triazole ring. Among these, in order to obtain a resin composition which is excellent in retardation fluctuation with respect to humidity fluctuation and excellent in durability, a pyrazole ring, a triazole ring or an imidazole ring is preferred, and a pyrazole ring is particularly preferred. . The pyrazole ring, the 1,2,3-triazole ring or the 1,2,4-triazole ring or the imidazole ring represented by T ₁ and T ₂ may also be a tautomer. The specific structure of the pyrrole ring, the pyrazole ring, the imidazole ring, the 1,2,3-triazole ring or the 1,2,4-triazole ring is as follows.

Wherein, ※ India represents (1) a general formula of L _1, L _2, L ₃ or L ₄ of the binding position. R ⁵ represents a hydrogen atom or a non-aromatic substituent. The non-aromatic substituent represented by R ⁵ may be the same as the non-aromatic substituent among the substituents which A ₁ may have in the above general formula (1). When the substituent represented by R ⁵ is a substituent having an aromatic group, A ₁ and T ₁ or B and T ₁ may become easily curled, and A ₁ , B and T _{1 may} not form and deuterated cellulose. The interaction is so that it is difficult to suppress variations in optical characteristics. In order to enhance the effect of suppressing variations in optical characteristics, an R ⁵ -based hydrogen atom, an alkyl group having 1 to 5 carbon atoms or a fluorenyl group having 1 to 5 carbon atoms is preferred, and a hydrogen atom is particularly preferred.

In the above general formula (1), T ₁ and T ₂ may have a substituent, and examples of the substituent include the same substituents as those of A ₁ and A ₂ in the above general formula (1).

In the above general formula (1), L ₁ , L ₂ , L ₃ and L ₄ each independently represent a single bond or a divalent linking group, and an aromatic hydrocarbon ring of five or less members separated by two or less atoms. Or an aromatic heterocyclic ring is linked. The atomic system which is separated by two or less represents the minimum number of atoms existing between the substituents which are bonded to the atoms constituting the linking group. The divalent linking group having two or less atomic number is not particularly limited, and is selected from an alkyl group, an alkenyl group, an alkynyl group, O, (C=O), NR, S, (O=S=O). A group of two-valent linking groups or a combination of two of these. R represents a hydrogen atom or a substituent. Examples of the substituent represented by R include an alkyl group (methyl, ethyl, n-propyl, isopropyl, tert-butyl, n-octyl, 2-ethylhexyl, etc.), a cycloalkyl group (ring) Hexyl, cyclopentyl, 4-n-dodecylcyclohexyl, etc., aromatic hydrocarbon ring (phenyl, p-tolyl, naphthyl, etc.), aromatic heterocyclic (2-furyl, 2- A thienyl group, a 2-pyrimidinyl group, a 2-benzothiazolyl group, a 2-pyridyl group or the like), a cyano group or the like. The divalent linking group represented by L ₁ , L ₂ , L ₃ and L ₄ may have a substituent, and the substituent is not particularly limited, and examples thereof include A ₁ and A ₂ in the above general formula (1). It may have the same substituents.

In the general formula (1), the planarity of the compound having the structure represented by the general formula (1) is increased, and the interaction with the resin adsorbing water becomes strong, and the variation in optical characteristics is suppressed. L ₁ , L ₂ , L ₃ and L ₄ are either a single bond or O, (C=O)-O, O-(C=O), (C=O)-NR or NR-(C=O) Preferably, a single button is preferred.

In the above general formula (1), n represents an integer of 0 to 5. When n represents an integer of 2 or more, the plural A ₂ , T ₂ , L ₃ , and L _{4 in the} above general formula (1) may be the same or different. When n is larger, the interaction between the compound having the structure represented by the general formula (1) and the resin adsorbing water becomes strong, and the effect of suppressing the change in optical characteristics is excellent, and if n is smaller, the resin adsorbing water is Excellent compatibility. Therefore, n is preferably an integer of 1 to 3, and preferably an integer of 1 to 2.

<Compound having a structure represented by the general formula (2)>

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

(wherein A ₁ , A ₂ , T ₁ , T ₂ , L ₁ , L ₂ , L ₃ and L ₄ are each in the above general formula (1), A ₁ , A ₂ , T ₁ , T ₂ , L ₁ , L ₂ , L ₃ and L _{4 are} synonymous. Each of A ₃ and T ₃ represents the same group as A ₁ and T ₁ in the general formula (1). L ₅ and L ₆ represent the above general formula (1) In the case where L _{1 is the} same base, m represents an integer of 0 to 4).

Since m is small, it is excellent in compatibility with deuterated cellulose. Therefore, m is preferably an integer of 0 to 2, and preferably an integer of 0 to 1.

<Compound having a structure represented by the general formula (1.1)>

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

(Wherein, A _1, B, L ₁ and L ₂ represent those in the above general formula _{(1) A 1, B,} L 1 and L _{2 are} the same group .k integer of 1 to 4 represented by the ₁ .T 1 , 2,4-triazole ring).

Further, the triazole compound having the structure represented by the general formula (1.1) is preferably a triazole compound having a structure represented by the general formula (1.2).

(wherein Z represents a structure of the following general formula (1.2a). q represents an integer of 2 to 3. At least two Z systems are bonded to an ortho or meta position with respect to at least one Z substituted on the benzene ring. ).

(wherein R ¹⁰ represents a hydrogen atom, an alkyl group or an alkoxy group. p represents an integer of 1 to 5. * represents a binding position to a benzene ring. T ₁ represents a 1,2,4-triazole ring).

The compound having the structure represented by the general formula (1), (2), (1.1) or (1.2) may also form a hydrate, a solvate or a salt. Further, in the present embodiment, the hydrate may also contain an organic solvent, and the solvate may also contain water. That is, "hydrate" and "solvate" include a mixed solvate containing any one of water and an organic solvent. Salts include acid addition salts formed with inorganic or organic acids. Examples of the inorganic acid include hydrohalic acid (hydrochloric acid, hydrobromic acid, etc.), sulfuric acid, phosphoric acid, etc., but are not limited thereto. Further, examples of the organic acid include acetic acid, trifluoroacetic acid, propionic acid, butyric acid, oxalic acid, citric acid, benzoic acid, alkylsulfonic acid (methanesulfonic acid, etc.), and allylsulfonic acid (benzenesulfonic acid). , 4-toluenesulfonic acid, 1,5-naphthalenedisulfonic acid, etc.), etc., but are not limited thereto. Among these, a hydrochloride, an acetate, a propionate, and a butyrate are preferred.

As an example of the salt, there may be mentioned a metal ion present in the acidic portion of the parent compound (for example, an alkali metal salt such as a sodium or potassium salt, an alkaline earth metal salt such as a calcium or magnesium salt, an ammonium salt alkali metal ion, or an alkaline earth type). a salt formed by substituting a metal ion or an aluminum ion or adjusting it to an organic base (ethanolamine, diethanolamine, triethanolamine, morpholine, piperidine, etc.), but not This is limited to this. Among these, a sodium salt or a potassium salt is preferred.

Examples of the solvent included in the solvate also include any of the general organic solvents. Specific examples thereof include an alcohol (for example, methanol, ethanol, 2-propanol, 1-butanol, 1-methoxy-2-propanol, t-butanol), an ester (for example, ethyl acetate), Hydrocarbons (for example, toluene, hexane, heptane), ethers (for example, tetrahydrofuran), nitriles (for example, acetonitrile), ketones (acetone), and the like. A solvate of an alcohol such as methanol, ethanol, 2-propanol, 1-butanol, 1-methoxy-2-propanol or t-butanol is preferred. These solvents may be the reaction solvent used in the synthesis of the above compounds, or the solvent used in the crystallization purification after synthesis, or may be mixed for this purpose.

Further, two or more types of solvents may be contained at the same time, and may be in the form of water and a solvent (for example, water and an alcohol (for example, methanol, ethanol, t-butanol, etc.)).

Further, even if the compound having the structure represented by the general formula (1), (2), (1.1) or (1.2) is added without containing water, a solvent or a salt, the optical film of the present embodiment ( Hereinafter, the "optical film" basically means a retardation film, and may also form a hydrate, a solvate or a salt.

The molecular weight of the compound having the structure represented by the general formula (1), (2), (1.1) or (1.2) is not particularly limited, and the smaller the compatibility with the resin, the larger the solubility relative to the environment. The higher the suppression effect of the change in the optical value of the humidity change, the 150 to 2000 is preferable, the 200 to 1500 is preferable, and the 300 to 1000 is more preferable.

Further, the nitrogen-containing heterocyclic compound of the present embodiment has The compound of the structure represented by the following general formula (3) is more preferable.

(In the formula, A represents a pyrazole ring, and each of Ar ₁ and Ar ₂ represents an aromatic hydrocarbon ring or an aromatic hetero ring, and may have a substituent. R ₁ represents a hydrogen atom, an alkyl group, a fluorenyl group, or a sulfonyl group. And 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 aromatic hydrocarbon ring or the aromatic heterocyclic ring represented by Ar ₁ and Ar ₂ is preferably an aromatic hydrocarbon ring or an aromatic heterocyclic ring of five or six members as exemplified in the general formula (1). Further, examples of the substituent of Ar ₁ and Ar ₂ include the same substituents as those shown for the compound having the structure represented by the general formula (1).

Specific examples of R ₁ include a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc.), and an alkyl group (methyl, ethyl, n-propyl, isopropyl, tert-butyl). , n-octyl, 2-ethylhexyl, etc.), mercapto (ethenyl, trimethylethylbenzylbenzyl, etc.), sulfonyl (eg, methylsulfonyl, ethylsulfonyl) And the like, an alkoxycarbonyl group (for example, a methoxycarbonyl group), an aryloxycarbonyl group (for example, a phenoxycarbonyl group, etc.), and the like.

q represents an integer from 1 to 2, and n and m represent integers from 1 to 3.

Specific examples of the compound having an aromatic hydrocarbon ring or an aromatic heterocyclic ring of five or six members are exemplified below. The above-mentioned compound having an aromatic hydrocarbon ring or an aromatic hetero ring having five or six members is not limited by the following specific examples. Further, as described above, the following specific examples may be tautomers, and may also form hydrates, solvates or salts.

Specific examples of the nitrogen-containing heterocyclic compound include compounds described in paragraphs [0140] to [0214] of International Publication No. WO2014/109350A1, in addition to the above-exemplified compounds 1 and 2.

<How to use the compound having the structure represented by the general formula (1)>

The compound having the structure represented by the general formula (1) can be adjusted to a suitable amount and then contained in the optical film. The amount of the compound to be added is preferably 0.1 to 10% by mass based on the amount of the resin constituting the optical film. In particular, it is preferably contained in an amount of 0.5 to 5% by mass. If it is within this range, the mechanical strength of the optical film can be prevented from being reduced, and the phase difference caused by the change in the environmental humidity can be reduced.

Further, as a method of adding the compound having the structure represented by the general formula (1), the resin forming the optical film may be added in the form of a powder, or may be added to the resin forming the optical film after being dissolved in a solvent. in.

[Organic ester]

The optical film (retardation film) of the present embodiment preferably contains at least one selected from the group consisting of a sugar ester, a polycondensation ester, and a polyol ester as an organic ester, and the above-mentioned polycondensation ester does not contain a nitrogen atom in the structure, so It is preferred that the liquid in the production line is cooled and adhered to the filter to further reduce the height of the filter of the nitrogen-containing heterocyclic compound filter. Further, since the sugar ester and the polycondensation ester function are used as the plasticizer, the phase difference film of the present embodiment which is suitable for reducing the film thickness unevenness in the film surface during film formation and reducing the variation in the retardation Rth is suitable.

(sugar ester)

The sugar ester refers to a compound containing at least one of a furanose ring or a pyranose ring, and may be a monosaccharide or a polysaccharide having a structure of 2 to 12 sugars. Further, the sugar ester is preferably a compound in which at least one of the OH groups of the sugar structure is esterified. The average ester substitution degree of the sugar ester is preferably in the range of 4.0 to 8.0, and preferably in the range of 5.0 to 7.5.

The sugar ester is not particularly limited, and examples thereof include a sugar ester represented by the following general formula (A).

General formula (A)(HO) _m -G-(OC(=O)-R ² ) _n

In the above general formula (A), G represents a residue of a monosaccharide or a disaccharide, R ² represents an aliphatic group or an aromatic group, and m is a number of hydroxyl groups directly bonded to a residue of a monosaccharide or a disaccharide. In total, n is the total of the number of -(OC(=O)-R ² ) groups bonded directly to the residue of the monosaccharide or disaccharide, 3≦m+n≦8, n≠0.

The sugar ester having the structure represented by the general formula (A) is difficult to separate the single species of the compound which is fixed as the number (m) of the hydroxyl group and the number (n) of the -(OC(=O)-R ² ) group. It is known that a compound in which m and n are different in the formula is mixed by a plurality of types. Therefore, the performance of the mixture of the number of the hydroxyl groups (m) and the number of the -(OC(=O)-R ² ) groups (n) is extremely important. In the case of the optical film of the present embodiment, the average ester is used. A sugar ester having a degree of substitution in the range of 5.0 to 7.5 is preferred.

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

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

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

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

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.

Further, in the general formula (A), m is a total of the number of hydroxyl groups directly bonded to a residue of a monosaccharide or a disaccharide, and n is a bond directly bonded to a residue of a monosaccharide or a disaccharide - (OC) (=O) - R ² ) The sum of the numbers. Moreover, it must be 3≦m+n≦8, preferably 4≦m+n≦8. Also, n≠0. Further, when n is 2 or more, the -(OC(=O)-R ² ) groups may be the same or may be mutually different.

The aliphatic group in the definition of R ² may be a straight chain, may be a branch, or may be a ring, preferably having a carbon number of 1 to 25, preferably 1 to 20, and 2 to 15 It is especially good. Specific examples of the aliphatic group include, for example, a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, a cyclopropyl group, an n-butyl group, an iso-butyl group, a tert-butyl group, and a pentyl group. , iso-pentyl, tert-pentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, bicyclooctyl, adamantyl, n-fluorenyl, tert-octyl, dodeca, Each of the sixteen bases, eighteen bases, and two bases.

Further, the aromatic group in the definition of R ² may be an aromatic hydrocarbon group or an aromatic heterocyclic group, and is preferably an aromatic hydrocarbon group. The aromatic hydrocarbon group is preferably a carbon number of 6 to 24, more preferably 6 to 12. Specific examples of the aromatic hydrocarbon group include, for example, each of benzene, naphthalene, anthracene, biphenyl, and terphenyl. The aromatic hydrocarbon group is particularly preferably a benzene ring, a naphthalene ring or a biphenyl ring. The aromatic heterocyclic group is preferably a ring containing at least one of an oxygen atom, a nitrogen atom or a sulfur atom. Specific examples of the heterocyclic ring include furan, pyrrole, thiophene, imidazole, pyrazole, pyridine, pyrazine, pyridazine, triazole, triazine, anthracene, oxazole, anthracene, thiazoline, and thiadipine. Azole, oxazoline, oxazole, oxadiazole, quinoline, isoquinoline, pyridazine, naphthyridine, quinoxaline, quinazoline, porphyrin, pteridine, acridine, phenanthroline, phenazine, tetra Each ring of azole, benzimidazole, benzoxazole, benzothiazole, benzotriazole, tetrazaindene, and the like. The aromatic heterocyclic group is particularly preferably a pyridine ring, a triazine ring or a quinoline ring.

The sugar ester system may also contain two or more different substituents in one molecule, and may also contain an aromatic substituent and an aliphatic substituent in one molecule, and may also contain two or more different fragrances in one molecule. Family substituents can also contain two or more aliphatic substituents in one molecule.

Further, it is also preferred to mix two or more types of sugar esters. It also preferably contains a sugar ester containing an aromatic substituent, and a sugar ester containing an aliphatic substituent.

Hereinafter, preferred examples of the sugar ester represented by the general formula (A) are exemplified below, but are not limited to the compounds exemplified herein.

<Synthesis Example: Synthesis Example of Sugar Ester Represented by General Formula (A)>

The synthesis examples of the sugar esters are exemplified below.

The four-neck eggplant type flask with a stirring device, a reflux condenser, a thermometer and a nitrogen introduction tube were respectively placed with sucrose 34.2 g (0.1 mol), anhydrous benzoic acid 180.8 g (0.8 mol), and pyridine 379.7 g (4.8 mol). Nitrogen gas was bubbled from a nitrogen gas introduction tube while stirring, and the temperature was simultaneously raised, and the esterification reaction was carried out at 70 ° C for 5 hours. Next, the inside of the eggplant type flask was depressurized to 4 × 10 ² Pa or less, and the excess pyridine was distilled off at 60 ° C, and then the inside of the eggplant type flask was depressurized to 1.3 × 10 Pa or less, and the temperature was raised to 120 ° C to distill off. Anhydrous benzoic acid, the majority of the benzoic acid produced. Then, 300 g of a sodium carbonate aqueous solution of 1 L of toluene and 0.5% by mass was added thereto, and the mixture was stirred at 50 ° C for 30 minutes, and allowed to stand, and the toluene layer was separated and taken out. Finally, 100 g of water was added to the separated toluene layer, and after washing at room temperature for 30 minutes, the toluene layer was separated and taken out, and toluene was distilled off at 60 ° C under reduced pressure (4 × 10 ² Pa or less) to obtain a compound A-1. , a mixture of A-2, A-3, A-4 and A-5. After the obtained mixture was analyzed by HPLC and LC-MASS, A-1 was 7 mass%, A-2 was 58 mass%, A-3 was 23 mass%, A-4 was 9 mass%, and A-5 was 3 mass. %, the average ester substitution degree of the sugar ester is 6.57. Further, a part of the obtained mixture was purified by a gel column chromatography to obtain A-1, A-2, A-3, A-4 and A-5 having a purity of 100%, respectively.

The amount of the sugar ester added is preferably in the range of 0.1 to 20% by mass, and preferably in the range of 1 to 15% by mass, based on the resin constituting the optical film (for example, fluorinated cellulose). .

The sugar ester is preferably a color of 10 to 300, and preferably 10 to 40.

(polyesterified ester)

In the optical film (retardation film) of the present embodiment, the organic ester is preferably a polycondensation ester having a structure represented by the following general formula (4). The polycondensation ester is preferably contained in an amount of from 1 to 30% by mass, more preferably from 5 to 20% by mass, based on the plasticizing effect of the resin.

General formula (4)B ₃ -(G ₂ -A) _n -G ₂ -B ₄

In the above general formula (4), B ₃ and B ₄ each independently represent an aliphatic or aromatic monocarboxylic acid residue or a hydroxyl group. G ₂ represents an alkylene glycol residue having 2 to 12 carbon atoms, an aryl diol residue having 6 to 12 carbon atoms, or an oxyalkylene glycol residue having 4 to 12 carbon atoms. A represents an alkylenedicarboxylic 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 polycondensation ester is a polycondensation ester comprising a repeating unit obtained by reacting a dicarboxylic acid with a diol, A represents a carboxylic acid residue in the polycondensation ester, and G ₂ represents an alcohol residue.

The dicarboxylic acid constituting the polycondensation 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 a single type or a mixture of two or more types. In particular, mixed aromatics and aliphatics are preferred.

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

Further, it is preferable to include a repeating unit obtained by reacting a dicarboxylic acid containing at least an aromatic dicarboxylic acid with a diol having 1 to 8 carbon atoms, so as to contain an aromatic dicarboxylic acid and an aliphatic dicarboxylic acid. The repeating unit obtained by reacting the dicarboxylic acid with a diol having 1 to 8 carbon atoms is more preferable.

The ends of the molecules of the polycondensation ester may be blocked or unblocked.

Specific examples of the alkylenedicarboxylic acid constituting the general formula (4) include 1,2-ethanedicarboxylic acid (succinic acid), 1,3-propanedicarboxylic acid (glutaric acid), 2 valence derived from 1,4-butane dicarboxylic acid (adipate), 1,5-pentane dicarboxylic acid (pimelic acid), 1,8-octane dicarboxylic acid (sebacic acid) The basis. Specific examples of the alkenyldicarboxylic acid constituting A include, for example, maleic acid and fumaric acid. Specific examples of the aryl dicarboxylic acid constituting A include, for example, 1,2-benzenedicarboxylic acid (capric acid), 1,3-benzenedicarboxylic acid, 1,4-benzenedicarboxylic acid, and 1, 5-naphthalenedicarboxylic acid and the like.

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

G ₂ in the general formula (4) represents a divalent group derived from an alkylene glycol having 2 to 12 carbon atoms, and a divalent group derived from an aryl diol having 6 to 12 carbon atoms. Or a divalent group derived from an alkylene glycol having 4 to 12 carbon atoms.

Examples of the divalent group derived from the alkylene glycol having 2 to 12 carbon atoms in G ₂ include ethylene glycol, 1,2-propylene glycol, 1,3-propanediol, and 1,2-butanediol. , 1,3-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-dihydroxymethylpentane), 2-n-butyl-2-ethyl- 1,3-propanediol (3,3-dimethylol heptane), 3-methyl-1,5-pentanediol, 1,6-hexanediol, 2,2,4-trimethyl-1 , 3-pentanediol, 2-ethyl-1,3-hexanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, and A divalent group derived from 1,12-octadecanediol or the like.

Examples of the divalent group derived from an aryl diol having 6 to 12 carbon atoms in G ₂ include 1,2-dihydroxybenzene (catechol) and 1,3-dihydroxybenzene (m-phenylene). A divalent base derived from diphenol), 1,4-dihydroxybenzene (hydroquinone) or the like. Examples of the divalent group derived from the oxygen alkylene glycol having 4 to 12 carbon atoms in G include those derived from diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, and the like. The basis of the price of 2.

G ₂ may be a single type or a combination of two or more types. Among them, 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.

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

The aromatic ring-containing monocarboxylic acid in the monovalent group derived from the aromatic ring-containing monocarboxylic acid is a carboxylic acid having an aromatic ring in the molecule, and includes not only an aromatic ring directly bonded to a carboxyl group but also an aromatic ring. It is bonded to a carboxyl group via an alkylene group or the like. Examples of the monovalent group derived from the aromatic ring-containing monocarboxylic acid include benzoic acid, p-tert-butyl benzoic acid, n-toluic acid, m-toluic acid, p-toluic acid, dimethyl benzoic acid, and B. base A monovalent group derived from benzoic acid, n-propyl benzoic acid, aminobenzoic acid, ethoxylated benzoic acid, phenylacetic acid, 3-phenylpropionic acid or the like. Among them, benzoic acid and p-toluic acid are preferred.

Examples of the monovalent group derived from an aliphatic monocarboxylic acid include a monovalent group derived from acetic acid, propionic acid, butyric acid, caprylic acid, caproic acid, capric acid, dodecanoic acid, stearic acid, oleic acid or the like. base. Among them, a monovalent group derived from an alkyl monocarboxylic acid having an alkyl group having 1 to 3 carbon atoms is preferred, and an acetamino group (a monovalent group derived from acetic acid) is preferred.

In the present embodiment, the weight average molecular weight of the polycondensation ester is preferably in the range of 500 to 3,000, and preferably in the range of 600 to 2,000. The weight average molecular weight can be measured by the aforementioned gel permeation chromatography (GPC).

Hereinafter, specific examples of the polycondensation ester having the structure represented by the general formula (4) are exemplified, but are not limited thereto.

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

<Polymeric ester P1>

180 g of ethylene glycol, 278 g of anhydrous citric acid, 91 g of adipic acid, 610 g of benzoic acid, and 0.191 g of tetraisopropyl titanate as an esterification catalyst were placed in a 2L neck with a thermometer, a stirrer, and a rapid cooling tube. The flask was stirred until it reached 230 ° C in a nitrogen stream, and the temperature was gradually raised. The degree of polymerization was observed and a dehydration condensation reaction was simultaneously carried out. After completion of the reaction, the unreacted ethylene glycol was distilled off under reduced pressure at 200 ° C to obtain a polycondensation ester P1. The acid value was 0.20 and the number average molecular weight was 450.

<Polymeric ester P2>

251 g of 1,2-propanediol, 103 g of anhydrous citric acid, 244 g of adipic acid, 610 g of benzoic acid, and 0.191 g of tetraisopropyl titanate as an esterification catalyst were placed in a 2 L equipped with a thermometer, a stirrer, and a rapid cooling tube. The four-necked flask was stirred until the temperature reached 230 ° C, and the temperature was gradually raised while stirring. The degree of polymerization was observed and a dehydration condensation reaction was simultaneously carried out. After completion of the reaction, unreacted 1,2-propanediol was distilled off under reduced pressure at 200 ° C to obtain the following polycondensation ester P2. The acid value was 0.10 and the number average molecular weight was 450.

<Polymeric ester P3>

330 g of 1,4-butanediol, 244 g of anhydrous citric acid, 103 g of adipic acid, 610 g of benzoic acid, and 0.191 g of tetraisopropyl titanate as an esterification catalyst were placed in a thermometer, a stirrer, and a rapid cooling tube. The 2 L four-necked flask was stirred until the temperature reached 230 ° C, and the temperature was gradually raised. The degree of polymerization was observed and a dehydration condensation reaction was simultaneously carried out. After completion of the reaction, the unreacted 1,4-butanediol was distilled off under reduced pressure at 200 ° C to obtain a polycondensation ester P3. The acid value was 0.50 and the number average molecular weight was 2000.

<Polymeric ester P4>

251 g of 1,2-propanediol, 354 g of citric acid, 610 g of benzoic acid, and 0.191 g of tetraisopropyl titanate as an esterification catalyst were placed in a 2 L four-necked flask equipped with a thermometer, a stirrer, and a rapid cooling tube. The nitrogen gas flow was stirred until it reached 230 ° C, and the temperature was gradually raised. The degree of polymerization was observed and a dehydration condensation reaction was simultaneously carried out. After completion of the reaction, the unreacted 1,2-propanediol was distilled off under reduced pressure at 200 ° C to obtain a polycondensation ester P4. The acid value was 0.10 and the number average molecular weight was 400.

<Polymeric ester P5>

251 g of 1,2-propanediol, 354 g of citric acid, 680 g of p-benzoic acid, and 0.191 g of tetraisopropyl titanate as an esterification catalyst were placed in a 2 L four-necked flask equipped with a thermometer, a stirrer, and a rapid cooling tube. In the nitrogen stream, until it reaches 230 ° C, the mixture is stirred and the temperature is gradually raised. Observe the degree of polymerization and The dehydration condensation reaction is simultaneously carried out. After completion of the reaction, unreacted 1,2-propanediol was distilled off under reduced pressure at 200 ° C to obtain the following polycondensation ester P5. The acid value was 0.30 and the number average molecular weight was 400.

<Polymeric ester P6>

180 g of 1,2-propanediol, 292 g of adipic acid, and 0.191 g of tetraisopropyl titanate as an esterification catalyst were placed in a 2 L four-necked flask equipped with a thermometer, a stirrer, and a rapid cooling tube in a nitrogen stream. Stir until the temperature becomes 200 ° C, while stirring slowly. The degree of polymerization was observed and a dehydration condensation reaction was simultaneously carried out. After completion of the reaction, the unreacted 1,2-propanediol was distilled off under reduced pressure at 200 ° C to obtain a polycondensation ester P6. The acid value was 0.10 and the number average molecular weight was 400.

<Polymeric ester P7>

180 g of 1,2-propanediol, 244 g of anhydrous citric acid, 103 g of adipic acid, and 0.191 g of tetraisopropyl titanate as an esterification catalyst were placed in a 2 L four-necked flask equipped with a thermometer, a stirrer, and a rapid cooling tube. In the flow of nitrogen until it reaches 200 ° C, stirring is carried out while slowly raising the temperature. Observational polymerization Degree and simultaneous dehydration condensation reaction. After the completion of the reaction, the unreacted 1,2-propanediol was distilled off at 200 ° C to obtain a polycondensation ester P7. The acid value was 0.10 and the number average molecular weight was 320.

<Polymeric ester P8>

251 g of ethylene glycol, 244 g of anhydrous citric acid, 120 g of succinic acid, 150 g of acetic acid, and 0.191 g of tetraisopropyl titanate as an esterification catalyst were placed in a 2 L four-necked flask equipped with a thermometer, a stirrer, and a rapid cooling tube. The temperature was raised until it reached 200 ° C in a nitrogen stream, and the temperature was gradually raised while stirring. The degree of polymerization was observed and a dehydration condensation reaction was simultaneously carried out. After completion of the reaction, the unreacted ethylene glycol was distilled off under reduced pressure at 200 ° C to obtain a polycondensation ester P8. The acid value was 0.50 and the number average molecular weight was 1200.

<Polymeric ester P9>

The same production method as the above-mentioned polycondensation ester P2, but changing the reaction conditions, a polycondensation ester P9 having an acid value of 0.10 and a number average molecular weight of 315 was obtained.

<Polyol esters>

It is also preferred that the retardation film of the present embodiment contains a polyol ester.

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

The polyol which can be preferably used in the present embodiment is represented by the following general formula (5).

General formula (5) R ₁₁ -(OH) _n

However, R ₁₁ is an n-valent organic group, n is a positive integer of 2 or more, and an OH group represents an alcoholic and/or phenolic hydroxyl group.

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

Examples thereof include campyrin, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, and 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-1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trishydroxyl Ethylethane, xylitol, and the like.

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

The monocarboxylic acid to be used as the polyol ester is not particularly limited, and a known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid or the like can be used. When an alicyclic monocarboxylic acid or an aromatic monocarboxylic acid is used, it is preferred because it can improve 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 linear or side chain having 1 to 32 carbon atoms can be preferably used. The carbon number is preferably 1~20, with 1 ~10 is especially good. It is preferred that the compatibility with cellulose acetate is increased by containing acetic acid, and it is also preferred to use acetic acid together with other monocarboxylic acids.

Preferred examples of the aliphatic monocarboxylic acid include acetic acid, propionic acid, butyric acid, oxalic acid, caproic acid, heptanoic acid, caprylic acid, capric acid, capric acid, 2-ethylhexanoic acid, and undecanoic acid. , lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, heptadecanoic acid, stearic acid, nonadecanoic acid, eicosanoic acid, behenic acid, twenty-four Saturated fatty acid, undecylenic acid, oleic acid, sorbic acid, linoleic acid, linseed oil, such as alkanoic acid, ceric acid, heptacosanoic acid, octadecanoic acid, beeswavic acid, lacquer wax An unsaturated fatty acid such as an acid or arachidonic acid.

As a preferable example of the alicyclic monocarboxylic acid, for example, cyclopentanecarboxylic acid, cyclohexanecarboxylic acid, cyclooctanecarboxylic acid, or the like can be mentioned.

As an example of a preferable aromatic monocarboxylic acid, an alkoxy group such as benzoic acid or a benzene ring of benzoic acid such as toluic acid is introduced into one to three alkyl groups, a methoxy group or an ethoxy group. An aromatic monocarboxylic acid having two or more benzene rings, such as a biphenylcarboxylic acid, a naphthalenecarboxylic acid or a tetrahydronaphthalenecarboxylic acid, or a derivative thereof. In particular, benzoic acid is preferred.

The molecular weight of the polyol ester is not particularly limited, and is preferably in the range of 300 to 1,500, more preferably in the range of 350 to 750. A larger molecular weight is preferred because it is less volatile, but it is preferably smaller on the surface of moisture permeability and compatibility with cellulose deuterated.

The carboxylic acid to be used for the polyol ester may be one type or a mixture of two or more types. Also, the OH group in the polyol may also be all ester Alternatively, a part may remain in the state of an OH group.

Specific compounds of the polyol ester are exemplified below.

The polyol ester is preferably contained in the range of 0.5 to 5% by mass, more preferably in the range of 1 to 3% by mass, based on the retardation film (cellulose ester resin). The range of 2% by mass is particularly preferable.

Polyol esters can be synthesized according to the conventional synthesis methods known in the past. Perform the synthesis.

[Other additives] Phosphate

The retardation film of this embodiment may contain a phosphate. Examples of the phosphate ester include a triaryl phosphate, a diaryl phosphate, a monoaryl phosphate, an arylphosphonic acid compound, an arylphosphine oxide compound, a condensed aryl phosphate, a halogenated alkyl phosphate, A halogen-containing condensed phosphate, a halogen-containing condensed phosphonate, a halogen-containing phosphite, or the like.

Specific examples of the phosphate include triphenyl phosphate, 9,10-dihydro-9-oxa-10-phosphinophen-10-oxide, phenylphosphonic acid, and stilbene (β-chloroethyl). Phosphate, ginseng (dichloropropyl) phosphate, ginseng (tribromoneopentyl) phosphate, and the like.

<Ester of Glycolic Acid>

Further, as one of the polyol esters, an ester of glycolic acid (glycolate compound) can be used. The glycolate compound is not particularly limited, and an alkyl phthalyl alkyl glycolate is preferably used.

Examples of the alkyl mercapto alkyl glycolate include methyl mercapto methyl glycolate, ethyl mercapto ethyl glycolate, and propyl mercaptopropyl glycolate. Butyl decyl butyl glycolate, octyl decyl octyl glycolate, methyl decyl ethyl glycolate, ethyl decyl methyl glycolate, ethyl decyl propyl Glycolate, methyl hydrazine Mercaptobutyl butyl glycolate, ethyl decyl butyl glycolate, butyl decyl methyl glycolate, butyl decyl ethyl glycolate, propyl decyl butyl glycolate Ester, butyl decyl propyl glycolate, methyl decyl octyl glycolate, ethyl decyl octyl glycolate, octyl decyl methyl glycolate, octyl hydrazine The ethyl ethyl glycolate or the like is preferably ethyl decyl ethyl glycolate.

<Microparticles (matting agent)>

In order to improve the smoothness of the surface, the retardation film may further contain fine particles (matting agent) as necessary.

The microparticles may be inorganic microparticles or organic microparticles. Examples of the inorganic fine particles include silica, titania, alumina, zirconia, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium citrate, hydrated calcium citrate, aluminum citrate, ruthenium Magnesium acid and calcium phosphate. Among them, cerium oxide or zirconium oxide is preferred, and in order to reduce the haze of the obtained film, cerium oxide is preferred.

Examples of the cerium oxide microparticles include AEROSIL R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600, NAX50 (above Japanese AEROSIL), SEAHOSTER KE-P10, KE-P30, KE - P50, KE-P100 (above Japanese catalyst (share) system), etc. Among them, AEROSIL R972V, NAX50, SEAHOSTER KE-P30, etc. can maintain the turbidity of the obtained film and reduce the friction coefficient, which is particularly preferable.

The primary particle diameter of the microparticles is in the range of 5 to 50 nm. Preferably, it is preferably in the range of 7 to 20 nm. If the primary particle diameter is better, the effect of improving the film smoothness is large, but the transparency is liable to be lowered. Therefore, the fine particle system may be contained as a secondary aggregate having a particle diameter of 0.05 to 0.3 μm. The size of the primary particles of the microparticles or the secondary agglomerates thereof can be determined by using a transmission electron microscope at a magnification of 50 to 2 million times to observe primary particles or secondary aggregates, and 100 particles as primary particles or secondary aggregates are obtained. The average of the particle diameters.

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

<phase difference control agent>

In order to improve the display quality of the image display device such as a liquid crystal display device, a phase difference controlling agent may be added to the retardation film, or a liquid crystal layer may be formed by forming an alignment film, and the phase difference between the protective film and the liquid crystal layer may be formed by the composite polarizing plate. It can impart optical compensation to the retardation film.

Examples of the phase difference controlling agent include an aromatic compound having two or more aromatic rings described in the specification of European Patent No. 911,656A2, and a rod-shaped compound described in JP-A-2006-2025. Further, two or more kinds of aromatic compounds may be used in combination. The aromatic ring of the aromatic compound is preferably an aromatic heterocyclic ring containing an aromatic heterocyclic ring in addition to the aromatic hydrocarbon ring. The aromatic heterocyclic ring is generally an unsaturated heterocyclic ring. Among them, the 1,3,5-triazine ring described in JP-A-2006-2026 is also preferred.

Further, a compound having a structure represented by the general formula (1) can also be used as a phase difference controlling agent.

The amount of the phase difference controlling agent to be added is preferably in the range of 0.5 to 20% by mass, and preferably in the range of 1 to 10% by mass, based on 100% by mass of the resin used as the film substrate.

[Method of Manufacturing Phase Difference Film]

The retardation film of the present embodiment can be produced, for example, by a solution casting film forming method or a melt casting film forming method. However, in the case of producing a retardation film of a film, in order to suppress a decrease in the retardation Rth, it is necessary to increase the amount of the nitrogen-containing heterocyclic compound to be added as a retardation enhancer. When the amount of the nitrogen-containing heterocyclic compound added is large, the nitrogen-containing heterocyclic compound cannot be melted by the melt-casting film forming method, and scorch is generated during the film formation, so that the solution is casted under the solution casting method. It is ideal for film formation. Hereinafter, an example in which the retardation film of the present embodiment is produced by the solution casting film forming method will be described.

(solution casting film forming method)

Fig. 2 is a view schematically showing an example of a device for producing a retardation film by a solution casting film forming method. The solution casting film forming method is carried out in sequence (1) at least an additive such as a cellulose ester resin, a retardation enhancer (for example, a nitrogen-containing heterocyclic compound), and an organic ester (for example, a sugar ester) is dissolved in a solvent to prepare an admixture. a step of doping, (2) a step of casting a dopant on a strip or a barrel of a metal support, and (3) evaporating a solvent of a dopant cast on the metal support And taking the step of the web (web), (4) stripping the net from the metal support a step of molding, (5) a step of extending the peeled web (film) and drying it, and (6) a step of winding after cooling the film.

(1) dopant modulation step

This step is to make the cellulose ester resin in the dissolution vessel 31, and the nitrogen-containing heterocyclic compound, sugar ester, polycondensation ester, polyol ester, or other compound is mainly used for the cellulose ester resin, as the case may be. The solvent is stirred in an organic solvent and dissolved simultaneously to form a dopant. Alternatively, a dopant containing a nitrogen-containing heterocyclic compound, a sugar ester, a polycondensation ester, a polyol ester, or another compound solution may be mixed with the cellulose ester-based resin solution to form a main solution.

When the retardation film is produced by the solution casting film forming method, the organic solvent for forming the dopant can be used without any limitation as long as it can dissolve the cellulose ester resin and other compounds at the same time.

For example, examples of the chlorine-based organic solvent include dichloromethane, and examples of the non-chlorine-based organic solvent include methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, and 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-2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, As the 2,2,3,3,3-pentafluoro-1-propanol, nitroethane or the like, dichloromethane, methyl acetate, ethyl acetate or acetone can be preferably used.

In addition to the above-mentioned organic solvent, the dopant is preferably a linear or branched chain aliphatic alcohol having a carbon number of 1 to 4 in the range of 1 to 40% by mass. When the ratio of the alcohol in the dopant becomes high, then the net The gelation is easy to separate from the metal support, and when the ratio of the alcohol is small, the dissolution of the cellulose ester resin and other compounds in the non-chlorine organic solvent system is also promoted. In the film formation of the retardation film, a method of forming a film using a dopant having an alcohol concentration of 0.5 to 15.0% by mass can be applied from the viewpoint of improving the planarity of the phase difference film obtained.

In particular, the deuterated cellulose and other compounds are dissolved in a range of 15 to 45 mass% in a solvent containing dichloromethane and a linear or branched chain aliphatic alcohol having 1 to 4 carbon atoms. A dopant composition is preferred.

Examples of the linear or branched chain aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-. Butanol. Among these, methanol and ethanol are preferred from the viewpoints of stability of the dopant, low boiling point, and good drying property.

The dissolution of the cellulose ester-based resin, the nitrogen-containing heterocyclic compound, the sugar ester, the polycondensation ester, and the polyol ester or other compound can be carried out by a method of performing at normal pressure or below the boiling point of the main solvent. A method of performing a cooling and dissolving method as described in JP-A-H09-95549, JP-A-H09-95557, JP-A-H09-95558, and JP-A-9-95538, Various methods of dissolving such as a method of performing high pressure as described in JP-A-11-21379, but it is preferable to carry out the method of pressurizing to the boiling point of the main solvent or more.

The concentration of the cellulose ester resin in the dopant is 10~ A range of 40% by mass is preferred. After dissolving and dispersing the compound added to the dopant in or after the dissolution, the filter material is used for filtration and defoaming, and the liquid is pumped to the next step.

The filtration system preferably uses a filter material having a particle diameter of 0.5 to 5 μm and a drainage time of 10 to 25 sec/100 ml.

In this method, the aggregates remaining when the particles are dispersed or the aggregates generated when the main dopant is added can be obtained by using a filter material having a particle diameter of 0.5 to 5 μm and a drainage time of 10 to 25 sec/100 ml. Only remove condensate. The concentration of the particles in the main dopant is also sufficiently thin compared to the additive liquid, so that no aggregation of the aggregates adheres to each other during filtration, resulting in an increase in the violent filtration pressure.

(2) Casting step

This step is such that the dopant in the dissolution vessel 31 is sent to the pressurizing die 32 by a liquid feeding pump (for example, a pressurized quantitative gear pump), and the casting position on the endless metal supporting body 33 that is infinitely transferred is carried out. The dopant is cast from the press mold 32. The pressurizing mold 32 is preferably a surface on which the thickness of the film can be made uniform by adjusting the slit shape of the die exit portion of the mold. The pressurizing mold 32 can be preferably used as a hanger type mold or a T mold. In order to increase the film forming speed, two or more press molds 32 may be provided on the metal support 33, and the dose may be doped in batches to form a plurality of layers.

The metal support body 33 is composed of a stainless steel belt that is stretched by two rolls 34‧34. As the metal support body 33, it is preferable that the surface is mirror-finished, and in addition to the above-mentioned stainless steel belt, it is also possible to use the body as a casting. The object is a metal drum whose surface has been plated.

The width of the casting (casting) can be made 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 -50 ° C - the temperature at which the solvent boils but does not foam, and is more preferably set in the range of -30 to 0 ° C. When the temperature is high, the drying speed of the net mold is increased, so that it is preferable, but if it is too high, the net mold is foamed and the flatness is deteriorated. The ideal support temperature is suitably determined within the range of 0 to 100 ° C, preferably in the range of 5 to 30 ° C. Alternatively, it is also an ideal method of peeling from the support in a state in which a large amount of residual solvent is contained by gelation by cooling and mesh molding.

The method of controlling the temperature of the metal support body 33 is not particularly limited, such as a method of blowing toward warm air or cold air, or a method of bringing warm water into contact with the back side of the metal support body 33. Since the heat transfer can be performed more efficiently using warm water, the time until the temperature of the metal support body 33 reaches a certain value is short, so that it is preferable. In the case of using warm air, it is considered that the temperature of the net mold is lowered due to the latent heat of evaporation of the solvent, and there is a case where the warm air above the boiling point of the solvent is used, and the wind is prevented from being foamed while using a wind having a temperature higher than the target temperature. In particular, it is preferable to efficiently dry the temperature of the support and the temperature of the dry air between casting and peeling.

(3) Solvent evaporation step

This step heats the solvent by evaporating the film (mesh) formed by the dopant cast on the metal support 33. The method of evaporating the solvent is to blow the surface from the surface of the net mold (opposite side to the metal support 33). The method, the method of heat transfer by liquid from the back surface of the metal support 33 (opposite to the mesh mold), the heat transfer from the front surface by radiant heat, etc., but the method of heat transfer from the back surface due to drying efficiency Good, so it is better. Moreover, it is also desirable to use a method of constituting these. It is preferred that the web on the cast metal support 33 is dried on the metal support 33 in an environment of 40 to 100 °C. It is preferable to heat the temperature at a temperature of 40 to 100 ° C to the top of the mesh mold, or to heat it by means of infrared rays or the like.

From the viewpoint of surface quality, moisture permeability, and peelability, it is preferable to peel the mesh mold from the metal support 33 within 30 to 120 seconds.

(4) Stripping step

This step is performed by peeling off the web on which the solvent on the metal support 33 is subjected to evaporation at a predetermined peeling position by the peeling roller 35. Hereinafter, the net mold after peeling is referred to as a net mold 36. Netmodel 36 is sent to the next step.

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.

Further, the amount of residual solvent of the mesh mold on the metal support 33 at the time of peeling is preferably 50 to 120% by mass in terms of the strength of the drying conditions and the length of the metal support 33. When the amount of residual solvent is large, when the peeling is performed at a point, if the mesh mold is too soft, the flatness at the time of peeling is impaired, and the peeling tension is likely to cause a vertical or vertical grain path, so that the economic speed and quality are both The amount of residual solvent at the time of peeling is determined after consideration. Further, the residual solvent amount of the mesh mold is as defined in the following formula.

Residual solvent amount (%) = (mass before heat treatment of net mold - mass after heat treatment of net mold) / (mass after heat treatment of net mold) × 100

Here, the heat treatment when measuring the amount of residual solvent means heat treatment at 115 ° C for 1 hour.

The peeling tension at the time of peeling the net mold from the metal support body 33 is usually in the range of 196 to 245 N/m, and when wrinkles are likely to occur at the time of peeling, it is preferable to perform peeling at a tension of 190 N/m or less.

In the present embodiment, the temperature at the peeling position on the metal supporting body 33 is preferably in the range of -50 to 40 ° C, preferably in the range of 10 to 40 ° C, preferably 15 to 30 ° C. The range is the best.

(5) Extension and drying steps

This step performs a preliminary drying step, an extending step, and a main drying step in this order. The preliminary drying system can be carried out as necessary.

<Preparation drying step>

The mesh mold 36 obtained by peeling off from the metal support 33 is dried. The drying of the net mold 36 can be carried out by transporting the net mold 36 by a plurality of rolls disposed on the upper and lower sides and drying them at the same time, or can be carried by pinching the both ends of the net mold 36 as in a tenter dryer. And at the same time make it dry.

The means for drying the net mold 36 is not particularly limited. Generally, it can be carried out by hot air, infrared rays, heating rolls, microwaves, etc., but it is preferable to carry out hot air from the viewpoint of simplicity.

The drying temperature in the drying step of the net mold 36 is preferably carried out at a glass transition temperature of -5 ° C or less at 100 ° C or higher for a heat treatment of 10 minutes or more and 60 minutes or less. The drying temperature is desirably in the range of 100 to 200 ° C, more preferably in the range of 110 to 160 ° C.

<Extension step>

This step is performed by peeling off the metal support 33 and, if necessary, subjected to preliminary drying, in the MD direction and/or the TD direction. At this time, it is preferable to extend at least in the TD direction by the tenter stretching device 37.

The extension under the extension step can be made as a uniaxial extension or a biaxial extension. The biaxial extension also includes a direction that extends in one direction and relaxes the tension in the other direction to cause it to contract.

The retardation film of the present embodiment preferably has a temperature of (Tg + 15) to (Tg + 50) ° C in the TD direction in order to make the film thickness after stretching into a desired range in the MD direction and/or the TD direction. The range is extended to be better. Further, Tg is the glass transition temperature (° C.) of the film. When the stretching is performed in the above temperature range, the adjustment of the retardation is facilitated, and the elongation stress is lowered, so that the haze is lowered. In addition, a retardation film for a polarizing plate which is excellent in planarity and coloring property of the film itself can be obtained. The extension temperature is preferably in the range of (Tg + 20) to (Tg + 40) °C.

Further, the glass transition temperature Tg referred to herein is measured at a temperature rising rate of 20 ° C / min using a commercially available differential scanning calorimeter, and the intermediate point glass transition temperature (Tmg) is determined according to JIS K7121 (1987). ). Method for measuring glass transition temperature Tg of specific phase difference film The measurement was carried out in accordance with JIS K7121 (1987) using a differential scanning calorimeter DSC220 manufactured by Seiko Instruments.

The retardation film of the present embodiment preferably extends the mesh mold 36 by 1.1 times or more in the TD direction. The extension range is preferably 1.1 to 1.5 times, and preferably 1.05 to 1.3 times, relative to the original width. Within the above range, not only the molecular movement in the film becomes large, but also the desired retardation value is obtained, and the behavior of the dimensional change of the film can be controlled within a desired range.

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

In order to extend in the MD direction, it is preferable to perform peeling at a peeling tension of 130 N/m or more, and particularly preferably 150 to 170 N/m. Since the mesh after peeling is in a high solvent residual state, the stretching in the MD direction can be performed by maintaining the same tension as the peeling tension. As the mesh mold is dried and the amount of residual solvent is reduced, the elongation in the MD direction is lowered.

Further, the extension magnification in the MD direction can be calculated from the rotation speed of the belt support and the tenter operation speed.

The extension in the TD direction is performed by, for example, the steps of all or a part of drying as shown in Japanese Laid-Open Patent Publication No. Sho 62-46625, in which the ends of the wide portions of the mesh mold are held in the width direction by using clips or pins. The method of drying the width (referred to as a tentering method), which is also ideally used in a tenter type using a clip, and a needle-type tenter using a needle.

The retardation film of the present embodiment is inevitably delayed by the extension system, and each value of the in-plane retardation Ro and the retardation Rt in the thickness direction can be automatically AbiScan (Axo Scan Mueller Matrix Polarimeter: Axometrics) The three-dimensional refractive index measurement was carried out at a wavelength of 590 nm in an environment of 23 ° C ‧55% RH, and was calculated from the obtained refractive indices nx, ny, and nz.

When the phase difference film of the present embodiment is provided in a VA mode liquid crystal display device, the in-plane direction defined by the following formula (i) can be improved from the viewpoint of improving the visibility by using only one retardation film. The retardation Ro and the retardation Rth in the thickness direction defined by the following formula (ii) are preferably in the range of the following. The retardation film can adjust the retardation Ro and Rth to the above range by adjusting the stretching ratio at least in the TD direction while extending.

50nm≦|Ro|≦80nm

200nm≦|Rth|≦300nm

Formula (i): Ro = (nx - ny) × d (nm)

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

<Main drying step>

The stretched mesh mold 36 is transported as a film F to the drying device 38, and then dried in the same manner as the above-described preliminary drying. Further, the drying conditions of the main drying step may also be different from the preliminary drying step. In the main drying step, the deviation from the orientation of the cellulose ester-based resin and the additive is less likely to occur, and the fluctuation of the retardation Rth caused by the moisture and the subsequent drying and moist heat fluctuation is suppressed, and the elongation is lower than the extension temperature after the extension. It is preferable that the temperature is 100 ° C or higher and dried for 5 minutes or more, and it is more preferably dried at 110 to 150 ° C for 10 to 20 minutes.

<Knurling processing>

After the main drying is completed, it is preferable to provide a cutter to cut the end portion of the film F before winding the film F, since a good winding posture can be obtained. Further, it is preferable to apply a roll pattern to both end portions of the film width.

The roll processing can be formed by pressing a heated embossing roll. Fine irregularities are formed on the embossing roll, and irregularities are formed on the film by pressing it, whereby the volume of the end portion can be increased. The height of the roll at both 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 up the film F using the winding device 39 after the amount of the residual solvent is 2% by mass or less. By setting the amount of the residual solvent to 0.4% by mass or less, a film having good dimensional stability can be obtained.

The winding method of the film F can be used by a general user, such as a fixed moment method, a fixed tension method, a taper tension method, and the like. The program tension control method such as the partial stress fixation may be performed separately.

[Physical properties of phase difference 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%, the transparency of the film becomes higher, and the film for optical use becomes more advantageous.

(balanced moisture content)

The retardation film of the present embodiment preferably has an equilibrium moisture content of 4% or less at 25 ° C and a relative humidity of 60%, and preferably 3% or less. By setting the equilibrium moisture content to 4% or less, it is easy to respond to changes in humidity, and it is preferable that optical characteristics or dimensions are less likely to change.

(film length, width, film thickness)

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

From the viewpoint of thinning and productivity of the display device, the film thickness of the retardation film is preferably in the range of 10 to 100 μm, and only one retardation film is formed to realize the above-described Ro and Rth, and the retardation film is formed. The film thickness is preferably 40 to 70 μm (if the film thickness of the retardation film is too thin, the desired Ro and Rth cannot be realized by one retardation film).

The film thickness error of the retardation film is preferably in the range of 0 to 5 μm in the thickness direction or the width direction, preferably in the range of 0 to 3 μm, more preferably in the range of 0 to 2 μm.

[Examples]

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto. In the examples, the expression "parts" or "%" is used, and when it is not specifically defined, it means "parts by mass" or "% by mass".

<Production of retardation film 1> <Microparticle Dispersion 1>

The mixture was stirred and mixed for 50 minutes in a dissolver, and then dispersed in a Manton-Gaulin homogenizer to prepare a fine particle dispersion 1.

<Microparticle Addition Liquid 1>

The dissolution tank containing methylene chloride was sufficiently stirred while the fine particle dispersion 1 was slowly added. Further, the particle size of the secondary particles can be made to be a predetermined size by dispersion using an attritor. Made with Japan Fine Line (Shares) Finemet NF filters this to prepare fine particle addition liquid 1.

<Modulation of dopants>

Next, methylene chloride and ethanol were added to the pressurized dissolution tank. Thereafter, the pressurized dissolution vessel containing the solvent was stirred and simultaneously charged with cellulose acetate butyrate having a total thiol substitution degree of 2.4. This was heated and stirred while completely dissolving, and this product was filtered using an Anion filter paper No. 244 made of an Anion filter paper to prepare a main dopant. Thereafter, the following was placed in a sealed dissolution vessel, and the mixture was stirred and dissolved to prepare a dopant.

"Composition of dopants"

Further, the above-mentioned sugar ester S is BzSc (benzylidene sucrose: a sugar residue is B-2, and a substituent is a mixture of a1 to a4 described in Chemical Formula 11, and the average degree of ester substitution is 5.5).

<film formation of film>

Next, on the stainless steel belt support, the solvent was evaporated so that the amount of residual solvent in the net mold formed by the cast (cast) dopant was 75% by mass, and secondly, the peeling tension was 130 N/m from the stainless steel. The mesh mold is peeled off on the belt support. Thereafter, the stripped net mold was extended by 30% in the width direction using a tenter. The residual solvent at the beginning of the extension was 15%. Moreover, the extension temperature on the tenter is 160 °C.

Next, the drying zone is conveyed by a plurality of rolls and the drying is ended at the same time. The drying temperature after stretching was 100 ° C, and the drying time was 5 minutes. By the above operation, the retardation film 1 having a dried film thickness of 60 μm was obtained.

<Production of retardation film 2>

In addition to preparing a dopant by replacing the nitrogen-containing heterocyclic compound A with a nitrogen-containing heterocyclic compound B (exemplified compound 2, a benzoxazole-based compound) as a retardation enhancer, and using the dopant to form a film, In the same manner as in the production of the retardation film 1, the phase difference film 2 was produced in the same manner.

<Production of retardation film 3>

The retardation film 3 was produced in the same manner as in the production of the retardation film 1 except that the film thickness was 80 μm.

<Production of retardation film 4>

A dopant is prepared by using a cellulose acetate butyrate having an ethyl ketone group substitution degree of 1.9, a butylate substitution degree of 0.5, and a total thiol substitution degree of 2.4 as a cellulose ester-based resin, and a film is prepared using the dopant. The retardation film 4 was produced in the same manner as in the production of the retardation film 3.

<Production of retardation film 5>

The retardation film 5 was produced in the same manner as in the production of the retardation film 1 except that the dopant was prepared without adding a retardation enhancer and the film was formed using the dopant. Further, in order to achieve the values of Table 1 in the retardation Ro and Rth, the retardation film 5 was formed to have a dry film thickness of 100 μm.

<Production of retardation film 6>

The retardation film 6 was produced in the same manner as in the production of the retardation film 3 except that a dopant was prepared without adding a sugar ester and a film was formed using the dopant.

<Production of retardation film 7>

The same procedure as in the production of the retardation film 3 was carried out except that a cellulose diacetate having a vinylidene group substitution degree of 2.4 was used as a cellulose ester-based resin to prepare a dopant, and a film was produced using the dopant. The retardation film 7 was produced.

<Production of retardation film 8>

The same procedure as in the production of the retardation film 3 was carried out except that a cellulose triacetate having a acetylation degree of 2.8 was used as a cellulose ester-based resin to prepare a dopant, and a film was produced using the dopant. The retardation film 8 was produced. Further, the dry film thickness of the retardation film 8 was set to 100 μm.

<Production of retardation film 9~12>

The phase difference film 9 to 12 was produced in the same manner as in the production of the retardation film 1 except that the degree of substitution of the butyl sulfonate of the cellulose ester resin and the film thickness of the film were changed as shown in Table 2.

<Measurement of Ro and Rth>

The retardation Ro in the in-plane direction of the above-described retardation films 1 to 12 and the retardation Rth in the thickness direction were measured using an automatic birefringence meter AxoScan (Axo Scan Mueller Matrix Polarimeter: manufactured by Axometrics Co., Ltd.). Ro and Rth are refractive indices n _x , n _y , and n _z obtained by measuring the three-dimensional refractive index in a temperature of 23 ° C and a relative humidity of 55% RH at a measurement wavelength of 590 nm, which are calculated according to the following formula. .

Ro=(n _x -n _y )×d(nm)

Rth={(n _x +n _y )/2-n _z }×d(nm) (wherein n _x represents a refractive index of the direction x in which the refractive index becomes the largest in the in-plane direction of the film. n _y represents a film The refractive index of the direction y orthogonal to the aforementioned direction x in the in-plane direction. n _z represents the refractive index of the thickness direction z of the film, and d represents the thickness (nm) of the film.

<Production of visible side polarizer> (production of polarizer)

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

(production of polarizing plate)

A commercially available polarizing plate protective film, that is, KC6UA manufactured by Konica Minolta having a thickness of 60 μm, was prepared as a film of a deuterated cellulose film bonded to the polarizer.

Step 1: The retardation film and KC6UA were immersed in a 2 mol/L sodium hydroxide solution at 60 ° C for 90 seconds, followed by washing with water and drying, and applying a saponification treatment to the side to which the polarizer was attached.

Step 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: Gently wipe off the excess adhesive attached to the polarizer in step 2, and place the retardation film processed in the configuration step 1 on the one side, and place the KC6UA on the opposite side.

Step 4: Laminating the phase difference film, the polarizer, and the KC6UA in the step 3 at a pressure of 20 to 30 N/cm ² and a conveying speed of about 2 m/min.

Step 5: The laminated body adhered in the step 4 was dried in a dryer at 80 ° C for 2 minutes to prepare a polarizing plate.

The above steps were carried out on the prepared retardation films 1 to 12, respectively, to form a polarizing plate on the visible side.

<Production of Backlight Side Polarizing Plate>

In addition to the zero retardation film (Konica Minolta Co., Ltd., KC4CZ) attached to one surface of the polarizer, the polarizing plate protective film (KC6UA) is attached to the other surface, and the other side and the visible side polarizing plate are produced. The backlight side polarizing plate was fabricated in the same manner. Further, the retardation Ro of the in-plane direction of the zero retardation film was 4 nm, and the retardation Rth in the thickness direction was 6 nm.

<Panel evaluation>

The polarizing plate which was bonded to both surfaces of the liquid crystal cell of the VA type liquid crystal display device (model: UN55HU-8500) manufactured by SAMSUNG was peeled off, and the visible side polarizing plate and the backlight side polarized light produced above were peeled off using an acrylic adhesive. The plates are respectively attached to the glass surface of the visible side and the backlight side for the liquid crystal cell. In this case, the retardation film of the visible-side polarizing plate is placed on the liquid crystal cell side, and the zero-phase retardation film of the backlight-side polarizing plate is placed on the liquid crystal cell side, and the polarizing plates are bonded together. And, after drying, continuous lighting liquid The backlight of the crystal display device was left for one hour, and the screen was displayed in black, and the presence or absence of unevenness and texture was observed, and visual evaluation was performed based on the following evaluation criteria. Further, this evaluation was performed for each of the liquid crystal display devices having the retardation films 1 to 12.

<Evaluation criteria>

◎: No unevenness and texture were observed at all.

○: Slight unevenness and texture were observed depending on the visual angle, but the degree was not caused.

△: A slight unevenness and texture were observed regardless of the visual angle, and the degree of the problem was caused.

×: Strong unevenness and texture were clearly observed on the screen under visual observation.

Tables 1 and 2 show the evaluation results of the respective retardation films 1 to 12. Further, the correspondence between the examples and the comparative examples is shown together in Tables 1 and 2.

According to Table 1, display unevenness was clearly observed in the liquid crystal display device using the retardation film 5. It is considered that since the retardation film 5 does not contain the retardation enhancer, in order to obtain the desired retardation (especially the retardation Rth in the thickness direction), the film thickness has to be made thick to 100 μm, and since the film thickness is When it is thick and the unevenness of the film thickness in the film surface is increased, the retardation Rth in the film surface fluctuates to cause display unevenness.

The display unevenness of the liquid crystal display device using the retardation film 6 is somewhat improved as compared with the liquid crystal display device using the retardation film 5, but it is difficult to say that it is sufficiently improved. It is considered that since the retardation film 6 contains a retardation enhancer, the desired retardation Ro and Rth have been obtained at a film thickness of 80 μm which is thinner than the retardation film 5, but since no sugar ester is contained, at the time of film formation The film becomes soft, and the retardation enhancer cannot be uniformly mixed in the film, so that the film thickness unevenness cannot be sufficiently improved.

The texture was clearly observed visually in the liquid crystal display device using the retardation films 7 and 8, respectively. It is considered that the cellulose ester-based resin contained in the retardation films 7 and 8 is deuterated cellulose (cellulose diacetate or cellulose triacetate) having no substituent other than an ethyl fluorene group. The peeling property from the support at the time of film formation is inferior, and the result of the peeling of the film is not good, and the grain|grain in the width direction of the film at the time of peeling is formed, and this pattern influences the display on liquid-crystal display apparatus. Moreover, the display unevenness under visual observation is considered to be caused by the texture.

On the other hand, the liquid crystal display devices using the retardation films 1 to 4, respectively, did not observe display unevenness and texture at all, and even if observed, Will not be the extent of the problem. In the case of the retardation film 1 to 4, cellulose acetate butyrate is used as the cellulose ester resin, and the film thickness is as thin as 80 μm or less, and the film can be favorably peeled off from the support at the time of film formation. Almost no tracers were observed. In addition, it is considered that the display unevenness is considered to be due to the retardation film and the sugar ester in the retardation films 1 to 4, and it is possible to realize a film having a film thickness of 80 μm or less and using it as a single one. It is necessary to have a high retardation Ro and Rth, and at the same time, it is possible to sufficiently improve the film thickness unevenness in the film surface, thereby reducing the deviation of the retardation Rth in the film surface.

Further, according to Table 2, the degree of substitution of the butyl group is in the range of 0.03 to 0.8, no texture is observed at all, or even if the texture is observed, there is no problem, so it can be considered that the film is formed from the support at the time of film formation. The peelability is good.

The retardation film, the polarizing plate, and the vertical alignment type liquid crystal display device of the present embodiment described above can be expressed as follows.

A retardation film comprising a cellulose ester resin having an acetyl group and a butyl group, a retardation enhancer, and a sugar ester; wherein the retardation of the in-plane direction of the film is set to Ro (nm), and the thickness of the film is When the delay of the direction is set to Rth (nm), it is 50 nm ≦ | Ro | ≦ 80 nm

200 nm ≦ | Rth | ≦ 300 nm.

2. The retardation film according to the above 1, wherein the film thickness is 40 μm or more and 70 μm or less.

3. The retardation film according to the above 1 or 2, wherein the aforementioned fiber The bisphenol-based resin simultaneously satisfies the following formulas (1) and (2).

1.8≦X+Y≦2.9‧‧‧(1)

0.03≦Y≦0.8‧‧‧(2)

However, X represents the degree of substitution of the ethyl group and Y represents the degree of substitution of the group.

A polarizing plate comprising the retardation film according to any one of the above 1 to 3, and a polarizer to which the retardation film is bonded.

A vertical alignment type liquid crystal display device comprising the polarizing plate of the above 4 and a liquid crystal cell to which the polarizing plate is bonded.

6. The vertical alignment type liquid crystal display device according to the above 5, wherein the polarizing plate is located on the visible side with respect to the liquid crystal cell, and the retardation film is attached to the liquid crystal cell side with respect to the polarizer. Liquid crystal cell.

[Industrial availability]

The retardation film of the present invention can be used for a polarizing plate and a VA type liquid crystal display device.

Claims (6)

A retardation film characterized by comprising a cellulose ester resin having an acetyl group and a butyl group, a retardation enhancer, and a sugar ester, and setting the retardation of the in-plane direction of the film to Ro (nm), and the thickness of the film When the retardation of the direction is set to Rth (nm), it is 50 nm ≦ | Ro | ≦ 80 nm 200 nm ≦ | Rth | ≦ 300 nm. The retardation film of claim 1, wherein the film thickness is 40 μm or more and 70 μm or less. The retardation film of claim 1 or 2, wherein the cellulose ester-based resin simultaneously satisfies the following formulas (1) and (2); 1.8≦X+Y≦2.9‧‧‧(1) 0.03≦Y≦0.8‧ ‧ (2) where X represents the degree of substitution of the thiol group and Y represents the degree of substitution of the butyl group. A polarizing plate characterized by having a retardation film according to any one of claims 1 to 3, and a polarizer to which the retardation film is bonded. A vertical alignment type liquid crystal display device comprising the polarizing plate of claim 4 and a liquid crystal cell to which the polarizing plate is bonded. The vertical alignment type liquid crystal display device of claim 5, wherein the polarizing plate is located on the visible side with respect to the liquid crystal cell, and the retardation film is bonded to the liquid crystal on the liquid crystal cell side with respect to the polarizer unit.