WO2007018267A1

WO2007018267A1 - Phase retardation film manufactured from cellulose derivative

Info

Publication number: WO2007018267A1
Application number: PCT/JP2006/315857
Authority: WO
Inventors: Hideyoshi Fujisawa; Kouichi Tanaka
Original assignee: Nippon Kayaku Kabushiki Kaisha; Polatechno Co., Ltd.
Priority date: 2005-08-11
Filing date: 2006-08-10
Publication date: 2007-02-15
Also published as: KR20080036958A; CN101218523A; JPWO2007018267A1

Abstract

Disclosed is a phase retardation film which is manufactured using a cellulose derivative having a hydroxyl group substituted by an aliphatic acyl group having 5 to 20 carbon atoms (A) at a substitution degree of 0.50 to 2.99 hydroxyl group per cellulose monomer unit. The film has an optically biaxial property which satisfies the following relationship: nx>ny>nz, wherein nx represents a refraction index in the slow axis direction on the film surface; ny represents a refraction index in the direction orthogonal to the slow axis direction on the film surface; and nz represents a refraction index in the thickness-wise direction. The film can be used as a phase retardation film for the compensation of VA mode. In such a film, when black display is performed under the VA cell-undriven state, the leakage of light occurring at the the observation at an inclined angle, which causes the deterioration in contrast, can be largely prevented in a wide range to keep a low brightness level, compared to conventional cellulose-containing phase retardation film, leading to the attainment of a wide view angle.

Description

Specification

Retardation film obtained from cellulose derivatives

[0001] The present invention is obtained by biaxial stretching of an aliphatic acyl-substituted cellulose derivative of C5 to C20, and is optically biaxial in that the refractive index in the film normal direction is smaller than the refractive index in the fast axis direction. The present invention relates to a retardation film having a polarizing plate, a polarizing plate using the same, and an image display device. Background art

[0002] Liquid crystal display devices are widely used in mobile applications such as mobile phones and PDAs (Personal Degital Assistance), car navigation monitors that require durability, and large-screen home TVs. . In particular, twisted nematic (TFT-TN mode) liquid crystal displays have been used for applications that require high display quality, such as high contrast and high viewing angle.

[0003] However, the TFT-TN mode has a disadvantage that the viewing angle is poor in principle. Therefore, when observed from an oblique direction, it causes a decrease in contrast and gradation inversion. For this reason, a new liquid crystal mode is required to replace the TFT-TN mode, one of which is the vertical alignment nematic (VA mode) liquid crystal display device. The VA mode is a display mode that can exhibit a wide viewing angle characteristic. For this reason, it has already been widely adopted in home TVs and recently used in small liquid crystal display devices such as mobile phones and digital camera monitors.

[0004] In the VA mode, a retardation film can be used for viewing angle compensation as in other liquid crystal display systems, and has two elements to be compensated. The first is compensation for so-called light leakage of the polarizing plate caused by the fact that the absorption axes of the two polarizing plates are apparently not orthogonal when the liquid crystal display device is observed from an oblique direction. For this compensation, a retardation film called a positive A plate and a positive C plate is usually used.

[0005] Secondly, when the VA cell is observed from an oblique direction, the birefringence of the liquid crystal molecules increases, and light leakage due to the cell occurs at the time of black display. is there. To compensate for the birefringence of vertically aligned liquid crystals, it is called a negative C plate. A phase difference film is required. Negative c-plate is a force that can be easily obtained by laminating retardation films. However, if a large number of films and cells are stuck together using an adhesive or the like, interface reflection occurs due to the difference in refractive index, and the contrast is reduced overall. There is also a problem that uneven interference occurs. Furthermore, by using a plurality of retardation films, the increase in production cost becomes remarkable, and a large amount of investment is required for the retardation film that is only a part of the optical member. In addition, the yield is inevitably lowered as the number of bonding steps increases. Terms such as positive A plate and negative C plate are described in Patent Document 1 below.

[0006] In Patent Document 1, a compensation method in which a positive A plate and a negative C plate are laminated with a specific combination of wavelength dispersion, a VA mode with high contrast and good color reproducibility without interference unevenness is realized. ing. However, since it is used for a plurality of compensation retardation films, it does not provide a fundamental solution to the problems caused by using the plurality of retardation films.

[0007] Patent Document 2 proposes a method of compensating for the VA mode by using a retardation film containing a disc-like compound oriented in a special direction instead of a stretched birefringent film. In this method, since the alignment of the liquid crystal can be controlled in a complicated manner, precise cell compensation becomes possible. However, in general, disk-like composites and processed products containing them are very expensive, and in the retardation film factory where both cost reduction and high performance are required, cost is reduced. The problem remains.

[0008] Patent Document 3 discloses a method for obtaining a viewing angle compensation phase difference film by stretching a norbornene-based cyclic olefin-based polymer and satisfying necessary optical characteristics with a single phase difference film. Yes. However, there are the following problems in the current situation where thinning and light weight of liquid crystal display members are strongly desired.

[0009] A polarizing element combined with a retardation film has a uniaxially stretched polyvinyl alcohol film containing a dichroic dye, and therefore has a low brittle temperature and moisture resistance, and thus a protective film such as triacetyl cellulose. The double-sided force is also pinched. The polarizing element with the protective film is called a polarizing film. The retardation film of Patent Document 3 is bonded using a polarizing film and an adhesive. Here, for example, protective film If the retardation film can be directly bonded to the polarizing element instead of the film, a polarizing film integrated with the retardation film can be obtained which is made thinner by one protective film. However, norbornene-based and other cyclic olefin-based polymer films have poor adhesion to polarizing elements, and it is not easy to integrate them while maintaining high durability.

As a retardation film material that can be integrated with a polarizing element, there is a cellulose polymer. It is known that triacetyl cellulose, which is often used for protective films, can be bonded to a polarizing element using a polyvinyl alcohol-based adhesive after the surface of the film is subjected to a ken treatment. Patent Document 4 discloses a method in which a retardation film integrated with a polarizing element is produced using a single cellulose acylate film, particularly cellulose acetate or cellulose propionate, and a VA cell is compensated. Patent Document 5 discloses a method of compensating for a single VA cell using cellulose acetate propionate.

Patent Document 6 describes a force VA mode display device in which a retardation film obtained by uniaxially stretching a cellulose derivative in which a hydroxyl group is substituted by an aliphatic acyl group (A) having 5 to 20 carbon atoms is described. The effect is not sufficient for improving the viewing angle characteristics.

Patent Document 1: Japanese Unexamined Patent Application Publication No. 2004-326089

Patent Document 2: Japanese Patent No. 2866372

Patent Document 3: Japanese Patent Laid-Open No. 11-95208

Patent Document 4: Japanese Patent Laid-Open No. 2005-134863

Patent Document 5: Japanese Patent Application Laid-Open No. 2004-133171

Patent Document 6: WO2005Z022215

Disclosure of the invention

Problems to be solved by the invention

However, the cellulose-based retardation film described in Patent Document 4 and Patent Document 5 is not yet satisfactory in view angle compensation effect according to the study by the present inventors. There was also a problem in improving the viewing angle with a large change in the phase difference value (environment resistance) when the humidity was changed near room temperature. Therefore, it can be easily integrated on the non-protected surface of the polarizing film and has excellent viewing angle compensation effect. Development of a retardation film with little change in the thickness is desired.

Means for solving the problem

[0012] As a result of diligent research to solve the above-mentioned problems, the present inventors have substituted a hydroxyl group with an aliphatic acyl group having 5 to 20 carbon atoms, and the substitution degree of the hydroxyl group is 0 per cellulose monomer unit. 50-2. A retardation film that is produced by biaxial stretching using a cellulose derivative that is 99 and that exhibits optical biaxiality has an excellent VA mode compensation effect, as well as film production. The present inventors have found that a retardation film having excellent environmental resistance can be obtained by selecting an additive at the time.

[0013] That is, the present invention provides

(1) A film comprising a cellulose derivative in which a hydroxyl group is substituted by an aliphatic acyl group having 5 to 20 carbon atoms (A), and the degree of substitution of the hydroxyl group is 0.50 to 2.99 per cellulose monomer unit. Retardation value Re in the film plane represented by the following formula (1), which is produced by biaxial stretching, is Onm or more and 200 nm or less, and the retardation value in the film normal direction represented by formula (2) Rth force ¾Onm or more An optically biaxial retardation film that is 300 nm or less and nx> ny> nz, where each symbol has the following meaning:

Re = (nx-ny) X d (1)

Rth = [(nx + ny) / 2-nz] X d (2)

nx: Refractive index in the slow axis direction in the film plane

ny: Refractive index in the fast axis direction in the film plane

nz: refractive index in the film normal direction

d: Film thickness

(2) The substituent of the cellulose derivative is either (1) an aliphatic acyl group having 5 to 20 carbon atoms (A) alone or (2) an aliphatic acyl group having 5 to 20 carbon atoms (A ) And other substituents (B), and the latter substituent (B) has a structure different from that of the aliphatic acyl group (A). The retardation film according to the above (1), wherein the alkyl group is a rubermoyl group, an aromatic group rubermoyl group, an acyl group having a tolan skeleton, an acyl group having a biphenyl skeleton, or a polymerizable group,

(3) An aliphatic acyl group having 5 to 20 carbon atoms (A) is a straight chain aliphatic acyl group having 5 to 7 carbon atoms. In the case of a linear aliphatic acyl group having 5 or 6 carbon atoms, the degree of substitution is 2.0 to 2.8, and in the case of an aliphatic acyl group having 7 carbon atoms, the degree of substitution is 1. The retardation film according to (2) above, which is a cellulose derivative that is 5 to 2.3.

(4) The above-mentioned cellulose derivative force Film force The above-mentioned (1) to (3) produced by a resin composition containing both the cellulose derivative and a reactive monomer or monomer and a polymerization initiator. ) Of the retardation film according to item 1,

(5) The retardation film according to (4), wherein the reactive monomer is a thermosetting compound.

(6) The retardation film according to the above (5), wherein the thermosetting compound is a silane coupling agent,

(7) The above (1) to (6), wherein the aliphatic acyl group (A) is an n-hexanol group, and the degree of substitution of the hydroxyl group with the n-hexanol group is 1.80-2.90. Retardation film,

(8) In-plane retardation value Re is 10 nm or more and 80 nm or less, film normal direction retardation value Rth is lOOnm or more and 250 nm or less, and film thickness d is 30 μm or more and 110 m or less. The retardation film according to any one of (1) to (7) above,

(9) When the phase difference value at a wavelength of 450 nm is Re450, the phase difference value at a wavelength of 550 nm is Re 550, and the phase difference value at a wavelength of 750 nm is Re750, the following equations (3), (4), and (5) The retardation film according to any one of (1) to (7), characterized in that:

Re450≤Re550≤Re750 (3)

0. 50≤Re450 / Re550 <0. 99 (4)

1. 00 <Re750 / Re550≤l. 50 (5)

(10) The retardation film according to any one of (1) to (9) above, wherein the film having the cellulose derivative strength is a film produced by a solvent casting method.

(11) The retardation film according to any one of the above (1) to (10) and the protective film protective surface or the polarizing element unprotected surface constituting the polarizing film are used with an adhesive or an adhesive. , Functional polarizing film bonded together,

(12) The retardation film according to any one of (1) to (10), and the functionality according to (9) An image display device comprising a polarizing film;

(13) The image display device according to (12), wherein the image display device is a vertical alignment nematic (VA) type liquid crystal display device,

About.

The invention's effect

[0014] An optically biaxial retardation film produced using the cellulose derivative used in the present invention (hereinafter also simply referred to as a cellulose derivative) is more than a conventional retardation film for cellulose-based VA compensation. Also show a much better viewing angle compensation effect. Since it is a cellulose derivative, it can be adhered to the polarizing element after the saponification treatment, and a retardation film integrated polarizing film can be produced. In addition, the retardation film of the present invention comprising a film obtained by polymerizing or cross-linking (hereinafter, also simply referred to as polymerization) a cellulose derivative containing a reactive monomer such as a silane coupling agent is durable and / or environmental resistant. Excellent performance and more preferable. Sarakuko has a sufficient viewing angle compensation effect with a single-use retardation film, which can contribute to thinning of the liquid crystal display device. In addition, although it is a cellulose derivative, it is soluble in non-halogen solvents, so it has excellent processability and environmental friendliness.

Brief Description of Drawings

[0015] [FIG. 1] VA mode using a polarizing film having a compensation function (Invention Example 4 and Comparative Example 1) and a polarizing film having a compensation function (Comparative Example 2), respectively, bonded with a retardation film This is a graph of the cross-section of the black luminance distribution in the normal direction of the film at 45 ° clockwise of the absorption axial force of the polarizing plate, based on the black luminance measurement data in all directions in the liquid crystal display device.

FIG. 2 shows the change in retardation value Re in the film surface in each environmental resistance test of the retardation film of Example 7 of the present invention and the retardation film of cellulose acetate propionate of Comparative Example 1 It is a graph.

FIG. 3 shows changes in the retardation value Rth in the film normal direction in each environmental resistance test of the retardation film of Example 7 of the present invention and the retardation film of the cellulose acetate propionate of Comparative Example 1 It is a graph. Explanation of symbols

[0016] FIG.

□: Functional polarizing film of Example 4

(Polarized film bonded with the retardation film of Example 3)

A: Polarizing film obtained by bonding a known retardation film of Comparative Example 1

X: Polarizing film having no compensation function of Comparative Example 2

2 and 3

O: Retardation film of Example 7

○: Retardation film of Comparative Example 4

A: Vacuum drying conditions (10mmHg, humidity 27%, temperature 30 ° C,)

The number after A indicates the number of times.

B: High humidity condition (normal pressure, humidity 80%, temperature 30 ° C)

The number after B indicates the number of times.

init: Indicates the initial value.

BEST MODE FOR CARRYING OUT THE INVENTION

[0017] The present invention will be described in detail.

In the present invention, a hydroxyl group is substituted by an aliphatic acyl group (A) having 5 to 20 carbon atoms used as a raw material for a retardation film, and the substitution degree of the hydroxyl group is 0.50-2.99 per one monomer unit of cellulose. The cellulose derivative is described in Patent Document 6 or is described, and in this case, it can be produced in accordance with it.

Cellulose that can be used as a starting material for the cellulose derivative is as shown in formula (6) regardless of the crystal form and the degree of polymerization.

[0018] [Chemical 1]

[0019] Any structure in which D-darcoviranose is linked by a -3, 1, 4 bond can be used.

Specific examples include natural cellulose, powdered cellulose, crystalline cellulose, regenerated cellulose, cellulose hydrate, and rayon.

[0020] The cellulose derivative used for the production of the retardation film of the present invention is one in which the hydroxyl group of cellulose is substituted as shown in the formula (7).

[0021] [Chemical 2]

In formula (7), Rl, R2, and R3 are hydrogen atoms or substituents, and Rl, R2, and R3 may be the same or different, but all of Rl, R2, and R3 Is not a hydrogen atom, and at least one is an aliphatic acyl group having 5 to 20 carbon atoms. In addition, these substituents may contain a substituent different from the aliphatic acyl group having 5 to 20 carbon atoms. When the different substituents are included, the abundance ratio of each substituent may be an arbitrary ratio. In the cellulose derivative having at least one kind of aliphatic acyl group having 5 to 20 carbon atoms, the sum of the number of substituents per unit of cellulose (degree of substitution) is 0.50-2.99, preferably Is 1. 00-2.90. In some cases, the degree of substitution is preferably in the range of 1.5 to 2.95, more preferably 2.0 to 2.8. Substituent is the aliphatic group It may be a sil group alone or may contain other substituents. When other substituents are included, the aliphatic acyl group preferably accounts for 40% or more, preferably 50% or more of the total substituents. Most preferred is a C5-C7 aliphatic acyl group.

Further, n is preferably an integer of 10 or more, more preferably 50 or more, and even more preferably 100 or more. In some cases, 300 or more, 400 or more, and more preferably 500 or more are preferable. Although there is no particular upper limit, it is usually 10,000 or less, preferably 5000 or less, more preferably 2000 or less. Accordingly, 300 to 10,000 is a preferable range of the degree of polymerization n, and more preferably 500 to 5,000. Here, n usually represents the weight average degree of polymerization.

Preferred as the aliphatic acyl group having 5 to 20 carbon atoms is a C5-C16 aliphatic acyl group, more preferably a C5-C12 aliphatic acyl group, more preferably a carbon number of 5-7. An aliphatic acyl group (preferably a linear aliphatic acyl group). In the case of a linear aliphatic acyl group having 5 or 6 carbon atoms, the degree of substitution is 2.0 to 2.8, preferably 2.0 to 2.6, and in the case of an aliphatic acyl group having 7 carbon atoms. The degree of substitution is 1.5 or more and less than 2.5, preferably 1.5 to 2.3. Specific examples of the aliphatic acyl group having 5 to 7 carbon atoms include n-pentanol group, n-hexanol group and n-heptanol group, and n-hexanol having 6 carbon atoms. Groups are most preferred. The degree of substitution with an n-pentanol or n-hexanol group should be in the above range !, but is preferably about 1.8 to 2.9, more preferably 2.0 to 2. About 8, more preferably about 2.0 to 2.6. The degree of substitution with the n-heptanol group is preferably about 1.5 to 2.5.

In the present invention, as the acyl group other than the aliphatic acyl group (A) having 5 to 20 carbon atoms, for example, an acyl group having a structure different from that of the aliphatic acyl group (A) (for example, an aliphatic acyl group, An aromatic acyl group, an acyl group having a tolan skeleton or a acyl group having a biphenyl skeleton), a rubamoyl group (for example, a substituent having 1 to 10 carbon atoms which may have a substituent such as a phenyl group or a halogen atom) Group or aromatic force rubamoyl group), or a polymerizable group, and more preferably those described as preferred in the next section describing the cellulose derivative of formula (7). . In formula (7), preferred substituents other than aliphatic acyl groups having 5 to 20 carbon atoms are rubamoyl groups, and alkyl groups other than aliphatic acyl groups having 5 to 20 carbon atoms are preferred. A silyl group or a polymerizable group, more preferably a strong rubermoyl group or an acyl group other than an aliphatic asil group having 5 to 20 carbon atoms.

As a preferable cellulose derivative, specifically, Rl, R2, and R3 in the formula (7) are provided that at least one is substituted with an aliphatic acyl group having 5 to 20 carbon atoms. In addition, Y-CO group alone or a compound substituted with both Y-CO group and Z-NH-CO group, more preferably only substituted with a group contained in Y-CO! Preferred. Y represents a substituted or unsubstituted hydrocarbon residue having 1 to 20 carbon atoms, for example, vinyl group, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl. Group, pentyl group, neopentyl group, hexyl group, cyclohexyl group, octyl group, nor group, decyl group, benzyl group, 1 naphthylmethyl group, trifluoromethyl group, aminomethyl group, 2-amino group An ethyl group, a 3-amino-1-n-propyl group, a 4-amino-n-butyl group, a substituent in which those amino groups are further converted to amidourethan, a hydroxy-substituted (C1-C4) alkyl group, or a hydroxy group thereof A group further substituted with a (C1 to C14) acyl group or (C1 to C14) alkyl group, (C1 to C3) a bur group optionally substituted with an alkyl group, Cyanobiphenol (C3 to C10) A An aliphatic group having an unsaturated bond having 1 to 10 carbon atoms, such as a kill group, acetylene group and cinnamoyl group, a phenyl group, a naphthyl group, an anthracenyl group, a fluorenyl group, a biphenyl group or a 4-trifluoromethylphenyl group. Examples of the acyl group having an aromatic group such as a group, and examples of Z include an aliphatic group having 1 to 10 carbon atoms which may have a substituent (for example, a phenyl group, a halogen atom, etc.). , Vinyl group, methyl group, ethyl group, propyl group, isopropyl group, n butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, cyclohexyl group, octyl group, nor Group, decyl group, benzyl group, 1-naphthylmethyl group, trifluoromethyl group and the like. These substituents are appropriately selected according to the purpose in consideration of the birefringence, wavelength dispersion characteristics, viscosity, ease of orientation, processability, reactivity, etc. of the cellulose derivative used in the present invention. 1 type or multiple types. Cellulose hydroxyl group Similarly, the degree of substitution with these substituents is also appropriately selected according to the purpose.

[0024] The cellulose derivatives used in the present invention are all known as described in WO2005Z022215 and the like, or can be easily synthesized according to the method described in the publication. For example, first, cellulose as a starting material is dissolved in an organic solvent. Any organic solvent may be used as long as it is a non-alcohol solvent. 1S A halogen solvent such as chloroform or dichloromethane, dimethylacetamide or dimethylformamide, acetone or cyclopentanone. Polar solvents are preferred. It is preferable that cellulose is impregnated with the organic solvent before dissolution because the solubility of cellulose is improved. Using the organic solvent, a 20% by weight, preferably 5 10% by weight, cell mouth solution is prepared. A reagent for introducing a substituent is added to this cellulose solution, and the reaction is carried out at a constant temperature. Substituent introduction reagents are acylating agents such as carboxylic acid anhydrides and carboxylic acid chlorides, and strong rumomoissing agents such as isocyanates and di-n-butyltin dilaurate. The reaction temperature is appropriately set according to the reactivity of cellulose and the reagent for introducing a substituent. After the reaction, reprecipitation is performed by adding a reaction solution in water or methanol, and the precipitated solid is dried, whereby the cellulose derivative used in the present invention can be obtained.

Adjustment of the degree of substitution of the cellulose derivative used in the present invention can be achieved by adjusting the amount of the substituent introduction reagent used in the synthesis of the cellulose derivative. The reagent for introducing substituents can be used in a range of 0.5 to: LOO equivalent to the amount of cellulose hydroxyl group used as a reaction raw material, and the greater the amount used, the higher the degree of substitution cellulose derivatives can be obtained. Since the reactivity with the cellulose hydroxyl group varies depending on the type of the group introduction reagent, the amount of the substituent introduction reagent necessary to achieve a certain degree of substitution varies. For example, when obtaining cellulose nxanate having a substitution degree of 2.14, the reaction is carried out for at least 4 hours using 1.05 equivalents of nxanoyl chloride relative to the hydroxyl group of cellulose. On the other hand, when obtaining cellulose nxanate having a degree of substitution of 2.74, use 1.50 equivalents of nxanoyl chloride for the hydroxyl group of cellulose for at least 4 hours.

[0025] By introducing a polymerizable group into the cellulose derivative, the alignment state is fixed by irradiating with ultraviolet rays after the alignment treatment in the presence of a photopolymerization initiator, thereby fixing the mechanical strength and reliability. A retardation film having excellent solvent resistance can be obtained. Examples of the polymerizable group include those in which Y or Z is a bulu group, that is, an attaloyl group or a meta attaroyl group. As the photopolymerization initiator, a compound used in a normal ultraviolet curable resin can be used. Specific examples of compounds that can be used include 2-methyl-1 [4 (methylthio) phenyl] -2- morpholinopropane-1 (Irgacure 907 manufactured by Ciba Specialty Chemicals), 1 hydroxycyclohexyl phenyl ketone (Cibas Specialty Chemicals Irgacure 1 184), 4- (2 Hydroxyethoxy) 1-phenyl (2 Hydroxy 2-propyl) Ketone (Ivasacure 1959 from Ciba Specialty Chemicals), 1- (4 dodecyl phenol) 2-Hydroxy-2-methylpropane 1-one (Merck's Darochi Your 953), 1- (4-Isopropylphenol) 2 Hydroxy 2-Methylpropane 1-one (Merck Darocur 1116), 2-Hydroxy-2 Methyl 1 Fuel Propan — 1—On (Irgacure 1173 from Ciba Specialty Chemicals) or Jet Such as acetophenone compounds such as acetophenone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether or 2,2 dimethoxy 2-phenylacetophenone (Irgacure 651 from Ciba Specialty One Chemicals) Benzoin compounds, benzoylbenzoic acid, methyl benzoylbenzoate, 4-phenol penzophenone, hydroxybenzophenone, 4-benzoyl 4'-methyldiphenylsulfide, or 3, 3 'dimethyl 4-methoxy benzophenone (Nippon Kayaku Co., Ltd. Benzophenone compounds such as MBP), thixanesone, 2-chlorothioxanthone (Nippon Kayaku Cacure 1 CTX), 2-methyl thixanthone, 2,4 dimethylthioxanthone (cacure) RTX), isopropyl thixanthone, 2,4 dicyclothixanthone (Nippon Kayaku Cacaure 1 CTX), 2,4 jetylthioxanthone (Nippon Kayaku Cacure 1 DETX), or 2,4 diisopropylpropyl thoxane Thixanesone compounds such as Sung (Nippon Yakuyaku Kaicure 1 DITX) are listed. These photopolymerization initiators can be used singly or in combination at any ratio.

When a benzophenone compound or thixanthone compound is used, an auxiliary agent can be used in combination to promote the photopolymerization reaction. Examples of such auxiliaries For example, triethanolamine, methyljetanolamine, triisopropanolamine, n-butylamine, n-methyljetanolamine, jetylaminoethyl metaarylate, Michler's ketone, 4, 4, -jetylamine. Examples thereof include amine compounds such as enone, 4-dimethylaminobenzoyl ethyl, 4 dimethylaminobenzoic acid (n-butoxy) ethyl or isoamyl 4-dimethylaminobenzoate. The content of the photopolymerization initiator is preferably 0.5 parts by weight or more with respect to 100 parts by weight of the (meth) alkyl toy compound (including an attaloyl group in the polymer). The amount is preferably 10 parts by weight or less, more preferably 2 parts by weight or more and 8 parts by weight or less. Further, the auxiliary agent is preferably about 0.5 to 2 times the amount of the photopolymerization initiator.

[0027] The irradiation amount of ultraviolet rays varies depending on the type of the liquid crystalline compounding composition, the type and addition amount of the photopolymerization initiator, and the film thickness, but is preferably about 100 to 1000 mjZcm2. In addition, the atmosphere during UV irradiation may be air or an inert gas such as nitrogen. However, if the film thickness is reduced, it will not cure sufficiently due to oxygen damage. In such a case, UV light is irradiated in an inert gas. And then let it harden.

[0028] In addition to the photopolymerization initiator, a reactive monomer different from the cellulose derivative may be included in the cellulose derivative for producing the retardation film of the present invention. The reactive monomer is preferably a compound that can be photopolymerized by ultraviolet irradiation or a compound that can be polymerized by heat treatment, in consideration of the treatment that can actually be performed on the production line. As the photopolymerizable compound, for example, a (meth) attarei toy compound can be mentioned. When the retardation film of the present invention is prepared from a cellulose derivative containing these, these additives are used in place of the cellulose derivative solution in the preparation of the retardation film of the present invention from the cellulose derivative described later. The cellulose derivative solution that is contained may be used in the same manner.

[0029] Examples of the (meth) atalyte toy compound include trimethylolpropane tri (meth) atrelate, pentaerythritol tri (meth) atarylate, pentaerythritol tetra (meth) atarylate, ditrimethylolpropane tetra ( (Meth) acrylate, dipentaerythritol penta acrylate, dipentaerythritol hexa acrylate, pentaerythritol tri (meth) acrylate and 1, 6 hexamethylene diisocyanate reaction product, penta erythritol Reaction product of rutri (meth) atalylate with isophorone diisocyanate, reaction product of tris (atarilochetyl) isocyanurate, tris (metaatari mouthkistil) isocyanurate, glycerol triglycidyl ether and (meth) acrylic acid , Reaction product of force prolatatone modified tolyl with (meth) acrylic acid, reaction product of triglycerol di (meth) acrylate, propylene glycol diglycidyl ether and (meth) acrylic acid, polypropylene glycol di (meth ) Atarylate, Tripropylene glycol di (meth) acrylate, Polyethylene glycol di (meth) acrylate, Tetraethylene glycol di (meth) acrylate, Triethylene glycol di (meth) acrylate, Pentaerythritol di ( T) Atalylate, 1, 6-Hexanediol diglycidyl ether and (meth) acrylic acid reaction product, 1, 6-Hexanediol di (meth) acrylate, glycerol di (meth) acrylate, ethylene Reaction product of glycol diglycidyl ether and (meth) acrylic acid, reaction product of diethyleneglycol diglycidyl ether and (meth) acrylic acid, bis (atalyloxychetyl) hydroxyethyl isocyanurate, bis (metaatari mouth chechtil) ) Hydroxyethylsyanurate, reaction product of bisphenol A diglycidyl ether with (meth) acrylic acid, tetrahydrofurfuryl (meth) acrylate, force prolataton modified tetrahydrofurfuryl (meth) acrylate, 2-hydroxy ester Chill (meta) atelate , 2-Hydroxypropyl (meth) acrylate, Polypropylene glycol (meth) acrylate, Polyethylene glycol (meth) acrylate, Phenoxyhydroxypropyl (meth) acrylate, Ataliloyl morpholine, Methoxy polyethylene glycol (meth) ate , Methoxytetraethylene glycol (meth) acrylate, methoxy triethylene glycol (meth) acrylate, methoxy ethylene glycol (meth) acrylate, methoxyethyl (meth) acrylate, glycidyl (meth) acrylate, glycerol (meta ) Atarylate, ethylcarbitol (meth) acrylate, 2-ethoxetyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, 2-cyanoethyl (meth) acrylate Rate, reaction products of butyl Dali ether and (meth) acrylic acid, butoxy triethylene glycol (meth) Atari rate or butanediol mono (meth) Atari rate, and the like. These compounds may be used alone or in combination. Such reactive compounds can be used for polymerization under appropriate conditions. Thus, the desired orientation state can be fixed.

[0030] When the cellulose derivative solution is used as a composition containing a compound that can be polymerized (including cross-linked) by heat treatment or the like (both heat-polymerizable compounds), heat treatment for producing a film by a solvent casting method. At the same time, the film can be cured, contributing to the improvement of the durability of the film, and the process is simplified. This method may be selected if it is more effective to perform thermosetting crosslinking after film stretching.

[0031] Examples of thermally polymerizable compounds include isocyanate compounds. For example, as hexamethylene isocyanate-based polyisocyanates, Asahi Kasei Biuret type isocyanates 24A-100, 22A-75PX, 21S-75E, 18H-70B, isocyanurate type isocyanates ΓΡΑ-100, THA-100, MFA — 90X, TSA—100, TSS—100, TS E—100, adduct isocyanurate P—301—75E, E—402—90T, Ε—405—8—, bifunctional prepolymer isocyanate D—101, D— 201, block type isocyanate M7B-60PX, TPA-B80X, MF-B60X, MF-K60X, 402-402-Β80Τ, water-dispersed isocyanate WB40-100 or monomer isocyanate 50. Not limited to these, an epoxy compound or an aldehyde compound can be used as long as it exhibits thermal polymerization crosslinkability. These compounds may be used alone or in combination. By using such a reactive compound for polymerization (crosslinking) under appropriate conditions such as heating, the orientation in the retardation film of the present invention can be fixed in a desired state, and the film It is possible to improve durability and heat resistance or environmental resistance performance under the heating conditions and wet heat conditions. The thermosetting temperature is usually in the range of 20 to 200 ° C, preferably 40 to 180 ° C, more preferably 60 to 160 ° C for the purpose of preventing thermal decomposition of the cellulose derivative. The thermosetting time is usually within 24 hours, preferably within 12 hours, and more preferably within 3 hours.

Note that the environmental resistance, even if the phase difference film is repeatedly exposed to a dry environment and high humidity environment, a change in the in-plane average retardation value R _e and film normal direction of the retardation value Rth is It is a performance that shows whether or not it can withstand a certain amount of conditions. When a retardation film is repeatedly exposed to dry and high-humidity environments, its Re and Rth may vary greatly depending on the type of film, etc., and is constantly stable regardless of environmental changes. Shi In order to obtain the compensation performance, it is desirable that the change in the phase difference value is small. The retardation film of the present invention to which a reactive polymer is added can improve the environmental resistance performance by this additive.

As the reactive polymer, any compound can be used as long as it is highly fat-compatible with the cellulose derivative of the present invention.

Preferred are the above (meth) atalytotoy compounds, isocyanate compounds, silane coupling agents, and the like, with silane coupling agents being more preferred. These compounds have the effect of improving the environmental resistance performance of the retardation film of the present invention and suppressing the change in retardation value.

Moreover, a silane coupling agent can be used as a thermally polymerizable compound other than isocyanate. Examples of silane coupling agents include butyltrichlorosilane, butylmethoxysilane, vinyltriethoxysilane, 2- (3,4 epoxy cyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-glycidoxypro. Pinolemetinoregetoxysilane, 3 glycidoxypropinoletriethoxysilane, 2- (3,4 epoxy cyclohexyl) ethyltrimethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-Methacryloxypropyltrimethoxysilane, 3-Methacryloxypropylmethyl jetoxysilane, 3-Methacryloxypropyltriethoxysilane, 3-Atalyloxypropyltrimethoxysilane, N-2 (aminoethyl) 3 Aminopropylmethyl Dimethoxysilane, N—2 (aminoethyl) 3 aminopropyltrimethoxysilane, N—2 (aminoethyl) 3 aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3 aminopropyltriethoxysilane, 3 Triethoxysilyl mono N— (1,3 dimethyl butylidene) propylamine, N-phenyl 3-aminopropyltrimethoxysilane, N— (bulubenzyl) 2 aminoethyl mono 3-aminopropyl trimethoxysilane hydrochloride , 3-ureidopropyltriethoxysilane, 3-cyclopropylpropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, bis (triethoxysilylpropyl) tetrasulfide, 3-isocyanatepropyltrie Such as oxysilane A monomer type silane coupling agent can be used. In addition to the monomer type, an alkoxy oligomer type can also be used, and examples thereof include X-41-1053 and X-41-1056 manufactured by Shin-Etsu Chemical Co., Ltd. Better Preferred examples include 2- (3,4 epoxy cyclohexyl) ethyltrimethoxysilane, 3-glycidyloxyxypropyltriethoxysilane, X-41-1053, and X-41 1056. The amount of the silane coupling agent added is 0.1 to 50 parts by weight, more preferably 1 to 40 parts by weight, and even more preferably 5 to 30 parts by weight with respect to 100 parts by weight of the cellulose derivative. The oligomer type is relatively mild and requires a catalyst to react well with cellulose. Examples of the catalyst include organic metal-based, acid-based, and amine-based compounds. The catalyst used in the present invention is preferably an acid-based catalyst. Examples of the acid catalyst include X 40-2309A (manufactured by Shin-Etsu Chemical Co., Ltd.). The amount to be added is about 0.1 to 50 parts by weight, preferably about 0.2 to 1 part by weight, based on 100 parts by weight of the silane coupling agent. The silane coupling agent may be added when the cellulose derivative is dissolved, or may be added to the cellulose derivative solution.

[0033] The retardation film produced from the cellulose derivative of the present invention is optically biaxial. In general, an optically biaxial film means that the refractive index in the slow axis direction in the film plane is nx, the refractive index in the fast axis direction in the film plane is ny, and the refractive index in the film normal direction. It is a film in which nx, ny, and nz show different values when nz is nz. The retardation film of the present onset bright also shows an optical biaxial property, but among them the film normal direction refractive index is smallest, and satisfies a relationship of nx> n _y> nz.

[0034] The retardation value Re in the retardation film plane and the retardation value Rth in the normal direction are:

Re =, nx—ny) X d

Rth = [(nx + ny) / 2-nz] X d

It is represented by Re and Rth of the biaxial retardation film can be calculated from the measurement results using an automatic birefringence meter (for example, KOBRA-21ADH manufactured by Oji Scientific Instruments). In the phase difference film of the present invention, Re is usually Onm or more and 200 nm or less, preferably 5 nm or more and 150 nm or less, more preferably 10 nm or more and 80 nm or less. Further, in some cases, 40 to 8 Onm is preferable. Rth is usually 80 nm or more and 300 nm or less, preferably 90 nm or more and 275 nm or less, and more preferably lOOnm or more and 250 nm or less. Further, in some cases, a force of 120 to 200 nm is preferable, and more preferably 135 to 200 nm. Re and R When th indicates a value in the above range, a phase difference film showing an excellent viewing angle compensation effect is obtained.

In addition, in the relationship between the Re value and the Rth value, it is preferable that the Rth value is larger than the Re value. The thickness of the Finolem is usually 20 to 200 μm, preferably 20 to 150 μm, and more preferably 30 to L0 / zm. In some cases, 30 ~: LOO / z m power is most preferred! / ヽ.

[0035] An ordinary material for producing a retardation film has a so-called positive wavelength in which a large retardation value is exhibited with respect to a short wavelength component of incident light, and a small retardation value is exhibited with a longer wavelength component. Dispersion characteristics are shown. However, the retardation film of the present invention has a reverse wavelength dispersibility, which shows a small retardation value with respect to the short wavelength component of incident light and a large retardation value as the wavelength component becomes longer. There are features.

[0036] The chromatic dispersion is determined by using, for example, an automatic birefringence meter (such as KOBRA-21ADH manufactured by Oji Scientific Instruments) with a phase difference value Re450 for incident light having a wavelength of 450 nm and a phase difference value Re550 for incident light having a wavelength of 550 nm. The phase difference value Re750 for incident light at 750 nm can be measured and evaluated using the values of the phase difference ratios Re450ZRe550 and Re750ZRe550. A value larger than Re450 / Re550 force is shown, / J from Re750 / Re550 force, and a small value indicates positive wavelength dispersion. Further, when it is less than Re450 / Re550 force and shows a value larger than Re750 / Re550 force S1, it is reverse wavelength dispersion.

[0037] The retardation film of the present invention always exhibits reverse wavelength dispersion. Preferably, the reverse wavelength dispersion is preferably 0.5≤Re450 / Re550 <0.99 and powerfully 1.00 <Re750 / Re550≤1.50, more preferably 0. 65≤Re450 / Re550 <0. 99 and force 1. 0 <Re750 / Re550≤l. 35, even more preferred ί until 0.8 ≤ Re450 / Re550 <0. 99 Yes, if Rel. 00≤750 / Re550 <1.20.

[0038] The retardation film of the present invention using a cellulose derivative is produced by forming a cellulose derivative solution and performing an alignment treatment. As a specific method, first, a cellulose derivative is dissolved in an appropriate solvent to obtain a cellulose derivative solution. Solvents include acetates such as ethyl acetate, butyl acetate or methyl acetate, alcohols such as methanol, ethanol, propanol, isopropanol or benzyl alcohol, 2-butanoic acid. Ketones such as acetone, acetone, cyclopentanone or cyclohexanone, basic solvents such as benzylamine, triethylamine or pyridine, cyclohexane, benzene, toluene, xylene, azole, hexane or heptane. Non-polar solvents. The weight concentration of the cellulose derivative is usually 1 to 99%, preferably 2.5 to 80%, more preferably 5 to 50%. More preferably, it is about 10% to 30%. These compounds may be blended alone or in combination with multiple components. Further, if necessary, necessary additives such as the above-mentioned reactive monomer, polymerization catalyst or plasticizer may be added. Plasticizers include phthalates such as dimethyl phthalate and jetyl phthalate, trimellitic esters such as tris (2-ethylhexyl) trimellitate, and dibasic aliphatic bases such as dimethyl adipate and dibutyl adipate. Examples include acid esters, orthophosphate esters such as tributyl phosphate and triphenyl phosphate, and acetate esters such as glyceryl triacetate and 2-ethylhexyl acetate. Only one kind of these compounds may be blended, or a plurality of components may be blended. The amount of the additive added as necessary is about 0 to 50 parts, preferably about 0 to 30 parts, per 100 parts (weight) of the cellulose derivative. Next, after the cellulose derivative solution is applied on a flat substrate having a releasability, the solvent is removed by natural drying or heat drying to obtain a transparent cellulose derivative film. Since the retardation film in the present invention can achieve a sufficient compensation effect only with the cellulose derivative used in the present invention, the orientation compound other than the cellulose derivative or the retardation value increasing agent (lettering value increasing) It is not necessary to add any agent. Further, since the retardation film of the present invention has a degree of flexibility that is usually required, it is usually unnecessary to add a plasticizer or the like. Therefore, as a preferable cellulose derivative film used for producing the retardation film of the present invention, the cellulose derivative film which does not normally contain these and the cellulose derivative film which does not contain these, and a reactive monomer (preferably a silane coupling agent). ) -Containing cellulose derivative film. However, these additions are not excluded.

Next, the film is subjected to biaxial orientation treatment, preferably biaxial stretching, so that the relationship between the refractive indexes (three-dimensional refractive indexes) satisfies nx>ny> nz. A bright retardation film can be obtained. As the biaxial orientation treatment in the present invention, Biaxial stretching can be mentioned. The biaxial stretching in the present invention includes all cases where stress is applied in two directions, ie, a stretching direction and a direction perpendicular thereto, and the stretching is substantially performed in two directions. For example, in addition to simultaneous biaxial stretching or sequential biaxial stretching, for example, in order to suppress shrinkage in the direction perpendicular to the stretching direction, the film is stretched in one direction while fixing both ends on the non-stretched side of the film using a tenter or chuck. The method of doing is also included. In this method, by fixing both sides in the direction perpendicular to the stretching direction, dimensional changes due to shrinkage in the fixing direction (neck-in (shrinkage) that occurs during normal uniaxial stretching) are suppressed. It is substantially stretched to give the film biaxiality. Simultaneous biaxial stretching is a method of simultaneously stretching in the direction perpendicular to each other in the film plane. Sequential biaxial stretching is a method in which a film first stretched in one direction is then stretched in a direction perpendicular to that direction. Each stretching process may be a multistage process. Preferred biaxial stretching is simultaneous biaxial stretching or sequential biaxial stretching.

[0040] The stretching temperature can be arbitrarily selected as long as the cellulose derivative does not yellow due to thermal decomposition or seizure. Optimum stretching temperature varies depending on the substituent and degree of substitution of the cellulose derivative. In the case of cellulose n-hexanate, it is usually 50 to 200 ° C, preferably 70 to 180 ° C, more preferably 90 to 160 ° C, more preferably It is about 90-140 ° C.

[0041] The optimum draw ratio varies depending on the substituent and degree of substitution of the cellulose derivative and cannot be generally specified, but is not particularly limited as long as the conditions of the present invention are satisfied. Usually, the film is stretched at a magnification of 1.05 to 5.0 in one direction, and stretched at a magnification of 1.04 to 4.8 in the direction perpendicular to this direction so that the stretching ratios in both directions are different. Is preferred. Preferably, the film is stretched in one direction at a magnification of 1.1 to 4.0 times, and stretched in a direction perpendicular to this direction at a magnification of 1.08 to 3.8 times. More preferably, the film is stretched at a magnification of 1.2 to 3.0 times in one direction, and stretched at a magnification of 1.18 to 2.8 times in a direction orthogonal to this direction. Further, in some cases, the stretching ratio in both directions is 1.4 times or more, more preferably 1.5 times or more, stretching within 3 times, preferably within 2.5 times, and the stretching ratio in one side is stretched in the other direction. It is preferable to use less than magnification. If the difference in draw ratio in both directions is too large, the refractive index condition of the present invention may not be satisfied.Therefore, the difference in draw ratio in both directions is preferably within a range of 2 times, preferably less. Is within 1 times, more preferably within 0.5 times, in some cases within 0.4 times or 0.3 times, It is preferably in the range of at least twice, preferably 0.05 times or more.

The above draw ratio means a value obtained by dividing the length after stretching by the length before stretching. When contraction occurs in the direction orthogonal to the stretching in one direction, the length after stretching is the value obtained by dividing the length after stretching in the orthogonal direction.

[0042] The three-dimensional refractive index, that is, the relationship between the above nx, ny and nz can be controlled by the draw ratio. Normally, the three-dimensional refractive index of a uniaxially stretched film is expressed as follows: na> nb ^ where the refractive index in the maximum stretching direction is na, the refractive index in the direction perpendicular to the film plane is nb, and the refractive index in the thickness direction is nc Force indicating nc relationship When producing a biaxial film, the stretching ratio in one direction (the refractive index in this direction is na) is fixed, and the stretching ratio in the direction perpendicular to this (the refractive index in this direction is set as the refractive index). n j8) becomes larger than 1.0 times, η α ^ η> η γ (refractive index in the thickness direction) or η α>η> η γ,> η α> η γ Axiality is exhibited, and when the draw ratio in the orthogonal direction exceeds a certain value, the properties of the uniaxially stretched film are again approached as> η _α η γ. As an example, when producing a film having optically strong biaxiality using cellulose η-hexane, the draw ratio in one direction is 1.7, and the draw ratio in the direction perpendicular thereto is 1. When it is 6, a retardation film having a relationship of _nj 8> η _α > η γ can be obtained. The direction showing the maximum value of the refractive index is the slow axis.

[0043] The retardation film of the present invention can be used in an image display device depending on its optical characteristics. For example, the optically biaxial retardation film of the present invention has a retardation value Re in the film plane at 550 nm of about 50 nm and a retardation value Rth in the film normal direction of about 170 nm. Relationship between the absorption axis of the film and the slow axis of the retardation film By laminating with roll-to-roll so as to be orthogonal, a functional polarizing film having a function of widening the viewing angle of a liquid crystal display device is obtained. Can do.

[0044] As the polarizing film, for example, a film in which both surfaces of the polarizing element are sandwiched by protective films such as triacetyl cellulose film may be used, or only one surface may be protected.

In the case of a polarizing film that is protected on both sides, it is generally sufficient to use a pressure-sensitive adhesive to attach the retardation film on one of the protective films. However, the retardation film of the present invention is bonded to a polarizing element by using, for example, a ken treatment, and using a polybutyl alcohol adhesive in the same manner as a triacetyl cellulose film generally used as a protective film. It has the feature that it can be combined. Therefore, it is possible to protect one side of a polarizing element without any change in the manufacturing process of the present polarizing film with a triacetyl cellulose film that has been subjected to a ken treatment, and to protect the other side with the retardation film of the present invention that has been saponified. This is possible, and the thickness of the film of the functional polarizing film in which the retardation film of the present invention and the polarizing element are integrated can be reduced, which is more preferable. However, the adhesive is not limited to the polyvinyl alcohol type, and is not particularly limited as long as it can adhere the polarizing element such as urethane type or isocyanate type adhesive and the retardation film of the present invention. The film obtained by integrating the retardation film and the polarizing element of the present invention thus obtained is called a functional polarizing film, and contributes to cost reduction and yield improvement by thinning the entire liquid crystal display device and reducing processing steps. it can.

Further, although it is possible to attach the non-protected surface of the single-side protected polarizing film with an adhesive or the like, it is preferable to directly bond with an adhesive or the like in terms of durability. In the case of direct bonding, the surface of the retardation film is preferably activated by a cane treatment, a corona discharge treatment or a plasma treatment, and then adhered using a polyvinyl alcohol-based adhesive. Any adhesive can be used as long as it can directly bond the non-protective surface of the polarizing film and the retardation film of the present invention to the polybulal alcohol type. By directly adhering or bonding the retardation film of the present invention to the unprotected surface of the polarizing film, a functional polarizing film integrated with the retardation film can be obtained, which contributes to the reduction in thickness of the entire cell.

The retardation film and functional polarizing film of the present invention can greatly contribute to widening the viewing angle of an image display device. For example, a transmission-type liquid crystal display device has a structure in which a liquid crystal cell is sandwiched between two polarizing films. In principle, light can leak significantly when observed at an angle of 45 ° to the left and right from the absorption axis of the polarizing film. To do. The ability to place the retardation film of the present invention between polarizing films, and more preferably, if the functional polarizing film of the present invention is used instead of the polarizing film, light leakage can be greatly improved. The wide viewing angle of the liquid crystal display device can be achieved.

[0046] In the functional polarizing film in which the retardation film of the present invention is integrated, the retardation film of the present invention functions as a protective film and a retardation film of the polarizing film, and therefore the functional polarizing film is used. Compared to the case of using a normal polarizing film and a retardation film each having a protective film on both sides, the liquid crystal display device can be made thinner because it has the same function in thickness and thickness. For example, in the case of a liquid crystal display device using a VA cell, the functional polarizing film using the retardation film of the present invention can achieve a reduction in the thickness of the entire cell, while being necessary for a VA cell. Two compensations can also be achieved by the film, and the force is particularly suitable because it can achieve a very wide viewing angle effect as compared with the conventional products.

Example

[0047] The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

Example 1 Synthesis of cellulose n-xanate (degree of substitution 2.30) and measurement of degree of substitution

Add 126 g of lithium chloride to Ν, Ν'-dimethylacetamide 1.51 and stir at 80 ° C for 30 minutes to completely dissolve. Then, Ν, Ν'-dimethylacetamide impregnated cellulose (containing cellulose) (Rate: 56.4 wt%) 30. Og was added. After stirring at 50 ° C for 30 minutes, 47.6 g of n-hexanol chloride (relative to the cellulose hydroxyl group) was heated again to 80 ° C and stirred for 4 hours. Stirring was stopped and the reaction contents were poured into water 21 to reprecipitate cellulose n-xanate. After filtration, the solid content obtained by washing three times with 100 ml of water and twice with 50 ml of methanol was vacuum-dried for 6 hours to obtain 35. Og of a white powder of cellulose n-hexanate.

The reaction mixture was analyzed by gas chromatography immediately before reprecipitation, and the reaction rate was calculated for the reduction force of n-hexanol chloride. The degree of substitution of cellulose n-hexanate (replacement of n-xanthate per cellulose monomer unit) Number) was 2.30.

Example 2 Production of Cast Film Using Cellulose n Xanate

The cellulose n-xanate synthesized in Example 1 was dissolved in cyclopentanone to form a 25% by weight solution of the polymer. Cellulose n-xanate solution on PET film After being cast with a dope thickness of 1.7 mm, it was dried at 110 ° C. for 40 minutes to produce a transparent film of cellulose n-hexanate.

Example 3 Production of optically biaxial retardation film using cellulose n-hexanate

The cast film obtained in Example 2 was stretched at 120 ° C until a magnification of 1.7, and then at a magnification of 1.6 at 100 ° C in a direction perpendicular to the initial stretching direction. A retardation film having optically biaxial properties was obtained. The obtained films were nx = l. 48500, ny = l. 48404, nz = l. 48154. Next, when the retardation ratio of the retardation film was determined using an automatic birefringence meter (KOBRA-21ADH, manufactured by Oji Scientific), Re4 50ZRe550 was 0.97 and Re750ZRe550 was 1.03, indicating reverse wavelength dispersion. showed that . Re showed 56 nm. The Rth calculated from the measurement result of the tilt phase difference value was 173 nm. The thickness d of the film was 58 μm.

Example 4 Production of functional polarizing film

The absorption film of the polarizing film and the slow axis of the retardation film are orthogonal to each other through the adhesive layer of the polarizing film UDN-10143P made only from one side protected with triacetylcellulose. Thus, a functional polarizing film of the present invention using cellulose n-hexanate was produced.

[0052] Example 5: Compensation performance evaluation by measuring the viewing angle when VA cell is not driven using cellulose n-hexanate

From the commercially available VA liquid crystal display device, the liquid crystal cell is left, and all other retardation films and polarizing films are removed. Instead, the retardation film of the present invention is applied to one side prepared in Example 4 on the observation surface. The polarizing film (functional polarizing film) is placed so that the retardation film surface is on the cell side. On the back surface, a polarizing film (SKN18243T) made by Boratechno was attached so that the absorption axes of the polarizing films were orthogonal to each other. With respect to the VA mode liquid crystal display device thus manufactured, the black luminance distribution in all directions was measured using Ez-contrast 60R manufactured by ELDIM. Figure 1 shows a graph of the cross-section of the black luminance distribution in the film normal direction, 45 ° clockwise from the absorption axis of the polarizing plate, from the black luminance measurement data in all directions. Example 6 Production of cast film containing silane coupling agent (thermopolymerizable compound) using cellulose n xanate

Cell mouth n-xanate synthesized in Example 1 was 25% by weight, 3-glycidoxypropyltriethoxysilane (silane coupling agent KBE-403 manufactured by Shin-Etsu Chemical Co., Ltd.) was 4% by weight, triphenyl phosphate 2 The compounded solution was prepared by dissolving in cyclopentanone so as to be in% by weight. The cellulose n-xanate solution was cast on a release PET film with a dope thickness of 1.7 mm and dried at 110 ° C for 40 minutes to produce a transparent film of cellulose n-hexanate.

Example 7 Production of Optically Biaxial Retardation Film Using Cellulose n-xanate Film Thermally Polymerized with Silane Coupling Agent

The cast film obtained in Example 6 is stretched at 120 ° C until the magnification becomes 1.7, and then the magnification is 1.6 at 100 ° C in the direction perpendicular to the first stretching direction. A retardation film having optically biaxial properties was obtained. The film obtained was nx = l. 48500 ny = l. 48440 nz = l. Next, when the retardation ratio of the retardation film was determined using an automatic birefringence meter (KOBRA-21ADH, manufactured by Oji Scientific), Re4 50ZRe550 was 0.97 and Re750ZRe550 was 1.03, indicating reverse wavelength dispersion. Re showed 61 nm. Further, the Rth calculated from the measurement result of the tilt phase difference value was 140 nm. The film thickness d was 100 μm.

[0055] Example 8 Environmental Resistance Test of Retardation Film Consisting of Cellulose nxanate Thermally Polymerized with Silane Coupling Agent

The retardation film produced in Example 7 was repeatedly held under a room temperature vacuum condition and a high humidity condition at room temperature humidity of 60% or more, and the change rates of the plane average retardation values Re and Rth were measured. The results are shown in Figs.

[0056] Comparative Example 1 Production of retardation film integrated polarizing film using KC8UCR-3

Cellulose phase difference film KC8UC R-3 (thickness 80 μm) (phase difference film made of cellulose acetate propionate) manufactured by Co-Camino Norta Holdings Co., Ltd. Polarizing film UDN—101 Absorption axis of polarizing film and slow phase of KC8UCR-3 through adhesive layer on non-protected surface of 43P Lamination was performed so that the axes were orthogonal to each other, and a retardation film integrated polarizing film for VA cell compensation using cellulose n-hexanate was produced. KC8UCR-3 Re is 38nm, Rth is

It was 132 nm.

[0057] Comparative Example 2 Preparation of Comparative Polarizing Film

A polarizing film UDN-10143P with triacetyl cellulose film (thickness 80 μm) protected on one side only with triacetyl cellulose UDN— 10143P through the adhesive layer, the polarizing film absorption axis is parallel to the MD direction of triacetyl cellulose Then, a comparative polarizing film was prepared.

Comparative Example 3 Viewing Angle Measurement of Polarizing Films Produced in Comparative Example 1 and Comparative Example 2 when VA Cell is not Driven

An omnidirectional black luminance distribution was measured in exactly the same manner as in Example 4 except that the polarizing film prepared in Comparative Examples 1 and 2 was used instead of the polarizing film prepared in Example 4. The results are shown in Fig. 1.

Comparative Example 4 Environmental Resistance Test of Retardation Film Comprising Cellulose Acetate Propionate Example except that a film made from cellulose acetate propionate was used instead of the retardation film produced in Example 7. The same environmental resistance test as in No. 8 was performed. The results are shown in Figs.

[0060] Examination of test results

From FIG. 1, the polarizing film of Comparative Example 3 has no compensation effect in the case of using the retardation film integrated polarizing film of the present invention and in the case of a polarizing film using a retardation film made of cellulose acetate propionate. Compared to the case of using, low luminance is maintained in a wide range with little increase in luminance around the circle in the figure at the time of inclination, and it can be seen that the luminance expression is excellent. In other words, light leakage during tilt observation, which is the cause of contrast reduction, is reduced, and a wide viewing angle is achieved. In other words, the polarizing film of the present invention has the advantage that it can be directly adhered to the polarizing film, as in the case of the cellulose-based retardation film of Comparative Example 1, and the performance is greatly improved as a compensation film for VA. is doing.

Further, from FIG. 2 and FIG. 3, Example 7 of the present invention polymerized (crosslinked) with a thermally polymerizable compound was obtained. The retardation film is a polymerized film that has superior environmental resistance performance compared to a retardation film made of cellulose acetate propionate, and has little change in retardation value and Rth even in a high humidity environment. It can be seen that the optical performance can be exhibited stably. That is, according to the present invention, the environmental conditions of vacuum drying conditions (10 mmHg, temperature 30 ° C, humidity 27%) for 20 hours and high humidity conditions (normal pressure, humidity 80%, temperature 30 ° C) for 2 hours. When the film is repeated four times, the change rate of the average retardation value Re in the film is within 10%, preferably within 8%, within the normal value of the retardation value Rth in the film normal direction, preferably 3 A retardation film within%, more preferably within 2% can be obtained.

Claims

The scope of the claims

[1] A film comprising a cellulose derivative in which a hydroxyl group is substituted by an aliphatic acyl group (A) having 5 to 20 carbon atoms, and the substitution degree of the hydroxyl group is 0.50 to 2.99 per cellulose monomer unit. The film in-plane retardation value Re represented by the following formula (1) is Onm or more and 200 nm or less, and the film normal direction retardation value represented by the following formula (2) Rth force ¾Onm More than 300 nm and less than 300 nm and nx> ny> nz and optically biaxial retardation film, where each symbol has the following meaning.

Re = (nx-ny) X d (1)

Rth = [(nx + ny) / 2-nz] X d (2)

nx: Refractive index in the slow axis direction in the film plane

ny: Refractive index in the fast axis direction in the film plane

nz: refractive index in the film normal direction

d: Film thickness

[2] The substituent of the cellulose derivative is (1) an aliphatic acyl group having 5 to 20 carbon atoms (A) alone, or (2) an aliphatic acyl group having 5 to 20 carbon atoms (A) And the other substituent (B), and the latter substituent (B) has a structure different from that of the aliphatic acyl group (A), an aliphatic acyl group, an aromatic acyl group, 2. The retardation film according to claim 1, wherein the retardation film is any one of an alkyl-strength rubermoyl group, an aromatic-strength rubermoyl group, a acyl group having a tolan skeleton, a acyl group having a biphenyl skeleton, or a polymerizable group.

[3] In the case where the aliphatic acyl group having 5 to 20 carbon atoms (A) is a linear aliphatic acyl group having 5 to 7 carbon atoms and a linear aliphatic acyl group having 5 or 6 carbon atoms The cell mouth derivative having a degree of substitution of 2.0 to 2.8 and an aliphatic asil group having 7 carbon atoms having a degree of substitution of 1.5 to 2.3. The retardation film described.

[4] The film according to claim 1, wherein the cellulose derivative is made of a resin composition containing the cellulose derivative and a reactive monomer or a reactive monomer and a polymerization initiator. Phase difference film.

5. The retardation film according to claim 4, wherein the reactive monomer is a thermosetting compound.

6. The retardation film according to claim 5, wherein the thermosetting compound is a silane coupling agent.

7. The retardation film according to claim 1, wherein the aliphatic acyl group (A) is an n-hexanol group, and the degree of substitution of the hydroxyl group by the n-hexanol group is 1.80-2.90.

[8] In-plane retardation value Re is lOnm or more and 80nm or less, film normal direction retardation value Rth is lOOnm or more and 250nm or less, and film thickness d is 30μm or more and 110ixm or less The retardation film according to claim 1.

[9] Re450 for phase difference at 450 nm wavelength, Re550 for phase difference value at 550 nm wavelength

2. The retardation film according to claim 1, wherein when the retardation value at a wavelength of 750 nm is Re750, the relationship of the following formulas (3), (4) and (5) is satisfied.

Re450≤Re550≤Re750 (3)

0. 50≤Re450 / Re550 <0. 99 (4)

1.00 <Re750 / Re550≤l. 50 (5)

[10] The retardation film according to [1] or [4], wherein the film having cellulose derivative strength is a film produced by a solvent casting method.

[11] A functional polarizing film obtained by bonding the retardation film according to any one of claims 1, 4, and 7 and a polarizing film.

[12] An image display device comprising the retardation film according to any one of claims 1, 4, and 7, or the functional polarizing film according to claim 11.

13. The image display device according to claim 12, wherein the image display device is a vertical alignment nematic (VA) liquid crystal display device.