KR20050031439A - Polarizing film and liquid crystal display - Google Patents

Abstract

A polarization plate, an LCD(Liquid Crystal Display) are provided to decrease a change of a transmission ratio and a polarization degree caused by heat and humidity and to prevent optical leakage by using the polarization plate in the LCD, wherein passivation films having different humidity transmission degrees are placed at both sides of a polarizer of the polarization plate, thereby improving display quality. A polarization plate is comprised of the first passivation film(1a), a polarizer(2) and the second passivation film(1b) which are stacked sequentially. A humidity transmission degree of the first passivation film is lower than that of the second passivation film.

Description

Polarizer and liquid crystal display using the same {POLARIZING FILM AND LIQUID CRYSTAL DISPLAY}

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

BACKGROUND ART Liquid crystal display devices have low power consumption and are increasingly used as image display devices with less space each year. A large drawback of the liquid crystal display device is that the large dependence of the viewing angle on an image is a problem. However, in recent years, a high-view angle liquid crystal mode such as a VA mode and an IPS mode has been put into practical use. Is expanding. Accordingly, much higher performances are beginning to be required for polarizers used in liquid crystal displays. In particular, the improvement of the durability with respect to temperature and humidity is a big subject of a polarizing plate.

A polarizing plate is generally produced by adsorbing iodine on a hydrophilic polymer film such as a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol, or an ethylene / vinyl acetate copolymer-based partially saponified film, followed by stretching. However, these polarizing plates have a problem that, in long-term use, an increase in transmittance of the entire screen and black light leakage occur in a frame shape.

The cause of the increase in the transmittance and light leakage of the frame shape is relaxation of the stretched hydrophilic polymer and decomposition of iodine, and it is known that water permeation from the outside world through the protective film is greatly affected. On the other hand, in patent document 1 and patent document 2, the method of manufacturing a polarizer and a bonded polarizing plate for the protective film with low moisture permeability is disclosed. In these methods, however, moisture permeation from the outside after the production of the polarizing plate can be suppressed, but evaporation of moisture from the inside to the outside during drying in the polarizing plate production process is prevented, and the polarizing plate is preserved in a state where the moisture content in the polarizer is high. The effect of improving durability was insufficient.

[Patent Document 1] Japanese Unexamined Patent Publication No. 2002-328223

[Patent Document 2] Japanese Unexamined Patent Publication No. 2002-341135

An object of the present invention is to provide a polarizing plate having a small change in transmittance and polarization degree due to heat and humidity.

Another object of the present invention is to provide a liquid crystal display device having a high display quality without causing problems such as light leakage by using a polarizing plate having a protective film having different moisture permeability on both sides of the polarizer in a liquid crystal display device.

As a result of careful examination, the present inventors have focused on the fact that the water evaporation from the polarizer during the production of the polarizing plate after the liquid crystal cell bonding is mainly carried out through a protective film (hereinafter also referred to as a first protective film) on the air interface side with respect to the polarizer. The liquid crystal cell side protective film (hereinafter also referred to as the second protective film) has a large permeability so that moisture in the polarizer can sufficiently evaporate during the production of the polarizing plate, and the air interface side protective film is provided from the outside of the polarizer after bonding. It was found that this problem can be solved by using a low water permeability so as not to cause water infiltration.

1) A polarizing plate in which a first protective film, a polarizer and a second protective film are laminated in this order, wherein the moisture permeability of the first protective film is lower than that of the second protective film.

2) The polarizing plate of 1) characterized by the difference of the water vapor transmission rate measured on the conditions of 60 degreeC 95% RH of a 1st protective film and a 2nd protective film.

3) The first and second protective films are both polymer films containing the same polymer as a main component, and the types and / or amounts of additives of the first and second protective films are different, according to 1) or 2). Polarizer.

4) The polarizing plate according to any one of 1) to 3), wherein the first and second protective films are cellulose acylate films.

5) The polarizing plate of 1) or 2) whose 1st and 2nd protective films are cellulose acylate films, and the kind of cellulose acylate which a 1st and 2nd protective film has is different.

6) The polarizing plate in any one of 1) -5) characterized by the water vapor transmission rate measured on the conditions of 60 degreeC 95% RH of a 1st protective film.

7) The polarizing plate in any one of 1) -6) characterized by the water vapor transmission rate measured on condition of 60 degreeC 95% RH of a 2nd protective film.

8) The thickness of the first protective film and the second protective film is not less than 40㎛ 120㎛, the thickness ratio of the first protective film and the second protective film is 0.5 or more 2 or less, in any one of 1) -7) The polarizing plate described.

9) The polarizing plate in any one of 1) -8) which has an adhesion layer.

10) The polarizing plate in any one of 1) -9) which has an antiglare layer on the surface on the opposite side to the surface which opposes the polarizer of a 1st protective film.

11) The polarizing plate in any one of 1) -10) characterized by having a reflection layer or a semi-transmissive reflection layer.

12) The polarizing plate in any one of 1) -11) which has a phase difference layer or (lambda) / 4 layer.

13) The polarizing plate in any one of 1) -12) which has a viewing angle compensation layer.

14) The polarizing plate in any one of 1) -13) which has a brightness improving layer.

15) A liquid crystal display device having a liquid crystal cell and two polarizing plates arranged on both sides thereof, wherein at least one polarizing plate is the polarizing plate according to any one of 1) to 14), wherein the second protective film of the polarizing plate is on the liquid crystal cell side. Liquid crystal display device characterized in that.

16) The liquid crystal display device according to 15), wherein the liquid crystal cell is a liquid crystal cell in TN mode.

17) The liquid crystal display device according to 15), wherein the liquid crystal cell is a liquid crystal cell of OCB mode.

18) The liquid crystal display device according to 15), wherein the liquid crystal cell is a liquid crystal cell in IPS mode.

19) The liquid crystal display device according to 15), wherein the liquid crystal cell is a liquid crystal cell in VA mode.

Best Mode for Carrying Out the Invention

1. Composition of Polarizer

First, the polarizer and protective film which comprise the polarizing plate of this invention are demonstrated.

(1) polarizer

The polarizer of the present invention is preferably composed of polyvinyl alcohol (PVA) and dichroic molecules. However, as described in Japanese Patent Laid-Open No. 11-248937, the polarizer is dehydrated and dechlorinated to remove poly The polyvinylene polarizer which produced the yen structure and orientated this can also be used.

Although PVA is a polymer material which saponified polyvinyl acetate, it may contain the component copolymerizable with vinyl acetate, such as unsaturated carboxylic acid, unsaturated sulfonic acid, olefins, vinyl ether, for example. Moreover, modified PVA containing an acetacetyl group, a sulfonic acid group, a carboxyl group, an oxyalkylene group, etc. can also be used.

Although the saponification degree of PVA is not specifically limited, From a viewpoint of solubility, etc., 80-100 mol% is preferable and 90-100 mol% is especially preferable. Moreover, although the polymerization degree of PVA is not specifically limited, 1000-10000 are preferable and 1500-5000 are especially preferable.

The syndiotacticity of PVA is preferably 55% or more in order to improve durability as described in Patent 2978219, but 45 to 52.5% described in Patent 3317494 can also be preferably used.

After PVA film-forming, it is preferable to introduce | transduce a dichroic molecule and comprise a polarizer.

As the method for producing a PVA film, a method of forming a film by casting a stock solution obtained by dissolving PVA-based resin in water or an organic solvent is generally used. The concentration of the polyvinyl alcohol-based resin in the stock solution is usually 5 to 20% by mass, and a PVA film having a film thickness of 10 to 200 µm can be produced by forming the stock solution by a casting method. The production of the PVA film can be carried out with reference to Patent No. 3342516, Japanese Patent Application Laid-Open No. 09-328593, Japanese Patent Application Laid-Open No. 2001-302817, and 2002-144401.

Although the crystallinity degree of a PVA film is not specifically limited, 50-75 weight% of average crystallinity degrees (Xc) described in patent 33251073, and in order to reduce in-plane color deviation, are described in Unexamined-Japanese-Patent No. 2002-236214. PVA films with a crystallinity of 38% or less can be used.

It is preferable that birefringence ((DELTA) n) of a PVA film is small, The birefringence described in patent 3342516 can use PVA film of 1.0x10 <^-3> or less suitably. However, as described in Japanese Laid-Open Patent Publication No. 2002-228835, the birefringence of the PVA film may be 0.002 or more and 0.01 or less in order to obtain high polarization while avoiding cutting during stretching of the PVA film. As described in -060505, the value of (nx + ny) / 2-nz may be 0.0003 or more and 0.01 or less. 0 nm or more and 100 nm or less are preferable, and, as for the retardation (in-plane) of a PVA film, 0 nm or more and 50 nm or less are more preferable. Moreover, 0 nm or more and 500 nm or less are preferable, and, as for Rth (film thickness direction) of a PVA film, 0 nm or more and 300 nm or less are more preferable.

In addition, in the polarizing plate of the present invention, a PVA film having a 1,2-glycol bond amount of 1.5 mol% or less described in Patent 3021494 and an optical foreign material of 5 μm or more described in JP 2001-316492A are 100 cm 2. 1 to 100 parts by weight of the polyhydric alcohol in the TD direction of the PVA film of 500 or less, the film described in JP 2002-030163 A, or the plasticizer described in JP 06-289225 A. The PVA film formed into a film from the solution which mixed more than weight% can be used preferably.

Although the film film thickness before extending | stretching a PVA film is not specifically limited, From a viewpoint of stability of a film support and extending | stretching homogeneity, 1 micrometer-1 mm are preferable, and 20-200 micrometers is especially preferable. As described in Japanese Laid-Open Patent Publication No. 2002-236212, a thin PVA film in which the stress generated when stretching four to six times in water is 10 N or less can also be used.

As the dichroic molecule, higher order iodine ions or dichroic dyes such as I ₃ ^- and I ₅ ^- can be preferably used. In the present invention, higher order iodine ions are particularly preferably used. Higher-order iodine ions are liquids and / or solutions in which iodine is dissolved in an aqueous potassium iodide, as described in "Application of Polarizing Plates", Nagatagawa, CMC Publications and Industrial Materials, Vol. 28, No. 7, p39-p45. PVA is immersed in boric-acid aqueous solution, and it can produce | generate in the state which adsorbed and aligned to PVA.

When using a dichroic dye as a dichroic molecule, an azo dye is preferable and a bis azo dye and a tris azo dye are especially preferable. The dichroic dye is preferably a water-soluble one, and for this reason, hydrophilic substituents such as sulfonic acid groups, amino groups and hydroxyl groups are introduced into the dichroic molecules, and are preferably used as free acids or salts of alkali metal salts, ammonium salts and amines.

Specific examples of such dichroic dyes include, for example, CIDirect Red 37, Congo Red (CIDirect Red 28), CIDirect Violet 12, CIDirect Blue 90, CIDirect Blue 22, CIDirect Blue 1, CIDirect Blue 151, Benzidine series such as CIDirect Green 1, Diphenyl urea series such as CIDirect Yellow 44, CIDirect Red 23, CIDirect Red 79, Stilbene series such as CIDirect Yellow 12, and dinaphthylamine series such as CIDirect Red 31 And acid systems such as CIDirect Red 81, CIDirect Violet 9, and CIDirect Blue 78. In addition, CIDirect Yellow 8, CIDirect Yellow 28, CIDirect Yellow 86, CIDirect Yellow 87, CIDirect Yellow 142, CIDirect Orange 26, CIDirect Orange 39, CIDirect Orange 72, CIDirect Orange 106, CIDirect Orange 107, CIDirect Red 2, CIDirect Red 39, CIDirect Red 83, CIDirect Red 89, CIDirect Red 240, CIDirect Red 242, CIDirect Red 247, CIDirect Violet 48, CIDirect Violet 51, CIDirect Violet 98, CIDirect Blue 15, CIDirect Blue 67, CIDirect Blue 71, CIDirect Blue 98, CIDirect Blue 168, CIDirect Blue 202, CIDirect Blue 236, CIDirect Blue 249, CIDirect Blue 270, CIDirect Green 59, CIDirect Green 85, CIDirect Brown 44, CIDirect Brown 106, CIDirect Brown 195, CIDirect Brown 210, CIDirect Brown 223, CIDirect Brown 224, CIDirect Black 1, CIDirect Black 17, CIDirect Black 19, CIDirect Black 54, etc., and also JP-A-62-70802, JP-A-1-61202, 1-172906, and The dichroic dye described in each publication of 1-172907, 1-183602, 1-248105, 1-265205, 7-261024, etc. can also be used preferably. In order to manufacture the dichroic molecule which has various colors, these dichroic dye may mix | blend 2 or more types. When using a dichroic dye, adsorption thickness may be 4 micrometers or more, as described in Unexamined-Japanese-Patent No. 2002-082222.

When the content of this dichroic molecule in the film is too small, the polarization degree is low, and even when the content of the dichroic molecule is too high, the single-sheet transmittance decreases, so that 0.01% by mass to 5% by mass relative to the polyvinyl alcohol polymer constituting the matrix of the film is usually used. Adjusted to the range.

As a preferable film thickness of a polarizer, 5 micrometers-40 micrometers are preferable, More preferably, they are 10 micrometers-30 micrometers. It is also preferable to make ratio of thickness of a polarizer and thickness of the protective film mentioned later into 0.01 <= A (polarizer film thickness) / B (protective film thickness) <= 0.16 described in Unexamined-Japanese-Patent No. 2002-174727.

(2) protective film

The protective film of the present invention is preferably a polymer film made of norbornene resin, polyethylene teretralate, polyethylene naphthalate, polycarbonate, polystyrene, polyallylate, polysulfone, cellulose acylate and the like.

In addition, it is preferable that both sides of the first and second protective films of the protective film of the present invention are substantially the same resin. Substantially the same means that the main component uses the same resin, and the additives other than the main component may be the same or different.

Among these, it is preferable to use a cellulose ester film, and it is most preferable to use cellulose acylate on both sides. The cellulose acylate film used by this invention is demonstrated below.

[Manufacture of Cellulose Acylate and Cellulose Acylate Film]

Although the acyl group of a cellulose acylate film does not have a restriction | limiting in particular, It is preferable to use an acetyl group, a propionyl group, butyryl group, and especially an acetyl group is preferable. 2.7-3.0 are preferable and, as for the substitution degree of all acyl groups, 2.8-2.95 are more preferable. When using the cellulose acetate whose total acyl group is an acetyl group, acetyl substitution degree is preferably 2.7-2.95, more preferably 2.8-2.95, and most preferably 2.84-2.89. Moreover, the acetyl substitution degree of 2.50 or more and 2.86 or less described in Unexamined-Japanese-Patent No. 2001-356214, and 2.75 or more and 2.86 or less described in Unexamined-Japanese-Patent No. 2001-226495 can also be used preferably. If it is too low, Re tends to be larger than a desired value due to the conveyance tension at the time of casting, and there is a problem that in-plane deviation is also likely to occur. In addition, as for substitution degree of the 6th-position acyl group, 0.9 or more are used preferably. In the case of the substitution degree of 0.9 or less, the deviation of Re and Rth tends to occur. In addition, the substitution degree of the acyl group in this patent adopts the value computed according to ASTMD817.

In the present invention, it is preferable to use cellulose acetate having an oxidation degree in the range of 59.0 to 61.5%.

The degree of acetylation means the amount of bound acetic acid per unit mass of cellulose. The degree of acetylation depends on the measurement and calculation of the degree of acetylation in ASTM: D-817-91 (test methods such as cellulose acetate).

As the cellulose acetate of the present invention, Synthesis Example 1 described in Paragraph Nos. 0043 to 0044 of JP-A-11-5851, Synthesis Example 2 described in Paragraphs 0048 to 0049, and Paragraph Nos. 0051 to 0402 The cellulose acetate obtained by the synthesis method of the said synthesis example 3 can be used.

Moreover, in this invention, the cellulose acylate which has two or more types of acyl groups of Unexamined-Japanese-Patent No. 8-231761 and 2003-170492 can also be used preferably.

It is preferable that it is 250 or more, and, as for the viscosity average polymerization degree (DP) of a cellulose acylate, it is more preferable that it is 290 or more.

Moreover, it is preferable that the cellulose acylate used for this invention has a narrow molecular weight distribution of Mw / Mn (Mw is mass mean molecular weight, Mn is number average molecular weight) by gel permeation chromatography. The specific value of Mw / Mn is preferably in the range of 1.0 to 1.7, more preferably in the range of 1.3 to 1.65, and most preferably in the range of 1.4 to 1.6.

The cellulose acetate obtained by the synthesis method can be used.

[Production of Cellulose Acylate Film]

The cellulose acylate film of this invention is manufactured by the solvent cast method. In the solvent cast method, a film is manufactured using the solution (dope) which melt | dissolved the cellulose acylate in the organic solvent.

The organic solvent preferably contains a solvent selected from ethers having 3 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, esters having 3 to 12 carbon atoms, and halogenated hydrocarbons having 1 to 6 carbon atoms. .

Ethers, ketones, and esters may have a cyclic structure. The compound which has two or more of functional groups (that is, -O-, -CO-, and -COO-) of an ether, a ketone, and ester can also be used as an organic solvent. The organic solvent may have other functional groups such as alcoholic hydroxyl groups. In the case of the organic solvent which has two or more types of functional groups, it is preferable that the carbon atom number exists in the preferable carbon atom number range mentioned above of the solvent which has any one functional group.

Examples of ethers having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phentol. Included.

Examples of ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclohexanone and methylcyclohexanone.

Examples of esters having 3 to 12 carbon atoms include ethyl formate, propyl promate, benzyl formate, methyl acetate, ethyl acetate and pentyl acetate.

Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol.

The number of carbon atoms of the halogenated hydrocarbon is preferably 1 or 2, most preferably 1. It is preferable that the halogen of a halogenated hydrocarbon is chlorine. The proportion of the hydrogen atom of the halogenated hydrocarbon substituted by halogen is preferably 25 to 75 mol%, more preferably 30 to 70 mol%, still more preferably 35 to 65 mol%, and 40 to 60 mol% Most preferred. Methylene chloride is a representative halogenated hydrocarbon.

Two or more types of organic solvents can also be mixed and used.

A cellulose acylate solution can be prepared by the general method which consists of processing at the temperature (normal temperature or high temperature) 0 degreeC or more. Preparation of the solution can be carried out using a method and apparatus for preparing a dope in a conventional solvent cast method. In the general method, it is preferable to use a halogenated hydrocarbon (particularly methylene chloride) as the organic solvent.

The amount of cellulose acylate is adjusted so as to contain 10 to 40 mass% in the solution obtained. The amount of cellulose acylate is more preferably 10 to 30% by mass. In the organic solvent (main solvent), you may add the arbitrary additive mentioned later.

A solution can be prepared by stirring a cellulose acylate and an organic solvent at normal temperature (0-40 degreeC). The high concentration solution may be stirred under pressurized and heated conditions. Specifically, the cellulose acylate and the organic solvent are put in a pressurized container and sealed, and the mixture is stirred while heating to a temperature not lower than the boiling point at normal temperature of the solvent and not boiling.

Heating temperature is 40 degreeC or more normally, Preferably it is 60-200 degreeC, More preferably, it is 80-110 degreeC.

Each component may be mixed in advance and then put in a container. Moreover, you may order to a container sequentially. The vessel needs to be configured to be able to stir. The vessel can be pressurized by injecting an inert gas such as nitrogen gas. It is also possible to use an increase in the vapor pressure of the solvent by heating. Or after sealing a container, you may add each component under pressure.

When heating, it is preferable to heat from the exterior of a container. For example, a jacket type heating device can be used. Moreover, the whole container can also be heated by installing and piping a plate heater outside the container, and circulating a liquid.

It is preferable to provide a stirring blade inside a container and to stir using this. The stirring vane is preferably of a length reaching the vicinity of the wall of the vessel. In order to update the liquid film of a container wall, it is preferable to provide a scraping blade at the end of the stirring blade.

Instruments may be provided with instruments such as pressure gauges and thermometers. Each component is dissolved in a solvent in a container. The prepared dope is taken out of the container after cooling or taken out, and then cooled using a heat exchanger or the like.

A solution can also be prepared by a cooling solution method. In the cooling dissolution method, the cellulose acylate can be dissolved in an organic solvent which is difficult to dissolve in the usual dissolution method. Moreover, even if it is a solvent which can melt | dissolve a cellulose acylate by a normal dissolution method, there exists an effect of obtaining a uniform solution promptly by the cooling dissolution method.

In the cooling solution method, the cellulose acylate is gradually cooled in the organic solvent at room temperature.

It is preferable to adjust the quantity of cellulose acylate so that it may contain 10-40 mass% in this mixture. The amount of cellulose acylate is more preferably 10 to 30% by mass. Moreover, you may add arbitrary additives mentioned later in a mixture.

The mixture is then cooled to -100 to -10 ° C (preferably -80 to -10 ° C, more preferably -50 to -20 ° C, most preferably -50 to -30 ° C). Cooling can be performed, for example, in a dry ice methanol bath (-75 ° C) or a cooled diethylene glycol solution (-30 to -20 ° C). The mixture of cellulose acylate and an organic solvent solidifies by cooling.

The cooling rate is preferably 4 ° C / minute or more, more preferably 8 ° C / minute or more, and most preferably 12 ° C / minute or more. The faster the cooling rate is, the better, but 10000 ° C / sec is the theoretical upper limit, 1000 ° C / sec is the technical upper limit, and 100 ° C / sec is the practical upper limit. The cooling rate is a value obtained by dividing the difference between the temperature at the start of cooling and the final cooling temperature by the time from when the cooling is started until the final cooling temperature is reached.

Moreover, when this is heated to 0-200 degreeC (preferably 0-150 degreeC, more preferably 0-120 degreeC, most preferably 0-50 degreeC), a cellulose acylate will melt | dissolve in an organic solvent. The temperature rising is enough just to stand in room temperature, and may be heated in a warm bath.

It is preferable that a heating rate is 4 degree-C / min or more, and if it is more preferable that it is 8 degree-C / min or more, it is most preferable that it is 12 degree-C / min or more. The higher the heating rate is, the better, but 10000 ° C / sec is the theoretical upper limit, 1000 ° C / sec is the technical upper limit, and 100 ° C / sec is the practical upper limit. In addition, the heating rate is a value obtained by dividing the difference between the temperature at the start of heating and the final heating temperature by the time from the start of heating until the final heating temperature is reached.

A homogeneous solution is obtained as mentioned above. If the solution is insufficient, the cooling and warming operations may be repeated. Whether or not dissolution is sufficient can be judged only by observing the appearance of the solution with the naked eye.

In the cooling dissolution method, it is preferable to use a sealed container in order to avoid water mixing due to condensation during cooling. In addition, in a cooling heating operation, when it pressurizes at the time of cooling and depressurizes at the time of heating, a dissolution time can be shortened. In order to perform pressurization and pressure reduction, it is preferable to use a pressure-resistant container.

In addition, a solution of 20% by mass in which cellulose acylate (acetylation degree: 60.9%, viscosity average degree of polymerization: 299) was dissolved in methyl acetate by a cooling dissolution method was determined to be solated at 33 ° C by a differential scanning calorimeter (DSC). The pseudo phase transition point of a state and a gel state exists, and it becomes a uniform gel state below this temperature. Therefore, this solution needs to be maintained at a temperature above the pseudo phase transition temperature, preferably at a gel phase transition temperature plus about 10 ° C. However, this pseudo phase transition temperature depends on the degree of acetylation of the cellulose acetate, the viscosity average polymerization degree, the solution concentration, or the organic solvent to be used.

From the prepared cellulose acylate solution (dope), a cellulose acylate film is manufactured by the solvent cast method. It is preferable to add the said retardation increasing agent to dope.

The dope is flexible on a drum or band and the solvent is evaporated to form a film. It is preferable to adjust the density | concentration of the dope before casting | flow_spread so that solid content may be 18 to 35%. It is preferable to finish the surface of a drum or a band in a mirror state. The dope is preferably cast on a drum or band having a surface temperature of 10 ° C or lower.

As for the drying method in the solvent cast method, U.S. Pat.Nos. 2336310, 2367603, 2492078, 2492977, 2492978, 2607704, 2739069, 2739070, British Patent 640731, 737392 Each specification of Unexamined-Japanese-Patent No. 45-4554, 49-5614, 60-176834, 60-203430, 62-115035 is described. Drying on a band or drum can be performed by blowing inert gas, such as air and nitrogen.

The obtained film may be removed from the drum or the band, and further dried by hot air having a temperature gradually changed to 100 to 160 ° C to evaporate the residual solvent. The above method is described in JP-A-5-17844. According to this method, the time from casting to taking out can be shortened. In order to carry out this method, it is necessary to gel dope at the surface temperature of the drum or band at the time of casting.

The prepared cellulose acylate solution (dope) may be used to cast two or more layers to form a film. In this case, it is preferable to produce a cellulose acylate film by the solvent cast method. The dope is flexible on a drum or band and evaporates the solvent to form a film. As for the dope before casting | flow_spread, it is preferable to adjust density | concentration so that solid content may become 10 to 40% of range. The surface of the drum or the band is preferably finished in a mirror state.

When plural cellulose acylate liquids of two or more layers are cast, a plurality of cellulose acylate solutions can be cast, and a solution containing cellulose acylate is cast respectively from a plurality of oil studies formed at intervals in the advancing direction of the support. It is also possible to produce a film while laminating and laminating. For example, the method described in Unexamined-Japanese-Patent No. 61-158414, Unexamined-Japanese-Patent No. 1-22419, and 11-198285 can be used. Moreover, it can also form into a film by softening a cellulose acylate solution from two oil studies. For example, the method described in each of Unexamined-Japanese-Patent No. 60-27562, Unexamined-Japanese-Patent No. 61-94724, 61-947245, 61-104813, 61-158413, and 6-6134933 is described. It is available. Moreover, the cellulose acylate film which encloses the flow of the high viscosity cellulose acylate solution of Unexamined-Japanese-Patent No. 56-162617 with the low viscosity cellulose acylate solution, and simultaneously extrudes the high viscosity low cellulose acylate solution. The flexible method of can also be used.

Moreover, using two oil studies, the film formed on the support body by the 1st oil study is peeled off, and a film can also be produced by performing 2nd casting | flexion to the side which contact | connected the support surface. For example, the method of Unexamined-Japanese-Patent No. 44-20235 is mentioned.

The same solution may be used for the flexible cellulose acylate solution, and another cellulose acylate solution may be used. In order to provide a function to a some cellulose acylate layer, the cellulose acylate solution suitable for the function may be extruded from each oil research. In addition, the cellulose acylate solution of the present invention may be flexible at the same time as other functional layers (such as an adhesive layer, a dye layer, an antistatic layer, an antihalation layer, an ultraviolet absorbing layer, a polarizing layer, etc.).

In the conventional monolayer liquid, in order to make a required film thickness, it is necessary to extrude the cellulose acylate solution of high viscosity with high concentration. In this case, the stability of the cellulose acylate solution is poor, and solids are generated, thereby causing problems or poor planarity. As a solution to this problem, by casting a plurality of cellulose acylate solutions from oil studies, high viscosity solutions can be extruded simultaneously on the support, so that the planarity is good, and not only an excellent planar film can be produced but also thick By using a cellulose acylate solution, reduction of a dry load can be achieved and a production cost of a film can be raised.

The following plasticizers can be used for the cellulose acylate film in order to improve mechanical properties. Phosphoric acid ester or carboxylic acid ester is used as a plasticizer. Examples of the phosphate ester include triphenyl phosphate (TPP) and tricresyl phosphate (TCP). Phthalic acid ester and citric acid ester are typical as carboxylic acid ester. Examples of phthalate esters include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP) and diethylhexyl phthalate (DEHP). . Examples of citric acid esters include triethyl o-acetyl citrate (OACTE) and tributyl o-acetyl citrate (OACTB). Examples of other carboxylic acid esters include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and various trimellitic acid esters. Phthalate ester plasticizers (DMP, DEP, DBP, DOP, DPP, DEHP) are preferably used. DEP and DPP are particularly preferred.

It is preferable that the addition amount of a plasticizer is 0.1-25 mass% of the quantity of cellulose acylate, It is more preferable that it is 1-20 mass%, It is most preferable that it is 3-15 mass%.

A deterioration inhibitor (for example, antioxidant, peroxide decomposer, radical inhibitor, metal deactivator, acid trapping agent, and amine) can also be added to a cellulose acylate film. The deterioration inhibitor is described in Japanese Unexamined Patent Publications No. 3-199201, 5-197073, 5-194789, 5-271471, and 6-107854. It is preferable that it is 0.01-1 mass% of the solution (dope) to prepare, and, as for the addition amount of a deterioration inhibitor, it is more preferable that it is 0.01-0.2 mass%. If the amount is less than 0.01% by mass, the effect of the deterioration inhibitor is hardly seen. When addition amount exceeds 1 mass%, the bleed out (save) of the antideterioration agent to a film surface may be observed. Examples of particularly preferred deterioration inhibitors include butylated hydroxytoluene (BHT) and tribenzylamine (TBA).

These processes from casting to post-drying can be performed even in an air atmosphere or under an inert gas atmosphere such as nitrogen gas. The winding machine used for manufacture of the cellulose acylate film used for this invention should just be a thing generally used, such as the static tensioning method, the static torque method, the taper tensioning method, the internal stress constant program tension control method, etc. It can be wound by winding method.

[Surface Treatment of Cellulose Acylate Film]

It is preferable to surface-treat a cellulose acylate film. Specific methods include corona discharge treatment, glow discharge treatment, flame treatment, acid treatment, alkali treatment or ultraviolet irradiation treatment. Moreover, it is also preferable to form an undercoat layer as described in Unexamined-Japanese-Patent No. 7-333433.

From the viewpoint of maintaining the planarity of the film, it is preferable that the temperature of the cellulose acylate film is set to Tg (glass transition temperature) or lower, specifically 150 ° C or lower, in these treatments.

When using it as a transparent protective film of a polarizing plate, it is especially preferable to perform acid treatment or alkali treatment, ie, saponification process with respect to a cellulose acylate, from an adhesive viewpoint with a polarizer.

The surface energy is preferably 55 mN / m or more, more preferably 60 mN / m or more and 75 mN / m or less.

The alkali saponification treatment will now be described in detail.

The alkali saponification treatment of the cellulose acylate film is preferably carried out in a cycle in which the film surface is immersed in an alkaline solution, neutralized with an acidic solution, washed with water and dried.

Examples of the alkali solution include potassium hydroxide solution and sodium hydroxide solution, and the prescribed concentration of hydroxide ions is preferably in the range of 0.1 to 3.0 N, more preferably in the range of 0.5 to 2.0 N. It is preferable to exist in room temperature to 90 degreeC, and, as for alkaline solution temperature, it is more preferable to exist in 40 to 70 degreeC range.

The surface energy of a solid can be calculated | required by the contact angle method, the wet heat method, and the adsorption method as described in "The basis and application of wetness" (issued by Riarise Co., 1989.12.10). In the case of the cellulose acylate film of this invention, it is preferable to use a contact angle method.

Specifically, two kinds of solutions of known surface energy are added dropwise to the cellulose acylate film, and the angle between the tangent formed on the droplet and the surface of the film at the intersection of the surface of the droplet and the surface of the film is formed. By defining the contact angle, the surface energy of the film can be calculated by calculation.

[Moisture permeability]

As the protective film used for the polarizing plate of the present invention, any resin may be used as long as the moisture permeability is different, but the first and second protective films are preferably the same type of polymer substrate film. In addition, it is preferable that the difference in the moisture permeability of the first and second protective films is given according to the type and / or amount of the additive.

The moisture permeability measures the moisture permeability of each sample in accordance with the method described in JIS Z 0208, and is calculated as the amount of water (g) evaporated in 24 hours per 1 m 2 of area. The moisture permeability of the protective film can be adjusted by various methods. Moreover, moisture permeability can be reduced by adding a hydrophobic compound to a cellulose acylate film and reducing the water absorption of a cellulose acylate film. In this case, the additive which has low compatibility with a cellulose acylate and a small plasticizing effect is especially preferable. The compound represented by the following general formula (I)-(III) can be used especially preferably.

Next, the compound represented by general formula (I) used by this invention is demonstrated in detail.

Formula (I)

In the general formula (I), R ²¹ , R ^22, and R ²³ are each independently a hydrogen atom or an alkyl group having 1 to 5 carbon atoms (eg, methyl, ethyl, propyl, isopropyl, butyl, amyl, isoamyl). ), Particularly preferably at least one of R ²¹ , R ²² and R ²³ is an alkyl group having 1 to 3 carbon atoms (eg methyl, ethyl, propyl, isopropyl). X ²¹ is a single bond, -O-, -CO-, an alkylene group (preferably having 1 to 6 carbon atoms, more preferably 1 to 3, such as methylene, ethylene, propylene) or an arylene group (preferably 6 to 24 carbon atoms, more preferably 6 to 12. For example, it is preferably a divalent linking group formed of at least one group selected from phenylene, biphenylene, naphthylene), and -O-, alkylene group. Or a divalent linking group formed of at least one group selected from an arylene group. Y ²¹ represents a hydrogen atom, an alkyl group (preferably having 2 to 25 carbon atoms, more preferably 2 to 20. For example, ethyl, isopropyl, t-butyl, hexyl, 2-ethylhexyl, t-octyl, dodecyl , Cyclohexyl, dicyclohexyl, adamantyl), aryl group (preferably having 6 to 24 carbon atoms, more preferably 6 to 18. For example, phenyl, biphenyl, terphenyl, naphthyl) or aralkyl group (Preferably having 7 to 30 carbon atoms, more preferably 7 to 20. For example, benzyl, cresyl, t-butylphenyl, diphenylmethyl, triphenylmethyl), and preferably an alkyl group, an aryl group or an aral. It is especially preferable that it is a kill group. A combination of -X ²¹ -Y ²¹ is still more preferable that the bullet is a small number of 0 to 40 -X ²¹ -Y ²¹ is preferred, 1 to 30, and most preferably 1-25.

Although the preferable example of a compound represented by these general formula (I) is shown below, this invention is not limited to these specific examples.

Next, the compound represented by general formula (II) is demonstrated.

General formula (II)

In the general formula (II), R ¹ represents an alkyl group or an aryl group, and R ² and R ³ each independently represent a hydrogen atom, an alkyl group or an aryl group. Moreover, it is especially preferable that the sum total of carbon atoms of R <^1> , R <^2> and R < ³ > is 10 or more. As the substituent, a fluorine atom, an alkyl group, an aryl group, an alkoxy group, a sulfone group and a sulfonamide group are preferable, and an alkyl group, an aryl group, an alkoxy group, a sulfone group and a sulfonamide group are particularly preferable. Further, the alkyl group may be linear, branched or cyclic, preferably having 1 to 25 carbon atoms, more preferably 6 to 25, and having 6 to 20 (eg, methyl, ethyl, propyl, isopropyl, butyl). , Isobutyl, t-butyl, amyl, isoamyl, t-amyl, hexyl, cyclohexyl, heptyl, octyl, bicyclooctyl, nonyl, adamantyl, decyl, t-octyl, undecyl, dodecyl, tridecyl , Tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, didecyl) are particularly preferred. The aryl group preferably has 6 to 30 carbon atoms, and particularly preferably 6 to 24 carbon atoms (e.g., phenyl, biphenyl, terphenyl, naphthyl, binaphthyl, triphenylphenyl).

Although the preferable example of a compound represented by general formula (II) is shown below, this invention is not limited to these specific examples.

Next, the compound of general formula (III) used by this invention is demonstrated in detail.

General formula (III)

In the general formula (III), X ² represents B, CR (R represents a hydrogen atom or a substituent), and N. R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ²¹ , R ²² , R ²³ , R ²⁴ , R ²⁵ , R ³¹ , R ³² , R ³³ , R ³⁴ to R ³⁵ represent a hydrogen atom or a substituent Indicates.

X represents B, CR (R represents a hydrogen atom or a substituent), N, P, P = O, and as X preferably B, CR (as R preferably an aryl group, a substituted or unsubstituted amino group, alkoxy Group, aryloxy group, acyl group, alkoxycarbonyl group, aryloxycarbonyl group, acyloxy group, acylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfonylamino group, hydroxy group, mercapto group, halogen atom (e.g. fluorine atom) , Chlorine atom, bromine atom, iodine atom), carboxyl group, more preferably aryl group, alkoxy group, aryloxy group, hydroxy group, halogen atom, more preferably alkoxy group, hydroxy group, and particularly preferably hydroxy group. ), N, P = O, more preferably CR, N, and particularly preferably CR.

R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ²¹ , R ²² , R ²³ , R ²⁴ , R ²⁵ , R ³¹ , R ³² , R ³³ , R ³⁴ to R ³⁵ represent a hydrogen atom or a substituent The substituent T mentioned later can be applied as a substituent. R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ²¹ , R ²² , R ²³ , R ²⁴ , R ²⁵ , R ³¹ , R ³² , R ³³ , R ³⁴ to R ³⁵ , preferably an alkyl group, Alkenyl group, alkynyl group, aryl group, substituted or unsubstituted amino group, alkoxy group, aryloxy group, acyl group, alkoxycarbonyl group, aryloxycarbonyl group, acyloxy group, acylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group , Sulfonylamino group, sulfamoyl group, carbamoyl group, alkylthio group, arylthio group, sulfonyl group, sulfinyl group, ureide group, phosphate amide group, hydroxy group, mercapto group, halogen atom (e.g., fluorine atom, chlorine atom) , Bromine atom, iodine atom), cyano group, sulfo group, carboxyl group, nitro group, hydroxamic acid group, sulfino group, hydrazino group, imino group, heterocyclic group (preferably 1 to 30 carbon atoms, more preferably 1-12, heteroatoms include, for example, nitrogen atoms, oxygen atoms and sulfur atoms Specifically, such as imidazolyl, pyridyl, quinolyl, furyl, piperidyl, morpholino, benzooxazolyl, benzimidazolyl, benzthiazolyl), silyl groups, and more preferred. Preferably it is an alkyl group, an aryl group, a substituted or unsubstituted amino group, an alkoxy group, an aryloxy group, More preferably, they are an alkyl group, an aryl group, and an alkoxy group. These substituents may be substituted. In addition, when there are two or more substituents, they may be same or different. In addition, if possible, they may be connected to each other to form a ring.

The substituent T mentioned above is demonstrated below. The substituent T is, for example, an alkyl group (preferably having 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms, particularly preferably 1 to 8 carbon atoms, for example methyl, ethyl, iso-propyl, tert-butyl, n-octyl, n-decyl, n-hexadecyl, cyclopropyl, cyclopentyl, cyclohexyl, etc.), an alkenyl group (preferably C2-C20, more preferably C2-C12, especially preferably C2-C2) -8, for example, vinyl, allyl, 2-butenyl, 3-pentenyl, etc.), an alkynyl group (preferably C2-C20, more preferably C2-C12, especially preferably C2-C) 2-8, for example, propargyl, 3-pentynyl group, etc.), aryl group (preferably C6-C30, more preferably C6-C20, particularly preferably C6-C12) , For example phenyl, p-methylphenyl, naphthyl, etc.), substituted or free Substituted amino group (preferably 0 to 20 carbon atoms, more preferably 0 to 10 carbon atoms, particularly preferably 0 to 6 carbon atoms, such as amino, methylamino, dimethylamino, diethylamino, dibenzylamino and the like Alkoxy group (preferably 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms, particularly preferably 1 to 8 carbon atoms, such as methoxy, ethoxy, butoxy, etc.), Aryloxy group (preferably 6 to 20 carbon atoms, more preferably 6 to 16 carbon atoms, particularly preferably 6 to 12 carbon atoms, for example phenyloxy, 2-naphthyloxy, etc.), acyl group (preferably Preferably it is C1-C20, More preferably, it is C1-C16, Especially preferably, it is C1-C12, For example, acetyl, benzoyl, formyl, pivaloyl, etc. are mentioned, The alkoxycarbonyl group (preferably 2 to 20 carbon atoms, more preferably Is C2-C16, Especially preferably, it is C2-C12, For example, methoxycarbonyl, an ethoxycarbonyl, etc. are mentioned, An aryloxy carbonyl group (preferably C7-20, More preferably, it is carbon number) 7-16, Especially preferably, it is C7-10, For example, phenyloxycarbonyl etc. are mentioned, Acyloxy group (Preferably C2-20, More preferably, C2-16, Especially preferably, Is C2-C10, for example, acetoxy, benzoyloxy, etc.), an acylamino group (preferably C2-C20, More preferably, it is C2-C16, Especially preferably, it is C2-C10, Acetylamino, benzoylamino, etc.) and an alkoxycarbonylamino group (preferably with 2 to 20 carbon atoms, more preferably 2 to 16 carbon atoms, particularly preferably 2 to 12 carbon atoms, for example, methoxyka And an aryloxycarbonylamino group (preferably having 7 to 20 carbon atoms, more preferably 7 to 16 carbon atoms, particularly preferably 7 to 12 carbon atoms), for example, phenyloxycarbonylamino and the like. The sulfonylamino group (preferably C1-C20, More preferably, it is C1-C16, Especially preferably, it is C1-C12, For example, methanesulfonylamino, benzenesulfonylamino, etc. are mentioned. Sulfamoyl group (preferably 0 to 20 carbon atoms, more preferably 0 to 16 carbon atoms, particularly preferably 0 to 12 carbon atoms, such as sulfamoyl, methyl sulfamoyl, dimethyl sulfamoyl, phenyl sulfamoyl, etc.). Carbaboyl group (preferably 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms, for example, carbamoyl, methylcarbamoyl, diethylcarba). bar 1, phenylcarbamoyl, etc.), an alkylthio group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms, for example, methylthio, ethylthio, etc.). Etc.), an arylthio group (preferably 6 to 20 carbon atoms, more preferably 6 to 16 carbon atoms, particularly preferably 6 to 12 carbon atoms, for example, phenylthio, etc.), and a sulfonyl group (Preferably 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms, for example, mesyl, tosyl, etc.), sulfinyl group (preferably 1 to 20 carbon atoms) More preferably, it is C1-C16, Especially preferably, it is C1-C12, For example, methanesulfinyl, benzenesulfinyl, etc. are mentioned, A ureide group (Preferably C1-C20, More preferably, 1 to 16 carbon atoms, particularly preferably 1-12, for example, ureide, methyl ureide, phenyl ureide and the like), phosphate amide group (preferably 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 carbon atom). To 12, for example, diethyl phosphate amide, phenyl phosphate amide, etc.), hydroxy group, mercapto group, halogen atom (for example, fluorine atom, chlorine atom, bromine atom, iodine atom), cyano group, sulfo group, carboxyl group , Nitro group, hydroxamic acid group, sulfino group, hydrazino group, imino group, heterocyclic group (preferably having 1 to 30 carbon atoms, more preferably 1 to 12 carbon atoms, and hetero atoms such as nitrogen atom and oxygen atom , Sulfur atoms, specifically, for example, imidazolyl, pyridyl, quinolyl, furyl, piperidyl, morpholino, benzooxazolyl, benzimidazolyl, benzthiazolyl, etc., silyl groups (preferably Preferably 3 to 40 carbon atoms, It is preferably, and the like that include a carbon number of 3 to 30, particularly preferably 3-24 carbon atoms, such as trimethylsilyl, and triphenylsilyl). These substituents may be substituted again. In addition, when there are two or more substituents, they may be same or different. In addition, if possible, they may be connected to each other to form a ring.

Although the specific example is given and demonstrated about the compound represented by general formula (III) below, this invention is not limited at all by the following specific examples.

The compound represented by General Formula (I)-(III) is 0.01-20 mass parts with respect to 100 mass parts of cellulose esters, Preferably 0.5-10 mass parts is used. By using the said compound in this range, the retardation and water permeability of a film can be controlled suitably. In use of less than 0.01 mass part, control of retardation and water permeability become inadequate. Use exceeding 20 mass parts becomes difficult for an additive to be compatible with a cellulose ester, and becomes easy to crystallize in a film.

Moreover, the disk shaped compound disclosed in Unexamined-Japanese-Patent No. 2001-166144 can also be used especially preferably. It is preferable to exist in 0.01-30 mass% with respect to the solution (dope) to adjust, and, as for the addition amount of the compound which has these hydrophobic groups, it is more preferable to exist in 0.1-20 mass% range.

In addition, the water vapor transmission rate can be reduced by stretching in the conveying direction and / or the width direction during film formation, and densifying the orientation of molecular chains of cellulose acylate. Stretching can be either uniaxial stretching or biaxial stretching.

There are simultaneous biaxial stretching methods and sequential biaxial stretching methods for biaxial stretching, but from the standpoint of continuous manufacturing, a sequential biaxial stretching method is preferred, and after dope is flexible, the film is removed from the band or drum and stretched in the width direction (length direction). Then, it extends in a longitudinal direction (width direction).

The method of extending | stretching in the width direction is each Unexamined-Japanese-Patent No. 62-115035, Unexamined-Japanese-Patent No. 4-152125, 4-284211, 4-298310, 11-48271, etc., for example. It is described in. Stretching of a film is performed under normal temperature or heating conditions. It is preferable that heating conditions are below the glass transition temperature of a film. The film can be stretched in the treatment during drying, and is particularly effective when a solvent remains. In the case of extending | stretching of a longitudinal direction, for example, if the speed of the conveyance roller of a film is adjusted and the winding speed of a film is made faster than the speed of peeling off a film, a film will be stretched. In the case of extending | stretching of the width direction, it can convey, maintaining a width of a film with a tenter, and extending | stretching a film can also extend | stretch the width of a tenter gradually. After drying of a film, extending | stretching using a drawing machine (preferably uniaxial stretching using a long drawing machine) is also possible. The stretching ratio of the film (the ratio of the increase by stretching to the original length) is preferably in the range of 5 to 50%, more preferably in the range of 10 to 40%, and in the range of 15 to 35%. Most preferred.

Moreover, moisture permeability can also be reduced by processing a cellulose acylate film at high temperature and increasing crystallinity. The treatment needs to be carried out at a temperature and time such that volatilization of the low molecular weight compound and pyrolysis of the cellulose acylate film itself are not a problem. As for processing temperature, 100 degreeC or more and 260 degrees C or less are preferable, and 140 degreeC-240 degrees C or less are more preferable. The treatment time is preferably 5 minutes or more and 2 hours or less, and more preferably 10 minutes or more and 1 hour or less.

50 g / m <2> or more and 5000 g / m <2> or less are preferable, and, as for the water vapor transmission rate of 60 degreeC 95% 24hr of the cellulose acylate film of this invention, 300 g / m <2> or more and 3000 g / m <2> or less are more preferable.

In the present invention, the moisture permeability measured under the condition of 60 ° C. 95% RH of the first protective film is preferably 250 g / m 2 · 24 hr or more and 1000 g / m 2 · 24 hr or less, and more preferably 400 g / m 2 · 24 hr or more and 1000 g. / M 2 · 24hr or less. The water vapor transmission rate measured under the conditions of 60 degreeC 95% RH of a 2nd protective film becomes like this. Preferably it is 500 g / m <2> * 24hr or more and 5000g / m <2> / 24hr or less, More preferably, it is 700g / m <2> * 24hr or more 3000g / m <2> * 24hr or less to be.

In addition, the difference in moisture permeability measured under the conditions of 60 ° C. 95 RH% of the first protective film and the second protective film is preferably 200 to 2000 g / m 2 · 24 hr, and more preferably 300 to 1500 g / m 2 · 24 hr. If this difference is too large, the curl of the polarizing plate is increased and a problem arises when the polarizing plate is bonded to the liquid crystal cell.

[Retardation of Film]

Re-retardation value and Rth retardation value of a film are defined by following formula (I) and (II), respectively.

(I) Re = (nx-ny) × d

(II) Rth = {(nx + ny) / 2-nz} × d

In Formulas (I) and (II), nx is a refractive index in the slow axis direction (direction in which the refractive index becomes maximum) in the film plane.

In Formulas (I) and (II), ny is a refractive index in the fast axis direction (direction in which the refractive index becomes minimum) in the film plane.

In formula (II), nz is the refractive index of the thickness direction of a film.

In Formula (I) and (II), d is film thickness which makes a unit nm.

In the present invention, the air interface protective film may use any retardation value. In addition, the thing of various retardation values can be used for the liquid crystal cell side protective film film according to the use.

It is also possible to use a liquid crystal cell protective film film itself as an optically anisotropic film. In this case, for OCB mode, Re is preferably 10 to 100, more preferably 20 to 700. Rth is preferably 50 to 300, more preferably 100 to 250.

It is preferable that it is 20-100, and, as for VA mode, it is more preferable that it is 30-70. Rth is preferably 50 to 250, and more preferably 80 to 180.

In addition, as for TN, Re is 0-50, and 2-30 are more preferable. Rth is preferably 10 to 200, more preferably 30 to 150.

In addition, an optically anisotropic layer may be coated on the liquid crystal cell side protective film to be used as an optical compensation film. In this case, the optical property of the liquid crystal cell side protective film alone is preferably 0 to 10, more preferably 0 to 5, for IPS / VA mode. Rth is more preferably 0 to 20, and more preferably 0 to 10.

In the OCB mode and the TN mode, an optically anisotropic layer may be coated on the liquid crystal cell side protective film having the retardation value, and used as an optical compensation film.

Moreover, it is preferable that birefringence ((DELTA) n: nx-ny) of a protective film exists in the range of 0.00-0.002 micrometer. Moreover, it is preferable that birefringence {(n + ny) / 2-nz} of the thickness direction of a support film and an opposing film exists in the range of 0.00-0.04.

Moreover, the thickness (dry film thickness) of a transparent protective film is 120 micrometers or less, 20-110 micrometers is preferable and 40-100 micrometers is more preferable.

Although the crossing angle of the slow axis of a protective film and the absorption axis of a polarizer may be arbitrary values, it is preferable that they are parallel or the azimuth angle of 45 +/- 20 degrees.

[Retardation synergist]

It is preferable to use an aromatic compound having at least two aromatic rings as the retardation increasing agent in the liquid crystal cell side protective film in order to increase the retardation. Examples of this retardation synergist include aromatic compounds having at least two aromatic rings, such as triazines (triphenyl-1,3,5-triazine, tri-m-tolyl-1,3,5-triazine, etc.), trans And diesters of -1,4-cyclohexanedicarboxylic acid (diesters of pn-hexylphenol, diesters of pn-amylphenol, and the like).

As another specific example, it is described in Unexamined-Japanese-Patent No. 2000-111914, 2000-275434, PCT / JP00 / 02619 specification.

You may use together 2 or more types of aromatic compounds. The aromatic ring of the aromatic compound includes an aromatic hetero ring in addition to the aromatic hydrocarbon ring.

It is preferable that the molecular weight of a retardation increasing agent is 300-800.

When using a cellulose acylate film as a liquid crystal cell side protective film, an aromatic compound is used in 0.01-20 mass parts with respect to 100 mass parts of cellulose acylates. It is preferable to use an aromatic compound in 0.05-15 mass parts with respect to 100 mass parts of cellulose acylate, and it is more preferable to use in 0.1-10 mass parts.

[Retardation lowering agent]

The liquid crystal cell side protective film can also be made low in retardation by an additive. The compounds of the general formulas (I) to (III) can also be preferably used for the purpose.

When using a cellulose acylate film as a liquid crystal cell side protective film, the compound of the said general formula (I)-(III) is used in 0.01-20 mass parts with respect to 100 mass parts of cellulose acylates. It is preferable to use an aromatic compound in 0.05-15 mass parts with respect to 100 mass parts of cellulose acylates, and it is more preferable to use in 0.1-10 mass parts.

[Photoelasticity]

The photoelastic coefficient of the protective film of the present invention is preferably 60 × 10 ^-8 cm 2 / N or less, more preferably 20 × 10 ^-8 cm 2 / N. The photoelastic coefficient can be obtained by ellipsometer.

[Glass Transition Temperature]

120 degreeC or more is preferable and, as for the glass transition temperature of the protective film of this invention, 140 degreeC or more is more preferable. The glass transition temperature is an average value of the temperature at which the baseline originating from the glass transition of the film starts to change when measured at a heating rate of 10 ° C./minute using a differential scanning calorimeter (DSC) and the temperature returns to the baseline again. To save.

The polarizing plate of this invention may have an adhesive layer, a separate film, and a protective film as a component other than the polarizer and protective film mentioned above.

2. Manufacturing process of polarizing plate

Next, the manufacturing process of the polarizing plate of this invention is demonstrated.

It is preferable that the manufacturing process of the polarizing plate in this invention consists of a polarizer swelling process, a polarizer dyeing process, a polarizer dura film process, a polarizer stretching process, a polarizer drying process, a protective film bonding process, and a post-bonding drying process. If the order of a dyeing process, a film | membrane process, and an extending process is changed arbitrarily, you may carry out combining some processes simultaneously. In addition, as described in patent 3333615, washing with water after the dura mater process can also be preferably performed.

In the present invention, it is particularly preferable to sequentially perform the swelling step, the dyeing step, the dura mating step, the stretching step, the drying step, the protective film laminating step, and the post-bonding drying step in the described order. In addition, you may form an online surface inspection process in the process mentioned above or later.

The swelling step is preferably performed only with water. However, as described in Japanese Patent Application Laid-open No. Hei 10-153709, the polarizing plate substrate is added to an aqueous solution of boric acid in order to avoid the occurrence of wrinkles of the polarizing plate substrate in the production line. By swelling, and the degree of swelling of the polarizing plate substrate can also be managed.

In addition, although the temperature and time of a swelling process can be arbitrarily determined, 10 degreeC or more and 60 degrees C or less, 5 second or more and 2000 second or less are preferable.

The dyeing process can use the method of Unexamined-Japanese-Patent No. 2002-86554. As the dyeing method, any means, such as immersion, application or spraying of iodine or dye solution, may be used. Moreover, as described in Unexamined-Japanese-Patent No. 2001-290025, you may use the method of dyeing, stirring, the density | concentration of iodine, dyeing bath temperature, the draw ratio in a bath, and the solution in a bath.

When using higher order iodine ion as a dichroic molecule, in order to obtain a high contrast polarizing plate, it is preferable to use the liquid which melt | dissolved iodine in the aqueous solution of potassium iodide for a dyeing process. In this case, 0.05-20 g / l of iodine of an aqueous solution of iodide-potassium iodide, 3-200 g / l of potassium iodide, and the weight ratio of iodine and potassium iodide are 1-2000 in the preferable range. 10-1200 second of dyeing time is preferable, and 10-60 degreeC of liquid temperature is preferable. More preferably, iodine is 0.5-2 g / l, potassium iodide is 30-120 g / l, the weight ratio of iodine and potassium iodide is 30-120, the dyeing time is 30-600 seconds, and the liquid temperature is 20-50 degreeC. good.

As described in Patent No. 3145747, boron-based compounds such as boric acid and borax may be added to the dyeing solution.

It is preferable that a film-forming process contains a crosslinking agent by immersing in a crosslinking agent solution or apply | coating a solution. Moreover, as described in Unexamined-Japanese-Patent No. 11-52130, a dura mater process can also be performed in several times.

As the crosslinking agent, those described in US Patent No. 232897 may be used, and as described in Patent No. 3357109, polyhydric aldehyde may be used as the crosslinking agent to improve dimensional stability, but boric acid is most preferably used. do.

When boric acid is used as a crosslinking agent used for a film-forming process, metal ion can also be added to boric-acid potassium iodide aqueous solution. Although zinc chloride is preferable as the metal ion, zinc salts such as zinc halides such as zinc iodide, zinc sulfate, and zinc acetate may be used instead of zinc chloride, as described in JP-A-2000-35512.

In the present invention, it is preferable to prepare a boric acid-potassium iodide aqueous solution to which zinc chloride is added, and to immerse the PVA film to form a film. The boric acid is preferably 1 to 100 g / l, the potassium iodide to 1 to 120 g / l, the zinc chloride is preferably 0.01 to 10 g / l, the film formation time is 10 to 1200 seconds, and the liquid temperature is preferably 10 to 60 ° C. More preferably, boric acid is 10 to 80 g / l, potassium iodide is 5 to 100 g / l, zinc chloride is 0.02 to 8 g / l, film time is 30 to 600 seconds, and liquid temperature is 20 to 50 ° C.

As the stretching step, a longitudinal uniaxial stretching method as described in US Pat. No. 2,454,515 or the like, or a tenter method as described in JP-A-2002-86554 can be preferably used. Preferable draw ratios are 2 times or more and 12 times or less, More preferably, they are 3 times or more and 10 times or less. In addition, the relationship between the draw ratio and the disk thickness 롸 polarizer thickness is set to (polarizer film thickness / disk thickness after protective film bonding) × (total draw ratio)> 0.17 described in JP-A-2002-040256, or the final bath The relationship between the width of the polarizer at the time of exiting and the width of the polarizer at the time of protective film bonding is 0.80≤ (the width of the polarizer at the time of leaving the polarizer width / final bath at the time of protective film bonding) described in JP-A-2002-040247. 0.95 can also be preferably performed.

The drying process may use a method known in Japanese Laid-Open Patent Publication No. 2002-86554, but a preferable temperature range is 30 ° C to 100 ° C, and a preferable drying time is 30 seconds to 60 minutes. Further, as described in Patent No. 3148513, a heat treatment is performed in which the water color fading temperature is 50 ° C or higher, or as described in Japanese Patent Application Laid-Open No. 07-325215 or Japanese Patent Application Laid-Open No. 07-325218. Aging can also be preferably performed in an atmosphere in which temperature and humidity are managed.

A protective film bonding process is a process of bonding both surfaces of the above-mentioned polarizer which exited the drying process with two protective films. The method of bonding with a pair of rolls is used preferably so that an adhesive liquid may be supplied just before joining, and a polarizer and a protective film may overlap. In addition, as described in Japanese Unexamined Patent Publication No. 2001-296426 and Japanese Unexamined Patent Publication No. 2002-86554, in order to suppress groove-shaped irregularities of the record resulting from the stretching of the polarizer, the moisture content of the polarizer at the time of bonding is adjusted. It is preferable. In the present invention, a water content of 0.1% to 30% is preferably used.

Although the adhesive agent of a polarizer and a protective film is not specifically limited, PVA system resin (including modified PVA, such as an acetacetyl group, a sulfonic acid group, a carboxyl group, an oxyalkylene group), aqueous solution of a boron compound, etc. are mentioned, Especially, PVA system resin is mentioned. desirable. 0.01-5 micrometers is preferable and, as for an adhesive bond layer thickness, 0.05-3 micrometers is especially preferable.

In addition, in order to improve the adhesive force of a polarizer and a protective film, it is preferable to carry out the surface treatment of a protective film, and to make it adhere | attach after making it hydrophilic. Although the method of surface treatment does not have a restriction | limiting in particular, A well-known method, such as a saponification method using an alkaline solution and a corona treatment method, can be used. In addition, an easy adhesive layer such as a gelatin undercoat layer may be formed after the surface treatment. As described in JP-A-2002-267839, the contact angle with water on the surface of the protective film is preferably 50 ° or less.

Although the drying conditions after joining follow the method of Unexamined-Japanese-Patent No. 2002-86554, the preferable temperature range is 30 degreeC-100 degreeC, and a preferable drying time is 30 second-60 minutes. Moreover, it is also preferable to age in the atmosphere which controlled temperature-humidity as described in Unexamined-Japanese-Patent No. 07-325220.

The element content in the polarizer is preferably 0.1 to 3.0 g / m 2 of iodine, 0.1 to 5.0 g / m 2 of boron, 0.1 to 2.0 g / m 2 of potassium and 0 to 2.0 g / m 2 of zinc. Moreover, even if potassium content is 0.2 weight% or less as described in Unexamined-Japanese-Patent No. 2001-166143, the zinc content in a polarizer is 0.04 weight%-0.5 weight% described in Unexamined-Japanese-Patent No. 2000-035512. You may.

In order to raise the dimensional stability of a polarizing plate, as described in patent 3323255, an organic titanium compound and / or an organic zirconium compound are added and used in any of the process of a dyeing process, an extending process, and a film | membrane process, and an organic titanium compound And at least one compound selected from organic zirconium compounds. In addition, a dichroic dye may be added to adjust the color of the polarizing plate.

3. Characteristics of polarizer

(1) transmittance and polarization degree

Although the preferable single plate transmittance of the polarizing plate of this invention is 42.5% or more and 49.5% or less, More preferably, they are 42.8% or more and 49.0% or less. The preferable ranges of polarization degree defined by Formula 4 are 99.900% or more and 99.999% or less, More preferably, they are 99.940% or more and 99.995% or less. The preferred range of parallel transmittance is 36% or more and 42% or less, and the preferred range of orthogonal transmittance is 0.001% or more and 0.05% or less. Although the preferable range of the dichroic ratio defined by Formula 5 is 48 or more and 1215 or less, More preferably, they are 53 or more and 525 or less.

The above-mentioned transmittance | permeability is defined by the following formula based on JISZ8701.

Here, K, S (λ), y (λ) and τ (λ) are as follows.

S (λ): Spectral distribution of standard light used for color display

y (λ): equivalence function in XYZ system

τ (λ): spectral transmittance

The iodine concentration and the single plate transmittance may be in the range described in Japanese Laid-Open Patent Publication No. 2002-258051.

The parallel transmittance is at least wavelength dependent, as described in Japanese Unexamined Patent Publication No. 2001-083328 and Japanese Unexamined Patent Publication No. 2002-022950. The optical characteristic in the case of arranging the polarizing plates in cross nicols may be in the range described in JP 2001-091736, and the relationship between parallel transmittance and orthogonal transmittance is in the range described in JP 2002-174728. Maybe tomorrow.

As described in Japanese Unexamined Patent Publication No. 2002-221618, the standard deviation of parallel transmittance every 10 nm between the wavelength of light and 420 to 700 nm is 3 or less, and the wavelength of light is 10 nm between 420 and 700 nm. The minimum value of (parallel transmittance / orthogonal transmittance) for each may be 300 or more.

Parallel transmittance and orthogonal transmittance at a wavelength of 440 nm, orthogonal transmittance, parallel transmittance at a wavelength of 550 nm, parallel transmittance and orthogonal transmittance at a wavelength of 550 nm, parallel transmittance and orthogonal transmittance at a wavelength of 610 nm are disclosed in Japanese Patent Application Laid-Open No. 2002-258042 or Japanese Patent Laid-Open. The range described in Japanese Patent Application Laid-Open No. 2002-258043 can also be preferably executed.

(2) color

The color of the polarizing plate of the present invention is preferably evaluated using the brightness index L * and chromaticity indexes a * and b * in the L * a * b * color system which is recommended as the CIE equal perceptual space. L *, a *, b * are defined by Formula 6 using X, Y, and Z described above.

Here, Xo, Yo, Zo represent three stimulus values of the illumination light source, Xo = 98.072, Yo = 100, Zo = 118.225 for standard light C, Xo = 95.045, Yo = 100 for standard light D ₆₅ , Zo = 108.892.

The range of preferable a * of a single polarizing plate is -2.5 or more and 0.2 or less, More preferably, it is -2.0 or more and 0 or less. The range of the preferable b * of a single piece of polarizing plate is 1.5 or more and 5 or less, More preferably, it is 2 or more and 4.5 or less. The preferable range of a * of parallel transmitted light of two polarizing plates is -4.0 or more and 0 or less, More preferably, they are -3.5 or more and -0.5 or less. The range with preferable b * of parallel transmitted light of two polarizing plates is 2.0 or more and 8 or less, More preferably, it is 2.5 or more and 7 or less. The preferable range of a * of orthogonal light of two polarizing plates is -0.5 or more and 1.0 or less, More preferably, they are 0 or more and 2 or less. The preferable range of b * of orthogonal light of two polarizing plates is -2.0 or more and 2 or less, More preferably, it is -1.5 or more and 0.5 or less.

The color may be evaluated by the chromaticity coordinates (x. Y) calculated from the above-described X, Y, and Z, for example, the chromaticity (x _p , y _p ) of the parallel transmitted light of the two polarizing plates and the chromaticity (x _c , y of the orthogonal transmitted light). _c ) is the range as described in Unexamined-Japanese-Patent No. 2002-214436, Unexamined-Japanese-Patent No. 2001-166136, 2002-169024, or the relationship between a color and an absorbance is disclosed in Unexamined-Japanese-Patent No. 2001-311827. It is also possible to carry out within the range described in the call.

(3) viewing angle characteristics

Transmittance ratio and xy chromaticity difference when the vertical light is incident when the polarizing plate is placed in cross nicol and the light having a wavelength of 550 nm is incident, and when the polarizing plate is incident at an angle of 40 degrees with respect to the normal from a 45 degree orientation with respect to the polarization axis. It is also preferable to set it as the range of Unexamined-Japanese-Patent No. 2001-166135 and Unexamined-Japanese-Patent No. 2001-166137. In addition, as described in Japanese Patent Application Laid-Open No. 10-068817, the light transmittance (T ₀ ) in the vertical direction of the polarizing plate laminate having cross nicol arrangement and the light transmittance (T) in the inclination direction of 60 ° from the normal line of the laminate (T ₀ ). ₆₀ ) to the ratio (T ₆₀ / T ₀ ) to 10000 or less, or as described in Japanese Unexamined Patent Publication No. 2002-139625, natural light is incident on the polarizing plate at any angle from the normal to the elevation angle of 80 degrees In this case, the transmittance difference of the transmitted light within the wavelength range of 20 nm within the wavelength range of 520 to 640 nm of the transmission spectrum is 6% or less, or any of the film forms described in JP 08-248201A. It is also preferable that the luminance difference of transmitted light at a place 1 cm away is within 30%.

(4) durability

(4-1) Moist Heat Durability

As described in Japanese Unexamined Patent Application Publication No. 2002-116922, it is preferable that the rate of change of light transmittance and polarization degree before and after the case of being left at 60 ° C. and 90% RH atmosphere for 500 hours is 3% or less based on absolute values. . In particular, the change rate of light transmittance is 2% or less, and the change rate of polarization degree is preferably 1.0% or less, more preferably 0.1% or less, based on the absolute value. Moreover, as described in Unexamined-Japanese-Patent No. 07-077608, it is also preferable that polarization degree after 80 degreeC, 90% RH, and 500 hours leaving is 95% or more, and the unit transmittance is 38% or more.

(4-2) dry durability

It is preferable that the rate of change of the light transmittance and polarization degree before and after when left to stand at 80 ° C. for 500 hours in a dry atmosphere is also 3% or less based on an absolute value. In particular, it is more preferable that the change rate of light transmittance is 2% or less, and the change rate of polarization degree is 1.0% or less and 0.1% or less based on an absolute value.

(4-3) other durability

Furthermore, as described in JP-A-06-167611, the shrinkage after leaving for 2 hours at 80 ° C is 0.5% or less, or the polarizing plate laminate having cross nicol disposed on both surfaces of the glass plate is 750 in an atmosphere of 69 ° C. two hours x-axis and y-axis after being allowed to stand by the JP-a-10-068818 into the Raman spectroscopy after the range described in the call, or processing 80 ℃, allowed to stand 90% RH atmosphere for 200 hours standing medieval 105㎝ ^{- It} is also preferable to make the change of the spectrum intensity ratio of ¹ and 157 cm <^-1> into the range as described in Unexamined-Japanese-Patent No. 08-094834 and Unexamined-Japanese-Patent No. 09-197127.

(5) alignment layer

The higher the alignment film of PVA, the better polarization performance is obtained, but 0.2 to 1.0 is a preferred range as an order parameter value calculated by means such as polarized Raman scattering or polarized light FT-IR. In addition, as described in Japanese Patent Laid-Open No. 59-133509, the difference between the orientation coefficient of the total amorphous polymer segment of the polarizer and the orientation coefficient (0.75 or more) of the occupant molecule is at least 0.15, or As described in 04-204907, the orientation coefficient of the amorphous region of the polarizer is preferably 0.65 to 0.85, or the degree of orientation of the higher order iodine ions of I ^- ₃ or I ^- ₅ is set to 0.8 to 1.0 as the order parameter value. Can be used.

(6) other characteristics

As described in Japanese Unexamined Patent Publication No. 2002-006133, the shrinkage force in the absorption axis direction per unit width when heated at 80 ° C. for 30 minutes is set to 4.0 N / cm or less, or is disclosed in Japanese Unexamined Patent Publication No. 2002-236213. As can be seen, when the polarizing plate is placed under heating conditions at 70 ° C. for 120 hours, the dimensional change rate in the absorption axis direction and the dimensional change rate in the polarization axis direction of the polarizing plate are both within ± 0.6%, or the moisture content of the polarizing plate is set to JP. As described in 090546, the content may be preferably 3% by weight or less. In addition, as described in Japanese Unexamined Patent Application Publication No. 2000-249832, the surface roughness in the direction perpendicular to the stretching axis becomes 0.04 µm or less based on the center line average roughness, or described in Japanese Unexamined Patent Publication No. 10-268294. As described above, the refractive index n ₀ in the transmission axis direction is larger than 1.6, or the relationship between the thickness of the polarizing plate and the thickness of the protective film can be preferably performed in the range described in JP-A-10-111411.

4. Functionalization of Polarizer

The polarizing plate of the present invention is an anti-reflection film for improving the visibility of a retardation plate or a λ / 4 plate and a reflective layer or a semi-transmissive layer, a display for application to an LCD viewing angle expansion film (viewing angle compensation layer), a reflective or semi-transmissive LCD. It is used suitably as a functionalized polarizing plate which combined the optical film which has functional layers, such as a brightness improving film (brightness improvement layer), a hard-coat layer, a front-scattering layer, and an antiglare layer.

The structural example which combined the polarizing plate of this invention and the functional optical film mentioned above is shown in FIG. As the protective film on one side of the polarizing plate, the functional optical film and the polarizer may be adhered through an adhesive (FIG. 1A), or the functional optical film may be adhered to the polarizing plate having protective films formed on both surfaces of the polarizer via an adhesive (FIG. 1). (B)). In the former case, an arbitrary transparent protective film can be used for the other protective film. It is also preferable to set the peeling strength between each layer, such as a functional layer and a protective film, to 4.0N / 25mm or more as described in Unexamined-Japanese-Patent No. 2002-311238. It is preferable to arrange | position a functional optical film in the liquid crystal module side according to the function made into the objective, or arrange | positioning on the opposite side to a liquid crystal module, ie, a display side or a backlight side.

Below, the functional optical film used in combination with the polarizing plate of this invention is demonstrated.

(1) viewing angle magnification film

The polarizing plate of the present invention is a viewing angle magnification film proposed in display modes such as twisted nematic (TN), in-plane switching (IPS), optimally compensated bend (OCB), vertically aligned (VA), and electrically controlled controlled wire (ECB). It can be used in combination with.

As a viewing angle expansion film for TN mode, Japanese Journal of Printing 36, 3 (1999) p40-44, monthly display August issue (2002) p20-24, Unexamined-Japanese-Patent No. 4-229828. WV films (manufactured by Fuji Photographic Film) described in JP-A-6-75115, 6-214116, 8-50206 and the like are preferably used in combination.

The preferable structure of the viewing angle expansion film for TN mode is to have an orientation layer and an optically anisotropic layer in this order on the transparent polymer film mentioned above. The viewing angle magnification film may be used by being bonded to the polarizing plate through an adhesive, but as described in SID '00 Dig., P551 (2000), it is also used as one side of the protective film of the polarizer in terms of applause. Particularly preferred.

The alignment layer can be provided by means such as rubbing treatment of an organic compound (preferably a polymer), evaporation of an inorganic compound, formation of a layer having a micro groove. Moreover, although the orientation layer which generate | occur | produces an orientation state by provision of an electric field, provision of a magnetic field, or light irradiation is known, the orientation layer formed by the rubbing process of a polymer is especially preferable. The rubbing treatment is preferably performed by rubbing the surface of the polymer layer several times in a predetermined direction with paper or cloth. It is preferable that the absorption axis direction of a polarizer and a rubbing direction are substantially parallel. As a kind of polymer used for an orientation layer, the polymer etc. which have a polymerizable group of polyimide, polyvinyl alcohol, Unexamined-Japanese-Patent No. 9-152509, etc. can be used preferably. It is preferable that it is 0.01-5 micrometers, and, as for the thickness of an orientation layer, it is more preferable that it is 0.05-2 micrometers.

It is preferable that an optically anisotropic layer contains a liquid crystalline compound. It is preferable that the liquid crystalline compound used for this invention has a discotic compound (discotic liquid crystal). Discotic liquid crystal molecules have a disk-like core portion like a traphenylene derivative, and have a structure in which side chains are extended radially therefrom. In addition, in order to impart time-lapse stability, it is also preferable to further introduce a group that reacts with light or the like. Preferable examples of the discotic liquid crystal are described in Japanese Patent Laid-Open No. 8-50206.

The discotic liquid crystal molecules are oriented substantially parallel to the film plane with a pretilt angle in the rubbing direction in the vicinity of the alignment layer, and the discotic liquid crystal molecules are oriented in a form close to perpendicular to the plane on the opposite air surface side. As a whole discotic liquid crystal layer, hybrid orientation is taken and by this layer structure, the viewing angle enlargement of TFT-LCD of TN mode can be implement | achieved.

The optically anisotropic layer is generally coated with a solution of a discotic compound and other compounds (e.g., a polymerizable monomer, a photoinitiator) in a solvent on an alignment layer and dried, followed by heating to a discotic nematic phase forming temperature. Then, it is obtained by superposing | polymerizing by irradiation of UV light etc. and cooling again. As discotic nematic liquid crystal phase-solid phase transition temperature of the discotic liquid crystalline compound used for this invention, 70-300 degreeC is preferable, and 70-170 degreeC is especially preferable.

In addition, any compound other than the discotic compound added to the optically anisotropic layer has compatibility with the discotic compound, and any compound as long as the liquid crystal discotic compound is provided with a change in the preferred tilt angle or the orientation is not inhibited. Can also be used. Among them, additives for orientation control on the air interface side, such as polymerizable monomers (eg, compounds having vinyl group, vinyloxy group, acryloyl group and methacryloyl group), and fluorine-containing triazine compounds, include cellulose acetate and cellulose acetate. And polymers such as propionate, hydroxypropyl cellulose, and cellulose acetate butyrate. These compounds are generally used in an amount of addition of 0.1 to 50% by mass, preferably 0.1 to 30% by mass relative to the discotic compound.

It is preferable that it is 0.1-10 micrometers, and, as for the thickness of an optically anisotropic layer, it is more preferable that it is 0.5-5 micrometers.

The preferable aspect of a viewing angle expansion film consists of the cellulose acylate film as a transparent base film, the orientation layer formed on it, and the optically anisotropic layer which consists of a discotic liquid crystal formed on this orientation layer, and an optically anisotropic layer is carried out by UV irradiation. It is crosslinked.

In addition to the above, in the case where the viewing angle expanding film and the polarizing plate of the present invention are combined, for example, as described in Japanese Patent Application Laid-Open No. 07-198942, a phase difference plate having an optical axis in a direction crossing the plate surface and exhibiting anisotropy in birefringence is provided. Lamination or as described in Japanese Laid-Open Patent Publication No. 2002-258052 can also preferably be carried out to make the dimensional change rate of the protective film and the optically anisotropic layer substantially equal. Further, as described in Japanese Laid-Open Patent Publication No. 2000-258632, the moisture content of the polarizing plate bonded to the viewing angle expanding film is set to 2.4% or less, or as described in Japanese Laid-Open Patent Publication No. 2002-267839. It is also preferable to make the contact angle with water 70 degrees or less.

The viewing angle magnification film for an IPS mode liquid crystal cell is used for the optical compensation of liquid crystal molecules aligned in parallel with the substrate surface and the viewing angle characteristic of the orthogonal transmittance of the polarizing plate in black display in an unattended field. In the IPS mode, the black display is performed in the state where no electric field is applied, and the transmission axes of the upper and lower pairs of polarizing plates are perpendicular to each other. However, when obliquely observed, the crossing angle of the transmission axis is not 90 degrees, and leakage light is generated to reduce the contrast. When using the polarizing plate of this invention for an IPS mode liquid crystal cell, in-plane phase difference described in Unexamined-Japanese-Patent No. 10-54982 is close to 0, and the viewing angle which has a phase difference in thickness direction in order to reduce leakage light. It is preferably used in combination with the magnifying film.

The viewing angle magnification film for liquid crystal cells of the OCB mode is used to perform optical compensation of the liquid crystal layer in which the liquid crystal layer is vertically aligned at the center of the liquid crystal layer by the application of an electric field, and is inclinedly aligned in the vicinity of the substrate interface, thereby improving the viewing angle characteristics of the black display. When using the polarizing plate of this invention for an OCB mode liquid crystal cell, it uses suitably in combination with the viewing angle expansion film which hybrid-oriented the disk-shaped liquid crystalline compound as described in US Pat. No. 5,805,253.

The viewing angle magnification film for the liquid crystal cell of VA mode improves the viewing angle characteristic of the black display in the state in which liquid crystal molecules were orientated perpendicularly to the substrate surface in the absence of an electric field. Such a viewing angle expanding film is a film having an in-plane retardation close to zero and having a retardation in the thickness direction as described in Patent No. 2866372, or a film in which discotic compounds are arranged in parallel to a substrate. It is preferably used in combination with a laminated film of a stretched film having an in-plane retardation value laminated so that the slow axis is orthogonal, or a film made of a rod-like compound such as liquid crystal molecules for preventing deterioration of orthogonal transmittance in the oblique direction of the polarizing plate. .

(2) λ / 4 plate

The polarizing plate of the present invention can be used as a circularly polarizing plate laminated with a λ / 4 plate. The circularly polarizing plate has a function of converting incident light into circularly polarized light, and is preferably used for a semi-transmissive liquid crystal display device such as a reflective liquid crystal display device, an ECB mode, or an organic EL element.

(Lambda) / 4 board used for this invention is a phase difference film which has retardation (Re) of about 1/4 of a wavelength in the range of the wavelength of visible light, in order to obtain substantially complete circularly polarized light in the range of the wavelength of visible light. Do. The term "retardation of approximately 1/4 in the visible light wavelength range" means that the longer the wavelength is, the longer the retardation is at the wavelength of 400 to 700 nm, the retardation value (Re 450) measured at the wavelength of 450 nm is 80 to 125 nm. The range which satisfies the relationship whose retardation value (Re 590) measured at the wavelength of 590nm is 120-160 nm is shown. It is more preferable that it is Re590-Re450≥5 nm, and it is especially preferable that Re590-Re450≥10 nm.

The λ / 4 plate used in the present invention is not particularly limited as long as the above conditions are satisfied. For example, a plurality of polymer films described in JP-A-5-27118, 10-68816, and 10-90521 may be used. (Lambda) / 4 plate which laminated | stacked (lambda) / 4 plate, WO00 / 65384, and one polymer film of WO00 / 26705, and the polymer film image of Unexamined-Japanese-Patent No. 2000-284126, 2002-31717. A well-known [lambda] / 4 plate, such as a [lambda] / 4 plate in which at least one or more optically anisotropic layers are formed, can be used. In addition, the direction of the slow axis of a polymer film, and the orientation direction of an optically anisotropic layer can be arrange | positioned in arbitrary directions according to a liquid crystal cell.

In the circular polarizing plate, the slow axis of the λ / 4 plate and the transmission axis of the polarizer may cross at any angle, but are preferably crossed in the range of 45 ° ± 20 °. However, the slow axis of the λ / 4 plate and the transmission axis of the polarizer may cross each other in the ranges other than the above.

When the lambda / 4 plate is formed by laminating the lambda / 4 plate and the lambda / 2 plate, the lambda / 4 plate and lambda as described in Patent No. 3236304 or Japanese Patent Application Laid-open No. Hei 10-68816 It is preferable to join so that the angle which the in-plane slow axis of a / 2 plate and the transmission axis of a polarizing plate make substantially 75 degrees and 15 degrees.

(3) antireflection film

The polarizing plate of the present invention can be used in combination with an antireflection film. As the antireflection film, any one of a film having a reflectance of about 1.5% that only gives a low refractive index material such as a fluorine-based polymer or a film having a reflectance of 1% or less using multilayer interference of a thin film can be used. In the present invention, a low refractive index layer and at least one layer (that is, a high refractive index layer and a medium refractive index layer) having a higher refractive index than that of the low refractive index layer are preferably used on the transparent support. Moreover, the antireflection film described in Nittogibo, vol. 38, No. 1, may, 2000, pages 26-28, etc. can also be preferably used. The refractive index of each layer satisfies the following relationship.

Refractive index of the high refractive index layer> refractive index of the medium refractive index layer> refractive index of the transparent support> refractive index of the low refractive index layer

As a transparent support body used for an antireflection film, the transparent polymer film used for the protective film of the polarizing layer mentioned above can be used preferably.

The refractive index of the low refractive index layer is 1.20 to 1.55, preferably 1.30 to 1.50. It is preferable to use the low refractive index layer as the outermost layer having scratch resistance and antifouling property. In order to improve the scratch resistance, it is also preferable to impart sliding property to the surface using a silicon group or a material containing fluorine.

Examples of the fluorine-containing compound include Japanese Patent Laid-Open No. 9-222503, Paragraph Nos. [0018] to [0026], and Japanese Patent Laid-Open No. 11-38202, Paragraph No. [0019] to [0030], and Japanese Patent Laid-Open No. 2001-40284. The compounds described in specification paragraphs [0027] to [0028], JP 2000-284102, and the like can be preferably used.

Although the silicon-containing compound is preferably a compound having a polysiloxane structure, reactive silicones (e.g., cyraplane (manufactured by Chisso Co., Ltd.) or polysiloxanes containing silanol groups at both ends (Japanese Patent Laid-Open No. 11-258403), etc.) are preferable. An organometallic compound such as a silane coupling agent and a fluorine-containing hydrocarbon group-containing silane coupling agent may be cured by a condensation reaction in the presence of a catalyst (JP-A-58-142958 and 58-147483). , Japanese Patent Application Laid-Open No. 9-157582, Japanese Patent Application Laid-Open No. 11-106704, Japanese Patent Application Laid-Open No. 2000-117902, Japanese Patent Laid-Open No. 2001-48590, Japanese Patent Laid-Open No. 2002-53804, etc.).

The low refractive index layer includes, as additives other than the above, a low refractive index inorganic compound having a primary particle average diameter of primary particles such as fillers (for example, silicon dioxide (silica) and fluorine-containing particles (magnesium fluoride, calcium fluoride, barium fluoride)); The organic fine particles described in paragraphs [0020] to [0038] of Japanese Patent Application Laid-Open No. 11-3820), a silane coupling agent, a lubricant, a surfactant, and the like can also be preferably carried out.

Although the low refractive index layer may be formed by a vapor phase method (vacuum deposition method, sputtering method, ion plating method, plasma CVD method, etc.), it is preferable to form by a coating method from the point that it can manufacture at low cost. As the coating method, a dip coating method, an air knife coating method, a curtain coating method, a roller coating method, a wire bar coating method, a gravure coating method or a microgravure method can be preferably used.

It is preferable that the film thickness of a low refractive index layer is 30-200 nm, It is more preferable that it is 50-150 nm, It is most preferable that it is 60-120 nm.

The medium refractive index layer and the high refractive index layer are preferably constituted by dispersing high refractive index inorganic compound ultrafine particles having an average particle diameter of 100 nm or less in the matrix material. As the high refractive index inorganic compound fine particles, inorganic compounds having a refractive index of 1.65 or more, for example, oxides such as Ti, Zn, Sb, Sn, Zr, Ce, Ta, La, In, composite oxides containing these metal atoms, etc. can be preferably used. have.

Such ultra-fine particles can be treated with a surface treatment agent (such as a silane coupling agent: Japanese Patent Laid-Open No. 11-295503, Japanese Patent Laid-Open No. 11-153703, Japanese Patent Laid-Open No. 2000-9908, an anionic compound or an organic metal couple). Ring agent: Japanese Laid-Open Patent Publication No. 2001-310432, etc.), a core shell structure composed of high refractive index particles as a core (Japanese Laid-Open Patent Publication No. 2001-166104, etc.), or using a specific dispersant in combination (e.g. 11-153703, Patent No. US6210858B1, Japanese Laid-Open Patent Publication No. 2002-2776069 and the like).

As the matrix material, conventionally known thermoplastic resins, curable resin coatings, and the like can be used, but the polyfunctionality described in Japanese Patent Application Laid-Open Nos. 2000-47004, 2001-315242, 2001-31871, 2001-296401, and the like. The curable film obtained from a material and the metal alkoxide composition of Unexamined-Japanese-Patent No. 2001-293818 etc. can also be used.

It is preferable that the refractive index of a high refractive index layer is 1.70-2.20. It is preferable that it is 5 nm-10 micrometers, and, as for the thickness of a high refractive index layer, it is more preferable that it is 10 nm-1 micrometer.

The refractive index of the medium refractive index layer is adjusted to be a value between the refractive index of the low refractive index layer and the refractive index of the high refractive index layer. The refractive index of the medium refractive index layer is preferably 1.50 to 1.70.

It is preferable that it is 5% or less, and, as for the haze of antireflection film, 3% or less is more preferable. The film strength is preferably at least H, more preferably at least 2H, and most preferably at least 3H in a pencil hardness test according to JIS K5400.

(4) brightness enhancement film

The polarizing plate of this invention can be used in combination with a brightness improving film. The brightness enhancement film has a separation function of circularly polarized light or linearly polarized light, and is disposed between the polarizing plate and the backlight, and either circularly polarized light or linearly polarized light is reflected back or scattered back toward the backlight. Since the re-reflected light from the backlight part partially changes the polarization state and partially transmits the light when it is reincident to the brightness enhancing film and the polarizing plate, the light utilization is improved by repeating this process, and the front luminance is about 1.4 times. Is improved. Anisotropic reflection system and anisotropic scattering system are known as a brightness improving film, and both can be combined with the polarizing plate of this invention.

In the anisotropic reflection method, a uniaxially stretched film and an unstretched film are laminated in multiple layers to increase the refractive index difference in the stretching direction, so that a brightness enhancement film having anisotropy of reflectance and transmittance is known, and a multilayer film method using the principle of dielectric mirror (WO95 / 17691, WO95 / 17692, WO95 / 17699) and cholesteric liquid crystal system (Patent No. 606940A2, Japanese Patent Laid-Open No. 8-271731) are known. DBEF-E, DBEF-D, DBEF-M (all manufactured by 3M) as a multilayer brightness enhancement film using the principle of dielectric mirror, NIPOCS as a cholesteric liquid crystal brightness enhancement film (Nitto Electric Co., Ltd.) ) Is preferably used in the present invention.

For NIPOCS, see Nittogibo, vol. 38, No. 1, may, 2000, pages 19 to 21, and the like.

In addition, in the present invention, the amount of intrinsic birefringence described in each specification of WO97 / 32223, WO97 / 32224, WO97 / 32225, WO97 / 32226, and Japanese Unexamined Patent Publications Nos. 9-274108 and 11-174231 It is also preferable to use it in combination with the brightness enhancement film of the anisotropic scattering system which uniaxially stretched and blended a polymer and a negative intrinsic birefringent polymer. As an anisotropic scattering system brightness improvement film, DRPF-H (made by 3M company) is preferable.

It is preferable to use the polarizing plate and brightness improvement film of this invention in the form bonded together via the adhesive, or the integral type which used one of the protective films of a polarizing plate as a brightness improvement film.

(5) other functional optical films

The polarizing plate of the present invention may also be used in combination with a functional optical film in which a hard coat layer, a forward scattering layer, an antiglare (antiglare) layer, a gas barrier layer, an active layer, an antistatic layer, an undercoat or a protective layer are formed. desirable. It is also preferable that these functional layers are used in combination with each other and in the same layer as the above-described antireflection layer, optically anisotropic layer and the like.

(5-1) Hard Coat Layer

In order to provide mechanical strength, such as abrasion resistance, in the polarizing plate of this invention, combining a hard coat layer with the functional optical film formed in the surface of a transparent support body is performed preferably. In the case where the hard coat layer is applied to the antireflection film described above and used, the hard coat layer is preferably formed between the transparent support and the high refractive index layer.

The hard coat layer is preferably formed by crosslinking or polymerization of the curable compound by light and / or heat. As a curable functional group, a photopolymerizable functional group is preferable, and, as for the organometallic compound containing a hydrolysable functional group, an organic alkoxy silyl compound is preferable. As a specific structural composition of a hard-coat layer, the thing of Unexamined-Japanese-Patent No. 2002-144913, 2000-9908, WO0 / 46617 can be used preferably, for example.

It is preferable that the film thickness of a hard-coat layer is 0.2-100 micrometers.

In the pencil hardness test according to JIS K5400, the strength of the hard coat layer is preferably H or more, more preferably 2H or more, and most preferably 3H or more. In the taper test according to JIS K5400, the smaller the amount of wear of the test pieces before and after the test, the better.

As the material for forming the hard coat layer, a compound containing an ethylenically unsaturated group and a compound containing a ring-opening polymerizable group can be used, and these compounds can be used alone or in combination. Preferable examples of the compound containing an ethylenically unsaturated group include ethylene glycol diacrylate, trimethylolpropane triacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, and dipentaerythritol pentaacryl. Polyarchelates of polyols such as late and dipentaerythritol hexaacrylate; Epoxy acrylates such as bisphenol A diglycidyl ether, diacrylate, and diacrylate of hexanediol diglycidyl ether; Urethane acrylate obtained by reaction of hydroxyl-containing acrylates, such as polyisocyanate and hydroxyethyl acrylate, is mentioned as a preferable compound. In addition, commercially available compounds include EB-600, EB-40, EB-140, EB-1150, EB-1290K, IRR214, EB-2220, TMPTA, TMPTMA (manufactured by Daicel UCP Co., Ltd.), UV- 6300 and UV-1700B (above Nippon Synthetic Chemical Co., Ltd. product) etc. are mentioned.

Preferable examples of the compound containing a ring-opening polymerizable group include ethylene glycol diglycidyl ether, bisphenol A diglycidyl ether, trimethylol ethane triglycidyl ether, and trimethylolpropane triglycidyl as glycidyl ethers. Ether, glycerol triglycidyl ether, triglycidyl trishydroxyethyl isocyanurate, sorbitol tetraglycidyl ether, pentaerythritol tetraglycidyl ether, polyglycidyl ether of cresol novolac resin, phenol novolac resin As alicyclic epoxy, such as polyglycidyl ether, Ceroxide 2021P, Ceroxide 2081, Eporide GT-301, Eporide GT-401, EHPE3150CE (above, the Daicel Chemical Industry Co., Ltd. product), a phenol novolak resin Examples of the oxetanes such as polycyclohexyl epoxy methyl ether of OXT-121, OXT-221, OX-SQ, PNOX-1009 (above, Toa Synthetic Co., Ltd.), etc. are mentioned. In addition, the polymer of glycidyl (meth) acrylate or the copolymer with the monomer copolymerizable with glycidyl (meth) acrylate can be used for a hard-coat layer.

The hard coat layer includes oxide fine particles such as silicon, titanium, zirconium, aluminum, polyethylene, polystyrene, to reduce hardening shrinkage of the hard coat layer, to improve adhesion to the substrate, and to reduce curl of the hard coat processed article of the present invention. It is also preferably performed to add crosslinked fine particles such as crosslinked particles such as poly (meth) acrylic acid esters and polydimethylsiloxane, and organic fine particles such as crosslinked rubber fine particles such as SBR and NBR. The average particle diameter of these crosslinked fine particles is preferably 1 nm to 20000 nm. In addition, the shape of crosslinked microparticles | fine-particles can be used without a restriction | limiting in particular, such as spherical shape, rod shape, needle shape, plate shape. It is preferable that it is 60 volume% or less of the hard-coat layer after hardening, and, as for the addition amount of microparticles | fine-particles, 40 volume% or less is more preferable.

In the case of adding the inorganic fine particles described above, since affinity with the binder polymer is generally poor, it contains metals such as silicon, aluminum and titanium, and further contains alkoxide groups, carboxylic acid groups, sulfonic acid groups, phosphonic acid groups and the like. Surface treatment using a surface treating agent having a functional group of is also preferably performed.

It is preferable to harden a hard coat layer using heat or an active energy ray, and it is preferable to use active energy rays, such as a radiation, a gamma ray, an alpha ray, an electron beam, and an ultraviolet-ray, among these, and an electron beam and an ultraviolet ray are considered in consideration of safety and productivity. Particular preference is given to using. In the case of curing by heat, considering the heat resistance of the plastic itself, the heating temperature is preferably 140 ° C. or lower, and more preferably 100 ° C. or lower.

(5-2) Forward Scattering Layer

The front scattering layer is used to improve viewing angle characteristics (color and luminance distribution) in the vertical, left, and right directions when the polarizing plate of the present invention is applied to a liquid crystal display device. In this invention, the structure which binder binder disperse | distributed the microparticles | fine-particles with which refractive index differs is preferable, for example, Unexamined-Japanese-Patent No. 11-38208 which specified the forward scattering coefficient, Unexamined-Japanese-Patent No. 2000 which made the relative refractive index of transparent resin and microparticles into the specific range -199809, Japanese Laid-Open Patent Publication No. 2002-107512, which defines a haze value of 40% or more, can be used. In addition, in order to control the viewing angle characteristic of a haze, it can also perform using the polarizing plate of this invention in combination with "Lumisti" described in the technical report "optical functional film" pages 31-39 of Sumitomo Chemical.

(5-3) Antiglare Layer

The antiglare layer (antiglare) layer is used to scatter reflected light or prevent reflection. The antiglare function is obtained by forming irregularities on the outermost surface (display side) of the liquid crystal display device. The haze of the optical film having an antiglare function is preferably 3 to 30%, more preferably 5 to 20%, and most preferably 7 to 20%.

The method of forming the irregularities on the surface of the film is, for example, a method of forming the irregularities on the surface of the film by adding fine particles (for example, Japanese Patent Application Laid-Open No. 2000-271878, etc.), and a small amount of relatively large particles (particle diameter of 0.05 to 2 µm) (0.1 To 50 mass%) to form a surface uneven film (for example, Japanese Unexamined Patent Application Publication Nos. 2000-281410, 2000-95893, 2001-100004, 2001-281407, etc.) and physically irregularities on the film surface. A method of transferring a shape (for example, as an embossing method, described in JP-A-63-278839, JP-A-11-183710, JP-A-2000-275401, etc.) can be preferably used. have.

These functional layers can form and use either one side or both sides of a polarizer side and a surface opposite to a polarizer side.

5. Liquid Crystal Display Using Polarizer

Next, a liquid crystal display device in which the polarizing plate of the present invention is used will be described. 2 is an example of a liquid crystal display device in which the polarizing plate of the present invention is used.

The liquid crystal display device shown in FIG. 2 has liquid crystal cells 15-19, and the upper polarizing plate 11 and the lower polarizing plate 22 arrange | positioned between the liquid crystal cells 15-19. Although a polarizing plate is sandwiched by a polarizer and a pair of transparent protective films, it is shown as an integrated polarizing plate in FIG. 2, and detailed structure is abbreviate | omitted. The liquid crystal cell is composed of a liquid crystal layer formed of an upper substrate 15 and a lower substrate 18 and liquid crystal molecules 17 sandwiched therebetween. The liquid crystal cell is a difference between the alignment states of the liquid crystal molecules displaying ON / OFF, TN (Twisted Nematic), IPS (In-Plane Switching), OCB (Optically Compensatory Bend), VA (Vertically Aligned), ECB (Electrically Controlled Birefringence) The polarizing plate of the present invention can be used in any display mode regardless of transmission and reflection type.

An alignment film (not shown) is formed on the surface (hereinafter may be referred to as an "inner surface") in contact with the liquid crystal molecules 17 of the substrates 15 and 18, and an electric field is performed by a rubbing treatment or the like performed on the alignment film. The orientation of the liquid crystal molecules 17 in the unapplied state or the low applied state is controlled. Moreover, the transparent electrodes (not shown) which can apply an electric field to the liquid crystal layer which consists of liquid crystal molecules 17 are formed in the inner surface of the board | substrates 15 and 18. FIG.

The rubbing direction in the TN mode is performed in the direction perpendicular to each other on the upper and lower substrates, and the magnitude of the tilt angle can be controlled by the strength, the number of rubbings, and the like. The alignment film is formed by applying a polyimide film and baking it. The magnitude of the twist angle (twist angle) of the liquid crystal layer is determined by the crossing angle of the rubbing direction of the upper and lower substrates and the chiral agent added to the liquid crystal material. Here, chiral agent with a pitch of about 60 micrometers was added so that twist angle might be set to 90 degrees.

The twist angle is about 90 ° (85 to 95 °) in the case of a notebook personal computer, a personal computer monitor, or a liquid crystal display device for a television. Set to. In addition, in the IPS mode or the ECB mode, the twist angle is 0 degrees. In the IPS mode, the electrode is disposed only on the lower substrate 18, and an electric field parallel to the substrate surface is applied. In addition, in the OCB mode, there is no twist angle, the tilt angle becomes large, and in the VA mode, the liquid crystal molecules 17 are oriented perpendicular to the upper and lower substrates.

Here, the magnitude of the product Δnd of the thickness d of the liquid crystal layer and the refractive index anisotropy Δn changes the brightness at the time of white display. For this reason, the range is set for each display mode to obtain the maximum brightness. The crossing angle of the absorption axis 12 of the upper polarizing plate 11 and the absorption axis 23 of the lower polarizing plate 22 is generally laminated vertically, and high contrast is obtained. The crossing angle between the absorption axis 12 of the upper polarizing plate 11 of the liquid crystal cell and the rubbing direction of the upper substrate 15 varies depending on the liquid crystal display mode, but is generally set parallel or vertical in the TN and IOS modes. It is often set to 45 ° in OCB and ECB modes. However, the optimum value is different in each display mode for adjustment of the color tone or the viewing angle of the display color, and is not limited to this range.

The liquid crystal display device in which the polarizing plate of the present invention is used is not limited to the configuration of FIG. 2 and may include other members. For example, a color filter may be disposed between the liquid crystal cell and the polarizer. In addition, the above-described viewing angle expansion filters 13 and 20 may be disposed separately between the liquid crystal cell and the polarizing plate. The polarizing plates 11 and 23 and the viewing angle magnification films 13 and 20 may be arranged in a laminated form bonded with an adhesive, or may be arranged in a so-called integrated elliptical polarizing plate in which one of the liquid crystal cell side protective films is used for expanding the viewing angle.

In addition, when using as transmitted light, the backlight which uses a cold cathode or a hot cathode fluorescent tube, or a light emitting diode, a field emission element, and an electroluminescent element as a light source can be arrange | positioned at the back surface. In addition, the liquid crystal display device in which the polarizing plate of the present invention is used may be a reflection type. In this case, only one polarizing plate may be arranged on the observation side, and a reflective film is provided on the rear surface of the liquid crystal cell or on the inner surface of the lower substrate of the liquid crystal cell. do. Of course, the front light using the said light source can also be formed in the liquid crystal cell observation side.

Example

Example 1

(Production of cellulose acylate films 1, 3, 4, 6, 8, 10, 11, 13, 15)

The following composition was thrown into the mixing tank, it stirred while heating, and each component was melt | dissolved and the cellulose acelate solution A was prepared.

<Cellulose Acylate Solution A Composition>

100 parts by mass of cellulose acetate having a degree of oxidation of 60.9%

Triphenyl phosphate (plasticizer) 7.8 parts by mass

Biphenyl diphenyl phosphate (plasticizer) 3.9 parts by mass

300 parts by mass of methylenechlorite (first solvent)

54 parts by mass of methanol (second solvent)

11 parts by mass of 1-butanol

The following composition was put into another mixing tank, it stirred while heating, each component was melt | dissolved, and the additive solution B-1-B-6 were prepared.

<Additive solution B-1-B-6 composition>

<Production of Cellulose Acylate Film 1>

20 mass parts of additive solution B-1 was added to 474 mass parts of cellulose acylate solution A, and it fully stirred, and dope was prepared.

The dope was cast on a drum cooled to 0 ° C. from oil studies. It remove | excludes outside of the solvent content rate 70 mass%, and fixes the both ends of the width direction of a film with a pin tenter (the pin tenter as described in FIG. 3 of Unexamined-Japanese-Patent No. 4-1009), and the solvent content rate is 3-5 mass% In the state, it dried, maintaining the space | interval which becomes an elongation of 3% of a horizontal direction (direction perpendicular | vertical to a machine direction). Then, it conveyed between the rolls of a heat processing apparatus, and dried again, and produced the cellulose acylate film 1 of thickness 80micrometer.

<Production of Cellulose Acylate Films (3), (4) and (6)>

Cellulose acylate films (3), (4), and (6) in the same manner as in the cellulose acylate film (1) except that the additive solution and the thickness thereof were changed to those in Table 2 in the production of the cellulose acylate film (1). Was produced.

Example 2

The following composition was put into the mixing tank, it stirred while heating, and each component was dissolved and the cellulose acylate solution C was prepared.

<Composition of Cellulose Acylate Solution C>

100.0 parts by mass of cellulose acylate having a degree of oxidation of 60.9%

Triphenyl phosphate (plasticizer) 7.0 parts by mass

Biphenyl diphenyl phosphate (plasticizer) 4.0 parts by mass

Methylene chloride (first solvent) 400.2 parts by mass

60.0 parts by mass of methanol (second solvent)

<Production of Cellulose Acylate Film 8>

573 mass parts of cellulose acylate solutions C were mixed with 24 mass parts of additive solution B-1, and it fully stirred, and prepared dope.

The obtained dope was cast using a band softener. After the film surface temperature on a band became 40 degreeC, it dried for 1 minute by the warm air of 70 degreeC, and removed the film from the band. Subsequently, the film was dried with a drying air at 140 ° C. for 10 minutes to prepare a cellulose acylate film 8 having a thickness of 80 μm at 0.3 mass%.

<Production of Cellulose Acylate Films (10), (11), and (13)>

The cellulose acylate films (10), (11), and (13) were prepared in the same manner as the cellulose acylate film (8) except that the additive solution and thickness were changed to those of Table 2 in the preparation of the cellulose acylate film (8). Produced.

<Production of Cellulose Acylate Film 15>

In the production of the cellulose acylate film 10, the cellulose acylate film 15 was similarly prepared except that the cellulose acylate of the cellulose acylate solution C was changed to cellulose acetate butyrate of acetylation degree 1.8 and propionylation degree 0.9. Was produced.

Example 3

(Saponification)

The cellulose acylate film was immersed in a 1.5% sodium hydroxide aqueous solution at 55 ° C for 2 minutes. It wash | cleaned in the water washing bath of room temperature, and it neutralized using 0.1 sulfuric acid at 30 degreeC. It wash | cleaned again in the water washing bath of room temperature again, and dried by warm air of 100 degreeC again. In this manner, the surface of the cellulose acylate film was saponified.

Example 4

Iodine was adsorbed to the stretched polyvinyl alcohol film to produce a polarizer, and the cellulose acylate film 6 produced in Example 1 was bonded to one side of the polarizer using a polyvinyl alcohol-based adhesive. The transmission axis of a polarizer and the slow axis of a cellulose acylate film were arrange | positioned so that it might become parallel.

Moreover, the cellulose acylate film 8 produced in Example 3 was adhere | attached on the opposite side to the polarizer using polyvinyl alcohol-type adhesive agent. In this way, the polarizing plate 1 was produced.

Example 5

In the same manner as in Example 4, polarizing plates (1) to (13) were produced by the combination of the cellulose acylate films shown in Table 3.

Example 6

The polarizing plate thus prepared was adhered to the glass plate such that the liquid crystal side cellulose acylate film was on the glass side, and then elapsed for 1000 hours at 90 ° C. at 60 ° C., and then the parallel and orthogonal transmittances were measured using a Shimadzu UV2200 spectrophotometer. Polarization degree was computed by Formula 4). In addition, the strength and weakness of the curl of the polarizing plate were visually determined. The results are shown in Table 4.

From this result, it turns out that the polarizing plate of this invention has a small change of the degree of polarization with respect to heat and temperature, a small curl, and excellent durability.

Example 7

The pair of polarizing plates installed on a 20-inch liquid crystal display device (LC-20V1, manufactured by Sharp Co., Ltd.) using a TN type liquid crystal cell was removed, and the optical compensation sheet was used instead of the polarizing plate produced in Example 10. It adhere | attached one by one on the observer side and the backlight side through an adhesive so that it might become a liquid crystal cell side. It was arrange | positioned so that the transmission axis of the polarizing plate of an observer side, and the transmission axis of the polarizing plate of a backlight side may orthogonally cross. In an environmental condition of a temperature of 25 ° C. and a relative humidity of 60%, the backlight was continuously turned on for 400 hours, and the black surface state of the entire surface was visually observed in the dark room to evaluate light leakage. As a result, in the polarizing plate of the comparative example, the frame-shaped light leakage was observed on the display screen of the liquid crystal display device, but it was not observed in the polarizing plate of the present invention.

This inventor succeeded in producing the polarizing plate which was excellent in durability with respect to heat and humidity.

The polarizing plate may be advantageously used in twisted nematic (TN) type, optically compensated bend (OCB) type, electrically controlled birefringence (ECB) type, vertically aligned (VA) type, and in-phase switching (IPS) type. have.

BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing which shows the structural example which combined the polarizing plate and functional optical film of this invention, The example (A) which adhered the functional optical film and polarizer through an adhesive agent as a protective film on one side of a polarizing plate, and a protective film on both surfaces of a polarizer. The example (B) which adhered the functional optical film to the polarizing plate which formed this through the adhesive is shown, respectively.

2 is an explanatory diagram showing an example of a liquid crystal display device in which the polarizing plate of the present invention is used.

* Description of Major Symbols in Drawings *

1, 1a, 1b: protective film

2: polarizer

3: functional optical film

4: adhesion layer

11: upper polarizer

12: upper polarizer absorption axis

13: upper optically anisotropic layer (viewing angle expanding film)

14: direction of orientation control of the upper optically anisotropic layer

15: upper electrode substrate of the liquid crystal cell

16: Upper substrate orientation control direction

17: liquid crystal layer

18: lower electrode substrate of the liquid crystal cell

19: Lower substrate orientation control direction

20: lower optically anisotropic layer (viewing angle expanding film)

21: direction of lower optically anisotropic layer orientation control

22: lower polarizer

23: lower polarizer absorption axis

Claims (13)

A polarizing plate comprising a first protective film, a polarizer, and a second protective film laminated in this order, wherein the moisture permeability of the first protective film is lower than that of the second protective film. The method of claim 1, The difference in water vapor transmission rate measured on 60 degreeC 95% RH conditions of a 1st protective film and a 2nd protective film is 200-2000g / m <2> * 24hr, The polarizing plate characterized by the above-mentioned. The method of claim 1, A polarizing plate, wherein both the first and second protective films are polymer films containing the same polymer as a main component, and the types and / or amounts of additives of the first and second protective films are different. The polarizing plate according to claim 1, wherein the first and second protective films are cellulose acylate films, and the types of cellulose acylates of the first and second protective films are different. The method of claim 1, The moisture permeability measured under the conditions of 60 degreeC 95% RH of a 1st protective film is 250-1000g / m <2> * 24hr, The polarizing plate characterized by the above-mentioned. The method of claim 1, The water vapor transmission rate measured on 60 degreeC 95% RH conditions of a 2nd protective film is 500-5000g / m <2> * 24hr, The polarizing plate characterized by the above-mentioned. The method of claim 1, It has an adhesion layer, The polarizing plate characterized by the above-mentioned. The method of claim 1, A polarizing plate having an antiglare layer on a surface on a side opposite to a surface of the first protective film that faces the polarizer. The method of claim 1, It has a reflection layer or a semi-transmissive reflection layer, The polarizing plate characterized by the above-mentioned. The method of claim 1, It has a retardation layer or (lambda) / 4 layer, The polarizing plate characterized by the above-mentioned. The method of claim 1, And a viewing angle compensation layer. The method of claim 1, It has a brightness enhancement layer, The polarizing plate characterized by the above-mentioned. A liquid crystal display device having a liquid crystal cell and two polarizing plates disposed on both sides thereof, wherein at least one polarizing plate is the polarizing plate according to any one of claims 1 to 12, and the second protective film of the polarizing plate is placed on the liquid crystal cell side. There is a liquid crystal display device.