JP2011248192A - Roll state polarizing plate, sheet-like polarizing plate and liquid crystal display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizing plate that prevents waviness or crack on a cut surface that is prone to occur when the roll state polarizing plate is cut by a laser beam and has an improved optical characteristic under high temperature and humidity, and a liquid crystal display device using the same.SOLUTION: The roll state polarizing plate comprises a cellulose ester film on both sides of a polarizer, in which an average acetyl group substitution degree is 2.0 or higher and smaller than 2.5, and a melting point thereof is within a range of 200-290°C.

Description

  The present invention relates to a roll-shaped polarizing plate, a sheet-shaped polarizing plate, and a liquid crystal display device using the same.

  The polarizing plate is usually constituted by laminating a polarizer protective film on at least one surface of a polarizer made of a polyvinyl alcohol resin to which a dichroic dye is adsorbed and oriented. In addition, an adhesive layer is provided on one side of the polarizing plate for bonding to a liquid crystal cell or other optical member, and the surface is covered with a separate film to protect it until use. It is distributed in a configuration in which a peelable protective film having an agent layer is provided. Furthermore, generally a polarizing plate is manufactured in the state wound by the elongate roll shape.

  In this application, a protective film is bonded to the surface of the polarizer protective film on one side in this way, and a separate film is bonded to the surface of the pressure-sensitive adhesive layer on the other side. Is referred to as a “roll-type polarizing plate”, and a piece cut therefrom to a predetermined size is referred to as a “sheet-like polarizing plate”.

  The term “polarizing plate” generally includes a polarizer composed of a polyvinyl alcohol-based resin or the like as an essential element, and a polarizer protective film composed of a transparent resin film is laminated on at least one surface of the polarizer. In the state where a pressure-sensitive adhesive layer for bonding to a liquid crystal cell or other optical member is provided, and in some cases, it may be used to include a roll-shaped polarizing plate or a sheet-shaped polarizing plate as described above. .

  On the other hand, in recent years, the “roll-to-panel manufacturing method” in which a roll-shaped polarizing plate is directly bonded to a liquid crystal panel in a manufacturing process of a liquid crystal panel has begun to be adopted. Generally, it is cut into a predetermined dimension by a laser slitter.

  At the time of this cutting, the portion of the polarizing plate to which the laser hits locally becomes high temperature, and if a soft resin having a low melting point such as cellulose acetate propionate (CAP) is used as the polarizer protective film, the cut surface is undulated. There was a malfunction.

  On the other hand, if a resin with a high melting point such as triacetyl cellulose (TAC) is used, the resin does not swell, but the resin is hard, so there is a problem that fine cracks are formed in the area where the laser hits, leading to deterioration of the panel strength. It was.

  Solutions to the problems that occur when cutting with the above-described laser slitter are disclosed in, for example, Patent Documents 1 and 2, and although there is a certain improvement effect, further improvements have been desired.

JP 2008-73742 A JP 2009-86675 A

  The present invention has been made in view of the above-mentioned problems and situations, and its solution is to prevent the occurrence of waviness and cracks on the cut surface, which are likely to occur when laser-cutting a roll-shaped polarizing plate, and to achieve high temperature and high humidity. It is to provide a polarizing plate having improved optical characteristics below and a liquid crystal display device using the same.

  The above-mentioned problem according to the present invention is solved by the following means.

  1. A roll shape characterized in that a cellulose ester film having an average degree of acetyl group substitution of 2.0 or more and less than 2.5 and a melting point in the range of 200 to 290 ° C. is provided on both sides of the polarizer. Polarizer.

  2. The difference ΔH (80% −20%) between the equilibrium moisture content at a temperature of 23 ° C. and a relative humidity of 20% and the equilibrium moisture content at a temperature of 23 ° C. and a relative humidity of 80% of the cellulose ester films on both sides of the polarizer. Absolute values are in the range of 3.0 to 5.0%, and the absolute value of the difference ΔH between the equilibrium water content of each cellulose ester film ΔH (80% -20%). Is in the range of 0 to 1.0%, the roll-shaped polarizing plate as described in the above item 1.

3. The said 1st or 2nd item | term characterized by the cellulose ester film of the both sides which pinches | interposes the said polarizer containing the at least 1 sort (s) of additive which satisfy | fills following formula 1 within the range of 0.01-30 mass%. Roll-shaped polarizing plate.
Formula 1: | SPt−SPc | <2.0
However, SPc in the formula is a solubility parameter of the cellulose ester measured by the Hoy method, and SPt is a solubility parameter of the additive measured by the same method.

  4). The film thickness of the said cellulose-ester film exists in the range of 10-60 micrometers, The roll-shaped polarizing plate as described in any one of said 1st term | claim to 3rd term | claim characterized by the above-mentioned.

  5). A sheet-like polarizing plate formed by cutting the roll-shaped polarizing plate according to any one of items 1 to 3.

  6). A liquid crystal display device produced by bonding the roll-shaped polarizing plate according to any one of the first to third items to a liquid crystal panel and cutting with a laser.

  By means of the above-mentioned means of the present invention, a polarizing plate that prevents the occurrence of waviness and cracks on the cut surface, which is likely to occur when laser-cutting a roll-shaped polarizing plate, and has improved optical properties under high temperature and high humidity, and use thereof A liquid crystal display device can be provided.

Cross-sectional schematic diagram showing an example of the layer structure of a roll-shaped polarizing plate or a sheet-shaped polarizing plate Cross-sectional schematic diagram showing a part of the rolled-up polarizing plate in an enlarged state

  The roll-shaped polarizing plate of the present invention is provided with a cellulose ester film having an average degree of acetyl group substitution of 2.0 or more and less than 2.5 and a melting point in the range of 200 to 290 ° C. on both sides of the polarizer. It is characterized by. This feature is a technical feature common to the inventions according to claims 1 to 6.

  As an embodiment of the present invention, the difference ΔH between the equilibrium moisture content at a temperature of 23 ° C. and a relative humidity of 20% and the equilibrium moisture content at a temperature of 23 ° C. and a relative humidity of 80% of the cellulose ester films on both sides of the polarizer. The absolute value of (80% -20%) is within the range of 3.0 to 5.0%, and the difference ΔH (80% -20%) in the equilibrium water content between the cellulose ester films on both sides. ) The absolute value of the difference ΔH is preferably in the range of 0 to 1.0%. Moreover, it is preferable that the cellulose-ester film of the both sides which pinches | interposes the said polarizer contains at least 1 type of additive which satisfy | fills said Formula 1 within the range of 0.01-30 mass%. Furthermore, it is preferable that the film thickness of the said cellulose-ester film exists in the range of 10-60 micrometers.

  The sheet-like polarizing plate formed by cutting the roll-shaped polarizing plate of the present invention with a laser can be suitably used for a liquid crystal display device.

  Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail.

(Cellulose ester film)
The cellulose ester film according to the present invention is required to have an average degree of acetyl group substitution of 2.0 or more and less than 2.5 and a melting point of 200 to 290 ° C. When the melting point of the cellulose ester film is lower than 200 ° C., the heat resistance against the laser heat is low, and thus the fracture surface is wavy. On the other hand, when the melting point of the cellulose ester film is 290 ° C. or higher, it is difficult to cut with a laser itself.

  The average acetyl group substitution degree is more preferably 2.2 to 2.5.

  The average degree of acetyl substitution here indicates the average value of the number of hydroxyl groups (hydroxyl groups) that are esterified among the three hydroxyl groups (hydroxyl groups) of anhydroglucose constituting cellulose, and is 0-3. Indicates the value.

  Moreover, when cutting a cellulose-ester film with a laser, the cellulose-ester resin provided with moderate hygroscopicity is preferable. Cellulose ester resin with hygroscopicity is supple, and it is difficult to generate chips and chips even when cutting with a laser. When the average degree of acetyl substitution of the cellulose ester resin exceeds 2.5, the hygroscopicity is remarkably lowered, so that the chipping and chips are likely to occur during laser cutting. Further, when the average degree of acetyl group substitution is less than 2.0, the moisture resistance and water resistance are remarkably deteriorated, so that there is a problem that the polarizing plate is easily contracted and the polarizer is easily deteriorated.

  As the cellulose ester resin according to the present invention, a particularly preferable cellulose ester resin is cellulose diacetate.

  In addition, the substitution degree of an acetyl group and the substitution degree of other acyl groups are obtained by a method prescribed in ASTM-D817-96 (testing method for cellulose acetate and the like).

  The number average molecular weight (Mn) of the cellulose ester according to the present invention is preferably in the range of 30,000 to 300,000 because the mechanical strength of the resulting film is strong. Furthermore, the thing of 50,000-200,000 is used preferably.

  The value of the ratio Mw / Mn of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the cellulose ester is preferably 1.4 to 3.0.

  The weight average molecular weight Mw and number average molecular weight Mn of the cellulose ester were measured using gel permeation chromatography (GPC).

  The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) Mw = 100000 to 500 calibration curves with 13 samples were used. Thirteen samples are used at approximately equal intervals.

  Although there is no limitation in particular as a cellulose of the raw material of the cellulose ester which concerns on this invention, Cotton linter, wood pulp, kenaf etc. can be mentioned. Moreover, the cellulose ester obtained from them can be mixed and used in arbitrary ratios, respectively.

  The cellulose ester according to the present invention can be produced by a known method. Generally, cellulose is esterified by mixing cellulose as a raw material, a predetermined organic acid (such as acetic acid or propionic acid), an acid anhydride (such as acetic anhydride or propionic anhydride), and a catalyst (such as sulfuric acid). The reaction proceeds until the triester is formed. In the triester, three hydroxyl groups (hydroxyl groups) of the glucose unit are substituted with an acyl acid of an organic acid. When two kinds of organic acids are used at the same time, a mixed ester type cellulose ester such as cellulose acetate propionate or cellulose acetate butyrate can be produced. Subsequently, the cellulose triester is hydrolyzed to synthesize a cellulose ester having a desired degree of acyl substitution. Thereafter, the cellulose ester is completed through steps such as filtration, precipitation, washing with water, dehydration, and drying.

  Specifically, it can be synthesized with reference to the method described in JP-A-10-45804.

  Examples of commercially available products include L20, L30, L40, and L50 manufactured by Daicel Chemical Industries, Ltd., and Ca398-3, Ca398-6, Ca398-10, Ca398-30, and Ca394-60S manufactured by Eastman Chemical Co., Ltd.

  The total amount of calcium and magnesium and the amount of acetic acid contained in the cellulose ester film according to the present invention preferably satisfy the following relational expression (a).

Relational expression (a): 1 ≦ (acetic acid amount) / (total amount of calcium and magnesium) ≦ 30
Calcium and magnesium are contained in the cellulose ester used as the raw material for the cellulose ester film, but metal oxides and metal hydroxides are used to neutralize and stabilize the acid catalyst (especially sulfuric acid) added to the cellulose ester production process. , And may be added as a metal salt (inorganic acid salt, organic acid salt). Moreover, you may add as a metal oxide, a metal hydroxide, and a metal salt (inorganic acid salt, organic acid salt) at the time of film forming of a cellulose ester film. The total amount of calcium and magnesium contained in the cellulose ester film referred to in the present invention refers to the total amount thereof.

  In the production process of cellulose ester, acetic anhydride or acetic acid is used as a reaction solvent or an esterifying agent. Unreacted acetic anhydride is hydrolyzed by a reaction stopper (water, alcohol, acetic acid, etc.) to produce acetic acid. The amount of acetic acid contained in the cellulose ester film in the present invention refers to the total amount of residual acetic acid and free acetic acid.

  In the above relational expression (a), when the amount of acetic acid / (total amount of calcium and magnesium) is less than 1, light scattering due to calcium and magnesium metal salts occurs, which is not preferable. On the other hand, when it is larger than 30, it is not preferable because after the cellulose ester is bonded to the polarizer, the deterioration of the polarizer is accelerated by acetic acid.

  The total amount of calcium and magnesium contained in the cellulose ester film is preferably 5 to 130 ppm, more preferably 5 to 80 ppm, and still more preferably 5 to 50 ppm.

  For the determination of calcium and magnesium contained in the cellulose ester film, a known method can be used. For example, after the dried cellulose ester is completely burned, the ash is dissolved in hydrochloric acid and pretreated. It can be measured by atomic absorption method. The measured value is obtained in units of ppm as the calcium and magnesium contents in 1 g of the completely dry cellulose ester.

  The amount of acetic acid contained in the cellulose ester film is preferably 20 to 500 ppm, more preferably 25 to 250 ppm, and still more preferably 30 to 150 ppm.

  A known method can be used for quantification of acetic acid contained in the cellulose ester film. For example, the following method can be used. The film is dissolved in methylene chloride, and methanol is added to perform reprecipitation. The amount of acetic acid can be obtained by filtering the supernatant and measuring the supernatant with gas chromatography.

  In the present invention, the melting point of the cellulose ester film is required to be in the range of 200 to 290 ° C. When the melting point of the cellulose ester film is lower than 200 ° C., the heat resistance against the laser heat is low, and thus the fracture surface is wavy. On the other hand, when the melting point of the cellulose ester film is 290 ° C. or higher, it is difficult to cut with a laser itself.

  Methods for adjusting the melting point within the above range include controlling the degree of substitution of the cellulose ester or adding a plasticizer.

<Change in humidity of equilibrium moisture content>
In the present invention, in order to easily cope with a change in humidity and to make the optical properties and dimensions more difficult to change, the equilibrium moisture content at a temperature of 23 ° C. and a relative humidity of 20% of each cellulose ester film sandwiching the polarizer, The absolute value of the difference ΔH (80% -20%) from the equilibrium water content at 23 ° C. and 80% relative humidity is in the range of 3.0 to 5.0%, and the cellulose ester films on both sides The absolute value of the difference ΔH between the respective equilibrium water content differences ΔH (80% -20%) is preferably in the range of 0 to 1.0%.

  Here, the “equilibrium moisture content” is the water content contained in the sample (film) in an equilibrium state as a percentage of the sample mass.

  As a specific method of obtaining the humidity change of the equilibrium moisture content, a sample 7 mm × 35 mm was conditioned at a temperature of 23 ° C. and a relative humidity of 20% RH for 2 hours, and the Karl Fischer method trace moisture meter LE-20S (Hiranuma Sangyo) The water content was calculated by dividing the moisture content (g) in the sample at a relative humidity of 20% by the sample mass (g). A similar sample was conditioned at a temperature of 23 ° C. and a relative humidity of 80% RH for 2 hours, measured with a Karl Fischer method trace moisture meter LE-20S (manufactured by Hiranuma Sangyo Co., Ltd.), and a sample at a relative humidity of 80%. The moisture content was calculated by dividing the moisture content (g) in the sample by the sample mass (g). The difference between the equilibrium moisture content at 20% relative humidity and the equilibrium moisture content at 80% relative humidity was determined as ΔH (80% -20%).

  Moreover, the difference (DELTA) H (80% -20%) difference of the said equilibrium water content of each said cellulose-ester film of the said both sides was calculated | required as (DELTA) H.

  As means for controlling the equilibrium moisture content within the above range, it can be carried out by adjusting the total substitution degree of the cellulose ester film and adjusting the kinds and amounts of various additives contained in the cellulose ester film.

<Relative relationship of solubility parameters>
In the invention, it is preferable that the cellulose ester films on both sides of the polarizer include at least one additive satisfying the following formula 1 within a range of 0.01 to 30% by mass. By adding the additive, the load applied to the resin during molding is reduced, and the front contrast is improved.
Formula 1: | SPt−SPc | <2.0
However, SPc in a formula is the value (SP value) of the solubility parameter of the cellulose ester measured by Hoy method, and SPt is the value (SP value) of the solubility parameter of the additive measured by the same method.

  “| SPt−SPc |” is the difference between the value of the solubility parameter of the additive measured by the Hoy method (SPt value) and the value of the solubility parameter of the cellulose ester measured by the Hoy method (SPc value) ( The absolute value of “ΔSP”).

  The Hoy method is described in POLYMER HANDBOOK FOUND EDITION.

  The preferred additive is not particularly limited as long as it satisfies the formula 1, but triazine-based compounds, polyester-based compounds, and sugar ester-based compounds that satisfy the formula 1 are particularly preferable.

<< Compound Represented by Formula (1) >>
In the present invention, the additive for satisfying the above formula 1 can be selected from various conventionally known compounds. The total average substitution degree represented by the following general formula (1) is 6.1. It is preferable to contain the compound which is -6.9.

In general formula (1), R _{1 to} R ₈ represent a substituted or unsubstituted alkylcarbonyl group or a substituted or unsubstituted allylcarbonyl group, and R _{1 to} R ₈ may be the same. , May be different.

  Although the compound represented by the said General formula (1) and a reference compound are described below, it is not limited to these.

  (Synthesis Example: Synthesis of Compound According to the Present Invention)

A four-headed colben equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen gas inlet tube was mixed with 34.2 g (0.1 mol) of sucrose, 180.8 g (0.8 mol) of benzoic anhydride, 379. 7 g (4.8 mol) was charged, the temperature was raised while bubbling nitrogen gas from a nitrogen gas introduction tube with stirring, and an esterification reaction was carried out at 70 ° C. for 5 hours. Next, the inside of the Kolben was depressurized to 4 × 10 ² Pa or less, and after excess pyridine was distilled off at 60 ° C., the inside of the Kolben was depressurized to 1.3 × 10 Pa or less and the temperature was raised to 120 ° C. Most of the acid and benzoic acid formed were distilled off. Then, 1 L of toluene and 300 g of a 0.5% by mass aqueous sodium carbonate solution were added, and the mixture was stirred at 50 ° C. for 30 minutes and then allowed to stand to separate a toluene layer. Finally, 100 g of water is added to the collected toluene layer, and after washing with water at room temperature for 30 minutes, the toluene layer is separated, and toluene is distilled off at 60 ° C. under reduced pressure (4 × 10 ² Pa or less). A mixture of A-1, A-2, A-3, A-4 and A-5 was obtained. When the obtained mixture was analyzed by HPLC and LC-MASS, A-1 was 7% by mass, A-2 was 58% by mass, A-3 was 23% by mass, A-4 was 9% by mass, A-5. Was 3% by mass. A part of the obtained mixture was purified by column chromatography using silica gel to obtain A-1, A-2, A-3, A-4 and A-5 having a purity of 100%, respectively. .

  The total average substitution degree of the compound represented by the general formula (1) added to the cellulose ester film in the present invention is 6.1 to 6.9, and the range of the substitution degree is 4 to 8. Is preferred. The substitution degree distribution may be adjusted to the desired substitution degree by adjusting the esterification reaction time or mixing compounds having different substitution degrees.

(Other additives)
The cellulose ester film according to the present invention preferably contains, as a plasticizer, an ester compound represented by the following general formula (2) from the viewpoint of dimensional stability in an environmental change that causes unevenness of the polarizing plate. .

General formula (2) B- (GA) n-GB
(Wherein B is a hydroxyl group or carboxylic acid residue, G is an alkylene glycol residue having 2 to 12 carbon atoms, an aryl glycol residue having 6 to 12 carbon atoms, or an oxyalkylene glycol residue having 4 to 12 carbon atoms) A represents an alkylenedicarboxylic acid residue having 4 to 12 carbon atoms or an aryldicarboxylic acid residue having 6 to 12 carbon atoms, and n represents an integer of 1 or more.)
In the general formula (2), the alkylene glycol component having 2 to 12 carbon atoms includes ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,2-propanediol, 2-methyl 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2 , 2-diethyl-1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3,3-dimethylolheptane), 3-methyl- 1,5-pentanediol 1,6-hexanediol, 2,2,4-trimethyl 1,3-pentanediol, 2-ethyl 1, -Hexanediol, 2-methyl 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, etc., and these glycols are one kind or a mixture of two or more kinds. Used as.

  In particular, an alkylene glycol having 2 to 12 carbon atoms is particularly preferable because of excellent compatibility with a cellulose ester.

  Examples of the aryl glycol component having 6 to 12 carbon atoms include hydroquinone, resorcin, bisphenol A, bisphenol F, bisphenol, and the like, and these glycols can be used singly or as a mixture of two or more.

  Examples of the oxyalkylene glycol component having 4 to 12 carbon atoms include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol. These glycols may be used alone or as a mixture of two or more. Can be used as

  Examples of the alkylene dicarboxylic acid component having 4 to 12 carbon atoms include succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, and the like. Used as a mixture of seeds and more. Examples of the arylene dicarboxylic acid component having 6 to 12 carbon atoms include phthalic acid, terephthalic acid, isophthalic acid, 1,5 naphthalene dicarboxylic acid, and 1,4 naphthalene dicarboxylic acid.

  The ester compound represented by the general formula (2) has a number average molecular weight of preferably 300 to 1500, and more preferably 400 to 1000.

  In the cellulose ester according to the present invention, a polyester compound having a hydroxyl group at the terminal is preferable in terms of compatibility.

  Although the specific compound of the ester compound represented by General formula (2) which concerns on this invention below is shown, this invention is not limited to this.

<Other additives>
(Plasticizer)
The cellulose-ester film which concerns on this invention can contain plasticizers other than the compound represented by General formula (2) as needed, when obtaining the effect of this invention.

  The plasticizer is not particularly limited, but is preferably a polycarboxylic acid ester plasticizer, a glycolate plasticizer, a phthalate ester plasticizer, a fatty acid ester plasticizer, a polyhydric alcohol ester plasticizer, or an ester plasticizer. Agent, acrylic plasticizer and the like.

  Of these, when two or more plasticizers are used, at least one plasticizer is preferably a polyhydric alcohol ester plasticizer.

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

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

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

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

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

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

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

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

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or side chain having 1 to 32 carbon atoms can be preferably used. The number of carbon atoms is more preferably 1-20, and particularly preferably 1-10. When acetic acid is contained, the compatibility with the cellulose ester is increased, and it is also preferable to use a mixture of acetic acid and another monocarboxylic acid.

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

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

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

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

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

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

  The glycolate plasticizer is not particularly limited, but alkylphthalylalkyl glycolates can be preferably used.

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

  Examples of the phthalate ester plasticizer include diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, dioctyl phthalate, dicyclohexyl phthalate, and dicyclohexyl terephthalate.

  Examples of the citrate plasticizer include acetyl trimethyl citrate, acetyl triethyl citrate, and acetyl tributyl citrate.

  Examples of fatty acid ester plasticizers include butyl oleate, methylacetyl ricinoleate, and dibutyl sebacate.

  The polyvalent carboxylic acid ester compound is composed of an ester of divalent or higher, preferably divalent to 20 valent polyvalent carboxylic acid and alcohol. The aliphatic polyvalent carboxylic acid is preferably 2 to 20 valent, and in the case of an aromatic polyvalent carboxylic acid or an alicyclic polyvalent carboxylic acid, it is preferably 3 to 20 valent.

  The polyvalent carboxylic acid is represented by the following general formula (b).

Formula (b) R ₁₂ (COOH) _m1 (OH) _n1
In the formula, R ₁₂ represents an (m1 + n1) -valent organic group, m1 represents a positive integer of 2 or more, n1 represents an integer of 0 or more, a COOH group represents a carboxyl group, and an OH group represents an alcoholic or phenolic hydroxyl group.

  Examples of preferred polyvalent carboxylic acids include the following, but the present invention is not limited to these.

  Trivalent or higher aromatic polyvalent carboxylic acids such as trimellitic acid, trimesic acid, pyromellitic acid or derivatives thereof, succinic acid, adipic acid, azelaic acid, sebacic acid, oxalic acid, fumaric acid, maleic acid, tetrahydrophthal An aliphatic polyvalent carboxylic acid such as an acid, an oxypolyvalent carboxylic acid such as tartaric acid, tartronic acid, malic acid and citric acid can be preferably used. In particular, it is preferable to use an oxypolycarboxylic acid from the viewpoint of improving retention.

  There is no restriction | limiting in particular as alcohol used for the polyhydric carboxylic acid ester compound which can be used for this invention, Well-known alcohol and phenols can be used.

  For example, an aliphatic saturated alcohol or aliphatic unsaturated alcohol having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. It is more preferable that it is C1-C20, and it is especially preferable that it is C1-C10.

  In addition, alicyclic alcohols such as cyclopentanol and cyclohexanol or derivatives thereof, aromatic alcohols such as benzyl alcohol and cinnamyl alcohol, or derivatives thereof can also be preferably used.

  When an oxypolycarboxylic acid is used as the polycarboxylic acid, the alcoholic or phenolic hydroxyl group of the oxypolycarboxylic acid may be esterified with a monocarboxylic acid. Examples of preferred monocarboxylic acids include the following, but the present invention is not limited thereto.

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. It is more preferable that it is C1-C20, and it is especially preferable that it is C1-C10.

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

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

  Examples of preferred aromatic monocarboxylic acids include those in which an alkyl group is introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, and two or more benzene rings such as biphenyl carboxylic acid, naphthalene carboxylic acid, and tetralin carboxylic acid. The aromatic monocarboxylic acid which has, or those derivatives can be mentioned. Particularly preferred are acetic acid, propionic acid, and benzoic acid.

  The molecular weight of the polyvalent carboxylic acid ester compound is not particularly limited, but is preferably in the range of 300 to 1000, and more preferably in the range of 350 to 750. The larger one is preferable in terms of improvement in retention, and the smaller one is preferable in terms of moisture permeability and compatibility with cellulose ester.

  The alcohol used for the polyvalent carboxylic acid ester that can be used in the present invention may be one kind or a mixture of two or more kinds.

  The acid value of the polyvalent carboxylic acid ester compound that can be used in the present invention is preferably 1 mgKOH / g or less, and more preferably 0.2 mgKOH / g or less. Setting the acid value in the above range is preferable because the environmental fluctuation of the retardation is also suppressed.

  In addition, an acid value means the milligram number of potassium hydroxide required in order to neutralize the acid (carboxyl group which exists in a sample) contained in 1g of samples. The acid value is measured according to JIS K0070.

(UV absorber)
The cellulose ester film according to the present invention can also contain an ultraviolet absorber. The ultraviolet absorber is intended to improve durability by absorbing ultraviolet rays of 400 nm or less, and in particular, the transmittance at a wavelength of 370 nm is preferably 10% or less, more preferably 5% or less, and further Preferably it is 2% or less.

  Although the ultraviolet absorber used in the present invention is not particularly limited, for example, oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, triazine compounds, nickel complex compounds, inorganic powders Examples include the body.

  For example, 5-chloro-2- (3,5-di-sec-butyl-2-hydroxylphenyl) -2H-benzotriazole, (2-2H-benzotriazol-2-yl) -6- (linear and side Chain dodecyl) -4-methylphenol, 2-hydroxy-4-benzyloxybenzophenone, 2,4-benzyloxybenzophenone, etc., and tinuvin 109, tinuvin 171, tinuvin 234, tinuvin 326, tinuvin 327, tinuvin 328, etc. These are commercially available products from Ciba Japan and can be preferably used.

  The UV absorbers preferably used in the present invention are benzotriazole UV absorbers, benzophenone UV absorbers, and triazine UV absorbers, particularly preferably benzotriazole UV absorbers and benzophenone UV absorbers. .

  In addition, a discotic compound such as a compound having a 1,3,5 triazine ring is also preferably used as the ultraviolet absorber.

  The polarizing plate protective film according to the present invention preferably contains two or more ultraviolet absorbers.

  As the UV absorber, a polymer UV absorber can also be preferably used, and in particular, a polymer type UV absorber described in JP-A-6-148430 is preferably used.

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

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

  The amount of the UV absorber used is not uniform depending on the type of UV absorber, the operating conditions, etc., but when the dry film thickness of the polarizing plate protective film is 30 to 200 μm, it is 0.5 with respect to the polarizing plate protective film. -10 mass% is preferable, and 0.6-4 mass% is still more preferable.

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

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

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

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

  The addition amount of these compounds is preferably 1 ppm to 1.0%, more preferably 10 to 1000 ppm in terms of mass ratio with respect to the cellulose derivative.

<Fine particles>
In order to improve the handleability, the cellulose ester film according to the present invention has, for example, silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, calcined calcium silicate, hydrated calcium silicate, silicic acid. It is preferable to include a matting agent such as inorganic fine particles such as aluminum, magnesium silicate and calcium phosphate, and a crosslinked polymer. Of these, silicon dioxide is preferable because it can reduce the haze of the film.

  The primary average particle diameter of the fine particles is preferably 20 nm or less, more preferably 5 to 16 nm, and particularly preferably 5 to 12 nm.

  These fine particles preferably form secondary particles having a particle diameter of 0.1 to 5 μm and are contained in the cellulose ester film, and the preferable average particle diameter is 0.1 to 2 μm, more preferably 0.2 to 0.6 μm. Thereby, the unevenness | corrugation about 0.1-1.0 micrometer high can be formed in the film surface, and this can give appropriate slipperiness to the film surface.

  The primary average particle diameter of the fine particles used in the present invention is measured by observing the particles with a transmission electron microscope (magnification 500,000 to 2,000,000 times), observing 100 particles, measuring the particle diameter, and measuring the average. The value was taken as the primary average particle size.

<Method for producing cellulose ester film>
Next, the manufacturing method of the cellulose-ester film which concerns on this invention is demonstrated.

  The cellulose ester film according to the present invention can be preferably used regardless of whether it is a film produced by a solution casting method or a film produced by a melt casting method.

  Production of the cellulose ester film according to the present invention by the solution casting method is a step of preparing a dope by dissolving a cellulose ester and an additive in a solvent, and casting the dope onto an endless metal support that moves infinitely. It is carried out by a step, a step of drying the cast dope as a web, a step of peeling from the metal support, a step of stretching or maintaining the width, a step of further drying, and a step of winding up the finished film.

  The process for preparing the dope will be described. The concentration of cellulose ester in the dope is preferably higher because the drying load after casting on the metal support can be reduced. However, if the concentration of cellulose ester is too high, the load during filtration increases and the filtration accuracy is poor. Become. As a density | concentration which makes these compatible, 10-35 mass% is preferable, More preferably, it is 15-25 mass%.

  The solvent used in the dope may be used alone or in combination of two or more, but it is preferable to use a mixture of a good solvent and a poor solvent of cellulose ester in terms of production efficiency, and there are many good solvents. This is preferable from the viewpoint of the solubility of the cellulose ester.

  The preferable range of the mixing ratio of the good solvent and the poor solvent is 70 to 98% by mass for the good solvent and 2 to 30% by mass for the poor solvent. With a good solvent and a poor solvent, what dissolve | melts the cellulose ester to be used independently is defined as a good solvent, and what poorly swells or does not melt | dissolve is defined as a poor solvent.

  Therefore, a good solvent and a poor solvent change with the acetyl group substitution degree of a cellulose ester.

  Although the good solvent used for this invention is not specifically limited, Organic halogen compounds, such as a methylene chloride, dioxolanes, acetone, methyl acetate, methyl acetoacetate, etc. are mentioned. Particularly preferred is methylene chloride or methyl acetate.

  Moreover, although the poor solvent used for this invention is not specifically limited, For example, methanol, ethanol, n-butanol, cyclohexane, cyclohexanone, etc. are used preferably. Moreover, it is preferable that 0.01-2 mass% of water contains in dope.

  Moreover, the solvent used for melt | dissolution of a cellulose ester collect | recovers the solvent removed from the film by drying at the film-forming process, and uses this again.

  The recovery solvent may contain trace amounts of additives added to the cellulose ester, such as plasticizers, UV absorbers, polymers, monomer components, etc., but even if these are included, they are preferably reused. Can be purified and reused if necessary.

  A general method can be used as a dissolution method of the cellulose ester when preparing the dope described above. When heating and pressurization are combined, it is possible to heat above the boiling point at normal pressure.

  It is preferable to stir and dissolve while heating at a temperature that is equal to or higher than the boiling point of the solvent at normal pressure and that the solvent does not boil under pressure, in order to prevent the generation of massive undissolved materials called gels and mamacos.

  A method in which a cellulose ester is mixed with a poor solvent and wetted or swollen, and then a good solvent is added and dissolved is also preferably used.

  The pressurization may be performed by a method of injecting an inert gas such as nitrogen gas or a method of increasing the vapor pressure of the solvent by heating. Heating is preferably performed from the outside. For example, a jacket type is preferable because temperature control is easy.

  The heating temperature with the addition of a solvent is preferably higher from the viewpoint of the solubility of the cellulose ester, but if the heating temperature is too high, the required pressure increases and the productivity deteriorates.

  A preferable heating temperature is 45 to 120 ° C, more preferably 60 to 110 ° C, and still more preferably 70 ° C to 105 ° C. The pressure is adjusted so that the solvent does not boil at the set temperature.

  Alternatively, a cooling dissolution method is also preferably used, whereby the cellulose ester can be dissolved in a solvent such as methyl acetate.

  Next, this cellulose ester solution is filtered using a suitable filter medium such as filter paper. As the filter medium, it is preferable that the absolute filtration accuracy is small in order to remove insoluble matters and the like, but there is a problem that the filter medium is likely to be clogged if the absolute filtration accuracy is too small.

  For this reason, a filter medium with an absolute filtration accuracy of 0.008 mm or less is preferable, a filter medium with 0.001 to 0.008 mm is more preferable, and a filter medium with 0.003 to 0.006 mm is still more preferable.

  There are no particular restrictions on the material of the filter medium, and ordinary filter media can be used. However, plastic filter media such as polypropylene and Teflon (registered trademark), and metal filter media such as stainless steel do not drop off fibers. preferable.

  It is preferable to remove and reduce impurities, particularly bright spot foreign matter, contained in the raw material cellulose ester by filtration.

Bright spot foreign matter means that when two polarizing plates are placed in a crossed Nicol state, an optical film or the like is placed between them, light is applied from one polarizing plate side, and observation is performed from the other polarizing plate side. It is a point (foreign matter) where light from the opposite side appears to leak, and the number of bright spots having a diameter of 0.01 mm or more is preferably 200 / cm ² or less.

More preferably, it is 100 pieces / cm < ² > or less, More preferably, it is 50 pieces / m < ² > or less, More preferably, it is 0-10 pieces / cm < ² > or less. Further, it is preferable that the number of bright spots of 0.01 mm or less is small.

  The dope can be filtered by a normal method, but the method of filtering while heating at a temperature not lower than the boiling point of the solvent at normal pressure and in a range where the solvent does not boil under pressure is the filtration pressure before and after filtration. The increase in the difference (referred to as differential pressure) is small and preferable.

  A preferred temperature is 45 to 120 ° C, more preferably 45 to 70 ° C, and still more preferably 45 to 55 ° C.

  A smaller filtration pressure is preferred. The filtration pressure is preferably 1.6 MPa or less, more preferably 1.2 MPa or less, and further preferably 1.0 MPa or less.

  Here, the dope casting will be described.

  The metal support in the casting (casting) step preferably has a mirror-finished surface. As the metal support, a stainless steel belt or a drum whose surface is plated with a casting is preferably used.

  The cast width can be 1 to 4 m. The surface temperature of the metal support in the casting step is −50 ° C. to a temperature lower than the boiling point of the solvent, and a higher temperature is preferable because the web can be dried faster. May deteriorate.

  A preferable support temperature is 0 to 55 ° C, and more preferably 25 to 50 ° C. Alternatively, it is also a preferable method that the web is gelled by cooling and peeled from the drum in a state containing a large amount of residual solvent.

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

  In order for the cellulose ester film to exhibit good flatness, the residual solvent amount when peeling the web from the metal support is preferably 10 to 150% by mass, more preferably 20 to 40% by mass or 60 to 130% by mass. Especially preferably, it is 20-30 mass% or 70-120 mass%.

  In the present invention, the amount of residual solvent is defined by the following formula.

Residual solvent amount (% by mass) = {(MN) / N} × 100
M is the mass of a sample collected during or after the production of the web or film, and N is the mass after heating M at 115 ° C. for 1 hour.

  Further, in the drying step of the cellulose ester film, the web is peeled off from the metal support, and further dried, and the residual solvent amount is preferably 1% by mass or less, more preferably 0.1% by mass or less, Especially preferably, it is 0-0.01 mass% or less.

  In the film drying step, generally, a roll drying method (a method in which webs are alternately passed through a plurality of rolls arranged above and below) and a method in which the web is dried while being conveyed by a tenter method are employed.

  In order to produce the cellulose ester film according to the present invention, it is particularly preferable to perform stretching in the width direction (lateral direction) by a tenter method in which both ends of the web are held with clips or the like. Peeling is preferably performed at a peeling tension of 300 N / m or less.

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

  The drying temperature in the web drying step is preferably increased stepwise from 40 to 200 ° C.

  Although the film thickness of the cellulose-ester film which concerns on this invention is not specifically limited, 10-200 micrometers is used. In particular, the film thickness is particularly preferably 10 to 100 μm. More preferably, it is 20-60 micrometers.

  The cellulose ester film according to the present invention has a width of 1 to 4 m. In particular, those having a width of 1.4 to 4 m are preferably used, and particularly preferably 1.6 to 3 m. If it exceeds 4 m, conveyance becomes difficult.

  Although the retardation required for the cellulose ester film according to the present invention differs depending on the required optical compensation effect, the retardation Ro defined by the formula (I) in the in-plane direction is used from the viewpoint of taking advantage of high retardation development. Is preferably 30 nm or more, more preferably in the range of 30 to 200 nm, still more preferably in the range of 30 to 90 nm, and the retardation Rt in the thickness direction defined by the formula (II) is 70 nm or more. It is preferable that it is in the range of 70 to 300 nm.

Formula (I) Ro = (nx−ny) × d
Formula (II) Rt = {(nx + ny) / 2−nz} × d
(Where nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, nz is the refractive index in the thickness direction of the film, and d is (The thickness of the film (nm).)
<Measurement of retardation Ro and Rt>
A 35 mm × 35 mm sample was cut out from the obtained film, conditioned at 25 ° C. and 55% RH for 2 hours, and measured with an automatic birefringence meter (KOBRA21DH, Oji Scientific Co., Ltd.) from the vertical direction at 590 nm and the film. It calculates from the extrapolation value of the retardation value measured similarly, inclining a surface.

  A method for adjusting the phase difference is not particularly limited, but a method of adjusting by a stretching process is common.

  In order to obtain the target retardation values Ro and Rt in the present invention, it is preferable that the cellulose ester film has the configuration of the present invention, and further the refractive index is controlled by controlling the transport tension and stretching.

  For example, the retardation value can be changed by lowering or increasing the tension in the longitudinal direction.

  In addition, the retardation value can be changed by biaxially stretching or uniaxially stretching sequentially or simultaneously with respect to the longitudinal direction (film forming direction) of the film and the direction orthogonal to the film plane, that is, the width direction. it can.

  The draw ratios in the biaxial directions perpendicular to each other are preferably in the range of 0.8 to 1.5 times in the casting direction and 1.1 to 2.5 times in the width direction, respectively. It is preferable to carry out in the range of 0.8 to 1.0 times in the direction and 1.2 to 2.0 times in the width direction.

  The stretching temperature is preferably 120 ° C. to 200 ° C., more preferably 150 ° C. to 200 ° C., and more preferably 150 ° C. to 190 ° C. or less.

  The residual solvent in the film is preferably 20 to 0%, more preferably 15 to 0%.

  Specifically, it is preferable that the residual solvent is stretched by 11% at 155 ° C., or the residual solvent is stretched by 2% at 155 ° C. Alternatively, it is preferable that the residual solvent is stretched at 11% at 160 ° C, or the residual solvent is stretched at less than 1% at 160 ° C.

  There is no particular limitation on the method of stretching the web. For example, a method in which a difference in peripheral speed is applied to a plurality of rolls, and the roll peripheral speed difference is used to stretch in the longitudinal direction, the both ends of the web are fixed with clips and pins, and the interval between the clips and pins is increased in the traveling direction. And a method of stretching in the vertical direction, a method of stretching in the horizontal direction and stretching in the horizontal direction, a method of stretching in the vertical and horizontal directions and stretching in both the vertical and horizontal directions, and the like. Of course, these methods may be used in combination.

  In the case of the so-called tenter method, driving the clip portion by the linear drive method is preferable because smooth stretching can be performed and the risk of breakage and the like can be reduced.

  These width maintenance or lateral stretching in the film forming step is preferably performed by a tenter, and may be a pin tenter or a clip tenter.

  When the slow axis or the fast axis of the cellulose ester film according to the present invention is present in the film plane and the angle formed with the film forming direction is θ1, θ1 is preferably −1 ° or more and + 1 ° or less, − More preferably, it is 0.5 ° or more and + 0.5 ° or less.

  This θ1 can be defined as an orientation angle, and θ1 can be measured using an automatic birefringence meter KOBRA-21ADH (Oji Scientific Instruments). Each of θ1 satisfying the above relationship can contribute to obtaining high luminance in a display image, suppressing or preventing light leakage, and contributing to obtaining faithful color reproduction in a color liquid crystal display device.

<Physical properties of cellulose ester film>
The moisture permeability of the cellulose ester film according to the present invention is preferably 300 to 1800 g / m ² · 24 h at 40 ° C. and 90% RH, more preferably 400 to 1500 g / m ² · 24 h, and 40 to 1300 g / m ² · 24 h. Is particularly preferred. The moisture permeability can be measured according to the method described in JIS Z 0208.

  The breaking elongation of the cellulose ester film according to the present invention is preferably 10 to 80%, and more preferably 20 to 50%.

  The visible light transmittance of the cellulose ester film according to the present invention is preferably 90% or more, and more preferably 93% or more.

  The haze of the cellulose ester film according to the present invention is preferably less than 1%, particularly preferably 0 to 0.1%.

<Roll-shaped polarizing plate and single-wafer-shaped polarizing plate>
The roll-shaped polarizing plate of the present invention is provided with a cellulose ester film having an average degree of acetyl group substitution of 2.0 or more and less than 2.5 and a melting point in the range of 200 to 290 ° C. on both sides of the polarizer. It is characterized by.

  In the present application, a polarizing plate manufactured in a rolled state is referred to as a “rolled polarizing plate”, and a piece cut from the polarizing plate is referred to as a “single sheet polarizing plate”. .

  The cellulose ester film according to the present invention can be used for a polarizing plate as a polarizer protective film or a retardation film, and for a liquid crystal display device using the polarizing plate.

  The polarizing plate of the present invention needs to be a polarizing plate bonded to at least one surface of a polarizer using the cellulose ester film according to the present invention as a polarizer protective film or a retardation film.

  The polarizing plate of the present invention can be produced by a general method. The cellulose ester film according to the present invention is preferably bonded to at least one surface of a polarizer prepared by subjecting the polarizer side to alkali saponification treatment and immersion drawing in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution. Also, it is necessary to use the same kind of cellulose ester film according to the present invention on the other surface.

  In addition to the antiglare layer or the clear hard coat layer, the polarizer protective film used on the surface side of the liquid crystal display device preferably has an antireflection layer, an antistatic layer, an antifouling layer, and a backcoat layer.

  In addition, the "polarizer" which is the main component of the polarizing plate is an element that passes only light having a polarization plane in a certain direction, and a typical polarizer currently known is a polyvinyl alcohol polarizing film, There are one in which iodine is dyed on a polyvinyl alcohol film and one in which a dichroic dye is dyed.

  For the polarizer, a polyvinyl alcohol aqueous solution is formed into a film and dyed by uniaxial stretching or dyed or uniaxially stretched and then preferably subjected to a durability treatment with a boron compound. The film thickness of the polarizer is preferably 5 to 30 μm, particularly preferably 10 to 20 μm.

  Further, the ethylene unit content described in JP-A-2003-248123, JP-A-2003-342322, etc. is 1 to 4 mol%, the degree of polymerization is 2000 to 4000, and the degree of saponification is 99.0 to 99.99 mol%. Ethylene-modified polyvinyl alcohol is also preferably used.

  Among them, an ethylene-modified polyvinyl alcohol film having a hot water cutting temperature of 66 to 73 ° C. is preferably used.

  A polarizer using this ethylene-modified polyvinyl alcohol film is excellent in polarization performance and durability, and has few color spots, and is particularly preferably used for a large-sized liquid crystal display device.

  The polarizer obtained as described above is usually used as a polarizing plate with a protective film bonded to both sides or one side. Examples of the adhesive used for pasting include a PVA-based adhesive and a urethane-based adhesive. Among them, a PVA-based adhesive is preferably used.

  Hereinafter, the roll-shaped polarizing plate or the sheet-shaped polarizing plate of the present invention will be described in more detail with reference to the drawings as appropriate.

  FIG. 1 is a schematic cross-sectional view showing an example of a layer configuration of a roll-shaped polarizing plate or a sheet-shaped polarizing plate.

  In the example shown in FIG. 1, a polarizer protective film 2 made of a transparent resin film is bonded to one surface of a polarizer 1, a retardation film 3 is bonded to the other surface of the polarizer 1, and further to the surface thereof. An outer pressure-sensitive adhesive layer 6 is provided to constitute the polarizing plate 4. A peelable protective film 5 is bonded to the surface of the polarizer protective film 2, and a separate film 7 is bonded to the surface of the outer pressure-sensitive adhesive layer 6, so that a roll-shaped polarizing plate or a sheet-shaped polarizing plate 10 is bonded. Is configured.

  Thus, in the present invention, the polarizer protective film 2 is bonded to one side of the polarizer 1, the pressure-sensitive adhesive layer 6 is directly provided on the other side of the polarizer 1, and the other side of the polarizer 1. The pressure-sensitive adhesive layer provided on the side is a single layer or a plurality of layers, and a separate film 7 is bonded to the surface of the outermost pressure-sensitive adhesive layer 6. The polarizing plate 4 to which the film 5 is bonded is wound up in a roll shape to produce a rolled polarizing plate 10.

  Further, for example, two or more retardation films 3 may be laminated to form a broadband circularly polarizing plate. Even in such a case, the separate film 7 is bonded to the surface of the outermost pressure-sensitive adhesive layer 6. The

  A polarizing plate 4 shown in FIG. 1 is provided on the surface of a polarizer 1, a polarizer protective film 2 provided on one side of the polarizer 1, a retardation film 3 on which the polarizer 1 is bonded, and a retardation film 3. It is comprised by the outer side adhesive layer 6 made. Also in this case, a peelable protective film 5 is bonded to the surface of the polarizer protective film 2, and a separate film 7 is bonded to the surface of the outer pressure-sensitive adhesive layer 6 to form a roll-shaped polarizing plate or sheet-like sheet. The polarizing plate 10 is used.

  In the roll-shaped polarizing plate or the sheet-like polarizing plate 10, the protective film 5 outside the polarizer protective film 2 and the separate film 7 outside the pressure-sensitive adhesive layer 6 are used when inspecting the sheet-like polarizing plate 10, or It is provided for the purpose of protecting the polarizing plate 4 and the pressure-sensitive adhesive layer 6 when the 10 is transported or stored.

  That is, the protect film 5 is provided for the purpose of protecting the surface of the polarizing plate 4 and is on the side opposite to the surface where the polarizing plate 4 is bonded to the liquid crystal cell. The protective film 5 is peeled off after the polarizing plate 4 is bonded to the liquid crystal cell.

  Moreover, the separate film 7 is provided on it in order to cover the adhesive layer 6, and this adhesive layer 6 becomes the surface side which bonds the sheet-like polarizing plate 10 to a liquid crystal cell or another optical member. . And the separate film 7 provided on it is peeled and removed immediately before bonding to a liquid crystal cell or another optical member.

  The protect film 5 is usually composed of a transparent base resin film provided with an adhesive layer on the surface. Moreover, the separate film 7 is normally comprised with the transparent resin film in which the mold release process was performed, and the mold release process surface is bonded together to the adhesive layer 6. FIG. As the resin film constituting the protect film 5 and the separate film 7, for example, a film made of polyester such as polyethylene terephthalate or polyethylene naphthalate can be used.

  In the present invention, when the polarizing plate on which the protective film 5 and the separate film 7 are respectively bonded is wound up in a roll shape, the protective film 5 is shown in a schematic sectional view in FIG. Is wound so that the inner side is the inner side and the separate film 7 is the outer side.

<Laser cutting>
The laser used in the present invention, for example, CO ₂ lasers, YAG lasers, are exemplified UV laser or the like, and among this, high applicability to a thickness range, CO ₂ laser from the viewpoint of cracking and indicia chipping does not occur Is preferred.

  In the laser irradiation, the output and speed are not limited, and the laser irradiation may be performed by single irradiation or multiple irradiation. The output of the laser irradiation is, for example, 10 to 800 W, preferably 100 to 350 W when cutting with one irradiation, and preferably 50 to 200 W when cutting with two irradiations.

<Liquid crystal display device>
By using the polarizing plate bonded with the cellulose ester film according to the present invention for a liquid crystal display device, the liquid crystal display device of the present invention excellent in various visibility can be produced.

  The cellulose ester film according to the present invention preferably has a function as a retardation film in particular, and is used for liquid crystal display devices of various drive systems such as STN, TN, OCB, HAN, VA (MVA, PVA), IPS, OCB. Can be used.

  A VA (MVA, PVA) type liquid crystal display device is preferable.

  In particular, even a large-screen liquid crystal display device having a screen size of 30 or more can provide a liquid crystal display device with excellent visibility such as uneven coloring and front contrast with little environmental fluctuation and reduced light leakage. .

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

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

<Fine particle additive solution>
Cellulose ester CE-1 listed in Table 1 was added to a dissolution tank containing methylene chloride and heated to completely dissolve, and then dissolved in Azumi filter paper No. 1 manufactured by Azumi Filter Paper Co., Ltd. Filtered using 244. The fine particle dispersion was slowly added thereto while sufficiently stirring the filtered cellulose ester solution. Further, the particles were dispersed by an attritor so that the secondary particles had a predetermined particle size. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution.

Methylene chloride 99 mass parts Cellulose ester CE-1 4 mass parts Fine particle dispersion 11 mass parts Cellulose ester CE-1 was used to prepare a main dope liquid having the following composition.

  First, methylene chloride and ethanol were added to the pressure dissolution tank. Cellulose ester CE-1 was added to a pressure dissolution tank containing a solvent while stirring. This was heated and stirred to dissolve completely, and this was dissolved in Azumi Filter Paper No. The main dope solution was prepared by filtration using 244.

  2 parts by mass of the fine particle additive solution is added to 100 parts by mass of the main dope solution and mixed thoroughly with an in-line mixer (Toray static type in-pipe mixer Hi-Mixer, SWJ). It was cast uniformly on the band support. On the stainless steel band support, the solvent was evaporated until the residual solvent amount became 110%, and the stainless steel band support was peeled off. When peeling, the film is stretched so that the longitudinal (MD) stretch ratio is 1.02, and then the both ends of the web are held by a tenter, and the stretch ratio in the width (TD) direction is 1.25. Residual solvent at the start of stretching, which was stretched to double, was 30%. After stretching, hold for several seconds while maintaining its width, release the width holding after relaxing the tension in the width direction, further carry for 30 minutes in the third drying zone set at 125 ° C., and perform drying, A cellulose ester film 101 according to the present invention having a thickness of 40 μm and a knurling width of 1.5 m, a width of 1 cm at the end, and a height of 8 μm was produced.

<Composition of main dope solution>
Methylene chloride 300 parts by mass Ethanol 30 parts by mass Cellulose ester CE-1 100 parts by mass (Production of cellulose ester films 102 to 109)
Cellulose ester films 102 to 109 were produced in the same manner as described above except that the cellulose ester shown in Table 1 was changed as shown in Table 2.

  The following abbreviations in the table are as follows.

TPP: Triphenyl phosphate Example 2
<Preparation of polarizing plate>
Using the obtained cellulose ester films 101 to 109, polarizing plates were produced by the following method.

  A 120 μm-thick polyvinyl alcohol film was uniaxially stretched (temperature: 110 ° C., stretch ratio: 5 times). This was immersed in an aqueous solution composed of 0.075 g of iodine, 5 g of potassium iodide and 100 g of water for 60 seconds, and then immersed in an aqueous solution of 68 ° C. composed of 6 g of potassium iodide, 7.5 g of boric acid and 100 g of water. This was washed with water and dried to obtain a polarizer.

  Next, a polarizer and the cellulose ester films 101 to 109 were bonded to both surfaces according to the following steps 1 to 6 to prepare a polarizing plate.

  Step 1: The cellulose ester film 101 was immersed in a 2 mol / l potassium hydroxide solution at 50 ° C. for 30 seconds, then washed with water and dried to obtain a cellulose ester film having a saponified surface.

  Process 2: The said polarizer was immersed in the polyvinyl alcohol adhesive tank of 2 mass% of solid content for 1-2 seconds.

  Step 3: The excess adhesive adhered to the polarizer in Step 2 was gently wiped off and placed on the cellulose ester film treated in Step 1, and the same cellulose ester film 101 was placed on the back side. .

Step 4: Step 3 Cellulose ester was laminated with a film 101 and the polarizer and the pressure of the cellulose ester film 101 on the back side 20-30 N / cm ^2, the conveyance speed was pasted at approximately 2m / min.

  Process 5: The sample which bonded the polarizer produced in the process 4, the cellulose-ester film, and the back side cellulose-ester film in the 80 degreeC dryer was dried for 2 minutes, and the polarizing plate was produced.

  Process 6: The surface of the cellulose ester film according to the present invention is bonded with a sheet-like adhesive in which an acrylic adhesive layer having a thickness of 25 μm is formed on a separate film 9 made of polyethylene terephthalate having a thickness of 38 μm. Then, a protective film (“AS3-304”, manufactured by Fujimori Kogyo Co., Ltd.) was bonded to the polarizer protective film side to produce a roll-shaped polarizing plate 101.

  Roll-like polarizing plates 102 to 109 were produced for the cellulose ester films 102 to 109 in the same manner as the cellulose ester film 101 in Steps 1 to 6 above.

  The solubility parameter of the cellulose ester was measured by the Hoy method as described above. In addition, the humidity change of the equilibrium moisture content was measured by conditioning a cellulose ester fill sample 7 mm × 35 mm for 2 hours at a temperature of 23 ° C. and a relative humidity of 20% RH. The water content was calculated by dividing the moisture content (g) in the sample at a relative humidity of 20% by the sample mass (g).

  A similar sample was conditioned at a temperature of 23 ° C. and a relative humidity of 80% RH for 2 hours, measured with a Karl Fischer method trace moisture meter LE-20S (manufactured by Hiranuma Sangyo Co., Ltd.), and a sample at a relative humidity of 80%. The moisture content was calculated by dividing the moisture content (g) in the sample by the sample mass (g).

  The difference between the equilibrium moisture content at 20% relative humidity and the equilibrium moisture content at 80% relative humidity was determined as ΔH (80% -20%) and expressed as an absolute value.

  Moreover, the difference (DELTA) H (80% -20%) difference of the said equilibrium moisture content of the said cellulose ester film of the both sides was calculated | required as (DELTA) H, and was represented by the absolute value.

<Production of liquid crystal display device>
A liquid crystal panel for viewing angle measurement was produced as follows, and the characteristics as a liquid crystal display device were evaluated.

VA mode type liquid crystal display device (SONY BRAVIAV1, 40-inch type) is peeled off the double-sided polarizing plate previously bonded, and precision processing CO ₂ from a position of 1 m from the surface side of the roll-shaped polarizing plate 101 produced above. Using a laser (trade name SILAS-SAM (SPL2305 type); manufactured by Sugaya Kogyo Co., Ltd.), a sheet cut out by laser irradiation under conditions of an output of 190 W, a conveyance speed of 250 mm / s, and an air assist gas pressure of 0.1 MPa. The sheet-like polarizing plate 101-2 cut out by irradiating the laser under the same conditions from a position 1 m from the center of the roll and the leaf-like polarizing plate 101-1, was bonded to both surfaces of the liquid crystal cell.

  In that case, it performed so that an absorption axis might turn to the same direction as the polarizing plate previously bonded, and each liquid crystal display device was produced.

  This liquid crystal display device was evaluated by the following method. In addition, each evaluation result is as showing in Table 1.

[Contrast]
The front contrast of the liquid crystal display device was evaluated as follows to evaluate the contrast. 1000 or more is a practically good range.

The measurement was performed after the backlight of each liquid crystal display device was lit continuously for one week in an environment of 23 ° C. and 55% RH. For measurement, EZ-Contrast 160D manufactured by ELDIM was used to measure the luminance from the normal direction of the display screen of white display and black display with a liquid crystal display device, and the ratio was defined as the front contrast. Front contrast = (brightness of white display measured from normal direction of display device) / (brightness of black display measured from normal direction of display device)
[Measurement of waviness of cut surface]
Using a laser microscope, the thickness in the vicinity of the cut surface along the absorption axis in the sheet-like polarizing plate 101 was measured, and the waviness of the cut surface was calculated using the following equation.
(Wave of cut surface) = (Maximum thickness of cut surface) − (Minimum value of thickness of cut surface) (μm)
Similarly, the sheet-like polarizing plates 102 to 109 were similarly evaluated.

[crack]
Using a precision processed CO ₂ laser (trade name SILAS-SAM (SPL2305 type); manufactured by Kasuya Kogyo Co., Ltd.), the sheet-like polarizing plate 101 is subjected to conditions of an output of 190 W, a conveying speed of 250 mm / s, and an air assist gas pressure of 0.1 MPa. The laser was irradiated and cut. The state of the edge and the state of generation of chips when the polarizing plate was cut were observed with a × 10 loupe, and the occurrence probability of edge flaking, cracking, and chips was determined. Similarly, the sheet-like polarizing plates 102 to 109 were similarly evaluated.

[Polarizer degradation]
(Polarizer degradation)
First, the parallel transmittance and the orthogonal transmittance of the sheet-like polarizing plate 101 were measured, and the degree of polarization was calculated according to the following formula. Thereafter, each polarizing plate was subjected to forced degradation for 1000 hours under the conditions of 60 ° C. and 90%, and then the parallel transmittance and the orthogonal transmittance were measured again, and the degree of polarization was calculated according to the following formula. The amount of change in polarization degree was determined by the following formula.

Polarization degree P = ((H0−H90) / (H0 + H90)) 1/2 × 100
Polarization degree change = P0−P1000
H0: Parallel transmittance H90: Orthogonal transmittance P0: Polarization degree before forced deterioration P1000: Polarization degree after forced degradation 1000 hours Similarly, the sheet-like polarizing plates 102 to 109 were similarly evaluated.

  The contents and evaluation results of the above samples are shown in Tables 1 and 2.

  As is clear from the sample contents and the evaluation results shown in Tables 1 and 2, it can be seen that the polarizing plate of the present invention has almost no waviness, cracks and polarizer deterioration, and excellent contrast.

  That is, by the above means of the present invention, a polarizing plate that prevents the occurrence of waviness and cracks on the cut surface, which is likely to occur when laser-cutting a roll-shaped polarizing plate, and has improved optical characteristics under high temperature and high humidity, and It can be seen that a liquid crystal display device using can be provided.

DESCRIPTION OF SYMBOLS 1 Polarizer 2 Polarizer protective film 3 Retardation film 4 Polarizing plate 5 Protective film 6 Adhesive layer 7 Separate film 10 Roll-shaped light board roll or sheet-like polarizing plate

Claims (6)

  A roll shape characterized in that a cellulose ester film having an average degree of acetyl group substitution of 2.0 or more and less than 2.5 and a melting point in the range of 200 to 290 ° C. is provided on both sides of the polarizer. Polarizer.   The difference ΔH (80% −20%) between the equilibrium moisture content at a temperature of 23 ° C. and a relative humidity of 20% and the equilibrium moisture content at a temperature of 23 ° C. and a relative humidity of 80% of the cellulose ester films on both sides of the polarizer. Absolute values are in the range of 3.0 to 5.0%, and the absolute value of the difference ΔH between the equilibrium water content of each cellulose ester film ΔH (80% -20%). Is in the range of 0 to 1.0%, the roll-shaped polarizing plate according to claim 1. The cellulose ester film on both sides sandwiching the polarizer contains at least one kind of additive satisfying the following formula 1 within a range of 0.01 to 30% by mass. Roll polarizing plate.
Formula 1: | SPt−SPc | <2.0
However, SPc in the formula is a solubility parameter of the cellulose ester measured by the Hoy method, and SPt is a solubility parameter of the additive measured by the same method.   The film thickness of the said cellulose-ester film exists in the range of 10-60 micrometers, The roll-shaped polarizing plate as described in any one of Claim 1- Claim 3 characterized by the above-mentioned.   A sheet-like polarizing plate, wherein the roll-shaped polarizing plate according to any one of claims 1 to 3 is cut and formed.   A liquid crystal display device produced by bonding the roll-shaped polarizing plate according to any one of claims 1 to 3 to a liquid crystal panel, and cutting with a laser.

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