TWI644131B - Polarizing plate, manufacturing method of polarizing plate and liquid crystal display device - Google Patents

Abstract

An object of the present invention is to provide a polarizing plate having improved durability and production efficiency, a method for producing the same, and a liquid crystal display device including the same.

The polarizing plate of the present invention is characterized in that a polarizing plate is formed in the order of a first protective film, a polarizer, and a second protective film from the viewing side, and the first protective film has super-birefringence in the plane at 380 nm. A polyester film having a light transmittance of 50% or more and a light-transmitting film having a light transmittance of less than 50% at 380 nm of the second protective film.

Description

Polarizing plate, manufacturing method of polarizing plate and liquid crystal display device

The present invention relates to a polarizing plate, a method for producing a polarizing plate, and a liquid crystal display device. More specifically, the present invention relates to a polarizing plate having improved durability and production efficiency, a method for producing the same, and a liquid crystal display device including the same.

In recent years, display devices such as liquid crystal display devices (hereinafter also referred to as LCDs) and organic electroluminescence display devices (hereinafter also referred to as OLEDs) have been thinned in recent years. Along with this, the thickness of the polarizing plate applied to the display device is expected to increase.

The polarizing plate is usually provided with a protective film for protecting the polarizer or the polarizing plate itself, and a polarizing plate using a polyester film is known as a protective film on the viewing (observation) side of the display device (for example, refer to Patent Document 1).

Conventionally, a polyester film used as a protective film on the viewing side is required to have high ultraviolet absorbing properties as one of protective functions.

As a method of imparting ultraviolet absorbing property to the polyester film produced by the melt casting method, a method of adding an ultraviolet absorber to the film itself or providing an ultraviolet absorbing layer or the like is used.

However, when an ultraviolet absorber is added to the polyester film itself, contamination occurs in the film production step or the polarizing plate manufacturing step due to bleeding or the like, and there is a problem that the yield is lowered due to the contamination. Therefore, in order to suppress bleeding, a method of suppressing bleeding by lamination is also proposed. However, the demand for high quality grade of the optical film used for the surface of the display device is improved, and the yield is lowered, and the production efficiency is improved. Lower and then require improvement. Here, "exudation" refers to a phenomenon in which a component such as an ultraviolet absorber contained in a film is leached to the surface of a film in a high-temperature and high-humidity environment to cause precipitation or volatilization.

Further, a method of providing an ultraviolet absorbing layer or a method of imparting ultraviolet absorbing property to a hard coat layer has a relatively large amount of ultraviolet absorbing agent in the layer of the film, so that step contamination is caused or the yield is lowered. And the production efficiency is reduced.

On the other hand, as described above, when the liquid crystal cell used in the liquid crystal display device is used to reduce the thickness of the glass plate or the film of the polarizer, the viewing side (observation side) is used in the high-temperature and high-humidity environment. The polyester film containing the ultraviolet absorber used for the protective film has a problem that the flatness is deteriorated or the step is contaminated by the bleeding during the production of the ultraviolet absorber, and the productivity (benefit) is easily lowered.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent No. 5167814

The present invention has been made in view of the above problems, and an object of the invention is to provide a polarizing plate having improved durability and production efficiency (benefit ratio), a method for producing the same, and a liquid crystal display device including the same.

As a result of the positive review of the above-mentioned problems, the present inventors have found that a polarizing plate having improved durability and productivity (benefit) can be obtained by the following polarizing plate, and the polarizing plate is characterized in that it is the first from the viewing side. a protective film, a polarizer, and a second protective film, wherein the first protective film is a polyester film having a super-birefringence in the plane and a light transmittance of 380 nm in an ultraviolet region of 50% or more. The second protective film has a light transmissive film having a light transmittance of less than 50% at 380 nm in the ultraviolet region.

That is, the above problems of the present invention can be solved by the following means.

1. A polarizing plate characterized in that a first protective film, a polarizing film, and a second protective film are formed in a order from a viewing side, and the first protective film has super-birefringence in a plane. A polyester film having a light transmittance of 380 nm of 50% or more, and the second protective film is a light-transmitting film having a light transmittance of less than 50% at 380 nm.

2. The polarizing plate of item 1, wherein the second protective film is The film contains a cellulose resin.

3. The polarizing plate of item 1, wherein the second protective film contains a cycloolefin resin.

4. The polarizing plate according to any one of the items 1 to 3, wherein the second protective film has a retardation value Ro (nm) in the in-plane of the film defined by the following formula (i) and is represented by the following formula (ii) The retardation value Rt (nm) of the defined film thickness direction satisfies the conditions specified by the following formulas (iii) and (iv), (i) Ro = (n _{x -} n _y ) × d

(ii) Rt=((n _x +n _y )/2-n _z )×d

(iii) 0≦Ro≦20

(iv)|Rt|≦25

[In the formula, n _x is a refractive index of the slow axis within the film plane, n _y is the vertical direction within the film plane to the slow axis direction of the refractive index, n _z is a refractive index in a direction perpendicular to the plane of the film, d It is the film thickness (nm)].

5. The polarizing plate according to any one of the items 1 to 4, wherein the second protective film contains at least one ester selected from the group consisting of a sugar ester and a polyester.

The polarizing plate according to any one of the items 1 to 5, wherein the second protective film contains at least one ultraviolet absorber selected from the group consisting of a benzotriazole-based compound and a triazine-based compound.

The polarizing plate according to any one of the items 1 to 6, wherein the first protective film has an ultraviolet curable resin layer.

A method of producing a polarizing plate according to any one of the items 1 to 7, characterized in that the film formed by the melt casting method has a light transmittance of less than 50% at 380 nm. Light through The second protective film mentioned above.

A method of producing a polarizing plate according to any one of the items 1 to 7, characterized in that the film formed by the solution casting method has a light transmittance of less than 50% at 380 nm. The second protective film of the light transmittance.

A liquid crystal display device comprising the polarizing plate according to any one of items 1 to 7 on a surface of a viewing side (front side) of the liquid crystal cell.

A liquid crystal display device comprising a polarizing plate according to any one of items 1 to 7 in a surface on a viewing side (front side) and a non-viewing side (rear side) of the liquid crystal cell.

12. The liquid crystal display device according to Item 10 or 11, wherein a thickness of the glass substrate of the liquid crystal cell is in a range of 0.3 to 0.7 mm.

According to the above-described means of the present invention, it is possible to provide a polarizing plate having improved durability and productivity (yield), a method for producing the same, and a liquid crystal display device including the same.

According to the configuration stipulated by the present invention, the above problems can be solved as presumed to be the following reasons.

As described above, as a configuration of the polarizing plate, the polyester film used as the first protective film is required to have high ultraviolet absorption as a protective function, for example, for polyethylene terephthalate (hereinafter abbreviated as PET) film. Add ultraviolet absorber or the like when it is sexual.

However, in order to impart ultraviolet absorbing property to the polyester film produced by the melt casting method, a method of adding an ultraviolet absorber to the polyester film itself, or separately providing an ultraviolet absorbing layer, or the like is exemplified. However, when the ultraviolet absorber is directly added to the polyester film, step contamination occurs due to the occurrence of bleeding or the like, which causes contamination of the film production step or the polarizing plate manufacturing step, and causes a problem of a decrease in yield. In order to suppress the bleed, a method of suppressing the bleed is proposed, and the optical film used for the surface of the liquid crystal display device is improved in quality requirements such as thinning, and the yield is lowered. The cause of the decrease in production efficiency. Further, when the constituent layer containing the ultraviolet absorbing layer is newly provided, or when the ultraviolet absorbing property is imparted to the hard coat layer, since the layer of the film contains a relatively large amount of the ultraviolet absorbing agent, it is contaminated by the above steps or caused by the above. The rate is lowered and the production efficiency is lowered.

In the present invention, when a polyester film is used as the protective film (first protective film) on the viewing side, the amount of the ultraviolet absorber added to the polyester film is preferably reduced, or the polyester film is preferably not contained in the form of the ultraviolet absorber. By setting the light transmittance of 380 nm in the ultraviolet region to 50% or more, it is possible to prevent a decrease in yield due to the above-described cause of adding a large amount of the above ultraviolet absorber. According to this configuration, it is found that there is a concern about the light resistance of the polarizer disposed below, but the influence is unexpectedly small. On the other hand, by adding a functional compound represented by an ultraviolet absorber for imparting ultraviolet absorbing properties to another protective film (second protective film), the light transmittance at 380 nm in the ultraviolet region is set to less than 50. %,able to provide A polarizing plate which is excellent in the ultraviolet ray durability necessary for the liquid crystal cell constituting the liquid crystal display device and which is excellent in yield can be used to reduce the manufacturing cost of the display device.

In particular, by reducing the film thickness of the glass substrate used in the liquid crystal cell, the quality of the polarizing plate is further improved, and the yield is lowered. However, the composition of the protective film defined by the present invention can be remarkably improved.

1‧‧‧Solution kettle

3, 6, 12, 15 ‧ ‧ filters

4, 13‧‧‧ raw material kettle

5, 14‧‧‧ liquid pump

8, 16‧‧‧ catheter

10‧‧‧UV absorber feed into the kettle

20‧‧ ‧ Confluence tube

21‧‧‧Mixer

30‧‧‧ Pressurized die mouth

31‧‧‧Metal support

32‧‧ ‧ blanks

33‧‧‧ peeling position

34‧‧‧Zoom extension

35‧‧‧Drying device

41‧‧‧Feed into the kettle

42‧‧‧ raw material kettle

43‧‧‧ pump

44‧‧‧Filter

51‧‧‧Polar plate

52, 102A, 102B‧‧‧ first protective film

53, 104A, 104B‧‧‧ polarizer

54, 105A, 105B‧‧‧2nd protective film

55‧‧‧UV hardened resin layer

100‧‧‧Liquid crystal display device

101A, 101B‧‧‧ polarizing plate

101C‧‧‧Liquid Crystal Unit

103A, 103B, 103C, 103D‧‧‧ UV curing adhesive

106‧‧‧Adhesive layer

107‧‧‧Liquid layer

400‧‧‧Manufacture of devices

410, 420‧‧‧cycloolefin film

430‧‧‧ film reel

510‧‧‧ module

516‧‧ ‧ mouth

520‧‧‧ casting rolls

521‧‧‧ outer perimeter

531, 532‧‧‧Electrostatic pinning device

540‧‧‧ peeling roller

550‧‧‧Finishing device

551, 552‧‧‧ trimming knife

Fig. 1A is a schematic cross-sectional view showing an example of a configuration of a polarizing plate of the present invention.

Fig. 1B is a schematic cross-sectional view showing another example of the configuration of a polarizing plate of the present invention.

Fig. 2 is a view schematically showing an example of a dope preparation step, a casting step, and a drying step which can be applied to the solution casting method of the present invention.

Fig. 3 is a view showing an example of the configuration of a liquid crystal display device of the present invention.

Fig. 4 is a view schematically showing an example of a dope preparation step, a casting step, and a drying step which can be applied to the melt casting method of the present invention.

The polarizing plate of the present invention is characterized in that a polarizing plate is formed in the order of the first protective film, the polarizing film, and the second protective film from the viewing side. The first protective film is a polyester film having a super-birefringence in the plane and a light transmittance of 380 nm of 50% or more, and the second protective film is transmitted through light having a light transmittance of less than 50% at 380 nm. Film. This feature is a common or corresponding technical feature of the invention associated with each request item.

As an embodiment of the present invention, it is preferable that the second protective film contains a cellulose resin or a cycloolefin resin from the viewpoint of exhibiting an effect of the object of the present invention, but based on the viewpoint of forming a high-quality protective film, It can be stabilized and contains UV absorbers.

Further, from the viewpoint of being able to be a protective film having excellent phase difference characteristics, it is preferable that the retardation value Ro (nm) of the film surface defined by the above formula (i) of the second protective film satisfies the condition specified by the above formula (iii). Further, the retardation value Rt (nm) in the film thickness direction defined by the above formula (ii) satisfies the condition specified by the above formula (iv).

Further, from the viewpoint of imparting high flexibility to the film, the second protective film preferably contains at least one ester selected from the group consisting of a sugar ester and a polyester.

Moreover, it is preferable that the second protective film contains at least one ultraviolet absorber selected from the benzotriazole-based compound and the triazine-based compound, from the viewpoint of exhibiting the effects of the present invention.

In order to impart the necessary ultraviolet absorbing property to the second protective film, it is necessary to increase the content of the ultraviolet absorbing agent or to increase the film thickness of the entire film. However, if the amount of the ultraviolet absorbing agent is increased, bleed is caused, and the phase separation is increased. The problem of large turbidity. Further, when the film thickness is increased, the retardation value is increased, so that both of them have a problem.

In the present invention, the second protective film contains a sugar ester or a polyester In the case where the ultraviolet absorber is contained, it is difficult to increase the retardation value, so that a thin film having a small film thickness can be provided by satisfying the ultraviolet absorber and a desired retardation value. As the ultraviolet absorber, a benzotriazole compound is preferred, wherein [2-(2H-benzotriazol-2-yl)-6-(1-methyl-1-phenylethyl)-4- (1,1,3,3-tetramethylbutyl)phenol] is excellent in ultraviolet absorbing property and desired retardation value, and can provide a film having a thin film thickness, so that it is particularly preferably used.

Moreover, it is preferable that the first protective film further has an ultraviolet curable resin layer from the viewpoint of obtaining excellent scratch resistance.

In a preferred embodiment of the present invention, the second protective film is formed by a melt casting method or a solution casting method.

Among them, a solution casting method is preferable because it can provide a manufacturing method in which a plurality of additives are contained at the same time, and the result is that the manufacturing method of the plurality of problems can be simultaneously solved.

Moreover, the liquid crystal display device of the present invention is characterized in that it has a surface on the viewing side (front side) of the liquid crystal cell, a surface on the viewing side (front side) of the liquid crystal cell, and a surface on the non-view side (rear side). The polarizing plate of the invention. Further, from the viewpoint of obtaining a thinner liquid crystal display device, the thickness of the glass substrate which is preferably applied to the liquid crystal cell is in the range of 0.3 to 0.7 mm.

Hereinafter, the present invention and its constituent elements and aspects for carrying out the invention will be described in detail. In addition, the "~" shown in the present invention is used in the sense that the numerical values described before and after are included in the lower limit and the upper limit. In the description of the drawings, the numerals in parentheses after the constituent elements indicate the symbols described in the respective drawings.

Polarizer

1A and 1B are schematic cross-sectional views showing an example of a configuration of a polarizing plate of the present invention.

As shown in FIG. 1A and FIG. 1B, the polarizing plate (51) of the present invention is characterized in that the first protective film (52), the polarizing film (53), and the second protective film (54) are formed from the viewing side. The first protective film (52) is a polyester film having super-birefringence in the plane and having a light transmittance of 380 nm in the ultraviolet region of 50% or more, and the second protective film (54) is in the ultraviolet region. A light transmissive film having a light transmittance of less than 50% at 380 nm.

Hereinafter, details of each component of the polarizing plate of the present invention will be described.

[First protective film]

The first protective film (52) constituting the polarizing plate of the present invention is characterized in that it has a super-birefringence in the plane and a light transmittance of 380 nm in the ultraviolet region of 50% or more (hereinafter also referred to as polyester). film).

The term "super-birefringence" as used in the present invention means that the retardation value Ro of the in-plane direction is in the range of 3,000 to 30,000 nm. Here, the retardation value Ro in the in-plane direction is defined by the following formula (i).

Formula (i)Ro=(n _x -n _y )×d

Further, the retardation Rt in the film thickness direction is defined by the following formula (ii).

Formula (ii) Rt=((n _x +n _y )/2-n _z )×d

In the formulas (i) and (ii), n _x is the refractive index in the slow axis direction in the plane of the film, n _y is the refractive index in the direction perpendicular to the slow axis direction in the plane of the film, and n _z is perpendicular to the film surface. The refractive index in the direction, d is the film thickness (nm).

The retardation value Ro in the in-plane direction and the retardation value Rt in the film thickness direction of the film can be self-contained using an automatic birefringence meter Axo Scan (Axo Scan Mueller Martrix Polarimeter: Axo Matrix) at 23 ° C ‧55% RH The refractive index nx, ny, and nz obtained by measuring the three-dimensional refractive index were calculated at a wavelength of 590 nm.

One of the characteristics of the first protective film is as described above, and the light transmittance at 380 nm in the ultraviolet region is 50% or more. That is, it is characterized by a low ultraviolet absorption energy in the ultraviolet region.

The light transmittance at a wavelength of 380 nm of the polyester film of the present invention can be determined by, for example, measurement using an ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation, product name: V7100). The light transmittance at 380 nm of 50% or more is preferably in the range of 60 to 95%, more preferably in the range of 70 to 95%, and particularly preferably in the range of 80 to 95%.

In the first protective film of the present invention, as a method of setting the light transmittance at 380 nm to 50% or more, it is effective to remove the additive having light absorption at 380 nm in the film, and it is particularly preferable that the film is not added to the ultraviolet region. Absorbed UV absorber.

The polyester film of the present invention, more specifically, the retardation value Ro of the stretched polyester film is preferably in the range of 3,000 to 30,000 nm from the viewpoint of exhibiting super birefringence. The lower limit of the retardation value of the stretched polyester film is preferably 4,500 nm or more, more preferably 6000 nm or more, still more preferably 8,000 nm or more, and particularly preferably 10,000 nm or more. On the other hand, the upper limit of the retardation value Ro of the stretched polyester film is not substantially improved by the use of the film having the retardation value Ro or more, and the film thickness is increased corresponding to the height of the retardation value Ro. However, the viewpoint of not being able to have both the requirements for thinning and the viewpoint of rational reduction as an industrial material is preferably set to 30,000 nm or less.

Further, as another viewpoint, when the first protective film having birefringence is provided between the two orthogonal polarizing plates, the linear polarized light emitted from the polarizing plate passes through the first protective film, causing disorder. The transmitted light in the plane of the first protective film exhibits a unique interference color for the retardation value Ro of the product of super birefringence and thickness. Therefore, by controlling the first protective film within the range of the specific retardation value Ro, the envelope shape of the spectrum of the transmitted light showing the interference color can be approximated to the light emission spectrum of the light source.

In order to exert the above effects, the first protective film used in the present invention preferably has a retardation value Ro of 3,000 to 30,000 nm. When the retardation value Ro is 3,000 nm or more, when the screen is observed through a polarizing plate such as sunglasses, a strong interference color is exhibited, and the envelope shape is similar to the light emission spectrum of the light source, thereby ensuring good visibility. Preferably, the lower limit value of the retardation value is 4500 nm, preferably the lower limit value is 6000 nm, and the lower limit is 8000 nm, and the lower limit is 10000 nm.

Further, when the ultraviolet ray absorbing agent is contained in the polyester film of the first protective film, the display of birefringence is lowered, and in order to secure super-birefringence, it is necessary to increase the stretching ratio at the time of producing the polyester film or to adjust the stretching temperature, but These will have the problem of causing an increase in turbidity and a decrease in the contrast of the display device. In addition, there is a method of increasing the film thickness of the polyester film to satisfy the birefringence value. However, in order to increase the size of the display device, it is required to increase the weight and thickness, and the polyester film becomes thicker. It is a cause of manufacturing troubles or malfunctions caused by a rational difference in the manufacture of a polarizing plate or a display device, but it is not necessary to contain ultraviolet rays in the polyester film of the first protective film by the constitution of the present invention. The absorbent can prevent these problems from occurring.

The ratio of the retardation value Ro of the in-plane direction of the stretched polyester film to the retardation value Rt in the thickness direction (Ro/Rt) is preferably 0.2 or more, more preferably 0.5 or more, still more preferably 0.6 or more. The larger the Ro/Rt, the more the isotropic effect of the birefringence, and the more effective the suppression of the stain on the screen.

The maximum value of Ro/Rt is 2.0 (i.e., a completely 1-axis symmetrical film), and as the film is nearly completely uniaxially symmetric, the mechanical strength in the direction orthogonal to the alignment direction tends to decrease. Therefore, the upper limit of the value of Ro/Rt of the polyester film is preferably 1.2 or less, more preferably 1.0 or less.

The retardation value of the stretched polyester film can be measured according to a conventional method. Specifically, the refractive index and thickness in the two-axis direction can be measured and determined. Also, a commercially available automatic birefringence measuring device (for example, Axo Scan (Axo Scan Mueller Matrix Polarimeter: Axo Matrix) can be used. System))).

The polyester of the raw material resin of the stretched polyester film is excellent in transparency and excellent in thermal properties and mechanical properties, and it is easy to control the retardation value by the stretching process. Among the polyesters, polyethylene terephthalate or polyethylene naphthalate is preferred. The polyester represented by polyethylene terephthalate and polyethylene naphthalate has a large intrinsic birefringence, and it is preferable to obtain a high retardation value even if the film thickness is thin. In particular, polyethylene naphthalate has a large intrinsic birefringence in the polyester, and is therefore more suitable for a case where the retardation value is particularly high or a film having a high retardation value while thinning the film thickness.

(Method for producing an extended polyester film)

Hereinafter, a method of producing the stretched polyester film will be described.

The polyester film can be obtained by condensing any dicarboxylic acid with a diol. Examples of the dicarboxylic acid include terephthalic acid, isophthalic acid, phthalic acid, 2,5-naphthalene dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, and 1,4-naphthalenedicarboxylic acid. 1,5-naphthalene dicarboxylic acid, diphenyl carboxylic acid, diphenoxy ethane dicarboxylic acid, diphenyl hydrazine carboxylic acid, hydrazine dicarboxylic acid, 1,3-cyclopentane dicarboxylic acid, 1, 3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, malonic acid, dimethylmalonic acid, succinic acid, 3, 3-diethyl succinic acid, glutaric acid, 2,2-dimethylglutaric acid, adipic acid, 2-methyladipate, trimethyl adipate, pimelic acid, sebacic acid, Dimer acid, sebacic acid, suberic acid, dodecane dicarboxylic acid, and the like.

The diol can be exemplified by, for example, ethylene glycol, propylene glycol, hexamethylene glycol, neopentyl glycol, 1,2-cyclohexanedimethanol, and 1,4-cyclohexane. Methanol, methylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-bis (4) -Hydroxyphenyl)propane, bis(4-hydroxyphenyl)anthracene, and the like.

One type of the dicarboxylic acid component and the diol component which are constituting the polyester film may be used alone or two or more types may be used. Specific polyester resins constituting the polyester film are, for example, polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and the like. It is preferably polyethylene terephthalate or polyethylene naphthalate, more preferably polyethylene naphthalate. The polyester resin may contain other copolymerization components, and the ratio of the copolymerization component is preferably 3 mol% or less, more preferably 2 mol% or less, and still more preferably 1.5 mol% or less, from the viewpoint of mechanical strength. These resins are excellent in transparency and excellent in thermal properties and mechanical properties. Moreover, the resins can be easily controlled by the elongation processing.

The polyester film can be obtained according to a general production method. Specifically, for example, the unoriented polyester film obtained by melting the polyester resin and extruding into a sheet is formed at a temperature equal to or higher than the glass transition temperature of the film, and is extended by the difference in the longitudinal direction of the roll. The stretched polyester film is stretched in the transverse direction by a tenter by heat treatment and relaxation treatment as needed. The stretched polyester film may be a uniaxially stretched film or a biaxially stretched film.

The manufacturing conditions for obtaining the polyester film can be appropriately set according to a conventional method. For example, the longitudinal stretching temperature and the lateral stretching temperature are usually 80 to 130 ° C, preferably 90 to 120 ° C. The stretching ratio is usually 1.0 to 3.5 times, preferably 1.0 to 3.0 times. Moreover, the horizontal extension ratio is usually 2.5~6.0 Times, preferably 3.0 to 5.5 times.

Controlling the retardation value to a specific range can be performed by appropriately setting the stretching ratio or the stretching temperature and the thickness of the film. For example, the higher the stretching ratio difference between the longitudinal stretching and the lateral stretching, the lower the stretching temperature, and the thicker the film thickness, the easier it is to obtain a high retardation value. Conversely, the lower the difference in stretch ratio between the longitudinal extension and the lateral extension, the higher the extension temperature, and the thinner the film thickness, the easier it is to obtain a low retardation value. Further, the higher the stretching temperature, the lower the total stretching ratio, and the film having a lower ratio of the retardation value to the thickness direction retardation value (Ro/Rt) is more easily obtained. Conversely, the lower the extension temperature, the higher the total stretching ratio, and the easier it is to obtain a film having a higher ratio of the retardation value to the thickness direction retardation value (Ro/Rt). Further, the heat treatment temperature is usually in the range of from 140 to 240 ° C, more preferably in the range of from 170 to 240 ° C.

The relaxation treatment temperature is usually in the range of 100 to 230 ° C, preferably in the range of 110 to 210 ° C, more preferably in the range of 120 to 180 ° C. The amount of relaxation is in the range of 0.1 to 20%, preferably in the range of 1 to 10%, more preferably in the range of 2 to 5%. The temperature and the amount of relaxation of the relaxation treatment are preferably such that the amount of slack and the temperature during the relaxation treatment are set such that the heat shrinkage ratio at 150 ° C of the polyester film after the relaxation treatment is 2% or less.

Further, in the uniaxial stretching treatment and the biaxial stretching treatment, after the lateral stretching, in order to alleviate the deformation of the alignment main shaft represented by the bending, the heat treatment and the stretching treatment can be performed again. The maximum value of the deformation of the alignment main axis due to the bending in the extending direction is preferably within 30 degrees, more preferably within 15 degrees, and even more preferably within 8 degrees. If the maximum value of the deformation of the alignment main shaft exceeds 30°, when the polarizing plate is formed and singulated in the subsequent steps, The optical characteristics are not uniform between the single sheets. The term "alignment axis" as used herein means extending the molecular alignment direction at any point on the polyester film. Further, the deformation of the alignment main axis with respect to the extending direction means the angular difference between the alignment main axis and the extending direction. Further, the maximum value means the maximum value of the value in the vertical direction with respect to the longitudinal direction. For example, a phase difference film, an optical material inspection device RETS (manufactured by Otsuka Electronics Co., Ltd.), or a molecular alignment meter MOA (manufactured by Oji Scientific Instruments Co., Ltd.) can be used.

In order to suppress the variation of the retardation value of the polyester film, it is preferred that the film spots are small. When the longitudinal stretching ratio is lowered in order to impart a delay value difference, the value of the vertical thickness spot (hereinafter also referred to as "thickness spot") may become high. Since the value of the longitudinal thickness spot is in a region where the stretching ratio becomes extremely high within a certain range, it is preferable to set the film forming conditions beyond these ranges.

The thickness of the stretched polyester film is preferably 5.0% or less, more preferably 4.5% or less, still more preferably 4.0% or less, and particularly preferably 3.0% or less.

The thickness of the film in the present invention can be measured by any means. For example, a strip sample (length: 3 m) is continuously taken in the film traveling direction, and a thickness of 100 points is measured at a pitch of 1 cm using a commercially available measuring instrument (for example, an electronic MICROMETER MILLITRON 1240 manufactured by SEIKO EM Co., Ltd.), and the maximum thickness is obtained. (dmax), the minimum value (dmin), and the average value (d), the thickness spot (%) can be calculated by the following formula.

Thickness spot (%) = ((dmax-dmin) / d) × 100

The thickness of the stretched polyester film is arbitrary, for example, in the range of 15 to 300 μm, preferably in the range of 30 to 200 μm, and particularly preferably When it is in the range of 60 to 80 μm, it is preferable because it can have both film formation and good visibility.

It is also possible to have a functional layer having various characteristics on at least one side of the stretched polyester film. As such functional layers, for example, a hard coat layer, an antiglare layer, an antireflection layer, a low reflection layer, a low reflection antiglare layer, an antireflection antiglare layer, an antistatic layer, a polysilicon layer, an adhesive layer, One or more selected from the group consisting of an antifouling layer, a fingerprint-resistant layer, a water-repellent layer, and a blue blocking layer. Further, from the viewpoint of obtaining an effect of further improving the color unevenness when viewed from the oblique direction, it is preferred to provide an antiglare layer, an antireflection layer, a low reflection layer, a low reflection antiglare layer or an antireflection antiglare layer.

When various functional layers are provided, it is preferred to provide an easy-adhesion layer on the surface of the stretched polyester film. At this time, based on the suppression of interference due to reflected light, the refractive index of the easily-adhesive layer is preferably adjusted to the vicinity of the multiplication and average of the refractive index of the functional layer and the refractive index of the extended polyester film. The refractive index adjustment of the easy-adhesion layer can be easily adjusted by a conventional method, for example, by containing titanium or zirconium or other metal species in the binder resin. The coating liquid used for the formation of the easy-adhesion layer is preferably an aqueous coating liquid containing at least one of a water-soluble or water-dispersible copolymerized polyester resin, an acrylic resin, and a polyurethane resin. For example, Japanese Patent No. 6-81714, Japanese Patent No. 3200929, Japanese Patent No. 3632204, Japanese Patent No. 4547644, Japanese Patent No. 4778971, and Japanese Patent No. In Japanese Patent No. 3,589, 927, Japanese Patent No. 3,589, 232, Japanese Patent No. 3,589, 233, Japanese Patent No. 3,900, 191, and Japanese Patent No. 4150982 A water-soluble or water-dispersible copolymerized polyester resin solution, an acrylic resin solution, a polyurethane resin solution, or the like.

(UV curable resin layer)

In the present invention, the first protective film preferably has a configuration of an ultraviolet curable resin layer.

1B is a polarizing plate (51) showing a configuration of a first protective film (52), a polarizer (53), and a second protective film (54), which is further provided on the upper portion of the first protective film (52) on the viewing side. An example of the configuration of the ultraviolet curable resin layer (55).

The details of the ultraviolet curable resin layer (hereinafter also referred to as hard coat layer) of the present invention will be described below.

The hard coat layer is a layer for the purpose of ensuring the hard coatability of the surface of the first protective film of the present invention, for example, a hard coat layer containing a UV curable resin and a photopolymerization initiator containing a resin which is cured by ultraviolet irradiation. The composition is coated and hardened to form.

The ultraviolet curable resin to which the present invention is applicable may, for example, be a compound having one or two or more unsaturated bonds, such as a compound having an acrylate functional group. Examples of the compound having one unsaturated bond are, for example, ethyl (meth)acrylate, ethylhexyl (meth)acrylate, styrene, methylstyrene, N-vinylpyrrolidone, and the like. Examples of the compound having two or more unsaturated bonds are, for example, polymethylolpropane tri(meth)acrylate, tripropylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, and pentaerythritol. (meth) acrylate, pentaerythritol tetra (A) Acrylate, dipentaerythritol hexa(meth) acrylate, dipentaerythritol penta (meth) acrylate, 1,6-hexanediol di(meth) acrylate, neopentyl glycol di(meth) acrylate An ester or the like and a polyfunctional compound modified with ethylene oxide or the like (abbreviation: EO) or a reaction product of the above polyfunctional compound with (meth) acrylate or the like (for example, poly(meth)acrylic acid of a polyhydric alcohol) Ester, etc.). In the present invention, the term "(meth)acrylate" means methacrylate or acrylate.

Among the above compounds, a polyester resin, a polyether resin, an acrylic resin, an epoxy resin, a urethane resin having a relatively low molecular weight (number average molecular weight of 300 to 80,000, preferably 400 to 5,000) having an unsaturated double bond An alkyd resin, a snail acetal resin, a polybutadiene resin, a polythiol polyolefin resin or the like can also be used as the above ultraviolet curable resin. Further, the resin in these cases contains all of the dimer, the oligomer, and the polymer other than the monomer.

Preferred compounds of the present invention are exemplified by compounds having three or more unsaturated bonds. When such a compound is used, the crosslinking density of the formed hard coat layer can be increased, and the hardness of the coating film can be made good.

Specifically, in the present invention, pentaerythritol triacrylate, pentaerythritol tetraacrylate, polyester polyfunctional acrylate oligomer (3-15 functional), urethane polyfunctional acrylate oligomer are preferably used in combination as appropriate. (3~15 functional) and so on.

The ultraviolet curable resin may be used in combination with a solvent-drying resin (a thermoplastic resin or the like which has a property of drying only a solvent added to adjust a solid component during coating to form a film). By using a solvent-drying resin in combination, it is possible to effectively prevent film defects on the coated surface. Can be combined with ultraviolet rays The solvent-drying resin to be used in combination with the curing resin is not particularly limited, and a general thermoplastic resin can be used.

The photopolymerization initiator is not particularly limited, and a known one can be used. Specific examples are acetophenones, benzophenones, M-benzoyl benzoate, and α-amidoxime esters. , thioxanthones, propiophenones, benzyl esters, benzoin, fluorenylphosphine oxides. Further, a light sensitizer is preferably used in combination, and specific examples thereof include, for example, n-butylamine, triethylamine, poly-n-butylphosphine, and the like.

As the photopolymerization initiator, when the ultraviolet curable resin is a resin having a radical polymerizable unsaturated group, it is preferred to use acetophenone, benzophenone, thioxanthone or benzoin alone or in combination. , benzoin methyl ether and the like. Further, when the ultraviolet curable resin is a resin having a cationically polymerizable functional group, it is preferred to use an aromatic diazo sulfonium salt, an aromatic sulfonium salt, an aromatic sulfonium salt, or a melamine as a photopolymerization initiator. a metal compound, a benzoin sulfonate or the like.

When the photopolymerization initiator used in the present invention is an ultraviolet curable resin having a radical polymerizable unsaturated group, it is preferably 1-hydroxyl based on the compatibility with the ultraviolet curable resin and the yellowing resistance. - cyclohexyl-phenyl ketone.

The content of the photopolymerization initiator in the composition for a hard coat layer is preferably from 1 to 10 parts by mass based on 100 parts by mass of the ultraviolet curable resin. When the amount is less than 1 part by mass, the hardness of the hard coat layer may not be a desired condition. When the amount is more than 10 parts by mass, the ionizing radiation may not reach the deep portion of the film to be coated, and the internal hardening may not be promoted, and the target hard coat may not be obtained. Layer table The expectation of the pencil hardness is the reason.

The lower limit of the content of the photopolymerization initiator is preferably 2 parts by mass, and more preferably the upper limit is 8 parts by mass. When the content of the photopolymerization initiator is within this range, the hardness distribution does not occur in the thickness direction, and it is easy to have a uniform hardness.

The composition for a hard coat layer may contain a solvent.

The solvent can be selected and used depending on the type and solubility of the resin component to be used, and examples thereof include ketones (for example, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, diacetone alcohol, etc.) and ethers. (e.g., dioxane, tetrahydrofuran, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, etc.), aliphatic hydrocarbons (e.g., hexane), alicyclic hydrocarbons (e.g., cyclohexane, etc.), aromatic hydrocarbons (e.g., toluene, xylene, etc.), halogenated hydrocarbons (e.g., dichloromethane, dichloroethane, etc.), esters (e.g., methyl acetate, ethyl acetate, butyl acetate, etc.), water, alcohols (e.g., ethanol) , isopropanol, butanol, cyclohexanol, etc.), cellosolve (such as methyl cellosolve, ethyl cellosolve, etc.), cellosolve acetate, and sulfoxide (such as dimethyl A hydrazine or the like (such as dimethylformamide, dimethylacetamide, etc.) may be a mixed solvent of these. In particular, in the present invention, it is preferably one of methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone of a ketone solvent, or at least for the reason of being excellent in compatibility with a resin and coating property. Containing such a mixture.

Or a composition for a hard coat layer may be added according to the purpose of improving hardness of a hard coat layer, suppressing hardening shrinkage, preventing adhesion, suppressing a refractive index, imparting anti-glare property, changing a surface property of a particle or a hard coat layer, and the like. Organic microparticles, inorganic microparticles, dispersants, surfactants, anti-static Electric agent, decane coupling agent, tackifier, coloring inhibitor, coloring agent (pigment, dye), antifoaming agent, leveling agent, flame retardant, ultraviolet absorber, adhesion promoter, polymerization inhibitor, antioxidant, Surface modifiers, etc. Further, the composition for a hard coat layer may be used by mixing a photosensitizer, and specific examples thereof include, for example, n-butylamine, triethylamine, poly-n-butylphosphine, and the like.

The method for preparing the composition for a hard coat layer is not particularly limited as long as the components can be uniformly mixed. For example, it can be carried out by a conventional device such as a paint shaker, a bead mill, a kneader or a kneader.

Further, the method of applying the composition for a hard coat layer to the first protective film of the present invention is not particularly limited, and examples thereof include a spin coating method, a dipping method, a spray method, and a die coating method. A conventional wet method such as a bar coating method, a roll coating method, a meniscus coating method, a soft printing method, a screen printing method, or a rapid coating method.

[2nd protective film]

The second protective film of the present invention is characterized by being a light transmissive film having a light transmittance of less than 50% at 380 nm. That is, in the ultraviolet region, it has a characteristic of having high ultraviolet absorbing energy.

Further, it is preferable that the second protective film is in a form composed of a cellulose resin or a form composed of a cycloolefin resin.

Further, it is preferable that the retardation value Ro (nm) in the in-plane of the film defined by the following formula (i) of the second protective film satisfies the condition specified by the following formula (iii) and is thicker than the film thickness defined by the following formula (ii) The retardation value Rt (nm) satisfies the condition defined by the following formula (iv).

(i) Ro = (n _{x -} n _y ) × d

(ii) Rt=((n _x +n _y )/2-n _z )×d

(iii) 0≦Ro≦20

(iv)|Rt|≦25

In the above formulas, n _x is the refractive index in the slow axis direction in the plane of the film, n _y is the refractive index in the direction perpendicular to the slow axis direction in the plane of the film, and n _z is the refractive index perpendicular to the direction of the film surface. d is the film thickness (nm).

The retardation value of the second protective film can be measured in accordance with a conventional method. Specifically, the retardation value Ro of the in-plane direction of the film and the retardation value Rt of the film thickness direction of the film can be automatically obtained by using an automatic birefringence meter Axo Scan (Axo Scan Mueller Matrix Polarimeter: Axo Matrix) at 23 ° C ‧55 In the environment of %RH, the refractive index nx, ny, and nz obtained by measuring the three-dimensional refractive index were calculated at a wavelength of 590 nm.

The retardation values expressed by the above formulas (iii) and (iv) are the retardation value Ro (nm) in the in-plane of the film defined by the above formula (i) and the film thickness direction defined by the above formula (ii). A protective film having a retardation value Rt (nm) of substantially zero. Here, the term is substantially zero with respect to the range of the Ro system 0≦Ro≦20, more preferably 0≦Ro≦15, and even more preferably 0≦Ro≦10. Further, the range of Rt is substantially zero system|Rt|≦25, more preferably |Rt|≦15, and even more preferably |Rt|≦20.

When the retardation value Ro of the film surface of the second protective film and the retardation value Rt of the film thickness direction are both substantially zero, the polarizing plate can be effectively prevented when the second protective film side is bonded to the liquid crystal cell. Light leakage when the black display of the obtained liquid crystal display device is displayed. And, because the second guarantee can be reduced Since the thickness of the protective film is made, it is preferable to make the polarizing plate and the liquid crystal display device thinner and lighter.

One of the features of the second protective film is a light transmissive film having a light transmittance of less than 50% at 380 nm.

The light transmittance of the second protective film of the present invention at a wavelength of 380 nm can be determined by measurement using an ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation, product name: V7100). The light transmittance at 380 nm is less than 50%, preferably less than 25%, more preferably less than 10%.

In the second protective film of the present invention, as a method of setting the light transmittance at 380 nm to less than 50%, it is effective to add an additive having light absorption at 380 nm to the film, and it is particularly effective to be added to the ultraviolet region. Absorbed UV absorber.

The details of the second protective film of the present invention will be further described below.

[Cellulose Resin Film]

One of preferred embodiments of the second protective film of the present invention is a cellulose resin film containing a cellulose resin.

The cellulose resin used for the second protective film of the polarizing plate is exemplified by a cellulose ester resin, a cellulose ether resin, a cellulose ether ester resin, and the like.

The cellulose ester used in the second protective film is not particularly limited, but as the cellulose ester, it may be a carboxylate having a carbon number of from 2 to 22, or an ester of an aromatic carboxylic acid, and particularly preferably a lower cellulose. Fatty acid esters.

The lower fatty acid in the lower fatty acid ester of cellulose means a fatty acid having 6 or less carbon atoms. The thiol group bonded to the hydroxy group may be a straight chain or a branched group, and may also form a ring. Further, it may be substituted with other substituents. When the degree of substitution is the same, the birefringence is lowered because the carbon number is large, and therefore it is selected as a ruthenium group having a carbon number of preferably 2 to 6 carbon atoms. Preferably, the cellulose ester has a carbon number of 2 to 4 and a carbon number of 2 to 3.

The cellulose ester may also be a thiol group derived from a mixed acid, and particularly preferably a fluorenyl group having 2 to 3 carbon atoms or 2 to 4 carbon atoms. The cellulose ester used in the present invention may be a propionate such as cellulose acetate propionate, cellulose acetate butyrate or cellulose acetate propionate butyrate which is bonded with propionate in addition to the ethyl acetate group. A mixed fatty acid ester of cellulose of an ester group or a butyrate group. Further, the butyl group forming the butyrate may be linear or branched. The cellulose ester preferably used in the present embodiment is, in particular, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate or cellulose acetate phthalate.

Further, the retardation value can be appropriately controlled by the kind of the above-mentioned mercapto group of the cellulose ester, the degree of substitution of the thiol group of the cellulose resin skeleton with respect to the piperanose ring, and the like.

The cellulose ester which is preferable in the present invention preferably satisfies the following formulae (A) and (B).

Formula (A) 2.0≦X+Y≦3.0

Equation (B)0≦Y≦2.0

In the above formula (A) and formula (B), X is an ethylidene group substitution degree, and Y is a substitution degree of a propyl group or a butyl group. A protective film suitable for producing a polarizing plate which satisfies the above-described formula 2 and exhibits excellent optical characteristics.

Among them, triacetyl cellulose and cellulose acetate propionate are particularly preferably used.

It is better to use 2.8 ≦ X ≦ 3.0 of triacetyl cellulose.

Cellulose acetate propionate, cellulose acetate butyrate is preferably 1.5 ≦ X ≦ 2.9, 0.1 ≦ Y ≦ 1.5, 2.8 ≦ X + Y ≦ 3.0. The method for determining the degree of substitution of thiol can be determined in accordance with ASTM-D817-96.

When the degree of substitution of the thiol group is too low, the number of unreacted sites of the hydroxyl group of the piperagose ring constituting the cellulose skeleton is increased, and the hydroxyl group is often left to have a delayed humidity change or a protective film for a polarizing plate. The ability to protect polarizers is reduced, so it is not good.

When the number average molecular weight of the cellulose ester used in the present invention is in the range of 60,000 to 300,000, the mechanical strength of the obtained film is high, which is preferable. Furthermore, it is preferably used in the range of 70,000 to 200,000.

The number average molecular weight of the cellulose ester can be determined by using a high-speed liquid chromatograph under the following conditions.

Solvent: Acetone

Pipe column: MPW×1 (TOSOH system)

Sample concentration: 0.2 (mass/volume)%

Flow rate: 1.0ml/min

Sample injection amount: 300μl

Standard sample: standard polystyrene

Temperature: 23 ° C

The cellulose as a raw material of the cellulose ester is not particularly limited, but may be exemplified by cotton linters, wood pulp, marijuana only, and the like. Further, the cellulose esters obtained by the above may be used in combination at any ratio.

When the cellulose ester is a anhydride (acetic anhydride, propionic anhydride, butyric anhydride) in a cellulose raw material, a solvent such as an organic acid of acetic acid or dichloromethane is used, and a reaction is carried out using a protic catalyst such as sulfuric acid. When the oxime agent is a ruthenium halide (CH ₃ COCl, C ₂ H ₅ COCl, C ₃ H ₇ COCl), a reaction is carried out using a basic compound such as an amine as a catalyst. Specifically, it can be synthesized by the method described in Japanese Laid-Open Patent Publication No. Hei 10-45804.

In the cellulose ester, the average degree of substitution of the thiol group at the 6 position of the preferred glucose unit is in the range of 0.5 to 0.9.

In the 6th position of the glucose unit constituting the cellulose ester, unlike the 2nd position and the 3rd position, a highly reactive primary hydroxyl group is present. The primary hydroxyl group preferentially forms a sulfate in the manufacture of a cellulose ester having sulfuric acid as a catalyst. Therefore, in the esterification reaction of cellulose, by increasing the amount of the catalyst sulfuric acid, the average degree of substitution of the 2 and 3 positions can be increased more than the 6-position of the glucose unit as compared with the usual cellulose ester. Further, if the cellulose is tolylized as necessary, since the hydroxyl group at the 6 position of the glucose unit can be selectively protected, the hydroxyl group at the 6 position is protected by the toluylation and esterified, and then the trimethylphenyl group is removed. (protecting group), and the average degree of substitution of 2 and 3 positions can be increased by 6 bits of the glucose unit. Specifically, a cellulose ester produced by the method described in JP-A-2005-281645 can also be preferably used.

In the case of acetaminophen, if the vinegarization rate is increased, the time of the acetification reaction must be prolonged. However, if the reaction time is too long, the decomposition of the acetaminophen cellulose is also caused, and the polymer chain is cleaved or the acetamino group is decomposed, which is a poor result. Therefore, in order to increase the degree of acetification and to suppress decomposition to a certain extent, it is necessary to set the reaction time within a certain condition range. When the reaction time is specified, the reaction conditions are various, and vary greatly depending on conditions such as a reaction apparatus or equipment, and thus are not appropriate means. As the polymer is decomposed, since the molecular weight distribution is broadened, in the case of the cellulose ester, the degree of decomposition can be defined by the ratio of the weight average molecular weight (Mw) / number average molecular weight (Mn) which is usually used. That is, by the acetification step of cellulose triacetate, the decomposition is not excessively excessively long, and the acetification is carried out in a sufficient time for the acetification reaction, so that the weight average molecular weight of one of the indexes of the reaction can be used ( The ratio of the ratio of Mw)/number average molecular weight (Mn).

One of the methods for producing a cellulose ester which can be suitably used in the present invention is exemplified below.

First, 100 parts by mass of cotton linters as a cellulose raw material were pulverized, 40 parts by mass of acetic acid was added, and the mixture was activated at 36 ° C for 20 minutes. Subsequently, 8 parts by mass of sulfuric acid, 260 parts by mass of acetic anhydride, and 350 parts by mass of acetic acid were added, and esterification was carried out at 36 ° C for 120 minutes. Next, after neutralizing with 11 parts by mass of a 24% magnesium acetate aqueous solution, saponification was carried out at 63 ° C for 35 minutes to obtain acetam cellulose. The obtained acetonitrile cellulose was stirred at room temperature for 160 minutes using a 10-fold aqueous solution of acetic acid (acetic acid: water = 1:1 (mass ratio)), filtered, and dried to prepare a purified acetonitrile cellulose having a degree of substitution of 2.75. . The acetonitrile cellulose Mn is 92,000. The Mw was 156,000 and the ratio of Mw/Mn was 1.7. Similarly, by adjusting the esterification conditions (for example, temperature, time, stirring) and hydrolysis conditions of the cellulose ester, it is possible to synthesize a cellulose ester having a different degree of substitution and a ratio of Mw/Mn. The ratio of the Mw/Mn ratio of the cellulose ester is preferably from 1.4 to 5.0.

Further, from the viewpoint of obtaining a cellulose ester of high quality, the cellulose ester which is preferably synthesized is purified to remove a low molecular weight component, and a component which is not vinegarized or has a low degree of acetification is removed by filtration.

Further, in the case of a mixed acid cellulose ester, it can be obtained by the method described in JP-A-10-45804.

Moreover, the quality of the cellulose ester is also affected by the trace amount of metal components in the cellulose ester. These are considered to be related to the water quality used in the manufacturing step, but the fewer the components that may become insoluble cores, the better the metal ions of iron, calcium, magnesium, etc., and the polymer having the possibility of containing an organic acidic group. The decomposition product or the like forms a salt and forms an insoluble matter, which is less preferable. The iron (Fe) component is preferably 1 ppm or less. In the calcium (Ca) component, a complex compound derived from an acidic component such as a carboxylic acid or a sulfonic acid and a complex compound with a plurality of ligands is easily formed, and a precipitate derived from a large amount of insoluble calcium is formed (insoluble precipitation, turbidity) ), so it is better to remove.

The calcium (Ca) component is 60 ppm or less, preferably 0 to 30 ppm. The magnesium (Mg) component is preferably from 0 to 70 ppm, particularly preferably from 0 to 20 ppm, since it is insoluble as much as possible. The metal component such as the content of iron (Fe), the content of calcium (Ca), and the content of magnesium (Mg) can be decomposed by sulfuric acid by using the dried cellulose ester in a micro-digestive wet decomposition apparatus to form a base. After pre-treatment by melting, ICP-AES (inductively coupled plasma luminescence splitting) Analysis device) obtained by analysis.

The cellulose resin to be applied to the second protective film is, for example, a cellulose ether resin or a cellulose ether ester resin, in addition to the cellulose ester resin described above.

The cellulose ether resin is one in which a part or all of the hydroxyl group of the cellulose is substituted with an alkoxy group. The carbon number of the alkoxy group is not particularly limited, but is preferably in the range of 2 to 20. Examples of such an alkoxy group include a methoxy group, an ethoxy group, a propoxy group, a butoxy group and the like, and a methoxy group or an ethoxy group is preferred, and an ethoxy group is more preferred. The alkoxy group contained in the cellulose ether resin may be one type or two or more types.

Specific examples of the cellulose ether resin include methyl cellulose, ethyl cellulose, and the like, and ethyl cellulose is preferred.

The total degree of substitution of the alkoxy group of the cellulose ether resin is not particularly limited, and may be 1.5 or more, less than 3.0, preferably 2.0 or more, less than 3.0, more preferably 2.5 or more, and 2.9 or less. The degree of substitution of the alkoxy group can be determined by the method described in ASTM D4794-94.

The weight average molecular weight, molecular weight distribution, and the like of the cellulose ether resin can be adjusted to the same range as the cellulose ester resin.

In addition, a cellulose ether resin, a cellulose ether ester resin, or a cellulose ester described in, for example, JP-A-2007-56787, JP-A-2007-99876, JP-A-2005-83997, and the like can be used. The resin is also used.

(Additive for cellulose resin film)

In the cellulose resin film constituting the second protective film of the present invention, various additives can be used depending on the purpose.

<delay reducing agent 1: sugar ester>

The second protective film of the polarizing plate preferably contains a retardation reducing agent together with the cellulose ester.

The retardation reducing agent may be a compound (A) having one furanose structure or a gellanose structure or at least one compound having two or more and 12 or less bonded furanose structures or a gellanose structure (B) a sugar ester or a sugar ester compound of a compound in which all or a portion of the OH group is esterified with an aliphatic thiol group.

Preferred examples of the compound (A) and the compound (B) are exemplified below, but the present invention is not limited thereto.

Examples of the compound (A) are glucose, galactose, maltose, fructose, xylose, arabinose and the like. Further, the compound (A) also contains maltitol which can be reduced by hydrogenation of maltose by a high pressure.

Examples of the compound (B) are lactose, sucrose, cellobiose, maltose, cellotriose, maltotriose, sucrose, and cane trisaccharide. In the compound (A) and the compound (B), it is particularly preferred to have both a furanose structure and a pumose structure. An example of this is sucrose.

The monocarboxylic acid used in the synthesis of the sugar ester is not particularly limited, and a conventional fatty acid monocarboxylic acid, alicyclic monocarboxylic acid or the like can be used. The carboxylic acid to be used may be one type or a mixture of two or more types.

Preferred aliphatic monocarboxylic acids are, for example, acetic acid, Propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, heptanoic acid, caprylic acid, capric acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecanoic acid, lauric acid, tridecanoic acid, Myristic acid, pentadecanoic acid, palmitic acid, heptadecanoic acid, stearic acid, nonadecanic acid, alginic acid, behenic acid, lauric acid, waxic acid, heptacosic acid, montanic acid, bee Saturated fatty acids such as folic acid and lacquer acid, unsaturated fatty acids such as undecylenic acid, oleic acid, sorbic acid, linoleic acid, linolenic acid, arachidonic acid, and octenoic acid.

Preferred examples of the alicyclic monocarboxylic acid include cyclopentanecarboxylic acid, cyclohexanecarboxylic acid, cyclooctanecarboxylic acid or the like.

The details of the production method of the above-mentioned compounds are described, for example, in Japanese Laid-Open Patent Publication No. Hei 8-245678.

In addition to the esterified compound of the above compound (A) and the compound (B), at least one compound having at least one of a furanose structure or a gellanose structure bonded to 3 to 12 may be used as the esterified compound of the oligosaccharide.

Oligosaccharides are produced by the action of enzymes such as amylase on starch, sucrose, and the like. Examples of the oligosaccharide which can be suitably used in the present invention include malto-oligosaccharide, isomaltoligosaccharide, milk oligosaccharide, galactooligosaccharide, and xylooligosaccharide. The oligosaccharide can also be esterified in the same manner as the above compound (A) and compound (B).

Next, an example of a production example of a sugar ester is shown. Acetic anhydride (200 ml) was added dropwise to a solution of pyridine (100 ml) added to glucose (29.8 g, 166 mmol) for 24 hours. Subsequently, the solution was concentrated with a rotary evaporator and placed in ice water. After standing for 1 hour, it was filtered through a glass filter, and the solid and water were separated, and the solid on the glass filter was dissolved in chloroform, and the mixture was cooled to a neutral state. After separating the organic layer, dry it with anhydrous sodium sulfate dry. After removing anhydrous sodium sulfate by filtration, chloroform was removed by a rotary evaporator, and then glucose pentaacetate (58.8 g, 150 mmol, 90.9%) was obtained by drying under reduced pressure. Further, the above monocarboxylic acid may be used instead of the above acid anhydride.

Specific examples of the sugar ester compound which can be used in the present invention are exemplified below, but the present invention is not limited thereto.

In order to suppress the deterioration of the polarizing function and the stability of the display quality, the second protective film preferably contains the above-mentioned sugar ester compound in the range of 1 to 35% by mass, particularly 5 to 30% by mass. According to this range, the excellent object effect of the present invention is exhibited and laminated in a roll form In the state in which the green sheet is stored, it is preferable that it does not bleed out or the like. Further, a sugar ester compound in which all of the OH is esterified and a sugar ester compound in which one or more OH groups remain may be used in combination. For example, a mixture of sucrose octaacetate, sucrose heptaacetate, sucrose hexaacetate or the like can be mentioned. The mixing ratio is not particularly limited, but examples are, for example, 30:30:30, 40:30:30, 40:50:10, 50:30:20, 60:30:10, 80:10:10, 90:7. :3, 95:5:0 and so on. These may be controlled by adjusting the reaction time in the esterification of the sugar or the amount of the monocarboxylic acid reacted with the sugar, or may be mixed individually.

(delay reducing agent 2: acrylic polymer)

An acrylic polymer having a number average molecular weight of 500 or more and 30,000 or less may be contained as the second retardation reducing agent in the second protective film. As such an acrylic polymer, those described in paragraphs [0059] to [0093] of International Publication No. WO 2008/044463 can be preferably used.

(delay reducing agent 3: polyester)

The second protective film may further contain a polyester represented by the following formula (B1) or (B2) as a third retardation reducing agent. These are derived from a divalent alcohol G having a carbon number of 2 to 12 and a 2 base acid having a carbon number of 2 to 12, a monocarboxylic acid B _{1 having a} carbon number of 1 to 12, or a B _{2 having} a monool having a carbon number of 1 to 12. Polyester.

Formula (B1)B ₁ -(GA-) _m GB ₁

In the above formula (B1), B ₁ represents a monocarboxylic acid having 1 to 12 carbon atoms, G represents a divalent alcohol having 2 to 12 carbon atoms, and A represents a 2-base acid having 2 to 12 carbon atoms. The ratio of the aromatic rings of any of B ₁ , G, and A is small or particularly excellent. m represents the number of repetitions.

General formula (B2)B ₂ -(AG-) _n AB ₂

In the above formula (B2), B ₂ represents a monohydric alcohol having 1 to 12 carbon atoms, G represents a divalent alcohol having 2 to 12 carbon atoms, and A represents a 2-base acid having 2 to 12 carbon atoms. The ratio of the aromatic ring of any of B ₂ , G, and A is small or particularly excellent. n represents the number of repetitions.

In the general formula (B1), the monocarboxylic acid represented by B ₁ is not particularly limited, and a conventional fatty acid monocarboxylic acid or alicyclic monocarboxylic acid can be preferably used.

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 linear or side chain having 1 to 32 carbon atoms can be preferably used. More preferably, the carbon number is 1 to 20, and the carbon number is preferably 1 to 12. When acetic acid is contained, it is preferred because it has an increased compatibility with the cellulose ester, and acetic acid and other monocarboxylic acids are preferably used in combination.

Preferred aliphatic monocarboxylic acids are, for example, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, heptanoic acid, caprylic acid, capric acid, capric acid, 2-ethyl-hexanecarboxylic acid, eleven Alkanoic acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, heptadecanoic acid, stearic acid, nonadecanic acid, alginic acid, behenic acid, lauric acid, waxy acid , saturated fatty acid such as heptacosanoic acid, montanic acid, melamine acid, lacquer acid, etc., undecylenic acid, oil An unsaturated fatty acid such as acid, sorbic acid, linoleic acid, linolenic acid or arachidonic acid.

In the general formula (B2), the monool component represented by B ₂ is not particularly limited, and a conventional alcohol can be used. For example, a linear or branched aliphatic aliphatic alcohol or an aliphatic unsaturated alcohol having a carbon number of 1 to 32 can be preferably used. The better carbon number is 1~20, especially the carbon number is 1~12.

In the general formula (B1) and the general formula (B2), the divalent alcohol component represented by G may be, for example, the following, but the present invention is not limited thereto. For example, ethylene glycol, diethylene glycol, 1,2-propylene glycol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1, 5-pentanediol, 1,6-hexanediol, 1,5-pentanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, etc., among which ethylene glycol can be preferably used. 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, Triethylene glycol is more preferably used as 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, or diethylene glycol.

In the general formula (B1) and the general formula (B2), the two-base acid (dicarboxylic acid) component represented by A is preferably an aliphatic two-base acid or an alicyclic two-base acid, for example, as a fat. Family 2 base acid, using malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedicarboxylic acid, dodecane As the carboxylic acid or the like, in particular, as the fatty acid dicarboxylic acid, those having 4 to 12 carbon atoms can be used, and at least one selected from them can be used. In other words, two or more kinds of two-base acids may be used in combination. In this case, an aromatic dicarboxylic acid such as phthalic acid, isophthalic acid or terephthalic acid may be used in combination.

m and n each represent a repeating number, and are preferably 1 or more and 170 or less.

The number average molecular weight of the polyester is preferably 20,000 or less, more preferably 10,000 or less. In particular, the polyester having a number average molecular weight of from 500 to 10,000 has good compatibility with the cellulose ester, and is preferably less likely to cause evaporation or volatilization during film formation.

Polycondensation of polyester is carried out by a conventional method. For example, by the direct reaction of the above 2-base acid with a diol, the above two base acid or the alkyl ester of such a base acid such as a 2-base acid methyl ester and a glycol, or a transesterification reaction The condensation method, or any method of reacting the ruthenium chloride of the acid with the dehydrohalogenation of the diol, is easy to synthesize, but the polyester having a number average molecular weight of not too large is preferably a direct reaction. The polyester having a high distribution on the low molecular weight side has a very good compatibility with the cellulose ester, and after the film is formed, a second protective film having a small moisture permeability and excellent transparency can be obtained.

The method of adjusting the molecular weight can be carried out by a conventional method without particular limitation. For example, depending on the polymerization conditions, in the method of blocking the terminal of the molecule with a monovalent acid (monocarboxylic acid) or a monovalent alcohol (monool), the molecular weight can be adjusted by controlling the amount of the monovalent compound added. . In this case, from the viewpoint of the stability of the polymer, a monovalent acid is preferred.

For example, as the monovalent acid, acetic acid, propionic acid, butyric acid or the like can be exemplified as a preferred example, but it may be selected not to be distilled off to the outside of the system in the polycondensation reaction, but to be stopped outside the reaction system. When the valence acid is removed to the outside of the system, it is easy to distill off, and it may be mixed and used. And in the case of direct reaction, the time at which the reaction is stopped is calculated by the amount of water distilled in the reaction, The number average molecular weight can be adjusted. Alternatively, it may be adjusted by biasing the amount of the diol or the 2-base acid which is fed, or by controlling the reaction temperature.

In the present invention, the polyester is preferably contained in an amount of from 1 to 40% by mass based on the total mass of the second protective film. Further, it is preferably contained in the range of 2 to 30% by mass. It is particularly preferably contained in the range of 3 to 15% by mass.

By using a film to which the above acrylic polymer or polyester is added, a polarizing plate which is less deteriorated by high temperature and high humidity can be obtained. Further, by using the polarizing plate, an IPS mode liquid crystal display device which maintains contrast or viewing angle stability for a long period of time and is excellent in surface planarity can be obtained.

<plasticizer>

The second protective film constituting the polarizing plate of the present invention may contain a plasticizer as needed. The plasticizer is not particularly limited, and is preferably a polyvalent carboxylate plasticizer, a glycolic acid plasticizer, a phthalate plasticizer, a fatty acid ester plasticizer, and a polyvalent alcohol ester plasticizer. , polyester plasticizers, acrylic plasticizers, etc. Moreover, these plasticizers sometimes act as a retardation reducing agent.

The glycolate-based plasticizer is not particularly limited, but an alkyl phthalic acid alkyl glycolate can be preferably used. Examples of the alkylphthalic alkyl alcohol glycolate are, for example, methyl phthalic acid methyl glycolate, ethyl phthalic acid ethyl glycolate, and propyl benzyl methacrylate. Glycolate, butyl phthalic acid butyl glycolate, octyl phthalyl octyl glycolate, methyl phthalic acid ethyl glycolate, ethyl phthalic acid Methyl glycolate, ethyl phthalic acid propyl glycolate, Methyl phthalic acid butyl glycolate, ethyl phthalic acid butyl glycolate, butyl phthalic acid methyl glycolate, butyl phthalic acid ethyl glycolic acid Ester, propyl phthalic acid butyl glycolate, butyl phthalic acid propyl glycolate, methyl phthalic acid octyl glycolate, ethyl phthalic acid Glycolate, octylphthalimyl methyl glycolate, octylphthalidyl ethyl glycolate, and the like.

Examples of the phthalate-based plasticizer are, for example, diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, ortho-benzene. Dibutyl formate, di-2-ethylhexyl phthalate, dioctyl phthalate, dicyclohexyl phthalate, dicyclohexyl terephthalate, and the like.

The citrate type plasticizer is exemplified by, for example, trimethyl citrate, triethyl citrate, tributyl citrate, and the like.

The fatty acid ester-based plasticizer is exemplified by, for example, butyl oleate, methyl phthalate of ricinoleic acid, dibutyl sebacate, and the like.

Examples of the phosphate-based plasticizer are triphenyl phosphate, tricresyl phosphate, tolyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, and trioctyl phosphate. , tributyl phosphate, and the like.

The polyvalent carboxylate compound is formed from an ester of a polyvalent carboxylic acid and an alcohol in a range of two or more valences, preferably 2 to 20 valence. Further, the aliphatic polyvalent carboxylic acid is preferably in the range of 2 to 20, and preferably in the range of 3 to 20 in the case of the aromatic polyvalent carboxylic acid or the alicyclic polyvalent carboxylic acid.

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

General formula (C)R ₂ (COOH) _m (OH) _n

In the general formula (C), R ₂ is a (m + n) valent organic group, m is a positive integer of 2 or more, n is an integer of 0, COOH group is a carboxyl group, OH group an alkoxy or phenolic hydroxyl group .

Examples of preferred polyvalent carboxylic acids include the following, but the present invention is not limited to these. A polyvalent carboxylic acid having a valence of 3 or more, such as benzoic acid, trimesic acid or pyromellitic acid, or a derivative thereof, such as succinic acid, adipic acid, sebacic acid or sebacic acid, can be preferably used. An aliphatic polyvalent carboxylic acid of oxalic acid, fumaric acid, maleic acid or tetrahydrophthalic acid, an oxygen polyvalent carboxylic acid such as tartaric acid, propanol diacid, malic acid or citric acid. The oxygen polyvalent carboxylic acid is preferably used in particular from the viewpoint of improving retention and the like.

The term "retention" as used in the present invention means a property of reducing the quality of a film by precipitation or volatilization of an additive such as a plasticizer or the like, and specifically, the sample is allowed to stand at 23 ° C, 55% RH for 1 day. The mass was then placed in an environment of 80 ° C and 90% RH for 2 weeks, and the sample which was further left for 2 weeks was allowed to stand in an environment of 23 ° C and 55% RH for 1 day, and the mass was measured, and the mass change ratio was determined. As a measure of retention.

The alcohol to be used as the polyvalent carboxylate is not particularly limited, and conventional alcohols and phenols can be used. For example, a linear or branched aliphatic saturated alcohol or an aliphatic unsaturated alcohol having a carbon number of 1 to 32 can be preferably used. More preferably, the carbon number is 1 to 20, and the carbon number is preferably 1 to 10. Further, an alicyclic alcohol such as cyclopentanol or cyclohexanol or a derivative thereof, benzyl alcohol, cinnamitol or the like can be preferably used. An aromatic alcohol or a derivative thereof.

When an oxygen polyvalent carboxylic acid is used as the polyvalent carboxylic acid, the alcoholic or phenolic hydroxyl group of the oxygen polyvalent carboxylic acid may be esterified with a monocarboxylic acid. As a preferable example of the monocarboxylic acid, the following are exemplified, but the present invention is not limited to these.

As the aliphatic monocarboxylic acid, a linear or branched fatty acid having 1 to 32 carbon atoms can be preferably used, more preferably 1 to 20 carbon atoms, and particularly preferably 1 to 10 carbon atoms.

Preferred aliphatic monocarboxylic acids are exemplified by acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, heptanoic acid, caprylic acid, capric acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecanoic acid, and laurel. Acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, heptadecanoic acid, stearic acid, nonadecanic acid, alginic acid, behenic acid, lauric acid, wax acid, twenty-seven Saturated fatty acids such as alkanoic acid, montanic acid, melamine acid, and lacquer acid, unsaturated fatty acids such as undecylenic acid, oleic acid, sorbic acid, linoleic acid, linolenic acid, and arachidonic acid.

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

Examples of the preferred aromatic monocarboxylic acid include benzoic acid, toluic acid, etc., which are introduced into a benzene ring of benzoic acid, a biphenyl carboxylic acid, a tetrahydronaphthalene carboxylic acid, or the like. More than one aromatic carboxylic acid of a benzene ring, or a derivative thereof. In particular, propionic acid and benzoic acid are preferred.

The molecular weight of the polyvalent carboxylate is not particularly limited, and the molecular weight is preferably in the range of 300 to 1,000, more preferably in the range of 350 to 750. From the viewpoint of improving retention, it is preferably preferred because it is based on moisture permeability and compatibility with cellulose ester.

The alcohol to be used in the polyvalent carboxylic acid ester may be one type or two or more types.

The acid value of the polyvalent carboxylic acid ester is preferably 1 mgKOH/g or less, more preferably 0.2 mgKOH/g or less. By setting the acid value within the above range, it is preferable because the environmental variation of the retardation can also be suppressed.

The acid value means the number of milligrams of potassium hydroxide necessary for neutralizing the acid contained in 1 g of the sample (the carboxyl group present in the sample). The acid value is determined in accordance with JIS K0070.

Examples of the particularly preferable polyvalent carboxylate compound are shown below, but the present invention is not limited thereto. Examples are, for example, triethyl toluenesulfonate, tributyl toluenesulfonate, etidyltriethyl toluenesulfonate (abbreviation: ATEC), etidinyl toluenesulfonate (abbreviation: ATBC), toluenesulfonic acid Benzopyridyl tributyl ester, etidyltriphenyl tosylate, ethyltribenzyl tosylate, dibutyl tartrate, dibutyl butyl tartrate, tributyl trimellitate, Tetrabutyl pyromellitate and the like.

The polyester-based plasticizer is not particularly limited, but a polyester-based plasticizer having an aromatic ring or a cycloalkyl ring in the molecule can be used. The polyester-based plasticizer is not particularly limited, and examples thereof include an aromatic terminal ester-based plasticizer represented by the following formula (D).

Formula _{(D) B- (GA) n} -GB

In the above formula (D), B represents a benzene monocarboxylic acid residue, and G represents an alkylene glycol residue having 2 to 12 carbon atoms or an aryl glycol residue having 6 to 12 carbon atoms or a carbon number. 4 to 12 oxyalkylene glycol residues, A represents an alkyl dicarboxylic acid residue having 4 to 12 carbon atoms or an aryl dicarboxylic acid residue having 6 to 12 carbon atoms, and n represents an integer of 1 or more.

The compound represented by the formula (D) is a benzene monocarboxylic acid residue represented by B and an alkylene glycol residue represented by G, an oxyalkylene glycol residue or an aryl diol residue and represented by A. The alkyl dicarboxylic acid residue can be obtained by the same reaction as a usual polyester plasticizer.

The benzene monocarboxylic acid component as the polyester-based plasticizer is, for example, benzoic acid, p-t-butylbenzoic acid, o-toluic acid, m-toluic acid, p-toluic acid, dimethylbenzoic acid, ethylbenzoic acid, and For example, propylbenzoic acid, aminobenzoic acid, ethoxylated benzoic acid, and the like may be used alone or as a mixture of two or more.

Examples of the alkanediol component having 2 to 12 carbon atoms as the polyester-based plasticizer are, for example, ethylene glycol, 1,2-propylene glycol, 1,3-propanediol, 1,2-butanediol, and 1,3-butylene. Alcohol, 1,2-propanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (new Pentanediol), 2,2-diethyl-1,3-propanediol (3,3-dihydroxymethylpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3, 3-dimethylol heptane), 3-methyl-1,5-pentanediol, 1,6-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, 2 -ethyl-1,3-hexanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-nonanediol, 1,12-octadecanediol The diol may be used alone or in combination of two or more. In particular, an alkanediol having 2 to 12 carbon atoms is particularly excellent in compatibility with a fiber plastic ester.

Further, as the aromatic terminal ester, the carbon number 4 to 12 oxyalkylene glycol component is, for example, diethylene glycol, triethylene glycol, tetraethylene glycol, or dipropylene. For the diol, the tripropylene glycol, and the like, the diols may be used alone or in combination of two or more.

The aromatic terminal ester has a carbon number of 4 to 12 alkyl dicarboxylic acid components such as succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, sebacic acid, sebacic acid, and dodecane dicarboxylic acid. For the acid or the like, one type may be used or a mixture of two or more types may be used. Examples of the aryldicarboxylic acid component having 6 to 12 carbon atoms include phthalic acid, terephthalic acid, isophthalic acid, 1,5-naphthalene dicarboxylic acid, and 1,4-naphthalenedicarboxylic acid.

The number average molecular weight of the polyester-based plasticizer is preferably from 300 to 1,500, more preferably from 400 to 1,000. Further, the acid value is 0.5 mgKOH/g or less, the hydroxyl value is 25 mgKOH/g or less, more preferably 0.3 mgKOH/g or less, and the hydroxyl value is 15 mgKOH/g or less.

A synthesis example of an aromatic terminal ester-based plasticizer which can be used in the present invention is shown below.

(Sample No. 1 (aromatic terminal ester sample))

410 parts of phthalic acid, 610 parts of benzoic acid, 737 parts of dipropylene glycol, and 0.40 parts of tetraisopropyl titanate as a catalyst were fed together in a reaction vessel, and stirred under a nitrogen stream with a reflux condenser. The excess monovalent alcohol was continuously heated at a temperature of from 130 to 250 ° C until the acid value became 2.0 mgKOH/g or less, and the generated water was continuously removed. Next, the distillation fraction was removed under a reduced pressure of 1.33 × 10 ⁴ Pa to a final 4 × 10 ² Pa at a temperature ranging from 200 to 230 ° C, followed by filtration to obtain a sample No. of the aromatic terminal ester having the following properties. .1.

Viscosity (25 ° C, mPa ‧ s): 43400

Acid value (mgKOH/g): 0.2

(Sample No. 2 (aromatic terminal ester sample))

In the same manner as in sample No. 1, except that 410 parts of phthalic acid, 610 parts of benzoic acid, 341 parts of ethylene glycol, and 0.35 parts of tetraisopropyl titanate as a catalyst were used in the reaction container, Sample No. 2 of the aromatic terminal ester of the following character.

Viscosity (25 ° C, mPa ‧ s): 31000

Acid value (mgKOH/g): 0.1

(Sample No. 3 (aromatic terminal ester sample))

The same as Sample No. 1, except that 410 parts of phthalic acid, 610 parts of benzoic acid, 418 parts of 1,2-propanediol, and 0.35 parts of tetraisopropyl titanate as a catalyst were used in the reaction container. Sample No. 3 having an aromatic terminal ester having the following properties was obtained.

Viscosity (25 ° C, mPa ‧ s): 38000

Acid price: 0.05

(Sample No. 4 (aromatic terminal ester sample))

In addition to the reaction vessel, 410 parts of phthalic acid and benzoic acid were used. An aromatic terminal ester having the following properties was obtained in the same manner as in Sample No. 1 except that 610 parts, 418 parts of 1,3-propanediol, and 0.35 parts of tetraisopropyl titanate as a catalyst.

Viscosity (25 ° C, mPa ‧ s): 37000

Acid value (mgKOH/g): 0.05

Hereinafter, specific compounds of the aromatic terminal ester-based plasticizer which can be used in the present embodiment are shown, but the present invention is not limited thereto.

(UV absorber)

The second protective film of the present invention contains an ultraviolet absorber and is the most effective means for making the light transmittance at 380 nm less than 50%.

The ultraviolet absorber absorbs ultraviolet rays of 400 nm or less, and for the purpose of improving durability, the transmittance at a wavelength of 380 nm is particularly preferably 25% or less, more preferably 10% or less, still more preferably 5% or less.

The ultraviolet absorber to be used is not particularly limited, and examples thereof include, for example, an oxybenzophenone compound, a benzotriazole compound, a salicylate compound, a benzophenone compound, and a cyanoacrylate compound. A triazine compound, a nickel salt fault compound, an inorganic powder or the like.

As the ultraviolet absorber applicable to the present invention, for example, 5-chloro-2-(3,5-di-secondbutyl-2-hydroxyphenyl)-2H-benzotriazole, (2-2H-benzo) Triazol-2-yl)-6-(linear and side chain dodecyl)-4-methylphenol, 2-hydroxy-4-benzyloxybenzophenone, 2,4-benzyloxy Benzophenone, etc., and TINUVIN class of TINUVIN 109, TINUVIN 171, TINUVIN 234, TINUVIN 326, TINUVIN 327, TINUVIN 328, TINUVIN 928, etc., all of which are commercially available from BASF Corporation of Japan, and preferably use.

The ultraviolet absorber which is preferably used is a benzotriazole-based ultraviolet absorber, a benzophenone-based ultraviolet absorber, a triazine-based ultraviolet absorber, a benzotriazole-based ultraviolet absorber, and a benzophenone-based system. UV absorber.

For example, a compound represented by the following formula (b) can be used as the benzotriazole-based ultraviolet absorber.

In the above formula (b), R ₁ , R ₂ , R ₃ , R ₄ and R ₅ may be the same or different and each represents a hydrogen atom, a halogen atom, a nitro group, a hydroxyl group, an alkyl group, an alkenyl group, an aryl group, alkoxy, acyl, aryloxy, alkylthio, arylthio, mono- or dialkylamino, acyl group or a 5- to 6-membered heterocyclic group, R ₄ and R ₅ may be closed Form a 5-6 member carbon ring. Further, the above-described groups may have any substituent.

Hereinafter, specific examples of the benzotriazole-based ultraviolet absorber are exemplified, but the present invention is not limited to these.

UV-1: 2-(2'-hydroxy-5'-methylphenyl)benzotriazole

UV-2: 2-(2'-hydroxy-3',5'-di-t-butylphenyl)benzotriazole

UV-3: 2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)benzotriazole

UV-4: 2-(2'-hydroxy-3',5'-di-t-butylphenyl)-5-chlorobenzotriazole

UV-5: 2-(2'-hydroxy-3'-(3",4",5",6"-tetrahydrobenzidine imine methyl)-5'-methylphenyl)benzotrien Azole

UV-6: 2,2-methylenebis(4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol)

UV-7: 2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)-5-chlorobenzotriazole

UV-8: 2-(2H-benzotriazol-2-yl)-6-(linear and side chain dodecyl)-4-methylphenol (trade name: TINUVIN 171, manufactured by BASF Corporation, Japan)

UV-9: Octyl-3-[3-t-butyl-4-hydroxy-5-(chloro-2H-benzotriazol-2-yl)phenyl]propionate and 2-ethylhexyl- Mixture of 3-[3-t-butyl-4-hydroxy-5-(5-chloro-2H-benzotriazol-2-yl)phenyl]propionate (trade name: TINUVIN 109, Japan BASF Corporation system)

Further, as the benzophenone-based ultraviolet absorber, a compound represented by the following formula (c) is preferably used.

In the above formula (c), Y represents a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an alkoxy group or a phenyl group, and the alkyl group, the alkenyl group and the phenyl group may have a substituent. A represents a hydrogen atom, an alkyl group, an alkenyl group, a phenyl group, a cycloalkyl group, an alkylcarbonyl group, an alkanesulfonyl group or a CO(NH) _n-1 -D group, and D represents an alkyl group, an alkenyl group or may have a substituent. Phenyl. m and n represent 1 or 2.

In the above, the alkyl group means, for example, a straight or branched aliphatic group having a carbon number of at most 24, the alkoxy group, for example, an alkoxy group having a carbon number of at most 18, and the alkenyl group, for example, an alkenyl group having a carbon number of at most 16, Express Allyl, 2-butenyl. Further, examples of the substituent of the alkyl group, the alkenyl group and the phenyl group include a halogen atom such as a chlorine atom, a bromine atom, a fluorine atom, a hydroxyl group, a phenyl group (the phenyl group may be substituted by an alkyl group or a halogen atom), and the like. .

Specific examples of the benzophenone-based ultraviolet absorber represented by the general formula (o) are shown below, but the present invention is not limited to these.

UV-10: 2,4-dihydroxybenzophenone

UV-11: 2,2'-dihydroxy-4-methoxybenzophenone

UV-12: 2-hydroxy-4-methoxy-5-sulfobenzophenone

UV-13: bis(2-methoxy-4-hydroxy-5-benzylidene methane)

Further, a discotic compound having a compound such as a 1,3,5-triazine ring or the like can be preferably used as an ultraviolet absorber.

In the present invention, as the ultraviolet absorber, especially "2-(2H-benzotriazol-2-yl)-6-(1-methyl-1-phenylethyl)-4- shown below) (1,1,3,3-tetramethylbutyl)phenol (trade name: TINUVIN 928, manufactured by BASF Corporation of Japan) can provide the second protective film of the present invention with both ultraviolet absorbing property and low retardation. The film is therefore preferably used.

The second protective film of the present invention may contain two or more kinds of ultraviolet absorbers.

Further, as the ultraviolet absorber, a polymer ultraviolet absorber can be preferably used, and in particular, a polymer type ultraviolet absorber described in JP-A-6-148430 can be preferably used.

The ultraviolet absorber is added by adding an ultraviolet absorber to an alcohol such as methanol, ethanol or butanol, or a solvent such as dichloromethane, methyl acetate, acetone or dioxane or a mixed solvent thereof. In the liquid, or directly added to the dope composition. If the inorganic fine particles are not dissolved in the organic solvent, it is preferably a method in which the organic solvent or the cellulose ester is dispersed in a dissolving device or a sand mill and then added to the dope.

The amount of the ultraviolet absorber to be used varies depending on the type of the ultraviolet absorber, the use conditions, and the like. However, when the dry film thickness of the second protective film is in the range of 10 to 100 μm, the total mass of the second protective film is preferably 0.5. Within the range of ~10% by mass, more preferably in the range of 0.6% to 4% by mass.

<microparticle>

The second protective film may contain fine particles. As the fine particles, examples of the inorganic fine particles include, for example, cerium oxide, titanium oxide, aluminum oxide, zirconium oxide, calcium carbonate, talc, clay, calcined kaolin, calcined calcium citrate, calcium citrate hydrate, aluminum silicate, and cerium. Magnesium acid and calcium phosphate. The inorganic fine particles contain a fine one, and it is preferable from the viewpoint that the turbidity becomes low, and particularly preferably cerium oxide. The term "fine particles" as used in the present invention means particles in which the average particle diameter of the primary particles is in the range of 5 to 400 nm.

The average particle diameter of the primary particles of the fine particles is preferably from 5 to 400 nm, more preferably from 10 to 300 nm. These may be mainly contained in a secondary aggregate having a particle diameter of 0.05 to 0.3 μm, and particles having an average particle diameter of 100 to 400 nm are preferably not aggregated and contained as primary particles. The content of the fine particles in the second protective film is preferably from 0.01 to 1% by mass, particularly preferably from 0.05 to 0.5% by mass. When the second protective film composed of a plurality of layers of the co-flow casting method is used, it is preferred to contain the added amount of fine particles on the surface.

The cerium oxide microparticles can be used, for example, under the trade names of AEROSIL R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, and TT600 (the above is manufactured by AEROSIL Co., Ltd.).

The fine particles of zirconia can be used, for example, under the trade names of AEROSIL R976 and R811 (above, manufactured by Japan AEROSIL Co., Ltd.).

Examples of the polymer constituting the organic fine particles include a polyoxyxylene resin, a fluororesin, and an acrylic resin. It is preferably a polyoxyl resin, In particular, it is preferably a product having a three-dimensional network structure, for example, sold under the trade names of TOSPEARL 103, TOSPEARL 105, TOSPEARL 108, TOSPEARL 120, TOSPEARL 145, TOSPEARL 3120, and TOSPEARL 240 (above, Toshiba Polyoxide Co., Ltd.). Can be used.

Among these, the inorganic fine particles AEROSIL 200V and AEROSIL R972V are particularly preferably used because the turbidity of the second protective film can be kept low and the friction coefficient is lowered. In the second protective film of the present invention, it is preferred that the dynamic friction coefficient of at least one side is 0.2 to 1.0.

Various additives may be added in batches to the dope containing the cellulose ester solution before film formation, or an additive solution may be additionally added. In particular, in order to reduce the load of the fine particles on the filter material, it is preferred to add a part or the whole amount by wire.

When the additive solution is added by a wire, in order to have good miscibility with the dope, it is preferred to add a small amount of the cellulose ester in advance and dissolve it. The amount of the cellulose ester is preferably from 1 to 10 parts by mass, more preferably from 3 to 5 parts by mass, per 100 parts by mass of the solvent.

In the present invention, for the purpose of mixing and mixing, it is preferable to use, for example, a static mixer (manufactured by Toray Engineering Co., Ltd.), a SWJ (Toray static in-line mixer Hi-Mixer), or the like.

(Method for producing cellulose resin film)

Next, a method of producing a cellulose resin film which is an example of the second protective film will be described.

The cellulose resin film may be a film produced by a solution casting method, or may be a film produced by a melt casting method, and any of them may be preferably used, and a film produced by a solution casting method is particularly preferable.

The method for producing a film by a solution casting method is carried out by the steps of dissolving a cellulose ester and an additive in a solvent to prepare a dope, and casting the dope onto the infinitely moving annular metal support. And the step of drying the cast dope as a green sheet, the step of peeling from the metal support, the step of extending or widening, the step of drying, and the step of taking up the processed film.

First, the steps of preparing the dope are described. When the concentration of the cellulose ester in the dope is relatively concentrated, the drying load after casting on the metal support can be reduced, but when the cellulose concentration is too high, the pressure load during filtration increases, and the filtration accuracy is lowered. The concentration is preferably in the range of 10 to 35% by mass, more preferably 15 to 25% by mass.

The solvent to be used in the preparation of the dope may be used singly or in combination of two or more. However, when a good solvent for mixing a cellulose ester and a weak solvent are used, it is preferable from the viewpoint of production efficiency, and when a good solvent is used, cellulose is used. The viewpoint of the solubility of the ester is preferred. The preferred range of the mixing ratio of the good solvent to the weak solvent is in the range of 70 to 98% by mass in the good solvent and 2 to 30% by mass in the weak solvent. Here, a good solvent or a weak solvent is defined as a good solvent in which a cellulose ester to be used alone is dissolved, and a weak solvent is defined as a weak solvent alone. Therefore, depending on the average degree of acetification of the cellulose ester (the degree of substitution of ethyl ketone), the good solvent, weak solvent, for example, in the case of acetone, the acetate of the cellulose ester (the degree of substitution of ethyl ketone: 2.4) ), cellulose B The acid ester propionate is a good solvent. The cellulose acetate (acetamid substitution degree: 2.8) becomes a weak solvent.

The solvent to be used is not particularly limited, and examples thereof include an organic halide such as dichloromethane or a dioxane, acetone, methyl acetate, methyl acetoxyacetate or the like. A preferred example is dichloromethane or methyl ester.

On the other hand, the weak solvent which can be used is not particularly limited, and for example, methanol, ethanol, n-butanol, cyclohexane, cyclohexanone or the like can be preferably used. Further, the water in the dope preferably contains 0.01 to 2% by mass. Further, the solvent used for dissolving the cellulose ester can be dried in the film forming step, removed from the film, and recovered, and reused. In the solvent recovery, additives such as a plasticizer, a UV absorber, a polymer, and a monomer component added to the cellulose ester may be contained in a small amount, and even if they are contained, they may be preferably reused, and if necessary, may be purified. Reuse.

As a method of dissolving the cellulose ester in the case of preparing the above-described dope, a general method can be used. For example, when the heating means and the press means are combined, the dope can be heated to a boiling point or higher at normal pressure. When the solvent is stirred at a temperature equal to or higher than the boiling point of the solvent under normal pressure and the solvent is not boiled under pressure, it is preferred to prevent gelation or blocky undissolved matter called noodles from occurring. Further, a method in which a cellulose ester is mixed with a weak solvent to wet or swell, and then a good solvent is added and dissolved can be preferably used.

The pressurization can be carried out by a method of injecting an inert gas such as nitrogen into the dissolution vessel or by increasing the vapor pressure of the solvent by heating. The heating is preferably carried out from the outside, and for example, the temperature control of the jacket type is easy and preferable.

When the heating temperature of the added solvent is high, based on cellulose ester The viewpoint of solubility is preferable, but when the heating temperature is too high, the pressure becomes high and the productivity is deteriorated. The preferred heating temperature is in the range of 45 to 120 ° C, more preferably in the range of 60 to 110 ° C, and more preferably in the range of 70 to 105 ° C. Also, the pressure is adjusted so as not to boil the solvent at a specific temperature.

Further, it is also preferred to use a cooling dissolution method whereby the cellulose ester can be dissolved in a solvent such as methyl acetate.

Next, the cellulose ester solution is filtered using a suitable filter material such as filter paper. As the filter material, in order to remove insoluble matter or the like, the absolute filtration accuracy is preferably as small as possible, but when the absolute filtration accuracy is too small, the filter material is likely to be clogged. Therefore, it is preferably a filter material having an absolute filtration accuracy of 0.008 mm or less, more preferably a filter material in the range of 0.001 to 0.008 mm, and more preferably a filter material in the range of 0.003 to 0.006 mm.

The material of the filter material is not particularly limited, and a general filter material can be used. However, a plastic filter material such as polypropylene or Teflon (registered trademark) or a metal filter material such as stainless steel is preferably not detached from the fiber. . It is preferred to remove and reduce impurities contained in the cellulose ester of the raw material, particularly bright spots, by filtration.

In the case of a bright spot foreign matter, two polarizing plates are arranged in a Conil's orthogonal state, and a second protective film is placed therebetween, and light is touched from one polarizing plate side, and light from the opposite side is seen from the other polarizing plate side. The point of leakage (foreign matter), the number of bright spots having a diameter of 0.01 mm or more is preferably 200 pieces/cm ² or less. More preferably, it is 100 / cm ² or less, more preferably 50 / cm ² or less, and still more preferably 0 to 10 / cm ² . The fewer the bright spots with a diameter of 0.01 mm or less, the better.

The method of filtering the dope may be carried out by a usual method, but the method of filtering while heating at a temperature above the boiling point of the solvent under normal pressure and under the condition that the solvent does not boil under pressure, the difference of the filtration pressure before and after the filtration (meaning the pressure difference) The rise is smaller and better. The preferred temperature is in the range of 45 to 120 ° C, more preferably in the range of 45 to 70 ° C, and more preferably in the range of 45 to 55 ° C.

The smaller the filter pressure, the better. The filtration pressure is preferably 1.6 MPa or less, more preferably 1.2 MPa or less, and still more preferably 1.0 MPa or less.

Here, the casting of the dope is explained. The metal support in the casting step is preferably a mirror-finished surface. As the metal support, a stainless steel strip or a drum which is cast on the surface by casting is preferably used. The width of the casting can be 1~4m.

The surface temperature of the metal support in the casting step is in the range of -50 ° C to the temperature at which the boiling point of the solvent is not reached, and the higher the temperature, the faster the drying speed of the green sheet is accelerated, but the sheet is likely to be produced when the temperature is too high. Bubble, but there is a case of flatness deterioration. The preferred support temperature is in the range of 0 to 40 ° C, more preferably in the range of 5 to 30 ° C. Further, the method of gelling the green sheet by cooling and peeling off from the drum in a state containing a large amount of residual solvent is also preferable.

The method of controlling the temperature of the metal support is not particularly limited, but examples thereof include a method of blowing warm air or cold air, and a method of contacting warm water on the back side of the metal support. Since the method of using warm water performs heat transfer efficiently, the time until the temperature of the metal support is constant is short, and it is preferable. When using warm air, there is a case where a wind having a temperature higher than the target temperature is used.

In order to make the protective film show good planarity, from the metal branch The residual solvent amount when the support strips the green sheet is preferably in the range of 10 to 150% by mass, more preferably 10 to 40% by mass or 60 to 130% by mass, particularly preferably 10 to 30% by mass or 70%. Within the range of 120% by mass. Here, the amount of residual solvent is defined by the following formula.

Residual solvent amount (% by mass) = {(M - N) / N} × 100

In the formula, the mass of the sample taken at any time during or after the production of the M-based green sheet or film, and the mass of the N-based mass M after heating at 115 ° C for 1 hour.

Further, in the drying step of the cellulose resin film, the green sheet is preferably peeled off from the metal support and further dried to have a residual solvent content of 1% by mass or less, more preferably 0.1% by mass or less, particularly preferably 0 to 0.01% by mass. Within the scope.

In the film drying step, a method in which a green sheet is dried by a roll drying method (such that a plurality of rolls are arranged alternately between the rolls and dried) or a tenter type is used.

In order to produce a cellulose resin film, it is preferred that the amount of residual solvent of the green sheet is extended in the transport direction (longitudinal direction) immediately after the metal support is peeled off, and the tenter is held at the ends of the green sheet by a jig or the like. Extend in the width direction (horizontal direction). Further, it may be a method of simultaneously extending in the transport direction (longitudinal direction) and the width direction (lateral direction).

In order to extend in the longitudinal direction immediately after peeling, the peeling tension is preferably 210 N/m or more, and particularly preferably in the range of 220 to 300 N/m.

The means for drying the green sheet is not particularly limited, and generally can be borrowed Hot air, infrared rays, heating rolls, microwaves, and the like are carried out, but it is preferably carried out by hot air based on a simple viewpoint.

The drying temperature in the drying step of the green sheet is preferably increased stepwise in the range of from 40 to 200 ° C, and is preferably carried out in the range of from 50 to 140 ° C because of good dimensional stability.

The film thickness of the cellulose resin film is not particularly limited, but is preferably in the range of 10 to 200 μm. The film thickness is better in the range of 10 to 60 μm, and particularly preferably in the range of 10 to 40 μm.

The cellulose resin film is used in a range of 1 to 4 m in width. In particular, it is preferably used in the range of 1.4 to 4 m in width, and particularly preferably in the range of 1.6 to 3 m. It is difficult to transport when it exceeds 4m.

(Extension operation, refractive index control)

The cellulose resin film is preferably a retardation value Ro represented by the following formula: 0 to 20 nm and Rt (absolute value) of 25 nm or less.

Formula (i): Ro = (n _{x -} n _y ) × d

Formula (ii): Rt = ((n _x + n _y ) / 2 - n _z ) × d

Where n _x is the refractive index in the slow axis direction in the plane of the film, n _y is the refractive index in the direction perpendicular to the slow axis direction in the plane of the film, n _z is the refractive index perpendicular to the direction of the film face, d is Film thickness (nm).

The refractive index can be determined by using Axo Scan (Axo Scan Mueller Matrix Polarimeter: manufactured by Axo Matrix Co., Ltd.) at a measurement wavelength of 590 nm in an environment of 23 ° C ‧55% RH.

When the retardation values Ro and Rt are obtained, the second protective film is preferably configured as the present invention, and the refractive index control is performed by the stretching operation.

For example, it may extend in the longitudinal direction of the film (film forming direction) and its direction orthogonal to the inside of the film surface, that is, sequentially or simultaneously in the width direction.

The stretching ratios of the mutually orthogonal two-axis directions are preferably 1.0 to 2.0 times in the casting direction and 1.01 to 2.5 times in the width direction, preferably 1.01 to 1.5 times in the casting direction and 1.05 in the width direction. It is carried out within a range of ~2.0 times.

The method of extending the green sheet is not particularly limited. For example, the circumferential speed difference is applied to the plurality of rolls, and the two sides of the green sheet are fixed by a jig or a needle by a method of extending the circumferential speed difference in the longitudinal direction, and the distance between the jig or the needle is widened in the traveling direction to extend in the longitudinal direction. The method is similar to the method of widening in the lateral direction and extending in the lateral direction, or the method of widening both vertically and horizontally and extending in both the longitudinal and lateral directions. Of course, these methods can be used in combination. Further, in the case of the tenter method, when the clamp portion is driven by the linear stretching method, the sliding portion can be smoothly extended, and the risk of breakage or the like can be reduced, which is preferable.

The width of the film forming step or the transverse direction is preferably carried out by a tenter, or by a pin tenter or a clamp tenter.

Preferably, the protective film has a slow axis or a fast axis in the film surface, and when the angle formed by the film forming direction is θ1, θ1 is preferably -1 or more and +1 or less, more preferably -0.5 or more. +0.5° or less. The θ1 can be defined as the alignment angle, and the θ1 can be measured using the automatic birefringence meter KOBRA-21ADH. (Prince measurement machine) is carried out. When θ1 satisfies each of the above relationships, high luminance in the display image can be obtained, which contributes to suppressing or preventing light leakage, and contributes to obtaining faithful color reproduction in the color liquid crystal display device.

Further, a specific procedure of a more detailed solution casting method will be described with reference to Fig. 2 in connection with a method for producing a cycloolefin film containing a cycloolefin resin to be described later.

[cycloolefin film]

A preferred other form of the second protective film of the present invention is a cycloolefin film containing a cycloolefin resin.

Since the cycloolefin-based resin is a hydrophobic resin, it is easy to separate if there is moisture in the film formation, and it is not preferable from the viewpoint of transparency. However, in the present invention, the cycloolefin-based resin preferably contains at least It is formed by a resin composition of a hydrogen bond accepting group, and since it can form a hydrogen bond with a hydroxyl group of an alcohol or a hydroxyl group of a hindered phenol type compound, it can maintain transparency even if it is a state of moisture content, and it is contrary by a transparency. Hydrogen bonding enhances the strength of the film. The "hydrogen bond accepting group" means a functional group that accepts a hydrogen atom when a hydrogen bond is formed.

Preferably, the cycloolefin resin of the present invention is formed from a resin composition containing at least one hydrogen bond accepting group.

The hydrogen bond accepting group is exemplified by, for example, an alkoxy group having 1 to 10 carbon atoms, a decyloxy group having 1 to 10 carbon atoms, an alkoxycarbonyl group having 2 to 10 carbon atoms, an allyloxycarbonyl group or a cyano group. , amidino group, a group containing a quinone imine ring, a triorganomethoxy group, a triorganoalkyl group, a fluorenyl group, a carbon number a polar group such as an alkoxyalkyl group of 1 to 10, a group containing a sulfo group, and a carboxyl group. When the polar group is further specifically described, the alkoxy group is exemplified by, for example, a methoxy group or an ethoxy group; and the decyloxy group is exemplified by an alkylcarbonyloxy group such as an ethoxycarbonyl group or a propyloxy group. And an arylcarbonyloxy group such as a benzamidineoxy group; as the alkoxycarbonyl group, for example, a methoxycarbonyl group, an ethoxycarbonyl group, etc.; and as the aryloxycarbonyl group, for example, a phenoxycarbonyl group, a naphthyloxycarbonyl group, an anthraceneoxycarbonyl group, a biphenyl group; An oxycarbonyl group or the like; as the triorganomethoxy group, for example, a trimethyl decyloxy group, a triethyl decyloxy group, etc.; and a triorganoalkylene group is exemplified by a trimethyl decyl group, a triethyl decyl group, etc.; The oxyalkylene group is exemplified by, for example, a trimethoxydecyl group, a triethoxydecyl group, and the like.

The amount of the hydrogen-bonding-receptive group-containing cycloolefin-based resin contained in the resin component is not particularly limited, but is preferably from 10 to 100% by mass based on the total mass of the second protective film. When the amount is 10% by mass or more, the ring-opening copolymer is preferably soluble in a solvent such as toluene or dichloromethane, and is preferably further, and further preferably 30 in terms of solubility, film strength, and transparency. ~100% by mass range.

The cycloolefin-based resin of the present invention is exemplified by a (co)polymer represented by the following formula (I).

In the above formula (I), p is 0 or 1, and m is an integer of 0 or more. R ¹ ~ R ⁴ each independently represent a hydrogen atom, a hydrocarbon group, a halogen atom or a hydrogen bond accepting group. Further, R ¹ to R ⁴ may be bonded to each other by two or more to form an unsaturated bond, a monocyclic ring or a polycyclic ring, and the monocyclic or polycyclic ring may have a double bond or may form an aromatic ring.

In the present invention, the ratio of the preferred hydrogen bond accepting group of the cycloolefin resin is preferably such that one or two of R ¹ to R ⁴ in the above formula (I) have a hydrogen bond accepting group.

Further, the retention ratio of the preferred hydrogen bond accepting group of the cycloolefin resin can be identified by, for example, carbon 13 nuclear magnetic resonance ( ¹³ C NMR) spectroscopy.

And in the general formula (I), R ¹ and R ³ are a hydrogen atom or a system having 1 to 10 carbon atoms, and further preferably from 1 to 4, particularly preferably a hydrocarbon group of from 1 to 2 of, R ² and R ⁴ is at least One of the hydrogen bond accepting groups having a polar group other than a hydrogen atom and a hydrocarbon group is preferred because p and m are preferably m=1 and p=0, because of the high glass transition temperature and excellent mechanical strength.

The halogen atom is exemplified by a fluorine atom, a chlorine atom and a bromine atom. The hydrocarbon group having 1 to 30 carbon atoms is exemplified by an alkyl group such as a methyl group, an ethyl group or a propyl group; a cycloalkyl group such as a cyclopentyl group or a cyclohexyl group; and an alkenyl group such as a vinyl group, an allyl group or a propenyl group. An aromatic group such as a phenyl group, a biphenyl group, a naphthyl group or an anthracenyl group. The hydrocarbon group may be substituted, and examples of the substituent include a halogen atom such as a fluorine atom, a chlorine atom or a bromine atom, and a phenylsulfonyl group.

The preferred molecular weight of the cycloolefin resin of the present invention is in the range of 0.2 to 5 cm ³ /g in terms of intrinsic viscosity [η]inh, more preferably in the range of 0.3 to 3 cm ³ /g, and particularly preferably 0.4 to 0.4. Within the range of 1.5 cm ³ /g. Further, the number average molecular weight (Mn) in terms of polystyrene measured by a gel permeation chromatography (GPC) is preferably in the range of 8,000 to 100,000, more preferably in the range of 10,000 to 80,000, and particularly preferably 12,000. Within the range of ~50000. The weight average molecular weight (Mw) is preferably in the range of 20,000 to 300,000, more preferably in the range of 30,000 to 250,000, and particularly preferably in the range of 40,000 to 200,000.

When the intrinsic viscosity [η]inh, the number average molecular weight, and the weight average molecular weight are in the above range, heat resistance, water resistance, chemical resistance, and mechanical properties of the cycloolefin resin can be obtained as the cycloolefin resin film of the present invention. Good formability.

The glass transition temperature (Tg) of the cycloolefin resin of the present invention is usually 110 ° C or higher, preferably 110 to 350 ° C, more preferably 120 to 250 ° C, and particularly preferably 120 to 220. Within the range of °C. When Tg is 110 ° C or more, it is preferable because it can be suppressed from being used under high temperature conditions or deformed by secondary processing such as coating or printing. Further, when the Tg is 350 ° C or lower, it is preferable because the deterioration of the resin due to the forming process or the heat during the forming process can be suppressed.

The cycloolefin-based resin described above can be preferably used as a commercially available product, and is commercially available as an example of JSR (shares) under the trade names of ARTON G, ARTON F, ARTON R, and ARTON RX. .

(Additive for cycloolefin film) (cerium oxide particles)

In the cycloolefin film of the present invention, in order to prevent the occurrence of scratches or deterioration of conveyance when the film to be produced is treated, and to use a protective film as a polarizing plate for the second protective film, cracking during the pressing of the polarizing plate or The second protective film in which the reduction of the powder is reduced preferably contains cerium oxide particles having a specific degree of hydrophobicity.

The preferred cerium oxide particle of the present invention is preferably a hydrophobization degree measured by a methanol wetting method, and the degree of hydrophobicity is 20% or less when methanol and pure water are used in a first solution having a volume ratio of 3:7, methanol and The cerium oxide particles having a degree of hydrophobization of 80% or more in the case of the second solution having a volume ratio of 6:4 in pure water. The degree of hydrophobization is determined by the MW method described above.

The cerium oxide particles are particles mainly composed of cerium oxide. The main component means 50% or more of the components constituting the particles, preferably 70% or more, more preferably 80% or more, and particularly preferably 90% or more.

Further, when the particles of the cerium oxide-based particles and the surface of which are hydrophobized by the alkylation treatment are added, the dispersibility to the solvent is good, and the occurrence of foreign matter can be suppressed.

The above hydrophobization treatment of the cerium oxide particles is preferably an alkylation treatment. The surface of the alkylated microparticles has an alkyl group, and the carbon number of the alkyl group is preferably in the range of 1 to 20, more preferably in the range of 1 to 12 carbon atoms, particularly preferably in the range of 1 to 8 carbon atoms. Inside.

Among the above cerium oxide particles, those having a surface having an alkyl group in the range of 1 to 20 carbon atoms can be obtained, for example, by treating the above-mentioned cerium oxide particles with octyldecane. And one of the examples having an octyl group on the surface is sold under the trade name of AEROSIL R805 (manufactured by Japan AEROSIL Co., Ltd.). use.

The average particle diameter of the primary particles of the cerium oxide particles is preferably in the range of 5 to 400 nm, more preferably in the range of 10 to 300 nm.

The average particle diameter of the secondary particles of the cerium oxide particles is preferably in the range of 100 to 400 nm. Preferably, if the average particle diameter of the primary particles is in the range of 100 to 400 nm, it is preferably not aggregated and contained in the primary particles.

(hindered phenolic compound)

The phenolic compound is a known compound, for example, as described in the columns 12 to 14 of the specification of U.S. Patent No. 4,839,405, and contains a 2,6-dialkylphenol derivative compound. The preferred compound among such compounds is preferably a compound represented by the following formula (II).

In the above formula (II), R ₅₁ to R ₅₆ each represent a hydrogen atom or a substituent. The substituent is exemplified by a halogen atom (e.g., a fluorine atom, a chlorine atom, etc.), an alkyl group (e.g., methyl, ethyl, isopropyl, hydroxyethyl, methoxymethyl, trifluoromethyl, tert-butyl) Etc.), cycloalkyl (eg cyclopentyl, cyclohexyl, etc.), aralkyl (eg benzyl, 2-phenylethyl, etc.), aryl (eg phenyl, naphthyl, p-tolyl, p- Chlorophenyl, etc.), alkoxy (eg methoxy, ethoxy, isopropoxy, butoxy, etc.), aryloxy (eg phenoxy, etc.), cyano, guanamine (eg B Anthranyl, propylamino, etc.), alkylthio (eg, methylthio, ethylthio, butylthio, etc.), arylthio (eg, phenylthio, etc.), sulfonamide (eg, methanesulfonyl) Amino group, benzenesulfonylamino group, etc.), ureido group (for example, 3-methylureido group, 3,3-dimethylureido group, 1,3-dimethylureido group, etc.), amine sulfonamide group ( Dimethylamine sulfonamide, etc.), amine methyl sulfhydryl (eg methylamine methyl thiol, ethylamine methyl sulfhydryl, dimethylamine carbhydryl, etc.), amine sulfonyl (eg ethylamine) Sulfonyl, dimethylamine sulfonyl, etc., alkoxycarbonyl (eg methoxycarbonyl, ethoxycarbonyl, etc.), aryloxycarbonyl (example) a phenoxycarbonyl group, etc., a sulfonyl group (for example, a methanesulfonyl group, a butanesulfonyl group, a phenylsulfonyl group, etc.), a mercapto group (e.g., an ethyl group, a propyl group, a butyl group, etc.), an amine group (A) Amino, ethylamino, dimethylamino, etc.), cyano, hydroxy, nitro, nitroso, amine oxide groups (eg pyridine-oxide groups), quinone imine groups (eg phthalic acid) Amine group, etc., disulfide group (for example, benzene disulfide group, benzothiazole-2-disulfide group, etc.), carboxyl group, sulfo group, heterocyclic group (for example, pyrazolyl, pyrrolidinyl, pyrazole) Base, imidazolyl, pyridyl, benzimidazolyl, benzothiazolyl, benzoxazolyl, etc.). These substituents may also be substituted.

Further, it is preferably a hydrogen atom of R _{51 type} , and R ₅₂ and R ₅₆ are each a phenol type compound of a third butyl group.

The hindered phenol-based compound of the present invention is not particularly limited, and specific examples thereof are exemplified.

Specific examples of the compound are n-octadecyl 3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, n-octadecyl 3-(3,5- Di-tert-butyl-4-hydroxyphenyl)acetate, n-octadecyl 3,5-di-t-butyl-4-hydroxybenzoate, n-hexyl 3,5-di third Butyl-4-hydroxyphenyl benzoate, n-dodecyl 3,5-di-t-butyl-4-hydroxyphenyl benzoate, neododecyl 3-(3,5 -di-tert-butyl-4-hydroxyphenyl)propionate, dodecyl beta (3,5-di-t-butyl-4-hydroxyphenyl)propionate, ethyl alpha-(4- Hydroxy-3,5-di-t-butylphenyl)isobutyrate, octadecyl α-(4-hydroxy-3,5-di-t-butylphenyl)isobutyrate, octadecane Α-(4-Hydroxy-3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2-(n-octylthio)ethyl 3,5-di-t-butyl-4 -hydroxybenzoate, 2-(n-octylthio)ethyl 3,5-di-t-butyl-4-hydroxyphenyl acetate, 2-(n-octadecylthio)ethyl 3,5-di-t-butyl-4-hydroxyphenyl acetate, 2-(n-octadecylthio)ethyl 3,5-di-t-butyl-4-hydroxybenzoate, 2-(2-hydroxyethylthio)ethyl 3,5-di-t-butyl-4-hydroxybenzoate, diethylene glycol bis-(3,5-di-t-butyl-4-hydroxyl Phenyl)propionate, 2-(n-octadecylthio)ethyl 3-(3 ,5-di-t-butyl-4-hydroxyphenyl)propionate, stearylamine N,N-bis[stretching ethyl 3-(3,5-di-t-butyl-4-hydroxyphenyl) Propionate], n-butylimido N,N-bis[stretch ethyl 3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 2-(2-hard Lipidoxyethylthio)ethyl 3,5-di-t-butyl-4-hydroxybenzoate, 2-(2-stearyloxyethylthio)ethyl 7-(3-methyl 5--5-butyl-4-hydroxyphenyl)heptanoate, 1,2-propanediol bis-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] , ethylene glycol bis-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], neopentyl glycol bis-[3-(3,5-di-t-butyl) -4-hydroxyphenyl)propionate], ethylene glycol bis-(3,5-di-t-butyl-4-hydroxyphenyl acetate), glycerol-1-n-octadecanoic acid Ester-2,3-bis-(3,5-di-3rd 4-hydroxyphenyl acetate), pentaerythritol-indole-[3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate], 1,1,1- Trimethylolethane-para-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], sorbitol hexa-[3-(3,5-di third Butyl-4-hydroxyphenyl)propionate], 2-hydroxyethyl 7-(3-methyl-5-tert-butyl-4-hydroxyphenyl)propionate, 2-stearyl oxime Base ethyl 7-(3-methyl-5-tert-butyl-4-hydroxyphenyl)heptanoate, 1,6-n-hexanediol-bis[(3',5'-di-t-butyl -4-hydroxyphenyl)propionate], pentaerythritol-indole-(3,5-di-t-butyl-4-hydroxyhydrocinnamate), and the like.

Specific examples of the useful hindered phenol-based antioxidants include the following exemplified compounds, but are not limited thereto.

Further, a phenol compound of the above type is sold, for example, from the Japanese company BASF Co., Ltd. under the trade names "Irganox 1035", "Irganox 1076" and "Irganox 1010".

The amount of the phenolic compound to be added to 100 parts by mass of the cycloolefin resin can be appropriately designed, but it is preferably in the range of 0.1 to 1.0 part by mass, more preferably 0.3 to 0.5 part by mass.

(other additives)

A polyester compound, a polyvalent alcohol ester compound, a polyvalent carboxylate compound (including a phthalate compound), a glycolate compound, and an ester compound described in the above-mentioned cellulose resin film can be similarly applied as the other additives. (including a fatty acid ester compound or a phosphate compound, etc.), an ultraviolet absorber, and the like.

[Manufacturing method of cycloolefin film]

The method for producing a cycloolefin film of the second protective film of the present invention may be a solution casting film forming method or a melt casting film forming method, but it is preferably produced by a solution casting film forming method.

(A. Solution casting film formation method)

The cycloolefin film of the present invention is preferably formed by a solution casting film forming method, and contains a cycloolefin resin having at least one hydrogen bond accepting group, cerium oxide particles satisfying the degree of hydrophobicity, and the hindered phenol system. a compound, and a concentrated solution of an organic solvent containing an alcohol solvent at a dissolution temperature Modulation in the range of 15~50 °C.

When the dissolution temperature is 15 ° C or higher, since the resin or the additive can be sufficiently dissolved, a film having less foreign matter is obtained. Further, if it is 50 ° C or less, it is preferable from the viewpoint of suppressing the coloring of the concentrated liquid due to the reaction between the alcohol and the hindered phenol compound and the color of the obtained film, even if cerium oxide particles having good affinity with alcohol are added. Suppress the effect of coloring.

The second protective film of the present invention is preferably produced by the step of preparing a dope containing at least a cycloolefin resin, cerium oxide particles, a hindered phenol compound, and an organic solvent containing an alcohol solvent (dope liquid preparation) Step), the step of casting the concentrated liquid on the support to form a green sheet (also referred to as a casting film) (casting step), the step of evaporating the solvent from the green sheet on the support (solvent evaporation step), and peeling the blank from the self-supporting body a sheet step (peeling step), a step of drying the obtained film (pre-drying step), a step of stretching the film (extension step), a step of further drying the stretched film (drying step), and a step of winding up the obtained film (rolling step).

The above steps are illustrated using a diagram.

Fig. 2 is a flow chart showing the steps of an example of a dope preparation step, a casting step, a drying step and a winding step of a preferred solution casting film forming method of the present invention.

The fine particle dispersion in which the cerium oxide particles are dispersed in a solvent by a disperser in advance is stored in the raw material tank (42) through the filter (44) from the feed tank (41), and on the other hand, the cycloolefin of the main dope is The resin is dissolved in the dissolution vessel (1) together with the solvent, and the fine particle dispersion liquid stored in the mixed raw material tank (42) is appropriately added to form a main concentrated liquid. The main concentrated liquid is supplied to the filter (3) The raw material kettle (4) is filtered by a filter (6), and the additive is added by the mixing pipe (20), mixed by the mixer (21), and sent to the pressurizing die (30).

On the other hand, an additive (a hindered phenol-based compound, an ultraviolet absorber, a phase difference increasing agent, etc. which are applicable in the present invention) is dissolved in a solvent, and is fed from the additive to the kettle (10) through the filter (12), and stored. In the raw material kettle (13). Subsequently, it is mixed with the main dope through a conduit (16) through a conduit (16) and a mixer (21) through a filter (15).

The main dope which is supplied to the pressurizing die (30) is cast onto the endless metal strip-shaped support (31) to form a green sheet (32), which is specifically dried and then peeled off at the peeling position (33) to obtain a film. The peeled green sheet (32) is dried by a plurality of conveyance rolls until it reaches a specific residual solvent amount, and then extends in the longitudinal direction or the width direction by the stretching device (34). After the stretching, the drying device (35) is dried by the conveying roller (36) until it becomes a specific residual solvent amount, and is wound into a roll shape by the winding device (37).

The following describes each step.

(1) Dope preparation step

In the organic solvent containing a cycloolefin-based resin as a good solvent as a main component, the cycloolefin-based resin and the hindered phenol-based compound are dissolved in a dissolution vessel while stirring, and a phase difference increasing agent, cerium oxide particles or other compound depending on the case The step of preparing a dope or mixing the hindered phenol-based compound, the phase difference increasing agent, the cerium oxide particles or other compound in the cycloolefin-based resin solution to prepare a dope of the main solution.

The second protective film of the present invention is produced by a solution casting method In the case of forming a dope, the useful organic solvent preferably dissolves the cycloolefin resin, the hindered phenol compound, or the phase difference increasing agent and other compounds.

As the usable organic solvent, the following solvents are preferably used.

The solvent used in the solution casting method is, for example, a chlorine-based solvent such as chloroform or dichloromethane; an aromatic solvent such as toluene, xylene, benzene or a mixed solvent thereof; methanol, ethanol, isopropanol, and n-butyl Alcohol solvent such as alcohol or 2-butanol; methyl cellosolve, ethyl cellosolve, butyl cellosolve, dimethylformamide, dimethyl hydrazine, dioxane, cyclohexanone, tetrahydrofuran , acetone, methyl ethyl ketone (MEK), ethyl acetate, diethyl ether; These solvents may be used alone or in combination of two or more.

When the solvent of the present invention is a mixed solvent of a good solvent and a weak solvent, the good solvent is, for example, dichloromethane as a chlorine-based organic solvent, and methyl acetate, ethyl acetate, amyl acetate, acetone as a non-chlorine-based organic solvent. Methyl ethyl ketone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3, 3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol, 1,1 ,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, nitroethane, methanol, ethanol, n-propanol, isopropyl An alcohol, n-butanol, a second butanol, a third butanol or the like, of which dichloromethane is preferred.

The weak solvent is mainly an alcohol solvent, and when it contains 10 to 1000 ppm in the second protective film, it is preferable in terms of the effects of the present invention.

The content of the above alcohol-based solvent contained in the cycloolefin film of the present invention is a so-called residual solvent amount, which means that the film is contained in the film after production. The content. The amount of the solvent can be quantified by headspace gas chromatography described later, which means that the measurement is performed after the film is produced and before the film is processed. Usually, after the film is produced and wound into a roll shape, it is stored in a quasi-sealed state by a protective sheet or the like, and is kept in this state until the processing, so that the amount of residual solvent is small.

The control of the amount of the residual solvent can be carried out by appropriately adjusting the composition ratio of the solvent, the drying temperature in the film formation, the drying conditions such as the drying time, and the film thickness.

The content of the alcohol solvent contained in the cycloolefin film of the present invention is preferably in the range of 10 to 1000 ppm, more preferably in the range of 20 to 500 ppm. The effect of the present invention can be exhibited by 10 ppm or more, and the peeling property from the metal support in the solution casting film formation is also improved. From the viewpoint of turbidity and environmental safety by 1000 ppm or less, it is preferable.

The alcohol-based solvent of the present invention is preferably selected from the group consisting of methanol, ethanol, and butanol, and is excellent in peelability and high-speed casting based on the effects of the present invention. Among them, ethanol is preferred based on the above viewpoint.

In the present invention, it is preferred to use 55% by mass or more of the above-mentioned good solvent with respect to the total mass of the solvent, more preferably 70% by mass or more, and still more preferably 80% by mass or more.

Further, the cycloolefin film of the present invention is preferably used in combination with an alcohol-based solvent having a hydroxyl group in view of productivity improvement, and it is preferred to add water to the dope and to contain 50 by weight of the residual solvent in the film. Water in the range of ~500ppm.

Because water has multiple hydrogen bonding properties in one molecule Therefore, it can be preferably used in order to increase the strength of the film. It is preferred to contain water in an amount of 0.1 to 1.0% by mass based on the total amount of the solvent. When it is 0.1% by mass or more, it is preferable to easily interact with other alcohol-based solvents or a hydrogen-bonding-receptive group-containing cycloolefin resin or cerium oxide particles, and when it is 1.0% by mass or less, a ring having strong hydrophobicity is suppressed. The gelation of the olefin resin suppresses the occurrence of foreign matter.

<Amount of residual solvent>

The residual amount of the aforementioned alcohol and water used as a solvent component in the film was carried out by the following measurement method.

The film cut into a certain shape was placed in a 20 ml sealed glass container and treated at 120 ° C for 20 minutes by a gas chromatograph (machine: HP 5890 Series II, column: J&W DB-WAX (inner diameter 0.32 mm) , length 30 m), detection: FID) The GC temperature rising condition was maintained at 40 ° C for 5 minutes, and the temperature was raised to 100 ° C at 80 ° C / minute.

The cycloolefin-based resin, the hindered phenol-based compound, and other compounds can be dissolved by a method of normal pressure, a method of performing the pressure below the boiling point of the main solvent, or a method of pressurizing at a boiling point or higher of the main solvent, such as Japanese Patent Publication No. 9 A method of performing a cooling and dissolving method described in Japanese Laid-Open Patent Publication No. Hei 9-95537, or a method of performing a high-pressure method as described in Japanese Laid-Open Patent Publication No. Hei. Various dissolution methods, but based on the viewpoint of solubility, it is preferably carried out in a pressure range of 0.8 to 4 MPa.

The concentration of the cycloolefin resin in the dope is preferably from 10 to 40. Within the range of mass %. The concentrated liquid containing the cycloolefin-based resin is added to the dissolved or dissolved concentrated liquid, dissolved, and dispersed, and then filtered, defoamed, and pumped with a filter medium to be pumped to the next step.

For the filtration of the dope, it is preferred to use a main filter (3) having a leaf disc filter. Preferably, the dope is, for example, 90% of the collected particle diameter is within a range of 10 to 100 times the average particle diameter of the microparticles. The filter material is filtered.

In the present invention, the filter medium used for filtration is preferably as small as possible, but the absolute filtration accuracy is too small, and the filter material is likely to be clogged, and the filter material must be frequently replaced, which has a problem of reduced productivity.

Therefore, in the present invention, the filter medium used for the concentrated liquid containing the cycloolefin-based resin preferably has an absolute filtration accuracy of 0.008 mm or less, more preferably 0.001 to 0.008 mm, and more preferably 0.003 to 0.006 mm. Filter media in range.

The material of the filter material is not particularly limited, and a normal filter material can be used. However, a filter material made of a plastic fiber such as polypropylene or Teflon (registered trademark) or a metal filter material such as stainless steel fiber is preferably not detached from the fiber.

In the present invention, the flow rate of the concentrated liquid at the time of filtration is in the range of 10 to 80 kg / (h ‧ m ² ), preferably in the range of 20 to 60 kg / (h ‧ m ² ). When the flow rate of the dope at the time of filtration is 10 kg/(h‧m ² ) or more, efficient productivity can be obtained, and if the flow rate of the concentrated liquid at the time of filtration is 80 kg/(h‧m ² ), it is applied to The pressure of the filter material is appropriate, and the filter material is not damaged.

The filtration pressure is preferably 3,500 kPa or less, more preferably 3,000 kPa or less, and still more preferably 2,500 kPa or less. Further, the filtration pressure can be controlled by appropriately selecting the filtration flow rate and the filtration area.

In most cases, the main dope can be used in the range of 10 to 50% by mass of the recycled material.

The recycled material is, for example, a film sheet obtained by finely pulverizing a cycloolefin film, a side portion of the film which is formed when the cycloolefin film is formed, or a cycloolefin film blank which exceeds a predetermined value of the film due to abrasion or the like. sheet.

Moreover, as a resin raw material used for preparation of a dope, it is preferable to use the granules, such as a cyclic olefin-type resin and other compounds, previously.

(2) Casting step (2.1) Casting of concentrated liquid

The concentrated liquid prepared as described above is sent to the pressurizing die mouth (30) by a liquid feeding pump (for example, a pressurized quantitative gear pump), and the dope is cast from the slit of the pressurizing die mouth (30) to the ring of infinite transfer. The metal support (31) is a casting position on a metal support such as a stainless steel belt or a rotating metal drum.

The metal support in the casting step is preferably a mirror-finished surface. As the metal support, it is preferred to use a stainless steel belt or a drum which is cast on the surface by casting. The width of the casting may be in the range of 1 to 4 m, preferably in the range of 1.3 to 3 m, more preferably in the range of 1.5 to 2.8 m. The surface temperature of the metal support in the casting step is set at -50 ° C - the solvent is not boiling below the foaming temperature, and is preferably set within the range of -30 to 0 ° C. The higher the temperature, the faster the drying speed of the green sheet (the thick liquid film formed by casting the concentrated liquid on the casting metal support) is preferable, but when the temperature is too high, the green sheet is foamed. There is a case of flatness deterioration. As a better The temperature of the support is suitably determined within the range of 0 to 100 ° C, more preferably in the range of 5 to 30 ° C. Alternatively, it is preferred to gel the green sheet by cooling and peel it off from the roll in a state containing a large amount of residual solvent.

The method of controlling the temperature of the metal support is not particularly limited, but examples thereof include a method of blowing warm air or cold air, and a method of contacting warm water on the back side of the metal support. Since the method of using warm water performs heat transfer efficiently, the time until the temperature of the metal support is constant is short, and it is preferable. When the warm air is used, it is sometimes considered that the temperature of the green sheet due to the latent heat of evaporation of the solvent is lowered, and the warm air having a boiling point or higher of the solvent is used, and there is a case where the wind is prevented from being foamed and the temperature higher than the target temperature is used. In particular, it is preferred to carry out drying efficiently by changing the temperature of the support and the temperature of the dry air from casting to peeling.

The die mouth is preferably a slit shape which can adjust the metal cover portion of the die mouth, and is easy to make the pressure die having a uniform film thickness. The pressurizing die mouth can be preferably used by a hanger type die mouth or a T die mouth. The surface of the metal support becomes a mirror surface. In order to increase the molding speed, two or more pressurizing nozzles may be provided on the metal support, and the amount of the concentrated liquid may be divided and laminated.

(2.2) Solvent evaporation step

The step of heating the green sheet on the metal support for casting to evaporate the solvent is a step of controlling the amount of residual solvent at the time of peeling described later.

When the solvent is evaporated, there is a method of blowing a hurricane from the side of the green sheet, a method of heat transfer by liquid from the back surface of the support, a method of transferring heat from the surface by radiant heat, etc., but the drying efficiency of the liquid heat transfer method of the back surface is good. . It is also possible to use a combination of these methods. The green sheet on the support after the better casting is dried on the support in an environment of 30 to 100 ° C. It is preferable to maintain the temperature of the temperature at 30 to 100 ° C by touching the warm air of the temperature on the surface of the blank or by means of infrared rays or the like.

From the viewpoint of surface quality, moisture permeability, and peelability, the green sheet is preferably peeled off from the support in a range of 30 to 180 seconds.

(2.3) Stripping step

The step of peeling off the green sheet on the metal support after the solvent is evaporated at the peeling position. The peeled green sheet is sent as a film to the next step.

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

The evaporation of the solvent in the green sheet of the solvent evaporation step of the present invention is preferably in the range of 15 to 100% by mass of the residual solvent amount of the green sheet on the metal support at the time of peeling. The control of the amount of the residual solvent is preferably carried out by the drying temperature and the drying time in the solvent evaporation step described above.

When the amount of the residual solvent is 15% by mass or more, it is preferable because the cerium oxide particles are uniformly dispersed in the film in the thickness direction without being distributed in the drying process on the support.

When the amount of the residual solvent is 100% by mass or less, the film is self-supporting, and the film peeling failure can be avoided, and the mechanical strength of the green sheet can be maintained. Therefore, the flatness at the time of peeling can be improved, and the peeling tension can be suppressed. Causes wrinkles or vertical stripes to occur.

The residual solvent amount of the green sheet or film is determined by the following formula (Z) Righteousness.

The amount of residual solvent (%) of formula (Z) = (mass before heat treatment of green sheet or film - mass after heat treatment of green sheet or film) / (mass after heat treatment of green sheet or film) × 100

Further, the heat treatment at the time of measuring the amount of residual solvent showed that the heat treatment was performed at 115 ° C for 1 hour.

When the green support is peeled off from the green sheet to form a film, the peeling tension is usually in the range of 196 to 245 N/m. However, when wrinkles are likely to occur during peeling, it is preferably peeled off at a tension of 190 N/m or less.

In the present invention, the temperature at the peeling position on the metal support is preferably in the range of -50 to 40 ° C, more preferably in the range of 10 to 40 ° C, and most preferably in the range of 15 to 30 ° C.

(3) Drying and stretching steps

The drying step can also be divided into a preliminary drying step and a formal drying step.

(3.1) Pre-drying step

The film obtained by peeling the green sheet from the metal support is preliminarily dried. The pre-drying of the film allows the film to be dried while being conveyed by a plurality of rolls arranged one above the other, or may be dried while being conveyed at both ends of the film by a clamp like a tenter.

The means for drying the green sheet is not particularly limited, and generally can be carried out by hot air, infrared rays, heating rolls, microwaves, etc., but based on the simple view The point is preferably carried out by hot air.

The drying temperature in the preliminary drying step of the green sheet is preferably a film (glass transition temperature (Tg) - 5 ° C) or less, and is preferably heat-treated at a temperature of 30 ° C or higher for 1 minute or longer and 30 minutes or shorter. Drying is carried out in the range of drying temperature of 40 to 150 ° C, more preferably 50 to 100 ° C.

(3.2) Extension step

The second protective film of the present invention is extended by the stretching device (34) under the residual solvent amount, and the resin in the film uniformly disperses the cerium oxide particles to improve the flatness of the film, and by controlling the molecular alignment in the film, The desired phase difference values Ro and Rt can be obtained.

In the method for producing a cycloolefin film of the present invention, in the step of stretching the film, the amount of residual solvent at the start of stretching is preferably 1.0% by mass or more and less than 15% by mass. More preferably in the range of 2.0 to 10% by mass, if it is in the range of the amount of the residual solvent described above, it is possible to prevent uneven stress from being applied to the film during stretching.

The cycloolefin film of the present invention preferably extends in the longitudinal direction (also referred to as the MD direction, the casting direction), the width direction (also referred to as the TD direction) or the oblique direction, and is preferably manufactured by extending at least in the width direction of the stretching device. .

The extension operation can also be divided into multi-stage implementations. Moreover, when biaxial stretching is performed, biaxial stretching can be performed simultaneously, or can be carried out in stages. In this case, the so-called phase can be, for example, sequentially extending in different directions. Stretching can also divide the extension in the same direction into multiple stages and apply extensions in different directions at any stage.

That is, for example, the following extension steps can be applied.

‧ Extend in the length direction → Extend in the width direction → Extend in the length direction → Extend in the width direction

‧Extension in the width direction →Extension in the width direction →Extension in the length direction →Extension in the length direction

‧Extension in the width direction→Extension in the oblique direction

Moreover, the simultaneous biaxial stretching also includes the case where the one side extends and the other side relaxes the tension and contracts.

The cycloolefin film of the present invention preferably has a film thickness after stretching in a desired range, and in a longitudinal direction and/or a width direction, preferably in a width direction, when the film peeling transition temperature is Tg, The temperature range of Tg+5)~(Tg+50)°C extends. If it extends in the above temperature range, the phase difference is also adjusted, and the elongation stress can be lowered, so that the turbidity is reduced. Further, the occurrence of cracking is suppressed, and a second protective film excellent in flatness and coloring property of the film itself is obtained. It is preferred to carry out the extension temperature in the range of (Tg + 10) to (Tg + 40) °C.

Here, the glass transition temperature is measured by a differential scanning calorimeter at a temperature of 20 ° C /min, and the intermediate point glass transition temperature (Tmg) is determined in accordance with JIS K7121 (1987). The method for measuring the glass transition temperature Tg of the specific film is measured in accordance with JIS K7121 (1987) using a differential scanning calorimeter DSC220 manufactured by SEIKO INSTUMEMTS (stock).

The cycloolefin film of the present invention preferably has a film extending at least in the width direction, and has an elongation ratio in the range of 1 to 40% of the original width, and further preferably 5 to 40% of the length direction and the width direction of the film, respectively. The extension of the range extends. In particular, the range of the elongation is further preferably extended in the range of 10 to 30% with respect to the original width. The term "elongation" as used in the present invention means the ratio (%) of the length of the film length or width after stretching to the length of the film length or width before stretching.

The method of extending in the longitudinal direction is not particularly limited. For example, the circumferential speed difference is applied to the plurality of rolls, and the two sides of the green sheet are fixed by a jig or a needle by a method of extending the circumferential speed difference in the longitudinal direction, and the distance between the jig or the needle is widened in the traveling direction to extend in the longitudinal direction. The method, or the method of extending both vertically and horizontally and extending in both directions. Of course, these methods can be used in combination.

For the extension in the width direction, a method of drying the whole step or a part of the steps in the width direction as shown in JP-A-62-46625, and maintaining the width of both ends of the width of the green sheet by a jig or a needle and drying it may be used (referred to as a method of drying and drying) The tenter method), in which the tenter type of the clamp is used, and the needle tenter is used.

When extending in the width direction, it is preferred to extend in the film width direction at an elongation speed in the range of 100 to 500%/min.

When the stretching speed is particularly 250%/min or more, since the film properties can be improved and the film is processed at a high speed, the viewpoint of production suitability is preferable, and if it is 500%/min or less, the film can be processed without being broken. good.

The preferred extension speed is in the range of 300 to 400%/min, which is effective at low magnification extension. The elongation speed is defined by the following formula (E).

Equation (E) Extension speed (%/min) = [(d ₁ /d ₂ )-1]×100(%)/t

In the formula (E), d ₁ is a width dimension of the second protective film of the present invention in the extending direction, and d ₂ is a width dimension of the second protective film of the present invention before the extending direction, t is The time required to extend (min).

The cycloolefin film of the present invention can impart a desired retardation value by stretching.

The film thickness of the cycloolefin film of the present invention is preferably in the range of 5 to 40 μm, particularly preferably in the range of 5 to 25 μm. When the in-plane retardation Ro at the measurement wavelength of 590 nm and the phase difference Rt in the thickness direction are (iii) 0 ≦ Ro ≦ 20 and (iv) | Rt | ≦ 25, respectively, when used as the second protective film, light can be provided. The polarizing plate of the film is preferably a viewpoint of imparting an optimum phase difference as a polarizing plate for an IPS mode liquid crystal display device. Further, it is preferably (iii) 0≦Ro≦10, (iv)|Rt|≦15.

The extension step is usually carried out after the extension and is maintained. That is, this step is preferably carried out in the order of the extension phase of the extension film, the retention phase of the film in the extended state, and the relaxation phase of the film in the extension direction. In the hold phase, the extension of the elongation achieved during the extension phase is maintained at the extension temperature in the extension phase. In the mitigation phase, to maintain the order After the extension of the segment is maintained in the extension phase, the elongation is relaxed by releasing the tension for extension. In the relaxation phase, it is only required to proceed below the extension temperature in the extension phase.

(3.3) Drying step

In the drying step, the stretched film is heated by a drying device (35) and dried.

The amount of the organic solvent contained in the film is adjusted so that the conditions of the drying step are appropriately adjusted.

When the film is heated by hot air or the like, it is preferable to use a nozzle which can vent the used hot air (air containing solvent or humid air) to prevent the hot air from being mixed. The hot air temperature is preferably in the range of 40 to 350 °C. Further, the drying time is preferably in the range of 5 seconds to 60 minutes, more preferably in the range of 10 seconds to 30 minutes.

Further, the heating and drying means is not limited to hot air, and for example, infrared rays, heating rolls, microwaves or the like can be used. From the viewpoint of simplicity, it is preferable to carry the film by the conveyance roller 36 arranged in a zigzag shape, and to dry it by hot air or the like. The drying temperature is preferably in the range of 40 to 350 ° C in consideration of the amount of residual solvent and the expansion ratio during transportation.

In the drying step, the film is preferably dried until the amount of the residual solvent is generally 0.5% by mass or less.

(4) Winding step (4.1) Roll processing

After the specific heat treatment or cooling treatment, it is preferred to provide the cutter to cut the end portion before the winding to obtain a good curling posture. Further, it is preferable to carry out the roll processing at both end portions of the width.

Roll processing can be formed by pressing a heated embossing roll against the end of the film width. A fine concavo-convex structure is formed on the embossing roll, and the concavo-convex structure is formed on the film by pressing it, and by loosening the end portion, adhesion of the front and back surfaces when the film is laminated into a roll shape can be prevented.

The roll pattern at both ends of the width of the second protective film of the present invention preferably has a height in the range of 4 to 20 μm and a width in the range of 5 to 20 mm.

(4.2)

As another means for obtaining a good curling posture, the overlapping masking film (also referred to as a protective film) may be simultaneously wound for the purpose of preventing the films from sticking to each other before being wound into a roll shape, and may also be used for stretching the film. At least one of the two ends, preferably the ends of the two sides are opened and the tape is taken up. The masking film is not particularly limited as long as it can protect the film, and examples thereof include a polyethylene terephthalate film, a polyethylene film, and a polypropylene film.

Further, in the present invention, the above-described roll processing is preferably carried out in the film forming step of the film, after the drying is completed and before the winding.

(4.3) Rolling step

When the amount of the residual solvent in the film is 2.0% by mass or less, the film is wound up, and the amount of the residual solvent is preferably 1.0% by mass or less, and then the film is wound up to obtain a film having good dimensional stability.

The winding method may be a general user, and examples thereof include a fixed torque method, a fixed tension method, a gradient tension method, and a program tension control method in which internal stress is fixed, and these may be used separately.

(B. Melt casting film forming method)

The cycloolefin film of the present invention can also be produced by a melt casting film formation method (hereinafter also referred to as a melt extrusion method), and an example thereof will be described below.

The method for producing a cycloolefin film by melt extrusion has a step of extruding a cycloolefin resin heated and melted at a temperature higher than a glass transition temperature (Tg) from a nozzle into a film to form a cycloolefin film (A), and The film forming support body supports the above-mentioned cycloolefin film to cool the film (B). The cyclic olefin resin heated at a temperature above the glass transition temperature (Tg) is melted, but the cycloolefin resin is hardened when cooled to below the glass transition temperature. Therefore, the soft cycloolefin resin having a glass transition temperature or higher is formed into a film shape, and then cooled and hardened to obtain a cycloolefin film of a desired shape.

In the above steps (A) and (B) in the method for producing a cycloolefin film, preferably at least in the step (B), a first stretching region is provided between the central region of the resin film and the first fixing region, and A second stretched region is disposed between the central region of the resin film and the second stretched region. Therefore, in the step (B), the cycloolefin film has, in the width direction thereof, a first fixed region, a first stretched region, a central region, a second stretched region, and a second fixed region. Further, when the same tension is applied to the first stretched region and the second stretched region, the elongation of the first stretched region and the second stretched region is set to be large The amount of elongation in the central region.

By having such a configuration, the method for producing a cycloolefin film can produce a cycloolefin film having a retardation Rt in the thickness direction of the center region of approximately zero.

Further, when an ultraviolet absorber is added to the cycloolefin film, since the retardation value increases, the selection or content of the ultraviolet absorber or the film thickness is important. The ultraviolet absorber is preferably a benzotriazole compound.

Next, the inclusion pattern will be described with respect to a method for producing a cycloolefin film by a melt casting method.

Fig. 4 is a view schematically showing an example of a dope preparation step, a casting step, and a drying step of a melt casting method to which the present invention is applicable.

As shown in Fig. 4, a manufacturing apparatus (400) for a cycloolefin film (410) includes a module (510), a casting roll (520) as a support, and an electrostatic pinning device (531 and 532) as an adhesion device, as A peeling roller (540) of the peeling device, a dressing device (550), and a take-up shaft (560) as a take-up device.

Module (510) based resin supply means disposed supplied from the not shown may be illustrated by arrow A ₁₁₀ is generally a single resin having a glass transition temperature of the above temperature. Further, the module (510) is configured such that the resin thus supplied can be extruded into a film shape through a die (516) to obtain a cycloolefin film (420) formed from a molten cycloolefin resin.

As shown in FIG. 4, the casting roll (520) has a support surface (521) which is a support surface of the cycloolefin film (420) extruded from the module (510). Roller. The casting roll (520) is disposed at a position opposite the module (510).

Further, the casting roll (520) is rotated in a direction indicated by an arrow A ₁₂₀ by a driving force given from a driving device (not shown). Therefore, the casting roll (520) has a configuration in which the cycloolefin film (420) supported by the outer peripheral surface (521) is conveyed by the rotation of the casting roll (520).

Further, a temperature adjustment means (not shown) is provided on the casting roll (520). By the temperature adjustment means, the casting roll (520) can cool the cycloolefin film (420) supported by the outer peripheral surface (521) to a desired temperature. The temperature of the casting roll (520) is set such that the cycloolefin film (420) can be held while the cycloolefin film (420) is held by the circumferential surface (521) of the casting roll (520) to be peeled off by the peeling roll (540). The glass transition temperature of the cycloolefin resin contained in the non-cycloolefin olefin film (420) is cooled.

Peeling roller (540) with lines to the casting rolls (520) in parallel, rotated in the direction of an arrow A _140. Further, the peeling roller (540) is self-casting by a casting roller (520) which is a cycloolefin film (420) which can be cooled to a glass transition temperature of a cycloolefin resin contained in the non-cycloolefin film (420). The outer peripheral surface (521) of the roller (520) is peeled off. Further, the peeling roller (540) is configured to feed the peeled cycloolefin film (420) to the dressing device (550).

The dressing device (550) is a device for cutting at least the ends from the cycloolefin film (420) peeled off by the peeling roller (540).

The dressing device (550) is provided with trimming blades (551 and 552) provided with a pair of blades on the outer circumference. The dressing device (550) is configured to feed the cycloolefin film (410) containing the remaining central region of the cut end film (428) from the cyclic olefin film (420) to the take-up shaft (560).

The take-up shaft (560) is rotated in a direction indicated by an arrow A ₁₆₀ by a drive device (not shown). Therefore, the winding device (560) has a loop olefin film (410) taken from the dressing device (550) to obtain a film roll (430).

As described above, a cycloolefin film (410) is obtained. The cycloolefin film (410) has a retardation Rt in the thickness direction close to zero. Further, the retardation Ro of the in-plane direction of the cycloolefin film (410) usually becomes a value close to zero.

Further, the cycloolefin film (410) produced by this method generally has high transparency from the viewpoint of use as the second protective film. Specifically, the total light transmittance of the cycloolefin film (410) in terms of 1 mm thick is preferably 80% or more, more preferably 90% or more. Further, the haze of the cycloolefin film in terms of 1 mm thick is preferably 0.3% or less, and particularly preferably 0.2% or less. Here, the total light transmittance is measured in accordance with JIS K7361-1997. Further, the turbidity can be measured in accordance with JIS K7136-1997.

For details of the production method of the cycloolefin film using the melt casting method and the applicable cyclic olefin resin, for example, the contents described in JP-A-2015-187629 can be referred to.

Polarizer

The polarizing plate of the present invention has a configuration in which the first protective film and the second protective film of the present invention are bonded to both surfaces of the polarizing film. It is preferable to use an ultraviolet curable adhesive or a water-based adhesive to bond the first protective film and the second protective film to both surfaces of the polarizer.

Moreover, the polarizing plate of the present invention uses polarized light as the viewing side When the plate is used, an anti-glare layer or a transparent hard coat layer, an anti-reflection layer, an antistatic layer, an anti-fouling layer, and the like are preferably provided on the protective film for the polarizing plate.

[Polarizer]

The polarizer of the main constituent elements of the polarizing plate of the present invention is an element which passes only light of a polarizing surface in a certain direction, and a representative polarizer which is known at present is a polyvinyl alcohol-based polarizing film. The polyvinyl alcohol-based polarizing film has a dyed iodine for a polyvinyl alcohol film and a dyed dichroic dye.

As the polarizer, a polarizer having a film formed by laminating a polyvinyl alcohol aqueous solution, uniaxially stretching and dyeing, or singulating thick, and then preferably performing durability treatment with a boron compound can be used. The film thickness of the polarizer is preferably in the range of 2 to 30 μm, and particularly preferably in the range of 2 to 15 μm.

In addition, it is also possible to use a vinyl unit content of 1 to 4 mol% as described in JP-A-2003-248123, JP-A-2003-342322, etc., and a degree of polymerization of 2000 to 4000, saponification. Ethylene-modified polyvinyl alcohol having a degree of 99.0 to 99.99 mol%. Among them, an ethylene-modified polyvinyl alcohol film having a hot water cut-off temperature in the range of 66 to 73 ° C is preferably used. The polarizer using the ethylene-modified polyvinyl alcohol film is excellent in color dispersibility and durability, and has a small color unevenness, and is particularly preferably used in a large liquid crystal display device.

[Production of polarizing plate]

The polarizing plate of the present invention can be produced by a general method. In the first aspect of the invention The surface of the protective film facing the polarizer is subjected to an appropriate surface treatment, and at least one surface of the polarizer produced by immersing and stretching in an iodine solution is bonded to each other by using an ultraviolet curable adhesive or a water-based adhesive described later. The second protective film was also bonded to the other side of the polarizer.

Preferably, the direction in which the polarizer is bonded is a method in which, for example, the absorption axis of the polarizer is orthogonal to the slow axis of each of the protective films.

(UV curing adhesive)

In the polarizing plate of the present invention, the protective film of the present invention and the polarizer are preferably passed through an ultraviolet curing adhesive.

In the present invention, when a protective film and a polarizer are bonded together, a polarizing plate having high strength and excellent planarity can be obtained by applying an ultraviolet curable adhesive.

<Composition of ultraviolet curing type adhesive>

As an ultraviolet curable adhesive composition for a polarizing plate, a photoradical polymerization type composition by photoradical polymerization, a photocationic polymerization type composition by photocationic polymerization, and a radical polymerization and photocation are used in combination. Polymerized hybrid composition.

The radically polymerizable compound containing a polar group such as a hydroxyl group or a carboxyl group and a radical polymerizable group containing no polar group in a specific ratio described in JP-A-2008-009329, is known. A composition of a compound or the like. In particular, the radically polymerizable compound is preferably a compound having a radically polymerizable ethylenically unsaturated bond. With Preferred examples of the compound having a radically polymerizable ethylenically unsaturated bond include a compound having a (meth) acrylonitrile group. Examples of the compound having a (meth) acrylonitrile group include an N-substituted (meth) acrylamide compound, a (meth) acrylate compound, and the like. (Meth)acrylamide refers to acrylamide or methacrylamide.

Further, as a cationic polymerization type composition, as disclosed in JP-A-2011-028234, (α) a cationically polymerizable compound, (β) a photocationic polymerization initiator, (γ) is compared with a longer wavelength of 380 nm. The ultraviolet ray-curable adhesive composition of each component of the light sensitizer and the (δ) naphthalene-based photo sensitization aid which is greatly absorbed by light is displayed. However, it is also possible to use an ultraviolet curing adhesive other than the above.

(1) Pre-processing steps

The pre-treatment step is a step of facilitating subsequent processing of the protective film and the bonding surface of the polarizer. Examples of easy subsequent processing are corona treatment, plasma treatment, and the like.

(coating step of ultraviolet curing type adhesive)

The coating step of the ultraviolet curable adhesive is applied to at least one of the bonding surface of the polarizer and the protective film for the polarizing plate, and the ultraviolet curable adhesive is applied. When the ultraviolet curable adhesive is directly applied to the surface of the polarizer or the protective film, the coating method thereof is not particularly limited, and for example, a doctor blade, a wire bar, a die coater, a comma coater, and gravure coating can be used. Various wet coating methods such as the device. Moreover, it can also be used for polarizers and protective films. After the ultraviolet curable adhesive is applied between the films, the film is uniformly pressed by a roller or the like.

(2) Lamination step

After the ultraviolet curable adhesive is applied by the above method, it is treated in the bonding step. This bonding step is to overlap the cellulose resin film thereon, for example, when the ultraviolet curing type adhesive is applied to the surface of the polarizing plate in the previous coating step. Further, when the ultraviolet curable adhesive is applied to the surface of the first or second protective film, the polarizer is superposed thereon. Further, when an ultraviolet curable adhesive is cast between the polarizer and the protective film, the polarizer and the protective film are superposed in this state. Next, in this state, the pressurization is usually sandwiched by the pressure roller from the side of the protective film on both sides. The material of the pressure roller can be metal or rubber. The pressure roller disposed on both sides can be the same material or different materials.

(3) Hardening step

In the hardening step, the ultraviolet curable adhesive is applied with ultraviolet rays to contain a cationically polymerizable compound (for example, an epoxy compound or an oxetane compound) or a radical polymerizable compound (for example, an acrylate compound, acrylamide). The ultraviolet curable adhesive layer of the compound or the like is cured, and the polarizer that has passed through the ultraviolet curable adhesive is attached to the protective film of the present invention. In the constitution of the present invention in which the protective film is bonded to both surfaces of the polarizer, the ultraviolet light-curable adhesive is applied to both surfaces of the polarizer, and the light-transmissive protective film is superposed, and ultraviolet rays are irradiated to cause two The method of simultaneously hardening the ultraviolet curing type adhesive of the surface is advantageous.

Any conditions suitable for curing the ultraviolet curable adhesive to be used in the present invention can be employed under the conditions of ultraviolet irradiation. The amount of ultraviolet irradiation is preferably in the range of 50 to 1,500 mJ/cm ² , more preferably in the range of 100 to 500 mJ/cm ² , based on the cumulative amount of light. In the present invention, it is also preferred to irradiate ultraviolet rays from the side of the first protective film from the viewpoint of improving the yield.

When the manufacturing process of the polarizing plate is performed in a continuous production line, the linear velocity varies depending on the hardening time of the adhesive, but is preferably in the range of 1 to 500 m/min, more preferably in the range of 5 to 300 m/min. More preferably in the range of 10 to 100 m/min. When the linear velocity is 1 m/min or more, productivity can be ensured, or damage in the protective film of the present invention can be suppressed, and a polarizing plate excellent in durability can be produced. In addition, when the linear velocity is 500 m/min or less, the curing of the ultraviolet curable adhesive is sufficient, and an ultraviolet curable adhesive and a polarizing plate having excellent hardness and adhesion can be formed.

"Liquid Crystal Display Device"

By using the liquid crystal display device in the case where the polarizing plate of the present invention to which the protective film of the present invention is applied is used, it is possible to produce a liquid crystal display device of the present invention which is excellent in various visibility.

The polarizing plate of the present invention can be used for liquid crystal display devices of various driving methods such as STN, TN, OCB, HAN, VA (MVA, PVA), IPS, OCB, and the like. Preferably, it is an IPS type liquid crystal display device.

The liquid crystal display device generally uses two polarizing plates of a polarizing plate on the viewing side and a polarizing plate on the backlight side, and the polarizing plate of the present invention is also preferably used. As a polarizing plate for both, it is also preferable to use it as a one-sided polarizing plate.

The bonding direction of the above-mentioned polarizing plate in the IPS type liquid crystal display device can be referred to Japanese Patent Laid-Open Publication No. 2005-234431.

The liquid crystal cell used in the present invention comprises a liquid crystal layer and a pair of substrates sandwiching the liquid crystal layer, wherein the pair of substrates has a thickness of 0.3 to 0.7 mm, and the liquid crystal display device is thinner and lighter. The language is better.

Fig. 3 is a schematic cross-sectional view showing an example of a configuration of a liquid crystal display device (100) in which the polarizing plates (101A and 101B) of the present invention described above are disposed on both surfaces of a liquid crystal cell (101C).

In Fig. 3, both sides of the liquid crystal layer (107) are sandwiched by a glass substrate (108A and 108B) as a transparent substrate to constitute a liquid crystal cell (101C), and an adhesive layer is transmitted through each surface of each of the glass substrates (108A and 108B). 106) The polarizing plates (101A and 101B) having the configuration shown in Fig. 2 are arranged to constitute a liquid crystal display device (100).

In the polarizing plates (101A and 101B), in the present invention, at least the first protective film is bonded to the positions of 102A and 102B, and the second protective film is attached to the positions of 105A and 105B. The protective film of the present invention is bonded to the polarizers (104A and 104B) by ultraviolet curing adhesives (103A to 103D), respectively. In particular, an IPS type liquid crystal display device is preferred.

The liquid crystal cell (101C) is configured by disposing an alignment film, a transparent electrode, and a glass substrate (108A and 108B) on both surfaces of the liquid crystal material.

In the liquid crystal display device (100), the polarizing plate of the present invention having excellent durability, flatness, and the like, and improved yield, even if When the glass substrate constituting the liquid crystal cell is made thinner, the panel is less likely to be bent, and as a result, a liquid crystal display device which is thinned can be obtained.

The material of the glass substrates (108A and 108B) which can be used in the liquid crystal cell (101C) is exemplified by, for example, soda lime glass, silicate glass, etc., preferably silicate glass, and more specifically, cerium oxide. Glass or borosilicate glass.

The glass constituting the glass substrate is an alkali-free glass which does not substantially contain an alkali component, and specifically, a glass having an alkali component content of 1000 ppm or less is preferable. The content of the alkali component in the glass substrate is preferably 500 ppm or less, more preferably 300 ppm or less. The glass substrate containing an alkali component undergoes cation replacement on the surface of the film, and a sodium blowing phenomenon is likely to occur. Thereby, the density of the surface layer of the film is easily lowered, and the glass substrate is easily broken.

The thickness of the glass substrates (108A and 108B) constituting the liquid crystal cell of the liquid crystal display device (100) is preferably in the range of 0.3 to 0.7 mm. When this thickness is set, it is preferable based on the viewpoint of contributing to the formation of a thin film formation of a liquid crystal display device.

The glass substrate is formed by a conventional method such as a float method, a down-draw method, an overflow down-draw method, or the like. Among them, the overflow down-draw method is preferable because the surface of the glass substrate is not in contact with the molded member at the time of molding, and the surface of the obtained glass substrate is not easily damaged.

Further, such a glass substrate can be obtained as a commercially available product, and examples thereof include an alkali-free glass AN100 (thickness: 500 μm) manufactured by Asahi Glass Co., Ltd., and a glass substrate EAGLE XG (r) Slim (thickness: 300 μm, 400 μm, etc.) manufactured by Corning Incorporated. Glass substrate made by Nippon Electric Glass Co., Ltd. (thick 100~200μm) and so on.

Further, the polarizing plates (101A, 101B) shown in Fig. 3 and the glass substrates (108A, 108B) constituting the liquid crystal cell (101C) are passed through the adhesive layer (106).

As the adhesive layer, a double-faced tape such as a two-sided tape (non-substrate tape MO-3005C) made of a thickness of 25 μm manufactured by LINTEC Co., Ltd., or the like, or a composition used in the formation of the above-mentioned active light-curable resin layer can be applied.

In addition to the effects of the present invention, the liquid crystal display device using the polarizing plate of the present invention has an advantage of excellent adhesion between layers, fading resistance, and ring-shaped unevenness of surface images.

The bonding of the surface of the retardation film side of the polarizing plate to at least one surface of the liquid crystal cell is carried out by a conventional method. Depending on the situation, it can be attached through the adhesive layer.

By using the polarizing plate of the present invention, it is possible to suppress the panel from being bent even when the screen is a large-screen liquid crystal display device having a size of 30 or more, and it is possible to obtain a liquid crystal which is excellent in visibility such as display unevenness and front contrast, and which is thin and lightweight. Display device.

[Examples]

The present invention will be specifically described below by way of examples, but the present invention is not limited thereto. In addition, in the embodiment, the expression "%" is used, and unless otherwise specified, "% by mass" is indicated.

Example 1 "Production of the first protective film"

The first protective film PET1 to PET4 of the polyester film was produced by the following method.

[Production of the first protective film PET1] (Modulation of Polyester Resin A)

Into the esterification reaction vessel, 86.4 parts by mass of terephthalic acid and 64.6 parts by mass of ethylene glycol were charged, and the mixture was heated while stirring at 200 ° C, and 0.017 parts by mass of antimony trioxide as a catalyst was introduced, and magnesium acetate tetrahydrate was added. 0.064 parts by mass and 0.16 parts by mass of triethylamine. The pressure esterification reaction was carried out under the conditions of a gauge pressure of 0.34 MPa and a temperature of 240 °C.

Next, the esterification reaction vessel was returned to normal pressure, and 0.014 parts by mass of phosphoric acid was added. Further, the temperature was raised to 260 ° C in 15 minutes, and 0.012 parts by mass of trimethyl phosphate was added. Next, after 15 minutes, the dispersion treatment was carried out in a high-pressure disperser, and after 15 minutes, the obtained esterification reaction product was transferred to a polycondensation reaction tank, and a polycondensation reaction under reduced pressure was carried out at 280 °C.

After completion of the polycondensation reaction, it was filtered by NASLON FILTER NF-05S manufactured by Nippon Seisen Co., Ltd., and extruded from a nozzle into a strand shape, and subjected to filtration treatment (pore diameter: 1 μm or less), and then cooled and solidified using cooling water. The resin was cut into pellets. The obtained polyester resin A (polyethylene terephthalate A) had an intrinsic viscosity of 0.62 cm ³ /g and contained substantially no inert particles and internal precipitated particles.

(Modulation of coating liquid for forming an intermediate layer)

The transesterification reaction and the polycondensation reaction are carried out by a usual method to prepare a terephthalic acid, 46 mol% of isophthalic acid and 8 mol, which are used as a dicarboxylic acid component (for the entire dicarboxylic acid component) of 46 mol%. 5% sodium sulfoisophthalate, a water-dispersible sulfonic acid-containing metal used as a diol component (for all diol components) 50 mol% ethylene glycol and 50 mol% neopentyl glycol Copolymerized polyester resin of bases.

Next, 51.4 parts by mass of mixed water, 38 parts by mass of isopropyl alcohol, 5 parts by mass of n-butyl cellosolve, and 0.06 parts by mass of a nonionic surfactant were heated and stirred, and after reaching 77 ° C, the above-mentioned water-dispersible sulphur was added. 5 parts by mass of the copolymerized polyester resin of the acid metal base, and the mixture was continuously heated and stirred until the solid of the resin disappeared, and then the aqueous resin dispersion was cooled to room temperature to obtain a uniform water-dispersible copolymerized polyester having a solid concentration of 5.0% by mass. Resin solution.

Further, 3 parts by mass of aggregated cerium oxide particles (manufactured by Fujitsu Sylvia Co., Ltd., SYLYSIA 310) was dispersed in 50 parts by mass of water. To 99.5 parts by mass of the water-dispersible copolymerized polyester resin liquid, 0.54 parts by mass of an aqueous dispersion of SYLYSIA 310 was added, and 20 parts by mass of water was added thereto with stirring to prepare a coating liquid for forming an adhesive layer.

(Production of polyester film PET1)

The above-prepared polyester resin A is dried by a usual method and supplied to an extruder, melted at 285 ° C, filtered with a stainless steel sintered body filter material (nominal filtration accuracy of 10 μm particles 95% cut off), and extruded from a die to a thin sheet. After being shaped, it is wound on a casting drum having a surface temperature of 30 ° C by electrostatic application casting. The film was cooled and solidified to produce an unstretched polyester film (PET film).

Then, the coating liquid for forming an adhesive layer for forming an adhesive layer was prepared by applying a coating liquid having a coating amount after drying to a thickness of 0.08 g/m ² on both sides of the unstretched PET film by a reverse roll method. Dry at 80 ° C for 20 seconds.

The unstretched film formed with the adhesion improving layer was introduced into a tenter stretching machine, and the end portion of the film was held by a jig at a temperature of 125 ° C in a heating zone extending 4.0 times in the width direction. Next, the film was maintained at a temperature of 225 ° C for 30 seconds while maintaining the width extending in the width direction, and further tempered by 3% in the width direction to prepare a uniaxially-oriented polyethylene terephthalate having a film thickness of 60 μm. The first protective film PET1 of the film.

[Production of the first protective film PET2]

In the production of the first protective film PET1, the first protective film PET2 was produced in the same manner except that the thickness of the stretched film was appropriately adjusted and the thickness after stretching was set to 80 μm.

[Production of the first protective film PET3]

10 parts by mass of a dry ultraviolet absorber (2,2'-(1,4-phenylene) bis(4H-3,1-benzoxazin-4-one)) and a polyester film (inherent viscosity is 0.62 cm ³ /g) 90 parts by mass was mixed and kneaded, and a first protective film PET3 containing a polyester film having a thickness of 110 μm containing a UV absorber was produced using a first extruder.

[Production of the first protective film PET4]

Using the first protective film PET1 produced above, a cured resin layer (hard coat layer) was formed on one surface side according to the following method, and this was used as the first protective film PET4.

(Formation of hardened resin layer (hard coat layer))

The following curable resin composition 1-1 was applied onto the first protective film PET1 having the adhesion modifying layer, and dried in a hot oven at 70 ° C for 60 seconds to evaporate the solvent in the coating film. The cumulative amount of light was 50 mJ/cm ^{2 and the} light was irradiated with ultraviolet rays to be semi-cured to form a covalent bond layer. Next, the following curable resin composition 2-1 as a second curable resin composition was applied onto the semi-cured covalent bond layer, and dried in a hot oven at 70 ° C for 60 seconds to form a coating film. After evaporating the solvent, the ultraviolet light was irradiated with light having a cumulative light amount of 200 mJ/cm ² to complete curing, and hardening (hardening) of a hard coat layer (upper layer) having a dry film thickness of 13 μm was formed on a covalent bond layer (lower layer) having a dry film thickness of 2 μm. Resin layer.

(Modulation of Curable Resin Composition 1-1)

(Modulation of Curable Resin Composition 2-1)

The characteristic values of PET1 to PET4 produced above are as follows.

PET1: film thickness = 60 m, the transmittance of ultraviolet of 380 nm = 50% = no hard coat layer, the retardation value Ro = 6 × 10 ³ nm

PET2: film thickness = 80 μm, ultraviolet transmittance at 380 nm = 50% or more, hard coat layer = none, retardation value Ro = 8 × 10 ³ nm

PET3: film thickness = 100 μm, ultraviolet transmittance at 380 nm = less than 50%, hard coat = none, retardation value Ro = 3 × 10 ³ nm

PET4: film thickness = 80 μm, ultraviolet transmittance at 380 nm = 50% or more, hard coat layer = yes, retardation value Ro = 8 × 10 ³ nm

The ultraviolet transmittance at 380 nm of the first protective film PET1 to PET4 produced above was measured by a UV-Vis spectrophotometer (product name: V7100, manufactured by JASCO Corporation), and the light transmittance (called ultraviolet light transmittance) at 380 nm was measured.

Further, the retardation value Ro in the film surface was three-dimensionally carried out at a wavelength of 590 nm in an environment of 23 ° C ‧55% RH using an automatic birefringence meter Axo Scan (Axo Scan Mueller Matrix Polarimeter: manufactured by Axo Matrix Co., Ltd.). The refractive index measurement was obtained by calculating the obtained refractive indices nx, ny, and nz.

"Production of the second protective film"

The second protective films 1 to 34 were produced using a cellulose resin according to the method described below.

[Cellulose resin, additive]

First, the details of the cellulose resin and various additives used in the production of the second protective films 1 to 34 are shown below.

(cellulose resin)

Cellulose resin A: triethyl hydrazine cellulose (acetamyl substitution = 2.9)

Cellulose resin B: cellulose acetate propionate (acetamyl substitution = 2.0, propyl ketone = 0.9)

Cellulose resin C: cellulose acetate butyrate (acetamyl substitution degree) =2.5, butyl group substitution = 0.4)

Cellulose resin D: triethyl hydrazine cellulose (acetylation degree = 2.85)

(sugar ester)

The details of the sugar esters A to F used are shown in Table 1 below.

(polyester compound) (Modulation of Polyester Compound A)

251 g of 1,2-propanediol, 278 g of phthalic anhydride, 91 g of adipic acid, 610 g of benzoic acid, and 0.191 g of tetraisopropyl titanate as an esterification catalyst were fed with a thermometer, a stirrer, and a rapid cooling tube. In a 2 L four-necked flask, the temperature was slowly raised to 230 ° C under the nitrogen flow. 15 small In the dehydration condensation reaction, after the completion of the reaction, unreacted 1,2-propanediol was distilled off at 200 ° C under reduced pressure to obtain a polyester compound A. The acid value was 0.10 mgKOH/g and the number average molecular weight was 450.

(Modulation of Polyester Compound B)

In the preparation of the above-mentioned polyester compound A, adipic acid as a dicarboxylic acid, ethylene glycol as a diol, and end-blocking of acetic acid as a monocarboxylic acid are used, and a polyester compound B (number average molecular weight) is also prepared. 2000).

(Modulation of polyester compound C~O)

In the preparation of the above-mentioned polyester compound A, the polyester compound C to O was prepared in the same manner except that the dicarboxylic acid, the diol, and the monocarboxylic acid were changed to those described in Table 2.

The details of the polyester compounds A to O prepared in the above manner are shown in Table 2.

(acrylic compound) (modulation of acrylic compound A)

The bulk polymerization is carried out by the polymerization method described in JP-A-2000-128911. Specifically, a methyl acrylate (MMA) as a monomer was placed in a flask equipped with a stirrer, a nitrogen gas introduction tube, a thermometer, an inlet, and a reflux cooling tube, and nitrogen was introduced into the flask to replace the nitrogen gas to obtain an acrylic compound.

Next, after adding thioglycerol, polymerization was carried out for 4 hours, the content was returned to room temperature, and 20 parts by mass of a tetrahydrofuran solution containing 5 mass% of hydroquinone was added thereto to terminate the polymerization. The contents were transferred to a rotary evaporator, and tetrahydrofuran, residual monomers, and residual thioglycerol were removed under reduced pressure at 80 ° C to obtain an acrylic compound A (polymethyl group) having a number average molecular weight of 1,000 as determined by GPC. Methyl acrylate).

(modulation of acrylic compounds B and C)

According to the preparation method of the above-mentioned acrylic compound A, the following acrylic compound B and acrylic compound C were prepared.

Acrylic Compound A: Polymethyl methacrylate (number average molecular weight = 1000)

Acrylic Compound B: Polybutyl acrylate (number average molecular weight = 1300)

Acrylic compound C: poly(methyl methacrylate / 2-ethylhexyl methacrylate) (mole ratio 9/1) (number average molecular weight = 1600)

(Benzotriazole compound: UV absorber 1)

Benzotriazole Compound A: TINUVIN 928 (manufactured by BASF Corporation, Japan)

Benzotriazole compound B: TINUVIN 109 (manufactured by BASF Corporation, Japan)

Benzotriazole compound C: TINUVIN 171 (manufactured by BASF Corporation, Japan)

Benzotriazole compound D: TINUVIN 326 (manufactured by BASF Corporation, Japan)

(triazine compound)

Triazine compound A: TINUVIN 466 (manufactured by BASF Corporation, Japan)

Triazine compound B: TINUVIN 477 (manufactured by BASF Corporation, Japan)

Triazine compound C: ADEKASTAB LA-F70 (made by ADEKA)

(microparticles)

Microparticle A: AEROSIL R972V (made by AEROSIL, Japan)

Microparticle B: AEROSIL 200V (manufactured by AEROSIL, Japan)

Microparticle C: AEROSIL R812 (manufactured by AEROSIL, Japan)

[Production of 2nd Protective Film 1] (modulation of main dope 1)

The main dope 1 of the following composition was prepared.

First, dichloromethane and ethanol as a solvent are added to a pressurized dissolution tank. Next, the cellulose resin A and each additive are sequentially introduced while stirring in a pressurized reaction tank to which a solvent is fed, and the mixture is heated and stirred to be completely dissolved. Further, the fine particles A were made into a 10% dispersion liquid using a part of the added ethanol, and placed in a pressurization dissolution tank.

The additive component was placed in a sealed container, dissolved while stirring, and filtered using Angstrom filter paper No. 244 made of Azure filter paper to prepare a main dope 1.

(film forming film)

The main dope 1 prepared above was uniformly cast on a stainless steel belt having a temperature of 22 ° C and a width of 2 m using a belt casting apparatus. On a stainless steel belt, the solvent was evaporated until the residual solvent amount was less than 100%, and the concentrated liquid film (green sheet) was peeled off from the stainless steel belt at a peeling tension of 160 N/m.

Next, the peeled green sheet is evaporated at 35 ° C and cut into 1.6 m wide, then using a tenter extension machine, extending the original width by 1.1 times in the width direction (TD direction) at a temperature of 160 °C. At this time, the amount of residual solvent at the time of starting the stretching by the tenter is 3 to 15% by mass.

Subsequently, the drying was carried out by conveying a plurality of rolls at a drying area of 120 ° C and 140 ° C, and the width was 1.3 m, and a roll having a width of 10 mm and a height of 2.5 μm was applied to both ends, and then the core was taken up to prepare a second roll. Protective film 1. The second protective film 1 had a film thickness of 50 μm and a winding length of 3,900 m.

[Production of 2nd Protective Film 2~34]

In the production of the second protective film 1 described above, the second protective film 2 was produced in the same manner except that the type of the cellulose resin contained in the dope, the type of each additive, the amount of addition, and the film thickness were changed to those described in Tables 3 and 4. ~34.

[Evaluation of characteristic values of the second protective film] (evaluation of UV transmittance)

For the second protective film produced as described above, an ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation, product name: V7100) was used, and the light transmittance (called UV transmittance) at 380 nm was measured, and the UV transmittance was measured in accordance with the following criteria. Evaluation.

A: The UV transmittance is less than 10%.

B: The UV transmittance is 10% or more and less than 25%.

C: The UV transmittance is 25% or more and less than 50%.

D: The UV transmittance is 50% or more and less than 80%.

E: The UV transmittance is 80% or more and less than 95%.

(Measurement of delay values Ro and Rt)

In the second protective film produced as described above, the retardation value Ro in the in-plane direction of the film and the retardation value Rt in the film thickness direction of the film were measured using an automatic birefringence meter Axo Scan (Axo Scan Mueller Matrix Polarimeter: Axo Matrix), at 23 In the environment of °C·55% RH, the three-dimensional refractive index measurement was performed at a wavelength of 590 nm, and the obtained refractive index nx, ny, and nz were calculated and found.

(Measurement of film thickness)

The film thickness of the second protective film was measured in accordance with a usual method.

The results obtained above are shown in Table 5.

"The production of polarizing plates"

Using the first protective films PET1 to 4 and the second protective films 1 to 34 produced above, polarizing plates 1 to 82 were produced according to the following methods.

[Production of Polarizing Plate 1] 1) Production of polarizer

The long-length polyvinyl alcohol film having a thickness of 60 μm is continuously conveyed through a guide roller, immersed in a dye bath (30 ° C) prepared with iodine and potassium iodide, and subjected to dyeing treatment, and subjected to a 2.5-fold extension treatment, and acidity of boric acid and potassium iodide is added thereto. In the bath (60 ° C), a total of 5 times extension treatment and crosslinking treatment were carried out, and an iodine-PVA-based polarizer having a thickness of 12 μm was dried in a dryer at 50 ° C for 30 minutes to obtain a polarizer having a moisture content of 4.9%.

2) Modulation of water-based adhesive A

The water-based adhesive A was prepared by mixing the following components.

3) Pre-treatment of the second protective film

The second protective film 1 was immersed in a saponification treatment liquid (aqueous sodium hydroxide solution at 60 ° C, concentration: 10% by mass) for 30 seconds. Further, the mixture was immersed in a water bath for 5 seconds for 2 times, and then washed with water for 5 seconds, and then dried. The drying conditions were 70 ° C for 2 minutes.

Next, the mixture was immersed in water at 30 ° C for 10 seconds for swelling treatment, and then dried at 40 ° C for 53 seconds, and then subjected to the following bonding.

4) Fit operation

After the first protective film PET2 and the second protective film 1 and the bonding surface side of the polarizing plate are subjected to corona treatment, the water-based adhesive A is applied and bonded to both surfaces of the polarizing film. Subsequently, it was immediately dried by a hot air circulating dryer set at 80 ° C for 5 minutes to prepare a polarizing plate 1.

[Production of polarizer 2~82]

In the production of the polarizing plate 1, the polarizing plates 2 to 82 were produced in the same manner except that the type of the first protective film (including the presence or absence of the cured resin layer) and the type of the second protective film were changed to the combinations of Tables 6 to 8.

Evaluation of Polarizers [Evaluation of yield (productive)]

The cleaning condition of the production step and the yield of the polarizing plate (the ratio of the good product) when the polarizing plates of the above-described respective polarizing plates were continuously produced for 10 days were measured, and the productivity (benefit) was evaluated in accordance with the following criteria.

◎ On the 10th day of continuous production, the yield of the state in which the cleaning step was not performed was 95%.

○ On the 7th day of continuous production, the yield of the state in which the cleaning step was not performed was 90%.

△ On the fifth day of continuous production, the yield of the state in which no cleaning step was performed was 85%.

× On the third day of continuous production, the yield of the state in which the cleaning step was not performed was 80%.

The results obtained above are shown in Tables 6 to 8.

"Production of Liquid Crystal Display Devices"

Using the polarizing plates 1 to 82 produced above, liquid crystal display devices 1 to 82 were produced in accordance with the following methods.

An IPS liquid crystal cell having two glass substrates having a thickness of 0.5 mm and a liquid crystal layer disposed therebetween was prepared as a liquid crystal cell. Then, the polarizing plates 1 to 82 produced as described above are bonded to each other so that the second protective film is on the liquid crystal cell side, and the liquid crystal display devices 1 to 82 are obtained. The bonding axis is such that the absorption axis of the polarizer of the polarizing plate (101A shown in FIG. 3) on the viewing side is orthogonal to the absorption axis of the polarizer of the polarizing plate (101B shown in FIG. 3) on the backlight side.

"Evaluation of Liquid Crystal Display Devices" [Durability Evaluation of Liquid Crystal Display Devices]

For each liquid crystal display device produced as described above, a super xenon weather meter SX120 (manufactured by SUGA Testing Co., Ltd.) was used from the viewing side of the liquid crystal display device, and the amount of light was 100 W/m ² at 50 ° C ‧ 65 ° C In the environment of %RH, ultraviolet rays (helium light) were irradiated, and durability evaluation was performed based on the following criteria.

○ For 30 minutes or more of ultraviolet irradiation, no deterioration of the liquid crystal display device was observed.

ΔIn the ultraviolet irradiation time of 10 minutes or more and less than 30 minutes, no deterioration of the liquid crystal display device was observed.

× Even if the ultraviolet irradiation time is less than 10 minutes, the liquid crystal display device is deteriorated, and it is difficult to visually recognize.

The results obtained above are shown in Tables 6 to 8.

As is apparent from the results of the above-described Tables 6 to 8, it is understood that the polarizing plate of the present invention is excellent in productivity and high in yield with respect to conventional products. Further, it is understood that the polarizing plate of the present invention can be effectively prevented from deteriorating the liquid crystal cell due to the external environment even after being stored for a long period of time in a light irradiation (high temperature and high humidity) environment by being incorporated in a liquid crystal display device.

Example 2 "Production of the second protective film: cycloolefin film" [Production of Second Protective Film 101] (Synthesis of cycloolefin resin 1)

8-methyl-8-methoxycarbonyltetracyclo[4.4.0.1 ^2,5 .17.10]-3-dodecene (DNM) 75 mass%, dicyclopentadiene (DCP) 24 mass%, 2 - 1% by mass of norbornene and 9 parts of 1-hexene of a molecular weight regulator and 200 parts of toluene were fed into a reaction vessel substituted with nitrogen and heated to 110 °C. 0.005 parts of triethylaluminum and 0.005 parts of methanol-modified WC16 (anhydrous methanol: PhPOCl ₂ :WC ₁₆ =103:630:427 mass ratio) were added thereto, and reacted for 1 hour to obtain a polymer. The solution of the obtained polymer was fed into an autoclave, and further 200 parts of toluene was added. Next, 0.006 parts of RuHCl(CO)[P(C ₆ H ₅ )] _{3 of a} hydrogenation catalyst was added, and after heating to 90 ° C, hydrogen gas was introduced into the reactor to set the pressure to 10 MPa. Subsequently, the pressure was maintained at 10 MPa, and the reaction was carried out at 165 ° C for 3 hours. After completion of the reaction, it was precipitated in a large amount of a methanol solution, and the precipitate was reprecipitated and purified using toluene and methanol to obtain a cycloolefin resin 1 of a copolymer.

The weight average molecular weight (Mw) of the cycloolefin tree 1 as determined by gel permeation chromatography (GPC) = 7.2 × 10 ⁴ , molecular weight distribution (Mw / Mn) = 3.3, and intrinsic viscosity (ηinh) = 0.59 cm ³ / g, glass transition temperature (Tg) = 143 °C. Further, after the methoxycarbonyl group addition ratio of the cycloolefin tree was determined by ¹³ C NMR measurement, it was confirmed that 75% by mass of a monomer having a methoxycarbonyl group was added. The cycloolefin resin obtained above has a cycloolefin resin having 75 mass% of a monomer having a methoxycarbonyl group as a hydrogen bond accepting group.

(modulation of fine particle dispersion)

The mixture was stirred and mixed for 50 minutes by a dissolving machine, and then dispersed using a high-pressure homogenizer to prepare a fine particle dispersion.

(modulation of microparticle addition solution 1)

The methylene chloride was introduced into the dissolution tank, and the fine particle dispersion prepared above was slowly added while stirring the dichloromethane to obtain 50% by mass. Further, the secondary particles have a particle size of a specific size and are dispersed by a pulverizer. This was filtered with FINEMAT NF manufactured by Nippon Seisaku Co., Ltd. to prepare a fine particle addition liquid 1.

(modulation of dope A)

In the pressurized dissolution tank to which methylene chloride was fed, the above-mentioned synthesized cycloolefin tree 1 was charged while stirring. Second, to become added in Table 1 The fine particle addition liquid was added in an amount, and the respective additives described below were added, and then heated at the dissolution temperature shown in Table 1 for 4 hours, and completely dissolved while stirring. Subsequently, filtration was carried out using an Anion filter paper No. 244 made of an Anion filter paper to prepare a dope A. The composition of the dope A is shown below.

(film formation)

The previously prepared dope A was cast on a casting support of a stainless steel belt (support temperature: 22 ° C) using a casting apparatus. The amount of the residual solvent in the dope A is preferably 20% by mass or less, and the both ends of the film in the width direction are held by a tenter, and the residual solvent amount is 10% by mass or more at a temperature of 126 ° C. It was dried by 1.01 times (1%) in the width direction. Subsequently, the film was further dried by a transfer between rolls of a heat treatment apparatus at 95 ° C for 30 to 40 minutes to prepare a second protective film 101 of a cycloolefin film. The thickness is 20 μm.

[Production of Second Protective Film 102]

In the production of the second protective film 101, the second protective film 102 was produced in the same manner except that the amount of the TINUVIN 928 was 0% by mass.

[Production of Second Protective Film 103]

In the production of the second protective film 101, the second protective film 103 was produced in the same manner as in the case of using the ARTON G7810 manufactured by JSR (manufactured) instead of the cycloolefin resin 1 and having a film thickness of 13 μm.

[Production of Second Protective Film 104]

In the production of the second protective film 103, the second protective film 104 was produced in the same manner except that the amount of the TINUVIN 928 was 0% by mass.

[Production of Second Protective Film 105]

The second protective film 105 was produced in accordance with the following method.

(Modulation of Resin Composition 2)

100 parts of a dried polymer resin having an alicyclic structure (manufactured by Zeon Corporation, Japan, glass transition temperature: 123 ° C) and benzotriazole-based ultraviolet absorber ("LA-31", manufactured by ADEKA) 5.5 parts by The twin-screw extruder was mixed, and next, the mixture was introduced into a hopper connected to an extruder, supplied to a single-shaft extruder, and melt-extruded to obtain a resin composition 2. The content of the ultraviolet absorber in the resin composition 2 was 5.2% by mass.

(Production of the front laminate 1 before extension)

The above-prepared resin composition 2 was placed in a double-flying type 50 mm single-axis extruder loaded with a polymer filter having a disk shape of 3 μm in mesh (ratio of screw effective length L to screw diameter D/L/D) In the hopper of =32), the molten resin was supplied to the manifold manifold of the module die having a surface roughness Ra of 0.1 μm at an extruder outlet temperature of 280 ° C and a gear pump rotation number of 10 rpm. On the other hand, a polymer resin having an alicyclic structure identical to that of the user of the resin composition 2 was placed in a 50 mm single-axis extruder (L) packed in a polymer filter having a leaf disc shape of 3 μm. In the hopper of /D=32), the molten resin was supplied to the manifold module at an extruder outlet temperature of 285 ° C and a gear pump rotation number of 4 rpm of the extruder. Next, a polymer resin having an alicyclic structure in a molten state, a resin composition in a molten state, and a polymer resin having an alicyclic structure in a molten state were respectively discharged from a manifold module at 280 ° C, and cast at a temperature adjustment. On the chill roll of 150 ° C, a surface layer (5 μm) made of a polymer resin having an alicyclic structure - an intermediate layer (15 μm) made of the resin composition 2 - was obtained by co-extrusion molding. A pre-extrusion laminate 1 having a width of 1400 mm and a thickness of 25 μm formed of two types of surface layers (5 μm) of a polymer resin having an alicyclic structure. Further, the amount of the air gap was set to 50 mm, and the method of casting the film in a molten state on the cooling roll was edge pinning. Both ends of the laminate were trimmed by 50 mm to form a second protective film 105.

[Production of Second Protective Film 106]

The second protective film 106 was produced in accordance with the following method.

An alicyclic olefin resin ("ZEONOR" manufactured by Zeon Corporation, Japan, glass transition temperature: 136 ° C) was passed through a die from a module and extruded to prepare a resin film. At this time, the module temperature is 260 ° C, the die length of the module is 1250 mm, and the die gap of the module die is 0.8 mm.

The obtained resin film was supported by a casting roll (diameter: 400 mm, temperature: 110 ° C), and conveyed by the rotation of the casting roll. Immediately after being supported by the outer peripheral surface of the casting roll, electrostatic charges were applied to both ends of the resin film by an electrostatic pinning device to adhere to the outer peripheral surface of the casting roll.

Subsequently, the resin film is cooled and hardened while being conveyed by the casting rolls. The hardened resin film was peeled off from the outer peripheral surface of the casting roll, and both ends were cut by a dressing device. Subsequently, the resin film formed from the central region is taken up in a roll shape and recovered. A recycled resin film having a thickness of 25 μm was produced.

"The production of polarizing plates"

Using the first protective films PET1 to PET4 produced in Example 1 and the second protective films 101 to 106 produced as described above, polarizing plates 101 to 114 were produced in accordance with the following methods.

[Production of Polarizing Plate 101] 1) Production of polarizer

A strip of polyvinyl alcohol film having a thickness of 60 μm is continuously conveyed through a guide roll and immersed in a dye bath (30 ° C) equipped with iodine and potassium iodide. After performing a dyeing treatment and applying a 2.5-fold extension treatment, a 5-fold extension treatment and a crosslinking treatment were carried out in an acidic bath (60 ° C) to which boric acid and potassium iodide were added to obtain an iodine-PVA-based polarizer having a thickness of 12 μm. It was dried in a dryer at 50 ° C for 30 minutes to obtain a polarizer having a moisture content of 4.9%.

2) Modulation of ultraviolet curing type adhesive B

The following components were mixed to prepare a liquid ultraviolet curable adhesive.

3) Lamination and polarizing plate production

After the first protective film PET4 was subjected to corona treatment on the bonding surface side, the ultraviolet curable adhesive B prepared as described above was applied to a thickness of 3 μm by a coating device having a chamber blade. After the corona treatment was applied to the bonding surface of the second protective film 101, the ultraviolet curable adhesive B was applied in the same thickness to a thickness of 3 μm.

After applying the ultraviolet curable adhesive to the first protective film PET4 and the second protective film 101, the film is bonded to the coated surface of each of the ultraviolet curable adhesives B by the roll coating on the single surface of the prepared polarizer. The first protective film PET4 is bonded to the first protective film 101 on the other surface. Subsequently, at a line speed of 20m / min, such that the integrated quantity of light of a wavelength of 280 ~ 320nm become 320mJ / cm ² of the embodiment from the first protective film is irradiated a metal halide lamp, so that both sides of the adhesive curing to obtain a polarizing plate 101.

[Production of polarizing plates 102 to 114]

In the production of the polarizing plate 101, the polarizing plates 102 to 114 were produced in the same manner except that the first protective film and the second protective film were changed to the combinations described in Table 9.

"Production of Liquid Crystal Display Devices"

Using the polarizing plate produced above, a liquid crystal display device was produced in accordance with the following method.

An IPS liquid crystal cell having two glass substrates having a thickness of 0.5 mm and a liquid crystal layer disposed therebetween was prepared as a liquid crystal cell. Then, the polarizing plate 101 produced as described above is bonded to the liquid crystal cell side so that the second protective film is formed on the liquid crystal cell side, and the liquid crystal display devices 101 to 114 are obtained. The bonding axis is such that the absorption axis of the polarizer of the polarizing plate (101A shown in FIG. 3) on the viewing side is orthogonal to the absorption axis of the polarizer of the polarizing plate (101B shown in FIG. 3) on the backlight side.

"Evaluation of Liquid Crystal Display Devices and Polarizers"

The durability and the yield were evaluated in the same manner as in the method described in Example 1, and the results are shown in Table 9.

As is apparent from the results of the above-described Table 9, it is understood that the polarizing plate of the present invention is excellent in productivity and high in yield with respect to the conventional product. Further, it is understood that the polarizing plate of the present invention can be effectively prevented from deteriorating the liquid crystal cell due to the external environment even after being stored for a long period of time in a light irradiation (high temperature and high humidity) environment by being incorporated in a liquid crystal display device.

[Industrial availability]

The polarizing plate of the present invention can be preferably used in liquid crystal display devices of various driving methods such as STN, TN, OCB, HAN, VA (MVA, PVA), IPS, OCB, etc., preferably an IPS type liquid crystal display device, even if The screen is a large-screen liquid crystal display device of 30 or more types, and it is also possible to suppress the panel from being bent, and it is possible to realize a liquid crystal display device which is excellent in visibility such as uneven display and front contrast, and which is thin and lightweight.

Claims (12)

A polarizing plate characterized in that a polarizing plate is formed in the order of a first protective film, a polarizing film, and a second protective film, and the first protective film has super-birefringence in a plane, and is 380 nm. a polyester film having a light transmittance of 50% or more but not having an ultraviolet absorber, and the second protective film having a light transmittance of less than 50% at 380 nm and containing an ultraviolet absorber, and a cellulose resin or a cycloolefin A light transmissive film of resin. The polarizing plate of claim 1, wherein the first protective film is polyethylene terephthalate or polyethylene naphthalate. The polarizing plate of claim 1, wherein the first protective film is polyethylene terephthalate. The polarizing plate according to any one of claims 1 to 3, wherein the second protective film has a retardation value Ro (nm) in the film surface defined by the following formula (i) and a film film defined by the following formula (ii) The retardation value Rt (nm) in the thickness direction satisfies the conditions specified by the following formulas (iii) and (iv), (i) Ro = (n _{x -} n _y ) × d (ii) Rt = ((n _x + n _{y ) / 2-n z) ×} d (iii) 0 ≦ Ro ≦ 20 (iv) | Rt | ≦ 25 [ wherein, n _x is a refractive index of the slow axis within the film plane, n _y is the plane of the film The refractive index perpendicular to the direction of the slow axis direction, n _z is the refractive index perpendicular to the direction of the film face, and d is the film thickness (nm)]. The polarizing plate of any one of claims 1 to 3, wherein the aforementioned second The protective film contains at least one ester selected from the group consisting of sugar esters and polyesters. The polarizing plate according to any one of claims 1 to 3, wherein the second protective film contains at least one ultraviolet absorber selected from the group consisting of a benzotriazole-based compound and a triazine-based compound. The polarizing plate according to any one of claims 1 to 3, wherein the first protective film has an ultraviolet curable resin layer. A method of producing a polarizing plate according to any one of claims 1 to 7, characterized in that the film having a light transmittance of less than 50% at 380 nm is formed by a melt casting method. The second protective film described above. A method of producing a polarizing plate according to any one of claims 1 to 7, characterized in that the film having a light transmittance of less than 50% at 380 nm is formed by a solution casting method. The second protective film described above. A liquid crystal display device comprising a polarizing plate according to any one of claims 1 to 7 on a surface of a viewing side (front side) of the liquid crystal cell. A liquid crystal display device comprising a polarizing plate according to any one of claims 1 to 7 on a side of a viewing side (front side) and a non-viewing side (rear side) of the liquid crystal cell. The liquid crystal display device of claim 10 or 11, wherein the film thickness of the glass substrate of the liquid crystal cell is in the range of 0.3 to 0.7 mm.