JP6524994B2 - Method of manufacturing polarizing plate - Google Patents

Description

  The present invention relates to a polarizing plate, a method of manufacturing a polarizing plate, and a liquid crystal display.

  BACKGROUND In recent years, the demand for liquid crystal display devices as liquid crystal displays of portable devices such as smartphones and tablet terminals has increased. Such a small liquid crystal display device 1 includes, for example, an IPS mode liquid crystal cell 3 having a touch panel module mounted thereon, and a pair of polarizing plates 5 and 7 for holding the liquid crystal cell 3 (see FIG. 3). The polarizing plate 5 includes a polarizer 5-1, a protective film 5-3A (F2) disposed on the surface on the liquid crystal cell side, and a protective film 5-3B (F1) disposed on the surface opposite thereto. And. Similarly, in the polarizing plate 7, a polarizer 7-1, a protective film 7-3A (F3) disposed on the surface on the liquid crystal cell side, and a protective film 7-3B disposed on the opposite surface And (F4).

  The polarizing plate includes, for example, a polarizer and two cellulose ester films as protective films sandwiching the polarizer, and among them, a cellulose ester film disposed on the liquid crystal cell side is: 0 nm ≦ Re (630) ≦ 20 nm, | Rth There is known a polarizing plate or the like which is a film satisfying (630) 例 え ば 25 nm (for example, Patent Document 1). In the document, in order to suppress display unevenness due to changes in humidity or temperature, the dimensional change rate of the cellulose ester film disposed on the liquid crystal cell side is made as small as possible, specifically 0.5% or less. It is shown.

  Such a polarizing plate is usually obtained by adhering a polarizer and a cellulose ester film with a polyvinyl alcohol-based adhesive (water glue) or the like (for example, Patent Document 1). In recent years, it is not necessary to use water in the manufacturing process of a polarizing plate, and it is possible to adhere well in a short time, so that an active energy ray curing adhesive is used instead of a polyvinyl alcohol adhesive (water glue). is there.

JP, 2008-217022, A

  However, a polarizing plate in which a conventional protective film as shown in Patent Document 1 and a polarizer are adhered via an active energy ray-curable adhesive tends to cause display unevenness of the liquid crystal display device, and the visibility is lowered. There was a problem that it was easy to do. This problem is particularly pronounced in small liquid crystal displays.

  The reason for the decrease in visibility is not necessarily clear, but is considered as follows. That is, when the inside of the liquid crystal display device 1 becomes high temperature and high humidity, the polarizers 5-1 and 7-1, particularly the polarizer 7-1 tend to undergo large dimensional changes (shrinkage); the glass substrate of the liquid crystal cell 3 has dimensions It is hard to change. Then, when the protective film 7-3A (F3) disposed between the polarizer 7-1 and the glass substrate of the liquid crystal cell 3 is bonded to the polarizer 7-1 with an active energy ray curable adhesive. Since the adhesive strength is stronger than that of the conventional water glue, the shrinkage of the polarizer 7-1 is easily transmitted to the protective film 7-3A (F3). At this time, when the dimensional change rate of the protective film 7-3A (F3) is small, the contraction force of the polarizer 7-1 applied to the protective film 7-3A (F3) becomes relatively large, and the protective film 7-3A (F3) Strain is likely to occur in F3). When such distortion occurs, it is considered that optical distortion (birefringence) is likely to occur and display unevenness of the display device is likely to occur.

  The small liquid crystal display device is exposed to a high temperature environment or a high humidity environment depending on the use conditions. Moreover, the small liquid crystal display device not only includes a rechargeable battery as a heat source, but also has a small device volume. As a result, heat and moisture tend to be accumulated in the device, particularly when charging or when used in a high temperature or high humidity environment, and optical distortion tends to be particularly likely to occur.

  The present invention has been made in view of the above circumstances, and is a polarizing plate in which a polarizer and a protective film are bonded via an active energy ray-curable adhesive layer, and the visibility of the liquid crystal display device is lowered. It is an object of the present invention to provide a polarizing plate capable of suppressing

[1] A polarizer, a protective film A disposed on one side of the polarizer, and a protective film B disposed on the other side of the polarizer, wherein at least the protective film A has active energy The protective film A is bonded to the polarizer via a cured product layer of a linear curing adhesive, and the protective film A contains a polyester compound obtained by polycondensation of a cellulose ester and a diol and a dicarboxylic acid, and The dimensional change rate of the film in the long side direction α of the protective film A after 100 hours of storage at 80 ° C. and 90% RH, the content of the polyester compound being 5 to 30% by mass with respect to the cellulose ester Assuming that (%) is A (α) and the dimensional change rate (%) in the short side direction β orthogonal to the long side direction α is A (β), the protective film A has the following formula (1) 2) full It is, a polarizing plate.
−1.5 ≦ A (α) ≦ −0.3 (1)
−1.5 ≦ A (β) ≦ −0.3 (2)
[2] The polyester compound has a weight between a dicarboxylic acid selected from the group consisting of aliphatic dicarboxylic acids and alicyclic dicarboxylic acids and a diol selected from the group consisting of aliphatic diols, alkyl ether diols and alicyclic diols The polarizing plate as described in [1], which is a compound obtained by condensation.
[3] The polarizing plate according to [1] or [2], wherein the protective film A satisfies the following formulas (3) and (4).
−1.5 ≦ A (α) <− 0.5 (3)
−1.5 ≦ A (β) <− 0.5 (4)
[4] The protective film B is adhered to the polarizer through a cured product layer of an active energy ray-curable adhesive, and the protective film B is stored for 100 hours at 80 ° C. and 90% RH. When the dimensional change (%) in the long side direction α of the film is B (α) and the dimensional change (%) in the short side direction β orthogonal to the long side direction α is B (β) The polarizing plate according to any one of [1] to [3], wherein the protective films A and B satisfy the following formulas (5) and (6).
| A (α) -B (α) | ≦ 0.4 (5)
| A (β) -B (β) | ≦ 0.4 (6)
[5] The polarizing plate according to any one of [1] to [4], wherein the thickness of the polarizer is 3 to 15 μm.
[6] The protective film A is defined by the following formula (I), and the retardation in the in-plane direction measured at a measurement wavelength of 590 nm is defined as Ro (590), and is measured by the following formula (II) When retardation in the thickness direction measured at a wavelength of 590 nm is Rth (590), any one of [1] to [5] satisfying | Ro (590) | ≦ 10 nm, | Rth (590) | ≦ 10 nm The polarizing plate described in.
Formula (I) Ro = (nx-ny) x t (nm)
Formula (II) Rth = {(nx + ny) / 2−nz} × t (nm)
(In the formulas (I) and (II),
nx represents the refractive index in the slow axis direction x where the refractive index is maximum in the in-plane direction of the film; ny represents the refractive index in the direction y orthogonal to the slow axis direction x in the in-plane direction of the film Nz represents the refractive index in the film thickness direction z; t (nm) represents the film thickness)
[7] The polarizing plate according to any one of [1] to [6], wherein the protective film A further contains a lubricant.
[8] The polarizing plate according to any one of [1] to [7], wherein the protective film B further contains a high hardness agent.
[9] The polarizing plate according to any one of [1] to [8], wherein the thickness of the protective film A is 10 to 60 μm.
[10] The polarizing plate according to any one of [1] to [9], wherein the protective film A is disposed so as to be on the liquid crystal cell side.
[11] The method for producing a polarizing plate according to any one of [1] to [10], wherein 1) a step of preparing a protective film A; and 2) a polarizer and one surface of the polarizer A laminate comprising the protective film A laminated via an active energy ray-curable adhesive layer, and a protective film B disposed on the other surface of the polarizer via an active energy ray-curable adhesive layer And 3) irradiating the laminate with active energy rays to cure the active energy ray-curable adhesive layer to obtain a polarizing plate; and 1) preparing the protective film A. The process includes 1A) a cellulose ester, and a polyester compound obtained by polycondensation of a diol and a dicarboxylic acid, and the content of the polyester compound is 5 to 30% by mass with respect to the cellulose ester. A step of obtaining a film-like material; 1B) a step of stretching the film-like material at a temperature of 110 to 135 ° C. at a draw ratio of 1.03 to 1.06 times; and 1C) obtained by stretching And drying the film at a temperature of 100 to 120 ° C. for 5 to 10 minutes while conveying the film at a tension of 70 to 80 N / m.

[12] A first polarizing plate, a liquid crystal cell, a second polarizing plate, and a backlight in this order, the second polarizing plate described in any of [1] to [10] The protective film A of the second polarizing plate is disposed on the liquid crystal cell, or both of the first polarizing plate and the second polarizing plate are [1] to [1]. 10] The liquid crystal display device according to any one of 10), wherein the protective film A of the first polarizing plate and the protective film A of the second polarizing plate are disposed on the liquid crystal cell.
[13] The liquid crystal display device according to [12], wherein the liquid crystal cell is an IPS mode or FFS mode liquid crystal cell.
[14] The liquid crystal display device according to [12] or [13], which is a small liquid crystal display device including a display unit having a length of 6 inches or less in a diagonal direction and a rechargeable battery.

  According to the present invention, it is a polarizing plate in which the polarizer and the protective film are bonded via the active energy ray-curable adhesive layer, and the visibility of the liquid crystal display is lowered, particularly the visibility of the small liquid crystal display It is possible to provide a polarizing plate that can suppress the decrease in

It is a figure which shows an example of a structure of the polarizing plate of this invention. It is a schematic diagram which shows an example of a small liquid crystal display device. It is a schematic diagram which shows an example of the basic composition of a liquid crystal display device.

1. Polarizing Plate The polarizing plate of the present invention includes a polarizer, a protective film A disposed on one side thereof, and a protective film B disposed on the other side.

  FIG. 1 is a view showing an example of the configuration of the polarizing plate of the present invention. As shown in FIG. 1, the polarizing plate 10 of the present invention comprises a polarizer 11, a protective film 13A (protective film A) disposed on one side, and a protective film 13B disposed on the other side. And a protective film B). The protective films 13A and 13B are bonded to the polarizer 11 through the cured product layers 15 and 15 of the active energy ray-curable adhesive, respectively. Of the protective films 13A and 13B, the protective film 13A is preferably disposed on a liquid crystal cell of a display device described later.

1-1. Polarizer 11
The polarizer 11 is an element which transmits only light having a polarization plane in a certain direction, and a typical polarizer known at present is a polyvinyl alcohol-based polarizing film. The polyvinyl alcohol-based polarizing film includes a polyvinyl alcohol-based film dyed with iodine and a dye dyed with a dichroic dye.

  The polyvinyl alcohol-based polarizing film may be a film obtained by uniaxially stretching a polyvinyl alcohol-based film and then dyed with iodine or a dichroic dye (preferably, a film further subjected to a durability treatment with a boron compound); After the alcohol-based film is dyed with iodine or a dichroic dye, it may be a uniaxially stretched film (preferably, a film further subjected to a durability treatment with a boron compound).

  The thickness of the polarizer 11 is preferably 2 to 30 μm, and more preferably 3 to 15 μm, because it can reduce the thickness of the polarizing plate and can reduce the shrinkage due to heat and humidity.

  As described above, when the polarizer and the protective film are bonded via the cured product layer of the active energy ray curable adhesive, the heat and humidity of the protective film disposed between the polarizer and the liquid crystal cell When the dimensional change rate due to is small, it is likely to cause display unevenness (deterioration in visibility) of the display device. On the other hand, the present inventors appropriately increase the dimensional change rate of the protective film 13A (protective film A) disposed between the polarizer and the liquid crystal cell to display unevenness (visibility) in the display device. Was found to be able to suppress

  Although the reason is not necessarily clear, it is considered as follows. The shrinkage force of the protective film 13A can be increased by setting the dimensional change rate of the protective film 13A (protective film A) disposed between the polarizer and the glass substrate of the liquid crystal cell to a certain value or more. As a result, the contraction force of the polarizer 11 applied to the protective film 13A can be relatively reduced, and the distortion generated in the protective film 13A can be reduced. As a result, it is considered that optical distortion (birefringence) of the protective film 13A can be reduced, and display unevenness can be reduced.

That is, in the present invention, the dimensional change (%) in the long side direction α of the protective film 13A disposed between the polarizer and the liquid crystal cell after storing for 100 hours under 80 ° C. and 90% RH. Where A (α) and the dimensional change (%) in the short side direction β orthogonal to the long side direction α is A (β), the protective film A satisfies the following formulas (1) and (2) Is preferred.
−1.5 ≦ A (α) ≦ −0.3 (1)
−1.5 ≦ A (β) ≦ −0.3 (2)

In order to further reduce the distortion generated in the protective film 13A, the protective film 13A more preferably satisfies the following formulas (3) and (4).
−1.5 ≦ A (α) <− 0.5 (3)
−1.5 ≦ A (β) <− 0.5 (4)

  The dimensional change of the film means the ratio of the dimensional change of the film after storage for 100 hours at 80 ° C. and 90% RH to the film before storage. The long side direction α of the protective film 13A indicates a long direction (MD direction) or a direction (TD direction) orthogonal to it in a roll of a long polarizing plate; preferably, a direction (TD perpendicular to the long direction) Direction). When the protective film 13A is a square sheet film, the long side direction α of the protective film 13A may be any one of two orthogonal sides. The longitudinal direction (MD direction) of the polarizing plate is orthogonal to or coincident with the absorption axis direction of the polarizer, and preferably coincides with the absorption axis direction of the polarizer.

  In order to make the dimensional change rate of the protective film 13A into the above range, for example, it is preferable to lower the orientation of the cellulose ester molecules constituting the protective film 13A. The orientation of the cellulose ester molecule can be adjusted by the composition of the protective film A and the production conditions (stretching conditions, drying conditions after stretching, and transport conditions). In order to increase the dimensional change rate of the protective film 13A, for example, 1) the content of the polyester compound is made constant or less; 2) the stretching conditions are set such that the stretching tension applied to the film is low; It is preferable to lower the tension, and it is more preferable to make the drying conditions after stretching in 4) in addition to the above 1) to 3) loose.

1-2. Protective film 13A
As described above, the protective film 13A may be disposed in contact with the liquid crystal cell directly or through another layer, and may have a phase difference adjusting function. The protective film A contains a cellulose ester as a main component.

(Cellulose ester)
The cellulose ester is a compound obtained by subjecting cellulose and at least one of an aliphatic carboxylic acid having 2 to 22 carbon atoms and an aromatic carboxylic acid to an esterification reaction.

  Examples of cellulose esters include cellulose triacetate, cellulose diacetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose benzoate, cellulose acetate benzoate and the like. Among them, those having low retardation expression are preferable, and cellulose triacetate is preferable.

  The total degree of substitution of the acyl group of the cellulose ester is about 2.0 to 3.0, preferably 2.5 to 3.0, more preferably 2.7 to 3.0, still more preferably 2.8 to It is 2.95. In order to lower the phase difference expression, it is preferable to increase the total degree of substitution of the acyl group.

  The number of carbon atoms of the acyl group contained in the cellulose ester is preferably 2 to 7, and more preferably 2 to 4. The acyl group contained in the cellulose ester preferably contains an acetyl group in order to obtain good heat resistance and the like. The degree of substitution of the acyl group having 3 or more carbon atoms is preferably 0.9 or less, and more preferably 0.

  The degree of substitution of the acyl group of the cellulose ester can be measured by the method defined in ASTM-D817-96.

The weight average molecular weight of the cellulose ester is preferably 5.0 × 10 ^{4 to} 5.0 × 10 ⁵ and 1.0 × 10 ^{5 to} 3.0 × in order to obtain a certain mechanical strength or more. more preferably from 10 ^5, even more preferably from 1.5 × ¹⁰ 5 to 2.8 × 10 ^5. The molecular weight distribution (weight average molecular weight Mw / number average molecular weight Mn) of the cellulose ester is preferably 1.0 to 4.5.

The weight average molecular weight and molecular weight distribution of the cellulose ester can be measured by gel permeation chromatography (GPC). The measurement conditions are as follows.
Solvent: methylene chloride Column: Three Shodex K806, K805, K803G (manufactured by Showa Denko KK) are connected and used.
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Science)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0 ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) A calibration curve with 13 samples of Mw = 1.0 × 10 ^{6 to} 5.0 × 10 ² is used. The 13 samples are preferably selected at approximately equal intervals.

(Polyester compound)
The protective film 13A preferably further includes a polyester compound in order to facilitate adjustment of the dimensional change rate and the retardation.

  The polyester compound is a compound obtained by polycondensation of a dicarboxylic acid and a diol. The dicarboxylic acid may be one or more selected from the group consisting of aliphatic dicarboxylic acids, alicyclic dicarboxylic acids, and aromatic dicarboxylic acids. The diol may be one or more selected from the group consisting of aliphatic diols, alkyl ether diols, alicyclic diols, and aromatic diols. Among them, a dicarboxylic acid selected from the group consisting of aliphatic dicarboxylic acids and alicyclic dicarboxylic acids, aliphatic diols, alkyl ether diols, and the like, since it is difficult to express retardation and the dimensional change rate does not become excessively small. And polyester compounds (aliphatic polyester compounds) obtained by polycondensation of a diol selected from the group consisting of and alicyclic diols are preferable.

That is, the polyester compound is preferably represented by the general formula (1) or (2).
General formula (1):
B _1- (GA-) mG-B ₁

  G in the general formula (1) represents a group derived from an aliphatic diol or an alkyl ether diol. It is preferable that the carbon atom number of aliphatic diol is 2-12. Examples of aliphatic diols include ethylene glycol, diethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1, 5-pentanediol, 1,6-hexanediol, 1,5-pentylene glycol and the like, preferably ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butylene glycol, It is 1, 3- butylene glycol, 1, 4- butylene glycol, 1, 6- hexanediol.

  It is preferable that the carbon atom number of alkyl ether diol is 4-12. Examples of alkyl ether diols include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol and the like.

  A in the general formula (1) represents a group derived from an aliphatic dicarboxylic acid or an alicyclic dicarboxylic acid. It is preferable that the carbon atom number of aliphatic dicarboxylic acid is 4-12. Examples of aliphatic dicarboxylic acids include malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid and the like.

B _{1 in the} general formula (1) represents a group derived from an aliphatic monocarboxylic acid or an alicyclic monocarboxylic acid. It is preferable that the carbon atom number of aliphatic monocarboxylic acid is 1-12. Examples of aliphatic monocarboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthate, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid Saturated fatty acids such as tridecyl acid, myristic acid, pentadecyl acid, palmitic acid, heptadecyl acid, stearic acid, nonadecanoic acid, arachic acid, behenic acid, lignoceric acid, cerotenic acid, heptacosanoic acid, montanic acid, melissic acid, lacceric acid, Acetic acid is preferred because it contains unsaturated fatty acids such as undecylenic acid, oleic acid, sorbic acid, linoleic acid, linolenic acid, arachidonic acid and the like and has good compatibility with the cellulose ester.

It is preferable that none of B ₁ , G and A in the general formula (1) contains an aromatic ring, for example, in order to make it difficult to express a phase difference. m represents the number of repetitions, and is preferably 1 or more and 170 or less.

Examples of the polyester compound represented by the general formula (1) include those shown in Table 1.

General formula (2):
B _2- (A-G-) nA-B ₂

G and A in the general formula (2) are defined in the same manner as G and A in the general formula (1), respectively. B _{2 in the} general formula (2) represents a group derived from an aliphatic monoalcohol or an alicyclic monoalcohol. It is preferable that the carbon atom number of aliphatic monoalcohol is 1-12. Examples of aliphatic monoalcohols include methanol, ethanol, propanol, isopropanol and the like; examples of alicyclic monoalcohols include cyclohexyl alcohol and the like.

It is preferable that none of B ₂ , G and A in the general formula (2) contains an aromatic ring, for the purpose of making it difficult to express a phase difference. n represents the number of repetitions, and is preferably 1 or more and 170 or less.

Examples of the polyester compound represented by the general formula (2) include those shown in Table 2.

  The weight average molecular weight Mw of the polyester compound is preferably 20000 or less, more preferably 5000 or less, and most preferably 3000 or less, from the viewpoint of improving the compatibility with the cellulose ester. On the other hand, the weight average molecular weight Mw of the polyester compound may be 400 or more, preferably 700 or more, and most preferably 1000 or more from the viewpoint of suppressing volatilization of the polyester compound during film formation.

  The content of the polyester compound is preferably 1 to 40% by mass, more preferably 5 to 30% by mass, with respect to the cellulose ester, from the viewpoint of obtaining a plastic effect of the film and a preferable retardation. It is more preferable that it is -20 mass%, and 10-18 mass% is the most preferable.

  The polyester compound represented by the general formula (1) or (2) has a smaller effect of orienting the cellulose ester molecules than the aromatic polyester compound, so the dimensional change of the protective film 13A due to heat and humidity is excessive. Is hard to get smaller. Moreover, the polyester compound represented by General formula (1) or (2) can reduce preferably the retardation of protective film 13A, especially Rth.

  The protective film 13A may optionally include various additives such as a peeling aid, an ultraviolet light absorber, a matting agent (fine particles) or a lubricant for imparting slipperiness, a high hardness agent described later, an impact reinforcing material for enhancing toughness, and the like. It may further comprise an agent.

(UV absorber)
The ultraviolet absorber may be a benzotriazole compound, a 2-hydroxybenzophenone compound, or a salicylic acid phenyl ester compound. Specifically, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- Triazoles such as (3,5-di-t-butyl-2-hydroxyphenyl) benzotriazole, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2,2'-dihydroxy-4 -Benzophenones such as methoxybenzophenone are mentioned.

  The UV absorber may be a commercially available product, for example, Tinuvin 109, Tinuvin 171, Tinuvin 234, Tinuvin 326, Tinuvin 327, Tinuvin 328, Tinuvin series such as Tinuvin 928 from BASF Japan, or 2, 2'-methylenebis [6- (2H-benzotriazol-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol] (molecular weight 659; an example of a commercially available product manufactured by ADEKA Corporation LA 31) etc. are included.

  When a protective film is arrange | positioned at the surface by the side of the liquid crystal cell of a polarizer (when it is used as protective film F2 or F3 mentioned later), an ultraviolet protection agent is not essential, and content of an ultraviolet absorber is cellulose ester. On the other hand, it may be about 0 to 0.5% by mass. On the other hand, when the protective film is disposed on the surface of the polarizer on the side opposite to the liquid crystal cell (when it is used as a protective film F1 or F4 described later), the content of the ultraviolet inhibitor is based on the mass of cellulose ester The ratio may be about 1 ppm to about 5.0%, preferably about 0.5 to about 3.0%.

(Lubricant)
The protective film 13A preferably further contains a lubricant. The protective film 13A is manufactured with a low conveying tension in order to make the dimensional change rate due to heat and humidity be a certain level or more. However, when the transport tension is lowered, contact failure between the protective film and the transport roll occurs, the surface of the protective film is easily scratched, and the haze tends to increase. Therefore, when the protective film 13A further includes a lubricant, poor contact with the roll can be suppressed, and an increase in haze due to the same can be suppressed.

The lubricant may be polydimethylsiloxane such as polydimethylsiloxane and polydiethylsiloxane, higher fatty acid, higher aliphatic alcohol, higher fatty acid amide, higher fatty acid metal salt, ester of higher fatty acid and higher aliphatic alcohol, and the like. Among these, the compound represented by the following general formula (3) is preferable.

  L in the general formula (3) contains at least an ester bond (-C (= O) O-), an amide bond (-C (= O) NH-) or a carbonyl group (-C (= O)-); Represents a group of valence. These carbonyl groups can impart good affinity to the cellulose ester to the compound represented by the general formula (3). Specifically, L is an ester bond, an amide bond, a carbonyl group, or an “ester bond, an amide bond or a carbonyl group, and an alkylene group, a nitrogen atom, an oxygen atom, a sulfur atom, a zinc atom, a calcium atom and a magnesium atom A divalent group in combination with one or more selected from the group consisting of: an ester bond, an amide bond or a carbonyl group, and an alkylene group, since a good affinity to a cellulose ester is easily obtained And "a divalent group in combination with one or more selected from the group consisting of nitrogen atom, oxygen atom, sulfur atom, zinc atom, calcium atom and magnesium atom".

Example of "a divalent group in which an ester bond, an amide bond or a carbonyl group is combined with one or more selected from the group consisting of an alkylene group, a nitrogen atom, an oxygen atom, a sulfur atom, a zinc atom, a calcium atom and a magnesium atom" To
_{-C (= O) -O-R} 3 -O-C (= O) -, - C (= O) -NH-R 3 -NH-C (= O) - (R 3 is 1 to carbon atoms 5 alkylene groups);
-C (= O) -O-M-O-C (= O)-(where M is a zinc atom, a calcium atom or a magnesium atom);
_{-C (= O) -R 4 -O} -R 4 -C (= O) -, - C (= O) -R 4 -S-R 4 -C (= O) -, - C (= O) -R ₄ -NH-R ₄ -C (= O)-(R ₄ is an alkylene group having 1 to 5 carbon atoms); and -C (= O) -R ₅ -C (= O)-(R ₅ ) Is an alkylene group having 1 to 5 carbon atoms) and the like.

R _{1 in the} general formula (3) represents an alkyl group having 8 to 26 carbon atoms or an alkenyl group having 8 to 26 carbon atoms. The number of carbon atoms of the alkyl group and the alkenyl group is more preferably 10 or more and 26 or less because good slipperiness can be easily obtained. The alkyl group and the alkenyl group may be linear or branched, and are preferably linear because good slipperiness is easily obtained.

R _{2 in the} general formula (3) represents a hydrogen atom, an alkyl group having 8 to 26 carbon atoms, or an alkenyl group having 8 to 26 carbon atoms; in order to obtain good slip, preferably It is an alkyl group having 8 to 26 carbon atoms, or an alkenyl group having 8 to 26 carbon atoms. The number of carbon atoms of the alkyl group and the alkenyl group is more preferably 10 or more and 26 or less because good slipperiness can be easily obtained. The alkyl group and the alkenyl group may be linear or branched, and are preferably linear because good slipperiness is easily obtained.

When R ₂ is a hydrogen atom, -LR ₂ may be -C (= O) OH, -C (= O) NH ₂ or the like.

R ₁ and R ₂ may optionally further have a substituent such as an OH group. Moreover, R ₁ and R ₂ may be the same as or different from each other.

Examples of the compound represented by the general formula (3) include the following.

  The content of the lubricant is preferably 0.05 to 5% by mass, and more preferably 0.1 to 3% by mass with respect to the protective film 13A. When the content of the lubricant is a certain amount or more, the slipperiness of the film at the time of film formation is enhanced, and the increase in haze due to the film surface being scratched can be suppressed. If the content of the lubricant is below a certain level, there is no risk of bleeding.

(Matting agent)
The matting agent can impart slipperiness to the protective film 13A. The matting agent may be fine particles made of an inorganic compound or an organic compound having heat resistance in the film forming step without impairing the transparency of the obtained film.

  Examples of inorganic compounds constituting the matting agent include silicon dioxide (silica), titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate , Aluminum silicate, magnesium silicate and calcium phosphate. Among these, silicon dioxide and zirconium oxide are preferable, and silicon dioxide is more preferable in order to reduce an increase in haze of the obtained film.

  Specific examples of silicon dioxide include Aerosil 200V, Aerosil R972V, Aerosil R972, R974, R812, 200, 300, R202, OX50, TT600, NAX50 (manufactured by Nippon Aerosil Co., Ltd.), Sea Hoster KEP-10, Sea Hoster KEP -30, SeaHoster KEP-50 (above, manufactured by Nippon Shokubai Co., Ltd.), Silo Hobik 100 (manufactured by Fuji Silysia), nip seal E220A (manufactured by Nippon Silica Kogyo), Adoma Fine SO (manufactured by Admatex), and the like.

  The particle shape of the matting agent may be amorphous, needle-like, flat or spherical, and may preferably be spherical from the viewpoint that the transparency of the obtained film tends to be good.

  The matting agent may be used alone or in combination of two or more. In addition, by simultaneously using particles different in particle diameter and shape (for example, needle shape and spherical shape etc.), both transparency and slipperiness may be highly achieved.

  The particle size of the matting agent is preferably smaller than the wavelength of visible light because light scatters and the transparency decreases when the size is close to the wavelength of visible light, and it is further preferable that the wavelength of visible light is 1 It is preferable that it is / 2 or less. However, if the particle size is too small, the effect of improving the slipperiness may not be exhibited, so the particle size is preferably in the range of 80 to 180 nm. The size of the particles means the size of aggregates when the particles are aggregates of primary particles. If the particles are not spherical, the size of the particles means the diameter of the circle corresponding to its projected area.

  The content of the matting agent can be about 0.05 to 1.0% by mass, preferably 0.1 to 0.8% by mass, with respect to the cellulose ester.

Physical properties of the protective film 13A (dimension change)
As described above, in order to reduce the optical distortion of the protective film 13A caused by changes in heat and humidity, it is preferable to set the dimensional change rate of the protective film 13A after storage under high temperature and high humidity to a certain level or more. . Specifically, the dimensional change rate (%) of the long side direction α of the film after storage of the protective film 13A at 80 ° C. and 90% RH for 100 hours is A (α), with respect to the long side direction α. It is preferable that the protective film A satisfy | fills following formula (1) and (2), when the dimensional-change rate (%) of short side direction (beta) to orthogonally cross is made into A ((beta)).
−1.5 ≦ A (α) ≦ −0.3 (1)
−1.5 ≦ A (β) ≦ −0.3 (2)

It is more preferable for the protective film 13A to satisfy the following formulas (3) and (4) because distortions occurring in the protective film 13A can be further reduced.
−1.5 ≦ A (α) <− 0.5 (3)
−1.5 ≦ A (β) <− 0.5 (4)

The dimensional change rate of the protective film 13A can be measured by the following method.
1) The protective film 13A is cut into a size of 10 × 10 cm ² to obtain a sample film. Mark two points separated by 100 mm in the TD direction (for example, direction α) of this sample film. Similarly, two points separated by 100 mm in the MD direction (direction β) orthogonal to the TD direction of the sample film are marked. The film is allowed to stand at 23 ° C. and 55% RH for 24 hours, and then the distance D 0 between two points is measured in each direction.
2) The sample film is then stored in an oven at 80 ° C. 90% RH for 100 hours. Thereafter, the sample film is taken out of the oven, conditioned at 23 ° C. and 55% RH for 24 hours, and then the distance D1 between two points marked in each direction is measured.
3) Then, the dimensional change rate (%) is calculated by applying D0 measured in 1) and D1 measured in 2) in each direction to the following equation. A negative value indicates that the film is shrinking.
Dimension change rate (%) = (D1-D0) / D0 x 100

  As described above, in order to make the dimensional change rate of the protective film 13A constant or higher, for example, 1) the content of the polyester compound (preferably the compound represented by the general formula (1) or (2)) is constant or lower 2) Stretching conditions are such that the stretching tension applied to the film is low; and 3) It is preferable to lower the transport tension; 4) Drying conditions after stretching in addition to the above 1) to 3) It is more preferable to make it loose.

  Specifically, in order to increase the dimensional change rate in the MD direction (preferably short side direction β) of the protective film 13A, a predetermined amount of a polyester compound may be contained, and the transport tension of the film may be set to a certain value or less. It is more preferable to contain a predetermined amount of a polyester compound, and to set all of the film transport tension, the drying temperature and the drying time at the time of drying while roll transporting after stretching to be constant or less. In order to increase the dimensional change of the protective film 13A in the TD direction (preferably, the short side direction β), it is preferable to contain a predetermined amount of polyester compound and keep the stretching temperature at a certain level or less; It is more preferable that both the stretching temperature and the stretching ratio be constant or less.

(Retardation)
The in-plane retardation R ₀ of the protective film 13A measured under the measurement wavelength of 590 nm and 23 ° C. 55% RH is preferably −20 nm or more and 20 nm or less, and is −10 nm or more and 10 nm or less Is more preferred. The retardation Rth in the thickness direction of the protective film 13A measured under the measurement wavelength of 590 nm and 23 ° C. and 55% RH is preferably −20 nm or more and 20 nm or less, and more preferably −10 nm or more and 10 nm or less preferable. The protective film 13A having such a retardation value is suitable, for example, as a retardation protective film (F2 or F3) of an IPS mode liquid crystal display device.

The retardations R ₀ and Rth are respectively defined by the following formulas.
Formula (I): R ₀ = (nx−ny) × d (nm)
Formula (II): Rth = {(nx + ny) / 2−nz} × d (nm)
(In the formulas (I) and (II),
nx represents the refractive index in the slow axis direction x where the refractive index is maximum in the in-plane direction of the film;
ny represents the refractive index in the direction y orthogonal to the slow axis direction x in the in-plane direction of the film;
nz represents the refractive index in the thickness direction z of the film;
d (nm) represents the thickness of the film)

The retardations R ₀ and R th can be determined, for example, by the following method.
1) The protective film 13A is conditioned at 23 ° C. and 55% RH. The average refractive index of the protective film 13A after humidity control is measured with an Abbe refractometer or the like.
A protective film 13A after 2) humidity, measuring the _{R 0} when the light is incident in parallel to the measurement wavelength 590nm to normal of the film surface, KOBRA21ADH, in Oji Scientific Corporation.
3) With KOBRA 21ADH, light having a measurement wavelength of 590 nm from the angle θ (incident angle (θ)) with respect to the normal to the surface of the film with the in-plane slow axis of the protective film 13A as the tilt axis (rotational axis) The retardation value R (θ) when light is incident is measured. The measurement of the retardation value R (θ) can be performed at six points every 10 ° in the range of θ of 0 ° to 50 °. The in-plane slow axis of the protective film 13A refers to the axis at which the refractive index is the largest in the film plane of the protective film 13A, and can be confirmed by KOBRA 21 ADH.
4) From the measured R ₀ and R (θ) and the above-described average refractive index and film thickness, nBR, ny and nz are calculated by KOBRA 21ADH to calculate Rth at a measurement wavelength of 590 nm. The measurement of retardation can be performed under conditions of 23 ° C. and 55% RH.

(Haze)
The haze of the protective film 13A is preferably 1.0% or less, more preferably 0.5% or less, and still more preferably 0.3% or less. The haze of the protective film 13A is the total haze, and may be measured with a haze meter (turbidimeter) (model: NDH 2000, manufactured by Nippon Denshoku Co., Ltd.) in accordance with JIS K-7136.

  In order to reduce the haze to a certain level or less, for example, a lubricant is preferably added to reduce the external haze. By the addition of the lubricant, the contact failure between the film during film formation and the transport roll can be suppressed, and the rise of the external haze due to the film surface being scratched can be suppressed.

(Thickness)
The thickness of the protective film 13A is preferably 10 to 60 μm, more preferably 15 to 45 μm, still more preferably 15 to 30 μm, in order to make the polarizing plate thinner. Being particularly preferred.

Method of Producing Protective Film 13A The protective film 13A is preferably produced by a solution casting method (cast) in order to reduce streaks and the like. That is, the protective film 13A is 1) obtaining a dope containing a cellulose ester, 2) casting the dope on a support and then drying to obtain a film, 3) a film obtained Is preferably produced through the steps of peeling the film from the support, 4) drying and stretching the film, and 5) winding the obtained film.

1) Dissolution process The organic solvent used for preparation of dope solution can be used without restriction | limiting, as long as it fully melt | dissolves said each components, such as a cellulose ester. Examples of chlorinated organic solvents include methylene chloride. Examples of non-chlorinated organic solvents include methyl acetate, ethyl acetate, amyl acetate, acetone, 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 1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, nitroethane and the like. Among these, methylene chloride is preferred.

  The dope preferably contains 1 to 40% by mass of a linear or branched aliphatic alcohol having 1 to 4 carbon atoms in addition to the organic solvent. By containing the alcohol in the dope solution, the film-like substance is gelled and the peeling from the metal support is facilitated.

  As a C1-C4 linear or branched aliphatic alcohol, methanol, ethanol, n-propanol, an iso-propanol, n-butanol, a sec-butanol, a tert- butanol can be mentioned. Among them, methanol and ethanol are preferable because the stability of the dope, the boiling point are relatively low, and the drying property is also good.

  The dissolution of cellulose ester etc. can be carried out under normal pressure, under the boiling point of the main solvent, under pressure above the boiling point of the main solvent, etc., but in particular under pressure above the boiling point of the main solvent Is preferred.

2) Casting Step The dope solution is fed to a pressure die through a feed pump (for example, a pressure type metering gear pump). Then, the dope solution is cast from the slit of the pressing die to the casting position on an endless metal support (for example, a stainless steel belt or a rotating metal drum) which is transported infinitely.

  It is preferable to use a pressure die which can adjust the slit shape of the die portion of the die and to make the film thickness uniform. The pressure dies include a coat hanger die and a T-die, and all of them are preferably used. The surface of the metal support is a mirror surface.

3) Solvent Evaporation / Peeling Step The dope solution cast on the metal support is heated on the metal support to evaporate the solvent in the dope solution to obtain a film.

  In order to evaporate the solvent, there are a method of blowing air from the dope liquid side, a method of transferring heat from the back of the support by liquid, a method of transferring heat from the front and back by radiant heat, etc. The drying efficiency is good and preferable. It is preferable to dry the dope solution on the metal support on the support under an atmosphere in the range of 40 to 100 ° C. In order to maintain the atmosphere within the range of 40 to 100 ° C., it is preferable to apply warm air of this temperature to the dope liquid surface on the metal support or to heat it by means such as infrared rays.

  The film obtained by evaporating the solvent on the metal support is peeled off at the peeling position. The temperature at the peeling position on the metal support is preferably in the range of 10 to 40 ° C, and more preferably in the range of 11 to 30 ° C.

The amount of residual solvent of the film-like material on the metal support at the time of peeling may be, for example, in the range of 50 to 120% by mass. The amount of residual solvent of the film-like substance is defined by the following equation.
Residual solvent amount (%) = (mass before heat treatment of film-like material-mass after heat treatment of film-like material) / (mass after heat treatment of film-like material) × 100
The heat treatment at the time of measuring the amount of residual solvent means performing heat treatment at 140 ° C. for one hour.

  Peeling tension for peeling the metal support and the film is usually in the range of 196 to 245 N / m, but when wrinkles are easily formed during peeling, it is preferable to peel at a tension of 190 N / m or less It is further preferable to peel off with a tension of 80 N / m or less.

4) Stretching step Stretching of the film-like material is preferably performed in at least one of the film width direction (TD direction), transport direction (MD direction) or oblique direction; it may be performed in the width direction (TD direction) More preferable. When stretching is performed in both the width direction (TD direction) and the transport direction (MD direction) of the film, the stretching in the width direction (TD direction) of the film and the stretching in the transport direction (MD direction) may be performed sequentially. You may do it at the same time.

  As described above, in order to obtain the protective film 13A in which the dimensional change is a certain degree or more, the film-like material is stretched under such conditions that the draw tension applied to the film-like material is low (stretching ratio, stretching temperature) Is preferred. Specifically, the dimensional change rate in the width direction (TD direction) is such that the stretching temperature in the stretching step in the width direction (TD direction) is made constant or less; preferably both the stretching temperature and the draw ratio are constant or less Can be moderately enhanced.

  The stretching ratio is preferably set to a lower value, and may be preferably 1.01 to 1.06 times, more preferably 1.03 to 1.06 times in each direction. In the case of stretching in both the width direction (TD direction) and the transport direction (MD direction) of the film, it is preferably 1.01 to 1.06 times, more preferably 1.03 to 1.06 times in each direction. It can be.

  The stretching temperature is also preferably set lower. The stretching temperature can be in the range of (Tg-40) to (Tg + 20) ° C., where Tg is the glass transition temperature of the cellulose ester. Specifically, when the main component of the film-like substance is cellulose triacetate, the stretching temperature is preferably 100 to 135 ° C., and more preferably 110 to 135 ° C.

  It is preferable to further dry the film in order to sufficiently remove the solvent in the film after stretching and to adjust the dimensional change of the film. Drying of the film is preferably carried out, for example, while transporting the film by a plurality of rollers arranged in a drying apparatus.

  Drying of the film is preferably performed under mild conditions (temperature, time) in order to obtain the protective film 13A such that the dimensional change rate is a certain level or more. Specifically, the dimensional change rate in the transport direction (MD direction) should be at least a constant transport tension of the film; preferably, all of the transport tension of the film, the drying temperature and the drying time in the drying step after stretching It can be moderately raised by making it below fixed.

  The drying temperature may be preferably 90 to 125 ° C, more preferably 100 to 120 ° C, and still more preferably 100 to 115 ° C. The drying time may be 5 to 15 minutes, preferably 5 to 10 minutes, more preferably 5 to 8 minutes, depending on the drying temperature.

  The transport tension of the film is preferably set lower in order to obtain the protective film 13A such that the dimensional change is a certain level or more. Specifically, the film transport tension is preferably 50 to 100 N / m, and more preferably 70 to 80 N / m.

  Therefore, in order to increase the dimensional change in both the width direction (TD direction) and the transport direction (MD direction), preferably, when stretching a film-like material containing a predetermined amount of polyester compound in the width direction (TD direction) It is preferable to set both the draw ratio and the draw temperature below a certain value; and the film transport tension, the drying temperature and the drying time at the time of drying with roll conveyance after the draw, all constant or less. Specifically, the stretching temperature is 110 to 135 ° C .; the stretching ratio is 1.03 to 1.06; the transport tension of the film is 70 to 80 N / m; the drying temperature is 100 to 120 ° C .; It is particularly preferable to set the time to 5 to 10 minutes.

  In the present invention, the slipperiness of the film at the time of film formation can be enhanced by further containing a lubricant in the protective film. As a result, even if the transport tension is lowered, contact failure between the protective film and the transport roll can be suppressed, and damage to the surface of the film can be suppressed. As a result, the increase in the haze of the resulting protective film 13A can be suppressed.

5) Winding-up process The obtained protective film may be provided in a long shape. The long protective film can be usually wound into a roll in the longitudinal direction (MD direction) to be a wound body. The length of the long protective film may range from 100 to 10000 m. The width of the long protective film may be in the range of 1 to 4 m, preferably in the range of 1.4 to 3 m.

1-3. Protective film 13B
The protective film 13B is not particularly limited, but it is preferable that the protective film 13B contains a cellulose ester as a main component, because the heat resistance is high. The cellulose ester is defined similarly to the cellulose ester in the protective film 13A and may preferably be cellulose triacetate.

  The protective film 13B may further contain the same polyester compound as the protective film 13A and various additives as needed. Examples of various additives which may be contained in the protective film 13B include not only additives similar to those of the protective film 13A but also high-hardness agents and the like.

(High hardness agent)
The high-hardness agent is preferably a polymer containing a repeating unit derived from a monomer represented by the following general formula (4), or a compound represented by the following general formulas (5) to (8). These high hardness agents can increase the density of the protective film 13B to reduce the diffusion path of boric acid in the polarizer. Thereby, deterioration of the polarizer can be suppressed.

R ^{1 in the} general formula (4) represents a hydrogen atom or an aliphatic group having 1 to 4 carbon atoms. Examples of the aliphatic group represented by R ¹ include a methyl group, an ethyl group and the like. R ² represents an aliphatic group or an aromatic group. Examples of the aliphatic group represented by R ² include an alkyl group, an alkenyl group, an alkynyl group and a cycloalkyl group, preferably an alkyl group having 1 to 6 carbon atoms, and more preferably a methyl group or t- It is a butyl group. Examples of the aromatic group include a phenyl group, a naphthyl group and a biphenyl group, preferably a phenyl group. (A) represents a 5- or 6-membered aromatic ring. The aromatic ring includes an aromatic ring containing no hetero atom and a saturated / unsaturated heterocyclic ring containing the hetero atom. n represents an integer of 0 to 4, preferably 0 to 2, more preferably 0 to 1.

The polymer containing the repeating unit derived from the monomer represented by General formula (4) may preferably be a copolymer represented by the following General Formula (4-1).

R < ²¹ >, R <^22> , R <^23> and R < ²⁴ > of General formula (4-1) respectively independently represent a substituent. x, y, z represent the molar ratio with respect to all the repeating units contained in a polymer, x represents 1 to 40%, y represents 5 to 95%, z represents 1 to 70%. m1 and m2 each independently represent an integer of 0 to 4; m3 represents an integer of 0 to 2; m4 represents an integer of 0 to 5; Each of R ¹⁰¹ , R ¹⁰² and R ¹⁰³ independently represents a hydrogen atom or an aliphatic group having 1 to 4 carbon atoms.

Specific examples of the polymer containing the repeating unit derived from the monomer represented by the general formula (4) include the following.

The weight average molecular weight of the polymer is preferably 200 to 10,000, more preferably 300 to 8,000, and still more preferably 400 to 4,000. The density of protective film 13B can be favorably improved as the above-mentioned weight average molecular weight is more than fixed. Thereby, the diffusion of boric acid from the polarizer can be suppressed, and the deterioration of the polarizer can be suppressed. When the weight average molecular weight is less than or equal to a certain level, the compatibility with the cellulose ester is unlikely to be impaired.

R ^{26 in the} general formula (5) represents an aryl group; preferably an aryl group having 6 to 12 carbon atoms, more preferably a phenyl group. R ²⁷ and R ²⁸ each independently represent a hydrogen atom, an alkyl group or an aryl group; preferably a hydrogen atom, an alkyl group having 1 to 12 carbon atoms (including a cycloalkyl group) or an aryl having 6 to 12 carbon atoms A hydrogen atom, an alkyl group having 1 to 6 carbon atoms (including a cycloalkyl group) or a phenyl group. R ²⁶ and R ²⁷ may each have a substituent. Examples of the substituent that R ²⁶ may have include a halogen atom or an alkyl group having 1 to 6 carbon atoms. Examples of the substituent that R ²⁷ may have include an aryl group having 6 to 12 carbon atoms.

Specific examples of the compound represented by the general formula (5) include the following.

  It is preferable that it is 200-1000, and, as for the weight average molecular weight of the compound represented by General formula (5), it is more preferable that it is 250-800.

R ^{1 in the} general formula (6) represents a hydrogen atom or a substituent. R ² represents a substituent represented by the following general formula (6-1). n1 represents an integer of 0 to 4, and when n1 is 2 or more, plural R ^{1 s} may be the same as or different from each other. n2 represents an integer of 1 to 5, and when n2 is 2 or more, plural R ^{2 s} may be the same as or different from each other.

A in the general formula (6-1) represents a substituted or unsubstituted aromatic ring. The aromatic ring is preferably a benzene ring. R ³ and R ⁴ each independently represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a substituent represented by General Formula (6-2). R ⁵ represents a single bond or an alkylene group having 1 to 5 carbon atoms. X represents a substituted or unsubstituted aromatic ring. The aromatic ring is preferably a benzene ring. n3 represents an integer of 0 to 10, and when n3 is 2 or more, a plurality of R ⁵ and X may be identical to or different from each other.

X in General Formula (6-2) represents a substituted or unsubstituted aromatic ring. The aromatic ring is preferably a benzene ring. R ^{6 to} R ⁹ each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. n5 represents an integer of 1 to 11, and when n5 is 2 or more, the plurality of R ^{6 to} R ⁹ and X may be identical to or different from each other.

Specific examples of the compound represented by the general formula (6) include the following.

  It is preferable that it is 200-1200, and, as for the weight average molecular weight of the compound represented by General formula (6), it is more preferable that it is 250-1000.

R _{1 in the} general formula (7) represents a formyl group or a substituted or unsubstituted alkylcarbonyl group having 2 to 15 carbon atoms. R _{2, R} 3, _{R 4} represents an alkyl group having 1 to 4 carbon atoms each independently. m and n each independently represent an integer of 0 or more, but can not be 0 simultaneously. When there are a plurality of R ₁ , R ₂ , R ₃ and R ₄ , they may be identical to or different from one another.

  The compound represented by the general formula (7) is also referred to as an acyl-modified novolac phenol resin. Acyl modification is obtained by acylating a hydroxyl group of a novolak-type phenol resin. The acyl group is preferably a formyl group or a substituted or unsubstituted alkylcarbonyl group having 2 to 15 carbon atoms, and among them, an acetyl group, a propionyl group, a butyryl group and a pivaloyl group are particularly preferable.

Preferred examples of the compound represented by the general formula (7) include the following.

R _{1 in the} general formula (8) represents a nitrogen atom or an oxygen atom. R ₂ represents a -COOH or -OH group. R ₃ represents an alkyl group having 1 to 10 carbon atoms, and examples thereof include a methyl group, an ethyl group and the like. R ₄ represents a substituent such as an alkyl group having 1 to 10 carbon atoms.

Specific examples of the compound represented by the general formula (8) include the following.

  The content of the compounds represented by the general formulas (4) to (8) is 0.1 to 15% by mass, preferably 0.5 to 10% by mass, and more preferably 0.5 to 3 based on the cellulose ester. It may be mass%. If the content of the compound is a certain amount or more, the density of the film can be sufficiently increased. If the content of the above-mentioned compound is below a fixed level, rise in bleed-out or haze can be suppressed.

  The same protective film 13B as the protective film 13A may be used.

Physical properties (rate of dimensional change) of protective film 13B
When the dimensional change rate of the protective film 13B and the dimensional change rate of the protective film 13A are largely different, distortion occurs inside the polarizing plate 10, and curling (warping) of the polarizing plate 10 is likely to occur. When such a curl of the polarizing plate 10 occurs, display unevenness due to the same is likely to occur anew.

Therefore, it is preferable to make the difference between the dimensional change of the protective film 13B and the dimensional change of the protective film 13A as small as possible. That is, after the protective film 13B is stored at 80 ° C. and 90% RH for 100 hours, the dimensional change rate (%) in the long side direction α of the film is B (α), and the short side direction β orthogonal to the direction α When the dimensional change (%) is B (β), the protective films A and B preferably satisfy the following formulas (5) and (6).
| A (α) -B (α) | ≦ 0.4 (5)
| A (β) -B (β) | ≦ 0.4 (6)

  In order to further suppress the curling of the polarizing plate, it is preferable that | A (α) -B (α) | and | A (β) -B (β) | Being particularly preferred.

(Retardation)
The retardation R0 in the in-plane direction and the retardation Rth in the thickness direction, which are measured under the measurement wavelength of 590 nm and 23 ° C. and 55% RH, of the protective film 13B may be in the same range as the protective film 13A.

(Thickness)
The thickness of the protective film 13B is preferably 10 to 60 μm, and more preferably 15 to 40 μm, in order to make the polarizing plate thinner.

1-4. Hardened material layer 15 of active energy ray-curable adhesive
The cured product layer 15 of the active energy ray-curable adhesive can be composed of a cured product of the active energy ray-curable adhesive. The active energy ray curable adhesive is a radical polymerization type active energy ray curable adhesive using photo radical polymerization, a cationic polymerization type active energy ray curable adhesive using photo cationic polymerization, or a combination thereof. It may be a hybrid type active energy ray curable adhesive.

  The radical polymerization type active energy ray-curable adhesive comprises a radically polymerizable compound containing a polar group such as a hydroxy group or a carboxy group as described in JP-A-2008-009329 and a radically polymerizable compound not containing a polar group. It may be a composition containing a specific proportion. The radically polymerizable compound is preferably a compound having a radically polymerizable ethylenic unsaturated bond. Preferred examples of the compound having a radically polymerizable ethylenic unsaturated bond include a compound having a (meth) acryloyl group. Examples of the compound having a (meth) acryloyl group include N-substituted (meth) acrylamide compounds, (meth) acrylate compounds and the like. (Meth) acrylamide means acrylamide or methacrylamide.

  The cationic polymerization type active energy ray-curable adhesive comprises (α) cationic polymerizable compound, (β) photo cationic polymerization initiator, (γ) from 380 nm as disclosed in JP-A-2011-028234. It may be a composition containing each component of a photosensitizer exhibiting maximum absorption to long wavelength light and a component of (δ) naphthalene based photosensitizer.

  Among these, radical polymerization type active energy ray-curable adhesives are preferable from the viewpoint of good adhesion and durability. The radical polymerization type active energy ray-curable adhesive contains a radical polymerizable compound and a photo radical polymerization initiator, and may further contain a photosensitizer and the like as needed.

  The radically polymerizable compound preferably contains an unsaturated compound having one or more ethylenic unsaturated bonds in the molecule. Examples of such unsaturated compounds are (meth) acrylic compounds; N-vinyl-2-pyrrolidone, divinyl adipate, vinyl compounds such as divinyl sebacate; triallyl isocyanurate, triallylamine, tetraallyl pyrol. Mellitate, N, N, N ', N'-tetraallyl-1,4-diaminobutane, tetraallyl ammonium salts, allyl compounds such as allylamine; unsaturated carboxylic acids such as maleic acid and itaconic acid, etc. And preferably (meth) acrylic compounds.

  Examples of (meth) acrylic compounds include (meth) acrylates, (meth) acrylamides, (meth) acrylic acid, (meth) acryloyl morpholine, (meth) acrylic aldehyde and the like.

  Examples of (meth) acrylates include alkyl (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate and propyl (meth) acrylate; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl Hydroxyalkyl (meth) acrylates such as meta) acrylate; alicyclic (meth) acrylates such as cyclohexyl (meth) acrylate and isobornyl (meth) acrylate; and having an aromatic ring such as benzyl (meth) acrylate (meth) Acrylates; (meth) acrylates of dihydric alcohols such as tripropylene glycol diacrylate and the like are included. Examples of (meth) acrylamides include hydroxyethyl acrylamide.

Examples of photo radical polymerization initiators are:
4'-phenoxy-2,2-dichloroacetophenone, 4'-tert-butyl-2,2-dichloroacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2-methyl-1- (4-methylthiophenyl)- Acetophenone photopolymerization initiators such as 2-morpholinopropan-1-one, 1-hydroxycyclohexyl phenyl ketone, α, α-diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one;
Benzoin ether photopolymerization initiators such as benzoin, benzoin methyl ether and benzoin ethyl ether; benzophenone photopolymerization initiators such as benzophenone, methyl o-benzoylbenzoate and 4-phenylbenzophenone;
Thioxanthone photopolymerization initiators such as thioxanthone photopolymerization initiators such as 2-isopropyl thioxanthone and 2,4-diethyl thioxanthone;
Acyl phosphine oxide type photoinitiators, such as 2,4,6- trimethyl benzoyl diphenyl phosphine oxide, etc. are contained.

  The radical polymerization type active energy ray-curable adhesive may further contain a photosensitizer. By including a photosensitizer, the reactivity can be improved, and the mechanical strength and the adhesive strength of the cured product can be improved. The photosensitizer may be, for example, a carbonyl compound, an organic sulfur compound, a persulfide, a redox compound, an azo or diazo compound, a halogen compound, a photoreducible dye and the like.

  Examples of photosensitizers include benzoin derivatives such as benzoin methyl ether, benzoin isopropyl ether, .alpha.,. Alpha.-dimethoxy-.alpha.-phenylacetophenone; and benzophenones such as benzophenone, 2,4-dichlorobenzophenone, methyl o-benzoylbenzoate and the like Derivatives; Thioxanthone derivatives such as 2-chlorothioxanthone, 2-isopropyl thioxanthone and the like are included.

  The thickness of the cured product layer 15 of the active energy ray-curable adhesive is usually 0.01 to 10 μm, preferably 0.5 to 5 μm.

1-5. Method of Manufacturing Polarizing Plate 10 The polarizing plate 10 of the present invention is manufactured through a process of bonding the polarizer 11 and the protective film 13A or 13B with an adhesive. Bonding of the polarizer 11 and the protective film 13A or 13B is carried out using a completely saponified polyvinyl alcohol-based adhesive, an acetoacetyl group-modified polyvinyl alcohol-based adhesive, an active energy ray-curable adhesive, or the like. be able to. In the present invention, it is preferable to use an active energy ray-curable adhesive because it is not necessary to use water, and the polarizer 11 and the protective film 13A or 13B can be adhered well in a short time. That is, it is preferable that the polarizing plate protective film and the polarizer be adhered via a cured product layer of an active energy ray curable adhesive.

  That is, in the polarizing plate 10, the above-mentioned activity is applied to at least one of the following steps: 1) a process of easily bonding the bonding surface of the protective film 13A or 13B with the polarizer, 2) the bonding surface of the polarizer and the polarizing plate protective film A step of applying an energy ray curable adhesive, 3) a step of bonding the polarizer 11 and the protective film 13A or 13B through the obtained adhesive layer, and 4) the polarizer 11 with the adhesive layer. It may be manufactured through the step of curing the adhesive layer in a state where the protective film 13A or 13B is bonded. The step 1) may be performed as necessary.

  Corona treatment, plasma treatment, etc. are mentioned as an example of the easy adhesion treatment in the step 1).

  In the step 4), the uncured active energy ray-curable adhesive layer is irradiated with active energy rays to cure the adhesive layer containing the epoxy compound and the oxetane compound. Thereby, the polarizer and the polarizing plate protective film are adhered via the cured product layer of the active energy ray curable adhesive.

  As the active energy rays, visible rays, ultraviolet rays, X-rays, electron beams and the like can be used, and since they are easy to handle and have a sufficient curing rate, electron beams or ultraviolet rays are generally preferably used.

  The irradiation conditions of the electron beam may be any suitable conditions as long as the adhesive can be cured. For example, in the electron beam irradiation, the acceleration voltage is preferably 5 to 300 kV, more preferably 10 to 250 kV. If the acceleration voltage is less than 5 kV, the electron beam may not reach the adhesive and curing may be insufficient. If the acceleration voltage exceeds 300 kV, the penetration through the sample is too strong and the electron beam bounces, and the polarizing plate protective film And may damage the polarizer. The irradiation dose is in the range of 5 to 100 kGy, more preferably in the range of 10 to 75 kGy. When the irradiation dose is less than 5 kGy, the curing of the adhesive is insufficient, and when it exceeds 100 kGy, the polarizing plate protective film and the polarizer are damaged, and the mechanical strength tends to decrease and yellowing occurs.

Irradiation conditions of ultraviolet light may be any suitable conditions as long as the adhesive can be cured. The dose of ultraviolet rays is preferably from 50~1500mJ / cm ² in accumulated light quantity, it is more preferably 100 to 500 mJ / cm ^2.

2. Liquid Crystal Display Device The liquid crystal display device of the present invention includes a first polarizing plate, a liquid crystal cell, a second polarizing plate, and a backlight in this order. And, at least the second polarizing plate, or both the first polarizing plate and the second polarizing plate can be used as the polarizing plate of the present invention. The polarizing plate of the present invention is preferably disposed so that the protective film A is on the liquid crystal cell side.

  The liquid crystal display device of the present invention may be a medium- or large-sized liquid crystal display device such as a television or a notebook computer; or a small liquid crystal display device such as a smartphone. Among them, since the effect of the present invention is easily obtained, the liquid crystal display device of the present invention has a small size of 10 inches or less, preferably 6 inches or less in the diagonal direction of a display area (not shown) such as a smartphone. It is preferably a liquid crystal display device.

  FIG. 2 is a schematic view showing an example of a small liquid crystal display device. As shown in FIG. 2, the small liquid crystal display device 30 includes a liquid crystal cell 50, a first polarizing plate 70 and a second polarizing plate 90 which sandwich the liquid crystal cell 50, and a backlight 110. The small liquid crystal display device 30 includes a cover glass 130 disposed on the surface on the viewing side of the first polarizing plate 70, a touch panel portion 150 disposed between the first polarizing plate 70 and the liquid crystal cell 50, and a back And a rechargeable battery 170 disposed on the back side of the light 110.

  The display mode of the liquid crystal cell 50 may be various display modes such as STN, TN, OCB, HAN, VA (MVA, PVA), IPS, FFS (Fringe Field Switching), etc. , IPS mode or FFS mode is preferable.

  The first polarizing plate 70 is disposed on the surface on the viewing side of the liquid crystal cell 50; and the protective film disposed on the surface of the first polarizer 71 opposite to the liquid crystal cell 50 of the first polarizer 71 73B (F1) and a protective film 73A (F2) disposed on the surface of the first polarizer 71 on the liquid crystal cell 50 side. The second polarizing plate 90 is disposed on the surface on the backlight side of the liquid crystal cell 50; and the protective film disposed on the surface of the second polarizer 91 and the second polarizer 91 on the liquid crystal cell 50 side. 93A (F3) and a protective film 93B (F4) disposed on the surface of the second polarizer 91 opposite to the liquid crystal cell 50. In FIG. 2, both of the first polarizing plate 70 and the second polarizing plate 90 are the polarizing plates of the present invention; the protective film 73A (F2) and the protective film 93A (F3) are the above-mentioned protective film A (or The cured film layers 75 and 95 of the active energy ray-curable adhesive are the cured film layers 15 of the active energy ray-curable adhesive described above.

  The touch panel unit 150 is disposed between the liquid crystal cell 50 and the first polarizing plate 70 (on-cell type). However, the position of the touch panel unit 150 is not limited to the mode shown in FIG. 2, and the touch panel unit 150 may be integrally provided on the cover glass 130 (cover glass integrated type); the inside of the liquid crystal cell 50 (In-cell type).

  The rechargeable battery 170 may be, for example, a lithium ion secondary battery.

  In the liquid crystal display device, the heat and the humidity are usually easily changed due to the heat of the backlight and the influence of the external environment. In particular, the small liquid crystal display device 30 as shown in FIG. 2 not only further includes a rechargeable battery 170 that generates heat during charge and discharge, but also has a small device volume, so heat and moisture are easily accumulated in the device. Therefore, the first polarizer 71 and the second polarizer 91 are likely to undergo dimensional change due to changes in heat and humidity in the device.

  In the present invention, the dimensional change rates of the protective films 73A (F2) and 93A (F3) are appropriately increased. Thus, the protective film 73A (F2) and the first polarizer 71 are added to the protective film 73A (F2) despite the fact that they are firmly adhered by the cured product layer 75 of the active energy ray-curable adhesive. The contraction force of the first polarizer 71 can be relatively reduced. Similarly, in spite of the fact that the protective film 93A (F3) and the second polarizer 91 are firmly adhered by the cured product layer 95 of the active energy ray curable adhesive, they are added to the protective film 93A (F3) The contraction force of the second polarizer 91 can be relatively reduced. As a result, distortions in the protective films 73A (F2) and 93A (F3) can be reduced, and optical distortion can be suppressed.

  Furthermore, the difference between the dimensional change of the protective film 73B (F1) and the dimensional change of the protective film 73A (F2), and the dimensional change of the protective film 93A (F3) and the dimensional change of the protective film 93B (F4) The difference between Thereby, the curl (warpage) of the first polarizing plate 70 and the second polarizing plate 90 can be suppressed, and the display unevenness due to the curl can be further suppressed.

  EXAMPLES Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.

1. Material of Protective Film <Cellulose ester>
Cellulose triacetate (Acetyl substitution 2.85, Mw 285000)

<Polyester compound>

<Lubricant>

<High hardness agent>

2. Production of Polarizing Plate (1) Production of Cellulose Ester Film <Cellulose Ester Film 101>
The following components were charged into a sealed container, heated to 70 ° C., and cellulose triacetate was completely dissolved while stirring. The time required for the dissolution was 4 hours. The resulting solution was filtered and made to dope.
(Composition of dope)
Cellulose triacetate (degree of acetyl substitution 2.85, Mw 285000): 100 parts by mass Polyester compound K 1: 3 parts by mass Methylene chloride: 475 parts by mass Methanol: 50 parts by mass Tinuvin 928: 2 parts by mass

  The obtained dope was uniformly cast on a stainless steel band support at 22 ° C. at a dope temperature of 35 ° C. using a belt casting apparatus. Thereafter, the dope on the support was dried to a peelable range, and then peeled off from the stainless steel band support to obtain a film. The amount of residual solvent in the dope at peeling was 25%.

  The obtained filmy material was dried while being stretched in the width direction (TD direction) under conditions of a stretching temperature of 125 ° C. and a stretching ratio of 1.05 times with a tenter. The width hold was then released and dried at 110 ° C. for 8 minutes while being conveyed by multiple rolls. The conveyance tension was 70 N / m. Thereafter, knurling with a width of 10 mm and a height of 5 μm was applied to both ends of the film to produce a cellulose ester film 101 with a thickness of 25 μm. The film width was 1300 mm and the winding length was 3000 m. The winding tension was set to an initial tension of 150 N / 1300 mm and a final winding tension of 100 N / 1300 mm.

<Cellulose ester films 102 to 107>
Cellulose ester films 102 to 107 were produced in the same manner as the cellulose ester film 101 except that the content of the polyester compound K1 was changed as shown in Table 4.

<Cellulose ester film 108-114>
The content of the polyester compound K1 is changed to 12 parts by mass, and at least one of the transport tension of the filmy material, stretching conditions (stretching temperature, stretching ratio) and drying conditions (drying temperature, drying time) is shown in Table 4. Cellulose ester films 108 to 114 were produced in the same manner as the cellulose ester film 101 except that they were changed as described above.

<Cellulose ester film 115 to 117>
In the same manner as the cellulose ester film 111 except that a lubricant shown in Table 4 was added, cellulose ester films 115 to 117 were produced.

<Cellulose ester film 118 to 120>
A cellulose ester film 118 to 120 is prepared in the same manner as the cellulose ester film 101 except that the polyester compound K1 is not added, the high hardness agent shown in Table 4 is added, and the manufacturing conditions are changed as shown in Table 4. Was produced.

<Cellulose ester films 121 to 123>
Cellulose ester films 121 to 123 were produced in the same manner as the cellulose ester film 105 except that the type of polyester compound was changed as shown in Table 4.

<Cellulose ester film 124>
Furthermore, the film corresponded to the transparent film 104 of the said gazette was produced with the following procedure with reference to stage 0161-0165 of Unexamined-Japanese-Patent No. 2008-217022.

The following components were dissolved to obtain a cellulose acylate solution.
(Cellulose acylate solution composition)
Cellulose triacetate Ce-1 (degree of acetyl substitution 2.94): 100 parts by mass Methylene chloride: 480.0 parts by mass Methanol: 71.7 parts by mass Silica particle dispersion having an average particle diameter of 16 nm: 0.15 parts by mass Optically Compound A-19 (KI) which decreases anisotropy: 9.0 parts by mass Wavelength dispersion regulator UV-105 (HB): 0.1 parts by mass Citric acid ester mixture (citric acid, monoethyl ester, diethyl ester, Triethyl ester mixture): 0.01 parts by mass

  The above cellulose acylate solution was cast using a band casting machine. The film was peeled off from the band with a residual solvent content of 30%, and dried at 130 ° C. for 40 minutes while being conveyed through a conveying roll to produce a cellulose acylate film 124. The conveyance tension was 100 N / m. The residual solvent content of the obtained cellulose acylate film was 0.1%, and the film thickness was 80 μm.

  The dimensional change (MD, TD direction), retardation (Ro, Rth) and haze of the obtained cellulose ester film were measured by the following method.

(Dimensional change rate)
1) The obtained film was cut into a size of 10 cm × 10 cm to make a sample film. Two points separated by 100 mm in the MD direction (direction β) of this sample film were marked. Similarly, two points separated by 100 mm in the TD direction (direction α) orthogonal to the MD direction of the sample film were marked. After the film was allowed to stand at 23 ° C. and 55% RH for 24 hours, the distance D 0 between two points was measured in each direction.
2) The film was then stored in an oven at 80 ° C. 90% RH for 100 hours. Thereafter, it was taken out of the oven and conditioned at 23 ° C. and 55% RH for 24 hours, and then the distance D1 between two points marked in each direction was measured.
3) Then, the ratio (%) of dimensional change before and after storage in an oven was calculated by applying the measured value D0 of the above 1) and the measured value D1 of the above 2) to the following equation. A negative value indicates that the film is shrinking.
Percentage of dimensional change (%) = (D1-D0) / D0 x 100

(Phase difference R ₀ , Rth)
1) The obtained film was conditioned at 23 ° C. and 55% RH. The average refractive index of the film after humidity control was measured with an Abbe refractometer or the like.
The film 2) moisture adjustment, the _{R 0} when the light is incident in parallel to the measurement wavelength 590nm to normal of the film surface, KOBRA21ADH, was measured by Oji Scientific Corporation.
3) With KOBRA 21ADH, light with a measurement wavelength of 590 nm was made incident from an angle of θ (incident angle (θ) with respect to the normal to the film surface, with the slow axis in the plane of the film as the tilt axis (rotational axis) The retardation value R (θ) of the time was measured. The measurement of retardation value R ((theta)) was performed six points for every 10 degrees in the range of (theta) 0 degree-50 degrees. The in-plane slow axis of the film was confirmed by KOBRA 21 ADH.
4) From the measured R ₀ and R (θ) and the above-described average refractive index and film thickness, nBR, ny and nz were calculated by KOBRA 21ADH to calculate Rth at a measurement wavelength of 590 nm. The measurement of retardation was performed under conditions of 23 ° C. and 55% RH.

(Haze)
The obtained film was cut out to 5 cm square to make a sample film. The haze of this sample film was measured using a haze meter (turbidimeter) (model: NDH 2000, manufactured by Nippon Denshoku Co., Ltd.) in accordance with JIS K-7136.

The evaluation results of the obtained films 101 to 123 are shown in Table 4.

  As shown in Table 4, each of the films 102 to 106 containing the polyester compound in a predetermined range can have a moderately large dimensional change at 80 ° C. and 90% RH, and can also lower the retardation (particularly Rth) I understand that. On the other hand, it is understood that the film 101 having an excessively small content of the polyester compound has an excessively large dimensional change or an excessively large retardation. Moreover, it turns out that the internal haze rises that the film 107 with too much content of a polyester compound.

  In view of the comparison between the films 108 and 109 or the comparison of the films 110 to 112, the dimensional change (MD direction, TD direction) of the obtained film can be increased by lowering the transport tension, the stretching ratio and the temperature. I understand. Moreover, it turns out that the dimensional-change rate (MD direction, TD direction) of the film obtained becomes large from the comparison of the films 113 and 114 by making drying temperature low.

  From the comparison between the films 111 and 115 to 117, it is understood that the haze of the resulting film can be lowered by further adding a lubricant. This is considered to be less likely to cause contact failure with the transport roll even if the transport tension is small, because the film containing the lubricant has good slip properties. As a result, it is considered that the film containing a lubricant was able to suppress the increase in external haze due to the film surface being scratched.

  From the comparison of the films 105, 121 and 122 with the film 123, the films 105, 121 and 122 using polyester compounds K1, K6 and K5 not containing an aromatic ring are better than the film 123 using a polyester compound K14 containing an aromatic ring. Also, it can be seen that the dimensional change rate is moderately high.

  As a result of measuring the dimensional change of the film 124 corresponding to the example of Patent Document 1 by the above measuring method, the dimensional change in the MD direction is -0.05%, and the dimensional change in the TD direction is -0.05%. Yes, it can be seen that it is extremely small.

<Fabrication of Polarizer>
A 30 μm thick polyvinyl alcohol film was swollen with water at 35 ° C. The obtained film was immersed in an aqueous solution consisting of 0.075 g of iodine, 5 g of potassium iodide and 100 g of water for 60 seconds, and further immersed in an aqueous solution of 45 g of potassium iodide 3 g, 7.5 g of boric acid and 100 g of water . The obtained film was uniaxially stretched under the conditions of a stretching temperature of 55 ° C. and a stretching ratio of 3 times. The uniaxially stretched film was washed with water and then dried to obtain a polarizer with a thickness of 5 μm. Similarly, by adjusting the thickness and stretching conditions of the raw film, polarizers with thicknesses of 2 μm, 3 μm, 10 μm, 15 μm and 20 μm were respectively produced.

<Production of Polarizing Plate>
Example 1
1) Preparation of active energy ray-curable adhesive solution 1 (radical polymerization type)
After mixing the following respective components, degassing was performed to prepare a radical polymerization type active energy ray-curable adhesive solution 1.
(Active energy ray curable adhesive solution 1)
Radically polymerizable compound 1: hydroxyethyl acrylamide (HEAA, homopolymer Tg 123 ° C., Kojinsha Co., Ltd.): 39.1 mass%
Radically polymerizable compound 2: tripropylene glycol diacrylate (ALONIX M-220, Tg 69 ° C. of homopolymer, manufactured by Toagosei Co., Ltd.): 19.0 mass%
Radically polymerizable compound 3: Acryloyl morpholine (ACMO, homopolymer Tg 150 ° C., Kojinsha Co., Ltd.): 39.1 mass%
Radical polymerization initiator 1: Diethyl thioxanthone (KAYACURE DETX-S, manufactured by Nippon Kayaku Co., Ltd.): 1.4% by mass
Radical polymerization initiator 2: 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one (IRGACURE 907, manufactured by BASF): 1.4% by mass

2) Preparation of Polarizing Plate First, the film 102 prepared above was prepared as a protective film A, and the surface was subjected to corona discharge treatment. The conditions for the corona discharge treatment were a corona output intensity of 2.0 kW and a line speed of 18 m / min. Next, the above prepared radical polymerization type active energy ray-curable adhesive solution 1 is coated on the corona discharge treated surface of the film with a bar coater so that the film thickness after curing becomes about 3 μm. An active energy ray-curable adhesive layer was formed. The produced polarizer with a thickness of 5 μm was bonded to the obtained active energy ray-curable adhesive layer.

  Subsequently, the film 102 prepared above was prepared as a protective film B, and the surface was also subjected to a corona discharge treatment under the same conditions as described above. Next, the prepared radical polymerization type active energy ray curable adhesive solution 1 was applied to the corona discharge treated surface of the film in the same manner as described above to form an active energy ray curable adhesive layer. .

  A polarizer with a film 102 is pasted onto this active energy ray curable adhesive layer, and a film 102 (protective film A) / active energy ray curable adhesive layer / polarizer / active energy ray curable adhesive A laminate in which the layer / film 102 (protective film B) was laminated was obtained.

An ultraviolet ray (gallium filled metal halide lamp) was used on one side of this laminate, using a belt conveyor and ultraviolet ray irradiation device (Fusion UV Systems, Inc. Light HAMMER 10 bulb: V bulb peak illuminance: 1600 mW / cm ² ). The active energy ray-curable adhesive layer was cured by irradiation with ultraviolet light so as to have an accumulated irradiation amount of 1000 / mJ / cm ² (wavelength 380 to 440 nm), to obtain a polarizing plate 202.

(Examples 2 to 13 and 29 to 31, Comparative Examples 1 to 5)
Polarizing plates 201, 203 to 217 and 233 to 236 were obtained in the same manner as in Example 1 except that protective films A and B were changed as shown in Table 5 or Table 7.

(Examples 14 to 18)
Polarizing plates 218 to 222 were obtained in the same manner as in Example 8 except that the thickness of the polarizer was changed as shown in Table 6.

(Example 19)
Preparation of Active Energy Ray-Curable Adhesive Liquid 2 (Cationic Polymerization Type) After mixing the following components, degassing was performed to prepare Active Energy Radiation-curable Adhesive Liquid 2. The triarylsulfonium hexafluorophosphate was formulated as a 50% propylene carbonate solution, and the solid content of the triarylsulfonium hexafluorophosphate was indicated below.
(Active energy ray curable adhesive solution 2)
3,4-Epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate: 45 parts by mass Epolide GT-301 (alicyclic epoxy resin manufactured by Daicel Chemical Industries, Ltd.): 40 parts by mass 1,4-butanediol diglycidyl ether: 15 parts by mass Triarylsulfonium hexafluorophosphate: 2.3 parts by mass 9, 10-dibutoxyanthracene: 0.1 parts by mass 1,4-diethoxynaphthalene: 2.0 parts by mass

  In the same manner as described above, the films 111 prepared above were prepared as the protective film A and the protective film B, respectively, and the surface was subjected to corona discharge treatment. Next, the above prepared radical polymerization type active energy ray curable adhesive solution 2 is coated on the corona discharge treated surface of the film with a bar coater so that the film thickness after curing becomes about 3 μm. An active energy ray-curable adhesive layer was formed. Then, a laminate in which film 111 (protective film A) / active energy ray-curable adhesive layer / polarizer / active energy ray-curable adhesive layer / film 111 (protective film B) was laminated was obtained.

An ultraviolet ray (gallium filled metal halide lamp) is applied to one side of this laminate using a belt conveyor and an ultraviolet ray irradiating apparatus (Light HAMMER 10 bulb manufactured by Fusion UV Systems, Inc., bulb: V bulb). The active energy ray-curable adhesive layer was cured by irradiation with ultraviolet rays so as to have a density of 300 cm / cm ² (wavelength: 380 to 440 nm), whereby a polarizing plate 223 was obtained.

(Examples 20 to 25)
Polarizing plates 224 to 229 were obtained in the same manner as in Example 8 except that the type of protective film B was changed as shown in Table 6.

(Examples 26 to 28)
Polarizing plates 230 to 232 were obtained in the same manner as in Example 17 except that the type of protective film B was changed as shown in Table 6.

  The following method evaluated the presence or absence of the curl of the obtained polarizing plate.

(Curl of polarizing plate)
The polarizing plate was cut into a size of 100 mm × 100 mm to obtain a polarizing plate sample. After storing the obtained polarizing plate sample in an environment of 80 ° C. and 90% RH for 300 hours, the polarizing plate sample was allowed to stand on a plane so that the protective film A was on the bottom. And the height from the plane of four corners of a polarizing plate sample was measured, those average values were computed, and it was set as "the value of a curl."
:: The height of the warped portion is less than 2 mm ○: The height of the warped portion is 2 mm or more and less than 4 mm △: The height of the warped portion is 4 mm or more and less than 6 mm ×: The height of the warped portion 6 mm or more

Furthermore, the liquid crystal display was produced with the following method using the obtained polarizing plate, and the display nonuniformity was evaluated.
(Display unevenness)
1) Production of Display Device An i-phone 5s manufactured by Apple Inc. was prepared as an IPS mode liquid crystal display device having a display area having a diagonal length of 4 inches, and then the two polarizing plates were peeled off. Subsequently, two polarizing plates (polarizing plates with the same number) manufactured under the same manufacturing conditions were prepared, and one of them was bonded to both sides of the touch panel integrated liquid crystal cell to obtain a display device. The bonding was performed so that the protective films A of the polarizing plates were in contact with the liquid crystal cells, respectively. The absorption axis of the polarizing plate was made to be in the same direction as the absorption axis of the polarizing plate attached in advance.

2) Evaluation The display unevenness of the obtained display device was evaluated by the following method.
That is, the obtained display was stored under the conditions of 50 ° C. and 80% RH for 3 hours. Thereafter, the display was stored in a dark room at 23 ° C. and 80% RH for a certain period of time, and the uniformity of the color (black) of the screen when black was displayed was evaluated by sensory evaluation.
:: no unevenness is seen over the whole surface ○: slightly uneven but practically acceptable :: unevenness is seen and bothered ×: unevenness is clearly observed

The evaluation results of Examples 1 to 13 and Comparative Examples 1 to 5 are shown in Table 5; the evaluation results of Examples 14 to 28 are shown in Table 6; the evaluation results of Examples 29 to 31 are shown in Table 7.

  As shown in Tables 5 to 7, all the display devices of Examples 1 to 31 in which the dimensional change of the protective film A (F2 or F3) is in the range of -0.3% to -1.5%. It can be seen that the display unevenness is small and the visibility is good. In addition, it is understood that the polarizing plates of Examples 1 to 28 have less curl.

  On the other hand, it can be seen that the display device of Comparative Example 3 in which the dimensional change rate of the protective film A (F2 or F3) is too small has large display unevenness. This is because the polarizer and the protective film A (F2 or F3) are firmly bonded by the active energy ray-curable adhesive, and therefore the optical strain (birefringence) is received largely due to the contraction force of the polarizer. It is believed that the cause of

  On the other hand, it can be seen that the display devices of Comparative Examples 1 and 4 in which the dimensional change rate of the protective film A (F2 or F3) is too large also cause large display unevenness. This is considered to be because the protective film had unnecessary birefringence because the dimensional change rate of the protective film was too large. Further, the polarizing plates of Comparative Examples 1 and 4 were slightly curled. It is considered that this is because the dimensional change rate of the protective film A is too large and distortion occurs with the glass substrate of the liquid crystal cell.

  Uneven display occurs in the display device of Comparative Example 2 because the content of the polyester compound in the protective film A (F2 or F3) is too large to be uniformly compatible with the cellulose ester, and the internal haze is increased. It is believed that there is. Moreover, the display of Comparative Example 2 also had low contrast.

  Furthermore, it can be seen that the display device of Comparative Example 5 using the film 124 causes display unevenness. This is considered to be due to the occurrence of display unevenness mainly due to optical distortion because the dimensional change rate of the film 124 is too small.

  Among the examples, the display device of Example 7 in which the absolute value of the dimensional change of the protective film A (F2 or F3) is 0.5% or more has an absolute value of the dimensional change of less than 0.5%. It can be seen that the visibility is particularly better than that of the display device of Example 6.

  Also, as shown in Table 7, the display devices of Examples 4 and 29 in which the polyester compound in the protective film A (F2 or F3) does not contain an aromatic ring are the polyester compounds in the protective film A (F2 or F3) It can be seen that the display unevenness is less than that of the display device of Example 31 having an aromatic ring or the display device of Example 30 in which the molecular weight of the polyester compound is large. From this, the polyester compound which does not contain an aromatic ring and whose molecular weight is less than or equal to a certain amount can easily increase the dimensional change of the protective film A moderately than the polyester compound which contains an aromatic ring and which has a certain or more molecular weight. Is suggested.

  Furthermore, it is understood that the display devices of Examples 15 to 17 in which the thickness of the polarizer is 15 μm or less have better visibility than the display device of Example 18 in which the thickness of the polarizer is 20 μm. This is considered to be because when the thickness of the polarizer is small, the contraction force of the polarizer is also small, and the distortion generated in the protective film is also small. In the display of Example 14 in which the thickness of the polarizer is 2 μm, the low visibility is presumed to be due to deterioration of the polarizer due to transmitted water and the like.

  Furthermore, in the display device of Example 25, no unevenness was observed at the center of the display screen, but unevenness was observed in the light amount at the end of the display screen. It is considered that this is not unevenness due to optical distortion of the protective film A, but unevenness due to curl of the polarizing plate was observed in the display device of Example 25.

  Furthermore, in the polarizing plates of Examples 22 to 23 and 26 to 28 in which the difference in dimensional change of the protective films A and B is 0.34% or less, the difference in dimensional change is 0.4% or more. It can be seen that the curling can be suppressed better than the polarizing plates 20 to 21 and 24 to 25.

  This application claims the priority based on Japanese Patent Application No. 2014-041830 filed on March 4, 2014. The contents described in the application specification and drawings are all incorporated herein by reference.

  According to the present invention, it is a polarizing plate in which a polarizer and a protective film are bonded via an active energy ray-curable adhesive layer, and it is possible to provide a polarizing plate capable of suppressing a decrease in the visibility of a liquid crystal display. .

DESCRIPTION OF SYMBOLS 1 liquid crystal display device 3, 50 liquid crystal cell 5, 70 1st polarizing plate 5-1, 71 1st polarizer 5-3A, 7-3A, 73A, 93A Protective film A
5-3B, 7-3B, 73B, 93B Protective film B
7, 90 Second Polarizing Plate 7-1, 91 Second Polarizer 10 Polarizing Plate 11 Polarizer 13A Protective Film A
13B Protective film B
15, 75, 95 Cured product layer of active energy ray-curable adhesive 30 Small liquid crystal display 110 Backlight 130 Cover glass 150 Touch panel part 170 Battery

Claims (9)

1 ) A dimensional change (%) in the long side direction α of the film after 100 hours of storage at 80 ° C. and 90% RH is A (α), and a dimensional change in the short side direction β orthogonal to the long side direction α Preparing a protective film A satisfying the following formulas (1) and (2), where A (β) is a percentage (%) ,
−1.5 ≦ A (α) ≦ −0.3 (1)
−1.5 ≦ A (β) ≦ −0.3 (2)
2) A polarizer, the protective film A laminated on one side of the polarizer via an active energy ray-curable adhesive layer, and an active energy ray-curable adhesive layer on the other side of the polarizer Obtaining a laminate comprising a protective film B disposed via
3) The laminate is irradiated with active energy rays to cure the active energy ray-curable adhesive layer, and the polarizer and the active energy ray-curable adhesive on one surface of the polarizer A polarizing plate comprising the protective film A disposed via a cured product layer, and the protective film B disposed on the other surface of the polarizer via the cured product layer of the active energy ray-curable adhesive. And obtaining the
The step 1) of preparing the protective film A
1A) A film-like product is obtained, which contains a cellulose ester, and a polyester compound obtained by polycondensation of a diol and a dicarboxylic acid, and the content of the polyester compound is 5 to 30% by mass with respect to the cellulose ester. Process,
1B) stretching the film at a temperature of 110 to 135 ° C. in a width direction at a draw ratio of 1.03 to 1.06;
1C) drying the film obtained by the stretching at a temperature of 100 to 120 ° C. for 5 to 10 minutes while conveying the film obtained at a tension of 70 to 80 N / m.
The manufacturing method of a polarizing plate. The polyester compound is prepared by polycondensation of a dicarboxylic acid selected from the group consisting of aliphatic dicarboxylic acids and alicyclic dicarboxylic acids with a diol selected from the group consisting of aliphatic diols, alkyl ether diols and alicyclic diols. The manufacturing method of the polarizing plate of Claim 1 which is a compound obtained. The manufacturing method of the polarizing plate of Claim 1 or 2 in which the said protective film A satisfy | fills following formula (3) and (4).
−1.5 ≦ A (α) <− 0.5 (3)
−1.5 ≦ A (β) <− 0.5 (4) After storage for 100 hours in front Symbol protective film under 80 ° C. 90% RH to B, the long side direction alpha dimensional change of film (%) and B (alpha), orthogonal to the long side direction alpha The protective films A and B satisfy the following formulas (5) and (6) when the dimensional change rate (%) in the short side direction β is B (β) : The manufacturing method of the polarizing plate as described in-.
| A (α) -B (α) | ≦ 0.4 (5)
| A (β) -B (β) | ≦ 0.4 (6) The manufacturing method of the polarizing plate as described in any one of Claims 1-4 whose thickness of the said polarizer is 3-15 micrometers. The protective film A is defined by the following formula (I) and has an in-plane retardation measured at a measurement wavelength of 590 nm as Ro (590), and is defined by the following formula (II) and at a measurement wavelength of 590 nm The retardation according to any one of claims 1 to 5, wherein when the retardation in the thickness direction to be measured is Rth (590), | Ro (590) | ≦ 10 nm, | Rth (590) | The manufacturing method of a polarizing plate.
Formula (I) Ro = (nx-ny) x t (nm)
Formula (II) Rth = {(nx + ny) / 2−nz} × t (nm)
(In the formulas (I) and (II),
nx represents the refractive index in the slow axis direction x where the refractive index is maximum in the in-plane direction of the film;
ny represents the refractive index in the direction y orthogonal to the slow axis direction x in the in-plane direction of the film;
nz represents the refractive index in the thickness direction z of the film;
t (nm) represents the thickness of the film) The manufacturing method of the polarizing plate as described in any one of Claims 1-6 in which the said protective film A further contains a lubricating agent . The manufacturing method of the polarizing plate as described in any one of Claims 1-7 in which the said protective film B further contains a high-hardness agent. The thickness of the said protective film A is 10-60 micrometers, The manufacturing method of the polarizing plate as described in any one of Claims 1-8.

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