KR20160122262A - Optical film, method for producing same, polarizing plate and liquid crystal display device - Google Patents

Abstract

An object of the present invention is to provide an optical film having a high toughness as well as being capable of suppressing deterioration of a polarizer even if the film thickness is thin. The optical film of the present invention comprises a cellulose ester, a polymer containing a repeating unit derived from a monomer represented by the formula (1), a compound represented by the formula (2), a compound represented by the formula (3) , And has a film thickness of 15 to 45 占 퐉, and the optical film is laminated on the optical film at a temperature of 23 占 폚 and 55% RH in the longitudinal direction? Of the optical film (MPa or N / mm ² ), the elongation at break is represented by E (%), the cross-sectional area of the optical film in the direction perpendicular to the tensile direction is A (mm) ² ), the toughness G expressed by the following formula is 7 to 20 in each of the long side direction? And the short side direction?.

Description

TECHNICAL FIELD [0001] The present invention relates to an optical film, a polarizing plate, and a liquid crystal display device,

The present invention relates to an optical film, a manufacturing method thereof, a polarizing plate, and a liquid crystal display device.

2. Description of the Related Art In recent years, a liquid crystal display device has been in increasing demand as a liquid crystal display for a portable device such as a smart phone or a tablet terminal. The liquid crystal display device usually includes a liquid crystal cell and a pair of polarizing plates for supporting the liquid crystal cell. The polarizing plate includes a polarizer and a pair of protective films for supporting the polarizer. BACKGROUND ART [0002] Liquid crystal display devices used in portable devices and the like are required to be thin, and thin protective films are also required. As the protective film, for example, a cellulose ester film is used. Further, it is desired that the protective film can suppress deterioration of the polarizer due to permeated water even under high temperature and high humidity. As such a protective film, there has been proposed a film comprising a cellulose acylate and a polarizer deterioration inhibitor such as a specific phenol compound (for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2013-174851

The protective film having a small film thickness is liable to be particularly susceptible to moisture, and thus the polarizer is liable to be deteriorated. That is, since the protective film having a thin film thickness is easy to permeate moisture, moisture is likely to penetrate into the polarizer. In the polarizer, the PVA polymer and the dichroic dye form a stabilized complex by boric acid crosslinking. When water penetrates into the polarizer, not only the boric acid crosslinking is broken but boric acid is easily scattered, and the deterioration of the polarizer is liable to occur.

The deterioration of the polarizer can be reduced by containing a polarizer deterioration inhibitor containing an aromatic ring as disclosed in Patent Document 1 in the protective film. However, the protective film containing the polarizer deterioration inhibitor did not exist, but tended to be low.

Further, the protective film having a thin film thickness is low in strength and easily deteriorated. In this case, if the lower film is wound in a roll shape, deformation of the roll body is likely to occur. If deformation of the roll body occurs, uneven tension is applied to the wound film, which may lower the optical characteristics of the film.

Thus, deterioration of the polarizer and deterioration of the optical characteristics of the protective film may lower the contrast and visibility of the display device.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a high optical film which is capable of suppressing deterioration of a polarizer even if the film thickness is thin.

(1) A polymer comprising a cellulose ester and a polymer comprising a repeating unit derived from a monomer represented by the formula (1), a compound represented by the formula (2), a compound represented by the formula (3) , And has a film thickness of 15 to 45 占 퐉 and the optical film is laminated on the optical film in a long side direction? Or a long side direction of the optical film under 23 占 폚 and 55% RH (MPa or N / mm ² ), the elongation at break is represented by E (%), the sectional area of the optical film in the direction orthogonal to the tensile direction (G) not represented by the following formula is 7 to 20 in each of the long side direction? And the short side direction? Of the optical film, where A (mm ² )

[Equation 1]

[Chemical Formula 1]

(1), R ¹ represents a hydrogen atom or an aliphatic group having 1 to 4 carbon atoms; R ² represents a substituent; (A) represents a group of atoms forming a 5-membered or 6-membered ring; n Represents an integer of 0 to 4)

(2)

(Wherein R ²⁶ represents an aryl group having 6 to 12 carbon atoms; R ²⁷ and R ²⁸ each independently represent a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, or an alkyl group having 6 to 12 carbon atoms And R < ²⁶ > and R < ²⁷ > each may have a substituent)

(3)

(3), R ¹ represents a hydrogen atom or a substituent, R ² represents a substituent represented by the following formula (3-1): n 1 represents an integer of 0 to 4, n 1 represents 2 , Plural R ^{1 s} may be the same or different, n 2 is an integer of 1 to 5, and when n 2 is 2 or more, plural R ^{2 s} may be the same or different)

[Chemical Formula 4]

(3-1), A represents a substituted or unsubstituted aromatic ring, R ³ and R ⁴ each independently represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms or a group represented by the formula (3-2 R ⁵ represents a single bond or an alkylene group of 1 to 5 carbon atoms; X represents a substituted or unsubstituted aromatic ring; n 3 represents an integer of 0 to 10; search n3 is 2 or more, when a plurality of R ⁵ and X are be the same or different from each other)

[Chemical Formula 5]

(3-2), X represents a substituted or unsubstituted aromatic ring; R ⁶ , R ⁷ , R ⁸ and R ⁹ are each independently 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, plural R ⁶ , R ⁷ , R ⁸ and X may be the same or different from each other)

[Chemical Formula 6]

(Wherein R ¹ 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, R ⁴ represents a substituent )

[2] The optical film according to [1], wherein the optical film comprises a core layer and a pair of skin layers which sandwich the core layer, and at least the skin layer contains the compound A.

[3] An optical film according to [1] or [2], wherein the film thickness is 15 to 30 μm.

[4] The optical film according to [2], wherein the core layer comprises a compound B comprising a polyester compound obtained by polycondensing a diol and a dicarboxylic acid.

[5] The optical film according to [2], wherein the ratio A / B of the compound A to the compound B in the core layer is 0 to 0.1.

[6] The optical film according to [2], wherein the content ratio B / A of the compound B to the compound A in the skin layer is 0 to 0.5.

[7] The retardation in the in-plane direction defined by the following formula (I) and measured at a measurement wavelength of 590 nm of the optical film is defined as Ro (590) and is defined by the following formula (II) Satisfies | Ro (590) |? 5 nm and | Rth (590) | 5 nm when the retardation in the thickness direction measured in the thickness direction is Rth (590) ≪ / RTI >

In formula (I) Ro = (nx-ny) x t (nm)

The formula (II) Rth = {(nx + ny) / 2-nz} x t (nm)

(In the formulas (I) and (II), nx represents the refractive index in the geographical axial direction x at which the refractive index becomes the maximum in the in-plane direction of the film; ny represents the refractive index in the in- N represents the refractive index in the thickness direction z of the film, and t (nm) represents the thickness of the film)

[8] A process for producing an optical film according to any one of [1] to [7], wherein the cellulose ester, the polymer comprising a repeating unit derived from a monomer represented by the formula (1) , A compound represented by the formula (3), and a compound represented by the formula (4); and a step of preparing a doped compound containing at least one compound A selected from the group consisting of a compound represented by the formula And a fourth step of drying the stretched film material to obtain the optical film, wherein the stretched film material is stretched after the stretching process, In the fourth step, the filmy material is dried at 125 to 150 DEG C for 10 to 15 minutes while conveying the filmy material at a tension of 100 to 150 N / m in 200 or more and 300 or less rolls.

[9] In the first step, a dope for a core layer containing a cellulose ester, a cellulose ester and a dope for a skin layer containing the compound A are prepared. In the second step, the dope for the core layer and the dope for the skin layer To obtain the optical film comprising a core layer and a pair of skin layers for holding the core layer therebetween, wherein the optical film is formed on the support, Way.

[10] A polarizer, comprising a polarizer and an optical film according to any one of [1] to [7], or an optical film obtained by the method described in [8] or [9].

[11] The polarizer according to [10], wherein the polarizer and the optical film are adhered via a cured layer of an active energy ray curable adhesive.

[12] A liquid crystal display device comprising an optical film according to any one of [1] to [7], or an optical film obtained by the production method according to [8] or [9].

[13] A liquid crystal display comprising a first polarizing plate, a liquid crystal cell, a second polarizing plate, and a backlight in this order, wherein the first polarizing plate has a first polarizer and a second polarizer, And a protective film F2 disposed on the side of the liquid crystal cell side of the first polarizer, wherein the second polarizer comprises a second polarizer and a second polarizer disposed on a side of the liquid crystal cell side of the second polarizer And a protective film F4 disposed on a surface opposite to the liquid crystal cell of the second polarizer, wherein at least one of the protective films F2 and F3 comprises the optical film. A liquid crystal display device comprising:

[14] The liquid crystal display according to [13], wherein the liquid crystal cell is a liquid crystal cell of an IPS mode or an FFS mode.

[15] A liquid crystal display device according to any one of [12] to [14], wherein the length of the display area in the diagonal direction is 10 inches or less.

According to the present invention, even if the film thickness is thin, it is possible not only to suppress the deterioration of the polarizer but also to provide a high optical film.

1 is a schematic diagram showing an example of the configuration of an optical film of the present invention.
Fig. 2 is a schematic view showing an example of a production process of the optical film of the present invention.
3 is a schematic diagram showing an example of a small-sized liquid crystal display device.
Fig. 4 is a diagram schematically showing the orientation of liquid crystal molecules in one pixel region of a liquid crystal cell used in the embodiment. Fig.

The inventors of the present invention have found that by including in the optical film at least one compound A selected from the group consisting of a polymer containing a repeating unit represented by the following general formula (1) and a compound represented by the general formulas (2) to (4) , It has been found that even if the film thickness is reduced, the deterioration of the polarizer can be sufficiently suppressed. It is considered that the optical film containing the compound A has a high density and can not only reduce the amount of water permeation but also reduce the acid value of boric acid from the polarizer.

On the other hand, the protective film containing the compound A tends to be hard and brittle although it can impart a polarizer deterioration inhibiting function. Therefore, the film becomes harder and tearable than the conventional film, and is not easily expressed as a function of the breaking point stress, the film cross-sectional area, and the breaking point elongation. This is because, in the optical film, a portion where the dispersion state of the compound A is uneven to a fine level occurs, and the compound A is likely to be broken starting from that portion; As a result, it is considered that the elongation at break is lowered. In addition, an optical film having a thin film thickness is not likely to be lower because the film has a low strength.

On the contrary, the inventors of the present invention found that adjusting the drying conditions in the drying step after stretching; That is, it has been found that the toughness of the optical film can be increased by increasing the number of the rolls for transporting the film, the tension of the film, the drying temperature or the drying time in the drying step of drying the film after the stretching. The reason for this is not necessarily clear, but it is considered that, by adjusting the drying conditions after stretching as described above, the orientation properties of the polymer constituting the optical film become high.

Specifically, the toughness of the optical film can be improved by controlling the dispersion state at the molecular level of the cellulose ester and the compound A in the drying step (solvent removing step) after stretching at the time of producing the optical film do. That is, a certain temperature and pressure are applied not only to the transport direction (MD direction) but also to the width direction (TD direction) of the optical film by drying the film at a drying time or drying temperature over a plurality of rolls while applying an appropriate tension , It is considered that Compound A can be dispersed very uniformly in the resin of the cellulose ester in a film containing a small amount of solvent. As a result, it is considered that the toughness of the optical film is improved in both the MD and TD directions.

In the state of the dope before drying, it is considered that the cellulose ester and the compound A are uniformly mixed, and it is considered that the dispersed state of the cellulose ester and the compound A tends to become uneven when dried. If the drying temperature is low, it is considered that the compound A is not easily dispersed uniformly by drying slowly. Therefore, it is preferable to increase the drying temperature in order to improve the toughness of the film. In order to improve the toughness of the film, it is desirable to reduce the amount of the residual solvent in the film. Therefore, it is preferable that the drying temperature is higher than a certain level and the drying time is also longer. It is considered that the transporting tension is such that the molecular chain of the cellulose ester can be sufficiently elongated (easy to orient) to make it difficult for the additive such as the compound A to move in the film. Therefore, in order to improve the toughness, . Since the roll can transmit the tension uniformly in the transport direction and the width direction to the film, it is preferable to set the number of rolls to a certain value or more in order to improve the toughness of the film.

Thereby, it was found that an optical film having high strength and hard to be torn can be obtained even if the film thickness is thin.

That is, the optical film of the present invention, which contains the compound represented by the general formulas (1) to (4) and is dried under specific drying conditions, can suppress the deterioration of the polarizer even though the film thickness is small, It can also have high toughness.

1. Optical film

As described above, the optical film of the present invention comprises a cellulose ester, a polymer containing a repeating unit represented by the formula (1), and at least one member selected from the group consisting of the compounds represented by the formulas (2) to (4) Compound A < / RTI >

≪ About cellulose ester >

The cellulose ester is a compound obtained by esterifying at least one of cellulose, an aliphatic carboxylic acid having 2 to 22 carbon atoms and an aromatic carboxylic acid.

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, cellulose acetate triacetate is preferable because of low retardation manifestation.

The total substitution degree 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 2.95. In order to lower the phase difference manifestation, it is preferable that the total substitution degree of the acyl group is increased.

The number of carbon atoms of the acyl group contained in the cellulose ester is preferably 2 to 7, more preferably 2 to 4. It is preferable that the acyl group contained in the cellulose ester includes an acetyl group in view of obtaining good heat resistance. The substitution degree of the acyl group having 3 or more carbon atoms is preferably 0.9 or less, more preferably 0.

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

The weight average molecular weight of the cellulose ester is preferably 5.0 x 10 ⁴ to 5.0 x 10 ⁵ , more preferably 1.0 x 10 ⁵ to 3.0 x 10 ⁵ , and more preferably 1.5 10 ⁵ to 5.0 x 10 ⁵ , More preferably 2.9 x 10 < ^{5 &} gt ;. 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 the 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 and K803G (manufactured by Showa Denko K.K.) are connected and used.

Column temperature: 25 ° C

Sample concentration: 0.1 mass%

Detector: RI Model 504 (manufactured by GL Science)

Pump: L6000 (manufactured by Hitachi Seisakusho Co., Ltd.)

Flow rate: 1.0 ml / min

Calibration curve: Standard polystyrene STK standard A calibration curve of 13 samples of polystyrene (manufactured by Tosoh Corporation) Mw = 1.0 × 10 ⁶ to 5.0 × 10 ² is used. 13 samples are preferably selected at substantially equal intervals.

The viscosity average degree of polymerization of the cellulose ester is preferably from 150 to 450, more preferably from 250 to 350, from the standpoint of making the mechanical strength of the film to be a certain level or more.

The viscosity of the 6 mass% solution obtained by dissolving the cellulose ester in dichloromethane is preferably from 50 to 900, more preferably from 100 to 600, and even more preferably from 200 to 200, 450 is most preferable.

<Compound A>

The compound A may be at least one selected from the group consisting of a polymer containing a monomer-derived repeating unit represented by the formula (1) and a compound represented by the formulas (2) to (4). Since these compounds have an aromatic ring and a rigid structure, an optical film containing these compounds can have a high density. As a result, not only the water permeation amount of the optical film can be reduced, but also the diffusion path of boric acid from the polarizer can be reduced, and deterioration of the polarizer can be suppressed.

(7)

R ¹ in the formula (1) 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 and an ethyl group. 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 and a t-butyl group. Examples of the aromatic group include a phenyl group, a naphthyl group and a biphenyl group, preferably a phenyl group. (A) represents an atomic group necessary for forming a 5 or 6-membered ring, and is preferably a 5 or 6-membered aromatic ring. The aromatic ring includes a saturated or unsaturated heterocycle including an aromatic ring containing no hetero atom and a 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 the formula (1) may preferably be a copolymer represented by the following formula (1-1).

(1-1)

[Chemical Formula 8]

R ²¹ , R ²² , R ²³ and R ²⁴ in the formula (1-1) each independently represent a substituent. x represents 1 to 40%, y represents 5 to 95%, and z represents 1 to 70%, wherein x, y and z represent molar ratios to all repeating units contained in the polymer. 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; R ¹⁰¹ , R ¹⁰² and R ¹⁰³ independently represent a hydrogen atom or an aliphatic group having 1 to 4 carbon atoms.

Specific examples of the polymer containing a monomer-derived repeating unit represented by the formula (1) include the following.

[Chemical Formula 9]

The weight average molecular weight of the polymer is preferably 200 to 10000, more preferably 300 to 8000, and still more preferably 400 to 4000. If the weight average molecular weight is more than a certain level, the density of the optical film can be increased well. Thereby, the diffusion of boric acid from the polarizer can be suppressed, and deterioration of the polarizer can be suppressed. When the weight average molecular weight is less than a certain value, compatibility with the cellulose ester is hardly impaired.

[Chemical formula 10]

R ²⁶ in the formula (2) 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 group having 6 to 12 carbon atoms; More preferably a hydrogen atom, an alkyl group having 1 to 6 carbon atoms (including a cycloalkyl group), or a phenyl group. Each of R ²⁶ and R ²⁷ may have a substituent. Examples of the substituent which R ²⁶ may have include a halogen atom or an alkyl group having 1 to 6 carbon atoms. Examples of the substituent which R ²⁷ may have include an aryl group having 6 to 12 carbon atoms.

Specific examples of the compound represented by the formula (2) include the following.

(11)

The weight average molecular weight of the compound represented by the formula (2) is preferably 200 to 1000, more preferably 250 to 800.

[Chemical Formula 12]

R ¹ in the formula (3) represents a hydrogen atom or a substituent. R ² represents a substituent represented by the following formula (3-1). n1 represents an integer of 0 to 4, and when n1 is 2 or more, plural R &lt; ^{1 &gt;} may be mutually the same or different. n2 represents an integer of 1 to 5, and when n2 is 2 or more, plural R ² may be the same or different.

[Chemical Formula 13]

A in the formula (3-1) 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 the formula (3-2). 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, plural R ⁵ and X may be the same or different.

[Chemical Formula 14]

X in the formula (3-2) represents a substituted or unsubstituted aromatic ring. The aromatic ring is preferably a benzene ring. Each of R ⁶ to R ⁹ independently represents 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, plural R ⁶ to R ⁹ and X may be the same or different.

Specific examples of the compound represented by the formula (3) include the following.

[Chemical Formula 15]

[Chemical Formula 16]

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

Specific examples of the compound represented by the formula (4) include the following.

[Chemical Formula 17]

The content of the polymer containing the monomer unit represented by the formula (1) and the compound represented by the formula (2) to (4) is 0.1 to 15 parts by mass, preferably 0.5 to 10 parts by mass, per 100 parts by mass of the cellulose ester More preferably 0.5 to 3 parts by mass. If the content of the compound is more than a certain level, the density of the optical film can be sufficiently increased, and sufficient polarizer deterioration inhibiting effect is easily obtained. If the content of the compound is less than a predetermined value, the film is hardly excessively hard or brittle, and the dispersed state of the compound A in the film is also uneven (difficult to be lumpy), so that the toughness of the film is remarkably There is no fear of degradation.

The optical film of the present invention preferably further comprises a polyester compound (compound B) in that it is easy to adjust the plasticity and retardation of the film.

&Lt; About the polyester compound (compound B) >

The polyester compound may be a compound obtained by polycondensing a dicarboxylic acid and a diol. The dicarboxylic acid may be at least one selected from the group consisting of an aliphatic dicarboxylic acid, an alicyclic dicarboxylic acid, and an aromatic dicarboxylic acid. The diol may be at least one 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 an aliphatic dicarboxylic acid and an alicyclic dicarboxylic acid, and a group consisting of an aliphatic diol, an alkyl ether diol and an alicyclic diol Is preferably a polyester compound obtained by polycondensation of a diol selected from the group consisting of: A polyester compound (aliphatic polyester compound) obtained by polycondensing an aliphatic dicarboxylic acid and an aliphatic diol is more preferable. In the polyester compound, the hydroxyl group at the molecular end may be sealed with a monocarboxylic acid, or the carboxyl group at the molecular end may be sealed with a monoalcohol.

That is, the polyester compound is preferably represented by the formula (5) or (6).

Formula (5):

[Chemical Formula 18]

G in the formula (5) represents a group derived from an aliphatic diol or an alkyl ether diol. The aliphatic diol preferably has 2 to 12 carbon atoms. 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, , 1,5-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, 1,3-butylene glycol, 1,4-butylene glycol, and 1,6-hexanediol.

The alkyl ether diol preferably has 4 to 12 carbon atoms. Examples of the alkyl ether diol include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol and the like. Each aliphatic diol or alkyl ether diol may be used alone or two or more thereof may be used in combination.

A in the formula (5) represents a group derived from an aliphatic dicarboxylic acid or an alicyclic dicarboxylic acid. The number of carbon atoms of the aliphatic dicarboxylic acid is preferably 4 to 12. Examples of aliphatic dicarboxylic acids include malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecandicarboxylic acid, dodecanedicarboxylic acid and the like . The aliphatic dicarboxylic acid or the alicyclic dicarboxylic acid may be used individually in one kind or in a combination of two or more kinds.

B ₁ in the formula (5) represents a group derived from an aliphatic monocarboxylic acid or an alicyclic monocarboxylic acid. The number of carbon atoms of the aliphatic monocarboxylic acid is preferably 1 to 12. Examples of aliphatic monocarboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2- ethylhexanecarboxylic acid, But are not limited to, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachic acid, behenic acid, lignoceric acid, Unsaturated fatty acids such as saturated fatty acids such as montanic acid, melissic acid and lactic acid, undecylenic acid, oleic acid, sorbic acid, linolenic acid, linolenic acid and arachidonic acid, and are excellent in compatibility with cellulose ester It is acetic acid.

It is preferable that B ₁ , G and A in the formula (5) do not include an aromatic ring because the purpose is to make it difficult to develop a retardation. m represents the number of repeats and is preferably 1 or more and 170 or less.

Examples of the polyester compound represented by the formula (5) include those shown in Table 1.

Formula (6):

[Chemical Formula 19]

G and A in the formula (6) are defined similarly to G and A in the formula (5), respectively. B ₂ in the formula (3) represents a group derived from an aliphatic monoalcohol or an alicyclic monoalcohol. The number of carbon atoms of the aliphatic monoalcohol is preferably 1 to 12. Examples of aliphatic monoalcohols include methanol, ethanol, propanol, isopropanol and the like; Examples of the alicyclic monoalcohols include cyclohexyl alcohol and the like.

It is preferable that B ₂ , G and A in the formula (6) do not include an aromatic ring because the purpose is to make it difficult to develop a phase difference. n represents the number of repeats and is preferably 1 or more and 170 or less.

Examples of the polyester compound represented by the formula (6) include those shown in Table 2.

The weight average molecular weight (Mw) of the polyester compound may preferably be 20,000 or less, more preferably 5000 or less, and still more preferably 3,000 or less, from the viewpoint of improving 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 more preferably 1000 or more, from the viewpoint of suppressing the volatilization of the polyester compound in the film.

The content of the polyester compound is preferably 1 to 45 parts by mass, more preferably 2 to 30 parts by mass, and most preferably 5 to 25 parts by mass, per 100 parts by mass of the cellulose ester, from the viewpoint of easy adjustment of the plasticity and retardation of the film Still more preferably from 10 to 20 parts by mass. That is, when the content of the polyester compound (preferably an aliphatic polyester compound) is more than a certain amount, the retardation in the thickness direction can be preferably lowered. If the content of the polyester compound is less than a certain level, the film strength is not significantly impaired and there is no possibility that the toughness is significantly lowered.

The optical film of the present invention may further contain various additives such as a plasticizer, an ultraviolet absorber, a release aid, a lubricant, a matting agent (fine particle), and an impact reinforcement as necessary.

<About the plasticizer>

Examples of the plasticizer include sugar derivatives, phosphate ester compounds and the like.

The saccharide derivative may be a compound in which at least part of the hydrogen atoms of the hydroxyl groups of the saccharide are substituted with substituents. The saccharide constituting the saccharide derivative preferably has a structure in which 1 to 12 of the furanose structure and the pyranose structure are bonded to each other or both; It is preferable that one or three, preferably two, structures of one or both of the furanose structure and the pyranose structure are bonded. Among them, it is preferable to include both the pyranose structure and the furanose structure.

Examples of the sugar constituting the sugar derivative include monosaccharides such as glucose, galactose, mannose, fructose, xylose and arabinose; 2 sugars such as lactose, sucrose, maltitol, cellobiose, and maltose; And a structure derived from a triple sugar such as celutriose, raffinose and the like.

The substituent constituting the sugar derivative is preferably an alkyl group (preferably an alkyl group having 1 to 22 carbon atoms, more preferably 1 to 12 carbon atoms, particularly preferably 1 to 8 carbon atoms such as a methyl group, an ethyl group, a propyl group, Ethyl group, hydroxypropyl group, 2-cyanoethyl group, benzyl group and the like); An aryl group (preferably an aryl group having 6 to 24 carbon atoms, more preferably 6 to 18, particularly preferably 6 to 12, for example, phenyl, naphthyl); (Preferably an acyl group having 1 to 22 carbon atoms, more preferably 2 to 12 carbon atoms, and particularly preferably 2 to 8 carbon atoms, such as an acetyl group, a propionyl group, a butyryl group, a pentanoyl group, , An octanoyl group, a benzoyl group, a toluyl group, a phthalyl group, a naphthalyl group, etc.) and the like, preferably an acyl group.

In the sugar derivative, the unreacted hydroxyl group which is not substituted with a substituent may be left as a hydroxyl group as it is.

The sugar derivative may be a mixture of a plurality of sugar derivatives having different degree of substitution. Such a mixture may contain an unsubstituted compound. The average substitution ratio in the mixture is preferably 62 to 94%. The average replacement ratio can be defined by the following equation.

Average substitution ratio = 100% x (content of each sugar derivative in the mixture) x (number of OH substituted in one molecule of each saccharide derivative) / (total number of OH in one molecule of the unsubstituted sugar)

Specific examples of sugar derivatives include the following.

[Chemical Formula 20]

Examples of the phosphoric acid ester compound include triphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate and tributyl phosphate, and the like.

The content of the plasticizer may be 1 to 40 parts by mass relative to 100 parts by mass of the cellulose ester.

&Lt; About ultraviolet absorber >

The ultraviolet absorber may be a benzotriazole-based compound, a 2-hydroxybenzophenone-based compound, or a salicylic acid phenyl ester-based compound. Specific examples thereof include 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis , Triazole compounds such as 2- (3,5-di-t-butyl-2-hydroxyphenyl) benzotriazole, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy- Phenone, and 2,2'-dihydroxy-4-methoxybenzophenone.

Examples of the ultraviolet absorber may be a commercially available product. Examples of the ultraviolet absorber include Tinuvin 109, Tinuvin 171, Tinuvin 234, Tinuvin 326, Tinuvin 327, Tinuvin 328 and Tinuvin 928 manufactured by BASF Japan Co., Series, or 2,2'-methylenebis [6- (2H-benzotriazol-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol] (molecular weight 659; LA31 manufactured by ADEKA Corporation) and the like.

When the optical film is disposed on the side of the liquid crystal cell of the polarizer (when it is used as the protective film F2 or F3 described later), the ultraviolet ray absorber is not essential and the content of the ultraviolet absorber is preferably 0 to 0.5 mass %. On the other hand, when the polarizer is disposed on the side opposite to the liquid crystal cell (when it is used as the protective film F1 or F4 described later), the content of the ultraviolet inhibitor is preferably about 1 to 5.0% by mass relative to the cellulose ester Can be about 0.5 to 3.0%.

<About matting>

The matting agent can impart more slidability to the optical film. The matting agent may be a fine particle containing an inorganic compound or an organic compound having heat resistance in a film forming process without impairing the transparency of the obtained film.

Examples of the inorganic compound 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, Magnesium silicate and calcium phosphate. Of these, silicon dioxide and zirconium oxide are preferable, and silicon dioxide is more preferable in order to reduce an increase in haze of the resulting 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., 10, Shihosta KEP-30, Shihosta KEP-50 (manufactured by Nippon Shokai Kabushiki Kaisha), Silo Fobik 100 (manufactured by Fuji Silicia), Nipil E220A Manufactured by Matex).

The particle shape of the matting agent may be amorphous, needle-like, flat or spherical, and may be spherical, in view of facilitating the transparency of the obtained film.

The matting agent may be used singly or in combination of two or more. In addition, by using particles having different particle diameters or shapes (for example, a needle shape and a spherical shape), high transparency and slidability can be achieved at the same time.

The particle size of the matting agent is preferably smaller than the wavelength of visible light, and is preferably not more than 1/2 of the wavelength of visible light, since the size of the particles of the matting agent is close to the wavelength of visible light. However, if the particle size is too small, the effect of improving the sliding property may not be exhibited. Therefore, the particle size is preferably in the range of 80 to 180 nm. The particle size means the size of the aggregate when the particles are aggregates of primary particles. When the particle is not spherical, the particle size means the diameter of the circle corresponding to the projected area.

The content of the mat agent may be about 0.05 to 1.0% by mass, preferably 0.1 to 0.8% by mass, based on the cellulose ester.

The optical film of the present invention may be a single layer film or a laminated film of a plurality of layers.

As described above, in the present invention, by adjusting the drying conditions of the film in the film production process to a specific range, a high toughness optical film can be obtained. On the other hand, a film containing both a polymer containing a repeating unit represented by the formula (1) or a compound represented by the formula (2) to (4) as a polarizer deterioration inhibitor and a polyester compound as a retardation- , There is a tendency that the effect of suppressing deterioration of the polarizer of the obtained optical film is not sufficiently obtained or the phase difference is not sufficiently reduced.

The reason for this is not necessarily clear, but is considered as follows. It is preferable that the oxygen containing substituent contained in the polymer containing the repeating unit represented by the formula (1) and the compound represented by the formula (2) to (4) and the ester moiety contained in the polyester compound are not intended Are expected to occur. As a result, it is considered that the polarizer deterioration inhibiting function of the compound represented by the formulas (1) to (4) and the retardation reducing function of the polyester compound are inhibited. The oxygen-containing substituent can be, for example, an oxygen atom moiety constituting the ring represented by (A) of the formula (1), a carbonyl group in the formulas (2) and (4), a hydroxyl group in the formula .

On the other hand, the inventors of the present invention have found that a laminated film of a plurality of layers of an optical film, and a polyester compound capable of functioning as a phase difference reducing agent and a polyester compound capable of functioning as a polarizer deterioration inhibitor, (1) to (4) and the polyester compound can be inhibited by fully localizing the compound in different layers, and the function of each compound can be sufficiently expressed.

That is, the optical film of the present invention is preferably a laminated film of two or more layers including at least a core layer and a skin layer. Each of the core layer and the skin layer included in the optical film may be one layer or two or more layers.

It is preferable that the optical film has a symmetrical laminated structure in that it is intended to suppress deformation of the optical film due to changes in ambient temperature or humidity. Preferable examples of the laminated structure of the optical film include a two-layer structure of a core layer / a skin layer, a three-layer structure of a skin layer / a core layer / a skin layer and the like, and preferably a skin layer / a core layer / Layer structure.

The core layer preferably contains the above-described cellulose ester and the above-described polyester compound in view of having a function of mainly controlling the phase difference. The core layer may further contain the above-described various additives such as a compound represented by the above-described formulas (1) to (4) and a matting agent, if necessary.

In order to suppress the unintended interaction of the compound (A) and the polyester compound (B) represented by the chemical formulas (1) to (4) in the core layer, (Compound A) represented by the general formula (4) is preferably relatively small relative to the content ratio of the polyester compound (compound B). Concretely, the content ratio A / B of the compound (A) to the polyester compound (compound B) represented by the formulas (1) to (4) in the core layer is preferably 0 to 0.1 , More preferably from 0 to 0.08.

From the viewpoint of imparting a good slipperiness to the surface of the optical film and facilitating the production of the retardation, it is preferable that the matting agent is localized in the skin layer. Specifically, the content of the matting agent in the core layer may be 5% or less of the content of the matting agent in the skin layer.

When there are a plurality of core layers, the compositions of the plurality of core layers may be the same or different.

The total thickness of the core layer may be at least 50%, preferably at least 70% of the total thickness of the optical film. The thickness of the core layer is preferably 10 to 50 占 퐉, preferably 10 to 28 占 퐉, more preferably 10 to 20 占 퐉, in view of sufficiently suppressing the permeation of moisture to the polarizer .

The skin layer mainly has a function of protecting the core layer and may further have a function of suppressing the deterioration of the polarizer as required. Therefore, it is preferable that the skin layer contains the above-mentioned cellulose ester and the compound represented by the above-mentioned formulas (1) to (4). The skin layer may further contain the above-mentioned various additives such as the above-mentioned polyester compound and matting agent if necessary.

In order to suppress the unintended interaction of the compound (A) and the polyester compound (B) represented by the chemical formulas (1) to (4) in the skin layer, the polyester compound B) is preferably relatively small relative to the content of the compound (compound A) represented by the formulas (1) to (4). Concretely, the content ratio B / A of the polyester compound (compound B) to the compound (compound A) represented by the formulas (1) to (4) in the skin layer is preferably 0 to 0.5 , More preferably from 0 to 0.15.

The total thickness of the skin layer may be 50% or less, preferably 30% or less of the total thickness of the optical film. The thickness of the skin layer is preferably in the range of 1 to 20 mu m, more preferably in the range of 1 to 10 mu m, and more preferably in the range of 1 to 5 mu m to the extent that sufficient adhesion with the polarizer can be obtained.

When there are a plurality of skin layers, the compositions of the plurality of skin layers may be the same or different.

1 is a schematic diagram showing an example of the configuration of an optical film of the present invention. As shown in Fig. 1, the optical film 10 of the present invention may have a core layer 11 and a pair of skin layers 13 and 15 for supporting it. The composition and thickness of the skin layers 13 and 15 may be the same or different.

&Lt; Physical properties of optical film >

(Film thickness)

The film thickness of the optical film is preferably from 15 to 45 탆, more preferably from 15 to 30 탆, for the purpose of thinning the polarizing plate.

(Toughness)

The optical film of the present invention can have a certain degree of toughness even if the film thickness is small by setting the drying conditions of the film in the manufacturing process within a specific range. Specifically, when the optical film of the present invention is stretched in its long-side direction? Or short-directional direction? Under 23 ° C and 55% RH, the breaking point stress is T (N / mm ² or MPa) And the cross-sectional area of the optical film in the direction orthogonal to the tensile direction is A (mm ² ), the toughness of the optical film represented by the following formula is expressed by the following equation , It is preferably 7 to 20, more preferably 10 to 20, and even more preferably 15 to 20.

&Quot; (2) &quot;

The long side direction? Of the optical film indicates the long direction (MD direction) of the elongated optical film of the roll; The short side direction? Is a direction orthogonal to the long side direction?, And indicates the width direction (TD direction) of the elongated optical film roll. When the sheet-like optical film is a square, one of two orthogonal sides may be a long side direction and the other side may be a short side direction. The long side direction? Of the optical film may be coincident with or orthogonal to the absorption axis direction of the polarizer, and particularly preferably coincides with the absorption axis direction of the polarizer.

The toughness in the long side direction? (Preferably the MD direction) and the short side direction? (Preferably the TD direction) of the optical film can be measured using a test piece, respectively. Specifically, the toughness in the MD direction of the optical film can be measured by the following procedure.

1) Five optical films are cut out in the direction of 120 mm (MD direction) × 10 mm (TD direction) and used as test pieces for MD direction measurement. The obtained test piece is conditioned for 24 hours under an environment of 23 ° C and 55% RH.

2) Then, the tensile modulus of the test piece was measured by the method described in JIS K7127. Tensilon RTC-1225 manufactured by Orientech Co., Ltd. was used as the tensile tester, and the upper and lower ends of the test piece in the longitudinal direction (MD direction) were bumped with a distance of 100 mm between the chucks (the margin was 10 mm each at the upper and lower ends of the test piece The tensile stress at break (T) and elongation (elongation at break (E)) of the test piece were measured respectively by tensile test in the longitudinal direction (MD direction) at a rate of 100 mm / The total is measured five times (for a total of five pieces). The measurement is performed in an environment of 23 ° C and 55% RH.

3) the maximum value of five measured values of the five measured values of the obtained breaking point stress (T) (N / mm ² or MPa), the elongation at break (E) (%) and the film thickness t mm) is applied to each of the following equations to calculate the toughness in the MD direction.

Toughness = tensile stress (T) (N / mm ² or MPa) × cross-sectional area of the specimen in the direction perpendicular to the drawing direction ^{(A) (mm 2) ×} ( elongation at break (E) (%) / 100 ) ^1/2

Sectional area of the test piece A (mm ² ) = width of the test piece 10 (mm) x thickness of the test piece (t) (mm)

Likewise, in the toughness in the TD direction of the optical film, five pieces of the optical film are cut out in a size of 120 mm (TD direction) × 10 mm (MD direction), and a test piece for measurement in the TD direction is prepared. The toughness in the TD direction is calculated by performing the same measurement as described above except that the test pieces are used to stretch in the longitudinal direction (TD direction) of the test piece.

The toughness of the optical film is determined by drying conditions in the drying process of the stretched film; Specifically, it can be adjusted by 1) the number of rolls in the drying process, 2) the tension of the film, 3) the drying temperature, and 4) the drying time. In order to increase the toughness of the optical film, for example, 1) the number of rolls is increased in the drying step, 2) the tension of the film is increased, 3) the drying temperature is increased, or 4) Is preferred; It is more preferable to carry out all of the above 1) to 4). Thereby, the highly dispersed state of the cellulose ester and the compound A from before drying can be maintained, and the orientation of the molecular chains of the cellulose ester can be further enhanced, so that the toughness in both the MD and TD directions can be preferably increased. Further, as described above, the toughness of the optical film can be adjusted also by the content of the additive such as the compound A and the compound B.

(Tear strength)

The optical film of the present invention can have a tear strength of a certain level or higher, even though the film thickness is thin, by setting the drying condition of the film in the manufacturing process within a specific range. The tearing load (mN) of the optical film in the Elmendorf method is preferably 20 mN or more, more preferably 30 mN or more, and still more preferably 35 mN or more. The upper limit of the tear strength may be, for example, about 50 mN.

The tear strength of the optical film can be measured in accordance with JIS K 7128-1991 using a light-weight tearing apparatus manufactured by Toyo Sekisui Kagaku Co., Ltd. The measurement can be carried out for each of the transport direction (MD direction) and the width direction (TD direction) of the film under the condition of 23 占 폚 and 55% RH, and can be obtained as an average value thereof.

Like the toughness, the tear strength of the optical film was evaluated by drying conditions in the film drying process after stretching; Specifically, it can be adjusted by 1) the number of rolls in the drying process, 2) the tension of the film, 3) the drying temperature, and 4) the drying time. Specifically, in order to set the tear strength of the optical film to a certain level or more, it is necessary to 1) increase the number of rolls, 2) increase the tension of the film, 3) increase the drying temperature, or 4) Is preferred; It is more preferable to carry out all the above 1) to 4). Further, as described above, the tear strength of the optical film can be adjusted also by the content of the additive such as the compound A or the compound B.

(Retardation)

The retardation (Ro) of the optical film measured in the in-plane direction under the conditions of a measurement wavelength of 590 nm and 23 캜 55% RH is preferably -10 nm or more and 10 nm or less, more preferably -5 nm or more and 5 nm or less. The retardation (Rth) in the thickness direction of the optical film measured under conditions of a measurement wavelength of 590 nm and 23 캜 55% RH is preferably -10 nm or more and 10 nm or less, more preferably -5 nm or more and 5 nm or less. The optical film having such a retardation value is suitable, for example, as a retardation film (F2 or F3) of an IPS mode liquid crystal display device or the like. In particular, the contrast and viewing angle of the liquid crystal display of the IPS mode can be improved by using the optical value.

The retardation (Ro and Rth) are respectively defined by the following formulas.

(I): Ro = (nx-ny) x t (nm)

Rth = {(nx + ny) / 2-nz} x t (nm)

(In the formulas (I) and (II)

nx represents a refractive index in the slow axis direction x at which the refractive index becomes the maximum in the in-plane direction of the film;

ny represents a refractive index in an in-plane direction of the film in a direction y perpendicular to the slow axis direction x;

nz represents the refractive index in the thickness direction z of the film;

t (nm) denotes the thickness of the film)

The retardation (Ro and Rth) can be obtained, for example, by the following method.

1) Humidify the optical film at 23 ° C and 55% RH. The average refractive index of the optical film after the humidity control is measured by an Abbe refractometer or the like.

2) The Ro when the light having a wavelength of 590 nm is incident on the optical film after the humidity control in parallel with the normal line of the surface of the film is measured with a COBRA 21ADH, Oji Keisuke Co., Ltd.

3) Using a KOBRA 21ADH, the slow axis in the plane of the optical film was used as a tilting axis (rotation axis), and light having a measurement wavelength of 590 nm was incident on the normal line of the surface of the film from an angle And the retardation value (R) (? The measurement of the retardation value (R) ([theta]) can be performed at six points every 10 degrees in the range of 0 DEG to 50 DEG. The in-plane slow axis refers to the axis at which the refractive index of the film is maximized, and can be confirmed by KOBRA 21ADH.

4) From the measured values of Ro and R (?) And the above-mentioned average refractive index and film thickness, nx, ny and nz are calculated by Cobra (KOBRA) 21ADH to calculate Rth at a measurement wavelength of 590 nm. The measurement of the retardation can be performed under conditions of 23 占 폚 and 55% RH.

The retardation of the optical film can be adjusted by stretching conditions, addition of the above-mentioned polyester compound having a phase difference adjusting function, and the like. In order to reduce Ro of the optical film to a certain value or less, it is preferable to set the stretching magnification to a certain value or less; In order to keep the Rth constant or less, for example, it is preferable to set the content of the polyester compound to a certain level or more.

(Hayes)

The haze of the optical film of the present invention is preferably 1% or less, more preferably 0.5% or less, and further preferably 0.3% or less. If the haze of the optical film is in the above range, good contrast can be easily obtained in the display device. The haze of the optical film can be measured with a haze meter (turbidity meter) (model: NDH 2000, manufactured by Nippon Denshoku Co., Ltd.) in accordance with JIS K-7136.

2. Manufacturing method of optical film

The optical film of the present invention can be produced by a solution casting method or a melt casting method. Since melting at high temperature is not required and a resin having a relatively large molecular weight is easily formed, it is preferable that the optical film of the present invention is produced by a solution casting film-forming method.

That is, the production process of the optical film of the present invention comprises: a first step of preparing a dope containing the above-mentioned cellulose ester and the compound A described above; A second step of softening the dope on a metal support, followed by drying and stripping to obtain a film-like material; A third step of stretching the film material; A fourth step of drying the film-like material to obtain an optical film; And a fifth step of winding the obtained film.

When the optical film of the present invention is a laminated film of two or more layers, in the first step, a dope for a core layer and a dope for a skin layer are prepared; In the second step, it is preferable to soften both the dope for the core layer and the dope for the skin layer on the metal support, followed by drying to obtain a film-like product.

&Lt; About the first step (dope preparing step) >

It is preferable to prepare the dope for the core layer and the dope for the skin layer by stirring and dissolving the organic solvent while adding the respective components described above.

The organic solvent used in the preparation of the dope solution can be used without limitation as long as it dissolves each of the above components sufficiently, such as cellulose ester. Examples of the chlorinated organic solvent include methylene chloride. Examples of the non-chlorine-based organic solvent include methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate and the like. Among them, methylene chloride is preferable.

The dope preferably further contains, in addition to the organic solvent, 1 to 40% by mass of a linear or branched aliphatic alcohol having 1 to 4 carbon atoms. By containing an aliphatic alcohol, the film-like material is gelled, and peeling from the metal support is facilitated. Examples of the straight chain or branched aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol and tert-butanol. Of these, methanol and ethanol are preferable in that the dope is relatively stable, the boiling point is relatively low, and the drying property is good.

The total concentration of resin components in the dope may be in the range of 15 to 45 mass% with respect to the total mass of the dope. The resin component in the dope indicates a cellulose ester in the dope for the core layer and the dope for the skin layer.

The dissolution of the cellulose ester and the like can be carried out by a method of performing the reaction at normal pressure, a method of performing the reaction at the boiling point of the main solvent or a method of pressurizing at a boiling point of the main solvent or the like. In order to remove aggregates and the like in the obtained dope, it is preferable to further filter the dope with a filter medium.

&Lt; Second process (flexible process) >

Fig. 2 is a schematic view showing an example of a production process of the optical film of the present invention. Fig. 2, the dope 21a for the core layer and the dope 21b for the skin layer are discharged from the die 23 and shared on the metal support 25 (see Fig. 2). The shared streaks can be successively shared and successively laminated by sequentially dope the dope for core layer 21a and the dope for skin layer 21b; The dope for the core layer and the dope for the skin layer can be flexibly laminated at the same time.

Examples of the sequentially stacked shared lines include the methods described in Japanese Patent Laid-Open Nos. 61-158414, 1-122419, and 11-198285. Examples of the simultaneous lamination and sharing are disclosed in Japanese Patent Publication Nos. 60-27562, 61-94724, 61-94725, 61-104813, 61-158413 And JP-A-6-134933.

The metal support 25 may be a metal belt, such as, for example, a stainless steel belt; A rotating metal drum or the like.

Subsequently, the common drawn dope is heated on the metal support 25 to evaporate the solvent to obtain the film-like material 27.

Examples of the method of evaporating the solvent include a method of blowing air on the surface of the dope, a method of transferring the liquid from the back surface of the metal support 25, and a method of transferring heat from the front and back of the dope by radiant heat. Among them, a method of transferring heat from the back surface of the metal support 25 by liquid is preferable in that the drying efficiency is high.

Drying of the dope on the metal support 25 is preferably carried out in an atmosphere of 40 to 100 캜. In order to set the atmosphere at 40 to 100 DEG C, it is preferable to heat the dope by bringing warm air at this temperature to the surface of the dope film or by irradiating infrared rays.

Subsequently, the film 27 obtained by evaporating the solvent on the metal support 25 is peeled off by a peeling roll 29 or the like (see Fig. 2). It is preferable to peel the film material 27 from the metal support 25 within 30 to 120 seconds after the softening in view of improving the surface quality and peeling property of the obtained film material 27. [

The amount of the residual solvent in the film 27 when peeling from the metal support 25 is preferably about 50 to 120% by mass, though it depends on the strength of the drying condition, the length of the metal support 25 and the like. When the film-like material 27 is peeled off at a point where the amount of the residual solvent is larger, if the film-like material 27 is too soft, it is unevenly stretched at the time of peeling, which tends to deteriorate planarity and tends to cause swelling and vertical streaks due to peeling tension. Therefore, the amount of the residual solvent at the time of peeling can be determined within a range that does not impair the planarity.

The amount of the residual solvent in the film material 27 is defined by the following formula.

Residual solvent amount (%) = (mass before heat treatment of film material-mass after heat treatment of film material) / (mass after heat treatment of film material) 占 100

The heat treatment at the time of measuring the residual solvent amount means that heat treatment is performed at 140 占 폚 for 1 hour.

The peeling tension when peeling the film-like material 27 from the metal support 25 is preferably 196 to 245 N / m. In the case where wrinkles tend to occur at the time of peeling, the peeling tension is preferably 190 N / m or less.

The temperature at the peeling position on the metal support 25 is preferably in the range of 10 to 40 占 폚 and more preferably in the range of 11 to 30 占 폚 in the case of the film formation using the stainless steel belt. Further, at the time of film formation using a metal drum, the temperature at the peeling position of the metal drum is preferably -20 to 10 占 폚.

&Lt; Third step (drying and stretching step) >

The peeled film 27 is dried while being conveyed in the tenter stretching device 31 or is conveyed in a plurality of rolls arranged in the drying device. The drying method is not particularly limited, but a method of blowing hot air on both surfaces of the film-like material 27 is generally used.

Since rapid drying tends to impair the flatness of the resulting film, drying at a high temperature is preferably carried out under the condition that the residual solvent is 8 mass% or less. Through the entire drying process, the drying temperature is preferably in the range of 40 to 190 占 폚, and more preferably in the range of 40 to 170 占 폚.

It is preferable to further stretch the film-like material 27 obtained after drying. The stretching may be performed in at least one direction or in two directions. The stretching in two directions (biaxial stretching) is preferably performed in the stretching direction (MD direction) and the width direction (TD direction), respectively. The biaxial stretching may be simultaneous biaxial stretching or stepwise biaxial stretching (sequential biaxial stretching).

The stretching ratio may be, for example, 1.01 to 1.5 times, preferably 1.01 to 1.3 times in each direction. The stretching temperature is preferably Tg to (Tg + 50) ° C, more preferably Tg to (Tg + 40) ° C. The specific stretching temperature may be, for example, about 100 to 200 占 폚.

In the case of stretching by the tenter stretching apparatus 31, the residual solvent amount of the film-like material at the start of the tenter stretching is preferably from 2 to 30 mass%. The drying is preferably carried out until the residual solvent amount of the film-like material becomes 10 mass% or less, preferably 5 mass% or less. The drying temperature is preferably in the range of 30 to 160 ° C, more preferably in the range of 50 to 150 ° C. The tenter system includes a clip tenter and a pin tenter, but from the viewpoint of productivity, a pin tenter is preferable.

&Lt; About the fourth step (drying step) >

In the present invention, from the viewpoint of not only sufficiently removing the solvent in the film but also obtaining a film having a high toughness, it is preferable to further dry the film. The drying of the film is preferably carried out while conveying the film to a plurality of rolls 33a arranged in the drying device 33 in plural.

As described above, in order to obtain a film with a high toughness, it is preferable that the tension of the film in the drying step, the number of the rolls 33a for transporting the film, the drying temperature and the drying time are respectively set to a certain value or more. Specifically, the number of the rolls 33a for transporting the film is preferably 200 to 300, more preferably 250 to 300. [ The tensile force of the film is preferably 100 to 150 N / m, more preferably 120 to 150 N / m.

The drying temperature is preferably 125 to 150 ° C, more preferably 135 to 150 ° C. The drying time varies depending on the drying temperature, but is preferably 10 to 15 minutes, more preferably 13 to 15 minutes.

Thereby, the optical film 10 having a toughness and a tear strength higher than a certain level can be obtained even though the film thickness is thin.

It is preferable to form an embossed portion at both end portions in the width direction of the optical film 10 in view of facilitating the winding of the obtained optical film 10. [ The method for forming the embossed portion is not particularly limited and includes a method of forming an embossed portion by pressing a roller such as an embossing ring on the film, a method of forming an embossed portion in a noncontact manner, and the like.

&Lt; About the fifth step (winding step) >

The long optical film 10 thus obtained can be rolled into a roll 39 on the winding core 37 by the winding device 35. [ The winding method may be a method of winding without applying normal vibration (straight winding); (Oscillating winding) by winding at least one of the film and the winding core while vibrating in the film width direction; They may be combined.

The optical film (10) of the present invention has a high toughness although the film thickness is very small. Therefore, even when wound by a normal method (straight winding), deformation of the obtained roll body can be reduced.

On the other hand, when the optical film 10 having the embossed portions at both ends in the width direction is wound by a normal method (straight winding), the embossed portions overlap each other, So that the deformation of the roll body 39 may occur. In order to highly suppress the deformation of the roll body 39, the optical film 10 is wound by a method in which at least one of the optical film 10 and the winding core 37 is wound while being vibrated in the film width direction Rate winding) is preferably employed. The roll body 39 wound in an oscillating winding has a wavy shape on both side surfaces in the axial direction.

The width of the elongated optical film 10 in the roll body 39 may be, for example, 1000 to 6000 mm, preferably 1400 to 4000 mm. The winding length of the optical film 10 may be, for example, 100 to 10000 m.

3. Polarizer

The polarizing plate of the present invention comprises a polarizer and two protective films for supporting the polarizer.

&Lt; About polarizer >

The polarizer is a device that allows only the birefringent light in a certain direction to pass. A typical polarizer currently known is a polyvinyl alcohol polarizing film. The polyvinyl alcohol polarizing film includes a polyvinyl alcohol film stained with iodine and a dichroic dye stained.

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

The thickness of the polarizer is preferably from 2 to 30 占 퐉, and more preferably from 5 to 15 占 퐉 in view of thinning the polarizing plate.

&Lt; Protective Film >

It is preferable that at least one of the two protective films for supporting and holding the polarizer is the optical film of the present invention. The other of the two protective films may be another protective film.

Examples of other protective films include (meth) acrylic resin films, polyester films, cellulose ester films and the like, preferably cellulose ester films. The cellulose ester contained in the cellulose ester film is defined in the same way as the cellulose ester contained in the optical film described above, preferably cellulose triacetate.

The retardation (Ro) in the in-plane direction measured under the conditions of a measurement wavelength of 590 nm and 23 占 폚 and 55% RH is preferably 0 to 20 nm, and more preferably 0 to 10 nm. The retardation (Rth) in the thickness direction of the protective film measured under conditions of a measurement wavelength of 590 nm and 23 占 폚 55% RH is preferably 0 to 80 nm, and more preferably 0 to 50 nm.

The thickness of the other protective film may be about 10 to 100 mu m, preferably 10 to 80 mu m.

The polarizing plate of the present invention can be obtained, for example, by a step of bonding the optical film of the present invention to at least one side of the polarizer with an adhesive. The adhesive to be used for bonding may be a completely saponified polyvinyl alcohol aqueous solution (water-soluble) or an active energy ray-curable adhesive. It is preferable to use an active energy ray curable adhesive in view of the fact that the elasticity of the obtained adhesive layer is high and the dimensional change of the polarizing plate is easily suppressed.

The active energy ray curable adhesive composition may be a photo radical polymerization type composition using photo radical polymerization, a photo cation polymerization type composition using photo cation polymerization or a hybrid type composition using photo radical polymerization and photo cation polymerization in combination.

The photo-radical polymerization type composition can be a composition containing a radical polymerizing compound containing a polar group such as a hydroxyl group or a carboxyl group and a radical polymerizing compound containing no polar group in a specific ratio as disclosed in Japanese Patent Application Laid-Open No. 2008-009329 have. The radical polymerizing compound is preferably a compound having a radically polymerizable ethylenically unsaturated bond. Preferable examples of the compound having a radically polymerizable ethylenically unsaturated bond include a compound having a (meth) acryloyl group. Examples of the compound having a (meth) acryloyl group include N-substituted (meth) acrylamide-based compounds, (meth) acrylate-based compounds and the like. (Meth) acrylamide means acrylamide or methacrylamide.

The cationic cationic polymerization type composition comprises a cationic polymerizable compound (a), a cationic photopolymerization initiator (?), And a cationic polymerization initiator (?) As disclosed in Japanese Patent Application Laid-Open Publication No. 2011-028234 A photosensitizer exhibiting absorption, and a composition containing each component of (delta) naphthalene-based photo-sensitization assistant.

Such a polarizing plate includes, for example, a step of performing an adhesion facilitating treatment (corona treatment, plasma treatment, or the like) on the surface of the optical film; Applying an active energy ray-curable adhesive to at least one of the polarizer and the optical film; Bonding the polarizer and the optical film via the obtained adhesive layer; And a step of curing the adhesive layer in a state where the polarizer and the optical film are bonded to each other.

As described above, the present invention includes a polymer comprising repeating units derived from a monomer represented by the formula (1) and at least one compound A selected from the group consisting of the compounds represented by the formulas (2) to (4) The optical film has a high density. Thereby, the amount of water permeation is reduced, and the diffusion of boric acid contained in the polarizer can be also reduced. As a result, in the polarizing plate of the present invention including the optical film of the present invention, deterioration of the polarizer is suppressed, and the decrease of the polarization degree can be suppressed.

Further, the optical film of the present invention may be a laminated film comprising a core layer and a skin layer, and the polyester compound B may be kneaded in the core layer, and a monomer unit derived from the monomer represented by the formula (1) It is preferable to localize at least one compound A selected from the group consisting of the polymer containing the compound (1) and the compound represented by the formula (2) to (4). Thereby, since the unintended interaction of the compound A and the polyester compound B in the optical film of the present invention is suppressed, the phase difference reducing function by the compound B and the compound A-inhibiting function of the polarizer are inhibited There is less concern. As a result, deterioration of the polarizer in the polarizing plate is suppressed, and deterioration of the polarization degree can be suppressed.

4. Liquid crystal display

A 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. At least one of the first and second polarizing plates may be a polarizing plate of the present invention. In the polarizing plate of the present invention, it is preferable that the optical film of the present invention is disposed so as to be on the liquid crystal cell side.

Specifically, the first polarizing plate includes a first polarizer, a protective film F1 disposed on a surface opposite to the liquid crystal cell of the first polarizer, and a protective film F2 disposed on the liquid crystal cell side surface of the first polarizer . The second polarizer includes a second polarizer, a protective film F3 disposed on the side of the liquid crystal cell side of the second polarizer, and a protective film F4 disposed on the side opposite to the liquid crystal cell of the second polarizer. At least one of the protective films F1, F2, F3 and F4; Preferably, at least one of F2 and F3 is an optical film of the present invention.

The liquid crystal display device of the present invention may be a medium or large liquid crystal display device such as a television or a notebook computer; Or a small liquid crystal display device such as a smart phone. Among them, the liquid crystal display device is preferably a small liquid crystal display device in which the length in the diagonal direction of the display area (not shown) is 10 inches or less, preferably 5 inches or less .

3 is a schematic diagram showing an example of a small-sized liquid crystal display device. 3, the small-size liquid crystal display device 50 includes a liquid crystal cell 70, a first polarizing plate 90 and a second polarizing plate 110 for supporting the liquid crystal cell 70, and a backlight 130 ; A touch panel unit 170 disposed between the first polarizing plate 90 and the liquid crystal cell 70 and a backlight unit 130 disposed between the first polarizing plate 90 and the liquid crystal cell 70. The cover glass 150 is disposed on the viewing side of the first polarizing plate 90, And a rechargeable battery 190 disposed on the back side of the rechargeable battery.

The display mode of the liquid crystal cell 70 may be any of various display modes such as STN, TN, OCB, HAN, VA (MVA, PVA), IPS and FFS (Fringe Field Switching) IPS mode or FFS mode.

The liquid crystal cell 70 of the IPS system typically includes a pair of transparent substrates and a liquid crystal layer disposed therebetween. On one of the pair of transparent substrates, a pixel electrode and a counter electrode for applying a voltage to the liquid crystal are disposed.

The liquid crystal layer includes a liquid crystal molecule having a positive dielectric anisotropy (??> 0) or a negative dielectric anisotropy (??> 0). The liquid crystal molecules are oriented horizontally with respect to the substrate surface when no voltage is applied. The product of the thickness d (占 퐉) of the liquid crystal layer and the refractive index anisotropy? N is in the range of 0.2 to 0.4 占 퐉 in the transmission mode in view of obtaining a high contrast and in the IPS mode having no twist structure .

In the thus configured liquid crystal cell, an electric field in a horizontal direction with respect to the substrate surface is generated between the pixel electrode and the counter electrode provided on one substrate. Thereby, the liquid crystal molecules horizontally aligned with respect to the substrate surface are rotated in a plane parallel to the substrate surface. Thereby, the liquid crystal molecules are driven to change the transmissivity and the reflectance of each sub-pixel to perform image display.

4 schematically shows an example of the orientation of liquid crystal molecules in one pixel region of the IPS mode liquid crystal cell 70. As shown in Fig. For example, in the case where active driving is performed using a nematic liquid crystal having positive dielectric anisotropy as a field effect type liquid crystal, in a state in which no voltage is applied between the electrodes 202 and 203, liquid crystal molecules 205a and 205b (Not shown) as indicated by the rubbing direction 204 of the alignment film (not shown). At this time, a black display is obtained. On the other hand, in a state where a voltage is applied between the electrodes 202 and 203, the liquid crystal molecules are oriented in accordance with the voltage as indicated by 206a and 206b. At this time, a name display is obtained.

The first polarizing plate 90 is disposed on the face side of the liquid crystal cell 70; The protective film 93 (F1) disposed on the side opposite to the liquid crystal cell 70 of the first polarizer 91 and the protective film 93 (F1) disposed on the opposite side of the liquid crystal cell 70 of the first polarizer 91, (F2) as a protective film disposed on the side of the optical film 10 (F2). The second polarizing plate 110 is disposed on the backlight side surface of the liquid crystal cell 70; The optical film 10 (F3) as a protective film disposed on the surface of the second polarizer 111 on the liquid crystal cell 70 side and the liquid crystal cell 70 (70) of the second polarizer 111, And a protective film 113 (F4) disposed on the opposite side of the protective film 113 (F4).

The touch panel unit 170 is disposed between the liquid crystal cell 70 and the first polarizing plate 90 (on-cell type). However, the arrangement of the touch panel unit 170 is not limited to that shown in Fig. 3, and the touch panel unit 170 may be integrally provided (cover glass integrated type) on the cover glass 150; Or may be provided inside the liquid crystal cell 70 (in-cell type).

The rechargeable battery 190 may be, for example, a lithium ion secondary battery.

As described above, at least both of the protective films F2 and F3 can include the optical film 10 of the present invention. The optical film (10) of the present invention can sufficiently suppress deterioration of the polarizer even though the film thickness is extremely small. Thereby, it is possible to suppress deterioration of the contrast and visibility of the display device.

Further, the optical film of the present invention can have a high toughness even though the film thickness is very thin. Thus, deformation of the roll of the optical film can be suppressed. In the optical film obtained from such a roll, it is difficult for uneven tension to be applied to the optical film due to the deformation of the roll, whereby uneven phase difference is manifested in the optical film, and the film thickness is not uneven. Therefore, deterioration of display performance accompanying deformation of the roll can be suppressed.

Example

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

1. Material of optical film

<Cellulose Ester>

Cellulose triacetate (acetyl group degree of substitution: 2.85, weight average molecular weight (Mw): 285000, viscosity average degree of polymerization: 306, viscosity of 6 mass% of dichloromethane solution: 315 mPa.s)

<Compound A>

1) a compound represented by the formula (1):

[Chemical Formula 21]

2) a compound represented by the formula (2):

[Chemical Formula 22]

3) The compound represented by the formula (3)

(23)

4) The compound represented by the formula (4)

&Lt; EMI ID =

&Lt; Compound B (polyester compound) >

<Other compounds>

Compound C-1: TPP (triphenylphosphate) / BDP (biphenyl diphenyl phosphate) = 50/50 (mass ratio)

Compound C-2: Benzyl Saccharose (substitution degree of benzyl group 7.5)

<Mat>

Aerosil R972 (silicon dioxide fine particles (average particle size: 15 nm, Mohs hardness: about 7) manufactured by Japan Aerosil Co., Ltd.)

2. Fabrication of optical film

&Lt; Example 1 >

1) Preparation of dope for core layer

The following components were put into a mixing tank and stirred to dissolve each component. The obtained solution was filtered with a filter paper having an average pore diameter of 34 탆 and a sintered metal filter having an average pore diameter of 10 탆 to prepare a dope for the core layer.

(Composition of Dope for Core Layer)

Cellulose triacetate (acetyl group degree of substitution: 2.85, weight average molecular weight (Mw): 285000, viscosity average degree of polymerization: 306, viscosity of 6 mass% of dichloromethane solution: 315 mPa.s)

Compound B-1 (polyester compound): 15 parts by mass

Dichloromethane: 320 parts by mass

Methanol: 83 parts by mass

1-butanol: 3 parts by mass

2) Preparation of dope for skin layer

A dope for a skin layer was prepared in the same manner as described above, except that the composition of the dope was changed as follows.

(Composition of Dope for Skin Layer)

Cellulose triacetate (acetyl group degree of substitution: 2.85, weight average molecular weight (Mw): 285000, viscosity average degree of polymerization: 306, viscosity of 6 mass% of dichloromethane solution: 315 mPa.s)

Compound A-1 (compound represented by the formula (1)): 3 parts by mass

Dichloromethane: 320 parts by mass

Methanol: 83 parts by mass

1-butanol: 3 parts by mass

Aerosil R972 (made by Mat): 0.05 parts by mass (solids content)

3) Production of optical film

The obtained dope for the core layer and the dope for the skin layer were jointly opened (simultaneously multilayered) by a flexible die on a running flexible band. The flexible dope was dried on a flexible band and then peeled to obtain a film-like product. The amount of the residual solvent in the film material immediately after peeling was about 30 mass%. The obtained film-like material was further dried with a tenter. The film-like material was stretched in the transverse direction (TD direction) at 120 deg. C with a draw ratio of 5% in a tenter, and then stretched at 120 deg. C in a film stretching direction (MD direction) at a draw ratio of 5% Respectively.

Subsequently, the obtained film was dried under the conditions of Process A of Table 4 below. Concretely, the film was dried while being conveyed to a plurality of rolls 33a disposed in the drying apparatus 33 as shown in Fig. 2 described above. The drying temperature was 140 占 폚, the drying time was 13 minutes, the number of rolls in the drying apparatus was 250, and the conveying tension of the film was 120 N / m. Thus, an optical film 101 having a three-layer structure of a skin layer / a core layer / a skin layer (3 mu m / 14 mu m / 3 mu m) and having a total thickness of 20 mu m was obtained.

&Lt; Example 2 >

A dope for core layer was obtained in the same manner as in Example 1 except that 3 parts by mass of Compound A-1 was further added to 100 parts by mass of cellulose triacetate. An optical film 102 was obtained in the same manner as in Example 1 except that only the obtained dope for core layer was used to obtain a single-layer film.

&Lt; Comparative Example 1 &

An optical film 103 was obtained in the same manner as in Example 2 except that the drying conditions were changed as shown in Table 5 to obtain a single-layer film.

&Lt; Comparative Example 2 &

An optical film 104 was obtained in the same manner as in Example 2 except that the dope for the core layer of Example 1 was used and the drying conditions were changed as shown in Table 5 to obtain a single layer film.

&Lt; Examples 3 to 5 and Comparative Examples 3 to 6 >

Optical films 105 to 111 were obtained in the same manner as in Example 1 except that the drying conditions were changed as shown in Table 6.

&Lt; Examples 6 to 8, Comparative Example 7 and Reference Example >

Optical films 112 to 116 were obtained in the same manner as in Example 1 except that the amounts of the dope for the core layer and the dope for the skin layer were adjusted so that the thicknesses of the core layer and the skin layer were changed as shown in Table 6. [

&Lt; Examples 9 to 22 >

Optical films 117 to 130 were obtained in the same manner as in Example 1 except that the composition of the dope for the skin layer was adjusted so that the kind of the compound A contained in the skin layer was changed as shown in Table 7. [

&Lt; Example 23 >

The compositions of the dope for the core layer and the dope for the skin layer were adjusted so that the kinds and contents of the compound A and the compound B contained in the core layer and the skin layer were changed as shown in Table 8 and the amount of softening of the dope for the core layer was adjusted , The thickness of each layer was changed as shown in Table 8, and an optical film 131 was obtained in the same manner as in Example 1.

&Lt; Examples 24 to 26 >

Optical films 132 to 134 were prepared in the same manner as in Example 23 except that the composition ratio of the dopes for the core layer was adjusted so that the content ratio (A / B) of the compound A and the compound B in the core layer was changed as shown in Table 8 .

&Lt; Examples 27 to 30 &

Optical films 135 to 138 were prepared in the same manner as in Example 23 except that the composition ratio of the compound A and the compound B (B / A) in the skin layer was changed as shown in Table 8 by adjusting the composition of the dope for the skin layer .

&Lt; Examples 31 to 34 >

Optical films 139 to 142 were obtained in the same manner as in Example 1 except that the composition of the dope for the core layer was adjusted so that the content of the compound B in the core layer was changed as shown in Table 9. [

&Lt; Example 35 >

Except that the composition of the dope for the core layer was adjusted so that the content of the compound B in the core layer was changed as shown in Table 9 and the stretching conditions were changed as shown in Table 9. As a result, 143.

&Lt; Examples 36 to 39 >

Optical films 144 to 147 were obtained in the same manner as in Example 1 except that the composition of the dope for the core layer was adjusted so that the kind of the compound B in the core layer was changed as shown in Table 9. [

Production conditions of the optical films of Examples 1 and 2 and Comparative Examples 1 and 2 are shown in Table 5; Production conditions of the optical films of Examples 3 to 8, Comparative Examples 3 to 7, and Reference Example are shown in Table 6; Production conditions of the optical films of Examples 9 to 22 are shown in Table 7; Production conditions of the optical films of Examples 23 to 30 are shown in Table 8; The production conditions of the optical films of Examples 31 to 39 are shown in Table 9.

The toughness and tear strength of the prepared optical film were evaluated by the following methods, respectively. For the optical films of Examples 1 and 23 to 39, the retardation was also evaluated.

(Toughness)

Measurement of toughness in MD direction:

1) Five sheets of the obtained film were cut out in a direction of 120 mm (MD direction) x 10 mm (TD direction) to obtain a test piece for measurement in the MD direction. The obtained test piece was humidity-conditioned at 23 캜 and 55% RH for 24 hours.

2) Then, the tensile modulus of the test piece was measured by the method described in JIS K7127. Tensilon RTC-1225 manufactured by Orientech Co., Ltd. was used as the tensile tester, and the upper and lower ends of the test piece in the longitudinal direction (MD direction) were drilled at a distance of 100 mm between the chucks (the margin was 10 mm each at the upper and lower ends of the test piece (N / mm ² or MPa) and elongation (elongation at break (tensile strength (T) (N / mm ² or MPa) at break of the test specimen) E) (%)) were measured respectively, and the measurement was carried out five times in total (five times in total). The measurement was carried out in an environment of 23 占 폚 and 55% RH.

3) the maximum value of five measured values of the five measured values of the obtained breaking point stress (T) (N / mm ² or MPa), the elongation at break (E) (%) and the film thickness t mm) was applied to each of the following formulas to calculate toughness in the MD direction.

Toughness = tensile stress (T) (N / mm ² or MPa) × tensile direction perpendicular to the cross-sectional area of the test piece in a direction ^{(A) (mm 2) ×} ( elongation at break (E) (%) / 100 ) 1 ^/2

Sectional area (A) of the test piece (mm ² ) = width of the test piece 10 (mm) x thickness of the test piece (t) (mm)

Toughness measurement in the TD direction:

Similarly to the above, five pieces of the obtained film were cut out in a size of 120 mm (TD direction) × 10 mm (MD direction), and used as a test piece for measurement in the TD direction. The toughness in the TD direction was calculated by conducting the same measurement as above except that the test piece for TD direction measurement was used to pull the test piece in the longitudinal direction (TD direction).

(Tear strength)

The tensile load (mN) of the Elmendorf method of the obtained film was measured in accordance with JIS K 7128-1991 using a light load tearing apparatus manufactured by Toyo Seiki Co., Ltd. The measurement was performed for each of the transport direction (MD direction) and the width direction (TD direction) of the film under the condition of 23 占 폚 and 55% RH.

The tear strength was evaluated by the following criteria.

?: Tear strength of 35 mN or more

○: Tear strength of 30 mN or more and less than 35 mN

DELTA: Tear strength less than 20 mN and less than 30 mN

X: Tear strength less than 20 mN

(Phase difference Ro, Rth)

1) The obtained film was humidity-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.

2) The Ro after the light having a wavelength of 590 nm was incident on the film after humidity control in parallel with the normal line of the surface of the film was measured with COBRA 21ADH, Oji Keisoku Co., Ltd.

3) Ribbons at the time when a light having a measurement wavelength of 590 nm was incident on an in-plane slow axis of the film as a tilting axis (rotation axis) with respect to the normal line of the film surface at an angle of? (Incident angle?) By KOBRA 21ADH (R) (&amp;thetas;) was measured. The retardation value (R) (&amp;thetas;) was measured at 6 points every 10 DEG in the range of 0 DEG to 50 DEG. The in-plane slow axis of the film was confirmed by KOBRA 21ADH.

4) From the measured values of Ro and R (?) And the above-mentioned average refractive index and film thickness, nx, ny and nz were calculated by Cobra (KOBRA) 21ADH to calculate Rth at the measurement wavelength (590 nm). The measurement of the retardation was carried out under the conditions of 23 占 폚 and 55% RH.

Further, a polarizing plate using the above-prepared optical film was produced by the following method to evaluate the deterioration of the polarizer.

(Polarizer deterioration)

1) Production of polarizer

A polyvinyl alcohol film having a thickness of 30 占 퐉 was swelled in water at 35 占 폚. The obtained film was immersed in an aqueous solution containing 0.075 g of iodine, 5 g of potassium iodide and 100 g of water for 60 seconds and immersed in an aqueous solution at 45 캜 containing 3 g of potassium iodide, 7.5 g of boric acid and 100 g of water. The resulting film was uniaxially stretched under the conditions of a stretching temperature of 55 캜 and a draw ratio of 3. The uniaxially stretched film was washed with water and then dried to obtain a polarizer having a thickness of 5 탆.

2) Preparation of active energy ray-curable adhesive liquid

The following components were mixed and defoamed to prepare a radical polymerization type active energy ray curable adhesive liquid.

(Composition of active energy ray curable adhesive liquid)

Radical Polymerizable Compound 1: Hydroxyethylacrylamide (HEAA, Tg of the homopolymer 123 deg. C, manufactured by GoJin Co., Ltd.): 39.1 mass%

Radopolymerizable compound 2: Tripropylene glycol diacrylate (Aronix M-220, Tg of the homopolymer: 69 ° C, manufactured by Toagosei Co., Ltd.): 19.0 mass%

Radical Polymerizable Compound 3: acryloylmorpholine (ACMO, Tg of homopolymer: 150 占 폚, manufactured by GoJin Co., Ltd.): 39.1 mass%

Radical polymerization initiator 1: 1.4 mass% Diethylthioxanthone (KAYACURE DETX-S, manufactured by Nippon Kayaku Co., Ltd.)

Radical polymerization initiator 2: 1.4 mass% of 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropane-1-one (IRGACURE 907, BASF)

3) Production of Polarizer

Two pieces of the same numbered optical films were prepared, and corona discharge treatment was performed on each surface. The conditions of the corona discharge treatment were a corona output power of 2.0 kW and a line speed of 18 m / min. Subsequently, the prepared active energy ray-curable adhesive liquid was coated and applied on the corona discharge treated surface of the film with a bar coater so as to have a film thickness after curing of about 3 mu m to form an active energy ray curable adhesive layer Respectively.

Subsequently, the prepared polarizer was sandwiched between the two optical films thus treated to obtain a laminate of an optical film / active energy ray curable adhesive layer / polarizer / active energy ray curable adhesive layer / optical film.

Ultraviolet rays (gallium-encapsulated metal halide lamp) were irradiated onto one side of the laminate using an ultraviolet irradiation apparatus (Light HAMMER 10 bulb: V bulb peak illuminance: 1600 mW / cm ² manufactured by Fusion UV Systems, Inc) equipped with a belt conveyor, And then irradiated with ultraviolet rays so as to have a cumulative dose of 1000 / mJ / cm ² (wavelength: 380 to 440 nm) to cure the active energy ray curable adhesive layer to obtain a polarizing plate.

4) Evaluation

The deterioration of the polarization degree in the obtained polarizing plate was evaluated by the following method.

1) The obtained polarizing plate was cut into a size of 4 cm x 4 cm, and used as a polarizing plate sample. This polarizing plate sample was subjected to a humidity control in an atmosphere of 23 ° C and 55% RH for 24 hours, and then a parallel transmittance and a perpendicular transmittance were measured at 23 ° C and 55% RH. The measured values obtained were applied to the following equations respectively, and the degree of polarization P0 before storage was calculated.

Polarization degree P = ((H0-H90) / (H0 + H90)) 0.5 占 100

(H0: parallel transmittance, H90: orthogonal transmittance)

2) After that, the polarizing plate sample was stored for 1000 hours under the conditions of 60 ° C and 90% RH, and then the parallel transmittance and the direct transmittance of the polarizing plate sample were measured in the same manner as described above. The obtained measured values were applied to the respective equations described above to calculate the degree of polarization P1000 after storage.

3) The degree of polarization degree P0 obtained in the above 1) and the value of the degree of polarization (P1000) obtained in the above 2) were applied to the following equation to calculate the degree of polarization degree of polarization.

Polarization degree change amount = P0 - P1000 (P0: degree of polarization before forced deterioration, P1000: degree of polarization after 1000 hours of forced deterioration)

The deterioration of the polarizer in the polarizing plate sample was evaluated based on the following criteria.

?: Less than 10% change in polarization degree

?: Polarization degree change rate 10% or more and less than 20%

?: Polarization degree change rate 20% or more and less than 30%

X: Change rate of polarization degree 30% or more

Using the optical films of Examples 1 and 23 to 39, a liquid crystal display was manufactured by the following method, and the contrast thereof was evaluated.

(Contrast)

1) Fabrication of IPS mode liquid crystal cell

As shown in Fig. 4, electrodes 202 and 203 were provided on one glass substrate so that the distance between adjacent electrodes 202 and 203 was 20 占 퐉. Subsequently, a polyimide film was formed on the electrodes 202 and 203, and rubbing treatment was performed to form an alignment film. The rubbing treatment was performed in the direction indicated by 204 in Fig. A polyimide film was formed on one surface of one glass substrate prepared separately and rubbed to form an alignment film. Two glass substrates were stacked so that the orientation films were opposed to each other so that the distance (gap; d) between the substrates was 3.9 mu m and the rubbing directions of the two glass substrates were parallel. A nematic liquid crystal composition having a refractive index anisotropy (? N) of 0.0769 and a dielectric anisotropy (? Epsilon) of 4.5 was sealed to obtain a liquid crystal cell having a d? N value of 300 nm in the liquid crystal layer.

2) Fabrication of liquid crystal display

The prepared polarizing plate was attached to both surfaces of the obtained IPS mode liquid crystal cell. The two polarizing plates were adhered to each other such that Cross Nicol was arranged therebetween to obtain a liquid crystal display device. The optical films of the two polarizing plates were of the same number as each other.

3) Evaluation

The frontal contrast of the obtained liquid crystal display device was evaluated by the following method.

That is, the above prepared liquid crystal display device and the substrate on which the electrodes of the liquid crystal cell were formed were placed on the Shaukastan set in the bright room so as to be on the shaukasten side. Then, the luminance at the time of white display and the luminance at the time of displaying black were respectively measured by a luminance meter (spectral radiance luminance meter CS-1000 manufactured by Minolta Co., Ltd.) located at a distance of 1 m in the normal direction of the liquid crystal cell . As a result, the ratio of luminance (luminance in white display / luminance in black display) was calculated to obtain a contrast ratio.

Then, the frontal contrast was evaluated based on the following criteria.

?: Contrast ratio of 400 or more

○: Contrast ratio is 360 or more and less than 400

?: Contrast ratio not less than 320 and less than 360

X: Contrast ratio less than 320

The evaluation results of the optical films of Examples 1 and 2 and Comparative Examples 1 and 2 are shown in Table 10; The evaluation results of the optical films of Examples 3 to 8, Comparative Examples 3 to 7, and Reference Example are shown in Table 11; Evaluation results of the optical films of Examples 9 to 22 are shown in Table 12; The evaluation results of the optical films of Examples 23 to 30 are shown in Table 13; The evaluation results of the optical films of Examples 31 to 39 are shown in Table 14.

As shown in Tables 10 to 14, the optical films of Examples 1 to 39 in which the drying conditions were changed from A to D were the optical films of Comparative Examples 1 to 5 in which the drying conditions were E to G, The toughness and the tear strength are higher than those of the optical film of Example 6.

Specifically, the film toughness and the tear strength of Comparative Examples 1 to 3 were low because the number of rolls in the drying step was small and sufficient tension could not be imparted to the film (Condition E). The film toughness and the tear strength of Comparative Example 4 were low because the drying temperature in the drying step was low and the drying time was short (condition F), so that the molecular chains of the cellulose ester constituting the film could not be sufficiently oriented . The film toughness and tear strength of Comparative Example 5 are low because the tension applied to the film in the drying step is low, the drying temperature is low, and the drying time is short (Condition G). Therefore, the molecular chains of the cellulose ester Could not be aligned. On the other hand, the film of Comparative Example 6 in which the number of rolls was large and the tension in the drying step was too large showed that the film was hard and brittle, and the toughness was low and the tear strength was lowered.

Further, as shown from the comparison with Examples 1 and 3 to 5, if both the number of rolls in the drying process, the tension of the film, the drying temperature and the drying time are both constant, the toughness and tear strength .

It is also understood that the optical films of Examples 1 to 39 can also reduce the deterioration of the polarizer as compared with the optical films of Comparative Examples 2 and 6. The optical film of Comparative Example 2 does not contain Compound A having a polarizer deterioration function; The reason why the optical film of Comparative Example 6 contains Compound A is that the total thickness of the optical film is too thin so that the permeated water can not be sufficiently reduced and that all of the deterioration of the polarizer can not be suppressed. The optical film of Reference Example is not suitable for small-sized display devices because the film thickness is too thick at first.

Further, as shown in the comparison between Example 1 of Table 10 or Example 9 of Table 12 and Example 2 of Table 10, the compound A (polarizer deterioration inhibitor) and the compound B (retardation reducing agent) , It can be understood that the retardation is sufficiently lower than that contained in the same layer and the deterioration of the polarizer can be reduced. This suppresses the interaction between the compound A (polarizer deterioration inhibitor) and the compound B (retardation reducing agent) when contained in the same layer, and suppresses the polarizer deterioration inhibiting function of the compound A (polarizer deterioration inhibitor) ) Is not likely to be inhibited from each other.

As shown by the contrast of Examples 23 to 26 in Table 13, when the content ratio (A / B) of the compound A to the compound B in the core layer of the optical film is large, the retardation value is not sufficiently lowered, The frontal contrast of the light-emitting layer is lowered. This is presumably because the compound A and the compound B coexist in the core layer of the optical film, and therefore, they interact with each other and the function of reducing the retardation of the compound B is impaired.

Also, as shown from the contrast of Examples 27 to 30 in Table 13, when the content ratio (B / A) of the compound B to the compound A in the skin layer of the optical film is too high, deterioration of the polarizer occurs It is suggested that it is easy. This is presumably because the compound A and the compound B interact with each other and thus the function of the compound A to inhibit the deterioration of the polarizer is liable to be inhibited.

Further, as shown in Table 14, in the display devices of Examples 32 to 33 and 36 to 37 in which the absolute value of the retardation of the optical film satisfies 5 nm or less, when the absolute value of the retardation of the optical film does not satisfy 5 nm or less 31, 34 to 35 and 38 to 39, the front contrast is high. Further, in the optical films of Examples 33 to 35 and 38, the deterioration of the polarizer can not be sufficiently suppressed because the content of the compound B contained in the core layer is so large that part of the compound B seeps from the core layer, It is thought that the compound A generated a slight unintended interaction with the compound A contained in the skin layer.

This application claims priority based on Japanese Patent Application No. 2014-060474, filed March 24, 2014. The contents of the present specification and drawings are all incorporated herein by reference.

[Industrial applicability]

According to the present invention, deterioration of the polarizer can be suppressed even if the film thickness is thin, and an optical film having high toughness can be provided.

10: Optical film 11: Core layer
13, 15: skin layer 21a: core layer doping
21b: Dope for skin layer 23: Die
25: metal support 27:
29: peeling roll 31: tenter stretching device
33: drying device 33a: roll
35: winding device 37: winding core
39: Roll body 50: Small liquid crystal display
70: liquid crystal cell 90: first polarizer plate
91: first polarizer 93, 113: protective film
110: second polarizer 111: second polarizer
130: backlight 150: cover glass
170: Touch panel unit 190: Rechargeable battery

Claims (15)

(1), a polymer comprising repeating units derived from a monomer represented by the formula (1), a compound represented by the formula (2), a compound represented by the formula (3) And at least one compound A selected from the group consisting of:
A film thickness of 15 to 45 mu m,
T (MPa or N / mm ² ) is the breaking point stress when the optical film is stretched in a long side direction? Of the optical film or in a short side direction? Perpendicular to the long side direction? Under 23 占 폚 and 55% (G) expressed by the following formula is represented by the following expression ( ¹ ), where E (%) is the elongation at break, and A (mm ² ) is the cross-sectional area of the optical film in the direction orthogonal to the tensile direction. Wherein the long side direction? And the short side direction? Are 7 to 20, respectively.
[Equation 1]

[Chemical Formula 1]

(In the formula (1)
R ¹ represents a hydrogen atom or an aliphatic group having 1 to 4 carbon atoms;
R ² represents a substituent;
(A) represents a group of atoms forming a 5 or 6-membered ring;
n represents an integer of 0 to 4)
(2)

(In the formula (2)
R ²⁶ represents an aryl group having 6 to 12 carbon atoms;
R ²⁷ and R ²⁸ each independently represent a hydrogen atom, an alkyl group having 1 to 12 carbon atoms or an aryl group having 6 to 12 carbon atoms;
R &lt; ²⁶ &gt; and R &lt; ²⁷ &gt; each may have a substituent)
(3)

(In the formula (3)
R ¹ represents a hydrogen atom or a substituent;
R ² represents a substituent represented by the following formula (3-1);
n1 represents an integer of 0 to 4, and when n1 is 2 or more, a plurality of R &lt; ^{1 &gt;} may be the same or different,
n2 represents an integer of 1 to 5, and when n2 is 2 or more, plural R &lt; ^{2 &gt;} may be the same or different)
[Chemical Formula 4]

(In the formula (3-1)
A represents a substituted or unsubstituted aromatic 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 the formula (3-2);
R ⁵ represents a single bond or an alkylene group of 1 to 5 carbon atoms;
X represents a substituted or unsubstituted aromatic ring;
n3 represents an integer of 0 to 10, and when n3 is 2 or more, plural R ⁵ and X may be the same or different)
[Chemical Formula 5]

(In the formula (3-2)
X represents a substituted or unsubstituted aromatic ring;
R ⁶ , R ⁷ , R ⁸ and 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, a plurality of R ⁶ , R ⁷ , R ⁸ and X may be the same or different)
[Chemical Formula 6]

(In the formula (4)
R ¹ represents a nitrogen atom or an oxygen atom;
R ² represents -COOH or -OH group;
R ³ represents an alkyl group having 1 to 10 carbon atoms;
R ⁴ represents a substituent) The method according to claim 1,
Wherein the optical film includes a core layer and a pair of skin layers for supporting the core layer,
At least the skin layer comprises the compound A. The method according to claim 1,
And a film thickness of 15 to 30 占 퐉. 3. The method of claim 2,
Wherein the core layer comprises a compound B comprising a polyester compound obtained by polycondensing a diol and a dicarboxylic acid. 3. The method of claim 2,
Wherein the content ratio of the compound A to the compound B in the core layer is 0 to 0.1. 3. The method of claim 2,
Wherein a content ratio B / A of the compound B to the compound A in the skin layer is 0 to 0.5. The method according to claim 1,
The retardation in the in-plane direction of the optical film defined by the following formula (I) and measured at a measurement wavelength of 590 nm is defined as Ro (590) and is defined by the following formula (II) Satisfies | Ro (590) |? 5 nm and | Rth (590) |? 5 nm when the retardation in the thickness direction is Rth (590).
(I) Ro = (nx-ny) x t (nm)
Rth = {(nx + ny) / 2-nz} x t (nm)
(In the formulas (I) and (II)
nx represents a refractive index in the slow axis direction x at which the refractive index becomes the maximum in the in-plane direction of the film; ny represents a refractive index in an in-plane direction of the film in a direction y perpendicular to the slow axis direction x; nz represents the refractive index in the thickness direction z of the film; t (nm) denotes the thickness of the film) A method for producing an optical film according to claim 1,
Wherein the cellulose ester is at least one selected from the group consisting of a polymer comprising a repeating unit derived from a monomer represented by the formula (1), a compound represented by the formula (2), a compound represented by the formula (3) A first step of preparing a dope containing at least one compound A selected from the group consisting of compounds represented by formula
A second step of softening the dope on a support and then drying the dope to obtain a film-like material;
A third step of stretching the film material,
And a fourth step of drying the stretched film material to obtain the optical film,
In the fourth step, the filmy material is dried at 125 to 150 DEG C for 10 to 15 minutes while conveying the filmy material at a tension of 100 to 150 N / m in 200 or more and 300 or less rolls. 9. The method of claim 8,
In the first step, a dope for a core layer containing a cellulose ester, a cellulose ester and a dope for a skin layer containing the compound A are prepared,
In the second step, the dope for the core layer and the dope for the skin layer are both softened on a support and dried to obtain a film-like material,
A method for producing an optical film, which comprises obtaining a core layer and a pair of skin layers for supporting the core layer. A polarizer comprising a polarizer and the optical film according to claim 1. 11. The method of claim 10,
Wherein the polarizer and the optical film are adhered via a cured layer of an active energy ray curable adhesive. A liquid crystal display device comprising the optical film according to claim 1. 13. The method of claim 12,
A first polarizing plate, a liquid crystal cell, a second polarizing plate, and a backlight in this order,
The first polarizer includes a first polarizer, a protective film F1 disposed on a surface opposite to the liquid crystal cell of the first polarizer, and a protective film F2 disposed on a surface of the first polarizer facing the liquid crystal cell and,
The second polarizer includes a second polarizer, a protective film F3 disposed on a side of the liquid crystal cell side of the second polarizer, and a protective film F4 disposed on a side opposite to the liquid crystal cell of the second polarizer and,
And at least one of the protective films F2 and F3 comprises the optical film. 14. The method of claim 13,
Wherein the liquid crystal cell is an IPS mode or FFS mode liquid crystal cell. 14. The method of claim 13,
And the length of the display area in the diagonal direction is 10 inches or less.

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