JP2014119539A - Polarizing plate protective film, polarizing plate and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizing plate protective film that exhibits a good moisture permeability reducing effect and can enhance optical characteristics of the polarizing plate.SOLUTION: The polarizing protective film includes a first resin layer and a second resin layer. An equilibrium moisture content Xa of the first resin layer at 25°C and 80% relative humidity and an equilibrium moisture content Xb of the second resin layer at 25°C and 80% relative humidity satisfy Xa<Xb; and an oxygen permeation coefficient Ya of the first resin layer at 25°C and 60% relative humidity and an oxygen permeation coefficient Yb of the second resin layer at 25°C and 60% relative humidity satisfy Ya>Yb. A moisture permeability (A) measured under the conditions of 40°C and 90% relative humidity on the first resin layer side, and a moisture permeability (B) measured under the conditions of 40°C and 90% relative humidity on the second resin layer side satisfy A>B, and B is 250 g/m/day or less.

Description

  The present invention relates to a polarizing plate protective film, a polarizing plate, and a liquid crystal display device.

  In recent years, liquid crystal display devices have been widely used for liquid crystal panels such as liquid crystal televisions, personal computers, mobile phones, and digital cameras. Usually, a liquid crystal display device has a liquid crystal panel member provided with polarizing plates on both sides of a liquid crystal cell, and the liquid crystal panel member functions to control light from a backlight member. The polarizing plate of the liquid crystal panel member is composed of a polarizer and protective films on both sides thereof. A general polarizer is obtained by dyeing a stretched polyvinyl alcohol (PVA) film with iodine or a dichroic dye. Moreover, the cellulose ester film etc. are used for the protective film.

Recent liquid crystal display devices have diversified applications, and there is a demand for improved durability. For example, when the liquid crystal display device is used outdoors, the liquid crystal display device may be exposed to a high-temperature and high-humidity environment, and stability to a harsh environment is required.
As a problem of a liquid crystal display device exposed to a high temperature and high humidity environment, there are generation of panel and display unevenness. These problems are caused by moisture permeating or desorbing into the polarizing plate and the protective film constituting the polarizing plate, causing a difference in the shrinkage balance between the polarizing plates on the front and back surfaces of the liquid crystal display device, causing the panel to warp, This is considered to be caused by uneven display caused by contact of the four corners and four sides with the casing and the member on the back side. For this reason, the polarizing plate protective film is required to improve humidity dependency and wet heat durability.

  For example, Patent Document 1 discloses a polarizing plate protective film using a cellulose ester film. Here, it is supposed to obtain a polarizing plate protective film having low moisture permeability and excellent dimensional stability by setting the water absorption rate, moisture permeability, and transmittance within predetermined ranges.

JP 2002-301788 A

  However, the conventional polarizing plate protective film as disclosed in Patent Document 1 is provided with a low moisture permeable layer on one surface of the film, and the moisture permeability is reduced depending on the arrangement of the low moisture permeable layer. It became clear by examination of this inventor that an effect is not fully acquired. In addition, when a conventional polarizing plate protective film is attached to a liquid crystal cell and placed in a high-temperature and high-humidity environment, there is a problem in that the dimensions change and the panel warps. In particular, when the liquid crystal display device is used for a device such as a liquid crystal television or a personal computer, after the liquid crystal cell is thinned, the polarizing plate is bonded to both surfaces of the liquid crystal cell (in this specification, the polarizing plate is attached to both surfaces of the liquid crystal cell This is a serious problem because “panel warping” is also likely to occur. In addition, in this specification, the curvature of a panel means the curvature of the whole member which bonded the polarizing plate on both surfaces of the liquid crystal cell single-piece | unit (member not containing a polarizing plate) in a liquid crystal display device.

  Moreover, since the polarizer which attaches a polarizing plate protective film is comprised from the hydrophilic polymer, the moisture content of a polarizer is high compared with the member of other liquid crystal display devices. When exposed to high temperature conditions with excessive moisture contained in the polarizing plate, the optical properties of the polarizing plate are deteriorated. Therefore, when the moisture content of the polarizing plate itself is controlled or the polarizing protective film is applied to the polarizer. In the drying step, excess water caused by the adhesive or the like is evaporated. However, when a low moisture-permeable layer as disclosed in Patent Document 1 is attached so as to be in contact with the polarizer, moisture contained in the polarizer or moisture due to the adhesive cannot escape, and 60 As a result, excessive moisture stays in the polarizing plate over time at a high temperature of not less than 0 ° C., which deteriorates the optical properties of the polarizing plate.

  Therefore, in order to solve the problems of the prior art, the inventors of the present application, in addition to providing a polarizing plate protective film that exhibits a good moisture permeability reduction effect even in a high temperature and high humidity environment, Investigations have been made for the purpose of providing a polarizing plate protective film that can suppress the occurrence of panel warpage after the polarizing plate is bonded to both sides of the liquid crystal cell. Furthermore, the inventors of the present application have made studies for the purpose of providing a polarizing plate protective film that can enhance the optical properties of the polarizing plate.

As a result of intensive studies to solve the above problems, the inventors of the present application have a polarizing plate protective film having two or more layers, and by defining the relationship between the moisture content of each layer and the oxygen transmission coefficient, It has been found that a good moisture permeability reduction effect can be exhibited and the occurrence of warping of the panel can be suppressed. Furthermore, the present inventors have found that the polarizing plate protective film according to the present invention is used to enhance the optical characteristics of the polarizing plate, and have completed the present invention.
Specifically, the present invention has the following configuration.

[1] A polarizing plate protective film including a first resin layer and a second resin layer, wherein the equilibrium moisture content at 25 ° C. and a relative humidity of 80% of the first resin layer is Xa, When the equilibrium moisture content at 25 ° C. and 80% relative humidity of the resin layer is Xb, Xa> Xb, and the oxygen permeability coefficient of the first resin layer at 25 ° C. and 60% relative humidity is Ya. When the oxygen transmission coefficient at 25 ° C. and relative humidity 60% of the resin layer 2 is Yb, Ya <Yb, and the first resin layer side is measured under the conditions of 40 ° C. and relative humidity 90%. When the moisture permeability is A, the moisture permeability measured when the second resin layer side is 40 ° C. and the relative humidity is 90% is B, A> B and B is 250 g / m ^2. / Day or less polarizing plate protective film However, the moisture permeability is a value obtained by converting a value measured according to JIS 0208 into a film thickness of 40 μm.)
[2] The polarizing plate protective film according to [1] preferably has an equilibrium water content Xb of 0.3% or less at 25 ° C. and a relative humidity of 80% of the second resin layer.
[3] The polarizing plate protective film according to [1] or [2] has an oxygen permeability coefficient Ya of 10 cc · mm / m ² / day / atm or less at 25 ° C. and 60% relative humidity of the first resin layer. It is preferable that
[4] The polarizing plate protective film according to any one of [1] to [3] has a moisture permeability B of 90 g / when measured with the first resin layer side at 40 ° C. and a relative humidity of 90%. m ² / day or less is preferable (however, the moisture permeability is a value obtained by converting a value measured according to JIS 0208 into a film thickness of 40 μm).
[5] In the polarizing plate protective film according to any one of [1] to [4], any one of the first resin layer and the second resin layer preferably includes a resin modifying additive. .
[6] The polarizing plate protective film according to any one of [1] to [5] preferably has a structure in which the first resin layer and the second resin layer are laminated adjacently in order.
[7] In the polarizing plate protective film according to any one of [1] to [6], the average film thickness of the first resin layer is α, and the average film thickness of the second resin layer is β. In this case, α> β is preferable.
[8] In the polarizing plate protective film according to any one of [1] to [7], the total thickness of the first resin layer and the second resin layer is preferably 60 μm or less.
[9] The polarizing plate protective film according to any one of [1] to [8] and a polarizer, wherein the first resin layer of the polarizing plate protective film is disposed on the polarizer side. A polarizing plate characterized by.
[10] A liquid crystal display device comprising: a liquid crystal cell; and the polarizing plate according to [9] disposed on at least one surface of the liquid crystal cell.

  According to this invention, the polarizing plate protective film which exhibits the outstanding moisture-permeation reduction effect can be obtained. For this reason, generation | occurrence | production of the curvature of a panel can be suppressed by using the polarizing plate protective film of this invention.

  Furthermore, by using the polarizing plate protective film of the present invention, the moisture contained in the polarizer or the moisture caused by the adhesive can escape in the drying step after the polarizing protective film is attached to the polarizer. However, it is possible to avoid the problem of deteriorating the optical characteristics of the polarizing plate due to excessive moisture remaining in the polarizing plate when it is aged at a high temperature of 60 ° C. or higher. Thereby, the optical characteristic of a polarizing plate can be improved.

Fig.1 (a) is schematic which represents the partial cross-section in an example of the polarizing plate protective film of this invention. FIG.1 (b) is schematic which represents the partial cross-section in an example when the polarizing plate protective film of this invention is laminated | stacked with a polarizer. FIG. 2 is a schematic view of a film production line that can be used when the first resin layer of the polarizing plate protective film of the present invention is formed by a solution film forming method.

Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be made based on typical embodiments and specific examples of the present invention, but the present invention is not limited to such embodiments and specific examples. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
“Acrylic resin” means a resin obtained by polymerizing methacrylic acid or a derivative of acrylic acid, and a resin containing the derivative. Further, when not particularly limited, “(meth) acrylate” represents acrylate and methacrylate, and “(meth) acryl” represents acryl and methacryl.

[Polarizing plate protective film]
The present invention relates to a polarizing plate protective film including a first resin layer and a second resin layer.
FIG. 1A is a schematic diagram showing a partial cross-sectional structure in an example of the polarizing plate protective film 10 of the present invention. As shown in FIG. 1A, the first resin layer 1 and the second resin layer 2 may have a two-layer structure laminated adjacent to each other, or may include other functional layers. . When the polarizing plate protective film includes another functional layer, the functional layer is included between any one surface of the polarizing plate protective film or between the first resin layer 1 and the second resin layer 2.

The equilibrium moisture content of the first resin layer and the second resin layer satisfies a predetermined relationship. When the equilibrium moisture content at 25 ° C. and relative humidity 80% of the first resin layer is Xa, and the equilibrium moisture content at 25 ° C. and 80% relative humidity of the second resin layer is Xb, Xa> Xb. However, the equilibrium water content Xa at 25 ° C. and 80% relative humidity of the first resin layer, and the equilibrium water content Xb at 25 ° C. and 80% relative humidity of the second resin layer are values obtained by measuring each layer in the laminated state. Even if it uses, the value when forming the 1st resin layer and the 2nd resin layer as a single-layer film, respectively, may be used, and when an additive other than resin is added to each layer, the influence of the additive is also included. The same applies to oxygen permeability coefficients Ya and Yb of each layer described later.
The equilibrium water content Xb of the second resin layer at 25 ° C. and relative humidity 80% is preferably 0.3% or less, more preferably 0.25% or less, and 0.2% or less. Is more preferable.
By setting the equilibrium moisture content of the second resin layer within the above range, it is possible to suppress moisture from adhering to the surface of the second resin layer. Thereby, the water vapor transmission rate of a polarizing plate protective film can be made low.
In addition, the measurement method of the equilibrium moisture content of the first resin layer and the second resin layer is as follows: a film sample 7 mm × 35 mm is used as a moisture measuring device, sample drying apparatuses “CA-03” and “VA-05” {both Mitsubishi Chemical It can be calculated by dividing the water content (g) measured by the Karl Fischer method by the sample mass (g).

Moreover, the oxygen permeability coefficient of the first resin layer and the second resin layer satisfies a predetermined relationship. If the oxygen permeability coefficient of the first resin layer at 25 ° C. and 60% relative humidity is Ya, and the oxygen permeability coefficient of the second resin layer at 25 ° C. and 60% relative humidity is Yb, then Ya <Yb.
The oxygen permeability coefficient Ya at 25 ° C. and 60% relative humidity of the first resin layer is preferably 10 cc · mm / m ² / day / atm or less, and 8 cc · mm / m ² / day / atm or less. Is more preferably 7 cc · mm / m ² / day / atm or less.
The oxygen transmission coefficient can be used as a parameter having a positive correlation with the moisture transmission rate (diffusion rate). In this invention, the transmission rate (diffusion rate) of the water | moisture content which permeate | transmits the whole polarizing plate protective film of this invention can be made small by making the oxygen permeability coefficient of a 1st resin layer into the said range. Thereby, the water vapor transmission rate of a polarizing plate protective film can be lowered more effectively.

By making the relationship of the equilibrium moisture content of the first resin layer and the second resin layer the above relationship, it is possible to suppress moisture from adhering to the surface of the polarizing plate protective film. Thereby, although not bound by any theory, it is possible to suppress the amount of moisture that can pass through the second resin layer of the polarizing plate protective film.
On the other hand, the oxygen permeability coefficient can be used as a parameter having a positive correlation with the moisture permeation rate (diffusion rate). By setting the relationship between the oxygen permeability coefficient of the first resin layer and the second resin layer to the above relationship, the moisture transmission rate (diffusion rate) in the second resin layer can be suppressed.
In addition to these effects, the amount of warpage of the panel when the polarizing plate protective film of the present invention is incorporated in a liquid crystal display device can be suppressed.
In addition, the polarizing plate protective film having a small equilibrium moisture content and a small oxygen transmission coefficient is expensive. According to the polarizing plate protective film of the present invention, the first and second resin layers satisfying the above relationship are provided. By using it, the effect of the present invention can be obtained by combining inexpensive materials with low performance of either the equilibrium moisture content or the oxygen permeability coefficient.

Furthermore, the water vapor transmission rate of the polarizing plate protective film of the present invention is as follows. Moisture permeability measured when the first resin layer side is measured at 40 ° C. and relative humidity 90% is A, and moisture permeability is measured when the second resin layer side is measured at 40 ° C. and relative humidity 90%. Is B, A> B, and B is 250 g / m ² / day (converted to a film thickness of 40 μm). Here, the moisture permeability is a value obtained by converting a value measured according to JIS 0208 into a film thickness of 40 μm. The converted value can be obtained by the following equation.
Moisture permeability in terms of 40 μm = measured moisture permeability × measured film thickness (μm) / 40 (μm).
The moisture permeability B of the polarizing plate protective film may be 250 g / m ² / day or less (converted to a film thickness of 40 μm), and preferably 200 g / m ² / day or less (converted to a film thickness of 40 μm), preferably 150 g / m ^2. / Day or less (converted to a film thickness of 40 μm) is more preferable, and 90 g / m ² / day or less (converted to a film thickness of 40 μm) is particularly preferable. When the moisture permeability B of the polarizing plate protective film is within the above range, the polarizing plate protective film can exhibit an extremely high moisture permeability reducing effect. Furthermore, by using the polarizing plate protective film of the present invention, it is possible to effectively suppress the warpage of the panel of the liquid crystal display device.

The moisture permeability can be determined by applying a water vapor pressure difference to both sides of the polarizing plate protective film and measuring the amount of water vapor that has passed through the polarizing plate protective film. As a high humidity condition when a water vapor pressure difference is applied, a condition of 40 ° C. and a relative humidity of 90% can be employed. The low humidity condition is a condition in which the humidity is lowered by a hygroscopic agent or the like.
In the present invention, the moisture permeability when the first resin layer side is set to a high humidity condition and the second resin layer side is set to a low humidity condition is that the second resin layer side is set to a high humidity condition. It becomes higher than the moisture permeability when the resin layer side is under a low humidity condition. That is, when the polarizing plate protective film of the present invention is attached to the polarizer, the polarizing plate protective film is attached so that the first resin layer is on the side of the polarizer having a high water content (corresponding to high humidity conditions). Thus, the moisture permeability reduction effect can be exhibited more effectively.

  FIG. 1B illustrates an embodiment in which the polarizing plate protective film 10 of the present invention is attached to the polarizer 5. As shown in FIG. 1B, it is preferable to stack the first resin layer 1 on the polarizer 5 and provide the second resin layer 2 on the side opposite to the polarizer 5. Thereby, a moisture permeability reduction effect can be obtained effectively.

  Furthermore, as shown in FIG. 1B, the first resin layer 1 is disposed on the polarizer 5 side in that the first resin layer 1 has a property of easily absorbing moisture of the polarizer 5. Is also preferable. As described above, the equilibrium moisture content of the first resin layer 1 is larger than the equilibrium moisture content of the second resin layer 2. That is, the first resin layer 1 has a property of easily adhering moisture as compared with the second resin layer 2. In this invention, the 1st resin layer 1 can adsorb | suck the water vapor | steam discharge | released at the drying process of a polarizing plate by arrange | positioning the 1st resin layer 1 in the polarizer 5 side. As a result, the moisture contained in the polarizer produced during the polarizing plate drying process or the moisture due to the adhesive cannot be removed, and excessive amounts are present in the polarizing plate over time at a high temperature of 60 ° C. or higher. As a result, moisture is retained, so that the problem of deteriorating the optical characteristics of the polarizing plate can be solved, and a polarizing plate having excellent optical characteristics can be obtained.

<Thermoplastic resin>
A thermoplastic resin is preferably used for the first resin layer and the second resin layer. The thermoplastic resin used in the present invention will be described below.
In the film of the present invention, examples of the optimum thermoplastic resin include (meth) acrylic resins, polycarbonate resins, polystyrene resins, cyclic polyolefin resins, and the like, and a mixture of these resins and a plurality of these resins. You can choose from resins.

  The (meth) acrylic resin is a concept including both a methacrylic resin and an acrylic resin. The (meth) acrylic resin also includes acrylate / methacrylate derivatives, particularly acrylate / methacrylate (co) polymers.

((Meth) acrylic resin)
The repeating structural unit of the (meth) acrylic acid resin is not particularly limited. The (meth) acrylic resin preferably has a repeating structural unit derived from a (meth) acrylic acid ester monomer as a repeating structural unit.

  The (meth) acrylic acid resin further polymerizes at least one selected from a hydroxyl group-containing monomer, an unsaturated carboxylic acid and a monomer represented by the following general formula (201) as a repeating structural unit. It may contain a repeating structural unit constructed by

Formula (201)
CH ₂ = C (X) R ²⁰¹

In General Formula (201), R ²⁰¹ represents a hydrogen atom or a methyl group, and X represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group, a —CN group, a —CO—R ²⁰² group, or —O—. It represents CO-R ²⁰³ groups, R ²⁰² and R ²⁰³ represents a hydrogen atom or an organic residue having 1 to 20 carbon atoms.

The (meth) acrylic acid ester is not particularly limited, and examples thereof include methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, cyclohexyl acrylate, and benzyl acrylate. Acrylic acid esters; methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate, methacrylic acid esters such as benzyl methacrylate; These may be used alone or in combination of two or more. Among these, methyl methacrylate is particularly preferable from the viewpoint of excellent heat resistance and transparency.
When using the said (meth) acrylic acid ester, the content rate in the monomer component with which it uses for a superposition | polymerization process becomes like this. -100 mass%, More preferably, it is 40-100 mass%, Most preferably, it is 50-100 mass%.

The hydroxyl group-containing monomer is not particularly limited. For example, 2- (hydroxyalkyl) acrylic acid ester such as α-hydroxymethylstyrene, α-hydroxyethylstyrene, methyl 2- (hydroxyethyl) acrylate; 2 2- (hydroxyalkyl) acrylic acid such as-(hydroxyethyl) acrylic acid; and the like. These may be used alone or in combination of two or more.
When the hydroxyl group-containing monomer is used, the content ratio in the monomer component to be subjected to the polymerization step is preferably 0 to 30% by mass, more preferably 0 to 0%, in order to sufficiently exhibit the effects of the present invention. 20 mass%, More preferably, it is 0-15 mass%, Most preferably, it is 0-10 mass%.

Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, crotonic acid, α-substituted acrylic acid, α-substituted methacrylic acid and the like. These may be used alone or in combination of two or more. You may use together. Among these, acrylic acid and methacrylic acid are preferable in that the effects of the present invention are sufficiently exhibited.
When the unsaturated carboxylic acid is used, the content ratio in the monomer component to be subjected to the polymerization step is preferably 0 to 30% by mass, more preferably 0 to 20%, in order to sufficiently exhibit the effects of the present invention. It is 0 mass%, More preferably, it is 0-15 mass%, Most preferably, it is 0-10 mass%.

Examples of the monomer represented by the general formula (201) include styrene, vinyl toluene, α-methyl styrene, acrylonitrile, methyl vinyl ketone, ethylene, propylene, vinyl acetate, and the like. You may use, and may use 2 or more types together. Among these, styrene and α-methylstyrene are particularly preferable in that the effects of the present invention are sufficiently exhibited.
When using the monomer represented by the general formula (201), the content ratio in the monomer component to be subjected to the polymerization step is preferably 0 to 30 mass in order to sufficiently exhibit the effects of the present invention. %, More preferably 0 to 20% by mass, still more preferably 0 to 15% by mass, and particularly preferably 0 to 10% by mass.

The monomer component may form a lactone ring after polymerization. In that case, it is preferable to polymerize the monomer component to obtain a polymer having a hydroxyl group and an ester group in the molecular chain.
As a polymerization reaction form for polymerizing the monomer component to obtain a polymer having a hydroxyl group and an ester group in the molecular chain, a polymerization form using a solvent is preferable, and solution polymerization is particularly preferable. .
For example, a lactone ring structure described in JP 2007-316366 A, JP 2005-189623 A, WO 2007/032304, WO 2006/025445 is also preferable. It is.

(Lactone ring-containing polymer)
The lactone ring-containing polymer is not particularly limited as long as it has a lactone ring, but preferably has a lactone ring structure represented by the following general formula (401).

General formula (401):

In the general formula (401), R ⁴⁰¹ , R ⁴⁰² and R ⁴⁰³ each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms, and the organic residue may contain an oxygen atom. . Here, the organic residue having 1 to 20 carbon atoms is preferably a methyl group, an ethyl group, an isopropyl group, an n-butyl group, a t-butyl group, or the like.

  The content ratio of the lactone ring structure represented by the general formula (401) in the structure of the lactone ring-containing polymer is preferably 5 to 90% by mass, more preferably 10 to 70% by mass, and still more preferably 10 to 60% by mass. %, Particularly preferably 10 to 50% by mass. By setting the content ratio of the lactone ring structure to 5% by mass or more, the heat resistance and surface hardness of the obtained polymer tend to be improved, and by setting the content ratio of the lactone ring structure to 90% by mass or less. The moldability of the obtained polymer tends to be improved.

  The method for producing the lactone ring-containing polymer is not particularly limited, but preferably, after obtaining a polymer (p) having a hydroxyl group and an ester group in the molecular chain by a polymerization step, the obtained polymer ( It is obtained by carrying out a lactone cyclization condensation step for introducing a lactone ring structure into the polymer by heat-treating p).

  The mass average molecular weight of the lactone ring-containing polymer is preferably 1,000 to 2,000,000, more preferably 5,000 to 1,000,000, still more preferably 10,000 to 500,000, particularly preferably. 50,000 to 500,000.

  The lactone ring-containing polymer has a mass reduction rate within a range of 150 to 300 ° C. in dynamic TG measurement, preferably 1% or less, more preferably 0.5% or less, and still more preferably 0.3% or less. It is good. As a method for measuring dynamic TG, the method described in JP-A-2002-138106 can be used.

  Since the lactone ring-containing polymer has a high cyclization condensation reaction rate, there is little dealcoholization reaction in the production process of the molded product, and bubbles and silver stripes (silver streaks) are formed in the molded product after molding due to the alcohol. The disadvantage of entering can be avoided. Furthermore, since the lactone ring structure is sufficiently introduced into the polymer due to a high cyclization condensation reaction rate, the obtained lactone ring-containing polymer has high heat resistance.

  The lactone ring-containing polymer has a coloring degree (YI) of preferably 6 or less, more preferably 3 or less, still more preferably 2 or less, and particularly preferably 1 or less when a chloroform solution having a concentration of 15% by mass is used. . If the degree of coloring (YI) is 6 or less, problems such as loss of transparency due to coloring are unlikely to occur, and therefore, it can be preferably used in the present invention.

  The lactone ring-containing polymer has a 5% mass reduction temperature in thermal mass spectrometry (TG) of preferably 330 ° C. or higher, more preferably 350 ° C. or higher, and still more preferably 360 ° C. or higher. The 5% mass reduction temperature in thermal mass spectrometry (TG) is an indicator of thermal stability, and by setting it to 330 ° C. or higher, sufficient thermal stability tends to be exhibited. The thermal mass spectrometry can use the apparatus for measuring the dynamic TG.

  The lactone ring-containing polymer has a glass transition temperature (Tg) of preferably 115 ° C. or higher, more preferably 125 ° C. or higher, further preferably 130 ° C. or higher, particularly preferably 135 ° C. or higher, and most preferably 140 ° C. or higher. .

  The total amount of residual volatile components contained in the lactone ring-containing polymer is preferably 5,000 ppm or less, more preferably 2,000 ppm or less, still more preferably 1,500 ppm, and particularly preferably 1,000 ppm. If the total amount of residual volatile components is 5,000 ppm or less, it is preferable because coloring defects due to alteration during molding, foaming, and molding defects such as silver streak are unlikely to occur.

  The lactone ring-containing polymer has a total light transmittance of 85% or more, more preferably 88% or more, and still more preferably measured by a method based on ASTM-D-1003 for a molded product obtained by injection molding. 90% or more. The total light transmittance is an index of transparency, and when it is 85% or more, the transparency tends to be improved.

In the case of a polymerization form using a solvent, the polymerization solvent is not particularly limited. For example, aromatic hydrocarbon solvents such as toluene, xylene, and ethylbenzene; ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone; ether solvents such as tetrahydrofuran Etc., and only one of these may be used, or two or more may be used in combination.
Further, in the production method of the present invention, since the (meth) acrylic resin is dissolved in an organic solvent and formed by solution casting, the organic solvent at the time of synthesizing the (meth) acrylic resin is a melt film formation. It is not limited as compared with the case where it is performed, and it may be synthesized using an organic solvent having a high boiling point.

During the polymerization reaction, a polymerization initiator may be added as necessary. Although it does not specifically limit as a polymerization initiator, For example, cumene hydroperoxide, diisopropylbenzene hydroperoxide, di-t-butyl peroxide, lauroyl peroxide, benzoyl peroxide, t-butylperoxyisopropyl carbonate, t-amyl Organic peroxides such as peroxy-2-ethylhexanoate; 2,2′-azobis (isobutyronitrile), 1,1′-azobis (cyclohexanecarbonitrile), 2,2′-azobis (2, Azo compounds such as 4-dimethylvaleronitrile), and the like. These may be used alone or in combination of two or more. The amount of the polymerization initiator used is not particularly limited as long as it is appropriately set according to the combination of the monomers used and the reaction conditions.
The weight average molecular weight of the polymer can be adjusted by adjusting the amount of the polymerization initiator.

  When performing the polymerization, it is preferable to control the concentration of the produced polymer in the polymerization reaction mixture to be 50% by mass or less in order to suppress gelation of the reaction solution. Specifically, when the concentration of the produced polymer in the polymerization reaction mixture exceeds 50% by mass, it is preferable that the polymerization solvent is appropriately added to the polymerization reaction mixture and controlled to be 50% by mass or less. . The concentration of the produced polymer in the polymerization reaction mixture is more preferably 45% by mass or less, still more preferably 40% by mass or less.

  The form in which the polymerization solvent is appropriately added to the polymerization reaction mixture is not particularly limited, and the polymerization solvent may be added continuously or intermittently. By controlling the concentration of the produced polymer in the polymerization reaction mixture in this way, the gelation of the reaction solution can be more sufficiently suppressed. The polymerization solvent to be added may be the same type of solvent used during the initial charging of the polymerization reaction or may be a different type of solvent, but is the same as the solvent used during the initial charging of the polymerization reaction. It is preferable to use different types of solvents. Further, the polymerization solvent to be added may be only one type of solvent or a mixed solvent of two or more types.

  The acrylic resin preferably has a mass average molecular weight Mw of 80000 or more. If the mass average molecular weight Mw of an acrylic resin is 80000 or more, mechanical strength is high and it is excellent in the handling ability at the time of film manufacture. In this respect, the acrylic resin preferably has a mass average molecular weight Mw of 100,000 or more.

A commercially available thing can also be used as an acrylic resin used for this invention. For example, Delpet 60N, 80N (Asahi Kasei Chemicals Co., Ltd.), Dianal BR80, BR85, BR88, BR102 (Mitsubishi Rayon Co., Ltd.), KT75 (Electrochemical Industry Co., Ltd.) and the like can be mentioned.
Two or more acrylic resins can be used in combination.

(Polycarbonate resin)
The thermoplastic resin can be used by adding an additive to the polycarbonate resin to appropriately control the peeling force and toughness. A commercially available product can be used as the polycarbonate resin in the present invention. Examples thereof include Panlite L-1225L, L-1250Y, K-1300Y, AD-5503 (manufactured by Teijin Chemicals), Novalex 7020R, 7022R, 7025R, 7027R, 7030R (manufactured by Mitsubishi Engineering Plastics), and the like.

(Polystyrene resin)
As the thermoplastic resin, it is possible to use a polystyrene resin in which an additive is added to a polystyrene resin to appropriately control peeling force and toughness. In order to control the physical properties, vinyl toluene, α-methylstyrene, acrylonitrile, methyl vinyl ketone, ethylene, propylene, vinyl acetate, maleic anhydride, etc. may be copolymerized. Can be used. For example, as polystyrene resin, PSJ polystyrene G9401, G9305, SGP-10 (manufactured by polystyrene Japan), high branch XC-540HB, XC-520, Dick styrene CR-250, CR-350, CR-450 (manufactured by DIC), As styrene-acrylonitrile copolymers, Sebian N020SF, 050SF, 070SF, 080SF (manufactured by Daicel Polymer), and as styrene-maleic anhydride copolymers, XIRAN SZ28110, SZ26180, SZ26120, SZ26080, SZ23110, SZ15170, SZ08250 (polyester) Scope Polymers BV) and the like.

(Cyclic polyolefin resin)
As the thermoplastic resin, a cyclic polyolefin resin can be used. Here, the cyclic polyolefin resin represents a polymer resin having a cyclic olefin structure.
Examples of the polymer resin having a cyclic olefin structure used in the present invention include (1) a norbornene polymer, (2) a monocyclic olefin polymer, (3) a cyclic conjugated diene polymer, (4) There are vinyl alicyclic hydrocarbon polymers and hydrides of (1) to (4).
A preferred polymer of the present invention is an addition (co) polymer cyclic polyolefin-based resin containing at least one repeating unit represented by the following general formula (II), and, if necessary, represented by the general formula (I). It is an addition (co) polymer cyclic polyolefin resin further comprising at least one repeating unit. Further, a ring-opening (co) polymer containing at least one cyclic repeating unit represented by the general formula (III) can also be suitably used.

In general formulas (I) to (III), m represents an integer of 0 to 4. R ^{1 to} R ⁶ are a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms, X ^{1 to} X ³ and Y ^{1 to} Y ³ are a hydrogen atom, a hydrocarbon group having 1 to 10 carbon atoms, a halogen atom, and a halogen atom. substituted hydrocarbon group having 1 to 10 carbon _{atoms, - (CH 2) n COOR} 11, - (CH 2) n OCOR 12, - (CH 2) n NCO, - (CH 2) n NO 2, - ( _{CH 2) n CN, - (} CH 2) n CONR 13 R 14, - (CH 2) n NR 13 R 14, - (CH 2) n OZ, - (CH 2) n W, or X ¹ and Y ¹ Alternatively, (—CO) ₂ O and (—CO) ₂ NR ¹⁵ composed of X ² and Y ² or X ³ and Y ³ are shown. R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , and R ¹⁵ are hydrogen atoms, hydrocarbon groups having 1 to 20 carbon atoms, Z is a hydrocarbon group or a hydrocarbon group substituted with a halogen, and W is SiR ¹⁶ _p. D _3-p (R ¹⁶ is a hydrocarbon group having 1 to 10 carbon atoms, D is a halogen atom, —OCOR ¹⁶ or —OR ¹⁶ , p is an integer of 0 to 3), n is an integer of 0 to 10 Show.

  Norbornene polymer hydrides are disclosed in JP-A-1-240517, JP-A-7-196736, JP-A-60-26024, JP-A-62-19807, JP-A-2003-115767, or JP-A-2004-309979. As disclosed in No. 1, etc., a polycyclic unsaturated compound is produced by addition polymerization or metathesis ring-opening polymerization and then hydrogenation.

In the norbornene-based polymer used in the present invention, R ^{5 to} R ⁶ are preferably a hydrogen atom or —CH ₃ , X ³ and Y ³ are preferably a hydrogen atom, Cl, —COOCH ₃ , and other groups are appropriately selected. The This norbornene-based resin is sold under the trade name Arton G or Arton F by JSR Corporation, and from Zeon Corporation, Zeonor ZF14, ZF16, Zeonex 250 or Zeonex. They are commercially available under the trade name 280 and can be used.

  Norbornene-based addition (co) polymers are disclosed in JP-A No. 10-7732, JP-T-2002-504184, U.S. Published Patent No. 200429129157A1 or WO2004 / 070463A1. It can be obtained by addition polymerization of norbornene-based polycyclic unsaturated compounds. If necessary, norbornene-based polycyclic unsaturated compounds and ethylene, propylene, butene; conjugated dienes such as butadiene and isoprene; nonconjugated dienes such as ethylidene norbornene; acrylonitrile, acrylic acid, methacrylic acid, maleic anhydride It is also possible to carry out addition polymerization with linear diene compounds such as acid, acrylic acid ester, methacrylic acid ester, maleimide, vinyl acetate and vinyl chloride. This norbornene-based addition (co) polymer is marketed by Mitsui Chemicals, Inc. under the name of Apel, and has different glass transition temperatures (Tg) such as APL8008T (Tg70 ° C), APL6013T (Tg125 ° C) or APL6015T ( Grades such as Tg145 ° C). Pellets such as TOPAS 8007, 6013, and 6015 are sold by Polyplastics Co., Ltd. Further, Appear 3000 is sold by Ferrania.

  Although there is no restriction | limiting in the glass transition temperature (Tg) of the said cyclic polyolefin resin, It is preferable that it is 80 degreeC or more, and it is more preferable that it is 100 degreeC or more. Within this range, preferable stability can be obtained even with long-term dimensional changes.

(Glutaric anhydride resin)
As the thermoplastic resin, a glutaric anhydride resin can be used. Here, the glutaric anhydride resin represents a polymer resin having a glutaric anhydride unit.

  The polymer having a glutaric anhydride unit preferably has a glutaric anhydride unit represented by the following general formula (101) (hereinafter referred to as a glutaric anhydride unit).

Formula (101):

In general formula (101), R ³¹ and R ³² each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. The organic residue may contain an oxygen atom. R ³¹ and R ³² particularly preferably represent the same or different hydrogen atoms or alkyl groups having 1 to 5 carbon atoms.

  The polymer having glutaric anhydride units is preferably an acrylic copolymer containing glutaric anhydride units. The acrylic thermoplastic copolymer preferably has a glass transition temperature (Tg) of 120 ° C. or higher from the viewpoint of heat resistance.

  As content of the glutaric anhydride unit with respect to an acrylic thermoplastic copolymer, 5-50 mass% is preferable, More preferably, it is 10-45 mass%. When the content is 5% by mass or more, more preferably 10% by mass or more, an effect of improving heat resistance can be obtained, and further an effect of improving weather resistance can be obtained.

The acrylic thermoplastic copolymer preferably further includes a repeating unit based on an unsaturated carboxylic acid alkyl ester. As the repeating unit based on the unsaturated carboxylic acid alkyl ester, for example, those represented by the following general formula (102) are preferable.
Formula _{(102): - [CH 2} -C (R 41) (COOR 42)] -

In the general formula (102), R ⁴¹ represents hydrogen or an alkyl group having 1 to 5 carbon atoms, and R ⁴² ) represents an aliphatic or alicyclic hydrocarbon group having 1 to 6 carbon atoms, or one or more carbon atoms. Represents an aliphatic or alicyclic hydrocarbon group having 1 to 6 carbon atoms substituted by the number of hydroxyl groups or halogen.

The monomer corresponding to the repeating unit represented by the general formula (102) is represented by the following general formula (103).
Formula _{(103): CH 2 = C} (R 41) (COOR 42)

  Preferred examples of such monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, (meth) acrylic acid. t-butyl, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, chloromethyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, (meth ) 3-hydroxypropyl acrylate, 2,3,4,5,6-pentahydroxyhexyl (meth) acrylate and 2,3,4,5-tetrahydroxypentyl (meth) acrylate, among others, methacryl Methyl acid is most preferably used. These may be used individually by 1 type, or may use 2 or more types together.

  The content of the unsaturated carboxylic acid alkyl ester unit relative to the acrylic thermoplastic copolymer is preferably 50 to 95% by mass, more preferably 55 to 90% by mass. An acrylic thermoplastic copolymer having a glutaric anhydride unit and an unsaturated carboxylic acid alkyl ester unit, for example, polymerizes a copolymer having an unsaturated carboxylic acid alkyl ester unit and an unsaturated carboxylic acid unit. It can be obtained by cyclization.

As an unsaturated carboxylic acid unit, what is represented, for example by the following general formula (104) is preferable.
Formula _{(104): - [CH 2} -C (R 51) (COOH)] -
Here, R ⁵¹ represents hydrogen or an alkyl group having 1 to 5 carbon atoms.

Preferable specific examples of the monomer for deriving the unsaturated carboxylic acid unit include a compound represented by the following general formula (105) which is a monomer corresponding to the repeating unit represented by the general formula (104), and Examples thereof include maleic acid and a hydrolyzate of maleic anhydride, and acrylic acid and methacrylic acid are preferable, and methacrylic acid is more preferable in terms of excellent thermal stability.
Formula _{(105): CH 2 = C} (R 51) (COOH)

  These may be used individually by 1 type, or may use 2 or more types together. As described above, an acrylic thermoplastic copolymer having a glutaric anhydride unit and an unsaturated carboxylic acid alkyl ester-based unit is, for example, a copolymer having an unsaturated carboxylic acid alkyl ester-based unit and an unsaturated carboxylic acid unit. Since the polymer can be obtained by cyclization of the polymer, it may have an unsaturated carboxylic acid unit in its constituent unit.

  As content of the unsaturated carboxylic acid unit with respect to said acrylic type thermoplastic copolymer, 10 mass% or less is preferable, More preferably, it is 5 mass% or less. By setting the content to 10% by mass or less, it is possible to prevent a decrease in colorless transparency and retention stability.

  The acrylic thermoplastic copolymer may have other vinyl monomer units that do not contain an aromatic ring as long as the effects of the present invention are not impaired. Specific examples of other vinyl monomer units that do not contain an aromatic ring include the corresponding monomers: vinyl cyanide monomers such as acrylonitrile, methacrylonitrile, ethacrylonitrile; allyl glycidyl ether Maleic anhydride, itaconic anhydride; N-methylmaleimide, N-ethylmaleimide, N-cyclohexylmaleimide, acrylamide, methacrylamide, N-methylacrylamide, butoxymethylacrylamide, N-propylmethacrylamide; aminoethyl acrylate, acrylic Propylaminoethyl acid, dimethylaminoethyl methacrylate, ethylaminopropyl methacrylate, cyclohexylaminoethyl methacrylate; N-vinyldiethylamine, N-acetylvinylamine, allylamine, methallylamino , N- methyl-allyl amine; 2-isopropenyl - oxazoline, 2-vinyl - oxazoline, 2-acryloyl - oxazoline, and the like. These may be used alone or in combination of two or more.

  As content of the other vinyl-type monomer unit which does not contain an aromatic ring with respect to said acrylic type thermoplastic copolymer, 35 mass% or less is preferable.

  For vinyl monomer units containing an aromatic ring (N-phenylmaleimide, phenylaminoethyl methacrylate, p-glycidylstyrene, p-aminostyrene, 2-styryl-oxazoline, etc.), they have scratch resistance and weather resistance. Since there exists a tendency to reduce, it is preferable to keep it as 1 mass% or less as content with respect to the said acrylic thermoplastic copolymer.

(Glutarimide resin)
A glutarimide resin can be used as the thermoplastic resin. Here, the glutarimide resin represents a polymer resin having a glutarimide unit.

The glutarimide resin is a thermoplastic resin having a substituted or unsubstituted imide group in the side chain. By having a substituted or unsubstituted imide group in the side chain, a desirable balance of properties can be expressed in terms of optical properties and heat resistance. The glutarimide-based resin has at least the following general formula (301):

で表されるグルタルイミド単位（但し、式中、Ｒ³⁰¹、Ｒ³⁰²、Ｒ³⁰³は独立に水素または炭素数１〜１２個の非置換のまたは置換のアルキル基、シクロアルキル基、アリール基である。）を２０質量％以上有するグルタルイミド樹脂を含有することが好ましい。 General formula (301)

Wherein R ³⁰¹ , R ³⁰² and R ³⁰³ are independently hydrogen or an unsubstituted or substituted alkyl group having 1 to 12 carbon atoms, a cycloalkyl group or an aryl group. It is preferable to contain a glutarimide resin having 20% by mass or more.

As preferable glutarimide units constituting the glutarimide resin, R ³⁰¹ and R ³⁰² are hydrogen or a methyl group, and R ³⁰³ is a methyl group or a cyclohexyl group. The glutarimide unit may be a single type, or may include a plurality of types in which R ³⁰¹ , R ³⁰² , and R ³⁰³ are different.

  A preferred second structural unit constituting the glutarimide-based resin is a unit composed of an acrylate ester or a methacrylate ester. Preferable acrylic acid ester or methacrylic acid ester structural unit includes methyl acrylate, ethyl acrylate, methyl methacrylate, methyl methacrylate and the like. Another preferred imidizable unit includes N-alkyl methacrylamide such as N-methyl methacrylamide and N-ethyl methacrylamide. These second structural units may be of a single type or may include a plurality of types.

  The content of the glutarimide unit represented by the general formula (301) in the glutarimide resin is 20% by mass or more based on the total repeating unit of the glutarimide resin. The preferable content of the glutarimide unit is 20% by mass to 95% by mass, more preferably 50 to 90% by mass, and still more preferably 60 to 80% by mass. When a glutarimide unit is smaller than this range, the heat resistance of the film obtained may be insufficient or transparency may be impaired. On the other hand, if it exceeds this range, the heat resistance is unnecessarily increased and it becomes difficult to form a film, the mechanical strength of the resulting film becomes extremely brittle, and the transparency may be impaired.

  The glutarimide-based resin may be further copolymerized with a third structural unit as necessary. Preferred examples of the third structural unit include styrene monomers such as styrene, substituted styrene and α-methylstyrene, acrylic monomers such as butyl acrylate, and nitrile monomers such as acrylonitrile and methacrylonitrile. , A structural unit obtained by copolymerizing maleimide monomers such as maleimide, N-methylmaleimide, N-phenylmaleimide, and N-cyclohexylmaleimide can be used. These may be directly copolymerized with the glutarimide unit and the imidizable unit in the glutarimide resin, and graft copolymerized with the resin having the glutarimide unit and the imidizable unit. It may be polymerized. When the third component is added, the content in the glutarimide resin is preferably 5 mol% or more and 30 mol% or less based on the total repeating units in the glutarimide resin.

  The glutarimide resin is described in US Pat. No. 3,284,425, US Pat. No. 4,246,374, JP-A-2-153904, and the like, and is obtained by using methyl methacrylate as a main raw material as a resin having an imidizable unit. It can be obtained by using a resin and imidizing the resin having an imidizable unit with ammonia or a substituted amine. When obtaining a glutarimide resin, a unit composed of acrylic acid, methacrylic acid, or an anhydride thereof may be introduced into the glutarimide resin as a reaction by-product. The presence of such a structural unit, particularly an acid anhydride, is not preferable because it reduces the total light transmittance and haze of the obtained film of the present invention. The acrylic acid or methacrylic acid content is 0.5 milliequivalent or less per gram of resin, preferably 0.3 milliequivalent or less, more preferably 0.1 milliequivalent or less. In addition, as seen in JP-A No. 02-153904, it is also possible to obtain a glutarimide resin by imidization using a resin mainly composed of N-methylacrylamide and methacrylic acid methyl ester.

The glutarimide resin preferably has a weight average molecular weight of 1 × 10 ⁴ to 5 × 10 ⁵ .

(Other thermoplastic resins)
In the present invention, as the thermoplastic resin, other thermoplastic resins other than the above-described resins may be included. Other thermoplastic resins are not particularly limited as long as they do not contradict the gist of the present invention, but thermoplastic resins that are thermodynamically compatible are preferred in terms of improving mechanical strength and desired physical properties.

  Examples of the other thermoplastic resins include olefinic thermoplastics such as polyethylene, polypropylene, ethylene-propylene copolymer, and poly (4-methyl-1-pentene); halogen-containing materials such as vinyl chloride and chlorinated vinyl resins. Acrylic thermoplastics such as polymethyl methacrylate; Styrene thermoplastics such as polystyrene, styrene-methyl methacrylate copolymer, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene block copolymer; polyethylene Polyester such as terephthalate, polybutylene terephthalate, polyethylene naphthalate; polyamide such as nylon 6, nylon 66, nylon 610; polyacetal; polycarbonate; polyphenylene oxide; polyphenylene sulfide; Polyetheretherketone; polysulfone; polyether sulfone; polyoxyethylene benzylidene alkylene; polyamideimide; polybutadiene rubber, rubber-like polymer such as ABS resin or ASA resin containing an acrylic rubber; and the like. The rubbery polymer preferably has a graph collar portion having a composition compatible with the lactone ring polymer of the present invention on the surface, and the average particle diameter of the rubbery polymer is transparency when formed into a film. From the viewpoint of improvement, it is preferably 100 nm or less, and more preferably 70 nm or less.

  Although the content of the present invention is not limited, among the resins described above, the (meth) acrylic resin and its lactone ring-containing polymer, glutaric anhydride are preferably used as the resin used for the core layer. Containing polymers, glutarimide-containing polymers, polycarbonate resins, cycloolefin resins, and the like. In particular, a (meth) acrylic resin and its lactone ring-containing polymer, glutaric anhydride-containing polymer, and glutarimide-containing polymer are more preferable. In addition, the first surface layer and the second surface layer are preferably used as a copolymer component of a polycarbonate resin, a polystyrene resin, a cycloolefin resin, or a (meth) acrylic resin as a hydrophobic component such as polystyrene. It contains 50% or more of all components. Particularly, among polystyrene resins, cycloolefin resins, and (meth) acrylic resins, those containing at least 50% of the hydrophobic components such as polystyrene as copolymerization components are more preferable. Further, even if the resin is out of the scope of these descriptions, the core layer, the first surface layer, and the second layer can be appropriately modified with the other thermoplastic resins described above and the resin modifier described below. It can be suitably used as a surface layer.

<Resin modification additive>
The polarizing plate protective film of the present invention preferably contains a resin modifying additive. In particular, at least one of the first resin layer and the second resin layer preferably contains a resin modifying additive. Thereby, the resin composition which comprises a layer can be modify | reformed and an equilibrium moisture content or an oxygen permeation coefficient can be reduced. Further, by adjusting the type and amount of the resin-modifying additive, the equilibrium water content and oxygen permeability coefficient of each of the first resin layer and the second resin layer can be set within desired ranges.

When the resin modification additive is included, it is preferable to satisfy the relationship of the following formula (3).
Formula (3) C / D ≦ 0.9
Here, in formula (3), C represents the moisture permeability of the polarizing plate protective film when 10% by mass of the resin-modifying additive is added to the mass of the thermoplastic resin, and D is the thermoplastic resin. And the moisture permeability of the polarizing plate protective film when no resin-modifying additive is added. However, the moisture permeability is a value obtained by converting a value after 24 hours at 40 ° C. and a relative humidity of 90% into a film thickness of 40 μm by the method of JIS 0208.
More preferably, the resin modification additive has a C / D of 0.8 or less and a C / D of 0.6 or less.
The resin modifying additive preferably has a molecular weight of 200 or more in order to reduce moisture permeation and desorption.

  The resin modifying additive may have a structure including one or more aromatic rings. Hydrophobic properties can be imparted to the film by the aromatic ring, and moisture permeation and desorption can be suppressed.

As the resin modification additive contained in the polarizing plate protective film of the present invention, a compound represented by the following general formula (A) can be preferably used.

In general formula (A), R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ each independently represent a hydrogen atom or a substituent.

In the general formula (A), R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ each independently represents a hydrogen atom or a substituent. The aforementioned substituent T can be applied. Further, these substituents may be further substituted with another substituent, and the substituents may be condensed to form a ring structure.

R ¹ , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁸ and R ^{9 in the} general formula (A) are preferably hydrogen atoms, alkyl groups, alkenyl groups, alkynyl groups, aryl groups, substituted or unsubstituted An amino group, an alkoxy group, an aryloxy group, a hydroxy group and a halogen atom, more preferably a hydrogen atom, an alkyl group, an aryl group, an alkyloxy group, an aryloxy group and a halogen atom, still more preferably a hydrogen atom, An alkyl group having 1 to 12 carbon atoms, particularly preferably a hydrogen atom or a methyl group, and most preferably a hydrogen atom.

R ² in the general formula (A) is preferably a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a substituted or unsubstituted amino group, an alkoxy group, an aryloxy group, a hydroxy group, a halogen atom, or more. Preferred are a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted amino group having 0 to 20 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryloxy group having 6 to 12 carbon atoms, and a hydroxy group. More preferably, it is a C1-C20 alkoxy group, Most preferably, it is a C1-C12 alkoxy group.

R ⁷ in the general formula (A) is preferably a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a substituted or unsubstituted amino group, an alkoxy group, an aryloxy group, a hydroxy group, a halogen atom, or more. Preferably, a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted amino group having 0 to 20 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryloxy group having 6 to 12 carbon atoms, and a hydroxy group More preferably a hydrogen atom or an alkyl group having 1 to 20 carbon atoms (preferably 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms, still more preferably a methyl group), particularly preferably a methyl group or a hydrogen atom. Is an atom.

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

As the resin modification additive contained in the polarizing plate protective film of the present invention, a compound represented by the following general formula (B) can be preferably used.
General formula (B)

In the general formula ^{(B), R 12, R} 13, R 14, R 15, R 16, R 21, R 23, R 24, R 25, R 32, R 33, R 34, R 35, R 36 are, Each represents a hydrogen atom or a substituent, and the substituent T described below can be applied as the substituent. Further, in the general formula (B), R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ , R ²¹ , R ²³ , R ²⁴ , R ²⁵ , R ³² , R ³³ , R ³⁴ , R ³⁵ and R ^At least one of ³⁶ is an amino group, an acylamino group, an alkoxycarbonylamino group, an aryloxycarbonylamino group, a sulfonylamino group, a hydroxy group, a mercapto group, or a carboxyl group.

Examples of the substituent T include an alkyl group (preferably having 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms, and particularly preferably 1 to 8 carbon atoms, such as a methyl group, an ethyl group, an isopropyl group, and tert-butyl. Group, n-octyl group, n-decyl group, n-hexadecyl group, cyclopropyl group, cyclopentyl group, cyclohexyl group, etc.), alkenyl group (preferably having 2 to 20 carbon atoms, more preferably 2 carbon atoms). To 12, particularly preferably 2 to 8 carbon atoms, such as vinyl group, allyl group, 2-butenyl group, and 3-pentenyl group), alkynyl group (preferably 2 to 20 carbon atoms, more preferably Has 2 to 12 carbon atoms, particularly preferably 2 to 8 carbon atoms, and examples thereof include a propargyl group and a 3-pentynyl group.), Aryl (Preferably having 6 to 30 carbon atoms, more preferably 6 to 20 carbon atoms, particularly preferably 6 to 12 carbon atoms, and examples thereof include a phenyl group, a p-methylphenyl group, and a naphthyl group.), An amino group (Preferably has 0 to 20 carbon atoms, more preferably 0 to 10 carbon atoms, and particularly preferably 0 to 6 carbon atoms. For example, amino group, methylamino group, dimethylamino group, diethylamino group, dibenzylamino group, etc. And an alkoxy group (preferably having 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms, particularly preferably 1 to 8 carbon atoms, and examples thereof include a methoxy group, an ethoxy group, and a butoxy group. ), An aryloxy group (preferably having 6 to 20 carbon atoms, more preferably 6 to 16 carbon atoms, particularly preferably 6 to 12 carbon atoms, such as phenyl A xy group, a 2-naphthyloxy group, etc.), an acyl group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, and particularly preferably 1 to 12 carbon atoms, such as an acetyl group, A benzoyl group, a formyl group, a pivaloyl group, etc.), an alkoxycarbonyl group (preferably having a carbon number of 2 to 20, more preferably a carbon number of 2 to 16, particularly preferably a carbon number of 2 to 12, such as methoxycarbonyl Group, an ethoxycarbonyl group, etc.), an aryloxycarbonyl group (preferably having 7 to 20 carbon atoms, more preferably having 7 to 16 carbon atoms, particularly preferably having 7 to 10 carbon atoms, such as a phenyloxycarbonyl group. An acyloxy group (preferably having 2 to 20 carbon atoms, more preferably 2 to 16 carbon atoms, especially Preferably it is C2-C10, for example, an acetoxy group, a benzoyloxy group, etc. are mentioned. ), An acylamino group (preferably having 2 to 20 carbon atoms, more preferably 2 to 16 carbon atoms, particularly preferably 2 to 10 carbon atoms, and examples thereof include an acetylamino group and a benzoylamino group), alkoxycarbonyl. An amino group (preferably having 2 to 20 carbon atoms, more preferably 2 to 16 carbon atoms, particularly preferably 2 to 12 carbon atoms, such as a methoxycarbonylamino group), an aryloxycarbonylamino group (preferably Has 7 to 20 carbon atoms, more preferably 7 to 16 carbon atoms, particularly preferably 7 to 12 carbon atoms, such as a phenyloxycarbonylamino group, and a sulfonylamino group (preferably 1 to 1 carbon atom). 20, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms. Nylamino group, benzenesulfonylamino group, etc.), sulfamoyl group (preferably having 0 to 20 carbon atoms, more preferably 0 to 16 carbon atoms, particularly preferably 0 to 12 carbon atoms, such as sulfamoyl group, methyl A sulfamoyl group, a dimethylsulfamoyl group, a phenylsulfamoyl group, etc.), a carbamoyl group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, and particularly preferably 1 to carbon atoms). 12 and examples thereof include a carbamoyl group, a methylcarbamoyl group, a diethylcarbamoyl group, a phenylcarbamoyl group, etc.), an alkylthio group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, and particularly preferably carbon atoms). Examples thereof include methylthio group and ethylthio group. ), An arylthio group (preferably having 6 to 20 carbon atoms, more preferably 6 to 16 carbon atoms, particularly preferably 6 to 12 carbon atoms, such as a phenylthio group), a sulfonyl group (preferably C1-C20, More preferably, it is C1-C16, Most preferably, it is C1-C12, For example, a mesyl group, a tosyl group, etc. are mentioned), a sulfinyl group (preferably C1-C20, More preferably, it is C1-C16, Most preferably, it is C1-C12, for example, a methanesulfinyl group, a benzenesulfinyl group, etc.), a ureido group (preferably C1-C20, more preferably carbon) The number is 1 to 16, particularly preferably 1 to 12, and examples thereof include a ureido group, a methylureido group, and a phenylureido group. ), A phosphoric acid amide group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, and particularly preferably 1 to 12 carbon atoms, such as a diethylphosphoric acid amide group and a phenylphosphoric acid amide group. Hydroxy group, mercapto group, halogen atom (eg fluorine atom, chlorine atom, bromine atom, iodine atom), cyano group, sulfo group, carboxyl group, nitro group, hydroxamic acid group, sulfino group, hydrazino group, imino group Group, heterocyclic group (preferably having 1 to 30 carbon atoms, more preferably 1 to 12 carbon atoms, and examples of the hetero atom include a nitrogen atom, an oxygen atom, and a sulfur atom, specifically, for example, an imidazolyl group, a pyridyl group, and a quinolyl group. Group, furyl group, piperidyl group, morpholino group, benzoxazolyl group, benzimidazolyl group, benzthiazolyl group, etc. ), A silyl group (preferably having 3 to 40 carbon atoms, more preferably 3 to 30 carbon atoms, particularly preferably 3 to 24 carbon atoms, and examples thereof include a trimethylsilyl group and a triphenylsilyl group. For example). Among these, an alkyl group, an aryl group, a substituted or unsubstituted amino group, an alkoxy group, and an aryloxy group are more preferable, and an alkyl group, an aryl group, and an alkoxy group are more preferable.
These substituents may be further substituted with a substituent T. Moreover, when there are two or more substituents, they may be the same or different. If possible, they may be linked together to form a ring.

Further, in the general formula ^{(B), R 12, R} 13, R 14, R 15, R 16, R 21, R 23, R 24, R 25, R 32, R 33, R 34, R 35, R 36 At least one of them is an amino group, an acylamino group, an alkoxycarbonylamino group, an aryloxycarbonylamino group, a sulfonylamino group, a hydroxy group, a mercapto group, or a carboxyl group, more preferably an amino group or a hydroxy group. A hydroxy group is preferred. These groups may be substituted with a substituent. As the substituent in this case, the above-described substituent T can be applied, and the preferred range is also the same.

  Preferred examples of the compound represented by formula (B) of the present invention are shown below, but the present invention is not limited to these specific examples.

As the resin modification additive contained in the polarizing plate protective film of the present invention, a novolac compound can also be preferably used.
Although it does not specifically limit as a novolak type phenol resin used for this invention, Generally what reacted phenols and aldehydes using an acidic substance as a catalyst is used preferably. Although it does not specifically limit as phenols used as the raw material of a novolak-type phenol resin, For example, cresol, such as phenol, o-cresol, m-cresol, and p-cresol, 2,3-xylenol, 2,4-xylenol, 2, 5-xylenol, 2,6-xylenol, 3,4-xylenol, xylenol such as 3,5-xylenol, ethylphenol such as o-ethylphenol, m-ethylphenol, p-ethylphenol, isopropylphenol, butylphenol, p -Alkylphenols such as butylphenol such as tert-butylphenol, p-tert-amylphenol, p-octylphenol, p-nonylphenol, p-cumylphenol, fluorophenol, chlorophenol, bromophenol, Halogenated phenols such as dephenol, monovalent phenol substitutes such as p-phenylphenol, aminophenol, nitrophenol, dinitrophenol and trinitrophenol, and monovalent phenols such as 1-naphthol and 2-naphthol, resorcin And polyhydric phenols such as alkylresorcin, pyrogallol, catechol, alkylcatechol, hydroquinone, alkylhydroquinone, phloroglucin, bisphenol A, bisphenol F, bisphenol S, and dihydroxynaphthalene. Although these can be used individually or in combination of 2 or more types, generally phenol and cresol are often used.

  In the polarizing plate protective film of the present invention, the resin modifying additive is preferably included in an amount of 1% by mass or more and 100% by mass or less with respect to the mass of the thermoplastic resin. More preferably, it is 2 to 90% by mass, and more preferably 5 to 80% by mass.

<Other additives>
(Matting agent fine particles)
Fine particles can be added as a matting agent to the polarizing plate protective film of the present invention. Fine particles used as a matting agent include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate and Mention may be made of calcium phosphate. Fine particles containing silicon are preferred in that the haze of the film is reduced, and silicon dioxide is particularly preferred. The silicon dioxide fine particles preferably have a primary average particle size of 20 nm or less and an apparent specific gravity of 70 g / liter or more. Those having an average primary particle size as small as 5 to 16 nm are more preferred because they can reduce the haze of the film. The apparent specific gravity is preferably 90 to 200 g / liter or more, and more preferably 100 to 200 g / liter or more. A larger apparent specific gravity is preferable because a high-concentration dispersion can be produced, and haze and aggregates are improved.

  These fine particles usually form secondary particles having an average particle diameter of 0.1 to 3.0 μm, and these fine particles are present as aggregates of primary particles in the film, and 0.1 to 0.1 μm on the film surface. An unevenness of 3.0 μm is formed. The average particle diameter of the secondary particles is preferably 0.2 to 1.5 μm, more preferably 0.4 to 1.2 μm, and most preferably 0.6 to 1.1 μm. The particle diameter of the primary particles and the secondary particles was determined by observing the particles in the film with a scanning electron microscope and determining the diameter of a circle circumscribing the particles as the particle diameter. In addition, 200 particles were observed at different locations, and the average value was taken as the average particle size.

  As fine particles of silicon dioxide, for example, commercially available products such as Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (manufactured by Nippon Aerosil Co., Ltd.) can be used. Zirconium oxide fine particles are commercially available, for example, under the trade names Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.) and can be used.

  Among these, Aerosil 200V and Aerosil R972V are fine particles of silicon dioxide having an average primary particle diameter of 20 nm or less and an apparent specific gravity of 70 g / liter or more, and the turbidity of the polarizing plate protective film is kept low. However, it is particularly preferable because the effect of reducing the friction coefficient is great.

In the present invention, in order to obtain a polarizing plate protective film having particles having a small average particle size of secondary particles, several methods can be considered when preparing a dispersion of fine particles. For example, a fine particle dispersion prepared by stirring and mixing a solvent and fine particles is prepared in advance, and this fine particle dispersion is added to a small amount of a separately prepared resin composition solution and dissolved by stirring. Liquid). This method is a preferred preparation method in that the dispersibility of the silicon dioxide fine particles is good and the silicon dioxide fine particles are more difficult to reaggregate. In addition, after adding a small amount of the resin composition solution to the solvent and dissolving with stirring, fine particles are added to this and dispersed with a disperser. This is used as a fine particle additive solution, and this fine particle additive solution is doped with an in-line mixer. There is also a method to mix well. The present invention is not limited to these methods, but the concentration of silicon dioxide when the silicon dioxide fine particles are mixed and dispersed with a solvent or the like is preferably 5 to 30% by mass, more preferably 10 to 25% by mass, and 15 to 20%. Mass% is most preferred. A higher dispersion concentration is preferable because the liquid turbidity with respect to the added amount is lowered, and haze and aggregates are improved.
The addition amount of the matting agent in the final dope solution is preferably 0.01 to 1.0 g, more preferably 0.03 to 0.3 g, and most preferably 0.08 to 0.16 g per 1 m ² . The addition amount of the matting agent is preferably 0.001% by mass or more and 0.4% by mass or less, and preferably 0.001% by mass or more and 0.2% by mass with respect to the total amount of resin used in the dope solution of the resin composition. The following is more preferable, and 0.01 mass% or more and 0.1 mass% or less is still more preferable. Further, when the polarizing plate protective film is formed from multiple layers, it is preferable not to add to the inner layer, but to add only to the surface layer side. The addition amount of the surface layer matting agent is preferably 0.001% by mass to 0.4% by mass, more preferably 0.001% by mass to 0.2% by mass, and 0.01% by mass to 0.0% by mass. 1 mass% or less is still more preferable.

  As the solvent used for dispersion, lower alcohols are preferable, and examples thereof include methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, and butyl alcohol. Although it does not specifically limit as solvents other than a lower alcohol, It is preferable to use the solvent used at the time of film forming of a polarizing plate protective film.

(Other additives)
In addition to the mat particles, the polarizing plate protective film of the present invention has other various additives (for example, retardation developing agent, plasticizer, ultraviolet absorber, deterioration inhibitor, release agent, infrared absorber, wavelength). Dispersion modifiers etc.) can be added and they can be solid or oily. That is, the melting point and boiling point are not particularly limited. For example, mixing of ultraviolet absorbing material at 20 ° C. or lower and 20 ° C. or higher, and similarly mixing of a plasticizer is described in, for example, JP-A-2001-151901. Furthermore, infrared absorbing dyes are described in, for example, JP-A No. 2001-194522. Moreover, the addition time may be added at any time in the dope preparation step, but may be added by adding an additive to the final preparation step of the dope preparation step. Furthermore, the amount of each material added is not particularly limited as long as the function is manifested. Moreover, when a polarizing plate protective film is formed from a multilayer, the kind and addition amount of the additive of each layer may differ. For example, it is described in Japanese Patent Application Laid-Open No. 2001-151902, and these are conventionally known techniques. For these details, materials described in detail on pages 16 to 22 in the Japan Institute of Invention Disclosure Technical Bulletin (Public Technical No. 2001-1745, published on March 15, 2001, Japan Institute of Invention) are preferably used.

A plasticizer having good compatibility with the resin composition to be used is less prone to bleed-out, has a low haze, and is effective in producing a film that realizes a liquid crystal display device excellent in light leakage, front contrast, and luminance.
You may use a plasticizer for the polarizing plate protective film of this invention. Although it does not specifically limit as a plasticizer, A phosphate ester plasticizer, a phthalate ester plasticizer, a polyhydric alcohol ester plasticizer, a polycarboxylic acid ester plasticizer, a glycolate plasticizer, a citrate ester Examples thereof include plasticizers, fatty acid ester plasticizers, carboxylic acid ester plasticizers, polyester oligomer plasticizers, sugar ester plasticizers, and ethylenically unsaturated monomer copolymer plasticizers.
Preferred are phosphate ester plasticizers, glycolate plasticizers, polyhydric alcohol ester plasticizers, polyester oligomer plasticizers, sugar ester plasticizers, ethylenically unsaturated monomer copolymer plasticizers, and more preferred. Is a polyester oligomer plasticizer, sugar ester plasticizer, ethylenically unsaturated monomer copolymer plasticizer, more preferably an ethylenically unsaturated monomer copolymer plasticizer, sugar ester plasticizer, particularly preferably Is an ethylenically unsaturated monomer copolymer plasticizer.
In particular, polyester oligomer plasticizers, ethylenically unsaturated monomer copolymer plasticizers, and sugar ester plasticizers are highly compatible with the polarizing plate protective film of the present invention, and are effective in reducing bleed out, low haze, and low moisture permeability. In addition, since the plasticizer is not easily decomposed and the film is hardly deteriorated or deformed due to changes in temperature and humidity or with time, it can be preferably used in the present invention.
In the present invention, the plasticizer may be used alone or in combination of two or more.

  The polarizing plate protective film of the present invention may contain acrylic particles. Japanese Patent Publication No. 60-17406, Japanese Patent Publication No. 3-39095 and the like describe that the addition of acrylic particles, particularly a multilayer structure acrylic granular composite, improves impact resistance and stress whitening resistance.

  In the polarizing plate protective film of this invention, when adding these additives, it is preferable that the total amount of an additive is 50 mass% or less with respect to a polarizing plate protective film, and it is 30 mass% or less. preferable.

<Characteristics of polarizing plate protective film>
(Retardation)
In the polarizing plate protective film of the present invention, Re and Rth (defined by the following formulas (I) and (II)) measured at a wavelength of 590 nm preferably satisfy the formulas (III) and (IV).
Formula (I) Re = (nx−ny) × d
Formula (II) Rth = {(nx + ny) / 2−nz} × d
Formula (III) −50 nm ≦ Re ≦ 50 nm
Formula (IV) −50 nm ≦ Rth ≦ 50 nm
In the above formulas (I) to (IV), nx is the refractive index in the slow axis direction in the film plane of the polarizing plate protective film, ny is the refractive index in the fast axis direction in the film plane, nz is the refractive index in the film thickness direction of the polarizing plate protective film, and d is the thickness (nm) of the polarizing plate protective film.
In the polarizing plate protective film of the present invention, the above formulas (III) and (IV) may be satisfied at at least one point in the film plane. It is preferable that (IV) is satisfied.
The “slow axis direction” of the film means the direction in which the refractive index is maximum within the film plane. Further, the “fast axis direction” means a direction orthogonal to the slow axis in the film plane.
Re is more preferably −20 nm to 20 nm, and particularly preferably −10 nm to 10 nm.
Rth is more preferably −20 nm to 20 nm, and particularly preferably −20 nm to 0 nm.

Re, Rth, and Nz at the wavelength λnm can be measured as follows.
Re is measured with KOBRA 21ADH (manufactured by Oji Scientific Instruments Co., Ltd.) by making light of wavelength λ nm incident in the normal direction of the film.
Rth was measured by making light having a wavelength λ nm incident from a direction inclined + 40 ° with respect to the normal direction of the film with the slow axis in the plane (determined by KOBRA 21ADH) as the tilt axis (rotation axis). A retardation value and a retardation value measured by making light of wavelength λ nm incident from a direction inclined by −40 ° with respect to the film normal direction with the in-plane slow axis as the tilt axis (rotation axis). Calculated by KOBRA 21ADH based on the retardation value measured in the direction. Here, as the assumed value of the average refractive index, the values in the thermoplastic handbook (John Wiley & Sons, Inc.) and catalogs of various polarizing plate protective films can be used. Those whose average refractive index is not known can be measured with an Abbe refractometer. The average refractive index values of the main polarizing plate protective films are exemplified below: cellulose acylate (1.48), cyclic polyolefin (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49) Polystyrene (1.59).
Nz is calculated by the formula (VI) based on Re and Rth. Note that nx, ny, and nz can be calculated by KOBRA 21ADH based on the assumed value of the average refractive index and the film thickness, and Nz can be calculated from the values of nx, ny, and nz by the formula (II).
In the measurement of the polarizing plate protective film of the present invention, the retardation is measured by setting the average refractive index of the polarizing plate protective film to 1.48.

  The above Re, Rth, and Nz can be adjusted by the substitution degree of cellulose ester, the ratio of cellulose ester and acrylic resin, the addition of a retardation developer, the film thickness, the stretching direction and stretching ratio of the film, and the like.

(Film thickness)
The thickness of the polarizing plate protective film of the present invention is preferably 100 μm or less, more preferably 40 μm or less, and particularly preferably 25 μm or less. When the thickness is 100 μm or less, the environment in which the liquid crystal display device is placed, that is, the unevenness of the panel accompanying the change in temperature and humidity can be reduced.
Moreover, it is preferable that the sum total of the film thickness of a 1st resin layer and a 2nd resin layer is 60 micrometers or less. The first resin layer and the second resin layer are preferably laminated adjacent to each other, and the total film thickness of the two layers is preferably 60 μm or less. The total film thickness of the two layers is preferably 60 μm or less, more preferably 50 μm or less, and even more preferably 40 μm or less.
By setting the upper limit of the total film thickness of the two layers to the above value, the film after stretching can be thinned, and the change in retardation at the time of humidity change, high temperature and high temperature and high humidity environment is reduced. Can do. Furthermore, it is preferable because an inexpensive film with less resin to be used can be produced. In addition, when it has a functional layer between the 1st resin layer and the 2nd resin layer, the sum total of each average film thickness of the 1st resin layer and the 2nd resin layer except the functional layer is the said range. It is preferable that

In the present invention, when the average film thickness of the first resin layer is α and the average film thickness of the second resin layer is β, it is preferable that α> β. That is, the average film thickness of the first resin layer is preferably thicker than the average film thickness of the second resin layer.
The thickness of the first resin layer is preferably 70% or more, more preferably 80% or more, and more preferably 90% or more with respect to the thickness of the entire film. It is particularly preferable to have a thickness. As a result, the moisture to be transmitted from the second resin layer side gives a large contribution of diffusion, resulting in a low moisture-permeable film, while the moisture to be transmitted from the polarizing plate side contributes to adsorption. This is because the permeation is promoted by giving a large value.
By making the relationship between the average thickness of the first resin layer and the second resin layer and the thickness of the first resin layer as described above, the polarizing plate protective film exhibits a more excellent moisture permeability reduction effect. Can do. Furthermore, by assembling the polarizing plate so that the first resin layer is on the polarizer side, it is possible to sufficiently adsorb moisture from the polarizer in the drying step after the polarizing protective film is attached to the polarizer. . Thereby, the polarizing plate excellent in the optical characteristic can be obtained. The average film thickness of the second resin layer may be thin as long as the function of the film can be expressed.

(Water permeability of film)
The moisture permeability of the film is measured under the conditions of 40 ° C. and 90% relative humidity based on JIS Z-0208.
The moisture permeability decreases as the film thickness increases, and increases as the film thickness decreases. Therefore, it is necessary to convert the samples having different film thicknesses by setting the reference to 40 μm. The film thickness can be converted according to the following mathematical formula.
Mathematical formula: moisture permeability in terms of 40 μm = measured moisture permeability × measured film thickness (μm) / 40 (μm).
In the present invention, the moisture permeability B when measured on the condition that the second resin layer side is 40 ° C. and the relative humidity is 90% may be 250 g / m ² / day or less (in terms of a film thickness of 40 μm), and 200 g / more preferably it is m ² / day or less (thickness 40μm equivalent) is preferably 150 g / m ² / day or less (thickness 40μm equivalent), at 90 g / m ² / day or less (thickness 40μm equivalent) It is particularly preferred. If the water vapor transmission rate is 90 g / m ² / day or less, it is possible to further suppress the warpage of the panel after the normal temperature, high humidity and high temperature and high humidity environment of the liquid crystal display device.

(Haze of film)
The polarizing plate protective film of the present invention preferably has a total haze value of 2.00 or less. When the total haze value is 2.00 or less, the transparency of the film is high, and the contrast ratio and the luminance of the liquid crystal display device are improved. The total haze value is more preferably 1.00 or less, further preferably 0.50 or less, particularly preferably 0.30 or less, and most preferably 0.20 or less. The lower the total haze value, the better the optical performance, but it is preferably 0.01 or more in consideration of raw material selection, production control, and roll film handling.
The internal haze value of the polarizing plate protective film of the present invention is preferably 1.00 or less. By setting the internal haze value to 1.00 or less, the contrast ratio of the liquid crystal display device can be improved and excellent display characteristics can be realized. The internal haze value is more preferably 0.50 or less, further preferably 0.20 or less, particularly preferably 0.10 or less, and most preferably 0.05 or less. It is preferable that it is 0.01 or more from viewpoints, such as raw material selection and manufacture control.
In particular, the polarizing plate protective film of the present invention preferably has a total haze value of 0.30 or less and an internal haze value of 0.10 or less.
The total haze value and internal haze value are the types and addition amounts of cellulose ester and acrylic resin of the film material, selection of additives (particularly, the particle size, refractive index, addition amount of matting agent particles), and film production conditions. It can be adjusted by (temperature during stretching, stretching ratio, etc.).
In addition, the measurement of a haze can measure the film sample 40mmx80mm of this invention at 25 degreeC and 60% of relative humidity, and according to JISK-6714 with a haze meter (HGM-2DP, Suga test machine).

(Elastic modulus of film)
The elastic modulus of the polarizing plate protective film of the present invention is preferably 1800 to 7000 MPa in the width direction (TD direction).
In the present invention, when the elastic modulus in the TD direction is within the above range, display unevenness at the time of black display after high humidity and high temperature and high humidity environment aging, transportability at the time of film production, end slit property and difficulty in breaking. It is preferable from the viewpoint of manufacturing suitability. If the TD elastic modulus is too small, display unevenness at the time of black display after high humidity and high temperature and high humidity environment is likely to occur, and there is a problem in manufacturing suitability. The elastic modulus is more preferably 1800 to 5000 MPa, and further preferably 1800 to 4000 MPa.
Moreover, 1800-4000 MPa is preferable and, as for the elasticity modulus of the conveyance direction (MD direction) of the polarizing plate protective film of this invention, it is more preferable that it is 1800-3000 MPa.
Here, the conveyance direction (longitudinal direction) of the film is the conveyance direction (MD direction) during film production, and the width direction is the direction (TD direction) perpendicular to the conveyance direction during film production.
The elastic modulus of the film depends on the type and amount of cellulose ester and acrylic resin used in the film material, selection of additives (particularly, the particle size, refractive index, and amount of addition of matting agent particles), and film production conditions (stretch ratio). Etc.).
The elastic modulus is obtained, for example, by measuring a stress at 0.5% elongation at a tensile rate of 10% / min in an atmosphere of 23 ° C. and 70 RH% using a universal tensile tester “STM T50BP” manufactured by Toyo Baldwin Co., Ltd. be able to.

(Glass transition temperature Tg)
The glass transition temperature Tg of the polarizing plate protective film of the present invention is preferably 100 ° C. or higher and 200 ° C. or lower, more preferably 100 ° C. or higher and 150 ° C. or lower, from the viewpoints of production suitability and heat resistance.
The glass transition temperature is a temperature at which the base line derived from the glass transition of the film starts to change and a temperature at which it returns to the base line again when measured at a heating rate of 10 ° C./min using a differential scanning calorimeter (DSC). It can be calculated as an average value.

(Equilibrium moisture content of film)
The equilibrium water content of the polarizing plate protective film as a whole of the present invention is such that the relationship between the equilibrium water content of the first resin layer and the second resin layer constituting the polarizing plate protective film of the present invention satisfies the above relationship. There are no particular restrictions.
When used as a protective film for a polarizing plate, the polarizing plate protective film of the present invention at 25 ° C. and a relative humidity of 80% irrespective of the film thickness so as not to impair the adhesiveness with water-soluble thermoplastics such as polyvinyl alcohol. It is preferable that the equilibrium water content as a whole is 0 to 1.5% by mass. More preferably, it is 0.1-1.0 mass%, and it is still more preferable that it is 0.2-0.8 mass%. If the equilibrium moisture content of the polarizing plate protective film as a whole of the present invention is 1.5% by mass or less, the dependency of retardation on humidity change does not become excessive, and the normal temperature, high humidity, and high temperature and high humidity of the liquid crystal display device are increased. This is also preferable from the viewpoint of suppressing display unevenness during black display after environmental aging.
The method for measuring the equilibrium moisture content of the polarizing plate protective film of the present invention was as follows: a film sample 7 mm × 35 mm was measured with a moisture meter, sample drying devices “CA-03” and “VA-05” {both manufactured by Mitsubishi Chemical Corporation. }, The water content (g) measured by the Karl Fischer method is divided by the sample mass (g).

(Oxygen permeability coefficient of film)
The oxygen transmission coefficient at 25 ° C. and 60% relative humidity as the whole polarizing plate protective film of the present invention is preferably 0.1 to 10 cc · mm / m ² / day / atm, and preferably 0.2 to 8 cc · mm. / M ² / day / atm is more preferable, and 0.5 to 7 cc · mm / m ² / day / atm is further preferable. The oxygen transmission coefficient can be used as a parameter having a positive correlation with the moisture transmission rate (diffusion rate). In the present invention, the moisture permeation rate (diffusion rate) can be reduced and the water vapor transmission rate can be lowered by setting the oxygen permeation coefficient within the above range.
The oxygen permeation amount of the film was measured by attaching a test piece cut to a diameter of 1.5 cm through silicon grease thinly applied to an oxygen electrode (MODEL3600, PFA manufactured by Orbis Fair Laboratories), and reducing the oxygen reduction current in a steady state. From the output value, the oxygen transmission amount was determined. The measurement was performed in an environment of 25 ° C. and a relative humidity of 60%.
Conversion to the oxygen permeability coefficient was obtained by creating a calibration curve using a sample with a known permeation amount.

(Dimensional change of film)
The dimensional stability of the polarizing plate protective film of the present invention is as follows: the dimensional change rate after standing for 24 hours under the conditions of 60 ° C. and 90% relative humidity (high humidity), and 80 ° C., DRY environment (relative humidity) It is preferable that the dimensional change rate after standing for 24 hours under the condition (5% or less) is 0.5% or less. More preferably, it is 0.3% or less, More preferably, it is 0.15% or less.

(Photoelastic coefficient)
When the polarizing plate protective film of the present invention is used as a protective film for a polarizing plate, birefringence (Re, Rth) may change due to stress due to contraction of the polarizer. The change in birefringence due to such stress can be measured as a photoelastic coefficient, but the range is preferably 15 Br or less, more preferably −3 to 12 Br, and further preferably 0 to 11 Br. preferable.

[Production method of polarizing plate protective film]
As a method for forming the polymer film, an inflation method, a T-die method, a calendar method, a cutting method, a casting method, an emulsion method, a hot press method, and the like can be used. From the viewpoint of suppression and suppression of optical defects such as die lines, it is preferable to employ solution casting.

The method for producing the polarizing plate protective film of the present invention may use a solution casting method or a melt casting method. In the case of the solution casting method, the first resin layer may be formed by casting a polymer solution (dope) containing the thermoplastic resin, the resin modifying additive and a solvent on a support. preferable. Furthermore, in addition to the first resin layer, it is more preferable that the second resin layer is formed by solution casting by a two-layer co-casting method.
Moreover, you may provide the resin composition which comprises each layer of the polarizing plate protective film of this invention by application | coating. In the coating solution, the above-described thermoplastic resin, resin improving additive, and other additives can be appropriately selected and mixed.

<Solution casting method>
(solvent)
A solvent useful for forming the dope can be used without limitation as long as it dissolves the thermoplastic resin, the resin-modifying additive, and other additives simultaneously.
In the present invention, any of a chlorinated solvent containing a chlorinated organic solvent as a main solvent and a non-chlorinated solvent not containing a chlorinated organic solvent can be used as the organic solvent. Two or more organic solvents may be mixed and used.

  In producing the dope, a chlorinated organic solvent is preferably used as the main solvent. In the present invention, the kind of the chlorinated organic solvent is not particularly limited as long as the object can be achieved within the range in which the thermoplastic resin can be dissolved, cast and formed. These chlorinated organic solvents are preferably dichloromethane and chloroform. Particularly preferred is dichloromethane. In addition, there is no particular problem in mixing an organic solvent other than the chlorinated organic solvent. In that case, it is necessary to use at least 50% by mass of dichloromethane in the total amount of the organic solvent. Other organic solvents used in combination with the chlorinated organic solvent in the present invention will be described below. That is, as another preferable organic solvent, a solvent selected from esters, ketones, ethers, alcohols, hydrocarbons and the like having 3 to 12 carbon atoms is preferable. The ester, ketone, ether and alcohol may have a cyclic structure. A compound having two or more functional groups of esters, ketones and ethers (that is, —O—, —CO— and —COO—) can also be used as a solvent. For example, other functional groups such as alcoholic hydroxyl groups can be used. You may have group simultaneously. In the case of a solvent having two or more types of functional groups, the number of carbon atoms may be within the specified range of the compound having any functional group.

  Examples of the esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate. Examples of ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone, and methylcyclohexanone. Examples of ethers having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phenetole. Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol.

Further, the alcohol used in combination with the chlorinated organic solvent may be linear, branched or cyclic, and among them, saturated aliphatic hydrocarbon is preferable. The hydroxyl group of the alcohol may be any of primary to tertiary. Examples of the alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butanol, 1-pentanol, 2-methyl-2-butanol and cyclohexanol. As the alcohol, fluorine-based alcohol is also used. Examples thereof include 2-fluoroethanol, 2,2,2-trifluoroethanol, 2,2,3,3-tetrafluoro-1-propanol and the like. Further, the hydrocarbon may be linear, branched or cyclic. Either aromatic hydrocarbons or aliphatic hydrocarbons can be used. The aliphatic hydrocarbon may be saturated or unsaturated. Examples of hydrocarbons include cyclohexane, hexane, benzene, toluene and xylene.
As other solvents, for example, the solvents described in JP-A-2007-140497 can be used.

(Preparation of dope)
The dope can be prepared by a general method including processing at a temperature of 0 ° C. or higher (ordinary temperature or high temperature). The dope of the present invention can be prepared using a dope preparation method and apparatus in a normal solvent cast method. In the case of a general method, halogenated hydrocarbon (especially dichloromethane) and alcohol (especially methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butanol, 1) -Pentanol, 2-methyl-2-butanol and cyclohexanol) are preferably used.
The total amount of the thermoplastic resin is preferably adjusted so as to be contained in the obtained polymer solution in an amount of 10 to 40% by mass.
The amount of the thermoplastic resin is more preferably 10 to 30% by mass. Arbitrary additives described later may be added to the organic solvent (main solvent).
The solution can be prepared by stirring the thermoplastic resin and the organic solvent at room temperature (0 to 40 ° C.). The high concentration solution may be stirred under pressure and heating conditions. Specifically, the thermoplastic resin and the organic solvent are placed in a pressure vessel and sealed, and stirred while being heated to a temperature equal to or higher than the boiling point of the solvent at normal temperature and in a range where the solvent does not boil.
The heating temperature is usually 40 ° C or higher, preferably 60 to 200 ° C, more preferably 80 to 110 ° C.

Each component may be coarsely mixed in advance and then placed in a container. Moreover, you may put into a container sequentially. The container needs to be configured so that it can be stirred. The container can be pressurized by injecting an inert gas such as nitrogen gas. Moreover, you may utilize the raise of the vapor pressure of the solvent by heating. Or after sealing a container, you may add each component under pressure.
When heating, it is preferable to heat from the outside of the container. For example, a jacket type heating device can be used. The entire container can also be heated by providing a plate heater outside the container and piping to circulate the liquid.
It is preferable to provide a stirring blade inside the container and stir using this. The stirring blade preferably has a length that reaches the vicinity of the wall of the container. A scraping blade is preferably provided at the end of the stirring blade in order to renew the liquid film on the vessel wall.
Instruments such as a pressure gauge and a thermometer may be installed in the container. Each component is dissolved in a solvent in the container. The prepared dope is taken out of the container after cooling, or taken out and then cooled using a heat exchanger or the like.

(Film production)
Next, a method for producing the first resin layer of the polarizing plate protective film of the present invention using the dope obtained above will be described.
FIG. 2 is a schematic view showing the film production line 20. However, the present invention is not limited to the film production line as shown in FIG. The film production line 20 includes a stock tank 21, a filtration device 30, a casting die 31, a casting band 34 stretched around rotating rollers 32 and 33, a tenter dryer 35, and the like. Further, an ear-cutting device 40, a drying chamber 41, a cooling chamber 42, a winding chamber 43, and the like are arranged.

  An agitator 61 that is rotated by a motor 60 is attached to the stock tank 21. The stock tank 21 is connected to the casting die 31 via the pump 62 and the filtration device 30.

  The width of the casting die 31 is not particularly limited, but is preferably 1.1 to 2.0 times the width of the film as the final product.

  A casting band 34 is provided below the casting die 31 so as to span the rotating rollers 32 and 33. The rotating rollers 32 and 33 are rotated by a driving device (not shown), and the casting band 34 travels endlessly with the rotation.

  In order to set the surface temperature of the casting band 34 to a predetermined value, it is preferable that a heat transfer medium circulation device 63 is attached to the rotary rollers 32 and 33. The casting band 34 is preferably one whose surface temperature can be adjusted to -20 ° C to 40 ° C.

The width of the casting band 34 is not particularly limited, but it is preferable to use a band having a range of 1.1 to 2.0 times the casting width of the dope 22. The length is preferably 20 m to 200 m, the film thickness is 0.5 mm to 2.5 mm, and the surface roughness is preferably polished to be 0.05 μm or less. The casting band 34 is preferably made of stainless steel, and more preferably made of SUS316 so as to have sufficient corrosion resistance and strength. Further, it is preferable to use a film having a film thickness unevenness of the entire casting band 34 of 0.5% or less.
It is also possible to use the rotating rollers 32 and 33 directly as a support.

  The casting die 31, the casting band 34 and the like are accommodated in the casting chamber 64. The casting chamber 64 is provided with a temperature control facility 65 for keeping the internal temperature at a predetermined value, and a condenser (condenser) 66 for condensing and recovering the volatile organic solvent. A recovery device 67 for recovering the condensed and liquefied organic solvent is provided outside the casting chamber 64. Further, it is preferable that a decompression chamber 68 for controlling the pressure of the back surface portion of the casting bead formed from the casting die 31 to the casting band 34 is disposed.

  Air blowing ports 70, 71, 72 are provided near the peripheral surface of the casting band 34 in order to evaporate the solvent in the casting film 69.

  The crossover portion 80 is provided with a blower 81, and the ear-cutting device 40 downstream of the tenter dryer 35 is used for finely cutting the waste at the side end (referred to as an ear) of the cut film 82. Crusher 90 is connected.

  The drying chamber 41 is provided with a number of rollers 91, and an adsorption / recovery device 92 for adsorbing / recovering the solvent gas generated by evaporation is attached. A forced static elimination device (static elimination bar) 93 for adjusting the charged voltage of the film 82 to a predetermined range (for example, −3 kV to +3 kV) is provided downstream of the cooling chamber 42. Furthermore, in this embodiment, a knurling application roller 94 for applying knurling to both edges of the film 82 by embossing is appropriately provided downstream of the forced static elimination device 93. Further, a winding roller 95 for winding the film 82 and a press roller 96 for controlling the tension at the time of winding are provided in the winding chamber 43.

Next, an example of a method for producing the film 82 using the film production line 20 as described above will be described below.
The dope 22 is always made uniform by the rotation of the stirrer 61. The dope 22 may be mixed with additives such as a retardation developer, a plasticizer, and an ultraviolet absorber even during the stirring.

The dope 22 is sent to the filtration device 30 by the pump 62 and filtered there, and then is cast from the casting die 31 onto the casting band 34.
A casting bead is formed from the casting die 31 to the casting band 34, and a casting film 69 is formed on the casting band 34. The temperature of the dope 22 during casting is preferably −10 ° C. to 57 ° C.
The dope 22 from the casting die 31 forms a casting bead and is cast on the casting band 34.
The casting film 69 moves as the casting band 34 moves.

  Next, the casting film 69 is continuously transported to the place where the air blowing port 73 is disposed at the upper part. Dry air is blown toward the casting film 69 from the nozzle of the air blowing port 73.

The casting film 69 is self-supporting as a result of evaporation of the solvent by drying, and is then peeled off from the casting band 34 while being supported by the peeling roller 75 as a wet film 74. The amount of residual solvent at the time of stripping is preferably 20% by mass to 250% by mass based on the solid content.
Thereafter, the transfer section 80 provided with a large number of rollers is conveyed, and the wet film 74 is fed into the tenter dryer 35. In the transfer part 80, the drying of the wet film 74 is advanced by sending the drying air of desired temperature from the air blower 81. FIG. At this time, the temperature of the drying air is preferably 20 ° C to 250 ° C.

The wet film 74 is preferably stretched in the width direction (TD direction) orthogonal to the transport direction (MD direction). By stretching in the width direction, unevenness generated at the time of drying and stripping on the support can be reduced, and a good surface shape can be obtained in the film plane. The stretching ratio in the width direction is preferably 10% or more, more preferably 20% or more, and further preferably 30% or more.
The wet film 74 sent to the tenter dryer 35 is dried while being conveyed by being gripped by clips at both ends thereof. In this case, stretching in the width direction can be performed using a tenter dryer 35.
It is preferable to divide the inside of the tenter dryer 35 into temperature zones and adjust the drying conditions appropriately for each of the zones.
As described above, the wet film 74 can be stretched in the width direction by the crossover 80 and / or the tenter dryer 35.
The film may be stretched in the transport direction, and the wet film 74 is given a draw tension in the transport direction by making the rotational speed of the downstream roller faster than the upstream roller. Can do.
Here, in the transfer section 80 and / or the tenter dryer 35, the wet film 74 is dried without being stretched, and the residual solvent amount in the film is 3.0% by mass or less, preferably 1.0% by mass or less, More preferably, the stretched film may be stretched after a dry film of 0.5% by mass or less, more preferably 0.3% by mass or less, and particularly preferably 0.2% by mass or less.
In addition, when extending | stretching a dry film, after producing a dry film with unstretched and winding up once, you may extend | stretch further.
The polymer film used for stretching may be a dry film or a wet film, but is more preferably a wet film.

  The draw ratio in the width direction is preferably 1.15 to 2.0 times, more preferably 1.3 to 2.0 times, and particularly preferably 1.3 to 1.6 times. The draw ratio in the conveying direction is preferably 1.0 to 1.4. Note that even if the film is not stretched intentionally by applying draw tension in the transport direction, a tension is applied by the transport, and as a result, a film stretched at a magnification of about 1.01 to 1.1 times may be obtained. .

  The temperature during stretching is preferably in the temperature range of Tg ± 30 ° C. with respect to the glass transition temperature Tg of the unstretched polymer film after drying. Here, the glass transition temperature of the unstretched polymer film after drying is the glass transition temperature of the thermoplastic resin, and as described above, 100 to 200 ° C is preferable, and 100 to 150 ° C is more preferable. Stretching in this temperature range has good film handling suitability, and a desired polarizing plate protective film can be produced without breaking the polymer film. By stretching at (Tg−30 ° C.) or more, the film can be prevented from being broken, and variations in Rth within the film can be suppressed. Moreover, by extending | stretching below (Tg + 30 degreeC), extending | stretching can be prevented by the dead weight of a film, and the dispersion | variation in Rth within a film can be suppressed. Moreover, the increase in the total haze and internal haze due to phase separation in the film can be suppressed. The temperature during stretching is preferably a temperature range of Tg ± 25 ° C., and more preferably a temperature range of Tg ± 20 ° C.

As described above, the stretching treatment may be performed in a drying process after the wet film 74 is formed and then passed through the transfer section 80 and the tenter dryer 35, or may be performed after the wet film 74 is wound up after being dried.
The casting condition is preferably performed under such a condition that the film thickness is 10 to 200 μm when the film is produced without being stretched, more preferably 20 to 150 μm, still more preferably 30 to 120 μm, 40 Most preferably, the conditions are set to ˜100 μm.
If it is within this range, the film thickness after stretching can be reduced, the change in retardation at the time of humidity change, high temperature and high temperature and high humidity environment is reduced, and an inexpensive film with less resin to be used can be produced. Therefore, it is preferable.

  The wet film 74 is dried to a predetermined residual solvent amount by the tenter dryer 35 and then sent to the downstream side as a film 82. Both ends of the film 82 are cut at both edges by the edge-cutting device 40. The cut side end portion is sent to the crusher 90 by a cutter blower (not shown). The crusher 90 pulverizes the film side end portion into a chip. Since this chip is reused for dope preparation, this method is effective in terms of cost. In addition, although it can also abbreviate | omit about the cutting process of this film both ends, it is preferable to carry out in any one from the said casting process to the process of winding up the said film.

  The film 82 from which both side ends have been removed is sent to the drying chamber 41 and further dried. Although the temperature in the drying chamber 41 is not specifically limited, It is preferable that it is the range of 50 to 160 degreeC. In the drying chamber 41, the film 82 is conveyed while being wound around a roller 91, and the solvent gas generated by evaporation here is adsorbed and recovered by an adsorption recovery device 92. The air from which the solvent component has been removed is blown again as dry air inside the drying chamber 41. The drying chamber 41 is more preferably divided into a plurality of sections in order to change the drying temperature.

  The film 82 is cooled to approximately room temperature in the cooling chamber 42. A humidity control chamber (not shown) may be provided between the drying chamber 41 and the cooling chamber 42, and air adjusted to a desired humidity and temperature can be blown onto the film 82 in the humidity control chamber. It is preferable. Thereby, generation | occurrence | production of the curling of the film 82 and the winding defect at the time of winding can be suppressed.

  Further, the forcible charge removal device (charge removal bar) 93 sets the charged voltage while the film 82 is being conveyed to a predetermined range (for example, −3 kV to +3 kV). Furthermore, it is preferable to provide a knurling roller 94 and to impart knurling to both edges of the film 82 by embossing.

  Finally, the film 82 is taken up by the take-up roller 95 in the take-up chamber 43. At this time, it is preferable to wind the sheet while applying a desired tension with the press roller 96. More preferably, the tension is gradually changed from the start to the end of winding. The film 82 to be wound is preferably at least 100 m in the longitudinal direction (casting direction). The width of the film 82 is preferably 600 mm or more, more preferably 1100 mm or more and 2900 mm or less, and further preferably 1800 mm or more and 2500 mm or less.

  In the solution casting method, at the time of casting the dope, two or more kinds of dopes can be simultaneously co-casting or sequentially stacking co-casting. Furthermore, you may combine both casting. When performing simultaneous lamination and co-casting, a casting die to which a feed block is attached may be used, or a multi-manifold casting die may be used. It is preferable that at least one of the thickness of the layer on the air surface side and the thickness of the layer on the support side is 0.5% to 30% of the film thickness of the entire film. . Furthermore, when performing simultaneous lamination co-casting, it is preferable that the high-viscosity dope is wrapped with the low-viscosity dope when the dope is cast from the die slit to the support. Moreover, when performing simultaneous lamination | stacking co-casting, it is preferable that the dope which contact | connects an external field has a larger alcohol composition ratio than an internal dope among the casting beads formed from a die slit to a support body.

From casting die, decompression chamber, support structure, co-casting, peeling method, stretching, drying conditions for each process, handling method, curl, winding method after flatness correction, solvent recovery method, film recovery method The details are described in paragraphs [0617] to [0889] of JP-A-2005-104148.
Moreover, although the example of the manufacturing method of the polarizing plate protective film of this invention demonstrated above by the example which cast the dope on the band, you may cast a dope on a drum.

<Coating method>
Next, a case where only the first resin layer is formed as a film by a method such as melt film formation or solution film formation, and the second resin layer is sequentially provided will be described. The second resin layer is prepared by dissolving the above-described resin composition using a solvent that can be suitably used as a solvent in the above-described solution casting method, and applying them sequentially or simultaneously to a film that becomes a core layer. It can also be obtained by drying and removing the solvent. The total amount of the resin composition in the coating solution is preferably adjusted so that it is contained in the resulting coating solution in an amount of 5 to 50% by mass. The solution can be prepared by stirring the thermoplastic resin and the organic solvent at room temperature (0 to 40 ° C.). Coating may be performed using a method such as a bar coater, a blade coater, a die coater, or a gravure coater, or a method such as curtain coating or dip coating. The drying conditions are appropriately set so as to have no residual volatile matter after adjusting the temperature, time, wind speed on the coating film, etc., but the drying temperature is preferably in the range of 40 ° C to 100 ° C. Moreover, providing the functional layer which is mentioned later, such as an easily bonding layer and a UV absorption layer, between the 1st resin layer and the 2nd resin layer does not restrict | limit the content of this invention.

<Surface treatment>
The polarizing plate protective film can achieve improved adhesion between the polarizing plate protective film and other layers (for example, a polarizer, an undercoat layer, and a back layer) by performing a surface treatment depending on the case. For example, glow discharge treatment, ultraviolet irradiation treatment, corona treatment, flame treatment, acid or alkali treatment can be used. The glow discharge treatment here may be low-temperature plasma that occurs under a low pressure gas of 10 ^{−3 to} 20 Torr, and plasma treatment under atmospheric pressure is also preferred. A plasma-excitable gas is a gas that is plasma-excited under the above conditions, and includes chlorofluorocarbons such as argon, helium, neon, krypton, xenon, nitrogen, carbon dioxide, tetrafluoromethane, and mixtures thereof. It is done. Details of these are described in detail in pages 30 to 32 in the Japan Institute of Invention Disclosure Technical Bulletin (Public Technical Number 2001-1745, published on March 15, 2001, Japan Institute of Invention), and are preferably used in the present invention. be able to.

<Functional layer>
Moreover, the polarizing plate protective film of this invention may laminate | stack a functional layer with a film thickness of 0.1-20 micrometers. The type of the functional layer is not particularly limited, but a hard coat layer, an antireflection layer (a layer having a adjusted refractive index such as a low refractive index layer, a medium refractive index layer, or a high refractive index layer), an antiglare layer, an antistatic layer, Examples include an ultraviolet absorbing layer. A functional layer can provide a functional layer between any one surface of a polarizing plate protective film, a 1st resin layer, and a 2nd resin layer.
The functional layer may be a single layer or a plurality of layers. The method of laminating the functional layer is not particularly limited, but co-casting of a thermoplastic resin and a polarizing plate protective film containing the resin modifying additive, or a polarizing plate comprising a thermoplastic resin and the resin modifying additive. It is preferable to coat and provide on a protective film.
When the functional layer is formed by coating and drying, it is preferable to use a monomer having an ethylenically unsaturated group as a binder. The monomer may be monofunctional or polyfunctional. Among them, it is preferable to use a polymerizable polyfunctional monomer, more preferably a photopolymerizable polyfunctional monomer, and particularly preferably a coating solution containing a monomer having two or more (meth) acryloyl groups. .

Specific examples of the monomer having two or more (meth) acryloyl groups include (meth) alkylene glycols such as neopentyl glycol acrylate, 1,6-hexanediol (meth) acrylate, and propylene glycol di (meth) acrylate. Acrylic acid diesters;
(Meth) acrylic acid diesters of polyoxyalkylene glycols such as triethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate;
(Meth) acrylic acid diesters of polyhydric alcohols such as pentaerythritol di (meth) acrylate;
(Meth) acrylic acid diesters of ethylene oxide or propylene oxide adducts such as 2,2-bis {4- (acryloxy · diethoxy) phenyl} propane and 2-bis {4- (acryloxy · polypropoxy) phenyl} propane ;
Etc.

  Furthermore, epoxy (meth) acrylates, urethane (meth) acrylates, and polyester (meth) acrylates are also preferably used as the photopolymerizable polyfunctional monomer.

Among these, esters of polyhydric alcohol and (meth) acrylic acid are preferable. A polyhydric alcohol means a dihydric or higher alcohol.
More preferably, a polyfunctional monomer having 3 or more (meth) acryloyl groups in one molecule is preferable. For example, pentaerythritol tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, ethylene oxide modified trimethylolpropane tri (meth) acrylate, propylene oxide modified trimethylolpropane tri (meth) acrylate, Ethylene oxide modified tri (meth) acrylate phosphate, trimethylolethane tri (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (Meth) acrylate, 1,2,3-cyclohexanetetramethacrylate, polyurethane polyacrylate, Li ester polyacrylate, caprolactone-modified tris (acryloyloxyethyl) isocyanurate.

  Furthermore, resins having three or more (meth) acryloyl groups, such as relatively low molecular weight polyester resins, polyether resins, acrylic resins, epoxy resins, urethane resins, alkyd resins, spiroacetal resins, polybutadiene resins, polythiol polyene resins And oligomers or prepolymers such as polyfunctional compounds such as polyhydric alcohols.

  As other polyfunctional monomers, for example, dendrimers described in JP-A-2005-76005 and JP-A-2005-36105 can be used.

As the polyfunctional monomer, esters of polyhydric alcohol and (meth) acrylic acid, and amides of polyhydric alcohol and isocyanate containing a plurality of (meth) acryloyl groups are also preferably used.
The polyhydric alcohol is not particularly limited, but is preferably an aliphatic alcohol, and more preferably an alcohol having a cyclic aliphatic hydrocarbon group. The aliphatic group of the monocyclic alicyclic alcohol is preferably a cycloalkyl group having 3 to 8 carbon atoms, and examples thereof include a cyclopentyl group, a cyclohexyl group, a cyclobutyl group, and a cyclooctyl group.
Examples of the aliphatic group of the polycyclic alicyclic alcohol include a group having a bicyclo, tricyclo, tetracyclo structure or the like having 5 or more carbon atoms, and a cycloalkyl group having 6 to 20 carbon atoms is preferable. Adamantyl group, norbornyl group, dicyclopentyl group, tricyclodecanyl group, tetracyclododecyl group, central skeleton of compounds described in claims of JP-A-2006-215096, compound described in JP-A-2001-10999 And the like. A part of carbon atoms in the cycloalkyl group may be substituted with a hetero atom such as an oxygen atom.
Among them, examples of the polycyclic alcohol include an adamantyl group, a norbornyl group, a dicyclopentyl group, a tricyclodecanyl group, a tetracyclododecyl group, and a central skeleton of the compound described in the claims of JP-A-2006-215096. Polyhydric alcohols having a central skeleton of the compounds described in JP-A No. 2001-10999 are particularly preferred from the viewpoint of reducing moisture permeability.

  Two or more kinds of polymerizable polyfunctional monomers may be used in combination. Polymerization of the monomer having an ethylenically unsaturated group can be performed by irradiation with ionizing radiation or heating in the presence of a photo radical initiator or a thermal radical initiator.

  It is preferable to use a photopolymerization initiator for the polymerization reaction of the photopolymerizable polyfunctional monomer. As the photopolymerization initiator, a photoradical polymerization initiator and a photocationic polymerization initiator are preferable, and a photoradical polymerization initiator is particularly preferable.

  It is also preferable to use the polymerizable polyfunctional monomer in combination with a monofunctional monomer.

  As the monofunctional monomer, a monomer having one (meth) acryloyl group is preferable, and a monomer having one (meth) acryloyl group is usually obtained from a monovalent alcohol and acrylic acid.

The monohydric alcohol may be an aromatic alcohol or an aliphatic alcohol.
As monohydric alcohol, methyl alcohol, n-propyl alcohol, iso-propyl alcohol, n-butyl alcohol, tert-butyl alcohol, n-amyl alcohol, diacetone alcohol, 1-methoxy-2-propanol, furfuryl alcohol 2-octanol, 2-ethylhexanol, nonanol, n-decanol, undecanol, n-dodecanol, trimethylnonyl alcohol, benzyl alcohol, phenethyl alcohol, ethylene glycol monoisoamyl ether, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, Examples include ethylene glycol monohexyl ether.
Moreover, about the aliphatic part of aliphatic alcohol, cycloaliphatic may be sufficient. The cycloaliphatic may be monocyclic, polycyclic, or may be bridged in the case of polycyclic. As the monocyclic type, a cycloalkyl group having 3 to 8 carbon atoms is preferable, and examples thereof include a cyclopentyl group, a cyclohexyl group, a cyclobutyl group, and a cyclooctyl group. Examples of the polycyclic type include groups having a bicyclo, tricyclo or tetracyclo structure having 5 or more carbon atoms, and a cycloalkyl group having 6 to 20 carbon atoms is preferable, for example, an adamantyl group, norbornyl group, dicyclopentyl group. , Tricyclodecanyl group, tetracyclododecyl group, central skeleton of the compound described in the claims of JP-A-2006-215096, central skeleton of the compound described in JP-A-2001-10999, and the like. . A part of carbon atoms in the cycloalkyl group may be substituted with a hetero atom such as an oxygen atom.

  The monovalent alcohol, whether it is an aromatic alcohol or an aliphatic alcohol, preferably has 6 or more carbon atoms.

  As (meth) acrylic acid, acrylic acid and methacrylic acid are preferable.

  In addition, various additions have been made to make an antireflection layer (a layer having a adjusted refractive index such as a low refractive index layer, a medium refractive index layer, a high refractive index layer), an antiglare layer, an antistatic layer, or an ultraviolet absorbing layer as a functional layer. A thing may be added.

  The thickness of the functional layer is more preferably 0.01 to 100 μm, and particularly preferably 0.02 to 50 μm. Furthermore, as a functional layer which reduces a water vapor transmission rate, it is more preferable that it is 0.1-20 micrometers in thickness.

The polarizing plate protective film of the present invention can also be used as an optical compensation film for liquid crystal display devices. A liquid crystal display device includes a liquid crystal cell having a liquid crystal supported between two electrode substrates, two polarizing elements disposed on both sides thereof, and at least one sheet between the liquid crystal cell and the polarizing element. More preferably, the polarizing plate protective film of the present invention is arranged as an optical compensation film. These liquid crystal display devices are preferably TN, IPS, FLC, AFLC, OCB, STN, ECB, VA and HAN mode liquid crystal display devices, more preferably TN, OCB, IPS and VA mode liquid crystal display devices. A mode liquid crystal display device is more preferable.
In that case, you may provide various functional layers to the polarizing plate protective film of this invention. Examples of the functional layer include an antistatic layer, a cured resin layer (transparent hard coat layer), an antireflection layer, an easy adhesion layer, an antiglare layer, an optically anisotropic layer, an alignment layer, and a liquid crystal layer. These functional layers and materials thereof include surfactants, slip agents, matting agents, antistatic layers, hard coat layers, etc., and are disclosed by the Japan Institute of Technology (Technical No. 2001-1745, March 15, 2001). (Nippon Issuance, Invention Association), page 32 to page 45, and can be preferably used in the present invention.

[Polarizer]
The polarizing plate of the present invention includes at least one polarizing plate protective film of the present invention as a protective film for a polarizer. The polarizing plate has a configuration in which the polarizer and the polarizing plate protective film described above are attached to the polarizer, and the first resin layer is disposed on the polarizer side.
The polarizing plate protective film of the present invention can be used as a polarizing plate protective film. In this case, it can serve as an optical compensation film for a liquid crystal display device and a protective film for a polarizing plate. When using as a protective film for polarizing plates, the production method of a polarizing plate is not specifically limited, It can produce by a general method. There is a method in which the obtained polarizing plate protective film is subjected to alkali treatment, and a polarizer prepared by immersing and stretching a polyvinyl alcohol film in an iodine solution is bonded to both surfaces using a completely saponified polyvinyl alcohol aqueous solution. Instead of alkali treatment, easy adhesion processing as described in JP-A-6-94915 and JP-A-6-118232 may be performed. Further, the surface treatment as described above may be performed.
Examples of the adhesive used to bond the protective film treated surface and the polarizer include polyvinyl alcohol adhesives such as polyvinyl alcohol and polyvinyl butyral, vinyl latexes such as butyl acrylate, and the like.
The polarizing plate is composed of a polarizer and a protective film that protects both surfaces of the polarizer, and further includes a protective film bonded to one surface of the polarizing plate and a separate film bonded to the other surface. The protective film and the separate film are used for the purpose of protecting the polarizing plate at the time of shipping the polarizing plate and at the time of product inspection. In this case, the protect film is bonded for the purpose of protecting the surface of the polarizing plate, and is used on the side opposite to the surface where the polarizing plate is bonded to the liquid crystal plate. Moreover, a separate film is used in order to cover the adhesive layer bonded to a liquid crystal plate, and is used for the surface side which bonds a polarizing plate to a liquid crystal plate.
In a liquid crystal display device, a substrate including a liquid crystal cell is usually disposed between two polarizing plates. A protective film for a polarizing plate to which the polarizing plate protective film of the present invention is applied protects either of the two polarizing plates. Although it can be used as a film, it is preferable that it is used as a protective film arrange | positioned with respect to a polarizer at the liquid crystal cell side among two protective films of each polarizing plate.

(Optical compensation film)
The polarizing plate protective film of the present invention can be used in various applications, and is particularly effective when used as an optical compensation film for a liquid crystal display device. The optical compensation film is generally used for a liquid crystal display device and refers to an optical material that compensates for a retardation, and is synonymous with a retardation plate, an optical compensation sheet, and the like. The optical compensation film has birefringence and is used for the purpose of removing the color of the display screen of the liquid crystal display device or improving the viewing angle characteristics.

  The polarizing plate protective film of the present invention may itself be an optical compensation film, or may be used as a support for the optical compensation film, and an optically anisotropic layer may be provided thereon. The optically anisotropic layer is not limited to the optical performance or driving method of the liquid crystal cell of the liquid crystal display device in which the polarizing plate protective film of the present invention is used, and any optical anisotropy required as an optical compensation film Layers can also be used in combination. The optically anisotropic layer used in combination may be formed from a composition containing a liquid crystalline compound or may be formed from a thermoplastic film having birefringence.

[Liquid Crystal Display]
The liquid crystal display device of the present invention includes a liquid crystal cell and the polarizing plate of the present invention disposed in at least one of the liquid crystal cells, and the polarizing plate protective film of the present invention contained in the polarizing plate is the outermost layer. It is arranged as follows.

(General liquid crystal display device configuration)
The liquid crystal display device includes a liquid crystal cell having a liquid crystal supported between two electrode substrates, two polarizing plates disposed on both sides thereof, and, if necessary, between the liquid crystal cell and the polarizing plate. At least one optical compensation film is arranged.
The liquid crystal layer of the liquid crystal cell is usually formed by sealing liquid crystal in a space formed by sandwiching a spacer between two substrates. The transparent electrode layer is formed on the substrate as a transparent film containing a conductive substance. The liquid crystal cell may further be provided with a gas barrier layer, a hard coat layer, or an undercoat layer (undercoat layer) (used for adhesion of the transparent electrode layer). These layers are usually provided on the substrate. The substrate of the liquid crystal cell generally has a thickness of 50 μm to 2 mm.

(Types of liquid crystal display devices)
The film of the present invention can be used for liquid crystal cells in various display modes. TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), AFLC (Anti-Ferroly Liquid Liquid Crystal), OCB (Optically QuantNW). Various display modes such as ECB (Electrically Controlled Birefringence) and HAN (Hybrid Aligned Nematic) have been proposed. In addition, a display mode in which the above display mode is oriented and divided has been proposed. The polarizing plate protective film of the present invention is effective in any display mode liquid crystal display device. Further, it is effective in any of a transmissive type, a reflective type, and a transflective liquid crystal display device.

  The features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

(Thermoplastic resin)
In the present invention, the following thermoplastic resins were used in Examples and Comparative Examples.
・ PMMA resin (Made by Mitsubishi Rayon Co., Ltd., trade name: Dinar BR88)
・ PS resin (product name: High Branch XC540HB, manufactured by DIC)
MS resin 1 (styrene-methyl methacrylate copolymer) (trade name Estyrene MS200, manufactured by Nippon Steel & Sumikin Chemical Co., Ltd. (styrene: methyl methacrylate = 8: 2 copolymer))
MS resin 2 (styrene-methyl methacrylate copolymer) (trade name Estyrene MS600, manufactured by Nippon Steel & Sumikin Chemical Co., Ltd. (styrene: methyl methacrylate = 4: 6 copolymer))
・ Norbornene resin (product name Arton F5023, manufactured by JSR)
Acrylic resin 1 (copolymer of methyl methacrylate / styrene / maleic anhydride) (manufactured by Asahi Kasei Chemicals, trade name Delpet 980N)
・ Acrylic resin 2 (Methyl methacrylate / styrene / glutarimide copolymer)

(Synthesis of cellulose ester CE-1)
In addition, cellulose ester CE-1 was synthesized and used as a cellulose ester in the following manner.
Sulfuric acid (7.8 parts by mass with respect to 100 parts by mass of cellulose) was added to cellulose as a catalyst, and carboxylic acid serving as a raw material for the acyl substituent was added to carry out an acylation reaction at 40 ° C. At this time, the substitution degree of the acetyl group and the propionyl group was adjusted by adjusting the amount of the carboxylic acid. In addition, aging was performed at 40 ° C. after acylation. Further, the low molecular weight component of this cellulose ester was removed by washing with acetone. As a result, cellulose ester CE-1 having an acyl group total substitution degree of 2.75, an acetyl substitution degree of 0.19, a propionyl substitution degree of 2.56 and a molecular weight of 200,000 was obtained.

(Preparation of acrylic resin 2)
According to the manufacture example 1 in the Example of Unexamined-Japanese-Patent No. 2011-127097, modification was added to the methyl methacrylate / styrene copolymer (styrene ratio 18%), and the acrylic resin 2 which partially cyclized the cyclization was obtained. The composition was (styrene / methyl methacrylate / methacrylic acid / glutaric anhydride = 18/76 / 2.6 / 2.9).

(UV absorber)
The ultraviolet absorber described below was used.
UV agent 1: Tinuvin 328 (Ciba Specialty Chemicals Co., Ltd.)

(Brittleness improver)
Moreover, the brittleness improving agent described below was used.
・ Brittleness improver 1: LA4285 manufactured by Kuraray Co., Ltd.

[Comparative Example 1]
<Preparation of polarizing plate protective film 100>
(Dope adjustment)
The composition described below was put into a mixing tank and stirred while heating to dissolve each component to prepare a dope.

(Dope composition)
-PMMA resin 100 parts by mass-UV agent 1 2.4 parts by mass-Brittleness improving agent 1 5.0 parts by mass-Dichloromethane 534 parts by mass-Methanol 46 parts by mass

(Film formation)
Using the band casting apparatus as shown in FIG. 2, the prepared dope was uniformly cast from a casting die onto a stainless steel endless band (casting support) having a width of 2000 mm. When the amount of residual solvent in the dope reaches 15% by mass, it is peeled off as a polymer film from the casting support, transported without being actively stretched by a tenter, and dried at 120 ° C. in a drying zone. It was.

(Examples 1-3)
<Preparation of polarizing plate protective films 101-103>
As an example, a polarizing plate protective film 100 produced in Comparative Example 1 was used as a first resin layer, and a microgravure coater was used so that the following coating liquid composition 1 was a dry film thickness of 1.5 μm on one side. It apply | coated and dried at 90 degreeC for 5 minute (s), the 2nd resin layer was formed, and the polarizing plate protective film 101 was obtained.
Hereinafter, in the production of the polarizing plate protective film 101, the polarizing plate protective film 102 was similarly used except that the coating liquid composition 2 was used instead of the coating liquid composition 1, and the same except that the coating liquid composition 3 was used. Thus, a polarizing plate protective film 103 was obtained.
These layer configurations are shown in Table 1 below.

(Coating liquid composition 1)
PS resin 7 parts by mass (manufactured by DIC, trade name High Branch XC540HB)
・ Methyl ethyl ketone 30 mass parts ・ Toluene 63 mass parts

(Coating liquid composition 2)
MS resin 1 (styrene-methyl methacrylate copolymer) 7 parts by mass (trade name Estyrene MS200, manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.)
(Styrene: methyl methacrylate = 8: 2 copolymer))
・ Methyl ethyl ketone 30 mass parts ・ Toluene 63 mass parts

(Coating liquid composition 3)
・ 7 parts by mass of norbornene-based resin (manufactured by JSR, trade name Arton F5023)
・ 93 parts by mass of methyl ethyl ketone

[Comparative Examples 2 to 4]
In preparation of the polarizing plate protective film 100 described above, the PMMA resin was changed as shown in Table 1, and the dichloromethane and methanol as solvents were changed to only dichloromethane, and then the solid content concentration was adjusted to 20% by mass. The polarizing plate protective films 120, 130, and 140 were obtained through the same process as in Example 1.

[Examples 4 to 12]
The coating liquids 1 to 3 are respectively applied to the polarizing plate protective films 120, 130, and 140 in the same manner as the polarizing plate protective films 101 to 103, and the polarizing plates 121 to 123 and 131 to 133 are applied. 141-143 were obtained.

[Comparative Examples 5 to 10]
In preparation of the polarizing plate protective film 100 described above, the PMMA resin was changed as shown in Table 1, and the dichloromethane and methanol as solvents were changed to only dichloromethane, and then the solid content concentration was adjusted to 20% by mass. The polarizing plate protective films 150, 160, and 170 were obtained through the same process as in No. 1. Moreover, the coating liquid composition 4 was apply | coated to the both surfaces of obtained polarizing plate protective film 150,160,170 in the same way as the above-mentioned polarizing plate protective film 101-103, and polarizing plate protective film 151, 161 and 171 were obtained.

(Coating liquid composition 4)
・ PMMA resin 7 parts by mass (Made by Mitsubishi Rayon Co., Ltd., trade name Dianar BR88)
・ Methyl ethyl ketone 30 mass parts ・ Toluene 63 mass parts

[Comparative Example 11]
<Creation of polarizing plate protective film 300>
A polarizing plate protective film 300 was obtained in the same manner as the polarizing plate protective film 100 except that the dope was prepared as follows.
(Dope composition)
Cellulose ester CE-1 30 parts by mass PMMA resin 70 parts by mass (manufactured by Mitsubishi Rayon Co., Ltd., trade name Dianal BR88)
-UV agent 1 2 parts by mass-Dichloromethane 447 parts by mass-Ethanol 61 parts by mass The total amount of cellulose ester and PMMA resin was 100 parts by mass.

[Example 13]
The coating liquid 1 was apply | coated to the above-mentioned polarizing plate protective film 300 in the same way as having obtained the above-mentioned polarizing plate protective films 101-103, and the polarizing plate protective film 301 was obtained.

[Examples 14 and 15]
On the polarizing plate film 100, the following coating liquid 5 and coating liquid 6 were applied in the same manner as the above polarizing plate protective films 101 to 103 to obtain polarizing plate protective films 105 and 106.

(Coating liquid composition 5)
PS resin 7 parts by mass (manufactured by DIC, trade name High Branch XC540HB)
Hydrophobizing agent 1 1 part by mass (1,3-diphenylbenzene)
・ Methyl ethyl ketone 30 mass parts ・ Toluene 63 mass parts

(Coating liquid composition 6)
PS resin 7 parts by mass (manufactured by DIC, trade name High Branch XC540HB)
・ Hydrophobizing agent 2 1 part by mass (product of BASF, trade name: CHIMASSORB 81)
・ Methyl ethyl ketone 30 mass parts ・ Toluene 63 mass parts

[Evaluation of polarizing plate protective film]
The film thickness was measured for each of the layers constituting the polarizing plate protective film of each of Examples and Comparative Examples, and the following physical property measurements and evaluations were performed. The results are shown in Table 1 below.

(Measurement of equilibrium moisture content)
In this example, a film sample 7 mm × 35 mm was placed in an atmosphere at 25 ° C. and 80% relative humidity for a sufficient time, and then a moisture measuring device, sample drying apparatus “CA-03” and “VA-05” {both Mitsubishi. The amount of water (g) measured by the Karl Fischer method was obtained by dividing by the sample mass (g). The equilibrium moisture content of each layer was not measured directly, but a value obtained by measuring the equilibrium moisture content when each layer was a single layer film was used.

(Measurement method of oxygen permeability coefficient)
The oxygen permeation amount of the film was measured by attaching a test piece cut to a diameter of 1.5 cm through silicon grease thinly applied to an oxygen electrode (MODEL3600, PFA manufactured by Orbis Fair Laboratories), and reducing the oxygen reduction current in a steady state. From the output value, the oxygen transmission amount was determined. Conversion of the output current value to the oxygen permeation coefficient was obtained by creating a calibration curve using a sample with a known permeation amount. The measurement was performed in an environment of 25 ° C. and a relative humidity of 60%. The oxygen permeability coefficient of each layer was not measured directly, but a value obtained by measuring the oxygen permeability coefficient when each layer was a single layer film was used.

(Water permeability of film)
The moisture permeability of the film was measured under the conditions of 40 ° C. and relative humidity 90% based on JIS Z-0208.
The moisture permeability decreases as the film thickness increases, and increases as the film thickness decreases. Therefore, it is necessary to convert the samples having different film thicknesses by setting the reference to 40 μm. The film thickness was converted according to the following formula.
Mathematical formula: moisture permeability in terms of 40 μm = measured moisture permeability × measured film thickness (μm) / 40 (μm).
For the polarizing plate protective film including two or more layers, A is the case where the layer (first resin layer) side to be disposed on the panel side is measured as the high humidity side, and the layer (first layer) to be disposed on the panel side. 1 was measured as the low-humidity side as B, and both were measured. The results are shown in Table 1.

(Polarization degree of polarizing plate)
Each polarizing plate protective film and a 70 μm-thick norbornene resin film (ZEONOR manufactured by Nippon Zeon Co., Ltd., water vapor transmission rate is 5 g / m ² / day) are bonded to each side of the PVA polarizer using aqueous PVA glue. A polarizing plate was created. The polarizing plate protective film was subjected to corona treatment on the adhesive surface as necessary. For the polarizing plate protective films 101, 102, 103, 121, 131, 141, 201, the b layer side was used as the adhesive surface. Bonding was performed by drying these after pressure bonding with a pair of rolls. The pressure of the roll pair was 0.1 MPa, the drying conditions were a temperature of 70 ° C., and a drying time of 2 minutes.
The obtained polarizing plate was measured by DOT-3 manufactured by Oji Scientific Instruments, and the degree of polarization was calculated. The evaluation results are shown in Table 2 below.

[Panel Evaluation]
<Implementation to IPS panel>
The upper and lower polarizing plates of the IPS mode liquid crystal cell (manufactured by LGD 42LS5600) were peeled off, and the polarizing plate was attached so that the ZRD 40 was on the liquid crystal cell side. The crossed nicols were arranged so that the transmission axis of the upper polarizing plate was in the vertical direction and the transmission axis of the lower polarizing plate was in the horizontal direction.
In addition, the structure of the polarizing plate of each Example and a comparative example at the time of mounting to an IPS panel was described in following Table 3.

(Panel warpage amount after aging in high temperature and high humidity environment (Δ Panel warpage amount))
The liquid crystal display device was allowed to pass for 72 hours at 50 ° C. and a relative humidity of 80%, and then the liquid crystal display device was disassembled in an environment of 25 ° C. and a relative humidity of 60%, and the amount of warpage of the panel was measured.
Further, Table 2 shows the difference between the amount of warpage of the panel when the polarizing plate protective film having the three-layer structure and the amount of warping of the panel when using the polarizing plate protective film having the one-layer structure are Δ panel warpage amounts. Described. In addition, the polarizing plate protective film made into 1 layer structure has only the intermediate | middle layer of 3 layer structure used as a comparison object as a layer structure. When the panel warpage amount is small as compared with the polarizing plate protective film having a single layer structure, the Δ panel warpage amount is represented by a negative value. The Δ panel warpage amount varies depending on the size of the liquid crystal cell and the like, but is preferably −0.1 mm or less, more preferably −0.5 mm or less when configured in the present embodiment.

According to Table 3 described above, in Examples 1 to 3, the amount of panel warpage was clearly suppressed as compared with Comparative Example 1 in which the laminated structure was not used. On the other hand, in the case of a laminated structure whose physical property relationship at each layer thickness of 40 μm did not satisfy the requirements of the invention, there is no significant change in the amount of warpage with the polarizing plate protective film before lamination. Further, when the moisture permeability B measured when the layer (second resin layer) side to be arranged on the panel side is measured as the high humidity side exceeds 250 g / m ² / day, there is an improvement effect due to the lamination, but the warp There are concerns about exceeding the tolerance.

  Also, according to Table 2 above, when heat drying was applied with a combination of a polarizing plate protective film and a polarizer, Examples and Comparative Examples 1 to 11 show that the polarizing plate protective film exhibits a certain degree of polarization. Although the internal moisture is adjusted, there is no effect on the adhesion between the pressure-sensitive adhesive and the polarizer. However, in Comparative Example 12, although the degree of polarization is reduced and the effect of suppressing panel warpage is seen, the internal moisture is excessively increased. It turns out that it is made to stay. It is estimated that this has a harmful effect on the polarizer performance.

  From the above, if the polarizing plate protective film of the present invention is used, the moisture permeability between the front and back sides is different, so that stable polarizing plate performance can be maintained even under the processing conditions of the polarizing plate while suppressing the amount of warping of the panel. It can be shown that you can.

  According to this invention, the polarizing plate protective film which exhibits the outstanding moisture-permeation reduction effect can be obtained. Moreover, if the polarizing plate protective film of this invention is used, generation | occurrence | production of the curvature of the panel containing a liquid crystal cell etc. can be suppressed. For this reason, this invention can be utilized suitably for a liquid crystal display device etc., and its industrial applicability is high.

DESCRIPTION OF SYMBOLS 1 1st resin layer 2 2nd resin layer 5 Polarizer 10 Polarizing plate protective film 20 Film production line 21 Stock tank 22 Dope 30 Filtration device 31 Casting die 32 Rotating roller 33 Rotating roller 34 Casting band 35 Tenter type drying Machine 40 Ear opener 41 Drying chamber 42 Cooling chamber 43 Winding chamber 60 Motor 61 Stirrer 62 Pump 63 Heat transfer medium circulating device 64 Casting chamber 65 Temperature control facility 66 Condenser (condenser)
67 Recovery device 68 Decompression chamber 69 Casting film 70 Blower port 71 Blower port 72 Blower port 73 Blower port 74 Wet film 75 Stripping roller 80 Crossing part 81 Blower 82 Film 90 Crusher 91 Roller 92 Adsorption / recovery device 93 bar)
94 Knurling roller 95 Winding roller 96 Press roller

Claims (10)

A polarizing plate protective film comprising a first resin layer and a second resin layer,
When the equilibrium moisture content at 25 ° C. and 80% relative humidity of the first resin layer is Xa, and the equilibrium moisture content at 25 ° C. and 80% relative humidity of the second resin layer is Xb, Xa> Xb Yes,
When the oxygen permeability coefficient of the first resin layer at 25 ° C. and a relative humidity of 60% is Ya, and the oxygen permeability coefficient of the second resin layer at 25 ° C. and a relative humidity of 60% is Yb, Ya <Yb Yes,
The moisture permeability measured when the first resin layer side is measured at 40 ° C. and a relative humidity of 90% is A, and the second resin layer side is measured at 40 ° C. and a relative humidity of 90%. When the water vapor transmission rate is B, A> B, and B is 250 g / m ² / day or less. However, the water vapor transmission rate was measured according to JIS 0208. The value is a value converted to a film thickness of 40 μm.).   2. The polarizing plate protective film according to claim 1, wherein the equilibrium moisture content Xb of the second resin layer at 25 ° C. and a relative humidity of 80% is 0.3% or less. 3. The polarizing plate protective film according to claim 1, wherein the first resin layer has an oxygen permeability coefficient Ya of 10 cc · mm / m ² / day / atm or less at 25 ° C. and a relative humidity of 60%. . 4. The water vapor transmission rate B measured when the first resin layer side is 40 ° C. and the relative humidity is 90% is 90 g / m ² / day or less. 5. (However, the moisture permeability is a value obtained by converting a value measured according to JIS 0208 into a film thickness of 40 μm.).   Either the said 1st resin layer and the said 2nd resin layer contain a resin modification additive, The polarizing plate protective film of any one of Claims 1-4 characterized by the above-mentioned.   The polarizing plate protective film according to any one of claims 1 to 5, wherein the polarizing plate protective film has a structure in which the first resin layer and the second resin layer are laminated adjacently in order.   The average film thickness of the first resin layer is α, and the average film thickness of the second resin layer is β, α> β is satisfied. The polarizing plate protective film of description.   The polarizing plate protective film according to claim 1, wherein the total thickness of the first resin layer and the second resin layer is 60 μm or less. It has the polarizing plate protective film of any one of Claims 1-8, and a polarizer,
The polarizing plate, wherein the first resin layer of the polarizing plate protective film is disposed on the polarizer side.   A liquid crystal display device comprising: a liquid crystal cell; and the polarizing plate according to claim 9 disposed on at least one surface of the liquid crystal cell.

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