JP2009251017A - Elliptical polarizing plate, and liquid crystal display using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an elliptical polarizing plate having high brightness of the extent capable of obtaining sufficient visibility even in the outdoors, and capable of preventing a contrast from getting worse even after irradiation with a direct type backlight for a long time, and a liquid crystal display of vertical alignment mode using the same. <P>SOLUTION: An in-plane phase difference in 550 nm of a protection film A is 125-150 nm, out of the two protection films A, B with an absorption type linear polarizer therebetween, and a smaller angle is about 45° out of the angles formed by a delay phase axis and an absorption axis of the absorption type linear polarizer, in this elliptical polarizing plate, and the other protection film B sandwiching the absorption type linear polarizer contains a reflecting type linear polarization layer, a reflecting axis of the reflecting type polarizing layer is substantially in parallel to the absorption axis of the absorption type linear polarizer, a film thickness of the protection film A is ≤200 μm, and a film thickness ratio B/A of the protection film A to the he protection film B is within a range of 0.4-2.0. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an elliptically polarizing plate and a liquid crystal display device using the elliptically polarizing plate.

  In recent years, applications of liquid crystal display devices are expanding. For example, there is a liquid crystal display device called digital signage provided in a public facility such as a station. Such a device is said to have an increasing need in the future, and is required to have sufficient visibility even outdoors in the daytime. For that purpose, it is necessary to realize very high luminance with low power consumption.

  For such needs, Patent Documents 1 and 2 disclose a configuration in which a liquid crystal cell in a vertical alignment mode is sandwiched between two polarizing plates, and there is a disclosure of a technology for providing the configuration and pixel electrode protrusions. However, there is a problem that the luminance is insufficient and the power consumption increases when a desired luminance is obtained. Furthermore, there is a problem that the contrast is lowered after irradiation for a long time in a large-sized image display device provided with a direct backlight that is advantageous for improving the durability, in particular, the luminance.

On the other hand, a reflective linear polarizer such as DBEF manufactured by 3M is generally used as a brightness enhancement film. However, the manufacturing process is complicated and expensive, and the commercially available DBEF is simply an elliptically polarizing plate. Even if it was attached to the protective film on one side of the film via an adhesive, the effect of improving contrast reduction after prolonged irradiation was insufficient.
JP 2007-24848 A JP 2007-316667 A

  Accordingly, an object of the present invention is to provide an elliptically polarizing plate that has high brightness enough to obtain sufficient visibility even outdoors and does not cause a decrease in contrast even after long-time irradiation of a direct backlight, and a vertical direction using the elliptically polarizing plate An object is to provide an alignment mode liquid crystal display device.

  As a result of intensive studies to solve the above-mentioned problems, the present inventor uses a protective film A, B sandwiching an absorption linear polarizer and a film having a λ / 4 plate and a reflective linear polarization layer. As a result, the inventors have found that it is possible to improve the brightness and decrease the contrast with time, and based on this finding, the present invention has been completed.

  That is, the said subject of this invention is achieved by the following structures.

1. In an elliptically polarizing plate formed by sandwiching an absorption type linear polarizer between two protective films A and B,
The protective film A has an in-plane retardation at 550 nm of 125 nm to 150 nm, and the smaller angle between the slow axis of the protective film A and the absorption axis of the absorption linear polarizer is approximately 45 °. Pasted on,
The other protective film B sandwiching the absorption linear polarizer includes a reflection linear polarization layer, and the reflection axis of the reflection polarization layer and the absorption axis of the absorption linear polarizer are substantially parallel to each other. Pasted,
And the film thickness of this protective film A is 200 micrometers or less, Ratio B / A of the film thickness of this protective film A and B is the range of 0.4-2.0, The elliptically polarizing plate characterized by the above-mentioned.

  2. The reflective linearly polarizing layer is a grid-type polarizing layer or a layer in which fine particles having an aspect ratio of 2 or more are dispersed in a resin in a state of being oriented in one direction. The elliptically polarizing plate described.

  3. 3. The elliptically polarizing plate as described in 1 or 2 above, wherein the protective films A and B contain a resin, and the resin is either a cellulose ester resin or a polyolefin resin.

  4). The elliptically polarizing plate according to any one of 1 to 3 is a long film, and the absorption axis of the absorptive linear polarizer is parallel to the longitudinal direction of the long film. Elliptical polarizing plate.

  5). 5. A liquid crystal display device comprising: a direct type backlight; the elliptically polarizing plate according to any one of items 1 to 4; and a vertical alignment mode liquid crystal panel arranged in this order.

  According to the present invention, an elliptically polarizing plate that is bright enough to provide sufficient visibility even outdoors and does not cause a decrease in contrast even after long-time irradiation of a direct backlight, and a vertical alignment mode using the same A liquid crystal display device can be provided.

  The best mode for carrying out the present invention will be described in detail below, but the present invention is not limited thereto.

The elliptically polarizing plate of the present invention is an elliptically polarizing plate in which an absorption linear polarizer is sandwiched between two protective films A and B.
The protective film A has an in-plane retardation at 550 nm of 125 nm to 150 nm, and the smaller angle between the slow axis of the protective film A and the absorption axis of the absorption linear polarizer is approximately 45 °. Pasted on,
The other protective film B sandwiching the absorption linear polarizer includes a reflection linear polarization layer, and the reflection axis of the reflection polarization layer and the absorption axis of the absorption linear polarizer are substantially parallel to each other. Pasted,
And the film thickness of this protective film A is 200 micrometers or less, Ratio B / A of the film thickness of this protective film A and B is the range of 0.4-2.0, It is characterized by the above-mentioned.

  The liquid crystal display device of the present invention is characterized in that a direct type backlight, the elliptically polarizing plate, and a vertical alignment mode liquid crystal panel are arranged in this order.

  Preferred configurations of the elliptically polarizing plate and the liquid crystal display device of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic view of an elliptically polarizing plate and a liquid crystal display device according to the present invention.

  The elliptically polarizing plate of the present invention is installed between a vertical alignment mode liquid crystal panel and a backlight, sandwiching an absorption linear polarizer, and the protective film A of the present invention and the protective film B of the present invention are bonded together to form a backlight. A side elliptical polarizing plate is formed. The slow axis of the protective film A of the present invention is about 45 ° with respect to the absorption axis of the absorption linear polarizer, and the reflection axis of the protection film B is the absorption axis of the absorption linear polarizer. It is almost parallel to.

  There is a viewing-side elliptical polarizing plate on the opposite side of the liquid crystal panel with respect to the backlight-side elliptical polarizing plate, and the absorption axis of the absorption-type linear polarizer is the absorption axis of the absorption-type linear polarizer of the backlight-side polarizing plate. Is orthogonal to. The protective film A of the present invention is preferably installed between the absorption linear polarizer and the liquid crystal cell, and the slow axis thereof is orthogonal to the slow axis of the protective film A of the present invention on the backlight side polarizing plate. is doing. For example, a commercially available polarizing plate protective film is bonded to the outermost surface of the viewing side elliptical polarizing plate.

  Further, a direct type backlight having a light diffusing plate and a reflecting plate are installed under the backlight side elliptical polarizing plate to constitute a preferred liquid crystal display device of the present invention.

  The film thickness of the protective film A is 200 μm or less, preferably 20 to 150 μm, and more preferably 20 to 100 μm. The value of the film thickness ratio B / A between the protective films A and B is 0.4 to 2.0, preferably 0.6 to 1.7, and more preferably 0.8 to 1.3.

  The relationship between the range of the film thickness of the protective film A and the film thickness of the protective films A and B is a very important factor in contrast stability under long-time irradiation of the direct backlight, as shown below.

  When the balance of the film thickness of the protective films A and B is extremely lost, the heat generated by long-time irradiation of the backlight causes warping of the elliptically polarizing plate due to the difference in contraction between the upper and lower sheets, and the reflective linearly polarizing layer There is a slight shift in the relationship between the reflection axis of the film and the absorption axis of the absorptive linear polarizer, and the relationship between the absorption axis of the absorptive linear polarizer and the in-plane slow axis of the protective film A, which adversely affects the brightness enhancement effect and contrast. Is likely to affect.

  Further, when the film thickness of the protective film A exceeds 200 μm, the temperature difference between the absorption linear polarizer side of the protective film A and the liquid crystal cell side becomes large due to long-time irradiation of the backlight, and the in-plane slow axis of Misalignment and unevenness are likely to occur, and there is a high possibility that the contrast will be adversely affected.

  Hereinafter, the present invention will be described in detail.

<Absorptive linear polarizer>
Absorptive linear polarizer is an element that allows only light with a plane of polarization in a certain direction to pass through. A typical polarizer known at present is a polyvinyl alcohol-based polarizing film, which contains iodine on a polyvinyl alcohol-based film. There are dyed dyes and dyed dichroic dyes, but it is not limited to these. For the polarizer, a polyvinyl alcohol aqueous solution is formed into a film and dyed by uniaxial stretching or dyed or uniaxially stretched and then preferably subjected to a durability treatment with a boron compound. A polarizer having a thickness of 5 to 30 μm is preferably used.

  Further, as the polarizer of the present invention, a film is formed from ethylene-modified polyvinyl alcohol having an ethylene unit content of 1 to 4 mol%, a polymerization degree of 2000 to 4000, and a saponification degree of 99.0 to 99.99 mol%. An ethylene-modified polyvinyl alcohol film having a temperature of 66 to 73 ° C. is preferably used.

  As the ethylene-modified polyvinyl alcohol (ethylene-modified PVA) used in the present invention, an ethylene-vinyl ester polymer obtained by copolymerizing ethylene and a vinyl ester monomer is saponified, and the vinyl ester unit is converted into a vinyl alcohol unit. Can be used. Examples of the vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valelate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, vinyl versatate, and the like. Of these, vinyl acetate is preferably used.

  The ethylene unit content (ethylene copolymerization amount) in the ethylene-modified PVA is 1 to 4 mol%, preferably 1.5 to 3 mol%, more preferably 2 to 3 mol%. When the content of the ethylene unit is in the above range, it is preferable because of improving polarization performance and durability and reducing color spots.

  Further, when copolymerizing ethylene and a vinyl ester monomer, if necessary, the copolymerizable monomer is within a range not impairing the effects of the invention (preferably 15 mol% or less, more preferably 5 mol% or less. Can also be copolymerized.

  Examples of monomers copolymerizable with such vinyl ester monomers include olefins having 3 to 30 carbon atoms such as propylene, 1-butene and isobutene; acrylic acid and salts thereof; methyl acrylate, ethyl acrylate, Acrylic esters such as n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate, etc. Methacrylic acid and salts thereof; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-methacrylic acid 2- Ethylhexyl, dodecyl methacrylate, methacrylic acid Methacrylic acid esters such as kutadecyl; acrylamide, N-methylacrylamide, N-ethylacrylamide, N, N-dimethylacrylamide, diacetoneacrylamide, acrylamidepropanesulfonic acid and its salt, acrylamidopropyldimethylamine and its salt, N-methylol Acrylamide derivatives such as acrylamide and derivatives thereof; methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidepropanesulfonic acid and salts thereof, methacrylamidepropyldimethylamine and salts thereof, N-methylolmethacrylamide and derivatives thereof Methacrylamide derivatives such as N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone and other N-vinylamides; methyl Vinyl ethers such as nyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether; nitriles such as acrylonitrile and methacrylonitrile; Vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride; maleic acid and its salts or esters thereof; itaconic acid and its salts or esters thereof; Vinylsilyl compounds such as methoxysilane; N-vinylamides such as isopropenyl acetate, N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone it can.

  The polymerization degree of the ethylene-modified PVA constituting the polarizer is 2000 to 4000, preferably 2200 to 3500, particularly preferably 2500 to 3000, from the viewpoint of polarization performance and durability. It is preferable that the degree of polymerization of the ethylene-modified PVA is in the above-mentioned range since there are effects of improving polarization performance and durability and reducing color spots.

  The degree of polymerization of ethylene-modified PVA is the weight average degree of polymerization determined from GPC measurement. This weight average degree of polymerization is a value obtained by performing GPC measurement at 40 ° C. using hexafluoroisopropanol (HFIP) in which 20 mmol / liter sodium trifluoroacetate is added to the mobile phase using monodispersed PMMA as a standard. is there.

  The saponification degree of the ethylene-modified PVA constituting the polarizer is 99.0 to 99.99 mol%, more preferably 99.9 to 99.99 mol%, from the viewpoint of the polarization performance and durability of the polarizing film. Particularly preferred is .95 to 99.99 mol%.

  As a method for producing an ethylene-modified PVA film, in addition to a film forming method by a melt extrusion method using ethylene-modified PVA containing water, for example, an ethylene-modified PVA solution in which ethylene-modified PVA is dissolved in a solvent is used for casting. A film forming method, a wet film forming method (discharge into a poor solvent), a gel film forming method (a method in which an ethylene-modified PVA aqueous solution is once cooled and gelated, and then the solvent is extracted and removed to obtain an ethylene-modified PVA film), and A method based on a combination of these can be employed. Among these, the casting film forming method and the melt extrusion film forming method are preferable from the viewpoint of obtaining a good ethylene-modified PVA film. The obtained ethylene-modified PVA film is subjected to drying and heat treatment as necessary.

  Examples of the solvent for dissolving the ethylene-modified PVA used in producing the ethylene-modified PVA film include dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerin, propylene glycol, diethylene glycol, and triethylene. Glycol, tetraethylene glycol, trimethylolpropane, ethylenediamine, diethylenetriamine, glycerin, water and the like can be mentioned, and one or more of these can be used. Among these, dimethyl sulfoxide, water, or a mixed solvent of glycerin and water is preferably used.

  The ratio of ethylene-modified PVA in the ethylene-modified PVA solution or water-containing ethylene-modified PVA used when producing an ethylene-modified PVA film varies depending on the degree of polymerization of ethylene-modified PVA, but is preferably 20 to 70% by mass. 25-60 mass% is more suitable, 30-55 mass% is still more suitable, and 35-50 mass% is the most suitable. If the proportion of ethylene-modified PVA exceeds 70% by mass, the viscosity of ethylene-modified PVA containing ethylene-modified PVA solution or water becomes too high, making filtration and defoaming difficult when preparing a stock solution of the film. It is difficult to obtain a film without any defects. On the other hand, when the proportion of the ethylene-modified PVA is lower than 20% by mass, the viscosity of the ethylene-modified PVA solution or the ethylene-modified PVA containing water becomes too low, and it becomes difficult to produce a PVA film having a target thickness. Further, this ethylene-modified PVA solution or ethylene-modified PVA containing water may contain a plasticizer, a surfactant, a dichroic dye, or the like, if necessary.

  When producing an ethylene-modified PVA film, it is preferable to add a polyhydric alcohol as a plasticizer. Examples of the polyhydric alcohol include ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, trimethylolpropane, etc., and one or more of these are used. can do. Among these, diglycerin, ethylene glycol, and glycerin are preferably used because of the effect of improving stretchability.

  As addition amount of a polyhydric alcohol, 1-30 mass parts is preferable with respect to 100 mass parts of ethylene modification PVA, 3-25 mass parts is still more preferable, and 5-20 mass parts is the most preferable. When the amount is less than 1 part by mass, the dyeability and stretchability may be deteriorated. When the amount is more than 30 parts by mass, the ethylene-modified PVA film becomes too flexible and the handleability may be deteriorated.

  When producing an ethylene-modified PVA film, it is preferable to add a surfactant. The type of the surfactant is not particularly limited, but an anionic or nonionic surfactant is preferable. As the anionic surfactant, for example, a carboxylic acid type such as potassium laurate, a sulfate type such as octyl sulfate, and a sulfonic acid type anionic surfactant such as dodecylbenzenesulfonate are suitable. Nonionic surfactants include, for example, alkyl ether types such as polyoxyethylene oleyl ether, alkylphenyl ether types such as polyoxyethylene octylphenyl ether, alkyl ester types such as polyoxyethylene laurate, and polyoxyethylene laurylamino. Alkylamine type such as ether, alkylamide type such as polyoxyethylene lauric acid amide, polypropylene glycol ether type such as polyoxyethylene polyoxypropylene ether, alkanolamide type such as oleic acid diethanolamide, polyoxyalkylene allyl phenyl ether, etc. Nonionic surfactants such as allyl phenyl ether type are preferred. These surfactants can be used alone or in combination of two or more.

  As addition amount of surfactant, 0.01-1 mass part is preferable with respect to 100 mass parts of ethylene modified PVA, 0.02-0.5 mass part is still more preferable, 0.05-0.3 mass part is Most preferred.

  The hot water cutting temperature of the ethylene-modified PVA film is preferably 66 to 73 ° C, more preferably 68 to 73 ° C, and still more preferably 70 ° C to 73 ° C. It is preferable that the hot water cutting temperature of the ethylene-modified PVA film is in the above range because the film is easily stretched and the polarizing performance of the polarizing film becomes high. When the ethylene-modified PVA film is subjected to drying and heat treatment, the hot water cutting temperature of the film can be adjusted by changing the temperature and time of the treatment.

  The ethylene-modified PVA film used for the production of the polarizer preferably has a thickness of 10 to 50 μm, and more preferably 20 to 40 μm. When the thickness is in the above range, uniform stretching is performed and color spots of the polarizing film are hardly generated.

  Moreover, in order to produce a polarizing film from an ethylene-modified PVA film, for example, the ethylene-modified PVA film may be dyed, uniaxially stretched, fixed, and dried, and further subjected to heat treatment as necessary. There is no particular limitation on the order of operations of the fixed processing. Moreover, you may perform uniaxial stretching twice or more.

  Dyeing can be performed before uniaxial stretching, during uniaxial stretching, or after uniaxial stretching. As dyes used for dyeing, iodine-potassium iodide; direct black 17, 19, 154; direct brown 44, 106, 195, 210, 223; direct red 2, 23, 28, 31, 37, 39, 79, 81 240, 242, 247; Direct Blue 1, 15, 22, 78, 90, 98, 151, 168, 202, 236, 249, 270; Direct Violet 9, 12, 51, 98; Direct Green 1, 85; Direct Dichroic dyes such as yellow 8, 12, 44, 86, 87; direct orange 26, 39, 106, 107 can be used in one kind or a mixture of two or more kinds. Ordinary dyeing is generally performed by immersing the PVA film in a solution containing the above-mentioned dye, but the processing conditions and processing method are particularly limited, such as mixing with the PVA film to form a film. is not.

  For uniaxial stretching, wet stretching or dry heat stretching can be used, using warm water such as an aqueous boric acid solution (in a solution containing the dye or in a fixing treatment bath described later) or an ethylene-modified PVA film after water absorption. Can be done in air. The stretching temperature is not particularly limited, but is preferably 30 to 90 ° C. when the ethylene-modified PVA film is stretched (wet stretching) in warm water, and 50 to 180 ° C. is suitable for dry heat stretching. Further, the stretching ratio of uniaxial stretching (the total stretching ratio in the case of multi-stage uniaxial stretching) is preferably 4 times or more, and most preferably 5 times or more from the viewpoint of the polarizing performance of the polarizing film. The upper limit of the stretching ratio is not particularly limited, but it is preferably 8 times or less because uniform stretching is easily obtained. 2-20 micrometers is preferable and, as for the thickness of the film after extending | stretching, 5-15 micrometers is more preferable.

  Fixing treatment is often performed for the purpose of strengthening the adsorption of the dye to the ethylene-modified PVA film. Boric acid and / or boron compounds are usually added to the treatment bath used for the fixing treatment. Moreover, you may add an iodine compound in a processing bath as needed.

  It is preferable to perform the drying process of the obtained polarizer at 30-150 degreeC, and it is more preferable to carry out at 50-150 degreeC.

<< Protective film A >>
The protective film A has an in-plane retardation Ro at 550 nm of 125 nm to 150 nm and a film thickness of 200 μm or less, and is the smaller of the slow axis of the protective film A and the absorption axis of the absorption linear polarizer. The elliptical polarizing plate is formed by being bonded to the absorptive linear polarizer so that the angle is about 45 °.

  The protective film A of the present invention refers to a film that exhibits λ / 4 in a wavelength region having a wide in-plane retardation. More specifically, the phase difference value Ro (550) measured at a wavelength of 550 nm is 125 nm to 150 nm, more preferably 130 to 145 nm, and particularly preferably 135 to 141 nm. When Ro is less than 125 nm or more than 150 nm, a sufficiently high luminance cannot be obtained as a liquid crystal display device, and the effect of suppressing external light reflection when viewing the liquid crystal display device in a bright place becomes small. Further, it is preferable that each phase difference when measured at wavelengths of 450 nm, 550 nm, and 650 nm has a wavelength dispersion of Ro (450) <Ro (550) <Ro (650).

  Although there is no limitation on the retardation Rth in the film thickness direction, Rth = 50 to 220 nm at 550 nm is preferable for obtaining a good viewing angle. That is, the Rth design that compensates for the retardation in the thickness direction of the liquid crystal cell portion when no voltage is applied in the liquid crystal display device in the vertical alignment mode with two λ / 4 films sandwiching the cell is favorable. It is preferable for obtaining a viewing angle.

  Here, the in-plane retardation Ro and the thickness direction retardation Rth are calculated according to the following equations.

Ro = (nx−ny) × d
Rth = {(nx + ny) / 2−nz} × d
(Where nx is the refractive index in the slow axis direction in the film plane (maximum refractive index in the plane), ny is the refractive index in the direction perpendicular to the slow axis in the film plane, and nz Is the refractive index in the thickness direction of the film, and d is the thickness (nm) of the retardation film.)
For the measurement of the phase difference, an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments) or the like can be used.

  The protective film A of the present invention is obtained by stretching a long base film made of a transparent resin in at least one direction. Moreover, it is also preferable to obtain by providing the layer which apply | coated and fixed the liquid crystal molecule orientated in the thickness direction of a film.

  The transparency of the transparent resin means that the visible light transmittance is 60% or more, preferably 80% or more, and particularly preferably 90% or more. Accordingly, the transparent resin is a resin having the above-described transmittance with respect to light having a desired wavelength, and is particularly preferably a thermoplastic resin. The transparent resin used in the present invention is preferably made of a resin having a positive intrinsic birefringence value. Examples of the transparent resin include cellulose ester, polyolefin, polysulfone, polycarbonate, polymethyl methacrylate, polyester, and polyvinyl alcohol. In particular, it is preferable to use a resin having a small photoelastic coefficient because retardation unevenness due to thermal strain can be suppressed, and cellulose ester resins, polyolefin resins, and the like are preferably used. Most preferred is a cellulose ester resin. The base film before stretching can be formed by a solution casting method or a melt casting method, but it is preferable to take an optimum method according to the characteristics of the resin to be selected.

  The protective film A of the present invention is bonded to the absorptive linear polarizer to form an elliptically polarizing plate in which the smaller angle between the slow axis and the absorption axis of the polarizer is about 45 °. It is. About 45 ° means a range of 43 ° to 47 °, and preferably a range of 44 ° to 46 °.

  Since a long absorption linear polarizer (polarizing film) having an absorption axis in the longitudinal direction and the protective film A are aligned and laminated, a long elliptical polarizing film can be obtained with high productivity. The slow axis of the protective film A of the present invention is preferably in the direction of about 45 ° with respect to the longitudinal direction.

  As a method for producing a long film having such characteristics, the following oblique film stretching apparatus and stretching method are generally used.

<Slant stretching device, oblique stretching method>
Hereinafter, a film using a thermoplastic resin as the protective film A (hereinafter referred to as a thermoplastic resin film) will be described as an example.

  The oblique stretching apparatus preferably used in the present invention has a preheating zone, a heating stretching zone and a cooling zone, and any heating apparatus used for stretching a conventional thermoplastic resin film can be used. The thermoplastic resin film is preheated in a preheating zone, stretched in a heating stretching zone, and oriented and fixed in a cooling zone to obtain a stretched film.

  As the clip of the oblique stretching apparatus used in the present invention, any clip can be used as long as it can grip the end portion of the thermoplastic resin film. For example, a clip used in a conventional tenter stretching machine is used. It is possible, and the groove | channel or the protrusion is installed so that it can drive to the machine element provided in the spiral.

  The machine element used in the present invention is provided with a groove or ridge in a spiral shape, and a clip is installed in the groove or ridge to drive it. For example, a screw, a ball screw, etc. Can be mentioned.

  The shape of the groove or protrusion is preferably a shape that facilitates driving of the clip, and is preferably a shape in which a portion of a sine wave or arc is continuous.

  In the present invention, the mechanical elements are installed on the left and right sides of the heating device, but in the heating and stretching zone, at least one of the mechanical elements has a helical pitch changed. That is, when the helical pitch changes, the moving speed of the clip changes, the distance between the pair of clips changes, and the thermoplastic resin film is stretched by the change.

  The material of the above machine element is preferably a metal having excellent heat resistance such as used in injection molding or extrusion molding, and the surface thereof is subjected to surface treatment such as heat treatment and abrasion resistance. Is preferred.

  Further, the drive source of the mechanical element is preferably one that can control the moving speed of the clip with high accuracy, and examples thereof include a servo motor, a stepping motor, and an inverter motor.

  The stretched film production apparatus of the present invention will be described with reference to the drawings. FIG. 2 is a schematic plan view showing an example of the stretched film production apparatus of the present invention.

  In the figure, 1 is a thermoplastic resin film, and 5 is a stretched film. The thermoplastic resin film 1 is gripped at both ends by clips 8 and 81, conveyed in the direction of arrow A, preheated in the preheating zone 2, stretched in the heating stretching zone 3, and oriented and fixed in the cooling zone 4 and stretched. Film 5 is obtained.

  The temperature of the heat-stretching zone 3 may be substantially the same as the glass transition temperature of the thermoplastic resin film to be stretched, and may be appropriately determined according to the required performance of the optical film to be manufactured.

  The heating means in the heating and stretching zone 3 is not particularly limited as long as the thermoplastic resin film can be uniformly heated, and examples thereof include heating devices such as a hot air type, a panel heater, and a halogen heater. A hot air type that can accurately control the temperature at the boundary between the zone 3 and the cooling zone 4 is preferable.

  The temperature of the cooling zone 4 should just be a temperature which can fix the orientation of the thermoplastic resin film by extending | stretching, and is generally set to below the glass transition temperature of the stretched thermoplastic resin film.

  The cooling means in the cooling zone 4 is not particularly limited as long as the cooling can be performed substantially parallel to the orientation direction of the thermoplastic resin film. For example, a heating device such as a hot air type, a panel heater, or a halogen heater, Examples thereof include a pipe through which a medium or a refrigerant is passed, and a hot air type capable of accurately controlling the temperature at the boundary between the heating and stretching zone 3 and the cooling zone 4 is preferable.

  The heating and stretching zone 3 and the cooling zone 4 mean a zone in which the thermoplastic resin film is substantially stretched and a zone that cools and fixes the orientation generated by stretching, and means a mechanically and structurally independent zone. Instead, it means a zone where the thermoplastic resin film is at or above the temperature at which it can be stretched, and a zone below that temperature.

  Reference numerals 6 and 7 denote screws installed on the left and right sides of the heating device. As shown in FIG. 3 (a), the screw 6 is provided with ridge flights 61 at the same pitch. Further, as shown in FIG. 3B, the screw 7 is provided so that the flight 71 of the ridge changes in pitch.

  That is, in the preheating zone 2 and the cooling zone 4, the pitch of the flight 71 is narrow and is the same as the pitch of the flight 61 of the screw 6, and in the heating and stretching zone 3, the pitch gradually becomes wider and then becomes narrower and becomes the pitch of the cooling zone 4. Is the same.

  A plurality of clips 8... 81 can be driven on the screws 6 and 7, and the clips 8 and 7 installed on the screw 6 on the root (preheating zone 2) side of the screws 6 and 7 are installed. The clip 81 is installed in a pair.

  Reference numerals 9 and 91 denote belts for conveying the clips 8 and 81 that have reached the tip of the screws 6 and 7 (cooling zone 4) to the base (preheating zone 2) of the screws 6 and 7, respectively.

  Next, a method for stretching the thermoplastic resin film will be described.

  In the stretched film manufacturing apparatus, the end portion of the supplied thermoplastic resin film 1 is gripped by the clips 8 and 81 and conveyed in the traveling direction of the thermoplastic resin film 1 (A direction in the figure). At this time, the conveyance speed of the thermoplastic resin film 1 and the speed of the clip 81 are set to the same speed so that the thermoplastic resin film 1 is not stretched in the traveling direction.

  The supplied thermoplastic resin film 1 is gripped at both ends by clips 8 and 81, preheated in the preheating zone 2, and conveyed to the heating and stretching zone 3. In the preheating zone 2, since the pitches of the flights 61 and 71 are the same, the moving speeds of the clips 8 and 81 are the same, and the thermoplastic resin film 1 is not stretched in any direction in the heating and stretching zone 3. Be transported.

  In the heating and stretching zone 3, the moving speed of the clip 81 is unchanged, but the moving speed of the clip 8 becomes faster than the moving speed of the clip 81 because the pitch of the flight 61 is gradually increased. The thermoplastic resin film 1 is stretched only in a direction different from the traveling direction of the thermoplastic resin film 1.

  Next, the stretched thermoplastic resin film 1 is conveyed to the cooling zone 4 and fixed in orientation. Since the pitch of the flight 71 and the pitch of the flight 61 in the cooling zone 4 are the same, the stretched thermoplastic resin film is oriented and fixed as it is.

  The stretched film 5 that has been stretched and fixed in orientation is discharged from the cooling zone 4 to obtain a stretched film 5 that is oriented in a direction different from the traveling direction of the thermoplastic resin film 1.

  That is, as shown in FIG. 4, in the obtained stretched film 5, the orientation axis (optical axis) is inclined with respect to the longitudinal direction of the stretched film.

  Therefore, as shown in FIG. 5, the obtained stretched film 21 (for example, linearly polarizing film) and the stretched film 24 (for example, retardation film) obtained by longitudinal uniaxial stretching are laminated as they are, and the traveling direction By cutting in a direction orthogonal to the direction of the optical axis 23 of the stretched film 21 and the direction of the optical axis 25 of the stretched film 24, a laminate 26 (that is, an elliptically polarizing plate) of films having different optical axes can be obtained. .

  When the clips 8 and 81 exit the cooling zone 4, the stretched film is released, and the belts 9 and 91 are conveyed to the vicinity of the entrance of the preheating zone 2 to prepare for gripping the next thermoplastic resin film.

  Next, a method of stretching in an oblique 45 ° direction using another stretched film manufacturing apparatus will be described.

  In order to obliquely stretch the thermoplastic resin film in a direction substantially 45 ° with respect to the longitudinal direction, it is preferable to use a tenter shown in FIG. FIG. 6 is a schematic diagram showing oblique stretching by a tenter. As shown in FIG. 6, the thermoplastic resin film 101 is stretched obliquely (45 °) using a tenter 102 while being transported in a constant transport direction 103. In FIG. 6, the change in the width of the film in the stretching direction is indicated by a dotted line. The film chucked at a certain position (104L and 104R) in FIG. 6 moves to the near position (105L) at the slow speed (106L) on the left side and to the far position (105R) at the high speed (106R) on the right side. Diagonal stretching is performed. The draw ratio is preferably 2 to 30 times, and more preferably 3 to 10 times. When stretching, assuming that the glass transition temperature of the thermoplastic resin film is Tg, the film is heated and stretched within the range of (Tg-30) to (Tg + 100) ° C, more preferably (Tg-20) to (Tg + 80) ° C. It is preferable. In particular, it is preferable that the film is stretched within a temperature range of (Tg-20) to (Tg + 20) ° C. and then heat-set. It is also preferable to perform relaxation treatment after the stretching step.

  Diagonal stretching may be carried out in several steps. In particular, in the case of high-magnification stretching, it is preferable to obtain a uniform stretching result by dividing the process into several steps. Further, for the purpose of preventing shrinkage in the width direction, a slight stretching process in the transverse direction or the longitudinal direction may be performed before the oblique stretching. Diagonal stretching can be carried out by performing tenter stretching, which is employed for normal film biaxial stretching, in steps different from each other as described above. Since the left and right layers are stretched at different speeds, the thickness of the film before stretching is adjusted to be different between the left and right sides. This may be adjusted so that the flow rate of the solution differs between the left and right when casting to form a film. The flow rate can be easily adjusted by a method that tapers the die.

  Further, the oblique stretching apparatus described in FIGS. 2 to 7 of JP-A-2004-20827, FIGS. 1 to 4 of JP-A-2007-94007, or FIGS. 1 to 4 of JP-A-2007-203556 are also suitable. Can be used.

  Moreover, when manufacturing the retardation film of this invention, it is preferable to perform the extending | stretching to the said diagonal direction before coating the liquid crystal layer mentioned later. At the time of stretching, in the sense of increasing the degree of freedom of control in the slow axis direction in the plane of the retardation film, the film is stretched in the longitudinal direction and then stretched obliquely with respect to the longitudinal direction, or It is preferable to stretch in the longitudinal direction after stretching in the oblique direction with respect to the longitudinal direction. As an example of a specific apparatus for realizing this, it is also preferable to use a film expansion / contraction apparatus described in JP-A-2007-30466.

  A preferred embodiment of the present invention will be described with reference to FIGS.

  7 and 8 show a plane and a cross section of a film stretching device (extension device) 401 according to an embodiment of the present invention. The film stretching apparatus 401 includes a supply apparatus 403 that supplies the film 402, a longitudinal stretching furnace 404 that heats the film, and a longitudinal stretching section (longitudinal stretching section) 406 that includes an intermediate transport apparatus 405 that transports the film 402 downstream. An oblique stretching machine 407 that is inclined with respect to the transport direction while transporting the film 402, and an oblique stretching furnace 408 that is provided so as to cover the central portion of the oblique stretching machine 407 and heats the film 402. And a winding device 410 that winds up the film 402.

  The supply device 403 is loaded with an original reel 411 around which a film 402 is wound, and the film 402 is sandwiched between a reference roll 412 and a nip roll 413 and sent out at a predetermined transport speed. The longitudinal stretching furnace 404 is a box made of a heat insulating material having hot air ducts (heating means) 414 for blowing hot air alternately on the film 402 from above and below. The intermediate transport device 405 sandwiches and transports the film 402 between the ratio roll 415 and the nip roll 416 and stretches it in the E1 direction parallel to the transport direction. The oblique stretching machine 407 stretches the film 402 in the E2 direction inclined by an angle α with respect to the transport direction while transporting the film 402 by the stretch chains 417 disposed on both sides of the film 402, and details will be described later. The oblique stretching furnace 408 is a box made of a heat insulating material having a hot air duct 418 that blows hot air on the film 402 from above and below. The winding device 410 winds the film 402 around the product reel 420 while adjusting the tension with the tension roll 419.

  FIG. 9 shows the configuration of the oblique stretching machine 407. The oblique stretching machine 407 includes two parallel stretching chains 417, a large number of bases 421 provided on the stretching chain 417 at regular intervals, and arms 422 attached to the respective bases 421 so as to be slidable in a certain direction. , And a clip 423 provided at the tip of each arm 422. The clip 423 can grip both side edges of the film 402, and the stretching chain 417 is looped around a sprocket 424 perpendicular to the surface of the film 402.

  FIG. 10 shows a more detailed structure of the oblique stretching machine 407. A base 421 is fixed to the extending chain 417 every other frame. The base 421 is provided with two sliding shafts 425 inclined by 45 ° (angle α in FIG. 7) with respect to the extending chain 417, and the arms 422 are slidable along the respective sliding shafts 425. ing. A positioning member 426 made of a bearing is provided on the upper portion of the arm 422, and the arm 422 is projected and retracted by guiding the positioning member 426 with a guide 427. The clip 423 provided at the tip of the arm 422 is a known film gripping mechanism, and is opened and closed by the guide 428 (the film 402 is gripped or released).

  The oblique stretching machine 407 causes the arms 422 to protrude from the base 421 of the stretching chain 417, grips both side edges of the film 402 with the clip 423, and transports the film 402 as the stretching chain 417 advances. During this time, the arm 422 is retracted while holding the film 402 with the clip 423, whereby the film 402 is stretched and widened in the sliding direction of the arm 422 (direction E2 in FIG. 7). At the time of widening, the retreating amounts of the arms 422 facing each other in the sliding direction of the arms 422 are equal. After the film 402 is widened, the clip 423 opens the film 402. The arm 422 then retracts further, preventing the clip 423 from contacting the film 402 when the stretch chain 417 is folded back along the sprocket 424.

  Next, stretching of the film 402 in the film stretching apparatus 401 having the above configuration will be described.

  In the longitudinal stretching unit 406, when the film 402 is sent out at a predetermined speed by the reference roll 412 and is transported at a speed faster than the reference roll 412 by the ratio roll 415, the heated part in the longitudinal stretching furnace 404 is transported. The film is stretched in the direction (E1 direction) at the same ratio as the ratio of the conveyance speed of the ratio roll 415 to the reference roll 412. By this stretching in the longitudinal direction, the molecules of the film 402 are aligned in the transport direction, and an orientation angle in the longitudinal direction is given.

  Furthermore, in the oblique stretching section 409, the film 402 is stretched in the E2 direction in a downwardly inclined direction by an angle α with respect to the transport direction. By stretching in the tilt direction, the film 402 is subjected to tensile force in the E2 direction and stress for deformation of the film 402, and stretching force that attempts to align molecules at a larger angle with respect to the transport direction than in the E2 direction. Acts to provide an orientation angle in the tilt direction.

  As a result, the film 402 obtains an orientation angle in a direction obtained by adding the orientation angle imparted in the longitudinal stretching portion 406 and the orientation angle imparted in the oblique stretching portion 409, and the longitudinal stretching portion 406 and the oblique stretching are obtained. A retardation value is given according to the strength of stretching (stretching ratio) in the portion 409.

  When the oriented film is produced by obliquely stretching the film 402 with the film stretching apparatus 1, the film 402 is actually stretched by the longitudinal stretching portion 406 and the oblique stretching portion 409, and the orientation angle of the obtained film 402 is measured. The stretching ratio in the longitudinal stretching unit 406 is adjusted by increasing or decreasing the speed of the ratio roll 415 so that a desired orientation angle is obtained. In addition, a desired retardation value is obtained by adjusting the stretching ratio in the oblique stretching portion 409.

  For example, when the speed of the reference roll 412 and the ratio roll 415 is set to be the same (stretching ratio in the longitudinal stretching portion 406 is 0%) and the oblique stretching portion 409 performs 18% oblique stretching at α = 45 °, Under the condition that the orientation angle of the film 402 is approximately 60 ° with respect to the transport direction, the longitudinal stretching portion 406 is stretched by about 10% without changing the stretching conditions of the oblique stretching portion 409 (the speed of the ratio roll 415). ) About 10% faster than the reference roll 412), the orientation angle of the film 402 could be 45 °.

  That is, in the film stretching apparatus 401, the angle α with respect to the transport direction in the stretching direction E2 of the tilt stretching machine 407 is set to an approximate value that a desired orientation angle is considered to be obtained empirically, and the film 402 is actually stretched. However, the orientation angle is adjusted by adjusting the speed of the ratio roll 415. The ratio roll 415 can be changed while being driven by an inverter or a continuously variable transmission, and a desired orientation angle can be easily obtained.

  In the above embodiment, the film 402 is stretched in the tilt direction. However, if the oblique stretching machine 407 is installed in the reverse direction and rotated reversely. The heat shrinkable film can be used as a device for restricting shrinkage in the E2 direction inside the oblique stretching furnace 408 and heat shrinking so that molecules are arranged in the tilt direction.

  In the case of the present invention, the film may be stretched in the tilt direction or the shrinkage may be regulated, and then the film may be stretched in the longitudinal direction or the shrinkage may be regulated.

<Cellulose ester>
The transparent resin used in the protective film A of the present invention is preferably a cellulose ester resin or a polyolefin resin described later, and more preferably a cellulose ester resin (hereinafter referred to as cellulose ester). More specifically, it is preferable to use a cellulose ester as a main component and a mixture of additives such as a plasticizer and an ultraviolet absorber.

  It is preferable that the protective film A of this invention contains 60-100 mass% of cellulose esters.

  The cellulose ester used in the present invention is a carboxylic acid ester having about 2 to 22 carbon atoms or an aromatic carboxylic acid ester, and particularly preferably a lower fatty acid ester having 6 or less carbon atoms.

  The acyl group bonded to the hydroxyl group may be linear or branched or may form a ring. Furthermore, another substituent may be substituted. When the degree of substitution is the same, birefringence decreases when the number of carbon atoms is large, and therefore, the number of carbon atoms is preferably selected from acyl groups having 2 to 6 carbon atoms. The cellulose ester preferably has 2 to 4 carbon atoms, more preferably 2 to 3 carbon atoms.

  Specific cellulose esters include cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate propionate, butyrate or phthalyl group in addition to acetyl groups such as cellulose acetate propionate but cellulose acetate phthalate. The mixed fatty acid ester can be used. The butyryl group forming butyrate may be linear or branched.

  As the cellulose ester preferably used in the present invention, cellulose acetate, cellulose acetate butyrate, and cellulose acetate propionate are particularly preferably used. Of these, cellulose acetate propionate is most preferred.

As the cellulose ester, those having a total acyl group substitution degree of 2.1 to 2.9 satisfying the following formulas (1) and (2) at the same time are preferable.
preferable.

Formula (1) 2.1 <= X + Y <= 2.9
Formula (2) 0 ≦ Y ≦ 1.5
In the formula, X is the degree of substitution of the acetyl group, and Y is the degree of substitution of the propionyl group or butyryl group, or a mixture thereof. In addition, the substitution degree of an acetyl group and the substitution degree of another acyl group can be determined by a method prescribed in ASTM-D817-96.

  Further, in order to obtain optical characteristics that meet the purpose, resins having different degrees of substitution may be mixed and used. The mixing ratio is preferably 10:90 to 90:10 (mass ratio).

  Of these, cellulose acetate propionate is particularly preferably used. In cellulose acetate propionate, 1.0 ≦ X ≦ 2.5, and preferably 0.1 ≦ Y ≦ 1.5 and 2.1 ≦ X + Y ≦ 2.9.

  The number average molecular weight of the cellulose ester used in the present invention is preferably in the range of 60,000 to 300,000 because the mechanical strength of the resulting film is strong. Furthermore, the thing of 70000-200000 is used preferably.

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

  The measurement conditions are as follows.

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

  In addition, this measuring method can be used also as a measuring method of the other polymer in this invention.

  The cellulose as a raw material for the cellulose ester is not particularly limited, and examples thereof include cotton linter, wood pulp, and kenaf. Moreover, the cellulose ester obtained from them can be mixed and used in arbitrary ratios, respectively.

  The cellulose ester can be produced by a known method. Specifically, it can be synthesized with reference to the method described in JP-A-10-45804.

  Cellulose esters are also affected by trace metal components in cellulose esters.

  These are considered to be related to water used in the production process, but it is preferable that there are few components that can become insoluble nuclei, and metal ions such as iron, calcium, and magnesium contain organic acidic groups. Insoluble matter may be formed by salt formation with a polymer degradation product or the like that may be present, and it is preferable that the amount is small.

  The iron (Fe) component is preferably 1 ppm or less. As for the calcium (Ca) component, it is easy to form a coordination compound, that is, a complex with an acidic component such as carboxylic acid or sulfonic acid, and many ligands. Starch, turbidity).

  The calcium (Ca) component is 60 ppm or less, preferably 0 to 30 ppm. The magnesium (Mg) component is preferably in the range of 0 to 70 ppm, particularly preferably 0 to 20 ppm, since too much will cause insoluble matter.

  Metal components such as iron (Fe) content, calcium (Ca) content, magnesium (Mg) content, etc. are pre-processed by completely digesting cellulose ester with micro digest wet cracking equipment (sulfuric acid decomposition) and alkali melting. After being performed, it can be analyzed using ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometer).

<Other additives>
The protective film A of the present invention can contain the following additives as required.

  In the present invention, the protective film A is an ester obtained by esterifying all or part of the OH groups in the (meth) acrylic polymer or the compound (A) having one furanose structure or pyranose structure in addition to the cellulose ester. Or an esterified compound obtained by esterifying all or part of the OH groups in the compound (B) in which at least one of the furanose structure or the pyranose structure is bonded in an amount of 2 or more and 12 or less. .

((Meth) acrylic polymer)
As the (meth) acrylic polymer used in the present invention, when it is contained in the protective film A, it preferably exhibits negative birefringence as a function with respect to the stretching direction, and the structure is not particularly limited. However, it is preferably a polymer having a weight average molecular weight of 500 or more and 30000 or less obtained by polymerizing an ethylenically unsaturated monomer.

  The (meth) acrylic polymer having a weight average molecular weight of 500 to 30,000 used in the present invention is a (meth) acrylic polymer having an aromatic ring in the side chain or a (meth) acrylic having a cyclohexyl group in the side chain. A polymer may be used.

  By controlling the composition of the polymer with a weight average molecular weight of 500 to 30,000, for example, when the cellulose ester is contained, the compatibility between the cellulose ester and the polymer is improved. Can do.

  For a (meth) acrylic polymer having an aromatic ring in the side chain or a (meth) acrylic polymer having a cyclohexyl group in the side chain, preferably if the weight average molecular weight is from 500 to 10,000, The film after film formation has excellent transparency and extremely low moisture permeability, and exhibits excellent performance even when applied to a protective film for a polarizing plate, for example.

  Since the polymer has a weight average molecular weight of 500 or more and 30000 or less, it is considered to be between the oligomer and the low molecular weight polymer. In order to synthesize such a polymer, it is difficult to control the molecular weight in normal polymerization, and it is desirable to use a method that can align the molecular weight as much as possible by a method that does not increase the molecular weight too much.

  In particular, the (meth) acrylic polymer used in the protective film A of the present invention includes an ethylenically unsaturated monomer Xa having no aromatic ring and hydroxyl group in the molecule, and no hydroxyl ring in the molecule. A polymer X having a weight average molecular weight of 2,000 to 30,000 obtained by copolymerization of an ethylenically unsaturated monomer Xb having Xb and a copolymerizable ethylenically unsaturated monomer excluding Xa and Xb, or an aromatic ring The polymer Y is preferably a polymer Y having a weight average molecular weight of 500 or more and 3000 or less, which is obtained by polymerizing a non-ethylenically unsaturated monomer Ya and an ethylenically unsaturated monomer copolymerizable with Ya.

[Polymer X, Polymer Y]
The method for adjusting Ro and Rth of the protective film A according to the present invention includes an ethylenically unsaturated monomer Xa having no aromatic ring and a hydroxyl group in the molecule, and ethylene having a hydroxyl group and no aromatic ring in the molecule. High molecular weight polymer X having a weight average molecular weight of 2,000 to 30,000 obtained by copolymerization of the polymerizable unsaturated monomer Xb and a copolymerizable ethylenically unsaturated monomer excluding Xa and Xb, and more preferably, Contains a low molecular weight polymer Y having a weight average molecular weight of 500 to 3,000 obtained by polymerizing an ethylenically unsaturated monomer Ya having no aromatic ring and an ethylenically unsaturated monomer copolymerizable with Ya It is preferable.

  The polymer X used in the present invention includes an ethylenically unsaturated monomer Xa having no aromatic ring and a hydroxyl group in the molecule and an ethylenically unsaturated monomer Xb having no hydroxyl ring in the molecule and having a hydroxyl group, Xa and Xb. Is a polymer having a weight average molecular weight of 2000 or more and 30000 or less obtained by copolymerization with a copolymerizable ethylenically unsaturated monomer other than.

  Preferably, Xa is an acrylic or methacrylic monomer having no aromatic ring and hydroxyl group in the molecule, and Xb is an acrylic or methacrylic monomer having no aromatic ring and having a hydroxyl group in the molecule.

  The polymer X used in the present invention is represented by the following general formula (X).

Formula (X)
-[Xa] m- [Xb] n- [Xc] p-
In the general formula (X), Xa represents an ethylenically unsaturated monomer having no aromatic ring and hydroxyl group in the molecule, and Xb represents an ethylenically unsaturated monomer having no aromatic ring and having a hydroxyl group in the molecule. Xc represents a copolymerizable ethylenically unsaturated monomer excluding Xa and Xb. m, n, and p each represent a molar composition ratio. However, m ≠ 0 and m + n + p = 100.

  Furthermore, the polymer X is preferably a polymer represented by the following general formula (X-1).

Formula (X-1)
_{- [CH 2 -C (-R1)} (- CO 2 R2)] m- [CH 2 -C (-R3) (- CO 2 R4-OH) -] n- [Xc] p-
In the general formula (X-1), R1 and R3 each represent a hydrogen atom or a methyl group. R2 represents an alkyl group having 1 to 12 carbon atoms or a cycloalkyl group. R4 is _{-CH 2 -, - C 2 H} 4 - or -C ₃ H ₆ - represents a. Xc _{is, [CH 2 -C (-R1)} (- CO 2 R2)] representing the a polymerizable monomer unit or _{[CH 2 -C (-R3) (} - - CO 2 R4-OH)]. m, n, and p represent a molar composition ratio. However, m ≠ 0 and m + n + p = 100.

  Although the monomer as a monomer unit which comprises the polymer X used for this invention is mentioned below, it is not limited to this.

  In X, the hydroxyl group means not only a hydroxyl group but also a group having an ethylene oxide chain.

  Examples of the ethylenically unsaturated monomer Xa having no aromatic ring and hydroxyl group in the molecule include methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), and butyl acrylate (n-, i-, s). -, T-), pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (n-, i-), octyl acrylate (n-, i -), Nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), acrylic acid (2-ethylhexyl), acrylic acid (ε-caprolactone), etc. The thing changed into acid ester can be mentioned. Among these, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, and propyl methacrylate (i-, n-) are preferable.

  The ethylenically unsaturated monomer Xb having no hydroxyl ring in the molecule and having a hydroxyl group is preferably acrylic acid or methacrylic acid ester as a monomer unit having a hydroxyl group, such as acrylic acid (2-hydroxyethyl), acrylic acid. (2-hydroxypropyl), acrylic acid (3-hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), or those obtained by replacing these acrylic acids with methacrylic acid. Preferred are acrylic acid (2-hydroxyethyl) and methacrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), and acrylic acid (3-hydroxypropyl).

  Xc is not particularly limited as long as it is a monomer other than Xa and Xb and is a copolymerizable ethylenically unsaturated monomer, but preferably has no aromatic ring.

  The molar composition ratio m: n of Xa and Xb is preferably in the range of 99: 1 to 65:35, more preferably in the range of 95: 5 to 75:25. P of Xc is 0-10. Xc may be a plurality of monomer units.

  When the molar composition ratio of Xa is large, the compatibility with the cellulose ester is improved, but the retardation value Rth in the film thickness direction is increased. When the molar composition ratio of Xb is large, the compatibility is deteriorated, but the effect of reducing Rth is high.

  Further, if the molar composition ratio of Xb exceeds the above range, haze tends to occur during film formation, and it is preferable to optimize these and determine the molar composition ratio of Xa and Xb.

  The molecular weight of the high molecular weight polymer X is more preferably 5,000 or more and 30,000 or less, and still more preferably 8,000 or more and 25,000 or less.

  By setting the weight average molecular weight to 5,000 or more, advantages such as little dimensional change of the protective film A under high temperature and high humidity and less curling as a polarizing plate protective film are preferable.

  When the weight average molecular weight is 30000 or less, compatibility with the cellulose ester is further improved, and bleeding out under high temperature and high humidity and further haze generation immediately after film formation are suppressed.

  The weight average molecular weight of the polymer X used in the present invention can be adjusted by a known molecular weight adjusting method. Examples of such a molecular weight adjusting method include a method of adding a chain transfer agent such as carbon tetrachloride, lauryl mercaptan, octyl thioglycolate, and the like.

  The polymerization temperature is usually from room temperature to 130 ° C., preferably from 50 ° C. to 100 ° C., and this temperature or the polymerization reaction time can be adjusted.

  The measuring method of a weight average molecular weight can be calculated | required by the following method.

(Average molecular weight measurement method)
The weight average molecular weight Mw and the number average molecular weight Mn were measured using gel permeation chromatography (GPC).

  The measurement conditions are as follows.

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

  The low molecular weight polymer Y used in the present invention is a polymer having a weight average molecular weight of 500 or more and 3000 or less obtained by polymerizing an ethylenically unsaturated monomer Ya having no aromatic ring. A weight average molecular weight of 500 or more is preferred because the residual monomer in the polymer is reduced.

  Moreover, it is preferable to set it as 3000 or less in order to maintain retardation value Rth fall performance. Ya is preferably an acrylic or methacrylic monomer having no aromatic ring.

  The polymer Y used in the present invention is represented by the following general formula (Y).

General formula (Y)
-[Ya] k- [Yb] q-
In the general formula (Y), Ya represents an ethylenically unsaturated monomer having no aromatic ring, and Yb represents an ethylenically unsaturated monomer copolymerizable with Ya. k and q each represent a molar composition ratio. However, k ≠ 0 and k + q = 100.

  The polymer Y according to the present invention is more preferably a polymer represented by the following general formula (Y-1).

General formula (Y-1)
_{- [CH 2 -C (-R5)} (- CO 2 R6)] k- [Yb] q-
In the general formula (Y-1), R5 represents a hydrogen atom or a methyl group, respectively. R6 represents an alkyl group having 1 to 12 carbon atoms or a cycloalkyl group. Yb represents a monomer unit copolymerizable with [CH ₂ —C (—R 5) (— CO ₂ R 6)]. k and q each represent a molar composition ratio. However, k ≠ 0 and k + q = 100.

Yb is a _{Ya [CH 2 -C (-R5)} (- CO 2 R6)] and is not particularly limited as long as it is copolymerizable ethylenically unsaturated monomers. Yb may be plural. k + q = 100, q is preferably 1-30.

  The ethylenically unsaturated monomer Ya constituting the polymer Y obtained by polymerizing the ethylenically unsaturated monomer having no aromatic ring is, for example, methyl acrylate, ethyl acrylate, propyl acrylate ( i-, n-), butyl acrylate (n-, i-, s-, t-), pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), acrylic Acid heptyl (n-, i-), octyl acrylate (n-, i-), nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), cyclohexyl acrylate, acrylic acid ( 2-ethylhexyl), acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypropiyl) ), Acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), methacrylic acid ester, the above acrylic acid ester changed to methacrylic acid ester; unsaturated acid, for example, acrylic acid, methacrylic acid And maleic anhydride, crotonic acid, itaconic acid and the like.

  Yb is not particularly limited as long as it is an ethylenically unsaturated monomer copolymerizable with Ya. Examples of vinyl esters include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate, vinyl pivalate, and vinyl caproate. Vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cyclohexanecarboxylate, vinyl octylate, vinyl methacrylate, vinyl crotonate, vinyl sorbate, vinyl cinnamate and the like are preferred. Yb may be plural.

  In order to synthesize the polymers X and Y, it is difficult to control the molecular weight in normal polymerization, and it is desirable to use a method that can make the molecular weights as uniform as possible without increasing the molecular weight.

  Such polymerization methods include a method using a peroxide polymerization initiator such as cumene peroxide and t-butyl hydroperoxide, a method using a polymerization initiator in a larger amount than normal polymerization, and a mercapto compound in addition to the polymerization initiator. And a method of using a chain transfer agent such as carbon tetrachloride, a method of using a polymerization terminator such as benzoquinone and dinitrobenzene in addition to the polymerization initiator, and further, Japanese Patent Application Laid-Open No. 2000-128911 or 2000-344823. Examples thereof include a compound having one thiol group and a secondary hydroxyl group, or a bulk polymerization method using a polymerization catalyst in which the compound and an organometallic compound are used in combination. Used.

  In particular, the polymer Y is preferably a polymerization method using a compound having a thiol group and a secondary hydroxyl group in the molecule as a chain transfer agent. In this case, the terminal of the polymer Y has a hydroxyl group and a thioether resulting from the polymerization catalyst and the chain transfer agent. The compatibility of Y and cellulose ester can be adjusted by this terminal residue.

  The hydroxyl values of the polymers X and Y are preferably 30 to 150 [mg KOH / g].

(Measurement method of hydroxyl value)
The measurement of the hydroxyl value is based on JIS K 0070 (1992). This hydroxyl value is defined as the number of mg of potassium hydroxide required to neutralize acetic acid bonded to a hydroxyl group when 1 g of a sample is acetylated.

  Specifically, sample Xg (about 1 g) is precisely weighed in a flask, and 20 ml of an acetylating reagent (a solution obtained by adding pyridine to 20 ml of acetic anhydride to 400 ml) is accurately added thereto. An air cooling tube is attached to the mouth of the flask and heated in a glycerin bath at 95-100 ° C. After 1 hour and 30 minutes, the mixture is cooled, 1 ml of purified water is added from an air condenser, and acetic anhydride is decomposed into acetic acid.

  Next, titration is performed with a 0.5 mol / L potassium hydroxide ethanol solution using a potentiometric titrator, and the inflection point of the obtained titration curve is set as the end point.

  Further, as a blank test, titration is performed without a sample, and an inflection point of the titration curve is obtained. The hydroxyl value is calculated by the following formula.

Hydroxyl value = {(BC) × f × 28.05 / X} + D
In the formula, B is the amount (ml) of 0.5 mol / L potassium hydroxide ethanol solution used for the blank test, C is the amount (ml) of 0.5 mol / L potassium hydroxide ethanol solution used for titration, f is a factor of a 0.5 mol / L potassium hydroxide ethanol solution, D is an acid value, and 28.05 is 1/2 of 1 mol amount 56.11 of potassium hydroxide.

  The above-mentioned polymer X and polymer Y are both excellent in compatibility with cellulose ester, excellent in productivity without evaporation and volatilization, good retention as a protective film for polarizing plates, low moisture permeability, and dimension stability. Excellent in properties.

The content of the polymer X and the polymer Y in the protective film A is preferably in the range satisfying the following formulas (i) and (ii). When the content of the polymer X is Xg (mass% = (mass of polymer X / mass of cellulose ester) × 100) and the content of the polymer Y is Yg (mass%),
Formula (i) 5 ≦ Xg + Yg ≦ 35 (mass%)
Formula (ii) 0.05 ≦ Yg / (Xg + Yg) ≦ 0.4
A preferable range of (Xg + Yg) in the formula (i) is 10 to 35% by mass. If the polymer X and the polymer Y are 5 mass% or more as a total amount with respect to the total mass of the cellulose ester, the polymer X and the polymer Y have a sufficient effect for adjusting the retardation value Rth. Moreover, if it is 35 mass% or less as a total amount, adhesiveness with polarizer PVA is favorable.

  The polymer X and the polymer Y can be directly added and dissolved as a material constituting the dope solution described later, or can be added to the dope solution after being previously dissolved in an organic solvent for dissolving the cellulose ester.

(Ester compound in which at least one pyranose structure or furanose structure is 1 to 12 and all or part of the OH groups in the structure are esterified)
The protective film A of the present invention preferably contains an ester compound in which at least one of the pyranose structure or furanose structure is 1 or more and 12 or less and all or part of the OH groups of the structure are esterified. In the present invention, the above ester compounds are collectively referred to as sugar ester compounds.

  Examples of the ester compound used in the present invention include the following, but the present invention is not limited to these.

  Glucose, galactose, mannose, fructose, xylose or arabinose, lactose, sucrose, nystose, 1F-fructosyl nystose, stachyose, maltitol, lactitol, lactulose, cellobiose, maltose, cellotriose, maltotriose, raffinose or kestose .

  In addition, gentiobiose, gentiotriose, gentiotetraose, xylotriose, galactosyl sucrose, and the like are also included.

  Among these compounds, compounds having both a pyranose structure and a furanose structure are particularly preferable.

  Examples include sucrose, kestose, nystose, 1F-fructosyl nystose, stachyose, and more preferably sucrose.

  The monocarboxylic acid used for esterifying all or part of the OH groups in the pyranose structure or furanose structure of the present invention is not particularly limited, and known aliphatic monocarboxylic acids, alicyclic monocarboxylic acids, An aromatic monocarboxylic acid or the like can be used. The carboxylic acid used may be one type or a mixture of two or more types.

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

  Examples of preferable alicyclic monocarboxylic acids include acetic acid, cyclopentanecarboxylic acid, cyclohexanecarboxylic acid, cyclooctanecarboxylic acid, and derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include aromatic monocarboxylic acids having an alkyl group or alkoxy group introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, cinnamic acid, benzylic acid, biphenylcarboxylic acid, and naphthalene. Examples thereof include aromatic monocarboxylic acids having two or more benzene rings such as carboxylic acid and tetralin carboxylic acid, or derivatives thereof. More specifically, xylyl acid, hemelic acid, mesitylene acid, prenylic acid, γ-isoduric acid, jurylic acid, mesitic acid, α-isoduric acid, cumic acid, α-toluic acid, hydroatropic acid, atropic acid, hydrocinnamic acid, salicylic acid, o-anisic acid, m-anisic acid, p-anisic acid , Creosote acid, o-homosalicylic acid, m-homosalicylic acid, p-homosalicylic acid, o-pyroca Succinic acid, β-resorcylic acid, vanillic acid, isovanillic acid, veratromic acid, o-veratrumic acid, gallic acid, asaronic acid, mandelic acid, homoanisic acid, homovanillic acid, homoveratrumic acid, o-homoveratrumic acid, phthalonic acid, p- Although coumaric acid can be mentioned, benzoic acid is particularly preferable.

  The oligosaccharide ester compound can be applied as a compound having 1 to 12 of at least one of a pyranose structure or a furanose structure used in the present invention.

  Oligosaccharides are produced by allowing an enzyme such as amylase to act on starch, sucrose, etc. Examples of oligosaccharides that can be applied to the present invention include maltooligosaccharides, isomaltoligosaccharides, fructooligosaccharides, galactooligosaccharides, and xylooligos. Sugar.

Moreover, the said ester compound is a compound which condensed 1 or more and 12 or less of at least 1 sort (s) of the pyranose structure or furanose structure represented with the following general formula (A). However, R < ₁₁ > -R < ₁₅ >, R < ₂₁ > -R < ₂₅ > represents a C2-C22 acyl group or a hydrogen atom, m and n represent the integer of 0-12 respectively, and m + n represents the integer of 1-12.

R _{11 to} R ₁₅ and R _{21 to} R ₂₅ are particularly preferably a benzoyl group or a hydrogen atom. The benzoyl group may further have a substituent R ₂₆ (p is 0 to 5), and examples thereof include an alkyl group, an alkenyl group, an alkoxyl group, and a phenyl group, and further, these alkyl groups, alkenyl groups, and phenyl groups. May have a substituent. Oligosaccharides can also be produced by the same method as the ester compound of the present invention.

  Although the specific example of the ester compound used for this invention below is given, this invention is not limited to this.

  The protective film A of the present invention preferably contains 1 to 30% by mass of the above ester compound of the protective film A in order to suppress the fluctuation of the retardation value and stabilize the display quality. It is preferable to contain -30 mass%. Within this range, it is preferable that the excellent effects of the present invention are exhibited and there is no bleeding out.

(Plasticizer)
The protective film A of the present invention can contain a plasticizer as necessary to obtain the effects of the present invention.

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

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

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

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

Formula (a) R1- (OH) n
However, R1 represents an n-valent organic group, n represents a positive integer of 2 or more, and the OH group represents an alcoholic and / or phenolic hydroxyl group.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

  Examples of the phosphate ester plasticizer include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate and the like.

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

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

Formula (b) R2 (COOH) m (OH) n
(Wherein R2 is an (m + n) -valent organic group, m is a positive integer of 2 or more, n is an integer of 0 or more, a COOH group is a carboxyl group, and an OH group is an alcoholic or phenolic hydroxyl group)
Examples of preferred polyvalent carboxylic acids include the following, but the present invention is not limited to these.

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

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

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

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

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

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

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

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

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

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

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

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

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

  Examples of particularly preferred polyvalent carboxylic acid ester compounds are shown below, but the present invention is not limited thereto.

  For example, triethyl citrate, tributyl citrate, acetyl triethyl citrate (ATEC), acetyl tributyl citrate (ATBC), benzoyl tributyl citrate, acetyl triphenyl citrate, acetyl tribenzyl citrate, dibutyl tartrate, diacetyl dibutyl tartrate, Examples include tributyl trimellitic acid and tetrabutyl pyromellitic acid.

  The polyester plasticizer is not particularly limited, and a polyester plasticizer having an aromatic ring or a cycloalkyl ring in the molecule can be used. Although it does not specifically limit as a polyester plasticizer, For example, the aromatic terminal ester plasticizer represented by the following general formula (c) can be used.

General formula (c) B- (GA) n-GB
(In the formula, B is a benzene monocarboxylic acid residue, G is an alkylene glycol residue having 2 to 12 carbon atoms, an aryl glycol residue having 6 to 12 carbon atoms, or an oxyalkylene glycol residue having 4 to 12 carbon atoms, A represents an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms or an aryl dicarboxylic acid residue having 6 to 12 carbon atoms, and n represents an integer of 1 or more.)
In the general formula (c), a benzene monocarboxylic acid residue represented by B and an alkylene glycol residue, oxyalkylene glycol residue or aryl glycol residue represented by G, an alkylene dicarboxylic acid residue or aryl dicarboxylic group represented by A It is composed of an acid residue and can be obtained by a reaction similar to that of a normal polyester plasticizer.

  Examples of the benzene monocarboxylic acid component of the polyester plasticizer used in the present invention include benzoic acid, para-tert-butylbenzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethylbenzoic acid, ethylbenzoic acid, and normalpropyl. There exist benzoic acid, aminobenzoic acid, acetoxybenzoic acid, etc., and these can be used as 1 type, or 2 or more types of mixtures, respectively.

  Examples of the alkylene glycol component having 2 to 12 carbon atoms of the polyester plasticizer that can be used in the present invention include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1, 3-butanediol, 1,2-propanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neo Pentyl glycol), 2,2-diethyl-1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3propanediol (3,3-dimethylolheptane) 3-methyl-1,5-pentanediol 1,6-hexanediol, 2,2,4-trimethyl 1,3-penta Diol, 2-ethyl 1,3-hexanediol, 2-methyl 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, and the like. It is used as one kind or a mixture of two or more kinds.

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

  In addition, examples of the oxyalkylene glycol component having 4 to 12 carbon atoms of the aromatic terminal ester include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol. It can be used as a seed or a mixture of two or more.

  Examples of the alkylene dicarboxylic acid component having 4 to 12 carbon atoms of the aromatic terminal ester include succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, and dodecanedicarboxylic acid. These are used as one kind or a mixture of two or more kinds. Examples of the arylene dicarboxylic acid component having 6 to 12 carbon atoms include phthalic acid, terephthalic acid, isophthalic acid, 1,5 naphthalene dicarboxylic acid, and 1,4 naphthalene dicarboxylic acid.

  The polyester plasticizer used in the present invention has a number average molecular weight of preferably 300 to 1500, more preferably 400 to 1000. The acid value is 0.5 mgKOH / g or less, the hydroxyl value is 25 mgKOH / g or less, more preferably the acid value is 0.3 mgKOH / g or less, and the hydroxyl value is 15 mgKOH / g or less.

  Specific examples of the aromatic terminal ester plasticizer that can be used in the present invention are shown below, but the present invention is not limited thereto.

(UV absorber)
The protective film A can also contain an ultraviolet absorber. The ultraviolet absorber is intended to improve durability by absorbing ultraviolet light having a wavelength of 400 nm or less, and the transmittance at a wavelength of 370 nm is particularly preferably 10% or less, more preferably 5% or less. Preferably it is 2% or less.

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

(Fine particles)
The protective film A preferably contains fine particles in order to prevent blocking between the films.

  As fine particles, examples of inorganic compounds include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, Mention may be made of magnesium silicate and calcium phosphate.

  Fine particles containing silicon are preferable in terms of low turbidity, and silicon dioxide is particularly preferable.

  The average primary particle diameter of the fine particles is preferably 5 to 400 nm, and more preferably 10 to 300 nm. These may be mainly contained as secondary aggregates having a particle size of 0.05 to 0.3 μm, and may be contained as primary particles without being aggregated if the particles have an average particle size of 100 to 400 nm. preferable.

  The content of these fine particles in the polarizing plate protective film is preferably 0.01 to 1% by mass, particularly preferably 0.05 to 0.5% by mass. In the case of a polarizing plate protective film having a multilayer structure by the co-casting method, it is preferable to contain fine particles of this addition amount on the surface.

  Silicon dioxide fine particles are commercially available, for example, under the trade names Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (manufactured by Nippon Aerosil Co., Ltd.). it can.

  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.

  Examples of the polymer include silicone resin, fluororesin, and acrylic resin. Silicone resins are preferable, and those having a three-dimensional network structure are particularly preferable. For example, Tospearl 103, 105, 108, 120, 145, 3120, and 240 (manufactured by Toshiba Silicone Co., Ltd.) It is marketed by name and can be used.

  Among these, Aerosil 200V and Aerosil R972V are particularly preferably used because they have a large effect of reducing the friction coefficient while keeping the turbidity of the polarizing plate protective film low. In the polarizing plate protective film used in the present invention, the dynamic friction coefficient of at least one surface is preferably 0.2 to 1.0.

  Various additives may be batch-added to a dope that is a cellulose ester-containing solution before film formation, or an additive solution may be separately prepared and added in-line. In particular, it is preferable to add a part or all of the fine particles in-line in order to reduce the load on the filter medium.

  When the additive solution is added in-line, it is preferable to dissolve a small amount of cellulose ester in order to improve mixing with the dope. The amount of the cellulose ester is preferably 1 to 10 parts by mass, more preferably 3 to 5 parts by mass with respect to 100 parts by mass of the solvent.

  In order to perform in-line addition and mixing in the present invention, for example, an in-line mixer such as a static mixer (manufactured by Toray Engineering), SWJ (Toray static type in-tube mixer Hi-Mixer) or the like is preferably used.

<Polyolefin>
In particular, polypropylene or polyethylene resin is preferably used as the polyolefin resin, but is not limited thereto. Two or more compatible resins may be used as these resins. Specific examples include the compounds described in JP2007-316603A.

  In the present invention, it is particularly preferable to use a cycloolefin resin. The cycloolefin resin used in the present invention is made of a polymer resin containing an alicyclic structure. A preferred cycloolefin resin is a resin obtained by polymerizing or copolymerizing a cyclic olefin. Examples of the cyclic olefin include norbornene, dicyclopentadiene, tetracyclododecene, ethyltetracyclododecene, ethylidenetetracyclododecene, tetracyclo [7.4.0.110, 13.02,7] trideca-2,4. Unsaturated hydrocarbons of polycyclic structures such as 6,11-tetraene and derivatives thereof; cyclobutene, cyclopentene, cyclohexene, 3,4-dimethylcyclopentene, 3-methylcyclohexene, 2- (2-methylbutyl) -1-cyclohexene, cyclo Examples thereof include monocyclic unsaturated hydrocarbons such as octene, 3a, 5,6,7a-tetrahydro-4,7-methano-1H-indene, cycloheptene, cyclopentadiene, cyclohexadiene, and derivatives thereof. These cyclic olefins may have a polar group as a substituent. Examples of the polar group include a hydroxyl group, a carboxyl group, an alkoxyl group, an epoxy group, a glycidyl group, an oxycarbonyl group, a carbonyl group, an amino group, an ester group, and a carboxylic acid anhydride group. Or a carboxylic anhydride group is preferred.

  Preferred cycloolefin resins may be those obtained by addition copolymerization of monomers other than cyclic olefins. Addition copolymerizable monomers include ethylene, propylene, 1-butene, 1-pentene, and other ethylene or α-olefins; 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl- Examples include dienes such as 1,4-hexadiene and 1,7-octadiene.

The cyclic olefin is obtained by an addition polymerization reaction or a metathesis ring-opening polymerization reaction. The polymerization is carried out in the presence of a catalyst. Examples of the addition polymerization catalyst include a polymerization catalyst composed of a vanadium compound and an organoaluminum compound. As a catalyst for ring-opening polymerization, a polymerization catalyst comprising a metal halide such as ruthenium, rhodium, palladium, osmium, iridium, platinum, nitrate or acetylacetone compound, and a reducing agent; or titanium, vanadium, zirconium, tungsten, molybdenum And a polymerization catalyst composed of a metal halide such as acetylacetone compound and an organoaluminum compound. The polymerization temperature, pressure and the like are not particularly limited, but the polymerization is usually carried out at a polymerization temperature of -50 ° C to 100 ° C and a polymerization pressure of 0 to 490 N / cm ² .

  The cycloolefin resin is preferably a resin obtained by polymerizing or copolymerizing a cyclic olefin, followed by a hydrogenation reaction to change the unsaturated bond in the molecule to a saturated bond. The hydrogenation reaction is performed by blowing hydrogen in the presence of a known hydrogenation catalyst. Examples of hydrogenation catalysts include cobalt acetate / triethylaluminum, nickel acetylacetonate / triisobutylaluminum, transition metal compounds such as titanocene dichloride / n-butyllithium, zirconocene dichloride / sec-butyllithium, tetrabutoxytitanate / dimethylmagnesium / alkyl. Homogeneous catalyst consisting of a combination of metal compounds; heterogeneous metal catalyst such as nickel, palladium, platinum; nickel / silica, nickel / diatomaceous earth, nickel / alumina, palladium / carbon, palladium / silica, palladium / diatomaceous earth And a heterogeneous solid-supported catalyst in which a metal catalyst such as palladium / alumina is supported on a carrier.

  Or the following norbornene-type resin is also mentioned as a cycloolefin type resin. The norbornene-based resin preferably has a norbornene skeleton as a repeating unit. Specific examples thereof include, for example, JP-A-62-252406, JP-A-62-2252407, and JP-A-2-133413. JP, JP 63-145324, JP 63-264626, JP 1-224017, JP 57-8815, JP 5-2108, JP 5-39403. JP-A-5-43663, JP-A-5-43834, JP-A-5-70655, JP-A-5-279554, JP-A-6-206985, JP-A-7-62028, JP-A-8-176411, JP-A-9-241484, JP-A-2001-277430, JP-A-2003-139 No. 50, JP-A No. 2003-14901, JP-A No. 2003-161832, JP-A No. 2003-195268, JP-A No. 2003-111588, JP-A No. 2003-211589, JP-A No. 2003-268187 Gazette, JP-A-2004-133209, JP-A-2004-309799, JP-A-2005-121183, JP-A-2005-164632, JP-A-2006-72309, JP-A-2006-178191, Although what was described in Unexamined-Japanese-Patent No. 2006-215333, Unexamined-Japanese-Patent No. 2006-268065, Unexamined-Japanese-Patent No. 2006-299199 etc. is mentioned, It is not limited to these. Moreover, these may be used individually by 1 type and may use 2 or more types together. Specifically, ZEONEX, ZEONOR manufactured by Nippon Zeon Co., Ltd., Arton manufactured by JSR Corporation, APPEL manufactured by Mitsui Chemicals, Inc. (APL8008T, APL6509T, APL6013T, APL5014DP, APL6015T) and the like are preferably used.

  The molecular weight of the cycloolefin resin is appropriately selected depending on the purpose of use, but is converted to polyisoprene or polystyrene measured by gel permeation chromatography method of cyclohexane solution (toluene solution when polymer resin does not dissolve) When the weight average molecular weight is usually in the range of 5,000 to 500,000, preferably 8,000 to 200,000, more preferably 10,000 to 100,000, the mechanical strength and molding processability of the molded body are highly balanced and suitable. is there.

<Protective film A manufacturing method>
Next, the manufacturing method of the protective film A of this invention is demonstrated.

  The protective film A of the present invention is preferably a cellulose ester film produced by a solution casting method or a melt casting method.

  The production of the protective film A of the present invention includes a step of dissolving a cellulose ester and an additive in a solvent to prepare a dope, a step of casting the dope on an endless metal support that moves infinitely, and a cast dope. It is carried out by a step of drying as a web, a step of peeling from a metal support, a step of stretching or maintaining the width, a step of further drying, and a step of winding up the finished film.

  The process for preparing the dope will be described. The concentration of cellulose ester in the dope is preferably higher because the drying load after casting on the metal support can be reduced, but if the concentration of cellulose ester is too high, the load during filtration increases and the filtration accuracy is poor. Become.

  As a density | concentration which makes these compatible, 10-35 mass% is preferable, More preferably, it is 15-25 mass%.

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

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

  Therefore, depending on the average acetylation degree (acetyl group substitution degree) of the cellulose ester, the good solvent and the poor solvent change. For example, when acetone is used as the solvent, the cellulose ester acetate ester (acetyl group substitution degree 2.4), cellulose Acetate propionate is a good solvent, and cellulose acetate (acetyl group substitution degree 2.8) is a poor solvent.

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

  Moreover, although the poor solvent used for this invention is not specifically limited, For example, methanol, ethanol, n-butanol, cyclohexane, cyclohexanone, etc. are used preferably. Moreover, it is preferable that 0.01-2 mass% of water contains in dope. Moreover, the solvent used for melt | dissolution of a cellulose ester collect | recovers the solvent removed from the film by drying at the film-forming process, and uses this again.

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

  It is preferable to stir and dissolve while heating at a temperature that is equal to or higher than the boiling point of the solvent at normal pressure and that the solvent does not boil under pressure, in order to prevent the generation of massive undissolved materials called gels and mamacos. Moreover, after mixing a cellulose ester with a poor solvent and making it wet or swell, the method of adding a good solvent and melt | dissolving is also used preferably.

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

  The heating temperature with the addition of a solvent is preferably higher from the viewpoint of the solubility of the cellulose ester, but if the heating temperature is too high, the required pressure increases and the productivity deteriorates. A preferable heating temperature is 45 to 120 ° C, more preferably 60 to 110 ° C, and still more preferably 70 ° C to 105 ° C. The pressure is adjusted so that the solvent does not boil at the set temperature.

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

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

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

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

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

The bright spot foreign matter was placed in a crossed Nicols state with two polarizing plates, a rolled cellulose ester was placed between them, and light was applied from the side of one polarizing plate, and observed from the side of the other polarizing plate. It is a point (foreign matter) that light from the opposite side appears to leak sometimes, and the number of bright spots having a diameter of 0.01 mm or more is preferably 200 / cm ² or less.

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

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

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

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

  Here, the dope casting will be described.

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

  The cast width can be 1 to 4 m. The surface temperature of the metal support in the casting step is −50 ° C. to a temperature lower than the boiling point of the solvent, and a higher temperature is preferable because the web can be dried faster. May deteriorate. A preferable support body temperature is 0-40 degreeC, and 5-30 degreeC is still more preferable.

  Alternatively, it is also a preferable method that the web is gelled by cooling and peeled from the drum in a state containing a large amount of residual solvent.

  The method for controlling the temperature of the metal support is not particularly limited, and there are a method of blowing hot air or cold air, and a method of contacting hot water with the back side of the metal support.

  It is preferable to use warm water because heat transfer is performed efficiently, so that the time until the temperature of the metal support becomes constant is short. When warm air is used, wind at a temperature higher than the target temperature may be used.

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

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

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

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

  In the film drying process, generally, a roll drying method (a method in which a plurality of rolls arranged on the upper and lower sides are alternately passed through and dried) or a tenter method is used while drying the web.

  In order to produce the protective film A of the present invention, the web is stretched in the conveying direction (= long direction) where the amount of residual solvent of the web immediately after peeling from the metal support is large, and both ends of the web are gripped with clips or the like. In the tenter method, stretching is preferably performed in the 45 ° direction.

<Optically anisotropic layer>
In the protective film A of the present invention, it is also preferred that a photopolymerizable curable liquid crystal compound is applied on a resin film support and is photopolymerized and cured to form an optically anisotropic layer.

  The optically anisotropic layer contains at least one liquid crystalline compound, for example, an optically anisotropic layer obtained by forming a low molecular liquid crystalline compound in a nematic orientation in a liquid crystal state and then immobilizing it by photocrosslinking or thermal crosslinking. Alternatively, an optically anisotropic layer obtained by fixing the alignment by forming a polymer liquid crystalline compound in a nematic alignment in a liquid crystal state and then cooling it can also be used.

  The polymerizable liquid crystal compound may be a polyfunctional polymerizable liquid crystal or a monofunctional polymerizable liquid crystal compound.

  The optically anisotropic layer may be composed of only one layer or a laminate of two or more optically anisotropic layers. In order to arbitrarily control the refractive index anisotropy in the three-dimensional direction, two or more optically anisotropic layers may be laminated.

  The liquid crystalline compound used for the optically anisotropic layer may be a discotic liquid crystalline compound or a rod-shaped liquid crystalline compound.

  The alignment state of the liquid crystal compound may be any of vertical alignment, horizontal alignment, hybrid alignment, and tilt alignment.

  The optically anisotropic layer comprises a coating liquid containing a liquid crystalline compound such as a rod-like liquid crystalline compound or a discotic liquid crystalline compound, and, if necessary, the following polymerization initiator, air interface alignment agent, and other additives. It can be formed by coating on a support.

  Specifically, it is preferable to form an alignment film on a support and apply the coating solution on the surface of the alignment film.

(Discotic liquid crystalline compounds)
In the present invention, the optically anisotropic layer is preferably formed using a discotic liquid crystalline compound.

  Examples of the discotic liquid crystalline compound include various documents (C. Destrade et al., Mol. Crysr. Liq. Cryst., Vol. 71, page 111 (1981); 22, Chemistry of Liquid Crystals, Chapter 5, Chapter 10, Section 2 (1994); B. Kohne et al., Angew. Chem. Soc. Chem. Comm., Page 1794 (1985); J. Zhang et al. , J. Am. Chem. Soc., Vol. 116, page 2655 (1994)).

  The polymerization of the discotic liquid crystalline compound is described in JP-A-8-27284.

  The discotic liquid crystalline compound preferably has a polymerizable group so that it can be fixed by polymerization.

  Specifically, a structure in which a polymerizable group is bonded as a substituent to a discotic core of a discotic liquid crystalline compound can be considered, but when a polymerizable group is directly connected to the discotic core, the orientation state is changed in the polymerization reaction. It becomes difficult to keep. Therefore, a structure having a linking group between the discotic core and the polymerizable group is preferable. That is, the discotic liquid crystalline compound having a polymerizable group is preferably a compound represented by the following formula.

D (-LP) n
However, in said formula, D is a disk shaped core, L is a bivalent coupling group, P is a polymeric group, n is an integer of 4-12. Preferred specific examples of the discotic core (D), the divalent linking group (L), and the polymerizable group (P) in the above formula are (D1) to (D1) described in JP-A No. 2001-4837, respectively. D15), (L1) to (L25), and (P1) to (P18), and the contents described in the publication can be suitably used.

  The discotic liquid crystalline compound having a polymerizable group is preferably a discotic compound having lost liquid crystallinity after being fixed by polymerization.

  In addition, the discotic nematic liquid crystal phase-solid phase transition temperature of the discotic liquid crystalline compound is preferably 70 to 300 ° C, and more preferably 70 to 170 ° C.

(Bar-shaped liquid crystalline compound)
In the present invention, it is also preferable to form an optically anisotropic layer using a rod-like liquid crystalline compound. Examples of the rod-like liquid crystalline compound include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines. Preferred examples thereof include phenyldioxanes, tolans, and alkenylcyclohexylbenzonitriles.

  As the rod-like liquid crystalline compound, not only the above low molecular liquid crystalline compound but also a high molecular liquid crystalline compound can be used.

  The rod-like liquid crystal compound is more preferably fixed in orientation by polymerization. As the liquid crystalline compound, those having a partial structure capable of causing polymerization or crosslinking reaction by actinic rays, electron beams, heat or the like are preferably used.

  The number of the partial structures is preferably 1 to 6, and more preferably 1 to 3. As the polymerizable rod-like liquid crystalline compound, Makromol. Chem. 190, 2255 (1989), Advanced Materials 5, 107 (1993), US Pat. No. 4,683,327, US Pat. No. 5,622,648, US Pat. No. 5,770,107, International Publication WO95 / 22586. No. 95/24455, No. 97/00600, No. 98/23580, No. 98/52905, JP-A-1-272551, No. 6-16616, and No. 7-110469. 11-80081, JP 2001-328773 A, and the like.

(Vertical alignment accelerator)
In order to uniformly and vertically align the discotic liquid crystalline compound or rod-shaped liquid crystalline compound, it is preferable to have an alignment film and to control the alignment of the liquid crystalline compound vertically on the alignment film interface side and the air interface side.

  For this purpose, a composition obtained by adding a compound having an effect of vertically aligning a liquid crystalline compound to the alignment film by an excluded volume effect, an electrostatic effect, or a surface energy effect may be used.

  In addition, with regard to alignment control on the air interface side, a compound that is unevenly distributed at the air interface during alignment of the liquid crystalline compound and acts to align the liquid crystalline compound vertically by its excluded volume effect, electrostatic effect, or surface energy effect is blended The composition (hereinafter, also simply referred to as “liquid crystalline composition”) may be used.

  A pyridinium derivative is preferably used as the compound (alignment film interface side vertical alignment agent) that promotes the vertical alignment of the molecules of the liquid crystal compound on the alignment film interface side.

The compound (air interface side vertical alignment agent) that promotes the vertical alignment of the molecules of the liquid crystal compound on the air interface side includes a fluoroaliphatic group that promotes the uneven distribution of the compound on the air interface side. One or more hydrophilic groups selected from the group consisting of: carboxyl group (—COOH), sulfo group (—SO ₃ H), phosphonoxy group {—OP (═O) (OH) ₂ }, and salts thereof A compound containing is preferably used. Further, by blending these compounds, for example, when a liquid crystalline composition is prepared as a coating solution, the coating property of the coating solution is improved, and the occurrence of unevenness and repellency is suppressed.

(Coating solvent)
As a coating solvent used for the preparation of the coating solution, an organic solvent is preferably used. Examples of the organic solvent include amide (eg, N, N-dimethylformamide), sulfoxide (eg, dimethyl sulfoxide), heterocyclic compound (eg, pyridine), hydrocarbon (eg, benzene, hexane), alkyl halide ( Examples include chloroform (dichloromethane), esters (eg, methyl acetate, butyl acetate), ketones (eg, acetone, methyl ethyl ketone), ethers (eg, tetrahydrofuran, 1,2-dimethoxyethane). Of these, alkyl halides and ketones are preferred. The said organic solvent may be used individually by 1 type, and may use 2 or more types together.

  The coating liquid can be applied by a known method such as an extrusion coating method, a direct gravure coating method, a reverse gravure coating method, or a die coating method.

(Polymerization initiator)
The vertically aligned liquid crystal compound is fixed while maintaining the alignment state. The fixing is preferably performed by a polymerization reaction of the polymerizable group (P) introduced into the liquid crystal compound.

  The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator. Among these, the photopolymerization reaction is preferable.

  Examples of the photopolymerization initiator include α-carbonyl compounds described in US Pat. Nos. 2,367,661 and 2,367,670, acyloin ethers described in US Pat. No. 2,448,828, and US Pat. No. 2,722,512. Α-hydrocarbon-substituted aromatic acyloin compounds described in US Pat. No. 3,049,027, polynuclear quinone compounds described in US Pat. Nos. 3,046,127 and 2,951,758, and triarylimidazole dimers described in US Pat. No. 3,549,367. And a combination of p-aminophenyl ketone, acridine compounds and phenazine compounds described in JP-A-60-105667, US Pat. No. 4,239,850, and oxadiazole compounds described in US Pat. No. 4,221,970. Can be mentioned.

  The amount of the photopolymerization initiator used is preferably 0.01 to 20% by mass, more preferably 0.5 to 5% by mass, based on the solid content of the coating solution.

The light irradiation for the polymerization of the discotic liquid crystalline compound preferably uses ultraviolet rays. Irradiation energy in the light irradiation is preferably 20~50J / cm ^2, and more preferably 100 to 800 mJ / cm ^2. In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions.

  The thickness of the optically anisotropic layer is preferably 0.1 to 10 μm, more preferably 0.5 to 5 μm, and particularly preferably 1 to 5 μm.

(Other additives)
In combination with the above liquid crystalline compounds, other additives such as plasticizers, surfactants, polymerizable monomers, etc. are used in combination to improve the uniformity of the coating film, the strength of the film, the orientation of the liquid crystalline compounds, etc. Can do. These other additives are preferably compatible with the liquid crystal compound and do not inhibit the alignment.

<< Protective film B >>
The protective film B of the present invention includes a reflective linearly polarizing layer, and the reflective axis of the reflective polarizing layer and the absorption axis of the absorbing linear polarizer are substantially parallel.

  Here, “substantially parallel” means that the smaller angle formed by the reflection axis and the absorption axis is 3 ° or less, preferably 1 ° or less, more preferably 0.5 ° or less.

  The reflective linearly polarizing layer is one in which one of two orthogonally polarized light incident on the polarizing layer and orthogonal to each other is transmitted as it is, and the other linearly polarized light is reflected to the light source side, When the incident polarized light is parallel to the reflection axis, the average reflectance at 400 nm to 700 nm is 50% or more, and when the incident polarized light is parallel to the transmission axis, the average reflectance at 400 nm to 700 nm is 30%. Refers to the following: Therefore, the reflection axis is a direction showing the maximum average reflectance.

  The average reflectance is obtained by, for example, using an integrating sphere device with a U-3310 spectrophotometer manufactured by Hitachi High-Technologies Corporation and placing the protective film B on the incident optical path from the light source. It is calculated | required as an average of the reflectance.

As a method of separating two linearly polarized light into transmission and reflection,
First, materials with different birefringence, such as 3M DBEF and DRPF, are combined, and one polarization component is transmitted with substantially no difference in refractive index between the materials. For one polarized component, a method of increasing the refractive index difference and backscattering or thin film interference reflection,
Second, a method in which the light is incident on an interface having a different refractive index at an incident angle near a so-called Brewster angle and separated using a principle in which the reflectance varies depending on the polarization component,
Thirdly, due to the structure of the fine metal wires arranged in parallel with each other at a nano-order period as disclosed in Japanese Unexamined Patent Application Publication No. 2006-330521, the polarized light of the component parallel to the fine metal wires is free electrons inside the metal. A method using the principle that the polarized light of the component orthogonal to the metal thin wire does not transmit due to interference between the scattered light emitted from and the light to be transmitted, and the free electrons inside the metal cannot be moved,
Fourth, a scatterer (fine particle) having a size anisotropy typified by a rod or needle that exhibits scattering anisotropy with respect to visible light has a refractive index different from that of the scatterer. In the optically continuous phase such as a transparent resin film having a method of separating by uniformly dispersed and oriented,
Etc.

  Among these, the reflective linearly polarizing layer according to the present invention is the third grid-type polarizing layer, or is dispersed in a state where fine particles having an aspect ratio of 2 or more are oriented in approximately one direction in the fourth resin. Is a layer (hereinafter referred to as a fine particle alignment layer).

<Grid-type polarizing layer>
The grid-type polarizing layer has a plurality of grid lines arranged substantially in parallel with each other on the surface and / or inside of the resin film serving as a base material. The grid lines are real parts of the complex refractive index. The absolute value of the difference between the imaginary part and the imaginary part is preferably 1.0 or more.

  The resin film is a film made of a transparent resin. The transparent resin film preferably has a smooth transmittance of 80% or more of light in the visible region of 400 to 700 nm. The resin used for the protective film A is preferably used as the base resin.

  Although there is no limitation in particular as transparent resin which comprises a resin film, it is preferable that the glass transition temperature of resin is 60-200 degreeC from a viewpoint of the workability to a film surface, and it is more preferable that it is 100-180 degreeC. . The glass transition temperature can be measured by differential scanning calorimetry (DSC).

  Examples of the transparent resin constituting the resin film include polycarbonate resin, polyethersulfone resin, polyethylene terephthalate resin, polyimide resin, polymethyl methacrylate resin, polysulfone resin, polyarylate resin, polyethylene resin, polyvinyl chloride resin, and cellulose diacetate. And cellulose ester resins such as cellulose triacetate, and alicyclic olefin polymers. Of these, alicyclic olefin polymers are preferred from the viewpoints of transparency, low hygroscopicity, dimensional stability, and processability. Examples of the alicyclic olefin polymer include those described in JP-A No. 05-310845, JP-A No. 05-097978, and JP-A No. 11-124429 in addition to the alicyclic olefin polymer. It is done.

  The transparent resin used in the present invention contains coloring agents such as pigments and dyes, fluorescent brighteners, dispersants, heat stabilizers, light stabilizers, ultraviolet absorbers, antistatic agents, antioxidants, lubricants, solvents, etc. An agent may be appropriately blended.

  The resin film can be obtained by molding the transparent resin by a known method. For example, a cast molding method, an extrusion molding method, an inflation molding method and the like can be mentioned. The resin film preferably has a small in-plane retardation from the viewpoint that it is preferable that the resin film has a small influence on the polarization of light. Specifically, the resin film has a wavelength of 550 nm, preferably 50 nm or less, more preferably 10 nm or less.

  The average thickness of the resin film suitably used is preferably 80 to 400 μm.

  The material used for the grid lines is preferably a material whose absolute value of the difference between the real part n and the imaginary part κ of the complex refractive index (N = n−iκ) is 1.0 or more, and the real part of the complex refractive index. And the imaginary part are large, and the absolute value of the difference can be appropriately selected from materials of 1.0 or more. Specific examples of materials whose absolute value of the difference between the real part and the imaginary part of the complex refractive index is 1.0 or more include metals; inorganic semiconductors such as silicon and germanium; polyacetylene, polypyrrole, polythiophene, poly-p-phenylene, etc. Conductive polymers, and organic conductive materials obtained by doping these conductive resins with dopants such as iodine, boron trifluoride, arsenic pentafluoride, perchloric acid; conductive resins such as gold and silver on insulating resins Examples thereof include organic-inorganic composite conductive materials obtained by drying a solution in which metal fine particles are dispersed. Among these, a metal material is preferable from the viewpoints of productivity and durability of the grid polarizing film. In order to efficiently separate polarized light in the visible range, each of the real part n and the imaginary part κ of the complex refractive index at a temperature of 25 ° C. and a wavelength of 550 nm is preferably such that n is 4.0 or less and κ is 3. 0 or more and the absolute value of the difference | n−κ | is 1.0 or more, more preferably n is 2.0 or less, κ is 4.5 or more, and | n−κ | .0 or more. Examples of the preferable range include silver, aluminum, chromium, indium, iridium, magnesium, palladium, platinum, rhodium, ruthenium, antimony, and tin. Examples of the more preferable range include aluminum, indium. , Magnesium, rhodium, tin and the like. In addition to the above, a material in which n is 3.0 or more and κ is 2.0 or less, preferably a material in which n is 4.0 or more and κ is 1.0 or less is also preferably used. be able to. Examples of such a material include silicon. The complex refractive index N is a theoretical relational expression of electromagnetic waves, and is expressed by N = n−iκ using the refractive index n of the real part and the extinction coefficient κ of the imaginary part.

  Although the details are unknown, the value of | n−κ | has the following significance. First, in the case of n <κ, the larger κ, the greater the conductivity, and the more free electrons that can vibrate in the direction of the grid line, so the polarization (polarized light in the direction parallel to the grid line) The electric field generated by the incident becomes strong, and the reflectance with respect to the polarized light increases. Since the width of the grid line is small, electrons do not move in the direction orthogonal to the grid line, and the above effect does not occur for polarized light in the direction orthogonal to the grid line, and is transmitted. In addition, since the wavelength in the medium of incident light is smaller when n is smaller, the size (line width, pitch, etc.) of the fine concavo-convex structure is relatively small, and is less susceptible to the effects of scattering, diffraction, Light transmittance (polarized light in a direction perpendicular to the grid lines) and reflectance (polarized light in a direction parallel to the grid lines) are increased. Here, | n−κ | is 1.0 or more, which means that larger κ and smaller n are preferable.

  On the other hand, in the case of n> κ, the larger n is, the larger the difference in refractive index n between the grid line and the adjacent portion (for example, air) becomes, and the structural birefringence is easily developed. On the other hand, if κ is large, light absorption increases, so it is preferable that κ is small in order to prevent light loss. Here, | n−κ | being 1.0 or more indicates that n is larger and κ is smaller.

  The grid lines are not particularly limited as long as they have a known grid structure as shown in FIG. That is, as shown in FIG. 11, the grid-type polarizing layer according to an embodiment of the present invention includes the above-described resin film 502 and a plurality of grid lines 501 arranged substantially parallel to each other on the upper surface of the resin film. It has. Here, “substantially parallel” means that, for example, even when the grid lines do not intersect and the pitch between the grid lines is widened or narrowed, for example, it is within ± 5% of the average pitch. The pitch between grid lines needs to be ½ or less of the wavelength of light to be used. The narrower the grid line width, the smaller the absorption of the polarization component in the transmission direction, which is preferable in terms of characteristics. In the grid polarizing film used for visible light, the pitch is usually 50 to 1000 nm, the line width is usually 25 to 600 nm, and the height is 10 to 800 nm.

  The grid-type polarizing layer preferably has a polarization reflection axis direction substantially parallel to the longitudinal direction of the film. By making the polarization reflection axis substantially parallel to the longitudinal direction of the film, the lamination with the absorption linearly polarizing film stretched so that the absorption axis is in the longitudinal direction is cut into single sheets while keeping the length. Therefore, it is excellent in productivity. The grid-type polarizing layer extends the grid lines substantially parallel to the longitudinal direction of the resin film. Accordingly, a grid having a polarization reflection axis in the longitudinal direction of the film in order to exhibit an effect of reflecting polarized light parallel to the grid line formed of the material and transmitting polarized light perpendicular to the grid line. Type polarizing layer.

  The pitch of the fine irregular shape of the grid line is preferably 50 to 1000 nm, and the width of the convex portion or the concave portion is shorter than the wavelength of normal light, preferably 25 to 600 nm, and the height of the convex portion or the concave portion. The depth is preferably 50 to 800 nm. The concavo-convex shape extends in the longitudinal direction of the lattice, and the length thereof is longer than the wavelength of normal light and is usually 800 nm or more.

  The method for producing the grid line is, for example, by continuously forming a fine concavo-convex shape on the surface of the resin film using a transfer roll having a fine concavo-convex shape, and then the difference between the real part and the imaginary part of the complex refractive index on the concavo-convex part. Although the grid line can be continuously formed by forming a film made of a material having an absolute value of 1.0 or more, the present invention is not limited to this.

  The transfer roll having a fine irregular shape used in the above production method is not particularly limited as long as it has fine irregularities on its peripheral surface. For example, a material having a Mohs hardness of 9 or higher is coated with a high energy beam. A tool formed by forming a protrusion having a width of 600 nm or less at the tip, and using the tool, the pitch is preferably 50 to 1000 nm on the peripheral surface of the roll member, and the width of the convex portion or the concave portion is preferable. Is a method of forming a concavo-convex shape in which the height of the convex portion or the depth of the concave portion is preferably 50 to 800 nm.

  The shape of the grid line is not particularly limited, and examples thereof include a rectangle, a triangle, a semicircle, a trapezoid, or a shape obtained by slightly deforming these shapes. Among these, those having a rectangular cross section are preferable because the grid lines can be easily formed by a thin film made of a material having an absolute value of the difference between the real part and the imaginary part of the complex refractive index of 1.0 or more.

  The arithmetic average roughness (Ra) of the protrusion formed at the tip is preferably 10 nm or less, more preferably 3 nm or less.

  Examples of the material having a Mohs hardness of 9 or more used for the tool include diamond, cubic boron nitride, and corundum. Single crystal diamond or cubic boron nitride is more preferable because of its high hardness, and single crystal diamond is particularly preferable.

  Examples of the high energy beam used for manufacturing the tool include a laser beam, an ion beam, and an electron beam. Among these, an ion beam and an electron beam are preferable.

  The roll used for fine processing is not particularly limited, but the roll peripheral surface is preferably formed of a material having an appropriate hardness for forming a fine lattice shape, for example, formed by electrodeposition or electroless plating. The metal film is formed. The material constituting the metal film is preferably a material that can obtain a metal film having a Vickers hardness of preferably 40 to 350, more preferably 200 to 300, specifically copper, nickel, nickel-phosphorus alloy, palladium. Of these, copper, nickel, and nickel-phosphorus alloys are preferable.

  The resin film is pressed and sandwiched between the transfer roll and the roll on the opposite side of the resin film, and the uneven shape on the peripheral surface of the transfer roll is transferred to the resin film. The pinching pressure between the transfer roll and the roll on the opposite side is preferably several MPa to several tens of MPa. The temperature during transfer is preferably Tg to (Tg + 100) ° C., where Tg is the glass transition temperature of the transparent resin constituting the resin film. The contact time between the resin film and the transfer roll can be adjusted by the feed speed of the resin film, that is, the roll rotation speed, and is preferably 5 to 600 seconds.

  As another method for continuously forming a fine uneven shape on the surface of the resin film, there is a method in which a photosensitive transparent resin is pressed against a transfer roll and exposed to transfer the uneven shape. Specifically, it is a method of casting a photosensitive transparent resin solution, removing the solvent, then pressing the transfer roll and simultaneously irradiating light to cure the photosensitive transparent resin and fix the uneven shape. .

  Next, a film made of a material having an absolute value of the difference between the real part and the imaginary part of the complex refractive index of 1.0 or more is formed on the unevenness, and a plurality of grid lines are arranged substantially parallel to each other by the film. The structure is formed continuously. The film is not particularly limited in its formation location as long as it forms the above structure.

  The method for forming a film made of a material having an absolute value of the difference between the real part and the imaginary part of the complex refractive index of 1.0 or more is not particularly limited. Depending on the materials used, various coatings by vacuum deposition processes such as vacuum deposition, sputtering, and ion plating, and wet processes such as microgravure, screen coating, dip coating, electroless plating, and electrolytic plating Can be used. Of these, vacuum vapor deposition and sputtering are preferred from the viewpoint of the uniformity of the grid structure.

  Furthermore, a transparent protective film is applied to the long grid polarizing film in order to prevent corrosion of the film made of a material having an absolute value of the difference between the real part and the imaginary part of the complex refractive index of 1.0 or more and to maintain the shape of the grid polarizing film. It is preferable to laminate. Depending on the purpose, the transparent protective layer may be formed only on one side of the long grid polarizing film (either the surface on which the grid lines are formed or the surface on which the grid lines are not formed) or both sides. You may form in. The transparent protective film is not particularly limited as long as it is a layer capable of transmitting light. For example, a transparent film made of cellulose esters such as cellulose acetate, cellulose acetate butyrate, and cellulose propionate, polycarbonate, polyolefin, polystyrene, polyester, and the like. An organic layer made of urethane, acrylic, etc., an organic / inorganic composite layer made of organoalkoxysilane, inorganic fine particle-dispersed acrylic, etc., an inorganic layer made of silicon nitride, aluminum nitride, silicon oxide, or the like.

  The method of laminating the transparent protective film is not particularly limited, but a method of laminating a long grid polarizing film and a transparent protective film using a laminator, and a coating agent containing a composition for forming a transparent protective layer are long grid. A method of laminating a transparent protective layer by applying to a polarizing film and drying, a method of forming a coating layer on a long grid polarizing film by the above method, and further curing by heat or light, vacuum deposition on the long grid polarizing film Examples thereof include a method of laminating a transparent protective layer by a method such as a method, an ion plating method, or a sputtering method.

  The grid-type polarizing layer used in the present invention is not limited to the above, and a method disclosed in JP-A-2006-47813 is also preferably used.

  For example, when the grid-type polarizing layer according to the present invention is disposed between the backlight device and the liquid crystal panel, the light emitted from the backlight device is separated into two linearly polarized light by the grid-type polarizing layer, The polarized light returns in the direction of the liquid crystal panel, and the other linearly polarized light returns in the direction of the backlight device. The backlight device is usually provided with a reflecting plate, and the linearly polarized light returning to the backlight device is reflected by the reflecting plate and returns to the grid-type polarizing layer again. The returned light is again separated into two polarized light by the grid polarizer. By repeating this, the light emitted from the backlight device is effectively used. As a result, light such as a backlight can be efficiently used for displaying an image on the liquid crystal display device, and an effect of brightening the screen can be obtained.

  In a transmissive liquid crystal display device, when this grid polarizer is placed between the reflector and the liquid crystal panel, natural light entering from the outside is separated into two polarized lights by the grid polarizer, and one polarized light is transmitted. Reach the reflector. The other polarized light is reflected and returns to the liquid crystal panel. The polarized light that has reached the reflecting plate is reflected by the reflecting plate and separated again into two polarized light by the grid polarizer. By repeating this, it is possible to increase the amount of light that is visible through the liquid layer panel.

<Fine particle orientation layer>
As disclosed in JP-A-11-509014, the fine particle orientation layer has a refractive index of an optical continuous phase (for example, the resin film) and a fine particle transmission axis side having optical anisotropy. By forming a film with substantially the same refractive index as that of the film, it is possible to selectively transmit predetermined polarized light, selectively scatter other polarized light, and improve brightness by reusing scattered light. It is something that can be done.

  The optical continuous phase refers to, for example, an optical phase in which the refractive index of each portion of the resin film is substantially constant and continuous, and the variation in each portion of the refractive index is less than 0.01. The variation in refractive index is preferably 0.005 or less, particularly preferably 0.001 or less. The fine particles having optical anisotropy refer to a minute region having a difference in refractive index between the major axis direction of the fine particles and the minor axis direction perpendicular thereto, and the difference in refractive index is preferably 0.01 or more.

  FIG. 12 is a schematic diagram of a fine particle alignment layer containing an optical continuous phase and fine particles.

  FIG. 12a shows a state in which fine particles having optical anisotropy are oriented in a substantially constant direction in the width direction (TD direction) of the film in the optical continuous phase. When the refractive index of the optical continuous phase (resin) is n1, the refractive index in the long axis direction of the fine particles is n2, and the refractive index in the short axis direction of the fine particles is n3, the fine particles are n1 = n2 and n2 <n3. The polarized light parallel to the major axis direction is transmitted through the resin film, and the polarized light parallel to the minor axis direction is scattered. If the transmitted polarized light is parallel to the transmission axis of the light absorbing polarizer, the polarized light is transmitted through the polarizer.

  FIG. 12 b shows a state in which fine particles having optical anisotropy are arranged in a substantially constant direction in the longitudinal direction (MD direction) of the resin film in the optical continuous phase. Also in this case, assuming that the refractive index of the optical continuous phase (resin) is n1, the refractive index in the long axis direction of the fine particles is n2, and the refractive index in the short axis direction of the fine particles is n3, n1 = n3 and n2 <n3. At some point, polarized light parallel to the minor axis direction of the fine particles is transmitted, and polarized light parallel to the major axis direction is scattered. If the transmitted polarized light is parallel to the transmission axis of the light absorbing polarizer, the polarized light is transmitted through the polarizer.

  The fine particles having optical anisotropy are fine particles having an aspect ratio defined by the above formula of 2 or more. The aspect ratio is preferably in the range of 2 to 100, more preferably in the range of 2 to 25.

  Evaluation of the orientation state and dispersion state of the fine particles in the resin film can be obtained using image data obtained by observing the fine particles in the resin film with an electron microscope.

  From the image data, an azimuth angle and an aspect ratio are obtained for each fine particle. The aspect ratio can be obtained by the above formula. The absolute maximum length corresponds to the length (major axis) of the long axis of the fine particles.

  Fine particles having an aspect ratio of less than 2 such as foreign particles or broken fine particles are noise, and are excluded from the calculation of the average azimuth angle and the average distance between the fine particles, and are obtained for each fine particle having an aspect ratio of 2 or more.

  The angle with the reference axis when taking the absolute maximum length of the fine particles is taken as the azimuth angle. The reference axis can be set arbitrarily, but can be set, for example, in the width direction of the film. The azimuth angle of each fine particle was determined, and the average value was taken as the average azimuth angle.

  Next, the direction of the obtained average azimuth angle was set as a new reference axis, the angle difference between the azimuth angle and the average azimuth angle direction was obtained for each fine particle, and the average of the absolute values of the angle differences was obtained. This is defined as [average value H of absolute values of angles formed by the direction of the average azimuth angle and the azimuth angle of each fine particle]. In the present invention, the average azimuth angle of the fine particles having optical anisotropy is preferably orthogonal or parallel to the film-forming direction of the resin film, and the “H” is preferably within 20 °.

  A specific evaluation method will be described. The produced film was photographed at a magnification of 20,000 with a transmission electron microscope, and the image was read with a scanner Canon Scan FB 636U by Canon Inc. in 300 dpi monochrome 256 gradation.

  The read image was imported into the image processing software WinROOF Ver3.60 (manufactured by Mitani Corp.) installed in Endeavor Pro720L (CPU: Athlon-1 GHz, memory: 512 MB), which is a personal computer manufactured by Epson Direct Corporation.

  Extraction of the captured image was performed for the range of 2 × 2 μm field of view (automatic binarization of the image) as image preprocessing, and image extraction of fine particles was performed. Confirm that 90% or more of the fine particles have been extracted on the screen after image extraction of the fine particles. If the extraction is not sufficient, manually adjust the detection level so that 90% or more of the fine particles are detected and extracted. Make adjustments.

  When the number of fine particles in the observation range was less than 1000, the same operation was performed for another 2 × 2 μm field of view until the total number of fine particles reached 1000 or more.

  The azimuth angle was measured for each fine particle of the image data extracted as described above. The azimuth angle of the fine particles will be described with reference to FIG.

  FIG. 13 shows an example of an image obtained by photographing a resin film containing fine particles at a magnification of 20,000 with a microscope and reading it with a scanner. For each fine particle, the azimuth of the absolute maximum length (long axis direction) of the fine particle with respect to the reference axis is obtained. a1, a2 ... an. The average value A = ave (a1 to an) of these azimuths is calculated and set as the average azimuth. As the number of fine particles (n), 1000 or more are measured, and an average value is calculated.

  When this average azimuth angle is within ± 5 ° with respect to the film forming direction of the resin film, it is said to be parallel to the film forming direction (longitudinal direction). Similarly, when the angle is within ± 5 ° with respect to the direction orthogonal to the film forming direction of the resin film (the width direction), the direction is orthogonal to the film forming direction of the resin film. Preferably, the average azimuth angle is preferably in the direction of ± 3 °, more preferably in the direction of ± 1 ° with respect to the film forming direction or the width direction of the resin film, particularly preferably ±±. It is in the direction of 0.5 °.

  [Average value H of the absolute value of the angle formed by the direction of the average azimuth angle and the azimuth angle of each fine particle] is preferably within 20 °.

FIG. 14 illustrates H. In the figure, b1, b2, b3... Bn are angles formed by the average maximum azimuth direction of the absolute maximum length direction (major axis direction) of each fine particle.
H = ave (| b1 | ˜ | bn |)
Thus, an average value H of the absolute values is obtained. With respect to this, similarly to the calculation of A, the measurement is performed on 1000 or more fine particles.

  H is preferably within 20 °, more preferably 2 to 19 °, and most preferably 2 to 11 °.

  As a method for dispersing and orienting fine particles, a method of stretching a film to TD or MD at the time of resin film production (casting), a method of creating a dope flow at the time of casting, and orienting fine particles along this flow, etc. It is possible to take Further, the orientation of the fine particles can be promoted by an electric field or a magnetic field.

  As a method of producing a resin film containing these fine particles, a dispersion liquid containing at least fine particles and a resin for dispersing the fine particles is prepared in advance, and then the dispersion liquid, a main part of the resin, and a solvent are mixed. It can obtain by the manufacturing method of the resin film which casts a solution using the dope prepared by. Similarly, a resin film can be obtained by a melt casting method.

  Hereinafter, the fine particles used will be further described.

  The material forming the fine particles of the present invention is not particularly limited, but is a polymer or polymer nanoparticle exhibiting negative birefringence in the stretching direction and the flow direction, positive in the stretching direction and the flow direction. It is preferable to use a liquid crystal polymer exhibiting birefringence as appropriate.

  In any case, birefringence can be exhibited by deforming the film by an external force in a state of being phase-separated in the film.

  The polymer or polymer nanoparticles exhibiting negative birefringence with respect to the stretching direction or the flow direction means a material exhibiting negative birefringence with respect to the stretching direction or the flow direction in the resin film.

  The mass fraction of the resin constituting the resin film and the polymer, polymer nanoparticle, or liquid crystal polymer has a relationship of 0 <[(polymer, polymer nanoparticle or liquid crystal polymer) / (resin)] <1.0. Is preferred. Furthermore, a relationship of 0.001 <[(polymer, polymer nanoparticle or liquid crystal polymer) / (resin)] <0.5 is preferable.

  In order to control the birefringence of the resin film, it is preferable to add at least one kind of the polymer, polymer nanoparticles or liquid crystal polymer, but two or more kinds may be used.

  Examples of the polymer oriented by stretching or flow and exhibiting negative birefringence include polystyrene and polymethyl methacrylate described in JP-A No. 2004-109355.

  In the present invention, it is preferable to use the following polymers or polymer nanoparticles that exhibit negative birefringence in the stretching direction and the flow direction.

  Whether or not the polymer or polymer nanoparticle exhibits negative birefringence by stretching can be determined by the following test method.

(Birefringence test of polymer or polymer nanoparticles)
Polymer or polymer nanoparticles were added to the resin, dissolved in a solvent, cast into a film, stretched in one direction, dried by heating, and evaluated for birefringence for a film having a transmittance of 80% or more. Refractive index measurement was performed using a multiwavelength light source for the Abbe refractometer 1T. The refractive index in the in-plane direction orthogonal to ny in the stretching direction was defined as nx. When the (ny-nx) difference for each refractive index at 550 nm shows a lower value or a negative value than the same refractive index difference of the film of the same draw ratio without the polymer or polymer nanoparticles, the polymer or polymer nano It is judged that the particles have negative birefringence in the stretching direction.

(polymer)
Although it is not particularly limited as a polymer showing negative birefringence with respect to the stretching direction and the flow direction used in the present invention, for example, a weight average molecular weight obtained by polymerizing an ethylenically unsaturated monomer is 500 or more. It is preferable to contain a polymer that is 10,000 or less.

  Furthermore, it is preferable that the resin film contains an acrylic polymer having a weight average molecular weight of 500 or more and 100,000 or less that exhibits negative birefringence with respect to the stretching direction, and the acrylic polymer is an acrylic polymer having an aromatic ring in the side chain. It is preferable that the polymer is an acrylic polymer having a side chain or a cyclohexyl group.

  By controlling the composition of the polymer having a weight average molecular weight of 700 to 50,000, the compatibility between the resin and the polymer can be improved, and neither evaporation nor volatilization occurs during film formation. In particular, an acrylic polymer, an acrylic polymer having an aromatic ring in the side chain, or an acrylic polymer having a cyclohexyl group in the side chain preferably has a weight average molecular weight of 500 to 5,000, in addition to the above. The subsequent resin film is excellent in transparency and has extremely low moisture permeability, and exhibits excellent performance as a protective film for polarizing plates.

  Since the polymer has a weight average molecular weight of 700 or more and 50000 or less, it is considered to be between the oligomer and the low molecular weight polymer. In order to synthesize such a polymer, it is difficult to control the molecular weight in normal polymerization, and it is desirable to use a method that can align the molecular weight as much as possible by a method that does not increase the molecular weight. Such polymerization methods include a method using a peroxide polymerization initiator such as cumene peroxide and t-butyl hydroperoxide, a method using a polymerization initiator in a larger amount than normal polymerization, and a mercapto compound in addition to the polymerization initiator. And a method of using a chain transfer agent such as carbon tetrachloride, a method of using a polymerization terminator such as benzoquinone and dinitrobenzene in addition to the polymerization initiator, and further, Japanese Patent Application Laid-Open No. 2000-128911 or 2000-344823. Examples thereof include a compound having one thiol group and a secondary hydroxyl group, or a bulk polymerization method using a polymerization catalyst in which the compound and an organometallic compound are used in combination. Although used, the method described in the publication is particularly preferable.

  Although the monomer as a monomer unit which comprises the polymer useful for this invention is mentioned below, it is not limited to this.

  The ethylenically unsaturated monomer unit constituting the polymer obtained by polymerizing the ethylenically unsaturated monomer is as a vinyl ester, for example, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate, vinyl pivalate, caproic acid. Vinyl, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cyclohexanecarboxylate, vinyl octylate, vinyl methacrylate, vinyl crotonate, vinyl sorbate, vinyl benzoate, vinyl cinnamate Etc .; As acrylate ester, for example, methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), butyl acrylate (n-, i-, s-, t-), pentyl acrylate (n -, I-, s-), hexyl acrylate (n I-), heptyl acrylate (n-, i-), octyl acrylate (n-, i-), nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), acrylic Cyclohexyl acid, acrylic acid (2-ethylhexyl), benzyl acrylate, phenethyl acrylate, acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3- Hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), acrylic acid-p-hydroxymethylphenyl, acrylic acid-p- (2-hydroxyethyl) phenyl, etc .; The above acrylic acid ester is changed to methacrylic acid ester; Examples thereof include acrylic acid, methacrylic acid, maleic anhydride, crotonic acid, itaconic acid and the like. The polymer composed of the above monomers may be a copolymer or a homopolymer, and is preferably a vinyl ester homopolymer, a vinyl ester copolymer, or a copolymer of vinyl ester and acrylic acid or methacrylic acid ester.

  In the present invention, an acrylic polymer (simply referred to as an acrylic polymer) refers to a homopolymer or copolymer of acrylic acid or methacrylic acid alkyl ester having no monomer unit having an aromatic ring or a cyclohexyl group. An acrylic polymer having an aromatic ring in the side chain is an acrylic polymer that always contains an acrylic acid or methacrylic acid ester monomer unit having an aromatic ring. The acrylic polymer having a cyclohexyl group in the side chain is an acrylic polymer containing an acrylic acid or methacrylic acid ester monomer unit having a cyclohexyl group.

  Examples of the acrylate monomer having no aromatic ring and cyclohexyl group include, for example, methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), butyl acrylate (n-, i-, s-, t-), pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (n-, i-), octyl acrylate (n-, i-) , Nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), acrylic acid (2-ethylhexyl), acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), acrylic acid 2-methoxy-ethyl), acrylic acid (2-ethoxyethyl), or the acrylic acid ester may include those obtained by changing the methacrylic acid ester.

  The acrylic polymer is a homopolymer or copolymer of the above-mentioned monomers, but the acrylic acid methyl ester monomer unit preferably has 30% by mass or more, and the methacrylic acid methyl ester monomer unit has 40% by mass or more. Is preferred. In particular, a homopolymer of methyl acrylate or methyl methacrylate is preferred.

  Examples of acrylic acid or methacrylic acid ester monomers having an aromatic ring include phenyl acrylate, phenyl methacrylate, acrylic acid (2 or 4-chlorophenyl), methacrylic acid (2 or 4-chlorophenyl), and acrylic acid (2 or 3 Or 4-ethoxycarbonylphenyl), methacrylic acid (2 or 3 or 4-ethoxycarbonylphenyl), acrylic acid (o or m or p-tolyl), methacrylic acid (o or m or p-tolyl), benzyl acrylate, Benzyl methacrylate, phenethyl acrylate, phenethyl methacrylate, acrylic acid (2-naphthyl) and the like can be mentioned, but benzyl acrylate, benzyl methacrylate, phenethyl acrylate, and phenethyl methacrylate are preferably used. That.

  In the acrylic polymer having an aromatic ring in the side chain, the acrylic acid or methacrylic acid ester monomer unit having an aromatic ring has 20 to 40% by mass, and the acrylic acid or methacrylic acid methyl ester monomer unit is 50 to 80% by mass. It is preferable to have. The polymer preferably has 2 to 20% by mass of acrylic acid or methacrylic acid ester monomer units having a hydroxyl group.

  Examples of the acrylate monomer having a cyclohexyl group include cyclohexyl acrylate, cyclohexyl methacrylate, acrylic acid (4-methylcyclohexyl), methacrylic acid (4-methylcyclohexyl), acrylic acid (4-ethylcyclohexyl), and methacrylic acid. (4-ethylcyclohexyl) and the like can be mentioned, but cyclohexyl acrylate and cyclohexyl methacrylate can be preferably used.

  In the acrylic polymer having a cyclohexyl group in the side chain, the acrylic acid or methacrylic acid ester monomer unit having a cyclohexyl group has 20 to 40% by mass and preferably 50 to 80% by mass. Moreover, it is preferable to have 2-20 mass% of acrylic acid or methacrylic acid ester monomer units having a hydroxyl group in the polymer.

  Polymers obtained by polymerizing the above ethylenically unsaturated monomers, acrylic polymers, acrylic polymers having an aromatic ring in the side chain, and acrylic polymers having a cyclohexyl group in the side chain are all, for example, cellulose ester resins Excellent compatibility.

  In the case of an acrylic acid or methacrylic acid ester monomer having these hydroxyl groups, it is not a homopolymer but a structural unit of a copolymer. In this case, it is preferable that the acrylic acid or methacrylic acid ester monomer unit having a hydroxyl group is contained in an acrylic polymer in an amount of 2 to 20% by mass.

  A polymer having a hydroxyl group in the side chain can also be preferably used. The monomer unit having a hydroxyl group is the same as the monomer described above, but acrylic acid or methacrylic acid ester is preferable. For example, acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3 -Hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), acrylic acid-p-hydroxymethylphenyl, acrylic acid-p- (2-hydroxyethyl) phenyl, or these acrylic acids. The thing replaced by methacrylic acid can be mentioned, Preferably, it is 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate. The acrylic acid ester or methacrylic acid ester monomer unit having a hydroxyl group in the polymer is preferably contained in the polymer in an amount of 2 to 20% by mass, more preferably 2 to 10% by mass.

  A polymer containing 2 to 20% by mass of the above-mentioned monomer unit having a hydroxyl group is not only excellent in compatibility with a resin, retention, and dimensional stability, and also has low moisture permeability. It is particularly excellent in adhesiveness with a polarizer as a protective film for a film and has an effect of improving the durability of the polarizing plate.

  In the present invention, when a polymer or polymer nanoparticles are blended with a resin, it is preferable that at least one end of the main chain of the acrylic polymer has a hydroxyl group in order to have compatibility. The method of having a hydroxyl group at the end of the main chain is not particularly limited as long as it has a hydroxyl group at the end of the main chain, but a radical having a hydroxyl group such as azobis (2-hydroxyethylbutyrate). A method using a polymerization initiator, a method using a chain transfer agent having a hydroxyl group such as 2-mercaptoethanol, a method using a polymerization terminator having a hydroxyl group, and a method of having a hydroxyl group at the terminal by living ion polymerization Bulk polymerization using a compound having one thiol group and a secondary hydroxyl group as described in JP-A No. 2000-128911 or 2000-344823, or a polymerization catalyst using the compound and an organometallic compound in combination The method described in the publication is particularly preferable. The polymer produced by the method related to the description in this publication is commercially available as Act Flow Series manufactured by Soken Chemical Co., Ltd., and can be preferably used. In the present invention, the polymer having a hydroxyl group at the terminal and / or the polymer having a hydroxyl group in a side chain has an effect of significantly improving the compatibility and transparency of the polymer.

  Furthermore, when polymer or polymer nanoparticles are blended into a resin, the polymer using styrene as an ethylenically unsaturated monomer exhibiting negative birefringence in the stretching direction and flow direction is negatively refractive. It is preferable to express Examples of styrenes include styrene, methyl styrene, dimethyl styrene, trimethyl styrene, ethyl styrene, isopropyl styrene, chloromethyl styrene, methoxy styrene, acetoxy styrene, chloro styrene, dichloro styrene, bromo styrene, and vinyl benzoic acid methyl ester. Although it is mentioned, it is not a thing limited to these. It may be copolymerized with the exemplified monomers listed as the unsaturated ethylenic monomer, or may be used by being compatible with a resin using two or more of the above polymers for the purpose of controlling birefringence.

  The polymer nanoparticles referred to herein are nano-level polymer ultrafine particles having a particle size of several nm to several hundred nm, and exhibit various surface effects because of their high specific surface area.

  The polymer nanoparticles used are preferably particles having a particle size of 1 nm to 500 nm, more preferably 10 nm to 350 nm, still more preferably 10 nm to 150 nm, and particularly preferably 10 nm to 100 nm. If it is less than 1 nm, the effect of controlling birefringence is insufficient, and if it exceeds 500 nm, an increase in haze is observed. The particle diameter in the present invention is defined as a value obtained on average as a volume particle diameter in terms of a sphere. The measurement method can be determined using techniques such as, but not limited to, standard dynamic light scattering, small angle neutron scattering NMR diffusion, X-ray scattering, and gel phase chromatography. For example, an average particle size index is obtained by gel permeation chromatography (GPC) elution time obtained for polymer nanoparticles. The particle size of the polymer nanoparticles can be determined by comparing the polymer nanoparticles to a polystyrene standard with known molecular weight and hydrodynamic radius. The gel permeation chromatography technique used uses a column containing a 10 μm PL gel to determine the elution time of the crosslinked polymer nanoparticles and the elution time of a polystyrene standard with known molecular weight and hydrodynamic radius. This is done by comparing.

  The material of the polymer nanoparticles is not particularly limited, but examples include (meth) acrylic, styrene, (meth) acryl-styrene, fluorine-substituted (meth) acrylic and fluorine-substituted (meth) acrylic. It is preferable to use polymer nanoparticles which are at least one (co) polymer selected from styrene.

  The polymer nanoparticles as a (meth) acrylic (co) polymer are used as a (co) polymer of a (meth) acrylic acid ester monomer or a copolymer with another monomer. Examples of the (meth) acrylate monomer include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, (meth) acrylic acid Butyl, isobutyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, lauryl (meth) acrylate, (meth) acrylic Acid nonyl, decyl (meth) acrylate, dodecyl (meth) acrylate, phenyl (meth) acrylate, methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, propoxyethyl (meth) acrylate, (meth ) Acrylic acid such as butoxyethyl acrylate and ethoxypropyl (meth) acrylate Acid alkyl esters; dialkylaminoalkyl (meth) acrylates such as diethylaminoethyl (meth) acrylate; (meth) acrylamides; (meth) acrylamides such as N-methylol (meth) acrylamide and diacetone acrylamide and glycidyl (meth) acrylates; (Poly) alkylene such as ethylene glycol diacrylate, diethyl glycol diacrylate, triethylene glycol diacrylate, polyethylene glycol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate Diacrylate of glycols; Dimethacrylate of ethylene glycol, Dimethacrylate of diethylene glycol (Poly) such as dicarboxylic acid ester of triethylene glycol, dimethacrylic acid ester of polyethylene glycol, dimethacrylic acid ester of propylene glycol, dimethacrylic acid ester of dipropylene glycol, dimethacrylic acid ester of tripropylene glycol, etc. Examples thereof include dimethacrylic acid esters of alkylene glycol.

  Other monomers other than the (meth) acrylic monomer described above include, for example, styrene, methylstyrene, dimethylstyrene, trimethylstyrene, ethylstyrene, diethylstyrene, triethylstyrene, propylstyrene, butylstyrene, hexylstyrene, heptyl. Alkyl styrenes such as styrene and octyl styrene; Halogenated styrenes such as fluorostyrene, chlorostyrene, bromostyrene, dibromostyrene, and chloromethylstyrene; Styrenes such as nitrostyrene, acetylstyrene, methoxystyrene, α-methylstyrene, and vinyltoluene Mention may be made of monomers.

  Furthermore, as monomers other than styrene monomers, for example, silicon-containing vinyl monomers such as vinyltrimethoxysilane and vinyltriethoxysilane; vinyl acetate, vinyl propionate, vinyl n-butyrate, vinyl isobutyrate, vinyl pivalate , Vinyl esters such as vinyl caproate, vinyl persuccinate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pt-butylbenzoate, vinyl salicylate; vinylidene chloride, vinyl chlorohexanecarboxylate, acrylic acid -2-chloroethyl, methacrylic acid-2-chloroethyl and the like.

  Furthermore, if necessary, as other monomers having a functional group, for example, acrylic acid, methacrylic acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, isocrotonic acid, norbornene dicarboxylic acid, bicyclo [ 2,2,1] hept-2-ene-5,6-dicarboxylic acid and the like, and as derivatives thereof, maleic anhydride, itaconic anhydride, citraconic anhydride, tetrahydrophthalic anhydride Acid, bicyclo [2,2,1] hept-2-ene-5,6-dicarboxylic acid anhydride, and for example, a polymerization reactive monomer having a hydroxyl group (OH; hydroxyl group) includes 2-hydridoacrylic acid. Xylethyl, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 1,1, -Trihydroxymethylethane triacrylate, 1,1,1-trishydroxymethylmethylethane triacrylate, 1,1,1-trishydroxymethylpropane triacrylate; hydroxyalkyl vinyl ethers such as hydroxy vinyl ether, hydroxypropyl vinyl ether, hydroxybutyl vinyl ether And hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl acrylate, and diethylene glycol mono (meth) acrylate, and the like. These single or two or more kinds of monomer composites are suitably used as appropriate. Can be used.

  Preparation of the polymer nanoparticles formed from the resin described above can be appropriately prepared by soap-free emulsion polymerization, suspension polymerization, emulsion polymerization or the like. When preparing a polymer nanoparticle suspension by soap-free emulsion polymerization, it is generally sufficient that persulfates such as potassium persulfate and ammonium persulfate are soluble in an aqueous medium during polymerization as a polymerization initiator. Moreover, what is necessary is just to add a polymerization initiator in 0.1-10 mass parts with respect to 100 mass parts of polymerization monomers normally, Preferably it is 0.2-2 mass parts. In the case of an emulsion polymerization method, a suspension thereof is prepared. As a polymerization initiator, a persulfate such as potassium persulfate or ammonium persulfate is used. An alkylbenzene sulfone such as sodium dodecylbenzenesulfonate is used with the above monomer as an emulsifier. An emulsifier such as an acid salt and polyethylene glycol alkyl ether such as polyethylene glycol nonylphenyl ether is usually 0.01 to 5 parts by weight, preferably 0.1 to 2 parts by weight, based on 100 parts by weight of the polymerization monomer. It is mixed with a medium to make an emulsified state. Similarly, usually, the polymerization initiator may be added in an amount of 0.1 to 10 parts by mass, preferably 0.2 to 2 parts by mass with respect to 100 parts by mass of the polymerization monomer. In addition, a method for producing fine particles of an organic compound by laser light irradiation described in JP-A-2001-113159 can also be applied.

  Among these, in order to exhibit negative birefringence with respect to stretching and flow, the composition of the polymer nanoparticles can be appropriately selected. In addition, the polymer constituting the polymer nanoparticles is not limited by the molecular weight of the polymer that affects the compatibility, and the particle size for preventing light from scattering in the visible light region may be in the above range.

  The method for adding the polymer nanoparticles is not particularly limited, but in-line addition with a matting agent or the like is preferable because it can be uniformly dispersed in the film.

The fine particles used are also preferably inorganic fine particles. Examples of the inorganic fine particles include TiO ₂ (rutile type), calcium silicate (wollastonite, zonotlite), potassium titanate, aluminum borate, basic magnesium sulfate, and glass. Fiber etc. are mentioned.

  On the other hand, examples of liquid crystal polymers exhibiting positive birefringence in the stretching direction include room temperature such as cyanobiphenyl, cyanophenylcyclohexane, cyanophenyl ester, benzoic acid phenyl ester, phenylpyrimidine, and mixtures thereof. Alternatively, a low molecular liquid crystal or a crosslinkable liquid crystal monomer exhibiting a nematic phase or a smectic phase at a high temperature, or a liquid crystal polymer exhibiting a nematic phase or a smectic phase at a room temperature or a high temperature. The crosslinkable liquid crystal monomer is usually subjected to an alignment treatment, and then subjected to a crosslinking treatment by an appropriate method using heat, light, or the like to obtain a polymer.

  The liquid crystal polymer that can be preferably used in view of the formability of a micro region having excellent uniformity of particle size distribution, thermal stability, moldability to a film, ease of alignment treatment, and the like, has a polymerization degree of 8 or more, especially 10 or more. In particular 15-5000.

  When using a liquid crystal polymer, the resin and one or more liquid crystal polymers for forming microregions are mixed to form a resin film containing the liquid crystal polymer dispersed in the microregion state. It can be performed by a method of performing orientation treatment and forming a region having different birefringence. In view of controlling the refractive index difference due to the alignment treatment, those exhibiting a nematic liquid crystal phase in a temperature range having a glass transition temperature of 50 ° C. or higher and lower than the glass transition temperature of the resin can be preferably used. Incidentally, specific examples thereof include a side chain type liquid crystal polymer having a monomer unit represented by the following general formula.

  In the above general formula, X is a skeleton group that forms the main chain of the liquid crystal polymer, and may be formed of an appropriate connecting chain such as linear, branched, or cyclic. Examples include polyacrylates and polymethacrylates, poly-α-haloacrylates and poly-α-cyanoacrylates, polyacrylamides and polyacrylonitriles, polymethacrylonitriles and polyamides, polyesters and polyurethanes. , Polyethers, polyimides, polysiloxanes and the like.

  Y is a spacer group branched from the main chain, and preferable spacer group Y is, for example, ethylene, propylene, butylene, pentylene, hexylene, octylene, decylene, etc. Undecylene, dodecylene, octadecylene, ethoxyethylene, methoxybutylene, and the like.

  On the other hand, Z is a mesogenic group that imparts liquid crystal alignment, and examples thereof include the following compounds.

  The terminal substituent A in the compound is, for example, a cyano group, an alkyl group, an alkenyl group, an alkoxy group, an oxaalkyl group, a haloalkyl group, a haloalkoxy group, or a haloalkenyl group in which one or more of hydrogen is substituted with fluorine or chlorine. It may be appropriate.

  In the above, the spacer group Y and the mesogenic group Z may be bonded via an ether bond, that is, —O—. Further, the phenyl group in the mesogenic group Z may have one or two hydrogens substituted with halogen, in which case chlorine or fluorine is preferred as the halogen.

  The nematic orientation side chain type liquid crystal polymer described above may be an appropriate thermoplastic polymer such as a homopolymer or copolymer having the monomer unit represented by the above general formula, and among them, those having excellent mono fine particle orientation. preferable.

  Formation of a resin film using a nematic liquid crystal polymer forms a resin film in which a liquid crystal polymer is dispersed and contained in a minute region, and then heat-treats the liquid crystal polymer that forms the fine particles to align it in a nematic liquid crystal phase. The orientation state can be cooled and fixed.

  Formation of the above-described resin film containing fine particles, that is, a film to be oriented can be obtained by an appropriate method such as a casting method, an extrusion molding method, an injection molding method, a roll molding method, or a casting method. It can also be carried out by a method of developing in a monomer state and polymerizing it by heat treatment or radiation treatment such as ultraviolet rays to form a film.

  From the viewpoint of obtaining a resin film excellent in the uniform distribution of fine particles, a method in which a mixed solution of a forming material through a solvent is formed by a casting method, a casting method, or the like is preferable. In that case, the size and distribution of the microscopic area can be controlled by the type of solvent, the viscosity of the liquid mixture, the drying speed of the liquid mixture developing layer, and the like. Incidentally, to reduce the area of the fine particles, it is advantageous to reduce the viscosity of the mixed liquid or to accelerate the drying speed of the mixed liquid spreading layer.

  The fine particle orientation treatment is, for example, uniaxial or biaxial, sequential biaxial or Z-axial stretching treatment method or rolling method, applying an electric field or a magnetic field at a temperature equal to or higher than the glass transition temperature or liquid crystal transition temperature, and quenching the orientation. One or two types of appropriate methods capable of controlling the refractive index by orientation, such as a method of fixing, a method of fluid orientation during film formation, and a method of self-aligning liquid crystals based on a slight orientation of an isotropic polymer The above can be used.

  The protective film B of the present invention may be the protective film B = the reflective linearly polarizing layer itself, or may be a laminate in which the transparent resin film and the reflective linearly polarizing layer are integrated via an adhesive layer or an adhesive layer. .

  The film thickness of the protective film A is 100 μm or less, preferably 10 to 90 μm, more preferably 20 to 80 μm, and the film thicknesses of the protective films A and B from the viewpoint of contrast stability under long-time irradiation of the direct type backlight. The value of the ratio B / A is preferably 0.8 to 1.2, more preferably 0.9 to 1.1.

  The resin used for the protective film B may be anything as long as it is a transparent resin in the visible light region. Like the transparent resin used for the protective film A, a polyolefin-based resin and a cellulose ester-based resin are preferable. It is more preferable that

《Method for manufacturing elliptically polarizing plate》
The method for producing an elliptically polarizing plate of the present invention is, for example, on a long protective film A having a slow axis inclined by 45 ° with respect to the longitudinal direction by obliquely stretching a cellulose ester substrate, or on a cellulose ester substrate. After applying an alignment film and rubbing it at an angle of 45 ° from above, a long protective film A in which the discotic liquid crystal is vertically aligned and photopolymerized and cured, and a reflection having a reflection axis in the longitudinal direction A protective film B containing a long cellulose ester comprising a linear linear polarizing layer is saponified, and an absorptive linear polarizer is sandwiched between the saponified A and B surfaces to form a long elliptical polarizing film. Can be made.

  In cases other than the cellulose ester resin, such as a polyolefin substrate, it can be laminated with an absorptive polarizer via an adhesive layer using a urethane-based adhesive.

<Liquid crystal display device>
The elliptically polarizing plate of the present invention can be used for liquid crystal display devices of various drive systems such as STN, TN, OCB, HAN, VA (MVA, PVA), IPS, FFS, OCB. An IPS, FFS, and VA (MVA, PVA) type liquid crystal display device is preferable, and a VA (MVA, PVA) type liquid crystal display device is particularly preferable. By using these liquid crystal display devices, a liquid crystal display device having a wide viewing angle and high front contrast and excellent visibility can be obtained.

  The backlight used in the liquid crystal display device of the present invention may be a sidelight type, a direct type, or a combination of these. From the viewpoint of A particularly preferred direct type backlight is an LED backlight for a color liquid crystal display device having a red (R) LED, a green (G) LED, and a blue (B) LED, for example, the peak of the red (R) LED. Preferably, the wavelength is 610 nm or more, the peak wavelength of the green (G) LED is in the range of 530 ± 10 nm, and the peak wavelength of the blue (B) LED is 480 nm or less. Examples of types of green (G) LEDs having a peak wavelength within the above range include DG1112H (manufactured by Stanley Electric Co., Ltd.), UG1112H (manufactured by Stanley Electric Co., Ltd.), and E1L51-3G (manufactured by Toyoda Gosei Co., Ltd.). E1L49-3G (manufactured by Toyoda Gosei Co., Ltd.), NSPG500S (manufactured by Nichia Chemical Co., Ltd.), and the like. The types of LEDs used as red (R) LEDs include, for example, FR1112H (manufactured by Stanley Electric Co., Ltd.), FR5366X (manufactured by Stanley Electric Co., Ltd.), NSTM515AS (manufactured by Nichia Corporation), GL3ZR2D1COS (Sharp) GM1JJ35200AE (manufactured by Sharp Corporation) and the like. As types of LEDs used as blue (B) LEDs, DB1112H (manufactured by Stanley Electric Co., Ltd.), DB5306X (manufactured by Stanley Electric Co., Ltd.), E1L51-3B (manufactured by Toyoda Gosei Co., Ltd.), E1L4E-SB1A (manufactured by Stanley Electric Co., Ltd.) Toyoda Gosei Co., Ltd.), NSPB630S (Nichia Chemical Co., Ltd.), NSPB310A (Nichia Chemical Co., Ltd.), and the like.

  The above-described three color LEDs can be combined to form a backlight. Alternatively, a white LED can be used.

  In addition, as a direct type backlight (or direct type), a direct type backlight described in JP-A No. 2001-281656, a direct type backlight using a point light source such as an LED described in JP-A No. 2001-305535, Examples include a direct type backlight described in JP-A-2002-311412, but are not limited thereto.

  Even when such a backlight is used, by using the elliptically polarizing plate of the present invention, a liquid crystal display device having a wide viewing angle and a high front contrast and a high visibility can be obtained over a long period of time.

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

<Measurement of retardation value>
The retardation value was measured using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments Co., Ltd.) at 23 ° C. and 55% RH in a wavelength of 550 nm and 1 cm in the width direction of the sample. The three-dimensional birefringence measurement was performed at intervals, and the measured value was substituted into the following equation.

Retardation value Ro = (nx−ny) × d
Retardation value Rth = {(nx + ny) / 2−nz} × d
(Where nx is the refractive index in the slow axis direction in the retardation film plane (maximum refractive index in the plane), and ny is the refractive index in the direction perpendicular to the slow axis in the retardation film plane) Nz is the refractive index in the thickness direction of the film, and d is the thickness (nm) of the retardation film.)
Example 1
<Production of absorption type linear polarizer>
A long film of polyvinyl alcohol having a thickness of 120 μm was uniaxially stretched in the longitudinal direction (temperature: 110 ° C., stretch ratio: 5 times). This was immersed in an aqueous solution composed of 0.075 g of iodine, 5 g of potassium iodide and 100 g of water for 60 seconds, and then immersed in an aqueous solution of 68 ° C. composed of 6 g of potassium iodide, 7.5 g of boric acid and 100 g of water. This was washed with water and dried to obtain an absorption linear polarizer.

<< Preparation of protective film A >>
<Preparation of protective film A-1>
A norbornene-based resin pellet (ZEONOR1420, manufactured by Nippon Zeon Co., Ltd.) is dried at 100 ° C. for 5 hours, supplied to an extruder, extruded through a polymer pipe and a polymer filter from a T die onto a casting drum, cooled, A long unstretched film having a thickness of 160 μm was obtained. The unstretched film was wound up on a roll.

  Next, the unstretched film was pulled out from the roll and continuously supplied to a tenter stretching machine as shown in FIGS. 7 to 10 to obtain a long protective film A-1 having an orientation angle of 45 °. The tenter drawing machine was drawn at a temperature of 148 ° C. and a draw ratio of 1.5 times.

<Preparation of protective film A-2>
(Polymer polymerization method)
The monomer component (repeating unit) which comprises the polycarbonate used in the Example below, and the monomer component (repeating unit) which comprises polystyrene, polyisopropenyl phenol, and a styrene-isopropenyl phenol copolymer are shown below.

  The styrene-isopropenyl phenol copolymer [C] + [D] having the above structure is a copolymer of styrene: isopropenyl = 50: 50 (mol%) in a molar ratio, and the composition ratio is a monomer charge amount. It was almost equivalent.

  Next, the monomer components [A], [B] having the above structure and the styrene-isopropenylphenol copolymer [C] + [D] are respectively converted into X: Y: Z (mol%, X + Y + Z = 100, provided that X, Y and Z indicate the molar ratio of the monomer components. Regarding Z, the total amount [C] + [D] of the polystyrene monomer component [C] and the polyisopropenyl monomer component [D] used at the time of synthesis is Copolymerization was carried out by the phosgene method at a ratio of (treated as the amount of the monomer component) to obtain a polycarbonate-polystyrene copolymer. The composition ratio of the obtained copolymer was equivalent to the charged amount of monomer.

  The monomer components [A] and [B] and the monomer component (styrene-isopropenylphenol copolymer) [C] + [D] are in a ratio of X: Y; Z = 40: 30: 30 (mol%). A copolymerized polycarbonate-polystyrene copolymer was used. This polycarbonate-polystyrene copolymer was dissolved in methylene chloride to prepare an 18% by mass dope. A cast film is prepared from this dope solution and continuously supplied to a tenter stretching machine as shown in FIGS. 7 to 10 at a temperature of 175 ° C. at a stretching ratio of 3 times, and the orientation angle is 45 °. Film A-2 was obtained.

<Preparation of protective film A-3>
(Pellet preparation)
Cellulose acetate propionate (acetyl group substitution degree 1.23, propionyl group substitution degree 1.31, number average molecular weight 75000) 100 parts by mass (meth) acrylic polymer A 5.5 parts by mass Sugar ester compound A 5.5 Part by weight Trimethylolpropane tris (3,4,5-trimethoxybenzoate)
1 part by mass IRGANOX-1010 (manufactured by Ciba Japan Co., Ltd.) 1 part by mass Sumilizer GP (manufactured by Sumitomo Chemical Co., Ltd.) 0.5 part by mass (meth) acrylic polymer A: polymerization described in JP 2000-128911 A Bulk polymerization was performed by the method. That is, methyl acrylate was introduced as a monomer into a flask equipped with a stirrer, a nitrogen gas inlet tube, a thermometer, an inlet, and a reflux condenser, and nitrogen gas was introduced and the inside of the flask was replaced with nitrogen gas while stirring. Added.

  After the addition of thioglycerol, polymerization was carried out for 4 hours, the contents were returned to room temperature, and 20 parts by mass of a 5% by mass benzoquinone tetrahydrofuran solution was added thereto to stop the polymerization. The contents were transferred to an evaporator, and tetrahydrofuran, residual monomer and residual thioglycerol were removed under reduced pressure at 80 ° C. to obtain a (meth) acrylic polymer A having a molecular weight of 1000.

Sugar ester compound A: Sugar ester compound exemplified compound 3
After adding 0.05 part by mass of silica particles to the above material and mixing for 30 minutes with a V-type mixer filled with nitrogen gas, a twin-screw extruder (PCM30 manufactured by Ikegai Co., Ltd.) equipped with a strand die was used. And a cylindrical pellet having a length of 4 mm and a diameter of 3 mm was produced. At this time, the shear rate was set to 25 (mm / s). The obtained pellets were dried at 100 ° C. for 5 hours to have a water content of 100 ppm and fed to a single screw extruder (GT-50; manufactured by Plastic Engineering Laboratory Co., Ltd.) equipped with a 300 mm wide T die. And T-die was set to 250 degreeC and it formed into a film. The surface of the T die was subjected to hard chrome plating and finished with a mirror finish with a surface roughness of 0.1S. The film from the T-die was dropped onto a first cooling roll with a chrome-plated mirror surface adjusted to 110 ° C.

  The film in close contact with the first cooling roll was pressed with an elastic touch roll after being transported around the circumference of the first cooling roll by a central angle of 10 °. At this time, it contacted with the pressure of 4 N / mm with respect to the whole width 250mm of a film. After the pressed film is brought into contact with the circumferential portion of the first cooling roll having a central angle of 150 °, a total of three cooling films, ie, a second cooling roll (temperature 110 ° C.) and a third cooling roll (temperature 80 ° C.) are cooled. The film was sequentially circumscribed on the roll, cooled and solidified to form a film, and peeled off by a peeling roll. Thereafter, using the apparatus (stretching machine A) described in Example 1 of Japanese Patent Application Laid-Open No. 2007-94007, the temperature is 170 ° C., the magnification is 2 times, and the slow axis is inclined at 45 ° to the film width direction. The film was stretched and dried to produce a long protective film A-3.

<Preparation of protective film A-4>
(Production of cellulose ester film)
Cellulose ester (acetyl group substitution degree 2.54, benzoyl group substitution degree 0.28)
100 parts by mass Retardation modifier C-1 12 parts by mass Methylene chloride 261 parts by mass Methanol 39 parts by mass The above composition was put into a pressure-resistant mixing tank and stirred for 6 hours to dissolve each component, and cellulose ester A solution (hereinafter also referred to as a dope) was prepared.

  The prepared cellulose ester solution was cast on a metal support with a band casting machine, and then dried, and the self-supporting dope casting film was peeled off from the band. The peeled dope film was dried while being held with a tenter so that the film width was maintained, and then wound on a roll to prepare a cellulose ester film having a thickness of 40 μm so that the width direction was 1.3 m.

(Formation of alignment film)
After surface saponification of the produced cellulose ester film, an alignment film coating solution having the following composition was continuously applied with a # 14 wire bar. A film was formed by drying with warm air of 60 ° C. for 60 seconds and further with warm air of 100 ° C. for 120 seconds. Next, the formed film was continuously rubbed in a direction of 45 ° with respect to the longitudinal direction of the film to form an alignment film.

The following modified polyvinyl alcohol 10 parts by weight Water 371 parts by weight Methanol 119 parts by weight Glutaraldehyde 0.5 parts by weight

(Formation of optically anisotropic layer)
An optically anisotropic layer coating liquid A containing a discotic liquid crystalline compound having the following composition was continuously applied on the prepared alignment film with a wire bar of # 3.6. In order to dry the solvent and ripen the orientation of the discotic liquid crystalline compound in the coating solution, the coating liquid was heated with hot air at 100 ° C. for 30 seconds and further with hot air at 130 ° C. for 60 seconds. Subsequently, the alignment of the liquid crystalline compound was fixed by UV irradiation to form an optically anisotropic layer, thereby obtaining a protective film A-4. The discotic liquid crystalline compound loses liquid crystallinity after formation of the optically anisotropic layer due to the fixation of the orientation, and becomes a discotic compound.

[Composition of Optically Anisotropic Layer Coating Liquid A]
91 parts by mass of the following discotic liquid crystalline compound 9 parts by mass of ethylene oxide-modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.) 3 parts by mass of photopolymerization initiator (Irgacure 907, manufactured by Ciba Japan) Part Sensitizer (Kaya Cure DETX, manufactured by Nippon Kayaku Co., Ltd.) 1 part by weight Methanol 30 parts by weight Methyl ethyl ketone 165 parts by weight

<Protective film A-5>
A protective film A-5 having a film thickness of 200 μm was produced in the same manner as the protective film A-3 except that the film thickness was changed and the stretching conditions were changed to a temperature of 190 ° C. and a magnification of 1.4 times.

<Protective film A-6>
A protective film A-6 having a film thickness of 250 μm was produced in the same manner as the protective film A-3 except that the film thickness was changed and the stretching conditions were changed to a temperature of 200 ° C. and a magnification of 1.4 times.

  Table 1 shows the phase difference Ro, the film thickness, and the angle between the film longitudinal direction and the slow axis of the protective films A-1 to A-6.

<< Preparation of protective film B >>
<Preparation of protective film B-1>
100 parts by mass of the following dope solution was sufficiently mixed with an in-line mixer (Toray static in-tube mixer Hi-Mixer, SWJ), and then uniformly cast on a stainless steel band support having a width of 2 m using a belt casting apparatus. . On the stainless steel band support, the solvent was evaporated until the residual solvent amount became 110%, and the stainless steel band support was peeled off. Tension is applied at the time of peeling so that the stretching ratio is 1.1 times in the longitudinal direction, then both ends of the web are gripped with a tenter so that the stretching ratio in the width direction is 1.1 times. Stretched. The residual solvent at the start of stretching was 30%. After stretching, hold for several seconds while maintaining its width, release the width holding after relaxing the tension in the width direction, further carry for 30 minutes in the third drying zone set at 125 ° C., and perform drying, Thereafter, the film was stretched 1.8 times in the longitudinal direction at 180 ° C., and a protective film B-1 having a width of 1.5 m, an end having a width of 1 cm and a height of 8 μm, a film thickness of 40 μm, and a winding length of 3000 m was produced. .

<Dope composition>
Methylene chloride 300 parts by weight Ethanol 40 parts by weight Cellulose ester (cellulose acetate propionate; acetyl group substitution degree 1.9, propionyl group substitution degree 0.7, total acyl group substitution degree 2.6) 100 parts by weight aromatic terminal ester Illustrative Compound 1 5.5 parts by mass Trimethylolpropane tris (3,4,5-trimethoxybenzoate)
5.5 parts by mass Ultraviolet absorber (Tinubin 109, manufactured by Ciba Japan Co., Ltd.) 1.2 parts by mass UV absorber (Tinuvin 171, manufactured by Ciba Japan Co., Ltd.) 0.8 parts by mass Particles (rod-like TiO ₂ , Ishihara Sangyo FTL-100 stearic acid surface-treated product)
2 parts by mass The average aspect ratio of the particles was 13 by the following measurement.

<Measurement of average aspect ratio of particles>
Particles dispersed in a solvent such as ethanol were photographed at a magnification of 20,000 with a transmission electron microscope, and the image was read in 300 dpi monochrome 256 gradation using a scanner Canon Scan FB 636U manufactured by Canon Inc. The read image was Epson Direct ( The image processing software WinROOF ver3.60 (manufactured by Mitani Corp.) installed in Endeavor Pro720L (CPU; Athlon-1 GHz, memory: 512 MB), which is a personal computer manufactured by Co., Ltd., was used. Extract the image of the captured image and confirm that there are more than 300 particles on the screen after extracting the image of the particle. If the extraction is not enough, perform manual adjustment of the detection level. Adjustments were made to detect and extract the particles. The absolute maximum length / diagonal width of each particle of the image data thus extracted is measured, the average absolute maximum length / average diagonal width for each of 300 or more particles is obtained, and the average aspect ratio is calculated. Calculated.

Aspect Ratio = Absolute Maximum Length / Diagonal Width Diagonal width refers to the shortest distance between two straight lines when an image of a particle projected by two straight lines parallel to the absolute maximum length is sandwiched.

  Moreover, in the level of the protective film B-1 produced by adding particles, the film surface was observed with a scanning electron microscope, and it was confirmed that the individual particles were uniformly dispersed.

<Preparation of protective film B-2>
(Production of long grid type polarizing film)
A focused ion beam processing apparatus (Seiko Instruments Inc., SMI3050) is formed on a 0.2 mm × 1 mm surface of a cuboidal single crystal diamond of dimensions 0.2 mm × 1 mm × 1 mm brazed to a SUS shank of 8 mm × 8 mm × 60 mm. ) Is used to perform a focused ion beam processing using an argon ion beam, and a groove having a width of 0.1 μm and a depth of 0.1 μm parallel to a side having a length of 1 mm is engraved with a pitch of 0.2 μm and a width of 0.1 μm. A cutting tool formed by forming 1,000 linear protrusions with a height of 0.1 μm at a pitch of 0.2 μm was produced.

  A cutting tool in which a nickel-phosphorous electroless plating with a thickness of 100 μm is applied to the entire peripheral surface of a cylindrical stainless steel SUS430 roll having a diameter of 200 mm and a length of 150 mm, and then a linear projection formed earlier is formed. Using a cylindrical grinder (Studa, Precision Cylindrical Grinding Machine S30-1), the nickel-phosphorous electroless plating surface is 0.1 μm wide, 0.1 μm high, and the pitch is parallel to the circumferential end surface of the cylinder. A transfer roll was obtained by cutting a 0.2 μm linear protrusion.

  In addition, the production of the cutting tool by focused ion beam machining and the cutting of the nickel-phosphorous electroless plating surface are performed at a temperature of 20.0 ± 0.2 ° C. and 0.5 Hz or more by a vibration control system (Showa Science Co., Ltd.) The vibration displacement was controlled in a constant temperature and low vibration chamber in which the displacement was controlled to 10 μm or less.

Using a nip roll made of a rubber roll having a diameter of 70 mm and a transfer device using the transfer roll, the transfer roll surface temperature is 160 ° C., the nip roll surface temperature is 100 ° C., the film transport tension is 0.1 kgf / mm ² , and the nip pressure Is transferred to the surface of a cycloolefin polymer film (trade name: ZF-14, manufactured by Nippon Zeon Co., Ltd.) having a thickness of 100 μm under the condition of 15 MPa. A film having a linear shape of 1 μm, height of 0.1 μm, and pitch of 0.2 μm was produced.

  Subsequently, aluminum was continuously vacuum-deposited on the projection surface to form grid lines made of aluminum on the film surface. Furthermore, continuously, a protective film made of triacetyl cellulose is laminated on the surface of the grid line via an adhesive layer using a urethane adhesive, and this laminate is supplied to the nip of a pressure roller and continuously pressed. Thus, a protective film B-2 having a film thickness of 80 μm, which is a long grid-type polarizing film, was produced.

<Preparation of protective film B-3>
Patent No. In accordance with the method described in No. 362215, DBEF having a film thickness of 110 μm was bonded to the TAC film 40 μm via the adhesive layer 10 μm to prepare a protective film B-3 having a total film thickness of 160 μm.

<Preparation of protective film B-4>
A protective film B-4 having a thickness of 40 μm was produced in the same manner as the protective film B-1, except that particles (rod-like TiO ₂ , FTL-100 stearic acid surface-treated product manufactured by Ishihara Sangyo Co., Ltd.) were not used.

<Protective film B-5>
After drying in the third drying zone, a protective film B-5 having a thickness of 40 μm was produced in the same manner as the protective film B-1, except that the stretching operation was not performed. When the film surface was observed with a scanning electron microscope, the dispersion of individual particles was not uniform.

<Protective film B-6>
Instead of particles (rod-like TiO ₂ , FTL-100 stearic acid surface-treated product manufactured by Ishihara Sangyo Co., Ltd.), except that spherical TiO ₂ : IT-S (Idemitsu Kosan) was used, A protective film B-6 having a thickness of 40 μm was produced.

The average aspect ratio of spherical TiO ₂ : IT-S (Idemitsu Kosan) was 1.

<Protective film B-7>
DBEF-D400 manufactured by 3M Company was bonded to a 40 μm TAC film via an adhesive layer to prepare a protective film B-7 having a thickness of 450 μm.

<Protective film B-8>
A protective film B-8 having a thickness of 250 μm, which is a long grid-type polarizing film, was produced in the same manner as the protective film B-2 except that the thickness of the cycloolefin polymer film was changed.

  The film thickness, average reflectance (reflection axis incident light, transmission axis incident light) of the protective films B-1 to B-8, and the degree of orientation H of the particles (the above [the direction of the average azimuth and the azimuth of each fine particle The average value of the absolute value of the angle H]), and the angle formed by the film longitudinal direction and the reflection axis were measured by the measurement method described above, and are shown in Table 2 below.

  Protective film B-5 and protective film B-6 were not the reflective linearly polarizing layer of the present invention from the measurement results of the average reflectance.

<Production of elliptically polarizing plate>
The protective film A, the absorptive linear polarizer, and the protective film B were laminated in this order in the longitudinal direction. However, in the case of a cellulose ester-based resin film, a saponification treatment was performed in advance, and in the case of other resin films, they were laminated with an absorption linear polarizer through an adhesive layer using a urethane-based adhesive.

  Table 3 shows combinations of the protective films A-1 to 6 and B-1 to 8 that sandwich the absorption linear polarizer.

<Production of liquid crystal display device>
The polarizing plate on the backlight side of a liquid crystal display panel (VA type) using a commercially available direct type backlight is carefully peeled off, and the protective film A side of the produced elliptical polarizing plates 1 to 12 with the polarization direction adjusted here is attached. It stuck on the glass surface of the liquid crystal cell, and produced the liquid crystal display devices 1-12. About the produced liquid crystal display device, the time-dependent change of front luminance and front contrast was evaluated by the following method. The results are shown in Table 3.

<Evaluation>
Front luminance ··· A relative value was displayed with the front luminance of the elliptically polarizing plate 9 as 1.

  Contrast change over time: The amount of transmitted light during black display and white display after each liquid crystal display device that has been lit for 3,000 hours and 6,000 hours is measured with EZ-CONTRAST manufactured by ELDIM. A change in front contrast represented by the following formula was evaluated according to the following criteria.

Front contrast = (brightness of white display measured from normal direction of display device) / (brightness of black display measured from normal direction of display device)
A: Level at which almost no change was observed from the initial stage after 3,000 hours and 6,000 hours. O: Almost no change was observed from the initial stage after 3,000 hours, and slightly changed after 6,000 hours. There is a level that does not cause a problem in practical use. Δ: A slight change is recognized from the beginning after 3,000 hours, and there is a clear change after 6,000 hours. At the time stage, a clear drop from the initial stage is recognized, causing a practical problem

  From the results of Table 3, the liquid crystal display devices 1 to 6 using the elliptically polarizing plates 1 to 6 of the present invention are elliptically polarized light excellent in temporal luminance and temporal change of the front contrast even after long-time irradiation of the direct type backlight. It is clear that it is a plate and a liquid crystal display device.

Example 2
Instead of the absorptive linear polarizer of the polyvinyl alcohol film of Example 1, the following ethylene-modified polyvinyl alcohol polarizer was prepared and the same elliptically polarizing plate and liquid crystal display device were prepared, and time elapsed before and after lighting for 10,000 hours. When contrast evaluation was carried out, the contrast aging characteristics were even better than those of the liquid crystal display device using the elliptically polarizing plate of the present invention produced in Example 1.

(Polarizer B: Ethylene-modified polyvinyl alcohol polarizer)
100 parts by mass of ethylene-modified polyvinyl alcohol having an ethylene unit content of 2.1 mol%, a saponification degree of 99.92 mol% and a polymerization degree of 3000 is impregnated with 10 parts by mass of glycerin and 200 parts by mass of water, and this is melt-kneaded. After defoaming, it was melt-extruded from a T-die into a metal roll and dried to obtain an ethylene-modified polyvinyl alcohol film having a thickness of 40 μm.

  The ethylene-modified polyvinyl alcohol film thus obtained was successively treated in the order of pre-swelling, dyeing, uniaxial stretching, fixing treatment, drying, and heat treatment to produce a polarizer. That is, the ethylene-modified polyvinyl alcohol film is preliminarily swollen in 30 ° C. water for 60 seconds, in an aqueous solution at 35 ° C. having a boric acid concentration of 40 g / liter, an iodine concentration of 0.4 g / liter, and a potassium iodide concentration of 60 g / liter. Soaked for 2 minutes. Subsequently, it was uniaxially stretched 6 times in an aqueous solution at 55 ° C. with a boric acid concentration of 4%, and in an aqueous solution at 30 ° C. with a potassium iodide concentration of 60 g / liter, a boric acid concentration of 40 g / liter, and a zinc chloride concentration of 10 g / liter. For 5 minutes, and fixed. Thereafter, the ethylene-modified polyvinyl alcohol film was taken out, dried with hot air at 40 ° C. under a constant length, and further subjected to heat treatment at 100 ° C. for 5 minutes.

  The obtained polarizer had a film thickness of 15 μm, a transmittance of 43%, and a polarization degree of 99.9%.

It is a schematic diagram of an elliptically polarizing plate and a liquid crystal display device of the present invention. It is a schematic plan view which shows an example of the manufacturing apparatus of a stretched film. It is a top view which shows an example of the screw installed in the right and left of the manufacturing apparatus of a stretched film, (A) is a screw with which the flight of the ridge was provided at the same pitch, (B) is the pitch of the ridge flight. It is a screw provided so that may change. It is a top view which shows an example of the stretched film obtained with the manufacturing apparatus of a stretched film. It is a top view which shows an example of the method of laminating | stacking and cutting the stretched film obtained with the manufacturing apparatus of a stretched film. It is a schematic plan view which shows an example of another manufacturing apparatus of a stretched film. It is another film stretching apparatus (stretching apparatus). It is another film stretching apparatus (stretching apparatus). It is a figure which shows the structure of an oblique drawing machine. It is a figure which shows the further detailed structure of an oblique drawing machine. It is a schematic diagram of a grid type polarizing layer. It is a schematic diagram of the polarization-scattering anisotropic layer containing an optical continuous phase and a domain. It is a figure which shows the azimuth angle of a domain. It is a figure which shows the angle which each domain makes with respect to the direction of an average azimuth.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Thermoplastic resin film 2 Preheating zone 3 Heating extension zone 4 Cooling zone 5 Stretched film 6,7 Screw 61,71 Flight 8,81 Clip 9,91 Belt 101 Thermoplastic resin film 102 Tenter 103 Conveying direction 104L Left chuck position 104R Right Chuck position 105L Film left moving position 105R Film right moving position 106L Left moving speed 106R Right moving speed 401 Film stretching device (stretching device)
402 Film 403 Supply Device 404 Longitudinal Furnace 405 Intermediate Conveying Device 406 Longitudinal Stretching Section 407 Oblique Stretching Machine 408 Oblique Stretching Furnace 409 Oblique Stretching Section 410 Winding Device 411 Raw Material Reel 412 Reference Roll 413 Nip Roll 414 Hot Air Duct 415 Ratio Roll 416 Nip roll 417 Stretch chain 418 Hot air duct 419 Tension roll 420 Product reel 421 Base 422 Arm 423 Clip 424 Sprocket 425 Slide shaft 426 Positioning member 427 Guide 428 Guide 501 Grid line 502 Resin film

Claims (5)

In an elliptically polarizing plate formed by sandwiching an absorption type linear polarizer between two protective films A and B,
The protective film A has an in-plane retardation at 550 nm of 125 nm to 150 nm, and the smaller angle between the slow axis of the protective film A and the absorption axis of the absorption linear polarizer is approximately 45 °. Pasted on,
The other protective film B sandwiching the absorption linear polarizer includes a reflection linear polarization layer, and the reflection axis of the reflection polarization layer and the absorption axis of the absorption linear polarizer are substantially parallel to each other. Pasted,
And the film thickness of this protective film A is 200 micrometers or less, Ratio B / A of the film thickness of this protective film A and B is the range of 0.4-2.0, The elliptically polarizing plate characterized by the above-mentioned. 2. The reflective linearly polarizing layer is a grid-type polarizing layer or a layer in which fine particles having an aspect ratio of 2 or more are dispersed in a resin in a state of being oriented substantially in one direction. The elliptically polarizing plate described in 1. The elliptical polarizing plate according to claim 1 or 2, wherein the protective films A and B contain a resin, and the resin is either a cellulose ester resin or a polyolefin resin. The elliptically polarizing plate according to any one of claims 1 to 3 is a long film, and the absorption axis of the absorptive linear polarizer is parallel to the longitudinal direction of the long film. An elliptically polarizing plate. A liquid crystal display device comprising a direct type backlight, the elliptically polarizing plate according to claim 1, and a vertical alignment mode liquid crystal panel arranged in this order.

Images