JP5626133B2 - VA liquid crystal display device - Google Patents

Description

  The present invention relates to a COA type VA liquid crystal display device with high contrast and improved display unevenness.

  The liquid crystal display device is advantageous in that it is thinner and lighter than a CRT (Cathode Ray Tube), can be driven at a low voltage, and consumes less power. Therefore, liquid crystal display devices are used in various electronic devices such as televisions, notebook PCs (personal computers), desktop PCs, PDAs (portable terminals), and mobile phones.

  In recent years, a vertical alignment type liquid crystal (liquid crystal with negative dielectric anisotropy) VA type (Vertical Alignment type) liquid crystal display device is a conventional TN (Twisted Nematic) type liquid crystal display device (with dielectric constant anisotropy). As viewing angle characteristics are superior to those of positive liquid crystals, it has been widely used.

  In recent years, in this VA liquid crystal display device, there has been an increasing demand for further power saving and cost reduction. Minimization of a light shielding portion (black matrix) and color filter on array (hereinafter abbreviated as “COA”). Etc.) is being promoted to increase the aperture ratio (see Patent Document 1). Further, by using a liquid crystal having positive dielectric anisotropy in a VA liquid crystal display device and providing a liquid crystal driving electrode only on one side, the usable pixel voltage range is increased, the transmittance is improved, and the driving unit It has also been proposed to reduce manufacturing costs and improve the aperture ratio of the display panel (see Patent Document 2).

  However, with the above movement, new problems are occurring. For example, with the increase in the brightness of a liquid crystal display device due to an increase in the aperture ratio, there is a problem that display unevenness that has not been noticed until now is observed. Furthermore, the above-described technique for increasing the aperture ratio causes the panel to be warped easily because the members are concentrated on one side (backlight side), and there is a problem that new display unevenness that has not been confirmed so far occurs. .

  In an optical compensation material (also referred to as a retardation film) used between a liquid crystal layer and a polarizing plate in a liquid crystal display device so far, a technique (see Patent Document 3) for controlling tensile elastic modulus and optical characteristics, Technology for controlling photoelasticity (see Patent Document 4), Technology for improving mechanical strength by making a polarizing plate configuration predetermined (see Patent Document 5), A technique for improving black luminance unevenness by adjusting the moisture content (see Patent Document 6) is disclosed.

  However, as a result of investigations by the present inventors, the above technique could not be completely solved. For example, conventionally, a polarizer in which an iodine complex is adsorbed on PVA has been used. From the viewpoint of adhesion to the polarizer and moisture permeability when drying the polarizer as a manufacturing process, an optical compensation material. Cellulose-based films have been preferably used, but in Patent Documents 4, 5, and 6, non-cellulosic resins are used, which is not preferable in terms of current polarizing plate manufacturing process, adhesion with a polarizer, cost, and the like. . In Patent Document 3, a discotic liquid crystal is applied to cellulose, but the degree of freedom in film design is low, which is not preferable in terms of thinning, cost, and the like.

JP 2008-146004 A JP 2009-301010 A JP 2008-217021 A JP 2011-95401 A JP 2010-217844 A JP 2010-243858 A

  The present invention has been made in view of the above problems, and its purpose is to provide a dielectric anisotropy using a retardation film having a high front contrast and a thin film thickness that leads to power saving, and improved display unevenness. Is to provide a COA type VA liquid crystal display device using positive liquid crystal.

  The above object of the present invention is achieved by the following configurations.

  1. A VA liquid crystal display device having a positive dielectric anisotropy, wherein the VA liquid crystal display device is a COA (color filter on array) method, and is represented by the following formula (II) at 589 nm at 23 ° C. and 55% RH. It has at least one retardation film having a reverse wavelength dispersion (a retardation increases as the wavelength increases) in which Rt is defined as a positive layer and a negative layer, and the positive layer has a negative film thickness. A VA liquid crystal display device having a thickness greater than that of the first layer.

Formula (II): Rt = {(n _x + n _y ) / 2−n _z } × d (nm)
(In the formulas, Rt, Rt is .d representing the retardation in the thickness direction of the positive layer, a negative layer, Rt represents a positive layer, the thickness of the negative layer, n _x is, Rt is positive layer, .n _y representing the refractive index of the maximum (slow axis direction) in the surface of the negative layer, Rt positive layer, a direction perpendicular to the slow axis in the plane of the negative layer (Susumu represents the refractive index of the axis direction), n _z is, Rt represents a refractive index in the thickness direction of the positive layer, a negative layer. the measurement conditions were the same as described above.)
The Ro defined by the following formula (I) at 589 nm at 22.23 ° C. and 55% RH is 30 to 100 nm, and the Rt defined by the following formula (II) is 100 to 300 nm. VA type liquid crystal display device described in 1.

Formula _{(I): Ro = (n} x -n y) × d (nm)
Formula (II): Rt = {(n _x + n _y ) / 2−n _z } × d (nm)
(Wherein, Ro represents in-plane retardation value of the retardation film, Rt is .d representing the retardation in the thickness direction of the retardation film represents the thickness of the retardation film, n _x is the phase difference film maximum in-plane (slow axis direction) .n _y representing the refractive index of the refractive index of the phase difference direction perpendicular to the slow axis in the plane of the film (fast axis direction), n _z is much Represents the refractive index in the thickness direction of the retardation film, and the measurement conditions are the same as above.)
The ratio of the phase difference Rt (450) at a wavelength of 450 nm and the phase difference Rt (630) at a wavelength of 630 nm (Rt (450) / Rt (630) defined by the following formula (II) at 23 ° C. and 55% RH. )) Is 0.85 or more and less than 0.95, 3. The VA liquid crystal display device according to 1 or 2 above.

Formula (II): Rt = {(n _x + n _y ) / 2−n _z } × d (nm)
(In the formulas, Rt .d representing the retardation in the thickness direction of the retardation film represents the thickness of the retardation film, n _x is the refractive index of the maximum (slow axis direction) in a plane of the retardation film .n _y representing the represents the refractive index of the phase difference direction perpendicular to the slow axis in the plane of the film (fast axis direction), n _z represents the refractive index in the thickness direction of the retardation film. Here, The measurement conditions are the same as above.)
4). In any one of the above 1 to 3, wherein the Rt contains a compound having a positive birefringence in the positive layer, and the Rt contains a compound having a negative birefringence in the negative layer VA type liquid crystal display device of description.

  5. 5. The VA type liquid crystal according to any one of 1 to 4, wherein the retardation film contains a cellulose ester resin, and the ester substitution degree of the cellulose ester resin is 2.00 to 2.75. Display device.

  6). 6. The VA liquid crystal display device according to any one of 1 to 5, wherein the retardation film has a thickness of 20 to 60 μm.

  According to the present invention, a COA type VA type liquid crystal display using a liquid crystal having a positive dielectric anisotropy, using a retardation film having a high front contrast leading to power saving and having a thin film thickness and improved display unevenness. An apparatus can be provided.

It is a conceptual diagram which shows an example of a structure of the VA type liquid crystal display device of this invention. It is a conceptual diagram which shows the roll to panel manufacturing method of the VA type liquid crystal display device of this invention.

  As a result of intensive studies in view of the above problems, the present inventors have found that the VA liquid crystal display device has a positive dielectric anisotropy, and the VA liquid crystal display device is a COA (color filter on array) system. Yes, a retardation film having a reverse wavelength dispersion (the retardation increases as the wavelength increases) in which Rt defined by the formula (II) at 589 nm at 23 ° C. and 55% RH is laminated. The COA method has at least one, and has a high front contrast leading to power saving and improved display unevenness by a VA liquid crystal display device in which the thickness of the positive layer is larger than the thickness of the negative layer As a result, the present invention has been realized.

  It is considered that such an effect is manifested for the following reason.

  By laminating Rt positive and negative layers, it is possible to efficiently obtain a thin film and reverse dispersion retardation film, thereby suppressing film-induced display unevenness due to film thickness, retardation unevenness, retardation fluctuation, etc. By making inverse dispersion, the green to red region with high visual sensitivity is effectively compensated, and the leakage light is made into the blue region with lower visual sensitivity to improve visual display unevenness.

  The present invention relates to a liquid crystal display device that enables display by vertically aligning a liquid crystal having positive dielectric anisotropy and providing lateral electrolysis by providing a drive electrode on one side substrate.

  In a VA liquid crystal display device in which a liquid crystal with positive dielectric anisotropy is sealed with two substrates and an electrode is used only on one side of the substrate, the generally known dielectric anisotropy has Similar to the negative VA liquid crystal display device, the liquid crystal layer is in a vertically aligned state during black display, so that the linearly polarized light passing through the backlight side polarizer and traveling in the normal direction (front direction) with respect to the substrate is the liquid crystal layer. The polarization state does not change even if it passes through, and in principle it is all absorbed by the absorption axis of the display surface side polarizer. That is, it can be said that there is no light leakage in the normal direction (front direction) during black display. However, the front transmittance at the time of black display of the VA liquid crystal display device is not zero. One reason for this is that liquid crystal molecules in the liquid crystal layer are fluctuating, and light incident on the liquid crystal layer is known to be scattered to some extent by the fluctuation. Particularly in VA type liquid crystal display device using a liquid crystal having positive dielectric anisotropy is used in the present invention, just immobile liquid crystal is present for one driving electrode, a negative dielectric anisotropy this effect It is necessary to make the liquid crystal layer thicker than the VA type liquid crystal display device using the above liquid crystal, and the influence of the liquid crystal fluctuation is considered to be large.

  In addition, the transmitted light of the liquid crystal display device passes through each member such as a polarizing plate, an optical compensation material, an alignment film, and a color filter in addition to the liquid crystal layer. Diffraction and scattering are expected to occur due to irregularities on the surface of each member, scattering factors, etc., and it is considered that even if it is the front direction, it is affected by the oblique direction. When the amount of transmitted light is increased as in the liquid crystal display device used in the present invention, it is considered that the influence in the oblique direction is particularly great.

  The transmitted light in the oblique direction, which is considered to have a large influence, has an apparent axial misalignment of the polarizer. In order to compensate for this in the visible light region, reverse wavelength dispersion is required. Therefore, it is considered that the optical compensation material is preferably reverse wavelength dispersion from the viewpoint of viewing angle and color shift.

  As a result of investigations by the present inventors, although it varies somewhat depending on the type and configuration of each member in the liquid crystal display device, when a retardation film of reverse wavelength dispersion is used in the VA liquid crystal display device, the order of forward wavelength dispersion is increased. It turned out that the color of the diagonal direction turns into blue compared with the case where a phase difference film is used.

  Each liquid crystal display device has different member types and configurations, and each has the above-mentioned “unevenness” elements. Therefore, it is very difficult to adjust the optical design of the optical compensation material to the optimum conditions. . However, the human visual sensitivity is blue <red <green, and it is thought that the luminance unevenness and the color unevenness can be improved more visually than the red region by setting the leaked light to the blue region. It was.

  Hereinafter, the present invention, its components, and embodiments for carrying out the present invention will be described in detail. In addition, in this application, "-" is used in the meaning which includes the numerical value described before and behind that as a lower limit and an upper limit.

(Outline of configuration of VA type liquid crystal display device)
A typical example of the configuration of the VA liquid crystal display device (hereinafter also referred to as a liquid crystal display device) of the present invention will be described with reference to the drawings.

  FIG. 1 is a conceptual diagram showing an example of the configuration of the VA liquid crystal display device of the present invention. In the liquid crystal display device shown in FIG. 1A, a first retardation film 2, a liquid crystal layer 3, a color filter 9, and a second retardation film are disposed between a pair of polarizers 1 and 5 having absorption axes orthogonal to each other. It is installed in order of 4. The absorption axis of the polarizer 1 adjacent to the slow axis of the first retardation film 2 is orthogonal. The position of the backlight (BL) may be on either the first retardation film side or the second retardation film side. However, as shown in FIG. 1A, the backlight (BL) may be disposed on the second retardation film side. As shown in b), it is more preferable to arrange on the first retardation film side.

  The liquid crystal display device shown in FIG. 1A will be described in more detail. The liquid crystal display device includes an upper polarizer 1 (display surface side) and a lower polarizer 5 which are arranged with the liquid crystal layer 3 interposed therebetween. The first retardation film 2 according to the present invention is between the upper polarizer 1 and the liquid crystal layer 3, and the second retardation is between the lower polarizer 5 and the liquid crystal layer 3. The phase difference film 4 is located.

  Hereinafter, each component of the liquid crystal display device will be described in detail.

<Phase difference film>
In the present invention, a polarizing plate is provided on each of the display surface side and the backlight side of the VA liquid crystal layer having a positive dielectric anisotropy, and at least one polarizing plate sandwiches a polarizer. This retardation film has a reverse wavelength dispersibility obtained by laminating a positive layer and a negative layer defined by the following formula (II) at 589 nm at 23 ° C. and 55% RH. It is a film, The film thickness of the said positive layer is larger than the film thickness of the said negative layer, It is characterized by the above-mentioned.

Formula (II): Rt = {(n _x + n _y ) / 2−n _z } × d (nm)
(In the formulas, Rt, Rt is .d representing the retardation in the thickness direction of the positive layer, a negative layer, Rt represents a positive layer, the thickness of the negative layer, n _x is, Rt is positive layer, .n _y representing the refractive index of the maximum (slow axis direction) in the surface of the negative layer, Rt positive layer, a direction perpendicular to the slow axis in the plane of the negative layer (Susumu represents the refractive index of the axis direction), n _z is, Rt represents a refractive index in the thickness direction of the positive layer, a negative layer. the measurement conditions were the same as described above.)
It is preferable that Ro defined by the following formula (I) at 589 nm at 23 ° C. and 55% RH is 30 to 100 nm, and Rt defined by the following formula (II) is 100 to 300 nm. In the present invention, it is more preferable that Ro is 40 to 90 nm and Rt is 120 to 280 nm.

Formula _{(I): Ro = (n} x -n y) × d (nm)
Formula (II): Rt = {(n _x + n _y ) / 2−n _z } × d (nm)
(Wherein, Ro represents in-plane retardation value of the retardation film, Rt is .d representing the retardation in the thickness direction of the retardation film represents the thickness of the retardation film, n _x is the phase difference film maximum in-plane (slow axis direction) .n _y representing the refractive index of the refractive index of the phase difference direction perpendicular to the slow axis in the plane of the film (fast axis direction), n _z is much Represents the refractive index in the thickness direction of the retardation film, and the measurement conditions are the same as above.)
In the present invention, the reverse chromatic dispersion means the property that the phase difference increases as the wavelength increases. As the wavelength dispersibility of the retardation film, the ratio of the retardation Rt (450) at a wavelength of 450 nm and the retardation Rt (630) at a wavelength of 630 nm defined by the following formula (II) at 23 ° C. and 55% RH ( Rt (450) / Rt (630)) is preferably 0.85 or more and less than 0.95, and more preferably 0.87 or more and less than 0.93.

Formula (II): Rt = {(n _x + n _y ) / 2−n _z } × d (nm)
(In the formulas, Rt .d representing the retardation in the thickness direction of the retardation film represents the thickness of the retardation film, n _x is the refractive index of the maximum (slow axis direction) in a plane of the retardation film .n _y representing the represents the refractive index of the phase difference direction perpendicular to the slow axis in the plane of the film (fast axis direction), n _z represents the refractive index in the thickness direction of the retardation film. Here, The measurement conditions are the same as above.)
The retardation film according to the present invention is preferably used on the liquid crystal layer side of the polarizing plate.

  The thickness of the retardation film is preferably 20 to 60 μm, and more preferably 30 to 50 μm.

  The retardation film according to the present invention is an inverse wavelength dispersive film obtained by laminating a positive layer and a negative layer defined by the above formula (II), and a layer having a negative Rt film thickness. It is characterized by being larger than the film thickness.

  The Rt-positive layer and the negative layer constituting the retardation film are formed by adding a compound having a positive birefringence and a compound having a negative birefringence, respectively, to a resin that is a base material for forming the layer. can do.

(Rt is positive layer)
The layer having a positive Rt (Re control layer) contains a compound having positive birefringence. Here, “positive birefringence” means that a phase difference occurs in the same direction as the stretching direction in the case of a film.

  The compound having positive birefringence is not particularly limited, but cellulose ester, polycarbonate polymer, polyester polymer such as polyethylene terephthalate and polyethylene naphthalate, polyolefin polymer such as polyethylene and polypropylene, polyamide, polyimide and polyether ketone. , Polyamideimide, polyesterimide, and cycloolefin-based polymers. Cellulose ester, polycarbonate-based polymer, polyester-based polymer, and cycloolefin-based polymer are particularly preferably used. These may be used alone or in combination of two or more. When the polymer is a copolymer, it may be a block copolymer or a random copolymer. Moreover, these may be used as a main component and may be used as a subcomponent (additive).

  Other materials (resin, additive, etc.) used for the positive layer of Rt will be described later because Rt is used in common with the negative layer.

  The thickness of the positive Rt layer is preferably 20 to 60 μm.

  The method for forming a positive Rt layer will be described later in the section of the method for producing a retardation film.

(Rt is negative layer)
The layer having negative Rt (DSP control layer, wavelength dispersion control layer) contains a compound having negative birefringence. Here, “negative birefringence” means that a phase difference occurs in the direction perpendicular to the stretching direction in the case of a film. A material whose refractive index decreases with respect to the stretching direction is defined as a material having negative birefringence.

  Although there is no restriction | limiting in particular as a compound which has a negative birefringence, Acrylic polymer, such as polymethylmethacrylate, Styrenic polymers, such as a polystyrene and a styrene-maleic anhydride copolymer (SMA resin), A cellulose ester (birefringence is And polymers such as polyester polymers (excluding those having positive birefringence), polymers having furanose or pyranose structures, acrylonitrile polymers, alkoxysilyl polymers, etc. Acrylic polymers, styrene polymers, and alkoxysilyl polymers are preferably used. These may be used alone or in combination of two or more. When the polymer is a copolymer, it may be a block copolymer or a random copolymer. Moreover, these may be used as a main component and may be used as a subcomponent (additive).

  Rt is used for the negative layer, and the resin, additive and the like will be described later.

  The thickness of the negative Rt layer is preferably 30 μm or less.

  A method for forming a negative Rt layer will be described later in the section of the method for producing a retardation film.

  Hereinafter, the retardation film of the present invention will be described in detail.

  The compounds that are particularly preferably used in the present invention are described as compounds having positive or negative birefringence.

(Resin as the base material for retardation film)
A thermoplastic resin is preferable as the resin used as the base material of the retardation film according to the present invention. Here, the “thermoplastic resin” refers to a resin that becomes soft when heated to a glass transition temperature or a melting point and can be molded into a desired shape.

  General thermoplastic resins include cellulose esters, polyethylene (PE), high density polyethylene, medium density polyethylene, low density polyethylene, polypropylene (PP), polyvinyl chloride (PVC), polyvinylidene chloride, polystyrene. (PS), polyvinyl acetate (PVAc), Teflon (registered trademark) (polytetrafluoroethylene, PTFE), ABS resin (acrylonitrile butadiene styrene resin), AS resin, acrylic resin (PMMA), etc., soluble in solvents It is preferable to dissolve the material appropriately and treat it by the method of the present invention.

  When strength and resistance to breakage are particularly required, polyamide (PA), nylon, polyacetal (POM), polycarbonate (PC), modified polyphenylene ether (m-PPE, modified PPE, PPO), polybutylene terephthalate (PBT) ), Polyethylene terephthalate (PET), glass fiber reinforced polyethylene terephthalate (GF-PET), cyclic polyolefin (COP), and the like.

  If higher heat distortion temperature and long-term use characteristics are required, polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), polysulfone, polyethersulfone, amorphous polyarylate, liquid crystal polymer, polyetherether A ketone, thermoplastic polyimide (PI), polyamideimide (PAI), or the like can be used.

  In addition, it is possible to perform the kind of resin and the combination of molecular weight according to the use of this invention.

  As for the thickness of the resin film, it is preferable to select an appropriate thickness according to the application. The upper limit of the thickness is not particularly limited, but in the case of forming a film by a solution casting method, the upper limit is about 150 μm from the viewpoint of applicability, foaming, solvent drying, and the like.

  The resin substrate preferably has a total light transmittance of 90% or more, more preferably 93% or more. Moreover, as a realistic upper limit, it is about 99%. In order to achieve excellent transparency expressed by such total light transmittance, it is necessary not to introduce additives and copolymerization components that absorb visible light, or to remove foreign substances in the polymer by high-precision filtration. It is effective to reduce the diffusion and absorption of light inside the film.

  Hereinafter, the resin preferably used for the retardation film in the present invention will be described.

<Cellulose ester resin>
In the present invention, the retardation film preferably contains a cellulose ester resin, and the ester substitution degree of the cellulose ester resin is preferably 2.00 to 2.75, and is 2.25 to 2.50. More preferably.

  By setting it within the above range, a film having excellent transparency and preferable wavelength dispersion can be obtained within a preferable range of retardation. Further, as means for adjusting within the above range, there are adjustment of esterification reaction conditions (time, temperature, sample concentration, etc.) and the like.

  Although the birefringence of the cellulose ester resin varies depending on the type of substituents, etc., it cannot be generally stated, but as a tendency, the closer the ester substitution degree is to 3.00, the more negative the birefringence, and the lower the ester substitution degree. A tendency to have positive birefringence is known, for example, in Patent Document WO 06/106639. Therefore, the positive and negative birefringence of the cellulose ester resin is determined by actual measurement.

  In the present invention, when a cellulose ester resin is used for a retardation film other than the retardation film on the liquid crystal layer side, the total ester group substitution degree of the cellulose ester resin may not necessarily be within the above range.

  In addition, the glucose unit which comprises cellulose with a β-1,4-glycoside bond has free hydroxyl groups (hydroxyl groups) at the 2nd, 3rd and 6th positions. The cellulose ester according to the present invention is a polymer obtained by esterifying a part or all of these hydroxyl groups (hydroxyl groups) with an ester group.

  “Ester group substitution degree” represents the total of the ratio of esterification of hydroxyl groups (hydroxyl groups) at the 2nd, 3rd and 6th positions of glucose of the repeating unit. Specifically, the degree of substitution is 1 when each of the hydroxyl groups (hydroxyl groups) at the 2nd, 3rd and 6th positions of cellulose is 100% esterified. Therefore, when all of the 2nd, 3rd and 6th positions of cellulose are 100% esterified, the degree of substitution is 3 at the maximum.

  In the present application, the “average ester group substitution degree” refers to an ester group substitution degree in which the ester group substitution degree of a plurality of glucose units constituting the cellulose ester is expressed as an average value per unit.

  In addition, the measuring method of ester group substitution degree can be measured according to ASTM-D817-96.

  Examples of ester groups include acetyl, propionyl, butanoyl, heptanoyl, hexanoyl, octanoyl, decanoyl, dodecanoyl, tridecanoyl, tetradecanoyl, hexadecanoyl, octadecanoyl, isobutanoyl. Group, tert-butanoyl group, cyclohexanecarbonyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group and the like.

  Among these, an acetyl group, a propionyl group, a butanoyl group, a dodecanoyl group, an octadecanoyl group, a tert-butanoyl group, an oleoyl group, a benzoyl group, a naphthylcarbonyl group, a cinnamoyl group, and the like are more preferable, and an acetyl group is particularly preferable. A propionyl group and a butanoyl group (when the acyl group has 2 to 4 carbon atoms), more preferably an acetyl group.

  Cellulose ester resins that can be used in the retardation film according to the present invention include cellulose (di, tri) acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate phthalate, and It is preferably at least one selected from cellulose phthalates.

  Among these, particularly preferable cellulose esters include cellulose triacetate, cellulose diacetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, and cellulose acetate butyrate.

  As the substitution degree of the mixed fatty acid ester, when the acyl group having 2 to 4 carbon atoms is used as the substituent, the substitution degree of the acetyl group is X, and the substitution degree of the propionyl group or butyryl group is Y. A cellulose resin containing a cellulose ester that simultaneously satisfies the following formulas (I) and (II) is preferable.

Formula (I) 1.5 ≦ X + Y ≦ 3.0
Formula (II) 0 ≦ X ≦ 2.5
Furthermore, as the cellulose ester resin used in the present invention, those having a weight average molecular weight Mw / number average molecular weight Mn ratio of 1.5 to 5.5 are preferably used, and particularly preferably 2.0 to 5.0, More preferably, it is 2.5-5.0, More preferably, the cellulose ester of 3.0-5.0 is used preferably.

  The raw material cellulose of the cellulose ester resin according to the present invention is not particularly limited, and examples thereof include cotton linters, wood pulp, and kenaf. Moreover, the cellulose ester obtained from them can be mixed and used in arbitrary ratios, respectively.

  The cellulose ester resin according to the present invention can be produced by a known method. Generally, cellulose is esterified by mixing cellulose as a raw material, a predetermined organic acid (acetic acid, propionic acid, etc.), an acid anhydride (acetic anhydride, propionic anhydride, etc.), and a catalyst (sulfuric acid, etc.). The reaction proceeds until the triester is formed. In the triester, three hydroxyl groups (hydroxyl groups) of the glucose unit are substituted with an acyl acid of an organic acid. When two kinds of organic acids are used at the same time, a mixed ester type cellulose ester resin such as cellulose acetate propionate or cellulose acetate butyrate can be produced. Subsequently, the cellulose triester is hydrolyzed to synthesize a cellulose ester having a desired degree of acyl substitution. Thereafter, the cellulose ester is completed through steps such as filtration, precipitation, washing with water, dehydration, and drying.

  Specifically, it can be synthesized with reference to the method described in JP-A-10-45804.

  In the present invention, 1 g of cellulose ester resin is added to 20 ml of pure water (electric conductivity 0.1 μS / cm or less, pH 6.8), and the pH is 6 when stirred in a nitrogen atmosphere at 25 ° C. for 1 hr. It is preferable that the electric conductivity is 1 to 100 μS / cm.

<acrylic resin>
An acrylic resin is a compound having negative birefringence.

  Methacrylic resin is also contained in the acrylic resin which can be used for the resin film base material used for retardation film, a polarizing plate, etc. which concern on this invention. Although it does not restrict | limit especially as resin, What consists of 50-99 mass% of methyl methacrylate units and 1-50 mass% of other monomer units copolymerizable with this is preferable.

  Other monomers that can be copolymerized include alkyl methacrylates having 2 to 18 carbon atoms, alkyl acrylates having 1 to 18 carbon atoms, acrylic acid, methacrylic acid, and the like. Saturated acids, maleic acids, fumaric acids, unsaturated divalent carboxylic acids such as itaconic acid, aromatic vinyl compounds such as styrene, α-methylstyrene, and nucleus-substituted styrene, α, β- such as acrylonitrile and methacrylonitrile Examples thereof include unsaturated nitrile, maleic anhydride, maleimide, N-substituted maleimide, glutaric anhydride, and the like. These can be used alone or in combination of two or more.

  Among these, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate, and the like are preferable, and methyl acrylate and n-butyl acrylate are particularly preferably used.

  A commercially available thing can also be used as an acrylic resin. For example, Delpet 60N, 80N (Asahi Kasei Chemicals Co., Ltd.), Dianal BR52, BR80, BR83, BR85, BR88 (Mitsubishi Rayon Co., Ltd.), KT75 (Denki Kagaku Kogyo Co., Ltd.) and the like can be mentioned. .

<Cycloolefin resin>
The cycloolefin resin is a compound having positive birefringence.

  In the present invention, it is also preferable to use a cycloolefin resin. Examples of the cycloolefin resin include norbornene resins, monocyclic cycloolefin resins, cyclic conjugated diene resins, vinyl alicyclic hydrocarbon resins, and hydrides thereof. Among these, norbornene-based resins can be suitably used because of their good transparency and moldability.

  Examples of the norbornene-based resin include a ring-opening polymer of a monomer having a norbornene structure, a ring-opening copolymer of a monomer having a norbornene structure and another monomer, a hydride thereof, and a norbornene structure. And an addition copolymer of a monomer having a norbornene structure and an addition copolymer of another monomer or a hydride thereof.

  Among these, a ring-opening (co) polymer hydride of a monomer having a norbornene structure is particularly suitable from the viewpoints of transparency, moldability, heat resistance, low hygroscopicity, dimensional stability, lightness, etc. Can be used.

Examples of the monomer having a norbornene structure include bicyclo [2.2.1] hept-2-ene (common name: norbornene) and tricyclo [4.3.0.1 ^2,5 ] deca-3,7-diene. (Common name: dicyclopentadiene), 7,8-benzotricyclo [4.3.0.1 ^2,5 ] dec-3-ene (common name: methanotetrahydrofluorene), tetracyclo [4.4.0. 1 ^2,5 . 1 ^7,10 ] dodec-3-ene (common name: tetracyclododecene), derivatives of these compounds (for example, those having a substituent in the ring), and the like. Here, examples of the substituent include an alkyl group, an alkylene group, and a polar group. Moreover, these substituents may be the same or different and a plurality may be bonded to the ring. Monomers having a norbornene structure can be used singly or in combination of two or more.

  Examples of the polar group include a hetero atom or an atomic group having a hetero atom. Examples of the hetero atom include an oxygen atom, a nitrogen atom, a sulfur atom, a silicon atom, and a halogen atom. Specific examples of the polar group include a carboxyl group, a carbonyloxycarbonyl group, an epoxy group, a hydroxyl group, an oxy group, an ester group, a silanol group, a silyl group, an amino group, a nitrile group, and a sulfone group.

  Other monomers capable of ring-opening copolymerization with monomers having a norbornene structure include monocycloolefins such as cyclohexene, cycloheptene, cyclooctene and derivatives thereof, cyclic conjugated dienes such as cyclohexadiene, cycloheptadiene, and the like. And derivatives thereof.

  A ring-opening polymer of a monomer having a norbornene structure and a ring-opening copolymer of a monomer having a norbornene structure and another monomer copolymerizable with the monomer have a known ring-opening polymerization catalyst. It can be obtained by (co) polymerization in the presence.

  Examples of other monomers that can be addition copolymerized with a monomer having a norbornene structure include α-olefins having 2 to 20 carbon atoms such as ethylene, propylene, and 1-butene, and derivatives thereof; cyclobutene, cyclopentene, And cycloolefins such as cyclohexene and derivatives thereof; non-conjugated dienes such as 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene, and the like. These monomers can be used alone or in combination of two or more. Among these, α-olefin is preferable and ethylene is more preferable.

  An addition polymer of a monomer having a norbornene structure and an addition copolymer of another monomer copolymerizable with a monomer having a norbornene structure can be used in the presence of a known addition polymerization catalyst. It can be obtained by polymerization.

  A hydrogenated product of a ring-opening polymer of a monomer having a norbornene structure, a hydrogenated product of a ring-opening copolymer of a monomer having a norbornene structure and another monomer capable of ring-opening copolymerization thereof, Hydrogenated products of addition polymers of monomers having a norbornene structure, and hydrogenated products of addition copolymers of monomers having a norbornene structure and other monomers capable of addition copolymerization with these A known hydrogenation catalyst containing a transition metal such as nickel or palladium is added to the polymer solution, and the carbon-carbon unsaturated bond is preferably hydrogenated by 90% or more.

Among norbornene-based resins, as repeating units, X: bicyclo [3.3.0] octane-2,4-diyl-ethylene structure and Y: tricyclo [4.3.0.1 ^2,5 ] decane-7 , 9-diyl-ethylene structure, the content of these repeating units is 90% by mass or more based on the entire repeating units of the norbornene resin, and the content ratio of X and the content ratio of Y The ratio of X: Y is preferably 100: 0 to 40:60. By using such a resin, it is possible to obtain a retardation film (optical film) having no dimensional change over a long period of time and having excellent optical property stability.

  The molecular weight of the cycloolefin resin used in the present invention is appropriately selected according to the purpose of use. Polyisoprene or polystyrene-converted weight average molecular weight (Mw) measured by gel permeation chromatography using cyclohexane (toluene if the polymer resin does not dissolve) as a solvent, usually 20,000 to 150,000. . Preferably it is 25,000-100,000, More preferably, it is 30,000-80,000. When the weight average molecular weight is in such a range, the mechanical strength and molding processability of the film are highly balanced and suitable.

  The glass transition temperature of the cycloolefin resin may be appropriately selected according to the purpose of use. From the viewpoint of durability and stretchability, it is preferably in the range of 130 to 160 ° C, more preferably 135 to 150 ° C.

  The molecular weight distribution (weight average molecular weight (Mw) / number average molecular weight (Mn)) of the cycloolefin resin is 1.2 to 3.5, preferably 1.5 to 3.0, from the viewpoint of relaxation time, productivity, and the like. More preferably, it is 1.8 to 2.7.

The cycloolefin resin used in the present invention preferably has an absolute value of photoelastic coefficient of 10 × 10 ⁻¹² Pa ⁻¹ or less, more preferably 7 × 10 ⁻¹² Pa ⁻¹ or less, and 4 × 10. It is particularly preferably ⁻¹² Pa ⁻¹ or less. The photoelastic coefficient C is a value represented by C = Δn / σ where birefringence is Δn and stress is σ.

  In the present invention, the cycloolefin resin preferably contains substantially no particles. Here, “substantially free of particles” means that even when particles are added to a film made of cycloolefin resin, the amount of increase in haze from the non-added state is acceptable up to 0.05% or less. Means you can. In particular, since alicyclic polyolefin resin lacks affinity with many organic particles and inorganic particles, when a cycloolefin resin film added with particles exceeding the above range is stretched, voids are easily generated, and as a result, There is a risk that a significant increase in haze may occur.

<Polycarbonate resin>
Polycarbonate resin is a compound having positive birefringence.

  In the present invention, various known polycarbonate resins can also be used. In the present invention, it is particularly preferable to use an aromatic polycarbonate. There is no restriction | limiting in particular about the said aromatic polycarbonate, and there will be no restriction | limiting in particular if it is an aromatic polycarbonate from which the various characteristics of a desired film are acquired.

  In general, a polymer material collectively referred to as polycarbonate is a generic term for a polymer material in which a polycondensation reaction is used in its synthesis method and the main chain is linked by a carbonic acid bond. , Phosgene, diphenyl carbonate and the like obtained by polycondensation. Usually, an aromatic polycarbonate represented by a repeating unit having 2,2-bis (4-hydroxyphenyl) propane called bisphenol-A as a bisphenol component is preferably selected, and various bisphenol derivatives should be appropriately selected. Thus, an aromatic polycarbonate copolymer can be constituted.

  In addition to this bisphenol-A, bis (4-hydroxyphenyl) methane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 9,9-bis (4-hydroxyphenyl) fluorene, 1,1 -Bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, 2,2-bis (4-hydroxy-3-methylphenyl) propane, 2,2-bis (4-hydroxyphenyl) -2-phenyl Ethane, 2,2-bis (4-hydroxyphenyl) -1,1,1,3,3,3-hexafluoropropane, bis (4-hydroxyphenyl) diphenylmethane, bis (4-hydroxyphenyl) sulfide, bis ( 4-hydroxyphenyl) sulfone, 1,1-bis (4-hydroxyphenyl) -3,3,5-tri Mention may be made of a chill cyclohexane, and the like.

  It is also possible to use an aromatic polyester carbonate partially containing a terephthalic acid and / or isophthalic acid component. By using such a structural unit as a part of the structural component of the aromatic polycarbonate composed of bisphenol-A, the properties of the aromatic polycarbonate, such as heat resistance and solubility, can be improved. The present invention is also effective for coalescence.

  If the aromatic polycarbonate used here has a viscosity average molecular weight of 10,000 or more and 200,000 or less, it is suitably used. A viscosity average molecular weight of 20,000 to 120,000 is particularly preferred. If a resin having a viscosity average molecular weight lower than 10,000 is used, the mechanical strength of the resulting film may be insufficient, and if it has a high molecular weight of 400000 or more, the viscosity of the dope becomes too large, causing problems in handling. The viscosity average molecular weight can be measured by commercially available high performance liquid chromatography.

  The glass transition temperature of the aromatic polycarbonate according to the present invention is preferably 200 ° C. or higher in order to obtain a highly heat-resistant film, and more preferably 230 ° C. or higher. These can be obtained by appropriately selecting the copolymerization component. The glass transition temperature can be measured with a DSC apparatus (differential scanning calorimetric analyzer). For example, the baseline is unevenly determined by a temperature rising condition of 10 ° C./min with RDC220 manufactured by Seiko Instruments Inc. It is the temperature that begins to do.

  In the present invention, the solvent used in the dope composition containing the aromatic polycarbonate is a mixed solvent containing 4 to 14 parts by mass of methylene chloride and a linear or branched aliphatic alcohol having 1 to 6 carbon atoms. It is preferable.

  The amount of the linear or branched aliphatic alcohol having 1 to 6 carbon atoms is preferably 4 to 12 parts by mass. By using such a mixed solvent, the web is peeled off at a higher residual solvent concentration than before, thereby suppressing the generation of strong static electricity when the web is peeled off, thereby causing damage to the belt, film streaks, unevenness, and minuteness. Scratches can be prevented from occurring.

  The type of alcohol added is limited by the solvent used. It is a necessary condition that the alcohol and the solvent are compatible. These may be added alone or in combination of two or more. The alcohol in the present invention is preferably a linear or branched aliphatic alcohol having 1 to 6, preferably 1 to 4, more preferably 2 to 4 carbon atoms. Specific examples include methanol, ethanol, isopropanol, and tertiary butanol. Of these, ethanol, isopropanol, and tertiary butanol can achieve almost the same effect, but methanol is slightly less effective. Although the reason is not clear, it is presumed that the boiling point of the solvent, that is, the ease of flying during drying is related. Higher alcohols higher than that are not preferred because they have a high boiling point and are likely to remain after film formation.

  The amount of alcohol added must be carefully selected. These alcohols are completely poor in solubility in aromatic polycarbonate and are completely poor solvents. Therefore, it cannot be added too much, and should be the minimum amount that provides satisfactory peelability. As mentioned above, it is 4-14 mass parts with respect to a methylene chloride, Preferably it is 4-12 mass parts. When the addition amount is in the range of 4 to 14 parts by mass with respect to the amount of methylene chloride, the solubility of the solvent in the polymer and the dope stability are improved, and the effect of improving the peelability is increased.

  The present invention comprises the above methylene chloride and aliphatic alcohol in the dope composition, but other solvents can also be used. The remaining solvent is not particularly limited as long as it dissolves the aromatic polycarbonate at a high concentration and is compatible with alcohol, and is a low-boiling solvent. For example, as a solvent having a solubility in aromatic polycarbonate, in addition to methylene chloride, halogen solvents such as chloroform, 1,2-dichloroethane, 1,1,2-trichloroethane, chlorobenzene, 1,3-dioxolane, 1, Examples include cyclic ether solvents such as 4-dioxane and tetrahydrofuran, and ketone solvents such as cyclohexanone.

  When using other solvent, there is no limitation in particular and it may use it in consideration of an effect. The effects here include mixing the solvent without sacrificing solubility and stability, for example, improving the surface properties of the film formed by the solution casting method (leveling effect), evaporation rate and system These include viscosity adjustment and crystallization inhibitory effects. What is necessary is just to determine the kind and addition amount of the solvent to mix by the degree of these effects, and you may use 1 type, or 2 or more types as a solvent to mix.

  Other solvents preferably used include halogen solvents such as chloroform and 1,2-dichloroethane, hydrocarbon solvents such as toluene and xylene, ketone solvents such as acetone, methyl ethyl ketone and cyclohexanone, ethyl acetate, butyl acetate and the like. Examples include ester solvents, ether solvents such as ethylene glycol dimethyl ether and methoxyethyl acetate.

  The dope composition according to the present invention may be prepared by any method as long as a transparent solution having a low haze is obtained as a result. A predetermined amount of alcohol may be added to the aromatic polycarbonate solution dissolved in a certain solvent in advance, or the aromatic polycarbonate may be dissolved in a mixed solvent containing alcohol. However, as described above, since alcohol is a poor solvent, the method of adding the latter after the former may cause clouding of the dope due to the precipitation of the polymer. Therefore, the method of dissolving in the latter mixed solvent is preferable.

<Polyester resin>
A polyester resin is a compound having positive birefringence.

  The polyester resin that can be used in the present invention is obtained by polymerizing a dicarboxylic acid and a diol, and 70% or more of dicarboxylic acid structural units (constituent units derived from dicarboxylic acid) are derived from aromatic dicarboxylic acid, and 70% or more of the diol constituent units (constituent units derived from the diol) are derived from the aliphatic diol.

  The proportion of the structural unit derived from the aromatic dicarboxylic acid is 70% or more, preferably 80% or more, more preferably 90% or more.

  The proportion of the structural unit derived from the aliphatic diol is 70% or more, preferably 80% or more, and more preferably 90% or more. Two or more polyester resins may be used in combination.

  Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, naphthalenedicarboxylic acid such as 2,7-naphthalenedicarboxylic acid, and 4,4′-biphenyldicarboxylic acid. 3,4'-biphenyldicarboxylic acid and the like and ester-forming derivatives thereof.

  As the polyester resin, aliphatic dicarboxylic acids such as adipic acid, azelaic acid, and sebacic acid, and monocarboxylic acids such as benzoic acid, propionic acid, and butyric acid can be used without departing from the object of the present invention.

  Examples of the aliphatic diol include ethylene glycol, 1,3-propylene diol, 1,4-butanediol, 1,4-cyclohexanedimethanol, 1,6-hexanediol, and the like, and ester-forming derivatives thereof.

  As the polyester resin, monoalcohols such as butyl alcohol, hexyl alcohol, and octyl alcohol, and polyhydric alcohols such as trimethylolpropane, glycerin, and pentaerythritol can be used as long as the object of the present invention is not impaired.

  A known esterification method or transesterification method can be applied to the production of the polyester resin. Examples of the polycondensation catalyst used in the production of the polyester resin include known antimony compounds such as antimony trioxide and antimony pentoxide, germanium compounds such as germanium oxide, titanium compounds such as titanium acetate, and aluminum compounds such as aluminum chloride. Although it can, it is not limited to these.

  Preferred polyester resins include polyethylene terephthalate resin, polyethylene terephthalate-isophthalate copolymer resin, polyethylene-1,4-cyclohexanedimethylene-terephthalate copolymer resin, polyethylene-2,6-naphthalene dicarboxylate resin, polyethylene-2, 6-naphthalene dicarboxylate-terephthalate copolymer resin, polyethylene-terephthalate-4,4'-biphenyldicarboxylate resin, poly-1,3-propylene-terephthalate resin, polybutylene terephthalate resin, polybutylene-2,6-naphthalene There are dicarboxylate resins and the like.

  More preferable polyester resins include polyethylene terephthalate resin, polyethylene terephthalate-isophthalate copolymer resin, polyethylene-1,4-cyclohexanedimethylene-terephthalate copolymer resin, polybutylene terephthalate resin, and polyethylene-2,6-naphthalene dicarboxylate. Resin.

  The intrinsic viscosity of the polyester resin (phenol / 1,1,2,2-tetrachloroethane = value measured at 25 ° C. in a 60/40 mass ratio mixed solvent) is preferably 0.7 to 2.0 dl / g, more Preferably it is 0.8-1.5 dl / g. Since the molecular weight of the polyester resin is sufficiently high when the intrinsic viscosity is 0.7 or more, the molded product comprising the polyester resin composition obtained by using the polyester resin has mechanical properties necessary for the molded product and is transparent. Property is improved. When the intrinsic viscosity is 2.0 or less, the moldability is good.

(Additives used for retardation films)
In addition to the resin film substrate, each additive can be used for the retardation film according to the present invention. Although the usage-amount of an additive can be changed with the target characteristic and it does not restrict | limit in particular, it is preferable that it is 0.1-30 mass parts with respect to 100 mass parts of said resin film base materials.

  The additive may be added at any timing of dope preparation, or may be added at the end of the dope preparation step.

  Hereinafter, the additive particularly preferably used in the present invention will be described in detail.

(Carboxylic acid sugar ester compound)
Carboxylic acid sugar ester compounds are compounds whose birefringence does not belong to either positive or negative.

  The laminated retardation film according to the present invention can use a carboxylic acid sugar ester compound as one of its constituent components.

  In the present application, the “carboxylic acid sugar ester compound” refers to a compound having an ester bond derived from a hydroxyl group (hydroxyl group) of a saccharide and a carboxyl group of a carboxylic acid.

  Examples of the carboxylic acid structural unit constituting the carboxylic acid sugar ester compound include aromatic carboxylic acids such as methylbenzoic acid (toluic acid), aromatic substituted aliphatic carboxylic acids such as phenylacetic acid, and fatty acids such as stearic acid. These carboxylic acids may be substituted with an alkoxy group, an alkylthio group, a halogen atom, a cyano group, or a nitro group.

  Examples of preferred aromatic carboxylic acids include aromatic monocarboxylic acids, cinnamic acid, benzylic acid, biphenylcarboxylic acid, naphthalenecarboxylic acid having an alkyl group or alkoxy group introduced into the benzene ring of benzoic acid such as benzoic acid or toluic acid. Examples thereof include aromatic monocarboxylic acids having two or more benzene rings such as acid and tetralincarboxylic acid, or derivatives thereof. More specifically, xylyl acid, hemelic acid, mesitylene acid, prenylic acid, γ -Isoduric acid, duryl 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-pyrocatec , Β-resorcylic acid, vanillic acid, isovanillic acid, veratromic acid, o-veratrumic acid, gallic acid, asaronic acid, mandelic acid, homoanisic acid, homovanillic acid, homoveratormic acid, o-homoveratormic acid, phthalonic acid, p-coumaric acid Among them, benzoic acid is particularly preferable.

  Preferred aliphatic carboxylic 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, 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, laccellic acid, etc., undecylen Examples thereof include unsaturated fatty acids such as acid, oleic acid, sorbic acid, linoleic acid, linolenic acid, arachidonic acid and octenoic acid.

  The saccharides constituting the carboxylic acid sugar ester compound usually include monosaccharides (monosaccharides), disaccharides (disaccharides), and oligosaccharides bonded with 3 to 6 monosaccharides, and among them, the number of carbon atoms is 6 ~ 48 saccharides are preferred, and monosaccharides and disaccharides are more preferred. Specific examples of monosaccharides include glucose, fructose, arabinose, mannose, and sorbitol, and examples of disaccharides include sucrose and maltose. From the viewpoint of supplying raw materials, glucose, fructose and sucrose are particularly preferable, and sucrose is most preferable.

  These saccharides have a plurality of hydroxyl groups (hydroxyl groups) in the molecule, and can form ester bonds with the aforementioned carboxylic acid structural units.

  In particular, when sucrose is used as a saccharide, there are 8 hydroxyl groups (hydroxyl groups) in the sucrose molecule, but the average number of ester bonds (also referred to as “average ester substitution degree”) is 1. 0.0 or more, preferably 3.0 to 8.0, and more preferably 3.5 to 7.5.

  In the present invention, it is particularly preferable to contain a compound represented by the following general formula (1) and having a total average substitution degree in the range of 3.5 to 7.5.

In general formula (1), R _{1 to} R ₈ represent a hydrogen atom, a substituted or unsubstituted alkylcarbonyl group, or a substituted or unsubstituted arylcarbonyl group, and R _{1 to} R ₈ are the same. It may or may not be.

Preferable specific examples of the compound represented by the general formula (1) include compounds shown in Table 1. In addition, R described in the following table represents any one of R _{1 to} R ₈ . As the substituent for the alkylcarbonyl group and the arylcarbonyl group, substituents such as a phenyl group and an alkoxy group included in the alkylcarbonyl group and the arylcarbonyl group shown in the following table are preferable.

  Although the compound represented by General formula (1) is described below, it is not limited to these.

  (Synthesis example of the compound represented by the general formula (1))

A four-headed colben equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen gas inlet tube was mixed with 34.2 g (0.1 mol) of sucrose, 180.8 g (0.8 mol) of benzoic anhydride, 379. 7 g (4.8 mol) was charged, the temperature was raised while bubbling nitrogen gas from a nitrogen gas introduction tube with stirring, and an esterification reaction was carried out at 70 ° C. for 5 hours. Next, the inside of the Kolben was depressurized to 4 × 10 ² Pa or less, and after excess pyridine was distilled off at 60 ° C., the inside of the Kolben was depressurized to 1.3 × 10 Pa or less and the temperature was raised to 120 ° C. Most of the acid and benzoic acid formed were distilled off. Then, 1 L of toluene and 300 g of a 0.5% by mass aqueous sodium carbonate solution were added, and the mixture was stirred at 50 ° C. for 30 minutes and then allowed to stand to separate a toluene layer. Finally, 100 g of water is added to the collected toluene layer, and after washing with water at room temperature for 30 minutes, the toluene layer is separated, and toluene is distilled off at 60 ° C. under reduced pressure (4 × 10 ² Pa or less). A mixture of compounds A-1, A-2, A-3, A-4 and A-5 was obtained. When the obtained mixture was analyzed by HPLC and LC-MASS, A-1 was 7% by mass, A-2 was 58% by mass, A-3 was 23% by mass, A-4 was 9% by mass, A-5. Was 3% by mass. A part of the obtained mixture was purified by column chromatography using silica gel to obtain A-1, A-2, A-3, A-4 and A-5 having a purity of 100%, respectively. It was.

  The substitution degree distribution may be adjusted to the desired substitution degree by adjusting the esterification reaction time or mixing compounds having different substitution degrees.

<Aromatic group-terminated polyester compound>
The aromatic group-terminated polyester compound is a compound having positive birefringence.

  In the present invention, a polyester compound can be used as the compound having positive birefringence in the laminated retardation film. As the polyester compound, various polyester compounds conventionally contained in optical films can be used.

  In the present invention, it is particularly preferable to use an aromatic group-terminated polyester compound represented by the following general formula (I).

General formula (I): B- (GA) n-GB
(In the formula, B is an arylcarboxylic 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 general formula (I), an arylcarboxylic acid residue represented by B and an alkylene glycol residue or oxyalkylene glycol residue or arylglycol residue represented by G, an alkylenedicarboxylic acid residue or aryldicarboxylic acid represented by A And is obtained by the same reaction as a normal polyester compound.

  As the arylcarboxylic acid component of the aromatic group-terminated polyester-based compound used in the present invention, for example, benzoic acid, p-tert-butylbenzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethylbenzoic acid, ethylbenzoic acid, There are normal propyl benzoic acid, aminobenzoic acid, acetoxybenzoic acid and the like, and these can be used as one kind or a mixture of two or more kinds, respectively.

  Examples of the alkylene glycol component having 2 to 12 carbon atoms of the aromatic group-terminated polyester compound that can be used in the present invention include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, and 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-propane Diol (neopentyl glycol), 2,2-diethyl-1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3,3-di) Methylol heptane), 3-methyl-1,5-pentanediol 1,6-hexanediol, 2,2,4-trimethyl 1 There are 3-pentanediol, 2-ethyl 1,3-hexanediol, 2-methyl 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, etc. These glycols are used as one or a mixture of two or more.

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

  Examples of the oxyalkylene glycol component having 4 to 12 carbon atoms of the aromatic group-terminated polyester compound include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol. Can be used as one or a mixture of two or more.

  Examples of the alkylene dicarboxylic acid component having 4 to 12 carbon atoms of the aromatic group-terminated polyester compound include succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, and dodecanedicarboxylic acid. These are each used as one or a mixture of two or more.

  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.

  In the aromatic group-terminated polyester compound used in the present invention, n is preferably 1 or more and 100 or less, and the number average molecular weight is preferably 300 to 1500, more preferably 400 to 1000. .

  The acid value is 0.5 mgKOH / g or less, the hydroxyl (hydroxyl) value is 25 mgKOH / g or less, more preferably the acid value is 0.3 mgKOH / g or less, and the hydroxyl (hydroxyl) value is 15 mgKOH / g or less. is there.

  The aromatic group-terminated polyester compound represented by the general formula (I) according to the present invention is preferably contained in an amount of 0.5 to 30% by mass with respect to the cellulose ester.

  Specific examples of the aromatic group-terminated polyester compound that can be used in the present invention are shown below, but the present invention is not limited thereto.

  The cellulose ester film according to the present invention contains the sugar ester compound according to the present invention in an amount of 0.5 to 30% by mass of the cellulose ester film in order to suppress the fluctuation of the retardation value and stabilize the display quality. It is preferable to contain 5-30 mass% especially.

  The content of the aromatic group-terminated polyester compound and the sugar ester compound represented by the general formula (I) according to the present invention can be selected in a mass ratio of 99: 1 to 1:99, and the whole of both compounds. The amount is preferably 1 to 40% by mass relative to the cellulose ester.

<Hydroxy group-terminated polyester>
The hydroxy group-terminated polyester is a compound having positive birefringence.

  In the present invention, as a polyester compound having positive birefringence, a polyester having a hydroxy group at the terminal portion of the chemical structural formula as represented by the following general formula (II) (also referred to as “hydroxyl-terminated polyester”) is also used. preferable.

(In the formula, B represents a linear or branched alkylene or cycloalkylene group having 2 to 6 carbon atoms, A represents an aromatic ring having 6 to 14 carbon atoms, and n represents a natural number of 1 or more. )
The compound represented by the above formula is obtained from a dicarboxylic acid having an aromatic ring (also referred to as an aromatic dicarboxylic acid) and a linear or branched alkylene or cycloalkylene diol having 2 to 6 carbon atoms. It is characterized by not being sealed with monocarboxylic acid.

  Examples of the aromatic dicarboxylic acid having 6 to 16 carbon atoms include phthalic acid, isophthalic acid, terephthalic acid, 1,5-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,3- And naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,8-naphthalenedicarboxylic acid, 2,2′-biphenyldicarboxylic acid, 4,4′-biphenyldicarboxylic acid, and the like. Among these, 2,6-naphthalenedicarboxylic acid and 4,4'-biphenyldicarboxylic acid are preferable.

  Examples of the linear or branched alkylene or cycloalkylene diol having 2 to 6 carbon atoms include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, and 1,3-butanediol. 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanediol 1,4-cyclohexanedimethanol and the like. Among these, ethanediol, 1,2-propanediol, 1,3-propanediol, and 1,3-butanediol are preferable.

  Among these, A is preferably a naphthalene ring or a biphenyl ring which may have a substituent, from the viewpoint of obtaining the effects of the present invention. Here, the substituent is an alkyl group having 1 to 6 carbon atoms, an alkenyl group, or an alkoxyl group.

  The hydroxy (hydroxyl group) value (OH value) of the hydroxy group-terminated polyester compound according to the present invention is preferably from 100 mgKOH / g to 500 mgKOH / g, and more preferably from 170 mgKOH / g to 400 mgKOH / g. Whether the hydroxyl (hydroxyl) value is larger or smaller than this range, the compatibility with cellulose acetate having a low acetyl substitution degree is lowered.

  If it is larger than this range, the hydrophobicity of the hydroxy group-terminated polyester compound will increase, and if it is smaller than this range, the intermolecular interaction (hydrogen bonding, etc.) between the hydroxy group-terminated polyester compounds will increase. This is thought to be because precipitation proceeds.

  Moreover, the measurement of a hydroxy (hydroxyl group) value can apply the acetic anhydride method etc. of Japanese Industrial Standard JISK1557-1: 2007.

  The number average molecular weight (Mn) of the polyester compound according to the present invention can be calculated from the following formula.

Mn = (number of hydroxy groups (hydroxyl groups) in the molecule) × 56110 / (hydroxy (hydroxyl group) value)
= 2 × 56110 / (hydroxyl (hydroxyl group) value)
The hydroxy group-terminated polyester compound according to the present invention may be prepared by a conventional method, such as a hot melt condensation method using a polyesterification reaction or a transesterification reaction between the dicarboxylic acid and a diol, or an interfacial condensation method between an acid chloride of these acids and a glycol. It can be easily synthesized by either method.

  Examples of the hydroxy group-terminated polyester compound according to the present invention are shown below.

  The compound represented by the general formula (II) is preferably added in an amount of 1% by mass to less than 5% by mass with respect to the cellulose acetate resin.

(Other additives)
The thermoplastic resin substrate according to the present invention can contain various compounds as additives depending on the purpose. For example, it contains retardation increasing agent, plasticizer, antioxidant, acid scavenger, light stabilizer, UV absorber, optical anisotropy control agent, matting agent, antistatic agent, release agent, etc. Can be made.

  The retardation increasing agent is preferably an aromatic compound having at least two aromatic rings. The aromatic compound is preferably used in the range of 0.01 to 20 parts by mass with respect to 100 parts by mass of the resin. And it is preferable to use in 0.05-15 mass parts, and it is still more preferable to use in 0.1-10 mass parts. Two or more aromatic compounds may be used in combination. The aromatic ring of the aromatic compound includes an aromatic hetero ring in addition to the aromatic hydrocarbon ring. The aromatic hydrocarbon ring is particularly preferably a 6-membered ring (that is, a benzene ring). The aromatic heterocycle is generally an unsaturated heterocycle. The aromatic heterocycle is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring. Aromatic heterocycles generally have the most double bonds. As the hetero atom, a nitrogen atom, an oxygen atom and a sulfur atom are preferable, and a nitrogen atom is particularly preferable. Examples of aromatic heterocycles include furan ring, thiophene ring, pyrrole ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, imidazole ring, pyrazole ring, furazane ring, triazole ring, pyran ring, pyridine ring , Pyridazine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring. Details of these are described in JP-A No. 2004-109410, JP-A No. 2003-344655, JP-A No. 2000-275434, JP-A No. 2000-1111914, JP-A No. 12-275434, and the like.

(Matting agent)
The thermoplastic resin substrate according to the present invention is added with fine particles as a matting agent in order to prevent the produced film from being scratched or having poor transportability when handled. It is also preferable.

  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, Examples thereof include 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 80 to 400 nm. preferable. The content of these fine particles in the film is preferably 0.01 to 1% by mass, particularly preferably 0.05 to 0.5% by mass. In the case of a retardation film (optical film) having a multilayer structure formed by the co-casting method, it is preferable that the surface contains this amount of fine particles.

  Silicon dioxide fine particles are commercially available under the trade names of, for example, 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 resin include a silicone resin, a fluororesin, and an acrylic resin. Silicone resins are preferable, and those having a three-dimensional network structure are particularly preferable. 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 haze of the retardation film (optical film) low. In the retardation film (optical film) according to the present invention, the dynamic friction coefficient of at least one surface is preferably 0.2 to 1.0.

(Method for producing retardation film)
As a method for producing the resin film substrate according to the present invention as a film, production methods such as a normal inflation method, a T-die method, a calendar method, a cutting method, a casting method, an emulsion method, and a hot press method can be used. However, the solution casting method by the casting method and the melt casting method are preferable from the viewpoints of suppression of coloring, suppression of defects of foreign matters, suppression of optical defects such as die lines, and the like.

  Hereinafter, the production method for producing the retardation film according to the present invention will be described in detail.

[Method for producing retardation film by solution casting method]
(Organic solvent)
When the retardation film (optical film) according to the present invention is produced by the solution casting method, the organic solvent useful for forming the dope is not limited as long as it dissolves a thermoplastic resin such as a cellulose ester resin. Can be used.

  For example, as the chlorinated organic solvent, methylene chloride, as the non-chlorinated organic solvent, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro- 2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, nitroethane, ethyl lactate, lactic acid , Diacetone alcohol and the like, methylene chloride, methyl acetate, ethyl acetate, acetone, ethyl lactate and the like are preferably used. That.

  In addition to the organic solvent, the dope may contain 1 to 40% by mass of a linear or branched aliphatic alcohol having 1 to 4 carbon atoms. When the proportion of alcohol in the dope increases, the web gels, facilitating peeling from the metal support, and when the proportion of alcohol is small, the dissolution of the thermoplastic resin in a non-chlorine organic solvent system is promoted. There is also a role.

  In particular, the thermoplastic resin should be a dope composition in which at least 10 to 45% by mass of the thermoplastic resin is dissolved in a solvent containing methylene chloride and a linear or branched aliphatic alcohol having 1 to 4 carbon atoms. preferable.

  Examples of the linear or branched aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Ethanol is preferred because of the stability of these dopes, the relatively low boiling point, and good drying properties.

  Hereinafter, a preferred method for forming a retardation film (optical film) according to the present invention (hereinafter also simply referred to as “film”) will be described.

1) Dissolution Step In this step, a thermoplastic resin and other additives are dissolved in an organic solvent mainly composed of a good solvent for the thermoplastic resin while stirring to form a dope.

  For the dissolution of the thermoplastic resin, a method carried out at normal pressure, a method carried out below the boiling point of the main solvent, a method carried out under pressure above the boiling point of the main solvent, JP-A-9-95544, JP-A-9-95557 Alternatively, various dissolution methods such as a cooling dissolution method as described in JP-A-9-95538 and a high-pressure method as described in JP-A-11-21379 can be used. The method of pressurizing at a boiling point or higher is preferred.

  Recycled material is a finely pulverized film, which is generated when the film is formed, cut off both sides of the film, or the original film that has been speculated out due to scratches, etc. Reused.

2) Casting process An endless metal belt, such as a stainless steel belt or a rotating metal drum, which supports the dope is fed to a pressure die through a liquid feed pump (for example, a pressurized metering gear pump) and supported infinitely. This is a step of casting a dope from a pressure die slit to a casting position on the body.

  A pressure die that can adjust the slit shape of the die base portion and can easily make the film thickness uniform is preferable. Examples of the pressure die include a coat hanger die and a T die, and any of them is preferably used. The surface of the metal support is a mirror surface. In order to increase the film forming speed, two or more pressure dies may be provided on the metal support, and the dope amount may be divided and stacked. Or it is also preferable to obtain the film of a laminated structure by the co-casting method which casts several dope simultaneously.

3) Solvent evaporation step In this step, the web (the dope is cast on the casting support and the formed dope film is called a web) is heated on the casting support to evaporate the solvent.

  To evaporate the solvent, there are a method of blowing air from the web side and / or a method of transferring heat from the back side of the support by a liquid, a method of transferring heat from the front and back by radiant heat, and the like. High efficiency and preferable. A method of combining them is also preferably used. The web on the support after casting is preferably dried on the support in an atmosphere of 40 to 100 ° C. In order to maintain the atmosphere at 40 to 100 ° C., it is preferable to apply hot air at this temperature to the upper surface of the web or to heat by means such as infrared rays.

  From the viewpoint of surface quality, moisture permeability, and peelability, it is preferable to peel the web from the support within 30 to 120 seconds.

4) Peeling process It is the process of peeling the web which the solvent evaporated on the metal support body in a peeling position. The peeled web is sent to the next process.

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

  In addition, it is preferable that the residual solvent amount at the time of peeling of the web on the metal support at the time of peeling is peeled in the range of 50 to 120% by mass depending on the strength of drying conditions, the length of the metal support, and the like. If the web is peeled off at a time when the amount of residual solvent is larger, if the web is too soft, the flatness at the time of peeling will be lost, and slippage and vertical stripes are likely to occur due to the peeling tension. The amount of solvent is determined.

  The residual solvent amount of the web is defined by the following formula.

Residual solvent amount (%) = (mass before web heat treatment−mass after web heat treatment) / (mass after web heat treatment) × 100
Note that the heat treatment for measuring the residual solvent amount represents performing heat treatment at 115 ° C. for 1 hour.

  The peeling tension at the time of peeling the metal support and the film is usually 196 to 245 N / m. However, when wrinkles easily occur at the time of peeling, it is preferable to peel with a tension of 190 N / m or less. It is preferable to peel at a minimum tension that can be peeled to 166.6 N / m, and then peel at a minimum tension to 137.2 N / m, and particularly preferably peel at a minimum tension to 100 N / m.

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

5) Drying and stretching step After peeling, using a drying device that alternately conveys the web through rolls arranged in the drying device and / or a tenter stretching device that clips and conveys both ends of the web with a clip, Dry the web.

  Generally, the drying means blows hot air on both sides of the web, but there is also a means for heating by applying microwaves instead of the wind. Too rapid drying tends to impair the flatness of the finished film. Drying at a high temperature is preferably performed from about 8% by mass or less of the residual solvent. Throughout the drying is generally carried out at 40-250 ° C. It is particularly preferable to dry at 40 to 160 ° C.

  When using a tenter stretching apparatus, it is preferable to use an apparatus that can independently control the film gripping length (distance from the start of gripping to the end of gripping) left and right by the left and right gripping means of the tenter. In the tenter process, it is also preferable to intentionally create sections having different temperatures in order to improve planarity.

  It is also preferable to provide a neutral zone between different temperature zones so that the zones do not interfere with each other.

  In addition, extending | stretching operation may be divided | segmented and implemented in multiple steps, and it is also preferable to implement biaxial stretching in a casting direction and a width direction. When biaxial stretching is performed, simultaneous biaxial stretching may be performed or may be performed stepwise.

  In this case, stepwise means that, for example, stretching in different stretching directions can be sequentially performed, stretching in the same direction is divided into multiple stages, and stretching in different directions is added to any one of the stages. Is also possible. That is, for example, the following stretching steps are possible.

-Stretch in the casting direction-Stretch in the width direction-Stretch in the casting direction-Stretch in the casting direction-Stretch in the width direction-Stretch in the width direction-Stretch in the casting direction-Stretch in the casting direction Simultaneous biaxial stretching includes stretching in one direction and contracting the other while relaxing the tension. The preferable draw ratio of simultaneous biaxial stretching can be taken in the range of x1.01 times to x1.5 times in both the width direction and the longitudinal direction.

  When the tenter is used, the residual solvent amount of the web is preferably 20 to 100% by mass at the start of the tenter, and it is preferable to perform drying while applying the tenter until the residual solvent amount of the web becomes 10% by mass or less. More preferably, it is 5% by mass or less.

  30-160 degreeC is preferable, as for the drying temperature in the case of performing a tenter, 50-150 degreeC is more preferable, and 70-140 degreeC is the most preferable.

  In the tenter process, it is preferable that the temperature distribution in the width direction of the atmosphere is small from the viewpoint of improving the uniformity of the film. The temperature distribution in the width direction in the tenter process is preferably within ± 5 ° C, and within ± 2 ° C. Is more preferable, and within ± 1 ° C. is most preferable.

6) Winding step This is a step of winding the film as a film by a winder after the amount of residual solvent in the web is 2% by mass or less. By reducing the amount of residual solvent to 0.4% by mass or less, dimensional stability can be improved. A good film can be obtained. It is particularly preferable to wind up at 0.00 to 0.10% by mass.

  As a winding method, a generally used method may be used. There are a constant torque method, a constant tension method, a taper tension method, a program tension control method with a constant internal stress, and the like.

  The film according to the present invention is preferably a long film. Specifically, the film is about 100 m to 10000 m, and is usually in the form of a roll. Moreover, it is preferable that the width | variety of a film is 1.3-4m, and it is more preferable that it is 1.4-2.5m.

  Although there is no restriction | limiting in particular in the film thickness of the film concerning this invention, It is preferable that it is 20-200 micrometers.

[Method for producing retardation film by melt casting method]
The method in the case of manufacturing the resin film base material which concerns on this invention as a retardation film by the melt-casting film forming method is demonstrated.

<Melted pellet manufacturing process>
The composition constituting the thermoplastic resin film used for melt extrusion is usually preferably kneaded in advance and pelletized.

  Pelletization may be performed by a known method. For example, a dry thermoplastic resin and an additive depending on the purpose are fed to an extruder with a feeder and kneaded using a uniaxial or biaxial extruder, and then formed into a strand from a die. Can be extruded, water-cooled or air-cooled, and then cut.

  It is important to dry the raw material before extruding to prevent decomposition of the raw material. In particular, since the cellulose ester easily absorbs moisture, it is preferable to dry it at 70 to 140 ° C. for 3 hours or more with a dehumidifying hot air dryer or a vacuum dryer to keep the moisture content at 200 ppm or less, and further 100 ppm or less.

  Additives may be fed into the extruder and fed into the extruder, or may be fed by individual feeders. In order to mix a small amount of additives such as an antioxidant uniformly, it is preferable to mix them in advance.

  The antioxidant may be mixed with each other, and if necessary, the antioxidant may be dissolved in a solvent, impregnated with a thermoplastic resin and mixed, or mixed by spraying. May be.

A vacuum nauter mixer or the like is preferable because drying and mixing can be performed simultaneously. Moreover, when contacting with air, such as an exit from a feeder part or a die, it is preferable that the atmosphere be dehumidified air or dehumidified N ₂ gas.

  The extruder is preferably processed at as low a temperature as possible so that the shearing force is suppressed and the resin can be pelletized so as not to deteriorate (molecular weight reduction, coloring, gel formation, etc.). For example, in the case of a twin screw extruder, it is preferable to rotate in the same direction using a deep groove type screw. From the uniformity of kneading, the meshing type is preferable.

  A film is formed using the pellets obtained as described above. It is also possible to feed the raw material powder directly to the extruder with a feeder and form a film as it is without pelletization.

<Process for extruding molten mixture from die to cooling roll>
First, using a single-screw or twin-screw type extruder, the melt temperature Tm at the time of extrusion is about 200 to 300 ° C., filtered through a leaf disk type filter or the like to remove foreign matters, and then from the T-die Coextruded into a film, solidified on a cooling roll, and cast while pressing with an elastic touch roll.

  When introducing from the supply hopper to the extruder, it is preferable to prevent oxidative decomposition or the like under vacuum or reduced pressure or in an inert gas atmosphere. Tm is the temperature of the die exit portion of the extruder.

  When foreign matter such as scratches or plasticizer aggregates adheres to the die, streak-like defects may occur. Such defects are also referred to as die lines, but in order to reduce surface defects such as die lines, it is preferable to have a structure in which the resin retention portion is minimized in the piping from the extruder to the die. . It is preferable to use a die that has as few scratches as possible inside the lip.

  The inner surface that comes into contact with the molten resin, such as an extruder or a die, is preferably subjected to surface treatment that makes it difficult for the molten resin to adhere to the surface by reducing the surface roughness or using a material with low surface energy. Specifically, a hard chrome plated or ceramic sprayed material is polished so that the surface roughness is 0.2 S or less.

  In the present invention, there is no particular limitation on the cooling roll, but it is a roll having a structure in which a heat medium or a refrigerant body whose temperature can be controlled flows through a high-rigidity metal roll, and its size is not limited. It is sufficient that the film is large enough to cool the film, and the diameter of the cooling roll is usually about 100 mm to 1 m.

  Examples of the surface material of the cooling roll include carbon steel, stainless steel, aluminum, and titanium. Further, in order to increase the hardness of the surface or improve the releasability from the resin, it is preferable to perform a surface treatment such as hard chrome plating, nickel plating, amorphous chrome plating, or ceramic spraying.

  The surface roughness of the chill roll surface is preferably 0.1 μm or less in terms of Ra, and more preferably 0.05 μm or less. The smoother the roll surface, the smoother the surface of the resulting film. Of course, it is preferable that the surface processed is further polished to have the above-described surface roughness.

  In the present invention, examples of the elastic touch roll include JP-A-03-124425, JP-A-08-224772, JP-A-07-1000096, JP-A-10-272676, WO97 / 028950, JP-A-11-235747, A silicon rubber roll coated with a thin film metal sleeve can be used as described in Japanese Unexamined Patent Application Publication No. 2002-36332, Japanese Patent Application Laid-Open No. 2005-172940 and Japanese Patent Application Laid-Open No. 2005-280217.

  When peeling the film from the cooling roll, it is preferable to control the tension to prevent deformation of the film.

<Extension process>
In the present invention, the film obtained as described above can be further stretched 1.01 to 3.0 times in at least one direction after passing through the step of contacting the cooling roll.

  Preferably, the film is stretched 1.1 to 2.0 times in both the longitudinal (film transport direction) and lateral (width direction) directions.

  As a stretching method, a known roll stretching machine, a tenter or the like can be preferably used. In particular, when the retardation film (optical film) also serves as a polarizer protective film, the stretching direction is set to the width direction, which is preferable because lamination with the polarizing film can be performed in a roll form.

  By stretching in the width direction, the slow axis of the retardation film (optical film) becomes the width direction.

  Usually, the draw ratio is 1.1 to 3.0 times, preferably 1.2 to 2 times, and the drawing temperature is usually in the temperature range of Tg to Tg + 50 ° C. of the resin constituting the film.

  The stretching is preferably performed under a uniform temperature distribution controlled in the longitudinal direction or the width direction. The temperature is preferably within ± 2 ° C, more preferably within ± 1 ° C, and particularly preferably within ± 0.5 ° C.

  When the film-like resin film produced by the above method is used as a retardation film, the film is formed in the longitudinal direction or width for the purpose of adjusting the retardation (retardation) of the retardation film (optical film) and reducing the dimensional change rate. It may be contracted in the hand direction.

  In order to shrink in the longitudinal direction, for example, there is a method of contracting the film by temporarily clipping out the width stretching and relaxing in the longitudinal direction, or by gradually narrowing the interval between adjacent clips of the transverse stretching machine.

  The uniformity in the slow axis direction is also important, and the angle is preferably −5 to + 5 ° with respect to the film width direction, more preferably in the range of −1 to + 1 °, and particularly −0. It is preferably in the range of 5 to + 0.5 °, particularly preferably in the range of −0.1 to + 0.1 °. These variations can be achieved by optimizing the stretching conditions.

  The retardation film according to the present invention is preferably a long film. Specifically, the retardation film has a thickness of about 100 m to 10000 m, and is usually provided in a roll shape. Moreover, it is preferable that the width | variety of a film is 1.3-4m, and it is more preferable that it is 1.4-2.5m.

  There is no restriction | limiting in particular in the film thickness of the retardation film which concerns on this invention, It is preferable to change according to the objective. For example, when using for a polarizer protective film, it is preferable that it is 20-200 micrometers.

[Production method of retardation film by co-casting and double casting method]
In the present invention, the obtained polymer solution can be formed by casting the two or more polymer solutions on a smooth band or drum as a support. There is no restriction | limiting in particular as a manufacturing method of the film of this invention other than the above, A well-known co-casting method can be used. For example, a film may be produced by casting and laminating a solution containing a polymer from a plurality of casting openings provided at intervals in the traveling direction of the metal support. For example, Japanese Patent Application Laid-Open No. 61-158414 The methods described in JP-A-1-122419 and JP-A-11-198285 can be applied. It is also possible to form a film by casting a polymer solution from two casting ports. For example, JP-B-60-27562, JP-A-61-94724, JP-A-61-947245, JP-A-6-247245 It can be carried out by the methods described in JP-A-61-104813, JP-A-61-158413, and JP-A-6-134933. Further, a cellulose acylate laminate in which a flow of a high-viscosity cellulose acylate solution described in JP-A-56-162617 is wrapped with a low-viscosity cellulose acylate solution and the high- and low-viscosity cellulose acylate solutions are simultaneously extruded. A film casting method may be used. Furthermore, it is also a preferred embodiment that the outer solution described in JP-A-61-94724 and JP-A-61-94725 contains a larger amount of an alcohol component which is a poor solvent than the inner solution.

  Alternatively, by using two casting ports, peeling the film formed on the metal support by the first casting port, and performing the second casting on the side that was in contact with the metal support surface, A film may be prepared, for example, a method described in Japanese Patent Publication No. 44-20235. The polymer solutions to be cast may be the same solution or different polymer solutions, and are not particularly limited. In order to give a function to a plurality of polymer layers, a polymer solution corresponding to the function may be extruded from each casting port. Furthermore, other functional layers (for example, an adhesive layer, a dye layer, an antistatic layer, an antihalation layer, a UV absorption layer, a polarizing layer, etc.) can be cast at the same time. Moreover, it is also preferable that the film formation is simultaneous or sequential multilayer casting film formation.

  In addition to the above, two or more types of polymer films can also be preferably produced by a method of bonding them with an adhesive.

  In the case of co-casting, the inner and outer thicknesses are not particularly limited, but preferably the outer side is preferably 1 to 50% of the total film thickness, and more preferably 2 to 30%. Here, in the case of co-casting with three or more layers, the total thickness of the layer in contact with the metal support and the layer in contact with the air side is defined as the outer thickness.

  In the case of co-casting, co-cast polymer solutions having different additive concentrations such as the compound having negative birefringence, the compound having positive birefringence, a plasticizer, an ultraviolet absorber, a matting agent, etc. A laminated film having a structure of skin layer / core layer / skin layer can be produced. The mode of addition of the compound having negative birefringence and the compound having positive birefringence is as described above. As for other additives, for example, the matting agent can be contained in the core layer more than the skin layer, or can be contained only in the core layer. The plasticizer and the ultraviolet absorber can be contained in the core layer more than the skin layer, and may be contained only in the core layer. In addition, the type of plasticizer and ultraviolet absorber can be changed between the core layer and the skin layer. For example, the skin layer contains a low-volatile plasticizer and / or an ultraviolet absorber, and the core layer has excellent plasticity. It is also possible to add a plasticizer or an ultraviolet absorber excellent in ultraviolet absorption. Moreover, it is also a preferable aspect that a release agent is contained only in the skin layer on the metal support side. It is also preferable to add more alcohol, which is a poor solvent, to the skin layer than the core layer in order to cool the metal support by the cooling drum method to gel the solution. The Tg of the skin layer and the core layer may be different, and the Tg of the core layer is preferably lower than the Tg of the skin layer. Further, the viscosity of the solution containing cellulose acylate during casting may be different between the skin layer and the core layer, and the viscosity of the skin layer is preferably smaller than the viscosity of the core layer. It may be smaller than the viscosity.

(Polarizer)
When the retardation film according to the present invention is also used as a polarizer protective film, the polarizing plate can be produced by a general method. It is preferable that an adhesive layer is provided on the back side of the retardation film according to the present invention, and is bonded to at least one surface of a polarizer produced by immersing and stretching in an iodine solution.

  The retardation film according to the present invention may be used on the other surface, or another polarizer protective film may be used. For example, a commercially available cellulose ester film (for example, Konica Minoltack KC8UX, KC4UX, KC5UX, KC8UY, KC4UY, KC12UR, KC8UCR-3, KC8UCR-4, KC8UCR-5, KC8UE, KC4R-4, KC4FR-3, KC4FR-3, KC4FR-3, KC4FR-3, KC4FR-3, KC4FR-3, -1, KC8UY-HA, KC8UX-RHA, manufactured by Konica Minolta Opto Co., Ltd.) and the like are preferably used.

  A polarizer, which is a main component of a polarizing plate, is an element that allows only light of a plane of polarization in a certain direction to pass. A typical polarizer currently known is a polyvinyl alcohol-based polarizing film, which is polyvinyl alcohol. There are one in which iodine is dyed on a system film and one in which dichroic dye is dyed.

  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.

As the pressure-sensitive adhesive used for the pressure-sensitive adhesive layer, a pressure-sensitive adhesive having a storage elastic modulus at 25 ° C. in the range of 1.0 × 10 ^{4 to} 1.0 × 10 ⁹ Pa in at least a part of the pressure-sensitive adhesive layer is used. Preferably, a curable pressure-sensitive adhesive that forms a high molecular weight body or a crosslinked structure by various chemical reactions after the pressure-sensitive adhesive is applied and bonded is suitably used.

  Specific examples include, for example, urethane adhesives, epoxy adhesives, aqueous polymer-isocyanate adhesives, curable adhesives such as thermosetting acrylic adhesives, moisture-curing urethane adhesives, polyether methacrylate types, Examples include anaerobic pressure-sensitive adhesives such as ester-based methacrylate types and oxidized polyether methacrylates, cyanoacrylate-based instantaneous pressure-sensitive adhesives, and acrylate-peroxide-based two-pack type instantaneous pressure-sensitive adhesives.

  The pressure-sensitive adhesive may be a one-component type or a type in which two or more components are mixed before use.

  In addition, the pressure-sensitive adhesive may be a solvent system using an organic solvent as a medium, or an aqueous system such as an emulsion type, a colloidal dispersion type, or an aqueous solution type that is a medium mainly containing water, It may be a solventless type. The density | concentration of the said adhesive liquid should just be suitably determined with the film thickness after adhesion, the coating method, the coating conditions, etc., and is 0.1-50 mass% normally.

(VA type liquid crystal display device)
The VA liquid crystal display device of the present invention includes a backlight, a VA liquid crystal layer in which liquid crystal is sandwiched between two transparent substrates, and one sheet on the display surface side and the backlight side of the VA liquid crystal layer. Each has a polarizing plate. The polarizing plate has two retardation films sandwiching a polarizer using polyvinyl alcohol, and the in-plane slow axis of the retardation film on the liquid crystal layer side of the polarizing plate absorbs the polarizer. It is orthogonal to the axis.

<VA liquid crystal layer>
The VA-type liquid crystal display device of the present invention is characterized by having a VA-type liquid crystal layer, and various conventionally known liquid crystal layers can be used as the liquid crystal layer according to the present invention.

  However, the present invention is characterized by using a VA type liquid crystal layer in which a liquid crystal having positive dielectric anisotropy is sandwiched between two transparent substrates. One of the transparent substrates has a thin film transistor (TFT) and a color filter. Regarding this point, the configuration of the liquid crystal display device described in Japanese Patent Application Laid-Open No. 2009-301010, particularly the configuration described in [0094] to [0107] is helpful. As the transparent substrate, conventionally known transparent glass or resin can be used.

  A liquid crystal layer is formed by enclosing a nematic liquid crystal having positive dielectric anisotropy between such glass substrates. As the nematic liquid crystal having positive dielectric anisotropy, known ones used in TN type and IPS type liquid crystal display devices can be used.

  In the present invention, for example, a nematic liquid crystal material having a positive dielectric anisotropy between Δn = 0.0815 and Δε = 4.5 between the upper and lower substrates can be used for the liquid crystal layer.

  The thickness d of the liquid crystal layer is not particularly limited, but can be set to, for example, about 3.5 μm when the liquid crystal having the above characteristics is used.

  Note that in a vertical alignment type (VA type) liquid crystal display device, the addition of a chiral material generally used in a TN mode liquid crystal display device is rarely used to degrade dynamic response characteristics, but alignment failure It may be added to reduce the amount.

  In addition, the multi-domain structure is advantageous for adjusting the alignment of the liquid crystal molecules in the boundary region between the domains.

  Note that the “multi-domain structure” refers to a structure in which one pixel of a liquid crystal display device is divided into a plurality of regions. For example, in a vertical alignment type (VA type) liquid crystal display device, the liquid crystal molecules are tilted during white display, so the birefringence of the liquid crystal molecules when viewed from an oblique direction differs between the tilt direction and the opposite direction. Although a difference occurs in luminance and color tone, a multi-domain structure is preferable because viewing angle characteristics of luminance and color tone are improved.

  Specifically, each pixel is composed of two or more regions having different initial alignment states of liquid crystal molecules and averaged, whereby luminance and color tone bias depending on the viewing angle can be reduced. Further, the same effect can be obtained even if each pixel is constituted by two or more different regions where the alignment direction of liquid crystal molecules continuously changes in a voltage application state.

  In order to obtain a uniform viewing angle in all directions, the number of divisions may be increased. However, a substantially uniform viewing angle can be obtained by using four or more divisions. In particular, it is preferable that the polarizing plate absorption axis can be set at an arbitrary angle when dividing into eight.

<Color filter>
The VA type liquid crystal display device of the present invention uses a VA type liquid crystal layer adopting a color filter on array (COA) system.

  For example, as described in Japanese Patent Application Laid-Open No. 10-206888, the COA method includes a color filter integrated drive substrate in which a color filter is directly formed on a drive side substrate of a liquid crystal layer, and a counter electrode (conductive layer). And a counter substrate with a spacer interposed therebetween, and a liquid crystal material is sealed in the gap, and a color filter is formed on the reflective electrode to provide a bonding margin in high definition. The yield and the aperture ratio can be improved by widening.

(Manufacturing method of liquid crystal display device)
The retardation film according to the present invention is particularly preferably used for a liquid crystal display device produced by a roll-to-panel manufacturing method.

  In the present application, the “roll-to-panel manufacturing method” means that the roll-shaped long polarizing plate is not cut into both the vertical and horizontal sizes of the liquid crystal layer in advance, and the vertical width of the liquid crystal layer and the horizontal width of the liquid crystal layer. This is a production method in which a polarizing plate is directly fed out from a long roll corresponding to the width of the film and bonded to a liquid crystal layer, and then cut into a liquid crystal layer size with a laser cutter or the like (see FIG. 2). In this case, the bonding roll is pressed when the polarizing plate is bonded to the liquid crystal layer. However, since it is a long polarizing plate, in general, an unreasonable force is easily applied at the time of bonding, and the polarizing plate is uneven. Although it is likely to occur, when the retardation film satisfying the above-described conditions according to the present invention is used, unevenness is hardly generated, and variation in optical performance between lots is negligible.

  Hereinafter, although an example is given and the present invention is explained, the present invention is not limited to these.

Example << Preparation of retardation film >>
(Preparation of retardation film 1)
A film was prepared by a solution casting method using the cellulose ester dope shown below.

(Preparation of dope 1 for Re control layer)
Methylene chloride 340 parts by weight Ethanol 64 parts by weight Cellulose acetate (acetyl group substitution degree 2.45) 100 parts by weight Re increasing agent A (positive) 4 parts by weight Polyester compound B (positive) 20 parts by weight Re control layer dope 1 is And a compound having a positive birefringence, and Rt is a positive layer (Re control layer).

<Polyester compound B>
Succinic acid / adipic acid / ethylene glycol copolymer, copolymer ratio 3: 2: 5, molecular weight 1000.

(Preparation of dope 2 for DSP control layer)
Methylene chloride 340 parts by weight Ethanol 64 parts by weight Cellulose acetate (acetyl group substitution degree 2.88) 100 parts by weight Polymer Y1 (negative) 12 parts by weight Aromatic terminal polyester compound (5) 5 parts by weight Fine particle additive 1 1 part by weight The DSP control layer dope 2 forms a negative layer (DSP control layer, wavelength dispersion control layer).

<Synthesis of polymer Y>
Bulk polymerization was performed by the polymerization method described in JP-A No. 2000-128911. That is, the following methyl acrylate or methyl methacrylate is introduced as a monomer Ya into a flask equipped with a stirrer, a nitrogen gas inlet tube, a thermometer, a charging port, and a reflux condenser, and nitrogen gas is introduced to introduce nitrogen gas into the flask. The following thioglycerol substituted with was added with stirring.

100 parts by weight of methyl acrylate or methyl methacrylate 5 parts by weight of thioglycerol After addition of thioglycerol, the temperature of the contents is appropriately changed, polymerization is performed for 4 hours, the contents are returned to room temperature, and 20% by weight of a 5% by weight benzoquinone tetrahydrofuran solution is added thereto. Part of the mixture was added 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 polymers Y1 and Y2.

  Y1 and Y2 are as follows.

Polymer Y1 Monomer Ya = methyl acrylate, weight average molecular weight = 1000
Polymer Y2 Monomer Ya = methyl methacrylate, weight average molecular weight: 1200
<Preparation of fine particle additive solution 1>
Methylene chloride 99 parts by mass Fine particle dispersion 1 5 parts by mass The following fine particle dispersion 1 was stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin. Thereafter, it was slowly added to the dissolution tank containing methylene chloride with sufficient stirring. Further, the particles were dispersed by an attritor so that the secondary particles had a predetermined particle size. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution 1.

<Fine particle dispersion 1>
Fine particles (Aerosil R972V manufactured by Nippon Aerosil Co., Ltd.) 11 parts by weight Ethanol 89 parts by weight The above composition was put into a mixing tank and stirred to dissolve each component, and then a filter paper having an average pore diameter of 34 μm and a fired paper having an average pore diameter of 10 μm Filtration was performed with a bonded metal filter to prepare cellulose ester dopes 1 and 2. The dope was co-cast with a band casting machine. When casting the dope, the above two types of dopes are co-cast from the casting die on the traveling casting band so as to have a three-layer configuration of DSP control layer / Re control layer / DSP control layer. did. Here, the core layer is made the thickest by adjusting the casting amount of each dope, and as a result, the multilayer film is cast so that the film thickness after stretching becomes the value shown in Table 1 below. Casting was performed to form a cast film. The film having a residual solvent amount of about 30% by mass and peeled off from the band was dried by applying hot air of 140 ° C. with a tenter. Thereafter, the tenter transport was shifted to the roll transport, and further dried at 120 to 150 ° C. and wound up.

  After widening to a stretch ratio of 32% using a tenter, the film was relaxed at 140 ° C. for 60 seconds so that the stretch ratio was 30%, whereby a retardation film 1 was obtained.

(Preparation of retardation film 2)
In the production of the retardation film 1, the Re control layer was changed to the following Re control layer dope 3, and the stretching temperature, the magnification, and the thickness of each layer after stretching were as described in Table 1, A phase difference film 2 was obtained.

(Preparation of dope 3 for Re control layer)
Methylene chloride 340 parts by weight Ethanol 64 parts by weight Cellulose acetate (acetyl group substitution degree 2.86) 100 parts by weight Re increasing agent A 4 parts by weight Polyester compound B 12 parts by weight The Re control layer dope 3 has positive birefringence. A layer having a positive Rt (Re control layer) is formed.

(Production of retardation films 3 and 4)
In the production of the retardation film 1, the Re control layer was changed to the following Re control layer dope 4, and the stretching temperature, the magnification, and the thickness of each layer after stretching were as described in Table 1, Phase difference films 3 and 4 were obtained.

(Preparation of dope 4 for Re control layer)
Methylene chloride 340 parts by mass Ethanol 64 parts by mass Cellulose acetate propionate (acetyl group substitution degree 1.88, propionyl group substitution degree 0.58) 100 parts by mass Carboxylic acid sugar ester compound: benzyl saccharose 9 having an average substitution degree of 6.5 3 parts by mass The Re control layer dope 4 contains a compound having positive birefringence and forms a layer having a positive Rt (Re control layer).

<Synthesis of carboxylic acid sugar ester compound>
Four-headed Kolben equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen gas inlet tube were charged with 34.2 g (0.1 mol) of sucrose, 180.8 g (0.6 mol) of benzoic anhydride, 379. 7 g (4.8 mol) was charged, the temperature was raised while bubbling nitrogen gas from a nitrogen gas introduction tube with stirring, and an esterification reaction was carried out at 70 ° C. for 5 hours.

  Next, the inside of the Kolben is reduced to 4 × 102 Pa or less, and after excess pyridine is distilled off at 60 ° C., the inside of the Kolben is reduced to 1.3 × 10 Pa or less, the temperature is raised to 120 ° C., benzoic anhydride, Most of the produced benzoic acid was distilled off. Finally, 100 g of water is added to the collected toluene layer, and after washing with water at room temperature for 30 minutes, the toluene layer is separated, and toluene is distilled off at 60 ° C. under reduced pressure (4 × 10 2 Pa or less) to obtain a carboxylic acid sugar. An ester compound was obtained.

  With respect to this carboxylic acid sugar ester compound, when the average substitution degree was measured from the area ratio of the chart showing the substitution degree distribution by high performance liquid chromatography by a conventional method, Example Compounds A-1 to A-5 were 1.3% and 13%, respectively. The mass ratios were 0.4%, 13.1%, 31.7%, and 40.5%, and the average substitution degree was 5.5.

  Carboxylic acid sugar ester compounds having an arbitrary degree of substitution can be synthesized in the same manner except that the amount of benzoic anhydride is adjusted.

  The carboxylic acid sugar ester compound is a compound having positive birefringence.

(Preparation of retardation film 5)
In the production of the retardation film 1, the DSP control layer is made into the following DSP control layer dopes 5 and 6, and the Re control layer is sandwiched between two types of DSP control layers, and the stretching temperature, magnification, and each layer after stretching. A retardation film 5 was obtained in the same manner as the preparation of the retardation film 1 except that the film thickness was described in Table 1.

(Preparation of dope 5 for DSP control layer)
Methylene chloride 340 parts by weight Ethanol 64 parts by weight Cellulose acetate (acetyl group substitution degree 2.86) 100 parts by weight Triphenyl phosphate 12 parts by weight Re raising agent A 4 parts by weight Fine particle additive 1 1 part by weight The DSP control layer dope 5 is , Which contains a large amount of a compound having positive birefringence and a positive Rt layer (DSP control layer, wavelength dispersion control layer).

(Preparation of dope 6 for DSP control layer)
Methylene chloride 340 parts by weight Ethanol 64 parts by weight Cellulose acetate (acetyl group substitution degree 2.86) 100 parts by weight Triphenyl phosphate 12 parts by weight Polymer Y2 8 parts by weight Re raising agent A 4 parts by weight Particulate additive liquid 1 1 part by weight DSP control The layer dope 6 contains a large amount of a compound having positive birefringence, and forms a layer having a positive Rt (DSP control layer, wavelength dispersion control layer).

(Preparation of retardation film 6)
In the production of the retardation film 1, the DSP control layer is made into the following DSP control layer dope 7 to have a two-layer configuration of DSP control layer / Re control layer, and the stretching temperature, magnification, and thickness of each layer after stretching are listed in Table 1. A retardation film 6 was obtained in the same manner as in the retardation film 1 except that.

(Preparation of dope 7 for DSP control layer)
Methylene chloride 300 parts by mass Ethanol 40 parts by mass Cellulose acetate propionate (acyl group total substitution degree 2.75, acetyl group substitution degree 0.19, propionyl group substitution degree 2.56) 30 parts by mass Dialnal BR85 (Mitsubishi Rayon ( 70 parts by mass Fine particle additive liquid 1 1 part by mass The DSP control layer dope 7 contains many compounds having negative birefringence, and Rt is a negative layer (DSP control layer, wavelength dispersion control layer). Form.

(Preparation of retardation film 7)
In the preparation of the retardation film 6, the Re control layer was changed to the Re control layer dope 4, and the stretching temperature, the magnification, and the thickness of each layer after stretching were as described in Table 1, A phase difference film 7 was obtained.

(Preparation of retardation film 8)
In the production of the retardation film 1, the Re control layer is the Dope 8 for the Re control layer, the DSP control layer is the Dope 6 for the DSP control layer, and the stretching temperature, magnification, and thickness of each layer after stretching are shown in Table 1. A retardation film 8 was obtained in the same manner as the retardation film 1 except that the value was changed.

(Preparation of Re control layer dope 8)
Methylene chloride 340 parts by weight Ethanol 64 parts by weight Cellulose acetate (acetyl group substitution degree 2.45) 100 parts by weight Polymer Y2 6 parts by weight Polyester compound C 12 parts by weight The DSP control layer dope 8 is a compound having positive birefringence And a positive Rt layer (DSP control layer, chromatic dispersion control layer) is formed.

<Polyester compound C>
Terephthalic acid / succinic acid / ethylene glycol copolymer, copolymer ratio 1: 1: 2, molecular weight 1000.

(Preparation of retardation film 9)
In the production of the retardation film 2, the DSP control layer was changed to the above-described DSP control layer dope 6, and the same as the retardation film 2 except that the stretching temperature, the magnification, and the thickness of each layer after stretching were set to the values shown in Table 1. A retardation film 9 was obtained.

(Preparation of retardation film 10)
A commercially available cycloolefin polymer film (trade name: ZEONOR, manufactured by Nippon Zeon Co., Ltd.) was fixed at 1.55 times in the MD direction and 1.8 times in the TD direction at a temperature of 142 ° C. A cycloolefin polymer film having a thickness of 40 μm was obtained. The cycloolefin polymer forms a positive Rt layer (Re control layer).

  The DSP control layer dope 7 was uniformly cast on a stainless steel band support at a temperature of 22 ° C. and a width of 2 m using a belt casting apparatus. With the stainless steel band support, the solvent was evaporated until the amount of residual solvent reached 100%, and peeling was performed from the stainless steel band support with a peeling tension of 162 N / m. The solvent was evaporated from the peeled acrylic resin web at 35 ° C., slit to 1.6 m width, and then dried at a drying temperature of 135 ° C. while stretching 1.1 times in the width direction with a tenter. At this time, the residual solvent amount when starting stretching with a tenter was 10%. After tenter stretching, relaxation is performed at 130 ° C. for 5 minutes, drying is finished while conveying the drying zones at 120 ° C. and 140 ° C. with a number of rolls, slitting to 1.5 m width, width of 10 mm and height of 5 μm at both ends of the film. A knurling process was performed, and the film was wound around a 6-inch inner diameter core with an initial tension of 220 N / m and a final tension of 110 N / m to obtain a cellulose ester film having a film thickness of 20 μm.

  Next, 7.0 g of hydrogenated epoxy resin (trade name; Epicote YX8000, manufactured by Japan Epoxy Resin Co., Ltd.), oxetane resin (3-ethyl-3-hydroxymethyloxetane (oxetane alcohol), trade name: Aron Oxetane 3.0 g of OXT101, manufactured by Toagosei Co., Ltd. and 4.0 g of a photocationic polymerization initiator (trade name; SP-500, manufactured by ADEKA) were mixed in a brown screw tube (No. 5). Thus, a curable resin composition was prepared.

Thereafter, the obtained two films were subjected to corona discharge treatment using a solid state corona treatment machine 6KVA (manufactured by Pillar Co., Ltd.), and the cellulose ester film / curability obtained by sandwiching the corona treated surfaces with the curable resin composition. A laminated film composed of a resin layer / cycloolefin polymer film is formed, and an ultraviolet irradiation device (trade name: CV-1100-G, manufactured by Fusion UV Systems Japan Co., Ltd., using a D bulb, output 80%, height 4 cm. The cycloolefin polymer film was passed through at a speed of 11 m / min) a predetermined number of times with the upper side (irradiation port side). The accumulated light amount when the laminate was passed through the ultraviolet irradiation device four times was about 600 mJ / cm ² (UVB).

  The retardation film 10 was obtained as described above.

(Preparation of retardation film 11)
What mixed 3 mass parts of photoinitiators (BASF Japan Ltd. make; brand name Irgacure 127) with 100 mass parts of N-hydroxyethyl acrylamide was used as an adhesive agent.

Using a lactonized polymethylmethacrylate film (lactonization rate 20%, thickness 30 μm), the adhesive prepared above was thickened using a micro gravure coater (gravure roll: # 300, rotational speed 140% / line speed). It was set as the transparent protective film with the adhesive agent coated so that it might become 5 micrometers in thickness. Lactonized polymethylmethacrylate forms a positive Rt layer (Re control layer). Next, the cellulose ester film of the dope 7 for DSP control layer used in the retardation film 10 and the transparent protective film with the adhesive are bonded to form a transparent protective film / adhesive / cellulose ester film layer structure on a roll machine. It was. The retardation film 11 was obtained by irradiating ultraviolet rays from the bonded transparent protective film side (both sides). The line speed was 20 m / min, and the integrated light quantity was 200 mJ / cm ² on one side.

(Preparation of retardation films 12 and 13)
The dope 4 for the Re control layer was put into a sealed container and dissolved while stirring to prepare a dope solution. Next, using an endless belt casting apparatus, the dope solution was uniformly cast on a stainless steel belt support at a temperature of 33 ° C. and a width of 1500 mm. The temperature of the stainless steel belt was controlled at 30 ° C. On the stainless steel belt support, the solvent was evaporated until the residual solvent amount in the cast (cast) film was 75%, and then peeled off from the stainless steel belt support with a peeling tension of 130 N / m. The peeled cellulose ester film was stretched 36% in the width direction using a tenter while applying heat at 150 ° C. The residual solvent at the start of stretching was 15%.

  Next, drying was terminated while the drying zone was conveyed by a number of rolls. The drying temperature was 130 ° C. and the transport tension was 100 N / m. As described above, a retardation film 12 having a dry film thickness of 40 μm was obtained.

  Further, a retardation film 13 was obtained in the same manner as the retardation film 12 except that the stretching temperature was 135 ° C. and the stretching ratio was 35%.

(Preparation of retardation film 14)
A polyimide synthesized from 2,2'-bis (3,4-dicarboxyphenyl) hexafluoropropane and 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl is dissolved in cyclohexanone. A 15% by weight solution was prepared. This polyimide solution was applied on a biaxially stretched polyester film (base material) and dried at 120 ° C. for 10 minutes to form a non-liquid crystalline polymer layer having a thickness of 4 μm to obtain a non-liquid crystalline polymer laminate. . Polyimide forms a layer with positive Rt (Re control layer).

  Next, the DSP control layer dope 2 was filtered, and uniformly cast on a stainless steel band support at a temperature of 22 ° C. and a width of 2 m using a belt casting apparatus. With the stainless steel band support, the solvent was evaporated until the amount of residual solvent reached 100%, and peeling was performed from the stainless steel band support with a peeling tension of 162 N / m. The peeled cellulose ester web was evaporated at 35 ° C., slit to 1.6 m width, and then dried at a drying temperature of 135 ° C. while stretching 1.1 times in the width direction with a tenter. At this time, the residual solvent amount when starting stretching with a tenter was 10%. After stretching with a tenter, relaxation was performed at 130 ° C. for 5 minutes, and then drying was completed while transporting a drying zone at 120 ° C. and 130 ° C. with many rolls, slitting to a width of 1.5 m, and a width of 10 mm at both ends of the film. A knurling process having a height of 5 μm was applied, and the film was wound around a 6-inch inner core with an initial tension of 220 N / m and a final tension of 110 N / m to obtain a cellulose ester film with a film thickness of 30 μm.

  The obtained non-liquid crystalline polymer laminate and the cellulose ester film were bonded using an adhesive. The surface of the non-liquid crystalline polymer layer was bonded to the surface of the cellulose ester film. Then, the base material was removed and the retardation film 14 was produced.

(Preparation of retardation film 15)
As the retardation film 15, a commercially available cycloolefin polymer film (trade name: ZEONOR, manufactured by Nippon Zeon Co., Ltd.) was used.

<< Evaluation of retardation film >>
(Measurement of retardation Ro and Rt)
From each of the obtained retardation films, and when the retardation film is composed of two or three layers, a single layer film is separately prepared in the same manner, and a sample 35 mm × 35 mm is cut out at 23 ° C. and 55% RH. Extrapolation of retardation value measured in the same manner while tilting the film surface with the value measured from the vertical direction at wavelengths of 450, 590, and 630 nm with an automatic birefringence meter (KOBRA21DH, Oji Scientific Co., Ltd.) Ro and Rt were calculated from the values.

  The retardation Ro in the in-plane direction was measured by making light having wavelengths of 450, 590, and 630 nm incident in the normal direction of the film in KOBRA21ADH. When the film was represented by a uniaxial or biaxial refractive index ellipsoid, Rt was calculated by the following method.

  Retardation Rt in the thickness direction is defined by using Ro, the slow axis in the plane (determined by KOBRA21ADH) as the tilt axis (rotary axis) (in the absence of the slow axis, any direction in the film plane is the rotational axis) And 6 points of light having a wavelength of 590 nm are incident in 10 degree steps from the normal direction to 50 degrees on one side with respect to the film normal direction, and the measured retardation value is measured in total. And KOBRA21ADH based on the assumed average refractive index and the input film thickness value.

In the above measurement, those whose average refractive index was not known were measured with an Abbe refractometer. By inputting the assumed value and the film thickness of the average refractive index, the _KOBRA21ADH, were calculated _{n x, n y, n z} .

  Table 1 shows the film thickness and the retardation value of each wavelength.

<Production of polarizing plate>
A 120 μm-thick polyvinyl alcohol film was uniaxially stretched (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 a polarizer.

  Next, in accordance with the following steps 1 to 5, the polarizer, the retardation film produced above, and Konica Minolta Tack KC4UY (Konica Minolta Opto's cellulose ester film) are bonded to the back surface side, and the retardation film 1 Polarizers 1 to 15 were prepared from ˜15, respectively.

  Moreover, the polarizing plate 16 which bonded together the polarizer and Konica Minolta Tac KC4UY (the cellulose ester film by Konica Minolta Opto Co., Ltd.) only on one side was also produced.

(Polarizing plate production process)
Of the retardation films 1 to 15, the cellulose ester film was saponified and bonded to a polarizer using a polyvinyl alcohol-based adhesive. Other cycloolefin films are corona-treated and bonded to polarizers using urethane-based easy-adhesion layers and poly vinyl alcohol adhesives, and acrylic films using photo-curing resins and UV curing methods. Bonded with a polarizer. At this time, the retardation films 1 to 15 were bonded so that the in-plane slow axis thereof was orthogonal to the absorption axis of the polarizer.

  In addition, about the phase difference films 5-7, 10, 11, and 14, although both surfaces differ, either surface may be bonded to the polarizer side. In this case, a polarizing plate was prepared with the layer B in Table 1 in the case of a two-layer laminated retardation film and the layer C in Table 1 in the case of a three-layer laminated retardation film, with the layer C in the polarizer side.

  Step 1: The cellulose ester film was immersed in a 2 mol / L sodium hydroxide solution at 60 ° C. for 90 seconds, then washed with water and dried to obtain a saponified cellulose ester film bonded to the polarizer.

  Process 2: The said polarizer was immersed in the polyvinyl alcohol adhesive tank of 2 mass% of solid content for 1-2 seconds.

  Step 3: Excess adhesive adhered to the polarizer in Step 2 was lightly wiped off and placed on the cellulose ester film treated in Step 1.

Step 4: Step 3 Cellulose ester film laminated with the polarizer and the pressure backside cellulose ester film 20-30 N / cm ^2, the conveyance speed was pasted at approximately 2m / min.

  Step 5: The polarizer prepared in Step 4 in a dryer at 80 ° C., each retardation film described in Table 1 and Konica Minolta Tack KC4UY were bonded to each other for 2 minutes to prepare polarizing plates 1 to 9. .

<Production of liquid crystal display device>
A liquid crystal panel for measuring display unevenness was produced as follows, and the characteristics as a liquid crystal display device were evaluated.

  Using the LED backlight unit of the VA mode type liquid crystal display device (BRAVIA KDL-46HX800 manufactured by SONY), a liquid crystal display device using the liquid crystal cell described in FIG. The polarizing plates 1 to 16 were bonded to both surfaces of the glass surface of the liquid crystal cell so as to have the combinations shown in Table 2, respectively.

  At that time, the direction of bonding of the polarizing plate is performed so that the surface of the retardation film is on the liquid crystal layer side and the absorption axis is directed in the same direction as the polarizing plate previously bonded, Liquid crystal display devices 1 to 11 were produced. In the liquid crystal layer of this liquid crystal display device, a color filter and a thin film transistor are disposed on one of the transparent substrates.

<Evaluation of display unevenness>
The liquid crystal display device was wet-heated for 24 hours in an environment of 23 ° C. and 55% RH, and the luminance and hue unevenness (strength) of the black display after 2 hours of lighting of the backlight and the effect of image display, 50 ° C., 90 ° In the% RH environment, wet heat treatment was performed for 24 hours, and the luminance and hue unevenness (strength) of the black display 2 hours after lighting the backlight were visually evaluated in accordance with the following criteria.

(Brightness and hue unevenness standard)
◎: Brightness unevenness is not visible ○: Weak brightness unevenness is visible but not noticeable in image display △: Brightness unevenness is strong, but hardly noticeable in image display ×: Brightness unevenness is strong, even in image display Evaluation Table 2 shows the results.

  As is apparent from Table 2, the VA liquid crystal display device of the present invention has improved display unevenness and is preferable.

DESCRIPTION OF SYMBOLS 1, 5 Polarizer 2 1st phase difference film 3 Liquid crystal layer 4 2nd phase difference film 6, 8 Absorption axis 7 Slow axis 9 Color filter 10 Polarizing plate roll 11 Bonding roll

Claims (5)

A VA liquid crystal display device having positive dielectric anisotropy, wherein the VA liquid crystal display device is a COA (color filter on array) system,
A retardation film having a reverse chromatic dispersion (a retardation increases as the wavelength increases) in which Rt is defined by the following formula (II) at 589 nm at 23 ° C. and 55% RH is laminated: Have one,
The thickness of the positive layer is rather larger than the thickness of the negative layer,
The ratio of the retardation Rt (450) at a wavelength of 450 nm defined by the following formula (II) and the retardation Rt (630) at a wavelength of 630 nm (Rt (450) / Rt (23) at 23 ° C. and 55% RH of the retardation film. 630)) is 0.85 or more and less than 0.95, VA type liquid crystal display device.
Formula (II): Rt = {(nx + ny) / 2−nz} × d (nm)
(In the formula, Rt represents the retardation in the thickness direction of the positive layer and negative layer, d represents the film thickness of the positive layer and negative layer, and nx represents the positive value of Rt. Represents the maximum refractive index (in the direction of the slow axis) in the plane of the negative layer and the negative layer, and ny is a direction perpendicular to the slow axis in the plane of the positive layer and the negative layer (the fast axis). Direction), and nz represents the refractive index in the thickness direction of the positive layer and negative layer of Rt (note that the measurement conditions are the same as above). The Ro defined by the following formula (I) at 589 nm at 23 ° C. and 55% RH is 30 to 100 nm, and the Rt defined by the following formula (II) is 100 to 300 nm. VA type liquid crystal display device of description.
Formula _{(I): Ro = (n} x -n y) × d (nm)
Formula (II): Rt = {(n _x + n _y ) / 2−n _z } × d (nm)
(Wherein, Ro represents in-plane retardation value of the retardation film, Rt is .d representing the retardation in the thickness direction of the retardation film represents the thickness of the retardation film, n _x is the phase difference film maximum in-plane (slow axis direction) .n _y representing the refractive index of the refractive index of the phase difference direction perpendicular to the slow axis in the plane of the film (fast axis direction), n _z is much Represents the refractive index in the thickness direction of the retardation film, and the measurement conditions are the same as above.) Wherein Rt is comprises a compound positive layers have positive birefringence, VA type according to claim 1 or 2, characterized in that it contains a compound wherein Rt is negative layer has negative birefringence Liquid crystal display device. The VA type according to any one of claims 1 to 3 , wherein the retardation film contains a cellulose ester resin, and the ester substitution degree of the cellulose ester resin is 2.00 to 2.75. Liquid crystal display device. VA-type liquid crystal display device according to any one of claims 1 to 4, the film thickness of the retardation film is characterized in that it is a 20 to 60 [mu] m.

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