WO2012096088A1

WO2012096088A1 - Vertically aligned liquid crystal display device and method for manufacturing same

Info

Publication number: WO2012096088A1
Application number: PCT/JP2011/078866
Authority: WO
Inventors: 梅田　博紀; 絢子稲垣; 矢野　健太郎
Original assignee: コニカミノルタオプト株式会社
Priority date: 2011-01-14
Filing date: 2011-12-14
Publication date: 2012-07-19
Also published as: JPWO2012096088A1; JP5835230B2; CN103314325A; CN103314325B; KR101530797B1; KR20130106420A

Abstract

The present invention addresses the issue of providing: a vertically aligned liquid crystal display device, which achieves improved front contrast that makes it possible to save power, and which has a reduced color shift and a wider view angle; and a method for manufacturing such vertically aligned liquid crystal display device. A vertically aligned liquid crystal display device of the present invention has: a backlight; a vertically aligned liquid crystal cell having a configuration wherein a liquid crystal having negative dielectric constant anisotropy is sandwiched between two transparent substrates; and polarization plates, which are disposed on the display surface side and the backlight side of the vertically aligned liquid crystal cell, respectively. The vertically aligned liquid crystal display device is characterized in meeting specific requirements.

Description

Vertical alignment type liquid crystal display device and manufacturing method thereof

The present invention relates to a vertical alignment type liquid crystal display device that achieves an improvement in front contrast that leads to power saving, a small color shift, and a wide viewing angle, and a method for manufacturing the same.

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 (mobile terminals), and mobile phones.

In recent years, a vertical alignment type liquid crystal display device (also referred to as a “VA (vertical alignment) type”) using vertical alignment type liquid crystal (liquid crystal having negative dielectric anisotropy) has been compared with a conventional TN type liquid crystal display device. Because of its excellent viewing angle characteristics, it has become widely used.

In recent years, in this vertical alignment type liquid crystal display device, there is an increasing demand for power saving, and miniaturization of a light-shielding portion and a high aperture ratio by a color filter on array (COA) are being promoted.

In addition, a method of increasing the transmittance of the polarizing plate has been proposed as a means of saving power, but if only the transmittance of the polarizing plate is increased, there is a problem that the degree of polarization decreases and the front contrast decreases. To do.

In order to solve this problem, methods such as retardation film and viewing angle widening film are used to suppress depolarization by a film (protective film) placed between the polarizing film and the liquid crystal cell. It can no longer be met.

Patent Document 1 and Non-Patent Document 1 disclose that the front contrast is increased by the configuration of the retardation film. Although these methods suggest the possibility that the front contrast can be maintained even if the transmittance of the polarizing plate is increased, the front contrast improving means using these methods causes a very large color shift. Originally, the vertical alignment type liquid crystal display device has a small color shift, but this configuration is a method of eliminating the goodness inherent in the vertical alignment type liquid crystal display device.

On the other hand, in recent years, in the manufacturing process of liquid crystal display devices, instead of the method of laminating a sheet-like polarizing plate on a liquid crystal panel, a “roll-to-panel manufacturing method” in which a roll-shaped polarizing plate is directly adhered is adopted. Although it has started, even in such a manufacturing method, it is desired that there is no variation in optical performance between lots of polarizing plates.

In the present application, a polarizing plate manufactured in a rolled state is referred to as a “rolled polarizing plate”, and a piece cut from the polarizing plate to a predetermined dimension is referred to as a “single sheet polarizing plate”.

JP 2010-54736 A

The present invention has been made in view of the above-described problems and circumstances, and a solution to the problem is a vertical that achieves an improvement in front contrast that leads to power saving, and has a small color shift and a wide viewing angle. An alignment type liquid crystal display device and a manufacturing method thereof are provided.

The above-mentioned problem according to the present invention is solved by the following means.

1. A vertical alignment type liquid crystal cell having a configuration in which a backlight and a liquid crystal having a negative dielectric anisotropy are sandwiched between two transparent substrates, and one sheet on the display surface side and the backlight side of the vertical alignment type liquid crystal cell A vertical alignment type liquid crystal display device having polarizing plates each satisfying the following requirements (a) to (c):
(A) One of the transparent substrates has a thin film transistor and a color filter.
(B) 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 cell side of the polarizing film is the polarized light. It is perpendicular to the absorption axis of the child.
(C) When the retardation film on the color filter side of one polarizing plate is used as the retardation film A and the retardation film on the liquid crystal cell side of the other polarizing plate is used as the retardation film B. The retardation values Rt in the thickness direction of the retardation films A and B measured at a measurement wavelength of 590 nm at 23 ° C. and 55% RH are Rt (A) and Rt (B), respectively, and in-plane When the values of the ratio of the retardation value Rt in the thickness direction to the retardation value Ro of Rt / Ro (A) and Rt / Ro (B) are respectively expressed by the following (Expression 1) to (Expression 5) The relationship represented by is satisfied.
(Formula 1): Rt (A) <Rt (B)
(Formula 2): 70 nm <Rt (A) <130 nm
(Formula 3): 130 nm <Rt (B) <200 nm
(Formula 4): 20 nm <Rt (B) −Rt (A) <130 nm
(Formula 5): Rt / Ro (A) <Rt / Ro (B)
[However, Ro and Rt are defined by the following formulas.
Formula (I): Ro = (n _x −n _y ) × d (nm)
Formula (II): Rt = {(n _x + n _y ) / 2−n _z } × d (nm)
In the above formula, Ro represents the in-plane retardation value in the retardation film, and Rt represents the retardation value in the thickness direction in the film. Further, d represents the thickness of the retardation film, n _x represents a refractive index of the maximum (slow axis direction) in a plane of the retardation film. n _y represents a refractive index in the direction perpendicular to the slow axis in the retardation film plane (fast axis direction), n _z represents the refractive index of the retardation film in the thickness direction. The measurement conditions are the same as above. ]
2. When the in-plane retardation values Ro of the retardation films A and B are respectively Ro (A) and Ro (B), the relationships represented by the following (Expression 6) to (Expression 8) are satisfied. 2. The vertical alignment type liquid crystal display device according to item 1, wherein the liquid crystal display device is a vertical alignment type liquid crystal display device.
(Formula 6): Ro (A) <Ro (B)
(Formula 7): 40 nm <Ro (A) <90 nm
(Formula 8): 45 nm <Ro (B) <100 nm
3. 3. The vertical alignment type liquid crystal display device according to

item

1 or 2, wherein the retardation film A or retardation film B contains a cellulose ester resin.

4. The in-plane retardation value Ro and the thickness direction retardation value Rt of the retardation film A are adjusted by the control by the draw ratio when the retardation film A is formed, and the in-plane of the retardation film B The vertical alignment according to any one of the first to third items, wherein the retardation value Ro and the retardation value Rt in the thickness direction are adjusted by controlling the stretching temperature and the film thickness. Type liquid crystal display device.

5. A manufacturing method of a vertical alignment type liquid crystal display device for manufacturing the vertical alignment type liquid crystal display device according to any one of items 1 to 4, wherein the retardation film A and the retardation film B A method for producing a vertical alignment type liquid crystal display device, comprising preparing a long roll-shaped polarizing plate having at least one retardation film, and laminating the liquid crystal cell by a roll-to-panel manufacturing method.

By the above-described means of the present invention, it is possible to provide a vertical alignment type liquid crystal display device that achieves an improvement in front contrast leading to power saving, a small color shift, and a wide viewing angle, and a manufacturing method thereof. .

1 is a conceptual diagram showing an example of a configuration of a vertical alignment type (VA type) liquid crystal display device of the present invention. Conceptual diagram showing an example of a configuration of a conventional liquid vertical alignment type (VA type) liquid crystal display device Conceptual diagram showing the roll-to-panel manufacturing method

The vertical alignment type liquid crystal display device of the present invention includes a backlight, a vertical alignment type liquid crystal cell having a structure in which a liquid crystal having negative dielectric anisotropy is sandwiched between two transparent substrates, and the vertical alignment type liquid crystal cell. A vertical alignment type liquid crystal display device having polarizing plates one by one on the display surface side and the backlight side, satisfying the requirements (a) to (c), and formulas (1) to (5) ) Is satisfied. This feature is a technical feature common to the inventions according to claims 1 to 5.

As an embodiment of the present invention, from the viewpoint of manifesting the effects of the present invention, when the in-plane retardation values Ro of the retardation films A and B are respectively Ro (A) and Ro (B), It is preferable that the relationships represented by Equations (6) to (8) are satisfied. Furthermore, it is preferable that the retardation film A or the retardation film B contains a cellulose ester resin.

In the present invention, the in-plane retardation value Ro and the retardation value Rt in the thickness direction of the retardation film A are adjusted by the control by the draw ratio when the retardation film A is formed, and The in-plane retardation value Ro and the thickness direction retardation value Rt of the retardation film B are preferably adjusted by controlling the stretching temperature and the film thickness.

As a manufacturing method of the vertical alignment type liquid crystal display device for manufacturing the vertical alignment type liquid crystal display device of the present invention, a long roll-shaped polarizing plate having at least one of the retardation film A and the retardation film B is used. It is preferable that it is a manufacturing method of the aspect which prepares and is bonded with the roll to panel manufacturing method with respect to the said liquid crystal cell.

Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In the present application, “˜” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.

(Phase difference films A and B)
In the liquid crystal display device of the present invention, the polarizing plate has two retardation films sandwiching a polarizer using polyvinyl alcohol (PVA), and the retardation film on the liquid crystal cell side of the polarizing film The in-plane slow axis is perpendicular to the absorption axis of the polarizer.

Also, among the retardation films, when the retardation film on the color filter side of one polarizing plate is the retardation film A, and the retardation film on the liquid crystal cell side of the other polarizing plate is the retardation film B, The retardation values Rt in the thickness direction of the retardation films A and B measured at a measurement wavelength of 590 nm are Rt (A) and Rt (B), respectively, and the thickness relative to the in-plane retardation value Ro. When the ratio value of the phase difference value Rt in the vertical direction is Rt / Ro (A) and Rt / Ro (B), the relations expressed by the following (Expression 1) to (Expression 5) are satisfied. It is characterized by.
(Formula 1): Rt (A) <Rt (B)
(Formula 2): 70 nm <Rt (A) <130 nm
(Formula 3): 130 nm <Rt (B) <200 nm
(Formula 4): 20 nm <Rt (B) −Rt (A) <130 nm
(Formula 5): Rt / Ro (A) <Rt / Ro (B)
However, Ro and Rt are defined by the following formula.
Formula (I): Ro = (n _x −n _y ) × d (nm)
Formula (II): Rt = {(n _x + n _y ) / 2−n _z } × d (nm)
In the above formula, Ro represents the in-plane retardation value in the retardation film, and Rt represents the retardation value in the thickness direction in the film. Further, d represents the thickness of the retardation film, n _x represents a refractive index of the maximum (slow axis direction) in a plane of the retardation film. n _y represents a refractive index in the direction perpendicular to the slow axis in the retardation film plane (fast axis direction), n _z represents the refractive index of the retardation film in the thickness direction. The measurement conditions are the same as above.

In the present invention, the above (formula 2) to (formula 4) are more preferably 80 nm ≦ Rt (A) ≦ 120 nm, 140 nm ≦ Rt (B) ≦ 185 nm, and 30 nm <Rt (B) −Rt (A ) <120 nm.

More preferably, 85 nm ≦ Rt (A) ≦ 115 nm, 145 nm ≦ Rt (B) ≦ 170 nm, and 35 nm <Rt (B) −Rt (A) <110 nm.
In the present invention, when the in-plane retardation values Ro of the retardation films A and B are respectively Ro (A) and Ro (B), they are expressed by the following (Expression 6) to (Expression 8). It is preferable that the relationship to be satisfied is satisfied.
(Formula 6): Ro (A) <Ro (B)
(Formula 7): 40 nm <Ro (A) <90 nm
(Formula 8): 45 nm <Ro (B) <100 nm
The liquid crystal display device of the present invention uses a vertical alignment type liquid crystal cell adopting a color filter on array (COA) system.

The COA method includes, for example, a color filter integrated drive substrate in which a color filter is directly formed on a drive side substrate of a liquid crystal cell, and a counter electrode (conductive layer) as described in JP-A-10-206888. ) 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, and a bonding margin is provided in high definition. The yield and aperture ratio can be improved by widening.

The arrangement of the retardation film according to the present invention with respect to the configuration of the liquid crystal cell is very important.

In the present invention, it is necessary to dispose retardation films on both sides of the liquid crystal cell. However, regarding the retardation value Rt in the thickness direction, the color filter side needs to be relatively small, and the difference Is greater than 20 nm and less than 130 nm, more preferably greater than 30 nm and less than 120 nm, and even more preferably greater than 35 nm and less than 110 nm. If this value is small, the front contrast of the liquid crystal display device cannot be improved, and if it is too large, the color shift of the liquid crystal display device becomes large. Especially, the color mixture when viewed from the periphery is remarkable, and the display quality of the liquid crystal display device is high. Is significantly reduced.

The Rt on the color filter side of the retardation film (or retardation layer) used on both sides (two places) of the liquid crystal cell in the liquid crystal display device of the present invention must be larger than 70 nm and smaller than 130 nm, which is opposite to the liquid crystal cell. The Rt of the retardation film on the negative side needs to be larger than 130 nm and smaller than 200 nm, more preferably, the Rt on the color filter side is 80 nm or more and 120 nm or less, and more preferably 85 nm or more and 115 nm or less.

On the other hand, the Rt of the retardation film on the opposite side of the liquid crystal cell is 140 nm or more and 185 nm or less, and more preferably 145 nm or more and 170 nm or less. The retardation value of these two retardation films affects the viewing angle of the liquid crystal display device. When each phase difference value falls within a desired range, it is possible to obtain viewing angle characteristics closer to the target in the vertical and horizontal directions.

The Rt / Ro value of the retardation film used on both sides (two places) of the liquid crystal cell in the liquid crystal display device of the present invention needs to be smaller on the color filter side of the liquid crystal cell. When the value of Rt / Ro on the color filter side of the liquid crystal cell is increased, the color shift is increased and the display quality of the liquid crystal display device is remarkably lowered.

In the liquid crystal display device of the present invention, Ro of the retardation film used on both sides (two places) of the liquid crystal cell is 40 nm <Ro <90 nm on the color filter side and 45 <Ro <100 nm on the side opposite to the color filter. The side opposite to the color filter is preferably large. In particular, the side opposite to the color filter is large, the viewing angle can be sufficiently widened by setting 45 nm <Ro <100 nm, and the color shift can be suppressed by arranging a relatively small Ro on the color filter side. it can.

The retardation film used on both sides (two places) of the liquid crystal cell in the liquid crystal display device of the present invention is preferably made by a film forming method. Moreover, it is preferable to make it while controlling the retardation value during film formation.

Examples of the retardation film used in the liquid crystal display device of the present invention include a cellulose ester film, a polyester film, a cycloolefin film, a polycarbonate film, a polyolefin film, a polyacryl film, and a mixed resin film of an acrylic resin and a cellulose ester resin.

Examples of the retardation film A include a stretched polymer film mainly composed of a polycarbonate-based, cellulose-based, polyethylene-based, or polypropylene-based resin. Particularly preferred are cellulose ester resins.

The retardation value control method for these retardation films is, for example, when using cellulose aether, changing the degree of ester substitution or substituent, changing the solvent, adding a retardation value control material, adjusting the stretching conditions, etc. However, when used in the liquid crystal display device of the present invention, the retardation value control of the retardation film used on the color filter side is mainly controlled by the draw ratio, and the retardation value control on the side opposite to the color filter is performed. More preferably, it is carried out by controlling the stretching temperature and the film thickness. By using a retardation film whose retardation value is controlled by this means, the warpage of the liquid crystal panel can often be alleviated. The reason for this is that the distortion remaining in the film changes depending on the retardation value control means, and the distortion can be balanced on both sides of the liquid crystal cell by controlling the retardation value on the color filter side and the opposite side by the above method. Therefore, it is estimated that the warpage of the liquid crystal cell may be alleviated.

The details of the resin film suitable for the retardation film used in the liquid crystal display device of the present invention will be described later.

(Polarizer)
When the retardation film according to the present invention is 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.

On the other side, the retardation film according to the present invention may be used, 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, KC4FR-4, KC4FR-3, KC4FR-3, KC4FR-4 -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.

The polarizer is formed by forming a polyvinyl alcohol aqueous solution into a film and dyeing the film by uniaxial stretching or dyeing or uniaxially stretching, and then performing a durability treatment with a boron compound.

As the pressure-sensitive adhesive used in 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. It is preferable to use 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.

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 type and oxidized polyether methacrylate, cyanoacrylate-based instantaneous pressure-sensitive adhesives, and acrylate-peroxide-based two-component instantaneous pressure-sensitive adhesives.

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

The pressure-sensitive adhesive may be a solvent system using an organic solvent as a medium, or may be an aqueous system such as an emulsion type, a colloidal dispersion type, or an aqueous solution type that is a medium containing water as a main component. It may be a solventless type. The concentration of the pressure-sensitive adhesive liquid may be appropriately determined depending on the film thickness after adhesion, the coating method, the coating conditions, and the like, and is usually 0.1 to 50% by mass.

(Vertical alignment type liquid crystal cell)
The liquid crystal display device of the present invention is characterized by having a vertical alignment type liquid crystal cell, and various conventionally known liquid crystal cells can be used as the liquid crystal cell according to the present invention.

However, the present invention is characterized in that a vertical alignment type liquid crystal cell having a configuration in which a liquid crystal having negative dielectric anisotropy is sandwiched between two transparent substrates is used. One of the transparent substrates has a thin film transistor (TFT) and a color filter. For this point, the configuration of the liquid crystal display device disclosed in Japanese Patent Application Laid-Open No. 2010-44362 is helpful. As the transparent substrate, conventionally known transparent glass or resin can be used.

A liquid crystal cell is formed by enclosing a nematic liquid crystal having negative dielectric anisotropy between such glass substrates. As the nematic liquid crystal having negative dielectric anisotropy, conventionally known ones described in JP-A-2004-204133, JP-A-2004-250668, JP-A-2005-047980, etc. should be used. Can do.

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

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

Further, when the multi-domain structure is used, it 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 orientation direction of the 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.

(Resin film substrate used for polarizing plates, etc.)
As the resin film substrate used for the polarizing plate or the like according to the present invention, it is preferable to use a thermoplastic resin. Here, the “thermoplastic resin” refers to a resin that becomes soft when heated to the glass transition temperature or 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 combine the kind of resin and molecular weight according to the use of the present invention.

It is preferable to select an appropriate thickness for the resin film according to the intended use. 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, a particularly suitable resin in the present invention will be described in detail.

<Cellulose ester resin>
Cellulose ester resins that can be used in the retardation film described in the present invention are cellulose (di, tri) acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate phthalate, And at least one selected from cellulose phthalate.

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

As the substitution degree of the mixed fatty acid ester, when an acyl group having 2 to 4 carbon atoms is used as a substituent, the substitution degree of the acetyl group is X, and the substitution degree of the propionyl group or butyryl group is Y. It is preferable that it is a cellulose resin containing the cellulose ester which satisfy | fills following formula (i) and (ii) simultaneously.

Formula (i) 1.5 ≦ X + Y ≦ 3.0
Formula (ii) 0 ≦ X ≦ 2.5
Further, the cellulose ester used in the present invention preferably has a weight average molecular weight Mw / number average molecular weight Mn ratio of 1.5 to 5.5, particularly preferably 2.0 to 5.0, The cellulose ester is preferably 2.5 to 5.0, more preferably 3.0 to 5.0.

The raw material cellulose of the cellulose ester used in the present invention may be wood pulp or cotton linter, and the wood pulp may be softwood or hardwood, but softwood is more preferable. A cotton linter is preferably used from the viewpoint of peelability during film formation. The cellulose ester made from these can be mixed suitably or can be used independently.

For example, the ratio of cellulose ester derived from cellulose linter: cellulose ester derived from wood pulp (coniferous): cellulose ester derived from wood pulp (hardwood) is 100: 0: 0, 90: 10: 0, 85: 15: 0, 50:50: 0, 20: 80: 0, 10: 90: 0, 0: 100: 0, 0: 0: 100, 80:10:10, 85: 0: 15, 40:30:30.

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.

《Sugar ester compound》
In the present invention, it is also preferable to include a cellulose ester resin and an ester compound in which at least one of the pyranose structure or the furanose structure is 1 to 12 and all or part of the OH groups in the structure are esterified.

The proportion of esterification is preferably 70% or more of the OH groups present in the pyranose structure or furanose structure.

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

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

Other examples include gentiobiose, gentiotriose, gentiotetraose, xylotriose, and galactosyl sucrose.

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

As examples, sucrose, kestose, nystose, 1F-fructosyl nystose, stachyose and the like are preferable, and sucrose is more preferable.

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

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

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

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

Oligosaccharide ester compounds can be applied as compounds having 1 to 12 of at least one of the pyranose structure or furanose structure according to the present invention.

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

Moreover, the said ester compound is a compound which condensed 1 or more and 12 or less of at least 1 type of the pyranose structure or furanose structure represented with the following general formula (A). R ₁₁ to R ₁₅ and R ₂₁ to R _{25 each} represents an acyl group having 2 to 22 carbon atoms or a hydrogen atom, m and n each represents an integer of 0 to 12, and m + n represents an integer of 1 to 12.

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

Specific examples of the ester compound according to the present invention will be given 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. In particular, it is preferable to contain 5 to 30% by mass.

<acrylic resin>
Methacrylic resin is also contained in the acrylic resin which can be used for the resin film base material used for the phase difference film of this invention, a polarizing plate, etc. The resin is not particularly limited, but a resin comprising 50 to 99% by mass of methyl methacrylate units and 1 to 50% by mass of other monomer units copolymerizable therewith is preferable.

Examples of other copolymerizable monomers include alkyl methacrylates having 2 to 18 alkyl carbon atoms, alkyl acrylates having 1 to 18 carbon atoms, alkyl acrylates such as acrylic acid and methacrylic acid. Saturated acids, maleic acids, fumaric acids, divalent carboxylic acids containing unsaturated groups such as itaconic acid, aromatic vinyl compounds such as styrene, α-methylstyrene, and nucleus-substituted styrene, α, β- such as acrylonitrile, methacrylonitrile, etc. 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 preferable.

Commercially available acrylic resins can also be used. For example, Delpet 60N, 80N (Asahi Kasei Chemicals Co., Ltd.), Dianal BR52, BR80, BR83, BR85, BR88 (Mitsubishi Rayon Co., Ltd.), KT75 (Electrochemical Industry Co., Ltd.) and the like can be mentioned. .

<Cyclic olefin resin>
In the present invention, it is also preferable to use a cyclic olefin resin. Examples of the cyclic olefin resin include norbornene resins, monocyclic olefin 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. An addition polymer of a monomer having a monomer, an addition copolymer of a monomer having a norbornene structure and 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, and the like. Can be used.

Examples of the monomer having a norbornene structure include bicyclo [2.2.1] hept-2-ene (common name: norbornene), 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) and derivatives of these compounds (for example, those having a substituent in the ring). Here, examples of the substituent include an alkyl group, an alkylene group, and a polar group. In addition, 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 heteroatoms or atomic groups having heteroatoms. 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 carboxy group, a carbonyloxycarbonyl group, an epoxy group, a hydroxy 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 monocyclic olefins such as cyclohexene, cycloheptene, and 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, for example, α-olefins having 2 to 20 carbon atoms such as ethylene, propylene, and 1-butene, and derivatives thereof; cyclobutene, cyclopentene, Examples thereof include cycloolefins such as cyclohexene and derivatives thereof; non-conjugated dienes such as 1,4-hexadiene, 4-methyl-1,4-hexadiene, and 5-methyl-1,4-hexadiene. 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, X: bicyclo [3.3.0] octane-2,4-diyl-ethylene structure and Y: tricyclo [4.3.0.1 ^2,5 ] decane-7 are used as repeating units. , 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 X content ratio and the Y content ratio are 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 cyclic olefin resin used in the present invention is appropriately selected according to the purpose of use. Polyisoprene or polystyrene-equivalent 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. . It is preferably 25,000 to 100,000, more preferably 30,000 to 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 cyclic olefin 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 cyclic olefin 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 cyclic olefin 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 more preferably 4 × 10 12 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, it is preferable that the cyclic olefin resin does not substantially contain particles. Here, “substantially free of particles” means that even if particles are added to a film made of a cyclic olefin resin, the amount of increase in haze from the non-added state is allowed to be in the range of 0.05% or less. Means you can. In particular, the alicyclic polyolefin resin lacks affinity with many organic particles and inorganic particles. Therefore, when a cyclic olefin resin film to which particles exceeding the above range are added is stretched, voids are easily generated, and as a result, There is a risk that a significant increase in haze may occur.

<Polycarbonate resin>
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. Various bisphenol derivatives should be selected as appropriate. 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-to It can be exemplified methyl cyclohexane.

It is also possible to use an aromatic polyester carbonate partially containing terephthalic acid and / or isophthalic acid components. 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.

The viscosity average molecular weight of the aromatic polycarbonate used here is preferably 10,000 to 200,000. 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 mixing 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 tert-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 to be 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 can provide satisfactory peelability. As described above, it is 4 to 14 parts by mass, preferably 4 to 12 parts by mass with respect to methylene chloride. 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 is composed of 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 solvents, there is no particular limitation, and the effect may be taken into consideration. The effects here include mixing the solvent within a range that does not sacrifice the solubility and stability, for example, improving the surface properties of the film formed by the solution casting method (leveling effect), the evaporation rate and the system These include viscosity adjustment and crystallization suppression 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 and butyl acetate. 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 with 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>
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, and 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, 2,7-naphthalenedicarboxylic acid, and the like, 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 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 to 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.

(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 may be added with fine particles as a matting agent in order to prevent scratching or deterioration of transportability when the produced film is handled. 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 size 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, for example, under the trade names Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (manufactured by Nippon Aerosil Co., Ltd.). it can.

Zirconium oxide fine particles are commercially available under the trade names of Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.) and can be used.

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

Among these, Aerosil 200V and Aerosil R972V are particularly preferably used because they have a large effect of reducing the friction coefficient while keeping the 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 a chlorinated organic solvent, methylene chloride, as a 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, etc., preferably methylene chloride, methyl acetate, ethyl acetate, acetone, ethyl lactate, etc. Get.

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 method using a cooling dissolution method as described in JP-A-9-95538 and a method using a high pressure 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, and has been cut off on both sides of the film, or a film original 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.

¡Pressure dies that can adjust the slit shape of the die base and make the film thickness uniform are preferred. 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, etc. 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 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.

The amount of residual solvent at the time of peeling of the web on the metal support at the time of peeling is preferably 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 amount of residual solvent in 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, if 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 of ˜166.6 N / m, and then peel at a minimum tension of ˜137.2 N / m, and particularly preferable to peel at a minimum tension of ˜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 passes the web through rolls arranged in the drying device and / or a tenter stretching device that clips and transports both ends of the web with clips. Dry the web.

The drying means is generally to blow hot air on both sides of the web, but there is also a means to heat by applying microwaves instead of 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, drying is generally carried out at 40-250 ° C. In particular, drying at 40 to 160 ° C. is preferable.

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 each zone does not cause interference.

The stretching operation may be performed in multiple stages, and it is also preferable to perform biaxial stretching in the casting direction and the 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 preferred draw ratio for simultaneous biaxial stretching can be in the range of x1.01 to x1.5 in both the width direction and the longitudinal direction.

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

When performing the tenter, the drying temperature is preferably 30 to 160 ° C., more preferably 50 to 150 ° C., and most preferably 70 to 140 ° C.

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 one may be used, and there are a constant torque method, a constant tension method, a taper tension method, a program tension control method with a constant internal stress, etc., and these may be used properly.

The film according to the present invention is preferably a long film, specifically a film having a thickness of about 100 m to 5000 m, and usually in a form provided in a roll shape. The film width is preferably 1.3 to 4 m, more preferably 1.4 to 2 m.

The film thickness according to the present invention is not particularly limited, but is preferably 20 to 200 μm.

<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 the raw material from being decomposed. In particular, since 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 so that the moisture content is 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 through 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. Further, if the contact with air, such as the exit from the feeder unit or die, it is preferable that the atmosphere such as dehumidified air and dehumidified N ₂ gas.

The extruder is preferably processed at as low a temperature as possible so as to be able to be pelletized so that the shear force is suppressed and the resin does not 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.

Film formation is performed 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 when extruding the pellets is about 200-300 ° C, filtered through a leaf disk type filter, etc. to remove foreign matter, Coextruded into a film, solidified on a cooling roll, and cast while pressing with an elastic touch roll.

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

∙ If foreign matter such as scratches or plasticizer aggregates adheres to the die, streaky defects may occur. Such a defect is also called a die line, but in order to reduce surface defects such as the die line, 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 processing 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 coolant that can be controlled in temperature flows with a highly rigid metal roll, and the 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.

The surface material of the cooling roll includes carbon steel, stainless steel, aluminum, titanium and the like. 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 cooling 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 the stretching method, a known roll stretching machine or tenter can be preferably used. In particular, when the retardation film (optical film) also serves as a polarizer protective film, it is preferable to make the stretching direction the width direction 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 stretching ratio is 1.1 to 3.0 times, preferably 1.2 to 2 times, and the stretching temperature is usually a temperature of Tg to Tg + 50 ° C., preferably Tg to Tg + 50 ° C. of the resin constituting the film. Done in a range.

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 in which the film is shrunk 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.

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 °, particularly −0. A range of 5 to + 0.5 ° is preferable, and a range of −0.1 to + 0.1 ° is particularly preferable. 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 is about 100 m to 10000 m, and is usually in the form of a roll. The width of the film is preferably 1.3 to 4 m, more preferably 1.4 to 2.5 m.

The film thickness of the retardation film according to the present invention is not particularly limited and is preferably changed according to the purpose. For example, when used for a polarizer protective film, the thickness is preferably 20 to 200 μm.

(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 length of the liquid crystal cell and the width of the liquid crystal cell are not cut in advance in both the vertical and horizontal sizes of the liquid crystal cell. This is a manufacturing 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 cell, and then cut into a liquid crystal cell size with a laser cutter or the like (see FIG. 3). In this case, the laminating roll is pressed when laminating the polarizing plate to the liquid crystal cell, but since it is a long polarizing plate, generally an unreasonable force is easily applied at the time of laminating, and unevenness is present in the polarizing plate. 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.

(Film production)
<Preparation of fine particle dispersion>
Fine particles (Aerosil R972V (Nippon Aerosil Co., Ltd.))
11 parts by mass (average primary particle diameter 16 nm, apparent specific gravity 90 g / liter)
More than 89 parts by mass of ethanol was stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin to obtain a fine particle dispersion.

<Fine particle additive solution>
Cellulose acetate (acetyl group substitution degree 2.10, Mn = 14000) was added to a dissolution tank containing methylene chloride and heated to completely dissolve it, and this was then added to Azumi Filter Paper No. 244 manufactured by Azumi Filter Paper Co., Ltd. While finely stirring the filtered cellulose acetate solution, the fine particle dispersion was slowly added thereto, and an attritor was used 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.

(Composition of fine particle addition liquid)
Methylene chloride 99 parts by weight Cellulose acetate (above) 4 parts by weight Fine particle dispersion 11 parts by weight A main dope solution having the following composition was prepared. First, methylene chloride and ethanol were added to the pressure dissolution tank. The cellulose ester was added to the pressure dissolution tank containing the solvent while stirring. This was heated and stirred to completely dissolve, and a plasticizer and an ultraviolet absorber were further added and dissolved. This was designated as Azumi Filter Paper No. The main dope solution was prepared by filtration using 244.

In addition to 100 parts by mass of the main dope solution and 5 parts by mass of the fine particle additive solution, thoroughly mix with an in-line mixer (Toray static type in-pipe mixer Hi-Mixer, SWJ), then use a belt casting device to It was cast uniformly on a 2 m stainless steel band support. On the stainless steel band support, the solvent was evaporated until the residual solvent amount became 110%, and the stainless steel band support was peeled off. Next, both ends of the web are gripped with a tenter, stretched in the width direction, held for 4 seconds with the width held after the stretching is finished, the width is released after the tension in the width direction is relaxed, and further 125 ° C. In the third drying zone set to 1, drying was carried out for 30 minutes, and protective films 101 to 122 having a width of 1.49 m and a knurling of 1 cm in width at the end were prepared, in which 118 was 1000 m and the remaining was 500 m. . The above method is referred to as “Prescription A”.

Table 1 and Table 2 show the conditions of the stretching zone (stretching ratio, heating temperature) and the amount of residual solvent when entering the tenter.

<Composition of main dope solution>
Methylene chloride 390 parts by mass Ethanol 80 parts by mass Cellulose acetate (total substitution degree 2.48, acetyl group substitution degree 1.58,
Propionyl group substitution degree 0.90, Mn = 16000) 100 parts by mass Sucrose benzoate (average substitution degree 5.5) 10.0 parts by mass Dope composition of cellulose acetate (total substitution degree 2.41, acetyl substitution degree 2.41) In the same manner except that Mn = 18000 was used, films 123 to 149 were prepared in increments of 1000 m for 148 and 500 m for the rest, and the manufacturing method of the films 123 to 149 is referred to as “Prescription B”.

The film was formed in the same manner except that cellulose acetate having a total substitution degree of 1.90, acetyl substitution degree of 1.90 and Mn = 14,000 was used, and sucrose benzoate having an average substitution degree of 5.1 was used. 150 to 185 were made 500 m each. The production method of the films 150 to 185 is defined as prescription C.

<Measurement of retardation value of retardation film>
After adjusting the humidity of the prepared retardation film at 23 ° C. and 55% RH, the retardation value was measured at a measurement wavelength of 590 nm using KOBRA 31WPR manufactured by Oji Scientific Instruments. For calculating Rt, the average refractive index is measured by measuring the refractive index in three directions with an Abbe refractometer and averaged using R 0 and the phase difference value when the slow axis is tilted by 40 ° with respect to the tilt axis. Was calculated.

Table 3 and Table 4 show the measurement results.

(Preparation of polarizing plate)
The prepared retardation film and Konica Minolta Op KC6UA-SW were saponified for 60 seconds using an aqueous KOH solution at 50 ° C. and 2N, washed with water and dried, and then subjected to polarizing plate processing as follows.

A polyvinyl alcohol film having a thickness of 75 μm was swollen with water at 35 ° C. and immersed in an aqueous solution consisting of 0.075 g of iodine, 5 g of potassium iodide, and 100 g of water, and then 3 g of potassium iodide and 7. It was immersed in a 45 ° C. aqueous solution consisting of 5 g and 100 g of water and uniaxially stretched (temperature 55 ° C., stretch ratio 5 times). This was washed with water and dried to obtain a polarizer.

Next, the saponified protective film (KC6UA-SW and each retardation film) is placed on both sides of the polarizer, and the pressure is 20-30 N / cm ^{2 in} a form in which the polarizer is sandwiched between both protective films using water paste. The transfer speed was about 10 m / min, and a drying process was performed at 70 ° C. for about 2 minutes and then at 60 ° C. for about 2 minutes, and wound up to prepare a polarizing plate roll. An adhesive layer was provided on the peeled polyethylene terephthalate film, and the surface of the adhesive layer was attached to the retardation film side of the obtained polarizing plate to prepare an adhesive polarizing plate roll. Tables 3 and 4 show the correspondence between the retardation films (101 to 185) and the polarizing plates (201 to 285).

(Production of liquid crystal display device)
Strip the polarizing plate of BRAVIA KDL52W5 manufactured by Sony, and paste the polarizing plate prepared above on the panel with the combinations described in Table 5, Table 6 and Table 7 to prepare liquid crystal display devices (1001 to 1072). The following evaluation was performed. The liquid crystal cell of this liquid crystal display device has a color filter and a thin film transistor disposed on one of the transparent substrates (see FIG. 1), and is a cell of the liquid crystal display device of the present invention. W is described. Subsequently, the polarizing plate of BRAVIA KDL52V1 manufactured by Sony was peeled off and bonded to the panel in the combinations of Table 5, Table 6 and Table 7 to prepare liquid crystal display devices (3001 to 3004), and the following evaluation was performed. The liquid crystal cell of this liquid crystal display device is a comparative example of the liquid crystal cell of the liquid crystal display device of the present invention in which the color filter and the thin film transistor are arranged on different transparent substrates (see FIG. 2). It is.

(Evaluation)
<Front contrast>
With the backlight turned on, white display and black display were displayed on the screen, front luminance was measured using CS2000 manufactured by Konica Minolta Sensing, and front contrast was calculated using this. Also, the calculated value is rounded down to the nearest tenth, with 25 or more and 50 or less set to 50, and values above that are rounded up.

The front contrast was evaluated according to the following criteria.
A: More than 3000 B: More than 2500 and less than 3000 X: 2500 or less <Viewing angle>
Using an EZ-Contrast 160D manufactured by ELDIM, white and black were displayed in the same manner as the front contrast measurement, and the minimum angle of contrast 50 in the range of 20 to 70 ° was set as the viewing angle. In addition, when the viewing angle exceeds 80 ° in all directions, it is described as 80 °.

The viewing angle was evaluated according to the following criteria.
◎: 70 ° or more ○: 60 ° or more, less than 70 ° ×: less than 60 ° <Color shift>
The color shift in black display was measured using EZ-Contrast 160D manufactured by ELDIM, and expressed as coordinates (u1 ′, v1 ′) in the CIE 1976 UCS chromaticity diagram, and measured at 360 ° with a tilt angle of 60 ° from the normal of the liquid crystal display device. Among the coordinates, a value having the longest distance between the front direction (u2 ′, v2 ′) and the coordinate is defined as a color shift. Color shift (ΔCS) = ((u1′−u2 ′) ² + (v1′−v2 ′) ² ) ^1/2
Color shift (ΔCS) was evaluated according to the following criteria.
A: Less than 0.040 B: 0.040 or more and 0.060 or less X: More than 0.060 The above evaluation results are summarized in Tables 5 to 9.

As is apparent from the results shown in Tables 5 to 9, it can be seen that the vertical alignment type liquid crystal display device of the present invention is excellent in evaluation of front contrast, viewing angle, and color shift.

(Relation between slit method of polarizing plate and uneven brightness)
The polarizing plate 218 is 1151 mm wide and the polarizing plate 248 is slit to a width of 647 mm using a laser slitter to prepare a polarizing plate roll 218A1 having a width of 1151 mm and a polarizing plate roll 248B1 having a width of 647 mm, and a polarizing plate roll set 218A1-248B1. did.

This was set in a manufacturing system of a liquid crystal display device, which is a panel bonding device for roll-shaped polarizing plates, and roll-bonded to 10 liquid crystal cells (liquid crystal display devices 2001 to 2010). In addition, 10 polarizing plates 218 and 248 were cut into 52-inch sizes, and were similarly bonded to 10 liquid crystal cells (liquid crystal display devices 2011 to 2020).

Each was returned to the original backlight configuration and evaluated for uneven brightness.

<village>
Applicable liquid crystal display device is wet-heated at 50 ° C / 90% RH for 24 hours, and the luminance unevenness (strength) in black display 2 hours after lighting the backlight and the effect of displaying the image are visually evaluated according to the following criteria. did.
◎: 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, and even in image display Table 10 shows the evaluation results.

As is apparent from the results shown in Table 10, as a method for manufacturing the vertical alignment type liquid crystal display device for manufacturing the vertical alignment type liquid crystal display device of the present invention, at least one of the retardation film A and the retardation film B is used. It turns out that the manufacturing method of the aspect which prepares the elongate roll-shaped polarizing plate which has this retardation film, and is bonded with the roll to panel manufacturing method with respect to the said liquid crystal cell is preferable.

1, 9 Polarizer 2 Retardation film B
3, 7 Transparent substrate 4 Liquid crystal with negative dielectric anisotropy 5 Color filter 6 Thin film transistor 8 Phase difference film A
DESCRIPTION OF SYMBOLS 10

Backlight

11, 13 Polarizing plate 12 Liquid crystal cell 20 Roll-shaped polarizing plate 21 Bonding roll D Bonding line advancing direction

Claims

A vertical alignment type liquid crystal cell having a configuration in which a backlight and a liquid crystal having a negative dielectric anisotropy are sandwiched between two transparent substrates, and one sheet on the display surface side and the backlight side of the vertical alignment type liquid crystal cell A vertical alignment type liquid crystal display device having polarizing plates each satisfying the following requirements (a) to (c):
(A) One of the transparent substrates has a thin film transistor and a color filter.
(B) 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 cell side of the polarizing film is the polarized light. It is perpendicular to the absorption axis of the child.
(C) When the retardation film on the color filter side of one polarizing plate is used as the retardation film A and the retardation film on the liquid crystal cell side of the other polarizing plate is used as the retardation film B. The retardation values Rt in the thickness direction of the retardation films A and B measured at a measurement wavelength of 590 nm at 23 ° C. and 55% RH are Rt (A) and Rt (B), respectively, and in-plane When the values of the ratio of the retardation value Rt in the thickness direction to the retardation value Ro of Rt / Ro (A) and Rt / Ro (B) are respectively expressed by the following (Expression 1) to (Expression 5) The relationship represented by is satisfied.
(Formula 1): Rt (A) <Rt (B)
(Formula 2): 70 nm <Rt (A) <130 nm
(Formula 3): 130 nm <Rt (B) <200 nm
(Formula 4): 20 nm <Rt (B) −Rt (A) <130 nm
(Formula 5): Rt / Ro (A) <Rt / Ro (B)
[However, Ro and Rt are defined by the following formulas.
Formula (I): Ro = (n x −n y ) × d (nm)
Formula (II): Rt = {(n x + n y ) / 2−n z } × d (nm)
In the above formula, Ro represents an in-plane retardation value in the retardation film, and Rt represents a retardation value in the thickness direction in the film. Further, d represents the thickness of the retardation film, n x represents a refractive index of the maximum (slow axis direction) in a plane of the retardation film. n y represents a refractive index in the direction perpendicular to the slow axis in the retardation film plane (fast axis direction), n z represents the refractive index of the retardation film in the thickness direction. The measurement conditions are the same as above. ]
When the in-plane retardation values Ro of the retardation films A and B are respectively Ro (A) and Ro (B), the relationships represented by the following (Expression 6) to (Expression 8) are satisfied. The vertical alignment type liquid crystal display device according to claim 1, wherein:
(Formula 6): Ro (A) <Ro (B)
(Formula 7): 40 nm <Ro (A) <90 nm
(Formula 8): 45 nm <Ro (B) <100 nm
The vertical alignment type liquid crystal display device according to claim 1 or 2, wherein the retardation film A or retardation film B contains a cellulose ester resin.
The in-plane retardation value Ro and the thickness direction retardation value Rt of the retardation film A are adjusted by the control by the draw ratio when the retardation film A is formed, and the in-plane of the retardation film B The vertical alignment type according to any one of claims 1 to 3, wherein the retardation value Ro and the retardation value Rt in the thickness direction are adjusted by controlling the stretching temperature and the film thickness. Liquid crystal display device.
It is a manufacturing method of the vertical alignment type liquid crystal display device which manufactures the vertical alignment type liquid crystal display device as described in any one of Claim 1 to 4, Comprising: Among the said retardation film A and retardation film B A method for producing a vertical alignment type liquid crystal display device, comprising preparing a long roll-shaped polarizing plate having at least one retardation film and laminating the liquid crystal cell by a roll-to-panel manufacturing method.