JP3810969B2 - Optical compensation polarizing plate and manufacturing method of liquid crystal display device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a thin optical compensation plate that is excellent in manufacturing efficiency and capable of forming a liquid crystal display device having excellent display quality.
[0002]
[Prior art]
Conventionally, as an optical compensation polarizing plate capable of forming a liquid crystal display device excellent in display quality in a wide viewing angle range by compensating a phase difference due to birefringence in a TFT type liquid crystal cell or the like with a wide angle in the front and perspective directions, a uniaxially stretched film is used. It is known that a retardation plate in which the stretching directions are orthogonally laminated is bonded to a polarizing plate. However, the use of a plurality of retardation plates increases the thickness of the liquid crystal display device, and requires a lamination process in which the optical axis of the retardation plate is regulated, resulting in poor manufacturing efficiency.
[0003]
[Technical Problem of the Invention]
The present invention is directed to the development of optical compensation polarizing plate excellent in manufacturing efficiency thin Ru bovine form a liquid crystal display device having excellent display quality.
[0004]
[Means for solving problems]
The present invention is a single layer made of a biaxially stretched film with an in-plane slow axis angle variation of ± 3 degrees or less , and a long retardation plate and a long polarizing plate are sequentially laminated. of the laminate was cut into a predetermined size, and a standard laminate of the same structure made of those cut cut of its the first and their phase difference plate side inward, and as a polarizing plate is crossed Nicols A method for producing an optical compensation polarizing plate , characterized in that the cut laminated body having a leakage light rate in the normal direction when arranged is 0.2% or less over the entire surface, and an optical compensation polarizing plate after the production The present invention provides a method for manufacturing a liquid crystal display device , which is arranged on at least one side of a liquid crystal cell.
[0005]
【The invention's effect】
According to the present invention, it is possible to efficiently obtain an optical compensation polarizing plate that is excellent in thinness by using one , that is, a single-layer retardation plate, and using it, TN type, π type, VA type, etc. A thin liquid crystal display device excellent in display quality such as contrast and display uniformity can be formed by compensating the phase difference of the TFT type liquid crystal cell. In particular, the phase difference plate R1 represents the phase difference in the normal direction, R2 represents the phase difference in the vertical direction with the slow axis as the rotation axis and the tilt angle of 40 degrees with respect to the normal direction as a reference, and R2 / R1 resulting therefrom is β when a, R1 ≦ 1000 nm, when it is the even you satisfied beta ≧ 1.12, the liquid crystal display excellent compensates the phase difference due to the liquid crystal cell in a wide viewing angle range of front and perspective display quality such as contrast A device can be formed.
[0006]
That is, the phase difference is defined by the product (Δnd) of the refractive index difference (Δn) of the birefringent light and the optical path length (d), in which case β means the angle-dependent characteristic of the phase difference. Therefore, by setting R1 ≦ 1000 nm and a small shift in which the optical axis variation is controlled, the phase difference particularly in the front direction of the TFT type liquid crystal display device and the like is highly compensated for high contrast and display uniformity. By satisfying β ≧ 1.12, the display quality can be improved by highly compensating for the phase difference in the oblique direction. Further, according to the present invention, it is possible to inspect the next formed as a standard laminated body sequentially between the adjacent optical compensation polarizing plates before and after the formation formed by cutting a long laminated body, and the inspection efficiency. Is excellent.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The production method according to the present invention is a single layer made of a biaxially stretched film with an in-plane slow axis angle variation of ± 3 degrees or less , and a long retardation plate and a long polarizing plate are sequentially laminated. and while cutting the laminate it to the predetermined size, and a standard laminate of the same structure made of those cut cut of its the first and their phase difference plate side inward, and the polarizing plate cross-Nicol so as leakage light ratio in the normal direction when arranged is Ru shall der to obtain an optical compensation polarizing plate consisting of 0.2% or less of the cutting laminate the entire surface. An example thereof is shown in FIG. 1 is an optical compensation polarizing plate, 11 and 14 are polarizing plates, and 12 and 13 are retardation plates. The figure illustrates a liquid crystal display device, 3 is a liquid crystal cell, and 2 is an adhesive layer.
[0008]
As the retardation plate, a biaxially stretched film made of a suitable light-transmitting polymer and having an in-plane slow axis angle variation of within ± 3 degrees is used as a single layer . In particular, a film having a light transmittance of 75% or more, particularly 85% or more is preferable. Moreover, what consists of a polymer which shows the positive birefringence from which the refractive index of a extending direction becomes high is preferable from the point which obtains the phase difference plate excellent in heat resistance.
[0009]
Incidentally, examples of the polymer exhibiting positive birefringence described above include polycarbonate, polyvinyl alcohol, cellulose resin, polyester such as polyethylene terephthalate and polyethylene naphthalate, polyarylate, polyimide, norbornene resin, polysulfone, polyethersulfone, polypropylene. And the like.
[0010]
The retardation plate used in the present invention can be obtained by, for example, stretching a long film made of a polymer or controlling the retardation characteristics by an appropriate method such as a method of controlling the refractive index in the thickness direction. it can. As the long film, for example, a film formed by an appropriate method such as a casting method such as a casting method or an extrusion method can be used. In particular, a long film with little thickness unevenness and alignment strain unevenness by a solution casting method such as a casting method can be preferably used.
[0011]
The film thickness can be appropriately determined depending on the retardation characteristics of the target retardation plate. In general, the thickness is 5 to 500 μm, especially 10 to 400 μm, especially 20 to 300 μm. The film to be treated may be non-oriented or may be an oriented film that has been subjected to appropriate orientation treatment such as uniaxial stretching in advance.
[0012]
Compensation of the phase difference in the perspective direction that suppresses the decrease in contrast in the front (normal) direction in the TN liquid crystal cell, and wide front and perspective by compensation of the phase difference between the front and the perspective in the π-type and VA-type liquid crystal cells. From the point of obtaining a liquid crystal display device with excellent display quality such as contrast at the viewing angle and display homogeneity, the phase difference in the normal direction is R1, and the slow axis is the rotation axis and the normal direction is tilted by 40 degrees. when the the R2 / R1 by their beta phase difference in the vertical direction as R2 in a state of being, R1 ≦ 1000 nm, phase difference plate you satisfied beta ≧ 1.12 may preferably used.
[0013]
Retardation plate showing a variation characteristic of the phase difference characteristics and the optical axis of the can, for example simultaneous method or a sequential method biaxial glass transition temperature near the stretching scheme forming the same film with a polymer, in particular a glass transition temperature or higher due to such It can obtain efficiently by the method of extending | stretching at the temperature of. In the biaxial stretching method , the stretching ratio in the minor axis direction, that is, the width (lateral) direction of the long film is set to 50% or less from the viewpoint of efficiently satisfying the deviation between R1 and β and the optical axis. preferable.
[0014]
In addition, the refractive index control in the thickness direction of the film described above is performed by, for example, bonding one or two or more heat-shrinkable films to one or both sides of the film via an adhesive layer or the like, and heating the heat-shrinkable film. It can be performed by a method in which a shrinkage force is applied to the film and the film is stretched or shrunk in one or both of the longitudinal and lateral directions under the action of the shrinkage force.
[0015]
The retardation plate that can be preferably used has as little variation as possible in the phase difference due to birefringence and the orientation axis such as the slow axis, and in particular, in the transmitted light in the normal direction perpendicular to the film surface. It is formed to 10 nm or less, particularly 5 nm or less. The characteristics such as R1 and β can be controlled by a method of changing conditions such as the type and thickness of the film, the draw ratio and the draw temperature.
[0016]
The optical compensation polarizing plate is obtained as a laminated body of retardation plates 12 and 13 and polarizing plates 11 and 14 as shown in the figure . This is achieved by sequentially laminating a long retardation plate and a long polarizing plate. It can be formed by cutting the laminate into a predetermined size . Such stacking can be performed by a method of sequentially stacking separately in the manufacturing process of the liquid crystal display device, but by stacking in advance, the stability of the quality and the stacking workability are excellent, and the manufacturing efficiency of the liquid crystal display device is improved. There are advantages. There are no particular restrictions on the angle of arrangement of the optical axis such as the slow axis and transmission axis of the retardation plate and polarizing plate during lamination, but in general, it is preferable to arrange them in a parallel relationship or an orthogonal relationship in view of the compensation effect and the like.
[0017]
An appropriate adhesive can be used for laminating the retardation plate and the polarizing plate, but an adhesive layer can be preferably used from the standpoint of maintaining optical characteristics by suppressing thermal stress. As the adhesive layer, for example, an appropriate material such as acrylic, silicone, polyester, polyurethane, polyether, or rubber can be used, and there is no particular limitation. In particular, acrylic materials are preferably used in view of heat resistance and optical characteristics.
[0018]
For the adhesive layer, for example, natural or synthetic resins, glass fibers or glass beads, fillers or pigments made of metal powder or other inorganic powders, coloring agents, antioxidants, etc. Additives can also be blended. Moreover, it can also be set as the adhesion layer which contains microparticles | fine-particles and shows light diffusibility.
[0019]
As the above-described long polarizing plate, an appropriate one can be used. For example, iodine and / or dichroic dyes are adsorbed on hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and ethylene / vinyl acetate copolymer partially saponified films. Examples thereof include a polarizing film made of a polyene oriented film such as a stretched product, a dehydrated polyvinyl alcohol product or a dehydrochlorinated polyvinyl chloride product.
[0020]
The polarizing plate may have a transparent protective layer on one side or both sides of the polarizing film. Further, the polarizing plate may be a reflective type or a transflective type having a reflective layer, a half mirror, or the like. The reflective polarizing plate is used to form a liquid crystal display device or the like that reflects incident light from the viewing side (display side) and displays a liquid crystal display that can omit the incorporation of a light source such as a backlight. It has an advantage that the display device can be easily thinned.
[0021]
The transparent protective layer can be appropriately formed as a polymer coating layer, a protective film adhesive layer, etc., and a polymer excellent in transparency, mechanical strength, thermal stability, moisture shielding properties, etc. is preferably used for its formation. It is done. Examples include polyester resins, acetate resins, polyether sulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, acrylic resins, acrylic resins, urethane resins, acrylic urethane resins, Examples thereof include thermosetting resins such as epoxy and silicone resins, and ultraviolet curable resins. The surface of the transparent protective layer may be formed in a fine concavo-convex structure by containing fine particles.
[0022]
The reflective polarizing plate can be formed by an appropriate method such as a method in which a reflective layer made of metal or the like is provided on one side of the polarizing plate via a transparent resin layer or the like as necessary. Specific examples thereof include a foil or a vapor deposition film made of a reflective metal such as aluminum on one side of a transparent resin layer such as a protective film matted as necessary, or a fine surface of the transparent resin layer containing fine particles. For example, a metal reflective layer provided on the concavo-convex structure by an appropriate method such as vapor deposition or plating. The transflective polarizing plate can be obtained by making the reflective layer a transflective type such as a half mirror.
[0023]
Each layer such as the retardation plate, polarizing plate, transparent protective layer and adhesive layer is made of an ultraviolet absorber such as a salicylic acid ester compound, a benzophenone compound, a benzotriazole compound, a cyanoacrylate compound, or a nickel complex compound. It can also be provided with ultraviolet absorbing ability depending on the type of treatment.
[0024]
The optically compensatory polarizing plate according to the present invention has a leak rate of light in the normal direction when it is arranged so that the standard laminated body having the same structure and the retardation plate side thereof are inward and the polarizing plate is crossed Nicol. That is, the ratio (percentage) of leaked light to incident light is 0.2% or less over the entire surface, but in this case, when a liquid crystal display device is obtained, nonuniform luminance due to variations in phase difference and polarization degree. Etc. can be prevented and the uniformity of display can be improved. The light leakage rate, which is more preferable than improvement in display uniformity, is 0.15% or less, especially 0.10% or less, particularly 0.08% or less.
[0025]
In addition, as a standard laminated body having the same structure as the optical compensation polarizing plate for determining the leakage light rate, one having a leakage light rate as small as possible of 0.2% or less was used as described above. However, from the viewpoint of inspection efficiency based on the manufacturing process of the optical compensation polarizing plate, each cut laminate obtained by cutting a long laminate of a long retardation plate and a polarizing plate into a predetermined size based on the optical compensation polarizer formed of, method of inspecting those then form what previously formed sequentially as a standard laminate the optical compensation polarizing plates of the adjacent before and after formation is preferable.
[0026]
The optical compensation polarizing plate according to the present invention is, for example, a TN type or STN type that compensates for a phase difference in a perspective direction that prevents a decrease in contrast in the front (normal) direction, and compensates for a phase difference between the front direction and the perspective direction. It can be preferably used for compensation of viewing angle characteristics due to birefringence in various liquid crystal cells such as type and π type. In practical use, it can also be applied as an optical member of an appropriate form, such as one provided with an adhesive layer on one or both sides for the purpose of bonding to another member such as a liquid crystal cell.
[0027]
Formation of a liquid crystal display device using an optical compensation polarizing plate can be performed according to the conventional method. In other words, a liquid crystal display device is generally formed by appropriately assembling components such as a liquid crystal cell, an optical compensation polarizing plate, and an illumination system as necessary, and incorporating a drive circuit. As described above, there is no particular limitation except that the optical compensation polarizing plate according to the present invention is used and provided on at least one side of the liquid crystal cell 3, and the conventional method can be applied.
[0028]
Therefore, a liquid crystal display device in which a polarizing plate is arranged on one or both sides of a liquid crystal cell, a transmission type or a reflection type using a backlight, a reflection plate or a semi-transmission type reflection plate in an illumination system, or a reflection / transmission type An appropriate liquid crystal display device can be formed. In that case, as shown in the figure, the optical compensation polarizing plate has retardation plates 12, 13 between the liquid crystal cell 3 and the polarizing plates 11, 14 on the viewing side or / and the viewing back side of the liquid crystal cell 3, particularly at least the viewing side. It is more preferable to arrange them so that they are positioned at the position of compensation.
[0029]
In the above description, the components for forming the liquid crystal display device may be laminated and integrated, or may be in a separated state. In forming the liquid crystal display device, appropriate optical elements such as a diffusion plate, an antiglare layer, an antireflection film, a protective layer and a protective plate can be appropriately disposed. Such an element can also be used for the formation of a liquid crystal display device in the form of the above-described optical member laminated with an optical compensation polarizing plate.
[0030]
【Example】
Example 1
A 20% by weight methylene dichloride solution of a polycarbonate having a molecular weight of about 80,000 consisting of a polycondensate of phosgene and bisfinol A was cast on a steel drum, and it was continuously peeled off and dried at a thickness of 60 μm. A phase difference plate is obtained by subjecting a long film with a phase difference of approximately 0 to a biaxial stretching process of 35% in the longitudinal direction and 35% in the transverse direction at 162 ° C. through a simultaneous biaxial stretching machine. An optical compensation polarizing plate was obtained by laminating a polarizing plate having an optical rate of 0.02% and an acrylic adhesive layer so that the slow axis and the transmission axis thereof were in a parallel relationship.
[0031]
Example 2
Example 1 except that a uniaxial stretching process was performed at 157 ° C. in the longitudinal direction at 157 ° C. with a roll stretching machine, followed by a uniaxial stretching process at 176 ° C. in the transverse direction at 40%. Similarly, a retardation plate was obtained and laminated with a polarizing plate to obtain an optical compensation polarizing plate.
[0032]
(Delete)
[0033]
Comparative Example Example of a sequential biaxial stretching method in which a uniaxial stretching process was performed at 160 ° C. in the longitudinal direction at 160 ° C. and then a uniaxial stretching process at 160 ° C. in the transverse direction at 55%. According to 1, a retardation plate was obtained and laminated with a polarizing plate to obtain an optical compensation polarizing plate.
[0034]
About the phase difference plate obtained in the evaluation test example and the comparative example, the phase difference and the slow axis angle variation (deviation) by the phase difference meter (KOBRA21-ADH, manufactured by Oji Scientific Instruments) based on the parallel Nicol rotation method. ) Was measured and β was calculated from the above.
[0035]
Moreover, about the optical compensation polarizing plate obtained by the Example and the comparative example, the two sheets cut out from the adjacent positions are arranged so that the retardation plate side is inside, and the polarizing plate is crossed Nicol, and the normal direction (Murakami Color Research Laboratory Co., Ltd., CMS-500).
[0036]
The results are shown in the following table.
R1 β Deviation (degree) Leakage rate (%)
Example 1 14 6.79 ± 3.0 0.03
Example 2 48 1.65 ± 1.5 0.06
Comparative Example 117 1.99 ± 6.0 3.3
[0037]
Example 1 The optical compensation polarizing plate obtained in 2 was adhered to both surfaces of a TN type liquid crystal cell so that the polarizing plate was on the outside, and a liquid crystal display device was formed. Excellent display quality with excellent contrast and display uniformity over a wide viewing angle range. From the above results and table, in the examples, the increase of the leakage light rate of the optical compensation polarizing plate can be suppressed to about several times the leakage light rate of the polarizing plate used. It can be seen that a liquid crystal display device excellent in display quality can be formed by compensating the phase difference caused by the liquid crystal cell in a wide viewing angle range.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an example of a liquid crystal display device (an example of an optical compensation polarizing plate).
[Explanation of symbols]
1: Optical compensation polarizing plate 11, 14: Polarizing plate 12, 13: Retardation plate 3: Liquid crystal cell

Claims (4)

In monolayer angle of dispersion of the slow axis in the plane consists of biaxially oriented film within 3 ° ±, and sequentially laminated with its laminate of a polarizing plate of the retardation plate and the elongate elongated and cut into a predetermined size, the standard laminate of the same structure made of those cut cut of its the first and them by the phase difference plate side inward, and the polarizing plate of the case of arranging so as to be in a cross nicol A method for producing an optically compensatory polarizing plate , comprising obtaining the cut laminate having a leakage light rate in the normal direction of 0.2% or less over the entire surface. The phase difference plate according to claim 1, wherein the retardation plate is made of a polymer exhibiting positive birefringence, and is tilted by 40 degrees with respect to the normal direction with the phase difference in the normal direction as R1 and the slow axis as the rotation axis. A method for producing an optically compensatory polarizing plate satisfying R1 ≦ 1000 nm and β ≧ 1.12 where R2 is a phase difference in the vertical direction of R2 and R2 / R1 is β. According to claim 1 or 2, process for producing an optical compensation polarizer for attaching a pressure-sensitive adhesive layer on one or both sides of the cut laminate. A method for producing a liquid crystal display device , comprising producing an optical compensation polarizing plate by the method according to claim 1, and then disposing the optical compensation polarizing plate on at least one side of a liquid crystal cell.

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