JP4475507B2 - Method for producing laminated retardation layer - Google Patents

Method for producing laminated retardation layer Download PDF

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JP4475507B2
JP4475507B2 JP2004083925A JP2004083925A JP4475507B2 JP 4475507 B2 JP4475507 B2 JP 4475507B2 JP 2004083925 A JP2004083925 A JP 2004083925A JP 2004083925 A JP2004083925 A JP 2004083925A JP 4475507 B2 JP4475507 B2 JP 4475507B2
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JP2004326089A (en
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啓二 鹿島
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大日本印刷株式会社
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  The present invention relates to a method for producing a laminated retardation layer, and more particularly to a method for producing a retardation layer for increasing the viewing angle of a liquid crystal display device and improving color reproducibility.

  The market for color liquid crystal display devices (hereinafter referred to as LCDs) has expanded rapidly, especially notebook computers, due to their thinness, light weight, small power consumption, and flickerless characteristics. Recently, as a part of such PC-use displays, there has been a demand for larger desktop monitors than notebook computers. In addition, not only for PCs but also for TVs where CRT has been the mainstream in the past, LCDs have come to be used.

  Here, as a problem of LCD, there is a problem of its narrow viewing angle. This is because, when the LCD is observed from an oblique direction, for example, in the vertical alignment mode (VA mode), the light that should be transmitted as linearly polarized light is converted into elliptically polarized light due to the loss of isotropic liquid crystal molecules. There is a cause that the polarizing plates in the crossed Nicols state arranged on both sides of the liquid crystal cell apparently disappear from the orthogonal state when viewed from an oblique direction. For these reasons, light leaks from the pixel that should normally display black, which causes inversion of contrast and prevents correct display. In view of such problems, even when the viewing angle is increased in a black display pixel using a retardation layer as in Patent Document 1, Patent Document 2, and Non-Patent Document 1, light leakage does not occur. A vertical alignment mode LCD with a viewing angle has been devised. A phase difference layer called a negative C plate (details will be described later) is mainly used to remove the cause of the loss of isotropy of liquid crystal molecules when viewed from an oblique direction (Patent Document 3). Also, in order to eliminate the cause of the fact that the polarizing plate in the crossed Nicols state is apparently no longer in the orthogonal state when viewed from an oblique direction, a phase difference called a positive A plate and a positive C plate (details will be described later) A layer is used (Non-Patent Document 2).

  On the other hand, as a positive A plate, it has been proposed to use a stretched polymer film having reverse wavelength dispersion characteristics in Patent Document 4, Patent Document 5, Patent Document 6, Patent Document 9, Non-Patent Document 3, and the like. In particular, those proposed in Patent Document 9 and Non-Patent Document 3 are sold under the trade name Pure Ace WR (registered trademark: Teijin Limited). Patent Document 10 discloses that two stretched films having different wavelength dispersion characteristics can be laminated, and Non-Patent Document 6 discloses that a composite film having reverse wavelength dispersion characteristics can be obtained by using such a technique. Has been. Further, Non-Patent Document 1 removes the cause of the fact that the oriented polymer film having such reverse wavelength dispersion characteristics is not apparently orthogonal when the polarizing plate in the orthogonal Nicol state is viewed in the oblique direction. It has been proposed to prevent a color shift when viewed from an oblique direction of a VA mode color LCD by using it as a positive A plate.

On the other hand, Non-Patent Document 4 proposes that the negative C plate can be composed of a polymerizable chiral nematic (cholesteric) liquid crystal having a reflection wavelength in the ultraviolet region. Further, it has been proposed in Non-Patent Document 5 that it can be constituted by a homeotropically aligned discotic liquid crystal.
JP-A-10-153802 Japanese Patent Laid-Open No. 11-258605 Japanese Patent Laid-Open No. 10-312166 JP 2000-137116 A JP 2002-14234 A JP 2002-48919 A JP-A-7-258638 Japanese National Patent Publication No. 10-508882 WO00 / 26705 Japanese Patent Laid-Open No. 2-120804 JP 2000-190385 A IDW '02 pp. 525-527 SID 00 DIGEST pp. 1094-1097 IDW '00 pp. 407-410 IDW '02 pp. 413-416 SID 00 DIGEST pp. 1091-1093 SID 01 DIGEST pp. 566-569

  When a negative C plate and a positive A plate are arranged in the LCD to improve the viewing angle characteristics, the polarizing plate and the optical axis of each other (absorption axis in the case of a polarizing plate, optical in the case of a retardation layer) Axis) is used to form a specific angle. However, the pressure-sensitive adhesive used in this case has a refractive index different from that of the polarizing plate and the retardation layer, so that reflection of light occurs at the interface, resulting in a decrease in overall display contrast. There was a problem that occurred.

  In particular, when the negative C plate and the positive A plate are respectively disposed on both sides of the liquid crystal cell based on Non-Patent Document 1, the above-described refractive index interface increases, and the above-described contrast reduction problem and interference unevenness problem occur. There were many.

  Further, based on Non-Patent Document 1, in order to prevent a color shift when viewed from an oblique direction as described above, even when a positive A plate having reverse wavelength dispersion characteristics is used, when viewed from an oblique direction. However, it is not always clear what kind of negative C plate should be used to remove the cause of the loss of isotropic liquid crystal molecules in the liquid crystal cell, and color shift may remain. is there.

  The present invention has been made in view of such problems of the prior art, and an object thereof is to specify a negative C plate and a positive A plate used for improving the viewing angle characteristics of a liquid crystal display device. By combining the wavelength dispersion characteristics into a laminate type, a liquid crystal display device with high contrast, no interference unevenness and no color shift, and good color reproducibility is made possible.

The method for producing a laminated retardation layer of the present invention that achieves the above object includes a retardation layer having a positive refractive index anisotropy and an optical axis in the layer surface, and a layer surface having a negative refractive index anisotropy. And a retardation layer having an optical axis in the normal direction of the optical layer, and having a positive refractive index anisotropy and having an optical axis in the layer plane, the optical path difference between extraordinary light and ordinary light As a retardation layer having a negative refractive index anisotropy and having an optical axis in the normal direction of the layer surface, using a stretched polymer film having a reverse wavelength dispersion characteristic that the retardation becomes smaller as the wavelength becomes shorter In the method for producing a laminated phase difference layer using a coating layer having a positive wavelength dispersion characteristic in which retardation, which is an optical path difference between extraordinary light and ordinary light, increases as the wavelength becomes shorter,
Using the stretched polymer film having the reverse wavelength dispersion property as a substrate, coating and aligning a polymerizable liquid crystal layer on one surface thereof, and then polymerizing to form a polymerizable liquid crystal layer having the normal wavelength dispersion property. This is a featured manufacturing method.

  In this case, as a stretched polymer film having reverse wavelength dispersion characteristics, a polycarbonate film having a fluorene skeleton prepared by stretching a film containing liquid crystal, a cellulose acetate film prepared by stretching the film, a positive wavelength dispersion A film made by stretching a mixture of a characteristic aromatic polyester polymer and an aromatic polyester polymer having reverse wavelength dispersion characteristics into a film, and a copolymer comprising monomer units that form polymers having different wavelength dispersion characteristics. A film prepared by stretching molecules into a film, or a composite film obtained by laminating two stretched films having different wavelength dispersion characteristics so that their fast axes are orthogonal to each other can be used.

  In addition, as a coating layer having positive wavelength dispersion characteristics, a polymerizable chiral nematic (cholesteric) liquid crystal layer, a homeotropically aligned polymerizable discotic liquid crystal layer, or a negative refractive index anisotropy when coated. A polymer material having an optical axis in the normal direction of the layer surface can be used.

  In the present invention, a retardation layer having a positive refractive index anisotropy and having an optical axis in the layer surface, and a retardation layer having a negative refractive index anisotropy and having an optical axis in the normal direction of the layer surface As a retardation layer having a positive refractive index anisotropy and an optical axis in the layer plane, the retardation, which is the optical path difference between extraordinary light and ordinary light, becomes smaller as the wavelength becomes shorter. Retardation which is an optical path difference between extraordinary light and ordinary light as a retardation layer having a negative refractive index anisotropy and an optical axis in the normal direction of the layer surface using a stretched polymer film having reverse wavelength dispersion characteristics Since a coating layer having a positive wavelength dispersion characteristic that increases as the wavelength becomes shorter is used, a positive A plate and a negative electrode can be easily manufactured without using a separate substrate, alignment layer, or adhesive layer. Consists of C plate, high contrast without color shift In a liquid crystal display device for improving the uneven interference no viewing angle characteristics, in particular it is possible to provide a laminated retardation layer for a liquid crystal display device of the VA mode.

  Before describing the laminated retardation layer of the present invention, first, the retardation layer will be described. As the retardation layer used in the present invention, a positive uniaxial retardation layer having an optical axis in the layer surface and a negative uniaxial retardation layer having an optical axis in the normal direction of the layer surface are used.

The two types of retardation layers will be described with reference to FIG. 7. As shown in the figure, the z-axis is taken in the normal direction of the layer surface S, the x-axis and y-axis are taken in the orthogonal direction in the layer surface S, and the x-axis direction, y axially, the refractive index of the z-axis direction n x, n y, and n z, as shown in FIG. 7 (a), the phase difference layer is a layer plane S in the relation of n x> n y = n z In the following description, it is referred to as a positive A plate. Further, as shown in FIG. 7 (b), the phase difference layer retardation layer having a relationship of n x = n y> n z has an optically negative uniaxial property in a direction normal to the layer plane S, In the following description, it will be referred to as a negative C plate.

In the liquid crystal display device according to the present invention, as described above, for example, in a vertical alignment mode (VA mode) liquid crystal display device, viewing angle characteristics deteriorate due to the loss of isotropic liquid crystal molecules when viewed from an oblique direction. A negative C plate for removing the cause, and a positive A plate for removing the cause of the deterioration of the viewing angle characteristics due to the fact that the polarizing plate in the crossed Nicol state apparently disappears from the orthogonal state when viewed from an oblique direction. It is what is used. FIGS. 2A and 2B schematically show the disposition positions of the positive A plates a and a ′ and the negative C plate c as an exploded perspective view. The liquid crystal cell is composed of, for example, a VA mode liquid crystal layer 3 disposed between the backlight side transparent substrate 1 ′ and the observation side transparent substrate 1. 2A, a positive A plate a is provided between one transparent substrate 1 and the observation-side polarizing plate 5. In FIG. 2B, both transparent substrates 1, 1 ′ and a polarizing plate 5 are provided. 5 ′, positive A plates a and a ′ are arranged. At that time, the optical axis of the positive A plate a is arranged in a positional relationship so as to be orthogonal to the absorption axis 6 of the polarizing plate 5 to constitute a liquid crystal display device. In FIG. 2B, another positive A plate a ′ is disposed between the backlight-side transparent substrate 1 ′ and the backlight-side polarizing plate 5 ′. The optical axis a ′ is arranged in a positional relationship so as to be orthogonal to the absorption axis 6 of the polarizing plate 5 ′. The negative C plate c is disposed on the liquid crystal layer 3 side of the positive A plate a. In the arrangement of FIG. 2A, another negative C plate c ′ (not shown) may be arranged on the liquid crystal layer 3 side of the backlight-side polarizing plate 5 ′, or FIG. In this arrangement, another negative C plate c ′ (not shown) may be arranged on the liquid crystal layer 3 side of the positive A plate a ′. In that case, the thickness direction retardations R th of the negative C plates c and c ′ arranged on both sides of the liquid crystal layer 3 are preferably equal to each other for optical compensation. 2A and 2B, the backlight and the observation side are reversed, and the positive A plate a and the negative C plate c are placed on the backlight side of the liquid crystal cell, and the positive A plate a ′ is placed on the backlight side. You may make it arrange | position to the observation side of a liquid crystal cell. In FIG. 2, an alignment layer for aligning the liquid crystal layer 3, an electrode layer, a TFT for controlling each pixel, a color filter disposed for each pixel, and the like are not shown.

  In such a configuration, the positive A plates a and a ′ are proposed in Patent Document 4, Patent Document 5, Patent Document 6, Patent Document 9, Patent Document 10, Non-Patent Document 3, Non-Patent Document 6, and the like. By using a stretched polymer film or a composite stretched film in which the retardation has a reverse wavelength dispersion characteristic, the color shift when viewed from an oblique direction can be reduced. As the positive A plates a and a ′, typically, a polycarbonate film having a fluorene skeleton (Patent Document 6, Non-Patent Document 3) prepared by forming a film containing liquid crystal and stretching, and stretching by film formation A cellulose acetate film (Patent Document 4), and a film prepared by stretching a mixture of an aromatic polyester polymer having a normal wavelength dispersion characteristic and an aromatic polyester polymer having a reverse wavelength dispersion characteristic (Patent Document 5) A film made by stretching a polymer made of a copolymer containing monomer units that form polymers having different wavelength dispersion characteristics (Patent Document 9), and two stretched films having different wavelength dispersion characteristics are laminated. Composite films (Patent Document 10, Non-Patent Document 6) and the like.

Here, the positive A plates a and a ′ having the reverse wavelength dispersion characteristic are wavelengths as shown in FIG. 6 as “WRF-Z, WRF-W, WRF-U, WRF-R, and WRF-G”. is an optical path difference between extraordinary light and ordinary light retardation R (λ) (= Δn · d) ( where in accordance becomes shorter, lambda: wavelength, Δn = | n e -n o |, d: film thickness, n e : extraordinary index, n o:. the ordinary refractive index) are those decreases (non-Patent Document 6), the characteristic difference from a comparison of the normal polycarbonate film (positive wavelength dispersion properties) is clearly positive wavelength In the case of dispersion characteristics, the retardation R (λ) increases as the wavelength becomes shorter.

  When the positive A plates a and a ′ having such inverse wavelength dispersion characteristics are used, the color shift can be reduced because the positive A plates a and a ′ are configured as shown in FIGS. The phase difference obtained by dividing the retardation R (λ) (= Δn · d) by the wavelength λ becomes substantially flat regardless of the wavelength. This can be interpreted as a wave plate having a constant phase difference in a wide wavelength band.

  By the way, in the configuration as shown in FIGS. 2A and 2B, the action of the negative C plate c is that, for example, when the VA mode liquid crystal layer 3 is viewed from an oblique direction, the isotropy of liquid crystal molecules is lost. And its action will be described based on Patent Document 3. FIG. 8 is a schematic diagram showing a refractive index ellipsoid of a positive uniaxial liquid crystal cell and a refractive index ellipsoid of a negative uniaxial optical compensation sheet (negative C plate) included in a normal liquid crystal. When the liquid crystal molecules in the liquid crystal cell 43 are vertically aligned to cause positive uniaxial optical anisotropy, the in-plane refractive indexes 44x and 44y and the thickness of the liquid crystal cell 43 are parallel to the substrate of the liquid crystal cell 43. The refractive index ellipsoid 44 formed by the refractive index 44z in the direction has a rugby ball standing shape as shown in FIG. When the liquid crystal cell 43 having such a non-spherical rugby ball-shaped refractive index ellipsoid is viewed from an oblique direction, retardation occurs. This retardation is canceled by the C plate 42 which is a negative uniaxial optical compensation sheet, and light leakage can be suppressed. In the negative C plate 42, the refractive index ellipsoid 41 of the negative C plate 42 formed by the main refractive indexes 41x and 41y in the plate surface and the main refractive index 41z in the thickness direction of the plate is as shown in FIG. Anpan shape. Therefore, the sum of 41x and 44x, the sum of 41y and 44y, and the sum of 41z and 44z are substantially the same value. As a result, the retardation that occurs in the liquid crystal cell when viewed from an oblique direction is canceled.

  A normal liquid crystal layer 3 (FIG. 2) for a liquid crystal display device has a positive wavelength dispersion characteristic, and its retardation R (λ) increases as the wavelength becomes shorter. The difference between the refractive index 44z and the refractive indexes 44x and 44y increases as the wavelength becomes shorter. Therefore, as is clear from the above description, the difference between the main refractive index 41z and the refractive indexes 41x and 41y, which is the retardation of the negative C plate 42, increases as the wavelength decreases, that is, the positive wavelength dispersion characteristic The color shift when viewed from an oblique direction cannot be prevented without using what it has.

  From the above examination, in the liquid crystal display device having the configuration as shown in FIGS. 2A and 2B, the positive A plates a and a ′ are disclosed in Patent Document 4, Patent Document 5, Patent Document 6, and Patent Document 9. , Patent Document 10, Non-Patent Document 3, Non-Patent Document 6 and the like, a stretched polymer film or a composite stretched film having a reverse wavelength dispersion property as a retardation, and a negative C plate c As a result, by using a retardation having the same positive wavelength dispersion characteristic as that of the liquid crystal layer 3, a color shift based on the wavelength dispersion can be more sufficiently prevented.

  By the way, as proposed in Non-Patent Document 4, a negative C plate composed of a polymerizable chiral nematic (cholesteric) liquid crystal layer having a reflection wavelength in the ultraviolet region usually has a retardation of positive wavelength dispersion characteristics. It has something. In addition, a negative C plate composed of a homeotropically oriented polymerizable discotic liquid crystal as proposed in Non-Patent Document 5 usually has a retardation of positive wavelength dispersion characteristics. Further, as proposed in Patent Document 11, a film-forming material having at least one kind of aromatic ring (polyamide, polyimide, polyamic acid, polyester, polyesteramide, or other polymers, or these polymers are given. The polymerizable low molecular weight compound and the like obtained have a negative refractive index anisotropy when coated and have an optical axis in the normal direction of the layer surface, and thus function as a negative C plate. It has the retardation of.

  Therefore, in the present invention, as the positive A plate a, a ′, a stretched polymer film or a composite stretched polymer film having a reverse wavelength dispersion property as a retardation is used, and the negative C plate c is as described above. Retardation with positive wavelength dispersion characteristics Reflective wavelength in the ultraviolet region Twisted polymerizable chiral nematic (cholesteric) liquid crystal layer, Homeotropically aligned polymerizable discotic liquid crystal layer, or negative when coated A coated layer made of a material that functions as a C-plate will be used.

  However, in order to configure such a liquid crystal layer as a negative C plate c, a substrate on which a liquid crystal layer or the like is formed is necessary in any case, and in particular, when a chiral nematic liquid crystal layer is used. Requires a planar alignment layer. Further, it is necessary to bond the positive A plate a and the negative C plate c formed on the substrate. Therefore, not only a separate bonding process is required, but also light reflection occurs at the interface with the adhesive (adhesive) used at that time, not only the display contrast is lowered, but also thin film interference due to interface reflection Unevenness may occur.

  Here, in the present invention, as shown in FIG. 1, the retardation used for the positive A plate a functions as a negative C plate c with the stretched polymer film 11 having reverse wavelength dispersion characteristics. A coating layer 12 having a positive wavelength dispersion characteristic is used as a substrate on which the coating layer 12 is formed. The stretched polymer film 11 functions as a twist alignment layer of a chiral nematic (cholesteric) liquid crystal layer and also as a homeotropic alignment layer of a discotic liquid crystal layer. Also disappear.

  That is, the laminated retardation layer 10 of the present invention has a positive refractive index anisotropy and a retardation layer (positive A plate a) having an optical axis in the layer plane, and a negative refractive index anisotropy. A retardation layer (negative C plate c) having an optical axis in the normal direction of the surface of the thin layer is laminated, and as the positive A plate a, the retardation becomes smaller as the wavelength becomes shorter. A stretched polymer film 11 having wavelength dispersion characteristics is used, and a polymerizable coating layer 12 having positive wavelength dispersion characteristics in which the retardation increases as the wavelength decreases as the negative C plate c.

  By adopting such a configuration, it is composed of a positive A plate a and a negative C plate c that can be easily manufactured without using a separate film formation substrate, alignment layer, or adhesive layer, and color shift is reduced. In addition, it is possible to obtain a multilayer retardation layer for a liquid crystal display device, particularly for a VA mode liquid crystal display device, which improves the viewing angle characteristics with high contrast and no interference unevenness.

  In order to maximize the effects of the present invention, it is preferable not to provide another layer between the positive A plate a and the negative C plate c. However, the solvent used for coating the coating layer is a stretched film. In the case where it is dissolved, a thin protective layer may be provided.

  In the present invention, the stretched polymer film 11 that functions as the positive A plate a and has a reverse wavelength dispersion characteristic that the retardation becomes smaller as the wavelength becomes shorter is prepared by forming a film containing liquid crystal and stretching. Polycarbonate film having a fluorene skeleton (Patent Document 6, Non-Patent Document 3), Cellulose Acetate Film (Patent Document 4) prepared by stretching into a film, Aromatic polyester polymer with positive wavelength dispersion characteristic and Fragrance with reverse wavelength dispersion characteristic A film prepared by stretching a mixture with a group polyester polymer (Patent Document 5), a film composed of a copolymer containing monomer units that form a polymer having different wavelength dispersion characteristics, and then stretching the film. The produced film (Patent Document 9), two stretched films with different wavelength dispersion characteristics Composite film obtained by laminating (Patent Document 10, Non-Patent Document 6) or the like is used.

  In the present invention, a twisted-oriented polymerizable chiral having a reflection wavelength in the ultraviolet region capable of three-dimensional crosslinking that can be used for the coating layer 12 that functions as a negative C plate c and has a retardation having a positive wavelength dispersion characteristic. Examples of liquid crystal monomer molecules (polymerizable liquid crystal molecules) used in the nematic (cholesteric) liquid crystal layer include a mixture of a liquid crystal monomer and a chiral compound as disclosed in Patent Document 7 and Patent Document 8, for example. As an example of such a polymerizable liquid crystal material, a compound as included in the following [Chemical Formula 11] or a mixture of two or more of the following [Chemical Formula 1] to [Chemical Formula 10] compounds is used. be able to. In the case of the liquid crystalline monomer represented by the general chemical formula [Chemical Formula 11], X is preferably 2 to 5 (integer).

  Further, as the chiral agent, for example, a chiral agent represented by the general chemical formulas [Chemical Formula 12] to [Chemical Formula 14] can be used. In the case of the chiral agent represented by the general chemical formulas [Chemical Formula 12] and [Chemical Formula 13], X is preferably 2 to 12 (integer), and in the case of the chiral agent represented by the general chemical formula [Chemical Formula 14]. , X is preferably 2 to 5 (integer).

Next, the Example of the lamination | stacking phase difference layer of this invention and its manufacturing method is demonstrated in detail.

Next, the Example of the lamination | stacking phase difference layer of this invention and its manufacturing method is demonstrated in detail.
(1) Stretched polymer film 11 as a base (positive A plate a)
A polycarbonate film (trade name: Pure Ace WR (registered trademark: Teijin Ltd.)) made of a copolymer containing monomer units that form a polymer with different wavelength dispersion characteristics produced by casting and stretching. retardation R shown in 3 (λ) (= Δn · d) (λ: wavelength, Δn = | n e -n o |, d: film thickness, n e: extraordinary refractive index, n o: ordinary refractive index) A polycarbonate film having a thickness of 80 μm was used for the stretched polymer film 11 (positive A plate a) as a base.

(2) Adjustment of ink As an ink for negative C plate c, a liquid crystal material having a polymerizable acrylate group at both ends and having a spacer between the mesogen in the central part and the acrylate is double-layered by 75 parts. 1 part by weight of Irgacure Irg184 (manufactured by Chiba Specialty Chemicals) as a starting material and 25 parts by weight of toluene as a solvent are mixed, and 10 parts by weight of a chiral agent having polymerizable acrylate groups at both ends is added as a chiral material. A polymerizable liquid crystal ink was produced.

(3) Film Formation of Chiral Nematic (Cholesteric) Liquid Crystal Layer 12 The adjusted ink was applied onto the stretched polymer film 11 of (1) using a spin coating method. In this embodiment, the spin coating method is applied, but it is not limited to this as long as it can be uniformly applied on the substrate. Die coating, slit coating, bar coating, slide coating, roll coating, microgravure The method may be a coating and a combination thereof, and is not particularly limited.

  Subsequently, the film coated with the polymerizable liquid crystal ink was heated on a hot plate at 100 ° C. for 5 minutes to remove the residual solvent, and a twisted liquid crystal structure was developed.

Subsequently, the applied liquid crystal layer was irradiated with ultraviolet rays (20 mJ / cm 2 , wavelength 365 nm) to obtain a laminated film structure of a chiral nematic (cholesteric) liquid crystal layer 12 having a thickness of 4.0 μm. The spiral pitch of the liquid crystal layer was 180 nm, and the reflection wavelength was 280 nm.

The resulting chiral nematic (cholesteric) birefringence of the liquid crystal layer 12 Δn (= | n e -n o |, n e: extraordinary refractive index, n o: ordinary index) wavelength dependence of 4 It can be seen that the retardation R (λ) (= Δn · d) has positive wavelength dispersion characteristics.

  Then, the birefringence measuring device shows the angle dependence of the retardation expressed by the optical path difference (nm) of the laminated retardation layer 10 formed by laminating the stretched polymer film 11 and the chiral nematic (cholesteric) liquid crystal layer 12 as described above. When measured with “COBRA” (registered trademark, manufactured by Oji Scientific Instruments Co., Ltd.), the result is as shown in FIG. 5, and the viewing angle characteristics of the VA mode liquid crystal display device configured as shown in FIG. It was found that the angle dependence of the phase difference required for improvement was obtained. FIG. 5 shows the result of measurement using sodium d line from the direction orthogonal to the optical axis of the positive A plate a.

(4) Configuration of Vertically Aligned Display A VA mode liquid crystal display device having the configuration shown in FIG. 2A is obtained by forming the laminated retardation layer 10 obtained by the same manufacturing method as the above (1) to (3). The stretched polymer film 11 is bonded to the observation-side polarizing plate 5 and the chiral nematic (cholesteric) liquid crystal layer 12 is in contact with the observation-side transparent substrate 1, and a negative dielectric difference is formed as the VA-mode liquid crystal layer 3. Liquid crystal MLC-6608 (manufactured by Merck & Co., Inc.) having anisotropy was injected to obtain a VA mode liquid crystal display device. At this time, the positive A plate was adjusted to a retardation value that substantially compensated for light leakage of the polarizing plate. On the other hand, the negative C plate compensates for the light leakage of the liquid crystal layer and the remaining light leakage of the polarizing plate (the sum of the thickness direction retardation of the liquid crystal layer (positive C plate) and that of the negative C plate). However, it was adjusted to the thickness direction retardation value.

  The light leakage at the time of black display of the obtained VA mode liquid crystal display device was compared with the case where the laminated retardation layer 10 was not provided as a comparative example. Using a light source of 450 nm as B (blue), 550 nm as G (green), and 610 nm as R (red), and using EZContrasut160R (manufactured by ELDIM) for measurement, it is made incident on the black state of the liquid crystal display device configured, The light leakage at that time was verified. The azimuth angles of the absorption axes of the two polarizing plates are 45 ° and 135 °. At each wavelength, in the case of the present embodiment, light leakage at azimuth angles of 0 °, 90 °, 180 °, and 270 ° is significantly reduced as compared with the case where the laminated retardation layer 10 is not provided. I understood. It was also found that there was almost no color shift even when R, G, and B were displayed and viewed obliquely from each azimuth direction. In particular, compared to the case where a positive A plate and a negative C plate were separately prepared and bonded with an adhesive, the contrast was excellent and no unevenness was seen.

  As mentioned above, although the laminated phase difference layer of the present invention, its manufacturing method, and the liquid crystal display device using the same have been described based on the principle and the examples, the present invention is not limited to these examples and various modifications are possible. It is.

  As is clear from the above description, in the multilayer retardation layer of the present invention, the manufacturing method thereof, and the liquid crystal display device using the same, the retardation having a positive refractive index anisotropy and having the optical axis in the layer plane. A layer and a retardation layer having a negative refractive index anisotropy and having an optical axis in the normal direction of the layer surface, and having the positive refractive index anisotropy and an optical axis in the layer surface As a retardation layer having a negative refractive index anisotropy, a stretched polymer film having reverse wavelength dispersion characteristics in which retardation, which is an optical path difference between extraordinary light and ordinary light, becomes smaller as the wavelength becomes shorter is used. As a retardation layer having an optical axis in the normal direction of the layer surface, a coating layer having a positive wavelength dispersion characteristic in which the retardation, which is the optical path difference between extraordinary light and ordinary light, increases as the wavelength becomes shorter is used. And without using alignment layer or adhesive layer, and easy Laminate position for liquid crystal display devices that can be manufactured and consists of a positive A plate and a negative C plate, improved in viewing angle characteristics without color shift, high contrast, and interference unevenness, especially for VA mode liquid crystal display devices A phase difference layer can be provided.

It is typical sectional drawing which shows the structure of the laminated phase difference layer by this invention. It is a disassembled perspective view which shows typically the structure of the liquid crystal display device to which the lamination | stacking phase difference layer of this invention is applied. It is a figure which shows the wavelength dependence of the retardation of the stretched polymer film used as the foundation | substrate used for 1 Example of the lamination | stacking phase difference layer of this invention. It is a figure which shows the wavelength dependence of the birefringence of the chiral nematic (cholesteric) liquid crystal layer used for one Example of the laminated phase difference layer of this invention. It is a figure which shows the angle dependence of the phase difference represented by the optical path difference of one Example of the lamination | stacking phase difference layer of this invention. It is a figure which shows the wavelength dependence of the retardation of the example of the positive A plate which has a reverse wavelength dispersion characteristic. It is a figure for demonstrating the positive uniaxial phase difference layer which has an optical axis in a layer surface, and the negative uniaxial phase difference layer which has an optical axis in the normal line direction of a layer surface. It is a figure for demonstrating the effect | action of a negative C plate.

Explanation of symbols

S ... layer surface a, a '... positive A plate c ... negative C plate 1 ... observation side transparent substrate 1' ... backlight side transparent substrate 3 ... VA mode liquid crystal layer 5 ... observation side polarizing plate 5 '... backlight Side polarizing plate 6: Absorption axis 10 of polarizing plate ... Laminated retardation layer 11 ... Stretched polymer film 12 with retardation having reverse wavelength dispersion characteristic ... Coating layer 41 with retardation having positive wavelength dispersion characteristic ... Negative negative C plate Refractive index ellipsoids 41x, 41y ... Main refractive index 41z in the plane of the negative C plate ... Main refractive index 42 in the thickness direction of the negative C plate ... Negative C plate 43 ... Liquid crystal cell 44 ... Liquid crystal cell refractive index ellipse Bodies 44x, 44y ... main refractive index 44z in the plane of the liquid crystal cell ... main refractive index in the thickness direction of the liquid crystal cell

Claims (9)

  1. A retardation layer having a positive refractive index anisotropy and having an optical axis in the layer surface and a retardation layer having a negative refractive index anisotropy and an optical axis in the normal direction of the layer surface are laminated. As a retardation layer having a positive refractive index anisotropy and having an optical axis in the layer plane, the retardation, which is an optical path difference between extraordinary light and ordinary light, has a reverse wavelength dispersion characteristic that decreases as the wavelength decreases. As a retardation layer having a negative refractive index anisotropy and having an optical axis in the normal direction of the layer surface, the retardation, which is the optical path difference between abnormal light and ordinary light, has a shorter wavelength. In the manufacturing method of the laminated phase difference layer using the coating layer having the positive wavelength dispersion characteristic that increases according to
    Applying and aligning a polymerizable liquid crystal layer on one surface of the stretched polymer film having the reverse wavelength dispersion property as a substrate, and then polymerizing to form a polymerizable liquid crystal layer having the normal wavelength dispersion property. A method for producing a laminated retardation layer.
  2. As stretched polymer film having the reverse wavelength dispersion characteristics, the laminated retardation layer according to claim 1, wherein the Ru with polycarbonate film having a fluorene skeleton was prepared by stretching in a film by containing a liquid crystal Manufacturing method .
  3. Examples stretched polymer film having reverse wavelength dispersion characteristics, a manufacturing method of a laminated retardation layer according to claim 1, wherein the Ru with cellulose acetate film produced by stretching in a film.
  4. As stretched polymer film having the reverse wavelength dispersion property, that Ru with a mixture was prepared by stretching a film of a film of an aromatic polyester polymer of an aromatic polyester polymer and reverse wavelength dispersion characteristics of the positive wavelength dispersion characteristics The manufacturing method of the lamination | stacking phase difference layer of Claim 1 characterized by the above-mentioned.
  5. Wherein the stretched polymer film having reverse wavelength dispersion characteristics, Ru with a film produced by stretching to a film of a polymer comprising a copolymer containing a monomer unit forming the polymer of different wavelength dispersion characteristics The method for producing a laminated retardation layer according to claim 1.
  6. Examples stretched polymer film having reverse wavelength dispersion characteristics, a manufacturing method of claim 1 laminated retardation layer, wherein the Ru using a composite film obtained by laminating two oriented films having different wavelength dispersion properties.
  7. Examples coating layer having a positive wavelength dispersion properties, method for producing a polymerizable chiral nematic (cholesteric) laminated retardation layer according to any one of claims 1, characterized in that Ru using the liquid crystal layer 6.
  8. Examples coating layer having a positive wavelength dispersion characteristics, homeotropic oriented method for manufacturing a laminated retardation layer according to any one of claims 1 to 6, characterized in that Ru with polymerizable discotic liquid crystal layer.
  9. Examples coating layer having a positive wavelength dispersion characteristics, claim 1, characterized in that Ru a material having an optical axis in the normal direction of the negative refractive index layer has an anisotropic surface when coated 6 The manufacturing method of the laminated phase difference layer of any one of Claims 1.
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