JP5364284B2 - Liquid crystal display element and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new liquid crystal display element using a viewing angle compensating film and a method for manufacturing thereof. <P>SOLUTION: This liquid crystal display element has a liquid crystal cell including a pair of substrates 1a, 1b facing each other, the viewing angle compensating film 3, which is formed on at least one of the pair of facing substrates and constituted by micro regions aligned at random, and which has a substantially uniform refractive index in plane and negative optical anisotropy so that the refractive index in the thickness direction is smaller than that in the in-plane direction, an electrode pattern formed on the facing surface sides of a pair of substrates, and a vertically aligned liquid crystal layer 7 held between a pair of facing substrates. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a liquid crystal display element having a viewing angle compensation film and a manufacturing method thereof.

  In order to improve the viewing angle characteristics of a vertical alignment type liquid crystal display element, a method using an optical film, ie, a so-called C plate, which is in the normal direction of the substrate and has negative uniaxial optical anisotropy is known. Japanese Patent Application Laid-Open No. Sho 62-210423 discloses a liquid crystal display element using a C plate.

  On the other hand, as a method for improving the viewing angle characteristics, a method using an optical film having a positive optical anisotropy, that is, a so-called A plate is known.

  Japanese Patent Laid-Open No. 2003-279956 discloses a liquid crystal display element in which an A plate is formed in a liquid crystal cell.

JP-A-62-210423 Japanese Patent Laid-Open No. 2003-279956

  There is a need for a further liquid crystal display element using a viewing angle compensation film. An object of the present invention is to provide a new liquid crystal display element having a viewing angle compensation film and a method for manufacturing the same.

According to one aspect of the present invention, a pair of opposing substrates and at least one of the opposing pair of substrates are formed of a plurality of fine regions randomly oriented with respect to each other, and substantially uniform in-plane refraction. A viewing angle compensation film having negative optical anisotropy having a refractive index in the thickness direction smaller than the refractive index in the in-plane direction, an electrode pattern formed on the opposing surface side of the pair of substrates, A liquid crystal cell including a vertically aligned liquid crystal layer sandwiched between a pair of opposing substrates, wherein the viewing angle compensation film is composed of a polymer liquid crystal or a liquid crystalline monomer polymer, and the length of the monomer is within the fine region. A vertical alignment type liquid crystal display element having axial directions aligned with each other is provided.

According to another aspect of the present invention, a) a step of preparing a pair of substrates, b) a polymer liquid crystal or a liquid crystalline monomer polymer is applied in a solution state to at least one of the pair of substrates, and then Forming a viewing angle compensation film composed of a plurality of fine regions randomly oriented to each other by film hardening, and in which the major axis directions of the monomers are aligned with each other ; c) the pair of pairs A step of forming an electrode pattern on the opposite surface of the substrate; and d) bonding the pair of substrates including the viewing angle compensation film on at least one side with a gap, and having a negative dielectric anisotropy in the gap. There is provided a method for manufacturing a vertical alignment type liquid crystal display element including a step of injecting liquid crystal to form a liquid crystal cell.

  ADVANTAGE OF THE INVENTION According to this invention, the new liquid crystal display element which has a viewing angle compensation film, and its manufacturing method can be provided.

  FIG. 1 is a schematic cross-sectional view of a liquid crystal display device according to an embodiment. If the lower side in the figure is the back side of the liquid crystal display element, the liquid crystal display element is, in order from the back side, the lower (back) polarizing plate 8a, the lower (back) substrate 1a, the alignment film 2, the viewing angle compensation film 3, and the lower side Back side: transparent electrode 4a, alignment film 5a, liquid crystal layer 7, alignment film 5b, sealing material 6 (also serves as a side wall of liquid crystal layer 7), upper side (front side) transparent electrode 4b, upper side (front side) substrate 1b, upper side (Front) It is composed of a polarizing plate 8b.

  Hereinafter, a method for producing a liquid crystal display element according to the embodiment will be described.

  2A and 2B are schematic cross-sectional views showing the manufacturing process of the alignment film 2, the viewing angle compensation film 3, and the electrode pattern 4a formed on the lower substrate.

  As shown in FIG. 2A, first, the lower substrate 1a is prepared. An alignment film 2 is formed by applying and baking an alignment film material PIA-3000 manufactured by Chisso Corporation on the surface of the lower substrate 1a. The alignment film 2 is a horizontal alignment film. Further, the alignment film 2 is not subjected to alignment treatment.

  As shown in FIG. 2B, a liquid crystalline monomer polymer solution, which is an ultraviolet polymerization material, is applied onto the alignment film 2 by a spin coating method. This may be applied by an inkjet method or a slit coater. In addition, the liquid crystalline monomer polymer means that the monomer itself exhibits a liquid crystal phase in a solution state before the polymerization reaction, and the functional group arranged at the end of the monomer is initiated by irradiation with ultraviolet rays, etc. It is characterized by causing bonding and polymerizing as a whole.

In the examples, this liquid crystalline monomer polymer is formed into a film state. In addition, the liquid crystal phase is limited here because the monomer itself has birefringence, and in the solution state, it is necessary to polymerize those aligned in the major axis direction of the monomer while maintaining the alignment state. Because there is. The liquid crystalline monomer polymer solution used here can be, for example, a material manufactured by Merck. Next, the liquid crystalline monomer polymer solution is pre-baked at 55 ° C., and then irradiated with ultraviolet rays to cause a crosslinking reaction to form the viewing angle compensation film 3. The amount of ultraviolet rays to be irradiated is about ² J / cm ² at a wavelength of 360 nm, for example.

FIG. 3 is a plan view showing a part of the viewing angle compensation film. As shown, viewing angle compensation film 3, since not subjected to alignment treatment such as rubbing, mutual plurality of minute areas (arrow in FIG oriented randomly denotes an optical axis. Region A the optical axis of the micro-region and The optical axes of the fine regions of the region B are in a randomly oriented relationship with each other).

  When the substrate having the viewing angle compensation film 3 was rotated between crossed Nicols polarizing plates, there was no light leakage at any angle, and therefore the viewing angle compensation film 3 had the same optical properties as the C plate. Seem. The retardation is 260 nm.

  Returning to FIG. Next, a transparent conductor such as indium tin oxide (ITO) is laminated on the viewing angle compensation film 3 by a sputtering method or the like, and then patterned by a photo patterning method to form a predetermined transparent electrode pattern 4a. An acrylic resin film may be provided as a smooth layer on the base of the transparent electrode 4a.

  FIG. 4 is a schematic cross-sectional view showing another example of the positional relationship among the substrate 1a, the alignment film 2, the viewing angle compensation film 3, and the electrode pattern 4a. In the figure, there is a liquid crystal layer above the substrate. As shown in the figure, the viewing angle compensation film may be disposed below the substrate (outside the liquid crystal cell).

  Returning to FIG. Next, the vertical alignment film 5a is formed so as to cover the transparent electrode 4a.

  On the other hand, the upper substrate 1b is prepared. An electrode pattern 4b is formed on the upper substrate 1b in the same manner as the substrate 1a. Next, a vertical alignment film 5b is formed so as to cover the electrode pattern 4b.

  For example, a vertical alignment film SE-1211 manufactured by Nissan Chemical Industries, Ltd. is used as the alignment films 5a and 5b formed on the respective substrates at positions close to the liquid crystal layer. Rubbing is performed so that the rubbing directions of the alignment films are antiparallel to each other.

  A sealing material 7 mixed with a spacer is applied to one side of the upper and lower substrates thus prepared, and the substrates are bonded together with a gap therebetween to create an empty cell. A liquid crystal cell is formed by injecting liquid crystal into the created empty cell by a vacuum injection method or the like. As the liquid crystal, for example, a liquid crystal having a birefringence of 0.9 and a negative dielectric anisotropy manufactured by Merck Co., Ltd. is used. Note that liquid crystal may be injected by a dropping injection method or the like before the substrates are bonded to each other. In the example, the cell thickness is 4 μm, and the retardation is 360 nm.

  A pair of polarizing plates 8a and 8b whose polarization axes are crossed Nicols are bonded to the front and back surfaces of the prepared liquid crystal cell. The polarizing plate has a structure in which a polarizer is sandwiched between TAC (triacetate cellulose) films. The TAC film has optical properties similar to those of the C plate, and each of the retardation values is about 50 nm. Thus, a liquid crystal display element is completed.

  FIG. 5 is a plane showing the in-plane direction of the tilt of the liquid crystal molecules, the polarizing plate polarization axis direction, and the optical axis of the viewing angle compensation film 3 when the liquid crystal display element in the example is viewed from the front (substrate normal direction). FIG.

  As shown in the figure, the optical axis of the viewing angle compensation film is in the normal direction of the substrate. The polarizing axis of the polarizing plate is arranged to take an angle of about 45 ° with the direction in which the liquid crystal molecules are tilted by the alignment treatment. The polarizing axis of the polarizing plate may be upside down.

  FIG. 6A is a plan view illustrating the viewing angle characteristics of the liquid crystal display element according to the embodiment with an isocontrast ratio curve. The viewing angle is an angle representing how much the liquid crystal display element is viewed with respect to the normal direction of the substrate. In the illustrated circular coordinates, the viewing angle increases as the distance from the center is 0 degree, and the scale on the left of the circular coordinates (0-60 °) represents the viewing angle in the radial direction.

  The isocontrast ratio curve is indicated by a solid line, and the contrast ratio (CR) is 80, 40, 10, 5, 2, 1 from the inside.

  FIG. 6B is a plan view showing the viewing angle characteristics of the liquid crystal display element according to the reference example in which the viewing angle compensation film 3 and the underlying alignment film 2 are removed from the liquid crystal display element of the embodiment as an isocontrast ratio curve.

  The contrast ratio was calculated from the ratio of the light transmittance in the display pattern to the light transmittance in the dark state.

  6A and 6B are compared. It can be seen that FIG. 6A has a higher equi-contrast ratio over a wider viewing angle than FIG. 6B. From this, it can be seen that the embodiment shown in FIG. 6A is superior in viewing angle characteristics. The function of the viewing angle compensation film was almost the same as that of the C plate having a retardation of 260 nm, although the viewing angle characteristics were slightly different from those of the C plate.

  The retardation of the viewing angle compensation film may be limited to about 300 nm due to material and film thickness limitations. The viewing angle compensation film may be provided outside the liquid crystal cell.

  According to the liquid crystal display element of the embodiment, the viewing angle characteristic is improved by providing the viewing angle compensation film having the same optical function as that of the C plate.

  Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. For example, the alignment film 2 is not essential and may not be according to the situation. Further, the viewing angle compensation film may be provided on the front substrate, or may be provided on both sides of the substrate and on both the upper and lower substrates.

  It will be apparent to those skilled in the art that other various modifications, improvements, combinations, and the like can be made.

FIG. 1 is a schematic cross-sectional view of a liquid crystal display device according to an embodiment. 2A and 2B are schematic cross-sectional views showing the manufacturing process of the alignment film 2, the viewing angle compensation film 3, and the electrode pattern 4a formed on the lower substrate. FIG. 3 is a plan view showing a part of the viewing angle compensation film. FIG. 4 is a schematic cross-sectional view illustrating another example of the positional relationship between the substrate and the alignment film 2, the viewing angle compensation film 3, and the electrode pattern 4a. FIG. 5 is a plan view showing the in-plane direction of the tilt of liquid crystal molecules, the polarization axis direction of the polarizing plate, and the optical axis of the viewing angle compensation film when the liquid crystal display element in the example is viewed from the front (substrate normal direction). It is. FIG. 6A is a plan view showing the viewing angle characteristics of the liquid crystal display element according to the embodiment as an iso-contrast ratio curve, and FIG. 6B shows the liquid crystal display element of the embodiment excluding the viewing angle compensation film 3 and the underlying alignment film 2. It is the top view which showed the viewing angle characteristic of the liquid crystal display element by the equal contrast ratio curve.

Explanation of symbols

1a, 1b Substrate 2, 5a, 5b Alignment film 3 Viewing angle compensation film 4a, 4b Transparent electrode 6 Sealing material 7 Liquid crystal layer 7m Liquid crystal molecule 8a, 8b Polarizing plate

Claims (10)

A pair of opposing substrates;
It is formed of at least one of a pair of opposing substrates and is composed of a plurality of fine regions randomly oriented to each other, has a substantially uniform refractive index in the plane, and has a refractive index in the thickness direction in the in-plane direction A viewing angle compensation film having negative optical anisotropy smaller than the refractive index;
An electrode pattern formed on the opposing surface side of the pair of substrates;
A liquid crystal cell including a vertically aligned liquid crystal layer sandwiched between the pair of opposed substrates,
The viewing angle compensation film is composed of a polymer liquid crystal or a liquid crystalline monomer polymer,
A vertical alignment type liquid crystal display element in which the major axis directions of the monomers are aligned with each other in the fine region. further,
The liquid crystal display element according to claim 1, further comprising an unaligned alignment film between the viewing angle compensation film and the substrate on which the viewing angle compensation film is formed.   The liquid crystal display element according to claim 2, wherein the alignment film is an alignment film for horizontal alignment.   Furthermore, the liquid crystal display element of any one of Claims 1-3 which are arrange | positioned at the front surface and the back surface of the said liquid crystal cell, and have a pair of polarizing plate whose polarization axis is crossed Nicols.   The liquid crystal display element according to claim 1, wherein the viewing angle compensation film is formed on inner surfaces of the pair of opposed substrates. a) preparing a pair of substrates;
b) A polymer liquid crystal or a liquid crystalline monomer polymer is applied to at least one of the pair of substrates in a solution state, and then cured to form a plurality of fine regions that are randomly oriented to each other. Forming a viewing angle compensation film in which the major axis directions of the monomers are aligned with each other in a region; and
c) forming an electrode pattern on the side of the pair of substrates that is opposed to each other;
d) Vertically including a step of bonding the pair of substrates including the viewing angle compensation film on at least one side with a gap and injecting a liquid crystal having a negative dielectric anisotropy into the gap to form a liquid crystal cell. A method for producing an alignment type liquid crystal display element. Step b)
b-1) In the substrate on which the viewing angle compensation film is formed, before forming the viewing angle compensation film, an alignment film material is applied and baked to form an alignment film;
and b-2) forming a viewing angle compensation film on the surface of the alignment film.   The method for manufacturing a liquid crystal display element according to claim 7, wherein the alignment film is an alignment film for horizontal alignment. After step d)
e) The manufacturing method of the liquid crystal display element of any one of Claims 6-8 which has a process of arrange | positioning a pair of polarizing plate whose polarization axis is crossed Nicols in the front surface and back surface of the said liquid crystal cell. The method for manufacturing a liquid crystal display element according to claim 6, wherein the viewing angle compensation film is formed on an inner surface of the pair of opposed substrates.

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