JP2010191240A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device wherein light leakage around a seal part can be suppressed without using a light shielding film. <P>SOLUTION: The liquid crystal display device includes a liquid crystal layer held between a lower substrate 12 and an upper substrate 14 and a seal member 22 sealing the liquid crystal layer inside. An alignment film 24 for aligning liquid crystal molecules 20 in a prescribed direction is provided on an inner wall on the liquid crystal layer side of the seal member 22. The alignment film 24 is a type different from those of alignment films 16 and 18 formed on an inner surface of the substrate used as the upper substrate. Therefore, alignment of liquid crystal molecules can be controlled even around the seal part, so that alignment abnormality in the neighborhood of the seal part can be prevented. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device in which the liquid crystal layer has a uniform liquid crystal molecular alignment.

  Liquid crystal display devices are widely put into practical use for display screens of thin televisions, mobile phones and the like. The liquid crystal display device includes a liquid crystal display element having a liquid crystal layer, and a drive circuit that supplies a drive signal for displaying an image on the display screen of the liquid crystal display element. The liquid crystal display element has a configuration in which two substrates having electrodes formed on the inner surface face each other and are bonded together through a minute gap, and a liquid crystal layer is sealed in the gap. A pair of polarizing plates is arranged so as to sandwich the liquid crystal layer. The liquid crystal layer includes a twisted nematic type (TN type) in which liquid crystal molecules are twisted by about 90 ° or about 180 ° from one substrate surface toward the other substrate surface, or a liquid crystal molecule in a direction perpendicular to the substrate surface. An aligned vertical alignment type is generally used.

  A case where a TN type liquid crystal is observed in a transmission type will be described below. When no voltage is applied to the electrodes sandwiching the liquid crystal layer, the polarized light beam that has passed through the lower polarizing plate rotates about 90 ° or about 180 ° along the twisted and aligned liquid crystal molecules and enters the upper polarizing plate. Light is transmitted when the polarization direction of light incident on the upper polarizing plate is parallel to the transmission axis of the upper polarizing plate, and light is not transmitted when orthogonal. When a voltage is applied to the liquid crystal layer, liquid crystal molecules having positive dielectric anisotropy rise in the vertical direction from the substrate surface in the direction of the electric field. When the liquid crystal molecules rise, the polarization characteristics are canceled, and the polarization axis of the light incident on the liquid crystal layer is emitted to the upper polarizing plate without rotating. Light is blocked when the transmission axes of the upper polarizing plate and the lower polarizing plate are orthogonal to each other, and transmitted when the transmission axes are parallel.

  A case where the vertically aligned liquid crystal is observed in a transmission type will be described below. When no voltage is applied to the electrodes sandwiching the liquid crystal layer, the polarized light incident on the liquid crystal layer passes through as it is. When a voltage is applied to the electrodes, the liquid crystal molecules having negative dielectric anisotropy are tilted with respect to the substrate surface. Then, optical anisotropy occurs in the liquid crystal layer, and the polarization axis of the incident polarized light beam changes. If the transmission axes of the two polarizing plates are orthogonal, light is blocked when no voltage is applied, and light is transmitted when a voltage is applied.

  In the case of a normal simple matrix type liquid crystal display element, a large number of striped electrodes are formed on the inner surfaces of two substrates so as to intersect each other, and this intersection constitutes a pixel. In the case of an active matrix type liquid crystal display device, a thin film transistor (TFT) is formed for each pixel on the inner surface of one substrate, and the amount of electric charge applied between the opposite electrode and the pixel electrode is controlled to display an image. Display.

  In recent years, efforts have been made to improve the quality and contrast of displayed images. In order to obtain a high contrast display, it is necessary to improve the black level density. In order to improve the black level density, unnecessary light leakage on the display surface should be reduced as much as possible. However, since an alignment film having low adhesion to the sealing material cannot be provided immediately below the seal portion, liquid crystal molecule alignment disorder is likely to occur in the vicinity of the seal portion. If there is a disorder in the alignment of the liquid crystal molecules, the polarization axis of the polarized light passing through this region is disturbed, and the black level density decreases. In order to suppress light leakage in the vicinity of the seal portion, a configuration is known in which a light shielding film is provided under the seal portion via a protective film (see, for example, Patent Document 1). Also known is a liquid crystal display device configured such that an end of a light shielding film overlaps a part of the bottom surface of the seal portion (see, for example, Patent Document 2).

Japanese Patent Laid-Open No. 8-21383 JP-A-8-278507

  In the liquid crystal display devices described in Patent Documents 1 and 2, a light shielding film is provided on the bottom surface of the seal portion. However, a process of forming the light shielding film, a process of applying a black matrix, and the like are required. Therefore, the number of manufacturing steps increases. In addition, in order to prevent disorder of liquid crystal molecule alignment in the vicinity of the seal portion, if the alignment film is extended to the bottom of the seal portion and the seal portion is formed on the alignment film, adhesion between the seal portion and the alignment film is achieved. As a result, the reliability of the liquid crystal display element decreased.

  Therefore, in order to solve the above problems, the liquid crystal display element of the present invention is provided with an alignment film for aligning liquid crystal molecules on the inner wall surface of a seal member that seals the liquid crystal layer between a pair of substrates. did.

  Here, an alignment film for horizontal alignment that aligns liquid crystal molecules in a horizontal direction with respect to the surface is used as the alignment film, and a vertical alignment that aligns liquid crystal molecules in a direction perpendicular to the surfaces is provided on the inner surfaces of the pair of substrates. An alignment film for alignment was provided.

  Further, the sealing member and the end portion of the vertical alignment film are provided apart from each other on the inner surface of the substrate.

  According to the present invention, since the alignment film for aligning liquid crystal molecules in a predetermined direction is provided on the inner wall surface of the seal member, the alignment direction of the liquid crystal molecules can be controlled even in the vicinity of the seal portion. In addition, light leakage due to abnormal alignment of liquid crystal molecules can be reduced.

It is a cross-sectional schematic diagram which shows the manufacturing method of the liquid crystal display element which concerns on the Example of this invention. It is a plane schematic diagram for demonstrating the liquid crystal display element which concerns on the Example of this invention.

  The liquid crystal display device of the present invention includes an upper substrate in which a transparent electrode and an alignment film are sequentially stacked on a transparent substrate, a lower substrate in which a counter electrode and an alignment film are sequentially stacked on a counter substrate, and a pair of these substrates And a seal member for sealing the liquid crystal layer inside. A second alignment film for aligning liquid crystal molecules in a predetermined direction is provided on the inner wall surface of the seal member on the liquid crystal layer side. The second alignment film is a different type of alignment film from the alignment film. Therefore, the orientation of the liquid crystal molecules can be controlled even in the vicinity of the seal portion, and an alignment abnormality in the vicinity of the seal portion can be prevented. As a result, light leakage from the vicinity of the seal portion can be reduced, and high-contrast image display can be realized.

  The alignment film formed on the inner surfaces of the pair of substrates is an alignment film for vertical alignment that aligns liquid crystal molecules in the vertical direction with respect to the surfaces. Therefore, the liquid crystal layer is in a vertically aligned state when no electric field is applied, and the liquid crystal molecules are tilted in the horizontal direction when the electric field is applied, so that high-speed response display can be obtained. The second alignment film is a horizontal alignment film that aligns liquid crystal molecules in the horizontal direction with respect to the surface. Therefore, the liquid crystal molecule alignment can be controlled in the direction perpendicular to the substrate surface even around the seal portion.

  Further, the seal member and the end portion of the alignment film are provided apart from each other on the inner surface of the substrate. Therefore, a liquid crystal display element can be configured without reducing the degree of adhesion between the seal member and the substrate surface.

  Note that a liquid crystal display device can be configured by providing a liquid crystal display element as described above and a driving circuit for supplying a driving signal for displaying an image on a display screen of the optical element or the liquid crystal display element.

  Hereinafter, the liquid crystal display element used in the liquid crystal display device of the present invention will be specifically described. FIG. 1A is a schematic cross-sectional view of the liquid crystal display element 10, and FIG. 1B shows an enlarged cross-sectional configuration of the seal portion region. FIG. 2 is a schematic plan view showing the liquid crystal display element 10 as viewed from above.

  As shown in FIG. 1A, the lower substrate 12 is configured by laminating a transparent planarization film 34 and a counter electrode 36 in this order on a counter substrate 32. The upper substrate 14 has a configuration in which a transparent electrode 44 is provided on a transparent substrate 42. Between the lower substrate 12 and the upper substrate 14, there are provided a seal member 22 for enclosing liquid crystal and a photo spacer 26 for keeping the substrate gap constant. Further, two polarizing plates (not shown) are installed so as to sandwich the liquid crystal display element 10. Here, the liquid crystal display element 10 is a vertical alignment type in which liquid crystal molecules are vertically aligned.

  Vertical alignment films 16 and 18 are provided on the lower substrate 12 and the upper substrate 14, respectively. The vertical alignment film is an alignment film for aligning the liquid crystal molecules 20 in the vertical direction, that is, in the vertical direction in which the lower substrate 12 and the upper substrate 14 face each other. The vertical alignment films 16 and 18 use a polyimide resin for vertical alignment. A polyimide resin was applied to the surfaces of the lower substrate 12 and the upper substrate 14 by a screen printing method and baked.

  As shown in FIG. 1B, the seal member 22 is installed near the outer periphery of the lower substrate 12. The seal member 22 has a width of about 0.3 mm and is formed with a distance d of about 10 μm from the end of the vertical alignment film 16. For the seal member 22, a thermosetting or ultraviolet curable adhesive can be used. The sealing member 22 bonds the upper substrate 14 and the lower substrate 12 with a gap therebetween, and seals the liquid crystal 20 on the inner peripheral side thereof.

  A horizontal alignment film 24 that aligns liquid crystal molecules in the horizontal direction with respect to the surface is provided on the inner wall surface of the seal member 22. The horizontal alignment film 24 is made of polyimide resin or the like, and is formed by applying to the inner wall surface of the sealing member 22 from an oblique or horizontal direction by a dispenser method, firing and curing. The thickness of the horizontal alignment film 24 was 0.1 μm to 10 μm. Since the horizontal alignment film 24 aligns the liquid crystal molecules 20 in the direction perpendicular to the substrate surface, the liquid crystal molecules 20 are continuously and vertically aligned from the vertical alignment film 16 to the inner wall surface of the seal member 22. Become.

  With reference to FIG. 2, the planar layout of the seal member 22, the horizontal alignment film 24, and the vertical alignment films 16 and 18 will be described. In FIG. 2, the transparent electrode 44, the counter electrode 36, and the photospacer 26 are not clearly shown. The liquid crystal display element 10 has a lower substrate 12 protruding on the right side. A flexible substrate (not shown) connected to an external circuit is connected to the protruding portion. A seal member 22 is provided along the outer periphery of the upper substrate 14. A horizontal alignment film is formed on the inner wall surface of the seal member 22 on the liquid crystal side. Further, on the inner peripheral side, vertical alignment films 16 and 18 are formed with a distance d from the inner wall surface.

  As described above, in the display area at the center of the liquid crystal display element 10, the liquid crystal molecules are vertically aligned by the vertical alignment films 16 and 18, and in the vicinity of the inner wall of the seal member 22, the liquid crystal molecules are also aligned by the substrate surface. Therefore, uniform liquid crystal molecule alignment can be formed on the entire inner surface of the seal member 22. As a result, light leakage particularly in the vicinity of the seal member 22 can be reduced.

  In the above-described embodiment, polyimide resin is used as the vertical alignment films 16 and 18 and the horizontal alignment film 24, but is not limited thereto. Other polymer materials and inorganic materials can be used. In addition, after the horizontal alignment film 24 is formed on the inner wall surface of the seal member 22, the alignment direction of the liquid crystal molecules can be defined by performing a rubbing process or the like in the direction perpendicular to the substrate surface with respect to the wall surface. Further, the distance d between the inner wall surface of the seal member 22 and the vertical alignment film 16 can be set within a range that the alignment regulating force of the horizontal alignment film 24 reaches, for example, several tens of μm.

  Here, translucent glass is used for the counter substrate 32 and the transparent substrate 42. Further, a light-transmitting plastic material can be used instead of glass. The transparent electrode 44 and the counter electrode 36 are formed by depositing indium tin oxide (ITO), tin oxide or zinc oxide on the substrate by sputtering or vapor deposition, and forming a pattern using photolithography and etching. did. The transparent electrode 44 and the counter electrode 36 are formed in stripes in directions orthogonal to each other.

  The transparent flattening film 34 was made of a thermosetting acrylic material. In addition, other light-transmitting polymer materials, inorganic oxides, or nitrides can be used. The transparent flattening film 34 is formed by applying a viscous transparent resin and then curing it. The liquid crystal layer is provided in order to prevent impurities such as moisture from entering and to flatten the surface and make the thickness of the liquid crystal layer uniform.

  The photo spacer 26 is formed by applying a photosensitive resin to the surface of the lower substrate 12 and patterning it so as to remain in the peripheral portion of the pixel region constituted by the transparent electrode 44 and the counter electrode 36 by photolithography. The photo spacer 26 is provided in order to make the thickness of the liquid crystal layer constant. In this embodiment, the photospacer 26 is formed to make the substrate gap uniform, but a gap holding material may be dispersed instead of the photospacer 26, or the photospacer 26 and the gap holding material need not be installed. Good. Moreover, in the said Example, although the transparent planarization film | membrane 34 was formed, it is not an essential requirement in this invention.

  In the above-described embodiments, the present invention is applied to the black and white liquid crystal display element 10. However, the present invention is not limited to this. Needless to say, the present invention may be applied to an active matrix display element in which a TFT is formed in each pixel.

DESCRIPTION OF SYMBOLS 10 Liquid crystal display element 12 Lower substrate 14 Upper substrate 16, 18 Vertical alignment film 20 Liquid crystal molecule 22 Seal member 24 Horizontal alignment film 26 Photo spacer 32 Opposite substrate 42 Transparent substrate 34 Transparent planarization film 36 Counter electrode 44 Transparent electrode

Claims (4)

An upper substrate in which a transparent electrode and an alignment film are sequentially laminated on the transparent substrate;
A lower substrate in which a counter electrode and an alignment film are sequentially stacked on the counter substrate;
A liquid crystal layer sandwiched between the upper substrate and the lower substrate;
A sealing member provided between the upper substrate and the lower substrate to enclose the liquid crystal layer;
A second alignment film provided over the inner wall surface of the seal member, and
The liquid crystal display device, wherein the alignment film and the second alignment film are different types of alignment films.   The alignment film is a vertical alignment film that vertically aligns liquid crystal molecules of the liquid crystal layer with respect to the surface, and the second alignment film aligns the liquid crystal molecules horizontally with respect to the surface. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is an alignment film for horizontal alignment.   The liquid crystal display element according to claim 2, wherein the seal member and the end portion of the alignment film are provided apart from each other on the inner surface of the substrate.   The liquid crystal display device according to claim 1, wherein the second alignment film is provided with a thickness of 0.1 μm to 10 μm.

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