JP2008170690A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device reducing peeling of an alignment layer. <P>SOLUTION: The liquid crystal display device includes a liquid crystal display panel having a first substrate, a second substrate, a liquid crystal held between the first substrate and the second substrate, and a plurality of spacers keeping the gap to be constant between the first substrate and the second substrate; wherein the liquid crystal display panel has a plurality of pixel regions; the first substrate has a light shielding film disposed around each pixel region; the spacer is formed on the light shielding film of the first substrate; and an alignment layer is not formed at least at the top end of the second substrate. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a liquid crystal display device and a manufacturing method thereof, and more particularly to formation of an alignment film.

  Currently, a commonly used liquid crystal display device is configured by disposing a substrate having a thin film transistor (TFT) element and a substrate having a color filter so as to face each other and enclosing a liquid crystal therebetween. A liquid crystal display panel.

  Spacers are formed between the substrates in order to maintain the spacing between the substrates. Generally, plastic beads having a uniform particle diameter are scattered on the spacer, or a columnar structure called a photo spacer is formed on one substrate by photolithography.

  The method using plastic beads is also scattered on the pixels, and there is a problem of a decrease in contrast due to light leaking around the plastic beads.

  Such a problem does not occur in the method using the photo spacer, but there is another problem. As an example showing the structure of the photo spacer, Patent Document 1 (Japanese Patent Laid-Open No. 2000-267114) is shown.

  In a normal manufacturing process of a liquid crystal display panel, a pair of substrates are formed separately, an alignment film is applied to both substrates, the substrates are bonded together, and liquid crystal is sealed between them. For this reason, as shown in Patent Document 1, an alignment film for controlling the alignment direction of the liquid crystal is uniformly applied to the photo spacer.

JP 2000-267114 A

  In such a configuration, the alignment film present at the tip of the photospacer becomes a problem. The photo spacer is formed so as to be in contact with the opposing substrate in terms of its function. For this reason, the alignment film applied to the front end portion of the photo spacer is pressed against the opposing substrate when the pair of substrates are bonded together. Due to such mechanical contact, the alignment film at the tip of the photo spacer is peeled off and floats in the liquid crystal. In addition, even after a pair of substrates are bonded to complete a liquid crystal display panel, there is a possibility that the alignment film is peeled off by rubbing the front end portion of the photo spacer due to vibration caused by product transportation.

  The alignment film peeled into the liquid crystal due to such a cause causes light leakage like the bead spacer, leading to a decrease in contrast.

  Conventionally, as shown in the above-mentioned Patent Document 1, there is an example in which the amount of the alignment film that is peeled off is reduced by thinning the alignment film at the tip of the photo spacer, but this has led to a radical solution. Not in.

  The present invention solves such a problem, and an object of the present invention is to provide a configuration capable of reducing alignment film peeling in a liquid crystal display device using a photospacer.

  In order to achieve the above object, the structure of the present invention includes a first substrate, a second substrate, a liquid crystal sandwiched between the first substrate and the second substrate, and the first substrate. A liquid crystal display panel having a plurality of spacers that maintain a constant spacing between the substrate and the second substrate, the liquid crystal display panel has a plurality of pixel regions, and the first substrate is A light-shielding film disposed around each of the pixel regions, wherein the spacer is formed on the light-shielding film of the first substrate, and an alignment film is provided at least on a tip portion on the second substrate side. It is characterized by not having.

  According to the present invention, since the alignment film is not formed on the photo spacer, it is possible to reduce the peeling of the alignment film caused by vibrations caused when the glass substrates are bonded or the liquid crystal display panel is transported.

<Overall configuration>
FIG. 2 is a block diagram showing an embodiment of a liquid crystal display device according to the present invention. FIG. 3 is a schematic circuit diagram showing an example of a circuit configuration of one pixel in the liquid crystal display device shown in FIG.

  In this embodiment, an example in which the present invention is applied to an active matrix liquid crystal display device will be described as an example. First, a schematic configuration of the active matrix liquid crystal display device will be briefly described.

  The active matrix liquid crystal display device includes, for example, a liquid crystal display panel 10, a data driver 11, and a gate driver 12, as shown in FIG. Although omitted in FIG. 2, the liquid crystal display device includes, for example, a circuit board for controlling operations of the data driver 11 and the gate driver 12 in addition to these. In the case of a transmissive or transflective liquid crystal display device, a backlight unit (light source) is also provided.

  The liquid crystal display panel 10 has a plurality of scanning signal lines GL and a plurality of video signal lines DL. The plurality of scanning signal lines GL are signal lines to which scanning signals are input from the gate driver 2, and the plurality of video signal lines DL are signal lines to which video signals are input from the data driver 12. Further, the scanning signal lines GL and the video signal lines DL are formed through an insulating layer, and one video signal line DL three-dimensionally intersects with a plurality of scanning signal lines GL through the insulating layer. is doing.

  In addition, the display area DA of the liquid crystal display panel 10 is located on the outermost side of the two scanning signal lines arranged on the outermost side of the plurality of scanning signal lines GL and the plurality of video signal lines DL. This is a rectangular area surrounded by two arranged video signal lines. The display area DA is composed of a large number of pixels arranged in the extending direction of the scanning signal lines GL and the extending direction of the video signal lines DL. The area occupied by one pixel is two adjacent areas. Corresponds to a region surrounded by two scanning signal lines GL and two adjacent video signal lines DL.

  One of the two scanning signal lines arranged on the outermost side is a dummy scanning signal line, and one of the two video signal lines arranged on the outermost side. One video signal line is a dummy video signal line. In the liquid crystal display panel 10 shown in FIG. 2, the scanning signal line farthest from the signal input end of the video signal line DL is a dummy scanning signal line, and the video signal line farthest from the signal input end of the scanning signal line GL is dummy. Video signal lines. As described above, by providing the dummy scanning signal line and the dummy video signal line, all the pixels constituting the display area DA are composed of two adjacent scanning signal lines and two adjacent video signal lines. It becomes an enclosed configuration.

  Although not shown in FIG. 2, each pixel constituting the display area DA is provided with an active element (sometimes referred to as a switching element). As the active element, for example, a MIS structure (including a MOS structure) TFT is used. When the TFTs used as the active elements are arranged at a ratio of one for one pixel, for example, as shown in FIG. 3, two adjacent scanning signal lines GLn and GLn + 1 (n is larger than 1). TFT (Tr) arranged for a region (pixel) that is surrounded by an integer) and two adjacent video signal lines DLm, DLm + 1 (m is an integer greater than 1), the gate (G) has a scanning signal. The drain (D) is connected to the video signal line DLm. At this time, the source (S) electrode of the TFT is connected to the pixel electrode PX. The pixel electrode PX forms a counter electrode CT (also referred to as a common electrode) and a liquid crystal layer LC and a pixel capacitor (also referred to as a liquid crystal capacitor) Clc.

In this embodiment, for the drain electrode and the source electrode of the TFT, the one connected to the video signal line DL is called the drain electrode, and the one connected to the pixel electrode PX is called the source electrode. Conversely, that is, the one connected to the video signal line DL may be referred to as a source electrode, and the one connected to the pixel electrode PX may be referred to as a drain electrode.
<Electrode configuration>
FIG. 4 is a plan view showing an example of the electrode configuration of the liquid crystal display panel 10. The liquid crystal display panel 10 of the present embodiment applies a vertical electric field between a pixel electrode formed on one glass substrate and a counter electrode formed on the other glass substrate of the pair of glass substrates. This is a so-called vertical electric field (VA) type liquid crystal display panel for driving liquid crystal molecules.

  In FIG. 3, the gate signal line GL, the drain signal line DL, and the pixel electrode PX are formed on one glass substrate side.

Further, BM is a light shielding film, and CF is a color filter. In FIG. 4, a dotted frame portion indicated by BM with an arrow represents an opening formed in the light shielding film (BM). The color filter (CF) and the light shielding film (BM) are formed on the other glass substrate side. In FIG. 4, TFT is a thin film transistor that constitutes an active element. Furthermore, 3 is a photo spacer for keeping a gap between the pair of glass substrates constant.
《Photo spacer configuration》
FIG. 1 is a cross-sectional view showing a cross-sectional structure taken along the line AA ′ in FIG. Hereinafter, the structure of the liquid crystal display panel 10 of the present embodiment will be described with reference to FIG.

  In the present embodiment, as shown in FIG. 1, one glass substrate 2 and the other glass substrate 1 are disposed so as to face each other via a liquid crystal layer LC. In this embodiment, the main surface side of the glass substrate 2 is the observation side.

  On the liquid crystal layer LC side of the glass substrate 2, in the order from the glass substrate 2 toward the liquid crystal layer LC, a light shielding film (BM) 8 and a color filter (CF) 7, a counter electrode (CT), a photo spacer (PS) 3, an alignment A film (AL2) 6 is formed. Further, a polarizing plate POL2 is formed outside the glass substrate 2. In FIG. 1, the counter electrode (CT) and the polarizing plate POL2 are not shown.

  Further, on the liquid crystal layer LC side of the glass substrate 1, the scanning signal line (GL), the gate insulating film (GI), the video signal line (DL), the interlayer insulating film (in order from the glass substrate 1 toward the liquid crystal layer LC). PAS), pixel electrode (PX), pedestal 4, alignment film (AL1) 9, etc. are formed. Further, a polarizing plate (POL1) is formed outside the glass substrate 1. In FIG. 1, the scanning signal line (GL), the gate insulating film (GI), the video signal line (DL), the interlayer insulating film (PAS), the pixel electrode (PX), and the polarizing plate POL1 are not illustrated.

  Here, in this embodiment or each embodiment described later, the photo spacer (PS) 3 is formed by, for example, a photolithography technique. Specifically, a material for forming a photo spacer is applied to a glass substrate as a photoresist, and then exposed to light according to the shape of the photo spacer, developed, and baked at a high temperature. The pedestal 4 is formed of a metal layer (specifically, a layer for forming a source electrode or a drain electrode of a TFT) formed on the glass substrate 1. In practice, an insulating film (passivation layer) is formed on the metal layer, but is omitted here.

  The shape of the photo spacer (PS) 3 and the pedestal 4 is larger than the pedestal 4 formed on the glass substrate 2 side in the photo spacer (PS) 3 formed on the glass substrate 1 side. When each glass substrate is bonded to the form of the liquid crystal display panel 1, the glass substrate is assembled by fitting so that the pedestal 4 is fitted into the tip portion of the photo spacer (PS) 3.

  The alignment film (AL1) 9 and the alignment film (AL2) 6 are applied after the photo spacer (P2) 3 or the base 4 is formed on each glass substrate. However, in this embodiment, as shown in FIG. 1, the alignment film (AL2) 6 is not applied to the tip portion of the photospacer (P2) 3. This is because the water repellency imparting material is mixed with the material forming the photospacer (P2) 3 in this embodiment.

  Examples of the water repellency-imparting material include fluorine-containing organic compounds and silicon-containing organic compounds. These compounds have poor wettability of the alignment film. By using these compounds as a material for the above-mentioned photoresist, the alignment film can be repelled from above the photospacer when the alignment film is applied. Specifically, the alignment film repelled from the surface of the photo spacer flows downward due to gravity, and as a result, an alignment film that does not adhere to the tip portion of the photo spacer is formed as shown in FIG.

  In general, the alignment film is applied by printing or by an inkjet method. However, the material used for the alignment film is lower in viscosity when used by the inkjet method. Therefore, this embodiment is particularly suitable for the alignment film application by the ink jet method.

  According to the present embodiment, when the glass substrate 1 and the glass substrate 2 are fitted together, the amount of the alignment film that is caught in the fitting between the photo spacer (PS) 3 and the pedestal 4 is greatly reduced. Can be reduced.

  The above is the embodiment of the present invention. According to the present invention, it is possible to prevent the alignment film from being peeled off from the spacer when the glass substrate is assembled or due to vibration caused by transportation of the liquid crystal display panel.

  In each of the above-described embodiments, the example of the vertical alignment type (VA) liquid crystal display panel has been described. However, the present invention also applies to other types of liquid crystal display panels such as a horizontal electric field type (IPS) and a TN type. Naturally applicable.

1 is a diagram illustrating a configuration of Example 1. FIG. It is a schematic block diagram of a liquid crystal display panel. It is a figure which shows schematic structure in a pixel area | region. It is a figure which shows schematic structure of several pixel area | region.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 ... Glass substrate, 3 ... Photo spacer (PS), 4 ... Base, 6 ... Orientation film (AL2), 7 ... Color filter (CF), 8 ... Light shielding film (BM), 9 ... Alignment film (AL1)

Claims (4)

A first substrate;
A second substrate;
A liquid crystal sandwiched between the first substrate and the second substrate;
A liquid crystal display panel having a plurality of spacers that maintain a constant distance between the first substrate and the second substrate;
The liquid crystal display panel has a plurality of pixel regions,
The first substrate has a light shielding film disposed around each pixel region,
The liquid crystal display device, wherein the spacer is formed on the light-shielding film of the first substrate and does not have an alignment film at least at a tip portion on the second substrate side.   The liquid crystal display device according to claim 1, wherein the spacer contains a water repellent material.   The liquid crystal display device according to claim 2, wherein the water repellent material is a fluorine-containing organic compound or a silicon-containing organic compound. On the second substrate at a position facing the spacer, a pedestal made of a metal layer is provided,
The liquid crystal display device according to claim 1, wherein the spacer and the pedestal are fitted together.

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