JP4660011B2 - Liquid crystal display device and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a normally white mode liquid crystal display device in which each pixel performs white display when no voltage is applied. In particular, the present invention relates to a normally white mode active matrix liquid crystal display device.
[0002]
[Prior art]
The liquid crystal display device is used in various fields as a display device such as a personal computer, a word processor or a TV, and further as a projection display device. Among them, an active matrix display device in which switching elements such as thin film transistors (TFTs) are electrically connected to each pixel electrode is widely used because it can realize a good display image without crosstalk between adjacent pixels. Yes.
[0003]
In recent years, the use of liquid crystal display devices has expanded, and the demand for display quality has increased. In particular, the demand for reduction or prevention of bright spots (points that always perform white display) has become increasingly severe. A bright spot is caused by a pixel in which a switching element does not operate in a normally white mode liquid crystal display device. However, the bright spot is very conspicuous on the display screen of the liquid crystal display device, and the display quality is greatly impaired.
[0004]
For this reason, when a bright spot is found at the inspection stage, a method of blackening (darkening) is performed in which a black dot (darkening) that is always displayed in black is converted.
[0005]
In order to make a black spot possible, a repair circuit for short-circuiting a pixel electrode related to a bright spot and a signal line or a scanning line is generally provided for each pixel opening (for example, a patent application). Hei 11-190080). At the time of manufacturing the array substrate, for example, a repair metal float pattern formed simultaneously with the scanning line is provided. Then, an extension portion of the signal line is provided so as to overlap with one end portion of the float pattern, and an extension portion of the source electrode is provided so as to overlap with the other end portion of the float pattern. When a bright spot is discovered during the lighting inspection of the liquid crystal display device, by melting each of the metal float pattern and the overlapping portion of the signal line extension portion and the source electrode extension portion by laser irradiation, The pixel electrode and the signal line are electrically connected to each other.
[0006]
In this way, the repair metal float pattern is used when the pixel electrode is a transmissive liquid crystal display device made of a transparent conductive material such as ITO (Indium-Tin-Oxide), directly with the pixel electrode and the signal line or scanning. This is because it is practically impossible to connect the line to each other by laser irradiation.
[0007]
However, when a metal float pattern for repair is provided and disposed, an undesired short circuit between the pixel electrode and the signal line or the scanning line may occur in the manufacturing process of the array substrate. Undesirable electric capacity is generated between the metal float pattern and the metal float pattern. Furthermore, the aperture ratio of the pixel is reduced by the amount of the repair circuit.
[0008]
In view of this, it has been proposed to reduce the brightness of the bright spot by irradiating the pixel aperture of the pixel related to the bright spot with laser light instead of the black spot by the repair circuit as described above (Japanese Patent Laid-Open No. Hei. 9-258155 (Japanese Patent Application No. 8-71584), JP-A-9-146060). If the alignment film is scratched by laser light irradiation, and the liquid crystal alignment action of the alignment film is reduced by this damage, the polarizing action of the liquid crystal layer is lost. Can be made. With such a method, the above-described problem does not occur because a repair metal float pattern is unnecessary.
[0009]
[Problems to be solved by the invention]
However, depending on the laser irradiation method, the luminance at the location where the bright spot is defective cannot be sufficiently reduced. In particular, it has often been found that the luminance is not sufficiently reduced when the luminance is reduced by performing laser irradiation efficiently within a short time.
[0010]
On the other hand, if the energy density of the laser irradiation is improved, the brightness of the bright spot defects can be reduced more reliably. In this case, however, other films that form the alignment film may be damaged or Impurities eluted from various films may contaminate the liquid crystal material layer.
[0011]
In addition, it has also been proposed to re-cut a large number of grooves in the alignment film in a direction perpendicular to the original alignment using a relatively expensive apparatus such as an excimer laser (Japanese Patent Laid-Open No. 2001-21890). However, this method is considered to increase the apparatus and process costs.
[0012]
The present invention has been made in view of the above problems, and provides a normally white mode liquid crystal display device and a method for manufacturing the liquid crystal display device that can reliably and easily blacken a defective spot.
[0013]
[Means for Solving the Problems]
The liquid crystal display device according to claim 1, a pair of insulating substrates bonded via a spacer and a sealing material, a liquid crystal layer held in a gap between the pair of insulating substrates and sealed by the sealing material, An alignment film provided on the surface of each insulating substrate so as to be in contact with the liquid crystal layer, a plurality of scanning lines arranged substantially in parallel, and a plurality of signal lines arranged substantially orthogonal to the scanning lines; A pixel electrode disposed at each intersection of the scanning line and the signal line, and a switching element provided for each pixel electrode for inputting a signal from the signal line to the pixel electrode in accordance with an applied voltage of the scanning line. In the liquid crystal display device provided, in the region on at least one of the pixel electrodes, substantially linear notches carved in the alignment film by laser light irradiation are arranged substantially in parallel over the entire region other than the periphery of the region. The a substantially straight indentations, the angle between the rubbing direction of the alignment film which is placed the notch is equal to or is within 10 °.
[0014]
With the above configuration, the bright spot can be surely and easily blackened.
[0015]
3. The liquid crystal display device according to claim 2, wherein the liquid crystal display device has the same configuration, in which an angle formed by the substantially linear notch and the rubbing direction of the alignment film is within 10 °, and a plurality of dots are formed on the alignment film. A mark-shaped marking portion is provided by laser beam irradiation, and the dot-shaped marking portion is sandwiched between the adjacent substantially straight score marks.
[0016]
Even with the above-described configuration, it is possible to reliably and easily make a bright spot a black spot.
[0017]
According to a third aspect of the present invention, there is provided a method of manufacturing a liquid crystal display device comprising: a pixel electrode arranged in a matrix on a first insulating substrate; a switching element arranged for each pixel electrode; A step of forming an alignment film on an electrode forming surface of the first insulating substrate and one main surface of the second insulating substrate, and the first and second insulating substrates through a sealing material. A step of injecting liquid crystal material between them, a step of performing pixel lighting inspection on the display panel assembled in this way,
When a defective bright spot is found by the pixel lighting inspection, the light transmission of the liquid crystal layer in the bright spot area is reduced by irradiating the alignment film in the bright spot area with laser light and damaging it. In the method of manufacturing a liquid crystal display device including a repairing step, a laser beam focused on the alignment film is scanned in a direction that forms an angle of 10 ° or less with respect to the rubbing direction of the alignment film. Thus, a plurality of substantially linear notches distributed over the entire area of the bright spot region are provided.
[0018]
According to a fourth aspect of the present invention, there is provided a method of manufacturing a liquid crystal display device, wherein the laser beam focused on the alignment film is scanned in a direction that forms an angle of 10 ° or less with respect to the rubbing direction of the alignment film in the same configuration. Instead, the repairing step includes irradiating a laser beam in the form of dots in the bright spot region to generate a vacuum bubble covering the bright spot region in the liquid crystal material layer, and the vacuum And scanning the laser beam in the bright spot region while avoiding the dot-shaped irradiation sites in the presence of bubbles.
[0019]
In the method of manufacturing a liquid crystal display device according to claim 5, a semiconductor laser beam having an output of 3.0 mW or less is used during the scanning, and the irradiation position is continuously moved at a speed of 400 to 1000 μm / second. Features.
[0020]
With such a configuration, the other films forming the base of the alignment film are not damaged, and as a result, impurities are not eluted into the liquid crystal material layer.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
A first embodiment of the present invention will be described with reference to FIGS.
[0022]
The plan view of FIG. 1 schematically shows a repaired pixel in the liquid crystal display device of the first embodiment. 2 is a schematic sectional view of the basic structure of the liquid crystal display device.
[0023]
As shown in FIG. 2, in the display panel 10 (liquid crystal cell) of the liquid crystal display device, the array substrate 1 (TFT substrate) and the counter substrate 2 are kept at a predetermined interval by a spacer, and the liquid crystal layer 3 is held therebetween. It becomes. A sealing material is disposed on the four circumferences of the liquid crystal layer 3 to seal the liquid crystal layer 3 and to join the array substrate 1 and the counter substrate 2 together.
[0024]
The liquid crystal layer 3 is made of, for example, a twisted nematic (TN) type liquid crystal material, and alignment films 15 and 25 made of polyimide resin or the like are arranged on the outermost layer in contact with the liquid crystal layer 3 of the array substrate 1 and the counter substrate 2, respectively. Is done.
[0025]
In the array substrate 1, the signal lines 11 and the scanning lines 12 are arranged on the glass substrate 16 so as to form a matrix, and a TFT 13 is disposed at each intersection of the signal lines 11 and the scanning lines 12. Each square-shaped region surrounded by the signal line 11, the scanning line 12, and the TFT 13 forms a pixel opening 5, and a pixel electrode 14 made of a transparent conductive material such as ITO is disposed so as to cover each pixel opening 5. Is done. In detail, the array substrate 1 can be manufactured by the method described in Japanese Patent Application No. 11-68034, for example.
[0026]
In the counter substrate 2, a color filter 12 in which a pattern of the light shielding layer 21 and red (R), green (G), and blue (B) color filter layers are arranged for each predetermined pixel on the glass substrate 26. The counter electrode 13 is provided so as to cover all of them. The counter electrode 13 is made of a transparent conductive material such as ITO similarly to the pixel electrode 14.
[0027]
In the illustrated embodiment, the peripheral edge of the pixel electrode 5 is overlapped with the signal line 11 and the scanning line 12 via the thick resin insulating film 17, and the edge 5 a of the pixel opening is the signal line 11 and the scanning line 12. Match the edges of the. In the vicinity of the TFT 13, as shown in FIG. 2, the edge of the light shielding layer 21 covering the TFT 13 forms the edge 5a of the pixel opening.
[0028]
When assembling the display panel 10 (liquid crystal cell) from the counter substrate 2 and the array substrate 1, for example, the following is performed. First, a polyimide resin film is formed on the pattern forming surfaces of both substrates 1 and 2, and liquid crystal alignment films 15 and 25 are formed by rubbing treatment. Next, a seal material is applied along the edge of the counter substrate 2 to create a seal material pattern that surrounds the entire display pixel area while leaving the liquid crystal injection port. When the counter substrate 2 and the array substrate 1 are bonded together via a sealing material, the rubbing angles of the alignment films 15 and 25 on both the substrates 1 and 2 are made to cross each other by 90 degrees. Thereafter, the liquid crystal material is vacuum-injected and then the injection port is sealed with a sealing material. Finally, polarizing plates 41 and 42 are attached to portions corresponding to the front and back surfaces of the display panel 10, that is, the outer surface of the counter substrate 2 and the outer surface of the array substrate 1, respectively. At this time, the absorption axes of the polarizing plates 41 and 42 are parallel to each other on the front and back of the display panel 10, and in each of the substrates 1 and 2, the absorption axis of the polarizing plate and the rubbing direction of the alignment films 15 and 25. To be parallel.
[0029]
After the display panel 10 is completed, a lighting inspection is performed, and if a bright spot defect is found, repair is performed by laser beam irradiation. The irradiation position is continuously changed by focusing the laser beam on the alignment film 15 on the array substrate in the region 51 (bright spot region) that is the bright spot, that is, in the region of the pixel opening 5 related to the bright spot. Let That is, the alignment film 15 is irradiated while scanning the laser beam within the bright spot region 51. At this time, in particular, the angle formed between the scanning direction and the rubbing direction is set to 10 ° or less.
[0030]
In this way, as shown in FIG. 1, a plurality of substantially straight notches 61 along the rubbing direction as the locus of the laser beam are provided over the entire pixel opening 5 related to the bright spot at substantially equal intervals.
[0031]
The laser beam output set value is set to 3.0 mW / sec or less and the laser beam scanning speed is set to 400 to 1000 μm / sec so as not to damage the resin interlayer insulating film which forms the base of the alignment film 15 during the laser beam scanning. Set within the range of sec. In the specific example, the output set value was 2.0 mW / sec, and the laser beam scanning speed was 600 μm / sec. Further, every time the creation of one linear notch 61 was completed, the laser beam was once stopped, the focus was set at the start position for creating the next notch 61, and laser irradiation was resumed.
[0032]
In a specific example, the size of the pixel opening 5 is, for example, 20 μm × 60 μm, and eight linear notches 61 are provided at an interval of about 5 μm.
[0033]
As a result of laser irradiation, almost complete black spots were achieved. In addition, no reduction in sunspot effect was observed even after a long-term continuous driving test.
[0034]
Next, Example 2 will be described with reference to FIG. FIG. 3 is a schematic plan view illustrating a repair state according to the second embodiment.
[0035]
In the second embodiment, one linear notch 61 and the next linear notch 61 are connected by a U-turn portion 62 that connects the end portions 61a and 61b adjacent to each other. In this way, all the linear notches 61 in the bright spot region 51 are connected in a single stroke. That is, the scanning trajectory of the laser beam forms a one-stroke writing.
[0036]
In Example 2, there was a case where the degree of blackening was slightly lower than that in Example 1, but it was practically unproblematic. According to the method of Example 2, the bright spot can be turned into a black spot by one continuous irradiation operation without stopping the laser beam, so that the repair work efficiency can be increased.
[0037]
When the direction of the linear notch 61 is largely shifted from the rubbing direction of the alignment film 15, for example, when the direction is along the signal line 11 or the scanning line 12, the laser beam exactly the same as in the first and second embodiments. Even with irradiation, sufficient black spots could not be achieved.
[0038]
It is not clear that black spots can be efficiently formed when laser light is scanned along the rubbing direction. However, it is presumed that the alignment film 15 made of polyimide resin is easily broken and broken when the notches 61 are along the rubbing direction.
[0039]
Next, Example 3 will be described with reference to the schematic diagram of FIG.
[0040]
In the repair of the third embodiment, first, “vacuum bubbles” over the entire bright spot region 51 are obtained by irradiating several points in the bright spot region 51 (pixel opening 5 related to defective bright spot) with laser light discontinuously. Generate temporary bubbles called. A vacuum bubble is generated by laser irradiation and disappears without a trace after a while, and is completely different from bubbles generated by air mixing.
[0041]
Subsequently, in the presence of this vacuum bubble, the alignment film 15 in the bright spot region 51 was provided with a plurality of indentations 61 arranged substantially in parallel by scanning with laser light substantially the same as in Example 1. At this time, a dot-shaped laser irradiation portion for providing a vacuum bubble is positioned in the middle between the indents 61.
[0042]
In the illustrated example, four points in the bright spot region 51 are irradiated with laser light whose output level is set to 1.5 mW / sec for 0.1 seconds each. As a result, a vacuum bubble covering almost the whole of the bright spot region 51 is generated. In this state, a laser beam having an output set value of 2.0 mW / sec was continuously irradiated at a scanning speed of 600 μm / sec.
[0043]
According to Example 3, since the laser beam is scanned in a state where the vacuum bubbles are generated, sufficient heat is applied to the alignment film 15 as compared with the case where the laser beams are scanned without generating the vacuum bubbles in advance. It is easy and can repair more efficiently by making black spots.
[0044]
In the fourth embodiment shown in FIG. 5, in the repair similar to the third embodiment, the scanning trajectory of the laser beam is formed in a single stroke by the U-turn portion 62 similar to the second embodiment.
[0045]
In the fifth embodiment shown in FIG. 6, in a repair similar to the fourth embodiment, a linear notch 64 in the direction along the scanning line 12 is formed instead of the linear notch 61 along the rubbing direction. Yes.
[0046]
Even in the case of Example 4, sufficient black spots could be achieved by irradiating with laser light in the presence of vacuum bubbles.
[0047]
As described above, according to the repair method of the embodiment, it is possible to reliably and easily darken a bright spot with a minimum number of steps.
[0048]
In the above embodiment, the alignment film 15 on the array substrate 1 side is described as being repaired by irradiating it with a laser beam. However, the same applies when the alignment film 25 on the counter substrate 2 side is irradiated with a laser beam. In this case, the linear notch 61 is provided along the alignment film 25 of the counter substrate 2.
[0049]
Although the liquid crystal display device has been described as being a light transmission type, the same applies to a light reflection type. In this case, the entire region on one pixel electrode 14 connected to the malfunctioning TFT 13 becomes the bright spot region 51.
[0050]
In the above embodiment, the locus by scanning with the laser beam is expressed as a notch, but it is not necessarily a continuous groove or recess, and if the scratches and breakage sufficient to disturb the alignment of the alignment films 15 and 25 are added. good.
[0051]
In the above embodiment, the switching element provided for each pixel electrode is described as a TFT. However, a thin film diode (TFD), that is, an MIM (metal-insulator-metal) element may be used.
[0052]
【The invention's effect】
In a normally white mode liquid crystal display device, it is possible to easily darken bright spots without providing a repair circuit or the like, and it is possible to prevent the effects of the black spotting process from disappearing with time. In particular, even in a liquid crystal display device including a resin flattening film, it is possible to easily make a bright spot a black spot without providing a repair circuit or the like.
[Brief description of the drawings]
FIG. 1 is a plan view schematically showing a repaired pixel in a liquid crystal display device of Example 1. FIG.
FIG. 2 is a cross-sectional view schematically illustrating a basic configuration of a liquid crystal display device.
FIG. 3 is a schematic plan view illustrating a repair state according to the second embodiment.
FIG. 4 is a schematic plan view illustrating a repair state according to a third embodiment.
FIG. 5 is a schematic plan view showing a state of repair in Example 4.
FIG. 6 is a schematic plan view illustrating a repair state according to the fifth embodiment.
[Explanation of symbols]
1 Array substrate 13 TFT
14 Pixel electrode 15 Alignment film 5 on the array substrate side Pixel opening 51 Bright spot region (region of pixel opening that always displays white)
61 Indentation by laser light along the rubbing direction of the alignment film

Claims (4)

A pair of insulating substrates bonded together via a spacer and a sealing material;
A liquid crystal layer held in the gap between the pair of insulating substrates and sealed with the sealing material;
An alignment film provided on the surface of each insulating substrate so as to be in contact with the liquid crystal layer;
A plurality of scanning lines arranged substantially in parallel, a plurality of signal lines arranged substantially orthogonal to the scanning lines, a pixel electrode arranged at each intersection of the scanning lines and the signal lines, and each pixel electrode In a normally white mode liquid crystal display device comprising a switching element that is provided in a switching element that performs signal input from the signal line to the pixel electrode according to an applied voltage of the scanning line,
In at least one region on the pixel electrode, a substantially linear notch carved into the alignment film by laser light irradiation is arranged substantially in parallel over the entire region other than the periphery of the region,
The liquid crystal display device, wherein an angle formed between the substantially linear notch and the rubbing direction of the alignment film in which the notch is formed is within 10 °. A pixel electrode arranged in a matrix, a switching element arranged for each pixel electrode, and a signal line connected to the switching element are provided on the first insulating substrate, and the first insulating substrate or the first Forming a scanning line on the two insulating substrates;
Forming an alignment film on the electrode forming surface of the first insulating substrate and one main surface of the second insulating substrate;
Bonding the first and second insulating substrates through a sealing material, and injecting a liquid crystal material therebetween;
A step of performing pixel lighting inspection on the display panel assembled by these steps;
A repair step of reducing the light transmittance of the liquid crystal layer in the bright spot region by irradiating the alignment film in the bright spot region with laser light when a bright spot failure is found by the pixel lighting inspection; In a method for manufacturing a liquid crystal display device comprising:
In the repair step, the irradiation position of the laser beam focused on the alignment film is irradiated continuously or intermittently while moving in a direction that forms an angle within 10 ° with respect to the rubbing direction of the alignment film. A method of manufacturing a liquid crystal display device, comprising: providing a plurality of substantially linear notches distributed over the entire area of the bright spot region. A pixel electrode arranged in a matrix, a switching element arranged for each pixel electrode, and a signal line connected to the switching element are provided on the first insulating substrate, and the first insulating substrate or the first Forming a scanning line on the two insulating substrates;
Forming an alignment film on the electrode forming surface of the first insulating substrate and one main surface of the second insulating substrate;
Bonding the first and second insulating substrates through a sealing material, and injecting a liquid crystal material therebetween;
A step of performing pixel lighting inspection on the display panel assembled by these steps;
A repair step of reducing the light transmittance of the liquid crystal layer in the bright spot region by irradiating the alignment film in the bright spot region with laser light when a bright spot failure is found by the pixel lighting inspection; In a method for manufacturing a liquid crystal display device comprising:
The repair process includes
Irradiating each of a plurality of points in the bright spot region with dot-like laser light in order to generate a vacuum bubble in the liquid crystal material layer so as to cover substantially the entire bright spot region;
In the bright spot region where the vacuum bubbles are generated by this step, by continuously or intermittently irradiating while moving the irradiation position of the laser beam, creating a plurality of indentations that are substantially linearly continuous; Tona is,
In the step of creating the notches, the irradiation position of the laser beam focused on the alignment film is moved continuously or intermittently in a direction that forms an angle of 10 ° or less with respect to the rubbing direction of the alignment film. A method of manufacturing a liquid crystal display device, comprising: providing a plurality of substantially linear notches distributed over the entire area of the bright spot region . The step of creating a plurality of the notches, wherein the irradiation position is continuously moved at a speed of 400 to 1000 μm / second while continuously irradiating a semiconductor laser beam having an output of 3.0 mW or less. 4. A method for producing a liquid crystal display device according to 2 or 3 .

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