JPH04301615A - Liquid crystal display device and defect correcting method for the same - Google Patents

Abstract

PURPOSE:To realize the liquid crystal display device which is applicable to both a projection device and a direct view type. CONSTITUTION:Once a bright point picture element 5 is detected, an excimer laser oscillator 11 irradiates the surface of a glass substrate 2, on the incidence side of a liquid crystal panel 1, on the same irradiation path with the bright point picture element 5 with a laser beam 12 to perform excimer laser etching, thereby forming a recessed part 18, which is so deep that the bottom surface is close to the bright point picture element 5, in the irradiated part of the glass substrate 2. At the same time, a rough surface 17 is formed as the bottom surface. Consequently, the light passing through the bright point picture element 5 is reduced to correct the bright point picture element so that the picture element is inconspicuous as compared normal peripheral picture elements 50. Further, the rough surface 17 is put close to the bright point picture element 5, and then the bright point picture element 5 is viewed in the corrected state at any view angle on the surface side of a projection-side glass substrate 3.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a transmissive liquid crystal panel in which a liquid crystal is sealed between a pair of transparent substrates and display pixels arranged in a matrix, and a transmissive liquid crystal panel that displays images from the back side of the transmissive liquid crystal panel. The present invention relates to a liquid crystal display device having a light source means for irradiating illumination light, and a defect repair method for repairing a bright spot defect occurring in a liquid crystal panel of the liquid crystal display device.

0002

2. Description of the Related Art An example of this type of liquid crystal display device is an active matrix drive type liquid crystal panel used in a projection device. In this liquid crystal panel, TFTs (thin film transistors) are connected to picture element electrodes arranged in a matrix on one of a pair of glass substrates to be bonded together, and each picture element electrode is connected by the switching operation of the TFT. Display operations are performed by selecting and deselecting. Therefore, crosstalk during non-selection, which is a drawback of a simple matrix, does not occur, and a high-quality display can be realized.

By the way, since a TFT has a multilayer structure in which a gate electrode, a source electrode, a drain electrode, etc. are laminated on a glass substrate, there are a process of laminating these metal thin films on a glass substrate, and a process of patterning the metal thin film. is repeated. Therefore, in order to manufacture a perfect TFT without any defects, great effort is required to maintain and control various conditions during the manufacturing process.

[0004] Therefore, in some cases, a defective TFT may be generated in which normal TFT characteristics are not obtained, and if the defect is repairable, it is attempted to repair it using the respective repair technology depending on the content of the defect. . An example of such a TFT defect is that it cannot be repaired on the circuit formation pattern, and when the display is driven, the picture element corresponding to the picture element electrode connected to the TFT becomes a bright spot on the display screen. There is a recognized bright spot defect.

One conventional example of a method for correcting bright spot defects is the method shown in FIGS. 4 to 6. This method is performed near the surface of the glass substrate 2 on the incident side corresponding to the bright spot picture element (picture element electrode) 5 of the liquid crystal panel 1 (hereinafter this position is referred to as the bright spot correction unit 6).
), a recess 18 with a depth of about 200 μm is created,
The bottom surface is roughened to form a rough surface 17. This rough surface 17 diffuses and attenuates the illumination light that enters the bright pixel 5 from the light source, making the bright pixel 5 less noticeable on the screen compared to the surrounding normal pixels (normal pixel electrodes) 50. Take corrective action.

[0006] For the bright spot correction unit 6 described above, a surface position of the glass substrate 2 is selected where the incident path of the bright spot picture element 5 and the illumination light from the light source are the same. More specifically, the surface position of the glass substrate 2 on the path A that passes through the bright spot picture element 5 of the light beam that enters the liquid crystal panel 1 from the light source through the condenser lens 7 and is converged on the projection lens 8 is determined. say. Figure 5 shows
It is schematically shown that the bright spot picture element 5 and the bright spot correction unit 6 are on the same path.

As shown in FIG. 6, a twisted nematic liquid crystal layer 30 is formed between the glass substrate 2 on the incident side and the glass substrate 3 on the output side.
Picture element electrodes 5 and 50 are provided on the inner surface side, and the TFT 29 switches the normal picture element electrode 50. Further, the above-described surface roughening treatment is performed by irradiating the surface of the glass substrate 2 on the incident side with an excimer laser beam.

[0008]

By the way, this type of liquid crystal panel is used not only for the above-mentioned projection device but also as a direct-view type liquid crystal display device. This direct-view liquid crystal display device is equipped with a backlight as an illumination means,
A user recognizes the illumination light emitted from the backlight, transmitted through the glass substrate on the incident side and the twisted nematic liquid crystal layer, and emitted from the glass substrate on the output side as display light (display image) of the liquid crystal display device. Take composition.

[0009] In such a direct view type liquid crystal display device, the above-mentioned bright spot pixel correction method cannot be applied. That is, since the viewing angle is not constant in a direct view type liquid crystal display device, the above correction method is a correction method that assumes that the bright spot picture element 5 and the bright spot correction unit 6 are always on the same irradiation path. It cannot be applied as is. More specifically, as shown in FIG.
This is because there is a problem in that the normal picture element 50 is visually recognized as a dimmed dark spot.

The present invention solves the drawbacks of the prior art, and provides a liquid crystal display device and a method for correcting defects in a liquid crystal display device, which can be applied not only to projection devices but also to direct-view devices. The purpose is to provide.

[0011]

[Means for Solving the Problems] The liquid crystal display device of the present invention comprises a transmissive liquid crystal panel in which liquid crystal is sealed between a pair of transparent substrates and display pixels are arranged in a matrix, and the transmissive liquid crystal panel. In a liquid crystal display device having a light source unit that irradiates illumination light for display from the back side of the panel, a light source unit on the incident side located on the irradiation path of the illumination light that irradiates the picture element where a bright spot defect has occurred. A recessed portion having a depth such that the bottom surface is close to the picture element is formed on the front side of the transparent substrate, and the bottom surface is formed into a rough surface shape exhibiting light scattering characteristics, thereby achieving the above object. Ru.

Preferably, the recessed portion is formed using an excimer laser beam, and the bottom surface is formed into a rough surface shape exhibiting light scattering characteristics.

Furthermore, the method for correcting defects in a liquid crystal display device according to the present invention includes a transmissive liquid crystal panel in which a liquid crystal is sealed between a pair of transparent substrates and display pixels are arranged in a matrix; In a method for correcting defects in a liquid crystal display device, the method includes light source means for irradiating illumination light for display from the back side of the panel, wherein the illumination light is irradiated onto the transmissive liquid crystal panel to produce bright spots on the picture element. In the process of detecting defects, the bottom surface is close to the picture element on the surface side of the transparent substrate on the incident side, which is located on the irradiation path of the illumination light that irradiates the picture element where the bright spot defect has occurred. , and forming a recessed part in which the bottom surface has a rough surface shape exhibiting light scattering properties,
This achieves the above objective.

Preferably, the step of forming the recessed portion is performed using an excimer laser beam.

[0015]

[Function] As described above, when a recessed part is formed on the surface side of the transparent substrate on the incident side, the bottom surface reaches a position close to the bright spot picture element, and the bottom surface is formed into a rough surface shape having light scattering characteristics. , the illumination light incident on this portion is diffused toward the surroundings by the bottom surface. Therefore, the brightness level of the bright spot defect is reduced to a level where it becomes inconspicuous compared to the surrounding picture elements. In other words, the bright spot picture element has been corrected.

In addition, since the bottom surface is close to the bright spot picture element, when the illumination light transmitted through the bright spot picture element is visually recognized from the transparent substrate side on the emission side, even if the viewing angle is different, the illumination light passing through the bright spot picture element is visible. The light incident on the recessed portion can be visually recognized as display light transmitted through the bottom surface and the bright spot picture element and emitted from the transparent substrate on the emission side. That is, the bright spot picture elements can be viewed in a corrected state from any viewing angle.

[0017]

[Embodiment] An embodiment of the present invention will be described below.

FIG. 1 schematically shows a defect correction method according to an embodiment of the present invention, in which an excimer laser oscillator 1
A laser beam 12 emitted from the laser beam 1 passes through a slit pattern 13, is reflected by an ultraviolet reflecting mirror 14, passes through a lens 15, and is focused on a bright spot correction unit 6 of a liquid crystal panel 1 set on a mounting table 16. irradiated. As described above, this bright spot correction unit 6 is located on the same incident path as the bright spot picture element 5 that generates a bright spot for the illumination light 40 (see FIG. 2).

As shown in FIG. 2, the bright spot correction unit 6 of this embodiment is arranged on the side of the pair of glass substrates 2 and 3 that are bonded together, on which illumination light 40 from the backlight enters the liquid crystal panel 1. Selected as glass substrate 2. Glass substrate 2 on the incident side
On the inner surface, color filters 24 of the three primary colors R (red), G (green), and B (blue) and black stripes 25 are arranged corresponding to the picture elements, and a counter electrode 26 for applying voltage to the liquid crystal is arranged. It is provided. Note that the color filter 24
may be arranged outside the glass substrate 2. On the other hand, on the inner surface of the glass substrate 3 on the side from which the illumination light 40 is emitted, there are picture element electrodes (picture elements) 5 and 50 arranged in a matrix and a TFT 29 that switches the power supply to the picture element electrodes 5 and 50. A twisted nematic liquid crystal layer 3 is formed between both glass substrates 2 and 3 and twisted by 90 degrees or more.
0 is included. In addition, picture element 5 indicates a bright spot picture element,
A picture element 50 indicates normal picture elements adjacent to the bright spot picture element.

The above-mentioned slit pattern 13 is formed with a pattern in which the outer size of the bright spot modifying section 6 is enlarged, and the laser beam 12 is directed to the bright spot modifying section by the reduction slit exposure through the slit pattern 13. It is designed to irradiate position 6 with high precision. Further, the mounting table 16 is movable, for example, in a horizontal plane in two orthogonal X-Y axes directions, and by moving the mounting table 16, the laser beam 12 can be irradiated to a desired bright spot correction section 6. It has become.

[0021] The detection of the bright pixel 5 is carried out in the previous step by irradiating the liquid crystal panel 1 with illumination light 40 from a backlight and by visually checking the display image of the liquid crystal panel 1 in the driving state. be exposed.

In FIG. 2, the thickness of the twisted nematic liquid crystal layer 30 is exaggerated compared to the thickness of the glass substrates 2 and 3 for convenience of explanation, and the actual structure of the liquid crystal panel 1 is similar to that shown in FIG. It has a similar structure. Although not shown in the figure, deflection plates are provided outside the glass substrates 2 and 3, respectively.

As shown in FIGS. 2 and 3, a recess 18 having a rough surface 17 on the bottom is formed in the bright spot correction section 6. As shown in FIGS. As shown in FIG. 3, the rough surface 17 is close to the bright spot picture element 5. That is, the recess 18 is formed to a depth such that its bottom surface reaches a position close to the bright spot picture element 5. The recess 18 and the rough surface 17 are formed as follows.

As shown in FIG. 3, the glass substrate 2 on the incident side
A laser beam 12 is irradiated onto the bright spot correction section 6 from the front surface side. As a result, the irradiation part is laser-etched, and a recess 18 is formed in the bright spot correction part 6 of the glass substrate 2 with a depth such that the bottom surface is close to the inner surface of the glass substrate, that is, the bottom surface is close to the bright spot pixel 5, Moreover, a rough surface 17 consisting of a finely uneven surface is formed on the bottom surface. The shape and depth of the recess 18 and the surface roughness of the rough surface 17 can be made variable by selecting an appropriate slit pattern 13 and setting the energy density of the laser beam 12 to an appropriate value.

[0025] Forming the above-described recess 18 and rough surface 17,
Thereafter, when illumination light is incident on this portion from the backlight, the incident light is diffused by the rough surface 17, and the illumination light that passes through the bright spot picture element 5 that closely opposes the rough surface 17 is attenuated. That is, the brightness level of the bright spot picture element is reduced. Therefore, the illumination light that passes through the bright spot pixels from the outside of the glass substrate 3 on the emission side, that is, the illumination light that passes through the bright spot pixels 5 when the liquid crystal panel 1 of this embodiment is used as a direct view type liquid crystal display device. The display light is visually recognized in a state where the brightness level of the display light is lowered to the brightness level of the display light that passes through the surrounding normal picture elements 50.

Furthermore, in the case of the embodiment shown in FIG.
A rough surface is formed to overlap a part of the adjacent picture element 50, and a part of the scattered light that has passed through the rough surface in this part is diffused in the direction of the adjacent picture element 5, and the adjacent picture element 50 is As a result, the color tone of 200 nm penetrates into the bright spot picture element 5 and is observed. Therefore,
At the same time, the shading of the bright spot picture element 5 and the surrounding normal picture element 50 become similar, and at the same time, the surrounding normal picture element 50 becomes in a state of "blurring" with respect to the bright spot picture element 5. As a result, the presence of the bright spot picture element 5 has been corrected to a state where it is less noticeable compared to the surrounding normal picture elements 50.

In addition, since the rough surface 17 is close to the bright spot picture element 5, the illumination light incident on the bright spot picture element 5 is not transmitted through the bright spot picture element 5 even if the viewing angle is different. glass substrate 3
It can be visually recognized as display light emitted from the surface. That is,
The bright spot picture element 5 can be seen in a corrected state from any viewing angle, and the normal picture element 5
The display light passing through the bright spot picture element 5 is not visually recognized. Therefore, the liquid crystal panel 1 of this embodiment can of course be applied to a liquid crystal display device for a projection device in which the bright spot correction unit 6 and the bright spot picture elements 5 are always the same with respect to the irradiation path of illumination light. This can also be applied to direct-view type liquid crystal display devices.

The above-mentioned surface roughening treatment, that is, the recess 18
The rough surface 17 can also be formed by laser etching using a CO2 laser, but this method has the following drawbacks.

[0029] If CO2 laser etching is used, the vicinity of the glass surface of the bright spot correction portion 6 will sag and the shape accuracy will be impaired.

(2) Since CO2 laser etching is a thermal process, the glass around the bright spot correction portion 6 is thermally damaged, and minute cracks are generated in this portion, which impairs the life of the liquid crystal panel 1.

On the other hand, laser etching using an excimer laser does not cause such defects. That is, since the excimer laser beam has the shortest oscillation wavelength among processing lasers, processing accuracy is high and shape accuracy is not impaired. Furthermore, since the excimer laser etching process uses an ablation phenomenon as its processing principle, it does not cause thermal damage to the glass substrate 2 and does not generate minute cracks.

[0032]Also, as another method, roughening treatment can be performed by engraving using a diamond needle or a cemented carbide needle, but according to the engraving method, the processing requires skill. The disadvantages are that it takes a long time and the machining accuracy is poor. Therefore, laser etching using an excimer laser beam is most preferred.

Furthermore, in excimer laser etching, ArF with an oscillation wavelength of 193 nm and ArF with an oscillation wavelength of 24 nm are used as filler gases.
KrF with a wavelength of 8 nm, XeCl with an oscillation wavelength of 308 nm, etc. are used, but according to the experimental results by the present inventors, ArF or It was confirmed that KrF is preferable.

In addition to the above configuration, the liquid crystal panel has a glass substrate with a TFT on the incident side of the illumination light 40, a glass substrate with a color filter on the output side, and a bright spot correction on the glass substrate side with the color filter. It is good also as a structure which forms the part 6.

[0035]

According to the present invention, the brightness level of a bright spot defect is reduced to a level where it becomes inconspicuous compared to the surrounding picture elements, and the illumination light is diffused, so that the illumination light is A portion of the light passes through the surrounding picture elements adjacent to the picture element in which the bright spot defect has occurred. Therefore, the presence of the bright spot picture element is corrected so that it is not noticeable compared to the surrounding normal picture elements.

In addition, since the bottom surface of the recessed part is close to the bright spot picture element, when the illumination light passing through the bright spot picture element is viewed from the transparent substrate side on the emission side, the viewing angle may be different. However, the light incident on the recessed portion can be visually recognized as display light transmitted through the bottom surface and the bright spot picture element and emitted from the transparent substrate on the emission side. That is, the bright spot picture element can be viewed in a modified state from any viewing angle. Therefore, according to the present invention, it is possible to realize a liquid crystal display device that can be applied not only to a projection device but also to a direct viewing type.

[0037] In particular, when forming a concave portion using an excimer laser beam and roughening the bottom surface as described in claim 2 or 3, the machining time can be shortened and the machining accuracy can be improved. This has the advantage of improving performance. Furthermore, there is an advantage that the transparent substrate is not thermally damaged and the life of the liquid crystal panel can be extended.

[Brief explanation of drawings]

FIG. 1 is a drawing schematically showing a defect repair method using an excimer laser device according to an embodiment of the present invention.

FIG. 2 is a sectional view showing the structure of a liquid crystal panel according to the present invention.

FIG. 3 is a sectional view showing the liquid crystal panel shown in FIG. 2 in a state closer to actual size.

FIG. 4 is a side view showing a conventional method.

FIG. 5 is a drawing showing the relationship between a bright spot correction unit and a bright spot picture element.

FIG. 6 is a sectional view taken along line BB in FIG. 5, showing a conventional example.

[Explanation of symbols]

1 Liquid crystal panel 2 Glass substrate on the incident side 3 Glass substrate on the output side 5 Bright spot picture element (bright spot picture element electrode) 6 Bright spot correction unit 11 Excimer laser oscillator 12 Laser beam 13 Slit pattern 16 Mounting table 17 Rough surface 18 Recessed part 29 TFT 30 Twisted nematic liquid crystal layer 50 Normal picture element (normal picture element electrode)

Claims (4)

[Claims] 1. A transmissive liquid crystal panel in which liquid crystal is sealed between a pair of transparent substrates and display pixels are arranged in a matrix, and illumination light for display is irradiated from the back side of the transmissive liquid crystal panel. In a liquid crystal display device having a light source means,
A recessed portion having a depth such that the bottom surface is close to the picture element is formed on the surface side of the transparent substrate on the incident side, which is located on the irradiation path of the illumination light that illuminates the picture element where the bright spot defect has occurred. A liquid crystal display device in which the bottom surface is formed into a rough surface shape exhibiting light scattering properties. 2. The liquid crystal display device according to claim 1, wherein the recessed portion is formed using an excimer laser beam, and the bottom surface is formed into a rough surface shape exhibiting light scattering characteristics. 3. A transmissive liquid crystal panel in which liquid crystal is sealed between a pair of transparent substrates and display pixels are arranged in a matrix, and illumination light for display is irradiated from the back side of the transmissive liquid crystal panel. A method for correcting defects in a liquid crystal display device, comprising: irradiating the illumination light onto the transmissive liquid crystal panel to detect a bright spot defect occurring in the picture element; A rough surface whose bottom surface is close to the picture element and which exhibits light scattering properties on the surface side of the transparent substrate on the incident side, which is located on the irradiation path of the illumination light that illuminates the picture element being generated. A method for correcting a defect in a liquid crystal display device, the method comprising: forming a recessed portion having a shape. 4. The method for correcting defects in a liquid crystal display device according to claim 3, wherein the step of forming the recessed portion is performed using an excimer laser beam.