JP2584905B2 - Liquid crystal display device and defect repair method for liquid crystal display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission type liquid crystal panel in which liquid crystal is sealed between a pair of transparent substrates and picture elements for display are arranged in a matrix, and a display is made from the rear side of the transmission type liquid crystal panel. The present invention relates to a liquid crystal display device having light source means for irradiating illumination light for use in a liquid crystal display, and a defect correction method for correcting a bright spot defect generated in a liquid crystal panel of the liquid crystal display device.

[0002]

2. Description of the Related Art As an example of this type of liquid crystal display device, there is an active matrix drive type liquid crystal panel used for a projection device. In this liquid crystal panel, a TFT (thin film transistor) is connected to pixel electrodes arranged in a matrix on one of a pair of glass substrates to be bonded, and the switching operation of the TFT causes each pixel electrode to be connected. The display operation is performed by selecting or not selecting.
For this reason, a high-quality display can be realized without generating crosstalk at the time of non-selection which is a disadvantage of the simple matrix.

Since a TFT has a multilayer structure in which a gate electrode, a source electrode, a drain electrode and the like are laminated on a glass substrate, a step of laminating these metal thin films on a glass substrate and a step of patterning the metal thin film Is repeatedly performed. Therefore, in order to manufacture a complete TFT without any defect, a great effort is required to maintain and control various conditions in the manufacturing process.

[0004] Therefore, in some cases, defective TFTs for which normal TFT characteristics are not obtained may occur. If a defect can be repaired, it is repaired using each repair technique according to the content of the defect. . As an example of such a defect of the TFT, a pixel corresponding to a pixel electrode connected to the TFT becomes a luminescent spot on the display screen when the display cannot be repaired and the display is driven. There are perceived bright spot defects.

FIGS. 4 to 6 show a conventional example of a method for correcting the bright spot defect. In this method, the vicinity of 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 correcting section 6)
A concave portion 18 having a depth of about 200 μm is formed, and the bottom surface thereof is roughened to form a rough surface 17. The rough surface 17 diffuses and diminishes the illumination light incident on the bright spot picture element 5 from the light source, and makes the bright spot picture element 5 inconspicuous with respect to the surrounding normal picture elements (normal picture element electrodes) 50 on the screen. Take corrective measures.

In the above-described bright spot correcting section 6, the surface position of the glass substrate 2 at which the incident path of the illumination light from the light source is the same as that of the bright spot picture element 5 is selected. More specifically, the surface position of the glass substrate 2 on the path A passing through the bright spot picture element 5 in the light flux that is incident on the liquid crystal panel 1 from the light source through the condenser lens 7 and converged on the projection lens 8 is determined. Say. FIG.
This schematically shows 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 outgoing side.
The picture element electrodes 5 and 50 are provided on the inner surface side of the TFT, and the TFT 29 switches the normal picture element electrode 50. In addition, the above-mentioned roughening treatment is performed on the glass substrate 2
The surface is irradiated with an excimer laser beam.

[0008]

Incidentally, this type of liquid crystal panel is used as a direct-view type liquid crystal display device in addition to the above-mentioned projection device. This direct-view type liquid crystal display device includes a backlight as illumination means,
A user recognizes 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 emission side as display light (display image) of the liquid crystal display device. Take the configuration.

In such a direct-view type liquid crystal display device, the above-described method for correcting a bright spot picture element cannot be applied. That is, since the viewing angle is not constant in a direct-view type liquid crystal display device, the above-described method, which is a correction method on the premise that the bright spot picture element 5 and the bright spot correction unit 6 are always on the same irradiation path, is used. It cannot be applied as is. More specifically, depending on the user's visual recognition position 100 as shown in FIG.
0, and as a result, the normal picture element 50
This is because there is a defect that is recognized as a darkened dark spot.

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

[0011]

A liquid crystal display device according to the present invention comprises a transmissive liquid crystal panel in which liquid crystal is sealed between a pair of transparent substrates and picture elements for display are arranged in a matrix. A light source means for irradiating illumination light for display from the back side of the panel, the light source means for irradiating the picture element having a bright spot defect, the incident side located on the irradiation path of the illumination light On the front side of the transparent substrate, a recessed portion having a depth whose bottom is close to the picture element is formed, and the bottom is formed in a rough surface shape exhibiting light scattering characteristics, thereby achieving the above object. You.

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

Further, according to a defect correcting method for a liquid crystal display device of the present invention, a liquid crystal is sealed between a pair of transparent substrates and picture elements for display are arranged in a matrix. A light source means for irradiating illumination light for display from the rear side of the panel, wherein the illuminating light is applied to the transmissive liquid crystal panel and the bright spots generated in the picture elements are illuminated. A step of detecting a defect, and on the front side of the transparent substrate on the incident side located on the irradiation path of the illumination light for irradiating the picture element in which the bright spot defect has occurred, the bottom surface is close to the picture element. And a step of forming a recessed portion in which the bottom surface is formed in a rough surface shape exhibiting light scattering characteristics,
Thereby, the above object is achieved.

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

[0015]

As described above, a recess is formed on the front side of the transparent substrate on the incident side so that 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 in the peripheral direction by the bottom surface. Therefore, the brightness level of the bright spot defect is reduced to a level at which it becomes inconspicuous with respect to surrounding picture elements. That is, the bright spot picture element is corrected.

In addition, since the bottom surface 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 exit side, even if the viewing angle is different, 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. In other words, the bright spot picture element can be visually recognized in a corrected state from any viewing angle.

[0017]

An embodiment of the present invention will be described below.

FIG. 1 schematically shows a defect correcting method according to an embodiment of the present invention.
The laser beam 12 emitted from 1 passes through the slit pattern 13, is reflected by the ultraviolet reflecting mirror 14, and is condensed via the lens 15 to the bright spot correction unit 6 of the liquid crystal panel 1 set on the mounting table 16. Irradiated. As described above, the bright spot correction unit 6 is 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 correcting section 6 of this embodiment is provided on the side of the pair of glass substrates 2 and 3 on which the illumination light 40 from the backlight is incident on the liquid crystal panel 1. Selected for the glass substrate 2. Glass substrate 2 on the incident side
A color filter 24 of three primary colors of R (red), G (green) and B (blue) and a black stripe 25 are arranged corresponding to the picture elements, and a counter electrode 26 for applying a voltage to the liquid crystal is provided on the inner surface of the. Is provided. The color filter 24
May be disposed 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 provided pixel electrodes (pixels) 5 and 50 arranged in a matrix and a TFT 29 for switching power supply to the pixel electrodes 5 and 50. A twisted nematic liquid crystal layer 3 formed between the glass substrates 2 and 3 and twisted and oriented 90 degrees or more.
0 is enclosed. Note that picture element 5 indicates a bright spot picture element,
The picture element 50 indicates a normal picture element adjacent to the periphery of 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 correcting section 6 is enlarged, and the laser beam 12 is irradiated with the reduced slit exposure through the slit pattern 13 so that the laser beam 12 is emitted. The position 6 is accurately irradiated. Further, the mounting table 16 is movable in the X-Y orthogonal two-axis direction, for example, in a horizontal plane, so that the laser beam 12 can be irradiated to a desired bright spot correction unit 6 by moving the mounting table 16. Has become.

The bright spot picture element 5 is detected by illuminating the liquid crystal panel 1 with illumination light 40 from a backlight in the previous process and inspecting the display image of the liquid crystal panel 1 in a driven state by an inspector. Will be

FIG. 2 shows the thickness of the twisted nematic liquid crystal layer 30 exaggerated in comparison with 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 FIG. It has a structured 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, the bright spot correcting portion 6 is formed with a concave portion 18 having a rough surface 17 on the bottom surface.
As shown in FIG. 3, the rough surface 17 is close to the bright spot picture element 5. That is, the concave portion 18 is formed at a depth such that its bottom surface reaches a position close to the bright spot picture element 5. The concave portion 18 and the rough surface 17 are formed as follows.

As shown in FIG. 3, the incident side glass substrate 2
The laser beam 12 is applied to the bright spot correction unit 6 from the surface side of the laser beam. Thereby, the irradiated portion is laser-etched, and a concave portion 18 is formed in the luminescent spot correcting portion 6 of the glass substrate 2 so that the bottom surface is close to the inner surface of the glass substrate, that is, the bottom surface is close to the luminescent spot pixel 5. In addition, a rough surface 17 composed of minute uneven surfaces is formed on the bottom surface. The shape and depth of the concave portion 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.

The above-mentioned concave portion 18 and rough surface 17 are formed,
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 transmitted through the bright spot picture element 5 approaching and facing the rough surface 17 is reduced.
That is, the brightness level of the bright spot picture element is dimmed. Accordingly, the illumination light transmitted through the bright spot picture element from outside the glass substrate 3 on the emission side, that is, the illumination light transmitted through the bright spot picture element 5 when the liquid crystal panel 1 of this embodiment is used as a direct-view type liquid crystal display device. The display is visually recognized in a state where the luminance level of the display light is lowered to the luminance level of the display light passing through the surrounding normal picture element 50.

Further, in the case of the embodiment shown in FIG.
The rough surface is formed so as to overlap a part of the adjacent picture element 50, and a part of the scattered light passing through the rough surface in this part is diffused in the direction of the adjacent picture element 5, and Is infiltrated into the bright spot picture element 5 and observed. Therefore,
At the same time, the density of the bright picture element 5 and the density of the surrounding normal picture elements 50 become similar to each other, and at the same time, the surrounding normal picture elements 50 become so-called "blurred" with respect to the bright picture element 5. As a result, the existence of the bright picture element 5 is corrected to be inconspicuous with respect to the surrounding normal picture elements 50.

In addition, since the rough surface 17 is close to the bright pixel 5, the illumination light incident on the bright pixel 5 is transmitted through the bright pixel 5 even when the viewing angle is different. And glass substrate 3
Can be visually recognized as display light emitted from the surface of. That is,
The bright spot picture element 5 can be viewed in a corrected state from any viewing angle, and the normal picture element
The display light that passes through the bright spot picture element 5 through the display is not visually recognized. Therefore, according to the liquid crystal panel 1 of the present embodiment, it is needless to say that the liquid crystal panel 1 can 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 element 5 are always the same with respect to the illumination light irradiation path. This can be applied to a direct-view type liquid crystal display device.

The above-described roughening treatment, that is, the recess 18
The formation of the rough surface 17 can be performed by laser etching using a CO ₂ laser, but this method has the following disadvantages.

According to the CO ₂ laser etching, the vicinity of the glass surface of the luminescent spot correcting portion 6 is sagged, and the shape accuracy is impaired.

Since the CO ₂ laser etching is a thermal process, the glass around the bright spot correcting portion 6 is thermally damaged, and minute cracks are generated in this portion.
The life of the device is impaired.

On the other hand, laser etching using an excimer laser does not cause such a disadvantage. That is, since the excimer laser beam has the shortest oscillation wavelength as a processing laser, the processing accuracy is high and the shape accuracy is not impaired. In addition, since the processing principle of the excimer laser etching is based on the ablation phenomenon, the glass substrate 2 is not thermally damaged, and no fine cracks are generated.

As another method, roughening treatment can be performed by engraving using a diamond needle or a needle made of cemented carbide. However, according to the engraving method, processing requires skill. There are drawbacks such as longer time and poor processing accuracy. Therefore, laser etching using an excimer laser beam is the most preferable in carrying out.

In the excimer laser etching, ArF having an oscillation wavelength of 193 nm and an oscillation wavelength of 248 nm are used as sealing gases.
KrF, XeCl having an oscillation wavelength of 308 nm, etc. are used. According to the experimental results of the present inventors, ArF or KrF is used as a sealing gas in order to perform a roughening process capable of reducing a target luminance level. Was confirmed to be preferable.

In addition to the above-described 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 emission side, and a bright spot correction on the glass substrate with a color filter. The configuration in which the portion 6 is formed may be adopted.

[0035]

According to the present invention described above, the luminance level of a bright spot defect is reduced to a level that makes it inconspicuous with surrounding picture elements, and the illumination light is diffused. Part of the light passes through the neighboring picture elements adjacent to the picture element having the bright spot defect. Therefore, the existence of the bright spot picture element is corrected to be inconspicuous with respect to the surrounding normal picture elements.

In addition, since the bottom surface of the recessed portion 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. Even so, 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 visually recognized in a corrected state from any viewing angle. Therefore, according to the present invention, it is possible to realize a liquid crystal display device applicable not only to a projection device but also to a direct-view type.

In the case where the recessed portion is formed by using an excimer laser beam and the bottom surface thereof is roughened, the processing time can be shortened and the processing accuracy can be reduced. There is an advantage that improvement can be achieved. Further, there is an advantage that the lifetime of the liquid crystal panel can be improved without the transparent substrate being thermally damaged.

[Brief description of the drawings]

FIG. 1 is a drawing schematically showing a defect repair method using an excimer laser device according to one 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 dimensions.

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

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

FIG. 6 is a sectional view taken along the line BB of FIG. 5 showing a conventional example.

[Explanation of symbols]

 Reference Signs List 1 liquid crystal panel 2 entrance-side glass substrate 3 exit-side glass substrate 5 bright spot picture element (bright spot picture element electrode) 6 bright spot correction section 11 excimer laser oscillator 12 laser beam 13 slit pattern 16 mounting table 17 rough surface 18 concave portion 29 TFT 30 Twisted nematic liquid crystal layer 50 Normal picture element (normal picture element electrode)

Claims (4)

(57) [Claims] 1. A transmissive liquid crystal panel in which liquid crystal is sealed between a pair of transparent substrates and picture elements for display are arranged in a matrix, and illumination light for display is illuminated from the rear side of the transmissive liquid crystal panel. Liquid crystal display device having
On the front side of the transparent substrate on the incident side located on the irradiation path of the illumination light for irradiating the picture element in which the bright spot defect is generated, a recessed portion having a bottom whose depth is close to the picture element is formed. Wherein the bottom surface is formed in a rough surface shape exhibiting light scattering characteristics. 2. The liquid crystal display device according to claim 1, wherein said recessed portion is formed using an excimer laser beam, and said bottom surface is formed in 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 picture elements for display are arranged in a matrix, and illumination light for display is illuminated from the rear side of the transmissive liquid crystal panel. Irradiating the illuminating light on the transmissive liquid crystal panel to detect a bright spot defect occurring in the picture element; and A rough surface having a bottom surface close to the picture element and a bottom surface exhibiting light scattering properties, on the front side of the transparent substrate on the incident side located on the irradiation path of the illumination light for irradiating the generated picture element; Forming a recessed portion formed in a shape. 4. The method according to claim 3, wherein the step of forming the recessed portion is performed using an excimer laser beam.