JPH06308443A - Method for relieving light transmission dot defect - Google Patents

Abstract

PURPOSE:To prevent the infiltration of light from a transparent substrate constituting a panel and to obscure defective points by directly depositing metals having light shieldability on display electrodes and a counter electrode. CONSTITUTION:A TFT substrate is first inspected and TFTs which are the light transmission dot defects and the display electrodes connected thereto are specified. Opaque light shieldable films 13 made of Al formed by decomposition and formation of (CH3)3Al by a laser CVD method are deposited on the ITO display electrodes 1 which are the light transmission dots on gate insulating films 4 made of silicon nitride. The materials of the light shieldable films 13 may be the metals, such as Cr, W and Mo. No hindrances are generated in coating of an oriented film made of polyimide if the thickness thereof is set at about 400Angstrom . The infiltration of the light based on diffraction is substantially eliminated when the light shieldable films 13 made of the metals are so deposited as to come into contact with the display electrodes 1 in such a manner. The use of the metallic light shieldable films 13 as the spacers of a liquid carystal display device is possible by forming the films at several mum thickness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pocket type, portable type or larger size television or OA device,
TFT used as a display device such as a projector
System LCD display device.

[0002]

2. Description of the Related Art Generally, there are TFT defects, alignment film defects, and pattern defects in the so-called light-transmitting dot defects.

A TFT defect has a low light transmittance when there is no electric field, that is, when the drain line and the display electrode are short-circuited by so-called NB, and a TFT defect that has a high light transmittance when there is no electric field, so-called NW with a drain line. In some cases, the display electrodes are cut off.

The alignment film defect is a phenomenon that the alignment film is chipped at the corners of the TFT substrate or the counter substrate when the alignment film is formed, or is peeled off at the corners of the display electrode due to rubbing.

The pattern defects are classified into the ones caused by the disturbance of the display electrodes and BM, and the ones caused by the misalignment between the TFT substrate and the counter substrate.

Regarding each light transmitting dot defect, the alignment film defect is large in area based on the TFT defect, but the light transmittance is small,
The pattern defect is small in area but has a large light transmittance.

In the past, dot defects of TFT type LCD panels, especially ON dots, were conspicuous as white defects when used in a projector or the like, so a resin was applied on the defective part to block light.

FIG. 7 shows a cross-sectional view of a TFT type LCD panel using a conventional light transmitting dot defect relief method.

As shown in the figure, display electrodes 1 arranged in a matrix are formed on a TFT substrate 2, and the display electrodes 1 are covered with a display electrode protective film 3.

A gate insulating film 4 and a gate 5 of the TFT covered with the gate insulating film are laminated on the display electrode protective film 3.

The semiconductor film 6 of the TFT is arranged on the gate insulating film 4, and the drain 7 and the source connected to the display electrode are formed on the semiconductor film 6.

The liquid crystal 8 is sandwiched by an alignment film 9 formed on the TFT substrate 2 and an alignment film 9 formed on the counter electrode 10.

Under the counter electrode 10, a BM 12 for blocking light in the area other than the display electrode and a transmissive portion for transmitting light in the area of the display electrode are arranged so as to be flat as a whole.

The BM 12 is supported by the counter substrate 11, and a light-shielding film 13 in which a light-shielding material such as graphite or Ti is dispersed in epoxy resin is applied at a position corresponding to a light transmission defect on the counter substrate 11. It was formed by means such as printing or transfer.

However, the light-shielding film 13 tends to be thick at the center and thin at the periphery, which may lack uniformity.

Further, when the sufficiently thick light-shielding film 13 is formed, a gap is formed between the polarizing plate 14 and the light-shielding film 13 as shown in FIG. 8, which hinders the display of adjacent normal dots. Or, when the conventional dot defect correction method is applied to a projector or the like in which the area of the light-shielding film 13 becomes large and the screen is enlarged to a large screen, the corrected portion becomes conspicuous and the commercial value may be impaired. It was

In addition, in a TFT type LCD in which a storage capacitor is formed by superimposing a display electrode and a gate line, the gate line is laser-welded to the display electrode to obtain an intermediate brightness.
There was a remedy to make the defect points inconspicuous.

However, since the voltage applied to the liquid crystal from the laser-welded display electrode is not AC, DC is applied to the liquid crystal.
The liquid crystal is electrolyzed by the application of (direct current), and there is a question from the viewpoint of high reliability.

[0019]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention pseudo-OFF dots are formed by directly depositing a metal having a light-shielding property on the display electrodes of a TFT type LCD panel so that light from the glass surface can be obtained. It is intended to prevent the wraparound and to make the defective portion inconspicuous. Further, even in the case of the glass surface, it is intended to obtain the same effect by forming a thin film.

[0020]

SUMMARY OF THE INVENTION The present invention is a method of remedying a defective always-light-transmitting dot defect as a normally-light-impermeable defect, in which a light-shielding metal is directly deposited on a display electrode or an opposing electrode. Thus, it is possible to prevent the light from wrapping around from the transparent substrate that constitutes the panel and to make the defective portion inconspicuous, thereby enhancing the commercial value of the TFT type LCD.

[0021]

According to the method of relieving the light-transmitting dot defect of the present invention, the defect caused by the high definition of the TFT type LCD panel can be easily repaired without lowering the effective area and the commercial value.

[0022]

EXAMPLES The present invention will be described in detail below based on examples.

FIG. 1 is a cross-sectional view of a TFT substrate of a TFT type LCD using the method for relieving light transmissive dot defects of the present invention.

As shown in FIG. 1, TF is formed on the TFT substrate 2.
T is formed, and the TFT is composed of a gate 5, a gate insulating film 4, a semiconductor film 6, a drain 7 and a source.

First, the TFT substrate is inspected to identify the TFTs and the display electrodes connected to the TFTs, which are defective in light-transmitting dots due to disconnection or short circuit.

Then, the gate insulating film 4 made of silicon nitride
On top of the ITO display electrode 1 (C
An opaque light-shielding film 13 made of Al produced by decomposing H ₃ ) ₃ Al by a laser CVD method is deposited.

The material of the light-shielding film deposited on the display electrode may be a metal such as Cr, W or Mo, and its thickness is 40.
If it is set to about 0Å, there will be no problem in covering the alignment film made of polyimide.

When a metal light-shielding film is deposited so as to be in contact with the display electrode as shown in FIG. 1, light wraparound due to the diffraction phenomenon is almost eliminated.

The thickness of the light-shielding film made of metal may be about several hundred Å, but conversely, the light-shielding film having a thickness of several μm may be used as a spacer of a liquid crystal display device.

FIG. 2 shows a sectional view of the TFT substrate of the TFT type LCD of the present invention in which a light shielding film is formed on the display electrode and the drain.

On the display electrode 1 of FIG. 2, a light-shielding film 13 having a thickness of 1 μm, which is equivalent to the thickness of the drain and the source, is laminated, and T
The light-shielding film 13 is formed only on the drain 7 of the FT.

As shown in FIG. 2, it is not on the drain line and T
By stacking the light-shielding film only on the drain of the FT and the display electrode, the panel spacing can be kept constant in the active matrix type ferroelectric liquid crystal display device without delaying the liquid crystal injection, and the light transmitting dot defect can be invisible. can do.

Next, an example will be shown in which a TFT defect and an alignment film defect coexist among the light transmitting dot defects.

FIG. 3 is a perspective view of a TFT substrate using the light transmitting dot defect relief method of the present invention.

In FIG. 3, the TFT on the TFT substrate 2
Are omitted in order to clearly show the display electrode 1 shown by a dotted line.

Since the alignment film 9 on the TFT substrate 1 is missing at the lower right corner due to peeling, the alignment state of the liquid crystal is disturbed and the corner of the TFT substrate becomes a light transmissive dot defect.

Therefore, a light-shielding film 13 made of Al having a thickness of about 200 Å is formed at a corner of the alignment film 9 corresponding to the alignment film defect.
At the same time, the metal light-shielding film 1 in which the drain line and the display electrode of the defective portion are connected on the alignment film 9 corresponding to the TFT defect
3 are deposited.

If a line-shaped light-shielding film is formed before rubbing, it is useful for eliminating static electricity generated by friction, and if a rectangular light-shielding film is formed after rubbing, light-transmissive dot defects due to the alignment film falling off due to rubbing are caused. It can be resolved.

In this embodiment, the light-shielding film is formed on the TFT substrate side of the TFT type LCD, but the light-shielding film may be formed on the counter substrate side.

FIG. 4 is a perspective view of a TFT-type LCD in which a light-shielding film is provided in a grid pattern on the outside of a counter substrate of the TFT-type LCD.

As shown in FIG. 4, the TFT type L on the side opposite to the surface of the counter substrate 11 on which the counter electrode 10 is provided.
A lattice-shaped light-shielding film 13 made of Ni is formed on the outer surface of the CD.

The openings of the grid-like light-shielding film 13 coincide with the display electrode regions shown by the dotted lines on the TFT substrate 2.

The shaded portion of the light-shielding film 13 closed with metal covers the light-transmissive dot defect of the TFT substrate and converts it into a light-impermeable defect.

If the metal lattice-shaped light-shielding film is connected to the ground, the probability that the TFT type LCD is destroyed by static electricity is reduced, and the spread of light due to the thickness of the liquid crystal can be dealt with.

Next, an embodiment will be described in which a light-shielding film having a thickness equal to or less than the thickness of liquid crystal is provided on the inner surface of the counter substrate.

FIG. 5 is a perspective view of a TFT-type LCD in which a light-shielding film is provided in a grid pattern inside a counter substrate of the TFT-type LCD.

In FIG. 5, since the light-shielding film 13 made of Al has a width of 10 μm and a thickness of 550Å, it has a size of 5 μm.
The resistance R of one side of one display electrode of 0 μm × 50 μm is R
= 2.65 × 10 ^-8 Ωm × 60 × 10 ^-6 m / (550 ×
10 ⁻¹⁰ × 10 × 10 ⁻⁶ ) = 2.89Ω.

In a high-definition TFT type LCD, if the resistance when the matrix is infinite horizontally is T, the circuit continues infinitely. Therefore, the first two resistors in the first row and the first column are removed, and the two resistors are removed. The combined resistance looking to the right is also considered to be equal to T.

Therefore, since the resistance obtained by connecting the resistance T to the two resistances is T, R is calculated from the formula of the combined resistance.
(R + T) / (R + R + T) = T, solving this equation, T
= (-1 + ● 5) R / 2 = 0.62R.

If the previously obtained R = 2.89 is used, the maximum resistance T is T = 0.62 × 2.89 in a normal display device that is horizontally long according to the recognition sensitivity of a human having eyes on the left and right. =
It becomes 1.8Ω.

The ITO used for the counter electrode has a light transmittance of 80%, a thickness of 550 Å, 100 Ω / sq, and a light transmittance of 7
It is 10Ω / sq at a thickness of 2000Å of 5%, 1 cm ²
The resistance between the diagonals is 100Ω to 10Ω, which is 1000 times or more higher than that of a metal such as Al.

Therefore, since the resistance of ITO can be almost ignored, the total resistance T = R × R / (R + R) = 0.5R in the case of one display electrode and the infinite number of display electrodes according to the structure of this embodiment. In this case, since the IR drop of the counter electrode can be suppressed within the range between the total resistance T = 0.62R, a large screen can be displayed uniformly.

The shaded portions in the figure indicate the light-transmitting dot defects made of the same metal as the lattice-shaped light-shielding film so that light cannot be transmitted.

Up to this point, the embodiments in which the light-shielding film is formed on the TFT type LCD panel have been described, but the light-shielding film may be formed outside the panel.

FIG. 6 shows a perspective view of a TFT type LCD in which a light shielding film is provided on a polarizing plate separated from the TFT type LCD.

The non-coherent light is converted from the TFT substrate 2 through the counter substrate 11 into a light beam 16 having the size of the display electrode portion 15 of the counter substrate 11 shown by the dotted line.

When the LCD and the polarizing plate 14 are separated from each other,
A region where the light flux 16 spreads and is transmitted from the polarizing plate 14 becomes a diffusion portion 17 shown by a solid line larger than the display electrode portion 15 shown by a dotted line.

With respect to the light transmitting dot defect, the light-shielding film 13 is provided in accordance with the size of the diffusion portion 17 of the polarizing plate 14.
It is provided on the 4th.

When the light-shielding film is formed apart from the TFT type LCD panel as shown in FIG. 6, even if the position of the light flux changes due to changes in the angle between the panel and the optical components, the incident angle of light, and the refractive index, it becomes easy. The advantage is that it can be shielded from light.

Here, the optical component is not limited to the polarizing plate, but may be a dichroic mirror or a λ / 4 plate.

[0061]

According to the method of relieving a light transmission defect of the present invention, there is no light leakage due to a reduction in the thickness of the periphery of the light-shielding film caused by transfer or printing on the substrate surface, so that the defect portion does not become large especially during magnified projection. Product value is significantly improved.

In particular, when a metal having a light shielding property is deposited on the display electrodes of the substrate or on the alignment film, the shape is the same as that of the OFF dot, which can be an effective means for a product with a large screen such as a high definition.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a liquid crystal panel using a thin metal film of the present invention.

FIG. 2 is a sectional view of a liquid crystal panel using a thick metal film of the present invention.

FIG. 3 is a perspective view of a TFT substrate using the linear metal film of the present invention.

FIG. 4 is a perspective view of a counter substrate using a grid-shaped metal film on the outer surface of the present invention.

FIG. 5 is a perspective view of a counter substrate using a grid-shaped metal film on the inner surface of the present invention.

FIG. 6 is a perspective view of a liquid crystal panel using a metal film for the polarizing plate of the present invention.

FIG. 7 is a cross-sectional view of a liquid crystal panel using a conventional dot defect correction method.

FIG. 8 is a cross-sectional view of a liquid crystal panel with a polarizing plate using a conventional dot defect correction method.

[Explanation of symbols]

 1 display electrode 2 TFT substrate 3 display electrode protective film 4 gate insulating film 5 gate 6 semiconductor film 7 drain 8 liquid crystal 9 alignment film 10 counter electrode 11 counter substrate 12 BM 13 light shielding film 14 polarizing plate 15 display electrode section 16 light flux 17 diffusion Department

Claims (3)

[Claims] 1. A method of relieving a light-transmitting dot defect, which comprises providing a light-shielding metal on a display electrode or an alignment film at a light-transmitting dot defect position of a TFT type LCD substrate. 2. A method of relieving a light-transmitting dot defect, which comprises providing a light-shielding metal on a counter substrate at a light-transmitting dot defect position of a TFT type LCD panel. 3. Relief of a light-transmitting dot defect, characterized in that a metal having a light-shielding property is provided on an optical component such as a color filter or a polarizing plate in a region corresponding to the light-transmitting dot defect apart from the TFT type LCD panel. Method.