JPH04342229A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To suppress the deterioration of a display quality and the conductive phenomenon caused by light irradiation by providing a black matrix consisting of an organic compound material on one transparent substrate of two pieces, and also, providing partially this black matrix. CONSTITUTION:In two pieces of transparent substrates SUB1, SUB2, a black matrix BM consisting of an organic compound material is provided on one transparent substrate, and also, in a seal part SL, the black matrix BM is provided partially. In this case, a reflection to the outside by the display screen of an external light caused by the black matrix can be prevented, therefore, the display quality can be improved. Also, since an irregular reflection in a cell can be prevented, a conductive phenomenon caused by light irradiation, that is, deterioration of a turn-off characteristic of a thin film transistor can be suppressed. Moreover, since the black matrix BM consisting of an organic compound material such as an acryl resin and an epoxy resin, etc., is provided partially in the seal part SL, peeling-off of the substrates SUB1, SUB2 can be suppressed.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a liquid crystal display device.
In particular, the present invention relates to a liquid crystal display device having a black matrix made of an organic material.

0002

2. Description of the Related Art An active matrix liquid crystal display device includes a nonlinear element (switching element) corresponding to each of a plurality of pixel electrodes arranged in a matrix. Theoretically, the liquid crystal in each pixel is constantly driven (duty ratio 1.0), so the active method has better contrast than the so-called simple matrix method, which uses a time-division drive method, especially for color liquid crystals. It is becoming an indispensable technology for display devices. A typical switching element is a thin film transistor (TFT).

[0003] In a liquid crystal display section (liquid crystal display panel), a thin film transistor, a transparent pixel electrode, a protective film for the thin film transistor, and a lower alignment film for setting the orientation of liquid crystal molecules are sequentially provided on a lower transparent glass substrate with a liquid crystal layer as a reference. The lower substrate and the upper substrate, in which a black matrix, a color filter, a protective film for the color filter, a common transparent pixel electrode, and an upper alignment film are sequentially provided on an upper transparent glass substrate, are stacked so that the alignment films face each other. The two substrates are then bonded together using a sealing material placed around the edges of the substrates, and the liquid crystal is sealed between the two substrates. Note that a backlight is arranged on the lower substrate side.

When external light (natural light or general lighting such as an indoor fluorescent light) or backlight shines on the semiconductor layer that forms the channel formation region of a thin film transistor, a conductive phenomenon due to the light irradiation, that is, deterioration of the off-characteristics of the thin film transistor, occurs. happens. A light shielding film is provided to prevent light from entering this semiconductor layer. Conventionally, in order to block light from the lower transparent glass substrate side, Cr was deposited on the lower transparent glass substrate.
Cr is provided between the color filters on the upper transparent glass substrate in order to provide a larger gate electrode and also function as a light shielding film, and to shield light from the upper transparent glass substrate side. A black matrix consisting of the following was set up. These films can prevent external light and backlight light from hitting the semiconductor layer. Also,
Since the black matrix makes the outline of pixels clear, the contrast of the liquid crystal display can be improved. Furthermore, the black matrix is also provided in the sealing part where the sealing material is provided, and prevents the backlight light emitted from the lower transparent glass substrate side from leaking to the display screen side at the sealing part, thereby reducing the deterioration of display quality. It's suppressed.

[0005] Active matrix type liquid crystal display devices using thin film transistors are described, for example, in ``12.5-inch active matrix type color liquid crystal display employing redundant configuration'', Nikkei Electronics, pp. 193-210, December 1986. It is known for being published by Nikkei McGraw-Hill on the 15th of May.

[0006]

[Problems to be Solved by the Invention] However, in the conventional liquid crystal display device as described above, the display screen side (viewing side)
On the inner surface of the upper transparent glass substrate, a black matrix is formed that is made of a reflective metal material such as Cr and occupies a large area of the display screen, so that external light on the display screen side is not reflected to the outside of the display screen. There are problems with reflections, making the screen difficult to see (mirror-like), reducing contrast, and reducing display quality.

[0007] Furthermore, backlight light emitted from the lower transparent glass substrate side is reflected inward by the black matrix formed on the inner surface of the upper transparent glass substrate, and the light impinges on the semiconductor layer that will become the channel formation region of the thin film transistor. ,
There is a problem that a conductive phenomenon occurs due to light irradiation, and the off-characteristics of the thin film transistor deteriorate.

In order to solve these problems, it has been proposed to make the black matrix not from metal but from an organic material such as acrylic resin or epoxy resin to which black dye or pigment is added. However, as mentioned above, when a black matrix made of an organic material is also provided in the seal part for the purpose of preventing light leakage from the backlight, the black matrix itself is fragile and has weak adhesion to other materials. There is a problem that the transparent glass substrate peels off at the matrix location.

The present invention has been made to solve the above problems, and its object is to provide a liquid crystal display device that can suppress deterioration in display quality and conductive phenomena caused by light irradiation.

Another object of the present invention is to provide a liquid crystal display device that can suppress peeling of substrates.

[0011]

[Means for Solving the Problems] In order to achieve the above object, the present invention has two transparent substrates stacked on top of each other with a predetermined gap in between so that the surfaces provided with transparent pixel electrodes face each other, and In a liquid crystal display device in which the two substrates are bonded together by a sealing portion provided around the edges of both substrates and the liquid crystal is sealed between the two substrates, a black matrix made of an organic material is provided on one of the transparent substrates. and the black matrix is partially provided in the seal portion.

0012

[Function] In the liquid crystal display device of the present invention, since the black matrix is formed of an organic material, it is possible to solve the problem that external light is reflected outward on the display screen due to the black matrix and the display quality deteriorates. Can be done. In addition, since the black matrix is made of an organic material, the backlight light emitted from one transparent substrate side is reflected inward by the black matrix formed inside the other transparent substrate, and the channel forming area of the thin film transistor is It is possible to suppress the problem that the semiconductor layer becomes exposed to light, a conductive phenomenon occurs due to the light irradiation, and the off-characteristics of the thin film transistor deteriorate. Further, since a black matrix made of an organic material, which causes peeling of the substrate, is partially provided in the sealing portion, peeling of the substrate can be suppressed.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An active matrix color liquid crystal display device to which the present invention is applied will be described below.

In all the drawings for explaining the liquid crystal display device, parts having the same functions are given the same reference numerals, and repeated explanations thereof will be omitted.

The structure of the present invention will be described below along with an embodiment in which the present invention is applied to an active matrix color liquid crystal display device.

In all the figures for explaining the embodiment, parts having the same functions are given the same reference numerals, and repeated explanations thereof will be omitted.

FIG. 1 shows an active circuit diagram of one embodiment of the present invention.
FIG. 3 is a cross-sectional view of a liquid crystal display portion of a matrix color liquid crystal display device (a view showing a cross section taken along the section line 1-1 in FIG. 2, which will be described later, and a cross section near a seal portion).

FIG. 2 is a plan view showing the periphery of one pixel of the liquid crystal display device, and FIG. 3 is a sectional view taken along the line 3--3 in FIG. Moreover, FIG. 4 (main part plan view) shows a plan view when a plurality of pixels shown in FIG. 2 are arranged.

(Overall cross-sectional structure of display section) As shown in FIG. 1, a thin film transistor TFT and a transparent pixel electrode ITO1 are formed on the lower transparent glass substrate SUB1 side with respect to the liquid crystal LC, and a color electrode is formed on the upper transparent glass substrate SUB2 side. A filter FIL and a light shielding film BM forming a light shielding black matrix pattern are formed. The lower transparent glass substrate SUB1 has a thickness of, for example, about 1.1 [mm]. In addition, transparent glass substrates SUB1 and SUB2
A silicon oxide film SIO formed by dip treatment or the like is provided on both sides of the substrate. Therefore, even if there is a sharp scratch on the surface of the transparent glass substrates SUB1 and SUB2, the sharp scratch can be covered with the silicon oxide film SIO, effectively preventing damage to the scanning signal line GL and color filter FIL. can do.

The center part of FIG. 1 shows a cross section of one pixel, the left side shows a cross section of the left edge of the transparent glass substrates SUB1 and SUB2 where external lead wiring is present, and the right side shows a cross section of the transparent glass substrate SUB1, SUB2. A cross section of the right edge portion of the glass substrates SUB1 and SUB2 where no external lead wiring is present is shown.

The sealing material SL shown on the left and right sides of FIG. 1 is configured to bond the transparent glass substrates SUB1 and SUB2 and seal the liquid crystal LC, and is designed to seal the liquid crystal LC (not shown). Transparent glass substrate except SU
It is formed along the entire periphery of B1 and SUB2. The sealing material SL is made of, for example, epoxy resin.

The common transparent pixel electrode ITO2 on the side of the upper transparent glass substrate SUB2 is connected at least in one place to an external lead wiring formed on the side of the lower transparent glass substrate SUB1 with a silver paste material SIL. This external lead wiring is formed in the same manufacturing process as each of the gate electrode GT, source electrode SD1, and drain electrode SD2.

Orientation films ORI1, ORI2, transparent pixel electrode ITO1, common transparent pixel electrode ITO2, protective film PSV1
, PSV2, and the insulating film GI are each made of a sealing material S.
Formed inside L. The polarizing plates POL1 and POL2 are formed on the outer surfaces of the lower transparent glass substrate SUB1 and the upper transparent glass substrate SUB2, respectively.

The liquid crystal LC is sealed between a lower alignment film ORI1 and an upper alignment film ORI2 that set the orientation of liquid crystal molecules, and is sealed by a seal portion SL.

The lower alignment film ORI1 is formed on the protective film PSV1 on the lower transparent glass substrate SUB1 side.

A light shielding film BM and a color filter FI are provided on the inner surface (liquid crystal LC side) of the upper transparent glass substrate SUB2.
L, protective film PSV2, common transparent pixel electrode ITO2 (CO
M) and an upper alignment film ORI2 are sequentially stacked.

This liquid crystal display device has a lower transparent glass substrate S.
The layers on the UB1 side and the upper transparent glass substrate SUB2 side are formed separately, and then the upper and lower transparent glass substrates SUB1 are formed.
, SUB2 are stacked on top of each other and a liquid crystal LC is sealed between them.

(Light shielding film BM) Upper transparent glass substrate SUB
A light shielding film BM is provided on the 2 side to prevent external light (light from above in FIG. 1) from entering the i-type semiconductor layer AS used as a channel formation region.
The pattern is shown in the hatching. Note that FIG. 7 shows the third conductive film d3 made of ITO film in FIG.
, is a plan view depicting only the color filter FIL and the light shielding film BM. The light shielding film BM is made of an organic material such as acrylic resin or epoxy resin to which black dye, pigment, or carbon is added, for example. As is clear from FIGS. 2, 7, and 1, the light shielding film BM overlaps the gate electrode GT made of a reflective opaque material and has a large area.

Therefore, thin film transistors TFT1, TF
The i-type semiconductor layer AS of T2 is sandwiched between the upper and lower light shielding films BM and the large gate electrode GT,
That part will not be exposed to external light or backlight. The light-shielding film BM is formed around the pixel, as shown by the hatched area in FIG. 7. In other words, the light-shielding film BM is formed in a lattice shape (black matrix), and the effective display area of one pixel is partitioned by this lattice. . Therefore, the outline of each pixel becomes clear due to the light shielding film BM, and the contrast is improved. In other words, the light shielding film BM has two functions: shielding the i-type semiconductor layer AS and serving as a black matrix.

[0030] Also, a portion opposite to the edge portion on the root side in the rubbing direction of the transparent pixel electrode ITO1 (lower right portion in FIG. 2)
is shielded from light by the light-shielding film BM, so even if a domain occurs in the above-mentioned portion, the domain will not be visible and the display characteristics will not deteriorate.

As shown in FIG. 1, the upper transparent glass substrate S
Black matrix BM made of organic material on UB2
is selectively formed, and color filters FIL(R), (G), (B) ((B
) are not shown), and a protective film PSV2, a common transparent pixel electrode ITO2, and an upper alignment film ORI2 are formed along the surface irregularities, respectively. black matrix B
The thickness of M is formed to be thicker than the color filter FIL.

[0032] Since the black matrix BM is formed of an organic material in this way, external light is reflected outward on the display screen due to the black matrix, making it difficult to see the screen (
This can solve the problem of "becoming like a mirror". In addition, the light of the backlight BL irradiated from the lower transparent glass substrate SUB1 side is reflected inward by the black matrix, and the light hits the semiconductor layer AS, which becomes the channel formation region of the thin film transistor TFT, and a conductive phenomenon occurs due to the light irradiation. The problem of deterioration of the off-characteristics of the thin film transistor can be suppressed. Organic materials have higher light transmittance than conventionally used metals, but they are also thicker, for example, by about 1 μm than the color filter FIL (for example, FIL is 1.5 μm thick,
Since the BM is formed to a thickness of approximately 2.5 μm, the light shielding effect is sufficient and the function as a black matrix is sufficiently performed. Furthermore, the black matrix BM, which is thicker than the color filter FIL, improves the selectivity of light, provides clear display, and reduces the influence of driving adjacent pixels.

Furthermore, the height of the black matrix BM section is higher than that of the pixel section in which only the color filter FIL is formed, and the cell gap between the two sections when combined with the lower transparent glass substrate SUB1 is different. Therefore, by setting a regular cell gap in the pixel portion, the liquid crystal does not operate as designed in the black matrix BM portion, which is 1 μm thicker than the color filter FIL. Therefore, by doing this, even if scattered light occurs within the cell, the unoperated liquid crystal L in the black matrix BM section
C acts as a wall against this scattered light and can suppress conductive phenomena caused by light irradiation.

Note that if the light of the backlight BL irradiated from the lower transparent glass substrate SUB1 side leaks at the seal portion SL, the display quality will deteriorate.
A black matrix BM is also provided in L to block light from the backlight BL. However, when the black matrix BM is made using an organic material to which dyes, pigments, carbon, etc. are added, the black matrix B
Since M itself is brittle and has weak adhesion to other materials,
The substrate SUB1 or SUB2 sometimes peeled off at this portion. However, in this embodiment, since the black matrix BM made of an organic material is partially provided in the sealing part SL (a part with the black matrix BM and a part without it), the light shielding effect of the backlight BL is achieved in the part where the black matrix BM is present. This allows the adhesive strength to be maintained in areas where there is no adhesive. Therefore, the problem of peeling off of the transparent glass substrates SUB1 and SUB2 can be suppressed. In addition, black matrix B
In order to prevent light leakage in the part where there is no black matrix BM, an upper transparent glass substrate S corresponding to the part where there is no black matrix BM is used.
A light shielding film is provided on top of the upper polarizing plate POL2 of UB2. However, it does not necessarily have to be provided.

The manufacturing process of this example will be explained. First, a black matrix BM is selectively formed on the upper transparent glass substrate SUB2 on which the silicon oxide film SIO is formed. That is, first, the upper transparent glass substrate SUB2
A dyed base material made of an organic material such as acrylic resin is formed on the surface of the dyed substrate, and a predetermined pattern is formed using photolithography technology, and then dyed. The color of the black matrix BM is preferably black in terms of light shielding. In addition, pigment,
A base material to which carbon or the like is added in advance may be formed on the substrate. In the present invention, since an organic material with higher light transmittance than conventional metals is used as the material of the black matrix BM, the light shielding effect is sufficient (Abs2.5 in the visible light region).
~3.0 or more), the film thickness of the color filter is approximately 1
Form to a thickness of μm.

Next, color filters FIL(R), (G), and (B) are formed between the black matrix BM. That is, first, a dyed base material such as acrylic resin is formed on the surface of the upper transparent glass substrate SUB2, and the dyed base material other than the red filter formation area is removed using photolithography technology. Thereafter, the dyed base material is dyed with a red dye and subjected to a fixing treatment to form a red filter (R). Next, a green filter (G) and a blue filter (G) are sequentially formed by performing similar steps. Of course, the color filter may also be formed by adding pigment to the base material in advance.

Next, a protective film PSV2 is formed by a spin coating method or a roll coating method in accordance with the unevenness of the surfaces of the black matrix BM and color filter FIL, and a common transparent pixel electrode ITO2 and an upper alignment film ORI2 are sequentially formed thereon. Form. The protective film PSV2 is made of, for example, a transparent resin material such as acrylic resin or epoxy resin. Protective film P
The technology to form SV2 according to the unevenness of the surface is as follows.
There are methods based on materials and methods based on process conditions.

In the above manufacturing method, the color filter FIL is formed between the black matrices BM selectively formed on the upper transparent glass substrate SUB2, and the protective film PSV2, the common transparent pixel electrode ITO2, and the upper The alignment film ORI2 was formed along the surface irregularities, but
After each color filter FIL is formed, a black matrix BM may be selectively formed thereon. In this case, there is an advantage that the color filter can be manufactured more easily than the case where the color filter is formed in the recessed portion of the black matrix BM.

Further, in the above manufacturing method, the protective film PSV
Although the protective film PSV2 is formed to match the unevenness of the surface, the protective film PSV2 may be formed flat so as to fill in the unevenness of the surface. Therefore, the common transparent pixel electrode ITO2, the upper alignment film ORI
The second layer is also formed flat on the protective film PSV2. In this case, since the concave portions of the black matrix BM are filled with the protective film PSV2, there is an advantage that the cell gap can be easily controlled even in the case of a large screen.

Furthermore, as shown in FIG. 1, the sealing material SL
Although the protective film PSV2 is provided between the seal material SL and the black matrix BM, the protective film PSV2 may not be provided between the seal material SL and the black matrix BM in the seal portion SL.

(Color Filter FIL) The color filter FIL is constructed by coloring a dyed base material made of a resin material such as acrylic resin with a dye. Color filter F
The IL is formed in a stripe shape at a position facing the pixel (
(Fig. 8) is dyed separately (Fig. 8 depicts only the third conductive film layer d3, the light shielding film BM, and the color filter FIL in Fig. 4, and each of the B, R, and G color filters FIL is shown in Fig. 8).
are hatched at 45°, 135°, and cross-hatched, respectively). As shown in FIG. 7, the color filter FIL is formed in a large size so as to cover the entire transparent pixel electrode ITO1, and the light shielding film BM is formed on the periphery of the transparent pixel electrode ITO1 so as to overlap with the edge portions of the color filter FIL and the transparent pixel electrode ITO1. It is formed more inward.

Color filter FIL can be formed as follows. First, a dyed base material is formed on the surface of the upper transparent glass substrate SUB2, and the dyed base material other than the red filter forming area is removed using photolithography technology. Thereafter, the dyed base material is dyed with a red dye and subjected to a fixing treatment to form a red filter R. Next, a green filter G and a blue filter B are sequentially formed by performing similar steps.

(Protective film PSV2) The protective film PSV2 is made of dyes that dye the color filter FIL in different colors.
This is provided to prevent leakage to C. The protective film PSV2 is made of a transparent resin material such as acrylic resin or epoxy resin.

(Pixel Arrangement) As shown in FIG. 2, each pixel is connected to two adjacent scanning signal lines (gate signal lines or horizontal signal lines) GL and two adjacent video signal lines (drain signal lines or horizontal signal lines). (vertical signal line) DL (in the area surrounded by four signal lines). Each pixel includes a thin film transistor TFT, a transparent pixel electrode ITO1, and a storage capacitor element Cadd. The scanning signal lines GL extend in the column direction, and a plurality of scanning signal lines GL are arranged in the row direction. The video signal lines DL extend in the row direction, and a plurality of video signal lines DL are arranged in the column direction.

(Thin Film Transistor TFT) The thin film transistor TFT operates such that when a positive bias is applied to the gate electrode GT, the channel resistance between the source and drain becomes small, and when the bias is reduced to zero, the channel resistance becomes large.

The thin film transistor TFT of each pixel is divided into two (plurality) within the pixel, and is composed of thin film transistors (divided thin film transistors) TFT1 and TFT2. Each of the thin film transistors TFT1 and TFT2 has substantially the same size (channel length and channel width are the same). Each of the divided thin film transistors TFT1 and TFT2 mainly consists of a gate electrode GT, a gate insulating film GI, and an i-type amorphous silicon (S
i) an i-type semiconductor layer AS consisting of a pair of source electrodes SD;
1. Consists of a drain electrode SD2. Note that the source and drain are originally determined by the bias polarity between them, and in the circuit of this liquid crystal display device, the polarity is reversed during operation, so it should be understood that the source and drain are interchanged during operation. However, in the following description, for convenience, one side is fixed as a source and the other side is fixed as a drain.

(Gate electrode GT) The gate electrode GT is shown in FIG.
As shown in detail in (a plan view depicting only the first conductive film g1, second conductive film g2, and i-type semiconductor layer AS in FIG. 2),
It has a shape that projects vertically (upward in FIGS. 2 and 5) from the scanning signal line GL (branched into a T-shape). The gate electrode GT is configured to protrude to the respective formation regions of the thin film transistors TFT1 and TFT2. Thin film transistor TFT1, T
Each gate electrode GT of FT2 is configured integrally (as a common gate electrode) and is formed continuously to the scanning signal line GL. The gate electrode GT is formed of a single-layer first conductive film g1 so as not to form a large step in the formation region of the thin film transistor TFT. The first conductive film g1 is formed using, for example, a chromium (Cr) film formed by sputtering, and has a thickness of about 1000 [Å].

As shown in FIGS. 2, 1 and 5, this gate electrode GT is formed to be larger than the i-type semiconductor layer AS so as to completely cover it (as viewed from below). Therefore, when a backlight BL such as a fluorescent lamp is attached below the lower transparent glass substrate SUB1, the gate electrode GT made of opaque chrome forms a shadow, and the backlight light does not shine on the i-type semiconductor layer AS. , a conductive phenomenon caused by light irradiation, that is, deterioration of the off-characteristics of the thin film transistor TFT becomes less likely to occur. Note that the original size of the gate electrode GT is the minimum required size to span between the source electrode SD1 and the drain electrode SD2 (including the alignment margin between the gate electrode GT, the source electrode SD1, and the drain electrode SD2). ), and its depth length that determines the channel width W is determined by the ratio of the distance (channel length) L between the source electrode SD1 and drain electrode SD2, that is, the factor W/L that determines the mutual conductance gm. It depends on what you do.

Gate electrode GT in this liquid crystal display device
Of course, the size is made larger than the original size mentioned above.

Note that considering only the gate and light shielding functions of the gate electrode GT, the gate electrode GT and the scanning signal line GL may be integrally formed in a single layer, and in this case, silicon is used as the opaque conductive material. Aluminum (Al), pure aluminum, palladium (Pd) containing
Aluminum, etc. containing can be selected.

(Scanning signal line GL) The scanning signal line GL is the first
Conductive film g1 and second conductive film g2 provided above it
It is composed of a composite membrane consisting of. This scanning signal line GL
The first conductive film g1 is formed in the same manufacturing process as the first conductive film g1 of the gate electrode GT, and is integrally configured. The second conductive film g2 is formed using, for example, an aluminum film formed by sputtering, and has a thickness of about 1000 to 5500 [Å]. The second conductive film g2 is configured to reduce the resistance value of the scanning signal line GL and increase the signal transmission speed (improve the writing characteristics of pixel information).

Furthermore, the width of the second conductive film g2 of the scanning signal line GL is made smaller than the width of the first conductive film g1. That is, the side wall of the scanning signal line GL has a gradual step shape.

(Insulating Film GI) The insulating film GI is used as a gate insulating film for each of the thin film transistors TFT1 and TFT2. The insulating film GI is formed on the gate electrode GT and the scanning signal line GL. For example, a silicon nitride film formed by plasma CVD is used as the insulating film GI,
It is formed with a film thickness of about 3000 [Å].

(I-Type Semiconductor Layer AS) As shown in FIG. 5, the i-type semiconductor layer AS is used as a channel forming region for each of the thin film transistors TFT1 and TFT2 which are divided into a plurality of parts. The i-type semiconductor layer AS is formed of an amorphous silicon film or a polycrystalline silicon film, and is formed to have a thickness of about 1800 [Å].

This i-type semiconductor layer AS was formed by the same plasma CVD process following the formation of the insulating film GI to be used as a gate insulating film made of Si3N4 by changing the composition of the supplied gas.
The plasma CVD device is formed without being exposed to the outside from the plasma CVD device. Further, a P-doped N(+) type semiconductor layer d0 (FIG. 1) for ohmic contact is similarly formed continuously to a thickness of about 400 [Å]. Thereafter, the lower transparent glass substrate SUB1 was taken out from the CVD apparatus, and the N(+) type semiconductor layer d0 and the i-type semiconductor layer AS were separated by photo processing technology as shown in FIGS. 2, 1, and 5. Patterned into islands.

As shown in detail in FIGS. 2 and 5, the i-type semiconductor layer AS is also provided between the scanning signal line GL and the video signal line DL at an intersection (crossover section). The i-type semiconductor layer AS at this intersection is configured to reduce short circuits between the scanning signal line GL and the video signal line DL at the intersection.

(Source electrode SD1, drain electrode SD2
) Thin film transistors TFT1 and TFT divided into multiple parts
2, each of the source electrode SD1 and drain electrode SD2
As shown in detail in FIGS. 2, 1 and 6 (a plan view depicting only the first to third conductive films d1 to d3 in FIG. 2),
They are provided separately on the i-type semiconductor layer AS.

[0058] The source electrode SD1 and the drain electrode SD2 each include a first conductive film d1, a second conductive film d2, and a third conductive film d from the lower layer side in contact with the N(+) type semiconductor layer d0.
3 are stacked one on top of the other in sequence. Source electrode SD
The first conductive film d1, the second conductive film d2, and the third conductive film d3 of No. 1 are formed in the same manufacturing process as the first conductive film d1, the second conductive film d2, and the third conductive film d3 of the drain electrode SD2. .

The first conductive film d1 is a chromium film formed by sputtering, and is formed with a thickness of 500 to 1000 Å (in this liquid crystal display device, the thickness is about 600 Å). If the chromium film is formed thickly, the stress increases, so the chromium film is formed to a thickness not exceeding about 2000 [Å]. The chromium film has good contact with the N(+) type semiconductor layer d0. The chromium film constitutes a so-called barrier layer that prevents aluminum of the second conductive film d2, which will be described later, from diffusing into the N(+) type semiconductor layer d0. First conductive film d1
In addition to chromium film, high melting point metals (Mo, Ti, T
a, W) film, high melting point metal silicide (MoSi2, Ti
It may also be formed using a Si2, TaSi2, WSi2) film.

After patterning the first conductive film d1 by photo processing, using the same photo processing mask or patterning the first conductive film d1,
Using the conductive film d1 as a mask, the N(+) type semiconductor layer d0 is removed. That is, the portions of the N(+) type semiconductor layer d0 remaining on the i-type semiconductor layer AS other than the first conductive film d1 are removed by self-alignment. At this time, since the N(+) type semiconductor layer d0 is etched so that its entire thickness is removed, the i-type semiconductor layer AS is also slightly etched on its surface, but the extent is controlled by the etching time. do it.

Thereafter, the second conductive film d2 is formed by aluminum sputtering to a thickness of 3000 to 5500 [Å] (
In this liquid crystal display device, the film thickness is approximately 3500 [Å]. Aluminum film has less stress than chrome film,
It is possible to form a thick film, and the source electrode SD1,
It is configured to reduce the resistance values of the drain electrode SD2 and the video signal line DL. The second conductive film d2 may be formed of an aluminum film containing silicon or copper (Cu) as an additive in addition to the aluminum film.

After patterning the second conductive film d2 using a photoprocessing technique, a third conductive film d3 is formed. This third conductive film d3 is a transparent conductive film (I) formed by sputtering.
ndium-Tin-Oxide ITO: Nesa film)
It is formed with a film thickness of 1000 to 2000 [Å] (in this liquid crystal display device, the film thickness is about 1200 [Å]). This third conductive film d3 constitutes the source electrode SD1, the drain electrode SD2, and the video signal line DL, and
A transparent pixel electrode ITO1 is configured.

Each of the first conductive film d1 of the source electrode SD1 and the first conductive film d1 of the drain electrode SD2 is located inward (
(into the channel region). That is, the first conductive film d1 in these parts is the second conductive film d2,
The structure is such that the channel length L of the thin film transistor TFT can be defined independently of the third conductive film d3.

Source electrode SD1 is transparent pixel electrode ITO1
It is connected to the. The source electrode SD1 has a stepped shape of the i-type semiconductor layer AS (corresponds to the sum of the thickness of the first conductive film g1, the thickness of the N(+)-type semiconductor layer d0, and the thickness of the i-type semiconductor layer AS). It is constructed along the steps (steps). Specifically, the source electrode SD1 includes a first conductive film d1 formed along the step shape of the i-type semiconductor layer AS, and a first conductive film d1 formed along the step shape of the i-type semiconductor layer AS.
In contrast, a transparent pixel electrode ITO1 is formed on the upper part of the conductive film d1.
a second conductive film d formed with a smaller size on the side connected to
2, and the first conductive film d1 exposed from the second conductive film d2.
and a third conductive film d3 connected to the third conductive film d3. The second conductive film d2 of the source electrode SD1 cannot overcome the step shape of the i-type semiconductor layer AS because the chromium film of the first conductive film d1 cannot be formed thickly due to increased stress, so the second conductive film d2 of the source electrode SD1 can overcome this i-type semiconductor layer AS. It is configured for. In other words, step coverage is improved by forming the second conductive film d2 thickly. Since the second conductive film d2 can be formed thickly, the resistance value of the source electrode SD1 (drain electrode SD2
(The same applies to the video signal line DL). Since the third conductive film d3 cannot overcome the step shape caused by the i-type semiconductor layer AS of the second conductive film d2, by reducing the size of the second conductive film d2,
It is configured to be connected to the exposed first conductive film d1. The first conductive film d1 and the third conductive film d3 not only have good adhesion, but also have a small step shape at the connection between them, so it is possible to reliably connect the source electrode SD1 and the transparent pixel electrode ITO1. can.

(Transparent pixel electrode ITO1) Transparent pixel electrode I
TO1 constitutes one of the pixel electrodes of the liquid crystal display section.

The transparent pixel electrode ITO1 is connected to the source electrode SD1 of the thin film transistor TFT1 and the thin film transistor T
It is connected to the source electrode SD1 of FT2. Therefore, when a defect occurs in one of the thin film transistors TFT1 and TFT2, for example, the thin film transistor TFT1, the thin film transistor TFT1 and the video signal line DL are separated by laser light or the like during the manufacturing process, and the thin film transistor TFT1 and the transparent pixel electrode ITO1 are separated. If these are separated, point defects and line defects will not occur, and since defects will rarely occur in the two thin film transistors TFT1 and TFT2 at the same time, the probability of point defects occurring can be extremely reduced.

(Protective film PSV1) Thin film transistor TF
A protective film PSV1 is provided on the T and transparent pixel electrode ITO1. The protective film PSV1 is formed mainly to protect the thin film transistor TFT from moisture etc.
Use a material that is highly transparent and has good moisture resistance. The protective film PSV1 is formed of, for example, a silicon oxide film or a silicon nitride film formed using a plasma CVD apparatus, and has a film thickness of 800 nm.
It is formed with a film thickness of about 0 [Å].

(Common Transparent Pixel Electrode ITO2) The common transparent pixel electrode ITO2 faces the transparent pixel electrode ITO1 provided for each pixel on the lower transparent glass substrate SUB1 side, and the optical state of the liquid crystal LC is determined by each pixel electrode ITO1. It changes in response to the potential difference (electric field) between the ITO2 and the common transparent pixel electrode ITO2. The configuration is such that a common voltage Vcom is applied to this common transparent pixel electrode ITO2. The common voltage Vcom is a low level drive voltage Vdmin and a high level drive voltage Vdm applied to the video signal line DL.
It is the intermediate potential between ax and ax.

(Equivalent circuit of entire display device) FIG. 9 shows a wiring diagram of the equivalent circuit of the display matrix section and its peripheral circuits. Although this figure is a circuit diagram, it is drawn to correspond to the actual geometrical arrangement. AR is a matrix array in which a plurality of pixels are arranged two-dimensionally.

In the figure, X means a video signal line DL, and subscripts G, B, and R are added corresponding to green, blue, and red pixels, respectively. Y means the scanning signal line GL, and the subscripts 1, 2, 3, . . . , end are added according to the order of scanning timing.

Video signal lines X (subscript omitted) are arranged alternately on the upper side (
(or odd number) video signal drive circuit He, and is connected to the lower (or even number) video signal drive circuit Ho.

[0072] The SUP uses a power supply circuit to obtain multiple divided and stabilized voltage sources from one voltage source and information for a CRT (cathode ray tube) from a host (upper processing unit) to a TFT liquid crystal display device. This is a circuit that includes a circuit that exchanges information for use.

(Structure of storage capacitor element Cadd) The transparent pixel electrode ITO1 is connected to the adjacent scanning signal line GL at the end opposite to the end connected to the thin film transistor TFT.
It is formed so that it overlaps with the As is clear from FIG. 3, this superposition is achieved by using a storage capacitance element (electrostatic capacitance element) Cadd in which the transparent pixel electrode ITO1 is used as one electrode PL2 and the adjacent scanning signal line GL is used as the other electrode PL1.
Configure. The dielectric film of this storage capacitor element Cadd is made of the same layer as the insulating film GI used as the gate insulating film of the thin film transistor TFT.

As is clear from FIG. 5, the storage capacitance element Cadd is formed in the widened portion of the first conductive film g1 of the scanning signal line GL. Note that the first conductive film g1 at the portion intersecting with the video signal line DL is made thin in order to reduce the probability of short circuit with the video signal line DL.

Similar to the source electrode SD1, the transparent pixel electrode ITO1 is disconnected when going over the step shape in a part between the transparent pixel electrode ITO1 and the electrode PL1 which are overlapped to form the storage capacitor element Cadd. An island region made up of the first conductive film d1 and the second conductive film d2 is provided to prevent this. This island region is configured to be as small as possible so as not to reduce the area (aperture ratio) of the transparent pixel electrode ITO1. (Equivalent circuit of storage capacitor element Cadd and its operation) Figure 1 shows the equivalent circuit of the pixel shown in Figure 2.
0. In FIG. 10, Cgs is a parasitic capacitance formed between the gate electrode GT and source electrode SD1 of the thin film transistor TFT. The dielectric film of the parasitic capacitance Cgs is an insulating film GI. Cpix is transparent pixel electrode ITO1
(PIX) and the common transparent pixel electrode ITO2 (COM). The dielectric film of the liquid crystal capacitor Cpix includes the liquid crystal LC, the protective film PSV1, and the alignment film OR.
I1 and ORI2. Vlc is a midpoint potential.

The storage capacitor element Cadd functions to reduce the influence of the gate potential change ΔVg on the midpoint potential (pixel electrode potential) Vlc when the thin film transistor TFT switches. This situation can be expressed as the following formula.

ΔVlc={Cgs/(Cgs+Cadd
+Cpix)}×ΔVg Here, ΔVlc represents the change in the midpoint potential due to ΔVg. This change ΔVlc causes a DC component applied to the liquid crystal LC, but the holding capacitance C
The larger add is, the smaller its value can be. Furthermore, the storage capacitor element Cadd also has the effect of lengthening the discharge time, so that image information is stored for a long time after the thin film transistor TFT is turned off. Reducing the DC component applied to the liquid crystal LC can improve the life of the liquid crystal LC and reduce so-called burn-in, in which the previous image remains when switching between liquid crystal display screens.

As described above, since the gate electrode GT is made large enough to completely cover the i-type semiconductor layer AS, the overlapping area with the source electrode SD1 and drain electrode SD2 increases, and therefore the parasitic capacitance Cgs increases. , the opposite effect occurs in that the midpoint potential Vlc becomes more susceptible to the influence of the gate (scanning) signal Vg. However, by providing the storage capacitor element Cadd, this disadvantage can also be eliminated.

From the pixel write characteristics, the storage capacitance of the storage capacitor element Cadd is 4 to 8 with respect to the liquid crystal capacitance Cpix.
(4・Cpix<Cadd<8・Cpix), 8 to 32 times the parasitic capacitance Cgs (8・Cgs<Cadd<
Set to a value of about 32 Cgs).

(How to connect storage capacitor element Cadd electrode wire) The first-stage scanning signal line GL (Y0), which is used only as a storage capacitor electrode line, is connected to the common transparent pixel electrode ITO2 (Vcom) as shown in FIG. Connecting. As shown in FIG. 1, the common transparent pixel electrode ITO2 is connected to an external wiring at the peripheral edge of the liquid crystal display device by means of a silver paste material SL. Furthermore, a part of the conductive film (g1 and g2) of this external wiring is formed in the same manufacturing process as the scanning signal line GL. As a result, the storage capacitor electrode line GL at the final stage can be easily connected to the common transparent pixel electrode ITO2.

The holding capacitor electrode line Y0 at the first stage is connected to the scanning signal line Yend at the final stage, or connected to a DC potential point (AC grounding point) other than Vcom, or one additional scanning pulse Y0 is applied from the vertical scanning path circuit V. You may also connect it so that it is received.

[0082] As described above, the invention made by the present inventor is as follows.
Although the present invention has been specifically described based on the above-mentioned embodiments, it goes without saying that the present invention is not limited to the above-mentioned embodiments, and can be modified in various ways without departing from the gist thereof.

For example, since the color filter FIL and the black matrix BM can use the same organic material, the black matrix BM can be used for each color filter FI
It may be formed by overlapping three layers of L(R), (G), and (B). In this case, the black matrix BM may be dyed with all the red, green, and blue dyes of each color filter FIL.

Further, the pattern of the black matrix BM partially provided in the seal part SL is not limited to the pattern shown in FIG. For example, a striped pattern may be used.

In the above embodiment, an inverted staggered structure in which gate electrode formation → gate insulating film formation → semiconductor layer formation → source/drain electrode formation was shown, but a staggered structure in which the vertical relationship or the order of formation is reversed is also possible. The present invention is effective.

[0086]

As described above, in the liquid crystal display device of the present invention, it is possible to prevent external light caused by the black matrix from being reflected outward on the display screen, thereby improving display quality. Further, since diffuse reflection within the cell can be prevented, it is possible to suppress the problem of conductive phenomena caused by light irradiation, that is, deterioration of the off-characteristics of thin film transistors. Furthermore, since a black matrix made of an organic material is partially provided in the sealing portion, peeling of the substrate can be suppressed.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a liquid crystal display portion of an active matrix color liquid crystal display device according to an embodiment of the present invention (a cross-sectional view showing a cross section taken along section line 1-1 in FIG. 2 and a cross section near a seal portion, which will be described later). It is.

FIG. 2 is a plan view of a main part showing one pixel of a liquid crystal display section.

FIG. 3 is a sectional view taken along section line 3-3 in FIG. 2;

4 is a plan view of a main part of a liquid crystal display section in which a plurality of pixels shown in FIG. 2 are arranged; FIG.

FIG. 5 is a plan view depicting only a predetermined layer of the pixel shown in FIG. 2;

FIG. 6 is a plan view depicting only a predetermined layer of the pixel shown in FIG. 2;

FIG. 7 is a plan view depicting only a predetermined layer of the pixel shown in FIG. 2;

8 is a plan view of main parts depicting only a pixel electrode layer, a light shielding film, and a color filter layer shown in FIG. 4; FIG.

FIG. 9 is an equivalent circuit diagram of a liquid crystal display section.

10 is an equivalent circuit diagram of the pixel shown in FIG. 2. FIG.

[Explanation of symbols]

SUB1...lower transparent glass substrate, TFT...thin film transistor, AS...i-type semiconductor layer, ITO1...transparent pixel electrode,
PSV1...TFT protective film, ORI1...lower alignment film, L
C...Liquid crystal, SUB2...Upper transparent glass substrate, BM...Black matrix, FIL...Color filter, PSV2...
Color filter protective film, ITO2...common transparent pixel electrode, ORI2...upper alignment film, SL...seal part, BL...backlight.

Claims (1)

[Claims] 1. Two transparent substrates are placed one on top of the other with a predetermined gap in between so that the surfaces provided with transparent pixel electrodes face each other, and the two substrates are bonded together by a seal portion provided around the edges of the two substrates. In addition, in the liquid crystal display device in which the liquid crystal is sealed between the two substrates, a black matrix made of an organic material is provided on one of the transparent substrates, and the black matrix is partially provided in the sealing portion. A liquid crystal display device characterized by: