JPH1090719A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid display device of a selective reflection type, etc., which has high light utilization efficiency and also has a high color level and a high contrast ratio and is free of a spot defect, etc. SOLUTION: An inter-layer insulating film 17 provided covering a TFT (thin film transistor) is formed of a black insulating material like black pigment dispersed resist, and on this inter-layer insulating film 17, a pixel electrode 19 formed of a black conductive material is provided and brought into direct contact with the electrode of the TFT at the part of a contact hole 18. Further, an inter-layer insulating film 17 consisting of, preferably, a black insulating material is provided and a pixel electrode 20 in two-layered structure consisting of a lower layer of black-lead dispersed photoresist, etc., and an upper layer of an ITO film, etc., is provided thereupon. Then the lower layer 20a fills the contact hole 18 of the inter-layer insulating film 17 to flatten it, and comes into contact with the electrode of the TFT.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a liquid crystal display device.

[0002]

2. Description of the Related Art Conventionally, in a display device of an information device in which portability is regarded as important, it is desired that the power consumption be low because of the necessity of driving a battery. As a liquid crystal display (LC
D) has been put to practical use, and among others, reflective liquid crystal display devices that do not require a backlight have become widespread. ECB (Electrically Controlled Birefring)
ence), GH (GuestHost), TN (Twisted)
Nematic) There is a liquid crystal system, a selective reflection liquid crystal system, etc., but from the viewpoint of light use efficiency, G which does not require a polarizing plate is used.
Display devices of the H type and the selective reflective liquid crystal type are most desirable.

In these systems, unlike ordinary transmission-type or reflection-type liquid crystal display systems, light absorption characteristics in a semiconductor array portion such as a TFT (thin film transistor) for driving a liquid crystal are important for display. There is. Therefore, in these types of display devices, a semiconductor array substrate having a pixel-mounted structure with high light use efficiency is used in order to improve light absorption characteristics in the array section.

That is, as shown in FIG.
Is disposed on the uppermost layer of the TFT 2, and the pixel electrode 1 is connected to the TF through a contact hole 4 provided in the interlayer insulating film 3.
In an overlaid pixel structure in contact with the source / drain electrode 5 of T2, the interlayer insulating film 3 may be formed of an insulating material having high light absorption (high black level) and capable of flattening the unevenness of the TFT2. It is considered. And
A light absorbing layer is formed by two layers of the black interlayer insulating film 3 and the pixel electrode 1 made of a transparent conductive material such as ITO, and the light transmitted through the liquid crystal layer is used by the light absorbing layer during display. Black is displayed by absorbing light, and white is displayed by light reflected by the liquid crystal layer. In the drawings, reference numeral 6 denotes a glass substrate, 7 denotes a gate electrode, 8 denotes a gate insulating film, and 9 denotes a semiconductor protective film.

A TFT having such a pixel-placed structure
In the array substrate, when a portion other than the contact hole 4 is covered with a black interlayer insulating film 3 having high light absorption, the aperture ratio is improved, and the deterioration of the characteristics of the TFT 2 and the like due to light leak is prevented, and the signal line is prevented. And the effect of preventing a short circuit with the gate line.

[0006]

However, since the transparent conductive film of ITO or the like is arranged as the pixel electrode 1 on the uppermost layer of the TFT 2 array, not only the reflection due to the surface reflection of the transparent conductive film occurs, but also the reflection occurs. Coloring due to interference occurs depending on the film thickness. Therefore, even if the interlayer insulating film 3 is made of a material having a high light absorbing property, reflection and coloring are inevitable, and a TFT array substrate with a high black level cannot be obtained. Further, there is a problem that a light scattering component becomes large in the contact hole 4 part, which deteriorates light absorption efficiency and makes black display insufficient.

In the formation of the pixel electrode 1 by ITO or the like, a film is formed mainly by a sputtering method.
In the sputtering method, disconnection at the edge of the contact hole 4 and a change in film thickness at the side surface are likely to occur due to poor step coverage. In addition, due to the mechanical fragility and the high electrical resistivity that are inherent properties of ITO, cracks at the edge portion and an increase in resistance at the portion where the film thickness decreases are likely to occur. There is a problem that a point defect occurs and a large variation in pixel resistance occurs.

Further, the pixel electrode 1 is transparent, and the underlying source / drain electrode 5 is exposed through the transparent pixel electrode 1 in the contact hole 4 portion.
There has been a problem that the color tone and reflection of the metal as the electrode material appear, and the light absorbency of the pixel portion decreases. Further, the contact hole 4 becomes a step on the pixel, and the gap of the liquid crystal cell greatly fluctuates at this portion, so that the aperture ratio of the pixel is reduced and the contact hole 4 is filled when the liquid crystal is injected.
There was a possibility that air bubbles would remain in the portion and the quality would deteriorate.

[0009] Further, in a semiconductor array substrate of a liquid crystal display device in which reflection is performed by a pixel electrode, a pixel-placed structure is employed in order to improve light use efficiency.

That is, in a TFT array substrate of a GH type reflection type liquid crystal display device, an interlayer insulating film made of a transparent insulating material such as acrylic resin capable of flattening unevenness of a lower layer and a metal such as A1. A light reflection layer is configured by two layers with the pixel electrode, and at the time of display, white light is displayed by reflecting light transmitted through the liquid crystal layer by the light reflection layer, and light transmitted through the liquid crystal layer is used for display. The colors (cyan, magenta, yellow) contained in the liquid crystal layer are displayed.

In addition, the T-mode transmission type liquid crystal display device has a T
The FT array substrate has a structure in which a pixel electrode made of a transparent conductive material such as ITO is arranged on an interlayer insulating film made of a transparent insulating material such as an acrylic resin capable of flattening lower unevenness. I have. However, these TFs
Also on the T array substrate, the pixel electrode and the TFT source
Since a large step is generated in the contact portion with the drain electrode, the material forming the pixel electrode is likely to be disconnected, and there is a possibility that a contact failure may occur. Also,
Particularly, in the reflective display method, there is a problem that the light use efficiency is reduced in the contact portion.

The present invention has been made to solve these problems, and it is a selective reflection type liquid crystal having a high light use efficiency, a high color level and a high contrast ratio and a high quality without point defects. It is an object to provide a display device.

[0013]

According to the present invention, there is provided a liquid crystal display device comprising: an insulating first substrate; a pixel electrode formed on the substrate to which a voltage is applied; A second substrate capable of applying an electric field therebetween, a liquid crystal layer interposed between the first and second substrates, and the pixel electrode as viewed from a direction in which the first and second substrates are overlapped and seen through. In a liquid crystal display device provided with an opaque interlayer insulating film formed so as to be overlapped and adjacent, the interlayer insulating film is formed of an insulating material that absorbs light in a specific wavelength region, and the pixel electrode is formed of the insulating material. And a conductive material that absorbs light in the same or a different wavelength region from the above, and emits a different color in the direction from the interlayer insulating film and the pixel electrode.

According to a second aspect of the present invention, there is provided a liquid crystal display device, comprising: an insulating first substrate; a pixel electrode formed on the substrate, to which a voltage is applied; A second substrate capable of applying an electric field between the electrodes, a liquid crystal layer interposed between the first and second substrates, and the pixel electrode as viewed from a direction in which the first and second substrates are overlapped and seen through In a liquid crystal display device having an opaque interlayer insulating film formed adjacent to and overlying the pixel electrode, the pixel electrode has a structure in which two layers made of different conductive materials are stacked, and The contact hole of the interlayer insulating film is buried and flattened by the conductive layer, and the conductive layer is brought into contact with a lower conductive layer.

In the first aspect of the present invention, there are various kinds of insulating materials that absorb light in a specific wavelength region, that is, have coloring properties, which constitute the interlayer insulating film. And a pigment-dispersed resist used as a black matrix (BM) of a TFT or the like. Pigment-dispersed resists such as black have good insulation properties, are excellent in dielectric properties and coloring properties, and, because they are resists, can be patterned only by a photo process. In order to form an interlayer insulating film using such a pigment-dispersed resist, it is desirable to form the film using a method such as spin coating, which can easily make unevenness flat and increase the thickness.

Further, as a conductive material that absorbs light in a specific wavelength region constituting the pixel electrode, that is, has a coloring property, for example, graphite excellent in light absorption in a visible region can be mentioned. Graphite is a conductive material having low surface reflection characteristics and excellent electrical conductivity, and can be formed by a sputtering method or a vacuum evaporation method. But,
Since the mechanical strength of the film is insufficient and the film may be peeled off, a polyimide film or a polyvinyl alcohol (PVA) film used as a liquid crystal alignment film is formed on the graphite film by a spin coating method. Peeling can be prevented. In addition, in order to form a polyimide film on the pixel electrode made of graphite, the polyimide film is dropped and allowed to sufficiently spread on the array during spin coating, and the concave portion (contact hole portion) of the graphite film is filled with polyimide. It is desirable that the edge be sufficiently covered with polyimide.

Further, as the coloring conductive material constituting the pixel electrode, metal compounds such as metal oxides, nitrides, carbides, and organic materials can be used. For example, Sr
TiO ₃ -δ is a black composite oxide having semi-conductivity and can be used as a black conductive material. In addition, there are metal composite oxides such as tungsten bronze (M _X WO ₃ ) that have conductivity and can have various colors depending on the composition, and these are used as electrode materials according to the application. Is possible.

Further, a pixel electrode can be constituted by a metal / metal oxide. That is, the surface of the metal electrode can be covered with an extremely thin layer of an oxide using an anodizing method and blackened while the electrode is formed of a metal. Examples of such a metal / metal oxide film include a two-layer or multilayer film of Cr / CrO _X. Cr / Cr
2-layer or multilayer film of O _X, the light-absorbing (black level) is very high, it is also used as a BM material such color filters. In general, Cr oxide is an insulator, and it is better that the thickness of the Cr oxide is thinner in order to increase the voltage applied to the liquid crystal, but a certain thickness is required to increase the black level. It will be a conflicting relationship. Therefore,
The thickness of the Cr oxide film in the Cr / CrO _X multilayer film is as follows:
It is appropriately set according to the driving voltage of the liquid crystal to be used and the characteristics of a semiconductor such as a TFT for driving the liquid crystal. Furthermore, among the CrO _X, but such CrO or Cr ₂ O ₃ is stable insulators, by shifting slightly composition from stoichiometry, the conductivity is known to be expressed, the Cr electrode By adding a reducing agent or an oxidizing agent during anodization,
A Cr oxide film having a high black level and good conductivity can also be formed.

Further, a dispersant is dispersed in a functional matrix as a conductive material for forming a pixel electrode,
Light absorption of a specific wavelength region, that is, coloring and conductivity,
Materials provided in at least one of the matrix and the dispersant can be used. At this time, the functional matrix and the dispersant may be provided with other functions. Examples of such a colored conductive material include, for example, a conductive material (graphite-dispersed photoresist) in which graphite is dispersed in an acrylic photoresist. This is because graphite, which is a dispersant, has both light absorbing and conductive functions, and the acrylic matrix, which is a functional matrix, has graphite holding properties and is used to fill contact holes and flatten them. It has fluidity during film formation and pixel moldability. As a functional matrix, instead of acrylic photoresist,
A polyimide-based photoresist can also be used.

The formation of a pixel electrode using such a conductive material is performed as follows. That is, an excessive amount of graphite-dispersed photoresist is left on the interlayer insulating film made of the insulating material having coloring properties and having a contact hole opened at a predetermined position, and the resist is placed in the contact hole. After sufficient infiltration and filling to fill the recess, film formation is performed by a spin coating method, and then a pixel electrode is formed by a normal photo etching process (PEP).

According to the first aspect of the present invention, the interlayer insulating film such as the semiconductor array substrate is made of an insulating material having a coloring property such as black and provided on the interlayer insulating film. Since the pixel electrode is also made of a conductive material having coloring properties such as black, a high color level without reflection or coloring can be obtained. At this time, the pixel electrode is made of a conductive material having a synergistic color effect such as the same color or a complementary color with respect to the color of the interlayer insulating film, so that a liquid crystal display having a pixel with a higher color level is formed. A device can be obtained. For example, when green display is important for visual protection, the interlayer insulating film and the pixel electrode are
A pixel with a high green level can be obtained by using an insulating material and a conductive material each colored green.

Further, the adoption of the pixel-placed structure improves the aperture ratio. Therefore, by using such a semiconductor array substrate, it is possible to obtain a reflection type liquid crystal display device having high light use efficiency, high color level and high contrast, and high quality.

Furthermore, in the first invention, when a colored conductive material in which a dispersant is dispersed in a functional matrix is used as a constituent material of the pixel electrode, the electrode can be formed only by a photo process. No etching or resist stripping process is required. In addition, since the colored conductive material sufficiently penetrates and fills the contact holes and fills the recesses to flatten, the occurrence of step breakage and defects in the contact portion is prevented, and the pixel electrode and the lower layer are not formed. There is no risk of contact failure with the semiconductor electrode. Further, since the contact hole is effectively used for display, the shape and size of the contact hole can be arbitrarily set, and the manufacture is easy.

Various functions can be added to such an interlayer insulating film and an electrode material. For example, in the case of coloring in black, the pixel electrode is formed of an acrylic graphite-dispersed photoresist, and when an acrylic pigment-dispersed resist is used as an insulating material for forming the interlayer insulating film, the interlayer insulating film is used. Since the compatibility between the film and the pixel electrode is good and the coefficients of thermal expansion are the same, the film can be formed without imposing a load on both layers, and the occurrence of cracks and the like can be prevented. In addition, since these constituent materials are organic materials, they have good compatibility with liquid crystal, and it is possible to eliminate the need to provide a protective film for protecting the liquid crystal layer.

Further, when a conductive material in which graphite is dispersed in a polyimide-based photoresist as a functional matrix is used as a constituent material of the pixel electrode, a liquid crystal material such as a TN liquid crystal which requires an alignment treatment is used. In use,
The pixel electrode can be directly used as an alignment film by performing a rubbing process. Further, at this time, the liquid crystal in the pixel electrode portion subjected to the alignment treatment is aligned, but the liquid crystal in contact with the interlayer insulating film of the acrylic photoresist which is not aligned even when rubbing is not aligned, so that black is always displayed between pixels. You can do so. Therefore, high-contrast display can be obtained without providing the BM on the counter substrate side.

In the second aspect of the present invention, the first (lower) conductive layer of the pixel electrode fills the contact hole of the interlayer insulating film and is flattened, and a semiconductor electrode (source / drain electrode) such as a TFT. As a material for forming such a layer, a conductive film forming material that can be filled in the contact hole and that can flatten the concave portion is used. In addition, depending on the display method of the liquid crystal display device, such as a selective reflection type or a transmission type, a conductive material having a light absorbing property, that is, a coloring property in a specific wavelength range is selected, or conversely, a light in a visible range is transmitted. Or a transparent conductive material to be used. Among these, as the conductive material having coloring property, a dispersing agent is dispersed in a functional matrix as exemplified in the first invention, and at least one of the matrix and the dispersing agent has coloring property and conductivity, respectively. For example, a graphite-dispersed photoresist can be used.

The material constituting the second conductive layer (upper layer) of the pixel electrode can serve as a pixel electrode together with the above-mentioned first conductive layer.
A conductive material having a function corresponding to the use can also be selected. For example, a transparent conductive material such as ITO or a metal material such as Mo whose surface is blackened by anodic oxidation or the like can be used. Further, as a material forming the interlayer insulating film, it is preferable to use an insulating material capable of flattening unevenness of a semiconductor such as a TFT in the lower layer as much as possible. It is not necessary and a structure in which two or more layers of different materials are stacked may be used.

According to the second aspect of the present invention, the first conductive layer of the pixel electrode having a two-layer structure fills the contact hole provided in the interlayer insulating film to flatten the concave portion, and forms a lower layer than the interlayer insulating film. Because it is in direct contact with the conductor layer located in the position above, the occurrence of disconnections and defects in the contact portion is prevented, and the contact with the semiconductor electrode is easily made, as compared with the conventional pixel-mounted structure. And no risk of contact failure. Further, since the contact hole is effectively used for display, the aperture ratio is improved, and the shape and size of the contact hole can be arbitrarily set, so that manufacturing is easy.

Further, the second conductive layer serves as a protective layer for the first conductive layer, and as a compensation layer for the first conductive layer, suppresses the increase in the resistance of the entire pixel electrode. In addition to preventing impurities from being mixed into the liquid crystal layer, it is possible to expand the choice of conductive materials forming the pixel electrode, including physical properties such as resistance.

Further, in a substrate such as a semiconductor array having a pixel electrode having such a two-layer structure, when a colored layer is considered to be black, for example, the interlayer insulating film is made of a black insulating material and one layer of the pixel electrode is formed. When the conductive layer of the eye is also made of a black conductive material, a light absorbing layer having a high black level can be obtained by the interlayer insulating film and the first conductive layer. By sandwiching the reflective liquid crystal, it is possible to obtain a reflective liquid crystal display device having high light utilization efficiency, high contrast ratio and high quality.

In the above description, a liquid crystal display device using a semiconductor element such as a TFT as a liquid crystal drive element (active element) has been described. However, the present invention can be similarly applied to an apparatus provided with an MIM element.

[0032]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 are cross-sectional views showing an embodiment of a TFT array substrate used in the liquid crystal display device of the present invention. These array substrates are used to drive the liquid crystal in a selective reflection type liquid crystal display device using a selectively reflective liquid crystal such as a cholesteric liquid crystal. The liquid crystal display device is configured by sandwiching the layers.

In FIG. 1, reference numeral 10 denotes a glass substrate, on which a gate electrode 11 made of a metal such as Al, Mo, W, Ta, or Ti is provided. On this gate electrode 11, an a-Si (amorphous silicon) film 13 and a channel protective film 14 made of silicon nitride or the like are sequentially provided via a gate insulating film 12 made of a silicon-based insulating material. On the Si film 13, n +
A source / drain electrode 16 made of a metal such as Mo, Al, W, or Ti is provided via the a-Si film 15. An interlayer insulating film 17 made of a black insulating material such as a black pigment-dispersed resist is provided so as to cover the TFT having such a structure, and a predetermined position of the interlayer insulating film 17 (on the source / drain electrode 16). ) Is provided with a contact hole 18. Further, a pixel electrode 19 made of a black conductive material such as graphite is provided on the interlayer insulating film 17, and the pixel electrode 19 is in direct contact with the source / drain electrode 16 at the contact hole 18. I have.

In the embodiment of FIG. 2, a black conductive material (eg, a graphite-dispersed photoresist) capable of flattening unevenness in which a dispersant is dispersed in a functional matrix is formed on the interlayer insulating film 17. Pixel electrode 19 is provided. The contact hole 18 is filled with the black conductive material constituting the pixel electrode 19 to flatten the recess, and the pixel electrode 19 is in direct contact with the source / drain electrode 16.

In the TFT array substrate of the embodiment shown in FIGS. 1 and 2, the interlayer insulating film 17 is made of a black insulating material, and the pixel electrode 19 is also made of a black conductive material. A high black level can be obtained without causing embossing or coloring. Therefore, such a T
In a selective reflection type liquid crystal display device having an FT array substrate, a high black level is displayed when the liquid crystal layer is in a transmission state, and a high contrast ratio and high quality display can be obtained.

In particular, in the TFT array substrate shown in FIG.
Since the contact hole 18 is filled with the black conductive material constituting the pixel electrode 19 and the concave portion is flattened, disconnection of the contact portion and occurrence of defects are prevented. Drain electrode 16
Contact is easy and there is no risk of failure. further,
Since the contact hole 18 is effectively used for display,
The shape and size of the hole can be arbitrarily set, and the manufacture is easy.

Next, T used in the liquid crystal display device of the present invention will be described.
Another embodiment of the FT array substrate is shown in FIG.

In the embodiment shown in FIG. 3, an interlayer insulating film made of a black insulating material such as a black pigment-dispersed resist is formed on a TFT having a structure similar to that of the embodiment shown in FIGS. 17, a first (lower) conductive layer 20a made of a black conductive material (for example, a graphite-dispersed photoresist) capable of flattening the unevenness of the lower layer.
And a second (upper) conductive layer 20b made of a transparent conductive material such as ITO. Then, the first conductive layer 20
a is the contact hole 1 provided in the interlayer insulating film 17
8, the recess is flattened, and is directly in contact with the source / drain electrode 16 of the TFT. The second layer of the pixel electrode 20 is formed on the flattened outer peripheral surface of the first conductive layer 20a. The conductive layer 20b is provided. Reference numeral 21 in the drawing denotes a semiconductor protective film made of silicon nitride or the like provided on the source / drain electrode 16 except for the contact position of the pixel electrode 20.

In the TFT array substrate having such a structure, a light having a high black level is provided by the interlayer insulating film 17 made of a black insulating material and the pixel electrode 20 having a two-layer structure in which the lower layer is made of a black conductive material. An absorption layer is formed. Also,
The first conductive layer 20a of the pixel electrode 20 is
7 is filled and flattened and is in direct contact with the source / drain electrodes 16 of the TFT, so that the occurrence of disconnections and defects in the contact portion is prevented, and the contact with the semiconductor electrode is prevented. Can be easily obtained and there is no possibility of contact failure. Further, since the contact hole 18 is effectively used for display, the aperture ratio is improved, and the shape and size of the hole can be arbitrarily set, so that manufacturing is easy.
Therefore, by sandwiching the selective reflection liquid crystal between such an array substrate and a counter substrate, a selective reflection type liquid crystal display device having high light use efficiency, good black display, high contrast ratio and high quality can be obtained. be able to.

In a TFT array substrate having such a two-layered pixel electrode, the interlayer insulating film is made of a transparent insulating material having light transmittance, and the upper and lower two layers forming the pixel electrode are Each of them can be made of a transparent conductive material having light transmissivity. In a transmissive liquid crystal display device using a transmissive liquid crystal using an array substrate configured in this way, light use efficiency is high, defects and the like are high. And a highly reliable display without any problem can be realized.

[0042]

EXAMPLES Specific examples of the present invention will be described below.

Example 1 A TFT array substrate having the structure shown in FIG. 3 was manufactured by the following method.

First, a gate electrode 11 made of a metal such as Al, Mo, W, Ta, Ti or the like, or a stack of these metals, or an alloy thereof is formed on a glass substrate 10 by magnetron sputtering. Formed. The gate electrode 11 may be made of a wiring material having a structure in which a pattern formed of Al or the like is covered with the metal or alloy. Further, an undercoat film made of silicon oxide or the like is formed on the glass substrate 10, and the gate electrode 1 is formed thereon.
1 may be formed.

Next, a 400-nm thick gate insulating film 12 made of a silicon-based insulating material is formed on the gate electrode 11.
After forming a 00 nm a-Si film 13 and a 300 nm thick channel protective film 14 made of silicon nitride in order by a CVD method, a positive photoresist is applied, and ultraviolet light is irradiated from the back surface of the substrate. Exposure and development were performed to form a resist pattern having substantially the same width as the gate electrode 11. Before development, by normal mask exposure,
It is desirable to determine the end of the channel protective film 14 in the direction orthogonal to the gate width. Further, the pattern of the channel protective film 14 may be formed only by mask exposure without using back surface exposure.

Next, after the channel protective film 14 is etched to form a pattern, a PH ₃ gas is introduced into the deposit by CVD and doped with phosphorus ions to form a 50 nm thick film.
An n + a-Si film 15 was formed. The channel protective film 1
4 is used as a mask, phosphorus atoms are directly implanted into the a-Si film 13 using an ion doping method or the like to form an n + a-Si film 15.
May be formed.

Next, the film thickness is determined by magnetron sputtering.
After forming a 50 nm Mo film, patterning is performed,
After the silicon island region was formed, a 1 μm thick film made of a metal such as Mo, Al, W, Ti or an alloy thereof was formed by magnetron sputtering to form the source / drain electrodes 16.

Next, after removing the n + a-Si film 15 on the channel protective film 14 using the source / drain electrodes 16 as a mask, a 200 nm thick silicon nitride film is formed by CVD.
A semiconductor protective film 21 having a thickness of nm was formed. Next, after removing the semiconductor protective film 21 in the contact region between the source / drain electrode 16 and the pixel electrode by reactive ion etching (RIE), a negative black pigment-dispersed resist is applied thereon by spin coating. And patterned by mask exposure to obtain a black interlayer insulating film 17 having a thickness of 2 μm.
Was formed.

Next, a graphite-dispersed photoresist is applied by spin coating to penetrate and fill the contact holes 18 so as to flatten the recesses.
After a black organic conductive layer (first conductive layer 20a) having a thickness of 200 nm is formed, a 200 nm thick ITO film (second conductive layer 20a) is formed thereon by magnetron sputtering.
b) was formed, and the pixel electrode 20 was composed of the black organic conductive layer and the ITO film. The black organic conductive layer, which is the first conductive layer 20a of the pixel electrode 20, was formed by patterning the second (upper) ITO film and then removing portions other than the ITO pattern. . As described above, the lower black organic conductive layer may be patterned using the same pattern as the upper ITO film, or may be patterned using different patterns. At this time, by making the pattern of the upper ITO film larger than the pattern of the lower black organic conductive layer, intrusion of impurities from the lower layer into the liquid crystal layer can be effectively prevented.

A liquid crystal display device was manufactured using the TFT array substrate manufactured in Example 1, the counter substrate on which the common electrode was formed, and the selective reflection liquid crystal such as cholesteric liquid crystal. This liquid crystal display device is referred to as T
In comparison with a conventional liquid crystal display device using a TFT array having a pixel-top structure, including the FT manufacturing process and the operation as a display device, a 5 to 15% improvement in reliability was achieved. In addition, the black display state was improved, and the contrast ratio between white and black display was improved by 10 to 20%. Further, the driving voltage was reduced by about 2 V as compared with a conventional liquid crystal display device in which a conductive layer was not filled in a contact hole portion (depth of 1 to 2 μm).

Example 2 A TFT array substrate having the structure shown in FIG. 1 was manufactured as follows. That is, as in the first embodiment, TF
After forming T, a predetermined pattern of an interlayer insulating film 17 made of a black pigment-dispersed resist is formed thereon, and then a graphite film is formed thereon by sputtering, and then patterned to form a pixel electrode 19. Formed.

Using the TFT array substrate thus manufactured, a selective reflection type liquid crystal display device was manufactured in the same manner as in Example 1, and good display was obtained.

[0053] As the black conductive material constituting the Example 3 pixel electrode 19, a multilayer film of Cr / CrO _X in place of the graphite, producing a TFT array substrate having the structure shown in FIG. 1 in the same manner as in Example 2 did. That is, the metal C is formed on the interlayer insulating film 17 having a predetermined pattern made of a black pigment-dispersed resist by sputtering.
r is formed to a thickness of about 300 nm, and the surface of the Cr film is oxidized using an anodic oxidation method to form a black Cr oxide film having a thickness of about 30 nm. Formed.

In the selective reflection type liquid crystal display device using the TFT array substrate manufactured as described above, a black level which can be used practically can be obtained. Further, since the thickness of the Cr oxide film is thin, a sufficient voltage is applied to the liquid crystal. Could be applied.

Example 4 An interlayer insulating film 17 of a predetermined pattern made of a black pigment-dispersed resist was formed on a TFT in the same manner as in Example 2, and then a graphite in which graphite was dispersed in an acrylic photoresist was formed thereon. The pixel electrode 19 was formed using the dispersed photoresist, and a TFT array substrate having the structure shown in FIG. 2 was manufactured.

That is, an excessive amount of graphite-dispersed photoresist is applied and left on the interlayer insulating film 17 having the contact hole 18 provided at a predetermined position, and the contact hole 18 is sufficiently penetrated and filled to form the concave portion. After filling, about 3
Film formation was performed by a spin coating method under the condition of 000 rpm, and then a pixel electrode 19 was formed through normal PEP. If the air in the holes remains as bubbles during the drop application of the graphite-dispersed photoresist, not only the electrical contact between the pixel electrode 19 and the source / drain electrode 16 deteriorates, but also the defoaming phenomenon during the baking process. For this reason, cracks and the like may occur in the pixel electrode 19, so that it is necessary to sufficiently penetrate the resist into the contact hole 18, and therefore, it is effective to drop the resist in a degassed state.

Using the TFT array substrate thus manufactured, a selective reflection type liquid crystal display device was manufactured in the same manner as in Example 2, and good display was obtained. Further, since the graphite-dispersed resist sufficiently penetrates and fills the contact holes 18 to flatten the concave portions, the electric field is made uniform and the pixel quality is improved. In addition, the conventional liquid crystal display device has a dead zone. The existing 18 contact holes can also be used as a display section, and the aperture ratio is improved.

Comparative Examples 1 and 2 An interlayer insulating film having a predetermined pattern made of a black pigment-dispersed resist was formed on a TFT in the same manner as in Example 2, and a film thickness of 100 nm was formed thereon by magnetron sputtering.
(Comparative Example 1) and an ITO film (Comparative Example 2) having a thickness of 300 nm were formed and patterned by a conventional method to form a pixel electrode.

In the selective reflection type liquid crystal display device manufactured in the same manner as in Example 2 using the TFT array substrate thus obtained, since the outermost surface of the pixel is an ITO film, the surface of the ITO film is smoothed. Reflection due to the nature and coloring due to interference appeared. That is, in Comparative Example 1, yellowish coloring was caused, and in Comparative Example 2, purpleish coloring was caused. Therefore, the black level of the interlayer insulating film was not sufficiently utilized, and high-quality display was not obtained.

Comparative Example 3 A light-absorbing TFT array substrate having the structure shown in FIG. 4 was manufactured by the following method. That is, when forming a TFT on the glass substrate 10 in the same manner as in Example 1, a-S
In the same layer as the i-film 13, graphite was formed by sputtering and patterned to form a pixel electrode 19. Next, using the BM on-array technology, portions other than the 19 pixel electrodes were covered with a black insulating layer (BM) 22 made of a black pigment-dispersed resist or the like to shield light.

In the TFT array substrate thus manufactured, light is not sufficiently absorbed due to the thin film thickness of the pixel electrode 19, and surface reflection and reflection of the glass substrate 10 appear, so that a sufficient black level can be obtained. Did not. And this T
In the selective reflection type liquid crystal display device manufactured in the same manner as in Example 2 using the FT array substrate, good display was not obtained. Further, in this structure, the pixel electrode 1 is provided to improve the light absorption of the array portion and to prevent light leakage of the TFT.
It is necessary to arrange the BM 22 so as to sufficiently overlap with No. 9, and a display with a high aperture ratio cannot be obtained.

In the above-described embodiment, the structure using the inversely staggered TFT which can be actively driven is shown as the semiconductor. However, the present invention is not limited to such a structure. Active devices, two-terminal active devices, simple matrix drive elements, etc.
The same applies. Further, the TFT array using the a-Si film has been described, but is not limited thereto.
Microcrystalline silicon (μc-
Si) or polycrystalline silicon (p-Si) may be used.

[0063]

As is apparent from the above description, according to the first aspect of the present invention, it is possible to obtain a pixel electrode structure which is excellent in light absorption at a specific wavelength, has low surface reflection and is not colored by interference. By using this, it is possible to obtain a reflective liquid crystal display device having a high light use efficiency and a high contrast ratio. In addition, by using a coloring conductive material in which a dispersing agent is dispersed in a functional matrix as a material for forming a pixel electrode, it is possible to fill a contact hole and flatten a concave portion, and to increase an aperture ratio. And a high-quality liquid crystal display device having high-quality pixels without defects.

Further, according to the second aspect of the present invention, in the pixel-placed structure in which the pixel electrode is arranged on the uppermost layer, the reliability can be improved, the light use efficiency is high, the contrast ratio is high and the quality is high. A high liquid crystal display device can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a TFT array substrate used in a liquid crystal display device according to the first invention of the present invention.

FIG. 2 is a sectional view showing another embodiment of the TFT array substrate used in the liquid crystal display device according to the first invention of the present invention.

FIG. 3 is a sectional view showing one embodiment of a TFT array substrate used in the liquid crystal display device according to the second invention of the present invention.

FIG. 4 is a cross-sectional view showing an example of a conventionally used light absorbing TFT array substrate.

FIG. 5 is a cross-sectional view showing the structure of a semiconductor array substrate having a pixel-placed structure, which is conventionally used in a reflective liquid crystal display device.

[Explanation of symbols]

Reference Signs List 10 Glass substrate 11 Gate electrode 12 Gate insulating film 13 a-Si film 16 Source / drain electrode 17 Interlayer insulating film made of black insulating material 18 ... contact hole 19 ... pixel electrode 20a made of black conductive material 20a ... first conductive layer 20b made of black conductive material that can be planarized 20b ... second conductive layer made of transparent conductive material Layer 20: Pixel electrode having a two-layer structure

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshihisa Mizutani 33, Shinisogo-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Inside Toshiba Production Technology Research Institute (72) Inventor Toshiya Kiyota 33, Shinisogo-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Company Toshiba Production Technology Laboratory

Claims (3)

[Claims] 1. An insulating first substrate, a pixel electrode formed on the substrate to which a voltage is applied, and a second substrate facing the substrate and capable of applying an electric field between the pixel electrodes. ,
A liquid crystal layer interposed between the first and second substrates, and an opaque interlayer insulating film that is formed adjacent to and overlaps with the pixel electrode when viewed from a direction in which the first and second substrates are overlapped and seen through. In the liquid crystal display device, the interlayer insulating film is made of an insulating material that absorbs light in a specific wavelength region, and the pixel electrode is made of a conductive material that absorbs light in the same or different wavelength region as the insulating material. A liquid crystal display device comprising a material, wherein a color different from the color of the interlayer insulating film and the pixel electrode is emitted in the direction. 2. An insulating first substrate, a pixel electrode formed on the substrate and applied with a voltage, and a second substrate facing the substrate and capable of applying an electric field between the pixel electrodes. ,
A liquid crystal layer interposed between the first and second substrates, and an opaque interlayer insulating film that is formed adjacent to and overlaps with the pixel electrode when viewed from a direction in which the first and second substrates are overlapped and seen through. In the liquid crystal display device, the pixel electrode has a structure in which two layers made of different conductive materials are stacked, and a contact hole of the interlayer insulating film is filled with a first conductive layer of the pixel electrode. A liquid crystal display device, which is flattened by being brought into contact with a lower conductive layer. 3. The method according to claim 1, wherein the interlayer insulating film is formed of a black insulating material, the first conductive layer of the pixel electrode is formed of a black conductive material, and is provided between the first and second substrates. 3. The liquid crystal display device according to claim 2, wherein a selectively reflective liquid crystal layer is interposed.