JP3754558B2 - Reflective liquid crystal display - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a reflection type liquid crystal display equipment.
[0002]
[Prior art]
A reflective liquid crystal display (hereinafter referred to as a reflective LCD) is a system in which external light incident from the front of the panel is modulated by a liquid crystal panel and reflected by a reflective plate provided on the back of the panel for display. Therefore, a backlight which is indispensable for a transmissive liquid crystal display (hereinafter referred to as a transmissive LCD) is not necessary, and power consumption can be reduced. For this reason, the reflective LCD is most suitable for a portable information terminal or a portable device.
[0003]
However, since the reflective LCD performs display by reflecting external light, it has no function of adjusting incident light. For this reason, when the illuminance of outside light is weak, for example, when used indoors or at night, there is a drawback that the display screen becomes very dark and the visibility deteriorates because the incident outside light is small. For this reason, in the reflective LCD, it is necessary to increase the reflectivity so that incident external light is reflected as efficiently as possible.
[0004]
As means for increasing the reflectivity, it is possible to prevent light propagation loss in the liquid crystal cell or the optical member and to increase the reflectivity on the reflector. As a method for reducing the light transmission loss by the liquid crystal cell or the optical member, paying attention to the largest light transmission loss in the polarizing plate, a guest-host type display method using no polarizing plate (patent publication: flat) 7-146469) and a single polarizing plate system (Patent Publication: Hei 7-84252) in which a single polarizing plate is used.
[0005]
In addition, as a method of increasing the reflectance at the reflector, a reflector that has been provided outside the conventional liquid crystal cell is provided inside the liquid crystal cell, and as a constituent material of the reflector, the reflectance is high and the electrical resistance value is low. A method of forming a reflective electrode having both a function as a reflector and a function as an electrode using aluminum (Patent Publication: Hei 8-101384) is known.
[0006]
As shown in FIG. 8, the conventional reflective LCD has a polarizing plate 1, a glass substrate 3, a color filter 4, a transparent electrode 5, a liquid crystal 7, a reflective electrode 8, an interlayer insulating film 17, and a thin film transistor (hereinafter referred to as TFT) 13. And a glass substrate 10. This reflection type LCD is a combination of a single polarizing plate method in which a single polarizing plate is provided and a method in which a reflective electrode is provided in a liquid crystal cell, and has an improved reflectivity.
[0007]
The reflective electrode 8 is formed on the interlayer insulating film 17 and is electrically connected to the drain electrode 14 of the TFT 13 through a minute hole (hereinafter referred to as a contact hole) 18 provided in the interlayer insulating film 17. . A voltage is applied to the reflective electrode 8 by the switching operation of the TFT 13. The reflective electrode 8 functions to apply a voltage to the liquid crystal 7 as a pixel electrode.
[0008]
[Problems to be solved by the invention]
When the reflective electrode and the TFT are not electrically connected, a predetermined voltage is not applied to the reflective electrode. For this reason, the liquid crystal is not modulated, and only that portion may become a display defect. Usually, the drain electrode is a connection line (hereinafter referred to as a mounting electrode) between a signal line (hereinafter referred to as a source electrode) for applying a voltage to the liquid crystal and a liquid crystal driving LSI (hereinafter referred to as a driver) for supplying a voltage to the source electrode. Are formed in the same process. Aluminum is used as a constituent material because it is necessary to reduce the connection resistance and the wiring resistance. Aluminum is very easily oxidized and easily forms an oxide film on the surface when left in air. The aluminum oxide film is insulative. Since the reflective electrode and the drain electrode cannot be formed in the same process, an aluminum oxide film is formed on the drain electrode, and the drain electrode and the reflective electrode are connected via the oxide film. For this reason, there is a problem that display defects are often caused by poor electrical connection.
[0009]
The present invention considers the problem with such a traditional reflective liquid crystal display device and a manufacturing method thereof described above, by reduce the resistance of the connection resistance between the drain electrode and the pixel electrode due to bad connection it is an object to provide a reflective liquid crystal display panel equipment which can reduce display defects.
[0010]
[Means for Solving the Problems]
In order to solve the above-described problem, the present invention of claim 1 is such that a gate electrode, a source electrode, and a thin film transistor arranged in a matrix are formed on one side, and a reflection-side electrode is formed thereon via an insulating layer. The reflective substrate, the reflective substrate facing the reflective substrate, and at least a transparent substrate formed on the opposing surface, and a space formed between the counter substrate and the reflective substrate is filled. In a reflective liquid crystal display device comprising a liquid crystal, wherein the reflective electrode and the drain electrode of the thin film transistor are electrically connected,
The insulating layer is composed of an inorganic insulating film and an organic insulating film, and the inorganic insulating film is disposed closer to the reflective substrate than the organic insulating film,
An opening is formed in the inorganic insulating film where the drain electrode is located,
The organic insulating film is formed in the opening, and a mortar-shaped contact hole is formed in the organic insulating film so that the drain electrode is exposed,
The area of the opening is larger than the area of the bottom surface of the mortar-shaped contact hole,
The drain electrode is formed by laminating an aluminum layer on a titanium layer,
The contact portion between the drain electrode and the reflective electrode is such that the reflective electrode and the titanium layer of the drain electrode are electrically connected .
This is a reflective liquid crystal display device.
[0012]
The present invention includes the following modifications.
The insulating layer is a laminate of an inorganic insulating film and an organic insulating film, the inorganic insulating film is disposed on the reflective substrate side, and the reflective side electrode is all or part of aluminum. A reflective electrode, wherein the reflective electrode and the drain electrode are electrically connected in a contact hole provided on the drain electrode of the insulating layer .
[0013]
The insulating layer is formed by laminating a reflective layer between an inorganic insulating film and an organic insulating film, the inorganic insulating film is disposed on the reflective substrate side, and the reflective electrode is A transparent electrode, all or part of which is indium tin oxide, and the reflective electrode and the drain electrode are electrically connected in a contact hole provided on the drain electrode of the insulating layer. It is characterized by .
[0014]
In addition, the contact hole, characterized in that it is a mortar shape.
[0015]
Further, at the position of the contact hole, the area of the inorganic insulating film is not formed part, characterized in that wider than the area of the contact hole bottom surface.
[0016]
In addition, there exist the following methods as a manufacturing method relevant to this invention.
After the inorganic insulating film forming step, an inorganic insulating film forming step of forming an inorganic insulating film on the one surface of the reflective substrate in which a thin film transistor having a drain electrode that is entirely or partially titanium is formed on one surface, An opening forming step for removing all or part of the inorganic insulating film on the drain electrode to form an opening, and an organic insulating film on the inorganic insulating film and the opening after the opening forming step After forming the organic insulating film and forming the organic insulating film, the organic insulating film at the position of the opening is removed to expose all or part of the titanium portion of the drain electrode. A contact hole forming step for forming a contact hole, and after the contact hole forming step, the contact hole and the exposed chip on the organic insulating film. It is a manufacturing method including a reflection side electrode to form a reflective side electrode on part of the emissions.
[0017]
In addition, before the opening forming step, a reflective layer forming step of forming a reflective layer on the inorganic insulating film, and before or simultaneously with the opening forming step, a portion of the reflective layer corresponding to the opening is formed. It is a manufacturing method including the reflective layer removal process to remove.
[0018]
Further, in the opening forming step, the area of the opening is wider manufacturing method than the area of the contact hole bottom surface.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
(First embodiment)
First, a first embodiment of the present invention will be described with reference to the drawings.
[0020]
FIG. 1 is a cross-sectional view showing a configuration of a reflective liquid crystal display device according to a first embodiment of the present invention. As shown in FIG. 1, the reflective liquid crystal display device according to the present embodiment has a gate electrode 11, a source electrode 12, and a TFT element 13 formed on one surface, and an inorganic interlayer insulating film 15 (an inorganic layer of the present invention). A reflective electrode 8 is formed through an insulating layer in which an organic interlayer insulating film 17 (corresponding to the organic insulating film of the present invention) is laminated, and an alignment film 6b is formed thereon. The reflective substrate 10 is opposed to the reflective substrate 10, and the color filter 4, the transparent electrode 5, and the alignment film 6 a are formed on the opposing surface, and the polymer film 2 and the polarizing film 1 are formed on the opposite surface. And the liquid crystal 7 filled in the space formed between the alignment film 6a of the counter substrate 3 and the alignment film 6b of the reflective substrate 10, and the reflective electrode 8 TFT element 13 The in-electrode 14, a contact hole 18 provided on the drain electrode 14 are electrically connected. The pixel portion is composed of the reflective electrode 8 on the reflective substrate 10, the transparent electrode 5 on the counter substrate 3, and the liquid crystal 7. The light incident from the counter substrate 3 side is modulated by the liquid crystal layer and is opposed to the reflective electrode surface. The display is performed by reflecting in the direction of the substrate.
[0021]
The drain electrode 14 is formed by laminating an aluminum layer 21 on a titanium layer 22, and the aluminum layer 21 in contact with the reflective electrode 8 is removed (see FIGS. 3 and 4).
[0022]
The inorganic interlayer insulating film 15 functions as an interlayer insulating film of the TFT element 13 and also functions as an electrode protective film in the driver mounting portion.
[0023]
FIG. 2 is a plan view showing the arrangement of TFT elements and the like in the reflective liquid crystal display device according to the first embodiment of the present invention. That is, FIG. 2 is a view of the state where the upper portion is removed from the inorganic interlayer insulating film 15 of FIG. The gate electrode 11 and the source electrode 12 are arranged in a matrix, and branches of the gate electrode 11 and the source electrode 12 extend in the vicinity of the intersection. These and the drain electrode 14 constitute a TFT element 13. .
[0024]
Next, a manufacturing method of the reflective liquid crystal display device in the present embodiment will be described. In addition, details of the configuration of the reflective liquid crystal display device in this embodiment in each step of the manufacturing method are also described.
[0025]
The counter substrate 3 shown in FIG. 1 is made of alkali-free glass, and the red, green, and blue stripe-shaped color filters 4 made of a pigment-dispersed resist are formed on the counter substrate 3.
[0026]
Thereafter, an indium tin oxide (hereinafter referred to as ITO) film is formed on the color filter 4 to form the transparent electrode 5.
[0027]
Next, the gate electrode 11 made of aluminum and tantalum, the source electrode 12 made of titanium and aluminum, and the drain electrode 14 are formed on the reflective substrate 10 using alkali-free glass by a predetermined method as shown in FIG. A TFT element 13 made of amorphous silicon is formed at each intersection of the gate electrode 11 and the source electrode 12 arranged in a matrix.
[0028]
Next, an inorganic interlayer insulating film 15 made of silicon nitride is formed on the reflective substrate 10. This step corresponds to the inorganic insulating film forming step of the present invention.
[0029]
Next, ultraviolet rays are irradiated using a photoresist and a predetermined photomask, and then silicon nitride of the inorganic interlayer insulating film 15 is etched by dry etching to form an opening 16 on the drain electrode 14. At this time, the opening 16 is, for example, a circle having a diameter of 16 μm. This step corresponds to the opening forming step of the present invention.
[0030]
Further, as shown in FIG. 3, the aluminum layer 21 of the drain electrode 14 in the opening 16 is removed by using a phosphoric acid-based etching solution, and the titanium layer 22 is exposed.
[0031]
Next, a photosensitive acrylic resin (for example, FVR: manufactured by Fuji Pharmaceutical Co., Ltd.) is applied to the entire surface of one side of the reflective substrate 10 (on the inorganic interlayer insulating film 15 and the opening 16) to form an organic interlayer insulating film. A film 17 is formed. This step corresponds to the organic insulating film forming step of the present invention.
[0032]
Then, after irradiating ultraviolet rays using a predetermined photomask, heat treatment is performed in a clean oven at 200 ° C. As a result, a contact hole 18 with the titanium layer 22 exposed at the bottom is formed at the same position as the opening 16 on the drain electrode 14. At this time, as shown in FIG. 4, the contact hole 18 is formed inside the opening 16 so as to have a mortar shape. When the area of the bottom surface of the contact hole 18 is S2 (shown two-dimensionally in FIG. 4), S2 is made smaller than the area S1 of the opening 16 (shown two-dimensionally in FIG. 4). For example, if the opening 16 is a circle having a diameter of 16 μm, the bottom surface of the contact hole 18 is a circle having a diameter of 8 μm. This step corresponds to the contact hole forming step of the present invention.
[0033]
Next, an aluminum film is formed on the organic interlayer insulating film 17, the contact hole 18 and the exposed titanium layer 22, irradiated with ultraviolet rays using a photoresist and a predetermined photomask, and then a phosphoric acid-based etching solution is applied. Using this, the reflective electrode 8 is formed. This step corresponds to the reflection side electrode forming step of the present invention.
[0034]
Next, a polyamic acid solution (SE-7111: Nissan Chemical Industries, Ltd.) having a solid content concentration of 5% by weight is printed on the transparent electrode 5 and the reflective electrode 8 and cured at 220 ° C. so as to have a TN orientation. Then, alignment treatment is performed by rotating rubbing using rayon cloth to form 120 nm thick alignment films 6a and 6b made of polyimide.
[0035]
Next, a thermosetting sealing material (for example, struct bond: manufactured by Mitsui Toatsu Chemical Co., Ltd.) is provided on the periphery of the counter substrate 3 by providing a liquid crystal injection port, and, for example, on the reflective electrode substrate 10, A spherical spacer made of plastic having a diameter of 4.5 μm is dispersed at 150 to 200 pieces / mm ² , the counter substrate 3 and the reflective substrate 10 are bonded to each other, and the sealing material is cured at 150 ° C.
[0036]
Next, liquid crystal 7 in which a chiral composition is added to a fluorine-based nematic liquid crystal composition having a refractive index anisotropy of 0.097 is vacuum-injected, and the injection port is sealed with an ultraviolet curable resin, thereby producing a liquid crystal cell. To do.
[0037]
On the counter substrate of the liquid crystal cell formed as described above, a polycarbonate film having a predetermined birefringence as a polymer film 2 is pasted at a predetermined angle, and the neutral gray polarizing film 1 has a predetermined absorption axis. By sticking in the direction, an active matrix type reflective LCD can be obtained.
[0038]
When the reflection type LCD was driven and the panel reflectance at the front was measured, the reflectance was 1.5% in the black state, and the reflectance was 16.3% in the white state. It was confirmed that the panel reflection characteristics can be realized. In addition, when a poor connection between the drain electrode 14 and the reflective electrode 8 occurs, sufficient black is not obtained and a dotted luminescent spot is observed. However, in the reflective liquid crystal display device according to the present embodiment, such a bright luminescent spot is obtained. No point was seen, and it was confirmed that display failure due to poor connection hardly occurred.
[0039]
In addition, in the contact hole forming step, it is confirmed that the contact hole 18 can be prevented from being disconnected at the side wall of the contact hole 18 as compared with the conventional contact hole shown in FIG. It was done. In the opening forming step, making the area of the opening 16 larger than the area of the bottom surface of the contact hole 18 makes it easier to form the contact hole 18 in a mortar shape.
[0040]
In the present embodiment, it has been described that aluminum is used as the constituent material of the reflective electrode 8, but the same effect can be obtained even when a laminated structure of titanium and aluminum is used.
[0041]
Further, in the present embodiment, the sectional shape of the opening and the contact hole of the present invention has been described as a circle, but the opening is a quadrangle and the contact hole is a shape in which a square frustum is inverted. Also good. At this time, the area of the opening needs to be larger than the area of the bottom surface of the contact hole.
[0042]
(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to the drawings.
[0043]
FIG. 5 is a cross-sectional view showing a configuration of a reflective liquid crystal display device according to the second embodiment of the present invention. The reflection type liquid crystal display device in the present embodiment is the reflection in the first embodiment described above except that the reflection-side electrode of the present invention is a transparent electrode and the insulating layer of the present invention has a reflection layer. The same as the liquid crystal display device. Therefore, in the present embodiment, the same reference numerals are given to the same components as those in the first embodiment, and the description thereof is omitted. In addition, those not specifically described are the same as those in the first embodiment.
[0044]
FIG. 5 is a cross-sectional view showing a configuration of a reflective liquid crystal display device according to the second embodiment of the present invention. As shown in FIG. 5, in the reflection type liquid crystal display device in this embodiment, a gate electrode 11, a source electrode 12, and a TFT element 13 are formed on one side, and an inorganic interlayer insulating film 15 (inorganic of the present invention) is formed thereon. The transparent electrode 20 is formed through the insulating layer in which the reflective layer 19 and the organic interlayer insulating film 17 (corresponding to the organic insulating film of the present invention) are laminated, and the orientation is formed thereon. The reflective substrate 10 on which the film 6b is formed and the reflective substrate 10 are opposed to each other, and the color filter 4, the transparent electrode 5 and the alignment film 6a are formed on the opposed surface, and the polymer film 2 is formed on the opposite surface. And the counter substrate 3 on which the change film 1 is formed, and the liquid crystal 7 filled in the space formed between the alignment film 6a of the counter substrate 3 and the alignment film 6b of the reflective substrate 10, Transparent electrode 20 and T The drain electrode 14 of the T element 13, a contact hole 18 provided on the drain electrode 14 are electrically connected.
[0045]
The planar arrangement of the TFT elements and the like of the reflective liquid crystal display device in this embodiment is the same as that of the reflective liquid crystal display device in the first embodiment shown in FIG.
[0046]
Next, a manufacturing method of the reflective liquid crystal display device in the present embodiment will be described. In addition, details of the configuration of the reflective liquid crystal display device in this embodiment in each step of the manufacturing method are also described.
[0047]
The process up to forming the inorganic interlayer insulating film 15 on the reflective substrate 10 (corresponding to the inorganic insulating film forming process of the present invention) is the same as the manufacturing method of the reflective liquid crystal display device in the first embodiment. is there.
[0048]
Next, a reflective layer 19 made of aluminum is formed. This step corresponds to the reflective layer forming step of the present invention.
[0049]
Next, ultraviolet rays are irradiated using a photoresist and a predetermined photomask, and then the aluminum of the reflective layer 19 is etched with a phosphoric acid-based etchant, and the silicon nitride of the inorganic interlayer insulating film 15 is etched by dry etching. Then, an opening 16 is formed on the drain electrode 14. At this time, the opening 16 is, for example, a circle having a diameter of 16 μm. This step corresponds to the reflective layer removing step and the opening forming step of the present invention.
[0050]
Further, as shown in FIG. 6, the aluminum layer 21 of the drain electrode 14 in the opening 16 is removed by using a phosphoric acid-based etching solution to expose the titanium layer 22.
[0051]
Next, a photosensitive acrylic resin (for example, FVR: manufactured by Fuji Pharmaceutical Co., Ltd.) is applied to the entire surface of one side of the reflective substrate 10 (on the reflective layer 19 and the opening 16), and the organic interlayer insulating film 17 is formed. Form. This step corresponds to the organic insulating film forming step of the present invention.
[0052]
Then, after irradiating ultraviolet rays using a predetermined photomask, heat treatment is performed in a clean oven at 200 ° C. As a result, a contact hole 18 with the titanium layer 22 exposed at the bottom is formed at the same position as the opening 16 on the drain electrode 14. At this time, as shown in FIG. 5, the contact hole 18 is formed inside the opening 16 so as to have a mortar shape. If the area of the bottom surface of the contact hole 18 is S2 (shown two-dimensionally in FIG. 5), S2 is made smaller than the area S1 of the opening 16 (shown two-dimensionally in FIG. 5). For example, if the opening 16 is a circle having a diameter of 16 μm, the bottom surface of the contact hole 18 is a circle having a diameter of 8 μm. This step corresponds to the contact hole forming step of the present invention.
[0053]
Next, ITO is formed on the organic interlayer insulating film 17, the contact hole 18 and the exposed titanium layer 22, irradiated with ultraviolet rays using a photoresist and a predetermined photomask, and then etched with hydrogen iodide. The transparent electrode 20 is formed using the liquid. This step corresponds to the reflection side electrode forming step of the present invention.
[0054]
After that, an active matrix type reflective LCD is obtained by performing the same process procedure as in the first embodiment.
[0055]
When the reflection type LCD was driven and the panel reflectivity at the front was measured, the reflectivity was 1.5% in the black state, and the reflectivity was 18.5% in the white state. It was confirmed that the panel reflection characteristics can be realized. Further, as in the first embodiment, it was confirmed that display failure due to poor connection between the drain electrode and the transparent electrode hardly occurred.
[0056]
Further, as in the first embodiment, in the contact hole forming step, the shape of the contact hole 18 is changed to a mortar shape so that the contact hole 18 has a side wall portion as compared with the conventional contact hole shown in FIG. It was confirmed that disconnection of the reflective electrode 8 can be prevented. In the opening forming step, making the area of the opening 16 larger than the area of the bottom surface of the contact hole 18 makes it easier to form the contact hole 18 in a mortar shape.
[0057]
In the first embodiment and the second embodiment described above, an example of a reflective liquid crystal display device having a single polarizing plate configuration is shown, but the present invention is not limited to this. It can be applied to a method that is not used.
[0058]
In the first embodiment and the second embodiment described above, the reflection-side electrode and the drain electrode of the present invention are electrically connected in the contact hole provided on the drain electrode of the insulating layer. However, the present invention is not limited to this, and the reflection side electrode and the drain electrode are electrically connected, and all or part of the contact portion of the drain electrode with the reflection side electrode is titanium. If so, an effect of reducing display defects due to poor connection can be obtained by reducing the connection resistance between the drain electrode and the pixel electrode.
[0059]
【The invention's effect】
As is apparent from the above description, the present invention relates to a reflective liquid crystal display panel device that can reduce display defects due to poor connection by reducing the connection resistance between the drain electrode and the pixel electrode, and its manufacture. A method can be provided.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a configuration of a reflective liquid crystal display device according to a first embodiment of the present invention.
FIG. 2 is a plan view showing the arrangement of TFT elements and the like in the reflective liquid crystal display device according to the first embodiment of the present invention.
FIG. 3 is a cross-sectional view showing an opening of the reflective liquid crystal display device according to the first embodiment of the present invention.
FIG. 4 is a cross-sectional view showing a contact hole of the reflective liquid crystal display device in the first embodiment of the present invention.
FIG. 5 is a cross-sectional view showing a configuration of a reflective liquid crystal display device according to a second embodiment of the present invention.
FIG. 6 is a cross-sectional view showing an opening of a reflective liquid crystal display device according to a second embodiment of the present invention.
FIG. 7 is a cross-sectional view showing a contact hole of the reflective liquid crystal display device in the first embodiment of the present invention.
FIG. 8 is a cross-sectional view showing a configuration of a conventional reflective liquid crystal display device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Polarizing film 2 Polymer film 3 Opposite substrate 4 Color filter 5 Transparent electrode 6a, 6b Alignment film 7 Liquid crystal layer 8 Reflecting electrode 9 Insulating film 10 Reflecting substrate 11 Gate electrode 12 Source electrode 13 TFT element 14 Drain electrode 15 Inorganic interlayer insulation Film 16 Opening 17 Organic interlayer insulating film 18 Contact hole 19 Reflective layer 20 Transparent electrode 21 Aluminum layer 22 Titanium layer

Claims (1)

A reflective substrate in which a gate electrode, a source electrode, and a thin film transistor arranged in a matrix are formed on one side and a reflective electrode is formed thereon via an insulating layer, and is opposed to the reflective substrate. A counter substrate on which at least a transparent electrode is formed, and a liquid crystal filled in a space formed between the counter substrate and the reflective substrate, the reflective electrode and the drain electrode of the thin film transistor In a reflective liquid crystal display device in which and are electrically connected,
The insulating layer is composed of an inorganic insulating film and an organic insulating film, and the inorganic insulating film is disposed closer to the reflective substrate than the organic insulating film,
An opening is formed in the inorganic insulating film where the drain electrode is located,
The organic insulating film is formed in the opening, and a mortar-shaped contact hole is formed in the organic insulating film so that the drain electrode is exposed,
The area of the opening is larger than the area of the bottom surface of the mortar-shaped contact hole,
The drain electrode is formed by laminating an aluminum layer on a titanium layer,
The contact portion between the drain electrode and the reflective electrode is such that the reflective electrode and the titanium layer of the drain electrode are electrically connected .
Reflective liquid crystal display device.

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