JP2007079595A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device which suppresses generation of interference light. <P>SOLUTION: The liquid crystal display device has substrates arranged opposite to each other via liquid crystal, pixel electrodes which reflect external light made incident via the other substrate provided in the respective pixel areas on the liquid crystal side of one of the substrate, projected parts are scattered and formed on the surface of the pixel electrode, there are two or more kinds of projected parts with different shapes when the pixel electrodes are superficially observed, the projected parts formed on the surfaces of the pixel electrodes are formed by island-like multilayer material layers positioned on the lower layer sides of the pixel electrodes and the projected parts in which the number of layers of the island-like multilayer material layers is different from each other exist. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device, and in particular, an active matrix type liquid crystal display of a so-called reflection type that performs display using reflected light of incident external light or a type that combines a transmission type and a reflection type. Relates to the device.

An active matrix type liquid crystal display device includes a gate signal line and y extending in the x direction and arranged in parallel in the y direction on the liquid crystal side surface of one of the substrates opposed to each other through the liquid crystal. A region surrounded by drain signal lines extending in the direction and juxtaposed in the x direction is defined as a pixel region,
Each of these pixel regions includes a thin film transistor that is driven by supply of a scanning signal from one side gate signal line, and a pixel electrode that is supplied with a video signal from one side drain signal line via this thin film transistor.

  The pixel electrode generates an electric field having a strength corresponding to the video signal between the counter electrode formed on the liquid crystal side surface of the other substrate and controls the light transmittance of the liquid crystal. .

  In such a liquid crystal display device, the pixel electrode is formed of a material (for example, Al) that reflects extraneous light incident through the other substrate (the substrate positioned on the viewer side), so-called. What is used as a reflection type is known.

In addition, the island-shaped material layer is scattered on the lower layer side of the pixel electrode so that the convex portions of the material layer are exposed on the surface of the pixel electrode, and the reflection is uniform and has good light scattering properties. Those having characteristics are also known (see, for example, Patent Document 1 and Patent Document 2 below).
JP 2000-98375 A Japanese Patent Laid-Open No. 11-337961

  However, in the liquid crystal display device configured in this way, each of the island-shaped material layers formed on the lower layer side of the pixel electrode has the same shape (including similar ones) when observed in a plane. Therefore, the side surfaces of the convex portions that are exposed on the surface of the pixel electrode by these material layers all have the same taper angle.

For this reason, it has been pointed out that the light reflected by the side surfaces of the convex portions of the pixel electrodes interfere with each other, and the interference light generated thereby causes inconvenience in improving the display quality.
The present invention has been made based on such circumstances, and an object thereof is to provide a liquid crystal display device capable of suppressing the generation of interference light.

  Of the inventions disclosed in the present application, the outline of typical ones will be briefly described as follows.

The liquid crystal display device according to the present invention includes, for example, a pixel electrode that reflects external light incident through the other substrate to each pixel region on the liquid crystal side of one of the substrates disposed to face each other through the liquid crystal. Prepared,
The pixel electrode is formed such that convex portions are scattered on the surface, and each convex portion has two or more types having different shapes when the pixel electrode is viewed in a plane. It is.

The liquid crystal display device configured as described above has two or more types of protrusions formed on the surface of the pixel electrode having different shapes when the pixel electrode is viewed in a plan view. The light reflected on the side surfaces of the convex portions of the projections hardly interfere with each other.
For this reason, display quality can be improved.

  As is apparent from the above description, the liquid crystal display device according to the present invention can suppress the generation of interference light.

  Hereinafter, embodiments of a liquid crystal display device according to the present invention will be described with reference to the drawings.

Example 1.
FIG. 2 is a plan view showing one embodiment of a pixel of the liquid crystal display device according to the present invention. Further, FIG. 1 shows a cross-sectional view taken along the line II of FIG.

  FIG. 2 shows one of a large number of pixels arranged in a matrix, and the other pixels arranged on the left, right, and upper and lower sides of this pixel have the same configuration.

  First, in FIG. 2, a gate signal line GL extending in the x direction and arranged in parallel in the y direction is formed on the liquid crystal side surface of the transparent substrate SUB1.

  The gate signal line GL is made of, for example, aluminum (Al), and its surface is anodized to form an Al oxide film AO. This is to avoid the occurrence of hillocks due to the subsequent heat treatment, for example, an electrical short circuit with the drain signal line DL.

  Then, several island-shaped Al layers are formed in a pixel region that is a region surrounded by a pair of adjacent gate signal lines GL and a pair of adjacent drain signal lines DL described later.

  This Al layer is a layer that is laminated with other island-shaped material layers to be described later to form a convex portion PR in the pixel region, and is referred to as a first convex portion PR1 in this embodiment. Further, the n-th convex part PRn (n = 1, 2, 3,...) In the following description means that one material layer of the convex part PR composed of a laminate.

  In this embodiment, the protrusions PR formed in the pixel region are formed as regularly arranged as shown in FIG. However, the Al layer composed of the first protrusion PR1 does not have to be formed at all positions where the respective protrusions PR are to be formed. The first protrusion PR1 is formed on a certain protrusion PR, and other protrusions The PR is not formed with the first convex part PR1.

  In addition, second protrusions PR2 made of, for example, an ITO (Indium-Tin-Oxide) film are formed so as to overlap some of the first protrusions PR1. In this embodiment, the second convex portion PR2 is formed with a center shifted from the first convex portion PR1. The reason for this is to make the shape as viewed in a plane different from other projections PR as much as possible.

  For this reason, there is also a portion where the second convex portion PR2 is formed in a region where the convex portion PR is to be formed and the first convex portion PR1 is not formed.

  An insulating film GI made of, for example, SiN is formed on the surface of the transparent substrate SUB1 so as to cover the gate signal line GL, the first protrusion PR1, and the second protrusion PR2.

  This insulating film GI functions as an interlayer insulating film with a gate signal line GL for a drain signal line DL described later, functions as a gate insulating film for a thin film transistor TFT described later, and a capacitive element Cadd described later. Has a function as a dielectric film.

  For this reason, this insulating film GI is usually formed over the entire area of each pixel region. In this embodiment, however, the insulating film GI is selectively formed in the formation region of the convex portion PR in the pixel region, The portion is formed as etched (see FIG. 1). The reason for this is that in each projection PR formed in the pixel region, the insulating film GI is not intended to be configured as a part thereof, that is, the third projection PR3.

  Then, on the insulating film GI overlapping with the gate signal line GL in the lower left of the pixel region, an i-type (intrinsic: conductivity type determining impurity is not doped) semiconductor layer AS made of, for example, a-Si is formed. Yes.

  The semiconductor layer AS is a semiconductor layer of a MIS type thin film transistor TFT having a part of the gate signal line GL as a gate electrode by forming a source electrode and a drain electrode on the upper surface thereof.

  Here, the semiconductor layer AS is also selectively formed in the formation region of the projection PR in the pixel region in this embodiment (see FIG. 1). This is because, like the insulating film GI, the semiconductor layer AS is formed as the fourth protrusion PR4 in each protrusion PR.

  The source electrode SD1 and the drain electrode SD2 of the thin film transistor TFT are formed simultaneously with the drain signal line DL formed on the insulating film GI.

  That is, by forming drain signal lines DL extending in the y direction and juxtaposed in the x direction in the figure, a part of the drain signal lines DL are extended to the upper surface of the semiconductor layer AS. The extending portion is formed as the drain electrode SD2 of the thin film transistor TFT.

  On the other hand, the source electrode SD1 is formed integrally with the pixel electrode PIX formed over most of the region in the pixel region.

  The drain signal line DL (drain electrode) and the pixel electrode PIX (source electrode) are both formed of the same material layer. In this embodiment, the drain signal line DL (drain electrode) and the pixel electrode PIX (source electrode) are formed by sequentially stacking chromium (Cr) and aluminum (Al). ing. The reason why chromium is used as the lower layer is that the connection with the semiconductor layer AS is considered, and the reason why aluminum is used as the upper layer is that the reflection efficiency of the pixel electrode PIX that functions as the reflection electrode is considered.

  The surface of the pixel electrode PIX thus formed becomes apparent on the surface with the shape of the convex part PR almost unchanged. Each of the convex portions PR has a different number of layers and is configured to have a different shape in plan view. Therefore, the direction of the reflected light becomes random, and these interfere with each other. There's no such thing as a fight. Therefore, the display quality can be improved.

  A semiconductor layer doped with impurities is formed at the interface between the drain electrode SD2 and the source electrode SD1 and the semiconductor layer AS, and this semiconductor layer functions as a contact layer.

  After forming the semiconductor layer AS, a thin semiconductor layer doped with impurities is formed on the surface thereof, and after forming the drain electrode SD2 and the source electrode SD1, the electrodes are exposed from the respective electrodes as a mask. The structure described above can be obtained by etching the semiconductor layer doped with impurities.

A protective film PSV made of, for example, SiN is formed on the surface of the transparent substrate SUB1 on which the drain signal line DL, the pixel electrode PIX, and the like are formed in this manner, covering the drain signal line DL and the like.
This protective film PSV is provided to avoid direct contact of the thin film transistor TFT with the liquid crystal.

  On the other hand, although not shown, a black matrix (a dotted line frame BM in FIG. 2) is formed so as to define each pixel area on the surface of the transparent substrate facing the transparent substrate SUB via the liquid crystal. Is formed).

  The black matrix BM is provided in order to avoid the irradiation of extraneous light to the thin film transistor TFT and to improve the display contrast.

  Furthermore, a color filter having a color corresponding to each pixel region is formed in the opening of the black matrix BM (a region through which light is transmitted and becomes a substantial pixel region).

  As this color filter, for example, filters of the same color are used in each pixel region arranged in parallel in the y direction. For example, red (R), green (G), and blue (B) filters are provided for each pixel region in the x direction. They are arranged in order.

  Hereinafter, an embodiment of a manufacturing method of the liquid crystal display device configured as described above will be described with reference to FIGS.

Step 1. (Fig. 3 (a))
First, an Al layer is formed on the transparent substrate SUB to a thickness of about 300 nm by using, for example, a sputtering method. A mask pattern of a photoresist resin film is formed on the Al layer by using a photolithography technique (hereinafter referred to as a “photo process”).

  After selectively etching the Al with a mixed solution of phosphoric acid, hydrochloric acid and nitric acid, the photoresist resin film is peeled off.

  As a result, the gate signal line GL and a plurality of scattered first projections PR1 that are exposed on the surface of the pixel electrode are formed by the pattern of the remaining Al layer.

Step 2. (Fig. 3 (b))
The surface of the patterned Al layer is anodized in a tartaric acid solution, thereby forming an anodized film AO having a thickness of about 180 nm.

  Thereafter, an ITO (Indium-Tin-Oxide) film having a thickness of about 100 nm is formed on the surface of the transparent substrate SUB by a sputtering method, for example, and the ITO film is selectively etched with an aqua regia solution through a photo process.

  The remaining ITO film is formed as second convex portions PR2 on some of the first convex portions PR1 among the first convex portions PR1 made of Al, or in the portions where the first convex portions PR1 are not formed. Two convex portions PR2 are formed.

Step 3. (Fig. 3 (c))
A silicon nitride film SiN is deposited on the surface of the transparent substrate SUB to a thickness of about 240 nm by using, for example, a CVD method. This silicon nitride film SiN is configured as an insulating film GI.

  Next, after depositing an amorphous silicon layer to a thickness of about 200 nm by a CVD method, an n (+) amorphous silicon layer doped with about 1% phosphorus (P) is deposited to a thickness of about 35 nm. A sequential stacked body of these amorphous silicon layers and n (+) amorphous silicon layers is configured as a semiconductor layer AS.

  After the photo process, the semiconductor layer AS and the insulating film GI are collectively dry-etched using sulfur hexafluoride gas.

  In this case, since the etching rate of the upper semiconductor layer is higher than the etching rate of the lower insulating film, the end of the insulating film has a forward taper angle of about 4 °, whereas the end of the semiconductor layer The part has a forward taper angle of about 70 °.

  In the dry selective etching of the semiconductor layer AS and the insulating film GI through the photo process at this time, the insulating film GI and the semiconductor layer AS are overlaid on the first protrusion PR1 (or the second protrusion PR2). A third convex part PR3 and a fourth convex part PR4 made of a laminate are formed.

  In the same figure, these 3rd convex part PR3 and 4th convex part PR4 are overlapped and formed on all the 1st convex parts PR1 (or 2nd convex part PR2), However, It is limited to this. Instead, it may be formed so as to overlap with some selected ones of the first protrusions PR1 (or the second protrusions PR2).

Step 4. (Fig. 3 (d))
On the surface of the transparent substrate SUB, chromium (Cr) is deposited to a thickness of about 30 nm by using, for example, a sputtering method, and aluminum (Al) is further deposited to a thickness of about 200 nm. These laminates of Cr and Al are configured as drain signal lines DL (drain electrodes SD1 and source electrodes SD2 of the thin film transistors TFT) or pixel electrodes PIX.

  After the photo step, Al is selectively etched using a mixed solution of phosphoric acid, hydrochloric acid, and nitric acid, and Cr is selectively etched using a cerium nitrate second ammonium solution.

  Then, the n (+) amorphous silicon layer exposed from the drain electrode SD1 and the source electrode SD2 on the semiconductor layer AS is removed by dry etching using sulfur hexafluoride gas.

Step 5. (Fig. 3 (e))
Silicon nitride (SiN) is deposited on the surface of the transparent glass substrate to a thickness of about 300 nm using, for example, a CVD method. This SiN film is configured as a protective film PSV.

  After the photo step, patterning is performed by dry etching using sulfur hexafluoride gas. Although not shown in the drawing, this patterning is a hole for exposing the terminal of the gate signal line GL or the drain signal line DL outside the area of the display portion composed of a set of pixel areas.

Example 2
FIG. 4 is a plan view showing another embodiment of the pixel of the liquid crystal display device according to the present invention and corresponds to FIG. FIG. 5 shows a cross-sectional view taken along line V-V in FIG.

  2 differs from the configuration of FIG. 2 in that the source electrode SD2 (the drain electrode SD1 and the drain signal line DL are the same) of the thin film transistor TFT and the pixel electrode PIX are positioned in different layers via the protective film PSV. PIX is that it is connected to the source electrode SD2 through a contact hole CH formed in the protective film PSV.

  Even in such a configuration, a large number of projections PR having different planar shapes are formed on the lower layer side of the pixel electrode PIX, and the projections PR are exposed on the surface of the pixel electrode PIX.

Hereinafter, an embodiment of a manufacturing method of the liquid crystal display device thus configured will be described with reference to FIG.
Since this manufacturing method is the same up to step 5 (FIG. 3E) in the manufacturing method having the configuration shown in Example 1 (FIG. 3), the subsequent steps will be described.

Step 6. (Fig. 6 (a))
A contact hole CH is formed in the protective film PSV formed on the surface of the transparent substrate SUB by exposing a part of the extending portion of the source electrode SD2 through a photo process.

Step 7. (Fig. 6 (b))
On the surface of the transparent substrate SUB, chromium (Cr) is deposited to a thickness of about 30 nm by using, for example, a sputtering method, and aluminum (Al) is further deposited to a thickness of about 200 nm. These laminates of Cr and Al are configured as pixel electrodes PIX.

  After the photo step, Al is selectively etched using a mixed solution of phosphoric acid, hydrochloric acid, and nitric acid, and Cr is selectively etched using a cerium nitrate second ammonium solution.

  Here, by forming the pixel electrode PIX on the upper surface of the protective film PSV in Step 7, the function of the sequential laminate of chromium and aluminum formed in Example 1 as the pixel electrode is impaired.

  Even if this laminated body is left as it is, there is no harmful effect as a liquid crystal display device, but it may be selectively formed in an island shape in the formation region of the projection PR.

  That is, when the drain signal line DL (drain electrode SD1) and the source electrode are formed, the fifth protrusion PR5 is formed by the metal layer (sequential laminate of Cr and Al), thereby forming the protrusion PR. The shape can be changed. FIG. 7 is a configuration diagram in such a case.

Step 8. (Fig. 6 (c))
Silicon nitride (SiN) is deposited on the surface of the transparent glass substrate to a thickness of about 300 nm using, for example, a CVD method. This SiN film is configured as a protective film PSV1.

  After the photo step, patterning is performed by dry etching using sulfur hexafluoride gas. Although not shown in the drawing, this patterning is a hole for exposing the terminal of the gate signal line GL or the drain signal line DL outside the area of the display portion composed of a set of pixel areas.

  As described above, each projection PR positioned below the pixel electrode PIX is configured to include at least two types of shapes when the pixel electrode PIX is observed in a plane. is there.

  Here, each aspect of each convex part from which a shape differs is demonstrated using FIG. 8 thru | or FIG. Each figure shows, for example, three adjacent projections PR among a large number of scattered projections PR, and shows the shapes of the three projections PR. Each figure (a) is a plan view, and (b) is ( Sectional drawing in the bb line of a) is shown.

  Moreover, in each figure, although the convex part PR is mainly formed using the circular-shaped material, it cannot be overemphasized that it may be a rectangle, a polygon, or other special shapes. .

  First, in FIG. 8, each convex part PR is composed of two material layers, and the first convex part and the second convex part have a circular shape.

  Here, the convex part of the second layer is arranged with the center shifted from the convex part of the first layer.

  By configuring in this way, when the convex portions are compared, the taper angles are arranged so that the taper angles on the side walls thereof are different and the directions are different even if they are the same.

  Further, in FIG. 9, each convex part PR includes a single layer material, a two layer material, and a three layer material, which are mixedly arranged.

  Even if it comprises in this way, when each convex part PR is compared, the taper angle in those side walls comes to differ.

  Further, in FIG. 10, each projection PR is formed of two material layers, and the second layer material has a different shape.

Even if it comprises in this way, when each convex part is compared, the taper angle in those side walls will differ.
And in implementation of this invention, it cannot be overemphasized that you may form so that each basic structure mentioned above may be combined.

  In the above-described embodiment, the protective film PSV formed in the lower layer on the pixel electrode PIX is an inorganic film such as SiN. However, the protective film PSV may be an organic film such as a resin film. A sequential laminated body with a film may be used. When these are formed as island-shaped material layers in the convex part PR, the convex part PR has a smooth top, so that the light reflected on the surface of the pixel electrode PIX in which the convex part PR is manifested is There is an effect that the direction is varied and the diffusibility is improved.

  In the first embodiment described above, the protective film PSV is provided on the pixel electrode PIX in the display area, and in the second embodiment, the protective film PSV1 is provided on the pixel electrode PIX in the display area. The effect of the present invention is not changed.

  Note that the liquid crystal display device shown in each embodiment has a pixel electrode formed of a reflective electrode in the most area of each pixel. However, in each pixel, a pixel electrode consisting of a transparent electrode is formed in almost half of the area, and a pixel electrode consisting of a reflective electrode is formed in the remaining area, so that it can also be applied to a so-called transmissive and reflective liquid crystal display device. Needless to say, it can be done.

FIG. 3 is a main part configuration diagram showing an embodiment of a liquid crystal display device according to the present invention, and is a cross-sectional view taken along the line II of FIG. 2. It is a top view which shows one Example of the pixel of the liquid crystal display device by this invention. It is process drawing which shows one Example of the manufacturing method of the liquid crystal display device by this invention. It is a top view which shows the other Example of the pixel of the liquid crystal display device by this invention. It is sectional drawing in the VV line of FIG. It is process drawing which shows the other Example of the manufacturing method of the liquid crystal display device by this invention. It is principal part sectional drawing which shows the other Example of the liquid crystal display device by this invention. It is explanatory drawing which shows the other Example of the liquid crystal display device by this invention. It is explanatory drawing which shows the other Example of the liquid crystal display device by this invention. It is explanatory drawing which shows the other Example of the liquid crystal display device by this invention.

Explanation of symbols

  SUB ... Transparent substrate, GL ... Gate signal line, DL ... Drain signal line, TFT ... Thin film transistor, PIX ... Pixel electrode, PR ... Convex part, PR1 ... First convex part, PR2 ... Second Convex part, PR3... Third convex part, PR4... Fourth convex part, PR5.

Claims (12)

A substrate disposed opposite to each other via a liquid crystal;
A pixel electrode that reflects extraneous light incident on each pixel region on the liquid crystal side of one of the substrates through the other substrate,
The pixel electrode is formed with projections scattered on the surface thereof,
Each of the convex portions has two or more types having different shapes when the pixel electrode is viewed in a plane.
The convex portion formed on the surface of the pixel electrode is formed by an island-shaped multilayer material layer positioned on the lower layer side of the pixel electrode,
The liquid crystal display device according to claim 1, wherein the convex portions having different numbers of layers of the island-shaped multilayer material layers exist.   The island-shaped multilayer material layer forming one of the convex portions includes a first layer and a second layer having a shape that is not the same as or similar to the first layer when viewed in a plan view. The liquid crystal display device according to claim 1, further comprising: a layer.   Each of the island-shaped multilayer material layers has a plane shape of one layer different from a plane shape of one layer of the other island-shaped multilayer material layer. 2. A liquid crystal display device according to 2.   4. The liquid crystal display device according to claim 1, wherein each of the island-shaped multilayer material layers has a taper formed on a side wall thereof and having different angles. A plurality of gate signal lines formed on the liquid crystal side surface of the one substrate;
A plurality of drain signal lines formed crossing the gate signal line on the liquid crystal side surface of the one substrate;
The pixel region is a region surrounded by the gate signal lines arranged adjacent to each other and the drain signal lines arranged adjacent to each other.
A thin film transistor that is driven by supplying a scanning signal from the gate signal line on one side to the pixel region;
5. The liquid crystal display device according to claim 1, wherein the pixel electrode is supplied with a video signal from the drain signal line on one side via the thin film transistor. 6.   The liquid crystal display device according to claim 5, wherein the pixel electrode is formed in most of the pixel region.   The liquid crystal display device according to claim 5, wherein the pixel electrode is formed in a part of the pixel region. A plurality of gate signal lines formed on the liquid crystal side surface of the one substrate;
A plurality of drain signal lines formed crossing the gate signal line on the liquid crystal side surface of the one substrate;
The pixel region is a region surrounded by the gate signal lines arranged adjacent to each other and the drain signal lines arranged adjacent to each other.
A thin film transistor that is driven by supplying a scanning signal from the gate signal line on one side to the pixel region;
The pixel electrode is supplied with a video signal from the drain signal line on one side via the thin film transistor,
The island-shaped multilayer material layer includes the same material layer as the gate signal line, the same material layer as the gate insulating film of the thin film transistor, the same material layer as the drain signal line, and a protective film covering the thin film transistor. 8. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is formed of a laminate of at least two material layers of the same material layer.   The liquid crystal display device according to claim 8, wherein the protective film includes an organic material or a sequentially laminated body of an inorganic material and an organic material.   The liquid crystal display device according to claim 1, wherein the island-shaped multilayer material layer is formed of an inorganic material.   11. The liquid crystal according to claim 1, wherein the island-shaped multilayer material layer is made of the same inorganic material as other constituent elements positioned below the pixel electrode. Display device.   12. The organic material layer or a sequential laminate of an inorganic material and an organic material is provided between the pixel electrode and the island-shaped multilayer material layer, according to any one of claims 1 to 11. Liquid crystal display device.

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