JP2000029030A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain excellent display quality without making rubbing lines conspicuous by subjecting only a first perpendicular alignment film to rubbing treatment and making a step formed on the first substrate by the rubbing treatment smaller than that on the second substrate. SOLUTION: In this device, an active matrix substrate 20 is provided on its surface of the liquid crystal side with a reflective electrode region 20R and a transmissive electrode region 20T different in height and a perpendicular alignment layer is formed on each surface of the liquid crystal layer sides of the substrate 20 and another substrate 60, to perform rubbing treatment on these layers in an R1 direction different from a conventional R2 direction. When the rubbing treatment is performed in the R2 direction, many rubbing lines are caused to obtain only low display quality. On the other hand, when the rubbing treatment is performed in the R1 direction, fewer rubbing lines are caused, to attain a well-aligned state and to obtain excellent display quality. Also, by performing the rubbing treatment in the R1 direction parallel to the longitudinal direction of the shape of a transmission section, the variation in pretilt angle due to the difference in level can be controlled to the minimum.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to a transflective liquid crystal display device having excellent visibility even in a bright place such as outdoors, indoors where little external light is present, or in darkness.

[0002]

2. Description of the Related Art A liquid crystal display device is characterized by its thinness and low power consumption, and is characterized by OA equipment such as a word processor and a personal computer, portable information equipment such as an electronic organizer, and a camera having a liquid crystal monitor. Widely used for body VTRs and the like. In many of these liquid crystal display devices, a TN (twisted nematic) is used in which a liquid crystal material having a positive dielectric anisotropy is horizontally aligned with respect to a substrate, and liquid crystal molecules are twisted by 90 degrees between upper and lower substrates. Mode is used. Further, since a higher contrast can be realized as compared with the TN mode, a DAP in which a liquid crystal material having a negative dielectric anisotropy is vertically aligned with respect to the substrate is used.
(Deformation Aligned Phase) mode has been actively developed.

[0003]

SUMMARY OF THE INVENTION However, DAP
Compared with the TN mode, when the voltage is applied, the surface of the alignment film for defining the alignment direction of the liquid crystal molecules is rubbed with a cloth (hereinafter referred to as a rubbing process). There has been a problem that luminance unevenness (hereinafter referred to as rubbing streak) is likely to occur and display quality is deteriorated.

In particular, a transflective liquid crystal display device using a DAP mode (Japanese Patent Application No. 9-201176 by the present applicant).
No. 2), there is a problem that rubbing lines are remarkably noticeable as compared with a conventional transmission type liquid crystal display device using a DAP mode.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has as its object to provide a liquid crystal display device having excellent display quality, in which rubbing lines are inconspicuous.

[0006]

A liquid crystal display device according to the present invention comprises a first and a second substrate, and a liquid crystal material having a negative dielectric anisotropy sandwiched between the first and the second substrates. The first and second substrates have first and second vertical alignment films on their respective liquid crystal layer side surfaces, and only the first vertical alignment film is subjected to a rubbing treatment. The first substrate has a configuration in which the step for the rubbing process is smaller than that of the second substrate, thereby achieving the above object.

[0007] The first substrate may further include a color filter layer, and the second substrate may include, for each of a plurality of picture element regions, a switching element and a picture element electrode connected to the switching element. Good.

A liquid crystal display device according to the present invention has first and second substrates and a liquid crystal layer made of a liquid crystal material having a negative dielectric anisotropy sandwiched between the first and second substrates. The first and second substrates are liquid crystal display devices each having a first and a second vertical alignment film on a surface of the liquid crystal layer side, wherein the second substrate has a reflective surface for each pixel region. An electrode region and a transmission electrode region, wherein the reflection electrode region is higher than the transmission electrode region and forms a step on the surface of the second substrate; and the second vertical alignment film has a step with respect to a rubbing process. Is rubbed in a direction in which the rubbing is minimized, and the first vertical alignment film is not rubbed, thereby achieving the above object.

It is preferable that a step formed on the surface of the second substrate by the reflective electrode region and the transmissive electrode region does not exist in the rubbing direction.

Hereinafter, the operation will be described.

In the liquid crystal display device of the present invention, disturbance of the rubbing process due to a step can be minimized, so that display defects (rubbing streaks) caused by uneven rubbing process can be reduced. Particularly, by applying the present invention to a transflective liquid crystal display device using a vertical alignment film and a liquid crystal material having negative dielectric anisotropy, excellent display quality can be realized. Further, the display quality can be further improved by adopting a configuration in which a step in the rubbing direction does not exist in the picture element region.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below by taking a transflective liquid crystal display device as an example. The transflective liquid crystal display device has a function of a transmissive liquid crystal display device that displays by using transmitted light from a backlight provided on the back of the liquid crystal panel, and displays by using ambient light on the front surface of the liquid crystal panel. This is a liquid crystal display device having the function of a reflection type liquid crystal display device (for example, Japanese Patent Application No. 9-201176 by the present applicant).
issue). The present invention has a large effect in a liquid crystal display device using a liquid crystal material having a negative dielectric anisotropy and a vertical alignment film formed on a surface having a large step, as described in detail below, but has a small step. And the present invention is not limited to the following embodiment.

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

Embodiment 1 FIG. 1 shows a transflective liquid crystal display device 100 according to Embodiment 1 of the present invention.
FIG. 1A is a plan view showing an active matrix substrate 20 constituting the liquid crystal display device 100. FIG.
FIG. 1B is a partial cross-sectional view of the liquid crystal display device 100, and FIG.
(A) corresponds to a cross section along the line BB '. A cross-sectional view taken along the line AA ′ of FIG. 1A is shown in FIG. 4B showing a manufacturing process.

As shown in FIG. 1B, the liquid crystal display device 100 includes an active matrix substrate 20, a counter substrate (color filter substrate) 60, and a liquid crystal layer 40 interposed therebetween. I have. A picture element serving as a minimum display unit of the liquid crystal display device 100 has a reflective area defined by the reflective electrode 19 and a transmissive area defined by the transparent electrode 18. The thickness of the liquid crystal layer 40 is dr in the reflection region and dt (dtｄ2dr) in the transmission region.
It has become. This is to make the optical path lengths of the light (reflected light in the reflection area and transmitted light in the transmission area) contributing to the display substantially equal. Although dt = 2dr is preferable, it may be appropriately set in relation to the display characteristics. At least dt> dr may be satisfied. Typically, dt is about 4-6 μm and dr is about 2-3 μm. That is, a step of about 2 to 3 μm is formed in the picture element region of the active matrix substrate 20. If the reflective electrode 19 has irregularities as shown, the average value may be set to dr.

As described above, in the transflective liquid crystal display device 100, regions having different thicknesses of the liquid crystal layer 40 (reflection region and transmission region) are formed. In this example, a reflective electrode region 20R and a transmissive electrode region 20T having different heights are provided on the liquid crystal side surface of the active matrix substrate 20.
A vertical alignment film (not shown) is formed on the surface of the substrates 20 and 60 on the liquid crystal layer 40 side. In this embodiment, the rubbing process is performed on the vertical alignment film on the active matrix substrate 20 in the direction indicated by the arrow R1 in FIG. For example,
A vertical alignment film JALS2004 (manufactured by Japan Synthetic Rubber) was printed so as to have a thickness of 80 nm, and baked at 180 ° C. for 2 hours. A rubbing process was performed on the active matrix substrate 60 using a rayon cloth at a roller rotation speed of 100 rpm and a substrate feed speed of 1000 mm / min.

The rubbing direction in a normal liquid crystal display device is a direction indicated by an arrow R2 in FIG. 1A (an angle of 45 ° with respect to the gate bus line 22 or the source bus line 24. However, the direction of R2). When the rubbing treatment was performed, rubbing streaks were often generated and only a liquid crystal display device with low display quality could be obtained. On the other hand, when the rubbing treatment was performed in the direction of R1, the occurrence of rubbing streaks was small and the alignment state was low. Display device 100 with good display quality and excellent display quality
was gotten.

This is because, when rubbing is performed in the direction of R1, the step at which the bristle of the rubbing cloth directly contacts the rubbing direction is only the sides α and β of the four sides of the transmission region 20T in FIG. However, when rubbing is performed in the direction of R2, the bristle of the rubbing cloth hits the step of the sides α, β, γ, and δ, and the step that hits the rubbing cloth is larger than that in the case of rubbing in the R1 direction ( The side of the step is long). As a result, the bristle of the rubbing cloth is disturbed, and uniform rubbing treatment becomes difficult, and as a result, defects such as rubbing streaks are caused. Therefore, by performing rubbing in the R1 direction parallel to the longitudinal direction of the shape of the transmitting portion, it is possible to minimize variations in pretilt angle due to steps.

The alignment of the liquid crystal molecules is determined by the regulating force of the alignment film formed on the substrate and the interaction between the liquid crystal molecules. In the case of a liquid crystal material having a negative dielectric anisotropy, when a voltage is applied, the liquid crystal molecules are re-aligned from a vertical alignment state to a horizontal alignment state. And must be uniform. If the directions in which the liquid crystal molecules fall are different, alignment defects (hereinafter, disclination) occur, and display quality is degraded. A rubbing process is performed to make the liquid crystal molecules fall uniformly in the same direction. At this time, the liquid crystal molecules are oriented in a state of being slightly inclined from the normal direction of the substrate to the direction in which the rubbing process is performed (this inclination angle is hereinafter referred to as a pretilt angle). Regarding the rubbing mechanism, a model in which the side chains of the polymers constituting the alignment film are arranged in the rubbing direction and the liquid crystal molecules are aligned along the side chains is generally considered. However, the side chain used in the vertical alignment film is often a long alkyl chain having 3 to 20 carbon atoms, and it is not easy to stably align the direction in one direction. If the underlayer of the alignment film, that is, the surface of the substrate is flat, the rubbing effect is uniform, but if there is a step, the rubbing effect varies depending on the location. It is thought to be visible. Therefore, particularly when a vertical alignment film and a liquid crystal material having a negative dielectric anisotropy are used, if there are many steps in the rubbing treatment, poor alignment is likely to occur.

The term "step relative to the rubbing process" as used herein refers to a step (discontinuous) having a side that is not parallel to the rubbing direction in the picture element region, and the total of the lengths of the sides is a step difference. Evaluate the quantity. Steps other than the picture element area
It does not need to be considered as it does not affect the display. If the difference in height of the step is less than about 1 μm, there is substantially no effect on the rubbing treatment, so that the difference in height is about 1 μm.
It is only necessary to consider the step difference of m or more.

Hereinafter, the configuration of the liquid crystal display device 100 of the present invention and a method of manufacturing the same will be described. The transmission-reflection type active matrix substrate 20 includes a plurality of gate bus lines 22 as scanning lines and source bus lines 24 as signal lines on a glass substrate 11 which is an insulating substrate.
Are provided so as to intersect alternately. In a rectangular area surrounded by each gate bus line 22 and each source bus line 24, a reflection electrode 19 made of a material having high light reflection efficiency and a transparent electrode made of a material having high light transmission efficiency are separately provided. The reflective electrode 19 and the transparent electrode 18 form a pixel electrode.

A gate electrode 23 extending from the gate bus line 22 toward the pixel electrode is branched at a corner in the area where each of the pixel electrodes is arranged. A thin film transistor (TFT) 21 is formed in a portion as a switching element. The gate electrode 23 forms a part of the TFT 21. TFT21
Is disposed above the gate electrode 23 formed on the glass substrate 11, as shown in FIG.
The gate electrode 23 is covered with the gate insulating film 11a.
The semiconductor layer 27 is stacked so as to cover the upper part of the semiconductor device.

A pair of contact layers 28 are formed so as to cover both ends on the semiconductor layer 27.

The source bus line 24 is electrically connected to the source electrode 25, and the tip of the source electrode 25 formed on the contact layer 28 is superposed on the gate electrode 23 in an insulated state. A part of.
The gate electrode 23 is spaced apart from the source electrode 25 and overlaps the gate electrode 23 in an insulated state.
A drain electrode 26 of T21 is provided on the contact layer 28. The drain electrode 26 is electrically connected to the pixel electrode via the base electrode 31a.

At this time, the auxiliary capacitance is formed by a structure in which the base electrode 31a and the next-stage gate bus line 24 overlap with the gate insulating film 11a interposed therebetween. Further, by forming the base electrode 31a in substantially the entire region where the uneven portion described later exists, it is possible to make the influence of the process uniform.

On the other hand, under the reflective electrode 19 made of the above-mentioned material having high light reflection efficiency, a high-height protrusion 14a and a low-height protrusion 14b randomly formed on the glass substrate 11 are provided. There is a polymer resin film 15 formed on these convex portions 14a and 14b.

The upper surface of the polymer resin film 15 has a continuous wavy shape due to the presence of the above-mentioned projections 14a and 14b.

The above-mentioned reflective electrode 19 is formed on a portion of the polymer resin film 15 which is present on the above-mentioned convex portions 14a and 14b and has a continuous upper surface in a wavy shape. The electrode 19 is formed of, for example, Al having high light reflection efficiency. The reflection electrode 19 is electrically connected to the drain electrode 26 via the contact hole 29.

In the transmission / reflection type liquid crystal display device of the present invention, a transparent electrode 18 is formed separately from the reflection electrode 19, and the transparent electrode 18 is made of a material having a high light transmission efficiency, for example, ITO (Indium). Tin Oxid
e) and the like. Next, a method for forming the reflective electrode 19 and the transparent electrode 18 which are the main parts of the active-matrix substrate 20 of the transmission / reflection type will be described with reference to the drawings. 2A, 2B, 3A, 3B, 4A, and 4B are process cross-sectional views taken along line AA of the liquid crystal display device shown in FIG.

First, as shown in FIG. 2A, a plurality of gate bus lines 22 (see FIG. 1) made of Cr, Ta, etc.
A gate electrode 23 branching from 2 is formed.

The gate insulating film 11 made of SiNx, SiOx or the like is formed on the entire surface of the glass substrate 11 so as to cover the gate bus line 22 and the gate electrode 23.
a, and a semiconductor layer 27 made of amorphous silicon (a-Si), polycrystalline silicon, CdSe, or the like is formed on the gate insulating film 11 a above the gate electrode 23. And, at both ends of the semiconductor layer 27,
Contact layers 28, 28 made of amorphous silicon (a-Si) or the like are formed.

On one of the contact layers 28, 28, a source electrode 2 made of Ti, Mo, Al or the like is formed.
5, a drain electrode 26 made of Ti, Mo, Al or the like is formed on the other side in the same manner as the source electrode 25.

In the first embodiment, the glass substrate 11
For example, Corning # 7059 having a thickness of 1.1 mm was used.

Then, as shown in FIG. 2B, a metal layer 31 constituting the source bus line 24 and this metal layer 3
1 and at the same time as the formation of the metal layer 31,
1a was formed by a sputtering method.

Subsequently, as shown in FIG. 3A, the ITO layer 30 constituting the source bus line 24 was patterned by a sputtering method.

In the first embodiment, the layers constituting the source bus lines 24 are two layers of the metal layer 31 and the ITO layer 30.
A layer structure was adopted. In this structure, even if a part of the metal layer 31 constituting the source line 24 has a film defect, the disconnection of the source bus line 24 can be reduced because it is electrically connected by the ITO layer 30. There is an advantage that you can.

Using the ITO layer 30, a transparent electrode 18 constituting a picture element electrode was formed simultaneously with the formation of the ITO layer 30. By doing so, the transparent electrode 18 can be formed simultaneously with the formation of the source bus line 24, and the number of layers does not increase.

Next, as shown in FIG. 3 (b), the convex portions 14a and 14b having a substantially circular cross section and made of a photosensitive resin resist film 12 are formed under the region where the reflective electrode 19 is to be patterned. Formed.

Here, the process of forming the projections 14a and 14b formed in the reflection area will be described with reference to FIG.
A brief description will be given using (a) to (d).

First, as shown in FIG. 5A, a glass substrate 11 (actually, as shown in FIG. 3B, a metal layer 31 and a base electrode 31a are already formed on the glass substrate 11). A resist film 12 made of a photosensitive resin is formed by spin coating. As the resist film 12, a photosensitive resin of OFPR-800, which is the same material as the polymer resin film 15 described later, is preferably spin-coated at 500 rpm to 3000 rpm, and in the first embodiment at 1500 rpm for 30 seconds. Membrane 1
2 had a thickness of 2.5 μm.

Next, the glass substrate 11 on which the resist film 12 is formed is prebaked at, for example, 90 ° C. for 30 minutes.

Subsequently, for example, as shown in FIG.
A photomask 13 in which two types of circular pattern holes 13a and 13b are formed in 3c is used. This photomask 13 is disposed above the resist film 12 as shown in FIG. Exposure is performed from above the photomask 13 as shown by arrows in the figure.

The photomask 13 according to the first embodiment has a circular pattern hole 13a having a diameter of 5 μm.
The circular pattern holes 13b having a diameter of 3 μm are arranged at random, and the intervals between the pattern holes adjacent to each other are separated by at least 2 μm. However, if they are separated too much, it is difficult for the upper surface of the polymer resin film 15 to have a continuous wavy shape.

Next, development is performed using a developing solution of 2.38% concentration, for example, made of NMD-3 manufactured by Tokyo Ohka. As a result, as shown in FIG. On the surface of the reflective area of the fine projections 14 having different heights.
a 'and 14b' are formed in large numbers. These convex portions 14
In the first embodiment in which the upper edges are angular, the heights a ′ and 14b ′ are 2.4 due to the pattern holes 13a having a diameter of 5 μm.
An 8 μm projection 14 a was formed, and a 1.64 μm height projection 14 b was formed by a 3 μm diameter pattern hole 13 b.

The height of the projections 14a 'and 14b' can be changed by the size of the pattern holes 13a and 13b, the exposure time, and the development time. However, the size is not limited to the above.

Next, as shown in FIG.
The glass substrate 11 on which a ′ and 14b ′ are formed is heated at 200 ° C. for 1 hour to perform heat treatment. As a result, FIG.
As shown in (c), the as-developed convex portions 14a 'and 14b' having a corner portion at the upper end portion are softened so that the corner portion is rounded, that is, the convex portion having a substantially circular cross section is cut off. Part 1
4a and 14b are formed.

The protrusions 14a, 1 as shown in FIG.
4b is formed by the process described above. next,
As shown in FIG. 4A, a polymer resin film is
A polymer resin film 15 was formed by spin-coating on 1 and patterning. As the polymer insulating film, the above-mentioned O
Using FPR-800, preferably at 1000 rpm
In the first embodiment in which the spin coating is performed at 3000 rpm, the spin coating is performed at 2000 rpm.

As a result, a high-molecular resin film 15 having a continuous upper surface is formed.

Next, as shown in FIG. 4B, a reflective electrode 19 made of Al was formed on a predetermined portion of the polymer resin film 15 by, for example, sputtering. Materials suitable for use in the reflective electrode 19 include:
In addition to Al and Al alloys, for example, Ta having high light reflection efficiency,
Ni, Cr, Ag, etc., can be used.
The thickness of 9 is suitably about 0.01 to 1.0 μm. The reflection electrode 19 formed of a material having a high light reflection efficiency formed in this manner has a continuous upper surface like a base film.

In the first embodiment, the transparent electrode 18 is formed simultaneously with the formation of the source bus line 24.
When the source bus line 24 is not a two-layer structure of the metal layer 31 and the ITO layer 30, but is a single layer of the metal layer 31,
The formation of the transparent electrode 18 and the formation of the source bus line 24 may be separate.

The pattern holes 13 of the photomask 13
Although the shapes of a and 13b are circular in the first embodiment, the shapes may be other shapes such as a rectangle, an ellipse, and a stripe.

In the first embodiment, two convex portions 14a and 14b having different heights are formed. However, the present invention is not limited to this, and three or more convex portions may be formed. Even if convex portions having different heights are formed, it is possible to form a reflective electrode having good reflection characteristics.

However, it can be seen that forming the projections with two or more projections having different heights can provide a reflection electrode having better wavelength dependence of the reflection characteristics than forming the projections with one height. ing.

Here, if a continuous wavy upper surface can be obtained only by forming the convex portions 14a and 14b, the continuous wavy shape is formed only by the resist film 12 to form the polymer resin film 15. And the reflective electrode 19 may be formed. This makes it possible to shorten the step of forming the polymer resin film 15. In the first embodiment, OFPR-800 manufactured by Tokyo Ohka Co., Ltd. is used as the photosensitive resin material. However, the present invention is not limited to this, and an exposure process is used regardless of whether it is a negative type or a positive type. Any material can be used as long as it is a photosensitive resin material that can be patterned. For example, OMR-83, OMR-
85, ONNR-20, OFPR-2, OFPR-83
0, or OFPR-500, or TF-20, 1300-2 manufactured by Shipley.
7, or 1400-27. In addition, Toray's Photo Nice, Sekisui Fine Chemical's R
W-101 and R101 and R633 manufactured by Nippon Kayaku may be used.

In the first embodiment, the TFT 21 is used as a switching element. However, the present invention is not limited to this, and other switching elements, for example, MIM (Metal
-Insulator-Metal) can be applied to an active matrix substrate using an element, a diode, a varistor, or the like.

The shape of the transmission section 20T is not limited to the above example. For example, as schematically shown in FIGS. 7A and 7B, the transmission region 20T 'may be formed so as to penetrate a plurality of pixel regions. FIG. 7B is a cross-sectional view taken along line CC ′ of FIG. 7A. In the above-described example (FIG. 1), since the transmission region exists in a form in which a part of the reflection electrode is hollowed out, the step felt by the rubbing cloth in the rubbing direction did not completely disappear. When the transmissive area 20T 'is formed as shown in FIG. 7 (a), there is no step felt by the rubbing cloth in the rubbing direction in the picture element area. And uniform rubbing can be realized. As a result, a liquid crystal display device having excellent display quality can be obtained.

(Embodiment 2) In this embodiment 2, a vertical alignment film (not shown) on the color filter substrate 60 of the liquid crystal display device 100 shown in FIG. An example in which a rubbing process is not performed on a film will be described.

FIG. 8 is a plan view of a color filter substrate 60 which is an opposing substrate, and FIG.
FIG. 9B is a sectional view taken along line D ′, and FIG.
It is sectional drawing which followed the E 'line. Red on the glass substrate 62,
Green and blue color filter layers 64R, 64G, 6
4B is formed with a thickness of about 1.2 μm, on which an ITO film 66 as a transparent electrode is formed. A light-shielding layer 67 made of Cr is provided between these color filter layers.
Are formed.

The vertical alignment film JALS200 is formed on the active matrix substrate 20 and the color filter substrate 60 described above.
4 (manufactured by Nippon Synthetic Rubber Co., Ltd.) was printed so as to have a thickness of 80 nm, and baked at 180 ° C. for 2 hours. A rubbing treatment was performed on the opposing substrate using rayon cloth at a roller rotation speed of 100 rpm and a substrate feeding speed of 1000 mm / min. At this time, the rubbing direction was parallel to the DD ′ line in FIG. 8 (Y direction). No rubbing treatment was performed on the active matrix substrate. The liquid crystal panel was manufactured by bonding the active matrix substrate 20 and the counter substrate 60 manufactured in the same manner as in the first embodiment with an epoxy resin via a 3 μm spacer. A liquid crystal material having negative dielectric anisotropy (MJ: manufactured by Merck & Co.) was injected into this panel, and a polarizing plate and a retardation plate were arranged. Thus, a transflective liquid crystal display device was completed. The counter substrate 60 can be formed by a known method. The surface of the counter substrate 60 has a step due to the color filter layer 64, but the step does not exist for the rubbing process in the Y direction. Accordingly, as apparent from the figure, the DD ′ direction is EE ′.
The rubbing process is performed in parallel with the direction and the DD ′ direction with a very small step compared to the direction and the active matrix substrate 20, so that a uniform alignment regulating force can be given to the liquid crystal layer 40. The interaction between the opposing substrate 60 provided with the uniform alignment regulating force and the liquid crystal molecules causes the liquid crystal molecules to fall in one direction without rubbing the active matrix substrate 20 having a large number of steps. Since it is regulated, rubbing streaks are greatly reduced without causing disclination.

(Embodiment 3) In Embodiment 1 described above, the reflection electrode region is formed by electrodes having reflection characteristics, whereas in this embodiment, reflection is performed using a reflection layer (reflection plate) and a transparent electrode. Configure the electrode region. The reflective electrode region refers to a region on the substrate having a reflective function and a function of applying a voltage to the liquid crystal layer. In the first embodiment, the reflective electrode having the irregularities on the surface is formed, but it is not always necessary.

FIG. 10A is a top view of the active matrix substrate 80 used in the liquid crystal display device of the present embodiment, and FIG. 10B is a cross-sectional view taken along line FF ′ of FIG. As shown in FIG. 10A, when the active matrix substrate 80 is observed from above, a transparent electrode region 80T is provided in the center of the picture element in a rectangular shape, and a reflective electrode region 80R is provided so as to surround it. I have. Reflective electrode area 8
The outline of 0R is a square along the edges of the gate wiring 82 and the source wiring 84. In this example, a layer having a high reflectance (reflective layer) formed of the same material as the gate electrode 83 (and the gate wiring 82) is formed in the reflective electrode region 80T.
89 are provided.

As shown in FIG. 10B, the reflection layer 89
Is covered with a gate insulating film 92, on which a transparent electrode 88 functioning as a picture element electrode is formed. The reflection layer 89 and the transparent electrode 88 are insulated. The reflective layer 89 and the transparent electrode 88 formed on the reflective layer 89 form a reflective electrode region 80R.

The active matrix substrate 80 is formed by depositing a conductive film made of a reflective material on an insulating substrate 81 such as a glass substrate and patterning the conductive film to form a gate electrode 83, a gate wiring 82 and a reflective layer 89. To form Gate electrode 83, gate wiring 82 and reflection layer 89
After forming a gate insulating film 92 covering the semiconductor layer 93,
Channel protection layer 94, n ^{+ serving as} source / drain electrodes
-Deposit and pattern the Si layer 95 in order,
81 is formed. Metal layer 9 to be a part of source wiring 84
7b and the drain-picture element electrode connection layer 96 are formed by the same process. The connection layer 96 partially overlaps and is electrically connected to the drain electrode 95 of the TFT 81. A transparent conductive material (for example, ITO) is formed by a sputtering method,
By patterning, an upper layer 97a of the transparent electrode 88 and the source wiring 84 is formed. The transparent electrode 88 is formed in the whole area of each picture element and functions as a picture element electrode. The transparent electrode 88 is electrically connected to the drain electrode 95 of the TFT 81 by partially overlapping the connection layer 96. After that, a passivation film 98 covering at least the TFT 81 is formed.

A vertical alignment film (not shown) covering these is formed, and as described above, the rubbing process is performed in the pixel region in a direction in which the step relative to the rubbing process is small (parallel to the long side of the transmission electrode region 80T). By performing this, an active matrix substrate with less occurrence of rubbing streaks is formed. The height of the reflective electrode region 80R is, for example, the reflective layer 8
The thickness can be controlled by providing a passivation film 98 in the reflective electrode region and adjusting the thickness.

[0065]

As described in detail above, according to the present invention,
The present invention provides a liquid crystal display device which does not cause alignment failure due to rubbing treatment and has excellent display quality. Particularly, by applying the present invention to a transflective liquid crystal display device using a vertical alignment film and a liquid crystal material having negative dielectric anisotropy, excellent display quality can be realized.

[Brief description of the drawings]

FIG. 1 shows a transflective liquid crystal display device 100 according to a first embodiment. 1A is a plan view showing an active matrix substrate 20 constituting the liquid crystal display device 100, and FIG. 2B is a partial sectional view of the liquid crystal display device 100.

FIG. 2 is a cross-sectional view illustrating a manufacturing process of the active matrix substrate 20.

FIG. 3 is a cross-sectional view illustrating another manufacturing process of the active matrix substrate 20.

FIG. 4 is a cross-sectional view illustrating another manufacturing process of the active matrix substrate 20.

FIG. 5 is a cross-sectional view for explaining a method of forming a projection formed in a reflection area of the active matrix substrate 20.

FIG. 6 is a plan view showing a photomask used for forming a convex portion in a reflective portion region.

FIG. 7 is a plan view showing another active matrix substrate used in the liquid crystal display device of the present invention, and FIG. 7 (b) is a cross-sectional view taken along line CC ′ of FIG.

FIG. 8 is a plan view of the color filter substrate 60.

9A is a sectional view taken along line DD ′ of FIG. 8, and FIG. 9B is a sectional view taken along line EE ′ of FIG.

FIG. 10 is a plan view showing another active matrix substrate used in the liquid crystal display device of the present invention, and FIG. 10 (b) is a cross-sectional view taken along line FF ′ of FIG.

[Explanation of symbols]

 18, 66 Transparent electrode 19 Reflective electrode 20 Active matrix substrate 20R Reflective electrode region 20T Transmission electrode region 40 Liquid crystal layer 60 Counter substrate (color filter substrate) 100 Liquid crystal display device

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yozo Narutaki 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka F-term (reference) 2H090 HA03 JB02 KA07 LA04 LA15 MA01 MA16 MB01 MB02 MB03 MB05

Claims (4)

[Claims] A first substrate, a first substrate and a second substrate;
A first liquid crystal layer formed of a liquid crystal material having a negative dielectric anisotropy sandwiched between the substrate and the first and second substrates; A liquid crystal display device having an alignment film, wherein only the first vertical alignment film has been subjected to a rubbing process, and wherein the first substrate has less steps for the rubbing process than the second substrate. 2. The method according to claim 1, wherein the first substrate further includes a color filter layer, and the second substrate includes, for each of a plurality of pixel regions, a switching element and a pixel electrode connected to the switching element. The liquid crystal display device according to claim 1. 3. The first and second substrates, and the first substrate and the second substrate.
A first liquid crystal layer formed of a liquid crystal material having a negative dielectric anisotropy sandwiched between the substrate and the first and second substrates; A liquid crystal display device having an alignment film, wherein the second substrate has, for each pixel region, a reflective electrode region and a transmissive electrode region, and the reflective electrode region is higher than the transmissive electrode region; A step is formed on the surface of the two substrates, the second vertical alignment film is rubbed in a direction that minimizes a step relative to the rubbing process, and the first vertical alignment film is not rubbed, Liquid crystal display. 4. The liquid crystal display device according to claim 3, wherein a step formed on the surface of the second substrate by the reflective electrode region and the transmissive electrode region does not exist in the rubbing direction.