JP3396773B2 - Method for manufacturing active matrix type liquid crystal display element - Google Patents

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 used for flat panel displays of AV equipment and personal computers, word processors, etc., and in particular, production of a horizontal electric field mode active matrix liquid crystal display device having little viewing angle dependence on display characteristics. It is about the method.

[0002]

2. Description of the Related Art Liquid crystal display devices have been applied to liquid crystal televisions, personal computers, word processors, etc., and have recently been widely used as OA displays and projection TVs, and their display quality has been improving year by year.

In particular, an active matrix type twisted nematic liquid crystal display device using a thin film transistor (hereinafter referred to as a TFT) as a switching element has a great feature that a high contrast is maintained even when a large capacity display is carried out. Very large market demand for laptops and laptops, as well as large engineering workstations,
It is being actively developed and commercialized as the center of a large-capacity full-color display.

In such an active matrix type liquid crystal display element, a Twisted Nematic (hereinafter referred to as TN) type is widely used as a liquid crystal display mode. In the TN method, a panel having a structure in which liquid crystal molecules are twisted by 90 ° is sandwiched between two polarizing plates between electrode substrates sandwiching a liquid crystal layer. When a voltage is applied between the electrode substrates, the liquid crystal molecules try to align themselves in the direction of the electric field while unwinding the twisted structure, and the alignment state of these molecules changes the polarization state of the light that passes through the panel, thus increasing the light transmittance. This is because it is modulated. However, even in the same molecular arrangement state, the polarization state of the transmitted light changes depending on the incident direction of the light incident on the liquid crystal panel, so that the light transmittance varies depending on the incident direction. That is, the characteristics of the liquid crystal panel have a viewing angle dependency. This viewing angle characteristic causes a phenomenon of brightness inversion when the viewpoint is tilted obliquely with respect to the main viewing angle direction, that is, the long axis direction of the liquid crystal molecules in the intermediate layer of the liquid crystal layer. That is, in this display mode, it means that the display brightness at a certain voltage becomes brighter than that at a lower voltage. Especially, the brightness reversal phenomenon when a high voltage is applied for black display is caused by the liquid crystal panel. Has become an important issue in terms of image quality.

In order to solve this problem, instead of applying an electric field in the direction perpendicular to the substrate as in the TN type liquid crystal display system, a lateral electric field system in which the direction applied to the liquid crystal is substantially parallel to the substrate. There is, for example, Japanese Examined Patent Publication Sho 63-2190
No. 7 and JP-A-6-160878. A general horizontal electric field type liquid crystal display element has a structure in which a panel in which liquid crystal is sandwiched between an electrode substrate in which a comb-shaped pixel electrode and a common electrode are engaged and a counter substrate is sandwiched by two polarizing plates. Here, by applying a voltage between the pixel electrode and the common electrode, the molecular alignment of the liquid crystal between the electrodes is changed in a plane, and the light transmittance is modulated to display an image. In this lateral electric field method, since the alignment change of liquid crystal molecules changes in parallel to the electrode substrate, the viewing angle dependence of light modulation is small.

In both the TN type and the in-plane switching type, a rubbing method of rubbing the surface of an alignment layer such as polyimide formed on an electrode substrate with a resin fiber cloth is generally used as a means for aligning liquid crystals. ing. A general rubbing method is to rotate a roll around rayon or nylon cloth having a hair length of about 1 to 5 mm, and the tip of the hair is 0.1 to 0.5 m.
The entire surface of the substrate is processed by moving the substrate or roll while touching it for about m. By this rubbing method, the orientation direction of the liquid crystal is determined in the direction in which the tips of the hairs rub the substrate.

At the time of rubbing the substrate, the influence of the end face of the substrate and the T for the actual active matrix type liquid crystal display element are used.
The pixel electrode formed on the FT array substrate and the electrode extraction electrode for receiving an electric signal from the external drive circuit and the signal wiring electrode for transmitting the signal to the inside of the substrate have a thickness of about 0.
When the rubbing cloth 42 wound around the rubbing roll 41 is rotated and the substrate 43 is rubbed in the direction of the arrow 44 as shown in FIG. 4 due to the influence of the unevenness of 1 to 1 μm, the substrate end face and the stepped portion are rubbed. As a result, the bristle tips are further separated, and unevenly distributed portions 45 are generated in the bristles of the rubbing cloth 42.

FIG. 5 (A) is a schematic view of the rubbing process, and FIG. 5 (B) is an enlarged view of the main part thereof. The rubbing cloth 52 wound around the rotated rubbing roll 51 has the electrode substrate 53 and the arrow 54. The rubbing process is performed by moving in the direction of. The diameter of one bristle 55 at this time is generally 10 to 30 μm, and when the tip of the bristles rubs the electrode substrate 53 in the direction of arrow 56, the convex portion 5 such as a pixel electrode formed on the electrode substrate 53 is formed.
Before and after 7, there is a region where the cloth does not rub, that is, a non-alignment region 58 in which the alignment direction of the liquid crystal cannot be defined. In the general TN mode liquid crystal display element as shown in FIG. 6, the non-alignment region 58 is the light shielding layer 62 provided on the counter substrate 61.
However, the projections 64 of the electrodes and wiring formed on the array substrate 63
Since the non-alignment region 65 generated by the above is attached so as to be hidden, the non-alignment region 65 does not affect the display quality. Here, 66 is a counter common electrode, 67 is a liquid crystal layer, 68
Is an alignment layer, 69 is a color filter layer, and 610 is a pixel electrode. However, in a general horizontal electric field type liquid crystal display element as shown in FIG. 7, the light-shielding layer 72 formed on the counter substrate 71 has a large amount of light transmission.
The wiring step portion 73 is arranged and bonded so as to hide only the wiring step portion 73. Therefore, the non-aligned region 76 generated in the step portion 75 of the comb-shaped electrode which is the pixel electrode on which the array substrate 74 is formed is
It is not completely hidden by the light shielding layer 72 of the counter substrate 71, and the non-aligned region 76 directly affects the display quality. That is, if there is a partial difference in size of the non-oriented region 76, display failure will occur. Here, 77 is an alignment layer, 78 is a color filter layer, and 79 is a liquid crystal layer.

As described above, in the rubbing process,
The rubbing process causes uneven distribution of the rubbing cloth under the influence of the unevenness of the substrate end surface and the substrate surface.
When rubbing the liquid crystal display element in the horizontal electric field mode, the size of the non-aligned region is different between the unevenly distributed portion and the normal portion of the rubbing cloth,
As shown in FIG. 4, streak-like unevenness 46 is generated on the display area in order to affect the traveling direction of the roll or the substrate. Such unevenness 46 causes uneven distribution of cloth as the number of rubbing-processed sheets increases, so that the occurrence state of uneven streaks becomes worse.

With respect to the stripe-shaped unevenness, reduction of the non-oriented region, that is, reduction of the step portion can be considered, and a method of forming a flat layer on the comb-shaped electrode can be considered as a means thereof, but the number of steps is increased. This causes an increase in cost, a decrease in yield, and a phenomenon of an effective voltage applied to the liquid crystal due to the flat layer. Further, as an alternative alignment method to the rubbing method, oblique vapor deposition of silicon oxide, Langmuir-Projet film, or alignment film formation by a chemical adsorption method has been tried, but it is significantly inferior to the rubbing method in terms of mass productivity.

[0011]

According to the present invention, a rubbing method having a comb-shaped electrode on a substrate and excellent in mass productivity in a lateral electric field mode can obtain a high-quality display element having no display unevenness as seen in the above-mentioned conventional example. The purpose is.

[0012]

For the above-mentioned object, the present invention provides a switching element provided corresponding to a plurality of signal wirings and scanning wirings arranged in a matrix and their respective intersections, and the switching element. An array substrate having comb-shaped pixel electrodes connected to each other and a comb-shaped common electrode formed by interlocking with the pixel electrodes; a counter substrate arranged to face the array substrate; and the array substrate. A liquid crystal layer sandwiched between the counter substrate and two polarizing plates disposed outside the array substrate and the counter substrate, and between the pixel electrode and the common electrode, with respect to the array substrate and the counter substrate. In the method of manufacturing an active matrix liquid crystal display element in which the alignment of liquid crystal molecules is changed by generating parallel electric fields, the comb-shaped electrodes are provided on the outer periphery of the array substrate outside the display region. It is a manufacturing method in which convex steps with equal intervals or less than the intervals are formed, and the alignment layer formed on the array substrate is rubbed with a resin fiber cloth to define the alignment direction of the liquid crystal. is there.

Further, the convex steps are formed by arranging a frame on the outer periphery of the array substrate in which the convex steps are formed at equal or smaller intervals than the comb-shaped electrode interval and are rubbed. To achieve the purpose of.

Further, the object of the present invention is achieved by rubbing the array substrate after rubbing a substrate on which convex steps are formed at equal intervals or less than the comb-shaped electrode interval.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention can be implemented in the form described in each claim, and as described in claim 1, corresponds to a plurality of signal wirings and scanning wirings arranged in a matrix and their intersections. And an array substrate having a comb-shaped pixel electrode connected to the switching element, and a comb-shaped common electrode formed by interlocking with the pixel electrode, and facing the array substrate. And a liquid crystal layer sandwiched between the array substrate and the counter substrate, and two polarizing plates disposed outside the array substrate and the counter substrate. In an active matrix type liquid crystal display device in which an array of liquid crystal molecules is changed by generating an electric field parallel to the array substrate and a counter substrate between electrodes, a display area of the array substrate Periphery the same or less space between the electrode spacing of the comb-shaped form equidistant projected step in the defines an alignment direction of the liquid crystal by the array substrate to rubbing treatment.

Further, as described in claim 2, a frame in which convex steps are formed at equal intervals or at intervals equal to or less than the comb-shaped electrode interval is arranged on the outer periphery of the array substrate on which the comb-shaped electrodes are formed. By rubbing, the orientation direction of the liquid crystal is defined.

According to a third aspect of the present invention, the substrate on which convex steps are formed at equal intervals or less than the inter-electrode interval of the comb-shaped electrodes of the array substrate on which the comb-shaped electrodes are formed is rubbed, and thereafter. The alignment direction of the liquid crystal is defined by rubbing the array substrate on which the comb-shaped electrodes are formed.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments according to the present invention will be described in detail below with reference to the drawings.

Example 1 FIG. 1A is a schematic front view of a lateral electric field mode TFT array substrate used in a method of manufacturing a liquid crystal display element in Example 1 of the present invention, and FIG.
It is an enlarged view of the (B) part in (A).

On the array substrate 1, a display area 2 in which switching elements and pixel electrodes are arranged in a matrix, a signal line lead-out portion 3 thereof, and a scanning line lead-out portion 4 are formed around the display area. The convex steps 5 having an equal pitch are formed. FIG. 1B is an enlarged view of the boundary portion inside and outside the display area of the array substrate 1. The scanning electrodes 6 were patterned on the array substrate 1 by using chromium in the shape shown in the figure. At the same time, the common electrode 7 was formed in the shape as shown in the figure along the long side direction of the pixel. The width of the common electrode 7 is 5 μm, and the material is not limited to chromium, and a conductive single-layer film or a multilayer film such as aluminum or a metal containing aluminum as a main component may be used. Silicon nitride (SiN _x ) is laminated thereon as a gate insulating film of the TFT. Next, TFT
The switching element 8 that controls the switching function of the plasma C
Amorphous silicon (α-Si) was laminated by the VD method, and an insulating layer of silicon nitride (SiN _x ) was formed and patterned again. After that, two layers of titanium / aluminum (Ti / Al) deposited by the sputtering method were deposited, and then the signal electrode 9 and the pixel electrode 10 were patterned together with the switching element by dry etching. The width of the pixel electrode 10 is 5 μm, and the material is not limited to titanium / aluminum (Ti / Al), and a single layer film or a multilayer film of a conductive metal may be used. At this time, the distance between the common electrode 7 and the pixel electrode 10 was 10 μm. The convex structure was 3000 Å from the substrate surface. Then, when the insulating film is formed, a circular convex step 5 having a diameter of 5 μm and a step of 3000 Å is 5 μm outside the display area.
Formed at intervals of. The material of the convex steps 5 is not limited to the insulating material, and a single layer film or a multilayer film of a conductive metal may be used.

A polyimide film was flexographically printed on the thus completed thin film transistor array substrate and a counter color filter substrate having a light-shielding band formed thereon, dried and cured to form an alignment layer, and subjected to rubbing treatment. For the rubbing treatment, one rayon cloth having a fiber diameter of 20 μm and a density of 20,000 fibers / cm ² was wound around a roll having a diameter of 100 mm, the roll was rotated at 800 rpm, and the fluff was applied to the substrate at a density of 0.
The array substrate and the counter substrate were processed in a predetermined direction while being pressed by 2 mm. Here, in the array substrate 1 on which the comb-shaped electrodes are formed, the rubbing cloth is the display area 2.
Before the rubbing process, the unevenness of the rubbing cloth is corrected by rubbing the convex steps of equal pitch formed outside the display area, so that the non-aligned areas generated in the comb-shaped electrode step portion of the display area are made uniform. be able to. After the rubbing treatment, the array substrate 1 and the counter substrate were bonded together, and liquid crystal was injected by a vacuum injection method to fabricate a liquid crystal display element. As a result, no stripe-shaped unevenness was generated. Also, 2 for each roll
A rubbing treatment of 000 sheets was performed to manufacture a liquid crystal display element, but no deterioration in display quality was observed.

In this embodiment, the convex step is formed in the area adjacent to the display area. However, even if the convex step is formed in the peripheral portion of the substrate as shown in FIG. As a result of manufacturing a horizontal electric field type liquid crystal display element by any method, uneven distribution of the rubbing cloth was corrected by the effect of the convex step, and no rubbing streak was observed. Where 2
1 is a horizontal electric field type array substrate, 22 is a display region, 23 is a signal line lead-out portion, 24 is a scanning line lead-out portion, 25 is a convex step, 26 is a scanning electrode, 27 is a common electrode, 28 is a switching element, Reference numeral 29 is a signal electrode, and 30 is a pixel electrode.

In this embodiment, the convex step 25 has a circular shape, but if the pitch is the same as or smaller than that of the comb-shaped electrode and the pitch is equal, the effect of correcting the rubbing cloth by the step does not change. With respect to the size of the step, as long as it is equal to or larger than the step of the array substrate 21, the same result was obtained.

(Comparative Example) A conventional lateral electric field TFT array substrate was prepared and rubbed by the same method and electrode configuration as those of Example 1 described above, in the case where convex steps at equal intervals were not formed in the peripheral portion of the substrate. A liquid crystal display device was manufactured by performing the treatment.
As a result, thin stripe-like unevenness was observed in the direction of travel of the substrate during rubbing. Then, when 100 rubbing treatments are performed on one rubbing roller, streaks are clarified,
The generation of streaks gradually became more prominent with each rubbing.

(Embodiment 2) FIG. 3A shows a lateral electric field mode TFT used in a liquid crystal display device according to Embodiment 2 of the present invention.
A schematic view of the array substrate, and FIG. 3B is an enlarged view of FIG.

In the conventional horizontal electric field type liquid crystal display array substrate 31 (conventional horizontal electric field type structure) manufactured in the comparative example, a circular convex step having a step of 5 μm in diameter and 1 μm is formed on the outer periphery of the surface plate of the rubbing device. The formed frame was placed and subjected to rubbing treatment. The uneven distribution of the rubbing cloth was corrected by rubbing the convex steps formed on the surface plate of the rubbing cloth arranged around the substrate at equal intervals, and uniform rubbing treatment was performed, and no rubbing streak was observed. Here, 31 is a conventional lateral electric field type array substrate, 32 is a display region, 33 is a signal line lead-out portion, 34 is a scanning line lead-out portion, 35 is a convex step forming frame, 36 is a scanning electrode, and 37 is common. Electrodes, 38 are switching elements, 39 is a signal electrode, and 40 is a pixel electrode.

Further, in this embodiment, the shape of the convex step is circular, but if the pitch is the same as or smaller than that of the comb-shaped electrode and the pitch is equal, no change in the correction effect of the rubbing cloth due to the step is observed. With respect to the size of the step, as long as it is equal to or more than the step of the array substrate, the same result was obtained.

(Embodiment 3) A substrate on which a 3000 Å SiN _x film is formed on a glass substrate and a rugged striped pattern of 3000 Å steps with a width of 5 μm and a pitch of 5 μm is formed by a photolithography method is prepared. By rubbing the conventional horizontal electric field comb type array substrate before rubbing treatment, there was no occurrence of rubbing stripes unevenly distributed depending on the pattern of the array substrate.

In this embodiment, the concavo-convex pattern having an equal pitch is a stripe pattern. However, if the pitch is the same as the comb-shaped electrodes or equal to the comb-shaped electrodes or less, the correction effect of the rubbing cloth is changed by the step pattern. Is not seen,
With respect to the size of the step, as long as it is equal to or more than the step of the array substrate, the same result was obtained.

[0030]

As described above, according to the present invention, the following effects as a liquid crystal display device can be obtained.

According to the first aspect of the present invention, the unevenly-spaced convex steps formed on the outer periphery of the display area of the substrate correct the uneven distribution of the rubbing cloth that occurs during rubbing, so that the display area is uniformly rubbed. Thus, a high quality liquid crystal display device can be manufactured.

According to the second aspect of the present invention, by disposing the frame in which the steps of equal pitch are formed around the substrate during rubbing, uneven distribution of the rubbing cloth occurring during rubbing is corrected, and the display area is A high-quality liquid crystal display device can be manufactured by being uniformly rubbed.

According to the third aspect of the present invention, the stepped dummy substrate having an equal pitch is rubbed, and then the product substrate is rubbed. As a result, uneven distribution of the rubbing cloth is corrected, the display area is uniformly rubbed, and a high-quality liquid crystal display device can be manufactured.

The present invention is a manufacturing method having a great advantage in manufacturing a liquid crystal display panel, and can manufacture a liquid crystal display device having high display performance.

[Brief description of drawings]

FIG. 1A is a schematic plan view of a liquid crystal display element according to a first embodiment of the present invention, and FIGS. 1B and 1A are enlarged views of circled portions.

FIG. 2A is a schematic plan view of another liquid crystal display element according to Embodiment 1 of the present invention, and FIG. 2B is an enlarged view of a portion indicated by a circle in FIG.

FIG. 3A is a schematic plan view of a liquid crystal display element according to a second embodiment of the present invention, and FIGS. 3B and 3A are enlarged views of a circled portion.

FIG. 4 is a conceptual explanatory view of uneven distribution of rubbing cloth.

FIG. 5 is a conceptual explanatory diagram of a rubbing process.

FIG. 6 is a schematic sectional view of a TN mode panel.

FIG. 7 is a schematic cross-sectional view of a lateral electric field mode using a comb-shaped electrode.

[Explanation of symbols]

1,21,31 array substrate 2,22,32 display area 3,23,33 Lead-out part of signal line 4,24,34 Scan line lead-out section 5,25 convex step 6,26,36 scanning electrodes 7, 27, 37 Common electrode 8, 28, 38 Switching element 9, 29, 39 Signal electrodes 10, 30, 40 pixel electrodes 35 Convex step forming frame

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-6-160878 (JP, A) JP-A-4-115225 (JP, A) JP-A-1-186913 (JP, A) JP-A-3- 69920 (JP, A) JP 5-181139 (JP, A) JP 7-181494 (JP, A) JP 9-292615 (JP, A) Actually open 4-46423 (JP, U) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G02F 1/1337 500 G02F 1/1343 G02F 1/1368

Claims (3)

(57) [Claims] 1. A plurality of signal wirings and scanning wirings arranged in a matrix and switching elements provided corresponding to respective intersections thereof, comb-shaped pixel electrodes connected to the switching elements, and the pixel electrodes. An array substrate having a comb-shaped common electrode formed by interlocking, a counter substrate arranged to face the array substrate, a liquid crystal layer sandwiched between the array substrate and the counter substrate, and the array substrate And an array of liquid crystal molecules by generating an electric field parallel to the array substrate and the counter substrate between the pixel electrode and the common electrode. In the active matrix type liquid crystal display device to be changed, convex steps are formed on the outer periphery of the array substrate outside the display area at equal intervals or less than the comb-shaped electrode interval. A method of manufacturing an active matrix type liquid crystal display device, which comprises forming an alignment layer formed on the array substrate and rubbing the alignment layer formed on the array substrate with a resin fiber cloth to define the alignment direction of the liquid crystal. 2. A plurality of signal wirings and scanning wirings arranged in a matrix and switching elements provided corresponding to respective intersections thereof, comb-shaped pixel electrodes connected to the switching elements, and the pixel electrodes. An array substrate having a comb-shaped common electrode formed by interlocking, a counter substrate arranged to face the array substrate, a liquid crystal layer sandwiched between the array substrate and the counter substrate, and the array substrate And an array of liquid crystal molecules by generating an electric field parallel to the array substrate and the counter substrate between the pixel electrode and the common electrode. In the active matrix type liquid crystal display element to be changed, a frame is formed on the outer periphery of the array substrate, in which convex steps are formed at equal intervals or less than the comb-shaped electrode interval. And rubbing the array substrate. A method of manufacturing an active matrix type liquid crystal display device. 3. A plurality of signal wirings and scanning wirings arranged in a matrix and switching elements provided corresponding to respective intersections thereof, comb-shaped pixel electrodes connected to the switching elements, and the pixel electrodes. An array substrate having a comb-shaped common electrode formed by interlocking, a counter substrate arranged to face the array substrate, a liquid crystal layer sandwiched between the array substrate and the counter substrate, and the array substrate And an array of liquid crystal molecules by generating an electric field parallel to the array substrate and the counter substrate between the pixel electrode and the common electrode. In the active matrix type liquid crystal display element to be changed, after rubbing a substrate on which convex steps are formed at equal intervals or less than the comb-shaped electrode interval, A method of manufacturing an active matrix type liquid crystal display device, which comprises rubbing a ray substrate.