JP2000258762A - Production of liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a liquid crystal display device having a reflection region which does not decrease the display quality due to the seam line of exposure by exposing a substrate to have such a region where a photosensitive thin film having a predetermined pattern of irregularities is not present in the border region between a first region and a second region. SOLUTION: A photomask having a circular light-shielding pattern arranged at random positions is disposed parallel to an insulating substrate to carry out first exposure. Then a photomask is disposed to be continued from the first exposure region, a light-shielding member is disposed to prevent light from falling on the first exposure region, and then second exposure is performed. The substrate is designed in such a manner that the seam of succeeding exposure shots if formed in a transmission region 13 or a contact hole region 12 and that the photosensitive resin on the transmission region 13 or the contact hole region 12 is to be removed. Thereby, the obtained electrode material has a reflection region with little photosensitive resin having a pattern of irregularities present on the seam of exposure shots.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a liquid crystal display device used for OA equipment such as a word processor or a personal computer, portable information equipment such as an electronic organizer, or a camera-integrated VTR equipped with a liquid crystal monitor. .

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices have been used in word processors, personal computers, televisions, video cameras, still cameras, in-vehicle monitors, portable OA equipment, portable game machines, etc. by utilizing the characteristics of being thin and having low power consumption. Widely used.

Such a liquid crystal display device includes a transmissive liquid crystal display device using a transparent electrode such as ITO (Indium Tin Oxide) as a pixel electrode and a reflective liquid crystal display device using a reflective electrode such as a metal as a pixel electrode. There is a liquid crystal display device.

A liquid crystal display device is not a self-luminous display device that emits light by itself unlike a CRT (CRT) or an EL (electroluminescence) device. A lighting device such as a fluorescent tube, a so-called backlight, is arranged behind the device,
The display is performed by the light incident from there. Further, in the case of a reflection type liquid crystal display device, display is performed by reflecting external incident light by a reflection electrode.

Here, in the case of a transmission type liquid crystal display device,
In order to perform display using the backlight as described above,
Although it has the advantage of being able to perform a bright and high-contrast display without being greatly affected by the surrounding brightness, a backlight typically accounts for 50% or more of the total power consumption of a liquid crystal display device. From consuming
There is also a problem that power consumption increases.

Further, in the case of the reflection type liquid crystal display device, since the backlight is not used as described above, it has an advantage that the power consumption can be extremely reduced. There is also a problem that the brightness and contrast of the display are affected by the use environment or use conditions.

As described above, the reflection type liquid crystal display device has a drawback that the visibility is extremely lowered in the use environment such as the surrounding brightness, especially when the external light is dark. On the other hand, the transmissive liquid crystal display device also has a problem in that, when the external light is very bright, the visibility in, for example, clear weather is reduced.

As means for solving these problems, a liquid crystal display device having both functions of a transmission type and a reflection type has been proposed, for example, in Japanese Patent Application No. 9-201176. The liquid crystal display device proposed by this patent application, by creating a reflection area for reflecting external light and a transmission area for transmitting light from the backlight in one display pixel, when the surroundings are completely dark, As a transmissive liquid crystal display device that performs display using light transmitted through a transmissive region from a backlight, and when external light is dark,
As a dual-use liquid crystal display device that performs display using both light transmitted through a transmission region from a backlight and light reflected by a reflection region formed by a film having a relatively high light reflectance, external light is further reduced. When it is bright, it can be used as a reflection type liquid crystal display device that performs display using light reflected by a reflection region formed by a film having a relatively high light reflectance. A display device.

The transmission / reflection type liquid crystal display device having such a structure can provide a liquid crystal display device always excellent in visibility regardless of the brightness of external light. In order to realize bright and high color purity color display with both reflection type, incident light from all angles
It is necessary to increase the intensity of light scattered in a direction perpendicular to the display screen. Further, in order to realize excellent display, it is necessary to enable paper white display when performing display using light reflected by the reflection area. For this reason, it is necessary to produce a reflection unit having high light use efficiency and having an optimal reflection characteristic to scatter incident light from all angles in the direction of an observer.

As a method for manufacturing such a reflection means, a method using both a photolithography step and a heat treatment step is known. For example, a photosensitive resin is applied on a substrate and circular light-shielding regions are arranged. By exposing and developing the photosensitive resin through a light-shielding means and then performing a heat treatment, a plurality of uneven portions are formed, and a reflector made of a metal thin film is formed on the uneven portions along the shape of the uneven portions. Is formed to scatter incident light.
In addition, when a reflection plate is formed outside the substrate (on the side opposite to the liquid crystal layer), which causes a problem of double reflection due to the thickness of the glass, the reflection plate is formed inside the substrate to form a pixel electrode and the reflection plate. The problem is solved by a structure that also serves as a reflective electrode.

In the exposure step for producing such a reflection means, an exposure machine such as a stepper exposure machine or a large batch exposure machine is used.

[0012]

However, the conventional method of manufacturing the reflecting means has the following problems.

Although the above-described large batch exposure apparatus can expose a large area at one time, the in-plane variation of the light irradiation intensity and the parallelism is large as compared with the stepper exposure apparatus. Therefore, when a reflector is manufactured using a large-scale batch exposure machine, the brightness is not uniform over the entire screen, for example, the vicinity of the exposure center is bright, and the end has a dark reflection characteristic. Was difficult. For this reason, in the manufacture of a reflection plate, a stepper exposure machine in which light from a light source approaches parallel light in a lens system to reduce in-plane variation has been generally used. However, as shown in FIG. 8A, since the area 11 that can be exposed at a time by the stepper exposure machine has a diameter of about 6 inches, the area 10 where the unevenness is formed is a square having a diagonal of about 6 inches at the maximum. .

Therefore, when exposing for example 6 inches or more, as shown in FIG. 8B, the first area 12a is exposed for the first time (exposure area 13a, exposure center 14a).
Thereafter, a method of exposing the second region 12b for the second time (exposure possible region 13b, exposure center 14b) has been used. However, even if a stepper exposure machine is used, in-plane variation of light rays (image distortion: parallelism of light rays is high at the center, but parallelism of light rays is low at the end) is inevitably present. The reflected plate generates interference fringes,
There was a problem that a "seam (boundary)" 15 of the first and second exposures was observed.

In order to reduce the in-plane variation of the light beam in the stepper exposure machine, the problem can be solved by reducing the area of the regions 12a and 12b exposed in one shot. However, this method has a problem that the production efficiency is remarkably reduced because more exposure steps and accompanying alignment steps are increased.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide a method of manufacturing a liquid crystal display device having a reflection region in which an exposure seam does not degrade display quality. Is to provide.

[0017]

A liquid crystal display device according to the present invention for achieving the above object has a structure in which one of a pair of substrates disposed opposite to each other with a liquid crystal layer interposed therebetween is formed on a substrate. In a method of manufacturing a liquid crystal display device including a plurality of pixel electrodes having a reflective region and a transmissive region, the method includes a step of forming a photosensitive thin film having an uneven shape in a reflective region constituting the plurality of pixel electrodes. The step of forming a photosensitive thin film on the surface of the one side substrate, and using a mask having a predetermined pattern for each of the first region and the second region adjacent to each other of the photosensitive thin film. First and second exposure steps of independently exposing each of the first and second exposure steps, and a step of forming a plurality of irregularities having a predetermined pattern by developing the exposed photosensitive thin film. 2 exposure Degree is in the boundary region between the first region and the second region is characterized by a photosensitive film having a predetermined pattern of the concavo-convex shape is a step of exposing to have an area that does not exist.

In this case, in the first and second exposure steps, a region where the photosensitive thin film having the predetermined pattern of the concavo-convex shape does not exist exists in a transmission region constituting the plurality of pixel electrodes. Is preferred.

Further, in the method of manufacturing a liquid crystal display device according to the present invention for achieving the above-mentioned object, a method of manufacturing a liquid crystal display device includes the steps of: In a method for manufacturing a liquid crystal display device including a plurality of pixel electrodes having a region and a plurality of switching elements connected to the plurality of pixel electrodes via contact holes, a reflection forming the plurality of pixel electrodes Forming a photosensitive thin film having a concavo-convex shape in the region, comprising the steps of: forming a photosensitive thin film on the surface of the one side substrate;
First and second exposure steps of independently exposing the region and the second region using a mask having a predetermined pattern, respectively, and developing a plurality of the predetermined patterns by developing the exposed photosensitive thin film. Forming a concave-convex pattern, wherein the first and second exposing steps do not include a photosensitive thin film having a predetermined pattern of the concave-convex shape in a boundary region between the first region and the second region. It is a step of exposing to have a region, in a region where there is no photosensitive thin film having a predetermined pattern of the uneven shape,
The present invention is characterized in that the contact hole exists.

Hereinafter, the operation of the present invention will be described.

According to the method of manufacturing a liquid crystal display device of the present invention, in order to form irregularities for obtaining an optimal reflection characteristic, in the step of exposing after applying a photosensitive resin film,
The above-described problem is solved by making the joint of the exposure shot a transmission region or a contact hole region.

More specifically, the distortion of the light beam of the stepper exposure machine will be described with reference to FIGS. 1 (a) and 1 (b). The actual image 18 projected by the stepper exposer is not a perfect collimated light beam because the beam of the stepper exposer is not perfectly collimated.
Is distorted from an ideal image 16 obtained by irradiating perfect parallel light to the mask. The degree of the distortion increases in the peripheral portion. When a mask for irradiating a plurality of circular regions is used, a circular pattern 18a is exposed at the central portion of the exposure region, but a predetermined pattern of a circle is not obtained at the peripheral portion, and elliptical shapes 18b to 18e are formed. Become.

[0023] Distortion of the lens of the exposure machine (including magnification error)
Is called a lens distortion. The distortion is exposed using a mask (reticle) having a pattern of a plurality of ideal lattice points (for example, square or rectangular vertices of different sizes), and the exposed pattern and the ideal lattice points are exposed. Is determined by measuring the deviation from

By exposing and developing the photosensitive thin film formed on the surface of the substrate in two exposure steps, a plurality of irregularities were formed as shown in FIG. 2 (a). The first area 12a was exposed in the first exposure step, and the second area 12b was exposed in the second exposure step. Here, a circle is used as the predetermined shape, and the center of gravity of each of the regions 12a and 12b is set as the center position of each exposure step. The position of the center of gravity of the regions 12a and 12b refers to the position of the center of gravity assuming that each region has a uniform thickness and a uniform density.

Regions 16a and 16b near the center of exposure
In FIG. 2, as shown in FIG. 2B, the shape of the obtained unevenness was circular. However, in the peripheral portions 17a and 17b of the exposure, as shown in FIG. 2C and FIG. 2D, the shape of the obtained unevenness was elliptical. The major axis of the ellipse was arranged in the radial direction of the circle centered on the exposure center, and the ellipse was longer in the major axis toward the outside. Therefore, the shape of the unevenness on both sides near the boundary 15 between the adjacent first region 12a and second region 12b is largely distorted from a circle. Furthermore, the corner portion 17a having the largest distortion,
The direction of the major axis of the uneven ellipse in 17a ', 17b, and 17b' is a mirror image of the boundary 15;
It changes greatly discontinuously on both sides of the boundary 15.

That is, an uneven shape is formed due to the distortion of the light beam of the stepper exposure machine. The reflection characteristics naturally change between the case where the incident light hits the isotropic circular uneven portion and the case where the incident light hits the elliptical uneven portion having anisotropy. If the concavo-convex shape is isotropic such as a circular shape, the reflection characteristic has isotropic reflection intensity without increasing the reflection intensity in a specific direction. On the other hand, if the uneven shape is anisotropic, such as an elliptical shape, the reflection intensity is increased in a specific direction, and the reflection intensity has anisotropic reflection characteristics. Then, as the shape of the ellipse becomes elongated and the anisotropy increases, the difference in the reflection intensity in the direction increases.

In a single exposure area, the distortion of the light beam is continuous, the unevenness gradually changes, and the change in the reflection characteristic becomes smooth accordingly, so that there is not much problem in the display quality. . However, at the boundary of the exposure region, as shown in FIGS. 2C and 2D, the distortion is large because it is far from the exposure center, and the direction of the distortion changes discontinuously. A large reflection characteristic changes discontinuously, and the amount of change in the reflection characteristic becomes much larger than in other regions, and joints are observed.

According to the method of manufacturing a liquid crystal display device of the present invention, for example, as shown in FIG. 5, in order to form an uneven shape for obtaining an optimal reflection characteristic, an uneven shape is formed on a photosensitive resin film. In the exposure step, the seam 15 of the shot for exposure is made to be a transmissive area, thereby making it possible to reduce the area where the photosensitive resin that forms the uneven shape in the boundary area is present. Therefore, since the region having the reflection characteristic with large anisotropy is reduced, the amount of change in the reflection characteristic in the boundary region can be reduced, and the joint can be made inconspicuous.

According to the method of manufacturing a liquid crystal display device of the present invention, for example, as shown in FIG. 3, in order to form an uneven shape for obtaining an optimum reflection characteristic, the uneven shape is formed on the photosensitive resin film. In the step of performing the exposure for forming, by making the seam 15 of the exposure shot a contact hole portion, it becomes possible to reduce the region where the photosensitive resin forming the uneven shape in the boundary region is present. Therefore,
Since the area having large anisotropic reflection characteristics is reduced,
The amount of change in the reflection characteristics in the boundary region can be reduced, and the joint can be made inconspicuous.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a liquid crystal display according to an embodiment of the present invention will be described with reference to the drawings.

FIGS. 4A to 4D show transmission and reflection regions in the pixel portion of the transflective liquid crystal display device used in the present embodiment, and TFTs as switching elements.
FIG. 4 is a cross-sectional view showing the process.

[0032] In the transmissive region and the reflective region and the TFT constituting the pixel portion of the liquid crystal display device of this embodiment, first, as shown in FIG. 4 (a), Ta ₂ O as a base coat film on the insulating substrate 1 ₅ , an insulating film such as SiO ₂ is formed (not shown), and then the insulating substrate 1
A metal thin film made of 1, Mo, Ta, or the like is formed by a sputtering method, and is patterned to form the gate electrode 2.

Next, a gate insulating film 4 is laminated on the insulating substrate 1 so as to cover the gate electrode 2 described above. In the present embodiment, the gate insulating film 4 is formed by stacking 3000 nm SiNx films by the P-CVD method. In order to enhance the insulating property, the gate electrode 2 is anodized, the anodic oxide film is used as the first gate insulating film 3, and the insulating film such as SiN is formed by CVD.
The second insulating film 4 may be formed by a method.

Next, the channel layer 5 (amorphous Si)
And an electrode contact layer 6 (amorphous Si or microcrystalline Si doped with an impurity such as phosphorus) are continuously formed on the gate insulating film 4 by CVD at 1500 ° C.
And an electrode contact layer 6 and a channel layer 5
Are formed by patterning by a dry etching method using HCl + SF ₆ mixed gas or the like.

Thereafter, as shown in FIG. 4 (b), a transparent conductive film (ITO) 7, 10 is laminated as an electrode material constituting the transmission region by sputtering at a thickness of 1500 °, followed by an Al, Mo, Ta film or the like. Metal thin films 8 and 9 are laminated. Then, by patterning these, source electrodes 7 and 8 and drain electrodes 9 and 10 are formed.

Next, as shown in FIG. 4C, a photosensitive resin film 11 is applied on the insulating substrate 1. here,
OFPR-800 (manufactured by Tokyo Ohka Co., Ltd.), which is a positive resist, was spin-coated at 500 to 30,000 rpm, and prebaked on a hot plate for about 30 seconds. Thereby, in this embodiment, the photosensitive resin film 11 having a thickness of 2 μm was obtained.

Here, a concavo-convex pattern is formed on the photosensitive resin film 11 existing in the reflection area in the pixel portion. The step of forming the concavo-convex pattern will be described with reference to FIGS.

In this embodiment, as shown in FIG. 6A, a photomask 130 as shown in FIG. 7A having a circular light-shielding pattern having a diameter of about 6 μm arranged at random positions and having an insulating property is used. The first exposure is performed while being arranged in parallel with the substrate 101. In FIG. 6, reference numeral 101 denotes an insulating substrate, and reference numeral 110a denotes a photosensitive resin film. Also, at this time, a blind is provided in an area where the second exposure is performed so that light does not hit the area.

Next, as shown in FIG. 6B, a photomask 130 is arranged so as to be continuous with the first exposure area, and a blind is set so that light does not hit the first exposure area. After that, the second exposure is performed.

At this time, the joint of each exposure shot is designed so as to be formed on the transmission region 13 or the contact hole region 12 as shown in FIG. The photosensitive resin on the hole region 12 is removed. As a result, the electrode material constituting the reflection region is formed in a state where the uneven photosensitive resin existing on the joint of each exposure shot is small, so that the conditions such as the exposure amount and the position for each exposure shot vary. Even so, the amount of change in the reflection characteristics of the electrode material constituting the reflection region can be reduced, and the joint of each exposure shot can be made inconspicuous.

Subsequently, in order to remove the photosensitive resin film existing on the transmission region 13 and the contact hole region 12, a photomask as shown in FIG. After exposure with stronger irradiation, development is performed.

As shown in FIG. 6C, a plurality of circular irregularities 11 are formed mainly in the area corresponding to the reflection area.
0b was formed.

Thereafter, as shown in FIG. 6 (d), a heat treatment is performed on the plurality of irregularities 110b at about 120 ° C. to 250 ° C., and the shape of the irregularities 110b is smoothed by heat dripping and thermosetting. Irregularities 110 were formed.

As shown in FIG. 4D, a laminated film 14 of Al and Mo is formed on the insulating substrate 1 including the concavo-convex pattern formed as described above, as an electrode material forming a reflection region.
(Al / Mo) by sputtering method to 1000 /
A film is formed with a thickness of 500 °.

Thereafter, using an etchant composed of nitric acid + acetic acid + phosphoric acid + water, Al / Mo, which is an electrode material constituting the reflection region, is simultaneously etched to form the reflection electrode 14.
Was formed. As described above, the TFT portion and the pixel portion of the liquid crystal display device according to the present embodiment are completed.

Finally, a backlight is provided on the back surface to form a transflective liquid crystal display device using a known method of manufacturing a liquid crystal display device such as coating an alignment film, bonding to an opposite substrate, and injecting liquid crystal. Completed.

When a display was performed with the obtained liquid crystal display device, it was possible to realize a uniform display in which the reflection characteristics did not vary over the entire panel and the seams between the exposure shots were not noticeable.

[0048]

As described above, according to the method of manufacturing a liquid crystal display device of the present invention, the unevenness is formed on the photosensitive resin film in order to form the unevenness for obtaining the optimum reflection characteristics. In the exposing step, the joint between the exposure shots is made to be a transmissive region or a contact hole, thereby making it possible to reduce the region in which the photosensitive resin that forms the concavo-convex shape in the boundary region is reduced. Therefore,
Since the area having large anisotropic reflection characteristics is reduced,
The amount of change in the reflection characteristics in the boundary region can be reduced, and the joint can be made inconspicuous.

[Brief description of the drawings]

FIG. 1A is a diagram schematically showing a light beam distortion of a stepper exposure machine, and FIG. 1B is a diagram schematically showing a shape change when a circular mask is used. FIG.

FIGS. 2A to 2D are diagrams schematically showing a change in a concave and convex shape depending on a position when a reflection plate is formed by using two exposures.

FIG. 3 is a plan view showing a transmissive region and a reflective region of a pixel portion and a switching element of the liquid crystal display device according to the embodiment.

FIGS. 4A to 4D are views showing process cross sections of a pixel portion of the liquid crystal display device according to the embodiment of the present invention.

5 (a) to 5 (d) are drawings showing process cross sections of the concave and convex portions of the reflector of the liquid crystal display device according to the embodiment of the present invention.

FIG. 6 is a plan view showing unevenness of a pixel portion of the liquid crystal display device according to the embodiment.

FIGS. 7A and 7B are plan views showing a photomask used in a process of the liquid crystal display device according to the present embodiment.

FIG. 8A is a drawing schematically showing an area that can be exposed at one time using a stepper exposure machine.
(B) is a drawing schematically showing a region that can be exposed by two exposures.

[Explanation of symbols]

 Reference Signs List 1 glass substrate 2 gate electrode 3 anodized film 4 insulating film 5 channel layer 6 electrode contact layer 7 source electrode (ITO) 8 source electrode (Ta) 9 drain electrode (Ta) 10 drain electrode (ITO) 11 photosensitive resin film 12 Contact hole 13 Transmissive part 14 Reflective electrode (Al / Mo) 15 Seam of shot when exposing photosensitive resin 16 Irregular part of reflective electrode

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kazuki Kobayashi F-term (reference) 2H091 FA14Y FA31Y FC10 FD04 FD12 GA03 GA13 2H092 HA02 HA05 JA34 JA36 JA37 JA39 JA46 KA05 MA16 MA18 MA19 MA24 MA25 MA35 NA01 5C094 AA03 AA55 BA02 BA43 EA04 ED11 ED15 GB01 HA07 HA08

Claims (3)

[Claims] 1. A liquid crystal display device comprising: a plurality of pixel electrodes having a reflection area and a transmission area formed on one of a pair of substrates arranged to face each other with a liquid crystal layer interposed therebetween. Forming a photosensitive thin film having a concave-convex shape on a reflection region constituting the plurality of pixel electrodes, and forming a photosensitive thin film on the one-side substrate surface. First and second exposing steps of independently exposing a mutually adjacent first region and a second region of the photosensitive thin film using a mask having a predetermined pattern, respectively; Forming a plurality of concavities and convexities having a predetermined pattern by developing the conductive thin film, wherein the first and second exposure steps are performed in a boundary region between the first region and the second region. Uneven shape A method for manufacturing a liquid crystal display device, comprising a step of exposing to a region having no photosensitive thin film having a predetermined pattern. 2. In the first and second exposure steps,
A method for manufacturing a liquid crystal display device, wherein a region where a photosensitive thin film having a predetermined pattern of unevenness does not exist exists in a transmission region constituting the plurality of pixel electrodes. 3. A plurality of pixel electrodes having a reflection region on one of a pair of substrates arranged to face each other with a liquid crystal layer interposed therebetween, and a plurality of pixel electrodes having a contact region interposed therebetween. A method for manufacturing a liquid crystal display device, comprising: a plurality of switching elements connected to each other, comprising a step of forming a photosensitive thin film having an uneven shape on a reflection region constituting the plurality of pixel electrodes. The step of forming a photosensitive thin film on the surface of the substrate on one side and the step of independently forming a first region and a second region of the photosensitive thin film adjacent to each other using a mask having a predetermined pattern. A first and second exposure step of exposing to light, and a step of forming a plurality of irregularities having a predetermined pattern by developing the exposed photosensitive thin film; The light step is a step of exposing a boundary region between the first region and the second region so as to have a region in which a photosensitive thin film having the predetermined pattern of the uneven shape does not exist. A method for manufacturing a liquid crystal display device, wherein the contact hole exists in a region where a photosensitive thin film having a pattern does not exist.