KR20080091324A - Transflective liquid crystal display device - Google Patents

Abstract

A semi-transmission type LCD(Liquid Crystal Display) is provided to prevent the deterioration of display quality by forming a reflecting film on a concave and convex pattern of an interlayer-insulating layer. A liquid crystal layer(29) is put between a TFT(Thin Film Transistor) array substrate and a counterpart substrate having a counterpart electrode(28). The TFT array substrate includes a gate line(2), a source line(10), and a TFT. A first interlayer-insulating layer(15) covers the gate line, the source line, and the TFT. At least a part of the first interlayer-insulating layer has a concave and convex pattern(16). A reflecting film(17) is formed on the concave and convex pattern of the first interlayer-insulating layer. A second interlayer-insulating layer(19) is formed to cover the reflecting film. A pixel electrode(23) is formed on the second interlayer-insulating layer correspondingly to the reflecting film. The pixel electrode is electrically connected to the TFT.

Description

Transflective Liquid Crystal Display {TRANSFLECTIVE LIQUID CRYSTAL DISPLAY DEVICE}

1 is a plan view of a TFT array substrate for a transflective liquid crystal display device according to a first embodiment.

FIG. 2 is a cross-sectional view showing a TFT array substrate for a transflective liquid crystal display device according to Example 1. FIG.

3 is a cross-sectional view illustrating a transflective liquid crystal display panel according to Example 1;

4 is a cross-sectional view showing a process for manufacturing a TFT array substrate for a transflective liquid crystal display device according to Example 1. FIG.

5 is a cross-sectional view showing another example of a TFT array substrate for a transflective liquid crystal display device according to the first embodiment.

6 is a plan view of a TFT array substrate for a transflective liquid crystal display device according to a second embodiment.

7 is a cross-sectional view showing a TFT array substrate for a transflective liquid crystal display device according to a second embodiment.

It is a figure which shows the cell sample which measures the offset potential which arises between the electrodes which oppose a liquid crystal layer.

[Explanation of symbols on the main parts of the drawings]

1 transparent insulating substrate 2 gate wiring

3: gate electrode 4: storage electrode

5 gate terminal 6 gate insulating film

7: semiconductor film 8: ohmic contact film

9 source electrode 10 source wiring

11 source terminal 12 drain electrode

13 TFT channel portion 14 protective insulating film

15: first interlayer insulating film 16: irregularities

17: reflective film 18: light shielding film

19: second interlayer insulating film 20: first contact hole

21: 2nd contact hole 22: 3rd contact hole

23 pixel electrode 24 gate terminal pad

25 source terminal pad 26 transparent insulating substrate

27 color filter layer 28 counter electrode

29 liquid crystal layer 30 liquid crystal alignment film

31: gap control layer

The present invention relates to a transflective liquid crystal display device having a reflective film.

Liquid crystal display devices are widely used in OA devices such as personal computers, portable information devices such as electronic notebooks and mobile phones, cameras equipped with liquid crystal display monitors, and other electrical appliances, taking advantage of their low power consumption. .

A liquid crystal display panel mounted in a conventional liquid crystal display device does not emit light by itself, unlike CRT (Brown Tube) or EL (Electroluminescence) display. For this reason, a so-called transmissive liquid crystal display device in which an illumination device made of a fluorescent tube called a backlight is provided on the back or side thereof, and the transmission amount of the backlight light is controlled by a liquid crystal display panel to perform image display has been mainly used.

However, in such a transmissive liquid crystal display panel, since the backlight generally occupies 50% or more of the total power consumption, it has become a cause of increasing power consumption.

In the transmissive liquid crystal display panel, the backlight light is darker than the ambient light in an environment such as outdoors where the ambient light is very bright, and it is difficult to recognize the display image.

As described above, the reflection type liquid crystal display device is adopted in a portable information device that has many opportunities for outdoor use and portable use. This is a liquid crystal display device in which a reflecting plate is provided in the image display portion of the liquid crystal display panel instead of the backlight light, and the display is performed by reflecting the ambient light from the reflecting plate surface. Such a structure is disclosed in FIGS. 1 and 2 of Patent Document 1, for example.

However, the reflection type liquid crystal display device using the reflected light of the ambient light has a drawback that, in contrast to the transmission type liquid crystal display device, the visibility is extremely degraded when the ambient light is dark.

In order to solve the problems of the above-mentioned transmissive and reflective liquid crystal display devices, a semi-transmissive liquid crystal display device which realizes both a transmissive display and a reflective display in one liquid crystal display panel is used. This forms two kinds of pixel electrodes of a transmissive electrode made of an ITO film or the like which transmits light to the pixel portion, and a reflective electrode made of an Al film or the like which reflects light. A portion of the backlight light is transmitted while simultaneously reflecting a portion of the ambient light. Such a structure is disclosed in FIGS. 1 and 2 of Patent Document 2, for example.

In the case of a liquid crystal display panel having an image display function by transmitted light and reflected light in one image display area, there is a problem that display quality is deteriorated. This is because display is performed by using light passing through the liquid crystal panel from the backlight light on the back of the image display surface and light incident on the image display surface and reflected by the light reflecting portion. Thus, even when the same voltage is applied to the liquid crystal layer, the brightness and contrast of the image are remarkably changed between the counter electrode and the transmissive electrode which oppose the liquid crystal and between the counter electrode and the reflective electrode. As one of the causes, there is a difference in the optical path length between the transmitted light and the reflected light. As a method of solving this problem, in the said patent document 2, the distance (cell gap length) between the opposing electrodes is changed in a transmissive electrode part and a reflective electrode part. Specifically, an organic resin film is formed under the reflective electrode to provide a step (Δ gap) with the transmissive electrode. By adjusting the height of the step, the optical path difference between the reflected light and the transmitted light is optimized to obtain suitable display characteristics. As described above, a method of substantially matching the optical path length of both is disclosed by changing the thickness of the liquid crystal layer between the electrodes.

[Patent Document 1] Japanese Patent Laid-Open No. 6-175126

[Patent Document 2] Japanese Patent Laid-Open No. 11-101992

However, even in the configuration in which the optical path lengths are matched in the transmission electrode section and the reflection electrode section as described above, it is difficult to optimize the display quality. In addition, a so-called sticking phenomenon may occur in which the previous image becomes an afterimage and degrades the display quality.

The reflective electrode and the transmissive electrode are mixed in the pixel electrode of the TFT array substrate in the transflective liquid crystal display device. Moreover, the counter electrode of the opposing board | substrate arrange | positioned facing a TFT array board | substrate is formed with the transmission electrode. Here, the reflective electrode is, for example, Al, and the transmissive electrode and the counter electrode are, for example, ITO. For this reason, in the ITO-ITO electrode and the ITO-Al electrode which interposed liquid crystal, the difference of the potential by local battery effect appears, and display property deteriorates.

In this way, it is considered that the difference in potential value due to the difference between the counter electrode facing the liquid crystal layer and the material used for the transmission electrode and the reflection electrode is the main cause of the sticking. Therefore, the present inventors measured the difference of this electric potential value using the cell sample of FIG. The cell sample was produced between the pixel electrode 23 and the counter electrode 28 through the liquid crystal aligning film 30 by sandwiching the liquid crystal layer 29. Here, the ITO film | membrane which is a permeable conductive material generally used was used for the counter electrode 28. As shown in FIG. As the pixel electrode 23 which is the other electrode, some kinds of conductive materials generally used as the pixel electrode 23 of the transflective liquid crystal display device were used. As the pixel electrode 23, ITO such as Al, Ag, Cr, Mo, Ti and Ta, which are metal materials, and the counter electrode 28 were used. And the electric potential difference which shows as a battery effect between the pixel electrode 23 and the counter electrode 28 was measured for each pixel electrode 23 material. In addition, the potential difference was measured as an offset potential value when the counter electrode 28 side was set to ground = 0V.

Table 1 shows the result of the offset potential value between electrodes measured by the present inventors. The offset potential value represents the potential difference at the counter electrode 28 of the pixel electrode 23 with the counter electrode 28 at 0V. Moreover, the reflectance in wavelength 550nm of each pixel electrode 23 material is also shown.

TABLE 1

Pixel electrode 23 material Offset potential (V) Reflectance (%) @ Wavelength 550nm Al (reflective electrode) -1.0 to -0.8 83-93 Ag (reflective electrode) -0.1 to 0.0 86-96 Cr (reflective electrode) -0.1 to 0.0 50 to 60 Mo (reflective electrode) 0.0 to +1.0 50 to 60 Ti (reflective electrode) -0.2 to 0.1 45 to 55 Ta (reflective electrode) -0.5 to -0.3 50 to 60 ITO (reflective electrode) 0.0

Referring to Table 1, the absolute value of the offset potential value between the electrodes is the largest when the Al film serving as the reflective electrode is used for the pixel electrode 23. From this, it can be seen that the largest potential value difference occurs between the ITO film and the Al film. In other words, in the transflective liquid crystal display device, the display characteristics of the structure using the ITO film as the counter electrode 28, the ITO film as the transmissive electrode of the pixel electrode 23, and the Al film as the reflective electrode of the pixel electrode 23 deteriorate. . In this case, even when the same potential signal is applied to the pixel electrode 23 in one image display area, the voltage applied to the liquid crystal layer is different by about 1 V in the transmission electrode portion and the reflection electrode portion. For this reason, in the transmitted light of the transmissive electrode portion and the reflected light of the reflective electrode portion, the change in optical characteristics is different, resulting in deterioration of display quality.

In order to reduce the potential difference between the two electrodes, a Cr, Mo, Ti, Ta film or the like whose offset potential value is close to the ITO film may be used as the reflective electrode material. However, as shown in Table 1, these materials have a smaller reflectance of light than Al films. For this reason, there exists a problem that the reflection efficiency of ambient light is low and a bright display characteristic cannot be obtained.

When the Ag film is used as the reflecting film material, the offset potential value is close to the ITO film, which is effective for countermeasures for deterioration of display quality. However, the Ag film is surface oxidized by leaving in the air between process steps or by washing with water. Therefore, the reflection characteristic changes greatly, and it is easy to reduce the reflectance or change the color characteristic. For this reason, in the case of the structure in which the reflective electrode part shown in the said patent document 2 is formed in the uppermost layer surface of a board | substrate, for example, there exists a problem that manufacturing process management for maintaining the outstanding reflection characteristic which Ag film has is difficult.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to obtain a transflective liquid crystal display device which can prevent deterioration of display characteristics.

A semi-transmissive liquid crystal display device according to the present invention includes a first substrate, a second substrate disposed opposite to the first substrate, having a counter electrode, the first substrate, and the second substrate. A semi-transmissive liquid crystal display device having a liquid crystal sandwiched therein, wherein a light reflection portion and a light transmission portion are provided in a pixel, wherein the first substrate comprises a plurality of gate wirings, a plurality of source wirings crossing the gate wirings, and a switching element. A first interlayer insulating film which covers the gate wiring, the source wiring and the switching element, and has an irregular shape at least in part, and a reflective film provided on a plurality of pixels in one pixel; And a second interlayer insulating film formed to cover the reflective film and a region in which the reflective film of the second interlayer insulating film is disposed and contacting the switching element through a contact hole. And a transparent pixel electrode connected by a miracle, wherein the transparent pixel electrode is formed by protruding from a region where the reflective film is disposed, and a portion of the transparent pixel electrode protruding from the region where the reflective film is disposed is a light transmitting portion. Will be.

Example 1.

The structure and manufacturing process of the transflective liquid crystal display device which concerns on a present Example are demonstrated using FIGS. 1 is a plan view showing the configuration of a pixel of a TFT array substrate which is the first substrate of the transflective liquid crystal display device according to the present embodiment. FIG. 2 is a cross-sectional view illustrating the structure of a gate terminal portion and a source terminal portion in addition to the A-A cross section of FIG. 1.

In the drawings, reference numeral 1 denotes a transparent insulating substrate, 2 gate wiring, 3 gate electrode, 4 storage capacitor electrode, 5 gate terminal, 6 gate insulating film, 7 semiconductor film, 8 ohmic contact film, and 9 A source electrode, 10 a source wiring, 11 a source terminal, 12 a drain electrode, 13 a TFT channel portion, 14 a protective insulating film, 15 a first interlayer insulating film, 16 unevenness, 17 a reflective film, 18 a light shielding film, 19 is a second interlayer insulating film, 20 is a first contact hole, 21 is a second contact hole, 22 is a third contact hole, 23 is a pixel electrode, 24 is a gate terminal pad, 25 is a source terminal pad, 26 A transparent insulating substrate, 27 a color filter layer, 28 a counter electrode, 29 a liquid crystal layer, 31 a gap control layer.

The gate wiring (scan signal wiring) 2, the gate electrode 3, the storage capacitor electrode 4 and the gate terminal 5 are formed on the transparent insulating substrate 1 made of glass or the like. The gate wiring 2 has a gate electrode 3, and a gate terminal 5 is provided at the end of the gate wiring 2. The gate electrode 3 constitutes a TFT (thin film transistor) to be a switching element. The storage capacitor electrode 4 is disposed in parallel with the gate wiring 2 and is located near the center of the pixel region. The storage capacitor electrode 4 constitutes a storage capacitor for maintaining a voltage applied to the pixel electrode 23 for a predetermined time. In the TFT array substrate, driver ICs to which various signals from the outside are supplied are arranged. The pad and the gate terminal 5 provided in the driver IC are electrically connected to each other. As a result, the image scan signal from the outside is input to the gate wiring 2 through the gate terminal 5. The gate wiring 2 then transmits an image scanning signal to the gate electrode 3.

The gate insulating film 6 made of a transparent inorganic insulating material is formed so as to cover the gate wiring 2, the gate electrode 3, the storage capacitor electrode 4, and the gate terminal 5. The semiconductor film 7 is formed over the gate wiring 2 and the gate electrode 3 through the gate insulating film 6 to form a TFT. The ohmic contact film 8 is formed on the semiconductor film 7. In addition, the ohmic contact film 8 is removed from a part of the gate electrode 3. Therefore, the ohmic contact film 8 is disposed at both ends of the semiconductor film 7.

The source electrode 9 extends from the source wiring (display signal wiring) 10 to constitute a TFT. In addition, the source electrode 9 is provided on the ohmic contact film 8 on the side opposite to the storage capacitor electrode 4. The source terminal 11 is at the end of the source wiring 10. Further, a driver IC to which various signals from the outside are supplied is disposed on the TFT array substrate. The pad and the source terminal 11 provided in the driver IC are electrically connected to each other. Accordingly, the external image signal is inputted to the source wiring 10 through the source terminal 11. The source wiring 10 then transmits an image signal to the source electrode 9. A plurality of source wirings 10 are provided in parallel on the TFT array substrate. Similarly, the plurality of gate wirings 2 are also provided in parallel. The gate wiring 2 and the source wiring 10 are formed to intersect with each other via the gate insulating film 6. In addition, a TFT is formed near the intersection point of the gate wiring 2 and the source wiring 10. In addition, a region surrounded by the adjacent gate wiring 2 and the source wiring 10 becomes a pixel, and the pixels are arranged in a matrix on the TFT array substrate.

A drain electrode 12 is formed on the ohmic contact film 8 on the side of the storage capacitor electrode 4 to form a TFT. At least a part of the drain electrode 12 overlaps the storage capacitor electrode 4 of the lower layer through the gate insulating film 6. As a result, charges may be accumulated between the storage capacitor electrode 4 and the drain electrode 12 to form a storage capacitor. The channel portion 13 of the TFT is a region sandwiched between the source electrode 9 and the drain electrode 12 of the semiconductor film 7.

The protective insulating film 14 is made of a transparent inorganic insulating material and is formed to cover the TFT, the gate wiring 2, and the source wiring 10. In other words, the protective insulating film 14 is formed on the source electrode 9 and the drain electrode 12. The first interlayer insulating film 15 is made of a transparent organic resin material and is formed to cover the protective insulating film 14.

In addition, several uneven | corrugated shapes 16 for scattering reflected light are formed in a part of 1st interlayer insulation film 15. As shown in FIG. Concave-convex shapes 16 are formed in the region except for the TFT among the storage capacitor electrodes 4 near the gate wiring 2 in each pixel region. As a result, the surface of the first interlayer insulating film 15 is roughened.

The reflective film 17 is formed on the uneven shape 16 of the first interlayer insulating film 15. That is, the reflective film 17 is provided in almost the same area as the uneven shape 16, and is formed in approximately half of each pixel area except for the TFT. The region in which the reflective film 17 is formed becomes a light reflection part. As a result, the light incident on the viewing side is reflected by the reflecting film 17 and exits to the viewing side. In addition, the light shielding film 18 is formed on the TFT portion of the first interlayer insulating film 15. As a result, the influence of the charge on the TFT can be prevented, and the incident light of the ambient light to the TFT is blocked. The reflective film 17 and the light shielding film 18 are formed of the same material.

The second interlayer insulating film 19 is made of a transparent organic resin material, covering the reflective film 17 and the light shielding film 18, and planarizing the entire substrate. That is, the second interlayer insulating film 19 is formed on the reflective film 17. Therefore, the reflective film 17 is formed on the pattern of the uneven | corrugated shape 16 of the 1st interlayer insulation film 15, and is coat | covered with the 2nd interlayer insulation film 19. FIG. For this reason, the reflective film 17 is not connected to the drain electrode 12 or the pixel electrode 23 mentioned later, but is electrically floating. That is, it does not function as an electrode.

The pixel electrode 23 is provided almost entirely of each pixel region except for the TFT. In addition, the pixel electrode 23 is disposed on the reflective film 17. The region where the reflective film 17 is formed under the pixel electrode 23 is a light reflection part, and the region where the reflective film 17 is not formed under the pixel electrode 23 is a light transmission part. Specifically, part of the pixel electrode 23 is formed to protrude from the region where the reflective film 17 is disposed. And the part of the pixel electrode 23 which protruded from the area | region in which the reflecting film 17 is arrange | positioned becomes a light transmission part. The pixel electrode 23 is a transparent pixel electrode made of a transparent conductive material, and provides a signal potential to the liquid crystal layer.

A first contact hole (pixel drain contact hole) 20 is formed on the drain electrode 12. The first contact hole 20 is formed to penetrate through the protective insulating film 14, the first interlayer insulating film 15, and the second interlayer insulating film 19. The pixel electrode 23 is connected to the drain electrode 12 of the lower layer through the first contact hole 20. The region where the first contact hole 20 is formed becomes the pixel / drain contact portion.

A second contact hole (gate terminal portion contact hole) 21 is formed on the gate terminal 5. The second contact hole 21 is formed to penetrate through the gate insulating film 6, the protective insulating film 14, the first interlayer insulating film 15, and the second interlayer insulating film 19. The gate terminal pad 24 is made of a transparent conductive material and is connected to the lower gate terminal 5 through the second contact hole 21. The region where the second contact hole 21 is formed becomes the gate terminal portion.

A third contact hole (source terminal portion contact hole) 22 is formed on the source terminal 11. The third contact hole 22 is formed to pass through the protective insulating film 14, the first interlayer insulating film 15, and the second interlayer insulating film 19. The source terminal pad 25 is made of a transparent conductive material and is connected to the source terminal 11 in the lower layer through the third contact hole 22. The region where the third contact hole 22 is formed becomes the source terminal portion. With the above structure, the TFT array substrate is comprised.

3 is a cross-sectional view illustrating a transflective liquid crystal display panel including the TFT array substrate of FIG. 2. As shown in FIG. 3, the opposing board | substrate which is a 2nd board | substrate is arrange | positioned at the TFT array board mentioned above. The opposing substrate is arranged to oppose the TFT array substrate. Here, the counter substrate has a transparent insulating substrate 26, a color filter layer 27, a counter electrode 28, and a gap control layer 31. The color filter layer 27 has a black matrix (BM) and the colored layer of red (R) green (G) blue (B), for example. The color filter layer 27 is formed in the pixel region of the bottom surface of the transparent insulating substrate 26 made of glass or the like to perform color display. The counter electrode 28 is arrange | positioned at the liquid crystal layer 29 side of an opposing board | substrate, and provides a common potential for supplying a signal potential to the liquid crystal layer 29. As shown in FIG. The gap control layer 31 is formed on the upper layer of the counter electrode 28 in the region facing the light reflection portion. As a result, the thickness of the liquid crystal layer 29 facing the light reflecting portion on the TFT array substrate side is about 1/2 of the thickness of the liquid crystal layer 29 facing the light transmitting portion. It is preferable to provide such a step | step. As a result, the optical path lengths of the transmitted light and the reflected light can be substantially matched, and the phase difference between the transmitted light and the reflected light is coincident, so that suitable display characteristics can be obtained even in the reflection mode and the transmission mode. Then, the TFT array substrate and the opposing substrate are opposed to each other by using a sealing material, and the liquid crystal layer 29 is sandwiched and sealed between them.

Moreover, the liquid crystal aligning film (not shown) is apply | coated and formed in the surface of a TFT array substrate and an opposing board | substrate for orientating a liquid crystal. The transflective liquid crystal display panel according to the present embodiment is configured as described above.

In the semi-transmissive liquid crystal display panel according to the present embodiment, a TFT, which is a switching element, is disposed in each pixel in order to drive the pixel electrode 23 formed of the transmission electrode. The pixel electrode 23 is electrically connected to the drain electrode 12 of the TFT. The gate electrode 3 of the TFT is connected to the gate wiring 2 to control the ON and OFF of the TFT by a signal input from the gate terminal 5. The source electrode 9 of the TFT is connected to the source wiring 10. When a voltage is applied to the gate electrode 3, a display voltage is applied from the source wiring 10 to the pixel electrode 23 connected to the drain electrode 12 of the TFT.

As a result, an electric field corresponding to the display voltage is generated between the pixel electrode 23 and the counter electrode 28. The liquid crystal is driven by the electric field generated between the substrates. That is, the alignment direction of the liquid crystal between the substrates is changed, and the polarization state of the light passing through the liquid crystal layer 29 is changed. In addition, by arbitrarily controlling the display voltage applied to the source electrode 9, the voltage (driving voltage) actually applied to the liquid crystal can be changed. Since the voltage applied to the liquid crystal can be controlled by the source electrode 9, the intermediate transmittance of the liquid crystal can also be freely set for the liquid crystal driving state.

In addition, a polarizing plate, a retardation plate, and the like are provided on the outer surface of the TFT array substrate and the counter substrate. In addition, a backlight unit or the like is disposed on the half-view side of the liquid crystal display panel. The polarizing plate absorbs light that vibrates in one direction, passes only light that vibrates in one direction, and creates linearly polarized light. The retardation plate mainly causes a specific phase difference such as λ / 2 or λ / 4. These are called λ / 2 plates and λ / 4 plates, respectively. Such a retardation plate is used for optical compensation and is also used for expanding the viewing angle.

In the light transmitting portion, light incident from the backlight unit passes through the polarizing plate on the TFT array substrate side and becomes linearly polarized light, and passes through the retardation plate to generate a specific phase difference. In addition, the light enters the liquid crystal layer 29 through the transparent insulating substrate 1. By passing through the liquid crystal layer 29, the polarization state of light is changed. Then, it passes through the transparent insulating substrate 26, the retardation plate, and the polarizing plate, becomes linearly polarized light, and it exits to the viewer side.

In the light reflection portion, light incident on the viewer side passes through the polarizing plate on the opposite substrate side to become linearly polarized light, and passes through the retardation plate to generate a specific phase difference. In addition, the light enters the liquid crystal layer 29 through the transparent insulating substrate 26. By passing through the liquid crystal layer 29, the polarization state of light is changed. Light incident on the liquid crystal layer 29 is reflected by the reflective film 17. This passes through the liquid crystal layer 29 again, and the polarization state of the light is changed. Then, it passes through the transparent insulating substrate 26, the retardation plate, and the polarizing plate, becomes linearly polarized light, and it exits to the viewer side.

The amount of light passing through the polarizing plate on the opposite substrate side changes depending on the polarization state. That is, the amount of light passing through the polarizing plate on the viewer side is changed among the transmitted light passing through the liquid crystal display panel from the backlight unit and reflected light of light incident from the outside. The orientation direction of a liquid crystal changes with the display voltage applied. Therefore, by controlling the display voltage, the amount of light passing through the polarizing plate on the viewing side can be changed. In other words, a desired image can be displayed by changing the display voltage for each pixel.

Hereinafter, the manufacturing process of the transflective liquid crystal display device which concerns on a present Example is demonstrated in detail using FIG. 4 is a cross-sectional view showing the manufacturing process of the TFT array substrate according to the present embodiment.

First, the gate wiring 2, the gate electrode 3, the storage capacitor electrode 4, and the gate terminal 5 are formed. First, a first metal thin film is formed on a transparent insulating substrate 1 such as glass by sputtering or the like. In this embodiment, a C (chromium) film is used as the first metal thin film. Then, Cr is formed to a thickness of 200 nm by the sputtering method using a known Ar gas. Next, a resist of photosensitive resin is applied on the first metal thin film by spin coating, and the first photolithography step of exposing and developing the applied resist is performed. As a result, the photoresist is patterned into a desired shape. After that, the Cr film is etched and the photoresist pattern is removed to form the gate wiring 2, the gate electrode 3, the storage capacitor electrode 4, and the gate terminal 5. In addition, a gate wiring 2 is formed at the gate / source intersection, a gate electrode 3 at the TFT, a storage capacitor electrode 4 at the storage capacitor wiring, and a gate terminal 5 at the gate terminal. In this embodiment, a solution containing cerium nitrate + perchloric acid known for etching is used. By this process, as shown to FIG. 4A, the pattern of a 1st metal thin film is formed on the transparent insulating substrate 1. As shown in FIG.

Subsequently, the gate insulating film 6, the semiconductor film 7, and the ohmic contact film 8 are sequentially formed by various CVD methods such as plasma CVD, and the semiconductor film 7 is subjected to the second photolithography and etching processes. ) And the ohmic contact film 8 are patterned. The patterns of the semiconductor film 7 and the ohmic contact film 8 are preferably formed not only in the region in which the TFT serving as the switching element is formed, but also in the region in which the gate wiring 2 and the source wiring 10 intersect. As a result, the step difference in the pattern of the gate wiring 2 can be relaxed by the patterns of the semiconductor film 7 and the ohmic contact film 8, thereby preventing the source wiring 10 from being disconnected at the stepped portion.

As the gate insulating film 6, SiN _x , SiO _y, or the like is used. As the semiconductor film 7, for example, a-Si (amorphous silicon) and p-Si (polysilicon) are used. The ohmic contact film 8 is an n-type semiconductor, and an n ⁺ a-Si film, an n ⁺ p-Si film, etc. doped with a small amount of P (phosphorus) or the like on a-Si or p-Si is used.

In this embodiment, by using a well-known chemical vapor deposition (CVD) method, 400 nm of SiN _x (x is an integer) as the gate insulating film 6, 200 nm of a-Si as the semiconductor film 7, and an ohmic contact film 8 ), N ⁺ a-Si doped with P (phosphorus) as an impurity in a-Si is formed into a film at a thickness of 50 nm. Then, the pattern of the semiconductor film 7 and the ohmic contact film 8 is formed by a known dry etching method using a fluorine-based gas. This forms the structure shown in FIG. 4B.

Thereafter, a second metal thin film which becomes a source wiring material is formed into a film by sputter | spatter etc., and a 3rd photolithography process and an etching process are performed. Thereby, the source electrode 9, the source wiring 10, the source terminal 11, and the drain electrode 12 are formed. Then, the ohmic contact film 8 is removed by etching or the like using the patterns of the source electrode 9, the source wiring 10 and the drain electrode 12 as a mask. By this process, the center part of the ohmic contact film 8 is removed, the semiconductor film 7 is exposed, and the channel part 13 is formed. Thereafter, the photoresist pattern is removed, and patterns of the source electrode 9, the source wiring 10, the source terminal 11, the drain electrode 12, and the channel portion 13 of the TFT are formed.

In this embodiment, a Cr film is used as the second metal thin film. First, Cr is formed into a film of 200 nm in thickness by the sputtering method using well-known Ar gas. Next, the photoresist is patterned to a desired shape by the third photolithography step. Thereafter, the Cr film is etched using a solution containing known cerium nitrate + perchloric acid. By this process, the pattern of the source electrode 9, the source wiring 10, the source terminal 11, and the drain electrode 12 is formed on a board | substrate. Next, the ohmic contact film 8 in the region sandwiched between the source electrode 9 and the drain electrode 12 is etched by a known dry etching method using a fluorine-based gas. By this process, the pattern of the channel portion 13 of the TFT is formed. By the above process, the structure shown in FIG. 4C is formed on a board | substrate.

Thereafter, a protective insulating film 14 formed of an insulating film made of SiN _x , SiO _y (where X and y are integers), a mixture thereof, and a laminate is formed by various CVD methods such as plasma CVD. Thereafter, the first interlayer insulating film 15 made of the photosensitive organic resin film is coated and formed, and the uneven shape 16 is formed in a part of the first interlayer insulating film 15 by the fourth photolithography process. In addition, the area | region in which the uneven shape 16 was formed is a light reflection part.

In this embodiment, first, a SiN _x (x is an integer) is formed to a thickness of 100 nm as the protective insulating film 14 using a known CVD method. Thereafter, a photosensitive organic resin film is formed as the first interlayer insulating film 15 by a spin coat method so as to have a film thickness of 1 µm to 3.5 µm. Here, the photosensitive organic resin film is made of JSR PC335 which is a light-transmitting acrylic organic resin. In addition, the first interlayer insulating film 15 may contain absorbent particles. Then, the pattern of the concave-convex shape 16 for scattering the reflected light in an arbitrary angular direction is formed using the fourth photolithography step. The uneven shape 16 uses a photomask for uneven pattern formation. For example, when the photoexposure amount required to completely remove the photosensitive organic resin film by development is 100%, exposure is performed at the exposure amount of about 20 to 40% with respect to the light reflection part. Thereafter, for example, the uneven shape 16 can be formed by developing with an organic alkali developer having a TMAH (tetramethyl ammonium hydroxide) concentration of about 0.4 wt%. Moreover, by changing the uneven shape 16, the scattering angle direction of external light incident from the surroundings is changed. Therefore, it is desirable to optimize the exposure amount or TMAH concentration of the developer so as to obtain the desired scattering angle characteristic required for the display device. In addition, by post-baking at a temperature of about 200 ° C. after development, it is possible to make the irregularities smoothly by the reflow effect. By the above process, the structure shown in FIG. 4D is formed on a board | substrate.

Next, a third metal thin film having high reflection characteristics is formed, and a fifth photolithography process and an etching process are performed. Thereby, the reflective film 17 which forms a light reflection part, and the light shielding film 18 which covers at least one part area | region or the whole area | region of TFT are formed. The reflective film 17 is formed on the uneven shape 16 formed on the first interlayer insulating film 15. In addition, the reflective film 17 and the light shielding film 18 are not connected to the pixel electrode 23, but are electrically floating. By forming the light shielding film 18, charging of the channel portion 13 of the TFT can be prevented, and deterioration of characteristics can be prevented.

In this embodiment, Al (aluminum) is formed into a thickness of 100 nm using a known sputtering method as the third metal thin film. Then, a photoresist pattern is formed by the fifth photolithography step. Next, etching is performed using a solution containing known phosphoric acid + nitric acid + acetic acid. Thereafter, the photoresist pattern is removed to form a reflective film 17 for forming the light reflection portion. At the same time, it is preferable to form the light shielding film 18 pattern so as to cover at least a partial region or the entire region on the TFT. By forming the light shielding film 18, the cause of the optical leak due to incidence of external light into the semiconductor film 7 can be suppressed. In addition, it is possible to suppress variation in the characteristics of the TFT due to moisture or other falling ions contained in the photosensitive organic resin film forming the first interlayer insulating film 15. By the above process, the structure shown in FIG. 4E is formed on a board | substrate.

Next, a second interlayer insulating film 19 made of a photosensitive organic resin film is applied and formed. In this embodiment, a photosensitive organic resin film is formed as a second interlayer insulating film 19 by a spin coat method so as to have a film thickness of 0.5 µm to 2.5 µm. The photosensitive organic resin film is made of J335 PC335 which is a light-transmitting acrylic organic resin. Then, the sixth photolithography step and etching step are performed. By this step, the first interlayer insulating film 15 and the second interlayer insulating film 19 of the contact portion are removed. That is, the protective insulating film 14 is exposed in the pixel / drain contact portion, the gate terminal portion, and the source terminal portion. By the above process, the structure shown in FIG. 4F is formed on a board | substrate.

After that, the first, second, and third contact holes 20, 21, and 22 are formed. In this embodiment, using the second interlayer insulating film 19 as a mask, the gate insulating film 6 and the protective insulating film 14 made of SiN _x are removed by a known dry etching method using a fluorine-based gas. By this process, the protective insulating film 14 is removed from the pixel / drain contact portion, and the drain electrode 12 made of the second metal thin film is exposed. As a result, the first contact hole 20 is formed. In addition, by the same process, the protective insulating film 14 and the gate insulating film 6 are removed in the gate terminal part, and the gate terminal 5 which consists of a 1st metal thin film is exposed. As a result, the second contact hole 21 is formed. In addition, by the same process, the protective insulating film 14 is removed from the source terminal part, and the source terminal 11 which consists of a 2nd metal thin film is exposed. As a result, a third contact hole 22 is formed. Therefore, conduction is performed between the transparent conductive film forming the pixel electrode 23 and the like to be formed later, and the drain electrode 12, the gate terminal 5, and the source terminal 11 of the TFT. By the above process, the structure shown in FIG. 4G is formed on a board | substrate.

Thereafter, a transparent conductive film such as indium tin oxide (ITO), SnO ₂ , InZnO, or the like is formed by a method such as sputtering, vapor deposition, coating, CVD, printing, or sol-gel method. This transparent conductive film may be a transparent conductive layer made of a laminated or mixed layer of ITO, SnO ₂ , InZnO, or the like. Then, the seventh photolithography process and etching process are performed. By this process, the pattern of the pixel electrode 23, the gate terminal pad 24, and the source terminal pad 25 is formed.

The pixel electrode 23 is formed almost entirely except the TFT of each pixel region. In addition, the pixel electrode is connected to the drain electrode 12 of the lower layer through the first contact hole 20 of the pixel / drain contact portion. The gate terminal pad 24 is formed in the second contact hole 21 of the gate terminal portion. The gate terminal pad 24 is also connected to the lower gate terminal 5 through the second contact hole 21 in the gate terminal portion. The source terminal pad 25 is formed in the third contact hole 22 of the source terminal portion. In addition, the source terminal pad 25 is connected to the source terminal 11 in the lower layer through the third contact hole 22 of the source terminal portion. In this manner, the transparent conductive film is electrically conductive with the drain electrode 12, the gate terminal 5, and the source terminal 11 by the first, second, and third contact holes 20, 21, and 22, respectively. have.

In this embodiment, ITO is formed into a film with a thickness of 100 nm using a known sputtering method as a transparent conductive film, and a photoresist pattern is formed using the seventh true plate making process. And etching is performed using the solution containing well-known hydrochloric acid + nitric acid. Thereafter, the photoresist pattern is removed to form the pixel electrode 23, the gate terminal pad 24, and the source terminal pad 25. By the above process, it becomes a structure shown in FIG. 4H.

Through such a series of steps, a TFT array substrate for driving liquid crystal can be formed.

In addition, in this embodiment, although the Al film was used as the reflecting film 17, it is not limited to this, Al alloy which added the impurity to Al may be used. Suitable examples are AlCu alloys in which 0.1 to 0.5 wt% of Cu (copper) is added to Al. Alternatively, at least one kind selected from Y (yttrium), La (lanthanum) Nd (neodymium), Sm (samarium), Gd (gadolinium) and other rare earth metals is added at least in the range of 0.3 to 1.0 wt%. One Al alloy may be used. In these cases, since the growth of crystal grains can be suppressed at the time of film formation by sputtering and a densely flat film can be obtained, a high reflectance can be obtained, which is preferable. Further, at least one element selected from Fe (iron), Co (cobalt), Ni (nickel), Ru (ruthenium), Pd (palladium), and Pt (platinum) is added to Al at least in a range of 1 to 10 wt%. Al alloy may be used. In this case, the transmittance of light having a short wavelength of 400 nm or less is increased as compared with pure Al alloy, and the reflectance characteristics can be made constant in the range of 350 nm to 750 nm in the visible light region. Therefore, since the paper white color characteristic of reflected light can be acquired, it is preferable.

The transflective liquid crystal display device according to the present embodiment has a light transmitting portion and a light reflecting portion in each pixel region. The reflective film 17 formed on the light reflection portion is covered with the second interlayer insulating film 19 and is not connected to the drain electrode. Therefore, it does not have a function as an electrode which applies electric potential to the liquid crystal layer 29. FIG. That is, the reflecting film 17 does not function as an electrode for driving the liquid crystal but has only a function of reflecting light incident from the outside. Therefore, in the TFT array substrate, only the transmissive electrode made of the transparent conductive film formed on the reflective film 17 functions as the pixel electrode 23 for driving the liquid crystal.

In this way, the voltage is applied to the liquid crystal to the pixel electrode 23 on the TFT array substrate side and the counter electrode 28 on the opposing substrate side, and both are formed of a transparent conductive film of the same material. That is, the supply of the signal potential to the liquid crystal layer 29 by the pixel electrode 23 on the TFT array substrate side is only by the transparent conductive film which is the same material as the counter electrode 28 which opposes the liquid crystal layer 29. Is done. Here, the transparent conductive film which comprises the pixel electrode 23 and the counter electrode 28 is an ITO film, for example. For this reason, between the pixel electrode 23 and the counter electrode 28 which oppose through the liquid crystal layer 29, the offset electric potential by a battery effect does not arise in principle. Therefore, a signal potential is uniformly applied to each pixel region including both the light transmitting portion and the light reflecting portion. In short, the difference in potential due to the local battery effect between the conventional ITO-ITO electrode and the ITO-Al electrode does not appear, and the optical characteristics of the transmitted light of the light transmitting portion and the reflected light of the light reflecting portion are constant.

Therefore, even when the Al film is used as the reflective film 17 as in the present embodiment, good display quality can be obtained without degrading display characteristics in the light transmitting portion and the light reflecting portion. As described above, even when the Al film is used for the light reflection portion, the difference in the offset potential value with the light transmission portion can be eliminated, and deterioration of display characteristics such as sticking can be prevented.

 In addition, in the present embodiment, since the reflective film 17 is covered with the second interlayer insulating film 19, the reflective film 17 is cut off from the outside air. Therefore, even when Ag or an Ag-based alloy film is used as the reflective film 17, surface oxidation in the air as in the prior art does not occur. For this reason, since the change of reflection characteristics, such as a reflectance fall, can be prevented, favorable display quality becomes possible.

In addition, the uneven shape 16 provided on the surface of the light reflection portion of the TFT array substrate is planarized by the second interlayer insulating film 19. For this reason, the disorder of the liquid-crystal orientation by unevenness | corrugation does not generate | occur | produce like a conventional structure. In addition, when forming the pixel electrode 23, the etching rate can be made constant, and the production capacity can be improved. As mentioned above, according to this embodiment, it becomes possible to obtain the transflective liquid crystal display device which combines high reflection efficiency and favorable display quality simultaneously.

Further, in the present embodiment, to form a protective insulating film 14 made of an inorganic insulating film of SiN _x light transmissive, it is possible to omit this. However, as in the present embodiment, by providing the protective insulating film 14 made of the SiN _x film, moisture or charge impurities contained in the first interlayer insulating film 15 and the second interlayer insulating film 19 of the organic resin system are provided. This effect can prevent the influence of the floating ions directly on the channel portion 13 of the TFT. Therefore, it is preferable to form the protective insulating film 14 because these can suppress variation in characteristics of the TFT.

As in the present embodiment, the first interlayer insulating film 15 having the uneven shape 16 on the surface, the reflective film 17 formed on the unevenness, and the reflective film 17 are completely covered, and the surface is planarized. By having the 2nd interlayer insulation film 19 for this, the transflective liquid crystal display device which has the outstanding display characteristic can be obtained.

It is also possible to connect the reflective film 17 and the lower storage capacitor electrode 4 to a common potential to form a charge storage capacitor. As a result, charges are accumulated between the reflective film 17 and the drain electrode 12 to form a storage capacitor. By setting it as this structure, more storage capacity can be ensured and the holding | maintenance characteristic of TFT improves.

5 is a view showing another example of a TFT array substrate for a transflective liquid crystal display according to the present embodiment. In the case of FIG. 5, the light shielding film 18 and the pixel electrode 23 are connected. In addition, about another structure, it is the same as FIG. In FIG. 2, the light shielding film 18 is not connected to the pixel electrode 23 and is electrically floating. However, as shown in FIG. 5, the light shielding film 18 may be electrically connected to the pixel electrode 23. Specifically, after the application of the second interlayer insulating film 19 is formed, a part of the second interlayer insulating film 19 on the light shielding film 18 is removed. Thereby, the light shielding film 18 is exposed and connected with the pixel electrode 23 formed continuously. And the light shielding film 18 and the pixel electrode 23 are connected, and the light shielding film 18 can be fixed to the pixel electrode 23 potential. In this case, it is preferable because the variation in characteristics of the TFT can be more suppressed in comparison with the floating state.

Example 2.

In this embodiment, a plurality of reflective films 17 spaced apart from each other are formed in one pixel. That is, the reflective film 17 formed in the light reflection portion does not have a function as an electrode for applying a potential to the liquid crystal layer 29, but has only a function of reflecting external light. Therefore, the reflective film 17 pattern does not need to be a continuous pattern in which the whole reflective film is electrically connected like the conventional structure. Therefore, the reflective film 17 can be formed as an aggregate of several isolation patterns.

6 and 7, the transflective liquid crystal display according to the present embodiment will be described. 6 is a plan view showing a TFT array substrate for a transflective liquid crystal display device according to the present embodiment. 7 is a cross-sectional view showing a TFT array substrate for a transflective liquid crystal display device according to the present embodiment. Since the present embodiment is the same as that of the first embodiment except for the shape of the reflective film 17, description thereof is omitted. In the present embodiment, a plurality of reflective films 17 are provided in an island shape on the uneven shape 16 of the first interlayer insulating film 15. As in the present invention, when the reflective film 17 is not used as the pixel electrode 23 for applying a potential to the liquid crystal layer 29, as shown in FIGS. 6 and 7, a plurality of discontinuous reflective films 17 are used. Can be formed.

According to the present embodiment, the pattern of the reflective film 17 is formed only in the concave portion of the uneven shape 16 formed in the first interlayer insulating film 15, but not in the flat portion of the first interlayer insulating film 15. Do not. For this reason, the specularly reflected light component in the flat portion, which is the main cause of the deterioration of the image in the light reflection portion, is removed, and only the scattered reflected light from the unevenness can be used for image display. Therefore, it is preferable because excellent display quality can be obtained like paper white and the display quality can be improved. Thus, if it is the recessed part of the uneven shape 16, the reflective film 17 can be formed into arbitrary shapes in arbitrary positions, and the semi-transmissive liquid crystal display device excellent in display characteristics can be obtained.

The semi-transmissive liquid crystal display device according to the first and second embodiments has a light transmitting portion and a light reflecting portion in each pixel region. In addition to the transflective liquid crystal display device, for example, by changing the area for forming the light reflection portion, it is possible to arbitrarily change the ratio of the light transmission portion and the light reflection portion.

In each pixel region, the region in which the light reflection portion is formed is preferably above the region in which the storage capacitor electrode 4 is formed. Since the storage capacitor electrode 4 is a metal thin film, it reflects external light. Therefore, by forming the reflective film 17 on the region where the storage capacitor electrode 4 is formed, the area of the light transmitting portion can be used efficiently. This is the same also in Example 1. In addition, the pattern of the uneven | corrugated shape 16 for light scattering formed in a light reflection part is not limited to the shape shown in a present Example. For example, it is also possible to make an elongate pattern shape aggregate so as to have directivity in the viewing angle of an image display, or to give regularity to the arrangement of the uneven pattern. Thus, it can arrange | position freely according to the requested display characteristic. Also in this embodiment, the same effects as in the first embodiment can be obtained. That is, even when the Al film is used for the light reflection portion, the difference in the offset potential value with the light transmission portion can be eliminated, and the effect of preventing deterioration of display characteristics due to sticking can be obtained.

According to the present invention, a transflective liquid crystal display device capable of preventing deterioration of display characteristics can be obtained.

Claims (7)

A first substrate, A second substrate disposed to face the first substrate and having a counter electrode; A semi-transmissive liquid crystal display device having a liquid crystal sandwiched between the first substrate and the second substrate, wherein a light reflecting portion and a light transmitting portion are provided in a pixel. The first substrate has a plurality of gate wirings, a plurality of source wirings intersecting the gate wirings, and a switching element, A first interlayer insulating film covering the gate wiring, the source wiring, and the switching element, the first interlayer insulating film having an irregular shape at least in part; A reflective film provided only on the concave-convex portions of the first interlayer insulating film and provided in a plurality of pixels; A second interlayer insulating film formed to cover the reflective film; A transparent pixel electrode formed on a region in which the reflective film of the second interlayer insulating film is disposed, and electrically connected to the switching device through a contact hole; And the transparent pixel electrode is formed to protrude from a region where the reflective film is disposed, and a portion of the transparent pixel electrode which protrudes from the region where the reflective film is disposed is a light transmitting portion. The method of claim 1, A transflective liquid crystal display device, wherein one or both of the first interlayer insulating film and the second interlayer insulating film are organic resin films. The method according to claim 1 or 2, A transflective liquid crystal display device, wherein a protective insulating film made of an inorganic material is provided under the first interlayer insulating film. The method according to claim 1 or 2, And a light shielding film is formed to cover at least a portion of the area where the switching element is formed. The method of claim 4, wherein And said light shielding film is electrically connected to said transparent pixel electrode. The method according to claim 1 or 2, A semi-transmissive liquid crystal display device, characterized in that a color filter for color display is formed on the second substrate. The method according to claim 1 or 2, An area facing the area where the reflective film of the first substrate is provided; In an area facing the area where the reflective film of the first substrate is not provided, A semi-transmissive liquid crystal display device characterized in that a step for generating another liquid crystal layer thickness is provided on the second substrate.

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