Reflection type liquid crystal display and method of fabricating the same

Reflective liquid crystal display device and its manufacturing method

The present invention relates to a liquid crystal display device, in particular to a reflective liquid crystal display device including an active matrix display including a thin film transistor as a switching device, and a passive matrix liquid crystal display device without a switching device. The invention also relates to a method of manufacturing such a reflective liquid crystal display device.

Description of related technologies

In recent years, liquid crystal display devices are widely used in pocket TVs and communication terminal devices due to their thin thickness and light weight. In particular, reflective liquid crystal display devices that do not use backlight are ultra-thin, ultra-light, and capable of mass production. It is widely demanded to reduce power consumption. However, even if the backlight is removed from the current emissive color liquid crystal display device and a light reflecting plate is installed on the lower surface of the display device, it may cause problems such as low light utilization efficiency and insufficient density.

To solve this problem, a variety of reflective liquid crystal display devices have been proposed that can improve light utilization efficiency. For example, the design of a reflective liquid crystal display device includes a pixel electrode with a reflective function, and the design of another type does not contain a polarizing plate.

As another example, the reflective liquid crystal display in the article "Bright reflective colorful liquid crystal display device addressed by silicon thin film transistor" proposed by S. Mitsuei et al. in Information Co., Ltd.'s 1992 Display Device Digest, pages 437-440 The device is a host-guest type liquid crystal, including the use of dichroism pigments as the original material of the liquid crystal. Figure 1 shows the structure of the proposed reflective liquid crystal display device.

The illustrated reflective liquid crystal display device includes an insulating substrate 41 and an opposite substrate 13 separated from the insulating substrate 41. The space between the substrates 41 and 13 is filled with liquid crystal 10. A color filter 12 is provided on the substrate 13, and a transparent common electrode 11 is provided on the color filter 12. A gate electrode 9 is provided on the insulating substrate 41. Both the gate electrode 9 and the insulating substrate 41 are covered with a gate insulating film 8, and a semiconductor layer 7 is provided on the gate insulating film 8 above the gate electrode 9. The active electrode 4 and the drain electrode 5 on the gate insulating film 8 are in contact with the semiconductor layer 7. The source electrode 4 and the drain electrode 5, the semiconductor layer 7, and the gate electrode 9 cooperate with each other to form a bottom gate type thin film transistor (TFT). A laminated insulating film 42 is formed and covers the source electrode 4, the drain electrode 5, the semiconductor layer 7 and the gate insulating film 8. The gate insulating film 42 has contact holes 44 all over it. An aluminum pixel electrode 43 is provided on the inner side wall of one of the overlapped insulating film 42 and the contact hole 44.

The drain electrode 5 of the thin film transistor passes through the overlapped insulating film 42 and contacts the pixel electrode 43. As shown in the figure, the overlapped insulating layer 42 is designed to have an uneven surface, so that the pixel electrode 43 serves as a reflector to diffuse the surrounding light. The light reflected from the pixel electrode 43 penetrates or is absorbed by the host-guest liquid crystal layer 10.

Since the reflective liquid crystal display device shown in FIG. 1 no longer needs to provide a large polarization and use the pixel electrode 43 as a light reflecting plate, the light utilization efficiency is significantly improved.

In the reflective liquid crystal display device shown in the figure, it is important that the pixel electrode 43 is designed as a light reflecting plate to have an uneven surface. If the pixel electrode 43 is designed to have a flat reflective surface, the reflected light will be more densely oriented, resulting in a narrower angle suitable for viewing the display (this angle is referred to as the "angle of view" hereinafter) and causes reflection The image of a pixel electrode 43 looks like a flat mirror. As a result, the visual effect of the display device is not good.

However, it is important that the light reflecting surface is concave and convex or designed to have convex and concave shapes, so that the surrounding light can be evenly scattered. However, if the overlapped insulating layer 42 is designed to have protrusions and recesses, and a plate is provided for the pixel electrodes 43 to scatter and diffuse light in the reflective liquid crystal display device as shown in FIG. 1, it is inevitable that the manufacturing process will be More complex, leading to higher manufacturing costs.

In the above-mentioned reflective liquid crystal display device, the overlapped insulating layer 42 is designed to have concavities and convexities by photolithography. However, it is difficult to produce and control micrometer-order concave-convex shapes with lithography technology, and the concave-convex parts are often trapezoidal. Another problem is that it is impossible to have uniform reflection and scattering characteristics.

The reflective liquid crystal display device of FIG. 1 still has the following problems. First, it is difficult to provide the contact hole 44 to allow the drain electrode 5 to connect to the pixel electrode 43 through the overlapped insulating film 42. Secondly, thin film transistors such as pixel electrodes 43 are arranged on the top surface. If the active matrix substrate 41 is to be made, at least six processes of photolithography technology are required. In other words, six photomasks must be made, and the exposure, development, and etching steps need to be performed six times, all of which will increase manufacturing costs and reduce productivity. In addition, the registration error between the mask and the substrate must be considered. Therefore, it is difficult to produce active matrix substrates with larger specifications.

In order to solve the above problems, for example, there is an example in Japanese Patent Application Laid-Open No. 4-338721, suggesting that the reflective film is made of a multilayer dielectric film. The proposed reflective film has an advantage, that is, if the light use efficiency is controlled, the reflective performance of the lens composed of a multilayer dielectric film can be improved. However, when a lens made of a multilayer dielectric film is used as a light reflecting plate, the light scattering is better, and the reflected light has a dense orientation, of course, it is impossible to obtain a wide viewing angle.

Japanese Patent Laid-Open No. 7-306404 published a proposal to adopt a liquid crystal display device with a light diffusion film on the upper surface of a transparent pixel electrode, and a flat reflector at the back of the transparent pixel electrode. However, in this liquid crystal display device, the light transmitted from the outside is scattered by the light reflection film provided on the upper surface of the pixel electrons before the light enters a liquid crystal layer. Therefore, in the liquid crystal display device, the lithography technology steps must be performed seven times, which causes the problems of increased manufacturing costs and reduced productivity. According to the proposed liquid crystal display device, it will be difficult to make a larger substrate.

As described above, the conventional liquid crystal display device has many problems. In order to be able to make a reflective surface with uneven portions at any time, there is an advantageous step, which is to use ground glass to make an insulating layer with uneven portions. The reflective surface with unevenness can then be produced, for example, an aluminum film is provided on the uneven insulating substrate. However, if the reflective surface is produced in this way, thin film transistors must be manufactured on the concave and convex parts, as published in Japanese Patent Laid-Open No. 59-100488. Of course, the halo phenomenon will occur at any time, because the reflective plate is exposed in the photolithography step, which may cause the problem of limited design principles. In addition, another problem is that unevenness may cause deterioration of transistor performance and reduce productivity.

To solve these problems, Japanese Patent Laid-Open No. 59-100488 also proposes that the substrate, that is, the thin film transistor on the substrate, should be kept flat, and only the area where there are pixel electrodes needs unevenness. However, this is not an ideal solution because the electro-etching step can be time-consuming to keep the first mentioned area flat. In addition, to manufacture an active matrix substrate, at least seven lithography steps must be performed, which causes the same problems as described above. That is, the production cost is increased, and it is difficult to manufacture a larger size active matrix substrate.

As described above, the prior art manufacturing substrate plane has uneven portions, and a cumbersome photo-etching step must be performed to produce a reflective plate with sufficient light diffusion performance, and this is partly a problem of increased production cost. In addition, it is difficult to control the reflection characteristics of the reflector.

Furthermore, to manufacture an active matrix substrate including a thin film transistor and a reflector, it is necessary to perform the lithography process at least six times. Therefore, at least six different photomasks must be fabricated, and the exposure and development steps must be performed at least six times. This increases production costs, costs and reduces manufacturing capacity. In addition, the recording error between the photomask and the substrate must also be taken into consideration. As a result, it is difficult to fabricate a larger active matrix substrate.

Summary of the invention

In view of the foregoing problems in the prior art, one object of the present invention is to provide a reflective liquid crystal display device, which includes a light diffusion and reflection plate, the surface of which has uneven portions and has excellent reflection characteristics.

Another object of the present invention is to provide a reflective liquid crystal display device, which can reduce the lithography steps required in the production of an active matrix substrate containing a thin film transistor, thereby reducing production costs and increasing productivity.

In one aspect of the present invention, the provided liquid crystal display device includes (a) a first substrate with a rough (concavo-convex) surface, (b) a second substrate opposite to the rough surface of the first substrate but separated from the first substrate, ( c) A liquid crystal layer is sandwiched between the first and second substrates, (d) a metal film is provided on the uneven surface of the first substrate to reflect light, (e) a transparent dielectric film is provided on the metal film, the transparent dielectric film It has a flat upper surface, and (f) at least one transparent pixel electrode is provided on the transparent dielectric layer.

Preferably, the recesses and protrusions formed on the uneven surface have an internal height between 0.1 micrometer (μm) and 5 micrometers. Preferably, the recesses and protrusions have an internal pitch between 0.5 micrometers and 50 micrometers. It is also preferable that the recessed and protruding parts have a wavy curved surface.

For example, the transparent dielectric film can be made of polyimide resin. The first substrate may be a glass substrate. The second substrate may include a transparent insulating substrate, a color filter is disposed on the transparent insulating substrate, a transparent conductive film is provided on the color filter, and an alignment film is provided on the conductive film.

The reflective liquid crystal display device further provided further includes: (a) a first substrate with a rough (concave and convex) surface, (b) a second substrate opposite to the rough surface of the first substrate but separated from the first substrate, (c) A liquid crystal layer is sandwiched between the first and second substrates, (d) a metal film is provided on the uneven surface of the first substrate to reflect light, (e) a transparent dielectric film is provided on the metal film, and the transparent dielectric film has a flat surface. The upper surface, and (f) there are a plurality of transparent pixel electrodes on the transparent dielectric layer, and (g) there are a plurality of switching devices on the transparent dielectric film, each switching device is electrically connected to each transparent pixel electrode, the pixel electrode and the switching device In a matrix configuration.

Preferably, the metal film is partially formed on the rough surface of the first substrate. For example, the metal film may be formed only under the transparent pixel electrode. Alternatively, the metal film may be formed on the rough surface of the first substrate, so that the metal film does not need to be provided under the switch.

Another provided liquid crystal display device includes: (a) a first substrate with a rough (concavo-convex) surface, (b) a second substrate opposite to the rough surface of the first substrate but separated from the first substrate, (c) first and A liquid crystal layer is sandwiched between the second substrate, (d) a metal film is provided on the uneven surface of the first substrate to reflect light, (e) a transparent dielectric film is provided on the metal film, and the transparent dielectric film has a flat upper surface , And (f) there are a plurality of transparent pixel electrodes on the transparent dielectric layer, and (g) there are a plurality of switching devices on the transparent dielectric film, each switching device is electrically connected to each transparent pixel electrode, and the pixel electrodes and the switching devices are arranged in a matrix , And (h) A film is sandwiched between the transparent dielectric film and the switch device to avoid direct contact between the switch device and the transparent dielectric film.

The film can be an inorganic film, for example, made of silicon dioxide and silicon nitrate. It is preferable that the internal thickness of the film is in the range of 0.03 micrometers to 0.2 micrometers.

In another aspect of the present invention, a method for manufacturing a reflective liquid crystal display device substrate is provided, which includes the steps of (a) making the surface of the substrate rough and uneven, (b) forming a thin film on the rough surface of the substrate to reflect light, (c) forming a metal film A transparent dielectric is formed on the upper surface so that the transparent dielectric film has a flat upper surface, and (d) at least one transparent pixel electrode is provided on the transparent dielectric film.

Preferably, the first step (a) includes the step (a-1) to mechanically polish the surface of the substrate, and (a-2) to polish the surface with a chemical treatment to polish the sharp portion. In step (a-1), garnet is preferably used to mechanically polish the surface of the substrate. In step (a-1), the surface of the substrate can be polished mechanically by adding fine sand. Alternatively, in step (a-1), the surface of the substrate can be mechanically polished by sandblasting. The chemicals used in step (a-2) can be hydrofluoric acid or buffered hydrogen fluoride.

Preferably, in the step (b), the metal film is formed on the rough surface of the substrate by a sputtering method. For example, a spin coating method can be used to coat a metal film with a polymer on a transparent dielectric film. If this is the case, the transparent dielectric film can be coated with a liquid prepolymer on the metal film, and the prepolymer can be coated on the metal film. So that the pre-polymer has an almost uniform thickness, and the steps of removing the pre-polymer are formed.

The polymer may be at least one of polyamide, polyimide, polyester, acrylic resin, epoxy resin, silicone resin, and polysilazane.

A method for manufacturing a reflective liquid crystal display device substrate is also provided, which includes the steps of (a) making the surface of the substrate rough and uneven, (b) forming a thin film on the rough surface of the substrate to reflect light, and (c) forming a transparent dielectric on the metal film , So that the transparent dielectric film has a flat upper surface, (d) at least one transparent pixel electrode is provided on the transparent dielectric film, and (e) a plurality of switching devices are formed on the transparent dielectric film, so that each switching device and each The transparent pixel electrodes are electrically connected, and the transparent pixel electrodes and the switching devices are arranged in a matrix.

For example, step (e) further includes step (e-1) forming a transparent conductive film on the transparent dielectric, (e-2) making the transparent conductive film into a pattern of pixels, source and drain electrodes, (e-3) A semiconductor film, a gate insulating film and a metal film are formed over the patterned conductive film and the transparent dielectric film, and (e-4) the thin film thus formed is patterned into a gate electrode.

Preferably, the metal film is partially formed on the rough surface of the first substrate in step (a). For example, the metal film can be almost formed under the transparent pixel electrode. Alternatively, the metal film may be formed on the rough surface of the first substrate so that the metal film does not exist under the switch device, for example, the remaining parts of the metal film are removed by photolithography and etching.

A method for manufacturing a reflective liquid crystal display device substrate is also provided, which includes the steps of (a) making the surface of the substrate rough and uneven, (b) forming a thin film on the rough surface of the base to reflect light, and (c) forming a film on the metal film Transparent dielectric, so that the transparent dielectric film has a flat upper surface, (d) forming a thin film on the transparent dielectric, (e) forming a plurality of transparent pixel electrodes on the inorganic film, and (f) forming a plurality of transparent pixel electrodes on the transparent dielectric film The switching device is such that each switching device is electrically connected to each transparent pixel electrode, and the transparent pixel electrode and the switching device are arranged in a matrix. For example, the thin film may be an inorganic film formed with an internal thickness between 0.03 μm and 0.2 μm.

According to the present invention, the substrate with concave and convex parts as a light diffusion and reflection plate can be manufactured in simple steps, such as mechanically polishing the surface of insulators, such as glass, and processing the polished glass with chemicals, such as hydrogen fluoride, To form a metal film on the surface of the treated glass. In addition, changing the polishing and chemical treatment can control the shape of the unevenness, and therefore it is also possible to control the viewing angle and reflection performance of the liquid crystal display device.

Even if the substrate has uneven portions when it is formed, it is possible to form a thin film transistor on the substrate, for example, spin-coating a layer of polyimide resin to smooth the surface of the substrate.

In addition, according to the above-mentioned invention, it is possible to manufacture an active matrix substrate with only two to three steps of lithography technology. Therefore, the number of photomasks and the number of manufacturing processes can be significantly reduced, thereby ensuring a reduction in manufacturing costs and an increase in manufacturing capacity. Because the errors recorded between the photomask and the substrate can be reduced, the problem of limited design principles can be solved, and a larger size substrate can be ensured.

Description of the preferred embodiment

According to the present invention, a reflective liquid crystal display device has a pair of insulating substrates, such as a glass substrate, which are arranged facing each other with a liquid crystal layer in between. The light emitted through the upper substrate is the light provided on the lower substrate. The diffuser and reflector plate reflects and diffuses to create a display device. Here, the light diffusion and reflection plate is arranged on the surface of the substrate with unevenness, and there is a metal film, such as an aluminum film. A transparent dielectric film has a flat surface, is arranged on a substrate with unevenness, and is made into a switching device, such as a thin film transistor. Therefore, the reflective liquid crystal display device with an active matrix substrate can be manufactured with a simpler structure.

The present invention is also applicable to reflective liquid crystal display devices with passive matrix substrates. In this passive matrix type liquid display device, a light diffusion and reflection plate with concavities and convexities is spin-coated with a transparent dielectric film, and no switching device is provided on the transparent dielectric film. The liquid crystal display device operates independently with the actual voltage change conducted to the liquid crystal. A thick transparent dielectric film is formed by the spin coating method, and the parasitic capacitance and wiring or pixel electrodes between the light diffusion and reflection plates can be reduced.

[First Embodiment]

FIG. 2 shows the active matrix substrate of the reflective liquid crystal display device according to the first embodiment, and FIG. 3 is a cross-sectional view of FIG. 2 taken along line AA.

As shown in Figure 3, the active matrix substrate in this specific embodiment has an insulating substrate 1 with a rough or uneven upper surface, covering the entire insulating substrate 1, and made of aluminum, silver, gold, or copper. The metal film 2, covering the entire metal film 2, is a transparent dielectric film 3 made of polyamide resin series, and has a flat surface. A plurality of transparent pixel electrodes 6 are arranged on the transparent dielectric film 3 and are made of indium tin It is made of oxide (ITO), a thin film transistor (TFT) 20 is provided on the transparent dielectric film 3, and an alignment film (not shown) is provided on the active matrix substrate to handle the alignment of liquid crystal molecules.

As shown in FIG. 2, a plurality of gate bus wires 21 and a plurality of source bus wires 22 are provided on the active matrix substrate. The gate bus wires 21 can be made of chromium, tantalum, molybdenum or aluminum, and are arranged parallel to each other. The source bus line 22 is made of indium oxide material, and is arranged parallel to each other and perpendicular to the gate bus line 21. At each place where the gate bus line 21 and the source bus line 22 intersect, a thin film transistor 20 is provided as a switch device. The part 9 extending from each gate bus line 21 becomes the gate electrode of the thin film transistor 20, and the part 4 extending from each source bus line 22 becomes the source electrode of the thin film transistor 20. As shown in FIG. 3, each drain electrode 5 of the thin film transistor 20 is connected to each transparent pixel electrode 6. The thin film transistor 20 has the following structure. Both the source electrode 4 and the drain electrode 6 are made of a transparent conductive film, such as an indium tin oxide film, and are formed on the transparent dielectric film 3. The drain electrode 5 is connected to the pixel electrode 6. There is an amorphous silicon semiconductor layer 7 on the source and drain electrodes 4 and 5 to connect with the source and drain electrodes 4 and 5. The semiconductor layer 7 is provided with a gate insulating film 8 made of silicon nitride, and a gate electrode 9 made of chromium, tantalum, molybdenum or aluminum is provided on the gate insulating film 8.

The substrate disposed facing the active matrix substrate includes a transparent insulating substrate 13 made of glass. A color filter 12 is formed on the substrate 13. The color filter 12 has a transparent conductive film such as an alignment film (not shown). show).

The manufacturing process of the reflective liquid crystal display device with the above structure is as follows. First, a glass substrate is mechanically made to roughen its surface. For example, surface frosting, frosting is usually used to make a flat glass. However, even if the glass substrate is frosted, the difference between the height of the bottom of the recess and the apex of the protrusion is only about 0.1 micrometers between the apexes of adjacent protrusions. Therefore, in this embodiment, the substrate is polished with garnet powder, and the height difference is between 1 micrometer and 2 micrometers, and the pitch is between 5 micrometers and 15 micrometers. Here, referring to Figure 4, the height between the bottom of the concave portion and the top of the convex portion is represented by height h, and the distance between the tops of adjacent convex portions is represented by length P.

Secondly, the rough glass substrate is immersed in liquid chemicals, such as hydrofluoric acid and buffered hydrogen fluoride. Because the surface of the rough glass substrate is mechanically polished, there are sharp concave and convex parts, which are polished with chemicals to form a metal film later. 2 Cover the glass plate, and make the metal film 2 have consistent light diffusion. The height between the bottom of the concave part and the top of the convex part depends on the special chemical used and/or the length of time the glass plate is immersed in the chemical. In this embodiment, the height difference between 1 μm and 2 μm becomes between 0.4 μm and 1.2 μm after the substrate is immersed in hydrofluoric acid with a concentration of 10% for five minutes.

With the simple steps described above, the glass substrate is designed to have a flattened concave-convex surface, the height difference of the concave-convex part is between 0.4 μm and 1.2 μm, and the pitch is between 5 μm and 15 μm.

A layer of aluminum, silver, gold, copper or an alloy containing these metals is deposited on the glass substrate by the sputtering method to form a highly reflective metal film with a thickness between 0.1 micron and 1 micron. The metal film thus formed serves as a light diffusion and reflection plate 2.

Next, a transparent dielectric 3 made of polyimide series resin is formed on the metal plate 2 by a spin coating method with a thickness between 2 μm and 5 μm, and the rough surface of the glass substrate 1 is made flat. In particular, the viscous liquid pre-polyester is coated on the metal plate 2, and then the surface is spread by a spin coater, so that the pre-polyester has an almost uniform thickness throughout the glass substrate 1. Then, the glass substrate 1 is placed, for example, Harden the pre-polyester in a room with a temperature of 250 degrees for 30 minutes. As a result, the transparent dielectric film 3 has a flat surface.

Then, the transparent conductive film of the material is sprayed on the entire transparent dielectric 3 to form a thickness of 0.01 to 0.3 microns. Then, the conductive film thus formed is made by lithography technology and dry etching to form the source bus line 22, the source electrode 4, the drain electrode 5 and the pixel electrode 6.

After the substrate 1 is treated with phosphine hydrogen plasma, the amorphous silicon layer used to manufacture the semiconductor layer 7 is plasma-enhanced chemical vapor deposition (CVD) on the entire source electrode 4, the transparent dielectric film 3 and the source electrode 5, the thickness is between 0.03 microns and 0.3 microns. The silicon nitride or silicon dioxide film used to make the gate insulating film 8 is formed on the entire amorphous silicon layer by a plasma-enhanced chemical vapor deposition method, and the thickness is between 0.2 μm and 0.6 μm. The metal film used to make the gate electrode 9, such as chromium, tantalum, molybdenum, or aluminum, is formed by spraying on the entire silicon nitride or silicon dioxide film, and the thickness is between 0.1 μm and 0.5 μm.

Then, the metal film is patterned by lithography technology and dry etching to form the gate electrode 9 and the gate bus line 21. Then, the silicon nitride or silicon dioxide film and the amorphous silicon layer are patterned by etching using the light-shielding mask commonly used to make the pattern mask of the gate electrode 9, or the patterned metal film after the light-shielding layer is removed. Thus, a gate insulating film 8 and a semiconductor layer 7 are formed. Therefore, the active matrix substrate is complete.

As described above, the manufacturing of the active matrix substrate according to this embodiment only requires two lithography steps.

On the other hand, for the facing substrates, a color filter 12 is formed on the glass substrate 13 during manufacture, and then a film is formed on the color filter 12 as a transparent common electrode 11 by a sputtering method. The color filter 12 includes an opaque portion and a portion including red, green, and blue portions.

Next, an alignment film is applied to the transparent common electrode 11 of the substrate 13 and the thin film transistor 20 and the pixel electrode of the substrate 1. Then, the substrates 1 and 13 are arranged to face each other, and plastic balls with a diameter of 3 to 8 microns are sandwiched therein, so that the alignment films face each other, and are closely adhered with a sealing resin. Then, the liquid crystal material is injected from a hole pre-set in a certain part of the sealing resin. The liquid crystal material contains two or more dichroic pigments, which are optically refined active materials. In this way, the reflective liquid crystal display device in the host and guest mode can be completed.

The host-guest mode utilizes a phenomenon that when two pigments with dichroic strip molecules are injected into the liquid crystal, the pigments are directed at a large angle according to the liquid crystal molecules. Specifically, the host-guest mode is based on the principle that the pigment molecules stand upright when the incident plate through which the liquid crystal molecules emit light is upright. In this case, the light penetrates the liquid crystal layer, and when the liquid crystal molecules are transverse to the incident plate through which the light emission penetrates, the pigment molecules are transverse. In this case, the light is absorbed by the pigment and cannot be emitted through the liquid crystal layer. The host-guest mode can be applied to optical switch devices.

The host-guest mode no longer needs to use the polarizing plate required by the conventional twisted nematic liquid crystal display device. Therefore, the problem that the polarizing plate can only use one polarizing element can be easily solved, and as a result, the light use efficiency is significantly increased.

In the above-mentioned first embodiment, the rough surface of the substrate 1 has concave and convex portions, and the height difference is defined by h between 0.4 μm and 1.2 μm, and the pitch is defined by p between 5 μm and 15 μm. According to the results of experiments conducted by the inventors, the height difference h is between 0.1 micrometers to 5 micrometers, and p is between 0.5 micrometers and 5 micrometers to obtain uneven portions with the best optical properties.

It should be noted that the insulating substrate 1 can be roughened by sandblasting, and a large number of fine particles are sprayed onto the surface of the substrate to form the required unevenness, instead of the sandblasting method.

In addition, the transparent dielectric film 3 can be made of polyester material, such as polyamide, polyimide, polyester, polypropylene resin, epoxy resin, and polysilazane, or include a large number of these materials and polyamide resin series The raw materials.

[Second Embodiment]

FIG. 5 illustrates a reflective liquid crystal display device according to the second embodiment. The second embodiment has almost the same structure as the first embodiment. The only difference from the first embodiment is that the metal film or the light diffusion and reflection film 2 is provided under the transparent pixel electrode 6, and the metal film 2 is located at the pixel electrode. All outside the area below 6 has been removed.

If the transparent pixel electrode 6 is formed under the thin film transistor 20, as in the first embodiment, the light reflected on the light diffusion and reflection plate 2 will often enter the semiconductor layer, which is indicated by a dotted line B. When light enters the semiconductor layer 6, the external resistance of the semiconductor is reduced. Of course, the leakage current increases and the display quality deteriorates. Therefore, in the second embodiment, the portion of the light diffusion and reflection plate 2 located on the semiconductor layer 7 is cut off, so as to significantly reduce the light entering from the semiconductor layer 7. That is, the light reflected by the light diffusion and reflection plate 2 will not face the semiconductor layer 7, as indicated by the solid line A.

According to the reflective liquid crystal display device of the second embodiment, the manufacturing process is as follows. First, a glass substrate 1 similar to the first embodiment is formed into rough concavities and convexities, and then a metal film is deposited on the rough substrate 1 by a sputtering method. The unnecessary part of the metal film is removed by photolithography and etching so that the light diffusion and reflection plate 2 is disposed under the pixel electrode 6. The subsequent steps are the same as in the first embodiment. Therefore, the reflective liquid crystal display device according to the second embodiment can be completed.

The manufacturing of the active matrix substrate according to the second embodiment only needs to perform the lithography process three times.

[Third Embodiment]

The reflective liquid crystal display device according to the third embodiment is almost the same as the first embodiment, except that an inorganic film 45 is used on the transparent dielectric film 3. A pixel electrode 6 and a thin film transistor 20 are provided on the inorganic film 45, similar to the first embodiment.

According to the reflective liquid crystal display device of the first embodiment, the transparent dielectric 3 and the semiconductor layer 7 are in direct contact. Therefore, depending on the material of the transparent dielectric film 3, a problem may arise, that is, the level of the interface between the dielectric film 3 and the semiconductor layer 7 may increase, and the semiconductor layer 7 may absorb the inside of the transparent dielectric film 3. Impurities, which weaken the performance of thin film transistors. An inorganic film 45 is provided between the transparent dielectric film 3 and the semiconductor layer 7 to avoid direct contact between the semiconductor layer 7 and the transparent dielectric film 3.

The inorganic film 45 can be made of a material used in the production site of a semiconductor device. For example, the inorganic film 45 can be made of silicon dioxide and silicon nitride. In this embodiment, the inorganic film 45 is designed to have a thickness between 0.03 μm and 0.2 μm.

[Fourth Embodiment]

The present invention is applicable to passive matrix type liquid crystal display devices. The fourth embodiment relates to a passive matrix type liquid crystal display device adopting the present invention. FIG. 7 illustrates a liquid crystal display device according to the fourth embodiment.

The passive matrix type liquid crystal display device displays according to the effective voltage conducted to the liquid crystal, and does not need to use a switching device such as a thin film transistor. As shown in FIG. 7, the reflective liquid crystal display device according to the fourth embodiment does not contain thin film transistors.

As shown in Figure 7, the passive matrix substrate in this embodiment includes an insulating substrate 1 with a rough or uneven upper surface, covering the entire insulating substrate 1, and made of aluminum, silver, gold, or copper. The metal film 2, covering the entire metal film 2, is a transparent dielectric film 3 made of a polyamide resin series, and has a flat surface. A plurality of transparent pixel electrodes 6 are arranged on the transparent dielectric film 3 and are made of indium tin Made of oxide (), a thin film transistor (thin film transistor) 20 is provided on the transparent dielectric film 3, and an alignment film (not shown) is provided on the active matrix substrate to handle the orientation of liquid crystal molecules.

The substrate disposed opposite to the active matrix substrate includes a transparent insulating substrate 13 made of glass. A color filter 12 is formed on the substrate 13. The color filter 12 has a plurality of column electrodes 47, extending in the same direction as the row electrodes 46. In a vertical direction, there is an alignment film 47 on the column electrode 47.

The row electrodes 46 and the column electrodes 47 work together to control the voltage conducted to the liquid crystal layer 10. Because the row electrodes 46 and the column electrodes 47 not only function as wiring, but also function as pixel electrodes, they are made of indium tin oxide, which is a transparent conductive material.

Since the passive matrix liquid crystal display device displays a liquid crystal by changing the effective voltage, if too much parasitic capacitance is coupled to the row electrodes 46, the driving pulses transmitted to the column electrodes 47 will be distorted, and the display quality will be significantly reduced as a result. Therefore, the transparent dielectric film 3 of this embodiment is formed into a thicker layer by the spin coating method to reduce the capacitance between the row electrode 46 and the metal film 2. In this embodiment, the transparent dielectric film 3 is designed to have a thickness of 5 microns. The transparent dielectric film 3 may be thicker. Since the transparent dielectric film 3 has a flat upper surface, there is no need to worry that the row electrodes 46 on the transparent dielectric film 3 will be damaged by the irregularities on the rough surface of the substrate 1.

Although the present invention has been described in conjunction with the preferred embodiments, according to the present invention, the concave-convex parts can be formed in simple steps to obtain a light diffusion and reflection plate with appropriate reflection characteristics. In addition, by forming a transparent dielectric film on the rough surface of the substrate and having a flat upper surface, manufacturing the active matrix substrate may only need to perform two or three lithography steps, which is less than the traditional method for manufacturing the active matrix substrate.

Therefore, the present invention provides a reflective liquid crystal display device with high display quality and more reliability with lower cost and higher productivity. In addition, the design principle of thin film transistors is no longer limited, and the reflective liquid crystal display device produced can be larger in size and higher in density.

Furthermore, the present invention provides a reflective liquid crystal display device with higher light efficiency. Because the reflective plate is arranged in the active matrix substrate, it is no longer necessary to use the polarizing plate in the host-guest mode.

The present invention is also applicable to passive matrix type liquid crystal display devices.

<p>12~color filter; 10~liquid crystal;</p><p>13~substrate; 11~common electrode;</p><p>43~pixel electrode; 42~overlapping insulating layer;</p><p>8~gate insulating film; 1, 41~insulating substrate;</p><p>20~Thin film transistor; 22~Source bus line;</p><p>4~Source electrode; 7~Semiconductor layer;</p><p>5~Drain electrode; 6~Pixel electrode;</p><p>9~gate electrode; 21~gate bus line;</p><p>45~Inorganic membrane; 2~Metal membrane;</p><p>47~Column electrode; 46~Row electrode.</p>

Figure 1 is a cross-sectional view of a conventional reflective liquid crystal display device.

FIG. 2 is a partial plan view of an active matrix substrate used in a reflective liquid crystal display device according to the first embodiment of the present invention.

Figure 3 is a cross-sectional view of Figure 2 taken along line AA.

FIG. 4 is an enlarged cross-sectional view of the reflective liquid crystal display device substrate according to the first embodiment of the present invention.

Figure 5 is a plan view of a reflective liquid crystal display device according to a second embodiment of the present invention.

Figure 6 is a plan view of a reflective liquid crystal display device according to a third embodiment of the present invention.

FIG. 7 is a partial plan view of an active matrix substrate used in a reflective liquid crystal display device according to a fourth embodiment of the present invention.