JP2004258350A - Active matrix substrate and method for manufacturing the same, liquid crystal device and electronic appliance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To certainly prevent an optical leakage current of a TFT (thin film transistor) in an active matrix substrate applied to a reflective or transflective liquid crystal device. <P>SOLUTION: A light shielding projecting and recessing body 13 composed of a single layer is disposed so as to cover scanning lines, signal lines 34 and a TFT 30 and a reflection electrode 14 is formed on the projecting and recessing body 13. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an active matrix substrate having a diffuse reflection electrode, a liquid crystal device and an electronic device provided with the active matrix substrate.
[0002]
[Prior art]
2. Description of the Related Art With the development of portable information terminal devices, liquid crystal devices that are small, lightweight, and highly portable have been widely used. Above all, the importance of the reflection type liquid crystal device has been increasing in recent years because a backlight is not required, so that power consumption can be greatly reduced and further reduction in thickness and weight can be achieved. In such a reflective liquid crystal device, in order to realize a wide viewing angle display, a diffuse reflector is provided on the back side of the liquid crystal layer, and display is performed by diffusing and reflecting external light incident from the display surface side. Has become.
[0003]
Further, in such a display device, high luminance and high definition are required, and while high definition is achieved by active matrix driving, a resin formed so as to cover various wirings such as scanning lines and signal lines. A reflective electrode (pixel electrode) formed on an insulating film to increase the aperture ratio has been put to practical use. In the case of a structure in which the reflective electrode is placed on the insulating film in this manner, an electrical short circuit may occur between the scanning line or signal line disposed in the lower layer of the insulating film and the reflective electrode disposed in the upper layer. Therefore, the reflective electrode can be formed with a large area so as to overlap with these wirings. Thereby, a bright display with a high aperture ratio can be achieved. In addition, by making the insulating film an uneven body, it becomes possible to provide a diffused reflection function to the reflective electrode formed thereon.
[0004]
By the way, in an active matrix type display device provided with a thin film transistor (hereinafter abbreviated as TFT), light leak current is generated by external light incident on the TFT from the display surface side, thereby deteriorating display quality. It is known. For this reason, a black mask as a light shielding means is usually formed on the substrate on the opposite side of the active matrix substrate. However, in this case, in order to completely block external light from entering the TFT, high alignment accuracy is required when the substrates are bonded to each other. Further, it is necessary to increase the line width of the black mask in order to shield light obliquely incident on the TFT, and there is a problem that the aperture ratio is reduced.
[0005]
In order to solve such a problem, a structure has been proposed in which an uneven body for imparting an uneven shape to a reflective electrode has a light shielding function (see Patent Document 1).
[0006]
As shown in FIG. 7, the uneven body 1000 includes a first resin film 1001 provided in a projecting manner on a circuit board 2000 on which a TFT is formed, and a substrate formed of the first resin film 1001. A second resin portion 1002 provided to make the upper unevenness a smooth curved uneven surface. The uneven body 1000 is formed by, for example, patterning a photosensitive resin applied on the circuit board 2000 to form a projecting resin film 1001, and then forming a second resin film 1002 on the resin film 1001. , A so-called two-layer coating method. At this time, by making the second resin film 1002 a black resin, the uneven body 1000 can have a light shielding function.
[0007]
In this manner, by covering the circuit board 2000 with the second resin film 1002 having a light-shielding property, generation of a light leak current can be suppressed without forming a black mask on the counter substrate side. In addition, when the second resin film 1002 is formed by application, the space between the adjacent protruding resin films 1001 is filled with the resin film 1002, so that smooth curved irregularities are formed on the substrate surface, and the upper surface is formed thereon. The diffused reflection function can be provided to the formed reflection electrode.
[0008]
[Patent Document 1]
JP-A-6-342153
[Problems to be solved by the invention]
However, in the above-described structure, the thickness P of the resin film 1002 formed on the top of the resin film 1001 is smaller than the thickness Q of the resin film 1002 formed between the adjacent resin films 1001 (that is, the thickness P). Since the thickness of the resin film 1002 varies in the substrate surface), the light blocking ability becomes uneven.
In the case where the uneven body 1000 is formed by the above method, if the resin film 1002 is too thick, the unevenness formed by the resin film 1001 is completely flattened. It needs to be thinner. As a result, there is a possibility that the light-shielding ability is insufficient particularly near the top of the resin film 1001.
[0010]
The present invention has been made in view of the above-described problems, and has as its object to provide a liquid crystal device capable of reliably preventing a light leakage current of a TFT with a high light-shielding ability.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, an active matrix substrate of the present invention includes a plurality of scanning lines and a plurality of signal lines provided to cross each other, and a thin film transistor conductively connected to the scanning lines and the signal lines. A reflective electrode conductively connected to the thin film transistor, and a light-shielding irregular body formed of a single layer interposed between the thin film transistor and the reflective electrode to form fine irregularities on the reflective electrode. It is characterized by having.
[0012]
According to this configuration, since the uneven body for forming the unevenness on the reflective electrode is formed in a single layer, the unevenness is formed by two-layer coating and one layer is a light-shielding layer. In comparison, the light-shielding ability is high, and light-shielding unevenness hardly occurs.
In the above structure, the thickness of the uneven body provided on the thin film transistor is preferably 2 μm or more and 5 μm or less. When the layer thickness of the uneven body is less than 2 μm, a sufficient light shielding function cannot be obtained. When the layer thickness exceeds 5 μm, a contact hole for making contact between the pixel electrode and the drain electrode becomes deep, and the pixel electrode becomes There is a risk of disconnection.
[0013]
In addition, it is preferable that the concave-convex body is configured such that no concave portion is provided in a region where the reflective electrode is not formed. The concave or convex portion of the uneven body is for imparting a diffused reflection function by imparting an uneven shape to the reflective electrode formed thereon, and in the region where the reflective electrode is not formed, the unevenness is originally unnecessary. It is. Moreover, when a concave portion is formed in such a region, the layer thickness of the concave-convex body becomes thin, and the light-shielding function may be impaired. For this reason, by not providing a concave portion at least in the above-described region, the light-shielding ability can be enhanced, and the occurrence of light leakage current can be more effectively prevented.
[0014]
The reflective electrode and the uneven body may be provided with openings communicating with each other, whereby an active matrix substrate applicable to a transflective display device is obtained. In this case, the area where the opening is provided becomes a transmissive display area, and the area where the reflective electrode is formed becomes a reflective display area.
In addition, the above-mentioned uneven body can be specifically configured as a black resin containing a black pigment (or dye) such as carbon.
[0015]
Further, the method for manufacturing an active matrix substrate of the present invention includes a plurality of scanning lines and a plurality of signal lines provided crossing each other on the substrate, and a thin film transistor conductively connected to the scanning lines and the signal lines. Forming a black photosensitive resin film on the substrate so as to cover the scanning lines, signal lines, and thin film transistors; and performing half exposure and development processing on the photosensitive resin film. Accordingly, the method includes a step of forming fine concave portions on the surface of the photosensitive resin film and a step of pattern-forming a reflective electrode on the photosensitive resin film.
[0016]
As described above, in the conventional two-layer coating method, the thickness of the second resin film (black resin) formed in the vicinity of the top of the first resin film having a protrusion shape is such that the thickness of the first resin film is Becomes extremely thin as compared with the thickness of the second resin film formed in the region. On the other hand, in the present manufacturing method, since a single-layer uneven body having an uneven surface can be formed by performing half exposure on the black photosensitive resin, the resin film thickness is extremely thin in the substrate surface. There is no area. Therefore, high light-shielding ability can be obtained over the entire surface of the substrate without causing light-shielding unevenness.
At this time, it is preferable that a concave portion is not formed in a region where the reflective electrode is not formed. This makes it possible to increase the thickness of the photosensitive resin in the above-mentioned region, thereby enhancing the light-shielding ability.
[0017]
Further, a liquid crystal device according to the present invention includes the above-described active matrix substrate. According to another aspect of the invention, an electronic apparatus includes the above-described liquid crystal device. As a result, the occurrence of light leakage current due to external light can be sufficiently prevented, and high quality display can be achieved by reliable switching.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
[First Embodiment]
Hereinafter, the liquid crystal device according to the first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a plan view of a main part showing a pixel structure of the liquid crystal device of the present embodiment, FIG. 2 is a cross-sectional view showing a main part structure of the liquid crystal device of the present embodiment, and FIG. 2 (a) and FIG. FIG. 1 is a diagram showing an AA ′ section and a BB section of FIG. 1, and FIG. 3 is a process chart for explaining a method of manufacturing an active matrix substrate. In all of the following drawings, the thickness of each component, the ratio of dimensions, and the like are appropriately changed in order to make the drawings easy to see.
[0019]
As shown in FIGS. 1 and 2, the liquid crystal device according to the present embodiment includes an active matrix substrate 10, a counter substrate 20, and a liquid crystal layer 40 as a light modulation layer held between the substrates 10, 20. ing.
[0020]
On the active matrix substrate 10, a plurality of scanning lines 33 and signal lines 34 are provided on a substrate body 10A made of glass, plastic, or the like in the X direction and the Y direction, respectively, so as to be electrically insulated. , A TFT (thin film transistor) 30 is provided corresponding to the intersection of the signal lines 34. The source of the TFT 30 is conductively connected to the signal line 34 via the contact hole 12a, the drain is conductively connected to the intermediate layer 35 via the contact hole 12b, and the intermediate layer 35 is connected to the contact hole 13a. Through a light-reflective pixel electrode (reflective electrode) 14 (outlined by a dotted line portion 14a). Hereinafter, the region where the pixel electrode 14 is formed, the region where the TFT 30 is formed, and the region where the scanning line 33 and the signal line 34 are formed on the substrate 10 are referred to as a pixel region, an element region, and a wiring region, respectively.
[0021]
The TFT 30 is provided on the underlying protective film 11 of the substrate 10A, and has a semiconductor film 31, a gate insulating film 32, and a gate electrode 33a stacked in this order from the lower layer side. A region of the semiconductor film 31 facing the gate electrode functions as a channel portion, and positions opposed to each other across the channel portion are a source portion and a drain portion. The drain portion of the semiconductor film 31 may be extended to form an electrode portion for a storage capacitor. The gate electrode 33a is formed integrally with the scanning line 33 provided in the X direction.
[0022]
The inorganic insulating film 12 is provided on the substrate 10A so as to cover the TFT 30 and the scanning line 33, and the signal line 34 and the intermediate layer 35 are provided on the insulating film 12. The insulating film 12 is provided with a contact hole 12a leading to the source portion of the TFT 30 and a contact hole 13a leading to the drain portion. The signal line 34 and the intermediate layer 35 are respectively formed through these contact holes 12a, 13a. It is conductively connected to the source part and the drain part.
[0023]
Further, an uneven body 13 made of an organic insulating film is provided on the substrate 10A so as to cover the insulating film 12, the signal line 33, and the intermediate layer 35. On the uneven body 13, a high reflection material such as Al or Ag is provided. A pixel electrode 14 made of a metal film having a high efficiency is provided. A plurality of the pixel electrodes 14 are formed in a matrix on the organic insulating layer 13, and are provided one by one corresponding to a region defined by the scanning lines 33 and the signal lines 34. The pixel electrode 120 is disposed so that its edge side overlaps the scanning line 33 and the signal line 34 in a plane, and substantially all the region of the substrate 10 including the wiring region is used as the pixel region. I have. Note that the pixel electrode 14 is conductively connected to the intermediate layer 35 via a contact hole 13a provided in the uneven body 13.
[0024]
Meanwhile, the above-mentioned uneven body 13 contains a black pigment (or dye) such as carbon, and functions as a light-shielding layer that prevents external light from being incident on the TFT 30 from between the adjacent pixel electrodes 14. have. The uneven body 13 has a smooth curved uneven surface formed on the surface. By providing a fine uneven shape on the surface of the pixel electrode 14 provided thereon, the pixel electrode 14 has a diffuse reflection function. Have.
[0025]
Such uneven body 13 is manufactured by the following method.
First, as shown in FIG. 3A, a positive photosensitive resin 101 containing a black pigment (or dye) such as carbon is formed on a substrate 10B on which an inorganic insulating film 12 covering the TFT 30 is formed. . At this time, the thickness of the resin film 101 is set to 2 μm or more and 5 μm or less, more preferably 3 μm or more and 4 μm or less, in order to obtain a sufficient light shielding ability.
[0026]
Next, as shown in FIG. 3B, the photosensitive resin 101 is subjected to half exposure, and a large number of fine concave portions g are formed on the surface of the resin 101 by development (see FIG. 3C). ). At this time, the viewing angle characteristics of the reflective display can be controlled by arbitrarily setting the place where the exposure is performed, the exposure area, and the exposure intensity. The above-described exposure is performed only on the region where the pixel electrode 14 is formed. As shown in FIG. 2A, not only the region where the TFT 30 is formed (element region) but also as shown in FIG. Also, the recess g is not formed in the region between the pixel electrodes corresponding to the wiring region. By preventing the uneven body 13 in a region (non-pixel region) between the adjacent pixel electrodes 14 from being thinned, the light shielding ability can be further enhanced. Note that the above-mentioned non-pixel region where the pixel electrode 14 is not formed is a region which does not contribute to display in the first place, and therefore the display is not affected by the presence or absence of the concave portion g.
Note that a negative photosensitive resin can be used as the photosensitive resin 101. In this case, it is necessary to change the exposure area and the non-exposure area in FIG.
[0027]
Next, as shown in FIG. 3D, the photosensitive resin 101 is subjected to a heat treatment to loosen the corners of the irregularities, thereby forming irregularities formed of a single layer having a smooth curved irregular surface. A body 13 is formed. Then, a metal reflective film is formed on the uneven body 13 thus formed, and is patterned into a predetermined shape, so that a diffuse reflective electrode (pixel electrode) having an uneven surface conforming to the outer shape of the uneven body 13 is formed. ) 14 is formed.
Further, the substrate configured as described above is further provided with an alignment film 15 made of polyimide or the like so as to cover the pixel electrode 14 and the uneven body 13.
[0028]
On the other hand, as shown in FIG. 2, a transparent counter electrode (common electrode) 24 such as ITO or IZO is provided on the counter substrate 20 on a substrate body 20A made of a light-transmitting substrate such as glass or plastic. Further, an alignment film 25 made of polyimide or the like is provided on the counter electrode 24.
The substrates 10 and 20 configured as described above are held in a state where they are fixedly separated from each other by a spacer (not shown), and a sealing material (not shown) applied in a frame shape around the substrate. Glued by Then, a liquid crystal is sealed in a space sealed by the substrates 10 and 20 and the sealing material, and a liquid crystal layer (light modulation layer) 40 is formed.
[0029]
As described above, in the present embodiment, the black photosensitive resin is subjected to half-exposure to form the light-blocking uneven body 13 formed of a single layer. Therefore, the uneven body is formed by two-layer coating. Compared with the conventional structure in which the layer (the second resin film 1002 in FIG. 6) is a light-shielding layer, there is no area in the substrate surface where the resin film thickness becomes extremely thin. For this reason, a high light-shielding ability can be obtained over the entire surface of the substrate without causing light-shielding unevenness, and it is possible to reliably prevent a display defect due to a light leak current.
In addition, since the light-blocking unevenness is also formed on the wiring between the pixels, light reflected from the wiring can be suppressed, and thus, a decrease in contrast can be suppressed.
[0030]
[Second embodiment]
Next, a liquid crystal device according to a second embodiment of the present invention will be described with reference to FIGS. In this embodiment, the same members as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.
As shown in FIG. 4, the liquid crystal device of the present embodiment is configured as a so-called transflective liquid crystal device having a transmissive display region T and a reflective display region R in one pixel.
[0031]
That is, as shown in FIG. 5, the active matrix substrate 10 ′ of the present liquid crystal device includes an uneven body 13 and a light-reflective first pixel electrode (reflective electrode) 141 provided on the uneven body 13. An opening 13b communicating with each other is provided, a region where the reflective electrode 141 is formed becomes a reflective display region R, and a region where the opening 13b is formed becomes a transmissive display region T. Then, in order to enable transmissive display, a transparent second pixel electrode 142 made of ITO or the like is provided so as to cover the reflective electrode 141 and the opening 13b, and further, a pixel electrode 14 '(first pixel electrode The alignment film 15 is provided so as to cover the first pixel electrode 141 and the second pixel electrode 142).
The rest is the same as the first embodiment.
Therefore, in the present embodiment, similarly to the first embodiment, it is possible to reliably prevent the occurrence of light leakage current due to external light.
[0032]
[Electronics]
Next, a specific example of an electronic apparatus including the liquid crystal device according to the above embodiment of the present invention will be described.
FIG. 6 is a perspective view showing an example of a mobile phone. In FIG. 6, reference numeral 500 denotes a mobile phone main body, and reference numeral 501 denotes a display unit using the liquid crystal display device.
Since the electronic device illustrated in FIG. 6 includes the display portion using the liquid crystal device of the above embodiment, generation of light leakage current due to external light can be sufficiently prevented, and high-quality display can be performed by reliable switching. It becomes.
[0033]
Note that the present invention is not limited to the above-described embodiment, and can be implemented with various modifications without departing from the spirit of the present invention.
For example, the structure on the lower layer side of the concavo-convex body 13 shown in each of the above embodiments is merely an example, and the present invention can be applied to various active matrix substrates having other structures. Further, in the above embodiment, the concave portion g of the concave-convex body 13 is formed by using a photo process. However, the concave portion g can be formed by a mechanical method such as embossing.
Further, by providing, for example, R, G, and B color filter layers on the opposing substrate 20, color display becomes possible.
[Brief description of the drawings]
FIG. 1 is a main part plan view of a liquid crystal device according to a first embodiment of the present invention.
FIG. 2 is a sectional view of a main part of the same liquid crystal device.
FIG. 3 is a manufacturing process diagram of the active matrix substrate.
FIG. 4 is a plan view of a main part of a liquid crystal device according to a second embodiment of the present invention.
FIG. 5 is a sectional view of a principal part of the liquid crystal device.
FIG. 6 is a perspective view illustrating an example of an electronic apparatus according to the invention.
FIG. 7 is a view showing a conventional uneven body.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Active matrix substrate, 13 ... Concavo-convex body, 13b ... Opening, 14, 141 ... Pixel electrode (reflection electrode), 30 ... Thin film transistor, 33 ... Scan line, 34 ... Signal line, 500 ... Electronic equipment

Claims (9)

A plurality of scanning lines and a plurality of signal lines provided to cross each other,
A thin film transistor conductively connected to the scanning line and the signal line,
A light-shielding concavo-convex body made of a single layer provided so as to cover the scanning lines, the signal lines, and the thin film transistors;
An active matrix substrate, comprising: a reflective electrode provided on the uneven body. 2. The active matrix substrate according to claim 1, wherein the thickness of the uneven body provided on the thin film transistor is 2 μm or more and 5 μm or less. The active matrix substrate according to claim 1, wherein the uneven body has no concave portion in a region where the reflective electrode is not formed. The active matrix substrate according to claim 1, wherein an opening communicating with each other is provided in the reflection electrode and the uneven body. The active matrix substrate according to claim 1, wherein the uneven body is made of a black resin. Forming a plurality of scanning lines and a plurality of signal lines provided crossing each other on a substrate, and a thin film transistor electrically connected to the scanning lines and the signal lines;
Forming a black photosensitive resin film on the substrate so as to cover the scanning lines, the signal lines, and the thin film transistors;
Performing a half-exposure and development process on the photosensitive resin film to form fine recesses on the surface of the photosensitive resin film;
Forming a reflective electrode on the photosensitive resin film by a patterning method. 7. The method for manufacturing an active matrix substrate according to claim 6, wherein the concave portion is not formed in a region where the reflective electrode is not formed. A liquid crystal device comprising the active matrix substrate according to claim 1. An electronic apparatus comprising the liquid crystal device according to claim 8.

Images