JP2008009397A - Semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device which can materialize a wide viewing angle and high image display with high contrast and can materialize high display quality, in particular, under external light. <P>SOLUTION: The liquid crystal display device has such configuration that one sheet of polarizing element having dichroism is held between a pair of substrates, wherein a light interference layer is disposed between a color filter and a glass substrate, thereby difference in refractive index is lessened and light reflection can be reduced. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a semiconductor device having a circuit formed of a thin film transistor (hereinafter referred to as TFT) and a manufacturing method thereof. For example, the present invention relates to an electronic apparatus in which an electro-optical device typified by a liquid crystal display panel is mounted as a component.

Note that in this specification, a semiconductor device refers to all devices that can function by utilizing semiconductor characteristics, and an electro-optical device, a semiconductor circuit, and an electronic device are all semiconductor devices.

In recent years, a technique for forming a thin film transistor (TFT) using a semiconductor thin film (having a thickness of about several to several hundred nm) formed on a substrate having an insulating surface has attracted attention. Thin film transistors are widely applied to electronic devices such as ICs and electro-optical devices, and development of switching devices for image display devices is urgently required.

A liquid crystal display device is known as an image display device. Active matrix liquid crystal display devices are often used because high-definition images can be obtained compared to passive liquid crystal display devices. In an active matrix liquid crystal display device, a display pattern is formed on a screen by driving pixel electrodes arranged in a matrix. Specifically, by applying a voltage between the selected pixel electrode and the counter electrode corresponding to the pixel electrode, optical modulation of the liquid crystal layer disposed between the pixel electrode and the counter electrode is performed. The optical modulation is recognized by the observer as a display pattern.

In a general transmissive liquid crystal display device, a liquid crystal layer is disposed between a pair of substrates (a first substrate and a second substrate), and a liquid crystal is formed on the first substrate (a substrate on which a pixel electrode is formed). The first polarizing element is disposed on the outer surface side not adjacent to the layer, and the second polarizing element is disposed on the outer surface side not adjacent to the liquid crystal layer in the second substrate (counter substrate).

When a color filter is used for full color display, the color filter is generally arranged on a surface different from the surface of the substrate (opposing substrate) on which the polarizing element is disposed. That is, it is common to arrange a color filter between the counter substrate and the liquid crystal layer.

Patent Document 1 discloses a technique for continuously forming a color filter using a roller. Further, in Patent Document 1, an optical thin film having a color filter function, an optical thin film having a fluorescence function, an optical thin film having an antireflection function, an optical thin film having a phase compensation function, and an optical having a light shielding function are provided on the front or back surface of the film. It is disclosed that at least two films selected from a thin film, a transparent thin film having conductivity, and a transparent thin film having an adhesive function are attached.
JP-A-8-234018

In recent years, liquid crystal display devices are required to improve display quality as well as to increase the resolution of displayed images. In the liquid crystal display device, when an observer views the display from a direction perpendicular to the substrate surface, the arrangement of the pixel electrodes and the position of the color filter (one colored layer corresponding to one pixel) are almost the same. The display quality as designed by the liquid crystal display device can be obtained. However, when an observer views the display from an oblique direction with respect to the substrate surface, an apparent position shift occurs due to parallax. In addition, light leakage occurs due to the parallax, and the display contrast decreases. Therefore, a viewing angle characteristic occurs in which display quality deteriorates when an observer views the display from an oblique direction with respect to the substrate surface. In particular, when the pixel size is made finer than the substrate thickness in order to increase the definition of the display image, the parallax becomes significant, and the viewing angle at which acceptable display characteristics can be ensured is limited.

In addition, the visibility of the liquid crystal display device depends on the brightness of the ambient light. Especially in portable liquid crystal display devices where the ambient light changes from daylight to daylight and night liquid crystal display devices, the transmissive or transflective type with a backlight is used to maintain a constant display visibility. Such a liquid crystal display device is convenient. However, in order to make the liquid crystal display device easy to see under daylight, if a strong light source is used as the backlight, light leakage due to parallax increases, so it is difficult to maintain the display contrast. is there.

The present invention provides a liquid crystal display device capable of realizing a high image quality display with a wide viewing angle and high contrast. In particular, a liquid crystal display device capable of realizing high display quality under external light is provided.

In order to solve the above-described problem, of the two polarizing elements, a first polarizing element having dichroism is disposed between a pair of substrates (a first substrate and a second substrate). The first polarizing element having chromaticity and the color filter are arranged as close as possible. An optical interference layer is disposed between the color filter and the first substrate. In addition, a transistor and a pixel electrode connected to the transistor are formed over the second substrate. In addition, the color filter and the pixel electrode are arranged as close as possible to ensure a wide viewing angle.

The second polarizing element having dichroism is attached to the second substrate in a crossed Nicol arrangement with the first polarizing element having dichroism. Between the first polarizing element having dichroism and the second polarizing element having dichroism, there is a second substrate and a liquid crystal layer, but no color filter is present. This is because the color filter contains pigment particles that cause light to scatter, and therefore, when placed between a pair of polarizing elements having dichroism, the contrast is lowered due to depolarization. Further, for the same reason, the fluorescent layer is not disposed between a pair of polarizing elements having dichroism. In addition, if the color filter and the liquid crystal layer are brought close to each other, bubbles may be generated from the color filter, or impurities from the color filter may contaminate the liquid crystal layer.

Some dichroic polarizing elements have a PVA (polyvinyl alcohol) film in which a dichroic dye is adsorbed and oriented between two protective films. TAC (triacetyl cellulose) or the like can be used as the protective film, and dichroic dyes include iodine and dichroic organic dyes. In addition, there are a dichroic polarizing element using a disk-shaped water-soluble lyotropic liquid crystal dye, and an inorganic polarizing element using aluminum or the like.

Further, the color filter is provided in the vicinity of the first polarizing element having dichroism, and the distance from the pixel electrode is made as close as possible. Therefore, the color filter is disposed between the color filter and the first polarizing element having dichroism. An optical sheet such as a light scattering layer or a fluorescent layer is not provided.

Note that the fluorescent layer is not used because it shines not only in the backlight but also in the outside light and causes a decrease in contrast under the outside light. In the present invention, a light interference layer is provided between the color filter and the first substrate in order to improve the contrast even under external light. The color filter includes a black matrix and a colored layer, and external light is reflected by a difference in refractive index between the black matrix and the first substrate. In particular, the light interference layer is effective when a chromium film is used as a black matrix. Even if the black matrix is a black resin, there is a difference in the refractive index with the first substrate, and the colored layer also has a difference in the refractive index with the first substrate, so that the external light is slightly reflected. For example, the refractive index of the glass substrate is about 1.5, and the colored layer has an average of about 1.6 for each color, but there are also about 1.8 for some materials. In addition, by providing a light interference layer between the color filter and the first substrate, the difference in refractive index can be relaxed and light reflection can be further reduced.

The light interference layer may be a single layer or a multilayer as long as light reflection caused by the black matrix or the colored layer can be prevented, and specifically, an anti-reflection (antireflection) film is used. A dielectric multilayer film can be used as the optical interference layer. The dielectric multilayer film has a structure in which a low refractive index thin film and a high refractive index thin film are laminated.

The structure of the invention disclosed in this specification includes a first substrate in which a light interference layer, a plurality of colored layers, and a first polarizing element having dichroism are sequentially stacked over an insulating surface, and a pixel A second substrate having an electrode and a thin film transistor formed on one surface; a liquid crystal layer between the first substrate and the second substrate; and a second substrate having dichroism on the other surface of the second substrate. A polarizing element.

In the structure of the semiconductor device, a first alignment film is provided between the pixel electrode and the liquid crystal layer. Further, the semiconductor device includes a second alignment film between the first polarizing element having dichroism and the liquid crystal layer. The semiconductor device includes a counter electrode between the first polarizing element having dichroism and the liquid crystal layer.

In the case of an IPS (In Plane Switching) liquid crystal display device, a light interference layer, a plurality of colored layers, and a dichroic first polarizing element are sequentially stacked on an insulating surface. 1 substrate, a second substrate having a pixel electrode, a common electrode, and a thin film transistor formed on one surface, a liquid crystal layer between the first substrate and the second substrate, and the other of the second substrate And a second polarizing element having dichroism on the surface.

In each structure of the semiconductor device, an adhesive layer having a light-transmitting property is provided between the first polarizing element having dichroism and the colored layer for fixing.

In each structure of the semiconductor device, a light shielding layer is provided between different colored layers among the plurality of colored layers. This light shielding layer has a difference in refractive index with the first substrate, and the optical interference layer relaxes the difference in refractive index.

Further, in realizing each of the above-described configurations, since a dichroic polarizing element is disposed between a pair of substrates, it is necessary to devise a method for dividing the substrate during mass production. In the conventional dividing method, after a pair of substrates are bonded together, one or both substrate surfaces are scribed with a diamond cutter or the like and then divided by applying pressure. In the conventional dividing method, it is difficult to cut a polarizing element having dichroism in addition to a pair of substrates. Therefore, the pair of substrates and the dichroic polarizing element are cut together with a dicer apparatus or with laser light.

In addition, since the polarizing element having dichroism has low heat resistance, it is preferable that the counter electrode is formed under film forming conditions that do not damage the polarizing element having dichroism. When the counter electrode is etched, it is preferable that the counter electrode be selectively etched under etching conditions that do not damage the dichroic polarizing element. However, when the liquid crystal driving method is the IPS method, the counter electrode and the pixel electrode are formed on the same substrate, and the above-described problem does not occur, which is preferable.

These means described above are not merely design matters, but the arrangement position of the color filter and the arrangement position of the polarizing element having the dichroism are appropriately selected, and a display device using the combination is produced to display an image. This is a matter that was invented after the inventors' deep examination.

According to the present invention, it is possible to realize a liquid crystal display device capable of high-quality display with a wide viewing angle and high contrast. In particular, high contrast can be realized under external light.

In addition, a polarizing element having a dichroism and a color filter are arranged inside the pair of glass substrates, and one of the pair of glass substrates can expose the glass substrate surface. When the glass substrate surface is exposed, a protective film that prevents scratches, an anti-reflection film that prevents external light from entering, an anti-static film that prevents dust from sticking, and an anti-glare (anti-glare) film are applied to the glass substrate surface. It becomes easy to attach. Note that another polarizing element having dichroism is attached to the other glass substrate that is not exposed.

Further, the exposed glass substrate can be thinned by polishing. In general, it is difficult to apply an optical film to a glass substrate that has been polished and thinned, because pressure is applied during the attaching operation. In the present invention, an optical film necessary between a pair of substrates is required before polishing. Since one polarizing element having dichroism is provided, it is unnecessary to attach an optical film to a glass substrate that has been polished and thinned. When the exposed glass substrate is polished, another dichroic polarizing element is attached to the other glass substrate that has not been polished.

In addition, when a plastic substrate or a hybrid substrate using a norbornene resin is used instead of the glass substrate, the thickness and weight of the entire liquid crystal display device can be made thinner and lighter.

Embodiments of the present invention will be described below.

(Embodiment 1)
Here, an example of manufacturing a direct-view type liquid crystal display device using TN (Twisted nematic) type liquid crystal will be described with reference to FIGS.

First, the light interference layer 113 is formed on one surface of the first substrate 112 which is a counter substrate. As the first substrate 112, a glass substrate is used.

The light interference layer 113 is provided in order to reduce reflection of external light by an interface formed by different refractive index materials. The optical interference layer 113 has a multilayer structure in which layers having different refractive indexes are laminated so that it is effective for a wide wavelength range of visible light, so that external light reflected at the interface of the laminated layers interferes with each other. Cancel each other and an antireflection effect is obtained. Here, the optical interference layer 113 reduces reflection of external light due to an interface between the first substrate and a light shielding layer to be formed later. In addition, the light interference layer 113 also reduces reflection of external light due to the interface between the first substrate and a colored layer to be formed later.

As the material of the optical interference layer 113, a single layer or a laminate selected from silicon, nitrogen, fluorine, oxide, nitride, and fluoride can be used. _{Specifically MgF 2, SiO 2, CeF 3} , Al 2 O 3, SiNx, ITO, is possible to use a ZrO 2, TiO _2, etc. can. As a method for forming the light interference layer 113, sputtering method, electron beam evaporation method, sol-gel method, dip coating method, air knife coating method, blade coating method, forward roll coating method, reverse roll coating method, gravure coating method, microgravity coating method, A gravure coating method, a wire bar coating method, a direct die method, or the like can be used. When the optical interference layer 113 functions as an anti-reflection film, the total thickness of the optical interference layer in which the material layers are stacked is set to about 0.5 μm.

Next, a light shielding layer 115 functioning as a black matrix is formed on the optical interference layer 113. The light-blocking layer 115 can be formed using a metal film such as chromium or a black resin, but it is preferable to use a metal film that has high light-blocking properties and can be finely etched.

Next, a colored layer is formed at a location corresponding to each pixel. Here, a red colored layer 114R, a green colored layer 114G, and a blue colored layer 114B are formed. In FIG. 1, for simplification, the film thicknesses of all the colored layers and the film thicknesses of the light shielding layers are shown as the same, but there is no particular limitation. Further, in FIG. 1, for the sake of simplification, the end portion of the light shielding layer and the end portion of the colored layer coincide with each other, but a part of the colored layer may overlap with the end portion of the light shielding layer. Then, an overcoat layer 116 that covers the light shielding layer and the colored layer is formed for planarization or protection.

In producing a color filter, the metal film has a higher light-shielding property than a black resin. Therefore, after forming a metal film such as a chromium film as a black matrix, the red, green, and blue colored layers are printed by the printing method, the inkjet method, It is desirable to form each by an etching method using a photolithography technique. When a black resin is used to block light, the stronger the external light, the greater the thickness of the black resin that is required, which increases the thickness of the entire color filter. In addition, when a black resin is used as the black matrix, the colored layer is also a resin material. Therefore, the material of the black resin is also limited in order to prevent the materials from being mixed at the time of formation.

Next, a first polarizing element 117 having dichroism is attached to the overcoat layer 116. Although not shown here, an adhesive layer is provided between the overcoat layer 116 and the first polarizing element 117 having dichroism. Further, if necessary, a retardation plate may be disposed on the first polarizing element 117 having dichroism.

Next, a counter electrode 118 made of a transparent conductive film is formed on the first polarizing element 117 having dichroism. When a retardation plate is provided, the retardation plate is disposed between the counter electrode 118 and the first polarizing element 117 having dichroism.

Next, an alignment film 119 is formed over the counter electrode 118. Next, a rubbing process for aligning liquid crystal molecules on the alignment film 119 is performed.

Through the steps so far, preparation of the counter substrate side, that is, the first substrate (before bonding to the second substrate) is completed.

A thin film transistor (TFT) serving as a switching element is formed over the second substrate 101. As the second substrate 101, a glass substrate is used. A first insulating layer 102 is formed after a semiconductor layer, here a polysilicon film, is formed using a known technique.

As the semiconductor layer, an amorphous semiconductor film, a semiconductor film including a crystal structure, a compound semiconductor film including an amorphous structure, or the like can be used as appropriate. Further, the active layer of the TFT is a semiconductor having an intermediate structure between an amorphous structure and a crystal structure (including single crystal and polycrystal) and having a third state that is stable in terms of free energy, and has a short distance. A semi-amorphous semiconductor film (also referred to as a microcrystalline semiconductor film or a microcrystal semiconductor film) including a crystalline region having order and lattice strain can be used. There is no limitation on the material of the semiconductor layer, but it is preferably formed of silicon or a silicon germanium (SiGe) alloy. Alternatively, an organic compound such as pentacene can be used for the semiconductor layer.

In the case where a semiconductor film including a crystal structure is used as the semiconductor layer, not only the switching element of the pixel portion but also a driver circuit can be formed using a thin film transistor, and the pixel portion and the driver circuit can be formed over the same substrate. it can. It is preferable to form the pixel portion and the driver circuit over the same substrate because the thickness of the driving IC is unnecessary, the entire liquid crystal display device can be thinned, and the driving IC attaching process can be reduced.

Next, the gate electrode 103 is formed over the semiconductor layer with the first insulating layer 102 interposed therebetween. Next, the semiconductor layer is doped with an impurity element imparting n-type or p-type using the gate electrode as a mask, so that a pair of impurity regions 106 and 107 functioning as a source region or a drain region are formed. A channel formation region 105 is formed between the pair of impurity regions in the semiconductor layer.

Next, a second insulating layer 108 that covers the gate electrode 103 is formed. Next, the second insulating layer and the first insulating layer are selectively etched using a mask to form a contact hole reaching the impurity region 106. Next, a pixel electrode 110 made of a transparent conductive film that is electrically connected to the impurity region 106 through the contact hole is formed. Next, although not shown here, columnar spacers are formed to maintain the distance between the pair of substrates.

Next, an alignment film 111 that covers the pixel electrode 110 and the columnar spacers is formed. The alignment film 111 is formed by a printing method or an inkjet method. Next, a rubbing process for aligning liquid crystal molecules on the alignment film 111 is performed. Note that the rubbing direction performed on the alignment film 111 and the rubbing direction performed on the alignment film 119 are orthogonal to each other.

Through the steps so far, preparation on the element substrate side, that is, the second substrate (before bonding to the first substrate) is completed.

Next, a sealant surrounding the pixel portion is drawn with a dispenser device or the like in a state where the alignment film 119 provided on the first substrate 112 which is a counter substrate faces the upper surface. Next, a TN liquid crystal material is dropped in a region surrounded by the sealant, and the processing chamber in which the first substrate 112 is placed is decompressed. Next, alignment with the first substrate is performed in a state where the alignment film 111 provided on the second substrate which is an element substrate faces the lower surface, and the substrate is bonded under reduced pressure. When pasting is completed, the reduced pressure state is changed to the atmospheric pressure state. Thus, the liquid crystal layer 120 is sealed between the pair of substrates. Here, an example in which a pair of substrates is bonded together under reduced pressure is shown, but the invention is not particularly limited, and a known technique may be used.

Next, if necessary, the substrate is divided. In this embodiment, since the first polarizing element having dichroism is disposed between the pair of substrates, the separation is performed by the dicer apparatus or the laser beam.

Finally, a second polarizing element 121 having dichroism is attached to the second substrate 101. Note that the second polarizing element 121 having dichroism is aligned with the first polarizing element 117 having dichroism so that the absorption axis direction is in a crossed Nicols arrangement. In a TN liquid crystal display device, the liquid crystal is twisted and aligned by 90 ° between a pair of substrates, and the dichroic polarizing element is arranged so that the absorption axis direction is substantially parallel to or substantially orthogonal to the rubbing direction. To do. In such a TN liquid crystal display device, when no voltage is applied to the pixel electrode, incident light from a light source such as a backlight is converted into linearly polarized light by a polarizing element having dichroism on the light source side. When the transmission axis of the polarizing element that propagates along the twist of the layer and the other dichroic light coincides with the azimuth angle of the linearly polarized light, all the linearly polarized light is emitted and displayed in white (normally white display) ) In this embodiment, since it passes through the color filter, color display is performed when no voltage is applied to the pixel electrode. In addition, when a voltage is applied to the pixel electrode, incident light from the light source is linearly polarized by a dichroic polarizing element on the light source side, and a unit vector indicating the average orientation direction of the liquid crystal molecular axes contained in the liquid crystal layer Since the direction of is oriented almost perpendicular to the substrate surface, the azimuth angle of the linearly polarized light on the light source side propagates unchanged and matches the absorption axis of the other dichroic polarizing element so that black is displayed. It becomes.

If necessary, a retardation plate may be disposed between the second substrate 101 and the second polarizing element 121 having dichroism.

In the liquid crystal display device having the liquid crystal panel thus obtained, the distance between the first polarizing element having dichroism and the second polarizing element having dichroism is narrow, and a wide viewing angle can be secured. In addition, by providing a color filter between the first polarizing element having dichroism and the first substrate, a decrease in contrast due to depolarization is prevented. In addition, by providing a light interference layer between the color filter and the first substrate in order to reduce the difference in refractive index between the first substrate and the color filter and prevent reflection of external light, high contrast can be achieved even under external light. Realized.

Note that the present invention can be applied to any thin film transistor as long as it can function as a switching element regardless of the structure of the switching element. Although FIG. 1 shows an example in which a top-gate thin film transistor is provided over an insulating substrate, a bottom-gate (reverse staggered) TFT or a forward staggered TFT can be used. Further, the TFT is not limited to a single-gate TFT, and may be a multi-gate TFT having a plurality of channel formation regions, for example, a double-gate TFT.

In this embodiment mode, an example in which full color display is performed using three colors of red, green, and blue is not particularly limited, but cyan, magenta, and yellow may be used.

Although an example of a TN liquid crystal display device is described in this embodiment, the present invention is not particularly limited and can be applied to liquid crystal display devices in various modes. For example, as a method for improving viewing angle characteristics, it can be applied to a lateral electric field method (also referred to as IPS) in which an electric field in a horizontal direction with respect to the main surface of a substrate is applied to a liquid crystal layer. Further, the present invention can be applied to a method in which a nematic liquid crystal material having negative dielectric anisotropy is used as the liquid crystal material and a vertical alignment film is used as the alignment film. This method using a vertical alignment film is one of voltage controlled birefringence (also referred to as ECB) methods, and controls the transmittance by utilizing the birefringence of liquid crystal molecules.

Further, as a method of improving the response speed, the response speed of the liquid crystal layer may be improved so as to be compatible with moving image display using a ferroelectric liquid crystal or an antiferroelectric liquid crystal.

Further, the present invention can be applied to a transmissive liquid crystal display device adopting an OCB (Optical Compensate Birefringence) mode. The OCB mode improves the response speed of the liquid crystal layer by setting the liquid crystal layer between a pair of substrates to a state called bend alignment. The pretilt angle of the first alignment film in contact with the liquid crystal layer and the pretilt angle of the second alignment film in contact with the liquid crystal layer are reversed to bend alignment. In this OCB mode, it is necessary to change the liquid crystal layer from the initial splay alignment to a state called bend alignment.

Further, the present invention can also be applied to a transmissive liquid crystal display device adopting a vertical alignment mode. In a transmissive liquid crystal display device employing a vertical alignment mode, one pixel is divided into a plurality of subpixels, and a convex portion is provided on the counter substrate located in the center of each subpixel, whereby one pixel is aligned and divided (multi-domain). However, a driving method that realizes a wide viewing angle may be employed. This driving method is called sub-pixel driving.

(Embodiment 2)
Although an example of a TN liquid crystal display device is described in Embodiment 1, an example of an IPS liquid crystal display device is illustrated in FIG. 2 in this embodiment. In this IPS liquid crystal display device, a pixel electrode and a common electrode are formed on one of a pair of substrates sandwiching liquid crystal, and liquid crystal molecules are arranged in a plane substantially parallel to the substrate surface generated between these electrodes. This is a method of performing display by switching light by rotating. Since the liquid crystal molecules are rotated in a substantially parallel plane, the viewing angle can be widened as compared with the TN method without inversion of gradation and color tone depending on the viewing angle. Note that the IPS system is different from the TN system in the arrangement of a pair of dichroic polarizing elements, and is arranged so as to display black when no voltage is applied to the pixel electrode.

In addition, although the thin film transistor in Embodiment 1 has an example of a top gate structure, an inverted staggered example is shown in this embodiment.

First, the light interference layer 213 is formed on one surface of the first substrate 212 to be the counter substrate.

The light interference layer 213 is provided in order to reduce reflection of external light by an interface formed by different refractive index materials. The optical interference layer 213 has a multilayer structure in which layers having different refractive indexes are laminated so that it is effective for a wide wavelength range of visible light, so that external light reflected at the interface of the laminated layers interferes with each other. Cancel each other and an antireflection effect is obtained. Here, the optical interference layer 213 reduces reflection of external light due to an interface between the first substrate and a light shielding layer to be formed later. In addition, the light interference layer 213 also reduces reflection of external light due to an interface between the first substrate and a colored layer to be formed later.

Next, a light shielding layer 215 functioning as a black matrix is formed on the optical interference layer 213. The light-blocking layer 215 can be formed using a metal film such as chromium or a black resin, but it is preferable to use a metal film that has high light-blocking properties and that can be finely etched.

Next, a colored layer is formed at a location corresponding to each pixel. Here, a red colored layer 214R, a green colored layer 214G, and a blue colored layer 214B are formed. Then, an overcoat layer 216 that covers the light shielding layer and the colored layer is formed for planarization or protection.

Next, a first polarizing element 217 having dichroism is attached to the overcoat layer 216. Although not shown here, an adhesive layer for attachment is provided between the overcoat layer 216 and the first polarizing element 217 having dichroism. If necessary, a retardation plate may be provided on the first polarizing element 217 having dichroism.

Next, an alignment film 219 is formed over the first polarizing element 217 having dichroism. Next, a rubbing process for aligning liquid crystal molecules on the alignment film 219 is performed.

Through the steps so far, preparation of the counter substrate side, that is, the first substrate (before bonding to the second substrate) is completed.

A thin film transistor (TFT) serving as a switching element is formed over the second substrate 201. After the gate electrode 203 is formed using a known technique, the first insulating layer 202 is formed.

Next, a semiconductor layer and an n-type semiconductor layer including an impurity imparting n-type conductivity to the semiconductor are stacked over the first insulating layer 202. As the semiconductor layer, an amorphous semiconductor film, a compound semiconductor film including an amorphous structure, or the like can be used as appropriate. Here, an amorphous silicon film is used as the semiconductor layer.

Next, after forming a mask, selective etching is performed to form an island-shaped semiconductor layer and an island-shaped n-type semiconductor layer, thereby forming a metal film. Next, after forming a mask, selective etching is performed to form electrodes 206 and 207 functioning as a source electrode or a drain electrode. Using the electrodes 206 and 207 as a mask, the island-shaped semiconductor layer and the island-shaped n-type semiconductor layer are etched in a self-aligned manner to form a semiconductor layer having the n-type semiconductor layers 204 and 209 and the channel formation region 205.

Next, a second insulating layer 208 that covers the channel formation region 205 is formed. Next, the common electrode 218 is formed over the second insulating layer 208. The common electrode 218 can be formed using a conductive metal film or a transparent conductive film. An electrode shape corresponding to the pixel electrode is formed so that a lateral electric field is formed with the pixel electrode to be formed later. Further, a structure called an FFS (Fringe Field Switching) method, specifically, the common electrode may have a shape having an electrode area larger than the shape of the pixel electrode.

Next, a third insulating layer 222 that covers the common electrode 218 is formed. Next, the third insulating layer and the second insulating layer are selectively etched using a mask, so that a first contact hole reaching the electrode 206 is formed. Further, the third insulating layer, the second insulating layer, and the first insulating layer are etched using the same mask to form a second contact hole reaching the gate electrode 203.

Next, a pixel electrode 210 that is electrically connected to the electrode 206 through the first contact hole is formed over the third insulating layer 222. The pixel electrode 210 has a comb-like electrode shape or a bent electrode shape, and a conductive metal film or a transparent conductive film can be used.

Note that it is preferable that one or both of the pixel electrode 210 and the common electrode 218 be a transparent conductive film because an aperture ratio is improved. Next, although not shown here, columnar spacers are formed to maintain the distance between the pair of substrates.

Next, an alignment film 211 that covers the pixel electrodes 210 and the columnar spacers is formed. The alignment film 211 is formed by a printing method or an inkjet method. Next, a rubbing process for aligning liquid crystal molecules on the alignment film 211 is performed. The rubbing direction to the alignment film 211 is performed so as to be parallel to the wiring direction of the pixel electrode or have an angle. Note that the rubbing direction performed on the alignment film 211 and the rubbing direction performed on the alignment film 219 are substantially parallel to each other.

Through the steps so far, preparation on the element substrate side, that is, the second substrate (before bonding to the first substrate) is completed.

Next, a sealant surrounding the pixel portion is drawn with a dispenser device or the like in a state where the alignment film 219 provided on the first substrate 212 which is the counter substrate faces the upper surface. Next, a liquid crystal material is dropped on a region surrounded by the sealant, and the inside of the processing chamber in which the first substrate 212 is placed is decompressed. Next, alignment is performed with the first substrate in a state where the alignment film 211 provided on the second substrate 201 which is an element substrate faces the lower surface, and the substrate is bonded under reduced pressure. When pasting is completed, the reduced pressure state is changed to the atmospheric pressure state. Thus, the liquid crystal layer 220 is sealed between the pair of substrates. In the present embodiment, the alignment of the liquid crystal layer 220 is set to a homogeneous alignment substantially parallel to the substrate in the initial state. Here, an example in which a pair of substrates is bonded together under reduced pressure is shown, but the invention is not particularly limited, and a known technique may be used.

Next, if necessary, the substrate is divided. In this embodiment, since the first polarizing element having dichroism is disposed between the pair of substrates, the separation is performed by the dicer apparatus or the laser beam.

Finally, a second polarizing element 221 having dichroism is attached to the second substrate 201. Note that the second polarizing element 221 having dichroism is aligned with the first polarizing element 217 having dichroism so that the absorption axis direction is in a crossed Nicols arrangement.

Further, if necessary, a retardation plate may be disposed between the second substrate 201 and the second polarizing element 221 having dichroism.

The liquid crystal display device having the liquid crystal panel thus obtained is an IPS system, and the distance between the first polarizing element having dichroism and the second polarizing element having dichroism is narrow, and a wide viewing angle is obtained. Can be secured. In addition, by providing a color filter between the first polarizing element having dichroism and the second substrate, a decrease in contrast due to depolarization is prevented. In addition, a light interference layer is provided between the color filter and the second substrate in order to reduce the difference in refractive index between the second substrate and the color filter and prevent reflection of external light, thereby providing high contrast even under external light. Realized.

Note that the present invention can be applied to any thin film transistor as long as it can function as a switching element regardless of the structure of the switching element. Although FIG. 2 shows an example in which a channel etch type inverted staggered thin film transistor is provided over an insulating substrate, a channel stop type inverted staggered thin film transistor may be used. A forward staggered TFT can also be used. Further, the TFT is not limited to a single-gate TFT, and may be a multi-gate TFT having a plurality of channel formation regions, for example, a double-gate TFT.

The present invention having the above-described configuration will be described in more detail with the following examples.

In this example, an example in which the liquid crystal panel obtained in Embodiment 1 or 2 is used as a liquid crystal module is shown in FIG.

FIG. 3 is an exploded perspective view of a liquid crystal module using an LED (light emitting diode) as a backlight. In the liquid crystal panel 302 obtained in Embodiment 1 or 2, a plurality of driving ICs 305 are provided on an element substrate, and an FPC 307 that is electrically connected to a terminal provided on the element substrate is also provided.

A backlight 303 is disposed below the liquid crystal panel 302. A plurality of LEDs are used for the backlight 303, and a current is supplied by a connection cord 306. Moreover, an inorganic material may be used as a light emitting material of LED, and an organic material may be used.

  The LED may use one type of white light emission, or may use three types of red light emission, blue light emission, and green light emission.

  By using the LED as the backlight of the liquid crystal panel, a backlight with reduced power consumption can be obtained. In addition, since the LED is a surface emitting lighting device and can have a large area, the backlight can have a large area and a display surface can have a large area. Further, since the LED is thin and has low power consumption, the display device can be thinned and the power consumption can be reduced.

In addition, the first casing 301 and the second casing 304 are arranged so as to sandwich the liquid crystal panel 302 and the backlight 303, and the peripheral edges of the casings are coupled to each other. Here, the window of the first housing 301 is the display surface of the liquid crystal module.

Only one dichroic polarizing element is disposed between the backlight-side substrate of the liquid crystal panel 302 and the backlight 303, and the structure is simple.

Alternatively, the LEDs may be arranged in a line at locations that do not overlap the display surface, and light may be supplied to the liquid crystal panel using a light guide plate. In that case, it is preferable to reflect light in a region overlapping with the display surface of the second housing 304.

In the present embodiment, an example of a liquid crystal module using a backlight using an LED as a light source has been shown. However, the present invention is not particularly limited, and a liquid crystal module using a backlight using a cold cathode tube as a light source and a light guide plate Also good.

In addition, this embodiment can be freely combined with Embodiment Mode 1 or Embodiment Mode 2.

As the liquid crystal display device and electronic device of the present invention, a video camera, a digital camera, a goggle type display (head mounted display), a navigation system, an audio playback device (car audio, audio component, etc.), a notebook type personal computer, a game device, A portable information terminal (mobile computer, cellular phone, portable game machine, electronic book, or the like), an image reproducing device (specifically, Digital Versatile Disc (DVD)) equipped with a recording medium is reproduced, and the image is displayed. A device having a display capable of displaying). Specific examples of these electronic devices are shown in FIGS.

FIG. 4A illustrates a large display device having a large screen of 22 inches to 50 inches, which includes a housing 2001, a support base 2002, a display portion 2003, a video input terminal 2005, and the like. A display unit 2003 corresponds to the liquid crystal module of the first embodiment. The display device includes all information display devices for personal computers, for receiving TV broadcasts, for interactive TV, and the like. According to the present invention, a large display device having a wide viewing angle and a high contrast can be realized even if a glass substrate of the fifth generation or later in which one side exceeds 1000 mm is used.

FIG. 4B illustrates a laptop personal computer including a main body 2201, a housing 2202, a display portion 2203, a keyboard 2204, an external connection port 2205, a pointing device 2206, and the like. According to the present invention, a notebook personal computer capable of high-contrast display even under daylight can be realized.

FIG. 4C illustrates a portable image reproducing device (specifically, a DVD reproducing device) provided with a recording medium, which includes a main body 2401, a housing 2402, a display portion A2403, a display portion B2404, and a recording medium (DVD or the like). A reading unit 2405, operation keys 2406, a speaker unit 2407, and the like are included. A display portion A2403 mainly displays image information, and a display portion B2404 mainly displays character information. Note that an image reproducing device provided with a recording medium includes a home game machine and the like. According to the present invention, it is possible to realize an image reproducing apparatus capable of displaying high contrast even under daylight.

FIG. 4D illustrates a TV that can carry only a display wirelessly. The housing 2602 includes a battery and a signal receiver, and the display portion 2603 and the speaker portion 2607 are driven by the battery. The battery can be repeatedly charged by the charger 2600. The charger 2600 can transmit and receive a video signal, and can transmit the video signal to a signal receiver of the display. The housing 2602 is controlled by operation keys 2606. The device illustrated in FIG. 4D can also be referred to as a video / audio two-way communication device because a signal can be sent from the housing 2602 to the charger 2600 by operating the operation key 2606. In addition, by operating the operation key 2606, a signal is transmitted from the housing 2602 to the charger 2600, and further, a signal transmitted by the charger 2600 is received by another electronic device, thereby controlling communication of the other electronic device. It can be said to be a general-purpose remote control device. According to the present invention, a relatively large (22 inches to 50 inches) portable TV can be taken outdoors, and a user can enjoy high-contrast display even under daylight.

The mobile phone shown in FIG. 5 includes a main body (A) 1901 provided with operation switches 1904, a microphone 1905, a display panel (A) 1908, a display panel (B) 1909, a main body (such as a speaker 1906). B) 1902 is connected to a hinge 1910 so that it can be opened and closed. The display panel (A) 1908 and the display panel (B) 1909 are housed in a housing 1903 of the main body (B) 1902 together with the circuit board 1907. The pixel portions of the display panel (A) 1908 and the display panel (B) 1909 are arranged so that they can be seen from an opening window formed in the housing 1903.

In the display panel (A) 1908 and the display panel (B) 1909, specifications such as the number of pixels can be set as appropriate depending on the function of the cellular phone 1900. For example, the display panel (A) 1908 can be combined as a main screen and the display panel (B) 1909 can be combined as a sub-screen.

The cellular phone according to the present embodiment can be transformed into various modes according to the function and application. For example, an image pickup device may be incorporated in the hinge 1910 so as to be a mobile phone with a camera. Alternatively, the operation switches 1904, the display panel (A) 1908, and the display panel (B) 1909 may be housed in one housing. According to the present invention, when a mobile phone is used outdoors, a high-contrast display can be displayed on the display panel (A) 1908 and the display panel (B) 1909 even under daylight.

  As described above, the liquid crystal display device obtained by implementing the present invention may be used as a display portion of any electronic device.

In addition, a liquid crystal display device may be mounted on a vehicle (such as an automobile or a train) or a store window.

6A and 6B show an example in which a liquid crystal display device is mounted on a vehicle, specifically, a passenger car. This liquid crystal display device is not intended to be viewed mainly by passengers of vehicles equipped with a liquid crystal display device, but it is shown to nearby pedestrians who are not in the vehicle and passengers of nearby vehicles, making the passenger's car stand out. It is for making it. Accordingly, the display surfaces of the first liquid crystal display device 2704 in FIG. 6A, the second liquid crystal display device 2705 in FIG. 6B, and the third liquid crystal display device 2706 are directed outside the vehicle 2701. Install. It is mainly provided on the side window 2702 and the rear window 2703 so as not to narrow the driver's field of view. In the case where a liquid crystal display device is provided in a window that is not opened and closed, the liquid crystal display device can be fixed to the window. In this embodiment, the second liquid crystal display device 2705 and the third liquid crystal display device 2706 are fixed to the rear window 2703.

When a liquid crystal display device is used as a decoration, it is required to have a wide viewing angle and to display a clear color image. In addition, it is desirable that the contrast is high under daylight such as daytime. The second liquid crystal display device 2705 and the third liquid crystal display device 2706 reflect daylight sunlight or nighttime car illumination, and reflected light enters the eyes of the driver of the surrounding car, causing driving. It is desirable not to interfere with the problem.

The liquid crystal display device of the present invention is capable of high-definition display with a wide viewing angle and high contrast, and can achieve high contrast particularly under external light. Therefore, the liquid crystal display device is installed in a vehicle (car, train, etc.) or store window. Ideal to do. The liquid crystal display device of the present invention can suppress the reflection of external light and provide a screen that is easy on the human eye without glare.

Further, the second liquid crystal display device 2705 and the third liquid crystal display device 2706 can be advertised by displaying an advertisement video through the rear window 2703.

In addition, this embodiment can be freely combined with any one of Embodiment Mode 1, Embodiment Mode 2, or Embodiment 1.

According to the present invention, it is possible to provide a screen that is free from glare and is easy on the human eye without glare.

It is a figure which shows an example of sectional drawing of a liquid crystal panel. It is a figure which shows an example of sectional drawing of a liquid crystal panel. It is a figure which shows the disassembled perspective view of a liquid crystal module. FIG. 14 illustrates an example of an electronic device. The exploded perspective view of an example of electronic equipment. The side view of the vehicle carrying an electronic device, and the rear view of the vehicle seen from back.

Explanation of symbols

101: second substrate 102: first insulating layer 103: gate electrode 105: channel formation region 106: impurity region 107: impurity region 108: second insulating layer 111: alignment film 112: first substrate 113: light Interference layer 114R: red colored layer 114G: green colored layer 114B: blue colored layer 115: light shielding layer 116: overcoat layer 117: first polarizing element 118 having dichroism: counter electrode 119: alignment film 120 : Liquid crystal layer 121: dichroic second polarizing element 201: second substrate 202: first insulating layer 203: gate electrode 204: n-type semiconductor layer 205: channel formation region 206: electrode 207: electrode 208 : Second insulating layer 209: n-type semiconductor layer 211: orientation film 212: first substrate 213: light interference layer 214 R: red colored layer 214 G: green colored layer 214 B: Colored colored layer 215: Light-shielding layer 216: Overcoat layer 217: Dichroic first polarizing element 218: Common electrode 219: Alignment film 220: Liquid crystal layer 221: Dichroic second polarizing element 222 : Third insulating layer 301: first casing 302: liquid crystal panel 303: backlight 304: second casing 305: driving IC
306: Connection code 307: FPC
1900 Mobile phone 1901 Body (A)
1902 Body (B)
1903 Case 1904 Operation switches 1905 Microphone 1906 Speaker 1907 Circuit board 1908 Display panel (A)
1909 Display panel (B)
2001 Housing 2002 Support stand 2003 Display unit 2005 Video input terminal 2201 Main body 2202 Housing 2203 Display unit 2204 Keyboard 2205 External connection port 2206 Pointing device 2401 Main body 2402 Housing 2403 Display unit A
2404 Display B
2405 Recording medium reading unit 2406 Operation key 2407 Speaker unit 2600 Battery charger (can send and receive)
2602 Housing 2603 Display unit 2606 Operation key 2607 Speaker unit 2701 Vehicle 2702 Side window 2703 Rear window 2704 First liquid crystal display device 2705 Second liquid crystal display device 2706 Third liquid crystal display device

Claims (6)

A first substrate in which a light interference layer, a plurality of colored layers, and a first polarizing element having dichroism are sequentially stacked on an insulating surface;
A second substrate having a pixel electrode and a thin film transistor formed on one surface;
A liquid crystal layer between the first substrate and the second substrate;
And a second polarizing element having dichroism on the other surface of the second substrate. 2. The semiconductor device according to claim 1, further comprising a first alignment film between the pixel electrode and the liquid crystal layer. 3. The semiconductor device according to claim 1, wherein a second alignment film is provided between the first polarizing element having the dichroism and the liquid crystal layer. 4. The semiconductor device according to claim 1, wherein a counter electrode is provided between the first polarizing element having the dichroism and the second alignment film. A first substrate in which a light interference layer, a plurality of colored layers, and a first polarizing element having dichroism are sequentially stacked on an insulating surface;
A second substrate having a pixel electrode, a common electrode, and a thin film transistor formed on one surface;
A liquid crystal layer between the first substrate and the second substrate;
And a second polarizing element having dichroism on the other surface of the second substrate. 6. The semiconductor device according to claim 1, wherein a light shielding layer is provided between different colored layers among the plurality of colored layers.

Images