JP2007199691A - Display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device equipped with stacked polarizing plates and having higher contrast ratio. <P>SOLUTION: The display device is provided with stacked polarizing plates stacked so as to be displaced from a parallel Nicol state. A pair of the stacked polarizing plates are arranged in a cross Nicol state, and at least one of the stacked polarizing plates is stacked so as to be displaced from a parallel state. A retardation plate may be provided between the stacked polarizing plates and a substrate. Consequently, the contrast ratio can be enhanced. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a configuration of a display device including a polarizing plate having a laminated structure in order to increase a contrast ratio.

Development of a so-called flat panel display, which is much thinner and lighter than conventional cathode-ray tubes, is being developed. Flat panel displays are competing with liquid crystal display devices with liquid crystal elements as display elements, light emitting devices with self-luminous elements, FED (field emission display) using electron beams, etc. Therefore, low power consumption and high contrast ratio are required.

In general, a liquid crystal display device is provided with one polarizing plate on each substrate, and maintains a contrast ratio. By darkening the black display, the contrast ratio can be increased, and high display quality can be provided when an image is viewed in a dark room like a home theater.

For example, in order to improve display non-uniformity and contrast ratio caused by insufficient polarization degree and polarization degree distribution of the polarizing plate, a first polarizing plate is provided outside the substrate on the viewing side of the liquid crystal cell, In order to increase the degree of polarization when a second polarizing plate is provided outside the opposite substrate and light from the auxiliary light source provided on the substrate side is polarized through the second polarizing plate and passes through the liquid crystal cell The structure which provides a 3rd polarizing plate is proposed (refer patent document 1).
International Publication No. 00/34821

However, the demand for increasing the contrast ratio does not stop, and studies for improving contrast in liquid crystal display devices have been made. In addition, there is a problem that a polarizing plate having a high degree of polarization is expensive.

In view of the above problems, the present invention provides a laminated polarizing plate, that is, a polarizing plate having a laminated structure, on one of translucent substrates arranged to face each other, and the laminated polarizing plates are parallel Nicols. It is arranged so that it may deviate from.

Further, the present invention provides a polarizing plate laminated on both of the translucent substrates arranged so as to face each other, and arranges the facing polarizing plates so as to be crossed Nicols, and the laminated polarizing plates are parallel Nicols. It is arranged so that it may deviate from. Alternatively, the opposing polarizing plates may be arranged so as to deviate from crossed Nicols. You may have a wavelength plate and a phase difference plate between the laminated polarizing plate and a board | substrate.

One embodiment of the present invention is sandwiched between a first light-transmitting substrate and a second light-transmitting substrate that face each other, and the first light-transmitting substrate and the second light-transmitting substrate. A display element, and a polarizing plate laminated on the outside of the first light-transmissive substrate or the second light-transmissive substrate, and the laminated polarizing plates have parallel transmission axes. The display device is arranged so as to deviate from Nicol.

Another embodiment of the present invention is sandwiched between a first translucent substrate, a second translucent substrate, and the first translucent substrate and the second translucent substrate that face each other. A display element; a first laminated polarizing plate outside the first translucent substrate; and a second laminated polarizing plate outside the second translucent substrate, The first laminated polarizing plates are arranged so that their transmission axes deviate from parallel Nicols, and the second laminated polarizing plates are arranged so that their transmission axes become parallel Nicols It is a display device characterized by this.

Another embodiment of the present invention is sandwiched between a first translucent substrate, a second translucent substrate, and the first translucent substrate and the second translucent substrate that face each other. A display element; a first laminated polarizing plate outside the first translucent substrate; and a second laminated polarizing plate outside the second translucent substrate, The first laminated polarizing plates are arranged so that their transmission axes are parallel Nicols, and the second laminated polarizing plates are arranged so that their transmission axes are deviated from parallel Nicols. It is a display device characterized by this.

In the present invention, the first laminated polarizing plate has a transmission axis that is crossed Nicol with the transmission axis of the second laminated polarizing plate.

In the present invention, among the polarizing plates having the laminated structure, the polarizing plate deviated from parallel Nicols is arranged on the viewing side.

The contrast ratio of the display device can be increased by a simple stacked structure in which a plurality of polarizing plates are stacked while being shifted.

Embodiments of the present invention will be described below with reference to the drawings. However, the present invention can be implemented in many different modes, and those skilled in the art can easily understand that the modes and details can be variously changed without departing from the spirit and scope of the present invention. Is done. Therefore, the present invention is not construed as being limited to the description of this embodiment mode. Note that in all the drawings for describing the embodiments, the same portions or portions having similar functions are denoted by the same reference numerals, and repetitive description thereof is omitted.

(Embodiment 1)
In this embodiment mode, the concept of the display device of the present invention will be described.

FIG. 1A illustrates a stacked polarizing plate (a polarizing plate having a stacked structure), and the polarizing plate having a stacked structure has a configuration in which the polarizing plates are arranged so as to be shifted from parallel Nicols. A cross-sectional view of a display device provided with a polarizing plate having such a stacked structure, and FIG. 1B is a perspective view of the display device. In this embodiment, a liquid crystal display device including a liquid crystal element as a display element is described as an example.

As shown in FIG. 1A, a layer 100 having a liquid crystal element is sandwiched between a first substrate 101 and a second substrate 102 which are arranged to face each other. The substrate is a light-transmitting insulating substrate (hereinafter also referred to as a light-transmitting substrate). For example, a glass substrate such as barium borosilicate glass or alumino borosilicate glass, a quartz substrate, or the like can be used. In addition, a substrate made of a plastic such as polyethylene-terephthalate (PET), polyethylene naphthalate (PEN), or polyethersulfone (PES), or a synthetic resin having flexibility such as acrylic can be used.

A polarizing plate having a stacked structure is provided outside the substrate that is not in contact with the layer having the liquid crystal element. That is, the first polarizing plate 103 and the second polarizing plate 104 having a stacked structure are provided outside the first substrate 101. At this time, the polarizing plates, that is, the first polarizing plate 103 and the second polarizing plate 104 are arranged shifted from parallel Nicols.

These polarizing plates can be formed from a known material. For example, an adhesive layer, a TAC (triacetyl cellulose), a mixed layer of PVA (polyvinyl alcohol) and iodine, and a structure in which TAC are laminated in that order from the substrate side are used. Can do. The degree of polarization can be controlled by a mixed layer of PVA (polyvinyl alcohol) and iodine. In addition, there is a polarizing plate made of an inorganic material. Moreover, a polarizing plate may be called a polarizing film from the shape.

As shown in FIG. 1B, the transmission axis (A) of the first polarizing plate 103 and the transmission axis (B) of the second polarizing plate 104 are stacked to be shifted. In this way, the contrast ratio can be increased by laminating the transmission axes of the polarizing plates.

FIG. 2 shows a top view of an angle formed by the transmission axis (A) of the first polarizing plate 103 and the transmission axis (B) of the second polarizing plate 104. The transmission axis (A) of the first polarizing plate 103 and the transmission axis (B) of the second polarizing plate 104 are stacked with a deviation angle θ. Of the stacked polarizing plates, the second polarizing plate 104 provided outside is shifted and stacked.

As in this embodiment mode, a structure including a polarizing plate stacked on one side of a substrate can be applied to a display device that can extract light from one side of the substrate.

Note that, due to the characteristics of the polarizing plate, there is an absorption axis in the direction orthogonal to the transmission axis. Therefore, even when the absorption axes are parallel to each other, it can be called parallel Nicol.

By disposing the laminated polarizing plates so as to deviate from parallel Nicols, light leakage in the transmission axis direction can be reduced. For this reason, the contrast ratio of the display device can be increased.

(Embodiment 2)
In this embodiment mode, a concept of a display device in which a retardation plate is provided in addition to the stacked polarizing plates will be described, unlike the above embodiment mode.

FIG. 3A is a cross-sectional view of a display device in which a polarizing plate (a polarizing plate having a stacked structure) stacked with a shift from parallel Nicol and a retardation plate is provided between the polarizing plate and the substrate, FIG. 3B is a perspective view of the display device. In this embodiment, a liquid crystal display device including a liquid crystal element as a display element is described as an example.

As shown in FIG. 3A, a first polarizing plate 103 and a second polarizing plate 104 are provided on the first substrate 101 side. At this time, the first polarizing plate 103 and the second polarizing plate 104 are arranged shifted from parallel Nicols. Further, a retardation plate 113 is provided between the stacked polarizing plates and the first substrate 101.

Examples of the retardation plate include a film in which liquid crystal is hybrid-aligned, a film in which liquid crystal is twisted and aligned, a uniaxial retardation plate, or a biaxial retardation plate. Such a retardation plate can achieve a wide viewing angle of the display device.

The uniaxial retardation plate is formed by stretching a resin in one direction. The biaxial retardation plate is formed by uniaxially stretching the resin in the lateral direction and then weakly uniaxially stretching in the longitudinal direction. The resin used here is cycloolefin polymer (COE), polycarbonate (PC), polymethyl methacrylate (PMMA), polystyrene (PS), polyethersulfone (PES), polyphenylene sulfide (PPS), polyethylene terephthalate (PET). , Polyethylene naphthalate (PEN), polypropylene (PP), polyphenylene oxide (PPO), polyarylate (PAR), polyimide (PI), polytetrafluoroethylene (PTFE), and the like.

The film in which the liquid crystal is hybrid-aligned is a film formed by hybrid-aligning a discotic liquid crystal or a nematic liquid crystal with a triacetyl cellulose (TAC) film as a support. The phase difference plate can be attached to the light-transmitting substrate in a state of being attached to the polarizing plate.

In the present embodiment, a configuration further including a reflecting plate may be employed. The reflection plate can be provided by being provided outside the second substrate 102 or by forming the pixel electrode from a highly reflective material.

As shown in FIG. 3B, the transmission axis (A) of the first polarizing plate 103 and the transmission axis (B) of the second polarizing plate 104 are stacked to be shifted. Further, the transmission axis (A) of the first polarizing plate 103 and the slow axis (E) of the phase difference plate 113 are arranged to be shifted by 45 °. By providing such a retardation plate, black display can be achieved and the viewing angle can be widened. Note that 45 ° is an example, and the angle is not limited to this angle as long as the viewing angle is widened, and may be a predetermined angle. Thus, the contrast ratio can be increased by laminating the transmission axes of the polarizing plates and providing the retardation plate.

In FIG. 4, the angle formed by the transmission axis (A) of the first polarizing plate 103, the transmission axis (B) of the second polarizing plate 104, and the slow axis (E) of the retardation film 113 is shown from the top. A view is shown. The transmission axis (A) of the first polarizing plate 103 and the transmission axis (B) of the second polarizing plate 104 are laminated at a deviation angle θ. Further, the transmission axis (A) and the slow axis (E) are arranged to form 45 °.

As in this embodiment mode, a structure including a polarizing plate stacked on one side of a substrate can be applied to a display device that can extract light from one side of the substrate.

Note that there is a fast axis in the direction orthogonal to the slow axis due to the characteristics of the retardation plate. Therefore, the arrangement can be determined based on the fast axis instead of the slow axis.

Thus, by laminating the polarizing plates so as to deviate from parallel Nicols and further providing a retardation plate, light leakage in the transmission axis direction can be reduced. For this reason, the contrast ratio of the display device can be increased.

(Embodiment 3)
In this embodiment mode, a concept of a display device provided with a pair of stacked polarizing plates will be described unlike the above embodiment mode.

FIG. 5A illustrates a display device including a pair of stacked polarizing plates and a structure in which at least one stacked polarizing plate (a polarizing plate having a stacked structure) is arranged so as to be shifted from parallel Nicols. A cross-sectional view and FIG. 5B are perspective views of the display device. In this embodiment, a liquid crystal display device including a liquid crystal element as a display element is described as an example.

In this embodiment mode, a polarizing plate having a stacked structure is provided outside the substrate. Specifically, as illustrated in FIG. 5A, a first polarizing plate 103 and a second polarizing plate 104 are sequentially provided on the outside of the first substrate 101. In addition, a third polarizing plate 105 and a fourth polarizing plate 106 are sequentially provided on the outer side of the second substrate 102. In this embodiment, in the pair of stacked polarizing plates, at least one of the stacked polarizing plates is shifted from parallel Nicols. Specifically, as shown in FIG. 5B, the transmission axis (A) of the first polarizing plate 103 and the transmission axis (B) of the second polarizing plate 104 are shifted from the parallel state and stacked. . Then, the third polarizing plate 105 is laminated so that the transmission axis (C) of the third polarizing plate 105 and the transmission axis (D) of the fourth polarizing plate 106 are in parallel, that is, parallel Nicols.

The first polarizing plate 103 and the third polarizing plate 105 are arranged so as to be crossed Nicols. That is, the third polarizing plate and the fourth polarizing plate having a laminated structure and the first polarizing plate are arranged so as to be crossed Nicols, and the second polarizing plate is shifted from the first polarizing plate. To do. The polarizing plate displaced in this way is preferably a polarizing plate disposed outside the stacked polarizing plates, that is, disposed on the viewing side.

Note that the first polarizing plate 103 and the third polarizing plate 105 may deviate from the crossed Nicols state within a range where a predetermined black display is obtained.

The transmission axis (B) of the second polarizing plate 104 is shifted so as to be aligned with the minor axis direction of the ellipse of the elliptically polarized light emitted from the first polarizing plate 103. That is, the absorption axis of the second polarizing plate 104 is shifted so as to be aligned with the major axis direction of the ellipse of the elliptically polarized light emitted from the first polarizing plate 103.

Although not illustrated in FIG. 5, irradiation means such as a backlight is disposed below the fourth polarizing plate 106. That is, a preferable polarizing plate for shifting is preferably a polarizing plate disposed on the outer side among the stacked polarizing plates on the viewing side where no irradiation unit is disposed.

In FIG. 6, the transmission axis (A) of the first polarizing plate 103, the transmission axis (B) of the second polarizing plate 104, the transmission axis (C) of the third polarizing plate 105, and the fourth The figure which looked at the angle | corner with the transmission axis (D) of the polarizing plate 106 from the upper surface is shown. The transmission axis (A) of the first polarizing plate 103 and the transmission axis (B) of the second polarizing plate 104 are stacked with a deviation angle θ. In this embodiment, the transmission axis (C) and the transmission axis (D) are arranged in parallel Nicols.

As in this embodiment, the pair of stacked polarizing plates can be applied to a display device that can extract light from a side facing a substrate on which a backlight is provided. In addition, when a light-transmitting backlight is used, a pair of stacked polarizing plates may be applied to a display device that can extract light from a substrate provided with the backlight, that is, light can be extracted from both sides.

In such a pair of stacked polarizing plates, light leakage in the direction of the transmission axis is reduced by stacking at least one, preferably so that the transmission axis of the stacked polarizing plate on the viewing side deviates from parallel Nicols. Can do. For this reason, the contrast ratio of the display device can be increased.

(Embodiment 4)
In this embodiment mode, a mode of stacked polarizing plates that are shifted so as to be different from the above embodiment modes will be described.

In the above embodiment, the first polarizing plate 103 and the third polarizing plate 105 are arranged so as to be crossed Nicols, but the present invention is not limited to this. For example, the third polarizing plate 105 and the first polarizing plate 103 and the second polarizing plate 104 having a laminated structure are arranged so as to deviate from crossed Nicols, and the first polarizing plate 103 and the second polarizing plate are arranged. 104 may be arranged in parallel Nicols.

In this case, the transmission axis (A) of the first polarizing plate 103 is shifted in the minor axis direction of the ellipse of the elliptically polarized light emitted from the liquid crystal element. When this is indicated by the absorption axis, it can be said that the absorption axis of the first polarizing plate 103 is shifted in the major axis direction of the elliptical polarized light emitted from the liquid crystal element.

Thus, in the polarizing plate having a pair of laminated structures, the contrast ratio can also be increased by shifting from the crossed Nicols.

(Embodiment 5)
In this embodiment mode, a concept of a display device provided with a retardation plate in addition to a pair of stacked polarizing plates will be described, unlike the above embodiment mode.

FIG. 7A illustrates a display device in which one of a pair of stacked polarizing plates is stacked with a shift from parallel Nicols, and a retardation plate is provided between the pair of polarizing plates and the substrate. A cross-sectional view and FIG. 7B are perspective views of the display device. In this embodiment, a liquid crystal display device including a liquid crystal element as a display element is described as an example.

As shown in FIG. 7A, a first polarizing plate 103 and a second polarizing plate 104 having a stacked structure are provided outside the first substrate 101. A third polarizing plate 105 and a fourth polarizing plate 106 having a stacked structure are provided outside the second substrate 102.

As shown in FIG. 7B, the first polarizing plate 103 and the second polarizing plate 104 having a stacked structure are arranged so as to be shifted from parallel Nicols. Further, a retardation plate 113 is provided between the polarizing plate having a stacked structure and the first substrate 101.

As shown in FIG. 7B, a third polarizing plate 105 and a fourth polarizing plate 106 having a stacked structure are provided outside the second substrate 102. The third polarizing plate 105 and the fourth polarizing plate 106 are arranged in parallel Nicols. Further, a retardation plate 114 is provided between the polarizing plate having a stacked structure and the second substrate 102.

Although not shown in FIG. 7, irradiation means such as a backlight is disposed below the fourth polarizing plate 106.

Note that in this embodiment, the first polarizing plate 103 and the third polarizing plate 105 are arranged so as to be crossed Nicols. The first polarizing plate 103 and the third polarizing plate 105 may be deviated from the crossed Nicols state within an angle range for obtaining a predetermined black display.

In FIG. 8, the transmission axis (A) of the first polarizing plate 103, the transmission axis (B) of the second polarizing plate 104, the transmission axis (C) of the third polarizing plate 105, and the fourth The figure which looked at the angle | corner which the transmission axis (D) of the polarizing plate 106 makes from the upper surface is shown. The transmission axis (A) of the first polarizing plate 103 and the transmission axis (B) of the second polarizing plate 104 are laminated at a deviation angle θ. The transmission axis (B) of the second polarizing plate 104 is shifted so as to coincide with the minor axis direction of the ellipse of the elliptically polarized light coming out from the transmission axis (A) of the first polarizing plate 103. This deviation angle is θ. In the present embodiment, the transmission axis (C) and the transmission axis (D) are arranged in parallel Nicols. The transmission axis (A) and the transmission axis (C) are arranged to form a crossed Nicol.

As in this embodiment, a pair of stacked polarizing plates can be applied to a display device that can extract light from both sides of a substrate.

In such a configuration having a pair of laminated polarizing plates and a retardation plate, at least one, preferably on the viewing side, by laminating the laminated polarizing plates so as to deviate from parallel Nicols, Light leakage can be reduced. For this reason, the contrast ratio of the display device can be increased.

(Embodiment 6)
In this embodiment mode, a mode having stacked polarizing plates and retardation plates that are shifted so as to be different from the above embodiment modes will be described.

In the above-described embodiment, the retardation plate is provided and the first polarizing plate 103 and the third polarizing plate 105 are arranged so as to be crossed Nicols. However, the present invention is not limited to this. . For example, a retardation plate is provided, the third polarizing plate 105, the first polarizing plate 103 and the second polarizing plate 104 having a laminated structure are arranged so as to deviate from crossed Nicols, and have a laminated structure. You may arrange | position so that the 1st polarizing plate 103 and the 2nd polarizing plate 104 may become parallel Nicol.

In this case, the transmission axis (A) of the first polarizing plate 103 is shifted in the minor axis direction of the ellipse of the elliptically polarized light emitted from the liquid crystal element. When this is indicated by an absorption axis, it can be said that the absorption axis of the first polarizing plate 103 is shifted in the major axis direction of the elliptical polarized light emitted from the liquid crystal element.

Thus, the contrast ratio can also be increased by shifting from crossed Nicols in a pair of laminated polarizing plates having a retardation plate.

(Embodiment 7)
In this embodiment, a structure of a liquid crystal display device which includes a pair of stacked polarizing plates and has a structure in which at least one stacked polarizing plate is arranged with a transmission axis shifted is described.

FIG. 9 shows a cross-sectional view of a liquid crystal display device having stacked polarizing plates.

The liquid crystal display device includes a pixel portion 205 and a driver circuit portion 208. In the pixel portion 205 and the drive circuit portion 208, a base film 302 is provided over the substrate 301. As the substrate 301, an insulating substrate similar to that in the above embodiment can be used. In general, synthetic resin substrates are feared to have a lower heat-resistant temperature than other substrates, but they are also adopted by transposing elements after the manufacturing process using a substrate with high heat resistance. It becomes possible to do.

In the pixel portion 205, a transistor serving as a switching element is provided through the base film 302. In this embodiment mode, a thin film transistor (TFT) is used as the transistor, which is referred to as a switching TFT 303. A TFT can be manufactured by many methods. For example, a crystalline semiconductor film is applied as the active layer. A gate electrode is provided over the crystalline semiconductor film with a gate insulating film interposed therebetween. An impurity element can be added to the active layer using the gate electrode. Thus, it is not necessary to form a mask for adding the impurity element by adding the impurity element using the gate electrode. The gate electrode can have a single-layer structure or a stacked structure. The impurity region can be a high concentration impurity region and a low concentration impurity region by controlling the concentration thereof. A TFT having such a low concentration impurity region is referred to as an LDD (Light Doped Drain) structure. The low concentration impurity region can be formed so as to overlap with the gate electrode, and such a TFT is referred to as a GOLD (Gate Overlapped LDD) structure. FIG. 9 shows a switching TFT 303 having a GOLD structure. The polarity of the switching TFT 303 is n-type by using phosphorus (P) or the like in the impurity region. When p-type is used, boron (B) or the like may be added. Thereafter, a protective film that covers the gate electrode and the like is formed. A dangling bond of the crystalline semiconductor film can be terminated by the hydrogen element mixed in the protective film. In order to further improve the flatness, an interlayer insulating film 305 may be formed. For the interlayer insulating film 305, an organic material, an inorganic material, or a stacked structure thereof can be used. Then, openings are formed in the interlayer insulating film 305, the protective film, and the gate insulating film, and wirings connected to the impurity regions are formed. In this way, the switching TFT 303 can be formed. Note that the present invention is not limited to the configuration of the switching TFT 303.

Then, a pixel electrode 306 connected to the wiring is formed.

In addition, the capacitor 304 can be formed at the same time as the switching TFT 303. In this embodiment, the capacitor 304 is formed using a stack of a conductive film, a protective film, an interlayer insulating film 305, and a pixel electrode 306 which are formed at the same time as the gate electrode.

In addition, by using a crystalline semiconductor film, the pixel portion and the driver circuit portion can be formed over the same substrate. In that case, the transistor in the pixel portion and the transistor in the driver circuit portion 208 are formed at the same time. A transistor used for the driver circuit portion 208 is referred to as a CMOS circuit 354 because it constitutes a CMOS circuit. The TFT constituting the CMOS circuit 354 can have the same structure as the switching TFT 303. Further, instead of the GOLD structure, an LDD structure can be used, and it is not always necessary to have the same configuration.

An alignment film 308 is formed so as to cover the pixel electrode 306. The alignment film 308 is rubbed. This rubbing process may not be performed in the liquid crystal mode, for example, the VA mode.

Next, a counter substrate 320 is prepared. A color filter 322 and a black matrix (BM) 324 can be provided inside the counter substrate 320, that is, on the side in contact with the liquid crystal. These can be manufactured by a known method. However, if formed by a droplet discharge method (typically, an inkjet method) in which a predetermined material is dropped, waste of the material can be eliminated. A color filter or the like is provided in a region where the switching TFT 303 is not disposed. That is, the color filter is provided so as to face the light transmission region, that is, the opening region. Note that the color filter or the like may be formed from a material exhibiting red (R), green (G), and blue (B) when the liquid crystal display device is set to full color display. What is necessary is just to form from the material which exhibits a color.

In addition, when an RGB diode (LED) or the like is disposed in the backlight and a continuous additive color mixing method (field sequential method) in which color display is performed by time division, a color filter may not be provided. The black matrix 324 is also provided to reduce reflection of external light due to the wiring of the switching TFT 303 and the CMOS circuit 354. Therefore, the switching TFT 303 and the CMOS circuit 354 are provided so as to overlap. Note that the black matrix 324 may be formed so as to overlap with the capacitor 304. This is because reflection by the metal film constituting the capacitor 304 can be prevented.

Then, a counter electrode 323 and an alignment film 326 are provided. The alignment films 308 and 326 are rubbed. This rubbing process may not be performed in the liquid crystal mode, for example, the VA mode.

Note that a wiring, a gate electrode, a pixel electrode 306, and a counter electrode 323 included in the TFT are indium tin oxide (ITO), IZO (indium zinc oxide) in which indium oxide is mixed with zinc oxide (ZnO), indium oxide in silicon oxide ( SiO ₂ ) mixed conductive material, organic indium, organic tin, tungsten (W), molybdenum (Mo), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), Choose from a metal such as chromium (Cr), cobalt (Co), nickel (Ni), titanium (Ti), platinum (Pt), aluminum (Al), copper (Cu), or an alloy thereof, or a metal nitride thereof. it can.

Such a counter substrate 320 is attached to the substrate 301 using a sealing material 328. The sealing material 328 can be drawn on the substrate 301 or the counter substrate 320 by using a dispenser or the like. In order to maintain a distance between the substrate 301 and the counter substrate 320, a spacer 325 is provided in part of the pixel portion 205 and the driver circuit portion 208. The spacer 325 has a columnar shape or a spherical shape.

A liquid crystal 311 is injected between the substrate 301 and the counter substrate 320 bonded in this manner. When injecting liquid crystal, it is preferable to perform in a vacuum. The liquid crystal 311 can be formed by a method other than an injection method. For example, the liquid crystal 311 may be dropped and then the counter substrate 320 may be attached. Such a dropping method is preferably applied when handling a large substrate to which the injection method is difficult to apply.

The liquid crystal 311 includes liquid crystal molecules, and the tilt of the liquid crystal molecules is controlled by the pixel electrode 306 and the counter electrode 323. Specifically, it is controlled by a voltage applied to the pixel electrode 306 and the counter electrode 323. Such control uses a control circuit provided in the drive circuit unit 208. Note that the control circuit is not necessarily formed over the substrate 301, and a circuit connected through the connection terminal 310 may be used. At this time, an anisotropic conductive film having conductive fine particles can be used to connect to the connection terminal 310. In addition, the counter electrode 323 is electrically connected to a part of the connection terminal 310, and the potential of the counter electrode 323 can be common. For example, conduction can be achieved using the bump 337.

Next, the configuration of the backlight unit 352 will be described. The backlight unit 352 includes a cold cathode tube, a hot cathode tube, a diode, an inorganic EL element, and an organic EL element as a light source 331 that emits fluorescence, a lamp reflector 332 for efficiently guiding the fluorescence to the light guide plate 335, and total reflection of the fluorescence. While having a light guide plate 335 for guiding light to the entire surface, a diffusion plate 336 for reducing unevenness in brightness, and a reflection plate 334 for reusing light leaked under the light guide plate 335. Yes.

A control circuit for adjusting the luminance of the light source 331 is connected to the backlight unit 352. The luminance of the light source 331 can be controlled by supplying a signal from the control circuit.

Further, stacked polarizing plates 315 and 316 are provided between the substrate 301 and the backlight unit 352, and stacked polarizing plates 313 and 314 are also provided on the counter substrate 320. The polarizing plate 315 provided on the backlight side and the polarizing plate 316 are arranged so as to be parallel Nicols, and the polarizing plate 313 provided on the viewing side and the polarizing plate 314 are arranged so as to deviate from parallel Nicols. The The present invention is characterized in that the transmission axis of one of the pair of laminated polarizing plates, preferably the laminated polarizing plate on the viewing side is shifted. As a result, the contrast ratio can be increased.

The stacked polarizing plates 315 and 316 and the stacked polarizing plates 313 and 314 are bonded to the substrate 301 and the counter substrate 320. Moreover, you may laminate | stack in the state which had the phase difference plate between the laminated polarizing plate and a board | substrate.

A contrast ratio can be increased by providing a laminated polarizing plate and shifting the transmission axis for such a liquid crystal display device. By shifting the stacked polarizing plates, the contrast ratio can be increased as compared with a structure in which the thickness of a single-layer polarizing plate is simply increased.

This embodiment mode can be freely combined with the above embodiment modes.

(Embodiment 8)
In this embodiment mode, a liquid crystal display device using a TFT having an amorphous semiconductor film, which is different from the above embodiment mode, is described.

FIG. 10 illustrates a structure of a transistor (hereinafter referred to as amorphous TFT) liquid crystal display device using an amorphous semiconductor film as a switching element. The pixel portion 205 is provided with a switching TFT 303 made of an amorphous TFT. The amorphous TFT can be formed by a known method. For example, in the case of the channel etch type, a gate electrode is formed on the base film 302 and the gate electrode is covered to cover the gate insulating film, the n-type semiconductor film, and the non-crystalline TFT. A crystalline semiconductor film, a source electrode, and a drain electrode are formed. An opening is formed in the n-type semiconductor film using the source electrode and the drain electrode. At this time, part of the amorphous semiconductor film is also removed, so that it is called a channel etch type. Thereafter, a protective film is formed, and an amorphous TFT can be formed. An amorphous TFT also has a channel protection type, and a protective film is provided so that an amorphous semiconductor film is not removed when an opening is formed in an n-type semiconductor film using a source electrode and a drain electrode. Other configurations can be the same as those of the channel etch type.

Then, an alignment film 308 is formed as in FIG. 9, and a rubbing process is performed. This rubbing process may not be performed in the liquid crystal mode, for example, the VA mode.

Further, a counter substrate 320 is prepared as in FIG. A liquid crystal display device can be formed by sealing liquid crystal 311 between them.

Similarly to FIG. 9, laminated polarizing plates 315 and 316 are provided between the substrate 301 and the backlight unit 352, and laminated polarizing plates 313 and 314 are also provided on the counter substrate 320. The backlight-side polarizing plate 315 and the polarizing plate 316 are arranged so as to be parallel Nicols, and the viewing-side polarizing plate 313 and the polarizing plates 314 are arranged so as to deviate from parallel Nicols. The present invention is characterized in that the transmission axis of the polarizing plate laminated in one of the pair of laminated polarizing plates, preferably on the viewing side, is shifted. As a result, the contrast ratio can be increased.

The stacked polarizing plates 315 and 316 and the stacked polarizing plates 313 and 314 are bonded to the substrate 301 and the counter substrate 320. Moreover, you may laminate | stack in the state which had the phase difference plate between the laminated polarizing plate and a board | substrate.

In this manner, when an amorphous TFT is used as the switching TFT 303 to form a liquid crystal display device, an IC 421 formed from a silicon wafer can be mounted as a driver in the driver circuit unit 208 in consideration of operation performance. it can. For example, a signal for controlling the switching TFT 303 can be supplied by connecting a wiring included in the IC 421 and a wiring connected to the switching TFT 303 by using an anisotropic conductor having conductive fine particles 422. . Note that the IC mounting method is not limited to this, and the IC can be mounted by a wire bonding method.

Still further, the control circuit can be connected via the connection terminal 310. At this time, an anisotropic conductive film having conductive fine particles 422 can be used to connect to the connection terminal 310.

Other configurations are the same as those in FIG.

A contrast ratio can be increased by providing a laminated polarizing plate and shifting the transmission axis for such a liquid crystal display device. Further, in the present invention, the plurality of polarizing plates are polarizing plates having a laminated structure in which transmission axes are shifted from each other, and are different from a structure in which a single-layered polarizing plate is simply thickened. This is preferable in that the contrast ratio can be further increased as compared with the structure in which the thickness of the polarizing plate is increased.

This embodiment mode can be freely combined with the above embodiment modes.

(Embodiment 9)
In this embodiment, operations of circuits and the like included in the liquid crystal display device are described.

FIG. 11 is a system block diagram of the pixel portion 700 and the drive circuit portion of the liquid crystal display device.

The pixel portion 700 includes a plurality of pixels, and a switching element is provided in an intersection region between the signal line 212 serving as each pixel and the scanning line 210. Application of a voltage for controlling the tilt of liquid crystal molecules can be controlled by the switching element. A structure in which switching elements are provided in each intersection region in this way is called an active type. The pixel portion of the present invention is not limited to such an active type, and may have a passive configuration. Since the passive type has no switching element in each pixel, the process is simple.

The driver circuit portion 208 includes a control circuit, a signal line driver circuit 722, a scanning line driver circuit 723, and the like. The control circuit has a function of performing gradation control in accordance with display contents of the pixel portion 700. Therefore, the control circuit inputs the generated signal to the signal line driver circuit 722 and the scan line driver circuit 723. When a switching element is selected via the scanning line 210 based on the scanning line driving circuit 723, a voltage is applied to the pixel electrode in the selected intersection region. The value of this voltage is determined based on a signal input from the signal line driver circuit 722 via the signal line.

Further, in the control circuit, a signal for controlling the power supplied to the lighting unit is generated, and the signal is input to the power source of the lighting unit. The backlight unit described in the above embodiment can be used as the illumination unit. The illumination means includes a front light in addition to the backlight. The front light is a plate-like light unit that is mounted on the front side of the pixel portion and is composed of a light emitter and a light guide that illuminate the whole. Such illumination means can illuminate the pixel portion evenly with low power consumption.

As illustrated in FIG. 11, the scan line driver circuit 723 includes circuits that function as a shift register 701, a level shifter 704, and a buffer 705. Signals such as a gate start pulse (GSP) and a gate clock signal (GCK) are input to the shift register 701. Note that the scanning line driving circuit of the present invention is not limited to the structure shown in FIG.

In addition, as illustrated in FIG. 11, the signal line driver circuit 722 includes circuits that function as a shift register 711, a first latch 712, a second latch 713, a level shifter 714, and a buffer 715. A circuit functioning as the buffer 715 is a circuit having a function of amplifying a weak signal and includes an operational amplifier and the like. A signal such as a start pulse (SSP) is input to the level shifter 714, and data (DATA) such as a video signal is input to the first latch 712. A latch (LAT) signal can be temporarily held in the second latch 713 and is input to the pixel portion 700 all at once. This is called line sequential driving. Therefore, the second latch can be omitted if the pixel performs dot sequential driving instead of line sequential driving. Thus, the signal line driver circuit of the present invention is not limited to the configuration shown in FIG.

Such a signal line driver circuit 722, the scan line driver circuit 723, and the pixel portion 700 can be formed using a semiconductor element provided over the same substrate. For example, the semiconductor element can be formed using a thin film transistor provided over a glass substrate. In this case, a crystalline semiconductor film is preferably used for the semiconductor element (see Embodiment Mode 5). Since the crystalline semiconductor film has high electrical characteristics, particularly mobility, a circuit included in the driver circuit portion can be formed. In addition, the signal line driver circuit 722 and the scan line driver circuit 723 can be mounted on a substrate using an IC (Integrated Circuit) chip. In this case, an amorphous semiconductor film can be applied to the semiconductor element in the pixel portion (see Embodiment Mode 6).

In such a liquid crystal display device, the contrast ratio can be increased by providing the laminated polarizing plates and shifting the transmission axes.

This embodiment mode can be freely combined with the above embodiment modes.

(Embodiment 10)
In this embodiment, a structure of a backlight is described. The backlight is provided in the display device as a backlight unit having a light source, and the reflector unit is provided so as to surround the light source in order to scatter light efficiently.

As shown in FIG. 12A, the backlight unit 352 can use a cold cathode tube 401 as a light source. In addition, a lamp reflector 332 can be provided in order to reflect light from the cold cathode tube 401 efficiently. The cold cathode tube 401 is often used for a large display device. This is due to the intensity of the luminance from the cold cathode tube. Therefore, a backlight unit having a cold cathode tube can be used for a display of a personal computer.

As shown in FIG. 12B, the backlight unit 352 can use a diode (LED) as a light source. For example, white diodes (W) 402 are arranged at a predetermined interval. In addition, a lamp reflector 332 can be provided in order to reflect light from the diode (W) 402 efficiently.

As shown in FIG. 12C, the backlight unit 352 can use diodes (LEDs) 403, 404, and 405 of each color RGB as light sources. By using the diodes (LEDs) 403, 404, and 405 of each color RGB, color reproducibility can be improved as compared with only the diode (W) 402 that emits white. In addition, a lamp reflector 332 can be provided in order to reflect light from the diode (W) 402 efficiently.

Furthermore, as shown in FIG. 12D, when the diodes (LEDs) 403, 404, and 405 of each color RGB are used as the light source, it is not necessary to make them the same number and arrangement. For example, a plurality of colors with low emission intensity (for example, green) may be arranged.

Further, a diode 402 that emits white light and diodes (LEDs) 403, 404, and 405 of each color RGB may be used in combination.

In the case of having RGB diodes, when the field sequential mode is applied, color display can be performed by sequentially turning on the RGB diodes according to time.

A diode is suitable for a large display device because of its high luminance. Further, since the color purity of each of the RGB colors is good, the color reproducibility is superior to that of the cold cathode tube, and the arrangement area can be reduced. Therefore, when the display is adapted to a small display device, the frame can be narrowed.

Further, it is not always necessary to arrange the light source as a backlight unit as shown in FIGS. For example, when a backlight having a diode is mounted on a large display device, the diode can be arranged on the back surface of the substrate. At this time, the diodes can maintain a predetermined interval, and the diodes of the respective colors can be arranged in order. The color reproducibility can be improved by the arrangement of the diodes.

A display device using such a backlight is provided with stacked polarizing plates and is arranged with a transmission axis shifted, so that an image with a high contrast ratio can be provided. In particular, a backlight including a diode is suitable for a large display device, and a high-quality image can be provided even in a dark place by increasing the luminance of white display of the large display device.

This embodiment mode can be freely combined with the above embodiment modes.

(Embodiment 11)
In the liquid crystal display device, there are a vertical electric field method in which a voltage is applied perpendicular to the substrate and a horizontal electric field method in which a voltage is applied in parallel to the substrate. The structure in which the stacked polarizing plates are arranged so that the transmission axes are shifted can be applied to either a vertical electric field method or a horizontal electric field method. Therefore, in this embodiment, various liquid crystal modes to which a polarizing plate that is stacked and arranged with a transmission axis shifted may be applied.

First, FIG. 23 shows a schematic diagram of a TN mode liquid crystal display device.

Similarly to the above embodiment mode, a layer 100 having a display element is sandwiched between a first substrate 101 and a second substrate 102 which are arranged to face each other. On the first substrate 101 side, the first polarizing plate 103 and the second polarizing plate 104 are arranged shifted from parallel Nicols. A third polarizing plate 105 and a fourth polarizing plate 106 are arranged on the second substrate 102 side so as to be parallel Nicols. Note that the first polarizing plate 103 and the third polarizing plate 105 are arranged to be crossed Nicols.

Although not shown, the backlight or the like is disposed outside the fourth polarizing plate 106. A first electrode 108 and a second electrode 109 are provided over the first substrate 101 and the second substrate 102, respectively. In addition, the first electrode 108 which is an electrode on the side opposite to the backlight, that is, the viewing side is formed so as to have at least translucency.

In the liquid crystal display device having such a structure, in the normally white mode, when voltage is applied to the first electrode 108 and the second electrode 109 (referred to as a vertical electric field mode), FIG. As shown, black display is performed. At this time, the liquid crystal molecules are aligned vertically. As a result, the light from the backlight cannot pass through the substrate, resulting in a black display.

As shown in FIG. 23B, when no voltage is applied between the first electrode 108 and the second electrode 109, white display is performed. At this time, the liquid crystal molecules are aligned side by side and twisted in a plane. As a result, the light from the backlight is a pair of laminated polarizing plates, and can pass through a substrate arranged by shifting the laminated polarizing plates on the viewing side from parallel Nicols, and display a predetermined image Is done.

At this time, a full color display can be performed by providing a color filter. The color filter can be provided on either the first substrate 101 side or the second substrate 102 side.

A known liquid crystal material may be used for the TN mode.

FIG. 24 is a schematic diagram of a VA mode liquid crystal display device. The VA mode is a mode in which liquid crystal molecules are aligned so as to be perpendicular to the substrate when there is no electric field.

Similarly to FIG. 23, a first electrode 108 and a second electrode 109 are provided over the first substrate 101 and the second substrate 102, respectively. In addition, the first electrode 108 which is an electrode on the side opposite to the backlight, that is, the viewing side is formed so as to have at least translucency. The 1st polarizing plate 103 and the 2nd polarizing plate 104 are arrange | positioned and shifted from parallel Nicol. A third polarizing plate 105 and a fourth polarizing plate 106 are arranged on the second substrate 102 side so as to be parallel Nicols. Note that the first polarizing plate 103 and the third polarizing plate 105 are arranged to be crossed Nicols.

In the liquid crystal display device having such a structure, when voltage is applied to the first electrode 108 and the second electrode 109 (vertical electric field method), white display is performed as illustrated in FIG. It becomes a state. At this time, the liquid crystal molecules are arranged side by side. Then, the light from the backlight can pass through the substrate provided with the polarizing plates that are stacked and deviated from parallel Nicols, and a predetermined video display is performed. At this time, a full color display can be performed by providing a color filter. The color filter can be provided on either the first substrate 101 side or the second substrate 102 side.

Then, as shown in FIG. 24B, when no voltage is applied between the first electrode 108 and the second electrode 109, black display, that is, an off state is obtained. At this time, the liquid crystal molecules are aligned vertically. As a result, the light from the backlight cannot pass through the substrate, resulting in a black display.

Thus, in the off state, the liquid crystal molecules rise perpendicularly to the substrate and display black, and in the on state, the liquid crystal molecules tilt horizontally with respect to the substrate and display white. Since the liquid crystal molecules are standing up in the off state, the light from the polarized backlight passes through the cell without being affected by the liquid crystal molecules and can be completely blocked by the polarizing plate on the counter substrate side. Therefore, it is a pair of laminated polarizing plates, and the contrast is expected to be further improved by disposing at least one of the laminated polarizing plates from the parallel Nicols.

In addition, the laminated polarizing plate of the present invention can be applied to an MVA (Multi-domain Vertical Alignment) mode in which the alignment of liquid crystal is divided.

As the liquid crystal material used in the VA (Vertical Alignment) mode or the MVA mode, a known material may be used.

FIG. 25 is a schematic diagram of a liquid crystal display device in OCB (Optical Compensated Bend) mode. In the OCB mode, the alignment of liquid crystal molecules forms an optically compensated state in the liquid crystal layer, which is called bend alignment.

Similarly to FIG. 23, a first electrode 108 and a second electrode 109 are provided over the first substrate 101 and the second substrate 102, respectively. Although not shown, a backlight or the like is disposed outside the fourth polarizing plate 106. In addition, the first electrode 108 which is an electrode on the side opposite to the backlight, that is, the viewing side is formed so as to have at least translucency. The 1st polarizing plate 103 and the 2nd polarizing plate 104 are arrange | positioned and shifted from parallel Nicol. A third polarizing plate 105 and a fourth polarizing plate 106 are arranged on the second substrate 102 side so as to be parallel Nicols. Note that the first polarizing plate 103 and the third polarizing plate 105 are arranged to be crossed Nicols.

In the liquid crystal display device having such a structure, when voltage is applied to the first electrode 108 and the second electrode 109 (vertical electric field method), black display is performed as shown in FIG. At this time, the liquid crystal molecules are aligned vertically. Then, the light from the backlight cannot pass through the substrate, and a black display is obtained.

Then, as shown in FIG. 25B, when no voltage is applied between the first electrode 108 and the second electrode 109, white display is performed. At this time, the liquid crystal molecules are arranged obliquely. As a result, light from the backlight can pass through the substrate provided with the stacked polarizing plates, and a predetermined video display is performed. At this time, a full color display can be performed by providing a color filter. The color filter can be provided on either the first substrate 101 side or the second substrate 102 side.

In such an OCB mode, birefringence generated in the liquid crystal layer can be compensated by arranging a pair of laminated polarizing plates on the viewing side so as to deviate from the parallel Nicols. it can. As a result, a wide viewing angle can be realized and the contrast ratio can be increased.

FIG. 26 is a schematic diagram of a liquid crystal display device in an IPS (in-plane switching) mode. The IPS mode is a mode in which liquid crystal molecules are always twisted in a plane with respect to a substrate, and an electrode adopts a lateral electric field method provided only on one substrate side.

The IPS mode is characterized in that the liquid crystal is controlled by a pair of electrodes provided on one substrate. Therefore, a pair of electrodes 111 and 112 is provided over the second substrate 102. The pair of electrodes 111 and 112 preferably have a light-transmitting property. The 1st polarizing plate 103 and the 2nd polarizing plate 104 are arrange | positioned and shifted from parallel Nicol. A third polarizing plate 105 and a fourth polarizing plate 106 are arranged on the second substrate 102 side so as to be parallel Nicols. Note that the first polarizing plate 103 and the third polarizing plate 105 are arranged to be crossed Nicols. Although not shown, a backlight or the like is disposed outside the fourth polarizing plate 106.

In the liquid crystal display device having such a structure, when a voltage is applied to the pair of electrodes 111 and 112, an on state in which white display is performed as illustrated in FIG. Then, the light from the backlight is a pair of laminated polarizing plates, and can pass through a substrate in which the polarizing plates laminated on the viewing side are displaced from parallel Nicols, and a predetermined video display is performed. Is called.

At this time, a full color display can be performed by providing a color filter. The color filter can be provided on either the first substrate 101 side or the second substrate 102 side.

Then, as shown in FIG. 26B, when no voltage is applied between the pair of electrodes 111 and 112, black display, that is, an off state is obtained. At this time, the liquid crystal molecules are aligned side by side and twisted in a plane. As a result, the light from the backlight cannot pass through the substrate, resulting in a black display.

As the liquid crystal material used for the IPS mode, a known material may be used.

When a configuration in which a pair of laminated polarizing plates according to the present invention are arranged so that the polarizing plates laminated on the viewing side are deviated from parallel Nicols is applied to a vertical electric field type liquid crystal display device, display with a higher contrast ratio It can be performed. Such a vertical electric field method is suitable for a computer display device or a large television used indoors.

Further, when the present invention is applied to a horizontal electric field type liquid crystal display device, a display with a high contrast ratio can be achieved in addition to a wide viewing angle. Such a horizontal electric field method is suitable for a portable display device.

FIG. 27 is a schematic diagram of a liquid crystal in an FLC (Ferroelectric Liquid Crystal) mode and an AFLC (Antiferroelectric Liquid Crystal) mode.

Similarly to FIG. 23, a first electrode 108 and a second electrode 109 are provided over the first substrate 101 and the second substrate 102, respectively. In addition, the first electrode 108 which is an electrode on the side opposite to the backlight, that is, the viewing side is formed so as to have at least translucency. The 1st polarizing plate 103 and the 2nd polarizing plate 104 are arrange | positioned and shifted from parallel Nicol. A third polarizing plate 105 and a fourth polarizing plate 106 are arranged on the second substrate 102 side so as to be parallel Nicols. Note that the first polarizing plate 103 and the third polarizing plate 105 are arranged to be crossed Nicols.

In a liquid crystal display device having such a structure, when voltage is applied to the first electrode 108 and the second electrode 109 (referred to as a vertical electric field mode), white display is performed as illustrated in FIG. Become. At this time, the liquid crystal molecules are aligned side by side and twisted in a plane. As a result, the light from the backlight is a pair of laminated polarizing plates that can pass through a substrate placed on the viewer side and arranged so that the laminated polarizing plates are displaced from parallel Nicols. Is displayed.

As shown in FIG. 27B, when no voltage is applied between the first electrode 108 and the second electrode 109, black display is performed. At this time, the liquid crystal molecules are arranged side by side. As a result, the light from the backlight cannot pass through the substrate, resulting in a black display.

At this time, a full color display can be performed by providing a color filter. The color filter can be provided on either the first substrate 101 side or the second substrate 102 side.

As the liquid crystal material used in the FLC mode and the AFLC mode, a known material may be used.

In addition, the present invention can be applied to an optical rotation mode, a scattering mode, a birefringence mode liquid crystal display device, and a display device in which polarizing plates are arranged on both sides of a substrate.

This embodiment mode can be freely combined with the above embodiment modes.

(Embodiment 12)
As electronic devices according to the present invention, portable information such as a television device (also simply referred to as a television or a television receiver), a digital camera, a digital video camera, a cellular phone device (also simply referred to as a cellular phone or a cellular phone), a PDA, etc. Examples include a terminal, a portable game machine, a computer monitor, a computer, an audio playback device such as a car audio, and an image playback device equipped with a recording medium such as a home game machine. A specific example will be described with reference to FIG.

A portable information terminal device illustrated in FIG. 28A includes a main body 9201, a display portion 9202, and the like. The display device of the present invention can be applied to the display portion 9202. As a result, a portable information terminal device with a high contrast ratio can be provided.

A digital video camera shown in FIG. 28B includes a display portion 9701, a display portion 9702, and the like. The display device of the present invention can be applied to the display portion 9701. As a result, a digital video camera with a high contrast ratio can be provided.

A cellular phone shown in FIG. 28C includes a main body 9101, a display portion 9102, and the like. The display device of the present invention can be applied to the display portion 9102. As a result, a mobile phone with a high contrast ratio can be provided.

A portable television device illustrated in FIG. 28D includes a main body 9301, a display portion 9302, and the like. The display device of the present invention can be applied to the display portion 9302. As a result, a portable television device with a high contrast ratio can be provided. In addition, the present invention can be applied to a wide variety of television devices, from a small one mounted on a portable terminal such as a cellular phone to a medium-sized one that can be carried and a large one (for example, 40 inches or more). The display device can be applied.

A portable computer shown in FIG. 28E includes a main body 9401, a display portion 9402, and the like. The display device of the present invention can be applied to the display portion 9402. As a result, a portable computer with a high contrast ratio can be provided.

A television device illustrated in FIG. 28F includes a main body 9501, a display portion 9502, and the like. The display device of the present invention can be applied to the display portion 9502. As a result, a television device with a high contrast ratio can be provided.

As described above, the display device of the present invention can provide an electronic device with a high contrast ratio.

In this example, the result of optical calculation for a TN liquid crystal element having stacked polarizing plates will be described.

First, as shown in FIG. 13, a liquid crystal element to be optically calculated was formed. In order from the backlight, polarizing plate 1, polarizing plate 2, TN liquid crystal, polarizing plate 3, and polarizing plate 4 were laminated. That is, in the liquid crystal element, two laminated polarizing plates are arranged on both sides of the TN liquid crystal. The TN liquid crystal has a dielectric anisotropy Δε = 5.2. The cell thickness of the liquid crystal element was 4 μm. Table 1 shows the value of birefringence Δn of the TN liquid crystal at a wavelength of 546.1 nm. From Table 1, it can be seen that the birefringence varies depending on the temperature.

As the polarizing plate, EG1425DU included in the LCD MASTER database was used, and the thickness of one polarizing plate was 180 μm. In such a liquid crystal element, the rubbing direction is set in a direction perpendicular to the absorption axis of the polarizing plate, that is, parallel to the transmission axis direction on the backlight side and the viewing side, respectively, so that a normally white mode is obtained.

At this time, the absorption axes of the polarizing plate 1 and the polarizing plate 2 provided on the backlight side were arranged to form 135 ° from the reference line. Moreover, the absorption axis of the polarizing plate 3 provided on the viewing side is 45 ° from the reference line, that is, the polarizing plate 1 and the polarizing plate 3 are arranged so as to be crossed Nicols. The absorption axis of the polarizing plate 4 was gradually shifted from a state where the absorption axis was 45 ° from the reference line. That is, the absorption axis of the polarizing plate 4 gradually shifted from the absorption axis of the polarizing plate 3. In this state, optical calculation was performed.

In FIG. 14, the result of contrast ratio with respect to the angle which the absorption axis of the polarizing plate 4 makes with a reference line is shown. Optical calculations were performed when the angle between the absorption axis and the reference line was between 35 ° and 55 °. The contrast ratio is obtained from the relative ratio between the luminance of white display and the luminance of black display. In order to perform black display, 4.5 V was applied to the liquid crystal element (on voltage), and in order to perform white display, 1.7 V was applied to the liquid crystal element (off voltage). And the contrast ratio of the liquid crystal element when the temperature of TN liquid crystal was 20 degreeC, 25 degreeC, 40 degreeC, and 60 degreeC was measured.

FIG. 14 shows that the contrast ratio varies depending on the temperature of the TN liquid crystal. For example, the contrast ratio becomes maximum at 20 ° C. when the angle between the absorption axis of the polarizing plate 4 and the reference line is 41.5 °. The contrast ratio becomes maximum at 60 ° C. when the angle between the absorption axis of the polarizing plate 4 and the reference line is 42.5 °. Further, from FIG. 14, in order to increase the contrast ratio more than when the absorption axis of the polarizing plate 4 is arranged at 45 ° with the reference line, the angle between the absorption axis of the polarizing plate 4 and the reference line is set to 38 °. It is understood that it is preferable that the angle with respect to the absorption axis of the polarizing plate 3 is within 7 °, particularly within 5 °.

It was found that the contrast ratio is increased by shifting the laminated polarizing plates. It was also found that when the stacked polarizing plates were shifted, the angle formed by the absorption axis of the polarizing plate 4 that maximized the contrast ratio showed temperature dependence.

In this embodiment, the result of optical calculation regarding the temperature dependence on the contrast ratio is shown. Here, a method of shifting the stacked polarizing plates and making the contrast ratio constant without depending on the temperature will be described.

FIG. 15 shows the white display transmittance with respect to the applied voltage when the angle between the absorption axis of the polarizing plate 4 shown in FIG. 13 and the reference line is 41.5 °. It can be seen that as the temperature of the TN liquid crystal rises, the transmittance in white display decreases. In order to make the contrast ratio constant with respect to the temperature of the TN liquid crystal, the transmittance in white display may be made constant. For example, the transmittance in white display is set to a constant value of 0.22.

Table 2 shows specific values of the voltage applied to the liquid crystal element for performing white display for each temperature of the TN liquid crystal.

Next, FIG. 16 shows the transmittance of black display with respect to the applied voltage when the angle between the absorption axis of the polarizing plate 4 and the reference line is 41.5 °. It can be seen that as the temperature of the TN liquid crystal rises, the transmittance in black display is lowered. In order to make the contrast ratio constant with respect to the temperature of the TN liquid crystal, the transmittance in black display may be made constant. For example, the transmittance in black display is set to a constant value of 1.17 × 10 ⁻⁵ .

Table 3 shows specific values of the voltage applied to the liquid crystal element for black display with respect to each temperature of the TN liquid crystal.

Next, FIG. 17 shows the result of plotting the contrast ratio with respect to the temperature of the TN liquid crystal. Also in this measurement, the absorption axis of the polarizing plate 4 is arranged so as to be 41.5 ° with respect to the reference line, that is, the polarizing plate 4 is arranged so as to be shifted to obtain a high contrast ratio. Further, as shown in Tables 2 and 3, the voltage applied to the liquid crystal element was controlled so that the white display transmittance and the black display transmittance were constant with respect to the temperature of the TN liquid crystal. As a comparative example, the result of a comparative element in which the absorption axis of the polarizing plate 4 is arranged at 45 ° with the reference line is also shown. For the comparison element, the applied voltage was 0 V for black display and 5 V for white display regardless of the temperature.

FIG. 17 shows that the liquid crystal element of the present invention can obtain a high contrast ratio, and a constant contrast ratio can be obtained when the temperature of the TN liquid crystal is 20 ° C. to 60 ° C. On the other hand, the comparison element has a low contrast ratio, and further, the contrast ratio varies depending on the temperature of the TN liquid crystal.

Thus, it was found that the liquid crystal element of the present invention obtains a high contrast ratio. Although the contrast ratio varies depending on the temperature of the TN liquid crystal, it can be seen that it is desirable to control the drive voltage so as to maintain a constant contrast ratio. In order to control the driving voltage, an element for detecting the transmittance may be arranged in the display device, and the driving voltage may be controlled based on the detection result. As an element for detecting the transmittance, a photosensor composed of an IC chip can be used. In the display device, an element for detecting temperature may be arranged, and the drive voltage may be controlled based on the detection result and the change in contrast ratio with respect to the temperature of the liquid crystal element. As an element for detecting the temperature, a temperature sensor composed of an IC chip can be used. At this time, the element for detecting the transmittance and the element for detecting the temperature are preferably arranged so as to be hidden in the housing portion of the display device.

In this example, optical calculation results for a VA liquid crystal element having stacked polarizing plates are shown.

First, as shown in FIG. 18, a liquid crystal element to be optically calculated was formed. In order from the backlight, a polarizing plate 1, a polarizing plate 2, a retardation plate, a VA liquid crystal, a retardation plate, a polarizing plate 3 and a polarizing plate 4 were laminated. That is, in the liquid crystal element, a phase difference plate and two laminated polarizing plates are arranged on both sides of the VA liquid crystal. In this embodiment, a phase difference plate is inserted in order to improve the viewing angle that affects the polarization state of incident light. The VA liquid crystal has a dielectric anisotropy Δε = −4.3. The cell thickness of the liquid crystal element was 2.44 μm. Table 4 shows the birefringence of the VA liquid crystal at a wavelength of 546.1 nm. From Table 4, it can be seen that the birefringence varies depending on the temperature.

As the polarizing plate, EG1425DU included in the LCD MASTER database was used, and the thickness of one polarizing plate was 180 μm. In such a liquid crystal element, the pretilt angle was 88 °.

At this time, the absorption axes of the polarizing plate 1 and the polarizing plate 2 provided on the backlight side were arranged so as to form 45 ° from the reference line. Further, the absorption axis of the polarizing plate 3 provided on the viewing side is arranged to be 135 ° from the reference line, that is, to be in crossed Nicols with the polarizing plate 1 and the polarizing plate 3. The absorption axis of the polarizing plate 4 was gradually shifted from a state where the absorption axis was 135 ° from the reference line.
Optical calculation was performed in this state.

FIG. 19 shows the result of the contrast ratio with respect to the angle formed by the absorption axis of the polarizing plate 4 and the reference line. Optical calculations were performed when the angle between the absorption axis and the reference line was between 125 ° and 145 °. In order to perform white display, 6.5 V was applied to the liquid crystal element (on voltage), and in order to perform black display, 0.6 V was applied to the liquid crystal element (off voltage). And the contrast ratio of the liquid crystal element when the temperature of VA liquid crystal was 20 degreeC, 25 degreeC, 40 degreeC, and 60 degreeC was measured.

FIG. 19 shows that the contrast ratio varies depending on the temperature of the VA liquid crystal. For example, the contrast ratio becomes maximum at 20 ° C. when the angle between the absorption axis of the polarizing plate 4 and the reference line is 139.5 °. The contrast ratio becomes maximum at 60 ° C. when the angle between the absorption axis of the polarizing plate 4 and the reference line is 139 °. Further, from FIG. 19, in order to increase the contrast ratio as compared with the case where the absorption axis of the polarizing plate 4 is arranged at 135 ° with the reference line, the angle between the absorption axis of the polarizing plate 4 and the reference line is set to 135 °. It is understood that it is preferable that the angle with respect to the absorption axis of the polarizing plate 3 is within 9 °, particularly within 7 °.

It was found that the contrast ratio increases when the absorption axis of the polarizing plates laminated in this way is shifted. Further, it was found that when the absorption axis of the laminated polarizing plate is shifted, the contrast ratio shows temperature dependency with respect to the angle formed by the absorption axis of the polarizing plate 4 at which the contrast ratio becomes maximum.

In this embodiment, the result of optical calculation regarding the temperature dependence on the contrast ratio is shown. Here, a method of shifting the stacked polarizing plates and making the contrast ratio constant without depending on the temperature will be described.

FIG. 20 shows the white display transmittance with respect to the applied voltage when the angle formed by the absorption axis of the polarizing plate 4 shown in FIG. 18 and the reference line is 139 °. It can be seen that as the temperature of the VA liquid crystal is increased, the transmittance in white display is decreased. In order to make the contrast ratio constant with respect to the temperature of the VA liquid crystal, the transmittance in white display may be made constant. For example, the white display transmittance may be set to 0.25.

Table 5 shows specific values of the applied voltage for performing white display at the temperature of each VA liquid crystal.

Next, FIG. 21 shows the transmittance of black display with respect to the applied voltage when the angle between the absorption axis of the polarizing plate 4 and the reference line is 139 °. It can be seen that as the temperature of the VA liquid crystal rises, the transmittance in black display is lowered. In order to make the contrast ratio constant with respect to the temperature of the VA liquid crystal, the transmittance in black display may be made constant. For example, the black display transmitted light may have a constant value of 8.79 × 10 ⁻⁷ .

Table 6 shows specific values of the applied voltage for performing black display at the temperature of each VA liquid crystal.

Next, FIG. 22 shows the result of plotting the contrast ratio with respect to the temperature of the VA liquid crystal. Also in this measurement, the absorption axis of the polarizing plate 4 is arranged so as to be 139 ° with respect to the reference line, that is, the polarizing plate 4 is arranged so as to be shifted to obtain a high contrast. Further, as shown in Tables 5 and 6, the voltage applied to the liquid crystal element was controlled so that the white display transmittance and the black display transmittance were constant with respect to the temperature of the VA liquid crystal. As a comparative example, the result of a comparative element in which the absorption axis of the polarizing plate 4 is arranged at 135 ° with the reference line is also shown. For the comparison element, the applied voltage was 0 V for black display and 5 V for white display regardless of temperature.

Table 7 shows configurations of the liquid crystal element of the present invention and the comparative element.

FIG. 22 shows that the liquid crystal element of the present invention was able to obtain a high contrast ratio, and that a constant contrast ratio could be obtained when the temperature of the VA liquid crystal was 20 ° C. to 60 ° C. However, although the contrast ratio at 60 ° C. is slightly increased, it can be improved by controlling the voltage more finely when controlling the transmittance of black display. On the other hand, the comparative element has a low contrast ratio, and further, the contrast ratio varies depending on the temperature of the VA liquid crystal.

Thus, it was found that the liquid crystal element of the present invention obtains a high contrast ratio. Further, although the contrast ratio varies depending on the temperature of the VA liquid crystal, it can be seen that it is desirable to control the drive voltage so as to maintain a constant contrast ratio. In order to control the driving voltage, an element for detecting the transmittance may be arranged in the display device, and the driving voltage may be controlled based on the detection result. As an element for detecting the transmittance, a photosensor composed of an IC chip can be used. In the display device, an element for detecting temperature may be arranged, and the drive voltage may be controlled based on the detection result and the change in contrast ratio with respect to the temperature of the liquid crystal element. As an element for detecting the temperature, a temperature sensor composed of an IC chip can be used. At this time, the element for detecting the transmittance and the element for detecting the temperature are preferably arranged so as to be hidden in the housing portion of the display device.

It is the figure which showed the display apparatus of this invention. It is the figure which showed the angle | corner which the polarizing plate of this invention makes. It is the figure which showed the display apparatus of this invention. It is the figure which showed the angle | corner which the polarizing plate of this invention makes. It is the figure which showed the display apparatus of this invention. It is the figure which showed the angle | corner which the polarizing plate of this invention makes. It is the figure which showed the display apparatus of this invention. It is the figure which showed the angle | corner which the polarizing plate of this invention makes. It is sectional drawing which showed the display apparatus of this invention. It is sectional drawing which showed the display apparatus of this invention. It is the block diagram which showed the display apparatus of this invention. It is the figure which showed the irradiation means which the display apparatus of this invention has. It is the figure which showed the experimental condition of this invention. It is the graph which showed the experimental result of this invention. It is the graph which showed the experimental result of this invention. It is the graph which showed the experimental result of this invention. It is the graph which showed the experimental result of this invention. It is the figure which showed the experimental condition of this invention. It is the graph which showed the experimental result of this invention. It is the graph which showed the experimental result of this invention. It is the graph which showed the experimental result of this invention. It is the graph which showed the experimental result of this invention. It is the schematic diagram which showed the mode of the liquid crystal element of this invention. It is the schematic diagram which showed the mode of the liquid crystal element of this invention. It is the schematic diagram which showed the mode of the liquid crystal element of this invention. It is the schematic diagram which showed the mode of the liquid crystal element of this invention. It is the schematic diagram which showed the mode of the liquid crystal element of this invention. It is the figure which showed the electronic device of this invention.

Claims (12)

A first translucent substrate and a second translucent substrate facing each other;
A display element sandwiched between the first translucent substrate and the second translucent substrate;
A polarizing plate having a laminated structure provided outside the first light-transmitting substrate or the second light-transmitting substrate;
The display device according to claim 1, wherein the polarizing plates having the laminated structure are arranged such that the transmission axes of the polarizing plates deviate from parallel Nicols. A first translucent substrate and a second translucent substrate facing each other;
A display element sandwiched between the first translucent substrate and the second translucent substrate;
A polarizing plate having a first laminated structure provided outside the first light-transmitting substrate;
A polarizing plate having a second laminated structure provided outside the second light-transmitting substrate;
The polarizing plate having the first laminated structure is disposed such that the transmission axes of the polarizing plates deviate from parallel Nicols.
The polarizing plate having the second laminated structure is arranged so that transmission axes thereof are parallel Nicols. A first translucent substrate and a second translucent substrate facing each other;
A display element sandwiched between the first translucent substrate and the second translucent substrate;
A polarizing plate having a first laminated structure provided outside the first light-transmitting substrate;
A polarizing plate having a second laminated structure provided outside the second light-transmitting substrate;
The polarizing plate having the first laminated structure is disposed such that the transmission axes of the polarizing plates are parallel Nicols,
The polarizing plate having the second laminated structure is disposed so that the transmission axes of the polarizing plates are deviated from parallel Nicols. 4. The display device according to claim 2, wherein the transmission axis of the polarizing plate having the first laminated structure and the transmission axis of the polarizing plate having the second laminated structure are crossed Nicols. 4. The display device according to claim 2, wherein a transmission axis of the polarizing plate having the first laminated structure and a transmission axis of the polarizing plate having the second laminated structure are deviated from crossed Nicols. . 6. The display device according to claim 2, wherein among the polarizing plates having the laminated structure, a polarizing plate deviated from parallel Nicol is disposed on the viewing side. A first translucent substrate and a second translucent substrate facing each other;
A display element sandwiched between the first translucent substrate and the second translucent substrate;
A polarizing plate having a laminated structure provided outside the first light-transmitting substrate or the second light-transmitting substrate;
A retardation plate provided between the first light-transmitting substrate or the second light-transmitting substrate and the polarizing plate having the laminated structure;
The polarizing plate having the laminated structure is arranged so that the transmission axes of each other are deviated from parallel Nicols,
The display device, wherein the polarizing plate having the laminated structure and the retardation plate are arranged at an angle that increases a viewing angle. A first translucent substrate and a second translucent substrate facing each other;
A display element sandwiched between the first translucent substrate and the second translucent substrate;
A polarizing plate having a first laminated structure provided outside the first light-transmitting substrate;
A polarizing plate having a second laminated structure provided outside the second light-transmitting substrate;
A first retardation plate provided between the first translucent substrate and the polarizing plate having the first laminated structure;
A second retardation plate provided between the second translucent substrate and the polarizing plate having the second laminated structure;
The polarizing plate having the first laminated structure is disposed such that the transmission axes of the polarizing plates deviate from parallel Nicols.
The polarizing plate having the second laminated structure is disposed so that the transmission axes of the polarizing plates are parallel Nicols,
The polarizing plate having the first laminated structure and the first retardation plate have an angle that widens the viewing angle,
The display device, wherein the polarizing plate having the second laminated structure and the second retardation plate are arranged at an angle that increases a viewing angle. A first translucent substrate and a second translucent substrate facing each other;
A display element sandwiched between the first translucent substrate and the second translucent substrate;
A polarizing plate having a first laminated structure provided outside the first light-transmitting substrate;
A polarizing plate having a second laminated structure provided outside the second light-transmitting substrate;
A first retardation plate provided between the first translucent substrate and the polarizing plate having the first laminated structure;
A second retardation plate provided between the second translucent substrate and the polarizing plate having the second laminated structure;
The polarizing plate having the first laminated structure is disposed such that the transmission axes of the polarizing plates are parallel Nicols,
The polarizing plate having the second laminated structure is disposed such that the transmission axes of the polarizing plates deviate from parallel Nicols.
The polarizing plate having the first laminated structure and the first retardation plate have an angle that widens the viewing angle,
The display device, wherein the polarizing plate having the second laminated structure and the second retardation plate are arranged at an angle that increases a viewing angle. 10. The display device according to claim 8, wherein a transmission axis of the polarizing plate having the first laminated structure and a transmission axis of the polarizing plate having the second laminated structure form a crossed Nicols. 10. The display device according to claim 8, wherein a transmission axis of the polarizing plate having the first laminated structure and a transmission axis of the polarizing plate having the second laminated structure are deviated from crossed Nicols. . 12. The display device according to claim 8, wherein among the polarizing plates having the laminated structure, a polarizing plate deviated from parallel Nicol is disposed on the viewing side.

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