JPH10268293A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To actualize a picture quality of clear colors which is based upon white and red and close to that of a CRT at a wide field angle by providing at least one specific phase plate between a display element which has a counter substrate, a specific pixel substrate and a specific liquid crystal layer and a polarizer. SOLUTION: This device has a liquid crystal display element 5, phase difference plates 2a and 2b arranged on both its sides, and a couple of polarizing plates 3 and 4 between which they are sandwiched. A glass substrate 7 used as a pixel substrate includes an inter-layer insulating film 40 of which the transmissivity to light of peak wavelength is improved more to approximately >=95%. The liquid crystal layer 12 is formed of liquid crystal which is set so that the difference Δn(450)-Δn(650) between refractive index anisotropy Δn(450) to light of 450 nm in wavelength and refractive index anisotropy Δn(650) to light of 650 nm is 0 to 0.01. The whole phase difference plate 2a totally has relation na=nc>nb on the average, where na, nb, and nc are three main refractive indexes of a refractive index elliptic body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a liquid crystal display device. More specifically, the present invention relates to a liquid crystal display device including a switching element such as a thin film transistor, which improves a visual characteristic and a display characteristic of a display screen and enables a display comparable to a CRT.

[0002]

2. Description of the Related Art Conventionally, a liquid crystal display device using a nematic liquid crystal display element has been widely used for a numerical segment type liquid crystal display device such as a timepiece and a calculator. Recently, it has been used as a display including a word processor, a computer and a navigation system.

Among the above-mentioned liquid crystal display devices, an active matrix type liquid crystal display device in which active elements such as TFTs are used as switching elements and pixels are arranged in a matrix is particularly well-known. ing. The liquid crystal display device is compared with a CRT display device,
It has the advantages of being extremely thin in thickness (depth), low power consumption, and being easy to be full-color, and its demand is growing in a wide range of fields such as personal computers, various monitors, portable televisions, and cameras. ing. However, they are still inferior in terms of luminance, color reproducibility, and the like as compared with CRT display devices.

The above-mentioned active matrix type liquid crystal display device has a light-transmitting substrate (active matrix substrate). The substrate is used to apply a voltage to a liquid crystal layer as shown in FIG. Are formed in a matrix. As active elements, which are switching means for selectively driving the pixel electrodes 51, thin film transistors (hereinafter, referred to as TFTs) 52 are formed on the substrate, and are connected to the pixel electrodes 51. In the case of performing color display, although not shown, a color filter layer of red, green, blue, or the like is provided over the substrate in addition to the above structure.

The scanning lines 53 are connected to the gate electrodes of the TFTs 52, and the signal lines 54 are connected to the source electrodes. The scanning lines 53 and the signal lines 5
4 are arranged so as to pass around the pixel electrodes 51 arranged in a matrix and to be orthogonal to each other. The driving of the TFTs 52 is controlled by inputting a gate signal through the scanning lines 53. When the TFTs 52 are driven by the signal lines 54,
Are input to the pixel electrodes 51 through.

Further, pixel electrodes 51 and additional capacitors 55 are connected to drain electrodes of the TFTs 52. The opposing electrodes of the additional capacitors 55 are connected to common wirings 56, respectively. The additional capacitors 55 are used to hold a voltage applied to the liquid crystal layer.

In an active matrix type liquid crystal display device, a liquid crystal layer is sandwiched between the active matrix substrate and a counter substrate facing the active matrix substrate. That is,
The liquid crystal layer is sandwiched between the pixel electrodes 51 formed on the active matrix substrate and the counter electrode formed on the counter substrate to form a liquid crystal capacitor. The additional capacitors 55 are connected in parallel with the liquid crystal capacitors.

The TFT 52 will be described in more detail.
As shown in FIG. 9, a gate electrode 62 is formed on a transparent insulating substrate 61, and a gate insulating film 6 is formed so as to cover the gate electrode 62.
3 are formed. A semiconductor thin film 64 is formed above the gate electrode 62 with a gate insulating film 63 interposed therebetween.
A channel protective layer 65 is formed on the central portion of the semiconductor thin film 64. A source electrode 66a made of an n ⁺ -silicon layer is formed on the source side of the channel protective layer 65 and the semiconductor thin film 64, and a drain electrode 66b also made of the n ⁺ -silicon layer is formed on the drain side.

A metal layer 67a serving as a source wiring is connected to the source electrode 66a.
A metal layer 67b serving as a drain wiring is connected to 6b. The surface of the TFT 52 is covered with an interlayer insulating film 68, on which a transparent conductive film serving as the pixel electrode 51 is formed. The pixel electrode 51 is connected via a contact hole 69 to a metal layer 67b serving as a drain wiring of the TFT 52. Although not shown, an alignment film for aligning liquid crystal is formed on the entire surface including the periphery of the pixel electrode 51.

As described above, the scanning lines 53 and the signal lines 5
4 and the transparent conductive film serving as the pixel electrode 51, the interlayer insulating film 68 is formed.
Can be laminated. Such a structure is disclosed in, for example, Japanese Patent Application Laid-Open No. 58-172687.
Thus, the aperture ratio of the pixels in the liquid crystal display device can be improved, and the electric field caused by the signal lines 54 and the like can be shielded by the interlayer insulating film 68 to suppress the alignment defect (disclination) of the liquid crystal.

Conventionally, the interlayer insulating film 68 is made of Si
An inorganic thin film such as N is used. The SiN film is
For example, by using a CVD method,
m.

Here, the liquid crystal molecules used as the liquid crystal layer have a refractive index anisotropy Δn. Further, the liquid crystal molecules are applied to a substrate (an active matrix substrate and a counter substrate) sandwiching the liquid crystal molecules. Since the liquid crystal molecules may be tilted and aligned, the contrast of the displayed image changes depending on the viewing direction and angle of the viewer, causing a problem that the viewing angle dependency increases.

With respect to the above problem, a twisted nematic (TN) liquid crystal display system which is often used in a nematic liquid crystal display device will be described. For example, as shown in FIG. 10, when a halftone display voltage is applied to the TN type liquid crystal display element 71,
The liquid crystal molecules 72 slightly rise. At this time, in the liquid crystal display element 71, linearly polarized light 75 passing through the normal direction of the surfaces of the substrates 73 and 74, and linearly polarized light 76 and 77 passing at an inclination to the normal direction are:
The angles at which the liquid crystal molecules 72 intersect will be different. The liquid crystal molecules 72 have a refractive index anisotropy Δn as described above.
Is present, the linearly polarized light 75, 76,
When 77 passes through the liquid crystal molecules 72, normal light and extraordinary light are generated. With the phase difference between the normal light and the extraordinary light, the linearly polarized lights 75, 76, and 77 are converted into elliptically polarized light, respectively, which is a source of viewing angle dependence.

Further, inside the actual liquid crystal layer, the liquid crystal molecules 72 are located near the intermediate portion between the substrates 73 and 74 and the substrate 7.
3 and the vicinity of the substrate 74 have different tilt angles, and the liquid crystal molecules 72 are twisted by 90 ° about the normal direction. As described above, the linearly polarized lights 75, 76, and 77 passing through the liquid crystal layer receive various birefringence effects depending on their directions and angles, and exhibit complicated viewing angle dependence.

As the above-mentioned viewing angle dependency, specifically, a phenomenon in which a display image is colored at a certain angle or more when the viewing angle is inclined from the normal direction of the screen to the normal viewing angle direction, which is the downward direction of the screen (hereinafter, referred to as the following). A phenomenon called “coloring phenomenon”) and a phenomenon in which black and white are reversed (hereinafter, referred to as “reversal phenomenon”) occur. Further, when the viewing angle is inclined in the opposite viewing angle direction, which is the upper direction of the screen, the contrast sharply decreases.

In addition, the above liquid crystal display device has a problem that the viewing angle becomes narrower as the display screen becomes larger. When a large liquid crystal display screen is viewed from the front at a short distance, colors displayed at the top and bottom of the screen may be different due to the effect of viewing angle dependence. This is because the viewing angle of the entire screen is increased, which is the same as viewing the liquid crystal display screen from a more oblique direction.

In order to improve such viewing angle dependency,
It has been proposed to insert a retardation film (retardation film) as an optical element having optical anisotropy between a liquid crystal display element and one polarizing plate (for example, see Japanese Patent Application Laid-Open No. 55-0 / 55).
00600, JP-A-56-0907318, etc.).

According to this method, the light converted from the linearly polarized light into the elliptically polarized light as described above is passed through a retardation plate interposed on one side or both sides of the liquid crystal layer, whereby the normal light and the extraordinary light generated at the viewing angle are obtained. Is compensated and reconverted into linearly polarized light to improve the viewing angle dependency.
Therefore, in this method, it is necessary to set not only the characteristics of the liquid crystal layer, that is, the liquid crystal display element but also the retardation plate.

Therefore, in order to further improve the viewing angle dependency, one retardation plate whose principal refractive index direction in the refractive index ellipsoid is parallel to the normal direction of the surface of the retardation plate is used as the retardation plate. On the other hand, the value of retardation Δn · d, which is the product of the refractive index anisotropy Δn of the liquid crystal material and the thickness d of the liquid crystal layer, is 2 as a liquid crystal display element.
A liquid crystal display device having a configuration in the range of 00 nm to 500 nm and interposing the above-mentioned retardation plate between the liquid crystal display element and the polarizing plate has been proposed (JP-A-5-313159). .

This method not only sets the characteristics of the phase difference plate and the liquid crystal display element, but also sets the rubbing direction of the alignment film forming the liquid crystal display element, the slow axis direction of the phase difference plate, and the transmission axis of the polarizing plate. Are set to be parallel to each other, thereby making it possible to further improve the viewing angle dependency.

Further, there has been proposed a method using a retardation plate in which the main refractive index direction of the refractive index ellipsoid is inclined with respect to the normal direction of the surface of the retardation plate (Japanese Patent Application Laid-Open No. Hei 6-1994). -75116). In this method, the following two types of retardation plates are used.

One is that, among the three main refractive indices of the refractive index ellipsoid, the direction of the minimum main refractive index is parallel to the surface, and one of the remaining two main refractive indices is the phase difference. Is inclined at an angle of θ with respect to the surface of the plate, and the other direction is also inclined at an angle of θ with respect to the normal direction of the surface of the retardation plate. This is a retardation plate satisfying °.

The other is that there is no refractive index anisotropy in the surface of the phase difference plate, and the main refractive index nb in the surface normal direction of the phase difference plate and the main refractive index na parallel to the surface of the phase difference plate. nc is
satisfies the relationship of na = nc> nb, that is, it has a negative uniaxial property, and further has one of the main refractive indices na and nc parallel to the above-mentioned retardation plate surface as an axis,
By rotating the main refractive index nb clockwise or counterclockwise from a state parallel to the surface of the retardation plate in a direction parallel to the normal direction to an inclined state, the refractive index ellipsoid is an inclined retardation plate. .

Regarding the above two types of retardation plates, the former can be a uniaxial one and a biaxial one, respectively. In the latter, not only one retardation plate is used, but also two retardation plates are combined, and the inclination direction of each of the main refractive indices nb in the normal direction of the surface of the retardation plate is set to an angle of 90 ° with each other. What is set so as to be used can be used.

In a liquid crystal display device comprising at least one such phase difference plate between a liquid crystal display element and a polarizing plate, the viewing angle dependency can be improved to some extent.

[0026]

However, according to the method disclosed in Japanese Patent Application Laid-Open No. 58-172885, the interlayer insulating film 68 is not provided.
As transparent insulating films of SiN _x , SiO ₂ , TaO
_{When X} or the like is formed by a CVD method or a sputtering method,
Underlying metal layers 67a and 67b and channel protection layer 65
Such irregularities on the surface will be reflected on the interlayer insulating film 68. Therefore, the pixel electrodes 51 are connected to the interlayer insulating film 68.
When formed on the upper surface, a larger step is formed based on the steps of various films serving as bases, which causes a problem of causing poor alignment (disclination) of liquid crystal molecules.

In the case where an organic film such as polyimide is applied to flatten a portion to be a pixel portion, the pixel electrode 51 is electrically connected to the drain electrode 66b. It is necessary to add a step of forming a contact hole. Specifically, an organic film such as polyimide is photo-patterned using a mask material, a contact hole is processed by etching, and finally, a step of removing unnecessary photoresist is added. There is a need.

In addition, in order to shorten the etching and stripping steps, a method of using a photosensitive polyimide film can be considered. In this case, the resin after forming the interlayer insulating film 68 looks colored. Will be. For this reason, in a liquid crystal display device requiring high translucency and transparency, there is a problem that it cannot be used as the interlayer insulating film 68.

Further, in the above-mentioned conventional method, by forming the interlayer insulating film 68, the scanning lines 53 and the signal lines 5 are formed.
When the aperture ratio of the liquid crystal display device is improved by laminating the pixel electrodes 51 on the scanning lines 53 and the signal lines 5.
4 and the pixel electrodes 51 are increased.

Specifically, an inorganic thin film such as a SiN film has a high relative dielectric constant of 8, and a film thickness of about 500 nm for forming the inorganic thin film using a CVD method. The scanning lines 53, the signal lines 54, and the pixel electrodes 5
The electric capacity between 1 and 2 will be greatly increased. For this reason, the following problems are caused.

When the signal lines 54 and the pixel electrodes 51 are laminated, the signal lines 54 and the pixel electrodes 51 are formed.
Is increased, the signal transmittance increases. For this reason, the data signal held in the pixel electrodes 51 during the signal holding period is subject to swing due to the potential of the data signal. For this reason, when the pixel electrodes 51 apply a voltage to the liquid crystal, the effective value (effective voltage) of the voltage fluctuates. However, there is a problem that vertical crosstalk is caused.

The signal lines 54 and the pixel electrodes 51 are formed.
For example, Japanese Patent Application Laid-Open No. 6-230422 discloses a method for reducing the influence of the electric capacitance between the data signal and the display signal on the display screen by inverting the polarity of a data signal input to a corresponding pixel for each signal line. There has been proposed a driving method for performing the above. This driving method can provide an effective effect for a liquid crystal display device having a high correlation between the display of adjacent pixels, for example, a liquid crystal display device for displaying black and white.

However, in a liquid crystal display device in which pixel electrodes are arranged in the form of vertical stripes, such as a normal notebook personal computer, adjacent pixels connected to one signal line 54 have different display colors. Will be different. In particular, in the case of performing color display, for example, three pixel electrodes 51 corresponding to three colors of red (R), green (G), and blue (B) are provided in an area of one pixel having a square shape. Are arranged in this order in a vertically long rectangular shape (the arrangement of the pixel electrodes 51 is hereinafter referred to as a vertical stripe shape).

In the case of a general color display having such an arrangement of pixels in the form of vertical stripes, if the drive for inverting the polarity of each signal line 54 is performed, the effect of reducing the vertical crosstalk is obtained. Will be insufficient.

When the scanning lines 53 and the pixel electrodes 51 are laminated, the scanning lines 53 and the pixel electrodes 51 are stacked.
, There is a problem that the field-through of the writing voltage to the pixel electrode 51 due to the switching signal for controlling the TFTs 52 increases.

The thickness of the inorganic thin film is set to 500 nm.
By forming a film having the above thickness, an increase in electric capacity can be suppressed. However, increasing the thickness of the inorganic thin film causes a problem that it takes too much time in the manufacturing process.

In the method disclosed in Japanese Patent Laid-Open No. Hei 5-313159, the viewing angle dependency of the display screen can be improved in a certain specific direction, but it cannot be improved in all directions. The problem has arisen.

Further, in the method disclosed in JP-A-6-75116, as described above, the conditions of the retardation plate are set so that the refractive index ellipsoid is inclined. On the other hand, as for the liquid crystal display element, as an example, a liquid crystal display element in which the refractive index anisotropy Δn of the liquid crystal material is 0.08 and the thickness d of the liquid crystal layer is 4.5 μm, that is, the retardation Δn of the liquid crystal layer It indicates that a liquid crystal display element having a value of d of 360 nm is used. But,
No further mention is made as to what conditions should be provided between the liquid crystal display element and the polarizing plate to interpose the retardation plate.

In the method of improving the viewing angle dependency by interposing a retardation plate between the liquid crystal display element and the polarizing plate,
It is necessary to set not only the phase difference plate but also the characteristics of the liquid crystal display element. Therefore, in the case of the above method, the above-mentioned retardation plate in order to most effectively compensate for the retardation,
It is not clear what range the value of Δn · d should be combined with the liquid crystal display element. for that reason,
Improving the viewing angle dependence of the liquid crystal display device using the above retardation plate has a problem that it is still insufficient.

The present invention solves the above-mentioned conventional problems, and aims at improving the aperture ratio of the liquid crystal display and suppressing the liquid crystal alignment defect (disclination) by overlapping a flat pixel electrode with each wiring. And a good display can be obtained by further reducing the influence of the crosstalk and the like on the display due to the capacitance component between each wiring and the pixel electrode, and a good display can be obtained. Improves coloring and reversal phenomena, high brightness, low power consumption, high definition and excellent color reproducibility, vivid image quality, especially
It is an object of the present invention to provide a liquid crystal display device that realizes image quality of a vivid color similar to that of a CRT centered on white and red in a wide viewing angle region of a viewing angle of 70 ° or more.

[0041]

According to a first aspect of the present invention, there is provided a liquid crystal display device, comprising: a counter substrate including a common electrode and a plurality of color filters; a scanning line and a signal line; A switching element provided in the vicinity of the intersection of the scanning line and the signal line, and a pixel electrode connected to the switching element. The switching element includes a gate electrode connected to the scanning line, A source electrode connected to the pixel line, and a drain electrode connected to the pixel electrode; a wavelength band of the color of the color filter emitted from the light source above the scanning line, the signal line, and the switching element; A pixel including a structure in which an interlayer insulating film made of an organic film having a transmittance of light having a peak wavelength in the vicinity of about 95% or more is provided, and the pixel electrode is provided on the interlayer insulating film; And a difference Δn (450) between the refractive index anisotropy Δn (450) for light having a wavelength of 450 nm and the refractive index anisotropy Δn (650) for light having a wavelength of 650 nm. ) −Δn (65
0) is a liquid crystal layer composed of liquid crystal set to a range of 0 or more and 0.01 or less, a liquid crystal display element having at least the counter substrate, the pixel substrate, and the liquid crystal layer, and disposed on both sides of the liquid crystal display element A pair of polarizers, and at least one retardation plate interposed between the liquid crystal display element and the polarizer, and at least in the representative layer, three main refractive indices na of an index ellipsoid, nb and nc are na = nc>
nb, one of the main refractive indices na and nc is parallel to the surface of the phase difference plate, and the main refractive index nb is set to the surface of the phase difference plate with the direction of the parallel main refractive index as the axis. By rotating clockwise or counterclockwise from a state parallel to the normal direction to an inclined state, the refractive index ellipsoid is provided with an inclined retardation plate.

According to the structure of the first aspect, when the wiring and the pixel electrode are laminated by the interlayer insulating film and the aperture ratio is improved, the interlayer insulating film made of an organic material is formed. In addition, a portion to be a pixel portion can be further flattened. For this reason, poor alignment (disclination) of the liquid crystal can be suppressed. Further, since the interlayer insulating film has a lower relative dielectric constant than the conventional inorganic thin film, the electric capacity between the wiring and the pixel electrode is reduced, and the signal transmittance is also suppressed. Therefore, the influence of the electric capacitance between the wiring and the pixel electrode on the display, such as crosstalk, can be further reduced, and the field through of the writing voltage to the pixel electrode can be reduced. In addition, since the above-mentioned interlayer insulating film can obtain a high-quality and highly transparent film with high productivity, it is possible to increase the film thickness and reduce an increase in electric capacity.

The interlayer insulating film has high transparency,
The transmittance of light having a peak wavelength when the light source transmits through the color filter is 95% or more. Therefore, light from the light source can be used efficiently (ie, with low power consumption). For this reason, even if the light amount of the light source is slightly reduced and the power consumption is low, it is possible to obtain a display with high brightness and a bright appearance, and it is possible to obtain a liquid crystal display device which is a display screen with a better, brighter and beautiful color. .

Here, optical elements such as a retardation plate and a polarizing plate usually have a problem that the refractive index anisotropy with respect to the wavelength of light is different. For example, many of those currently used as retardation plates have a refractive index anisotropy of:
It is small on the short wavelength side and large on the high wavelength side. However, by using a liquid crystal having a small difference between the refractive index anisotropy on the short wavelength side and the refractive index anisotropy on the high wavelength side in combination with the retardation plate, normal light and extraordinary light generated according to the viewing angle are used. Can be more effectively compensated than before.

In particular, in the present invention, it is possible to convert elliptically polarized light into linearly polarized light in a wide range of viewing angles by using the above-described combination of the liquid crystal and the phase difference plate. That is, by the combination of the liquid crystal and the retardation plate described above, it is possible to eliminate the coloring phenomenon and the reversal phenomenon due to a change in the viewing angle at a viewing angle of about 70 ° as a limit value. For this reason, the viewing angle dependency can be reduced as compared with the conventional liquid crystal display device, and the image quality of the CRT display device is comparable to that of the conventional liquid crystal display device. A device can be obtained.

The liquid crystal display device according to claim 2 of the present invention is
In order to solve the above problems, in addition to the configuration of the above claim 1, further comprising a connection electrode connecting the pixel electrode and the drain electrode, the switching element, the scanning line, the signal line and the The interlayer insulating film is provided on the connection electrode, and the pixel electrode is provided on the interlayer insulating film,
At least one of the scanning line and the signal line is provided so as to partially overlap, and the connection electrode and the pixel electrode are connected via a contact hole penetrating the interlayer insulating film. I have.

According to the configuration of the second aspect, when the pixel electrode is connected to the drain electrode of the switching element via the connection electrode, even if the switching element is small,
A contact hole having smooth side walls without irregularities can be formed. Further, by embedding a conductive material in the interlayer insulating film, the connection electrode can be easily formed with little disconnection and high yield.

Further, when the connection electrode is formed as a transparent conductive film that is planarly overlapped with the pixel electrode via an interlayer insulating film, the aperture ratio of the pixel can be further improved.

The liquid crystal display device according to claim 3 of the present invention is
In order to solve the above-described problem, in addition to the configuration of the above-described claim 2, the semiconductor device has an additional capacitor for holding a voltage applied to the liquid crystal layer, and the contact hole is connected to the additional capacitor. Or the scanning line.

According to the third aspect of the present invention, the alignment of the liquid crystal is disturbed by providing the contact hole above the light-shielding portion, for example, the light-shielding wiring connected to the additional capacitance, or the scanning line. Since the light leakage due to the light leakage can be hidden, the contrast of the display screen does not decrease. In addition, since the contact hole can be formed on the same substrate, the positional accuracy of the light shielding material and the contact hole is improved, and the aperture ratio of the pixel can be further improved. Therefore, a liquid crystal display device having a bright and low power consumption display screen can be obtained.

A liquid crystal display device according to a fourth aspect of the present invention is:
In order to solve the above-mentioned problem, in addition to the configuration according to claim 1, a refractive index anisotropy Δn (435) for light having a wavelength of 435 nm and a refractive index anisotropy Δn for light having a wavelength of 610 nm are provided. (610) difference Δn (435) −Δ
It is characterized by using a liquid crystal in which n (610) is set in a range of 0.00875 or less.

According to the configuration of the fourth aspect, since the light transmission between the liquid crystal layer and the color filter is balanced, light can be efficiently used (low power consumption).
In addition, it is possible to obtain a liquid crystal display device with improved display quality, in which coloring when viewed from an oblique direction is further improved.

The liquid crystal display device according to the fifth aspect of the present invention provides:
In order to solve the above problem, in addition to the configuration according to any one of claims 1 to 4, the color filter may further include a transmittance of light having at least one peak wavelength in light incident through a pixel substrate. Is 85% or more.

According to the above configuration, it is possible to obtain a liquid crystal display device in which light can be more efficiently used (low power consumption) and display quality is further improved.

A liquid crystal display device according to a sixth aspect of the present invention comprises:
In order to solve the above problems, in addition to the configuration according to any one of claims 1 to 5, the retardation plate includes a layer made of a compound having a discotic structural unit, and the discotic It is characterized in that the inclination angle between the disk surface of the structural unit and the surface of the phase difference plate changes continuously or discontinuously in the depth direction of the phase difference plate.

According to the structure of the sixth aspect, the retardation plate can be easily manufactured at a low cost by the coating method, as compared with a conventional manufacturing method such as a stretch manufacturing method type, and at the same time, the size can be increased. Even with this, it is possible to obtain a retardation plate with little variation in quality. For this reason, a liquid crystal display device having a large display screen on which a viewing angle difference is easily recognized on a display screen, especially a liquid crystal display device having a screen size of 20 ″ or more to about 40 ″, is a display screen of high quality display. Can be realized.

At this time, the inclination angle of the optically anisotropic axis of the phase difference plate can be easily changed in the thickness direction of the phase difference plate by appropriately selecting the orientation treatment and material of the base. For this reason, it is easy to optimize the characteristic matching between the liquid crystal display element and the retardation plate. In addition, it is possible to easily obtain an optimal structure of the retardation plate according to the characteristics such as the refractive index of the liquid crystal layer on the inner side (liquid crystal side) and the outer side (atmosphere side) of the liquid crystal display element.

A liquid crystal display device according to a seventh aspect of the present invention comprises:
In order to solve the above problem, in addition to the configuration described in claim 6, the average value of the inclination angle is 15 ° to 75 °.

According to the configuration of the seventh aspect, the effects of the retardation plate and the liquid crystal are more reliably exhibited, and a liquid crystal display device with higher quality display can be obtained.

The liquid crystal display device according to claim 8 of the present invention provides
In order to solve the above problem, in addition to the configuration according to any one of claims 1 to 7, the liquid crystal display device has a configuration in which the liquid crystal of the liquid crystal layer is oriented in a 90 ° twisted state. And the display method is a normally white method.

According to the structure of the eighth aspect, the liquid crystal is oriented in a twisted state of 90 °, and the display contrast of the display screen and the color reproducibility are adopted by employing the normally white display method. , And a display screen with more improved viewing angle dependence. In particular, in the normally white mode, from the above viewpoint, it is possible to provide a display screen which is more excellent than the normally black mode, which is white, and which is whiter and clearer.

[0062]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. Note that the present invention is not limited by this.

As shown in FIG. 1A, the liquid crystal display device 1 of the present invention has a liquid crystal display element 5, a retardation plate 2a disposed on one side of the liquid crystal display element 5, and a liquid crystal display element 5 disposed on the other side. Retardation plate 2b to be formed, and a polarizing plate 3 as a pair of polarizers sandwiching the liquid crystal display element 5 and the retardation plates 2a and 2b.
・ 4.

The liquid crystal display element 5 has a structure in which a glass substrate 6 as a counter substrate and a glass substrate 7 as a pixel substrate are disposed between the glass substrate 6 and the glass substrate 7 as a pixel substrate.
The liquid crystal layer 12 is sealed by a sealing material 13.
On the surface of the glass substrate 6, a transparent electrode layer 8 as a common electrode made of ITO (indium tin oxide) and the like, and an alignment film 1 made of polyimide, polyvinyl alcohol, etc.
0 and a plurality of color filters that are divided and arranged for each pixel (not shown).

Similarly, the surface of the glass substrate 7 is
And a plurality of transparent electrode layers 9 as pixel electrodes, and an alignment film 11 made of polyimide or the like.
The transparent electrode layers 9 are usually arranged in units of several hundreds, and are formed at positions corresponding to the plurality of color filters.

As the glass substrates 6 and 7, non-alkali glass is used. As the liquid crystal used for the liquid crystal layer 12, a nematic liquid crystal is used in the present embodiment. As the sealing material 13, a thermosetting resin, an ultraviolet curable resin, or the like is used. Note that the above members are not limited to these.

The liquid crystal display device 1 has a transparent electrode layer 9.
, A light source 14 having an elongated cylindrical shape and a light guide 15 for guiding light emitted from the light source 14 to the liquid crystal display element 5 are arranged at a position on the back side when viewed from the side. I have. The light source 14 and the light guide 15 form one backlight unit, and the backlight unit irradiates the light from the light source 14 onto the entire surface of the liquid crystal display device 1 corresponding to the display screen. Can be.

The surfaces of the alignment films 10 and 11 have been rubbed in advance so that the intervening liquid crystal molecules are twisted at about 90 °. Specifically, as shown in FIG. 3, in the case of the alignment film 10 on the glass substrate 6 in the liquid crystal display element 5, the rubbing treatment is performed so as to be in the direction of the arrow 21. Upper alignment film 1
In the case of 1, the rubbing process is performed so as to be in the direction of arrow 22 orthogonal to arrow 21. In addition,
Arrows 21 and 22 are hereinafter referred to as a rubbing direction 21 and a rubbing direction 22.

In the liquid crystal display device 1 of the present invention, as shown in FIG. 4, the polarizing plates 3 and 4 are arranged so that their absorption axes 23 and 24 are orthogonal to each other. Therefore, when no voltage is applied to the liquid crystal layer 12 of the liquid crystal display element 5,
The liquid crystal display device 1 is of a normally white display type in which the liquid crystal layer 12 transmits light to perform white display. At this time, the absorption axis 23 of the polarizing plate 3 and the rubbing direction 21 of the alignment film 10 are set to be parallel to each other. Similarly, the absorption axis 24 of the polarizing plate 4 and the rubbing direction 22 of the alignment film 11 are also set to be parallel to each other.

Here, in the phase difference plates 2a and 2b, the direction of the main refractive index nb inclined in a direction for giving anisotropy to the phase difference plates 2a and 2b is projected on the surfaces of the phase difference plates 2a and 2b. Are defined as 25a and 25b, respectively.
At this time, in the liquid crystal display device 1, as shown in FIG. 4, the direction 25a of the retardation plate 2a and the rubbing direction 21
Are set so as to be parallel to each other and opposite to each other. Further, the direction 25b of the retardation plate 2b and the rubbing direction 22 are set so as to be parallel to each other and to be the same as each other.

The phase difference can be compensated if at least one of the phase difference plates 2a and 2b is interposed between any one of the polarizing plates 3 and 4. further,
Between the polarizing plate 3 and the liquid crystal display element 5, or between the polarizing plate 4 and the liquid crystal display element 5, the phase difference plate 2a or the phase difference plate 2
b may be interposed two or more. In addition, the liquid crystal display element 5
And retardation plates 2a and 2b between the polarizers 3 and 4,
Two or more sheets each may be interposed.

As shown in FIG. 2, the retardation plate 2a used in the liquid crystal display device 1 has at least three layers of refractive index ellipsoids in the representative layer or on the whole retardation plate 2a on average. When the refractive index na · nb · nc is na = n
c> nb, that is, a relationship where the refractive index anisotropy is negative. Thus, the retardation plate 2a has uniaxiality in which only one optical axis exists. Further, when an orthogonal coordinate system xyz in which the surface of the phase difference plate 2a is an xy plane is defined, the direction of the main refractive index nb is the direction of the arrow A with respect to the normal direction z axis of the surface of the phase difference plate 2a. At an angle θ.
Further, the main refractive index nc is also x parallel to the surface of the retardation plate 2a.
It is inclined at an angle θ in the direction of arrow B with respect to the axial direction.

That is, in the retardation plate 2a, the refractive index ellipsoid as a whole is formed with the direction of the main refractive index na as an axis.
It is in a state of being inclined at an angle θ counterclockwise. The inclination of the refractive index ellipsoid may be clockwise around the direction of the main refractive index na. Note that the phase difference plate 2b has the same configuration as that of the phase difference plate 2a, and a description thereof will be omitted.

In the present embodiment, as the retardation plates 2a and 2b, the inclination of the main refractive index nb whose angle θ is about 20 ° is used. At this time, the angle θ is also about 20 ° for the main refractive index nc. That is, the refractive index ellipsoid is inclined by 20 ° counterclockwise about the direction of the main refractive index na.

By setting different retardation values for the phase difference plates 2a and 2b, a phase difference compensation function can be reliably obtained. The retardation value includes a first retardation value and a second retardation value. The first retardation value includes a difference between a main refractive index nc and a main refractive index nb as a whole of the retardation plates 2a and 2b, and a difference between the retardation plates 2a and 2b. · 2b of the thickness d _f product (nc-
na) is an × d _f. In contrast, the second retardation value, the main refractive index and nc and the difference between the principal refractive index nb, a product of the phase difference plates 2a, 2b of the thickness _{d f (nc-nb) ×} d f
It is.

In this embodiment, as the retardation plates 2a and 2b, specifically, a discotic liquid crystal is applied to a transparent support (for example, triacetyl cellulose (TAC) or the like), and the discotic liquid crystal is tilted. Oriented ones having the first retardation value of 0 nm and the second retardation value of 100 nm are used.

The discotic liquid crystal obliquely aligned on the retardation plates 2a and 2b forms a layer with a discotic structure having a disc shape in liquid crystal molecules as one structural unit. In one unit of the discotic structure, the inclination angle between the disk surface and the surfaces of the phase difference plates 2a and 2b changes continuously or discontinuously in the depth direction of the phase difference plates 2a and 2b. At this time, it is preferable that the inclination angle has an average value of 15 ° to 75 °.

The formation of the discotic liquid crystal layer is as follows.
Since it can be formed by a coating method as compared with a conventional manufacturing method such as a stretch manufacturing method type, the retardation plate 2a.
2b can be easily manufactured at low cost. Further, since the manufacturing method is easy and the cost is low, the phase difference plates 2a and 2b can be made larger than conventional ones, and higher quality phase difference plates 2a and 2b can be obtained. .

Here, the conventional liquid crystal display device has a problem that the larger the display screen, the larger the difference between the left and right viewing angles on the display screen. In particular, on a display screen having a screen size of 20 ″ or more, the viewer moves the display screen from a position at a vertical distance of 50 cm from the display screen and a viewing angle of 70 ° or more with respect to the center of the display screen. When viewed, a remarkable coloring phenomenon was observed at the end far from the viewer.

However, in the retardation plate for forming the discotic liquid crystal as described above, in addition to the fact that the retardation plate can be increased in size, the variation in quality due to the increase in size is reduced. For this reason, higher quality phase difference plates 2a and 2b can be obtained. Therefore, in the liquid crystal display device of the present invention, a liquid crystal display device having a large display screen on which a viewing angle difference is easily recognized on a display screen, in particular, a home or business use, a monitor for OA has recently been demanded. Further, even with a liquid crystal display device whose screen size is being developed from 20 ″ or more to about 40 ″, a display screen of high quality display can be realized.

At this time, the inclination angles of the optically anisotropic axes in the phase difference plates 2a and 2b can be easily adjusted in the thickness direction of the phase difference plates 2a and 2b by appropriately selecting the orientation treatment of the base material and the material. Can change. For this reason, it is easy to optimize the characteristic matching between the liquid crystal display element 5 and the retardation plates 2a and 2b. In addition, the phase difference plates 2a and 2b
The optimum structure can be easily obtained according to the characteristics such as the refractive index of the liquid crystal layer 12 on the inner side (liquid crystal side) and the outer side (atmosphere side) of the liquid crystal display element 5.

When the above-mentioned retardation plates 2a and 2b were used for the liquid crystal display device 1 and the display screen was visually checked from the left, right, and upward directions of 50 °, no coloring or inversion was observed under any of the conditions. , Beautiful display was seen.

Further, as the above-mentioned retardation plates 2a and 2b,
A discotic liquid crystal is applied to a transparent support, and the discotic liquid crystal is hybrid-aligned. The first retardation value is 0 nm, and the second retardation value is 0 nm.
Was used in the liquid crystal display device 1 in the same manner as described above.

Also in this case, when the display screen of the liquid crystal display device 1 was visually checked from the left and right and from an upper direction of 50 ° to 70 °, coloring and inversion were not seen under any of the conditions, and a beautiful display was seen.

Since the phase difference between the normal light and the extraordinary light generated according to the viewing angle is compensated by using the above-mentioned retardation plates 2a and 2b, the light can be converted into linearly polarized light over a wide range of the viewing angle. Thus, the coloring phenomenon and the reversal phenomenon accompanying the change in the viewing angle can be eliminated, so that the liquid crystal display device 1 with little viewing angle dependence can be obtained.

In the liquid crystal display device 1 of the present invention, the liquid crystal layer 12 together with the phase difference plates 2a and 2b serves as a liquid crystal layer having a wavelength of 450 nm.
Anisotropy of refractive index Δn (450) for light of m and wavelength 65
Difference Δ of refractive index anisotropy Δn (650) for light of 0 nm
It is preferable to use a liquid crystal in which n (450) -Δn (650) is set in a range of 0 or more and 0.01 or less (hereinafter, conditioned on these setting conditions).

Further, in addition to the above conditions, the wavelength 435
index anisotropy Δn (435) for light of nm and wavelength 6
A liquid crystal in which the difference Δn (435) −Δn (610) of the refractive index anisotropy Δn (610) with respect to the light of 10 nm is set in the range of 0.00875 or less (hereinafter, the setting condition is a condition). It is more preferable to use.

In the optical elements such as the retardation plates 2a and 2b and the polarizers 3 and 4, the refractive index anisotropy with respect to the wavelength of light is usually different in each part of the optical element. For example, the refractive index anisotropy of many of the retarders currently used as the retardation plates 2a and 2b is small on the short wavelength side and large on the high wavelength side. Therefore, by using a liquid crystal having a small difference between the refractive index anisotropy on the short wavelength side and the refractive index anisotropy on the high wavelength side in combination with the retardation plates 2a and 2b, the normal light generated according to the viewing angle is used. And the phase difference between the extraordinary light and the extraordinary light can be more effectively compensated than in the related art.

In particular, in the present invention, by using the liquid crystal layer 12 and the retardation plates 2a and 2b in the above-described combination, even if the viewer views the display screen with the viewing angle further greatly inclined. That is, even if the viewing angle is in a wider range, it becomes possible to convert elliptically polarized light to linearly polarized light,
It is possible to obtain the liquid crystal display device 1 having a display screen with less dependence on the viewing angle with improved coloring and reversal phenomena.

In the present embodiment, specifically, the liquid crystal layer 1
2, the refractive index anisotropy Δ for light having a wavelength of 550 nm.
n (550) is 0.070, 0.080 and 0.09
5 is used. Each of the above liquid crystal materials is capable of obtaining the above conditions and the liquid crystal layer 12 satisfying the conditions. At this time,
The cell thickness of the liquid crystal display element 5 is set to about 5 μm.

By combining the liquid crystal layer 12 using the above liquid crystal and the phase difference plates 2a and 2b, the coloring and reversal phenomena accompanying the change of the viewing angle in the liquid crystal display element 5 are limited to a viewing angle of about 70 °. Can be confirmed by visual inspection. For this reason, the viewing angle dependency can be reduced as compared with the conventional liquid crystal display device, and the liquid crystal display has a color display that is not inferior to the image quality of the CRT display device, particularly, a bright white and red color even in a wide viewing angle region of about 70 ° or more. A display device can be obtained.

In the configuration shown in FIG. 4, in the liquid crystal layer 12, the liquid crystal is oriented in a state of being twisted by 90 °. In addition, since a normally white display method is employed, display contrast, color reproducibility, and viewing angle dependency of a display screen can be further improved. In particular, the normally white method is preferable to the normally black method because a clearer display screen can be obtained in which white is more white.

Next, the structure of the pixel substrate used in the liquid crystal display device 1 of the present invention will be described below. The glass substrate 7 used as a pixel substrate in the liquid crystal display element 5 of the present invention has a plurality of TFTs 31 as switching elements on the glass substrate 7 as shown in FIG.
. Are formed, and a plurality of transparent electrode layers (pixel electrodes) 9 are further formed thereon (note that
In FIG. 6, only one TFT 31 is shown, and as the pixel electrode 9, the pixel electrode 9a and the pixel electrode 9b are shown).

More specifically, one TFT 31 for controlling the pixel electrode 9a is provided above a gate electrode 32 formed on the glass substrate 7 via a gate insulating film 33 formed so as to cover the same. The semiconductor thin film includes a formed semiconductor thin film, a source electrode formed on a source portion of the semiconductor thin film, and a drain electrode formed on a drain portion of the semiconductor thin film.

The signal line 37 a is connected to the source electrode 35 of the TFT 31, and the pixel electrode 9 is connected to the drain electrode 36.
The connection electrode 38 to a is connected. These TFT3
1. An interlayer insulating film 40 is formed so as to cover the signal lines 37a and the connection electrodes 38. The connection electrode 38 is further connected to the pixel electrode 9a via the contact hole 39.

The interlayer insulating film 40 is made of an acrylic photosensitive resin or benzocyclobutene.
And a resin such as transparent photosensitive polyimide. These photosensitive resins have high transparency and excellent translucency. In the present embodiment, specifically, a positive photosensitive acrylic resin obtained by mixing a naphthoquinonediazide-based positive photosensitive material with a base polymer composed of a copolymer of methacrylic acid and glycidyl methacrylate is used as an interlayer. Used as the insulating film 40.

In the interlayer insulating film 40 using the above materials,
As shown in the graph 40a of FIG.
In the low wavelength region of nm to 540 nm, absorption due to coloring derived from the unreacted photosensitive material is observed. After developing the interlayer insulating film 40, a graph 40b of FIG.
As shown in the figure, by irradiating ultraviolet light such as i-ray (365 nm), absorption due to coloring observed in the graph 40a disappears, and transmission of light having a peak wavelength in light emitted from the light source 14 is performed. The transmittance becomes approximately 95% or more, and the interlayer insulating film 40 with further improved transmittance is obtained. For example, in the present embodiment, the peak spectrum of the blue light of the light from the light source 14 is 435 nm. At this time, the transmittance of the interlayer insulating film 40 is approximately 95%.

Therefore, the light from the light source 14 can be used efficiently (ie, with low power consumption). For this reason, even if the light amount of the light source 14 is slightly reduced and the power consumption is low, it is possible to obtain a display with high brightness and a bright appearance, and to obtain the liquid crystal display device 1 which is a display screen with a better, brighter and beautiful color. Can be.

In addition, as shown in FIG. 6, the pixel electrode 9a is partially laminated on the signal line 37b connected to the TFT 31 (not shown) in the adjacent pixel electrode 9 (not shown in FIG. 6). The pixel electrode 9b is partially laminated on the signal line 37a for inputting an image signal to the pixel electrode 9a (FIG. 6).
In the following, the laminated portion is indicated as C ′). Further, as shown in FIG. 1B, the interlayer insulating film 40 has a planar region including the gate electrode 32 and the additional capacitance 41 as a lower region, and a planar region including the pixel electrode 9 as a lower layer. Each region can be partially laminated as an upper layer region (FIG. 1).
In (b), the layered portion of the gate electrode 32 is indicated as D, and the layered portion of the additional capacitance 41 is indicated as E).

As a result, the aperture ratio of the pixel can be further improved. In addition, since a portion serving as a pixel portion can be flattened as compared with the case where an inorganic thin film is formed, defective orientation of liquid crystal can be suppressed, and the inclination of the liquid crystal can be controlled more uniformly than in the conventional case, and multi-gradation display can be performed. Therefore, the color sensation of the viewer on the display screen can be further improved.

Further, since the relative dielectric constant is lower than that of the conventional inorganic thin film, the signal line 37, the gate electrode 32 and the pixel electrode 9 can be formed by using the interlayer insulating film 40.
Is reduced, and the signal transmittance is also suppressed. For this reason, the influence of the electric capacity on the display screen, such as crosstalk, can be further reduced, and the field-through of the writing voltage to the pixel electrode 9 can be reduced.
In addition, since the interlayer insulating film 40 can obtain a high-quality and highly transparent film with high productivity, it is possible to increase the film thickness and further reduce an increase in electric capacity.

In FIG. 6, the drain electrode 36 and the pixel electrode 9a are connected near the TFT 31, but the connection electrode 38 is connected to the adjacent gate electrode 32 and the additional capacitance 41 (not shown in FIG. 6). May be formed to extend to the upper part of the upper part. Alternatively, the gate electrode 32 may be connected to the pixel electrode 9a by forming a contact hole at the tip of the extension. The connection electrode 38 may be made of the same material as the drain electrode 36 or may be made of a different material. The material of the connection electrode 38 can be easily selected from the structure of the glass substrate 7, the manufacturing process, the restrictions on the manufacturing line, and the like.

By using the above-mentioned connection electrode 38, even when the TFT 31 is small, a contact hole 39 having a smooth side wall without unevenness can be formed.
In addition, the connection electrode 38 can be easily formed with little disconnection and high yield by embedding a conductive material inside the interlayer insulating film 40.

Although not shown, the connection electrode 38
In the case where the extension is formed as described above, in particular, it may be formed as a transparent conductive film that is planarly overlapped with the pixel electrode 9 with the interlayer insulating film 40 interposed therebetween. By forming the connection electrode 38 in this manner, the aperture ratio of the pixel can be further improved.

As shown in FIG. 6, the contact hole 39 is provided on the light-shielding connection electrode 38 or on a light-shielding wiring connected to an additional capacitor (not shown). In this manner, by providing the contact hole 39 on a light-shielding portion such as a light-shielding wiring, light leakage due to disorder in alignment of liquid crystal can be hidden. For this reason,
No reduction in contrast occurs in the obtained display screen. In addition, since the contact hole 39 can be formed on the same glass substrate 7 as the light shielding portion, the positional accuracy between the light shielding portion and the contact hole 39 can be improved. Therefore, the aperture ratio of the pixel can be further improved.

The light source 14 used in this embodiment is
As shown in FIG. 7A, light having peak spectra in three colors of blue (B), green (G), and red (R) is irradiated. The light from the light source 14 passes through the above-described interlayer insulating film 40 and reaches the plurality of pixel electrodes 9,
Further, the light passes through a color filter formed thereon. The color filters used in this embodiment are shown in FIG.
As shown in FIG. 7B, the light having the spectrum shown in FIG. 7A is transmitted with a higher transmittance than the conventional color filter.

Specifically, the graph shown by the solid line in FIG. 7B shows the transmittance of the conventional dyed color filter 42b.
The graph shown by the broken line is the transmittance of the high-transmission color filter 42a used in the present embodiment. The high transmission color filter 42a has a higher overall transmittance than the conventional color filter 42b,
In particular, the peak value of red light shows a transmittance of 85% or more. In addition, the interlayer insulating film 40
Also, since the light transmittance is high as described above, bright colors can be displayed, and the light from the light source 14 can be used efficiently. For this reason, it is possible to obtain a display with higher brightness and a bright appearance, and to obtain the liquid crystal display device 1 which is a display screen with better, brighter, and beautiful colors.

As described above, the liquid crystal display device of the present invention has the following features.
Since each of the above-described configurations is provided, visual dependency on the display screen can be further improved, and adverse effects on the display screen due to the structure of the pixel substrate can be further suppressed. Therefore, the liquid crystal display device of the present invention can be suitably used in a wide range of fields as a display such as a word processor, a computer, and a navigation system in order to enable a display comparable to a CRT.

[0109]

As described above, according to the liquid crystal display device of the first aspect of the present invention, the counter substrate including the common electrode and the plurality of color filters, the scanning line and the signal line, and the intersection of the scanning line and the signal line are provided. A switching element provided in the vicinity of the portion, and a pixel electrode connected to the switching element,
The switching element has a gate electrode connected to the scanning line, a source electrode connected to the signal line, and a drain electrode connected to the pixel electrode. An interlayer insulating film made of an organic film emitted from a light source and having a transmittance of light having a peak wavelength near 95% or more in the vicinity of the color wavelength band of the color filter is provided on the element. A pixel substrate including a structure in which the pixel electrode is provided,
Interposed between the opposing substrate and the pixel substrate, a wavelength of 450 n
Anisotropy of refractive index Δn (450) for light of m and wavelength 65
Difference Δ of refractive index anisotropy Δn (650) for light of 0 nm
a liquid crystal layer comprising a liquid crystal in which n (450) -Δn (650) is set in a range of 0 or more and 0.01 or less; a liquid crystal display element having at least the counter substrate, the pixel substrate, and the liquid crystal layer; A pair of polarizers disposed on both sides of the liquid crystal display element, and a retardation plate interposed between the liquid crystal display element and the polarizer, at least one of which is provided. Three principal refractive indices na, n
b and nc have a relationship of na = nc> nb, and one of the main refractive indices na and nc is parallel to the surface of the phase difference plate, and the main refractive index is defined with the direction of the parallel main refractive index as an axis. By rotating the ratio nb clockwise or counterclockwise from a state parallel to the normal direction of the surface of the retardation plate to an inclined state, thereby providing a retardation plate in which the refractive index ellipsoid is inclined. Configuration.

Therefore, in the above configuration, when the wiring and the pixel electrode are stacked by the interlayer insulating film and the aperture ratio is improved, the pixel portion is formed by forming the interlayer insulating film made of an organic material. The part can be flattened more. For this reason, poor alignment (disclination) of the liquid crystal can be suppressed. Further, since the interlayer insulating film has a lower relative dielectric constant than the conventional inorganic thin film, the electric capacity between the wiring and the pixel electrode is reduced, and the signal transmittance is also suppressed. For this reason, the influence of the electric capacitance between the wiring and the pixel electrode on the display, such as crosstalk, is further reduced,
Field through of the write voltage to the pixel electrode can be reduced. In addition, since the interlayer insulating film can obtain a high-quality and highly transparent film with high productivity,
By increasing the film thickness, an increase in electric capacity can be reduced.

The interlayer insulating film has high transparency,
The transmittance of light having a peak wavelength when the light source transmits through the color filter is 95% or more. Therefore, light from the light source can be used efficiently (ie, with low power consumption). For this reason, even if the light amount of the light source is slightly reduced and the power consumption is low, it is possible to obtain a display with high brightness and a bright appearance, and it is possible to obtain a liquid crystal display device which is a display screen with a better, brighter and beautiful color. .

Further, in the present invention, by using the above-described combination of the liquid crystal and the retardation plate, it becomes possible to convert elliptically polarized light into linearly polarized light in a wide range of viewing angles. For this reason, the viewing angle dependency can be reduced as compared with the conventional liquid crystal display device, and the liquid crystal display device which is not inferior to the image quality of the CRT display device, and in particular, has a vivid white and red color even in a wide viewing angle region of 70 ° or more. It has the effect of being able to.

A liquid crystal display device according to a second aspect of the present invention is
As described above, in addition to the configuration according to claim 1, further comprising a connection electrode connecting the pixel electrode and the drain electrode, the switching element, the scanning line, the signal line, and an upper portion of the connection electrode. The interlayer insulating film is provided, and the pixel electrode is provided on the interlayer insulating film so as to partially overlap at least one of the scanning line and the signal line, and the connection electrode and the pixel electrode Is
The connection is made via a contact hole penetrating the interlayer insulating film.

Therefore, in the above configuration, when the pixel electrode is connected to the drain electrode of the switching element via the connection electrode, a contact hole having smooth side walls without unevenness can be formed even when the switching element is small. . Further, by embedding a conductive material in the interlayer insulating film, the connection electrode can be easily formed with little disconnection and high yield. Further, when the connection electrode is formed as a transparent conductive film which is planarly overlapped with the pixel electrode via an interlayer insulating film, there is an effect that the aperture ratio of the pixel can be further improved.

The liquid crystal display device according to the third aspect of the present invention provides:
As described above, in addition to the configuration of the above-described claim 2, it has an additional capacitance for holding a voltage applied to the liquid crystal layer,
The contact hole may be provided so as to be located above an electrode connected to the additional capacitance or the scanning line.

Therefore, in the above configuration, the contact hole is provided above the light-shielding portion, for example, the light-shielding wiring connected to the additional capacitance, or the scanning line.
Since light leakage due to disorder in the orientation of the liquid crystal can be hidden, the contrast of the display screen does not decrease. In addition, since the contact hole can be formed on the same substrate, the positional accuracy of the light shielding material and the contact hole is improved, so that the aperture ratio of the pixel can be further improved.
Therefore, there is an effect that a liquid crystal display device having a bright and low power consumption display screen can be obtained.

A liquid crystal display device according to a fourth aspect of the present invention is
As described above, in addition to the configuration according to claim 1, the refractive index anisotropy Δn with respect to light having a wavelength of 435 nm.
(435) and the difference Δn (435) −Δn (610) between the refractive index anisotropy Δn (610) for light having a wavelength of 610 nm.
However, the liquid crystal is set to a range of 0.00875 or less.

Therefore, in the above configuration, since the light transmission between the liquid crystal layer and the color filter is balanced, light can be efficiently used (low power consumption), and the color when viewed from an oblique direction can be improved. Is obtained, and a liquid crystal display device with improved display quality can be obtained.

A liquid crystal display device according to a fifth aspect of the present invention is
As described above, in addition to the configuration according to any one of claims 1 to 4, the color filter has a transmittance of at least one peak wavelength of light incident through the pixel substrate of 85% or more. The configuration is as follows.

Therefore, the above configuration has an effect that a liquid crystal display device with more efficient light utilization (low power consumption) and higher display quality can be obtained.

A liquid crystal display device according to a sixth aspect of the present invention comprises:
As described above, in addition to the configuration according to any one of claims 1 to 5, the retardation plate includes a layer made of a compound having a discotic structural unit, and a circle of the discotic structural unit. The tilt angle between the board surface and the surface of the phase difference plate changes continuously or discontinuously in the depth direction of the phase difference plate.

Therefore, in the above configuration, the retardation plate can be easily manufactured at low cost by the coating method as compared with the conventional manufacturing method such as the stretch manufacturing method type, and even if the size is large, the quality is not uniform. Can be obtained. For this reason, a liquid crystal display device having a large display screen on which a viewing angle difference is easily recognized on a display screen, especially a liquid crystal display device having a screen size of 20 ″ or more to about 40 ″, is a display screen of high quality display. Can be realized.

At this time, the inclination angle of the optically anisotropic axis in the phase difference plate can be easily changed in the thickness direction of the phase difference plate by appropriately selecting the orientation treatment and the material of the base. For this reason, it is easy to optimize the characteristic matching between the liquid crystal display element and the retardation plate. In addition, the retardation plate can easily obtain an optimal structure according to the properties such as the refractive index of the liquid crystal layer on the inner side (liquid crystal side) and the outer side (atmosphere side) of the liquid crystal display element. It works.

A liquid crystal display device according to a seventh aspect of the present invention comprises:
As described above, in addition to the configuration described in claim 6, the average value of the inclination angles is 15 ° to 75 °.

Therefore, in the above configuration, the effects of the phase difference plate and the liquid crystal are more reliably exhibited, and an effect is obtained that a liquid crystal display device with higher quality display can be obtained.

The liquid crystal display device according to the eighth aspect of the present invention,
As described above, in addition to the configuration according to any one of claims 1 to 7, the liquid crystal display device has a configuration in which the liquid crystal of the liquid crystal layer is 90%.
° The liquid crystal is oriented in a twisted state, and the display method is a normally white method.

Therefore, in the above configuration, the liquid crystal is oriented in a twisted state of 90 °, and the display method of the normally white mode is adopted, so that the display contrast, color reproducibility, and viewing angle dependency of the display screen are obtained. Can improve the display screen. In particular, in the normally white mode, from the viewpoint described above, there is an effect that a display screen which is more excellent in white than in the normally black mode and is whiter and clearer can be obtained.

[Brief description of the drawings]

FIG. 1A is an exploded cross-sectional view showing a partially simplified configuration of a liquid crystal display device according to an embodiment of the present invention;
(B) is an explanatory view showing a configuration of a pixel substrate in the liquid crystal display device of (a).

FIG. 2 is a perspective view showing a main refractive index of a retardation plate of the liquid crystal display device.

FIG. 3 is an explanatory diagram showing an alignment relationship between a rubbing direction of an alignment film and a normal viewing direction in the liquid crystal display device.

FIG. 4 is an exploded perspective view showing an optical arrangement of a polarizing plate and a retardation plate in the liquid crystal display device.

FIG. 5 is a graph showing light transmittance of an interlayer insulating film used in the liquid crystal display device.

FIG. 6 is a sectional view of a pixel substrate in the liquid crystal display device.

FIG. 7A is a graph showing a spectrum of light emitted from a light source used in the liquid crystal display device, and FIG.
3 is a graph showing transmission characteristics of two types of color filters used in the liquid crystal display device.

FIG. 8 is a circuit diagram showing a configuration of a conventional transmission type liquid crystal display device including an active matrix substrate.

FIG. 9 is a sectional view of a TFT portion of an active matrix substrate in a conventional liquid crystal display device.

FIG. 10 is a schematic diagram showing a twist alignment of liquid crystal molecules in a TN type liquid crystal display device.

[Explanation of symbols]

 Reference Signs List 1 liquid crystal display device 2a retardation plate 2b retardation plate 3 polarizing plate 4 polarizing plate 5 liquid crystal display element 7 glass substrate (pixel substrate) 9 transparent electrode layer (pixel electrode) 11 alignment film 12 liquid crystal layer 31 TFT 36 drain electrode 37 signal Line 38 connecting electrode 39 contact hole 40 interlayer insulating film

Claims (8)

[Claims] An opposing substrate including a common electrode and a plurality of color filters; a scanning line and a signal line; a switching element provided near an intersection of the scanning line and the signal line; and a switching element connected to the switching element. A pixel electrode; the switching element includes a gate electrode connected to the scan line, a source electrode connected to the signal line, and a drain electrode connected to the pixel electrode; An interlayer insulating film made of an organic film, which is emitted from a light source and has a transmittance of about 95% or more at a peak wavelength in the vicinity of the color wavelength band of the color filter, is provided above the line, the signal line, and the switching element. A pixel substrate including a structure in which the pixel electrode is provided on the interlayer insulating film; and a pixel substrate having a wavelength of 450 nm interposed between the counter substrate and the pixel substrate.
Anisotropy of refractive index Δn (450) for light of m and wavelength 65
Difference Δ of refractive index anisotropy Δn (650) for light of 0 nm
a liquid crystal layer comprising a liquid crystal in which n (450) -Δn (650) is set in a range of 0 or more and 0.01 or less; a liquid crystal display element having at least the above-mentioned counter substrate, pixel substrate and liquid crystal layer; A pair of polarizers disposed on both sides of the liquid crystal display element; and a retardation plate interposed between the liquid crystal display element and the polarizer, wherein at least one of the retardation plates is provided. The two main refractive indices na, nb, nc are:
na = nc> nb, and one of the main refractive indices na and nc is parallel to the surface of the retardation plate, and the main refractive index nb is expressed by By rotating clockwise or counterclockwise from a state parallel to the normal direction of the surface of the phase difference plate to a state of inclination, or by rotating counterclockwise, the refractive index ellipsoid comprises a phase difference plate with an inclination. Liquid crystal display device. 2. The semiconductor device according to claim 1, further comprising a connection electrode connecting the pixel electrode and the drain electrode, wherein the interlayer insulating film is provided on the switching element, the scanning line, the signal line, and the connection electrode. The pixel electrode is provided on the interlayer insulating film so as to partially overlap at least one of the scanning line and the signal line. The connection electrode and the pixel electrode are in contact with each other through the interlayer insulating film. 2. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is connected via a hole. 3. An additional capacitor for holding a voltage applied to the liquid crystal layer, wherein the contact hole is provided above an electrode connected to the additional capacitor or above the scanning line. 3. The method according to claim 2, wherein
The liquid crystal display device as described in the above. 4. The difference Δn (435) −Δn (61) between the refractive index anisotropy Δn (435) for light having a wavelength of 435 nm and the refractive index anisotropy Δn (610) for light having a wavelength of 610 nm.
4. The liquid crystal display device according to claim 1, wherein a liquid crystal in which 0) is set in a range of 0.00875 or less is used. 5. The color filter according to claim 1, wherein the color filter has a transmittance of at least 85% of light having at least one peak wavelength in light incident through the pixel substrate. Liquid crystal display device. 6. The retardation plate has a layer made of a compound having a discotic structural unit, and the inclination angle between the disc surface of the discotic structural unit and the surface of the retardation plate is the retardation. 6. The liquid crystal display device according to claim 1, wherein the liquid crystal display changes continuously or discontinuously in a depth direction of the plate. 7. The liquid crystal display device according to claim 6, wherein an average value of the inclination angles is 15 ° to 75 °. 8. The liquid crystal display device according to claim 1, wherein the liquid crystal of the liquid crystal layer is 90
The liquid crystal display device according to any one of claims 1 to 7, wherein the liquid crystal display device is oriented in a twisted state, and a display method thereof is a normally white method.