JPH09127499A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device which has a high contrast, a high transmitted light luminance, less tone change, and is superior in visual characteristic. SOLUTION: At least a liquid crystal layer LC interposed between a pair of substrates SUB1 and SUB2 having electrodes 1701 and 1702, oriented films OR11 and OR12 formed on interfaces to the liquid crystal layer, a pair of polarizing plates POL1 and POL2 provided on both sides of the liquid crystal layer, and a control means TFT which applies a binary or more valued voltage between electrodes to change the quantity of transmitted light of the liquid crystal layer are provided. Polarizing plates are so arranged that the quantity of transmitted light in the change state of the angle of inclination of liquid crystal molecules is smaller than that for application of a maximum voltage V1 at the time of applying a voltage V2 lower than the maximum voltage V1 of a binary or more valued voltage, and a double refraction medium PUL which has a phase difference equal or close to the residual phase difference of liquid crystal molecules in the interface parts to substrates in applying the voltage V2 is arranged between polarizing plates and the liquid crystal layer. Thus, relations of the transmittance to applied voltage of respective colors of a filter layer are approximately equalized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix type liquid crystal display device having a high contrast, a small change in transmitted light brightness and color tone, and a good viewing angle characteristic.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices have been used in many fields as image display devices.

This type of liquid crystal display device includes an upper frame having a display window, a liquid crystal cell having a pair of transparent substrates such as a glass substrate integrated with a driving circuit substrate, a light diffusing plate and a light guide plate. And the like, a middle frame on which a linear bakulite light source is mounted on at least one side, a lower frame, etc., which are laminated in the above order, and the upper frame and lower frame are connected and fixed. It is generally done. In addition, there is also a type in which the intermediate frame and the lower frame are integrated.

Scanning electrodes, signal electrodes, alignment films, and other functional film groups are provided on the liquid crystal facing surfaces of the pair of glass substrates, and the facing gaps thereof are substantially spherical or have a cross section made of silica or plastic. A pair of substrates is held with a predetermined cell thickness (hereinafter, also simply referred to as a gap) by dispersing and interposing circular micro spacers.

In a color-compatible liquid crystal display device, a color filter layer of a plurality of colors is started on the inner surface of one glass substrate (for example, an upper glass substrate) of the pair of glass substrates, and one of the glass substrates is used for pixel selection. A functional film group such as a transparent electrode is formed on the other glass substrate (lower glass substrate) and a switching element such as a thin film transistor is used as a control means for controlling a transparent electrode for applying a signal (pixel lighting / non-lighting). In an active type liquid crystal display device such as a TFT type, a lower glass substrate is provided with a functional film group having a configuration different from that of the one glass substrate such as a switching element such as a thin film transistor for pixel selection and its signal electrode). .

It is known that the liquid crystal display device of this type changes in contrast, transmitted light brightness or color tone in the viewing angle direction.

Conventionally, in order to realize a liquid crystal display device having good viewing angle characteristics, one pixel is divided into two regions, the viewing angle directions of the respective regions are made opposite to each other, and a display in which the average viewing angle is obtained for all the pixels A device has been proposed (1992)
Japan Display Proceedings p591-594).

[0008]

As a liquid crystal display device capable of displaying a large capacity, there are known a super twisted nematic type (STN) and a thin film transistor (TFT) type active matrix type liquid crystal display device. However, as described above, in these liquid crystal display devices, the transmittance and the display color change significantly when the display device is viewed obliquely, and the adjacent grayscale levels are inverted when grayscale display is performed, or There is a problem that the halftone color tone changes during color display.

Therefore, in the conventional TFT type liquid crystal display device, the pixel is divided into two regions, the rubbing direction of the alignment film is made different in each region, and the viewing angle directions in each region are made opposite to each other so that the viewing angle direction of one pixel is set. A method of averaging has been proposed. As a result, the viewing angle characteristics in the vertical direction (vertical direction) become symmetrical, and the reversal of the gradation level is suppressed to some extent.

However, the problem remains that the contrast ratio when the display screen is viewed from the front is lowered, and the viewing angle range is narrower than in the left-right direction (horizontal direction). The cause is a domain (non-alignment area) at the boundary of the two divided areas in one pixel.
Occurs and the contrast ratio is lowered.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art and to provide a liquid crystal display device of active matrix type, in particular, which has high contrast and excellent viewing angle characteristics with little change in transmitted light luminance and color tone. is there.

[0012]

A structure for achieving the above object will be described with reference to FIG.

FIG. 1 is a schematic cross-sectional view for explaining the basic structure of a liquid crystal display device according to the present invention, which is SUB1, SUB2.
Is a pair of substrates, ITO1 and ITO2 are transparent electrodes, FIL
Is a color filter layer, LC is a liquid crystal layer, ORI1, ORI
Reference numeral 2 is an alignment film, POL1 and POL2 are polarizing plates, SL is a seal, SRS is a spacer, PUL is a birefringent medium, and CHI is a drive circuit chip.

That is, according to the first aspect of the present invention, at least one of the opposing electrodes is transparent and has the electrode IT.
A pair of substrates SUB1 and SUB2 having O1 and ITO2
A liquid crystal layer LC sandwiched between the substrates, a color filter layer FIL of at least two colors arranged on one of the pair of substrates, and an alignment film OR formed at the interface between the liquid crystal layers.
I and OR2, a spacer SRS sandwiched between the pair of substrates to provide a constant gap between the substrates, and a pair of polarizing plates POL1 and POL2 sandwiching the liquid crystal layer.
A control means TFT for changing the amount of transmitted light of the liquid crystal layer by applying a binary voltage between the electrodes, and a drive circuit chip CHI for generating a voltage waveform for changing the amount of transmitted light of the liquid crystal layer. When a voltage V ₂ lower than the highest voltage V ₁ of the two or more voltages is applied, the amount of transmitted light in a state in which the tilt angle of the liquid crystal molecules constituting the liquid crystal layer between the pair of substrates is changed is The polarizing plate is arranged so as to be lower than when the maximum voltage V ₁ is applied, and when the voltage V ₂ is applied, it is equal to or close to the residual phase difference of liquid crystal molecules at the interface with the substrate. A birefringent medium PUL having a phase difference is arranged between at least one of the polarizing plate and the liquid crystal layer, and the magnitude relationships of the transmittances of the respective colors of the color filter layer at each applied voltage are substantially equal. Characterized by To.

According to a second aspect of the present invention, the color filter FIL in the first aspect comprises dots of three colors of red (R), green (G) and blue (B), and the opening ratio of each color dot O _R respectively, O _G,
When O _B , it is characterized in that O _G ≧ O _R ≧ O _B.

Further, a third aspect of the present invention provides a third aspect of the present invention,
The birefringent medium PUL in the first or second invention is made of an organic polymer film having a twisted structure, and the retardation of the birefringent medium PUL in the state where no voltage is applied is set smaller than the retardation of the liquid crystal layer LC. It is characterized by having done.

Further, a fourth invention according to claim 4 is
In the third invention, the organic polymer film is used as the pair of substrates SUB1 and SUB2 and the polarizing plates POL1 and PO.
One of each is arranged between L2, and the size of the twist structure of the organic polymer film, that is, the twist angle θ _{2 is set} to half or less of the twist structure of the liquid crystal layer LC, that is, the twist angle θ _1. .

Further, a fifth aspect of the present invention provides a fifth aspect of the present invention,
The twist angle θ ₁ of the liquid crystal layer LC in the first or third invention is 10 degrees or more and 110 degrees or less, and the refractive index anisotropy Δn of the liquid crystal layer is 0.02 or more and 0.12 or less, and The product Δ of the thickness d of the liquid crystal layer and the refractive index anisotropy Δn
n · d ₁ (μm) is 0.2 or more and 0.7 or less, the phase difference Δn · d ₂ (μm) of the birefringent medium PUL is 0.05 or more and 0.65 or less, and the optical axis of the birefringent medium is Intersects with the rubbing axis of either one of the alignment films.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, according to the present invention, a pair of substrates, at least one of which is transparent and has electrodes, facing each other, a liquid crystal layer sandwiched between the substrates, and one of the substrates are arranged. A liquid crystal cell having at least two color filters, an alignment film formed on each interface of the liquid crystal layer, and a spacer that holds a constant gap between the substrates, and an upper liquid crystal cell above and below the upper liquid crystal cell so as to sandwich the liquid crystal layer. A pair of polarizing plates provided, control means for changing the amount of transmitted light of the liquid crystal layer by applying a binary voltage or more between the electrodes, and an LSI for generating a voltage waveform for changing the amount of transmitted light of the liquid crystal layer. In a liquid crystal display device provided with a drive circuit (drive circuit chip), in the first invention, when a voltage V ₂ lower than the highest voltage V ₁ of the above-mentioned two or more voltages is applied, a voltage is applied between the pair of substrates. Liquid crystal layer The polarizing plate is arranged so that the amount of transmitted light in the state where the tilt angle of the liquid crystal molecules is changed is lower than that when the maximum voltage V _{1 is} applied, and when the voltage V ₂ is applied, the interface portion with the substrate is formed. A birefringent medium having a retardation equal to or close to the residual retardation of liquid crystal molecules is disposed between at least one of the polarizing plate and the liquid crystal layer,
In addition, the magnitude relationship of the transmittance of each color of the color filter at each applied voltage is made constant.

Here, the relationship between the applied voltage of the liquid crystal display device and the transmitted light brightness will be described.

FIG. 2 is an explanatory diagram of electro-optical characteristics showing the relationship between the applied voltage and the relative transmittance of the liquid crystal display device. The applied voltage (V) is plotted on the horizontal axis and the relative transmittance T (% is plotted on the vertical axis. ), The solid line 4 in the figure shows a curve showing the electro-optical characteristic of a normally black (black state when not lit) system, and the broken line 5 shows an electro-optical characteristic of a normally white (white state when not lit) system. It is a curve.

In the liquid crystal display device, the liquid crystal molecules constituting the liquid crystal layer change from an alignment state substantially parallel to the substrate to an alignment state parallel to an electric field formed by the applied voltage in response to the application of a voltage. However, the transmitted light brightness changes. For example, in a TN method with a twist angle of 90 °, the liquid crystal molecules have a 90 ° angle between the long axes of the molecules in the vicinity of the upper and lower substrates when no voltage is applied, and the liquid crystal molecules have a helical structure between the substrates. It has a twisted structure. When a voltage is applied to this state, the liquid crystal molecules try to change from an alignment state substantially parallel to the substrate to an alignment state parallel to the electric field,
The molecules rise from the substrate and decay the twisted structure, eventually changing to an orientation perpendicular to the substrate. The intensity of transmitted light of the liquid crystal display device also changes due to the change in the alignment state.

At this time, as the applied voltage increases (that is, as the electric field strength increases), the bright display changes to the dark display, which is the normally white method shown by the broken line 5 in the figure, and the dark display to the bright display. There is a normally black system shown by a solid line 4 in the figure which changes to a display.

A method having excellent viewing angle characteristics is a normally black method in which black (dark) display is obtained in a state where liquid crystal molecules are aligned parallel to the substrate when a low voltage is applied.

In this method, a black display is obtained with a low applied voltage, but in the case of a liquid crystal display device having a twist angle θ ₁ of 90 °, the absorption axis of the lower polarizing plate is made to coincide with the lower rubbing axis and the upper polarized light is polarized. This display is obtained by arranging the plate absorption axis orthogonal to the lower polarizing plate absorption axis.

In the normally white mode, the lower polarizing plate absorption axis is aligned with the lower rubbing axis in FIG. 2, and the upper polarizing plate absorption axis is arranged orthogonal to the lower polarizing plate absorption axis. At this time, when no voltage is applied, the polarization component incident parallel to the lower rubbing axis propagates along the twisted structure of the molecule, and is 90 °.
Emit in the rotated state. However, the rotation (optical activity) of the plane of polarization has wavelength dependency, and the plane of polarization is not rotated by 90 ° at all wavelengths. In the case of the normally white method, since white display is performed, the influence of the wavelength dependence of the optical rotatory power is small, but it cannot be ignored in the normally black method. This is because the human eye is sensitive to dark display.

However, at this time, since the degree of optical rotatory power differs depending on the wavelength of light, there is a problem that perfect black (dark display) cannot be obtained and the contrast ratio is lowered.

In order to solve this problem, a birefringent medium having a retardation equal to that of the liquid crystal layer may be arranged. Here, the phase difference is determined by the sum of the product Δn · d (μm) of the twist angle, the thickness d, and the refractive index anisotropy Δn.

In order to obtain a high contrast ratio,
It is preferable to obtain a black display with a slight voltage applied.

As the material of the birefringent medium, it is possible to use a polycarbonate film, a polysulfone film, a polyvinyl alcohol film, a polyarylate film, or a polyester polymer liquid crystal film. Alternatively, a liquid crystal element having a twisted structure sandwiched between glass substrates may be used.

In order to realize color display in a liquid crystal display device, a color filter is arranged inside the substrate, that is, between the substrate and the electrode. If the backlight is collimated light, the same effect can be obtained outside the substrate. is there.

The color of the color filter is generally of the three primary colors of red (R), green (G) and blue (B), but its complementary colors are yellow (Y), purple (M), It is also possible to use three colors of cyan (C). Furthermore, a combination of two colors (red-blue, red-green, blue-yellow) and four colors (red-blue-green-white) is also possible.

In the second invention, the color filter is composed of three colors of red (R), green (G), and blue (B), and the aperture ratio of each color dot is O _R , O _G , When O _B , O _G > O _R > O _B.

The aperture ratio is the ratio of the area of the effective display area to the front area of the liquid crystal display device, and generally corresponds to the electrode area corresponding to the pixel. The aperture ratio of each filter color may be the same, but in order to increase the transmission high brightness, it is preferable to maximize the aperture ratio of the green filter, which has the highest human visibility.

The voltage at each color dot at this time-
The transmittance characteristics will be described.

FIG. 3 is an explanatory diagram of the electro-optical characteristics showing the relationship between the applied voltage and the transmittance of the liquid crystal display device of the present invention. The applied voltage (V) is plotted on the horizontal axis and the relative transmittance T (is plotted on the vertical axis. %), The solid line 1 in the figure is the electro-optical characteristic of the green pixel, and the broken line 2 is
Is the electro-optical characteristic of the red pixel, and the dotted line 3 is the electro-optical characteristic of the blue pixel.

As shown in the figure, the graph of the voltage-transmittance characteristic of each color does not intersect even if the magnitude of the applied voltage is different, and the magnitude relation of the transmittance is the same at any voltage.

Applied voltages V1, V2 and V3 shown in FIG.
The display range of each color will be described with reference to FIG.

FIG. 4 is a CIE chromaticity coordinate diagram for explaining the color display range of the liquid crystal display device according to the present invention. In the figure, the range indicated by ◯ mark is V1, the range indicated by □ mark is V2, and Δ mark. The range shown by corresponds to each voltage application of V3.

As shown in the figure, the range of display color at each voltage is almost the same, and good viewing angle characteristics can be obtained without changing the color tone of halftone display.

On the other hand, FIG. 5 is an explanatory diagram of the electro-optical characteristics showing the relationship between the applied voltage and the transmittance of the conventional liquid crystal display device, in which the applied voltage (V) is plotted on the horizontal axis and the relative transmittance T is plotted on the vertical axis.
In the figure, the solid line 1 indicates the electro-optical characteristic of the green pixel, the broken line 2 indicates the electro-optical characteristic of the red pixel, and the dotted line 3 indicates the electro-optical characteristic of the blue pixel.

In the conventional liquid crystal display device, as shown in the figure, the voltage-transmittance characteristic of each color dot is shown, and the magnitude relationship of the transmittance of each color dot is small when the applied voltages Va and Vb are small. Is reversed.

FIG. 6 is a CIE chromaticity coordinate diagram for explaining the color display range of the above conventional liquid crystal display device. In the figure, the range indicated by the white circle plot curve is Vc, and the range indicated by the white square plot curve is Vb. The range indicated by the white triangle plot curve corresponds to each Va voltage application.

As described above, in the conventional liquid crystal display device, the range of the display color at each applied voltage is different, and the color tone of the halftone color display changes.

On the other hand, as shown in FIG. 4, the liquid crystal display device according to the present invention does not have such a problem.
Good viewing angle characteristics can be obtained without changing the color tone of the halftone display.

Further, in the third invention, the birefringent medium PUL is composed of an organic polymer film having a twisted structure, so that the phase difference of the birefringent medium in the absence of voltage application can be adjusted to the position of the liquid crystal layer. It is smaller than the phase difference.

The normally black method, which has an excellent viewing angle characteristic, can obtain a black display with a low applied voltage, and in order to obtain a high contrast ratio, a black display can be obtained with a slight voltage applied. Preferably, for that purpose, the phase difference of the birefringent medium PUL in the state where no voltage is applied is preferably smaller than the phase difference of the liquid crystal layer LC.

This is because the active matrix display device is not in the voltage non-applied state (V = 0) in the off state, but a slight voltage is applied. When the voltage is gradually applied to the liquid crystal display device by the normally black method, the transmittance also increases. When the transmittance is the lowest when no voltage is applied, the transmittance increases and the contrast ratio decreases when the voltage is V1. On the other hand, in FIG. 1, even if the transmittance is not the minimum when no voltage is applied, a high contrast ratio can be obtained if the transmittance is the lowest at V1. Further, it is a condition for obtaining a high contrast ratio that the wavelengths of blue, green and red lights are the same potential and the transmittance is minimum.

This is because when a voltage is applied to the liquid crystal layer LC, the above-mentioned phase difference gradually decreases, and black display is obtained when the phase differences of the birefringent medium PUL are the same.

Further, in the fourth invention, the birefringent medium PUL having the twisted structure is provided in the pair of substrates SUB.
1, SUB2 and polarizing plates POL1 and POL2 are arranged one by one, and the size of the twist structure of the birefringent medium PUL is set to be half or less of the twist structure of the liquid crystal layer LC.

The reason why the phase difference of the liquid crystal layer LC is reduced by the application of voltage is that the twist of the liquid crystal molecules is attenuated and the liquid crystal molecules tend to be oriented parallel to the electric field. The change in the orientation of the obtainable molecules forming the liquid crystal layer particularly starts from the liquid crystal layer in the central portion between the pair of substrates.

Therefore, the orientation change of the liquid crystal molecules near each interface between the upper substrate (SUB2) and the lower substrate (SUB1) is the last. In order to cancel the phase difference for obtaining the black display, it is preferable to dispose the birefringent medium PUL near each substrate.

Further, in the fifth invention, the size of the twisted structure of the liquid crystal layer LC (the twist angle θ ₁ is 10 degrees or more and 110 degrees or less, and the refractive index anisotropy Δn of the liquid crystal layer is
Is 0.02 or more and 0.12 or less, the product Δn · d (μm) of the thickness d of the liquid crystal layer and the refractive index anisotropy Δn is 0.2 or more and 0.7 or less, and the birefringent medium PUL is used. Phase difference Δ
n · d (μm) is set to 0.05 or more and 0.65 or less, and the optical axis of the birefringent medium intersects with one of the rubbing axes.

The refractive index anisotropy Δnd of the liquid crystal layer PUL needs to be set to a specific value at each twist angle in order to maximize the white display brightness. For example, in the case of 90 ° twist, Δnd is 0.35 or more and 0.6 μm or less, in the case of 80 ° twist, Δnd is 0.30 or more and 0.55 μm or less, and in the case of 70 ° twist, Δnd is 0.25 or more. In case of 0.50 μm or less and 100 ° twist, Δnd
Is 0.40 or more and 0.65 μm, and in the case of a 110 ° twist, a good white display can be obtained by setting Δnd to 0.45 or more and 0.70 μm or less.

Δnd ₂ of the birefringent medium is Δnd of the liquid crystal layer.
It is preferably smaller than _{1 and} smaller than 0.05 μm.

Here, when the birefringent medium has a twist structure similar to that of the liquid crystal, Δnd of the birefringent medium and Δn of the liquid crystal.
It is desirable that d has the same wavelength dependence, and that the optical rotatory power of the birefringent medium and the optical rotatory power of the liquid crystal have the same wavelength dependence (however,
The rotation direction of the optical rotation is opposite).

If this condition is satisfied, STN, T
The present invention can be applied to any display device utilizing birefringence such as N, parallel alignment nematic, ferroelectric liquid crystal, antiferroelectric liquid crystal mode.

The reason why the liquid crystal display device according to the present invention can obtain good viewing angle characteristics with high contrast and little change in transmitted light brightness and color tone is that the normally black method allows the viewing angle characteristics to be widened and the birefringence to be increased. Arrange the medium,
The contrast ratio is high because black display is obtained with a slight voltage applied, and the color tone at the time of halftone display is the same because the voltage-transmittance magnitude relationship in each color dot does not change. This is because the bright state transmissivity is increased by changing the above and maximizing the aperture ratio of the green dot.

[0059]

Embodiments of the present invention will be described below in detail with reference to the drawings.

[Embodiment 1] FIG. 7 is a schematic diagram of a schematic configuration for explaining a first embodiment of a liquid crystal display device according to the present invention. SUB1 is a lower substrate, SUB2 is an upper substrate, and L is a substrate.
C is a liquid crystal layer, LCB is a liquid crystal molecule, POL1 is a lower polarizing plate, POL2 is an upper polarizing plate, BL is a backlight, PU
L is the birefringent medium, XA is the rubbing direction of the lower substrate, and XB is
Is the rubbing direction of the upper substrate, XC is the transmission axis of the lower polarizing plate, XD is the transmission axis of the upper polarizing plate, and XE is the optical axis of the birefringent medium.

The lower substrate SUB1 and the upper substrate SUB
An electrode formed on the side of the second liquid crystal layer LC, a color filter,
The orientation film, other functional films, seals, etc. are not shown. Therefore, the rubbing directions of the upper alignment film and the lower alignment film will be described as the rubbing direction of the lower substrate and the rubbing direction of the upper substrate for convenience sake.

In the figure, as the pair of upper and lower substrates SUB1 and SUB2, glass substrates having a thickness of 1.1 mm and whose surfaces are polished are used. Between the pair of upper and lower substrates SUB1 and SUB2, the dielectric anisotropy Δε is positive and its value is 4.
5 and the birefringence Δn is 0.087 (589 nm, 20
The nematic liquid crystal composition (liquid crystal molecule LCB) of (° C) is sandwiched.

Then, the polyimide type alignment film (also referred to as an alignment control film) applied to the surfaces of the upper and lower substrates SUB1 and SUB2 is rubbed to have a pretilt angle of 3.5 degrees. The rubbing directions XB and XA on the interfaces of the upper and lower substrates SUB1 and SUB2 in contact with the liquid crystal layer LC are substantially orthogonal to each other so that the twist angle is 90 °.

The gap d between the upper and lower substrates SUB1 and SUB2 is 5.2 μ in a state where liquid crystal LC is sealed by holding spherical polymer beads (not shown) dispersed between both substrates.
m. Therefore, Δn · d is 0.45 μm.

The liquid crystal panel constructed as described above is sandwiched between two polarizing plates, a lower polarizing plate POL1 and an upper polarizing plate POL2 (product name G1220DU manufactured by Nitto Denko Corporation), and the transmission axis XD of the upper polarizing plate POL2 is sandwiched. Is substantially parallel to the rubbing direction XB, and the transmission axis XC of the lower polarizing plate POL1 is set to the rubbing direction X.
It was parallel to A, that is, crossed Nicols. As a result, normally black characteristics were obtained.

Between the upper polarizing plate POL1 and the liquid crystal layer LC, a birefringent medium PUL having a twist angle of −90 ° (θ ₁
Reverse twist), Δnd = 0.40 μm (measurement wavelength 58
A liquid crystal cell of 9 nm) was arranged. This birefringent medium PU
L may be a polymer film made of, for example, triacetyl cellulose (TAC) or the like, which has a small transmittance attenuation and parallax shift, and is arranged outside the upper substrate SUB2, but between the substrate SUB2 and the liquid crystal layer LC, Alternatively, it may be arranged between the upper polarizing plate POL2 and the liquid crystal layer LC.

Further, the polymer film is used as the upper substrate SU.
B2 and upper polarizing plate POL2, or lower substrate SUB1
One sheet or two sheets may be disposed between the lower polarizing plate POL1 and the lower polarizing plate POL1.

Here, Δn of the liquid crystal element and the birefringent medium 8 is
The wavelength dependence of d is equal, and Δnd at a wavelength of 590 nm is 1
And Δnd at a wavelength of 450 nm is 1.10,
Δnd at a wavelength of 633 nm was 0.992.

Further, as the above-mentioned birefringent film, in addition to the triacetyl cellulose (TAC) film, polycarbonate (PC), polyvinyl alcohol (PV
A), polyether sulfone (PES), polyethylene terephthalate (PET) or other birefringent plastic stretched film or a polymeric liquid crystal film may be used, and the structure is not limited to the TAC film. .

In this embodiment, since display is performed by active matrix driving, one substrate (for example, lower substrate SUB)
1) The above thin film transistor is formed in an inverted staggered pattern, and the other substrate (for example, the upper substrate SUB2) is provided with a common electrode and a stripe-shaped color filter of R, G, and B pigment colors.

Then, a transparent resin for flattening the surface was laminated on the color filter. An epoxy resin was used as the material of this transparent resin. Furthermore, a polyimide-based alignment film was applied onto this transparent resin. A chip such as a drive LSI (not shown) is connected to the liquid crystal panel.

Thus, the viewing angle characteristics in the vertical and horizontal directions of the screen when 8-gradation display was performed were measured by a luminance meter PR-1980A manufactured by Photo Research.

FIG. 8 is an explanatory view of the viewing angle characteristics of the liquid crystal display device of the present embodiment. FIG. 8A is a vertical viewing angle characteristic in which the horizontal axis shows the vertical viewing angle (θ °) and the vertical axis shows the luminance (cd / cd / m ² ) and (b) show the left-right viewing angle characteristics, where the horizontal axis shows the left-right viewing angle (θ
°), and the luminance (cd / m ² ) is plotted on the vertical axis.

From FIGS. 11A and 11B, each gradation level from the solid curve which is the luminance in the normally black state (black display) to the black rhombus plot curve which is the maximum luminance (white display) is not inverted. The viewing angle range was 40 degrees in the vertical direction of (a) and 30 degrees in the horizontal direction of (b).

The maximum contrast ratio (ratio of white display transmittance and black display transmittance) was 200: 1.

FIG. 9 is an explanatory view of the contrast map in all directions of the screen of the liquid crystal display device of this embodiment, and CR indicates the contrast ratio.

From the figure, it can be seen that good viewing angle characteristics with a high contrast ratio can be obtained in all directions of the screen.

[Embodiment 2] FIG. 10 is a plan view of a pixel of a second embodiment of the liquid crystal display device according to the present invention, in which the vertical size of each pixel is the same 300 μm, and the width of the red pixel (R pixel) is the same. The lateral size of the green pixel (G pixel) is 100 μm, and the lateral size of the blue pixel (B pixel) is 60 μm.

That is, the R pixel, the G pixel shown in FIG.
The aperture ratio of the B pixel is 0.9: 1: 0.6. The other structure is the same as that of the first embodiment.

With this structure, the white display transmittance is improved by 10%. In addition, the same viewing angle characteristics as those of the first embodiment were obtained in the vertical and horizontal viewing angle characteristics when 8-gradation display was performed.

The graphs of the voltage-transmittance characteristics of the respective colors at this time do not intersect, and the magnitude relationship of the transmittance is the same at any voltage. The color display range at the voltages V1, V2, and V3 is shown on the CIE chromaticity coordinates of FIG. The range of display color at each voltage was almost the same, and good viewing angle characteristics were obtained without changing the color tone of the halftone display.

In order to clarify the effect of each of the above-mentioned embodiments, an example of a liquid crystal display device which does not use a birefringent medium will be described.

Comparative Example 1 In the first comparative example, a normally white display was obtained when the other structures were the same as those in the first example except that the birefringent medium was not arranged.

FIG. 11 is an explanatory view when 8-gradation display is performed in the liquid crystal display device having the structure of the first comparative example. Like FIG. 8, (a) shows the vertical viewing angle characteristic. The horizontal axis shows the vertical viewing angle (θ °), the vertical axis shows the luminance (cd / m ² ), and (b) shows the horizontal viewing angle characteristic, and the horizontal axis shows the horizontal viewing angle (θ °).
Is shown by taking the luminance (cd / m ² ) on the vertical axis.

From FIGS. 11A and 11B, the viewing angle range in which the gradation level is not reversed is 30 degrees in the vertical direction and 45 in the horizontal direction.
Degree.

Further, FIG. 12 is an explanatory view of a contrast map in all directions of the screen of the liquid crystal display device of this comparative example, and CR shows the contrast ratio as in FIG.

From the figure, the range in which the contrast ratio is high is only in the left-right direction.

[Embodiment 3] In the first embodiment, the birefringent medium PUL is used as the upper substrate SUB2 and the upper polarizing plate POL.
One between the two, the lower substrate SUB1 and the lower polarizing plate POL
One sheet was placed between the first and second sheets. Further, the twist angle of each birefringent medium was −45 ° and Δnd was 0.2 μm.

As a result of measuring the viewing angle characteristics in the vertical and horizontal directions at the time of displaying 8 gradations with the liquid crystal display device configured as described above with a brightness meter PR-1980A (trade name) manufactured by Photo Research The viewing angle range in which the level was not inverted was 50 degrees in the vertical direction and 50 degrees in the horizontal direction.

[Embodiment 4] In the fourth embodiment, the liquid crystal layer L is used.
The twist angle of C is 80 °, Δnd is 0.35 μm,
The other structure is the same as that of the first embodiment.

As a result, the vertical and horizontal viewing angle characteristics at the time of 8-gradation display are measured by the luminance meter PR of Photo Research.
When measured at -1980A, the viewing angle range in which the gradation level is not inverted was 70 degrees in the vertical direction and 50 degrees in the horizontal direction.

The maximum contrast ratio (ratio of white display transmittance and black display transmittance) was 100: 1, and the viewing angle characteristics in the vertical and horizontal directions were symmetrical.

Although the twist angle is 70 degrees, similar results can be obtained within the range of 30 to 100 degrees. By reducing the twist angle, the vertical viewing angle range becomes wider.

Next, a specific example of the liquid crystal display device to which the present invention is applied will be described.

FIG. 13 is a cross-sectional view for explaining in detail the main structure of the liquid crystal display layer to which the present invention is applied. SUB1 is a lower substrate, SUB2 is an upper substrate, ITO1, 0TO2 are electrodes, TFT1 is a thin film transistor, FIL is a color filter, BM is a black matrix (light shielding film), PSV
1, PSV2 is a protective film, ORI1 and ORI2 are alignment films,
LC is a liquid crystal layer, POL1 and POL2 are polarizing plates, and PUL is a birefringent medium.

SIO is a silicon oxide film, SD1
(D3, d2, d0), SD2 (d3, d2), AO
F, GT, g2, AS, GI and the like are various electrodes and insulating films that constitute the TFT, and other functional thin films.

In the figure, a thin film transistor TFT and a transparent pixel electrode ITO1 are formed on the lower substrate SUB1 side with the liquid crystal layer LC as a reference, and a lower alignment film ORI1 is formed via a protective film PSV1.

A color filter FIL and a light-shielding black matrix pattern BM are formed on the side of the upper substrate SUB2.

On both surfaces of the upper and lower substrates SUB1 and SUB2, a silicon oxide film SI formed by dip processing or the like is formed.
O is provided.

Inside the upper substrate SUB2 (liquid crystal layer LC side)
A light shielding film BM, a color filter FIL, a protective film PSV2, a common transparent pixel electrode ITO2 (COM), and an upper alignment film ORI2 are sequentially laminated on the surface of the.

On the inner surface of the lower substrate SUB1, the thin film transistor TFT1, the pixel electrode ITO1, and the protective film PSV are provided.
1, a lower alignment film ORI1 is formed.

Then, the upper substrate SUB2 and the upper polarizing plate P
A film of triacetyl cellulose is inserted as a birefringent medium PUL between the film and OL1.

FIG. 14 is a developed perspective view illustrating a structural example of a TFT type liquid crystal display module assembled using the liquid crystal display device according to the present invention.

In the figure, MDL is a liquid crystal display module, SHD is a metal shield case which is an upper frame, WD is a display window which defines the effective screen of the liquid crystal display module, PNL is a liquid crystal panel consisting of liquid crystal display elements, and PC.
B1 is a drain side circuit board, PCB2 is a gate side circuit board, PCB3 is an interface circuit board, PRS is a prism sheet, SPS is a diffusion sheet, GLB is a light guide,
RFS is a reflection sheet, BL is a backlight, LP is a cold cathode fluorescent lamp constituting a lamp of the backlight BL, LS is a reflection sheet, GC is a rubber bush, LPC is a lamp cable, and MCA is an opening for installing a light guide GLB. A lower case having an MO, JN1,2,3 are joiners connecting circuit boards, TCP1,2 are tape carrier packages,
INS 1, 2 and 3 are insulating sheets, GC is a rubber cushion, BAT is a double-sided adhesive tape, and ILS is a light-shielding spacer.

The above-mentioned components are laminated between the metal shield case SHD and the lower case MCA and sandwiched and fixed to form the liquid crystal display module MDL.

As shown in FIG. 13, the birefringent medium according to the present invention is laminated on the liquid crystal panel PNL, and various circuit boards are attached around the birefringent medium to drive the image display.

On the back surface of the liquid crystal panel PNL, there is provided a backlight BL in which various optical sheets are laminated on the light guide GLB, and the image formed on the liquid crystal display panel PNL is illuminated and displayed on the display window WD. indicate.

FIG. 15 is a block diagram showing a TFT liquid crystal display panel of an active matrix type TFT liquid crystal display module using thin film transistors as switching elements and a circuit arranged on the outer peripheral portion thereof.

In the figure, the drain drivers IC _{1 to} IC _M and the gate drivers IC _{1 to} IC _N arranged on only one side of the liquid crystal display panel are formed on one transparent insulating substrate SUB1 of the liquid crystal display element. Chip-on-glass mounting (COG mounting) is performed with the drain-side lead line and the gate-side lead line and an anisotropic conductive film, an ultraviolet curable resin SIL, or the like.

This liquid crystal display element has an XGA specification of 80.
It is applied to a liquid crystal display device having 0 × 3 × 600 effective dots. Therefore, on the transparent insulating substrate of the liquid crystal display element, 10 drain driver ICs _{1 to} IC _M having 240 outputs (M = 10) are provided on the long side of the liquid crystal panel, and 10 drain drivers IC _{1 to} IC _M are provided on the short side.
Six 1-output gate driver IC _{1 to} IC _N (N =
6) and are COG mounted.

From the number of pixels, the gate driver ICs _{1 to} I
A total of 600 outputs of C _N are sufficient, but since the additional gate lines are formed above and below the effective pixel portion, the uppermost 10
It has one output, 100 outputs in the central part × 4, and 101 outputs in the lowermost part.

It should be noted that with the same gate driver IC, 1
It is possible to properly use the 00 and 101 outputs.

As described above, the drain driver section 103 is arranged on the upper side of the liquid crystal display panel, the gate driver section 104 is arranged on the side surface, and the controller section 101 and the power supply section 102 are arranged on the other side surface. Has been done.

Controller section 101 and power supply section 10
2, drain driver unit 103, gate driver unit 10
4 are electrical connection means (joiner) JN1,
Interconnected by JN3.

In this constitution, 80 XGA panels are used.
0.times.3.times.600 dots 10.4 inch screen size T
An FT liquid crystal display module was designed. Therefore, the size of each dot of red (R), green (G), and blue (B) is 2
The size is 64 μm (gate line pitch) × 88 μm (drain line pitch), and one pixel is a combination of three dots of red (R), green (G), and blue (B), and is 264 μm.
It is m square. For this reason, if the drain lead wire DTM is 800 × 3, the lead wire pitch is 1
This is less than 00 μm, which is less than the connection pitch limit of currently available tape carrier package (TCP) mounting. In COG mounting, depending on the material such as the anisotropic conductive film used, the pitch of the bumps BUMP of the driving IC chip is about 70 μm and the crossing area with the underlying wiring is about 40 μm square. It can be called a value.
Therefore, in this example, the drain driver ICs are arranged in a line on one long side of the liquid crystal panel, the drain lines are drawn out to the long side, and the pitch of the drain line lead-out wiring DTM is set to 88 μm.

Therefore, the bump pitch of the driving IC chip is about 70 μm and the area of intersection with the underlying wiring is about 40 μm.
It was possible to design in μm square, and it became possible to connect with the underlying wiring with higher reliability.

Since the gate line pitch is 264 μm, which is sufficiently large, the gate line is drawn out on the short side on one side. It is also possible to lead out the gate line lead lines alternately.

FIG. 16 is an explanatory diagram showing the flow of display data and clock signals for the gate driver 104 and the drain driver 103 in the TFT liquid crystal display module shown in FIG.

The display control device 101 receives a control signal (clock, display timing signal, synchronizing signal) from the main computer (host), and outputs a clock D1 (CL1) and a shift clock D2 as control signals to the drain driver 103. (CL2) and display data are generated, and at the same time, a frame start instruction signal, a clock, and display data are generated as control signals to the gate driver 104.

The carry output of the previous stage of the drain driver 103 is the same as that of the drain driver 103 of the next stage.
Is input to the carry input of.

FIG. 17 is an explanatory diagram of the common voltage applied to the electrode (common electrode) on the upper substrate, the drain voltage applied to the drain, the level of the gate voltage applied to the gate electrode, and the waveform thereof.

The drain waveform shows the drain waveform when black is displayed.

In the figure, the gate on level waveform (direct current) and the gate off level waveform change in level between -9 and -14 volts, and the gate is turned on at 10 volts. The drain waveform (when displayed in black) and the common voltage Vcom waveform are 0
Level changes between ~ 3 volts.

For example, in order to change the black level drain waveform every horizontal period (1H), the logic processing circuit inverts the logic bit by bit and inputs it to the drain driver.

The off-level waveform of the gate is the common voltage V
It operates with substantially the same amplitude and phase as the com waveform.

FIG. 18 is a perspective view of a notebook type personal computer or word processor as an example of electronic equipment in which the liquid crystal display device according to the present invention is mounted.

In the figure, the liquid crystal panel PN of the driving IC
By adopting COG mounting on L and bending mounting on the multilayer flexible substrate as a peripheral circuit for the drain and gate drivers in the outer peripheral portion, the external size can be significantly reduced compared to the conventional case.

In this example, since the drain driver peripheral circuit mounted on one side can be arranged above the display section above the hinge of the information device, compact mounting is possible.

A signal from the information device first goes to a display control integrated circuit element (TCON) from a connector located substantially in the center of the interface board PCB on the left side of FIG.
The display data converted here flows to the drain driver peripheral circuit.

As described above, by using the flip chip method and the multi-layer flexible substrate, the restriction on the outer shape of the width of the information equipment can be eliminated, and the small-sized and low power consumption information equipment can be provided.

The present invention has been specifically described above based on the embodiments. However, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. is there.

[0132]

As described above, according to the present invention,
It is possible to obtain an active matrix type liquid crystal display device having high contrast and good viewing angle characteristics with little change in transmitted light brightness and color tone.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view illustrating a basic configuration of a liquid crystal display device according to the present invention.

FIG. 2 is an explanatory diagram of electro-optical characteristics showing a relationship between an applied voltage and a relative transmittance of the liquid crystal display device.

FIG. 3 is an explanatory diagram of electro-optical characteristics showing a relationship between applied voltage and transmittance of the liquid crystal display device of the present invention.

FIG. 4 is a CIE chromaticity coordinate diagram illustrating a color display range of the liquid crystal display device according to the present invention.

FIG. 5 is an explanatory diagram of electro-optical characteristics showing a relationship between an applied voltage and a transmittance of a conventional liquid crystal display device.

FIG. 6 is a diagram C for explaining a color display range of a conventional liquid crystal display device.
It is an IE chromaticity coordinate diagram.

FIG. 7 is a schematic view of a schematic configuration for explaining a first embodiment of a liquid crystal display device according to the present invention.

FIG. 8 is an explanatory diagram of viewing angle characteristics of the liquid crystal display device of the first embodiment of the liquid crystal display device according to the present invention.

FIG. 9 is an explanatory diagram of a contrast map in all directions of the screen of the liquid crystal display device of the first embodiment of the liquid crystal display device according to the present invention.

FIG. 10 is a plan view of a pixel of a second embodiment of the liquid crystal display device according to the present invention.

FIG. 11 is an explanatory diagram when performing 8-gradation display on the liquid crystal display device having the configuration of the first comparative example.

FIG. 12 is an explanatory diagram of a contrast map in all directions of the screen of the liquid crystal display device of the first comparative example.

FIG. 13 is a cross-sectional view illustrating in detail a main part structure of a liquid crystal display layer to which the present invention is applied.

FIG. 14 is an exploded perspective view illustrating a structural example of a TFT type liquid crystal display module assembled using the liquid crystal display device according to the present invention.

FIG. 15 is a block diagram showing a TFT liquid crystal display panel of an active matrix type TFT liquid crystal display module using a thin film transistor as a switching element and a circuit arranged on an outer peripheral portion thereof.

16 is an explanatory diagram showing the flow of display data and clock signals for a gate driver and a drain driver in the TFT liquid crystal display module shown in FIG.

FIG. 17 is an explanatory diagram of a common voltage applied to an electrode (common electrode) on the upper substrate, a drain voltage applied to a drain, a level of a gate voltage applied to a gate electrode, and a waveform thereof.

FIG. 18 is a perspective view of a notebook-type personal computer or word processor as an example of an electronic apparatus in which the liquid crystal display device according to the present invention is mounted.

[Explanation of symbols]

1 ... Electro-optical characteristic of green pixel, 2 ... Electro-optical characteristic of red pixel, 3 ... Electro-optical characteristic of blue pixel, 4 ...
... Normally black electro-optical characteristics, 5 ...
..Normally white electro-optical characteristics, SUB1
.... Lower substrate, SUB2 .... Upper substrate, ITO
1, ITO2 ... Transparent electrode, FIL ... Color filter layer, LC ... Liquid crystal layer, ORI1 ... Lower alignment film, ORI2 ... Upper alignment film, POL1, P
OL2 ・ ・ ・ ・ Polarizing plate, SL ・ ・ ・ ・ Seal, SRS ・
・ ・ ・ Spacer, PUL ・ ・ ・ ・ Birefringent medium, CHI ・
・ ・ ・ Drive circuit chip, XA ・ ・ ・ ・ ・ ・ Transmission axis of lower substrate, XB ・ ・ ・ ・ Transmission axis of upper substrate, XC ・ ・ ・ ・ Transmission axis of lower polarizing plate, VD ・ ・ ・ ・ ・ ・ Upper polarization Transmission axis of plate, M
DL ... Liquid crystal display module, SHD ... Upper frame, WD ... Display window that defines effective screen of liquid crystal display module, PNL ... Liquid crystal display panel, PC
B1 ... Drain side circuit board, PCB2 ... Gate side circuit board, PCB3 ... Interface circuit board, PRS ... Prism sheet, SPS ...
・ Diffusion sheet, GLB ... Light guide, RFS ...
Reflective sheet, BL ... Backlight, LP ...
Cold cathode fluorescent lamp, LS ... Reflective sheet, GC ...
Rubber bush, LPC ... Lamp cable, MCA
.... Lower case, JN1, 2, 3 ... Joiner for connecting circuit boards, TCP1, 2 ... Tape carrier package, INS1, 2, 3 ... Insulation sheet, GC ... Rubber cushion, BAT ... Double-sided adhesive tape, ILS ...

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tatsunori Bunkura 3681 Hayano, Mobara City, Chiba Prefecture Inside Hitachi Device Engineering Co., Ltd. (72) Inventor Hazimi 3681 Hayano, Mobara City, Chiba Prefecture Hitachi Device Engineering Co., Ltd. Inside

Claims (5)

[Claims] 1. A pair of substrates, at least one of which is arranged to face each other, is transparent and has electrodes, a liquid crystal layer sandwiched between the substrates, and at least two of which are arranged on one of the pair of substrates.
Color filter layers, an alignment film formed at the interface of the liquid crystal layer, spacers sandwiched between the pair of substrates to provide a constant gap between the substrates, and a pair sandwiching the liquid crystal layer. Of the polarizing plate, control means for changing the amount of transmitted light of the liquid crystal layer by applying a binary voltage between the electrodes, and a drive circuit chip for generating a voltage waveform for changing the amount of transmitted light of the liquid crystal layer. And a tilt angle of liquid crystal molecules forming a liquid crystal layer between the pair of substrates when a voltage V ₂ lower than the highest voltage V ₁ of the two or more voltages is applied. The polarizing plate is arranged so that the amount of transmitted light in the changed state is lower than that when the maximum voltage V ₁ is applied, and when the voltage V ₂ is applied, the liquid crystal molecules at the interface with the substrate are Phase equal to or close to residual phase difference A birefringent medium having at least one of the polarizing plate and the liquid crystal layer is arranged, and the transmittances of the respective colors of the color filter layer are substantially equal in magnitude to each applied voltage. Characteristic liquid crystal display device. 2. The color filter according to claim 1, wherein the color filter is composed of dots of three colors of red (R), green (G) and blue (B), and the opening ratio of each color dot is O _R ,
A liquid crystal display device, wherein O _G ≧ O _R ≧ O _B when O _G and O _B. 3. The birefringent medium according to claim 1, comprising an organic polymer film having a twisted structure,
A liquid crystal display device, wherein a phase difference of the birefringent medium in a state where no voltage is applied is set smaller than a phase difference of the liquid crystal layer. 4. The organic polymer film according to claim 3, wherein one organic polymer film is provided between the pair of substrates and the polarizing plate.
A liquid crystal display device, wherein the size of the twist structure of the organic polymer film, that is, the twist angle θ _{2 is set} to half or less of the twist structure of the liquid crystal layer, that is, the twist angle θ ₁ . 5. The liquid crystal layer according to claim 1, wherein a twist angle θ _{1 of the} liquid crystal layer is 10 degrees or more and 110 degrees or less, and a refractive index anisotropy Δn of the liquid crystal layer is 0.02 or more and 0.12 or less. And the liquid crystal layer thickness d and refractive index anisotropy Δ
The product Δn · d ₁ (μm) of n is 0.2 or more and 0.7 or less, the phase difference Δn · d ₂ (μm) of the birefringent medium is 0.05 or more and 0.65 or less, and A liquid crystal display device, wherein an optical axis intersects with a rubbing axis of one of the alignment films.