JP2000010096A - Liquid crystal display - Google Patents

Abstract

[PROBLEMS] To provide a liquid crystal display device provided with a backlight having a high light utilization rate capable of increasing luminance and reducing weight of a large liquid crystal display device. A liquid crystal panel composed of a liquid crystal layer SC sandwiched between a pair of substrates SUB1 and SUB2 each having an electrode on at least one of the opposing electrodes, and a pair of polarizing plates POL1 arranged so as to sandwich the liquid crystal panel. , POL2,
Control means for applying a voltage to the electrodes in accordance with a display image signal, and an illumination light source B for illuminating the liquid crystal panel from the back
L, and the illumination light source BL includes a flat light guide plate GLB-P and wedge-shaped light guides GLB-W1, GLB-W.
A light guide plate assembly obtained by laminating at least one of each of the two;
The light guide plate assembly was composed of at least one linear light source LP installed along the side surface of the light guide plate assembly, and a reflection sheet LS for reflecting light emitted from the linear light source in the light guide plate direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device having a high light utilization efficiency, a bright and lightweight illumination light source.

[0002]

2. Description of the Related Art Liquid crystal displays are widely used as devices for displaying various images including still images and moving images.

[0003] This type of liquid crystal display device basically has two (a pair) of at least one made of transparent glass or the like.
Constitute a so-called liquid crystal panel with a liquid crystal layer sandwiched between substrates,
A type in which a predetermined voltage is selectively applied to various electrodes for pixel formation formed on the substrate of the liquid crystal panel to turn on and off a predetermined pixel. The active elements are formed by forming the various electrodes and an active element for pixel selection. Is selected, a predetermined pixel is turned on and off.

[0004] In particular, the latter type of liquid crystal display device is called an active matrix type, and has become the mainstream of the liquid crystal display device because of its contrast performance, high-speed display performance and the like. An active matrix type liquid crystal display device employs a so-called vertical electric field method in which an electric field for changing the orientation direction of a liquid crystal layer is applied between an electrode formed on one substrate and an electrode formed on the other substrate, and a so-called vertical electric field method. There is known a so-called in-plane switching (IPS) liquid crystal display device in which the direction of an applied electric field is substantially parallel to the substrate surface.

[0005] The above-mentioned various liquid crystal display devices are provided with a light source device (generally called a backlight) for illuminating the liquid crystal panel from the back. This backlight has a lamp (linear light source: cold cathode fluorescent tube) on the side of the light guide plate.
There is a side-edge type in which a lamp is installed and a direct type in which a lamp is installed directly below a liquid crystal panel.

[0006] In particular, notebook computers that require thinness and light weight generally employ a side-edge type backlight.

FIG. 13 is an exploded perspective view for explaining an example of the configuration of the liquid crystal display device. SHD is a shield case (also called a metal frame) made of a metal plate, WD is a display window, I
NS1 to 3 are insulating sheets, PCB1 to 3 are circuit boards (P
CB1 is a drain-side circuit board: a video signal line driving circuit board, PCB2 is a gate-side circuit board, PCB3 is an interface circuit board), and JN1 to 3 are circuit boards PCB1 to PCB1.
Joiner, TCP1, TCP for electrically connecting the three
2 is a tape carrier package, PNL is a liquid crystal display panel, GC is a rubber cushion, ILS is a light shielding spacer, P
RS is a prism sheet, SPS is a diffusion sheet, GLB is a light guide plate, RFS is a reflection sheet, MCA is a lower case (mold frame) formed by integral molding, MO is an opening of MCA, LP is a fluorescent tube, and LPC is a fluorescent tube. Lamp cable, GB is a rubber bush that supports the fluorescent tube LP, BAT
Denotes a double-sided adhesive tape, BL denotes a backlight made of a linear light source (cold cathode fluorescent tube: simply referred to as a fluorescent tube in the figure), LP light guide plate GLB, etc., and a liquid crystal display by stacking diffusion plate members in the arrangement shown in FIG. The module MDL is assembled. In the illustrated liquid crystal display device, the reflection sheet RFS is disposed on the lower surface (back surface) of the backlight BL, and one diffusion sheet SPS and one prism sheet PRS are laminated on the upper surface. There is also one in which one diffusion sheet SPS is laminated. In this configuration, one linear light source LP is provided on one side of the light guide plate GLB having a wedge-shaped cross section. However, a flat light guide plate is used, and linear light sources are provided on two parallel sides thereof. There is also. It should be noted that other components are described with reference numerals and names in FIG.

The liquid crystal display module MDL has two kinds of storage / holding members of a lower case MCA and a shield case SHD, and includes insulating sheets INS1 to INS3 and circuit boards PCB1 to PCB1.
3. A metal shield case SHD in which the liquid crystal display panel PNL is housed and fixed, and a lower case MCA in which a backlight BL including a fluorescent tube LP, a light guide plate GLB, a prism sheet PRS, and the like are housed are combined.

[0009] An integrated circuit chip for driving each pixel of the liquid crystal display panel PNL is mounted on the video signal line driving circuit board PCB1.
The B3 includes an integrated circuit chip that receives a video signal from an external host, receives a control signal such as a timing signal, and a timing converter TCON that processes a timing to generate a clock signal.

The clock signal generated by the timing converter is integrated on the video signal line driving circuit board PCB1 via the clock signal line CLL laid on the interface circuit board PCB3 and the video signal line driving circuit board PCB1. Supplied to the circuit chip.

The interface circuit board PCB3 and the video signal line driving circuit board PCB1 are multilayer wiring boards, and the clock signal line CLL is connected to the interface circuit board PCB3 and the video signal line driving circuit board PC
It is formed as an inner wiring of B1.

The liquid crystal display panel PNL has a drain-side circuit board PCB1, a gate-side circuit board PCB2, and an interface circuit board PC for driving TFTs.
B3 is connected by tape carrier packages TCP1 and TCP2, and the circuit boards are connected by joiners JN1, JN2, JN3.

FIG. 14 is a schematic sectional view for explaining a laminated structure of the liquid crystal display device shown in FIG.
A liquid crystal layer LC is sandwiched between the upper substrate SUB2 and the lower substrate SUB1 and the upper substrate SUB2.
The lower surface of the lower phase difference plate PHD1 and the lower deflector P
OL1, an upper retardation plate PHD2, and an upper deflection plate POL2 are stacked.

A backlight BL is provided on the back (back side) of the liquid crystal panel.
An optical sheet formed by laminating two diffusion sheets SPS1 and SPS2 and a prism sheet PRS is interposed therebetween.

The backlight BL is of a side edge type, and has a linear light source (cold cathode fluorescent tube) LS and a reflection sheet L on one side surface of a light guide GLB-W having a wedge-shaped cross section.
P is installed. In the backlight BL, high brightness is achieved by using two cold cathode fluorescent tubes LP. Note that a reflection film RFS is disposed on the back surface of the backlight BL.

FIG. 15 is a cross-sectional view for explaining another configuration example of a conventional backlight for increasing luminance. This backlight is composed of two laminated plate-shaped light guides GLB.
-P1 and GLB-P2 are used, and a cold cathode fluorescent lamp LP and a reflection sheet LP are respectively installed on their parallel side surfaces. For this type of backlight, see "SID
96 DIGEST "PP. 753 to 756.

[0017]

The size of the liquid crystal display device has been increasing year by year, and the backlight thereof has been increasing accordingly. There is also a strong demand for higher brightness,
There is a need to develop a strong (bright) backlight.

A problem with the backlight is that the weight increases as the size of the backlight increases. In addition, it is necessary to increase the number of linear light sources in order to cope with higher brightness.In the direct type, high brightness can be achieved by arranging many cold cathode fluorescent tubes on the back of the liquid crystal panel. There is a problem that the thickness of the entire display device increases.

To cope with this increase in thickness, a side edge method is suitable, but an increase in size results in an increase in the weight of the light guide.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a liquid crystal display device provided with a backlight having a high light utilization factor capable of increasing the brightness and reducing the weight of a large liquid crystal display device.

[0021]

Means for Solving the Problems In order to achieve the above object, the present invention has the following constitutions (1) to (6).

(1) A pair of substrates having electrodes on at least one of the opposing electrodes, a liquid crystal panel comprising a liquid crystal layer sandwiched between the pair of substrates, and a pair of liquid crystal panels arranged to sandwich the liquid crystal panel. A polarizing plate, a control unit for applying a voltage to the electrode according to a display image signal, and at least an illumination light source for illuminating the liquid crystal panel from the back, wherein the illumination light source has a flat light guide plate and a wedge shape. A light guide plate assembly obtained by laminating at least one of the light guides, at least one linear light source installed along the side surface of the light guide plate assembly, and light emitted from the linear light source. And a reflection sheet for reflecting light in the direction of the light guide plate.

(2) A light reflection pattern for reflecting light is provided on the back surface of the plurality of light guides laminated in (1).

(3) Linear light sources are arranged on at least two of the four side surfaces of the light guide in (1), and the total light amount of each linear light source is different.

(4) As means for making the total light quantity of each linear light source in (3) different, the diameter of each linear light source is made different.

(5) As means for varying the total light quantity of each linear light source in (3), the number of linear light sources installed on each side was varied.

(6) The linear light source in (1) is installed on each of two parallel sides of the light guide assembly, and the viewing angle dependency of light transmitted through the liquid crystal panel is a center line parallel to the two sides. The brightness of each linear light source was set so as to be asymmetrical with respect to.

In a side edge type backlight used for a large liquid crystal display device, it is necessary to increase the thickness of a light guide formed by injection molding of an acrylic resin or the like in order to obtain high luminance. However, the weight increases as the thickness increases. Although the weight can be reduced by making the light guide a wedge-shaped cross section, the thickness of the side face on the incident light side (the side face on the side where the linear light source is installed) is improved in order to improve the reduction in luminance due to the enlargement of the light guide. Need to increase. For this reason, the molding accuracy is reduced and deformation is apt to occur.

In the structure of the present invention, the thickness of the side face on the incident light side is increased by laminating the flat light guide on the wedge light guide, thereby preventing the wedge light guide from being deformed. High brightness can be achieved.

In a large-sized liquid crystal display device, a linear light source is disposed on at least two of the four side surfaces of the light guide for higher brightness. Normally, one or two lines are arranged on the upper side and the lower side in use, and the visual characteristics of the upper side and the lower side are symmetric. However, the display screen is rarely observed from the lower side, and the light emitted toward the lower side is not effectively used.

Therefore, the power consumption of the backlight is made more efficient by reducing the amount of emitted light, especially in the lower side direction, so that the total light amount of the light sources on each side is different from each other.

Further, by changing the tube current of the linear light source, changing the diameter of the linear light source, or changing the number of the linear light sources, the light amount of the upper side and the lower side can be changed.

[0033]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to examples.

FIG. 1 is a conceptual diagram for explaining the overall structure of a first embodiment of the liquid crystal display device according to the present invention. SUB1 is a lower substrate, SUB2 is an upper substrate, and a liquid crystal total LC is provided between both substrates. A liquid crystal panel is configured by being sandwiched. A lower polarizer POL1 and an upper polarizer PO are provided on the lower and upper surfaces of the liquid crystal panel, respectively.
L2 is stacked. In this embodiment, the lower substrate SU
A lower retardation plate PHD1 between B1 and a lower polarizer POL1;
An upper retardation plate PHD2 is interposed between the upper substrate SUB2 and the upper polarizing plate POL2.

On the back of the liquid crystal panel, a lower light diffusion sheet S
PS1, prism sheet PRS, upper light diffusion sheet SPS
The backlight BL is arranged via an optical sheet composed of two. The backlight BL is a flat light guide GLB-
Wedge-shaped light guides GLB-W1 on the lower surface and the upper surface of P, respectively.
A multi-layer light guide plate assembly in which GLB-W2s are laminated, and a cold cathode fluorescent lamp LP and a reflection sheet LS as two linear light sources are arranged on two parallel sides of the light guide plate assembly. One of the side surfaces on which the cold cathode fluorescent tubes LP are arranged is the upper side when used,
The other is on the lower side.

In a general liquid crystal display device, the display changes from white to black display or from black to white display according to a change in applied voltage. In this embodiment, the twist angle of the liquid crystal layer LC is about 90 degrees. Nematic (TN) type or vertical alignment type TFT drive or twist angle of 200
Degrees to 260 degrees super twisted nematic (S
The present invention can be applied to any liquid crystal display device of a so-called lateral electric field type which responds to an electric field in a direction horizontal to the substrate surface by time division driving of a TN) type.

In the case of the TN type and the horizontal electric field type liquid crystal display device, the product Δnd of the refractive index anisotropy Δn of the liquid crystal layer LC and the cell gap (thickness of the liquid crystal layer) d is 0.2 to 0.6 μm.
The range of m is preferable for achieving both the contrast ratio and the brightness. In the case of the STN type, the range is 0.5 to 1.2 μm.
The range is 0.2 to 1.0μ for the vertical alignment type.
It is preferably in the range of m.

As the lower and upper substrates SUB1 and SUB2, glass substrates having a thickness of 0.7 mm and a surface polished and transparent electrodes of ITO (indium tin oxide) formed by a sputtering method are used. A nematic liquid crystal composition having a positive dielectric anisotropy Δnε, a value of 4.5 and a birefringence Δn of 0.13 (589 nm, 20 ° C.) is sandwiched between these substrates, and the cell gap is 6 μm, Δnd
Was set to 0.78 μm. After applying the polyimide-based orientation control film applied on the surface of the substrate with a spinner,
And a rubbing treatment was performed to obtain a pre-tilt angle of 3.5 degrees (measured by a rotating product method).

The rubbing directions on both substrates were set such that the twist angle (twist angle) of the liquid crystal molecules was 240 degrees in order to perform time-division driving. Here, the twist angle is defined by the rubbing direction and the type and amount of the optical rotatory substance added to the nematic liquid crystal. The torsion angle is limited to a maximum value of 260 degrees as an upper limit, and a lower limit value is limited by contrast, and 200 degrees is a limit, since the lighting state in the vicinity of the threshold value has an orientation of scattering light.

The purpose of this embodiment is to provide a liquid crystal panel capable of displaying black and white images with sufficient contrast even when the number of scanning lines is 200 or more. Further, one retardation film made of polycarbonate and having a Δnd = 0.4 μm was disposed between each polarizing plate of both substrates.

The prism sheet PRS has a function of condensing the light from the backlight BL with two mutually intersecting prism grooves, and the light diffusion sheets SPS1 and SPS2 are provided to interfere with the light reflection patterns of the prism sheet and the light guide. It has the function of diffusing stripes. However, the wedge-shaped light guides GLB-W1, GL
Since B-W2 has a light collecting function, the prism sheet may be omitted.

In order to converge light by the wedge-shaped light guides GLB-W1 and GLB-W2, it is preferable to form a light reflection pattern by printing or laser processing, or to form a groove similar to a prism sheet at the time of injection molding. In addition, a plate-shaped light guide GLB-P
In the case of lamination, the surfaces having no light reflection pattern are brought into contact with each other, so that the light utilization rate is improved and the total thickness of the light guide assembly can be reduced.

A total of four cold cathode fluorescent tubes are provided, two on each of the upper and lower side surfaces of the light guide assembly. The diameter of the cold-cathode fluorescent tube is 2.6 mm, the tube current is 6 mA, the voltage is equal, the amount of light emitted from the upper side and the lower side is equal when the liquid crystal display device is used, and the vertical viewing angle of the screen luminance Dependencies are symmetric.

According to the structure of this embodiment, a bright, thin, lightweight, large-screen liquid crystal display device can be provided.

FIG. 2 is a sectional view of a backlight assembly for explaining a second embodiment of the liquid crystal display device according to the present invention. This backlight assembly is installed on the back of the liquid crystal panel and the optical sheet shown in FIG. In this embodiment, the wedge-shaped light guide GLB-W is laminated on the flat light guide GLB-P, and the light-entering surface (side surface having a large thickness) of the wedge-shaped light guide GLB-W is formed. One cold cathode fluorescent lamp LP is installed on each of the side surfaces of the lower plate-shaped light guide GLB-P, and the wedge-shaped light guide GLB-W has smaller thickness) and the lower portion. One cold-cathode fluorescent tube LP is installed in common on the side surface of the flat light guide GLB-P on the side. The diameter of the cold cathode fluorescent tube used is the same as in the first embodiment, and the tube current and the voltage are equal. A light reflection pattern is formed on the rear surface of the flat light guide GLB-P such that light reflection is increased corresponding to the thinner side of the wedge diameter light guide GLB-W. Therefore, the amount of emitted light in the upper side direction is larger than that in the lower side direction, and the visual dependency is an asymmetric pattern biased toward the upper side. As described above, the screen is rarely observed from the lower side direction, and sufficient luminance can be ensured even with such an emitted light amount pattern, and power consumption can be reduced.

FIG. 3 is a sectional view of a backlight assembly for explaining a third embodiment of the liquid crystal display device according to the present invention. This backlight assembly is installed on the back of the liquid crystal panel and the optical sheet shown in FIG. In this embodiment, similarly to FIG. 2, a wedge-shaped light guide GLB-W is replaced with a flat light guide GLB-W.
It is laminated on P. One large-diameter cold-cathode fluorescent lamp is common to the light-entering surface (side surface with a large thickness) of the wedge-shaped light guide GLB-W and the side surface of the flat light guide GLB-P below it. In addition to installing the tube LP, one small-diameter cold-cathode fluorescent tube is commonly provided on the side surface of the wedge-shaped light guide GLB-W having a small thickness) and the side surface of the flat light guide GLB-P thereunder. LP is installed. The diameter of the cold cathode fluorescent tube used is such that one large diameter on the lower side has a diameter of 4 mm and the tube current is 9 mA, and one small diameter on the upper side has a diameter of 2.6 mm and the tube current is 6 mA. A light reflection pattern is formed on the rear surface of the flat light guide GLB-P such that light reflection is increased corresponding to the thinner side of the wedge diameter light guide GLB-W.

Also in this configuration, the amount of light emitted in the upper side direction is larger than that in the lower side direction, and the viewing angle dependency is an asymmetric pattern biased toward the upper side. As described above, the screen is rarely observed from the lower side direction, sufficient luminance can be ensured even with such an emitted light pattern, and power consumption can be reduced as compared with the first embodiment.

FIG. 4 is an explanatory diagram of the intensity pattern of the light emitted from the backlight in the first, second and third embodiments. (A) shows the emitted light pattern of the first embodiment, and (b) shows the emitted light patterns of the second and third embodiments. In the figure, “above” on the horizontal axis indicates the upper side of the screen, “lower” indicates the lower side of the screen, and the arrow on the vertical axis indicates the intensity of the emitted light.

In the first embodiment as well, by controlling the distribution of the light reflection pattern formed on the light guide, a light reflection pattern as shown in FIG. FIG. 5 is a sectional view of a backlight assembly for explaining a fourth embodiment of the liquid crystal display device according to the present invention. In this embodiment, a flat light guide GL is placed on a wedge-shaped light guide GLB-W.
BP are stacked, and the arrangement and the number of cold cathode fluorescent tubes are the same as in the second embodiment. According to this embodiment,
The same effect as in the second embodiment can be obtained.

FIG. 6 is a sectional view of a backlight assembly for explaining a fifth embodiment of the liquid crystal display device according to the present invention. In this embodiment, a flat light guide GLB-P is laminated on a light guide GLB-W having a wedge diameter, and the arrangement and the number of cold cathode fluorescent tubes are the same as in the third embodiment. . According to this embodiment, the same effect as that of the third embodiment can be obtained.

Next, an example of the overall configuration of a liquid crystal display device to which the present invention is applied will be described in detail for an in-plane switching mode (IPS).

In a horizontal electric field type liquid crystal display device, various electrodes for pixel selection and switching elements are formed on one substrate (generally, a lower substrate), and only a color filter is formed on the other substrate (upper substrate). A method for controlling lighting / non-lighting by forming an electric field in a direction substantially parallel to the substrate plane on a liquid crystal layer sandwiched between the two substrates and changing the orientation direction of liquid crystal molecules forming the liquid crystal layer within the substrate plane. It is.

FIG. 7 is a cross-sectional view of one pixel of a liquid crystal display device of a horizontal electric field type, wherein CT is a common electrode, GI is a gate insulating film, DL is a video signal electrode, PX is a pixel electrode, and ORI1 is a lower alignment film. , ORI2 is an upper alignment film, LC is a liquid crystal (here, shown in the form of liquid crystal molecules), SUB1 is a lower substrate, SUB
2 is an upper substrate, POL1 is a lower polarizing plate, POL2 is an upper polarizing plate, E is an electric field, BM is a black matrix, FIL is a color filter, OC is an overcoat film, and PSV1 is an insulating film.

In the figure, a lower substrate SUB1 has a thin film transistor TFT (described later), a video signal electrode (pixel electrode) PX as an electrode for driving liquid crystal, and a common electrode CT as a silicon nitride film (SiN) as an insulating film. An insulating film PSV1 is formed on the GI and covers these electrodes. The upper substrate SUB2 is provided with a plurality of color filters FIL partitioned by a black matrix BM. The layer LC is sandwiched. The lower polarizer POL is provided on the outer surface of the lower substrate SUB1 and the outer surface of the upper substrate SUB2, respectively.
1. The upper polarizing plate POL2 is laminated. The video signal electrode and the common electrode CT that are in direct contact with the alignment film and the liquid crystal layer are formed of ITO (Indium Tin Oxide) in consideration of metal corrosion.
xide: indium tin oxide).

FIG. 8 is a conceptual diagram of a driving circuit of the liquid crystal display device shown in FIG.
Denotes a scanning electrode driving circuit, H denotes a signal electrode driving circuit, CD denotes a common electrode driving circuit, and AR denotes a display area of a liquid crystal panel.
Incidentally, C _LC is the capacitance component of the liquid crystal, the C _S indicates a holding capacitance.

The TFTs for switching the pixels constituting the display area AR of the liquid crystal panel are selectively turned on / off by the scan electrode drive circuit V, the signal electrode drive circuit H, and the common electrode drive circuit CD. This on / off is controlled by the control circuit CONT.

The liquid crystal layer in which the alignment direction of the molecule changes when the TFT is turned on / off is in the initial state in the alignment state (alignment control ability) of the lower and upper alignment films ORI1 and ORI2 formed on both substrates SUB1 and SUB2. The orientation direction is set.

In this configuration, polyimide was used as the alignment film, and the surface of the polyimide film was irradiated with polarized UV light in order to impart alignment controllability to the surface. The KrF excimer laser (wavelength 248 n)
m), and irradiation was performed at an irradiation energy of 5 mJ / cm ² in 76 shots. The lower substrate SUB1 on which the alignment film was formed was fed at a constant speed, and the feeding speed was set so that the irradiation surface was uniformly irradiated with 76 shots of polarized UV.

The upper substrate S, which is a color filter substrate,
A polyimide was applied to the outermost surface of UB2, and irradiated with polarized UV as described above. Note that the liquid crystal layer LC is oriented in a direction perpendicular to polarized light.

FIG. 9 is an explanatory view of the definition of the alignment control direction of the alignment film and the direction of the transmission axis of the polarizing plate.
DR is the orientation control direction of the orientation film, and PDR is the transmission axis direction of the polarizing plate.

In the present embodiment, as shown in the figure, the easy axes of the alignment molecules of the liquid crystal on the interface with the upper and lower alignment films are substantially parallel to each other, and are formed with the direction of the applied electric field. The angle was set to 75 degrees (φ _LC1 = φ _LC2 = 75 °).

The dielectric anisotropy Δε is positive between the two substrates, the value is 7.3, and the refractive index anisotropy Δn is 0.07.
4 (wavelength 589 nm, 20 ° C.) to form a liquid crystal layer with a nematic liquid crystal composition interposed therebetween.

The gap between the two substrates, that is, the cell gap d, was set by dispersing spherical polymer beads between the substrates, and was set to 4.0 μm when the liquid crystal was sealed. Therefore,
Δn · d is 0.296 μm.

Two polarizing plates (for example, a G plate manufactured by Nitto Denko Corporation)
1220 DU) sandwiching the liquid crystal panel, the polarization transmission axis of one polarizing plate is set to φ _p1 = 75 °, and the other is orthogonal to this.
That is, φ _p2 = −15 °. In this embodiment, a normally-closed characteristic is employed in which a dark state occurs at a low voltage (V _OFF ) and a bright state occurs at a high voltage (V _ON ).

FIG. 10 is a schematic diagram for explaining the operation of the liquid crystal molecules in the bright state and the dark state in the liquid crystal display device of the in-plane switching mode, and the reference numerals are the same as those in FIG.

FIG. 7A is a cross-sectional view of a dark state at an applied voltage (V _OFF ), FIG. 7B is a cross-sectional view of a dark state at a bright state at an applied voltage (V _ON ), and FIG. (V _OFF ) is a sectional view of a dark state in a dark state, and (d) is a plan view of an applied voltage (V _ON ) in a bright state.

In the dark state shown in (a) and (c), since no electric field exists between the common electrode CT and the pixel electrode PX, the liquid crystal molecules LC constituting the liquid crystal layer are in an initial alignment state.
Illumination light from a backlight (not shown) installed on the lower surface of the lower substrate SUB1 does not reach the upper substrate SUB2.

On the other hand, in the bright state shown in (b) and (d), an electric field E exists between the common electrode CT and the pixel electrode PX. Backlight (not shown) installed on the lower surface of SUB1
From the light reaches the upper substrate SUB2 side.

As described above, in the liquid crystal display device of the in-plane switching mode, the liquid crystal molecules LC rotate in a plane parallel to the plane of the substrate, that is, in the horizontal direction, and form an image by switching between a bright state and a dark state.

FIGS. 11A and 11B are explanatory views of an example of an electrode structure in a liquid crystal display device of a horizontal electric field type, in which FIG. 11A is a plan view seen from a direction perpendicular to the substrate, and FIG. 11B is a cross section taken along line AA in FIG. Figure,
(C) is a sectional view taken along line BB of (a).

The thin film transistor TFT includes a pixel electrode (source electrode) PX, a video signal electrode (drain electrode) DL, a scanning electrode (gate electrode) GL, and amorphous silicon a-Si. Scan electrode GL and part CT-a of common electrode, video signal electrode DL and part PX of pixel electrode
-A was formed by patterning the same metal layer. Further, after forming the insulating film GI, a part CT-b of the common electrode, which is a part for driving the liquid crystal, is connected to a part CT-a of the common electrode by a through hole, and the pixel electrode is also formed through the transistor part. A portion PX-b of the pixel electrode was formed by making contact with the hole. Part of the common electrode CT-b and part of the pixel electrode PX-b were formed using ITO.

The capacitive element 16 forming a storage capacitor is formed in a structure in which an insulating protective film (gate insulating film) GI is sandwiched between the pixel electrode PX and the common electrode CT in a region connecting between the two common electrodes 1. The pixel electrodes are arranged between the three common electrodes CT as shown in the plan view (a). The pixel pitch is 100 μm in the horizontal direction (ie, between video signal wiring electrodes), and 3 μm in the vertical direction (ie, between scanning wiring electrodes).
00 μm. The electrode width is set such that a scanning electrode, a signal electrode, and a common electrode wiring portion (a portion extending in a direction parallel to the scanning wiring electrode (a horizontal direction in FIG. 12 described later)), which are wiring electrodes extending over a plurality of pixels, are widened. Avoid flaws. Their widths are 10 μm, 8 μm and 8 μm, respectively.

On the other hand, the widths of the pixel electrodes formed independently for each pixel and the portions of the common electrode extending in the longitudinal direction of the signal wiring electrode were slightly reduced to 5 μm and 6 μm, respectively.
By reducing the width of these electrodes, the possibility of disconnection due to the incorporation of foreign matter or the like increases, but in this case, a partial defect of one pixel is sufficient, and no line defect occurs. The signal electrode DL and the common electrode CT were provided at an interval of 2 μm via the insulating film 25. The number of pixels is 640 × 3 (R, G, B) signal wiring electrodes and 48
640 × 3 × 480 electrodes were formed by using zero wiring electrodes.

FIGS. 12A and 12B are explanatory views of the structure of a color filter substrate with a black matrix. FIG. 12A is a plan view as viewed from a direction perpendicular to the substrate surface, and FIG. FIG. 3C is a sectional view taken along line BB ′ of FIG.

A material obtained by mixing carbon and an organic pigment was used as the black matrix BM. The arrangement of the black matrix BM with respect to the electrode substrate is indicated by a broken line in FIG.

After the formation of the black matrix BM, R, G, and B pigments were dispersed in a photosensitive resin, and each of the color filters FIL was formed by coating, patterning exposure, and development. Then, an epoxy-based polymer thin film was applied and formed as an overcoat film OC on the color filter FIL.

The liquid crystal display device thus obtained is
It is possible to obtain an image display with a wide viewing angle at which gradation inversion does not occur and excellent display uniformity while maintaining a contrast of 10 or more at 80 degrees, up, down, left, and right.

The present invention is not limited to the above-described in-plane switching mode liquid crystal display device, but can be similarly applied to other types of active matrix type liquid crystal display devices, simple matrix type and other liquid crystal display devices. .

[0079]

As described above, according to the present invention,
It is possible to provide a thin and lightweight liquid crystal display device that can achieve high luminance required with an increase in the size of a liquid crystal panel, and has high light use efficiency.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram illustrating an overall configuration of a first embodiment of a liquid crystal display device according to the present invention.

FIG. 2 is a sectional view of a backlight assembly illustrating a second embodiment of the liquid crystal display device according to the present invention.

FIG. 3 is a sectional view of a backlight assembly illustrating a liquid crystal display according to a third embodiment of the present invention;

FIG. 4 is an explanatory diagram of an intensity pattern of light emitted from a backlight in the first embodiment, the second embodiment, and the third embodiment.

FIG. 5 is a cross-sectional view of a backlight assembly illustrating a liquid crystal display according to a fourth embodiment of the present invention.

FIG. 6 is a cross-sectional view of a backlight assembly illustrating a liquid crystal display according to a fifth embodiment of the present invention.

FIG. 7 is a cross-sectional view of one pixel of a horizontal electric field type liquid crystal display device.

8 is a conceptual diagram of a driving circuit of the liquid crystal display device shown in FIG.

FIG. 9 is an explanatory diagram of definitions of an alignment control direction of an alignment film and a transmission axis direction of a polarizing plate.

FIG. 10 is a schematic diagram illustrating the operation of liquid crystal molecules in a bright state and a dark state in a liquid crystal display device of an in-plane switching mode.

FIG. 11 is an explanatory diagram of an example of an electrode structure in a liquid crystal display device of an in-plane switching mode.

FIG. 12 is a structural explanatory view of a color filter substrate with a black matrix.

FIG. 13 is an exploded perspective view illustrating a configuration example of a liquid crystal display device.

14 is a schematic cross-sectional view illustrating a layered structure of the liquid crystal display device shown in FIG.

FIG. 15 is a cross-sectional view illustrating another configuration example of a conventional backlight for increasing luminance.

[Explanation of symbols]

 SUB1 Lower substrate SUB2 Upper substrate ORI1 Lower alignment film ORI2 Upper alignment film LC Liquid crystal layer POL1 Lower polarizing plate POL2 Upper polarizing plate PHD1 Lower retardation plate PHD2 Upper retardation plate SPS1, SPS2 Diffusion sheet PRS Prism sheet BL Backlight GLP-P Flat plate Light guide GLP-W1, GLP-W2 Wedge shaped light guide LP Linear light source (cold cathode fluorescent tube) LS Reflective sheet.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Masuyuki Ota 3300 Hayano, Mobara-shi, Chiba Electronic Device Division, Hitachi, Ltd. (72) Inventor Masahiro Ishii 3300 Hayano, Mobara-shi, Chiba Electronic Device Business, Hitachi, Ltd. (72) Inventor Yoshiaki Nakayoshi 3300 Hayano, Mobara City, Chiba Prefecture Inside the Electronic Devices Division, Hitachi, Ltd. (72) Inventor Nobuyuki Suzuki 3300 Hayano, Mobara City, Chiba Prefecture, F-term Electronic Device Division, Hitachi, Ltd. (Reference) 2H038 AA52 AA55 2H091 FA08X FA08Z FA11X FA11Z FA14Z FA21Z FA23Z FA31Z FA41Z FB02 FB12 FB13 FC10 FC23 FD01 FD03 FD06 GA06 GA08 GA11 GA13 HA07 HA10 KA01 KA02 KA04 LA03 LA11 LA16 5G435 AA03 FF03 BB01 FF01 GG26 HH02

Claims (2)

[Claims] 1. A liquid crystal panel comprising a pair of substrates having electrodes disposed on at least one of them facing each other, a liquid crystal panel sandwiched between the pair of substrates, and a pair of polarized light disposed so as to sandwich the liquid crystal panel. A liquid crystal display device comprising at least a plate, control means for applying a voltage to the electrode according to a display image signal, and an illumination light source for illuminating the liquid crystal panel from the back, wherein the illumination light source is a flat plate. Light guide plate assembly formed by laminating at least one of each of a light guide plate and a wedge-shaped light guide, at least one linear light source installed along a side surface of the light guide plate assembly, and the line A liquid crystal display device comprising: a reflection sheet for reflecting light emitted from the light source in the direction of the light guide plate. 2. The linear light source is installed on each of two parallel sides of the light guide assembly, and a viewing angle dependency of light transmitted through the liquid crystal panel is asymmetric with respect to a center line parallel to the two sides. 2. The liquid crystal display device according to claim 1, wherein the brightness of each of said linear light sources is set as possible.