JPH11133420A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain high contrast and excellent visibility by providing a light absorption processing surface Oil a part of a display window of an upper frame facing on a liquid crystal panel and prolonging/arranging an upper polarizing plate until the lower layer of the upper frame. SOLUTION: A pair of transparent substrates SUB1, SUB2 provided with pixel selecting electrodes are arranged oppositely, and a liquid crystal layer is held between both substrates, and the liquid crystal panel PNL is constituted, and the upper polarizing plate POL and a lower polarizing plate are arranged holding the liquid crystal panel PNL between them. Then, a backlight BL provided on the rear surface of the liquid crystal panel PNL is fixed by the upper frame SHD and a lower frame successively provided with this. At this time, a chrome metallic film added with double hatching is formed on the part of the display window of the upper frame SHD facing on the liquid crystal panel PNL to be made it the light absorption processing surface BKD, and the upper polarizing plate POL stuck to the upper substrate SUB2 of the liquid crystal panel PNL is prolonged to the lower layer of the upper frame SHD. Thus, a light leakage between a display area and the upper frame when the frame is narrowed is shielded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device having high contrast and excellent visibility.

[0002]

2. Description of the Related Art A high-definition and color display liquid crystal display device for a notebook computer or a computer monitor is provided with a light source (so-called backlight) for illuminating a liquid crystal panel from behind. As the backlight, there are known a side edge type in which a linear lamp is arranged on a side surface of a transparent plate formed of an acrylic resin or the like called a light guide plate, and a direct type in which a lamp is arranged just below the back of a liquid crystal panel. I have.

In particular, a notebook-type computer which requires a thinner type employs a side-edge method, and a liquid crystal display device for a monitor also uses a side-edge method to reduce the depth.

This type of liquid crystal display device basically forms a so-called liquid crystal panel in which a liquid crystal layer is sandwiched between two substrates at least one of which is made of transparent glass or the like, and is formed on the liquid crystal panel substrate. A method of selectively applying a voltage to the various electrodes for forming a pixel to turn on and off a predetermined pixel, forming the various electrodes and an active element for pixel selection, and selecting the active element to form a predetermined pixel. Are turned on and off.

[0005] The latter type of liquid crystal display device is called an active matrix type, and is the mainstream of the liquid crystal display device because of its contrast performance, high-speed display performance and the like. A conventional 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. I was

In recent years, a so-called lateral electric field method (I
A liquid crystal display device of the PS type is also realized. As this in-plane switching mode liquid crystal display device, a device in which a very wide viewing angle is obtained by using a comb electrode on one of two substrates is known (Japanese Patent Publication No. 63-21907,
U.S. Pat. No. 4,345,249).

[0007]

The size of liquid crystal display devices for computer monitors of various information processing devices, not only notebook type computers, is increasing year by year, and the demand for narrower frames is increasing. When the frame of the liquid crystal display device is narrowed, the distance between the edge of the device and the display area becomes narrow, so that it is difficult to sufficiently shield light leakage from the backlight to the display area.

FIG. 6 is a schematic cross-sectional view illustrating an example of the structure of a main part of a conventional liquid crystal display device. A liquid crystal is sandwiched between two substrates SUB1 (lower substrate) and SUB2 (upper substrate). Polarizer POL on upper and lower surfaces (only upper polarizer is shown in the figure)
Are fixed to an upper frame SHD and a lower frame (not shown) to form a liquid crystal module.

This liquid crystal module is housed in a case CASE such as a notebook personal computer or a computer monitor to be mounted to form a display device such as the computer monitor.

However, in this type of liquid crystal display device, since the upper frame is formed of a metal plate for suppressing electromagnetic radiation and for securing mechanical strength, light reflection on the surface thereof is performed. At a high rate, light leakage from the backlight at the outer edge of the display area is reflected by the inner peripheral area of the display window of the upper frame, and a bright edge phenomenon occurs in which the periphery of the display area becomes bright. FIG. 7 is an enlarged view of a portion A in FIG. 6 for explaining occurrence of light leakage in a conventional liquid crystal display device.

The liquid crystal panel PNL includes an upper substrate SUB1 and a lower SUB2, and an upper polarizing plate POL is provided on an upper surface of the upper substrate.
Is affixed. This upper polarizer POL is composed of an upper substrate SUB
It is in a position retracted inward from the edge of No. 2. In addition, the width of the upper frame SHD is reduced for narrowing the frame.

The backlight BL and the liquid crystal panel P for preventing light from leaking from the periphery of the liquid crystal panel PNL.
The light shielding spacer ILS is sandwiched between the NLs.

However, as indicated by the arrow in FIG. 1, part of the light from the backlight emitted from the edge of the polarizing plate POL is reflected by the side edge of the upper frame SHD, or the liquid crystal panel and the upper frame SHD are reflected. The light is reflected between the insides and is emitted toward the display surface. This brightens the periphery of the display area, and the bright edge phenomenon described above occurs.

This bright edge phenomenon causes a reduction in the contrast of a displayed image and a deterioration in visibility.

An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a liquid crystal display device having high contrast and good visibility.

[0016]

In order to achieve the above object, the present invention provides a liquid crystal panel having a liquid crystal layer sandwiched between a pair of transparent substrates having at least one of them opposed to each other and having a pixel selection electrode. And an upper polarizing plate and a lower polarizing plate disposed on both sides of the liquid crystal panel, a driving unit for applying a voltage according to a display signal to the electrodes, and a backlight installed on the back surface of the liquid crystal panel. A liquid crystal display device fixed by an upper frame having a display window and a lower frame connected to the upper frame, wherein at least a portion of the display window of the upper frame facing the liquid crystal panel has an absorption processing surface, and It is characterized in that a polarizing plate is arranged so as to extend to a lower layer of the upper frame.

According to the above configuration, it is possible to prevent the light emitted from the backlight from leaking from between the display area and the upper frame, or to be reflected on the metal frame and leaking in the display direction. The light-shielding effect can be further improved by extending the lower surface of the device.

The light-absorbing treatment applied to at least the portion of the display window of the upper frame facing the liquid crystal panel is performed by applying a black metal coating such as chrome or a black paint on a glossy metal surface such as stainless steel, iron or aluminum. Obtained by baking. Further, the material of the upper frame itself may be formed of chrome or another black metal plate.

Further, a light-shielding frame may be formed of a black resin, and the light-shielding frame may be embedded inside the window of the upper frame, or a black plastic tape may be attached.

At this time, it was experimentally confirmed that if the reflectance of the surface of the upper frame facing the liquid crystal panel is set to 5% or less, it is possible to prevent a decrease in contrast and a deterioration in visibility due to leaked light.

In the present invention, by changing the voltage applied to the liquid crystal layer, the transmission / non-transmission of the illumination light from the backlight is controlled to change from white display to black display or from black display to white display. The present invention relates to a twisted nematic (TN type) liquid crystal having a twist angle of about 90 degrees and a super twisted nematic (STN) liquid crystal having a twist angle of 200 to 260 degrees.
Type) Liquid crystal display device using liquid crystal, vertical alignment type (vertical electric field type) TFT, horizontal electric field type liquid crystal display device operated by electric field parallel to the substrate surface, and other types of liquid crystal display devices Applicable.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to examples.

FIG. 1 is a schematic cross-sectional view of a main part of a liquid crystal display device according to a first embodiment of the present invention, wherein SUB1 is a lower substrate, SUB2 is an upper substrate, POL is an upper polarizing plate, GLB is a light guide plate, LP indicates a light source lamp, LS indicates a reflector, SHD indicates an upper frame, BKD indicates an absorption processing surface, and CASE indicates a case forming a display unit such as a computer to be mounted.

When the liquid crystal display device is of the TN type or vertical alignment type vertical electric field type, the product Δn · d of the refractive index anisotropy Δn of the liquid crystal layer 2 and the cell gap (gap between the upper and lower substrates) is 0. The range of 0.2 to 0.6 μm is preferable in order to achieve both the contrast ratio and the brightness.
A range of 5 to 1.2 μm is preferable, and a range of 0.2 to 0.5 μm is preferable in the horizontal electric field method.

Here, as the upper and lower substrates 3b and 3a,
Two glass substrates each having a thickness of 0.7 mm, a surface polished, and a transparent electrode of ITO (indium tin oxide) formed by a sputtering method are used. The dielectric anisotropy Δnε between these upper and lower substrates 3b and 3a is positive, the value is 4.5, and the birefringence Δn is 0.19 (589 nm, 20 ° C.).
And a cell gap of 6 μm
Therefore, Δn · d was 1.41 μm.

Then, the polyimide-based orientation control film applied to the substrate surface was applied by a spinner, baked at 250 ° C. for 30 minutes, and rubbed to form a pretilt angle of 3.5 degrees. The pretilt angle was measured by a rotating crystal method. The rubbing directions of the upper and lower 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 maximum value of the torsion angle is limited because the lighting state near the threshold value is an orientation that scatters light, the upper limit is 260 degrees, the lower limit is limited by contrast, and the limit is 200 degrees.

The purpose of this embodiment is to provide a liquid crystal display capable of displaying black and white with sufficient contrast even when the number of scanning lines is 200 or more. Further, the lower substrate 3a, the upper substrate 3b, and the polarizing plates 1a and 1
Δn · d = 0.4 made of polycarbonate during b
One μm retardation film was disposed on each sheet (not shown).

In this embodiment, the light absorption surface BKD is provided on the portion of the upper frame SHD for fixing the liquid crystal panel PNL facing the liquid crystal panel, that is, on the inside and the inside edge of the window of the upper frame SHD. At the same time, the upper polarizing plate POL attached to the upper substrate SUB2 of the liquid crystal panel PNL was extended to below the upper frame SHD.

FIG. 2 is a partial view for explaining the structure of the upper frame of the first embodiment of the liquid crystal display device according to the present invention.

FIG. 3A is a partial perspective view showing the back surface of the upper frame SHD. A chromium metal film with double hatching is formed on the back surface and the inner edge of the inner peripheral edge surrounding the window WD. This is the light absorption treated surface BKD.

FIG. 2B is a partial sectional view showing the section taken along the line BB of FIG. In this embodiment, the light absorption processing surface BKD is provided only on the back surface and the inner edge of the inner peripheral edge surrounding the window portion WD, but the same light absorption processing surface BKD may be formed on the upper surface edge indicated by the arrow C in the drawing. Further, a similar light absorption processing surface BKD may be formed on a part or the whole of the remaining portion of the upper frame SHD.

By adopting the configuration of this embodiment, light leakage from between the display area of the liquid crystal panel and the upper frame when the frame is narrowed is suppressed, and a liquid crystal display device with high contrast and excellent visibility is provided. Obtainable.

FIGS. 3A and 3B are completed views of the liquid crystal display device according to the present invention, wherein FIG. 3A is a plan view on the display surface side, FIG. 3B is a left side view, FIG. 3C is a right side view, and FIG. Upper side, (E)
Shows a lower side view.

In the figure, SHD is the upper frame, AR
Is the display area, MCA is the lower frame (lower case), HLD
1-4 are mounting holes, LCT is connection connector, LPC
Reference numerals 1 and 2 are lamp cables, CT1 is an interface connector, and WD is an opening exposing a display area. Also,
POL is affixed to the upper surface of the liquid crystal panel PNL with an upper polarizing plate.

This liquid crystal display device is incorporated by using two kinds of storage / holding members of an upper frame SHD and a lower frame ML, and is mounted on display portions of an information processing device such as a notebook personal computer or a monitor through mounting holes HLD1 to HLD4. Is done.

In the recess between the mounting holes HLD1 and HLD3, a backlight inverter is incorporated, and the connector LCT and the lamp cables LPC1, LPC2 are connected.
Supplies power to the cold cathode fluorescent lamp (light source lamp) constituting the backlight assembly. In this example, the fluorescent tubes are incorporated on the upper and lower sides of the back of the liquid crystal display element PNL.

Signals from the main body computer (host) and necessary power are supplied through an interface connector CT1 located on the back surface.

The illustrated liquid crystal display has a large outer diameter,
The so-called frame area that does not contribute to the display is small despite the display area AR also being large. Furthermore, the weight is also reduced, and a large-screen display that is easy to view without losing the portability of the portable information processing device can be obtained.

FIG. 4 is an exploded perspective view for explaining the entire structure of the liquid crystal display device according to the present invention. FIG. 1 illustrates a specific structure of a liquid crystal display device (module: MDL) in which a liquid crystal display panel, a circuit board, a backlight, and other components are integrated.

SHD is an upper frame (also called a shield case or metal frame) made of a metal plate, WD is a display window, INS1 to 3 are insulating sheets, PCB1 to 3 are circuit boards (PCB1 is a drain side circuit board: video signal line). Driving circuit board, PCB2 is gate side circuit board, PCB3 is interface circuit board), JN1-3 are circuit boards PC
Joiner for electrically connecting B1 to B1, TCP1,
TCP2 is a tape carrier package, PNL is a liquid crystal display panel, POL is an upper polarizing plate, GC is a rubber cushion,
ILS is a light shielding spacer, PRS is a prism sheet, SP
S is a diffusion sheet, GLB is a light guide plate, RFS is a reflection sheet, MCA is a lower frame (lower case: mold frame) formed by integral molding, MO is an opening of MCA, and BAT is a double-sided adhesive tape. The liquid crystal display module MDL is assembled by stacking the diffusion plate members in the above arrangement. The illustration of the light source lamp is omitted.

This liquid crystal display device (liquid crystal display module MDL) has two kinds of storage / holding members of a lower frame CA and an upper frame SHD, and includes insulating sheets INS1-3, circuit boards PCB1-3, and a liquid crystal display panel. The lower frame MCA in which the PNL is stored and fixed and the backlight including the light guide plate GLB is stored is combined with the upper frame SHD.

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 supplied to the integrated circuit chip mounted on the video signal line driving circuit board PCB1.

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. 5 is an external view of a personal computer for explaining an example of an information processing apparatus in which the liquid crystal display device shown in FIG. 4 is mounted. An inverter power supply for driving and a CPU are a host-side central processing unit.

According to the personal computer shown in the figure, an image display with a wide viewing angle, uniform contrast and good visibility can be obtained.

It should be noted that the present invention is not limited to the above-mentioned horizontal electric field type active matrix type liquid crystal display device, but is applicable to a vertical electric field type or simple matrix type liquid crystal display device. The unnecessary method and device can be similarly applied.

[0050]

As described above, according to the present invention,
Light leakage from between the display area of the liquid crystal panel and the upper frame when the frame is narrowed is suppressed, and a liquid crystal display device with high contrast and excellent visibility can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a principal part explaining a first embodiment of a liquid crystal display device according to the present invention.

FIG. 2 is a partial view illustrating a configuration of an upper frame of the first embodiment of the liquid crystal display device according to the present invention.

FIG. 3 is an assembled view of the liquid crystal display device according to the present invention.

FIG. 4 is an exploded perspective view illustrating the overall configuration of the liquid crystal display device according to the present invention.

5 is an external view of a personal computer illustrating an example of an information processing device equipped with the liquid crystal display device shown in FIG.

FIG. 6 is a schematic cross-sectional view illustrating an example of a main part structure of a conventional liquid crystal display device.

FIG. 7 is an enlarged view of a portion A in FIG. 6 for explaining occurrence of light leakage in a conventional liquid crystal display device.

[Explanation of symbols]

SUB1 Lower substrate SUB2 Upper substrate POL Upper polarizing plate GLB Light guide plate LP Light source lamp LS reflector SHD Upper frame BKD Absorption processing surface CASE Case that constitutes a display unit such as a computer to be mounted.

Claims (1)

[Claims] 1. A liquid crystal panel having a liquid crystal layer sandwiched between a pair of transparent substrates having a pixel selection electrode on at least one of them opposed to each other, an upper polarizer disposed on both sides of the liquid crystal panel, and A lower polarizing plate, a driving unit for applying a voltage corresponding to a display signal to the electrode, and a backlight installed on the back of the liquid crystal panel, an upper frame having a display window and a lower frame connected to the upper frame. In a liquid crystal display device fixed by a frame, at least a portion of the display window of the upper frame facing the liquid crystal panel has an absorption processing surface, and the upper polarizing plate is arranged to extend to a lower layer of the upper frame. A liquid crystal display device characterized by the above-mentioned.