JPH117010A - Liquid crystal display - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a liquid crystal display device which can suppress a change in liquid crystal characteristics due to ultraviolet rays from backlight light, and has high display quality and high reliability. An ultraviolet cut filter that cuts a component having a light wavelength of 380 nm or less is adhered to an entire end surface of a light guide on a side where a cold cathode fluorescent tube is arranged by an adhesive layer. The ultraviolet-cut resin film 3 having the same characteristics was provided on the outer surface of each of the outer surfaces of the substrate 11 and the lower electrode substrate 12 where the polarizing plates 15 and 16 were not arranged.

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, and more particularly to a technique for suppressing a change in liquid crystal characteristics due to ultraviolet rays from a light source.

[0002]

2. Description of the Related Art Conventional liquid crystal display devices (ie, LCDs)
(Liquid Crystal Display)) is called a twisted nematic type, which is composed of a nematic liquid crystal having a positive dielectric anisotropy between two electrode substrates.
It has a twisted helical structure, and a pair of polarizing plates is arranged outside both electrode substrates so that their polarization axes (or absorption axes) are orthogonal or parallel to the axes of liquid crystal molecules adjacent to the electrode substrates. (Japanese Patent Publication No. 51-136)
No. 66).

[0003] Such a liquid crystal display element having a twist angle of 90 ° has problems in the steepness γ of the change in the transmittance of the liquid crystal layer with respect to the voltage applied to the liquid crystal layer and the viewing angle characteristics. 64 corresponding to the number of electrodes) was the practical limit. However, in order to cope with recent demands for improving the image quality and increasing the amount of display information for liquid crystal display elements, the twist angle α of the liquid crystal molecules sandwiched between a pair of polarizing plates is set to be larger than 180 °, and the voltage applied to this liquid crystal layer is increased. Applied physics letter is to improve the time-sharing drive characteristics and increase the number of time-sharing by detecting the change in the birefringence effect of the liquid crystal layer due to
45, No. 10, 1021, 1984 (Applied Physics Letter,
T. J. Scheffer, J .; Nehring: “A new, highly multip
lexable liquid crystal display "), and a super twisted birefringence effect (SBE) liquid crystal display device has been proposed.

A liquid crystal display device (ie, a liquid crystal display module) is made of, for example, two sheets of glass or the like at a predetermined interval so that the surfaces on which an electrode made of a transparent conductive film and an alignment film are laminated face each other. The two substrates are laminated together and the liquid crystal is sealed between the two substrates inside the seal material by providing a sealing material provided in a frame shape (a square shape) around the edge between the two substrates. And a liquid crystal display element having a polarizing plate provided outside each of the substrates, a backlight disposed below the liquid crystal display element to supply light to the liquid crystal display element, and an outer peripheral part of the liquid crystal display element. A liquid crystal driving circuit board, a frame-shaped body made of a plastic molded product holding these members, and a housing for each of these members, covering the periphery of the liquid crystal display element and exposing the display area thereof. Metal shield case having an opening and a (metal frame) and the like.

In a simple matrix type liquid crystal display device, a plurality of transparent electrodes are formed in a strip shape on each substrate in parallel with each other, and when viewed from a direction perpendicular to the substrate surface, the two substrates intersect at right angles. Assembled and assembled. The portion where the upper and lower transparent electrodes overlap is a pixel,
By applying a pulse voltage between the transparent electrodes of the two substrates one after another, the shape of the liquid crystal is displaced by the voltage, the liquid crystal molecules are driven, and a predetermined display is performed.

The backlight is, for example, a rectangular parallelepiped made of a transparent acrylic or other synthetic resin plate for guiding light emitted from the light source to a direction away from the light source and uniformly irradiating the entire liquid crystal display element with the light. A light guide, a fluorescent tube which is a linear light source arranged along at least one end surface (side surface) of the light guide, and a fluorescent tube covering substantially the entire length of the fluorescent tube and having a substantially U-shaped cross section; A lamp reflection sheet for returning light to the light guide so as not to leak light to the outside; a diffusion sheet disposed on the light guide for diffusing light from the light guide; and one or two prisms for improving brightness It comprises a sheet and a reflection sheet disposed below the light guide and reflecting light from the light guide toward the liquid crystal display element. Such a backlight is called an edge light system.

The light incident on the light guide from the fluorescent tube is guided while totally reflecting the light inside the light guide. However, the light is emitted from the upper surface of the light guide by diffuse reflection. Are a plurality of light-diffusing circular dot patterns printed with white ink, convex portions provided integrally with the bottom surface, holes,
The grooves are regularly arranged and formed.

In addition, a plurality of fluorescent tubes arranged in parallel with each other via a diffusion plate below the liquid crystal display device, and arranged below the fluorescent tube to reflect light from the fluorescent tube toward the liquid crystal display device. There is also a so-called direct-type backlight composed of a reflective plate that makes the light reflected from the light source.

Such a conventional liquid crystal display device is disclosed in, for example, Japanese Patent Publication No. 60-19474 and Japanese Utility Model Laid-Open Publication No. 4-22780.
No., published in Japanese Unexamined Patent Publication No.

[0010]

Conventionally, in order to eliminate the influence of ultraviolet rays on the liquid crystal, the outer surfaces of a pair of substrates constituting the liquid crystal display element have a characteristic of cutting off ultraviolet rays of, for example, λ = 380 nm or less. A polarizing plate is attached to each (a protective layer made of a plastic film on both sides of the polarizing layer contains an ultraviolet absorber).

However, when the polarizing plate is provided with an intersection of the production and the attachment, and when the polarizing plate protrudes out of the substrate, the electrical connection on the inner surface of the substrate is supported. Is slightly smaller than the size of the substrate, and no polarizing plate is formed on the outer peripheral portion (peripheral portion) of each substrate of the liquid crystal display device. For this reason, ultraviolet rays of the backlight light enter from the outer peripheral portion, and particularly, the threshold voltage of the liquid crystal in the vicinity of the light source changes, and there is a problem that display unevenness (appears white in a negative type) on a screen. .

Conventionally, the outer surface of the substrate, which is not covered with a polarizing plate, is partially overlapped with the polarizing plate, such as ABS (acrylonitrile butadiene styrene) or P
Some screens are provided with a blind plate made of C (polycarbonate) or the like, but the blind plate is provided for ultraviolet light included in external light, and has no effect on ultraviolet light included in backlight light.

It is an object of the present invention to provide a liquid crystal display device which can suppress a change in liquid crystal characteristics due to ultraviolet rays from backlight light, and has high display quality and high reliability.

[0014]

According to the present invention, there is provided a liquid crystal display device comprising: a pair of substrates overlapped with a predetermined gap therebetween; a liquid crystal is sealed in the gap by a sealing material; In a liquid crystal display device having a liquid crystal display element in which a polarizing plate is disposed on the outer surface of the liquid crystal display and a backlight disposed below the liquid crystal display element, an ultraviolet light cut is provided between the liquid crystal display element and the backlight. A filter or an ultraviolet cut resin film is provided.

A liquid crystal display element in which a pair of substrates are overlapped with a predetermined gap therebetween, a liquid crystal is sealed in the gap with a sealing material, and a polarizing plate is disposed on an outer surface of each of the substrates; In a liquid crystal display device having a light guide disposed below a display element and a linear light source disposed along at least one end face of the light guide, between the linear light source and an end face of the light guide. A UV cut filter or a UV cut resin film.

Further, an ultraviolet cut filter or an ultraviolet cut resin film is provided on a portion of the outer surface of at least one of the substrates where the polarizing plate is not disposed.

Further, the present invention is characterized in that the polarizing plate has an ultraviolet cut characteristic.

In the present invention, by providing an ultraviolet cut filter or an ultraviolet cut resin film between the backlight and the liquid crystal display element, it is possible to prevent the ultraviolet light contained in the backlight or the like from entering the liquid crystal. And a change in liquid crystal characteristics due to ultraviolet rays can be suppressed. For this reason, it is possible to suppress the occurrence of display unevenness due to a change in the threshold voltage of the liquid crystal material, and it is possible to improve display quality and reliability.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings. In the drawings described below, those having the same functions are denoted by the same reference numerals, and the repeated description thereof will be omitted.

FIG. 1 is a sectional view of a main part (near a light source of a backlight) of a simple matrix type liquid crystal display module according to an embodiment of the present invention.

63 is a liquid crystal display module, 62 is a liquid crystal display element, 11 is an upper electrode substrate, 12 is a lower electrode substrate, 15 is an upper polarizing plate, 16 is a lower polarizing plate, and 35 is a circuit board for driving the liquid crystal display element 62 , 34 are a driving IC chip, 65 is a tape carrier package (TCP) for mounting the driving IC chip 34 and electrically connecting the circuit board 35 and the liquid crystal display element 62, 37 is a light guide, and 36 is a wire. A cold-cathode fluorescent tube as a light source; 66, a lamp reflecting sheet; 67, two prism sheets for improving the brightness of the backlight;
9 is a diffusion sheet, 68 is a reflection sheet, 42 is the light guide 3
7. A frame-like body made of a plastic molded product for holding a backlight composed of the cold cathode fluorescent tube 36 and the like and holding the backlight and the liquid crystal display element 62, 41 is a metal upper shield case, 69 is a metal lower shield The side shield case, 1 is an ultraviolet cut filter, 2 is an adhesive layer, and 3 is an ultraviolet cut resin film. Note that, in this figure, a liquid crystal layer, a transparent electrode, an alignment film and the like are not shown (see FIG. 3).

FIG. 2A is an overall front view of a simple matrix type liquid crystal display device showing an embodiment of the present invention.
(B) is sectional drawing in the AA cutting line of (a).

Reference numeral 50 denotes a liquid crystal layer, 52 denotes a sealing material, 51 denotes a liquid crystal sealing port, and 70 denotes a liquid crystal sealing material. In FIG. 2A, the portion where the ultraviolet-ray cut resin film 3 provided on the outer surface of the upper electrode substrate 11 is provided is hatched to the right.

As shown in FIG. 1, a liquid crystal display element 62 having an upper polarizing plate 15 and a lower polarizing plate 16 on each outer surface, and an interface circuit board 35 are connected by a tape carrier package 65 on which a driving IC 34 is mounted. The two prism sheets 67, the diffusion sheet 39,
A light guide 37, a reflection sheet 68, a cold cathode fluorescent tube 36 as a light source, and a lamp reflection sheet 66 are arranged, and these are housed and held by a frame 42, an upper frame 41 made of a metal plate, and a lower frame 69. Have been.

The trajectory of the light source light in this structure will be described. The direct light from the cold cathode fluorescent tube 36 as the light source and the light reflected through the lamp reflection sheet 66 are transmitted through the light guide 3.
7 and the reflection sheet 39, and the diffusion sheet 3
9. The light enters from the lower surface of the liquid crystal display element 62 via the prism sheet 67 and exits from the upper surface. This liquid crystal display element 6
As described above, the polarizers 15 and 16 have the characteristic of cutting incident light having a light wavelength of 380 nm or less, for example, as described above. Therefore, the wavelength of the incident light from the portion where the polarizers 15 and 16 are disposed is 380 nm or more. Whereas, the polarizing plate 15,
Incident light from a portion where no 16 is formed has a wavelength component of 380 nm or less.

On the other hand, generally, a liquid crystal has a light wavelength of 380 n.
It is known that characteristics change due to light components of m or less. Therefore, the polarizing plates 15 and 16 of the liquid crystal display element 62
Since the wavelength component of the incident light from the light source is different between the portion passing through and the portion not passing through, the change in the liquid crystal characteristics becomes remarkable, and display unevenness occurs. In order to suppress this, in the embodiment of the present invention shown in FIGS. 1 and 2, for example, a component having a light wavelength of 380 nm or less is cut over the entire end surface of the light guide 37 on the side where the cold cathode fluorescent tubes 36 are disposed. An ultraviolet cut filter 1 having the following characteristics was adhered by an adhesive layer 2.

As shown in FIGS. 1 and 2, the polarizers 15 and 1 on the outer surfaces of the upper electrode substrate 11 and the lower electrode substrate 12 respectively.
An ultraviolet-cut resin film 3 having a property of cutting, for example, a component having a light wavelength of 380 nm or less is provided on the outer peripheral portion where the components 6 are not arranged.

That is, in the present embodiment, the cold cathode fluorescent tube 36 and the ultraviolet cut filter 1 provided on the end face of the light guide 37 along the cold cathode fluorescent tube 36 and the ultraviolet cut resin film 3 provided on the outer peripheral portions of the substrates 11 and 12 are provided. Since the wavelength components of 380 nm or less from the cold cathode fluorescent tube 36 and the external light are cut off, the change in the threshold voltage characteristic of the liquid crystal material is suppressed,
In particular, the occurrence of display unevenness on the liquid crystal screen near the cold cathode fluorescent tube 36 can be suppressed. As a result, a liquid crystal display module 63 having high display quality and high reliability can be provided.

Incidentally, instead of the ultraviolet light cut filter 1 provided on the end face of the light guide 37, an ultraviolet light cut resin film 3 may be provided, or the ultraviolet light cut resin film 3 provided on the outer peripheral portions of the substrates 11 and 12 may be provided. Alternatively, an ultraviolet cut filter 1 may be provided.

FIG. 3 is a perspective view of an essential part of the liquid crystal display element 62 of the simple matrix type liquid crystal display device.

In FIG. 3, in order to align liquid crystal molecules in a twisted helical structure between the two upper and lower electrode substrates 11 and 12 sandwiching the liquid crystal layer 50, a transparent upper layer made of, for example, glass is used. A method of rubbing the surfaces of the alignment films 21 and 22 made of, for example, an organic polymer resin made of polyimide on the lower electrode substrates 11 and 12 in contact with the liquid crystal in one direction with a cloth, for example, is called a rubbing method. ing. The rubbing direction at this time, that is, the rubbing direction, the rubbing direction 6 for the upper electrode substrate 11, and the rubbing direction 7 for the lower electrode substrate 12 are the alignment directions of the liquid crystal molecules. The two upper and lower electrode substrates 1 thus oriented are treated.
The _first and second electrode substrates 11 and 12 are notched for injecting a liquid crystal, with the gaps d1 therebetween so that the rubbing directions 6 and 7 intersect each other at approximately 180 degrees to 360 degrees. When a nematic liquid crystal having a positive dielectric anisotropy and having a predetermined amount of a rotatory substance added thereto is sealed with a frame-shaped sealing material 52 having a portion (that is, a liquid crystal charging port) 51, The molecules have a helical molecular arrangement with a twist angle θ in the figure between the electrode substrates. In addition, 31 and 32 are, for example, indium oxide (IT
O: Indium Tin Oxide)
Transparent upper and lower electrodes. A member (hereinafter, referred to as a birefringent member) 40 that provides a birefringence effect is disposed above the upper electrode substrate 11 of the liquid crystal cell 60 configured as described above.
Upper and lower polarizing plates 15 and 16 are provided with 0 interposed therebetween.

The twist angle θ of the liquid crystal molecules in the liquid crystal 50 can take a value in the range of 180 ° to 360 °, and is preferably 200 ° to 300 °, but the twist angle θ is close to the threshold value of the transmittance-applied voltage curve. From the practical viewpoint of avoiding a phenomenon in which the lighting state becomes an orientation that scatters light and maintaining excellent time division characteristics, the range of 230 degrees to 270 degrees is more preferable. This condition basically acts to make the response of the liquid crystal molecules to the voltage more sensitive and to realize excellent time division characteristics. In order to obtain excellent display quality, the product Δn of the refractive index anisotropy Δn ₁ of the liquid crystal layer 50 and its thickness d ₁ is used.
₁ · d ₁ is preferably set in the range of 0.5 μm to 1.0 μm, more preferably in the range of 0.6 μm to 0.9 μm.

The birefringent member 40 functions to modulate the polarization state of light transmitted through the liquid crystal cell 60, and converts a liquid crystal cell 60, which could only be displayed in a colored state, to a black and white display. Thus the birefringent member 40 refractive index anisotropy [Delta] n ₂ and is extremely important product [Delta] n ₂ · d ₂ of a thickness d _2, preferably 0.8μm from 0.4 .mu.m, more preferably 0.5μm To a range of 0.7 μm.

Further, since the liquid crystal display element 62 uses elliptically polarized light due to birefringence, the axes of the polarizing plates 15 and 16 and the optical axis thereof when a uniaxial transparent birefringent plate is used as the birefringent member 40. And the electrode substrate 11 of the liquid crystal cell 60,
The relationship between the twelve liquid crystal alignment directions 6 and 7 is extremely important.

However, as shown in FIG.
Red, green, blue color filters 33R, 33G, 33 on top
B. By providing the light shielding film 33D between the filters, multi-color display is possible.

In FIG. 4, each filter 33
On the R, 33G, 33B and the light shielding film 33D, a smooth layer 23 made of an insulator is formed to reduce the influence of these irregularities, and then an upper electrode 31 and an alignment film 21 are formed.

FIG. 5 shows a liquid crystal display element 62 different from the liquid crystal display module shown in FIG.
FIG. 6 is an exploded perspective view showing a liquid crystal display module 63 in which a driving circuit for driving the LCD and a light source are compactly integrated.

Semiconductor IC 3 for driving liquid crystal display element 62
The tape carrier package 65 on which the liquid crystal display element 4 is mounted has a window for fitting the liquid crystal display element 62 at the center, and is mounted on a frame-shaped printed circuit board 35 on which a circuit for driving liquid crystal is formed. The printed circuit board 35 in which the liquid crystal display element 62 has been fitted is fitted in the window of the frame 42 formed of plastic mold, and the metal frame 41 is overlaid thereon.
The frame 41 is fixed to the frame 42 by bending the claws 43 into cuts 44 formed in the frame 42.

A cold cathode fluorescent lamp 36 disposed at the upper and lower ends of the liquid crystal display element 62; a light guide 37 made of an acrylic plate for uniformly irradiating the liquid crystal display cell 60 with light from the cold cathode fluorescent lamp 36; A reflecting plate 38 formed by applying a white paint to a metal plate and a milky white diffusing plate 39 for diffusing light from the light guide 37 are fitted into the window of the frame 42 from the back side in the order shown in FIG. It is. An inverter power supply circuit (not shown) for lighting the cold cathode fluorescent lamp 36 is provided with a concave portion (not shown) provided on the right-side back portion of the frame body 42.
5. ). Diffusing plate 3
9, light guide 37, cold cathode fluorescent lamp 36 and reflector 38
The tongue piece 46 provided on the reflection plate 38 is
Is fixed by folding it into the fore-edge 47 provided in the front end.

In the liquid crystal display module 63 shown in FIG. 5, the light guides 3 along the two cold cathode fluorescent lamps 36 are also provided.
7, the ultraviolet cut filter 1 is provided on the two end surfaces via the adhesive layer 2, and the outer peripheral portions of the electrode substrates 11 and 12 where the polarizing plate 15 (the polarizing plate 16 is not visible) are not formed. Since the ultraviolet-cut resin film 3 is provided (the lower electrode 12 side is not visible, but is provided in the same manner), it is possible to suppress a change in liquid crystal characteristics due to ultraviolet light from the light source light of the backlight or external light.

FIGS. 6 and 7 show a case where the liquid crystal display module 63 shown in FIG. 5 is used for a display section of a laptop personal computer.

FIG. 6 is a block diagram thereof, and FIG.
FIG. 7 shows a diagram mounted on a laptop personal computer 64. The result calculated by the microprocessor 49 is to drive the liquid crystal display module 63 by the driving semiconductor IC 34 via the control LSI 48.

Although the present invention has been described in detail with reference to examples, the present invention is not limited to the above-described embodiments, and it is needless to say that various modifications can be made without departing from the spirit of the present invention. .

[0044]

As described above, according to the present invention,
An ultraviolet cut filter or an ultraviolet cut resin film provided between the liquid crystal display element and the backlight or on the outer peripheral portion of the substrate of the liquid crystal display element cuts ultraviolet light from a light source or external light, so that the threshold voltage of the liquid crystal material is reduced. The change can be suppressed, and the occurrence of uneven liquid crystal display can be suppressed. Thereby, a liquid crystal display device having high display quality and high reliability can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part (near a light source of a backlight) of a liquid crystal display module according to an embodiment of the present invention.

2A is an overall front view of a simple matrix type liquid crystal display device showing an embodiment of the present invention, and FIG. 2B is a cross-sectional view taken along the line AA in FIG.

FIG. 3 is an exploded perspective view of a main part of an example of a liquid crystal display element.

FIG. 4 is a partially cutaway perspective view of an example of an upper electrode substrate portion of a liquid crystal display element.

FIG. 5 is an overall exploded perspective view of a liquid crystal display module according to another embodiment of the present invention.

FIG. 6 is a block diagram of an example of a laptop personal computer.

FIG. 7 is a perspective view of an example of a laptop personal computer.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... UV cut filter, 2 ... adhesive layer, 3 ... UV cut resin film, 11 ... Upper electrode substrate, 12 ... Lower electrode substrate,
15 upper polarizing plate, 16 lower polarizing plate, 34 driving IC chip, 35 driving circuit board, 36 cold cathode fluorescent tube, 3
7: light guide, 39: diffusion sheet, 41: metal upper shield case, 42: frame, 50: liquid crystal layer, 51: liquid crystal sealing port, 52: sealing material, 62: liquid crystal display element, 63 ...
Liquid crystal display module, 65: Tape carrier package, 66: Lamp reflection sheet, 67: Prism sheet,
68: Reflective sheet, 69: Metal lower shield case,
70 ... Liquid crystal sealing material.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Makiko Kida 3300 Hayano, Mobara-shi, Chiba Electronic Device Division, Hitachi, Ltd.

Claims (4)

[Claims] 1. A liquid crystal display device comprising: a pair of substrates stacked on each other with a predetermined gap therebetween; a liquid crystal sealed in the gap with a sealing material; and a polarizing plate disposed on an outer surface of each of the substrates. In a liquid crystal display device having a backlight disposed below the liquid crystal display element, an ultraviolet cut filter or an ultraviolet cut resin film is provided between the liquid crystal display element and the backlight. apparatus. 2. A liquid crystal display device comprising: a pair of substrates overlapped with a predetermined gap therebetween; a liquid crystal sealed in the gap with a sealing material; and a polarizing plate disposed on an outer surface of each of the substrates. In a liquid crystal display device having a light guide disposed below the liquid crystal display element and a linear light source disposed along at least one end face of the light guide, the linear light source and an end face of the light guide are provided. A liquid crystal display device provided with an ultraviolet cut filter or an ultraviolet cut resin film therebetween. 3. A liquid crystal display device comprising: a pair of substrates superposed with a predetermined gap therebetween; a liquid crystal sealed in the gap with a sealing material; and a polarizing plate disposed on an outer surface of each of the substrates. In a liquid crystal display device having a backlight disposed below the liquid crystal display element, an ultraviolet cut filter or an ultraviolet cut resin film is provided on a portion of the outer surface of the substrate where the polarizing plate is not disposed. Characteristic liquid crystal display device. 4. The liquid crystal display device according to claim 1, wherein said polarizing plate has an ultraviolet cut characteristic.