JP2002040414A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device which prevents the generation of bright-lines, enhances luminance and achieves a high display grade even if the device is formed to a smaller thickness and size. SOLUTION: A backlight unit 15 of the liquid crystal display device 14 is disposed with a CFL 3 at the end face of a light transmission plate 2, is successively laminated with a light diffusion plate 6 and a lens sheet 7 on the light transmission plate 2 and is provided with a light reflecting plate 5 on the other main surface. Light shieldable dot patterns 16 are disposed near the CFL 3 between the light transmission plate 2 and the light diffusion plate 6. The dot density of the light shieldable dot patterns 16 is made smaller in both of the segments near the CFL 3 and the segments most distant from the CFL 3 and the regions where the dot density is maximized are disposed linearly along the longitudinal direction of the CFL 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a liquid crystal display device having an edge light type illumination device (backlight).

[0002]

2. Description of the Related Art A liquid crystal display device is frequently used as a display device of a word processor, a personal computer, or the like, and a backlight is provided in a lighting device for that purpose. In recent years, with respect to portable word processors and personal computers, liquid crystal display devices mounted thereon have been required to be thin and small.

[0003] In response to such a demand, an edge light type backlight has been proposed. A conventional liquid crystal display device will be described with reference to FIGS. FIG. 5 is a schematic plan view of the liquid crystal display device 1, and FIG. 6 is a schematic sectional view thereof.

[0004] Reference numeral 2 denotes a light guide plate made of a transparent material, 3 denotes a cold cathode discharge tube (hereinafter abbreviated as CFL) disposed on an end face of the light guide plate 4, and 4 denotes a light-reflective reflector attached so as to cover the CFL 3. Reference numeral 5 denotes a light reflecting plate, 6 denotes a light diffusing plate for diffusing the light entering the light guide plate 2 when the light is emitted while being reflected by the light reflecting plate 5, and 7 denotes a light diffusing plate 6. Is a lens sheet that collects outgoing light that has passed through.

[0005] A liquid crystal display 9 is provided on such a backlight unit 8 and the backlight unit 8 is provided.
The liquid crystal display 9 is supported and fixed by the housing 10.

In recent years, as the liquid crystal display device 1 has become thinner and smaller, a narrower frame is required, and the distance between the effective display area 11 and the CFL 3 is further reduced.

For this reason, there is a problem that the luminance becomes extremely high in the vicinity of the CFL 3 and a bright line is generated in the vicinity of the CFL 3 in the effective display area 11 of the liquid crystal display 9, thereby deteriorating the display quality.

In order to solve such a problem, a light absorbing layer 12 is printed in a band shape below the light diffusing plate 6 near the CFL 3. Alternatively, the light absorbing layer 13 is printed and formed in a band shape on the light reflecting plate 5 near the CFL 3. Further, the light absorbing layer 12 and the light absorbing layer 13 may be provided. Further, the light absorbing layer 12 and the light absorbing layer 13 may be printed in a solid pattern or may be formed in a dot shape so that the light absorption rate can be changed. Furthermore, a light-shielding dot pattern may be printed in a band shape below the light diffusion plate 6 near the CFL 3 instead of the light absorbing layer 12 (see JP-A-8-240720 and JP-A-10-161119). ).

[0009]

However, the liquid crystal display device 1 equipped with the backlight unit 8 proposed above.
According to this, market demands for thinning and miniaturization in recent years are becoming increasingly higher, and satisfactory performance has not yet been achieved.

That is, when the liquid crystal display device 1 is made thinner and smaller, the bright lines become stronger than before, and in order to reduce the bright lines, the light absorption rates of the light absorbing layers 12 and 13 are further increased. On the other hand, the color of the light absorption layer 12 and the light absorption layer 13 becomes darker,
Thus, there is a problem that the degree of absorption of the emitted light of No. 3 increases, resulting in a loss of light quantity and a decrease in the luminance of the entire backlight. Moreover, such a light absorbing layer 12 having a high light absorption rate
There is also a problem that the presence thereof is visually recognized on the display with the light absorbing layer 13.

Even when the light shielding ratio is further increased by the light shielding dot pattern, the degree of absorption of the light emitted from the CFL 3 is also increased, resulting in a loss of light amount, and the brightness of the entire backlight is reduced, The dot pattern was visible on the display.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a liquid crystal display device which prevents the generation of bright lines, increases luminance and achieves high display quality even when the liquid crystal display device is made thinner and smaller.

[0013]

According to the present invention, there is provided a liquid crystal display device comprising a light guide plate having a tubular light source disposed on an end face, a light reflecting member provided on one main surface and a light scattering member provided on the other main surface. An apparatus configuration in which a liquid crystal display panel is mounted on a light scattering member, and further, a light shielding dot pattern is provided near a tubular light source of the light scattering member, which reduces bright lines emitted from a light guide plate near the tubular light source. In order to reduce the dot density of the light-shielding dot pattern in both the portion close to the tubular light source and the portion farthest from the tubular light source, the maximized region is linearly formed along the longitudinal direction of the tubular light source. It is characterized by being provided.

According to the liquid crystal display device of the present invention, the dot density of the light-shielding dot pattern is reduced both in the portion near the tubular light source and in the portion farthest from the tubular light source, as described above. Is reduced, thereby reducing the loss of light quantity, and as a result, the brightness of the entire backlight is increased.

Further, in the present invention, as described above, the region where the dot density of the light-shielding dot pattern is maximized is provided linearly along the longitudinal direction of the tubular light source. Bright lines emitted from the light guide plate near the tubular light source are reduced or eliminated, and as a result, display quality can be improved.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A liquid crystal display device according to the present invention will be described with reference to FIGS. FIG. 1 is a schematic plan view of the liquid crystal display device 14, and FIG. 2 is a schematic sectional view thereof. FIG. 3 shows the dot density of the light shielding dot pattern, and FIG. 4 shows the dot pattern density of the light absorbing layer. The same parts as those in the liquid crystal display device 1 shown in FIGS. 5 and 6 are denoted by the same reference numerals.

In the backlight unit 15, a CFL 3 as the tubular light source is disposed on an end face of a rectangular light guide plate 2 made of a transparent material such as an acrylic resin, and the CFL 3 is formed by a semi-cylindrical light reflective reflector 4. Covering. On the light exit surface of the light guide plate 2, a light diffusion plate 6 as a light scattering member and a lens sheet 7 (the lens sheet 7 is composed of only one sheet or has a laminated structure of a plurality of sheets) are sequentially laminated. The other main surface is provided with a light reflection plate 5 as the light reflection member.

The light reflection plate 5 has a reflection layer provided on the surface of a white sheet such as PET, and guides light incident on the light guide plate 2 to a light emission surface. The light diffusing plate 6 has fine irregularities (for example, embossed) on one surface of a white sheet such as PC or PET, and scatters light emitted from the light guide plate 2.

The CF between the light guide plate 2 and the light diffusion plate 6
A light shielding dot pattern 16 is provided in the vicinity of L3, and a black light absorbing dot pattern 17 is formed between the light guide plate 2 and the light reflection plate 5.

Backlight unit 1 having such a configuration
The liquid crystal display 9 is disposed on the display 5, and the backlight unit 15 and the liquid crystal display 9 are supported and fixed by the housing 10. (Light shielding dot pattern 16) Next, the light shielding dot pattern 16 will be described. As shown in FIG. 3, in order to change the light concealing ratio, for example, white dots of a UV curing system are arranged in a circular dot pattern. In the section 11a in the effective display area 11 of the liquid crystal display 9, an area p in which the concealment ratio is maximized is provided linearly along the longitudinal direction of the CFL3. Such a concealment ratio is defined by the dot density of the light-shielding dot pattern. In addition, the dot density of the light-shielding dot pattern is reduced in both a portion close to the CFL 3 and a portion farthest from the CFL 3 to form a gradation shape. In the figure,
Although the pitch of the light-shielding dot pattern along the CFL 3 is substantially the same, it may be changed for each line.

By providing the light-shielding dot pattern 16 having the above structure, the light emitted from the light guide plate 2 is blocked, and a part of the light is absorbed by the light-shielding dot pattern 16. Considerably small, rather, being reflected inside the light guide plate 2 by the light shielding dot pattern 16,
Light loss is reduced and luminous efficiency is increased. (Light-absorbing dot pattern 17) The light-absorbing dot pattern 17 provided so as to face the light-shielding dot pattern 16 via the light guide plate 2 is formed into circular black dots by using, for example, UV curing black ink. Form, and
As shown in FIG. 4, the dot pattern is formed in a so-called gradation shape so that the area occupied by the dot pattern decreases as the distance from the CFL 3 with respect to the normal direction of the CFL 3 increases. in this case,
The dot patterns extending in the axial direction (longitudinal direction) of the CFL 3 have the same circular shape and are arranged at the same pitch, but are not limited thereto.

As described above, the light absorbing dot pattern 1
7 is formed on the light reflecting plate 5 to form the light shielding dot pattern 1
Although 6 is formed on the lower surface of the diffusion plate 6, these may be formed by screen printing or the like in plate making.

Thus, according to the liquid crystal display device 14 having the above-described structure, even if the distance L between the CFL 2 and the effective display area 11 of the liquid crystal display 9 becomes 4.5 mm or less, the light shielding dots can be formed. The dot density of pattern 16 is CFL
3 and the part farthest from the CFL 3, the degree of absorption of the light emitted from the CFL 3 is reduced or eliminated. As a result, the loss of light is reduced, thereby reducing the loss of light quantity. As a result, the brightness of the entire backlight unit 15 can be increased.

Further, since the region p in which the dot density of the light shielding dot pattern 16 is maximized is provided linearly along the longitudinal direction of the CFL 3, light is emitted from the light guide plate 1 near the CFL 3 in that region. The number of bright lines was reduced or eliminated, and as a result, the display quality could be improved.

According to an experiment repeatedly performed by the present inventor, it has been found that the section 11 in the effective display area 11 of the liquid crystal display 9
The width of “a” may be 5 mm or less, and the gradation may be such that an area where the dot density of the light-shielding dot pattern 16 is maximized is provided in such a section 11a, thereby providing the most excellent display quality. Was obtained.

It should be noted that the present invention is not limited to the above embodiment, and various changes and improvements can be made without departing from the scope of the present invention. For example, in this example, both the light-shielding dot pattern 16 and the light-absorbing dot pattern 17 are provided, but instead of forming the light-absorbing dot pattern 17, only the light-shielding dot pattern 16 is provided. Is also good.

Further, in addition to forming the light-shielding dot pattern 16 with circular white dots as in the present embodiment, the shape, arrangement, color tone and color density of the dots are appropriately changed according to the required characteristics. You may.

[0027]

As described above, according to the liquid crystal display device of the present invention, the dot density of the light-shielding dot pattern is reduced both in the portion near the tubular light source and in the portion farthest from the tubular light source. The area where the light emitted from the tubular light source is absorbed is reduced, thereby reducing the loss of light quantity, increasing the overall brightness of the backlight, and maximizing the dot density of the light shielding dot pattern. , The bright lines emitted from the light guide plate in the vicinity of the tubular light source are reduced or eliminated in that area, and as a result, the bright lines are generated even when the thickness and thickness are reduced. The liquid crystal display device of high performance and high quality which is reduced in thickness and size and which achieves high display quality while improving the brightness while preventing the display.

[Brief description of the drawings]

FIG. 1 is a schematic plan view of a liquid crystal display device of the present invention.

FIG. 2 is a schematic sectional view of the liquid crystal display device of the present invention.

FIG. 3 is a plan view of a main part showing a light-shielding dot pattern shape.

FIG. 4 is a plan view of a main part showing a light-absorbing dot pattern shape.

FIG. 5 is a schematic plan view of a conventional liquid crystal display device.

FIG. 6 is a schematic sectional view of a conventional liquid crystal display device.

[Explanation of symbols]

2 light guide plate, 3 CFL, 4 reflector, 5 light reflection plate, 6 light diffusion plate, 7 lens sheet, 9 liquid crystal display, 10 housing, 14 liquid crystal display, 15 back Light unit, 16: light-shielding dot pattern, 17:
Light-absorbing dot pattern, p: Area where the concealment ratio is maximized

Claims (1)

[Claims] A liquid crystal display panel is mounted on a light-scattering member of a lighting device having a light-guiding member provided on one main surface of a light guide plate having a tubular light source disposed on an end face and a light-scattering member provided on the other main surface. A liquid crystal display device further comprising a light-shielding dot pattern provided in the vicinity of a tubular light source of a light-scattering member, wherein the light-shielding dot pattern has dots in order to reduce bright lines emitted from a light guide plate near the tubular light source. A liquid crystal display device wherein the density is reduced both in a portion near the tubular light source and in a portion farthest from the tubular light source, and a maximized region is provided linearly along the longitudinal direction of the tubular light source. .