KR20010035196A - Non printed light guide pipe with two kind patterns and backlight - Google Patents

Abstract

PURPOSE: A non printed light guide panel comprising two kinds of pattern and backlight using the same are provided to design easily an illumination pattern with high brightness and uniform distribution of brightness, and provide easy manufacturing method of a light guide panel. CONSTITUTION: The backside of a light guide panel is divided into the part(A) close to a cool cathode fluorescent lamp(CCFL) and the part distant from the CCFL. The dimming pattern is comprises of short lines(B) with convex or concave cross section in the part(A) and plural curved lines(20,21) with convex or concave cross section in the part distant from the CCFL. Intervals(C) of starting points in the light source side of the curved pattern are changed little by little. As the gradients of the curved lines become slow, the propagating direction of the light and the progressing direction of the curved lines(20,21) cross with large crossing angle each other. Therefore, the brightness is uniform in the front of the light guide panel because the light emitted toward the front of the light guide panel becomes much in the inclined surface of the pattern-forming grooves.

Description

Non-printed light guide plate composed of heterogeneous patterns and backlight using the same {Non printed light guide pipe with two kind patterns and backlight}

Industrial use

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light guide plate of a flat dimming device used as a backlight in a liquid crystal display device used for a notebook computer, a personal computer, an information device, and the like, and also relates to a liquid crystal image display device using the dimming device.

Conventional technology

Since a thin film transistor liquid crystal display (TFT-LCD) does not emit light on its own, a device called a normal backlight is required on the back of the liquid crystal display to illuminate the liquid crystal display. In this backlight, a cold cathode fluorescent lamp (CCFL) having a small diameter is used for one or both of the top and bottom sections, and the light emitted therefrom is sent to the front of the liquid crystal display using a transparent light guide plate. A dimming pattern is applied on the back side of the transparent light guide plate to achieve uniform light emission. This is for the purpose of eliminating the occurrence of luminance unevenness as the emission surface becomes dark as the distance from the light source becomes brighter when the surface shape of the back surface of the light guide plate is uniform. The most representative example of the dimming pattern is shown in FIG. 7, wherein a small circular diffuse reflection surface with a small diameter is arranged on the rear side of the transparent light guide plate close to the light source, and a circular diffuse reflection surface having a larger diameter is densified away from the light source. The dimming patterns are arranged so as to increase the amount of reflected light, that is, the light emitted from the surface of the light guide plate, as the distance from the light source increases. As another example, a concave portion or a convex portion may be provided on the rear side of the light guide plate, and a dimming pattern for adjusting the amount of light may be provided by varying the depth or the height depending on the distance from the light source. As another example, a dimming pattern is provided on the rear surface of the light guide plate so as to be substantially perpendicular to an end at which the light source is installed and at an end opposite to the light source so that a curve that is substantially parallel is not overlapped at regular intervals.

The installation of the circular reflective surface on the backside of the light guide plate is a two-step process of forming and printing the light guide plate, and it is difficult to control the distribution of the circular reflective surface and it is expensive to manufacture. In addition, a recess or a convex portion is provided on the rear surface of the light guide plate, and the design for uniformly emitting the light by controlling the reflection and diffusion of incident light by changing the density and size thereof gradually is difficult and difficult to manufacture. In addition, a curved pattern that meets almost vertically at the end with the light source and almost parallel at the end opposite to the light source also has a design difficulty. In other words, the amount of light emitted to the surface of the light guide plate should be constant at the part close to the light source and at the part far from the light source. When the curves between the curves have a small distance from the adjacent curves, the light source is It is bright and the side facing the light source is too dark. On the other hand, when the distance between curves is large, the light source side is dark, and the side facing the light source is also dark. In other words, it is very difficult to obtain a consistently high luminance overall.

The present invention can solve the problems of the prior art, it is possible to easily design a dimming pattern having a high overall brightness, uniform distribution of brightness in the exit surface of the light guide plate, and to provide a light guide plate with an easy manufacturing method. A flat dimming apparatus using the same and a liquid crystal image display apparatus using the same are provided.

1 is a plan view showing a transparent light guide plate having a dimming pattern as an embodiment of the present invention.

2 is a plan view showing a transparent light guide plate having a dimming pattern as another embodiment of the present invention.

3 is a plan view showing a transparent light guide plate having a dimming pattern as another embodiment of the present invention.

4 is a cross-sectional view showing the principle of operation of the dimming pattern of the present invention.

5 is a perspective view showing a schematic configuration of the planar dimmer and liquid crystal image display device of the present invention.

6 is a perspective view showing a schematic configuration of a flat dimming device and a liquid crystal image display device as another embodiment of the present invention.

7 is a plan view showing a typical representative dimming pattern.

Explanation of symbols on the main parts of the drawings

1: light guide plate 2, 3: light source (CCFL)

4, 5: Reflector 6: Reflective Sheet

7: Diffusion Sheet 8, 9: Prism Sheet

10: concave portion of the light guide plate 50: thin film transistor liquid crystal plate

The present invention relates to a planar light control device in which a light source is disposed on a side surface of a transparent light guide plate, wherein the rear surface of the light guide plate is divided into a portion close to the light source, that is, a remote part far from the light source other than the portion A of FIG. Light guide plate, characterized in that a light guide plate is provided with a short straight line (B) formed of a concave portion or a convex portion, and a part far from the light source is formed with a plurality of curves 20, 21 formed with a concave portion or a convex portion in cross section. The above problem is solved by the configuration. Instead of the short straight lines described above, a circular diffused reflection plate may be used with a constant spacing.

In addition, the present invention is a side light source type flat dimming device having a light source disposed on one side of the transparent light guide plate by dividing the rear surface of the light guide plate into two zones to install different dimming patterns, between the short length of straight lines forming the dimming pattern It provides a light guide plate, characterized in that installed while changing the interval of the interval or the starting point of the curve slightly.

The present invention also provides a liquid crystal display panel and a light source at one side or two opposite side surfaces of the light guide plate for irradiating the light from the rear side, and a side light source type flat light control device having a reflective sheet disposed on the back side of the light guide plate, and the flat light control device. And a diffusion sheet and a prism sheet disposed between the liquid crystal display panel and the liquid crystal display panel, wherein the back surface of the light guide plate of the planar dimmer device includes a dimming pattern portion formed of a short straight line having a concave portion or a convex portion at a cross section; There is provided a liquid crystal image display device, characterized in that a dimming pattern portion having a plural curve composed of a concave portion or a convex portion is provided, and is configured while the interval between straight lines or curves constituting the dimming pattern is slightly changed.

A feature of the present invention lies in the pattern provided on the back side of the transparent light guide plate, and the pattern intends to

(1) It is what constitutes a suitable dimming pattern according to the intensity | strength of the light quantity which reaches | attains the effective display surface of a light guide plate from a light source. (2) The dimming pattern composed of short straight lines provided adjacent to the light source is intended to have an arbitrary density in consideration of the light emission intensity characteristic of the light source.

(3) In the remote part except the light source, the area occupied by the dimming pattern that emits light from the light guide plate in the portion close to the light source is small in proportion to the area of the entire light guide plate, and continuously moves away from the light guide plate. The ratio of the area occupied by the dimming pattern to be emitted is increased. (4) The distance between adjacent curves of curves constituting the dimming pattern is slightly changed to prevent the intersection of the curves from appearing in parallel with the side surface of the light source at a constant distance from the light source.

Hereinafter, embodiments of the present invention shown in the drawings will be described in detail.

FIG. 1 shows a typical example of straight and curved patterns used when the light source is provided only on one side of the light guide plate as the first embodiment of the present invention. In the portion from the light source side surface portion of the light guide plate to a constant distance A, a pattern B made of short straight lines is shown. Curved patterns 20 and 21 are shown in the portion where the distance is greater than A on the light source side surface. The interval C between the light source side starting points of the curved pattern is slightly changed, and the slope of the curve is steep so that the area occupied by the pattern becomes smaller than the area other than the pattern. The inclination of the film is gentle and the area occupied by the pattern is formed to become larger than the area other than the pattern. The curved direction of the curve also consists of curves 21 which are bent to the left, as opposed to those that are bent to the right.

Each light beam emitted from the light source is diffused in short straight lines adjacent to the light source, part of which is emitted to the upper surface of the light guide plate, and most of the light is propagated to a remote region where a curved pattern is formed. Short straight lines adjacent to the light source are arranged closer to the light source to control the amount of light emitted to the upper surface of the light guide plate. The size of the adjacent light source is suitably within 20 mm from the light source. In the remote area where the curved pattern is formed, the light rays emitted from the light source are reflected from the inclined surface of the groove and emitted to the upper surface of the light guide plate. There are few components and a large amount of light propagates in the direction away from the light source. However, as the slope of the curve becomes more and more gentle, the light propagation direction and the curve traveling direction cross each other at a large angle, so that the light is emitted from the inclined surface of the groove part of the pattern to the front of the light guide plate. In this way, the luminance is uniform on the front of the light guide plate as a whole. The degree to which the slope of the curve changes and the interval between the curves depends on the depth or height of the groove portion of the cross section forming the curve, the size of the light guide plate, and the intensity of the light source used. In the case of the light guide plate used for the 14.1-inch display device, the interval of the starting point of the curved pattern is appropriately in the range of 1 mm to 3 mm, and the depth of the concave portion or the height of the convex portion is appropriately about 0.01 to 0.3 mm, and deeply away from the light source. It is desirable to increase the diffusion efficiency. In addition, it is preferable that the spacing of the starting point of the curve pattern is formed while giving a random change within a range of about 10%. In this way, the intersections of the curves can be prevented from occurring in a line at a constant distance along the side surface of the light guide plate on which the light source is installed. This is preferable to distribute the luminance of the light guide plate evenly.

FIG. 2 shows an example in which the light source is provided on both side surfaces of the light guide plate facing each other as the second embodiment. As in the first embodiment, a pattern consisting of short straight lines is formed on both of the light source adjacent parts A1 and A2 opposite to the light guide plate, and a curved pattern is formed on the central part of the light guide plate that is remote from the light source. In this embodiment, the starting point of the curve pattern has a constant interval.

FIG. 3 is a third embodiment, which is formed in the same shape as in the second embodiment but with a slight change in the interval between the starting points of the curved patterns.

The curves 20 and 21 used in the first, second and third embodiments of the light guide plate used cubic curves. As shown in FIG. 4, the cross-sectional shape of the curved concave portion 10 or the convex portion constituting the pattern is preferably a shape where the vertex is an arc and both inclined surfaces are close to straight lines. The pattern having such a shape can be processed by cutting, but can be manufactured using a stamper mold to improve productivity.

When the plate shape of the light guide plate is a plate shape having a constant thickness as shown in FIG. 4, the dimming pattern shown in FIG. 2 and FIG. 3 is preferable, and the light guide plate having a wedge shape that becomes thin as it moves away from the light source is shown in FIG. The dimming pattern shown is preferred.

Transparent plastics such as polycarbonate, acrylic resin, and polystyrene may be used as the material of the transparent light guide plate, but PMMA resin is particularly preferable in terms of ease of molding, high transparency, and hard to be scratched.

In the planar dimmers 30 and 31 using the light guide plate 1 of the present invention shown in FIG. 5 and FIG. 6, the light incident from the light source CCFL as shown in FIG. Light rays incident on the concave portion 10 or the convex portion of (11) are partially reflected and proceed directly to the exit surface of the light guide plate or to another concave or convex portion, but there is also a transmitted light. In this way, it is preferable to arrange a separate reflecting sheet 6 in close proximity to the back of the light guide plate in order to return the light rays transmitted through the back surface 11 of the light guide plate itself back to the light guide plate in order to effectively use the light rays. As the reflection sheet, a reflection sheet such as an aluminum vapor deposition sheet or a white light reflection sheet may be used.

As shown in FIG. 5, the liquid crystal image display apparatus using the flat dimming apparatus of the present invention is basically a liquid crystal panel 50, a prism sheet 8, 9, a diffusion sheet 7, a flat dimming apparatus 30, or the like. It consists of. The prism sheets 8 and 9 described above may improve the luminance of the angle only in the specific viewing direction. The prism sheets 8 and 9 may arrange the prism face on the light diffusion sheet 7 or may reverse the same. It is also possible to use a lenticular lens sheet in place of the prism sheet.

Next, specific examples of the present invention will be described. The pattern of the transparent light guide plate used in the first embodiment is composed of cubic curves. The size of the light guide plate is 291 mm in the horizontal direction and 220 mm in the longitudinal direction, and the thickness of the cross section on the light source side is about 2 mm. The cross section of the side opposite to the light source is about 0.8 mm. The distance between the light source adjacent portions where the pattern consisting of short straight lines is formed is about 10 mm from the light source side, and the distance between the starting points of the curves is about 1.8 mm. The cross section of each curve constituting the pattern is composed of a recess (groove), the cross section of which is a circular arc with a peak of about 60 degrees and a depth of about 0.1 mm. A cold cathode fluorescent tube (CCFL) which serves as a light source along the lower side. The fluorescent tube is covered with semi-circular reflecting plates 4 and 5 to increase the illuminance efficiency.

According to the present invention, it is possible to adjust many parameters such as the size of the adjacent light source, the dimming pattern of the adjacent light source, the shape of the curved pattern of the remote part from the light source, the interval between the curves, the concave portion, the depth or height of the convex portion, and the cross-sectional shape thereof. It is easy to design a dimming pattern with high luminance and excellent uniformity, and it is possible to easily manufacture the designed light guide plate. As a result, not only the luminance is high but also the luminance uniformity is high, and it is possible to provide a dimmer using the same at a low cost.

Claims (10)

In a flat dimming device in which a light source is disposed on one or two opposite side surfaces of a light guide plate used in a rear light dimming device of a thin film transistor liquid crystal display, a dimming pattern is provided on the rear surface of the light guide plate by dividing the light source into a portion adjacent to the light source. The light guide plate characterized by the above-mentioned. The light guide plate according to claim 1, wherein a plurality of short straight lines or a plurality of circular reflection patterns are provided on the light source adjacent portion of the rear surface of the light guide plate. The light guide plate according to claim 1, wherein a plurality of cubic or higher order curves are provided at portions other than the light source adjacent portion on the back side of the light guide plate. The light guide plate according to claim 2, wherein intervals between a plurality of short straight lines are not constant and are provided with a slight change. 4. The light guide plate according to claim 3, wherein the light guide plate is provided with a change so as not to make the interval between the starting points between the plurality of curves expressed by the higher order equation constant. 4. The light guide plate according to claim 3, wherein a plurality of curves are formed by concave portions or convex portions in the higher order. 4. The light guide plate according to claim 3, wherein the cross-sections of the plurality of curves in the higher order form a vertex arc and both inclined surfaces are formed in a curve close to a straight line. The light guide plate according to claim 1, wherein the thickness of the light guide plate decreases in sequence from the light source side side portion toward another cross section opposite thereto. The light guide plate of claim 1 wherein the thickness of the light guide plate is substantially constant. In a rear light dimming device used for a thin film transistor liquid crystal display, a light source is disposed on one or two side surfaces of a light guide plate used in the light dimming device, and the dimming pattern is divided into a portion adjacent to the light source and other portions on the rear surface of the light guide plate. A rear dimming device using a light guide plate characterized in that the installation.