CN1580901A - Back light assembly and its light guide board - Google Patents

Abstract

The invention discloses a backlight module and a light guide plate thereof. The backlight module includes a light guide plate and a point light source. The light guide plate includes a light incident surface, a light exit surface intersecting the light incident surface, and a bottom surface opposite to the light exit surface. The light incident surface enters the light guide plate to form multiple incident light intensity areas, and the light exit surface is provided with multiple gratings, and the multiple gratings are distributed in the incident light intensity areas adjacent to the point light sources. The invention can reduce the incident dark band of the light guide plate, so that the light guide plate and the backlight module adopting the light guide plate have higher light output uniformity.

Description

Backlight module and its light guide plate

【Technical field】

The invention relates to a backlight module and its light guide plate, in particular to a backlight module and its light guide plate applied to liquid crystal displays.

【Background technique】

Due to the advantages of lightness, thinness, and low power consumption, liquid crystal displays are widely used in modern information equipment such as notebook computers, mobile phones, and personal digital assistants. Because the liquid crystal itself does not have light-emitting properties, it is necessary to provide a backlight module for it to realize the display function.

As we all know, the backlight module needs to have high light uniformity, so as to improve the color contrast, the brightness effect of the full screen area and the viewing angle of the whole machine of the liquid crystal display using the backlight module.

The prior art backlight module includes a light source and a light guide plate. The light source is arranged relative to the light incident surface of the light guide plate. The light guide plate guides the transmission direction of the light beam emitted from the light source, and converts the line light source or point light source into a surface light source to emit. A plurality of dots are distributed on the bottom surface of the light guide plate to destroy the total reflection condition of the light beam transmitted inside the light guide plate and scatter them to improve the uniformity of the light beam emitted by the light guide plate, thereby improving the overall performance of the backlight module. The density and size of the dots can be designed in different ways to suit different backlight modules.

A prior art backlight module can be referred to FIG. 1 . The backlight module 9 is composed of a light guide plate 10 , a translucent material plate 20 , a reflective material box 30 and a light source 40 . The translucent material plate 20 is stacked on the light guide plate 10, and the periphery and the bottom surface 12 of the light guide plate 10 are contained in the reflective material box 30, and a positioning groove 31 for accommodating the light source 40 is provided on one side of the reflective material box 30. . When working, the light beam emitted by the light source 40 is incident from one side of the light guide plate 10, and after being acted on by the gradient wave pattern on the bottom surface 12 of the light guide plate 10 and the light-reflecting material box 30, a plane light is generated, and emerges from the light exit surface 11 of the light guide plate 10 , the translucent material plate 20 makes the plane light distribution more uniform.

Please also refer to FIG. 2, since the light source 40 has a certain emission angle, such as a light emitting diode, the emission angle can be 30 to 130 degrees, and the side of the light guide plate 10 opposite to the light source 40 is a plane, so that the light beam emitted by the light source 40 passes through the After the side refraction enters the light guide plate 10, its divergence angle will be further reduced, and the maximum is about 119.653 degrees, forming an incident light intensity area (not marked), thereby producing a large dark band 13 on the incident side of the light guide plate 10, thereby reducing The utilization rate of the light beam affects the luminance and light uniformity of the backlight module 9 and even the liquid crystal display using the backlight module 9 .

Please refer to FIG. 3 , China Taiwan Patent No. 530,919 published on May 1, 2003 discloses a backlight module capable of reducing the incident dark area of the light guide plate. The backlight module is provided with a plurality of concave holes 50 on the light guide plate 3 , and the plurality of concave holes 50 are arranged in a row directly in front of the incident point 2 of the point light source. A series of multiple concave holes 50 are respectively arranged in front of the incident point 2 of each point light source. The multiple concave holes 50 can penetrate the light guide plate 3, and when the incident light touches the outer edge of the concave hole 50, a light refraction or total light reflection effect is generated. It can destroy the strong optical directivity of the point light source and increase the light divergence angle, which helps to improve the defect of the dark area on the incident side of the light guide plate 3 .

However, the concave hole 50 is arranged near the light-incident surface of the light guide plate 3, and the light total reflection effect that occurs when the incident light touches the surface causes part of the incident light that has entered the light guide plate 3 to be reflected back, and the amount of light that continues to be transmitted toward the inside of the light guide plate 3 reduce the light utilization rate and the luminance of the backlight module; and, the plurality of concave holes 50 are formed inside the light guide plate 3, and the refraction and reflection of the light on the surface of the concave holes 50 make the energy of the light incident into the light guide plate interior loss; in addition, the refractive index of the concave hole 50 is different from that of the light guide plate 3, which hinders the in-depth transmission of the incident light. Factors such as the reduction of the cavity 50, the obstruction of the concave hole 50, and the loss of scattering energy make the light intensity transmitted to the larger area weak, which affects the uniformity and luminance of the light emitted by the light guide plate.

【Content of invention】

In order to overcome the defect of low light uniformity in the prior art backlight system, the present invention provides a backlight module with high light uniformity.

The invention also provides a light guide plate with high light uniformity.

The technical solution of the present invention to solve the technical problem is to provide a backlight module, including a light guide plate and a point light source, the light guide plate includes a light incident surface, a light exit surface intersecting the light incident surface, and a bottom surface opposite to the light exit surface The light beam emitted by the point light source enters the light guide plate through the light incident surface with a specific light field distribution, forming multiple incident light intensity areas, and the light exit surface is provided with multiple gratings, and the multiple gratings are distributed in the incident light intensity areas.

The present invention also provides a light guide plate with high uniformity of light output. The light guide plate is used to cooperate with a point light source, and includes a light incident surface for receiving a light beam, a light exit surface intersecting with the light incident surface and guiding the light beam to exit, and a light exit surface connected to the light exit surface. The opposite bottom surface, and a plurality of gratings are arranged on the light exit surface, and the plurality of gratings are distributed in the incident light intensity area formed by the light beam emitted by the point light source.

Compared with the prior art, the beneficial effect of the present invention is that since the light exit surface of the light guide plate of the present invention is provided with multiple gratings, and the multiple gratings are distributed in the incident light intensity area formed by the specific light field distribution of the point light source , so that the property that the multiple gratings can diffuse the beam propagation direction outwards allows the light beams emitted by the point light source to diffuse through the multiple gratings and then enter the light intensity area, so as to reduce or even eliminate the phenomenon of incident dark bands on the light guide plate , so that the light guide plate and the backlight module using the light guide plate have higher light uniformity.

【Description of drawings】

FIG. 1 is an exploded perspective view of a prior art backlight module.

FIG. 2 is a schematic diagram of part of the optical path of the prior art backlight module shown in FIG. 1 .

Fig. 3 is a plan view of another prior art backlight module.

FIG. 4 is a perspective view of the first embodiment of the backlight module of the present invention.

FIG. 5 is a schematic diagram of grating distribution of the backlight module shown in FIG. 4 .

FIG. 6 is a schematic diagram of dot distribution of the backlight module shown in FIG. 4 .

FIG. 7 is a perspective view of the second embodiment of the backlight module of the present invention.

FIG. 8 is a perspective view of a third embodiment of the backlight module of the present invention.

FIG. 9 is a schematic diagram of dot distribution of the backlight module shown in FIG. 8 .

【Detailed ways】

Please refer to FIG. 4 , which is a first embodiment of the backlight module of the present invention. The backlight module 100 includes a plurality of point light sources 110 and a light guide plate 120 . The point light source 110 emits light beams, and the light guide plate 120 guides the transmission direction of the light beams emitted by the point light source 110 and converts them into planar light sources for emission.

The point light source 210 may be a light emitting diode or a small light bulb, and a plurality of light emitting diodes or small light bulbs of different colors may be configured to adjust the desired display color and brightness.

The light guide plate 120 is a flat light guide plate made of transparent materials such as acrylic, glass or polycarbonate, and includes a light incident surface 121, a light exit surface 122 connected to the light incident surface 121, and a light exit surface connected to the light exit surface 121. 122 opposite to the bottom surface 123 and the side surface 124 .

The light incident surface 121 receives the light beam emitted by the point light source 110 , and an anti-reflection film (not shown) may be provided on the area where the light beam emitted by the point light source 110 is coupled, so as to improve the efficiency of the light beam.

Please also refer to FIG. 5 , the light emitting surface 122 can be processed into a rough surface with a certain roughness. Since the light beams emitted by the point light sources 110 have a specific light field distribution, incident light intensity regions (not shown) are formed at corners of the light guide plate adjacent to the light incident surface 121 and between two point light sources. In order to fully diffuse the light beam into the intensity area of the incident light, a plurality of gratings 130 are arranged on the intensity area of the incident light on the light exit surface 122 of the light guide plate 120 . The multiple gratings 130 include grating stripes 131 and spacers 132, wherein the grating stripes 131 are a plurality of flat protrusions with a fixed period, of course they can also be grooves, and the spacers 132 are the intervals between the grating stripes 131 . The distribution direction of the grating stripes 131 of the plurality of gratings 130 is parallel to the direction of the beam emission angle of the point light source 110 . By adjusting the size, shape and pitch of the grating 130, its effect on the passing light can be changed. Generally speaking, the width of the grating stripes 131 and the width of the spacers 132 should be less than 2 μm, and the height of the protrusions of the grating stripes 131 is about 0.5-1.5 μm. The shape of the grating stripes 131 can be triangle, trapezoid or rectangle.

Please refer to FIG. 6 , the bottom surface 123 of the light guide plate 120 is provided with a plurality of dots 140 to improve the luminance and uniformity of the light beam emitted from the light guide plate 120 . The size of the dots 140 increases along the direction away from the light incident surface 121 , and they are cylindrical. Certainly, the dots 140 may also be in the shape of a sphere, a cube, a pyramid or other suitable shapes. The dots 140 can be distributed on the bottom surface 123 of the light guide plate 120 by printing or injection molding. In addition, a plurality of V-shaped grooves (not shown) may also be provided on the bottom surface 123 to replace the plurality of dots 140 . The bottom _{surface 123} of the light guide plate 120 can be provided with a reflective film (not shown). The bottom surface 123 of the light guide plate 120 escapes, thereby reducing the energy loss of the light beam and improving the overall optical performance of the light guide plate 120 . The reflective film can be formed by methods such as chemical vapor deposition, electron beam evaporation, sputtering, etc., and its reflectivity in the visible light region can reach more than 98%.

Please refer to FIG. 7 , which is a second embodiment of the backlight module of the present invention. The backlight module 200 includes a plurality of point light sources 210 and a light guide plate 220 . The light guide plate 220 is a wedge-shaped light guide plate, including a light incident surface 221, a bottom surface 223 obliquely intersecting with the light incident surface 221, a light exit surface 222 opposite to the bottom surface 223, and a side surface 224. The point light source 210 is arranged opposite to the light incident surface 221. .

A plurality of gratings 230 are distributed on the light emitting surface 222 corresponding to incident light intensity regions (not shown) of the point light source 210 . Common manufacturing methods for the plurality of gratings 230 include mechanical scribing, vacuum coating replication, and holographic methods. The mechanical scribing method is to deposit aluminum or gold film on the light guide plate substrate, and then scribing. In order to control the shape of the grating stripes 231 and the positions of the grating stripes 231 and the spacers 232 , the motion accuracy of the grating scribing machine, the shape accuracy of the tool, and the temperature and humidity of the environment are relatively high. The vacuum coating replication method is to use the grating made by the mechanical scribing method as the master mold, and use the vacuum coating method to evaporate the separation layer and aluminum on the master mold, and then attach the aluminum to the blank of the replicated grating under the action of the adhesive. Copy raster. The holographic method of making gratings is also called the interference method, which uses laser holography to make gratings. The grating made by holography has denser grating stripes and smaller spacing error than the mechanically scribed grating.

A plurality of dots (not shown) are distributed on the bottom surface 223 , and the size and density of the dots gradually increase along the direction away from the light incident surface 221 , so as to improve the uniformity of light beams emitted from the light guide plate 220 and the backlight module 200 .

Please refer to FIG. 8 , which is the third embodiment of the backlight module of the present invention. The backlight module 300 includes a plurality of point light sources 310 and a light guide plate 320 . The light guide plate 320 is flat and includes two light incident surfaces 321, a bottom surface 323 vertically connected to the light incident surface 321, a light exit surface 322 opposite to the bottom surface 323, and a side surface 324. The point light source 310 is relatively incident to the two light Face 321 is provided.

A plurality of gratings 330 are distributed on both ends of the light emitting surface 322 corresponding to incident light intensity regions (not shown) of the point light source 310 . The plurality of gratings 330 are made inside the light guide plate 320 by using femtosecond (10-15 seconds) laser to irradiate the light guide plate 320 at different angles from 60° to 120°. The plurality of gratings 330 has the property of diffusing the light beam propagation direction outward, so that the light beam emitted by the point light source can diffuse through the plurality of gratings 330 and then enter the light intensity area, so as to reduce or even eliminate the incident dark band phenomenon of the light guide plate.

Please refer to FIG. 9 , a plurality of dots 340 are distributed on the bottom surface 323 . The plurality of dots 340 are uniformly distributed on the bottom surface 323 of the light guide plate 320 , and are in the shape of a cylinder, or a cube, a truncated cone, a sphere or a rectangle. The bottom surface 323 of the light guide plate 320 has a reflective film (not shown) to prevent the light beam from escaping from the bottom surface 323 of the light guide plate 320 , thereby reducing the energy loss of the light beam and improving the overall optical performance of the light guide plate 320 . Of course, a reflective plate (not shown) may also be provided on a side adjacent to the bottom surface 323 of the light guide plate 320 to realize this function.

Claims (10)

1. module backlight, comprise pointolite and light guide plate, the light-emitting face that this light guide plate comprises light entrance face, intersect with this light entrance face and with the light-emitting face opposed bottom surface, this pointolite emitted light beams enters light guide plate with the specific light field distribution through light entrance face, form the weak district of a plurality of incident intensities, it is characterized in that: this light guide plate also comprises a plurality of gratings that are arranged on light-emitting face, and a plurality of grating pair answers the weak district of incident intensity to distribute.

2. module backlight as claimed in claim 1 is characterized in that: these a plurality of gratings comprise grating fringe and the spacer portion between grating fringe.

3. module backlight as claimed in claim 2 is characterized in that: the distribution arrangement of this grating fringe is the beam emissions angular direction that is parallel to pointolite.

4. module backlight as claimed in claim 2 is characterized in that: this grating fringe is the projection in many secured in parallel cycles.

5. module backlight as claimed in claim 4 is characterized in that: the shape of this grating fringe is triangle, trapezoidal or rectangle.

6. module backlight as claimed in claim 4 is characterized in that: the width of this grating fringe and the width of spacer portion are all less than 2 μ m, and the height of grating fringe is 0.5-1.5 μ m.

7. module backlight as claimed in claim 2 is characterized in that: this grating fringe is the groove in many secured in parallel cycles.

8. module backlight as claimed in claim 1 is characterized in that: these a plurality of gratings are to adopt mechanical scratching method, vacuum coating replica method or holography method to make.

9. module backlight as claimed in claim 1 is characterized in that: this pointolite is a light emitting diode.

10. light guide plate, in order to the points of engagement light source, comprise the light entrance face of receiving beam, intersect with light entrance face and the light-emitting face of lead beam outgoing and with the light-emitting face opposed bottom surface, it is characterized in that: this light guide plate also comprises a plurality of gratings that are arranged on light-emitting face, and a plurality of grating pair answers the weak district of incident intensity of pointolite to distribute.

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