CN101788128A - Light guide plate and backlight module - Google Patents

Abstract

The invention provides a light guide plate and a backlight module. The light guide plate includes a first light guide part and a second light guide part. The first light guide part has a first refractive index. The second light guide part has a second refractive index, and the first refractive index is greater than the second refractive index. The light source is arranged on the side surface of the first light guide part, and the first light guide part and the second light guide part are sequentially arranged along the light emitting direction of the light source. The invention can improve the light transmission efficiency of the light guide plate, so that the light emitting of the backlight module is more uniform.

Description

Light guide plate and backlight module

technical field

The invention relates to a light guide plate and a backlight module, in particular to a light guide plate capable of improving light transmission efficiency and a backlight module using the light guide plate.

Background technique

At present, flat panel displays have gradually become the mainstream of display products, such as liquid crystal displays (LCDs), organic light emitting displays (OLEDs) or plasma displays (PDPs). Among them, liquid crystal displays are widely used in display screens of consumer electronic products such as mobile phones, computers, and televisions. It is worth noting that the liquid crystal panel must provide the required surface light source with the backlight module. Generally speaking, the backlight module can be divided into direct type backlight module and edge type backlight module according to the way the light source is provided. The direct-lit backlight module uses a plurality of light tubes placed flat in the box to directly provide the surface light source required by the liquid crystal panel. The light source of the edge-lit backlight module is arranged on the side of the light guide plate, and the light emitted by the light source enters the light guide plate from the side of the light guide plate, and exits from the top surface of the light guide plate to form a surface light source that can be projected to the liquid crystal panel.

Whether it is a direct-lit or edge-lit backlight module, the efficiency of the formed surface light source is determined by the light source and the light guide plate in the backlight module. The design of the light guide affects how light travels through it. For example, light may be emitted through the bottom surface of the light guide plate but not emitted from the top surface of the light guide plate, or the light gradually loses energy when passing through the light guide plate, and fails to travel a long distance in the light guide plate. With the development of large-size liquid crystal panels, it is more necessary to make the light emitted by the light guide plate to be uniform.

Contents of the invention

In view of the above technical problems, the present invention designs a new type of light guide plate by using the arrangement of light guide parts with different refractive indices, so that the backlight module including the light guide plate emits light more uniformly.

One of the objectives of the present invention is to provide a light guide plate for a backlight module with a light source, the light guide plate includes a first light guide portion and a second light guide portion. The first light guide has a first refractive index. The second light guiding part has a second refractive index, and the first refractive index is greater than the second refractive index. Wherein, the light source is arranged on the side of the first light guide part, and the first light guide part and the second light guide part are arranged in sequence along the light emitting direction of the light source.

Another object of the present invention is to provide a backlight module, which includes a light source and a light guide plate. The light guide plate includes a first light guide part and a second light guide part. The first light guide has a first refractive index. The second light guiding part has a second refractive index, and the first refractive index is greater than the second refractive index. Wherein, the light source is arranged on the side of the first light guide part, and the first light guide part and the second light guide part are arranged in sequence along the light emitting direction of the light source.

The invention makes the backlight module emit more uniform light, saves the process of designing dots on the light guide plate, and reduces the manufacturing cost in mass production.

Description of drawings

FIG. 1 is a schematic perspective view of a light guide plate according to an embodiment of the present invention;

2 is a side view of a light guide plate according to an embodiment of the present invention;

3 is a schematic diagram of a light guide plate according to another embodiment of the present invention;

4a and 4b are top views of light guide plates according to another embodiment of the present invention;

5a and 5b are top views of a light guide plate according to yet another embodiment of the present invention;

FIG. 6 is a schematic diagram of a light guide plate according to another embodiment of the present invention.

Detailed ways

In order to have a further understanding of the purpose, structure, features, and functions of the present invention, the following detailed descriptions are provided in conjunction with the embodiments.

Please refer to FIG. 1 . FIG. 1 is a perspective view of a light guide plate 10 according to an embodiment of the present invention. The light guide plate 10 is used in a backlight module with a light source 20 , and the light guide plate 10 includes a first light guide portion 11 and a second light guide portion 13 . The first light guide part 11 has a first refractive index n1. The second light guide part 13 has a second refractive index n2, wherein the first refractive index n1 is greater than the second refractive index n2. The light source 20 is disposed on the side surface 112 of the first light guide part 11 , and the first light guide part 11 and the second light guide part 13 are arranged in sequence along the light emitting direction L of the light source 20 . In this embodiment, the light source 20 may be a lamp, especially a cold cathode fluorescent lamp (CCFL). Continue to refer to FIG. 2 , which is a side view of the light guide plate 10 according to an embodiment of the present invention. FIG. 2 also shows a reflector 22 for better gathering the light emitted by the light source 20 onto the light incident surface of the first light guiding portion 11 .

In practical applications, the first light guide part 11 and the second light guide part 13 of the light guide plate 10 can be formed by doping different impurities in the same medium, or can be formed by using mediums with different refractive indices with similar materials. optical glue bonding to form.

In order to explain in detail that the light guide plate of the present invention can indeed increase the light transmission effect, the principle is introduced as follows. According to Snell's law in optics:

n _c sinθ _c ＝n _a sinθ _a

Assuming that n _c represents the refractive index of the light guide, and n _a represents the refractive index of air, it can be deduced that the critical angle of total light emission in the light guide is:

θ _c = sin ^-1 (l/n _c )

It can be known that the larger the refractive index n _c of the light guide part is, the smaller the critical angle θ _c at which total reflection occurs. That is to say, since the critical angle of the light guide part with a larger refractive index is smaller, the light is less likely to exit from the light guide part into the air.

In this embodiment, the first refractive index n1 of the first light guiding part 11 is greater than the second refractive index n2 of the second light guiding part 13, so that the light emitted by the light source 20 is less emitted in the first light guiding part 11, and the light More of the total reflection passes through the first light guide part 11 to the second light guide part 13, and the second light guide part 13 emits more light. In this way, the light emitted by the light source 20 can reach a farther distance, and further achieve better light extraction efficiency.

According to experiments, the difference between the first refractive index n1 and the second refractive index n2 is related to the light transmission efficiency of the light guide plate 10 . For example, n1=1.59586, n2=1.59102, Δn=n1-n2=0.00484, at this time, the light transmission efficiency is increased by 25.3% compared with Δn=0. In contrast, n1=1.59102, n2=1.53419, Δn=n1-n2=0.05683, which is 8.6% higher than the light transmission efficiency when Δn=0; n1=1.59102, n2=1.49309, Δn=n1-n2=0.09793 , at this time, the light transmission efficiency is reduced by 15.6% compared with Δn=0. Therefore, when the difference between the first refractive index n1 and the second refractive index n2 is within 0.057, the light transmission efficiency is improved; when the difference between the first refractive index n1 and the second refractive index n2 is less than 0.005, the light transmission efficiency is greatly improved. improve.

Please refer to FIG. 3 , which shows a schematic diagram of a light guide plate 30 according to another embodiment of the present invention. The light guide plate 30 includes a first light guide part 31 , a second light guide part 33 , a third light guide part 35 and a fourth light guide part 37 . The light guiding parts respectively have a first refractive index, a second refractive index, a third refractive index and a fourth refractive index which decrease in order. Wherein, the light emitted by the light source 40 passes through the first light guide part 31 , the second light guide part 33 , the third light guide part 35 and the fourth light guide part 37 in sequence. In this embodiment, the light source 40 may be a light emitting diode (LED) or a light tube.

Please refer to FIG. 4a and FIG. 4b. FIG. 4a and FIG. 4b are respectively top views of a light guide plate 30a and a light guide plate 30b according to another embodiment of the present invention. The light guide plate 30a includes a first light guide part 31a, a second light guide part 33a, a third light guide part 35a, and a fourth light guide part 37a. The light guiding parts respectively have a first refractive index, a second refractive index, a third refractive index and a fourth refractive index which decrease in order. Wherein, the light emitted by the light source 40a sequentially passes through the first light guide portion 31a, the second light guide portion 33a, the third light guide portion 35a and the fourth light guide portion 37a. The light guides are arranged side by side along the light emitting direction of the light source 40a. In this embodiment, the light source 40a may be a line light source.

The light guide plate 30b includes a first light guide part 31b, a second light guide part 33b, a third light guide part 35b, and a fourth light guide part 37b. The light guiding parts respectively have a first refractive index, a second refractive index, a third refractive index and a fourth refractive index which decrease in order. Wherein, the light emitted by the light source 40b sequentially passes through the first light guide portion 31b, the second light guide portion 33b, the third light guide portion 35b and the fourth light guide portion 37b. The light guides are arranged together along the light emitting direction of the light source 40b. In this embodiment, the light source 40b is a point light source, the area where the light guides are located is fan-shaped with the light source 40b as the center, and the light source 40b changes from emitting light at one corner to emitting light at one side.

Please refer to FIG. 5 a and FIG. 5 b , which are top views of a light guide plate 50 and a light guide plate 70 according to another embodiment of the present invention, respectively. The light guide plate 50 includes a plurality of first light guide parts 51 and second light guide parts 53 , and the first refractive index n1 of the first light guide parts 51 is greater than the second refractive index n2 of the second light guide parts 53 . The first light guide portions 51 are disposed around the second light guide portion 53 . The light source 60 is disposed around the side of the first light guide part 51 . In this embodiment, the light source 60 may be a lamp tube, or a combination of LEDs. Since the first refractive index n1 is greater than the second refractive index n2, less light exits the first light guide part 51, and more light is totally reflected through the first light guide part 51 to the second light guide part 53, while the second light guide part 51 The light guide portion 53 has a smaller refractive index so that more light is emitted. With such a design, the light can be emitted evenly, so that the central part can achieve better light emission efficiency. It should be noted that the present invention is not limited to light guides with two refractive indices, and a third light guide can be added in addition to the second light guide according to requirements, and arranged according to the above design concept. In practical applications, the combination of these light guide parts can use optical glue with similar material to reduce the total reflection of light at the interface of the light guide parts.

The main difference between the light guide plate 70 and the light guide plate 50 is that the first light guide part 71 is integral and surrounds the second light guide part 73 , and the first refractive index n1 of the first light guide part 71 is greater than that of the second light guide part 73 The second refractive index n2. The light source 80 is disposed around the side of the first light guide portion 71 .

Please refer to FIG. 6 , which is a schematic diagram of a light guide plate 90 according to another embodiment of the present invention. The light guide plate 90 includes a first light guide part 91 , a second light guide part 93 and a third light guide part 95 . The light guiding portions respectively have a first refractive index, a second refractive index and a third refractive index which decrease in order. The corner 911 of the side of the first light guiding portion 91 has a light incident surface, and the light source 92 is disposed corresponding to the light incident surface at the corner 911 . Likewise, the side corners 931 and 951 of the second light guide part 93 and the third light guide part 95 respectively have light incident surfaces, and the light source 92 is respectively disposed on the light incident surfaces at the corners 931 and 951 . In the design of the laminated light guide plate in this embodiment, the difference in refractive index of the material can affect the length of each light guide part, so as to meet the requirements of various future applications.

In summary, the present invention designs a new type of light guide plate by utilizing the arrangement of light guide parts with different refractive indices, so that the backlight module including the light guide plate emits light more uniformly; process, reducing manufacturing costs in mass production.

The present invention has been described by the above-mentioned related embodiments, however, the above-mentioned embodiments are only examples for implementing the present invention. It must be pointed out that the disclosed embodiments do not limit the scope of the present invention. Changes and modifications made without departing from the spirit and scope of the present invention all belong to the scope of patent protection of the present invention.

Claims (10)

1. A light guide plate for a backlight module with a light source, characterized in that the light guide plate comprises: The first light guide part has a first refractive index; a second light guiding portion having a second refractive index, the first refractive index being greater than the second refractive index; Wherein, the light source is arranged on the side of the first light guide part, and the first light guide part and the second light guide part are arranged in sequence along the light emitting direction of the light source. 2. The light guide plate according to claim 1, wherein the area where the first light guide part and the second light guide part are located is fan-shaped with the light source as the center. 3. The light guide plate according to claim 1, characterized in that the light guide plate further comprises: a third light guide portion having a third refractive index, the third refractive index is smaller than the second refractive index, wherein the light emitted by the light source The light passes through the first light guide part, the second light guide part and the third light guide part in sequence. 4. The light guide plate according to claim 1, wherein the first light guide part is disposed around the second light guide part. 5. The light guide plate according to claim 4, wherein the light source is disposed around the side surface of the first light guide part. 6 . The light guide plate according to claim 1 , wherein a light-incident surface is provided at a side corner of the first light-guiding portion and the second light-guiding portion, and the light source is correspondingly disposed on the light-incident surface. 7 . 7. The light guide plate according to claim 1, characterized in that: the first light guide part and the second light guide part are joined by media with different refractive indices using optical glue, or doped in the same medium Different impurities are formed. 8. The light guide plate as claimed in claim 1, wherein the difference between the first refractive index and the second refractive index is less than 0.057. 9. The light guide plate as claimed in claim 8, wherein the difference between the first refractive index and the second refractive index is less than 0.005. 10. A backlight module, characterized in that it comprises: light source; and The light guide plate according to any one of claims 1-9.

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