CN100432792C - Backlight module - Google Patents

Abstract

The invention discloses a Light Guide Plate (LGP) which is applied to a backlight module. The light guide plate comprises a first surface and a second surface opposite to the first surface. The second surface has a plurality of optical structures, and each optical structure includes: a projection (projection) portion; a groovingport connected to the protrusion; and a flat portion (flat portion) having one end connected to the recess portion. Wherein the lengths (pitch) of the optical structures are not identical.

Description

Backlight module

technical field

The present invention relates to a light guide plate and a backlight module applied thereto, in particular to a light guide plate capable of effectively improving the brightness in a small viewing angle range of a liquid crystal display device and a backlight module applied thereto.

Background technique

Liquid crystal display devices that can produce rich and bright graphics are widely used in portable information products such as notebook computers and personal digital assistants due to their thin and light appearance, low power consumption, and no radiation pollution, and are even gradually replacing The cathode ray tube (Cathode Ray Tube, CRT) monitor traditionally used in desktop computers.

The liquid crystal display device is mainly composed of a display unit, a backlight module and a casing with a frame. The display unit includes a display panel, a circuit board capable of processing data signals, and a supporting thin film package (Tape Carrier Package, TCP). The backlight module is located under the display unit to provide a uniform light source for the display unit of the liquid crystal display device. According to the way of providing the light source, it can be further divided into an edge-lit backlight module or a direct-lit backlight module. In the case of edge-lit backlight modules, line light sources or point light sources are placed on the sides of films such as light guide plates and diffusion films, and optical films such as light guide plates and diffusion films are used to improve light uniformity and luminous efficiency.

FIG. 1 is a schematic diagram of a conventional backlight module. The backlight module 1 includes: a light source 11 , a light guide plate 13 , a reflection sheet 15 and a plurality of optical films 17 . Wherein, the light source 11 that generates light is located on the side of the light guide plate 13 , and a shield 19 protects the light source 11 . The general light source is a Cold Cathode Fluorescent Lamp (CCFL), which is mounted on a lamp holder (not shown), and a lamp line (not shown) extends from the lamp holder to be electrically connected with a connector.

A light guide plate 13 is used to change the path of light. Therefore, the light emitted from the light source 11 can be guided by the light guide plate 13 to reach the display panel (not shown). In the traditional backlight module 1, due to the phenomenon of refraction when the light from the light source 11 enters the light guide plate 13, the light emitting angle of the light source will become narrow, so a V-shaped structure (V-Cut) 131 is formed on the light incident side of the light guide plate 13, In order to make the light emitting range of the light source become wider. The reflective sheet 15 below the light guide plate 13 is used to reflect the light leaking out of the light guide plate 13 to improve the light reflection efficiency.

A plurality of optical sheets 17 above the light guide plate 13 are used to further process the light, such as concentrating, diffusing or softening the light. For the light guide plate 13 with the V-shaped structure 131 , the optical film 17 includes a prism sheet 171 and a diffusion sheet 173 . There can be one or more diffusion sheets 173 . With the optical film 17 , the light with a wider light output range (the light source passes through the light guide plate 13 of the V-shaped structure 131 ) can be concentrated to the direction of the normal viewing angle. However, also due to the existence of the optical film 17 , it is difficult to control the overall brightness uniformity of the backlight module 1 .

Contents of the invention

In view of this, the object of the present invention is to provide a light guide plate and a backlight module for its application. By forming a special optical structure design on the light guide plate, the overall optical brightness of the backlight module can be improved, especially the optical brightness within a small viewing angle range. brightness.

According to the purpose of the present invention, a light guide plate (LGP) is proposed, which is used in a backlight module in cooperation with a light source. The light guide plate includes a first surface, a second surface opposite to the first surface, a third surface, and a light-incident side, on which the light source is arranged. The second surface has a plurality of optical structures, and each optical structure includes: a projecting portion; a grooving portion, connected to the convex portion; and a flat portion, one end connected to the concave portion . Wherein, the lengths (pitches) of the optical structures are not completely the same, the third surface is opposite to the light-incident side, and the two ends of the optical structures are respectively located on the light-incident side and the third surface.

According to the purpose of the present invention, a backlight module is proposed, which is applied in a liquid crystal display device. The backlight module at least includes a light guide plate (LGP), a light source (light source), and is arranged on the side of the light guide plate; and an optical sheet , located above the light guide plate. The light guide plate includes a first surface and a second surface opposite to the first surface. The second surface has a plurality of optical structures, and each optical structure includes: a projecting portion; a grooving portion connected to the convex portion; and a flat portion connected to the concave portion at one end. Wherein, the lengths (pitches) of the optical structures are not completely the same.

In order to make the above-mentioned objects, features, and advantages of the present invention more comprehensible, preferred embodiments will be described in detail below together with the attached drawings.

Description of drawings

FIG. 1 is a schematic diagram of a traditional backlight module;

2A and 2B are schematic cross-sectional views and perspective views of a first-type light guide plate according to a preferred embodiment of the present invention;

Fig. 3 is the relationship diagram of the length and the position of the optical structure in Table 1;

4 is a schematic cross-sectional view of a second-type light guide plate in a preferred embodiment of the present invention;

5 is a schematic cross-sectional view of a third-type light guide plate according to a preferred embodiment of the present invention;

FIG. 6 is a schematic diagram of a backlight module according to a preferred embodiment of the present invention.

Explanation of schematic symbols

1, 6: Backlight module

11, 61: light source

2, 13, 63: light guide plate

131: V-shaped structure

21, 631: The first surface

22, 632: second surface

231, 241, 251: convex part

233, 243, 253: Recesses

235, 245, 255: flat part

15, 65: reflective sheet

17, 67: Optical film

171, 671: Prism sheet

6712: lower surface

6714: Groove

173, 673: Diffuser

19, 69: shielding

P1, P2, P3: the length of the optical structure

Ap: The maximum width of the bottom surface of the convex part

Ag: The maximum opening width of the recess

Af: Width of flat part

hp: the height of the convex part

Dg: depth of recess

Detailed ways

The present invention proposes a light guide plate, which is applied to the backlight module of a liquid crystal display device, mainly to form a special optical structure design (or a gradient prism structure design) on the light guide plate to improve the overall optical brightness of the backlight module, especially Optical brightness in a small viewing angle range. The following is a detailed description of the present invention with a preferred embodiment, however, this embodiment will not limit the protection scope of the present invention. In addition, unnecessary elements are omitted in the diagrams to clearly show the technical characteristics of the present invention.

Please refer to FIG. 2A and FIG. 2B , which illustrate a schematic cross-sectional view and a perspective view of a first-type light guide plate according to a preferred embodiment of the present invention. As shown in FIG. 2A , a light guide plate (LGP) 2 includes a first surface 21 and a second surface 22 opposite to the first surface 21 . The second surface 22 has a plurality of optical structures (not shown), and each optical structure includes: a projecting portion 231; a grooving portion 233 connected to the protruding portion 231; and a flat portion (flat portion) 235, one end of which is connected to the concave portion 233, and the other end is connected to the convex portion 241 of another adjacent optical structure. In addition, in this embodiment, it is described that the flat portion 235 is parallel to the first surface 21 , and the height (height) hp of the convex portion is greater than the depth (depth) Dg of the concave portion.

The length (pitch, P) of each optical structure is determined by the maximum width of the bottom surface of the convex part, the maximum opening width of the concave part and the width of the flat part. Taking the 3rd optical structure in Fig. 2A as an example, the length P3 is the sum of the maximum width Ap of the bottom surface of the convex portion 251, the maximum opening width Ag of the concave portion 253, and the width Af of the flat portion 255 (abbreviated as P3=Ap+Ag+ Af). The pitches of the optical structures on the light guide plate 2 are not exactly the same, that is, P1≠P2 or P1≠P3 or P2≠P3.

In the following, the length of the optical structure forms a periodic change for illustration. Table 1 discloses a length cycle variation of the preferred embodiment. FIG. 3 is a diagram showing the relationship between the length and the position of the optical structure in Table 1. FIG. in:

(1) A total of 20 groups of optical structures are formed on the light guide plate;

(2) The optical structures of the first group and the 20th group are located at the outermost two ends of the light guide plate;

(3) The length of the optical structure located on the outermost side of the light guide plate (that is, the length of the first group and the 20th group is 0.0797mm) is greater than the length of the optical structure located in the center of the light guide plate (that is, the length of the 10th and 11th group is 0.0533mm) ;

(4) The length of the optical structure decreases from the outermost side of the light guide plate to the center; that is, the length of the optical structure is the longest in the first group (0.0797mm), and slightly decreased in the second group (0.0784mm), until the tenth group ( 0.0533mm) is the minimum.

Table I

group Length (mm) group Length (mm) 1 0.0797 11 0.0533 2 0.0784 12 0.0544 3 0.0756 13 0.0566 4 0.0719 14 0.0597 5 0.0677 15 0.0635 6 0.0635 16 0.0677 7 0.0597 17 0.0719 8 0.0566 18 0.0756 9 0.0544 19 0.0784 10 0.0533 20 0.0797

In practical applications, the period formed by the length of the optical structure can be properly adjusted according to the uniformity of the brightness distribution, and is not limited to the data disclosed in Table 1.

optical simulation

For the light guide plate with periodic change in optical structure length, the optical simulation is carried out with the traditional light guide plate with V-shaped structure, and the results are shown in Table 2.

In Table 2, the conventional light guide plate with a V-shaped structure is shown as the light guide plate 13 in FIG. 1 . Both the first type and the second type of light guide plates have optical structure lengths with periodic changes as shown in Table 1 and FIG. 3 . But the difference is: in the first type of light guide plate, the height hp of the convex portion 231 is greater than the depth Dg of the concave portion 233 (hp>Dg), as shown in FIG. 2A; while in the second type of light guide plate, the height of the convex portion 231 is less than The depth Dg (hp<Dg) of the concave portion 233 is shown in FIG. 4 .

According to the experimental results: whether it is the first type or the second type of light guide plate, the overall brightness can indeed be increased in the small viewing angle range of 1-10 degrees, and the light guide plate of the preferred embodiment can be compared with the traditional V-shaped structure in terms of a viewing angle of 2 degrees. The light guide plate increases the brightness by about 47%.

Table II

Viewing angle 90 degrees (R90) Viewing angle 10 degrees (R10) Viewing angle 2 degrees (R2) Traditional light guide plate with V-shaped structure 100.00% 100.00% 100.00% Light guide plate with periodic change in optical structure length (Type 1) 120.84% 103.32% 148.57% Light guide plate with periodic change in optical structure length (type 2) 120.97% 101.60% 147.69%

It should be noted that although in FIG. 2A and FIG. 2B , the height of the convex portion is greater than the depth of the concave portion (hp>Dg) as an example for description. However, the present invention is not limited thereto. In addition to the first-type light guide plate in FIG. 2A , the second-type light guide plate in FIG. 4 (that is, the height of the convex portion is smaller than the depth of the concave portion, hp<Dg) and the third-type light guide plate in FIG. 5 (that is, the height of the convex portion is equal to The depth of the concave portion, hp=Dg), can improve the overall brightness in the small viewing angle range.

In addition, although in the above-mentioned embodiment, with linear cross-section (linear cross-section), that is, convex portion 231, 241, 251 and concave portion 233, 243, 253 are triangular cross-section (triangular cross-section), and flat portion 235, 245, 255 are straight lines, as an illustration of the optical structure, however, the present invention is not limited thereto, the optical structure can also be a curved cross-section, for example, the convex portion or/and concave portion is made into a circular convex Bump can also achieve the effect of increasing brightness.

If the light guide plate of the above-mentioned embodiment is applied to the backlight module, a prism structure can be formed on the first surface (i.e., the light output side) 21 of the light guide plate 2. At this time, the original prism sheet 171 in the traditional backlight module 1 can be omitted, and also The prism sheet can be kept. Please refer to FIG. 6 , which shows a schematic diagram of a backlight module according to a preferred embodiment of the present invention. Wherein, the backlight module 6 includes: a light source 61 , a light guide plate 63 with an optical structure, a reflection sheet 65 and a plurality of optical films 67 . Wherein, the light source 61 is located at the side of the light guide plate 63 and is protected by a shield 69 . For the optical structure of the light guide plate 63 , please refer to FIG. 2A , FIG. 2B and related descriptions above. A reflecting sheet 65 is disposed under the light guide plate 63 and opposite to the second surface 632 . The optical film 67 includes a prism sheet (prism sheet) 671 and one or more diffusion sheets (diffusion sheet) 673 . Wherein, the lower surface 6712 of the prism sheet 671 is opposite to the first surface 631 of the light guide plate 63, and the lower surface 6712 has a plurality of grooves (furrow) 6714, and the extending direction of these grooves 6714 is in line with the convex portion of the light guide plate 63. perpendicular to the extending direction of the recess. The light emitted from the light source 61 can pass through the light guide plate 63 , the prism sheet 671 and the diffusion sheet 673 to reach the panel of the display device. The light guide plate with the optical structure of the present invention can concentrate the outgoing light to the direction of the normal viewing angle, especially the overall brightness in the small viewing angle range can be greatly improved.

In summary, although the present invention has been disclosed in conjunction with the above preferred embodiments, it is not intended to limit the present invention. Any person familiar with the art can make various changes without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be defined by the appended claims.

Claims (11)

1. a backlight module comprises light source and the light guide plate that cooperates with light source, and wherein, this light guide plate comprises:

One light incident sides, this light source is arranged at this light incident sides;

One first surface;

One second surface, relative with this first surface, this second surface has a plurality of optical textures, and each optical texture comprises:

One protuberance;

One recess is connected with this protuberance; And

One par, the one end is connected with this recess;

Wherein, the length of those optical textures is incomplete same; With

One the 3rd surface, relative with this light incident sides, wherein the two ends of those optical textures lay respectively at this light incident sides and the 3rd surface.

2. backlight module as claimed in claim 1, wherein the length of those optical textures is to form the one-period variation.

3. backlight module as claimed in claim 1 wherein is positioned at the length of the length of outermost this optical texture of this light guide plate greater than this optical texture that is positioned at this light guide plate center.

4. backlight module as claimed in claim 3, wherein the length of those optical textures is to successively decrease toward center position from this light guide plate outermost.

5. backlight module as claimed in claim 1, wherein in each optical texture, the height of this protuberance is greater than this concave depth.

6. backlight module as claimed in claim 1, wherein in each optical texture, the height of this protuberance is less than this concave depth.

7. backlight module as claimed in claim 1, wherein in each optical texture, the height of this protuberance equals this concave depth.

8. backlight module as claimed in claim 1, wherein this optical texture has a linear type cross section.

9. backlight module as claimed in claim 1, wherein this optical texture has an arc section.

10. backlight module as claimed in claim 1, wherein this recess and this protuberance have a triangular-section.

11. backlight module as claimed in claim 1 wherein comprises a prism structure on this first surface.

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