CN113552747A

CN113552747A - Front light module and display device with same

Info

Publication number: CN113552747A
Application number: CN202010331616.2A
Authority: CN
Inventors: 廖经桓; 黄信道
Original assignee: E Ink Holdings Inc
Current assignee: E Ink Holdings Inc
Priority date: 2020-04-24
Filing date: 2020-04-24
Publication date: 2021-10-26
Anticipated expiration: 2040-04-24
Also published as: CN113552747B

Abstract

A front light module and a display device having the same. The front light module comprises a light source and a light guide plate. The light source is provided with a light emergent surface. The light guide plate comprises a microstructure area, wherein the microstructure area comprises a first microstructure and at least one second microstructure. The first microstructure is positioned between the light emitting surface of the light source and the second microstructure. A first angle is formed between one surface of the first microstructure, close to the light source, and one optical axis direction of the light source, a second angle is formed between the surface of the first microstructure, far away from the light source, and the optical axis direction, a third angle is formed between the surface of the second microstructure, far away from the light source, and the optical axis direction, the first angle is in a range of about 30 degrees to 50 degrees, and the second angle and the third angle are in a range of about 60 degrees to 90 degrees. Through the design, the probability of light mixing between two adjacent pixels can be reduced, the color saturation of the display device is increased, light guide diffusion caused by the light guide plate is reduced, and the light emitting collimation of the light guide plate is improved.

Description

Front light module and display device with same

Technical Field

The present disclosure relates to a front light module and a display device having the same.

Background

The existing front optical module guides light by using a dot structure of a light guide plate, and the dot structure usually has a volcano-mouthed dot or a linear groove and non-discrete design. When the design is applied to a reflective display panel, the width of light guiding light is large, and the problem of low light collimation degree is caused. In addition, the angle of the light guiding light deviating from the vertical direction (i.e. the normal direction of the light guiding plate) is large, so that the light between two adjacent pixels is easy to mix and the color saturation of the display panel is reduced.

Disclosure of Invention

One aspect of the present disclosure is a front light module.

In some embodiments, a front light module includes a light source and a light guide plate. The light source is provided with a light emergent surface. The light guide plate comprises a microstructure area, wherein the microstructure area comprises a first microstructure and at least one second microstructure. The first microstructure is positioned between the light emitting surface of the light source and the second microstructure. A first angle is formed between one surface of the first microstructure, close to the light source, and one optical axis direction of the light source, a second angle is formed between the surface of the first microstructure, far away from the light source, and the optical axis direction, a third angle is formed between the surface of the second microstructure, far away from the light source, and the optical axis direction, the first angle is in a range of about 30 degrees to 50 degrees, and the second angle and the third angle are in a range of about 60 degrees to 90 degrees.

In some embodiments, the first and second microstructures are recessed from the top surface of the light guide plate.

In some embodiments, the top view shape of the first microstructure and the second microstructure is circular, elliptical or diamond.

In some embodiments, the first microstructures and the second microstructures respectively have a first length along an optical axis of the light source and a second length along a horizontal direction perpendicular to the optical axis, and a ratio of the first length to the second length is in a range of about 0.5 to 2.5.

In some embodiments, a fourth angle is formed between the surface of the second microstructure close to the light source and the optical axis direction, and the fourth angle is the same as the first angle.

In some embodiments, the second angle is the same as the third angle.

In some embodiments, the number of the second microstructures is plural, and the third angles of the second microstructures are the same.

In some embodiments, a color filter layer is further included, the color filter layer has sub-pixels, and the number of the second microstructures increases as the width of the sub-pixels decreases.

In some embodiments, adjacent ones of the first and second microstructures have a pitch therebetween, and the pitch is in a range of about 1 micron to 20 microns.

In some embodiments, the first microstructure and the second microstructure are contiguous.

In some embodiments, the number of the second microstructures is plural, and the second microstructures are connected to each other.

Another aspect of the present disclosure is a display device.

In some embodiments, a display device includes a front light module and a display panel. The front light module comprises a light source and a light guide plate. The light source is provided with a light emergent surface. The light guide plate comprises a microstructure area, wherein the microstructure area comprises a first microstructure and at least one second microstructure. The first microstructure is positioned between the light emitting surface of the light source and the second microstructure. A first angle is formed between one surface of the first microstructure, close to the light source, and one optical axis direction of the light source, a second angle is formed between the surface of the first microstructure, far away from the light source, and the optical axis direction, a third angle is formed between the surface of the second microstructure, far away from the light source, and the optical axis direction, the first angle is in a range of about 30 degrees to 50 degrees, and the second angle and the third angle are in a range of about 60 degrees to 90 degrees. The display panel is positioned below the light guide plate.

In some embodiments, the second angle is the same as the third angle.

In some embodiments, adjacent ones of the first and second microstructures have a pitch therebetween, and the pitch is in a range of about 1 micron to 20 microns. In the above embodiments, by disposing the first microstructure and the at least one second microstructure in one microstructure region, and adjusting the first angle and the second angle of the first microstructure and the third angle of the second microstructure, an angle between a light beam incident toward the display panel and a vertical direction (a normal direction of the light guide plate) can be reduced. Therefore, the probability of light mixing between two adjacent pixels can be reduced, and the color saturation of the display device can be increased. In addition, since the light reflected by the second microstructure can travel downwards more nearly vertically, the light beam incident towards the display panel is more concentrated, and therefore, the light line width can be narrower. Therefore, the light guide plate can reduce light guide diffusion caused by the light guide plate and improve the light emitting collimation of the light guide plate.

Drawings

FIG. 1 is a cross-sectional view of a display device according to an embodiment of the present disclosure;

FIG. 2A is a top view of the light source and the light guide plate of FIG. 1;

FIG. 2B is a top view of a light source and a light guide plate according to another embodiment of the present disclosure;

FIG. 3 is a top view of a light source and a light guide plate according to an embodiment of the disclosure;

FIG. 4 is an enlarged view of the light source, the light guide plate and the optical adhesive layer in FIG. 1;

FIG. 5A is a schematic diagram of the optical path of an exemplary display device;

FIG. 5B is a diagram of beam width simulation of the display device of FIG. 5A;

FIG. 6A is a schematic diagram of an optical path of the display device according to FIG. 1;

FIG. 6B is a diagram of beam width simulation of the display device of FIG. 6A;

FIG. 7 is a diagram illustrating a relationship between a first angle and a light angle according to an embodiment of the present disclosure;

FIG. 8 is a graph illustrating a relationship between a first angle and a light width according to an embodiment of the present disclosure;

FIG. 9 is a cross-sectional view of a display device according to another embodiment of the present disclosure;

10A-10D are top views of microstructure areas according to various embodiments of the present disclosure;

FIG. 11 is a simulation diagram of the optical line width in the horizontal direction of the display device of FIG. 6A;

FIG. 12 is a graph of a ratio of a first length to a second length versus a width of light in a horizontal direction according to various embodiments of the present disclosure;

fig. 13 is a data diagram of the first length, the second length, and the light width in the horizontal direction according to fig. 11.

[ notation ] to show

10,20 display device

100 front light module

110 light source

112 light-emitting surface

120,120A, 120', 720 light guide plate

122,122A, 122', 122A,122b,122c,122d,222,722 microstructure areas

1222,1222A,1222a,1222b,1222c,1222d,2222,7222A first microstructure

1224,1224A,1222a,1224b,1224c,1224d,2224,7224 second microstructure

124 top surface

200 display panel

210 drive substrate

220 display medium layer

230 adhesive layer 300,800 color filter layer

310,320,330,810,820,830 sub-pixel

400: cover plate

500 optical adhesive layer

600 touch layer

1-1: line segment

D1 optical axis direction

D2 horizontal direction

D3 vertical direction

d1, d2, d3 distance

S1, S2, S3, S4, S5 surface

Theta 1 first angle

Theta 2 to the second angle

Theta 3 third angle

Theta 4 to fourth angle

L0 incident ray

L1, L2, L3 reflected light

L1 ', L2' transmitting light

I1, I2 incident light

IR1, IR2 Beam boundaries

R1, R2 reflected light

RR1, RR2 Beam boundaries

A1, A2 light ray angle

W1, W2, W3 optical line width

l1 first Length

l2 second Length

l3 length

P1, P2 position

Detailed Description

In the following description, for purposes of explanation, numerous implementation details are set forth in order to provide a thorough understanding of the various embodiments of the present invention. It should be understood, however, that these implementation details are not to be interpreted as limiting the invention. That is, in some embodiments of the invention, such implementation details are not necessary. In addition, for the sake of simplicity, some conventional structures and elements are shown in the drawings in a simple schematic manner. And the thickness of layers and regions in the drawings may be exaggerated for clarity, and the same reference numerals denote the same elements in the description of the drawings.

Fig. 1 is a cross-sectional view of a display device 10 according to an embodiment of the present disclosure. The display device 10 includes a front light module 100 and a display panel 200. The front light module 100 includes a light source 110, a light guide plate 120, a color filter layer 300, and a cover plate 400. The light guide plate 120 is located between the cover plate 400 and the color filter layer 300. The color filter layer 300 is located between the display panel 200 and the light guide plate 120. The display panel 200 may be an electrophoretic display panel or a liquid crystal display panel, but the disclosure is not limited thereto, as long as the display panel can be used to match with the front light module 100.

Fig. 2A is a top view of the light source 110 and the light guide plate 120 in fig. 1. Fig. 1 is a cross-section taken along line 1-1 of fig. 2A. The cover plate 400 and other structures above the light guide plate 120 are omitted in fig. 2A for clarity. Please refer to fig. 1 and fig. 2A. The light source 110 has an exit surface 112, and the exit surface 112 faces the light guide plate 120. The light guide plate 120 comprises a microstructure region 122, wherein the microstructure region 122 comprises a first microstructure 1222 and at least one second microstructure 1224. The light source 110 has an optical axis direction D1, and is directed from the light source 110 toward the light guide plate 120, i.e., a horizontal direction in fig. 1. The first microstructure 1222 is located between the light emitting surface 112 of the light source 110 and the second microstructure 1224. In other words, the first microstructure 1222 in each microstructure area 122 is located closer to the light source 110, while the second microstructure 1224 is located farther from the light source 110. That is, light from the light source 110 passes through the first microstructure 1222 and then the second microstructure 1224. The first microstructure 1222 and the second microstructure 1224 each have a first length l1 along the optical axis direction D1 and a second length l2 along the horizontal direction D2.

In the present embodiment, the light guide plate 120 has a top surface 124 facing the cover plate 400, and a portion of the top surface 124 extends to a position between the first microstructure 1222 and the second microstructure 1224, and the portion of the top surface 124 is a plane. In other words, as shown in fig. 1, the top surface 124 of the light guide plate 120 is saw-toothed, and has a plane located between the first microstructures 1222 and the second microstructures 1224, or between two adjacent second microstructures 1224. That is, the first microstructure 1222 and the second microstructure 1224 are recessed from the top surface 124 of the light guide plate 120. Adjacent ones of the first and

second microstructures

1222, 1224 have a pitch d1 therebetween, and the pitch d1 is in the range of about 1 micron to 20 microns. In other words, each of the first and

second microstructures

1222, 1224 are separated from each other. As shown in fig. 2A, the top surface 124 surrounds the first microstructure 1222 and the second microstructure 1224, and the spacing d1 is the shortest distance between the first microstructure 1222 and the second microstructure 1224 or between two adjacent second microstructures 1224.

Fig. 2B is a top view of the light source 110 and the light guide plate 120A according to another embodiment of the disclosure. The light guide plate 120A is substantially the same as the light guide plate 120 of fig. 2A, except that there is no space between the first microstructures 1222A and the second microstructures 1224A of the microstructure region 122A of the light guide plate 120A. In other words, in the present embodiment, the first microstructure 1222A and the second microstructure 1224A or two adjacent second microstructures 1224A are connected to each other.

The top view of the first microstructure 1222 and the second microstructure 1224 is circular, oval, or diamond, such as oval in fig. 2B. In the present embodiment, each microstructure area 122 includes two second microstructures 1224. In some other embodiments, the number of the second microstructures 1224 may be one to five, which may be determined by the actual situation and will be illustrated in the following paragraphs.

Fig. 3 is a top view of a light source 110 and a light guide plate 120 according to an embodiment of the disclosure. The light guide plate 120 of fig. 3 may be the same as the light guide plate 120 shown in fig. 1 and 2A. The light guide plate 120 includes a plurality of microstructure regions 122. The length l3 of microstructure region 122 along optical axis direction D1 is in the range of about 60 microns to 100 microns. The distance between each microstructure area 122 varies with the distance from the light source 110. In the present embodiment, the area of the light guide plate 120 farther from the light source 110 has denser microstructure areas 122, and the area of the light guide plate 120 closer to the light source 110 has sparser microstructure areas 122. For example, microstructure regions 122 that are farther from light source 110 are spaced apart by a distance d3, and microstructure regions 122 that are closer to light source 110 are spaced apart by a distance d 2. The distance d3 is smaller than the distance d2, so that the light guided out from the entire light guide plate 120 has uniform brightness.

Referring to fig. 1, the display device 10 further includes two optical adhesive layers 500 respectively disposed on two opposite sides of the light guide plate 120. In some embodiments, the optical glue layer 500 may be composed of a silicon-based material and have a refractive index of about 1.41. In some other embodiments, the optical glue layer 500 may be composed of an acrylic-based material and have a refractive index of about 1.47. The color filter layer 300 includes a plurality of sub-pixels 310,320, 330. For example, subpixels 310,320,330 may correspond to a red subpixel, a blue subpixel, and a green subpixel, respectively. The display panel 200 includes a driving substrate 210, a display medium layer 220 and an adhesive layer 230. The adhesive layer 230 is located between the color filter layer 300 and the display medium layer 220, and the display medium layer 220 is located between the adhesive layer 230 and the driving substrate 210.

Fig. 4 is an enlarged view of the light source 110, the light guide plate 120 and the optical adhesive layer 500 in fig. 1. In the present embodiment, microstructure regions 122 with a spacing d1 between adjacent first microstructures 1222 and/or second microstructures 1224 are taken as an example. The first microstructure 1222 has a surface S1 close to the light source 110 and a surface S2 far from the light source 110, and the cross-sectional views of the surface S1 and the surface S2 along the optical axis direction D1 are zigzag. In other words, the surface S1 is located between the surface S2 and the light emitting surface 112 of the light source 110. The surface S2 is located between the surface S1 and the second microstructure 1224. The surface S1 of the first microstructure 1222 has a first angle θ 1 with the optical axis direction D1, and the first angle θ 1 is in a range of about 30 degrees to 50 degrees. The surface S2 of the first microstructure 1222 has a second angle θ 2 with the optical axis direction D1, and the second angle θ 2 is in a range of about 60 degrees to 90 degrees.

The second microstructure 1224 has a surface S3 close to the light source 110 and a surface S4 away from the light source 110, and the cross-sectional view of the surface S1 and the surface S2 along the optical axis direction D1 shows a sawtooth shape. In other words, the surface S3 is located between the surface S4 and the first microstructure 1222. The surface S4 is located between the surface S3 and another second microstructure 1224. The surface S3 of the second microstructure 1224 has a fourth angle θ 4 with the optical axis direction D1 that is the same as the first angle θ 1 of the first microstructure 1222. The surface S4 of the second microstructure 1224 has a third angle θ 3 with the optical axis direction D1, and the third angle θ 3 is in a range of about 60 degrees to 90 degrees.

The first angle θ 1, the second angle θ 2, and the third angle θ 3 may be determined according to a difference between a refractive index of a material of the light guide plate 120 and a refractive index of a material adjacent to the light guide plate 120. In some embodiments, the number of the second microstructures 1224 is multiple, and the third angle θ 3 of each of the second microstructures 1224 is the same. In some embodiments, the second angle θ 2 of the first microstructure 1222 can also be the same as the third angle θ 3 of the second microstructure 1224.

For example, in the embodiment shown in fig. 4, the material of the light guide plate 120 is Polycarbonate (PC), and the refractive index is about 1.59. The optical adhesive layer 500 above the light guide plate 120 is composed of an acrylic-based material and has a refractive index of about 1.47. The refractive index difference between the light guide plate 120 and the optical adhesive layer 500 on the top surface 124 of the light guide plate 120 is about 0.1-0.12. In the present embodiment, the first angle θ 1 of the first microstructure 1222 is preferably in the range of about 32.5 degrees to 37.5 degrees. The vertical direction D3 shown in the figure is a direction perpendicular to the optical axis direction D1, i.e., a direction from the cover 400 toward the display panel 200 in fig. 1. The optical axis direction D1, the horizontal direction D2, and the vertical direction D3 are perpendicular to each other.

As shown in fig. 4, the reflected light L1 represents a portion of the incident light L0 from the light source 110 reflected by the surface S1 of the first microstructure 1222, and the light travels downward in the figure. The transmitted light L1' represents the incident light L0 transmitted through the surface S1 of the first microstructure 1222. The reflected light L2 represents a portion of the transmitted light L1' after being transmitted through the surface S2 and then subsequently reflected by the surface S3 of the second microstructure 1224. The reflected light ray L2 travels downward more nearly vertically than the reflected light ray L1, i.e., the angle between the reflected light ray L2 and the vertical direction D3 is smaller than the angle between the reflected light ray L1 and the vertical direction D3. The transmitted light L2 'represents the light transmitted by the transmitted light L1' through the surface S3 of the second microstructure 1224. The reflected light L3 represents a portion of the transmitted light L2' after being transmitted through the surface S4 of the second microstructure 1224 and then being reflected by the surface S5 of another second microstructure 1224. The reflected light ray L3 travels downward more nearly vertically than the reflected light ray L2, i.e., the angle between the reflected light ray L3 and the vertical direction D3 is smaller than the angle between the reflected light ray L2 and the vertical direction D3.

It can be seen that by disposing the first microstructures 1222 and the at least one second microstructure 1224 in one microstructure region 122, the angle between the light beam incident toward the display panel 200 (i.e. the sum of the reflected light L1, the reflected light L2, and the reflected light L3) and the vertical direction D3 can be reduced. Thus, the probability of light mixing between two adjacent pixels can be reduced, and the color saturation of the display device 10 can be increased. In addition, since the reflected light rays L2, L3 reflected by the second microstructures 1224 can travel more vertically downward, so that the light beam incident toward the display panel 200 is more concentrated, and thus can have a narrower light line width. Thus, the light guide diffusion caused by the light guide plate 120 can be reduced and the light emitting collimation of the light guide plate 120 can be improved.

Please refer to fig. 5A and fig. 5B. Fig. 5A is a schematic diagram of an optical path of an exemplary display device. FIG. 5B is a diagram of beam width simulation of the display device of FIG. 5A. Fig. 5B is a graph simulating a light intensity contour plot (upper side in fig. 5B) and a light intensity distribution plot (lower side in fig. 5B) along the optical axis direction D1 of the incident light I1 in fig. 5A. The microstructures 122 'of the light guide plate 120' of the display device 10 in FIG. 5A are, for example, conventional linear groove designs.

As shown in fig. 5A, the incident light I1 traveling toward the display panel 200 after being guided through the light guide plate 120' travels through the area of the corresponding sub-pixel 310. The traveling direction of the incident light I1 has a light angle a1 with the vertical direction D3 (i.e., the normal direction of the light guide plate 120), and the light angle a1 is about in the range of 62.5 degrees to 67.5 degrees. As shown in fig. 5B, the peak of the light intensity distribution of the incident light I1 is located at the position P1, which corresponds to the position P1 deviating from the vertical direction D3 by about 65 degrees in fig. 5A, and the light angle a1 in fig. 5A can be derived therefrom. The angle of the incident light I1 from the perpendicular direction D3 will be described directly in the following paragraphs with the light angle a 1.

As shown in fig. 5A, the incident light I1 has a linewidth W1 defined by the beam boundary IR1, and the linewidth W1 is about 30 degrees. As shown in fig. 5B, the light intensity distribution diagram of the incident light I1 has the same full width at half maximum (FWHM) as the light width W1, and the full width at half maximum is about 30 degrees, corresponding to the light width W1 in fig. 5A. It should be understood that, as shown in fig. 5A and 5B, the beam width of the incident light I1 should be a divergent region having a solid angle (stepadian). For convenience of description, the light width W1 in the optical axis direction D1 is used as a comparison basis for the divergence degree of the incident light I1.

As can be seen from fig. 5A and 5B, the incident light I1 is reflected by the display panel 200 to form a reflected light R1 towards the light guide plate 120', and the reflected light R1 has a light emitting width defined by the light beam boundary RR 1. Since the incident light I1 has a wide emission width, and the reflected light R1 also has a wide emission width, the reflected light R1 travels through the regions corresponding to the sub-pixels 310 and 320. In other words, if the incident light I1 deviates from the vertical direction D3 by a large angle, the probability of light mixing between two adjacent pixels is increased, thereby reducing the color saturation of the display device 10.

Please refer to fig. 6A and fig. 6B. Fig. 6A is a schematic diagram of the optical path of the display device 10 according to fig. 1. The microstructures in fig. 6A can be, for example, the first microstructure 1222 and the second microstructure 1224 shown in fig. 4. In the embodiment shown in fig. 6A, the material and refractive index are the same as those of the light guide plate 120 and the optical adhesive layer 500 shown in fig. 4. Fig. 6B is a beam width simulation diagram of the display device 10 according to fig. 6A. Fig. 6B simulates a light intensity contour diagram (above fig. 6B) of the incident light I2 of fig. 6A and a light intensity distribution diagram (below fig. 6B) along the optical axis direction D1.

As shown in fig. 6A, the incident light I2, which is guided through the light guide plate 120 and travels toward the display panel 200, travels through the region of the corresponding sub-pixel 332. The traveling direction of the incident light I2 and the vertical direction D3 have a light angle a2, and the light angle a2 is in the range of about 32.5 degrees to 37.5 degrees. As shown in fig. 6B, the peak of the incident light I2 is located at a position P2, which corresponds to a position P2 deviating from the vertical direction D3 by about 35 degrees in fig. 6A, from which the light angle a2 in fig. 6A can be deduced. The angle of the incident light I2 from the perpendicular direction D3 will be described at a light angle a2 in the following paragraphs.

As shown in fig. 6A, the incident light I2 has a linewidth W2 defined by the beam boundary IR2, and the linewidth W2 is about 15 degrees. As shown in fig. 6B, the light intensity distribution diagram of the incident light I2 has the same full width at half maximum (FWHM) as the optical line width W2, and the full width at half maximum is about 15 degrees, corresponding to the optical line width W2 in fig. 6A. It should be understood that, as shown in fig. 6A and 6B, the beam width of the incident light I2 should be a divergent region having a solid angle (stepadian). For convenience of description, the light width W2 in the optical axis direction D1 is used as a comparison basis for the divergence degree of the incident light I1.

As can be seen from fig. 6A and 6B, the incident light I2 is reflected by the display panel 200 to form a reflected light R2 toward the light guide plate 120, and the reflected light R2 has a light emitting width defined by a light beam boundary RR 2. Since the incident light I2 has a small light width W2, the reflected light R2 also has a small light emission width. The reflected light R2 travels through the area of the corresponding sub-pixel 310 and does not travel through the area of the corresponding sub-pixel 320. In other words, by disposing the first microstructures 1222 and the at least one second microstructure 1224 in one microstructure region 122, light can be directed more than once to more vertically drop into the display panel 200 to reduce the angle of incident light I2 from the vertical direction D3 (e.g., from the light angle a1 to the light angle a2 of fig. 5A). Therefore, the probability of light mixing between two adjacent pixels can be reduced, and the color saturation of the display device 10 can be further improved. In addition, since the reflected light L2, L3 (see fig. 4) reflected by the second microstructures 1224 can travel downward more nearly vertically, the incident light I2 (i.e. the sum of the reflected light L1, the reflected light L2 and the reflected light L3 in fig. 4) toward the display panel 200 is more concentrated to have a narrower light line width W2 (e.g. from the light line width W1 in fig. 5A to the light line width W2). Thus, light guide diffusion can be reduced and the light emitting collimation of the light guide plate 120 can be improved.

FIG. 7 is a diagram illustrating a relationship between a first angle θ 1 and a light angle according to an embodiment of the disclosure. FIG. 8 is a graph illustrating a relationship between a first angle θ 1 and a light width according to an embodiment of the disclosure. The data in fig. 7 and 8 are calculated according to the material and refractive index of the light guide plate 120 and the optical adhesive layer 500 in fig. 4. As shown in fig. 7, when the first angle θ 1 of the first microstructure 1222 (see fig. 4) increases from about 25 degrees to about 45 degrees, the corresponding light emitting angle (i.e., the angle of incident light from the vertical direction) decreases from about 50 degrees to about 20 degrees. As shown in fig. 8, when the first angle θ 1 of the first microstructure 1222 (see fig. 4) increases from about 25 degrees to about 45 degrees, the corresponding light emitting width decreases from about 23 degrees to about 40 degrees, and then increases to about 25 degrees.

Specifically, taking the incident light ray L0 in fig. 4 as an example, when the first angle θ 1 is about 40 degrees to 45 degrees, the incident angle of the incident light ray L0 decreases. At this time, the incident light ray L0 is caused to have almost no total reflection while passing through the first microstructures 1222, so that the transmitted light ray L1' increases and the light line width is expanded due to divergence. On the contrary, when the first angle θ 1 is smaller than 30 degrees, the angle between the reflected light L1 and the vertical direction D3 is too large, which increases the probability of light mixing between two adjacent pixels. Therefore, it can be concluded from the data in fig. 7 and 8 that the first angle θ 1 of the present embodiment is preferably in the range of about 32.5 degrees to 37.5 degrees.

Therefore, through the matching of the first angle θ 1 of the first microstructure 1222 and the second microstructure 1224 of fig. 4, not only the increase of the light line width caused by the overlarge first angle θ 1 can be avoided, but also the transmitted light L1 'and the transmitted light L2' are guided again to generate the reflected light L2 and the reflected light L3 closer to the vertical direction, so that the incident light toward the display panel can have a smaller light angle and light width at the same time.

Referring to fig. 1, for example, in some embodiments, when the refractive index of the optical adhesive layer 500 is about 1.41, the difference between the refractive index of the optical adhesive layer 500 and the refractive index (1.59) of the light guide plate 120 is about 0.15-0.25. The first angle θ 1 may preferably be in the range of about 37.5 degrees to 42.5 degrees. In some embodiments, an air layer (refractive index of 1.0) is further interposed between the top surface 124 of the light guide plate 120 and the optical adhesive layer 500, and the difference between the refractive index of the air layer and the refractive index (1.59) of the light guide plate 120 is about 0.55-0.60. The first angle θ 1 may preferably be in a range of about 42.5 to 47.5 micrometers. In other words, the first angle θ 1 between the first microstructure 1222 and the optical axis direction D1 of the present disclosure may preferably be in a range of about 30 microns to 50 microns.

Referring to fig. 1, in the present embodiment, the display device 10 further includes a touch layer 600 located between the cover 400 and the optical adhesive layer 500, but the disclosure is not limited thereto. Specifically, the display device 10 may have a stacked structure with different functions, and those skilled in the art may increase or decrease the stacked structure of the display device 10 according to actual needs.

Fig. 9 is a cross-sectional view of a display device 20 according to another embodiment of the present disclosure. The display device 20 is substantially the same as the display device 10 in fig. 5B, except that the width of the sub-pixels 810,820, and 830 is smaller, and the number of the second microstructures 7224 corresponding to each of the sub-pixels 810,820, and 830 is larger. Referring to fig. 6A and 9, the total thickness of the display device 10 and the display device 20 is about 2050 μm. In other embodiments, the total thickness is in the range of about 1700 microns to 2400 microns, which may be adjusted according to practical functional requirements and material thickness limitations.

As shown in fig. 6A, taking the thickness T of the adhesive layer 230 as an example, when the thickness T is smaller, the chance of light mixing between two adjacent pixels is lower. However, taking the width P of the sub-pixel 330 as an example, when the width P is larger, the chance of light mixing between two adjacent sub-pixels is lower. Specifically, for a display panel having a resolution of 300dpi, the width P of the Stripe (Stripe) sub-pixels 310,320, and 330 is about 80 μm, and the width of the Mosaic (Mosaic) sub-pixels is about 120 μm. When the display panel has the same size and a larger resolution, the width P of the sub-pixels 310,320,330 is smaller. In this case, the light angle and the light width have a greater influence on the probability of light mixing, i.e., on the color saturation. Therefore, the smaller the width P of the sub-pixels 310,320,330, the greater the number of the second microstructures 1224 to enhance the degree of light being directed to the near-vertical direction D3. Specifically, as shown in fig. 9, the number of second microstructures 7224 can be up to five.

Therefore, for a display device with higher resolution, the color saturation is more influenced by the light angle and the light width, so that the display device of the present disclosure can reduce the light angle and the light width by adjusting the number of the second microstructures in the microstructure region and the angles of the first microstructures and the second microstructures (i.e., the first angle θ 1, the second angle θ 2, the third angle θ 3, and the fourth angle θ 4 in fig. 4), and can meet the display quality required by display devices with different resolutions. Therefore, the design of the microstructure area disclosed by the invention can be suitable for display devices with different resolutions, and has better universality.

Fig. 10A to 10D are top views of microstructure areas according to various embodiments of the present disclosure. The microstructure area 122a of fig. 10A has a first microstructure 1222a and a second microstructure 1224a that are both circular (the first length l1 is equal to the second length l 2). The microstructure area 122B of fig. 10B has a first microstructure 1222a and a second microstructure 1224a that are both elliptical (the first length l1 is greater than the second length l 2). In some embodiments, it may also be that the second length l2 is greater than the first length l 1). The microstructure area 122C of fig. 10C has a first microstructure 1222C that is circular and a second microstructure 1224C that is elliptical. The microstructure area 122D of fig. 10D has an elliptical first microstructure 1222D and a circular second microstructure 1224D. In some embodiments, the plurality of second microstructures 1224 may also have different top down shapes (e.g., diamond shapes) as long as the second angle θ 2 and the third angle θ 3 corresponding to fig. 4 are the same.

Fig. 11 is a simulation diagram of the optical line width of the display device 10 in the horizontal direction according to fig. 6A. Fig. 11 is a graph simulating a light intensity contour plot of the incident light I2 of fig. 6A and a light intensity distribution plot along the horizontal direction D2. From the light intensity distribution of the incident light I2, the full width at half maximum (FWHM) of the incident light I2 in the horizontal direction D2 corresponds to the light width W3. As mentioned above, the incident light I2 is a divergent region having a solid angle, and the width W3 of the light line along the horizontal direction D2 is used as a comparison.

FIG. 12 is a graph of a ratio of a first length to a second length versus a light width in a horizontal direction according to various embodiments of the present disclosure. Fig. 13 is a data diagram of the first length, the second length, and the light width in the horizontal direction according to fig. 11. Referring to fig. 12 and 13, when the ratio of the first length l1 to the second length l2 is less than 0.5, such as in the conventional elongated trench design, the light width W3 in the horizontal direction D2 is close to 80 degrees or more. When the ratio between the first length l1 and the second length l2 is in the range of about 0.5 to 2.5, the light width W3 in the horizontal direction D2 may be less than about 70 degrees. And the ratio between the first length l1 and the second length l2 is close to 2.5, the light width W3 in the horizontal direction D2 can be reduced to about 30 degrees. For example, when the ratio of the first length l1 to the second length l2 is about 2, the optical line width W3 is about 32 degrees to 38 degrees. It can be seen that by designing the top view shapes of the first microstructure 1222 and the second microstructure 1224 to be circular, elliptical, or diamond, and making the ratio between the first length l1 and the second length l2 be in the range of about 0.5 to 2.5, the light width W3 in the horizontal direction D2 can be reduced, and the light-emitting collimation of the light guide plate 120 can be improved.

In summary, by disposing the first microstructure and the at least one second microstructure in one microstructure region, and adjusting the first angle and the second angle of the first microstructure and the third angle of the second microstructure, the angle between the light beam incident toward the display panel and the vertical direction (the normal direction of the light guide plate) can be reduced. Therefore, the probability of light mixing between two adjacent pixels can be reduced, and the color saturation of the display device can be increased. In addition, since the light reflected by the second microstructure can travel downwards more nearly vertically, the light beam incident towards the display panel is more concentrated, and therefore, the light line width can be narrower. Therefore, the light guide plate can reduce light guide diffusion caused by the light guide plate and improve the light emitting collimation of the light guide plate.

Although the present invention has been described with reference to the above embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention.

Claims

1. A front light module, comprising:

a light source having a light-emitting surface; and

a light guide plate, comprising a microstructure area, wherein the microstructure area comprises a first microstructure and at least one second microstructure, the first microstructure is located between the light emitting surface of the light source and the second microstructure, a first angle is formed between a surface of the first microstructure close to the light source and an optical axis direction of the light source, a second angle is formed between a surface of the first microstructure far away from the light source and the optical axis direction, a third angle is formed between a surface of the second microstructure far away from the light source and the optical axis direction, the first angle is in a range of 30 degrees to 50 degrees, and the second angle and the third angle are in a range of 60 degrees to 90 degrees.

2. The front light module as claimed in claim 1, wherein the first and second microstructures are recessed from a top surface of the light guide plate.

3. The front light module of claim 1, wherein the first microstructure and the second microstructure are circular, elliptical or diamond in top view.

4. The front light module as claimed in claim 1, wherein the first and second microstructures have a first length along an optical axis of the light source and a second length along a horizontal direction perpendicular to the optical axis, respectively, and a ratio of the first length to the second length is in a range of 0.5 to 2.5.

5. The front light module of claim 1, wherein a fourth angle is formed between a surface of the second microstructure close to the light source and the optical axis direction, and the fourth angle is the same as the first angle.

6. The front light module of claim 1, wherein the second angle is the same as the third angle.

7. The front light module as claimed in claim 1, wherein the number of the second microstructures is plural, and the third angles of the second microstructures are the same.

8. The front light module of claim 1, further comprising a color filter layer, wherein the color filter layer has sub-pixels, and the number of the second microstructures increases as the width of the sub-pixels decreases.

9. The front light module of claim 1, wherein adjacent ones of the first and second microstructures have a pitch therebetween, and the pitch is in a range of 1 micron to 20 microns.

10. The front light module as claimed in claim 1, wherein the first microstructure and the second microstructure are connected.

11. The front light module as claimed in claim 1, wherein the number of the second microstructures is plural, and the second microstructures are connected to each other.

12. A display device, comprising:

a front light module, comprising:

a light source having a light-emitting surface; and

a light guide plate, comprising a microstructure region, wherein the microstructure region comprises a first microstructure and at least one second micro junction region, the first microstructure is located between the light emitting surface of the light source and the second microstructure, a first angle is formed between a surface of the first microstructure close to the light source and an optical axis direction of the light source, a second angle is formed between a surface of the first microstructure far away from the light source and the optical axis direction, a third angle is formed between a surface of the second microstructure far away from the light source and the optical axis direction, the first angle is in a range of 30 degrees to 50 degrees, and the second angle and the third angle are in a range of 60 degrees to 90 degrees; and

a display panel under the light guide plate.

13. The display device of claim 12, wherein the first and second microstructures are recessed from a top surface of the light guide plate.

14. The display device of claim 12, wherein the first microstructure and the second microstructure have a circular, elliptical, or diamond shape in a top view.

15. The display device of claim 12, wherein the first and second microstructures each have a first length along an optical axis of the light source and a second length along a horizontal direction perpendicular to the optical axis, and a ratio of the first length to the second length is in a range of 0.5 to 2.5.

16. The display device according to claim 12, wherein a fourth angle is formed between a surface of the second microstructure close to the light source and the optical axis direction, and the fourth angle is the same as the first angle.

17. The display device according to claim 12, wherein the second angle is the same as the third angle.

18. The display device of claim 12, wherein the number of the second microstructures is plural, and the third angles of the second microstructures are the same.

19. The display device of claim 12, further comprising a color filter layer, wherein the color filter layer has sub-pixels, and the number of the second microstructures increases as the width of the sub-pixels decreases.

20. The display device of claim 12, wherein adjacent ones of the first and second microstructures have a pitch therebetween, and the pitch is in a range of 1 micron to 20 microns.