CN116256832A - Optical film set, backlight module and display device - Google Patents

Abstract

The invention relates to an optical film set, a backlight module and a display device. The optical film group is configured to guide out light from the light guide plate of the backlight module. The optical film set comprises a lower prism sheet and an upper prism sheet. The lower prism sheet has a plurality of lower prism structures, and each lower prism structure extends along a first direction. The upper prism sheet is disposed above the lower prism sheet, wherein the upper prism sheet has a plurality of upper prism structures, and each of the upper prism structures extends along a second direction, the second direction being different from the first direction. The second direction has an included angle ranging from 25 degrees to 50 degrees or from 130 degrees to 155 degrees with the extending direction of the light incident surface of the light guide plate, and the included angle comprises an endpoint value.

Description

Optical film set, backlight module and display device

Technical Field

The disclosure relates to a diaphragm assembly and an application thereof, and more particularly to a diaphragm assembly applicable to a backlight module, and a backlight module and a display device using the same.

Background

The common backlight module mainly comprises a light guide plate and a plurality of optical films, wherein the optical films can refract light emitted from the light guide plate so as to emit light at a front view angle. However, the backlight module cannot be applied to the peep-proof display product. Therefore, how to generate a good anti-peeping effect by changing the matching design of the optical film and the light guide plate has become a target of active efforts of related industries.

Disclosure of Invention

Therefore, an objective of the present disclosure is to provide an optical film set, and a backlight module and a display device using the same, which can maintain the light output from the front view and reduce the stray light from the side direction.

According to the above-mentioned objects of the present disclosure, an optical film set is provided, which is configured to guide light from a light guide plate of a backlight module. The optical film set comprises a lower prism sheet and an upper prism sheet. The lower prism sheet has a plurality of lower prism structures, and each lower prism structure extends along a first direction. The upper prism sheet is disposed above the lower prism sheet, wherein the upper prism sheet has a plurality of upper prism structures, and each of the upper prism structures extends along a second direction, wherein the second direction is different from the first direction. The second direction has an included angle ranging from 25 degrees to 50 degrees or from 130 degrees to 155 degrees with the extending direction of the light incident surface of the light guide plate, and the included angle comprises an endpoint value.

According to an embodiment of the disclosure, the second direction has an included angle ranging from 115 degrees to 140 degrees or from 220 degrees to 245 degrees with respect to the extending direction of the light incident surface of the light guide plate, and the included angle includes an end point value.

According to an embodiment of the disclosure, the first direction and the second direction are perpendicular to each other.

According to an embodiment of the disclosure, the optical film set further includes a lower diffuser disposed below the lower prism sheet, and the lower diffuser includes a plurality of diffuser particles, wherein the diffuser particles make the lower diffuser have a haze of 50% to 60%, and the diffuser includes an endpoint value.

According to an embodiment of the disclosure, the optical film set further includes an upper diffusion sheet disposed above the upper prism sheet. Wherein the upper diffusion sheet comprises a plurality of diffusion particles, and the diffusion particles enable the upper diffusion sheet to have haze of less than 30% and comprise an endpoint value.

According to an embodiment of the disclosure, the optical film set further includes a lower diffusion sheet and an upper diffusion sheet. Wherein the haze ratio of the lower diffusion sheet to the upper diffusion sheet is 1.6 to 6, and the end point value is included.

According to an embodiment of the disclosure, the lower diffusion sheet is disposed below the lower prism sheet, and the upper diffusion sheet is disposed above the upper prism sheet. After the light from the light guide plate sequentially passes through the lower diffusion sheet, the lower prism sheet, the upper prism sheet and the upper diffusion sheet, one part of the light is emitted from the upper diffusion sheet along the front view direction, and the other part of the light is emitted from the upper diffusion sheet along the side view direction, wherein the ratio of the light emitting quantity of the light emitted from the side view direction to the light emitting quantity of the light emitted from the front view direction is less than 0.07.

According to an embodiment of the disclosure, the front view direction is parallel to the light emitting normal line of the upper diffusion sheet, and an included angle between the side view direction and the light emitting normal line is greater than 45 degrees.

According to an embodiment of the disclosure, each of the lower prism structures and each of the upper prism structures are stripe structures.

According to the above object of the present disclosure, a backlight module is provided. The backlight module comprises a light guide plate, a light source and the optical film set. The light guide plate is provided with a light incident surface and a light emergent surface. The light source is adjacently arranged on the light incident surface. The optical film group is arranged above the light-emitting surface.

According to the above object of the present disclosure, a display device is also provided. The display device comprises a light guide plate, a light source, the optical film set and a display panel. The light guide plate is provided with a light incident surface and a light emergent surface. The light source is adjacently arranged on the light incident surface. The optical film group is arranged above the light-emitting surface. The display panel is arranged above the optical film group.

Therefore, the optical film set disclosed by the invention is designed mainly by the included angle between the extending direction of the upper prism structure of the upper prism sheet and the light incident surface, and is matched with the change of the included angle between the extending direction of the lower prism structure of the lower prism sheet and the light incident surface, so that the light quantity of the light emitted from the side view angle is reduced on the premise of maintaining the light quantity of the light emitted from the front view angle, and the optical requirement of peep-proof display is met. In addition, when the upper prism sheet and the lower prism sheet are combined with the diffusion sheets with different haze, the effect of reducing stray light emitted from a side view angle can be further achieved.

Drawings

For a more complete understanding of the embodiments and advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

fig. 1 is a schematic diagram of a backlight module according to a first embodiment of the disclosure;

fig. 2 is a front view illustrating a lower prism sheet according to a first embodiment of the present disclosure;

fig. 3 is a front view illustrating an upper prism sheet according to a first embodiment of the present disclosure;

FIG. 4 is a graph showing the comparison of front-view luminance and side-view luminance generated by the angle design of the upper prism sheet according to the first embodiment of the present disclosure;

FIG. 5 is a side view of a lower diffuser according to a first embodiment of the present disclosure;

FIG. 6 is a schematic diagram of a backlight module according to a second embodiment of the disclosure; and

fig. 7 is a schematic diagram of a display device according to an embodiment of the disclosure.

Detailed Description

Fig. 1 is a schematic diagram of a backlight module according to a first embodiment of the disclosure. The backlight module 100 of the present embodiment mainly includes a light guide plate 110, a light source 120, and an optical film set 200. The light source 120 mainly provides light to the light guide plate 110, and the optical film set 200 is disposed in front of the light guide plate 110. The optical film set 200 is mainly used for reducing the light quantity of the light emitted from the light guide plate 110 from the side view angle and maintaining the light quantity of the light emitted from the light guide plate 110 from the front view angle, so that the backlight module 100 can be applied to the peep-proof display product.

As shown in fig. 1, the light guide plate 110 has a light incident surface 111 and a light emergent surface 112. The light source 120 is disposed adjacent to the light incident surface 111, and light provided by the light source 120 enters the light guide plate 110 from the light incident surface 111 of the light guide plate 110, and then exits from the light emergent surface 112 of the light guide plate 110. In the present embodiment, the optical film set 200 includes a lower diffuser 210, a lower prism sheet 220 and an upper prism sheet 230, wherein the lower diffuser 210, the lower prism sheet 220 and the upper prism sheet 230 are sequentially stacked in front of the light emitting surface 112 of the light guide plate 110.

Referring to fig. 2 and 3, front views of a lower prism sheet and an upper prism sheet according to a first embodiment of the present disclosure are shown. In the present embodiment, the lower prism sheet 220 has a plurality of lower prism structures 221, and each lower prism structure 221 is a bar-shaped structure and extends along the first direction D1. The first direction D1 forms an angle α with the extending direction A1 of the light incident surface 111 of the light guide plate 110. The upper prism sheet 230 has a plurality of upper prism structures 231, and each upper prism structure 231 is a bar-shaped structure and extends along the second direction D2. Wherein the second direction D2 is different from the first direction D1. The second direction D2 forms an angle β with the extending direction A1 of the light incident surface 111 of the light guide plate 110. In this embodiment, the included angle β is in the range from 25 degrees to 50 degrees or from 130 degrees to 155 degrees. Accordingly, after the light emitted from the light emitting surface 112 of the light guide plate 110 sequentially passes through the lower diffusion sheet 210, the lower prism sheet 220, and the upper prism sheet 230, a part of the light (e.g., the light L1 of fig. 1) is emitted from the upper prism sheet 230 in the front view direction (or the front view angle), and another part of the light (e.g., the light L2 of fig. 1) is emitted from the upper prism sheet 230 in the side view direction (or the side view angle). For example, when the user faces the backlight module 100 shown in fig. 1, the user looks at the central position of the backlight module 100, and defines an extension line P1 passing through the central position on the light-emitting surface of the backlight module 100, the plane P2 (the plane P2 includes the shadow region shown in fig. 1) formed by the extension line P1 and the front view direction has a side view direction, wherein the front view direction refers to a direction in which the light is parallel to the normal direction of the upper prism sheet 230, and the side view direction refers to a direction having an angle θ between the plane P2 and the front view direction.

Referring to fig. 4, fig. 4 is a diagram showing a comparison of front-view luminance and side-view luminance generated by the design of the included angle of the upper prism sheet according to the first embodiment of the present disclosure. As can be seen from fig. 4, when the included angle β of the upper prism sheet 230 is in the range from 25 degrees to 50 degrees or from 130 degrees to 155 degrees (i.e. the range selected from the dashed square in fig. 4), the overall backlight module 100 can generate a larger front view angle light-emitting luminance and a smaller side view angle light-emitting luminance, which makes the ratio (also referred to as the side view angle light-emitting ratio) of the light-emitting amount of the light-emitting beam from the side view direction to the light-emitting amount of the light-emitting beam from the front view direction smaller, for example, smaller than 0.07, which means that the side light-emitting amount can be reduced by utilizing the design of the upper prism sheet 230 with the included angle β in the range from 25 degrees to 50 degrees or from 130 degrees to 155 degrees (and including the end point values).

Referring to the following table one and table two, the first and second are the light-emitting results of the light L1 and the light L2 generated by the angle matching of the included angle α of the lower prism sheet 220 and the included angle β of the upper prism sheet 230.

List one

Watch II

As can be seen from the above table one and table two, when the included angle β of the upper prism sheet 230 ranges from 25 degrees to 50 degrees or from 130 degrees to 155 degrees, the light-emitting ratio of the side view angle is less than 10%, even less than 7%, which can satisfy the requirements of the peep-proof product. It can be seen that the angle α of the lower prism sheet 220 can be designed to be 115 to 140 degrees or 220 to 245 degrees, and includes the end points; or the second direction D2 of the upper prism structure 231 of the upper prism sheet 230 and the first direction D1 of the lower prism structure 221 of the lower prism sheet 220 are perpendicular to each other, so as to achieve the effect of reducing the side view light extraction ratio as described above.

Referring to fig. 5, a side view of a lower diffuser according to a first embodiment of the present disclosure is shown. In one embodiment, the lower diffuser 210 includes a plurality of diffuser particles 211. The bottom diffuser 210 of the present disclosure mainly reduces stray light emitted from a side view angle (i.e., an included angle θ between a front view direction and a side view direction is greater than 45 °), wherein the stray light refers to diffuse light caused by diffuse particles, which belongs to light with no specific directivity. When the parallel light ray L3 enters the lower diffuser 210, a portion of the light ray (e.g., the light ray L4) will penetrate the lower diffuser 210 in parallel, and another portion of the light ray (e.g., the light ray L5) will be scattered by the diffusion particles 211 to penetrate the lower diffuser 210, wherein the deviation angle of the light ray L5 with respect to the parallel light ray L3 is greater than 2.5 degrees. The ratio of the transmittance of the light L5 scattered through the lower diffuser 210 to the sum of the transmittance of the light L4 and the transmittance of the light L5 can be defined as the haze of the lower diffuser 210. In this embodiment, the lower diffuser 210 has a haze of 50% to 60%, and includes the end point value. When the haze of the lower diffuser 210 is 0%, the light uniformity requirement of the light emitting surface near the light incident side cannot be met although the same lower side view angle light emitting ratio can be achieved; when the haze of the lower diffuser 210 is 90%, although a lower side view angle light-emitting ratio can be achieved, the light-emitting brightness requirement of the front view angle cannot be satisfied, and the product peep-proof effect is impaired because the stray light measured at the side view angle is more. Therefore, when the haze of the lower diffusion sheet 210 is 50% to 60%, the product can be prevented from peeping, and less stray light can be generated at a side view angle. It should be noted that, compared with the case that a high haze lower diffusion sheet (for example, a 90% haze lower diffusion sheet) is used in the conventional backlight module, more stray light is easy to generate, the present disclosure uses a 50% to 60% low haze lower diffusion sheet, which can satisfy the optical appearance required by customers on one hand, and can reduce the generation of stray light on the other hand, so as to satisfy the requirements of peep-proof products.

The backlight module of the present disclosure may also have different structural designs. Fig. 6 is a schematic diagram of a backlight module according to a second embodiment of the disclosure. The structure of the backlight module 300 of the present embodiment is substantially the same as that of the backlight module 100 shown in fig. 1, except that the backlight module 300 further includes an upper diffusion plate 440. As shown in fig. 6, the backlight module 300 mainly includes a light guide plate 310, a light source 320, and an optical film set 400. The light source 320 mainly provides light to the light guide plate 310, and the optical film set 400 is disposed in front of the light guide plate 310. The optical film set 400 is mainly used for reducing the light quantity of the light emitted from the light guide plate 310 from the side view angle and at least maintaining the light quantity of the light emitted from the light guide plate 310 from the front view angle, so that the backlight module 300 can be applied to the peep-proof display product.

As shown in fig. 6, in the present embodiment, the optical film set 400 includes a lower diffusion sheet 410, a lower prism sheet 420, an upper prism sheet 430 and an upper diffusion sheet 440, wherein the lower diffusion sheet 410, the lower prism sheet 420, the upper prism sheet 430 and the upper diffusion sheet 440 are sequentially stacked in front of the light emitting surface of the light guide plate 310. The structures of the lower prism sheet 420 and the upper prism sheet 430 are substantially the same as those of the lower prism sheet 220 and the upper prism sheet 230 shown in fig. 1 to 3, and thus are not described herein. In the present embodiment, the effect of the upper diffuser 440 is to ensure that the product with better optical quality, such as better uniformity, is better, and particularly the haze of the upper diffuser 440 is lower than that of the lower diffuser 410, so that the light emitted from the upper diffuser 440 will not generate excessive stray light, and the product with the optical film set of the present disclosure further satisfies the peep-proof property.

In the present embodiment, the lower diffuser 410 and the upper diffuser 440 have the diffuser particles 211 shown in fig. 5, for example, and the diffuser particles can make the lower diffuser 410 have a haze of 50% to 60% (inclusive) and the upper diffuser 440 has a haze lower than that of the lower diffuser 410, for example, 30% or less, inclusive. Referring to table three, the above-mentioned range of the included angle between the prism structure of the upper prism sheet 430 and the extending direction of the light incident surface 311 of the light guide plate 310 is from 25 degrees to 50 degrees or from 130 degrees to 155 degrees, and the haze of the lower diffusion sheet 410 and the upper diffusion sheet 440 is varied, so that the amount of stray light is still within the allowable range of the anti-peeping product. As seen from table three, less stray light can be generated when the haze of the lower diffusion sheet 410 is in the range of 50% to 60% and the haze of the upper diffusion sheet 440 is 30% or less. In addition, as can be seen from the results of table three, when the haze ratio of the lower diffuser 410 to the upper diffuser 440 ranges from 1.6 to 6 (and includes the end point value), the product with the anti-peeping property can be satisfied, and less stray light is generated, and besides, the optical taste of the backlight module of the present embodiment is also considered, for example, better uniformity is achieved.

Watch III

Fig. 7 is a schematic diagram of a display device according to an embodiment of the disclosure. The display device 500 of the present embodiment includes the backlight module 100 and the display panel 510 shown in fig. 1. The display panel 510 is disposed in front of the backlight module 100. Therefore, the display device 500 can maintain the light output from the positive viewing angle and reduce the light output from the side viewing angle through the design of the optical film set 200 in the backlight module 100, and thus the description thereof is omitted. The embodiment of the invention is shown in fig. 1, in which the backlight module 100 is applied to the display device 500 for illustration only, and is not intended to limit the disclosure. The backlight module 300 of the other embodiments (e.g. the backlight module 300 shown in fig. 6) can be applied to a display device to generate the same peep-proof effect.

According to the embodiment of the disclosure, the optical film set is designed mainly by the angle between the extending direction of the upper prism structure of the upper prism sheet and the light incident surface, and is matched with the change of the angle between the extending direction of the lower prism structure of the lower prism sheet and the light incident surface, so that the light output quantity of the light emitted from the side view angle is reduced on the premise of maintaining the light output quantity of the light emitted from the front view angle, thereby meeting the optical requirement of peeping-proof display. In addition, when the upper prism sheet and the lower prism sheet are combined with the diffusion sheets with different haze, the effect of reducing stray light emitted from a side view angle can be further achieved.

Although the embodiments of the present disclosure have been described above, it should be understood that the present disclosure is not limited thereto, and that various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the embodiments of the present disclosure, and the scope of the embodiments of the present disclosure is defined by the appended claims.

[ list of reference numerals ]

100: backlight module

110: light guide plate

111: light incident surface

112: light-emitting surface

120: light source

200: optical film set

210: lower diffusion sheet

211: diffusion particles

220: lower prism sheet

221: lower prism structure

230: upper prism sheet

231: upper prism structure

300: backlight module

310: light guide plate

311: light incident surface

320: light source

400: optical film set

410: lower diffusion sheet

420: lower prism sheet

430: upper prism sheet

440: upper diffusion sheet

500: display device

510: display panel

A1: direction of extension

D1: first direction

D2: second direction

L1: light ray

L2: light ray

L3: light ray

L4: light ray

L5: light ray

P1: extension wire

P2: plane surface

Alpha: included angle

Beta: included angle

θ: and an included angle.

Claims (11)

1. An optical film set configured to guide light from a light guide plate of a backlight module, the optical film set comprising:

a lower prism sheet having a plurality of lower prism structures, each of the lower prism structures extending along a first direction; and

the upper prism sheet is arranged above the lower prism sheet, wherein the upper prism sheet is provided with a plurality of upper prism structures, each upper prism structure extends along a second direction, the second direction is different from the first direction, an included angle is formed between the second direction and the extending direction of the light incident surface of the light guide plate, and the included angle is in the range from 25 degrees to 50 degrees or from 130 degrees to 155 degrees and comprises an endpoint value.

2. The optical film set according to claim 1, wherein the second direction has an included angle between the extending direction of the light incident surface of the light guide plate and the range from 115 degrees to 140 degrees or from 220 degrees to 245 degrees, and the included angle includes an end point value.

3. The set of optical films of claim 2, wherein the first direction and the second direction are perpendicular to each other.

4. The set of optical films of claim 1, further comprising a lower diffuser disposed below the lower prism sheet, wherein the lower diffuser comprises a plurality of diffuser particles that provide the lower diffuser with a haze of 50% to 60% and an endpoint value.

5. The set of optical films of claim 1, further comprising an upper diffuser disposed above the upper prism sheet, wherein the upper diffuser comprises a plurality of diffuser particles that provide the upper diffuser with a haze of 30% or less and an endpoint value.

6. The optical film set of claim 1, further comprising a lower diffuser and an upper diffuser, wherein the haze ratio of the lower diffuser to the upper diffuser is 1.6 to 6 and comprises an endpoint value.

7. The optical film set according to claim 6, wherein the lower diffusion sheet is disposed below the lower prism sheet, and the upper diffusion sheet is disposed above the upper prism sheet, wherein a portion of the light rays from the light guide plate, after passing through the lower diffusion sheet, the lower prism sheet, the upper prism sheet, and the upper diffusion sheet in this order, exit the upper diffusion sheet in a front view direction, and another portion of the light rays exit the upper diffusion sheet in a side view direction, and wherein a ratio of an amount of light exiting the side view direction to an amount of light exiting the front view direction is less than 0.07.

8. The set of optical films of claim 7, wherein the front view direction is parallel to the light exit normal of the upper diffuser, and the side view direction has an included angle greater than 45 degrees with the light exit normal.

9. The optical film assembly of claim 1, wherein each of the lower prism structures and each of the upper prism structures are stripe-shaped structures.

10. A backlight module, comprising:

a light guide plate having a light incident surface and a light emergent surface;

the light source is adjacently arranged on the light incident surface; and

the optical film set according to any one of claims 1 to 9, which is disposed above the light-emitting surface.

11. A display device, comprising:

a light guide plate having a light incident surface and a light emergent surface;

the light source is adjacently arranged on the light incident surface;

the optical film set according to any one of claims 1 to 9, which is disposed above the light-emitting surface of the light guide plate; and

and a display panel disposed above the optical film group.

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