CN114114752B

CN114114752B - Backlight module and display device

Info

Publication number: CN114114752B
Application number: CN202111451752.6A
Authority: CN
Inventors: 王小萍
Original assignee: Xiamen Tianma Microelectronics Co Ltd
Current assignee: Xiamen Tianma Microelectronics Co Ltd
Priority date: 2021-12-01
Filing date: 2021-12-01
Publication date: 2024-03-19
Anticipated expiration: 2041-12-01
Also published as: CN114114752A

Abstract

The embodiment of the application provides a backlight module and a display device, wherein the backlight module comprises a light source array layer and a first optical film arranged on one side of the light source array layer, which faces the light emitting surface of the backlight module; the light source array layer comprises a plurality of light sources which are arranged along a first direction and a second direction; the first optical film comprises a substrate and a first film layer arranged on one side of the substrate facing the light source array layer; the substrate comprises a plurality of concave structures on one side facing the first film layer, and the refractive index of substances in the concave structures is smaller than that of the first film layer; and along the thickness direction of the backlight module, the concave structure at least partially overlaps with the light source. Through setting up indent structure on the substrate to match the material refractive index in the indent structure with the refractive index of first rete, under the condition that need not to increase the light mixing distance and/or increase the light source density, can increase the light mixing degree between the adjacent light source in the light source array, and guaranteed that backlight unit has less thickness.

Description

Backlight module and display device

[ field of technology ]

The application relates to the technical field of display, in particular to a backlight module and a display device.

[ background Art ]

In the field of flat panel display, a backlight module is generally an important component. For example, in a liquid crystal display, since liquid crystal molecules cannot actively emit light, it is necessary to provide a backlight module to provide a light source. For example, in the organic light emitting display, a backlight module may be added to improve the display brightness and contrast.

The backlight module generally includes a side-entrance backlight module and a direct-type backlight module. The side-in backlight module is characterized in that a light source is arranged on the side face of a light guide plate, and after light emitted by the light source enters the light guide plate, the light is guided out through reflection and scattering of a reflecting sheet and a screen point, so that the formed picture has relatively poor contrast and cannot be subjected to local dimming. The light source of the direct type backlight module is made into a dense lattice, the light emitted by the light source directly irradiates the screen after passing through the optical module, and the direct type backlight module has clear image quality, vivid color and contrast draft-brightness contrast effect and gradually becomes the main stream trend of the market.

Currently, sub-millimeter light emitting diodes (mini-LEDs) are applied to backlight modules, and the development of the backlight modules is greatly promoted. For example, the price of the liquid crystal television panel adopting the mini-LED backlight module is only 60% -80% of that of the traditional OLED television panel, but the brightness and the image quality are similar to those of the traditional OLED television panel or the image effect is better, the power saving efficiency is higher, and the liquid crystal display adopting the mini-LED is hopeful to become the main stream of the market again.

However, there is also a certain technical shortboard in the development of the direct type backlight module, for example, improving the brightness uniformity of the direct type backlight module has been the focus of the research in the field.

[ MEANS FOR SOLVING PROBLEMS ]

In view of the above, the embodiments of the present application provide a backlight module and a display device to solve the above problems.

In a first aspect, the present application provides a backlight module, including:

the light source array layer comprises a plurality of light sources which are arranged along a first direction and a second direction, and the first direction and the second direction are crossed;

the first optical film is arranged on one side of the light source array layer facing the light emitting surface of the backlight module; the first optical film comprises a substrate and a first film layer, and the first film layer is arranged on one side of the substrate facing the light source array layer;

the substrate comprises a plurality of concave structures on one side facing the first film layer, and the refractive index of substances in the concave structures is smaller than that of the first film layer; and the concave structure at least partially overlaps with the light source along the thickness direction of the backlight module.

In one implementation of the first aspect, the refractive index of the first film layer is less than the refractive index of the substrate.

In one implementation of the first aspect, the substance within the concave structure is air.

In one implementation manner of the first aspect, the refractive index of the first film layer is 1.46-1.48.

In one implementation of the first aspect, the first film layer is an atomized film.

In one implementation of the first aspect, the first optical film further includes a plurality of polyhedral structures disposed on a side of the substrate facing away from the first film layer.

In an implementation manner of the first aspect, along a thickness direction of the backlight module, the concave structures overlap with the light sources in a one-to-one correspondence manner.

In an implementation manner of the first aspect, along a thickness direction of the backlight module, the concave structure covers the corresponding light source.

In an implementation manner of the first aspect, a cross section of the concave structure along a thickness direction of the backlight module is any one of a rectangle, a rounded rectangle, and an arc.

In one implementation manner of the first aspect, the light source is at least one of a sub-millimeter light emitting diode and a micrometer light emitting diode.

In an implementation manner of the first aspect, the backlight module further includes a diffusion film, a brightness enhancement film, and a quantum dot film that are stacked;

any one of the diffusion film, the brightness enhancement film and the quantum dot film is arranged on one side of the first optical film far away from the light source array layer.

In a second aspect, a display device includes a backlight module and a display panel provided in the first aspect, where the display panel is disposed on a light-emitting surface side of the backlight module.

In the embodiment of the application, the concave structure is arranged on the substrate, and the refractive index of the substance in the concave structure is matched with the refractive index of the first film layer, so that the light mixing degree between adjacent light sources in the light source array can be increased without increasing the light mixing distance and/or increasing the light source density, and the backlight module is ensured to have smaller thickness. Namely, the backlight module with better backlight brightness uniformity can be obtained on the premise of ensuring the smaller thickness of the backlight module.

[ description of the drawings ]

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic diagram of a backlight module according to an embodiment of the present disclosure;

fig. 2 is a schematic plan view of a backlight module according to an embodiment of the present disclosure;

fig. 3 is a schematic view of an optical path in a backlight module according to an embodiment of the present disclosure;

fig. 4 is a schematic diagram of another backlight module according to an embodiment of the present disclosure;

fig. 5 is a schematic diagram of a backlight module according to another embodiment of the present disclosure;

fig. 6 is a schematic diagram of a backlight module according to another embodiment of the present disclosure;

fig. 7 is a schematic diagram of a backlight module according to still another embodiment of the present disclosure;

fig. 8 is a schematic diagram of a backlight module according to another embodiment of the present disclosure;

fig. 9 is a schematic diagram of a display device according to an embodiment of the present application.

[ detailed description ] of the invention

For a better understanding of the technical solutions of the present application, embodiments of the present application are described in detail below with reference to the accompanying drawings.

It should be understood that the described embodiments are merely some, but not all, of the embodiments of the present application. All other embodiments, based on the embodiments herein, which would be apparent to one of ordinary skill in the art without making any inventive effort, are intended to be within the scope of the present application.

The terminology used in the embodiments of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this application and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

It should be understood that the term "and/or" as used herein is merely one relationship describing the association of the associated objects, meaning that there may be three relationships, e.g., a and/or B, may represent: a exists alone, A and B exist together, and B exists alone. In addition, the character "/" herein generally indicates that the front and rear associated objects are an "or" relationship.

In the description of the present specification, it is to be understood that the terms "substantially," "approximately," "about," "approximately," "substantially," and the like as used in the claims and examples herein refer to values that are generally agreed upon, rather than exact, within reasonable process operating ranges or tolerances.

It should be understood that although the terms first, second, etc. may be used in embodiments of the present application to describe directions, etc., these directions, etc. should not be limited by these terms. These terms are only used to distinguish one direction or the like from another. For example, the first direction X may also be referred to as the second direction Y, and similarly, the second direction Y may also be referred to as the first direction X without departing from the scope of embodiments of the present application.

The applicant has provided a solution to the problems existing in the prior art by intensive studies.

In the prior art, the light sources in the direct type backlight module generally use LEDs (light-emitting diode), gaps exist between the LED light sources, and a light mixing area for light emitted by the LEDs is above the area between the gaps. However, in the prior art, the brightness of the light mixing area is lower than that of the area above the LED, so the direct type backlight module generally has the problem of "stars of a full sky", that is, the direct type backlight module presents a situation that regular bright and dark areas are alternately distributed. The reason for this problem is mainly due to insufficient mixing of the light emitted by the different light sources.

In order to solve the above-described problems, the following two technical means are easily conceived. Firstly, increasing the setting density of the light sources reduces the distance between the adjacent light sources, so that the light mixing path length between the adjacent light sources can be improved, but the scheme can increase the cost and the power consumption; secondly, the light mixing distance of the light is increased, namely the distance between the light source and the optical module in the backlight module is increased, but the proposal is contrary to the development trend of light and thin of the current display device.

Fig. 1 is a schematic diagram of a backlight module 001 according to an embodiment of the present application, and fig. 2 is a schematic plan view of the backlight module 001 according to an embodiment of the present application.

Referring to fig. 1 and fig. 2, a backlight module 001 provided in the embodiment of the present application includes a light source 10 array layer 01 and a first optical film 02, where the first optical film 02 is disposed on a side of the light source 10 array layer 01 facing a light emitting surface of the backlight module 001. The backlight module 001 can provide backlight for the display panel, and the side where the display panel is located is the light emitting surface side of the backlight module 001.

The light source 10 array layer 01 includes a plurality of light sources 10 arranged in a first direction X and a second direction Y, the first direction X intersecting the second direction Y. Alternatively, the first direction X may be perpendicular to the second direction Y, and the light sources 10 in the array layer 01 of the light sources 10 are arranged in a matrix. Correspondingly, the backlight module 001 provided in the embodiment of the present application may be a direct type backlight module 001.

The first optical film 02 includes a substrate 21 and a first film layer 22, and the first film layer 22 is disposed on a side of the substrate 21 facing the array layer 01 of the light sources 10, that is, light emitted from the light sources 10 in the array layer 01 of the light sources 10 passes through the first film layer 22 and then passes through the substrate 21.

In the embodiment of the present application, a side of the substrate 21 facing the first film layer 22 includes a plurality of concave structures 210, and the concave structures 210 at least partially overlap the light source 10 along the thickness direction of the backlight module 001. Wherein the refractive index of the substance within the concave structures 210 is smaller than the refractive index of the first film layer 22.

In the process of transmitting the light emitted by the light source 10 in the array layer 01 of the light source 10 to the light-emitting surface side of the backlight module 001, a part of the light must pass through the first film layer 22 and then pass through the concave structure 210. Fig. 3 is a schematic diagram of an optical path in a backlight module 001 according to an embodiment of the present application. As shown in fig. 3, the light source 10 emits light of at least three types, namely light L1, light L2 and light L3, toward the concave structure 210. The light L3 is light emitted by the light source 10 and is affected by the concave structure 210, and the light path change is not obvious, which is not described in detail herein.

Since the refractive index of the substance located in the concave structure 210 is smaller than that of the first film layer 22, the light L1 greater than the critical angle is totally reflected when being emitted by the first film layer 22 to the concave structure 210, and part of the light enters the first film layer 22 to be reflected, refracted, etc., and then is emitted into the substrate 21 by the first film layer 22. As can be seen from fig. 2, since the light L1 is totally reflected inside the first optical film 02, the light L1 actually propagates in the lateral direction of the first optical film 02, that is, the path along which the light propagates in the arrangement direction of the adjacent light sources 10 increases in the first optical film 02. Therefore, the embodiment of the application can obviously increase the light mixing degree of the light source 10 in the array layer 01 of the light source 10 in the first optical film 02, and further obviously increase the brightness uniformity of the backlight module 001.

In this embodiment, by disposing the concave structure 210 on the substrate 21 and matching the refractive index of the substance in the concave structure 210 with the refractive index of the first film layer 22, the light mixing degree between adjacent light sources 10 in the array of light sources 10 can be increased and the backlight module 001 is ensured to have a smaller thickness without increasing the light mixing distance and/or the density of the light sources 10.

In one embodiment of the present application, the refractive index of the first film layer 22 is smaller than the refractive index of the substrate 21, and then the refractive index of the substance in the concave structure 210 is also smaller than the refractive index of the substrate 21. Assuming that the refractive index of the first film layer 22 is n1, the refractive index of the base material 21 is n2, and the refractive index of the substance in the concave structure 210 is n3, n2 > n1 > n3.

In the present embodiment, since the refractive index of the substrate 21 is greater than that of the material in the concave structure 210, the angle of the light L2 incident on the sidewall of the concave structure 210 and incident on the substrate 21 from the first film 22 is different between the substrate 21 and the concave structure 210. Specifically, the angle between the light L2 and the normal perpendicular to the sidewall is smaller in the substrate 21 than in the concave structures 210. The angle between the light L2 and the thickness direction of the backlight module 001 is larger than that of the concave structure 210 when the substrate 21 is disposed.

That is, by setting the refractive index of the base material 21 to be larger than that of the substance in the concave structure 210, the sidewall of the concave structure 210 causes the propagation path of the light L2 in the lateral direction of the first optical film 02 to be increased when the light L2 is incident from the concave structure 210 to the base material 21. That is, the path along which the light L2 propagates in the arrangement direction of the adjacent light sources 10 increases in the first optical film 02. Therefore, the light mixing degree of the light source 10 in the array layer 01 of the light source 10 in the first film layer 22 can be further increased, so as to obviously increase the brightness uniformity of the backlight module 001.

In addition, when the refractive index of the first film layer 22 is set smaller than that of the substrate 21, the light emitted by the light source 10 is incident on the first optical film 02, and passes through the first film layer 22 with a relatively smaller refractive index instead of the substrate 21 with a larger refractive index, so that the light emitted by the light source 10 is prevented from generating larger interface reflection loss at the beginning of being incident on the first optical film 02.

In one implementation of the present embodiment, the refractive index of the first film layer 22 may be 1.46 to 1.48. The first film layer 22 may be made of a resin material.

Further, the base material 21 may be a resin material or glass. For example, the substrate 21 may be white glass, and the refractive index of the white glass is 1.51, so that the refractive index difference between the first film layer 22 and the substrate 21 is small, and the reflection loss of the light incident on the first optical film 02 at the interface between the first film layer 22 and the substrate 21 can be reduced.

Wherein the light sources 10 in the array of light sources 10 are at least one of sub-millimeter light emitting diodes (mini-LEDs) and micro-light emitting diodes (micro-LEDs). The chip size of mini-LEDs is typically between 50-200 μm, with micro-LEDs being below 50 μm. Therefore, when the mini-LED or micro-LED is applied to the backlight module 001, the light source 10 in the backlight module 001 has smaller volume and denser spacing, and the backlight module 001 using the mini-LED or micro-LED as the light source 10 has various advantages of high brightness, high contrast ratio, low power consumption, lighter weight, long service life, and the like. In addition, the direct type backlight module 001 adopting mini-LEDs or micro-LEDs can realize local dimming.

Fig. 4 is a schematic diagram of another backlight module 001 according to an embodiment of the present application.

In an embodiment of the present application, referring to fig. 2 and 4, a cross section of the concave structure 210 along the thickness direction of the backlight module 001 is any one of a rectangle, a rounded rectangle, and an arc. It should be noted that, when the width of the cross section of the concave structure 210 along the thickness direction of the backlight module 001 is changed, the width of the cross section near the edge of the first film layer 22 is larger than the width of the other positions, i.e. the concave structure 210 has a larger entrance allowing light to be incident therein.

In addition, as shown in fig. 4, when the cross section of the concave structure 210 is any one of rounded rectangle and arc, the side walls of the shapes each include a concave structure facing the concave structure 210. The proportion of light incident to the concave structures 210 that is changed in the optical path by the sidewalls of the concave structures 210 increases, that is, the proportion of light L2 entering the substrate 21 from the concave structures 210 through the sidewalls of the concave structures 210 increases. Therefore, as analyzed above, the brightness uniformity of the backlight module 001 can be further increased.

Fig. 5 is a schematic diagram of a backlight module 001 according to another embodiment of the present application.

In another embodiment of the present application, the substance in the concave structures 210 may be air, as shown in fig. 2. On the one hand, the refractive index of air is smaller, and more selection spaces are available when the first film 22, the substrate 21 and other films are selected according to the difference of the refractive indexes; on the other hand, the manufacturing steps can be reduced without increasing the cost of the backlight module 001.

In another embodiment of the present application, as shown in fig. 5, the material in the concave structures 210 may be other low refractive index materials 21a than air. On the one hand, the low refractive index substance 21a filled in the concave structure 210 can be selected according to the refractive index of the first film layer 22, the substrate 21, etc., so that the matching of the substances in the first film layer 22, the substrate 21 and the concave structure 210 further improves the brightness uniformity of the backlight module 001; on the other hand, the mechanical strength of the base material 21 can be increased by filling the appropriate low refractive index substance 21a.

It should be noted that, in fig. 5, in order to clearly illustrate that the concave structures 210 are filled with other low refractive index substances 21a except air, the low refractive index substances 21a in the concave structures 210 are not overfilled, and in actual products, the concave structures 210 may be completely filled with the low refractive index substances 21a.

In the embodiment of the present application, as shown in fig. 2 and 5, along the thickness direction of the backlight module 001, the concave structures 210 overlap the light sources 10 in a one-to-one correspondence manner. That is, each light source 10 in the array layer 01 of the light sources 10 may have a corresponding concave structure 210, so that when the light emitted by each light source 10 passes through the concave structure 210 and the substances filled therein, a considerable proportion of light L1 and light L2 are generated, and the light L1 and light L1, the light L2 and the light L2, the light L1 and the light L2, etc. can be mixed effectively at the positions corresponding to the areas between the adjacent concave structures 210 in the substrate 21.

Further, please continue with fig. 2 and 5, along the thickness direction of the backlight module 001, the concave structure 210 covers the corresponding light source 10, that is, the area of the concave structure 210 is larger than the area of the light source 10 and the light emitting surface of the light source 10. More light may be made incident into the concave structures 210.

Fig. 6 is a schematic diagram of a backlight module 001 according to another embodiment of the present application.

In one embodiment of the present application, as shown in fig. 6, the first film layer 22 is an atomized film, that is, an atomized film is disposed on a side of the substrate 21 facing the array layer 01 of the light source 10. The atomizing film is used for scattering light emitted by the light sources 10 in the array layer 01 of the light sources 10 to form emergent light with uniform atomization effect, and part of emergent light with uniform atomization effect enters the substrate 21 through substances in the concave structure 210.

Since the light sources 10 in the array layer 01 of the light sources 10 are granular, and the light emitted by the light sources 10 is densely distributed in the middle and sparsely distributed toward the surrounding, the light entering the first optical film 02 is atomized by the atomizing film, so that the light entering the concave structure 210 and the substrate 21 is relatively uniformly distributed in all directions toward the light-emitting surface. Further, more light becomes light L1 and light L2, that is, total reflection occurs and the light quantity of the light path changed by the side wall of the concave structure 210 increases, so as to effectively improve the brightness uniformity of the backlight module 001.

Fig. 7 is a schematic diagram of a backlight module 001 according to still another embodiment of the present application.

In one embodiment of the present application, as shown in fig. 7, the first optical film 02 further includes a plurality of polyhedral structures 23, the polyhedral structures 23 being disposed on a side of the substrate 21 facing away from the first film layer 22. The polyhedral structure 23 included in the first optical film 02 may specifically be a pyramid structure, and may be, for example, a triangular pyramid, a rectangular pyramid, a pentagonal pyramid, a hexagonal pyramid, or the like. The polyhedral structure 23 can disperse light emitted from the base material 21 into light in a plurality of directions.

The polyhedral structure 23 may be made of a resin material, for example, polyethylene terephthalate (PET) having a refractive index of 1.65, and the refractive index difference between the polyhedral structure 23 and the base material 21 is small, so that the interfacial reflection loss of the light incident to the first optical film 02 between the polyhedral structure 23 and the base material 21 can be reduced.

Fig. 8 is a schematic diagram of a backlight module 001 according to another embodiment of the present application.

In one embodiment of the present application, as shown in fig. 8, the backlight module 001 further includes a diffusion film 26, a brightness enhancement film 25, a quantum dot film 24, and the like which are stacked, that is, the backlight module 001 may include other optical films in addition to the first optical film 02.

Any one of the diffusion film 26, the brightness enhancement film 25, and the quantum dot film 24 is disposed on the side of the first optical film 02 away from the array layer 01 of the light source 10. That is, the light emitted from the first optical film 02 is further processed by the diffusion film 26, the brightness enhancement film 25, and the quantum dot film 24.

In one implementation, the first optical film 02 is provided with a quantum dot film 24, a brightness enhancement film 25 and a diffusion film 26 in order towards one side of the light emitting surface of the backlight module 001.

As shown in fig. 9, an embodiment of the present application further provides a display device, including the backlight module 001 provided in any one of the embodiments. In addition, the display device provided in the embodiment of the present application further includes a display panel 002, and the display panel 002 is disposed on one side of the light emitting surface of the backlight module 001, that is, the backlight module 001 provides backlight for the display panel 002. The display panel 002 may be a liquid crystal display panel 002 or an organic light emitting display panel 002.

The display device provided in the embodiment of the application may be a mobile phone, and in addition, the display device provided in the embodiment of the application may also be a display device such as a computer, a television, and the like.

In the display device provided in this embodiment, the substrate 21 of the first optical film 02 of the backlight module 001 is provided with the concave structure 210 facing the light source array layer 01, and the refractive index of the substance in the concave structure 210 is matched with the refractive index of the first film layer 22, so that light with a critical angle greater than the critical angle is totally reflected when being emitted from the first film layer 22 to the concave structure 210, and part of the light enters the first film layer 22 to be reflected, refracted, etc., and then is emitted into the substrate 21 from the first film layer 22. Since the light L1 is totally reflected inside the first optical film 02, the light L1 actually propagates in the lateral direction of the first optical film 02, that is, the path along which the light propagates in the arrangement direction of the adjacent light sources 10 increases in the first optical film 02. Therefore, the embodiment of the application can obviously increase the light mixing degree of the light source 10 in the first optical film 02 in the array layer 01 of the light source 10 without increasing the light mixing distance and/or increasing the density of the light source 10, thereby obviously increasing the brightness uniformity of the backlight module 001 and ensuring that the backlight module 001 has smaller thickness.

The foregoing description of the preferred embodiments of the present invention is not intended to limit the invention to the precise form disclosed, and any modifications, equivalents, improvements and alternatives falling within the spirit and principles of the present invention are intended to be included within the scope of the present invention.

Claims

1. A backlight module, comprising:

2. A backlight module according to claim 1, wherein the refractive index of the first film layer is smaller than the refractive index of the substrate.

3. A backlight module according to claim 1, wherein the substance in the concave structure is air.

4. A backlight module according to any of claims 1-2, wherein the refractive index of the first film layer is 1.46-1.48.

5. The backlight module according to claim 1, wherein the first film layer is an atomized film.

6. A backlight module according to claim 1 or 5, wherein the first optical film further comprises a plurality of polyhedral structures disposed on a side of the substrate facing away from the first film layer.

7. A backlight module according to claim 1, wherein the concave structures overlap the light sources in a one-to-one correspondence along a thickness direction of the backlight module.

8. A backlight module according to claim 7, wherein the concave structures cover the corresponding light sources in the thickness direction of the backlight module.

9. A backlight module according to claim 1, wherein the cross section of the concave structure along the thickness direction of the backlight module is any one of rectangle, rounded rectangle, and arc.

10. The backlight module according to claim 1, wherein the light source is at least one of a sub-millimeter light emitting diode and a micro light emitting diode.

11. The backlight module according to claim 1, further comprising a diffusion film, a brightness enhancement film, and a quantum dot film stacked;

12. A display device, comprising a backlight module according to any one of claims 1 to 11 and a display panel, wherein the display panel is disposed on a light-emitting surface side of the backlight module.