CN108227068A - Side entrance back module and display device - Google Patents

Abstract

The invention relates to a side-entry backlight module and a display device. The side-entry backlight module includes: a light guide plate, a light-emitting part, a substrate layer, a coupling grating layer and a collimation take-out grating layer; between the light incident surface of the light guide plate; the substrate layer is provided with a groove for accommodating the light-emitting element; the coupling grating layer is located between the substrate layer and the light incident surface of the light guide plate; the collimating take-out grating layer is arranged on the light exit surface of the light guide plate ; The light emitted by the light-emitting element enters the coupling grating layer after passing through the substrate layer, and the coupling grating layer couples the received light to the light incident surface of the light guide plate, and the light entering the light guide plate becomes perpendicular to the Parallel light on the light-emitting surface. According to the embodiments of the present invention, not only the light efficiency can be improved, but also the light guide plate can be made thinner, which is beneficial to the development of thinner display devices.

Description

Side-entry backlight module and display device

technical field

The invention relates to the field of display technology, in particular to an edge-type backlight module and a display device.

Background technique

In the related art, point light sources and lenses are often used to achieve backlight collimation. However, in this structure, the dot matrix light source is located on the focal plane of the lenses in the lens array, and one lens can only collimate the incident light within the aperture of the lens, and the light outside the aperture of the lens will be incident on the adjacent The lens cannot be collimated, which seriously affects the overall collimation effect and light extraction efficiency. If the light outside the aperture is blocked, the collimation can be improved, but most of the light will be lost, and the light extraction efficiency is very low.

Contents of the invention

The invention provides a side-entry backlight module and a display device to solve the deficiencies in the related art.

According to the first aspect of the embodiments of the present invention, there is provided an edge-type backlight module, including: a light guide plate and a light emitting element; the edge-type backlight module further includes: a substrate layer, a coupling grating layer, and a collimation extraction grating Floor;

The substrate layer is located between the light-emitting element and the light incident surface of the light guide plate; the substrate layer is provided with a groove for accommodating the light-emitting element; the coupling grating layer is located between the substrate layer and the light-emitting element. Between the light incident surfaces of the light guide plate; the collimation and take-out grating layer is arranged on the light exit surface of the light guide plate or the surface opposite to the light exit surface;

The light emitted by the light-emitting element enters the coupling grating layer after passing through the substrate layer, and the coupling grating layer couples the received light to the light incident surface of the light guide plate, and the light entering the light guide plate passes through The collimated take-out grating layer is diffracted and becomes parallel light perpendicular to the light-out surface.

In one embodiment, the refractive index of the substrate layer is lower than that of the light guide plate.

In one embodiment, the substrate layer includes a first side and a second side, the first side is located on the side of the light-emitting surface, and the second side is opposite to the first side; the first side and the second side are The light-emitting surface is flush, and the second side is flush with the surface opposite to the light-emitting surface;

The coupling grating layer includes a third side and a fourth side, the third side is located on the side of the light exit surface, the fourth side is opposite to the third side; the third side is flush with the light exit surface flat, the fourth side is flush with the surface opposite to the light-emitting surface;

The distance between the first side and the second side and the distance between the third side and the fourth side are both equal to the thickness of the light guide plate.

In one embodiment, the substrate layer further includes a fifth side, the fifth side is perpendicular to the light-emitting surface and is located on a side away from the coupling grating layer; the groove is located on the fifth side center of.

In one embodiment, the side-lit backlight module further includes a reflective layer;

The reflective layer is disposed on the first side and/or the second side.

In one embodiment, the coupling grating layer is a slit grating or an echelle grating.

In one embodiment, when the coupling grating layer is an echelle grating, the coupling grating layer includes several sub-gratings, and the sub-gratings are echelle gratings.

In one embodiment, when the light-emitting element is a Lambertian body, the sub-grating is circular or annular.

In one embodiment, the collimation extraction grating layer is a multi-step echelle grating.

According to a second aspect of the embodiments of the present invention, there is provided a display device, including the above-mentioned edge-lit backlight module.

According to the above embodiments, it can be seen that by providing a substrate layer between the light-emitting element and the light incident surface of the light guide plate, the distribution range of the light beam emitted by the light-emitting element can be narrowed, so that more light energy can be coupled by the coupling grating layer. to the light guide plate, and finally collimated and taken out by the collimated and taken out grating layer. In this way, not only the light efficiency can be improved, but also the light guide plate can be made thinner, which is beneficial to the development of thinner display devices.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention.

Description of drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description serve to explain the principles of the invention.

Fig. 1 is a schematic structural diagram of an edge-lit backlight module according to an embodiment of the present invention.

Fig. 2 is a schematic structural diagram of another side-type backlight module according to an embodiment of the present invention.

Fig. 3 is a schematic diagram showing the propagation of light between a coupling grating layer and a light guide plate according to an embodiment of the present invention.

Fig. 4 is a schematic diagram of a coupling grating layer according to an embodiment of the present invention.

Fig. 5 is a schematic diagram of a periodic structure of a sub-grating according to an embodiment of the present invention.

Fig. 6 is a schematic diagram of a two-dimensional structure of a coupling grating layer according to an embodiment of the present invention.

7 to 9 are schematic diagrams showing angle tolerances of sub-gratings according to an embodiment of the present invention.

Fig. 10 is a schematic diagram of grating diffraction according to an embodiment of the present invention.

Fig. 11 is a schematic diagram of a periodic structure of an 8-step echelle grating according to an embodiment of the present invention.

12-13 are schematic diagrams showing simulation results of an 8-step echelle grating according to an embodiment of the present invention.

Fig. 14 is a schematic structural diagram of a display device according to an embodiment of the present invention.

Detailed ways

Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, the same numerals in different drawings refer to the same or similar elements unless otherwise indicated. The implementations described in the following exemplary examples do not represent all implementations consistent with the present invention. Rather, they are merely examples of apparatuses and methods consistent with aspects of the invention as recited in the appended claims.

1 to 2 are side-entry backlight modules 1 shown according to an embodiment of the present invention. The side-entry backlight module 1 includes: a light guide plate 11, a light-emitting element 12, a substrate layer 13, a coupling grating layer 14 and a collimation extraction Grating layer 15.

As shown in FIG. 1 , the substrate layer 13 is located between the light emitting element 12 and the light incident surface of the light guide plate 11 . The substrate layer 13 is provided with a groove 131 for accommodating the light emitting element 12 . The coupling grating layer 14 is located between the substrate layer 13 and the light incident surface 113 of the light guide plate 11 . The collimating and extracting grating layer 15 is disposed on the light-emitting surface (as shown in FIG. 1 ) or the surface opposite to the light-emitting surface (as shown in FIG. 2 ) of the light guide plate 11 .

The light emitted by the light-emitting element 12 enters the coupling grating layer 14 after passing through the substrate layer 13, and the coupling grating layer 14 couples the received light to the light incident surface 113 of the light guide plate 11, and the light entering the light guide plate 11 is collimated and taken out of the grating layer After 15 diffraction, it becomes parallel light perpendicular to the light-emitting surface.

In this embodiment, the refractive index of the substrate layer 13 is greater than that of air, and the light beam emitted by the light emitting element 12 is refracted by the substrate layer 13. After the light beam is refracted by the substrate layer 13, the angle of the light beam relative to the incident normal becomes smaller. The light beam is shrunk, and a greater proportion of the light energy emitted by the light emitting element 12 can be coupled to the light incident surface 113 of the light guide plate 11 through the coupling grating layer 14, thereby improving the light efficiency. At the same time, since the light beam emitted by the light-emitting element 12 is refracted by the substrate layer 13, the angle of the light beam relative to the incident normal becomes smaller. When the light is coupled to the light incident surface 113 of the light guide plate 11, the included angle of the light relative to the incident normal is reduced again, so that the thickness of the light guide plate can be made thinner, which is conducive to the development of thinner display devices.

In this embodiment, by setting the substrate layer between the light-emitting element and the light incident surface of the light guide plate, the distribution range of the light beam emitted by the light-emitting element can be narrowed, so that more light energy can be coupled to the light guide plate by the coupling grating layer, and finally Take out by collimating the grating layer. In this way, not only the light efficiency can be improved, but also the light guide plate can be made thinner and the overall thickness of the backlight module can be reduced, which is beneficial to the development of thinner display devices.

In one embodiment, the refractive index of the substrate layer 13 is lower than that of the light guide plate 11 . In this way, matching the refractive index of the substrate layer 13 with the refractive index of the light guide plate 11 can reduce the angle of the outgoing light coupled to the grating layer 14 , and finally increase the incident angle of the light on the upper and lower surface layers of the light guide plate 11 . In an exemplary embodiment, the refractive index of the substrate layer 13 can be 1.5, the refractive index of the light guide plate 11 can be 1.8, the refractive index of the coupling grating layer 14 can also be 1.8, and the refractive index of the collimation extraction grating layer 15 can be is 1.8. The substrate layer 13 can be a transparent material, and materials such as ITO (Indium Tin Oxide Semiconductor Transparent Conductive Film) or Si3N4 (Silicon Nitride) can be selected. The light guide plate 11 is made of a transparent material, while ensuring the parallelism of the surface. The coupling grating layer 14 and the collimating extraction grating layer 15 are also transparent dielectric materials.

In one embodiment, as shown in FIGS. 1-2 , the substrate layer 13 includes a first side 132 and a second side 133 , the first side 132 is located on the side of the light-emitting surface 111 , and the second side 133 is opposite to the first side 132 ; One side 132 is flush with the light emitting surface 111 , and the second side 133 is flush with the surface 112 opposite to the light emitting surface 111 . The coupling grating layer 14 includes a third side 141 and a fourth side 142 . The third side 141 is located on the side of the light emitting surface 111 , the fourth side 142 is opposite to the third side 141 ; The distance between the first side 132 and the second side 133 and the distance between the third side 141 and the fourth side 142 are equal to the thickness of the light guide plate 11 . In an exemplary embodiment, the thickness of the light guide plate 11 is 0.7 mm.

In one embodiment, as shown in FIGS. 1-2 , the substrate layer 13 further includes a fifth side 134 , the fifth side 134 is perpendicular to the light-emitting surface 111 and is located on the side away from the coupling grating layer 14 ; the groove 131 is located on the second side. On the five sides 134 . In an exemplary embodiment, the groove 131 is located at the center of the fifth side 134 . Certainly, the groove 131 may not be located at the center of the fifth side 134 , but be located at other positions of the fifth side 134 .

In one embodiment, the light emitting element 12 may be an LED light source, specifically an LED chip (including a Micro-LED chip), and the LED chip may be directly transferred onto the fifth side 134 of the substrate layer 13 . In one embodiment, the light emitting element 12 can also be an OLED light source.

In one embodiment, as shown in FIG. 1 , the edge-lit backlight module 1 further includes reflective layers 16 , 17 . The reflective layers 16 and 17 may be metal film layers, or multi-layer dielectric films. The reflective layer 16 is disposed on the first side 132 of the substrate layer 13 , and the reflective layer 17 is disposed on the second side 133 of the substrate layer 13 and the surface 112 opposite to the light-emitting surface 111 of the light guide plate 11 . Since the coupling grating layer 14 and the collimation extraction grating layer 15 will inevitably diverge other unnecessary diffraction losses (light energy loss accounts for less than 5%), the reflective layers 16, 17 can make the light incident to the reflective layers 16, 17 Be reused to further improve light efficiency.

In another embodiment, as shown in FIG. 2 , the edge-lit backlight module 1 further includes reflective layers 16 , 18 , 19 . The reflective layers 16, 18, 19 may be metal film layers, or multi-layer dielectric films. The reflective layer 16 is disposed on the first side 132 of the substrate layer 13 , the reflective layer 18 is disposed on the second side 133 of the substrate layer 13 , and the reflective layer 19 is disposed on the surface 112 opposite to the light emitting surface 111 of the light guide plate 11 .

In one embodiment, the coupling grating layer 14 is a micro-nano structure, specifically a slit grating or an echelle grating. In an exemplary embodiment, as shown in FIGS. 4-5 , the coupling grating layer 14 is an echelle grating, and the coupling grating layer 14 includes several sub-gratings 42 , and the sub-gratings 42 are also echelle gratings. For ease of understanding, an example is given below.

Continuing the above exemplary embodiment, as shown in FIGS. 1-2, the light-emitting element is an LED surface light source, and the normal line of the light emitted by the LED surface light source incident on the substrate layer 13 is parallel to the light-emitting surface 111, and the light emitted by the LED surface light source is The energy is concentrated within the range of +/-60° included angle with the normal, where the incident angle of the incident light on the side of the light emitting surface 111 may be positive. The coupling grating layer 14 needs to diffract and modulate the light emitted by the LED surface light source into a large-angle (incident angle of 80°-90°) light that is transmitted through the total reflection in the light guide plate 11 . As shown in FIG. 3 , the angle c is the incident angle when the light is transmitted to the surface 112 of the light guide plate 11 in the light guide plate 11 , that is, c=80°˜90°. It can be seen from the geometric relationship that the refraction angle b of the light on the light incident surface 113 of the light guide plate 11 is 0° to 10°. In this exemplary embodiment, the refractive index of the substrate layer 13 is 1.5, the refractive index of the light guide plate 11 is 1.8, and the refractive index of the coupling grating layer 14 is also 1.8. Moreover, there is a gap between the coupling grating layer 14 and the light incident surface 113 of the light guide plate 11 , the gap can be filled with a medium whose refractive index is lower than that of the light guide plate 11 . According to the above-mentioned refractive index matching relationship, the diffraction angle a of the grating should satisfy a=0-12°. Therefore, in the embodiment of the present invention, the coupling grating layer 14 needs to be able to modulate and diffract the Lambertian light emitted by the LED surface light source, and the diffraction angle should be in the range of 0-12°.

When it comes to the structure of the coupling grating layer 14, it is considered that the grating is very sensitive to the incident angle of the light, that is, the grating structure of the same structure has different diffraction effects on the light of different incident angles, and the divergence angle of the light is related to the aperture and the size of the light source , that is, the aperture of the optical system limits the divergence angle of the finite-size light source, and the light-emitting angle of the LED surface light source is designed in blocks.

Continuing the above-mentioned exemplary embodiment, as shown in FIG. 4 , the projected area of the light emitted by the LED surface light source on the light incident surface 113 is divided into N parts, and each part corresponds to a different light emitting angle of the LED surface light source, wherein, N is an integer greater than 1. A sub-grating 42 is designed for each chief ray 41 in the projected area, so that the diffraction coupling modulation effect of each sub-grating 42 is as above. That is, a coupling grating layer 14 is composed of several sub-gratings 42 with different parameters.

Continuing the above exemplary embodiment, as shown in FIG. 4 , the light emitting angle of the LED surface light source can be quantified as angles of six chief rays 411 to 416 above 35°, 30°, 25°, 20°, 15°, and 10° (The light emitting angle of the LED surface light source is distributed in the range of +/-60°, after entering the substrate layer 13, due to refraction, the refracted light will mainly be distributed in the range of +/-35°). Based on this, the coupling grating layer 14 includes six sub-gratings 421 - 426 . The periodic structure of each sub-grating can be shown in Figure 5, including M transparent medium sheets h1~hM with the same thickness and different heights, wherein the height of each transparent medium layer is determined according to the corresponding chief light rays 411~416, and each of different heights The transparent medium layer forms grating steps of different heights, P is the grating period of the sub-grating 42, and x1-xM are the coordinates of division points of the grating steps of different heights within one grating period.

Continuing with the above-mentioned exemplary embodiment, the LED surface light source is a Lambertian body, and the light emitted by the LED surface light source is distributed in two dimensions, so the overall two-dimensional structure of the coupling grating layer 14 can be shown in FIG. 6 , and the sub-grating 421 is The circles, or the sub-gratings 422-426 are ring structures.

The simulation results obtained by simulating the diffraction modulation of the above six sub-gratings 421-426 are shown in Tables 1-7, and the coupling efficiency and parameters of the coupling grating layer 14 are shown in Table 8. Among them, Tables 1 to 7 are the simulation results of incident light with incident angles of 35, 30, 25, 20, 15, and 10, respectively.

From the simulation results in Tables 1 to 7, it can be seen that if the coupling grating structure is designed in this way, the incident light from 0° to 35° can be efficiently diffracted and modulated into a small angle (0 to 10°, b) outgoing light, reaching expected result. Table 8 summarizes the final coupling efficiency and parameters of the coupling grating layer 14. It can be seen that the coupling grating layer 14 can efficiently couple the light emitted by the LED surface light source into the light guide layer 11 for a large angle (incidence angle is 80°-90°). ) total reflection transmission. For the other small part of the diffracted light which is not coupled, it is reflected by the reflective layer 16, 18, 19 or 16, 17 and can be used again. To improve the collimation rate of light, this part of light (other uncoupled small part of diffracted light) can also be absorbed by the absorbing layer and not be used.

Table 1

Table 2

table 3

Table 4

table 5

Table 6

Table 8

angle of incidence Large angle (80-90°) coupling efficiency cycle line width 35° 72% 1μm 200nm 30° 72% 1.2μm 200nm 25° 71% 1.2μm 200nm 20° 74% 1.4μm 200nm 15° 76% 1.6μm 200nm 10° 80% 1.6μm 200nm

Although the above-mentioned coupling grating layer 14 is designed for the chief ray, according to the sub-area design method, each sub-grating 411-416 has a certain angle tolerance, that is, when the light emitted by the LED surface light source passes through each sub-grating All the light rays of the gratings 411-416 have very high coupling efficiency. For details, please refer to FIGS. 7-9, wherein FIGS.

In one embodiment, the collimation extraction grating layer 15 is a multi-step echelle grating. Wherein, the multi-step echelle grating is not sensitive to the angle of the above-mentioned large-angle incident light. The multi-step grating can highly collimate and take out the light transmitted through the large-angle total reflection in the light guide plate 11 to provide collimated backlight. Wherein the angle between the outgoing light and the normal can be less than 5°. The collimation extraction grating layer 15 in the embodiment of the present invention can also make the light output uniform and provide a uniform backlight.

In an exemplary embodiment, as shown in FIG. 10 , the grating can generate many diffraction orders, for example, light 161 is 0-order diffracted light, ray 162 is +1-order diffracted light, and ray 163 is +2-order diffracted light, Ray 164 is -1 order diffracted light, and ray 165 is -2 order diffracted light. In actual implementation, only one of the levels is required, while light rays of other levels need to be eliminated. The embodiment of the present invention adopts a multi-step echelle grating, which can eliminate stray light and optimize the outgoing light around 0°.

In the embodiment of the present invention, the required order of diffracted light can be obtained according to the grating equation:

n ₁ sinθ1-n2sinθ2=mL/λ,

Among them, m=0, ±1, ±2,...; n1 is the refractive index of the medium where the incident light is located, θ1 is the incident angle, n2 is the refractive index of the outgoing light medium, and θ2 is the diffraction angle; L is the grating for collimating and taking out the grating layer 15 Period, λ is the wavelength of the incident light.

For the multi-step echelle grating in the embodiment of the present invention, θ1 can be 85°, and θ2 can be 0°. If the grating period L and wavelength λ are known, the diffraction order of the 0° light can be obtained. Certainly, the embodiment of the present invention does not limit the angle of θ1.

In an exemplary embodiment, an 8-step echelle grating may be used, as specifically shown in FIG. 11 , the 8-step echelle grating includes a substrate 171 and eight dielectric layers 172 disposed on the substrate 171. The eight dielectric layers 172 have the same thickness, The heights are different, and the relationship between the heights is determined according to the above-mentioned relevant parameters.

Please refer to Figures 12 to 13 to simulate the above-mentioned 8-step echelle grating, fix other parameters, and change the incident angle. 4.79°, basically no effect. When other parameters are fixed and the incident angle is changed, the output angle varies with the incident angle. The result is: the incident angle fluctuates from 84° to 89°, and the light output efficiency > 80%, basically has no effect. From the simulation results in Figures 12 to 13, it can be seen that the incident light at a large angle has no effect on the collimation and light extraction efficiency of the multi-step grating.

Embodiments of the present invention also propose a display device, as shown in FIG. 14 , the display device includes a display module 2 and the edge-type backlight module 1 of any of the above-mentioned embodiments.

In one embodiment, the display module 2 may be a liquid crystal panel. The display module 2 may include a lower polarizer (POL) 21 , a TFT (thin film transistor) substrate 22 , a liquid crystal (LC) layer 23 , a CF (color filter) substrate 24 and an upper polarizer 25 .

It should be noted that the display device in this embodiment can be any product or component with a display function, such as electronic paper, mobile phone, tablet computer, television, notebook computer, digital photo frame, and navigator.

It should be noted that in the drawings, the dimensions of layers and regions may be exaggerated for clarity of illustration. Also it will be understood that when an element or layer is referred to as being "on" another element or layer, it can be directly on the other element or intervening layers may be present. Further, it will be understood that when an element or layer is referred to as being "under" another element or layer, it can be directly under the other element, or one or more intervening layers or elements may be present. In addition, it will also be understood that when a layer or element is referred to as being "between" two layers or elements, it can be the only layer between the two layers or elements, or one or more intervening layers may also be present. or components. Like reference numerals designate like elements throughout.

In the present invention, the terms "first" and "second" are used for descriptive purposes only, and should not be understood as indicating or implying relative importance. The term "plurality" means two or more, unless otherwise clearly defined.

Other embodiments of the invention will be readily apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed herein. The present invention is intended to cover any modification, use or adaptation of the present invention. These modifications, uses or adaptations follow the general principles of the present invention and include common knowledge or conventional technical means in the technical field not disclosed in the present invention . The specification and examples are to be considered exemplary only, with a true scope and spirit of the invention being indicated by the following claims.

It should be understood that the present invention is not limited to the precise constructions which have been described above and shown in the accompanying drawings, and various modifications and changes may be made without departing from the scope thereof. The scope of the invention is limited only by the appended claims.

Claims (10)

1. a kind of side entrance back module, including：Light guide plate and illuminating part；It is characterized in that, the side entrance back module is also Including：Substrate layer, coupling grating layer and collimation take out grating layer；

The substrate layer is between the illuminating part and the incidence surface of the light guide plate；The substrate layer is equipped with described in receiving The groove of illuminating part；The coupling grating layer is between the substrate layer and the incidence surface of the light guide plate；The collimation takes Go out grating layer and be set to the light-emitting surface of the light guide plate or the face opposite with the light-emitting surface；

The light of the illuminating part transmitting enters the coupling grating layer after the substrate layer, and the coupling grating layer will receive The incidence surface for being optically coupled to the light guide plate, into the light in the light guide plate through it is described collimation take out grating layer diffraction after become Into the directional light perpendicular to the light-emitting surface.

2. side entrance back module according to claim 1, which is characterized in that the refractive index of the substrate layer is less than described The refractive index of light guide plate.

3. side entrance back module according to claim 1, which is characterized in that the substrate layer includes first side and the Two side faces, the first side are located at the light extraction surface side, and the second side is opposite with the first side；First side Face is flushed with the light-emitting surface, and the second side face opposite with the light-emitting surface flushes；

The coupling grating layer includes third side and the 4th side, and the third side is located at the light extraction surface side, and described the Four sides are opposite with the third side；The third side is flushed with the light-emitting surface, the 4th side and the light extraction The opposite face in face flushes；

Between the distance between the first side and the second side and the third side and the 4th side Distance is equal to the thickness of the light guide plate.

4. side entrance back module according to claim 3, which is characterized in that the substrate layer further includes the 5th side, 5th side is located remotely from the side of the coupling grating layer perpendicular to the light-emitting surface；The groove is located at described The center of 5th side.

5. side entrance back module according to claim 3, which is characterized in that further include reflecting layer；

The reflecting layer is set to the first side and/or the second side.

6. side entrance back module according to claim 1, which is characterized in that the coupling grating layer for slit grating or Person's echelon.

7. side entrance back module according to claim 6, which is characterized in that when the coupling grating layer is echelon When, the coupling grating layer includes several sub-gratings, and the sub-gratings are echelon.

8. side entrance back module according to claim 7, which is characterized in that when the illuminating part is lambert's body, institute It is round or circular to state sub-gratings.

9. side entrance back module according to claim 1, which is characterized in that it is multistage rank that the collimation, which takes out grating layer, Terraced grating.

10. a kind of display device, which is characterized in that including claim 1 to 9 any one of them side entrance back module.