Light-emitting device and preparation method thereof, and backlight module

Abstract

The present invention provides a light-emitting device, a preparation method thereof, and a backlight module, wherein the light-emitting device includes: a flip-chip LED chip; a fluorescent adhesive layer provided on the light-emitting side surface of the flip-chip LED chip; a light-emitting layer provided on the surface of the fluorescent adhesive layer on the light-emitting side surface opposite to the electrode side surface of the flip-chip LED chip, the light-emitting layer containing light-reflecting particles for reflecting back part of the light emitted from the light-emitting side surface; and a light-reflecting layer provided on the electrode side surface of the flip-chip LED chip for reflecting back the light emitted from the electrode side surface. The light-emitting layer provided on the surface of the fluorescent adhesive layer on the light-emitting side surface opposite to the electrode side surface of the flip-chip LED chip reflects part of the light emitted from the light-emitting side surface back and emits it through the side, thereby increasing the light-emitting angle of the entire light-emitting device (to 170°), meeting the light-emitting angle requirement of the light-emitting device in a direct-lit backlight scenario.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a light-emitting device and a preparation method thereof, and a backlight module. Background Art

[0002] With the rapid development of display technology, people's demand for displays is getting higher and higher, and LED backlight displays have been widely used. Based on the light input method, LED backlight displays on the market are mainly divided into two types: side-entry and direct-down. Among them, the side-entry type is to install the LED lamp beads of the backlight module on the four sides of the LCD screen, and the direct-down type is to install the LED lamp beads of the backlight module on the front and back of the LCD screen. After the light of the LED lamp beads passes through the lens, it enters the light guide plate evenly to form a surface light source. Although direct-down backlight displays are relatively low in cost, they will increase the thickness of the display. How to reduce the thickness of the display while reducing the cost has become a problem that needs to be solved.

[0003] In direct-lit backlight applications, there are requirements for the thickness and luminous angle of LED lamp beads. However, the luminous angle of LED lamp beads obtained by packaging LED chips using the existing method is between 120° and 150°, and a lens is required to emit light, which cannot meet the requirements of direct-lit backlights. Summary of the Invention

[0004] In order to overcome the above shortcomings, the present invention provides a light-emitting device and a preparation method thereof, and a backlight module, which effectively solve the problem that the existing LED lamp beads have a small light-emitting angle and need to be equipped with a lens.

[0005] The technical solution provided by the present invention is:

[0006] A light-emitting device, comprising:

[0007] Flip-chip LED chips;

[0008] A fluorescent adhesive layer is provided on the light-emitting side surface of the flip-chip LED chip;

[0009] A light emitting layer is provided on the surface of the fluorescent glue layer on the light emitting side surface opposite to the electrode side surface of the flip-chip LED chip, wherein the light emitting layer contains light reflecting particles for reflecting back part of the light emitted from the light emitting side surface; and

[0010] The light reflecting layer provided on the electrode side surface of the flip-chip LED chip is used to reflect back the light emitted from the electrode side surface.

[0011] The present invention also provides a method for preparing a light-emitting device, comprising:

[0012] forming a light emitting layer containing reflective particles on the surface of the supporting film;

[0013] Preparing a first fluorescent adhesive layer on the surface of the light emitting layer;

[0014] Preparing a second fluorescent adhesive layer with adhesiveness on the surface of the first fluorescent adhesive layer, wherein the viscosity of the second fluorescent adhesive layer is greater than 10000 mPa.s;

[0015] Arranging a plurality of flip-chip LED chips on the surface of the second fluorescent adhesive layer and pressing them together;

[0016] curing the pressed second fluorescent adhesive layer;

[0017] Preparing a light reflecting layer on the electrode side surface of the flip-chip LED chip;

[0018] Cutting to obtain a single light-emitting device.

[0019] The present invention further provides a backlight module, comprising a base plate and a plurality of light-emitting devices as described above arranged on the surface of the base plate.

[0020] In the light-emitting device and its preparation method, and the backlight module provided by the present invention, a light-emitting layer is provided on the surface of the fluorescent glue layer on the light-emitting side surface opposite to the electrode side surface in the flip-chip LED chip, and part of the light emitted from the light-emitting side surface is reflected back and emitted through the side, thereby increasing the light-emitting angle of the entire light-emitting device (up to 170°), meeting the demand for the light-emitting angle of the light-emitting device in the direct backlight scene. In addition, the light-emitting layer is implemented by a film-mounting operation, which can achieve precise control of the height and color point of the light-emitting device. Furthermore, the electrode pad is wrapped by a light-reflecting layer, which can avoid the loss of LED light at the substrate after the application end is pasted with the aluminum substrate. Compared with conventional LED lamp beads, the luminous flux of the backlight module formed by the light-emitting device is higher. Finally, the lens can be omitted in the light-emitting device, saving material cost and lens mounting cost, while making the backlight module thinner, and the OD distance can be achieved to 0mm, which can further reduce the thickness of the entire TV. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the structure of the light-emitting device in the present invention;

[0022] Figure 2 is a light emitting angle diagram of a light emitting device in an embodiment of the present invention;

[0023] Figure 3 Schematic diagram of the process for preparing the light-emitting device of the present invention.

[0024] Reference numerals:

[0025] 10-flip-chip LED chip, 20-fluorescent adhesive layer, 21-first fluorescent adhesive layer, 22-second fluorescent adhesive layer, 30-light output layer, 40-chip electrode, 50-light reflection layer, 60-support film, 70-high-temperature film. DETAILED DESCRIPTION

[0026] In order to more clearly illustrate the implementation cases of the present invention or the technical solutions in the prior art, the specific embodiments of the present invention will be described below with reference to the accompanying drawings. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings and other embodiments can be obtained based on these drawings without inventive work.

[0027] like Figure 1 FIG2 is a schematic diagram of the structure of the light-emitting device provided by the present invention. As can be seen from the figure, the light-emitting device includes: a flip-chip LED chip 10; a fluorescent glue layer 20 provided on the light-emitting side surface of the flip-chip LED chip 10; a light-emitting layer 30 provided on the surface of the fluorescent glue layer 20 on the light-emitting side surface opposite to the electrode side surface of the flip-chip LED chip 10, the light-emitting layer 30 containing light-reflecting particles for reflecting back part of the light emitted from the light-emitting side surface; and a light-reflecting layer 50 provided on the electrode side surface of the flip-chip LED chip for reflecting back the light emitted from the electrode side surface.

[0028] In this light-emitting device, the light-emitting layer 30 is prepared from titanium dioxide powder and silica gel in a certain mass ratio, and the mass ratio of titanium dioxide powder to silica gel is 0.1:1 to 1:1. For example, in one embodiment, the mass ratio of titanium dioxide powder to silica gel is 0.2:1; in another embodiment, the mass ratio of titanium dioxide powder to silica gel is 0.5:1, etc. In forming the light-emitting layer 30, titanium dioxide powder and silica gel are uniformly mixed according to the required ratio, coated on a support film (such as a transparent PET support film) and cured at high temperature to form a light-emitting layer with a thickness of 10 to 100 μm. In this light-emitting layer 30, because it contains light-reflecting titanium dioxide particles, it can reflect part of the light emitted from the light-emitting side surface opposite to the electrode side surface of the flip-chip LED chip 10 back and emit it through the side, thereby increasing the light output angle of the entire light-emitting device without the need for further mounting a lens.

[0029] The light reflection layer 50 is similar to the light output layer 30. Its purpose is to reflect light emitted from the electrode side surface (light incident on the substrate) back to avoid luminous flux loss caused by substrate light absorption during the SMT process (for CSP chips with five-sided light output, nearly 30% of the light will be emitted towards the substrate). Therefore, the composition can be the same as that of the light output layer 30, and the proportions can also be adjusted according to actual conditions.

[0030] The fluorescent glue layer 20 is provided on the other five side surfaces of the flip-chip LED chip 10 except the electrode side surface, and in the fluorescent glue layer 20, the mass ratio of the fluorescent powder to the silica gel is 0.5:1 to 0.9:1. For example, in one embodiment, the mass ratio of the fluorescent powder to the silica gel is 0.7:1. In the preparation of the fluorescent glue layer 20, the first fluorescent glue layer 20 is first coated on the surface of the light emitting layer 30 and cured to form a double-layer film structure including the light emitting layer 30 and the first fluorescent glue layer. Then, a second fluorescent glue layer with viscosity is prepared on the surface of the first fluorescent glue layer to facilitate the subsequent pressing of the flip-chip LED chip 10 into the second fluorescent glue layer. Here, having viscosity specifically refers to the second fluorescent glue layer being in an uncured state, that is, a state where solid and liquid coexist and cannot flow. At this time, the viscosity of the second fluorescent glue layer is greater than 10,000 mPa.s. In order to ensure that the chip emits light and the fluorescent glue does not overflow to the electrode side surface after the chip is pressed, the thickness of the first fluorescent glue layer is 50~100μm, and the thickness of the second fluorescent glue layer is 100~200μm (smaller than the thickness of the flip-chip LED chip. Generally speaking, the thickness of the flip-chip LED chip is 150~250μm).

[0031] In one example, the mass ratio of titanium dioxide powder to silica gel in the light emitting layer and the light reflecting layer is 0.5:1, and the mass ratio of phosphor to silica gel in the fluorescent glue layer is 0.7:1. The thickness of the light emitting layer is 50 μm, and the thickness of the light reflecting layer is the same as the height of the chip electrode. The luminous angle diagram is as follows: Figure 2 As shown in the figure, it can be seen that the luminous angle reaches 170°, which is significantly improved compared to existing LED lamp beads.

[0032] The present invention also provides a method for preparing a light emitting device, such as Figure 3 As shown, the method for preparing the light-emitting device includes the following steps:

[0033] A light emitting layer 30 including reflective particles is formed on the surface of the support film 60. Figure 3 As shown in Figure (a), titanium dioxide powder and silica gel are mixed in the required mass ratio (mass ratio ranges from 0.1:1 to 1:1) to form a mixture to complete the preparation of the slurry. The mixture is then coated on a support film 60 (such as a transparent PET support film) and cured at high temperature to form a titanium dioxide silica gel film with a thickness of between 10 and 100 μm, i.e., the light extraction layer 30.

[0034] Prepare a first fluorescent adhesive layer 21 on the surface of the light emitting layer 30, such as Figure 3 (b) Specifically, a mixture of phosphor powder and silica gel is coated on the surface of the light emitting layer 30 and cured to form a double-layer film structure including the light emitting layer 30 and the first phosphor adhesive layer 21. The mass ratio of phosphor powder to silica gel is 0.5:1 to 0.9:1, and the thickness is 50 to 100 μm.

[0035] A second fluorescent adhesive layer 22 having adhesiveness is prepared on the surface of the first fluorescent adhesive layer 21. The viscosity of the second fluorescent adhesive layer 22 is greater than 10000 mPa.s. Figure 3 (c) Specifically, a mixture of phosphor and silica gel is coated on the surface of the first phosphor glue layer 21 and baked at a low temperature to form a second phosphor glue layer 22 with viscosity, which facilitates the subsequent pressing of the flip-chip LED chip 10 into the second phosphor glue layer 22. Here, viscosity specifically refers to the second phosphor glue layer 22 being in an uncured state, i.e., a state where solid and liquid coexist and cannot flow. At this time, the viscosity of the second phosphor glue layer 22 is greater than 10,000 mPa.s. The mass ratio of phosphor to silica gel is 0.5:1 to 0.9:1, and the thickness is 100 to 200 μm.

[0036] Arrange multiple flip-chip LED chips 10 on the surface of the second fluorescent adhesive layer 22 and place them in a vacuum pressing device for pressing. After the pressing is completed, the second fluorescent adhesive layer 22 is completely cured. In addition, before pressing, replace the support film 60 under the light emitting layer 30 with a high temperature resistant film 70. Figure 3 (d) shown.

[0037] A light reflecting layer 50 is prepared on the electrode side surface of the flip-chip LED chip, such as Figure 3 (e) As shown. Specifically, titanium dioxide powder and silica gel are configured in the required mass ratio (mass ratio range is 0.1:1 to 1:1) to obtain a mixture, which is then coated on the chip electrode side surface and cured. Figure 3 (e) The semi-finished product shown is ground and thinned until the electrode 40 (such as a copper column, etc.) pad is exposed, and a metal layer for welding (such as a Ni / Au layer, etc.) is plated by chemical plating. Figure 3 (f) shown.

[0038] Cut the whole piece of material and remove the high temperature film 70 to obtain a single light emitting device, such as Figure 3 (g) and Figure 3 (h) shown.

[0039] The present invention also provides a backlight module for use in liquid crystal display devices such as televisions. The backlight module comprises a base plate and a plurality of the aforementioned light-emitting devices arranged on the base plate surface. The number and arrangement of the light-emitting devices are determined based on practical needs. Because lenses are not required for the light-emitting devices, the backlight module is thinner, meeting the requirements of direct-lit backlight applications and reducing the overall thickness of the liquid crystal display device.

[0040] It should be noted that the above embodiments can be freely combined as needed. The above description is only a preferred embodiment of the present invention. It should be pointed out that those skilled in the art can make several improvements and modifications without departing from the principles of the present invention, and such improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a light-emitting device, characterized in that: include: forming a light emitting layer containing reflective particles on the surface of the supporting film; A first fluorescent adhesive layer is prepared on the surface of the light emitting layer and cured to form a double-layer film structure including the light emitting layer and the first fluorescent adhesive layer; A second fluorescent adhesive layer having adhesiveness is prepared on the surface of the first fluorescent adhesive layer, wherein the viscosity of the second fluorescent adhesive layer is greater than 10000 mPa.s; Arranging a plurality of flip-chip LED chips on the surface of the second fluorescent adhesive layer and pressing them together; curing the pressed second fluorescent adhesive layer; Preparing a light reflecting layer on the electrode side surface of the flip-chip LED chip; Cutting to obtain a single light-emitting device.

2. The method for preparing a light-emitting device according to claim 1, wherein: The light-emitting layer is prepared from titanium dioxide powder and silica gel in a certain mass ratio, and the mass ratio of the titanium dioxide powder to the silica gel is 0.1:1 to 1:

1.

3. The method for preparing a light-emitting device according to claim 1 or 2, wherein: The thickness of the light-emitting layer is 10-100 μm.

4. The method for preparing a light-emitting device according to claim 1 or 2, wherein: The thickness of the first fluorescent glue layer is 50-100 μm.

5. The method for preparing a light-emitting device according to claim 1 or 2, wherein: The thickness of the second fluorescent adhesive layer is smaller than the thickness of the flip-chip LED chip, and ranges from 100 to 200 μm.

6. The method for preparing a light-emitting device according to claim 1 or 2, wherein: After the step of preparing a light reflection layer on the electrode side surface of the flip-chip LED chip, the method further includes: grinding the reflection layer until the chip electrode is exposed.

7. A light-emitting device prepared by the method according to any one of claims 1 to 6, characterized in that: include: Flip-chip LED chips; A fluorescent adhesive layer is provided on the light-emitting side surface of the flip-chip LED chip; A light emitting layer is provided on the surface of the fluorescent glue layer on the light emitting side surface opposite to the electrode side surface of the flip-chip LED chip, wherein the light emitting layer contains light reflecting particles for reflecting back part of the light emitted from the light emitting side surface; The light reflecting layer provided on the electrode side surface of the flip-chip LED chip is used to reflect back the light emitted from the electrode side surface.

8. The light emitting device according to claim 7, wherein: The light-emitting layer is prepared from titanium dioxide powder and silica gel in a certain mass ratio, and the mass ratio of the titanium dioxide powder to the silica gel is 0.1:1 to 1:

1.

9. The light emitting device according to claim 7 or 8, characterized in that: The thickness of the light-emitting layer is 10-100 μm.

10. A backlight module, characterized in that: The invention comprises a base plate and a plurality of light emitting devices according to any one of claims 7 to 9 arranged on the surface of the base plate.

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