WO2012083776A1

WO2012083776A1 - Photoresist composition, led device and method of preparing the same

Info

Publication number: WO2012083776A1
Application number: PCT/CN2011/082556
Authority: WO
Inventors: Guobing HU
Original assignee: Byd Company Limited
Priority date: 2010-12-23
Filing date: 2011-11-21
Publication date: 2012-06-28
Also published as: CN102540721A; CN102540721B

Abstract

A photoresist composition, a method of forming a fluorescent layer on a surface of an LED chip, a method of preparing an LED chip and an LED device prepared therefrom may be provided. The photoresist may comprise: about 20 wt% to about 40 wt% of a resin; about 20 wt% to about 30 wt% of a monomer corresponding to the resin; about 1 wt% to about 16 wt% of a photosensitizer; and about 24 wt% to about 50 wt% of a solvent, in which the resin is at least one selected from the group consisting of methacrylic resin, silicone modified acrylic resin, epoxy acrylic resin, polyurethane acrylic resin, polyester acrylic resin, polyether acrylic resin, and poly(propyl acrylate) resin.

Description

PHOTORESIST COMPOSITION, LED DEVICE AND METHOD

OF PREPARING THE SAME

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and benefits of Chinese Patent Application No. 201010602414.3, filed with the State Intellectual Property Office, P. R. C. on December 23, 2010, the entire content of which is incorporated herein by reference.

FIELD

The present disclosure relates to the photoelectric field, more particularly to a photoresist composition, an LED device, a method of forming a fluorescent layer on a surface of an LED chip surface and a method of preparing an LED device.

BACKGROUND

An LED, i.e. Light-Emitting Diode, is a light-emitting device, which may directly convert electric energy into visible light energy and radiation energy. The LED has the advantages of high efficiency, low power consumption, long lifespan, high light-emitting quality, pure light color, high reliability, low driving voltage, and firm structure etc. Light-induced conversion of exciting fluorescent powders using an LED chip is one of the most commonly used methods of obtaining white light. For example, a white light LED device is mainly formed by coating yellow fluorescent powders on a blue light LED chip. Therefore, the structure, the thickness, and the properties of the fluorescent layer may have a large influence on the performance of an LED lamp.

A photoresist is mainly used to mix with the fluorescent powders so that the fluorescent powders may be uniformly dispersed. Currently, acrylic resin is mainly used as the photoresist in the market. However, because acrylic resin has low viscosity, the thick fluorescent layer on the chip surface of the LED chip is hard to form, and acrylic resin is hard to uniformly disperse in the photoresist.

Presently, an packaging process is one of the most commonly used methods of manufacturing the LED lamp and, mainly, comprises steps of, firstly, mixing the fluorescent powders with silicone resin or epoxy resin evenly to form a mixture and then dispensing the mixture on the surface of the LED chip. The fluorescent layer formed by the packaging process may have uneven thickness. For example, the thickness of the center of the fluorescent layer is greater than that of around edges of the fluorescent layer, resulting yellow lights converted by the fluorescent powders at the center of the fluorescent layer of the LED lamp being obviously more than that at the edges of the fluorescent layer. Thus, white lights emitted from the LED lamp are uneven, and uneven yellow or blue light spots may appear locally on the LED lamp. In addition, because the amount of the mixture on each LED chip is difficult to control, the LED lamps fabricated in the same batch may have different color temperature. Therefore, the LED lamps may have poor consistency, which may limit their application in the field having high requirements for the consistency of the color temperature.

SUMMARY

In viewing thereof, the present disclosure is directed to solve at least one of the problems existing in the prior art. Accordingly, a photoresist composition may need to be provided, which may have higher viscosity. Further, a method of forming a fluorescent layer on a surface of an LED chip and a method of preparing an LED chip, which may provide the LED chip with the fluorescent layer having substantially even thickness as well as enhanced consistency of the color temperature. In addition, an LED device made therefrom may also need to be provided accordingly.

According to an aspect of the present disclosure, a photoresist composition may be provided. The photoresist may comprise: about 20 wt to about 40 wt of a resin; about 20 wt to about 30 wt of a monomer corresponding to the resin; about 1 wt to about 16 wt of a photosensitizer; and about 24 wt to about 50 wt of a solvent, in which the resin is at least one selected from the group consisting of methacrylic resin, silicone modified acrylic resin, epoxy acrylic resin, polyurethane acrylic resin, polyester acrylic resin, polyether acrylic resin, and poly(propyl acrylate) resin.

According to another aspect of the present disclosure, a method of forming a fluorescent layer on a surface of an LED chip may be provided. The method may comprise the steps of: mixing fluorescent powders and a photoresist composition as descried hereinabove to form a mixture, then coating the mixture on the chip surface to form a fluorescent coating layer; exposing and developing the fluorescent coating layer, then heating to form a fluorescent layer surface; and coating an antireflection agent on the fluorescent layer to form an antireflection layer. According to still another aspect of the present disclosure, a method of preparing an LED chip may be provided. The method may comprise the steps of: coating a mixture of fluorescent powders and a photoresist composition as described hereinabove on a surface of the LED chip device to form a fluorescent coating layer; and exposing and developing the fluorescent coating layer, then heating to form a fluorescent layer on the surface .

According to yet another aspect of the present disclosure, an LED device may be provided. The LED device may comprise a chip with at least a surface being coated with fluorescent layer. The fluorescent layer is formed by coating a mixture of fluorescent powders and the aforementioned photoresist composition on a surface of the chip of the LED device to form a fluorescent coating layer, exposing and developing the fluorescent coating layer, and then heating to form the fluorescent layer on the surface of the chip.

With the photoresist composition according to an embodiment of the present disclosure, by selecting the resin type and controlling the amounts of the resin and the monomer corresponding to the resin within suitable ranges, the photoresist composition may have appropriate viscosity, and the fluorescent powders may be well dispersed in the photoresist composition. Thus, a fluorescent layer with a thickness of about 10 μιη to about 100 μιη may be formed on the surface of the LED chip accordingly.

With the method of the present disclosure, the photoresist composition may have appropriate viscosity, and the fluorescent powders may be evenly dispersed in the photoresist composition. In addition, by forming the fluorescent layer on the surface of the LED chip via coating, the amount of fluorescent powders coated on the surface of the LED chip may be controlled, and the fluorescent layer may have an even thickness, so that the LED device may emit even white light with high consistency of color temperature.

Additional aspects and advantages of the embodiments of the present disclosure will be given in part in the following descriptions, become apparent in part from the following descriptions, or be learned from the practice of the embodiments of the present disclosure.

DETAILED DESCRIPTION

Reference will be made in detail to embodiments of the present disclosure. The embodiments described herein are explanatory, illustrative, and used to generally understand the present disclosure. The embodiments shall not be construed to limit the present disclosure. According to an aspect of the present disclosure, a photoresist composition is provided. The photoresist composition may comprise: about 20 wt to about 40 wt of a resin; about 20 wt to about 30 wt of a monomer corresponding to the resin; about 1 wt to about 16 wt of a photosensitizer; and about 24 wt to about 50 wt of a solvent. The resin may be at least one selected from the group consisting of: methacrylic resin, silicone modified acrylic resin, epoxy acrylic resin, polyurethane acrylic resin, polyester acrylic resin, polyether acrylic resin, and poly(propyl acrylate) resin.

It has been found by the inventors that, according to an embodiment of the present disclosure, by selecting the type of the resin described above, the fluorescent powders may be well dispersed in the photoresist composition. In addition, the viscosity of the photoresist composition may be controlled by adjusting the amounts of the resin and the monomer corresponding to the resin in the photoresist composition, so that a fluorescent layer with a thickness of 10 μιη to about 100 μιη may be formed on the surface of the LED chip. In one embodiment, in some embodiments, in the photoresist composition, the amount of the resin may range from about 20 wt to about 40 wt , the amount of the monomer may range from about 20 wt to about 30 wt , the amount of the photosensitizer may range from about 1 wt to about 16 wt , and the amount of the solvent may range from about 24 wt to about 50 wt .

In one embodiment, in the photoresist composition, the amount of the resin ranges from about 30 wt to about 40 wt , and the amount of the monomer corresponding to the resin ranges from about 20 wt% to about 25 wt%.

In some embodiments, the resin may be an acrylic resin. In one embodiment, the resin may be at least one selected from the group consisting of methacrylic resin, silicone modified acrylic resin, epoxy acrylic resin, polyurethane acrylic resin, polyester acrylic resin, polyether acrylic resin, and poly(propyl acrylate) resin.

In some embodiments, the photosensitizer may be a quinone azide compound known in the art. For example, the photosensitizer may be at least one selected from the group consisting of azodiisobutyronitrile (AIBN), 1,2-quinone diazide-4- sulfonate, 1,2-quinone diazide-5-sulfonate, and 1,2-quinone diazide-6-sulfonate.

In one embodiment, the solvent may be at least one selected from the group consisting of propylene glycol monomethyl ether acetate, cyclohexanone, and ethyl lactate.

According to another aspect of the present disclosure, a method of forming a fluorescent layer on a surface of an LED chip is provided. The method may comprise the steps of: mixing fluorescent powders and the aforementioned photoresist composition to form a mixture, then coating the mixture on the surface of the LED chip to form a fluorescent coating layer; exposing and developing the fluorescent coating layer, then heating to form a fluorescent layer on the surface of the LED chip; and coating an antireflection agent on the fluorescent layer to form an antireflection layer.

In some embodiments, the fluorescent powders and the photoresist composition are mixed evenly to form the mixture, and then the mixture is coated on the surface of the LED chip, thus forming the fluorescent coating layer on the surface of the LED chip. In one embodiment, about 100 weight parts of fluorescent powders and about 200 weight parts to about 1000 weight parts of the photoresist composition are mixed to form the mixture.

In one embodiment, before the fluorescent coating layer is formed, the surface of the LED chip may be coated with tackifier to form a tackifying layer on the chip surface. The tackifying layer may be used for enhancing the adhesive force between the chip surface and the fluorescent coating layer formed in subsequent steps, thus preventing the fluorescent coating layer from peeling off the surface of the LED chip in use. The taktifier may be any silane coupling agent known in the art, such as HMDS (hexamethyldisilazane), KH-560, KH-570, or KH-550. The thickness of the tackifying layer should not be too large, in order to avoid the reduction of the blue light transmittance of the LED chip. Therefore, the amount of the tackifier coated on the chip surface should not be too large. In one embodiment, the LED chip may be bathed or immersed in a tackifier spray, thus coating the tackifier on the surface of the LED chip to form the tackifying layer.

In one embodiment, the fluorescent coating layer may be exposed and developed on the surface of the LED chip. The exposing and developing steps are known in the art. For example, the chip surface coated with the fluorescent coating layer may be exposed to ultraviolet light. The region of the fluorescent coating layer that has been exposed to ultraviolet light may be remained on the surface of the LED chip, and the remaining region of the fluorescent coating layer that has not been exposed to ultraviolet light may be removed during the developing. Therefore, the fluorescent coating layer with a desired pattern may be formed on the surface of the LED chip. In one embodiment, the exposing step may be performed with an exposure dose of about 100 mj/cm 2 to about 500 mj/cm². After the developing step, the fluorescent layer may be heated to form a fluorescent layer, thus improving the adhesive force between the surface of the LED chip and the fluorescent layer. In one embodiment, the heating step may be performed at a temperature about 100°C to about 150°C for about 30 minutes to about 50 minutes.

In one embodiment, an antireflection agent may be coated on the fluorescent layer and, then dried to form an antireflection layer. The antireflection agent may be an isopropanol solution comprising a silane resin, and the amount of the silane resin in the antireflection agent may range from about 1 wt to about 3 wt . The antireflection layer may improve the transmittance of visible light, especially yellow light, thus improving the transmittance of yellow light converted by the fluorescent powders. Therefore, the amount of the fluorescent powders may be reduced, thus reducing the cost and the scattering effect on the light caused by the fluorescent powders. The antireflection layer covering the fluorescent layer may have high hardness and may be water-proof and moisture-proof, thus effectively protecting the fluorescent layer.

In one embodiment, the fluorescent layer may have a thickness of about 10 μιη (microns) to about 100 μιη. In one embodiment, the antireflection layer may have a thickness of about 1 μιη to about 3 μιη.

In some embodiments, in the steps of coating the mixture on the surface of the LED chip or on the tackifying layer and coating the antireflection agent on the fluorescent layer, the coating method may be any of those known in the art. For example, the coating method may be at least one selected from the group consisting of spin coating, brush coating, dip-coating, spraying, and screen printing etc. In one embodiment, the mixture of fluorescent powders and the photoresist composition may be coated on the surface of the LED chip or on the tackifying layer by screen printing, and the antireflection agent may be coated on the fluorescent layer by spraying. A uniform fluorescent layer may be formed on the surface of the LED chip or on the tackifying layer by coating, so that the LED chip may emit more uniform colors and have better color temperature consistency in comparison with the packaging technique in the prior art.

According to still another aspect of the present disclosure, a method of preparing an LED device may be provided. The method may comprise the steps of: coating a mixture of fluorescent powders and the aforementioned photoresist composition on a surface of a chip of the LED device to form a fluorescent coating layer; and exposing and developing the fluorescent coating layer, then heating to form a fluorescent layer on the surface of the LED chip.

In one embodiment, the method further comprises a step of: coating an antireflection agent on the fluorescent layer to form an antireflection layer.

In one embodiment, the method further comprises a step of: coating tackifier on the chip surface to form a tackifying layer before the fluorescent coating layer is formed.

In one embodiment, the tackifier may be a silane coupling agent.

In one embodiment, the LED chip coated with the fluorescent coating layer is exposed to ultraviolet light with an exposure dose of about 100 mj/cm² to about 500 mj/cm² in the exposing step.

In one embodiment, the heating step is performed at a temperature of about 100°C to about 150°C for about 30 minutes (min) to about 50 minutes.

In one embodiment, the antireflection agent may be an isopropanol solution comprising a silane resin, and the amount of the silane resin in the antireflection agent ranges from about 1 wt to about 3 wt .

According to yet another aspect of the present disclosure, an LED device comprising a chip with at least a surface coated with a fluorescent layer may be provided. The fluorescent layer is formed by coating a mixture of fluorescent powders and the aforementioned photoresist composition on the surface of the chip to form a fluorescent coating layer, exposing and developing the fluorescent coating layer, then heating to form the fluorescent layer on the surface of the chip.

The process of manufacturing an LED lamp from the LED device may any of those known in the art, thus the detailed description thereof is omitted here for clarity purpose. In some embodiments, additional steps including die bonding, wire bonding, disporting, and choosing etc. may be performed before or after the formation of the antireflection layer.

Hereinafter, the present disclosure will be described in detail with reference to the following examples.

Example 1

The method of preparing an LED chip comprises the following steps.

1) Preparation of photoresist composition SI

The photoresist composition SI was prepared by: about 30 wt of methacrylic resin, about 30 wt of methacrylic monomer, about 16 wt of photosensitizer AIBN, and about 24 wt of propylene glycol monomethyl ether acetate, based on the total weight of the photoresist composition SI. 2) Formation of tackifying layer

The LED chip was placed in a tackifier HMDS spray to form a tackifying layer on the surface of the LED chip.

3) Formation of fluorescent coating layer

About 100 weight parts of fluorescent powders and about 500 weight parts of the photoresist composition prepared in step 1) were mixed uniformly to form a mixture, and the mixture was coated on the tackifying layer formed in step 2) by screen printing, to form a fluorescent coating layer on the tackifying layer.

4) Formation of fluorescent layer

The LED chip was exposed to ultraviolet light with an exposure dose of about 150 mj/cm . Then, the fluorescent coating layer is developed, then heated in an oven at a temperature of about 120°C for about 40 min to form a fluorescent layer on the tackifying layer. The thickness of the fluorescent layer was about 30 μιη.

5) Formation of antireflection layer

An isopropanol solution comprising a silane resin was sprayed on the fluorescent layer to form an antireflection layer. The amount of the silane resin in the isopropanol solution was about 1 wt . After dried at room temperature, the antireflection layer had a thickness of about 1 μιη. The LED chip formed in the aforementioned steps was labeled as Sll.

Example 2

The method of preparing an LED chip in Example 2 was substantially the same as that in Example 1, with the following exception.

1) Preparation of photoresist composition S2

The photoresist composition S2 was prepared by: about 15 wt of poly(propyl acrylate) resin, about 15 wt of polyester acrylic resin, about 10 wt of poly (propyl acrylate) monomer, about 10 wt of polyester acrylic monomer, about 10 wt of 1,2-quinone diazide-4- sulfonate, and about 40 wt of a mixed solvent of propylene glycol monomethyl ether acetate and cyclohexanone (with a volume ratio of 1: 1), based on the total weight of the photoresist composition S2.

The LED chip formed in the aforementioned steps was labeled as S22.

Example 3

The method of preparing an LED chip comprises the following steps.

1) Preparation of photoresist composition S3 The photoresist composition S3 was prepared by: about 30 wt of methacrylic resin, about 30 wt of methacrylic monomer, about 16 wt of photosensitizer AIBN, and about 24 wt of propylene glycol monomethyl ether acetate, based on the total weight of the photoresist composition S3.

2) Formation of fluorescent coating layer

About 100 weight parts of fluorescent powders and about 1000 weight parts of the photoresist composition prepared in step 1) were mixed uniformly to form a mixture, and the mixture was coated on the surface of the LED chip by screen printing, to form a fluorescent coating layer on the surface of the LED chip.

3) Formation of fluorescent layer

The LED chip was exposed to ultraviolet light with an exposure dose of about 300 mj/cm . Then, the fluorescent coating layer was developed, and then heated in an oven at a temperature of about 120°C for about 40 min to form a fluorescent layer on the chip surface. The thickness of the fluorescent layer was about 80 μιη.

4) Formation of antireflection layer

An isopropanol solution comprising a silane resin was sprayed on the fluorescent layer to form an antireflection layer. The amount of the silane resin in the isopropanol solution was about 2 wt . After drying at room temperature, the antireflection layer had a thickness of about 2 μιη. The LED chip formed in the aforementioned steps was labeled as S33.

Example 4

The method of preparing an LED chip in Example 4 was substantially the same as that in Example 1, with the following exception.

3) Formation of fluorescent coating layer

About 100 weight parts of fluorescent powders and about 200 weight parts of the photoresist composition prepared in step 1) were mixed uniformly to form a mixture, and the mixture was coated on the tackifying layer formed in step 2) by screen printing, to form a fluorescent coating layer on the tackifying layer.

The LED chip formed in the aforementioned steps was labeled as S44.

Example 5

The method of preparing an LED chip in Example 5 was substantially the same as that in Example 1, with the following exception. 4) Formation of fluorescent layer

The LED chip was exposed to ultraviolet light with an exposure dose of about 200 mj/cm . Then, the fluorescent coating layer is developed, and then heated in an oven at a temperature of about 150°C for about 50 min to form a fluorescent layer on the tackifying layer. The thickness of the fluorescent layer was about 60 μιη.

The LED chip formed in the aforementioned steps was labeled as S55.

Test

The LED chips S11-S55 were subjected to the following tests, and the test results were shown in Table 1 accordingly.

1) Hardness

The hardness of the antireflection layer on the surface of each of the LED chips S11-S55 was tested according to a method disclosed in GB/6739T. On a pencil hardness tester, the surface of the tested LED chip was scribed with a Mitsubishi pencil under a force of 1 kg for three times. If the surface of the antireflection layer has no scratches, it was recorded as OK. Otherwise, it was recorded as NO.

2) Adhesive force

The surface of the tested LED chip was scribed with a sharp knife, thus forming 100 square grids each with a size of about 1mm x 1 mm on the surface of the LED chip. The number of the square grids in which the fluorescent layer peeled off was recorded as Nl. A transparent adhesive tape with a width of about 24 mm was closely pasted on the surface of the LED chip having square grids. After 5 min, the tape was removed under a force vertical to the surface of the LED chip, and the number of the square grids in which the fluorescent layer shed was recorded as N2. The adhesion coefficient was calculated according to the formula of: Z = [(100-N1-N2)/100] x 100%.

Table 1

S55 60 μηι 1 μηι OK 95%

As shown in Table 1, a fluorescent layer having a thickness ranging from about 30 μιη to about 80 μιη may be formed on the surface of the LED chip, and the viscosity of the photoresist composition is appropriate, so that the fluorescent powders may be well dispersed in the photoresist composition. By comparing the test results of the LED chips Sll, S22, S44 and S55 with the test results of the LED chip S33, it is indicated that the formation of a tackifying layer on the chip surface of the LED chip may greatly improve the adhesive force between the fluorescent layer and the surface of the LED chip.

Although explanatory embodiments have been shown and described, it would be appreciated by those skilled in the art that changes, alternatives, and modifications all falling into the scope of the claims and their equivalents may be made in the embodiments without departing from spirit and principles of the present disclosure.

Claims

WHAT IS CLAIMED IS:

1. A photoresist composition, comprising:

about 20 wt to about 40 wt of a resin;

about 20 wt to about 30 wt of a monomer corresponding to the resin;

about 1 wt to about 16 wt of a photosensitizer; and

about 24 wt to about 50 wt of a solvent, wherein the resin is at least one selected from the group consisting of methacrylic resin, silicone modified acrylic resin, epoxy acrylic resin, polyurethane acrylic resin, polyester acrylic resin, polyether acrylic resin, and poly(propyl acrylate) resin.

2. The photoresist composition according to claim 1, wherein in the photoresist composition, the amount of the resin ranges from about 30 wt to about 40 wt , and the amount of the monomer ranges from about 20 wt to about 25 wt .

3. The photoresist composition according to claim 1 or 2, wherein the photosensitizer is a quinone azide compound.

4. The photoresist composition according to claim 1 or 2, wherein the solvent is at least one selected from the group consisting of propylene glycol monomethyl ether acetate, cyclohexanone, and ethyl lactate.

5. A method of forming a fluorescent layer on a surface of an LED chip, comprising the steps of:

mixing fluorescent powders and a photoresist composition according to any one of claims 1-4 to form a mixture, then coating the mixture on the surface to form a fluorescent coating layer;

exposing and developing the fluorescent coating layer, then heating to form a fluorescent layer on the surface of the LED chip; and

coating an antireflection agent on the fluorescent layer to form an antireflection layer.

6. The method according to claim 5, further comprising a step of:

coating a tackifier on the surface of the LED chip to form a tackifying layer before the fluorescent coating layer is formed.

7. The method according to claim 6, wherein the tackifier is a silane coupling agent.

8. The method according to claim 5, wherein about 100 weight parts of fluorescent powders and about 200 weight parts to about 1000 weight parts of the photoresist composition are mixed to form the mixture.

9. The method according to claim 5, wherein the surface coated with the fluorescent coating layer is exposed to ultraviolet light with an exposure dose of about 100 mj/cm to about 500 mj/cm in the exposing step.

10. The method according to claim 5, wherein the heating step is performed at a temperature of about 100°C to about 150°C for about 30 min to about 50 min.

11. The method according to claim 5, wherein the antireflection agent is an isopropanol solution comprising a silane resin, and the amount of the silane resin in the antireflection agent ranges from about 1 wt to about 3 wt .

12. The method according to claim 5, wherein the fluorescent layer has a thickness of about 10 μιη to about 100 μιη, and the antireflection layer has a thickness of about 1 μιη to about 3 μιη .

13. A method of preparing an LED chip, comprising the steps of:

coating a mixture of fluorescent powders and a photoresist composition according to any one of claims 1-4 on a surface of the LED chip to form a fluorescent coating layer; and

exposing and developing the fluorescent coating layer, then heating to form a fluorescent layer on the surface of the LED chip.

14. The method according to claim 13, further comprising a step of:

15. The method according to claim 14, further comprising a step of:

coating tackifier on the surface of the LED chip to form a tackifying layer before forming the fluorescent coating layer.

16. The method according to claim 15, wherein the tackifier is a silane coupling agent.

17. The method according to claim 13, wherein the surface of the LED chip coated with the fluorescent coating layer is exposed to ultraviolet light with an exposure dose of about 100 mj/cm to about 500 mj/cm² in the exposing step.

18. The method according to claim 13, wherein the heating step is performed at a temperature of about 100°C to about 150°C for about 30 minutes to about 50 minutes.

19. The method according to claim 14, wherein the antireflection agent is an isopropanol solution comprising a silane resin, and the amount of the silane resin in the antireflection agent ranges from about 1 wt to about 3 wt .

20. An LED device, comprising a chip with at least a surface being coated with a fluorescent layer, wherein the fluorescent layer is formed by: coating a mixture of a fluorescent powder and a photoresist composition according to any one of claims 1-4 on the surface of the chip to form a fluorescent coating layer,

exposing and developing the fluorescent coating layer, and then heating to form the fluorescent layer on the surface of the chip.