CN101140964A - Thin film used for enhancing light emitting efficiency of LED and film coating method - Google Patents

Abstract

When the light from LED chip sends out chips, majority of the light is returned by interface formed by the chips and exterior, which leads the lost of LED chip light. The invention provides a membrane and metallic-membrane method for improving the lighting efficiency of LED chip. The membrane is deposited on the surface of LED chip with the film coefficient of monolayer reflection reducing coating, which is made of TiO2 and the thickness is a quarter of the wavelength of the bright dipping. The membrane and metallic-membrane method is a method to deposit the membrane by electron gun evaporating. Plating the membrane on LED chip can improve the bright dipping efficiency of the LED chip by 10%.

Description

A kind of film and film plating process that is used to improve the LED light extraction efficiency

Technical field

Patent of the present invention relates to a kind of film and film plating process that is used to improve the led chip light extraction efficiency.

Technical background

The semiconductor lighting industry is risen in the whole world.In country's medium-term and long-term program for the development of science and technology strategy investigation meeting, " new century illuminating engineering " is recommended as major project, development semiconductor lighting engineering is to the new period.The light efficiency of power type white light LED has been brought up to 25～30lmPW now, enters general illumination market and really can replace incandescent lamp and fluorescent lamp, and its light efficiency need reach 150lmPW.This requires to improve constantly the quantum efficiency of LED on the one hand in the making of chip, also require simultaneously to improve light extraction efficiency in the process as far as possible encapsulation and the designing and producing of light fixture of LED.One of reason that existing LED light extraction efficiency is low is, the refractive index of led chip is higher, and the light that LED sends has quite a few light by the boundary reflection of chip with extraneous (epoxy resin) in the outgoing chip, therefore cause the loss of led chip light.

Summary of the invention

For overcoming above-mentioned shortcoming, the present invention proposes a kind of led chip film and film plating process that is used to improve light extraction efficiency, and this film can reduce the reflection of light when led chip sends, and improves the light extraction efficiency of led chip.Its basic principle is: led chip material refractive index height reaches 3.6 in the visible light refractive index.As the direct outgoing of light that fruit chip sends, then owing to boundary reflection, the luminous energy of loss has: $R={\left(\frac{3.6-1}{3.6+1}\right)}^2=31.9\%;$

The LED structure of prior art is to use epoxy encapsulation in led chip outside, but this way still can allow 20% optical energy loss, and result of calculation is as follows:

Interface one: epoxy resin, led chip:

The refractive index of epoxy resin is 1.56 at visible light.Therefore, the reflection at this interface is: $R={\left(\frac{3.6-1.56}{3.6+1.56}\right)}^2=15.6\%;$

Interface two: epoxy resin, air:

$R={\left(\frac{1.56-1}{1.56+1}\right)}^2=4.78\%;$

Therefore, the light that led chip sends through two boundary reflections after, light intensity becomes

T ₁＝(1-15.6％)(1-4.78％)＝80.3％；

The present invention plates one deck TiO outside led chip ₂(optical thickness be optical wavelength 1/4), and then add epoxy encapsulation.After the present invention's processing, the LED light extraction efficiency can improve 10%.Carry out the calculating of this structured light transmissive rate below.

Interface one: TiO ₂, led chip.

TiO ₂Refractive index be 2.2 at visible light.Therefore, the reflection at this interface is

$R={\left(\frac{3.6-2.2}{3.6+2.2}\right)}^2=5.8\%$

Interface two: epoxy resin, TiO ₂

The reflection at this interface is

$R={\left(\frac{2.2-1.56}{2.2+1.56}\right)}^2=2.8\%$

Interface three: epoxy resin, air.

$R={\left(\frac{1.56-1}{1.56+1}\right)}^2=4.78\%$

Therefore, the light that led chip sends through three boundary reflections after, light intensity becomes

T ₂＝(1-5.8％)(1-2.8％)(1-4.78％)＝87.19％。

As seen, through plating one deck TiO on led chip ₂, the more existing structure of light extraction efficiency has improved

(T ₂-T ₁)/T ₁＝9.96％≈10％。

Technical scheme of the present invention is a kind of anti-reflection film of design, is coated with this film on led chip, carries out Vacuum Package then, can make the light extraction efficiency of LED improve about 10%.

A kind of film that is used to improve the led chip light extraction efficiency is characterized in: film is to be deposited on the led chip surface, and film is a single layer anti reflective coating, material selection TiO ₂, thickness is 1/4th times of optical wavelength.

The film plating process of film is characterized in: adopt electron gun evaporation deposit film method.

Description of drawings

Below in conjunction with drawings and Examples the present invention is described in detail.

Accompanying drawing is the structural representation of LED luminescence chip of the present invention.

1.LED luminescence chip, 2. single layer anti reflective coating.

Embodiment

Add plating single layer anti reflective coating 2 on the surface of LED luminescence chip 1, single layer anti reflective coating material selection TiO ₂, film thickness is 1/4 times of optical wavelength.Film plating process is taked electron gun evaporation deposit film method.

(1) led chip is cleaned up;

(2) chip is put into coating machine, put into TiO ₂Target;

(3) be evacuated to 2 * 10 ^-2Pa, the beginning evaporation;

(4) use optical monitor, treat TiO on the led chip ₂Optical thickness closes plate washer to 1/4 of supervisory wavelength, stops evaporation.

The present invention adds the plating anti-reflection film on the surface of LED luminescence chip, can improve the light emission rate about 10% of LED luminescence chip.Can be widely used in the making of all kinds of luminescence chips.

Claims (2)

1. film that is used to improve the led chip light extraction efficiency, it is characterized in that: film is to be deposited on the led chip surface, and film is a single layer anti reflective coating, material selection TiO ₂, thickness is 1/4th times of optical wavelength.

2. a coating thin film method that is used to improve the led chip light extraction efficiency is characterized in that: adopt electron gun evaporation deposit film method.

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