Display substrate with bragg reflection unit for each of the display units of at least three primary colors

The present invention relates to the technical field of display, and provides a display substrate and a preparing method thereof which can solve the problem of lower light-emitting efficiency of the display substrate in the prior art. The display substrate of the present invention comprises a plurality of display units of at least two different colors. The display substrate further comprises a plurality of bragg reflection units in different regions corresponding to respective display units, each bragg reflection unit comprises first structural layer and second structural layer which are alternately stacked with each other and have different refractive indexes; thickness of each of the first and second structural layers is ¼n wavelength of incident light from corresponding display unit, wherein n is refractive index of the first or the second structural layer. The display substrate of the present invention has higher light-emitting efficiency and is applicable to full-color display.

This is a National Phase Application filed under 35 U.S.C. 371 as a national stage of PCT/CN2014/078504, filed May 27, 2014, an application claiming benefit from Chinese Patent Application No. 201310729311.7 filed on Dec. 25, 2013, the content of each of which is hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to the technical field of display, and particularly to a display substrate and a preparing method thereof.

BACKGROUND OF THE INVENTION

Bragg reflection structure (i.e. Distributed Bragg Reflector, DBR) is formed generally by alternately stacking high-refractive index material layers and low-refractive index material layers. It is required that the material should not absorb visible light. A DBR for improving light-emitting efficiency of semiconductor microcavity light-emitting diode is described in Chinese Paten Application CN 101478025A.

In the technical field of display, liquid crystal display dependent on normal light-emitting diode (LED) backlight has been used widely. In addition, Organic Light-Emitting Diode (OLED) device is paid more and more attention due to its advantages of uniform luminance, flicker free, sufficient safeness for environment, and so on. However, both of normal LED and OLED have lower light-emitting efficiency. For example, owing to influences of absorption, loss, interface scattering and reflection, light-emitting efficiency of OLED is only about 20%. Thus, it is an important research subject in the display technical field to improve light-emitting efficiency.

SUMMARY OF THE INVENTION

An object of the invention is to solve the problem that the display substrate in the prior art has low light-emitting efficiency, and provides a display substrate which has a high light-emitting efficiency and can achieve a full-color display, and a preparing method thereof.

The solution of the invention for solving the above problem is a display substrate, comprising a plurality of display units of at least two different colors, wherein, the display substrate further comprises a plurality of bragg reflection units located in different regions corresponding to respective display units, each bragg reflection unit comprises a first structural layer and a second structural layer which are alternately stacked with each other and have different refractive indexes; thickness of the first structural layer is ¼n1of wavelength of incident light from corresponding display unit, wherein n1is refractive index of the first structural layer; and thickness of the second structural layer is ¼n2of wavelength of incident light from corresponding display unit, wherein n2is refractive index of the second structural layer.

The display substrate of the invention has the Bragg reflection units in which the thicknesses of the first and second structural layers have the above characteristics, thus can improve the light-emitting efficiency of incident light and achieve a full-color display.

Preferably, the refractive index of the first structural layer is smaller than that of the second structural layer, and the incident light enters into the bragg reflection unit from the second structure layer.

Preferably, each bragg, reflection unit comprises at least two first structural layers and two second structural layers.

Preferably, material of the first structural layer is SiO2.

Preferably, material of the second structural layer is SiNxor TiO2.

Preferably, the display units include three types of display units, each type of which has a color selected from three primary colors.

More preferably, the three primary colors are red, green and blue,

Preferably, the display units each comprise an organic light-emitting device emitting corresponding color light, and the bragg reflection units are disposed nearer to light-emitting side of the display substrate than the organic light-emitting devices.

Preferably, the display units each comprise a color filter of corresponding color, and the bragg reflection units are disposed nearer to light-emitting side of the display substrate than the color filters.

Another object of the invention is to provide a preparing method of display substrate which has a high light-emitting efficiency and can achieve a full-color display the method comprising following steps of:

1) forming a first structural layer, wherein

depositing a first material layer on a substrate, and forming a plurality of patterns of first structural layer n different regions by patterning process, wherein thickness of each of the patterns of first structural layer in a respective region is ¼n1of wavelength of incident light from a display unit corresponding to this region, wherein n1is refractive index of the first structural layer;

2) forming a second structural layer, wherein

depositing a second material layer on the first structural layer, and forming a plurality of patterns of second structural layer located in the different regions by patterning process, wherein thickness of each of the patterns of second structural layer in a respective reunion as ¼n2of wavelength of incident light horn a display unit corresponding to this region, wherein is refractive index of the second structural layer; and

3) repeating the steps 1) and 2).

Preferably, the step of forming the patterns of first structural layer by patterning process comprises:

forming photoresist which has different thicknesses at positions in the different. regions on the first material layer respectively and

performing plasma etching on the first material layer with photoresist formed. thereon so as to form a plurality of the patterns of first structural layer in the different regions such that the thickness of each of the patterns of first structural layers is ¼n1of wavelength of incident light from a display unit corresponding to the region in which this pattern of first structural layer is located, wherein n1is refractive index of the first structural layer.

Preferably, the step of forming the patterns of second structural layer by patterning process comprises:

forming photoresist which has different thicknesses at positions in the different regions on the second material layer respectively; and

performing plasma etching on the second material layer with photoresist formed thereon so as to form a plurality of the patterns of second structural layer in the different regions such that the thickness of each of the patterns of second structural layer is ¼n2of wavelength of incident light from a display unit corresponding to the region in which this patterns of second structural layer is located, wherein n2is refractive index of the second structural layer.

The present invention provides a display substrate and a preparing method thereof. The display substrate of the present invention comprises a plurality of display units of at least two different colors. The display substrate further comprises a plurality of bragg reflection units in different regions corresponding to respective display units, each bragg reflection unit comprises a first structural layer and a second structural layer which are alternately stacked with each other and have different refractive indexes; thickness of each of the first and second structural layers is ¼n of wavelength of incident light from corresponding display unit, wherein n is refractive index of the first or the second structural layer. The display substrate of the present invention has a higher light-emitting efficiency and is applicable to a full-color display.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments in order that a skilled person in the art can understand the solution of the invention better.

As shown inFIG. 1, the present embodiment provides a display substrate which comprises a plurality of display units6of at least two different colors. The display substrate further comprises a plurality of bragg reflection units7which are located in different regions corresponding to respective display units6. Each bragg reflection unit7comprises a first structural layer1and a second structural layer2which are alternately stacked with each other and have different refractive indexes. Thickness of the first structural layer1is ¼n1of wavelength of incident light from a display unit corresponding to the region in which this first structural layer1is located, wherein n1is refractive index of the first structural layer1; and thickness of the second structural layer2is ¼n2of wavelength of incident light from a display unit corresponding to the region in which this second structural layer2is located, wherein n2is refractive index of the second structural layer2When preparing such display substrate, the bragg reflection units7are aligned with the substrate on which the display units6are disposed so as to form a cell.

Preferably, in each bragg reflection unit7, the refractive index of the first structural layer1is smaller than that of the second structural layer2, in which the incident light enters into the bragg reflection unit7from the second structure layer2. That is, in the direction of the incident light, the second structural layer2is the outermost layer, which is nearest to the incident light side, in each bragg reflection unit7.

Preferably, each bragg reflection unit7comprises at least two first structural layers1and two second structural layers2. In the example as shown inFIG. 1, there are three first structural layers1and three second structural layers2alternately stacked. Each bragg reflection unit7may be constructed by alternately stacking more first structural layers1and more second structural lavers2, which can obtain a higher luminance of emitting light.

Preferably, material of the first structural layer1is SiO2.

Preferably, material of the second structural layer2is SiNxor TiO2.

Preferably, the display units6include three types of display units, each type of which has a color selected from three primary colors. The three primary colors are red, green and blue.

Preferably, the different regions correspond to the display units6in one-to-one manner.

Preferably, the display substrate may be a liquid crystal display substrate, and display units6comprise color filters with corresponding colors respectively. Preferably, the color filters are three-primary-color filters for full-color display, and more preferably, are red (R), green (CO and blue (B) color filters. Obviously, other type of three primary colors may be used. The bragg reflection units7are disposed nearer to light-emitting side of the display substrate than the color filters. That is, light emitting from R, G, and B color filters passes through the bragg reflection units7corresponding respectively to R, G, and B color filters and emits out. Emitting light having passed through the bragg reflection units7has advantages of concentrative direction, enhanced luminance, improved efficiency gain, and reduced light loss.

Preferably, the display substrate may be an organic light-Emitting display substrate, and the display units6may be the organic light-Emitting devices that emit corresponding color light. Preferably, the organic light-Emitting devices emit light of three primary colors for full-color display. More preferably, three primary colors are red (R), green (G) and blue (B). Obviously, other type of three primary colors may be used. The bragg reflection wins7are disposed nearer to light-emitting side of the display substrate than the organic light-Emitting devices. That is, light emitting from the organic light-Emitting devices passes through the bragg reflection units corresponding respectively to R, G, and B organic light-Emitting devices and emits out. Emitting light having passed through the bragg reflection units has advantages of concentrative direction, enhanced luminance, improved efficiency gain, and reduced light loss.

The present invention further provides a preparing method of the above display substrate comprising following steps of:

1) forming a first structural layer, wherein

depositing a first material layer on a substrate, and forming a plurality of patterns of first structural layer in different regions by patterning process, wherein thickness of each of the patterns of first structural layer in a respective region is ¼n1of wavelength of incident light from a display unit corresponding to this region, wherein n1is refractive index of the first structural layer;

2) forming a second structural layer, wherein

depositing a second material layer on the first structural layer, and forming a plurality of patterns of second structural layer in the different regions by patterning process, wherein thickness of each of the patterns of second structural layer in a respective region is ¼n2of wavelength of incident light from a display unit corresponding to this region, wherein n, is refractive index of the second structural layer; and

3) repeating the steps and 2).

Preferably, the step of forming the patterns of first structural layer by patterning process comprises:

forming photoresist which has different thicknesses at positions in the different regions on the first material layer respectively; andperforming plasma etching on the first material layer with photoresist formed thereon so as to form a plurality of the patterns of first structural layer in the different regions such that the thickness of each of the patterns of first structural layer is ¼n1of wavelength of incident light from a display unit corresponding to the region in which this first structural layer is located, wherein in is refractive index of the first structural layer.

Preferably, the step of forming the patterns of second structural layer by patterning process comprises:

forming photoresist which has different thicknesses at positions in the different regions on the second material layer respectively; and

performing plasma etching on the second material layer with photoresist formed thereon so as to form a plurality of the patterns of second structural layer in the different regions such that the thickness of each of the patterns of second structural layer is ¼n2of wavelength of incident light from a display unit corresponding to the region in which this second structural layer is located, wherein n2is refractive index. of the second structural layer.

The foregoing preparing method of display substrate will be described below in conjunction with a specific application example.

The foregoing preparing method of display substrate may comprise following steps of:

1) Forming a First Structural Layer

1.1 Depositing a Layer of Material with Low Refractive Index

As shown inFIG. 2, the material with low refractive index of the first structural layer1in the present embodiment is SiO2. A SiO2layer is deposited on a substrate3, thickness of the SiO2layer being ¼nSiO2of wavelength of red light, wherein nSiO2is refractive index of the SiO2layer. The SiO2layer may be deposited by any known deposition method, for example, Chemical Vapor Deposition.

1.2 Exposing and Developing Photoresist

As shown inFIG. 3, positive photoresist5is applied with a thickness of 2.0 μm on the SiO2layer by spinning. The photoresist5applied by spinning is exposed by using a prepared mask. Light exposure is controlled in regions corresponding to display units of different colors such that the thickness of the photoresist5is different in respective regions after developing. For example, it is assumed that the display units have three colors of red (R), green (G) and blue (B). Light exposures in regions corresponding to the display units of the three colors are controlled such that, when the regions are developed, photoresist5in region corresponding to display units of R color is not removed, photoresist5in region corresponding to display units of G color is partially removed, and photoresist5in region corresponding to display units of B color is completely removed. In this way, a pattern of photoresist with different thicknesses in different regions which corresponds respectively to the display units of R, and B colors as shown inFIG. 3is obtained.

As shown inFIG. 4, the above-mentioned SiO2layer, which is formed as a plurality of patterns of photoresist having different thicknesses in different regions which correspond respectively to the display units of R, G, and B colors, is etched by plasma etching process. Etching speed is controlled with respect to respective regions so as to obtain an etching result capable of satisfying the following three conditions simultaneously:

photoresist5in region corresponding to display units of R color is completely removed, and the SiO2layer is substantially not etched;

photoresist5in region corresponding to display units of G color is completely removed, and the SiO2layer is etched such that thickness of remaining SiO2layer is ¼nSiO2of wavelength of green light, wherein nSiO2is refractive index of the SiO2layer; and

photoresist5in region corresponding to display units of B color is completely removed, and the SiO2layer is etched such that thickness of remaining SiO2layer is ¼nSiO2of wavelength of blue light, wherein nSiO2is refractive index of the SiO2layer.

Thereby, patterns of first structural layer1forming a stairs-like shape as shown inFIG. 4are obtained.

2) Forming a Second Structural Layer2

The second structural layer2is fabricated on the first structural layer1formed by the above manner. The steps for fabricating the second structural layer2are substantially the same as those for fabricating the first structural layer1. The only difference between them is that, the second structural layer2is formed by using material with high refractive index, for example, SiNxor TiO2. Patterns of second structural layer obtained are as shown inFIG. 5.

3) Forming a Bragg Reflection Structure

The first structural layer1and the second structural layer2are alternately and repeatedly formed so as to form the bragg reflection structure as shown inFIG. 1. Preferably, in the structure of alternately stacked first structural layer1and second structural layer2, there may he multiple first structural layers1and multiple second structural layers2. Such structure can enhance luminance of the emitting light.

4) Forming the Display Substrate

The bragg reflection structure prepared as above is aligned with a substrate, on which the display units6are disposed, so as to form a cell, wherein the display units6of different colors are disposed respectively opposite to the bragg reflection units7in corresponding regions, so that the display substrate is formed.

It will be understood that the foregoing embodiments are merely exemplary embodiments used for describing the principle of the present invention. However, the present invention is not limited to this. A person having ordinary skill in the relevant art may also make various modifications and variations without departing from the spirit and scope of the present invention, so these modifications and variations shall fall into the protection scope of the present invention.