WO2020042627A1

WO2020042627A1 - Liquid crystal display device, pixelated quantum dot color conversion film and preparation method therefor

Info

Publication number: WO2020042627A1
Application number: PCT/CN2019/082825
Authority: WO
Inventors: 孙小卫; 王恺; 周子明; 李尚�; 赵冰心
Original assignee: 深圳扑浪创新科技有限公司
Priority date: 2018-08-30
Filing date: 2019-04-16
Publication date: 2020-03-05
Also published as: CN109100888A

Abstract

Disclosed are a pixelated quantum dot color conversion film (7) and a liquid crystal display device. The color conversion film is provided between a light source of a liquid crystal light-emitting device and a polarizer (6) to reduce self-absorption of traditional quantum dot brightness enhancement films and the light energy loss caused by means of the light filtering of a color filter, and reduce the problem of low contrast of the display device caused by the absorption and reemission of the ambient light by the traditional color filter, so as to display a wider gamut. Also disclosed is a preparation method for a pixelated quantum dot color conversion film (7).

Description

Liquid crystal display device, pixelated quantum dot color conversion film and preparation method thereof

This application claims priority from a Chinese patent application filed with the Chinese Patent Office on August 30, 2018 with an application number of 201811003767.4, the entire contents of which are incorporated herein by reference.

Technical field

The present application belongs to the field of display technology, and relates to a liquid crystal display device, for example, a liquid crystal display device, a pixelated quantum dot color conversion film, and a preparation method thereof.

Background technique

Most LCD screens work similarly: as shown in Figure 1, first place a layer of polarizer in front of the LCD cell to filter out half of the light in the backlight that is perpendicular to the orientation of the polarizer, and the other half is oriented with the polarizer Parallel rays enter the liquid crystal cell through the polarizer. A liquid crystal cell is made by filling liquid crystal molecules between two conductive glass columns arranged with mutually perpendicular (intersecting at 90 degrees) fine grooves. That is, if the molecules on one plane are aligned in the north-south direction, the molecules on the other plane are aligned in the east-west direction, and the molecules located between the two planes are forced into a 90 ° twisted state. Since the polarized light entering the liquid crystal cell propagates along the arrangement direction of the molecules, the polarization direction of the light is also twisted by 90 ° after passing through the liquid crystal cell. However, when a specific voltage is applied to the liquid crystal cell, the molecules will re-align vertically, so that the light can be directly emitted without any twisting of the polarization direction. There is also a polarizer on the rear surface of the liquid crystal cell. The orientation of the polarizer is parallel to the polarization direction of the light emitted when the electric field is not applied to the liquid crystal cell. Therefore, almost all light can pass through the polarizer at this time. The state is the maximum on; when the alignment of the liquid crystal molecules is not twisted when voltage is applied, almost all light will be blocked by the polarizer, and the displayed state is off; and when the voltage is adjusted, the twist angle of the liquid crystal molecules can be adjusted at Between 0 ° and 90 °, only a part of the light will pass through the polarizer, and the displayed light intensity will change. In this way, the liquid crystal display adjusts the light intensity of a single pixel. Between the liquid crystal cell and the second layer of polarizer, there will be a layer of color filter, which can filter the previous white light into one of the three primary colors of red, green and blue, but the price paid will lose 67% of the light energy. By using the liquid crystal cell to adjust the light intensity of the red, green, and blue pixels, the mixed color of the three colors can be controlled.

From the working principle of the entire traditional liquid crystal display, it can be seen that a lot of light energy will be lost in the middle of the entire process. In addition, due to the huge application range of liquid crystal displays, reducing the energy loss in the process of liquid crystal display and improving the energy utilization rate of liquid crystal display technology have become the focus of research. The color gamut of the actual LCD display is not high. The reason is that the performance of the filter is not good enough, and the backlight is a white mixed light source. These factors will cause the monochromaticity of the three primary colors after the color filter is not good enough. At present, there are generally the following solutions to these two problems: One method is to improve the performance of the filter, so as to filter out colors with better monochromaticity. However, because this filter is expensive, it cannot be widely applied to Among the display fields facing the public. Another new technology is to add a red and green quantum dot mixed brightness enhancement film before the first polarizer, and change the light source to a blue light source (or a red, green and blue quantum dot mixed brightness enhancement film and an ultraviolet light source). However, although this method will improve the overall efficiency to some extent, since the color filter still consumes other color light, it cannot fundamentally solve the problem of high loss of the color filter. Therefore, in order to fundamentally solve the loss of the color filter, the color filter can only be improved, and the role of the color filter can be replaced by a nearly lossless energy. Therefore, the third solution is to replace the traditional filters with red-green pixelated quantum dot color filters, and replace the light source with a blue light source (or red-green-blue pixelated quantum dot color filters instead of traditional filters). , While changing the light source to an ultraviolet light source). The half-peak width of the quantum dots can be achieved to about 30nm, and the light emission has good monochromaticity, which will increase the color gamut value of the liquid crystal display. However, because a part of the natural light in the environment is also easily absorbed by the quantum dot color filter, and then emits light, the displayed black is not pure black, and the color coordinates will also be biased (as shown in Figure 1). The contrast ratio of the display device is much lower than that of the conventional liquid crystal display device.

Summary of the Invention

The present application provides a pixelated quantum dot color conversion film, a preparation method thereof, and a liquid crystal display device. The pixelated quantum dot color conversion film is placed between a backlight source and a liquid crystal cell of a conventional liquid crystal display device, thereby improving liquid crystal. The color gamut, contrast, and energy efficiency of the display have huge development potential.

The present application provides a pixelized quantum dot color conversion film. The color conversion film is disposed between a light source of a liquid crystal light emitting device and a polarizer.

In one embodiment, the quantum dots in the color conversion film are red quantum dots, blue quantum dots, and green quantum dots.

In one embodiment, the quantum dots include at least one of: CdSe, CdTe, CdS, ZnSe, ZnTe, ZnS, CuInS, CuInSeS, AgInS, AgInSeS, InP, CuZnSe, ZnMnSe, PbS, PbSe, an alloy material, or calcium Titanium ore material.

The present application proposes a pixelated quantum dot color conversion film (P-QDCC) placed on the inside of a liquid crystal cell, so that blue light (or ultraviolet light) first excites the quantum dots to emit light of a corresponding wavelength, and then passes through Light comes out behind the LCD box. As shown in Figure 2, when a certain liquid crystal pixel point is opaque, the natural light in the environment cannot be absorbed by the quantum dot color filter through the liquid crystal cell, so that it can completely display black; as shown in Figure 3, when a When the liquid crystal pixels transmit light, the natural light in the environment also needs to be reflected and lost by the multilayer film to be absorbed by the quantum dot color filter. The light emitted is unpolarized light, which also needs to pass through the polarizer loss and other layers. Multiple reflections and losses, the actual intensity of the emitted light will be greatly attenuated, and the effect on the color coordinates of the displayed light will be greatly reduced. This new structure not only retains the advantages of low loss and high color gamut brought by quantum dot color filters, but also can overcome the shortcomings of low contrast faced by liquid crystal displays based on quantum dot color filters. . Moreover, as shown in FIG. 4, the pixelized quantum dot color conversion sheet is made of pixels, and the black matrix is used to avoid crosstalk between pixels, which is different from the traditional integration of red and green quantum dots. The brightness enhancement film also fundamentally overcomes the shortcomings of the low energy efficiency of the quantum dot brightness enhancement film. While applying this pixelated quantum dot color conversion film, the related reflective brightness enhancement film (DBEF) technology can be used, which is a layer of multilayer refractive index anisotropic thin film material overlapping Brightening film. The unpolarized light emitted from the quantum dot light emitting diode (Light Emitting Diode, LED), after entering the DBEF, the P-polarized light passes; and the S-polarized light is reflected by the DBEF, and then becomes unpolarized light after diffuse reflection of the backlight module substrate. Re-enter DBEF. In this way, the S-polarized light can be recycled through DBEF, thereby further improving the utilization rate of light energy incident on the liquid crystal panel.

The present application provides a method for preparing the pixelated quantum dot color conversion film, including:

The quantum dots of any one of three colors are mixed with a photoresist to obtain a mixture of the quantum dots and a photoresist, and the mixture of the quantum dots and the photoresist is spin-coated on a liquid crystal cell near a light source. Side, first baking the spin-coated sample;

Performing a UV exposure on the first baked sample using the mask corresponding to the color, and performing a second baking after the UV exposure;

Washing the sample after the second baking with a developing solution, and performing the third baking after the cleaning;

The quantum dots of the remaining two colors among the three colors are respectively subjected to the processes of first baking, second baking, and third baking to prepare pixel dots to obtain the pixelized quantum dot color conversion film.

In an embodiment, when the quantum dots of any one of the three colors are mixed with the photoresist, the mass fraction of the quantum dots of any one of the colors is 0.5 to 20%, such as 1%, 2%, 5%, 8%, 10%, 12%, 15%, 18%, or 19%, etc., but it is not limited to the listed values, and other unlisted values within this range are also applicable.

The photoresist includes at least one of the following: SU-8 photoresist, polyester adhesive, cyclized rubber, epoxy-based adhesive, vinyl-based adhesive, episulfide compound-based adhesive, phenolic resin-based adhesive, Acrylic methyl ester-based adhesives, disulfone-based adhesives, and diazo-based adhesives. Typical but non-limiting examples of such combinations are: SU-8 photoresist and polyester adhesive combinations, polyester and cyclized rubber combinations , Combination of cyclized rubber and epoxy-based rubber, combination of epoxy-based rubber and vinyl-based rubber, combination of vinyl-based rubber and episulfide-based rubber, episulfide-based rubber and phenolic resin-based rubber Combination of phenol resin glue and methacryl methyl glue, combination of methacryl methyl glue and dilute sulfone glue, combination of dilute sulfone glue and diazo glue or SU-8 lithography Rubber, and the combination of polyester rubber and cyclized rubber.

Before spin coating the mixture of the quantum dots and the photoresist on a side of the liquid crystal cell near the light source, the method further includes: homogenizing the mixture of the quantum dots and the photoresist.

The rotation speed of the homogenizer is 100 to 2000 rpm, such as 200 rpm, 500 rpm, 800 rpm, 1000 rpm, 1200 rpm, 1500 rpm, or 1800 rpm, etc., but it is not limited to the listed values, and other unlisted values in the value range are also applicable.

The homogenization time is 2 to 20 s, such as 5 s, 8 s, 10 s, 12 s, 15 s, or 18 s, etc., but it is not limited to the listed values, and other unlisted values in this range are also applicable.

The rotation speed of the spin coating is 1000 to 5000 rpm, such as 1500 rpm, 2000 rpm, 2500 rpm, 3000 rpm, 3500 rpm, 4000 rpm, or 4500 rpm, etc., but it is not limited to the listed values, and other unlisted values in this value range are also applicable.

The spin coating time is greater than 10 s, such as 15 s, 20 s, 30 s, 40 s, 50 s, 60 s, 90 s, or 120 s, etc., but it is not limited to the listed values, and other unlisted values in the value range also apply.

The first baking temperature is 50 to 200 ° C, such as 60 ° C, 80 ° C, 100 ° C, 120 ° C, 150 ° C, or 180 ° C, etc., but it is not limited to the listed values. Other values in this range are not listed. The same applies.

The first baking time is 5-20 minutes, such as 6min, 8min, 10min, 12min, 15min, or 18min, etc., but it is not limited to the listed values, and other unlisted values in this value range are also applicable.

In one embodiment, the UV exposure time is 3 to 300s, 5s, 10s, 20s, 50s, 80s, 100s, 150s, 200s, or 250s, etc., but it is not limited to the listed values. Other values within this range Unlisted values also apply.

The second baking temperature is 40 to 150 ° C, such as 50 ° C, 60 ° C, 70 ° C, 80 ° C, 90 ° C, 100 ° C, 110 ° C, 120 ° C, 130 ° C, or 140 ° C, but it is not limited to The listed values are also applicable to other unlisted values within the numerical range.

The second baking time is 3-15 minutes, such as 4min, 5min, 6min, 7min, 8min, 9min, 10min, 11min, 12min, 13min, or 14min, etc., but it is not limited to the listed values, and the value range Other values not listed apply.

In an embodiment, the cleaning time for washing the second baked sample using a developer is greater than 1 min, such as 2 min, 5 min, 8 min, 10 min, 12 min, 15 min, 18 min, 20 min, 25 min, or 30 min. , But it is not limited to the listed values, and other unlisted values in this value range also apply.

The third baking temperature is 50 to 200 ° C, such as 60 ° C, 80 ° C, 100 ° C, 120 ° C, 150 ° C, or 180 ° C, etc., but it is not limited to the listed values. Other values in this range are not listed. The same applies.

The third baking time is 5-20 minutes, such as 6min, 8min, 10min, 12min, 15min, or 18min, etc., but it is not limited to the listed values, and other unlisted values in this value range are also applicable.

The present application provides a liquid crystal display device. The liquid crystal display device includes a light source, a pixelated quantum dot color conversion film, a polarizer, a liquid crystal cell, and a polarizer.

In one embodiment, the light source is an LED light source of any one of blue light, purple light, or ultraviolet light.

Compared with related technical solutions, this application has at least the following beneficial effects:

(1) This application can fundamentally reduce the self-absorption of traditional quantum dot brightness enhancement films and the loss of light energy due to color filter filtering;

(2) The present application reduces the low contrast problem of a display device caused by the absorption and re-emission of ambient light by a traditional quantum dot color filter. At the same time, it retains the advantages of traditional quantum dot brightness enhancement films and quantum dot color filters, and can also display a wider color gamut.

Overview of the drawings

FIG. 1 is a schematic diagram of ambient light excitation and emission of a liquid crystal display device based on a conventional quantum dot color filter;

FIG. 2 is a schematic diagram of a liquid crystal display device based on a pixelated quantum dot color conversion film provided in the present application under the condition of no light transmission; FIG.

FIG. 3 is a schematic diagram of a liquid crystal display device based on a pixelated quantum dot color conversion film provided by the present application under ambient light excitation and light emission;

FIG. 4 is a typical pixel structure of a pixelated quantum dot color conversion film provided by the present application.

In the picture: 1-ambient light, 2-light emitted from the device after excitation by ambient light, 3-conventional quantum dot color filter, 4-polarizer when light exits, 5-liquid crystal cell, 6-polarizer, 7-the pixelized quantum dot color conversion film, 8-black matrix, 9-green sub-pixel, 10-red sub-pixel, 11-blue sub-pixel.

The application is described in further detail below. However, the following examples are merely simple examples of this application, and do not represent or limit the scope of protection of the rights of this application. The scope of protection of this application is subject to the claims.

detailed description

The technical solutions of the present application will be further described below with reference to the accompanying drawings and application embodiments.

In one embodiment, the quantum dots include at least one of the following: CdSe, CdTe, CdS, ZnSe, ZnTe, ZnS, CuInS, CuInSeS, AgInS, AgInSeS, InP, CuZnSe, ZnMnSe, PbS, PbSe, alloy materials, or calcium Titanium ore material.

In one embodiment, a black matrix is disposed between pixels in the color conversion film.

The pixelated quantum dot color conversion film provided in this embodiment is placed between a backlight source and a liquid crystal box of a conventional liquid crystal display device, which improves the color gamut, contrast, and energy utilization ratio of a liquid crystal display, and has huge development potential.

The present application provides a method for preparing a pixelated quantum dot color conversion film, including: step 110 to step 140.

In step 110, a quantum dot of any one of three colors is mixed with a photoresist to obtain a mixture of the quantum dot and the photoresist, and the mixture of the quantum dot and the photoresist is spin-coated. On the side of the liquid crystal cell near the light source, first baking the spin-coated sample.

In step 120, using the mask corresponding to the color to perform UV exposure on the first baked sample, and then perform second baking after the UV exposure.

In step 130, the sample after the second baking is washed using a developing solution, and a third baking is performed after the cleaning.

In step 140, the quantum dots of the remaining two colors among the three colors are respectively subjected to the first baking, the second baking, and the third baking to prepare pixel points, and the pixelized quantum dot color conversion is obtained. membrane.

In an embodiment, when the quantum dots of any one of the three colors are mixed with the photoresist, the mass fraction of the quantum dots of any one of the colors is 0.5 to 20%;

The photoresist includes at least one of the following: SU-8 photoresist, polyester adhesive, cyclized rubber, epoxy-based adhesive, vinyl-based adhesive, episulfide compound-based adhesive, phenolic resin-based adhesive, Acrylic methyl ester-based glue, dilute sulfone-based glue and diazo rubber;

Before spin coating the mixture of quantum dots and photoresist on a side of the liquid crystal cell near the light source, the method further includes: homogenizing the mixture of quantum dots and photoresist;

The speed of homogenization is 100-2000 rpm; the time of homogenization is 2-20 s; the speed of spin coating is 1000-5000 rpm; the time of spin coating is greater than 10 s; the first baking temperature The temperature is 50 to 200 ° C; the first baking time is 5 to 20 minutes.

In one embodiment, the ultraviolet exposure time is 3 to 300 seconds; the second baking temperature is 40 to 150 ° C; and the second baking time is 3 to 15 minutes.

In one embodiment, the cleaning time of the second baking sample using a developer is greater than 1 min; the temperature of the third baking is 50-200 ° C; The time is 5-20 minutes.

The pixelated quantum dot color conversion film provided in the application example section of this application uses the following preparation method:

(1) The quantum dots of any color are mixed with the photoresist at a mass fraction of 0.5 to 20%, and the mixture of the quantum dots and the photoresist is homogenized at a rotation speed of 100 to 2000 rpm for 2 to 20 seconds. Spin-coated at 5000 rpm on the side of the liquid crystal cell near the light source. The spin-coated time was greater than 10s. The sample after spin-coated was first baked at 50-200 ° C for 5-20 minutes.

(2) Use the mask corresponding to the color to UV-expose the sample after step (1) for 3 to 300 s, and perform a second baking for 3 to 15 min after exposure at 40 to 150 ° C.

(3) Use the developer to clean the sample after the baking in step (2). The cleaning time is longer than 1 minute. After cleaning, the third baking is performed at 50 to 200 ° C. for 5 to 20 minutes.

(4) Repeat steps (1) to (3) to prepare pixel points using the remaining two color quantum dots to obtain the pixelized quantum dot color conversion film.

The quantum dots used in Examples 1-5 of this application are shown in Table 1:

Table 1

The display device contrast is defined as the ratio of the brightness of the brightest white and the darkest black that the device can display. Compared to the liquid crystal display device 1 based on the conventional quantum dot color filter, the contrast of the liquid crystal display device of the quantum dot pixel color conversion film provided herein may be increased by 10 ¹ to 10 ⁴ times as shown. At the same time, compared with traditional liquid crystal display devices, the display devices provided in this application have higher color and can reach more than 100% of NTSC ((United States) National Television Standards Committee Standard); the energy loss is smaller and can reach traditional liquid crystal display devices 0.2 to 0.8 times the energy loss.

The applicant states that the present application describes the detailed structural features of the present application through the foregoing embodiments, but the present application is not limited to the detailed structural features described above, which does not mean that the present application must rely on the detailed structural features described above in order to be implemented. Those skilled in the art should understand that any improvement to this application, equivalent replacement of components used in this application, addition of auxiliary components, selection of specific methods, etc., all fall within the scope of protection and disclosure of this application.

The application embodiments of the present application have been described in detail above. However, the present application is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present application, various simple modifications can be made to the technical solution of the present application. These simple modifications All belong to the protection scope of this application.

In addition, it should be noted that the specific technical features described in the foregoing specific embodiments can be combined in any suitable manner without conflicts. In order to avoid unnecessary repetition, this application provides The combination is not explained separately.

In addition, various embodiments of the present application can also be arbitrarily combined, as long as it does not violate the idea of the present application, it should also be regarded as the content disclosed in the present application.

Claims

A pixelized quantum dot color conversion film is disposed between a light source of a liquid crystal light emitting device and a polarizer.
The color conversion film according to claim 1, wherein the quantum dots in the color conversion film are red quantum dots, blue quantum dots, and green quantum dots.
The color conversion film according to claim 2, wherein the quantum dots include at least one of: CdSe, CdTe, CdS, ZnSe, ZnTe, ZnS, CuInS, CuInSeS, AgInS, AgInSeS, InP, CuZnSe, ZnMnSe , PbS, PbSe, alloy materials or perovskite materials.
The color conversion film according to any one of claims 1 to 3, wherein a black matrix is provided between pixels in the color conversion film.
A method for preparing a pixelated quantum dot color conversion film according to any one of claims 1-4, comprising:

The quantum dots of any one of three colors are mixed with a photoresist to obtain a mixture of the quantum dots and a photoresist, and the mixture of the quantum dots and the photoresist is spin-coated on a liquid crystal cell near a light source. Side, first baking the spin-coated sample;

Performing a UV exposure on the first baked sample using the mask corresponding to the color, and performing a second baking after the UV exposure;

Washing the sample after the second baking with a developing solution, and performing the third baking after the cleaning;

The pixels of the remaining two colors among the three colors are respectively subjected to the processes of the first baking, the second baking, and the third baking to prepare pixel points, and the pixelized quantum dot colors are obtained. Conversion film.
The method according to claim 5, wherein when the quantum dots of any one of the three colors are mixed with a photoresist, the mass fraction of the quantum dots of any one of the colors is 0.5 to 20% ;

The photoresist includes at least one of the following: SU-8 photoresist, polyester adhesive, cyclized rubber, epoxy-based adhesive, vinyl-based adhesive, episulfide compound-based adhesive, phenolic resin-based adhesive, Acrylic methyl ester-based glue, dilute sulfone-based glue and diazo rubber;

Before spin coating the mixture of quantum dots and photoresist on a side of the liquid crystal cell near the light source, the method further includes: homogenizing the mixture of quantum dots and photoresist;

The rotation speed of the homogenizer is 100-2000 rpm;

The time for homogenizing is 2-20s;

The rotation speed of the spin coating is 1000 to 5000 rpm;

The spin coating time is greater than 10s;

The first baking temperature is 50-200 ° C;

The first baking time is 5-20 minutes.
The preparation method according to claim 5 or 6, wherein the ultraviolet exposure time is 3 to 300 s;

The second baking temperature is 40-150 ° C;

The second baking time is 3-15 minutes.
The preparation method according to any one of claims 5 to 7, wherein the washing time of the second baked sample using a developing solution is greater than 1 min;

The third baking temperature is 50-200 ° C;

The third baking time is 5-20 minutes.
A liquid crystal display device includes a light source, a pixelated quantum dot color conversion film according to any one of claims 1-4, a polarizer, a liquid crystal cell, and a polarizer.
The liquid crystal display according to claim 9, wherein the light source is an LED light source of any one of blue light, purple light, or ultraviolet light.