TWI776576B - Display device - Google Patents

Abstract

A display device including a substrate, a cholesteric liquid crystal layer, a circular polarization plate, a liquid crystal layer, an electrode layer and a light absorption layer is provided. The cholesteric liquid crystal layer includes a plurality of reflective units. The liquid crystal layer includes a plurality of encapsulation particles, and these encapsulation particles contain liquid crystal molecules therein. The liquid crystal layer is disposed between the cholesteric liquid crystal layer and the circular polarization plate. The electrode layer includes a plurality of common electrodes and pixel electrodes. The electrode layer is disposed on the liquid crystal layer to drive the liquid crystal molecules in these encapsulation particles. The cholesteric liquid crystal layer is disposed between the liquid crystal layer and the light absorption layer. An average particle size of these encapsulation particles is within the range from 10 nm to 400 nm.

Description

display device

The present invention relates to a display device.

In the current era and trend of high energy saving, a thin, light and power-saving display device has become one of the development priorities in the current display field, and a bistable liquid crystal display device has attracted more attention. Among them, Cholesteric Liquid Crystal Display (ChLCD) has the advantages of low power consumption, no backlight module, no blue light damage to eyes, etc., and can continue to maintain bright and dark states when the electric field is removed Two different states, so it has become the focus of the development of bistable displays.

Cholesteric liquid crystal is a liquid crystal molecule with Bragg reflection and bistable properties. It can reflect incident light with a wavelength equivalent to its helical pitch and with the same optical rotation, and can be switched to a reflective state (planar state) or a transmissive state under the driving of an electric field. (focal-conic state) these two steady states. In the reflective state, the cholesteric liquid crystal will reflect light of a specific wavelength, so the corresponding pixel will appear in a bright state; in the transmissive state, the light will penetrate and be absorbed by the light-absorbing layer arranged behind it, so the corresponding pixel will be in a bright state. Appears dark.

However, the reaction time of cholesteric liquid crystal is relatively long. When the cholesteric liquid crystal is to be converted from the transmissive state to the reflective state, a threshold voltage must be provided to drive the cholesteric liquid crystal Crystal, the threshold voltage is usually greater than 40 volts, and requires a special waveform voltage. A higher voltage is also required when switching to the penetration state. In addition, the voltage retention rate of cholesteric liquid crystal is low, and cannot be used with active devices. Therefore, there is an urgent need to provide a display device to solve the problems existing in the prior art.

The present invention provides a display device with good display quality.

According to an embodiment of the present invention, a display device is provided, which includes a substrate, a cholesteric liquid crystal layer, a circular polarizer, a liquid crystal layer, an electrode layer, and a light absorption layer. The cholesteric liquid crystal layer includes a plurality of reflective units arranged on the substrate. The circular polarizer is arranged on the cholesteric liquid crystal layer. The liquid crystal layer includes a plurality of encapsulated particles, and liquid crystal molecules are accommodated in the encapsulated particles, and the liquid crystal layer is disposed between the cholesteric liquid crystal layer and the circular polarizer. The electrode layer includes a plurality of common electrodes and a plurality of pixel electrodes, and the electrode layer is disposed on the liquid crystal layer to drive the liquid crystal molecules in the encapsulated particles. The cholesteric liquid crystal layer is disposed between the liquid crystal layer and the light absorption layer. The average particle size of these encapsulated particles falls within the range between 10 nm and 400 nm.

According to an embodiment of the present invention, the average particle size of the encapsulated particles falls within a range of 150 nm to 250 nm, and the polymer dispersibility index of the encapsulated particles is less than 1.2.

According to an embodiment of the present invention, when no driving voltage is applied to the liquid crystal layer, the alignment directions of the liquid crystal molecules in the encapsulated particles are consistent.

According to an embodiment of the present invention, the light absorption layer is disposed on the substrate and the cholesterol solution between the crystal layers.

According to an embodiment of the present invention, the substrate is disposed between the light absorption layer and the cholesteric liquid crystal layer.

According to an embodiment of the present invention, the helical pitches of the cholesteric liquid crystals in different reflection units are different.

According to an embodiment of the present invention, the electrode layer is disposed between the circular polarizer and the liquid crystal layer.

According to an embodiment of the present invention, the liquid crystal layer is disposed between the circular polarizer and the electrode layer.

According to an embodiment of the present invention, the display device further includes a blocking layer disposed between the cholesteric liquid crystal layer and the liquid crystal layer.

According to an embodiment of the present invention, the dielectric constant of the liquid crystal molecules in the encapsulated particles falls within the range of 10F/m to 30F/m.

According to an embodiment of the present invention, the birefringence difference of the liquid crystal molecules in the encapsulated particles falls within the range of 0.23 to 0.32.

According to an embodiment of the present invention, the liquid crystal layer is fabricated by a high pressure homogeneous emulsification or SPG film emulsification process.

According to an embodiment of the present invention, the liquid crystal layer further includes fully alkalized polyvinyl alcohol.

According to an embodiment of the invention, the particle walls of the encapsulated particles comprise partially alkalized polyvinyl alcohol.

Based on the above, the display device provided by the embodiments of the present invention includes a liquid crystal layer. By applying a voltage to the liquid crystal layer, instead of applying a drive to the cholesteric liquid crystal layer in the prior art The method of dynamic voltage avoids the problems existing in various conventional technologies. In addition, the display device provided by the embodiment of the present invention optimizes the average particle size of the encapsulated particles, thereby greatly improving the display quality of the display device.

In order to make the above-mentioned features and advantages of the present invention more obvious and easy to understand, the following embodiments are given and described in detail with the accompanying drawings as follows.

100, 200, 300, 400: Display device

101: Substrate

102: Cholesterol liquid crystal layer

102R, 102G, 102B: Reflective unit

103, 303: circular polarizer

104: Liquid crystal layer

104B: Encapsulated Particles

104C, 204C, 404C: common electrode

104E, 204E, 404E: electrode layer

104P, 204P, 404P: pixel electrode

104S: Support part

105: light absorbing layer

106, 206, 406: Substrate

207, 407: Barrier layer

LC: Liquid Crystal Molecule

1A and FIG. 1B are schematic cross-sectional views of a display device in a bright state and a dark state, respectively, according to the first embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating the encapsulated particles of the display device according to the first embodiment of the present invention.

3 is a schematic cross-sectional view of a display device according to a second embodiment of the present invention.

4A and 4B are schematic cross-sectional views of a display device in a dark state and a bright state, respectively, according to a third embodiment of the present invention.

FIG. 5 is a schematic cross-sectional view of a display device according to a fourth embodiment of the present invention.

Referring to FIG. 1A , it is a schematic cross-sectional view of a display device in a bright state according to a first embodiment of the present invention. The display device 100 includes a substrate 101 and a cholesteric liquid crystal layer 102 , a circular polarizer 103 , a liquid crystal layer 104 , an electrode layer 104E, a substrate 106 and a light absorption layer 105 . The cholesteric liquid crystal layer 102 includes reflective units 102R, 102G, and 102B, which are arranged on the substrate 101 and have the same rotation. The circular polarizer 103 is disposed on the cholesteric liquid crystal layer 102 . The liquid crystal layer 104 includes a plurality of encapsulated particles 104B and a support portion 104S. The encapsulated particles 104B accommodate liquid crystal molecules LC, and the liquid crystal layer 104 is disposed between the cholesteric liquid crystal layer 102 and the circular polarizer 103 . The electrode layer 104E includes a plurality of common electrodes 104C and a plurality of pixel electrodes 104P, and the electrode layer 104E is disposed on the liquid crystal layer 104 to drive the liquid crystal molecules LC in the encapsulated particles 104B. The cholesteric liquid crystal layer 102 is disposed between the liquid crystal layer 104 and the light absorption layer 105 . The light absorption layer 105 is disposed between the substrate 101 and the cholesteric liquid crystal layer 102 . The average particle size of these encapsulated particles 104B falls within the range between 10 nm and 400 nm.

In this embodiment, the circular polarizer 103 allows right-handed polarized light to pass through. The cholesteric liquid crystal layer 102 is in a planar state, wherein the reflective units 102R, 102G, and 102B can reflect right-handed polarized light, and the cholesteric liquid crystals in the reflective unit 102R, the reflective unit 102G, and the reflective unit 102B have different helical pitches, which can reflect different wavelength of right-handed circularly polarized light. In this embodiment, the reflecting unit 102R can reflect red right-handed circularly polarized light, the reflecting unit 102G can reflect green right-circularly polarized light, and the reflecting unit 102B can reflect blue right-circularly polarized light. However, the present invention is not limited to this. In another embodiment of the present invention, the circular polarizer 103 allows left-handed polarized light to pass through. The cholesteric liquid crystal layer 102 is in a planar state, wherein the reflection units 102R, 102G, and 102B can reflect red, green, and blue left-handed polarized light, respectively.

Referring to FIG. 1A and FIG. 2 at the same time, in this embodiment, when the electrode layer is not used 104E applies a driving voltage, the alignment directions of the liquid crystal molecules LC in the plurality of encapsulated particles 104B in the liquid crystal layer 104 are consistent, and the long axes of the liquid crystal molecules LC are all parallel to the normal direction of the substrate 101 . Specifically, since the average particle size of the encapsulated particles 104B falls within the range of 10 nm to 400 nm, the long axes of each liquid crystal molecule LC can be oriented in the same direction and parallel to each other, as shown in FIG. 1A and FIG. 2 . Show. On the contrary, if the average particle size of the encapsulated particles 104B is too large, the long axis of each liquid crystal molecule LC will not be able to face the same direction without voltage driving. In another embodiment of the present invention, the liquid crystal layer having the encapsulated particles 104B with an average particle diameter in the range of 150 nm to 250 nm can be manufactured by high pressure homogeneous emulsification or SPG (Shirasu Porous Glass) film emulsification process 104, and the polymer dispersity index (PDI) of these encapsulated particles 104B is less than 1.2, the polymer dispersity index is small, the molecular weight distribution is average, and the particle size is similar.

In the first embodiment of the present invention, referring to FIG. 1A , when light (white light) outside the display device 100 enters the display device 100 from above the circular polarizer 103 , only right-handed polarized light will transmit the circular polarizer 103 . When no driving voltage is applied through the electrode layer 104E, the long axes of the liquid crystal molecules LC in the plurality of encapsulated particles 104B in the liquid crystal layer 104 are all parallel to the normal direction of the substrate 101 , and the light does not pass through the liquid crystal layer 104 . Change its polarization state, maintaining the right-handed polarization. The light continues to travel toward the cholesteric liquid crystal layer 102 and is reflected by the reflection unit 102R, the reflection unit 102G, and the reflection unit 102B to generate red right-handed polarized light, green right-handed polarized light, and blue right-handed polarized light, respectively. The right-handed polarized light of each color still maintains the right-handed polarization state after passing through the liquid crystal layer 104 , and then exits the display device 100 after passing through the circular polarizer 103 . The display device 100 Displayed in bright state.

Next, referring to FIG. 1B , which is a schematic cross-sectional view of the display device according to the first embodiment of the present invention in a dark state. When a driving voltage is applied through the electrode layer 104E, and the long axes of the liquid crystal molecules LC in the plurality of encapsulated particles 104B in the liquid crystal layer 104 are all perpendicular to the normal of the substrate 101, the right-handed polarization of the circular polarizer 103 is transmitted through After the light penetrates the liquid crystal layer 104, its polarization state will be changed to become left-handed polarized light. These light rays continue to travel toward the cholesteric liquid crystal layer 102 , pass through the reflection units 102R, 102G, and 102B and be absorbed by the light absorption layer 105 , and the display device 100 is displayed in a dark state.

Specifically, the display device 100 provided in the first embodiment includes a liquid crystal layer 104 . According to different gray scale requirements, a voltage is applied to the liquid crystal layer 104 to change the orientation of the liquid crystal molecules LC in the encapsulated particles 104B, which replaces the method of applying a driving voltage to the cholesteric liquid crystal layer in a display device in the prior art, and avoids various conventional methods. Problems such as high threshold voltage, long response time, and low voltage maintenance rate that exist in the technology. In addition, according to the display device 100 provided by the first embodiment of the present invention, the average particle size of the encapsulated particles 104B is optimized, and the display quality of the display device 100 is greatly improved.

According to an embodiment of the present invention, the dielectric coefficient of the liquid crystal molecules LC in the encapsulated particles 104B falls within the range of 10F/m to 30F/m, and the birefringence difference of the liquid crystal molecules LC falls within the range of 0.23 to 0.32 . The Kerr effect is enhanced by maximizing dielectric anisotropy and optical anisotropy. In addition, the operating voltage of the electrode layer 104E is reduced by maximizing the dielectric anisotropy.

According to an embodiment of the present invention, the support portion 104S of the liquid crystal layer 104 includes a complete Fully-hydrolyzed polyvinyl alcohol, the alkalization rate of which falls in the range of 98% to 99%. Because the support portion 104S must support the entire liquid crystal layer 104 to prevent the encapsulated particles 104B from being damaged by external force, fully hydrolyzed fully alkalized polyvinyl alcohol is selected to achieve this goal.

According to an embodiment of the present invention, the particle walls of the encapsulated particles 104B include partially-hydrolyzed polyvinyl alcohol, and the alkalinity rate thereof falls within the range of 80% to 96%. Because the particle walls of the encapsulated particles 104B must be strong enough to prevent leakage of the liquid crystal molecules LC, and need to be compatible with water and liquid crystals, partially hydrolyzed partially alkalized polyvinyl alcohol is selected.

In the first embodiment shown in FIGS. 1A and 1B , the light absorption layer 105 is disposed between the substrate 101 and the cholesteric liquid crystal layer 102 . However, the present invention is not limited thereto. According to an embodiment of the present invention, the substrate 101 may be disposed between the light absorption layer 105 and the cholesteric liquid crystal layer 102 .

In order to fully illustrate the various embodiments of the present invention, other embodiments of the present invention will be described below. It must be noted here that the following embodiments use the element numbers and part of the contents of the previous embodiments, wherein the same numbers are used to represent the same or similar elements, and the description of the same technical contents is omitted. For the description of the omitted part, reference may be made to the foregoing embodiments, and repeated descriptions in the following embodiments will not be repeated.

In the first embodiment shown in FIGS. 1A and 1B , the electrode layer 104E is disposed between the circular polarizer 103 and the liquid crystal layer 104 . However, the present invention is not limited thereto. Referring to FIG. 3 , it is a schematic cross-sectional view of a display device according to a second embodiment of the present invention. The display device 200 is different from the display device 100 in that the liquid crystal layer 104 is disposed between the circular polarizer 103 and the electrode layer 204E. The circular polarizer 103 can be directly attached to the liquid crystal layer 104 . The display device 200 may further include a blocking layer 207 disposed between the cholesteric liquid crystal layer 102 and the liquid crystal layer 104 . The barrier layer 207 includes silicon nitride (SiN _x ) and silicon oxide (SiO _x ), etc., but the invention is not limited thereto, and the display device 200 may not include the barrier layer 207 .

Referring to FIG. 4A , it is a schematic cross-sectional view of a display device in a dark state according to a third embodiment of the present invention. Compared with the cross-sectional schematic diagram of the display device of the first embodiment shown in FIG. 1A in a bright state, the display device 300 shown in FIG. 4A is different in that the circular polarizer 303 is a left-handed circular polarizer, which allows left-handed polarized light to pass through. through.

The optical performance of the display device 300 shown in FIG. 4A is described here: when the light outside the display device 300 enters the display device 300 from above the circular polarizer 303 , only the left-handed polarized light transmits the circular polarizer 303 . When no driving voltage is applied through the electrode layer 104E, the long axes of the liquid crystal molecules LC in the plurality of encapsulated particles 104B in the liquid crystal layer 104 are all parallel to the normal direction of the substrate 101 , and the light does not pass through the liquid crystal layer 104 . Change its polarization state, maintaining left-handed polarization. These light rays continue to travel toward the cholesteric liquid crystal layer 102 , pass through the reflection units 102R, 102G, and 102B and be absorbed by the light absorption layer 105 , and the display device 300 is displayed in a dark state.

Next, referring to FIG. 4B , which is a schematic cross-sectional view of the display device according to the third embodiment of the present invention in a bright state. When light from outside the display device 300 enters the display device 300 from above the circular polarizer 303 , only the left-handed polarized light will transmit through the circular polarizer 303 . When a driving voltage is applied through the electrode layer 104E, the long axes of the liquid crystal molecules LC in the plurality of encapsulated particles 104B in the liquid crystal layer 104 are all perpendicular to the normal direction of the substrate 101 . The light will change its polarization state after penetrating the liquid crystal layer 104 to become right-handed polarization. The light continues to travel toward the cholesteric liquid crystal layer 102 and is reflected by the reflection unit 102R, the reflection unit 102G, and the reflection unit 102B to generate red right-handed polarized light, green right-handed polarized light, and blue right-handed polarized light, respectively. The right-handed polarized lights of each color pass through the liquid crystal layer 104 and become left-handed polarized lights. After passing through the circular polarizer 303 , they exit the display device 300 , and the display device 300 displays a bright state.

Referring to FIG. 5 , a schematic cross-sectional view of a display device according to a fourth embodiment of the present invention is shown. The display device 400 is different from the display device 300 in that the liquid crystal layer 104 is disposed between the circular polarizer 303 and the electrode layer 404E. The circular polarizer 303 can be directly attached to the liquid crystal layer 104 . The display device 400 may further include a barrier layer 407 disposed between the cholesteric liquid crystal layer 102 and the liquid crystal layer 104 , but the invention is not limited thereto, and the display device 400 may not include the barrier layer 407 .

To sum up, the display device provided by the embodiments of the present invention includes a liquid crystal layer. According to different gray-scale requirements, a voltage is applied to the liquid crystal layer to change the orientation of the liquid crystal molecules in the encapsulated particles, which replaces the method of applying a driving voltage to the cholesteric liquid crystal layer in a display device in the prior art, and avoids the existence of various conventional technologies. problems such as high threshold voltage, long response time, and low voltage maintenance rate. In addition, the display device provided according to the embodiment of the present invention also optimizes the average particle size of the encapsulated particles, which greatly improves the display quality of the display device.

100: Display device

101: Substrate

102: Cholesterol liquid crystal layer

102R, 102G, 102B: Reflective unit

103: Circular polarizer

104: Liquid crystal layer

104B: Encapsulated Particles

104C: Common electrode

104E: Electrode layer

104P: pixel electrode

104S: Support part

105: light absorbing layer

106: Substrate

LC: Liquid Crystal Molecule

Claims (13)

A display device, comprising: a substrate; a cholesteric liquid crystal layer, including a plurality of reflection units, the reflection units are arranged on the substrate; a circular polarizer, arranged on the cholesteric liquid crystal layer; a liquid crystal layer, including a plurality of capsules encapsulated particles, liquid crystal molecules are accommodated in the encapsulated particles, and the liquid crystal layer is arranged between the cholesteric liquid crystal layer and the circular polarizer; an electrode layer includes a plurality of common electrodes and a plurality of pixel electrodes, and the An electrode layer is arranged on the liquid crystal layer to drive the liquid crystal molecules in the encapsulated particles; and a light absorption layer, wherein the cholesteric liquid crystal layer is arranged between the liquid crystal layer and the light absorption layer, wherein the encapsulated particles are The average particle size falls within the range of 10 nm to 400 nm, wherein when the liquid crystal layer is not applied with a driving voltage, the alignment directions of the liquid crystal molecules in the encapsulated particles are consistent. The display device of claim 1, wherein the average particle size of the encapsulated particles falls within a range of 150 nm to 250 nm, and the polymer dispersibility index of the encapsulated particles is less than 1.2. The display device of claim 1, wherein the light absorption layer is disposed between the substrate and the cholesteric liquid crystal layer. The display device of claim 1, wherein the substrate is disposed between the light absorption layer and the cholesteric liquid crystal layer. The display device according to claim 1, wherein the helical pitches of the cholesteric liquid crystals in different reflection units are different. The display device according to claim 1, wherein the electrode layer is disposed between the circular polarizer and the liquid crystal layer. The display device of claim 1, wherein the liquid crystal layer is disposed between the circular polarizer and the electrode layer. The display device of claim 7, further comprising a blocking layer disposed between the cholesteric liquid crystal layer and the liquid crystal layer. The display device of claim 1, wherein the dielectric coefficient of the liquid crystal molecules in the encapsulated particles falls within a range of 10F/m to 30F/m. The display device of claim 1, wherein the birefringence difference of the liquid crystal molecules in the encapsulated particles falls within a range of 0.23 to 0.32. The display device of claim 1, wherein the liquid crystal layer is manufactured by a high pressure homogeneous emulsification or SPG film emulsification process. The display device of claim 1, wherein the liquid crystal layer further comprises fully alkalized polyvinyl alcohol. The display device of claim 1, wherein the particle walls of the encapsulated particles comprise partially alkalized polyvinyl alcohol.

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