CN104155800A - Reflective liquid-crystal display - Google Patents

Abstract

The invention relates to a reflective liquid crystal display, comprising a liquid crystal layer located between two substrates, a light source and a light guide plate located on one side of the liquid crystal layer, a reflective layer and an absorbing plate located on the other side of the liquid crystal layer; the absorbing plate is used to absorb The light directed to the absorbing plate, the absorbing plate and the liquid crystal layer are respectively located on both sides of the reflective layer; the light source is a polarized light source; the reflective layer includes a quarter-wave plate and a cholesteric liquid crystal layer, and the quarter-wave plate is located layer and the cholesteric liquid crystal layer. The reflective liquid crystal display provided by the invention has higher light transmittance and brightness.

Description

A reflective liquid crystal display

technical field

The invention relates to the technical field of liquid crystal display, in particular to a reflective liquid crystal display.

Background technique

According to the type of light source used and the way the light source is set up, liquid crystal displays can be classified into transmissive liquid crystal displays, semi-transmissive liquid crystal displays, and reflective liquid crystal displays. As far as the reflective liquid crystal display is concerned, it displays images by reflecting ambient light or reflecting light emitted by a light source disposed in front of the display panel.

FIG. 1 is a schematic structural diagram of a conventional reflective liquid crystal display. As shown in Figure 1, a reflective liquid crystal display 1 includes a polarizer 2, a quarter-wave plate 3, an upper substrate (not shown in the figure), a lower substrate (not shown in the figure), and an upper substrate and a lower substrate between the liquid crystal layer 4 and the reflection plate 5 . Wherein, the liquid crystal layer 4 is in MTN mode.

When a voltage is applied on the MTN mode, as shown in Figure 1, the natural light or the light emitted by the light source passes through the polarizer 2, the quarter-wave plate 3 and the liquid crystal layer 4 sequentially from the top to the bottom, and becomes right-handed circularly polarized light ( Left-handed circularly polarized light) is directed to the reflector 5; through the reflection of the reflector 5, the polarization state of the right-handed circularly polarized light (left-handed circularly polarized light) changes, becoming left-handed circularly polarized light (right-handed circularly polarized light); This left-handed circularly polarized light (right-handed circularly polarized light) passes through the liquid crystal layer 4 and the quarter-wave plate 3 sequentially from the bottom direction, and becomes linearly polarized light whose polarization state is at right angles to the light at the time of initial incident. Therefore, it cannot Through the polarizer 2, the reflective liquid crystal display 1 displays a dark state.

When no voltage is applied on the MTN mode, as shown in Figure 2, natural light or light emitted by a light source passes through the polarizer 2, the quarter-wave plate 3 and the liquid crystal layer 4 sequentially from the top to the bottom, and becomes linearly polarized light; and Reflected by the reflector 5, it is emitted upwards with the original polarization state; it passes through the liquid crystal layer 4 and the quarter-wave plate 3 in turn, and it still maintains the same polarization state as the first incident light, so it can pass through the The polarizer 2, so that the reflective liquid crystal display 1 displays a bright state.

The above-mentioned reflective liquid crystal display 1 has the following problems in practical application: since the light emitted by natural light or a light source needs to pass through the polarizer 2, it can be directed to the quarter-wave plate 3, the liquid crystal layer 4 and the reflector 5. In the process of passing through the polarizer 2, the polarizer 2 will absorb 50% of the light, therefore, this will cause the proportion of the light emitted through the polarizer 2 to the incident light, that is, the light transmittance is relatively small; Generally, the light transmittance is only 35-39%, so that the brightness of the reflective liquid crystal display 1 is relatively low.

Contents of the invention

The present invention aims to solve at least one of the technical problems in the prior art, and proposes a reflective liquid crystal display whose light source has higher brightness and higher light transmittance, so that it has a higher high brightness.

In order to realize the object of the present invention, a reflective liquid crystal display is provided, comprising a liquid crystal layer positioned between two substrates, a light source and a light guide plate positioned on one side of the liquid crystal layer, and a reflective layer positioned on the other side of the liquid crystal layer and an absorbing plate for absorbing light directed at the absorbing plate; the absorbing plate and the liquid crystal layer are located on both sides of the reflective layer; the light source is a polarized light source; the reflective layer includes a quarter wave plate and a cholesteric liquid crystal layer, and the quarter wave plate is located between the liquid crystal layer and the cholesteric liquid crystal layer.

Wherein, the rotation direction of the helical pitch of the cholesteric liquid crystal in the cholesteric liquid crystal layer is left-handed, and the cholesteric liquid crystal layer allows transmission of right-handed circularly polarized light, and can reflect left-handed circularly polarized light to the four A quarter-wave plate; or the direction of rotation of the helical pitch of the cholesteric liquid crystal in the cholesteric liquid crystal layer is right-handed, and the cholesteric liquid crystal layer allows left-handed circularly polarized light to transmit, and can right-handed circularly polarized Light is reflected towards the quarter wave plate.

Wherein, the light guide plate is made of polymer material.

Wherein, the orientation birefringence and photoelastic birefringence of the polymer material are zero.

Wherein, the polarized light source emits linearly polarized light to the light guide plate, and the angle between the polarization direction of the linearly polarized light and the upper and lower surfaces of the light guide plate is 90 degrees.

Wherein, the polarized light source emits linearly polarized light to the light guide plate, and the polarization direction of the linearly polarized light is parallel to the upper and lower surfaces of the light guide plate.

Wherein, the thickness of the cholesteric liquid crystal layer ranges from 7 to 22 μm.

Wherein, the liquid crystals in the liquid crystal layer are nematic liquid crystals.

Wherein, the polarized light source is a side-type light source.

Wherein, the substrates located on both sides of the liquid crystal layer are an array substrate and a color filter substrate, and the array substrate is located between the liquid crystal layer and the reflective layer, and the color filter substrate is located between the liquid crystal layer and the reflective layer. between the light guide plates; the array substrate and the color filter substrate are respectively provided with transparent electrodes.

The present invention has the following beneficial effects:

The reflective liquid crystal display provided by the present invention, its light source is a polarized light source, compared with the combination of an existing light source and a polarizer, under the same power, it has higher brightness; and, because the light source is a polarized light source, the present invention The reflective liquid crystal display provided by the invention does not need to be provided with a polarizer, which avoids light being absorbed by the polarizer, so that the linearly polarized light emitted by the light source has a higher transmittance in the reflective liquid crystal display; furthermore, the reflection provided by the present invention Type LCD display has higher brightness.

Description of drawings

The accompanying drawings are used to provide a further understanding of the present invention, and constitute a part of the description, together with the following specific embodiments, are used to explain the present invention, but do not constitute a limitation to the present invention. In the attached picture:

FIG. 1 is a schematic structural view of an existing reflective liquid crystal display;

Fig. 2 is a schematic diagram showing a bright state of the reflective liquid crystal display shown in Fig. 1;

FIG. 3 is a schematic diagram of a reflective liquid crystal display provided by an embodiment of the present invention.

Explanation of reference signs

1: reflective liquid crystal display; 2: polarizer; 3: quarter wave plate; 4: liquid crystal layer; 5: reflector;

10: reflective liquid crystal display; 11: liquid crystal layer; 12: light source; 13: light guide plate; 14: reflective layer; 15: absorbing plate; 16: array substrate; 17: color filter substrate; 140: quarter wave plate ; 141: cholesteric liquid crystal layer.

Detailed ways

Specific embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. It should be understood that the specific embodiments described here are only used to illustrate and explain the present invention, and are not intended to limit the present invention.

FIG. 3 is a schematic diagram of a reflective liquid crystal display provided by an embodiment of the present invention. As shown in Figure 3, a reflective liquid crystal display 10 includes a liquid crystal layer 11 between two substrates, a light source 12 and a light guide plate 13 on one side of the liquid crystal layer 11, a reflective layer 14 and an absorbing layer on the other side of the liquid crystal layer 11. plate 15; wherein, the light source 12 is a side-type light source; the absorbing plate 15 is used to absorb the light incident on the absorbing plate 15; In this embodiment, the liquid crystals in the liquid crystal layer 11 are nematic liquid crystals.

The reflective layer 14 includes a quarter wave plate 140 and a cholesteric liquid crystal layer 141 , and the quarter wave plate 140 is located between the liquid crystal layer 11 and the cholesteric liquid crystal layer 141 . Specifically, the rotation direction of the helical pitch of the cholesteric liquid crystal in the cholesteric liquid crystal layer 141 is left-handed. One wave plate 140; Or, the direction of rotation of the helical pitch of the cholesteric liquid crystal in the cholesteric liquid crystal layer 141 is right-handed, that is, the cholesteric liquid crystal layer 141 allows left-handed circularly polarized light to transmit, and can right-handed circle The polarized light is reflected towards quarter wave plate 140 . According to the above, it can be known that the quarter-wave plate 140 and the cholesteric liquid crystal layer 141 are used as the reflective layer 14, so that the reflective layer 14 can not only reflect the light, but also allow the light to pass through; thereby utilizing the characteristic of the reflective layer 14, By controlling the light reaching the cholesteric liquid crystal layer 141 to be left-handed circularly polarized light or right-handed circularly polarized light, that is, by controlling the voltage applied to both sides of the liquid crystal layer 11, the reflective liquid crystal display 10 can be made to display a dark state and a bright state, respectively. state.

Specifically, in this embodiment, the substrates located on both sides of the liquid crystal layer 11 are the array substrate 16 and the color filter substrate 17 respectively, and the array substrate 16 is located between the liquid crystal layer 11 and the reflective layer 14, and the color filter substrate 17 is located between the liquid crystal layer 11 and the light guide plate 13; and, the array substrate 16 and the color filter substrate 17 are respectively provided with transparent electrodes.

In this embodiment, the light source 12 is a polarized light source, which emits linearly polarized light to the light guide plate 13 . The polarized light source includes an ordinary light source, a reflective plate and a reflective polarizer; specifically, the ordinary light source emits light, and in this part of the light, a part of the light passes through the reflective polarizer and is directed to the light guide plate 13; while the other part cannot pass through the reflective polarizer. The light from the polarizer is reflected by the reflective polarizer to the reflective plate, and the reflective plate then reflects the light to the reflective polarizer, and during the reflection process of the reflective plate, part of the light becomes light that can pass through the reflective polarizer , it is directed to the light guide plate 13 after passing through the reflective polarizer, and the other part of the light that cannot pass through the reflective polarizer repeats the above process until it gradually becomes light that can pass through the reflective polarizer, and passes through the reflection polarizer, and directed to the light guide plate 13. Therefore, the light emitted by the polarized light source has a higher light transmittance than the combination of a common light source and a polarizer; that is, under the same power, the light source 12 can have higher brightness.

In this embodiment, the light source 12 emits linearly polarized light to the light guide plate 13, and the linearly polarized light is either directly irradiated to the lower surface of the light guide plate 13, or is first irradiated to the upper surface of the light guide plate 13, and forms reflection at the upper surface, and then irradiates The lower surface of the light guide plate 13 ; the light incident on the lower surface of the light guide plate 13 is directed to the liquid crystal layer 11 through the lower surface of the light guide plate 13 . Wherein, the “upper surface” of the light guide plate 13 is the surface of the light guide plate 13 facing the viewer, and the “lower surface” is the surface of the light guide plate 13 facing away from the viewer. Preferably, the polarization direction of the linearly polarized light emitted by the light source 12 is perpendicular to the upper surface and the lower surface of the light guide plate 13 , and the angle between them is 90 degrees.

Table 1:

Specifically, as shown in Table 1, it is taken as an example that the angle between the linearly polarized light emitted by the light source 12 and the upper and lower surfaces of the light guide plate 13 is 90 degrees. When no voltage is applied to the transparent electrodes on the array substrate 16 and the color filter substrate 17, when the linearly polarized light is projected from the lower surface of the light guide plate 13 to the liquid crystal layer 11, its polarization direction remains unchanged; when passing through the liquid crystal layer 11, the linearly polarized light The polarized light passes through the liquid crystal layer 11, and during this process, its polarization direction remains unchanged; then, the linearly polarized light passes through a quarter wave plate 140, which becomes right-handed circularly polarized light, and the right-handed circularly polarized light The light continues downward toward the cholesteric liquid crystal layer 141, and the cholesteric liquid crystal layer 141 allows the right-handed circularly polarized light to pass through. After passing through, it is absorbed by the absorbing plate 15, so that the light cannot pass through the light guide plate 13. The upper surface is directed toward the viewer, ie, causes the reflective liquid crystal display 10 to display a dark state.

In the above process, the pitch rotation direction of the cholesteric liquid crystal in the cholesteric liquid crystal layer 141 is left-handed, and accordingly, the linearly polarized light becomes right-handed circularly polarized light after passing through the quarter-wave plate 141; In application, the pitch rotation direction of the cholesteric liquid crystal in the cholesteric liquid crystal layer 141 can also be right-handed. In this case, the linearly polarized light becomes transparent after passing through the quarter wave plate 141. The left-handed circularly polarized light of the phase liquid crystal layer 141.

As shown in Table 1, when a voltage is applied to the transparent electrodes on the array substrate 16 and the color filter substrate 17, the liquid crystal molecules are deflected in the electric field. In this case, the linearly polarized light passes through the liquid crystal layer downward from the light guide plate 13 At 11 o'clock, its polarization direction changes and becomes parallel to the light guide plate 13; after the linearly polarized light continues to pass through the quarter wave plate 140 downward, it becomes left-handed circularly polarized light; and shoots to the cholesteric liquid crystal layer 141, and the cholesteric phase liquid crystal layer 141 reflects the left-handed circularly polarized light to the quarter-wave plate 140, becomes linearly polarized light, and passes through the liquid crystal layer 11 and the light guide plate 13 in turn, and is emitted to the viewer, that is, Make the reflective liquid crystal display 10 display a bright state.

In the above process, the pitch rotation direction of the cholesteric liquid crystal in the cholesteric liquid crystal layer 141 is left-handed, and accordingly, the linearly polarized light becomes left-handed circularly polarized light after passing through the quarter-wave plate 140; Among them, the pitch rotation direction of the cholesteric liquid crystal in the cholesteric liquid crystal layer 141 can also be right-handed, in this case, the linearly polarized light becomes able to be absorbed by the cholesteric liquid crystal Layer 141 reflects right-handed circularly polarized light towards quarter wave plate 140 .

In this embodiment, the reflective liquid crystal display 10 does not include a polarizer, that is to say, it does not utilize natural light, and all the light used for display comes from the light source 12; but according to the above, in this embodiment, the light source 12 is Polarized light source, compared with the combination of the existing light source and polarizer, it has higher brightness; and, due to the cancellation of the polarizer, there will be no light during the movement of light from top to bottom and from right to bottom It is absorbed by the polarizer, so that the light emitted by the light source 12 can have a higher transmittance. Furthermore, compared with the reflective liquid crystal display in the prior art, the reflective display 10 provided by this embodiment has higher brightness.

In this embodiment, the light guide plate 13 is made of a polymer material, so that the linearly polarized light emitted by the light source 12 can be reflected between the upper and lower surfaces of the light guide plate 13, and is emitted from the lower surface of the light guide plate 13 to the liquid crystal layer. 11, but not from between the upper surfaces of the light guide plate 13 to the viewer. Preferably, the orientation birefringence and photoelastic birefringence of the polymer material for preparing the light guide plate 13 are 0; offset.

In this embodiment, a spacer is provided between the quarter-wave plate 140 and the absorbing plate 15 to control the thickness of the cholesteric liquid crystal layer 141 . Preferably, the spacers are glass beads; the thickness of the cholesteric liquid crystal layer 141 is 7-22 μm. Further preferably, the thickness of the cholesteric liquid crystal layer 141 is 10 μm.

To sum up, the light source 12 of the reflective liquid crystal display 10 provided in this embodiment is a polarized light source, which has higher brightness under the same power than the combination of the existing light source and polarizer; and, Since the light source 12 is a polarized light source, there is no need to set a polarizer in the reflective liquid crystal display provided by this embodiment, which avoids light being absorbed by the polarizer, so that the linearly polarized light emitted by the light source 12 has a higher The transmittance; furthermore, the reflective liquid crystal display 10 provided by this embodiment has higher brightness.

It should be noted that, in this embodiment, the angle between the polarization direction of the linearly polarized light emitted by the light source 12 and the upper and lower surfaces of the light guide plate 13 and the light guide plate 13 is 90 degrees, but the present invention is not limited thereto. In application, the polarization direction of the linearly polarized light emitted by the light source 12 to the light guide plate 13 can also be parallel to the upper and lower surfaces of the light guide plate 13; and, there can also be a preset angle between the above two, and the range of the preset angle is Between 0 and 90 degrees.

It can be understood that, the above embodiments are only exemplary embodiments adopted for illustrating the principle of the present invention, but the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also regarded as the protection scope of the present invention.

Claims (10)

1. a reflective liquid-crystal display, comprise the liquid crystal layer between two substrates, be positioned at light source and the light guide plate of described liquid crystal layer one side, be positioned at the reflection horizon of described liquid crystal layer opposite side, it is characterized in that, described reflective liquid-crystal display also comprises baffle, for absorbing the light of baffle described in directive; Described baffle and liquid crystal layer lay respectively at the both sides in described reflection horizon;

Described light source is polarized light source; Described reflection horizon comprises quarter-wave plate and cholesteric crystal layer, and described quarter-wave plate is between described liquid crystal layer and described cholesteric crystal layer.

2. reflective liquid-crystal display according to claim 1, it is characterized in that, the sense of rotation of the pitch of the cholesteric liquid crystal in described cholesteric crystal layer is left-handed, described cholesteric crystal layer allows right-circularly polarized light transmission, and left circularly polarized light can be reflected to described quarter-wave plate; Or

The sense of rotation of the pitch of the cholesteric liquid crystal in described cholesteric crystal layer is dextrorotation, and described cholesteric crystal layer allows left circularly polarized light transmission, and right-circularly polarized light can be reflected to described quarter-wave plate.

3. reflective liquid-crystal display according to claim 1, is characterized in that, described light guide plate adopts polymeric material to make.

4. reflective liquid-crystal display according to claim 3, is characterized in that, the orientation birefringence rate of described polymeric material and photoelasticity birefringence rate are 0.

5. reflective liquid-crystal display according to claim 1, is characterized in that, described polarized light source sends linearly polarized light to described light guide plate, and angle between the polarization direction of this linearly polarized light and the upper and lower surface of light guide plate is 90 degree.

6. reflective liquid-crystal display according to claim 1, is characterized in that, described polarized light source sends linearly polarized light to described light guide plate, and parallel between the polarization direction of this linearly polarized light and the upper and lower surface of light guide plate.

7. reflective liquid-crystal display according to claim 1, is characterized in that, the scope of the thickness of described cholesteric crystal layer is 7～22 μ m.

8. reflective liquid-crystal display according to claim 1, is characterized in that, the liquid crystal in described liquid crystal layer is nematic liquid crystal.

9. reflective liquid-crystal display according to claim 1, is characterized in that, described polarized light source is side entering type light source.

10. reflective liquid-crystal display according to claim 1, it is characterized in that, the substrate that is positioned at described liquid crystal layer both sides is respectively array base palte and color membrane substrates, and described array base palte is between described liquid crystal layer and described reflection horizon, and described color membrane substrates is between described liquid crystal layer and described light guide plate;

On described array base palte and described color membrane substrates, be respectively equipped with transparency electrode.