KR101107692B1 - Reflective type Liquid Crystal Display System - Google Patents

Abstract

The present invention includes a lower substrate, an upper substrate, and a liquid crystal layer formed between the two substrates, and a reflective liquid crystal display device having the light absorbing layer and the CLC layer formed on the light absorbing layer and the reflection on the lower substrate. The present invention relates to a reflective liquid crystal display system comprising a polarizer for irradiating polarized light to a liquid crystal display device.

According to the present invention, the image can be reproduced only through an external light source polarized in a specific direction, so that the image can be reproduced only to a specific person possessing a specific polarizer, so that it can be used as a liquid crystal display device containing information that requires confidentiality. Can be.

Reflective liquid crystal display device, polarized light

Description

Reflective liquid crystal display system

1 is a schematic cross-sectional view of a conventional reflective liquid crystal display device.

2 is a schematic cross-sectional view of a reflective liquid crystal display system according to the present invention.

3 is an exploded perspective view of a reflective liquid crystal display device according to the present invention.

<Description of the symbols for the main parts of the drawings>

100: lower substrate 200: upper substrate

300: liquid crystal layer 400: polarizer

140: light absorption layer 160: CLC layer

The present invention relates to a liquid crystal display device, and more particularly to a reflective liquid crystal display device.

The liquid crystal display device is composed of a lower substrate and an upper substrate facing each other at a predetermined interval, and a liquid crystal layer formed between the two substrates. The liquid crystal layer is driven by an electric field formed between the two substrates, and the driving thereof is performed. It is an element which displays an image by adjusting the light transmittance through the liquid crystal layer.

Since the liquid crystal display device does not have a light emitting source in the device itself, a separate light source is required. In some cases, a backlight disposed below the liquid crystal display may be used as the light source, or external light may be used as the light source.

In general, the case of using a backlight is called a transmissive liquid crystal display device, and the case of using external light is called a reflective liquid crystal display device.

The transmissive liquid crystal display device has limitations in making it extremely lightweight and ultra-thin due to the weight and volume of the backlight, and has a problem in that power consumption increases due to the backlight driving. There is a problem that the brightness of the light emitted through is extremely low.

On the contrary, since the reflective liquid crystal display does not include a separate light source, all of the problems of the transmissive liquid crystal display may be solved.

Hereinafter, a conventional reflective liquid crystal display device will be described with reference to the drawings.

1 is a schematic cross-sectional view of a conventional reflective liquid crystal display device.

As shown in FIG. 1, the conventional reflective liquid crystal display device includes a lower substrate 10, an upper substrate 20, and a liquid crystal layer 30 formed between both substrates 10 and 20.

The reflective plate 12 is formed on the lower substrate 10, and the polarizer 25 is attached to the outside of the upper substrate 20. The polarizer 25 is mainly composed of a linear polarizing plate 22 and a retardation film 24.

In the reflective liquid crystal display device having such a configuration, the external light is polarized while passing through the polarizer 25, and then passes through the liquid crystal layer 30, and after the passed light is reflected by the reflector 12, the polarizer is again. As a principle of reproducing an image by passing through 25 and reproducing to the outside, the principle will be described below in more detail.

It is assumed that the linear polarizing plate 22 is a linear polarizing plate in the vertical direction, the retardation film 24 is a 1/4 lambda retardation film, and the liquid crystal layer 30 assumes a 1/4 lambda retardation change when an electric field is applied.

When the electric field is not applied, the external light is linearly polarized after passing through the linear polarizing plate 22 and then changed into right circularly polarized light while passing through the retardation film 24 to pass through the liquid crystal layer 30. When the electric field is not applied, the light passing through the liquid crystal layer 30 is transmitted as it is without changing the phase difference and is reflected by the lower reflector 12. The light reflected by the reflector 12 is changed to left circularly polarized light, and passes through the liquid crystal layer 30 as it is, and is linearly polarized in the horizontal direction while passing through the retardation film 24. Therefore, the image cannot be passed through the linear polarizing plate 22 in the vertical direction, and the image displays black.

When the electric field is applied, the external light is linearly polarized in the vertical direction after the linear polarizing plate 22, and is changed into right circularly polarized light while passing through the retardation film 24 to pass through the liquid crystal layer 30. When the electric field is applied, light passing through the liquid crystal layer 30 is linearly polarized in the horizontal direction. The light reflected by the reflector 12 maintains linear polarization in the horizontal direction, changes to right circular polarization while passing through the liquid crystal layer 30, and linearly polarizes in the vertical direction while passing through the retardation film 24. Therefore, the linear polarizer 22 passes through the image to display white.                         

In the conventional reflective liquid crystal display device, an image is reproduced by adjusting a polarization direction of incident and reflected light according to whether an electric field is applied, and together with the reflector 12, a polarizer 25 for polarization is an essential component. It is included.

While the present inventors have studied cholesteric liquid crystal (hereinafter, referred to as CLC) which is one of liquid crystals used in liquid crystal display devices, when the CLC is applied to the conventional reflective liquid crystal display device, The present invention was completed by confirming that it is possible to develop a display device capable of reproducing an image only through a specific light source.

That is, when the CLC is applied to a conventional reflective liquid crystal display device, the image can be reproduced only by using a specific external light source, so that the image can be reproduced only by a specific person who owns the external specific light source. Will be utilized as a liquid crystal display device containing.

The present invention includes a lower substrate, an upper substrate, and a liquid crystal layer formed between the two substrates, wherein the light absorbing layer and the CLC layer are formed on the light absorbing layer on the lower substrate. Provided is an element.

The present invention also provides a reflective liquid crystal display system comprising a reflective liquid crystal display device having the light absorption layer and the CLC layer formed on a lower substrate, and a polarizing device for irradiating polarized light to the liquid crystal display device.

The CLC reflects light when polarized light having the same direction as the rotational direction is reflected, while transmitting the light when polarized light having a direction different from the rotational direction is received.

Therefore, when the CLC layer is formed on the reflective liquid crystal display device in place of the conventional reflecting plate and the light absorption layer is formed below, only the light polarized in the same direction as the rotation direction of the CLC layer is reflected on the CLC layer so that the image is white. The other is transmitted through the CLC layer and absorbed by the light absorbing layer below it, so that the image displays black, so that the information displayed by the image can be viewed only through the light polarized in the specific direction.

Hereinafter, the present invention will be described in detail with reference to the drawings.

2 is a schematic cross-sectional view of a reflective liquid crystal display device and a system thereof according to the present invention.

As can be seen in FIG. 2, the reflective liquid crystal display device according to the present invention includes a lower substrate 100, an upper substrate 200, and a liquid crystal layer 300 formed between both substrates 100 and 200. .

The light absorption layer 140 is formed on the lower substrate 100, and the CLC layer 160 is formed on the light absorption layer 140. The light absorption layer 140 is for absorbing the light transmitted through the CLC layer 160 so that the image is displayed in black, the material and formation method of the light absorption layer 140 can be changed within a range apparent to those skilled in the art. have.

Unlike the related art, the polarizer 25 is not attached to the outside of the upper substrate 200. However, light polarized through the polarizer 400 from the outside of the liquid crystal display is incident to the liquid crystal display, and the liquid crystal display and the polarizer 400 form a liquid crystal display system.

Referring to the operation of the reflective liquid crystal display device and the system according to the present invention having such a configuration,

When external light is incident from the polarizer 400, the light transmitted through the liquid crystal layer 300 and the light transmitted through the liquid crystal layer 300 meet the CLC layer 160. At this time, when the light transmitted through the liquid crystal layer 300 is polarized in the same direction as the rotation direction of the CLC layer 160, the image is reflected and the image is displayed white, but the light transmitted through the liquid crystal layer 300 is the CLC layer ( When polarized in a direction different from the rotation direction of the 160, the light is transmitted and absorbed by the light absorbing layer 140 so that the image displays black.

In the present invention, the white or black image is determined by the polarization state of the external light incident from the polarizer, the rotation direction of the CLC layer, and the phase difference change of the liquid crystal layer formed between the lower substrate and the upper substrate. Accordingly, by appropriately adjusting the polarization state of the external light, the rotation direction of the CLC layer, and the phase difference change of the liquid crystal layer, only the owner of the specific light source can see the image.

Hereinafter, the principle of the present invention will be described in detail with some examples.

First Embodiment (Examples 1 through 4)

1. First embodiment

An external light source receives right circularly polarized light, and the liquid crystal layer 300 has a 1 / 2λ phase difference change when an electric field is applied, and the rotation direction of the CLC layer 160 may be designed in a left circle direction.                     

Looking at the reproduction of the image in this form,

When no electric field is applied, the right circularly polarized light incident from the outside passes through the liquid crystal layer 300 as it is, and the transmitted light also transmits the CLC layer 160 because the rotation direction of the CLC layer 160 is designed in the left circle direction. It is absorbed in the light absorbing layer 140. As a result, the image displays black.

When the electric field is applied, the right circularly polarized light incident from the outside is changed to the left circularly polarized light while passing through the liquid crystal layer 300, and the left circularly polarized light is reflected by the CLC layer 160. The image eventually displays white.

2. Second Embodiment

The external light source is incident to the left circularly polarized light, the liquid crystal layer 300 is changed by 1 / 2λ phase difference when the electric field is applied, the rotation direction of the CLC layer 160 can be designed in the left circle direction.

When no electric field is applied, the left circularly polarized light incident from the outside passes through the liquid crystal layer 300 as it is, and the transmitted light is reflected by the CLC layer 160. The image eventually displays white.

When the electric field is applied, the left circularly polarized light incident from the outside is changed into right circularly polarized light while passing through the liquid crystal layer 300, and the right circularly polarized light is transmitted through the CLC layer 160 and is absorbed by the light absorbing layer 140. . As a result, the image displays black.

3. Third embodiment

An external light source receives right circularly polarized light, the liquid crystal layer 300 has a 1 / 2λ phase difference change when an electric field is applied, and the CLC layer 160 may be designed in the right direction.

When no electric field is applied, right circularly polarized light incident from the outside passes through the liquid crystal layer 300 as it is, and the transmitted light is reflected by the CLC layer 160. The image eventually displays white.

When the electric field is applied, the right circularly polarized light incident from the outside is changed into the left circularly polarized light while passing through the liquid crystal layer 300, and the left circularly polarized light is transmitted through the CLC layer 160 and is absorbed by the light absorption layer 140. As a result, the image displays black.

4. Fourth embodiment

An external light source enters a left circularly polarized light, the liquid crystal layer 300 may undergo a 1/2 lambda phase shift when an electric field is applied, and the CLC layer 160 may be designed in a right circumferential direction.

When no electric field is applied, the left circularly polarized light incident from the outside passes through the liquid crystal layer 300 as it is, and the transmitted light passes through the CLC layer 160 and is absorbed by the light absorbing layer 140. As a result, the image displays black.

When the electric field is applied, the left circularly polarized light incident from the outside is changed into the left circularly polarized light while passing through the liquid crystal layer 300, and the left circularly polarized light is reflected by the CLC layer 160. The image eventually displays white.

The above is summarized in Table 1 below.

TABLE 1

First embodiment Second embodiment Third embodiment Fourth embodiment External light source U-Polar Polarization Left circular polarization U-Polar Polarization Left circular polarization Liquid crystal layer 1 / 2λ 1 / 2λ 1 / 2λ 1 / 2λ CLC layer Left circle direction Left circle direction Right direction Right direction burn Without voltage black White White black When voltage is applied White black black White

As described above, in the case of applying the liquid crystal layer 300 in which a 1/2 lambda retardation change occurs when the electric field is applied, right circularly polarized light or left circularly polarized light can be appropriately selected as an external light source according to the rotation direction of the CLC layer 160.

Therefore, only the user having the right circularly polarizing device or the left circularly polarizing device as the polarizer 400 for injecting the external light can check the information displayed by the liquid crystal display device.

Second Embodiment (Examples 5 to 6)

5. Fifth Embodiment

An external light source enters a linearly polarized light in a horizontal direction, and the liquid crystal layer 300 undergoes a -1 / 4λ to 1 / 4λ phase difference change when an electric field is applied, and the rotation direction of the CLC layer 160 is designed in a left circle direction. can do.

Looking at the reproduction of the image in this form,

When no electric field is applied, horizontally linearly polarized light incident from the outside penetrates the -1 / 4λ liquid crystal layer 300 to become right circularly polarized light, and the transmitted light passes through the CLC layer 160 and the light absorbing layer 140 Is absorbed. The image will eventually display black.

When the electric field is applied, the horizontally linearly polarized light incident from the outside passes through the 1 / 4λ liquid crystal layer 300 while passing through the liquid crystal layer 300, and is changed into left circularly polarized light, and the left circularly polarized light is transferred from the CLC layer 160. Will be reflected. The image eventually displays white.

6. Sixth embodiment

An external light source enters a linearly polarized light in a vertical direction, and the liquid crystal layer 300 undergoes a -1 / 4λ to 1 / 4λ phase difference change when an electric field is applied, and the rotation direction of the CLC layer 160 is designed in a left circle direction. can do.

When no electric field is applied, vertically polarized light incident from the outside passes through the -1 / 4λ liquid crystal layer 300 to become left circularly polarized light, and the left circularly polarized light is reflected by the CLC layer 160. The image eventually displays white.

When the electric field is applied, the linearly polarized light incident from the outside is changed into right circularly polarized light while passing through the 1 / 4λ liquid crystal layer 300, and the right circularly polarized light is transmitted through the CLC layer 160, and the light absorbing layer 140 Is absorbed. The image will eventually display black.

7. Seventh embodiment

An external light source enters a linearly polarized light in a horizontal direction, and the liquid crystal layer 300 has a -1 / 4λ to 1 / 4λ phase difference change when an electric field is applied, and the CLC layer 160 may be designed in the right direction. .

Looking at the reproduction of the image in this form,

When no electric field is applied, horizontally linearly polarized light incident from the outside passes through -1 / 4λ liquid crystal layer 300 to become right circularly polarized light, and right circularly polarized light is reflected by the CLC layer 160. The image eventually displays white.

When the electric field is applied, the horizontally linearly polarized light incident from the outside is changed to the left circularly polarized light while passing through the 1 / 4λ liquid crystal layer 300, and the left circularly polarized light is transmitted through the CLC layer 160 and the light absorption layer 140 Is absorbed. The image will eventually display black.

8. Eighth Embodiment

An external light source enters a linearly polarized light in a vertical direction, and the liquid crystal layer 300 undergoes a -1 / 4λ to 1 / 4λ phase difference change when an electric field is applied, and the rotation direction of the CLC layer 160 is designed in the right direction. can do.

When no electric field is applied, vertically polarized light incident from the outside passes through the -1 / 4λ liquid crystal layer 300 to become left circularly polarized light, and left circularly polarized light passes through the CLC layer 160 and is absorbed by the light absorption layer 140. do. The image will eventually display black.

When the electric field is applied, the linearly polarized light incident from the outside is changed into right circularly polarized light while passing through the 1 / 4λ liquid crystal layer 300, and the right circularly polarized light is reflected by the CLC layer 160. The image eventually displays white.

The above is summarized in Table 2 below.

Table 2

Fifth Embodiment Sixth embodiment Seventh embodiment Eighth Embodiment External light source Horizontal polarization Vertical polarization Horizontal polarization Vertical polarization Liquid crystal layer -1 / 4λ to 1 / 4λ -1 / 4λ to 1 / 4λ -1 / 4λ to 1 / 4λ -1 / 4λ to 1 / 4λ CLC layer Left circle direction Left circle direction Right direction Right direction burn Without voltage black White black White When voltage is applied White black White black

As described above, when the liquid crystal layer 300 in which -1 / 4λ to 1 / 4λ retardation changes occur when applying an electric field is applied, horizontal polarization or vertical polarization is appropriately applied as an external light source depending on the rotation direction of the CLC layer 160. You can choose. Therefore, only a user having a horizontal polarizer or a vertical polarizer as the polarizer 400 for injecting the external light can check the information displayed by the liquid crystal display.

9. Ninth Embodiment

A horizontal linear polarizer and a -λ / n retardation plate (n is a non-zero positive integer) are attached to an unpolarized external light source, and the liquid crystal layer 300 is-(n + 4) λ / 4n and ( n-4) lambda / 4n phase difference change occurs, the rotation direction of the CLC layer 160 can be designed in the left circle direction.

Looking at the reproduction of the image in this form,

When no electric field is applied, unpolarized light incident from the outside passes through the horizontal linear polarizer, the -λ / n retardation plate, and the-(n + 4) λ / 4n liquid crystal layer 300 to become right circularly polarized light, and transmitted light The light penetrates the CLC layer 160 and is absorbed by the light absorbing layer 140. The image will eventually display black.

When the electric field is applied, the incident unpolarized light incident from the outside is changed to the left circularly polarized light through the horizontal linear polarizer, the -λ / n retardation plate, the (n-4) λ / 4n liquid crystal layer 300, The left circularly polarized light is reflected by the CLC layer 160. The image eventually displays white.

10. Tenth embodiment

A vertical linear polarizer and a -λ / n phase difference plate (n is a non-zero positive integer) are attached to an unpolarized external light source, and the liquid crystal layer 300 is-(n + 4) λ / 4n and ( n-4) lambda / 4n phase difference change occurs, the rotation direction of the CLC layer 160 can be designed in the left circle direction.

Looking at the reproduction of the image in this form,                     

When no electric field is applied, unpolarized light incident from the outside passes through the vertical linear polarizer, the -λ / n phase difference plate, and the-(n + 4) λ / 4n liquid crystal layer 300 to become left circularly polarized light, and left circularly polarized light is Reflected by the CLC layer 160. The image eventually displays white.

When the electric field is applied, the incident unpolarized light incident from the outside passes through the vertical linear polarizer, the -λ / n phase difference plate, the (n-4) λ / 4n liquid crystal layer 300, and becomes right circularly polarized light, and is transmitted. The light is transmitted through the CLC layer 160 and absorbed by the light absorbing layer 140. The image will eventually display black.

11. Eleventh Embodiment

A horizontal linear polarizer and a -λ / n phase difference plate (n is a nonzero positive integer) are attached to an unpolarized external light source, and the liquid crystal layer 300 is (3n-4) λ / 4n and (n -4) [lambda] / 4n phase shift occurs, and the rotational direction of the CLC layer 160 can be designed in the left circle direction.

Looking at the reproduction of the image in this form,

When no electric field is applied, unpolarized light incident from the outside passes through the horizontal linear polarizer, the -λ / n phase difference plate, the (3n-4) λ / 4n liquid crystal layer 300 to become right circularly polarized light, and the transmitted light is It passes through the CLC layer 160 and is absorbed by the light absorbing layer 140. The image will eventually display black.

When the electric field is applied, the incident unpolarized light incident from the outside passes through the horizontal linear polarizer, the -λ / n phase difference plate, the (n-4) λ / 4n liquid crystal layer 300, and is changed into left circularly polarized light, The left circularly polarized light is reflected by the CLC layer 160. The image eventually displays white.                     

12. Twelfth Embodiment

A vertical linear polarizer and a -λ / n phase difference plate (n is a non-zero positive integer) are attached to an unpolarized external light source, and the liquid crystal layer 300 is (3n-4) λ / 4n and (n -4) [lambda] / 4n phase shift occurs, and the rotational direction of the CLC layer 160 can be designed in the left circle direction.

Looking at the reproduction of the image in this form,

When no electric field is applied, unpolarized light incident from the outside passes through the vertical linear polarizer, the -λ / n phase difference plate, and the-(n + 4) λ / 4n liquid crystal layer 300 to become left circularly polarized light, and left circularly polarized light is Reflected by the CLC layer 160. The image eventually displays white.

When the electric field is applied, the incident unpolarized light incident from the outside passes through the vertical linear polarizer, the -λ / n phase difference plate, the (n-4) λ / 4n liquid crystal layer 300, and becomes right circularly polarized light, and is transmitted. The light is transmitted through the CLC layer 160 and absorbed by the light absorbing layer 140. The image will eventually display black.

The present invention is not limited to the above twelve embodiments and may be appropriately changed within the scope of the technical idea of the present invention.

Hereinafter, the configuration of the liquid crystal display device to which the basic principle of the present invention is applied will be described in detail.

3 is an exploded perspective view of one embodiment of a reflective liquid crystal display device according to the present invention.

As can be seen in Figure 3,

In the upper substrate 200, a plurality of gate lines 220 are formed in the horizontal direction, and a plurality of data lines 240 are formed in the vertical direction so as to cross each other to define a pixel area.

At the intersection of the gate line 220 and the data line 240, a thin film transistor T including a gate electrode, a semiconductor layer, a source electrode, and a drain electrode is formed as a switching element.

A pixel electrode 260 connected to the drain electrode of the thin film transistor T is formed in the pixel area.

The light absorbing layer 140 and the CLC layer 160 are sequentially formed on the lower substrate 100. In addition, the common electrode 180 is formed on the CLC layer 160, thereby driving a vertical electric field together with the pixel electrode 260 of the upper substrate 200 to drive a liquid crystal layer (not shown). .

Although not shown, an alignment layer for initial alignment of liquid crystals is formed on at least one of the upper substrate 200 and the lower substrate 100.

Meanwhile, in order to realize a color image, a color filter layer should be formed. As the color filter layer, although red, green, and blue color filters may be formed for each cell between the CLC layer 160 and the common electrode 180 of the lower substrate 100, the color filter layer is not formed separately. The color image may be implemented using the CLC layer 160.

That is, by designing the CLC layer 160 to have different rotation pitches for each cell to reflect only red, green, and blue light for each cell, a color image can be realized without forming a separate color filter layer.                     

As described above, the liquid crystal display device illustrated in FIG. 3 corresponds to an embodiment of the present invention, and the liquid crystal display device according to the present invention may be variously changed within the scope of the technical idea of the present invention. The material and the method of forming the element can likewise be changed.

Since the reflective liquid crystal display device according to the present invention can reproduce an image only through an external light source polarized in a specific direction, the image can be reproduced only by a specific person who owns a specific polarizer, so that confidentiality is required. It can be used as a liquid crystal display device containing information.

Claims (12)

delete delete delete delete delete It comprises a lower substrate, an upper substrate, and a liquid crystal layer formed between the both substrates, A reflective liquid crystal display device having a light absorption layer and a CLC (Cholesteric Liquid Crystal) layer formed on the lower substrate; And a polarizer for irradiating polarized light to the reflective liquid crystal display device. The method of claim 6, The polarizer is a right circular polarizer or a left circular polarizer, The liquid crystal layer of the reflection type liquid crystal display device is a reflection type liquid crystal display system, characterized in that the change of 1 / 2λ phase difference occurs when an electric field is applied. The method of claim 6, The polarizer is a horizontal polarizer or a vertical polarizer, The liquid crystal layer of the reflective liquid crystal display device is a reflection type liquid crystal display system, characterized in that -1 / 4λ ~ 1 / 4λ phase difference change occurs when an electric field is applied. The method of claim 6, The polarizer includes a device having a phase difference of λ / n in a horizontal polarizer or a vertical polarizer, The liquid crystal layer of the reflective liquid crystal display device is a reflection type liquid crystal display system, characterized in that-(n + 4) λ / 4n to (n-4) λ / 4n retardation changes. The method of claim 6, The polarizer includes a device having a phase difference of λ / n in a horizontal polarizer or a vertical polarizer, And (3n-4) λ / 4n to (n-4) λ / 4n phase shifts in the liquid crystal layer of the reflective liquid crystal display device. The method of claim 6, The CLC layer is a reflection type liquid crystal display system characterized in that the rotation pitch is different for each cell is designed to reflect only the red, green, blue light for each cell. The method of claim 6, And a red, green, and blue color filter layer further formed on the CLC layer.

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