KR20010110849A - Transparent and Reflective Type Liquid Crystal Display Apparatus - Google Patents

Abstract

The present invention relates to a transmissive reflective liquid crystal display device for enhancing the light efficiency.

Transmissive reflective liquid crystal display device of the present invention is installed on the back of the front substrate absorbing color filter for transmitting only visible light of a specific band, and is installed between the liquid crystal layer and the back substrate to reflect the light incident from the front substrate and In addition, a metal reflector plate having a hole for passing light from the backlight unit installed under the back substrate, and an external light incident through the front substrate and the light incident from the backlight unit in a non-display operation mode mixed in the liquid crystal layer Dichroic dye for absorbing light is provided.

According to the present invention, according to the present invention, in the transmissive reflection type liquid crystal display, a dichroic dye is added to the liquid crystal layer to express white color in the transmissive mode. In addition, two quarter wave plates are removed, thereby maximizing optical efficiency and minimizing manufacturing costs. Furthermore, the state of black can be expressed without the polarizing plate by the dichroic dye mixed with the liquid crystal layer. Therefore, not only high light efficiency can be obtained but also color purity can be improved.

Description

Transparent and Reflective Type Liquid Crystal Display Apparatus}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a transmissive reflective liquid crystal display device for enhancing light efficiency.

An active matrix liquid crystal display device displays a natural moving image using a thin film transistor (hereinafter, referred to as TFT) as a switching element. Such a liquid crystal display device can be miniaturized compared to a CRT and commercialized as a monitor such as a portable television or a laptop-type personal computer.

Since the liquid crystal display is not a self-light emitting device, a separate light source is required. The liquid crystal display may be represented by a transmissive type or a reflective type depending on a light source. In the transmissive liquid crystal display device, a backlight unit is installed to face a rear substrate of two transparent substrates into which liquid crystal is injected to transmit light incident from the backlight unit toward the projection surface. On the other hand, the reflective liquid crystal display device forms a reflective surface on the rear substrate of the two transparent substrates into which the liquid crystal is injected to display external light incident to the rear substrate via the front substrate or a separate auxiliary light. It is reflected toward.

Recently, research on a transmissive reflective liquid crystal display device, which can have advantages of a transmissive type and a reflective type, has been activated.

Referring to FIG. 1, a conventional transmissive reflection type liquid crystal display device includes a front substrate 16 and a rear substrate 8 into which a liquid crystal 12 is injected, and a second quarter wave stacked on the front surface of the front substrate 16. Quarter Wave Plate (hereinafter referred to as "QWP") 18 and the second linear polarizer 20, the absorption type color filter 14 provided between the front substrate 16 and the liquid crystal 12, and the back A first QWP 6 and a first linear polarizing plate 4 stacked on the rear surface of the substrate 8 and a metal reflecting plate 10 provided between the rear substrate 8 and the liquid crystal 12 are provided. Holes 13 are formed in the metal reflector 10 at predetermined intervals. The external light is converted into specific linearly polarized light by the second linear polarizer 20, and then converted into circularly polarized light by the second QWP 18 to pass the metal reflector plate through the absorption type color filter 14 and the liquid crystal 12. It is incident on the reflecting surface 11 of 10). The external light incident on the reflecting surface 11 of the metal reflecting plate 105 travels toward the display surface by traveling back to the optical path. In this case, the absorption type color filter 14 transmits only visible light of a specific wavelength band and absorbs light beams of other wavelengths. The light incident from the backlight unit 2 is converted into a specific linearly polarized light by the first linear polarizer 4 and is converted into circularly polarized light by the first QWP 6 to pass through the back substrate 8, and then a metal reflector plate ( 10). The light incident on the metal reflector 10 from the backlight unit 2 is incident on the liquid crystal 12 through the hole 13 of the metal reflector 10, and then proceeds toward the display surface via the liquid crystal 12. do.

Referring to FIG. 2A, when the power is not applied, the transmissive operation will be described in detail. First, the light emitted from the backlight unit 2 is incident to the first linear polarizer 4. Of the light incident from the backlight unit 2 to the first linear polarizer 4, only linearly polarized light equal to the optical axis of the first linear polarizer 4 passes through the first linear polarizer 4. The light passing through the first linear polarizing plate 4 has an optical axis of 45 degrees. Light passing through the first linear polarizer 4 is converted into left circular polarization by the first QWP 6. The light changed to the left circularly polarized light by the first QWP 6 enters the liquid crystal 12 through the holes 13 of the back substrate 8 and the metal reflecting plate 10. The left circularly polarized light incident on the liquid crystal 12 is converted into linearly polarized light by the liquid crystal 12. At this time, the linearly polarized light converted from the liquid crystal 12 is perpendicular to the optical axis of the first linearly polarized light 4 by 90 degrees. The linearly polarized light passing through the liquid crystal 12 passes through the absorption type color filter 14 and the front substrate 16 and enters the second QWP 18. The second QWP 18 converts linearly polarized light incident from the liquid crystal 12 into right polarized light. Light changed into right polarized light by the second QWP 18 is incident on the second polarizing plate 20. The second polarizing plate 20 passes only a specific linearly polarized light having an angle of 135 degrees among the right polarized light. That is, the second polarizing plate 20 passes only a specific linearly polarized light having an optical axis of 135 degrees among the left circularly polarized light incident from the second QWP 18. Accordingly, the liquid crystal display device displays gray.

Referring to the transmission type operation process in detail when the power is applied, first, the light emitted from the backlight unit 2 is incident to the first linear polarizer (4). Of the light incident on the backlight unit 2 to the first linear polarizer 4, only a specific linear polarization identical to the optical axis of the first linear polarizer 4 passes through the first linear polarizer 4. The light passing through the first linear polarizing plate 4 has an optical axis of 45 degrees. Light passing through the first linear polarizer 4 is converted into left circular polarization by the first QWP 6. The light changed to the left circularly polarized light by the first QWP 6 enters the liquid crystal 12 through the holes 13 of the back substrate 8 and the metal reflecting plate 10. The left circularly polarized light incident on the liquid crystal 12 passes through the liquid crystal 12, the absorption type color filter 14, and the front substrate 16 and enters the second QWP 18. That is, the liquid crystal 12 changes the circularly polarized light incident when the power is not applied to the specific linearly polarized light, and passes the light incident when the power is applied. The left circularly polarized light incident from the liquid crystal 12 into the second QWP 18 is changed into linearly polarized light having an angle of 45 degrees by the second QWP 18 and is incident on the second polarizing plate 20. Since the second polarizing plate 20 passes only linearly polarized light having an optical axis of 135 °, the linearly polarized light having an optical axis of 45 ° incident from the second polarizing plate 20 does not pass through the second polarizing plate 20. That is, the liquid crystal display displays black.

Referring to FIG. 2B, the reflective operation process when the power is not applied will be described in detail. First, light is incident on the second polarizing plate 20 from an external light source. The second polarizing plate 20 passes only specific linearly polarized light having an optical axis of 135 degrees among the light incident from the external light source. The linearly polarized light passing through the second polarizing plate 20 is incident to the second QWP 18. The second QWP 18 changes linearly polarized light incident from the second polarizing plate 20 into right circularly polarized light. Light changed into right polarized light by the second QWP 18 passes through the front substrate 16 and the absorption type color filter 14 and is incident to the liquid crystal 12. The liquid crystal 12 changes the circularly polarized light incident from the second QWP 18 into linearly polarized light having an optical axis of 135 degrees. Light changed into linearly polarized light having an optical axis of 135 degrees by the liquid crystal 12 is reflected by the reflecting surface 11 of the metal reflecting plate 10 and is incident on the liquid crystal 12. The liquid crystal 12 changes linearly polarized light having an optical axis of 135 degrees incident from the reflecting surface 11 into right polarized light. Light changed into right polarized light by the liquid crystal 12 is incident on the second QWP 18. The second QWP 18 changes the right circularly polarized light incident from the liquid crystal 12 into linearly polarized light having an optical axis of 135 degrees. That is, it changes in the same manner as the optical axis of the second polarizing plate 20. Light changed from the second QWP 18 to linearly polarized light having an optical axis of 135 degrees passes through the second polarizing plate 20. That is, the liquid crystal display may express white.

Referring to the reflective operation process in detail when the power is applied, first light is incident on the second polarizing plate 20 from an external light source. The second polarizing plate 20 passes only specific linearly polarized light having an optical axis of 135 degrees among the light incident from the external light source. The linearly polarized light passing through the second polarizing plate 20 is incident to the second QWP 18. The second QWP 18 changes linearly polarized light incident from the second polarizing plate 20 into right circularly polarized light. Light changed into right polarized light by the second QWP 18 passes through the front substrate 16, the absorption type color filter 14, and the liquid crystal 12, and is incident on the reflecting surface 11 of the metal reflector 10. The reflecting surface 11 of the metal reflecting plate 10 changes the right circularly polarized light incident from the liquid crystal 12 into the left circularly polarized light. Light changed to left circularly polarized light by the reflecting surface 11 of the metal reflecting plate 10 passes through the liquid crystal 12, the color filter 14, and the front substrate 16 and is incident to the second QWP 18. The second QWP 18 changes the left circularly polarized light input from the reflecting surface 11 of the metal reflecting plate 10 into linearly polarized light having an optical axis of 45 degrees. That is, it changes perpendicularly to the optical axis of the second polarizing plate 20. Light changed from the second QWP 18 to linearly polarized light having an optical axis of 45 degrees does not pass through the second polarizing plate 20. That is, the LCD displays black.

As described above, in the transmissive reflection type liquid crystal display, only a part of the light irradiated from the backlight unit 2 passes through the second polarizing plate 20 and thus cannot express white color. That is, in the case of displaying an image or an image in a transmissive type, only a part of the light generated from the backlight unit 2 is used as the display light, thereby reducing the light efficiency. In addition, since the first and second QWPs 6 and 18 are stacked in order to control the direction of the optical axis, the manufacturing cost is increased.

Accordingly, an object of the present invention relates to a transmissive reflective liquid crystal display device for enhancing the light efficiency.

1 is a cross-sectional view showing a conventional transmissive reflection type liquid crystal display device.

FIG. 2A is a diagram illustrating a transmissive mode operation process of the LCD shown in FIG. 1; FIG.

FIG. 2B is a view illustrating a reflective mode operation process of the LCD shown in FIG. 1; FIG.

3 is a cross-sectional view showing a transmissive reflective liquid crystal display device of the present invention.

4A and 4B are detailed views of the liquid crystal layer of the liquid crystal display shown in FIG.

FIG. 5A is a view illustrating an operation process of a transmissive mode of the LCD shown in FIG. 3.

FIG. 5B is a view illustrating an operation process of the reflective mode of the LCD shown in FIG. 3; FIG.

<Description of Symbols for Main Parts of Drawings>

2,36: backlight unit 4,20,22,34: linear polarizer

6,18: QWP 8,32: back board

10,30: metal reflecting plate 11,31: reflecting surface

12,28,38 Liquid Crystal 13,33 Hall

14,26: Absorption type color filter 16,24: Front substrate

40: dichroic dye

In order to achieve the above object, the transmissive reflection type liquid crystal display device of the present invention is installed on the rear surface of the front substrate, and is an absorption type color filter for transmitting only visible light of a specific band, and is installed between the liquid crystal layer and the rear substrate to enter from the front substrate. A metal reflector plate having a hole for reflecting light and passing light from the backlight unit provided below the rear substrate, and a light and front substrate mixed in the liquid crystal layer and incident from the backlight unit in a non-display operation mode. It is provided with a dichroic dye for absorbing the external light incident via.

Other objects and features of the present invention in addition to the above object will be apparent from the description of the embodiments with reference to the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described with reference to FIGS. 3 to 5B.

3 is a cross-sectional view showing a transmissive reflective liquid crystal display device of the present invention.

Referring to FIG. 3, the transparent reflection type liquid crystal display device according to the present invention includes a front substrate 24 and a rear substrate 32 into which the liquid crystal layer 28 is injected, and a second stacked on the front surface of the front substrate 24. An absorption type color filter 26 disposed between the polarizing plate 22, the front substrate 24, and the liquid crystal layer 28, the first polarizing plate 34 laminated on the rear surface of the rear substrate 32, and the rear surface. A metal reflector 30 is provided between the substrate 32 and the liquid crystal layer 28. The holes 33 are formed in the metal reflecting plate 30 at predetermined intervals. In the liquid crystal layer 28 of the present invention, the liquid crystal 38 and the dichroic dye (Dye) 40 are mixed as shown in FIGS. 4A and 4B. In the dichroic dye 40 mixed in the liquid crystal layer 28, the absorption of light varies depending on the polarization direction.

Referring to FIG. 5A, when the power is not applied, the transmissive operation will be described in detail. First, light emitted from the backlight unit 36 is incident to the first linear polarizer 34. Of the light incident from the backlight unit 36 to the first linear polarizer 34, only 45 ° linearly polarized light equal to the optical axis of the first linear polarizer 34 passes through the first linear polarizer 34. The linearly polarized light that has passed through the first linear polarizing plate 34 passes through the holes 33 of the back substrate 32 and the metal reflecting plate 30 and enters the liquid crystal layer 28. At this time, the dichroic dye 40 mixed in the liquid crystal layer 28 is horizontally arranged as shown in FIG. 4A. That is, the major axis of the dichroic dye 40 is the same as the vibration direction of light. Accordingly, the dichroic dye 40 absorbs light, and the liquid crystal display device displays black.

Referring to the transmission type operation process in detail when the power is applied, first, the light emitted from the backlight unit 36 is incident to the first linear polarizer 34. Of the light incident from the backlight unit 36 to the first linear polarizer 34, only 45 ° linearly polarized light equal to the optical axis of the first linear polarizer 34 passes through the first linear polarizer 34. The linearly polarized light that has passed through the first linear polarizing plate 34 passes through the holes 33 of the back substrate 32 and the metal reflecting plate 30 and enters the liquid crystal layer 28. At this time, the dichroic dye 40 mixed in the liquid crystal layer 28 is vertically arranged as shown in FIG. 4B. That is, since the dichroic dye 40 vibrates in the uniaxial direction, most of the light is not absorbed by the dichroic dye 40. Light having 45 ° linearly polarized light incident from the metal reflecting plate 30 into the liquid crystal layer 28 is changed to 135 ° linearly polarized light by the twist angle of the liquid crystal layer 28. That is, it changes in the same manner as the optical axis of the second linear polarizing plate 22. Light passing through the liquid crystal layer 28 passes through the absorption type color filter 26 and the front substrate 24 and is incident on the second linear polarizer 22. At this time, since the optical axis of the linearly polarized light incident from the liquid crystal layer 28 to the second linear polarizer 22 and the optical axis of the second linear polarizer 22 are the same, the linearly polarized light passes through the second linear polarizer 22. That is, the liquid crystal display displays a white state.

Referring to FIG. 5B, when the power is not applied, the reflective operation process will be described in detail. First, light is incident on the second polarizer 22 from an external light source. The second polarizing plate 22 passes only linearly polarized light having an optical axis of 135 degrees among the light incident from the external light source. The linearly polarized light passing through the second polarizing plate 22 passes through the front substrate 24 and the absorption type color filter 26 and is incident to the liquid crystal layer 28. At this time, the dichroic dye 40 mixed in the liquid crystal layer 28 is horizontally arranged as shown in FIG. 4A. That is, the major axis of the dichroic dye 40 is the same as the vibration direction of light. Accordingly, the dichroic dye 40 absorbs light, and the liquid crystal display device displays black.

Referring to the reflective operation process when the power is applied, first, light is incident on the second polarizer 22 from an external light source. The second polarizing plate 22 passes only linearly polarized light having an optical axis of 135 degrees among the light incident from the external light source. The linearly polarized light passing through the second polarizing plate 22 passes through the front substrate 24 and the absorption type color filter 26 and is incident to the liquid crystal layer 28. At this time, the dichroic dye 40 mixed in the liquid crystal layer 28 is vertically arranged as shown in FIG. 4B. That is, since the dichroic dye 40 vibrates in the uniaxial direction, most of the light is not absorbed by the dichroic dye 40. Light incident on the liquid crystal layer 28 from the second polarizing plate 22 is changed into linearly polarized light of 45 degrees by the twist angle of the liquid crystal 38. The linearly polarized light of 45 degrees passing through the liquid crystal layer 28 is reflected by the reflecting surface 31 of the metal reflecting plate 30 and is incident on the liquid crystal layer 28. The liquid crystal layer 28 changes 45 ° linearly polarized light incident from the metal reflector 30 to 135 ° linearly polarized light. That is, it changes in the same manner as the optical axis of the second linear polarizing plate 22. Light passing through the liquid crystal layer 28 passes through the absorption type color filter 26 and the front substrate 24 and is incident on the second linear polarizer 22. At this time, since the optical axis of the linearly polarized light incident from the liquid crystal layer 28 to the second linear polarizer 22 and the optical axis of the second linear polarizer 22 are the same, the linearly polarized light passes through the second linear polarizer 22. That is, the liquid crystal display displays a white state.

The liquid crystal display of the present invention may display a white state when no power is applied, and display a black state when an electric power is applied.

In the transmissive reflection type liquid crystal display device of the present invention, the dichroic dye 40 may be added to the liquid crystal layer 28 to display a black state regardless of the presence or absence of the polarizing plates 22 and 34. Therefore, the polarizing plates 22 and 34 may be removed in the transmissive reflection liquid crystal display of the present invention.

As described above, according to the present invention, the transmissive reflection type liquid crystal display device adds a dichroic dye to the liquid crystal layer to express white color in the transmissive mode. In addition, two quarter wave plates are removed, thereby maximizing optical efficiency and minimizing manufacturing costs. Furthermore, the state of black can be expressed without the polarizing plate by the dichroic dye mixed with the liquid crystal layer. Therefore, not only high light efficiency can be obtained but also color purity can be improved.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (5)

In a transmissive liquid crystal display device comprising a liquid crystal layer between a front substrate and a back substrate, An absorption type color filter installed on a rear surface of the front substrate to transmit only visible light of a specific band; A metal reflector plate disposed between the liquid crystal layer and the rear substrate to reflect light incident from the front substrate and to pass light from the backlight unit disposed below the rear substrate; And a dichroic dye mixed in the liquid crystal layer to absorb light incident from the backlight unit in a non-display operation mode and external light incident through the front substrate. The method of claim 1, The dichroic dye is a transmissive liquid crystal display device, characterized in that the absorption rate of the long axis and short axis are different. The method of claim 1, A first linear polarizing plate installed on the front substrate to pass only light having a specific polarization axis; And a second linear polarizer disposed under the rear substrate and having a polarization axis in a direction orthogonal to the first linear polarizer. The method of claim 1, And wherein the long axis of the dichroic dye is vertically arranged when the power is applied between the front substrate and the rear substrate, and horizontally otherwise. The method of claim 1, And wherein the long axis of the dichroic dye is arranged horizontally and vertically otherwise, when power is applied between the front and back substrates.