KR20040025474A - Liquid crystal display device - Google Patents

Abstract

PURPOSE: A liquid crystal display is provided to attach a transmission type liquid crystal panel and a reflection type liquid crystal panel to each other to improve transmission luminance and reflection luminance. CONSTITUTION: A liquid crystal display includes a transmission/reflection liquid crystal panel(200), a main body(400), and a rotating unit. The transmission/reflection liquid crystal panel is constructed in a manner that a transmission panel(200a,200b) and a reflection panel are attached to each other. The main body transmits data to the transmission/reflection liquid crystal panel. The rotating unit rotates the liquid crystal panel vertically and horizontally with respect to the main body. The transmission panel includes the first and second substrates opposite to each other, a liquid crystal layer formed between the first and second substrates, a pixel electrode formed on the first substrate, and a back light provided under the first substrate.

Description

Liquid crystal display {LIQUID CRYSTAL DISPLAY DEVICE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device in which a transmissive liquid crystal panel and a reflective liquid crystal panel can be selectively used depending on a location.

In recent years, with the expansion of communication infrastructures, the use of computer networks has rapidly expanded, and an environment in which anyone can use necessary information anytime, anywhere has been created. Accordingly, as the market for information and communication devices such as personal information and communication devices, web terminals, and portable terminals that require mobility is exploding, demand for displays having light weight and low power consumption is increasing. Unlike the related art, there is a demand for a display device capable of expressing a variety of information including a still image beyond a level of performing only on / off of numbers or a predetermined image. In such a request, the demand for mobile devices capable of displaying color images is rapidly expanding. The characteristics required for mobile devices are that they can be used for a long time with a thin, light weight and low power consumption.

Liquid crystal display devices are widely applied to such portable information and communication devices because they are light, thin, and low power consumption. However, general transmissive liquid crystal display devices require a backlight device. Power consumption not only shortens the usage time after one-time charging of the portable device, but also causes a problem of poor portability due to the weight and thickness of the backlight. Recently, in order to overcome these problems, a reflective liquid crystal display device has been proposed.

Since the reflective liquid crystal display uses ambient light as a light source, there is no power consumption by the backlight which occupies about 70% or more of power consumption, and there is no increase in thickness and weight by the backlight. Therefore, an information display element having excellent display quality with very little power can be realized. In addition, in mobile devices, the adaptability of outdoor use becomes important, but in the conventional transmissive LCD, there is a problem in visibility that the color contrast is degraded by reflection of the panel surface under a bright external environment. Rather, there is a characteristic that looks more clearly.

However, since the ambient light such as natural light or artificial light source does not always exist, the reflective liquid crystal display may be used in the daytime when natural light exists, or in offices and buildings where external artificial light exists, but natural light exists. I cannot use it at night when I do not do it.

Accordingly, in order to solve the above problems, a semi-transmissive liquid crystal display device that can be used simultaneously in day, night, indoor and outdoor while accepting the advantages of the reflective liquid crystal display device and the transmissive liquid crystal display device has been developed.

Hereinafter, the transflective liquid crystal display device as described above will be described in detail with reference to the accompanying drawings.

1 is a cross-sectional view of a general transflective liquid crystal display device.

As shown in the drawing, a general transflective liquid crystal display device includes an upper substrate 10 having a color filter 5 and a common electrode 7 formed thereon on a transparent substrate 1, a transmissive portion in the pixel region and the pixel region. And a liquid crystal layer 30 filled between the upper substrate 10 and the lower substrate 20 and the lower substrate 20 having the pixel electrode 19 having the T and the reflector R formed thereon. The passivation layer 12 is interposed between the pixel electrode 19 of the lower substrate 20 and the transparent substrate 11.

On the opposite side of the upper substrate 10 on which the common electrode 7 is formed, a phase wave plate 6 having a λ / 4 plate characteristic and a polarizer 8 are sequentially stacked.

In addition, a lower portion of the lower substrate 20 includes a backlight unit 40 that generates a light beam in the transmission mode and uniformly supplies the back light unit 40.

The pixel electrode 19 formed on one surface of the lower substrate 20 facing the upper substrate 10 has a structure in which a transparent electrode 19a and a reflecting electrode 19b are stacked in succession, and the transparent electrode 19a is reflected. An insulating layer may be further interposed between the electrodes 19b.

On the opposite side of the lower substrate 20 on which the pixel electrode 19 is formed, a phase difference plate 16 and a lower polarizing plate 18 are stacked.

The liquid crystal filled between the lower substrate 10 and the upper substrate 20 has optical anisotropy and is designed such that Δnd₁ of the liquid crystal layer positioned at the reflecting portion is λ / 4 (λ = 550 nm). As shown in 1], the cell gap d2 of the transmission part is formed about twice the cell gap d₁ of the reflection part.

d₁ △ n = λ / 4

Here, since d2 = 2dV, d2Δn = lambda / 2.

In Equation 1, d₁ is a cell gap of the liquid crystal layer corresponding to the reflecting unit, and d2 is a cell gap of the liquid crystal layer corresponding to the transmitting unit T. Also, λ / 4 is a phase change value of light passing through the liquid crystal layer 30 once in the reflection mode.

If the cell gaps of the liquid crystal layer according to the transmissive part and the reflecting part are differently formed as described above, a difference in the progress of the light propagating through the reflecting part and the propagating state of the light propagating through the transmissive part can be minimized, thereby obtaining high luminance characteristics. There is a number.

In addition, the reflective electrode 19b formed on the reflective part R of the lower substrate 20 is made of an opaque metal material having excellent reflectance, and the color filter 5 receives light L 빛 incident from the outside in the reflective mode. Reflecting the upper substrate 10 formed, the transmission electrode 19a formed in the transmission portion (T) transmits the light (L₂) generated in the backlight 40 to the upper substrate 10. . In this case, when a signal is applied to the reflective electrode 19a to the transmissive electrode 19b by switching (not shown) formed in a matrix form on the lower substrate 20, the arrangement of the liquid crystal layer 30 is changed. The light transmitted or reflected by the liquid crystal layer 30 may be colored by the color filter 5 formed on the upper substrate 10 to be viewed as a color screen.

In the transflective liquid crystal display device configured as described above, the transmissive electrode 19a formed in the transmissive portion T transmits the light L2 generated by the backlight 40 to the upper substrate 10 in the transmissive mode. The reflective electrode 19b formed in the reflector R serves to reflect the light L ′ incident from the outside onto the upper substrate 10.

However, since the light beam of the backlight incident to the reflector in the transmissive mode is blocked by the reflecting electrode formed in the reflector, the transmittance of luminance is lower than that of the entire transmissive liquid crystal display.

In addition, even in the reflection mode, since all external light incident to the transmission part is not transmitted and used, there is a problem in that the reflection brightness is lower than that of the total reflection type liquid crystal display device.

Accordingly, the present invention has been made to solve the above problems, and provides a liquid crystal display device which can improve transmission and reflection luminance by bonding the transmissive liquid crystal panel and the reflective liquid crystal panel back and forth to be selectively used as necessary. For that purpose.

Other objects and features of the present invention will be described in detail in the configuration and claims of the following invention.

1 is a cross-sectional view showing a general transflective liquid crystal display device.

2A-2B illustrate an embodiment of the invention applied to a notebook.

3 is a cross-sectional view showing unit pixels of a transmissive liquid crystal panel;

4 is a cross-sectional view showing unit pixels of a reflective liquid crystal panel;

5 is a schematic view illustrating a method of driving a liquid crystal display device according to the present invention.

*** Explanation of symbols for main parts of drawing ***

200: liquid crystal panel 200a: transmissive panel

200b: reflective panel 210: upper substrate

220: lower substrate 230: liquid crystal layer

300a: first hinge portion 300b: second hinge portion

302: third hinge portion 303: hinge cover

According to an aspect of the present invention, there is provided a liquid crystal display device comprising: a transmissive / reflective liquid crystal panel in which a transmissive panel and a reflective panel are bonded to each other; A main body transmitting data to the transmissive / reflective liquid crystal panel; Rotating means for electrically connecting the main body and the liquid crystal panel and enabling vertical and horizontal rotation to selectively use the liquid crystal panel; A protective plate for protecting the transmissive panel or the reflective panel is included.

The transmissive and reflective liquid crystal panel includes first and second substrates; A pixel electrode formed on the first substrate; The liquid crystal layer is filled between the first substrate and the second substrate. In the case of a transmissive panel, a backlight is separately provided below the first substrate.

The pixel electrode is determined according to the type of the liquid crystal panel, the transmissive panel is made of a transparent metal material, and the reflective panel is made of an opaque metal material having excellent reflection characteristics.

The rotating means serves to electrically and mechanically connect the main body and the liquid crystal panel, and includes a hinge having a two-axis rotating shaft capable of simultaneously rotating vertically and horizontally.

The main body includes all the devices in which the liquid crystal display panel can be used as the display unit, for example, a notebook, a mobile phone or a TV.

Hereinafter, a liquid crystal display according to the present invention will be described in detail with reference to the accompanying drawings.

2A to 2B illustrate an embodiment of the present invention applied to a notebook.

As shown in the figure, the liquid crystal display device of the present invention applied to a notebook is a liquid crystal panel 200 and a keyboard 401 in which the liquid crystal panel 200 and the keyboard 401 are bonded to each other. The liquid crystal panel 200 and the main body 400 are electrically and mechanically connected to each other, and the rotating means rotates the panel 200 vertically and horizontally.

The liquid crystal panel 200 is formed by combining a transmissive panel and a reflective panel back and forth. Each panel is filled with an upper substrate including a color filter, a lower substrate including a thin film transistor, and a pixel electrode. It consists of a liquid crystal layer.

Hereinafter, the transmissive panel and the reflective panel will be described in more detail with reference to the accompanying drawings.

3 is a cross-sectional view illustrating a unit pixel of a transmissive liquid crystal panel.

As shown in the drawing, a transmissive liquid crystal panel which is generally used is disposed such that the upper substrate 210 including the color filter 205 and the lower substrate 220 including the thin film transistor are opposed to each other, and the liquid crystal between them. A layer 230 is formed, and a backlight 240 is provided below the lower substrate 220 to generate a light beam and to inject uniform light toward the liquid crystal panel.

A black matrix 203 is formed on the upper substrate 210 to prevent light leakage between pixels in portions corresponding to the thin film transistor and the gate / data line (not shown), and a red matrix is formed between the black matrices 203. (R), green (G), and blue (B) color filters 205 are formed. In addition, a common electrode 207 made of a transparent material is formed on an entire surface of the upper portion of the color filter 205, and an overcoat layer is added to planarize the color filter 205 and to improve adhesion to the common electrode 207. It may be formed as.

The lower substrate 220 includes a thin film transistor disposed at each pixel to apply and block a signal voltage to the liquid crystal, and include a thin film transistor including gate / source / drain electrodes 221, 224a and 224b and an active layer; The pixel electrode 219 made of a transparent metal material is formed.

The thin film transistor is formed on the transparent substrate 211 and has a gate electrode 221 to which a scan signal is applied, and a semiconductor layer 222 and upper portions of both sides of the semiconductor layer 222 that transmit data signals in response to the scan signal. An active layer comprising an n + doped ohmic contact layer 223, a gate insulating layer 213 electrically separating the active layer and the gate electrode 221, and formed on the active layer A source electrode 224a for applying a signal and a drain electrode 224b for applying a data signal to the pixel electrode.

In addition, a passivation layer 212 is formed on the thin film transistor and the substrate to protect the source / drain electrodes 224a and 224b and to expose a portion of the drain electrode 224b. The pixel electrode 219 formed at the upper portion is electrically connected to the drain electrode 224b.

The pixel electrode 219 is made of a transparent metal material such as ITO so that the backlight light incident from the backlight 240 can be transmitted to the upper substrate well, and is formed on the outer surfaces of the upper substrate 210 and the lower substrate 220. Polarizing plates 208 and 218 are stacked.

The transmissive liquid crystal panel 200a configured as described above has a low contrast ratio when used outdoors, leading to poor visibility. However, when used in the indoor environment there is an advantage that the brightness is higher than the reflective and transflective liquid crystal panel.

4 is a cross-sectional view of a reflective liquid crystal panel, in which elements other than the pixel region are the same as the transmissive liquid crystal panel illustrated in FIG. 3. In addition, since the reflective liquid crystal panel uses external light as a light source, no backlight is required.

That is, as shown in the drawing, in the reflective liquid crystal panel, the upper substrate 310 including the color filter 305 and the lower substrate 320 including the thin film transistor are disposed to face each other, and the liquid crystal layer therebetween. 330 is formed and a pixel electrode 319 made of an opaque metal material capable of efficiently reflecting external light is formed on the lower substrate 320.

A black matrix 303 is formed on the upper substrate 310 to prevent light leakage between pixels in portions corresponding to the thin film transistor and the gate / data line (not shown), and a red matrix is formed between the black matrices 303. (R), green (G), and blue (B) color filters 305 are formed. In addition, a transparent common electrode 307 is formed on an entire surface of the upper portion of the color filter 305, and an overcoat layer may be further formed to planarize the color filter 305 and to improve adhesion to the common electrode 307. It may be.

The lower substrate 320 includes a thin film transistor disposed at each pixel to apply and block a signal voltage to the liquid crystal, the thin film transistor including gate / source / drain electrodes 321, 324a and 324b and an active layer; The pixel electrode 319 made of an opaque metal material is formed.

The thin film transistor is formed on the transparent substrate 311 and has a gate electrode 321 to which a scan signal is applied, and a semiconductor layer 322 and upper portions of both sides of the semiconductor layer 322 that transmit data signals corresponding to the scan signal. An active layer formed of an n + doped ohmic contact layer 323, a gate insulating layer 313 electrically separating the active layer and the gate electrode 321, and formed on the active layer A source electrode 324a for applying a data signal and a drain electrode 324b for applying a data signal to the pixel electrode.

In addition, a passivation layer 312 may be formed on the thin film transistor and the substrate to protect the source / drain electrodes 224a and 224b and to expose a portion of the drain electrode 324b. The pixel electrode 319 formed at is electrically connected to the drain electrode 324b.

The pixel electrode 319 is made of a material having excellent reflection characteristics such as aluminum (Al) or aluminum alloy (AlNd) to efficiently reflect external light, and has an uneven layer (not shown) to further improve reflection efficiency. ) May be formed. The uneven layer serves to improve the reflected brightness by increasing the efficiency of the reflected light reflected by the external electrode is reflected by the reflective electrode to the upper substrate.

In addition, the compensation film 306 and the polarizing plate 308 are stacked on the outer surfaces of the upper substrate 310 and the lower substrate 320.

The reflective liquid crystal panel configured as described above cannot be used in an indoor environment in which external light does not exist, and even if the reflective liquid crystal panel is equipped with a front light, the luminance is lower than that of the transmissive liquid crystal panel in the room. However, in the outdoor where external light exists, the luminance is higher than that of the transmissive and transflective liquid crystal panels.

Therefore, the liquid crystal panel used in the present invention is a combination of the two liquid crystal panels back and forth so as to accommodate only the advantages of the transmissive liquid crystal panel and the reflective liquid crystal panel indoors and outdoors.

In addition, although not shown in the drawings, a protective plate for protecting a panel that is not used covers the panel, the protective plate can be removed or not.

In addition, a rotating means of the panel is provided to selectively use the transmissive / reflective liquid crystal panel according to the location.

Following the description of FIG. 2, the rotating means includes first and second hinge parts 300a and 300b and a first and second hinge part 300 to enable the liquid crystal panel 200 to be rotated on the x-axis (up and down). The hinge cover 303 covering between 300a and 300b and the hinge cover 303 are located at the center, and electrically connect the hinge cover 303 and the liquid crystal panel 200 mechanically and at the same time. It consists of the 3rd hinge part 302 which enables rotation of the y-axis (left and right) of a. At this time, the liquid crystal panel 200 and the hinge cover 303 are connected only through the third hinge part 302.

The shaft of the hinge portion 1.2.3 may be formed individually or in one axis but may have two axes of rotation.

The main body 400 includes a keyboard 401 for inputting an image command to be displayed on a panel, a central processing unit for transmitting a command received from the keyboard toward the liquid crystal panel unit 200, and peripheral circuits for performing other commands. have.

The liquid crystal display device configured as described above selectively transmits or reflects a liquid crystal panel according to a place such as indoor or outdoor by rotating the y-axis (left and right) of the liquid crystal panel by means of the third hinge portion 302 of the rotating means. Can be used. FIG. 2A is a view showing the liquid crystal panel rotated in the y direction by the third hinge unit.

In other words, by using a panel suitable for indoor and outdoor use, it is possible to reduce power consumption and increase brightness. To explain this in more detail, indoors can use a transmissive panel to improve the luminance than a conventional transflective panel, while outdoors use a reflective panel to use external light, so compared to conventional transmissive panels Consumption can be reduced, and the reflectance can be increased because the area of the reflective electrode occupying the pixel area is larger than that of the semi-transmissive panel.

5 is a schematic view for explaining a method of driving a liquid crystal display according to the present invention.

In the present invention, only one panel of the transmissive / semi-transmissive liquid crystal panel is driven in view of power consumption. That is, the reflective panel is turned off when the transmissive panel is driven indoors, and the backlight and the transmissive panel is turned off when the reflective panel is driven outdoors. As such, the selective drive of each panel is controlled by a keyboard configured in the body.

For example, if the user wants to switch driving from the transmissive panel to the reflective panel, as shown in FIG. 5, when one of the function keys in the keyboard is input, the transmissive panel is turned off and the reflective panel is turned off. To be on. As the transmissive panel is turned off, the backlight is turned off. That is, the video signal inputted to the transmissive panel is interrupted by the operating system (OS) driving command of the CPU and is changed to the reflective panel. The same applies when switching from a reflective panel to a transmissive panel.

As described above, according to the present invention, the transmissive liquid crystal panel and the total reflection type liquid crystal panel may be bonded together to be selectively used as necessary to improve transmission and reflection luminance as well as to reduce power consumption. .

Claims (8)

A transmissive / reflective liquid crystal panel in which a transmissive panel and a reflective panel are bonded to each other; A main body transmitting data to the transmissive / reflective liquid crystal panel; And rotation means for allowing the liquid crystal panel to rotate vertically and horizontally with respect to the main body. The liquid crystal panel of claim 1, wherein First and second substrates facing each other; A liquid crystal layer filled between the first and second substrates; A pixel electrode formed of a switching element formed on the first substrate and a transparent metal material; And a backlight disposed under the first substrate. The liquid crystal display device according to claim 2, wherein the pixel electrode is made of ITO. The liquid crystal panel of claim 1, wherein the reflective liquid crystal panel First and second substrates facing each other; A liquid crystal layer filled between the first and second substrates; A pixel electrode formed of a switching element formed on the first substrate and an opaque metal material; The liquid crystal display of claim 4, wherein the pixel electrode is made of aluminum (Al) or aluminum alloy (AlNd). The liquid crystal panel of claim 1, wherein the rotating means is formed on both sides of the liquid crystal panel, and includes first and second hinge portions for rotating in the x-axis direction and third hinge portions for rotating the liquid crystal panel in the y-axis direction. A liquid crystal display device, characterized in that consisting of. The liquid crystal display device according to claim 1, wherein a protective plate is further formed in the transmissive or reflective liquid crystal panel. The liquid crystal display device according to claim 7, wherein the cover is detachable.