KR100989248B1 - Dual LCD with Dual Front Lights - Google Patents

Abstract

The present invention discloses a dual liquid crystal display using dual front lights. A dual liquid crystal display using a dual front light according to the present invention includes a liquid crystal panel formed by injecting liquid crystal between an upper plate and a lower plate; First and second polarizing plates respectively attached to both surfaces of the liquid crystal panel; A first front light attached to a front portion of the liquid crystal panel; A second front light attached to a rear portion of the liquid crystal panel; A first scattering film provided on the first front light; It is characterized in that it comprises a second scattering film provided on the second front light.

The dual liquid crystal display using the dual front light according to the present invention includes a scattering film having a haze characteristic in the dual liquid crystal display using the dual front light, thereby realizing a high brightness and clear image quality by removing the moiré phenomenon caused by the dual front light. Can be.

Front light, liquid crystal panel, scattering film, haze characteristics

Description

Dual liquid crystal display using dual front lights {DUAL LIQUID CRYSTAL DISPLAY USING OF DUAL FRONT LIGHT}

1 is a view schematically illustrating a structure of a front light unit of a reflective liquid crystal display device according to the related art.

2 is a cross-sectional view of FIG.

3 is a diagram schematically illustrating a structure of a dual liquid crystal display using dual front lights according to the present invention.

4 is a view showing the luminance characteristics according to the position of the scattering film according to the present invention.

5 is a view showing the transmittance of light according to the haze distribution value of the scattering film according to the present invention.

6 is a schematic illustration of what is displayed when the first front light is on in accordance with the present invention;

7 shows schematically what is displayed when the second front light according to the invention is in an on state;

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

301 --- liquid crystal panel 302 --- first front light

303 --- Second Front Light 304 --- First Polarizer                 

305 --- second polarizer 306 --- first microreflective film

307 --- Second microreflective film 308 --- First scattering film

309 --- Second Scattering Film

The present invention relates to a dual liquid crystal display using a dual front light, and in particular, a dual liquid crystal display using a dual front light is provided with a scattering film having a haze characteristic to remove the moiré phenomenon caused by the dual front light, high brightness and clear image quality The present invention relates to a dual liquid crystal display using dual front lights.

In general, the liquid crystal display is a flat panel display having advantages of small size, thinness, and low power consumption, and is used as a portable computer such as a notebook PC, office automation equipment, and audio / video equipment.

Such a liquid crystal display device displays an image or an image by controlling an electric field applied to a liquid crystal material having dielectric anisotropy to transmit or block light. Liquid crystal display devices, unlike display elements that emit light by themselves, such as electro-luminescence (EL), cathode ray tube (CRT), and light emitting diode (LED), emit light by themselves. It does not occur and uses external light.

In general, liquid crystal displays are roughly classified into a transmission type and a reflection type according to a method of using light. The transmissive liquid crystal display device includes a liquid crystal display panel in which a liquid crystal material is injected between two glass substrates, and a backlight for supplying light to the liquid crystal display panel.

However, the transmissive liquid crystal display device has difficulty in thinning and weighting due to the volume and weight of the backlight, and has been pointed out as an excessive power consumption of the backlight. In response to this trend, research and development of a reflective liquid crystal display device that does not use a backlight have been recently conducted.

Since the reflective liquid crystal display device does not have its own light source, it displays an image depending on natural light (or ambient light). Therefore, since a separate backlight is not required, power consumption is low, so it is widely used as a portable display device such as an electronic notebook or personal information terminal.

However, the reflection type liquid crystal display device has a problem in that when the natural light does not have a sufficient amount of light (for example, when the surroundings are dark), the luminance level of the display image is lowered and the displayed information cannot be read. In order to solve this problem, a front light unit (FLU), which is separately installed in the reflective LCD and supplies light beams to the reflective liquid crystal display when the ambient light is dark, is used.

1 is a view schematically illustrating a structure of a front light unit of a reflective liquid crystal display according to the related art, and FIG. 2 is a cross-sectional view of FIG. 1. 1 and 2, the reflective liquid crystal display device includes a reflective liquid crystal panel 101 and a front light positioned above the reflective liquid crystal panel 101 to supply light beams to the reflective liquid crystal panel 101. Unit 102. The reflective liquid crystal panel (Diffusing reflective electrode) of the lower portion of FIG. 2 is formed in the reflective liquid crystal panel 101 to reflect natural light (or auxiliary light) incident on the display surface of the liquid crystal panel 101.

The front light unit 102 includes a light source 201 for generating a light beam, a light guide plate 202 for uniformly emitting the light beam toward the display surface of the liquid crystal panel, and a light source 201 in the light source 201. The reflector 203 reflects the generated light beam toward the light guide plate 202, and the reflector 204 prevents the light beam from leaking from the light guide plate 202.

Here, since the upper surface of the light guide plate 202 is a prism pattern, the light guide plate 202 changes a traveling path of light incident obliquely to the light guide plate 202 with respect to the display surface.

Therefore, the light incident on the light guide plate 202 is incident in the vertical direction of the reflective liquid crystal panel 101 positioned below the light guide plate 202. Light vertically incident on the reflective liquid crystal panel 101 is reflected by the reflective liquid crystal panel 101 and proceeds upwards of the light guide plate 202.

The present invention provides a dual liquid crystal display device using a dual front light, which is capable of realizing a clear image quality of high brightness by eliminating moiré phenomena caused by the dual front light by providing a scattering film having haze characteristics in the dual liquid crystal display device using the dual front lights. The purpose is to provide.

In order to achieve the above object, the dual liquid crystal display using the dual front light according to the present invention,

A liquid crystal panel formed by injecting liquid crystal between the upper plate and the lower plate;

First and second polarizing plates respectively attached to both surfaces of the liquid crystal panel;

A first front light attached to a front portion of the liquid crystal panel;

A second front light attached to a rear portion of the liquid crystal panel;

A first scattering film provided on the first front light;

It is characterized in that it comprises a second scattering film provided on the second front light.

Here, in particular, the first scattering film and the second scattering film is characterized in that it is formed of a film having a haze characteristic.

Here, in particular, the haze distribution value of the first scattering film and the second scattering film is characterized in that it has a 50 <H <80.

Here, in particular, the second scattering film is characterized in that when the transmitted light by the first front light is displayed on the rear portion of the liquid crystal panel, the moiré phenomenon caused by the regular contrast pattern is removed.

Here, in particular, the first scattering film is characterized in that when the transmitted light by the second front light is displayed on the front portion of the liquid crystal panel, the moiré phenomenon caused by the regular contrast pattern is removed.

Here, in particular, it is characterized in that it further comprises a first microreflective film between the first polarizing plate and the first front light and a second microreflective film between the second polarizing plate and the second front light.

Here, in particular, the first microreflective film reflects an external light source at the same time when the transmitted light by the first front light is displayed on the rear portion of the liquid crystal panel, and the second microreflective film is transmitted light by the second front light It is characterized by reflecting external light sources at the same time when it is displayed on the front part of the liquid crystal panel.

In particular, the first front light is displayed in the rear part of the liquid crystal panel when the ON state, and the second front light is displayed in the front part of the liquid crystal panel when the ON state. have.

Here, in particular, a retardation film may be further formed on at least one of the upper and lower plates of the liquid crystal panel.

In particular, the liquid crystal of the liquid crystal panel is characterized in that the TN, ECB, OCB, IPS or VA mode.

In particular, the first and second polarizing plates are characterized in that they are attached to both sides of the liquid crystal panel at 90 ° to each other.

In particular, a TFT (Thin Film Transistor) (TFT), which functions as a switching element, is formed at the intersection of the gate bus line and the data bus line, respectively, on the lower plate of the liquid crystal panel, and the BM (Black Matrix: BM), color filter layer, and common electrode on the upper plate. This feature is characterized in that it is formed.                     

In particular, the TFT (Thin Film Transistor) (TFT) formed on the lower plate of the liquid crystal panel is characterized by being formed of an amorphous thin film transistor (TFT).

In particular, the TFT (Thin Film Transistor) formed on the lower plate of the liquid crystal panel is characterized by being formed of a polysilicon thin film transistor (TFT).

According to the present invention, by providing a scattering film having a haze characteristic in the dual liquid crystal display device using the dual front light, it is possible to implement a clear image quality of high brightness by removing the moire phenomenon caused by the dual front light.

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

3 is a diagram schematically illustrating a structure of a dual liquid crystal display using a dual front light according to the present invention. As shown in the drawing, the dual liquid crystal display using the dual front lights includes a liquid crystal panel 301 formed by injecting liquid crystal between an upper plate and a lower plate; First and second polarizing plates 304 and 305 respectively attached to both surfaces of the liquid crystal panel 301; A first front light (302) attached to the front portion of the liquid crystal panel (301); A second front light 303 attached to a rear portion of the liquid crystal panel 301; A first scattering film 308 provided on the first front light 302; And a second scattering film 309 provided on the second front light 303.

In addition, a first microreflective film 306 between the first polarizing plate 304 and the first front light 302 and a second microreflective film between the second polarizing plate 305 and the second front light 303. 307 is further included.                     

The first microreflective film 306 reflects an external light source at the same time when the transmitted light by the first front light 302 is displayed on the rear surface of the liquid crystal panel 301, the second microreflective film 307 When the transmitted light by the second front light 303 is displayed on the front portion of the liquid crystal panel 301 at the same time to reflect the external light source.

In more detail, when displaying the transmissive liquid crystal panel in a place where the external light is bright, the brightness of the light by the first and second front lights 302 and 303 is relatively lower than the brightness of the external light and is displayed on the liquid crystal panel. Difficult to see screen

Therefore, when the external light is bright by applying the first and second microreflective films 306 and 307, the light efficiency is improved by reflecting the external light so that the screen displayed on the liquid crystal panel 301 can be viewed. do.

The liquid crystal panel 301 is a transmissive type and is provided with a first substrate (thin film transistor substrate) and a second substrate (color filter substrate) facing each other at a predetermined interval.

In more detail with respect to the liquid crystal panel 301, the first substrate (thin film transistor substrate) has a gate bus line and a data bus line formed on an inner surface of one transparent substrate in a matrix.

Thin film transistors (TFTs), which function as switching elements, are formed at intersections of the gate bus lines and the data bus lines, and square pixel electrodes contacting the drain electrodes of the TFTs are surrounded by the gate bus lines and the data bus lines. It is formed in the form of each.                     

Here, a thin film transistor (TFT) formed on the lower plate of the liquid crystal panel 301 is amorphous containing hydrogen without periodicity of lattice according to the crystal state of a semiconductor layer which is an active layer among the constituent elements. An amorphous thin film transistor (amorphous TFT) using a silicon (amorphous silicon) is applied or a polysilicon thin film transistor (poly silicon TFT) using a polycrystalline solid (polycrystalline silicon) is applied.

The second substrate (color filter substrate) facing the transparent substrate on which the plurality of pixel electrodes is formed has a BM (Black Matrix: BM), a color filter layer, and a common electrode formed on an inner surface of the transparent substrate.

When one gate bus line and one data bus line of the liquid crystal panel configured as described above are selected and a voltage is applied, only a TFT (Thin Film Transistor (TFT)) to which the voltage is applied is turned on, and the on TFT is turned on. Charges are accumulated in the pixel electrode connected to the drain electrode of to change the angle of the liquid crystal molecules between the common electrode and the common electrode.

Therefore, an electric field applied to liquid crystal molecules having dielectric anisotropy is transmitted to block or transmit light to display an image or an image. Here, the liquid crystal is TW (Twist Nematic) mode is applied. At this time, the liquid crystal has been described for the TN mode by way of example, it is possible to form a liquid crystal panel to which the ECB, OCB, IPS or VA mode is applied.

In addition, first and second polarizing plates 304 and 305 are attached to both surfaces of the liquid crystal panel 301 at 90 ° to both sides of the liquid crystal panel 301, respectively.

The first and second polarizers 304 and 305 serve to transmit only light that vibrates in one direction in order to polarize natural light.

In addition, a retardation film (not shown) may be further formed on at least one substrate outer surface of the liquid crystal panel 301. The retardation film (not shown) serves to widen the area without gray inversion by compensating the viewing angle in a direction perpendicular to the substrate and a direction in which the viewing angle changes, and to increase the contrast ratio in the oblique direction. One may be formed of a negative uniaxial film or a negative biaxial film having two optical axes, but a negative biaxial film is more preferable in terms of wide viewing angle.

Meanwhile, in the first front light 302 provided on the front surface of the liquid crystal panel 301, when light is emitted from the light source, the light is incident on the light guide plate to change the linear light source into a uniform surface light source.

In the light guide plate, since the upper surface of the light guide plate has a prism pattern, the traveling path of light incident obliquely to the light guide plate is changed perpendicular to the display surface.

The light changed from the light guide plate to the surface light source is scattered by the diffusion plate and transmitted through the liquid crystal cell.

Meanwhile, a moire phenomenon in which stripes appear on a screen displayed by a pattern of a predetermined rule of the light guide plate portions of the first and second front lights 302 and 303 is generated.

Here, the moire phenomenon refers to an interference fringe formed when two or more periodic patterns overlap, and overlap two or more similarly spaced grids to shine light. This is a stripe with a large period separate from the two grids.

Therefore, in order to remove the moiré phenomenon, the first scattering film 308 on the first front light 302 and the second scattering film 309 on the second front light 303 are provided.

In more detail, the first scattering film 308 and the second scattering film 309 are formed of a film having a haze characteristic. That is, the first scattering film 308 and the second scattering film 309 form a diffusion layer having a haze characteristic to scatter light to remove the moiré phenomenon.

At this time, the haze distribution value, which is an optical characteristic, varies according to the size, shape, and density of the material forming the diffusion layer.

On the other hand, Figure 4 is a view showing the luminance characteristics according to the position of the scattering film according to the present invention. As shown in the drawing, Type I and Type II have different positions of the scattering film for removing the moire phenomenon in the liquid crystal display, and then the x-axis (parts [au]) representing the intensity of the light source and the y representing the luminance. The relationship with the luminescence [nit] is shown.

At this time, the haze distribution value for removing the moiré phenomenon of the said scattering film applied to the said Type I and Type II is formed equal.

In more detail, Type I includes the first and second scattering films 308 and 309 in the dual liquid crystal display device using the dual front light according to the present invention of FIG. 3. The characteristic in the case of arrange | positioning between 2nd front lights 302 and 303 is shown.

And type II has shown the characteristic at the time of forming the said 1st, 2nd scattering films 308, 309 in the outer surface of the said 1st, 2nd front lights 302, 303. FIG.

However, it can be seen that the case where the scattering film is arranged as in Type I is lowered in the intensity of the same light source than when the scattering film is arranged as in Type II.

5 is a view showing the transmittance of light according to the haze distribution value of the scattering film according to the present invention. As shown here, it can be seen that the lower the haze distribution value of the scattering film, the higher the light transmittance.

At this time, the first scattering film 308 and the second scattering film 309 according to the present invention of Figure 3 is formed with a 50 <H <80 haze distribution value that can improve the brightness while removing the moiré phenomenon Done. At this time, the optimum haze distribution value of the first and second scattering films 308 and 309 may be set to 60.

Therefore, as mentioned in FIG. 4, when the scattering film having the same haze distribution value is disposed, the luminance is increased for Type II than for Type I.

6 is a view schematically showing the display when the first front light according to the present invention is in an on state. As shown in FIG. 1, when the liquid crystal panel 301 is in the normally white mode, the first front light 302 is on and light is not applied to the liquid crystal panel 301. The path of the second polarizing plate 305 provided with light passing through the first polarizing plate 304 provided on one surface of the liquid crystal panel 301 is twisted along the liquid crystal molecules array 90 degrees to the other surface of the liquid crystal panel 305 Will pass).

That is, in the state where no voltage is applied as described above, the light passes and the rear part is implemented in white.

However, in the state where the voltage is applied to the liquid crystal panel 301, the liquid crystal molecules rise along the direction of the electric field and transmit the light passing through the first polarizing plate 304 to the crossed second polarizing plate 305 as it is. Is blocked by the polarizer. That is, when the voltage is applied, the light is blocked, and the rear part is implemented in black.

Therefore, by selectively applying the voltage to adjust the light passing through the liquid crystal panel 301 to display a desired screen on the rear of the liquid crystal panel 301.

In this case, when the transmitted light by the first front light 302 is displayed on the rear surface of the liquid crystal panel 301, the second scattering film 308 may remove the moiré phenomenon caused by the regular contrast pattern. do.

7 is a diagram schematically showing what is displayed when the second front light according to the present invention is turned on. As shown in FIG. 2, when the liquid crystal panel 301 is in the normally white mode, the second front light 303 is on and light is not applied to the liquid crystal panel 301. The path of the first polarizing plate 304 provided with light passing through the second polarizing plate 305 provided on one surface of the liquid crystal panel 301 is twisted along the array of liquid crystal molecules 90 degrees to the other surface of the liquid crystal panel. Will pass).

That is, in the state where no voltage is applied as described above, light passes, and the front part is implemented in white.

However, in the state where the voltage is applied to the liquid crystal panel 301, the liquid crystal molecules rise along the direction of the electric field and transmit the light passing through the second polarizing plate 305 to the crossed first polarizing plate 304 as it is. Blocked by the polarizer. In other words, when the voltage is applied, the light is blocked and the front part is realized in black.

Therefore, by selectively applying the voltage to adjust the light passing through the liquid crystal panel 301 to display a desired screen on the front of the liquid crystal panel.

In this case, when the transmitted light by the second front light 303 is displayed on the front surface of the liquid crystal panel 301, the first scattering film 309 removes the moiré phenomenon caused by a regular contrast pattern. do.

As mentioned above, the front or rear surface of the liquid crystal panel 301 is displayed depending on whether the first front light 302 or the second front light 303 is turned on.

Although the present invention has been described with reference to the embodiments illustrated in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

As described above, the dual liquid crystal display using the dual front light according to the present invention is provided with a scattering film having a haze characteristic in the dual liquid crystal display using the dual front light, thereby eliminating the moiré phenomenon caused by the dual front light, thereby providing high brightness. Clear picture quality can be achieved.

Claims (15)

A liquid crystal panel formed by injecting liquid crystal between the upper plate and the lower plate; First and second polarizing plates respectively attached to both surfaces of the liquid crystal panel; A first front light attached to a front portion of the liquid crystal panel; A second front light attached to a rear portion of the liquid crystal panel; A first scattering film provided on the first front light; And a second scattering film provided on the second front light. The method of claim 1, And the first scattering film and the second scattering film are formed of a film having a haze characteristic. The method of claim 1, The haze distribution value of the first scattering film and the second scattering film is 50 <H <80, characterized in that the dual front light using a dual front light. The method of claim 1, The haze distribution value of the first scattering film and the second scattering film is 60, characterized in that the dual liquid crystal display using a dual front light. The method of claim 1, The second scattering film, when the transmitted light by the first front light is displayed on the rear portion of the liquid crystal panel, the dual liquid crystal display using the dual front light, characterized in that to remove the moiré phenomenon caused by the regular contrast pattern Device. The method of claim 1, The first scattering film is a dual liquid crystal using a dual front light, characterized in that when the transmitted light by the second front light is displayed on the front portion of the liquid crystal panel, the moiré phenomenon caused by a regular contrast pattern Display. The method of claim 1, A dual liquid crystal display using dual front lights further comprising a first micro reflective film between the first polarizing plate and the first front light and a second micro reflective film between the second polarizing plate and the second front light. . The method of claim 7, wherein The first micro-reflective film reflects an external light source at the same time when the transmitted light by the first front light is displayed on the rear portion of the liquid crystal panel, the second micro-reflective film is transmitted by the second front light is the liquid crystal A dual liquid crystal display using dual front lights, characterized by reflecting external light sources simultaneously when displayed on the front of the panel. The method of claim 1, The dual front lights may be displayed on the rear part of the liquid crystal panel when the first front light is ON, and displayed on the front parts of the liquid crystal panel when the second front light is ON. Dual liquid crystal display using. The method of claim 1, A dual liquid crystal display using dual front lights, characterized in that a phase difference film is further formed on at least one of the upper and lower plates of the liquid crystal panel. The method of claim 1, The liquid crystal of the liquid crystal panel is a dual liquid crystal display using a dual front light, characterized in that the TN mode, ECB, OCB, IPS or VA mode. The method of claim 1, And the first and second polarizing plates are attached to both surfaces of the liquid crystal panel by 90 ° to each other. The method of claim 1, In the lower panel of the liquid crystal panel, TFTs (Thin Film Transistors) (TFTs), which function as switching elements, are formed at the intersections of the gate bus lines and the data bus lines, respectively, and a BM (Black Matrix: BM), a color filter layer, and a common electrode are formed on the upper plates. Dual LCD using dual front lights, characterized in that. The method of claim 1, The TFT (Thin Film Transistor: TFT) formed on the lower plate of the LCD panel is formed of an amorphous thin film transistor (TFT). The method of claim 1, Thin film transistors (TFTs) formed on the lower plate of the liquid crystal panel are formed of polysilicon thin film transistors (TFTs).

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