KR20040049538A - Liquid crystal display - Google Patents

Abstract

PURPOSE: An LCD(Liquid Crystal Display) is provided to increase the light amount of the second light, thereby enhancing the reflective efficiency of a semi-transmissive sheet. CONSTITUTION: The semi-reflective LCD(700) comprises an LCD panel(400) for displaying an image, a backlight unit(500) for generating the first light(L1) and supplying the LCD panel(400) with the first light(L1), and a semi-transmissive sheet(600) interposed between the LCD panel(400) and the backlight unit(500). The LCD panel(400) comprises the first substrate(100), the second substrate(200) facing to the first substrate(100) and a liquid crystal layer(300) interposed between the first and second substrates(100,200). The second substrate(200) has a condensing film(240) having a plurality of convex portions formed on a surface of the second glass substrate(110), protruded toward the first substrate(100).

Description

Liquid Crystal Display {LIQUID CRYSTAL DISPLAY}

The present invention relates to a liquid crystal display device, and more particularly, to a transflective liquid crystal display device capable of improving light efficiency.

Among the display devices used to visually check the information processed by the information processing device, the liquid crystal display device is thinner and lighter than other display devices, and has a low power consumption and a low driving voltage, and thus is widely used in various electronic devices.

Such a liquid crystal display converts a change in optical properties of a liquid crystal into a visual change by applying a voltage to a specific molecular array of the liquid crystal, and displays an image by using light modulation by the liquid crystal.

The liquid crystal display device is a transmissive liquid crystal display device for displaying an image using light provided from a backlight unit located at the rear of the liquid crystal panel, a reflective liquid crystal display device for displaying an image using external natural light, and an external environment. It is classified into a semi-transmissive liquid crystal display device which displays an image by using the built-in light source of or displays the image by reflecting external incident light.

The transflective liquid crystal display device includes a liquid crystal panel including a first substrate, a second substrate disposed to face the first substrate, a liquid crystal layer interposed between the first and second substrates, and a backlight disposed on a rear surface of the liquid crystal panel. It includes a unit.

The first substrate includes a thin film transistor (TFT), a transparent electrode connected to the TFT, and a reflective electrode. The transparent electrode transmits first light incident from the backlight unit and incident through the first substrate. The reflective electrode reflects second light incident through the second substrate.

A first polarizing plate and a second polarizing plate for polarizing incident light are respectively attached to one side of each of the first and second substrates. The first and second polarizers are installed such that the polarization axes are perpendicular to each other.

A first quarter-wave retardation plate is disposed between the first substrate and the first polarizing plate, and a second quarter-wave retardation plate is disposed between the second substrate and the second polarizing plate. The first and second quarter-wave retardation plates provide a phase difference of about 1/4 wavelength with respect to two polarization components that are parallel to and perpendicular to the optical axis of the retardation plate, thereby changing linear polarization to circular polarization or linear polarization to linear polarization. It changes the role.

However, this quarter-wave retardation plate increases the product cost of the reflection-transmissive liquid crystal display device compared to the transmissive liquid crystal display device. Also, when operating in the transmissive mode, the transmittance is reduced and the contrast ratio is lower than that of the transmissive liquid crystal display.

Therefore, recently, the transflective liquid crystal display device adopts a structure capable of reflecting or transmitting light from the outside of the liquid crystal panel while using the liquid crystal panel of the transmissive liquid crystal display device as it is. That is, the transflective liquid crystal display device includes a transflective sheet disposed between the liquid crystal panel and the backlight unit to transmit the first light and reflect the second light.

However, in the transflective liquid crystal display having such a structure, the second light passes through the first and second substrates several times and passes through a plurality of layers formed on the first and second substrates. Thus, the second light is scattered between the layers, whereby the reflection effect by the transflective sheet is lowered. That is, the amount of light of the second light reflected by the transflective sheet and then emitted to the second substrate is significantly lower than the amount of light of the second light incident on the second substrate, thereby reducing the light efficiency of the liquid crystal display device. This deterioration problem occurs.

Accordingly, an object of the present invention is to provide a liquid crystal display device for improving the light efficiency.

1 is a cross-sectional view of a transflective liquid crystal display device according to an exemplary embodiment of the present invention.

FIG. 2 is a plan view illustrating a relationship between a plurality of convex parts and a unit pixel illustrated in FIG. 1.

FIG. 3 is a diagram illustrating the liquid crystal display panel illustrated in FIG. 1 in detail.

4 is a view illustrating in detail a liquid crystal display panel used in a transflective liquid crystal display device according to another embodiment of the present invention.

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

100: first substrate 200: second substrate

220: light shielding film 230: color filter

240: light collecting film 300: liquid crystal layer

400: liquid crystal display panel 500: backlight unit

600: transflective sheet 700: liquid crystal display device

According to an aspect of the present invention, there is provided a liquid crystal display device including a first substrate having a plurality of unit pixels, and a second substrate having a plurality of convex portions formed on a surface facing the first substrate. And a liquid crystal layer interposed between the first substrate and the second substrate; A backlight unit for providing first light to the liquid crystal panel; And a transflective member disposed between the liquid crystal panel and the backlight unit to transmit the first light and reflect the second light incident after passing through the liquid crystal panel, wherein the plurality of convex portions The second light is collected and provided to the transflective member.

According to the liquid crystal display device, the liquid crystal display panel includes a plurality of convex portions formed on the second substrate, thereby condensing the second light provided by the transflective member disposed between the backlight unit and the liquid crystal display panel. Therefore, the light efficiency of the liquid crystal display device can be improved.

Hereinafter, with reference to the accompanying drawings, it will be described in detail a preferred embodiment of the present invention.

1 is a cross-sectional view illustrating a transflective liquid crystal display device according to an exemplary embodiment of the present invention, and FIG. 2 is a plan view illustrating a relationship between a plurality of convex portions and a unit pixel illustrated in FIG. 1.

Referring to FIG. 1, the transflective liquid crystal display 700 according to an exemplary embodiment of the present invention generates a liquid crystal display panel 400 for displaying an image and a first light L1 to generate an image. And a transflective sheet 600 interposed between the backlight unit 500 and the liquid crystal display panel 400 and the backlight unit 500.

The liquid crystal display panel 400 may include a first substrate 100, a second substrate 200 facing the first substrate 100, and a gap between the first substrate 100 and the second substrate 200. It is made of a liquid crystal layer 300 interposed.

The first substrate 100 is a substrate on which a plurality of unit pixels 140 are formed in a matrix form on the first glass substrate 110. In detail, the unit pixels 140 are sequentially driven in units of rows by signals provided from the outside.

Meanwhile, the second substrate 200 has a plurality of convex portions 241 protruding toward the first substrate 100 on one surface of the second glass substrate 110 facing the first substrate 100. It is a substrate on which the light collecting film 240 is formed. The plurality of convex parts 241 condenses the second light L2 provided to the transflective sheet 600 after passing through the second glass substrate 210 to reflect the reflectance of the transflective sheet 600. Improve. In addition, the plurality of convex portions 241 is incident on the second light L2 incident after being reflected from the transflective sheet 600 and the first light L1 transmitted through the transflective sheet 600. To spread). Therefore, the viewing angle of the transflective liquid crystal display 700 may be improved.

As shown in FIGS. 1 and 2, each of the plurality of convex portions 241 has a convex lens shape having a predetermined curvature. In addition, each of the plurality of convex portions 241 is formed to have a size corresponding to the three unit pixels.

In FIG. 2, the plurality of convex portions 241 has a circular or elliptical shape when viewed from the side of the second glass substrate 210. However, the plurality of convex portions 241 may include the unit pixels. It may have a rectangular shape to correspond to 140.

Thereafter, when the first substrate 100 and the second substrate 200 are combined, the liquid crystal layer 300 is interposed between the first substrate 100 and the second substrate 200. The liquid crystal layer 300 is formed using a 90 ° twisted nematic (TN) liquid crystal composition.

The backlight unit 500 includes a lamp unit 510 for generating light and a light guide plate 520 for guiding the light toward the liquid crystal display panel 400.

The lamp unit 510 includes a lamp 511 for generating the first light L1 and a lamp reflector 513 for reflecting the first light L1 to the light guide plate 520. The lamp unit 510 is disposed on one side surface of the light guide plate 520.

The light guide plate 520 includes an emission surface for emitting the first light L1, a reflection surface for reflecting the first light L1, and a plurality of side surfaces connecting the emission surface and the reflection surface. The lamp unit 510 is disposed on one side of the plurality of side surfaces, and the light is incident through the one side.

The backlight unit 500 is disposed below the light guide plate 520 and reflects light leaked from the reflective surface (not shown) and the first light disposed on the light guide plate and exited from the exit surface. A plurality of optical sheets (not shown) for improving the optical characteristics of the light L1 may be further provided.

The transflective sheet 600 is interposed between the liquid crystal display panel 400 and the backlight unit 500. The transflective sheet 600 has a structure in which two transparent layers having different refractive indices, that is, first and second layers are alternately stacked. Specifically, when the thickness direction of the transflective sheet 600 is referred to as the z direction and the surface is referred to as the xy plane, the refractive indices in the x and z directions of the first layer and the second layer are the same and the y direction The refractive indices are different. When unpolarized light is incident on the transflective sheet 600 in the vertical direction (ie, z direction), all polarization components in the x direction are transmitted by the Fresnel's equation, and the polarization components in the y direction are transmitted. All are reflected.

Therefore, the transflective sheet 600 reflects a part of the second light L2 and transmits the other part.

When displaying an image by the second light L2 provided from the outside of the transflective liquid crystal display 700, the second light L2 passes through the second substrate 200 through the liquid crystal display. The display device 700 is provided. The second light L2 incident through the second substrate 200 is collected by the plurality of convex portions 241 and provided to the transflective sheet 600.

Subsequently, the transflective sheet 600 reflects the incident second light L2 and provides the second light L2 to the liquid crystal display panel 400 and passes through the liquid crystal layer 300 to include image information. The two lights L2 are diffused by the plurality of convex portions 241. Therefore, the transflective liquid crystal display 700 may improve the light efficiency of the second light L2 provided from the outside by the plurality of convex portions 241, and may expand the overall viewing angle.

FIG. 3 is a view illustrating the liquid crystal display panel illustrated in FIG. 1 in detail.

Referring to FIG. 3, the liquid crystal display panel 400 includes a first substrate 100, a second substrate 200 facing the first substrate 100, and a first substrate 100 and a second substrate ( It consists of the liquid crystal layer 300 interposed between 200 and. The transflective sheet 600 is disposed under the liquid crystal display panel 400.

The first substrate 100 is a substrate in which a plurality of unit pixels 140 are formed in a matrix form. Each of the plurality of unit pixels 140 includes a data line (not shown), a gate line (not shown), a TFT 120, and a pixel electrode 130. In detail, a data line extending in a first direction and a gate line extending in a second direction perpendicular to the first direction are formed on the first glass substrate 110. The TFT 120 connected to the data line and the gate line is formed in a region partitioned by the data line and the gate line. In addition, a pixel electrode 130 connected to the TFT 120 and formed of indium tin oxide (ITO), which is a transparent and conductive material, is formed in the region.

Meanwhile, the second substrate 200 is a substrate on which the color filter 230, the light blocking film 220, the light collecting film 240, and the common electrode 250 are formed on the second glass substrate 210. In detail, the light blocking film 220 covers an invalid display area of the TFT substrate 100, such as a position corresponding to the TFT 120, the data line, and the gate line of the second glass substrate 210. Thereafter, a color filter 230 including R (Red), G (Green), and B (Blue) color pixels is formed on the second glass substrate 200 by a photoresist process. The color filter 230 is formed at a position corresponding to the pixel electrode 130. The light blocking film 220 is interposed between the color pixels to increase the contrast ratio of the transflective liquid crystal display 700.

Thereafter, on the second glass substrate 210 on which the light blocking film 220 and the color filter 230 are formed, the second transmissive sheet L collects the second light L2 incident through the second glass substrate 210. The condensing film 240 for providing to the 600 is formed. Specifically, a plurality of protrusions 241 protruding toward the TFT substrate 100 are formed in the light collecting film 240. Each of the plurality of protrusions 241 is formed in a convex lens shape, and each of the plurality of protrusions 241 has a size corresponding to the three unit pixels 140.

Accordingly, each of the plurality of convex portions 241 corresponds to an R.G.B color pixel, and in particular, the pitch of each of the plurality of convex portions 241 preferably corresponds to the G color pixel. That is, since the G color pixel is more responsive to visibility effects than the R and B color pixels, the area corresponding to the G color pixel has a larger curvature than the area corresponding to the R and G color pixels.

Next, the common electrode 250 is stacked on the light collecting film 240 to have a uniform thickness to complete the second substrate 200. However, the common electrode 250 may be formed to have a flat surface structure on the light collecting film 240.

Methods of forming the light collecting film 240 having the plurality of protrusions 241 are various, but only two of them are representatively presented here.

First, a method of forming the plurality of protrusions 241 by a photoresist process is presented. Specifically, a photosensitive organic insulating film (not shown) is coated on the second glass substrate 210 on which the light blocking film 220 and the color filter 230 are formed. Subsequently, a mask having a pattern corresponding to the plurality of protrusions 241 is formed on the photosensitive organic insulating layer, and then the photosensitive organic insulating layer is exposed. When the exposed photosensitive organic insulating film is developed by reacting with a developer, an insulating layer (not shown) having an uneven structure is formed. Thereafter, when the insulating layer is baked, the light collecting film 240 having the plurality of protrusions 241 having a convex lens shape is completed.

Second, a method of forming the light collecting film 240 in which the plurality of protrusions 241 are formed by using a patterned roller (not shown) is provided. Specifically, a first layer (not shown) is formed on the second glass substrate 210 on which the light blocking film 220 and the color filter 230 are formed, and the rollers correspond to the plurality of protrusions 241. A patterned second layer (not shown) is formed. Thereafter, the roller is disposed on the first layer, and then rotated in a specific direction while pressing the first layer at a predetermined pressure. Accordingly, patterns corresponding to the plurality of protrusions 241 are formed in the first layer. As a result, the light collecting film 240 having the plurality of protrusions 241 formed thereon is completed.

Although two methods of forming the light collecting film 240 have been described above, the light collecting film 240 may be sufficiently formed by methods other than the two methods.

4 is a cross-sectional view showing in detail a liquid crystal display panel used in a reflection-transmissive liquid crystal display device according to another embodiment of the present invention.

Referring to FIG. 4, the liquid crystal display panel 400 according to another exemplary embodiment of the present invention may include a first substrate 100, a second substrate 200 facing the first substrate 100, and the first substrate ( The liquid crystal layer 300 is interposed between the second substrate 200 and the second substrate 200. The transflective sheet 600 is disposed under the liquid crystal display panel 400.

The second substrate 200 is a substrate on which the color filter 230, the light blocking film 220, the light collecting film 260, and the common electrode 250 are formed on the second glass substrate 210. Specifically, on the second glass substrate 210, a color filter 230 including R (Red), G (Green), and B (Blue) color pixels, and the light shielding film 220 interposed between the respective color pixels. Is formed.

Subsequently, on the second glass substrate 210 on which the light blocking film 220 and the color filter 230 are formed, the second light L2 incident through the second glass substrate 210 is focused to the transflective sheet. A light collecting film 260 for providing is formed. Specifically, the light collecting film 260 is formed with a plurality of protrusions 261 protruding toward the TFT substrate 100. Each of the plurality of protrusions 261 is formed in a convex lens shape, and each of the plurality of protrusions 261 has a size corresponding to one unit pixel 140.

Next, the common electrode 250 is stacked on the light collecting film 260 to have a uniform thickness to complete the second substrate 200.

In FIG. 4, the light collecting film 260 having the plurality of convex parts 261 is formed on the light blocking film 220 and the color filter 230. However, the light collecting film 220 may be integrally formed with the color filter 230. That is, each color pixel of the color filter 230 is patterned into a convex lens shape. Accordingly, each of the color pixels condenses the second light L2 incident through the second glass substrate 210 and provides the second light L2 to the transflective sheet 600.

According to such a liquid crystal display device, the liquid crystal display panel includes a plurality of convex portions on the second substrate to condense the second light provided by the transflective member disposed between the backlight unit and the liquid crystal display panel.

Therefore, by increasing the amount of light of the second light provided to the transflective sheet, the reflection efficiency of the transflective sheet can be improved, and the light efficiency of the liquid crystal display device can be improved.

Although described with reference to the embodiments above, those skilled in the art will understand that the present invention can be variously modified and changed without departing from the spirit and scope of the invention as set forth in the claims below. Could be.

Claims (5)

A first substrate having a plurality of unit pixels, a second substrate having a plurality of convex portions formed on a surface facing the first substrate, and a liquid crystal layer interposed between the first substrate and the second substrate; A liquid crystal panel; A backlight unit for providing a first light to the liquid crystal panel; And A reflection member disposed between the liquid crystal panel and the backlight unit to reflect the second light transmitted through the first light and incident through the liquid crystal panel; And the plurality of convex portions collect the second light and provide the second light to the reflective member. The method of claim 1, wherein the second substrate, A color filter consisting of R, G, and B color pixels; A light collecting film formed on the color filter and having the plurality of convex portions formed thereon; And And a transparent electrode stacked on the light collecting film. The liquid crystal display device according to claim 1, wherein each of the plurality of convex portions has a convex lens shape. The liquid crystal display of claim 1, wherein each of the plurality of convex portions corresponds to the unit pixel, respectively. The liquid crystal display of claim 1, wherein each of the plurality of convex portions corresponds to one pixel consisting of three unit pixels.