KR20080067041A - Transflective liquid crystal pannel - Google Patents

Abstract

A transflective LCD panel is provided to control a refractive index of blue phase LC(Liquid Crystal) by differentiating a gap between pixel electrodes and common electrodes formed in reflective and transmissive regions, thereby removing a fault generated by a low cell gap. A transflective LCD(Liquid Crystal Display) panel(100) comprises a color filter substrate(110) where a color filter(114) is formed in a first glass substrate(112), a TFT(Thin Film Transistor) substrate(120) where a pixel electrode(128) and a common electrode(127) are formed in a second glass substrate(122), and LC(130) filled between the color filter substrate and the TFT substrate. The LCD panel is divided into a reflective region and a transmissive region. A gap(H1) between a pixel electrode and a common electrode formed in the reflection region is greater than a gap(H2) between a pixel electrode and a common electrode formed in the transmissive region. The LC is blue phase LC of a cylindrical array form where molecules are arranged by being twisted in a three-dimensional spiral direction.

Description

Transflective Liquid Crystal Display Panel {TRANSFLECTIVE LIQUID CRYSTAL PANNEL}

1 is a view showing the structure of a transflective liquid crystal panel according to an embodiment of the present invention;

2 is a diagram illustrating the structure of a pixel electrode and a common electrode illustrated in FIG. 1; and

FIG. 3 is a diagram illustrating another structure of the pixel electrode and the common electrode illustrated in FIG. 1.

<Code Description of Main Parts of Drawing>

100: liquid crystal display panel 110: color filter substrate

112: upper glass substrate 114: color filter

120: thin film transistor substrate 122: lower glass substrate

124: insulating film 126: reflector

127: common electrode 128: pixel electrode

RR: reflection area TR: transmission area

H1, H2: cell gap h1, h2: color filter thickness

d1, d2: gap between the pixel electrode and the common electrode

The present invention relates to a transflective liquid crystal display device, and more particularly, to a transflective liquid crystal display panel having a dual cell gap type.

In general, a liquid crystal display device arranges two substrates on which electric field generating electrodes are formed so that the surfaces on which the two electrodes are formed face each other, injects a liquid crystal between the two substrates, and then generates an electric field generated by applying a voltage to the two electrodes. By moving the liquid crystal by the, it is a device for expressing the image by adjusting the light transmittance that varies accordingly.

The liquid crystal display does not emit light by itself and thus requires a separate light source. The liquid crystal display may be classified into a transmission type and a reflection type according to a light source to be used.

The transmissive liquid crystal display is a form in which light emitted from a backlight, which is a rear light source attached to the rear side of the liquid crystal panel, is incident on the liquid crystal panel to display color by adjusting the amount of light according to the arrangement of liquid crystals. The light transmittance is adjusted according to the arrangement of liquid crystals by reflecting natural light or artificial light, which is an ambient light source.

Although the transmissive liquid crystal display uses a rear light source, a bright image can be realized even in a dark external environment, but power consumption has a significant disadvantage, while the reflective liquid crystal display has a structure that depends on the ambient light source. Although it consumes less power, it can't be used in dark places.

Accordingly, a semi-transmissive liquid crystal display device, which is a liquid crystal display device that combines reflection and transmission, has been proposed as a device capable of appropriately selecting and using two modes according to a necessary situation. The transflective liquid crystal display operates in a reflection mode when the ambient light is sufficient, and in a transmissive mode using a backlight which is a back light source when the ambient light is insufficient.

Such a transflective liquid crystal display has a dual cell gap method and a single cell gap in which a cell gap of a transmission region is doubled to a cell gap of a reflection region, and a transmission region and a reflection region according to an alignment structure. There is a single cell gap method having an optical phase difference of.

However, the conventional dual cell gap type transflective liquid crystal display has a high defect rate due to high over defect due to the low cell gap of the reflection area, and uniformity of the cell gap of the reflection area having a low cell gap. ), The image quality difference for each pixel occurs in the Normal White Mode, and light leakage occurs in the Normal Black Mode. In addition, the light reflected by the reflecting plate of the reflecting region exhibits scattering characteristics different from the transmission region due to the nonuniformity of the cell gap, which causes a problem of unevenness of color or luminance.

Accordingly, an object of the present invention is to provide a semi-transmissive liquid crystal display panel which eliminates defects caused by a low cell gap of a reflective region.

A semi-transmissive liquid crystal display panel of the present invention for achieving the above object, the color filter substrate formed with a color filter on the first glass substrate; A thin film transistor substrate having a pixel electrode and a common electrode formed on a second glass substrate; And a liquid crystal filled between the color filter substrate and the thin film transistor substrate, wherein the liquid crystal is divided into a reflection region and a transmission region, and a gap between the pixel electrode and the common electrode formed in the reflection region is a pixel electrode formed in the transmission region. It is desirable to be larger than the spacing between common electrodes.

The liquid crystal is preferably a blue phase liquid crystal in which molecules form a cylindrical array arranged by twisting in a three-dimensional spiral direction.

The first cell gap, which is a gap between the color filter substrate and the thin film transistor substrate in the reflective region, may be larger than the second cell gap, which is a gap between the color filter substrate and the thin film transistor substrate in the transmission region.

In addition, the second cell gap is preferably larger than the optically active thickness of the liquid crystal.

In addition, the thin film transistor substrate includes a reflector formed in the reflective region.

In addition, the color filter of the reflective region is preferably smaller than the color filter of the transmissive region.

In addition, the pixel electrode and the common electrode preferably have a horizontal electrode switching (IPS) mode structure, or the pixel electrode and the common electrode have a super horizontal electrode switching (S-IPS) mode structure.

The transflective liquid crystal display panel of this invention is a color filter substrate in which the color filter was formed in the 1st glass substrate; A thin film transistor substrate having a pixel electrode and a common electrode formed on a second glass substrate; And a blue phase liquid crystal filled between the color filter substrate and the thin film transistor substrate, wherein the first interval is divided into a reflection region and a transmission region and is a distance between a pixel electrode and a common electrode formed in the reflection region. It is preferable that the birefringence of the blue phase liquid crystal positioned in the reflection area and the transmission area is greater than a second distance that is a distance between the pixel electrode and the common electrode formed in the area, and the first and second distances are adjusted. .

Other technical problems and features of the present invention other than the above technical problem will become apparent from the description of the embodiments with reference to the accompanying drawings. Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention.

1 illustrates a structure of a transflective liquid crystal display panel according to an exemplary embodiment of the present invention. As shown in FIG. 1, the transflective liquid crystal display panel 100 according to an exemplary embodiment of the present invention is a dual cell gap transflective liquid crystal display panel, which includes a color filter substrate 110 and a thin film transistor substrate 120. And a liquid crystal 130 filled between the color filter substrate 110 and the thin film transistor substrate 120.

Here, the dual cell gap method means that the cell gap H1 of the reflective region (RR) is larger than the cell gap H2 of the transmissive region (TR) so that the optical characteristics of the reflective region RR and the transparent region TR are The method of compensating for the phase difference.

The color filter substrate 110 includes an upper glass substrate 112 and a color filter 114 formed on the upper glass substrate 112. The color filter 114 includes a red (R) filter, a green (G) filter, and a blue (B) filter corresponding to the unit pixel. The red (R) filter, the green (G) filter, and the blue (B) filter express various colors by absorbing or transmitting light of a specific wavelength through the pigments contained therein.

The thickness h1 of the reflection region RR of the color filter 114 is preferably 1/2 of the thickness h2 of the transmission region TR of the color filter 114. This is caused when the thickness of the color filter 114 of the reflection region RR and the transmission region TR is equal to each other, and the light passes through the color filter 114 twice as light enters and exits the reflection region RR. This is to correct the color coordinate difference between the reflection region RR and the transmission region TR.

The thin film transistor substrate 120 includes a lower glass substrate 122 having a thin film transistor (not shown), an insulating film 124 coated on the lower glass substrate 122 having a thin film transistor, and a pixel electrode formed on the insulating film 124. 128 and the common electrode 127.

Here, the pixel electrode 128 and the common electrode 127 are formed to face each other in the horizontal direction to have an electrode structure of a horizontal electrode switching (IPS) mode. The pixel electrode 128 and the common electrode 127 may be formed of a transparent conductive material, for example, indium tin oxide (ITO) or indium zinc oxide (IZO).

When the gray scale display voltage V is applied to the pixel electrode 128 and the common electrode 127, the liquid crystal 130 positioned between the color filter substrate 110 and the thin film transistor substrate 120 rotates in the horizontal direction to adjust the gray scale. The bright and dark states corresponding to the display voltage V are displayed.

On the other hand, the pixel electrode 128 and the common electrode 127 have a gap d1 and d2 between them in the reflection region RR and the transmission region TR. The distance d1 between the pixel electrode 128 and the common electrode 127 in the reflection region RR is greater than the distance d2 between the pixel electrode 128 and the common electrode 127 in the transmission region TR. desirable.

In addition, the thin film transistor substrate 120 may include a reflector 126 formed in the reflective region RR between the lower glass substrate 122 and the insulating layer 124. The reflecting plate 126 performs a function of reflecting the external incident light incident from the front side of the reflective region RR back to the front side. The reflector plate 126 preferably has an embossed surface (not shown) on its surface in order to increase reflection efficiency.

The liquid crystal 130 is preferably a blue phase liquid crystal in which molecules form a cylindrical array arranged by twisting in a three-dimensional spiral direction. The cell gap H1 of the reflective region RR in which the liquid crystal 130 is filled between the color filter substrate 110 and the thin film transistor substrate 120 is preferably larger than the cell gap H2 of the transmission region TR. .

More preferably, the cell gap H1 of the reflection region RR is twice the cell gap H2 of the transmission region TR. This is because the external incident light is reflected by the reflecting plate 126 in the reflection region RR and emitted to the outside, so that the light path is twice as large as that of the transmission region TR.

Here, the cell gap H1 of the reflective region RR has a thickness equal to or greater than an optically active thickness of the blue phase liquid crystal, and the refractive index of the liquid crystal 130 positioned in the reflective region RR is positioned in the transmission region TR. It is preferable to make it 1/2 of the refractive index of the liquid crystal 130.

The relationship between the applied gradation display voltage and the refractive index induced by the electric field and the electric field according to the horizontal gap between the pixel electrode and the common electrode will be described in more detail.

The horizontal spacing d1 between the pixel electrode 128 formed in the reflective region RR and the common electrode 127 is the horizontal spacing d2 between the pixel electrode 128 formed in the transmissive region TR and the common electrode 127. Since the difference in electric field intensity is greater than), the refractive index of the liquid crystal 130 positioned in the reflection region RR is smaller than that of the liquid crystal 130 positioned in the transmission region TR. That is, the intensity of the electric field E generated in the reflection region RR is smaller than the intensity of the electric field E generated in the transmission region TR.

The relationship between these equations is represented by equation (1).

In Equation 1, Δn is the birefringence induced, λ is the wavelength of light, K is the Kerr constant, E is the intensity of the electric field due to the voltage applied to the pixel electrode and the common electrode, d is the distance between the pixel electrode and the common electrode, that is, d1 Or d2.

Referring to Equation 1, the electric field causes local reorientation of the blue phase liquid crystal, and the birefringence Δn induced through the blue phase liquid crystal is proportional to the square of the intensity E of the electric field. In addition, since the intensity E of the electric field is inversely proportional to the distance d1 or d2 between the pixel electrode 128 and the common electrode 127, the birefringence Δn induced through the blue phase liquid crystal is due to the pixel electrode 128 and the common electrode. It can be seen that it is inversely proportional to the square of the interval d1 or d2 between (128).

According to the experimental data, the optically active thickness of the blue phase liquid crystal is determined by the electric field strength, the properties of the liquid crystal, and the structure of the electrode. Preferably the optically activatable thickness of the blue phase liquid crystal is 7 μm.

In other words, the blue phase liquid crystal is not affected by the birefringence induced by the nonuniformity of the cell gap when the thickness of the blue liquid crystal is greater than the optically active thickness, and the voltage and the pixel electrode applied to the pixel electrode and the common electrode, as described in Equation 1, It operates by birefringence, which is defined as a function of the spacing between common electrodes.

A semi-transmissive liquid crystal display panel according to an exemplary embodiment of the present invention has a cell gap of a reflective region having a thickness greater than an optically active thickness of a blue phase liquid crystal, a gap between a pixel electrode of a reflective region and a common electrode, and a pixel electrode of a transmissive region. Since the birefringence of the liquid crystal positioned in the reflective region and the transmissive region can be adjusted by adjusting the spacing between the common electrodes, it can be used in a transflective liquid crystal display.

In the case of a liquid crystal panel using a conventional nematic liquid crystal, retardation is defined by the product of the intrinsic birefringence and the cell gap regardless of the display operation mode, so that the retardation is defined and the cell gap is dependent. The uniformity of was very important for the operation of the liquid crystal panel.

However, the transflective liquid crystal display panel according to an exemplary embodiment of the present invention may operate independently of the cell gap when the cell gap of the reflective region has a thickness greater than the optically active thickness of the blue phase liquid crystal. Therefore, the transflective liquid crystal display panel according to the exemplary embodiment of the present invention can eliminate defects due to thickness nonuniformity of the conventional low cell gap portion.

In addition, in the conventional semi-transmissive liquid crystal display device, in order to match the refractive index in the reflection area and the transmission area, the cell gap of the reflection area with the long light path is 1/2 of the cell gap of the transmission area. In addition, since the light in the reflection area passes through the color filter twice at the time of incidence and reflection, the color filter thickness of the reflection area is 1/2 of the color filter thickness of the transmission area, thereby adjusting color reproducibility. The result was a thickening of the gap, which required a Clear Over Coating layer to prevent this.

However, in the transflective liquid crystal display panel according to the exemplary embodiment of the present invention, the birefringence of the blue phase liquid crystal in which the cell gap of the reflection region is blue is adjusted at different intervals in the reflection region and the transmission region. Therefore, it has a structure capable of matching the retardation of the reflection area and the transmission area. Therefore, the transflective liquid crystal display panel according to the exemplary embodiment of the present invention does not require the conventional clear overcoat layer, and thus has an advantage of simplifying the manufacturing process.

FIG. 2 is a diagram illustrating the structure of the pixel electrode and the common electrode illustrated in FIG. 1. As illustrated in FIG. 2, the pixel electrode and the common electrode formed in the reflection area and the transmission area have an electrode structure of an In-Plane Switching (IPS) mode. The pixel electrode and the common electrode are in the form of a strip.

The distance d1 between the pixel electrode 128 formed in the reflective region RR and the common electrode 127 is greater than the distance d2 between the pixel electrode 128 formed in the transmissive region TR and the common electrode 127. Big. As described in Equation 1, the reflection area is adjusted by adjusting horizontal gaps between the pixel electrode 128 and the common electrode 127 formed at different distances d1 and d2 in the reflection area RR and the transmission area TR. It is possible to match the retardation of RR and the transmission region TR.

In operation, when no voltage is applied to the pixel electrode 128 and the common electrode 127, the liquid crystal 130 is inclined to a certain degree with respect to the electrode direction in the initial alignment state, and the pixel electrode 128 and the common electrode are arranged. When a voltage is applied to 127, a horizontal electric field is formed on the pixel electrode 128 and the common electrode 127 to arrange the liquid crystal 130 in the horizontal direction. Therefore, since the liquid crystal 130 rotates in a plane parallel to the color filter substrate and the thin film transistor substrate, the difference in the anisotropy of the refractive index of the liquid crystal viewed by the observer is reduced, thereby realizing a wide viewing angle.

FIG. 3 is a diagram illustrating another structure of the pixel electrode and the common electrode illustrated in FIG. 1. As illustrated in FIG. 3, the pixel electrode and the common electrode formed in the reflection area and the transmission area have an electrode structure of a super in-plane switching (S-IPS) mode. In this case, the pixel electrode and the common electrode have a chevron shape.

The distance d1 between the pixel electrode 128 formed in the reflective region RR and the common electrode 127 is greater than the distance d2 between the pixel electrode 128 formed in the transmissive region TR and the common electrode 127. Big. As described in Equation 1, the horizontal spacing between the pixel electrode 128 and the common electrode 127 formed at different intervals in the reflection region RR and the transmission region TR is adjusted to transmit the reflection region RR and transmission. The retardation of the area TR can be matched.

In operation, when no voltage is applied to the pixel electrode 128 and the common electrode 127, the liquid crystal 130 is arranged in the same direction as the electrode direction in the initial alignment state, and the pixel electrode 128 and the common electrode 127 are arranged. When a voltage is applied to the Rc, an inclined electric field of the upper side and the lower side is generated due to the chevron electrode structure, and the liquid crystals 130 are arranged in the left and right directions, respectively, to form two domain structures. Therefore, the side visibility of the liquid crystal is improved as the arrangement on the left and right is symmetrical.

Meanwhile, in the liquid crystal display panel according to an exemplary embodiment of the present invention, the pixel electrode and the common electrode have the IPS mode and the S-IPS mode structures, but the pixel electrode and the common electrode structure are not limited thereto. For example, the pixel electrode and the common electrode may be formed on the thin film transistor substrate, but not formed on the same plane, so that the molecules of the liquid crystal are rearranged by a horizontal electric field and a vertical electric field. have.

When the pixel electrode and the common electrode have an FFS mode structure, similarly to those described with reference to FIGS. 2 and 3, the distance between the pixel electrode and the common electrode formed in the reflection area is greater than the distance between the pixel electrode and the common electrode formed in the transmission area. It is desirable to be large.

The refractive index of the liquid crystal positioned between the color filter substrate and the thin film transistor substrate may be adjusted by adjusting the distance between the pixel electrode and the common electrode, and through this, the retardation of the reflection region and the transmission region may be matched. Since it can be easily inferred by those skilled in the art from what is described in Equation 1, a detailed description thereof will be omitted.

Since the transflective liquid crystal display according to the present invention has a structure in which the refractive index of the blue phase liquid crystal can be adjusted by varying the distance between the pixel electrode and the common electrode formed in the reflective region and the transmissive region, it is generated depending on the low cell gap. There is an effect that can remove the defect.

In the detailed description of the present invention described above with reference to the preferred embodiment of the present invention, those skilled in the art or those skilled in the art having ordinary knowledge of the present invention described in the claims to be described later It will be understood that various modifications and variations can be made in the present invention without departing from the spirit and scope of the art.

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 (10)

A color filter substrate on which a color filter is formed on the first glass substrate; A thin film transistor substrate having a pixel electrode and a common electrode formed on a second glass substrate; And a liquid crystal filled between the color filter substrate and the thin film transistor substrate, and divided into a reflection region and a transmission region. The transflective liquid crystal display panel having a gap between the pixel electrode and the common electrode formed in the reflective area is larger than a gap between the pixel electrode and the common electrode formed in the transmissive area. The semi-transmissive liquid crystal display panel of claim 1, wherein the liquid crystal is a blue phase liquid crystal in which molecules form a cylindrical array arranged by twisting in a three-dimensional spiral direction. The transflective liquid crystal display panel of claim 2, wherein the first cell gap, which is a gap between the color filter substrate and the thin film transistor substrate in the reflective region, is larger than the second cell gap, which is a gap between the color filter substrate and the thin film transistor substrate in the transmission region. . The transflective liquid crystal display panel of claim 3, wherein the second cell gap is larger than an optically active thickness of the liquid crystal. The liquid crystal display panel of claim 4, wherein the thin film transistor substrate comprises a reflector formed in the reflective region. The transflective liquid crystal display panel of claim 5, wherein the color filter of the reflective region is smaller in thickness than the color filter of the transmissive region. The transflective liquid crystal display panel of claim 6, wherein the pixel electrode and the common electrode have a horizontal electrode switching (IPS) mode structure. The transflective liquid crystal display panel of claim 7, wherein the pixel electrode and the common electrode have a super horizontal electrode switching (S-IPS) mode structure. A color filter substrate on which a color filter is formed on the first glass substrate; A thin film transistor substrate having a pixel electrode and a common electrode formed on a second glass substrate; And a blue phase liquid crystal filled between the color filter substrate and the thin film transistor substrate, and divided into a reflection region and a transmission region. The first interval, which is the interval between the pixel electrode and the common electrode formed in the reflective region, is greater than the second interval, which is the interval between the pixel electrode and the common electrode formed in the transmission region, A semi-transmissive liquid crystal display panel in which the birefringence of the blue phase liquid crystal positioned in the reflection region and the transmission region is adjusted by adjusting the first interval and the second interval. 10. The method of claim 9, wherein the first cell gap, which is a gap between the color filter substrate and the thin film transistor substrate in the reflective region, is greater than the second cell gap, which is a gap between the color filter substrate and the thin film transistor substrate in the transmission region, wherein the second cell A transflective liquid crystal display panel, wherein a gap is larger than an optically active thickness of the liquid crystal.

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