KR20020042928A - Semi-transmission type liquid crystal display using fringe filed switching mode - Google Patents

Abstract

PURPOSE: A semi-transmissive liquid crystal display using fringe field switching mode is provided to obtain wide viewing angle and to control the degree of reflectivity and transmissivity. CONSTITUTION: A semi-transmissive liquid crystal display using fringe field switching mode has an electrode structure of realizing reflective and transmissive electrodes(39,40) simultaneously. The electrode structure is constructed of a reflective electrode formed of an opaque metal and a transmissive electrode formed of a transparent material. The reflective and transmissive parts have different rubbing orientations. A polarizer axis of a lower substrate of the transmissive part accords with or is perpendicular to the rubbing orientation of the lower substrate. A polarizer axis of an upper substrate is perpendicular to the polarizer axis of the lower substrate to represent the normally dark state. The reflective part has a rubbing orientation different from the rubbing orientation of the polarizer axis of the upper substrate to represent the normally dark state. The reflective and transmissive parts have the same driving condition.

Description

Semi-transmissive liquid crystal display using fringe field switching mode {SEMI-TRANSMISSION TYPE LIQUID CRYSTAL DISPLAY USING FRINGE FILED SWITCHING MODE}

The present invention relates to a transflective liquid crystal display using a fringe field switching mode, and more particularly, to a transflective liquid crystal display using a fringe field switching mode enabling both reflection and transmission by the same driving.

In the conventional transmissive liquid crystal display, since a light source must be used in itself, the use of a backlight under the lower substrate is essential. Accordingly, a reflection type liquid crystal display device that can be driven by using this light source when there is an external light source without using a backlight has attracted attention.

On the other hand, if there is an external light source, and if there is no external light source, a semi-transmissive mode that uses a back light using its own backlight has also been proposed and used.

On the other hand, such a transflective type has been proposed by using a wide viewing angle mode called a fringe field switching (FFS) mode. Here, a method of dividing a pixel into two parts and using one side as a transmission type and the other type as a reflection type or a method that can use both transmission and reflection using a pixel electrode or a counter electrode as a reflection plate has been proposed.

However, the semi-transmissive modes using the FFS mode presented up to now have a problem of separately driving the reflective and the transmissive driving because the driving conditions of the reflection and the transmission are different.

SUMMARY OF THE INVENTION An object of the present invention is to provide a semi-transmissive liquid crystal display device using a fringe field switching mode that enables both reflection and transmission by the same driving. have.

1 is an electrode structure diagram of a transflective liquid crystal display using a fringe field switching mode according to the present invention.

2 is a view showing an electrode structure and rubbing angle of a transflective liquid crystal display using a fringe field switching mode according to the present invention.

3 is a graph showing an angle and driving voltage of A when α = 0 ° when a positive liquid crystal is used in a transflective liquid crystal display using a fringe field switching mode according to the present invention.

4 is a graph showing an angle and driving voltage of A when α = 0 ° when a negative liquid crystal is used in a transflective liquid crystal display using a fringe field switching mode according to the present invention.

FIG. 5 is a side view of the transflective liquid crystal display using the fringe field switching mode and the axial direction of each component in the case of using the polarizing reflective electrode.

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

10: reflective electrode 20: transmissive electrode

32: upper polarizing plate 34: upper glass

36 lower pixel electrode 38 insulating film

39, 40: lower counter electrode (transmission, reflection electrode)

42: lower glass 44: lower polarizing plate

According to a preferred embodiment of the present invention for achieving the above object, in the electrode structure using the fringe field switching mode, by dividing the pixel to realize a portion of the counter electrode to reflect the opaque metal A liquid crystal display device having an electrode structure that is formed of a reflective structure and a reflective electrode, and an electrode structure that forms a counter electrode part using a transparent electrode in a transmissive manner, thereby simultaneously implementing a reflective and transmissive electrode structure. The rubbing direction of the part is different, and the lower polarization axis of the transmissive part indicates the same or vertical direction as the lower rubbing direction, and the upper polarization axis is normal to the lower polarization axis, indicating a normal dark state, and the reflective part indicates the rubbing direction. It becomes normal dark state by making it different from top polarization axis, and the same sphere is same There is provided a transflective liquid crystal display using a fringe field switching mode to have the same condition.

Further, in the present invention, the sum of the reflection angle and the rubbing angle of the transmission type is ± 45 ° along the axial direction, and the sum of each rubbing direction is ± 45 ° or ± 135 °.

Further, in the present invention, the value of dΔn of the liquid crystal used preferably has a value of λ (2n + 1) / 4, (λ = 550 nm ± 10 nm, n = 0 or a positive integer), whereby the reflection type The portion used as is characterized in that the normal dark state.

In addition, in the present invention, by adjusting the values of the reflection angle of α and β so that the driving voltage of the reflection type and the transmission type is similar or the same, when using a liquid crystal having positive dielectric anisotropy, A, α, B The difference between and β is 0 ° to 45 °, and when the liquid crystal having negative dielectric anisotropy is used, the difference between A and α, B and β is 45 ° to 90 °.

In the present invention, a liquid crystal display element using a conductor having a reflectance of 80% or more when forming a counter electrode used as a reflector can be formed simultaneously with the gate metal using a metal such as a gate metal.

In addition, in the present invention, when rubbing the reflective and transmissive portions, a method of photoalignment is used or a double rubbing method using a mask is used.

In addition, in the present invention, when forming the reflector, the particles may be formed in a predetermined direction to form light in a specific direction, so that the reflective portion is in a normal dark state without having to change the rubbing direction of the reflective and transmissive portions. The transmission axis of the polarization axis of the upper plate and the transmission axis of the polarization reflector are characterized by being vertical.

Further, in the present invention, the liquid crystal used is characterized by maximizing both the reflectance and the transmittance by allowing dΔn to have a value of 0.27 to 0.47 µm.

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

1 is an electrode structure diagram of a transflective liquid crystal display using a fringe field switching mode according to the present invention, Figure 2 is an electrode structure diagram showing a rubbing angle in a transflective liquid crystal display using a fringe field switching mode according to the present invention. As shown here, in the case of the reflective electrode 10 using the fringe field switching mode, the polarizer 32 (see FIG. 5) of the upper plate, the rubbing axis of the liquid crystal, and the dΔn of the liquid crystal used. However, it has already been suggested that the cell gap d and Δn can be used in the normal black mode by adjusting the refractive index anisotropy of the liquid crystal. At this time, the rubbing angle should ideally have a 45 ° value with the polarizing plate axis of the upper plate. In the case of the transmissive electrode 20, when the rubbing angle with the polarizing plate reaches 45 °, light is leaked, so that the same driving as the reflective type is difficult. do.

Therefore, by dividing the pixels into different rubbing directions, reflection and transmission can be simultaneously realized. In the case of the transmittance and reflectance according to the voltage application, the increase rate is different depending on the degree of application of the voltage in the normally black mode. This problem is caused by adjusting the angles of the electrodes of the divided pixels differently. By adjusting the angle between the direction and the liquid crystal director (director) can be solved by making the increase rate of the reflectance and transmittance similar to the application of the voltage.

On the other hand, in the present invention, as shown in FIG. 1, the pixel is divided into two, one side uses the counter electrode part using a transparent electrode, and the other side uses an opaque electrode having a large reflectance to replace the reflecting plate.

The ratio of dividing the lower counter electrode 40 (see FIG. 5) into two parts is that the ratio of the opaque metal and the transparent metal is set between 8 and 1: 1 when the use of the reflective type is prioritized according to the purpose of the reflective type and the transparent type. If the use is prioritized, the ratio of transparent metal to opaque metal should be about 8 to 1: 1. In the case of the opaque metal, the same metal as the gate metal may be formed at the same time as forming the gate line, and if the transparent metal is formed in the same manner as the counter electrode, the existing process may be used as it is. .

In this case, the pixel electrode is formed to use the transmissivity or the reflectance to the maximum using a transparent electrode, but the electrode forming direction of each divided portion is formed differently. That is, in Fig. 1, the values of α ° and β °, which are the respective reflection angles in the reflection type and the transmission type, have different values, and preferred values are the rubbing angles in the reflection type and the transmission type as shown in FIG. The rubbing angles are selected by considering A ° and B °.

The rubbing angle uses a method of double rubbing using photo-alignment or a mask such that each divided portion has a different rubbing angle. Rubbing in anti-parallel or parallel top and bottom, but rubbing as shown in Figure 2 rubbing angles A and B, but preferably A + B = 45 °. Briefly describing the driving method based on the above description, first, the difference between α in FIG. 1 and A in FIG. 2 in the case of a transmissive portion has a value between 0 ° and 45 ° when a positive liquid crystal is used. In addition, the difference between β of FIG. 1 and B of FIG. 2 also has a value between 0 ° and 45 °. In the case of negative liquid crystals, both cases have a 45 ° to 90 ° value. On the other hand, the sum of A and B preferably has a value of 45 ° as described above, in which the polarizer and the analyzer are placed vertically in the transmission type, and when the transmission axis of the polarizer is coincident with or perpendicular to the rubbing axis of the lower plate, It is normally dark. At the same time, by adjusting dΔn of the liquid crystal in the reflection type, it is possible to create a normal dark mode at the same time as the transmission type. At this time, dΔn of the liquid crystal has a value of λ (2n + 1) / 4 to form a dark state (where n is an integer).

3 is a graph showing an angle and driving voltage of A when α = 0 ° when a positive liquid crystal is used in a transflective liquid crystal display using a fringe field switching mode according to the present invention, and FIG. 4 is a fringe according to the present invention. A graph showing the angle and driving voltage of A when α = 0 ° in the case of using a negative liquid crystal in a semi-transmissive liquid crystal display using the field switching mode, as shown therein, while the driving voltage is as specified above. This can be achieved by adjusting the value between rubbing and the electrode. 3 and 4 are diagrams showing the change in driving voltage according to the rubbing angle in the transmission type when the positive dielectric anisotropy and the negative dielectric anisotropy are used. Reflective trends show the same trend, which can be used to adjust the angles of A, α, B, and β to match or maintain the drive voltages of the reflective and transmissive types.

When the panel is manufactured as described above, both the voltage applying transmission type and the reflection type have a dark state, and when voltage is applied, light starts to leak, so that the transmission conditions and the reflectance at the same voltage are maximized, respectively. . Therefore, it is possible to have the same driving conditions even when using either the transmissive or reflective type.

In another embodiment of the present invention, the counter electrode 44 is used as a reflecting plate when the particles are regularly arranged in a predetermined direction so as to polarize light when forming the reflecting plate as the counter electrode 44 and then coated with a conductive material. ) May serve as a polarizer.

Therefore, by arranging the transmission axis of the polarizing plate substitute reflector to match the transmission axis of the transmissive lower polarizing plate, both normal transmission and reflection can be obtained in a normally dark state. As shown in FIG. 5, which is a side view and an axial direction of each component in the transflective liquid crystal display using the mode, the driving voltage between the two may be matched by adjusting only the electrode direction. Reference numerals 34 and 42 denote upper and lower glass, 44 denote lower polarizing plates, 36 denote lower pixel electrodes, and 38 denote insulating films. Reference numerals 39 and 40 denote transmissive and reflective electrodes that form the lower counter electrode.

Therefore, according to the semi-transmissive liquid crystal display device using the fringe field switching mode according to the present invention, it is possible to produce a liquid crystal display device having a wide viewing angle, the effect of arbitrarily adjusting the degree of reflectance and transmittance, In the dark, it is possible to manufacture products that can be used as a transmissive type, and the existing process can be used as it is, and the same driving method is used to drive the reflective type and the transmissive type.

In addition, preferred embodiments of the present invention described above are disclosed for the purpose of illustration, and those skilled in the art will be able to make various modifications, changes, additions, etc. within the spirit and scope of the present invention, such modifications, modifications and the like are within the scope of the claims It should be seen as belonging.

Claims (8)

In the electrode structure using the fringe field switching mode, By dividing the pixel into two parts, a part of the counter electrode is formed into an opaque metal to form a reflective type, and an electrode formed of an opaque metal is well reflected, and a counter electrode is used to form another counter electrode part using a transparent electrode. A liquid crystal display device having an electrode structure implemented, The liquid crystal display device has a rubbing direction different from that of the reflective and transmissive portions, The lower polarization axis of the transmissive portion points in the same or vertical direction as the lower rubbing direction, The upper polarization axis is normal dark with normal to the lower polarization axis, and the reflective part is a normal dark state by making the rubbing direction different from the upper polarization axis, so that the fringe field switching has the same driving conditions for both the top and transmissive types. Semi-transmissive liquid crystal display using mode. The fringe field switching mode of claim 1, wherein the sum of the reflection angles and the rubbing angles of the transmission type is ± 45 ° along the axial direction, and the sum of each rubbing direction is ± 45 ° or ± 135 °. Transflective liquid crystal display device. The value of dΔn of the liquid crystal used is preferably a value of λ (2n + 1) / 4, (λ = 550 nm ± 10 nm, n = 0 or a positive integer). The transflective liquid crystal display device using the fringe field switching mode characterized by having the part used as a reflection type become a normal dark state by having the following. 2. The method of claim 1, wherein the reflection angles α and β are adjusted so that the driving voltages of the reflection type and the transmission type have the same or the same value, but the liquid crystals having positive dielectric anisotropy have A, α, B and When the difference between β is 0 ° to 45 ° and the liquid crystal having negative dielectric anisotropy is used, the transflective liquid crystal using the fringe field switching mode is characterized in that the difference between A, α, B, and β is 45 ° to 90 °. Display device. The fringe field according to claim 1, wherein a liquid crystal display device using a conductor having a reflectance of 80% or more when forming a counter electrode used as a reflector can be formed simultaneously with the gate metal using a metal such as a gate metal. Semi-transmissive liquid crystal display using switching mode. 4. The transflective type using the fringe field switching mode according to any one of claims 1 to 3, wherein the rubbing of the reflective and transmissive portions uses a photo-alignment method or a double rubbing method using a mask. Liquid crystal display. In the electrode structure using the fringe field switching mode, it is possible to form light in a specific direction by forming particles in a certain direction when forming the reflector, so that the reflective portion can be formed without having to change the rubbing direction of the reflective and transmissive portions. A transflective liquid crystal display using a fringe field switching mode, wherein the transmission axis of the polarization axis of the upper plate and the transmission axis of the polarization reflector are perpendicular to each other so as to be in a normal dark state. 8. The transflective liquid crystal display device using the fringe field switching mode according to claim 7, wherein the liquid crystal used has a maximum value of d2n of 0.27 to 0.47 mu m, thereby maximizing both reflectance and transmittance.