KR101271523B1 - Liquid crystal display device of viewing angle control - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device in which mode switching between a wide viewing angle and a narrow viewing angle is free.

A feature of the present invention is that each of the first liquid crystal layer and the second liquid crystal layer are configured in spaces of three substrates spaced apart from each other. The first liquid crystal cell has a wide viewing angle, and the second liquid crystal cell has a voltage. Characterized in that it can be configured to implement the narrow viewing angle according to the authorization.

That is, when a voltage is applied to the second liquid crystal layer, the viewing angle characteristic is lowered, thereby switching to a narrow viewing angle mode, and in order to implement a wide viewing angle, the voltage is not applied to the second liquid crystal layer or a voltage below a threshold voltage is applied. By applying the display characteristics of the wide viewing angle mode of the first liquid crystal cell as it is, it is possible to implement a wide viewing angle.

As a result, it is possible to provide a liquid crystal display device that can switch between wide viewing angle and narrow viewing angle mode freely according to a user's situation.

Narrow viewing angle, wide viewing angle, ECB mode, VA mode, HAN mode, liquid crystal display

Description

Liquid crystal display device of viewing angle control

1 is an exploded perspective view of a general liquid crystal display module.

FIG. 2 schematically illustrates a liquid crystal display module including the liquid crystal panel of FIG. 1 and freely switching between wide viewing angle and narrow viewing angle modes. FIG.

3 is an exploded perspective view schematically showing a liquid crystal display module according to an embodiment of the present invention.

4 is a schematic cross-sectional view of the liquid crystal panel of FIG. 3.

5A and 5B are graphs illustrating simulation results of luminance and contrast ratios according to viewing angles at wide viewing angles of liquid crystal panels including first and second liquid crystal layers according to an exemplary embodiment of the present invention.

6A and 6B are graphs illustrating simulation results of luminance and contrast ratios according to viewing angles of a narrow viewing angle of a liquid crystal panel including first and second liquid crystal layers according to an exemplary embodiment of the present invention.

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

111: liquid crystal panel 153: first substrate

151: second substrate 165: third substrate

155: Black matrix 157a, 157b, 157c: Color filter

159: first liquid crystal layer 161: pixel electrode

163: common electrode 167, 169: first and second electrodes

171: second liquid crystal layer 181: first liquid crystal cell

183: second liquid crystal cell DL: data wiring

P: pixel area

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device in which mode switching between a wide viewing angle and a narrow viewing angle is free.

The image realization principle of a general liquid crystal display device uses the optical anisotropy and polarization property of the liquid crystal. The liquid crystal has a thin and long molecular structure and polarization in which the direction of the molecular array changes according to its size when placed in an electric field and an anisotropy having an orientation in the array. It has a nature. The liquid crystal display is an essential component of a liquid crystal panel composed of a pair of transparent insulating substrates, each having a liquid crystal layer interposed therebetween, and having a field generating electrode formed therebetween. By controlling the arrangement direction of the molecules artificially, various images are displayed by using the light transmittance that is changed.

Since the liquid crystal panel does not have a light emitting element, it requires a separate light source. Accordingly, a backlight unit having a lamp is provided on the rear side to irradiate light toward the front of the liquid crystal panel, thereby realizing an image of identifiable luminance.

1 is a perspective view schematically showing a liquid crystal panel of a conventional liquid crystal display device.

As shown in the drawing, in the general liquid crystal panel 11, the first substrate 53 and the second substrate 51 are bonded to each other at a predetermined interval, and the pixel area is vertically intersected with each other on one surface of the first substrate 53. The data line DL and the gate line GL defining P are formed, and the thin film transistor T is formed at the intersection of the two lines.

In the pixel region P, a pixel electrode 61 in contact with the thin film transistor T is formed.

On the other hand, one surface of the second substrate 51 facing the first substrate 53 is a black matrix 55 having a lattice shape, and color filters 57a, 57b, and 57c in a region corresponding to the pixel region P. FIG. ), And a transparent common electrode 63 is formed on the entire surface of the second substrate 51 including the color filters 57a, 57b, 57c and the black matrix 55.

The liquid crystal layer 59 is formed in the spaced space between the first substrate 53 and the second substrate 51.

Such a liquid crystal display device is very important to the viewing angle characteristics that can look at the screen from a variety of angles, it should be able to realize a clear and undistorted image quality even in a wide viewing angle range. For this reason, such a wide viewing angle technology continues to be developed.

However, as the needs of users become more diverse, in addition to the wide viewing angle mode, only the person sitting in front of the screen can see the image on the screen, which is necessary for working with confidential documents or performing tasks that require security. Narrow viewing angle modes for privacy are also required.

FIG. 2 is a view schematically illustrating a conventional LCD module including the liquid crystal panel of FIG. 1 and freely switching between wide viewing angle and narrow viewing angle modes. Referring to FIG.

As shown, the viewing angle adjusting liquid crystal display device includes the first and second liquid crystal panels 11a and 11b and the backlight unit 20, the support main 27, the cover bottom 35, and the top cover 13. Include.

That is, as shown in the drawing, the backlight unit 20 and the first and second liquid crystal panels 11a and 11b are sequentially stacked on the upper surface of the rectangular main frame support main 27 having one edge open. The cover bottom 35 is coupled along the rear surface of the one open edge of the support main 27 to prevent the deformation of the shape 27, and the first and second liquid crystal panels 11a and 11b are fixed to both of them. The top cover 13 bordering the edge of the support main 27 and the cover bottom 35 is assembled and fastened.

In this case, the first and second liquid crystal panels 11a and 11b are divided into an image panel and a viewing angle control panel, respectively. The first liquid crystal panel 11a, which is the image panel, implements the image as described above with reference to FIG. 1. It is a general liquid crystal panel and a wide viewing angle is implemented. In addition, the second liquid crystal panel 11b, which is the viewing angle control panel, is a liquid crystal panel for converting a light viewing angle implemented by the first liquid crystal panel 11a into a narrow viewing angle as necessary.

That is, when a voltage equal to or greater than a predetermined value is applied to the second liquid crystal panel 11b, the liquid crystal molecules of the second liquid crystal panel 11b are uniformly arranged in an inclined direction so that the left and right viewing angles become worse. The viewing angle of the display device is implemented.

A printed circuit board 17 connected through at least one side of the first liquid crystal panel 11a is connected through a flexible printed circuit board.

The backlight unit 20 is arranged along the longitudinal direction inside one open edge of the support main 27, and interposed between the lamp 29 including the lamp holder 31 at both ends and an upper surface of the support main 27. It includes a reflecting plate 25 of the white or silver sheet, the light guide plate 23 is mounted on the reflecting plate 25 and a plurality of optical sheets 21 covering them.

A lamp guide 33 for guiding the lamp 29 is further provided at one side of the reflecting plate 25, and a first polarizing plate 37b is disposed on the outer surface of each of the first and second liquid crystal panels 11a and 11b, respectively. And the second polarizing plate 37a are attached.

In addition, the liquid crystal layer of the second liquid crystal panel 11b needs to further insert the intermediate polarizer 37b between the first and second liquid crystal panels 11a and 11b by using a general twisted nematic (TN) mode. do.

However, such a liquid crystal display device has a problem that it is easy to switch between wide viewing angle and narrow viewing angle mode, but becomes bulky.

The present invention is to solve the above problems, and to provide a display that can be switched (switchable) by the narrow viewing angle mode and the wide viewing angle mode electrically on / off It is for the first purpose.

In addition, the second object is to reduce the weight and thickness and the process cost.

In order to achieve the object as described above, the present invention comprises a first substrate and a second substrate; A pixel electrode formed on the first substrate; A black matrix formed on one surface of the second substrate facing one surface of the first substrate, a color filter, and a common electrode; A first liquid crystal cell comprising the first and second substrates and a first liquid crystal layer formed in the spaced space between the two substrates, and a third substrate facing the other surface of the first substrate; First and second electrodes formed on surfaces of the first substrate and the third substrate facing each other; A second liquid crystal cell comprising the first and third substrates and a second liquid crystal layer formed in the spaced space between the two substrates; Provided is a viewing angle control liquid crystal display device that can be switched to a narrow viewing angle mode or a wide viewing angle mode according to the application of the voltage of the second liquid crystal layer.

The second liquid crystal layer is configured to be selected from one of an electrically controlled birefringence (ECB) mode, a VA (vertical alignment) mode, and a HAN (hybrid aligned nematic) mode having a parallel alignment property and a shortening property of the liquid crystal. When the second liquid crystal layer is configured in the ECB mode, the first and second electrodes may be deposited in advance before configuring the thin film transistor on the first substrate.

In addition, when the second liquid crystal layer is configured in the ECB mode, the alignment layer is characterized by using a low-temperature type polyimide, and when the second liquid crystal layer is configured in the VA mode, for alignment of liquid crystal molecules It is characterized by rubbing the alignment film or by patterning the first and second electrodes in a stripe form.

In addition, the ECB mode and the VA mode, when voltage is applied, the liquid crystal molecules are arranged such that the long axis of the liquid crystal to the transmission axis of the light is about 5 ° ~ 20 ° to the electric field to implement a narrow viewing angle, the HAN mode When the voltage is not applied, the liquid crystal molecules are characterized in that the long axis of the liquid crystal is arranged in the electric field of about 5 ° to 20 ° with the transmission axis of light to implement a narrow viewing angle.

The second liquid crystal cell is positioned between the first liquid crystal cell and the first polarizing plate or the second polarizing plate, and the alignment direction of the second liquid crystal layer and the transmission axis of the first polarizing plate or the second polarizing plate are mutually different. Characterized in parallel.

The first liquid crystal cell may further include data and gate wirings vertically intersecting on the first substrate to define pixel regions, and thin film transistors formed at intersections of the gates and data wirings. The liquid crystal display device includes a cover bottom; A support main formed on the cover bottom and having a rectangular frame shape; A lamp arranged along the longitudinal direction of the support main, and a lamp guide for guiding the lamp; A backlight unit including a reflection plate sequentially formed on the support main and a light guide plate seated on the reflection plate; It characterized in that it further comprises a top cover assembled to the support main and cover bottom.

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

3 is an exploded perspective view schematically showing a liquid crystal display module according to an embodiment of the present invention.

As shown, the liquid crystal display module includes a liquid crystal panel 111 and a backlight unit having a first substrate 153 of FIG. 4, a second substrate 151 of FIG. 4, and a third substrate 165 of FIG. 4 bonded together. 120, and a support main 127, a cover bottom 135, and a top cover 113.

That is, as shown in the figure, the backlight unit 120 and the liquid crystal panel 111 are sequentially stacked on the upper surface of the rectangular main frame support main shape 127 having one edge open, thereby preventing the deformation of the support main shape 127. The cover bottom 135 is coupled along the rear surface of the opened one edge of the support main 127, and the top cover 113 bordering the edge of the liquid crystal panel 111 is fixed to the support main (127). 127 and the cover bottom 135 to be assembled.

In this case, a printed circuit board 117 connected through a flexible printed circuit board is connected along at least one side of the liquid crystal panel 111.

The backlight unit 120 is arranged along the length direction inside the opened one edge of the support main 127, and interposed between the lamp 129 including the lamp holder 131 at both ends and the upper surface of the support main 127. It includes a reflector plate 125 of the white or silver sheet, the light guide plate 123 is mounted on the reflector plate 125 and a plurality of optical sheets 121 covering them.

One side of the reflective plate 125 is provided with a lamp guide 133 for guiding the lamp 129.

In addition, a first polarizing plate 137b and a second polarizing plate 137a are attached to an outer surface of each of the liquid crystal panels 111.

In this case, the backlight unit 120 having the above-described structure is generally called a side light method, and according to the purpose, a plurality of lamps 129 may be arranged in a plurality of layers along the inner longitudinal direction of both edges of the support main 127 facing each other. Although not shown in a separate drawing, it is also possible to use a backlight unit of a direct type, in which case a plurality of lamps are arranged side by side in a state where the light guide plate 123 is omitted in the above-described structure, The optical sheet 121 may be interposed.

4 is a schematic cross-sectional view of the liquid crystal panel of FIG. 3.

As illustrated, the liquid crystal panel 111 is bonded to the first substrate 153 and the second substrate 151 by a predetermined interval apart. In this case, a data line DL and a gate line (not shown) defining a pixel area P cross each other vertically on one surface of the first substrate 153, and a thin film transistor is formed at an intersection point of the two lines. It constitutes (not shown).

The pixel region P includes a pixel electrode 161 in contact with a thin film transistor (not shown).

On the other hand, one surface of the second substrate 151 facing the first substrate 153 has a black matrix 155 having a lattice shape, and color filters 157a, 157b, and 157c in a region corresponding to the pixel region P. FIG. ), And a transparent common electrode 163 is formed on the entire surface of the second substrate 151 including the color filters 157a, 157b, and 157c and the black matrix 155.

The first liquid crystal layer 159 is formed in the spaced space between the first substrate 153 and the second substrate 151. In this case, the first liquid crystal layer 159 has a polarization direction of the light emitted from the backlight unit (120 of FIG. 3), which is horizontal or perpendicular to the panel, for example, an IPS mode in which a wide viewing angle can be realized. Or any mode such as VA (vertical alignment) mode.

In addition, the third substrate 165 is configured to be spaced apart from each other on the other side of the first substrate 153 which is spaced apart from each other with the second substrate 151 and the first liquid crystal layer 159 interposed therebetween.

In this case, a second liquid crystal layer 171 is formed in the spaced space between the first substrate 153 and the third substrate 165, and each of the first and third substrates 153 and 165 facing each other. Surfaces constitute first and second electrodes 167 and 169 capable of receiving a voltage to enable a vertical electric field.

A driving circuit (not shown) for applying an electric field to the first and third substrates 153 and 165 includes a printed circuit board (117 of FIG. 3) of the first and second substrates 153 and 151. A driving circuit may be driven by connecting a second printed circuit board (not shown) to one side, or on a printed circuit board (117 of FIG. 3) for driving the first and second substrates 153 and 151. The furnace may be mounted.

In this case, the first liquid crystal cell 181 including the first and second substrates 153 and 151 and the first liquid crystal layer 159 disposed between the first and second substrates 153 and 151 is referred to as a first liquid crystal cell 181. The second liquid crystal cell 183 includes the first and third substrates 153 and 165 and the second liquid crystal layer 171 formed between the first and third substrates 153 and 165. I'll do it.

Liquid crystals are generally oval shaped and exhibit refractive index anisotropy according to the direction of light passing through the liquid crystal. In particular, when the optical axis passes through the long axis of the liquid crystal, a 90 ° phase delay occurs, so that the viewing angle of the image is different depending on the viewing angle. Will cause a difference. In particular, the viewing angle characteristic of the side surface becomes worse when the liquid crystals are arranged obliquely close to the perpendicular to the electric field, that is, when the long axis of the liquid crystal is arranged at an angle of about 5 ° to 20 ° with the transmission axis of light.

For this reason, the second liquid crystal layer 171 of the second liquid crystal cell 183 of the present invention is not an twisted structure but an electrically controlled birefringence (ECB) mode in which the arrangement directions of all liquid crystal molecules are parallel, and VA in which the liquid crystals are arranged vertically. The mode may be configured as a hybrid aligned nematic (HAN) mode in which upper and lower liquid crystal molecules are arranged differently. In addition, any mode having a parallel alignment and shortening characteristics of the liquid crystal may be used.

In more detail, the ECB mode is a cell having liquid crystal molecules that are cultured in parallel, and when no voltage is applied, the liquid crystal molecules are close to horizontal between the first and third substrates 153 and 165. When the voltage is above a threshold voltage, the liquid crystal molecules are arranged obliquely perpendicular to each other, and the long axis of the liquid crystal is arranged to form about 5 ° to 20 ° with the transmission axis of light.

That is, when the voltage is applied, the viewing angle characteristic is not good due to the liquid crystal molecules arranged obliquely close to the vertical by the electric field generated between the first and third substrates 153 and 165 to implement a narrow viewing angle. It becomes possible.

If the viewing angle control is to be performed in the horizontal direction of the substrates 153 and 165, the orientation direction should be oriented in a vertically orthogonal direction corresponding thereto, and if the viewing angle is to be controlled in the vertical direction of the substrates 153 and 165 correspondingly, It should be in the horizontal direction of the substrates 153 and 165.

In addition, in the ECB mode, since the alignment direction and the rotation direction of the liquid crystal molecules are formed in the same plane, the first and second electrodes deposited on the respective surfaces of the first and third substrates 153 and 165 facing each other. It is constructed by coating polyimide on ITO (167, 169) and then rubbing.

In this case, the ITO is deposited before the thin film transistor (not shown) on the first substrate 153 of the first liquid crystal cell 181, and the polyimide, an alignment layer, is a thin film transistor, which is a sensitive element using a low temperature type. Not affected).

In addition, in the VA mode, before the electric field is formed, the liquid crystal molecules are vertically arranged on the first and third substrates 153 and 165 due to the influence of the vertical alignment layer. By twisting the liquid crystal molecules obliquely to the vertical, the long axis of the liquid crystal is arranged to form about 5 ° to 20 ° with the transmission axis of light.

This makes it possible to implement a narrow viewing angle.

The VA mode is configured by rubbing an alignment layer formed on opposite surfaces of the first and third substrates 153 and 165, respectively, or by arranging ITO which is the first and second electrodes 167 and 169 to align the liquid crystal molecules. The liquid crystal molecules of the region in which the ITO is formed may be vertically oriented by patterning the stripe in a direction perpendicular to the desired direction.

In this case, in the ECB mode and the VA mode, the rubbing direction of the vertical alignment layer is the same or opposite to each other, and the direction of the alignment layer is determined according to the viewing angle adjustment direction.

In the HAN mode, when the voltage is not applied, the liquid crystal molecules are arranged vertically in one alignment layer and in a horizontal state in the other alignment layer. However, when voltage is applied, the long axis of all liquid crystal molecules is about 5 ° to the transmission axis of light. It will be arranged at an angle close to 20 ° vertical.

The second liquid crystal cell 183 may be configured above the first liquid crystal cell 181, except that the alignment direction of the second liquid crystal layer 171 is the polarization axis of the adjacent polarizers (137a and 137b of FIG. 3). Should be the same as

The liquid crystal panel 111 has a wide viewing angle by configuring the aforementioned second liquid crystal cell 183 in a liquid crystal mode having a parallel alignment property including an ECB mode, a VA mode, and a HAN mode, and having a characteristic of shortening liquid crystal. And narrow viewing angle can be implemented.

That is, when the electric field is formed on the second liquid crystal layer 171, the inclination direction of the liquid crystal molecules is arranged obliquely to the vertical to implement a narrow viewing angle, and when the electric field is not applied, the original first liquid crystal cell ( Since the viewing angle characteristic of the wide field of view 181 is maintained as it is, the wide field of view can be realized.

5A and 5B are graphs illustrating simulation results of luminance and contrast ratios according to viewing angles of a wide viewing angle of a second liquid crystal cell according to an exemplary embodiment of the present invention.

FIG. 5A illustrates the characteristics of the viewing angle and luminance when driving the wide viewing angle, and as shown in FIG. 5A, it can be seen that the voltage has a constant luminance in a wide viewing angle range when no voltage is applied (OFF). It can be seen that the state (On) shows a low transmittance.

5B illustrates the characteristics of the contrast ratio according to the viewing angle at the time of driving the wide viewing angle, and it can be seen that the contrast ratio is constant within the designated viewing angle range (−90 ° to 90 °).

As a result, when driving the wide viewing angle, an image having a clear image quality may be realized regardless of the top, bottom, left, and right sides of the liquid crystal panel 111 of FIG. 4.

 6A and 6B are graphs illustrating simulation results of luminance and contrast ratios according to a viewing angle of a narrow viewing angle of a second liquid crystal cell according to an exemplary embodiment of the present invention.

FIG. 6A illustrates the characteristics of the viewing angle and the luminance when driving the narrow viewing angle. As shown in FIG. 6A, the luminance of the front surface is increased when the voltage is not applied (Off), and the constant voltage is applied (On). At -80 ° to -60 ° and 60 ° to 80 °, the transmittance is high. This is because the liquid crystal molecules of the second liquid crystal cell (171 of FIG. 4) are polarized to stand diagonally close to the vertical, resulting in poor viewing angle characteristics at the side viewing angle.

6B illustrates the characteristics of contrast ratio according to the viewing angle when driving a narrow viewing angle. When the viewing angle range is 0 °, the contrast ratio is high to realize clear image quality, but as the viewing angle range approaches -90 ° and 90 °, respectively, You can see that appears low.

Thus, it can be seen that clear image quality is not realized on both sides of the liquid crystal panel 111 of FIG. 4.

Therefore, according to the present invention, when the voltage is applied to the first liquid crystal cell (181 of FIG. 4) having a wide viewing angle, the second liquid crystal cell (183 of FIG. 4), which realizes the narrow viewing angle mode, is further configured, The wide viewing angle mode can be freely switched to provide a viewing angle characteristic according to a user's needs.

The present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention.

As described above, the first liquid crystal layer and the second liquid crystal layer are respectively formed in spaced spaces of three substrates spaced apart from each other according to the present invention, thereby determining whether the first liquid crystal cell having a wide viewing angle and voltage are applied. Accordingly, by configuring a second liquid crystal cell capable of realizing a narrow viewing angle, there is an effect of selectively implementing a wide viewing angle and a narrow viewing angle mode as necessary.

In addition, there is a light and thin effect, there is an effect of reducing the process cost.

Claims (11)

A first substrate and a second substrate; A pixel electrode formed on the first substrate; A black matrix formed on one surface of the second substrate facing one surface of the first substrate, a color filter, and a common electrode; A first liquid crystal cell comprising the first and second substrates and a first liquid crystal layer formed in the spaced space between the two substrates; A third substrate facing the other surface of the first substrate; First and second electrodes formed on front surfaces of the first and third substrates facing each other; A second liquid crystal cell composed of the first and third substrates and a second liquid crystal layer formed in a spaced space between the two substrates; / RTI &gt; The second liquid crystal layer is configured in an electrically controlled birefringence (ECB) mode having parallel alignment and characterized by uniaxial property of liquid crystals, It is possible to switch to the narrow viewing angle mode or the wide viewing angle mode depending on whether the vertical electric field is generated between the first and second electrodes by voltage application. The first and second electrodes are formed in advance before configuring the thin film transistor on the first substrate, And forming a thin film using polyimide of low temperature type on the first and second electrodes, wherein the alignment layer is oriented in a direction perpendicular to the direction of viewing angle control. delete delete delete delete The method of claim 1, In the ECB mode, when the voltage is applied, the liquid crystal molecules are arranged such that the long axis of the liquid crystal forms an angle of 5 ° to 20 ° with the transmission axis of light in the electric field to implement a narrow viewing angle. delete The method of claim 1, And the second liquid crystal cell is positioned between the first liquid crystal cell and the first polarizing plate or the second polarizing plate. The method of claim 1, And an alignment direction of the second liquid crystal layer and parallel to a transmission axis of the first polarizing plate or the second polarizing plate. The method of claim 1, The first liquid crystal cell further includes data and gate wirings vertically intersecting on the first substrate to define pixel regions, and thin film transistors formed at intersections of the gates and data wirings. Device. The method of claim 1, The liquid crystal display includes a cover bottom; A support main formed on the cover bottom and having a rectangular frame shape; A lamp arranged along the longitudinal direction of the support main, and a lamp guide for guiding the lamp; A backlight unit including a reflection plate sequentially formed on the support main and a light guide plate seated on the reflection plate; And a top cover assembled to the support main and cover bottom.

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