KR20130130474A - Liquid crystal display for preventing a light vent - Google Patents

Abstract

A liquid crystal display panel according to one embodiment of the present invention includes a first substrate, a second substrate which holds a liquid crystal between the first substrate and the second substrate, a top polarization plate which is attached on the first substrate and includes a light absorption axis which is formed in the first direction, and a bottom polarization plate which is attached on the second substrate and includes a light absorption axis which is formed in a second direction which is orthogonal to the first direction. At least one among the top polarization plate and the bottom polarization plate reduces deformation along the light absorption axis by elongating the light absorption axis which is arranged in the center than the light absorption axis which is arranged in the outside. Thereby, the warpage of the liquid crystal display panel due to the deformation of the polarization plate is prevented and as a result, a light leakage is prevented. [Reference numerals] (AA) Length;(BB) Deformation force;(CC) Placement;(DD) Deformation force (length)

Description

Liquid crystal display for preventing a light vent}

The present invention relates to a liquid crystal display panel which prevents light leakage.

A liquid crystal display device displays an image by adjusting light transmittance of a liquid crystal. A liquid crystal display panel formed by sandwiching a liquid crystal between substrates displays an image by adjusting a transmittance of light supplied from a backlight unit.

The liquid crystals sandwiched between the substrates form an initial arrangement according to the alignment direction of the alignment film provided on the substrate, and when the electric field is applied, the alignment direction is changed in accordance with the electric field direction to control the amount of light transmitted. By the way, when the initial arrangement state of the liquid crystal is changed by various factors, there is a problem that light leakage occurs in the liquid crystal display panel.

For example, when the alignment layer is damaged by the column spacer, light leakage occurs in the portion because the liquid crystal is not arranged in the desired direction at the portion where the alignment layer is damaged.

Alternatively, in addition to the case where the liquid crystal display panel is defective, light leakage occurs even when the LCD panel is bent due to mechanical defects in the process of modularizing the liquid crystal display panel.

For example, the cover bottom is coupled to the top case with the liquid crystal display panel and the backlight unit interposed therebetween to modularize them. In this process, when a difference occurs in the bonding force applied to the liquid crystal display panel, the liquid crystal display panel is bent, and thus light leakage occurs in the liquid crystal display panel.

The present invention was devised in such a background, and reduces the occurrence of light leakage in the liquid crystal display panel.

According to an embodiment of the present invention, a liquid crystal display panel includes a first substrate, a second substrate sandwiching liquid crystal between the first substrate, and a light absorption formed on the first substrate and formed in a first direction. An upper polarizer having an axis, and a lower polarizer attached below the second substrate, the lower polarizer having a light absorption axis formed in a second direction perpendicular to the first direction, wherein at least one of the upper polarizer and the lower polarizer is less than a center. The length of the light absorption shaft disposed at the outer side is configured to be long, thereby reducing the deformation force propagated along the light absorption shaft.

The length of the light absorption axis is shortest in the center, longest in the outskirts, and increases linearly or stepwise from the center to the outskirts.

The upper polarizer and the lower polarizer are symmetrical in the up / down direction and the left / right direction.

At least one of the four corners of the upper polarizer and at least one of the four corners of the lower polarizer are perpendicular.

In one embodiment of the present invention, since the deformation force propagates along the light absorption axis of the polarizing plate, the length of the light absorption axis may be configured differently to balance the deformation force applied to the polarizing plate while reducing the magnitude of the deformation force. Accordingly, the liquid crystal display panel can be prevented from bending due to the deformation force, and as a result, light leakage can be prevented from occurring in the liquid crystal display panel.

1 illustrates a liquid crystal display panel according to an exemplary embodiment of the present invention.
2 is a diagram illustrating an upper polarizer and a lower polarizer.
3 illustrates a difference in warpage of a liquid crystal display panel in a general environment and a reliability environment.
Figure 4 shows the change in the polarizing plate occurs when shrinkage occurs along the light absorption axis.
5 to 10 show embodiments in which the length of the absorption axis becomes smaller from the outermost portion of the polarizer toward the center when the light absorption axis is 0 °.
FIG. 11 shows an embodiment in which the length of the absorption axis becomes smaller as the light absorption axis is 90 °, and toward the center from the outermost portion of the polarizing plate.
FIG. 12 is a schematic cross-sectional view of a liquid crystal display panel, and is divided into a display area and a non-display area.
FIG. 13 is a plan view illustrating a polarizer disposed in accordance with FIG. 12.
FIG. 14 shows a result of experiments in which the deflection of the liquid crystal display panel can be improved by adjusting the length of the light absorption axis.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Like reference numerals throughout the specification denote substantially identical components. In the following description, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

1 illustrates a liquid crystal display panel according to an exemplary embodiment of the present invention. In FIG. 1, the liquid crystal display panel 100 includes a color filter substrate 10, a thin film transistor array substrate 20, an upper polarizer 41, and a lower polarizer 43, and the color filter substrate 10 and the thin film transistors. The liquid crystal 30 is sandwiched between the array substrates 20.

The color filter substrate 10 includes an upper glass substrate 11, a black matrix 12, a color filter 13 for color implementation, and a planarization film 14 for planarizing a step of the color filter 13.

The thin film transistor array substrate 20 includes a pixel array formed on the lower glass substrate 21. The pixel array includes gate lines 22, data lines 23 intersecting the gate lines 22 with the gate insulating layer GI interposed therebetween, and liquid crystal cells formed at the intersections thereof. A passivation layer (PAS) for protecting the thin film transistors 24 connected to the pixel electrodes 25 of the liquid crystal cells, the common electrode 26 facing the pixel electrode 25, and the pixel electrode 25 and the common electrode 26. And a common line 27 for supplying a common voltage to the common electrode 26.

The thin film transistor 24 supplies the pixel signal of the data line 23 to the pixel electrode 25 in response to the gate signal of the gate line 22. For this purpose, the gate electrode of the thin film transistor 24 is connected to the gate line 22 and the source electrode is connected to the data line 23. The drain electrode of the thin film transistor 24 is connected to the pixel electrode 25.

The common electrode 26 may be formed on the lower glass substrate together with the pixel electrode 25 as shown in a horizontal electric field driving method such as an IPS (In Plane Switching) mode or a FFS (Fringe Field Switching) mode. Alternatively, in a vertical electric field driving method such as twisted nematic (TN) mode and vertical alignment (VA) mode, the upper glass substrate may be formed.

The upper polarizer 41 is attached to the surface of the color filter substrate 10, and the lower polarizer 43 is attached to the surface of the thin film transistor array substrate 20.

The upper polarizer 41 and the lower polarizer 43 will be described in detail with reference to FIG. 2.

In the upper polarizer 41 and the lower polarizer 43, the light absorption axes Lx1 and Lx2 are perpendicular to each other. The light absorption axis Lx1 of the upper polarizer 41 may be formed in a direction (0 °) parallel to the long side direction (x-axis direction of the drawing), and the light absorption axis Lx2 of the lower polarizer 43 is an upper polarizer. It may be formed in a direction parallel to the short side direction (y-axis direction in the drawing) perpendicular to the light absorption axis (Lx1) of (41). In addition, on the contrary, the light absorption axis Lx1 of the upper polarizing plate 41 may be formed in a direction (90 °) parallel to the short side direction (y-axis direction of the drawing), and the light absorption axis of the lower polarizing plate 43 Lx2 may be formed in a direction parallel to the long side direction (x-axis direction of the drawing) perpendicular to the light absorption axis (Lx1) of the upper polarizing plate (41).

The polarizing plate 40 is a polyvinyl alcohol-based resin film is stretched to align the iodine molecules in the stretching direction to form a light absorption axis in the stretching direction.

However, since the polarizing plate 40 made as described above contracts along the light absorption axes Lx1 and Lx2 while the water evaporates under a high temperature condition, strain is generated and consequently causes the liquid crystal display panel to bend. 3 illustrates a difference in warpage of a liquid crystal display panel in an environment before reliability and an environment after reliability. Here, the environment after reliability refers to a condition exposed to a temperature of 60 degrees Celsius for 96 hours as a harsh condition, and the environment before reliability refers to a condition in contrast to the harsh condition. Through this comparative experiment, it was found that the warpage amount of the liquid crystal display panel in the environment before reliability was 0.72 (mm), but the warpage amount increased significantly to 2.68 (mm) in the environment after reliability. As a result, it can be seen from this comparative experiment that the liquid crystal display panel is bent due to shrinkage of the polarizing plate 40.

On the other hand, Figure 4 shows a change in the polarizing plate 40 occurs when shrinkage occurs along the light absorption axis. When the light absorption axis Lx1 is 0 °, that is, when the light absorption axis is formed in the long side direction, the stress propagates therein along the light absorption axis Lx1, and there are more light absorption axes than the edges. It is big in the middle part. For this reason, when the light absorption axis Lx1 is 0 degrees, the polarizing plate 40 is convex downward when cut | disconnected in the long side direction (refer FIG. 4 (A)).

On the contrary, even when the light absorption axis Lx2 is 90 °, that is, even when the light absorption axis is formed in the short side direction, the stress propagates therein along the light absorption axis Lx2, and relatively more light absorption axis than the edges. This is great in the middle part of existence. For this reason, when the light absorption axis Lx2 is 90 degrees, the polarizing plate 40 is convex upward when cut | disconnected in the short side direction (refer FIG. 4 (B)).

Therefore, when the upper polarizing plate 41 has a light absorption axis Lx1 of 0 ° and the lower polarizing plate 43 has a light absorption axis Lx2 of 90 °, the liquid crystal display panel to which they are attached is bent in a saddle shape ( (C) of FIG. 4).

As described above, the difference in the deformation force of the polarizing plate 40 causes bending of the liquid crystal display panel and causes light leakage. Therefore, in the present invention, the polarizing plate 40 is formed to have the least deformation. In the example of FIG. 2, the upper polarizing plate 41 is formed with a light absorption axis Lx1 in a long side direction (x-axis direction of the drawing), and is deformed into a convex shape downward, which is the outside of the polarizing plate 40. It grows from the middle to the middle. In addition, since the deformation force propagates therein along the light absorption axis, the deformation force may be regarded as being proportional to the length of the absorption axis. Therefore, the polarizing plate 40 can be prevented from being deformed by adjusting the length of the absorption axis according to the position.

In the polarizing plate 40 having a light absorption axis of 0 °, the deformation force is increased from the outside of the polarizing plate 40 toward the center, and accordingly, the length of the absorption axis is formed to be smaller from the outside of the polarizing plate 40 toward the inside.

5 to 10 show embodiments in which the length of the absorption axis Lx1 becomes smaller from the outside of the polarizer 40 toward the center when the light absorption axis is 0 °.

In FIG. 5, the left short side 41a of the polarizing plate 40 has an arc shape, and has an up / down symmetry with respect to the center O of the polarizing plate 40. The right short side 41b of the polarizing plate 40 also has an arc shape, and forms a state of up / down symmetry with respect to the center O of the polarizing plate 40. In addition, the left short side 41a of the polarizing plate 40 has a mirror symmetry with the right short side 41b of the polarizing plate 40.

Since the left short side 41a and the right short side 41b of the polarizing plate 40 are thus formed, the deformation force and the length of the absorption axis are inversely proportional to each other. That is, as shown in FIG. 5, the deformation force gradually increases from the outside of the polarizer 40 toward the center O, and decreases again as the number goes from the center toward the outside. In comparison, the length of the absorption axis gradually decreases from the outside toward the center (O), as opposed to the deformation force, gradually increases from the center (O) toward the outside, the longest at both edges (L1), and the shortest in the middle ( L2).

As a result, both edges of the polarizing plate 40 have a small deformation force but a long absorption axis, and a center O of the polarizing plate 40 has a high deformation force but a short absorption axis. However, since the strain force propagates along the absorption axis, the strain force is balanced regardless of the position. Therefore, it is possible to prevent the liquid crystal display panel from warping due to the difference in strain.

6 shows another embodiment of the polarizer 40 when the light absorption axis is 0 °. 6, only the shape of the corner 51 of the polarizing plate 40 is different from the embodiment of FIG. 6, and the rest is the same as the embodiment of FIG.

In the embodiment of FIG. 6, the corners 51 of the polarizing plate 40 form a right angle, but the embodiment of FIG. 5 differs in that it forms an acute angle. When attaching the polarizing plate 40 to the substrate, since the corner shape is used as the alignment mark, when the acute angle is made as in the embodiment of FIG. 5, alignment is not easy, and thus the polarizing plate 40 is like the embodiment of FIG. 6. It is preferable that the corner 51 of) forms a right angle.

7 shows still another embodiment of the polarizer 40 when the light absorption axis is 0 °. When the embodiment of FIG. 7 is compared with the embodiment of FIG. 5, there are only differences in the shapes of the short sides 41a and 41b.

In the exemplary embodiment of FIG. 7, the left short side 41a of the polarizer 40 forms an inclined inclined shape inwardly and is symmetrical with respect to the center O. The right short side 41b of the polarizing plate 40 also forms an obliquely inclined inward shape, and forms an up / down symmetry with respect to the center O. FIG.

8 shows still other embodiments of the polarizer 40 when the light absorption axis is 0 °. When the embodiment of FIG. 8 is compared with the embodiment of FIG. 7, the embodiment of FIG. 7 is formed to have one inclination to the center O, while FIG. 8 is different in that it is formed of two diagonal lines having different inclinations. When bisecting between the centers O at the long sides of the polarizing plate 40, the left / right short side slope of the first section I is α, while the left / right short side slope of the second section II is β. In addition, the left and right short sides are symmetrical with respect to the center.

9 shows still other embodiments of the polarizer 40 when the light absorption axis is 0 °. This embodiment is different from other embodiments in that the left and right short sides are formed in a downhill step shape inward, and the left and right short sides are symmetrical with respect to the center O.

FIG. 10 shows further embodiments of the polarizer 40 when the light absorption axis is 0 °. In FIG. 10, in this embodiment, in order to selectively reduce the length of the light absorption axis disposed at the center, another embodiment is provided in that the grooves 61 are formed at the left and right short sides 41a and 41b corresponding to the center O. FIG. This is different from the examples. In this embodiment as well, the polarizing plate 40 is configured to achieve a balance possible in the up / down symmetry with respect to the center (O) possible deformation.

5 to 10 have been described with respect to the polarizing plates 40 having a light absorption axis of 0 °. However, the same applies to the case where the light absorption axis is 90 °. An example of FIG. 11 is as follows.

FIG. 11 shows that when the light absorption axis is 90 °, the length of the light absorption axis Lx2 disposed at the center having the largest deformation force is the shortest as in the embodiment of FIG. 5, and conversely, The length of Lx2) is the longest.

In FIG. 11, the upper long side 43a of the polarizing plate 40 has an arc shape, and has an up / down symmetry with respect to the center O of the polarizing plate 40. The lower long side 43b of the polarizing plate 40 also has an arc shape, and has an up / down symmetry with respect to the center O of the polarizing plate 40. In addition, the upper long side 43a of the polarizing plate 40 has a mirror symmetry with the lower long side 43b of the polarizing plate 40.

Since the upper long side 43a and the lower long side 43b of the polarizing plate 40 are formed in this way, the deformation force and the length of the absorption axis are inversely proportional to each other. That is, as shown in FIG. 11, the deformation force gradually increases from the outside of the polarizer 40 toward the center O, and decreases again as the number goes from the center to the outside. In comparison, the length of the absorption axis gradually decreases from the outside toward the center (O), as opposed to the deformation force, gradually increases from the center (O) toward the outside, the longest at both edges (L1), and the shortest in the middle ( L2).

As a result, both edges of the polarizing plate 40 have a small deformation force but a long absorption axis, and a center O of the polarizing plate 40 has a high deformation force but a short absorption axis. However, since the strain force propagates along the absorption axis, the strain force is balanced regardless of the position. Therefore, it is possible to prevent the liquid crystal display panel from warping due to the difference in strain.

As such, even when the light absorption axis is 90 °, the light absorption axis described with reference to FIGS. 5 to 10 may be formed in the same manner as when the light absorption axis is 0 °.

FIG. 12 is a schematic cross-sectional view of a liquid crystal display panel, which shows that the display panel is divided into a display area and a non-display area, and FIG. 13 is a plan view showing that a polarizing plate is disposed accordingly. In this application, the display area is an area where an image is displayed, and the non-display area is an area where no image is displayed, and is a portion that is covered by the bezel.

12 and 13, the gate insulating layer GI and the passivation layer PAS are sequentially stacked on the lower glass substrate 21. The gate insulating layer GI may be formed of an inorganic layer, and the passivation layer PAS may be formed of an organic layer. In this case, since the sealing material 71 is generally formed of an inorganic material, the insulating film GI is exposed in the non-display area N / B in order to increase the adhesiveness of the sealing material 71.

As the upper glass substrate 11, a first black matrix 121 and a color filter 13 that separate the display area A / A and the non-display area N / B are formed on the same layer, and planarized thereon. A film 14 is formed and covers them. In general, the non-display area in which an image is not displayed has a width within approximately 10 (mm) in consideration of a margin on a work process or the like.

The sealing material 61 is positioned on the exposed surface of the upper glass substrate 11 and the gate insulating film GI of the lower glass substrate 21 to seal between the two substrates.

As such, the liquid crystal display panel forms a non-display area in which no image is displayed from the end of the substrate to a predetermined distance d1. Therefore, by arranging the long side or short side of which the length of the light absorption axis is adjusted in this non-display area, light leakage can be prevented from occurring in the display area.

FIG. 13 illustrates a plan view in which the upper polarizing plate 41 having a light absorption axis of 0 ° is attached to the liquid crystal display panel 100 as in the embodiment of FIG. 5.

According to the exemplary embodiment of FIG. 5, the left short side 41a and the right short side 41b of the polarizing plate are arc-shaped, respectively, and are disposed between the short sides 101a and 101b of the liquid crystal display panel at the center O and the boundary of the display area. The distance d2 is minimal. By the way, the polarizing plate should be formed at least in the entire display area, and considering the margin of the work process of attaching the polarizing plate, the distance d2 between the short edges 101a and 101b of the liquid crystal display panel at the boundary of the display area is at least 2 (mm). Must be greater than or equal to

FIG. 14 shows a result of experiments showing that the bending of the liquid crystal display panel can be improved by adjusting the length of the light absorption axis as in the above-described embodiments. In the experiment, "after reliability" means a state where the liquid crystal display panel is exposed to a temperature of 60 degrees Celsius for 96 hours under severe conditions, and "before reliability" means a condition that is in contrast with the harsh conditions. In the table, the displacement amount is a numerical value representing the degree of deflection of the panel quantitatively by subtraction operation when the LCD panel is bent in the same direction before and after reliability, and by adding operation when the LCD panel is bent in the opposite direction. The difference is obtained from the difference between Max and Max.

The experiment was conducted on a 32-inch model with the upper polarizer at 0 ° and the lower polarizer at 90 °. Comparative Examples 1 and 2 (ref. 1, ref. 2) are comparative data and are cases where no change is made in the shape of the polarizing plate.

Cases 1 to 4 are experimental results for examining the relationship between the lower polarizer and the panel warpage. Cases 1 to 3 are cases in which only the shape of the lower polarizer is changed regardless of the length of the light absorption axis, and case 4 is a case in which the long side shape is modified in accordance with the direction of the light absorption axis of the lower polarizer. In this case, the length is shortened.

The cases 1 to 4 show that the length of the light absorption axis correlates with the warpage of the liquid crystal display panel, and the warpage of the liquid crystal display panel can be reduced by reducing the length of the light absorption axis in accordance with the deformation force.

Cases 5 to 10 are the results of experiments to determine how the upper polarizer and the lower polarizer are simultaneously related to the warpage of the liquid crystal display panel. As can be seen from case 4, when the length of the light absorption axis was adjusted to the deformation force (case 9), it was found that the bending of the liquid crystal display panel could be ideally prevented.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. 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.

10: color filter substrate 20: thin film transistor array substrate
40: polarizing plate 41: upper polarizing plate 43: lower polarizing plate
100: liquid crystal display panel Lx1, Lx2: light absorption axis

Claims (6)

A first substrate,
A second substrate sandwiching the liquid crystal between the first substrate,
An upper polarizer attached to the first substrate and having a light absorption axis formed in a first direction;
A lower polarizer plate attached below the second substrate and having a light absorption axis formed in a second direction perpendicular to the first direction,
And at least one of the upper polarizer and the lower polarizer is longer than the center of the light absorption axis. The method of claim 1,
The length of the light absorption axis is the shortest in the center, the longest in the outer LCD panel. 3. The method of claim 2,
The length of the light absorption axis is increased from the center to the outside of the liquid crystal display panel. The method of claim 3,
The length of the light absorption axis increases linearly from the center to the outside, or grows stepwise. The method according to claim 3 or 4,
The upper polarizer and the lower polarizer are symmetrical in the up / down direction and the left / right direction, respectively. The method of claim 1,
And at least one of four corners of the upper polarizer and at least one of four corners of the lower polarizer to form a right angle.

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