KR20180113021A - Curved display panel - Google Patents

Abstract

An objective of the present invention is to prevent light leakage caused by retardation of a substrate in a curved liquid crystal display panel. The curved liquid crystal display panel comprises: a first substrate having a curved shape; a second substrate having a curved shape; and a liquid crystal layer filled between the first and second substrates. The first substrate or the second substrate has a thickness (t) according to a condition of a mathematical expression. Here, t is the thickness of the substrate, Re is the retardation of the substrate, β is the photoelastic constant, E is the young′s modulus, L is length of a major axis the substrate, R is the curvature of the substrate, and θ is an azimuth angle in a slow axis direction.

Description

[0001] Curved display panel [

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a curved display panel, and more particularly, to a substrate thickness of a curved liquid crystal display panel capable of preventing light leakage in the form of edge mura due to stress due to a curved surface.

2. Description of the Related Art Recently, display panels using liquid crystal display (Liquid Crystal Display) and OLED display panels using organic light emitting diodes (OLED) are typical display panels for displaying images using digital data.

The liquid crystal display panel of the display panel includes a thin film transistor array substrate on which a thin film transistor array is formed on a glass substrate, a color filter array substrate on which a color filter array is formed, A liquid crystal layer filled between the filter array substrate and a voltage is applied to the electric field generating electrode to generate an electric field in the liquid crystal layer to thereby determine the direction of the liquid crystal molecules in the liquid crystal layer and control the polarization of incident light to display an image . Alternatively, the organic light emitting display panel has self-emission characteristics and does not require a separate light source, and displays an image through a display substrate on which the thin film transistor and the organic light emitting device are formed.

As the size of the display panel becomes larger, there arises a problem that the visual difference increases depending on whether the viewer views the center portion of the screen or both left and right sides of the screen.

In order to compensate for such a visual difference, a liquid crystal display panel in which a liquid crystal display panel is curved in a concave or convex shape and has a curved surface has been developed.

Such a curved surface liquid crystal display panel is used for applying various curvatures to an automobile as an auto display device and can be classified into a waterfall type, an L-curved type and a trapezoidal type depending on the curved surface state of the display panel. And a trapezium-curved type.

Fig. 1 is an explanatory view for explaining tensile stress and compressive stress at the central part and edge part of a general water pole type curved liquid crystal display panel. Fig. 2 shows tensile stress and compressive stress at the central part and edge part of a general L- FIG. 3 is an explanatory view for explaining tensile stress and compressive stress at the central portion and the edge portion of a general trapezoidal curve type curved liquid crystal display panel, and FIG. 4 is an explanatory view for explaining the compressive stress, Sectional view illustrating a tensile stress and a compressive stress of the thin film transistor array substrate and the color filter array substrate.

In the case where the liquid crystal display panel is curved and formed into a curved surface, tensile stress and compressive stress correspond to the neutral axis of the substrate in the central portion of the substrate ("A" in FIGS. 1 to 3) of the curved liquid crystal display panel, Since the retardation is canceled, there is no influence on retardation of the substrate, so that light leakage does not occur. However, a light leakage phenomenon occurs at the edge portions (portions "B" in Figs. 1 to 3) where the color filter array substrate and the thin film transistor array substrate are bonded together by sealant.

That is, at the edge portion of the curved liquid crystal display panel, the thin film transistor array substrate has a compressive stress greater than a tensile stress with respect to a neutral axis (compressive stress> tensile stress), and a color filter array substrate has a tensile stress with respect to a neutral axis (Compressive stress < tensile stress), and the retardation direction of the substrate is asymmetric. Therefore, the retardation of the liquid crystal panel is increased to cause light leakage.

As shown in Fig. 4, when the color filter array substrate CF and the thin film transistor array substrate (TFT) each have a thickness of 0.5 t, the retardation increases at the edge of the curved liquid crystal display panel, do.

For example, in FIG. 4, when the retardation rotates 10 nm in the clockwise direction around the compression optical axis at 12 points and rotates 2 nm in the clockwise direction around the tensile optical axis at 23 points, the Poincare Sphere shifts the LC optical axis Is rotated in the clockwise direction by 300 nm around the LC optical axis at 34 points, which is located in the second quadrant rather than S1, the black luminance is generated due to the increase in retardation due to the difference from S1, A phenomenon occurs in which the retardation increases by a rotation of 2 nm in the clockwise direction centering on the liquid crystal layer LC and a rotation of 10 nm in the clockwise direction around the tensile optical axis at 56 point. Due to this phenomenon, light leakage phenomenon occurs in the waterfall type, L-curved type and trapezium-curved type curved surface liquid crystal display panel on the same principle.

Therefore, in order to improve such a phenomenon, it is necessary to improve the retardation of the substrate (glass), and it is important to select the thickness condition of the substrate under various conditions.

The present invention has been devised to prevent light leakage caused by retardation of the substrate in such a curved liquid crystal display panel. The thickness of the substrate is selected in consideration of the stress corresponding to the curvature of the curved liquid crystal display panel It has its purpose.

Another object of the present invention is to provide a curved surface liquid crystal display panel formed of a substrate having such a selected thickness

According to an aspect of the present invention, there is provided a curved liquid crystal display panel including: a first substrate having a curved shape; A second substrate having a curved shape; And a liquid crystal layer filled between the first and second substrates. The first substrate or the second substrate has a thickness t according to the following mathematical expression.

Here, t is the thickness of the substrate, Re is the retardation of the substrate, β is the photoelastic constant, E is the young's modulus, L is the long axis length of the substrate, R is the curvature of the substrate, and θ is the azimuth angle in the slow axis direction.

Here, the curved liquid crystal display panel having a curvature of 500R or less is characterized by having a first substrate or a second substrate having a thickness of 0.125t or less.

The curved liquid crystal display panel having a curvature of 750R or less is characterized by having a first substrate or a second substrate having a thickness of 0.16t or less.

The curved surface liquid crystal display panel having a curvature of 1000R or less has a first substrate or a second substrate having a thickness of 0.22t or less.

The curved liquid crystal display panel having a curvature of 1500R or less is characterized by having a first substrate or a second substrate having a thickness of 0.275t or less.

The curved liquid crystal display panel having a curvature of 1750R or less is characterized by having a first substrate or a second substrate having a thickness of 0.28t or less.

The curved liquid crystal display panel having a curvature of 2000R or less is characterized by having a first substrate or a second substrate having a thickness of 0.3t or less.

The curved-surface liquid crystal display panel according to the present invention having the above-described characteristics has an appropriate substrate thickness according to the curvature, and thus has the effect of improving the light leakage (edge mura) at the edge portion of the curved liquid crystal display panel.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an explanatory diagram for explaining tensile stress and compressive stress at a central portion and an edge portion of a general water-
2 is an explanatory diagram for explaining tensile stress and compressive stress at the central portion and the edge portion of a general L-curve type curved surface liquid crystal display panel
3 is an explanatory diagram for explaining tensile stress and compressive stress at the central portion and the edge portion of a general trapezoid curve type curved surface liquid crystal display panel
4 is an explanatory diagram for explaining tensile stress and compressive stress of the thin film transistor array substrate and the color filter array substrate at the edge portion of a general curved liquid crystal display panel
5 is a view for explaining tensile stress and compressive stress of the thin film transistor array substrate and the color filter array substrate at the edge portion of the curved liquid crystal display panel according to the present invention.
6 is a graph showing the relationship between the substrate thickness of the curved liquid crystal display panel according to the present invention and the retardation of the substrate
FIG. 7 is a graph showing the "C" partial enlargement graph
8 is a graph showing the relationship between the substrate thickness and the curvature for the curved liquid crystal display panel according to the present invention
9 is a graph showing the thickness of a substrate according to the curvature that can satisfy light leakage in a curved liquid crystal display panel according to the present invention.

The curved-surface liquid crystal display panel according to the present invention having the above-described characteristics will now be described in more detail with reference to the accompanying drawings.

5 is an explanatory view for explaining tensile stress and compressive stress of the thin film transistor array substrate and the color filter array substrate at the edge portion of the curved liquid crystal display panel according to the present invention.

First, in the curved liquid crystal display panel, the thin film transistor array substrate and the color filter array substrate are bent by an external force. Thus, when the substrate is bent, a bending moment is generated, and the behavior of any deformable substrate to which the bending moment is applied causes the material in the bottom portion of the substrate to be stretched and the material in the top portion to be compressed. Accordingly, the stress retardation of the liquid crystal panel can be modeled based on a neutral axis in which the length of the line in the longitudinal direction is not changed at an arbitrary position between the uppermost portion and the lowermost portion of the substrate. When the curvature due to the external force is realized, the position of the neutral axis in the substrate is shifted from the center portion of the liquid crystal panel to the edge portion of the liquid crystal panel, It is possible to select the thickness of the substrate by simulating the edge mura by calculating the bending moment.

Compressive stress and tensile stress are determined by the moment of inertia (I) and the bending moment (M) with respect to the central axis when a bending stress occurs in the liquid crystal panel (substrate).

Here, the moment of inertia (I) is expressed by the following equation (1).

Where b is the short axis length of the substrate and t is the thickness of the substrate.

The bending moment M is expressed by the following equation (2).

Where d is the amount of bending deflection, E is young's modulus, and L is the length of the major axis of the substrate.

The amount of flexural deflection d is influenced by the curvature R of the substrate, the long axis length of the substrate, and the azimuth angle? In the slow axis direction. Therefore, the amount of bending warpage d is expressed by the following equation (3).

Here,? Is an azimuth angle in the slow axis direction.

In addition, when a bending stress is generated in the liquid crystal display panel (substrate), tensile stress (? 1) and compressive stress (? 2) with respect to the central axis are as shown in the following formula (4).

Here, C1 is the thickness of the substrate subjected to tensile stress around the neutral axis in the color filter array substrate CF or the thin film transistor array substrate (TFT) in the curved liquid crystal display panel as shown in Fig. 5, Is the thickness of the substrate subjected to compressive stress around the neutral axis.

Also, the light leakage value K in the curved liquid crystal display panel is influenced by the azimuth angle? And the retardation Re of the substrate as shown in the following equation (5).

As a result, in order to minimize the light leakage, it is necessary to satisfy the relational expression (6) below with respect to the retardation (Re) of the substrate, the thickness (t) of the substrate, the tensile stress and the compressive stress.

Here, β is a photoelastic constant.

In Equation (6), the thickness (t) of the substrate is calculated by substituting the tensile stress and the compressive stress,

이다.

to be.

이고, 굽힘 휨량(d)를 대입하면, 두께(t)는 아래의 [수학식 8]과 같다.therefore,

, And the amount of bending deflection (d) is substituted, the thickness t is expressed by the following equation (8).

이다.

to be.

Therefore, in the curved liquid crystal display panel, when the thickness t of the color filter array substrate or the thin film transistor array substrate satisfies the condition (8), the color filter array substrate and the thin film transistor array substrate are adhered The light leakage phenomenon at the edge of the curved liquid crystal display panel can be minimized.

When the stress occurs in the curved liquid crystal display panel, the direction of the retardation of only the substrate can not be easily recognized due to a large number of birefringence factors in the liquid crystal panel. However, since the retardation direction of the substrate is the same depending on the thickness of the substrate, the stress of the liquid crystal panel can be estimated only by the retardation size of the substrate. Therefore, the retardation induced in the substrate according to the size and curvature conditions of the liquid crystal panel is calculated The following results are obtained.

FIG. 6 is a graph showing the relationship between the substrate thickness according to the present invention and the retardation of the substrate, and FIG. 7 is a partial enlarged graph of "C" in FIG.

That is, the 21.5-inch model increases the retardation of about 800 nm from 0.25 t to form the curved surface of the R2000, and the light leakage level can be satisfied at this time. Therefore, when the retardation is found to be 800 nm or less, a 25-inch waterfall type curved liquid crystal display panel having a curvature of R500 has a substrate thickness of about 0.1 t, and a 21.5-inch L- The liquid crystal display panel has a substrate thickness of about 0.125t. The 14.45 inch trapezoidal curved surface liquid crystal display panel having the curvature of R1000 can satisfy the light leakage level when the substrate thickness is about 0.15t, It can be seen that the mura is improved.

8 is a graph showing the relationship between the thickness of the substrate and the curvature of the curved liquid crystal display panel according to the present invention.

It is possible to select the thickness of the substrate according to the curvature in all curved liquid crystal display panels such as a waterfall type, an L-curve type, and a trapezium-curved type.

9 is a table showing the thickness of a substrate according to the curvature that can satisfy light leakage in a curved liquid crystal display panel according to the present invention.

As shown in Fig. 9, when the thickness of the substrate is selected according to the respective curvatures regardless of the curved shape, the light leakage can be satisfied.

For example, a curved surface liquid crystal display panel having a curvature of 500R or less has a substrate thickness of 0.125t or less, a curved surface liquid crystal display panel having a curvature of 750R or less has a substrate thickness of 0.16t or less, The substrate thickness is selected to 0.22t or less and the curved surface liquid crystal display panel having a curvature of 1500R or less is selected to have a substrate thickness of 0.275t or less and the curved liquid crystal display panel having a curvature of 1750R or less is selected to have a thickness of 0.28t or less, If the thickness of the curved surface liquid crystal display panel of 2000R or less is 0.3t or less, the light leakage condition can be satisfied.

As described above, in the curved liquid crystal display panel, when the thickness of the substrate is appropriately selected according to the curvature, there is an effect that the light leakage (edge mura) at the edge portion of the curved liquid crystal display panel can be improved.

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 general inventive concept as defined by the appended claims and their equivalents. Will be clear to those who have knowledge of.

Claims (7)

A first substrate having a curved shape;
A second substrate having a curved shape; And
And a liquid crystal layer filled between the first and second substrates, wherein the first substrate or the second substrate has a thickness (t) according to the following mathematical expression.

Here, t is the thickness of the substrate, Re is the retardation of the substrate, β is the photoelastic constant, E is the young's modulus, L is the long axis length of the substrate, R is the curvature of the substrate, and θ is the azimuth angle in the slow axis direction. The method according to claim 1,
Wherein the thickness of the first substrate or the second substrate of the curved surface liquid crystal display panel having a curvature of 500R or less is 0.125t or less. The method according to claim 1,
Wherein the thickness of the first substrate or the second substrate of the curved surface liquid crystal display panel having a curvature of 750R or less is 0.16t or less. The method according to claim 1,
Wherein the thickness of the first substrate or the second substrate of the curved surface liquid crystal display panel having a curvature of 1000R or less is 0.22t or less. The method according to claim 1,
Wherein the thickness of the first substrate or the second substrate of the curved surface liquid crystal display panel having a curvature of 1500R or less is 0.275t or less. The method according to claim 1,
Wherein the thickness of the first substrate or the second substrate of the curved liquid crystal display panel having a curvature of 1750R or less is 0.28t or less. The method according to claim 1,
Wherein the thickness of the first substrate or the second substrate of the curved liquid crystal display panel having a curvature of 2000R or less is 0.3t or less.

Images