KR102279281B1 - Curved display panel - Google Patents

Abstract

여기서, t는 기판의 두께, Re는 기판의 리타데이션, β는 광탄성 정수, E는 young's Modulus, L은 기판의 장축 길이, R은 기판의 곡률, θ는 지상축 방향의 방위각이다.The present invention is to prevent light leakage caused by retardation of a substrate in a curved liquid crystal display panel, comprising: 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, wherein the first or second substrates have a thickness t according to the following equation.

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 in the slow axis direction.

Description

Curved liquid crystal display panel

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 edge mura-type light leakage due to stress caused by a curved surface.

Recently, as a display panel that displays an image using digital data, a liquid crystal display (LCD) using liquid crystal and an OLED display panel using an organic light emitting diode (OLED) are representative.

Among the display panels, the liquid crystal 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 on a glass substrate, the thin film transistor array substrate and the color filter array substrate. A liquid crystal layer filled between the filter array substrates is provided, a voltage is applied to the electric field generating electrode to generate an electric field in the liquid crystal layer, and through this, the direction of liquid crystal molecules in the liquid crystal layer is determined and an image is displayed by controlling the polarization of incident light. . Unlike this, the organic light emitting display panel has self-luminous characteristics, does not require a separate light source, and displays an image through a display substrate on which a thin film transistor and an organic light emitting device are formed.

As the size of the display panel increases, there is a problem in that the time difference increases depending on when the viewer looks at the center of the screen and when the viewer sees the left and right ends 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 bent into a concave or convex shape to form a curved surface has been developed.

Such a curved liquid crystal display panel is an auto display device and is used to apply various curvatures to a vehicle, and depending on the curved state of the display panel, a water-fall type, an L-curved type, and a trapezoidal type. It is classified as a trapezium-curved type.

1 is an explanatory diagram for explaining tensile stress and compressive stress in the center and edge portions of a general waterfall-type curved liquid crystal display panel, and FIG. 2 is an explanatory diagram illustrating tensile stress and compressive stress in the center and edge portions of a typical L-curve curved liquid crystal display panel. It is an explanatory diagram for explaining compressive stress, and FIG. 3 is an explanatory diagram for explaining tensile stress and compressive stress in the center and edge portions of a general trapezoidal curved liquid crystal display panel, and FIG. 4 is an edge of a general curved liquid crystal display panel It is an explanatory diagram for explaining the tensile stress and compressive stress of the thin film transistor array substrate and the color filter array substrate in part.

When the liquid crystal display panel is bent to form a curved surface, in the central portion of the substrate (the portion “A” in FIGS. 1 to 3 ) of the curved liquid crystal display panel, tensile stress and compressive stress correspond to the neutral axis of the substrate, and the retardation of the substrate Since retardation is canceled, there is no effect on retardation of the substrate, so that light leakage does not occur. However, a light leakage phenomenon occurs at an edge portion (a portion “B” in FIGS. 1 to 3 ) where the color filter array substrate and the thin film transistor array substrate are bonded by a sealant.

That is, at the edge of the curved liquid crystal display panel, the thin film transistor array substrate has a compressive stress greater than the tensile stress with respect to the neutral axis (compressive stress > tensile stress), and the color filter array substrate has a tensile stress greater than the compressive stress with respect to the neutral axis. Since it is large (compressive stress < tensile stress), the retardation direction of a board|substrate becomes asymmetrical. Accordingly, the increase in retardation of the liquid crystal panel causes 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, at the edge of the curved liquid crystal display panel, retardation increases and light leakage occurs. do.

For example, in Fig. 4, when the retardation rotates 10 nm clockwise about the compression optical axis at 12 points and 2 nm clockwise about the tension optical axis at 23 points, the LC optical axis on the Poincare Sphere If it is located in the second quadrant instead of S1 and rotates 300 nm clockwise around the LC optical axis at the 34 point, black luminance is generated due to the increase in retardation due to the difference from S1, and the compressed optical axis is reduced at 45 point. It rotates 2 nm clockwise around the center, rotates 10 nm clockwise about the tensile optical axis at 56 points, and the increased retardation further increases as it passes through the liquid crystal layer (LC). Due to this phenomenon, light leakage occurs in the same principle in the Waterfall type, L-Curved type, and Trapezium-Curved type curved liquid crystal display panel.

Therefore, in order to improve this 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 was devised to prevent light leakage caused by retardation of the substrate in such a curved liquid crystal display panel. Among the conditions of the substrate, the thickness of the substrate is selected in consideration of the stress suitable for the curvature of the curved liquid crystal display panel. There is a purpose.

In addition, it is another object to provide a curved liquid crystal display panel formed of a substrate having a thickness selected as described above.

According to an aspect of the present invention, there is provided a curved liquid crystal display panel comprising: 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, wherein the first or second substrates have a thickness t according to the following equation.

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 in the slow axis direction.

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

In addition, the curved liquid crystal display panel having a curvature of 750R or less includes a first substrate or a second substrate having a thickness of 0.16t or less.

In addition, the curved liquid crystal display panel having a curvature of 1000R or less includes a first substrate or a second substrate having a thickness of 0.22t or less.

In addition, the curved liquid crystal display panel having a curvature of 1500R or less includes a first substrate or a second substrate having a thickness of 0.275t or less.

In addition, the curved liquid crystal display panel having a curvature of 1750R or less includes a first substrate or a second substrate having a thickness of 0.28t or less.

In addition, the curved liquid crystal display panel having a curvature of 2000R or less includes a first substrate or a second substrate having a thickness of 0.3t or less.

Since the curved liquid crystal display panel according to the present invention having the above characteristics has an appropriate substrate thickness according to the curvature, it is possible to improve light leakage (edge mura) at the edge of the curved liquid crystal display panel.

1 is an explanatory diagram illustrating tensile stress and compressive stress in a central portion and an edge portion of a general waterfall-type curved liquid crystal display panel;
FIG. 2 is an explanatory diagram for explaining tensile stress and compressive stress in the center and edge portions of a general L-curve curved liquid crystal display panel; FIG.
3 is an explanatory diagram for explaining tensile stress and compressive stress in a central portion and an edge portion of a general trapezoidal curved liquid crystal display panel;
4 is an explanatory view for explaining tensile stress and compressive stress of a thin film transistor array substrate and a color filter array substrate at an edge portion of a general curved liquid crystal display panel;
5 is an explanatory view for explaining tensile stress and compressive stress of a thin film transistor array substrate and a color filter array substrate at an edge portion of a 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 and the retardation of the substrate according to the present invention;
7 is an enlarged graph of the part "C" of FIG.
8 is a graph showing a relationship between a thickness and a curvature of a substrate for a curved liquid crystal display panel according to the present invention;
9 is a table showing the thickness of the substrate according to the curvature that can satisfy light leakage in the curved liquid crystal display panel according to the present invention;

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

5 is an explanatory diagram for explaining tensile stress and compressive stress of a thin film transistor array substrate and a color filter array substrate at an edge portion of a 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. When the substrate is bent in this way, 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 to be compressed. Therefore, it is possible to model the stress retardation of the liquid crystal panel based on the neutral axis in which the length of the line in the longitudinal direction is not changed at any position between the uppermost part and the lowermost part of the substrate. The bending moment increases in proportion to the curvature, and at this time, a resisting force is generated. If the magnitude of the force is called the moment of inertia with respect to the neutral axis, when curvature by an external force is realized, the position of the neutral axis within the substrate is determined by the central portion and the edge portion of the liquid crystal panel. Since it is different from , it is possible to select the thickness of the substrate by simulating the edge mura by calculating the bending moment.

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

Here, the moment of inertia (I) is as shown in [Equation 1] below.

Here, b is the minor axis length of the substrate, and t is the thickness of the substrate.

In addition, the bending moment (M) is as shown in [Equation 2] below.

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

The bending deflection amount (d) is affected by the curvature (R) of the substrate and the azimuth angle (θ) in the long axis length and slow axis direction of the substrate. Therefore, the amount of bending deflection (d) is as shown in [Equation 3] below.

Here, θ is the azimuth in the slow axis direction.

In addition, when bending stress is generated in the liquid crystal display panel (substrate), the tensile stress (σ1) and the compressive stress (σ2) with respect to the central axis are as shown in [Equation 4] below.

Here, C1 is the thickness of the substrate subjected to tensile stress about 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, and C2 is It is the thickness of the substrate subjected to compressive stress about the neutral axis.

In addition, in the curved liquid crystal display panel, the light leakage value (K) is affected by the azimuth angle (θ) and the retardation (Re) of the substrate as shown in Equation 5 below.

After all, in order to minimize light leakage, it is related to the retardation (Re) of the substrate, the thickness (t) of the substrate, and the tensile and compressive stresses, and the relational expressions shown in [Equation 6] below must be satisfied.

Here, β is a photoelastic constant.

In [Equation 6], substituting the tensile stress and compressive stress, and calculating the thickness (t) of the substrate, it is as shown in [Equation 7] below,

이다.

to be.

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

, and substituting the amount of bending deflection (d), the thickness (t) is as shown in [Equation 8] below.

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 as in [Equation 8], the color filter array substrate and the thin film transistor array substrate are bonded by the sealant. It is possible to minimize light leakage at the edge of the curved liquid crystal display panel.

When stress is generated in a curved liquid crystal display panel, the retardation direction of only the substrate cannot be easily known due to many birefringent 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. The following results can be obtained.

6 is a graph showing the relationship between the thickness of the substrate and the retardation of the substrate according to the present invention, and FIG. 7 is an enlarged graph of the portion “C” of FIG. 6 .

That is, the 21.5-inch model increases the retardation of about 800 nm at 0.25t to form the curved surface of R2000, and at this time, the light leakage level can be satisfied. Therefore, when the retardation is found for the substrate thickness of 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 0.1t and a 21.5-inch L-curve curved surface having a curvature of R600. When the liquid crystal display panel has a substrate thickness of about 0.125t, and a 14.45 inch trapezoidal curved liquid crystal display panel having a curvature of R1000 has a substrate thickness of about 0.15t, the light leakage level can be satisfied, and the edge caused by light leakage It can be seen that the mura has improved.

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

In all curved liquid crystal display panels such as a Waterfall type, an L-Curvew type, and a Trapezium-Curved type, the thickness of the substrate may be selected according to the curvature.
That is, as shown in FIG. 8, the curved liquid crystal display panel having a curvature of 500R or less and greater than 400R includes a first substrate or a second substrate having a thickness of 0.125t or less and 0.08t or more, and a curved liquid crystal display with a curvature of 750R or less and 500R or more. The panel includes a first substrate or a second substrate having a thickness of 0.16t or less and 0.125t or more, and a curved liquid crystal display panel having a curvature of 1000R or less and 750R or more has a first substrate or a second substrate having a thickness of 0.22t or less and 0.16t or more, , The curved liquid crystal display panel having a curvature of 1500R or less and 1000R or more includes a first substrate or a second substrate having a thickness of 0.275t or less and 0.22t or more, and the curved liquid crystal display panel having a curvature of 1750R or less and 1500R or more has a thickness of 0.28t or less and 0.275t or more When a curved liquid crystal display panel having a first substrate or a second substrate and having a curvature of 2000R or less and 1750R or more has a first substrate or a second substrate having a thickness of 0.3t or less and 0.28t or more, luminescence phenomenon at the edge of the curved liquid crystal display device can be improved

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

As shown in FIG. 9 , regardless of the shape of the curved surface, if the thickness of the substrate is selected according to each curvature, light leakage may be satisfied.

For example, for a curved liquid crystal display panel having a curvature of 500R or less, the substrate thickness is selected as 0.125t or less, for a curved liquid crystal display panel having a curvature of 750R or less, the substrate thickness is selected as 0.16t or less, and a curved liquid crystal display panel having a curvature of 1000R or less Select a substrate thickness of 0.22t or less, and select a substrate thickness of 0.275t or less for a curved liquid crystal display panel with a curvature of 1500R or less, and select a substrate thickness of 0.28t or less for a curved liquid crystal display panel with a curvature of 1750R or less, and select a substrate thickness of 0.28t or less. This 2000R or less curved liquid crystal display panel can satisfy the light leakage condition if the substrate thickness is selected to be 0.3t or less.

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

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and it is common in the technical field to which the present invention pertains that various substitutions, modifications and changes are possible without departing from the technical spirit of the present invention. It will be clear to those who have the knowledge of

Claims (7)

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 is provided, and the first or second substrate has a thickness according to the condition of the following equation, under the condition to prevent light scattering at the edge of the liquid crystal display panel. A curved liquid crystal display panel having (t).

where 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, θ is the azimuth in the slow axis direction, The retardation (Re) is 800 nm or less. The method of claim 1,
A curved liquid crystal display panel having a curvature of 500R or less and a thickness of the first or second substrate of the curved liquid crystal display panel greater than 400R being 0.125t or less and 0.08t or more. The method of claim 1,
The thickness of the first substrate or the second substrate of the curved liquid crystal display panel having a curvature of 750R or less and 500R or more is 0.16t or less and 0.125t or more. The method of claim 1,
The thickness of the first substrate or the second substrate of the curved liquid crystal display panel having a curvature of 1000R or less and 750R or more is 0.22t or less and 0.16t or more. The method of claim 1,
The thickness of the first substrate or the second substrate of the curved liquid crystal display panel having a curvature of 1500R or less and 1000R or more is 0.275t or less and 0.22t or more. The method of claim 1,
The thickness of the first substrate or the second substrate of the curved liquid crystal display panel having a curvature of 1750R or less and 1500R or more is 0.28t or less and 0.275t or more. The method of claim 1,
The thickness of the first substrate or the second substrate of the curved liquid crystal display panel having a curvature of 2000R or less and 1750R or more is 0.3t or less and 0.28t or more.

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