KR102171284B1 - Optical Film and Liquid Crystal Display comprising the Optical Film - Google Patents

Abstract

The present application relates to a liquid crystal display including an optical film. In this application, a liquid crystal display capable of preventing changes in brightness and color of light in the front direction and inclination angle by applying an optical film of a specific structure, improving the uniformity of the outgoing light, and solving the so-called color washout phenomenon. Can be provided.

Description

Optical Film and Liquid Crystal Display comprising the Optical Film

The present application relates to a liquid crystal display including an optical film. Specifically, the present application relates to a liquid crystal display capable of solving a color washout phenomenon occurring in a liquid crystal display, particularly, a vertically aligned (VA) mode liquid crystal display through the optical film.

A liquid crystal display (LCD) is a display device utilizing the anisotropy of liquid crystal. A liquid crystal display generally has a structure including a liquid crystal panel including a liquid crystal layer having a liquid crystal material and polarizing plates disposed on both sides thereof, and implements a black and white state by changing the orientation of the liquid crystal layer, and displays an image.

In general, since a liquid crystal panel is polarized to match light perpendicularly incident on the panel, a problem arises in that the brightness of the light changes or the color changes with respect to the light in an inclined direction.

In order to solve such a problem, for example, as in the case of Patent Document 1, a method of disposing a so-called optical compensation film or the like on the viewing side of a liquid crystal panel is known.

Meanwhile, in the liquid crystal display, various modes exist according to the alignment of liquid crystals in the liquid crystal panel, and typically, there are TN (Twisted Nematic), VA (Vertical Alignment), or IPS (In Plane Switching) modes.

Among the above modes, the VA mode generally has an excellent contrast ratio and excellent color reproducibility, but a so-called color washout phenomenon occurs when the contrast ratio is lowered when viewing the display from an inclined angle compared to the case of viewing the display from the front direction. do.

Korean Patent Publication No. 2009-0080133

The present application provides a liquid crystal display. One object of the present application is to solve a color washout phenomenon occurring in a liquid crystal display, particularly a liquid crystal display in a vertically aligned (VA) mode, through a specific optical film.

The liquid crystal display of the present application may include a liquid crystal panel and an optical film. In the display of the present application, the optical film may be disposed on the surface of the liquid crystal panel on the viewer side. In the present application, the term “viewing-side surface” of a liquid crystal panel refers to a surface closer to an observer who observes an image when the display displays an image among the upper and lower surfaces of the liquid crystal panel. In addition, the term rear surface of the liquid crystal panel refers to a surface of the upper surface and the lower surface opposite to the viewing surface.

The liquid crystal panel of the present application may be, for example, a vertical alignment (VA) type liquid crystal panel. The inventors of the present invention secured uniformity of the emitted light from the front and viewing angles in various types of liquid crystal panels by arranging a unique optical film to be described later on the viewing side surface of the liquid crystal panel, and so-called color mixing that may occur in a white state ( It was confirmed that color washout) phenomenon can be solved, and this effect is particularly appropriately expressed in a liquid crystal display of VA mode.

A specific configuration of the liquid crystal panel applied in the present application is not particularly limited, and all known configurations of a general liquid crystal panel may be applied.

For example, the liquid crystal panel may be a transmissive, reflective, or transflective liquid crystal panel. In the present application, the driving method of the liquid crystal panel is not particularly limited, and for example, a passive matrix method, an active matrix method using an active electrode such as a TFT (Thin Film Transistor) electrode or a TFD (Thin Film Diode) electrode, and a plasma address method A known driving method such as the like may be applied.

The liquid crystal panel generally includes a liquid crystal layer including a liquid crystal material interposed between two transparent substrates. The transparent substrate of the liquid crystal panel may have a property of aligning a liquid crystal material constituting a liquid crystal layer in a specific alignment direction. For example, the substrate itself has a property of aligning a liquid crystal, or the substrate itself has no alignment ability, but a transparent substrate having an alignment layer or the like having a property of aligning a liquid crystal material may be used. A known electrode such as ITO (Indium Tin Oxide) may be applied as the electrode of the liquid crystal panel. Such an electrode can be provided on the surface of a transparent substrate in which the liquid crystal layer is usually in contact, and when a transparent substrate having an alignment film is used, it may be provided between the substrate and the alignment film.

As the liquid crystal material included in the liquid crystal layer, materials having various negative or positive dielectric anisotropy generally used in the construction of a liquid crystal panel may be used. Examples of such materials include various low-molecular liquid crystal materials, high-molecular liquid crystal materials, and mixtures thereof, but are not limited thereto. In addition, the liquid crystal layer of the liquid crystal panel may include a pigment, a chiral agent, or a non-liquid crystalline material within a range that does not impair the liquid crystal properties of the liquid crystal material.

In addition, a transflective liquid crystal panel may be configured by replacing one substrate in the liquid crystal panel, for example, a substrate on the rear side with a substrate having a reflective region and a transmissive region. A region with a reflective function (hereinafter, may be referred to as a reflective layer) included in the transflective electrode used in such a liquid crystal panel is not particularly limited, but a metal such as aluminum, silver, gold, chromium, platinum, or one of them Examples include alloys including the above, oxides such as magnesium oxide, multilayer films of dielectrics, liquid crystals exhibiting selective reflection, or combinations thereof. These reflective layers may be flat or curved. In addition, the reflective layer may be formed by processing a surface shape such as an uneven shape to have diffuse reflectivity, a structure in which an electrode on the transparent substrate is combined on the rear side of a liquid crystal panel, or a combination thereof.

The liquid crystal panel may include other constituent members in addition to the constituent members. For example, by providing a color filter, a color liquid crystal display device capable of providing multicolor or pure color display with high color purity can be manufactured.

An optical film is disposed on the surface of the liquid crystal panel on the viewing side. In the present application, the fact that the optical film is disposed on the viewer-side surface means that the optical film is disposed in contact with the viewer-side surface, as well as when other constituent members exist between the optical film and the viewer-side surface. May also be included. For example, the liquid crystal display of the present application may further include a polarizing plate, and such a polarizing plate may be disposed between the optical film and the surface on the viewing side.

In one example, the optical film has a refractive index divided by an interface including a plurality of inclined surfaces having an arithmetic average inclination angle of greater than 0 degrees and less than 90 degrees in relation to the normal of the surface on the viewing side of the liquid crystal panel. Different first and second regions may be formed.

1 is a diagram illustrating a cross-sectional shape when the optical film 20 is disposed on a liquid crystal panel 10 by way of example. As shown in the drawing, the optical film 20 on the liquid crystal panel 10 may have a first region 2011 and a second region 202 divided by an interface including an inclined surface 201. In the above, the first region may be a region formed in the optical film.

Meanwhile, in the above structure, the inclined surface may form an angle (inclination angle) within a predetermined range with the normal line of the liquid crystal panel 10. When a plurality of inclined surfaces are formed, the inclination angles of each inclined surface may be the same or different from each other, and the arithmetic average value of the plurality of inclination angles, that is, the arithmetic average inclination angle may be in a range of more than 0 degrees and less than 90 degrees. In another example, the arithmetic mean inclination angle may be about 5 degrees or more, about 10 degrees or more, about 15 degrees or more, about 20 degrees or more, or about 25 degrees or more. The arithmetic mean inclination angle may be, for example, about 85 degrees or less, 80 degrees or less, 75 degrees or less, 70 degrees or less, 65 degrees or less, 60 degrees or less, 55 degrees or less, 40 degrees or less, or about 35 degrees or less. In the above, the angle of inclination is, for example, as described in FIG. 2, when the optical film 20 is virtually cut in the direction of the virtual normal 101 and the normal 101 to the surface of the liquid crystal panel 10. It is an angle (AG) formed by the shape of the inclined surface 201 that can be identified at the time, and means a smaller value when two or more angles exist. In the above, cutting in the direction of the normal line 101 may be performed so that the area of the liquid crystal panel or the optical film can be roughly divided into two based on a case observed from the top. In addition, when the shape of the inclined surface 201 is not a straight line, the inclination angle is obtained through a virtual straight line connecting the start point and the end point of the inclined surface 201. The object of the present application may be more effectively achieved in the range of the arithmetic mean inclination angle as described above.

When there are a plurality of inclined surfaces, the inclination angle may be the same or different for each inclined surface. In this case, the standard deviation of the inclination angle may be, for example, about 0 degrees to 10 degrees. The standard deviation may be about 9 degrees or less, about 8 degrees or less, about 7 degrees or less, about 6 degrees or less, about 5 degrees or less, about 4 or less, about 3 or less, about 2 or less, or about 1 or less in another example.

As shown in FIG. 3, in the optical film 20, the light emitted from the liquid crystal panel 10 passes through the first region and the second region in the order, that is, the first region first. It may be disposed to be discharged through the second region later or discharged through the second region.

In the form as described above, the second region may have a higher refractive index than the first region. In the present application, the term refractive index is a refractive index for light having a wavelength of about 550 nm unless otherwise specified.

For example, the first region and the second region may satisfy Equation 1 below.

[Equation 1]

6 <A 135×Δn <17

In Equation 1, A is the arithmetic mean inclination angle, and Δn is an absolute value of the difference between the refractive indices of the first region and the second region measured based on a wavelength of 550 nm.

In Equation 1, A 135×Δn may be about 7 or more, about 8 or more, about 9 or more, about 10 or more, about 11 or more, or about 12 or more in another example. The A 135×Δn may be about 16 or less or about 15 or less in another example.

In the case where the refractive index and the inclination angle are adjusted in the above relationship, the object of the present application can be achieved more efficiently.

In one example, the absolute value of the difference between the refractive indexes of the first region and the second region may be about 0.1 or more. In another example, the absolute value of the difference in refractive index may be about 1 or less, about 0.9 or less, about 0.8 or less, about 0.7 or less, about 0.6 or less, about 0.5 or less, about 0.4 or less, about 0.3 or less, or about 0.2 or less.

In the present application, the refractive index of each of the first region and the second region is not particularly limited as long as the relationship is satisfied. For example, the refractive index of the first region may be in the range of about 1.39 to 1.49. Various transparent materials having a refractive index in this range are known. As a part of the optical film forming the first region, for example, a material having a refractive index within the above range among known optical adhesives or adhesives, for example, acrylic adhesives, etc. may be exemplified, but is limited thereto. It does not become.

The refractive index of the second region may be in the range of about 1.50 to 1.67, and as a transparent material having a refractive index in this range, a known material may be used without particular limitation. For example, materials used in the manufacture of so-called prism sheets in the industry can be used. In addition, ultraviolet (UV) or thermosetting resins such as acrylate-based materials may be exemplified as known materials. For example, after forming a layer in which the convex portion to be described later is formed on the surface of the UV curable resin or the like, the above-described optical film may be manufactured by applying the pressure-sensitive adhesive or adhesive to the surface.

In the present application, the arithmetic mean value of the distances between the plurality of inclined surfaces may be in the range of about 0 μm to 100 μm. In other examples, the distance between the inclined surfaces is about 90 μm or less, about 80 μm or less, about 70 μm or less, about 60 μm or less, about 50 μm or less, about 40 μm or less, about 30 μm or less, about 20 μm or less, or about 10 It may be less than or equal to µm. In the above, the distance between the inclined surfaces is, for example, a distance between the starting point of one inclined surface shape 201 and the shape 201 of another inclined surface adjacent thereto, and the distance is between the shapes 201 It means the shortest distance or the longest distance.

The interface formed as described above may be formed by, for example, a convex portion formed in the first or second region. 5 is an exemplary view of the optical film 20 including the convex portion 203 as described above, and FIG. 6 is a view showing a cross-section of the optical film 20 of FIG. 5 cut in the AB line direction . In FIG. 6, the above-described first region 2011, second region 202, inclination angle AG, inclined surface 201, and normal line 101 are displayed.

As shown in FIG. 5, the convex portions may be multidimensionally arranged when observed from the surface direction of the optical film. In the above, the fact that the convex portions are multidimensionally arranged may mean a case where the convex portions do not have a linear shape when viewed from the surface direction of the optical film, but are arranged on the entire surface of the surface in a dot shape.

In another example, the multidimensional arrangement may mean a case in which the convex portions are arranged along a specific axis when observed from the surface direction, and there are two or more such axes. For example, when there are two or four axes in which the convex portions are arranged, and they have a relationship of 0 degrees and 90 degrees, the convex portions may include portions arranged in a square shape, and the axes are three or more. And, when the angles between them are 0 degrees, 30 degrees, and 60 degrees, portions arranged in a triangular shape may be included.

The shape of the convex portion as described above is not particularly limited. For example, the convex portion may be in the form of a polygonal pyramid or a cone such as a square pyramid, a shape in which a vertex portion of the polygonal pyramid is truncated, or a shape in which a vertex portion of the cone is truncated. The convex portion 203 in FIG. 5 is an example of a truncated square pyramid shape.

In one example, when the optical film is observed from the surface, the convex portions may be present in a ratio of 4 pieces/mm ² to 15000 pieces/mm ² per unit area. In another example, the above ratio is 10 pieces/mm ² or more, 20 pieces/mm ² or more, 30 pieces/mm ² or more, 40 pieces/mm ² or more, 50 pieces/mm ² or more, 60 pieces/mm ² or more, 70 pieces. /mm ² or more, 80 /mm ² or more, 90 /mm ² or more, 100 /mm ² or more, 150 /mm ² or more, 200 /mm ² or more, 250 /mm ² or more, 300 / It may be mm ² or more, 350/mm ² or more, 400/mm ² or more, 450/mm ² or more, or 500/mm ² or more. In addition, the ratio is 14000 pieces / mm ² or less, 13000 pieces / mm ² or less, 12000 pieces / mm ² or less, 11000 pieces / mm ² or less, 10000 pieces / mm ² or less, 9000 pieces / mm ² or less, 8000 pieces/mm ² or less, 7000 pieces/mm ² or less, 6000 pieces/mm ² or less, 5000 pieces/mm ² or less, 4000 pieces/mm ² or less, 3000 pieces/mm ² or less, 2000 pieces/mm ² or less, 1000 The number of pieces/mm ² or less, 900 pieces/mm ² or less, 800 pieces/mm ² or less, 700 pieces/mm ² or less, or 600 pieces/mm ² or less may be used. In this case, the object of the present application can be achieved more effectively.

In the above structure, the pitch of the convex portions may be in the range of 10 to 1000 μm. In the above, the pitch may be the shortest distance or the longest distance from a point where one convex portion starts to a point where another convex portion starts. In another example, the pitch may be about 15 μm or more, 20 μm or more, 25 μm or more, 30 μm or more, 35 μm or more, or 40 μm or more. In addition, the pitch is about 900㎛ or less, 800㎛ or less, 700㎛ or less, 600㎛ or less, 500㎛ or less, 400㎛ or less, 300㎛ or less, 200㎛ or less, 100㎛ or less, 90㎛ or less, 80㎛ It may be less than or equal to 70 μm, less than or equal to 60 μm, or less than or equal to 50 μm.

The height of the convex portion in the above structure may be in the range of about 3 to 1100 μm. The height may be about 5 μm or more, 10 μm or more, 15 μm or more, or 20 μm or more in other examples. In addition, the height is about 1000㎛ or less, about 900㎛ or less, 800㎛ or less, 700㎛ or less, 600㎛ or less, 500㎛ or less, 400㎛ or less, 300㎛ or less, 200㎛ or less, 100㎛ or less, 90㎛ in other examples Hereinafter, it may be 80 μm or less, 70 μm or less, 60 μm or less, or 50 μm or less.

In the present application, a method of arranging the optical film as described above on the surface on the viewing side of the liquid crystal panel is not particularly limited. For example, in the process of assembling a liquid crystal display, the optical film may be simply placed on the viewer's surface, or a method of attaching the optical film to the surface of the liquid crystal panel using an appropriate double-sided adhesive or pressure-sensitive adhesive may be applied. I can.

The liquid crystal display may include members constituting other known liquid crystal displays in addition to the liquid crystal panel and the optical film. As such a member, for example, a polarizing plate, a backlight module, or a reflecting plate may be exemplified, but is not limited thereto.

In this application, a liquid crystal display capable of preventing changes in brightness and color of light in the front direction and inclination angle by applying an optical film of a specific structure, improving the uniformity of the outgoing light, and solving the so-called color washout phenomenon. Can be provided.

1 to 3 are diagrams showing an arrangement state of an exemplary optical film and a liquid crystal panel.
4 to 6 are forms of exemplary optical films.
7 to 9 show results of measuring gray levels in Examples.
10 to 12 show gray level measurement results in a comparative example.

Hereinafter, the manufacturing method of the present application will be described through Examples and Comparative Examples according to the present application, but the scope of the present application is not limited by the following Examples.

Example One.

By arranging an optical film as shown in FIG. 5 on the viewing side polarizing plate of a general VA mode liquid crystal panel in which polarizing plates are arranged on both sides, a liquid crystal display is constructed so that the cross-sectional shape shown in FIG. 2 is formed, and a gray level Was measured. In the structure as shown in FIG. 2, the first region is formed of a known acrylic pressure-sensitive adhesive having a refractive index of about 1.48, the refractive index is about 1.48, and the second region is formed of an acrylate UV curable resin, and the refractive index is about It was about 1.61. In addition, the arithmetic mean value of the inclination angle of the inclined surface 201 with the normal line 101 with respect to the liquid crystal panel surface was about 32, and the standard deviation was about 0.5. The average pitch between the convex portions 203 forming the inclined surface was about 42.2 μm, the height of the convex portions 203 was about 25 μm, and when the optical film 20 was observed from the surface, the convex portions were about 561 per unit area. There were pcs/mm ² . In the above, the gray level was defined by measuring the ratio of luminance for each viewing angle, and after measuring the luminance value for each gray color coordinate, the ratio of the luminance value divided by the luminance of the white display state (color coordinate 255) based on the same viewing angle is shown as a graph. Done. Attached Figures 7 to 9 show the gray level measurement results when the azimuthal angle is 0 degrees (Fig. 7), 45 degrees (Fig. 8), and 90 degrees (Fig. 9), respectively. For each drawing, the measured results are shown by changing the altitude at 0 degrees, 15 degrees, 30 degrees, 45 degrees, and 60 degrees in each azimuth angle.

Comparative example One.

Except that the optical film was not applied, the gray level was measured in the same manner as in Example 1 for the liquid crystal panel of the VA mode used in Example 1. The attached FIGS. 10 to 12 show the measurement results of gray levels when the azimuthal angle is 0 degrees (FIG. 10), 45 degrees (FIG. 11), and 90 degrees (FIG. 12), respectively.

Comparing the results of FIGS. 4 to 6 with FIGS. 7 to 9, it can be seen that the gray level decreases at a large inclination angle in the embodiment.

10: liquid crystal panel
20: optical film
201: slope
202: second area
2011: area 1
101: liquid crystal panel surface normal
30: exit light
203: convex portion
AG: Inclination angle
P: distance between slopes

Claims (13)

A liquid crystal panel in VA mode; And an optical film disposed on the surface of the liquid crystal panel on the viewing side,
In the optical film, a first having different refractive indices divided by an interface including a plurality of inclined surfaces having an arithmetic average inclination angle of greater than 0 degrees and less than 90 degrees in relation to the normal of the viewing-side surface of the liquid crystal panel A region and a second region are formed,
The optical film is disposed so that the light emitted from the liquid crystal panel passes through the first region and the second region in the order and is discharged, or is discharged through the second region,
The second region has a higher refractive index than the first region,
A liquid crystal display satisfying the following Equation 1:
[Equation 1]
6 <A 135×Δn< 17
In Equation 1, A is the arithmetic mean inclination angle of the inclined surface, and Δn is the absolute value of the difference between the refractive indices of the first region and the second region measured based on the 550 nm wavelength. delete delete The liquid crystal display according to claim 1, wherein the absolute value of the difference between the refractive index of the first region (based on a wavelength of 550 nm) and the refractive index of the second region (based on the wavelength of 550 nm) is 0.1 or more. The liquid crystal display according to claim 1, wherein the refractive index of the first region is in the range of 1.39 to 1.49 based on a wavelength of 550 nm. The liquid crystal display according to claim 1, wherein the refractive index of the second region is in the range of 1.50 to 1.67 based on a wavelength of 550 nm. The liquid crystal display according to claim 1, wherein inclination angles of the plurality of inclined surfaces are the same or different from each other, and a standard deviation of the inclination angles is within a range of 0 degrees to 10 degrees. The liquid crystal display according to claim 1, wherein the average tilt angle is in the range of 25 degrees to 55 degrees. The liquid crystal display according to claim 1, wherein the arithmetic mean value of the distances between the plurality of inclined surfaces is in the range of 0 to 100 µm. The liquid crystal display according to claim 1, wherein the interface between the first region and the second region is formed by convex portions formed in the second region. The liquid crystal display according to claim 10, wherein the convex portions are present in a range of 4 pieces/mm ² to 15000 pieces/mm ² per unit area based on the surface direction of the optical film. The liquid crystal display according to claim 10, wherein the pitch of the convex portions is within a range of 10 to 1000 mu m. The liquid crystal display according to claim 10, wherein the height of the convex portion is in the range of 3 to 1100 mu m.

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