KR20170128896A - Optical Film and Liquid Crystal Display comprising the Optical Film - Google Patents

Abstract

The present invention relates to a liquid crystal display including an optical film. The liquid crystal display applies an optical film with a specific structure to prevent changes in brightness and color in a front direction and an inclination angle, improve the uniformity of outgoing light, and eliminate a so-called color washout phenomenon. The liquid crystal display comprises: a liquid crystal panel; and an optical film.

Description

TECHNICAL FIELD The present invention relates to an optical film and a liquid crystal display including the same,

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, in particular, a VA (Vertically Aligned) mode liquid crystal display through the optical film.

BACKGROUND ART Liquid crystal displays (LCDs) are display devices using anisotropy of liquid crystal. A liquid crystal display has a structure including a liquid crystal panel including a liquid crystal layer having a liquid crystal material and polarizers disposed on both sides thereof, and changes the orientation of the liquid crystal layer to realize a monochrome state and display an image.

Since the liquid crystal panel is designed to align the polarized light with respect to the light vertically incident on the panel in general, there arises a problem that the brightness of the light changes or the color changes with respect to the light in the inclined direction.

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

On the other hand, various modes exist in the liquid crystal display according to the orientation of the liquid crystal in the liquid crystal panel, and typically TN (Twisted Nematic), VA (Vertical Alignment) or IPS (In plane switching) modes exist.

Among the above modes, the VA mode generally has excellent contrast ratio and excellent coloring ability, but a so-called color washout phenomenon occurs in which the contrast ratio is lowered when the display is observed at the inclination angle than when the display is observed in the front direction do.

Korea Patent Publication No. 2009-0080133

The present application provides a liquid crystal display. The present application aims at solving a color washout phenomenon occurring in a liquid crystal display, in particular, a VA (Vertically Aligned) mode liquid crystal display 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 visual side surface of the liquid crystal panel. The visible side surface of the liquid crystal panel in the present application means a surface closer to an observer who observes the image when the display displays the image on the upper surface and the lower surface of the liquid crystal panel. The term " rear surface of the liquid crystal panel " means the surface of the upper surface and the lower surface opposite to the viewer-side surface.

The liquid crystal panel of the present application may be, for example, a VA (Vertical Alignment) type liquid crystal panel. The present inventors have found that by disposing a specific optical film to be described later on the visual side surface of a liquid crystal panel, it is possible to ensure the uniformity of light emitted from the front and the viewing angle in various types of liquid crystal panels, color washout phenomenon can be solved, and it is confirmed that these effects are appropriately expressed in a liquid crystal display of VA mode in particular.

The specific configuration of the liquid crystal panel applied in the present application is not particularly limited, and any known general liquid crystal panel configuration can be applied.

For example, the liquid crystal panel may be a transmissive, reflective or transflective liquid crystal panel. The driving method of the liquid crystal panel in the present application is not particularly limited. For example, an active matrix method using an active electrode such as a passive matrix method, a TFT (Thin Film Transistor) electrode or a TFD (Thin Film Diode) And the like can be applied.

A liquid crystal panel typically includes a liquid crystal layer containing a liquid crystal material interposed between two transparent substrates. The transparent substrate of the liquid crystal panel may have a property of orienting the liquid crystal material constituting the liquid crystal layer in a specific alignment direction. For example, a transparent substrate on which the substrate itself has a property of aligning liquid crystals, or on which an alignment film having a property of aligning a liquid crystal material is provided, although the substrate itself has no alignment capability. As the electrode of the liquid crystal panel, a known electrode such as ITO (Indium Tin Oxide) can be applied. Such an electrode can be provided on the surface of a transparent substrate on which the liquid crystal layer is in contact with the electrode. In the case of using a transparent substrate having an alignment film, the electrode can be provided between the substrate and the alignment film.

As the liquid crystal material contained in the liquid crystal layer, a material having various negative or positive dielectric anisotropy, which is generally used in the constitution of a liquid crystal panel, can be used. Examples of such materials include, but are not limited to, various low-molecular liquid crystal materials, polymer liquid crystal materials, and mixtures thereof. In addition, the liquid crystal layer of the liquid crystal panel may contain a dye, a chiral agent, or a non-liquid crystalline substance within a range that does not impair the liquid crystallinity of the liquid crystal material.

In addition, a transflective liquid crystal panel may be constituted by replacing one substrate, for example, a substrate on the rear side of the liquid crystal panel, with a substrate having a reflective function area and a transmissive function area. A region (hereinafter, referred to as a reflection layer) having a reflection function 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, An oxide such as magnesium oxide, a multilayer film of a dielectric, a liquid crystal showing selective reflection, or a combination of these. These reflective layers may be planar or curved. The reflective layer may be formed by imparting diffusive reflectivity to a surface shape such as a concavo-convex shape, or by combining electrodes on the transparent substrate on the back side of the 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 viewer-side surface of the liquid crystal panel. 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 components are present between the optical film and the viewer- May also be included. For example, the liquid crystal display of the present application may further include a polarizing plate, and the polarizing plate may be disposed between the optical film and the viewer side surface.

In one example, the optical film has a refractive index that is divided by an interface including a plurality of inclined planes having an arithmetic average inclination angle exceeding 0 degree and less than 90 degrees in relation to the normal line of the visual side surface of the liquid crystal panel The first region and the second region may be formed.

Fig. 1 is a view exemplarily showing a cross-sectional shape when the optical film 20 is disposed on the liquid crystal panel 10. Fig. The optical film 20 on the liquid crystal panel 10 may have a first region 2011 and a second region 202 which are divided by the interface including the inclined plane 201. In this case, The first region may be a region formed in the optical film.

In the above structure, the inclined surface may form an angle (inclined angle) with a normal line of the liquid crystal panel 10 to a predetermined range. In a case where a plurality of inclined planes are formed, the inclination angles of the respective inclined planes may be equal to or different from each other. The arithmetic average value of the plurality of inclination angles, that is, the arithmetic average inclination angle, may be within the range of more than 0 degrees and less than 90 degrees. The arithmetic mean tilt angle may be greater than about 5 degrees, greater than about 10 degrees, greater than about 15 degrees, greater than about 20 degrees, or greater than about 25 degrees in other examples. The arithmetic mean tilt 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. 2, the virtual normal line 101 to the surface of the liquid crystal panel 10 and the optical film 20 in the direction of the normal line 101 are virtually cut off (AG) formed by the shape of the sloping surface 201 which can be confirmed at the time of measurement, and means a smaller value when two or more angles are present. The cutting in the direction of the normal line 101 can be performed so that the area of the liquid crystal panel or the optical film can be approximately halved on the basis of the case observed from above. When the shape of the inclined surface 201 is not linear, the inclination angle is obtained through a virtual straight line connecting the starting point and the end point of the inclined surface 201. The object of the present application can be achieved more effectively in the range of the arithmetic average inclination angle as described above.

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

As shown in FIG. 3, the optical film 20 is formed so that the outgoing light 30 from the liquid crystal panel 10 passes through the first area and the second area in this order, And then discharged after passing through the second region or passing through the second region.

In the above-described mode, the second region may have a higher refractive index than the first region. The term refractive index in the present application is a refractive index for light with a wavelength of about 550 nm unless otherwise specified.

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

[Equation 1]

6 < A 135 x? N < 17

In Equation 1, A is the arithmetic average inclination angle, and? N is the absolute value of the difference between the refractive indexes of the first region and the second region measured based on the wavelength of 550 nm.

In another embodiment, A 135 x? N 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. The A 135 x? N may be less than or equal to about 16 or less than or equal to about 15 in other examples.

In the case where the refractive index and the tilt 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 in refractive index between the first and second regions may be greater than or equal to about 0.1. In another example, the absolute value of the difference in refractive index difference 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 indices of the first region and the second region are not particularly limited as long as they satisfy the above relationship. For example, the refractive index of the first region may be in the range of about 1.39 to 1.49. Transparent materials having such a range of refractive index are known variously. As the portion of the optical film forming the first region, for example, a well-known optical pressure-sensitive adhesive or an adhesive, for example, a material having a refractive index within the above range, such as an acrylic pressure-sensitive adhesive, It is not.

The refractive index of the second region may be within a range of about 1.50 to 1.67, and a transparent material having such a refractive index may be a known material without any particular limitation. For example, materials used in the manufacture of so-called prism sheets in the industry can be used. As a known material, an ultraviolet (UV) or thermosetting resin such as an acrylate series may be exemplified. For example, the above-mentioned optical film may be produced by applying the above-mentioned pressure-sensitive adhesive or adhesive onto the surface of the convex portion, which will be described later, with a UV curable resin or the like.

The arithmetic average value of the distances between the plurality of slopes in the present application may be in the range of about 0 mu m to 100 mu m. In another example, the distance between the slopes is about 90 占 퐉, about 80 占 퐉, about 70 占 퐉, about 60 占 퐉, about 50 占 퐉, about 40 占 퐉, about 30 占 퐉, about 20 占 퐉, Mu m or less. The distance between the inclined planes is, for example, a distance between a point where one inclined plane 201 starts and another inclined plane 201 adjacent thereto as shown in Fig. 4, Means the shortest distance or the longest distance.

The interface formed as described above may be formed, for example, by 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 cross-sectional view of the optical film 20 of FIG. 5 cut along the AB line direction . In FIG. 6, the first region 2011, the second region 202, the inclination angle AG, the inclined plane 201, and the normal line 101 are displayed.

As shown in Fig. 5, the convex portions may be arranged in a multidimensional arrangement when viewed from the surface direction of the optical film. The fact that the convex portions are arranged in a multidimensional manner means that the convex portions do not have a linear shape when viewed from the surface direction of the optical film but are arranged on the front surface of the surface in a point shape.

In another example, the multidimensional arrangement may mean that the convex portion is arranged along a specific axis when viewed from the surface direction, and the number of such axes is two or more. For example, when two or four axes in which the convex portions are arranged and have a relationship of 0 degrees and 90 degrees, the convex portions as a whole may include portions arranged in a rectangular shape, And may include a portion arranged in a triangular shape when the angle therebetween is 0 degree, 30 degrees, and 60 degrees.

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

In one example there may be at a rate of 4 per area unit of the convex portion in the case of observing the optical film at the surface / mm ² to 15,000 / mm ^2. In another example, the ratio is 10 / mm ² , 20 / mm ² , 30 / mm ² , 40 / mm ² , 50 / mm ² , 60 / mm ² , / mm ² or higher, 80 / mm ² or higher, 90 / mm ² or more, to 100 / mm ² or more, 150 / mm ² or more, to 200 / mm ² or more, to 250 / mm ² or more, 300 / mm ^{2, not} less than 350 / mm ^{2, not} less than 400 / mm ^{2, not} less than 450 / mm ^2, or not less than 500 / mm ² . In addition, the rate of 14,000 pieces / mm ² or less, 13000 / mm ² or less, 12,000 pieces / mm ² or less, 11,000 pieces / mm ² or less, 10,000 / mm ² or less, 9,000 / mm ² or less in other examples, 8000 / mm ² or less, 7,000 / mm ² or less, 6,000 / mm ² or less, to 5000 / mm ² or less, 4,000 / mm ² or less, to 3000 / mm ² or less, to 2000 / mm ² or less, 1000 Mm ² or less, 900 mm ² or less, 800 mm ² or less, 700 mm ² or less or 600 mm ² or less. In this case, the object of the present application can be achieved more effectively.

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

The height of the convex portion in the above structure may be in the range of about 3 to 1100 占 퐉. In another example, the height may be about 5 탆 or more, 10 탆 or more, 15 탆 or more, or 20 탆 or more. In another example, the height may be about 1000 탆 or less, about 900 탆 or less, about 800 탆 or less, about 700 탆 or less, about 600 탆 or less, about 500 탆 or less, about 400 탆 or less, about 300 탆 or less, about 200 탆 or less, Or less, 80 mu m or less, 70 mu m or less, 60 mu m or less, or 50 mu m or less.

The method of arranging the above optical film on the visual side surface of the liquid crystal panel in the present application is not particularly limited. For example, a method of simply placing the optical film on the visual side surface in the process of assembling the liquid crystal display, or attaching the optical film to the surface of the liquid crystal panel by using a suitable double-sided adhesive or pressure sensitive adhesive is applied .

The liquid crystal display may include a member constituting another known liquid crystal display in addition to the liquid crystal panel and the optical film. Examples of such members include, but are not limited to, a polarizing plate, a backlight module, or a reflector.

The present application discloses a liquid crystal display (LCD) capable of preventing brightness and color variation of light in frontal and oblique angles by applying an optical film having a specific structure, improving the uniformity of outgoing light, and eliminating the phenomenon of so- May be provided.

Figs. 1 to 3 are views showing the arrangement of an exemplary optical film and a liquid crystal panel. Fig.
Figures 4-6 are illustrative optical film forms.
7 to 9 show the results of measuring the gray level in the embodiment.
10 to 12 show the gray level measurement results in the comparative example.

Hereinafter, the production method of the present application will be described with reference to 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.

A liquid crystal display is configured to have a cross-sectional shape as shown in FIG. 2 by arranging an optical film as shown in FIG. 5 on a viewer-side polarizing plate of a general VA mode liquid crystal panel in which polarizing plates are disposed on both sides, Were measured. 2, the first region is formed of a known acrylic pressure-sensitive adhesive having a refractive index of about 1.48, and its refractive index is about 1.48. The second region is formed of an acrylate-based UV curable resin, and its refractive index is about 1.61. In addition, the arithmetic mean value of the inclination angle of the inclined surface 201 with respect to the normal line 101 to the surface of the liquid crystal panel was about 32, and the standard deviation was about 0.5. The average pitch of the convex portions 203 forming the inclined surface was about 42.2 mu m and the height of the convex portions 203 was about 25 mu m. When observing the optical film 20 on the surface, the convex portions were about 561 / Mm &lt; ² &gt; The gray level is defined by measuring the ratio of luminance to the viewing angle. The luminance value is measured for each color coordinate and then the luminance value is divided by the luminance of the white display state (color coordinate 255) on the basis of the same viewing angle. . 7 to 9 show measurement results of the gray level when the azimuthal angle is 0 degree (Fig. 7), 45 degree (Fig. 8) and 90 degree (Fig. 9), respectively. 15 degrees, 30 degrees, 45 degrees, and 60 degrees of altitude at the respective azimuth angles according to the drawings.

Comparative Example  One.

The gray level was measured in the same VA mode liquid crystal panel as that used in Example 1 except that the optical film was not applied in the same manner as in Example 1. [ FIGS. 10 to 12 show measurement results of the gray level 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 is reduced at a large inclination angle in the embodiment.

10: liquid crystal panel
20: Optical film
201: slope
202: second region
2011: 1st zone
101: Surface normal of liquid crystal panel
30: Outgoing light
203: convex portion
AG: inclination angle
P: distance between slopes

Claims (13)

A liquid crystal panel; And an optical film disposed on the visual side surface of the liquid crystal panel,
Wherein the optical film has a first refractive index different from the first refractive index which is divided by an interface including a plurality of inclined surfaces having an arithmetic average inclination angle exceeding 0 degrees and less than 90 degrees in relation to a normal line of a visual side surface of the liquid crystal panel, Region and a second region are formed,
Wherein the optical film is arranged such that light emitted from the liquid crystal panel passes through the first region and the second region in the order and is discharged through the second region,
And the second region has a higher refractive index than the first region. The liquid crystal display according to claim 1, wherein the liquid crystal panel is a VA mode liquid crystal panel. 2. The liquid crystal display according to claim 1,
[Equation 1]
6 < A 135 x? N < 17
In Equation 1, A is the arithmetic average inclination angle of the inclined surface, and? N is the absolute value of the difference between the refractive indexes of the first region and the second region measured based on the wavelength of 550 nm. The liquid crystal display according to claim 1, wherein an absolute value of a difference between a refractive index (based on a wavelength of 550 nm) of the first region and a refractive index (based on a wavelength of 550 nm) of the second region 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 of 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 the inclination angles of the plurality of inclined surfaces are equal to or different from each other, and the standard deviation of the inclination angles is within a range of 0 to 10 degrees. The liquid crystal display according to claim 1, wherein the average inclination angle is within a range of 25 degrees to 55 degrees. The liquid crystal display according to claim 1, wherein the arithmetic average value of the distances between the plurality of slopes is in the range of 0 to 100 mu m. The liquid crystal display according to claim 1, wherein the interface between the first region and the second region is formed by a convex portion formed in the second region. The method of claim 10, wherein the surface area direction convexes unit on the basis of the optical film 4 / mm ² to 15,000 / mm ² to present a liquid crystal display. 11. The liquid crystal display according to claim 10, wherein the pitch of the convex portions is in the range of 10 to 1000 mu m. 11. The liquid crystal display according to claim 10, wherein a height of the convex portion is in the range of 3 to 1100 占 퐉.

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