Contrast improvement optical film

Abstract

A contrast improvement optical film includes a high refractive layer having a plurality of spaced-apart intaglio patterns on one surface, and a low refractive layer bonded to one surface of the high refractive layer while filling the intaglio patterns. The intaglio patterns include a recessed flat portion recessed at a central region and horizontally formed. The intaglio patterns include a convex curved inclined portion protruding from the high refractive layer to the low refractive layer and inclined in a curved surface form between the recessed flat portion and one surface of the high refractive layer.

Description

Technical Field

[0001] This invention relates to an optical film. More specifically, this invention relates to an optical film capable of improving viewing angle by enhancing lateral brightness. Background Technology

[0002] Liquid crystal displays (LCDs) operate by emitting light from a backlight unit through a liquid crystal panel. In LCDs, the brightness and contrast are high in the front of the screen, and lower on the sides. High contrast is essential for accurately representing both bright and dark areas of the screen, resulting in superior image quality.

[0003] In recent years, as LCD screens have become larger, image quality from the sides has become important in addition to image quality from the front. Therefore, efforts are underway to achieve high brightness and contrast on the sides of the screen.

[0004] A liquid crystal display device may include a laminate having a structure in which a first polarizing plate, a liquid crystal panel, and a second polarizing plate are stacked. The first polarizing plate is attached to the lower portion of the liquid crystal panel to polarize incident light. The liquid crystal panel is attached between the first and second polarizing plates to allow light incident from the first polarizing plate to be transmitted to the second polarizing plate, and may include a liquid crystal layer as a display medium. The second polarizing plate is attached to the upper portion of the liquid crystal panel to polarize and diffuse light passing through the liquid crystal panel, thereby improving lateral brightness and contrast. The second polarizing plate may have a stacked structure of polarizers, optical films, protective layers, etc.

[0005] Figure 1a and Figure 1b This is a cross-sectional view showing an existing optical film used in polarizing plates.

[0006] like Figure 1a and Figure 1b As shown, existing optical films 110 and 120 can be formed by stacking high-refractive-index layers 111 and 121 and low-refractive-index layers 112 and 122. The high-refractive-index layers 111 and 121 can have a recessed gravure pattern. The gravure pattern has inclined portions S1 and S2 between the recessed flat portions F1 and F2 and one surface of the high-refractive-index layers 111 and 121. Figure 1a As shown, the inclined portions S1 and S2 are configured as a straight line S1. Alternatively, as... Figure 1b As shown, the inclined portions S1 and S2 are configured to be recessed (i.e. bent) from the low-refractive layer 122 to the high-refractive layer 121, i.e., the concave curved inclined portion S2.

[0007] However, as Figure 1a and 1bAs shown, if the intaglio pattern of the high-refractive layer is formed as a straight line S1 or a concave curved inclined portion S2, it is not easy to meet the high-quality standard values ​​for frontal relative brightness (relative brightness based on the frontal brightness without the optical film) and 60° side relative brightness (relative brightness based on the frontal brightness) in the implemented product (display device) (frontal relative brightness of 92% or more, and 60° side relative brightness of 14% or more of the frontal relative brightness). Therefore, currently used display devices require a frontal relative brightness of 90% or more and a 60° side relative brightness of 13% or more.

[0008] However, ongoing efforts are underway to improve the relative brightness at the front to over 92% and the relative brightness at the 60° side to over 14% by improving the material of the optical film or the gravure pattern. Summary of the Invention

[0009] Technical issues

[0010] The purpose of this invention is to improve the shape of the intaglio pattern formed on the high-refractive layer of the optical film, so as to increase the relative brightness at the front to more than 92% and the relative brightness at the 60° side to more than 14%.

[0011] Technical solution

[0012] The contrast-enhancing optical film of the present invention for achieving this purpose may include: a high-refractive-index layer having a plurality of spaced-apart gravure patterns on one surface; and a low-refractive-index layer that is bonded to the gravure patterns on one surface of the high-refractive-index layer.

[0013] In contrast-enhancing optical films, gravure patterns may include recessed flat portions and convex inclined portions. The recessed flat portions may be recessed in a central region and formed horizontally. The convex inclined portions may protrude from the high-refractive layer to the low-refractive layer between the recessed flat portions and a surface of the high-refractive layer, and be inclined in a curved shape.

[0014] In the contrast-improving optical film of the present invention, the convex inclined portion can have a radius of curvature of 50 μm to 150 μm.

[0015] In the contrast-improving optical film of the present invention, the gravure pattern can have a length and width of 10 μm to 20 μm and a short width of 5 μm to 15 μm.

[0016] In the contrast-improving optical film of the present invention, the relative brightness at the front can be more than 92% of the brightness at the front before the optical film is stacked, and the relative brightness at the 60° side can be more than 14% of the relative brightness at the front.

[0017] In the contrast-improving optical film of the present invention, the high-refractive-index layer may have a refractive index of 1.57 to 1.70, and the low-refractive-index layer may have a refractive index of 1.42 to 1.50.

[0018] In the contrast-improving optical film of the present invention, the refractive index difference between the high-refractive layer and the low-refractive layer can be from 0.07 to 0.28.

[0019] The polarizing plate according to the present invention may include the contrast-improving optical film described above.

[0020] The display device according to the present invention may include the polarizing plate described above.

[0021] Invention Effects

[0022] The present invention, with this structure, forms a curved inclined portion in the gravure pattern of the high-refractive layer, which is configured as a shape that protrudes from the high-refractive layer to the low-refractive layer while bending, i.e., a convex curved slope. Thus, compared with the prior art in which the inclined portion of the gravure pattern is configured as a straight line or a concave curved slope, the present invention can minimize the degradation of the relative brightness at the front while maximizing the relative brightness at the 60° side.

[0023] Furthermore, the present invention sets the radius of curvature of the inclined portion of the convex surface to 50 μm to 150 μm. As a result, the present invention can increase the relative brightness from directly in front to over 92% and the relative brightness from the 60° side to over 14%. Therefore, the present invention can meet the high-quality standard values ​​for both the relative brightness from directly in front and the relative brightness from the 60° side. Attached Figure Description

[0024] Figure 1a and 1b This is a cross-sectional view showing an optical film according to the prior art.

[0025] Figure 2 This is a cross-sectional view showing the optical film according to the present invention.

[0026] Figure 3 This is a cross-sectional view showing a modified example of the optical film according to the present invention. Detailed Implementation

[0027] The invention will now be described in detail with reference to the accompanying drawings.

[0028] Figure 2 This is a cross-sectional view showing the optical film according to the present invention.

[0029] like Figure 2 As shown, the optical film 210 of the present invention can be configured to include a high-refractive-index layer 211 and a low-refractive-index layer 212.

[0030] The high-refractive-index layer 211 may have an intaglio pattern RP formed on its surface facing the low-refractive-index layer 212. The intaglio pattern RP may include a recessed flat portion F3 and a convex curved inclined portion S3.

[0031] The recessed flat portion F3 is formed by recessing a predetermined depth D in the central region of the intaglio pattern RP. The recessed flat portion F3 can be formed horizontally parallel to a surface of the high-refractive layer 211. Figure 2 (The surface that is bonded to the low-refractive layer 212).

[0032] The convex curved inclined portion S3 can be formed as a surface of the high refractive layer 211 at both ends of the concave flat portion F3. Figure 2 The surfaces that are connected at an angle to the high-refractive-index layer 211 and the low-refractive-index layer 212 are connected at an angle. The convex curved slope portion S3 can be formed into a shape that protrudes (or bends) in a curved manner along the direction from the high-refractive-index layer 211 to the low-refractive-index layer 212, i.e., a convex curved slope.

[0033] It is known that when the length and width (LW) and the short width (SW) are 5 to 20 μm and the depth (D) is 5 to 15 μm, the gravure pattern RP has a large light diffusion effect. Therefore, in this invention, the length and width (LW) can be set to 10 to 20 μm, the short width (SW) to 5 to 15 μm, and the depth (D) to 5 to 15 μm. The gravure pattern RP can be formed as multiple gravure patterns RP spaced apart.

[0034] The high-refractive-index layer 211 can be formed from an ultraviolet-curable composition comprising, for example, at least one resin selected from (meth)acrylic, polycarbonate, silicone, and epoxy resins. The high-refractive-index layer 211 may have a refractive index of 1.57 to 1.70.

[0035] The low-refractive-index layer 212 can be bonded to one surface of the high-refractive-index layer 211 while simultaneously filling (or embedding) the gravure pattern RP of the high-refractive-index layer 211. Figure 2 (the lower surface of the middle).

[0036] The low-refractive-index layer 212 can be formed from a UV-curable transparent resin such as (meth)acrylic, polycarbonate, silicone, or epoxy resins. The low-refractive-index layer 212 can have a refractive index of 1.42 to 1.50.

[0037] Table 1 below shows the changes in relative brightness from the front and from the 60° side depending on the shape of the gravure pattern RP. The high-refractive layer 211 uses an acrylic resin with a refractive index of 1.58. The low-refractive layer 212 uses an epoxy resin with a refractive index of 1.44. The gravure pattern RP is configured with a length and width LW of 10 μm, a width SW of 5 μm, a depth D of 15 μm, and a period T of 29 μm. The relative brightness from the front and from the 60° side were measured while changing the radius of curvature R of the convex inclined portion S3. Furthermore, to compare the technical effects of the convex inclined portion S3 according to the present invention with the inclined portion (straight line, concave inclined surface slope) according to the prior art, the relative brightness from the front and from the 60° side were also measured for the inclined portion (straight line, concave inclined surface slope) according to the prior art.

[0038] [Table 1]

[0039]

[0040] As shown in Table 1 above, when the inclined portion is formed as a straight line and a concave curved slope, the relative brightness directly in front exceeds 92% in some experimental examples, but the relative brightness at 60° to the side does not exceed 14%. On the other hand, when the inclined portion is formed as a convex curved slope, the measurement results show that the relative brightness directly in front exceeds 92% when the radius of curvature R is 50 to 150 μm, and the relative brightness at 60° to the side exceeds 14% when the radius of curvature R is 30 to 150 μm. However, in actual products (display devices), it is preferable that the relative brightness directly in front and the relative brightness at 60° to the side meet 92% or more and 14% or more, respectively. Therefore, in this invention, it is preferable to limit the radius of curvature R of the convex curved inclined portion S3 to 50 to 150 μm. This limitation of the radius of curvature R may have technical significance.

[0041] Table 2 below shows the results of measuring the relative brightness from the front and the relative brightness from the side at 60° after changing the shape of the gravure pattern RP to be different from that in Table 1 above, while altering the radius of curvature R of the convex inclined portion S3. The high-refractive-index layer 211 and the low-refractive-index layer 212 use the same materials as in Table 1 above. The gravure pattern RP is configured with a length and width LW of 15 μm, a short width SW of 10 μm, a depth D of 15 μm, and a period T of 29 μm. To compare the technical effects of the convex inclined portion S3 according to the present invention with the inclined portion (straight line, concave inclined surface slope) according to the prior art, the relative brightness from the front and the relative brightness from the side at 60° were also measured for the inclined portion (straight line, concave inclined surface slope) according to the prior art.

[0042] [Table 2]

[0043]

[0044] As shown in Table 2 above, when the inclined portion is formed as a straight line and a concave curved slope, the measurement results show that in some experimental examples, the relative brightness directly in front exceeds 92%, but the relative brightness at 60° to the side does not exceed 14%. On the other hand, when the inclined portion is formed as a convex curved slope, the measurement results are the same as those in Table 1 above, that is, the relative brightness directly in front exceeds 92% when the radius of curvature R is 50 to 150 μm, and the relative brightness at 60° to the side exceeds 14% when the radius of curvature R is 30 to 150 μm. Similarly, in actual products, it is required that the relative brightness directly in front and the relative brightness at 60° to the side meet 92% or more and 14% or more, respectively. Therefore, for the convex curved inclined portion S3 of the present invention, it is preferable to limit the radius of curvature R of the convex curved surface to 50 to 150 μm.

[0045] Table 3 below shows the results of measuring the relative brightness from the front and the relative brightness from the side at 60° after changing the shape of the gravure pattern RP to be different from that in Tables 1 and 2 above, while altering the radius of curvature R of the convex inclined portion S3. The high-refractive-index layer 211 and the low-refractive-index layer 212 use the same materials as in Table 1 above. The gravure pattern RP is configured with a length and width LW of 20 μm, a short width SW of 15 μm, a depth D of 15 μm, and a period T of 29 μm. To compare the technical effects of the convex inclined portion S3 according to the present invention with the inclined portion (straight line, concave inclined surface slope) according to the prior art, the relative brightness from the front and the relative brightness from the side at 60° were also measured for the inclined portion (straight line, concave inclined surface slope) according to the prior art.

[0046] [Table 3]

[0047]

[0048] As shown in Table 3 above, when the inclined portion is formed as a straight line and a concave curved slope, the measurement results show that the relative brightness at the front exceeds 92% in all experimental examples, but the relative brightness at the 60° side does not exceed 14%. On the other hand, when the inclined portion is formed as a convex curved slope, the measurement results are the same as those in Tables 1 and 2 above, that is, the relative brightness at the front exceeds 92% when the radius of curvature R is 50 to 150 μm, and the relative brightness at the 60° side exceeds 14% when the radius of curvature R is 30 to 150 μm. However, in actual display devices, it is necessary to meet a relative brightness of 92% or more at the front and 14% or more at the 60° side. Therefore, for the convex curved inclined portion S3 of the present invention, it is preferable to limit the radius of curvature R of the convex surface to 50 to 150 μm.

[0049] Summarizing the results in Tables 1 to 3 above, in the optical film of the present invention, the gravure pattern RP preferably has an inclined portion formed as a convex curved surface slope. Furthermore, when the length and width LW are 10 to 20 μm and the short width SW are 5 to 15 μm, the radius of curvature R of the convex surface is preferably set to 50 to 150 μm.

[0050] On the other hand, while changing the materials (refractive indices) of the high-refractive layer 211 and the low-refractive layer 212, changes in the relative brightness from the front and from the side at 60° were measured. It was confirmed that changes in the materials (refractive indices) of the high-refractive layer 211 and the low-refractive layer 212 did not affect the results in Tables 1 to 3 above, i.e., the measured values ​​of the relative brightness from the front and from the side at 60°. Therefore, in the optical film of the present invention, the high-refractive layer 211 can be made of a material with a refractive index of 1.57 to 1.70. In the optical film of the present invention, the low-refractive layer 212 can be made of a material with a refractive index of 1.42 to 1.50. In this case, the refractive index difference between the high-refractive layer 211 and the low-refractive layer 212 can be 0.07 to 0.28.

[0051] Figure 3 This is a cross-sectional view showing a modified example of the optical film according to the present invention.

[0052] like Figure 3 As shown, the deformable optical film 220 can be configured such that only the low-refractive-index layer 212 is filled inside the intaglio pattern RP of the high-refractive-index layer 211, but one surface of the high-refractive-index layer 211 ( Figure 3 The lower surface of the film (220) is not bonded to the low-refractive layer 212. This minimizes the thickness of the deformable optical film 220, thus contributing to the thinning of the display device.

[0053] exist Figure 3 In the deformable optical film 220, other components are similar to... Figure 2 The corresponding configuration is the same. Therefore, a detailed description of other configurations of the deformable optical film 220 will be provided by [the relevant authority / organization]. Figure 2 Replace with the relevant description.

[0054] The aforementioned optical film can be used as part of a polarizing plate. In this case, the polarizing plate may, for example, have a structure in which the aforementioned optical film is inserted between a polarizer and a protective film and stacked together.

[0055] In addition, the aforementioned optical film can be used in a variety of display devices other than liquid crystal panels, such as plasma panels, electroluminescent panels, and organic light-emitting diode panels.

[0056] The present invention has been described above through several embodiments, which are intended to illustrate the invention. Those skilled in the art will be able to modify or alter these embodiments in other forms. However, since the scope of the invention is defined by the appended claims, such modifications or alterations can be interpreted as being included within the scope of the invention.

[0057] [Explanation of reference numerals in the attached figures]

[0058] 110, 120, 210, 220: Optical film

[0059] 111, 121, 211, 221: High-refractive-index layer

[0060] 112, 122, 212, 222: Low-refractive-index layer

[0061] F1, F2, F3: Concave flat portion; S1: Straight inclined portion

[0062] S2: Inclined portion of concave curved surface; S3: Inclined portion of convex curved surface

[0063] RP: Gravure pattern; LW: Length and width of the gravure pattern.

[0064] SW: Width and shortness of the intaglio pattern; D: Depth of the intaglio pattern.

[0065] T: Period of the intaglio pattern; R: Radius of curvature of the inclined portion of the convex surface.

Claims

1. A contrast-improving optical film, comprising: A high-refractive layer having multiple spaced-apart intaglio patterns on one surface; and A low-refractive-index layer, which, while filling the gravure pattern, is bonded to one surface of the high-refractive-index layer. The intaglio pattern includes: The concave flat portion is formed horizontally in the central region; and A convex curved inclined portion, which protrudes from the high-refractive layer toward the low-refractive layer between the recessed flat portion and one surface of the high-refractive layer, and is inclined in a curved shape. The intaglio pattern has a length and width of 10μm to 20μm and a short width of 5μm to 15μm, and the convex curved inclined portion has a radius of curvature of 50μm to 150μm, such that the relative brightness in front is more than 92% of the brightness in front before the optical film is stacked, and the relative brightness on the 60° side is more than 14% of the relative brightness in front.

2. The contrast-improving optical film according to claim 1, wherein the high-refractive-index layer has a refractive index of 1.57 to 1.70, and the low-refractive-index layer has a refractive index of 1.42 to 1.

50.

3. A polarizing plate comprising the contrast-improving optical film according to claim 1 or 2.

4. A display device comprising a polarizing plate according to claim 3.

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