KR101481175B1 - Prism sheet - Google Patents

Abstract

The present invention relates to an optical film having a structured surface, in which a lenticular pattern is formed and a lenticular pattern in which a single lentic pattern and two lentic patterns are superimposed are mixed, And an optical film having a wide viewing angle.

Description

Optical films having structured surfaces {Prism sheet}

The present invention relates to an optical film having a structured surface.

BACKGROUND ART A backlight unit (BLU) widely used in a liquid crystal display uses a light source such as a cold cathode fluorescent lamp (CCFL) to sequentially pass light emitted from a light guide plate, a light diffusion plate, and a prism sheet, . The light emitted from the light source is transmitted through the light guide plate so as to be distributed over the entire surface of the liquid crystal panel in a planar shape. The light source passing through the light guide plate can obtain a uniform light intensity over the entire screen through the light diffusion plate. And performs a light path control function for converting light rays in various directions through the diffusion sheet to a range of viewing angles suitable for an observer to recognize an image. In addition, a reflection plate is provided at the lower portion of the light guide plate to increase the utilization efficiency of the light source by allowing light that is not transmitted to the liquid crystal panel to be reflected and used again.

In addition, many kinds of plates or films are used in order to allow the maximum amount of light generated from the light source to reach the liquid crystal device.

The light diffusing plate serves to provide uniformity of luminance of the light emitted from the light source lamp and to conceal the bright line of the lamp. It also serves as a support for the above-mentioned various optical films. To this end, the light diffusing plate is doped with various light diffusers, which cause light refraction, scattering, reflection phenomenon, and diffusion effect.

Various materials such as a light diffusion film and a prism film should be mounted so as to collect a large amount of light from the light diffusing plate to the front. Such a multi-layered material raises a problem that the unit price is increased and the productivity is lowered have.

On the other hand, the prism sheet plays an important role in improving the luminance by controlling the path of the light so that the light deviates from the field of view axis to the field of view axis.

The prism sheet has a structure in which a plurality of three-dimensional patterns are repeatedly formed. For example, a three-dimensional pattern of a triangular cross-sectional shape is repeated to form a bone and a peak, thereby maximizing the condensing effect in the prism mountain, have.

However, as the front luminance increases, the half-value angle becomes relatively narrow and the viewing angle characteristic such as a cut-off phenomenon in which the luminance at a specific viewing angle is rapidly lowered occurs. Also, due to the pattern, a bright line was visible. In order to conceal it and to compensate for the viewing angle, additional protective film had to be used.

In view of the above, Korean Patent Laid-Open Publication No. 2006-665871 discloses a backlight assembly capable of obtaining a high luminance characteristic by forming a random microlens array on one side of a prism sheet.

1, the prism sheet includes a lens surface (i.e., a pattern layer) on which a microlens array is randomly arranged on a base layer 10 And the light incident on the lens surface is refracted in various directions so that uniform optical characteristics can be obtained over a wide range and a wide viewing angle characteristic can be ensured. In addition, when lenses are arranged with lenses having different sizes, it is also described that, when two or more sheets of the same sheet are laminated, a moire phenomenon can be prevented, which is an optical phenomenon in which a pattern such as ripples is formed on a screen .

However, when the microlenses are arranged at random, the gap between the lens and the lens is kept different from each other, so that there is a problem that the bright line can not be sufficiently covered, and furthermore, the brightness and the viewing angle are not sufficiently improved.

The present invention provides an optical film having a multi-type lens-like structure and having a single lens-like pattern and a plurality of lens-like patterns superimposed on each other, .

It is an object of the present invention to provide an optical film having excellent hiding properties against bright lines and having improved viewing angle and brightness.

In one embodiment of the present invention, a patterned layer having a structured surface and having a transparent polymer composition; In an optical film comprising a substrate layer adjacent a flat surface of a pattern layer, the pattern layer has a structured surface in which a plurality of lens-like patterns are formed in a continuous phase, wherein a single lens-like pattern and two lens- Shaped pattern in which two lenticular patterns are overlapped, a virtual circle is drawn along a cross section taken along the apex of each lenticular pattern, and the circle is adjacent to the base layer And the radius of the adjacent lenticular pattern is defined as R2 and the line passing through the half-diameter point formed by each pattern adjacent to the base layer is defined as L R1, R2 and L satisfy the following equations (1) and (2).

Equation 1

5 mu m < R1 or R2 < 80 mu m

Equation 2

| R1 - R2 | <L <(R1 + R2)

In the optical film according to one embodiment of the present invention, a lens-like pattern in which two lens-like patterns are superimposed is formed by drawing a virtual circle along a cross section about an apex and drawing a tangent line on the surface adjacent to the base layer The inclination angle &amp;thetas; with the base layer may satisfy the following expression (3).

Equation 3

90 &lt; [theta] &lt; 180

In the optical film according to one embodiment of the present invention, R1 and R2 may be the same or different from each other.

In the optical film according to one embodiment of the present invention, the lenticular pattern in the form of overlapping two lens-like patterns may be formed at a ratio of 50 to 95% with respect to the total pattern layer area.

According to one embodiment of the present invention, by partially arranging a lenticular pattern in which two lenticular patterns are superimposed on a pattern layer, it is possible to provide an optical film having an improved hiding property to a bright line and a wider viewing angle.

In addition, it is possible to provide an optical film having no problem in exerting a function inherent to a prism sheet by satisfying not only an obscuration to a bright line and an improvement in a viewing angle but also an appropriate brightness.

As a result, in the optical sheet assembly for backlight, the protective film added to compensate for the concealment of the prism sheet and to compensate for the viewing angle can be omitted, so that an increase in cost due to the use of the additional optical film can be suppressed and the productivity can be improved.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

An optical film, usually comprising an optical structural surface, is composed of a substrate layer and a pattern layer, which has a structured surface and is made of a transparent polymer composition. In particular, the structuring generally has a structure in which a plurality of three-dimensional patterns are repeatedly formed to repeat the bone and the peak.

FIG. 2 is a perspective view of the optical film according to the present invention, FIG. 3 is a sectional view, and FIG. 4 is a partially enlarged sectional view.

2 to 4, the optical film according to one embodiment of the present invention comprises a base layer 100 and a pattern layer 200, and the pattern layer has a single lenticular pattern 201 and two And the lenticular pattern 202 having the overlapped shape of the lenticular pattern has a mixed structured surface. In particular, the lenticular pattern 202 in which two lenticular patterns are superimposed on each other in the pattern layer 200 of the optical film of the present invention is obtained by drawing a virtual circle along a cross section about the apex of each lentic pattern, The radius of one of the lens-shaped patterns formed adjacent to the base layer is represented by R1, the radius of the adjacent lens-shaped pattern is represented by R2, And L are formed so as to satisfy the following equations (1) and (2).

Equation 1

5 mu m &lt; R1 or R2 &lt; 80 mu m

Equation 2

| R1 - R2 | <L <(R1 + R2)

If the value of R1 or R2 is as small as 5 mu m or less, the degree of luminance improvement may be small, and if it is larger than 80 mu m, the appearance may be disadvantageous.

If the L value is less than the absolute value of R1-R2, the degree of brightness improvement decreases as the two hemispheres overlap, and when the total value of R1 and R2 is larger than the sum of R1 and R2, the concealment capability may deteriorate.

2 to 4, when a single lens-shaped pattern 201 and two lens-like patterns have a structured surface in which an overlapped type of lens-like pattern 202 is mixed, light incident into the lens pattern The angle of scattering or scattering is widened as compared with the case of using only a single lens-shaped pattern, so that the viewing angle can be widened and the concealability can be improved. In addition, brightness can be improved by exhibiting a light-converging function inherent to the lens-shaped pattern.

Meanwhile, in the optical film according to one embodiment of the present invention, a single lenticular pattern 201 and / or a lenticular pattern 202 in which two lens-like patterns are superimposed are formed along a section along an apex The inclination angle &amp;thetas; with the base layer formed by drawing a virtual circle and forming a tangent line on the surface adjacent to the base layer may satisfy the following expression (3).

Equation 3

90 &lt; [theta] &lt; 180

If the value of? Is smaller than 90 占 the unnecessary light scattering reduces the degree of brightness enhancement and may be disadvantageous in view angle.

In the optical film according to one embodiment of the present invention, R 1 and R 2 may be the same or different from each other. In other cases, when two or more optical films according to the present invention are laminated and used, It is advantageous in that it can prevent a moiré phenomenon which is an optical phenomenon that occurs, and in the case of the same, it can be advantageous in terms of luminance improvement.

Also, it is preferable that the lens-shaped pattern 202 in which two lens-like patterns are overlapped in the pattern layer 200 of the present invention is formed at 50 to 95% of the total area of the pattern layer, It may be advantageous in terms of reinforcement.

On the other hand, the transparent polymer composition constituting the prism layer is not particularly limited, and conventionally known resins used for a prism sheet or a prism film can be used. For example, a composition comprising a monomer or oligomer mixture for ultraviolet polymerization and a photoinitiator.

Further, in the optical film having the optical structure surface of the present invention, the base layer may have a thickness of about 10 to 400 탆, and the base layer may be a conventional prism sheet or a sheet made of a transparent resin used for a prism film . For example, a polyethylene terephthalate film, a polycarbonate film, a polypropylene film, a polyethylene film, a polystyrene film or a polyepoxy film can be given.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Do.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the scope of the present invention is not limited to these Examples.

&Lt; Comparative Example 1 &

A polyethylene terephthalate film was used as a substrate layer, and 80 parts by weight of low refractive acrylate, 15 parts by weight of 2-phenylethyl methacrylate, 3 parts by weight of 1,6-hexanediol acrylate, 2 parts by weight of BAPO- An optical film in which a prism layer was formed so as to have a structured surface on which a random microlens array pattern arranged as shown in Fig. 1 was formed was fabricated.

At this time, the lens diameter was adjusted so that the number of lenses of the microlens array was 34 per 300 mu m square.

&Lt; Example 1 >

2 to 4, a part of the pattern layer is formed into a lenticular pattern 202 in which two patterns are superimposed on each other to form a single lens pattern ( 201 and a patterned layer 202 in which two patterns were superimposed on each other.

At this time, in the lenticular pattern 202 having the two patterns superimposed on each other, a pattern was formed such that R1 and R2 were both 60 mu m and L was 115 mu m.

At this time, the angle?

In addition, the lenticular pattern 202 in the form of overlapping two lens-like patterns has 50 to 80% of the total pattern layer area.

&Lt; Examples 2 to 16 >

As shown in the following Table 1, in the same manner as in Example 1 except that R1, R2 and L, and a pattern layer were formed while adjusting the areas where the two types of lenticular patterns were overlapped, An optical film was produced.

&Lt; Comparative Examples 2 to 5 >

An optical film was prepared in the same manner as in Example 1, except that a pattern layer was formed while controlling R1, R2 and L as shown in Table 1 below.

R1 (占 퐉) R2 (占 퐉) L (占 퐉) θ (°) The area ratio (%) of the lenticular pattern having the shape in which the two lens-like patterns are superposed Example 1 60 60 115 95 70 Example 2 60 60 110 105 70 Example 3 60 60 115 105 70 Example 4 60 60 110 95 70 Example 5 30 30 55 95 50 Example 6 30 30 50 105 50 Example 7 30 30 55 105 50 Example 8 30 30 50 95 50 Example 9 40 70 105 95 80 Example 10 40 70 100 105 80 Example 11 40 70 105 105 80 Example 12 40 70 100 95 80 Example 13 20 70 85 95 60 Example 14 20 70 80 105 60 Example 15 20 70 85 105 60 Example 16 20 70 80 95 60 Comparative Example 1 30 30 75 85 0 Comparative Example 2 3 3 10 85 0 Comparative Example 3 20 40 80 75 0 Comparative Example 4 90 90 190 80 0 Comparative Example 5 20 80 120 70 0

The viewing angles, hiding properties and luminance were measured for each of the optical films obtained according to the examples and comparative examples, and the results are shown in Table 2 below.

The specific evaluation method is as follows.

(1) Brightness

The brightness was measured using a BM-7 from Topcon Co. The values were obtained by removing all sheets except for the reflective sheet and the diffuser plate in a backlight unit (BLU, 24 inch) , The brightness of each example and the comparative example was evaluated with a relative value when the brightness of the combination of the optical sheets including the comparative example 1 was taken as 100. [

(2) Viewing angle

The viewing angles were measured using a BM-7 from Topcon Co. The values were obtained by removing all sheets except for the reflective sheet and the diffuser plate in the backlight unit (BLU, 24 inches) and measuring &quot; one sheet of light diffusing film / (Viewing angle = 0 ° position) according to each combination of optical sheets, a viewing angle at a position having a luminance value half of the luminance of the front (viewing angle = 0 ° position) luminance was measured.

(3) Hiding property

The concealability was measured using BM-7 of Topcon Co. The values were obtained by removing all sheets except for the reflective sheet and the diffuser plate in the backlight unit (BLU, 24 inch) "Is used to measure the hiding power of the optical film by the ratio of the fluctuation value of the luminance to the maximum value of the measured luminance value by using the step point measuring method in the vertical direction of the BLU according to the combination of the respective optical sheets Specifically, it is as follows.

(%) = (Wave width of luminance) / (measured maximum luminance value) * 100

= (Maximum value of luminance waves - minimum value of luminance waves) / (maximum luminance value measured) * 100

division Viewing angle (°) Concealability Brightness (%) Example 1 50 28 115 Example 2 51 26 112 Example 3 54 27 110 Example 4 50 29 118 Example 5 51 32 110 Example 6 52 33 108 Example 7 54 31 106 Example 8 50 29 113 Example 9 52 31 107 Example 10 53 32 105 Example 11 51 30 104 Example 12 50 32 109 Example 13 54 29 105 Example 14 51 28 103 Example 15 52 30 102 Example 16 53 27 107 Comparative Example 1 49 35 100 Comparative Example 2 53 38 75 Comparative Example 3 47 42 83 Comparative Example 4 45 56 95 Comparative Example 5 51 48 88

From the results shown in Table 2, it can be seen that the hiding power, viewing angle and luminance of the optical film provided by the present invention are excellent.

1 is a perspective view of a conventional prism sheet;

2 is a perspective view of a prism sheet according to an embodiment of the present invention;

3 is a cross-sectional view of a prism sheet according to one embodiment of the present invention.

Claims (4)

A pattern layer having a structured surface and having a transparent polymer composition; In an optical film comprising a base layer adjacent to a flat surface of a pattern layer, The pattern layer has a structured surface in which a plurality of lenticular patterns are formed in a continuous phase, wherein a single lenticular pattern and a lenticular pattern in which two lentic patterns are superimposed are mixed, Shaped pattern is defined as a radius of one of the lens-shaped patterns formed adjacent to the base layer by drawing a virtual circle along a cross section taken along the apex of each lens-shaped pattern, and R1 R2 is a radius of the lenticular pattern, and L is a line connecting the 1/2 diameter points formed adjacent to the base layer, R1, R2, and L satisfy the following equations (1) and (2) Wherein the lens-like pattern in which the two lens-like patterns are overlapped is formed at a ratio of 50 to 95% with respect to the total area of the pattern layer. Equation 1 5 mu m &lt; R1 or R2 &lt; 80 mu m Equation 2 | R1 - R2 | <L <(R1 + R2) 2. The method of claim 1, wherein the lenticular pattern in which two lenticular patterns are superimposed is formed by drawing a virtual circle along a cross section about an apex, And satisfies the following expression (3). Equation 3 90 &lt; [theta] &lt; 180 The optical film according to claim 1, wherein R1 and R2 are the same or different from each other. delete

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