KR20150035403A - Condensing Type Optical Sheet - Google Patents

Abstract

The present invention relates to a condensing type optical sheet and, more specifically, to a condensing type optical sheet to improve color uniformity and to minimize a decrease in brightness through the curvature of the cross-sectional slope of a three-dimensional structure on the structural layer of the condensing type optical sheet. According to the present invention, the condensing type optical sheet comprises: a base material layer; and the structural layer which is formed on one or both sides of the base material and on which a plurality of three-dimensional structures are arranged. The three-dimensional structure of the structural layer has a streamlined longitudinal section and includes a slope part extending in both directions on the basis of a peak point.

Description

Condensing Type Optical Sheet

The present invention relates to a light-converging type optical sheet used in a liquid crystal display.

As the industrial society develops into a highly information age, the importance of electronic display devices as media for displaying and transmitting various information is increasing day by day. (PDP), a field emission display (FED), and an organic electroluminescent display (EL) have been widely used because of the limitations of the conventional CRT (Cathode Ray Tube) Various flat panel display devices have been replaced. Among such flat panel display devices, in particular, a liquid crystal display device (LCD) has been researched and developed as a technology-intensive device in which liquid crystal and semiconductor technologies are combined, thin, light and low in power consumption In addition to the areas where liquid crystal displays have been widely used in the past, such as notebook computers, monitors for desktop computers, portable personal communication devices (PDAs and cellular phones), and the like, And it is widely regarded as a new display device that can replace the CRT, which is a synonym for display.

Since the liquid crystal display (LCD) device can not emit light, a separate light source is provided on the back surface of the device, and light and shade are controlled by controlling the intensity of the light passing through the liquid crystal provided in each pixel. . More specifically, the liquid crystal display device is a device for adjusting the transmittance of light using the electrical characteristics of a liquid crystal material, and is a device that emits light from a light source lamp on the back side of the device, passes through various functional prism films or sheets, An indirect light emitting method of implementing an image by controlling the light and shade of each pixel by means of an electric method by allowing light to pass through a color filter to realize colors of red, blue, and green (R, G, B) As a display device, a light emitting device that provides a light source is an important part for determining the image quality such as brightness and uniformity of a liquid crystal display device.

BACKGROUND ART [0002] A backlight unit (BLU) is widely used as the light emitting device. Generally, light emitted by using a plurality of light sources such as a cold cathode fluorescent lamp (CCLF) is sequentially diffused, And passes through a sheet such as a sheet to reach the liquid crystal panel. Here, the diffusion sheet has a function of obtaining a uniform light intensity over the entire surface of the screen, and also functions to conceal an apparatus such as a light source mounted under the diffusion sheet from being seen from the front surface. On the other hand, the prism sheet performs a light path control function for converting light rays in various directions through the diffusion sheet into a range of a viewing angle ([theta]) suitable for an observer to recognize an image.

On the other hand, the demand for high quality and high reliability products in the recent display market is increasing, and in particular, the uniformity of color according to the visual field is becoming an important factor.

In this regard, in the case of a conventional optical sheet in which the apex angle of the prism pattern formed on the entire surface of the optical sheet is 90 degrees and the hypotenuse is linear, the apex angle is designed to be obtuse to improve the uniformity of color according to the visual field, An attempt was made to give a round.

However, such a conventional art has a significant deterioration in luminance and an improvement in the uniformity of color tones, such as a uniformity of color tones according to viewing angles, to 1/1000.

To improve this, Korean Patent Laid-Open Publication No. 10-2011-0011931 (published on Mar. 2, 2011) filed by the present applicant discloses that the three-dimensional structure of the structure layer is streamline in the longitudinal section and includes an inclined portion with respect to one peak point, The inclined portion describes an optical sheet having a shape that is a part of imaginary first and second circles. Such an optical sheet was advantageous in terms of not causing a yellow band or a rainbow phenomenon.

SUMMARY OF THE INVENTION The present invention aims to provide a light-converging type optical sheet capable of minimizing a luminance drop and improving color uniformity according to visual field.

Accordingly, the present invention provides, as a first preferred embodiment, a substrate layer; And a structural layer formed on one side or both sides of the substrate layer and having a plurality of three-dimensional structures arranged therein, wherein the three-dimensional structure of the structure layer has a streamline profile in its longitudinal direction and has a slope extending in both directions with respect to one peak point Wherein the inclined portion is symmetrical or asymmetric with respect to a peak point and each inclined portion is a part of a circumference of a superposed imaginary first ellipse and a second ellipse, And the shape of the light-converging optical sheet is defined by the light-converging optical sheet.

<Formula 1>

In the above formula, x and y are each a real number, and a and b are integers satisfying 0 < a < b < 10, and a: b is 2: 1 to 100:

The inclined portion according to the embodiment may include one contact among the contacts formed by overlapping the first ellipse and the second ellipse as peak points.

The inclined portion according to the embodiment may be a part of the first ellipse and the second ellipse adjacent to the hypotenuse of the triangle formed by connecting the three contacts of the contacts formed by overlapping the first ellipse and the second ellipse.

The first ellipse and the second ellipse according to the above embodiment may be such that the long axes of the first ellipse and the second ellipse are orthogonal to each other, and the centers of the respective long axes are superimposed.

The center of the base of the three-dimensional structure according to the embodiment may be the center of the intersection of the long axes of the first ellipse and the second ellipse.

The base layer according to the embodiment may be formed of a resin selected from a polyethylene terephthalate resin, a polymethyl methacrylate resin, a polycarbonate resin, a polypropylene resin, a polyethylene resin, a polystyrene resin and a styrene-acrylic copolymer resin.

The structural layer according to this embodiment may be formed of a resin selected from among ultraviolet curable resin or polymer resin including a thermosetting resin.

The present invention also provides, as a second preferred embodiment, a backlight unit assembly including the light-converging optical sheet.

According to the present invention, by optimizing the curvature of a pattern including a streamline formed in the structure layer of the light-converging optical sheet, it is possible to provide a light-converging type optical sheet having improved uniformity of color tone according to a viewing angle .

FIG. 1 shows an elliptic curve according to Equation 1 defining the shapes of the first ellipse and the second ellipse associated with the inclination curvature of the three-dimensional structure formed on the structure layer of the light-converging optical sheet according to the present invention.
2 is a cross-sectional view of a three-dimensional structure formed on the structure layer of the light-converging optical sheet according to the present invention.
FIG. 3 is a schematic view of a three-dimensional structure formed by a first ellipse and a second ellipse in the light-converging optical sheet according to the present invention.
FIG. 4 is a schematic view showing a first ellipse and a second ellipse orthogonally overlapping in the light-converging type optical sheet according to the present invention.
5 is a scanning electron microscope (SEM) photograph (magnification: (a) Cross section x 500, Left Slop or Right Slop x) of a cross section of a three-dimensional structure formed on the structure layer of the light- (B) Cross section × 500, Left Slop or Right Slop × 3,000 (c) Left × 4,000, Right × 500 (d) Left × 4,000, Right × 500 (e) Left × 1,500, Right × 300 (f) left x 1,500, right x 500).
FIG. 6 is a CIE chromaticity diagram of a color coordinate (u ', v') as a reference for measuring the color uniformity of the light-converging optical sheet in the present invention.
7 is a graph showing the results of measurement of color balance uniformity measured on the light-convergence type optical sheets of Example 1 (B), Example 2 (C) and Ref. (A).
8 shows an example of the inclined portion of the three-dimensional structure formed by the first ellipse and the second ellipse in the light-converging optical sheet according to the present invention.

Hereinafter, the present invention will be described in more detail.

The present invention relates to a substrate layer; And a structural layer formed on one side or both sides of the substrate layer and having a plurality of three-dimensional structures arranged therein, wherein the three-dimensional structure of the structure layer has a streamline profile in its longitudinal direction and has a slope extending in both directions with respect to one peak point Wherein the inclined portion is symmetrical or asymmetric with respect to a peak point and each inclined portion is a part of a circumference of a superposed imaginary first ellipse and a second ellipse, And the shape of the light-converging optical sheet is defined by the light-converging optical sheet.

<Formula 1>

In the above formula, x and y are each a real number, and a and b are integers satisfying 0 < a < b < 10, and a: b is 2: 1 to 100: That is, an ellipse may be defined by the values of a and b in the x-y coordinate system including the x-axis and the y-axis.

The first ellipse and the second ellipse may have an elliptical shape as shown in Fig. 1 according to Equation (1).

The inclined portion may be formed by including one contact among the contacts formed by overlapping the first ellipse and the second ellipse as peak points.

For example, as shown in FIG. 8, one of the four contacts formed by superimposing the first ellipse and the second ellipse is regarded as a peak point, and the peak point and the center of the first ellipse and the second ellipse Can be connected to form an inclined portion.

The contact point of one of the four contact points formed by superimposing the first ellipse and the second ellipse is set as a peak point and the distance between the peak point and another contact point and a peak point and the circumference of the first ellipse and the second ellipse Any one of them may be connected to form an inclined portion.

The inclined portion may be formed by connecting three contact points out of the four contact points formed by overlapping the first ellipse and the second ellipse.

In the light-converging optical sheet of the present invention, the three-dimensional structure 10 formed on the structure layer has, as shown in Fig. 1, a longitudinal section of which has a streamline shape and which is inclined at two peak- And the slope portion 12 may be symmetrical or asymmetric with respect to the peak point 11. [ In the case where the inclined portion 12 is symmetrical, each first ellipse and second ellipse extending including each inclined portion have the same shape, and when the inclined portion 12 is asymmetric, the first and second ellipses have different shapes .

As shown in FIG. 3, the inclined portion 12 of the three-dimensional structure is a part of the circumference of the overlapping imaginary first ellipse 21 and second ellipse 22, The shape of the two ellipses 22 can be defined by Equation (1).

<Formula 1>

In the above formula, x and y are each a real number, and a and b are integers satisfying 0 < a < b < 10, and a: b is 2: 1 to 100:

If a = b in the above Equation 1, the circle is not an ellipse, and if a = ∞ or b = ∞, the inclined portion of the three-dimensional structure may be a nonlinear straight line.

On the other hand, since the inclined portion is streamlined and is a part of the circumference of the first ellipse and the second ellipse, the curvature can be determined by the shape of the ellipse.

The shape of the first ellipse and the second ellipse may vary depending on the value of a: b in the formula 1, and a: b may be from 2: 1 to 100: 1. When a: b is less than 2: 1, There is a serious problem. When the ratio is more than 100: 1, there is a problem in that the uniformity of color tone according to the visual field is not improved. Preferably, a: b is from 2: 1 to 8: 1.

3, the inclined portion 12 includes any three contacts A, B, and C among the four contacts formed by overlapping the first ellipse 21 and the second ellipse 22, May be a part of the first ellipse and the second ellipse adjacent to the hypotenuse D of the triangle formed by connecting the first ellipse and the second ellipse.

4, each of the first ellipse 21 and the second ellipse 22 may be one in which the long axes 23 are orthogonal to each other, and when the long axes intersect at 90 degrees or less, Becomes an acute angle prism and becomes an obtuse angle prism when it is 90 degrees or more. It is advantageous in terms of luminance improvement that the prism pattern is formed so that the long axes 23 are orthogonal to each other and overlapped with each other, as compared with an acute angle or an obtuse angle.

In addition, the center of the base of the three-dimensional structure and the center of the intersection of the long axes of the first ellipse and the second ellipse may coincide with each other.

On the other hand, the base layer may be formed of a resin selected from a polyethylene terephthalate resin, a polymethyl methacrylate resin, a polycarbonate resin, a polypropylene resin, a polyethylene resin, a polystyrene resin and a styrene-acrylic copolymer resin.

Further, the structure layer is not particularly limited as long as it is a curable resin and is a light-transmitting material. For example, unsaturated fatty acid esters, aromatic vinyl compounds, unsaturated fatty acids and their derivatives, unsaturated dibasic acid, and unsaturated dibasic acid can be used without limitation as long as they are selected from among ultraviolet curable resins and polymer resins including thermosetting resins. And derivatives thereof, vinyl cyanide compounds such as methacrylonitrile, and the like. At this time, the polymer resin to be used can be controlled in consideration of the refractive index with respect to the base layer.

The thickness of the base layer may be 10 to 1000 占 퐉, preferably 15 to 400 占 퐉, from the viewpoint of preventing loss of transmitted light so as to be advantageous in terms of mechanical strength, thermal stability and flexibility.

On the other hand, although not shown, when a structural layer is formed on one side of the base layer, the bottom layer may be cured on the other side of the base layer, and organic or inorganic particles may be used as known light diffusing particles .

The present invention can provide a backlight unit assembly including the above-described light-converging optical sheet, and can provide a backlight unit assembly in which the light-converging optical sheet is formed on the uppermost layer and does not further include an additional protective sheet .

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 the following Examples.

Example 1

A polyethylene terephthalate film T600 (Mitsubishi) (refractive index: 1.49) of 250 mu m was used as the substrate layer.

In order to design the three-dimensional structure of the structure layer, the longitudinal section of the three-dimensional structure is streamlined as shown in FIG. 1, and the inclined portion is designed to include one peak point and a symmetrical center around the peak point.

At this time, the curvature of the streamlined inclined portion is set so that the curvature of the curved portion of the curved portion adjacent to the two hypotenuses of the triangle formed by connecting the three contact points formed by orthogonalizing the long axes of the first ellipse and the second ellipse of the same shape and size defined by Equation 1 &lt; / RTI &gt; and 2 &lt; nd &gt; At this time, in Equation 1, a: b was set to 6: 1.

The three-dimensional structure of the structure layer was arranged linearly.

A mold with a three-dimensional structure designed as described above was fabricated, and a structure layer (refractive index: 1.60) formed by ultraviolet curing the acryl-based ultraviolet-curable resin composition (refractive index: 1.57) was formed to prepare a light-converging type optical sheet.

The cross-section of the obtained light-converging type optical sheet was observed using a scanning electron microscope (SEM), and the results are shown in Fig. 5 (a).

Example 2

A light-converging optical sheet was prepared in the same manner as in Example 1, except that a: b was changed to 2: 1 in the formula (1).

The cross section of the obtained light-converging type optical sheet was observed using a scanning electron microscope (SEM), and the result is shown in Fig. 5 (b).

Example 3

A light-convergence type optical sheet was prepared in the same manner as in Example 1 except that a: b was changed to 4: 1 in Formula 1 (not shown).

Example 4

A light-convergence type optical sheet was prepared in the same manner as in Example 1 except that a: b was changed to 8: 1 in the formula (1) (not shown).

Comparative Example 1

A light-converging type optical sheet was prepared in the same manner as in Example 1, except that the three-dimensional structure of the structure layer was a triangular prism having a triangular-shaped apex angle of 80 degrees.

The cross-section of the obtained light-converging type optical sheet was observed using a scanning electron microscope (SEM), and the result is shown in Fig. 5 (c).

Comparative Example 2

A light-converging optical sheet was prepared in the same manner as in Example 1, except that the three-dimensional structure of the structure layer was an obtuse-angle prism having a triangular-shaped obtuse angle (100 degrees) at its cross-section.

The cross section of the obtained light-converging type optical sheet was observed using a scanning electron microscope (SEM), and the result is shown in Fig. 5 (d).

Comparative Example 3

A light-converging type optical sheet was prepared in the same manner as in Example 1, except that a: b was changed to 1.5: 1 in the formula (1).

The cross section of the obtained light-converging type optical sheet was observed using a scanning electron microscope (SEM), and the result is shown in Fig. 5 (e).

Comparative Example 4

A light-converging type optical sheet was prepared in the same manner as in Example 1, except that a: b was changed to 200: 1 in the formula (1).

The cross section of the obtained light-converging type optical sheet was observed using a scanning electron microscope (SEM), and the result is shown in Fig. 5 (f).

Comparative Example 5

A light-converging optical sheet was prepared in the same manner as in Example 1 except that a: b was changed to 1: 1 in the formula (1) (not shown).

That is, in the three-dimensional structure including the inclined portion whose longitudinal cross-section is streamlined and which is symmetrical about one peak point and the peak point, the streamlined portion is a part of the circular circumference, not the ellipse.

The light-convergence type optical sheets prepared in Examples and Comparative Examples were measured for brightness and color uniformity in the following manner, and the results are shown in Table 1.

(1) Luminance measurement

A DBEF (Dual Brightness Enhancement Film), a focusing type optical sheet (Example or Comparative Example) and a diffusion film were sequentially laminated on a backlight unit (BLU) (27-inch LED 1vertical) ), And the average value was calculated.

The luminance of the prism film was set as a reference (Ref.), And the relative luminance value to the above Ref. Was measured. At this time, the prism formed on the prism film has a vertex angle of 90 degrees, a curvature R of 0, and a pitch of 50 mu m.

(2) Measurement of color uniformity

A DBEF (Dual Brightness Enhancement Film), a light-converging optical sheet (Example or Comparative Example) and a lower diffusion film (KOLON, XC210) were sequentially laminated on a BLU (27 inch LED 1vertical) , TOPCON Co., Ltd.), and then converted into u 'and v' color coordinates using the following equation (2) after measurement of x and y color coordinates.

<Formula 2>

In the formula (2), in the XYZ color space coordinate system of the CIE, the amounts of the three primary colors to be mixed in order to produce the same color as the given color are referred to as X, Y, and Z (three-pole value).

The X, Y, and Z can be represented by x and y using the following equation (3).

<Formula 3>

The color can be obtained by applying the color coordinates (u ', v') obtained as described above to the CIE chromaticity diagram as shown in FIG.

On the other hand, the color uniformity is obtained by the following equation (4) with the color coordinate of the prism film as a reference (Ref.), And the color uniformity (Δu ', Δv') becomes better as the minus value becomes larger.

<Formula 4>

Color uniformity = (color coordinate of Ref.) - (color coordinate of the example or comparative example)

Luminance
(%) Color uniformity Horizontal Vertical Δu Δv Δu Δv Ref. 100 Ref. Ref. Ref. Ref. Example 1 99 -0.0005 -0.0007 0 0 Example 2 97 -0.0006 -0.0029 0 -0.0008 Example 3 98 -0.0005 -0.0018 0 -0.0002 Example 4 99 -0.0004 -0.0003 0.0001 0 Comparative Example 1 90 -0.0004 -0.0008 0.0003 -0.001 Comparative Example 2 94 -0.0011 -0.0012 0.0012 0.0002 Comparative Example 3 95 0.0009 -0.0013 0.0017 -0.0011 Comparative Example 4 89 0.0001 -0.0022 0.0024 -0.0019 Comparative Example 5 93 -0.0005 -0.0028 0.0001 -0.0004

As a result of the physical property measurement, it can be seen that the color uniformity is improved when the brightness reduction is minimized in the light-converging type optical sheets of Examples 1 to 4 as shown in Table 1. [

Referring to FIG. 7, a part of color hue uniformity measurement results are shown, where A represents Ref., And B represents Example 1 and C represents the color uniformity measurement result of Example 2.

However, in Comparative Example 1, the color uniformity was excellent, but the luminance decline was significant.

In addition, in Comparative Examples 2 to 4, the luminance decreased and the Vertical Δu 'value was increased, and in Comparative Example 3, both Horizontal and Vertical Δu' were found to increase.

10: three-dimensional structure
11: peak, 12: inclined portion
21: first ellipse, 22: second ellipse, 23: long axis

Claims (8)

A base layer; And a structural layer formed on one or both surfaces of the substrate layer and having a plurality of steric structures arranged therein,
Wherein the three-dimensional structure of the structure layer has an inclined portion whose longitudinal direction is streamlined and extends in both directions with respect to one peak point,
Wherein the inclined portion is symmetrical or asymmetric with respect to a peak point, each inclined portion is a part of a circumference of an overlapping virtual first ellipse and a second ellipse,
Wherein the first ellipse and the second ellipse each have a shape defined by Equation (1).
<Formula 1>

In the above formula, x and y are each a real number, and a and b are integers satisfying 0 < a < b < 10, and a: b is 2: 1 to 100: The method according to claim 1,
Wherein the inclined portion includes one contact point among the contacts formed by overlapping the first ellipse and the second ellipse as peak points. The method according to claim 1,
Wherein the inclined portion is a portion of a first ellipse and a second ellipse adjacent to a hypotenuse of a triangle formed by connecting three contact points of the contacts formed by overlapping the first ellipse and the second ellipse. The method of claim 3,
Wherein the first ellipse and the second ellipse each have a major axis that is orthogonal to each other, and the centers of the major axes are superposed on each other. The method according to claim 1,
Wherein the center of the base of the steric structure and the center of the major axis of the first ellipse and the major axis of the second ellipse coincide with each other. The method according to claim 1,
Wherein the base layer is formed of a resin selected from the group consisting of a polyethylene terephthalate resin, a polymethyl methacrylate resin, a polycarbonate resin, a polypropylene resin, a polyethylene resin, a polystyrene resin and a styrene-acrylic copolymer resin. The method according to claim 1,
Wherein the structure layer is formed of a resin selected from a UV-curable resin or a polymer resin including a thermosetting resin. A backlight unit assembly comprising the light-converging optical sheet according to any one of claims 1 to 7.

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