KR102091261B1 - Condensing Type Optical Sheet - Google Patents

Abstract

The present invention relates to a condensing type optical sheet, and more particularly, to a condensing type optical sheet capable of improving color uniformity while minimizing decrease in luminance by curvature of a cross-sectional inclined portion formed in a structural layer of the condensing type optical sheet. It is about.

Description

Condensing Type Optical Sheet}

The present invention relates to a condensing type optical sheet used in a liquid crystal display.

As the industrial society develops into a high information age, the importance of an electronic display device as a medium for displaying and transmitting various information is increasing day by day. CRT (Cathode Ray Tube), which has been widely used in the related art, has limitations in installation space, so it is difficult to increase the size. Therefore, liquid crystal displays (LCDs), plasma display panels (PDPs), field emission displays (FEDs), and organic ELs It is being replaced by various flat panel display devices. Among these flat panel display devices, in particular, in the case of a liquid crystal display device (LCD), the structure and manufacturing technology have been researched and developed due to the advantages of being thin, light and low power consumption as a technology-intensive device in which liquid crystal and semiconductor technology are combined. In addition to the areas in which liquid crystal displays have been widely used, such as notebook computers, desktop computer monitors, and portable personal communication devices (PDAs and cell phones), large-sized technologies are gradually exceeding their limits, and high-definition (HD) TV-class CRT, which is synonymous with displays, has been spotlighted as a new display device that can be substituted for large TVs.

Since such a liquid crystal display (LCD) device cannot emit light itself, a separate light source is installed on the back of the device, and the intensity of the passing light is adjusted through the liquid crystal installed in each pixel to make it light and shade. Implement Looking at this in more detail, the liquid crystal display device is a device that controls the transmittance of light by using the electrical properties of the liquid crystal material, which emits light from a light source lamp on the back of the device and passes through various functional prism films or sheets to control uniformity and directionality. The indirect light emission method that realizes the image by passing light through the color filter to realize the colors of red, blue, and green (R, G, B), and controlling the light and shade of each pixel in an electric way. As a display device, a light emitting device that provides a light source is an important component for determining image quality such as luminance and uniformity of a liquid crystal display device.

As the light emitting device, a backlight unit (BLU) is widely used, and in general, light emitted using a plurality of light sources such as a cold cathode fluorescent lamp (CCLF) is sequentially diffuser, diffusion sheet, and prism. The sheet is passed through a sheet or the like to reach the liquid crystal panel. Here, the diffusion sheet performs a function of concealing such that a device such as a light source mounted on the bottom of the diffusion sheet is not visible from the front while allowing uniform light intensity to be obtained across the entire screen. On the other hand, the prism sheet performs a light path control function that allows light rays of various directions through the diffusion sheet to be converted into a viewing angle θ range suitable for an observer to recognize an image.

Meanwhile, in the recent display market, demand for high-quality and high-reliability products is increasing, and in particular, uniformity of color according to the field of view has emerged as an important factor.

In this regard, in the case of an existing optical sheet having a 90-degree apex angle and a hypotenuse straight on the front surface of the prism pattern formed on the front of the optical sheet, the apex angle is designed at an obtuse angle to improve the uniformity of color according to the field of view, or on the mountain of the prism pattern. An attempt was made to give a round.

However, such a conventional technique has a small effect of improving the uniformity of color, such as a significant decrease in luminance and a uniformity of color sense depending on a viewing angle, which is improved to 1/1000 level.

In order to improve this, in Korean Patent Application Publication No. 10-2011-0011931 (published on Feb. 09, 2011), which has been previously filed and published by the applicant, the three-dimensional structure of the structural layer has a streamlined longitudinal section and includes an inclined portion based on one peak point. The inclined portion describes an optical sheet having a shape that is a part of virtual first and second circumferences. This optical sheet was advantageous in terms of not generating a yellow band or a rainbow phenomenon.

The present invention is to provide a condensing type optical sheet capable of minimizing luminance degradation and improving color uniformity according to a visual field.

Accordingly, the present invention is a preferred first embodiment, the base layer; And a structural layer formed on one side or both sides of the base layer and having a plurality of three-dimensional structures arranged, wherein the three-dimensional structure of the structure layer has a longitudinal cross-section and a slope extending in both directions based on one peak point. It includes a portion, the inclined portion is symmetrical or asymmetrical with respect to the peak point, each inclined portion is a part of the circumference of the overlapping virtual first ellipse and the second ellipse, the first ellipse and the second ellipse are respectively equation 1 It provides a condensing type optical sheet characterized in that the shape is defined by.

<Equation 1>

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

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

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

Each of the first ellipse and the second ellipse according to the embodiment may be orthogonal to each major axis, and the center of each major axis may be overlapped.

The center of the base of the three-dimensional structure according to the embodiment may be the same as the center where the long axes of the first and second ellipses intersect each other.

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

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

The present invention also provides a backlight unit assembly including the condensing optical sheet as a second preferred embodiment.

According to the present invention, by optimizing the curvature of the pattern including the streamline formed on the structure layer of the light-converging optical sheet, it is possible to provide a light-converging optical sheet with improved brightness and uniformity of color according to the viewing angle while optimizing the curvature of the pattern. There is.

1 shows an elliptic graph by Equation 1 that defines the shapes of the first ellipse and the second ellipse associated with the curvature of the inclined portion of the three-dimensional structure formed in the structural layer of the condensing optical sheet according to the present invention.
Figure 2 shows the cross-sectional shape of the three-dimensional structure formed on the structural layer of the light-converging optical sheet according to the present invention.
Figure 3 shows a schematic diagram in which a cross section of a three-dimensional structure is formed by a first ellipse and a second ellipse in the condensing type optical sheet according to the present invention.
Figure 4 shows a schematic diagram of the first and second ellipses orthogonally overlap in the condensing optical sheet according to the present invention.
FIG. 5 is a scanning electron microscope (SEM) photograph of a cross-sectional structure formed in a structural layer of a condensing optical sheet according to an embodiment and a comparative example of the present invention (magnification: (a) Cross section × 500, Left Slop or Right Slop × 3,000; (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 × 1,500, Right × 500).
6 is a color coordinate (u ', v') CIE chromaticity diagram as a reference when measuring color uniformity for a condensing optical sheet in the present invention.
7 is a graph showing the measurement results of color uniformity measured for the light-converging optical sheets of Example 1 (B), Example 2 (C), and Ref. (A).
Figure 8 shows an example of the inclined portion of the three-dimensional structure formed by the first ellipse and the second ellipse in the condensing type optical sheet according to the present invention.

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

The present invention is a substrate layer; And a structural layer formed on one side or both sides of the base layer and having a plurality of three-dimensional structures arranged, wherein the three-dimensional structure of the structure layer has a longitudinal cross-section and a slope extending in both directions based on one peak point. It includes a portion, the inclined portion is symmetrical or asymmetrical with respect to the peak point, each inclined portion is a part of the circumference of the overlapping virtual first ellipse and the second ellipse, the first ellipse and the second ellipse are respectively equation 1 It relates to a condensing type optical sheet characterized in that the shape is defined by.

<Equation 1>

In the above formula, x and y are each a real number, a and b are integers where 0 <a <b <10, and a: b is 2: 1 to 100: 1. That is, an ellipse may be defined by a and b values in an x-y coordinate system including an x-axis and a 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 point among the contact points formed by overlapping the first ellipse and the second ellipse as a peak point.

For example, as shown in FIG. 8, any one of the circumferences of the peak point and the first ellipse and the second ellipse is regarded as one of four contact points formed by overlapping the first ellipse and the second ellipse as a peak point. Two of the can be connected to form a slope.

In addition, one of the four contacts formed by the overlapping of the first ellipse and the second ellipse is a peak point, and the peak point, another contact point and the peak point, and the circumference of the first ellipse and the second ellipse Any one may be connected to form an inclined portion.

Further, the inclined portion may be formed by connecting three contact points among 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 structural layer has an inclination extending in both directions based on one peak point 11, as shown in FIG. It includes a portion 12, the inclined portion 12 may be symmetrical or asymmetrical with respect to the peak point (11). When the inclined portions 12 are symmetric, each of the first ellipse and the second ellipse extending including the respective inclined portions is in the same shape, and in the case of asymmetric, the first oval and the second ellipse are in different shapes. It is the case.

The inclined portion 12 of the three-dimensional structure is a part of the circumferences of the superimposed virtual first ellipse 21 and the second ellipse 22, as shown in FIG. 3, and the first ellipse 21 and the 2 The shape of the ellipse 22 can be defined by Equation 1.

<Equation 1>

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

When a = b in Equation 1, a circle is formed instead of an ellipse, and when a = ∞ or b = ∞, the inclined portion of the three-dimensional structure may be a straight line rather than a streamline.

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, its 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 Equation 1 above, and a: b may be 2: 1 to 100: 1, and a: b is less than 2: 1, deteriorating luminance There is a severe problem, and if it is more than 100: 1, there is a problem that color uniformity according to the field of view does not improve. Preferably a: b is from 2: 1 to 8: 1.

Specifically, as shown in FIG. 3, the inclined portion 12 has any three contacts (A, B, C) among four contacts formed by overlapping the first ellipse 21 and the second ellipse 22 It may be part of the first ellipse and the second ellipse adjacent to the hypotenuse (D) of the triangle formed by connecting.

At this time, the first ellipse 21 and the second ellipse 22, as shown in Figure 4, each of the long axes 23 may be orthogonally overlapped, and if the long axis crosses less than 90 degrees prism pattern Becomes an acute angle prism and an obtuse angle prism when it is 90 degrees or more. When the prism pattern is formed so that the long axes 23 overlap orthogonally, it may be more advantageous in terms of luminance improvement than an acute angle or an obtuse angle.

In addition, the center of the base of the three-dimensional structure and the center where the long axes of the first ellipse and the second ellipse each intersect may be coincident.

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

In addition, the said structural layer is curable resin, and if it is a light transmissive material, it will not be specifically limited. That is, any resin selected from among polymer resins including UV curable resins or thermosetting resins can be used without limitation, for example, unsaturated fatty acid esters, aromatic vinyl compounds, unsaturated fatty acids and derivatives thereof, and unsaturated dibasic acids And its derivatives, vinyl cyanide compounds such as methacrylonitrile, and the like can be used. At this time, the polymer resin used may be adjusted in consideration of the refractive index with the base layer.

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

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

The present invention can provide a backlight unit assembly including the condensing optical sheet described above, and the condensing optical sheet is formed on the uppermost layer to provide a backlight unit assembly that does not further include an additional protective sheet. .

Hereinafter, the present invention will be described in more detail through examples, but the scope of the present invention is not limited to the following examples.

Example 1

As a base layer, a polyethylene terephthalate film T600 (Mitsubishi Co., Ltd.) having a thickness of 250 μm (refractive index: 1.49) was used.

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

At this time, the curvature of the inclined portion of the streamlined portion is a product adjacent to two hypotenuses of a triangle formed by connecting three contact points formed by orthogonalizing the long axes of the first and second ellipses of the same shape and size as defined by Equation 1. It was taken as part of the circumference of the ellipse and the second ellipse. At this time, in equation 1, a: b was set to 6: 1.

The three-dimensional structure of the structural layer was arranged in a linear fashion.

A mold having a three-dimensional structure designed as described above was produced, and an acrylic ultraviolet curable resin composition (refractive index: 1.57) was added to form a UV cured structural layer (refractive index: 1.60) to prepare a condensing type optical sheet.

The cross-section of the obtained condensing type optical sheet was observed using a scanning electron microscope (SEM), as shown in FIG. 5 (a).

Example 2

In Equation 1, a condensed optical sheet was prepared in the same manner as in Example 1, except that a: b was set to 2: 1.

The cross-section of the obtained condensing type optical sheet was observed using a scanning electron microscope (SEM), as shown in Fig. 5 (b).

Example 3

In Equation 1, a light-converging optical sheet was prepared in the same manner as in Example 1, except that a: b was set to 4: 1 (not shown).

Example 4

In Equation 1, a light-converging optical sheet was prepared in the same manner as in Example 1, except that a: b was set to 8: 1 (not shown).

Comparative Example 1

A condensing type optical sheet was prepared in the same manner as in Example 1, except that the three-dimensional structure of the structural layer was an acute prism having a triangular shape with an acute angle (80 degrees) of its cross section.

The cross-section of the obtained condensing type optical sheet was observed using a scanning electron microscope (SEM), as shown in FIG. 5 (c).

Comparative Example 2

A condensing type optical sheet was prepared in the same manner as in Example 1, except that the three-dimensional structure of the structural layer was an obtuse prism having a triangular shape with a vertex angle of 100 degrees.

The cross section of the obtained condensing type optical sheet was observed using a scanning electron microscope (SEM), as shown in FIG. 5 (d).

Comparative Example 3

In Formula 1, a: b was prepared in the same manner as in Example 1, except that 1.5: 1 was used, and a condensed optical sheet was prepared.

The cross section of the obtained condensing optical sheet is observed using a scanning electron microscope (SEM), as shown in FIG. 5 (e).

Comparative Example 4

In Formula 1, a: b was prepared in the same manner as in Example 1, except that 200: 1 was used, and a condensed optical sheet was prepared.

The cross section of the obtained condensing optical sheet is observed using a scanning electron microscope (SEM), as shown in Fig. 5 (f).

Comparative Example 5

In Equation 1, a: b was prepared in the same manner as in Example 1, except that 1: 1 was used, and a condensed optical sheet was prepared (not shown).

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

For the condensing type optical sheet prepared in Examples and Comparative Examples, luminance and color uniformity were measured in the following manner, and the results are shown in Table 1.

(1) Luminance measurement

After sequentially stacking a DBEF (Dual Brightness Enhancement Film), a condensing type optical sheet (Example or Comparative Example) and a diffusion film on a BLU (Backlight Unit, 27 inch LED 1vertical), the luminance measurement equipment (BM-7A, TOPCON) After measuring 13 points using), an average value was calculated.

The luminance of the prism film was measured as a reference (Ref.), And the relative luminance value for the Ref. 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 µm.

(2) Color uniformity measurement

After sequentially stacking DBEF (Dual Brightness Enhancement Film), condensing type optical sheet (example or comparative example) and lower diffusion film (KOLON, XC210) on BLU (27 inch LED 1vertical), color uniformity measurement equipment (SR3 , TOPCON company), after measuring the x and y color coordinates, it was converted to u 'and v' color coordinates using Equation 2 below.

<Equation 2>

In Equation 2, in the XYZ color space coordinate system of the CIE, the amount of the stimuli of the three primary colors to be mixed to produce the same color sense as the given color is referred to as X, Y, and Z (three stimulus values), and Y represents luminance.

The X, Y, and Z can be expressed by x and y using the following Equation 3.

<Equation 3>

When the color coordinates (u ', v') obtained as described above are applied to the CIE chromaticity diagram as shown in FIG. 6, the color can be obtained.

On the other hand, the color uniformity was obtained by using the color coordinate of the prism film as a reference (Ref.) By Equation 4 below, and the color uniformity (Δu ', Δv') is excellent as the negative value increases.

<Equation 4>

Color uniformity = (Color coordinate of Ref.)-(Color coordinate of 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 measuring the physical properties, as shown in Table 1, it can be seen that the condensed optical sheets of Examples 1 to 4 are improved in color uniformity when luminance degradation is minimized.

For reference, FIG. 7 shows a part of the measurement results of color uniformity, where A is Ref., B is Example 1 and C is the result of color uniformity measurement of Example 2.

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

In addition, Comparative Example 2 to Comparative Example 4 was accompanied by a decrease in brightness, and the vertical Δu 'value was found to increase. In particular, Comparative Example 3 was found to increase both Horizontal and Vertical Δu'.

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

Claims (8)

Base layer; And a structural layer formed on one or both surfaces of the substrate layer and arranged in a plurality of three-dimensional structures,
The three-dimensional structure of the structural layer has a streamlined longitudinal section, and includes an inclined portion extending in both directions based on one peak point,
The inclined portion is symmetrical or asymmetrical with respect to the peak point, and each inclined portion is a part of the circumferences of the superimposed virtual first ellipse and the second ellipse,
Each of the first ellipse and the second ellipse is defined by Equation 1,
The inclined portion is a condensed optical sheet characterized in that the first ellipse and the second ellipse are part of the first ellipse and the second ellipse adjacent to the hypotenuse formed by connecting three contact points formed by overlapping the contact points.
<Equation 1>

In the above formula, x and y are each a real number, a and b are integers where 0 <a <b <10, and a: b is 2: 1 to 100: 1. According to claim 1,
The inclined portion is a condensed optical sheet, characterized in that the first ellipse and the second ellipse include one contact point of a contact point formed by overlapping. delete According to claim 1,
The first ellipse and the second ellipse are condensed optical sheets, wherein each major axis is orthogonal, but the center of each major axis is superimposed. According to claim 1,
A condensing optical sheet characterized in that the center of the base of the three-dimensional structure coincides with the center where the major axes of the first and second ellipses intersect. According to claim 1,
The base layer is a condensed optical sheet, characterized in that it is formed of a resin selected from polyethylene terephthalate resin, polymethyl methacrylate resin, polycarbonate resin, polypropylene resin, polyethylene resin, polystyrene resin and styrene-acrylic copolymer resin. According to claim 1,
The structural layer is a condensing type optical sheet, characterized in that it is formed of a resin selected from polymer resins including UV curable resins or thermosetting resins. A backlight unit assembly comprising the condensing optical sheet according to any one of claims 1, 2, and 4 to 7.

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