WO2013180384A1

WO2013180384A1 - Optical sheet and method for manufacturing same

Info

Publication number: WO2013180384A1
Application number: PCT/KR2013/003090
Authority: WO
Inventors: 김영길
Original assignee: 주식회사 코아옵틱스
Priority date: 2012-05-31
Filing date: 2013-04-12
Publication date: 2013-12-05
Also published as: KR101195337B1

Abstract

Suggested are an optical sheet of which the luminance can be enhanced and a method for manufacturing same. The optical sheet that is suggested is used in a backlight unit in which a light source is positioned on at least one side surface, wherein the optical sheet comprises a micro lens having an x-axis and a y-axis of different lengths, when an axis that is parallel to the light source is the x-axis and an axis that is perpendicular to the x-axis is the y-axis.

Description

Optical sheet and its manufacturing method

The present invention relates to an optical sheet and a method for manufacturing the same, and more particularly, to an optical sheet capable of improving luminance and a method for manufacturing the same.

In the information display technology, the display device has occupied a position that CRT has been unique for more than half a century, but in the rapidly evolving information age, a larger and thinner display technology is required. As a result, flat panel display technology that can be enlarged and thinned has been developed. Liquid crystal display (LCD), projection display, and plasma display (PDP) have become mainstream, and field emission display (FED) and electroluminescent display ( ELD) has been developed along with the improvement of related technologies.

Compared with CRTs, LCDs are flat and large in size, and thus their use is expanding in display fields such as monitors and TVs, accounting for 80% of the flat panel market. The LCD includes a panel in which a liquid crystal and an electrode matrix are disposed between a pair of light absorbing optical films. In an LCD, the liquid crystal portion moves the liquid crystal portion by an electric field generated by applying a voltage to two electrodes, thereby having an optical state that is changed, and displaying an image using a polarized light in a specific direction. . Thus, the LCD includes a front optical film and a back optical film that induce polarization.

Since the LCD is not a self-luminous display but a non-luminous display, it includes a backlight unit on the back and uses the light generated therefrom. The backlight unit used in such a non-light emitting display includes an edge type backlight unit that supplies light from a side of the display panel and a direct backlight unit that directly supplies light from a rear side of the display panel. In the case of an edge type backlight unit, a light guide plate is provided to radiate light emitted from a light source upwardly, and at least one optical sheet, for example, a diffusion sheet, is disposed above the light guide plate to adjust optical characteristics of light passing through the light guide plate. Or a prism sheet.

With the trend toward larger and thinner flat panel displays, efforts have been made to secure a predetermined amount of light and luminance supplied to the display panel while maintaining or minimizing the number of light sources. Accordingly, an optical sheet was added to improve the light quantity and brightness of the backlight unit, which caused a problem contrary to the trend of thinning of the display.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an optical sheet capable of improving luminance and a manufacturing method thereof.

The optical sheet according to an aspect of the present invention for achieving the above object is an optical sheet used in the backlight unit in which the light source is located on at least one side, the axis parallel to the light source is called the x-axis, and When the vertical axis is referred to as the y axis, the length of the x axis and the length of the y axis include micro lenses different from each other.

The microlens may have an x-axis length longer than the y-axis length, and the microlens may collect light from the light source in the x-axis direction. Such a micro lens may be, for example, a water droplet in a plane shape, a shape having a concave portion on the x axis, or a shape having the longest y axis length in the center.

When the central y-axis length is in the longest form, the microlens may have a 2: 1 ratio of the x-axis length and the y-axis length. In this case, the ratio of the length and height of the y-axis of the micro lens may be 6: 4.

In addition, when the optical sheet includes two or more micro lenses, the two or more micro lenses are preferably arranged such that the porosity between the micro lenses has a maximum value closer to the light source.

In addition, when the optical sheet includes two or more micro lenses, the two or more micro lenses may be arranged such that the porosity between the micro lenses is minimized. At this time, the porosity may be 3 to 10% or less.

Further, when the optical sheet includes two or more micro lenses, the two or more micro lenses may be arranged in a honeycomb manner.

According to another aspect of the present invention, a method of manufacturing an optical sheet for a backlight unit in which the light source is located on at least one side, the axis parallel to the light source is called the x-axis, the axis perpendicular to the x-axis is called the y-axis At this time, the optical sheet manufacturing method comprising a; forming a microlens so that the length of the x-axis and the length of the y-axis on the substrate are different from each other.

At this time, the micro lens may be formed by an inkjet method.

Alternatively, forming the microlens may include inkjetting the UV ink onto the substrate; And irradiating the UV ink with ultraviolet rays, wherein the substrate may move, and the shape of the microlens may vary depending on the amount of UV ink and the moving speed of the substrate.

According to another aspect of the invention, the light guide plate; A light source positioned on at least one side of the light guide plate; And an optical sheet disposed on an upper surface of the light guide plate and having an axis parallel to the light source being an x axis, and an axis perpendicular to the x axis being a y axis, the optical sheet including micro lenses having different lengths of the x axis and length of the y axis. A backlight unit is provided.

The backlight unit including the optical sheet according to the present invention has the effect of improving the maximum brightness without additional optical sheet.

In addition, an optical sheet including a microlens can be manufactured by an inkjet method, so that an optical sheet including a microlens having a desired arrangement can be obtained by a simpler process.

1 is a cross-sectional view of a backlight unit including an optical sheet according to an embodiment of the present invention, Figure 2 is a perspective view of the backlight unit of FIG.

3 is a view illustrating an emission profile in a backlight unit including a light source and a light guide plate.

4 and 5 are perspective views of optical sheets according to other embodiments of the present invention.

6 is a view illustrating a micro lens according to another embodiment of the present invention.

7 is a graph illustrating luminance according to a change in x-axis length with respect to the y-axis length of the microlens, and FIG. 8 is a graph illustrating luminance according to a change in height with respect to the y-axis length of the microlens.

9 is a diagram illustrating an arrangement of microlenses according to another exemplary embodiment of the present invention.

10 is a view provided to explain the manufacturing method of the optical sheet according to another embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below. Embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art. In the accompanying drawings, there may be a component having a specific pattern or having a predetermined thickness, but this is for convenience of description or distinction. It is not limited only.

1 and 2, the backlight unit according to the present invention includes a light guide plate 130, a light source 120 positioned on a side surface of the light guide plate 130, and an optical sheet 110 positioned on an upper surface of the light guide plate 130. It includes. 2, when the axis parallel to the light source 120 is referred to as the x-axis, and the axis perpendicular to the x-axis is referred to as the y-axis, the optical sheet 110 has a length of the x-axis and a length of the y-axis different from each other. ).

The light source 120 is for supplying light from the back of the display device. For example, a light source such as a cold cathode fluorescent lamp (CCFL) or a light emitting diode (LED) may be used. . The light source 120 may be located on one side of the light guide plate 130 or on a plurality of side surfaces as shown in FIG. 1, but the shape of the microlens 112 of the optical sheet 110 may vary. .

The light guide plate 130 is made of a resin made of a transparent material such as polymethyl methacrylate (PMMA), and guides light from the light source 120 to the emission surface to uniformly transmit light to the entire surface of the display device. A reflecting plate (not shown) may be provided on the opposite side of the emitting surface of the light guide plate 130 to reflect the light traveling toward the opposite surface side of the emitting surface back to the emitting surface side, and the upper surface of the light guide plate 130 may be provided on the light emitting plate 130. A diffusion plate (not shown) for uniformly diffusing the light traveling from 130 may be provided.

The optical sheet 110 is positioned at the exit surface side of the light guide plate 130, and includes a micro lens 112 for condensing and improving luminance of the light emitted from the light guide plate 130.

The microlens 112 is a micrometer sized structure formed of a light transmissive material positioned on a light transmissive substrate 111. The substrate 111 is a substrate on which the microlenses 112 are positioned, and includes a transparent material such as glass, polycarbonate, polyallylate, polyethersulfone, amorphous polyolefin or polyethylene terephthalate, polymethylmethacrylate, or the like. Light transmissive material).

The microlens 112 may include a light transmissive resin, for example, an acrylic resin such as polymethyl methacrylate, polyhydroxyethyl methacrylate or polycyclohexyl methacrylate, polydiethylene glycol bisallyl Allyl resin, such as carbonate or polycarbonate, methacryl resin, polyurethane resin, polyester resin, polyvinyl chloride resin, polyvinyl acetate resin, cellulose resin, polyamide resin, fluorine resin, polypropylene It may include at least one of a resin and a polystyrene resin.

The microlens 112 may be formed by applying heat to the above-mentioned light-transmissive resin and curing, or may be used as a photocurable resin by adding a photopolymerization initiator to such light-transmissive resin. That is, the microlens 112 may be formed by irradiating and curing light on a mixture in which a photopolymerization initiator is added to the light transmissive resin.

In the present invention, when the microlens 112 has an axis parallel to the light source 120 as the x-axis and an axis perpendicular to the x-axis as shown in FIG. 2, the length of the x-axis and the y-axis are different from each other. Microlens 112. This is because the light collecting performance or the light collecting direction is different depending on the shape of the microlens 112.

In this regard, the light emission profile of the backlight unit including the light source 220 and the light guide plate 230 will be described with reference to FIG. 3. Light incident from the light source 220 to the light guide plate 230 represents an x-axis optical profile 241, which is an optical profile in a direction parallel to the light source 220, and a y-axis optical profile 242 perpendicular thereto. The x-axis optical profile 241 and the y-axis optical profile 242 are different from each other, depending on the position of the light source 220. Since the optical sheet 110 according to the present invention is used in a backlight unit in which a light source is located on the side surface, the microlens 112 on the optical sheet 110 preferably has a shape considering an optical profile according to the position of the light source. .

Here, as shown in FIG. 2, the x-axis refers to a direction parallel to a direction in which light from each light source 120 directly enters the light guide plate 130, and thus, an 'axis parallel to the light source' means “light guide plate from a light source. Means an axis parallel to the light incident vertically ". In addition, the y-axis means a direction perpendicular thereto.

In FIG. 3, when comparing the x-axis optical profile 241 and the y-axis optical profile 242, it can be seen that the light is further skewed in the x-axis direction. This makes it possible to predict that uniform surface light emission will not occur when light incident on the light guide plate exits the light guide plate. Therefore, the microlens 112 of the present invention has a longer x-axis length, and the microlens 112 can condense the light from the light source 120 in the x-axis direction. That is, since the x-axis length of the microlens 112 is formed longer than the y-axis length, condensation of light having the same profile as the x-axis optical profile 241 can be made more efficiently, so that uniform surface light emission is possible and overall Brightness can be improved.

In FIGS. 1 and 2, the shape of the microlens 112 having different x-axis lengths and y-axis lengths is illustrated as a drop shape in which one diameter is smaller than the other diameter, but the shape of the microlenses in the present invention is limited thereto. It doesn't work.

4 and 5 are perspective views of optical sheets according to other embodiments of the present invention. 4 and 5 illustrate optical sheets on which the

microlenses

312 and 322 having different x-axis lengths and y-axis lengths are positioned on the

substrates

311 and 321. In FIG. 4, the microlens 312 has a concave portion on the x-axis, and in FIG. 5, the microlens 322 has the longest y-axis in the center. The microlens 312 of FIG. 4 has a shape in which any one of axes in a direction parallel to the light source in the microlens is recessed and drawn into the inside.

The microlenses of FIGS. 2, 4, and 5 all have different shapes, but since the x-axis lengths are longer than the y-axis lengths, all of the micro lenses can be condensed in the x-axis direction so that the overall light can be uniformly and efficiently. have.

6 is a view illustrating a micro lens according to another embodiment of the present invention. The x-axis length of the microlens 412 is referred to as Dx, the y-axis length is referred to as Dy, and the height is referred to as Dz. The height refers to the height of the highest point in the micro lens 412. In FIG. 6, the microlens 412 has a shape having the longest central y-axis length. In other words, the hemispherical microlens is elongated in the x-axis direction. Therefore, light condensing in the x-axis direction is efficiently performed.

In this regard, the luminance change according to the relative change of the x-axis length, the y-axis length, and the height will be described with reference to FIGS. 7 and 8. 7 is a graph illustrating luminance according to a change in x-axis length with respect to the y-axis length of the microlens, and FIG. 8 is a graph illustrating luminance according to a change in height with respect to the y-axis length of the microlens.

In the hemispherical microlens, the y-axis length Dy was fixed to 30 µm, and the x-axis length Dx was changed to the following to obtain a luminance gain value.

Table 1

x-axis length (μm)	y-axis length: x-axis length	Luminance gain
60	1: 2	1.83
90	1: 3	1.65
120	1: 4	1.42
150	1: 5	1.41

As can be seen from Table 1 and FIG. 7, when the x-axis length is longer than the y-axis length, the luminance gain value is 1 or more, and thus the luminance may be improved when the x-axis length and the y-axis length are implemented differently. In addition, in the case of the microlens 412 as shown in FIG. 4, when the y-axis length is fixed, it can be seen that the greatest gain of luminance is when the ratio of the x-axis length and the y-axis length is 2: 1. .

Also, in the hemispherical micro lens, the x-axis length (Dx) is fixed to 120 µm and the y-axis length (Dy) to 60 µm, and the z-axis length (Dz), which is a height, is changed as follows to simulate the luminance gain value and the viewing angle. Got.

TABLE 2

z-axis length (μm)	y-axis length: z-axis length	Luminance gain	Viewing angle
20	6: 2	1.46	122
30	6: 3	1.86	95
40	6: 4	2.01	80
50	6: 5	1.87	71

As can be seen from Table 2 and FIG. 8, when the x-axis length and the y-axis length are fixed at 2: 1 and the height is changed, the luminance gain value is the highest when the ratio of the y-axis length and the height is 6: 4. It can be seen that. In addition, when the ratio of the length and height of the y-axis is 6: 4, the viewing angle is narrow to 80 degrees, which is expected to be excellent in terms of luminance.

9 is a diagram illustrating an array of micro lenses according to an embodiment of the present invention. When two or more micro lenses in the optical sheet are arranged along the light source 120 as shown in FIG. 2, the micro lens 112 has a different shape of the x-axis length and the y-axis length, thereby enabling efficient condensing.

However, when the densities of the

micro lenses

712, 713, 714, and 715 located on the substrate 711 are arranged differently according to the distance from the light source, as shown in FIG. 9, the light can be collected more efficiently. That is, when the micro lenses positioned from the light source 720 are referred to as the first micro lens 712, the second micro lens 713, the third micro lens 714, and the fourth micro lens 715, the light guide plate 730 may be used. The micro lens positioned closest to the light source 720 positioned on the side of the first micro lens 712 is the micro lens positioned farthest is the fourth micro lens 715.

In FIG. 9, the first micro lens 712 includes three micro lenses, the second micro lens 713 includes four micro lenses, and the third micro lens 714 includes five micro lenses. In addition, the fourth micro lens 715 includes six micro lenses. That is, the second micro lens 713 than the first micro lens 712, the third micro lens 714 than the second micro lens 713, and the fourth micro lens 715 than the third micro lens 714. The density of the microlenses is high. That is, the porosity between the micro lenses of the first micro lens 712 is the largest, and the porosity between the micro lenses of the fourth micro lens 715 is the smallest. This is to place as few micro lenses as possible near the light source and to place as many micro lenses as possible while minimizing the porosity as far as possible in order to enhance the condensing at the position away from the light source. In FIG. 9, for convenience of description, the micro lenses are illustrated as being arranged in a line, but may be arranged differently.

If the microlenses are arranged as much as possible in the optical sheet of the same area, the light collecting efficiency may be maximized. Thus, when the optical sheet includes two or more micro lenses, the two or more micro lenses may be arranged such that the porosity between the micro lenses is minimized. At this time, the porosity may be 3 to 10% or less.

The microlenses may be arranged in a honeycomb manner in order to minimize the porosity between the microlenses. The microlenses may be formed in an inkjet manner to facilitate adjustment of the arrangement or control of the porosity.

10 is a view provided to explain the manufacturing method of the optical sheet according to another embodiment of the present invention. In the method for manufacturing an optical sheet of the present invention, an optical sheet used for a backlight unit in which a light source is located on at least one side surface is produced. An axis parallel to the light source is referred to as an x axis, and an axis perpendicular to the x axis is referred to as a y axis. In this case, an optical sheet is manufactured by forming a microlens so that the length of the x-axis and the length of the y-axis are different from each other on the substrate.

There are a method of manufacturing a microlens using a method of molding using a mold, a method of molding using a stamper, a method using a photolithography method, or a method using an inkjet method.

The microlens of the present invention is characterized in that the x-axis length and the y-axis length are different. Such a micro lens may be, for example, a water droplet in a plane shape, a shape having a concave portion on the x axis, or a shape having the longest y axis length in the center. The micro lens of such a shape can be more simply and precisely adjusted when using the inkjet method. In addition, in the inkjet method, when the ultraviolet ray curable ink is used as the ink, since the shape change due to heating is small, a microlens having a desired shape can be manufactured.

Therefore, the microlens passes through the surface modification portion 851 for reforming the surface of the substrate 811 while moving the substrate 811 using the roller 854 as shown in FIG. When the UV ink is discharged from the unit 852 to form a microlens on the surface of the substrate 811, UV is irradiated from the UV irradiator 853 to cure the microlens. At this time, the shape of the micro lens is changed according to the amount of UV ink and the moving speed of the substrate 811, it is easy to adjust the shape.

The invention is not to be limited by the foregoing embodiments and the accompanying drawings, but should be construed by the appended claims. In addition, it will be apparent to those skilled in the art that various forms of substitution, modification, and alteration are possible within the scope of the present invention without departing from the technical spirit of the present invention.

Claims

An optical sheet used for a backlight unit in which the light source is located on at least one side,

When the axis parallel to the light source is called the x-axis, and the axis perpendicular to the x-axis is called the y-axis,

The optical sheet including a micro lens having a different length of the x-axis and a length of the y-axis.
The method according to claim 1,

The microlens is optical sheet, characterized in that the x-axis length is longer than the y-axis length.
The method according to claim 1,

And the micro lens collects light from the light source in the x-axis direction.
The method according to claim 1,

The micro lens is an optical sheet, characterized in that the plane shape of the water droplets.
The method according to claim 1,

The microlens is an optical sheet, characterized in that the concave portion on the x-axis.
The method according to claim 1,

The micro lens is the optical sheet, characterized in that the longest y-axis length of the center.
The method according to claim 6,

The micro lens has an optical sheet having a ratio of x-axis length and y-axis length of 2: 1.
The method according to claim 6,

The micro-lens is an optical sheet, characterized in that the ratio of the y-axis length and height is 6: 4.
The method according to claim 1,

Including two or more microlenses,

The two or more microlenses are arranged such that the porosity between the microlenses is closest to the light source to have a maximum value.
The method according to claim 1,

Including two or more microlenses,

The two or more micro lenses are arranged such that the porosity between the micro lenses is minimized.
The method according to claim 10,

The porosity is an optical sheet, characterized in that less than 3 to 10%.
The method according to claim 1,

Including two or more microlenses,

The two or more micro lens is an optical sheet, characterized in that arranged in a honeycomb (honeycomb) method.
A method of manufacturing an optical sheet for use in a backlight unit in which a light source is located on at least one side surface, wherein an axis parallel to the light source is referred to as an x axis, and an axis perpendicular to the x axis is referred to as a y axis. and forming a microlens such that the length of the x-axis and the length of the y-axis are different from each other.
The method according to claim 13,

The micro lens is an optical sheet manufacturing method, characterized in that formed by the inkjet method.
The method according to claim 13,

Forming the micro lens,

Inkjetting a UV ink onto the substrate; And

Irradiating ultraviolet rays to the UV ink; optical sheet manufacturing method comprising a.
The method according to claim 15,

The substrate is an optical sheet manufacturing method characterized in that the movement.
The method according to claim 16,

The shape of the micro lens is an optical sheet manufacturing method, characterized in that it changes depending on the amount of the UV ink and the moving speed of the substrate.
Light guide plate;

A light source positioned on at least one side of the light guide plate; And

Located on the upper surface of the light guide plate,

When the axis parallel to the light source is called the x-axis, and the axis perpendicular to the x-axis is called the y-axis,

And an optical sheet including micro lenses having different lengths of the x-axis and lengths of the y-axis.