JP2010078980A - Optical control stack, backlight unit using the same and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical control stack satisfying thinness, high brightness and high symmetry of a display device; and to provide an illuminator, an electronic signboard, a backlight unit and a display device using the optical control stack. <P>SOLUTION: In the optical control stack 201 including light sources 41, a dimming sheet 26 formed on the light sources 41 and having a surface structure on the surface opposite to the light sources 41, a diffusion plate 25 on top parts of the surface structure, and a compensation sheet 1 on the diffusion plate 25, wherein the surface structure comprises the top parts transmitting light incident from an incident surface of the dimming sheet 26 and side parts 101 totally reflecting or/and retroreflecting the incident light. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention can be used for various display devices such as an illumination device such as a backlight unit, a liquid crystal display device, an electronic signboard, electronic paper, and an organic EL display device.

In recent years, liquid crystal display devices using TFT-type liquid crystal panels and STN-type liquid crystal panels have been commercialized mainly for color notebook PCs, personal computers, mobile phones and the like in the OA field.
In such a liquid crystal display device, a so-called backlight method in which a light source is arranged on the back side (observer side) of the liquid crystal panel and the liquid crystal panel is illuminated with light from the light source is employed.

The backlight unit employed in this type of backlight system is roughly divided into a light source lamp such as a cold cathode tube (CCFT) or LED (Light Emitting Diode), a flat plate made of acrylic resin or the like having excellent light transmittance. There are a “light guide plate light guide method” (so-called edge light method) in which multiple reflections are made within a light guide plate and a “direct type” method that does not use a light guide plate.

In recent years, liquid crystal display devices have been used for television applications, and in large-sized liquid crystal televisions, direct type backlights having a plurality of cold cathode tubes) and LEDs are employed.
Such direct type backlights have the problem that uneven luminance (lamp image) of the light source is visible and a uniform luminance distribution cannot be obtained, so that there is a problem between the image display element and the light source. In addition, a resin plate having a strong light scattering property is used so that luminance unevenness due to a cold cathode tube or an LED as a light source is not visually recognized. For this reason, a product having a uniform luminance distribution, that is, a product having a high degree of uniformity has not been obtained.

Conventionally, a diffusion plate used in a direct type backlight is intended to diffuse light emitted from a cold cathode tube, which is a light source, and reduce luminance unevenness (lamp image). However, it is difficult to completely erase the lamp image.

If the number of diffusing particles is forcibly increased in order to completely eliminate the lamp image, the total light transmittance is lowered too much, causing a decrease in luminance. Further, if the diffusion particles of the diffusion plate are reduced so as not to reduce the total light transmittance, the diffusion effect is also lowered.

Furthermore, since the liquid crystal television tends to be thinner year by year, the distance between the light source and the diffusion plate tends to be narrower, and further improvement of the uniform luminance distribution is demanded.

For example, a prism array arranged on a diffusing plate (Patent Documents 1 and 2) is known. However, with this alone, a sufficiently thin backlight cannot be obtained.
Further, a method is known in which two lenticular lens-like lens sheets are overlapped to obtain a uniform luminance distribution from a point light source (Patent Document 3). In such a case, although the light can be diffused by the lens, the luminance directly above the light source cannot be sufficiently reduced, and a thin and uniform luminance distribution cannot be obtained.

Further, from the viewpoint of mercury-free and low power consumption, LEDs are often used as a light source for backlights, and there are those using an edge light method in combination, etc., which obtain a planar light source from a point light source. . (Patent Document 4) These have a problem that the number of parts is large and the assembling is complicated, resulting in high costs.

In addition, there is known a technique (Patent Document 5) characterized in that two diffusion layers are used and a gap is used in one diffusion layer. In this document, although it is described that light is diffused, there is no description to reduce the luminance directly above the light source, and luminance unevenness immediately above the light source where the luminance is highest cannot be reduced. Furthermore, in this document, since the gap extends in one direction, it cannot be applied to a point light source.

Moreover, the thing (patent document 6, 7, 8) of the structure which can contain the part similar to this structure is known. According to this, it is written that the prismatic rib and the optical film are bound together through the adhesive layer. With such a configuration, the FIG. 1 and FIG. In the configuration described in FIG. 14, an attempt was made to make the luminance uniform. However, when the distance between the light source and the diffusion plate was wide, a uniform luminance distribution was obtained. When the distance between the light source and the diffusion plate was reduced so as to obtain a thin backlight unit that could be accommodated, the luminance directly above the light source was high and a uniform luminance distribution could not be obtained.

Further, although the light management package described in Patent Document 7 is disposed immediately above the light source, it is not sufficiently rigid and cannot be held while maintaining a certain distance. In addition, since light does not transmit immediately above the light source, the luminance is excessively lowered, so that a strip-shaped dark portion is recognized and a uniform luminance distribution cannot be obtained. Similarly, a uniform luminance distribution could not be obtained in the same manner even when other prism-shaped ribs intended to improve the luminance in the planar view direction F described in this document were used.

There is known a technique in which light condensed by a lens array sheet 30 disposed on the light source 41 side is incident on a light guide plate 31 to make the luminance uniform (Patent Document 9). However, in such a lens array sheet 30, as shown in FIG. 17 of the present application, the light source 41 is in a planar view direction F (the planar view direction is a direction perpendicular to the panel on the observer side). Since most of the emitted light is transmitted through the lens array sheet 30 as it is, the luminance is increased directly above the light source 41, and a sufficiently uniform luminance distribution cannot be obtained.

The above-mentioned various problems do not have to be solved, but all need to be solved simultaneously. As described above, it is difficult to say that the conventional device sufficiently satisfies the above problems, and the user can realize a liquid crystal display device with low price, high luminance, high display quality, and low power consumption. Development of a backlight unit and a display device is awaited.
JP 2007-103321 A JP 2006-195276 A JP 2007-12517 A JP 2008-27756 A JP 2008-78085 A JP 2008-3233 A Special table 2007-50210 gazette JP 2008-122525 A JP 2008-166057 A

The present invention has been made in view of such circumstances, such as a light control stack satisfying thinning, high brightness, and high uniformity of a display device, and a backlight unit using the light control stack. It is an object to provide various display devices such as an illumination device, a liquid crystal display device, an electronic signboard, electronic paper, and an organic EL display device.

  In order to achieve the above object, the present invention takes the following measures.

The invention of claim 1 is a light source, a light control sheet having a surface structure on the surface opposite to the light source on the light source, a diffusion plate on the surface structure, and correction on the diffusion plate And the surface structure diffuses the light incident from the incident surface of the light control sheet without being in contact with the diffusion plate, and the top structure that transmits the light incident from the incident surface of the light control sheet A light control stack comprising a bent portion and a side portion that totally reflects the incident light and returns and / or transmits the incident light to the light source side.
The invention of claim 2 is directed to a light source, a light control sheet having a surface structure on the surface opposite to the light source on the light source, a diffusion plate on the surface structure, and correction on the diffusion plate. Sheet and
The surface structure is composed of a top portion that is in contact with the diffusion plate, a bent portion that is not in contact with the diffusion plate and includes a protrusion, a recess, and a step, and a side portion that is between the top portion or the bent portion. Is a light control stack characterized by
According to a third aspect of the present invention, in the light control stack according to the first or second aspect, the surface structure has a periodic structure at least one of the top portion, the bent portion, and the side portion. It is.
According to a fourth aspect of the present invention, in the light control stack according to the first or second aspect, the surface structure includes any of the top portion, the bent portion, and the side portion having a random structure. .
The invention according to claim 5 is the light control stack according to claim 1 or 2, wherein the surface structure has at least one bent portion between the adjacent top portions.
The invention according to claim 6 is the light control stack according to claim 1 or 2, wherein the top part and the bent part are 3% or more and 40% or less of the area of the incident surface.
A seventh aspect of the present invention is the light control stack according to the first or second aspect, wherein the total light transmittance of the light incident from the incident surface is 25% or more and 70% or less.
The invention of claim 8 is a backlight unit using the light control stack according to claims 1 to 7.
A ninth aspect of the present invention is a display device including the backlight unit according to the eighth aspect.

The present invention provides a light control stack that satisfies the above-mentioned means to achieve a thin display, high brightness, and high uniformity of the display device, and a lighting device such as a backlight unit using the light control stack, a liquid crystal display device, and an electronic device. Various display devices such as a signboard, electronic paper, and an organic EL display device can be provided.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

FIG. 1 shows a liquid crystal display device 200 used by incorporating the light control stack 201 of the present invention.
The backlight unit 13 is configured by a reflective plate 43, a light source 41, a light control sheet 26, a diffusion plate 25, and a correction sheet 1 disposed in this order from the back side. Here, a stack of the light control sheet 26, the diffusion plate 25, and the correction sheet 1 is referred to as a light control stack 201. A display unit 21 is disposed on the backlight unit 13 described above.

The light source 41 is a light supply source used for image display of the display unit 21. As the light source 41 in the present embodiment, a linear light source such as a thin rod-shaped cold cathode tube or a point light source such as an LED is used.
The light source 41 is not limited to such a cold cathode tube, and may be any other light source as long as it is a linear light source. That is, in addition to the cold cathode tube, for example, a normal fluorescent tube, a hot cathode tube, an external electrode tube, a mercury-less rare gas fluorescent lamp, a light emitting diode (hereinafter referred to as LED) arranged in a line, a semiconductor laser, etc. Can be used as the light source 41, and it is particularly preferable to use an external electrode tube or a light emitting diode arranged in a line.

Further, an LED light source using a cylindrical or prismatic transparent light guide having a length equivalent to the parallel groove of the light guide plate and LEDs arranged on the top and bottom surfaces of the light guide is used as the light source 41. Also good. This LED light source is configured such that LED light can be incident from the top and bottom surfaces of the light guide, and the LED light can be emitted from the side surfaces of the light guide.

The light source 41 may be a point light source, and the point light source is preferably an LED that does not use mercury and has high luminous efficiency, such as a cold cathode tube.

In FIG. 2A, a blue LED element 50 that emits blue light used in a mobile device such as a mobile phone is covered with an LED lens 53, and the inner spherical surface of the LED lens 53 emits yellow light. The phosphor 51 is coated. As a result, the white LED 46 of the type that emits pseudo white light is obtained.
This method has an advantage that pseudo white light emission can be realized simply by covering the phosphor with a single-color LED element. Further, the emission colors of the LED and the phosphor are not limited to those described above, but may be in other forms as long as one single-color LED element is covered with at least one kind of phosphor.

FIG. 2B shows a white LED 46 in which a prism shape 70 is added to the LED lens 53 of FIG. By using the prism shape 54, the light distribution of the light emitted from the white LED 46 can be adjusted.

FIG. 2C shows a method of emitting pseudo white light by combining LED elements (red LED element 48, green LED element 49, blue LED element 50) that emit light of a single color as another method of LEDs emitting pseudo white light. It is. In this case, compared with the case of FIG. 2A as described above, the problem that the phosphor 51 deteriorates due to the heat generated from the LED elements can be avoided, and any color can be achieved by adjusting the light quantity of each LED element. Can be obtained.

FIG. 3 shows a point light source unit 52 formed by combining single color LEDs (red LED 54, green LED 55, blue LED 56) that emit light in a single color. In this case, the red LED 54, the green LED 55, and the blue LED 56 may be combined one by one as shown in FIG. 3B to constitute the point light source unit 52, or the light output is weak as shown in FIG. 3C. A plurality of (for example, green LEDs 55) may be arranged to constitute the point light source unit 52.
By configuring this point light source unit 52, it is possible to perform color display using a field sequential method in which LEDs of each color are colored in a time-sharing manner.

In the point light source unit 52, the number of LEDs is not limited. When a plurality of the point light source units 52 are arranged, if the light emission colors of the adjacent point light source units 52 are the same, the intensity of the color is partially increased and the color unevenness is recognized from the planar view direction F. The point light source units 52 preferably have different emission colors.

The point light source is not limited to the above-described LED. For example, as shown in FIG. 4, the light of a monochromatic semiconductor laser (red semiconductor laser 57, green semiconductor laser 58, blue semiconductor laser 59) May be mixed and emitted from the semiconductor laser lens 61. In addition, the point light source may be a normal fluorescent lamp or a halogen lamp.

The point light source described above may be divided and driven for each arrangement location. As a result, the light source 41 at the arrangement location corresponding to the place where the bright image is displayed is caused to emit light, and the light source 41 at the arrangement location corresponding to the place where the dark image is displayed is turned off or the light emission amount is reduced. It becomes larger and the contrast can be increased.

At this time, it is desirable that each divided area has a light distribution that is uniform and reduces the light leakage between the areas.
Therefore, it is desirable that the light is reduced at a certain place where the light is made uniform as a lens.

Next, an arrangement mode of a plurality of point light sources will be described. FIG. 5 is a plan view schematically showing the arrangement of a plurality of point light sources 41b or point light source units 52. As shown in FIG.

As shown in FIG. 5A, the first mode in which a plurality of point light sources 41b or point light source units 52 are arranged is arranged at predetermined intervals in a matrix along the vertical and horizontal directions of the backlight unit 13. The configuration is as follows.

Further, as a second mode, as shown in FIG. 5 (b), the point light source 41b in FIG. 5 (a) or C1-C4 of the point light source unit 52 is removed, that is, four squares. The point light source 41b or the point light source unit 52 is arranged at each vertex, and the point light source 41b or the point light source unit 52 is arranged at the intersection of the rectangular diagonal lines.

Further, as a third aspect, as shown in FIG. 5 (c), a point light source 41b or a point light source unit 52 is arranged at each vertex of a honeycomb structure in which regular hexagons are continuously formed. can do. Alternatively, as shown in FIG. 5D, the point light source 41b or the point light source unit 52 may be arranged linearly.

In the above aspects, the distance between the point light source 41b or the point light source unit 52 may be uniform in all places, or may be partially changed.
As an example of this, there is one in which the distance between the point light sources is narrowed at the center of the backlight unit 13 or the like.

Moreover, it is preferable that the distance between the centers of the light source 41 as an adjacent point light source is 15 mm-150 mm, and it is more preferable that it is 20 mm-60 mm. When it is less than 15 mm, the influence of heat generation from the light source becomes too strong, and heat dissipation becomes insufficient. Furthermore, when it is 20 mm or more, sufficient heat radiation can be performed without a special mechanism for heat radiation. Also, when the distance is longer than 150 mm, the area for changing the brightness becomes too wide at the time of local dimming, which can display a high-contrast image by changing the brightness according to the input signal, resulting in an unnatural image. End up. Further, when the distance is narrower than 60 mm, local dimming capable of dealing with high-definition video is possible. By setting it within this range, it is possible to realize the backlight unit 13 that can perform appropriate heat dissipation in the backlight unit 13 and can display a high-quality image.

A part of the light emitted from the light source 41 is incident on and reflected by the reflector 43 installed so as to cover the light source 41 from the back side. The reflection plate 43 may be formed of any material as long as it can reflect light from the light source 41. For example, a filler or air is kneaded and stretched in PET, PP (polypropylene), or the like. Resin sheet with increased reflectivity by forming voids, a sheet with a mirror surface formed by vapor deposition of aluminum on the surface of a transparent or white resin sheet, a resin sheet carrying a metal foil or metal foil such as aluminum, or sufficient on the surface It can be formed of a thin metal plate having excellent reflectivity.

Moreover, after dispersing fillers such as resin incompatible with PET, titanium oxide (TiO2), and barium sulfate (BaSO4) in PET, the PET is stretched by a biaxial stretching method. What formed the bubble around it can also be used.

In addition, when a linear light source is employ | adopted as the light source 41, it installs so that the dimension of the shortest distance of the entrance plane 26a of the light control sheet 26 and the center position of a linear light source may be 2 mm-30 mm or less, and is 5 mm-25 mm. More preferably. When the distance from the light control sheet 26 is less than 2 mm, the diffusion plate 25 is distorted due to heat generated by the light source 41. When the distance is larger than 30 mm, the light H of the light source 41 is excessively diffused between the light control sheet 26 and the light source 41, so that the luminance is lowered. If the distance is less than 5 mm, the image of the light source 41 cannot be erased. Note that, by setting the distance to the light control sheet 26 to 25 mm or less, the thickness in the depth direction of a display device such as a liquid crystal television can be reduced.

Further, when the point light source 41b or the point light source unit 52 is adopted as the light source 41, the dimension of the shortest distance between them and the incident surface 26a of the light control sheet 26 is the thickness and brightness uniformity of the direct type backlight device. However, it is preferably 1 mm to 30 mm, more preferably 3 mm to 25 mm. When the distance from the light control sheet 26 is less than 1 mm, the light control sheet 26 is distorted due to heat generated by the light source 41. When the distance is larger than 30 mm, the light H of the light source 41 is excessively diffused between the light control sheet 26 and the light source 41, so that the luminance is lowered. Moreover, if it is less than 3 mm, the image of the light source 41 cannot be erased. Note that, by setting the distance to the light control sheet 26 to 25 mm or less, the thickness in the depth direction of a display device such as a liquid crystal television can be reduced.

A part of the light emitted from the light source 41 as described above and the light reflected by the reflecting plate 43 enter the incident surface 26 a of the light control sheet 26.

The light control sheet 26 transmits, totally reflects, and diffuses the light incident from the light source 41.
6 shows that light emitted from the light source 41 in the planar view direction F is incident from the incident surface 26a of the light control sheet 26, and is emitted from the light emitting surface side having the surface structure to the diffusion plate 25 and to the light source 41 side. The returning light will be described.

Light emitted from the light source 41 in the planar view direction F, incident from the incident surface 26 a of the light control sheet 26, and incident on the side portion 101 of the light control sheet 26 is totally reflected by the side portion 101.
Among them, there is a light H11 returning to the light source 41 side, and then a light H12 that passes through any of the light control sheets 26 (101, 102, 103) and is emitted to the diffusion plate 25.
Of these, the light H11 that is totally reflected and returns to the light source 41 side has an effect of lowering the luminance of the highest luminance portion directly above the light source 41.

Light H21 emitted from the light source 41 in the planar view direction F, incident from the incident surface 26a of the light control sheet 26, and incident on the portion of the top portion 102 that contacts the diffusion plate 25 is transmitted as it is and emitted to the diffusion plate 25. The light H22 incident on the portion not in contact with the diffusion plate 25 is diffused on the surface of the light control sheet 26 and is emitted as diffusion light to the diffusion plate 25.

Since the top part 102 is in contact with the diffusion plate 25, the top part 102 is damaged by vibration during transportation. In order to prevent the above, the top portion 102 may be rounded. Furthermore, if the number of the top portions 102 is increased or / and the area is widened, the generation of scratches can be suppressed.

Light emitted from the light source 41 in the planar view direction F is incident from the incident surface 26a of the light control sheet 26, and the light H3 incident on the bent portion 103 of the light control sheet 26 is diffused by the bent portion 103 and is not diffused. The light is emitted to the diffusion plate 25 as light. The bent portion 103 is not in contact with the diffuser plate 25 and includes a protrusion, a depression, and a step.
Since the bent portion 103 does not contact the diffusing plate 25, the diffusion of light can be controlled by changing the shape, the number, and the area of the bent portion 103. Therefore, even with respect to light emitted from the light source 41 in an oblique direction, the light diffusibility can be controlled by controlling the shape, the number, and the area of the bent portions 103, so that the luminance is uniform. Distribution can be obtained.

The top portion 102 and the bent portion 103 are surrounded by the side portion 101 or the end surface 26b. That is, the top part 102 and the bending part 103 do not contact | connect.

The area ratio of the area obtained by adding the top part 102 and the bent part 103 to the area of the incident surface 26a is desirably 3% or more and 40% or less. When the above-mentioned area ratio is less than 3%, the ratio of the side portion 101 is large, and the light emitted from the light source 41 in the planar view direction F is totally reflected. On the contrary, the brightness increases in the vicinity. That is, the portion directly above the light source 41 is darker than the surrounding area, and a uniform luminance distribution cannot be obtained.
On the other hand, when the area ratio is greater than 40%, the ratio of the side portion 101 is small, and the ratio of the light emitted from the light source 41 in the planar viewing direction F is small. The brightness increases at the same time, and conversely the brightness decreases at the periphery. That is, the portion directly above the light source 41 is bright with respect to the periphery thereof, and a uniform luminance distribution cannot be obtained.

The above-mentioned ratio can be obtained by measuring by placing the incident surface 26a of the light control sheet 26 on the light source side of the measuring instrument in the method for measuring the total light transmittance defined in JIS K7105. When the area ratio is 3%, the transmittance is 25%. Further, when the area ratio is 40%, the transmittance is 70%. Therefore, the total light transmittance defined in JIS K7105 of the light control sheet 26 is desirably 25% to 70%.

In addition, the ratio of the area of the top part 102 and the bent part 103 can be appropriately selected from the above-described area ratios that are not easily damaged and have a uniform luminance distribution.

By the way, moiré occurs between those having a periodic structure. On the other hand, in the display device 200 of the present application, since the diffusion plate 25 is provided between the light control sheet 26 and the display unit 21, the diffusion plate is used even if the light control sheet 26 and the display unit 21 have periodicity. 25, the light of the light control sheet 26 is disturbed, so that moire does not occur. Therefore, the concavo-convex shape including the side portion 101, the top portion 102, and the bottom portion 103 may be a periodic structure. The period pitch of these uneven shapes is suitably 30 μm to 300 μm. That is, when the pitch is smaller than 30 μm, it is difficult to cut the mold used for molding, and unevenness due to the shift of the pitch of the cycle occurs. On the other hand, if it exceeds 300 μm, the resin does not sufficiently enter the groove of the mold when the light control sheet 26 is molded, and it becomes difficult to mold the resin.

Moreover, as thickness of the light control sheet | seat 26, between 50 micrometers-500 micrometers is desirable, More desirably, they are 125 micrometers-500 micrometers. By making the thickness thicker than 50 μm, it is possible to suppress the occurrence of the wobbling of the light control sheet 26 by attaching the protrusion-shaped or ring-shaped holding portion 110 as shown in FIG. Furthermore, by setting it as 125 micrometers, the rigidity of the light control sheet 26 can be increased and a twist can be prevented. If it is thicker than 500 μm, it becomes difficult to hold the light control sheet 26 in a roll shape, and the material cost is also increased.

The light control sheet 26 can be manufactured on the translucent substrate 17 using an ionizing radiation curable resin such as a UV curable resin. Here, as the translucent substrate 17, PET (polyethylene terephthalate), PP (polypropylene), PC (polycarbonate) PMMA (polymethyl methacrylate), benzyl methacrylate, MS resin, other acrylic resins, or COP (cycloolefin) It is preferable to use an optically transparent member such as a polymer.
Alternatively, the technology using PET (polyethylene terephthalate), PC (polycarbonate), PMMA (polymethyl methacrylate), COP (cycloolefin polymer), PAN (polyacrylonitrile copolymer), AS (acrylonitrile styrene copolymer), etc. It may be formed by an extrusion molding method, injection molding method, or hot press molding method well known in the field.

Moreover, it is also possible to have a diffusion effect by mixing translucent fine particles into the translucent substrate 17. Moreover, the same effect can be given by using the light incident surface 26a as a mat. At this time, it is necessary to fall within the above-described total light transmittance range.

FIG. 8 illustrates a method for producing the light control sheet 26. FIG. 8A shows the cutting of the mold 301. At this time, since the portion corresponding to the apex 102 of the light control sheet 26 in contact with the diffusion plate 25 is cut with the cutting tool 302, it is not necessary to make the surface before cutting flat. FIG. 8B shows that the resin 19 is embedded in the mold 301 and the shape is molded on the light control sheet 26. The resin 19 is filled in the mold 301 and then cured. Then, the light control sheet 26 can be produced by peeling from the mold 301 as shown in FIG.
In the light control sheet 26 manufactured by such a manufacturing method, since the vertex part cut by the cutting tool 302 is transferred as it is as the top part 102, the top part 102 extending linearly is formed.

In addition, irrespective of the above, a duplicate plate may be further produced from the above-described mold 301 and the light control sheet 26 may be produced using the duplicate.

The metal mold 301 can also be manufactured by forming a recess with a laser on a metal roll that has been plated with copper and mirror-polished, and then performing etching. In such a manufacturing method, the accuracy of the surface of the mold 301 is not high because waviness is generated during mirror polishing, but since the processing is performed in a non-contact manner with a laser, the mold 301 can be manufactured without any problem. it can.

In FIG. 9, the perspective view which shows an example of the light control sheet | seat 26 of this invention is shown.
The light control sheet 26 includes a large number of concave portions having side portions 101 such that the apex angle γ is 90 degrees. Such a light control sheet 26 can be manufactured using the metal mold | die 301 produced with the above-mentioned laser.

10, 11, and 12 are cross-sectional views illustrating an example of the light control stack 201 of the present invention.
The apex angle γ of the light control sheet 26 of FIGS. 10, 11, and 12 is approximately 90 degrees. By setting the apex angle γ to approximately 90 degrees, the light emitted from the light source 41 in the planar view direction F at the side portion 101 can be totally reflected and efficiently returned to the light source 41 side.

FIG. 12 has one convex bent portion 103 and two concave bent portions 103 between the top portions 102.
In addition, the ratio of the area of the top part 102 and the bending part 103 of FIG. 12 is 1: 3. In this case, the uniformity of the light emitted from the light control stack 201 was high, and the lamp image of the light source 41 was not seen visually. Further, the ratio of the areas of the top portion 102 and the bent portion 103 can be set as appropriate.

FIG. 13 shows a light control sheet 26 in which substantially quadrangular pyramid prism shapes are arranged in a matrix. The top portion 102 extends in a direction crossing each other (a direction orthogonal in the present embodiment).

Such a shape is suitable for the light sources 41 arranged in an array.

The cross sections of the structure extending in the intersecting direction may have substantially the same shape or may have different shapes, but the mold 301 can be easily created by using the same shape.

The diffusion plate 25 has a function of diffusing light incident from the above-described light control sheet 26.
The diffusion plate 25 is a substantially plate-like member formed by dispersing a light diffusion region in a transparent resin, and the light incident from the light control sheet 26 is converted into an uneven structure on the incident surface of the diffusion plate 25, the diffusion plate 25 diffuses due to the difference in refractive index between the diffusion region inside 25 and the transparent resin, and the uneven structure of the exit surface of the diffusion plate 25.

As the transparent resin constituting the diffusion plate 25, a thermoplastic resin, a thermosetting resin, or the like can be used. For example, polycarbonate resin (PC), acrylic resin, fluorine acrylic resin, silicone acrylic resin, epoxy An acrylate resin, polystyrene resin (PS), cycloolefin polymer (COP), methylstyrene resin, fluorene resin, polyethylene terephthalate (PET), polypropylene (PP), acrylonitrile styrene copolymer (AS), or the like is used.

Moreover, it is preferable that the light-diffusion area | region disperse | distributed to this transparent resin consists of light-diffusion particle | grains from which suitable diffusion performance can be obtained easily.
As the light diffusing particles, transparent particles made of an inorganic oxide or a resin can be used. As the transparent particles made of an inorganic oxide, for example, silica, alumina or the like can be used. The transparent particles made of resin include acrylic particles, styrene particles, styrene acrylic particles and crosslinked products thereof, melamine-formalin condensate particles, PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxy resin), FEP (tetrafluoroethylene). Fluoropolymer particles such as fluoroethylene-hexafluoropropylene copolymer), PVDF (polyfluorovinylidene), and ETFE (ethylene-tetrafluoroethylene copolymer), silicone resin particles, and the like can be used.
Moreover, you may use combining 2 or more types of transparent particles from the transparent particle described previously. Furthermore, the size and shape of the transparent particles are not particularly defined.

In addition, when a thermoplastic resin is used as the transparent resin, bubbles formed in the thermoplastic resin may be used as the light diffusion region. The inner surface of the bubbles causes diffused reflection of light, and a light diffusing function equal to or higher than that when light diffusing particles are dispersed can be exhibited. Thereby, the film thickness of the diffusion plate 25 can be further reduced.

Examples of the thermoplastic resin include polyethylene terephthalate (PET), polyethylene-2, 6-naphthalate, polypropylene terephthalate, polybutylene terephthalate, cyclohexanedimethanol copolymer polyester resin, isophthalic acid copolymer polyester resin, and spiroglycol copolymer polyester. Resins, polyester resins such as fluorene copolymer polyester resins, polyolefin resins such as polyethylene, polypropylene, polymethylpentene, and alicyclic olefin copolymer resins, acrylic resins such as polymethyl methacrylate, polycarbonate, polystyrene, polyamide, polyether , Polyester amide, polyetherester, polyvinyl chloride, cycloolefin polymer, acrylonitrile polystyrene copolymer Copolymers to the body and these as a component, or the like can be used a mixture of these resins are not particularly limited.

The thickness of the diffusion plate 25 is preferably 1 to 5 mm. When it is less than 1 mm, distortion occurs, and when it exceeds 5 mm, light absorption increases and luminance decreases.

Furthermore, an uneven shape (not shown) may be formed on the surface of the diffusion plate 25. With this uneven shape, the light emitted from the diffusion plate 25 can be diffused to further improve the uniformity of the light. In this case, the concavo-convex shape is preferably a prism shape or a lens shape having a center line average roughness Ra of 3 μm to 1,000 μm. In the case of the prism shape, the prism shape is preferably polygonal, and the prism apex angle is preferably 40 ° to 170 °, and the prism pitch is more preferably 20 μm to 700 μm. The prism shape may be a pyramid shape or a truncated pyramid shape. The uneven shape described above may be changed in accordance with the illuminance or luminance of light incident on the uneven shape. For example, in the region where the illuminance or luminance of light incident on the uneven shape is large, the prism tops described above may be used. You may make a corner small.

The uneven shape may be formed on a matte surface such as a satin finish.
Furthermore, the total light transmittance of the diffusion plate 25 in this case is preferably 40% or more and 98% or less, and the haze is preferably 20% to 100%.

The diffusion member 25 having such a configuration can be manufactured by using a known technique such as a co-extrusion molding method, an injection molding method, a heat press method, a cast polymerization method, or the like.
In addition, as a method for forming the uneven shape on the diffusion plate 25, during the formation of the diffusion plate 25 by the above-described coextrusion forming method or injection molding method, pressure is applied to the mold for forming the uneven shape. Uneven shape can be transferred. Alternatively, the concavo-convex shape can be formed on the entrance surface or the exit surface of the diffusion plate 25 using a radiation curable resin such as a UV curable resin. For example, the diffusion plate 25 can be formed as a plate-like member by a coextrusion method. After molding, the concave and convex shape can be formed by UV molding on the incident surface or the emission surface of the diffusion plate 25.

The light emitted from the diffusing plate 25 enters the correction sheet 1. The correction sheet 1 is configured to be able to control at least one of the light emission direction, range, color, and luminance distribution when the incident light is emitted from the emission surface.

As the correction sheet 1, a sheet in which hemispherical convex lenses are arranged in an array on the observer side F of the translucent substrate 17 can be used.

At this time, the pitch between the apexes of the convex lens is 30 μm to 100 μm, and it is preferable that the convex lens has no periodicity as long as it has no periodicity.

Further, the correction sheet 1 can be a sheet in which prism shapes such as 3M BEFF are arranged. At this time, if the apex of the prism shape is rounded, the correction sheet 1 can be prevented from being damaged.

At this time, the pitch between the apexes of the prism shape is 25 μm to 150 μm.

As a method for manufacturing the correction film 1 having the uneven shape, the type is not particularly limited as long as it is an ionizing radiation curable resin (such as a UV curable resin or a material curable by UV or radiation) on the translucent substrate 17. ). Here, as the translucent substrate 17, PET (polyethylene terephthalate), PP (polypropylene), PC (polycarbonate) PMMA (polymethyl methacrylate), benzyl methacrylate, MS resin, other acrylic resins, or COP (cycloolefin) It is preferable to use an optically transparent member such as a polymer.
Alternatively, the technology using PET (polyethylene terephthalate), PC (polycarbonate), PMMA (polymethyl methacrylate), COP (cycloolefin polymer), PAN (polyacrylonitrile copolymer), AS (acrylonitrile styrene copolymer), etc. It may be formed by an extrusion molding method, injection molding method, or hot press molding method well known in the field.

The light control stack 201 is obtained by sequentially stacking the light control sheet 26, the diffusion plate 25, and the correction sheet 1 on the light source 41 at a certain distance.
The light control stack 201 has a condensing function for increasing the intensity of light in the planar view direction F and a diffusing function for diffusing the light to make the light uniform.
Thereby, the light of the uniform planar view direction F can be obtained while increasing the brightness of the planar view direction F. Further, the distance between the light control stack 201 and the light source 41 can be shortened as compared with the case where only the light source 41 and the diffusion plate 25 are configured, and as a result, the backlight unit 13 and the display device 200 thickness reduction is realizable.

Further, a diffusion film may be disposed between any of the light control sheet 26, the diffusion plate 25, and the correction sheet 1 for the purpose of preventing scratches and preventing optical adhesion. The above diffusion film has a function of preventing scratches, preventing optical adhesion, and diffusing or / and condensing light incident on the diffusion film.

In addition, as a method of holding the light control stack 201, the light control stack 201 may be sandwiched by a casing as shown in FIG. 14, but may be bonded using an adhesive / adhesive.

The light control stack 201 in FIG. 15 further includes a reflecting portion 20 on the back surface side of the cylindrical lens sheet 1 in which the cylindrical lens 1a is formed on the substrate 1b, and the gap 4 is provided between the adjacent reflecting portions 20. Have. Furthermore, the reflection part 20 is the structure of the light control stack 201 integrated with the light diffusing plate 25 through the optical contact material 18a.

FIG. 16 shows a configuration of the light control stack 201 in which the light control sheet 26 and the diffusion plate 25 are further integrated through the optical contact material 18b in the above-described configuration. In other words, the light control stack 201 has a single configuration.

In addition, a sticky / adhesive can be used as the optical contact materials 18a and 18b, and examples of such a sticky / adhesive include acrylic, urethane, rubber, and silicone based sticky / adhesives. .

In either case, since it is used in a high-temperature backlight, it is desirable that the storage elastic modulus G ′ is 1.0E + 04 Pa or more at 100 ° C. If the value is lower than this, the diffusion plate 25 and the correction sheet 1 may be misaligned during use. Moreover, in order to ensure the space | gap 4 stably, you may mix particles, such as transparent acryl and a silica, in a contact and an adhesive layer. The adhesive may be a double-sided tape with a carrier or a single layer.

As the translucent fine particles (transparent particles or diffusible fine particles) mixed in the adhesive or the substrate 1b, transparent particles made of inorganic oxide or transparent particles made of resin can be used. For example, examples of the transparent particles made of an inorganic oxide include particles made of silica, alumina or the like. Transparent resin particles include acrylic resin particles, styrene resin particles, styrene acrylic copolymer particles and cross-linked products thereof, melamine resin particles, melamine-formalin condensate particles, PTFE (polytetrafluoroethylene), PFA. (Perfluoroalkoxy resin), FEP (tetrafluoroethylene-hexafluoropropylene copolymer), PVDF (polyfluorovinylidene), ETFE (ethylene-tetrafluoroethylene copolymer) and other fluorine-containing polymer particles, silicone resin particles, etc. Can be mentioned. These transparent particles may be used as a mixture of two or more.

The overall thickness of the light control stack 201 is preferably 2 mm to 6 mm. When the thickness is less than 2 mm, the light control stack 201 is distorted when used in a large television. On the other hand, if it is thicker than 6 mm, light absorption increases and luminance decreases.

Example 1
The light control sheet 26 has a thickness in which square pyramid depressions as shown in FIG. 13 are arranged in an array by applying a UV curable resin on a 188 μm PET film and curing the UV light while adhering it to the mold roll 301. A light control sheet 26 having a thickness of 250 μm was obtained. The mold roll 301 has a vertical angle γ of 90 degrees, and a flat part 102 having a width of 10 μm is formed as the top part 102 of the light control sheet 26. The pitch is 250 μm and the circumferential direction of the mold roll 301 is perpendicular to the circumferential direction. Cutting was performed in various directions. As a result, an area having an area ratio of about 8% with respect to the incident surface 26a was obtained by adding the top portion 102 and the bent portion 103 to each other. The total light transmittance of the light control sheet 26 defined by JIS K7105 was 31%. The light control sheet 26 was disposed on the LED light sources 41 arranged as shown in FIG. Further, on the light control sheet 26, a diffusion plate 25 having a haze of 80% and a thickness of 2 mm was disposed. Furthermore, the brightness enhancement film RBEF manufactured by 3M Company was disposed, and the backlight unit 13 in which the light control stack 201 was disposed on the light source 41 was obtained. With this configuration, the light source 41 was turned on, and it was confirmed that there was no luminance unevenness due to the light source 41, and at the same time, it was confirmed that sufficient luminance of about 10000 cd / m 2 was obtained. Furthermore, in this state, it was allowed to stand for about 1 hour, and it was confirmed that no distortion occurred in the light control stack 201. In addition, in the vibration test assuming the transportation state, it was confirmed that there were no visible scratches on the light control sheet 26 and the diffusion plate 25. The vibration test conditions were as follows: frequency 5 to 50 Hz, acceleration 1 G, amplitude 0.2 to 19.8 mm, vibration direction / time 60 minutes up and down, left and right 15 minutes, front and back 15 minutes, 90 minutes in total Three directions were used.

(Example 2)
As the light control sheet 26, a recess made by a laser at a pitch of about 80 μm was formed on a copper roll that had been mirror-polished in advance by a laser plate making system, and a die 301 having a surface shape as shown in FIG. 9 was obtained by etching. . From this mold 301, this mold 301 was further duplicated using a silicone resin. The duplicated version was further extruded into acrylonitrile styrene copolymer resin to obtain a light control sheet 26 having a thickness of 250 μm in which dents were arranged in an array as shown in FIG. As a result, an area having an area ratio of about 35% with respect to the incident surface 26a was obtained by adding the top portion 102 and the bent portion 103 to each other. The total light transmittance of the light control sheet 26 defined by JIS K7105 was 62%. This light control sheet 26 is arranged on the LED light source 41 in which the LED light source 41 is arranged as shown in FIG. Further, a 3 mm thick diffuser plate 25 having a haze of 90% was disposed on the light control sheet 26. Furthermore, as the correction sheet 1, UTE-II manufactured by MNTECH was arranged, and the backlight unit 13 in which the light control stack 201 was arranged on the light source 41 was obtained. With this configuration, the light source 41 was turned on, and it was confirmed that there was no luminance unevenness due to the light source 41, and at the same time, it was confirmed that sufficient luminance of about 10000 cd / m 2 was obtained. Furthermore, in this state, it was allowed to stand for about 1 hour, and it was confirmed that no distortion occurred in the light control stack 201. In addition, in the vibration test assuming the transportation state, it was confirmed that there were no visible scratches on the light control sheet 26 and the diffusion plate 25. The vibration test conditions were as follows: frequency 5 to 50 Hz, acceleration 1 G, amplitude 0.2 to 19.8 mm, vibration direction / time 60 minutes up and down, left and right 15 minutes, front and back 15 minutes, 90 minutes in total Three directions were used.

(Comparative Example 1)
As the light control sheet 26, a light control sheet 26 having a thickness of 250 μm in which projections of square pyramids are arranged in an array with a pitch of 300 μm on the surface is obtained by extrusion molding to a polycarbonate resin. As a result, an area where the sum of the top portion 102 and the bent portion 103 is approximately 2% with respect to the incident surface 26a is obtained. The total light transmittance of the light control sheet 26 defined by JIS K7105 was 22%. This sheet was placed on the LED light source 41 with the LED light source 41 arranged as shown in FIG. Further, a 0.8 mm thick diffuser plate 25 having a haze of 80% was disposed on the light control sheet 26. Furthermore, the brightness enhancement film BEF III manufactured by 3M Company was disposed, and the backlight unit 13 in which the light control stack 201 was disposed on the light source 41 was obtained. With this configuration, when the light source 41 was turned on, a black shadow was seen in the portion directly above the light source 41, and uneven brightness was confirmed. At the same time, it was confirmed that sufficient luminance of about 10,000 cd / m 2 was obtained. Further, when left in this state for about 1 hour, the light control stack 201 was distorted. Further, in the vibration test assuming the transportation state, visible scratches were generated on the light control sheet 26 and the diffusion plate 25. The vibration test conditions were set to three directions of 5 to 50 Hz, acceleration of 1 G, vibration direction / time of 60 minutes in the vertical direction, 15 minutes in the left and right direction, and 15 minutes in the front and back, 90 minutes in total.

Sectional drawing which shows an example of the liquid crystal display device of this invention The figure which shows an example of the light source of this invention The figure which shows an example of the light source of this invention The figure which shows an example of the light source of this invention The figure which shows arrangement | positioning of the light source of this invention Sectional drawing which shows the side part, top part, bending part of the plate-shaped light control stack of this invention The figure which shows an example of the light control sheet of this invention which has a holding | maintenance part Explanatory drawing which shows an example of the preparation methods of the light control sheet of this invention The perspective view which shows an example of the surface shape of the light control sheet of this invention Sectional drawing which shows an example of the plate-shaped light control stack of this invention Sectional drawing which shows an example of the plate-shaped light control stack of this invention Sectional drawing which shows an example of the plate-shaped light control stack of this invention The perspective view which shows an example of the surface shape of the light control sheet of this invention Sectional drawing which shows an example of the holding method of the light control stack of this invention Sectional drawing which shows an example of the structure which adhered the correction sheet | seat and diffusion sheet of this invention through the optical contact | adherence material Sectional drawing which shows an example of the structure which closely_contact | adhered the correction sheet | seat, diffusion sheet, and light control sheet of this invention through the optical contact material Sectional view showing a conventional backlight unit

Explanation of symbols

F: Plane view direction, C4: Point light source or point light source unit arrangement position, H: Light, H11, H12: Light incident on the side portion 101, H21, H22: Light incident on the top portion 102, H3: Bending Light incident on the portion 103, 1 ... correction sheet, 1a ... lens forming portion, 1b ... base material, 4 ... gap, 13 ... backlight unit, 17 ... translucent base material, 18, 18a, 18b ... optical adhesion material , 19 ... Resin, 20 ... Reflector, 21 ... Display, 25 ... Diffuser, 26 ... Light control sheet, 26a ... Light control sheet incident surface, 26b ... Light control sheet end surface, 27 ... Display device, 33B ... Binder matrix , 33P ... particles, 41 ... light source, 41a ... line light source, 41b ... point light source, 43 ... reflector (reflective film), 46 ... white LED, 47 ... LED substrate, 48 ... red LED light emitting element, 49 ... green LED light emission element DESCRIPTION OF SYMBOLS 50 ... Blue LED light emitting element, 51 ... Phosphor, 52 ... Point light source unit, 53 ... LED lens, 54 ... Red LED, 55 ... Green LED, 56 ... Blue LED, 57 ... Red semiconductor laser, 58 ... Green semiconductor laser , 59 ... blue semiconductor laser, 60 ... optical fiber, 61 ... lens for semiconductor laser, 70 ... prism shape, 101 ... side part, 102 ... top part, 103 ... bent part, 104 ... gap, 110 ... holding part, 200 ... display Equipment 201 ... Light control stack 301 ... Mold 302 ... Byte, 401, 402 ... Holding frame 410 ... Stand γ ... Vertical angle

Claims (9)

A light source;
A light control sheet having a surface structure on the surface opposite to the light source on the light source;
A diffusion plate on the surface structure;
A correction sheet on the diffusion plate;
The surface structure is
The top that transmits light incident from the incident surface of the light control sheet; and
A bent portion that diffuses light incident from the incident surface of the light control sheet without being in contact with the diffusion plate;
A light control stack comprising: a side portion that totally reflects the incident light and returns and / or transmits the light to the light source side. A light source;
A light control sheet having a surface structure on the surface opposite to the light source on the light source;
A diffusion plate on the surface structure;
A correction sheet on the diffusion plate;
The surface structure is
A top in contact with the diffusion plate;
A bent portion that is not in contact with the diffuser plate, and is formed of a protrusion, a depression, and a step;
A light control stack comprising a top portion or a side portion between the bent portions. The light control stack according to claim 1, wherein at least one of the top portion, the bent portion, and the side portion of the surface structure has a periodic structure. 3. The light control stack according to claim 1, wherein each of the top portion, the bent portion, and the side portion of the surface structure has a random structure. 4. The light control stack according to claim 1, wherein the surface structure includes at least one bent portion between the adjacent top portions. The light control stack according to claim 1, wherein the top portion and the bent portion are 3% or more and 40% or less of an area of the incident surface. The light control stack according to claim 1, wherein the total light transmittance of light incident from the incident surface is 25% or more and 70% or less. A backlight unit using the light control stack according to claim 1. A display device comprising the backlight unit according to claim 8.

Images