JP2009237475A - Optical sheet, back light unit using the same, and display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical sheet in which the separation of fixing elements and supporting elements is prevented, the collapse of an air layer is prevented, light utility efficiency is excellent and unevenness of luminance is suppressed, to provide a back light unit using the optical sheet and to provide a display. <P>SOLUTION: The optical sheet has the supporting elements 5 on the light emission face side of an optical control sheet 1, and the light emission face side of a diffusion layer and the supporting elements are integrated via the fixing elements, wherein the separation strength α[gf/inch] of the supporting elements and the fixing elements satisfies the relation 30≤α and area ratio β of the supporting elements with respect to the light incident face of the optical control sheet is lager than 50%. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention irradiates, from the back side, a liquid crystal panel in which a transmission / non-transmission lens sheet and a display optical sheet in pixel units or a display element in which a display pattern is defined according to a transparent state / scattering state is arranged. The present invention relates to a backlight unit and a display device.

In recent years, liquid crystal display devices using TFT liquid crystal panels and STN liquid crystal panels have been commercialized mainly for color notebook PCs (personal computers) in the OA field.

In such a liquid crystal display device, a so-called backlight method is employed in which a light source is disposed on the back side (counter-viewer side) of the liquid crystal panel and the liquid crystal panel is irradiated with light from the light source.

As a backlight unit employed in this type of backlight system, a light source lamp such as a cold cathode fluorescent lamp (CCFT) is roughly divided into a flat light guide plate made of acrylic resin having excellent light transmittance. There are a “light guide plate light guide method” (so-called edge light method) for reflection and a “direct type method” that does not use a light guide plate.

As a liquid crystal display device on which a light guide plate light guide type backlight system is mounted, for example, one having a configuration as shown in FIG. 5 is generally known.

A liquid crystal panel 72 sandwiched between polarizing plates 71 and 73 is provided, and a light guide plate 79 made of a transparent base material such as a substantially rectangular plate-like PMMA (polymethyl methacrylate) or acrylic is disposed on the lower surface side thereof. A diffusion film (diffusion layer) 78 is provided on the upper surface (light emission surface) of the light guide plate.

Further, on the lower surface of the light guide plate 79, a scattering reflection pattern portion for efficiently scattering and reflecting the light introduced into the light guide plate 79 in the direction of the liquid crystal panel 72 is provided by printing or the like. A reflection film (reflection layer) 77 is provided below the scattering reflection pattern portion (not shown).

Further, the light guide plate 79 is provided with a light source lamp 76 at the side end, and further covers the back side of the light source lamp 76 so that the light from the light source lamp 76 can be efficiently incident on the light guide plate 79. Thus, a high-reflectance lamp reflector 81 is provided. The scattering reflection pattern portion is formed by printing, drying, and forming a mixture of white titanium dioxide (TiO2) powder in a solution such as a transparent adhesive in a predetermined pattern, for example, a dot pattern. The light incident on the light plate 79 is imparted with directivity and guided to the light exit surface side, which is a device for increasing the brightness.

Further, recently, in order to increase the light utilization efficiency and increase the brightness, as shown in FIG. 6, a prism film (prism layer) having a light condensing function between the diffusion film 78 and the liquid crystal panel 72 is used. ) 74 and 75 are proposed. The prism films 74 and 75 are configured to collect the light emitted from the light exit surface of the light guide plate 79 and diffused by the diffusion film 78 on the effective display area of the liquid crystal panel 72 with high efficiency.

However, in the apparatus illustrated in FIG. 5, the control of the viewing angle is entrusted only to the diffusibility of the diffusion film 78, but it is difficult to control the viewing angle. The part is unavoidably dark. In particular, there are various problems due to a large decrease in luminance relative to the front when the display is viewed from the side.
Furthermore, FIG. 6 is an apparatus using the above-described diffusion film and further a prism film, and two prism films are used to widen the field of view in the horizontal and vertical directions, but the incident light of the prism film is absorbed. The front brightness will decrease. Moreover, since the number of members increased, it also caused the cost to increase.

On the other hand, many direct type systems are employed for displays such as large liquid crystal TVs.

As a direct liquid crystal display device, a device illustrated in FIG. 7 is generally known. In this case, a liquid crystal panel 72 sandwiched between polarizing plates 71 and 73 is provided at the uppermost part of the apparatus, and is emitted from a light source 51 made of a fluorescent tube or the like on its lower surface side and diffused by an optical sheet such as a diffusion film 82. The collected light is condensed on the effective display area of the liquid crystal panel 72 with high efficiency.
In order to efficiently use the light from the light source 51 as illumination light, a reflector 52 is disposed on the back surface of the light source 51.

However, even in the apparatus illustrated in FIG. 7, the control of the visual field range is left only to the diffusibility of the diffusion film 82, but this control is difficult, and when the display is viewed from the front, the center of the display is bright. It is inevitable that the surrounding area will be dark.
In particular, there are various problems due to a large decrease in luminance relative to the front when the display is viewed from the side. In addition, the device using a diffusion film and a prism film uses two prism films in order to widen the horizontal and vertical fields of view. However, since the incident light of the prism film is absorbed, the front luminance decreases. End up. Moreover, since the number of members increased, it also caused the cost to increase.

There is also an attempt to reduce the number of light sources 51 by increasing the interval between the light sources 51, but in that case, luminance unevenness due to the light sources is likely to occur on the display, resulting in an increase in power consumption. It was.

By the way, in the display as described above, there is a strong demand as a market need for light weight, low power consumption, high brightness, and thinning. Accordingly, the backlight unit mounted on the display is also light weight, low consumption. Power and high brightness are required.

However, it is difficult to say that the conventional devices as described above sufficiently meet the demands for high brightness and low power consumption, and the user has low price, high brightness, high display quality, and low power consumption. The development of a backlight unit capable of realizing a power liquid crystal display device is awaited.

In view of the above-described situation, the applicant of the present invention includes, for example, a liquid crystal panel and a light source unit that irradiates light to the liquid crystal panel from the back side as in Patent Document 1, and the light source unit includes light from the light source. A liquid crystal display device has been proposed in which a lens layer for guiding the liquid crystal panel to the liquid crystal panel is provided and a light-shielding portion having an opening in the vicinity of the focal plane of the lens layer.

The above-mentioned Patent Document 1 discloses a configuration in which a lens sheet having a light shielding portion is disposed between a liquid crystal panel and a backlight unit as shown in FIGS. In all of FIGS. 10A and 10B, the lens sheet has a concavo-convex shape constituting a lens portion on the liquid crystal panel side.

The effect obtained by interposing the lens sheet described above has a concavo-convex shape that forms a lens portion on the liquid crystal panel side by modulating the diffusivity of light emitted from the light guide plate by the lens action.

The effect obtained by interposing the lens sheet described above is that the diffusibility of the light emitted from the light guide plate can be modulated by the lens action so that the liquid crystal panel can be aligned and emitted. .

In addition, by forming an opening at a specific location, it is possible to selectively increase the amount of light incident on the pixels of the liquid crystal panel, improving the use efficiency of the backlight and controlling the shape of the opening. In this way, it is possible to control the visual field region of the display light.

Further, in recent years, with an increase in manufacturing efficiency and a reduction in the thickness of a display device, an optical sheet having a simple structure in which an optical functional member and a light diffusing member are joined together by a fixing element as in Patent Document 2 has been developed.

However, when integrating the brightness control member and the diffusion layer, it is difficult to hold the air layer formed between adjacent support elements without deformation. Therefore, it is conceivable to form an air layer between the reflective layers by using a reflective layer having an air layer as a spacer between the brightness control member and the diffusion layer. Thereby, the shape of the air layer can be held without being deformed by bonding the diffusion layer and the luminance control member together via the fixing element.
JP 2000-284268 A JP 2006-106197 A

However, the configuration as described above has the following problems.
That is, in order to bond the diffusion layer and the brightness control member using the fixing material, it is necessary to reduce the thickness of the fixing material to such an extent that the air layer is not crushed. However, by making the fixing material thin, there is a problem that the surface irregularities of the diffusion layer are raised in the air layer, the adhesion of the fixing element is lowered, and the fixing element is peeled off.
In addition, in order to ensure sufficient adhesion between the diffusion layer and the brightness control member, when a flexible adhesive or pressure-sensitive adhesive is used as the fixing material, the fluidity of the adhesive or pressure-sensitive adhesive is high, so that it is extruded by the reflective layer. As a result, the air layer is buried.
As a result, the air layer is crushed and there is a problem that luminance unevenness occurs.

Therefore, the present invention has been made in view of the above-described problems, and can prevent separation of the fixing element and the support element and prevent collapse of the air layer, is excellent in light utilization efficiency, and can suppress luminance unevenness. An optical sheet, a backlight unit including the optical sheet, and a display device are provided.

In order to solve the above problems, the first invention is characterized in that one surface is a light incident surface, the back surface of the light incident surface is a light exit surface, and a diffusion layer that diffuses light incident from the light incident surface; A light control sheet that controls at least one of the emission direction, range, color, and luminance distribution of the light when the incident light is emitted from the emission surface, and on the light incident surface side of the light control sheet There is a support element, which is an optical sheet in which the light emitting surface side of the diffusion layer and the support element are integrated via a fixing element, and a peel strength α [gf between the supporting element and the fixing element / Inch] satisfies 30 ≦ α.
According to this configuration, it is possible to prevent the fixing element from peeling off when the light emitting surface side of the diffusion layer and the support element are bonded together.

2nd invention is characterized by the area ratio (beta) with respect to the said light-incidence surface of the said light control sheet of the said support element being larger than 50%.
According to this configuration, it is possible to prevent the fixing element from peeling off when the light emitting surface side of the diffusion layer and the support element are bonded together.

A third invention is characterized in that the surface of the support element is a shielding surface. According to this configuration, the light use efficiency is excellent, and luminance unevenness can be suppressed.

A fourth invention is characterized in that the fixing element is an adhesive.
According to this configuration, it is possible to prevent the fixing element from peeling off when the light emitting surface side of the diffusion layer and the support element are bonded together.

According to a fifth aspect of the present invention, the constituent material of the fixing element is at least one of acrylic, rubber, silicone, and vinyl resin materials, and the thickness t of the fixing element is set to 5 μm ≦ t ≦ 50 μm. It is characterized by being.
According to this configuration, by setting the thickness t of the fixing element to 5 μm ≦ t, it is possible to prevent the fixing element from peeling off when the light emitting surface side of the diffusion layer and the support element are bonded together. In addition, by setting the thickness t of the fixing element to t ≦ 50 μm, it is possible to prevent the opening serving as the air layer from being crushed. Thereby, since the shape of an opening part can be ensured, the light radiate | emitted from a light source can acquire a desired refraction effect.

A sixth invention is characterized in that the fixing element contains light diffusing fine particles having a particle size of 30 μm or less in a weight ratio of 10% or more and 30% or less.
According to this configuration, by setting the weight ratio of the light diffusing fine particles in the fixing element to 10% or more, the collapse of the opening can be suppressed, and the weight ratio of the light diffusing fine particles is set to 30% or less. Thus, the adhesion of the fixing element can be maintained.

A seventh invention is a backlight unit comprising at least a light source and the optical sheet according to any one of claims 1 to 6.
According to this configuration, since the optical sheet that is excellent in light utilization efficiency and can suppress luminance unevenness is provided, a high-performance backlight unit can be provided.

An eighth invention is characterized by comprising an image display element that defines a display image in accordance with transmission / shielding in pixel units, and the backlight unit according to claim 7 on the back of the image display element. It is a display device. According to this configuration, a high-performance display device can be provided because the backlight unit is excellent in light utilization efficiency and can suppress luminance unevenness.

According to the present invention, it is possible to achieve both prevention of peeling of the optical sheet and prevention of collapse of the air layer. Thereby, a desired refraction effect can be obtained with respect to the light diffused by the diffusion layer, and the light incident on the optical element at a large incident angle can be condensed. Therefore, it is possible to provide an optical sheet that is excellent in light utilization efficiency and has no luminance unevenness.

The best mode for carrying out the present invention will be described below with reference to the drawings.
FIG. 1A is a side view showing an example of a backlight unit and a display device according to an embodiment of the present invention.
First, the backlight unit according to the embodiment of the present invention includes a plurality of cylinder-shaped lamps 20c housed in a lamp house 20a and a liquid crystal layer 22 sandwiching light P from each lamp 20c between polarizing plates 24 and 25. An optical sheet 21 to be supplied is provided. In the figure, reference numeral 20b denotes a light reflecting plate disposed on the back side of the plurality of lamps 20c.
In addition, the display device 29 according to the embodiment of the present invention includes a light source 20 and an optical sheet 21 including the lamp house 20a, the plurality of lamps 20c, and the light reflection plate 20b, and further polarizing plates 24 and 25. This is a device including a liquid crystal panel 26 composed of sandwiched liquid crystal layers 22. In this case, the display device is a liquid crystal display device. However, the display device is not limited thereto, and may be a display device that displays an image using light, such as a projection screen device, a plasma display, or an EL display including the optical sheet 21 described above. Any type is acceptable.

As shown in FIG. 1A, in the display device of this embodiment, the light source 20, the optical sheet 21, and the liquid crystal panel 26 are laminated in this order, and the image signal is directed from the liquid crystal panel 26 toward the upper side in the figure. By emitting display light whose display is controlled by the above, an image having a rectangular shape in plan view is displayed.
The light source 20 and the optical sheet 21 constitute a backlight unit 23.
Hereinafter, based on such an arrangement, the upward direction F in FIG. 1A is simply referred to as the display screen side (light emission side), and the downward direction is simply referred to as the back side.
FIG. 1B shows a lens sheet 27 arranged on the back surface of the diffusion layer 7 of the optical sheet 21 shown in FIG.
Thereby, compared with FIG. 1A, the condensing and diffusing action of the lens sheet 27 is given, and the lamp image of the light source 20 can be reduced.

The light source 20 includes a plurality of lamps 20c in which line-shaped light emitting portions extending in the left-right direction on the paper surface are arranged at equal intervals along the depth direction of the paper surface, the lamp 20c and the lamp house 20a are covered from the back side, and the display screen side is open. A direct type system composed of the reflecting plate 20b is employed.
As the lamp 20c, for example, a cold cathode tube may be used as a linear light source, or a point light source using an LED element 50 as described below may be employed.
FIG. 2 shows a method of covering a blue LED element 50 that emits blue light, which is used in a mobile device such as a mobile phone, with a phosphor 51 that emits yellow light applied inside the LED lens 53 and emits light in a pseudo white color. White LED 46.
This method has an advantage that pseudo white light emission can be realized simply by covering the phosphor with a single-color LED element. In addition, the light source 1 used in the present invention is not limited to the above-described one, and may be one in which one single-color LED element is covered with at least one kind of phosphor.
Furthermore, the light source 20 is not limited to such a configuration as long as it can emit white light to the back side of the optical sheet 21 such as an EL and a laser, and any well-known light source may be adopted.

The optical sheet 21 collects a part of light emitted from the light source 20 to the display screen side, transmits the light to the display screen side, reflects other light to the light source 20 side, and re-enters the light source 20. The diffusion layer 7, the fixing element 6, the support element 5, and the light control sheet 1 are laminated in this order from the back side toward the display screen side. That is, in the formation area of the air layer 5a formed by the support element 5, the fixing element 6 and the light control sheet 1 are laminated in this order.

  Here, the diffusion layer 7 diffuses the light from the light source 20, and includes a transparent resin and transparent particles dispersed in the transparent resin. And the refractive index of the transparent particles must be different. The difference between the refractive index of the transparent resin and the refractive index of the transparent particles is preferably 0.02 or more. If the difference in refractive index is smaller than this, sufficient light scattering performance cannot be obtained. Further, the refractive index difference may be 0.5 or less.

The diffusion layer 7 needs to transmit the light P incident on the diffusion layer 7 while scattering the light P. For this reason, it is desirable that the transparent particles contained in the diffusion layer 7 have an average particle diameter of 0.5 to 10.0 μm. Preferably it is 1.0-5.0 micrometers.
Alternatively, the diffusion layer 7 has a structure having a fine cavity containing air in the transparent resin, and diffusion performance may be obtained by a difference in refractive index between the transparent resin and air.

  As the transparent resin, for example, polycarbonate resin, acrylic resin, fluorine acrylic resin, silicone acrylic resin, epoxy acrylate resin, polystyrene resin, cycloolefin polymer, methylstyrene resin, acrylonitrile polystyrene copolymer, fluorene resin, PET Polypropylene or the like can be used.

Here, the linear expansion coefficients of polycarbonate, polystyrene, methylstyrene resin, and cycloolefin polymer are 6.7 × 10 ⁻⁵ (cm / cm / ° C.) and 7.0 × 10 ⁻⁵ ((cm / cm / ° C.), respectively. ) is ^{7.0 × 10 -5 (cm / cm} / ℃) and ^{6~7.0 × 10 -5 (cm / cm} / ℃). On the other hand, the optical sheet 1 is, for example, may include a PET, the PET The linear expansion coefficient is 2.7 × 10 ⁻⁵ (cm / cm / ° C.), and the linear expansion coefficient of the diffusion layer 7 is larger. Warpage occurs on the layer 7 side.
However, in the embodiment of the present invention, considering that the linear expansion coefficient of the optical sheet 21 is small, the linear expansion coefficient of the diffusion layer 7 is set to 7.0 × 10 ⁻⁵ (cm / cm / ° C.) or less. Thus, the above-described deformation can be prevented.
In addition, when the optical sheet 21 is produced by using polycarbonate as a material by an extrusion method, warpage does not occur because the linear expansion coefficient is almost equal to that of other transparent resins.

  Moreover, as transparent particles, 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 particles, styrene particles, styrene acrylic particles and their cross-linked products, melamine-formalin condensate particles, polytetrafluoroethylene, perfluoroalkoxy resin, and tetrafluoroethylene-hexafluorobroylene. Examples thereof include fluorine-containing polymer particles such as polymers, polyvinylidene, and ethylene-tetrafluoroethylene copolymers, and silicone resin particles. These transparent particles may be used as a mixture of two or more.

And plate-like diffusion layer 7 can be manufactured by dispersing transparent particles in these transparent resins and extrusion-molding them. The thickness is desirably 1 to 5 mm.
If the thickness is less than 1 mm, the diffusion layer 7 is thin and has no defect, so that it has a drawback of bending. On the other hand, if it exceeds 5 mm, there is a drawback that the transmittance of light from the light source 20 is deteriorated.

Furthermore, the diffusion layer 7 may have fine unevenness on the surface, and the surface may have light diffusibility due to the fine unevenness on the surface. In this case, the diffusion layer 7 is formed by an extrusion method, a casting method, or a method using both the extrusion method and the casting method, which are well known in the art. As a specific example, as shown in FIG. 1, FIG. 1 (a) shows one in which a fine unevenness is produced on one side of the diffusion layer 7. Here, examples of the fine unevenness include a convex cylindrical shape, a lens shape, and a triangular prism shape, but are not limited thereto, and the light diffusion function of the diffusion layer 7 is provided with fine unevenness. The shape is not limited to the above as long as it has a concavo-convex shape which is improved as compared with the above.
Furthermore, forming fine irregularities on the surface of the scattering layer 7 is not limited to the light diffusion function described above, and it is possible to secure the air layer 5a.
That is, the air layer 5a can be secured by the fine irregularities formed on the light emitting surface of the diffusion layer 7 when the light emitting surface of the diffusion layer 7 and the light incident surface of the optical sheet 21 are bonded. In this case, as the fine unevenness, for example, the shape of the fine unevenness includes a rib and a microlens. However, the shape is not limited thereto, and may be any uneven shape that can secure the air layer 5a.

  Further, FIG. 1C shows a case where the fine particle layer 28 is attached to the both surfaces of the diffusion layer 7, and the fine particle layer 28 is not limited to the both surfaces but may be attached to one surface. The fine particle layer 28 may be, for example, a transparent ink containing beads, spacers, etc., but the thickness of the fine particle layer, the type and size of the fine particles are not limited, and the light diffusion of the diffusion layer 7 Any function may be used as long as the function is improved as compared with that before the fine particle layer 28 is applied.

  As described above, when the diffusion layer 7 is formed with a fine cavity containing air in a transparent resin, it may be prepared by foaming a foaming agent contained in the transparent resin in advance. The transparent resin contains a resin that is incompatible with each other, and is produced by a method of stretching at least in a uniaxial direction.

The support element 5 is installed on the light incident surface side of the light control sheet 1 to secure an air layer 5 a between the light control sheet 1 and the diffusion layer 7.
Here, the reflection layer has a rectangular shape in cross-sectional view extending in the depth direction on the paper surface on the back side of the light control sheet 1, and a plurality of reflection layers are arranged at regular intervals along the left-right direction on the paper surface, and are formed in stripes.

Here, the surface of the support element 5 may be a shielding surface. This shielding is to shield light, so that it may reflect light, or absorbs light like carbon black. Things can be used.
Here, FIG. 1A shows the case where the surface of the fixed element is a light reflecting layer. That is, the reflection layer reflects light incident on the reflection layer out of the light P emitted from the light source 20 to the back side, and re-reflects the reflected light by the reflection plate 20b. And the light utilization efficiency can be improved by injecting the light re-reflected by the reflecting plate 20b to the display screen side again.

In addition, the material of the reflective layer is, for example, a metal particle, or an ink formed by dispersing and mixing high refractive index transparent particles such as titanium dioxide, calcium carbonate, or a transfer layer, a metal foil laminated, What vapor-deposited a metal material etc. can be employ | adopted.
The cross-sectional shape of the reflective layer is not limited to a rectangular cross section as shown in FIG. For example, a trapezoidal cross section that is reduced in width toward the back side, a rectangular cross section, a cross-sectional shape obtained by rounding a corner on the back side of the trapezoidal cross section, or the like can be employed.

An open gap is formed between adjacent reflective layers, and this gap is used as an air layer 5a. The air layer 5 a regulates the incident range of light with respect to each of the plurality of light control units in the light control sheet 1 between the surface on the display screen side of the fixed element 6 and the interface on the back side of the light control sheet 1. Is. The air layer 5a is configured to have a refractive index lower than that of the fixed element 6, and light once diffused in the diffusion layer 7 passes through the air layer 5a due to interface refraction between the fixed element 6 and the air layer 5a. Thus, the light incident on the light control sheet 1 with a large incident angle can be collected again in the center.

The light control sheet 1 collects diffused light that passes through the air layer 5a to the display screen side, so that a plurality of optical elements, for example, lenses are arranged in an array at equal intervals so as to face different air layers 5a. It is an arrangement.

The light control sheet 1 in FIG. 1A is a convex cylindrical lens array in which a light control unit 1a formed convex on the display screen side uses a convex cylindrical lens extending in the depth direction of the drawing sheet as a unit lens. Become. That is, it is configured as a lenticular lens.
As the shape of the lens surface, a well-known appropriate lens surface shape such as a spherical surface or an elliptical surface may be adopted depending on the required light collecting performance. Further, in order to improve the light collection efficiency, an aspherical shape in which an ellipsoidal surface is used as a reference surface and correction is performed using a higher order term may be used.
The light control unit 1a uses, for example, a PET resin, a PC resin, a polymethyl methacrylate, a cycloolefin polymer, an acrylonitrile polystyrene copolymer, an extrusion molding method, an injection molding method, or the like well known in the art. It can be formed by a hot press molding method. Alternatively, it can be molded using an ultraviolet (UV) curable resin.

The fixing element 6 is for stacking and integrating the diffusion layer 7 on the light control sheet 1 provided with the support element 5, and the diffusion layer 7 and the support element 5 are interposed via the fixing element 6. It is pasted.
Examples of the constituent material of the fixing element 6 include a light-transmitting adhesive. The main raw material of the pressure-sensitive adhesive of this embodiment is composed of at least one of acrylic, rubber-based, silicone-based, vinyl-based and other polymer materials, and in these polymer materials, a tackifier, a tackifier, and the like. Those containing additives are preferred. The pressure-sensitive adhesive contains light diffusing fine particles having a spherical or amorphous shape and made of organic or inorganic fine particles.

As a specific method for producing the pressure-sensitive adhesive used for the fixing element 6, first, a light-diffusing fine particle is obtained by mixing and stirring a main raw material polymer material and various additives in an organic solvent in which the light-diffusing fine particle is dispersed. Is dispersed in an adhesive to produce a dispersion. Furthermore, a pressure-sensitive adhesive can be obtained by mixing a crosslinking agent with this dispersion, and applying and drying the substrate. The base material used at this time may be a film obtained by subjecting an inexpensive base material such as PET to a release treatment. Moreover, there is no restriction | limiting in particular as the application method to a base material, and a drying system.

By the way, in order to bond the diffusion layer 7 and the fixing element 6 with the adhesive, it is necessary to make the adhesive thin to such an extent that the air layer 5a in the fixing element 6 is not crushed. However, when the pressure-sensitive adhesive is made thin, the surface irregularities of the diffusion layer 7 are raised in the air layer 5a, the adhesion of the fixing element 6 is lowered, and the fixing element 6 is peeled off. Moreover, in order to ensure sufficient adhesion between the diffusion layer 7 and the fixing element 6, when a flexible adhesive and pressure-sensitive adhesive are used, the fluidity is high, so that the adhesive or pressure-sensitive adhesive enters the air layer 5 a, There is a problem that the air layer 5a is buried and the air layer 5a is crushed.

Therefore, the inventor of the present application sets the thickness of the pressure-sensitive adhesive used for the above-described fixing element 6 and the particle size, added amount, etc. of the light diffusing fine particles contained in the fixing element 6 to an appropriate value, thereby peeling off the fixing element 6. It has been found that both the prevention of air flow and the prevention of collapse of the air layer 5a can be achieved.

The light diffusing fine particles contained in the pressure-sensitive adhesive are not particularly limited as long as the fixing element 6 is adjusted so as to have a desired refractive index and the particle size thereof is sufficiently smaller than the thickness of the fixing element 6. However, when mixed with an adhesive, the particle size is preferably 30 μm or less. When the particle diameter of the light expanding fine particles exceeds 30 μm, the film strength of the fixing element 6 is lowered, and the collapse of the air layer 5a cannot be suppressed.

The thickness t of the fixing element 6 is preferably 5 μm ≦ t ≦ 50 μm.
When the thickness t of the fixing element 6 is smaller than 5 μm, good adhesion cannot be obtained. When the thickness t is larger than 50 μm, the light emitted from the fixing element 6 is greatly diffused, and the light control sheet. The light that enters the light control sheet 1 from the front direction (light that can obtain a desired light refraction action by the light control sheet 1) decreases, and the light that enters the light control sheet 1 from an oblique direction with respect to the front direction (stray light). This is because the front luminance of the display device 29 decreases as a result.

Furthermore, the light diffusing fine particles are preferably mixed with the fixing element 6 at a weight ratio c of 10% ≦ c ≦ 30%. This is because if the weight ratio c of the light diffusing fine particles in the fixing element 6 is higher than 30%, the adhesion cannot be maintained, and if it is lower than 10%, the collapse of the air layer 5a cannot be suppressed.

Next, the present invention will be described more specifically with reference to examples and comparative examples. In addition, this invention is not limited to the content of the Example.
Here, the inventor of the present application has a configuration similar to that of the optical sheet 21 in the present embodiment described above, and is a sample sheet (polystyrene resin 10 cm × x) having a different area ratio β to the light incident surface of the light control sheet of the support element 5. 30 cm × 2 mm), and an environmental test, an indentation return test, and a peel strength test were performed using these sample sheets. And the state of the collapse of the air layer, the diffusion layer, and the peeling of the reflective layer after the test was evaluated.

In the evaluation method of this environmental test, the above-described sample sheet was exposed to an environment of a temperature of 90 ° C. and a humidity of 0% for 24 hours, and the subsequent change of the sample sheet was visually confirmed.
FIG. 3 is a plan view of a sample sheet (optical sheet) and is an explanatory diagram for explaining an evaluation standard for an environmental test. 3 indicates a range of 4 × 4 mm ^{2 at} the four corners of the sample sheet.
Air layer collapse “◎” indicates no air layer collapse on the surface of the sample sheet, “◯” indicates that the air layer at the four corners of the sample sheet is slightly collapsed, but the range of the medium chain line G “×” indicates a state where the collapse of the air layer exceeds the range of the chain line G in the sample sheet, or along the lens arrangement direction of the light control unit (in this embodiment, the lens unit) It was evaluated as a case where the collapse of the air layer was observed in a different shape.
In addition, peeling “」 ”indicates that the diffusion layer and the reflection layer are not peeled off at all, and“ ◯ ”indicates that the diffusion layer and the reflection layer are slightly peeled off at the four corners of the sample sheet. The state of being in the range, “x”, was evaluated as a state in which the peeling of the diffusion layer and the reflective layer exceeded the range of the chain line G in the sample sheet. Based on the above evaluation, when the evaluation of both the collapse of the air layer and the peeling of the diffusion layer and the reflective layer is an evaluation of “◯” or more, it is determined that the optical sheet is a good product.

The evaluation method for the indentation 4 test is to place a rectangular parallelepiped rubber plate 10 mm high, 50 mm long and 50 mm wide on the lens sheet side, and a rectangular silicon rubber plate 3 mm high, 150 mm long and 150 mm wide on the diffusion layer side, and the lens surface. Restoration was visually evaluated after pressing for 1 minute with a hydraulic press at 160 gf / mm ² load from the side.
Compared with the state after the lapse of 5 minutes, the case where the state completely returned to the original state was evaluated as ◯, and the case where the collapse of the air layer was clearly visually confirmed even after the lapse of 5 minutes was evaluated as ×.

As shown in FIG. 4 (1), the peel test was evaluated by cutting a 1-inch width horizontally with a cutter as shown in FIG. 4 (1), and cutting the lens sheet into 1 inch as shown in FIG. 4 (2). Adhere PET film to the edge. Subsequently, as shown in FIG. 4 (3), the end of the PET film is lifted, peeled by a tensile tester (manufactured by INSTRON) at an angle of 180 ° and a pulling speed of 1000 mm / min for 100 mm or more, and the average value is obtained. Measure and evaluate.

Next, examples of the present invention will be described.
In Example 1, the area ratio of the support element to the light incident surface of the light control sheet is β: 62%.
In Example 2, the area ratio of the support element to the light incident surface of the light control sheet is β: 59%.
In Example 3, the area ratio β of the support element to the light incident surface of the light control sheet is 58%.
In Example 4, the area ratio β of the support element to the light incident surface of the light control sheet is 57%.
In Example 5, the area ratio of the support element to the light incident surface of the light control sheet is β: 50%.
As a result of performing various measurements under the above conditions, the results shown in Table 1 were obtained. As shown in Table 1, in Example 1 (β was 62%), it was confirmed that good results were obtained in all of the environmental test, the indentation return test, and the peel strength test. However, in Example 5 (β is 50%), all the results were bad.

Thus, according to the above-described embodiment, it is possible to achieve both prevention of peeling of the fixing element 6 and prevention of crushing of the air layer 5a, and variation in the shape of the air layer 5a can be prevented. Thereby, a desired refraction effect can be obtained for the light diffused by the diffusion layer 7, and the light incident on the light control sheet 1 at a large incident angle can be condensed. Therefore, it is excellent in light utilization efficiency, and luminance unevenness can be suppressed.
Further, by setting the thickness t of the fixing element 6 to 5 μm ≦ t ≦ 50 μm, it is possible to achieve both prevention of peeling of the fixing element 6 and prevention of crushing of the air layer 5a, and variation in the shape of the air layer 5a. Can be prevented. Thereby, a desired refraction effect can be obtained for the light diffused by the diffusion layer 7.

Furthermore, even when the optical sheet 21 is exposed to a high temperature, the adhesiveness of the fixing element 6 can be maintained and peeling of the diffusion layer 7 and the reflective layer can be prevented. Therefore, the high quality optical sheet 21 can be provided.
Further, by setting the particle size of the light diffusing fine particles to 30 μm or less, it is possible to prevent the air layer 5a from being crushed and the diffusion layer 7 and the reflection layer from being peeled off while securing the coating strength of the fixing element 6.
Further, by containing the light diffusing fine particles in the fixing element 6 in a weight ratio of 10% or more and 30% or less, the air layer 5a can be prevented from being crushed and the adhesion of the fixing element 6 can be maintained.
As described above, the optical sheet 21 is provided with both the prevention of the collapse of the air layer 5a and the prevention of the fixing element 6 from peeling, the light utilization efficiency being excellent, and the luminance unevenness being suppressed. A unit 23 and a display device can be provided.

It should be noted that the technical scope of the present invention is not limited to the above-described embodiments, and includes those in which various modifications are made to the above-described embodiments without departing from the spirit of the present invention.

(A) It is typical sectional drawing which shows schematic structure of the display apparatus in embodiment of this invention. (B) It is typical sectional drawing which shows schematic structure of the display apparatus in embodiment of this invention. (C) It is typical sectional drawing which shows schematic structure of the display apparatus in embodiment of this invention. It is a figure which shows the structural example of the point light source by a prior art. It is a top view of the sample sheet | seat used for the environmental test in embodiment of this invention, and is a figure which shows the evaluation criteria of an environmental test. (1) It is a figure which shows the evaluation method of the peeling strength test in embodiment of this invention. (2) It is a figure which shows the evaluation method of the peeling strength test in embodiment of this invention. (3) It is a figure which shows the evaluation method of the peeling strength test in embodiment of this invention. It is explanatory drawing which shows the structural example of the liquid crystal display device by a prior art. It is explanatory drawing which shows the structural example of the liquid crystal display device by a prior art. It is explanatory drawing which shows the structural example of the liquid crystal display device by a prior art. It is explanatory drawing which shows the structural example of the liquid crystal display device by a prior art. It is explanatory drawing which shows the structural example of the liquid crystal display device by a prior art. It is explanatory drawing which shows the structural example of the liquid crystal display device by a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Light control sheet 1a ... Light control part 5 ... Supporting element 5a ... Air layer 6 ... Fixed element 7 ... Diffusion layer 20 ... Light source 20a ... Lamp house 20b ... Light reflecting plate 20c ... Lamp 21 ... Optical sheet 22 ... Liquid crystal layer 23 ... Backlight unit 24, 25 ... Polarizing plate 26 ... Liquid crystal panel 27 ... Lens sheet 28 ... Fine particle layer 29 ... Display device

Claims (8)

One surface is a light incident surface, the back surface of the light incident surface is a light emitting surface, a diffusion layer that diffuses light incident from the light incident surface, and when the incident light is emitted from the emitting surface, A light control sheet that controls at least one of an emission direction, a range, a color, and a luminance distribution, and has a support element on the light incident surface side of the light control sheet, and the light emission surface of the diffusion layer An optical sheet in which a side and the support element are integrated via a fixing element, wherein a peel strength α [gf / inch] between the support element and the fixing element satisfies 30 ≦ α. Optical sheet. 2. The optical sheet according to claim 1, wherein an area ratio β of the support element with respect to the light incident surface of the light control sheet is larger than 50%. The optical sheet according to claim 1, wherein the surface of the support element is a shielding surface. The optical sheet according to claim 1, wherein the fixing element is an adhesive or an adhesive. The fixing element is made of at least one of acrylic, rubber, silicone, and vinyl resin materials, and the thickness t of the fixing element is set to 5 μm ≦ t ≦ 50 μm. Item 5. The optical sheet according to Item 1. The optical sheet according to claim 1, wherein the fixing element contains light diffusing fine particles having a particle size of 30 μm or less in a weight ratio of 10% to 30%. A backlight unit comprising at least a light source and the optical sheet according to any one of claims 1 to 6. 8. A display device comprising: an image display element that defines a display image according to transmission / light shielding in pixel units; and the backlight unit according to claim 7 on a back surface of the image display element.

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