JP2012226290A - Diffusion sheet and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve local dimming (brightness adjustment for each area) reduced in spread of light by a simple configuration without generating bright lines or dark lines in a surface light source device of an edge light system.SOLUTION: A diffusion sheet 13 has a plurality of grooves 14, which are parallel and random to each other, at least on one surface thereof, and the grooves are formed such that the average pitch of the plurality of grooves 14 is equal to or less than 30 μm while the average depth of the plurality of grooves 14 is 1 to 50 μm.

Description

  The present invention relates to a diffusion sheet, and more particularly to a diffusion sheet suitable for use in an edge light type surface light source device that performs local dimming (for example, scanning using local dimming).

  In the liquid crystal display device, a surface light source device is used as a backlight because the liquid crystal material does not emit light. There are two types of surface light source devices: a direct light method having a light source on the back surface of the liquid crystal display panel and an edge light method having a light source on the side surface of the liquid crystal display panel. Many are used. Such an edge light type surface light source device generally includes a light guide plate that emits light from the light source to the liquid crystal display panel side, and an LED (light emitting diode) or CCFL (cold cathode) disposed on the side of the light guide plate. A light source such as a tube) and a prism sheet that directs light emitted from the light guide plate toward the liquid crystal display panel. The light guide plate generally guides light incident from its side (light incident surface) by repeatedly reflecting the light inside the plate, and guides the guided light from the light exit surface to the liquid crystal display panel side by a light emitting mechanism provided on the back surface. To emit.

  In the CRT display device, each pixel emits light for only one frame in order to display an image by scanning the phosphor surface with an electron gun, whereas in the liquid crystal display device, each pixel is lit while the backlight is lit. Keeps emitting light. Therefore, in the liquid crystal display device, a decrease in contrast and blurring of moving images occur due to the afterglow characteristics of human eyes. As a countermeasure, a technique called local dimming (brightness adjustment for each area) is known in which liquid crystal display devices perform area control so that only a part of the region emits light and other regions do not emit light. With this local dimming technology, the liquid crystal display device can be improved in image quality and power saving. In addition, this local dimming technology is used, for example, when a 3D image / video is displayed by a glasses shuttering method in a liquid crystal display device. It is also used for a light emission method in which light is divided and sequentially emitted one area at a time from top to bottom.

In order to emit light only in a part of the area in the edge light type surface light source device, a plurality of light sources arranged in the vicinity of the light incident surface of the light guide plate are divided into two or more groups and only necessary groups are turned on. However, in this case, since the light emitted from the light source is not completely parallel light but has diffusibility, the light exiting surface also has a region other than the region desired to emit light depending on the critical angle of the material of the light guide plate. There is a problem that light spreads in a range where total reflection continues between the light exit surface and the back surface.
For example, if the light spreads beyond the region desired to emit light in the above-described scanning when displaying a three-dimensional image / video, it is impossible to completely prevent the right eye image and the left eye image from being mixed together. Causes a crosstalk problem and the image / video deteriorates.

  As a technique for suppressing the spread of light in the light guide plate when performing such local dimming, Patent Document 1 discloses dividing the light guide plate into strips. Further, Patent Document 2 discloses that a cut of at least half the thickness of the light guide plate is provided on the bottom surface of the light guide plate. Further, in Patent Document 3, a convex portion is provided on the light incident surface of the light guide plate and a light source is disposed on the top portion thereof, and a lenticular lens is disposed on the light incident surface of the light guide plate and a light source is disposed at the focal position. Disposition is disclosed.

JP 2001-210122 A JP 2009-199926 A JP 2009-199927 A

  However, the technique disclosed in Patent Document 1 has a fatal problem for a display device in which bright lines or dark lines are generated between the light guide plate and the light guide plate. In addition, since there are a plurality of light guide plates, it is difficult to fix each light guide plate and to manage dimensions, and it is actually difficult to manufacture a display device using the light guide plates.

  The technique disclosed in Patent Document 2 also has a problem of generating bright lines or dark lines because a deep cut is formed in the light guide plate. Moreover, it is difficult to manufacture a light guide plate having a cut of half or more of the thickness, and even if it can be manufactured, it is very expensive.

  Since the technique disclosed in Patent Document 3 requires strict accuracy in alignment between the light source and the light guide plate, it is difficult to manufacture the surface light source device, and when the position shift occurs, intense luminance unevenness occurs. .

  The present invention has been made in view of such a point, and in an edge light type surface light source device, it is possible to realize local dimming with a simple configuration and a small light spread without generating bright lines and dark lines. Objective.

  As a result of intensive studies, the present inventors have found that a random groove structure is substantially parallel to the light propagation direction in the light guide plate (that is, perpendicular to the light incident surface) on the light exit surface and / or the opposite surface of the light guide plate. It has been found that when a diffusion sheet having a thickness is laminated, light from a light source can be emitted linearly, and neither bright lines nor dark lines are generated. And when such a light-guide plate was utilized, it discovered that local dimming with little spreading of light could be performed using a common one light-guide plate, and completed this invention.

That is, the present invention is as follows.
A diffusion sheet having a plurality of random and parallel grooves on at least one surface.

  If the diffusion sheet of the present invention is used in combination with a normal light guide plate, light from the light source can be emitted linearly and only a specific area of the light exit surface can be emitted, so that a special light guide plate is not used. Local dimming with less light spread can be realized without generating bright lines or dark lines.

  Furthermore, since the effect of the direct evolution of light according to the present invention can be obtained regardless of the size of the groove structure, the groove structure is made finer, and another quality deterioration called moire generated between the display panel and other optical sheets. You can avoid causing problems. Therefore, if the groove structure is made minute, it is possible to provide a highly versatile light guide plate that can realize high-quality local dimming without causing moire even when combined with a wide variety of display panels and optical sheets. it can.

It is the schematic of the diffusion sheet of this invention. It is a surface profile figure which shows an example of the groove structure formed in the diffusion sheet of this invention. It is the schematic which shows an example of the surface which has the groove structure of the diffusion sheet of this invention. It is the schematic which shows an example of the surface which has the groove structure of the diffusion sheet of this invention. It is explanatory drawing of the specific example of the formation method of a groove structure. It is explanatory drawing of the specific example of the formation method of a groove structure. It is sectional drawing of the multilayer film for diffusion sheet manufacture. It is explanatory drawing of a diffusion angle. It is the front schematic of the surface light source device of this invention. It is the schematic of the point light source (LED) which can be utilized for the surface light source device of this invention. It is sectional drawing of the display apparatus of this invention. It is the front schematic of the liquid crystal display panel using the light-guide plate of this invention. It is a figure which shows the structure of the television receiver of this invention. It is a figure which shows the example of the laminated constitution of the diffusion sheet of this invention. It is explanatory drawing of the average gradient of the inner surface of a groove | channel. It is a figure which shows the specific example of the light emission distribution of an Example and a comparative example. It is explanatory drawing of the light straightness evaluation 1 in an Example and a comparative example. It is explanatory drawing of the light straightness evaluation 2 in an Example and a comparative example. It is a graph showing the relationship between G 'and G _0'.

The diffusion sheet of the present invention will be specifically described below.
The diffusion sheet of the present invention has a plurality of parallel and random plural grooves (hereinafter, “multiple grooves” may be referred to as “groove structure”) on at least one surface.
Here, the plurality of grooves being parallel to each other means that the center lines of the grooves are substantially parallel, and the plurality of grooves being random means that the cross-sectional shape, pitch, and It means that at least one of the depths is different randomly (irregularly).

There is no limitation in the cross-sectional shape of each groove | channel, For example, it can be set as V shape or U shape. Further, the cross-sectional shape and width of the groove may change along the extending direction of the groove.
The pitch of the grooves refers to the horizontal distance between the valley bottoms of adjacent grooves (the horizontal distance in the direction parallel to the surface having the groove structure). When the valley bottom is flat, the pitch is determined with the center as the valley bottom.
The depth of the groove is defined as the vertical distance between the top of the higher mountain and the valley bottom of the groove (distance in the direction perpendicular to the surface having the groove structure) (the peak and the valley bottom). Difference in elevation).
The cross-sectional shape, pitch and depth of the groove are observed and measured with a microscope (scanning electron microscope, laser confocal microscope, etc.) on an arbitrary vertical cross section (vertical cross section parallel to the light incident surface) of the surface having the groove structure. Can be determined by

  Specific examples of the groove structure that can be preferably used in the present invention are shown in FIGS. FIG. 2A shows a specific example of a groove structure having anisotropic diffusion characteristics in which a diffusion angle in a direction perpendicular to the groove structure (described later) is 30 degrees and a diffusion angle in a direction horizontal to the groove structure is 1 degree. It is a profile figure. FIG. 2B is a surface profile diagram showing a specific example of a groove structure having anisotropic diffusion characteristics in which a diffusion angle in a direction perpendicular to the groove structure is 60 degrees and a diffusion angle in a direction horizontal to the groove structure is 1 degree. is there.

The average pitch of the groove structure is not limited, but is preferably 30 μm or less, more preferably 25 μm or less, and further preferably 20 μm or less. Moreover, it is preferable that the average pitch of a groove structure is 580 nm (center wavelength of visible light) or more, More preferably, it is 780 nm (visible light whole region) or more.
Since the pixel pitch of the display panel used in combination with the diffusion sheet and the structure pitch of the optical sheet are approximately 100 to 600 μm and 50 to 150 μm, respectively, if the average pitch of the groove structure is set to such a value, Generation of moire due to spatial interference with a display panel or an optical sheet used in combination can be prevented. Furthermore, when the average pitch is set to such a value, the claw and the like are hardly caught on the groove structure during handling, and handling is improved. Furthermore, since the light diffused by the diffusion sheet of the present invention is visible light (electromagnetic wave of 380 nm to 780 nm), the lower limit value of the average pitch is the above in order to fully exhibit the effect of direct evolution of light by the groove structure. Such a value is preferable.
The average depth of the groove structure is not limited, but is preferably 1 to 50 μm, more preferably 1 to 40 μm, and still more preferably 1 to 30 μm.
The average pitch and the average depth of the groove structure are the pitch and depth of the groove existing within a distance of 300 μm arbitrarily extracted from an arbitrary cross section (cross section perpendicular to the groove) of the surface having the groove structure. The average value of

Also, by changing the pitch and depth of the groove structure (numerical range of pitch and depth) for each area, the straightness of light can be controlled more actively, and the degree of light reaching the center of the light exit surface can be increased. It becomes possible to improve.
For example, as shown in FIG. 3, the numerical range (average pitch and average depth) of the pitch and depth of the groove structure may be changed between the center portion of the surface having the groove structure and both side portions thereof. Furthermore, for example, the numerical range (average pitch and average depth) of the pitch and depth of the groove structure gradually changes from the edge of the diffusion sheet toward the center (the gradation changes and changes sequentially). It is also preferable to do so.

Moreover, it is preferable that the average value of the average gradient of the inner surface of each groove | channel of a groove structure is 0.3-2.0.
Here, the average gradient of the inner surface of the groove is an average gradient of the inner surface of each groove appearing in a vertical cross section in a direction perpendicular to the plurality of grooves of the diffusion sheet. The vertical distances H1 and H2 (the difference in elevation, the distance in the direction perpendicular to the horizontal plane of the diffusion sheet) from the bottom of the valley are divided by the horizontal distances L1 and L2 (the distance in the direction parallel to the horizontal plane of the diffusion sheet) therebetween. Values (H1 / L1, H2 / L2) are referred to (see FIG. 15), and are defined for both inner surfaces of each groove. (In addition, when the mountain top or valley bottom is flat, the horizontal distance between the mountain top and valley bottom means the shortest horizontal distance between them.
The average value of the average gradient of the inner surface of the groove is defined as the values of both inner surfaces of the groove existing between the horizontal distances of 300 μm arbitrarily extracted from any vertical cross section in the direction perpendicular to the plurality of grooves of the diffusion sheet. The average value of the average slope.
When the average value of the average gradient of the inner surface of each groove is less than 0.3, the effect of direct light evolution may not be sufficiently obtained. On the other hand, when the average value of the average slope of the inner side surface of each groove is 2.0 or more, it is difficult to produce, and the effect of direct evolution of light is not improved even if the average value is increased further.

  A smaller standard deviation of the average gradient of the inner surface of each groove of the groove structure is preferable because the effect of direct evolution of light can be obtained. However, if the standard deviation is less than 0.1, moire may occur. Therefore, it is preferable that the standard deviation of the average gradient of the inner surface of each groove of the groove structure is 0.1 to 0.5.

Furthermore, it is preferable that the proportion of the surface constituting the groove of the groove structure with the slope angle in the range of 40 degrees to 60 degrees is 5% or more. More preferably, it is 10% or more. Of these, the greater the proportion of 45 ° ± 5 ° contributes to the improvement in straightness.
Here, the “slope angle” is a general term for an angle formed by a surface having a groove structure and a tangent to the surface constituting each groove in a cross section perpendicular to the groove of the surface having the groove structure of the diffusion sheet.
And about the ratio which a slope angle has in the range of 40 degree-60 degree | times, the arbitrary vertical cross section (groove structure) of the surface which has a groove structure by microscope observation (a scanning electron microscope, a laser confocal microscope, etc.) A range with a distance of 300 μm is extracted arbitrarily from the cross section perpendicular to the surface, and a tangent line with points every 0.5 μm from the end of the range is extracted, and these and a surface having a groove structure are formed. It shall be determined by measuring the angle (acute angle).
The slope angle of the groove has a great influence on the straightness of light. That is, in the diffusing sheet of the present invention, it is considered that light going to spread outside is reflected by the inclined surface of the groove and returned to the inside direction to improve the straightness of the light. Therefore, the slope angle of each groove is preferably 40 to 60 degrees.

  In FIGS. 1 and 3, the grooves 14 and 33 cross the diffusion sheet from end to end. However, even if they do not necessarily cross from end to end, the effect of direct evolution of light can be obtained by the groove structure. . Accordingly, in consideration of the manufacturing conditions of the diffusion sheet, the light guide plate used in combination with the diffusion sheet, the display panel, the required display quality, etc., as shown in FIG. Good.

  The diffusion sheet of the present invention is not limited in size or configuration as long as it has a plurality of random grooves parallel to each other on the surface, but the size is the light exit surface of the light guide plate used in combination Or slightly smaller than the facing surface. Specifically, the width and length are preferably shorter by about 0.1 to 100 mm than the width and length of the light exit surface and the opposing surface. For example, when the diffusion sheet of the present invention is laminated from a position of 0.1 to 50 mm from the end that becomes the light incident surface on the light exit surface or the opposing surface of the light guide plate, it is matched with the period in which the plurality of light sources are arranged The unevenness of light and darkness (hot spot unevenness) generated can be suppressed.

The material of the diffusion sheet is not particularly limited as long as it is translucent. For example, typical polyethylene terephthalate can be used as the base material of the optical sheet. Moreover, as materials other than polyethylene terephthalate, for example, the transparency generally used as a material for optical parts such as polymethacrylic acid methacrylate, polystyrene methacrylate, polystyrene, and polycarbonate is high (for example, the total light transmittance is 90). % Or more, haze is 1.0 or less), and an inorganic material such as a polymer material or glass that hardly warps due to temperature and humidity when bonded to the light guide plate can be used.
For diffusion sheets, organic and inorganic dyes and pigments, heat stabilizers, flame retardants, antistatic agents, antifoaming agents, color stabilizers, antioxidants, UV absorbers, impurity scavengers, You may contain additives, such as a viscosity agent and a surface modifier, in the range which does not impair the objective of this invention. In particular, it is preferable to add an ultraviolet absorber or a dye (bluing agent) to prevent discoloration.
The diffusion sheet is preferably not stretched from the viewpoint of warpage prevention.

Moreover, the structure of a diffusion sheet may be a single layer thing, and can be set as the laminated body containing the sheet-like base material and the layer which has a groove structure. This laminated body may further have an adhesive layer.
Specifically, it may be a laminate structure (see FIG. 14A) having a layer having a plurality of grooves on one side of the sheet-like substrate and an adhesive layer on the other side, or the first A layer having a plurality of grooves on one surface of the sheet-like base material, and further laminating a first adhesive layer, a second sheet base material, and a second adhesive layer on the layer. It is good also as a body structure (refer FIG. 14B).

In this case, the thickness of a sheet-like base material can be 1-500 micrometers, for example, and it is more preferable to set it as 50-250 micrometers from a viewpoint of curvature prevention or productivity.
Regarding the material for the sheet-like substrate, all the matters described for the material for the diffusion sheet described above apply. Further, the sheet-like substrate is also preferably not stretched from the viewpoint of preventing warpage.
White printing can also be performed on one or both sides of the sheet-like substrate. By performing white printing, it is possible to control the brightness in the plane in detail.

  If the thickness of the adhesive layer is, for example, 1 to 300 μm, it is possible to suppress the warpage of the diffusion sheet or the light guide plate on which this is laminated and fixed.

There is no restriction | limiting in particular in the material which comprises an contact bonding layer, A general adhesive agent can be used.
For example, hot melt adhesives, thermosetting adhesives, pressure sensitive adhesives, energy ray curable adhesives, hygroscopic adhesives, dry adhesives, UV curable adhesives, polymerization adhesives, two-component reactions Of these, transparent ones such as mold adhesives and anaerobic adhesives can be preferably used. Among these, a pressure-sensitive adhesive is most preferable from the viewpoint of workability. The pressure-sensitive adhesive is generally called “adhesive”.

Specifically, an acrylic adhesive, a urethane adhesive, or a rubber adhesive can be used.
A urethane resin adhesive is a general term for an adhesive having a urethane group as a main component, and includes a structure derived from an isocyanate group, a hydroxy group, or the like. For example, a combination of a polyol having a hydroxyl group at the terminal and a polyisocyanate, a combination of an oligomer having a carboxylic acid in the side chain and a polyisocyanate, a combination of a urethane prepolymer having an isocyanate group at the terminal and a polyol, and a urethane pre having an isocyanate group at the terminal. A combination of a polymer and an oligomer having a carboxylic acid in the side chain, and the like can be mentioned. In addition, there is an example in which an adhesive is obtained by humidifying or heating a mixed liquid of a urethane prepolymer and a catalyst.
Examples of the rubber adhesive include natural rubber, a copolymer of natural rubber and an acrylic component such as methyl methacrylate, a styrene block copolymer and a hydrogenated product thereof, and a styrene-butadiene-styrene block copolymer and Examples thereof include hydrogenated products. Among these, a copolymer of natural rubber and an acrylic component such as methyl methacrylate is preferable. These may be used singly or in combination of two or more.

Acrylic adhesives are the most commonly used adhesives from the viewpoints of transparency, durability, reworkability (reworkability), and cost.
The acrylic adhesive can be prepared by the method described later, or a generally available acrylic adhesive can be used. Examples of such adhesives include MO-3006C (manufactured by Lintec Corporation), MO-3012C (manufactured by Lintec Corporation), SA10-010 (manufactured by Lintec Corporation), 8171 JR (manufactured by 3M Corporation). ), 8172 JR (manufactured by 3M Co., Ltd.), Panaclean PD-S1 (manufactured by Panac Co., Ltd.), MASTACK TR-1801 (manufactured by Fujimori Kogyo Co., Ltd.), MASTACK TR-1802 (manufactured by Fujimori Kogyo Co., Ltd.), CCL / D2-L / T5T5 (manufactured by Shin-Tac Kasei Co., Ltd.), CCL / D1 / T3T3 (manufactured by Shin-Tac Kasei Co., Ltd.), EXC10-076 (manufactured by Toyo Ink Co., Ltd.), LUCIACS CS9621T (Nitto Denko ( Co., Ltd.), LUCIACS HJ9150W (manufactured by Nitto Denko Corporation), 700A50 (manufactured by Kyodo Giken Co., Ltd.), and the like, but are not particularly limited thereto.
Such an adhesive sheet is usually formed of three layers of a light release type separate layer / adhesive layer / heavy release type (a high release type compared to the light release type). In general, a separate layer is obtained by subjecting a base material to silicon treatment, and the thickness thereof is about 10 to 500 μm. Polyethylene terephthalate is generally used as the substrate. In this case, the thickness of the adhesive layer is about 1 to 300 μm.

  As the acrylic adhesive, for example, a (meth) acrylic polymer obtained by copolymerizing 0.1 to 10% by weight of a hydroxyl group-containing monomer or 0.1 to 10% by weight of a carboxyl group-containing monomer is particularly preferable.

Specific examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 6-hydroxyhexyl (meth) acrylate.
Especially, it is preferable from the surface of the heat resistance of a (meth) acrylic-type polymer to use the hydroxyl-containing monomer whose carbon number of a side chain is 4 or more.
When the hydroxyl group-containing monomer is used, it is copolymerized in an amount of 0.1 to 10% by weight, preferably 0.3 to 7% by weight. If the content of the hydroxyl group-containing monomer is too small, the long-term durability may be lowered.

Examples of the carboxyl group-containing monomer include acrylic acid, methacrylic acid, itaconic acid, maleic acid and the like, and acrylic acid and methacrylic acid are particularly preferably used. These may be used singly or in combination of two or more. These carboxyl group-containing monomers are effective from the viewpoint of heat resistance due to improved adhesion and increased cohesive strength.
When the carboxyl group-containing monomer is used, it is copolymerized in an amount of 0.1 to 5% by weight, preferably 0.2 to 3% by weight. If the amount of the carboxyl group-containing monomer is too small, the adhesiveness is inferior. If the amount is too large, it becomes hard and the durability may be inferior, or the compatibility with the tackifier may be greatly reduced and the adhesive may become cloudy.

  In addition to these, a (meth) acrylic monomer having a copolymerizable alkyl group is used for the (meth) acrylic polymer. Examples of such (meth) acrylic monomers include ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, pentyl (meth) acrylate, isoamyl (meth) acrylate, Examples include hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, and isomyristyl (meth) acrylate. These may be used singly or in combination of two or more. Among these, from the viewpoint of imparting flexibility to the adhesive, n-butyl (meth) acrylate is preferably used, and in that case, it is preferably used in an amount of 30 to 99% by weight in the (meth) acrylic polymer. More preferably, it is 50 to 99% by weight.

  Furthermore, another copolymerizable monomer (monomer component) may be appropriately copolymerized with the (meth) acrylic polymer. Examples of the copolymerizable monomer include methyl (meth) acrylate, vinyl acetate, acrylamide, dimethylaminoalkylamide, acryloylmorpholine, glycidyl acrylate, styrene derivatives such as styrene and α-methylstyrene, vinyl toluene and α- Examples thereof include high refractive index monomers such as vinyltoluene derivatives, benzyl (meth) acrylate, naphthyl (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxybutyl (meth) acrylate, and the like.

  The (meth) acrylic polymer is a (meth) acrylic polymer containing 0.1 to 30% by weight of a carboxyl group-containing monomer and 30 to 99.9% of n-butyl (meth) acrylate as a copolymerization component. It is preferable that the gel fraction of the (meth) acrylic polymer is adjusted to 30 to 90% by weight. When such a (meth) acrylic polymer is used, it is possible to improve both the internal cohesive force and the flexibility of the adhesive layer, so that when the diffusion sheet including the adhesive layer is used by being bonded to the light guide plate, the adhesive layer No foaming phenomenon at the interface between the light guide plate and peeling of the adhesive layer from the light guide plate.

  The (meth) acrylic polymer has a weight average molecular weight of usually 600,000 or more, preferably 700,000 to 3,000,000. If the weight average molecular weight is too small, the durability is poor, and if it is too large, the workability deteriorates, which is not preferable.

For the production of the (meth) acrylic polymer, any known production method such as solution polymerization, bulk polymerization, and emulsion polymerization can be employed.
For example, in solution polymerization, it is preferable to use 0.01 to 0.2 parts by weight of a polymerization initiator such as azobisisobutyronitrile (AIBN) with respect to 100 parts by weight of the (meth) acrylic polymer, More preferably, 0.05 to 0.15 parts by weight are used. It can be obtained by reacting at 50 to 70 ° C. for 8 to 30 hours under a nitrogen stream using a polymerization solvent such as ethyl acetate.

Modification treatment can also be performed for the purpose of adjusting the refractive index of the (meth) acrylic polymer thus obtained, increasing the internal cohesive force, and increasing the heat resistance.
For example, as the modification treatment, in the presence of 100 parts by weight of the obtained (meth) acrylic polymer, a monomer and / or a monomer component different from the monomer component contained in the monomer component of the (meth) acrylic polymer is used. The monomer (monomer component) is added in an amount of 10 to 200 parts by weight, preferably 10 to 100 parts by weight, and the medium is adjusted as necessary to give a peroxide of 0.02 to 5 parts by weight, preferably 0.04 to Using 2 parts by weight, the graft polymerization reaction is carried out.
Here, the monomer contained in the monomer component of the (meth) acrylic polymer and / or the monomer different from the monomer component are not particularly limited, but examples thereof include benzyl (meth) acrylate, phenoxy (meth) acrylate, and naphthyl. High refractive index monomers such as (meth) acrylic monomers such as (meth) acrylate and isobornyl (meth) acrylate, styrene derivatives such as styrene and α-methylstyrene, and derivatives such as vinyltoluene and α-vinyltoluene can give. By graft polymerization of the high refractive index monomer, the refractive index of the (meth) acrylic polymer can be increased.
As a graft polymerization method, in the case of solution polymerization, a necessary monomer and a solvent whose viscosity is adjusted are added to a solution of a (meth) acrylic polymer, followed by nitrogen substitution, and then a peroxide of 0.02 to 5 Part by weight, preferably 0.04 to 2 parts by weight, is added and heated at 50 to 80 ° C. for 4 to 15 hours to carry out the graft polymerization reaction.
For emulsion polymerization, add water to adjust the amount of solids to the aqueous dispersion of (meth) acrylic polymer, add the necessary monomers, and replace with nitrogen with stirring. After the monomer is absorbed into the polymer particles, a water-soluble peroxide aqueous solution is added, and the reaction is terminated by heating at 50 to 80 ° C. for 4 to 15 hours.
Thus, by polymerizing the monomer in the presence of the (meth) acrylic polymer, a homopolymer of this monomer is also produced, but graft polymerization to the (meth) acrylic polymer also occurs. The polymer consisting of the homopolymer is uniformly present in the (meth) acrylic polymer. In this case, if the amount of peroxide used as an initiator is small, it takes too much time for the graft polymerization reaction, and if it is too large, a large amount of monomer homopolymer is generated.

In addition to a base polymer such as a (meth) acrylic polymer, an adhesion-imparting agent such as a tackifier may be appropriately added to the adhesive. The transparency is preferably a Gardner hue of 1 or less in a 50% by weight toluene solution.
Although it does not specifically limit as said tackifier, A non-colored and transparent thing is preferable. As the tackifier, for example, a tackifier having an aromatic ring and having a refractive index in the range of 1.51 to 1.75 is preferably used. Moreover, it is preferable that the weight average molecular weights of a tackifier are 1000-3000, and it is preferable that a softening point is 90 degrees C or less. If the weight average molecular weight exceeds 3000 or the softening point exceeds 90 ° C., the compatibility with the (meth) acrylic polymer may be reduced. If the weight average molecular weight is less than 1000, the cohesive strength of the adhesive May decrease.
Specifically, styrene oligomer, phenoxyethyl acrylate oligomer, copolymer of styrene and α-methylstyrene, copolymer of vinyltoluene and α-methylstyrene, hydrogenated product of C9 petroleum resin, terpene phenol Examples thereof include hydrogenated products, rosin and hydrogenated derivatives thereof. At this time, the tackifier having a softening point of 40 ° C. or lower is used in an amount of less than 30 parts by weight, and the tackifier having a softening point of 50 ° C. or higher is used in combination with 20 parts by weight or more in terms of heat resistance. Is preferable.
The amount of these tackifiers used is 10 to 150 parts by weight, preferably 20 to 100 parts by weight, with respect to 100 parts by weight of the (meth) acrylic polymer solid content, and is adjusted to a predetermined refractive index. If the amount is too small, the refractive index will not increase sufficiently, and if it is too large, it will become hard and the adhesiveness will deteriorate, which is not preferable.

A crosslinking agent can be appropriately used for the adhesive. In particular, when a (meth) acrylic polymer is used as the base polymer, it is preferable because the cohesive force and durability are improved by crosslinking.
Examples of the crosslinking agent include an isocyanate crosslinking agent, an epoxy crosslinking agent, an oxazoline crosslinking agent, and a peroxide.
Diisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, diisocyanate adducts modified with various polyols, isocyanurate rings, burettes, and allophanates And a polyisocyanate compound in which is formed. In particular, aliphatic and alicyclic isocyanates are preferably used because the cross-linked product becomes transparent.
In addition, in an aqueous dispersion of a modified (meth) acrylic polymer produced by emulsion polymerization, an isocyanate crosslinking agent is often not used, but when used, the isocyanate group easily reacts with water. An isocyanate-based cross-linking agent may be used.

As the peroxide, any peroxide can be used as long as it generates radicals by heating to advance the crosslinking of the base polymer of the adhesive. For example, di (2-ethylhexyl) peroxydicarbonate, di (4-t-butylcyclohexyl) peroxydicarbonate, di-sec-butylperoxydicarbonate, t-butylperoxyneodecanoate, t-hexyl Peroxypivalate, t-butyl peroxypivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, di ( 4-methylbenzoyl) peroxide, dibenzoyl peroxide, t-butylperoxyisobutyrate, 1,1-di (t-hexylperoxy) cyclohexane and the like. Among these, di (4-t-butylcyclohexyl) peroxydicarbonate, dilauroyl peroxide, dibenzoyl peroxide, and the like are preferably used because of particularly excellent crosslinking reaction efficiency.
The peroxide may be used alone, or two or more kinds may be mixed and used, but the total content is 0.1% of the peroxide with respect to 100 parts by weight of the base polymer. It is preferable to contain 03-2 weight part, It is more preferable to contain 0.04-1.5 weight part, It is more preferable to contain 0.05-1 weight part. If the amount is less than 0.03 parts by weight, the cohesive force may be insufficient. On the other hand, if the amount exceeds 2 parts by weight, the crosslinking may be excessively formed and the adhesiveness may be poor.

  In addition, when an aromatic isocyanate compound is used as a crosslinking agent, the cured adhesive may be colored, so in the application of the present invention (diffusion sheet) where transparency is required, Aliphatic and alicyclic isocyanates are preferably used.

  The amount of the crosslinking agent as described above varies depending on the material used, but is usually 0.03 to 2 parts by weight, preferably 0.05 to 1 part by weight, based on 100 parts by weight of the (meth) acrylic polymer. Used in part range. When the amount is too small, the cohesive force is insufficient, and when the amount is too large, the adhesiveness is lowered, which is not preferable.

Moreover, a silane coupling agent can be suitably added to the adhesive.
Examples of the silane coupling agent include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 2- (3,4-epoxycyclohexyl). Epoxy group-containing silane coupling agents such as ethyltrimethoxysilane, 3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N- (1, (3-dimethylbutylidene) propylamine, amino group-containing silane coupling agents such as N-phenyl-3-aminopropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane ( (Meth) acrylic group-containing Silane coupling agents, such as Inshianeto group-containing silane coupling agents such as 3-isocyanate propyl triethoxysilane and the like. Use of such a silane coupling agent is preferable for improving durability. Moreover, the adhesiveness with respect to a glass base material also improves.

  The silane coupling agent may be used alone or in combination of two or more, but the total content is 100 parts by weight of the (meth) acrylic polymer. It is preferable to contain 0.01-2 weight part of silane coupling agents, and it is more preferable to contain 0.02-1 weight part. If it is less than 0.01 part by weight, the durability improving effect may be inferior, while if it exceeds 2 parts by weight, the adhesive force may increase excessively and the removability may be inferior.

  The adhesive may contain an organic solvent in a very small amount, such as methanol, ethyl alcohol, isopropyl alcohol, n-butyl alcohol, cyclohexanol, benzyl alcohol, ethyl ether, 1,4-dioxane. , Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether acetate, chloroform, toluene, m-xylene, p-xylene, o-xylene, n-hexane, cyclohexane, methyl acetate, acetic acid Ethyl, isopropyl acetate, propyl acetate, isobutyl acetate, butyl acetate, pentyl acetate (amyl acetate), isopentyl acetate, acetone, methyl ethyl ketone (MEK), cyclohexanone, N, N-dimethyl Le formamide (DMF), dimethylsulfoxide (DMSO) or the like is used is not particularly limited. These organic solvents are preferably contained in an amount of 0.001 to 1 part by weight, more preferably 0.001 to 0.5 part by weight, based on 100 parts by weight of the (meth) acrylic polymer. More preferably, 1 part by weight is contained. If the content is 1 part by weight or more, the organic solvent generated from the adhesive may dissolve the sheet-like substrate or the light guide plate, which is not preferable. When the content is less than 0.001 part by weight, it is not preferable because it takes a drying time and a drying cost.

  The adhesive may contain other known additives, such as powders such as vulcanizing agents, adhesion-imparting agents, colorants, pigments, dyes, surfactants, plasticizers, surface lubrication. For applications that use agents, leveling agents, softeners, antioxidants, anti-aging agents, light stabilizers, UV absorbers, polymerization inhibitors, inorganic or organic fillers, metal powders, particles, foils, etc. It can be added as appropriate. Moreover, you may employ | adopt the redox system which added a reducing agent within the controllable range.

In addition, the adhesive can be prepared in the form of being laminated on the support that has been subjected to the release treatment when the diffusion sheet is manufactured. For example, the adhesive can be coated, dried and cross-linked on a release-treated support to obtain a sheet with an adhesive layer. Specifically, a pressure-sensitive adhesive is applied and dried on a release-treated support, and a release-treated film having a relatively low peel strength is bonded thereon to produce a sheet with a pressure-sensitive adhesive. Alternatively, the pressure-sensitive adhesive may be applied and dried on the support that has been subjected to the peeling treatment, and then immediately bonded to the substrate.
Examples of such a support material include polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, acrylic resins such as polymethyl methacrylate, thermoplastic resins such as polycarbonate resin, polystyrene resin, and polymethylpentene resin. And resins obtained by curing an ionizing radiation curable resin comprising an oligomer such as polyester acrylate, urethane acrylate, epoxy acrylate, and / or an acrylate monomer with electromagnetic radiation such as ultraviolet rays or electron beams. Moreover, as a peeling process, a silicone layer is apply | coated or an emboss shape is provided.
As the method of applying the adhesive, any coating method such as reverse coater, comma coater, lip coater, die coater, etc. is used so that the adhesive thickness after drying is usually 2 to 500 μm, preferably 5 to 100 μm. Is done.

<Gel fraction>
When the adhesive contains a crosslinking agent, it is applied and dried on a sheet-like substrate or the above-exfoliated support, and the gel fraction of the adhesive after crosslinking is 30 to 90% by weight, preferably 40 to 90%. Cross-linking treatment may be performed so that the amount is 5% by weight, more preferably 45 to 85% by weight.
If the gel fraction is too small, the cohesive force is inferior, and if it is too large, it is not preferable because the adhesiveness is inferior. Even if the monomer is generated, the foaming phenomenon at the adhesive interface between the base material and the adhesive layer can be suppressed. Here, the gel fraction of the adhesive refers to the proportion of the adhesive that does not dissolve in ethyl acetate, and is an index indicating the proportion (mass%) of the crosslinked one.
(Measurement of gel fraction)
The gel fraction can be measured as follows.
Take out W ₁ g of adhesive and soak it in ethyl acetate at room temperature (about 25 ° C.) for 7 days, then remove the soaked adhesive (insoluble matter) from ethyl acetate and dry it at 130 ° C. for 2 hours. W ₂ g was measured, and the gel fraction was determined as follows: Gel fraction (% by weight) = (W ₂ / W ₁ ) × 100
Calculate as

<Storage modulus>
The storage elastic modulus at 100 ° C. of the material constituting the adhesive layer is preferably in the range of 20,000 to 320,000 Pa, more preferably 20,000 to 200,000 Pa, still more preferably 20,000 to 180,000 Pa, even more preferably 20,000-100,000 Pa, particularly preferably 20,000 Pa-80,000 Pa, particularly preferably 75,000 Pa. If the storage elastic modulus is too small, peeling or the like after sticking tends to occur, and if it is too large, the adhesiveness is inferior. In addition, if the storage elastic modulus is too small, foaming occurs at the time of sticking to the acrylic plate, which is not preferable.
Here, the storage elastic modulus G ′ at 100 ° C. is a value obtained by measuring the storage elastic modulus G ′ at 90 ° C. or higher and lower than 110 ° C. based on the results obtained under the following conditions. As the measuring device, for example, ARES manufactured by TA Instruments Inc. can be used.
-Deformation mode: Torsion-Measurement frequency: Constant frequency 1 Hz
-Rate of temperature increase: 5 ° C / min-Strain: 0.2%
・ Measurement temperature: Measured from near the glass transition temperature of the adhesive to 200 ° C ・ Measuring part shape: Parallel plate 8mmφ
・ Sample thickness: 0.8-1mm
Pretreatment: vacuum drying at a temperature of 50 ° C. and a vacuum degree of −0.02 MPa for 30 minutes. The storage elastic modulus G ′ at 100 ° C. in the present invention is obtained in the same manner except that the following conditions are adopted as measurement conditions. There is a one-to-one correlation with the value (G ₀ ′). The correspondence is shown in FIG.
Deformation mode: Torsion Measurement frequency: Constant frequency 1 rad / s
-Rate of temperature increase: 5 ° C / min-Strain: 2%
・ Measurement temperature: Measured from near the glass transition temperature of the adhesive to 200 ℃ ・ Measurement shape: Parallel plate 25mmφ
・ Sample thickness: 0.8-2mm
・ Pretreatment: None

(Foaming test when pasting on acrylic plate)
<Foaming test>
The foam test was performed under the following conditions.
After affixing an adhesive to a polyethylene terephthalate film (Toyobo Cosmo Shine A4300, 75 μm thickness), the size was cut to 160 mm × 90 mm, and the same size acrylic plate (Kanase Kogyo, Kanaselite 1300, thickness: 2 mm, Size 25 cm × 3 cm), put into a dryer at 100 ° C., and visually observed for foaming after 24 hours.

<Thermomechanical analysis (TMA)>
The displacement of TMA (thermomechanical analysis) at 100 ° C. of the material constituting the adhesive layer is preferably in the range of −1 to 2 μm, more preferably 0 to 1 μm, still more preferably 0 to 0.5 μm. is there. If the displacement of the TMA is too small, peeling or the like after sticking is likely to occur, and if it is too large, undulation is caused by heat, which is not preferable.
(Measurement of thermal mechanical analysis (TMA) displacement)
The thermomechanical analysis was performed under the following conditions.
・ Device: Seiko Instruments TMA / SS120
-Probe: Needle-in probe (tip diameter: 1 mm)
・ Load: 10mN (1.02g)
・ Atmosphere: Air ・ Temperature range: 30 to 200 ° C
Temperature rising time: 5 ° C./minute Measurement sample: 25 μm-thick adhesive layer was cut into 5 mm square and attached to a quartz disk (10 mmφ).

<Thermogravimetric analysis (TG / DTA)>
The material constituting the adhesive layer preferably has a TG / DTA (weight reduction rate) at 100 ° C. in the range of 0 to −0.4%, more preferably 0 to −0.3%, still more preferably. 0 to -0.2% adhesive is used. If the TGA is too large, the adhesive is deteriorated by heat, which is not preferable.
(Measurement of thermogravimetric analysis)
Thermogravimetric analysis was performed under the following conditions.
・ Device: TG / DTA220 manufactured by Seiko Instruments Inc.
・ Atmosphere: Nitrogen (Flow rate: 250ml / min)
-Temperature range: 30 ° C to 200 ° C
Temperature rising time: 10 ° C./min Sample preparation: A 25 μm thick adhesive layer was folded over so that the total weight was about 10 mg and set in a sample container.

<Peel strength>
The peel strength of the material constituting the adhesive layer is preferably in the range of 0.3 to 1.5 N / mm, more preferably 0.4 to 1.2 N / mm, still more preferably 0.5 to 1.0 N. A / mm adhesive is used. If the peel strength is too low, peeling or the like after sticking is likely to occur.
(Measurement of peel strength)
The peel strength was measured under the following conditions.
・ Device: RTG-1210 manufactured by A & D
・ Peeling angle: 90 °
・ Peeling speed: 50 mm / min
・ Measurement distance: 50mm
Test environment: temperature 23 ° C, humidity 50%
-Adhesive sample: After affixing an adhesive layer to a polyethylene terephthalate film (Toyobo Cosmo Shine A4300, 75 μm thickness), the width was cut to 3.5 mm, and an acrylic plate (manufactured by Kanase Industry, Kanaselite 1300, thickness: 2 mm, size 25 cm × 3 cm) and left for 1 day in an environment of temperature 23 ° C. and humidity 50% was used as a measurement sample.

<Refractive index>
The material for the adhesive layer is preferably a material having high transparency. (For example, the total light transmittance is 90% or more, and the haze is 1.0 or less.) The refractive index of the material of the adhesive layer is preferably in the range of 1.40 to 1.70, more preferably 1. 45 to 1.65, more preferably 1.45 to 1.60.
(Measurement of refractive index)
The refractive index was measured under the following conditions.
Under an atmosphere of 25 ° C., sodium D line (589 nm) was irradiated, and the refractive index was measured using an Abbe refractometer (manufactured by ATAGO, DR = M4).

The material of the layer having a plurality of grooves (groove structure) is not limited. However, when the groove structure is formed by UV transfer shaping or speckle pattern exposure described later, the photopolymerizable resin composition is cured. Things will be used.
Examples of the photopolymerizable resin composition include (A) 70-99.9% by mass of an addition polymerizable monomer having at least one terminal ethylenically unsaturated group, and (B) a photopolymerization initiator: 0.1-30. What contains the mass% is preferable.

(A) As the addition polymerizable monomer having at least one terminal ethylenically unsaturated group, for example, a compound represented by the following general formula (I) can be used. In general formula (I), R represents a hydrogen atom or a methyl group, A represents an alkylene group having 1 to 4 carbon atoms, and n represents an integer of 1 to 3.

As the above-mentioned (A) addition polymerizable monomer having at least one terminal ethylenically unsaturated group, in addition to the compound represented by the above general formula (I), a compound having a known (meth) acrylate group or allyl group Can be used.
For example, nonylphenol acrylate, alkoxylation (1) o-phenylphenol acrylate, 2-hydroxy-3-phenoxypropyl acrylate, β-hydroxypropyl-β ′-(acryloyloxy) propyl phthalate, 1,4-tetramethylene glycol di ( (Meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,4-cyclohexanediol di (meth) acrylate, octapropylene glycol di (meth) acrylate, glycerol (meth) acrylate, 2-di (p-hydroxy) Phenyl) propane di (meth) acrylate, glycerol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, polyoxypropyltrimethylolpropane tri (meth) acrylate Polyoxyethyltrimethylolpropane tri (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, trimethylolpropane triglycidyl ether tri (meth) acrylate, bisphenol A diglycidyl ether di (Meth) acrylate, diallyl phthalate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, bis (triethylene glycol methacrylate) nonapropylene glycol, bis (tetraethylene glycol methacrylate) polypropylene glycol, bis (triethylene glycol) Methacrylate) polypropylene glycol, bisarylfluorene derivatives, bis (diethyl) (Lene glycol acrylate) polypropylene glycol, compounds containing both ethylene oxide chain and propylene oxide chain in the molecule of bisphenol A (meth) acrylate monomer. Among these, alkoxylated (1) o-phenylphenol acrylate is preferable from the viewpoint of refractive index, and ethoxylated (1) o-phenylphenol acrylate (for example, product name A-LEN-10, manufactured by Shin-Nakamura Chemical Co., Ltd.) is particularly preferable. preferable.
A urethanized compound of a polyvalent isocyanate compound such as hexamethylene diisocyanate or tolylene diisocyanate and a hydroxy acrylate compound such as 2-hydroxypropyl (meth) acrylate can also be used. The urethanized compound in this case is preferably less than 10,000 in terms of polystyrene-reduced number average molecular weight by gel permeation chromatography (GPC).
The above-mentioned (A) addition polymerizable monomer having at least one terminal ethylenically unsaturated group may be used alone or in combination of two or more.

  The content of the (A) addition polymerizable monomer in the photopolymerizable resin composition is 70% by mass or more and 99.9% by mass or less based on the total mass of the photopolymerizable resin composition. Preferably they are 75 mass% or more and 95 mass% or less. From the viewpoint of sufficient curing, the content is 70% by mass or more, and is 99.9% by mass or less in consideration of blending an initiator component, other polymerization inhibitors, dyes, and the like.

Examples of the photopolymerization initiator (B) in the photopolymerizable resin composition include benzyl dimethyl ketal, benzyl diethyl ketal, benzyl dipropyl ketal, benzyl diphenyl ketal, benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, Benzoin phenyl ether, thioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2,4-diisopropylthioxanthone, 2-fluorothioxanthone, 4-fluorothioxanthone, 2-chloro Thioxanthone, 4-chlorothioxanthone, 1-chloro-4-propoxythioxanthone, benzophenone, 4,4'-bis (dimethylamino) benzofe Aromatic ketones such as non [Michler's ketone], 4,4′-bis (diethylamino) benzophenone, 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one , Biimidazole compounds such as 2- (o-chlorophenyl) -4,5-diphenylimidazolyl dimer, acridines such as 9-phenylacridine, α, α-dimethoxy-α-morpholino-methylthiophenylacetophenone, 2,4 , 6-trimethylbenzoyldiphenylphosphine oxide, phenylglycine, N-phenylglycine, 1-phenyl-1,2-propanedione-2-O-benzoyloxime, ethyl 2,3-dioxo-3-phenylpropionate 2- (O-benzoylcarbonyl) -oxime Oxime esters such as p-dimethylaminobenzoic acid, p-diethylaminobenzoic acid, and p-diisopropylaminobenzoic acid, and esterified products thereof with these alcohols, p-hydroxybenzoic acid ester, 3-mercapto-1,2 Triazoles such as 1,4-triazole, tetrazoles, N-phenylglycine, N-phenyl-N-phenylglycine, N-phenylglycine such as N-ethyl-N-phenylglycine, and 1-phenyl-3- Styryl-5-phenyl-pyrazoline, 1- (4-tert-butyl-phenyl) -3-styryl-5
And pyrazolines such as 1-phenyl-3- (4-tert-butyl-styryl) -5- (4-tert-butyl-phenyl) -pyrazoline.
Among these, 2-hydroxy-2-methyl-1-phenyl-propan-1-one (for example, product name DAROCURE 1173, manufactured by Ciba Specialty Chemical) is preferable.

The content of the photopolymerization initiator (B) in the photopolymerizable resin composition is 0.1% by mass or more and 30% by mass or less, preferably 1% by mass based on the total mass of the photopolymerizable resin composition. It is 20 mass% or less.
When the content of (B) is 0.1% by mass or more, sufficient photocuring sensitivity can be obtained, and when it is 30% by mass or less, storage stability as a liquid resin before photocuring is obtained. .

In order to improve thermal stability and storage stability, it is preferable to contain a radical polymerization inhibitor in the photopolymerizable resin composition.
Examples of such radical polymerization inhibitors include p-methoxyphenol, hydroquinone, pyrogallol, naphthylamine, t-butylcatechol, cuprous chloride, 2,6-di-t-butyl-p-cresol, 2,2 Examples include '-methylenebis (4-ethyl-6-t-butylphenol), 2,2'-methylenebis (4-methyl-6-t-butylphenol), and the like.
The content of the radical polymerization inhibitor is preferably 0.001% by mass or more and 1% by mass or less based on the total mass of the photopolymerizable resin composition.

  The photopolymerization resin composition may contain an organic solvent in a small amount. For example, methanol, ethyl alcohol, isopropyl alcohol, n-butyl alcohol, cyclohexanol, benzyl alcohol, ethyl ether, 1,4 -Dioxane, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether acetate, chloroform, toluene, m-xylene, p-xylene, o-xylene, n-hexane, cyclohexane, methyl acetate , Ethyl acetate, isopropyl acetate, propyl acetate, isobutyl acetate, butyl acetate, pentyl acetate (amyl acetate), isopentyl acetate, acetone, methyl ethyl ketone (MEK), cyclohexanone, N, N Dimethylformamide (DMF), dimethylsulfoxide (DMSO) or the like is used is not particularly limited. These organic solvents are preferably contained in an amount of 0.001 to 1 part by weight, more preferably 0.001 to 0.5 part by weight, and even more preferably 0.001 to 0.1 part by weight. If it is contained in an amount of 1 part by weight or more, the organic solvent generated from the photopolymerization resin composition may dissolve other materials that are in contact with it, such being undesirable. When the content is less than 0.001 part by weight, it is not preferable because it takes a drying time and a drying cost.

The refractive index of the photopolymerizable resin composition after curing is preferably in the range of 1.40 to 1.70, more preferably 1.45 to 1.70, still more preferably 1.45 to 1.65. .
If the refractive index is lower than 1.40, the effect of direct evolution of light may not be sufficiently obtained. On the other hand, if the refractive index is higher than 1.70, manufacturing becomes difficult, and even if the refractive index is higher than this, the effect of direct evolution of light is not improved so much.

  The thickness of the layer having a groove structure can be, for example, about 2 to 100 μm.

When the diffusion sheet of the present invention is laminated on the light exit surface and / or the opposing surface of the light guide plate so that the plurality of grooves are perpendicular to the light entrance surface, the light incident on the light guide plate from the light entrance surface can be obtained. Straightness is improved.
The reason why the straightness of the light is improved is not clear, but when the light incident from the light incident surface comes out of the light guide plate and hits the groove of the diffusion sheet and totally reflects, in a plane perpendicular to the light propagation direction It is presumed that the reflection is made so as to return to the incident direction. However, the mechanism is not limited to this.

There is no limitation on the method of forming the groove structure on the surface of the diffusion sheet of the present invention.
For example, (1) a method of forming a groove structure using a mold having an uneven pattern corresponding to the groove structure, (2) a method of transferring the groove structure using a transfer mold having an uneven pattern corresponding to the groove structure, 3) A method of forming a layer for forming a groove structure by speckle pattern exposure can be used.

As a method of (1), for example, in the case of injection molding, by placing a stamper having a concavo-convex pattern corresponding to the groove structure at a position opposite to the surface on which the groove structure of the mold for forming the diffusion sheet is formed. From the beginning, a light guide plate having a groove structure can be formed. This method is suitable for manufacturing a comparatively small (about 32 or less) diffusion sheet for a light guide plate.
In the case of cast molding, a diffusion sheet having a groove structure from the beginning is provided by providing an uneven pattern corresponding to the groove structure on the base plate (mold) used when the cast resin or resin composition is hardened. Can be molded. After molding, the sheet is cut into a predetermined size (and further subjected to cutting or the like as necessary) to produce a light guide plate.
Further, in the case of extrusion molding, while the resin or resin composition 52 coming out of the die 51 is hot, it passes through a roller 53 having a concavo-convex pattern corresponding to the groove structure, thereby having a groove structure from the beginning. A raw sheet for manufacturing a diffusion sheet can be formed (see FIG. 5). After forming, the sheet is cut into a predetermined size (and further subjected to cutting or the like as necessary) to produce a diffusion sheet.

As a method of (2), for example, after forming a diffusion sheet (raw sheet for diffusion sheet production) that does not have a groove structure by extrusion molding or cast molding, the surface on which the groove structure is formed corresponds to the groove structure The groove structure can be transferred using a transfer mold having an uneven pattern.
FIG. 6 shows a specific example of this method. In the method of FIG. 6, the groove structure is transferred by pressing a transfer roller 62 having a concavo-convex pattern corresponding to the groove structure while heating the transparent substrate 61 cut to a predetermined size. Instead of the transfer roller 62, a flat stamper may be used.

  In addition, there is no limitation in the method of forming the uneven | corrugated pattern and groove structure corresponding to a groove structure in the metal mold | die (stamper) used by the method of the above-mentioned (2), and a transfer mold (transfer roller). The groove structure formed by speckle pattern exposure, which will be described later in the method (3), is used as a submaster mold, and a metal is applied to the submaster mold by a method such as electroforming. It can be produced by depositing and transferring a concavo-convex pattern corresponding to the groove structure to this metal. A method using speckle pattern exposure is suitable for forming a fine three-dimensional structure of about 10 μm or less, which is difficult by machining.

As a method of forming a layer for forming a groove structure by speckle pattern exposure in (3), specifically, a random groove structure can be formed as follows.
For example, a speckle pattern having a random stripe pattern is generated by interference exposure using laser light, and this is irradiated to a layer made of a photopolymerizable composition such as a photoresist. Next, when the exposed photopolymerizable composition is developed by a known method, a random groove structure corresponding to the speckle pattern is formed in the cured photopolymerizable composition layer.
Random striped speckle patterns can be generated, for example, by diffusing laser light with a highly anisotropic diffusion layer or the like. Normally, when the laser beam is diffused in the diffusion layer and irradiated to the exposed surface, speckles are generated as circular unevenness, but if the diffusion layer is highly anisotropic, the speckles can be striped. . Furthermore, a desired random stripe pattern can be obtained by appropriately changing the wavelength of the laser light, the conditions for diffusing the laser light, and the like. Specifically, it can be generated by the method disclosed in paragraphs 0047 to 0057 of JP-T-2004-508585.
In addition, a method for producing a fine concavo-convex pattern using a speckle pattern by interference exposure is well known, and is disclosed in, for example, Japanese Patent No. 3341519, Japanese translations of PCT publication No. 2003-525472 and Japanese translations of PCT publication No. 2004-508585. Yes.

Moreover, when a diffusion sheet is a laminated body of the layer which has a contact bonding layer, a sheet | seat base material, and a groove structure, a diffusion sheet can be manufactured as follows, for example.
On a transparent sheet substrate made of polyethylene terephthalate, polycarbonate, polystyrene, etc., for example, a method in which an ultraviolet curable resin layer is applied, and a roll-shaped metal stamper is used to continuously perform UV transfer molding in a roll-to-roll manner, etc. A layer having a groove structure is formed by, for example, forming a groove structure in the ultraviolet curable resin layer.
Next, a translucent adhesive is applied to the surface opposite to the surface on which the groove structure of the sheet base material is formed, and a release film made of polyethylene terephthalate or the like is bonded thereto, or the release film A multi-layer film in which the adhesive side is covered with a release film is produced, for example, by sticking together the translucent adhesive layer of the attached adhesive film. A specific example of the layer structure of such a multilayer film is shown in FIG. 7a and 7b in FIG. 7 are both multilayer films provided with a release film on one side. In the multilayer film 7a, a release film 71, an adhesive layer 72, a base film 73, and a layer 74 having a groove structure are laminated in order from the bottom. In the multilayer film 7b, an adhesive layer and a backing film layer are further provided on the layer 74 on which the groove structure is formed, and the release film 71, the adhesive layer 72, the base film 73, and the groove structure are formed in this order from the bottom. The formed layer 74, adhesive layer 75, and mount film 76 are laminated. Note that the release film 71 and the mount film 76 serve as a mount or a protective film during manufacture of the diffusion sheet or when bonded to the light guide plate, and there is no limitation on the thickness thereof. Although it depends, it can be 10-200 micrometers.
And a diffusion sheet is obtained by cut | disconnecting this multilayer film 7a or 7b to the size of a diffusion sheet. The size at this time may be the same as the surface (light exit surface / opposing surface) that forms the groove structure of the light guide plate, or may be slightly smaller than this. If the size of the diffusion sheet is smaller than the surface of the light guide plate where the groove structure is formed, there will be no risk of sticking out even if there is a slight shift during bonding, and the highly reliable light guide plate will not peel off. Can be provided. In addition, the likelihood of the bonding accuracy is increased and the productivity is improved.

In addition, the diffusion sheet having such a multilayer structure is bonded to the light guide plate (base material) as follows in the manufacturing process of the light guide plate and the assembly process of the surface light source device having the light guide plate.
In the case of the diffusion sheet obtained from the multilayer film 7a, the film (72 to 74) on which the groove structure is formed is peeled off from the release film 71 and bonded to the light guide plate via the adhesive layer 72. In the case of a diffusion sheet obtained from the multilayer film 7b, the film (71 to 74) on which the groove structure is formed is peeled off from the adhesive layer 75, and then the release film 71 is peeled off and attached to the light guide plate via the adhesive layer 72. Match. Finally, if necessary, the air between the film and the light guide plate may be brought into close contact with a roller or the like.
Prior to bonding, the surface of the adhesive layer 72 and / or the surface of the light guide plate where the groove structure is provided is subjected to surface treatment such as excimer UV treatment or corona treatment, and immediately after the surface molecular bonds are cut, Bonding strength can also be improved by closely contacting the light guide plate.

The groove structure provided in the diffusion sheet of the present invention has an anisotropic diffusion whose surface has a maximum diffusion angle in a direction perpendicular to the groove structure and a minimum diffusion angle in a direction parallel to the groove structure. Show properties.
There is no limitation on the specific value of the diffusion angle (the diffusion angle (FWHM) of the emitted light when a light beam is vertically incident on the groove structure), but the diffusion angle in the direction perpendicular to the groove structure is 40 ° or more. It is preferable that it may be 40 ° to 90 °, 50 ° to 70 °, or 65 °. On the other hand, the diffusion angle in the direction parallel to the groove structure can be set to 10 ° or less, for example.
If the groove structure has a surface shape that gives such a diffusion angle, the effect of direct evolution of light can be sufficiently obtained.
Both the diffusion angle in the direction parallel to and perpendicular to the groove structure can be adjusted by appropriately changing the shape of each groove, the depth and pitch of the groove structure, and the like using a speckle pattern. When the groove structure is formed, these can be adjusted by appropriately changing the conditions for diffusing the laser beam.
Further, it is preferable that the diffusion characteristic is substantially constant in the entire region of the groove structure.

  Here, the “diffusion angle” refers to an angle (FWHM: Full Width Half Maximum) that is twice the angle (half-value angle) at which the transmitted light intensity attenuates to half of the peak intensity (see FIG. 8). This diffusion angle can be measured by, for example, Photon Inc. Using a variable angle colorimeter such as Goniometric Radiometers Real-Time Far-Field Angular Profiles Model LD8900 manufactured by Nippon Denshoku Industries Co., Ltd. or GC5000L manufactured by Nippon Denshoku Industries Co., Ltd., the groove structure (the groove structure was formed). It can be determined by measuring the angular distribution of the transmitted light intensity of the light incident on the material (the distribution of the intensity of the transmitted light with respect to the outgoing angle). Here, the normal direction of the groove structure refers to the direction indicated by 16 in FIG.

Next, the light guide plate of the present invention will be described with reference to FIG. 1 showing a schematic diagram of an example thereof.
The light guide plate 1 of the present invention has a light exit surface 11, a facing surface (not shown) facing the light exit surface, and at least one light incident surface 12 sandwiched between the light exit surface and the facing surface. Here, the “light exit surface” refers to a surface that faces the display panel (liquid crystal panel) to be irradiated with light when a surface light source device incorporating the light guide plate is disposed in the display device. Say. Usually, it is designed so that the luminance when light enters from the light incident surface is the highest among the surfaces of the light guide plate.
Furthermore, in the light guide plate of the present invention, the above-described diffusion sheet 13 of the present invention is formed on at least one of the light exit surface and the opposing surface, and the plurality of grooves 14 formed on the surface thereof are the light incident surface 12 of the light guide plate. Are stacked so as to be perpendicular to the light incident surface 12 (perpendicular to the side 15 in contact with the light exit surface 11).
In the light guide plate of the present invention, light of a light source arranged in the vicinity is incident on the light guide plate from the light incident surface 12, and is repeatedly reflected between the inside of the plate and the diffusion sheet to guide the light. Is emitted toward the light exit surface 11 by an exit mechanism (not shown) and is emitted from the light exit surface 11 to the outside.

The diffusion sheet may be laminated only on one of the light outgoing surface and the opposing surface, or may be laminated on both the light outgoing surface and the opposing surface. Lamination on both surfaces is preferable because warpage of the light guide plate can be suppressed.
Moreover, the diffusion sheet is only required to be laminated on at least a part of the light exit surface and / or the opposing surface, and there is no limitation on the region to be laminated, but for example, 0 from the end (each side) of the light exit surface and the opposing surface. It is preferable to be laminated on the entire inner surface of 1 to 50 mm.

  The diffusion sheet may be simply laminated on the light guide plate, or may be laminated (fixed) via an adhesive or an adhesive. When the diffusion sheet is a multilayer structure including an adhesive layer, the adhesive sheet can be used to fix the diffusion sheet to the light guide plate.

The shape (outer shape) of the light guide plate of the present invention is not particularly limited as long as it has a light exit surface, a facing surface facing the light exit surface, and a light incident surface sandwiched between them. Further, it is sufficient that there is at least one light incident surface, and there may be two light incident surfaces. Although there is no limitation on the thickness of the light guide plate (the distance between the light exit surface and the opposing surface in the light incident surface), the thickness can be, for example, about 1.0 to 10.0 mm.
When the light guide plate has two light incident surfaces, the shape of the light guide plate is preferably a flat rectangular parallelepiped having the light output surface and the opposed surface as a main surface, and the two light incident surfaces are opposed to each other. Is preferred. In this case, since two opposing light incident surfaces have the same length, there is a merit that the number and type of point light sources can be made the same and parts can be shared.

  In addition, the light guide plate of the present invention includes organic and inorganic dyes and pigments, matting agents, heat stabilizers, flame retardants, antistatic agents, antifoaming agents, color stabilizers, antioxidants, UV absorption as necessary. An additive such as an agent, an impurity scavenger, a thickener, a surface conditioner, and a release agent may be contained within a range not impairing the object of the present invention.

On the opposing surface and / or the light exit surface of the light guide plate of the present invention, an exit mechanism for emitting the guided light from the light exit surface can be provided.
Specific examples of the emission mechanism include a printing pattern using white ink or diffusion ink (transparent ink containing a diffusion material), a texture pattern by thermal transfer / injection molding, a laser pattern using a CO ₂ laser, etc. Light scattering patterns such as (pattern).
In order to make the light emission distribution (brightness distribution) uniform on the light exit surface, it is preferable that the exit mechanisms be provided sparsely in the vicinity of the light entrance surface and denser as the distance from the light entrance surface increases. For example, a light scattering pattern having gradation toward the direction away from the light incident surface can be formed.
As the light scattering pattern, for example, a dot or concavo-convex shape is a gradation pattern that gradually increases in area as it moves away from the light incident surface, or the same size dot or concavo-convex shape becomes narrower as it moves away from the light source. A gradation pattern that can be used. In this case, examples of the shape of the dots and irregularities include a circle and a quadrangle, and the size can be, for example, about 0.1 to 2.0 mm.

Next, the surface light source device of the present invention will be described.
FIG. 9 shows a schematic diagram of an example of the surface light source device of the present invention.
The surface light source device 9 of the present invention includes the light guide plate 91 of the present invention and a plurality of point light sources 92 disposed in the vicinity of the light incident surface of the light guide plate.
Although there is no limitation in a point light source, it is preferable to use LED (light emitting diode). There is no limitation on the type of LED, for example, a one-chip type pseudo white LED that excites green and red phosphors by a blue LED, a multi-chip type that combines white / red / green / blue LEDs to produce white light, and the near ultraviolet One-chip type pseudo white LED that combines an LED and a red / green / blue phosphor may be used.
FIG. 10 shows a schematic diagram of an example of a box-type LED 10 that can be used in the present invention. The outer shape of the LED and the size of the light emitting surface are not limited, but the outer shape is about 5.6 mm (width) × 3.0 mm (height) × 1.0 mm (thickness), and the lateral width 102 of the light emitting surface 101 is 5 mm. The following are commonly used:

  Although there is no limitation on the arrangement method of the point light source, it is arranged on the straight line along the light incident surface of the light guide plate (parallel to the light emitting surface) at regular intervals (“equal interval” includes an error of ± 10%). It is preferable to do. In this case, the arrangement pitch P of point light sources is generally about 0.2 mm to 50 mm, for example. From the viewpoint of preventing uneven brightness, the point light sources are preferably arranged as densely as possible, and in view of mounting restrictions on the substrate, it is preferable that the distance is increased to some extent. The arrangement pitch of the point light sources is preferably 0.5 mm to 30 mm, more preferably 1 to 15 mm.

  Further, since the surface light source device of the present invention uses the light guide plate of the present invention suitable for local dimming as the light guide plate, a plurality of point light sources arranged in the vicinity of the light incident surface are provided so that local dimming can be performed. It may be divided into two or more groups so that the brightness (flashing) of each point light source can be controlled independently for each group. Furthermore, if a plurality of point light sources are divided into a plurality of groups (preferably equally divided from the end in order), and the point light sources belonging to each group are controlled to light up sequentially in the vertical direction (in some cases, left and right in some cases), 3 Scanning used for displaying a three-dimensional image becomes possible.

  In the surface light source device of the present invention, in addition to the light guide plate and the point light source, an optical element generally employed in a so-called edge light type surface light source device such as a reflection sheet can be further included. Specifically, the reflection sheet can be disposed below the facing surface of the light guide plate. In addition, on the light output surface of the light guide plate, a prism sheet, a condensing sheet such as a lenticular lens sheet and a micro lens sheet, and a polarizing reflection sheet for avoiding optical loss in the polarizing plate of the liquid crystal panel Or it can also arrange | position combining several sheets.

Next, the display device of the present invention will be described.
The display device of the present invention includes a display panel having a display area for displaying by adjusting light transmission of the surface light source device, and the above-described surface light source device disposed on the back surface of the display panel.
FIG. 11 shows a cross-sectional view of an example of the display device 11 of the present invention. In FIG. 11, a diffusion sheet 112 having a groove structure is laminated on the light output surface of the light guide plate 111, and an emission mechanism 113 is formed on the opposite surface of the light guide plate. An LED 114 is disposed in the vicinity of the light incident surface of the light guide plate, a reflective sheet 115 is disposed below the facing surface, and a display panel 118 is disposed above the light emitting surface via a diffusion sheet 116 and a prism sheet 117. Is housed in the backlight chassis 119.
In the display device 11 of FIG. 11, a liquid crystal display panel is used as the display panel 118, which includes a liquid crystal layer (not shown), two glass plates 1181 sandwiching the liquid crystal layer, and a glass plate. It is comprised by the polarizing plate 1182 provided in the front and back.

  The pixel pitch of the display panel is not limited, but when the pitch of the groove structure provided in the light guide plate is about 10 to 20 μm, the generation of moire can be sufficiently reduced by setting the pixel pitch of the display panel to 100 μm or more.

On the light exit surface of the light guide plate, uneven brightness may occur in the vicinity of the light entrance surface, and sufficient display quality may not be guaranteed. Therefore, the display area (active area) of the display panel is from the inside of the light entrance surface of the light guide plate. It is preferably designed to start.
That is, the horizontal distance G between the light incident surface 93 of the light guide plate 91 and the display area (the distance between the region 94 and the light incident surface 93 when the region 94 corresponding to the display area is projected on the light guide plate 91 ( It is preferably designed to ensure a certain level or more).

When the light guide plate of the present invention has two light incident surfaces, the arrangement pitch of the point light sources disposed in the vicinity of the first light incident surface is P1, and the point light sources disposed in the vicinity of the second light incident surface. When the arrangement pitch is P2, the horizontal distance between the first light incident surface and the display area is G1, and the horizontal distance between the second light incident surface and the display area is G2, P1 / G1: P2 / G2 = 100: 90 to 100: 110 is preferable, and P1 / G1: P2 / G2 = 100: 95 to 100: 105 is more preferable.
G1 and G2 are not necessarily the same.

The display panel is preferably a liquid crystal display panel. Conventionally used liquid crystal display panels can be used as the liquid crystal display panel. An example of the configuration is schematically shown in FIG. 12 and described below.
FIG. 12 is a schematic front view of an example of the liquid crystal display panel 12. The inside of the dotted line 121 is the display area 122. A black matrix 123 for preventing light leakage is provided outside the display area 122, and panel wiring (not shown) and the like exist on the back side. In FIG. 12, reference numerals 124 and 125 respectively denote a source chip which is a driver IC for applying a voltage to a source line (described later, not shown), and a voltage for applying a voltage to a gate line (described later, not shown). It is a gate chip which is a driver IC.

  In a transmissive liquid crystal display panel, generally, a large number of pixel electrodes arranged in a matrix on a transparent substrate are driven by active matrix elements arranged on the transparent substrate. An active matrix substrate in which an active matrix element and pixel electrodes are provided on a transparent substrate is provided with a liquid crystal layer in a stacked state, and a counter substrate is disposed so as to face the active matrix substrate with the liquid crystal layer interposed therebetween. ing. The counter substrate is a transparent substrate provided with a counter electrode, and this counter electrode is opposed to the display region in the liquid crystal layer.

  The active matrix element provided on the active matrix substrate is provided with a TFT (thin film transistor) as an active element connected to each pixel electrode. The active matrix element includes a plurality of gate lines arranged in parallel to each other along the row direction and a plurality of source lines arranged in parallel to each other along the column direction orthogonal to each gate line. Each TFT is disposed in the vicinity of the intersection between each gate line and each source line. Each TFT is connected to each of a gate line and a source line that form adjacent intersections.

  Each TFT is configured to be turned on by a gate signal supplied from a gate line to which each TFT is connected, and to supply a source signal supplied from a source line to which each TFT is connected to a pixel electrode connected thereto. Has been.

  In such a liquid crystal display panel, gate signals (horizontal synchronization) are usually line-sequentially arranged in the order along the column direction for each gate line arranged along the row direction on the active matrix substrate for each frame. Signal), and gate signals are continuously supplied to gate lines adjacent in the column direction.

  When such a liquid crystal display panel is used as a display panel, the display panel is arranged so that the direction of the gate line matches the direction of the plurality of grooves of the diffusion sheet laminated on the light guide plate (parallel). It is preferable to arrange a light guide plate (surface light source device).

The display device of the present invention is configured to perform scanning as a surface light source device (divides a plurality of point light sources into a plurality of groups (preferably equally from the end in order)), and belongs to each group. Is suitable for displaying a three-dimensional image. In this case, it is preferable that the display panel alternately display the right-eye image and the left-eye image, and it is preferable to provide a frame memory that stores one or more video signals. The pixel pitch of the display panel is preferably 100 μm or more.
When displaying a three-dimensional image, it is preferable to synchronize the lighting control for each light source group of the surface light source device with the adjustment of the light transmission of the display panel. Specifically, the light sources belonging to each group include: It is preferable that the display panel is turned on sequentially in synchronization with the operation of the gate of the display panel (following the gate scanning (in the direction of the arrow in FIG. 12)).

The display device 131 of the present invention is combined with a front cabinet 132 provided with a speaker 1321; various circuit boards such as a TV tuner circuit board 133, a power supply circuit board 134, and a control circuit board 135; a back cabinet 136, a stand 137, and the like. Thus, a television receiver can be manufactured. FIG. 13 shows an example of the configuration of such a television receiver 13.
Further, the display device of the present invention can also be suitably used for a monitor used for games and the like. The configuration of such a monitor is the same as that of the television receiver 13 in FIG. 13 except that the television tuner circuit board 133 is not provided, and the speaker 1321 may not be provided in some cases.

[Example 1]
An ultraviolet curable resin layer having a groove structure having the characteristics shown in Table 1 on one surface of a transparent sheet-like base material made of polycarbonate having a thickness of 125 μm (Panlite PC-2151 manufactured by Teijin Chemicals Ltd.), and the other Acrylic adhesive (G ′ = 77,000 Pa (G ₀ ′ = 18,000 Pa)) film (Panaclean PD-S1 manufactured by Panac Co., Ltd., adhesive film thickness) laminated on release paper : 25 μm, TG / DTA (weight reduction rate) at 100 ° C.−0.06%) was bonded to prepare a diffusion sheet with an adhesive layer.
This diffusion sheet with an adhesive layer is cut to the same size as the light exit surface of a PMMA light guide plate (a flat plate having a width of 400 mm, a length of 700 mm, and a thickness of 4 mm) taken out from the SONY liquid crystal television BRAVIA 32EX700, and on the light exit surface, The light guide plate was produced by bonding through an adhesive layer. Under the present circumstances, it bonded so that the several groove | channel formed in the diffusion sheet surface might become perpendicular | vertical with respect to the light-incidence surface of a light-guide plate.
Specifically, first, the diffusion sheet was temporarily fixed on the light exit surface of the light guide plate so that the adhesive layer and the light guide plate were in contact with each other, and then bonded using a laminator while peeling the release sheet of the diffusion sheet.
On the light exit surface of the light guide plate fabricated as described above, another diffusion sheet (TDF187 manufactured by Toray Sehan Co., Ltd.) is laminated, and nine LEDs are arranged along the light entrance surface with an arrangement pitch of 42 mm. Thus, the surface light source device was manufactured by substantially evenly arranging. At this time, the emission width was 89 mm. The light emission width represents the distance between the LEDs at both ends that are lit.
The LED is turned on, and the luminance at positions corresponding to the inner side of the light incident surface on the diffusion sheet laminated on the light guide plate is 10 mm, 200 mm, and 10 cm inside, the two-dimensional color luminance meter (CA-2000) manufactured by Konica Minolta The straightness ratio and the divergence angle described later were obtained.

<Straightness evaluation 1>
From the luminance cross section (FIG. 17) in a straight line parallel to the light incident surface having a distance of 10 cm from the LED light source on the light exit surface of the light guide plate, the straightness ratio was determined.
The straight running ratio is the integrated value of the luminance in the luminance cross section S, and the light incident range of the LED in the luminance cross section (the portion sandwiched between the light emitting surfaces of the nine lighted LEDs and these light emitting surfaces) When the integral value of the luminance of the portion corresponding to (A) is a value expressed by A / S × 100, the larger the value (the higher the ratio of A), the light enters the light guide plate. It indicates that the light travels straight without spreading, that is, the straightness is high (see FIG. 17).
When compared with a light guide plate without a groove structure (BRAVIA KDL-32EX700 built-in by Sony Corporation)
◎, where the straightness ratio increase is 10% or more,
○, where the increase in straightness ratio is 5% or more and less than 10%
△, where the increase in straight running rate is 1% or more and less than 5%
Those with an increase in straightness ratio of less than 1% or those with a low straightness ratio ×
As evaluated. The results are shown in Table 1.

<Straightness evaluation 2>
As shown in FIG. 18, a FWHM (Full Width Half Maximum) A-A ′ having a linear luminance cross section (FIG. 17) parallel to the light incident surface having a distance of 10 mm from the LED on the light exit surface, and from the LED, In FWHM B-B ′ of a luminance cross section (not shown) in a direction parallel to the light incident surface having a distance of 200 mm, and C-C ′ in which A-A ′ is translated 190 mm from the LED to a distance of 200 mm, The value of the angle 値 BAC formed by BA and CA (tan ⁻¹ ((FWHM of a luminance section at a distance of 200 mm−FWHM of a luminance section at a distance of 10 mm) / 380) was compared. This angle (hereinafter referred to as “spreading angle”). The smaller the value, the higher the straightness.
If the spread angle is less than 10 °, ◎,
○ in which the spread angle is 10 ° or more and less than 15 °
Δ in which the spread angle is 15 ° or more and less than 20 °
X with a spread angle of 20 ° or more
As evaluated.
The comparison results are shown in Table 1.

<Evaluation of light reachability>
The luminance profile obtained by plotting the average value of the luminance at the measurement point within the range of the light incident range of LED + 3 cm on the left and right with respect to the light propagation direction was used as a luminance cross section for light reachability evaluation.
The light reachability is evaluated according to how much the peak brightness (maximum value of brightness) in the brightness cross section for light reachability evaluation of the embodiment is increased as compared with that of the light guide plate of Comparative Example 1 having no groove structure. did.
The rate of increase in peak luminance for a light guide plate without a groove structure is
◎ 0% or more and less than 40%
40% or more and less than 80%
△ 80% or more
As evaluated. The results are shown in Table 1.

<Evaluation of warpage>
The diffusion sheet used in Example 1 was bonded to an acrylic plate (manufactured by Kanase Kogyo, Kanaselite 1300, thickness: 2 mm, size 25 cm × 3 cm) having a size of 160 mm × 90 mm, and the resulting laminate was heated to 60 ° C. After 24 hours, it was stored in a constant temperature and humidity chamber having a humidity of 90 RH%. Thereafter, the sample was left at room temperature for 10 minutes, and the amount of displacement from a horizontal table was measured with a ruler. The measured value was an average value of four points at the corners of the acrylic plate and evaluated as follows.
Displacement less than 0.1 mm: ◎
Displacement amount of 0.1 mm to less than 0.3 mm: ○
Displacement is 0.3 mm or more and less than 0.5 mm: Δ
Displacement amount 0.5mm or more: ×

<Hot spot evaluation>
The LED was turned on, and the presence / absence of a hot spot on the light-emitting surface was visually confirmed and evaluated as follows.
No hot spots are observed: ○
A few hot spots are observed:
Hot spots are clearly observed: ×
In addition, the example of the light emission distribution applicable to the above (circle), (triangle | delta), and x is shown in FIG.

[Example 2]
The same measurement as in Example 1 was performed except that the characteristics of the groove structure of the diffusion sheet were changed as shown in Table 1.
[Example 3]
The same measurement as in Example 1 was performed except that the characteristics of the groove structure of the diffusion sheet were changed as shown in Table 1.
[Example 4]
The same measurement as in Example 1 was performed except that the characteristics of the groove structure of the diffusion sheet were changed as shown in Table 1.
[Example 5]
The same measurement as in Example 1 was performed except that the sheet-like base material having a groove structure of the diffusion sheet was changed to a polymethyl methacrylate film (manufactured by Kaneka Corporation, Sanduren SD014NST, thickness 50 μm).

[Example 6]
Acrylic pressure-sensitive adhesive (G ′ = 84,000 Pa (G ₀ ′ = 19,800 Pa)) film (TR-1801A manufactured by Fujimori Kogyo Co., Ltd., pressure-sensitive adhesive film thickness) laminated on release paper. The measurement was carried out in the same manner as in Example 1 except that TG / DTA (weight reduction rate) at 0.05C, 0.05%, peel strength: 0.63 N / mm) was changed.
[Example 7]
Acrylic pressure-sensitive adhesive (G ′ = 68,000 Pa (G ₀ ′ = 16,900 Pa)) film (New Tack Kasei Co., Ltd. CCL / D1 / T3T3, pressure-sensitive adhesive film) Thickness: 25 μm Peel strength: 0.61 N / mm) The measurement was performed in the same manner as in Example 1 except that the thickness was changed.
[Example 8]
Acrylic pressure-sensitive adhesive (G ′ = 44,000 Pa (G ₀ ′ = 10,700 Pa)) film (EXC10-076 manufactured by Toyo Ink Co., Ltd., pressure-sensitive adhesive film thickness) laminated on release paper The measurement was performed in the same manner as in Example 1 except that the thickness was changed to 50 μm.
[Example 9]
A film (MO-3006C manufactured by Lintec Corporation, pressure-sensitive adhesive film thickness) made of an acrylic pressure-sensitive adhesive (G ′ = 160,000 Pa (G ₀ ′ = 44,600 Pa)) laminated on a release paper. : 25 μm, TG / DTA (weight reduction rate) at 100 ° C.—0.09%)) The measurement was performed in the same manner as in Example 1 except that the change was made.
[Example 10]
A film (MO-3012C manufactured by Lintec Corporation, pressure-sensitive adhesive film thickness) made of an acrylic pressure-sensitive adhesive (G ′ = 30,000 Pa (G ₀ ′ = 6,100 Pa)) laminated on release paper : 25 μm, TG / DTA (weight reduction rate) at 100 ° C. (0.10%) was measured in the same manner as in Example 1, except that the measurement was performed.

[Example 11]
The measurement was performed in the same manner as in Example 1 except that the diffusion sheet was cut to be 20 mm shorter than the light exit surface of the light guide plate and bonded from the inside 10 mm from the light entrance surface of the light guide plate.

[Comparative Example 1]
The same measurement as in Example 1 was performed using a PMMA light guide plate (a flat plate having a width of 400 mm, a length of 700 mm, and a thickness of 4 mm) used for taking out from the Sony liquid crystal television BRAVIA 32EX700 without bonding a diffusion sheet. went.

Table 1 shows the measurement results related to the comparative example, Example 1 and Example 4.
From Table 1, it was confirmed that when the diffusion sheet having the groove structure of the present invention was used, the straightness of light from the point light source was greatly improved without impairing the light reachability. Moreover, it has also confirmed that the curvature at the time of bonding a diffusion sheet to a light-guide plate can be suppressed by selecting the material of the adhesion layer and sheet-like base material of a diffusion sheet. Furthermore, it has also been confirmed that the hot spot can be reduced by selecting the bonding position from the end face of the light guide plate of the diffusion sheet.

  The diffusion sheet of the present invention is useful for an edge-light type surface light source device using a point light source such as an LED, and can guide light from the light source with very high straightness. ) Can be suitably used for a surface light source device. Furthermore, it can be suitably used for a liquid crystal display device that displays a three-dimensional image or video.

DESCRIPTION OF SYMBOLS 1 Light-guide plate 11 Light exit surface 12 Light entrance surface 13 Diffusion sheet 14 Groove | flood 15 Side | surface 16 which contact | connects the light exit surface of the light entrance surface Normal direction 33 of the light exit surface 41 Roller 61 having concave / convex pattern to be transferred Transparent substrate 62 Transfer roller 7a Multilayer film 7b having a layer in which a groove structure is formed Multilayer film 71 having a layer in which a groove structure is formed Release film 72 Adhesive layer 73 Sheet substrate 74 Groove structure Formed layer 75 Adhesive layer 76 Mount film 9 Surface light source device 91 Light guide plate 92 Point light source 93 Light incident surface 94 Area corresponding to display area 10 LED
101 Light Emitting Surface 102 Width of Light Emitting Surface 111 Light Guide Plate 112 Groove Structure 113 Emitting Mechanism 114 LED
115 Reflective sheet 116 Diffusion sheet 117 Prism sheet 118 Display panel 1181 Glass plate 1182 Polarizing plate 119 Backlight chassis 12 Liquid crystal display panel 122 Display area 123 Black matrix 124 Source chip 125 Gate chip 13 Television receiver 131 Display device 132 Front cabinet 1321 Speaker 133 TV tuner circuit board 134 Power supply circuit board 135 Control circuit board 136 Back cabinet 137 Stand G Horizontal distance P between light incident surface of light guide plate and display area Pitch of point light sources

Claims (30)

  A diffusion sheet having a plurality of random and parallel grooves on at least one surface.   The diffusion sheet according to claim 1, wherein an average pitch of the plurality of grooves is 30 μm or less.   The diffusion sheet according to claim 1 or 2, wherein an average depth of the plurality of grooves is 1 to 50 µm.   The diffusion sheet according to any one of claims 1 to 3, wherein the plurality of grooves are formed by speckle pattern exposure.   The diffusion sheet according to any one of claims 1 to 4, wherein an average value of an average gradient of inner surfaces of the plurality of grooves is 0.3 to 2.0.   The diffusion sheet according to any one of claims 1 to 5, wherein a standard deviation of an average gradient of inner surfaces of the plurality of grooves is 0.1 to 0.5.   The light guide plate according to any one of claims 1 to 6, wherein a ratio of a slope angle of 40 degrees to 60 degrees among surfaces constituting the plurality of grooves is 5% or more.   The diffusion sheet according to any one of claims 1 to 7, wherein a diffusion angle in a direction perpendicular to the plurality of grooves is 40 degrees or more.   The diffusion sheet according to any one of claims 1 to 8, wherein a diffusion angle in a direction parallel to the plurality of grooves is 10 degrees or less. A sheet-like substrate;
A layer having a plurality of parallel and random grooves provided on at least one surface of the sheet-like substrate;
The diffusion sheet according to claim 1, comprising:   The said sheet-like base material consists of a resin composition containing the at least 1 high molecular compound selected from the group which consists of a polymethacrylic acid methacrylate, a styrene-methylmethacrylate copolymer, a polystyrene, and a polycarbonate. Diffusion sheet.   The diffusion sheet according to claim 10 or 11, further comprising an adhesive layer.   The diffusion sheet according to claim 12, wherein the adhesive layer is made of a material having a storage elastic modulus G ′ at 100 ° C. of 20,000 to 200,000 Pa.   The diffusion sheet according to claim 12 or 13, wherein the adhesive layer has a thickness of 1 to 300 µm.   The diffusion sheet according to any one of claims 12 to 14, wherein a layer having the plurality of grooves is provided on one surface of the sheet-like base material, and the adhesive layer is provided on the other surface. A light guide plate having a light exit surface, a facing surface facing the light exit surface, and at least one light incident surface sandwiched between the light exit surface and the facing surface,
The light guide plate by which the diffusion sheet of any one of Claims 1-15 is laminated | stacked on at least one of the said light emission surface and an opposing surface. A light guide plate having a light exit surface, a facing surface facing the light exit surface, and at least one light incident surface sandwiched between the light exit surface and the facing surface,
The light guide plate by which the diffusion sheet of any one of Claims 1-15 is laminated | stacked on both the said light emission surface and an opposing surface.   The light guide plate according to claim 16 or 17, wherein the diffusion sheet is laminated in a region 0.1 to 50 mm inside from an end of the light exit surface and / or the facing surface.   The light guide plate according to claim 16, wherein the facing surface has an emission mechanism. The light guide plate according to any one of claims 16 to 19,
A plurality of light sources arranged in the vicinity of the at least one light incident surface of the light guide plate;
A surface light source device.   21. The surface light source device according to claim 20, wherein the plurality of light sources are partitioned into two or more groups, and the brightness of each light source can be controlled independently for each group. A display panel having a display area for displaying light by adjusting light transmission;
The surface light source device according to claim 20 or 21, which is disposed on the back surface of the display panel;
A display device. The display panel is
A source for supplying a display voltage to at least one side;
A gate for controlling a line for writing a voltage supplied by the source on at least one side orthogonal to the at least one side;
The display device according to claim 22.   24. The display device according to claim 23, wherein a direction of the line and a direction of a plurality of grooves of the diffusion sheet laminated on the light guide plate coincide with each other.   The display device according to claim 23 or 24, wherein a light source of the surface light source device is configured to light up sequentially in synchronization with the operation of the gate.   The display device according to any one of claims 22 to 25, wherein brightness control for each light source group of the surface light source device is configured to be synchronized with adjustment of light transmission of the display panel.   The display device according to any one of claims 22 to 26, wherein the display panel is configured to alternately display a right-eye image and a left-eye image.   The display device according to claim 22, wherein a pixel pitch of the display panel is 100 μm or more.   The display device according to any one of claims 22 to 28, further comprising a frame memory for storing one or more video signals. A display device according to any one of claims 22 to 29;
A tuner for receiving broadcast video signals;
A television receiver.