JP2006133528A - Anti-static light diffusion sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anti-static light diffusion sheet having anti-static performance and high light transmission, little in the variation of luminance and being capable of emitting uniform diffused light. <P>SOLUTION: The anti-static light diffusion sheet 1 is formed by laminating a translucent anti-static layer 3, having 10<SP>6</SP>-10<SP>11</SP>Ω/square for the surface resistivity on one surface of a light diffusion sheet body 2. The light diffusion sheet body 2 is preferably a single layer sheet or a laminated sheet, comprising a core layer and a surface layer which contain 0.1-35 mass% light diffusing agent. In the laminated sheet, the light-diffusing agent is contained only in the core layer or in both the core layer and the surface layer; and it is preferable that one surface of the sheet have fine irregularities. The translucent anti-static layer 3 is formed from a layer in which metallic particles or very fine conductive fibers, such as carbon nanotubes, are dispersed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a light diffusing sheet having antistatic performance.

  A light diffusing sheet is used for backlight units such as liquid crystal displays, electric signboards, and illumination covers in order to obtain uniform high-luminance illumination by diffusing light from point light sources or linear light sources. Common examples of such light diffusing sheets are translucent synthetic resin sheets in which fine irregularities are formed on one or both sides, and synthetic resin sheets containing a light diffusing agent, but these are easily charged with static electricity. There was a problem that dust was easily attached.

In order to deal with this problem of dust adhesion, a large number of fine irregularities are provided on one side of the transparent resin sheet, and along the irregularities, an antistatic layer comprising 100 parts by weight of a transparent resin binder and 0.2 to 50 parts by weight of an electrolyte. There has been proposed a light diffusion sheet provided with (Patent Document 1).
JP-A-7-181307

  However, as in the light diffusing sheet described in Patent Document 1, a sheet provided with an antistatic layer composed of a transparent resin binder and an electrolyte gradually deposits the electrolyte contained in the antistatic layer on the surface, so-called bleed out. There was a problem that the antistatic effect was lost.

  The present invention has been made in order to cope with the above-described circumstances, and an object of the present invention is to provide an antistatic light diffusing sheet capable of maintaining uniform antistatic performance and emitting uniform diffused light with high total light transmittance. It is a solution subject to provide.

In order to achieve the above object, the antistatic light diffusing sheet according to the present invention has a translucent antistatic layer having a surface resistivity of 10 ⁶ to □ 10 ¹¹ Ω / □ on at least one surface of the light diffusing sheet body. It is characterized by being laminated. Here, the “sheet” is a term having a broad concept including a film having a thickness of about 30 μm and a plate having a thickness of about 10 mm.

  In the antistatic light diffusing sheet of the present invention, the light diffusing sheet body contains a light diffusing agent, the light diffusing agent is contained in an amount of 0.1 to 35% by mass, and at least one surface of the light diffusing sheet. It is desirable that fine irregularities be formed on the surface. The light diffusion sheet body is a laminated sheet comprising at least a core layer and a surface layer, the core layer contains a light diffusion agent and the surface layer does not contain a light diffusion agent, the core layer has No light diffusing agent is contained, the surface layer contains a light diffusing agent, the core layer and the surface layer both contain a light diffusing agent, and the translucent resin used for the surface layer is contained in the core layer. It is desirable that the resin has a lower light refractive index than the translucent resin to be used, and that at least the surface layer contains an ultraviolet absorber.

  Furthermore, the light diffusing sheet body is made of a translucent polypropylene resin containing 15 to 35% by mass of a talc light diffusing agent, and fine irregularities are formed on both surfaces of the light diffusing sheet, the light diffusing sheet A main body is a laminated sheet in which a surface layer made of a translucent resin is laminated on at least one side of a core layer made of a translucent polypropylene resin containing 15 to 35% by mass of a talc light diffusing agent, The light diffusing sheet body has at least one surface of a core layer made of a translucent polycarbonate resin containing 0.1 to 20% by mass of an acrylic light diffusing agent. It is also desirable that each of the laminated sheets has a surface layer made of a translucent resin.

  In the antistatic light diffusing sheet of the present invention, the translucent antistatic layer is preferably a layer in which metal fine particles or ultrafine conductive fibers are dispersed.

  Further, the ultrafine conductive fibers to be contained in the light-transmitting antistatic layer are dispersed without contacting each other and brought into contact with each other, or are separated one by one or a bundle of a plurality of bundles. It is desirable that the bundles are dispersed and in contact with each other in a separated state. The ultrafine conductive fiber is desirably a carbon nanotube.

Furthermore, it is also desirable that the basis weight of the carbon nanotubes contained in the translucent antistatic layer is 1 to 20 mg / m ² .
Furthermore, it is also desirable that the total light transmittance of the antistatic light diffusing sheet is 50 to 95% and the haze is 30 to 95%. It is also desirable to laminate a translucent resin coating layer that covers the translucent antistatic layer.

In the antistatic light diffusing sheet of the present invention, since the surface resistivity of the translucent antistatic layer laminated on one side is 10 ⁶ to 10 ¹¹ Ω / □, the translucent antistatic layer provides good control. Electric performance is demonstrated. And the light which permeate | transmits is diffused by the light-diffusion sheet main body, and light-diffusion performance is exhibited simultaneously.

  In the antistatic light diffusing sheet of the present invention, when a light diffusing agent is contained in the light diffusing sheet body or fine irregularities are formed on the surface, light is diffused by the light diffusing agent or by the fine irregularities. Thus, the diffused light uniformly diffused from the light diffusing sheet main body is emitted, and the concealing property is improved. Even if the light diffusing sheet is thin, the light diffusing agent contained in the amount of 0.1 to 35% by mass decreases the linear expansion coefficient of the light diffusing sheet body and increases the elastic modulus. Even if heated, thermal expansion and contraction is suppressed, and an antistatic light diffusing sheet that is less prone to wrinkles can be obtained.

Further, in the antistatic light diffusing sheet of the present invention, when the light diffusing sheet body is a laminated sheet comprising a core layer containing a light diffusing agent and a surface layer not containing the same, the same effects as the above effects are obtained. In addition to being obtained, the light diffusing agent can be prevented from falling off at the surface layer.
Also, if the light diffusing sheet body is a laminated sheet comprising a core layer not containing a light diffusing agent and a surface layer containing this, the content of the light diffusing agent is reduced, and the total light transmittance is improved accordingly. Can do. Furthermore, if the light diffusing sheet is a laminated sheet composed of a core layer and a surface layer both containing a light diffusing agent, the light transmission amount and brightness can be adjusted to the required quality by changing the content and type of the light diffusing agent. it can.

Also, if the light-transmitting resin of the surface layer has a lower refractive index than that of the light-transmitting resin of the core layer, the surface layer is used as the light incident surface, so that more light is incident on the surface layer from the air and the amount of light transmitted Becomes higher and the luminance can be improved.
Furthermore, when the surface layer contains an ultraviolet absorber, the surface layer and the core layer are prevented from being photodegraded by disposing the surface layer on the backlight or the like so as to be on the light source side, resulting in yellowing. It becomes difficult and it can be set as the light-diffusion sheet with a large light transmission amount over a long period of time.

Moreover, in the electromagnetic wave shielding light diffusion sheet of the present invention, when the translucent antistatic layer is a layer in which metal fine particles are dispersed, the translucency is good and the layer thickness is about 0.4 to 2.0 μm. Even if it is thin, it has a surface resistivity of about 10 ⁶ to 10 ¹¹ Ω / □, so that good antistatic performance is exhibited. In addition, if the translucent antistatic layer is a layer in which ultrafine conductive fibers are dispersed, sufficient conduction between the ultrafine conductive fibers is ensured even if the thickness is extremely thin to provide good translucency. Therefore, it is easy to set the surface resistivity to about 10 ⁶ to 10 ¹¹ Ω / □, and sufficient antistatic performance is exhibited.

In addition, the ultrafine conductive fibers contained in the light-transmitting antistatic layer are dispersed without contacting each other and are in contact with each other, or separated one by one or a plurality of bundles gathered into a bundle If the bundles are dispersed in contact with each other and are in contact with each other, the fine conductive fibers can be undissolved and sufficient electrical conduction can be ensured by the amount that the fibers are not agglomerated, thereby obtaining good antistatic properties. Can do. Therefore, even if the amount of ultrafine conductive fiber is small or the antistatic layer is thinned, the antistatic property of 10 ⁶ to 10 ¹¹ Ω / □ can be secured, and the amount of ultrafine conductive fiber is reduced or the amount of transparency is transparent. Can be improved.
If the ultrafine conductive fibers are carbon nanotubes, the carbon nanotubes are thin and long, so that the mutual contact can be further ensured, and the surface resistivity can be easily controlled to 10 ⁶ to 10 ¹¹ Ω / □. Thus, a highly transparent translucent antistatic layer can be obtained.

  Furthermore, in the antistatic light diffusing sheet of the present invention, when a translucent resin coating layer that covers the translucent antistatic layer is laminated, the translucent antistatic layer can be protected from being damaged.

  Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings, but the present invention is not limited only to these embodiments.

  FIG. 1 is a cross-sectional view of an antistatic light diffusing sheet according to an embodiment of the present invention, and an imaginary line indicates an edge light type backlight unit.

This antistatic light diffusing sheet 1 (hereinafter sometimes simply referred to as “light diffusing sheet 1”) has a light transmittance of 10 ⁶ to 10 ¹¹ Ω / □ on one surface (upper surface) of the light diffusing sheet body 2. The antistatic layer 3 is laminated and integrated. The light diffusing sheet 1 is used by being incorporated into an edge light type backlight unit or the like as indicated by a virtual line in FIG. It goes without saying that it can be used by being incorporated in the direct-type backlight unit shown in FIG.

  The light diffusing sheet main body 2 of the antistatic light diffusing sheet 1 is composed of a single layer sheet of a translucent resin containing 0.1 to 35% by mass of a light diffusing agent. Concavities and convexities are formed, and the translucent and antistatic layer 3 is laminated in a concavity and convexity along the concavities and convexities on the upper surface serving as the light exit surface. Such unevenness may be formed by pressing the surface of the light diffusing sheet 1 with a roll with embossing and transferring the unevenness of the roll, or fine unevenness on the light diffusing sheet main body with embossing roll or the like. Concavities and convexities are formed on the light diffusion sheet main body depending on the particle size, content, and the like of the light diffusing agent that is formed or contained, and the translucent antistatic layer 3 may be laminated along the concavities and convexities. The unevenness on both the upper and lower surfaces of the light diffusing sheet body 2 is such that the tip of the convex portion is formed with a roundness, and the tip of the convex portion of the translucent antistatic layer 3 laminated in the concave-convex shape is also rounded. preferable. When the light diffusing sheet 1 is incorporated between the light guide plate 5 and the lens film 6 of the backlight unit indicated by phantom lines, the light guide plate 5 and the lens film 6 are formed by the tip of the convex portion. There is no worry about hurting. In addition, the fine unevenness | corrugation formed in the upper and lower surfaces of the light-diffusion sheet main body 2 is not necessarily required, The upper and lower surfaces may be made flat, or one surface may be made uneven and the other surface may be made flat.

  The upper and lower surfaces of the light diffusing sheet 1 are formed with the above-described fine irregularities so that the arithmetic average roughness (arithmetic average roughness Ra measured based on JIS B 0601) is 0.5 to 10.0 μm, Preferably it is the range of 0.6-8.0 micrometers. Thus, when the arithmetic average roughness Ra of both surfaces of the light diffusing sheet 1 is in the range of 0.5 to 10.0 μm, light easily enters from the light guide plate 5 and the diffusibility of emitted light is good. Therefore, uniform diffused light can be emitted while suppressing light loss to a minimum. The magnitude relationship between the arithmetic average roughness of the lower surface of the light diffusing sheet 1 (the lower surface of the light diffusing sheet main body 2) and the arithmetic average roughness of the upper surface (the surface of the translucent antistatic layer 3) is shown in FIG. The arithmetic mean roughness of the lower surface may be larger than the arithmetic average roughness of the upper surface by making the depth of the concave and convex portions on the lower surface to be greater than the depth of the upper and lower surfaces serving as the light-emitting surface. May be made substantially the same, and conversely, the arithmetic average roughness of the lower surface may be smaller than the arithmetic average roughness of the upper surface.

On the other hand, the surface area ratio due to the unevenness of the upper and lower surfaces of the light diffusing sheet 1 [refers to the ratio of the actual surface area S to the area S ₀ (S / S ₀ ) when the measurement surface is assumed to be a flat surface]. It is desirable that the surface area ratio of the upper surface serving as the light exit surface is equal to or greater than the surface area ratio of the lower surface serving as the light incident surface.
This makes it easier for light to enter from the lower surface and has the advantage of being strongly diffused and emitted from the upper surface. The light diffusion sheet 1 shown in FIG. 1 has a surface area ratio of the upper surface within the range of the above surface area ratio by making the distribution density of the unevenness on the upper surface of the light diffusion sheet body 2 higher than the distribution density of the unevenness on the lower surface. The surface area ratio is made larger so that the amount of incident light from the lower surface is increased and uniform strong diffused light can be emitted from the upper surface.

  As the translucent resin of the light diffusing sheet body 2, polycarbonate and polyester having high total light transmittance (for example, polyethylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, ethylene-1,4-cyclohexanedimethylene terephthalate). Copolymer, etc.), polyethylene, polypropylene, olefin copolymer (eg, ethylene-propylene copolymer, poly-4-methylpentene-1, etc.), cyclic olefin polymer (eg, norbornene resin), cyclic olefin copolymer ( For example, thermoplastic resins such as ethylene-norbornene copolymer), polyvinyl chloride, acrylic resin, polystyrene, polyamide (for example, nylon 6, nylon 6, 6), and ionomer are preferably used.

    Among these, when the degree of crystallinity of polypropylene is increased, the elastic modulus is improved and thermal deformation and wrinkles of the light diffusing sheet body 2 are less likely to occur, and the difference in light refractive index from the light diffusing agent due to the increase in light refractive index. Therefore, it is preferably used as a resin for producing the thin light diffusing sheet 1. In particular, polypropylene having a crystallinity of 40 to 80% has a large rigidity and also has a high refractive index of 1.48 to 1.52 that approximates the light refractive index (1.54) of talc described later, which is preferably used as a light diffusing agent. Since the light diffusing sheet body 2 is formed in combination with talc, the light diffusing sheet body 2 having a large amount of light transmission and high luminance can be obtained. A more preferable crystallinity of polypropylene is 42 to 60%.

  Polycarbonate and acrylic are also preferably used because they have good heat resistance, high mechanical strength, good transparency, and rigidity. Therefore, as shown in FIG. 6, the light source is suitable as the light diffusing sheet 1 incorporated in a direct type backlight unit that has a linear shape directly under the light diffusing sheet 1 and needs to have a thickness of about 1 to 5 mm. Moreover, when setting it as the light-diffusion sheet 1 of an electrical decoration signboard or a lighting cover, there exists an advantage which can be used as a part of structural member. Furthermore, cyclic polyolefin and the like are also preferably used as a resin for a light diffusion sheet for a direct backlight unit because it has high rigidity and very good transparency.

  The light diffusing agent contained in the light diffusing sheet main body 2 mainly plays a role of diffusing light. In addition, when the light diffusing sheet 1 is thin, the light diffusing sheet 1 also plays a role of preventing wrinkles by suppressing thermal expansion and contraction. Inorganic particles, metal oxide particles, and organic polymer particles having a light refractive index different from that of the light transmissive resin of the light diffusing sheet body 2 are used alone or in combination. As inorganic particles, particles such as glass, silica, mica, synthetic mica, calcium carbonate, magnesium carbonate, barium sulfate, talc, montmorillonite, kaolin clay, bentonite, hectorite, etc. are used, and as metal oxide particles, Particles such as titanium oxide, zinc oxide, and alumina are used, and particles such as acrylic, styrene, and benzoguanamine are used as the organic polymer particles.

  Among these, inorganic particles having a low coefficient of linear expansion are preferably used from the viewpoint of suppressing thermal expansion and contraction of the thin light diffusing sheet body 2, and in particular, the talc powder has a large aspect ratio of 50 to 1000 and the light diffusing sheet body. Since the linear expansion coefficient of 2 can be reduced, it is preferably used. When the translucent resin is polypropylene, it also acts as a nucleating agent for the resin, and the crystal grain size can be finely and uniformly dispersed while increasing the crystallinity of the polypropylene. It is preferably used for the reason that the rate can be improved and the mechanical strength of the light diffusion sheet main body 2 can be improved with a low addition amount.

  In addition, even if the glass particles are inorganic particles, they themselves are translucent, so light transmission is not hindered, and even if they are incorporated in a large amount to reduce the linear expansion coefficient, the light transmission amount can be reduced. It is preferably used because it does not reduce the volatility. Among these glass particles, the A glass particles (soda lime glass particles) can be remarkably suppressed from lowering the luminance, and are preferably used for the light diffusion sheet 1 that places importance on the luminance.

  On the other hand, the acrylic particles are preferably used because they are transparent per se and do not decrease the light transmission amount of the light diffusion sheet 1, and the transmitted light is refracted many times inside the light diffusion sheet body 2. It is particularly useful for 1-5 mm sheets. When these acrylic particles are contained in a light-transmitting resin having rigidity such as polycarbonate resin, acrylic resin, or cyclic polyolefin resin, it is not necessary to consider the thermal expansion and contraction so that it becomes a preferable combination.

  As these light diffusing agents, those having an average particle diameter of 0.1 to 100 μm, preferably 0.5 to 80 μm, more preferably 1 to 50 μm are used. If the particle size is smaller than 0.1 μm, the particles easily disperse, resulting in poor dispersibility. Even if the particles can be evenly dispersed, the light wavelength is larger and the light scattering efficiency is deteriorated. Therefore, particles having a size of 0.5 μm or more, and further 1.0 μm or more are preferably used. On the other hand, if the particle size is larger than 100 μm, light scattering becomes non-uniform, and there is a disadvantage that the amount of light transmission decreases and particles are visible. Therefore, particles up to 80 μm and even up to 50 μm are preferably used.

When the light diffusing agent is an inorganic particle other than glass, it is preferable to use a fine particle having an average particle diameter since the particle does not transmit light, and those having a mean particle size of 0.5 to 50 μm, more preferably 1 to 20 μm. used. On the other hand, when the light diffusing agent is a glass particle or an organic polymer particle, it is preferable to use a particle having a slightly larger average particle diameter so as not to aggregate because the particle transmits light. 3 to 80 μm is used.
These light diffusing agents are desirably used in combination of particles having different types and average particle diameters to optimize the luminance, the total light transmittance, and the like.

  The content of the light diffusing agent in the light diffusing sheet body 2 is preferably 0.1 to 35% by mass. If it is less than 0.1% by mass, light diffusion is not sufficiently performed and the hiding property is inferior, the haze of the light diffusion sheet 1 cannot be increased to 30% or more, and the dots formed on the light guide plate, the line light source directly below, There is a risk that the light source of the signboard will be visible. On the other hand, if it is 35% by mass or more, the light transmission amount of the light diffusing sheet body 2 decreases due to light scattering, reflection, and refraction by the light diffusing agent, and the total light transmittance of the light diffusing sheet 1 cannot be made 50% or more. Even if the light diffusing sheet 1 using such a light diffusing sheet main body 2 is incorporated in a backlight unit, for example, and the display is illuminated from behind, there is a disadvantage that display is difficult to see.

  When the light diffusing agent is inorganic particles such as talc and the translucent resin used for the light diffusing sheet body 2 is polypropylene, the content is preferably 15 to 35% by mass, more preferably 18 to 30%. Mass%. If the inorganic particles are less than 15% by mass, the suppression of thermal expansion and contraction of the polypropylene is insufficient, so that the sheet is liable to be wrinkled. In particular, when the light diffusion sheet 1 is as thin as 30 to 200 μm, thermal expansion and contraction immediately appears on the sheet and causes wrinkles, so it is necessary to set the content to 15% by mass or more. On the other hand, if it exceeds 35% by mass, the proportion of inorganic particles that do not transmit light increases so much that the amount of light transmitted through the light diffusing sheet body 2 decreases, so that light diffusion using such a light diffusing sheet body 2 is performed. The sheet 1 has a disadvantage that the display is difficult to see as described above.

  On the other hand, when the light diffusing agent is organic polymer particles such as acrylic particles, and the thickness of the light diffusing sheet 1 is 0.5 to 10 mm, the rigidity is also increased. It can be reduced to 20% by mass, more preferably 1 to 10% by mass. Thus, even if the content is reduced to 20% by mass or less, problems such as wrinkles due to thermal expansion and contraction do not occur. Further, since the organic polymer particles transmit light and the content thereof is small, the light diffusion sheet 1 having sufficient light transmittance can be obtained. As the translucent resin containing the organic polymer particles, it is preferable to use a resin having excellent heat resistance such as polycarbonate or cyclic polyolefin, or a resin having excellent transparency such as acrylic.

  The thickness of the light diffusing sheet body 2 is desirably 30 μm to 10 mm. When the thickness is less than 30 μm, the light transmission amount and the luminance are improved, but the rigidity of the light diffusion sheet main body 2 is reduced, so that wrinkles are easily generated and the light diffusion is weakened, so that the concealability is lowered. Conversely, if the thickness of the light diffusing sheet main body 2 is greater than 10 mm, thermal expansion and contraction of the light diffusing sheet is suppressed and wrinkles do not enter, and concealment is improved. It becomes difficult to see the display.

    In the edge light type backlight unit shown in FIG. 1, since a thin display is required, the light diffusion sheet main body 2 having a thickness of 250 μm or less is preferable. A more preferred thickness is 50 to 200 μm, and a further preferred thickness is 70 to 180 μm. With such a thickness, the amount of light transmission can be increased. The resin is preferably a resin such as polyethylene terephthalate, polypropylene, or polycarbonate.

    In the direct type backlight unit shown in FIG. 6, since rigidity is required, it is preferable to set the thickness to 0.3 to 10 mm. A more preferable thickness is 0.5 to 5 mm, and a more preferable thickness is 1 to 3 mm. And as resin, resin, such as a polycarbonate with high light transmittance, an acryl, and a cyclic olefin, is used preferably.

The light-transmitting antistatic layer 3 laminated along the unevenness of the upper surface serving as the light exit surface of the light diffusing sheet body 2 is made of a layer in which metal fine particles are dispersed, or an ultrafine conductive fiber. It is necessary to have a surface resistivity of 10 ⁶ to 10 ¹¹ Ω / □. A layer having a low surface resistivity of 10 ⁶ Ω / □ or less is not antistatic but conductive, and may cause other problems such as sparks. High surface resistance of 10 ¹¹ Ω / □ or more A layer having a rate cannot exhibit antistatic performance. More preferably, the translucent antistatic layer 3 having a surface resistivity of 10 ⁷ to 10 ¹⁰ Ω / □ is preferable.

The translucent antistatic layer 3 composed of a layer in which metal fine particles are dispersed is obtained by uniformly depositing metal fine particles having known conductivity such as tin oxide, tin oxide containing antimony, tin oxide containing indium on the binder resin. It is distributed. In particular, antimony-containing tin oxide metal fine particles having a particle size of 0.15 to 0.5 μm are preferably used because they are less likely to impair translucency by being uniformly dispersed. And these electroconductive metal microparticles | fine-particles can be made into the surface resistivity of 10 < ⁶ > -10 < ¹¹ > (omega | ohm) / (square) by making it contain in 50 to 80 weight% in a translucent antistatic layer.

As the binder resin used for the light-transmitting antistatic layer, a light-transmitting resin is preferably used. For example, vinyl chloride resin, polycarbonate resin, acrylic resin, polyethylene resin, olefin resin such as polypropylene, polystyrene, polyethylene A terephthalate resin, a polydimethylcyclohexane terephthalate resin, an ester resin such as an aromatic polyester, an ABS resin, or a copolymer resin of each of these resins is used. A resin having a rate and a haze of 5% or less is used.
In addition, transparent curable resins that are cured by heat, ultraviolet rays, electron beams, radiation, etc., for example, silicone resins such as melamine acrylate, urethane acrylate, epoxy resin, polyimide resin, and acrylic-modified silicate are also preferably used. If it exists, since the surface hardness becomes high after curing, the surface of the antistatic layer 3 is not damaged, the translucency can be maintained, and the appearance can be kept good.

  Further, the translucent antistatic layer 3 made of a layer containing ultrafine conductive fibers has a structure in which the ultrafine conductive fibers 3a are dispersed without being aggregated and are in contact with each other, as shown in FIGS. preferable. In other words, the fine conductive fibers 3a may be dispersed and in contact with each other in a state in which the fine conductive fibers 3a are separated one by one without being entangled, or in a state where a plurality of bundles are separated into one bundle. Is preferred. When the translucent antistatic layer 3 is mainly formed of the ultrafine conductive fibers 3a and a transparent binder, as shown in FIG. 7A, the ultrafine conductive fibers 3a are dispersed in the binder. 7 and dispersed in contact with each other, or as shown in FIG. 7B, a part of the ultrafine conductive fiber 3a enters the binder, and the other part protrudes or is exposed from the binder surface and dispersed in the above dispersed state. However, some of the fine conductive fibers 3a are in contact with the inside of the binder as shown in FIG. 7A, and the other fine conductive fibers 3a are projected or exposed from the surface as shown in FIG. 7B. Are dispersed and in contact with each other.

The dispersion state seen from the plane of these ultrafine conductive fibers 3a is schematically shown in FIG. As can be understood from FIG. 8, the fine conductive fibers 3a are slightly bent, but are separated one by one or one bundle, and do not intricately entangle each other, that is, do not agglomerate. It is dispersed inside or on the surface of the optical antistatic layer 3 and is in contact at each intersection. When dispersed in this way, compared to the case of agglomeration, the fibers are loose and exist in a wide range, so the chance of contact between these fibers increases significantly, resulting in conduction and antistatic properties. Can be significantly increased. If the ultrafine conductive fiber is dispersed without being unraveled, it is necessary to contain a large amount in order to obtain a surface resistivity of 10 ⁶ to 10 ¹¹ Ω / □, and as a result, the antistatic layer 3 is colored black to transmit light. Inhibits sex. However, if the fine conductive fibers 3a are dispersed as described above, the same contact opportunity can be obtained even if the amount of the fine conductive fibers 3a is reduced, and the amount of the fine conductive fibers 3a can be reduced accordingly. It can be done. As a result, the transparency is improved by the amount of the ultrafine conductive fiber 3a that hinders the transparency, and the translucent antistatic layer 3 can be made thinner, thereby further improving the transparency. Can do.
The ultrafine conductive fibers 3a do not have to be separated and dispersed completely one by one or one bundle, and there may be small agglomerates that are intertwined with each other, but the average diameter is 0. It is preferably not more than 5 μm.

  The ultrafine conductive fibers 3a used for the transparent antistatic layer 3 include ultrafine carbon fibers such as carbon nanotubes, carbon nanohorns, carbon nanowires, carbon nanofibers, graphite fibrils, platinum, gold, silver, nickel, silicon, etc. Conductive ultrafine fibers having a diameter of 0.3 to 100 nm, such as ultrafine metal fibers such as metal nanotubes and nanowires, metal oxide nanotubes such as zinc oxide, and ultrafine metal oxide fibers such as nanowires are preferably used. The length of these conductive ultrafine fibers is 0.1 to 20 μm, preferably 0.1 to 10 μm. These ultrafine conductive fibers 3a are dispersed one by one or one bundle without agglomeration, so that the light transmittance of the transparent antistatic layer 3 is 90% or more. In addition, the said light transmittance shows the transmittance | permeability of the light of the wavelength of 550 nm by a spectrophotometer.

Among these ultrafine conductive fibers 3a, the carbon nanotubes are extremely thin and have a diameter of 0.3 to 80 nm, so that the carbon nanotubes are less likely to inhibit light transmission by being dispersed one by one or one bundle. It is particularly preferable for obtaining a transparent antistatic layer 3 having a light transmittance of 50% or more. The carbon nanotubes are also dispersed one by one in a state of being bundled one by one or in a bundle in a state where the carbon nanotubes are not agglomerated inside or on the surface of the translucent antistatic layer 3, and are in contact with each other to conduct. The sex is secured. Therefore, the surface resistivity can be freely set to 10 ⁶ to 10 ¹¹ Ω / □ by adding the carbon nanotube 3a to the translucent antistatic layer 3 in an amount corresponding to the basis weight of 1 to ²⁰ mg / m ^2. Can be controlled. The basis weight is determined by observing the translucent antistatic layer 3 with an electron microscope, measuring the area ratio of the carbon nanotubes 3a in the plane area, and measuring the thickness of the carbon nanotubes 3a with the specific gravity of the carbon nanotubes (graphite It is a value calculated by multiplying the average value 2.2 of the literature values 2.1 to 2.3.

  Here, “not agglomerated” means that the translucent antistatic layer 3 is observed with an optical microscope, and if there is an agglomerated lump, the major axis and the minor axis are measured, and the average value is 0. It means that there is no lump of 5 μm or more.

The carbon nanotube includes a multi-walled carbon nanotube concentrically provided with a plurality of cylindrically closed carbon walls having different diameters around the central axis, and a single cylindrically closed carbon wall around the central axis. Single-walled carbon nanotubes. The former multi-walled carbon nanotubes are dispersed and contact each other in a separated state, and the latter single-walled carbon nanotubes are dispersed in contact with each other in a state where a plurality of bundles are bundled and separated one by one. It is preferable because the amount of light transmission can be increased after the surface resistivity is made 10 ⁵ Ω / □ or less.

The former multi-walled carbon nanotubes are composed of multiple cylindrically closed carbon walls with different diameters stacked around the central axis, and this carbon wall forms a hexagonal network structure of carbon graphite. It is made. Preferred multi-walled carbon nanotubes are those in which the carbon walls are overlapped by 2 to 30 layers, more preferably 2 to 15 layers, and if the layers overlap in this range, the number of walls is small and the light transmission amount and haze are improved. be able to. As shown schematically in FIG. 8, most of the multi-walled carbon nanotubes are separated one by one and dispersed in the light-transmitting antistatic layer 3 in a state of being simply crossed without being intertwined in a complicated manner. Are in contact at each intersection.
Some of the two- to three-walled carbon nanotubes are separated one by one, but some are dispersed one by one in a bundled state, and this is not excluded.

  On the other hand, the single-walled carbon nanotube is composed of a single-walled carbon wall closed in a cylindrical shape around the central axis, and the carbon wall is also formed by carbon graphite forming a hexagonal network structure. Such single-walled carbon nanotubes are difficult to exist alone, and exist in a bundle of two or more. As shown schematically in FIG. 8, most of the bundles are one by one. The bundles are separated and dispersed in the light-transmitting antistatic layer 3 in a simply crossed state without being intricately entangled, and are in contact with each intersection. As the single-walled carbon nanotube, 10 to 50 bundles are suitably used. In the present invention, the case where single-walled carbon nanotubes are dispersed one by one is not excluded.

As described above, when the carbon nanotubes are in contact with the translucent antistatic layer 3 without being entangled, even if the thickness of the translucent antistatic layer 3 is extremely thin, the carbon nanotubes are sufficiently separated from each other. Since conduction is ensured, the surface resistivity can be 10 ⁶ to 10 ¹¹ Ω / □. Specifically, when the carbon nanotube is 1 to 20 mg / m ² , the translucent conductive layer 3 has a thickness of 500 nm or less, preferably 100 nm or less, and more preferably 50 nm or less to improve translucency. Even if it makes it, the surface resistivity can be made into the range of 10 < ⁶ > -10 < ¹¹ > ohm / square.

  It is preferable to increase the dispersibility of the carbon nanotubes in order to develop good antistatic performance and translucency by including a small amount of carbon nanotubes in the translucent antistatic layer 3. For this purpose, the dispersibility is excellent. It is preferable to use carbon nanotubes having a thickness and length, and to use a dispersant in combination. Multi-walled carbon nanotubes having an outer diameter of 1 to 20 nm and an aspect ratio of 50 to 10000, particularly those having an outer diameter of 5 to 15 nm and an aspect ratio of 100 to 1000 have excellent dispersibility. In addition, the single-walled carbon nanotube has a bundle outer diameter of 1 to 20 nm and a length of 0.1 to 10 μm, particularly a bundle outer diameter of 5 to 15 nm and a length of 0.5 to 5 μm. Has excellent dispersibility.

  Examples of the dispersant added to the translucent antistatic layer 3 include polymeric dispersants such as an alkyl ammonium salt solution of an acidic polymer, a tertiary amine-modified acrylic copolymer, and a polyoxyethylene-polyoxypropylene copolymer. A coupling agent or the like is preferably used, and the addition amount thereof is about 5 to 85% by mass, preferably about 10 to 40% by mass with respect to the carbon nanotube.

  The translucent antistatic layer 3 containing carbon nanotubes may be a layer made of only carbon nanotubes, but is preferably dispersed and contained in the binder resin. Examples of the binder resin include the same kind of light-transmitting thermoplastic resin as that of the light diffusion sheet main body 2 described above, or a thermoplastic resin such as a compatible light-transmitting thermoplastic resin, or a light-transmitting curable resin. Used. Preferred translucent binder resins include thermoplastic resins such as polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polymethyl methacrylate, nitrocellulose, chlorinated polyethylene, chlorinated polypropylene and vinylidene fluoride, and melamine acrylate. , Urethane acrylate, epoxy resin, polyimide resin, silicone resin such as acryl-modified silicate, transparent curable resin that is cured by heat, ultraviolet ray, electron beam, radiation etc. such as fluororesin, these transparent binders and the above carbon The translucent antistatic layer 3 made of nanotubes is made to be a transparent layer. In addition, an inorganic material such as colloidal silica may be added to these binders. When a binder containing a curable resin or colloidal silica is used as the binder, an antistatic light diffusing sheet having excellent abrasion resistance can be obtained. Thus, since the translucent antistatic layer 3 is formed on the surface of the light diffusing sheet body 2, a binder suitable for the required weather resistance, surface hardness, wear resistance, etc. should be selected and used. Is desirable.

  Moreover, you may provide the thin 20-500 nm transparent resin layer which consists only of the said binder on the surface of the translucent antistatic layer 3. FIG. When this transparent resin layer is formed, the chemical resistance of the antistatic layer 3 is improved and the ultrafine conductive fibers can be prevented from falling off, so that antistatic performance over a long period can be maintained. In particular, if the transparent antistatic layer 3 is a layer composed of only carbon nanotubes (which may contain a very small amount of resin), the carbon nanotubes may fall off, and therefore it is very preferable to provide the transparent resin layer. . In this case, part of the carbon nanotubes may enter the transparent resin layer, and further pass through the transparent resin layer and protrude to the surface. Therefore, the antistatic layer 3 and the transparent resin layer may be regarded as a combined layer containing carbon nanotubes.

  Further, the translucent antistatic layer 3 containing ultrafine conductive fibers such as carbon nanotubes may contain conductive metal fine particles such as tin oxide within a range that does not impair the transparency, and absorbs ultraviolet rays. Additives such as agents, surface modifiers and stabilizers may be added as appropriate to improve weather resistance and other physical properties.

  The antistatic light diffusing sheet 1 as described above can be manufactured, for example, by the following method. In addition, in the following manufacturing method, when fine unevenness is not formed on the surface of the light diffusing sheet 1, a flat roll or press plate can be used without using a textured roll or a fine uneven press plate. Good.

  One method is to first extrude a translucent resin in which a light diffusing agent is dispersed into a sheet and pass it between a pair of upper and lower embossing rolls, or with a press plate having fine irregularities. By pressing, the light diffusion sheet main body 2 having fine irregularities on both the upper and lower surfaces is produced. Then, an antistatic coating material in which metal fine particles are dispersed in a binder resin and a solvent is applied to one side of the light diffusing sheet main body 2, or the ultrafine conductive fibers 3a are dispersed in a solvent or the ultrafine conductive fibers 3a. The light diffusing sheet 1 is manufactured by forming a light-transmitting antistatic layer 3 by applying and solidifying an antistatic coating material in which is dispersed in a solvent and a binder resin.

  Another method is to produce a light diffusing sheet main body with no irregularities on both sides by extruding a translucent resin in which a light diffusing agent is dispersed into a sheet, and the metal fine particles or ultrafine conductive material on one side of the resin film. The light-diffusing sheet 1 is manufactured by applying and solidifying an anti-static coating material in which fibers are dispersed to form a light-transmitting anti-static layer 3 and then pressing with an embossing roll or a press plate having fine irregularities. To do.

  Still another method is to extrude a light-transmitting resin in which a light diffusing agent is dispersed into a sheet shape, and make fine irregularities on the upper and lower surfaces of the light diffusing sheet main body with the light diffusing agent on or near the surface. The light diffusing sheet 1 in which the light transmissive antistatic layer 3 is formed is manufactured by applying and solidifying the antistatic coating material in which the metal fine particles or ultrafine conductive fibers are dispersed on one surface of the light diffusing sheet body 2.

  Still another method is to produce a light diffusing sheet main body having no irregularities on both sides by extruding a translucent resin in which a light diffusing agent is dispersed into a sheet shape, and translucent to an adhesive resin film. An antistatic film is formed by applying and solidifying the antistatic coating material in which the metal fine particles or ultrafine conductive fibers are dispersed to the antistatic layer 3 and laminating the antistatic film on the light diffusion sheet body. Then, the light diffusion sheet 1 is manufactured by pressing with an embossing roll or a press plate having fine irregularities.

  Still another method is to produce a light diffusing sheet main body with no irregularities on both sides by extruding a translucent resin in which a light diffusing agent is dispersed into a sheet shape, and translucent to a resin film having peelability. An antistatic transfer film formed by applying and solidifying the antistatic coating material in which the metal fine particles or ultrafine conductive fibers are dispersed to the antistatic layer 3 and an adhesive layer made of an adhesive resin such as acrylic is produced. After transferring the adhesive layer and the antistatic layer 3 to the light diffusing sheet main body using the antistatic transfer film, the light diffusing sheet 1 is formed by pressing with an embossing roll or a press plate having fine irregularities. To manufacture.

  The antistatic light diffusing sheet 1 obtained by the above method has good transparency and a total light transmittance in the range of 50 to 95%, good diffusibility and a haze in the range of 30 to 95%. is there. When such a light diffusing sheet 1 is incorporated between the light guide plate 5 and the lens film 6 of the backlight unit for an edge light type display shown in phantom lines in FIG. 1, for example, as described above, the light diffusing sheet 1 Since the lower surface, which is the light incident surface, has an arithmetic average roughness Ra and a surface area ratio suitable for incident light by forming irregularities, almost all of the light incident on the light guide plate 5 from the light source 7 is in the light diffusion sheet 1. Light enters the light diffusing sheet main body 2 substantially uniformly from the entire lower surface. The incident light is diffused by the light diffusing agent in the light diffusing sheet main body 2, and the upper surface of the light diffusing sheet main body 2 on which the unevenness is formed, and the translucency formed in an uneven shape along the unevenness. It is further diffused with the surface of the antistatic layer 3 and emitted toward the lens film 3. Since the light exit surface of the light diffusion sheet 1 has the arithmetic average roughness Ra suitable for light diffusion by forming irregularities and the surface area ratio larger than the lower surface as described above, the light diffusion is strong and uniform. Therefore, the light diffusing sheet 1 has little light loss, can emit uniform scattered light, has no partial luminance variation, has good concealment properties, and does not see the dots on the back surface of the light guide plate 5. Moreover, even if the light diffusion sheet 1 is as thin as 30 to 200 μm, the linear expansion coefficient of the light diffusion sheet body 2 is reduced by containing 15 to 35 mass% of the light diffusing agent in the light diffusion sheet body 2. In addition, since the elastic modulus is improved, even if the backlight unit has heat, the thermal expansion and contraction of the sheet is suppressed and no wrinkles are generated.

In addition, since the light diffusing sheet 1 exhibits the antistatic performance by the translucent antistatic layer 3 having a surface resistivity of 10 ⁶ to 10 ¹¹ Ω / □, the light diffusing sheet 1 is used as a backlight or a backlight driving circuit or the like. Therefore, the light transmission medium can be maintained.

  FIG. 2 is a cross-sectional view of an antistatic light diffusing sheet according to another embodiment of the present invention.

This antistatic light diffusing sheet 1 is made of a translucent resin as a light diffusing sheet main body 20 above and below a core layer 2a made of a translucent resin containing a light diffusing agent of 0.1 to 35% by mass. It differs from the light diffusion sheet shown in FIG. 1 described above in that a laminated sheet having a three-layer structure in which the surface layers 2b and 2b are laminated and fine irregularities are formed on both upper and lower surfaces thereof is used.
The surface layer may be provided only on one side of the core layer. Further, it is not always necessary to form fine irregularities.
Since the same thing as what was demonstrated in the said embodiment is used for the antistatic layer 3, it attaches | subjects the same code | symbol and abbreviate | omits description.

  The core layer 2a of the light diffusing sheet main body 20 is the same as the light diffusing sheet main body 2 described above, and the translucent resin and the light diffusing agent used for the light diffusing sheet main body 2 are used. . In order to increase the light transmission amount and light diffusibility of the core layer 2a and to reduce the linear expansion coefficient and improve the elastic modulus when the core layer 2a is as thin as 30 to 200 μm, the content of the light diffusing agent Is 15 to 35% by mass in the same manner as the light diffusion sheet main body 2 described above.

  On the other hand, the surface layers 2b and 2b of the light diffusing sheet main body 20 are layers of a translucent resin that does not contain a light diffusing agent. By covering both surfaces of the core layer 2a, the light diffusing agent from the light diffusing sheet 1 is covered. This is to prevent falling off, to prevent the light guide plate and lens film of the backlight unit from being damaged, or to contain the UV absorber in the surface layer 2b to suppress the light deterioration of the light diffusion sheet 1. . Moreover, at the time of manufacture, when the light-diffusion sheet main body 20 is three-layer coextrusion-molded as described later, it also serves to prevent the light diffusing agent from adhering to the periphery of the extrusion port. Therefore, the surface layers 2b and 2b need to have a thickness that can cover the light diffusion sheet body 20 and exhibit the above-described effects, and therefore the thickness needs to be 4 μm or more. The preferred thickness is 4 to 200 μm. If the thickness of the light diffusion sheet 1 is 30 to 200 μm, the thickness is about 4 to 50 μm, preferably about 5 to 30 μm, more preferably about 6 to 10 μm. When the thickness is 1 to 10 mm, the thickness is about 20 to 200 μm, preferably about 30 to 100 μm. If the surface layer 2b is thinner than 4 μm, the light diffusing sheet main body 20 is not sufficiently covered, and conversely, even if it is formed thicker than 200 μm, the corresponding effects cannot be obtained. In addition, when the ratio of the surface layer 2b to the thickness of the light diffusion sheet 1 increases, thermal expansion and contraction cannot be suppressed, and on the other hand, it causes wrinkles. In particular, the thickness of the light diffusion sheet 1 is 30 to 200 μm. Is preferably 50 μm or less.

  As the translucent resin forming the surface layer 2b, the same translucent resin as that of the core layer 2a described above or a resin compatible with the resin is used. When a resin compatible with the core layer 2a is selected as the resin for the surface layer 2b, it is desirable to select a resin having a lower refractive index than the resin for the core layer 2 as the resin for the surface layer 2b. With this selection, the difference in the optical refractive index between the air and the resin of the surface layer 2b is smaller than the difference in the optical refractive index between the air and the resin of the core layer 2a. Compared with the amount of light transmitted through the light diffusing sheet 1 formed only by the core layer 2a, the amount of light transmitted through the light diffusing sheet 1 when transmitted through the air 2a and released into the air on the opposite side. As a result, the amount of light transmission is increased, and as a result, the luminance can be improved. In addition, when the surface layer 2b is formed only on one side of the core layer 2a, the above-described effects can be obtained by using the surface layer 2b as a light incident surface.

  As a combination of the translucent resin of the core layer 2a and the surface layer 2b, for example, the translucent resin of the core layer 2a is a polycarbonate resin, and the translucent resin of the surface layer 2b is an optical refractive index (1. 58) A combination of acrylic resins having a smaller optical refractive index (1.49) is most preferred. In such a combination, both the resins are originally high light transmittance resins, and the acrylic resin is a resin excellent in light resistance, and the difference in the refractive index between air and the acrylic resin is Since the difference in optical refractive index between acrylic resin and polycarbonate resin is 0.09, and the optical refractive index difference between polycarbonate resin and air is 0.58, the light transmittance as the light diffusion sheet 1 is 0.49. It becomes 91.2% (theoretical value), which is 1.1% higher than the light transmittance (90.1%) when light passes only through the core layer 2a, and the luminance can be improved.

  As the ultraviolet absorber to be contained in the surface layer 2b, conventionally known benzotriazole-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, and the like are preferably used, but triazine-based ultraviolet absorbers are also used. . When the light diffusing sheet 1 is incorporated in a backlight unit or the like, it is light-degraded and colored (yellowing) by the light from the light source. To prevent this, the surface layer 2b contains an ultraviolet absorber to suppress coloring. However, it is preferable because excellent light transmission and luminance can be obtained over a long period of time. The core layer 2a may also contain an ultraviolet absorber.

  FIG. 3 is a cross-sectional view of an antistatic light diffusing sheet according to another embodiment of the present invention.

This antistatic light diffusing sheet 1 is a light diffusing sheet main body 30, and a surface layer made of a translucent resin containing a light diffusing agent on the upper surface of a core layer 3 a made of a translucent resin containing no light diffusing agent. It differs from the light diffusion sheet shown in FIG. 1 in that a laminated sheet having a two-layer structure in which 3b is laminated and fine irregularities are formed on the surface of the surface layer 3b is used.
In addition, the fine unevenness | corrugation in which the surface layer 3b was formed is not necessarily required, and may be flat, and conversely, you may form a fine unevenness | corrugation in the lower surface of the core layer a. The surface layer 3b may be laminated not only on the upper surface of the core layer 3a but also on the lower surface to form a three-layer structure. At that time, it is preferable that the content of the light diffusing agent in the surface layer 3b on the lower surface side is smaller than that in the surface layer 3b on the upper surface side because more light can enter.
Since the same thing as what was demonstrated in embodiment of the said FIG. 1 is used for the antistatic layer 3, it attaches | subjects the same code | symbol and abbreviate | omits description.

The core layer 3a of the light diffusing sheet body 30 is made of the translucent resin used for the light diffusing sheet body 2 described above, and the core layer 3a does not contain a light diffusing agent.
On the other hand, the surface layer 3b is made of a translucent resin layer containing a light diffusing agent, and covers one side of the core layer 3a to allow light diffusion. The same translucent resin and light diffusing agent as those described above are used for the surface layer 3b, but the content thereof needs to be increased to 5 to 60% by mass. Because the thickness of the surface layer 3b is 4 to 200 [mu] m, which is thinner than the core layer 3a, it is desirable that the surface layer 3b with the thickness be sufficiently light diffused to obtain concealment, so that it is contained in the above range. is there. And since the fine unevenness | corrugation of the surface layer 3b contains a large amount of light-diffusion agents, it will be formed with the light-diffusion agent which exists in the surface vicinity. In addition, it does not exclude forming unevenness with a texture roll or the like.
Further, it is desirable that the core layer 3a and / or the surface layer 3b contain an ultraviolet absorber to suppress discoloration.
The other light diffusing agent, translucent resin, fine irregularities on the surface layer 3b, and the transparent antistatic layer 3 are the same as those in the above embodiment, and thus the description thereof is omitted.

Such an antistatic light diffusing sheet 1 is formed by, for example, using a two-layer coextrusion molding machine to extrude a translucent resin that does not contain a light diffusing agent into a sheet, and at the same time, add 5 light diffusing agent thereon. A light diffusing sheet main body 30 composed of a two-layer laminated sheet in which the surface layer 3b is laminated on the core layer 3a is produced by overlapping and extruding a translucent resin containing ˜60% by mass, and translucent on one side thereof. The antistatic layer 3 is manufactured by laminating and forming the same method as described above.
In addition, the core layer 3a is manufactured by extruding a light-transmitting resin not containing a light diffusing agent into a sheet shape, while the resin film including the light diffusing agent is prepared and the light-transmitting antistatic layer 3 is formed on one side as described above. A translucent resin film formed by the same method as above is prepared, and this translucent resin film is overlaid on the core layer 3a so that the translucent antistatic layer 3 is on the outer side. It can be manufactured by laminating 3b and translucent antistatic layer 3.

  FIG. 4 is a cross-sectional view of an antistatic light diffusing sheet according to still another embodiment of the present invention.

  The light diffusing sheet 1 is a light diffusing sheet main body 40. The light diffusing sheet 1 is different from the core layer 4a on both upper and lower surfaces of a core layer 4a made of a translucent resin containing 0.1 to 35% by mass of a light diffusing agent. If the same diffusing agent is used, or the surface layers 4b and 4b made of a translucent resin containing 0.1 to 35% by mass of the content different from that of the core layer are laminated, and the surfaces of the surface layers 4b and 4b are laminated. It differs from the light diffusion sheet shown in FIG. 1 described above in that a laminated sheet having a three-layer structure in which fine irregularities are formed is used.

  The translucent resin and light diffusing agent used in the antistatic light diffusing sheet 1 are the same as those described above, but the light diffusing agents contained in the core layer 4a and the surface layer 4b are different from each other. It is desirable to contain the agent in the range of 0.1 to 35% by mass, or to use different contents when the same light diffusing agent is used. For example, the core layer 4a contains a talc light diffusing agent in an amount of 0.1 to 35% by mass, preferably 5 to 30% by mass, and the surface layers 4b and 4b contain 0.1 to 35% by mass of a glass light diffusing agent. %, Preferably in the range of 15 to 35% by mass, or containing different amounts of glass light diffusing agent in the core layer 4a and 15 to 35% by mass in the surface layer 4b. Is desirable.

Thus, when the core layer 4a and the surface layer 4b contain a light diffusing agent, the heat diffusibility of the light diffusing sheet main body 40 is reduced, and the generation of wrinkles can be suppressed, and the light diffusing agent contained in both the layers 4a and 4b. Therefore, the light can be diffused in each layer and the concealability can be improved. In particular, when the core layer 4a contains a talc light diffusing agent having a large aspect ratio and the surface layer 4b contains a translucent glass light diffusing agent, thermal expansion and contraction is suppressed by the talc light diffusing agent of the core layer 3a and the surface layer. Suppressed by the glass particles 3b to prevent generation of wrinkles in the light diffusing sheet 1 and has a concealing property, and the glass light diffusing agent of the surface layer 3b does not inhibit the translucency so much. A light diffusing sheet body 40 having the following can be obtained.
The other translucent antistatic layer 3 and fine irregularities are the same as described above, and thus the description thereof is omitted. Note that fine irregularities are not always necessary, and the surface may be flat. Further, the surface layer may be provided only on one side, and the light-transmitting antistatic layer may be formed on the other side.

  Such a light diffusing sheet 1 is formed by, for example, using a three-layer coextrusion molding machine to extrude a translucent resin containing 0.1 to 35% by weight of a light diffusing agent into a sheet, and at the same time, A light diffusing sheet body 40 composed of a three-layer laminated sheet in which the surface layers 4b and 4b are laminated on the upper and lower sides of the core layer 4a by extruding a translucent resin containing 0.1 to 35% by weight of a diffusing agent. It is manufactured by manufacturing and laminating the translucent antistatic layer 3 on one surface thereof by the same method as the above-described manufacturing method.

  FIG. 5 is a cross-sectional view of an antistatic light diffusing sheet according to still another embodiment of the present invention.

  This antistatic light diffusing sheet 1 is formed on the flat upper surface of a light diffusing sheet main body 50 made of a single layer sheet of translucent resin containing 0.1 to 35% by mass of a light diffusing agent. And a light-transmitting resin coating layer 4 that covers the light-transmitting antistatic layer 3 are stacked to form fine irregularities on the lower surface of the light diffusion sheet body 50 and the upper surface of the light-transmitting resin coating layer 4. It is a thing.

  The translucent resin coating layer 4 is a layer made of a translucent resin that does not contain a light diffusing agent, and serves to protect the translucent antistatic layer 3 from being damaged. Examples of the translucent resin for the covering layer 4 include the same as the translucent resin for the light diffusing sheet body 2 and the core layer 2a in the above-described light diffusing sheet, and other hard coat resins such as silicone and urethane acrylate. used. The thickness of the coating layer 4 is suitably about 0.05 to 50 μm, preferably about 0.1 to 10 μm.

  The light diffusing sheet main body 50 and the light transmissive antistatic layer 3 are the same as the light diffusing sheet main body 2 and the light transmissive antistatic layer 3 in the light diffusing sheet 1 described above. The arithmetic average roughness and surface area ratio of the upper surface of the light transmissive resin coating layer 4 are also the same as those on the upper and lower surfaces of the light diffusion sheet body 2 in the light diffusion sheet 1 described above.

  The antistatic light diffusing sheet 1 having such a configuration, like the above-described light diffusing sheet, has a large amount of light transmission, can emit uniform and high-intensity diffused light, has good concealing properties, and has antistatic performance. In addition to having the function and effect of exhibiting, it also has the function and effect of protecting the translucent antistatic layer 3 from being damaged by the translucent resin coating layer 4.

Such an antistatic light diffusing sheet 1 is produced by extruding a translucent resin containing a light diffusing agent into a sheet to produce a light diffusing sheet main body 50 and forming the translucent antistatic layer 3 on one side. The light-transmitting resin film (resin film that becomes the light-transmitting resin coating layer 4) is overlaid on the light diffusion sheet body 50 so that the light-transmitting antistatic layer 3 is on the light diffusion sheet body side. It can be manufactured by a method such as thermocompression bonding with an attached roll or a press plate on which fine irregularities are formed.
The light diffusing sheet thus laminated with the translucent resin coating layer 4 is not limited to the light diffusing sheet main body 50 described above, and the two or three layers described in the other embodiments are used. It may be a thing. Further, fine irregularities on the surface are not necessarily required, and the surface may be smooth.

  FIG. 6 is a cross-sectional view of a light diffusion sheet according to still another embodiment of the present invention.

  This antistatic light diffusing sheet 1 has ultraviolet light on a flat lower surface of a core layer 6a made of a light-transmitting resin single layer sheet containing 0.1 to 35% by mass of a light diffusing agent as a light diffusing sheet body 60. In the above-described FIG. 1, the light-transmitting antistatic layer 3 is laminated on the flat upper surface of the core layer 6 a using a laminated sheet obtained by laminating a surface layer 6 b made of a translucent resin containing an absorbent. It differs from the light diffusion sheet 1 shown.

FIG. 6 shows a case where the light diffusion sheet 1 is incorporated in a direct backlight unit. The light diffusing sheet 1 is incorporated with the surface layer 6b containing the ultraviolet absorber located on the line light source 7 side and the core layer 6a containing the light diffusing agent located on the opposite side. As a result, the translucent antistatic layer 3 is positioned on the uppermost side. When incorporated in this way, the light emitted from the linear light source 7 enters the surface layer 6b and is transmitted, diffused and emitted by the light diffusing agent of the core layer 6a, but the light source light including ultraviolet rays or the like is the ultraviolet light of the surface layer 6b. Since it is absorbed by the absorbent, ultraviolet degradation of the surface layer 6b and the core layer 6a is suppressed, and the light diffusing sheet 1 is hardly yellowed. The light diffusing sheet 1 used for such a direct-type backlight unit has many large units, and the supporting members are only around. Therefore, as the translucent resin, a resin having rigidity such as polycarbonate or acrylic is used. The thickness is preferably 0.3 to 10 mm. More preferable thickness is 0.5 to 5 mm, and further preferable thickness is 1 to 3 mm. The other light-transmitting resin, light diffusing agent, and light-transmitting antistatic layer are the same as those in the embodiment of FIG. Since there is, description is abbreviate | omitted.

  This antistatic light diffusing sheet 1 also has a large amount of light transmission, can emit uniform and high-intensity diffused light, has good concealment properties, and can exhibit sufficient antistatic performance.

  Such an antistatic light diffusing sheet 1 is formed by simultaneously extruding a translucent resin containing a light diffusing agent in an amount of 0.1 to 35% by using a two-layer coextrusion molding machine, A light diffusing sheet body composed of a two-layer laminated sheet in which a surface layer 6b is laminated on the lower side of a core layer 6a by extruding and extruding a translucent resin containing no light diffusing agent and containing an ultraviolet absorber on the lower side 60 is produced. The light diffusion sheet main body 60 is coated with an antistatic coating in which the metal fine particles or ultrafine conductive fibers are dispersed and solidified to form an antistatic layer, or the metal fine particles or ultrafine conductive fibers are dispersed. The antistatic film obtained by applying the antistatic coating is laminated or transferred by a method such as lamination.

It is sectional drawing of the antistatic light diffusion sheet which concerns on one Embodiment of this invention. It is sectional drawing of the antistatic light diffusion sheet which concerns on other embodiment of this invention. It is sectional drawing of the antistatic light-diffusion sheet which concerns on other embodiment of this invention. It is sectional drawing of the antistatic light-diffusion sheet which concerns on other embodiment of this invention. It is sectional drawing of the antistatic light-diffusion sheet which concerns on other embodiment of this invention. It is sectional drawing of the antistatic light-diffusion sheet which concerns on other embodiment of this invention. A and B are cross-sectional views for explaining a dispersion state of ultrafine conductive fibers of the translucent antistatic layer. It is a schematic plan view which shows the dispersion state of the ultrafine conductive fiber in a translucent electrical control layer.

Explanation of symbols

1. Antistatic light diffusing sheet 2, 20, 30, 40, 50, 60 Light diffusing sheet body 2a, 3a, 4a, 6a Core layer 2b, 3b, 4b, 6b Surface layer 3 Translucent antistatic layer 3a Extra fine conduction fiber

Claims (20)

An antistatic light diffusing sheet characterized by laminating a translucent antistatic layer having a surface resistivity of 10 ⁶ to 10 ¹¹ Ω / □ on at least one surface of a light diffusing sheet body.   The antistatic light diffusing sheet according to claim 1, wherein the light diffusing sheet main body contains a light diffusing agent.   The antistatic light diffusing sheet according to claim 2, wherein the light diffusing agent is contained in an amount of 0.1 to 35% by mass.   The antistatic light diffusion sheet according to any one of claims 1 to 3, wherein fine irregularities are formed on at least one surface of the light diffusion sheet.   The light diffusing sheet body is a laminated sheet comprising at least a core layer and a surface layer, wherein the core layer contains a light diffusing agent, and the surface layer does not contain a light diffusing agent. The antistatic light diffusion sheet according to any one of the above.   The light diffusing sheet main body is a laminated sheet comprising at least a core layer and a surface layer, wherein the core layer does not contain a light diffusing agent, and the surface layer contains a light diffusing agent. The antistatic light-diffusion sheet in any one of -4.   5. The antistatic device according to claim 1, wherein the light diffusing sheet main body is a laminated sheet including at least a core layer and a surface layer, and the core layer and the surface layer contain a light diffusing agent. Light diffusion sheet.   The light diffusing sheet main body is a laminated sheet composed of at least a core layer and a surface layer, and the translucent resin used for the surface layer is a resin having a lower refractive index than the translucent resin used for the core layer. The antistatic light-diffusion sheet in any one of Claims 5-7.   The antistatic light diffusing sheet according to claim 5, wherein an ultraviolet absorber is contained in at least the surface layer.   The light diffusing sheet body is made of a translucent polypropylene resin containing 15 to 35% by mass of a talc light diffusing agent, and fine irregularities are formed on both surfaces of the light diffusing sheet. The antistatic light diffusion sheet according to any one of the above.   A light diffusing sheet body is a laminated sheet in which a surface layer made of a translucent resin is laminated on at least one side of a core layer made of a translucent polypropylene resin containing 15 to 35% by mass of a talc light diffusing agent, The antistatic light diffusion sheet according to any one of claims 5 to 9, wherein fine irregularities are formed on both sides of the diffusion sheet.   The light diffusing sheet main body is a laminated sheet in which a surface layer made of a translucent resin is laminated on at least one surface of a core layer made of a translucent polycarbonate resin containing 0.1 to 20% by mass of an acrylic light diffusing agent. The antistatic light diffusing sheet according to any one of claims 5 to 9, wherein   13. The antistatic light diffusing sheet according to claim 1, wherein the translucent antistatic layer is a layer in which metal fine particles are dispersed.   The antistatic light diffusion sheet according to any one of claims 1 to 12, wherein the translucent antistatic layer is a layer in which ultrafine conductive fibers are dispersed.   The antistatic light diffusing sheet according to claim 14, wherein the ultrafine conductive fibers are dispersed without being aggregated and are in contact with each other.   15. The method according to claim 14, wherein the ultrafine conductive fibers are separated one by one, or a plurality of bundles of bundles are separated and are in contact with each other in a separated state. 15. The antistatic light diffusion sheet according to 15.   The antistatic light diffusion sheet according to any one of claims 14 to 16, wherein the ultrafine conductive fiber is a carbon nanotube. Antistatic light diffusing sheet of claim 17, basis weight of the carbon nanotubes contained in the light-transmissive antistatic layer is characterized by a 1 to 20 mg / m ^2.   The antistatic light diffusing sheet according to any one of claims 1 to 18, wherein the antistatic light diffusing sheet has a total light transmittance of 50 to 95% and a haze of 30 to 95%.   20. The antistatic light diffusion sheet according to any one of claims 1 to 19, wherein a translucent resin coating layer that covers the translucent antistatic layer is laminated.

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