TWI440898B - Light diffusion film and back light device equipped with the same - Google Patents

Description

Light diffusing film and backlight device equipped therewith

The present invention relates to a light-diffusing film excellent in diffusibility and adhesion of light, and a backlight device incorporating the same.

Light diffusing films are widely used as members of various lighting fixtures, display devices, or screens. In this case, the light-diffusing film may be used by being adhered to an adhesive or an adhesive for workability or shape stability, in addition to being used only in combination with other members. For example, in the case of being incorporated in a planar light source device or a backlight device, the light-diffusing film is applied to the surface of the light guide plate with an adhesive or an adhesive (see, for example, Patent Documents 1 to 3). However, in this method, a step of laminating an adhesive or the like is necessary, which may cause economic disadvantage.

In Patent Document 1, a light-diffusing film of a surface light-diffusion type of a bead coating method is bonded to the surface of a light guide plate by a UV curable adhesive, but the effect of improving the brightness due to bonding is not mentioned.

In Patent Document 2, a light diffusing film of a directivity is bonded to an emitting surface of a light guide plate by an optical diffusing agent containing fine particles. However, as in Patent Document 1, the brightness is improved by the bonding. Not mentioned.

In Patent Document 3, a liquid resin composed of an acrylic prepolymer is applied to a surface of a light guide plate made of an acrylic resin, and a light diffusion film made of a polycarbonate resin is laminated on the coated surface, and then the liquid resin is formed. Harden and integrate. In Patent Document 3, it is described that the interface between the light guide plate and the diffusion film prevents the incorporation of air or foreign matter, and suppresses the decrease in light emission or diffusion. This method describes that the brightness is higher than that of the double-sided adhesive tape, and teaches that the refractive index difference between the light guide plate and the light-diffusing film affects the brightness, but the effect is not clearly explained. Further, the light-diffusing film composed of a polycarbonate resin has a surface-diffusion type light-diffusing film in which light is diffused or scattered by surface protrusions, but the specific content or optical characteristics are not described. reveal.

Further, in Patent Document 4, an optical film which has been subjected to a concavo-convex processing to increase the surface area is bonded to the surface of the base unit of the backlight device with an adhesive layer. In the object of the invention of the patent document 4, the "adhesive optical sheet which is provided with the optical adhesive layer is adhered to the adherend of the emitted light to emit light with good light efficiency", but In the examples, only the three sheets of the diffusion plate, the BEF, and the diffusion plate provided on the backlight device used for the brightness evaluation are similarly carried, but are not disclosed in the same optical film. The effect of the fit.

Further, Patent Document 5 discloses a light-scattering laminated film in which at least one surface of a light-scattering layer is formed of a continuous phase and a particulate dispersed phase having different refractive indices, and a transparent resin layer is laminated, but is transparent. The resin layer is an unmodified polypropylene resin which is insufficient in adhesion.

In Patent Document 6, although a light-reflecting film in which an adhesive layer is provided is disclosed, an adhesive layer is not provided on the light-diffusing film.

Prior technical literature Patent literature

Patent Document 1 Japanese Patent Laid-Open No. 09-159837

Patent Document 2 Japanese Patent Laid-Open Publication No. 2005-50654

Patent Document 3 Japanese Patent Publication No. 06-324216

Patent Document 4 Japanese Patent Laid-Open Publication No. 2009-75595

Patent Document 5 Japanese Patent Laid-Open Publication No. 2002-1858

Patent Document 6 Japanese Patent Laid-Open Publication No. 2007-178998

The object of the present invention is to provide a light-diffusing film and a backlight device equipped therewith, which is excellent in light diffusibility or light resistance and excellent in economy, and Excellent adhesion to other members.

The present invention is composed of the following (1) to (9).

(1) A light-diffusing film which is attached to at least one side of a light-diffusing layer containing two kinds of mutually non-miscible polyolefin-based resins as a main component, and a laminate having a polyolefin resin containing a polar group as a main component The layer is made the outermost surface, the light diffusing film has a total light transmittance of 66 to 100%, and the film has a haze of 20 to 100%.

(2) The light-diffusing film according to item (1), wherein the diffused light in the main dispersion direction of the transmitted light measured at an incident angle of 0 degrees is 140 to 180 degrees.

(3) The light-diffusing film of item (1) or (2), wherein the light of the main diffusion direction has a degree of recursion of from 1 to 100%.

(4) The light-diffusing film according to any one of (1) to (3), wherein the two mutually non-miscible polyolefin-based resins are composed of a polypropylene-based resin and ethylene and/or butene. Made of polyolefin resin.

(5) The light-diffusing film according to any one of (1) to (3), wherein the two polyolefin resins which are mutually non-miscible are made of a cyclic polyolefin resin and a polyethylene resin. Composition.

(6) The light-diffusing film according to any one of (1) to (5), wherein the polyolefin resin containing a polar group contains a carboxyl group.

(7) A backlight device comprising a surface layer of a light-diffusing film according to any one of the items (1) to (6), which is bonded to a surface of a substrate on a light-emitting surface of a basic unit of the backlight.

(8) The backlight device of item (7), wherein the basic unit of the backlight is a light guide plate of an edge light-emitting type.

(9) The backlight device of item (7) or (8), wherein a refractive index difference between the substrate and the adhesive layer is -0.2 to +0.5.

The light-diffusing film of the present invention is excellent in both light transmittance and diffusibility, and has good light resistance, and is excellent in adhesion to other members. For example, it can be easily bonded to other members by thermocompression bonding, and the economy is also economical. Excellent. Therefore, it can be suitably used for optical apparatuses and apparatuses, such as various luminaires, display apparatuses, and screens. Moreover, by using the light-diffusing film of the present invention in a backlight device, the light-emitting efficiency of the backlight device can be improved, and the luminance of the backlight device can be increased. Furthermore, the economics of the backlight device can be improved by reducing the output of the backlight source or reducing the number of sheets of various optical films.

Mode for carrying out the invention (light diffusing film)

The light-diffusing film of the present invention is formed by laminating at least one side of a light-diffusing layer containing two kinds of mutually non-miscible polyolefin-based resins as a main component, and laminating a polyolefin resin containing a polar group as a main component. The light diffusing film has a total light transmittance of 66 to 100%, and the film has a haze of 20 to 100%.

The light-diffusing layer of the present invention contains two kinds of polyolefin-based resins which are mutually incompatible with each other as a main component. Here, the main component means that the content ratio is 50% by mass or more, preferably 70% by mass or more. In general, since the polyolefin-based resin does not have an aromatic ring, it is less susceptible to deterioration by ultraviolet irradiation. Therefore, since yellowing due to ultraviolet irradiation can be suppressed, it is suitable as a constituent material of the light-diffusing film.

The two kinds of polyolefin resins which are mutually incompatible with each other are not limited as long as they are mutually incompatible resins, and are preferably composed of a polyolefin resin containing a polypropylene resin and ethylene and/or butene.

Further, it is preferred that the two polyolefin resins which are mutually non-miscible are composed of a cyclic polyolefin resin and a polyethylene resin.

By the above two combinations, the control of the optical characteristics caused by the light diffusion layer can be stably performed over a wide range. Further, the above two combinations are suitable even from the viewpoint of light resistance or economy. In the above two combinations, a nanocrystalline structure-controlled polyolefin elastomer resin may be further combined.

When the polyolefin resin is 70 mol% or more, it is not limited as long as it is composed of an olefin monomer. The ratio of the olefin monomer is preferably 90% by mole or more, more preferably 95% or more, and most preferably 98% or more. The polyolefin resin may, for example, be a polyolefin resin such as a polyethylene resin, a polypropylene resin, a polybutene resin, a cyclic polyolefin resin or a polymethylpentene resin, or a copolymer thereof. Wait. Further, a modified polyolefin resin in which a functional group such as a carboxyl group, an ester group or a hydroxyl group is introduced into the resin can be suitably used. Further, a copolymer having no monomer such as acrylic acid, methacrylic acid or an aromatic ring such as the ester derivative may be used.

The polyethylene resin may be a single polymer or a copolymer. In the case of a copolymer, it is more appropriate to use 50 mol% or more of the ethylene component. The density of the resin, the polymerization method, and the like are not limited, but the use of a copolymer having a density of 0.909 or less is suitable. For example, a copolymer with octene can be exemplified. The polymerization method may be any one of a metallocene catalyst method and a non-metallocene catalyst method.

The polypropylene resin may be a single polymer or a copolymer. In the case of a copolymer, it is preferred to use 50 mol% or more of the propylene component. The method for producing the resin, the molecular weight, and the like are not limited, but from the viewpoint of heat resistance and the like, a substance having high crystallinity is suitable. Specifically, the crystallinity can be judged by the heat of fusion of a differential scanning calorimeter (DSC), and the heat of fusion is preferably 65 J/g or more.

The polyolefin-based resin containing ethylene and/or butene may, for example, be a homopolymerized vinyl resin, a homopolymerized butene resin, and a copolymer of these resins with other olefin-based monomers, acrylic acid or methyl group. Acrylic acid and copolymers of these and ester derivatives, and the like. In the case of a copolymer with other olefin-based monomers, it may be any of random, block and graft copolymers. Further, it may be a dispersion of EP rubber or the like. The method for producing the resin, the molecular weight, and the like are also not particularly limited. For example, it is preferred to use the above polyethylene resin or a copolymer of ethylene and butene.

The cyclic polyolefin-based resin may, for example, be a cyclic polyolefin structure such as norbornene or tetracyclododecene. Specifically, (1) a ring-opening (co)polymer of a norbornene-based monomer, which is subjected to polymerization such as maleic acid addition or cyclopentadiene addition as needed. After the modification, the resin to be hydrogenated, (2) the resin to be subjected to addition polymerization of the nortenyl group-containing monomer, and (3) the olefin-based monomer such as a norbornene-based monomer and ethylene or an α-olefin The body is subjected to addition copolymerization of a resin or the like. The polymerization method and the hydrogenation method can be carried out in a usual manner.

The nanocrystalline structure-controlled polyolefin-based elastomer resin is a crystalline/amorphous structure of a polymer which is controlled by a nanometer grade, and the crystal is a nanometer-grade thermoplastic polyolefin elastomer having a mesh structure, and is exemplified. For example, Notio (registered trademark) manufactured by Mitsui Chemicals Co., Ltd. The conventional polyolefin-based elastomer resin has a crystal size of micron order, whereas the nanocrystal structure-controlled polyolefin-based elastomer resin has a feature that the crystal size is controlled by the nanometer grade. Therefore, compared with the conventional polyolefin-based elastomer resin, it is often excellent in transparency, heat resistance, flexibility, rubber elasticity, and the like. Therefore, by arranging the nanocrystalline structure-controlled polyolefin-based elastomer resin, the appearance of the obtained film can be improved.

The blending ratio of the two mutually non-miscible polyolefin-based resins is preferably 10/90 to 90/10, more preferably 20/80 to 80/20, and more preferably 30/70 to 70/30. At least two kinds of non-miscible polyolefin-based resins may be prepared by blending the respective resins in a film forming step, or may be previously prepared by kneading or the like.

In the present invention, it is also possible to mix two kinds of resins other than the polyolefin resin which are mutually non-miscible, and to use an additive such as a remelting agent or a dispersion diameter adjusting agent for improving the affinity of the respective resins. Further, an additive such as an antioxidant or an ultraviolet absorber or an antistatic agent may be blended. Further, as long as it does not inhibit the above optical characteristics, fine particles such as inorganic particles or polymer beads may be added.

The melt flow rate of the polyolefin resin which is mutually incompatible with each other is not particularly limited as long as it satisfies the above optical characteristics. The respective resins are suitably selected from a melt flow rate of from 0.1 to 100, preferably from 0.2 to 50, as measured at 230 °C.

The adhesive layer of the present invention contains a polyolefin resin containing a polar group as a main component. Here, the main component means that the content ratio is 10% by mass or more, preferably 30% by mass or more. The polyolefin resin containing a polar group is preferably a monomer containing at least one of ethylene, propylene, butylene, hexene, octene, methylpentene, and a cyclic olefin. It may be a homopolymer using one of the above monomers, or two or more kinds of copolymers may be used.

The polar group contained in the polyolefin resin may, for example, be a carboxyl group, a sulfonic acid group, a phosphonic acid group, a hydroxyl group, a glycidyl group, an isocyanate group, an amine group or a quinone imine group. An oxazoline group, an ester group, an ether group, a metal carboxylate, a metal sulfonate, a metal phosphonate, a tertiary amine base or a quaternary amine base. The polar group may be one type or two or more types. The polar group preferably has at least a carboxyl group.

The polar group may be directly introduced into the polymer chain of the polyolefin resin, or may be introduced into another resin and added to and mixed with the polyolefin resin. Further, the polyolefin resin may be reacted with a compound which can be reacted with, for example, a carboxyl group or a hydroxyl group introduced at the end or inside of the molecular chain, and modified.

The polyolefin resin containing a polar group may be used alone or in combination of two or more. Further, it may be a formulation of a polyolefin resin or a resin of another type which does not contain a polar group. The adhesive layer of the present invention can also be heated by the use of a polyolefin resin containing a polar group.

When the light-diffusing film of the present invention is laminated on at least one side of the light-diffusing layer so that the adhesive layer becomes the outermost surface, the constitution or production method is not limited.

The layer may then be laminated on one or both sides of the light diffusing layer. The total thickness of the film is not limited, but is preferably from 10 to 500 μm. Next, the thickness of the layer, the thickness of one side is preferably 2 to 100 μm.

Further, the thickness ratio of the light diffusion layer/sublayer layer in the light diffusion film is preferably from 10/1 to 3/1, more preferably from 6/1 to 4/1. By setting the ratio of such thicknesses, the smoothness of the adhesive layer can be sufficiently obtained.

The light diffusing film of the present invention has a total light transmittance of 66 to 100%, preferably 68% or more, more preferably 70% or more, and 100% is most suitable. In addition, the full light transmittance is in principle, 100% is the upper limit. When the total light transmittance is less than 66%, the utilization efficiency of the amount of light emitted from the light source is lowered, which is not preferable.

The light diffusing film of the present invention has a haze of 20 to 100%, preferably 25% or more, more preferably 30% or more. In addition, haze is in principle 100% of its upper limit. In the case of being used as a light-diffusing film for a backlight device, the haze of the film is preferably 72% or more, more preferably 75% or more. When the haze is less than 20%, the light diffusibility is too low, and the effect of controlling the diffusibility is insufficient, which is not preferable.

In the light-diffusing film of the present invention, the variable angle photometer measured by the method described in the examples preferably has a degree of diffusion of 140 to 180 degrees in the main diffusion direction of the transmitted light measured at an incident angle of 0 degrees. The degree of diffusion is preferably from 145 to 180 degrees, and most preferably from 150 to 180 degrees. By setting the degree of diffusion within this range, for example, when a light-diffusing film used as a backlight device is used, a remarkable brightness enhancement effect can be exhibited. When the degree of diffusion is less than 140 degrees, the light diffusibility is too low, and there is a possibility that the diffusibility control effect is insufficient. On the one hand, the degree of diffusion is theoretically limited to 180 degrees.

In the light-diffusing film of the present invention, it is preferred that the light in the main diffusion direction measured by the method described in the examples has a degree of recursion of from 1 to 100%. The degree of recursion of light is more preferably from 2 to 100%, more preferably from 5 to 100%. By setting the degree of refraction of light to this range, for example, when a light-diffusing film used as a backlight device is used, a remarkable brightness enhancement effect can be exhibited.

The method for producing the light-diffusing film is not particularly limited as long as it satisfies the above optical characteristics, and from the viewpoint of economy, a method of forming a film by a melt extrusion method is suitable. In the present invention, the non-melting fine particles are not contained, but the polyolefin-based resin blended with the film can provide light diffusibility, and even if it is carried out by melt extrusion molding, the molten resin can be reduced in the film forming step. The filter is clogged, the productivity is excellent, and the transparency of the obtained film is also high.

In the method of laminating the light-diffusing layer and the adhesive layer, for example, a so-called multilayer extrusion method in which each layer is pressed by a plurality of individual extruders, and the film is joined and formed into a film in the mold; Forming a film separately from the film of the adhesive layer, and adhering the film to the adhesive or the adhesive; and extruding the respective adhesive layer or the light diffusion layer in the light diffusion layer film or the adhesive film to laminate the two layers The so-called squeeze paste law. From the viewpoint of the adhesion between the light-diffusing layer and the adhesive layer, a multilayer extrusion method is preferred.

The melt extrusion method is not particularly limited, and may be, for example, any of a T-die method and an inflation method. Further, it may be a film which is not stretched as it is, or may be a material which is subjected to elongation treatment.

(backlight device)

The backlight device of the present invention is formed by bonding the subsequent layers of the light-diffusing film to the surface of the substrate on the light-emitting surface of the basic unit of the backlight device.

The basic unit of the backlight device of the present invention is not particularly limited as long as it has a light exit surface on at least one side. For example, it may be any of the edge illumination method and the direct type. Moreover, it can also be a two-sided light emission type. The surface of the substrate on the light exit surface of the basic unit of the backlight means, for example, in the case of an edge light-emitting method, which is the light exit surface of the light guide plate. Further, the case of the direct type refers to the surface of the upper substrate. Moreover, the case where the light pattern is emitted on both sides means the surface of both sides of the light guide plate of the edge light-emitting type.

Generally, in a backlight device, in order to increase the brightness of the light exit surface, a reflective film or a reflector is used on the opposite side of the light exit surface. The reflective film or the reflector may, for example, be a diffused type formed of a white body, a highly directivity which is reflected by a metallic luster, or a substance having both characteristics.

Further, in the backlight device of the edge light-emitting type, in order to suppress the attenuation of the luminance due to the distance from the light source, a method of giving an emission light pattern by printing, engraving, engraving, or the like is employed, but it is not limited to the presence or absence of the emitted light pattern. . The method of the present invention is similar to the previously described method of merely superimposing various optical members. Since the outline of the emitted light is greatly different, it is preferable to design the emitted light pattern to be suitable for the method of the present invention. In the method of the present invention, since the amount of emitted light at a short distance is increased from the light source, it is appropriate to make the emission light pattern obliquely stronger.

The basic unit of the backlight device is preferably a light guide plate of an edge light-emitting type. Thereby, the conduction in the light guide plate is continued, and the amount of light emitted from the surface of the backlight device due to the change in the critical angle of the incident light is increased, and the effect of improving the brightness is further increased. Moreover, since the thickness of the backlight device can be made thinner than the direct-down type, it is easy to meet the market demand for thinning the display device or the illumination device.

The reason why the brightness enhancement effect of the backlight device of the present invention is improved is as follows. That is, for example, when the conduction in the light guide plate is continued, the light exceeding the critical angle causes reflection at the interface between the light guide plate and the light diffusion film, and does not emit light on the surface of the light guide plate. In the case where the light diffusing film to be widely used previously overlaps only the surface of the light guide plate, an air layer exists between the light diffusing film and the substrate. The refractive index of air is lower than the refractive index of the substrate, so that the refractive index is remarkably lowered, and since the critical angle is decreased, the amount of light emitted from the surface of the substrate is lowered, and as a result, the luminance is lowered. Generally, the refractive index of the resin used in the light diffusing film is larger than that of air. Therefore, by bonding the light-diffusing film, the critical angle of the light that continues to be conducted in the light guide plate is increased, so that the amount of light emitted from the surface of the light guide plate is increased, and as a result, the brightness is increased.

The above-mentioned brightness enhancement effect is first discovered by the applicant using the light-diffusing film of the present invention, but the use of a previously used molding method or a transparent film surface, for example, by coating a light-diffusing component such as a bead This effect is small in the surface diffusion type light-diffusing film which is a scattering effect of the surface unevenness light. The light-diffusing film of the present invention is a so-called internal diffusion film which provides light diffusibility by light scattering caused by light-scattering bodies which are formed by mutually incompatible resins existing in the film, and a light diffusion film of a surface diffusion type. The light diffusion effect is very different. In the case of a surface light-diffusing film, the light diffusing property provides light diffusibility by the scattering effect of the surface unevenness, and the light scattering is controlled only by the light-scattering layer of one surface of the substantially surface. In contrast, the light-diffusing film of the present invention, Light scattering is a multi-layer scattering pattern generated in the entire interior of the film. Since the light scattering acts in multiple layers, the light emitted from the surface of the light guide plate is expanded by the critical angle to effectively increase the brightness. . Furthermore, in the present invention, by limiting the optical characteristics of the light-diffusing film to the above-described range, the brightness can be effectively improved.

In the present invention, the method of bonding the subsequent layer of the light-diffusing film to the surface of the substrate is not particularly limited as long as the air layer existing between the light-diffusing film and the substrate can be excluded. For example, it may be adhered by an adhesive or an adhesive, or it may be liquid-tightly bonded. Since the light-diffusing film has thermal adhesion, it is suitable to bond the two by heat bonding.

In the present invention, by bonding the light-diffusing film to the substrate, for example, it is possible to have a secondary effect of suppressing dimensional change due to environmental changes such as the temperature of the light-diffusing film.

In the present invention, the difference in refractive index between the adhesive layer of the light-diffusing film and the substrate is preferably from -0.2 to +0.5. The refractive index difference is preferably from -0.1 to +0.2, and most preferably from zero. The refractive index is generally expressed by a decimal point or less to three digits. However, in the present invention, it is preferable to evaluate the difference between a decimal point and a single digit (two digits below the decimal point). In the present invention, the measurement of the refractive index is measured by a usual method using a refractometer. Resins with reference values are preferred for use with reference values. In the case of a mixture of resins, the value of the individual resin is used, and the value obtained by the weighted average of the composition ratio is used.

In the backlight device of the present invention, it is preferable to use only one sheet of the light-diffusing film. Since the multilayer diffusion film has high brightness, uniformity of brightness, and disappearance of the emitted light pattern, the optical film which does not use a lens film or a brightness enhancement film is also excellent. However, in combination with the lens film, it is possible to further increase the brightness, or to reduce the output of the lamp used in the backlight device.

The backlight device of the present invention can be used as a light source for a display device. Since the backlight device of the present invention has high luminance, when the light source used as the display device is used, the brightness of the display device can be improved, and the visibility of the display screen can be improved. In the case where high brightness is not necessary, since the amount of light of the backlight can be reduced, the manufacturing cost or energy consumption of the display device can be reduced. The display device is not limited as long as it has a function of transmitting certain information by light emitted from the backlight device. For example, an LCD display device for a transport device such as a personal computer, a TV, or a vehicle can be exemplified. Further, a non-animated display device such as an advertisement or a guide plate may be exemplified.

Further, the backlight device of the present invention can be used as a light source for illumination. Since the backlight device of the present invention has high luminance, that is, because of high illuminance, the brightness of the illumination device as a light source for illumination can be improved. In the case where high illumination is not necessary, the manufacturing cost or energy consumption of the lighting device can be reduced as well. The backlight unit itself can also be used as a light source for illumination.

Example

The present invention is further described by the following examples, but the present invention is not limited by the following examples, and may be appropriately modified and implemented as being within the scope of the present invention, and these are all included in the present invention. Within the technical scope. Further, the measurement and evaluation methods employed in the examples are as follows. In addition, in the embodiment, "%" means "% by mass" unless otherwise specified. "%" means "% by mass" unless otherwise specified.

1. Full light transmittance and haze

The haze meter "NDH-2000" manufactured by Nippon Denshoku Industries Co., Ltd. was used in accordance with JIS-K-7136.

The winding direction of the film is fixed to the sample stage of the measuring device in the vertical direction and the horizontal direction, and the average value of the measured values in the two directions is further obtained by using the average value of the measured values measured three times. To express. The corresponding setting is such that the parallel light transmittance is increased in the vertical direction and the horizontal direction in the winding direction of the film.

Further, the sample which was laminated on one side of the layer was subjected to measurement by incident light on the side of the layer. In the case where the laminate layer is laminated on both surfaces and the surface roughness of both surfaces is different, light is incident from the surface having a small surface roughness and measured.

2. The degree of diffusion through the direction of light diffusion

The measurement was performed using an automatic variable angle photometer (GP-200: Murakami Color Research Co., Ltd.).

Through the measurement mode, the incident angle of light is 0° (the angle between the upper and lower sides and the right and left sides with respect to the sample surface), the light receiving angle: -90° to 90° (the angle on the equator line), and the filter: ND10 is used. , the beam gate: 10.5mm (VS-13.0), the shutter: 9.1mm (VS-34.0), SENSITIVITY: 950, HIGH VOLTON: 600 and the angular separation interval of 0.1 degrees, obtained by making the receiver from - The degree of the angle between the peak standing angle of the variable angle illuminance curve of the transmitted light and the angle at which the peak is completed is measured until 90 degrees is moved to +90 (refer to Fig. 1). From the perspective of the rise and the completion of the crest, these parts are observed with a magnifying glass of 10 times, and the angle of the foremost end of the disappearance of the crest line is taken as the respective angle.

In addition, the face of the moving photoreceiver is defined as an equatorial plane.

The angle is fixed such that the winding direction of the film is parallel to the upper and lower directions of the sample fixing table and the horizontal direction, and the value of the larger angle is used as the diffusion degree.

Further, the sample laminated on one side was measured by incident light from the side of the subsequent layer. In the case where the thickness of the surface of the both surfaces is different, and the thickness of the surface is different, the incident light is measured from the surface having a small surface roughness and measured.

The film direction of the diffuser is taken as the main diffusion direction.

At the time of measurement, a light-up film (registered trademark) 100DX2 film of a light-diffusing film manufactured by Kimoto Co., Ltd. was fixed to a sample fixing table so that the winding direction of the film was parallel to the vertical direction. Further, the diffusion layer side was set to the emission light side, and the variable angle photometric measurement was performed under the same conditions as above. In this measurement, the height of the peak apex of the variable angle luminosity curve is relative to the full scale, in the case of more than 80%, or less than 70%, the value is a slight adjustment of the value of the SENSITIVITY or HIGH VOLTON dial relative to the whole The scale becomes 70 to 80%.

3. The degree of recursion of light

The measurement was performed using an automatic variable angle photometer (GP-200: Murakami Color Research Co., Ltd.).

Through the measurement mode, the incident angle of light: 0° (the angle between the upper and lower sides and the right and left sides at right angles to the sample surface), the light receiving angle: -90° to 90° (the angle on the equator line), filter: use ND10, beam gate: 10.5mm (VS-13.0), shutter: 9.1mm (VS-34.0) and variable angle interval of 0.1 degrees, obtained: by changing the setting of SENSITIVITY or HIGH VOLTON The peak of the light peak is 40 to 90% of the graph, and the peak height (H0) of the transmitted light obtained is measured; and the incident angle of the light is changed to 60. Other than the angle (the angle on the equatorial plane), the other is the height (H60) of the peak angle of the transmitted light when measured under the same conditions as above. Using H60 and H0 obtained in this way, the degree of recursion was obtained by the following formula. Refer to Figure 2.

Light refraction = H60/H0×100 (%)

In addition, the face of the moving photoreceiver is defined as the equatorial plane.

The degree of recursion of light is determined by measurement in the main diffusion direction.

4. The adhesion of the light diffusing film to the substrate

A smooth and transparent acrylic plate (manufactured by Mitsubishi Rayon Co., Ltd.: Acrylite) having a thickness of 3 mm was mounted on a fixing table of a hot press, and a sample was placed on the acrylic plate, and further, a thickness of 3 mm was applied thereon. The polyoxyethylene rubber sheet (hardness HsA50°) was pressed from the above-mentioned polyoxysulfide rubber sheet with a pressure indenter whose surface temperature was set to 180 ° C, and pressed at a pressure of 49 N/cm ² for 30 seconds. After heating and pressing, the mixture was allowed to stand for 30 minutes in an environment of a temperature of 23 ° C and a relative humidity of 65%, and a "Tensilon" (UTM-IIIL) manufactured by Toyo Seiki Co., Ltd. was used to peel off 180 degrees at a speed of 300 mm/min. The resistance value is set to the force.

The determination of the force is then carried out on the basis of the following criteria.

Then the force is 0.1N/15mm or more: good

Then the force is lower than 0.1N/15mm: bad

5. Melt flow rate of thermoplastic resin

It was measured under the conditions of 2.16 kgf in accordance with JIS-K-7210 A method.

6. Front brightness

The light-diffusing films of Examples 1 to 5 and Comparative Examples 1 to 5 and Reference Example 1 were bonded to the backlight unit, and the front luminances of Examples 6 to 10 and Comparative Examples 6 to 10 and Reference Example 2 were measured. . The measurement methods are as described in the respective examples, comparative examples, and reference examples.

7. The disappearance of the emitted light pattern

In the front luminance measurement, the opening was visually observed in a state where the backlight was turned on, and was determined based on the following criteria.

No observing the grid of the light guide plate: good

Vaguely visible grid of light guide plate: slightly bad

Clearly see the grid of light guides: bad

(Example 1)

Using a first extruder, 35 parts by mass of a cyclic polyolefin resin (melt flow rate: 2.0 (230 ° C) manufactured by TOPAS (TM) 6013S-04 Topas Advanced Polymers Co., Ltd.) was used in a two-stage melt extruder. a light-diffusing layer composed of 65 parts by mass of a block copolymer resin (INFUSE (TM) D9817.15 melt flow rate: 26 (230 ° C) manufactured by Dow Chemical Co., Ltd.) composed of ethylene and octene, and a second extruder was used. The melt-co-extrusion was carried out by a T-die method to form a maleic acid-based polypropylene resin ((melmer flow rate: 5.7 (190 ° C) manufactured by Mitsui Chemicals Co., Ltd.) as an adhesive resin. After the two layers of the light-diffusing layer were formed, the light-diffusing film having a total thickness of 400 μm laminated on both surfaces of the light-diffusing layer was obtained by cooling with a mirror-finished cooling roll. The adhesion was carried out using a vacuum chamber, and the layer thickness composition (adhesion layer/light diffusion layer/sublayer layer) was 40/320/40 (μm).

The characteristics of the obtained light-diffusing film are shown in Table 1.

The light-diffusing film obtained in the present Example is excellent in light-diffusing properties and excellent in adhesion.

(Comparative Example 1)

In the method of the first embodiment, the resin of the adhesive layer formed by the second extruder was changed to a cyclic polyolefin resin (melt flow rate = 2.0 by TOPAS (TM) 6013S-04 Topas Advanced Polymers Co., Ltd. A light-diffusing film was obtained in the same manner as in Example 1 except for 230 ° C).

The characteristics of the obtained light-diffusing film are shown in Table 1.

The light-diffusing film obtained in this comparative example was excellent in light-diffusion characteristics, but the adhesion was deteriorated.

(Example 2)

A light-diffusing film was obtained in the same manner as in Example 1 except that the total thickness of the light-diffusing film was changed to 175 μm and the layer thickness configuration was changed to 25/125/25 (μm) in the method of Example 1.

The characteristics of the obtained light-diffusing film are shown in Table 1.

The light-diffusing film obtained in the present Example is excellent in light-diffusing properties and excellent in adhesion.

(Comparative Example 2)

In the method of the second embodiment, the resin of the adhesive layer formed by the second extruder was changed to a cyclic polyolefin resin (melt flow rate: 2.0 (230) manufactured by TOPAS (TM) 6013S-04 Topas Advanced Polymers Co., Ltd. Other than °C)), a light-diffusing film was obtained in the same manner as in Example 2.

The characteristics of the obtained light-diffusing film are shown in Table 1.

The light-diffusing film obtained in this comparative example was excellent in light-diffusion characteristics, but the adhesion was deteriorated.

(Example 3)

In the method of the first embodiment, the resin of the light-diffusing layer formed by the first extruder was changed to a melt flow rate of 0.41 by a cyclic polyolefin-based resin (TOPAS (TM) 6015 Topas Advanced Polyrners Co., Ltd. ( 230 parts by weight), 50 parts by mass, and 50 parts by mass of a block copolymer resin (INFUSE (TM) D9817.15 melt flow rate: 26 (230 ° C)) manufactured by Dow Chemical Co., Ltd.) A light diffusion film was obtained in the same manner as in Example 1.

The characteristics of the obtained light-diffusing film are shown in Table 1.

The light-diffusing film obtained in the present Example is excellent in light-diffusing properties and excellent in adhesion.

(Comparative Example 3)

50 parts by mass of a cyclic polyolefin resin (melt flow rate: 0.41 (230 ° C) manufactured by TOPAS (TM) 6015 Topas Advanced Polymers Co., Ltd.) at a resin temperature of 250 ° C using a PCM45 extruder manufactured by Chiba Iron Works Co., Ltd. And 50 parts by mass of a block copolymer resin (INFUSE (TM) D9817.15 melt flow rate: 26 (230 ° C)) made of ethylene and octene, melt-mixed, and extruded in a T-die. The satin-finished cooling roll (Ra = 0.55) was cooled, whereby a light-diffusing film having a thickness of 400 μm was obtained. On the opposite side of the above-mentioned cooling roll, a press roll which was subjected to a release treatment (Ra = 1.0) on the surface was used.

The characteristics of the obtained light-diffusing film are shown in Table 1.

The light-diffusing film obtained in this comparative example was excellent in light-diffusion characteristics, but the adhesion was deteriorated.

(Example 4)

A light-diffusing film was obtained in the same manner as in Example 3 except that the total thickness of the light-diffusing film was changed to 200 μm and the layer thickness was changed to 20/160/20 (μm) in the method of Example 3.

The characteristics of the obtained light-diffusing film are shown in Table 1.

The light-diffusing film obtained in the present Example is excellent in light-diffusing properties and excellent in adhesion.

(Comparative Example 4)

A light-diffusing film was obtained in the same manner as in Comparative Example 3 except that the total thickness of the light-diffusing film was changed to 200 μm and the layer thickness was changed to 20/160/20 (μm) in the method of Comparative Example 3.

The characteristics of the obtained light-diffusing film are shown in Table 1.

The light-diffusing film obtained in this comparative example was excellent in light-diffusion characteristics, but the adhesion was deteriorated.

(Example 5)

In the method of the first embodiment, the resin of the light-diffusing layer was blended, and changed to 65 parts by mass of a polypropylene resin (manufactured by Sumitomo Chemical Co., Ltd., Sumitomo Nobrene FS2011 DG3), and a block copolymer resin composed of ethylene and octene. An unstretched sheet was obtained in the same manner as in Example 1 except that INFUSE (TM) D9817.15 melt rate: 26 (230 ° C) of 35 parts by mass. Next, the unstretched sheet was stretched 4.5 times at an extension temperature of 118 ° C by the difference in the peripheral speed of the longitudinal stretcher, and then subjected to corona treatment on one side thereof to obtain a light-diffusing film having a thickness of 200 μm.

The characteristics of the obtained light-diffusing film are shown in Table 1.

The light-diffusing film obtained in the present Example is excellent in light-diffusing properties and excellent in adhesion.

(Comparative Example 5)

In addition to the method of the fifth embodiment, the resin of the adhesive layer formed by the second extruder was used from a polypropylene-based adhesive resin (melt flow rate: 5.7 (190 ° C) manufactured by Mitsui Chemicals Co., Ltd.). A light-diffusing film was obtained in the same manner as in Example 5 except that it was changed to a polypropylene resin (manufactured by Sumitomo Chemical Co., Ltd., Sumitomo Nobrene FS2011 DG3).

The characteristics of the obtained light-diffusing film are shown in Table 1.

The light-diffusing film obtained in this comparative example was excellent in light-diffusion characteristics, but the adhesion was deteriorated.

(Examples 6 to 10 and Comparative Examples 6 to 10)

In the acrylic plate of the light-emitting side of the backlight unit of the backlight unit of the 19-inch light guide plate type (grid pattern using white reflective film) on the long-diameter side (lateral direction) of each of the three cold cathode tubes In the central part, an evaluation sample of 40 mm × 60 mm square (the horizontal direction of 60 mm side) was set, and in the surface of the polyoxyethylene rubber sheet on the surface thereof, a flat surface having a surface temperature of about 180 ° C was formed from the surface of the polyoxyethylene rubber sheet. The heating jig was pressed and pressed for about 1 minute, and a black shading paper having a shearing portion of 30 mm × 50 mm square (the lateral direction of the 50 mm side) was set so that the center of the shearing portion became the center portion of the evaluation sample. The brightness was measured in a dark room. The black shading paper is fixed by covering the entire size of the backlight unit, and is measured in such a manner that light is not leaked out.

Further, the backlight unit is horizontally disposed and measured.

For the brightness, the Topcon Spectroradiometer SR-3A manufactured by Topcon Techno House Co., Ltd. was used to measure the angle of 2 degrees, and the distance from the surface of the backlight unit was 40 cm, and the center of the sample for evaluation was measured directly below.

The measurement system is installed such that the main diffusion direction of the evaluation sample and the longitudinal direction of the cold cathode tube are orthogonal to each other.

The light-diffusing films of Examples 1 to 5 and Comparative Examples 1 to 5 were used as evaluation samples, and the results obtained were each as Examples 6 to 10 and Comparative Examples 6 to 10, and as shown in Table 2.

The light-diffusing film of Examples 1 to 5 is followed by an adhesive layer on the surface of the acrylic plate, and the air between the acrylic plate and the light-diffusing film is excluded. In order to make the refractive index difference of the interface only slightly, the front brightness is increased. . Further, since the optical characteristics of the degree of recursion or the degree of diffusion are in an appropriate range, the disappearance of the emitted light pattern is also excellent.

On the one hand, in the light-diffusing film of Comparative Examples 1 to 5, since the adhesion between the acrylic plate and the light-diffusing film is weak, the air between the two materials cannot be excluded, so the refractive index at the interface between the two members is extremely poor, compared to the implementation. In the light-diffusing films of Examples 1 to 5, the front luminance was significantly deteriorated.

Further, the light guide plate was placed in an oven at 80 ° C, and the mixture was allowed to stand for 240 hours.

In the evaluation of dimensional stability, it is excellent in the case of maintaining the size and shape as in the case of heating, and it is excellent. Further, by the warming treatment, it is seen that the curled or reduced size material is deteriorated and becomes defective. The results are shown in Table 2.

The light-diffusing films obtained in Examples 1 to 5 were not deformed and kept the same size and shape as before heating, but the light-diffusing films obtained in Comparative Examples 1 to 5 were curled by the heat treatment. And the size is reduced.

(Reference example 1)

100 parts by mass of a polypropylene resin WF836DG3 (manufactured by Sumitomo Chemical Co., Ltd., Sumitomo Nobrene) was melted using a first extruder, and a base layer A was formed, and a polypropylene resin WF836DG3 was used by a second extruder. 17 parts by mass of propylene/ethylene copolymer HF3101C (manufactured by Polypro Co., Ltd., Japan) was melt-mixed to form a light-diffusion layer B, and melt-coextrusion was carried out in a mold by a T-die method (manufactured by Sumitomo Chemical Co., Ltd., Sumitomo Nobrene). After pressing, the base layer A and the light diffusion layer B were laminated, and then cooled by a casting roll at 20 ° C to obtain an unstretched sheet. Next, using the difference in the peripheral speed of the roller of the longitudinal stretcher, the unstretched sheet was stretched 4.8 times at an extension temperature of 120 ° C, followed by a tenter stretching machine, and after heating at 165 ° C, at an extension temperature of 155 ° C in the transverse direction. Perform a 9-fold extension. Subsequently, heat fixation was carried out at 166 ° C to obtain a light-diffusing film each having a thickness of the base layer A/light diffusion layer B of 22.2 / 2.8 (μm). The corona treatment was performed on the surface of the base layer A just before winding.

The characteristics of the obtained light-diffusing film are shown in Table 1. Further, using the obtained light-diffusing film, the front luminance, the dimensional stability, and the disappearance of the emitted light pattern were measured in the same manner as in Examples 6 to 10 and Comparative Examples 6 to 10. The results are shown in Table 2.

In the light-diffusing film of the present reference example, since there is no adhesive layer, dimensional stability is deteriorated. Moreover, since the degree of recursion or the degree of diffusion is low, high brightness cannot be obtained. Moreover, the disappearance of the emitted light pattern also deteriorates.

(Reference example 2)

Approximately 19 cold cathode tubes are mounted on the long-diameter side (lateral direction) on both sides of the 19-inch light guide plate type (the grid pattern using a white reflective film) on the light-emitting side of the backlight unit. In the center, a light-diffusing film obtained by referring to Example 1 of 40 mm × 60 mm square (the horizontal direction of 60 mm side) was adhered to an acrylic optical adhesive tape (two-sided separation film type), and a 30 mm × 50 mm square (50 mm side was provided). The black shading paper of the cut portion in the lateral direction was set, and the shading paper was set so that the center of the cut portion became the center portion of the evaluation sample, and the brightness was measured in the dark room. The black light-shielding paper is fixed to cover the entire size of the backlight unit and is fixed so as not to leak light.

Further, the backlight unit is horizontally disposed and measured.

For the brightness, the Topcon Spectroradiometer SR-3A manufactured by Topcon Techno House Co., Ltd. was used to measure the angle of 2 degrees, the distance from the surface of the backlight unit was 40 cm, and the center of the sample for evaluation was directly below.

The measurement is performed such that the main diffusion direction of the sample for evaluation is orthogonal to the longitudinal direction of the cold cathode tube.

Further, the bonding is performed such that the side of the layer A of the light-diffusing film becomes the adhesive tape side.

Further, in the same manner as in Examples 6 to 10 and Comparative Examples 6 to 10, the dimensional stability and the disappearance of the emitted light pattern were measured. The results are shown in Table 2.

The light-diffusing film of the present reference example has a lower degree of recursion or a lower degree of diffusion than the light-diffusing film obtained in Examples 1 to 5, and thus is different from the light-diffusing film obtained in Examples 1 to 5, and shows a result of lamination. The brightness enhancement effect is small. Moreover, the disappearance of the emitted light pattern also deteriorates.

[Industrial availability]

The optical dispersion film of the present invention is excellent in both light transmittance and diffusibility, and has good light resistance, and can be easily adhered to other members by thermal compression bonding, and further excellent in economic efficiency. It can be suitably used for optical devices or devices such as various lighting fixtures, display devices, and screens. Further, by using the light-diffusing film of the present invention in a backlight device, it is possible to achieve high luminance of the backlight device and to improve the economic efficiency of the backlight device.

Fig. 1 is a transmission luminosity curve with respect to a light receiving angle measured by an incident angle of 0 degree of an automatic variable angle photometer.

Figure 2 is an auxiliary diagram of the calculation method of the degree of recursion.

Claims (9)

A light-diffusing film which is provided on at least one side of a light-diffusing layer containing two kinds of mutually non-miscible polyolefin-based resins as a main component, and a laminate having a polyolefin resin containing a polar group as a main component As the outermost surface, the light diffusing film has a total light transmittance of 66% to 100%, and the film has a haze of 20% to 100%. The light-diffusing film of claim 1, wherein the diffusivity of the transmitted light in the direction of incidence of 0 degrees is from 140 degrees to 180 degrees. The light-diffusing film of claim 1, wherein the light in the main diffusion direction has a degree of refraction of 1% to 100%. The light-diffusing film according to any one of claims 1 to 3, wherein the two mutually non-miscible polyolefin-based resins are made of a polyolefin resin containing a polypropylene-based resin and ethylene and/or butene. Composition. The light-diffusing film according to any one of claims 1 to 3, wherein the two polyolefin resins which are mutually non-miscible are composed of a cyclic polyolefin resin and a polyethylene resin. The light-diffusing film according to any one of claims 1 to 3, wherein the polyolefin resin containing a polar group contains a carboxyl group. A backlight device characterized in that a surface of a substrate of a light-emitting surface of a basic unit of a backlight is bonded to a subsequent layer of a light-diffusing film according to any one of claims 1 to 6. Such as the backlight device of claim 7 of the patent scope, wherein the basic one of the backlight The light guide plate of the edge light-emitting mode of the elementary system. The backlight device of claim 7 or 8, wherein the difference in refractive index between the substrate and the adhesive layer is from -0.2 to +0.5.