JP2021149060A - Reflector - Google Patents

Abstract

To provide a reflector which has good reflection characteristics, and can suppress occurrence of luminance unevenness when being used in a backlight unit and desorption of particles contained in a surface layer of the reflector.SOLUTION: A reflector has such a configuration that a resin layer (B) containing a polyolefin resin and a fine powdery filler, a resin layer (A) containing a polyolefin resin and organic particles, and a resin layer (C) containing a polyolefin resin and no organic particles having a particle diameter of 5 μm or more are layered in this order. A diameter of projections in plan view on the surface of the resin layer (C) is 5 μm to 20 μm, a content of the organic particles in the resin layer (A) is 3 mass% or more and 6 mass% or less, and any one or more layers of the resin layers (A) to (C) have voids.SELECTED DRAWING: None

Description

The present invention relates to a reflective material. More specifically, the present invention relates to a reflective material that can be suitably used as a constituent member of a liquid crystal display, a lighting fixture, a lighting sign, or the like of a portable information processing terminal such as a smartphone or a tablet terminal.

Reflective materials are used in many fields such as liquid crystal displays, lighting fixtures, and lighting signs. Recently, in the field of liquid crystal displays, the size has increased and the display performance has become more sophisticated, and it has become necessary to supply as much light as possible to the liquid crystal to improve the performance of the backlight unit. However, even better light reflectivity (also simply referred to as "reflectivity") is required.
As a reflective material of this type, for example, a reflective film for a liquid crystal display using a white polyester film whose main raw material is an aromatic polyester resin is known (see Patent Document 1).
However, when an aromatic polyester resin is used as the material of the reflective material, the aromatic ring contained in the molecular chain absorbs ultraviolet rays, so that the film is deteriorated and yellowed by the ultraviolet rays emitted from a light source such as a liquid crystal display device. As a result, there is a problem that the light reflectivity of the reflective film is lowered.

Further, a reflective material (see Patent Document 2) in which fine voids are formed in the film by stretching a film formed by adding a filler to a polypropylene resin to cause light scattering reflection, or a polyolefin resin. A polyolefin resin light reflector having a laminated structure composed of a base material layer containing the filler and a layer containing a polyolefin resin is also known (see Patent Document 3).
A reflective film using such a polyolefin resin has a feature that there is little problem of film deterioration and yellowing due to ultraviolet rays.
Further, there is known a biaxially stretched reflective sheet having a reduced heat shrinkage rate, which contains a polypropylene resin and at least one of a resin incompatible with the polypropylene resin (see Patent Document 4). This reflective sheet has a feature that it exhibits a higher reflectance than a conventional reflective sheet having the same basis weight and density even if it does not contain a large amount of inorganic powder.

In recent years, the liquid crystal display is required to be further thinned, and the backlight provided in the liquid crystal display is also required to be thinned.
When the backlight is made thinner, it is necessary to make the members such as the back housing and the light guide plate thinner as well as the above-mentioned reflective sheet. However, if these members are made thinner, the mechanical strength of the backlight is reduced. Therefore, for example, when an external force is applied to the display body, the light guide plate and the reflective material come into strong local contact with each other, resulting in uneven brightness or uneven color (color unevenness or color unevenness). Hereinafter, it causes "brightness unevenness"). Therefore, the backlight used in the thinned liquid crystal display is required to have a reflective material further provided with a function of preventing uneven brightness.
As a means for solving such a problem of uneven brightness, a reflector in which particles are contained in the surface layer of the reflector (see Patent Documents 5 and 6) has been proposed.

Japanese Unexamined Patent Publication No. 04-239540 Japanese Unexamined Patent Publication No. 11-174213 Japanese Unexamined Patent Publication No. 2005-031653 Japanese Unexamined Patent Publication No. 2008-158134 Japanese Unexamined Patent Publication No. 2015-163896 JP 2015-001596

According to the study by the present inventors, the reflective material as disclosed in Patent Documents 5 and 6 has an effect of solving the problem of uneven brightness, but the light guide plate is scraped and scratched. It was confirmed that the components such as the backlight unit and the backlight unit may be contaminated.
Further, it was confirmed that such a phenomenon is likely to occur in a reflective material using a polyolefin resin.

Therefore, an object of the present invention is to have a reflective material using a polyolefin resin, which has good reflective characteristics, and suppresses the occurrence of uneven brightness and contamination of the constituent members when used as a constituent member of a thin backlight. The purpose is to provide a reflective material that can be used.

The present invention contains a resin layer (B) containing a polyolefin resin and a fine powder filler, a resin layer (A) containing a polyolefin resin and organic particles, and a polyolefin resin having a particle size of 5 μm or more. The resin layer (C) containing no organic particles is laminated in this order, and the planoscopic diameter of the protrusions on the surface of the resin layer (C) is 5 μm to 20 μm, and the resin layer (A) We propose a reflective material in which the content of organic particles in the resin is 3% by mass or more and 6% by mass or less, and any one or more of the resin layers (A) to (C) has voids.

According to the reflective material proposed by the present invention, it has good reflection characteristics, and when it is used for a constituent member such as a backlight unit, it is possible to suppress the occurrence of uneven brightness and contamination of the constituent member. The reflective material proposed by the present invention is compatible with a thin backlight that can be mounted on a small portable information processing terminal. Therefore, the reflective material proposed by the present invention can be suitably used as a reflective material for a liquid crystal display of a small portable information processing terminal.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the embodiments described below, and can be arbitrarily modified and implemented without departing from the gist of the present invention.

<< This reflector >>
The reflective material (referred to as “the present reflective material”) according to an example of the embodiment of the present invention includes a resin layer (B) containing a polyolefin resin and a fine powder filler, and a resin layer containing a polyolefin resin and organic particles (referred to as “the present reflective material”). A) and a resin layer (C) containing a polyolefin resin and not containing organic particles having a particle size of 5 μm or more are laminated in this order.
Further, in the present reflective material, any one or more of the resin layers (A) to (C) has voids, and the planar viewing diameter of the protrusions on the surface of the resin layer (C) is 5 μm to 20 μm. Yes, the content of organic particles in the resin layer (A) is 3% by mass or more and 6% by mass or less.

Here, the technical concept when designing this reflective material will be described. However, the present invention is not limited to the scope of the following technical ideas.
As described above, as a measure for preventing uneven brightness, a measure has been conventionally taken in which a reflective material is formed in a laminated structure and particles (particularly organic particles having a large particle size) are contained in the surface layer thereof. This is because the surface layer of the reflective material contains particles to form protrusions on the surface. Since the protrusions are present on the surface of the reflective material, it is possible to prevent the light guide plate and the reflective material from coming into strong local contact with each other, and it is possible to suppress uneven brightness. For this reason, when particles are contained in order to form protrusions on the surface of the reflective material, it has been adopted to include the particles in the outermost layer of the laminated structure.

On the other hand, according to the study by the present inventors, such a reflective material has an effect of solving the problem of uneven brightness, but the selection of the material constituting the reflective material, the layer structure of the reflective material, and the manufacturing conditions It has been confirmed that these reflective materials may damage the light guide plate or contaminate the constituent members such as the backlight unit depending on the above. If the light guide plate is scratched or the components are contaminated, it is presumed that the liquid crystal display incorporating such components causes defects in the liquid crystal screen.
It was also found that such a phenomenon is likely to occur in a reflective material using a polyolefin resin.
As a result of this study, it was confirmed that one of the main causes is that the particles contained in the reflective material are detached from the surface layer. Furthermore, it is considered that the desorption of these particles can occur not only during the manufacture of the reflector, but also during storage of the manufactured reflector, the backlight unit assembly process, and vibration due to product handling after assembly. Be done.
When the desorbed particles are incorporated into the backlight unit in a state of being attached to the surface of the reflector, or when the particles are desorbed from the reflector in the backlight unit, the particles aggregate and become larger in particle size, and become the reflector. It exists in a state of being sandwiched between the light guide plate and the light guide plate. If deformation stress is applied to the backlight unit in this state, stress concentration occurs in the aggregated particle portion, and the light guide plate and the reflector itself are scraped and scratched, and as a result, it is presumed that the liquid crystal screen is defective.
In this respect as well, it can be understood that problems are likely to occur in the flexible (low elastic modulus) polyolefin resin-based reflector as compared with the relatively rigid (high elastic modulus) polyester resin-based reflector.
Therefore, the present inventors do not use the organic particle-containing layer for forming the protrusions as the outermost layer, even if the reflective material uses a polyolefin resin, and the outer layer is on the surface layer side of the organic particle-containing layer. We found that it is possible to suppress the detachment of particles existing on the surface of the reflector while exerting the effect of suppressing the uneven brightness by providing the layer corresponding to the above, and based on this finding, we designed this reflector. It is a thing.

Further, in this reflective material, the functions of the resin layer (A), the resin layer (B), and the resin layer (C) can be separated from each other. Effect can be obtained. However, it is not limited to these effects.
(I) The resin layer (B) can be made to have light reflectivity, while the resin layer (A) and the resin layer (C) can be made to have heat resistance. Or,
(Ii) While the resin layer (B) is provided with light reflectivity, the resin layer (A) and the resin layer (C) can be provided with rigidity as a reflective material. Or,
(Iii) Light can be surface-reflected by the resin layer (C), while light transmitted through the resin layer (C) can be reflected in the resin layer (A) or the resin layer (B). ..
Since the functions of the resin layer (A), the resin layer (B), and the resin layer (C) can be separated in this way, it is possible to obtain even higher reflection performance and further excellent heat resistance and folding resistance. be able to.

<Resin layer (A)>
The resin layer (A) is a layer containing a polyolefin resin and organic particles.
Further, in the resin layer (A), the polyolefin resin is preferably a main component resin.
By using the polyolefin resin as the main component resin in the resin layer (A), it has an affinity with the resin layer (B) or the resin layer (C), and the interlayer adhesiveness can be improved. Further, since the resin layer (A) contains organic particles, it is possible to form appropriate protrusions on the surface of the present reflector, usually the surface on the resin layer (C) side, so that uneven brightness can be suppressed. can.

In the present invention, the "main component resin" means the resin having the largest mass ratio among the resins constituting each layer, and contains other resins within a range that does not interfere with the function of the main component resin. Tolerate. At this time, the content ratio of the main component resin occupies 50% by mass or more, preferably 70% by mass or more, and particularly preferably 90% by mass or more (including 100% by mass) of the resin constituting each layer.

(Polyolefin resin)
The type of the polyolefin resin as the main component resin of the resin layer (A) is not limited. For example, polypropylene-based resins such as polypropylene, propylene / ethylene copolymer, propylene / α-olefin copolymer; polyethylene-based resins such as high-density polyethylene, low-density polyethylene, ethylene / α-olefin copolymer; polymethylpentene and the like. Cycloolefin resin such as α-olefin resin and ethylene-cyclic olefin copolymer; at least one selected from olefin elastomers such as ethylene-propylene rubber (EPR) and ethylene-propylene-dienter polymer (EPDM). Polyolefin resin can be mentioned.
Among these, polypropylene resin, cycloolefin resin, or a combination of both is preferable from the viewpoint of mechanical properties and flexibility. Among them, it is particularly preferable to use a cycloolefin resin as a main component resin. Since the cycloolefin resin absorbs less visible light and has heat resistance, it is suitable as the main component resin of the resin layer (A).

The content of the polyolefin resin in the resin layer (A) is not limited, and is usually 50% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, and further preferably 90% by mass or more. When the content of the polyolefin resin is at least the above lower limit value, it is possible to impart good flexibility to the present reflector, which is preferable.
Further, the upper limit of the content of the polyolefin resin in the resin layer (A) is not limited, and all except the organic particles may be the polyolefin resin. It is preferably 99% by mass or less, more preferably 98% by mass or less, and further preferably 97% by mass or less. When the content of the polyolefin resin is not more than the above upper limit value, the fracture resistance, bending resistance, and brightness unevenness prevention function of this reflective material are good, which is preferable.
Here, the content of the polyolefin resin means the total amount of all the polyolefin resins in the resin layer (A).

(Cycloolefin resin)
Next, a cycloolefin resin, which is particularly preferable among the above-mentioned polyolefin resins, will be described as the main component resin of the resin layer (A).

The cycloolefin resin is a polymer compound having a carbon-carbon bond in the main chain and having a cyclic hydrocarbon structure in at least a part of the main chain. This cyclic hydrocarbon structure is introduced by using a compound (cycloolefin) having at least one olefinic double bond in the cyclic hydrocarbon structure as a monomer, such as norbornene and tetracyclododecene. Will be done.

Cycloolefin resins are classified into cycloolefin addition polymers or hydrogen additions thereof, cycloolefin and α-olefin addition polymers or hydrogen additions thereof, cycloolefin ring-opening polymers or hydrogen additions thereof, and any of these. Can also be used as a cycloolefin resin. Further, the cycloolefin resin may be either a cycloolefin homopolymer or a cycloolefin copolymer.

Specific examples of the cycloolefin resin include monocyclic cycloolefins such as cyclopentene, cyclohexene, cyclooctene, cyclopentadiene, and 1,3-cyclohexadiene;
Bicyclo [2.2.1] hepta-2-ene (trivial name: norbornene), 5-methyl-bicyclo [2.2.1] hepta-2-ene, 5,5-dimethyl-bicyclo [2.2. 1] Hept-2-ene, 5-ethyl-bicyclo [2.2.1] hepta-2-ene, 5-butyl-bicyclo [2.2.1] hepta-2-ene, 5-ethylidene-bicyclo [ 2.2.1] Hept-2-ene, 5-hexyl-bicyclo [2.2.1] hepta-2-ene, 5-octyl-bicyclo [2.2.1] hepta-2-ene, 5- Octadecyl-bicyclo [2.2.1] hepta-2-ene, 5-methylidene-bicyclo [2.2.1] hepta-2-ene, 5-vinyl-bicyclo [2.2.1] hepta-2- Bicyclic cycloolefins such as ene, 5-propenyl-bicyclo [2.2.1] hepta-2-ene;

Tricyclic cycloolefins such as tricyclo [4.3.0.12.5] deca-3,7-diene (trivial name: dicyclopentadiene);
Tetracyclo [4.4.0.12,5.17,10] Dodeca-3-ene (also simply referred to as tetracyclododecene) and other tetracyclic cycloolefins;
8-Cyclopentyl-tetracyclo [4.4.0.12,5.17,10] dodeca-3-ene, tetracyclo [8.4.14,7.01, 10.03,8] pentadeca-5,10, 12,14-Tetraene (also referred to as 1,4-methano-1,4,4a, 5,10,10a-hexahydroanthracene); polycyclic cycloolefins such as cyclopentadiene tetramers can be mentioned. can.
These cycloolefin resins can be used alone or in combination of two or more as a copolymer.

Specific examples of α-olefins that can be copolymerized with cycloolefins include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-pentene, 3-methyl-1-pentene, and 3 -Ethyl-1-pentene, 4-methyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1- The number of carbon atoms of hexene, 3-ethyl-1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, etc. Examples thereof include 2 to 8 ethylenes or α-olefins. These α-olefins can be used alone or in combination of two or more.

The cycloolefin resin is a resin containing a cycloolefin component as a main component, preferably 50% by mass or more, more preferably 60% by mass or more.
At this time, the above-mentioned "main component" means the component having the largest mass ratio among the components constituting the cycloolefin resin, and it is allowed to contain other components within a range that does not interfere with the function of the main component. .. At this time, the content ratio of the main component occupies 50% by mass or more, preferably 70% by mass or more (including 100% by mass) of the components constituting the cycloolefin resin. The same applies to the main components of other resins.

When the cycloolefin resin is a copolymer of a cycloolefin such as norbornene and an α-olefin, the effect of improving the processing performance such as stretching by using the α-olefin as a copolymerization component and the copolymerization of the cycloolefin From the viewpoint of obtaining a well-balanced effect of heat resistance by using the component as the main component, the content ratio of the cycloolefin component in the cycloolefin resin is preferably 60 to 90% by mass, particularly 65% by mass or more or 80. It is more preferably mass% or less.
There are no particular restrictions on the method of polymerizing cycloolefin or cycloolefin and α-olefin and the method of hydrogenating the obtained polymer, and the method can be carried out according to a known method.

The melt flow rate (MFR) of the cycloolefin resin is not limited. For example, in accordance with JIS K7210, the value measured at 230 ° C. and a load of 21.18 N is preferably 0.1 to 20 g / 10 minutes, particularly 0.5 g / 10 minutes or more or 10 g / 10 minutes or less. Is more preferable.

The cycloolefin resin may be crystalline or amorphous. Above all, it is preferably amorphous.
The glass transition temperature (Tg) of the cycloolefin resin is not limited. From the viewpoint of heat resistance, it is preferably 70 ° C. or higher, more preferably 80 ° C. or higher, further preferably 85 ° C. or higher, preferably 170 ° C. or lower, more preferably 160 ° C. or lower, still more preferably 150 ° C. or lower. ..
When the glass transition temperature of the cycloolefin resin is in the above range, the stretchability tends to be good.
Here, the "glass transition point (Tg)" is heated from −50 ° C. to 250 ° C. at a rate of 10 ° C./min by a differential scanning calorimeter, and then maintained at an isothermal temperature for 1 minute at a rate of 10 ° C./min. The value is taken as the value read when the temperature is cooled to −50 ° C., maintained at an isothermal temperature for 1 minute, and then raised to 250 ° C. again at a rate of 10 ° C./min.
In addition, two or more kinds of cycloolefin resins may be combined and mixed, and the glass transition point (Tg) of the mixed resin may be adjusted within the above range.

As the cycloolefin resin, one type may be used alone, or two or more types having different compositions, physical properties, etc. may be mixed and used. For example, two or more types of cycloolefin resins may be combined and mixed to adjust the MFR and Tg of the mixed resin within the above range.

The content of the cycloolefin resin in the resin layer (A) is not limited. It is preferably 30% by mass or more, more preferably 35% by mass or more, and further preferably 40% by mass or more. When the content of the cycloolefin resin is at least the above lower limit value, it is possible to impart good heat resistance to the present reflector, which is preferable.
Further, the upper limit of the content of the cycloolefin resin in the resin layer (A) is not limited. It is preferably 85% by mass or less, more preferably 80% by mass or less, and further preferably 75% by mass or less.
When the content of the cycloolefin resin is not more than the above upper limit value, the fracture resistance, bending resistance, and brightness unevenness prevention function of the present reflective material are good, which is preferable.

As the cycloolefin resin, a commercially available product can be used. For example, "Zeonoa (registered trademark)" manufactured by Nippon Zeon Co., Ltd. (hydrogenated additive of ring-opening polymer of cyclic olefin) and "Apel (registered trademark)" manufactured by Mitsui Chemicals Co., Ltd. (additional copolymer of ethylene and tetracyclododecene). ), "TOPAS (registered trademark)" manufactured by Polyplastics Co., Ltd. (additional copolymer of ethylene and norbornene) and the like. Among them, "Zeonoa" and "TOPAS" are preferable because they have little light absorption action and can obtain a reflective material having high reflection performance.

(Other polyolefin resins)
When a cycloolefin resin is used as the polyolefin resin which is the main component resin of the resin layer (A), a polyolefin resin other than the cycloolefin resin (hereinafter referred to as “other polyolefin resin”) is blended to form the resin layer (A). By forming, it may be possible to further improve folding resistance and heat resistance.
Further, the cycloolefin resin may not be used as the main component resin of the resin layer (A), and only "other polyolefin resins" may be used as the main component resin.

The melt flow rate (MFR) of "other polyolefin resins" is not limited. Above all, according to JIS K7210, the value measured at 230 ° C. and a load of 21.18 N is preferably 0.1 to 20 g / 10 minutes, and above all, 0.5 g / 10 minutes or more or 10 g / 10 minutes or less. Is more preferable.
When the cycloolefin resin and "other polyolefin resin" are used in combination, it is preferable to adjust the MFR of the cycloolefin resin to the above range. Adjusting the MFRs of both in this way tends to improve the mechanical properties of the reflective material.

As the "other polyolefin resin", one or more of the polyolefin resins exemplified as the main component resin of the resin layer (A) can be used in combination. Among them, polyethylene-based resin and polypropylene-based resin are preferable, and among them, polypropylene-based resin is preferable from the viewpoint of high melting point, excellent heat resistance, and high mechanical properties such as elastic modulus. However, it is not limited to these.

When the "other polyolefin resin" is a polypropylene resin, the melt flow rate (MFR) is 0.1 as a value measured at 230 ° C. and a load of 21.18 N in accordance with JIS K7210 from the viewpoint of extrusion moldability. It is preferably ~ 20 g / 10 minutes, and more preferably 0.2 g / 10 minutes or more or 10 g / 10 minutes or less, and more preferably 0.5 g / 10 minutes or more or 5 g / 10 minutes or less.

When a cycloolefin resin and "other polyolefin resin" are used in combination as the resin component constituting the resin layer (A), the cycloolefin resin MFR ("MFR (CO)") and "other polyolefin resin" The relationship with the MFR (“MFR (PO)”) is preferably MFR (CO): MFR (PO) = 1: 0.05 to 1:20, preferably 1: 0.1 to 1:10. More preferably.
When the relationship between the two MFRs is within the above range, other polyolefin resins tend to be oriented in the cycloolefin resin, and the mechanical properties as a reflective material tend to be improved, which is preferable.

The content of the "other polyolefin resin" in the resin layer (A) is not limited. When used in combination with a cycloolefin resin, it is preferably 2% by mass or more (with respect to 100% by mass of the resin layer (A)), more preferably 5% by mass or more, and further preferably 10% by mass or more. Moreover, the upper limit is not limited. It is preferably 40% by mass or less, more preferably 30% by mass or less, and further preferably 25% by mass or less.
When the content of the "other polyolefin resin" is at least the above lower limit value, it is possible to more effectively suppress the breakage of the resin layer (A) during stretching, and the resin layer (A) and the resin layer (B), Alternatively, it is preferable because the interlayer adhesiveness between the resin layer (A) and the resin layer (C) is kept even higher. On the other hand, when the content of the "other polyolefin resin" is not more than the above upper limit value, the heat resistance and the function of preventing uneven brightness tend to be further improved.

Further, if the polyolefin resin which is the main component resin of the resin layer (A) and the polyolefin resin which is the main component resin of the resin layer (C) are the same, the adhesiveness between the resin layer (A) and the resin layer (C) is high. Therefore, it is preferable. However, it is not limited to being the same.
Further, if the polyolefin resin which is the main component resin of the resin layer (A) and the polyolefin resin contained in the resin layer (B), preferably contained as the main component resin, are the same, the resin layer (A) and the resin layer ( B) is preferable because it increases the adhesiveness. However, it is not limited to being the same.

(Organic particles)
The resin layer (A) of this reflective material contains organic particles.
Here, the "organic particles" are applicable as long as they are particulate matter containing an organic substance as a main component. At this time, the "main component" means the component having the largest mass ratio among the components constituting the organic particles, and it is allowed to contain other components within a range that does not interfere with the function of the main component. At this time, the content ratio of the main component occupies 50% by mass or more, preferably 70% by mass or more (including 100% by mass) of the components constituting the organic particles.
The organic particles are preferably resin particles, and examples thereof include so-called polymer beads and polymer hollow particles.
The types of organic particles as resin particles are not limited, and for example, (meth) acrylate-based resin particles, styrene-based resin particles, silicone-based resin particles, nylon-based resin particles, polyethylene-based resin particles, benzoguanamine-based resin particles, etc. Examples thereof include urethane-based resin particles.
These organic particles may be homopolymers or copolymers. These can be used by any one kind or a mixture of two or more kinds.

Among these organic particles, (meth) acrylate-based resin particles are preferable, among them, methyl methacrylate-based resin particles or butyl methacrylate-based resin particles are preferable, and methyl methacrylate-based resin particles are particularly preferable. In these cases, it may be a copolymer containing methyl methacrylate or butyl methacrylate as a main component.
Here, "(meth) acrylate" means acrylate or methacrylate.

The shape of the organic particles contained in the resin layer (A) is not limited, and may be, for example, spherical, rod-shaped, flat plate-shaped, crushed matter or agglomerate having no specific shape, or amorphous one. good. Among these, the shape of the organic particles is preferably spherical.
Here, "spherical" does not necessarily mean only a true sphere, but corresponds to a visually substantially spherical shape. Specifically, for example, a particle having a cross-sectional shape of a circle, a substantially circular shape, an ellipse, a substantially elliptical shape, or a shape surrounded by an arc having a curvature is applicable.

When the resin layer (A) contains organic particles, the surface of the adjacent resin layer (C), and by extension, the surface of the resin layer (C) even when "another layer" is laminated on the surface of the resin layer (C). That is, an appropriate protrusion can be formed on the surface of the present reflective material on the resin layer (C) side. At this time, when the organic particles contained in the resin layer (A) are spherical, the height, size, shape, etc. of the protrusions are relatively uniform as compared with the case where the organic particles are amorphous particles. can do. By aligning the height, size, shape, etc. of the protrusions formed on the surface of the resin layer (C) and the surface of the reflective material on the resin layer (C) side in this way, uneven brightness can be suppressed and particles can be suppressed. It is possible to further suppress the detachment of the resin.

Further, the organic particles are preferably crosslinked particles (referred to as “crosslinked particles”). Since the organic particles are crosslinked, it becomes easy to maintain the shape of the particles even in a state where deformation stress is applied in a heated state at the time of extrusion film formation.
Whether or not the organic particles are crosslinked particles can be confirmed, for example, by swelling without dissolving when immersed in a solvent (good solvent) that would dissolve if not crosslinked. At that time, it may be heated as appropriate. In addition, it can be confirmed by a nuclear magnetic resonance spectrum (NMR), an infrared absorption spectrum (IR), or the like.
The solvent (good solvent) that dissolves if not crosslinked differs depending on the resin type constituting the organic particles, but in the case of (meth) acrylate-based resin particles, for example, acetone, toluene, ethyl acetate, etc. Methyl ethyl ketone and the like can be mentioned.
In order to use the organic particles as crosslinked particles, for example, a compound having a polyfunctional polymerizable group such as divinylbenzene, polyacrylate, pentaerythritol, and trimellitic acid may be used as a polymerization raw material.

The glass transition point (also simply referred to as “Tg”) of the organic particles contained in the resin layer (A) is preferably 120 ° C. or higher. By incorporating the organic particles having a Tg of 120 ° C. or higher in the resin layer (A), it is possible to impart appropriate hardness to the surface of the present reflector, and it is possible to suppress uneven brightness. The lower limit of Tg of the organic particles is preferably 125 ° C. or higher, more preferably 130 ° C. or higher for the same reason as described above.
Further, the upper limit of Tg of organic particles is not limited, and is preferably 260 ° C. or lower. When the Tg is 260 ° C. or lower, the hardness of the surface of the reflective material tends to be suppressed from becoming excessively high. The upper limit of Tg of organic particles is preferably 240 ° C. or lower, more preferably 200 ° C. or lower, for the same reason as described above.
Here, the glass transition point (Tg) is a value of the glass transition point read when the temperature is raised at a heating rate of 30 ° C./min by a differential scanning calorimeter, and the particles themselves are measured. When there are a plurality of glass transition points (Tg), at least one glass transition point (Tg) may be in the above range.

As a method of setting the Tg of the organic particles within the above range, the organic particles are made of resin particles, the type of resin skeleton (for example, (meth) acrylate-based skeleton or styrene-based skeleton, etc.), and the type of monomer (in the case of copolymerization). It can be adjusted by the type and composition ratio of the monomer), the molecular weight (the degree of cross-linking in the case of cross-linked particles), and the like.
Normally, the Tg of organic particles is changed by cross-linking. This is because the molecular motion of the polymer chain is constrained by the cross-linking point.
In the present invention, it is particularly preferable that the organic particles are crosslinked particles and the Tg thereof is in the above range from the viewpoint of suppressing uneven brightness.

The heat capacity (ΔCp) of the organic particles contained in the resin layer (A) at the glass transition point is preferably 0.75 J / (g · ° C.) or less. By incorporating organic particles having a ΔCp of 0.75 J / (g · ° C.) or less in the resin layer (A), it becomes possible to further suppress the uneven brightness of the reflective material.
For the same reason as above, the upper limit of ΔCp of the organic particles is preferably 0.60 J / (g · ° C) or less, more preferably 0.50 J / (g · ° C) or less, still more preferably 0.40 J / (g).・ ℃) or less.
The lower limit of ΔCp of the organic particles is not limited, and is preferably 0.10 J / (g · ° C.) or more, more preferably 0.15 J / (g · ° C.) or more.
Here, the heat capacity (ΔCp) at the glass transition point is the value of ΔCp at the glass transition point read when the temperature is raised at a heating rate of 30 ° C./min by a differential scanning calorimeter, and the particles themselves are measured. When there are a plurality of Tg, the value of the heat capacity (ΔCp) at the lowest temperature Tg in the range of 115 to 260 ° C. is used.

As a method of setting ΔCp of the organic particles in the above range, the organic particles are made of resin particles, and the type of resin skeleton (for example, (meth) acrylate-based skeleton or styrene-based skeleton) and the type of monomer (monomer in the case of copolymerization). It can be adjusted according to the type and composition ratio of the particles), the molecular weight (in the case of crosslinked particles, the degree of crosslinking), and the like. Above all, the influence of the degree of cross-linking is large.
The glass transition point is the temperature at which the polymer material starts the Micro Brownian motion, and the heat capacity (ΔCp) corresponds to the momentum at that time. That is, even if the resins have similar compositions, if the degree of cross-linking is high, the molecular chains are constrained, so that the value of ΔCp becomes small. Therefore, a low value of ΔCp means that the molecule is constrained and the degree of cross-linking is high.

The average particle size of the organic particles is preferably 5 to 20 μm. When the average particle size of the organic particles is 5 μm or more, protrusions having a height effective for suppressing uneven brightness tend to be efficiently formed on the surface. On the other hand, when the average particle size of the organic particles is 20 μm or less, the detachment of the particles tends to be suppressed.
From the above viewpoint, the lower limit of the average particle size of the organic particles is more preferably 8 μm or more, further preferably 10 μm or more, and particularly preferably 12 μm or more. The upper limit of the average particle size of the organic particles is more preferably 19 μm or less, further preferably 18 μm or less, and particularly preferably 15 μm or less.

The average particle size of the organic particles can be measured as follows.
The average particle size of the organic particles as a raw material can be measured as the average particle size (D50) obtained from the volume-based particle size distribution measured by a dynamic light scattering method or the like.
The average particle size of the organic particles contained in the resin layer (A) is determined by observing the surface of the resin layer (A) or the cross section of the reflective material using an optical microscope or a scanning electron microscope (SEM). The diameters of one or more particles can be measured and calculated as the average value. At that time, when the cross-sectional shape is not circular (for example, when it is elliptical), the average value of the longest diameter and the shortest diameter can be measured as the diameter of each particle.
If the shape of the organic particles contained in the resin layer (A) is not significantly deformed from the shape of the organic particles of the raw material, the average particle size of the organic particles of the raw material is used as the resin layer (A). It can be regarded as the average particle size of the contained organic particles.

The content of the organic particles in the resin layer (A) is preferably 3 to 6% by mass (relative to 100% by mass of the resin layer (A)), particularly 3.5% by mass or more or 5% by mass or less. Is more preferable. When the content of the organic particles is not less than the above lower limit value, it is preferable because it is possible to more easily impart a specific hardness and roughness to the surface of the present reflector, and when the content of the organic particles is not more than the above upper limit value. This is preferable because it enables more efficient production without impairing the continuous productivity during extrusion film formation.

(Fine powder filler)
The resin layer (A) may contain a fine powder filler other than the organic particles (hereinafter referred to as "fine powder filler") together with the organic particles.
By containing the fine powder filler in the resin layer (A), in addition to light scattering due to the difference in refractive index between the polyolefin resin and the like and the fine powder filler, the surroundings of the fine powder filler in the process of producing this reflective material This reflection is also caused by light scattering due to the difference in refractive index between the cavity formed in and the polyolefin resin, etc., and further from light scattering due to the difference in refractive index between the cavity formed around the fine powder filler and the fine powder filler. The reflective properties of the material tend to be further improved. If sufficient light reflectivity can be ensured by the resin layer (B), it is not necessary to include the fine powder filler in the resin layer (A).

Regarding the type, particle size, and surface treatment method of the fine powder filler that can be used for the resin layer (A), the same as those described as the fine powder filler that can be used for the resin layer (B) described later. It can be used, and the same applies to preferred examples. Here, among the items described later as the fine powder filler used for the resin layer (B), "resin layer (B)" shall be read as "resin layer (A)".

The fine powdery filler contained in the resin layer (A) preferably has an average particle size of 0.05 μm or more and 5 μm or less, more preferably 0.1 μm or more or 2 μm or less.
When the average particle size of the fine powder filler is 0.05 μm or more, the dispersibility in the polyolefin resin does not decrease, so that a more homogeneous reflective material can be obtained. Further, when the average particle size is 5 μm or less, the interface between the polyolefin resin and the fine powder filler is densely formed, and a highly reflective reflective material can be obtained.

The average particle size of the fine powder filler can be measured as follows.
The average particle size of the fine powder filler as a raw material is the average particle size (D50) obtained from the volume-based particle size distribution measured by a dynamic light scattering method or the like, or a centrifugal sedimentation type particle size distribution measuring device is used. The integrated (mass-based) 50% particle size in the measured equivalent spherical distribution can be measured as the average particle size (D50).
For the average particle size of the fine particle filler contained in the resin layer (A), use an optical microscope or a scanning electron microscope (SEM) and observe the surface of the resin layer (A) or the cross section of the reflective material. The diameters of 10 or more particles can be measured and obtained as the average value thereof. At that time, when the cross-sectional shape is not circular, the average value of the longest diameter and the shortest diameter can be measured as the diameter of each particle. The same applies to the fine powder filler contained in the resin layer (B) described later, but in that case, a method of observing the cross section of the present reflector is preferable.
If the shape of the fine powder filler contained in the resin layer (A) does not show any significant deformation from the shape of the raw material fine powder filler, the average particle size of the raw material fine powder filler is used. It can be regarded as the average particle size of the fine powder filler contained in the resin layer (A).

When the resin layer (A) contains a fine powder filler, the content of the fine powder filler in the resin layer (A) is not limited. Considering the light reflectivity, mechanical strength, productivity, etc. of this reflector, it should be 10 to 80% by mass with respect to the entire resin layer (A) (that is, with respect to 100% by mass of the resin layer (A)). Is preferable, and more preferably 20% by mass or more or 70% by mass or less. When the content of the fine powder filler is 10% by mass or more, the area of the interface between the resin constituting the resin layer (A) and the fine powder filler can be sufficiently secured, which is higher than that of this reflective material. Reflectivity can be imparted. When the content of the fine powder filler is 80% by mass or less, the mechanical strength required for the reflective material can be secured more effectively, which is preferable.

(Other ingredients)
The resin layer (A) may further contain components other than the polyolefin resin, organic particles, and fine powder filler as "other components".
"Other components" include resin components (including thermoplastic elastomers) other than the above, antioxidants, light stabilizers, heat stabilizers, dispersants, ultraviolet absorbers, optical brighteners, compatibilizers, etc. Examples thereof include fillers other than lubricants and fine powder fillers.

Further, the resin layer (A) may contain a recycled raw material generated in the manufacturing process of the present reflector as long as the performance of the present reflector is not impaired.
The content ratio of the recycled raw material is not limited, and is preferably 1 to 60% by mass (relative to 100% by mass of the resin layer (A)) with respect to the total mass of the resin layer (A), particularly 10% by mass. It is more preferably% or more or 50% by mass or less. If the content is 1% by mass or more, there is a cost advantage by using the recycled raw material, and if it is 60% by mass or less, the light reflectivity and mechanical strength required for the reflective material are not impaired. It is in.
However, if the recycled raw material is contained in the resin layer (A), the surface roughness of the present reflector may become unstable or the reflectance may become unstable. It is preferable to include it in the resin layer (B) as described above.

<Resin layer (B)>
The resin layer (B) in this reflective material is a layer containing a polyolefin resin.
The resin layer (B) may contain another resin as long as it contains a polyolefin resin. However, from the viewpoint of enhancing the adhesion with the resin layer (A), it is preferable to contain the polyolefin resin as the main component resin.

(Polyolefin resin)
The polyolefin resin used for the resin layer (B) is not limited, and can be selected and used from those exemplified as the polyolefin resin of the resin layer (A). For example, polypropylene resins such as polypropylene and propylene-ethylene copolymers, polyethylene resins such as high-density polyethylene, low-density polyethylene and ethylene / α-olefin copolymers, and cycloolefin resins such as ethylene-cyclic olefin copolymers. In addition, at least one polyolefin resin selected from olefin-based elastomers such as ethylene-propylene rubber (EPR) and ethylene-propylene-dienter polymer (EPDM) can be mentioned. Among these, polypropylene resin and polyethylene resin are preferable from the viewpoint of mechanical properties and flexibility, and polypropylene (a homopolymer of propylene) is most preferable.

The polyolefin resin of the resin layer (B) may be a polyolefin resin different from the polyolefin resin which is the main component resin of the resin layer (A). However, from the viewpoint of enhancing the adhesion between the resin layers (A) and (B), it is preferable to use a polyolefin resin containing a monomer unit common to the polyolefin resin which is the main component resin of the resin layer (A).

From the viewpoint of extrusion moldability, the polyolefin resin used for the resin layer (B) has a melt flow rate (MFR) of 0.1 to 20 g as a value measured at 230 ° C. and a load of 21.18 N in accordance with JIS K7210. It is preferably / 10 minutes, more preferably 0.2 g / 10 minutes or more or 10 g / 10 minutes or less, and further preferably 0.5 g / 10 minutes or more or 5 g / 10 minutes or less. preferable.

The content of the polyolefin resin in the resin layer (B) is not limited, and is preferably 15% by mass or more, more preferably 20% by mass or more, and further preferably 25% by mass (with respect to 100% by mass of the resin layer (B)). % Or more. When the content of the polyolefin resin is at least the above lower limit value, the strength of the resin layer (B) is further maintained, which is preferable.
Further, the upper limit of the content of the polyolefin resin in the resin layer (B) is not limited, and it may be composed of only the polyolefin resin, but it is preferably 90% by mass or less, more preferably 80% by mass or less, still more preferable. Is 70% by mass or less.
When the content of the polyolefin resin is not more than the above upper limit value, the strength is maintained without lowering the reflectance, which is preferable.

(Fine powder filler)
The resin layer (B) preferably contains a fine powder filler together with the polyolefin resin from the viewpoint of obtaining further reflection performance.
When the resin layer (B) contains a fine powder filler, the incident light is diffusely reflected by the fine powder filler to improve the reflection characteristics, and when the resin layer (B) is a stretched body, voids are formed. Is easy to form.

The fine powder filler contained in the resin layer (B) is not limited, and examples thereof include inorganic fine powder and organic fine powder. As the organic fine powder, the same organic particles as those used for the resin layer (A) can be used. Among these, the resin layer (B) preferably contains the inorganic fine powder as a fine powder filler. Further, the inorganic fine powder and the organic fine powder may be used in combination.

Examples of the organic fine powder that can be contained in the resin layer (B) include polymer beads, polymer hollow particles, and the like, and any one or a mixture of two or more of these can be used. ..
Further, as will be described later, the present reflective material may be used as a part of the raw material of the resin layer (B) by using the scraps generated in the manufacturing process of the reflective material as a recycled raw material. In that case, the organic particles contained in the resin layer (A) are also contained in the resin layer (B).

Examples of the inorganic fine powder include calcium carbonate, magnesium carbonate, barium carbonate, magnesium sulfate, barium sulfate, calcium sulfate, zinc oxide, magnesium oxide, calcium oxide, titanium oxide, aluminum oxide, zinc oxide, alumina, and aluminum hydroxide. Examples thereof include hydroxyapatite, silica, magnesium silicate, mica, talc, kaolin, clay, glass powder, asbestos powder, zeolite, and clay silicate. These can be used by any one kind or a mixture of two or more kinds.
Among these, in consideration of the difference in refractive index from the resin constituting the resin layer (B), those having a large refractive index are preferable, and calcium carbonate, barium sulfate, titanium oxide or oxidation having a refractive index of 1.6 or more is preferable. It is particularly preferable to use zinc.

Among them, titanium oxide has a significantly higher refractive index than other inorganic fine powders, and the difference in refractive index from the resin constituting the resin layer (B) can be significantly increased. Therefore, another filler is used. Excellent light reflectivity can be obtained with a smaller blending amount than in the case of. Further, by using titanium oxide, high light reflectivity can be obtained even if the thickness of the present reflector is reduced.
The content of titanium oxide is not limited, and is preferably 30% or more of the total mass of the inorganic fine powder. When the organic fine powder and the inorganic fine powder are used in combination as the fine powder filler, it is preferable that 30% or more of the total mass is titanium oxide.
As the titanium oxide, for example, commercially available products such as those manufactured by Ishihara Sangyo Co., Ltd., The Chemours Company, and KRONOS Co., Ltd. can be used.

In order to improve the dispersibility of these inorganic fine powders in the resin, inorganic fine powders whose surfaces have been surface-treated with silicon-based compounds, polyhydric alcohol-based compounds, amine-based compounds, fatty acids, fatty acid esters, etc. are used. You may.

The fine powder filler preferably has an average particle size of 0.05 to 15 μm, and more preferably 0.1 μm or more or 10 μm or less. When the average particle size of the fine powder filler is 0.05 μm or more, the dispersibility in the resin constituting the resin layer (B) is good, so that a more homogeneous reflective material can be obtained. Further, when the average particle size of the fine powder filler is 15 μm or less, the interface between the resin constituting the resin layer (B) and the fine powder filler is densely formed to obtain a highly reflective reflective material. be able to.
Here, the "average particle size" can be measured by the method described above.

The content of the fine powder filler contained in the resin layer (B) is based on the mass of the entire resin layer (B) (that is, in consideration of the light reflectivity, mechanical strength, productivity, etc. of the present reflector). (With respect to 100% by mass of the resin layer (B)), preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably 30% by mass or more. When the content of the fine powder filler is equal to or higher than the lower limit value, a sufficient area of the interface between the resin constituting the resin layer (B) and the fine powder filler can be sufficiently secured, and the reflective material has higher reflectivity. Can be given.
Further, the upper limit of the content of the fine powder filler is not limited, and is preferably 80% by mass or less, more preferably 75% by mass or less, and further preferably 70% by mass or less. When the content of the fine powder filler is not more than the upper limit value, the mechanical strength required for the reflective material can be more effectively secured.

(Other ingredients)
The resin layer (B) may further contain components other than the polyolefin resin and the fine powder filler as "other components".
"Other components" include resin components (including thermoplastic elastomers) other than polyolefin resins, crystal nucleating agents, antioxidants, light stabilizers, heat stabilizers, dispersants, ultraviolet absorbers, and fluorescent whitening agents. , Elastomers, lubricants and other additives and the like.

Further, as long as the performance of the resin layer (B) is not impaired, the recycled raw material generated in the manufacturing process of the present reflective material may be contained.
The content ratio of the recycled raw material is not limited, and is preferably 1 to 60% by mass, particularly 10% by mass or more, based on the total mass of the resin layer (B) (that is, with respect to 100% by mass of the resin layer (B)). Alternatively, it is more preferably 50% by mass or less. When the content is 1% by mass or more, it is preferable because the cost merit of using the recycled raw material is generated. On the other hand, when the content is 60% by mass or less, it is preferable because the light reflectivity and mechanical strength required for the reflective material are not impaired.
Normally, the thickness of the resin layer (B) accounts for a large proportion of the total thickness of the reflective material. Therefore, when the recycled raw material is contained in the resin layer (B), fluctuations in various characteristics of the reflective material are reduced. It is preferable because it can be used.

<Resin layer (C)>
The resin layer (C) is a layer containing a polyolefin resin and not containing organic particles having a particle size of 5 μm or more.
The presence of the resin layer (C) as a layer containing a polyolefin resin and not containing organic particles having a particle size of 5 μm or more causes the organic particles contained in the resin layer (A) to be removed from the present reflector. It is possible to suppress the separation. Furthermore, since the hardness of the organic particles contained in the resin layer (A) is reduced from directly affecting the surface hardness of the reflective material, it is guided when the reflective material comes into contact with a light guide plate or the like. It is expected that damage to the light plate and the like will be suppressed.
Further, in the resin layer (C), the polyolefin resin is preferably a main component resin.
In order to make the resin layer (C) have such a structure, the type and content ratio of the organic particles contained in the raw material used for the resin layer (C), that is, the resin composition C described later (including the case where the resin layer (C) is not contained at all). It is preferable to adjust. However, the method is not limited to this method.
In the above description, it is more preferable to read "organic particles having a particle size of 5 μm or more" as "organic particles having a particle size of 3 μm or more" and to make the same specifications, and "the particle size is 2 μm or more". It is more preferable to read it as "organic particles" and make the same specifications, and it is particularly preferable to read it as "organic particles having a particle size of 1 μm or more" and make the same specifications.

Further, the resin layer (C) preferably does not contain a fine powder filler having a particle size of 5 μm or more, and the reason is the same as that of the organic particles. The fine powder filler has the same meaning as the fine powder filler contained in the resin layer (B).
In order to make the resin layer (C) have such a structure, the type and content ratio of the raw material used for the resin layer (C), that is, the fine powder filler contained in the resin composition C described later (when it is not contained at all). Including) is preferably adjusted. However, the method is not limited to this method.

In the above description, it is more preferable to read "fine powder filler having a particle size of 5 μm or more" as "fine powder filler having a particle size of 3 μm or more" and to make the same specification. It is more preferable to read "fine powder filler having a particle size of 2 μm or more" and make the same specifications, and particularly to read "fine powder filler having a particle size of 1 μm or more" and make the same specifications. preferable.

The phrase "does not contain organic particles or fine powder filler having a particle size of 5 μm or more" means that it does not substantially contain organic particles or fine powder filler having a particle size of 5 μm or more, and has a particle size of 5 μm. The case where the content of the above organic particles or fine powder filler in the resin layer (C) is 1% by mass or less is allowed and included. At this time, the content ratio of the organic particles or the fine powder filler having a particle size of 5 μm or more in the resin layer (C) is preferably 0.5% by mass or less (relative to 100% by mass of the resin layer (C)). , More preferably 0.2% by mass or less, still more preferably 0.1% by mass or less, and it is particularly preferable that the content is not contained at all.
When the content of the organic particles or fine powder filler having a particle size of 5 μm or more in the resin layer (C) is 1% by mass or less, it is possible to prevent the organic particles or fine powder filler from desorbing from the present reflector. Therefore, the effect of the present invention can be achieved.

It can be confirmed by the following method that the resin layer (C) "does not contain organic particles or fine powder filler having a particle size of 5 μm or more".
The raw material of the resin layer (C) does not contain organic particles or a fine powder filler having an average particle size (D50) of 5 μm or more obtained from a volume-based particle size distribution measured by a dynamic light scattering method or the like. It can be confirmed by.
On the other hand, regarding the organic particles or the fine powder filler in the resin layer (C), it is first confirmed whether or not the organic particles or the fine powder filler is contained in the resin layer (C). If contained, any three or more organic particles or fine powder fillers are selected and the diameters of those particles are measured using an optical microscope or scanning electron microscope (SEM). Then, it is determined whether or not the measured diameter is 5 μm or more, and if none of the particles has a diameter of 5 μm or more, the resin layer (C) “fills with organic particles or fine powder having a particle size of 5 μm or more”. It can be confirmed that it does not contain any agent.
In addition, "does not contain organic particles or fine powder filler having a particle size of 3 μm or more", "does not contain organic particles or fine powder filler having a particle size of 2 μm or more", and "organic particles having a particle size of 1 μm or more". Alternatively, "does not contain a fine particle filler" can be similarly confirmed by replacing the above "5 μm" with "3 μm", "2 μm", and "1 μm", respectively.

The resin layer (C) is the same as the aspect of the resin layer (A) except that the content ratio of the organic particles and the fine powder filler is within the above range from the structure of the resin layer (A). That is, regarding the types of polyolefin resins and cycloolefin resins that can be used for the resin layer (C), other polyolefin resins, fine powder fillers, and other components, the polyolefins that can be used for the resin layer (A) described above. Resins, cycloolefin resins, other polyolefin resins, fine powder fillers, and other components can be used in the same manner, and preferred examples and preferred embodiments are also the same except for the content ratio of organic particles and fine powder filler. Is. Here, the above-mentioned matters as the aspect of the resin layer (A) can be applied by replacing "resin layer (A)" with "resin layer (C)".

If the polyolefin resin that is the main component resin in the resin layer (A) and the polyolefin resin that is the main component resin in the resin layer (C) are the same or have high affinity, the resin layer (in this reflective material) There may be cases where the boundary between A) and the resin layer (C) does not exist or cannot be confirmed. Even in such a case, if the region (layer) containing the organic particles and the region (layer) in which the organic particles do not exist can be distinguished, these are referred to as the resin layer (A) and the resin layer (the resin layer). It can be regarded as C). Furthermore, even when the content ratio of the organic particles continuously changes in the thickness direction, the content ratio of the organic particles can be regarded as the resin layer (A) and the resin layer (C). It is possible. Even in such a case, the effects of the resin layer (A) and the resin layer (C) in the present invention can be exhibited.

<Gap>
In this reflective material, the reflection characteristics can be enhanced by having any layer having voids.
Even if only one of the resin layer (A), the resin layer (B), and the resin layer (C) has the void, any two of these layers have the void. Also, all layers may have. Alternatively, a layer other than these layers (other layers) may have. When the voids are provided in the resin layer (A) or the resin layer (C) and the mechanical properties such as heat resistance and elastic modulus are deteriorated, it is preferable to provide the voids only in the resin layer (B). By providing such voids only in the resin layer (B), the heat resistance of the entire film can be improved.
The voids can be formed by containing a fine powdery filler in the composition constituting each layer and stretching, preferably biaxially stretching. Alternatively, it can be formed by containing an incompatible resin in the polyolefin resin constituting each layer and stretching, preferably biaxially stretching.

<This reflector>
(Layer structure)
The present reflective material may have a configuration having any other layer as long as the resin layer (B), the resin layer (A), and the resin layer (C) are laminated in this order. For example, the surface of the resin layer (B) or the resin layer (C) may have an "other layer", or between the layers of the resin layer (A) and the resin layer (B) or the resin layer (A). ) And the resin layer (C), for example, an "other layer" such as an adhesive layer may be interposed.
The "other layer" also includes a layer provided by coating or thin film deposition.

Further, it may have a configuration of four or more layers having at least two or more layers of at least one of the resin layer (A), the resin layer (B) and the resin layer (C). In the case of a configuration of four or more layers, it is preferable that the resin layer (B) is the core layer, the resin layers (A) are provided on both sides of the resin layer (B), and the two resin layers (A) are formed. A configuration having a resin layer (C) on both sides, that is, a configuration having five layers of "resin layer (C) / resin layer (A) / resin layer (B) / resin layer (A) / resin layer (C)". Is more preferable.

By laminating the resin layer (B), the resin layer (A), and the resin layer (C) in this order, the functions of each layer can be separated, and reflection performance, heat resistance, folding resistance, and uneven brightness can be generated. Performance such as reduction of particle desorption can be improved. For example, the resin layer (B) is mainly provided with a role of imparting light reflectivity, and the resin layer (A) is provided with a role of reducing the occurrence of uneven brightness in addition to heat resistance. In addition to heat resistance, C) can have a role of reducing particle desorption.
Any layer may be used as the outermost layer of the reflective material, but since the resin layer (C) can have a role of reducing particle desorption, the surface layer of the reflective material, especially the surface used for reflection, is the most. It is preferable to arrange the resin layer (C) as the outer layer.

(Forms of resin layer (A), resin layer (B) and resin layer (C))
If the resin layer (A), the resin layer (B), and the resin layer (C) are all in the form of a film, that is, in the form of a thin film, there are no restrictions on the more specific shape or manufacturing method. Above all, it is preferable that each layer is in the form of a film formed by an extrusion method.
When each layer is in the form of a film, each layer may be a non-stretched film or a uniaxial or biaxially stretched film. Above all, a stretched film obtained by stretching at least 1.1 times in the uniaxial direction, particularly a biaxially stretched film is preferable.
Further, although it is possible to manufacture a film corresponding to each layer in advance and then laminating them to form a laminated structure, it is preferable to manufacture by a coextrusion method capable of forming a laminated structure at one time. It is more preferable to stretch after forming a laminated structure by a coextrusion method because all the layers will be stretched.

(Thickness)
The thickness of the reflective material is preferably 30 μm to 200 μm. Considering the handleability in terms of practical use, the thickness of the present reflector is more preferably 50 μm or more or 150 μm or less, and further preferably 60 μm or more or 110 μm or less.

The thickness of the resin layer (A) is not particularly limited, and is preferably 0.1 to 20 μm, more preferably 0.5 μm or more or 15 μm or less, and 1 μm or more or 10 μm or less. Is even more preferable. When the thickness of the resin layer (A) is within the above range, the uneven brightness tends to be suppressed more effectively. Here, the thickness of the resin layer (A) means the average thickness. When a plurality of resin layers (A) are provided in the present reflective material, it means the thickness of each layer.

The thickness of the resin layer (B) (when two or more layers of the resin layer (B) are provided, the total thickness thereof) is not particularly limited. For example, it is preferably 20 to 120 μm, more preferably 30 μm or more or 100 μm or less, and further preferably 40 μm or more or 80 μm or less. When the thickness of the resin layer (B) is within the above range, the reflection characteristics tend to be good. Here, the thickness of the resin layer (B) means the average thickness.
Even when the polyolefin resin which is the main component resin in the resin layer (A) and the polyolefin resin contained in the resin layer (B) as the main component resin are the same or have a high affinity, the reflective material is used. In some cases, the boundary between the resin layer (A) and the resin layer (B) does not exist or cannot be confirmed. In such a case, the thickness of each of the above-mentioned layers and the thickness ratio of each of the following layers can be obtained from the ratio of raw materials used and the ratio of extrusion amount of each layer when producing the present reflector.

The thickness of the resin layer (C) is not particularly limited, and is preferably, for example, 1 to 10 μm, and more preferably 2 μm or more or 9 μm or less. When the thickness of the resin layer (C) is within the above range, the detachment of particles tends to be suppressed. Here, the thickness of the resin layer (C) means the average thickness. When a plurality of resin layers (C) are provided in the present reflective material, it means the thickness of each layer.
If the polyolefin resin that is the main component resin in the resin layer (A) and the polyolefin resin that is the main component resin in the resin layer (C) are the same or have high affinity, the resin layer (in this reflective material) There may be cases where the boundary between A) and the resin layer (C) does not exist or cannot be confirmed. In such a case, the thickness of each of the above-mentioned layers and the thickness ratio of each of the following layers can be obtained from the ratio of raw materials used and the ratio of extrusion amount of each layer when producing the present reflector.

In this reflector, the thickness ratio of the resin layer (C) to the resin layer (A) is preferably in the range of 0.8: 0.2 to 0.2: 0.8, preferably 0.7: 0.3. More preferably, it is in the range of ~ 0.3: 0.7.
When the thickness ratio of the resin layer (C) is 0.8 or less, the organic particles contained in the resin layer (A) are less likely to be buried in the present reflector, so that uneven brightness can be suppressed more effectively. Tend to be able to. On the other hand, when the thickness ratio of the resin layer (C) is 0.2 or more, the organic particles contained in the resin layer (A) can be covered with a sufficient thickness by the resin layer (C). The holding power of the particles by the A) and the resin layer (C) is improved, and the detachment of the particles tends to be suppressed.

The resin layer (A) and the resin layer (C) are adjacent to each other, such as "resin layer (C) / resin layer (A) / resin layer (B) / resin layer (A) / resin layer (C)". When a plurality of configurations are present in the present reflective material, the thickness ratio in at least one combination may be in the above range. Here, "the resin layer (A) and the resin layer (C) are adjacent to each other" means that the resin layer (A) and the resin layer (C) are present on the same side with respect to the resin layer (B). , Even if any other layer exists between the resin layer (A) and the resin layer (C).

In this reflector, the ratio of the thickness of the resin layer (B) to the thickness of the resin layer (A) ((B) / (A)) is preferably 1 to 40, and is preferably 2 or more or 30 or less. Is more preferable, and 5 or more or 20 or less is further preferable. When the thickness ratio of the resin layer (B) to the resin layer (A) is 1 times or more, the reflection characteristics tend to be good, and the flexibility tends to be good, so that the bending workability tends to be improved. Further, when the thickness ratio of the resin layer (B) to the resin layer (A) is 40 times or less, the heat resistance tends to be good.
When the structure has two or more resin layers (A) or resin layers (B), the thickness ratio means the thickness ratio of the total thickness of each layer.

In this reflector, the ratio of the thickness of the resin layer (B) to the total thickness of the resin layer (A) and the resin layer (C) ((B) / ((A) + (C))) is 2 to 20. It is preferably 3 or more, or more preferably 10 or less. If the thickness ratio of the resin layer (B) to the total thickness of the resin layer (A) and the resin layer (C) is twice or more, the reflection characteristics tend to be good, and the flexibility is further improved, so that the resin layer (B) is bent. Workability tends to improve. Further, when this thickness ratio is 20 times or less, the heat resistance tends to be good. When the structure has two or more resin layers (A), resin layers (C), or resin layers (B), the thickness ratio means the ratio of the total thickness of each layer.

(Protrusions on the surface)
The planar viewing diameter of the protrusions on the surface of the resin layer (C) side of the reflective material is preferably 5 μm to 20 μm, more preferably 8 μm or more or 19 μm or less, and more preferably 10 μm or more or 18 μm or less. When the plane viewing diameter of the protrusions on the surface of the resin layer (C) side of the reflective material is within the range, it tends to be possible to suppress the desorption of particles and the uneven brightness, which is preferable.

Here, the "planar view diameter of the protrusion on the surface of the resin layer (C) side" is obtained by observing the surface of the reflective material from the upper surface using an optical microscope or a scanning electron microscope (SEM), that is, in a plan view. Therefore, it is possible to select three or more arbitrary protrusions that can be discriminated as protrusions, measure the plane view diameter of the protrusions, that is, the diameter when the protrusions are viewed in a plane view, and obtain the average value thereof.
The "resin layer (C) side surface" of the reflective material is the "resin layer (C) side surface" such as "resin layer (C) / resin layer (A) / resin layer (B) / resin layer (A) / resin layer (C)". When it is on both surfaces, the plane viewing diameter of the protrusions on at least one of the surfaces may be within the above range. The same applies to the "projection density having a planar optic tract of 5 to 20 μm", the maximum height Rz, and the arithmetic mean roughness Ra, which will be described later.

In this reflector, the resin layer (C) is laminated on the resin layer (A) containing organic particles. Therefore, when the resin layer (C) is the surface layer of the reflector, the inside of the resin layer (A) The organic particles of the above cause protrusions on the surface of the resin layer (C), that is, on the surface of the reflective material on the resin layer (C) side. Further, when the "other layer" is laminated on the surface of the resin layer (C), protrusions are generated on the surface of the "other layer", that is, the surface on the resin layer (C) side of the present reflector.
However, when measuring the plane viewing diameter of the protrusions on the surface of the resin layer (C), it is not limited to the protrusions caused by the organic particles in the resin layer (A). Therefore, it is not necessary to confirm that the protrusions are caused by the organic particles contained in the resin layer (A).

Examples of the method for adjusting the plane viewing diameter of the protrusions on the surface of the resin layer (C) include the type and blending ratio of the organic particles contained in the resin layer (A), the thickness ratio of the resin layer (A) and the resin layer (C), and the thickness ratio of the resin layer (A) and the resin layer (C). It can be optimized depending on the type and blending ratio of the polyolefin resin which is the main component resin of the resin layer (A) and the resin layer (C), the stretching conditions when producing the reflective material, and the like. However, the method is not limited to these methods.

The surface of the resin layer (C) side of the reflective material preferably has a protrusion density of 10 to 210 pieces / mm ² , among which 30 pieces / mm ² or more or 180 pieces / mm ² or less, and 40 pieces among them. It is more preferably / mm ² or more and 160 pieces / mm ^{2 or less.} It is preferable that the protrusions have a density in the above range because the uneven brightness tends to be effectively suppressed.
The density of the protrusions can be adjusted according to the type and blending ratio of the organic particles contained in the resin layer (A), the stretching conditions for producing the reflective material, and the like.

(Maximum height Rz)
The maximum height Rz of the surface of the resin layer (C) side of the reflective material is not particularly limited, and is preferably 3.0 μm or more, more preferably 3.2 μm or more, and further preferably 3.4 μm or more. When the maximum height Rz of the surface of the resin layer (C) side of the present reflective material is at least the above lower limit value, the reflection characteristics are good and the uneven brightness tends to be further suppressed, which is preferable.
Further, the upper limit of the maximum height Rz of the surface of the resin layer (C) side of the present reflector is not limited, and is preferably 7.0 μm or less, more preferably 6.0 μm or less, and further preferably 5.5 μm or less. When the maximum height Rz of the surface of the resin layer (C) side of the present reflective material is not more than the upper limit value, the reflection characteristics are good and the desorption of particles tends to be suppressed, which is preferable.

As a method of adjusting the maximum height Rz of the surface on the resin layer (C) side, the thickness ratio between the resin layer (A) and the resin layer (C), the main component resin of the resin layer (A) and the resin layer (C) is used. It can be optimized by the type and blending ratio of a certain polyolefin resin, the type and blending ratio of organic particles contained in the resin layer (A), the stretching conditions when producing a reflective material, and the like.
The measurement of the maximum height Rz shall be based on JIS B0601 and, in more detail, based on the method of Examples described later.

(Arithmetic Mean Roughness Ra)
The arithmetic mean roughness Ra of the surface of the resin layer (C) side of the reflective material is not particularly limited, and is preferably 0.3 μm or more, more preferably 0.35 μm or more, and further preferably 0.4 μm or more. .. When the arithmetic mean roughness Ra of the surface of the resin layer (C) side of the reflective material is at least the above lower limit value, the reflection characteristics are good and the brightness unevenness tends to be further suppressed, which is preferable.
Further, the upper limit of the arithmetic mean roughness Ra of the surface of the resin layer (C) side of the present reflector is not limited, and is preferably 0.9 μm or less, more preferably 0.8 μm or less, and further preferably 0.7 μm or less. .. When the arithmetic mean roughness Ra of the surface of the resin layer (C) side of the reflective material is not more than the upper limit value, the reflection characteristics are good and the desorption of particles tends to be suppressed, which is preferable.

As a method for adjusting the arithmetic average roughness Ra of the surface on the resin layer (C) side, the thickness ratio between the resin layer (A) and the resin layer (C), the main component resin of the resin layer (A) and the resin layer (C) is used. It can be optimized by the type and blending ratio of a certain polyolefin resin, the type and blending ratio of organic particles in the resin layer (A), the stretching conditions when producing a reflective material, and the like.
The measurement of the arithmetic mean roughness Ra shall be based on JIS B0601 and, in more detail, based on the method of Examples described later.

(Reflectance)
This reflective material can have high reflective performance.
There is no limitation on the reflective performance of this reflective material, and the average reflectance on at least one side can be 95% or more, further 96% or more, and particularly 97% or more. If the reflective material has such a reflective performance, the screen of a liquid crystal display or the like incorporating this reflective material can realize sufficient brightness.
Here, the "reflectance" means the average reflectance for light having a wavelength of 420 to 700 nm, and a more detailed measurement method will be described in Examples described later.

(Porosity)
The present reflective material preferably has voids in order to enhance the reflective performance.
The presence of voids in the reflector can be confirmed, for example, by observing the cross section of the reflector with a microscope (electron microscope or optical microscope).
The porosity of this reflector is not limited. It is preferably 10% or more, more preferably 20% or more, while the upper limit is preferably 80% or less, more preferably 70% or less.
When the porosity of the present reflector is at least the above lower limit value, the whitening of the present reflector proceeds sufficiently, so that it tends to have high light reflectivity. Further, when the porosity of the present reflector is not more than the upper limit value, the mechanical strength of the present reflector tends to be suitable.

The porosity of the resin layer (B) is not limited. It is preferably 20% or more, more preferably 25% or more, still more preferably 30% or more, while the upper limit is preferably 80% or less, more preferably 75% or less, still more preferably 70% or less. .. When the porosity of the resin layer (B) is equal to or higher than the lower limit value, the whitening of the present reflective material proceeds sufficiently, so that the resin layer (B) tends to have higher light reflectivity. Further, when the porosity of the resin layer (B) is equal to or less than the upper limit value, the mechanical strength of the present reflector tends to be more preferable.

The porosity of this reflector is substantially targeted at the resin layer (A), the resin layer (B), and the resin layer (C), and when another layer is provided between these layers, the porosity is substantially the same. This shall also be included. On the other hand, when other layers such as a resin plate and a metal plate are provided on the outer surface of the resin layer (A), the resin layer (B) and the resin layer (C), these layers have the porosity of the reflective material. Not included in the calculation.

The porosity of this reflector can be determined by the following method.
(1) When a void is formed by stretching, it can be obtained by the following formula by measuring the density of the reflective material before and after stretching.
Porosity (%) = {(Density of film before stretching-Density of film after stretching) / Density of film before stretching} x 100
(2) When the density and blending ratio of each raw material are clear, the density when there is no void can be calculated from the density and blending ratio of each raw material, and can be calculated by the following formula.
Porosity (%) = {(Density without voids-Density of reflector) / Density without voids} x 100
(3) Further, it can be obtained by measuring the density of the reflective material and then calculating the density after melting, reducing the pressure, cooling and solidifying the reflective material to remove voids.

<Manufacturing method of this reflective material>
Below, as an example of the manufacturing method of this reflector, "resin layer (C) / resin layer (A) / resin layer (B) / resin layer (A) / resin layer (C)" manufactured by the coextrusion method. This five-layered reflective material will be described. However, the manufacturing method is not limited to the following. For example, instead of the coextrusion method, it is possible to form a laminated structure by coating, extrusion laminating, heat fusion, adhesive or the like.

Conventionally, a coating method has been mainly adopted as a method for providing a layer containing a large amount of organic particles having a large particle size. However, if the organic particle-containing layer is provided by the coating method, although the surface roughness becomes high, problems such as desorption of particles and deterioration of recyclability (self-recyclability) may occur, and coating from the base material may occur. Problems such as layer peeling, curling (rolling habit), and reduction in manufacturing efficiency may occur.
On the other hand, in the method for producing this reflective material, the main component resin constituting the layer containing organic particles (resin layer (A)) is used as the resin constituting the resin layer (B) and the resin layer (C). By using the same type, that is, a polyolefin resin, a configuration suitable for the coextrusion method can be obtained. If this reflector is manufactured by the coextrusion method, it is not necessary to provide a layer containing organic particles by coating, so that the surface roughness is increased, the desorption of particles is suppressed, and the recyclability (self-recycling) is further achieved. The property) is also good, there is no peeling or curling of the surface layer from the base material, and the manufacturing efficiency can be significantly improved. On the other hand, in contrast to the above configuration such as this reflective material, when the main component resin of the resin layer (A) or the resin layer (A) and the resin layer (C) is an acrylic resin, for example, a coextrusion method is used. It becomes difficult to adopt the above-mentioned effect, and it becomes difficult to achieve the above-mentioned effect.

(Resin Composition A)
A resin composition A containing a polyolefin resin, organic particles, and if necessary, other additives as a raw material for the resin layer (A) is prepared. Specifically, after mixing these raw materials with a ribbon blender, a tumbler, a Henschel mixer, etc., a temperature equal to or higher than the resin flow start temperature (for example, 220 ° C.) is used using a Banbury mixer, a single-screw extruder, or a twin-screw extruder. The resin composition A can be obtained by kneading at (~ 270 ° C.).
Further, the resin composition A can be obtained by adding a predetermined amount of each raw material with a separate feeder or the like. Alternatively, a part of the raw material can be prepared as a masterbatch and used as the raw material. Alternatively, a resin composition A can be obtained by preliminarily preparing a resin composition using a part of the raw materials and kneading the resin composition with other raw materials.

(Resin composition B)
As a raw material for the resin layer (B), a resin composition B is prepared by blending a polyolefin resin with a fine powder filler and, if necessary, other additives. Specifically, after mixing these raw materials with a ribbon blender, a tumbler, a Henschel mixer, etc., a temperature equal to or higher than the melting point of the resin (for example, 190 ° C. to 270 ° C.) is used using a Banbury mixer, a single-screw extruder, or a twin-screw extruder. The resin composition B can be obtained by kneading at (° C.).
Further, as with the resin composition A, it can be produced using a feeder or the like, a part of the raw material can be used as a masterbatch, or a part of the raw material can be used as a resin composition in advance.

(Resin composition C)
A resin composition C containing a polyolefin resin as a raw material for the resin layer (C) and, if necessary, other additives is prepared. Specifically, after mixing these raw materials with a ribbon blender, a tumbler, a Henschel mixer, etc., a temperature equal to or higher than the resin flow start temperature (for example, 220 ° C.) is used using a Banbury mixer, a single-screw extruder, or a twin-screw extruder. The resin composition C can be obtained by kneading at (~ 270 ° C.).
Further, the resin composition C can be obtained by adding a predetermined amount of each raw material with a separate feeder or the like. Alternatively, a part of the raw material can be prepared as a masterbatch and used as the raw material. Alternatively, a part of the raw materials may be used as a resin composition in advance, and the resin composition and other raw materials may be kneaded to obtain the resin composition C.
When only the polyolefin resin is used for the resin layer (C), it corresponds to the resin composition C without any compounding or the like.

Next, the resin composition A, the resin composition B, and the resin composition C thus obtained are dried as necessary, then supplied to separate extruders and heated to a predetermined temperature or higher. Melt.
Conditions such as extrusion temperature are arbitrary. For example, the extrusion temperature of the resin composition A and the resin composition C is preferably 220 ° C. to 270 ° C., and the extrusion temperature of the resin composition B is preferably 190 to 270 ° C.

After that, the molten resin composition A, the resin composition B, and the resin composition C are merged with the T-die for 3 types and 5 layers, extruded in a laminated manner from the slit-shaped discharge port of the T-die, and solidified in close contact with the cooling roll. To form a cast sheet.

The obtained cast sheet is preferably stretched in at least one axial direction. By stretching, the interface between the polyolefin resin and the fine powder filler inside the resin layer (B) is peeled off to form voids, whitening of the sheet progresses, and the light reflectivity of the film can be enhanced.
Further, it is more preferable that the cast sheet is stretched in the biaxial direction. The voids formed by uniaxial stretching are only in a fibrous form extending in one direction, but by biaxial stretching, the voids are elongated in both vertical and horizontal directions to form a disk shape.
That is, by biaxial stretching, the peeled area at the interface between the polyolefin resin and the fine powder filler inside the resin layer (B) increases, the whitening of the sheet further progresses, and as a result, the light reflectivity of the film is improved. It can be further enhanced. Further, when biaxially stretched, the anisotropy in the shrinkage direction of the film is reduced, so that the heat resistance of the film can be improved and the mechanical strength of the film can be increased.

The stretching temperature when stretching the cast sheet is a temperature within the range of the glass transition temperature (Tg) or more and (Tg + 50) ° C. or lower of the polyolefin resin contained in the resin layer (A) or the resin layer (C). preferable.
When the stretching temperature is equal to or higher than the glass transition temperature (Tg), the film can be stably carried out without breaking during stretching. Further, when the stretching temperature is (Tg + 50) ° C. or lower, the stretching orientation becomes high, and as a result, the porosity becomes large, so that a film having a high reflectance can be easily obtained.

The stretching order of the biaxial stretching is not particularly limited, and for example, simultaneous biaxial stretching or sequential stretching may be used. A cast sheet in a molten state may be obtained, then stretched in the flow direction (MD) by roll stretching, and then stretched in the lateral direction (TD) by tenter stretching, or biaxially stretched by tubular stretching or the like. good.
The draw ratio in the case of biaxial stretching is not limited. The area magnification is usually 4 times or more, preferably 5 times or more, more preferably 6 times or more, and the upper limit is usually 25 times or less, preferably 20 times or less, more preferably 15 times or less. By setting the area magnification within the above range, the porosity of the reflective material can be controlled within an appropriate range, and excellent reflection performance can be exhibited, which is preferable.
When sequential biaxial stretching is performed, the magnification of the first axial stretching is preferably 1.1 to 5.0 times, more preferably 1.5 to 3.5 times, and the magnification of the second axial stretching is high. It is preferably 1.1 to 5.0 times, more preferably 2.5 to 4.5 times.

After stretching, it is preferable to perform heat fixing in order to impart dimensional stability (morphological stability of voids) to the reflective material. The treatment temperature for heat-fixing the film is preferably 130 to 165 ° C. The treatment time required for heat fixation is preferably 1 second to 3 minutes.
Further, the stretching equipment and the like are not particularly limited, but it is particularly preferable to perform tenter stretching capable of performing a heat fixing treatment after stretching.

<Use>
The use of this reflector is not limited. Since this reflective material is excellent in reflective performance, it is useful as a reflective member used in a liquid crystal display device such as a liquid crystal display. In particular, it is useful for liquid crystal displays of thin portable information processing terminals such as smartphones and tablet terminals.
Generally, a liquid crystal display is composed of a liquid crystal panel, a polarizing reflection sheet, a diffusion sheet, a light guide plate, a reflection sheet, a light source, a light source reflector, and the like.
This reflective material can be suitably used as a reflective material that plays a role of efficiently incident light from a light source onto a liquid crystal panel or a light guide plate, and collects irradiation light from a light source arranged at an edge portion. It can also be suitably used as a light source reflector having a role of incident light on the light guide plate.

This reflective material is suitable as a reflective material provided in the backlight unit of the liquid crystal display. By using this reflective material, it is possible to reduce the occurrence of uneven brightness and the detachment of particles. There are no restrictions on the material of the light guide plate, for example, a backlight unit provided with various light guide plates made of polymethylmethacrylate (PMMA) resin, methylmethacrylate / styrene copolymer (MS resin), cycloolefin resin, etc. It can be suitably used for a backlight unit provided with a light guide plate made of MS resin.
Therefore, it is possible to provide a backlight unit including the present reflector and a light guide plate made of polymethylmethacrylate (PMMA) resin, methylmethacrylate / styrene copolymer (MS resin), cycloolefin resin, or the like. ..

This reflective material can be used as it is as a reflective material having the above-mentioned layer structure.
Further, it can be used as a structure laminated on a metal plate or a resin plate (collectively referred to as "metal plate or the like"), and is used for the above-mentioned applications, that is, liquid crystal display devices such as liquid crystal displays, lighting fixtures, lighting signs and the like. It is useful as a reflector as a constituent member.
Therefore, it is possible to provide a liquid crystal display device, a lighting fixture, or a lighting signboard using the present reflective material as a constituent member.

Examples of the metal plate on which the present reflective material is laminated include an aluminum plate, a stainless steel plate, and a galvanized steel plate.
The method of laminating the present reflective material on a metal plate or the like is not particularly limited. For example, a method using an adhesive, a method of heat-sealing, a method of adhering via an adhesive sheet, a method of extrusion coating, and the like can be mentioned.
More specifically, an adhesive such as polyester, polyurethane, or epoxy can be applied to the surface on the side where the reflective material such as a metal plate is bonded, and the reflective material can be bonded.
Next, the coated surface is dried and heated by an infrared heater and a hot air heating furnace, and while the surface of the metal plate or the like is maintained at a predetermined temperature, the reflective material is immediately coated and cooled by using a roll laminator to reflect the reflection. You can get a board.

Further, the present reflective material can be used for various purposes other than the above, for example, various industrial materials, packaging materials, optical materials, electric materials and the like.

<Explanation of terms>
In the present invention, the term "film" shall include a "sheet", and the term "sheet" shall also include a "film".
In the present invention, "reflection" means reflection of light unless otherwise specified, and more specifically, reflection of visible light.
When expressed as "X to Y" (X, Y are arbitrary numbers) in the present invention, unless otherwise specified, they mean "X or more and Y or less", and "preferably larger than X" and "preferably smaller than Y". Including the meaning of.
Further, when expressed as "X or more" (X is an arbitrary number), it includes the meaning of "preferably larger than X" unless otherwise specified, and when expressed as "Y or less" (Y is an arbitrary number). Unless otherwise specified, it includes the meaning of "preferably smaller than Y".

Examples will be shown below, and the present invention will be described in more detail. However, the present invention is not limited to these examples, and various applications are possible within a range that does not deviate from the technical idea of the present invention.

<Measurement and evaluation method>
The measurement method and evaluation method of the samples obtained in Examples and Comparative Examples will be described below.

(Glass transition temperature of organic particles and heat capacity of glass transition point (ΔCp))
Glass transition point (change between baseline shifts) when organic particles are heated to 250 ° C at a heating rate of 30 ° C / min using a differential scanning calorimeter (manufactured by PerkinElmer Japan, model name: DSC8500). The heat capacity of the inflection point) and the glass transition point was measured.

(Thickness of reflector)
The thickness of all layers of the reflector was measured with a film thickness meter.
Further, the total thickness of the resin layer (A) and the resin layer (C) and the thickness of the resin layer (B) were confirmed by observing the cross section of the reflective material with an electron microscope.
Regarding the three types and five layers of the reflective material (sample), the thickness of the resin layer (A) and the resin layer (C) is difficult to distinguish between the layer interfaces with a microscope, so the resin layer (A) and the resin layer It was obtained by multiplying the total thickness of (C) by the extrusion amount ratio at the time of sheet molding and rounding off to the first decimal place.

(Shape of organic particles in the resin layer (A))
Regarding the reflective material (sample) of the 3rd type 5 layer and the 2nd type 5 layer, it was confirmed whether or not the organic particles were deformed at the time of cross-sectional observation for thickness measurement, and the judgment was made according to the following criteria.
No deformation: It was almost the same as the particle shape of the raw material. In addition, "almost the same" means that the ratio (L / D) of the long side to the short side of the organic particles is 1.8 times or less when the resin layer (A) of the reflective material is observed with an optical microscope. .. In this case, the average particle size of the raw material particles can be regarded as the average particle size of the particles in the resin layer (A).
Deformed: It was deformed from the particle shape of the raw material. The resin layer (A) of the reflective material is observed with an optical microscope, and when the ratio (L / D) of the long side to the short side of the organic particles exceeds 1.8 times, it is judged to be "deformed". bottom. In this case, the average particle size of the raw material particles cannot be regarded as the average particle size of the particles in the resin layer (A).

(Average particle size of organic particles)
The average particle size of the organic particles in the resin layer (A) was as follows.
When the shape confirmation of the organic particles was "no deformation", the value of the average particle size of the raw material particles was adopted.
If the shape of the organic particles is confirmed to be "deformed", the surface of the resin layer (A) of the reflector is observed with an optical microscope, the diameters of three or more particles are measured, and the average value is obtained. rice field. At that time, when the cross-sectional shape was not circular, the average value of the longest diameter and the shortest diameter was used.

(Porosity)
The density of the laminated sheet before stretching (unstretched sheet density) and the density of the laminated sheet after stretching (stretched sheet density) are measured, and the porosity (%) of the reflective material (sample) made of the laminated sheet is calculated by the following formula. ) Was asked.
Porosity (%) = {(Unstretched sheet density-Stretched sheet density) / Unstretched sheet density} x 100

(Surface roughness)
With the reflector (sample) standing on a flat surface, Rz and Ra were measured for three randomly selected resin layer (C) side surfaces (one of the front and back surfaces), and the average value was calculated. The reflectors (samples) were Rz (μm) and Ra (μm).
For the measurement, "Surftest SJ-210" manufactured by Mitutoyo Co., Ltd. was used, and the measurement was performed with λc: 0.8 mm and λs: 2.5 mm based on JIS B0601 (2001).

(Planar optic tract of protrusion)
A scanning electron microscope (SEM, observation magnification of about 300 to 500 times) is used to measure the plane viewing diameter of the protrusions on the resin layer (C) side surface (one of the front and back surfaces) of the reflective material (sample). The surface of the reflective material, that is, the surface of the reflective material on the resin layer (C) side was observed from above, and the diameters of three or more arbitrary protrusions were measured and determined as the average value.

(Average reflectance)
The reflectance of the reflector (sample) when an integrating sphere is attached to a spectrophotometer (Hitachi High-Technologies Corporation "U-3900H") and the alumina white plate is 100% is 0.5 nm over a wavelength of 420 to 700 nm. Measured at intervals. The average value of the obtained measured values was calculated and used as the average reflectance (%).

(Evaluation of uneven brightness)
Using an edge light type backlight unit, we created an evaluation model in which the light guide plate is the outermost layer. Arrange the reflective material (sample) between the metal piece having a thickness of 0.5 mm and the light guide plate so that the resin layer (C) side (either the front or the back side) is on the light guide plate side, and place a weight (300 g) on the light guide plate. I turned on the edge light with it on. With a camera installed on the top of the light guide plate, it was confirmed whether or not brightness unevenness occurred in the vicinity of the metal piece, and the judgment was made according to the following criteria.
⊚ (excellent): No uneven brightness due to the edge of the metal piece was observed.
◯ (good): Although the brightness unevenness caused by the end of the metal piece is thin, it is suitable as a reflective material for a thin backlight or the like.
X (poor): Clear brightness unevenness was generated from the end of the metal piece, and it was not suitable as a reflective material for a thin backlight or the like.

(Tape peeling evaluation)
After attaching an adhesive tape (manufactured by 3M Japan Ltd., trade name "Scotch Ultratransparent Tape S BK-18") to the resin layer (C) side surface (one of the front and back sides) of the reflective material (sample). , The adhesive tape was peeled off, and the surface of the reflective material (sample) after the peeling was visually inspected, and the judgment was made according to the following criteria.
◎ (excellent): Peeling of the surface of the reflective material (sample) is hardly confirmed visually.
○ (better): Peeling of the surface of the reflective material (sample) is slightly confirmed visually.
Δ (good): Partial peeling of the surface of the reflective material (sample) is confirmed.
× (poor): Large peeling and a large amount of partial peeling on the surface of the reflective material (sample) are confirmed.

<Raw materials>
The raw materials used in Examples and Comparative Examples will be described below.
(COP-A)
Amorphous cycloolefin resin (MFR (230 ° C., 21.18N): 1.5g / 10 minutes, Tg: 129 ° C.)
(COP-B)
Amorphous cycloolefin resin (MFR (230 ° C., 21.18N): 15 g / 10 minutes, Tg: 105 ° C.)

(PP)
Polypropylene resin ("Novatec PP FY6HA" manufactured by Japan Polypropylene Corporation, MFR (230 ° C, 21.18N): 2.3 g / 10 minutes)
(Organic particles)
Methyl methacrylate-based crosslinked resin particles (Tg: 138 ° C., ΔCp: 0.20 J / (g · ° C.), average particle size (D50): 12 μm)

(Titanium oxide)
"KRONOS2450" manufactured by KRONOS (rutile type titanium oxide produced by the chlorine method and surface-treated with alumina and silica, TiO ₂ content 96.0%, average particle size (D50): 0.31 μm)
(Calcium carbonate)
"Softon 3200" manufactured by Bikita Powder Industry Co., Ltd. (Average particle size (D50): 0.70 μm)

<Example 1>
(Preparation of Resin Composition A)
COP-A, COP-B, PP pellets and organic particles are mixed in a mass ratio of COP-A / COP-B / PP / organic particles = 50: 25: 21: 4, and then a twin-screw extruder is used. The mixture was melt-kneaded at 220 ° C. and pelletized to prepare a resin composition A as a raw material for the resin layer (A).
(Preparation of Resin Composition B)
The PP pellets and the fine powder filler are mixed at a mass ratio of PP: titanium oxide: calcium carbonate = 55: 40: 5, and then melt-kneaded at 270 ° C. using a twin-screw extruder to pelletize the resin layer. A resin composition B was prepared as a raw material of (B).
(Preparation of Resin Composition C)
The pellets of COP-A, COP-B, and PP are mixed at a mass ratio of COP-A / COP-B / PP = 50: 25: 25, and then melt-kneaded at 220 ° C. using a twin-screw extruder. It was pelletized to prepare a resin composition C as a raw material for the resin layer (C).

(Making reflective material)
The resin compositions A, B, and C are supplied to the extruders A, B, and C, which are gradually heated to 220 ° C., and melted in each of the extruders, and then the resin layer (C) and the resin layer ( The extrusion amount of A) is adjusted to be 3.0 kg / h and 1.1 kg / h, respectively, and the thickness ratio of the resin layer (C) to the resin layer (A) is 0.7: 0.3. Then, it is merged with the T-die for 3 types and 5 layers so as to have a resin layer (C) / resin layer (A) / resin layer (B) / resin layer (A) / resin layer (C) 5 layer structure. It was extruded into a sheet and cooled and solidified to form a non-stretched laminated sheet.
The obtained laminated sheet was roll-stretched 2.3 times in the film flow direction (MD) at a temperature of 142 ° C., and then biaxially stretched by tenter stretching 3 times in the orthogonal direction (TD) at 136 ° C. Then, the heat fixing treatment was further performed at 158 to 162 ° C. for 2 minutes to obtain a reflective material (sample) composed of a laminated sheet having a total thickness of 71 μm.
The obtained reflective material was evaluated for the shape of organic particles, void ratio, surface roughness, plane viewing diameter of protrusions, average reflectance, luminance unevenness evaluation and tape peeling evaluation, and the results are shown in Tables 1 and 2.

<Example 2>
The extrusion amounts of the resin layer (C) and the resin layer (A) are 2.8 kg / h and 3.0 kg / h, respectively, and the thickness ratio of the resin layer (C) and the resin layer (A) is 0.5: 0. A reflector (sample) was obtained in the same manner as in Example 1 except that the extrusion amount of the extruder A to which the resin composition A was supplied was adjusted so as to be 5. The obtained reflective material (sample) was evaluated in the same manner as in Example 1, and the results are shown in Tables 1 and 2.

<Example 3>
The extrusion amounts of the resin layer (C) and the resin layer (A) are 1.1 kg / h and 3.1 kg / h, respectively, and the thickness ratio of the resin layer (C) and the resin layer (A) is 0.3: 0. Except for adjusting the extrusion amounts of the extruder A to which the resin composition A is supplied and the extruder C to which the resin composition C is supplied so as to be 7, and setting the heat fixing treatment temperature between 157 and 162 ° C. Obtained a reflective material (sample) in the same manner as in Example 1. The obtained reflective material (sample) was evaluated in the same manner as in Example 1, and the results are shown in Tables 1 and 2.

<Comparative example 1>
Using the resin composition C instead of the resin composition A, a resin layer (C) / resin layer (C) / resin layer (B) / resin layer (C) / resin layer (C) is composed of two types and five layers. The resin layer (C) was extruded into a sheet at 2.6 kg / h and 2.7 kg / h, respectively, and the heat fixing treatment temperature was between 157 and 162 ° C. A reflective material (sample) was obtained in the same manner. The obtained reflective material (sample) was evaluated in the same manner as in Example 1, and the results are shown in Tables 1 and 2.

<Comparative example 2>
Using the resin composition A instead of the resin composition C, a resin layer (A) / resin layer (A) / resin layer (B) / resin layer (A) / resin layer (A) is composed of two types and five layers. The resin layer (A) was extruded into a sheet at 3.0 kg / h and 2.9 kg / h, respectively, and the heat fixing treatment temperature was between 157 and 162 ° C. A reflective material (sample) was obtained in the same manner. The obtained reflective material (sample) was evaluated in the same manner as in Example 1, and the results are shown in Tables 1 and 2.

<Comparative example 3>
In the preparation of the resin composition A, the pellets and organic particles of COP-A, COP-B, and PP were set to a mass ratio of COP-A / COP-B / PP / organic particles = 50:25:17: 8, and the resin was prepared. The extrusion amounts of the layer (C) and the resin layer (A) are 1.8 kg / h and 3.0 kg / h, respectively, and the thickness ratio of the resin layer (C) and the resin layer (A) is 0.4: 0.6. Except for adjusting the extrusion amounts of the extruder A to which the resin composition A is supplied and the extruder C to which the resin composition C is supplied so that the heat fixing treatment temperature is between 157 and 162 ° C. A reflective material (sample) was obtained in the same manner as in Example 1. The obtained reflective material (sample) was evaluated in the same manner as in Example 1, and the results are shown in Tables 1 and 2.

<Comparative example 4>
The extrusion amounts of the resin layer (C) and the resin layer (A) are 1.1 kg / h and 3.1 kg / h, respectively, and the thickness ratio of the resin layer (C) and the resin layer (A) is 0.2: 0. The reflective material (sample) was prepared in the same manner as in Comparative Example 3 except that the extrusion amounts of the extruder A to which the resin composition A was supplied and the extruder C to which the resin composition C was supplied were adjusted so as to be 8. Obtained. The obtained reflective material (sample) was evaluated in the same manner as in Example 1, and the results are shown in Tables 1 and 2.

As is clear from Tables 1 and 2, in Examples 1 to 3, the resin layer (A) containing organic particles is laminated between the resin layer (C) and the resin layer (B). It was confirmed that the reflectance was high and the uneven brightness was suppressed, and that the surface of the reflective material was less peeled off, and the desorption of organic particles contained in the resin layer (A) was suppressed.
On the other hand, it was confirmed that the reflective material of Comparative Example 1 having no resin layer (A) could not suppress the uneven brightness, and the reflective material of Comparative Example 2 having no resin layer (C) was on the surface of the reflective material. It was confirmed that there is a problem in practical use because the particles are easily detached due to the large amount of peeling.
Further, in Comparative Example 3 and Comparative Example 4 in which the organic particle content of the resin layer (A) is 8% by mass, the uneven brightness is suppressed, but the particles are easily detached because the surface of the reflective material is often peeled off. It was confirmed that there was a problem in practical use.

Claims (9)

A resin layer (B) containing a polyolefin resin and a fine powder filler, and
A resin layer (A) containing a polyolefin resin and organic particles,
A resin layer (C) containing a polyolefin resin and not containing organic particles having a particle size of 5 μm or more is laminated in this order.
The plane viewing diameter of the protrusions on the surface of the resin layer (C) side is 5 μm to 20 μm.
The content of organic particles in the resin layer (A) is 3% by mass or more and 6% by mass or less.
A reflective material in which any one or more of the resin layers (A) to (C) has voids. The reflective material according to claim 1, wherein the thickness ratio of the resin layer (C) to the resin layer (A) is in the range of 0.8: 0.2 to 0.2: 0.8. The reflective material according to claim 1 or 2, wherein the organic particles are crosslinked particles. The reflective material according to any one of claims 1 to 3, wherein the porosity is 10 to 80%. The reflection according to any one of claims 1 to 4, wherein either one or both of the polyolefin resin of the resin layer (A) and the polyolefin resin of the resin layer (C) are polypropylene resin or cycloolefin resin. Material. The reflective material according to any one of claims 1 to 5, wherein the polyolefin resin of the resin layer (A) and the resin layer (C) is the same resin. The reflective material according to any one of claims 1 to 6, which is used as a constituent member of the backlight unit. The reflective material according to any one of claims 1 to 7, which is used as a constituent member of any of a liquid crystal display, a lighting fixture, and a lighting signboard. A liquid crystal display, a lighting fixture, or a lighting signboard having the reflective material according to any one of claims 1 to 8 as a constituent member.