JP2020011430A - Reflector - Google Patents

Abstract

To provide a reflector that has excellent reflection characteristics, can reduce the occurrence of uneven luminance and damage to a light guide plate when used in a backlight unit, and can accommodate the slimming down of liquid crystal displays.SOLUTION: A reflector has a resin layer (A) containing a polyolefin resin as a main component resin and organic particles, and a resin layer (B) containing a polyolefin resin. The reflector has cavities, and the organic particles in the resin layer (A) have a deformation stress of 1.5-2.2 kgf/mm.SELECTED DRAWING: None

Description

  The present invention relates to a reflector. More specifically, the present invention relates to a reflector that can be suitably used as a constituent member of a liquid crystal display, a lighting fixture, a lighting signboard, and the like.

  Reflectors are used in many fields, such as liquid crystal displays, lighting equipment and lighting signs. In recent years, in the field of liquid crystal displays, the size of the device and the sophistication of display performance have advanced, and it has been required to improve the performance of the backlight unit by supplying even a little light to the liquid crystal. , There is a demand for even better light reflectivity (also simply referred to as "reflectivity").

As this type of reflective material, for example, a reflective film for a liquid crystal display using a white polyester film mainly composed of 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 light, so that the film is deteriorated and yellowed by ultraviolet light 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 reduced.

In addition, a film formed by adding a filler to a polypropylene resin is stretched to form a fine void in the film to generate light scattering reflection (see Patent Document 2), or a polyolefin resin. There is also known a polyolefin resin light reflector having a laminated structure composed of a base material layer containing a polyolefin resin and a layer containing a polyolefin resin (see Patent Document 3).
The reflection film using such a polyolefin resin is characterized in that there is little problem of deterioration and yellowing of the film due to ultraviolet rays.

  Further, there is known a biaxially stretched reflective sheet containing a polypropylene resin and at least one resin incompatible with the polypropylene resin and having a reduced heat shrinkage (see Patent Document 4). This reflective sheet has a feature that even if it does not contain a large amount of inorganic powder, it exhibits a higher reflectance than a conventional reflective sheet having the same basis weight and density.

In recent years, liquid crystal displays have been required to be thinner, and backlights provided in liquid crystal displays have also been required to be thinner.
When the backlight is made thin, members such as the rear housing and the light guide plate need to be thin. However, when these members are thinned, the mechanical strength of the backlight is reduced. For example, when an external force is applied to the display main body, the light guide plate and the reflective material locally come into strong contact with each other, causing uneven brightness and uneven color ( Hereinafter, it will be referred to as “brightness unevenness”). Therefore, for a backlight used for a thinned liquid crystal display, a reflective material further provided with a function of preventing luminance unevenness is required.
As a means for solving such a problem of luminance unevenness, a reflector in which specific particles are applied to a specific reflector has been proposed (Patent Document 5).

JP 04-239540 A JP-A-11-174213 JP 2005-031653 A JP 2008-158134 A JP-A-2015-163986

Conventionally, a light guide plate used for a backlight unit of a liquid crystal display is mainly made of polymethyl methacrylate (PMMA) resin. However, since it is easy to form a dot shape (concave shape) necessary for the function of the light guide plate, in recent years, it is made of a methyl methacrylate / styrene copolymer (hereinafter, also referred to as “MS resin”). The use of light guide plates is increasing.
According to the study of the present inventors, the light guide plate made of MS resin has a feature that it is more easily deformed than the light guide plate made of PMMA, and the thinner the light guide plate, the more easily it is deformed. When the reflector disclosed in Document 5 is used in combination with a light guide plate made of MS resin, there is a problem that the reflector and the light guide plate easily come into contact with each other due to an external force applied to the liquid crystal display main body. It has been found that the light guide plate may be scratched and scratched. If the light guide plate is damaged, a screen error causes a product defect.

  Accordingly, an object of the present invention is to have a favorable reflection characteristic, to reduce the occurrence of uneven brightness and to prevent the light guide plate from being damaged when used in a backlight unit, and to be able to cope with a thin liquid crystal display. The object of the present invention is to provide a reflective material.

The present invention is a reflective material having a resin layer (A) containing a polyolefin resin and organic particles as a main component resin, and a resin layer (B) containing a polyolefin resin, and having a void. A reflective material is proposed in which the organic particles contained in the layer (A) have a deformation stress of 1.5 to 2.2 kgf / mm ² .

  ADVANTAGE OF THE INVENTION According to the reflective material which this invention proposes, it has favorable reflection characteristics, and when it is used for a backlight unit, it is possible to reduce the occurrence of luminance unevenness and the damage to the light guide plate. It is a reflective material that can respond to the development. Therefore, the reflecting material proposed by the present invention can be suitably used as a reflecting material for a liquid crystal display device such as a liquid crystal display, a lighting fixture, or a lighting signboard.

  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 reflective material >>
The reflecting material (referred to as “the present reflecting material”) according to an example of the embodiment of the present invention includes a resin layer (A) containing a polyolefin resin and organic particles as main component resins, and a resin layer containing a polyolefin resin ( B), and having a void.

  In the present invention, the “main component resin” means a resin having the largest mass ratio among the resins constituting each layer, and is allowed to contain another resin within a range not to impair the function of the main component resin. I do. At this time, the content ratio of the main component resin accounts for 50% by mass or more, preferably 70% by mass or more, particularly preferably 90% by mass or more (including 100%) of the resin constituting each layer.

<Resin layer (A)>
The resin layer (A) is a layer containing a polyolefin resin as a main component resin and containing organic particles.

  In the configuration of the present reflecting material, the arrangement of the resin layer (A) is not limited. For example, as described later, it is preferable to dispose as a surface layer of the reflection material, specifically, as a surface layer on the reflection use surface side. On the other hand, the arrangement in the backlight member is preferably located on the surface that comes into contact with the light guide plate.

The technical idea of the present invention can be considered as follows. However, the present invention is not at all limited by the scope of the following technical idea.
In a backlight unit using a light guide plate made of PMMA resin, which has been conventionally used, when a reflecting material made of polyolefin resin is used, luminance unevenness rarely occurs. On the other hand, when the backlight unit is made thinner and the light guide plate is made of MS resin, the use of a polyolefin resin-made reflector tends to cause uneven brightness.
According to the present inventor, the causes are (1) a decrease in mechanical strength due to the reduction in thickness of the backlight and an increase in the degree of deformation with respect to external force, and (2) a convex shape made of PMMA resin. It is considered that the shape of the light guide plate has been changed to a concave shape when made of MS resin, and the contact area with the reflector has increased, and (3) the light guide plate has been softened, so that the light guide plate has become easier to contact with the reflector. Was done.
It has also been found that such a phenomenon is more remarkable in a flexible (low elastic modulus) polyolefin resin-based reflector than in a relatively rigid (high elastic modulus) polyester resin-based reflective material. did.
Therefore, as a result of a study of suppressing luminance unevenness in a polyolefin resin-based reflective material, specific organic particles are contained in a layer containing a polyolefin resin as a main component resin (also referred to as a “polyolefin resin layer”), and projections are formed on the surface layer. It has been confirmed that by forming a layer, over contact with the light guide plate can be suppressed, and luminance unevenness can be suppressed.
On the other hand, simply avoiding excessive contact with the light guide plate due to the protrusions of the organic particles may cause stress concentration at the protrusions at the time of contact, which may scratch the flexible light guide plate made of MS resin at the protrusions of the reflective material. found. According to the present inventors, it has been found that, by optimizing the organic particles, luminance unevenness can be suppressed and abrasion to a light guide plate made of MS resin can be suppressed.

Conventionally, a coating method has been mainly used as a technique for providing a layer containing a large amount of organic particles having a large particle diameter. However, when the organic particle-containing layer is provided by a coating method, although the surface roughness increases, problems such as falling off of particles and a decrease in recyclability (self-recycling) may occur. Problems such as curl (curling habit) and reduction in production efficiency may also occur.
On the other hand, according to the present invention, the organic particles are contained in the polyolefin resin layer, thereby eliminating the need to provide a layer containing the organic particles by coating. For example, it is possible to adopt a co-extrusion method, so that the surface roughness is increased, the falling of particles is suppressed, the recyclability (self-recycling property) is improved, and there is no peeling or curling from the substrate. Also, the manufacturing efficiency can be greatly improved. The method of providing the resin layer (A) in the present invention does not exclude a coating method.

(Polyolefin resin)
The type of the polyolefin resin as the main component resin of the resin layer (A) is not limited. For example, polypropylene resins such as polypropylene, propylene-ethylene copolymer, propylene / α-olefin copolymer; polyethylene resins such as high-density polyethylene, low-density polyethylene, ethylene / α-olefin copolymer; polymethylpentene Α-olefin resin, cycloolefin resin such as ethylene-cyclic olefin copolymer, and at least one selected from olefin elastomers such as ethylene-propylene rubber (EPR) and ethylene-propylene-diene terpolymer (EPDM). Polyolefin resin.
Among these, a polypropylene resin, a cycloolefin resin, or a combination of both is preferred from the viewpoint of mechanical properties and flexibility. Among them, it is particularly preferable to use a cycloolefin resin as a main component resin. The cycloolefin resin has low absorption of visible light and has heat resistance, and thus is suitable as a 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. It is preferable that the content of the polyolefin resin is equal to or more than the above lower limit, since it becomes possible to impart good flexibility to the present reflective material.
Also, the upper limit of the content of the polyolefin resin in the resin layer (A) is not limited, and is preferably 99% by mass or less, more preferably 98% by mass or less, and further preferably 97% by mass or less. It is preferable that the content of the polyolefin resin is equal to or less than the upper limit value, because the rupture resistance, bending resistance, luminance unevenness prevention function, and the like of the present reflective material are improved.
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 as a main component resin of the resin layer (A) will be described.

  The cycloolefin resin is a polymer compound having a main chain composed of carbon-carbon bonds 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 typified by norbornene or tetracyclododecene. Is done.

  Cycloolefin resins are classified as cycloolefin addition polymers or hydrogenated products thereof, cycloolefin and α-olefin addition polymers or hydrogenated products thereof, cycloolefin ring-opened polymers or hydrogenated products thereof, Can also be used as the cycloolefin resin. Further, the cycloolefin resin may be a cycloolefin homopolymer or a cycloolefin copolymer.

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

Tricyclic cycloolefins such as tricyclo [4.3.0.12,5] deca-3,7-diene (common name: dicyclopentadiene);
4-cyclic cycloolefins such as tetracyclo [4.4.0.12,5.17,10] dodec-3-ene (also referred to simply as tetracyclododecene);
8-cyclopentyl-tetracyclo [4.4.0.12,5.17,10] dodec-3-ene, tetracyclo [8.4.14,7.01,10.0,8] pentadeca-5,10, Polycyclic cycloolefins such as 12,14-tetraene (also referred to as 1,4-methano-1,4,4a, 5,10,10a-hexahydroanthracene); tetramer of cyclopentadiene and the like can be mentioned. it can.
These cycloolefin resins can be used alone or in combination of two or more as a copolymer.

  Specific examples of the α-olefin copolymerizable with the cycloolefin include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene, 3-methyl-1-pentene, -Ethyl-1-pentene, 4-methyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1- Hexene, 3-ethyl-1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, etc. Examples include 2 to 8 ethylene or α-olefin. 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 “main component” means a 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 hinder the function of the main component. . At this time, the content ratio of the main component accounts for 50% by mass or more, preferably 70% by mass or more (including 100%) of the component 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 processing performance such as stretching by using the α-olefin as a copolymer component, and copolymerizing the cycloolefin. From the viewpoint of obtaining a good balance of the heat resistance effect of the component as the main component, the content of the cycloolefin component in the cycloolefin resin is preferably from 60 to 90% by mass, more preferably 65% by mass or more or 80% by mass or more. It is more preferable that the content is not more than mass%.
The method for polymerizing cycloolefin or cycloolefin with α-olefin and the method for hydrogenating the obtained polymer are not particularly limited, and can be carried out according to a known method.

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

The cycloolefin resin may be crystalline or amorphous. Especially, it is preferable that it is 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, and still more preferably 150 ° C. or lower. .
When the glass transition temperature of the cycloolefin resin is in the above range, the stretching processability tends to be good.
Here, the “glass transition temperature (Tg)” is a value read by a differential scanning calorimeter when the temperature is increased at a rate of 10 ° C./min.
In addition, two or more types of cycloolefin resins may be combined and mixed, and the glass transition temperature (Tg) of the mixed resin may be adjusted to the above range.

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

The content of the cycloolefin resin in the resin layer (A) is not limited. It is preferably at least 30% by mass, more preferably at least 35% by mass, still more preferably at least 40% by mass. When the content of the cycloolefin resin is equal to or more than the lower limit, it is possible to impart good heat resistance to the present reflective material, 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 at most 85% by mass, more preferably at most 80% by mass, further preferably at most 75% by mass.
It is preferable that the content of the cycloolefin resin is equal to or less than the above upper limit, because the breakage resistance, bending resistance, luminance unevenness prevention function, and the like of the reflective material are improved.

  Commercial products can be used as the cycloolefin resin. For example, "Zeonor (registered trademark)" (hydrogenated product of a cyclic olefin ring-opening polymer) manufactured by Zeon Corporation, "Apel (registered trademark)" (addition copolymer of ethylene and tetracyclododecene) manufactured by Mitsui Chemicals, Inc. ) And “TOPAS (registered trademark)” (addition copolymer of ethylene and norbornene) manufactured by Polyplastics Co., Ltd. Among them, "ZEONOR" and "TOPAS" are preferable since they have a small light absorbing effect and can provide a reflective material having high reflective performance.

(Other polyolefin resins)
When a cycloolefin resin is used as the polyolefin resin which is the main 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). In some cases, the formation can further enhance the folding resistance and heat resistance.
Further, only the “other polyolefin resin” may be used without using the cycloolefin resin as the resin layer (A).

The melt flow rate (MFR) of the “other polyolefin resin” is not limited. Among them, the value measured at 230 ° C. and a load of 21.18 N according to JIS K7210 is preferably 0.1 to 20 g / 10 min, and more preferably 0.5 g / 10 min or more or 10 g / 10 min or less. Is more preferable.
When the cycloolefin resin is used in combination with the “other polyolefin resin”, the MFR of the cycloolefin resin is preferably adjusted to the above range. Adjusting the MFR of the two in this manner tends to improve the mechanical properties of the reflector.

  As the “other polyolefin resin”, one or a combination of two or more of the polyolefin resins exemplified above as the main component resin of the resin layer (A) can be used. Among them, polyethylene-based resins and polypropylene-based resins are preferred, and among them, polypropylene-based resins are preferred from the viewpoints 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-based resin, the melt flow rate (MFR) is 0.1 to 20 g / 10 min as a value measured at 230 ° C. and a load of 21.18 N from the viewpoint of extrusion moldability. It is preferable that it is not less than 0.2 g / 10 min or not more than 10 g / 10 min, more preferably not less than 0.5 g / 10 min or not more than 5 g / 10 min.

When a cycloolefin resin and “another polyolefin resin” are used in combination as a resin component constituting the resin layer (A), the MFR of the cycloolefin resin (“MFR (CO)”) and the “other polyolefin resin” Is preferably MFR (CO): MFR (PO) = 1: 0.05 to 1:20, and 1: 0.1 to 1:10. More preferably, there is.
When the relationship between the two MFRs is within the above range, it is preferable because the other polyolefin resin tends to be oriented in the cycloolefin resin and the mechanical properties as a reflector tend to be improved.

The content of the “other polyolefin resin” in the resin layer (A) is not limited. When used in combination with a cycloolefin resin, the content is preferably 2% by mass or more, more preferably 5% by mass or more, and still more preferably 10% by mass or more. Also, the upper limit is not limited. It is preferably at most 40% by mass, more preferably at most 30% by mass, even more preferably at most 25% by mass.
When the content of the “other polyolefin resin” is equal to or more than the lower limit, it is possible to more effectively suppress the breakage of the resin layer (A) during stretching, and to reduce the resin layer (A) and the resin layer (B). Is preferable because the adhesiveness of the film is kept higher. When the adhesiveness is equal to or less than the above upper limit, the heat resistance and the function of preventing uneven brightness tend to be further improved.

(Organic particles)
The resin layer (A) of the present reflector contains organic particles.
Here, “organic particles” correspond to any particulate matter composed of an organic substance. Preferred are resin particles, and examples thereof include so-called polymer beads and polymer hollow particles.
The type of the organic particles as the resin particles is not limited. For example, (meth) acrylate-based resin particles, styrene-based resin particles, silicone-based resin particles, nylon-based resin particles, polyethylene-based resin particles, and benzoguanamine-based resin spherical particles And urethane-based resin spherical particles.
Here, “(meth) acrylate” means acrylate or methacrylate.
These organic particles may be a homopolymer or a copolymer. These can be used alone or in combination of two or more.

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

The shape of the organic particles contained in the resin layer (A) is not limited, and may be, for example, a sphere, a rod, a flat plate, a pulverized product or an agglomerate having no specific shape, or an amorphous product. Good. Among these, the shape of the organic particles is preferably spherical.
Here, the term “spherical” does not necessarily mean only a true sphere, but corresponds to a visual sphere. Specifically, for example, a particle having a circular, substantially circular, elliptical, substantially elliptical, or a shape surrounded by a circular arc having a curvature corresponds to the shape of the particle.

  When the resin layer (A) is located on the outermost layer, which is the reflection surface of the reflection material, spherical organic particles are contained in the resin layer (A) to form projections on the surface of the resin layer (A). The height, the size, and the shape of the projection can be made relatively uniform, as compared with the case where the projection is formed using regular particles. By adjusting the height, size, and shape of the projections in this way, it is possible to further suppress sticking between the reflective film and the light guide plate and further suppress damage to particles.

The organic particles are preferably particles that have been subjected to a crosslinking treatment (referred to as “crosslinked particles”). By performing the cross-linking treatment, it is easy to maintain the shape of the particles even in a state where a deformation stress is applied in a heating state during extrusion film formation.
Whether or not the organic particles are crosslinked particles can be confirmed by, for example, swelling without dissolving when immersed in a solvent (good solvent) that dissolves if not crosslinked. In that case, you may heat suitably. In addition, it can be confirmed by a nuclear magnetic resonance spectrum (NMR) or an infrared absorption spectrum (IR).
In order to make the organic particles into 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 deformation stress of the organic particles contained in the resin layer (A) is preferably from 1.5 to 2.2 kgf / mm ² . Here, the deformation stress of the organic particles can be defined as a value measured by a method described in Examples described later.
When the deformation stress of the organic particles is equal to or more than the above lower limit, even when an external force is applied to the display body and the light guide plate and the reflective material come into contact with each other in the backlight unit, the occurrence of luminance unevenness is more effectively suppressed. It is possible to do. It is considered that this is because excessive contact between the light guide plate and the reflector is suppressed by the protrusions on the surface of the reflector formed by the organic particles.
On the other hand, when the deformation stress of the organic particles is equal to or less than the upper limit, since the organic particles are not too hard, even when a light guide plate made of MS resin is used, it is possible to prevent the light guide plate surface from being shaved. Thus, it is considered that the effect of preventing damage can be further achieved.
Note that these effects are not exhibited only by the organic particles themselves, but that the main component resin constituting the resin layer (A) containing the organic particles is a polyolefin resin. Apart from this, it is also considered important to have a laminated structure having a resin layer (B) containing a polyolefin resin.

For the same reason as described above, the lower limit of the deformation stress of the organic particles is more preferably 1.55 kgf / mm ² or more, still more preferably 1.6 kgf / mm ² or more, and the upper limit is more preferably 2.1 kgf / mm ^2. mm ^2, and still more preferably not more than 2.0 kgf / mm ^2.
As a method for controlling the deformation stress of the organic particles within the above range, when the organic particles are resin particles, a resin skeleton (for example, (meth) acrylate type, styrene type, etc.), a monomer (copolymerization In some cases, it can be adjusted by the type of the monomer and the composition ratio, the molecular weight (in the case of crosslinked particles, the degree of crosslinking) and the like.

The glass transition temperature (Tg) of the organic particles contained in the resin layer (A) is preferably 150 ° C. or higher. By including the organic particles having a Tg of 150 ° C. or more in the resin layer (A), it is possible to impart a specific hardness to the surface of the reflective material, and it is possible to more effectively suppress luminance unevenness. Tend. The lower limit of the Tg of the organic particles is preferably at least 150 ° C, more preferably at least 160 ° C, still more preferably at least 170 ° C, particularly preferably at least 180 ° C.
The upper limit of the Tg of the organic particles is preferably 260 ° C. or less. By including organic particles having a Tg of 260 ° C. or lower in the resin layer (A), the hardness of the reflector surface is prevented from becoming excessively high. Tends to be possible. The upper limit of the Tg of the organic particles is preferably at most 260 ° C, more preferably at most 240 ° C.
Here, the glass transition temperature is a value 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.
In general, Tg changes by crosslinking organic particles. This is because the molecular motion of the polymer chain is restricted by the crosslinking point.
In the present invention, when the organic particles are crosslinked particles and the Tg is within the above range, it is particularly preferable in terms of suppressing luminance unevenness and suppressing abrasion of the light guide plate.

The average particle size of the organic particles is preferably 15 to 60 μm. When the average particle size of the organic particles is 15 μm or more, there is a tendency that protrusions having a height of 10 μm or more can be efficiently formed on the surface. On the other hand, when the average particle size of the organic particles is 60 μm or less, there is a tendency that falling off of the particles can be more suitably suppressed.
From the above viewpoint, the lower limit of the average particle size of the organic particles is more preferably 17 μm or more, and further preferably 20 μm or more. The upper limit of the average particle size of the organic particles is more preferably 55 μm or less, and further preferably 50 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 an average particle size (D50) determined from a volume-based particle size distribution measured by a dynamic light scattering method or the like.
The average particle diameter of the organic particles contained in the resin layer (A) can be 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 diameter of more than one particle can be measured and determined as the average value. At that time, when the cross-sectional shape is elliptical, the average value of the longest diameter and the shortest diameter can be measured as the diameter of each particle.

  The content of the organic particles in the resin layer (A) is preferably 0.5 to 20% by mass, more preferably 1% by mass or more and 10% by mass or less, and particularly preferably 2% by mass or more or 5% by mass or less. It is particularly preferred that the content be not more than mass%. When the content of the organic particles is equal to or more than the lower limit, it is preferable that the specific hardness or roughness can be more easily applied to the surface of the reflective material.If the content of the organic particles is equal to or less than the upper limit, This is preferable because production can be performed more efficiently without impairing continuous productivity during extrusion film formation.

(Fine powder filler)
The resin layer (A) may contain, together with the organic particles, a fine powder filler other than the organic particles (hereinafter, referred to as “fine powder filler”).
By containing the fine powder filler in the resin layer (A), in addition to light scattering due to the difference in the refractive index between the polyolefin resin and the like and the fine powder filler, around the fine powder filler in the process of manufacturing the reflective material The light scattering due to the difference in the refractive index between the formed cavity and the polyolefin resin, and the light scattering due to the difference in the refractive index between the cavity formed around the fine powder filler and the fine powder filler, etc. The reflection characteristics tend to be further improved. When sufficient light reflectivity can be ensured by the resin layer (B), the resin layer (A) does not need to contain a fine powder filler.

  Regarding the type, particle size, and surface treatment method of the fine powder filler that can be used for the resin layer (A), those described as the fine powder filler that can be used for the resin layer (B) described below can be similarly used. It can be used, and preferred examples are also the same. Here, among the matters described below as the fine powder filler used for the resin layer (B), “resin layer (B)” is to be read as “resin layer (A)”.

The average particle size of the fine powder filler contained in the resin layer (A) is preferably 0.05 μm or more and 15 μm or less, 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 polyolefin resin does not decrease, so that a more uniform reflector can be obtained. Further, when the average particle size is 15 μm or less, the interface between the polyolefin resin and the finely divided filler is formed densely, so that a higher-reflection reflective material with higher reflectivity can be obtained.

The average particle size of the finely divided filler can be measured as follows.
The average particle size of the finely divided filler as a raw material is determined by using an average particle size (D50) obtained from a volume-based particle size distribution measured by a dynamic light scattering method or the like, or by using a centrifugal sedimentation type particle size distribution measuring device. The average particle size (D50) can be measured as the particle size of 50% of the integrated (mass basis) in the measured equivalent spherical distribution.
The average particle size of the fine powder filler contained in the resin layer (A) can be determined by observing the surface of the resin layer (A) or the cross section of the present reflector using an optical microscope or a scanning electron microscope (SEM). The diameter of 10 or more particles can be measured and the average value can be obtained. At that time, in the case of non-spherical particles, 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 reflecting material is preferable.

  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. In consideration of the light reflectivity, mechanical strength, productivity, and the like of the present reflective material, the content is preferably 10 to 80% by mass, and more preferably 20% by mass or more and 70% by mass or less based on the entire resin layer (A). It is even more preferred. 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 ensured, and the reflection material can provide higher reflection. Properties can be imparted. It is preferable that the content of the fine powder filler is 80% by mass or less, because the mechanical strength required for the reflector can be more effectively secured.

(Other ingredients)
The resin layer (A) may further contain components other than the polyolefin resin, the organic particles, and the fine powder filler as “other components”.
"Other components" include resin components other than the above (including thermoplastic elastomers), antioxidants, light stabilizers, heat stabilizers, dispersants, ultraviolet absorbers, fluorescent brighteners, compatibilizers, Fillers other than lubricants and finely divided fillers can be mentioned.

In addition, as long as the performance of the present reflector is not impaired, a recycled material generated in the manufacturing process of the present reflector may be contained in the resin layer (A).
The content ratio of the recycled raw material is not limited, and is preferably 1 to 60% by mass, more preferably 10% by mass or more and 50% by mass or less based on the total mass of the resin layer (A). . If the content is 10% by mass or more, a cost advantage of using a recycled material occurs, and if the content is 50% by mass or less, the light reflectivity required for the reflector and the mechanical strength tend not to be impaired. It is in.

<Resin layer (B)>
The resin layer (B) in the present reflecting material is a layer containing a polyolefin resin.
By providing the resin layer (B) together with the resin layer (A), the present reflector can obtain the following effects (i) to (iii), for example. That is, (i) the resin layer (B) is provided with light reflectivity, and the resin layer (A) is provided with heat resistance, or (ii) the resin layer (B) is provided with light reflectivity. (A) is given rigidity as a reflecting material, or (iii) light is reflected on the surface of the resin layer (A), and light transmitted through the resin layer (A) is reflected in the resin layer (B). For example, there is an advantage that functions can be separated, and further excellent heat resistance and folding resistance can be obtained together with higher reflection performance.

  The resin layer (B) may contain another resin as long as it contains a polyolefin resin. However, from the viewpoint of improving the adhesion to the resin layer (A), it is preferable to contain a polyolefin resin as a main component resin.

(Polyolefin resin)
The polyolefin resin used for the resin layer (B) is not limited, and may be selected from those exemplified as the polyolefin resin for the resin layer (A). For example, polypropylene, polypropylene resins such as propylene-ethylene copolymers, high-density polyethylene, low-density polyethylene, polyethylene resins such as ethylene-α-olefin copolymers, and cycloolefin resins such as ethylene-cyclic olefin copolymers And at least one polyolefin resin selected from olefin elastomers such as ethylene-propylene rubber (EPR) and ethylene-propylene-diene terpolymer (EPDM). Among these, polypropylene resin and polyethylene resin are preferable from the viewpoint of mechanical properties and flexibility, and among them, polypropylene (propylene homopolymer) is most preferable.

  In addition, the polyolefin resin of the resin layer (B) may be a polyolefin resin different from the polyolefin resin that is the main component resin of the resin layer (A). However, from the viewpoint of increasing the adhesion between the resin layers (A) and (B), it is preferable to use a polyolefin resin containing the same monomer unit as the polyolefin resin that is the main component resin of the resin layer (A).

  The polyolefin resin used for the resin layer (B) has a melt flow rate (MFR) of 0.1 to 20 g / 10 minutes as measured at 230 ° C. under a load of 21.18 N from the viewpoint of extrusion moldability. It is more preferably 0.2 g / 10 min or more or 10 g / 10 min or less, and even more preferably 0.5 g / 10 min or more or 5 g / 10 min.

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 or more. It is preferable that the content of the polyolefin resin is equal to or more than the lower limit, because the strength of the resin layer (B) is further maintained.
Further, the upper limit of the content of the polyolefin resin in the resin layer (B) is not limited, and the resin layer (B) may be composed of only the polyolefin resin, but is preferably 90% by mass or less, more preferably 80% by mass or less, and still more preferably. Is 70% by mass or less.
When the content of the polyolefin resin is equal to or less than the upper limit, the strength is further maintained without lowering the reflectance, which is preferable.

(Fine powder filler)
It is preferable that the resin layer (B) contains a fine powder filler together with the polyolefin resin from the viewpoint of further improving the reflection performance.
When the resin layer (B) contains a fine powder filler, incident light is irregularly reflected by the fine powder filler to improve reflection characteristics, and when the resin layer (B) is a stretched body, a void is 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. Above all, it is preferable that the resin layer (B) contains an inorganic fine powder. Further, inorganic fine powder and 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 these can be used alone or in combination of two or more. .

  In addition, as will be described later, the present reflective material may be a part of the raw material of the resin layer (B) by using the scrap material generated in the manufacturing process of the present reflective material or the like as a recycled raw material. In that case, the organic particles contained in the resin layer (A) will also be 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, 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 alone or in combination of two or more.
Among these, considering the refractive index difference from the resin constituting the resin layer (B), those having a large refractive index are preferable, and calcium carbonate, barium sulfate, titanium oxide or oxide having a refractive index of 1.6 or more is preferred. It is particularly preferred to use zinc.

Above all, titanium oxide has a remarkably higher refractive index than other inorganic fine powders, and can significantly increase the difference in the refractive index from the resin constituting the resin layer (B). Excellent light reflectivity can be obtained with a smaller blending amount than in the case where the above method is used. Further, by using titanium oxide, high light reflectivity can be obtained even when the thickness of the 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 organic fine powder and inorganic fine powder are used in combination as the fine powder filler, it is preferable that 30% or more of the total mass thereof is titanium oxide.
As the titanium oxide, for example, commercially available products such as those manufactured by Ishihara Sangyo, Kemers, and KRONOS can be used.

  In order to improve the dispersibility of these inorganic fine powders in the resin, use is made of inorganic fine powders whose surfaces are surface-treated with a silicon compound, a polyhydric alcohol compound, an amine compound, a fatty acid, a fatty acid ester, or the like. 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 uniform reflector can be obtained. 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 formed densely, and a highly reflective reflector is obtained. 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 preferably based on the total weight of the resin layer (B) in consideration of the light reflectivity of the reflector, mechanical strength, productivity, and the like. It is at least 10% by mass, more preferably at least 20% by mass, further preferably at least 30% by mass. When the content of the finely divided filler is equal to or more than the lower limit, the area of the interface between the resin constituting the resin layer (B) and the finely divided filler can be sufficiently ensured, and the reflective material has higher reflectivity. Can be provided.
Also, 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 equal to or less than the upper limit, the mechanical strength required for the reflector can be more effectively secured.

(Other components)
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 other than polyolefin resins (including thermoplastic elastomers), crystal nucleating agents, antioxidants, light stabilizers, heat stabilizers, dispersants, ultraviolet absorbers, fluorescent brighteners , A compatibilizer, a lubricant and other additives.

In addition, as long as the performance of the resin layer (B) is not hindered, a recycled raw material generated in the manufacturing process of the present reflective material or the like may be contained.
The content ratio of the recycled material is not limited, and is preferably 1 to 60% by mass, more preferably 10% by mass or more and 50% by mass or less based on the total mass of the resin layer (B). When the content is 10% by mass or more, it is preferable because the cost merit of using the recycled material is generated. On the other hand, when the content is 50% by mass or less, the light reflectivity required for the reflector and the mechanical strength are less likely to be impaired.

<Void>
In the present reflecting material, any one of the layers has a void, thereby enhancing the reflection characteristics.
The void may be present in one of the resin layer (A) and the resin layer (B), in both, or in another layer. In a configuration including the resin layers (A) and (B) such as the resin layer (A) / the resin layer (B) / the resin layer (A), if a void is provided in the resin layer (A), the heat resistance and the elastic modulus are increased. In the case where the mechanical characteristics such as the above-mentioned are deteriorated, it is preferable to provide the above-mentioned space 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 increased, and there is no possibility that the heat resistance is reduced.
The voids can be formed by allowing the composition constituting each layer to contain a fine powder filler, and then stretching, preferably biaxially stretching.

<This reflective material>
(Layer structure)
The present reflective material may be configured to have any other layer as long as it has the resin layer (A) and the resin layer (B). That is, another layer may be provided on the surface of the resin layer (A) or the resin layer (B), or between the resin layer (A) and the resin layer (B), for example, an adhesive layer. Another layer may be interposed.
The “other layer” includes a layer provided by coating or vapor deposition.
Further, a configuration having at least one of the resin layer (A) and the resin layer (B) in two or more layers may be employed. As such a configuration, a configuration having a resin layer (A) on both surfaces of a resin layer (B), that is, a configuration having three layers of “resin layer (A) / resin layer (B) / resin layer (A)” It is preferred that

By laminating the resin layer (A) and the resin layer (B), the functions of each layer can be separated, and the reflection performance, heat resistance, folding resistance, occurrence of luminance unevenness, and damage to the light guide plate can be reduced. Performance such as reduction can be improved. For example, the resin layer (B) mainly has a role of imparting light reflectivity, and the resin layer (A) reduces the occurrence of luminance unevenness and damage to the light guide plate in addition to heat resistance. Can have a role.
In the above various configurations, the resin layer (A) has a surface layer of the present reflective material, especially a reflective surface, from the viewpoint of imparting a role of reducing the occurrence of luminance unevenness and damage to the light guide plate, in addition to heat resistance. It is preferable to arrange as the outermost layer.

(Form of Resin Layer (A))
The resin layer (A) may be a layer composed of a sheet, or may be a layer formed by forming a thin film without forming a sheet by extruding or applying a molten resin composition. . However, in order to cope with the thinning of the liquid crystal display, a sheet is preferable.
When the resin layer (A) is formed of a sheet, the sheet is preferably formed by an extrusion method, and may be an unstretched film or a uniaxial or biaxially stretched film. Among them, a stretched film obtained by stretching at least 1.1 times or more in a uniaxial direction, particularly a biaxially stretched film is preferable.

(Form of Resin Layer (B))
The resin layer (B) is preferably a sheet formed by an extrusion method. When the resin layer (B) is a sheet, the sheet may be an unstretched film or a uniaxially or biaxially stretched film. Among them, a stretched film obtained by stretching at least 1.1 times or more in a uniaxial direction, particularly a biaxially stretched film is preferable.

(Thickness)
The thickness of the present reflector is not particularly limited. Especially, it is preferable that it is 30 micrometers-1500 micrometers. In consideration of handleability in practical use, the thickness of the present reflective material is preferably about 50 to 1000 μm.
For example, the thickness of the reflective material for liquid crystal display is preferably 50 to 700 μm, and the thickness of the reflective material for lighting fixtures and signboards is preferably 70 to 1000 μm.

  The thickness of the resin layer (A) (in the case of two or more layers, the total thickness thereof) is not particularly limited, and is preferably, for example, 5 to 100 μm, and more preferably 10 μm or more or 80 μm or less. When the thickness of the resin layer (A) is within the above range, luminance unevenness tends to be more effectively suppressed. Here, the thickness of the resin layer (A) means an average thickness, and is a thickness obtained by averaging projections formed by organic particles.

  The thickness of the resin layer (B) (in the case of two or more layers, the total thickness thereof) is not particularly limited. For example, it is preferably 20 to 1400 μm, and more preferably 50 μm or more or 600 μm or less. When the thickness of the resin layer (B) is within the above range, the reflection characteristics tend to be good.

  In the present reflection material, the thickness ratio of the resin layer (A) to the resin layer (B) is preferably resin layer (A): resin layer (B) = 1: 2-1: 15. When the thickness ratio of the resin layer (B) to the resin layer (A) is twice or more, the reflection characteristics tend to be good, and the flexibility is good, so that the bending workability tends to be improved. When the thickness ratio of the resin layer (B) to the resin layer (A) is 15 times or less, the heat resistance tends to be good. In addition, the said thickness ratio means the thickness ratio of the total thickness of each layer, when it is the structure which has two or more resin layers (A) or resin layers (B).

Regarding the resin layer (A), the ratio (Dmax / Dav) of the maximum thickness (Dmax) to the average thickness (Dav) of the resin layer (A) is preferably from 1.1 to 4.0, and particularly preferably 1. More preferably, it is 2 or more or 3.0 or less.
Since Dmax generally corresponds to a convex portion formed by the organic particles, a large value of Dmax / Dav means that a significant convex portion is formed. Therefore, it is preferable that the value of Dmax / Dav is within the optimal range, since it is possible to reduce the occurrence of uneven brightness and the damage to the light guide plate.

(Surface roughness Rz)
The surface roughness Rz of the present reflector is not particularly limited, and is preferably 5 μm or more, more preferably 7 μm or more, and further preferably 8 μm or more. It is preferable that the surface roughness Rz of the present reflective material be equal to or larger than the lower limit value, because the reflection characteristics become more favorable and the luminance unevenness tends to be further suppressed.
Also, the upper limit of the surface roughness Rz of the present reflector is not limited, and is preferably 30 μm or less, more preferably 20 μm or less, and further preferably 15 μm or less. It is preferable that the surface roughness Rz of the present reflective material be equal to or less than the upper limit value, since the possibility of occurrence of scratches when contacting the light guide plate is further reduced.

Here, the surface of the reflective material having the surface roughness Rz within the above range may be any of the resin layer (A), the resin layer (B), and other layers. The resin layer (A) preferably forms at least one of the surfaces of the reflective material, and the surface of the resin layer (A) preferably achieves the above-described surface roughness Rz.
The method for adjusting the surface roughness Rz of the surface of the resin layer (A) is optimal depending on the type and the mixing ratio of the polyolefin resin as the main component resin, the type and the mixing ratio of the organic particles, the stretching conditions when manufacturing the reflective material, and the like. Can be
The measurement of the surface roughness Rz is based on JIS B0601, and more specifically, is based on the method described in Examples below.

(Surface roughness Ra)
The surface roughness Ra of the present reflector is not limited, and is preferably 0.5 μm or more, more preferably 0.6 μm or more, and further preferably 0.7 μm or more. It is preferable that the surface roughness Ra of the present reflective material be equal to or more than the lower limit value, because the reflective characteristics are more excellent and the luminance unevenness tends to be more effectively suppressed.
In addition, the upper limit of the surface roughness Ra of the reflector is not limited, and is preferably 3.0 μm or less, more preferably 2.0 μm or less, and further preferably 1.5 μm or less. It is preferable that the surface roughness Ra of the present reflecting material be equal to or less than the above upper limit, because the scratches can be more effectively suppressed when the reflecting material comes into contact with the light guide plate.

  Here, the surface of the reflective material having the surface roughness Ra within the above range may be any of the resin layer (A), the resin layer (B), and other layers. It is preferable that at least one of the surfaces of the reflecting material is formed by the resin layer (A), and the surface of the resin layer (A) achieves the above value of the surface roughness Ra.

  The method for adjusting the surface roughness Ra of the surface of the resin layer (A) is optimal depending on the type and the mixing ratio of the polyolefin resin, which is the main component resin, the type and the mixing ratio of the organic particles, and the stretching conditions when manufacturing the reflective material. Can be

  The measurement of the surface roughness Ra is based on JIS B0601, and more specifically, is based on the method described in Examples below.

(Reflectance)
The reflective material can have high reflective performance.
There is no restriction on the reflection performance of the present reflector, and the average reflectance of at least one surface can be 97% or more, further 98% or more, particularly 99% or more. As long as the reflective material has such a reflective performance, a liquid crystal display or the like incorporating the reflective material can realize a sufficient screen brightness.
Here, “reflectance” means an 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 reflective material preferably has a void in order to enhance the reflective performance.
The presence of voids in the reflecting material can be confirmed, for example, by observing the cross section of the reflecting material with a microscope (an electron microscope or an optical microscope).
The porosity of the present reflector is not limited. It is preferably at least 10%, more preferably at least 20%, preferably at most 90%, more preferably at most 80%.
When the porosity of the reflective material is equal to or more than the lower limit, the whitening of the reflective material proceeds sufficiently, so that the reflective material tends to have high light reflectivity. When the porosity of the reflective material is equal to or less than the upper limit, the mechanical strength of the reflective material tends to be suitable.

  The porosity of the resin layer (B) is not limited. It is preferably at least 20%, more preferably at least 25%, even more preferably at least 30%, preferably at most 80%, more preferably at most 75%, even more preferably at most 70%. When the porosity of the resin layer (B) is equal to or more than the lower limit, the whitening of the reflective material proceeds sufficiently, and the resin tends to have higher light reflectivity. When the porosity of the resin layer (B) is equal to or less than the upper limit, the mechanical strength of the reflective material tends to be more suitable.

  In addition, the porosity of the present reflective material substantially covers the resin layer (A) and the resin layer (B), and includes other layers when these layers are provided between these layers. 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) and the resin layer (B), these layers are not included in the calculation of the porosity of the reflector.

The porosity of the reflector can be determined by the following method.
(1) In the case where the voids are formed by stretching, the voids can be obtained by measuring the density of the reflecting material before and after stretching to obtain the following formula.
Porosity (%) = {(density of film before stretching−density of film after stretching) / density of film before stretching} × 100
(2) When the density and the mixing ratio of each raw material are clear, the density in the case where there is no void is calculated from the density and the mixing ratio of each raw material, and can be obtained by the following formula.
Porosity (%) = {(density without voids−density of reflective material) / density without voids} × 100
(3) Furthermore, after measuring the density of the reflecting material, it can be obtained by calculating the density after melting, depressurizing, cooling and solidifying the reflecting material to remove voids.

<Production method of the present reflective material>
Hereinafter, as an example of a method for manufacturing the present reflector, a reflector having a three-layer structure of “resin layer (A) / resin layer (B) / resin layer (A)” manufactured by a co-extrusion method will be described. However, it is not limited to the following manufacturing method. For example, instead of the co-extrusion method, it is also possible to form a laminated structure by application, extrusion lamination, heat fusion, an adhesive or the like.

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

On the other hand, a fine powder filler, other additives, and the like are added to the polyolefin resin as needed to prepare a resin composition B. Specifically, after mixing these raw materials in a ribbon blender, tumbler, Henschel mixer, or the like, using a Banbury mixer, a single-screw or twin-screw extruder or the like, a temperature equal to or higher than the melting point of the resin (for example, 190 ° C. to 270 ° C.) C) to obtain a resin composition B.
Moreover, similarly to the resin composition A, it can be manufactured using a feeder or the like, a part of the raw material can be used as a master batch, or a part of the raw material can be used as a resin composition in advance.
When only the polyolefin resin is used for the resin layer (B), it corresponds to the resin composition B without any mixing or the like.

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

  Thereafter, the melted resin composition A and the resin composition B are combined into a two-type, three-layer T-die, extruded from the slit-shaped discharge port of the T-die into a laminated shape, and tightly solidified with a cooling roll to form a cast sheet. Form.

The obtained cast sheet is preferably stretched in at least one axis direction. By stretching, the interface between the polyolefin resin and the fine powder filler inside the resin layer (B) is peeled off, voids are formed, the whitening of the sheet proceeds, and the light reflectivity of the film can be enhanced.
Further, the cast sheet is more preferably stretched in the biaxial direction. The voids formed only by uniaxial stretching have a fibrous shape extending in one direction, but by biaxial stretching, the voids are elongated in both the vertical and horizontal directions, resulting in a disk-like shape.
That is, by biaxially stretching, the peeling area at the interface between the polyolefin resin and the fine powder filler in the resin layer (B) increases, and the whitening of the sheet further progresses. Can be even higher. Further, the biaxial stretching reduces the anisotropy in the shrinkage direction of the film, so that the heat resistance of the film can be improved and the mechanical strength of the film can be increased.

The stretching temperature at the time of stretching the cast sheet is preferably a temperature in the range from the glass transition temperature (Tg) of the polyolefin resin contained in the resin layer (A) to (Tg + 50 ° C.) or less.
When the stretching temperature is equal to or higher than the glass transition temperature (Tg), the film can be stably performed without breaking the film during stretching. Further, if the stretching temperature is not higher than (Tg + 50) ° C., the stretching orientation increases, and as a result, the porosity increases, so that a film having a high reflectance is easily obtained.

The stretching order of the biaxial stretching is not particularly limited, and may be, for example, simultaneous biaxial stretching or sequential stretching. After being cast into a molten cast sheet, it may be stretched in the machine direction (MD) by roll stretching and then stretched in the transverse direction (TD) by tenter stretching, or biaxially stretched by tubular stretching or the like. Good.
The stretching 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 reflecting material can be controlled to an appropriate range, and excellent reflection performance can be exhibited.
When performing sequential biaxial stretching, the stretching ratio of the first axis is preferably 1.1 to 5.0 times, more preferably 1.5 to 3.5 times, and the stretching ratio of the second axis is: Preferably it is 1.1 to 5.0 times, more preferably 2.5 to 4.5 times.

After the stretching, it is preferable to perform heat fixing to impart dimensional stability (form stability of voids) to the reflecting material. The processing temperature for heat setting the film is preferably from 130 to 160 ° C. The processing time required for heat setting is preferably 1 second to 3 minutes.
The stretching equipment and the like are not particularly limited, but it is particularly preferable to perform tenter stretching in which a heat setting treatment can be performed after stretching.

<Application>
The application of the reflector is not particularly limited. Because of its excellent reflection performance, it is useful as a reflection member used for a liquid crystal display device such as a liquid crystal display, a lighting fixture, a lighting signboard and the like.
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.
The reflector can be suitably used as a reflector that plays a role of efficiently causing light from a light source to enter a liquid crystal panel or a light guide plate, and collects irradiation light from a light source disposed at an edge portion. It can also be suitably used as a light source reflector having a role of causing light to enter the light guide plate.

The present reflector is suitable as a reflector provided in a backlight unit of a liquid crystal display. The use of the reflective material can reduce unevenness in luminance and damage to the light guide plate, and there is no restriction on the material of the light guide plate. For this reason, it can be suitably used for a backlight unit having various light guide plates made of polymethyl methacrylate (PMMA) resin, methyl methacrylate / styrene copolymer (MS resin), cycloolefin resin, etc. It is suitable for a backlight unit having a light guide plate made of MS resin.
Therefore, it is possible to provide a backlight unit including the reflective material and a light guide plate made of polymethyl methacrylate (PMMA) resin, methyl methacrylate / styrene copolymer (MS resin), cycloolefin resin, or the like. .

The present reflecting material can be used as it is as a reflecting material having the above-mentioned layer configuration.
Furthermore, it is also possible to use it as a structure laminated on a metal plate or a resin plate (collectively referred to as “metal plate or the like”). It is useful as a reflector as a constituent member.
Therefore, a liquid crystal display device, a lighting fixture, or a lighting signboard can be provided by using the reflective material as a constituent member.

In addition, as a metal plate on which the reflective material is laminated, for example, an aluminum plate, a stainless steel plate, a galvanized steel plate, or the like can be given.
The method for laminating the present reflector on a metal plate or the like is not particularly limited. For example, a method using an adhesive, a method of heat fusion, a method of bonding via an adhesive sheet, a method of extrusion coating, and the like can be mentioned.
More specifically, an adhesive such as a polyester-based, polyurethane-based, or epoxy-based adhesive can be applied to the surface on the side where the reflective material such as a metal plate is to be bonded, and the reflective material can be bonded.
Next, the coating 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 reflection material is immediately coated and cooled using a roll laminator to reflect the light. You can get a board.

  In addition, the reflective material can be used for various uses other than the above, such as various industrial materials, packaging materials, optical materials, and electric materials.

<Explanation of terms>
In the present invention, the term "film" includes "sheet", and the term "sheet" includes "film".
In the present invention, "reflection" means reflection of light unless otherwise specified, and more specifically, reflection of visible light.

In the present invention, when expressed as “X to Y” (X and Y are arbitrary numbers), “preferably larger than X” and “preferably smaller than Y” together with “X or more and Y or less” unless otherwise specified. Including the meaning of.
When expressed as “X or more” (X is an arbitrary number), the meaning of “preferably larger than X” is included unless otherwise specified, and when expressed as “Y or less” (Y is an arbitrary number), Unless otherwise specified, the meaning of “preferably smaller than Y” is included.

  Hereinafter, the present invention will be described more specifically with reference to Examples. However, the present invention is not limited to these embodiments, and various applications are possible without departing 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 are described below.

(Glass transition temperature of organic particles)
Using a differential scanning calorimeter (manufactured by PerkinElmer, model name: Diamond DSC), the glass transition temperature (between the baseline shift) when the organic particles were heated to 250 ° C. at a rate of 30 ° C./min. (Inflection point) was measured.

(Deformation stress of organic particles)
As the deformation stress of the organic particles, a value measured by the following method was adopted.
Using a micro-compression tester, a load was applied to one organic particle at a constant loading speed to compress it, and the amount of deformation of the organic particle in the process was measured. The value calculated by the following equation from the stress (load) when the particle diameter was deformed by 10% and the radius of the particle before the start of the load application was defined as the deformation stress. In the case where there is a variation in the deformation stress, the values of the particles having such a negligible variation were averaged.
Deformation stress (kgf / mm ² ) = 2.8 × load (kgf) / {π × (particle radius (mm)) ² }

(Average particle size of organic particles)
The average particle size of the organic particles in the resin layer (A) was determined by observing the surface of the resin layer (A) of the reflector with an optical microscope, measuring the diameters of 10 or more particles, and calculating the average value. When the organic particles were non-spherical particles, the average value of the longest diameter and the shortest diameter was defined as the diameter of each particle.

(Thickness of reflective material)
The thickness of all layers of the reflecting material was measured by a film thickness meter (micrometer). The thickness of each layer of the resin layer (A) and the resin layer (B) was confirmed by observing the cross section of the reflector using an optical microscope.

(Porosity)
The density of the laminated sheet before stretching (unstretched sheet density) and the density of the laminated sheet after stretching (stretched sheet density) were measured, and the porosity (%) of the reflector (sample) composed of the laminated sheet was calculated by the following formula. ).
Porosity (%) = {(unstretched sheet density−stretched sheet density) / unstretched sheet density} × 100

(Surface roughness)
In a state where the reflecting material (sample) is left on a flat surface, Rz and Ra are measured on five randomly selected surfaces, and the average value is taken as Rz (μm) and Ra (μm) of the reflecting material (sample). ).
For the measurement, "Surf Test SJ-210" manufactured by Mitutoyo Corporation was used, and the measurement was performed with λc: 0.8 mm and λs: 2.5 mm based on JIS B0601 (2001).

(Average reflectance)
An integrating sphere was attached to a spectrophotometer (“U-3900H” manufactured by Hitachi High-Technologies Corporation), and the reflectance of the reflector (sample) when the alumina white plate was set to 100% was 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 defined as the average reflectance (%).

(Evaluation of sharpness of light guide plate)
A light guide plate (thickness of about 2 mm) made of MS resin with a concave dot shape and a reflective material (sample) are superimposed on a friction fastness tester (manufactured by Daiei Kagaku Seiki Seisakusho, Gakushin type friction tester RT-300). The reflector was rubbed 50 times under the conditions of a load of 500 g and a stroke of 100 mm. The state of the surface of the light guide plate after the friction was observed, and the evaluation was made based on the following criteria.
((Good): There was little scraping, and there was no practical problem.
× (poor): There was a lot of scraping, and there was a practical problem.

(Evaluation of uneven brightness)
A light guide plate made of MS resin and having a thickness of about 2 mm was used, and an evaluation model of an edge light type backlight unit was created.
A light guide plate was placed on a reflector (sample), and an edge light was turned on with a weight (2 kg) placed on the light guide plate. Using a camera installed on the upper part of the light guide plate, it was confirmed whether or not luminance unevenness occurred near the weight, and judgment was made based on the following criteria.
((Good): No luminance unevenness was generated, and the composition was suitable as a reflector for a thin backlight or the like.
X (poor): Unevenness in luminance occurred, and was unsuitable as a reflector for a thin backlight or the like.

<Raw materials>
The raw materials used in Examples and Comparative Examples will be described below.

<COP-1>
Amorphous cycloolefin resin (MFR (230 ° C., 21.18 N): 1.2 g / 10 min, Tg: 127 ° C.)
<COP-2>
Amorphous cycloolefin resin (MFR (230 ° C., 21.18 N): 12 g / 10 min, Tg: 100 ° C.)

<PP-1>
Polypropylene resin (“Novatech PP EG6D” manufactured by Nippon Polypropylene Co., Ltd., MFR (230 ° C., 21.18N): 1.9 g / 10 minutes)
<PP-2>
Polypropylene resin (“Novatech PP FY6HA” manufactured by Nippon Polypro, MFR (230 ° C., 21.18N): 2.4 g / 10 minutes)

<Organic particles-1>
Butyl methacrylate / methyl methacrylate copolymer-based crosslinked resin particles (spherical particles; Tg: 187.2 ° C., deformation stress: 1.8 kgf / mm ² , average particle diameter (D50): 30 μm)
<Organic particles-2>
Methyl methacrylate-based crosslinked resin particles (spherical particles; Tg: 132.7 ° C., deformation stress: 2.4 kgf / mm ² , average particle diameter (D50): 30 μm)
<Organic particles-3>
Methyl methacrylate-based crosslinked resin particles (spherical particles; Tg: 132.7 ° C., deformation stress: 2.4 kgf / mm ² , average particle diameter (D50): 40 μm)

<Titanium oxide>
KRONOS Inc. "KRONOS2450" (produced by chlorine method, titanium oxide surface treated rutile type alumina and silica, TiO ₂ content of 96.0%, an average particle diameter (D50): 0.31 .mu.m)
<Calcium carbonate>
Bihoku Powder Chemical Industry Co., Ltd. “Softon 3200” (Average particle size (D50): 0.70 μm)

<Example 1>
(Preparation of resin composition A)
PP-1 pellets and organic particles-1 were mixed at a mass ratio of PP-1 / organic particles-1 = 90: 10, and then pelletized using a twin-screw extruder. A mixture was obtained. Thereafter, COP-1, COP-2 pellets and a mixture of PP-1 and organic particles-1 were mixed at a mass ratio of COP-1 / COP-2 / PP-1 / organic particles-1 = 40: 20: 40. After mixing, the mixture is pelletized using a twin-screw extruder, and as a raw material for the resin layer (A), the mass ratio of COP-1 / COP-2 / PP-1 / organic particles-1 = 40: 20: 36: 4. Was prepared.

(Preparation of resin composition B)
The PP-2 pellets and the fine powder filler are mixed at a mass ratio of PP-2: titanium oxide: calcium carbonate = 55: 40: 5, and then pelletized using a twin-screw extruder heated at 270 ° C. A resin composition B was prepared as a raw material for the resin layer (B).

(Production of reflective material)
The resin compositions A and B are respectively supplied to extruders A and B heated stepwise to 250 ° C., melted by each extruder, and then combined with a T-die for two or three layers, The sheet was extruded into a sheet so as to have a three-layer structure of layer (A) / resin layer (B) / resin layer (A), and was cooled and solidified to form a non-stretched laminated sheet.
The obtained laminated sheet is roll-stretched 2.3 times in the machine direction (MD) of the film at a temperature of 132 ° C., and further biaxially stretched by tenter stretching in the orthogonal direction (TD) at 141 ° C. A reflective material (sample) composed of a laminated sheet having a total thickness of 216 μm was obtained.
The obtained reflector was measured or evaluated for porosity, surface roughness, average reflectance, light guide plate abrasion evaluation and luminance unevenness evaluation, and the results are shown in Table 2.

<Comparative Example 1>
Except that the organic particles-1 in the raw material of the resin layer (A) were changed to the organic particles-2, the thickness of the reflecting material was as shown in Table 2, and the stretching temperature in the film flow direction (MD) was 142 ° C. A reflector (sample) was obtained in the same manner as in Example 1. The obtained reflector (sample) was measured and evaluated in the same manner as in Example 1, and the results are shown in Table 2.

<Comparative Example 2>
In the production of the resin composition A, COP-1, COP-2 pellets and a mixture of PP-1 and organic particles-2 were mixed with a mixture of COP-1 / COP-2 / PP-1 and organic particles-2 = 50: 25. : After mixing at a weight ratio of 25, pelletized using a twin screw extruder, and as a raw material of the resin layer (A), the weight ratio was COP-1 / COP-2 / PP-1 / organic particles-2 = 50: A reflector (sample) was obtained in the same manner as in Comparative Example 1, except that a resin composition A of 25: 22.5: 2.5 was prepared. The obtained reflector (sample) was measured and evaluated in the same manner as in Example 1, and the results are shown in Table 2.

<Comparative Example 3>
In the production of the resin composition A, the pellets of PP-1 and the organic particles-2 were mixed at a mass ratio of PP-1 / organic particles-2 = 85: 15, and then pelletized using a twin screw extruder. After obtaining the PP-1 / organic particle-2 mixture, the COP-1, COP-2 pellets and the PP-1 / organic particle-2 mixture are converted into COP-1 / COP-2 / PP-1 / organic particle- After mixing at a weight ratio of 2 mixture = 50: 25: 25, the mixture was pelletized using a twin screw extruder, and the weight ratio was COP-1 / COP-2 / PP-1 / organic as a raw material of the resin layer (A). A reflector (sample) was obtained in the same manner as in Comparative Example 1, except that a resin composition A in which particles-2 = 50: 25: 21.25: 3.75 was prepared. The obtained reflector (sample) was measured and evaluated in the same manner as in Example 1, and the results are shown in Table 2.

<Comparative Example 4>
A reflector (sample) was obtained in the same manner as in Comparative Example 1, except that the organic particles-2 of the resin layer (A) were changed to the organic particles-3. The obtained reflector (sample) was measured and evaluated in the same manner as in Example 1, and the results are shown in Table 2.

As is clear from Tables 1 and 2, in Example 1, the resin layer (A) contains organic particles having a deformation stress in the range of 1.5 to 2.2 kgf / mm ² , thereby increasing the reflectance. It was confirmed that not only the luminance unevenness was suppressed but also that the light guide plate was not shaved even when MS resin was used as the light guide plate.
On the other hand, the reflecting materials of Comparative Examples 1 to 4 containing the organic particles whose deformation stress is out of the range of 1.5 to 2.2 kgf / mm ^{2 in} the resin layer (A) have abrasion against the light guide plate made of MS resin. It was confirmed that there was a problem in practical use.

Claims (13)

A reflector comprising a resin layer (A) containing a polyolefin resin and organic particles as a main component resin, and a resin layer (B) containing a polyolefin resin, and having a void,
A reflective material, wherein the organic particles contained in the resin layer (A) have a deformation stress of 1.5 to 2.2 kgf / mm ² .   The reflector according to claim 1, wherein the organic particles are crosslinked particles.   The reflective material according to claim 1, wherein the organic particles have a glass transition temperature of 150 ° C. or more and 260 ° C. or less.   The reflective material according to claim 1, wherein the organic particles have an average particle size of 15 to 60 μm.   The reflector according to claim 1, wherein the resin layer (A) contains the organic particles in an amount of 0.5 to 20% by mass.   The reflector according to claim 1, wherein the surface roughness Rz is 5 to 30 μm.   The reflector according to any one of claims 1 to 6, wherein the porosity is 10 to 90%.   The reflective material according to any one of claims 1 to 7, wherein the resin layer (A) is disposed as a surface layer.   The reflective material according to any one of claims 1 to 8, wherein the polyolefin resin as a main component resin of the resin layer (A) is a polypropylene resin or a cycloolefin resin.   The reflector according to any one of claims 1 to 9, wherein the resin layer (B) contains a fine powder filler.   A backlight unit comprising the reflector according to claim 1 and a light guide plate made of a methyl methacrylate / styrene copolymer.   The reflector according to any one of claims 1 to 10, wherein the reflector is used as any one of a liquid crystal display device, a lighting fixture, and a lighting signboard.   A liquid crystal display device, a lighting fixture, or a lighting signboard comprising the reflecting material according to claim 1 as a constituent member.