JP2008233290A - Reflecting film and reflecting plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a novel reflecting film capable of obtaining superior light reflection properties, even though it has low porosity. <P>SOLUTION: In the reflection film having a resin composition layer containing a polyolefin based resin and a titanium oxide, the titanium oxide is provided with an inactive inorganic oxide layer comprises at least one inactive inorganic oxide selected from among a group consisting of silica, alumina and zirconia and occupying 0.5 to 5 mass% of the total mass of the titanium oxide on the surface of a high-purity titanium oxide, having 500 ppm or higher for the niobium content and 5 ppm or lower for the vanadium content. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a reflective film and a reflective plate, and more particularly to a reflective film and a reflective plate used for a liquid crystal display device, a lighting fixture, a lighting signboard, and the like.

  Reflectors are used in many fields such as liquid crystal display devices, projection screens, planar light source members, lighting fixtures, and lighting signs. Recently, especially in the field of liquid crystal display devices, the size of the device and the advancement of display performance have progressed, and it has been demanded to improve the performance of the backlight unit by supplying as much light as possible to the liquid crystal. Further, more excellent light reflectivity has been demanded for a reflecting plate, particularly a reflecting film constituting the reflecting plate.

As this type of reflective film, for example, a white sheet formed by adding titanium oxide to an aromatic polyester resin is known (see Patent Document 1).
A white sheet formed by adding a fine powder filler to a polyolefin resin is also known (see, for example, Patent Documents 2 and 3).

JP 2002-138150 A Japanese Patent No. 3617535 Japanese Patent No. 3755905

Many of the reflection films conventionally known need to increase the porosity in order to improve the light reflectivity, so that the mechanical strength of the reflection film is insufficient, and there is a possibility of breaking during film formation or use.
Therefore, an object of the present invention is to provide a new reflective film and a reflector using the same, which can obtain excellent light reflectivity even with a low porosity.

  The present invention is a reflective film having a resin composition layer comprising a polyolefin resin and titanium oxide, the titanium oxide having a niobium content of 500 ppm or less and a vanadium content of 5 ppm or less. An inert inorganic oxide layer comprising at least one type of inert inorganic oxide selected from the group consisting of silica, alumina and zirconia on the surface of pure titanium oxide and occupying 0.5 to 5% by mass of the total mass of titanium oxide The present invention proposes a reflective film characterized in that it is a titanium oxide comprising

In general, the term “sheet” refers to a product that is thin by definition in JIS and generally has a thin thickness that is small instead of length and width. In general, a “film” is a thin flat product whose thickness is extremely small compared to the length and width and whose maximum thickness is arbitrarily limited, and is usually supplied in the form of a roll. (Japanese Industrial Standard JISK6900). However, since the boundary between the sheet and the film is not clear and it is not necessary to distinguish the two in terms of the present invention, in the present invention, even when the term “film” is used, the term “sheet” is included and the term “sheet” is used. In some cases, “film” is included.
Further, in the present invention, when expressed as “X to Y” (X and Y are arbitrary numbers), unless otherwise specified, “X or more and Y or less” means “preferably larger than X and smaller than Y”. Is included.

Since the reflective film of the present invention can obtain excellent light reflectivity (also referred to as “reflectivity”) from refractive scattering due to the difference in refractive index between the polyolefin resin and titanium oxide, it is excellent even at a low porosity. The light reflectivity can be obtained.
Therefore, the reflection plate formed by laminating the reflection film of the present invention on a metal plate or a resin plate can realize high light reflectivity, and thus is particularly used for liquid crystal display devices, lighting fixtures, lighting signs, and the like. It is suitable as a plate.

Embodiments of the present invention will be described below, but the scope of the present invention is not limited to the embodiments described below.
Note that the expression “main component” in the present specification includes the meaning of allowing other components to be contained within a range that does not hinder the function of the main component unless otherwise specified. At this time, although the content ratio of the main component is not specified, the main component (when two or more components are main components, the total amount thereof) is 50% by mass or more, preferably 70% in the composition. It usually occupies at least 90% by mass, particularly preferably at least 90% by mass (including 100%).

  The reflective film according to the present embodiment (hereinafter referred to as “the present reflective film”) is a reflective film having a resin composition layer A containing a polyolefin resin and titanium oxide.

(Base resin)
Examples of the polyolefin resin as the base resin of the resin composition layer A (resin forming the main component of the resin composition layer A) include monoolefin polymers such as polyethylene and polypropylene, or copolymers thereof. it can. Specific examples include low density polyethylene, linear low density polyethylene (ethylene-α-olefin copolymer), medium density polyethylene, polyethylene resin such as high density polyethylene, polybutylene resin, polypropylene, ethylene-propylene copolymer, etc. And polypropylene resin, poly-4-methylpentene, polybutene, and ethylene-vinyl acetate copolymer. These resins may be used alone or in combination of two or more.
The polyolefin resin includes those produced using a multisite catalyst such as a Ziegler catalyst and those produced using a single site catalyst such as a metallocene catalyst.

  Further, a polyolefin-based thermoplastic elastomer obtained by dispersing and compounding ethylene / propylene rubber or the like in these polyolefin-based resins can also be used.

  Considering the moldability at the time of molding into a sheet shape and the heat resistance at the time of molding into a sheet shape, among the polyolefin resins, linear low density polyethylene resins such as ethylene-α-olefin copolymers, polypropylene, Preferred are polypropylene resins such as ethylene-propylene copolymer, propylene-butene copolymer, ethylene-propylene-butene terpolymer, ethylene-propylene-diene terpolymer, among which polypropylene resin, In particular, an ethylene-propylene copolymer such as polypropylene and an ethylene-propylene random copolymer is preferable.

  Further, from the viewpoint of improving the reflectance, polyolefins having a small refractive index are preferable, and it is particularly preferable to use a polyolefin resin having a refractive index of less than 1.52. For example, a polypropylene resin, a low density polyethylene resin, a polybutylene resin, polymethylpentene, and a mixture or copolymer thereof can be exemplified. Among them, a polypropylene resin having a refractive index of 1.50 or less is used. preferable.

As polypropylene resins, homopolypropylene resins, copolymers having propylene such as ethylene-propylene copolymers, specifically, random polypropylene resins such as ethylene-propylene random copolymers, block polypropylene resins, propylene-ethylene rubber And so on.
As a polymerization method for obtaining a polypropylene resin, known methods such as a solvent polymerization method, a bulk polymerization method, and a gas phase polymerization method can be employed. Moreover, as a polymerization catalyst, well-known catalysts, such as a titanium trichloride type catalyst, a magnesium chloride carrying | support catalyst, a metallocene catalyst, are employable, for example.

The melt flow rate (MFR) of the polyolefin resin is not particularly limited, but in the case of a polyethylene resin, it is 0.2 to 40 g / 10 min (190 ° C., load 2.16 kg), particularly 1 to 20 g / 10 min. Of these, 3 to 10 g / 10 min is particularly preferable. In the case of a polypropylene resin, it is preferably 1 to 50 g / 10 min (230 ° C., load 2.16 kg), particularly 3 to 25 g / 10 min, and particularly preferably 5 to 15 g / 10 min.
In the present invention, MFR is measured based on the method defined in ASTM D-1238. However, the measurement means that measurement is performed under each condition shown in parentheses.
If the MFR of the polyolefin resin is too small, it is necessary to increase the extrusion temperature at the time of melt molding. As a result, the reflectance is reduced due to yellowing due to oxidation of the polyolefin resin itself and thermal degradation of the fine powder filler, particularly titanium oxide. May be reduced. On the other hand, if the MFR of the polyolefin-based resin is too large, sheet production by melt molding may become unstable.

  A commercially available product may be used as the polyolefin resin as the base resin. For example, “Novatech PP”, “WINTEC”, “Toughmer XR” (manufactured by Nippon Polypro), “Mitsui Polypro” (manufactured by Mitsui Chemicals), “Sumitomo Noblen”, “Tough Selenium”, “Excellen EPX” (manufactured by Sumitomo Chemical), Examples thereof include polypropylene resins such as “IDEMISU PP”, “IDEMITSU TPO” (manufactured by Idemitsu Kosan Co., Ltd.), “Adflex”, “Adsyl” (manufactured by Sun Allomer). In addition, these copolymers can be used individually or in mixture of 2 or more types, respectively.

(Titanium oxide)
Titanium oxide has a significantly higher refractive index than other inorganic fine powders, and can significantly increase the difference in refractive index from the base resin, so it can be used in a smaller amount than when other fillers are used. Excellent reflectivity can be obtained. Further, by using titanium oxide, a reflective film having high reflectivity can be obtained even when the film is thin.

  As the titanium oxide, a crystalline titanium oxide such as anatase type or rutile type is preferable. Among them, a titanium oxide having a refractive index of 2.7 or more is preferable from the viewpoint of a large refractive index difference from the base resin. In this respect, rutile type titanium oxide is preferable.

  Further, it is particularly preferable to use high-purity titanium oxide having high purity among titanium oxides. Here, high-purity titanium oxide means titanium oxide having a small light absorption ability for visible light, that is, titanium oxide having a small content of coloring elements such as vanadium, iron, niobium, copper, and manganese. Then, titanium oxide having a niobium content of 500 ppm or less and a vanadium content of 5 ppm or less is referred to as high-purity titanium oxide.

  In high-purity titanium oxide, it is important that the niobium content is 500 ppm or less, preferably 400 ppm or less, and more preferably 200 ppm or less. The vanadium content is important to be 5 ppm or less, but preferably 4 ppm or less.

Examples of high-purity titanium oxide include those produced by a chlorine process.
In the chlorine method process, rutile ore containing titanium oxide as a main component is reacted with chlorine gas in a high-temperature furnace of about 1000 ° C. to produce titanium tetrachloride first, and then this titanium tetrachloride is burned with oxygen, High purity titanium oxide can be obtained.
There is a sulfuric acid process as an industrial method for producing titanium oxide, but the titanium oxide obtained by this method contains a large amount of colored elements such as vanadium, iron, copper, manganese, niobium, etc. Absorption capacity increases. Therefore, it is difficult to obtain high-purity titanium oxide by the sulfuric acid method process.

As a titanium oxide used for this reflective film, what equipped the surface with the inert inorganic oxide layer formed from the inert inorganic oxide is preferable. By coating the surface of titanium oxide with an inert inorganic oxide, the photocatalytic activity of titanium oxide can be suppressed, and the film can be prevented from being deteriorated by the photocatalytic action of titanium oxide.
As the inert inorganic oxide, it is preferable to use at least one selected from the group consisting of silica, alumina, and zirconia. If these inert inorganic oxides are used, the light resistance of the film can be enhanced without impairing the high light reflectivity exhibited when titanium oxide is used. Further, it is more preferable to use two or more kinds of inert inorganic oxides in combination, and among them, a combination in which silica is essential is particularly preferable.

As said silica, what was manufactured by the gaseous-phase method is preferable, and it is preferable to form an inactive inorganic oxide layer only from the silica manufactured especially by the gaseous-phase method. That is, it is preferable to coat titanium oxide with silica produced by a vapor phase method. When titanium oxide is coated using silica formed by a gas phase method, moisture adsorption of titanium oxide is prevented, and aggregation of titanium oxide particles can be prevented, that is, dispersibility can be improved.
As a gas phase method (dry method), a method using high-temperature gas phase hydrolysis of silicon halide (flame hydrolysis method), silica sand and coke are heated and reduced and vaporized by an arc in an electric furnace, and this is converted into air. And a method of oxidizing with (arc method). For example, as a flame hydrolysis method, silica is produced by burning silicon tetrachloride with hydrogen and oxygen, or silanes such as methyltrichlorosilane and trichlorosilane are used alone or mixed with silicon tetrachloride instead of silicon tetrachloride. And a method of producing silica by using them.

The inert inorganic oxide layer preferably occupies 0.5 to 5% by mass, particularly 1 to 3% by mass, based on the total mass of titanium oxide. If the amount of the inert inorganic oxide layer is 0.5% by mass or more, it is preferable because the effect of suppressing the photocatalytic activity of titanium oxide is obtained. Moreover, if it is 5 mass% or less, since the dispersibility to polyolefin resin becomes favorable and a homogeneous film is obtained, it is preferable.
At this time, when the inert inorganic oxide layer is formed from silica produced by the gas phase method, the silica accounts for 0.5 to 5% by mass, particularly 1 to 3% by mass of the total mass of titanium oxide. Is preferred.
The ratio of the inert inorganic oxide layer to the total mass of titanium oxide is the ratio of the total mass of the inert inorganic oxide used for the surface treatment in the total mass of titanium oxide after the surface treatment (in percentage). ).

Moreover, as titanium oxide, in order to improve the dispersibility to base resin, what has the organic compound layer formed from the organic compound on the surface is preferable.
The organic compound layer is, for example, a siloxane compound, a silane coupling agent, a polyhydric alcohol, a titanium coupling agent, an alkanolamine or a derivative thereof, and an organic compound such as a higher fatty acid or a metal salt thereof, and the surface of titanium oxide or It can be formed by coating the surface of the inert inorganic oxide layer. In particular, it is preferable to coat with at least one organic compound selected from the group consisting of siloxane compounds, polyhydric alcohols, and silane coupling agents, and in particular, selected from the group consisting of polyhydric alcohols and silane coupling agents. It is preferable to coat with at least one organic compound. These two or more kinds of compounds may be used in combination.
These organic compounds can improve the hydrophobicity, dispersibility, and affinity with the resin of titanium oxide by physical adsorption or chemical reaction with hydroxyl groups on the surface of titanium oxide.

Here, examples of the siloxane compound include dimethyl silicone, methyl hydrogen silicone, and alkyl-modified silicone, and these can be used alone or in combination of two or more.
As the silane coupling agent, for example, alkoxysilanes having an alkyl group, alkenyl group, amino group, aryl group, epoxy group and the like, chlorosilanes, and polyalkoxyalkylsiloxanes are preferable, and aminosilane coupling agents are more preferable. is there. Specifically, for example, n-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, n-β (aminoethyl) γ-aminopropylmethyltrimethoxysilane, n-β (aminoethyl) γ-aminopropylmethyltrimethoxysilane. Aminosilane coupling agents such as ethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, n-phenyl-γ-aminopropyltrimethoxysilane, dimethyldimethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, Propyltrimethoxysilane, n-butyltrimethoxysilane, n-butyltriethoxysilane, n-butylmethyldimethoxysilane, n-butylmethyldiethoxysilane, isobutyltrimethoxysilane, isobutyltriethoxysilane, isobutyl Examples include alkyl silane coupling agents such as rumethyldimethoxysilane, tert-butyltrimethoxysilane, tert-butyltriethoxysilane, tert-butylmethyldimethoxysilane, and tert-butylmethyldiethoxysilane. Two or more types can be used in combination.
Examples of the polyhydric alcohol include trimethylol ethane, trimethylol propane, tripropanol ethane, pentaerythritol, and pentaerythritol. Among them, trimethylol ethane and trimethylol propane are more preferable. These polyhydric alcohol compounds can be used alone or in combination of two or more.

The organic compound layer preferably occupies 0.01 to 5% by mass, particularly 0.05 to 3% by mass, particularly 0.1 to 2% by mass, based on the total mass of titanium oxide.
If the organic compound layer occupies 0.01% by mass or more of the entire titanium oxide, it is possible to prevent titanium oxide from adsorbing water and prevent aggregation of the titanium oxide particles, thereby improving the dispersibility of the titanium oxide. . If the dispersibility of titanium oxide is improved, the occurrence of irregularities is suppressed, and the appearance of the film product surface is not damaged, and troubles of breakage are not caused at the time of stretch film formation. Moreover, since the area of the interface between the base resin and titanium oxide is sufficiently secured, high light reflectivity can be imparted to the film. On the other hand, when the organic compound layer is 5% by mass or less of the entire titanium oxide, the lubricity of the titanium oxide particles becomes appropriate, and stable extrusion and film formation become possible.
The ratio that the organic compound layer occupies in the total mass of titanium oxide is determined by the ratio (in percentage) of the total mass of the organic compound used for the surface treatment in the total mass of titanium oxide after the surface treatment.

  The particle size of titanium oxide is preferably 0.1 μm to 1.0 μm, and more preferably 0.2 μm to 0.5 μm. If the particle size of titanium oxide is 0.1 μm or more, the dispersibility in the base resin is good and a homogeneous film can be obtained. If the particle size of titanium oxide is 1.0 μm or less, the interface between the base resin and titanium oxide is densely formed, and high light reflectivity can be imparted to the reflective film.

  The content of titanium oxide is preferably 10 to 80% by mass, particularly 20 to 70% by mass with respect to the total mass of the reflective film, considering the light reflectivity, mechanical properties, productivity, etc. of the film. Is more preferable. If the content of titanium oxide is 10% by mass or more, the area of the interface between the base resin and titanium oxide can be sufficiently secured, and high light reflectivity can be imparted to the film. Moreover, if content of a titanium oxide is 80 mass% or less, the mechanical property required for a film can be ensured.

(Other ingredients)
The resin composition layer A may contain a resin other than the polyolefin resin as described above as long as the effects of the polyolefin resin and titanium oxide are not impaired. Addition of antioxidants, light stabilizers, heat stabilizers, lubricants, dispersants, UV absorbers, white pigments, fluorescent brighteners, and other additives within the range that does not impair the effects of polyolefin resins and titanium oxide An agent may be contained.

(Form of resin composition layer A)
Even if the resin composition layer A was a layer formed from a film, it was formed into a thin film (without forming a film) by extruding or applying the molten resin composition to another layer. It may be a layer.
When the resin composition layer A is formed from a film, the film may be an unstretched film, a uniaxial or biaxially stretched film, but is preferably a biaxially stretched film.

(Porosity)
The reflective film, particularly the resin composition layer A, preferably has voids therein. If it has voids, it can be from refractive scattering due to refractive index difference between polyolefin resin and titanium oxide, and from refractive scattering due to refractive index difference between polyolefin resin and void (air), and between titanium oxide and void (air). Can also be reflective.

In order to form voids in the present reflective film, particularly the resin composition layer A, for example, a film containing titanium oxide may be stretched. This is because the stretching behavior of the base resin and titanium oxide is different when stretched. In other words, if stretching is performed at a stretching temperature suitable for the base resin, the base resin as a matrix is stretched, but the titanium oxide tends to remain as it is, so that the interface between the base resin and the titanium oxide peels off. A void is formed. Therefore, by effectively including titanium oxide in a dispersed state, voids can be formed in the reflective film, and further excellent reflectivity can be imparted to the film.
Moreover, a foaming agent can be added to this reflection film, especially the resin composition layer A, and a void can be formed in the resin composition layer A by foaming.

The porosity of the reflective film, particularly the resin composition layer A, that is, the proportion of the volume portion of the voids in the resin composition layer A is preferably 35% or less, particularly 25% or less, and particularly preferably 10% or less. When the porosity is 35% or less, the mechanical strength of the film is ensured, and the film does not break during film production, and durability such as heat resistance does not become insufficient during use.
In consideration of the improvement in reflectance, the porosity is more preferably 3% or more, particularly 5% or more, and more preferably 7% or more within the above range.
In addition, the porosity at the time of extending | stretching a film can be substituted for the following formula, and the porosity of a film can be calculated | required (hereinafter the same).
Porosity (%) = {(density of film before stretching−density of film after stretching) / density of film before stretching} × 100

  However, when the above-described high-purity titanium oxide is used, even when the porosity existing inside the film is small, specifically, the porosity is 35% or less, particularly 25% or less, particularly 10%. Even in the case of less than or equal to%, it is possible to achieve high light reflectivity, and it is possible to earn a high reflectance even if there is no void inside. This is presumed to be due to the fact that titanium oxide has a high refractive index and a high hiding power. Further, if the amount of filler used can be reduced, the number of voids formed by stretching can be reduced, so that the mechanical properties of the film can be improved while maintaining high reflection performance. Furthermore, even if the filler is used in a large amount, the mechanical properties can be improved in the same manner by reducing the stretch amount and reducing the voids. These are also advantageous in improving the dimensional stability of the film. Moreover, if high reflection performance is ensured even if it is thin, it can be used, for example, as a reflective film for small and thin liquid crystal displays such as notebook personal computers and mobile phones.

[Laminated structure of the reflective film]
If this reflective film is provided with a resin composition layer A containing a polyolefin-based resin and titanium oxide, even if it is a single-layer film made of the resin composition layer A, a layer other than the resin composition layer A The film provided with.
For example, the structural example which laminates | stacks a metal thin film layer and a protective layer in this order on the back surface side of the resin composition layer A, ie, the surface on the opposite side to a reflective use surface, can be given.

At this time, the metal thin film layer can be formed by vapor-depositing a metal, for example, by a vacuum vapor deposition method, an ionized vapor deposition method, a sputtering method, an ion plating method, or the like.
The vapor-deposited metal material can be used without particular limitation as long as it has a high reflectivity, but generally silver, aluminum and the like are preferable, and among these, silver is particularly preferable.

In addition, the metal thin film layer is a single-layer product or a laminate of metal, a single-layer product or a laminate of metal oxide, or a laminate of two or more layers of a single-layer product of metal and a single-layer product of metal oxide. But you can.
The thickness of the metal thin film layer varies depending on the material forming the layer, the layer forming method, and the like, but is usually preferably in the range of 10 nm to 300 nm, and more preferably in the range of 20 nm to 200 nm. If the thickness of the metal thin film layer is 10 nm or more, sufficient reflectance can be obtained. On the other hand, if the thickness of the metal thin film layer is 300 nm or less, the production efficiency is good and preferable.

As the metal thin film layer, a metal thin film laminated film is prepared by laminating a metal thin film layer on an intermediate layer made of a synthetic resin film or the like, and this metal thin film laminated film is laminated on the resin composition layer A. You may do it.
As a lamination method at this time, for example, even if the metal thin film layer of the metal thin film laminate film and the resin composition layer A are overlapped, the intermediate layer of the metal thin film laminate film and the resin composition layer A are overlapped. They may be combined, and at that time, they may be simply overlapped, or may be overlapped and bonded partially or entirely.
As a bonding method, a method of bonding by a known method using various adhesives, a known thermal bonding method, or the like can be used.
In the present reflective film, it is possible to maintain a high reflectance by maintaining the voids in the resin composition layer A by adopting an adhesive method that does not apply heat or a method of thermal bonding at a temperature of 210 ° C. or lower. Therefore, it is preferable.

Examples of the laminated structure in the case of having a metal thin film layer include, for example, a resin composition layer A / (optional anchor coat layer) / metal thin film layer / protective layer layer structure, or resin composition layer A / Intermediate layer / (optional anchor coat layer) / metal thin film layer / protective layer layer structure, or resin composition layer A / protective layer / metal thin film layer / (optional anchor coat layer) / intermediate Examples of the layer structure include layers.
However, the resin composition layer A may be disposed on the reflective use surface side (the side irradiated with light), or may have other layers between the respective layers. Moreover, each layer, such as the resin composition layer A and the metal thin film layer, may be independently formed from a plurality of layers.

[Thickness]
Although the thickness of this reflective film is not specifically limited, Usually, it is 30 micrometers-500 micrometers, and when the handleability in practical use is considered, it is preferable to exist in the range of about 50 micrometers-300 micrometers.
If a reflective film having such a thickness is used, it can also be used for small and thin liquid crystal displays and the like such as notebook computers and mobile phones.

[Reflectance]
As for the reflectance of the present reflective film, the reflectance of the film surface with respect to light having a wavelength of 550 nm, measured from the reflective use surface side, is preferably 96% or more, and more preferably 97% or more. If the reflectance is 96% or more, the present reflective film exhibits good reflective properties, and a liquid crystal display or the like incorporating this reflective film does not have a yellowish tint, and has good color.

[Production method]
Below, although an example is given and demonstrated about the manufacturing method of this reflective film, the manufacturing method of this reflective film is not limited to the following manufacturing method at all.

  This reflective film is prepared by mixing a polyolefin resin and titanium oxide, and if necessary, additives such as antioxidants to prepare a resin composition, melting the resin composition to form a film, and Accordingly, the reflective film may be produced by stretching. Hereinafter, this manufacturing method will be described in detail.

  First, a resin composition is prepared by blending a polyolefin resin with titanium oxide and, if necessary, additives such as an antioxidant. Specifically, titanium oxide is added to the polyolefin resin, and further additives such as antioxidants are added as necessary. After mixing with a ribbon blender, tumbler, Henschel mixer, etc., a Banbury mixer or uniaxial or biaxial extrusion A resin composition is obtained by kneading using a machine or the like at a temperature equal to or higher than the melting point of the base resin.

  In addition, a resin composition can also be obtained by adding a predetermined amount of titanium oxide and an additive such as an antioxidant to the polyolefin resin with separate feeders. In addition, a so-called master batch in which titanium oxide or the like is blended at a high concentration with a polyolefin resin may be prepared in advance, and this master batch and the polyolefin resin may be mixed to obtain a resin composition with a desired concentration.

Next, the resin composition thus obtained is melted to form a film.
For example, the resin composition is dried, supplied to an extruder, and melted by heating to a temperature equal to or higher than the melting point of the base resin. At this time, the resin composition may be supplied to the extruder without drying, but if not dried, it is preferable to use a vacuum vent during melt extrusion.
Conditions such as the extrusion temperature are preferably set in consideration of a decrease in molecular weight due to decomposition. For example, the extrusion temperature is preferably in the range of 170 ° C to 230 ° C.

  After extrusion, for example, the molten resin composition is extruded from a slit-shaped discharge port of a T-die and is solidified by being adhered to a cooling roll to form a cast sheet (unstretched state) to obtain an unstretched film.

The obtained unstretched film is preferably stretched 1.1 times or more in at least a uniaxial direction as necessary.
By stretching, a void having titanium oxide as a nucleus is formed inside the film, and an interface between the base resin and the void and an interface between the void and the titanium oxide are formed. Since it increases, the light reflectivity of a film can further be improved.

  The stretching temperature at the time of stretching is preferably in the range from the glass transition temperature (Tg) of the base resin to the melting point (Tm) or less. Specifically, it is good to set it as 60-160 degreeC, for example. If the stretching temperature is within this range, the film can be stably stretched without breaking during stretching, and the stretching orientation becomes high, and as a result, the porosity increases, so that the film has a high reflectance. Can be obtained.

The unstretched film is more preferably biaxially stretched.
By biaxially stretching, the porosity can be further increased, and the light reflectivity of the film can be further enhanced. Further, when the film is only uniaxially stretched, the formed voids are only in a fibrous form extending in one direction, but by biaxially stretching, the voids are in a disk-like form stretched in both the vertical and horizontal directions. That is, by biaxially stretching, the peeled area at the interface between the base resin and titanium oxide increases, and the whitening of the film proceeds. As a result, the light reflectivity of the film can be increased. Furthermore, since biaxial stretching eliminates anisotropy in the shrinking direction of the film, the heat resistance of the film can be improved, and the mechanical strength of the film can be increased.

The order of stretching when biaxially stretching is not particularly limited. For example, simultaneous biaxial stretching or sequential stretching may be used.
Also, the stretching method is not particularly limited. For example, after melt film formation, the film may be stretched in the MD (film take-up direction) by roll stretching, and then stretched in the TD (direction perpendicular to the MD) by tenter stretching, or tubular stretching, etc. Biaxial stretching may be performed by However, when heat treatment is performed after stretching, tenter stretching is preferred.

  In the case of uniaxial stretching or biaxial stretching, the stretching ratio is preferably 7 times or more, more preferably 25 times or more as the area magnification. By stretching to 7 times or more in the area magnification, a porosity of 3% or more can be given inside the film, and by stretching to 25 times or more, a porosity of 7% or more can be given.

Further, in order to impart heat resistance and dimensional stability to the obtained film, it is preferable to perform heat treatment (also referred to as heat setting treatment).
The heat treatment temperature is preferably 90 to 160 ° C, and more preferably 110 to 140 ° C.
The treatment time required for the heat treatment is preferably 1 second to 5 minutes.

(Use)
The reflective film can be formed by laminating the reflective film on a metal plate (for example, an aluminum plate, a stainless steel plate, a galvanized steel plate, etc.) or a resin plate. This reflecting plate is useful as a reflecting plate used for liquid crystal display devices, lighting fixtures, lighting signs, and the like.
Below, an example is given and demonstrated about the manufacturing method of such a reflecting plate.

As a method of laminating a reflective film on a metal plate or a resin plate, a method using an adhesive, a method of heat-sealing without using an adhesive, a method of bonding via an adhesive sheet, a method of extrusion coating, etc. There is. However, it is not limited to these methods.
For example, apply an adhesive such as polyester, polyurethane, or epoxy on the surface of the metal plate or resin plate (collectively referred to as “metal plate”) to which the reflective film is to be bonded, and bond the reflective film. Can do. In this method, commonly used coating equipment such as reverse roll coater, kiss roll coater, etc. is used, and it is adhered to the surface of a metal plate or the like so that the adhesive film thickness after drying is about 2 μm to 4 μm. Apply the agent. Next, the coated surface is dried and heated with an infrared heater and a hot air heating furnace, and the surface of the metal plate or the like is kept at a predetermined temperature, and immediately, the roll film laminator is used to coat and cool the reflective film.
In this case, when the surface of the metal plate or the like is held at 210 ° C. or lower, the light reflectivity of the reflecting plate can be maintained high. However, the surface temperature of the metal plate or the like is preferably maintained at 160 ° C. or higher.

The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to these examples, and various applications are possible without departing from the technical idea of the present invention.
In addition, the measured value and evaluation which are shown to an Example were performed as shown below. Here, the film take-up (flow) direction is indicated by MD, and its orthogonal direction is indicated by TD.

(1) Refractive index The refractive index of resin was measured based on A method of JIS K-7142.

(2) Niobium content in titanium oxide (ppm)
The niobium content was measured based on JIS M-8321 “Titanium Ore-Niobium Determination Method”. That is, 0.5 g of a sample was weighed, and this sample was transferred to a nickel crucible containing 5 g of a molten mixture [sodium hydroxide: sodium peroxide = 1: 2 (mass ratio)] and stirred. The surface of the sample was covered with 2 g of anhydrous sodium carbonate, and the sample was heated and melted in a crucible to form a melt. The melt was allowed to cool in the state of being put in a crucible, and then 100 mL of warm water and 50 mL of hydrochloric acid were added to the melt to dissolve it, and water was further added to make up to 250 mL. This solution was measured with an ICP emission spectrometer, and the niobium content was determined. However, the measurement wavelength was set to 309.42 nm.

(3) Vanadium content in titanium oxide (ppm)
0.6g of titanium oxide sample is weighed in a container, 10ml of nitric acid is added and decomposed in the microwave sample digester, the resulting solution is made up to 25ml, and quantitative analysis is performed using ICP emission spectrometer. went. The microwave sample decomposition apparatus used was MDS-2000 manufactured by Astec Corporation, and the decomposition operation was performed according to the steps in Table 1. The measurement wavelength was 311.07 nm.

(4) Average particle diameter of titanium oxide 3 g of sample in a sample cylinder having a cross-sectional area of 2 cm ² and a height of 1 cm using a powder specific surface measuring instrument (transmission method) of model “SS-100” manufactured by Shimadzu Corporation. Was calculated from the time of air permeation of 20 cc with a 500 mm water column.

(5) Porosity (%)
Measure the density of the film before stretching (denoted as “unstretched film density”) and the density of the film after stretching (denoted as “stretched film density”), and substitute into the following formula to determine the porosity of the film. Asked.
Porosity (%) = {(Unstretched film density−Stretched film density) / Unstretched film density} × 100

(6) Reflectance (%)
An integrating sphere was attached to a spectrophotometer (“U-4000”, manufactured by Hitachi, Ltd.), and the reflectance with respect to light having a wavelength of 550 nm was measured.
Before the measurement, the photometer was set so that the reflectance of the alumina white plate was 100%.

[Example 1]
The surface of a rutile type titanium oxide (average particle size: 0.28 μm, niobium content: 370 ppm, vanadium content: 4 ppm) obtained by a so-called chlorine process for vapor-phase oxidation of titanium halide is not formed of alumina. After forming the active inorganic oxide layer, an organic compound layer made of trimethylolethane was formed.
Here, the formation of the inert inorganic oxide layer made of alumina was performed by adding sodium aluminate and dilute sulfuric acid to a liquid in which titanium oxide was dispersed in water, followed by aging.
At this time, the amount of alumina in the inert inorganic oxide layer was 3% by mass with respect to titanium oxide, and the amount of trimethylolethane in the organic compound layer was 0.3% by mass with respect to titanium oxide. .

A pellet of an ethylene-propylene random copolymer (MFR: 7 g / 10 min, refractive index: 1.50) and the above titanium oxide were mixed at a mass ratio of 30:70 to obtain a mixture. This mixture was pelletized using a twin screw extruder to produce a so-called master batch.
This master batch and polypropylene (MFR: 5 g / 10 min, refractive index: 1.49) were mixed at a mass ratio of 43:57 to obtain a resin composition. Thereafter, the resin composition is supplied to an extruder heated to 200 ° C. and kneaded at 200 ° C. using the extruder, and then the molten resin composition is extruded into a sheet form from a T-die and cooled. Solidified to form a film.
The obtained film was simultaneously biaxially stretched 5 times to MD and 5 times to TD at a temperature of 155 ° C. to obtain a reflective film having a thickness of 75 μm. In addition, the content rate of the titanium oxide with respect to the whole film mass obtained in this way was 30 mass% (43 * 70/100).
The resulting reflective film was evaluated for porosity and reflectance, and the results are shown in Table 2.

[Example 2]
From the alumina and silica on the surface of a rutile type titanium oxide (average particle size: 0.28 μm, niobium content: 370 ppm, vanadium content: 4 ppm) obtained by a so-called chlorine process for vapor phase oxidation of titanium halide. After forming the inert inorganic oxide layer, an organic compound layer made of trimethylolethane was formed.
Here, the formation of the inert inorganic oxide layer made of alumina and silica was performed by adding sodium aluminate, sodium silicate and dilute sulfuric acid to a liquid in which titanium oxide was dispersed in water, followed by aging.
At this time, the amounts of alumina and silica in the inert inorganic oxide layer are 2% by mass and 1% by mass, respectively, based on titanium oxide, and the amount of trimethylolethane in the organic compound layer is based on titanium oxide. It was 0.3% by mass.

In the production of the resin composition of Example 1, except that the mixing ratio of the masterbatch and polypropylene was changed to a mass ratio of 71:29, and the stretching temperature was changed to 150 ° C. in the production of the film. A reflective film was obtained in the same manner as in Example 1. In addition, the content rate of the titanium oxide with respect to the whole film mass obtained in this way was 50 mass% (71 * 70/100).
The resulting reflective film was evaluated for porosity and reflectance, and the results are shown in Table 2.

[Example 3]
On the surface of rutile-type titanium oxide (average particle size: 0.28 μm, niobium content: 370 ppm, vanadium content: 4 ppm) obtained by a so-called chlorine process for vapor phase oxidation of titanium halide, alumina, silica and After forming an inert inorganic oxide layer made of zirconia, an organic compound layer made of trimethylolethane was formed.
Here, the formation of an inert inorganic oxide layer made of alumina, silica and zirconia is accomplished by first adding zirconium sulfate and malic acid to a liquid in which titanium oxide is dispersed in water, followed by aging to form an inert inorganic oxide layer made of zirconia. An oxide layer was formed. Next, after adjusting the pH of the aqueous dispersion to 7 with an aqueous solution of sodium hydroxide, sodium aluminate, sodium silicate and dilute sulfuric acid are added, followed by aging to form an inert inorganic oxide layer composed of alumina and silica. I let you.
At this time, the amounts of alumina, silica, and zirconia in the inert inorganic oxide layer are 1% by mass, 0.5% by mass, and 0.5% by mass, respectively, with respect to titanium oxide. The amount of methylolethane was 0.3% by mass with respect to titanium oxide.

In the production of the resin composition of Example 1, except that the mixing ratio of the masterbatch and polypropylene was changed to a mass ratio of 85:15, and the stretching temperature was changed to 140 ° C. in the production of the film. A reflective film was obtained in the same manner as in Example 1. In addition, the content rate of the titanium oxide with respect to the whole film mass obtained in this way was 60 mass% (85 * 70/100).
The resulting reflective film was evaluated for porosity and reflectance, and the results are shown in Table 2.

[Example 4]
In the preparation of the resin composition of Example 3, except that the mixing ratio of the masterbatch and polypropylene was changed to a mass ratio of 100: 0, and the drawing temperature was changed to 135 ° C. in the preparation of the film. A reflective film was obtained in the same manner as in Example 3. In addition, the content rate of the titanium oxide with respect to the whole film mass obtained in this way was 70 mass% (100x70 / 100).
The resulting reflective film was evaluated for porosity and reflectance, and the results are shown in Table 2.

[Example 5]
A reflective film was obtained in the same manner as in Example 1 except that methyltrimethoxysilane was used in place of trimethylolethane in the production of titanium oxide in Example 1.
The resulting reflective film was evaluated for porosity and reflectance, and the results are shown in Table 2.

[Comparative Example 1]
Titanium oxide was produced in the same manner as in Example 1.
A pellet of polyethylene terephthalate (refractive index: 1.58) and the above titanium oxide were mixed at a mass ratio of 50:50 to obtain a mixture. This mixture was pelletized using a twin screw extruder to produce a so-called master batch.
This master batch and the polyethylene terephthalate were mixed at a mass ratio of 60:40 to obtain a resin composition. Thereafter, this resin composition is supplied to an extruder heated to 280 ° C. and kneaded at 280 ° C. using this extruder, and then the molten resin composition is extruded into a sheet form from a T-die and cooled. Solidified to form a film.
The obtained film was successively stretched 2.5 times to MD and 90 times to TD at 90 ° C., and further heat-treated at 140 ° C. to obtain a reflective film having a thickness of 75 μm.
Thus, the content rate of the titanium oxide with respect to the whole film mass obtained was 30 mass% (50 * 60/100).
The resulting reflective film was evaluated for porosity and reflectance, and the results are shown in Table 2.

[Comparative Example 2]
In the production of titanium oxide of Example 1, instead of titanium oxide obtained by the chlorine method process, titanium oxide obtained by a so-called sulfuric acid method process in which a titanium sulfate solution is hydrolyzed (average particle size: 0.29 μm, Niobium content: 950 ppm, vanadium content: 8 ppm) and the amounts of alumina and silica in the inert inorganic oxide layer formed on the surface thereof were 4% by mass and 3% by mass, respectively, with respect to titanium oxide. Except for the points described above, a reflective film was obtained in the same manner as in Example 1.
The resulting reflective film was evaluated for porosity and reflectance, and the results are shown in Table 2.

As is clear from Table 2, the reflective films of the present invention of Examples 1 to 5 have a high light reflectivity with a reflectivity of 96% or more, even though the porosity is 10% or less. I found out.
On the other hand, the reflective films of Comparative Examples 1 and 2 had a reflectance of less than 96%, and were found to be inferior to the reflective films of Examples 1 to 5 in terms of light reflectivity.

[Example 6]
On the surface of rutile titanium oxide (average particle size: 0.28 μm, niobium content: 180 ppm, vanadium content: 4 ppm) obtained by a so-called chlorine method process that vapor-phase oxidizes titanium halide by a vapor phase method. After forming the produced inert inorganic oxide layer made of silica, an organic compound layer made of isobutyltriethoxysilane was formed.
At this time, the amount of silica in the inert inorganic oxide layer was 3% by mass with respect to titanium oxide, and the amount of isobutyltriethoxysilane in the organic compound layer was 0.3% by mass with respect to titanium oxide. It was.

A pellet of ethylene-propylene random copolymer (MFR: 7 g / 10 min, refractive index: 1.50) and the above titanium oxide were mixed at a mass ratio of 30:70 to obtain a mixture. This mixture was pelletized using a twin screw extruder to produce a so-called master batch.
This master batch and polypropylene (MFR: 5 g / 10 min, refractive index: 1.49) were mixed at a mass ratio of 45:55 to obtain a resin composition. Thereafter, the resin composition is supplied to an extruder heated to 200 ° C. and kneaded at 200 ° C. using the extruder, and then the molten resin composition is extruded into a sheet form from a T-die and cooled. Solidified to form a film.
The obtained film was simultaneously biaxially stretched 5 times to MD and 5 times to TD at a temperature of 155 ° C. to obtain a reflective film having a thickness of 75 μm. In addition, the content rate of the titanium oxide with respect to the whole film mass obtained in this way was 32 mass% (45 * 70/100).
The resulting reflective film was evaluated for porosity and reflectance, and the results are shown in Table 3.

[Example 7]
In the production of the resin composition of Example 6, except that the mixing ratio of the masterbatch and polypropylene was changed to a mass ratio of 70:30, and in the production of the film, the stretching temperature was changed to 150 ° C. A reflective film was obtained in the same manner as in Example 6. In addition, the content rate of the titanium oxide with respect to the whole film mass obtained in this way was 49 mass% (70 * 70/100).
The resulting reflective film was evaluated for porosity and reflectance, and the results are shown in Table 3.

[Example 8]
In the production of the resin composition of Example 6, except that the mixing ratio of the master batch and polypropylene was changed to a mass ratio of 85:15, and that the stretching temperature was changed to 140 ° C. in the production of the film. A reflective film was obtained in the same manner as in Example 6. In addition, the content rate of the titanium oxide with respect to the whole film mass obtained in this way was 60 mass% (85 * 70/100).
The resulting reflective film was evaluated for porosity and reflectance, and the results are shown in Table 3.

[Example 9]
In the production of the resin composition of Example 6, except that the mixing ratio of the masterbatch and polypropylene was changed to a mass ratio of 100: 0, and the drawing temperature was changed to 135 ° C. in the production of the film. A reflective film was obtained in the same manner as in Example 6. In addition, the content rate of the titanium oxide with respect to the whole film mass obtained in this way was 70 mass% (100x70 / 100).
The resulting reflective film was evaluated for porosity and reflectance, and the results are shown in Table 3.

[Example 10]
In the production of titanium oxide of Example 6, a reflective film was obtained in the same manner as in Example 6 except that dimethyl silicone was used instead of isobutyltriethoxysilane.
The resulting reflective film was evaluated for porosity and reflectance, and the results are shown in Table 3.

[Comparative Example 3]
Titanium oxide was produced in the same manner as in Example 6.
A pellet of polyethylene terephthalate (refractive index: 1.58) and the above titanium oxide were mixed at a mass ratio of 50:50 to obtain a mixture. This mixture was pelletized using a twin screw extruder to produce a so-called master batch.
This master batch and the polyethylene terephthalate were mixed at a mass ratio of 60:40 to obtain a resin composition. Thereafter, this resin composition is supplied to an extruder heated to 280 ° C. and kneaded at 280 ° C. using this extruder, and then the molten resin composition is extruded into a sheet form from a T-die and cooled. Solidified to form a film.
The obtained film was successively stretched 2.5 times to MD and 90 times to TD at 90 ° C., and further heat-treated at 140 ° C. to obtain a reflective film having a thickness of 75 μm.
Thus, the content rate of the titanium oxide with respect to the whole film mass obtained was 30 mass% (50 * 60/100).
The resulting reflective film was evaluated for porosity and reflectance, and the results are shown in Table 3.

As is clear from Table 3, the reflective films of Examples 6 to 10 of the present invention have a high light reflectivity with a reflectivity of 96% or more, even though the porosity is 10% or less. I found out. Moreover, since the reflective films of Examples 6 to 10 had good dispersibility of titanium oxide, they were excellent in appearance and film formability.
On the other hand, the reflective film of Comparative Example 3 had a reflectance of less than 96%, and was found to be inferior to the reflective films of Examples 6 to 10 in terms of light reflectivity.

Claims (10)

A reflective film having a resin composition layer comprising a polyolefin-based resin and titanium oxide,
The titanium oxide has at least one inert inorganic oxide selected from the group consisting of silica, alumina and zirconia on the surface of high-purity titanium oxide having a niobium content of 500 ppm or less and a vanadium content of 5 ppm or less. It is a titanium oxide provided with the inert inorganic oxide layer which consists of and consists of 0.5-5 mass% of the titanium oxide whole mass.   2. The reflective film according to claim 1, wherein the inert inorganic oxide layer of titanium oxide is made of silica produced by a vapor phase method, and the silica is contained in an amount of 1 to 5 mass% of the total mass of titanium oxide. .   The titanium oxide is composed of at least one organic compound selected from the group consisting of a siloxane compound, a polyhydric alcohol and a silane coupling agent on the surface, and occupies 0.01 to 5% by mass of the total mass of titanium oxide. It is a titanium oxide provided with the compound layer, The reflective film of Claim 1 or 2 characterized by the above-mentioned.   The reflective film according to claim 1, wherein the titanium oxide has an average particle size of 0.1 μm to 1 μm.   The reflective film according to any one of claims 1 to 4, wherein the titanium oxide is contained in an amount of 10 to 80% by mass based on the total mass of the reflective film.   The reflective film according to claim 1, wherein the polyolefin resin is polypropylene, an ethylene-propylene copolymer, or a mixed resin thereof.   It is a stretched film obtained by stretching a film obtained by melting and forming a resin composition containing a polyolefin-based resin and titanium oxide at least 1.1 times in a uniaxial direction. The reflective film according to any one of claims 1 to 6.   The reflective film according to claim 1, wherein the porosity of the resin composition layer is 35% or less.   The reflective film according to claim 1, wherein the reflectance of the film surface on the reflective use surface side with respect to light having a wavelength of 550 nm is 96% or more. A reflecting plate comprising the reflecting film according to claim 1.