JP5097381B2 - Shielding film and method for producing the same - Google Patents

Description

  The present invention relates to a light-shielding film and a method for producing the same, and more particularly, is useful as a light-shielding member for various optical devices such as cameras, video cameras, copiers, and developing machines. The present invention relates to a light shielding film having a low degree and a method for producing the same.

  Recently, the size of the camera has been reduced to a pocket size, and digital cameras have become widespread due to the development of digital technology. This digital camera has become thinner and more compact, with a business card size and a camera added to a mobile phone. Has come out. Video cameras are also becoming smaller and lighter, but, like cameras, in addition to further miniaturization, higher performance is being promoted.

As described above, with the miniaturization of cameras and video cameras, parts constituting them are required to be miniaturized and lightweight. For example, a metal is used for a light shielding member such as a shutter or a diaphragm. However, a synthetic resin film is increasingly used with a reduction in size, weight, and cost. Under such circumstances, as a light-shielding film used for an optical device, a surface of a polyester film mixed with carbon black is roughened by sandblasting, and an electron conductive type conductive agent is applied (Patent Document 1). Has been proposed. Further, a light shielding layer comprising a binder resin, a black fine powder having an average particle diameter of 1 μm or less, an organic filler having an average particle diameter of 0.5 to 10 μm, and a lubricant having an average particle diameter of 0.1 to 10 μm is provided on at least one surface of the base film. Provided (Patent Document 2) or at least one side of a base film, a binder resin composed of a thermoplastic resin having a Tg of 40 ° C. or higher and a softening point of 80 ° C. or higher, a black fine powder having an average particle size of 1 μm or less, an average particle size of 0 There has been proposed (Patent Document 3) provided with a light-shielding layer comprising an organic filler of 5 to 10 μm and a lubricant having an average particle diameter of 0.1 to 10 μm. In addition to this, for example, a black ink film having a light shielding property and a solvent resistance is applied to at least one surface of a blade material made of para-aromatic polyamide and having an optical density of 2 or more. A light-shielding blade (Patent Document 4) having a thickness of about 50 to 200 μm, which is provided with a black paint having lubricity so that the optical density becomes 8 or more, has been proposed.
JP-A-1-12503 Japanese Unexamined Patent Publication No. 7-319044 JP 2003-29314 A Japanese Patent Laid-Open No. 10-31200

  In the invention described in Patent Document 1, since the light shielding property is obtained by the polyester film mixed with carbon black, it is necessary to increase the amount of carbon black blended in the polyester film. As the amount of carbon black used increases, the mechanical and other physical properties of the film change, which is disadvantageous in terms of the flatness and cost of the film. In addition, since the surface is roughened by sandblasting, there is a problem that surface irregularities are easily crushed by rubbing between films, and the film surface is glossy after long-term use.

  On the other hand, reducing the thickness of the light-shielding film contributes to higher performance of cameras and video cameras. For example, if a light-shielding film made thin is used for the shutter of a camera, the diaphragm of a video camera, etc., it is lightweight, so not only can the power required to drive the shutter and diaphragm be kept low, but also the camera or video camera. It can be made thinner and more compact. Furthermore, since the reflection of light at the cross section can be suppressed by reducing the thickness, the reliability of the shutter and the diaphragm can be improved.

  However, the light-shielding films described in Patent Document 2 and Patent Document 3 and the light-shielding blades described in Patent Document 4 are not always satisfactory from the viewpoint of thinning and light-shielding properties. For thinning, it is necessary to make the base film and the light-shielding layer thinner than those conventionally used. However, if the light-shielding layer is made thinner, the light-shielding property is lowered and the glossiness of the surface of the light-shielding layer is increased. There is a problem that a phenomenon (reflection) occurs in which a light source (light, sun, etc.) is reflected on the surface.

  The present invention has been made in view of the above-described problems, and is a light-shielding film that has excellent light-shielding properties, is suitable for thinning, has a low glossiness, and reduces the occurrence of reflection on the surface of the light-shielding layer, and a method for producing the same It is characterized by providing.

  In order to achieve the above object, the present invention provides the following light-shielding film and method for producing the same.

[1 ] A light-shielding film comprising a base film (base material) and a light-shielding layer disposed on at least one surface of the base material, wherein the light-shielding layer is a binder resin, 5 to 55% by mass. The first light-shielding layer containing the binder resin and the black pigment is a region close to the surface in contact with the base material of the light-shielding layer. And the concentration of the black pigment contained in the first light-shielding layer is 30 to 60% by mass, and a region near the surface of the light-shielding layer contains a binder resin, a black pigment and a filler. It is composed of two light-shielding layers, and the concentration of the black pigment contained in the second light-shielding layer is 3% by mass or more and lower than the concentration of the black pigment contained in the first light-shielding layer. Shading of less than 40μm Irumu.

[ 2 ] The light-shielding film according to [1 ], wherein the light-shielding layer is disposed on both surfaces of the base material, and the thickness of the light-shielding layer on one side is 8 μm or less.

[ 3 ] The light-shielding film according to [1] or [ 2], wherein the filler is organic resin particles and / or inorganic particles.

[ 4 ] The light-shielding film according to any one of [1] to [ 3 ], wherein the binder resin contains a polyester resin having a glass transition temperature (Tg) of 10 to 150 ° C.

[ 5 ] The light shielding film according to any one of [1] to [ 4 ], wherein the optical density is 5.0 or more and the glossiness is 6.0% or less.

[6 ] A first light-shielding layer coating solution containing a binder resin and a water-dispersible black pigment of 30 to 60% by mass after drying is applied to at least one surface of the substrate film (substrate). A step of obtaining a first light-shielding layer having a total thickness of 1 to 6 μm by drying, and a binder resin, a water-dispersible black pigment and a filler on the surface of the first light-shielding layer, A second light-shielding layer coating solution having a concentration of 3% by mass or more as a content after drying and lower than the concentration of the black pigment in the first light-shielding layer coating solution is applied and dried, and the total thickness is A step of obtaining a second light-shielding layer of 6 to 10 μm, wherein the binder resin is water-soluble or water-dispersible, and the whole light-shielding layer formed of the first light-shielding layer and the second light-shielding layer The thickness is 15 μm or less and the concentration of the black pigment is 5 to 55% by mass. Method for producing a light shielding film to be.

[ 7 ] The first light-shielding layer coating solution and the second light-shielding layer coating solution are applied to both surfaces of the base material, the total thickness of one side is 8 μm or less, and the thickness of the first light-shielding layer on one side is The method for producing a light shielding film according to [ 6], wherein the thickness is 0.5 to 3 μm, and the thickness of the second light shielding layer on one side is 3 to 6 μm.

[ 8 ] The method for producing a light-shielding film according to [ 6 ] or [ 7], wherein the binder resin contains a polyester resin having a glass transition temperature (Tg) of 10 to 150 ° C.

[ 9 ] The method for producing a light-shielding film according to any one of [ 6 ] to [ 8 ], wherein the light-shielding film having an optical density of 5.0 or more and a glossiness of 6.0% or less is produced.

[1 0 ] The method for producing a light-shielding film according to any one of [ 6 ] to [ 9 ], wherein the black pigment is carbon black.

  According to the light-shielding film of the present invention, the concentration of the black pigment in the region close to the surface in contact with the base material does not contact the base material in the thickness direction of the light-shielding layer disposed on the base film (base material). Since it is higher than the concentration of the black pigment in the region close to the surface (surface), even if the thickness of the light shielding layer is as thin as 15 μm or less, the light shielding property is excellent. And the thickness of the whole light shielding film can be made into the thin thing of 40 micrometers or less. Moreover, since the light shielding layer contains a filler, the glossiness is low, and the occurrence of reflection on the surface of the light shielding layer can be reduced. Thereby, the light-shielding film of the present invention can be suitably used as a material for shutters, diaphragms and the like for optical devices that are required to be thin and compact. Moreover, the manufacturing method of the light-shielding film of this invention can manufacture the said light-shielding film of this invention efficiently.

  BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the best mode for carrying out the present invention will be specifically described. However, the present invention is not limited to the following embodiment, and is within the scope of the present invention without departing from the spirit of the present invention. It should be understood that design changes, improvements, and the like can be made as appropriate based on the knowledge.

  One embodiment of the light-shielding film of the present invention is a light-shielding film comprising a base film (base material) and a light-shielding layer disposed on at least one surface of the base material, wherein the light-shielding layer is a binder resin. The black pigment and the filler, and the total thickness thereof is 15 μm or less, and the concentration of the black pigment in the region close to the surface in contact with the substrate in the thickness direction of the light shielding layer does not contact the substrate. The light-shielding film has a concentration higher than that of the black pigment in a region close to the surface (surface) and an overall thickness of 40 μm or less. The details will be described below.

  In the light-shielding film of the present embodiment, the light-shielding layer disposed on one surface or both surfaces of the light-shielding layer has a surface in which the concentration of black pigment in a region close to the surface in contact with the substrate does not contact the substrate It is higher than the concentration of the black pigment in the region close to (surface). The concentration distribution of the black pigment in the thickness direction of the light-shielding layer may be continuously decreased from the surface in contact with the substrate toward the surface, or the concentration on the surface side may be intermittently decreased. The case where the density of the black pigment on the surface side is intermittently lowered is, for example, that the light shielding layer comprises a layer (first light shielding layer) constituting a region close to the surface in contact with the substrate and a region close to the surface. This is a case where the concentration of the black pigment contained in the first light shielding layer is higher than the concentration of the black pigment contained in the second light shielding layer. Here, the term “region of the light shielding layer close to the surface in contact with the substrate in the thickness direction” refers to the case where the concentration of the black pigment continuously changes in the thickness direction within the light shielding layer. From the surface of the layer in contact with the base material to the position corresponding to ½ of the thickness of the light shielding layer. When the light shielding layer is composed of two layers, the layer on the side in contact with the base material (the first light shielding layer) Layer). In addition, “the area close to the surface of the light shielding layer in the thickness direction” means that if the concentration of the black pigment continuously changes in the thickness direction in the light shielding layer, the light shielding layer is shielded from the surface of the light shielding layer. It refers to a position corresponding to 1/2 of the thickness of the layer, and when the light shielding layer is composed of two layers, it refers to a surface side layer (second light shielding layer). When the light shielding layer is composed of three or more layers, the “region of the light shielding layer close to the surface in the thickness direction” means a layer located on the most surface side of the light shielding layer. The “region close to the surface in contact with the substrate in the thickness direction” refers to other layers excluding the layer located on the most surface side of the light shielding layer. The term “total thickness of the light shielding layer” refers to the thickness of the light shielding layer when the light shielding layer is provided only on one side (one side) of the substrate. When the light shielding layers are provided on both sides, it means the total thickness of both the light shielding layers. Similarly, when the “total thickness of the first light shielding layer” is referred to, when the light shielding layer is disposed only on one surface (one surface) of the base material, the first light shielding layer constituting the light shielding layer is formed. It means the thickness of one light shielding layer, and when light shielding layers are provided on both surfaces of the substrate, it means the total thickness of the first light shielding layers constituting both light shielding layers. Furthermore, the case of “the entire thickness of the second light shielding layer” is the same as that of the first light shielding layer.

  As a result, the light shielding film of the present embodiment has excellent light shielding properties even when the total thickness of the light shielding layer is reduced to 15 μm or less, and the total thickness of the light shielding film is as thin as 40 μm or less. Can do. And since it is possible to add more surface area filler as much as the black pigment in the area on the surface side of the light shielding layer decreases, the glossiness is low and the occurrence of reflection on the surface of the light shielding layer is reduced. be able to.

  The total thickness of the light shielding layer is 15 μm or less, preferably 8 to 14 μm. When the light shielding layer is disposed only on one side of the substrate, the thickness of the light shielding layer (the total thickness of the light shielding layer) is preferably 10 to 14 μm. When the light shielding layer disposed only on one side is composed of two layers, a first light shielding layer (layer on the side in contact with the substrate) and a second light shielding layer (layer on the surface side), the first 1-6 micrometers is preferable and, as for the thickness of a light shielding layer, 1-5 micrometers is still more preferable. Moreover, 6-10 micrometers is preferable and, as for the thickness of a 2nd light shielding layer, 7-10 micrometers is still more preferable. Moreover, when arrange | positioning a light shielding layer on both surfaces of a base material, as the whole thickness of the light shielding layer arrange | positioned at one side (one side), 8 micrometers or less are preferable, and 4-8 micrometers is still more preferable, 5-7 micrometers is especially preferable. When each of the light shielding layers disposed on both sides is composed of two layers, a first light shielding layer (layer on the side in contact with the substrate) and a second light shielding layer (layer on the surface side), The thickness of the first light-shielding layer constituting the light-shielding layer on one side is preferably 0.5 to 3 μm, and more preferably 0.5 to 2.5 μm. Moreover, 3-6 micrometers is preferable and, as for the thickness of a 2nd light shielding layer, 4-5 micrometers is still more preferable.

  The concentration of the black pigment contained in the light shielding layer is preferably 3 to 60% by mass as a whole, and more preferably 5 to 55% by mass. When the amount is less than 3% by mass, the light shielding property and the electrical conductivity may be lowered. When the amount is more than 60% by mass, the coating film strength may be lowered, and the cost is increased. When the light-shielding layer is composed of two layers, a first light-shielding layer (layer on the side in contact with the substrate) and a second light-shielding layer (layer on the surface side), the black pigment contained in the first light-shielding layer The concentration of is preferably 30 to 60% by mass, more preferably 45 to 55% by mass. Moreover, it is preferable that the density | concentration of the black pigment contained in a 2nd light shielding layer is 3 mass% or more, and it is still more preferable that it is 4-10 mass%.

  As described above, in the light shielding film of the present invention, the light shielding layer may be composed of one layer or two layers as long as the concentration of the black pigment in the light shielding layer is increased on the substrate side. Although it may be comprised from the above, it is preferable that it is two or more layers from a viewpoint of productivity, light-shielding property, glossiness, and thickness reduction. As described above, when the light shielding layer is composed of the first light shielding layer (layer on the side in contact with the base material) and the second light shielding layer (layer on the surface side), the first light shielding layer In order to enhance the light-shielding property, it is preferable to keep the concentration of the black pigment as high as possible within a range in which the coating film strength can be maintained. Therefore, the first light shielding layer is preferably a layer containing a binder resin and a black pigment, and more preferably a layer containing only the binder resin and the black pigment. And it is preferable that the 2nd light shielding layer provided in the surface of a 1st light shielding layer is a layer containing binder resin, a black pigment, and a filler. By comprising in this way, it becomes possible to make the density | concentration of a black pigment high so that the 1st light shielding layer does not contain a filler, and it becomes possible to improve light-shielding property, although it is a thin layer. And by making a 2nd light shielding layer contain a filler, it will be in the state in which a filler will be exposed on the surface, it becomes possible to reduce glossiness and to reduce generation | occurrence | production of a reflection on the light shielding layer surface. Since the filler is exposed to the surface of the light shielding layer to reduce the glossiness, it is not necessary to contain the filler in the first light shielding layer located on the substrate side. And as a filler contained in a 2nd light shielding layer, a spherical organic resin particle, especially an acrylic resin particle are preferable from the surface of sliding property and abrasion resistance.

  The method of blending the binder resin, black pigment, and filler in each layer when the light shielding layer is two or more layers is not limited to the above-described form. For example, when the light shielding layer has two layers, the first light shielding layer (the layer on the side in contact with the base material) contains a binder resin and a black pigment (does not contain a filler), and the second light shielding layer (the surface side) The layer) can contain a binder resin and an organic filler (no black pigment). In addition, when the light shielding layer has two layers, the first light shielding layer contains a binder resin, a black pigment and a filler, and the second light shielding layer contains a binder resin, a black pigment and a filler, You may make it make the black pigment density | concentration of a 1st light shielding layer higher than a pigment density | concentration. Further, the light shielding layer is composed of three layers, and the first light shielding layer (the layer on the side in contact with the base material) contains a binder resin and a black pigment (no filler is contained), and the intermediate light shielding layer (the first light shielding layer and the second light shielding layer). Binder resin, black pigment and filler are contained in the light shielding layer located between the light shielding layers), and the binder resin and organic filler are contained in the second light shielding layer (surface side layer) (no black pigment is contained). )be able to.

  The light shielding film of this embodiment preferably has an optical density of 5.0 or more, and a glossiness of 6.0% or less. When the optical density is less than 5.0, the light shielding property may be insufficient. When the glossiness exceeds 6.0%, the effect of reducing the occurrence of reflection on the surface of the light shielding layer may be lowered. The optical density of the light shielding film is a value measured using an optical densitometer (Macbeth TD-904). The glossiness is a value obtained by measuring the specular glossiness using a glossmeter (MMX-202, manufactured by Murakami Color Research Laboratory).

  The light-shielding film of this embodiment has a thickness of 40 μm or less, preferably 30 to 40 μm. If it exceeds 40 μm, it is not satisfactory in terms of the required thinning. Moreover, since the light reflection preventing property at the cross section is lowered, it is not preferable because it impedes performance enhancement as a shutter or a diaphragm.

  In the light shielding film of this embodiment, as the base film (base material), synthetic resin films such as polycarbonate, polyester, polystyrene, polyimide, polyamide, and liquid crystal polymer are used. It is suitable because of its excellent balance. The base film can be a transparent polyester film, a foamed polyester film, a synthetic resin film containing black pigment such as carbon black, or other pigments. In this case, the base film can be selected appropriately depending on the application. For example, a black resin-containing synthetic resin film can be used when higher light shielding properties are required, and a transparent or foamed synthetic resin film can be used otherwise. The thickness of the base film varies depending on the purpose of use and the field of use, but is preferably 5 to 25 μm, more preferably 12 to 25 μm, from the object of the present invention aiming for further reduction in thickness.

  In the light shielding film of the present embodiment, examples of the binder resin include polyurethane resin, poly (meth) acrylic acid resin, polyester resin, polyvinyl acetate resin, polyvinyl chloride resin, polybutyral resin, cellulose resin, polystyrene / Examples thereof include thermoplastic resins such as polybutadiene resin, and these can be used alone or in combination. As the binder resin used in the present invention, a water-soluble or water-dispersible resin is used in order to make the particle size of the black pigment used to make the light-shielding layer thin and highly light-shielding as small as possible and uniformly disperse. Is preferred. Further, as the binder resin, Tg (glass transition temperature) is preferably 10 ° C. or higher, more preferably 10 to 150 ° C., and particularly preferably 15 to 140 ° C. in terms of flatness, slidability and heat resistance. . The softening point temperature is preferably 80 ° C. or higher, more preferably 80 to 300 ° C., particularly preferably 85 to 290 ° C., and most preferably 90 to 290 ° C.

  More preferably, a polyester resin is used as the binder resin. The present inventors have found that when a polyester resin is used as a binder resin, a light-shielding film having excellent hardness and scratch resistance and excellent flatness can be obtained. The polyester resin can be easily obtained by reacting a polyol and a polybasic acid under a catalyst by a conventionally known production method. Examples of the polyol include 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, and tetraethylene glycol. Examples of polybasic acids include aromatic dicarboxylic acids, unsaturated aliphatic dicarboxylic acids, their lower alkyl esters, and their acid anhydrides. Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, and naphthalenedicarboxylic acid. Examples of the unsaturated aliphatic dicarboxylic acid include fumaric acid, maleic acid, itaconic acid, citraconic acid and the like.

  In this embodiment, Tg is measured by differential scanning calorimetry (DSC), and the softening point temperature is measured by the penetration method or ring-and-ball method.

  The content of the binder resin in the light shielding layer is preferably 20 to 60% by mass and more preferably 25 to 55% by mass with respect to the total mass of the binder resin and the black pigment and filler described below. If it is less than this range, the adhesiveness between the base film and the light shielding layer is lowered, and if it is more than this range, it becomes difficult to balance the light shielding property and thickness reduction and the glossiness of the surface of the light shielding layer.

  The binder may be crosslinked with a crosslinking agent. The crosslinking agent used in this case may be appropriately selected from crosslinking agents having reactivity with the functional groups of the binder resin, and examples thereof include water-soluble urea resins, melamine resins, isocyanate compounds, and aziridine compounds. The blending ratio of the crosslinking agent is usually in the range of 5 to 15 parts by mass with respect to 100 parts by mass of the binder resin component. If the amount of the crosslinking agent used is less than this range, improvement of the coating film strength and heat resistance cannot be expected, and further improvement cannot be expected even if blended beyond this range.

  In the light shielding film of this embodiment, as a black pigment, various conventionally known pigments, for example, inorganic pigments such as carbon black and titanium black, organic pigments such as aniline black, and the like can be used. The average particle size of the black pigment is preferably 1 μm or less, more preferably 0.5 μm or less. The lower limit is usually about 0.01 μm. When the average particle size is larger than this range, the glossiness is sufficiently low, but the light shielding property is lowered, which is not preferable. By uniformly dispersing such pigments without agglomerating, it becomes possible to cope with high light shielding properties and thinning. As such a pigment, it is preferable to use a black pigment previously dispersed in an aqueous solvent.

  In the present invention, it is more preferable to use carbon black as the black pigment. The present inventors have found that when carbon black is used as a black pigment, a light-shielding film having particularly excellent light-shielding properties can be obtained. The black pigment to be contained in the light shielding layer needs to have a higher concentration of black pigment on the light shielding layer substrate side than on the light shielding layer surface side. By doing so, it is possible to have a sufficient light-shielding layer, which is a feature of the present invention, and to that extent, the amount of filler added on the surface side of the light-shielding layer can be increased, so that the glossiness is sufficiently lowered. In addition, the film thickness can be reduced. The black pigment content in the light shielding layer is preferably 3 to 60% by mass, and more preferably 5 to 55% by mass. By making a black pigment into such a range, it can be excellent in light-shielding property, maintaining favorable the electroconductivity and coating-film intensity | strength of a light-shielding film. When the amount is less than this range, the light shielding property and conductivity are lowered. When the amount is more than this range, the coating film strength is lowered and the cost is increased.

  In the light shielding film of the present embodiment, organic resin particles and / or inorganic particles can be used as the filler. By including such a filler, the coating film surface can be uneven, and as a result, the glossiness can be lowered.

  Examples of the organic resin particles used in the light-shielding film of the present embodiment include various synthetic resin particles such as melamine resin, benzoguanamine resin, benzoguanamine / melamine / formaldehyde resin, acrylic resin, urethane resin, and styrene resin. Examples of the inorganic particles include those made of powder such as synthetic silica, natural silica, kaolin, talc, clay, calcium carbonate, titania, alumina, zirconia, zeolite, barium sulfate, magnesium hydroxide, calcium phosphate, and glass. These fillers can be used alone or in combination of two or more. The shape of the filler may be either a spherical product or a pulverized product, but the use of a spherical product is preferable because the static friction coefficient is lowered and the slidability is improved. The filler content in the light-shielding layer is 5 to 70% by mass, preferably 10 to 65% by mass. If the content is outside this range, the glossiness of the surface may increase or the slidability may decrease. . The average particle size of the filler is 0.1 to 7 μm, preferably 0.2 to 6 μm. If it is larger than this range, it may be difficult to reduce the thickness, and if it is smaller, the glossiness of the film surface may be increased. is there. Also, several kinds of fillers having different average particle diameters can be mixed and used. For example, a filler of less than 1 μm and a filler of 1 to 6 μm may be mixed so that the glossiness becomes low for all angles from the low angle to the high angle of the light incident on the light shielding layer surface. Particularly preferred. Furthermore, the filler may be colored black or dark. In addition, the average particle diameter of a filler is the value measured by the same measuring method as the measuring method of the average particle diameter of the said black pigment.

  In the light-shielding film of this embodiment, the light-shielding layer may contain various known additives as necessary in addition to the above-described binder resin, black pigment, and filler. Examples of the additive include a filler surface treatment agent such as a lubricant and a coupling agent, a surfactant, an antistatic agent, a lubricant, and an antifoaming agent.

  Among these additives, as the lubricant, various conventionally known lubricants such as hydrocarbon lubricants such as polyethylene, aliphatic lubricants such as stearic acid, alcohol lubricants such as stearyl alcohol, molybdenum disulfide, and the like. Examples include solid lubricants, silicon-based resin particles, fluorine-containing resin particles, cross-linked polymethyl methacrylate particles, and cross-linked polystyrene particles. The shape of the lubricant may or may not be spherical, but the spherical shape is preferred from the viewpoint of slidability and gloss. The content of the lubricant is 5 to 20% by mass, preferably 7 to 15% by mass in the light-shielding layer, and if it is out of this range, the slidability and the glossiness become insufficient. The average particle size of the lubricant is 0.1 to 3 μm, preferably 0.15 to 2 μm. If the average particle size is larger than this range, it is difficult to reduce the thickness and the sliding effect is reduced. If it is smaller than the range, the glossiness becomes high and the anti-reflection property is inferior.

  As described above, the light-shielding film of the present invention can satisfy both the light-shielding property and the thinning at the same time, has a low glossiness, and can prevent the occurrence of reflection on the surface of the light-shielding layer. Therefore, it is suitable as a light-shielding member for optical equipment such as a shutter for an optical equipment and a diaphragm. Since the thickness can be reduced, it is easy to prevent reflection of light at the cross section of the light shielding member, and thus it can sufficiently cope with optical devices that require higher precision and the like. In the light-shielding film of the present invention, by adjusting the content of the black pigment in the light-shielding layer, it is excellent in light-shielding property and low glossiness while maintaining a thin thickness, and is reflected on the surface of the light-shielding layer. Therefore, it is possible to cope with various light shielding materials for optical devices.

  Next, one embodiment of the method for producing a light shielding film of the present invention will be described.

  In one embodiment of the method for producing a light-shielding film of the present invention, a first light-shielding layer coating solution containing a binder resin and a black pigment is applied to at least one surface of a base film (base material), dried, and dried. A step of obtaining a first light-shielding layer having a thickness of 2 to 6 μm, a binder resin, a black pigment and a filler on the surface of the first light-shielding layer, and the concentration of the black pigment in the first light-shielding layer coating solution A lower second light-shielding layer coating solution is applied and dried to obtain a second light-shielding layer having a thickness of 6 to 10 μm, and the light-shielding formed from the first light-shielding layer and the second light-shielding layer. The thickness of the layer is 15 μm or less. By this method, a light shielding film having two light shielding layers (a first light shielding layer and a second light shielding layer) can be produced.

  First, the 1st light shielding layer coating liquid containing binder resin and a black pigment is apply | coated to the one surface or both surfaces of a base material. The first light-shielding layer coating solution is obtained by dissolving or dispersing a binder resin and a black pigment in a solvent, and adding and mixing various additives as necessary. As the solvent, water, an organic solvent, a mixture of water and an organic solvent, or the like can be used. In the present embodiment, the substrate, binder resin, black pigment, and various additives may be those listed in the description of the light shielding film of the present invention. Particularly, black pigments are preferable in that carbon black is water-dispersible and can be uniformly dispersed throughout the coating liquid. The same applies to the black pigment contained in the second light shielding layer coating solution. Further, the binder resin is preferably water-soluble or water-dispersible from the viewpoint that it can be uniformly dispersed throughout the coating liquid. The same applies to the binder resin contained in the second light shielding layer coating solution. And the compounding quantity of each compound in a 1st light shielding layer coating liquid is content of each compound of the 1st light shielding layer in the said light shielding film of the said invention, when it dries and forms a 1st light shielding layer It is preferable to prepare such that

  Here, prior to the formation of the light-shielding layer, a surface treatment that is commonly used for improving the adhesion between the light-shielding layer and the substrate film can be applied to the substrate, if necessary. Such surface treatments include corona discharge treatment, glow discharge treatment, plasma treatment, flame treatment, ultraviolet treatment, electron beam treatment, radiation treatment, etc .; rough surfaces such as sand mat treatment, hairline treatment, etc. Physical treatment such as chemical treatment; chemical surface treatment such as ozone treatment and chemical treatment; anchor layer made of thermoplastic resin such as polyester, polyamide, acrylic resin, thermosetting resin or ultraviolet curable resin Anchor treatment for forming

  Next, the base material coated with the first light shielding layer coating liquid is dried to form the first light shielding layer. The drying method is not particularly limited, and a known method can be used, but hot air drying is preferable. The thickness of the first light-shielding layer after drying is 1 to 6 μm and preferably 1 to 5 μm when the light-shielding layer is disposed only on one side of the substrate. Moreover, when arrange | positioning the light shielding layer on both surfaces of a base material, the whole thickness of a 1st light shielding layer is 1-6 micrometers. When disposing the light shielding layer on both surfaces of the substrate, the thickness of the first light shielding layer on one side is preferably 0.5 to 3 μm, and more preferably 0.5 to 2.5 μm.

  Next, a second light shielding layer coating solution containing a binder resin, a black pigment, and a filler and having a black pigment concentration lower than the black pigment concentration in the first light shielding layer coating solution is applied to the surface of the first light shielding layer. To do. The second light shielding layer coating solution is obtained by dissolving or dispersing a binder resin, a black pigment, and a filler in a solvent and adding various additives as necessary. As the solvent, water, an organic solvent, a mixture of water and an organic solvent, or the like can be used. The blending amount of each compound in the second light-shielding layer coating liquid is the content of each compound in the second light-shielding layer in the light-shielding film of the present invention when dried to form the second light-shielding layer. It is preferable to prepare as follows.

  Next, the base material coated with the second light-shielding layer coating liquid is dried to form a light-shielding layer composed of the first light-shielding layer and the second light-shielding layer, whereby the light-shielding film of this embodiment can be obtained. The drying method is not particularly limited, and a known method can be used, but hot air drying is preferable. The thickness of the second light-shielding layer after drying is 6 to 10 μm and preferably 7 to 10 μm when the light-shielding layer is disposed only on one side of the substrate. Moreover, when arrange | positioning a light shielding layer on both surfaces of a base material, the whole thickness of a 2nd light shielding layer shall be 6-10 micrometers. When disposing the light shielding layer on both surfaces of the substrate, it is preferable that the thickness of the first light shielding layer on one side is 0.5 to 3 μm.

  The thickness of the light shielding layer formed from the first light shielding layer and the second light shielding layer (the total thickness of the light shielding layer) is preferably 15 μm or less, and preferably 8 to 14 μm. When the light shielding layer is disposed only on one side of the base material, the total thickness of the light shielding layer is preferably 7 to 14 μm. Moreover, when arrange | positioning a light shielding layer on both surfaces of a base material, as thickness (one side thickness) for one layer, 8 micrometers or less are preferable, 4-8 micrometers is still more preferable, and 5-7 micrometers is especially preferable.

  The obtained light-shielding film preferably has an optical density of 5.0 or more and a glossiness of 6.0% or less. When the optical density is less than 5.0, the light shielding property may be insufficient. When the glossiness exceeds 6.0%, the effect of reducing the occurrence of reflection on the surface of the light shielding layer may be lowered.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. Moreover, the measuring method of various physical-property values and the evaluation method of various characteristics are shown below.

(1) Light shielding properties:
The optical density of the light shielding film was measured with an optical densitometer TD-904 manufactured by Macbeth. A case where the optical density was 5 or less was evaluated as “good”, and a case where the optical density was higher than 5 was determined as “bad”.

(2) Glossiness (%):
The glossiness at 60 ° was measured with a gloss meter (GMX-202, manufactured by Murakami Color Research Laboratory). A case where the glossiness was 6% or less was evaluated as “good”, and a case where the glossiness was higher than 6% was evaluated as “bad”.

(3) Thickness (μm):
Three points were measured with a paper thickness measuring instrument (MEI-10 manufactured by Citizen Co., Ltd.), and the average value was obtained.

Example 1
After applying a first light-shielding layer coating solution having the following formulation (composition) on both sides of a carbon black-containing polyester film having a thickness of 25 μm and drying at 100 ° C. for 2 minutes to form a first light-shielding layer having a thickness of 2 μm, On this 1st light shielding layer, the 2nd light shielding layer coating liquid of the following prescription (composition) was apply | coated, and it dried for 2 minutes at 100 degreeC, and obtained the light shielding film by forming a 4 micrometers-thick 2nd light shielding layer. It was. In addition, the thickness of the whole light shielding film was 37 micrometers. About the obtained light shielding film, light-shielding property and glossiness were measured by the said method. The results are shown in Table 1.

First light shielding layer coating solution:
Binder resin; polyester emulsion (water dispersion with a solid content of 25%)
(Number average molecular weight = (15000), Tg = 20 ° C.) 40.9 parts by mass Black pigment; Carbon black water dispersion (31% solids water dispersion)
(Particle size = (0.3) μm) 35.1 parts by mass Methyl ethyl ketone; 19.2 parts by mass Water; 4.8 parts by mass

Second light shielding layer coating solution:
Binder resin; polyester emulsion (water dispersion with a solid content of 34%)
(Number average molecular weight = (15000), Tg = 67 ° C.) 26.0 parts by mass Black pigment; carbon black water dispersion (water dispersion with a solid content of 31%)
(Particle size = (0.3) μm) 6.0 parts by mass Filler; benzoguanamine / melamine / formaldehyde resin (particle size = 0.4 μm) 3.0 parts by mass Filler; Benzoguanamine / melamine / formaldehyde resin (particle size = 2) 0.5 μm) 8.8 parts by mass Filler; Benzoguanamine / melamine / formaldehyde resin (particle size = 4.5 μm) 5.0 parts by mass Coupling agent; ((manufactured by Chisso) Silaace S510) 0.2 parts by mass ethyl alcohol; 21.5 parts by weight water; 29.5 parts by weight

(Example 2)
A light shielding film was obtained in the same manner as in Example 1 except that the thickness of the first light shielding layer was 1 μm and the thickness of the second light shielding layer was 5 μm. In addition, the thickness of the whole light shielding film was 37 micrometers. About the obtained light shielding film, light-shielding property and glossiness were measured by the said method. The results are shown in Table 1.

(Example 3)
A light shielding film was obtained in the same manner as in Example 1 except that the thickness of the first light shielding layer was 3 μm and the thickness of the second light shielding layer was 4 μm. In addition, the thickness of the whole light shielding film was 39 micrometers. About the obtained light shielding film, light-shielding property and glossiness were measured by the said method. The results are shown in Table 1.

(Comparative Example 1)
50 parts by mass of the first light-shielding layer coating solution and 100 parts by mass of the second light-shielding layer coating solution used in Example 1 were mixed and made uniform to obtain a coating solution A. The obtained coating liquid A was applied on both sides of the same carbon black-containing polyester film as in Example 1, dried at 100 ° C. for 2 minutes to form a 6 μm thick light shielding layer, and a light shielding film was obtained. In addition, the thickness of the whole light shielding film was 37 micrometers. About the obtained light shielding film, light-shielding property and glossiness were measured by the said method. The results are shown in Table 1.

(Comparative Example 2)
A coating solution having the same composition as the second light-shielding layer coating solution used in Example 1 was applied to both sides of the same carbon black-containing polyester film as in Example 1, dried at 100 ° C. for 2 minutes, and a thickness of 2 μm. Next, a coating solution having the same composition as the first light shielding layer coating solution used in Example 1 was applied to the surface of the first light shielding layer and dried at 100 ° C. for 2 minutes. A light shielding film was obtained by forming a second light shielding layer having a thickness of 4 μm. In addition, the thickness of the whole light shielding film was 37 micrometers. About the obtained light shielding film, light-shielding property and glossiness were measured by the said method. The results are shown in Table 1.

  From Table 1, it turns out that the light shielding film of Examples 1-3 is excellent in the light-shielding property compared with the light shielding film of Comparative Examples 1 and 2. This is considered to be because the light-shielding films of Examples 1 to 3 have more carbon black in the first light-shielding layer, and the carbon black is concentrated in a narrow range, so that the light-shielding property is further improved. It is done. And it turns out that the light shielding film of Examples 1-3 is excellent also in the glossiness compared with the light shielding film of Comparative Examples 1 and 2.

  The present invention can be suitably used as a light shielding member for various optical devices such as cameras, video cameras, copying machines, and developing machines.

Claims (10)

A light-shielding film comprising a base film (base material) and a light-shielding layer disposed on at least one surface of the base material,
The light shielding layer contains a binder resin, 5 to 55% by mass of a black pigment and a filler, and the total thickness is 15 μm or less,
A region of the light shielding layer close to the surface in contact with the substrate is constituted by a first light shielding layer containing a binder resin and a black pigment,
The concentration of the black pigment contained in the first light shielding layer is 30 to 60% by mass,
A region near the surface of the light shielding layer is constituted by a second light shielding layer containing a binder resin, a black pigment and a filler,
The concentration of the black pigment contained in the second light shielding layer is 3% by mass or more and lower than the concentration of the black pigment contained in the first light shielding layer,
A light-shielding film having an overall thickness of 40 μm or less. The light shielding film according to claim 1, wherein the light shielding layer is disposed on both surfaces of the base material, and the thickness of the light shielding layer on one surface is 8 μm or less. Shielding film according to claim 1 or 2 wherein the filler is an organic resin particles and / or inorganic particles. The light-shielding film according to any one of claims 1 to 3 , wherein the binder resin contains a polyester resin having a glass transition temperature (Tg) of 10 to 150 ° C. And the optical density of 5.0 or more, the light-shielding film according to any one of claims 1-4 glossiness is less than 6.0%. A first light-shielding layer coating solution containing a binder resin and a water-dispersible black pigment of 30 to 60% by mass after drying is applied to at least one surface of the substrate film (substrate) and dried. Obtaining a first light-shielding layer having an overall thickness of 1 to 6 μm;
The surface of the first light-shielding layer contains a binder resin, a water-dispersible black pigment and a filler, the concentration of the black pigment is 3% by mass or more after drying, and the first light-shielding layer coating is applied Applying and drying a second light-shielding layer coating liquid lower than the concentration of the black pigment in the liquid to obtain a second light-shielding layer having an overall thickness of 6 to 10 μm,
The binder resin is water-soluble or water-dispersible,
A method for producing a light-shielding film, wherein a thickness of the light-shielding layer formed from the first light-shielding layer and the second light-shielding layer is 15 μm or less and a concentration of the black pigment is 5 to 55% by mass. The first light-shielding layer coating solution and the second light-shielding layer coating solution are applied to both surfaces of the base material, the total thickness of one surface is 8 μm or less, and the thickness of the first light-shielding layer on one surface is 0.5. The method for producing a light-shielding film according to claim 6 , wherein the thickness of the second light-shielding layer on one side is 3 to 6 μm. The method for producing a light-shielding film according to claim 6 or 7 , wherein the binder resin contains a polyester resin having a glass transition temperature (Tg) of 10 to 150 ° C. And the optical density of 5.0 or more, a manufacturing method of the light-shielding film according to any one of claims 6-8 gloss to produce a light-shielding film is not more than 6.0%. Method for producing a light-shielding film according to any one of the black pigment according to claim 6-9 is carbon black.