Light-shielding film, light-shielding member formed using same, lens unit, and camera module

Abstract

Provided is a light-shielding film for obtaining a light-shielding member capable of visually distinguishing the front and back surfaces while suppressing the occurrence of glare and ghosting. (A) is the glossiness with respect to light at an incidence angle of 60 degrees, (B) is the reflectance with respect to light at a wavelength of 550 nm, (C) is the L value in a CIELAB color system based on the SCE method, and (D) is the optical density (OD). In this case, the light-shielding film (100) is a light-shielding film for obtaining a light-shielding member for an optical device, and has at least a first light-shielding layer (21) and a second light-shielding layer (31). The outermost surfaces (A), (B), (C), and (D) of the surfaces on which the first light-shielding layer (21) and the second light-shielding layer (31) are formed are 2% or less, 4.5% or less, 26 or less, and 1.0 or more, respectively. The difference (B) and the difference (C) between the outermost surface of the surface on which the first light-shielding layer (21) is formed and the outermost surface of the surface on which the second light-shielding layer (31) is formed are 2% or less and 4 or more, respectively.

Description

Technical Field

[0001] The present invention relates to a light-shielding film, and a light-shielding component, a lens unit and a camera module formed using the light-shielding film. Background Art

[0002] Camera modules for photographing subjects and converting them into image signals are built into electronic devices such as smartphones, tablet terminals, and digital cameras. The camera module needs to eliminate scattered light (hereinafter referred to as "unnecessary light") such as incident light and reflected light that are unnecessary for the imaging of the subject image on the imaging element, and prevent the occurrence of halos, lens glare, and afterimages (hereinafter referred to as "glare and afterimages") to improve the image quality of the captured image. To this end, a light shielding component for removing unnecessary light is assembled into the lens unit used in the camera module.

[0003] Such a known light shielding member is obtained by processing a light shielding film having light shielding layers containing carbon black, a lubricant, fine particles and a binder resin formed on both surfaces of a film substrate into a desired shape (for example, Patent Document 1).

[0004] When a shading component of a desired shape is manufactured from a shading film, or when the manufactured shading component is assembled into a camera module, if the front and back sides of the shading film or the shading component cannot be distinguished, manufacturing failures such as poor assembly may occur. In the past, in order to distinguish the front and back sides, a coating made of water-based ink was printed on the shading layer on one side of the shading film as a mark, and its thickness did not affect the optical properties of the shading layer, for example, less than 1 μm. However, when the shading film or the shading component is transported or assembled into a camera module, the coating made of the water-based ink may fall off from the shading layer on one side formed due to slight stimulation such as contact, and become a contaminant (called contamination).

[0005] In order to solve this problem without printing a mark on the light-shielding layer, for example, Patent Document 2 discloses a technology in which the glossiness of both the light-shielding layer on one side and the light-shielding layer on the other side is set to less than 10%, and a glossiness difference is provided between the light-shielding layer on one side and the light-shielding layer on the other side.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: WO2006 / 16555

[0009] Patent Document 2: Patent No. 6368445 (Paragraph 0030) Summary of the invention

[0010] Problem that the invention aims to solve

[0011] In the technology of Patent Document 2, since no mark is printed on the shading layer, the above-mentioned pollution problem can be solved. However, according to the technology of Document 2, the glossiness of the shading film or shading member is high, and the glossiness of the shading layers on both sides is less than 10%. Therefore, even if there is a difference in glossiness between the two shading layers, it may not be possible to fully remove unnecessary light. A camera module in which a shading film or shading member that cannot fully remove unnecessary light is assembled in the lens unit is prone to glare and afterimages, resulting in a decrease in the quality of the camera image.

[0012] The present invention is proposed in view of the above situation. The purpose of the present invention is to provide a light-shielding film for obtaining a light-shielding component that suppresses the generation of glare and afterimage in a camera module assembled in a lens unit and can visually distinguish the front and back sides, and also to provide a light-shielding component, a lens unit and a camera module formed using the light-shielding film.

[0013] Solutions to the problem

[0014] After in-depth research, the inventors have discovered that by satisfying the following requirements, the generation of glare and afterimages in a camera module assembled into a lens unit can be reduced, and at the same time, the front and back sides of the shading component and the shading film can be visually and effectively identified.

[0015] - having at least a specific first light-shielding layer and a second light-shielding layer, the outermost surfaces of which have a plurality of prescribed optical properties, in particular, an extremely low glossiness of 2% or less and a low reflectivity of 4.5% or less.

[0016] - As the first light-shielding layer and the second light-shielding layer, the prescribed optical properties of the outermost surfaces, in particular, the difference in L value and reflectivity, are within prescribed ranges.

[0017] Based on the above new insights, the inventors have completed the invention provided below to solve the above problems. Hereinafter, glossiness relative to light at an incident angle of 60° is abbreviated as (A), reflectivity relative to light of a wavelength of 550 nm is abbreviated as (B), L value in the CIELAB colorimetric system based on the SCE method is abbreviated as (C), and optical density (OD) is abbreviated as (D).

[0018] According to the present invention, there is provided a light-shielding film for obtaining a light-shielding member for an optical device.

[0019] At least a first light-shielding layer and a second light-shielding layer are provided.

[0020] The outermost surfaces (A), (B), (C) and (D) of the surfaces formed by the first light-shielding layer and the second light-shielding layer are respectively less than 2%, less than 4.5%, less than 26 and greater than 1.0, and,

[0021] The difference in (B) and the difference in (C) between the outermost surface of the surface formed by the first light-shielding layer and the outermost surface of the surface formed by the second light-shielding layer are 2% or less and 4 or more, respectively.

[0022] The light shielding film may include the following aspects.

[0023] - The difference in (A) between the outermost surface of the surface formed by the first light-shielding layer and the outermost surface of the surface formed by the second light-shielding layer may be 0.5% or less.

[0024] - The outermost surface of the surface formed by the first light-shielding layer may have 2.4% or less of the (B).

[0025] - The outermost surface of the surface formed by the second light-shielding layer may have 2.8% or more of the above (B).

[0026] - The outermost surface of the surface formed by the first light shielding layer may have 18 or less of the above (C).

[0027] - The outermost surface of the surface formed by the second light-shielding layer may have 17 to 25 of the above (C).

[0028] - The outermost surface of the surface formed by the first light-shielding layer may have the above (D) of 2.0 or more.

[0029] - The outermost surface of the surface formed by the second light-shielding layer may have the (D) of 1.5 or less.

[0030] According to the present invention, there is provided a light shielding member which is formed of the light shielding film and is used in a lens unit including a lens group composed of a plurality of lenses stacked in an optical axis direction in a holder.

[0031] According to the present invention, there is provided a lens unit including a lens group composed of a plurality of lenses stacked in an optical axis direction in a holder, and the light shielding member is interposed between at least a pair of lenses.

[0032] According to the present invention, a camera module is provided, which includes the lens unit and an imaging element, and the imaging element captures an image of a subject through the lens unit.

[0033] Effects of the Invention

[0034] The present invention can provide a shading film for obtaining a shading component that suppresses the generation of glare and afterimages in a camera module assembled in a lens unit and can visually distinguish the front and back sides. Also provided are a shading component, a lens unit and a camera module formed using the shading film. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic cross-sectional view showing a light-shielding film according to the first embodiment of the present invention.

[0036] Figure 2 This is a schematic exploded perspective view showing a lens unit and a camera module in which a light shielding member according to the first embodiment of the present invention is incorporated. DETAILED DESCRIPTION

[0037] The best embodiment of the present invention is described below. However, the present invention is not limited to the following embodiments. Without departing from the spirit of the present invention, those skilled in the art may make appropriate changes and improvements to the following embodiments based on their general knowledge, and these also fall within the scope of the present invention.

[0038] In the numerical range described in the present specification, the upper limit or lower limit described in some numerical ranges may be replaced with a numerical value shown in the Examples.

[0039] In this specification, when there are multiple substances corresponding to each component in the composition, the content rate or content of each component in the composition means the total content rate or content of the multiple substances present in the composition unless otherwise specified.

[0040] <Light-shielding film>

[0041] like Figure 1 As shown, the light shielding film 100 according to the first embodiment of the present invention comprises at least: a base film 11; a first light shielding layer 21, which is arranged on one main surface 11a side of the base film 11; and a second light shielding layer 31, which is arranged on the other main surface 11b side of the base film 11. The light shielding film 100 has a stacked structure (three-layer structure), and the stacked structure is arranged in the order of at least the light shielding layer 21, the base film 11 and the light shielding layer 31.

[0042] The so-called "arranged on one side (the other side) of the main surface of the base film" means not only including the method of directly placing the light-shielding layers 21 and 31 on the surface of the base film 11 (for example, the main surface 11a or the main surface 11b), but also including the method of sandwiching any layer (for example, an anchoring layer, an adhesive layer, etc.) between the surface of the base film 11 and the light-shielding layers 21 and 31. In addition, the so-called stacked structure including at least the first light-shielding layer 21 and the second light-shielding layer 31 means not only including the structure in which only the first light-shielding layer 21 and the second light-shielding layer 31 are directly stacked, but also including the above-mentioned three-layer structure, and the structure in which any layer is further arranged in the three-layer structure.

[0043] -Basement membrane-

[0044] The type of the base film 11, which is one of the elements of the shading film 100, is not particularly limited as long as it can support the shading layers 21 and 31. From the viewpoints of dimensional stability, mechanical strength, and lightweight, it is preferred to use a synthetic resin film. Specific examples of synthetic resin films include polyester films, ABS (acrylonitrile-butadiene-styrene) films, polyimide films, polystyrene films, and polycarbonate films. In addition, acrylic, polyolefin, cellulose, polysulfone, polyphenylene sulfide, polyether sulfone, and polyether ether ketone films can also be used. Among these, as the base film 11, polyester films and polyimide films are preferably used. In particular, uniaxial or biaxially stretched films, especially biaxially stretched polyester films, are particularly preferred due to their excellent mechanical strength and dimensional stability. In addition, uniaxially or biaxially stretched polyimide films are particularly preferred for heat-resistant purposes. These can be used alone or in combination of two or more.

[0045] The thickness of the base film 11 can be appropriately set according to the desired performance and purpose, and there is no particular restriction. From the viewpoint of light weight and thinness, the thickness of the base film 11 is preferably 0.5 μm to 50 μm, more preferably 1 μm to 25 μm, further preferably 4 μm to 10 μm, and particularly preferably 5 μm to 7 μm. In addition, from the viewpoint of improving the adhesion with the light shielding layers 21 and 31, various known surface treatments such as anchoring treatment and corona treatment can be applied to the surface of the base film 11 as needed.

[0046] The appearance of the base film 11 can be any one of transparent, translucent or opaque, and there is no particular restriction. For example, a foamed synthetic resin film such as a foamed polyester film, or a synthetic resin film containing a black pigment such as carbon black or other pigments can also be used. The pigment that can be contained is not particularly limited, and any one of resin particles and inorganic particles can also be used. As resin particles, there can be listed: melamine resin, benzoguanamine resin, benzoguanamine / melamine / formalin condensate, acrylic resin, urethane resin, styrene resin, fluororesin and silicone resin, etc. As inorganic particles, there can be listed: silicon dioxide, aluminum oxide, calcium carbonate, barium sulfate, titanium oxide, magnetite black, copper / iron / manganese black, titanium black, carbon black and aniline black, etc. These pigments can be used alone or in combination of two or more.

[0047] The content ratio of the pigment in the base film 11 can be appropriately set according to the required performance, etc., and is not particularly limited. For example, it is 0.3 mass % or more, preferably 0.4 mass % or more, and for example, it is 15 mass % or less, preferably 12 mass % or less, relative to the base film 11.

[0048] Before setting the surface of the base film 11 and the light shielding layers 21 and 31, an anchoring layer may also be set to improve the adhesion between the surface of the base film 11 and the light shielding layers 21 and 31. As the anchoring layer, a urea resin layer, a melamine resin layer, an urethane resin layer, a polyester resin, etc. can be applied. For example, the urethane resin layer is obtained by applying a solution containing polyisocyanate and active hydrogen-containing compounds such as diamines and diols to the surface of the base film 11 and curing it. In addition, urea resins and melamine resins can be obtained by applying a solution containing a water-soluble urea resin or a water-soluble melamine resin to the surface of the base film 11 and curing it. Polyester resins can be obtained by applying a solution dissolved or diluted with an organic solvent (methyl ethyl ketone, toluene, etc.) to the surface of the base film 11 and drying it.

[0049] -Light-shielding layer-

[0050] The light-shielding film 100 includes light-shielding layers 21 and 31, each of which has (A) of less than 2%, (B) of less than 4.5%, (C) of less than 26%, and (D) of greater than 1.0 on its surface.

[0051] Here, if the light shielding layers 21 and 31 are exposed on the outermost surface, as described above, the surface of each layer only needs to have the above-defined (A), (B), (C), and (D). On the other hand, when other layers are coated on the light shielding layers 21 and 31, the surface of the other layers, that is, the outermost surface of the light shielding film 100 only needs to have the above-defined (A), (B), (C), and (D). Hereinafter, these surfaces are collectively referred to as "outermost surface".

[0052] The light shielding layers 21 and 31, which are one of the elements of the light shielding film 100, have a light shielding film having (A) of less than 2%, (B) of less than 4.5%, (C) of less than 26, and (D) of more than 1.0 on each outermost surface, wherein the difference in (B) between the outermost surface of the light shielding layer 21 and the outermost surface of the light shielding layer 31 is set to less than 2%, and the difference in (C) is set to more than 4. If necessary, the difference in (A) between the outermost surface of the light shielding layer 21 and the outermost surface of the light shielding layer 31 can be further set to less than 0.5%.

[0053] -(A) Glossiness relative to light with an incident angle of 60°-

[0054] In the present specification, (A) is a value obtained by measuring the gloss (specular gloss) of each outermost surface of the light shielding layers 21 and 31 at an incident light receiving angle of 60° using a gloss meter (VG 7000: Nippon Denshoku Industries) in accordance with JIS Z8741. From the viewpoint of effectively preventing glare and afterimage phenomena caused by diffuse reflection of light, (A) of each outermost surface of the light shielding layer 21 and the light shielding layer 31 is preferably 1.5% or less, more preferably 1% or less, and further preferably 0.7% or less. From the viewpoint of suppressing glare and afterimage phenomena caused by unnecessary light, (A) of the outermost surface of the light shielding layer 21 is preferably 1% or less, more preferably 0.5% or less, and further preferably 0.3% or less. On the other hand, from the viewpoint of suppressing glare and afterimage phenomena caused by unnecessary light, (A) of the outermost surface of the light shielding layer 31 is preferably 1.5% or less, more preferably 1% or less, and further preferably 0.7% or less.

[0055] -(B) Reflectivity with respect to light of wavelength 550nm-

[0056] (B) is a value obtained by measuring the reflectivity of each outermost surface of the light-shielding layers 21 and 31 for light of a wavelength of 550 nm using a spectrophotometer (CM-5: Konica Minolta) according to JIS Z8722. From the viewpoint of more effectively preventing glare and afterimage phenomena caused by diffuse reflection of light, (B) of each outermost surface of the light-shielding layer 21 and the light-shielding layer 31 is preferably 4.4% or less, more preferably 4.2% or less, and further preferably 4.0% or less. From the viewpoint of suppressing glare and afterimage phenomena caused by unnecessary light and making it easier to visually distinguish the front and back surfaces, the upper limit of (B) of the outermost surface of the light-shielding layer 21 is preferably 2.4% or less, more preferably 2.2% or less, and further preferably 2% or less. The lower limit of (B) is not particularly limited, and for example, it is preferably 0.8% or more, more preferably 1.0% or more, and further preferably 1.1% or more. On the other hand, from the viewpoint of visually making it easier to distinguish the front and back surfaces, (B) of the outermost surface of the light shielding layer 31 is preferably 2.8% or more, more preferably 3.0% or more, and even more preferably 3.1% or more.

[0057] -(C) L value in CIELAB color system based on SCE method-

[0058] (C) is an index indicating blackness, which is the brightness L* value of the outermost surface in the CIE 1976 L*a*b* (CIELAB) colorimetric system using the SCE method. The SCE method is a method that excludes regular reflected light, that is, a method for measuring color by excluding regular reflected light. The definition of the SCE method is specified in JIS Z8722: 2009. In the SCE method, regular reflected light is excluded for measurement, so the color is close to the color actually seen by the naked eye.

[0059] CIE is the abbreviation of Commission Internationale de 1'Eclairage, which stands for International Commission on Illumination. The CIELAB colorimetric system is a uniform color space recommended in 1976 and specified in JIS Z8781:2013, which is used to measure color differences caused by differences in perception and equipment. The three coordinates of CIELAB are represented by L*, a*, and b* values. The L* value represents brightness and is expressed on a scale of 0 to 100. An L* value of 0 represents black, and an L* value of 100 represents a diffuse white color. The a* value represents a color between red and green. A negative a* value represents a greenish color, and a positive a* value represents a reddish color. The b* value represents a color between yellow and blue. A negative b* value represents a bluish color, and a positive b* value represents a yellowish color.

[0060] This (C) is a value obtained by measuring the brightness L* value of each outermost surface of the light shielding layers 21 and 31 in the CIE 1976 L*a*b* (CIELAB) color system using a spectrophotometer (CM-5: Konica Minolta) using the SCE method in accordance with JIS Z8781-4:2013.

[0061] From the viewpoint of suppressing glare and afterimage due to unnecessary light and enhancing blackness to improve designability, the (C) of each outermost surface of the light shielding layer 21 and the light shielding layer 31 is preferably 25 or less, and more preferably 23 or less. From the viewpoint of suppressing glare and afterimage due to unnecessary light and enhancing blackness to further improve designability, the (C) of the outermost surface of the light shielding layer 21 is preferably 18 or less, more preferably 17 or less, more preferably 16 or less, further preferably 15 or less, further preferably 14 or less, and most preferably 13 or less. On the other hand, from the viewpoint of suppressing glare and afterimage due to unnecessary light and making it easier to visually distinguish the front and back sides, the (C) of the outermost surface of the light shielding layer 31 is preferably 17 or more, more preferably 18 or more, and further preferably 19 or more.

[0062] -(D) Optical density-

[0063] (D) is a value calculated by irradiating a vertical transmission light beam to each outermost surface side of the light-shielding layers 21 and 31 using a densitometer (X-rite 361T (Ortho filter): Japan Lithographic Materials Co., Ltd.), and expressing it in log (logarithm) as a ratio to the state without the light-shielding layers 21 and 31. From the viewpoint of imparting a higher light-shielding property, each outermost surface of the light-shielding layer 21 and the light-shielding layer 31 has a (D) of 1.0 or more. From the viewpoint of suppressing glare and afterimage phenomena caused by unnecessary light, and making it easy to visually distinguish the front and back surfaces, while achieving a high light-shielding property of the light-shielding layer, the outermost surface of the light-shielding layer 21 preferably has a (D) of 2.0 or more, and from the viewpoint of obtaining good substrate adhesion, it is more preferable to have a (D) of 2.0 or more and 2.4 or less. On the other hand, from the perspective of suppressing glare and afterimages caused by unnecessary light, making it easier to visually distinguish the front and back surfaces, and obtaining better substrate adhesion, the (D) of the outermost surface of the shading layer 31 is preferably less than 1.5, and more preferably less than 1.4.

[0064] In addition, when the light shielding layer 21 and the light shielding layer 31 are stacked, the (D) of the stacked body is preferably 3.0 to 5.0, and more preferably 3.5 to 4.0. In this case, for example, a stacked body having a total (D) of 3.0 to 5.0 is formed by using a light shielding layer 21 having a (D) of 2.0 or more and a light shielding layer 31 having a (D) of 1.0 to 1.5 or less, and making the front and back sides of the stacked structure have different optical densities, because the front and back sides of the stacked structure can be more clearly distinguished, and therefore it is preferred.

[0065] - Configuration Example -

[0066] The light shielding layers 21, 31 having such characteristics may be composed of components including a resin component, particles, and a coloring / conductive agent.

[0067] -Resin ingredients-

[0068] The resin component becomes a binder for particles and coloring / conductive agent. The material of the resin component is not particularly limited, and any of thermoplastic resins and thermosetting resins can also be used. Specific thermosetting resins include: acrylic resins, urethane resins, phenolic resins, melamine resins, urea resins, diallyl phthalate resins, unsaturated polyester resins, epoxy resins, alkyd resins, etc. In addition, thermoplastic resins include: polyacrylate resins, polyvinyl chloride resins, butyral resins, styrene-butadiene copolymer resins, etc. From the viewpoint of heat resistance, moisture resistance, solvent resistance and surface hardness, it is preferred to use thermosetting resins. As thermosetting resins, acrylic resins are particularly preferred in consideration of flexibility and toughness of the film.

[0069] By adding a curing agent as a constituent component of the light-shielding layers 21 and 31, the cross-linking of the resin component can be promoted. As the curing agent, urea compounds, melamine compounds, isocyanate compounds, epoxy compounds, aziridine compounds, oxazoline compounds, etc. having functional groups can be used. Among these, isocyanate compounds are particularly preferred. The mixing ratio of the curing agent is preferably 10 to 50% by mass relative to 100% by mass of the resin component. By adding the curing agent within the above range, a light-shielding layer with a more suitable hardness can be obtained, and the optical properties of the surface of the light-shielding layers 21 and 31 can be maintained for a long time even when sliding with other components.

[0070] When a curing agent is used, a reaction catalyst may be used in combination to promote the reaction. Examples of the reaction catalyst include ammonia and ammonium chloride. The mixing ratio of the reaction catalyst is preferably in the range of 0.1 to 10% by mass relative to 100% by mass of the curing agent.

[0071] - Particles and coloring / conductive agents -

[0072] The light shielding layers 21 and 31 may contain particles and coloring / conductive agents. For example, by using two or more particle groups having different particle sizes and particle size distributions as particles and coloring / conductive agents, the above-specified optical properties of each outermost surface of the light shielding layers 21 and 31 can be preferably controlled within the specified range of the present invention.

[0073] For example, when two particle groups of different sizes are used, the particle size of the large particle group is preferably 10 to 40 times that of the small particle group. When three or more particle groups are used, the particle size of the largest particle group and the particle size of the smallest particle group are adjusted to satisfy the above relationship.

[0074] In the following description, the large particle group is referred to as large particles 1 and the small particle group is referred to as small particles 2.

[0075] The light shielding layers 21 and 31 of the first embodiment preferably contain, as a particle group, large particles 1 having an average particle size of 2 to 6 μm and small particles 2 having an average particle size of 0.06 to 0.4 μm. The average particle size of the large particles 1 is preferably 3 to 5 μm, more preferably 3 to 4 μm. The average particle size of the small particles 2 is 0.06 to 0.4 μm, more preferably 0.1 to 0.3 μm.

[0076] By combining large particles 1 and small particles 2 having such a particle size, and embedding small particles 2 between large particles 1 in the recesses, the above-specified optical properties of each outermost surface of the light-shielding layers 21 and 31 can be preferably controlled within the specified range of the present invention.

[0077] The content of the particles depends on the average particle size of the particle group, the particle size distribution, the film thickness of the light shielding layer 21, 31 and the surface shape of the base film 11. Assuming that the light shielding layer 21, 31 as a whole is 100 volume%, it is preferably 20 volume % to 50 volume %. In addition, the mixing ratio of the large particles 1 and the small particles 2 is not particularly limited, as long as the above-mentioned prescribed optical properties of each outermost surface of the light shielding layer 21, 31 can be adjusted within the prescribed range of the present invention, preferably 1.5:1 to 3.5:1 (volume occupied by large particles 1: volume occupied by small particles 2). In addition, the volume content (volume occupancy) of the particles in the light shielding layer 21, 31 can be obtained by converting it into an area occupancy calculated by image analysis or other methods from a cross-sectional photograph of the light shielding layer 21, 31.

[0078] As the large particles 1, any of resin particles and inorganic particles can be used. Examples of the resin particles include melamine resin, benzoguanamine resin, benzoguanamine / melamine / formalin condensate, acrylic resin, urethane resin, styrene resin, fluororesin, and silicone resin. On the other hand, examples of the inorganic particles include silicon dioxide, aluminum oxide, calcium carbonate, barium sulfate, titanium oxide, and carbon. These can be used alone or in combination of two or more.

[0079] In order to obtain more excellent properties, inorganic particles are preferably used as the large particles 1. By using inorganic particles as the large particles 1, a light-shielding film 100 with lower glossiness and higher optical density can be obtained. The inorganic particles used as the large particles 1 are preferably silicon dioxide. The shape of the large particles 1 is not particularly limited, but in order to control the above-mentioned prescribed optical properties of each outermost surface of the light-shielding layer 21, 31 within the prescribed range of the present invention, it is preferred to use a particle group with a clear particle size distribution.

[0080] In addition, in order to further reduce (A), it is preferred to use irregularly shaped particle groups. Among these, porous irregularly shaped silica particles are particularly preferred. By using such a particle group, light is repeatedly refracted on the surface and inside of the large particle 1, thereby further reducing (A).

[0081] In order to suppress light reflection, the large particles 1 may be colored black with an organic or inorganic colorant. Examples of such a colored material include composite silica, conductive silica, and black silica.

[0082] As composite silica, for example, carbon black and silica can be synthesized and composited at the nanometer level. As conductive silica, for example, conductive particles such as carbon black can be coated on silica particles to obtain. As black silica, for example, natural ores containing graphite in silica can be cited.

[0083] On the other hand, the material of the small particles 2 is also not particularly limited, and any of resin particles and inorganic particles can be used. Examples of resin particles include: melamine resin, benzoguanamine resin, benzoguanamine / melamine / formalin condensate, acrylic resin, urethane resin, styrene resin, fluororesin, and silicone resin. On the other hand, examples of inorganic particles include: silicon dioxide, aluminum oxide, calcium carbonate, barium sulfate, titanium oxide, and carbon. These can be used alone or in combination of two or more.

[0084] For example, carbon black added as a coloring / conductive agent may be used as the small particles 2. By using carbon black as the small particles 2, the light shielding layers 21 and 31 are colored, thereby improving the antireflection effect and obtaining a good antistatic effect.

[0085] -Optional Ingredients-

[0086] In the first embodiment, as constituent components of the light shielding layers 21 and 31 , a leveling agent, a thickener, a pH adjuster, a lubricant, a dispersant, a defoaming agent, etc. may be further added as needed.

[0087] The thickness of the light-shielding layers 21 and 31 is not particularly limited, but the average film thickness is preferably 2 μm or more and 20 μm or less. In addition, the upper limit of the average film thickness of the light-shielding layers 21 and 31 is more preferably 15 μm, and more preferably 10 μm. In the present invention, even if the thickness of the light-shielding layer is 5 μm or less, a light-shielding film 100 having low gloss, high optical density, low reflectivity and high blackness can be obtained. In addition, the average film thickness of the light-shielding layers 21 and 31 includes the height of the portion protruding from the surface of the base film 11 by the large particles 1 and the small particles 2 of the light-shielding layers 21 and 31. The above-mentioned average film thickness of the light-shielding layers 21 and 31 can be measured based on JIS K7130.

[0088] From the viewpoint of weight reduction and thinning, the total thickness of the light shielding film 100 is preferably 0.15 μm to 50 μm or less, more preferably 1 μm or more, more preferably 5 μm or more, more preferably 40 μm or less, and more preferably 25 μm or less.

[0089] - Difference between (B) and (C), adjustment method -

[0090] In the light-shielding film 100 according to the first embodiment of the present invention, the outermost surfaces of the light-shielding layer 21 and the light-shielding layer 31 have (A) of less than 2%, (B) of less than 4.5%, (C) of less than 26, and (D) of more than 1.0, and the characteristic is that the difference in (B) between the outermost surface of the light-shielding layer 21 and the outermost surface of the light-shielding layer 31 is less than 2%, and the difference in (C) is more than 4. As described above, in the light-shielding layers 21 and 31 having specific optical characteristics on their outermost surfaces, by making the (B) and (C) of the outermost surfaces of the light-shielding layer 21 and the light-shielding layer 31 different, the front and back sides of the light-shielding film 100 can be distinguished non-contactly, that is, visually, based on the difference in the blackness of their reflection and appearance.

[0091] From the viewpoint of suppressing glare and afterimage phenomena caused by unnecessary light and making it easy to distinguish the front and back surfaces visually, the difference in (B) between the outermost surfaces of the light shielding layer 21 and the light shielding layer 31 is preferably 1.5% or less, and more preferably 1.35% or less. In order to set the above difference in (B), for example, as described above, the (B) of the outermost surface of the light shielding layer 21 is set to 2.4% or less, and the (B) of the outermost surface of the light shielding layer 31 is set to 2.8% or more and 4.4% or less.

[0092] There are no particular limitations on the method for adjusting (B) of each outermost surface of the light shielding layer 21 and the light shielding layer 31, and examples thereof include: a method of making the black particle content of the light shielding layer 21 and the light shielding layer 31 different, a method of using particle groups with different shapes in the light shielding layer 21 and the light shielding layer 31, a method of using particle groups with different particle diameters in the light shielding layer 21 and the light shielding layer 31, a method of using particle groups with different particle size distributions in the light shielding layer 21 and the light shielding layer 31, a method of using particle groups of different materials (for example, organic and inorganic, the same applies hereinafter) in the light shielding layer 21 and the light shielding layer 31, a method of making the thickness of the light shielding layer 21 and the light shielding layer 31 different, etc. These adjustment methods may be used alone or in combination as appropriate.

[0093] From the viewpoint of being able to easily distinguish the front and back surfaces visually, the difference in (C) between the outermost surfaces of the light-shielding layer 21 and the light-shielding layer 31 is preferably 4.5 or more, and more preferably 5 or more. In order to set the above difference in (C), for example, as described above, the (C) of the outermost surface of the light-shielding layer 21 is set to 18 or less, and the (C) of the outermost surface of the light-shielding layer 31 is set to 17 or more and 25 or less.

[0094] There are no particular limitations on the method for adjusting the (C) of each outermost surface of the light shielding layer 21 and the light shielding layer 31, and examples thereof include: a method of making the black particle content of the light shielding layer 21 and the light shielding layer 31 different, a method of using particle groups with different shapes in the light shielding layer 21 and the light shielding layer 31, a method of using particle groups with different particle sizes in the light shielding layer 21 and the light shielding layer 31, a method of using particle groups with different particle size distributions in the light shielding layer 21 and the light shielding layer 31, a method of using particle groups with different materials in the light shielding layer 21 and the light shielding layer 31, a method of making the thickness of the light shielding layer 21 and the light shielding layer 31 different, a method of including a plurality of particle groups with different particle sizes only on one side of the light shielding layer 21 and the light shielding layer 31, a method of including a plurality of particle groups with different materials only on one side of the light shielding layer 21 and the light shielding layer 31, and a method of including a plurality of particle groups with different shapes only on one side of the light shielding layer 21 and the light shielding layer 31. These adjustment methods may be used alone or in combination as appropriate.

[0095] - Difference and adjustment method of (A) -

[0096] In addition to the difference in (B) and (C) of each outermost surface of the light shielding layer 21 and the light shielding layer 31, when the (A) of each outermost surface of the light shielding layer 21 and the light shielding layer 31 is different, the difference in (A) of each outermost surface of the light shielding layer 21 and the light shielding layer 31 can be appropriately set in consideration of suppressing glare and afterimage phenomena caused by unnecessary light, and there is no particular limitation, but it is preferably 0.45% or less. In order to set such a difference in (A), for example, as described above, the (A) of the outermost surface of the light shielding layer 21 is set to 1% or less, and the (A) of the outermost surface of the light shielding layer 31 is set to 1.5% or less.

[0097] There are no particular limitations on the method for adjusting the (A) of each outermost surface of the light shielding layer 21 and the light shielding layer 31, and examples thereof include: a method of making the black particle content of the light shielding layer 21 and the light shielding layer 31 different, a method of using particle groups with different shapes in the light shielding layer 21 and the light shielding layer 31, a method of using particle groups with different particle sizes in the light shielding layer 21 and the light shielding layer 31, a method of using particle groups with different particle size distributions in the light shielding layer 21 and the light shielding layer 31, a method of using particle groups with different materials in the light shielding layer 21 and the light shielding layer 31, a method of making the thickness of the light shielding layer 21 and the light shielding layer 31 different, a method of including a plurality of particle groups with different particle sizes only on one side of the light shielding layer 21 and the light shielding layer 31, a method of including a plurality of particle groups with different materials only on one side of the light shielding layer 21 and the light shielding layer 31, and a method of including a plurality of particle groups with different shapes only on one side of the light shielding layer 21 and the light shielding layer 31. These adjustment methods may be used alone or in combination as appropriate.

[0098] From the viewpoint of having sufficient antistatic performance, the surface resistivity of the light shielding layers 21 and 31 is preferably less than 1.0×10 8 Ω, preferably less than 1.0×10 5 Ω, more preferably less than 5.0×10 4 Ω. In this specification, the surface resistivity is a value measured in accordance with JIS K6911:1995.

[0099] <Method for producing light-shielding film>

[0100] The method for manufacturing the light shielding film 100 involved in the embodiment is not particularly limited as long as the light shielding film of the above structure can be obtained. From the viewpoint of manufacturing the light shielding layers 21 and 31 on the base film 11 with good reproducibility, simplicity and low cost, a conventionally known coating method such as scraping, dipping, roller coating, rod coating, die coating, knife coating, air knife coating, kiss-roll coating, spray coating, spin coating, etc. can be applied.

[0101] For example, a coating liquid is applied to the main surface of the base film 11, and the coating liquid contains the above-mentioned components (resin component, particles, coloring / conductive agent) and any components as needed in a solvent (organic solvent or water), and after drying, the light shielding layers 21 and 31 can be formed on the base film 11 by heat treatment, pressure treatment, etc. as needed. As an organic solvent used as a solvent for the coating liquid, for example, methyl ethyl ketone, toluene, propylene glycol monomethyl ether acetate, ethyl acetate, butyl acetate, methanol, ethanol, isopropanol, butanol, etc. can be listed. In addition, in order to improve the adhesion between the base film 11 and the light shielding layers 21 and 31, anchoring treatment, corona treatment, etc. can be performed as needed. Further, as needed, an intermediate layer such as a primer layer and an adhesive layer can also be provided between the base film 11 and the light shielding layers 21 and 31. In addition, the desired shape of the light shielding film 100 can be easily obtained by various well-known molding methods, such as compression molding, injection molding, blow molding, transfer molding, and extrusion molding. Alternatively, the material may be first formed into a sheet and then vacuum formed, pressure formed, or the like.

[0102] In the light-shielding film 100 according to the first embodiment, the first light-shielding layer 21 and the second light-shielding layer 31 are light-shielding films whose outermost surfaces have (A) of less than 2%, (B) of less than 4.5%, (C) of less than 26, and (D) of greater than 1.0, and the difference in (B) between the outermost surface of the light-shielding layer 21 and the outermost surface of the light-shielding layer 31 is set to less than 2%, and the difference in (C) is set to greater than 4. Therefore, by using it as a light-shielding member of a lens unit, a camera module, etc., unnecessary light can be fully removed, glare and afterimages can be suppressed, and the image quality of a captured image can be improved.

[0103] In addition, in the above-mentioned stacked structure (i.e., the shading layer 21 and the shading layer 31 whose outermost surfaces have specific optical properties), the difference in (B) between the outermost surface of the shading layer 21 and the outermost surface of the shading layer 31 is adjusted to be less than 2%, and the difference in (C) is adjusted to be greater than 4, so the front and back sides can be distinguished non-contactly, i.e., by visual observation, based on the difference in their reflectivity and the blackness of their appearance.

[0104] In addition, the present invention can be arbitrarily changed and implemented without departing from its main purpose. For example, in the above-mentioned embodiment, the shading layer 21 and the shading layer 31 are arranged on the front and back surfaces of the base film 11, but a laminated structure (two-layer structure) of the shading layer 21 and the shading layer 31 can also be used without providing the base film 11. In addition, the shading layers 21 and 31 can be formed by more than two shading films. For example, a laminated shading layer formed by laminating shading films 21a and 21b can be applied as the shading layer 21. The same applies to the shading layer 31. At this time, the shading film 21a and the shading film 21b are stacked as a laminate, and can satisfy the various performances and physical properties required for the outermost surface of the shading layer 21 as described above. The same applies to the shading layer 31.

[0105] <Camera module, lens unit, light shielding member>

[0106] like Figure 2 As shown, the camera module 1 involved in the first embodiment of the present invention has a lens unit 2. The lens unit 2 has a lens group consisting of five lenses 41, 43, 45, 47, and 49 stacked along the optical axis direction X. The number of lenses constituting the lens group is not limited to five. In this example, among the five lenses 41, 43, 45, 47, and 49 constituting the lens group, light-shielding members 61, 63, and 65 are sandwiched between three pairs of lenses (lenses 41 and 43, lenses 43 and 45, and lenses 47 and 49). The lens group and the light-shielding members 61, 63, and 65 are all made of resin or metal, etc., and are placed in a multi-stage cylindrical bracket (lens barrel) 8. The bracket 8 of this example is provided with three step portions 81, 83, and 85 on its inner circumference. Through these step portions 81, 83, and 85, the lens group and the light-shielding members 61, 63, and 65 are stored and arranged at a specified position in the bracket 8 in a stacked state arranged on the same optical axis. Lenses 41, 43, 45, 47, 49 may be various lenses (convex lenses, concave lenses, etc.), their curved surfaces may be spherical or aspherical, and their materials may be resin (e.g., cycloolefin resin (COC or COP), polycarbonate resin, liquid crystal polymer, etc.) or glass.

[0107] The camera module 1 and the lens unit 2 both have an imaging element 9. The imaging element 9 is disposed on the optical axis of the lens unit 2, and captures an image of a subject through the lens unit 2. The imaging element 9 is composed of a CCD image sensor, a CMOS image sensor, or the like.

[0108] The light shielding members 61, 63, and 65 of this example are light shielding plates that are annular in shape (ring-shaped) in plan view and have a cylindrical hollow portion in the center in cross-sectional view. Figure 1 The light shielding film 100 shown is formed by punching out a ring shape. Figure 1 The light shielding members 63 and 65 have the same laminated structure as the light shielding film 100 shown in the figure. The light shielding members 63 and 65 have the same structure as the light shielding member 61 except that the outer diameters and the outer diameters of the hollow portions are different.

[0109] In the light shielding members 61, 63, and 65 involved in the first embodiment, the outermost surfaces of the first light shielding layer 21 and the second light shielding layer 31 are light shielding films having (A) of less than 2%, (B) of less than 4.5%, (C) of less than 26, and (D) of more than 1.0, and the difference in (B) between the outermost surface of the light shielding layer 21 and the outermost surface of the light shielding layer 31 is set to less than 2%, and the difference in (C) is set to more than 4. Therefore, by using it as a light shielding member of a lens unit, a camera module, etc., unnecessary light can be fully removed, glare and afterimages can be suppressed, and the image quality of the captured image can be improved.

[0110] Furthermore, in the above-mentioned laminated structure (i.e., the light shielding layer 21 and the light shielding layer 31 whose outermost surfaces have specific optical characteristics), the difference in (B) between the outermost surface of the light shielding layer 21 and the outermost surface of the light shielding layer 31 is adjusted to be 2% or less, and the difference in (C) is adjusted to be 4 or more, so that the front and back surfaces of the light shielding members 61, 63, and 65 can be easily distinguished non-contactly, i.e., visually, based on the difference in blackness of their reflection and appearance. Therefore, the lens unit 2 and the camera module 1 using these light shielding members 61, 63, and 65 can prevent manufacturing failures such as assembly failure due to misidentification of the front and back surfaces even during storage and assembly.

[0111] In addition, the present invention can be arbitrarily changed and implemented without departing from the main purpose thereof. For example, the outer shape of the light shielding film 100 (light shielding members 61, 63, 65) can be any shape such as a polygon such as a rectangle, square, hexagon, an ellipse, an irregular shape, etc. in a plan view. In addition, in the present embodiment, the shape of the hollow portion of the light shielding members 61, 63, 65 is circular in a plan view, but the outer shape thereof is not particularly limited. For example, a polygon such as a rectangle, square, hexagon, an ellipse, an irregular shape, etc. in a plan view can be adopted.

[0112] Explanation of symbols:

[0113] 100: Light-shielding film

[0114] 11: Basement membrane

[0115] 11a: Surface (main surface)

[0116] 11b: Surface (main surface)

[0117] 21: Light shielding layer (first light shielding layer)

[0118] 31: Light shielding layer (second light shielding layer)

[0119] 1: Camera module

[0120] 2: Lens unit

[0121] 41, 43, 45, 47, 49: Lens

[0122] 61, 63, 65: Light shielding components

[0123] 8: Bracket

[0124] 9: Camera element.

Claims

1. A light-shielding film for obtaining a light-shielding member for an optical device, At least a first light-shielding layer and a second light-shielding layer are provided. The outermost surfaces (A), (B), (C), and (D) of the surfaces formed by the first light-shielding layer and the second light-shielding layer are respectively less than 2%, less than 4.5%, less than 26%, and greater than 1.0, and The difference between the (B) and the (C) of the outermost surface of the surface formed by the first light-shielding layer and the outermost surface of the surface formed by the second light-shielding layer is 2% or less and 4 or more, respectively, wherein, (A) is the glossiness for light with an incident angle of 60°, (B) is the reflectance for light with a wavelength of 550 nm, (C) is the L value in the CIELAB color system based on the SCE method, (D) is the optical density.

2. The light-shielding film according to claim 1, wherein: The difference in (A) between the outermost surface of the surface formed by the first light-shielding layer and the outermost surface of the surface formed by the second light-shielding layer is 0.5% or less.

3. The light-shielding film according to claim 1, wherein: The outermost surface of the surface on which the first light-shielding layer is formed has 2.4% or less of the (B).

4. The light-shielding film according to claim 3, wherein: The outermost surface of the surface where the second light-shielding layer is formed has 2.8% or more of (B). 5 . A light shielding member, which is formed of the light shielding film according to claim 1 and is used in a lens unit including a lens group composed of a plurality of lenses stacked in an optical axis direction in a holder. 6 . A lens unit comprising a lens group composed of a plurality of lenses stacked in an optical axis direction in a holder, wherein the light shielding member according to claim 5 is interposed between at least a pair of lenses. 7 . A camera module comprising the lens unit according to claim 6 and an imaging element, wherein the imaging element captures an image of a subject through the lens unit.

Images