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

Abstract

To provide a light-shielding film for obtaining a light-shielding member allowing a user to visually distinguish between front and back surfaces while suppressing flare and ghost.SOLUTION: Supposing that glossiness for light with an incident angle of 60° is (A), reflectance for light with a wavelength of 550 nm is (B), an L value in a CIE Lab color system by an SCE method is (C), and optical density (OD) is (D). Then, a light-shielding film 100 for obtaining a light-shielding member for optical devices, the light-shielding film includes at least a first light-shielding layer 21 and a second light-shielding layer 31. The first light shielding layer 21 and the second light shielding layer 31 are so formed that (A), (B), (C) and (D) of an outermost surface of a surface on which each layer is formed are respectively 2% or less, 4.5% or less, 26 or less, and 1.0 or more. Differences in (B) and (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 respectively 2% or less and 4 or more.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Electronic devices such as smartphones, tablet terminals, and digital cameras are equipped with a built-in camera module for capturing an image of a subject and converting it into an image signal. The camera module is required to remove scattered light such as incident light and reflected light (hereinafter simply referred to as "unnecessary light") that is not necessary for forming an image of the subject on the imaging element, prevent halation, lens flare, ghosting, etc. (hereinafter abbreviated as "flare and ghosting"), and improve the quality of the captured image. For this reason, a light-shielding member for removing unnecessary light is incorporated into the lens unit used in the camera module. A known example of this type of light-shielding material is a light-shielding film that has a light-shielding layer containing carbon black, lubricant, fine particles, and binder resin formed on both sides of a film substrate, and is then processed into a desired shape (for example, Patent Document 1).

[0003] When preparing a light-shielding member of a desired shape from a light-shielding film, or when assembling the prepared light-shielding member into a camera module, if it is not possible to distinguish between the front and back sides of the light-shielding film or light-shielding member, this can cause manufacturing failures such as assembly defects. Conventionally, in order to distinguish between the front and back sides, a coating film made of water-based ink has been printed as a mark on one of the light-shielding layers of the light-shielding film with a thickness (for example, less than 1 μm) that does not affect the optical properties of the light-shielding layer. However, this coating film made of water-based ink can become a contaminant (called contamination) by falling off one of the formed light-shielding layers due to slight stimulation such as contact when the light-shielding film or light-shielding member is transported or assembled into a camera module. 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 one light-shielding layer and the other light-shielding layer are both less than 10% and a difference in glossiness is created between the one light-shielding layer and the other light-shielding layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] WO2006 / 16555 publication [Patent Document 2] Patent No. 6368445 (Paragraph 0030) Summary of the Invention [Problem to be solved by the invention]

[0005] The technology of Patent Document 2 does not have a mark printed on the light-shielding layer, so the above-mentioned problem of contamination can be solved. However, the light-shielding film and light-shielding member of the technology of Patent Document 2 have a high glossiness of less than 10% for both light-shielding layers, so even if there is a difference in glossiness between the two light-shielding layers, it may not be possible to sufficiently remove unnecessary light. In a camera module in which a light-shielding film or light-shielding member that does not sufficiently remove unnecessary light is incorporated into a lens unit, flare and ghosting occur, which tends to cause a deterioration in the quality of the captured image.

[0006] The present invention has been made in view of the above circumstances, and aims to provide a light-shielding film for obtaining a light-shielding member that suppresses the occurrence of flare and ghosts in a camera module incorporated in a lens unit and that allows visual discrimination between the front and back, as well as a light-shielding member, a lens unit, and a camera module formed using the light-shielding film. [Means for solving the problem]

[0007] After extensive research, the inventors have discovered that satisfying the following requirements is effective in suppressing the occurrence of flare and ghosting in a camera module incorporated into a lens unit while enabling visual discrimination between the front and back of light-shielding materials and light-shielding films.

[0008] The outermost surface of the layer has at least a specific first light-shielding layer and a second light-shielding layer having a plurality of predetermined optical properties (particularly, extremely low gloss of 2% or less and low reflectance of 4.5% or less). The first and second light-shielding layers have a difference in predetermined optical properties (particularly L value and reflectance) of the outermost surfaces of the layers within a predetermined range.

[0009] Based on these new findings, the present inventors have completed the invention provided below and have solved the above-mentioned problems. In what follows, the gloss level for light with an incidence angle of 60° is abbreviated as (A), the reflectance for light with a wavelength of 550 nm is abbreviated as (B), the L value in the CIELAB color system according to the SCE method is abbreviated as (C), and the optical density (OD) is abbreviated as (D).

[0010] According to the present invention, A light-shielding film for obtaining a light-shielding member for an optical device, comprising: At least a first light-shielding layer and a second light-shielding layer are provided, The first light-shielding layer and the second light-shielding layer have (A), (B), (C), and (D) of the outermost surface on which each layer is formed, which are 2% or less, 4.5% or less, 26 or less, and 1.0 or more, respectively; and a difference in (B) between the outermost surface on which the first light-shielding layer is formed and a difference in (C) between the outermost surface on which the second light-shielding layer is formed being 2% or less and 4 or more, respectively; is provided.

[0011] The above-mentioned light-shielding film may include the following aspects. The difference in (A) between the outermost surface on which the first light-shielding layer is formed and the outermost surface on which the second light-shielding layer is formed may be 0.5% or less.

[0012] According to the present invention, there is provided a light-shielding member for use in a lens unit having a lens group made of a plurality of lenses stacked in the optical axis direction in a holder, the light-shielding member being formed from the light-shielding film described above. is provided.

[0013] According to the present invention, in a lens unit including a lens group made up of a plurality of lenses stacked in the optical axis direction in a holder, the above-mentioned light-shielding member is interposed between at least a pair of lenses. is provided.

[0014] According to the present invention, there is provided a camera module having the above lens unit and an image sensor for capturing an image of a subject through the above lens unit. is provided. Effect of the Invention

[0015] According to the present invention, there is provided a light-shielding film for obtaining a light-shielding member that suppresses the occurrence of flare and ghosts in a camera module incorporated into a lens unit and allows visual identification of the front and back, as well as a light-shielding member, lens unit and camera module formed using the same. [Brief description of the drawings]

[0016] [Figure 1] 1 is a cross-sectional view illustrating a light-shielding film according to one embodiment of the present invention. [Diagram 2] 1 is an exploded perspective view showing a lens unit and a camera module in which a light blocking member according to an embodiment of the present invention is incorporated; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The best mode for carrying out the present invention will be described below. However, the present invention is not limited to the following embodiment. Appropriate modifications and improvements to the following embodiment based on the ordinary knowledge of a person skilled in the art are also within the scope of the present invention, provided they do not deviate from the spirit of the present invention.

[0018] In the numerical ranges described in this specification, the upper or lower limit value described in a certain numerical range may be replaced with a value shown in the examples. In this specification, the content or amount of each component in a composition means, when multiple substances corresponding to each component are present in the composition, the total content or amount of those multiple substances present in the composition, unless otherwise specified.

[0019] <Light-shielding film> 1, light-shielding film 100 according to one embodiment of the present invention includes at least a base film 11, a first light-shielding layer 21 provided on one main surface 11a side of this base film 11, and a second light-shielding layer 31 provided on the other main surface 11b side. Light-shielding film 100 has a layered structure (three-layer structure) in which light-shielding layer 21, base film 11, and light-shielding layer 31 are arranged at least in this order.

[0020] The phrase "provided on one (the other) main surface side of the base film" refers to not only an embodiment in which the light-shielding layer 21, 31 is directly placed on the surface (e.g., the main surface 11a or the main surface 11b) of the base film 11, but also an embodiment in which an arbitrary layer (e.g., an anchor layer, an adhesive layer, etc.) is interposed between the surface of the base film 11 and the light-shielding layer 21, 31. In addition, the laminated structure including at least the first light-shielding layer 21 and the second light-shielding layer 31 refers to not only a structure in which only the first light-shielding layer 21 and the second light-shielding layer 31 are directly laminated, but also the above-mentioned three-layer structure and a structure in which an arbitrary layer is further provided on the three-layer structure.

[0021] -Base film- The type of the base film 11 as one element of the light-shielding film 100 is not particularly limited as long as it can support the light-shielding layers 21 and 31. From the viewpoints of dimensional stability, mechanical strength, and weight reduction, a synthetic resin film is preferably used. Specific examples of the synthetic resin film include polyester film, ABS (acrylonitrile-butadiene-styrene) film, polyimide film, polystyrene film, and polycarbonate film. In addition, acrylic, polyolefin, cellulose, polysulfone, polyphenylene sulfide, polyethersulfone, and polyetheretherketone films can also be used. Among these, polyester films and polyimide films are preferably used as the base film 11. In particular, uniaxially or biaxially stretched films, especially biaxially stretched polyester films, are particularly preferred because they have excellent mechanical strength and dimensional stability. In addition, uniaxially or biaxially stretched polyimide films are particularly preferred for heat-resistant applications. These can be used alone or in combination of two or more.

[0022] The thickness of the base film 11 can be appropriately set depending on the required performance and application, and is not particularly limited. From the viewpoint of weight reduction and thinning, the thickness of the base film 11 is preferably 0.5 μm or more and 50 μm or less, more preferably 1 μm or more and 25 μm or less, further preferably 4 μm or more and 10 μm or less, and particularly preferably 5 μm or more and 7 μm or less. Note that, from the viewpoint of improving adhesion to the light-shielding layers 21 and 31, various known surface treatments such as anchor treatment and corona treatment can be performed on the surface of the base film 11 as necessary.

[0023] The appearance of the base film 11 may be transparent, semi-transparent, or opaque, and is not particularly limited. 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 may be used. The pigment that may be contained is not particularly limited, and either resin particles or inorganic particles may 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. Examples of the inorganic particles include silica, alumina, calcium carbonate, barium sulfate, titanium oxide, magnetite black, copper-iron-manganese black, titanium black, carbon black, and aniline black. These pigments may be used alone or in combination of two or more.

[0024] The content ratio of the pigment in the base film 11 is not particularly limited and can be appropriately set according to the required performance, etc. The content of the pigment in the base film 11 is, for example, about 0.3 mass % or more, preferably 0.4 mass % or more, for example, 15 mass % or less, preferably 12 mass % or less, based on the base film 11.

[0025] Before providing the surface of the base film 11 and the light-shielding layers 21 and 31, an anchor layer may be provided to improve adhesion between the surface of the base film 11 and the light-shielding layers 21 and 31. As the anchor layer, a urea-based resin layer, a melamine-based resin layer, a urethane-based resin layer, a polyester-based resin, or the like can be applied. For example, the urethane-based resin layer is obtained by applying a solution containing a polyisocyanate and an active hydrogen-containing compound such as a diamine or diol to the surface of the base film 11 and curing it. In addition, in the case of a urea-based resin or a melamine-based resin, it is obtained by applying a solution containing a water-soluble urea-based resin or a water-soluble melamine-based resin to the surface of the base film 11 and curing it. The polyester-based resin is obtained by applying a solution dissolved or diluted in an organic solvent (methyl ethyl ketone, toluene, etc.) to the surface of the base film 11 and drying it.

[0026] -Light blocking layer- Light-shielding layers 21 and 31 as elements of light-shielding film 100 are light-shielding films whose layer surfaces each have (A) of 2% or less, (B) of 4.5% or less, (C) of 26 or less, and (D) of 1.0 or more.

[0027] Here, if the light-shielding layers 21, 31 are exposed on the outermost surface, then it is sufficient that the surface of each layer has the above-mentioned (A), (B), (C), and (D). On the other hand, if another layer is coated on the light-shielding layers 21, 31, then it is sufficient that the surface of the other layer (i.e., the outermost surface of the light-shielding film 100) has the above-mentioned (A), (B), (C), and (D). Hereinafter, these surfaces are collectively referred to as the "outermost surface of the layer."

[0028] The light-shielding layers 21 and 31 as one element of the light-shielding film 100 are light-shielding films whose outermost surface has (A) of 2% or less, (B) of 4.5% or less, (C) of 26 or less, and (D) of 1.0 or more, 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 be 2% or less, and the difference in (C) to be 4 or more. 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 may be further set to be 0.5% or less.

[0029] -(A) Glossiness at an incident angle of 60 degrees- In this specification, (A) is a value obtained by measuring the glossiness (specular glossiness) of the outermost surface of each 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 Co., Ltd.) in accordance with JIS Z8741. From the viewpoint of effectively preventing the flare and ghost phenomenon caused by diffuse reflection of light, each of the outermost surface of the light-shielding layer 21 and the light-shielding layer 31 preferably has an (A) of 1.5% or less, more preferably 1% or less, and even more preferably 0.7% or less. From the viewpoint of suppressing the occurrence of flare and ghost due to unnecessary light, the outermost surface of the light-shielding layer 21 preferably has an (A) of 1% or less, more preferably 0.5% or less, and even more preferably 0.3% or less. On the other hand, from the viewpoint of suppressing the occurrence of flare and ghost due to unnecessary light, the outermost surface of the light-shielding layer 31 preferably has an (A) of 1.5% or less, more preferably 1% or less, and even more preferably 0.7% or less.

[0030] -(B) Reflectance for light with a wavelength of 550 nm- (B) is a value obtained by measuring the reflectance of the outermost surface of each of the light-shielding layers 21 and 31 for light with a wavelength of 550 nm using a spectrophotometer (CM-5: Konica Minolta) in accordance with JIS Z8722. From the viewpoint of more effectively preventing the flare and ghost phenomenon caused by diffuse reflection of light, each of the outermost surface of the light-shielding layer 21 and the light-shielding layer 31 preferably has a (B) of 4.4% or less, more preferably 4.2% or less, and even more preferably 4.0% or less. From the viewpoint of suppressing the occurrence of flare and ghost caused by unnecessary light, the outermost surface of the light-shielding layer 21 preferably has a (B) of 2.4% or less as an upper limit, more preferably 2.2% or less, and even more preferably 2% or less. The lower limit is not particularly limited, but for example, it is preferably 0.8% or more (B), more preferably 1.0% or more, and even more preferably 1.1% or more. On the other hand, from the viewpoint of suppressing the occurrence of flare and ghosts due to unnecessary light and making it easier to visually distinguish between the front and back, the outermost surface of the light-shielding layer 31 preferably has a (B) of 2.8% or more and 4.4% or less, more preferably 3.0% or more and 4.2% or less, and even more preferably 3.1% or more and 4.0% or less.

[0031] -(C)L value in the CIELAB color system according to the SCE method- (C) is an index of blackness, and is the lightness L* value of the top surface of a layer in the CIE 1976 L*a*b* (CIELAB) color system according to the SCE method. The SCE method is a method of measuring color by removing specular reflected light. The definition of the SCE method is stipulated in JIS Z 8722 (2009). Since the SCE method removes specular reflected light when measuring, the color is closer to what the human eye actually sees. CIE is an abbreviation of Commission Internationale de l'Eclairage, which means International Commission on Illumination. CIELAB display color is a uniform color space recommended in 1976 and specified in JIS Z 8781 (2013) to measure color differences due to differences in perception and devices. The three coordinates of CIELAB are L* value, a* value, and b* value. L* value indicates lightness and is expressed as 0 to 100. An L* value of 0 means black, and an L* value of 100 means diffuse white color. a* value indicates a color between red and green. If the a* value is negative, it means a color leaning toward green, and if it is positive, it means a color leaning toward red. b* value indicates a color between yellow and blue. If b* is negative, it means a color leaning toward blue, and if it is positive, it means a color leaning toward yellow. This (C) is the value obtained by measuring the lightness L* value in the CIE 1976 L*a*b* (CIELAB) color system according to the SCE method on the outermost surface of each of the light-shielding layers 21, 31 using a spectrophotometer (CM-5: Konica Minolta) in accordance with JIS Z8781-4:2013. From the viewpoints of suppressing the occurrence of flare and ghost caused by unwanted light and enhancing the design by highlighting the blackness, the outermost surface of each of the light-shielding layers 21 and 31 preferably has a (C) of 25 or less, more preferably 23 or less. From the viewpoints of suppressing the occurrence of flare and ghost caused by unwanted light and enhancing the design by highlighting the blackness, the outermost surface of the light-shielding layer 21 preferably has a (C) of 12 or more and 18 or less, more preferably 13 or more and 17 or less, and even more preferably 14 or more and 16 or less. On the other hand, from the viewpoints of suppressing the occurrence of flare and ghost caused by unwanted light and facilitating visual discrimination between the front and back, the outermost surface of the light-shielding layer 31 preferably has a (C) of 17 or more and 25 or less, more preferably 18 or more and 24 or less, and even more preferably 19 or more and 23 or less.

[0032] -(D)Optical density- (D) is a value calculated by irradiating the outermost surface side of each of the light-shielding layers 21 and 31 with a perpendicular transmitted light beam using an optical densitometer (X-rite 361T (orthofilter): Nippon Plane Machinery Co., Ltd.) and expressing the ratio in log (logarithm) to a state in which the light-shielding layers 21 and 31 are not present. From the viewpoint of providing higher light-shielding properties, it is preferable that each of the outermost surface of the light-shielding layers 21 and 31 has a (D) of 1.0 or more. From the viewpoints of suppressing the occurrence of flare and ghost caused by unnecessary light, making it easy to visually distinguish the front and back, and realizing high light-shielding properties and good adhesion to the substrate of the light-shielding layer, it is preferable that the outermost surface of the light-shielding layer 21 has a (D) of 2.0 or more, more preferably 2.0 or more and 2.4 or less. On the other hand, from the viewpoints of suppressing the occurrence of flare and ghost caused by unnecessary light, making it easy to visually distinguish between the front and back, and achieving high light-shielding properties and good adhesion to the substrate of the light-shielding layer, it is preferable that the outermost surface of the light-shielding layer 31 has (D) of 1.0 or more and 1.5 or less, and more preferably 1.0 or more and 1.4 or less. Furthermore, when the light-shielding layer 21 and the light-shielding layer 31 are laminated, the (D) of the laminate is preferably 3.0 or more and 5.0 or less, more preferably 3.5 or more and 4.0 or less. In this case, for example, a laminate having a total (D) of 3.0 or more and 5.0 or less is formed using the light-shielding layer 21 having a (D) of 2.0 or more and the light-shielding layer 31 having a (D) of 1.0 or more and 1.5 or less, and the front and back surfaces of the laminated structure are made to have different optical densities, which is preferable because the front and back surfaces of the laminated structure can be more clearly distinguished.

[0033] -Composition example- The light-shielding layers 21 and 31 having such characteristics may contain resin components, particles, and coloring and conductive agents.

[0034] -Resin component- The resin component serves as a binder for the particles and the coloring / conductive agent. The material of the resin component is not particularly limited, and either a thermoplastic resin or a thermosetting resin can be used. Specific examples of the thermosetting resin include acrylic resins, urethane resins, phenolic resins, melamine resins, urea resins, diallyl phthalate resins, unsaturated polyester resins, epoxy resins, and alkyd resins. Examples of the thermoplastic resin include polyacrylic ester resins, polyvinyl chloride resins, butyral resins, and styrene-butadiene copolymer resins. From the viewpoints of heat resistance, moisture resistance, solvent resistance, and surface hardness, it is preferable to use a thermosetting resin. As the thermosetting resin, acrylic resins are particularly preferable in terms of flexibility and toughness of the coating.

[0035] By adding a curing agent as a component of the light-shielding layers 21 and 31, crosslinking of the resin components can be promoted. As the curing agent, a urea compound, a melamine compound, an isocyanate compound, an epoxy compound, an aziridine compound, an oxazoline compound, or the like having a functional group can be used. Among these, an isocyanate compound is particularly preferable. The blending ratio of the curing agent is preferably 10 to 50 mass% with respect to 100 mass% of the resin components. By adding the curing agent in 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 period of time even when sliding against other members.

[0036] When a curing agent is used, a reaction catalyst can be used in combination to accelerate 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 mass% relative to 100 mass% of the curing agent.

[0037] -Particles, colorants, and conductive agents- Particles and a coloring / conductive agent can be contained in the light-shielding layers 21 and 31. For example, by using two or more particle groups having different particle diameters and particle size distributions as the particles and the coloring / conductive agent, the above-mentioned predetermined optical properties of the outermost layer of each of the light-shielding layers 21 and 31 can be suitably controlled within the range specified in the present invention. For example, when two particle groups having different sizes are used, the particle size of the larger particle group is preferably 10 to 40 times that of the smaller particle group. When three or more particle groups are used, the particle sizes of the largest particle group and the smallest particle group may be adjusted so as to satisfy the above-mentioned relationship. In the following description, the large particle group will be referred to as large particles 1 and the small particle group will be referred to as small particles 2. The light-shielding layers 21 and 31 according to one embodiment preferably contain, as particle groups, large particles 1 having an average particle size of 2 μm to 6 μm and small particles 2 having an average particle size of 0.06 μm to 0.4 μm. The average particle size of the large particles 1 is more preferably 3 μm to 5 μm, and even more preferably 3 μm to 4 μm. The average particle size of the small particles 2 is preferably 0.06 μm to 0.4 μm, and more preferably 0.1 μm to 0.3 μm. By combining large particles 1 and small particles 2 of such particle diameters, the small particles 2 are embedded between the large particles 1 in the recesses, and the above-mentioned specified optical properties of the outermost layers of each of the light-shielding layers 21, 31 can be suitably controlled within the specified range of the present invention.

[0038] The content of the particles is preferably 20% by volume to 50% by volume, taking the entire light-shielding layer 21, 31 as 100% by volume, although it depends on the average particle size of the particle group, particle size distribution, and film thickness of the light-shielding layer 21, 31, and the surface shape of the base film 11. The mixing ratio of the large particles 1 and the small particles 2 is not particularly limited as long as the above-mentioned predetermined optical properties of the outermost layer of each of the light-shielding layers 21, 31 can be adjusted to the range specified in the present invention, but is preferably 1.5:1 to 3.5:1 (volume occupied by the large particles 1:volume occupied by the small particles 2). The volume content (volume occupancy) of the particles in the light-shielding layers 21, 31 can be calculated by converting a cross-sectional photograph of the light-shielding layers 21, 31 into an area occupancy calculated by image analysis or the like.

[0039] As the large particles 1, either resin particles or 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, silicone resin, etc. On the other hand, examples of the inorganic particles include silica, alumina, calcium carbonate, barium sulfate, titanium oxide, carbon, etc. These can be used alone or in combination of two or more.

[0040] In order to obtain better properties, it is preferable to use inorganic particles as the large particles 1. By using inorganic particles as the large particles 1, it is possible to obtain a light-shielding film 100 with lower gloss and higher optical density. Silica is preferable as the inorganic particles used as the large particles 1. The shape of the large particles 1 is not particularly limited, but in order to control the above-mentioned predetermined optical properties of the outermost layers of the light-shielding layers 21 and 31 within the range specified in the present invention, it is preferable to use a particle group with a sharp particle size distribution. In order to further reduce (A), it is preferable to use a group of particles with an irregular shape. Among these, it is particularly preferable to use porous, irregular silica particles. By using such a group of particles, light is repeatedly refracted on the surface and inside of the large particles 1, so that (A) can be further reduced. In order to suppress light reflection, the large particles 1 can be colored black with an organic or inorganic colorant. Examples of such colored materials include composite silica, conductive silica, black silica, etc. An example of the composite silica is a composite of carbon black and silica synthesized at the nano level. An example of the conductive silica is silica particles coated with conductive particles such as carbon black. An example of the black silica is a natural ore containing graphite in silica stone.

[0041] On the other hand, the material of the small particles 2 is not particularly limited, and either resin-based particles or inorganic particles can be used. Examples of resin-based 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 silica, alumina, calcium carbonate, barium sulfate, titanium oxide, and carbon. These can be used alone or in combination of two or more. For example, carbon black, which is added as a coloring and conductive agent, can 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, improving the antireflection effect and providing a good antistatic effect.

[0042] -Optional ingredients- In one embodiment, the light-shielding layers 21 and 31 may further contain, as necessary, a leveling agent, a thickening agent, a pH adjuster, a lubricant, a dispersant, an antifoaming agent, and the like.

[0043] The thickness of the light-shielding layer 21, 31 is not particularly limited, but the average thickness is preferably 2 μm or more and 20 μm or less. The upper limit of the average thickness of the light-shielding layer 21, 31 is more preferably 15 μm, and even 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 reflectance and high blackness can be obtained. The average thickness of the light-shielding layer 21, 31 is the height including the part protruding from the surface of the base film 11 by the large particles 1 and the small particles 2 of the light-shielding layer 21, 31. The above average thickness of the light-shielding layer 21, 31 can be measured based on JIS K7130.

[0044] From the viewpoint of reducing weight and thickness, the total thickness of the light-shielding film 100 is preferably 0.5 μm or more and 50 μm or less, more preferably 1 μm or more, even more preferably 5 μm or more, more preferably 40 μm or less, and even more preferably 25 μm or less.

[0045] -Difference between (B) and (C) and adjustment method- The light-shielding film 100 according to one embodiment of the present invention is characterized in that, in the light-shielding layers 21 and 31 whose outermost surfaces have (A) of 2% or less, (B) of 4.5% or less, (C) of 26 or less, and (D) of 1.0 or more, 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 1.5% or less, and the difference in (C) is 4 or more. In this way, in the light-shielding layers 21 and 31 whose outermost surfaces have specific optical properties, by making (B) and (C) different between the outermost surfaces of the light-shielding layers 21 and 31, it becomes possible to distinguish the front and back of the light-shielding film 100 without contact, i.e. visually, based on the difference in the reflectivity and the blackness of the appearance.

[0046] The difference in (B) between the outermost layers 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, from the viewpoints of suppressing the occurrence of flare and ghost caused by unnecessary light and facilitating visual discrimination between the front and back. To provide such a difference in (B), for example, as described above, (B) of the outermost layer surface of the light-shielding layer 21 may be set to 0.8% or more and 2.4% or less, and (B) of the outermost layer surface of the light-shielding layer 31 may be set to 2.8% or more and 4.4% or less.

[0047] Methods for adjusting (B) on the outermost surface of each of the light-shielding layers 21 and 31 include, but are not limited to, a method of making the content of black particles different between the light-shielding layers 21 and 31, a method of using particle groups having different shapes between the light-shielding layers 21 and 31, a method of using particle groups having different particle sizes between the light-shielding layers 21 and 31, a method of using particle groups having different particle size distributions between the light-shielding layers 21 and 31, a method of using particle groups made of different materials (e.g., organic, inorganic, etc.; the same applies below) between the light-shielding layers 21 and 31, a method of making the thickness of the light-shielding layers 21 and 31 different, etc. These adjustment methods can be performed by using various methods alone or in appropriate combination.

[0048] From the viewpoint of facilitating visual discrimination between the front and back, the difference in (C) between the outermost layer of the light-shielding layer 21 and the light-shielding layer 31 is preferably 4.5 or more, and more preferably 5 or more. To provide such a difference in (C), for example, as described above, the (C) of the outermost layer surface of the light-shielding layer 21 may be set to 12 or more and 18 or less, and the (C) of the outermost layer surface of the light-shielding layer 31 may be set to 17 or more and 25 or less.

[0049] Methods for adjusting (C) on the outermost surface of each of the light-shielding layers 21 and 31 include, for example, a method of making the content of black particles different between the light-shielding layers 21 and 31, a method of using particle groups having different shapes between the light-shielding layers 21 and 31, a method of using particle groups having different particle sizes between the light-shielding layers 21 and 31, a method of using particle groups having different particle size distributions between the light-shielding layers 21 and 31, a method of using particle groups made of different materials between the light-shielding layers 21 and 31, a method of making the thickness between the light-shielding layers 21 and 31 different, a method of containing multiple particle groups having different particle sizes in only one of the light-shielding layers 21 and 31, a method of containing multiple particle groups made of different materials in only one of the light-shielding layers 21 and 31, a method of containing multiple particle groups having different shapes in only one of the light-shielding layers 21 and 31, and the like, but are not particularly limited thereto. These adjustment methods can be carried out either alone or in appropriate combination.

[0050] -(A) Difference, Adjustment Method- In addition to the difference in (B) and (C) between the outermost layers of the light-shielding layer 21 and the light-shielding layer 31, when the outermost layers of the light-shielding layer 21 and the light-shielding layer 31 are made different in (A), the difference in (A) between the outermost layers of the light-shielding layer 21 and the light-shielding layer 31 may be appropriately set in consideration of suppressing the occurrence of flare and ghost caused by unnecessary light, and is not particularly limited, but is preferably 0.45% or less. To provide such a difference in (A), for example, as described above, the (A) of the outermost layer surface of the light-shielding layer 21 may be set to 1% or less, and the (A) of the outermost layer surface of the light-shielding layer 31 may be set to 1.5% or less.

[0051] Methods for adjusting (A) on the outermost surface of each of the light-shielding layers 21 and 31 include, for example, a method of making the content of black particles different between the light-shielding layers 21 and 31, a method of using particle groups having different shapes between the light-shielding layers 21 and 31, a method of using particle groups having different particle sizes between the light-shielding layers 21 and 31, a method of using particle groups having different particle size distributions between the light-shielding layers 21 and 31, a method of using particle groups made of different materials between the light-shielding layers 21 and 31, a method of making the thicknesses of the light-shielding layers 21 and 31 different, a method of containing multiple particle groups having different particle sizes in only one of the light-shielding layers 21 and 31, a method of containing multiple particle groups made of different materials in only one of the light-shielding layers 21 and 31, a method of containing multiple particle groups having different shapes in only one of the light-shielding layers 21 and 31, and the like, but are not particularly limited thereto. These adjustment methods can be carried out either alone or in appropriate combination.

[0052] From the viewpoint of providing sufficient antistatic performance, the light-shielding layers 21 and 31 have a thickness of 1.0×10 8 It is preferred that the surface resistivity is less than 1.0×10 5 Ω or less, more preferably 5.0×10 4 In this specification, the surface resistivity is a value measured in accordance with JIS-K6911:1995.

[0053] <Method of manufacturing light-shielding film> The method for producing the light-shielding film 100 according to one embodiment is not particularly limited as long as the above-mentioned configuration can be obtained. From the viewpoint of producing the light-shielding layers 21, 31 on the base film 11 easily and with good reproducibility at low cost, a conventionally known coating method such as doctor coating, dip coating, roll coating, bar coating, die coating, blade coating, air knife coating, kiss coating, spray coating, or spin coating is suitably used.

[0054] For example, a coating liquid containing the above-mentioned components (resin components, particles, and coloring / conductive agents) and optional components blended as necessary in a solvent (organic solvent or water) is applied onto the main surface of the substrate film 11, dried, and then heat treatment, pressure treatment, or the like is performed as necessary, to form the light-shielding layers 21, 31 on the substrate film 11. Examples of organic solvents used as the solvent for the coating liquid include methyl ethyl ketone, toluene, propylene glycol monomethyl ether acetate, ethyl acetate, butyl acetate, methanol, ethanol, isopropyl alcohol, and butanol. In order to improve the adhesion between the substrate film 11 and the light-shielding layers 21, 31, anchor treatment, corona treatment, or the like can be performed as necessary. Furthermore, an intermediate layer such as a primer layer or an adhesive layer can be provided between the substrate film 11 and the light-shielding layers 21, 31 as necessary. In addition, the light-shielding film 100 having a desired shape can be easily obtained by various known molding methods such as compression molding, injection molding, blow molding, transfer molding, and extrusion molding. In addition, after forming into a sheet, it may be subjected to vacuum forming, pressure forming, or the like.

[0055] In a light-shielding film 100 according to one embodiment, a first light-shielding layer 21 and a second light-shielding layer 31 are adopted in which the outermost surface of each layer is a light-shielding film having (A) of 2% or less, (B) of 4.5% or less, (C) of 26 or less, and (D) of 1.0 or more, and the difference in (B) between the outermost surface of light-shielding layer 21 and the outermost surface of light-shielding layer 31 is set to be 1.5% or less, and the difference in (C) to be 4 or more. Therefore, by using this as a light-shielding member for a lens unit, a camera module, or the like, unnecessary light can be sufficiently removed, the occurrence of flare and ghost can be prevented, and the image quality of a captured image can be improved.

[0056] Moreover, in the above-mentioned laminated structure (i.e., light-shielding layer 21 and light-shielding layer 31 whose outermost surfaces have specific optical properties), the difference in (B) between the outermost surface of light-shielding layer 21 and the outermost surface of light-shielding layer 31 is adjusted to be 2% or less, and the difference in (C) to be 4 or more, so that the front and back surfaces can be easily distinguished without contact, i.e. by visual inspection, based on the difference in reflectivity and blackness of appearance.

[0057] The present invention can be modified as desired without departing from the scope of the present invention. For example, in the above-mentioned embodiment, the light-shielding layer 21 and the light-shielding layer 31 are provided on the front and back sides of the base film 11, but the light-shielding layer 21 and the light-shielding layer 31 may be laminated (two-layer structure) without providing the base film 11. The light-shielding layers 21 and 31 may be formed from two or more light-shielding films. For example, a laminated light-shielding layer in which the light-shielding film 21a and the light-shielding film 21b are laminated can be used as the light-shielding layer 21. The same applies to the light-shielding layer 31. In this case, it is sufficient that the laminate of the light-shielding film 21a and the light-shielding film 21b satisfies the above-mentioned various performances and physical properties required for the outermost layer surface of the light-shielding layer 21. The same applies to the light-shielding layer 31.

[0058] <Camera modules, lens units, light-shielding materials> As shown in FIG. 2, a camera module 1 according to an embodiment of the present invention includes a lens unit 2. The lens unit 2 includes a lens group consisting of five lenses 41, 43, 45, 47, and 49 stacked in 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 interposed between three pairs of lenses (lenses 41 and 43, lenses 43 and 45, and lenses 47 and 49). Both the lens group and the light shielding members 61, 63, and 65 are placed in a multi-stage cylindrical holder (lens barrel) 8 made of resin, metal, or the like. The holder 8 in this example has three stepped portions 81, 83, and 85 on the inner circumference, and these stepped portions 81, 83, and 85 are used to store and arrange the lens group and the light blocking members 61, 63, and 65 in a stacked state on the same optical axis at a predetermined position in the holder 8. The lenses 41, 43, 45, 47, and 49 may be various lenses (convex lenses, concave lenses, etc.). The curved surface may be spherical or aspherical, and the material may be resin (for example, cyclic olefin resin (COC or COP), polycarbonate resin, liquid crystal polymer, etc.) or glass. The camera module 1 has an image sensor 9 together with a lens unit 2. The image sensor 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 image sensor 9 is configured with a CCD image sensor, a CMOS image sensor, or the like.

[0059] The light-shielding members 61, 63, and 65 of this example are light-shielding plates that have an annular (ring-shaped) outer shape when viewed in plan and a shape with a cylindrical hollow part in the center when viewed in cross section, and are formed by punching the light-shielding film 100 shown in Fig. 1 into a ring shape. Therefore, the light-shielding members 61, 63, and 65 have the same layered structure as the light-shielding film 100 shown in Fig. 1. The light-shielding members 63 and 65 have the same configuration as the light-shielding member 61, except that the outer diameter size and the outer diameter size of the hollow part are different from each other.

[0060] Also in the light-shielding members 61, 63, and 65 according to one embodiment, the first light-shielding layer 21 and the second light-shielding layer 31 are adopted, in which the outermost surface of each layer is a light-shielding film having (A) of 2% or less, (B) of 4.5% or less, (C) of 26 or less, and (D) of 1.0 or more, 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 be 2% or less, and the difference in (C) to be 4 or more. Therefore, by using this as a light-shielding member for a lens unit, a camera module, or the like, unnecessary light can be sufficiently removed, the occurrence of flare and ghost can be prevented, and the image quality of a captured image can be improved.

[0061] Moreover, in the above-mentioned laminated structure (i.e., the light-shielding layer 21 and the light-shielding layer 31 whose outermost surface has specific optical properties), 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) to be 4 or more, so that the front and back surfaces of the light-shielding members 61, 63, 65 can be easily distinguished from each other without contact, i.e., visually, based on the difference in reflectivity and blackness of the appearance. Therefore, the lens unit 2 and the camera module 1 using these light-shielding members 61, 63, 65 are prevented from manufacturing failures such as assembly defects due to misidentification of the front and back surfaces even during storage or assembly.

[0062] The present invention can be modified as desired without departing from the scope of the present invention. For example, the outer shape of the light-shielding film 100 (light-shielding members 61, 63, 65) can be any shape, such as a polygonal shape, such as a rectangular shape, a square shape, or a hexagonal shape, an elliptical shape, or an indefinite shape, in a plan view. In addition, the shape of the hollow portion of the light-shielding members 61, 63, 65 is also formed to be a circle in a plan view in this embodiment, but the outer shape is not particularly limited. For example, any shape, such as a polygonal shape, such as a rectangular shape, a square shape, or a hexagonal shape, an elliptical shape, or an indefinite shape, in a plan view, can be used. [Explanation of symbols]

[0063] 100... Light-shielding film 11... Base film 11a…Surface (principal surface) 11b…Surface (principal surface) 21... Light shielding layer (first light shielding layer) 31... Light shielding layer (second light shielding layer) 1. Camera module 2... Lens unit 41,43,45,47,49… Lenses 61, 63, 65... Light blocking member 8… Holder 9... Image sensor

Claims

1. A light-shielding film for obtaining a light-shielding member for an optical device, comprising: At least a first light-shielding layer and a second light-shielding layer are provided, The first light-shielding layer and the second light-shielding layer each have (A), (B), (C), and (D) of an outermost surface on which each layer is formed, which are 2% or less, 4.5% or less, 26 or less, and 1.0 or more, respectively; and the difference in (B) and the difference in (C) between the outermost surface on which the first light-shielding layer is formed and the outermost surface on which the second light-shielding layer is formed are 2% or less and 4 or more, respectively; A light-shielding film, wherein the first light-shielding layer and the second light-shielding layer are both composed of two particle groups having different particle sizes, the particle groups including large particles having an average particle size of 2 μm to 6 μm and small particles having an average particle size of 0.06 μm to 0.4 μm. (A) Glossiness for light with an incident angle of 60° (B) Reflectance for light with a wavelength of 550 nm (C) L value in the CIELAB color system according to the SCE method (D) Optical density

2. A light-shielding film as described in claim 1, wherein the large particles have an average particle size that is 10 to 40 times the average particle size of the small particles.

3. A light-shielding film as described in claim 1 or 2, wherein the ratio of the volume occupied by large particles having an average particle size of 2 μm to 6 μm in each light-shielding layer to the volume occupied by small particles having an average particle size of 0.06 μm to 0.4 μm in each light-shielding layer is 1.5 to 3.

5.

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

5. 3. A light-shielding member used in a lens unit having a lens group consisting of a plurality of lenses stacked in the optical axis direction in a holder, the light-shielding member being formed from the light-shielding film according to claim 1 or 2.

6. 6. A lens unit comprising a lens group, consisting of a plurality of lenses stacked in the optical axis direction, in a holder, the lens unit comprising the light-shielding member according to claim 5 interposed between at least one pair of lenses.

7. A camera module comprising: the lens unit according to claim 6; and an image sensor that captures an image of a subject through the lens unit.

Images