Patent Description:
A camera module for taking an image of an object and converting it into an image signal is built into electronic equipment, for example, an information communication terminal such as a cellular phone or a smartphone, or a digital camera. This camera module comprises an image pickup device for picking up an image of an object, and a lens unit for forming the image of the object on this image pickup device. The lens unit is usually composed of a combination of a plurality of lenses.

In this type of camera module, it is required to remove unnecessary incident light and reflected light, prevent the occurrence of halation, lens flare, a ghost, and the like, and improve the image quality of a picked-up image. Therefore, lens units, camera modules, and the like having light-blocking members for cutting unnecessary light are proposed.

As such light-blocking members, light-blocking films in which light-blocking layers containing carbon black, a lubricant, fine particles, and a binder resin are formed on both surfaces of a substrate film are proposed (see Patent Literatures <NUM> and <NUM>).

<CIT> discloses an optical lens with the features in the preamble of present claim <NUM>. Another conventional multilayer film is described in <CIT>.

In recent years, modularization has advanced worldwide, and modules have been manufactured and controlled in manufacturing plants in the countries of the world in the form of a lens unit including a plurality of lenses and light-blocking plates stacked in the optical axis direction, a camera module in which an image pickup device is further incorporated into this lens unit, or the like. With this, a light-blocking film or a light-blocking member that is one part of each module is also conveyed, and manufactured and controlled, in each place.

Here, when a light-blocking member having a desired shape is made from a light-blocking film, or when a light-blocking member is incorporated into a module, manufacturing failure such as poor incorporation can be caused unless the front and back surfaces of the light-blocking film or the light-blocking member are discriminated. In these days when transworld modularization advances, it is not easy to promote the thoroughness of the control (the confirmation of the front and back surfaces) of a light-blocking film or a light-blocking member worldwide.

In addition, due to the advancement of the miniaturization and film thinning of camera modules, light-blocking members of extremely small size have been mounted. For example, for a light-blocking film in which black light-blocking layers are provided, when the size is several centimeters square or less, it is extremely difficult to discriminate the front and back of the light-blocking film. Especially, for a light-blocking film having high optical density, this tendency is significant.

The present invention has been made in view of the above problems. Specifically, it is an object of the present invention to provide a multilayer light-blocking film whose front and back surfaces are easy to discriminate while it has light-blocking layers having high optical density whose front and back are usually difficult to discriminate, and a light-blocking ring for optical equipment, a lens unit, a camera module, and the like using the same.

The present inventors have studied diligently from a human engineering approach in order to solve the above problems. As a result, the present inventors have found that the above problems can be solved by setting a predetermined color difference ΔE*ab between a first light-blocking layer and a second light-blocking layer, and by further allowing the end surfaces to function as marks as needed, and completed the present invention.

The solution provided by the present invention is defined in appended claim <NUM>. The dependent claims relate to preferred embodiments.

According to the present invention, it is possible to provide a multilayer light-blocking film and a light-blocking ring for optical equipment whose front and back are easy to discriminate while they have light-blocking layers having high optical density. By using these multilayer light-blocking film and light-blocking ring for optical equipment, handling properties at a module manufacturing site are improved, and the burden of parts control can be reduced. Therefore, the occurrence of manufacturing failure such as poor incorporation can be suppressed, and the yield can be improved. Therefore, a lens unit, a camera module, and the like using these have excellent productivity and economy.

Embodiments of the present invention will be described in detail below with reference to the drawings. Positional relationships such as top, bottom, left, and right are based on the positional relationships shown in the drawings unless otherwise noted. The dimensional ratios in the drawings are not limited to the ratios shown. However, the following embodiments are illustrations for explaining the present invention, and the present invention is not limited to these. As used herein, for example, the description of the numerical value range "<NUM> to <NUM>" includes both the upper limit value "<NUM>" and the lower limit value "<NUM>". The same applies to the description of other numerical value ranges.

<FIG> is a perspective view schematically showing a multilayer light-blocking film <NUM> and its web roll <NUM> in a first embodiment of the present invention, and <FIG> is a cross-sectional view showing the main part of the multilayer light-blocking film <NUM> (the II-II cross section in <FIG>). <FIG> is a plan view of the multilayer light-blocking film <NUM>. This multilayer light-blocking film <NUM> comprises at least a substrate film <NUM>, a first light-blocking layer <NUM> provided on one major surface 11a side of this substrate film <NUM>, and a second light-blocking layer <NUM> provided on the other major surface 11b side. The multilayer light-blocking film <NUM> has a multilayer structure (three-layer structure) in which the light-blocking layer <NUM>, the substrate film <NUM>, and the light-blocking layer <NUM> are at least arranged in this order. In this multilayer structure, the first light-blocking layer <NUM> is disposed on the outermost surface on the front side, and the second light-blocking layer <NUM> is disposed on the outermost surface on the back side, and as shown in <FIG>, the first and second light-blocking layers <NUM> and <NUM> are disposed on the outermost surfaces on the front side and the back side respectively in an exposed state. By winding this multilayer light-blocking film <NUM> in the form of a cored or coreless roll, the rolled web <NUM> that is a wound body is formed.

As used herein, "provided on one (the other) major surface side of the substrate film " means including not only a mode in which the light-blocking layer <NUM> or <NUM> is directly placed on a surface (for example, the major surface 11a or the major surface 11b) of the substrate film <NUM> as in this embodiment, but a mode in which an optional layer (for example, a primer layer or an adhesive layer) is interposed between a surface of the substrate film <NUM> and the light-blocking layer <NUM> or <NUM>. A multilayer structure comprising at least the first light-blocking layer <NUM> and the second light-blocking layer <NUM> means including not only a structure in which only the first light-blocking layer <NUM> and the second light-blocking layer <NUM> are directly layered, but the above-described three-layer structure and a multilayer structure of four or more layers in which an optional layer or optional layers are further provided in a three-layer structure.

The type of the substrate film <NUM> is not particularly limited as long as it can support the light-blocking layers <NUM> and <NUM>. From the viewpoint of dimensional stability, mechanical strength, weight reduction, and the like, synthetic resin films are preferably used. Specific examples of the synthetic resin films include polyester films, ABS (acrylonitrile-butadiene-styrene) films, polyimide films, polystyrene films, and polycarbonate films. Acrylic, polyolefin-based, cellulosic, polysulfone-based, polyphenylene sulfide-based, polyethersulfone-based, and polyetheretherketone-based films can also be used. Among these, as the substrate film <NUM>, polyester films and polyimide films are preferably used. Especially, uniaxially or biaxially stretched films, particularly biaxially stretched polyester films, have excellent mechanical strength and dimensional stability and therefore are particularly preferred. For heat-resistant applications, uniaxially or biaxially stretched polyimide films are particularly preferred. One of these can be used alone, and two or more of these can also be used in combination.

The thickness of the substrate film <NUM> can be appropriately set according to the required performance and the application and is not particularly limited. From the viewpoint of weight reduction and film thinning, the thickness of the substrate film <NUM> is preferably <NUM> or more and <NUM> or less, more preferably <NUM> or more and <NUM> or less, further preferably <NUM> or more and <NUM> or less, and particularly preferably <NUM> or more and <NUM> or less. From the viewpoint of improving adhesiveness to the light-blocking layers <NUM> and <NUM>, the surfaces of the substrate film <NUM> can also be subjected to various known surface treatments such as anchor treatment and corona treatment as needed.

Inclined end surfaces <NUM> are provided on the outer peripheral side surfaces (outer peripheral end surfaces) of the substrate film <NUM>. Due to these inclined end surfaces <NUM>, the cross-sectional structure of the substrate film <NUM> has a trapezoidal shape in which the lower base is longer than the upper base, so that the film width of the substrate film <NUM> increases from the light-blocking layer <NUM> toward the light-blocking layer <NUM> (see <FIG>).

These inclined end surfaces <NUM> are provided so as to be exposed in a planar view from the normal direction of the major surface 11a of the substrate film <NUM> so as to be visible from the major surface 11a side of the substrate film <NUM> when the substrate film <NUM> is brought into a flat state as shown in <FIG> (see <FIG>). Specifically, the inclination angle θ (depression angle θ) between the major surface 11a and the inclined end surface <NUM> of the substrate film <NUM> is set to be <NUM> to <NUM>°. From the viewpoint of improving the visibility of the inclined end surfaces <NUM> in a planar view from the major surface 11a side, maintaining the strength of the end surfaces of the substrate film <NUM>, maintaining productivity, and the like, the inclination angle θ is preferably <NUM> to <NUM>°, more preferably <NUM> to <NUM>°, and further preferably <NUM> to <NUM>°. As long as the inclined end surfaces <NUM> are visible from the major surface 11a side of the substrate film <NUM>, for example, transparent or semitransparent protective layers or the like may be provided on the inclined end surfaces <NUM> for film end surface strengthening.

The appearance of the substrate film <NUM> may be any of transparent, semitransparent, and opaque appearance and is not particularly limited. For example, foamed synthetic resin films such as foamed polyester films, and synthetic resin films in which black pigments such as carbon black or other pigments are contained can also be used. From the viewpoint of improving the visibility of the inclined end surfaces <NUM> in a planar view from the major surface 11a side, the substrate film <NUM> preferably has a total light transmittance of <NUM> to <NUM>%, more preferably <NUM> to <NUM>%, and further preferably <NUM> to <NUM>%.

The light-blocking layers <NUM> and <NUM> are light-blocking films having an optical density (OD) of <NUM> or more in total. As used herein, the optical density (OD) is a value obtained by measuring in accordance with JIS-K7651: <NUM> using an optical densitometer (TD-<NUM>: GretagMacbeth) and a UV filter. From the viewpoint of having higher light-blocking properties, the light-blocking layers <NUM> and <NUM> each preferably have an optical density (OD) of <NUM> or more for a single layer and each more preferably have an optical density (OD) of <NUM> or more for a single layer. When the light-blocking layers <NUM> and <NUM> are layered, the optical density (OD) of the layered body is preferably <NUM> to <NUM>, more preferably <NUM> to <NUM>, further preferably <NUM> to <NUM>.

When the difference between the <NUM>-degree glossinesses of the light-blocking layers <NUM> and <NUM> is set, it is easier to discriminate the front and back. Here, the <NUM>-degree glossiness is a value obtained by measuring the glossiness (specular glossiness) (%) of the surface of the light-blocking layer <NUM> or <NUM> at incidence and acceptance angles of <NUM>° in accordance with JIS-<NUM>: <NUM> using a digital variable angle glossmeter (UGV-<NUM>: manufactured by Suga Test Instruments Co. From the viewpoint of the balance of light-blocking properties, low gloss, low reflectivity, light absorption properties, and the like, at least one of the light-blocking layer <NUM> and the light-blocking layer <NUM> preferably has a <NUM>-degree glossiness of more than <NUM>% and <NUM>% or less. Examples of one of preferred modes thereof include a mode in which the <NUM>-degree glossiness of the light-blocking layer <NUM> is <NUM>% or more and <NUM>% or less, more preferably <NUM>% or more and <NUM>% or less, and further preferably <NUM>% or more and <NUM>% or less, and the <NUM>-degree glossiness of the light-blocking layer <NUM> is more than <NUM>% and <NUM>% or less, more preferably <NUM>% or more and <NUM>% or less, and further preferably <NUM>% or more and <NUM>% or less. The light-blocking layer <NUM> and the light-blocking layer <NUM> each have a <NUM>-degree glossiness of less than <NUM>%, and the light-blocking layer <NUM> and the light-blocking layer <NUM> preferably have different <NUM>-degree glossinesses so that the difference between the <NUM>-degree glossiness of the light-blocking layer <NUM> and the <NUM>-degree glossiness of the light-blocking layer <NUM> is <NUM> to <NUM>%, preferably <NUM> to <NUM>%, and further preferably <NUM> to <NUM>%.

One feature of the multilayer light-blocking film <NUM> in this embodiment is that from a human engineering approach, a configuration in which in the light-blocking layer <NUM> and the light-blocking layer <NUM> having the above-described optical density and <NUM>-degree glossiness, further the color difference ΔE*ab is <NUM> or more is adopted. The color difference ΔE*ab means a value calculated as the difference between the hues, L* values, a* values, and b* values, of the light-blocking layer <NUM> and the light-blocking layer <NUM> each obtained in accordance with JIS-Z8730: <NUM> using a color meter. At this time, the color difference ΔE*ab between the light-blocking layer <NUM> and the light-blocking layer <NUM> should be appropriately set considering the balance of the visual discriminability of the front and back surfaces and the optical density (light-blocking properties) and is not particularly limited but is preferably <NUM> or more, more preferably <NUM> or more, further preferably <NUM> or more, and particularly preferably <NUM> or more. The upper limit value of the color difference ΔE*ab between the light-blocking layer <NUM> and the light-blocking layer <NUM> is not particularly limited, but usually <NUM> is taken as a rough standard.

Here, further, when the lightness of the light-blocking layer <NUM> and the lightness of the light-blocking layer <NUM> are differentiated, it is easier to discriminate the front and back of the multilayer light-blocking film <NUM>. Here, the difference in lightness can be represented by the lightness index L* in the CIE <NUM>*a*b* color system. Specifically, the lightness index L* of the light-blocking layer <NUM> is <NUM> or more and <NUM> or less, the lightness index L* of the light-blocking layer <NUM> is <NUM> or more and <NUM> or less, and the difference between the lightness index L* of the light-blocking layer <NUM> and the lightness index L* of the light-blocking layer <NUM> is <NUM> or more and <NUM> or less, preferably <NUM> to <NUM>, more preferably <NUM> to <NUM>, and further preferably <NUM> to <NUM>.

As a material of the light-blocking film having such properties (light-blocking layers <NUM> and <NUM>), those known in the industry can be used, and the type of the light-blocking film is not particularly limited. As the light-blocking film having high optical density, a dark light-blocking film provided with one or more dark pigments or dyes such as black, gray, purple, blue, brown, red, and green pigments or dyes is preferably used. For example, as the black-based light-blocking film, a black light-blocking film (in other words, a black light-blocking layer <NUM> or <NUM>) containing at least a binder resin and a black pigment, and a dark pigment or dye blended as needed is preferably used. This black light-blocking film will be described in detail below as an example.

Examples of the binder resin include, but are not particularly limited to, thermoplastic resins or thermosetting resins such as poly(meth)acrylic acid-based resins, polyester-based resins, polyvinyl acetate-based resins, polyvinyl chloride-based resins, polyvinyl butyral-based resins, cellulosic resins, polystyrene/polybutadiene resins, polyurethane-based resins, alkyd resins, acrylic resins, unsaturated polyester-based resins, epoxy ester-based resins, epoxy-based resins, epoxy acrylate-based resins, urethane acrylate-based resins, polyester acrylate-based resins, polyether acrylate-based resins, phenolic resins, melamine-based resins, urea-based resins, and diallyl phthalate-based resins. Thermoplastic elastomers, thermosetting elastomers, ultraviolet curable resins, electron beam curable resins, and the like can also be used. One of these can be used alone, and two or more of these can also be used in combination. The binder resin can be appropriately selected and used according to the required performance and the application. For example, in applications where heat resistance is required, thermosetting resins are preferred.

The content (total amount) of the binder resin in the light-blocking layer <NUM> or <NUM> is not particularly limited but is preferably <NUM> to <NUM>% by mass, more preferably <NUM> to <NUM>% by mass, and further preferably <NUM> to <NUM>% by mass from the viewpoint of adhesiveness, light-blocking properties, scratch resistance, sliding properties, flatting properties, and the like.

The black pigment colors the binder resin black to provide light-blocking properties. Specific examples of the black pigment include, but are not particularly limited to, black resin particles, magnetite-based black, copper-iron-manganese-based black, titanium black, and carbon black. Among these, black resin particles, titanium black, and carbon black are preferred because of excellent concealing properties, and carbon black is more preferred. One of these can be used alone, and two or more of these can also be used in combination. Similarly, the dark pigment or dye blended as needed should also be appropriately selected and used from among known ones.

As the carbon black, those made by various known manufacturing methods, such as oil furnace black, lamp black, channel black, gas furnace black, acetylene black, thermal black, and ketjen black, are known, but the type of the carbon black is not particularly limited. From the viewpoint of providing conductivity to the light-blocking layer <NUM> or <NUM> to prevent electrostatic charging, conductive carbon black is particularly preferably used. The history of carbon black is old, and various grades of carbon black simple substances and carbon black dispersions are commercially available from, for example, Mitsubishi Chemical Corporation, Asahi Carbon Co. , MIKUNI COLOR LTD. , RESINO COLOR INDUSTRY CO. , Cabot, and DEGUSSA. The carbon black should be appropriately selected from among these according to the required performance and the application. The particle size of the carbon black can be appropriately set according to the required performance and the like and is not particularly limited. The average particle diameter D<NUM> of the carbon black is preferably <NUM> to <NUM>, more preferably <NUM> to <NUM>, and further preferably <NUM> to <NUM>. The average particle diameter herein means a volume-based median diameter (D<NUM>) measured by a laser diffraction particle size distribution measuring apparatus (for example, SHIMADZU CORPORATION: SALD-<NUM>).

The content (total amount) of the black pigment in the light-blocking layer <NUM> or <NUM> is not particularly limited but is preferably <NUM> to <NUM>% by mass, more preferably <NUM> to <NUM>% by mass, and further preferably <NUM> to <NUM>% by mass in terms of solids based on all resin components contained in the light-blocking layer <NUM> or <NUM> (phr) from the viewpoint of dispersibility, film-forming properties, handling properties, adhesiveness, slip properties, flatting properties, abrasion resistance, and the like.

The thicknesses of the light-blocking layers <NUM> and <NUM> can be appropriately set according to the required performance and the application and are not particularly limited. From the viewpoint of high optical density, weight reduction, and film thinning, the thicknesses of the light-blocking layers <NUM> and <NUM> are each preferably <NUM> or more, more preferably <NUM> or more, further preferably <NUM> or more, and particularly preferably <NUM> or more and preferably <NUM> or less, more preferably <NUM> or less, further preferably <NUM> or less, and particularly preferably <NUM> or less on the upper limit side.

From the viewpoint of weight reduction and film thinning, the total thickness of the multilayer light-blocking film <NUM> is preferably <NUM> or more and <NUM> or less, more preferably <NUM> or more, and further preferably <NUM> or more, and more preferably <NUM> or less, and further preferably <NUM> or less.

One feature of the multilayer light-blocking film <NUM> in this embodiment is that from a human engineering approach, a configuration in which in the light-blocking layer <NUM> and the light-blocking layer <NUM> having the above-described optical density and <NUM>-degree glossiness, further the color difference ΔE*ab is <NUM> or more is adopted. By adopting the light-blocking layer <NUM> and the light-blocking layer <NUM> further provided with the color difference ΔE*ab in this manner, the optical density, the gloss, the luster, the color difference, and the like are combined, and as a result, the perceptual color difference increases, and thus it is extremely easy to discriminate the front and back of the multilayer light-blocking film <NUM> in a noncontact manner, that is, visually.

The method for adjusting the color difference ΔE*ab between the light-blocking layer <NUM> and the light-blocking layer <NUM> includes, but is not particularly limited to, a method of differentiating the content of the black pigment between the light-blocking layer <NUM> and the light-blocking layer <NUM>, a method of using black pigments having different blacknesses for the light-blocking layer <NUM> and the light-blocking layer <NUM>, a method of using black pigments of different sizes for the light-blocking layer <NUM> and the light-blocking layer <NUM>, a method of differentiating surface roughness between the light-blocking layer <NUM> and the light-blocking layer <NUM>, a method of using binder resins having different hues for the light-blocking layer <NUM> and the light-blocking layer <NUM>, a method of using a black pigment and a dark pigment or dye in combination for only one of the light-blocking layer <NUM> and the light-blocking layer <NUM>, and a method of differentiating the types of the black pigment and the dark pigment or dye used, between the light-blocking layer <NUM> and the light-blocking layer <NUM>. It is also possible to adjust lightness, hue, and/or saturation by blending various known additives used in light-blocking films. For these adjustment methods, the various methods can each be performed alone or can be performed in appropriate combination.

In addition, the method for adjusting the <NUM>-degree glossinesses of the light-blocking layer <NUM> and the light-blocking layer <NUM> includes, but is not particularly limited to, a method of differentiating the content of the black pigment between the light-blocking layer <NUM> and the light-blocking layer <NUM>, a method of using black pigments having different blacknesses for the light-blocking layer <NUM> and the light-blocking layer <NUM>, a method of using black pigments of different sizes for the light-blocking layer <NUM> and the light-blocking layer <NUM>, a method of differentiating surface roughness between the light-blocking layer <NUM> and the light-blocking layer <NUM>, a method of using binder resins having different hues for the light-blocking layer <NUM> and the light-blocking layer <NUM>, a method of using a black pigment and a dark pigment or dye in combination for only one of the light-blocking layer <NUM> and the light-blocking layer <NUM>, and a method of differentiating the types of the black pigment and the dark pigment or dye used, between the light-blocking layer <NUM> and the light-blocking layer <NUM>. It is also possible to adjust lightness, hue, and/or saturation by blending various known additives used in light-blocking films. For these adjustment methods, the various methods can each be performed alone or can be performed in appropriate combination.

On the outer peripheral side surfaces of the light-blocking layer <NUM> or <NUM>, inclined end surfaces <NUM> or <NUM> (outer peripheral end surfaces <NUM> or <NUM>) having an inclination angle θ corresponding to that of the above-described inclined end surfaces <NUM> are provided on both side surfaces (two places). These inclined end surfaces <NUM> and <NUM> are provided so as to be exposed in a planar view from the normal direction of the major surface 21a of the light-blocking layer <NUM> so as to be visible from the major surface 21a side of the light-blocking layer <NUM> when the light-blocking layers <NUM> and <NUM> are brought into a flat state as shown in <FIG> (see <FIG>). Specifically, the inclination angle θ between the major surface 21a of the light-blocking layer <NUM> and the inclined end surface <NUM> or <NUM> is set to be <NUM> to <NUM>°. As long as the inclined end surfaces <NUM> and <NUM> are visible from the major surface 21a side of the light-blocking layer <NUM>, for example, transparent or semitransparent protective layers or the like may be provided on the inclined end surfaces <NUM> and <NUM> for film end surface strengthening. If configuring the light-blocking layers <NUM> and <NUM> in this manner and using the difference in hue, saturation, lightness, transparency, <NUM>-degree glossiness, total light transmittance, or the like between the substrate film <NUM> and the light-blocking layers <NUM> and <NUM>, the discriminability of the light-blocking layers <NUM> and <NUM> improves further. Here, the inclination angle θ of the inclined end surface <NUM> or <NUM> is not particularly limited but is preferably <NUM> to <NUM>°, more preferably <NUM> to <NUM>°, further preferably <NUM> to <NUM>°, and particularly preferably <NUM> to <NUM>° like the inclined end surface <NUM>. By setting an inclination angle equal or nearly equal to that of the inclined end surface <NUM>, the end surface strength tends to be easily maintained high, and the productivity tends to be easily improved.

The light-blocking layers <NUM> and <NUM> may contain various additives known in the industry. Specific examples thereof include, but are not particularly limited to, matting agents (flatting agents), lubricants, conductive agents, flame retardants, antimicrobial agents, fungicides, antioxidants, plasticizers, leveling agents, flow-adjusting agents, antifoaming agents, and dispersing agents. Examples of the matting agents include, but are not particularly limited to, organic fine particles such as crosslinked polymethyl methacrylate particles and crosslinked polystyrene particles, and inorganic fine particles such as silica, magnesium aluminometasilicate, and titanium oxide. Examples of the lubricants include, but are not particularly limited to, hydrocarbon-based lubricants such as polyethylene, paraffins, and waxes; fatty acid-based lubricants such as stearic acid and <NUM>-hydroxystearic acid; amide-based lubricants such as stearic acid amide, oleic acid amide, and erucic acid amide; ester-based lubricants such as butyl stearate and stearic acid monoglyceride; alcohol-based lubricants; solid lubricants such as metallic soaps, talc, and molybdenum disulfide; silicone resin particles, and particles of fluororesins such as polytetrafluoroethylene waxes and polyvinylidene fluoride. Among these, particularly organic lubricants are preferably used. When an ultraviolet curable resin or an electron beam curable resin is used as the binder resin, for example, a sensitizer such as n-butylamine, triethylamine, or tri-n-butylphosphine, and an ultraviolet absorbing agent may be used. One of these can be used alone, and two or more of these can also be used in combination. The content of these is not particularly limited, but the content of each is generally preferably <NUM> to <NUM>% by mass in terms of solids based on all resin components contained in the light-blocking layer <NUM> or <NUM>.

In addition, the light-blocking layers <NUM> and <NUM> preferably have a visible light reflectance of <NUM>% or less. Here, the visible light reflectance means relative total light reflectance when light is allowed to enter at an incidence angle of <NUM>° to the light-blocking layer <NUM> or <NUM> using a spectrophotometer (spectrophotometer SolidSpec-<NUM> manufactured by SHIMADZU CORPORATION, or the like) and barium sulfate as a standard plate. From the viewpoint of having higher light-blocking properties, and the like, the visible light reflectances of the light-blocking layers <NUM> and <NUM> are more preferably <NUM>% or less, further preferably <NUM>% or less, and particularly preferably <NUM>% or less. From the viewpoint of increasing the discriminability of the light-blocking layers <NUM> and <NUM>, the difference in visible light reflectance between the light-blocking layer <NUM> and the light-blocking layer <NUM> is preferably <NUM>% or more. As the multilayer light-blocking film <NUM>, the diffuse reflectance in the range of infrared light (<NUM> to <NUM>) other than visible light is preferably <NUM>% or less, more preferably <NUM>% or less, further preferably <NUM>% or less, and particularly preferably <NUM>% or less.

Further, the light-blocking layers <NUM> and <NUM> preferably have a surface resistivity of less than <NUM> × <NUM><NUM> Ω, more preferably less than <NUM> × <NUM><NUM> Ω, and further preferably less than <NUM> × <NUM><NUM> Ω from the viewpoint of having sufficient antistatic performance. As used herein, the surface resistivity is a value measured in accordance with JIS-K6911: <NUM>.

The method for manufacturing the multilayer light-blocking film <NUM> is not particularly limited as long as one having the above-described configuration is obtained. From the viewpoint of manufacturing the light-blocking layers <NUM> and <NUM> on the substrate film <NUM> with good reproducibility, simply, and at low cost, conventionally known application methods such as doctor coating, dip coating, roll coating, bar coating, die coating, blade coating, air knife coating, kiss coating, spray coating, and spin coating are preferably used.

For example, the light-blocking layer <NUM> or <NUM> can be formed on the substrate film <NUM> by applying onto a major surface of the substrate film <NUM> an application liquid containing in a solvent the binder resin and the black pigment described above and additives as optional components blended as needed, drying the application liquid, and then performing heat treatment, pressurization treatment, and the like as needed. As the solvent of the application liquid used here, water; ketone-based solvents such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ester-based solvents such as methyl acetate, ethyl acetate, and butyl acetate; ether-based solvents such as methyl cellosolve and ethyl cellosolve; alcohol-based solvents such as methyl alcohol, ethyl alcohol, and isopropyl alcohol, and mixed solvents thereof, and the like can be used. In order to improve the adhesion between the substrate film <NUM> and the light-blocking layer <NUM> or <NUM>, anchor treatment, corona treatment, or the like can also be performed as needed. Further, an intermediate layer such as a primer layer or an adhesive layer can also be provided between the substrate film <NUM> and the light-blocking layer <NUM> or <NUM> as needed. The multilayer light-blocking film <NUM> having the desired shape can also be simply obtained by various known forming methods such as compression molding, injection molding, blow molding, transfer molding, and extrusion. Once a sheet shape is formed, then vacuum forming, pressure forming, or the like can also be performed.

The method for forming the inclined end surfaces <NUM>, <NUM>, and <NUM> is not particularly limited either. The inclined end surfaces <NUM>, <NUM>, and <NUM> having any inclination angle θ can be made by appropriately applying various known methods. For example, the inclined end surfaces <NUM>, <NUM>, and <NUM> can be simply provided by providing a multilayer light-blocking film in which the light-blocking layer <NUM> and the light-blocking layer <NUM> are provided on the substrate film <NUM>, and cutting off (cutting out) its outer peripheral side surfaces at the above-described inclination angle. When the inclined end surfaces <NUM> and <NUM> are unnecessary, it is recommended to provide the substrate film <NUM> previously provided with the inclined end surfaces <NUM> having any inclination angle θ and provide the light-blocking layer <NUM> and the light-blocking layer <NUM> on this substrate film <NUM>.

In the multilayer light-blocking film <NUM> and the web roll <NUM> in this embodiment, the first light-blocking layer <NUM> and the second light-blocking layer <NUM> having an optical density of <NUM> or more in total, having a predetermined <NUM>-degree glossiness and a predetermined color difference ΔE*ab are adopted. Therefore, by using these as a light-blocking member for optical equipment such as a lens unit or a camera module, unnecessary incident light and reflected light can be removed, the occurrence of halation, lens flare, a ghost, and the like can be prevented, and the image quality of a picked-up image can be improved.

Moreover, in the above-described multilayer structure, the optical densities, <NUM>-degree glossinesses, and color difference ΔE*ab of the first light-blocking layer <NUM> and the second light-blocking layer <NUM> exposed on the front and back surfaces are adjusted, and therefore the perceptual color difference is increased, and thus the discrimination of the front and back surfaces can be extremely easily performed in a noncontact manner, that is, visually. In addition, the inclined end surfaces <NUM> visibly exposed in a planar view are recognizable as bright portions having a glossy feeling and luster, and therefore the discrimination of the front and back surfaces of the multilayer light-blocking film <NUM> can be especially easily performed in a noncontact manner, that is, visually. This is due to the difference in hue, saturation, lightness, transparency, <NUM>-degree glossiness, total light transmittance, or the like between the first light-blocking layer <NUM> or the second light-blocking layer <NUM> and the inclined end surfaces <NUM> (the substrate film <NUM>).

Also when the multilayer light-blocking film <NUM> and the web roll <NUM> in this embodiment are handled in a dark place, the inclined end surfaces <NUM> function effectively. In other words, the inclined end surfaces <NUM> (the substrate film <NUM>) are clearly recognizable as bright portions having a glossy feeling and luster, even with a little light, due to the difference from the first light-blocking layer <NUM> and the second light-blocking layer <NUM>. In addition, the discrimination of the front and back surfaces can also be performed by directly touching the inclined end surface <NUM> with fingers or the like to confirm its inclination direction.

The present invention can be carried out by making any changes without departing from the scope defined in the claims. For example, only the inclined end surfaces <NUM> may be provided without providing the inclined end surfaces <NUM> and <NUM>. In addition, for the place where the inclined end surface <NUM> is formed, the inclined end surface <NUM> should be provided on at least part of the outer peripheral side surfaces of the substrate film <NUM>. Further, the inclined end surface <NUM> may be provided on both side surfaces (two places) of the substrate film <NUM> so as to extend in the MD direction of the multilayer light-blocking film <NUM> as in this embodiment, or provided on one side surface (one place) or both side surfaces (two places) of the substrate film <NUM> so as to extend in the TD direction of the substrate film <NUM>. Alternatively, the inclined end surfaces <NUM> may be provided over all of the outer peripheral side surfaces (entire periphery) of the substrate film <NUM>. In addition, the inclined end surfaces <NUM> extending in the MD direction and/or the TD direction may be continuously formed as in this embodiment and may be intermittently formed. Further, in the above-described embodiment, a mode in which the light-blocking layer <NUM> and the light-blocking layer <NUM> are provided on the front and back of the substrate film <NUM> has been shown, but a multilayer structure (two-layer structure) of the light-blocking layer <NUM> and the light-blocking layer <NUM> may be provided without providing the substrate film <NUM>. In addition, the above-described multilayer structure should be in a state in which the light-blocking layer <NUM> and the light-blocking layer <NUM> are exposed on the front and back surfaces during the handling of the multilayer light-blocking film <NUM>, and additional layers such as protective layers and other light-blocking layers may be formed so as to cover the exposed surfaces of the light-blocking layer <NUM> and the light-blocking layer <NUM>, during subsequent use and mounting. Further, the light-blocking layer <NUM> or <NUM> may be formed of two or more light-blocking films. For example, a multilayer light-blocking layer in which a light-blocking film 21a and a light-blocking film 21b are layered can be applied as the light-blocking layer <NUM>. The same applies to the light-blocking layer <NUM>. At this time, the above-described various performances and physical properties required of the light-blocking layer <NUM> should be satisfied as the layered body of the light-blocking film 21a and the light-blocking film 21b. The same applies to the light-blocking layer <NUM>.

<FIG> is an exploded perspective view schematically showing a lens unit <NUM> and a camera module <NUM> in a second embodiment of the present invention. The lens unit <NUM> is composed of a lens group <NUM> (lenses 42A, 42B, 42C, 42D, and 42E), a multistage cylindrical holder <NUM>, and light-blocking rings 100A, 100B, and 100C for optical equipment (the multilayer light-blocking films <NUM>) as light-blocking spacers. A plurality of height difference portions 43a, 43b, and 43c are provided in the inner peripheral portion of the holder <NUM>. Using these height difference portions 43a, 43b, and 43c, the lens group <NUM> and the light-blocking rings 100A, 100B, and 100C for optical equipment are housed and disposed at predetermined positions in the holder <NUM> in a state of being coaxially (on the same optical axis) disposed and stacked. Here, as the lenses 42A, 42B, 42C, 42D, and 42E, various lenses such as convex lenses and concave lenses can be used, and their curved surfaces may be spherical or aspherical. On the other hand, the camera module <NUM> is composed of the above-described lens unit <NUM> and an image pickup device <NUM> such as a CCD image sensor or a CMOS image sensor that is disposed on the optical axis of this lens unit <NUM> and picks up an image of an object through the lens unit <NUM>.

<FIG> is a cross-sectional view schematically showing the light-blocking ring 100A for optical equipment. The light-blocking ring 100A for optical equipment is obtained by stamping the multilayer light-blocking film <NUM> in the first embodiment described above into a ring shape (hollow tubular shape). Therefore, the light-blocking ring 100A for optical equipment has the same multilayer structure as the multilayer light-blocking film <NUM> in the first embodiment described above.

The light-blocking ring 100A for optical equipment is a light-blocking plate whose outer shape is a ring shape (hollow tubular shape) in which a circular hollow portion S is provided at a generally central position in a planar view. In this embodiment, the above-described inclined end surfaces <NUM>, <NUM>, and <NUM> are not provided on the outer peripheral side surface of the light-blocking ring 100A for optical equipment, and these outer peripheral side surfaces are formed in a rectangular shape in a cross-sectional view. In other words, in the light-blocking ring 100A for optical equipment in this embodiment, the inclination angle θ of the outer peripheral end surface is <NUM>°. On the other hand, in the light-blocking ring 100A for optical equipment in this embodiment, inclined end surfaces <NUM>, <NUM>, and <NUM> corresponding to the above-described inclined end surfaces <NUM>, <NUM>, and <NUM> are provided on the inner peripheral end surface. The light-blocking rings 100B and 100C for optical equipment have the same configuration as the light-blocking ring 100A for optical equipment except that the size of the outer diameter and the size of the outer diameter of the hollow portion S are each different, and redundant description is omitted here.

Also in the light-blocking rings 100A, 100B, and 100C for optical equipment in this embodiment, the light-blocking layer <NUM> and the light-blocking layer <NUM> having an optical density of <NUM> or more in total, having a predetermined <NUM>-degree glossiness and a predetermined color difference ΔE*ab are adopted. Therefore, by using these as light-blocking members for optical equipment such as a lens unit or a camera module, unnecessary incident light and reflected light can be removed, the occurrence of halation, lens flare, a ghost, and the like can be prevented, and the image quality of a picked-up image can be improved.

Moreover, in the above-described multilayer structure, the optical densities, <NUM>-degree glossinesses, and color difference ΔE*ab of the light-blocking layer <NUM> and the light-blocking layer <NUM> exposed on the front and back surfaces are adjusted, and therefore the perceptual color difference is increased, and thus the discrimination of the front and back surfaces of the light-blocking rings 100A, 100B, and 100C for optical equipment can be extremely easily performed in a noncontact manner, that is, visually. Therefore, for the lens unit <NUM> and the camera module <NUM> using these light-blocking rings 100A, 100B, and 100C for optical equipment, also during their storage and incorporation, manufacturing failure such as poor incorporation based on the false recognition of the front and back surfaces is inhibited.

Furthermore, in the light-blocking ring 100A for optical equipment in this embodiment, the inclined end surfaces <NUM>, <NUM>, and <NUM> are provided, and the discriminability of the light-blocking layers <NUM> and <NUM> is further increased. By providing the inclined end surfaces <NUM>, <NUM>, and <NUM> on the end surface on the optical axis side (inner peripheral end surface) in this manner, unnecessary reflected light can be removed, the occurrence of halation, lens flare, a ghost, and the like can be prevented, and the image quality of a picked-up image can be improved.

The present invention can be carried out by making any changes without departing from the scope defined in the claims. For example, for the outer shape of the multilayer light-blocking film <NUM> (the light-blocking ring 100A, 100B, or 100C for optical equipment), 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 irregular shape in a planar view can be adopted. In addition, also for the shape of the hollow portion S of the light-blocking ring 100A, 100B, or 100C for optical equipment, the hollow portion S is formed in a circular shape in a planar view in this embodiment, but its 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 irregular shape in a planar view can be adopted. Further, in this embodiment, the above-described inclined end surfaces <NUM>, <NUM>, and <NUM> are not provided, but either one or both of the inclined end surface <NUM> and the inclined end surfaces <NUM> and <NUM> can be appropriately provided as needed. Further, in the above-described embodiment, a mode in which the light-blocking layer <NUM> and the light-blocking layer <NUM> are provided on the front and back of the substrate film <NUM> has been shown, but a multilayer structure (two-layer structure) of the light-blocking layer <NUM> and the light-blocking layer <NUM> may be provided without providing the substrate film <NUM>. In addition, the above-described multilayer structure should be in a state in which the light-blocking layer <NUM> and the light-blocking layer <NUM> are exposed on the front and back surfaces during the handling of the multilayer light-blocking film <NUM>, and additional layers such as protective layers and other light-blocking layers may be formed so as to cover the exposed surfaces of the light-blocking layer <NUM> and the light-blocking layer <NUM>, during subsequent use and mounting. Further, the light-blocking layer <NUM> or <NUM> may be formed of two or more light-blocking films. For example, a multilayer light-blocking layer in which a light-blocking film 21a and a light-blocking film 21b are layered can be applied as the light-blocking layer <NUM>. The same applies to the light-blocking layer <NUM>. At this time, the above-described various performances and physical properties required of the light-blocking layer <NUM> should be satisfied as the layered body of the light-blocking film 21a and the light-blocking film 21b. The same applies to the light-blocking layer <NUM>.

Claim 1:
A multilayer light-blocking film (<NUM>) for optical equipment, comprising:
a multilayer structure comprising at least a first light-blocking layer (<NUM>) and a second light-blocking layer (<NUM>), wherein
the first light-blocking layer (<NUM>) and the second light-blocking layer (<NUM>) have an optical density of <NUM> or more in total,
the first light-blocking layer (<NUM>) and the second light-blocking layer (<NUM>) each have a <NUM>-degree glossiness of less than <NUM>%, and
characterized in that
a color difference ΔE*ab between the first light-blocking layer (<NUM>) and the second light-blocking layer (<NUM>) is <NUM> or more in a CIE <NUM>*a*b* color system,
the first light-blocking layer (<NUM>) and/or the second light-blocking layer (<NUM>) have inclined end surfaces (<NUM>, <NUM>, <NUM>, <NUM>) so that a film width increases from the first light-blocking layer (<NUM>) toward the second light-blocking layer (<NUM>), and
the inclined end surface is exposed in a planar view seen from a normal direction of a major surface (21a) of the first light-blocking layer (<NUM>).