JP2002277612A - Nd filter, method for manufacturing nd filter, device for controlling light quantity, and image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such problems that, when an antireflection film and a transmittance controlling film are formed by vapor deposition, the number of vapor deposition increases and this decreases the productivity in an ND filter. SOLUTION: The ND filter used for controlling the light quantity is manufactured by forming an antireflection film 8-4 by a wet method for forming films on at least one of the top and back faces of a plastic substrate 8-3. A transmittance controlling film is formed by vapor deposition on the opposite face to the antireflection film of the plastic substrate or on the antireflection film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light amount adjusting device provided in a photographing device such as a video camera and a digital camera, and an ND (neutral density) filter used for the device.

[0002]

2. Description of the Related Art A conventional digital video camera is shown in FIG.
The imaging optical system 7 shown in FIG. The photographing optical system 7 includes, in order from the object side, a first-group lens L1, an aperture device S, a second-group lens L2, a third-group lens L3, a fourth-group lens L4, a low-pass filter 5, and a CCD 4 as a solid-state image sensor. It is configured.

An aperture device (light amount adjusting device) S controls the amount of light passing therethrough by changing the aperture diameter by a pair of aperture blades 2 that open and close on an aperture base plate 3.

As shown in FIG. 10, an ND filter 1 is provided on a portion of the aperture blade 2 corresponding to a small aperture diameter.
Is pasted.

[0005] This is because if the captured image is too bright, the aperture blade 2 moves in the closing direction to reduce the amount of light, but if the aperture diameter is made smaller than a certain size (that is, if the aperture is made smaller), a light beam diffraction phenomenon occurs. This is because the resolution of the image is reduced. In order to further reduce the transmission amount at the time of the small aperture, the amount of light reaching the CCD 6 is reduced by the ND filter 1.

[0006] The ND filter used in the conventional diaphragm device is a film-like material (cellulose acetate, P
ET, vinyl chloride, etc.) and an organic dye or pigment that absorbs light is mixed and kneaded.

[0007] The use of a plastic film without using a glass substrate for the ND filter 1 is because the plastic film does not break like glass and the drawing device can be made thin. Lens L1
This is because the distance between the second lens group L2 and the second lens unit L2 can be reduced, and a higher magnification image can be obtained.

The plastic film is 100 μm
It can be made as thin as
It can be made as thin as 0 μm.

By the way, the N attached to the diaphragm blade 2
The D filter 1 has the plastic surface exposed. For this reason, when the aperture blade 2 opens and closes according to the brightness of the field of view, the ND filter 1 rubs against the other aperture blade 2 and the aperture base plate 3, and the ND filter surface is damaged. In recent years, as the sensitivity of the image sensor has been improved, there has been a problem that the resolution is reduced due to the scratch.

As a method for solving this problem, Japanese Patent Laid-Open No.
In JP-A-133253 and JP-A-10-133254, a plurality of inorganic hard films having two or more kinds of different refractive indices and at least one of which is a light absorbing film are formed on one or both surfaces of a plastic film by vapor deposition. It has been proposed to film.

In this case, the structure of the ND filter is as follows.
The structure shown in FIGS. 12 and 13 is employed. 20 shown in FIG.
Reference numerals −2, 20-3, and 21-2 illustrated in FIG. 13 are transmittance control films formed by vapor deposition on a plastic substrate (PET).

Further, 20-1 and 21-2 are regions where the plastic substrate remains as it is because the adhesion of the vapor deposition surface to the diaphragm blade is poor.

[0013]

However, FIG.
In the ND filter shown in (1), the surface of the PET substrate comes out on the optical path, and this portion has a reflectance of about 8%.

On the other hand, in the ND filter shown in FIG.
Since a transmittance control film is formed on the ET base material by vapor deposition and an antireflection film such as MgF2 can be provided as a final layer, it is possible to suppress reflection usually within 3%.

In order to reduce the reflection on both sides as described above,
The number of depositions is two. In this case, since a vacuum is once required to be brought to the atmospheric pressure for the production, and then the work of reversing the work is required, the work time is twice as long as the case of manufacturing the ND filter shown in FIG.

Further, with the recent improvement in the resolution of the CCD, the density of the transmittance control film tends to increase. In this case, the difference in transmittance between the ND filter and the air part becomes large, which causes inconveniences such as a reduction in resolution and a dark end portion of the screen. As a method for preventing this, a two-density ND filter is used as in Japanese Patent No. 275418.

In this ND filter, the transmittance on the boundary side with the air is increased so as to approach the air, and the transmittance decreases as the air enters the ND filter. In this case, the structure shown in FIG. 14 is adopted.

22-1 is PET for bonding to the diaphragm blade
This is the area where the base material is left. Also, 22-2 and 22-
3 is shifted by changing the evaporation mask, and the overlapping portion 22 is shifted.
-3 is the addition of the densities of 22-2 and 22-3, and the transmittance decreases, and the non-overlapping portion 22-4 has the density of 22-2. In this way, a two-density ND filter can be produced.

However, in this case, the transmittance control film is set to 2
Despite the multiple evaporation, the surface of 22-4 has P
The ET substrate is exposed, and the reflectance of this portion increases. In order to prevent this, it is necessary to further apply an anti-reflection film to this portion, and the number of depositions is three. As a result, the vapor deposition requires about 2 to 4 hours each time, so that the productivity and the defective rate deteriorate.

As described above, in the case of physical film formation, reflection and transmission can be easily controlled by attaching a laminate of various materials. Further, partial film formation can be performed by attaching a mask.

However, they have the following disadvantages. (1) The production time is long, the number of productions per production is small, and productivity and economic efficiency are poor. (2) Coating cannot be performed on a wide film with a large amount of degas because it is coated in a high vacuum. (3) The substrate may be exposed to a high temperature state during manufacture, and cannot be used with a substrate having low heat resistance. In addition, wrinkles due to heat shrinkage are generated even when having some heat resistance. (4) The utilization efficiency of the raw materials to be laminated is low, resulting in poor economic efficiency.

[0022]

In order to solve the above-mentioned problems, according to the present invention, an ND filter used for adjusting the amount of light is reflected on at least one of the front and back surfaces of a plastic substrate by a wet film forming method. It is manufactured by forming a protective film.

Specifically, for example, an antireflection paint dispersed or dissolved in an organic solvent is applied to one or both surfaces of a plastic substrate (film), or a monomer or oligomer of an organic resin is applied. And an anti-reflection film by curing and polymerizing with heat or ultraviolet rays.

In general, physical film formation is called dry coating, whereas the above film formation is called wet film formation or wet coating.

By forming a transmittance control film on the WET-coated antireflection film or on the opposite surface by vapor deposition or sputtering, it is possible to lower the reflectance on both surfaces of the plastic substrate. In addition, the number of times of vapor deposition (or sputtering) can be reduced by one, and the productivity and economy of the ND filter can be improved. In addition, it is also possible to reduce the thermal change of the filter by reducing the number of depositions.

Further, the antireflection film formed by the wet film forming method may be harder than the plastic substrate. This makes it possible to prevent the surface of the antireflection film or the plastic substrate from being damaged by the operation of the light amount adjusting device.

Further, the antireflection film formed by the wet film forming method may have an adhesive property equal to or higher than that of the plastic substrate. Thus, the ND filter can be easily adhered and fixed to the light shielding blades constituting the light amount adjusting device while being coated with the antireflection film.

A two-layer antireflection film is formed on at least one of the front surface and the back surface of the plastic substrate by a wet film forming method, and the antireflection film on the plastic substrate side among the two antireflection films is formed. May be made hard, and the anti-reflection film on the surface layer may be made to have easy adhesion.

The WET coat may be a knife coater, a bar coater, a blade coater, a squeeze coater, a reverse roll coater, a gravure roll coater, a curtain coater, a spray coater, a spin coater, or the like, depending on the state of the plastic substrate and the coating liquid. A coating machine such as a dip coater may be used.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of the present invention, N
The D filter will be described. When forming an anti-reflection film on a PET or PEN plastic film, it is effective to form the film based on optical theory.

When the antireflection film is formed of a single layer film, the optical film thickness (nf × d, nf × d
Is the refractive index of the single-layer antireflection film, and d is the mechanical film thickness) is λ
When / 4 (λ is the wavelength of light and the center value of human visible light of 550 nm is used for a camera or the like), there is a theoretical formula that is the lowest value.

The refractive index nf at this time is as follows: nf = √ (no × nk)

(However, no: refractive index of air = 1.0 nk: refractive index of plastic substrate In the case of PET, nk = 1.65 and nf is 1.284.) The same as this value If an anti-reflection film is formed, 550
Although the reflectivity at nm approaches zero, there is practically no such low index material.

For this reason, a material close to this is Mg
F ₂ (nf = 1.38) or SiO ₂ (nf = 1.46)
Is used. Since these cannot be wet coated as they are, in the case of MgF ₂ , the refractive index is reduced by using sodium fluoride magnesium sol or using an organic substance containing fluorine (for example, vinylidene fluoride). In addition, a wet coating is possible.

When SiO ₂ is used, the hydrolysis product of silicon alkoxide (hereinafter referred to as silica sol)
By doing so, it is possible to perform WET coating.

FIG. 9 shows a simulation value of the reflectance when an antireflection film having the same refractive index as MgF ₂ is formed. As can be seen from this figure, a reflectance of 1% or less is possible at a wavelength of 550 nm.

When the number of antireflection films is two or more, it is possible to more effectively reduce the reflectance over a wide wavelength range.

However, if the number of layers is too large, there is a problem of productivity. Therefore, two or three layers are preferable. This time, the case of two layers will be described.

The optical characteristics when forming two layers of antireflection films have been theoretically elucidated. An antireflection film having a refractive index higher than the refractive index of the plastic substrate and a material having a lower refractive index than the base material are used. Are stacked in order.

When the optical thickness of the high refractive index layer is λ / 2 and the optical thickness of the low refractive index layer is λ / 4 with respect to the design wavelength λ, the reflectance spectrum becomes W-shaped, and Very low reflectivity characteristics are obtained in the region. The optical film thickness is indicated by the product of the mechanical film thickness of the antireflection film and the refractive index.

When there is back surface reflection, it becomes quite difficult and deviates from the optimum thickness this time. Therefore, it is desirable to consider the refractive index of the opposite surface and the refractive index, thickness and absorption coefficient of the plastic substrate.

In the case of the WET coat, since it is impossible to perform a partial mask, if it is necessary to make the WET coat side an adhesive surface to the light-shielding blade, it is necessary to form an area where the plastic substrate is exposed. Can not.

In such a case, since the surface of the WET coat serves as an adhesive surface, the WET coat requires easy adhesion. In this case, the easy adhesion is desirably equal to or higher than that of the plastic substrate.

For this reason, when fluorine element is contained, such as MgF ₂ having a low refractive index, the adhesiveness is deteriorated, so that it is necessary to avoid it. On the other hand, alkoxides containing Si groups have excellent adhesion.

Further, it is also possible to give the antireflection film formed by wet-type film hardness. Since the plastic substrate used in the present embodiment is used as an optical component, high transparency (having a low haze value) is required, and it is important that there is no optical scattering.

When making such a PET substrate, it is difficult to mix inorganic particles and hard molecules. PET is very soft and easily damaged, and when the surface is damaged, optical scattering and refraction occur. Therefore, the anti-reflective coating is hard (for example, harder than a plastic substrate)
Is effective.

Although it is important to form a hard film in order to reduce damage, a certain thickness is required, and the thickness is preferably 3 μm or more. For this reason, as described above, the structure of the anti-reflection film is a two-layer coating, and the outermost layer is made thin (they can be made to have a low level of adhesion) so that the layer has a high adhesion. Is formed as a thick and hard layer (3 μm or more) so that each layer has a different role.

It is possible to reduce the reflection characteristics based on the refractive index and the absorption coefficient of the two types of layers and the refractive index and the absorption coefficient of the plastic substrate, and to select an optimum film thickness having both easy adhesion and hardness. is important.

Here, as the antireflection film having a high refractive index and a high hardness, it is preferable to use an acrylic oligomer or a material obtained by mixing a radical polymerization type ultraviolet curable resin with an acrylic monomer and cured by ultraviolet rays. Further, inorganic titanium alkoxide or zirconium alkoxide may be used. Furthermore, it is also possible to mix these two types.

Each of them is used by dissolving it in an organic solvent. As the organic solvent, hydrocarbon type, alcohol type, ketone type and the like are used.

The case where a highly transparent plastic substrate is used has been described above, but the plastic substrate in the present invention is not limited thereto.

As a commercially available product, a kneading type ND filter is sold by Fuji Film Co., Ltd. This is an ND filter obtained by mixing a light-absorbing dye into a TAC (cellulose triacetate) base material. .

A graph 15-1 shown in FIG. 15 is obtained by measuring the reflectance of the ND filter (density 1.0) manufactured by Fuji Film Co., Ltd.

The reflectivity is about 5%, and the substrate is soft and easily damaged. Since the refractive index is 1.50 and the substrate is different from PET (refractive index 1.65), it is necessary to design a two-layer antireflection film different from the above-mentioned one.

(Embodiment 1) FIGS. 1 and 2 show the structure of an ND filter as Embodiment 1 of the present invention. In this figure, reference numeral 8-3 denotes a plastic substrate, and transparent PE
T is used. The haze value of the plastic substrate 8-3 is 0.5, and a material having a high total transmittance is used. The transmittance of the plastic substrate 8-3 is 90%.
As described above, the reflectance is about 8%.

Reference numeral 8-2 denotes a portion where a multilayer film (9-3 to 9-9 in FIG. 2) including a transmittance control film attached to one surface of the plastic substrate 8-3 by vapor deposition is formed. In the embodiment, the transmittance is 10% at a wavelength of 400 nm to 700 nm.
It is set to be. The reflectance was set to 3% or less.

Reference numeral 8-4 denotes a two-layer antireflection film (9-4, 9-2) formed by wet film formation, and the reflectance was set to 4% or less.

Reference numeral 8-1 denotes a portion to be adhered to the light-shielding blade, which remains as a PET substrate.

It should be noted that there is no problem even if the bonding portion is the portion 8-4 'on the back side because the adhesiveness on the surface layer side of the two-layer antireflection film 8-4 is high.

Hereinafter, a method of manufacturing the ND filter will be described in detail. As for the used PET, a raw material is manufactured by the method shown in FIG.

In FIG. 3, after the PET in the dissolved state is cast, it is subjected to longitudinal stretching and transverse stretching to form a film-like substrate having a predetermined thickness (for example, 75 μm).

Then, two layers of an antireflection film are applied to the whole surface of one side of the PET substrate by two doctor blades.

As the hard coat (hardness) antireflection paint of the first layer directly applied to the PET base material, a UV-curable polyether acrylate as a main component and a viscosity adjusted with an alcohol-based solvent are used. . This first layer hard coat anti-reflection coating is applied to a thickness of 5 μm, and then cured by irradiation with ultraviolet rays. The refractive index of the first layer is 1.56.

Then, on the first layer, an SiO ₂ colloid having a low refractive index and easy adhesion having a diameter of about 10 nm and a silicon alkoxide suspended in a propanol solvent were added to form 8.
8 nm was applied, heated at 120 ° C. and hydrolyzed with moisture in the air to form a low refractive index layer as a second layer. The refractive index of the second layer is 1.45.

In this case, the surface reflectance was 4% or less as shown in a graph 10-1 in FIG. In addition, waviness is generated due to light interference, but is suppressed to such an extent that there is no problem in human visual perception.

After coating the anti-reflection film in this way, slitting is performed to a required width. After that, press blanking is performed to attach to the vapor deposition jig on the back surface. In this embodiment,
Press punching was performed on a 150 mm square.

FIG. 2 shows a film configuration of the ND filter of this embodiment. 9-1 and 9-2 are antireflection films formed by wet film formation. Reference numerals 9-3 to 9-9 denote transmittance control films with an antireflection film formed by vapor deposition.

Reference numeral 9-9 denotes an antireflection film, which comprises MgF ₂ ,
It is formed by vapor deposition so as to have a thickness of 550 nm of λ / 4.

9-3, 9-5 and 9-7 are Al ₂ O ₃ films having a refractive index of 1.67. 9-4, 9-6,
Reference numeral 9-8 denotes a TiO film having a refractive index of 1.71. This TiO film has an absorption coefficient, which lowers the transmittance.

[0070] Although decreases reflectivity by superposing thus different refractive indexes film alternately, MgF ₂ on the outermost layer film
When the mark is added, the reflectance is further reduced to 3% or less.

At this time, of the transmittance control films 9-3 to 9-8, the first layer Al ₂ O ₃ film 9-3 and the second layer TiO film 9
The film thickness of −4 needs to be selected in consideration of the back surface reflection. The thicknesses of the two types of films formed by the above-mentioned wet film formation method were obtained by performing vapor deposition on the back surface in advance and considering the back surface reflection and conducting experiments.

The ND filter manufactured as described above is
As shown in FIG. 10, it is adhered to a light shielding blade (aperture blade). The adhesive surface is the side of the wet-formed antireflection film.

Chloroprene rubber is used as the adhesive. In this case, the adhesive strength of the second layer by wet film formation is P
It showed the same strength as when the ET substrate was directly adhered.

The ND filter of this embodiment is as follows. An opening / closing test was performed 100,000 times in a state where the ND filter was incorporated in the iris device, but no scratch was generated on the surface of the ND filter.

The graph 10-2 shown in FIG.
The transmittance of the D filter is shown (10%), and graph 10-3 is shown.
Indicates the reflectance.

The structure of the transmittance control film is not limited to the combination example described above, but may be TiO / SiO ₂ , Fe-
A film having a different refractive index such as Cr / SiO ₂ and having an absorption coefficient in one film may have another configuration. Further, the antireflection film formed by vapor deposition may be made of not only MgF ₂ but also SiO ₂ .

(Embodiment 2) FIG. 5 shows Embodiment 2 of the present invention.
The configuration of the ND filter is as follows. This ND filter is a two-density type ND filter.

12-1 is PET which is a plastic substrate
It is a substrate and has a thickness of 75 μm. Reference numeral 12-2 denotes an antireflection film formed by a wet method. 12-3, 12
Reference numeral -4 denotes a transmittance control film with an antireflection film formed by vapor deposition.

In this ND filter, regarding the backside reflection, there are a portion where the transmittance control film is provided and a portion where only the antireflection film formed by the wet process is formed. Therefore, the thickness of the deposited film should be determined in consideration of both. .

In this case, the transmittance control film 12-3 (Ti
In the portion where the O film is on the back surface, the amount of light reflected on the back surface is attenuated again by the transmittance control film, so that it is not necessary to consider much. For this reason, the film thickness should be determined by giving priority to a portion having no transmittance control film on the back surface. See Example 1 for details.
Almost the same composition was used.

(Embodiment 3) FIG. 6 shows Embodiment 3 of the present invention.
This ND filter is a commercially available TAC substrate manufactured by Fuji Film and has a thickness of 1%.
It is configured by using one having a thickness of 00 μm and a transmittance of 10%.

Reference numeral 13-1 denotes a TAC substrate having a refractive index of 1.50. Hard wet-processed antireflection film 13
Nos. -2 and 13-3 have a first layer of 5000 nm of a polyether acrylate having the same composition as in Example 1, and a second layer of the same mixture of SiO ₂ colloid and silicon alkoxide as in Example 1 having a thickness of 90 nm by a wet method. It is what was made to adhere with.

In this example, since the front and back surfaces have the same film thickness, the antireflection agent was applied to a commercially available four-piece ND filter by using a dip method.

As a result, the reflectance was changed to the value shown in graph 14 of FIG.
As in the case of -1, the reflectivity was significantly reduced as compared with the reflectance shown in FIG. In addition, the anti-scratch property of the surface could be improved.

(Embodiment 4) FIG. 8 shows Embodiment 4 of the present invention.
Is shown. The ND filter is capable of moving back and forth on the optical path by driving separately from the aperture blade, and is used for an aperture unit for a digital camera.

15-1 is a PET base material having a thickness of 100 μm
Of thickness. This ND filter first has 15
Base material 15-1 coated with two layers by wet film formation of -2
Is punched into a shape shown in FIG. 8, and thereafter, a transmittance control film of 15-3 (transmittance 30%, reflectance 3%) is formed on one side by vapor deposition.
Was formed.

Further, the PET base material 15-1 is inverted and
15-4 transmittance control film (transmittance 30% <transmittance 10% together with the transmittance control film 15-3 on the back surface>), reflectance 3
%) Was deposited. As a result, a two-density ND filter that is driven separately from the diaphragm blades is obtained. The thickness and the film configuration may be determined according to the first embodiment.

The configuration, film thickness, film composition, and the like of the ND filter described in each of the above embodiments are merely examples, and any other configuration may be used as long as the configuration requirements of the present invention are satisfied.

[0089]

As described above, according to the present invention,
Since the anti-reflection film is formed on at least one of the front surface and the back surface of the plastic substrate by a wet film formation method, the reflectance of both surfaces of the plastic substrate can be reduced, and the transmittance can be reduced by vapor deposition (or sputtering). Even when the control film is formed, a smaller number of vapor depositions is sufficient as compared with the case where the antireflection film is formed by vapor deposition. Therefore, N
The productivity and economy of the D filter can be improved. In addition, by reducing the number of depositions, the thermal change of the filter can be reduced.

Further, by providing the anti-reflection film formed by the wet film forming method with rigidity, it is possible to prevent the surface of the anti-reflection film and the plastic substrate from being damaged by the operation of the light amount adjusting device. it can.

Furthermore, if the anti-reflection film formed by the wet film forming method is made to have easy adhesion, it is possible to easily coat the ND filter with the anti-reflection film and easily apply the light to the light shielding blades constituting the light amount adjusting device. Can be adhesively fixed.

Incidentally, at least one of the front surface and the back surface of the plastic substrate, a two-layer anti-reflection film is formed by a wet film forming method, and the anti-reflection film on the plastic substrate side of the two-layer anti-reflection film is formed. If the anti-reflection film on the surface layer is made to have easy adhesion, the surface of the anti-reflection film and the plastic substrate can be easily adhered to the light-shielding blades. Nature can be secured.

Further, there are the following effects.

(1) The wet film forming method is a continuous film forming method and can be applied to a wide range, and can be performed continuously with the production of a plastic substrate. Productivity can be greatly improved.

(2) Since the curing after the wet film formation can be performed by ultraviolet curing or the like or low thermal curing, deformation of the ND filter due to heat can be almost eliminated.

(3) In the wet film formation, the surface has easy adhesion, and the film under the film is hard, so that the film is not damaged in the post-process and the product function. Further, since there is no need to provide a portion that is specially bonded to the blade, the ND filter can be densely pressed.

(4) By forming an anti-reflection film by wet film formation on the front surface and a transmittance control film by physical film formation on the back surface, the transmittance control film having a required transmittance can be freely formed on the physical film formation side. Can be made.

(5) An anti-reflection film can be applied not only to a transparent plastic substrate but also to a substrate having a concentration.

(6) Since multilayer film formation is possible by wet film formation, the reflectance can be optimized and another function separation film can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an ND filter according to a first embodiment of the present invention.

FIG. 2 is a film configuration diagram of an ND filter according to the first embodiment.

FIG. 3 is a view showing a wet film forming process of the ND filter of the first embodiment.

FIG. 4 is a spectral characteristic diagram showing a transmittance and a reflectance of the ND filter of the first embodiment.

FIG. 5 is a configuration diagram of an ND filter that is Embodiment 2 of the present invention.

FIG. 6 is a configuration diagram of an ND filter according to a third embodiment of the present invention.

FIG. 7 is a spectral characteristic diagram showing a reflectance of the ND filter of the third embodiment.

FIG. 8 is a configuration diagram of an ND filter according to a fourth embodiment of the present invention.

FIG. 9 is a spectral characteristic diagram showing a simulation result of the reflectance in the ND filter of the present invention.

FIG. 10 is a perspective view of an aperture blade.

FIG. 11 is a configuration diagram of a photographing optical system having an aperture device.

FIG. 12 is a configuration diagram of a conventional ND filter.

FIG. 13 is a configuration diagram of a conventional ND filter.

FIG. 14 is a configuration diagram of a conventional ND filter.

FIG. 15 is a spectral characteristic diagram showing the reflectance of a conventional ND filter.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ND filter 2 Aperture blade 8-2, 12-3, 15-3, 15-4 Transmittance control film 8-3, 12-1, 13-1, 15-1 Plastic substrate 8- 4,12-2,13-2,13-3,15-2 Two-layer antireflection film formed by wet film formation

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 5/238 G02B 1/10 Z F Term (Reference) 2H002 CC21 HA03 JA07 2H042 AA02 AA08 AA22 2H080 AA20 AA31 2K009 AA05 BB24 BB28 CC03 CC06 CC09 CC24 CC26 CC34 DD02 DD03 EE00 5C022 AA00 AB14 AC55

Claims (23)

[Claims] 1. An ND filter used for adjusting the amount of light, wherein the ND filter has an antireflection film formed by a wet film forming method on at least one of a front surface and a back surface of a plastic substrate. 2. A method according to claim 1, wherein the surface and the back surface of the plastic substrate are formed on the anti-reflection film formed by a wet film forming method or on a surface opposite to the surface on which the anti-reflection film is formed by vapor deposition or sputtering. The ND filter according to claim 1, wherein a transmittance control film is formed. 3. The ND filter according to claim 2, wherein an anti-reflection film is formed on the transmittance control film by vapor deposition or sputtering. 4. The ND filter according to claim 1, wherein the anti-reflection film formed by the wet film forming method has a higher rigidity than the plastic substrate. 5. The ND according to claim 1, wherein the anti-reflection film formed by the wet film forming method has an adhesion property equal to or higher than that of the plastic substrate. filter. 6. The plastic substrate according to claim 1, wherein two or more antireflection films are formed on at least one of a front surface and a rear surface of the plastic substrate by a wet film forming method. ND filter. 7. The two-layer anti-reflection film, wherein the anti-reflection film on the plastic substrate side is harder than the plastic substrate, and the anti-reflection film on the surface layer is equal to or smaller than the plastic substrate. 7. The ND filter according to claim 6, wherein the ND filter has a higher adhesive property. 8. The plastic substrate is made of PET or P
The ND filter according to claim 1, wherein the ND filter is formed of a transparent material of EN. 9. The ND filter according to claim 1, wherein the plastic substrate contains a light-absorbing organic dye or pigment. 10. The N according to claim 1, wherein
A light amount adjusting device, wherein a D filter is attached to a light shielding blade that adjusts an amount of light by changing an opening diameter by an opening and closing operation. 11. A photographing apparatus comprising the light amount adjusting device according to claim 10. 12. A method for manufacturing an ND filter used for adjusting the amount of light, wherein an antireflection paint is formed on at least one of a front surface and a back surface of a plastic substrate by a wet film forming method. Manufacturing method. 13. The method for manufacturing an ND filter according to claim 12, wherein an antireflection agent is applied to at least one of the front surface and the back surface of the plastic substrate to form an antireflection film. 14. The ND filter according to claim 12, wherein an anti-reflection film is formed by applying an organic resin monomer or oligomer to at least one of the front surface and the back surface of the plastic substrate. Production method. 15. An evaporation or sputtering method on the surface or the back surface of the plastic substrate on the antireflection film formed by the wet film formation method or on the surface opposite to the surface on which the antireflection film is formed. The ND according to any one of claims 12 to 14, wherein a transmittance control film is formed.
Manufacturing method of filter. 16. The method according to claim 15, wherein an anti-reflection film is formed on the transmittance control film by vapor deposition or sputtering. 17. The N film according to claim 12, wherein an antireflection film having a hardness higher than that of the plastic substrate is formed by the wet film forming method.
A method for manufacturing a D filter. 18. An anti-reflection film having an adhesion property equal to or higher than that of the plastic base material is formed by the wet film forming method.
The method for manufacturing an ND filter according to any one of the above. 19. The method according to claim 12, wherein two antireflection films are formed on at least one of the front surface and the back surface of the plastic substrate by a wet film forming method.
5. The method for manufacturing an ND filter according to any one of 4. 20. The anti-reflection film on the plastic substrate side of the two-layer anti-reflection film is harder than the plastic substrate, and the anti-reflection film on the surface layer is equal to or smaller than the plastic substrate. 20. The method for manufacturing an ND filter according to claim 19, wherein the ND filter has higher adhesiveness. 21. The method for manufacturing an ND filter according to claim 12, wherein the plastic substrate is formed of a transparent material such as PET or PEN. 22. The method for producing an ND filter according to claim 12, wherein a light-absorbing organic dye or pigment is contained in the plastic substrate. 23. Use of one or more of a doctor knife, a bar coater, a gravure roll coater, a curtain coater, a knife coater, a dip coater and a roll coater for wet coating of the antireflection film. The method of manufacturing an ND filter according to claim 12, wherein: