JP2018116177A - Optical member and imaging device - Google Patents

Abstract

An optical member having desired antireflection properties and hydrophilicity and high surface strength is provided. An optical member having a porous layer on a substrate, the porous layer having silica particles having an average particle diameter of not less than 10 nm and not more than 80 nm and a binder. In the thickness direction, the two-dimensional packing degree of the silica particles 11 on the half of the base layer 14 side of the porous layer 10 is not less than 0.75 and not more than 0.88, and the silica particles 11 on the surface side half of the porous layer 14 An optical member having a two-dimensional filling degree of 1.02 to 1.40 times. [Selection] Figure 1

Description

  The present invention relates to an imaging device such as an optical member and a monitoring camera.

Currently, surveillance cameras are used for various purposes such as crime prevention in stores, hotels, banks, and stations. The surveillance camera is attached to the ceiling via installation parts or embedded in the ceiling. A camera cover is attached to the surveillance camera body for the purpose of protection from various environments. The camera cover is made of a resin material such as polycarbonate or acrylic from the viewpoint of transparency and impact resistance. Surveillance cameras are often installed outdoors, and in rainy weather, water drops adhere to the camera cover in a spherical shape and adversely affect the captured image. For this reason, a technique is known in which a hydrophilic film is formed on the surface of the camera cover, and the water droplet is turned into a liquid film even when the water droplet adheres, thereby reducing the adverse effect on the photographed image in rainy weather. In some cases, an antireflection film is formed on the surface of the camera cover in order to prevent reflection of the camera's own image on the surveillance camera cover and to prevent occurrence of ghost and flare. Therefore, a hydrophilic film having antireflection performance is preferable as the coating film on the surface of the camera cover for outdoor use.
Patent Document 1 describes an antifogging and antifouling agent that is made of silica and exhibits antireflection properties and is hydrophilic. By using the antifogging and antifouling agent of Patent Document 1 for a camera cover, desired antireflection properties and hydrophilicity can be expressed.

Japanese Patent No. 5804996

However, the hydrophilic film having antireflection performance formed by the antifogging and antifouling agent of Patent Document 1 has a problem that the film strength is insufficient.
The present invention has been made in view of the above problems of the prior art, and provides an optical member having desired antireflection properties and hydrophilicity and high surface strength.

  The optical member of the present invention is an optical member having a porous layer on a substrate, the porous layer having silica particles having an average particle diameter of 10 nm to 80 nm and a binder, In the thickness direction, the two-dimensional packing degree of the silica particles in the substrate-side half of the porous layer is 0.75 or more and 0.88 or less, and 2 of the silica particles in the surface-side half of the porous layer. It is characterized by being 1.02 times or more and 1.40 times or less of the dimension filling degree.

  According to the present invention, it is possible to provide an optical member having desired antireflection properties and hydrophilicity and high surface strength.

It is a schematic diagram which shows the cross section of the thickness direction of one Embodiment of the optical member of this invention. It is a mimetic diagram showing one embodiment of an imaging device of the present invention. 2 is a scanning transmission electron micrograph of a cross section in the thickness direction of the optical member of Example 1. FIG.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

≪Optical member≫
FIG. 1 is a schematic diagram showing a cross section in the thickness direction (direction parallel to the normal of the substrate surface) of one embodiment of the optical member of the present invention. In the figure, the optical member of the present invention has a porous layer 10 on a substrate 14, and the porous layer 10 has silica particles 11 and a binder 12. In FIG. 1, the porous layer 10 has a plurality of silica particles 11 stacked on the surface of the base material 14, and a binder 12 is filled between the silica particles 11. The silica particles 11 are bonded by a binder 12, and a plurality of voids 13 are formed in a portion made of the binder 12.

<Porous layer 10>
In the thickness direction of the porous layer 10, the two-dimensional filling degree of the silica particles 11 in the base-side half of the porous layer 10 (hereinafter sometimes referred to as “lower layer”) is 0.75 or more and 0.88 or less. It is.

  Here, the two-dimensional filling degree of the silica particles 11 is an area ratio with respect to the entire surface of the silica particles 11 in an arbitrary surface. This area ratio can be measured by image processing obtained by observing a cross section in the thickness direction of the porous layer 10 with a scanning transmission electron microscope. As the image processing method, commercially available image processing such as image Pro PLUS (manufactured by Media Cybernetics) can be used. In a predetermined image region, if necessary, contrast adjustment is performed as appropriate, the particle area is measured by particle measurement, and a ratio to the area of the predetermined image region can be calculated and obtained.

  The two-dimensional filling degree indicates the arrangement state of the particles. The larger the filling degree, the more the particles are arranged. As a result, the gap between the particles becomes smaller. When the particles are true spheres and are arranged most closely, the hexagonal packing arrangement is obtained, and the two-dimensional packing degree is about 0.90. When the two-dimensional filling degree is lowered, the gaps between the particles are increased, so that the gaps 13 are increased. Therefore, when the two-dimensional filling degree is less than 0.75, a large gap 13 is generated and the film strength is lowered. Moreover, although it is preferable that the particle arrangement is high, it is substantially difficult to produce a film having a secondary packing degree higher than 0.88.

  The two-dimensional filling degree of the silica particles 11 in the lower layer of the porous layer 10 is 1 of the two-dimensional filling degree of the silica particles 11 in the surface side half of the porous layer 10 (hereinafter sometimes referred to as “upper layer”). 0.02 times to 1.40 times, preferably 1.20 times to 1.40 times. Within this range, the film strength as the porous layer 10 is improved by forming a high-filling layer in which the silica particles 11 are densely arranged in the lower layer of the porous layer 10. Further, by forming a sparsely arranged low-filling layer containing many voids 13 in the upper layer of the porous layer 10, the refractive index of the upper layer of the porous layer 10 can be lowered. Therefore, the antireflection performance superior to the porous layer 10 in which the silica particles 11 are uniformly arranged in the lower layer and the upper layer can be expressed.

  The film thickness of the porous layer 10 is preferably 20 nm or more and 300 nm or less. If the film thickness is 20 nm or more, the film strength is sufficient, and if it is 300 nm or less, low reflectance in the visible light region can be sufficiently realized.

[Silica particles 11]
The silica particles 11 have an average particle diameter of 10 nm to 80 nm, preferably 10 nm to 60 nm. When the average particle diameter of the silica particles 11 is less than 10 nm, the particles are densely arranged and it is difficult to lower the refractive index, and the antireflection performance of the film cannot be sufficiently exhibited. On the other hand, when the average particle diameter of the silica particles 11 exceeds 80 nm, the gaps 13 between the particles become large, and the film strength is not sufficient. The variation coefficient (standard deviation / average particle diameter) of the average particle diameter of the silica particles 11 is preferably 20% or less.

  Here, the average particle diameter of the silica particles 11 is an average ferret diameter. This average ferret diameter can be measured by image processing of an observation image observed with a transmission electron microscope image. As the image processing method, commercially available image processing such as image Pro PLUS (manufactured by Media Cybernetics) can be used. In a predetermined image area, if necessary, the contrast is adjusted appropriately, the average ferret diameter of each particle is measured by particle measurement, and the average value can be calculated and obtained.

The silica particles 11 are preferably solid silica particles from the viewpoint of particle hardness and refractive index, but may be hollow silica particles or solid chain particles in which solid silica particles are connected in a chain, You may mix and use these. Incidentally, the porous layer 10, in addition to the silica particles 11, MgF _2, fluorine, particles of a metal oxide or an organic resin such as silicone, preferably may contain solid particles.

[Binder 12]
A plurality of voids 13 are contained inside the binder 12 of the porous layer 10. The void 13 is contained inside the binder 12 when the portion made of the binder 12 has the void 13, and the portion made of the binder 12 has the void 13, thereby refraction of the porous layer 10. The rate can be lowered.

  The content of the voids 13 contained in the binder 12 under the porous layer 10 is preferably 5% by volume to 15% by volume, and more preferably 5% by volume to 10% by volume. Further, the content of the voids 13 contained in the upper binder 12 of the porous layer 10 is preferably 10% by volume to 25% by volume, and more preferably 15% by volume to 25% by volume. Here, “volume%” is the ratio (volume ratio) of the volume of the entire void to the volume of each layer. By controlling the voids contained in the binder within the above range, it is possible to achieve both desired film strength and low reflectance.

  The binder 12 can be appropriately selected depending on the abrasion resistance, adhesion, and environmental reliability of the film, but a silane alkoxy hydrolysis condensate such as ethyl orthotetrasilicate (TEOS) and a silane coupling agent are preferable. .

<Substrate 14>
As the base material 14, a resin such as an acrylic resin, a polycarbonate resin, or a polyester resin, glass, or the like can be used. The shape of the base material 14 is not limited, and may be a plate shape or a film shape, and may be a flat plate shape or a shape having a curved surface, a concave surface or a convex surface, for example, a hemispherical dome. It may be a shape or the like.

<Manufacturing method>
Next, an example of the method for producing an optical member according to the present invention will be described.

  The porous layer 10 is coated with a dispersion liquid containing silica particles 11, a binder 12, and a dispersion medium (hereinafter sometimes referred to as "silica particle / binder-containing coating liquid") and dried. Can be formed. Further, after coating a dispersion liquid containing silica particles 11 and a dispersion medium (hereinafter referred to as “silica particle-containing coating liquid”), a coating liquid containing binder 12 (hereinafter referred to as “binder”). It may be formed by coating and drying.

  At that time, after coating a coating liquid containing a primer material for binding the base material 14 and the silica particles 11 on the base material 14 (hereinafter sometimes referred to as “primer-containing coating liquid”), It is preferable to form the porous layer 10 from above. By doing so, since the two-dimensional filling degree of the interface part of the base material 14 is improved, the two-dimensional filling degree of the lower layer is improved. A silane coupling agent is mentioned as a primer material. When selecting the silane coupling agent, it is preferable to select a material that binds the base material 14 and the silica particles 11 and does not alter the binder 12.

  As another method, it may be formed by applying the silica particle / binder-containing coating solution or the silica particle-containing coating solution a plurality of times to improve the binder concentration in the lower layer region. As a method for improving the binder concentration in the lower layer region, the binder concentration may be increased in the coating liquid for forming the lower layer region. Moreover, after forming the area | region used as a lower layer, you may improve the binder density | concentration of the area | region used as a lower layer by coating a binder containing coating liquid from the top.

  The concentration of the silica particles contained in the silica particle / binder-containing coating solution or the silica particle-containing coating solution is desirably low within a range where a desired film thickness can be formed. When the solid content concentration is increased, the viscosity is increased, so that the arrangement of the particles is deteriorated and the dispersed state is deteriorated, so that it is difficult to form uniform voids inside. Therefore, it is desirable to form a film under conditions that allow film formation with a lower solid content concentration.

  In addition, the binder concentration of the binder-containing coating solution may be formed at a concentration that provides a desired content with respect to the formed film, and the concentration can be appropriately selected depending on the solvent and the film forming conditions.

  As a dispersion medium or a solvent used for the coating liquid, one having a good affinity with silica particles or a binder can be appropriately selected. If the affinity with the silica particles is low, aggregation may occur. Further, if the affinity with the binder is low, the binder may not be compatible. Even if the coating liquid is well dispersed or compatible, it may cause aggregation or separation during film formation, resulting in a whitening phenomenon. As the dispersion medium or solvent, those having a boiling point of 100 ° C. or higher and 200 ° C. or lower are preferably used. For example, 1-methoxy-2-propanol, 2-ethyl-1-butanol, methyl cellosolve, ethyl cellosolve, butyl cellosolve, or the like or a mixture thereof can be used.

  As the coating method, there is no particular limitation on the paint containing particles and a solvent. However, when it is necessary to apply the silica particle / binder-containing coating solution or the silica particle-containing coating solution a plurality of times, the dipping method such as dip coating may cause loss of particles attached to the substrate. Therefore, it is not preferable. Other than that, there is no particular limitation, and a general coating method of a liquid coating solution such as a spin coating method or a spray coating method can be used. From the viewpoint of missing particles and the ability to form a uniform film thickness on a curved substrate, the coating is preferably formed by spin coating.

  Dry after coating. For drying, a dryer, a hot plate, an electric furnace or the like can be used. The drying conditions are a temperature and a time that do not affect the base material 14 and can evaporate the organic solvent in the porous layer 10. In general, it is preferable to use a temperature of 300 ° C. or lower. When the substrate 14 is a resin, it is preferable to use a temperature of 120 ° C. or lower.

≪Imaging device≫
2A and 2B are schematic diagrams showing an embodiment of the imaging apparatus of the present invention. FIG. 2A is a fixed point observation type surveillance camera, and FIG. 2B is a swivel type capable of pan / tilt / zoom drive. Is a surveillance camera. 2 includes an apparatus main body 1 and a protective cover 2, and the apparatus main body 1 includes an optical system that acquires video data. Further, the protective cover 2 covers at least the optical system of the apparatus main body 1 and protects against dust and impact from the outside. The protective cover 2 in FIG. 2A is a planar box shape, and the protective cover 2 in FIG. 2B is a hemispherical dome shape, but the shape of the protective cover is not limited thereto.

  The imaging apparatus of the present invention constitutes an imaging system together with, for example, a controller for controlling the imaging apparatus and video data, a data storage unit that stores the acquired video data, and a transfer unit that transfers the acquired data to the outside. can do. Here, the controller controls, for example, imaging of the imaging apparatus, pan / tilt for adjusting the angle of view, imaging conditions, and the like. The transfer means can transfer data in and out by connecting to an external network.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist. Items common to the embodiments are as follows.

1. Manufacturing process (1) Process 1
On the substrate, 0.3 ml of the primer-containing coating solution is dropped, and a film is formed using a spin coater under conditions of 1500 rpm and 30 seconds. The formed substrate is heated at 90 ° C. for 10 minutes. The sample is then removed from the oven and returned to room temperature (25 ° C.).
(2) Step 2
0.3 ml of a silica particle / binder-containing coating solution is dropped, and a film is formed using a spin coater under conditions of 1500 rpm and 30 seconds.
(3) Process 3
0.3 ml of a binder-containing coating solution is dropped, and a film is formed using a spin coater under conditions of 1500 rpm and 30 seconds.

2. Material (1) Preparation of primer-containing coating solution 3- (2-aminoethyl) aminopropyltrimethoxysilane (Z-6094 manufactured by Toray Dow Corning Co., Ltd.), which is an amino silane, was added to 1-methoxy-2. -Diluted with 100 g of propanol (special grade manufactured by Kanto Chemical). This adjusted the primer containing coating liquid (solid content concentration 0.1 wt%).
(2) Substrate A polycarbonate substrate having a diameter of 40 mm and a thickness of 2 mm was used.

3. Evaluation method (1) Film thickness of porous layer, average particle diameter of silica particles, and two-dimensional filling degree The porous layer was cut out by a focused ion beam apparatus (SMI3050 manufactured by SII Nanotechnology) in the cross-sectional direction of the substrate. The cross-sectional state was observed through a bright field with a scanning transmission electron microscope (S-5500, manufactured by Hitachi High-Technology Co., Ltd.) with a field of magnification of 50000 times. The voids were observed with white highlighting, and the transmission photographed image was subjected to particle measurement using image Pro PLUS (manufactured by Media Cybernetics) to measure the average particle diameter. For the two-dimensional filling degree of the upper layer and the lower layer, the area of the particle part was obtained by particle measurement for an arbitrary region, and the area ratio of the particle part to the evaluation area was obtained.

(2) Hydrophilicity As the hydrophilicity evaluation, the contact angle of water is evaluated. For the contact angle evaluation of water, a contact angle measuring device (DM-701, manufactured by Kyowa Interface Science Co., Ltd.) was used. As a method for evaluating the contact angle, the contact angle was determined using the θ / 2 method.

(3) Pencil hardness This is a test according to the pencil hardness test specified in JIS K5600-5-4 (1999). Using a pencil hardness tester, a pencil of various hardnesses is pressed against the surface of the porous layer of the optical member with a load of 750 g, and the surface is scratched with a pencil by moving the pencil hardness tester about 5 cm in this state. The scratched part was observed visually or with an optical microscope to confirm the presence or absence of scratches on the porous layer surface. If a flaw is found, record one of the lower hardness values. If no scratch is confirmed, the same test is performed with a pencil having one hardness, and the test is repeated until the pencil hardness is confirmed.

(4) Solvent wipe test After impregnating cotton cloth (Clint manufactured by Asahi Kasei Chemicals Corporation) with ethanol (special grade manufactured by Kanto Chemical), applying a load of 200 g / cm ² and reciprocating the porous layer surface of the optical member 10 times. The presence or absence of film peeling was confirmed visually or with an optical microscope.

(5) Reflectance Using a lens reflectometer (USPM-RU, manufactured by Olympus Corporation), the reflectance from a wavelength of 400 nm to 700 nm was measured, and the reflectance value at the wavelength having the lowest reflectance was obtained.

<Example 1>
(1) Preparation of silica particle / binder-containing coating solution A solid silica slurry dispersion (EXCEL PURE, manufactured by Chuo Automobile Co., Ltd.) was used. This liquid contains ethyl orthotetrasilicate (TEOS) which is a silane alkoxy hydrolysis condensate as a binder.

(2) Manufacture of optical member After performing each process in order of the process 1 and the process 2, it preserve | saved at room temperature for 24 hours, the film | membrane was formed, and the optical member was obtained. The evaluation results are shown in Table 1. Further, a scanning transmission electron micrograph showing a cross section in the thickness direction is shown in FIG.

<Comparative Example 1>
An optical member was obtained in the same manner as in Example 1 except that Step 1 was not performed. The evaluation results are shown in Table 1.

<Examples 2 to 4, Comparative Example 2>
(1) Preparation of silica particle / binder-containing coating solution [Examples 2 and 4]
50 g of the same solid silica slurry dispersion as in Example 1 was diluted with 50 g of 1-methoxy-2-propanol.

[Example 3]
50 g of the same solid silica slurry dispersion as in Example 1 was diluted with 100 g of 1-methoxy-2-propanol.

[Comparative Example 2]
50 g of the same solid silica slurry dispersion as in Example 1 was diluted with 150 g of 1-methoxy-2-propanol.

(2) Adjustment of binder-containing coating solution [Examples 2 and 3, Comparative Example 2]
A 0.1 wt% solution of 1-methoxy-2-propanol of 3- (2-aminoethyl) aminopropyltrimethoxysilane, which is an amino silane, was prepared in the same manner as the primer-containing coating solution.

[Example 4]
Silane alkoxy hydrolysis-condensation product (Acnegrass T-11 (111) manufactured by Honeywell) (1.5 g) was diluted with 29.5 g of 2-n-butoxyethanol (special grade manufactured by Kishida Chemical).

(3) Production of optical member [Examples 2 and 4]
After performing each process in order of the process 1, the process 2, the process 3, and the process 2, it preserve | saved at room temperature for 24 hours, the film | membrane was formed, and the optical member was obtained. The evaluation results are shown in Table 1.

[Example 3]
Each step was performed in the order of step 1, step 2, step 3, step 2, step 3, and step 2, and then stored at room temperature for 24 hours to form a film to obtain an optical member. The evaluation results are shown in Table 1.

[Comparative Example 2]
After performing each step in the order of step 1, step 2, step 3, step 2, step 3, step 2, step 3, and step 2, store at room temperature for 24 hours to form a film to obtain an optical member It was. The evaluation results are shown in Table 1.

<Example 5, Comparative Examples 3-4>
(1) Preparation of silica particle / binder-containing coating solution [Example 5]
To 16 g of water, 1.4 g of ethanol (manufactured by Wako Pure Chemical Industries), 0.01 g of 2N hydrochloric acid and 0.1 g of tetraethyl orthosilicate (TEOS) (manufactured by Wako Pure Chemical Industries) were sequentially added to obtain a TEOS solution.

  To 18 g of solid silica slurry aqueous dispersion (Snowtex ST-0YL, manufactured by Nissan Chemical Industries, Ltd.) It was adjusted.

[Comparative Example 3]
A solid silica slurry aqueous dispersion was prepared in the same manner as in Example 5 except that 36 g of a solid silica slurry aqueous dispersion (Snowtex ST-OXS manufactured by Nissan Chemical Industries, Ltd.) was used.

[Comparative Example 4]
A solid silica slurry aqueous dispersion was prepared in the same manner as in Example 5 except that 12 g of a solid silica slurry aqueous dispersion (organosilica sol IPA-ST-ZL manufactured by Nissan Chemical Industries, Ltd.) was used.

(2) Preparation of binder-containing coating solution In the same manner as the primer-containing coating solution, 3- (2-aminoethyl) aminopropyltrimethoxysilane, 1-methoxy-2-propanol, 0.1 wt. % Solution was prepared.

(3) Manufacture of optical member After performing each process in order of the process 1, the process 2, the process 3, and the process 2, it preserve | saved at room temperature for 24 hours, the film | membrane was formed, and the optical member was obtained. The evaluation results are shown in Table 1.

  As shown in Tables 1 and 2, it is confirmed that Examples 1 to 5 of the present invention can form a hydrophilic film showing excellent properties in each of the items of hydrophilicity, film strength, solvent wiping resistance, and antireflection characteristics. It was done. The excellent characteristics are a contact angle of 10 degrees or less, a pencil hardness of B or more, no film peeling by solvent wiping, and a reflectance of 0.1% or less. On the other hand, Comparative Examples 1 and 2 in which the ratio of the two-dimensional filling degree between the lower layer and the upper layer was outside the range of the present invention had low pencil hardness and solvent wiping resistance in Comparative Example 1, and low pencil hardness in Comparative Example 2. Further, Comparative Examples 3 and 4 in which the silica particle diameter was outside the range of the present invention had low antireflection characteristics in Comparative Example 3, and low pencil hardness in Comparative Example 4.

10: Porous layer, 11: Silica particles, 12: Binder, 13: Void, 14: Base material

Claims (8)

An optical member having a porous layer on a substrate,
The porous layer has silica particles having an average particle diameter of 10 nm to 80 nm and a binder,
In the thickness direction of the porous layer, the two-dimensional filling degree of the silica particles in the substrate side half of the porous layer is 0.75 or more and 0.88 or less, and the surface side half of the porous layer is half An optical member characterized by being 1.02 times to 1.40 times the two-dimensional filling degree of the silica particles.   The two-dimensional filling degree of the silica particles in the substrate side half of the porous layer is 1.20 times or more and 1.40 times or less of the two-dimensional filling degree of the silica particles in the surface side half of the porous layer. The optical member according to claim 1.   The optical member according to claim 1, wherein the silica particles are solid silica particles.   The optical member according to claim 1, wherein the base material is made of an acrylic resin, a polycarbonate resin, or a polyester resin.   The optical member according to any one of claims 1 to 4, wherein the base material has a flat plate shape or a dome shape.   The content of voids on the substrate side half of the porous layer is 5% by volume or more and 15% by volume or less, and the content of voids on the surface side half of the porous layer is 10% by volume or more and 25% by volume or less. The optical member according to claim 1, wherein the optical member is an optical member.   The optical member according to claim 1, wherein a coefficient of variation of an average particle diameter of the silica particles is 20% or less.   An image pickup apparatus, comprising: an apparatus main body including an optical system; and a protective cover that covers at least the optical system, wherein the protective cover includes the optical member according to claim 1.

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