JP2023111159A - Optical member and sensor - Google Patents

Abstract

To provide an optical member in which the reflectance of incident light entering in a front and an oblique direction is low, and which includes a crack occurrence suppressed porous film, and a sensor that includes the optical member.SOLUTION: Provided is an optical member that includes a substrate, and a porous film which is disposed on the substrate and includes silica. The film thickness of the porous film is 1000 nm or greater, the rate of hole area in the porous film, when the cross section of the porous film is observed, satisfies a prescribed requirement, and the rate of hole area in a region from the surface on the side of the porous film that is reverse from the substrate side toward a 100 nm depth position D, with a 100 nm position defined as the 100 nm depth position D, when the cross section of the porous film is observed, is 80 to 95%. The ratio of the proportion of carbon atoms at a 100 nm depth position from the surface of the porous film on the substrate side toward the surface side of the porous film that is reverse to the substrate side, to the proportion of carbon atoms at a 100 nm depth position from the surface of the porous film that is reverse to the substrate side toward the substrate side, is 5.0 or greater.SELECTED DRAWING: None

Description

The present invention relates to optical members and sensors.

In recent years, the development of automatic driving support technology for vehicles has been actively carried out. In order to realize safe automatic driving, a sensor for detecting external information of the vehicle, position information, etc. is necessary.
The sensors described above are required to have highly accurate detection and stable detection performance. Therefore, it is desired to prevent stray light inside the sensor housing from entering the sensor light receiving section.

On the other hand, Patent Literature 1 discloses a gradient index multilayer thin film having a predetermined structure and functioning as an antireflection film. The refractive index gradient multilayer thin film is a porous film having holes (voids) therein.

JP 2007-052345 A

As mentioned above, in order to prevent stray light inside the sensor housing from entering the sensor light-receiving part, it is necessary to use a member that has a low reflectance even if the incident angle of incident light (especially infrared light) changes. Become. In particular, it is desired that both the reflectance of the incident light incident from the front direction and the reflectance of the incident light incident obliquely on the surface of the member be low. In other words, there is a need for members whose reflectance is less dependent on the angle of incidence.
The inventors of the present invention have evaluated the characteristics of the gradient refractive index multilayer thin film specifically described in the example column of Patent Document 1, and found that when the incident light is incident from the front direction of the gradient refractive index multilayer thin film (more specifically, Specifically, when the incident light is incident at an angle of 5° with respect to the normal direction of the gradient index multilayer thin film), and when the incident light is incident from an oblique direction (more specifically, when the gradient index multilayer film When the incident light is incident at an angle of 60° with respect to the normal direction of the thin film), a low reflectance cannot be achieved in both cases, and it does not necessarily meet the recent demands.
In addition, it is required to suppress the occurrence of cracks in the thin film exhibiting low reflection characteristics as described above.

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention provides an optical member including a porous film having low reflectance for both frontal and obliquely incident light and in which crack generation is suppressed. Make it an issue.
An object of the present invention is to provide a sensor including the above optical member.

The inventors have found that the above problems can be solved by the following configuration.

(1) a substrate;
an optical member comprising a porous film containing silica disposed on a substrate,
The film thickness of the porous film is 1000 nm or more,
When observing the cross section of the porous membrane, from the surface of the porous membrane opposite to the substrate side toward the substrate side, the position of 20% of the total thickness of the porous membrane is the depth position D20. Depth position D40 is the position of 40% of the total thickness of the porous membrane, D60 is the position of 60% of the total thickness of the porous membrane, D80 is the position of 80% of the total thickness of the porous membrane, The area from the surface of the porous membrane opposite to the substrate side to the depth position D20 is area A, the area from the depth position D20 to the depth position D40 is area B, and the depth position from the depth position D40 to the depth position. When the area up to D60 is area C, the area from depth position D60 to depth position D80 is area D, and the area from depth position D80 to the substrate side surface of the porous membrane is area E, The pore area ratio A in A, the pore area ratio B in region B, the pore area ratio C in region C, the pore area ratio D in region D, and the pore area ratio E in region E satisfy the relationship of formula (1). ,
Formula (1) Pore area ratio A> Pore area ratio B> Pore area ratio C> Pore area ratio D> Pore area ratio E
When observing the cross section of the porous membrane, when the position of 100 nm from the surface of the porous membrane opposite to the substrate side toward the substrate side is defined as the depth position D 100 nm, the base of the porous membrane The hole area ratio in the region from the surface opposite to the material side to the depth position D 100 nm is 80 to 95%,
From the surface of the porous membrane on the substrate side to the substrate side of the porous membrane with respect to the ratio of carbon atoms at a depth of 100 nm from the surface of the porous membrane opposite to the substrate side toward the substrate side The optical member, wherein the ratio of the proportion of carbon atoms at a depth position of 100 nm toward the surface opposite to is 5.0 or more.
(2) The optical member according to (1), wherein the porous film has a thickness of 2000 nm or more.
(3) The optical member according to (1) or (2), wherein the porous film has an average pore size of 20 to 400 nm.
(4) The optical member according to any one of (1) to (3), wherein the substrate contains an infrared absorbing material.
(5) A sensor comprising the optical member according to any one of (1) to (4).

According to the present invention, it is possible to provide an optical member that includes a porous film that has low reflectance for incident light that is incident from both the front direction and the oblique direction and that suppresses the occurrence of cracks.
According to the present invention, it is possible to provide a sensor including the above optical member.

It is a schematic diagram which shows an example of embodiment of an optical member.

The present invention will be described in detail below.
In this specification, the numerical range represented by "-" means a range including the numerical values before and after "-" as lower and upper limits.

As a feature of the optical member of the present invention, first, the pore area ratio in the cross section of the porous membrane is gradually changed in the thickness direction, and the pore area ratio near the surface of the porous membrane on the side opposite to the base material is set to a predetermined value. By adjusting the range, a reduction in the incident angle dependence of the reflectance is achieved. In particular, the above characteristics are obtained by adjusting the pore area ratio in the vicinity of the surface of the porous membrane on the side opposite to the base material within a predetermined range. In addition, by adjusting the ratio of the number of carbon atoms near the substrate side and the number of carbon atoms near the surface opposite to the substrate in the porous film to a predetermined range, the internal stress in the porous film is relaxed. It was found that such plasticity can be obtained, and crack generation in a porous film having a large film thickness of 1000 nm or more is suppressed.

The above embodiment will be described below with reference to the drawings. It should be noted that the figures shown below are shown in a form different in scale from the actual data so that the contents of the invention can be easily understood.

The optical member 10 shown in FIG. 1 has a substrate 12 and a porous film 14 . In FIG. 1, the substrate 12 and the porous membrane 14 are in direct contact with each other.
Each member will be described in detail below.

<Base material>
The substrate serves to support the porous membrane.
A transparent substrate is preferable as the substrate. The transparent substrate is intended to be a substrate having a visible light and near-infrared light transmittance of 60% or more, preferably 80% or more, more preferably 90% or more.
Note that visible light refers to light of 380 to 780 nm. Near-infrared light means light of 780 to 2500 nm.

The shape of the base material is not particularly limited, and examples thereof include a flat plate shape and a hemispherical shape.

The type of substrate is not particularly limited, and known substrates can be used, including plastic substrates and glass substrates.

A polymer is preferable as the material constituting the base material.
Examples of polymer films that can be used as a substrate include cellulose acylate films (e.g., cellulose triacetate film (refractive index: 1.48), cellulose diacetate film, cellulose acetate butyrate film, cellulose acetate propionate film). , polyolefin films such as polyethylene and polypropylene, polyester films such as polyethylene terephthalate and polyethylene naphthalate, polyethersulfone films, polyacrylic films such as polymethylmethacrylate, polyurethane films, polycarbonate films, polysulfone films, polyether films, polymethylpentene Films, polyether ketone films, (meth)acrylonitrile films, and films of polymers having an alicyclic structure (norbornene resin (Arton: trade name, manufactured by JSR Corporation, amorphous polyolefin (Zeonex: trade name, Japan ))) manufactured by Zeon.

The substrate may contain various additives (eg, microparticles, plasticizers, UV inhibitors, antidegradants, release agents, etc.).

The structure of the substrate may be a single layer structure or a multilayer structure.
When the substrate has a multilayer structure, it preferably has a support and a light absorption layer, for example.
Examples of the support include plastic substrates and glass substrates, and examples of plastic substrates include polymer films that can be used as the substrates described above.
The light-absorbing layer is a layer containing a light-absorbing material, and examples of the light-absorbing material include ultraviolet light-absorbing materials, visible light-absorbing materials, and infrared light-absorbing materials, with infrared light-absorbing materials being preferred. As for the light absorbing material, an optimum material is appropriately selected according to the type of the sensor light receiving portion of the sensor that provides the optical member. In particular, a light-absorbing material that absorbs light having a wavelength of light received by the sensor light-receiving part is preferable.
Even when the substrate has a single-layer structure, the substrate may contain a light-absorbing material.
That is, whether the structure of the base material is a single layer structure or a multi-layer structure, the base material may contain a light absorbing material (preferably an infrared absorbing material).

As described above, the light absorbing layer is preferably a layer containing an infrared absorbing material (infrared absorbing layer).
The infrared absorption layer preferably contains a black pigment.
As the black pigment, carbon black, titanium black, titanium oxide, iron oxide, manganese oxide, or graphite are preferable because high optical density can be achieved with a small amount. The infrared absorption layer preferably contains at least one of carbon black and titanium black, more preferably titanium black.

Titanium black is black particles containing titanium atoms, preferably low order titanium oxide or titanium oxynitride. Titanium black may be surface-modified titanium black particles, if necessary, for the purpose of improving dispersibility and suppressing aggregation.

Titanium black is preferably particulate, and the average primary particle size of individual titanium black particles is preferably small. Specifically, titanium black particles having an average primary particle size of 10 to 45 nm are preferred.
The particle size, that is, the particle diameter, is the diameter of a circle having an area equal to the projected area of the outer surface of the particle (equivalent circle diameter).

Commercial products of titanium black include titanium black 10S, 12S, 13R, 13M, 13M-C, 13R, 13R-N, and 13M-T (trade names: manufactured by Mitsubishi Materials Corporation), and Ti Tilac D (trade name: manufactured by Ako Kasei Co., Ltd.) can be mentioned.

The infrared absorbing layer contains, together with titanium black, composite oxides such as Cu, Fe, Mn, V, and Ni, cobalt oxide, iron oxide, carbon black, and aniline for the purpose of adjusting dispersibility and colorability. One or two or more black pigments made of materials such as black may be included.

In addition to the black pigment, the infrared absorption layer may contain an extender pigment as necessary. Extender pigments include, for example, barium sulfate, barium carbonate, calcium carbonate, silica, basic magnesium carbonate, alumina white, gloss white, titanium white, and hydrotalcite.
In addition to the black pigment, the infrared absorption layer may also contain colored organic pigments such as red, blue, yellow, green, and purple, if necessary.

The infrared absorbing layer preferably contains a dispersant. A dispersant contributes to the dispersibility improvement of black pigments, such as titanium black mentioned above.
Dispersants include polymer compounds (e.g., polyamidoamine and its salts, polycarboxylic acids and their salts, high molecular weight unsaturated acid esters, modified polyurethanes, modified polyesters, modified poly(meth)acrylates, (meth)acrylic co- polymers and naphthalenesulfonic acid formalin condensates), polyoxyethylene alkyl phosphate esters, polyoxyethylene alkylamines, and pigment derivatives.
Polymer compounds can be classified into straight-chain polymers, terminal-modified polymers, graft-type polymers, and block-type polymers according to their structures.

Specific examples of the polymer compound include "Disperbyk-161, 162, 163, 164, 165, 166, 170, 190 (trade name, polymer copolymer)" manufactured by BYK Chemie, and "EFKA4047" manufactured by EFKA. , 4050, 4010, 4165 (trade name, polyurethane-based), EFKA4330, 4340 (trade name, block copolymer)”.
A dispersing agent may be used individually and may be used in combination of 2 or more type.

The infrared absorbing layer may contain a polymer obtained by polymerizing a polymerizable compound.
As the polymerizable compound, a compound having at least one addition-polymerizable ethylenically unsaturated group and having a boiling point of 100° C. or higher at normal pressure is preferable.

A polymerizable compound may be used individually by 1 type, and may be used in combination of 2 or more type.
Preferred combinations of polymerizable compounds include, for example, a combination of two or more polymerizable compounds selected from the polyfunctional acrylate compounds described above, one example of which is dipentaerythritol hexaacrylate and pentaerythritol triacrylate. A combination is mentioned.

As the polymer, a polymer obtained by polymerizing the polymerizable compound using a polymerization initiator is preferable.
The polymerization initiator is not particularly limited and can be appropriately selected from known polymerization initiators. It may be an activator that produces some action with the sensitizer to generate active radicals, or an initiator that initiates cationic polymerization depending on the type of monomer.

The infrared absorbing layer may contain a binder polymer.
Examples of binder polymers include linear organic polymers, and from the viewpoint of heat resistance, polyhydroxystyrene resins, polysiloxane resins, acrylic resins, acrylamide resins, or acrylic/acrylamide copolymer resins. is preferred.

The infrared absorbing layer may contain an adhesion agent.
Examples of adhesion agents include silane coupling agents and titanium coupling agents.
The infrared absorption layer may contain an ultraviolet absorber.
UV absorbers include salicylate, benzophenone, benzotriazole, substituted acrylonitrile, and triazine UV absorbers.
The infrared absorbing layer may contain a surfactant.
Surfactants include fluorine surfactants, nonionic surfactants, cationic surfactants, anionic surfactants, and silicone surfactants.

The infrared absorbing layer may contain components other than the above components. Other components include, for example, sensitizers, co-sensitizers, cross-linking agents, curing accelerators, fillers, thermosetting accelerators, polymerization inhibitors, plasticizers, diluents, sensitizers, adhesion promoters, conductive soluble particles, fillers, defoamers, flame retardants, leveling agents, release accelerators, antioxidants, fragrances, surface tension modifiers, chain transfer agents, and the like.

The thickness of the substrate is not particularly limited, but is preferably 10 to 5000 μm, more preferably 50 to 1000 μm.
The thickness of the substrate is obtained by measuring 20 arbitrary points on the substrate with a contact-type film thickness meter (manufactured by Mitutoyo) and averaging the measured values. As the contact terminal, a columnar terminal having a bottom surface of 0.5 cm in diameter is used. The measurement pressure is 0.1N.

<Porous membrane>
A porous membrane is a layer having a plurality of pores (pores).
The porous membrane contains silica (silicon dioxide). Although the content of silica is not particularly limited, it is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more, relative to the total mass of the porous membrane. Although the upper limit is not particularly limited, it may be less than 100% by mass.
As will be described later, the silica may be a component derived from a hydrolyzable silicon compound.

The porous membrane may contain components other than silica, and contains carbon atoms. As will be described later, the carbon atoms are arranged so that the number of carbon atoms has a predetermined ratio depending on the position in the thickness direction of the porous film.
The method of introducing carbon atoms into the porous film is not particularly limited, and as described later, by using so-called silane coupling as a material for forming the porous film, silica and carbon atoms can be introduced.

The film thickness of the porous film is 1,000 nm or more, and is preferably 2,000 nm or more, more preferably 3,000 nm or more, and even more preferably 4,000 nm or more because the incident angle dependency of the reflectance of the optical member is lower. Although the upper limit is not particularly limited, it is preferably 20000 nm or less, more preferably 10000 nm or less, from the viewpoint of thinning.
The film thickness of the porous membrane is measured by preparing a section having a cross section along the thickness direction of the porous membrane, and examining the obtained section with a scanning electron microscope (SEM) or a transmission electron microscope. Observe with (TEM: Transmission Electron Microscope), measure the film thickness at 10 randomly selected locations, and arithmetically average them to obtain the film thickness of the porous film. That is, the thickness of the porous membrane is the average thickness.

When observing the cross section of the porous membrane, from the surface of the porous membrane opposite to the substrate side toward the substrate side, the position of 20% of the total thickness of the porous membrane is the depth position D20. The position of 40% of the total thickness of the porous membrane is the depth position D40, the position of 60% of the total thickness of the porous membrane is the depth position D60, and the depth position of the entire thickness of the porous membrane is D80. The area from the surface opposite to the base material side to the depth position D20 is the area A, the area from the depth position D20 to the depth position D40 is the area B, and the area from the depth position D40 to the depth position D60 is area C, the area from depth position D60 to depth position D80 is area D, and the area from depth position D80 to the surface of the porous membrane on the substrate side is area E, the pore area in area A The ratio A, the pore area ratio B in the region B, the pore area ratio C in the region C, the pore area ratio D in the region D, and the pore area ratio E in the region E satisfy the relationship of formula (1).
Formula (1) Pore area ratio A> Pore area ratio B> Pore area ratio C> Pore area ratio D> Pore area ratio E
The formula (1) will be described below.

When measuring the pore area ratio of each region of the porous membrane, first, the cross section of the porous membrane is observed. As an observation method, the porous membrane is cut along a direction orthogonal to the surface of the porous membrane (a direction parallel to the normal direction of the surface) to expose a cross section (cut surface) of the porous membrane.
Next, as shown in FIG. 1, from the surface of the porous membrane 14 opposite to the base material 12 side toward the base material 12 side, the position of 20% of the total thickness of the porous membrane 14 is the depth position. D20, the position of 40% of the total thickness of the porous membrane is the depth position D40, the position of 60% of the total thickness of the porous membrane is the depth position D60, the depth position of 80% of the total thickness of the porous membrane is D80.
Next, as shown in FIG. 1, the area from the surface of the porous membrane 14 opposite to the substrate 12 side to the depth position D20 is area A, and the area from the depth position D20 to the depth position D40 is Region B, the region from depth position D40 to depth position D60 is region C, the region from depth position D60 to depth position D80 is region D, the depth position D80 to the substrate 12 side of the porous membrane 14 A region E is defined as a region up to the surface.
In other words, the above procedure divides the entire thickness of the porous membrane 14 into five regions.

Next, the pore area ratio in each region A to E is calculated. The hole area ratio represents the area ratio of holes included in each region to the entire region {(hole area/total area of each region)×100}.
As a method for calculating the pore area ratio, first, a cross section of the porous membrane is observed with a scanning electron microscope to obtain an image (magnification: 50000 times). Next, image processing (binarization) of the obtained image is performed using image processing software (ImageJ). Next, from the obtained binarized image, the area of the hole portion in each region and the area of the other portion (matrix portion) are separated, and the ratio of the area of the hole portion to the total area of the region (hole area rate).
Through the above procedure, the pore area ratio A in the region A, the pore area ratio B in the region B, the pore area ratio C in the region C, the pore area ratio D in the region D, and the pore area ratio E in the region E are calculated. In the porous membrane of the present invention, the calculated pore area ratios A to E satisfy the relationship of formula (1) above.

Formula (1) means that the pore area ratio gradually decreases from the surface of the porous membrane opposite to the substrate side toward the substrate side. In such a structure, the refractive index of the porous film gradually decreases from the surface opposite to the substrate side toward the substrate side, and as a result, the effects of the present invention can be obtained.

The size of the hole area ratio A is not particularly limited as long as it satisfies the above formula (1), and is preferably 70 to 99%, and 80 to 80%, in terms of lower incidence angle dependence of the reflectance of the optical member. 95% is more preferred.
The size of the hole area ratio B is not particularly limited as long as it satisfies the above formula (1), and is preferably 50 to 90%, more preferably 60%, in that the dependency of the reflectance of the optical member on the angle of incidence is lower. 80% or more is more preferable.
The size of the hole area ratio C is not particularly limited as long as it satisfies the above formula (1), and is preferably 30 to 70%, more preferably 40%, in that the dependency of the reflectance of the optical member on the angle of incidence is lower. more preferably less than 60%.
The size of the hole area ratio D is not particularly limited as long as it satisfies the above formula (1), and is preferably 10 to 50%, more preferably 20%, in that the dependency of the reflectance of the optical member on the angle of incidence is lower. more preferably less than 40%.
The size of the hole area ratio E is not particularly limited as long as it satisfies the above formula (1), and is preferably 0 to 30%, such as 0%, in terms of lower incident angle dependence of the reflectance of the optical member. More preferably, it should be less than 20%.

Although the difference between the hole area ratio A and the hole area ratio B is not particularly limited, it is preferably 5 to 25%, more preferably 10 to 20%, in terms of lowering the incident angle dependency of the reflectance of the optical member.
Although the difference between the hole area ratio B and the hole area ratio C is not particularly limited, it is preferably 5 to 25%, more preferably 10 to 20%, in terms of lowering the incident angle dependence of the reflectance of the optical member.
Although the difference between the hole area ratio C and the hole area ratio D is not particularly limited, it is preferably 5 to 25%, more preferably 10 to 20%, in terms of lowering the incident angle dependency of the reflectance of the optical member.
Although the difference between the hole area ratio D and the hole area ratio E is not particularly limited, it is preferably 5 to 25%, more preferably 10 to 20%, in terms of lowering the incident angle dependency of the reflectance of the optical member.

In the above, the pore area ratio in the regions A to E obtained by dividing the entire thickness of the porous film into 5 is defined. It is preferable that the pore area ratios in the regions 1 to 10 satisfy predetermined requirements.
More specifically, when observing the cross section of the porous membrane, from the surface of the porous membrane opposite to the substrate side toward the substrate side, 10% of the total thickness of the porous membrane is positioned. Depth position D10, 20% of the total thickness of the porous membrane is depth position D20, 30% of the total thickness of the porous membrane is depth position D30, 40% of the total thickness of the porous membrane. The depth position D40, the position of 50% of the total thickness of the porous membrane is the depth position D50, the position of 60% of the total thickness of the porous membrane is the depth position D60, the position of 70% of the total thickness of the porous membrane The position is the depth position D70, the position of 80% of the entire thickness of the porous membrane is the depth position D80, the position of 90% of the entire thickness of the porous membrane is the depth position D90, and the substrate side of the porous membrane. The area from the opposite surface to the depth position D10 is area 1, the area from the depth position D10 to the depth position D20 is area 2, the area from the depth position D20 to the depth position D30 is area 3, and the depth The area from depth position D30 to depth position D40 is area 4, the area from depth position D40 to depth position D50 is area 5, the area from depth position D50 to depth position D60 is area 6, and depth position The area from D60 to depth position D70 is area 7, the area from depth position D70 to depth position D80 is area 8, the area from depth position D80 to depth position D90 is area 9, and the area from depth position D90 is When the region to the surface of the porous membrane on the substrate side is defined as region 10, the pore area ratio in region 1 is 1, the pore area ratio is 2 in region 2, the pore area ratio is 3 in region 3, and the pore area ratio is in region 4. 4, pore area ratio 5 in region 5, pore area ratio 6 in region 6, pore area ratio 7 in region 7, pore area ratio 8 in region 8, pore area ratio 9 in region 9, and pore area ratio in region 10 10 preferably satisfies the relationship of equation (2).
Formula (2) Pore area ratio 1> Pore area ratio 2> Pore area ratio 3> Pore area ratio 4> Pore area ratio 5> Pore area ratio 6> Pore area ratio 7> Pore area ratio 8> Pore area ratio 9> Hole Area ratio 10

The method for calculating the pore area ratios 1 to 10 can be carried out in the same manner as the above-described method for calculating the pore area ratios A to E by changing the depth position.

When observing the cross section of the porous membrane, when the position of 100 nm from the surface of the porous membrane opposite to the base material toward the base material side is defined as the depth position D 100 nm, the base material of the porous membrane The hole area ratio is 80 to 95% in the region from the surface opposite to the side to a depth position D of 100 nm. Among them, 85 to 95% is more preferable because the incident angle dependency of the reflectance of the optical member is lower.
The method of calculating the pore area ratio can be carried out in the same manner as the above-described methods of calculating the pore area ratios A to E by changing the depth position.

The ratio R1 of carbon atoms at a depth position of 100 nm from the surface of the porous membrane opposite to the substrate side toward the substrate side from the surface of the porous membrane on the substrate side to the substrate side of the porous membrane A ratio (R2/R1) of a ratio R2 of carbon atoms at a depth position of 100 nm toward the surface side opposite to is 5 or more. Among them, 6 or more is preferable in terms of further suppressing the occurrence of cracks in the porous film. Although the upper limit is not particularly limited, it is preferably 20 or less, more preferably 10 or less.
A method for calculating the above ratio is as follows.
First, in order to calculate the ratio R1 of carbon atoms at a depth position of 100 nm from the surface of the porous membrane opposite to the substrate side toward the substrate side, the surface of the porous membrane opposite to the substrate side was The porous film is etched to a depth of 100 nm from the surface of the substrate toward the substrate side. Next, the ratio of carbon atoms is calculated by X-ray photoelectron spectroscopy with respect to the exposed surface at a depth of 100 nm. The ratio of carbon atoms in X-ray photoelectron spectroscopy is the ratio (atomic %) to the total amount of carbon atoms, oxygen atoms, nitrogen atoms, silicon atoms and titanium atoms. Moreover, the measurement conditions of the X-ray photoelectron spectroscopy are as follows.
X-ray source: monochromatic Al-α
Measurement area: F1s, C1s, O1s, N1s, Si2p, Ti2p
Take-off angle: 45°
The method of calculating the ratio R2 of carbon atoms at a depth position of 100 nm from the surface of the porous membrane on the substrate side toward the surface side opposite to the substrate side of the porous membrane is the same as the above ratio R1. From the surface of the porous membrane on the side of the substrate toward the side of the porous membrane opposite to the substrate side to a depth of 100 nm, and from the surface of the porous membrane on the side opposite to the substrate side toward the substrate side. Then, the porous film is etched, and the carbon atom ratio R2 is calculated for the exposed surface by the above-described X-ray photoelectron spectroscopy.

Although the average pore diameter of the porous film is not particularly limited, it is preferably 20 to 400 nm, more preferably 30 to 200 nm, from the viewpoint of further reducing the reflectance.
A method for calculating the average pore size is as follows.
The average pore diameter (unit: nm) of the pores contained in the porous membrane is obtained by arbitrarily selecting 200 pores in an SEM cross-sectional image of the porous membrane (magnification: 50000) and calculating the equivalent circle diameter for each selected pore. It is obtained by calculating and arithmetically averaging them. Note that the equivalent circle diameter is the diameter of a perfect circle having the same projected area as the projected area of the hole during observation.

Silica is an example of a material that constitutes the porous membrane, as described above.
Among them, the porous membrane preferably contains a hydrolytic condensate of a hydrolyzable silicon compound, in terms of easy production of the porous membrane.
A hydrolytic condensate of a hydrolyzable silicon compound means a compound obtained by hydrolyzing a hydrolyzable group of a hydrolyzable silicon compound and condensing the resulting hydrolyzate. In addition, as the hydrolytic condensate, even if all the hydrolyzable groups are hydrolyzed and the hydrolyzate is all condensed (complete hydrolytic condensate), a part of the hydrolysis It may be one in which the functional group is hydrolyzed and a part of the hydrolyzate is condensed (partially hydrolyzed condensate). That is, the hydrolytic condensate may be a complete hydrolytic condensate, a partial hydrolytic condensate, or a mixture thereof.

By hydrolyzable silicon compound is intended a compound having a hydrolyzable group attached to a silicon atom.
A compound represented by the following formula (X) is preferable as the hydrolyzable silicon compound.

In the formula, R ¹ and R ² each independently represent a monovalent organic group having 1 to 6 carbon atoms.
^R3 and ^R4 each independently represent an alkyl group, vinyl group, epoxy group, styryl group, (meth)acrylic group, amino group, isocyanurate group, ureido group, mercapto group, sulfide group, polyalkyleneoxyalkyl group , a carboxy group, and an organic group having a group selected from the group consisting of a quaternary ammonium group.
Each m independently represents an integer of 0 to 2.
n represents an integer from 1 to 20;

Here, the hydrolytic condensate of the compound represented by the formula (X) means the compound represented by the formula (X) and at least the substituent on the silicon atom in the compound represented by the formula (X) It refers to a compound in which a compound selected from the group consisting of compounds partially hydrolyzed to form silanol groups (hydrolysates) is condensed.

The organic group having 1 to 6 carbon atoms for R ¹ and R ² may be linear, branched, or have a cyclic structure.
Examples of organic groups having 1 to 6 carbon atoms include alkyl groups and alkenyl groups, with alkyl groups being preferred.
Examples of alkyl groups having 1 to 6 carbon atoms include methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, tert-butyl group, n-pentyl group, n-hexyl group and cyclohexyl group. mentioned.
R ¹ and R ² are each independently preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, and still more preferably a methyl group or an ethyl group.

R ³ is preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, and even more preferably a methyl group or an ethyl group.

^R4 is an unsubstituted alkyl group, vinyl group, or vinyl group, epoxy group, styryl group (vinylphenyl group), (meth)acryloyloxy group, (meth)acrylamide group, amino group, isocyanurate group, ureido group , mercapto groups, sulfide groups, polyalkyleneoxyalkyl groups, carboxy groups and quaternary ammonium groups.
R ⁴ is preferably a group represented by formula (Y).
Formula (Y) R ⁵ -L-*
^R5 is a vinyl group, epoxy group, styryl group (vinylphenyl group), (meth)acryloyloxy group, (meth)acrylamide group, amino group, isocyanurate group, ureido group, mercapto group, sulfide group, polyalkyleneoxy It represents an alkyl group, a carboxy group, or a quaternary ammonium group.
L represents an alkylene group. Although the number of carbon atoms in the alkylene group is not particularly limited, it is preferably 1-10, more preferably 1-5.

m is preferably 1 or 2 from the viewpoint of the strength and haze of the porous membrane. When m is 1, the compound represented by formula (X) corresponds to a so-called silane coupling agent.
n is preferably an integer of 1 to 20, more preferably an integer of 1 to 5, from the viewpoint of the strength and haze of the porous film.

Commercially available products of the compound represented by formula (X) include Shin-Etsu Chemical Co., Ltd. KBE-04, KBE-13, KBM-13, KBE-22, KBE-1003, KBM-303, KBE-403, KBM- 1403, KBE-503, KBM-5103, KBE-903, KBE-9103P, KBE-585, KBE-803, KBE-846, KR-500, KR-515, KR-516, KR-517, KR-518, X-12-1135, X-12-1126, and X-12-1131; Dynasylan 4150 manufactured by Evonik Japan; MKC silicates MS-51, MS-56, MS-57, and MS-56S manufactured by Mitsubishi Chemical and Ethyl Silicate 28, N-Propyl Silicate, N-Butyl Silicate, and SS-101 manufactured by Colcoat Co., Ltd.;

In the porous film, m is 1 in that at least one of the effect of lower incident angle dependence of the reflectance of the optical member and the further suppression of cracks in the porous film can be obtained. and a hydrolytic condensate of a compound represented by the formula (X) in which m is 2.

The porous membrane may contain components other than the hydrolytic condensate of the hydrolyzable silicon compound. Examples thereof include surfactants used in the method for producing a porous membrane, which will be described later.

(Method for producing porous membrane)
The method for producing the porous membrane is not particularly limited, and is not particularly limited as long as the porous membrane having the above characteristics can be produced. A method of performing the step of forming a silica-containing film using a composition containing is mentioned.
Since the core-shell particles, which will be described later, contain a solvent in the core portion, the solvent evaporates to form voids when the silica-containing film is formed. This void corresponds to the pores of the porous membrane. Therefore, the pore area ratio of the formed silica-containing film can be adjusted by adjusting the content of the core-shell particles in the composition.
For example, after forming a first silica-containing film using the above composition, a composition having a higher content of core-shell particles than the composition used for forming the first silica-containing film is used to form the first silica-containing film. By forming the second silica-containing film having the same film thickness as the first silica-containing film on the film, the pore area ratio of the second silica-containing film can be made higher than that of the first silica-containing film. Further, as the hydrolytic condensate of the hydrolyzable silicon compound, for example, when the hydrolytic condensate of the hydrolyzable silicon compound containing carbon atoms is used, The content of the hydrolytic condensate of the hydrolyzable silicon compound containing carbon atoms is less than the content of the hydrolytic condensate of the hydrolyzable silicon compound containing carbon atoms in the composition used for forming the second silica-containing film. By also increasing the number of carbon atoms in the first silica-containing film, the number of carbon atoms in the second silica-containing film can be made larger. Therefore, by adjusting the composition of the components contained in the composition as described above and repeating the formation of the silica-containing film at least a plurality of times (for example, 5 times or more), the above-described predetermined requirements of the present invention are satisfied. Porous membranes can be produced.
A method for producing a porous membrane using the above composition will be described in detail below.

The core-shell particles contained in the composition contain a solvent in the core portion and a hydrolytic condensate of a hydrolyzable silicon compound in the shell portion. When a silica-containing film is produced using a composition containing such core-shell particles, pores can be formed by volatilizing the solvent contained in the core during production of the silica-containing film, and silica can be used as a matrix component constituting the silica-containing film. can remain.
The solvent contained in the core portion is not particularly limited, and includes water and organic solvents.
Examples of the organic solvent include hydrocarbon compounds, fluorocarbon compounds, and silicone compounds. Hydrocarbon compounds are preferred from the viewpoint of the light transmittance and haze of the porous film.

The hydrocarbon compound may be an aliphatic hydrocarbon compound or an aromatic hydrocarbon compound, but from the viewpoint of the light transmittance and haze of the porous film, an aliphatic hydrocarbon compound is preferable, and an alkane is more preferred.
The hydrocarbon compound may be linear or branched, may have a ring structure, or may have an unsaturated bond. The hydrocarbon compound is preferably a straight-chain or branched-chain hydrocarbon compound, more preferably a straight-chain hydrocarbon compound, from the viewpoint of the light transmittance and haze of the porous film. Moreover, as the hydrocarbon compound, a compound having no unsaturated bond is preferable.
The number of carbon atoms in the hydrocarbon compound is preferably 7 or more, more preferably 8 to 20, even more preferably 10 to 19, from the viewpoints of light transmittance and haze of the porous film.

In the core-shell particles, 20% by mass or more of the solvent contained as the core material is a non-polar solvent having a boiling point of 90 to 350 ° C. in terms of suppressing residue in the porous film after production and improving the haze of the porous film. Solvents are preferred.
As used herein, the term "boiling point" refers to the boiling point at 1 atmosphere (101,325 Pa). The term "non-polar solvent" refers to an organic solvent having a solubility in water of 0.1% by mass or less at 20°C and a dielectric constant of 10 or less.
The boiling point of the non-polar solvent is preferably 100 to 340°C, more preferably 120 to 320°C, and even more preferably 200 to 310°C, from the viewpoints of light transmission and haze of the porous film.

Non-polar solvents having a boiling point in the range of 90 to 350° C. include, for example, n-heptane (boiling point: 98° C.), n-octane (boiling point: 125° C.), n-dodecane (boiling point: 216° C.), n- Tetradecane (boiling point: 254°C), n-hexadecane (boiling point: 287°C), n-heptadecane (boiling point: 302°C), n-octadecane (boiling point: 317°C), n-icosane (boiling point: 343°C), cyclooctane (boiling point: 149°C), toluene (boiling point: 111°C), p-xylene (boiling point: 138°C), m-xylene (boiling point: 139°C), and o-xylene (boiling point: 144°C).

The solvents contained as the core portion of the core-shell particles may be used alone or in combination of two or more.
The content of the non-polar solvent having a boiling point of 90 to 350° C. is preferably 20% by mass or more, preferably 50% by mass, based on the total mass of the solvent contained as the core material, from the viewpoint of the light transmittance and haze of the porous film. 70% by mass or more is more preferable, 90% by mass or more is particularly preferable, and 99 to 100% by mass is most preferable.

The shell portion of the core-shell particles contains a hydrolytic condensate of a hydrolyzable silicon compound.
The hydrolytic condensate of the hydrolyzable silicon compound includes hydrolytic condensate of the hydrolyzable silicon compound contained in the porous membrane described above.
The content of the hydrolyzed condensate of the hydrolyzable silicon compound is preferably 50% by mass or more with respect to the total mass of the shell portion of the core-shell particles.
As the hydrolytic condensate of the hydrolyzable silicon compound contained in the shell portion of the core-shell particles, a hydrolytic condensate of a hydrolyzable silicon compound in which m is 2 and n is 1 in formula (X) is preferred.

The mass ratio of the core part to the shell part (core part/shell part) in the core-shell particles is 1/99 to 99/1 from the viewpoint of the strength, light transmittance and haze of the porous film. preferably 5/95 to 5/95, even more preferably 10/90 to 90/10.

The volume average particle diameter of the core-shell particles is preferably 0.02 to 1.5 μm, more preferably 0.02 to 1.0 μm, more preferably 0.05 to 0, from the viewpoints of strength, light transmittance and haze of the porous membrane. 0.6 μm is more preferred.
The volume average particle size of core-shell particles means the median size, and can be measured using a laser diffraction/scattering particle size distribution analyzer (model number: Microtrac MT3300EXII, manufactured by Microtrac Bell Co., Ltd.).

The core-shell particles may be used alone or in combination of two or more.
The content of the core-shell particles is preferably 0.05 to 40% by mass, more preferably 0.1 to 20% by mass, based on the total mass of the composition, from the viewpoints of strength, light transmittance and haze of the porous film. .

The method for producing the core-shell particles is not particularly limited. For example, after preparing an emulsion by emulsifying an organic solvent, which is a core material, in water, a shell portion is formed on the surface of the core material contained in the emulsion as a dispersoid. , is preferably made. More specifically, an organic solvent, which is a core material, a surfactant, and water are mixed, the organic solvent is dispersed in water, a hydrolyzable silicon compound is added, and the hydrolyzable silicon compound is added. A method of forming a shell portion on the surface of a dispersed organic solvent by decomposition and condensation to produce core-shell particles containing a core portion containing an organic solvent and a shell portion containing a hydrolytic condensate of a hydrolyzable silicon compound. mentioned.
A condensation catalyst that promotes condensation may be added together with the hydrolyzable silicon compound.

Surfactants include nonionic surfactants, anionic surfactants that are ionic surfactants, cationic surfactants, and amphoteric surfactants.
Among these surfactants, nonionic surfactants or cationic surfactants are preferred, and cationic surfactants are more preferred, from the viewpoint of the light transmittance and haze of the porous membrane.
As the cationic surfactant, a quaternary ammonium salt type, pyridinium salt type or polyamine type surfactant is preferable, and a quaternary ammonium salt type or pyridinium salt type surfactant is more preferable.

Examples of condensation catalysts include acid catalysts, alkali catalysts, and organometallic catalysts, with acid catalysts being preferred.
Acid catalysts include phosphoric acid, nitric acid, hydrochloric acid, sulfuric acid, acetic acid, chloroacetic acid, formic acid, oxalic acid, and p-toluenesulfonic acid.

Examples of the method for emulsifying the core material include a method for emulsifying the core material by applying a shearing force. More specifically, a method using a rotor (rotating blade) or a stator (fixed blade), ultrasonic Examples include a method using cavitation, a method using grinding media such as balls or beads, a method in which raw materials collide with each other at high speed, and a method in which a core material is emulsified by passing it through a porous membrane (membrane emulsification).
Apparatuses used in the method of emulsifying the core material include an automixer model 20 manufactured by Primix Co., Ltd., an ultrasonic homogenizer Sonifier SFX250 manufactured by Emerson Japan, OMEGA LAB manufactured by Ashizawa Finetech Co., Ltd., and Sugino Co., Ltd. Starburst 10 manufactured by Machine Co., Ltd. and KH-125 manufactured by SPG Techno Co., Ltd. can be mentioned.

The composition contains a hydrolytic condensate of a hydrolyzable silicon compound.
The definition of hydrolyzable silicon compound is as described above.
Preferably, the composition comprises a hydrolytic condensate of a hydrolyzable silicon compound containing carbon atoms. Hydrolyzable silicon compounds containing carbon atoms include so-called silane coupling agents, more specifically, m is 1 and R ⁴ is a group represented by formula (Y), the formula ( Examples include compounds represented by X).
Among others, the composition comprises a compound represented by formula (X), wherein m is 2; and a compound represented by formula (X), wherein m is 1 and ^R4 is a group represented by formula (Y). It preferably contains a hydrolytic condensate of a hydrolyzable silicon compound containing the represented compound.
The content of the hydrolytic condensate of the hydrolyzable silicon compound is preferably 30 to 99% by mass, preferably 50 to 95% by mass, based on the total mass of the composition, from the viewpoint of the strength, light transmittance and haze of the porous film. % is more preferred.

The composition may contain components other than the core-shell particles and the hydrolyzed condensate of the hydrolyzable silicon compound.
Other ingredients include surfactants and condensation catalysts as described above. In particular, as described above, when core-shell particles are formed using surfactants and condensation catalysts, these components may be included in the composition.
Other ingredients include solvents (water and organic solvents).

A method of preparing the composition is not particularly limited, and a method of preparing a solution 1 containing core-shell particles and a solution 2 containing a hydrolyzed condensate of a hydrolyzable silicon compound and mixing them is preferred.
Methods for preparing solution 1 include the methods described above.
As a method for preparing solution 2, a method of adding a hydrolyzable silicon compound to a solvent and allowing hydrolysis and condensation reactions to proceed is preferred.
By adjusting the mixing ratio of solutions 1 and 2, the pore area ratio and carbon number in the formed silica-containing film can be adjusted as described above.

The method of applying the composition is not particularly limited, and examples thereof include known coating methods such as spin coating, spray coating, brush coating, roller coating, bar coating, and dip coating.
In addition, from the viewpoint of improving the film-forming property, when the composition is applied to the substrate, before applying the composition, the surface of the substrate is subjected to corona discharge treatment, glow treatment, atmospheric pressure plasma treatment, Surface treatments such as flame treatment and ultraviolet irradiation (UV) treatment are preferred.

Spray coating is preferable when the composition is applied to the surface of a three-dimensional structure having various surface shapes such as curved surfaces and irregularities. When the composition is applied to the substrate by spray coating, the method of setting the substrate is not particularly limited. Depending on the shape of the base material, the orientation of the base material can be changed as appropriate to the direction of application, such as the horizontal direction or the vertical direction.

A coating film formed by applying the composition may be subjected to a drying treatment, if necessary.
Drying of the coating film may be carried out at room temperature (25° C.) or by heating, but heating to 40 to 700° C. is preferable from the viewpoint of sufficiently volatilizing the organic solvent. When a resin base material is used, it is necessary to heat at a temperature below the decomposition temperature of the base material, and specifically, heating to 40 to 200° C. is preferable. Further, from the viewpoint of suppressing thermal deformation of the base material, heating to 40 to 120° C. is more preferable.
The heating time for heating is not particularly limited, but is preferably 1 to 30 minutes.
The method of heat treatment is not particularly limited, and can be performed by known heating means such as hot plate, oven and furnace.

The atmosphere in which the coating film is dried is not particularly limited, and includes an inert atmosphere and an oxidizing atmosphere. An inert atmosphere can be achieved with inert gases such as nitrogen, helium, and argon. The oxidizing atmosphere can be realized by a mixed gas of these inert gases and oxidizing gases, or air may be used. Oxidizing gases include, for example, oxygen, carbon monoxide, and oxygen dinitride.
The coating film can be dried under pressure, normal pressure, reduced pressure, and vacuum.

The coating film formed using the composition is cured by condensation of the hydrolyzable silicon compound due to the reduction of solvent such as water in the drying step after coating. Further, in the drying step after coating, the organic solvent, which is the core material of the core-shell particles, volatilizes, forming pores (voids) in the porous film.

By repeating the formation of the silica-containing film using the above composition while changing the proportions of the components in the composition, a porous film having a plurality of laminated silica-containing films is formed.

<Other aspects>
In FIG. 1, the porous membrane 14 is arranged only on one surface side of the base material 12, but the present invention is not limited to this embodiment, and the porous membranes are arranged on both sides of the base material. may
When porous membranes are placed on both sides of the substrate, the porous membranes placed on both sides of the substrate both meet the above requirements.

<Application>
INDUSTRIAL APPLICABILITY The optical member of the present invention can be applied to various uses, for example, it can be applied to a sensor having a sensor light receiving portion. As described above, by arranging the optical member of the present invention inside the sensor housing in which the sensor light receiving section is arranged, stray light entering the sensor light receiving section can be reduced.

Examples of the sensors include LiDAR using infrared rays. More specifically, for example, a sensor including the optical member of the present invention is mounted on a vehicle as a moving body, scans and irradiates a laser beam in front of the moving body, and emits laser light from the moving body to the front of the moving body. You can measure the distance to an object that
The optical member of the present invention is not limited to sensors for vehicles, and can be used, for example, as sensors for detecting external information such as crime prevention, security, abnormality detection, and behavior analysis, such as monitoring cameras.

EXAMPLES The characteristics of the present invention will be described more specifically below with reference to examples and comparative examples. The materials, amounts used, proportions, processing details, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the gist of the present invention. Therefore, the scope of the present invention should not be construed as being restricted by the specific examples shown below.

<Preparation of core-shell particle dispersion>
Hexadecylpyridinium chloride monohydrate (cationic surfactant, manufactured by Wako Pure Chemical Industries, Ltd.) (10 parts by mass) was diluted with distilled water (90 parts by mass) to prepare a 10% aqueous solution of hexadecylpyridinium chloride. .
Next, distilled water (85.6 parts by mass), hexadecylpyridinium chloride 10% aqueous solution (8.9 parts by mass), and hexadecane (nonpolar solvent, n-hexadecane, manufactured by Wako Pure Chemical Industries, Ltd.) ( 5.5 parts by mass) are mixed, cooled with ice water using an ultrasonic homogenizer Sonifier 450 manufactured by Emerson Japan Co., Ltd., and stirred for 20 minutes to obtain emulsion particles in which a hexadecane emulsion is present in water. A dispersion was obtained.

Next, emulsion particle dispersion (71.9 parts by mass), distilled water (20.0 parts by mass), acetic acid (diluted with 5% distilled water) (2.5 parts by mass), and tetraethoxysilane (trade name: After mixing KBE-04 (manufactured by Shin-Etsu Chemical Co., Ltd.) (5.6 parts by mass), the mixture was stirred at 25°C for 42 hours to obtain core-shell particles containing a non-polar solvent as a core material, a surfactant and water. A core-shell particle dispersion liquid 1 containing was obtained.

<Preparation of aqueous solution for refractive index adjustment>
Distilled water (90.0 parts by mass), acetic acid (0.07 parts by mass), 3-glycidoxypropyltriethoxysilane (trade name: KBE-403, manufactured by Shin-Etsu Chemical Co., Ltd.) (7.61 parts by mass) ), and tetraethoxysilane (trade name: KBE-04, manufactured by Shin-Etsu Chemical Co., Ltd.) (2.32 parts by mass) were mixed and then stirred at 25 ° C. for 6 hours to obtain a hydrolyzed condensate-containing An aqueous solution was obtained.
Next, distilled water (62.5 parts by mass) was added to the hydrolytic condensate-containing aqueous solution (37.5 parts by mass), and the mixture was stirred at 25°C for 1 hour to obtain an aqueous solution for refractive index adjustment.

<Preparation of coating liquid 1>
Distilled water (63.6 parts by mass) was added to core-shell particle dispersion 1 (36.4 parts by mass), and the mixture was stirred at 25°C for 1 hour to obtain coating liquid 1.

<Preparation of coating liquid 2>
A coating liquid 2 was obtained by adding an aqueous solution for refractive index adjustment (11 parts by mass) to coating liquid 1 (89 parts by mass) and stirring the mixture at 25° C. for 1 hour.

<Preparation of coating liquid 3>
An aqueous solution for refractive index adjustment (22 parts by mass) was added to coating liquid 1 (78 parts by mass), and the mixture was stirred at 25° C. for 1 hour to obtain coating liquid 3.

<Preparation of coating liquid 4>
A coating liquid 4 was obtained by adding an aqueous solution for refractive index adjustment (33 parts by mass) to coating liquid 1 (67 parts by mass) and stirring the mixture at 25° C. for 1 hour.

<Preparation of coating liquid 5>
An aqueous solution for refractive index adjustment (44 parts by mass) was added to coating liquid 1 (56 parts by mass), and the mixture was stirred at 25° C. for 1 hour to obtain coating liquid 5.

<Preparation of coating liquid 6>
A coating liquid 6 was obtained by adding an aqueous solution for refractive index adjustment (56 parts by mass) to coating liquid 1 (44 parts by mass) and stirring the mixture at 25° C. for 1 hour.

<Preparation of Coating Liquid 7>
An aqueous solution for refractive index adjustment (67 parts by mass) was added to coating liquid 1 (33 parts by mass), and the mixture was stirred at 25° C. for 1 hour to obtain coating liquid 7 .

<Preparation of coating liquid 8>
An aqueous solution for refractive index adjustment (78 parts by mass) was added to coating liquid 1 (22 parts by mass), and the mixture was stirred at 25° C. for 1 hour to obtain coating liquid 8.

<Preparation of coating liquid 9>
A coating liquid 9 was obtained by adding an aqueous solution for refractive index adjustment (89 parts by mass) to coating liquid 1 (11 parts by mass) and stirring the mixture at 25° C. for 1 hour.

<Preparation of coating liquid 10>
The coating liquid 10 was obtained by stirring the refractive index adjusting aqueous solution (100 parts by mass) at 25° C. for 1 hour.

<Preparation of coating liquid 11>
Core-shell particle dispersion liquid C2 (15.04 parts by mass) of Comparative Example 2 of International Publication No. WO 2019/167944 and distilled water (84.96 parts by mass) were stirred at 25°C for 1 hour to prepare coating liquid 11. Obtained.

<Preparation of coating liquid 12>
Emulsion particle dispersion (71.9 parts by mass), distilled water (19.1 parts by mass), acetic acid (diluted with 5% distilled water) (2.5 parts by mass), and tetraethoxysilane (trade name: KBE-04 , manufactured by Shin-Etsu Chemical Co., Ltd.) (6.5 parts by mass) and then stirred at 25 ° C. for 42 hours to obtain core-shell particles containing a non-polar solvent as a core material, a surfactant and a core-shell containing water. A particle dispersion 2 was obtained.
Next, distilled water (63.6 parts by mass) was added to core-shell particle dispersion 2 (36.4 parts by mass), and the mixture was stirred at 25°C for 1 hour to obtain coating liquid 12 .

<Preparation of coating liquid 13>
A coating liquid 13 was obtained by adding an aqueous solution for refractive index adjustment (6 parts by mass) to coating liquid 1 (94 parts by mass) and stirring the mixture at 25° C. for 1 hour.

<Preparation of coating liquid 14>
A coating liquid 14 was obtained by adding an aqueous solution for refractive index adjustment (15 parts by mass) to coating liquid 1 (85 parts by mass) and stirring the mixture at 25° C. for 1 hour.

<Preparation of coating liquid 15>
A coating liquid 15 was obtained by adding an aqueous solution for refractive index adjustment (25 parts by mass) to coating liquid 1 (75 parts by mass) and stirring the mixture at 25° C. for 1 hour.

<Preparation of coating liquid 16>
A coating liquid 16 was obtained by adding an aqueous solution for refractive index adjustment (30 parts by mass) to coating liquid 1 (70 parts by mass) and stirring the mixture at 25° C. for 1 hour.

<Preparation of coating liquid 17>
A coating liquid 17 was obtained by adding an aqueous solution for refractive index adjustment (39 parts by mass) to coating liquid 1 (61 parts by mass) and stirring the mixture at 25° C. for 1 hour.

<Example 1>
One surface of a polycarbonate substrate (PC) (average thickness: 0.5 mm) was subjected to corona discharge treatment under conditions of 730 J/m ² . After that, the coating liquid 10 was applied to the surface of the polycarbonate substrate treated with corona discharge using a spin coater, and the obtained coating film was dried at 100° C. for 2 minutes to form a first layer having an average film thickness of 200 nm. Obtained.
Next, the surface of the first layer was subjected to corona discharge treatment under conditions of 730 J/m ² . After that, the coating liquid 9 was applied to the surface of the first layer that had been subjected to the corona discharge treatment using a spin coater, and the obtained coating film was dried at 100° C. for 2 minutes to form a second layer having an average thickness of 200 nm. Obtained.
Next, the surface of the second layer was subjected to corona discharge treatment under conditions of 730 J/m ² . Thereafter, the coating liquid 8 was applied to the surface of the second layer that had been subjected to the corona discharge treatment using a spin coater, and the resulting coating film was dried at 100°C for 2 minutes to form a third layer having an average film thickness of 200 nm. Obtained.
Next, the surface of the third layer was subjected to corona discharge treatment under conditions of 730 J/m ² . After that, the coating liquid 7 was applied to the surface of the third layer that had been subjected to the corona discharge treatment using a spin coater, and the obtained coating film was dried at 100° C. for 2 minutes to form a fourth layer having an average thickness of 200 nm. Obtained.
Next, the surface of the fourth layer was subjected to corona discharge treatment under conditions of 730 J/m ² . Thereafter, the coating liquid 6 was applied to the surface of the fourth layer that had been subjected to the corona discharge treatment using a spin coater, and the obtained coating film was dried at 100° C. for 2 minutes to form a fifth layer having an average thickness of 200 nm. Obtained.
Next, the surface of the fifth layer was subjected to corona discharge treatment under conditions of 730 J/m ² . Thereafter, the coating liquid 5 was applied to the surface of the fifth layer that had been subjected to the corona discharge treatment using a spin coater, and the resulting coating film was dried at 100°C for 2 minutes to form a sixth layer having an average thickness of 200 nm. Obtained.
Next, the surface of the sixth layer was subjected to corona discharge treatment under conditions of 730 J/m ² . After that, the coating liquid 4 was applied to the corona discharge-treated surface of the sixth layer using a spin coater, and the obtained coating film was dried at 100° C. for 2 minutes to form a seventh layer having an average thickness of 200 nm. Obtained.
Next, the surface of the seventh layer was subjected to corona discharge treatment under conditions of 730 J/m ² . After that, using a spin coater, the coating liquid 3 was applied to the surface of the seventh layer that had been subjected to the corona discharge treatment, and the obtained coating film was dried at 100°C for 2 minutes to form an eighth layer having an average thickness of 200 nm. Obtained.
Next, the surface of the eighth layer was subjected to corona discharge treatment under conditions of 730 J/m ² . After that, using a spin coater, the coating liquid 2 was applied to the surface of the eighth layer that had been subjected to the corona discharge treatment, and the resulting coating film was dried at 100°C for 2 minutes to form a ninth layer having an average film thickness of 200 nm. Obtained.
Next, the surface of the ninth layer was subjected to corona discharge treatment under conditions of 730 J/m ² . Then, using a spin coater, the coating liquid 1 was applied to the corona discharge-treated surface of the ninth layer, and the resulting coating film was dried at 100° C. for 2 minutes to obtain a tenth layer having an average film thickness of 200 nm. Ta.
By the above procedure, a porous film consisting of the 1st to 10th layers was formed on one surface of the polycarbonate substrate.
The other surface of the polycarbonate substrate was also treated in the same manner as described above to form a porous film composed of the 1st to 10th layers.
That is, an optical member 1 having porous films on both sides of a polycarbonate substrate was produced.

<Examples 2 to 4, Comparative Examples 1 to 4>
Optical members 1 to 4 and optical members C1 to C4 were produced according to the same procedure as in Example 1, except that the coating liquid used and the thickness of each layer were changed as shown in Tables 1 and 2 below.

<Evaluation>
<Measurement of pore area ratio>
The pore area ratio of each region in the porous membrane was measured by the following method.
The optical member of each example and comparative example was cut along the direction orthogonal to the surface, and the cut surface was observed with a scanning electron microscope (SEM) to obtain an SEM cross-sectional image of the porous membrane.
The obtained SEM cross-sectional image (magnification of 50000 times) was subjected to image processing (binarization) using image processing software (ImageJ). was separated, and the area ratio (hole area ratio) of the total area of the hole portions in each region was calculated.

(Measurement of carbon ratio)
The porous film in each of the optical members of Examples and Comparative Examples was etched from the surface of the porous film opposite to the base material to a depth of 100 nm toward the base material. The exposed surface of the porous film was analyzed by X-ray photoelectron spectroscopy to calculate the carbon atom ratio R1 (atomic %).
In addition, the optical member of each example and comparative example was expanded to a depth of 100 nm from the substrate side of the porous film in the optical member of each example and comparative example toward the surface side opposite to the substrate side. The porous membrane was etched from the surface opposite to the substrate side of the inner porous membrane toward the substrate side. The exposed surface of the porous film was analyzed by X-ray photoelectron spectroscopy to calculate the carbon atom ratio R2 (atomic %).
Next, the ratio (R2/R1) of the ratio R2 to the ratio R1 was calculated.
The ratio of carbon atoms in X-ray photoelectron spectroscopy is the ratio (atomic %) to the total amount of carbon atoms, oxygen atoms, nitrogen atoms, silicon atoms and titanium atoms. Moreover, the measurement conditions of the X-ray photoelectron spectroscopy are as follows.
X-ray source: monochromatic Al-α
Measurement area: F1s, C1s, O1s, N1s, Si2p, Ti2p
Take-off angle: 45°

(Reflectance evaluation)
The substrate surface of the optical member prepared in each example and comparative example on the side opposite to the porous film side was laminated to the adhesive surface of a black PET film (Kukkiri Mieru, manufactured by Tomoegawa Seisakusho Co., Ltd.) using a roller. A measurement sample was prepared by
The reflection spectrum of the incident light incident from a direction of 5° or 60° with respect to the normal direction of the optical member was measured with an ultraviolet-visible-near-infrared spectrometer (manufactured by JASCO Corporation, V-670, using an integrating sphere unit ISN-723). was used to measure at intervals of 5 nm in the wavelength range of 300 to 2500 nm. Among the obtained reflectances, the average reflectance at a wavelength of 900 to 1600 nm was calculated.

-Evaluation criteria-
A: Average reflectance less than 0.5%.
B: Average reflectance of 0.5% or more and less than 1%.
C: Average reflectance of 1% or more and less than 2%.
D: Average reflectance of 2% or more.

(Haze evaluation)
The haze of the optical member produced in each example and comparative example was measured using a haze meter (model number: NDH 5000, manufactured by Nippon Denshoku Industries Co., Ltd.). The haze of the porous membrane was obtained by subtracting the haze of the base material only from the obtained measured value. It means that the lower the haze, the more suppressed the occurrence of cracks in the porous film. Evaluation criteria are as follows. Practically, A or more is preferable.

-Evaluation criteria-
A: Less than 1% haze B: 1% or more haze

In Tables 1 and 2, the "surface layer region pore area ratio" column indicates that when the cross section of the porous membrane is observed, the surface of the porous membrane opposite to the substrate side toward the substrate side is 100 nm. It represents the pore area ratio in the region from the surface of the porous membrane opposite to the substrate side to the depth position D100 nm when the position is the depth position D100 nm.

As shown in Table 1, it was confirmed that the optical members of the present invention exhibit desired effects.
In particular, it was confirmed from a comparison between Examples 1 and 2 that the incident angle dependency of the reflectance was lower when the film thickness of the porous film was 2000 nm or more.
Further, from a comparison between Examples 1 and 4, it was confirmed that when the film thickness of the porous film is 3000 nm or more, the incident angle dependency of the reflectance is lower.
Further, from a comparison between Examples 1 and 3, it was confirmed that the incident angle dependency of the reflectance was lower when the hole area ratio of each region and the surface layer region hole area ratio were within predetermined ranges.
In Comparative Example 2, the film thickness of the porous film did not satisfy the predetermined requirements, and the incident angle dependency of the reflectance was large.
Moreover, Comparative Example 3 did not satisfy the predetermined requirements for the carbon ratio, and was inferior in haze.
In addition, Comparative Example 4 did not satisfy the predetermined requirements for the carbon ratio and did not satisfy the requirements of formula (1), was inferior in haze, and had a large dependence of the reflectance on the incident angle.

<Example 5>
An optical member was prepared in the same manner as in Example 1, except that an infrared absorbing layer-attached substrate, in which an infrared absorbing layer was provided in advance on a polycarbonate substrate, was used instead of the polycarbonate substrate. manufactured.

(Preparation of composition for forming infrared absorption layer)
-Preparation of Titanium Black A-1-
120 g of titanium oxide TTO-51N (trade name: manufactured by Ishihara Sangyo Co., Ltd.) having a BET specific surface area of 110 m ² /g, 25 g of silica particles AEROSIL 300 (registered trademark) 300/30 (manufactured by Evonik) having a BET surface area of 300 m ² /g, and 100 g of dispersant Disperbyk 190 (trade name: manufactured by BYK-Chemie) was weighed and mixed with 71 g of ion-exchanged water. Using MAZERSTAR KK-400W manufactured by KURABO, the mixture was treated for 30 minutes at a revolution speed of 1360 rpm and a rotation speed of 1047 rpm to obtain a uniform aqueous solution. This aqueous solution was filled in a quartz container and heated to 920° C. in an oxygen atmosphere using a small rotary kiln (manufactured by Motoyama Co., Ltd.). After that, the atmosphere in the small rotary kiln was replaced with nitrogen, and ammonia gas at the same temperature was flowed into the small rotary kiln at 100 mL/min for 5 hours to carry out nitriding reduction treatment. The powder recovered after completion was pulverized in a mortar to obtain titanium black (A-1) containing Si atoms, powdery, and having a specific surface area of 85 m ² /g.

-Preparation of titanium black dispersion (TB dispersion 1)-
Resin 2 represented by the following formula was obtained according to the production method described in paragraphs 0338 to 0340 of JP-A-2010-106268. Resin 2 had a weight average molecular weight of 40,000, an acid value of 100 mgKOH/g, and a graft chain of 117 atoms (excluding hydrogen atoms).

The components shown in composition I below were mixed for 15 minutes using a stirrer (EUROSTAR manufactured by IKA) to obtain a dispersion a.
(Composition I)
・The above titanium black (A-1): 25 parts by mass ・Propylene glycol monomethyl ether acetate 30% by mass solution of specific resin 2: 25 parts by mass ・Propylene glycol monomethyl ether acetate (PGMEA) (solvent): 23 parts by mass ・Butyl acetate (Solvent): 27 parts by mass

The obtained dispersion a was subjected to dispersion treatment using NPM-Pilot manufactured by Shinmaru Enterprises Co., Ltd. under the following conditions to obtain a titanium black dispersion (hereinafter referred to as TB dispersion 1). got

(Dispersion condition)
・Bead diameter: φ0.05 mm, made of zirconia ・Bead filling rate: 65% by volume
・Mill peripheral speed: 10m/sec
・ Separator peripheral speed: 11 m / s
・Amount of mixed liquid to be dispersed: 15 kg
・Circulation flow rate (pump supply amount): 60 kg/hour
・Processing liquid temperature: 19 to 21°C
・Cooling water: water ・Number of passes: 90 passes

-Preparation of composition for forming infrared absorption layer-
A composition for forming an infrared absorption layer was prepared by mixing the following components.
・TB dispersion liquid 1 43.4 parts by mass ・Cychromer P (ACA) 230AA (binder polymer; solid content 54%) manufactured by Daicel Chemical Industries, Ltd. 13.2 parts by mass ・KAYARAD DPHA manufactured by Nippon Kayaku Co., Ltd. (polymerization compound) 7.1 parts by mass KAYARAD RP-1040 (polymerizable compound) manufactured by Nippon Kayaku Co., Ltd. 7.1 parts by mass IRGACURE OXE02 (polymerization initiator) manufactured by Chibake Specialty Chemical Co., Ltd. 2.1 parts by mass 4-methoxy Phenol (polymerization inhibitor) 0.007 parts by mass ・DIC Corporation Megafac F781F (fluoropolymer type surfactant) 0.02 parts by mass ・Propylene glycol monomethyl ether acetate (solvent) 22.7 parts by mass ・Butyl acetate (solvent) 1.14 parts by mass Compound 1 (adherence agent) 1.14 parts by mass

(Preparation of substrate with infrared absorbing layer)
The obtained composition for forming an infrared absorbing layer is applied to the surface of a polycarbonate substrate (average thickness 0.5 mm) by a spin coater, and the resulting coating film is heated to 120°C using a hot plate at 100°C. Second heat treatment (pre-baking) was performed. Then, the coating film was exposed with an exposure amount of 1000 mJ/cm ² using an i-line stepper exposure apparatus FPA-3000i5+ (manufactured by Canon Inc.). After that, heat treatment (post-baking) was performed using a hot plate at 130° C. for 1 hour to form an infrared absorbing layer having a thickness of 3.5 μm, thereby producing a substrate with an infrared absorbing layer.

REFERENCE SIGNS LIST 10 optical member 12 base material 14 porous film

Claims (5)

a base material;
an optical member comprising a porous film containing silica disposed on the substrate,
The film thickness of the porous film is 1000 nm or more,
When observing the cross section of the porous membrane, the position of 20% of the total thickness of the porous membrane is deepened from the surface of the porous membrane opposite to the substrate side toward the substrate side. depth position D20, 40% of the total thickness of the porous membrane is the depth position D40, 60% of the total thickness of the porous membrane is the depth position D60, and 80% of the total thickness of the porous membrane. The depth position of is D80, the region from the surface of the porous membrane opposite to the substrate side to the depth position D20 is region A, and the region from the depth position D20 to the depth position D40 a region B, a region from the depth position D40 to the depth position D60 as a region C, a region from the depth position D60 to the depth position D80 as a region D, and from the depth position D80 to the porous film When the region to the surface on the substrate side is defined as region E, the hole area ratio A in the region A, the hole area ratio B in the region B, the hole area ratio C in the region C, the hole in the region D The area ratio D and the hole area ratio E in the region E satisfy the relationship of formula (1),
Formula (1): said pore area ratio A> said pore area ratio B> said pore area ratio C> said pore area ratio D> said pore area ratio E
When observing the cross section of the porous membrane, when the position of 100 nm from the surface of the porous membrane opposite to the substrate side toward the substrate side is set to a depth position D of 100 nm, the The pore area ratio in the region from the surface of the porous membrane opposite to the substrate side to the depth position D100 nm is 80 to 95%,
From the surface of the porous membrane on the substrate side to the porous An optical member, wherein the ratio of the proportion of carbon atoms at a depth position of 100 nm toward the surface side of the film opposite to the substrate side is 5.0 or more. 2. The optical member according to claim 1, wherein the film thickness of said porous film is 2000 nm or more. 3. The optical member according to claim 1, wherein the porous film has an average pore size of 20 to 400 nm. The optical member according to any one of claims 1 to 3, wherein the base material contains an infrared absorbing material. A sensor comprising the optical member according to any one of claims 1 to 4.