JP2024038311A - Optical member and protection method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical member having an adhesive film pasted thereon and being capable of suppressing deterioration of hydrophilicity on a surface thereof even when stored under a high-temperature, high-humidity environment.

SOLUTION: An optical member comprises, on a substrate, a lower-layer hydrophilic film, a hydrophilic polymer, and an upper-layer silica particle film in this order, where the upper-layer silica particle film contains silica particles formed of silicon dioxide, has a refractive index of 1.22 to 1.23 for light having a wavelength of 500 nm, and has a film thickness of 400 nm to 800 nm.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to an optical member using a hydrophilic porous silica membrane and a method for protecting the optical member.

Currently, surveillance cameras are used for crime prevention purposes in various places such as stores, hotels, banks, and stations. A camera cover is attached to the surveillance camera body for the purpose of protection from various environments. Materials such as acrylic resin and polycarbonate resin are used for camera covers from the viewpoint of transparency and impact resistance.

Surveillance cameras are often installed outdoors, and during rainy weather, water droplets adhere to the camera cover in the form of spheres, adversely affecting captured images. Therefore, a technique is known in which a hydrophilic film is formed on the surface of a camera cover to turn water droplets into a liquid film even when water droplets adhere to the camera cover, thereby reducing the adverse effect on captured images in rainy weather.

Products with a hydrophilic film formed on their surfaces, such as the camera cover described above, are packaged and stored from the time they are manufactured at a factory until they are installed outdoors. It is known that during storage, hydrophobic contaminants such as siloxane compounds are adsorbed onto the surface of the camera cover, resulting in a decrease in hydrophilicity. Furthermore, if the surface of the product is scratched due to handling before being installed outdoors, the scratches will increase light scattering and reduce the optical performance of the product.

Patent Document 1 describes a method of applying a water-soluble coating agent as a protective film on a hydrophilic member in order to protect the hydrophilic member from deterioration of surface hydrophilicity and generation of scratches during storage. ing. Moreover, Patent Document 1 further describes an invention in which a protective film on a hydrophilic member is covered with a protective film such as high-quality paper.

Japanese Patent Application Publication No. 2002-46225

The protective film and protective film described in Patent Document 1 have a problem in that they cannot sufficiently prevent the adsorption of hydrophobic contaminants and the occurrence of scratches on the surface of the hydrophilic member when stored in a high temperature and high humidity environment. .

The present invention provides an optical member that can suppress a decrease in hydrophilicity on the surface of the optical member even when an adhesive film is attached as a protective film on the optical member and the optical member is stored in a high-temperature, high-humidity environment. The purpose is to provide. Another object of the present invention is to provide a method for protecting an optical member that can suppress a decrease in hydrophilicity on the surface of the optical member even when the manufactured optical member is stored in a high-temperature, high-humidity environment.

The above problems are solved by the following invention. That is, the optical member according to the present invention has a lower hydrophilic film, a hydrophilic polymer layer, and an upper silica particle film in this order on a base material, and the upper silica particle film contains silica particles made of silicon dioxide. The upper silica particle film has a refractive index of 1.22 or more and 1.23 or less for light having a wavelength of 500 nm, and the upper silica particle film has a thickness of 400 nm or more and 800 nm or less.

Moreover, the method for protecting an optical member according to the present invention is characterized in that it includes pasting an adhesive film as a protective film on the optical member.

According to one aspect of the present invention, it is possible to suppress a decrease in hydrophilicity on the surface of the optical member even when an adhesive film is attached as a protective film on the optical member and stored in a high temperature and high humidity environment. A possible optical member can be provided. In addition, according to another aspect of the present invention, protection of an optical member that can suppress a decrease in hydrophilicity on the surface of the optical member even when the manufactured optical member is stored in a high temperature and high humidity environment. method can be provided.

FIG. 1 is a schematic diagram showing an embodiment of an optical member according to the present invention. FIG. 3 is a diagram showing the relationship between the contact angle of the surface of the optical member with water and the thickness of the upper layer silica particle film in a region in close contact with the adhesive film. FIG. 3 is a diagram showing the relationship between the contact angle of the surface of the optical member with water and the thickness of the upper layer silica particle film in a region where the adhesive film is not in close contact with the surface of the optical member.

Patent Document 1 describes coating a hydrophilic member with a polymer having hydrophilic properties. As a result, during the storage period of the hydrophilic member after manufacture, the hydrophilic polymer layer acts as a barrier, and adsorption of hydrophobic contaminants to the hydrophilic member is suppressed. Further, by further pasting a protective film on the hydrophilic polymer and storing the hydrophilic member, it is possible to suppress the occurrence of scratches on the surface of the hydrophilic member.

However, protective films cannot be applied without gaps to parts that are not flat, such as dome-shaped or ribbed parts such as camera covers, and there are spaces between the surface of the part and the protective film. . Therefore, the protective film formed of a hydrophilic polymer comes into contact with the outside air in a portion including a space between the surface of the member and the protective film.

According to studies conducted by the present inventors, the fluidity of hydrophilic polymers increases in high temperature and high humidity environments, and uneven thickness of the protective film formed from hydrophilic polymers occurs in areas where the protective film comes into contact with the outside air. There was a case. Therefore, in areas where the film thickness is reduced, adsorption of hydrophobic contaminants to the surface of the hydrophilic member may not be sufficiently prevented in some cases.

Furthermore, from the viewpoint of simplicity, it is preferable that the protective film be an adhesive film that is pasted through an adhesive material, but if the hydrophilic polymer layer is thin, it may be difficult to protect the film from hydrophobic substances emitted from the adhesive film or from the adhesive material. Contamination of the hydrophilic member cannot be sufficiently prevented. Furthermore, when the hydrophilic polymer layer is thick, the adhesive film may peel off in a high temperature and high humidity environment.

As a result of extensive studies, the present inventors have found that by using the optical member according to the present invention, an adhesive film as a protective film is pasted on the optical member, and even when stored in a high temperature and high humidity environment, the optical member It has been found that the decrease in hydrophilicity on the surface of the member can be suppressed.

The present invention will be explained in detail below.
[Optical member]
FIG. 1 is a schematic diagram showing one embodiment of an optical member according to the present invention. The optical member 10 according to the present invention has a lower hydrophilic film 1, a hydrophilic polymer layer 15, and an upper silica particle film 2 on a base material 14 in this order.

As shown in FIG. 1, in the present invention, the optical member further has an upper layer silica particle film 2 on a hydrophilic polymer layer 15. As shown in FIG. Therefore, the fluidity of the hydrophilic polymer increases in a high-temperature, high-humidity environment, and it is possible to suppress the occurrence of film thickness unevenness due to this increase.

When an adhesive film as a protective film is attached to the optical member 10 and stored, the portion where the adhesive film is in close contact with the upper silica particle film 2 is contaminated by hydrophobic contaminants and adhesive material emitted from the adhesive film. . However, when the adhesive film is peeled off and the optical member 10 is used, a portion of the upper silica particle film 2 contaminated by hydrophobic contaminants and adhesive material is removed together with the adhesive film. Thereby, the surface of the optical member 10 can be maintained in a highly hydrophilic state.

The thickness of the upper layer silica particle film 2 is 400 nm or more and 800 nm or less. By having a film thickness of 400 nm or more, even when the optical member 10 is stored with the adhesive film attached, it is possible to prevent hydrophobic contaminants and adhesive material emitted from the adhesive film from contaminating the lower hydrophilic film 1. . Further, by having a film thickness of 800 nm or less, an increase in haze of the optical member 10 due to the provision of the upper layer silica particle film 2 can be suppressed.

Further, the refractive index of the upper layer silica particle film 2 for light having a wavelength of 500 nm is 1.22 or more and 1.23 or less. The refractive index correlates with the proportion of voids 13 contained in the upper silica particle film 2. Since the air contained in the voids 13 (refractive index of 1.0) is lower than the refractive index of the silica particles 12, the percentage of voids is small, and the silica particles 12 of the upper silica particle film 2 and the binder 11 are tightly bonded to each other. The higher the refractive index of the upper silica particle film 2 becomes. If the refractive index of the upper layer silica particle film 2 for light having a wavelength of 500 nm is 1.22 or more, the density of the upper layer silica particle film 2 is sufficiently high, and the fluidity of the hydrophilic polymer increases in a high temperature and high humidity environment. By doing so, it is possible to suppress the occurrence of film thickness unevenness. Moreover, if the refractive index of the upper layer silica particle film 2 for light having a wavelength of 500 nm is 1.23 or less, the density of the upper layer silica particle film 2 will not become too high. Therefore, when the adhesive film is peeled off, a portion of the upper silica particle film 2 contaminated by hydrophobic contaminants and adhesive can be removed together with the adhesive film.

As mentioned above, an adhesive film cannot be applied to an optical member that is not flat, for example, an optical member that has a dome shape or a shape with ribs, such as a camera cover, without any gaps over the entire surface. Therefore, when an adhesive film is attached to an optical component and stored in a high-temperature, high-humidity environment, the decrease in hydrophilicity is suppressed both in areas where the adhesive film is in close contact with the surface of the optical component and in areas where it is not. There is a need.

Therefore, the present inventors applied an adhesive film to the surface of an optical member and stored it in a high-temperature, high-humidity environment, and then identified areas on the surface of the optical member where the film was in close contact and areas where the film was floating and not in close contact. A test was conducted to evaluate the hydrophilicity of each of these.

In the test, the optical member with the adhesive film attached to the surface was stored for 286 hours in a high temperature and high humidity environment of 60° C. and 90%. Subsequently, after peeling off the adhesive film, hydrophilicity was evaluated by measuring the contact angle of the surface of the optical member with respect to water. Specifically, the contact angle of the surface of the optical member with water is preferably 30 degrees or less.

FIG. 2 is a diagram showing the relationship between the contact angle of the surface of the optical member with water and the thickness of the upper layer silica particle film in the area where the adhesive film is in close contact. FIG. 2 shows a substrate having a lower hydrophilic film, a hydrophilic polymer layer, and an upper silica particle film in this order, and the upper silica particle film has a refractive index of 1.22, 1.23, and 1, respectively. .24 is shown.

In the optical member with a refractive index of 1.22 and the optical member with a refractive index of 1.23, the contact angle decreased as the film thickness increased. In particular, for an optical member with a refractive index of 1.22, the contact angle was 30 degrees or less when the film thickness was 300 nm or more. Further, in an optical member having a refractive index of 1.23, the contact angle was 30 degrees or less when the film thickness was 150 nm or more. On the other hand, in the case of an optical member having a refractive index of 1.24, the contact angle was approximately 60 degrees regardless of the film thickness.

In areas where the adhesive film is in close contact, the adhesive of the adhesive film flows during storage in a high temperature and high humidity environment, filling the irregularities and voids in the upper silica particle film. As a result, the adhesion between the adhesive film and the upper silica particle film increases. As described above, when the adhesive film is peeled off, the silica particles in the area where the hydrophobic contaminants from the adhesive and the adhesive film have permeated are also peeled off. As a result, silica particles that have not penetrated the adhesive and hydrophobic contaminants appear on the surface, and it is thought that the hydrophilicity of the surface of the optical member can be maintained.

However, in an optical member having an upper layer silica particle film with a refractive index of 1.24, the interparticle bonding force is greater than in an optical member having an upper layer silica particle film with a refractive index of 1.22 and 1.23, respectively. . Therefore, when the adhesive film was peeled off, the particle film to which the adhesive was adsorbed was not peeled off together with the adhesive film and remained as it was, and as a result, the contact angle with water on the surface of the optical member became large.

Furthermore, even in optical members having upper layer silica particle films with refractive indexes of 1.22 and 1.23, respectively, when the thickness of the upper layer silica particle film is small, the value of the contact angle becomes large. This is considered to be due to the fact that when the film thickness is small, the adhesive and hydrophobic contaminants from the adhesive film permeate the upper silica particle film and reach the hydrophilic polymer layer and the lower hydrophilic film. That is, when the thin upper silica particle film is removed together with the adhesive film, the lower hydrophilic film partially appears on the surface of the optical member due to uneven thickness of the hydrophilic polymer layer or highly fluid hydrophilic polymer layer. Conceivable. At this time, if the thickness of the upper layer silica particle film is small, the hydrophilic polymer layer and the lower layer hydrophilic film are contaminated with adhesive and hydrophobic contaminants, resulting in the surface of the optical component after the adhesive film is peeled off. It is thought that the value of the contact angle at was increased.

FIG. 3 is a diagram showing the relationship between the contact angle of the surface of the optical member with water and the thickness of the upper layer silica particle film in a region where the adhesive film is not in close contact with the surface of the optical member. In FIG. 3, a lower hydrophilic film, a hydrophilic polymer layer, and an upper silica particle film are provided in this order on a base material, and the upper silica particle film has refractive indexes of 1.22 and 1.23, respectively. The results of tests on optical members are shown. Further, FIG. 3 further shows that the substrate does not have a hydrophilic polymer layer, but has a lower hydrophilic film and an upper silica particle film in this order on the base material, and the upper silica particle film has a refractive index of 1.22. The results of testing a certain optical member are also shown.

In all optical members, the change in contact angle value with respect to the film thickness of the upper layer silica particle film was small. In all of the optical members having the configuration shown in FIG. 1, the contact angle was less than 30 degrees, whereas in the optical member without a hydrophilic polymer layer, the contact angle was greater than 40 degrees.

In non-adhesive areas where the adhesive film is floating, hydrophobic contaminants such as siloxane compounds generated from the adhesive film will be adsorbed to the surface of the optical component during storage in high temperature and high humidity environments, causing a decrease in hydrophilicity. . Hydrophobic contaminants such as siloxane compounds have a tendency to be particularly easily adsorbed onto silica.

Both the optical member having the configuration shown in FIG. 1 and the optical member having the configuration shown in FIG. 1 that does not have the hydrophilic polymer layer 15 have the upper layer silica particle film 2 on the surface. Therefore, it seems that the degree to which hydrophobic contaminants are adsorbed to any optical member is the same. However, according to the test results, the contact angle value of the optical member having the hydrophilic polymer layer 15 was smaller than that of the optical member not having the hydrophilic polymer layer 15. The reason for this is thought to be as follows.

In manufacturing the optical member having the configuration shown in FIG. 1, when forming the upper layer silica particle film 2 on the hydrophilic polymer layer 15, a portion of the hydrophilic polymer diffuses into the upper layer silica particle film. Hydrophobic contaminants are easily adsorbed on silica particles, but are less adsorbed on hydrophilic polymers. Therefore, it is considered that a portion of the hydrophilic polymer diffused into the upper layer silica particle film suppressed the adsorption of hydrophobic contaminants to the surface of the optical member.

Each component of the optical member 10 will be described in detail below.
(Base material)
The material of the base material 14 preferably includes acrylic resin, polycarbonate resin, and the like. Further, the shape of the base material 14 is not limited, and may be a flat surface, a curved surface, or a dome shape.

(hydrophilic membrane)
The hydrophilic film is formed by laminating a lower hydrophilic film 1, a hydrophilic polymer layer 15, and an upper silica particle film 2 in this order on a base material 14.

The upper layer silica particle film 2 contains silica particles 12 made of silicon dioxide (silica). Moreover, it is preferable that the lower hydrophilic film 1 contains silica particles 12 made of silicon dioxide (silica). The contact point between the silica particles 12 may be a portion where the silica particles 12 are directly bonded to each other, or may be a portion where the silica particles 12 are bonded to each other via the binder 11.

Further, when the upper silica particle film 2 and the lower hydrophilic film 1 contain silica particles 12, the lower hydrophilic film 1 has voids 13 between the silica particles 12. Due to the air (refractive index 1.0) contained in the voids 13, the refractive index of the film is lower than that of the constituent material of the film other than the voids. The void 13 may be a single hole or a communicating hole. The proportion of voids 13 in the lower hydrophilic film 1 and the upper silica particle film 2 is determined by the ratio of the silica particles 12 to the binder 11.

The thickness of the lower hydrophilic film 1 is preferably 350 nm or more and 900 nm or less. Further, the refractive index of the lower hydrophilic film 1 for light having a wavelength of 500 nm is preferably 1.23 or more and 1.26 or less. If the thickness and refractive index of the lower hydrophilic film 1 are within the above ranges, the optical member 10 will be protected even if the hydrophilic polymer layer 15 is washed away and removed due to water wetting when the optical member 10 is used outdoors. It functions well as a hydrophilic membrane.

The hydrophilic polymer layer 15 preferably contains an acrylic polymer (hereinafter also referred to as "water-soluble polymer") having a silanol group at one end of a polymer of an acrylic monomer having a hydrophilic group.

In forming the hydrophilic polymer layer 15, an aqueous solution containing a water-soluble polymer is coated on the lower hydrophilic film 1 and baked, so that the terminal silanol groups are condensed with the silanol of the silica particles, and the polymer is immobilized. It becomes a hydrophilic polymer brush. Furthermore, when forming the upper layer silica particle film, a portion of the water-soluble polymer diffuses into the upper layer silica particle film, forming a hydrophilic polymer brush also within the upper layer silica particle film. This suppresses adsorption of hydrophobic contaminants to the upper silica particle film.

The water-soluble polymer preferably has an amphoteric hydrophilic group. Examples of the amphoteric hydrophilic group include a sulfobetaine group, a carboxybetaine group, and a phosphobetaine group.

The thickness of the hydrophilic polymer layer 15 is preferably 5 nm or more and 100 nm or less.
If the thickness is 5 nm or more, it can be highly effective in suppressing the adhesion of hydrophobic contaminants, and if the thickness is 100 nm or less, it can increase the fluidity of hydrophilic polymers in high temperature and high humidity environments. Concomitant problems such as peeling of the upper silica particle film can be suppressed.

The thickness of the hydrophilic polymer layer is defined as the thickness of the part consisting only of the hydrophilic polymer and the thickness of the part where the hydrophilic polymer penetrates and the hydrophilic polymer layer overlaps with the lower hydrophilic film and the upper silica particle film. It is a combination. In addition, from the results shown in FIG. 3, it is considered that a part of the hydrophilic polymer diffuses within the upper silica particle film until reaching the surface. However, it is thought that the amount of hydrophilic polymer that has diffused to reach the surface layer is extremely small. In other words, the upper layer silica particle film contains a part where the hydrophilic polymer is densely permeated and is included as the thickness of the hydrophilic polymer layer, and a part where the hydrophilic polymer is further diffused in a very small amount from there, but the part of the hydrophilic polymer layer is It is considered that the thickness includes two parts: a part that is not included in the thickness.

As mentioned above, the thickness of the upper layer silica particle film 2 is 400 nm or more and 800 nm or less. Further, the refractive index of the upper silica particle film 2 for light having a wavelength of 500 nm is 1.22 or more and 1.23 or less. The refractive index of the upper layer silica particle film is determined by spectroscopy after forming the upper layer silica particle film on a silicon substrate for checking the refractive index of the upper layer silica particle film prepared separately from the actual product under the same coating conditions as the actual product. This is a value measured with an ellipsometer.

The thicknesses of the upper silica particle film, the hydrophilic polymer layer, and the lower hydrophilic film can be measured as follows.

First, a cross section of the hydrophilic film was observed using a scanning transmission electron microscope (S-TEM), and the areas of the upper silica particle film, hydrophilic polymer layer, and lower hydrophilic film were determined from the contrast differences in bright field images (BF images). Certify. The upper silica particle film and the lower hydrophilic film can be determined by measuring the thickness of each certified area.

Regarding the thickness of the hydrophilic polymer layer, first, based on the above-mentioned difference in contrast, the thickness of the region (dark region) containing only the hydrophilic polymer is measured. In addition, the C element is mapped on each cross section of the lower hydrophilic film and the upper silica particle film by energy dispersive X-ray spectroscopy (TEM-EDS), and the thickness of the region containing the C element is measured. Thereby, the thickness of the portion where the hydrophilic polymer layer overlaps with the lower hydrophilic film and the upper silica particle film is determined. Next, the thickness of the portion containing only the hydrophilic polymer determined above and the thickness of the portion where the hydrophilic polymer layer overlaps with the lower hydrophilic film and the upper silica particle film are added up to determine the thickness of the hydrophilic polymer layer. Thickness.

(Silica particles)
The average particle diameter of the silica particles 12 contained in the upper layer silica particle film 2 is preferably 10 nm or more and 20 nm or less. The density of the upper layer silica particle film 2 can be suitably adjusted because the average particle diameter of the silica particles 12 is 10 nm or more and 20 nm or less.

Moreover, when the lower hydrophilic film 1 contains the silica particles 12, the average particle diameter of the silica particles 12 is preferably 10 nm or more and 60 nm or less. If the average particle size of the silica particles 12 is 10 nm or more, the particles will not be densely arranged, a desired porosity can be achieved, and hydrophobic contaminants can be diffused (absorbed) into the film during outdoor exposure. Hydrophilicity can be maintained for a long period of time. Furthermore, if the average particle size of the silica particles 12 is 60 nm or less, the voids between the particles will not become too large, and light scattering caused by the particles themselves can be suppressed.

The shape of the silica particles 12 may be spherical or chain-like (an average of 2 to 8 spherical particles connected irregularly). When the silica particles 12 are chain-shaped, the spherical particles forming the chain may have an average particle diameter within the above-mentioned preferred range. Examples of the silica particles 12 include IPA-ST-30 (registered trademark), IPA-ST-O (registered trademark), Snowtex (registered trademark)-UP, IPA-ST-UP (registered trademark), and MEK-ST. -UP (registered trademark) (all manufactured by Nissan Chemical Co., Ltd.), etc.

The average particle diameter of the silica particles and how many spherical particles are made up of chain-like silica particles can be determined as follows. That is, first, the particle diameter and the number of consecutive spherical particles are measured for 50 or more silica particles 12 in the field of view of a transmission electron microscope image. Next, the average value of the measured values is determined.

(binder)
The lower hydrophilic film 1 includes a binder 11. Further, the upper layer silica particle film 2 may contain a binder 11. When the upper layer silica particle film 2 contains the binder 11 , it is preferable that the contact points between the silica particles 12 include contacts bonded by the binder 11 . Increasing the ratio of binder 11 to silica particles 12 reduces the porosity in the film and increases the film density.

It is preferable to use a material for the binder 11 that forms a siloxane bond with the silica particles 12 to bond the silica particles 12 together. As a material that forms siloxane bonds with the silica particles 12, a solution containing a hydrolyzed condensate of alkoxysilane can be used. A solution containing a hydrolyzed condensate of alkoxysilane can be prepared by hydrolyzing alkoxysilane and then condensing it.

Since alkoxysilane, which is a precursor of a hydrolyzed condensate of alkoxysilane, is not compatible with water, two layers of alkoxysilane and water are separated at the initial stage of the reaction. As the reaction progresses, the alkoxysilane becomes silanol due to hydrolysis of the alkoxy group and is dissolved in the aqueous layer, so that it is mixed uniformly.

In order to prepare a solution containing a hydrolyzed condensate of alkoxysilane, it is preferable to use 5 to 20 equivalents of water relative to the alkoxysilane. An acid or base may be added as a catalyst to promote hydrolysis. As the catalyst, a catalyst containing one or more acids or bases selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, ammonia, phosphinic acid, and phosphonic acid may be used at a concentration of 1% by mass or less. preferable.

The degree of progress of the hydrolysis and condensation reaction of alkoxysilane can be evaluated based on the average particle size of the hydrolyzed condensate of alkoxysilane. The average particle diameter of the hydrolyzed condensate of alkoxysilane is preferably 8 nm or more and 30 nm or less when a reaction solution containing alkoxysilane and water is measured by a dynamic light scattering method. Further, the average particle diameter is more preferably 8 nm or more and 15 nm or less.

[Method for manufacturing optical members]
Next, an example of a method for manufacturing an optical member according to the present invention will be described.
First, the lower hydrophilic film 1 is formed on the base material 14. In forming the lower hydrophilic film 1, first, a dispersion containing a solution containing components necessary for forming the binder 11, silica particles, and a solvent is applied onto the base material 14. Thereafter, the base material coated with the dispersion liquid is dried. As a result, the lower hydrophilic film 1 in which the silica particles 12 are bound together by the binder 11 is formed.

Next, a coating liquid for forming a hydrophilic polymer layer is applied onto the lower hydrophilic film 1 and dried.

Subsequently, on the layer of the coating liquid for forming the dried hydrophilic polymer layer, a solution containing silica particles, a solvent, and, if necessary, components necessary for forming the binder 11 is added. Apply the dispersion liquid. Thereafter, the base material coated with the dispersion liquid is dried. Thereby, an upper layer silica particle film is formed and an optical member according to the present invention is obtained.

The dispersion containing silica particles and the coating liquid for forming the hydrophilic polymer layer are applied using known methods such as dip coating, spin coating, spray coating, slit coating, and printing. be able to. For drying, a dryer, hot plate, electric furnace, etc. can be used. The drying conditions for the dispersion containing silica particles are such that the temperature and time are such that the solvent not coordinated with the silica particles contained in the lower hydrophilic film 1 and the upper silica particle film 2 can be vaporized without affecting the base material. do. Generally, it is preferable to use a temperature of 150° C. or lower. Further, the coating solution for forming the hydrophilic polymer layer can be dried by heating at 90° C. for 15 minutes in a hot air circulating oven, for example.

[How to protect optical components]
A method for protecting an optical member according to another aspect of the present invention includes applying an adhesive film as a protective film on the optical member described above.

The adhesive included in the adhesive film may be elastomer-based, rubber-based, acrylic-based, or silicone-based. Further, the film base material of the adhesive film may be polypropylene or polyethylene.

Examples of the adhesive film used as a protective film include Aptec AF-012R (registered trademark) (manufactured by Shikoku Kako), EC-755 (registered trademark) (manufactured by Sumilon), and Hishibopetak M-11 (registered trademark) (Ichiji Hayashi). ), etc.

Hereinafter, the present invention will be specifically explained with reference to Examples. However, the present invention is not limited to such embodiments.
A dispersion containing silica particles and a coating solution for forming a hydrophilic polymer layer were prepared in the following manner.

(a) Preparation of dispersion containing silica particles (Dispersion 1)
IPA was removed by an evaporator from a 2-propanol (IPA) dispersion of silica particles in which spherical silica particles were connected in a chain, and then the silica particles were dispersed in 1-ethoxy-2-propanol as a solvent. In this way, a 1-ethoxy-2-propanol dispersion of silica particles (solid content concentration 31.07 wt%) was prepared. As the IPA dispersion of silica particles, IPA-ST-UP (registered trademark) (manufactured by Nissan Chemical Co., Ltd.) with a particle diameter of 40 to 100 nm as measured by dynamic light scattering and a solid content concentration of 15 wt% was used.

54 g of 0.01 mol/L diluted hydrochloric acid was gradually added to a solution of 62.6 g of ethyl silicate and 36.8 g of 1-ethoxy-2-propanol, and the mixture was stirred at room temperature for 5 hours to give a solid concentration of 11.8% by mass. A binder solution was prepared.

8.90 g of 1-ethoxy-2-propanol was added to 9.01 g of the 1-ethoxy-2-propanol dispersion of silica particles, and 2.37 g of the above binder solution was gradually added, followed by stirring at room temperature for 2 hours. A dispersion liquid 1 of silica particles was prepared.

(Dispersion liquid 2)
IPA was removed from the IPA dispersion of spherical silica particles using an evaporator, and then the silica particles were dispersed in 1-ethoxy-2-propanol as a solvent. In this way, a 1-ethoxy-2-propanol dispersion of silica particles (solid content concentration 31.07 wt%) was prepared. IPA-ST-30 (registered trademark) (manufactured by Nissan Chemical Co., Ltd.) having an average particle diameter of 12 nm and a solid content concentration of 15 wt% was used as the IPA dispersion of silica particles.

14.21 g of 1-ethoxy-2-propanol was added to 5.79 g of the obtained 1-ethoxy-2-propanol dispersion of silica particles, and the mixture was stirred at room temperature for 2 hours to prepare a silica particle dispersion 2.

(Dispersion liquid 3)
IPA was removed from the IPA dispersion of spherical silica particles using an evaporator, and then the silica particles were dispersed in 1-ethoxy-2-propanol as a solvent. In this way, a 1-ethoxy-2-propanol dispersion of silica particles (solid content concentration 31.07 wt%) was prepared. IPA-ST-30 (registered trademark) (manufactured by Nissan Chemical Co., Ltd.) having an average particle diameter of 12 nm and a solid content concentration of 15 wt% was used as the IPA dispersion of silica particles.

10.02 g of 1-ethoxy-2-propanol was added to 9.98 g of the obtained 1-ethoxy-2-propanol dispersion of silica particles, and the mixture was stirred at room temperature for 2 hours to prepare a dispersion 3 of silica particles.

(Dispersion liquid 4)
IPA was removed from the IPA dispersion of spherical silica particles using an evaporator, and then the silica particles were dispersed in 1-ethoxy-2-propanol as a solvent. In this way, a 1-ethoxy-2-propanol dispersion of silica particles (solid content concentration 31.07 wt%) was prepared. IPA-ST-30 (registered trademark) (manufactured by Nissan Chemical Co., Ltd.) having an average particle diameter of 12 nm and a solid content concentration of 15 wt% was used as the IPA dispersion of spherical particles.

13.67 g of 1-ethoxy-2-propanol was added to 5.79 g of the obtained 1-ethoxy-2-propanol dispersion of silica particles, and 0.61 g of the binder solution was gradually added, followed by 2 hours at room temperature. A dispersion liquid 4 of silica particles was prepared by stirring.

The binder solution used here was prepared as follows. That is, 54 g of 0.01 mol/L dilute hydrochloric acid was gradually added to a solution of 62.6 g of ethyl silicate and 36.8 g of 1-ethoxy-2-propanol, and the mixture was stirred at room temperature for 5 hours to obtain a solid concentration of 11.8 mass. % binder solution was prepared.

(Dispersion liquid 5)
IPA was removed from the IPA dispersion of spherical silica particles using an evaporator, and then the silica particles were dispersed in 1-ethoxy-2-propanol as a solvent. In this way, a 1-ethoxy-2-propanol dispersion of silica particles (solid content concentration 31.07 wt%) was prepared. IPA-ST-30 (registered trademark) (manufactured by Nissan Chemical Co., Ltd.) having an average particle diameter of 12 nm and a solid content concentration of 15 wt% was used as the IPA dispersion of silica particles.

9.10 g of 1-ethoxy-2-propanol was added to 9.98 g of the obtained 1-ethoxy-2-propanol dispersion of silica particles, and 1.05 g of the binder solution was gradually added, followed by 2 hours at room temperature. A dispersion liquid 5 of silica particles was prepared by stirring.

The binder solution used here was prepared as follows. That is, 54 g of 0.01 mol/L dilute hydrochloric acid was gradually added to a solution of 62.6 g of ethyl silicate and 36.8 g of 1-ethoxy-2-propanol, and the mixture was stirred at room temperature for 5 hours to obtain a solid concentration of 11.8 mass. % binder solution was prepared.

(Dispersion liquid 6)
IPA was removed from the IPA dispersion of spherical silica particles using an evaporator, and then the silica particles were dispersed in 1-ethoxy-2-propanol as a solvent. In this way, a 1-ethoxy-2-propanol dispersion of silica particles (solid content concentration 31.07 wt%) was prepared. IPA-ST-30 (registered trademark) (manufactured by Nissan Chemical Co., Ltd.) having an average particle diameter of 12 nm and a solid content concentration of 15 wt% was used as the IPA dispersion of silica particles.

8.74 g of 1-ethoxy-2-propanol was added to 11.26 g of the obtained 1-ethoxy-2-propanol dispersion of silica particles, and the mixture was stirred at room temperature for 2 hours to prepare silica particle dispersion 6.

(Dispersion liquid 7)
IPA was removed from the IPA dispersion of spherical silica particles using an evaporator, and then the silica particles were dispersed in 1-ethoxy-2-propanol as a solvent. In this way, a 1-ethoxy-2-propanol dispersion of silica particles (solid content concentration 31.07 wt%) was prepared. IPA-ST-30 (registered trademark) (manufactured by Nissan Chemical Co., Ltd.) having an average particle diameter of 12 nm and a solid content concentration of 15 wt% was used as the IPA dispersion of silica particles.

13.13 g of 1-ethoxy-2-propanol was added to 5.79 g of the obtained 1-ethoxy-2-propanol dispersion of silica particles, and 1.22 g of the binder solution was gradually added, followed by 2 hours at room temperature. A dispersion liquid 7 of silica particles was prepared by stirring.

The binder solution used here was prepared as follows. That is, 54 g of 0.01 mol/L dilute hydrochloric acid was gradually added to a solution of 62.6 g of ethyl silicate and 36.8 g of 1-ethoxy-2-propanol, and the mixture was stirred at room temperature for 5 hours to obtain a solid concentration of 11.8 mass. % binder solution was prepared.

(b) Preparation of coating liquid for forming a hydrophilic polymer layer Add 50 g of pure water to 50 g of LAMBIC-771W (manufactured by Osaka Organic Chemical Industry Co., Ltd.), which is an aqueous solution of an acrylic polymer having a sulfobetaine group, to dilute it. A coating solution for forming a hydrophilic polymer layer was prepared by stirring at room temperature for 10 minutes.

Optical members according to the following Examples and Comparative Examples were produced using the above-mentioned dispersion liquid and coating liquid for forming a hydrophilic polymer layer.

(Example 1)
Two substrates were used: a polycarbonate substrate (nd=1.58, vd=30.2) with a diameter (φ) of 50 mm and a thickness of 4 mm, and a silicon substrate with a diameter of 3 inches. Optical members fabricated using polycarbonate substrates were used to evaluate the hydrophilicity and haze of the optical member surfaces after being stored in a high-temperature, high-humidity environment. Further, only the upper layer silica particle film was formed on the silicon substrate, and the resulting member was used to measure the film thickness and refractive index of the upper layer silica particle film.

0.4 mL of dispersion liquid 1 was dropped onto a polycarbonate substrate, and spin coating was performed at 1500 rpm for 30 seconds. Thereafter, it was heated at 90° C. for 15 minutes in a hot air circulation oven. 0.4 mL of a coating solution for forming a hydrophilic polymer layer was dropped, and spin coating was performed at 2000 rpm for 20 seconds. Thereafter, it was heated at 90° C. for 15 minutes in a hot air circulation oven. Subsequently, 0.4 mL of dispersion liquid 2 was dropped and spin coating was performed at 1500 rpm for 30 seconds. Thereafter, it was heated at 90° C. for 15 minutes in a hot air circulation oven to produce an optical member.

Further, 0.4 mL of dispersion liquid 2 was dropped onto the silicon substrate and spin coating was performed at 1500 rpm for 30 seconds. Thereafter, it was heated in a hot air circulation oven at 90° C. for 15 minutes to prepare a substrate for measuring the thickness and refractive index of the upper silica particle film.

(Example 2)
An optical member and a substrate for measuring the thickness and refractive index of the upper silica particle film were prepared in the same manner as in Example 1, except that Dispersion 3 was used instead of Dispersion 2.

(Example 3)
An optical member and a substrate for measuring the thickness and refractive index of the upper silica particle film were prepared in the same manner as in Example 1, except that Dispersion 4 was used instead of Dispersion 2.

(Example 4)
An optical member and a substrate for measuring the thickness and refractive index of the upper silica particle film were prepared in the same manner as in Example 1, except that Dispersion 5 was used instead of Dispersion 2.

(Comparative example 1)
An optical member and a substrate for measuring the thickness of the upper silica particle film and the refractive index were prepared in the same manner as in Example 1 except that the hydrophilic polymer film was not formed.

(Comparative example 2)
An optical member and a substrate for measuring the thickness of the upper silica particle film and the refractive index were prepared in the same manner as in Example 2, except that the hydrophilic polymer film was not formed.

(Comparative example 3)
An optical member and a substrate for measuring the thickness and refractive index of the upper silica particle film were prepared in the same manner as in Example 1, except that Dispersion 6 was used instead of Dispersion 2.

(Comparative example 4)
An optical member and a substrate for measuring the thickness and refractive index of the upper silica particle film were prepared in the same manner as in Example 1, except that Dispersion 7 was used instead of Dispersion 2.

[Evaluation of optical members]
The optical members and the thickness of the upper silica particle film and the substrate for measuring the refractive index obtained in the above Examples and Comparative Examples were evaluated by the following method.

(1) Measurement of film thickness and refractive index Using a spectroscopic ellipsometer (product name: VASE (registered trademark), manufactured by JA Woollam Japan), the film thickness of the upper silica particle film and the substrate for refractive index measurement were measured at wavelength Measurements were performed using light from 380 nm to 800 nm. Based on the obtained results, analysis was performed assuming that the upper silica particle film was a single layer Cauchy model, and the film thickness and refractive index at a wavelength of 500 nm were determined.

Further, the thicknesses of the hydrophilic polymer layer and the lower hydrophilic film were determined by the method described above. However, for Comparative Examples 1 and 2, the thickness of the upper silica particle film was measured using a spectroscopic ellipsometer on the substrate for refractive index measurement based on the thickness of the entire hydrophilic film confirmed by S-TEM of the cross section of the hydrophilic film. The thickness of the lower hydrophilic film was determined by subtracting the .

(2) Evaluation of hydrophilicity and haze on the surface of optical members after storage in a high-temperature, high-humidity environment. 755 (manufactured by Sumilon) was attached. At this time, two types were prepared: one in which the adhesive film was adhered to the entire surface, and one in which a part of the adhesive film was lifted and was not brought into close contact. Subsequently, each optical member was stored in an environment of 60°C and 90% for 286 hours. Thereafter, the adhesive film was peeled off, and the contact angle and haze of the surface of each optical member with respect to water were measured.

The haze value was measured using a haze meter (trade name: NDH2000, manufactured by Nippon Denshoku Industries Co., Ltd.). In addition, the contact angle with water was measured using a fully automatic contact angle meter (product name: DM-701, manufactured by Kyowa Interface Science Co., Ltd.). was measured. Note that the measured value is an average value that includes both the adhesive film contact area and the adhesive film floating area.
The results are shown in Table 1.

From the results shown in Table 1, the following was confirmed.
When the refractive index of the upper layer silica particle film for light having a wavelength of 500 nm is 1.22 or more and 1.23 or less, and the film thickness is 400 nm or more and 800 nm or less, the area where the adhesive film is in close contact with and the area where it is floating. In all cases, the contact angle was less than 30 degrees and the haze was 2.5 or less.

Even if the refractive index was 1.22, when the film thickness was 900 nm (Comparative Example 3), the haze deteriorated to 3.5.

In addition, when the refractive index of the upper layer silica particle film for light having a wavelength of 500 nm is 1.22 or more and 1.23 or less and the film thickness is 400 nm or more and 800 nm or less but there is no hydrophilic polymer layer (Comparative Example 1 and 2), the contact angle exceeded 30 degrees in the area where the adhesive film was floating.

Furthermore, when the refractive index of the upper layer silica particle film exceeds 1.23 (Comparative Example 4), the contact angle exceeds 30 degrees both in the area where the adhesive film is in close contact with the adhesive film and in the area where it is floating. The contact angle in the close contact area was 60 degrees, and the hydrophilicity was greatly reduced.

1: Lower layer hydrophilic film 2: Upper layer silica particle film 10: Optical member 11: Silica particles 12: Binder 13: Voids
14: Base material 15: Hydrophilic polymer

The above problems are solved by the following invention. That is, the optical member according to the present invention has a lower hydrophilic film, a hydrophilic polymer layer, and an upper layer in this order on a base material, and the upper layer contains a plurality of silica particles and has a wavelength of 500 nm. It is characterized by having a refractive index for light of 1.22 or more and 1.23 or less , and a film thickness of 400 nm or more and 800 nm or less.

Furthermore, from the viewpoint of simplicity, it is preferable that the protective film be an adhesive film that is pasted through an adhesive, but if the hydrophilic polymer layer is thin, it may be difficult to protect the protective film from hydrophobic substances emitted from the adhesive film or from the adhesive . Contamination of the hydrophilic member cannot be sufficiently prevented. Furthermore, when the hydrophilic polymer layer is thick, the adhesive film may peel off in a high temperature and high humidity environment.

When an adhesive film as a protective film is attached to the optical member 10 and stored, the portion where the adhesive film is in close contact with the upper silica particle film 2 is contaminated by hydrophobic contaminants and adhesive emitted from the adhesive film. . However, when the adhesive film is peeled off and the optical member 10 is used, a portion of the upper silica particle film 2 contaminated by hydrophobic contaminants and adhesive is removed together with the adhesive film. Thereby, the surface of the optical member 10 can be maintained in a highly hydrophilic state.

The thickness of the upper layer silica particle film 2 is 400 nm or more and 800 nm or less. By having a film thickness of 400 nm or more, even when the optical member 10 is stored with the adhesive film attached, hydrophobic contaminants and adhesive emitted from the adhesive film can be prevented from contaminating the lower hydrophilic film 1. . Further, by having a film thickness of 800 nm or less, an increase in haze of the optical member 10 due to the provision of the upper layer silica particle film 2 can be suppressed.

Further, the refractive index of the upper layer silica particle film 2 for light having a wavelength of 500 nm is 1.22 or more and 1.23 or less. The refractive index correlates with the proportion of voids 13 contained in the upper silica particle film 2. Since the air contained in the voids 13 (refractive index of 1.0) is lower than the refractive index of the silica particles 12, the percentage of voids is small, and the silica particles 12 of the upper silica particle film 2 and the binder 11 are tightly bonded to each other. The higher the refractive index of the upper silica particle film 2 becomes. If the refractive index of the upper layer silica particle film 2 for light having a wavelength of 500 nm is 1.22 or more, the density of the upper layer silica particle film 2 is sufficiently high, and the fluidity of the hydrophilic polymer increases in a high temperature and high humidity environment. By doing so, it is possible to suppress the occurrence of film thickness unevenness. Moreover, if the refractive index of the upper layer silica particle film 2 for light having a wavelength of 500 nm is 1.23 or less, the density of the upper layer silica particle film 2 will not become too high. Therefore, when the adhesive film is peeled off, a portion of the upper silica particle film 2 contaminated by hydrophobic contaminants and adhesive can be removed together with the adhesive film.

Claims (9)

having a lower hydrophilic film, a hydrophilic polymer layer, and an upper silica particle film in this order on the base material,
The upper layer silica particle film contains silica particles made of silicon dioxide,
The upper layer silica particle film has a refractive index of 1.22 or more and 1.23 or less for light having a wavelength of 500 nm,
An optical member characterized in that the thickness of the upper layer silica particle film is 400 nm or more and 800 nm or less. The optical member according to claim 1, wherein the silica particles have an average particle size of 10 nm or more and 20 nm or less. 3. The optical member according to claim 1, wherein the hydrophilic polymer layer contains an acrylic polymer having a silanol group at one end of a polymer of an acrylic monomer having a hydrophilic group. The optical member according to any one of claims 1 to 3, wherein the thickness of the hydrophilic polymer layer is 5 nm or more and 100 nm or less. The optical member according to any one of claims 1 to 4, wherein the lower hydrophilic film contains silica particles made of silicon dioxide. The optical member according to any one of claims 1 to 5, wherein the contact point between the silica particle and the silica particle includes a contact point bonded with a binder. The optical member according to claim 6, wherein the binder contains a siloxane bond. The optical member according to any one of claims 1 to 7, wherein the material of the base material contains polycarbonate resin. A method for protecting an optical member, comprising applying an adhesive film as a protective film on the optical member according to any one of claims 1 to 8.