JP2011252949A - Paint for optical element, film, optical element and optical instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a paint for an optical element which allows forming a film facilitating acquisition of a raw material, and having sufficient durability against an organic solvent and sufficient light internal antireflection effect to a substrate having a refractive index of 1.70 or more; the film; an optical element equipped with the film; and an optical instrument equipped with the optical element.SOLUTION: Compounded are an epoxy resin precursor having a d-line refractive index of 1.60 or more, a bifunctional or more aromatic polyamine having a d-line refractive index of 1.68 or more, a curing catalyst and black particles. Provided are a paint for an optical element which has a mass ratio of 1/1 to 20/1 of [compounding amount of the epoxy resin precursor]/[compounding amount of the aromatic polyamine]; a film comprising a cured product of the paint; an optical element equipped with a substrate and the film formed on the substrate; and an optical instrument equipped with the optical element.

Description

  The present invention relates to a coating for an optical element such as a lens or a prism, a coating formed using the coating, an optical element including the coating, and an optical apparatus including the optical element.

  In an optical system configured by combining optical elements such as lenses and prisms, stray light is likely to be generated due to irregular reflection or scattering at the periphery, edge, ridge, etc. of each optical element. Particularly in an imaging optical system, stray light causes image ghosting and flare, which is one of the causes of image quality degradation. Therefore, in order to suppress such deterioration of optical performance due to stray light, black paint for black ink or glass is applied to the rough surface with relatively large scattering present at the periphery, edge, ridge, etc. of the optical element. Thus, a film is often formed.

In recent years, it has been desired to reduce the size and weight of optical systems, and optical elements having a refractive index of 1.70 or more have been used. A new paint for forming a film having an effect of preventing internal reflection of light has also been proposed for the material.
For example, Patent Document 1 discloses a black paint in which a coal tar derivative and a polyisocyanate precursor are mixed with coal tar or coal tar pitch as a light absorbing material, and Patent Document 2 discloses a particle size as a light absorbing material. Discloses a black paint containing black inorganic fine particles having a refractive index of 1.5 μm or less and a refractive index of 1.5 or more.

JP-A-9-258005 JP-A-7-82510

However, coal tar and coal tar pitch, which are paint components, are easily dissolved in organic solvents used in the optical element cleaning process, and the formed film is not sufficiently durable against these organic solvents. Therefore, there has been a problem that color fading or the like occurs. Furthermore, since coal tar and coal tar pitch contain carcinogenic substances such as pyrene, they have already been banned from being sold to general consumers, making it difficult to obtain raw materials.
Further, the black inorganic fine particles having a particle size of 0.1 μm or less have a property that it is difficult to uniformly disperse and the particles are easily aggregated. The particle diameter is enlarged, and the formed film has a problem that a desired light reflection preventing effect cannot be obtained.

  The present invention has been made in view of the above circumstances, and it is easy to obtain raw materials, has sufficient durability against an organic solvent, and is sufficient for a substrate having a refractive index of 1.70 or more. It is an object of the present invention to provide a coating for an optical element capable of forming a film having an antireflection effect on the inner surface of light, the film, an optical element including the film, and an optical apparatus including the optical element.

One aspect of the present invention is an epoxy resin precursor having a refractive index at d-line of 1.60 or more, a bifunctional or higher aromatic polyamine having a refractive index at d-line of 1.68 or more, a curing catalyst, Black particles are blended, and the mass ratio of [blending amount of the epoxy resin precursor] / [blending amount of the aromatic polyamine] is 1/1 to 20/1. It is a paint.
Another aspect of the present invention is a film characterized by comprising a cured product of the paint for optical elements of the present invention.
Another aspect of the present invention is an optical element comprising a substrate and a film formed on the substrate, wherein the film is the film of the present invention. It is.
Another aspect of the present invention is an optical apparatus comprising the optical element of the present invention.

  According to the coating for an optical element of the embodiment of the present invention, it is easy to obtain raw materials, has sufficient durability against an organic solvent, and has sufficient light for a substrate having a refractive index of 1.70 or more. A film having an inner surface antireflection effect can be formed. Moreover, the optical element provided with the said membrane | film | coat, the said membrane | film | coat, and this optical element can be provided.

It is a figure explaining the internal reflection of the light in an optical element. It is a schematic sectional drawing which shows the structure of the sample for evaluation which formed the film | membrane using the coating material for optical elements in Examples 3-4 and Comparative Examples 3-5. It is a schematic block diagram which shows the measurement system of the internal reflectance of the light of the sample for evaluation in Examples 3-4 and Comparative Examples 3-5.

<Paints for optical elements>
In the optical element, the film formed on the surface of the base material has the effect of preventing reflection of light from the inner surface. Light that oozes from the base material into the film is absorbed inside the film, and the return light to the base material side is absorbed. By decreasing. For example, in the case of the optical element shown in FIG. 1, light 6 incident on the interface between the substrate 1 and the coating 2 at an incident angle θ oozes from the substrate 1 to the coating 2 side by a distance d under total reflection conditions. Then, the light is absorbed inside the coating 2, and the return light to the substrate 1 side is reduced.
In order to reduce the return light from the film 2 to the base material 1, it is necessary to increase the light absorption amount per unit optical path length of the film 2 or to increase the light bleed distance d into the film 2. . The distance d is obtained from the following formula (I) in terms of physical optics.
d = λ / [2π (sin ² θ− (n ₂ / n ₁ ) ² ) ^1/2 ] (I)
(In the formula, λ is the wavelength of light, θ is the incident angle, n ₁ is the refractive index of the substrate 1, and n ₂ is the refractive index of the coating 2.)

From formula (I), it can be seen that the refractive index n ₂ of the coating 2 should be close to the refractive index n ₁ of the substrate 1 in order to increase the distance d. That is, when the refractive index n _{1 of the} substrate 1 is high, the refractive index n ₂ of the coating 2 may be increased.
In addition, if the refractive index n ₂ of the coating 2 is made close to the refractive index n ₁ of the substrate 1, the critical angle θ _T of total reflection given by the following formula (II) can be increased. The larger the critical angle theta _T, it satisfies the total reflection condition incident angle range is narrowed at the interface of the substrate 1 and the film 2.
sin θ _T = n ₂ / n ₁ ... (II)
(Where n ₁ is the refractive index of the substrate 1, n ₂ is the refractive index of the coating 2, and θ _T is the critical angle of total reflection of the light 6 incident on the interface between the substrate 1 and the coating 2. .)

In general, a film used as an inner surface antireflection film is composed of a vehicle component that determines adhesion to a substrate, hardness, scratch resistance, and the like, and a light absorbing material. The conventional vehicle component has a refractive index of less than 1.65, which is insufficient for use as an inner surface antireflection film for a high refractive index substrate having a refractive index of 1.70 or more.
If the vehicle component is made to have a high refractive index, the infiltration distance d of light into the film 2 is increased and the critical angle θ _T is also increased. Alternatively, it was presumed that a film having a high effect of preventing internal reflection could be obtained without using black fine particles, and various resin properties were measured and evaluated. As a result, an epoxy resin precursor having a refractive index at d-line of 1.60 or higher, a bifunctional or higher aromatic polyamine having a refractive index at d-line of 1.68 or higher, a curing catalyst, and black particles. A paint having a mass ratio of [the blending amount of the epoxy resin precursor] / [the blending amount of the aromatic polyamine] of 1/1 to 20/1 is applied onto the substrate and cured. For example, a film containing a vehicle component having a refractive index of 1.65 or more can be formed, and such a film has a sufficient effect of preventing the internal reflection of light against a high refractive index substrate having a refractive index of 1.70 or more. Found to have.
That is, the optical element paint according to the present embodiment includes an epoxy resin precursor having a refractive index of 1.60 or more at d-line, a bifunctional or higher aromatic polyamine having a refractive index of 1.68 or more at d-line, and The curing catalyst and black particles are blended, and the mass ratio of [blending amount of the epoxy resin precursor] / [blending amount of the aromatic polyamine] is 1/1 to 20/1. And

(Epoxy resin precursor having a refractive index at d-line of 1.60 or more)
In the coating material of this embodiment, examples of the epoxy resin precursor having a refractive index at d-line of 1.60 or more include epoxy resin precursors having two or more epoxy groups. Bis (2,3-epoxypropoxy) naphthalene, 9,9′-bis [4- (2,3-epoxypropyloxy) phenyl] fluorene, bis [4- (2,3-epoxypropylthio) phenyl] sulfide, Bis [4- (2,3-epoxypropylthio) phenyl] disulfide, 2,5-di (2,3-epoxypropylthio) -1,4-dithiane, 4,4′-di (2,3-epoxy) Propyloxy) -1,1′-biphenyl, 2,2′-di (2,3-epoxypropyloxy) -9,9′-spirobi [9H-fluorene], 5,5′-di (2,3- Epo Examples thereof include xyloxyoxy) -1,1′-binaphthalene and 5,5′-di (2,3-epoxypropyloxy) -1,1′-diylcarbodiimide.
The said epoxy resin precursor may be used individually by 1 type, and may use 2 or more types together.

  The upper limit of the refractive index at the d-line of the epoxy resin precursor is not particularly limited. For example, when the refractive index at the d-line of the substrate is 1.70 to 1.85, it is 1 from the viewpoint of practicality. .75 is preferred.

  In the coating material of this embodiment, the epoxy resin precursor preferably contains 1,6-bis (2,3-epoxypropoxy) naphthalene, and is 1,6-bis (2,3-epoxypropoxy) naphthalene. More preferably.

  The compounding amount of the epoxy resin precursor in the total amount of the compounding components is preferably 15 to 50% by mass, more preferably 15 to 40% by mass, and particularly preferably 20 to 40% by mass. . By setting the blending amount to 15% by mass or more, characteristics such as adhesion to the base material of the film formed by curing the paint, hardness, and scratch resistance are further improved. On the other hand, when the blending amount is 50% by mass or less, the viscosity of the coating does not become too high, and the coating workability is further improved.

(A bifunctional or higher aromatic polyamine having a refractive index at d-line of 1.68 or more)
In the coating material of the present embodiment, a bifunctional or higher aromatic polyamine having a refractive index of 1.68 or higher at the d-line acts as a curing agent for the epoxy resin precursor. The aromatic polyamine has, for example, less odor than an aliphatic polythiol and a long pot life as a paint. By using the aromatic polyamine as a curing agent, the refractive index at the d-line of the film can be increased to 1.65 or more, and at the same time, the curing degree of the epoxy resin precursor can be increased.

Specific examples of the aromatic polyamine include 4,4′-dithiodianiline, 4,4′-diselenodianiline, 2,2′-dithiodianiline, 2,2′-diselenodianiline, 3, Examples thereof include 5-diaminodithiobenzene, 3,5-diaminodiselenobenzene, 3,3 ′, 5,5′-tetraaminodiselenobenzene and the like.
The said aromatic polyamine may be used individually by 1 type, and may use 2 or more types together.

  The upper limit of the refractive index at the d-line of the aromatic polyamine is not particularly limited. For example, when the refractive index at the d-line of the substrate is 1.70 to 1.85, 1. 78 is preferred.

  In the coating material of the present embodiment, the aromatic polyamine preferably contains at least one of 4,4′-dithiodianiline and 2,2′-dithiodianiline, and 4,4′-dithiodianiline and 2 More preferably, it is at least one of 2,2'-dithiodianiline.

  The mass ratio of [the amount of the epoxy resin precursor] / [the amount of the aromatic polyamine] is 1/1 to 20/1, preferably 1.5 / 1 to 15/1. More preferably, it is 5/1 to 9/1. By setting the mass ratio to be 1/1 or more, it is possible to suppress the crosslinking density from becoming too large and the coating from becoming brittle. On the other hand, by setting the mass ratio to 20/1 or less, curability at 80 ° C. or less is significantly improved.

(Curing catalyst)
The epoxy resin precursor and aromatic polyamine are characterized by being cured at a temperature of room temperature or higher by using a curing catalyst, and particularly excellent in curability at 80 ° C. or lower. Curing shrinkage at this time is 3 to 5%. Further, at the time of curing, it can be cured in the air without oxygen inhibition of the coating film surface, which is often a problem with acrylic resin coatings.

Specific examples of the curing catalyst include aliphatic tertiary amines.
Specific examples of the aliphatic tertiary amine include benzyldimethylamine, 2- (dimethylaminomethyl) phenol, 2,4,6-tris (dimethylaminomethyl) phenol, triethanolamine, and N, N′-dimethyl. Examples include piperazine and 1,4-diazabicyclo [2.2.2] octane.
The said curing catalyst may be used individually by 1 type, and may use 2 or more types together.

  The curing catalyst is blended in an amount of 0.1 to 10 with respect to 100 parts by mass of the total amount of the epoxy resin precursor and aromatic polyamine in order to cure at an appropriate speed without deteriorating the physical properties of the film. It is preferable that it is a mass part.

(Black particles)
In the coating material of this embodiment, specific examples of preferable black particles include black inorganic particles such as carbon black, acetylene black, graphite, nickel, silicon carbide, silicon nitride, and titanium black.
In addition to these black inorganic particles, black organic particles can be used in the same manner as long as they have sufficient elution resistance to the cleaning agent for optical elements.
The black particles may be used alone or in combination of two or more.
In the coating material of this embodiment, it is preferable that the black particles include at least one of carbon black and titanium black.

  The average particle diameter of the black particles is preferably 0.3 to 10 μm. Here, the average particle diameter refers to a sphere equivalent diameter measured by a light scattering method. By setting it as such a range, the still higher effect which suppresses the external appearance deterioration of the film | membrane accompanying aggregation is acquired.

  The blending amount of the black particles in the total amount of blending components is preferably 3 to 30% by weight, more preferably 5 to 20% by weight, and particularly preferably 5 to 15% by weight. When the blending amount is 3% by mass or more, the light-shielding property of the film is improved, and stray light that penetrates the film from the outside and enters the inside of the optical element can be further suppressed. On the other hand, by making the blending amount 30% by mass or less, the coating workability is further improved without excessively increasing the viscosity of the paint, and the higher effect of suppressing the deterioration of the appearance of the film due to the aggregation of the black particles is obtained. can get.

(Additive)
The paint of this embodiment may be blended with various additives for adjusting the storage stability, coating workability, or other physical properties of the paint as necessary.
Specific examples of the additive include various dispersants such as pigment dispersants and color separation inhibitors for adjusting the storage stability; various anti-sag agents such as sagging inhibitors and anti-settling agents for adjusting the coating workability. Modifiers: water repellents, slip agents, leveling agents, surface modifiers such as defoaming / antifoaming agents, matting agents, rust inhibitors, fungicides, crosslinking agents An adhesion improver etc. can be illustrated.

(solvent)
The coating material of this embodiment may be diluted with a solvent or the like as necessary.
The solvent is not particularly limited as long as it does not hinder the curing reaction of the epoxy resin precursor and aromatic polyamine. Specifically, alkylbenzenes such as toluene, ethylbenzene, o-xylene, m-xylene and p-xylene; cellosolves such as 2-methoxyethanol and 2-ethoxyethanol; tetrahydrofuran, tetrahydropyran, 1,4-dioxane, Ethers such as dimethoxyethane; ketones such as methyl ethyl ketone and cyclopentanone; esters such as ethyl acetate, n-propyl acetate, isopropyl acetate, methyl propionate, ethyl propionate; 1-butanol, 2-methylpropane-1 Examples include alcohols such as -ol (isobutanol) and 2-methyl-2-propanol (tert-butanol).
The said solvent may be used individually by 1 type, and may use 2 or more types together.

  Although the compounding quantity of a solvent is not specifically limited, It is preferable that it is 30-70 mass% with respect to the total amount of a mixing component, and it is more preferable that it is 40-60 mass%.

(Manufacturing method of paint for optical elements)
The coating material of this embodiment can be manufactured by adding and mixing each compounding component. At this time, all of the blending components may be added and then mixed, or the blending components may be mixed while being sequentially added, or some of the blending components may be added together. Mixing may be performed, for example, by stirring using a stirrer equipped with a stirring blade or the like, or may be performed by kneading using a mixer such as a high-speed rotation type mixer. You may use together.

  The paint of this embodiment is suitable for producing a film having an effect of preventing reflection of light from the inner surface, which will be described later. In addition, it is easy to obtain raw materials.

<Film>
The film of the present embodiment is characterized by comprising a cured product of the paint of the present invention.
The film of this embodiment can be produced, for example, by applying the coating material of the present invention to the substrate surface of the optical element and curing it.

As a method for applying the paint, usual methods such as brush coating, roller coating, and spray coating can be appropriately applied.
The heating conditions for curing the paint are not particularly limited, and may be appropriately selected according to the composition of the paint. For example, conditions for heating at 90 to 150 ° C. for about 0.2 to 10 hours can be given.

  The material of the base material to which the paint is applied may be selected according to the optical element that forms the film, and is not particularly limited, but various optical glasses and plastics are suitable. Among them, a high refractive index base material having a refractive index of 1.70 or more is preferable, and a refractive index at the d-line of the base material is preferably 1.70 or more, and is 1.70 to 1.85. More preferred. Even for such a high refractive index base material, the film of the present embodiment has a sufficient effect of preventing internal reflection of light.

  It is preferable that the film of this embodiment has a refractive index at d-line of 1.65 or more. Such a film is particularly suitable for forming on a high refractive index substrate.

  The thickness of the film of the present embodiment is not particularly limited, and may be appropriately set depending on the purpose. For example, in a lens etc., it is preferable that it is 5-30 micrometers.

  The film of the present embodiment reflects the composition of the paint of the present invention that forms the film, and has sufficient durability against the organic solvent. Therefore, even in the cleaning process of the optical element using the organic solvent, discoloration, etc. Is suppressed. Here, as the organic solvent used in the washing step, lower alcohols such as methanol, ethanol, 1-propanol and 2-propanol; hydrofluoroethers such as perfluorobutyl methyl ether and perfluorobutyl ethyl ether; 1 , 1,1,2,2,3,4,5,5,5-decafluoropentane and the like; and perfluoroalkyl tertiary amines such as N, N, N-triperfluorooctylamine and the like it can.

<Optical element>
The optical element of this embodiment is an optical element provided with a base material and a film formed on the base material, wherein the film is the film of the present invention.
The base material in the optical element is a base material to which a paint is applied in the above description of the film.
The optical element of the present embodiment is provided with the coating of the present invention, so that even when a base material having a refractive index of 1.70 or more is applied, the light inner reflectance is sufficiently reduced, and stray light. Is suppressed. Here, the internal reflectance refers to a value when the wavelength of light is preferably 400 to 700 nm.
Moreover, the optical element of this embodiment can implement | achieve size reduction and weight reduction by applying the base material of a high refractive index.

<Optical equipment>
An optical apparatus according to this embodiment includes the optical element according to the present invention.
As described above, the optical device of the present embodiment is not only reduced in the internal reflectance of light and suppressed generation of stray light, but also by applying a high refractive index substrate in the optical element, It is possible to reduce the size and weight of the optical system.

As explained so far, in the coating material of the present invention, the epoxy resin precursor and the aromatic polyamine that have a refractive index at d-line or higher are used. Further, as the base material in the film and optical element of the present invention, those having a refractive index at d-line or more are exemplified as preferable ones. Here, the refractive index at the d-line is only one of the components specifying the present invention.
Therefore, the application of the paint, film, optical element, and optical apparatus of the present invention is not limited to the use of d-line.

  Hereinafter, the present invention will be described in more detail with reference to specific examples. However, these examples show examples of embodiments of the present invention, and the present invention is not limited to the following examples.

(1) Preparation of coating material for optical element [Example 1]
As the epoxy resin precursor, 1,6-bis (2,3-epoxypropoxy) naphthalene having a refractive index at d-line of 1.62 is used as the aromatic polyamine, and the refractive index at d-line is 1.72. Each 4,4′-dithiodianiline is used, and as shown in Table 1, 70 parts by mass of the epoxy resin precursor, 30 parts by mass of the aromatic polyamine, and carbon black as a black particle (trade name: Talker Black) # 8500F, manufactured by Tokai Carbon Co., Ltd.) 15 parts by mass and black organic pigment (trade name: NCC319BS, manufactured by Noma Chemical Co., Ltd.) 10 parts by mass, toluene: 2-methoxyethanol = 2: 1 (volume ratio) mixed solvent 90 parts by mass, 5 parts by mass of ultra fine powder amorphous silica (trade name: Fine Seal FM-30, manufactured by Tokuyama Corporation) as a matting agent As a powder, 5 parts by mass of high-molecular polyester acid amide amine salt (trade name: HIPLAAD ED-216, manufactured by Kashiwagi Kasei Co., Ltd.) was added and kneaded with a high-speed revolving mixer.
Next, 5 parts by mass of 2,4,6-tris (dimethylaminomethyl) phenol as a curing catalyst is added to the mixture, and further 45 parts by mass of a mixed solvent of toluene: 2-methoxyethanol = 2: 1 (volume ratio). Added and stirred.
Finally, the agglomerated particles were removed using a 200-mesh metal net to prepare an optical element coating material A. The removed aggregated particles were mainly black particles, but the amount thereof was very small and did not clearly change the composition ratio of the blended components.
In the optical element coating material A, the mass ratio of [1,6-bis (2,3-epoxypropoxy) naphthalene blending amount] / [4,4′-dithiodianiline blending amount] is 7/3.

[Example 2]
As shown in Table 1, in place of 4,4′-dithiodianiline, 2,2′-dithiodianiline having a refractive index of 1.69 at the d-line was used as the aromatic polyamine. The optical element paint B was prepared in the same manner as in Example 1.
In the optical element coating material B, the mass ratio of [1,6-bis (2,3-epoxypropoxy) naphthalene blending amount] / [2,2′-dithiodianiline blending amount] is 7/3.

[Comparative Example 1]
As shown in Table 1, as the epoxy resin precursor, bisphenol having a molecular weight of about 370 and a refractive index at d-line of 1.55 instead of 1,6-bis (2,3-epoxypropoxy) naphthalene Optical element paint C was prepared in the same manner as in Example 1 except that A-type epoxy resin (trade name: jER828, manufactured by Japan Epoxy Resin Co., Ltd.) was used.
In the optical element coating material C, the mass ratio of [the blending amount of bisphenol A type epoxy resin] / [the blending amount of 4,4′-dithiodianiline] is 7/3.

[Comparative Example 2]
As shown in Table 1, as the aromatic polyamine, instead of 4,4′-dithiodianiline, except that 3,4′-diaminodiphenyl ether having a refractive index of 1.65 at the d-line was used, In the same manner as in Example 1, an optical element paint D was prepared.
In the optical element coating material D, the mass ratio of [1,6-bis (2,3-epoxypropoxy) naphthalene blending amount] / [3,4'-diaminodiphenyl ether blending amount] is 7/3.

(2) Formation of film [Example 3]
As shown in FIG. 2, the antireflection film 3 having a reflectance at 430 nm of 0.1% or less on one surface of the flat substrate 1 having a refractive index of 1.77 at d-line and an Abbe number of 50. The optical element paint A prepared in “(1) Example 1” was applied with a brush to the other surface where the antireflection film 3 was not formed. Next, the coating film 2 was formed by heating at 120 ° C. for 1 hour to cure the optical element paint A, and an evaluation sample 4 of the optical element paint A was produced. The obtained film 2 had a refractive index of 1.68.

[Example 4]
Sample 4 for evaluation was produced by the same method as Example 3 except having used paint B for optical elements prepared by "(1) Example 2" instead of paint A for optical elements. The obtained coating film 2 had a refractive index of 1.67.

[Comparative Example 3]
An evaluation sample 4 was produced in the same manner as in Example 3 except that the optical element paint C prepared in “(1) Comparative Example 1” was used instead of the optical element paint A.

[Comparative Example 4]
An evaluation sample 4 was produced in the same manner as in Example 3 except that the optical element paint D prepared in “(1) Comparative Example 2” was used instead of the optical element paint A.

[Comparative Example 5]
Instead of the optical element paint A, a commercially available epoxy paint E (trade name: GT-7, manufactured by Canon Kasei Co., Ltd.) in which a dye or the like is blended as a colorant is used. Instead, a sample 4 for evaluation was produced in the same manner as in Example 3 except that this was heated and cured at 120 ° C. for 40 minutes.

(3) Evaluation of the effect of preventing reflection of light from the inner surface of the film Using the spectrophotometer having the configuration shown in FIG. 3, the reflection of light at the wavelength of 430 nm of each sample 4 for evaluation of Examples 3 to 4 and Comparative Examples 3 to 5 The rate was measured. The measurement results are shown in Table 2.
In FIG. 3, the measurement light 6 having a wavelength of 430 nm emitted from the monochromator 5 is incident on the surface of the evaluation sample 4 on which the antireflection film 3 is formed, passes through the evaluation sample 4, and the film 2 is formed. The incident light enters the formed surface from the inside. Then, the measurement light 6 reflected by the surface on which the film 2 is formed passes through the evaluation sample 4 again and is emitted from the surface on which the antireflection film 3 is formed. The measurement light 6 emitted from the evaluation sample 4 enters a detector 7 having an integrating sphere, and the amount of light is measured.

  As a result of the measurement, the internal reflectance of light at the wavelength of 430 nm of the sample 4 for evaluation was 0.05% in Example 3 and 0.07% in Example 4. On the other hand, it was 0.53% in Comparative Example 3, 0.33% in Comparative Example 4, and 0.08% in Comparative Example 5. On the other hand, the internal reflectance of light at a wavelength of 430 nm of the reference sample on which the film 2 was not formed was 7.64%.

Here, when the internal reflection prevention efficiency of light is defined by the following formula (III), the internal reflection prevention efficiency at the wavelength of 430 nm of the evaluation sample 4 is 99.3 in Example 3, as shown in Table 2. 4 was 99.1. On the other hand, it was 93.0 in Comparative Example 3, 95.7 in Comparative Example 4, and 99.0 in Comparative Example 5.
{1- (Internal reflectance of sample for evaluation / Internal reflectance of reference sample)} × 100 (III)

Since the internal reflectance was suppressed by 99% or more by the coating formed from the optical element coating A of Example 1 and the optical element coating B of Example 2, the coating of the present invention had a high value of 1.77. It was confirmed that even a refractive index base material has an excellent antireflection effect on the inner surface.
Further, the internal reflectance of the evaluation sample 4 is 7.5 to 9.6 times higher in Comparative Example 3 than that in Examples 3 to 4, and 4.6 to 6.0 times higher in Comparative Example 4. High and comparable in Comparative Example 5. That is, it was confirmed that the films of Examples 3 to 4 were more excellent in the inner surface antireflection effect than the films of Comparative Examples 3 to 4, and had an inner surface antireflection effect equivalent to or greater than that of the film of Comparative Example 5.

(4) Evaluation of durability of film to organic solvent Samples 4 for evaluation in Examples 3 to 4 and Comparative Example 5 were immersed in 1 ml of 2-propanol per 1 mg of the film and allowed to stand at room temperature for 15 hours.
As a result, in the case of the sample 4 for evaluation of Examples 3 to 4, no coloring was observed in 2-propanol. From this result, it was confirmed that the films of Examples 3 to 4 formed from the coating materials A and B for optical elements of the present invention, in which black particles were blended as a light absorber, had sufficient durability against organic solvents. .
On the other hand, in the case of the sample 4 for evaluation of Comparative Example 5, 2-propanol was markedly colored (orange). This is considered to be due to the elution of a colorant such as a dye from the film which is a cured product of the coating material E for optical elements.
From the above results, it was confirmed that the film of the present invention was more excellent in durability against organic solvents than a film formed from a commercially available paint.

  The present invention can be used for all optical devices including various optical elements such as lenses and prisms.

  DESCRIPTION OF SYMBOLS 1 ... Flat base material, 2 ... Film | membrane, 3 ... Antireflection film, 4 ... Sample for evaluation, 5 ... Monochromator, 6 ... Measuring light, 7 ... Detector

Claims (13)

  An epoxy resin precursor having a refractive index at d-line of 1.60 or more, a bifunctional or higher aromatic polyamine having a refractive index at d-line of 1.68 or more, a curing catalyst, and black particles are blended. The mass ratio of [the amount of the epoxy resin precursor] / [the amount of the aromatic polyamine] is 1/1 to 20/1.   2. The paint for optical elements according to claim 1, wherein the epoxy resin precursor is 1,6-bis (2,3-epoxypropoxy) naphthalene.   The optical element paint according to claim 1 or 2, wherein the aromatic polyamine contains at least one of 4,4'-dithiodianiline and 2,2'-dithiodianiline.   The optical element paint according to any one of claims 1 to 3, wherein the curing catalyst is an aliphatic tertiary amine.   5. The coating composition for an optical element according to claim 4, wherein the aliphatic tertiary amine is 2,4,6-tris (dimethylaminomethyl) phenol.   The optical element paint according to any one of claims 1 to 5, wherein the black particles include at least one of carbon black and titanium black.   The coating amount for an optical element according to any one of claims 1 to 6, wherein a blending amount of the epoxy resin precursor in a total amount of blending components is 15 to 50% by mass.   The optical element coating material according to any one of claims 1 to 7, wherein a blending amount of the black particles in a total amount of blending components is 3 to 30% by mass.   A film comprising a cured product of the coating for optical elements according to any one of claims 1 to 8.   The film according to claim 9, wherein the refractive index at d-line is 1.65 or more.   An optical element comprising a base material and a film formed on the base material, wherein the film is the film according to claim 9 or 10.   The optical element according to claim 11, wherein a refractive index of the base material at d-line is 1.70 or more.   An optical apparatus comprising the optical element according to claim 11.

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