JP6744751B2 - Thermal barrier film for optical equipment, thermal barrier coating for optical equipment, and optical equipment using them - Google Patents

Description

INDUSTRIAL APPLICABILITY The present invention provides a lens barrel for an optical device such as a camera, a video device, and a broadcasting device, and other optical devices such as a camera body, a video body, a surveillance camera, and a weather camera that may be used outdoors. The present invention relates to a heat film and a heat shield paint.

The heat shield film is a film having a function of suppressing a temperature rise of a member due to sunlight when used outdoors. Conventionally, as a method of suppressing a temperature rise of a member due to sunlight, a method of reflecting incident light 1 from the sun as reflected light 2 by an infrared reflection film 4 as shown in FIG. 1 is known. By increasing the ratio of the reflected light 2, heat generation by the transmitted light 3 can be suppressed. As another heat shielding method, there is a method of providing a heat insulating layer having a low heat conductivity in place of the infrared reflecting film 4, providing a heat radiating layer for radiating heat to the outside, or combining them.

On the other hand, since the optical device performs focus adjustment and the like, position accuracy is very important. For example, as shown in FIG. 2, the lens barrel 8 of the optical device is composed of the lens 6 and its lens barrel cover, etc., and is provided with a sliding fitting portion 7 for focus adjustment. By providing the heat shield film 9 on the surface layer of the base material 5, even if the optical device is exposed to sunlight, the temperature rise of the optical device due to sunlight can be suppressed, and the positional accuracy of the focus and the like can be maintained.

Patent Document 1 discloses a heat shield film for a lens barrel, the film including a colored layer, an infrared reflective layer, and a heat insulating layer. In Patent Document 1, not only the infrared reflecting layer but also a heat insulating layer having a film thickness of 500 μm to 2000 μm is provided to enhance the heat shielding effect.

JP, 2009-139856, A

However, when a heat insulating layer having a film thickness of 500 μm to 2000 μm is provided as in Patent Document 1, the film thickness itself of the lens barrel becomes thick, and it is difficult to obtain sufficient positional accuracy of the sliding fitting portion.

The present invention has been made in view of such background art, and has a high reflectance even in a thin film, and a heat shield film for an optical device in which a temperature rise due to sunlight is small, a heat shield coating for an optical device, and an optical device. Is provided.

The optical device of the present invention is a lens and an optical device having a lens barrel in which the lens is arranged, having a heat shield film on at least a part of an outer peripheral surface of the lens barrel, The thermal barrier film has particles having a d-line refractive index of 2.5 or more and 3.2 or less and a resin having a d-line refractive index of 1.32 or more and 1.42 or less, and the particles have an average particle size of It is characterized in that it is 2 μm or more and 5 μm or less and the ratio of the particle diameter of the particles is 1.5 μm or less is 35% by mass or less.
The heat shield film of the present invention is a heat shield film comprising particles having a d-line refractive index of 2.5 to 3.2 and a resin having a d-line refractive index of 1.32 to 1.42. The particles have an average particle size of 2 μm or more and 5 μm or less, and the ratio of the particle size of the particles of 1.5 μm or less is 35% by mass or less.
The heat-shielding paint of the present invention is a heat-shielding paint having a solvent having a d-line refractive index of 2.5 to 3.2 and a resin having a d-line refractive index of 1.32 to 1.42, and a solvent. The particles have an average particle size of 2 μm or more and 5 μm or less, and a ratio of the particle size of the particles of 1.5 μm or less is 35% by mass or less.

ADVANTAGE OF THE INVENTION According to this invention, since it has high reflectance with respect to sunlight, and a thin film has a high heat-shielding effect, the heat-shielding film for optical devices, the heat-shielding paint for optical devices, and optical equipment which require positional accuracy are provided. Can be provided.

3 is a schematic cross-sectional view showing the state of reflection and absorption of sunlight when the infrared reflection film 4 is formed on the upper surface of the base material 5. FIG. 3 is a schematic sectional view of a lens barrel 8. FIG. 5 is a schematic cross-sectional view showing reflection at the interface between particles 10 and resin 11. FIG. It is a schematic diagram of a reflectance measurement mode by a spectrophotometer. It is a schematic diagram which shows the evaluation method of temperature.

Hereinafter, preferred embodiments of the present invention will be described.
First, a method for improving the reflectance of sunlight will be described. Next, the heat-shielding coating for an optical device, the heat-shielding film for an optical device, and the optical device of the present invention for improving the reflectance of sunlight will be described. The optical device of the present invention has a lens and a lens barrel in which the lens is arranged, and has a heat shield film on at least a part of an outer peripheral surface of the lens barrel.
In the present invention, the “particle diameter” is a diameter converted from the volume of particles, and is determined by a laser diffraction type viscosity analyzer.
Moreover, the median diameter was used for the "average particle diameter" in this invention.

[Mechanism for improving sunlight reflectance]
The wavelength of sunlight is in the range of about 0.3 μm to about 3 μm, and when the light of these wavelengths becomes the transmitted light 3 as shown in FIG. 1, it is converted into heat energy and the base material 5 generates heat. Therefore, in order to suppress heat generation due to sunlight without the heat insulating layer, it is necessary to increase the ratio of the reflected light 2 to the incident light 1 as much as possible and suppress heat generation due to the transmission of light to the inside.

The range of 0.3 μm to 3 μm, which is the wavelength of sunlight, is the Mie scattering region for particles with a particle size of several μm. Calculation of Mie scattering shows that the Mie scattering is about 1 μm. Highest reflectance. Therefore, the particle size of the reflective particles of sunlight is generally around 1 μm. For the calculation of Mie scattering, the formula of Light Scattering Theory (Department of Mechanical and Aerospace Engineering University of Florida; David W. Hahn) was used.

The present inventor, after earnestly studying further improvement of reflectance, greatly improves the reflectance by setting the particle diameter of particles, the range of refractive index and particle size distribution, and the refractive index of resin to an appropriate range. I found that I could do it.

First, it was found that the reflectance increases when particles having a d-line refractive index of 2.5 or more and 3.2 or less and an average particle diameter of 2 μm or more are used. This particle size is larger than 1 μm, which is the optimum solution for the calculated value of Mie scattering. A typical Mie scattering calculation calculates the sum of scattering in all 360° azimuths for incident light. However, the only light that actually reflects the incident light and goes out of the film is backscattering. Therefore, the larger the particle size is, the larger the shielding effect is and the less the forward scattering is. Therefore, in order to actually improve the reflectance, the particle size needs to be 2 μm or more. Further, if the average particle size exceeds 5 μm, the unevenness of the film becomes large and the film thickness accuracy deteriorates. Therefore, the average particle diameter of the particles in the present invention is 2 μm or more and 5 μm or less.

Furthermore, there is a correlation between the refractive index of the resin and the refractive index of the particles, and the d-line refractive index of the resin is 2.5 to 3.2 and the d-line refractive index of the resin is 1.32 to 1. It was found that the reflectance was highest at 42 or less. As shown in FIG. 3, when the refractive index of the resin 11 is high, the difference in the refractive index with the particles 10 is small and the amount of the reflected light 2 with respect to the incident light 1 is reduced, but when the refractive index of the resin 11 is too low, the particles 10 are too small. It is presumed that the light entering the particle 10 due to the too large difference in the refractive index between and cannot be emitted to the resin 11 side by repeating the reflection 12 inside the particle and the light is confined, and conversely the reflectance decreases. It Therefore, when the d-line refractive index of the particles is 2.5 or more and 3.2 or less and the d-line refractive index of the resin is 1.32 or more and 1.42 or less, the reflectance is most improved to enhance the temperature reduction effect. Can be done.

[Thermal coating for optical equipment]
The material constitution of the thermal barrier coating for optical equipment of the present invention and the method for producing the thermal barrier coating of the present invention will be described below.

<Material composition>
The thermal barrier coating for optical devices of the present invention contains at least particles having a d-line refractive index of 2.5 or more and 3.2 or less, a resin, and a solvent.

(Particles with d-line refractive index of 2.5 to 3.2)
First, the particles having a d-line refractive index of 2.5 to 3.2 according to the present invention will be described.
For the particles having a d-line refractive index of 2.5 or more and 3.2 or less according to the present invention, rutile type titanium oxide or anatase type titanium oxide can be used as the most preferable material. Further, when it is necessary to adjust the color, chromium oxide, titanium, copper oxide, tungsten, platinum, iron oxide, hematite or the like which has absorption in the visible light region can be used. However, as compared with titanium oxide, which has a low extinction coefficient in the visible to infrared range, the material having a particularly high extinction coefficient in the visible range tends to have a slightly reduced reflectance of sunlight. By adjusting the particle size in the range of 1, it is possible to obtain a higher sunlight reflectance. The particles having a d-line refractive index of 2.5 or more and 3.2 or less may be used alone or as a mixture of a plurality thereof.

The particles having a d-line refractive index of 2.5 or more and 3.2 or less of the present invention have an average particle size of 2 μm or more and 5 μm or less. When the average particle diameter is less than 2 μm, the reflectance of sunlight decreases. Further, if the average particle size exceeds 5 μm, the unevenness of the film becomes large and the film thickness accuracy deteriorates.

Further, when the number of particles having a particle size of 1.5 μm or less increases, the ratio of sunlight passing through increases, so that absorption occurs in the coating film and the reflectance of sunlight decreases. In the present invention, the ratio of the d-line refractive index of 2.5 or more and 3.2 or less and the particle diameter of 1.5 μm or less is adjusted to 35% by mass or less.

Further, the particles having a d-line refractive index of 2.5 or more and 3.2 or less according to the present invention may have their surfaces coated with any organic material or inorganic material. Further, the shape may be irregular, spherical, flake shaped, or hollow, but is more preferably a shape having few surface irregularities.

The content of the particles having a d-line refractive index of 2.5 or more and 3.2 or less of the present invention is preferably 10% by weight or more and 90% by weight or less with respect to the thermal barrier coating. When the content of the particles is less than 10% by weight, the amount of light reaching the base material increases and the reflectance of sunlight decreases. Further, when the content of particles exceeds 90% by weight, the brittleness of the coating film is deteriorated.

(resin)
Next, the resin of the present invention will be described.
The resin of the present invention has a d-line refractive index of 1.32 or more and 1.42 or less. When the d-line refractive index of the resin exceeds 1.42, the difference in the refractive index between the resin and the particles is small, so that the reflectance at the interface between the resin and the particles decreases. Further, when the d-line refractive index of the resin is less than 1.32, the refractive index difference between the resin and the particles becomes too large, the light transmitted inside the particles is trapped and the sunlight is absorbed, and the reflectance decreases. ..

As the resin having a d-line refractive index of 1.32 or more and 1.42 or less according to the present invention, any material can be used as long as it falls within the range. For example, a silicone resin, a fluororesin, or a fluorine group is introduced. The resins mentioned above are preferred. Examples of the silicone-based resin include methyl-based, methyl/phenyl-based, propyl/phenyl-based, epoxy resin-modified, alkyd resin-modified, polyester resin-modified, rubber-based resins, and resins and oligomers thereof. Further, in order to adjust the refractive index of the resin, low refractive index particles having a particle size of 100 nm or less may be mixed and used. As the low refractive index particles, organic particles or inorganic particles may be used. Examples of the material include fluorine-based materials, MgF ₂ , silica and the like. The shape may be spherical, amorphous, hollow, or have pores. Examples of the hollow particles include silica, magnesium fluoride, and organic resin. As the silicone resin, for example, KC-89S (Shin-Etsu Silicone) or KR-400 (Shin-Etsu Silicone) can be used. Examples of the resin having a d-line refractive index of 1.42 include X-41-1810 (Shin-Etsu Silicone), X-41-1805 (Shin-Etsu Silicone), X-41-1818 (Shin-Etsu Silicone), and KR251 (Shin-Etsu Silicone). Can be used.

Further, the content of the resin of the present invention is preferably 5% by weight or more and 50% by weight or less, and more preferably 7% by weight or more and 30% by weight or less with respect to the thermal barrier coating. When the content of the resin of the present invention is less than 5% by weight, the adhesion with the base material deteriorates. Further, when the content of the resin of the present invention exceeds 50% by weight, the reflectance of sunlight deteriorates.

(solvent)
Next, the solvent will be described.
Any material may be used as the solvent. Examples of the solvent include water, thinner, ethanol, isopropyl alcohol, n-butyl alcohol, ethyl acetate, propyl acetate, isobutyl acetate, butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, propylene glycol monomethyl ether, toluene, xylene, acetone, cellosolve. Examples thereof include glycol ethers, glycol ethers and ethers. These solvents may be used alone or as a mixture of plural kinds.

The preferable viscosity of the heat-shielding coating is 10 mPa·s or more and 10000 mPa·s or less. When the viscosity of the heat-shielding paint is less than 10 mPa·s, there are cases where the thickness of the heat-shielding film after application becomes thin. On the other hand, when it is more than 10,000 mPa·s, the coating property of the heat-shielding paint is deteriorated.

(Additive)
The thermal barrier coating composition of the present invention may contain any other additive as a part of the resin as long as the d-line refractive index of the resin is within the range of 1.32 or more and 1.42 or less. As examples thereof, a dispersant, a curing agent, a curing catalyst, a plasticizer, a thixotropic agent, a leveling agent, an infrared transmissive organic colorant, an infrared transmissive inorganic colorant, a preservative, an ultraviolet absorber, an antioxidant, Examples thereof include coupling agents, inorganic particles and organic particles having a d-line refractive index of 2.5 or less, and inorganic particles having a d-line refractive index of 3.2 or more. The dispersants are DISPERBYK-118 (Big Chemie Japan), DISPERBYK-110 (Big Chemie Japan), DISPERBYK-111 (Big Chemie Japan), DISPERBYK-102 (Big Chemie Japan), DISPERBYK-190 (Big Chemie Japan). , DISPERBYK-106 (Big Chemie Japan), DISPERBYK-180 (Big Chemie Japan), DISPERBYK-108 (Big Chemie Japan), and Demol EP (Kao) can be used.

<Method for producing heat-shielding paint>
The method for producing the thermal barrier coating composition of the present invention will be described below.
As a method for producing the heat-shielding coating material of the present invention, any method can be used as long as the particles having a d-line refractive index of 2.5 or more and 3.2 or less of the present invention can be dispersed in a solution containing a resin and a solvent. Examples include bead mills, ball mills, jet mills, three rollers, planetary rotation devices, mixers, ultrasonic dispersers, and the like.

[Heat shield film for optical equipment]
The material constitution and film constitution of the heat shield film for optical equipment of the present invention will be explained below.

<Material composition>
The material constitution of the heat shield film for optical equipment of the present invention will be described below.
The heat-shielding film of the present invention has particles having a d-line refractive index of 2.5 or more and 3.2 or less and a resin.

(Particles having a d-line refractive index of 2.5 or more and 3.2 or less)
In the heat shield film formed by applying the above heat shield coating by the following method, the content of particles having a d-line refractive index of 2.5 or more and 3.2 or less of the present invention is 20 with respect to the heat shield film. It is preferably not less than 60% by volume and not more than 60% by volume. If the content of the particles is less than 20% by volume, the amount of light reaching the base material increases, so that the reflectance of sunlight decreases. Further, if the content of particles exceeds 60% by volume, the brittleness of the coating film deteriorates.

(resin)
The content of the above-mentioned resin is preferably 10% by volume or more and 78% by volume or less, more preferably 20% by volume or more and 70% by volume or less with respect to the heat shield film. If the content of the resin of the present invention is less than 10% by volume, the adhesion with the substrate will deteriorate. Further, when the content of the resin of the present invention exceeds 78% by volume, the reflectance of sunlight deteriorates.

(Additive)
The heat-shielding film of the present invention may contain any other additive as a part of the resin as long as the d-line refractive index of the resin is within the range of 1.32 or more and 1.42 or less. As examples thereof, a dispersant, a curing agent, a curing catalyst, a plasticizer, a thixotropic agent, a leveling agent, an infrared transmissive organic colorant, an infrared transmissive inorganic colorant, a preservative, an ultraviolet absorber, an antioxidant, Examples thereof include coupling agents, inorganic particles and organic particles having a d-line refractive index of 2.5 or less, and inorganic particles having a d-line refractive index of 3.2 or more.

<Membrane composition>
The heat shield film 9 of the present invention is formed at least outside the base material 5. As a form thereof, it may be in close contact with the base material 5, or a primer layer for improving the adhesiveness may be provided between the base material 5 and the heat shield film 9.

(Base material)
As the base material, any material can be used, but metal or plastic is preferable. Examples of the metal material include aluminum, titanium, stainless steel, magnesium alloy and the like. Examples of plastic materials include polycarbonate resin, acrylic resin, ABS resin, fluororesin, and the like.

The substrate may have any thickness, but it is preferably 0.5 mm or more and 5 mm or less, more preferably 0.5 mm or more and 2 mm or less. If the film thickness is less than 0.5 mm, it is difficult to maintain the shape of the lens barrel. Moreover, if the film thickness exceeds 5 mm, the cost of the member increases.

(Primer)
Although any material can be used as the primer, examples thereof include epoxy resin, urethane resin, acrylic resin, silicone resin, and fluororesin. Further, the primer particles of the present invention and particles other than the present invention, colorants, dispersants, curing agents, curing catalysts, plasticizers, thixotropic agents, leveling agents, organic colorants, inorganic colorants, preservatives, An ultraviolet absorber, an antioxidant, a coupling agent, and a solvent residue may be contained.

Further, the film thickness of the primer is preferably 2 μm or more and 30 μm or less, more preferably 5 μm or more and 20 μm or less. If the film thickness is less than 2 μm, the adhesion of the film may decrease, and if it exceeds 30 μm, the positional accuracy may be adversely affected.

(Thickness of the heat shield film of the present invention)
The average film thickness of the heat shield film of the present invention is preferably 10 μm or more and 70 μm or less. When the film thickness is less than 10 μm, light is transmitted to the base material side and the reflectance of sunlight is deteriorated. If the film thickness exceeds 70 μm, the positional accuracy deteriorates. The film thickness accuracy is preferably ±15 μm with respect to the standard value, and more preferably ±10 μm.

<<Method of forming heat shield film of the present invention>>
For the heat shield film of the present invention, any coating method and curing method can be used as long as the heat shield coating composition of the present invention can be uniformly applied so that the film thickness after curing is 10 μm or more and 70 μm or less.

Examples of the coating method of the heat shield film for the optical device of the present invention include brush coating, spray coating, dip coating, transfer and the like. Further, the heat-shielding film may be a single-layer coating or a multi-layer coating, and may be embossed for improving its design.

In addition, as a method of curing the heat shield film for the optical device of the present invention, it may be left at room temperature, or may be accelerated by an arbitrary heat or may be irradiated with ultraviolet rays. Examples of the method of applying heat to cure include a heating furnace, a heater, and infrared heating. The curing temperature is preferably room temperature to 400°C, more preferably room temperature to 200°C.

The preferred embodiments of the present invention will be described below.
Preparation of the heat-shielding coating, preparation of the heat-shielding film, evaluation of reflectance, evaluation of temperature, and evaluation of film thickness accuracy in Examples 1 to 15 were carried out by the following methods.

<Method of measuring reflectance>
The reflectance was measured using a spectrophotometer (U-4000; Hitachi High-Tech) as shown in FIG.
For the sample for measurement, the heat shield coating of the present invention was applied to a metal plate having a side of 30 mm and a thickness of 1 mm and cured to form the heat shield film of the present invention. For the metal plate, any one of stainless steel, aluminum, titanium, magnesium alloy and the like was used. Further, the heat shield film of the present invention was applied to the surface of the metal plate by a spin coater so as to have a desired film thickness, and was baked.

Next, a method of measuring reflectance will be described. As shown in FIG. 4, incident light 1 having a wavelength of 400 nm to 2600 nm was made incident on the integrating sphere 13. First, a test piece tilted at an incident angle of 5° with respect to the incident light 1 was set on a mounting portion 14 as a blank of an alumina sintered body that causes 100% reflection, and a baseline measurement was performed. Then, instead of the blank, a test piece on which the light-shielding film of the present invention was formed was placed in the test piece attachment portion 14, light of 400 nm to 2600 nm was made incident, and the detection portion 15 detected and measured the reflectance. As the reflectance, the average reflectance value every 1 nm in 400 nm to 2600 nm is shown. The reflectance has a correlation with the temperature evaluation result, and a good value was shown in the temperature evaluation result below at 94% or more. From this, it can be said that a heat shield film having a reflectance of 94% or more is a good heat shield film.

<Evaluation method of temperature reduction effect>
FIG. 5 is a schematic diagram showing a temperature evaluation method. As shown in FIG. 5, the lamp 16, the temperature measurement jig 19, and the temperature evaluation test piece 17 were used for temperature measurement. The temperature was measured at the temperature measuring point 18.

As the test piece 17 for temperature evaluation, a heat shield film of the present invention was formed on a 100 mm square and 1 mm thick metal plate and used. For the metal plate, any one of stainless steel, aluminum, titanium, magnesium alloy and the like was used. Further, the heat shield film of the present invention was applied to the surface of the metal plate by a spin coater so as to have a desired film thickness, and was baked. A cardboard box having a white surface of 120 mm×120 mm×120 mm was used as the temperature measurement jig 19, and a 90 mm×90 mm square window portion was provided in the mounting portion of the test piece 17 for temperature evaluation.
As the lamp 16, Hilux MT150FD6500K (Iwasaki Electric) was used.

Next, the test piece 17 for temperature evaluation was attached to the jig 19 for temperature measurement, and the thermocouple was attached to the temperature measurement location 18 on the back surface of the test piece 17 for temperature evaluation. The temperature measuring jig 19 to which the test piece 17 for temperature evaluation was attached was installed so that the distance from the lamp 16 was 100 mm. Next, the lamp 16 was irradiated for 60 minutes, and the temperature after 60 minutes was measured.

Regarding the temperature reducing effect, a black blank was formed on the surface of the test piece 17 for temperature evaluation, the temperature was measured, and the difference from the temperature measurement result of the heat shield film of the example was calculated to obtain the temperature reducing effect.

As a black blank film, 20 g of carbon black (MA100; Mitsubishi Kagaku), 100 g of epoxy resin (jER828; Mitsubishi Kagaku), 70 g of amine curing agent (ST11; Mitsubishi Kagaku), and 20 g of thinner were mixed with a planetary rotating device for temperature evaluation. It was prepared by applying it to the surface of the test piece 17 for use in the application and firing it.

When the temperature reduction effect was 15°C to 20°C, it was evaluated as a good heat shield film (the following table: ◯). Moreover, when the temperature reduction effect was less than 15° C., it was evaluated as not a good heat shield film (the following table: x).

<Evaluation method of film thickness accuracy>
The method of evaluating the film thickness accuracy will be described below. Positioning accuracy of optical equipment is severe, but if the accuracy of film thickness varies, the positioning accuracy deteriorates. For the sample for evaluation of film thickness accuracy, the heat insulating film of the present invention was applied to a metal plate having a side of 30 mm and a thickness of 1 mm by spraying so as to have a desired film thickness, and the sample was baked. Twenty sheets of samples for evaluation were prepared, and the thickness of each sheet was measured with a micrometer at five locations, and the average value was calculated as the film thickness. Further, the average value of the film thickness of 20 test pieces was calculated, and the maximum deviation amount from the average value was used as the value of the film thickness variation. In addition, the maximum amount of deviation is the maximum amount of deviation for 100 test points in total of 20 test pieces×5 points.

If the film thickness variation is within ±10 μm, the film thickness uniformity was evaluated as good (the following table: ◯). If the variation in the film thickness exceeds ±10 μm and is within ±15 μm, the positional accuracy is slightly inferior, but it is evaluated as the film thickness uniformity that can be used as an optical device (the following table: Δ). If the variation in film thickness exceeds ±15 μm, the positional accuracy deteriorates, making it difficult to use as an optical device (the following table: x).

(Example 1)
<Preparation of thermal barrier paint>
In Example 1, a thermal barrier coating material was produced by the following method. Titanium oxide HT0210 (Toho Titanium; average particle size 2.25 μm) 210 g, silicone resin 40 g, dispersant 2.4 g, solvent 30 g are weighed and stirred for 10 minutes with a planetary rotation device (Awatori Kentaro; Shinky). The heat-shielding coating material of Example 1 was obtained.

<Preparation of heat shield film>
In Example 1, under the materials and conditions described in Table 1, a heat shield film was produced by the following method. The above heat-shielding paint was applied to a test piece for reflectance measurement, a test piece 17 for temperature evaluation, and a test piece for film thickness accuracy evaluation so that the film thickness would be 40 μm, and cured at room temperature for 1 hour. The heat shield film of Example 1 was obtained.

(Examples 2 to 15)
In Examples 2 to 15, thermal barrier paints and thermal barrier films were produced in the same manner as in Example 1 except that the materials and conditions shown in Tables 1 to 3 were used. HT0110 (Toho Titanium) is used for titanium oxide having an average particle diameter of 3 μm, and titanium oxide having an average particle diameter of 5 μm is dried at a low temperature in a rotary kiln at a temperature of 1100° C. It was made by firing for 2 hours.
For resins with a d-line refractive index of 1.42, any of X-41-1810 (Shin-Etsu Silicone), X-41-1805 (Shin-Etsu Silicone), X-41-1818 (Shin-Etsu Silicone), and KR251 (Shin-Etsu Silicone). Was used.
Zefl (Daikin; d-line refractive index 1.40) was used as the fluororesin.

In all of the examples, the d-line refractive index was adjusted to 2.5 or more and 3.2 or less and the proportion of particles having a particle diameter of 1.5 μm or less was adjusted to 35% by mass or less.

<Evaluation results>
Tables 4 to 6 show the results of evaluating the reflectance and the temperature reducing effect of the heat shield films of Examples 1 to 15 by the above method.

As a measurement result, it is preferable that the reflectance of the heat shield film is 94% or more. Further, it is preferable that the difference in temperature reduction effect from the blank is 15° C. or more. Further, the film thickness accuracy is preferably within ±15 μm, and more preferably the film thickness accuracy is within ±10 μm.

In Example 1, as shown in Table 1, titanium oxide having an average particle diameter of 2.25 μm and silicone resin having a d-line refractive index of 1.39 were used. Table 4 shows the results of evaluating the reflectance and the temperature reducing effect of the obtained heat shield film. The evaluation result of the reflectance was 96%, which was good. Further, the temperature reducing effect was 15° C. or higher, which was favorable. The evaluation result of the film thickness accuracy was within ±10 μm, which was good.

In Example 2, as compared with Example 1, titanium oxide having a large average particle size of 3 μm was used. Table 4 shows the results of evaluating the reflectance, the temperature reduction effect, and the film thickness accuracy of the obtained heat shield film. The evaluation result of the reflectance was 96%, which was good. Further, the temperature reducing effect was 15° C. or higher, which was favorable. The evaluation result of the film thickness accuracy was within ±10 μm, which was good.

In Example 3, titanium oxide having an average particle size of 5 μm, which is larger than that of Example 1, was used. Table 4 shows the results of evaluating the reflectance, the temperature reduction effect, and the film thickness accuracy of the obtained heat shield film. The evaluation result of the reflectance was 95%, which was good. Further, the temperature reducing effect was 15° C. or higher, which was favorable. The evaluation result of the film thickness accuracy was within ±10 μm, which was good.

In Example 4, the titanium oxide particles (JR-1000; TAYCA) having an average particle diameter of 1 μm were used so that the ratio of particles having a particle diameter of 1.5 μm or less to all particles was 35% by volume. Titanium oxide added and adjusted was used. Table 4 shows the results of evaluating the reflectance, the temperature reduction effect, and the film thickness accuracy of the obtained heat shield film. The evaluation result of the reflectance was 95%, which was good. Further, the temperature reducing effect was 15° C. or higher, which was favorable. The evaluation result of the film thickness accuracy was within ±10 μm, which was good.

In Example 5, adjustment was made so that the ratio of titanium oxide to the heat shield film was 20% by volume as compared with Example 1. Table 4 shows the results of evaluating the reflectance, the temperature reduction effect, and the film thickness accuracy of the obtained heat shield film. The evaluation result of the reflectance was 94%, which was good. Further, the temperature reducing effect was good although it was slightly inferior at 15°C. The evaluation result of the film thickness accuracy was within ±10 μm, which was good.

In Example 6, adjustment was made so that the ratio of titanium oxide to the heat shield film was 22% by volume as compared with Example 1. Table 5 shows the results of evaluating the reflectance, the temperature reduction effect, and the film thickness accuracy of the obtained heat shield film. The evaluation result of the reflectance was 95%, which was good. Further, the temperature reducing effect was 15° C. or higher, which was favorable. The evaluation result of the film thickness accuracy was within ±10 μm, which was good.

In Example 7, as compared with Example 1, the ratio of titanium oxide to the heat shield film was adjusted to be 59% by volume. Table 5 shows the results of evaluating the reflectance, the temperature reduction effect, and the film thickness accuracy of the obtained heat shield film. The evaluation result of the reflectance was 98%, which was good. Further, the temperature reducing effect was 15° C. or higher, which was favorable. The evaluation result of the film thickness accuracy was within ±10 μm, which was good.

In Example 8, as compared with Example 1, adjustment was made so that the ratio of titanium oxide to the heat shield film was 60% by volume. Table 5 shows the results of evaluating the reflectance, the temperature reduction effect, and the film thickness accuracy of the obtained heat shield film. The evaluation result of the reflectance was 98%, which was good. The temperature reduction effect was 15° C. or more, which was good, but the brittleness was slightly deteriorated, but it was at a usable level. The evaluation result of the film thickness accuracy was within ±10 μm, which was good.

In Example 9, the fluororesin was used instead of the silicone resin in Example 1. Table 5 shows the results of evaluating the reflectance, the temperature reduction effect, and the film thickness accuracy of the obtained heat shield film. The evaluation result of the reflectance was 95%, which was good. Further, the temperature reducing effect was 15° C. or higher, which was favorable. The evaluation result of the film thickness accuracy was within ±10 μm, which was good.

In Example 10, as compared with Example 1, hollow particles were mixed in a silicone resin to adjust the d-line refractive index to 1.32. Table 5 shows the results of evaluating the reflectance, the temperature reduction effect, and the film thickness accuracy of the obtained heat shield film. The evaluation result of the reflectance was 95%, which was good. Further, the temperature reducing effect was 15° C. or higher, which was favorable. The evaluation result of the film thickness accuracy was within ±10 μm, which was good.

In Example 11, as compared with Example 1, a silicone resin having a d-line refractive index of 1.42 was used as the resin. Table 6 shows the results of evaluating the reflectance, the temperature reduction effect, and the film thickness accuracy of the obtained heat shield film. The evaluation result of the reflectance was 95%, which was good. Further, the temperature reducing effect was 15° C. or higher, which was favorable. The evaluation result of the film thickness accuracy was within ±10 μm, which was good.

In Example 12, as compared with Example 1, the film thickness was adjusted to 9 μm. Table 6 shows the results of evaluating the reflectance, the temperature reduction effect, and the film thickness accuracy of the obtained heat shield film. The evaluation result of the reflectance was 94%, which was good. The temperature reduction effect was 15° C., which was somewhat inferior but was good. The evaluation result of the film thickness accuracy was within ±10 μm, which was good.

In Example 13, as compared with Example 1, the film thickness was adjusted to 10 μm. Table 6 shows the results of evaluating the reflectance, the temperature reduction effect, and the film thickness accuracy of the obtained heat shield film. The evaluation result of the reflectance was 96%, which was good. Further, the temperature reducing effect was 15° C. or higher, which was favorable. The evaluation result of the film thickness accuracy was within ±10 μm, which was good.

In Example 14, the film thickness was adjusted to 70 μm as compared with Example 1. Table 6 shows the results of evaluating the reflectance, the temperature reduction effect, and the film thickness accuracy of the obtained heat shield film. The evaluation result of the reflectance was 96%, which was good. Further, the temperature reducing effect was 15° C. or higher, which was favorable. The evaluation result of the film thickness accuracy was within ±10 μm, which was good.

In Example 15, as compared with Example 1, the film thickness was adjusted to 80 μm. Table 6 shows the results of evaluating the reflectance, the temperature reduction effect, and the film thickness accuracy of the obtained heat shield film. The evaluation result of the reflectance was 96%, which was good. Further, the temperature reducing effect was 15° C. or higher, which was favorable. In addition, the evaluation result of the film thickness accuracy was ±11 to 15 μm, which was at a level that could be used for an optical device, although it was somewhat inferior.

[Comparative Examples 1 to 5]
Adjustment of a heat-shielding paint for comparison, preparation of a heat-shielding film, evaluation of reflectance, evaluation of temperature reduction effect, and evaluation of film thickness accuracy were performed in the same manner as in Examples 1 to 15 described above. Differences from Examples 1 to 15 are shown below.
Tables 7 and 8 show materials and contents of the heat shield films of Comparative Examples 1 to 7.
Tables 9 and 10 show the results of evaluation using the heat shield films of Comparative Examples 1 to 7, respectively.

In Comparative Example 1, zinc oxide particles (#F; Sakai Chemical Co., Ltd.) having an average particle diameter of 3.8 μm were used as compared with Example 1. Table 9 shows the results of evaluating the reflectance, the temperature reduction effect, and the film thickness accuracy of the obtained heat shield film. The reflectance evaluation result was 78%, which was poor. Further, the effect of reducing the temperature was also poor at less than 15°C. The evaluation result of the film thickness accuracy was within ±10 μm, which was good.

In Comparative Example 2, silicon having an average particle size of 5 μm (SIE23PB; high-purity chemical) was used as compared with Example 1. Table 9 shows the results of evaluating the reflectance, the temperature reduction effect, and the film thickness accuracy of the obtained heat shield film. The reflectance evaluation result was 81%, which was poor. Further, the effect of reducing the temperature was also poor at less than 15°C. The evaluation result of the film thickness accuracy was within ±10 μm, which was good.

In Comparative Example 3, as compared with Example 1, titanium oxide (JR-1000; TAYCA) having an average particle size of 1 μm was used. Table 9 shows the results of evaluating the reflectance, the temperature reduction effect, and the film thickness accuracy of the obtained heat shield film. The evaluation result of the reflectance was 85%, which was poor. Further, the effect of reducing the temperature was also poor at less than 15°C. The evaluation result of the film thickness accuracy was within ±10 μm, which was good.

In Comparative Example 4, titanium oxide having an average particle size of 7 μm was used as compared with Example 1. Table 9 shows the results of evaluating the reflectance, the temperature reduction effect, and the film thickness accuracy of the obtained heat shield film. The evaluation result of the reflectance was 95%, which was good. The temperature reduction effect was also good, being 15° C. or higher. However, the evaluation result of the film thickness accuracy was ±16 μm or more, which was bad.

In Comparative Example 5, titanium oxide particles (JR-1000; Takea) having an average particle size of 1 μm were used in comparison with Example 1 such that the ratio of particles having a particle size of 1.5 μm or less to all particles was 40% by volume. Titanium oxide added and adjusted was used. Table 9 shows the results of evaluating the reflectance, the temperature reduction effect, and the film thickness accuracy of the obtained heat shield film. The evaluation result of the reflectance was 93%, which was rather bad. Further, the effect of reducing the temperature was 14° C., which was rather bad. The evaluation result of the film thickness accuracy was within ±10 μm, which was good.

In Comparative Example 6, the d-line refractive index was adjusted to 1.30 by using hollow particles as compared with Example 1. Table 10 shows the results of evaluating the reflectance, the temperature reduction effect, and the film thickness accuracy of the obtained heat shield film. The evaluation result of the reflectance was 93%, which was rather bad. Further, the effect of reducing the temperature was 14° C., which was rather bad. The evaluation result of the film thickness accuracy was within ±10 μm, which was good.

In Comparative Example 7, urethane resin was used so that the d-line refractive index was about 1.50 as compared with Example 1. Table 10 shows the results of evaluating the reflectance, the temperature reduction effect, and the film thickness accuracy of the obtained heat shield film. The evaluation result of the reflectance was 87%, which was poor. Moreover, the effect of reducing the temperature was also poor at less than 15°C. The evaluation result of the film thickness accuracy was within ±10 μm, which was good.

The light-shielding film for an optical device of the present invention is a lens barrel of an optical device such as a camera, a video device, and a broadcasting device, and other camera bodies that may be used outdoors, a video body, a surveillance camera, a weather camera, etc. It can be used as a light-shielding film for optical devices.

1. Incident light
2. reflected light
3. Transmitted light
4. Infrared reflective film
5. Base material
6. lens
7. Mating part
8. Lens barrel 9. Heat shield film
10. particle
11. resin
12. Reflection in particles
13. Integrating sphere
14. Test piece attachment part
15. Detector
16. lamp
17. Test piece for temperature evaluation
18. Temperature measurement point

Claims (15)

An optical device having a lens and a lens barrel in which the lens is arranged, having a heat shield film on at least a part of an outer peripheral surface of the lens barrel,
The heat shield film has particles having a d-line refractive index of 2.5 or more and 3.2 or less and a resin having a d-line refractive index of 1.32 or more and 1.42 or less,
The optical device, wherein the particles have an average particle size of 2 μm or more and 5 μm or less, and a ratio of particles having a particle size of 1.5 μm or less to the entire particles is 35% by mass or less. The optical device according to claim 1, wherein the heat shield film has an average reflectance of 94% or more for light having a wavelength of 400 nm to 2600 nm that is incident at an incident angle of 5°. The optical device according to claim 1 or 2, wherein the particles are titanium oxide. The optical device according to any one of claims 1 to 3, wherein the heat shield film has a content of the particles of 20% by volume or more and 60% by volume or less. The optical device according to any one of claims 1 to 4, wherein an average film thickness of the heat shield film is 10 µm or more and 70 µm or less. The optical device according to any one of claims 1 to 5, wherein the resin is a silicone resin or a fluororesin. A heat shield film comprising particles having a d-line refractive index of 2.5 or more and 3.2 or less and a resin having a d-line refractive index of 1.32 or more and 1.42 or less,
The particles have an average particle size of 2 μm or more and 5 μm or less, and a ratio of particles having a particle size of 1.5 μm or less to the entire particles is 35% by mass or less. The heat shield film according to claim 7, which is a heat shield film for an optical device, which is provided on at least a part of the outer peripheral surface of the lens barrel. 9. The heat shield film according to claim 7, wherein the average reflectance of light having a wavelength of 400 nm to 2600 nm that is incident at an incident angle of 5° is 94% or more. 10. The heat shield film according to claim 7, wherein the particles are titanium oxide. The thermal barrier film according to any one of claims 7 to 10, wherein the particles have a content of 20% by volume or more and 60% by volume or less. The thermal barrier film according to claim 7, wherein the average film thickness is 10 μm or more and 70 μm or less. The heat shield film according to claim 7, wherein the resin is a silicone resin or a fluororesin. A thermal barrier paint comprising a solvent having a d-line refractive index of 2.5 or more and 3.2 or less, a d-line refractive index of 1.32 or more and 1.42 or less, and a solvent,
The thermal barrier coating material, wherein the particles have an average particle size of 2 μm or more and 5 μm or less, and a ratio of particles having a particle size of 1.5 μm or less with respect to the entire particles is 35% by mass or less. The thermal barrier coating according to claim 14, wherein the thermal barrier coating is used as a thermal barrier for an optical device to be provided on at least a part of the outer peripheral surface of the lens barrel.

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