JP7125272B2 - Transparent black body film and transparent black body paint - Google Patents

Description

TECHNICAL FIELD The present invention relates to a transparent blackbody film and a transparent blackbody paint used for infrared thermography inspection and the like.

Infrared thermography is a device that can measure temperature using images.It is characterized by non-contact photography and real-time measurement.As one of the temperature measurement methods, it is widely used from research to simple inspection. ing. Also, there is a well-known method of inspecting internal defects of structures and defects of inspected objects such as corrosion of automobile steel plates from the temperature distribution by infrared thermography. This method utilizes the fact that when the object to be inspected has defects such as scratches inside, the temperature of the surface where there is an internal defect differs from the temperature of the surface where there is no defect when the object is heated. and non-destructive inspection using infrared thermography. However, when the object to be inspected is a low-emissivity material such as metal, it is difficult to perform accurate measurement.
Therefore, for example, as described in Patent Document 1, a paint containing a carbon-based black pigment, a solvent containing alcohol and an aliphatic hydrocarbon, and a dispersant is applied to the surface of the object to be inspected, and the coating film is formed. , a defect inspection by infrared thermography for acquiring a thermal image, and a method of removing the coating film by washing with water after the defect inspection is known.
This method utilizes the fact that the intensity of infrared rays emitted from the paint layer itself provided on the surface of the object to be inspected differs depending on the temperature difference due to the presence or absence of defects. Objects can be inspected non-destructively.

JP 2001-108634 A

In the conventional inspection method, a coating film was formed with a paint containing a carbon-based black pigment. It is possible to carry out an inspection.
However, once such a paint forms a coating film, the coating film exhibits a black color due to the carbon-based black pigment contained in the coating film until it is removed with an appropriate organic solvent or the like. It was difficult to confirm the state of the surface, for example, visually.
In addition, when the coating film is removed by solvent washing after the inspection, the waste liquid has a black color due to the carbon-based black pigment, so the appearance of the waste liquid is poor, and the waste liquid that falls on the ground dries and turns the ground black. Therefore, it was necessary to give special consideration to the treatment and management of the waste liquid. Furthermore, when droplets or the like remain on the surface of the object to be inspected, they dry up, leaving black stains, spots, or traces of flow on the surface of the object to be inspected, which deteriorates the appearance.
Moreover, in recent years, the carcinogenicity of conventional black body paints has been pointed out, and there is an increasing demand for safer alternative black body paints.
In the present invention, it is difficult to visually confirm the surface state of an object to be inspected at the same time as inspection by infrared thermography, and furthermore, it is difficult to dispose of the waste liquid after washing with a solvent, and the appearance of the surface of the object to be inspected after inspection is deteriorated. The purpose is to eliminate

The present invention for solving the above problems is as follows.
1. A transparent black body film containing a polyvinyl alcohol-based resin.
2. 2. The transparent black body film according to 1, wherein an adhesive layer is laminated on a layer containing a polyvinyl alcohol-based resin.
3. 3. The transparent black body film according to 1 or 2, wherein a substrate layer is provided on the side of the layer containing the polyvinyl alcohol-based resin.
4. 4. The transparent black body film according to any one of 1 to 3, which is used for infrared thermography inspection of the surface of an object to be inspected.
5. A transparent black body paint containing a polyvinyl alcohol-based resin.
6. 5. The transparent black body paint according to 5, which is used for infrared thermography inspection of the surface of an object to be inspected.

According to the transparent black body film of the present invention, it is possible to accurately perform inspection by infrared thermography while maintaining a state in which visual inspection and confirmation of the surface of the object to be inspected is possible. In addition, it is easy to dispose of the waste liquid after washing with water, and obtains the effect that the appearance of the surface of the object to be inspected can be maintained after the inspection is completed.
Further, according to the transparent black-body paint of the present invention, in addition to the effects of the transparent black-body film, it is possible to accurately inspect an object having a more complicated surface shape.

Diagram showing inspection results in visible light Diagram showing infrared inspection results

The transparent black-body film and the transparent black-body paint of the present invention are based on containing a polyvinyl alcohol-based resin.

(polyvinyl alcohol resin)
The polyvinyl alcohol resin used in the present invention may be water-soluble or water-insoluble, but is not particularly limited as long as it has a high infrared emissivity. Resins obtained by saponifying a vinyl ester-based polymer obtained by polymerizing a vinyl ester-based compound can be widely used. In addition, such polyvinyl alcohol-based resins may be used in combination of not only one type but also two or more types.
Vinyl ester compounds include vinyl acetate, vinyl formate, vinyl trifluoroacetate, vinyl propionate, vinyl butyrate, vinyl caprate, vinyl laurate, vinyl versatate, vinyl palmitate, vinyl stearate, and the like. 1 type, or 2 or more types are used.

As the polyvinyl alcohol-based resin, an anionic group-modified polyvinyl alcohol resin or a cationic group-modified polyvinyl alcohol resin may be used. Of course, non-denatured polyvinyl alcohol resin may also be used.
When using a water-soluble polyvinyl alcohol resin, an anionic group-modified polyvinyl alcohol resin is preferable. Examples of anionic groups include, but are not limited to, carboxyl groups, sulfonic acid groups, and phosphoric acid groups.
Examples of the anionic group-modified polyvinyl alcohol resin include, but are not limited to, maleic acid-modified polyvinyl alcohol resin, itaconic acid-modified polyvinyl alcohol resin, acrylic acid-modified polyvinyl alcohol resin, methacrylic acid-modified polyvinyl alcohol resin, and 2-acrylamide-2. -Methylpropanesulfonic acid-modified polyvinyl alcohol resin and the like.
The modification amount of the anionic group-modified polyvinyl alcohol resin is preferably 0.1 to 10 mol %, more preferably 0.5 to 8 mol %, particularly preferably 1 to 6 mol %, in terms of the modified unit content. 0.1 mol % or more is preferable from the viewpoint of solubility in water, and 10 mol % or less is preferable from the viewpoint of productivity and cost of the resin.

The polyvinyl alcohol-based resin used in the present invention may be copolymerized with, for example, the following monomers.
Olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, α-octadecene, etc. Complete alkyl esters of unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, etc. , acrylonitrile, nitriles such as methacrylonitrile, amides such as acrylamide, methacrylamide, alkyl vinyl ethers, N-acrylamidomethyltrimethylammonium chloride, allyltrimethylammonium chloride, dimethyldiallylammonium chloride, dimethylallyl vinyl ketone, N-vinylpyrrolidone , Polyoxyalkylene (meth)allyl ether such as vinyl chloride, vinylidene chloride, polyoxyethylene (meth)allyl ether, polyoxypropylene (meth)allyl ether, polyoxyethylene (meth)acrylate, polyoxypropylene (meth)acrylate Polyoxyalkylene (meth)acrylates such as polyoxyethylene (meth)acrylamide, polyoxyalkylene (meth)acrylamides such as polyoxypropylene (meth)acrylamide, polyoxyethylene (1-(meth)acrylamide-1,1- dimethylpropyl) ester, polyoxyethylene vinyl ether, polyoxypropylene vinyl ether, polyoxyethylene allylamine, polyoxypropylene allylamine, polyoxyethylene vinylamine, polyoxypropylene vinylamine, diacrylacetoneamide and the like.

Furthermore, N-acrylamidomethyltrimethylammonium chloride, N-acrylamidoethyltrimethylammonium chloride, N-acrylamidopropyltrimethylammonium chloride, 2-acryloxyethyltrimethylammonium chloride, 2-methacryloxyethyltrimethylammonium chloride, 2-hydroxy-3- Cationic group-containing monomers such as methacryloyloxypropyltrimethylammonium chloride, allyltrimethylammonium chloride, methallyltrimethylammonium chloride, 3-butenetrimethylammonium chloride, dimethyldiallylammonium chloride and diethyldiallylammonium chloride are also included.
These monomers can be contained, for example, in an amount of 0.01 to 10 mol % within a range that does not impede the object of the present invention.

The average degree of saponification of the polyvinyl alcohol-based resin is not particularly limited. For example, when the film is required to be water-soluble from the viewpoint of removal of the coating film, it is preferably 60 to 100 mol%, more preferably 65 to 96 mol%, and particularly preferably 70 to 94 mol%.
In addition, said average degree of saponification is measured based on JISK67263.5.

The degree of polymerization of the polyvinyl alcohol resin is not particularly limited, but when used as a black body film, it is preferably 300 to 8000, more preferably 500 to 4000, and particularly preferably 1000 to 3000, from the viewpoint of film strength. On the other hand, when used as a black body paint, it is preferably from 100 to 3,000, more preferably from 200 to 2,000, particularly preferably from 200 to 1,000, from the solution viscosity.

(Thickness of polyvinyl alcohol-based resin film and coating thickness of transparent black body paint, etc.)
When the polyvinyl alcohol-based resin in the present invention is used as a black body film in the form of a film, the thickness of the film is not particularly limited, but is preferably 10 to 100 μm, more preferably 13 to 100 μm, and particularly preferably 15 to 90 μm. If the thickness is within this range, the strength as a black body film for infrared thermography inspection can be maintained appropriately.
Preferably, the transparent black body film of the present invention is transparent and has flat surfaces on both sides. By being transparent, when the adhesive layer is also transparent, the state of the surface of the object to be inspected can be visually confirmed through the transparent black body film of the present invention during infrared thermography inspection, so the inspection result can be confirmed. The surface of the object to be inspected can be inspected visually. Moreover, when both surfaces of the polyvinyl alcohol-based resin film are flat, the inspection accuracy can be further improved when the film is used as a transparent blackbody film for infrared thermography inspection.
Moreover, when the polyvinyl alcohol-based resin film is water-soluble, it is possible to remove the film by washing with water after the infrared thermography inspection.
If the polyvinyl alcohol is water-insoluble, it can remain attached to the surface of the film to be inspected even after the infrared thermography inspection, and can be inspected again thereafter. Moreover, in the case of being soluble in a solvent, it can be removed with a solvent when it becomes unnecessary.
It is preferable that the coating thickness of the transparent black body paint is approximately the same as the thickness of the black body film. Also, if the inspection method and the polyvinyl alcohol-based resin are water-soluble, the coated film can be removed by washing with water after the infrared thermography inspection, as in the case of the film.

(Adhesive layer)
As the adhesive used in the adhesive layer to be laminated on the transparent black body film in the present invention, a known adhesive may be used, and acrylic resins, polyethylene vinyl acetate resins, polyvinyl alcohol resins, etc. can be used. When the film is removed by washing with water after the infrared thermography inspection, the adhesive is preferably water-soluble. When the adhesive is water-soluble, the adhesive layer can be removed at the same time as the transparent black body film is removed by washing with water.
However, since the adhesive layer is used exclusively for infrared thermography inspection to fix the transparent black body film to the surface of the object to be inspected, it can be widely adhered to various materials on the surface of the object to be inspected. is necessary. Further, a more appropriate adhesive layer can be provided depending on the material, shape, etc. of the surface of the object to be inspected.

(Thickness of adhesive layer, etc.)
Both surfaces of the pressure-sensitive adhesive layer are preferably flat. Furthermore, since the adhesive layer is visually transparent, when the polyvinyl alcohol-based resin film is visually transparent, the surface of the object to be inspected during infrared thermography inspection passes through the transparent black body film for infrared thermography inspection of the present invention. Therefore, the surface of the object to be inspected can be visually inspected while confirming the inspection result.
The thickness of the adhesive layer is not particularly limited. 1 to 50 μm is preferable, 5 to 40 μm is more preferable, and 15 to 30 μm is particularly preferable. If the thickness is within this range, the pressure-sensitive adhesive layer can have sufficient adhesive strength.
The layer of the pressure-sensitive adhesive layer that is not on the side of the polyvinyl alcohol-based resin layer is preferably flat.
As means for laminating such an adhesive layer on the polyvinyl alcohol-based resin layer, for example, the adhesive layer is formed by known means such as casting or extrusion on the release surface of the release film shown below. and dry to remove solvent if necessary. Then, the pressure-sensitive adhesive layer and the polyvinyl alcohol-based resin layer thus formed are superimposed on each other by means of pressure bonding or the like, and a means of laminating the pressure-sensitive adhesive layer on one side of the polyvinyl alcohol-based resin layer can be employed.
When a pressure-sensitive adhesive layer is provided on the release film, the product can be obtained without peeling the release film.

(Plasticizer)
The transparent black body film, the pressure-sensitive adhesive layer, and the transparent black body paint can each contain a plasticizer within a range that does not impair the functions of those layers or the formed coating film. The plasticizer is not particularly limited, and known plasticizers can be applied. For example, polyglycerols such as glycerin and diglycerin, sugars such as glucose, fructose, lactose, sorbitol and mannitol, sugar alcohols, low molecular weight polyethylene glycol (molecular weight: 600 or less), ethylene glycol, propylene glycol, trimethylolpropane, 2 -Methyl-1,3-propanediol and other polyhydric alcohol plasticizers. A plasticizer may be used individually by 1 type, and may be used in mixture of 2 or more types.
The content (total amount) of the plasticizer is not particularly limited. For example, 0 to 50 parts by mass is preferable, 5 to 40 parts by mass is more preferable, and 8 to 30 parts by mass is particularly preferable with respect to 100 parts by mass of polyvinyl alcohol-based resin. If the content is within this range, a plasticizing effect can be obtained, the bleeding of the plasticizer to the surface can be suppressed, and sufficient film strength or coating strength can be obtained. By adding a plasticizer, the transparent black body film and the coating film become soft and easily follow the surface of the object to be inspected when they are attached to the object to be inspected.
Furthermore, since these plasticizers have radiation properties different from those of polyvinyl alcohol-based resins, the addition of the plasticizer to the transparent black body film and transparent black body paint contributes to the improvement of the emissivity.

(Surfactant)
The transparent black body film, the pressure-sensitive adhesive layer and the transparent black body paint can all contain surfactants within a range that does not impair the functions of these layers and coating films. The surfactant is not particularly limited, and known surfactants can be applied. As surfactants, ionic surfactants (anionic surfactants, cationic surfactants, amphoteric surfactants), nonionic surfactants, and polymeric surfactants can be applied. Surfactants may be used alone or in combination of two or more.
The content of the surfactant is not particularly limited. 0.01 to 3.0 parts by mass is preferable, 0.03 to 2.5 parts by mass is more preferable, and 0.05 to 1.5 parts by mass is particularly preferable with respect to 100 parts by mass of the polyvinyl alcohol-based resin. This is because if the content is within this range, the handling of the film during the formation of the polyvinyl alcohol-based resin layer and the coatability of the transparent black body paint become easy, thereby improving the productivity.

(Other additives)
Various other additives can be contained in the transparent black body film, the pressure-sensitive adhesive layer, and the transparent black body coating as long as the functions of these layers and coating films are not impaired. As additives, colorants, fragrances, bulking agents, antifoaming agents, release agents, ultraviolet absorbers, inorganic powders and the like are used as necessary.
Additives may be added to the polyvinyl alcohol-based resin layer, the pressure-sensitive adhesive layer, and the transparent black body paint to the extent that they become opaque.
Inorganic fillers and organic fillers can be contained in the polyvinyl alcohol-based resin layer, the pressure-sensitive adhesive layer, and the transparent black-body paint as long as the functions of these layers are not impaired. Examples of inorganic fillers include, but are not limited to, silica, talc, clay, hydrotalcite, diatomaceous earth, kaolin, mica, gypsum, graphite, glass balloons, glass beads, calcium sulfate, barium sulfate, ammonium sulfate, and calcium sulfite. , calcium carbonate, whisker-like calcium carbonate, magnesium oxide, magnesium hydroxide, zinc oxide, magnesium carbonate, dawsonite, dolomite, potassium titanate, carbon black, glass fiber, alumina fiber, boron fiber, processed mineral fiber, carbon fiber, carbon Hollow sphere, bentonite, montmorillonite, copper powder, sodium sulfate, potassium sulfate, zinc sulfate, copper sulfate, iron sulfate, magnesium sulfate, aluminum sulfate, aluminum potassium sulfate, ammonium nitrate, sodium nitrate, potassium nitrate, aluminum nitrate, ammonium chloride, sodium chloride , potassium chloride, magnesium chloride, calcium chloride, sodium phosphate, potassium chromate, calcium citrate and the like.
Examples of the organic filler include, but are not particularly limited to, various resins such as starch and melamine resins.
The filler content is not particularly limited. It is preferably 0 to 100 parts by mass, more preferably 0.1 to 50 parts by mass, and particularly preferably 1 to 10 parts by mass, based on 100 parts by mass of the polyvinyl alcohol-based resin. By adding a filler, the anti-blocking property of the transparent black body film and coating film may be improved, and the filler may also act as a dissolution aid when washed with water.

Also, the polyvinyl alcohol-based resin may be mixed with other water-soluble polymers. Examples of water-soluble polymers include gelatin, casein, gum arabic, polyvinylpyrrolidone, pullulan, methylcellulose, hypromellose, and ethylcellulose. The amount of the water-soluble polymer added is preferably 20 parts by mass or less with respect to 100 parts by mass of the polyvinyl alcohol resin.

(Manufacturing method of transparent blackbody film)
The transparent black body film of the present invention can be obtained by, for example, casting an aqueous solution of a polyvinyl alcohol-based resin on a smooth surface and drying it. It can also be obtained by forming a film from a melted polyvinyl alcohol-based resin by known means such as extrusion molding.
Also, water may be added to the raw material. The amount of water added is not particularly limited. Usually, it is 25 to 10,000 parts by mass, more preferably 40 to 1,000 parts by mass, based on 100 parts by mass of the polyvinyl alcohol-based resin. This is because within this range, the film-forming efficiency is improved.

(base material sheet)
When the transparent black body film of the present invention is provided with a layer comprising a substrate sheet, workability is improved when the film is attached to an object to be inspected during infrared thermography inspection. By adhering the surface of the pressure-sensitive adhesive layer on the transparent black body film on the base sheet to the surface of the object to be inspected, the surface of the object to be inspected is covered with the transparent black body film together with the base sheet. After that, by peeling the base sheet from the transparent black body film, the surface can be covered with the transparent black body film exposed.
Examples of such a base sheet include glassine paper, kraft paper, clay-coated paper, paper laminated with a film such as polyethylene, paper coated with a resin such as polyvinyl alcohol or acrylic acid ester copolymer, polyester, polypropylene, and the like. A synthetic resin film or the like coated with a release agent such as fluororesin or silicone resin, if necessary.

(release sheet)
For the purpose of stable storage, the transparent black body film of the present invention is preferably covered with a release sheet on the pressure-sensitive adhesive layer side to improve storage stability.
As such a release sheet, a release sheet for adhesive tape can be used. For example, glassine paper, kraft paper, clay coated paper, paper laminated with a film such as polyethylene, paper coated with a resin such as polyvinyl alcohol or acrylic acid ester copolymer, synthetic resin film such as polyester or polypropylene, etc. Depending on the circumstances, there may be mentioned those coated with a release agent such as a fluororesin or a silicone resin.

(Method for producing transparent black body paint)
The transparent black body paint of the present invention may contain the above plasticizer, surfactant and other additives in addition to the above polyvinyl alcohol resin. When the paint is water-soluble, it contains water and, if necessary, a polar organic solvent. When it is non-water-soluble, a polar organic solvent can be used. Here, as the polar organic solvent, known ones such as methanol, ethanol, ethylene glycol, acetone, ethyl acetate, 1-methyl-2-pyrrolidone can be used, and the polyvinyl alcohol resin is dissolved or dispersed. It is not limited to these as long as it is possible.
Additives for paints such as plasticizers and tackifiers may be added in arbitrary amounts as long as the effects of the present invention are not impaired.

(Infrared thermography inspection object)
The object to be inspected for infrared thermography inspection using the transparent black body film and transparent black body paint of the present invention may be any object that has been conventionally inspected using infrared thermography. Parts such as walls, floors, ceilings, doors, and piping; structures such as bridges, tunnels, breakwaters, and seawalls; industrial equipment such as tanks, pipes, and cranes; Artifacts, daily necessities, antiques, and the like, as well as composite structural materials such as honeycomb panels and FRP, which have been increasingly used in recent years, can be targets.
As a result of the inspection, it becomes clear whether or not the surface or inside of the object to be inspected has defects such as delamination, thin portions, cracks, and the like.

<Infrared thermography inspection method>
Before attaching the transparent black body film to the object to be inspected or before applying the transparent black body paint to the object to be inspected, if necessary, remove dirt from the surface of the object to be inspected, and if necessary, wash it with water, etc. wash.
Next, the transparent black body film of the present invention is adhered to the surface of the object to be inspected by means of an adhesive layer provided in advance or by an adhesive or the like. If there is no adhesive layer, the film surface or the entire film can be dissolved with water, hot water, a polar solvent, or the like, or the film can be attached to the object to be inspected by heating to the melting point or above. Alternatively, a transparent black body paint is applied to the surface of the object to be inspected by any means.
In any case, if air enters between the surface of the object to be inspected and the adhesive layer, there is a possibility that this air portion will be detected as a defect during infrared thermography inspection, so it is important not to introduce air. .
Since the transparent film of the present invention is transparent, air bubbles can be visually confirmed, and the validity of the inspection can be easily confirmed before the inspection. Furthermore, the air bubbles can be removed by making a fine hole with a needle or the like, and the inspection itself is not affected. Alternatively, air bubbles can be prevented from entering by pre-perforating the entire surface of the film to the extent that the accuracy required for inspection is not hindered. Although the shape and size of the hole are not particularly limited, for example, if it is circular, it is preferably 1 cm or less, more preferably 5 mm or less. becomes possible. In addition, even without making holes in the transparent film, it is possible to form an air layer between the surface of the object to be inspected and the transparent film by making the adhesive layer dot-shaped or by adding groove-shaped unevenness, allowing the air to escape. You can also make it easier.
When adhering, the release sheet may be laminated on the surface of the pressure-sensitive adhesive layer until immediately before adhering, and the release sheet may be peeled off at the time of adhering.

To the surface of the test object after bonding the transparent black body film to the surface or after applying the transparent black body paint, or before bonding the transparent black body film to the surface or before applying the transparent black body paint If necessary, the surface of the object to be inspected is heated by an infrared lamp or the like. If the object to be inspected is plate-shaped or tubular, the surface opposite to the surface on which the temperature is detected by infrared thermography may be heated.
By heating the surface of the object to be inspected by supplying the amount of heat as uniformly as possible in this way, if there is no defect inside or outside the object to be inspected, the temperature can be made uniform, and the inspection accuracy of the object to be inspected can be improved. can.
When performing inspection by applying transparent black body paint, it is possible to check the temperature distribution of the object to be inspected by heating. It can also be inspected by checking the distribution of the temperature drop.
Such inspection using the heat of vaporization does not require a device for heating the surface of the object to be inspected, so the required device can be reduced. In addition, when conducting an inspection using the heat of vaporization, it is possible to perform accurate measurement by using a solvent with a higher vapor pressure as long as the solvent is capable of dissolving or dispersing the resin. Alcohols and the like are preferred.

Subsequently, an infrared thermography inspection is performed using a known infrared camera or the like, and image processing or the like is performed to obtain the intensity distribution of the detected infrared rays. At this time, the infrared camera is preferably directed perpendicularly to the plane of the inspection area of the surface of the object to be inspected.

(Example 1)
An aqueous solution having a solid concentration of 15% by weight was prepared by adding 10 parts by weight of glycerin to 100 parts by weight of polyvinyl alcohol (degree of saponification: 88 mol %, degree of polymerization: 1500). This aqueous solution was cast on a 75 μm PET sheet, dried at 80° C., and peeled off to obtain a transparent black body film sample. The thickness of the sample after drying was adjusted to 15 μm by adjusting the film thickness during casting.

(Example 2)
An aqueous solution of polyvinyl alcohol (degree of saponification 88 mol %, degree of polymerization 1500) having a solid concentration of 15% by weight was prepared. This aqueous solution was cast on a 75 μm PET sheet, dried at 80° C., and peeled off to obtain a transparent black body film sample. The thickness of the sample after drying was adjusted to 40 μm by adjusting the film thickness during casting.

(Example 3)
A sample of a transparent black body film having a sample thickness of 75 μm was obtained in the same manner as in Example 1, except that the film thickness during casting was adjusted.

(Example 4)
An aqueous solution having a solid concentration of 15% by weight was prepared by adding 10 parts by weight of glycerin to 100 parts by weight of polyvinyl alcohol (degree of saponification: 99.6 mol %, degree of polymerization: 1700). After this aqueous solution was sprayed on a test piece for measurement, it was dried at 80° C. and peeled off to obtain a sample of a transparent black body film. The thickness of the sample after drying was adjusted to 25 μm by adjusting the film thickness during casting.

(Example 5)
A sample of a transparent black body film having a sample thickness of 90 μm was obtained in the same manner as in Example 4, except that the film thickness during casting was adjusted.

(Example 6)
An aqueous solution having a solid concentration of 15% by weight was prepared by adding 10 parts by weight of glycerin to 100 parts by weight of carboxyl group-modified polyvinyl alcohol (degree of saponification: 88 mol %, degree of polymerization: 1700). This aqueous solution was cast on a 75 μm PET sheet, dried at 80° C., and peeled off to obtain a transparent black body film sample. The thickness of the sample after drying was adjusted to 30 μm by adjusting the film thickness during casting.

(Example 7)
An aqueous solution having a solid concentration of 25% by weight was prepared by adding 10 parts by weight of glycerin to 100 parts by weight of polyvinyl alcohol (degree of saponification: 70 mol %, degree of polymerization: 500). This aqueous solution was cast on a 75 μm PET sheet, dried at 80° C., and peeled off to obtain a transparent black body film sample. The thickness of the sample after drying was adjusted to 50 μm by adjusting the film thickness during casting.

(Example 8)
An aqueous solution having a solid concentration of 15% by weight was prepared by adding 10 parts by weight of glycerin to 100 parts by weight of polyvinyl alcohol (degree of saponification: 88 mol %, degree of polymerization: 1500). After casting this aqueous solution on a 75 μm PET sheet, it was dried at 80° C. to obtain a sample of a transparent black body film with a 75 μm PET sheet base. At this time, the film thickness at the time of casting was adjusted so that the polyvinyl alcohol resin film layer would have a thickness of 30 μm after drying.

(Example 9)
An aqueous solution of polyvinyl alcohol (degree of saponification 88 mol %, degree of polymerization 1500) having a solid concentration of 15% by weight was prepared. After casting this aqueous solution on a 75 μm PET sheet, it was dried at 80° C. to obtain a sample with a 75 μm PET sheet substrate. At this time, the film thickness during casting was adjusted so that the polyvinyl alcohol film layer had a thickness of 20 μm after drying. Furthermore, a 15 μm thick acrylic water-soluble adhesive layer was laminated on the polyvinyl alcohol resin layer to obtain a transparent black body film sample with an adhesive.

(Example 10)
A transparent black body paint was prepared as a methanol solution of polyvinyl alcohol (degree of saponification: 35 mol %, degree of polymerization: 250) with a solid concentration of 15% by weight. This methanol solution was applied to the test object using a sprayer and dried at room temperature. The thickness of the sample after drying was adjusted to 30 μm by adjusting the coating amount.

(Example 11)
A transparent black body paint was prepared as an acetone solution of polyvinyl alcohol (degree of saponification: 9 mol %, degree of polymerization: 250) with a solid concentration of 15% by weight. This acetone solution was applied to the test object using a sprayer and dried at room temperature. The thickness of the sample after drying was adjusted to 50 μm by adjusting the coating amount.

(Example 12)
A transparent black body paint was prepared as an aqueous solution with a solid content concentration of 15% by weight by adding 10 parts by weight of glycerin to 100 parts by weight of polyvinyl alcohol (degree of saponification: 98 mol %, degree of polymerization: 200). This aqueous solution was applied to the test object using a sprayer and dried at room temperature. The thickness of the sample after drying was adjusted to 40 μm by adjusting the coating amount.

(Comparative example 1)
Black body tape (manufactured by Chino Co., Ltd., polyimide resin film)

(Comparative example 2)
An aqueous solution of polyethylene oxide (molecular weight: 150,000) with a solid concentration of 20% by weight was prepared, cast on a 75 μm PET sheet, dried at 80° C. and solidified by cooling to obtain a sample with a 75 μm PET sheet substrate. The film thickness during casting was adjusted so that the polyethylene oxide layer had a thickness of 15 μm after drying.

(Comparative Example 3)
An aqueous solution of polyvinylpyrrolidone (K value 94.0) having a solid concentration of 15% by weight was prepared, cast on a 75 μm PET sheet, dried at 80° C., and peeled off to obtain a sample. The film thickness during casting was adjusted so that the thickness of the sample after drying was 15 μm.

(Comparative Example 4)
Low-density polyethylene (density 0.92, MFR 2.0) was hot-pressed at 180° C. to prepare a sample with a thickness of 50 μm.

(Comparative Example 5)
Heat resistant paint spray black (manufactured by Asahipen Co., Ltd., silicon resin paint)

(Comparative Example 6)
An acetone solution of polyvinyl acetate (degree of polymerization: 500) having a solid concentration of 15% by weight was prepared. This acetone solution was applied to the test object using a sprayer and dried at room temperature. The thickness of the sample after drying was adjusted to 40 μm by adjusting the coating amount.

(emissivity measurement)
A Fourier transform infrared spectrophotometer (FT-IR) (manufactured by Thermo Fisher Scientific, Nicolet 6700), a black body furnace (manufactured by Chino Co., Ltd., IR-R24), and a test piece heating device are used to measure the emissivity of the sample. board.
A sample is pasted or sprayed on the surface of a copper piece with a thickness of 2 mm to make a test piece for measurement. The temperature was maintained at 100° C., and the radiation intensity of the surface of the blackbody furnace and the measurement sample was measured.
In addition, except for Example 9, Comparative Example 1, and Comparative Example 5, the samples were attached to the copper pieces using spray glue. For the sample with the substrate, the substrate was peeled off after attaching the sample to the copper piece.
In addition, since the radiation intensity from the heat source inside the FT-IR device is added during measurement, a gold-evaporated mirror (manufactured by Sigma Koki Co., Ltd., reflectance 0.99, 30 mm × 30 mm × 5.0 mm) is used. Radiation intensity measurements were taken and disturbances were removed by subtracting the radiation intensity of the gold-coated mirror from the radiation intensity of the specimen and black body furnace measured by FT-IR. Emissivity was obtained by dividing the radiant intensity of the test piece after removal by the radiant intensity of the blackbody furnace.
From the measurement results of the emissivity using this FT-IR, the average emissivity in the region of 8 to 14 μm, which is the region used by long-wavelength infrared cameras, is calculated. , and less than 0.8 were evaluated as x.

(inner visibility)
After attaching, applying, or spraying the sample, check if the surface of the copper piece can be seen from the side where the sample is attached. ○: If the surface condition can be confirmed; △ if the color of the adherend can be confirmed but the surface condition cannot be confirmed , and the case where it could not be confirmed at all was marked as x.

(Heat-resistant)
After sticking or spraying the sample, it was confirmed whether or not the sample was in a state capable of withstanding the measurement without any deformation or melting when the emissivity was measured at 100°C. When the measurement was possible without problems, it was evaluated as ◯, and when it was not possible, it was evaluated as ×.

(Film strength)
When a sample of 100 mm×100 mm was peeled off from the PET sheet base material, the sample was rated as ◯ when the film was not torn at all, and x when the film was partially torn.

(Curved surface followability)
A sample was attached or applied to a watch glass (150 mm in diameter) to confirm its appearance. The case where the entire surface could be adhered without any air bubbles was evaluated as ◯, and the case where the entire surface could not be adhered due to wrinkles, air bubbles, or the like was evaluated as x.

(Evaluation results)
Table 1 shows the evaluation results of the transparent black body film.

According to Examples 1 to 9 using the transparent black body film of the present invention, a high emissivity of 0.8 or more is achieved in the wavelength region (8 to 14 μm) of a generally used long wavelength infrared camera. At the same time, the surface of the copper piece could be confirmed visually. Furthermore, since it has excellent heat resistance, it was possible to perform highly accurate measurements under higher temperature conditions. In addition, since it has a sufficiently strong film strength, it is also excellent in handleability.
On the other hand, in Comparative Example 1, since the conventional black body tape was used, the visibility was poor, and the inspection could not be performed while visually confirming the surface of the copper piece. In Comparative Example 2, since polyethylene oxide was used instead of polyvinyl alcohol, the emissivity was inferior, and furthermore, the visibility was slightly poor due to the high crystallinity, and detailed observation of the surface of the copper piece was not possible. Since polyvinylpyrrolidone was used in Comparative Example 3, the heat resistance was poor and the emissivity could not be measured. Comparative Example 4 was inferior in emissivity due to the use of low-density polyethylene.

Table 2 shows the evaluation results of the paint of the present invention.

According to Examples 10 to 12 using the transparent black body paint of the present invention, a high emissivity of 0.8 or more is achieved in the wavelength region (8 to 14 μm) of a generally used long-wavelength infrared camera. At the same time, it was possible to visually confirm the surface of the copper piece. Furthermore, even when the object to be inspected has a curved surface, the followability was excellent.
On the other hand, in Comparative Example 1, since the conventional black body tape was used, the visibility was poor, and since it was in the form of a sheet, it could not be attached to the object to be inspected without entraining air. In Comparative Example 5, since the black body paint was used, the inspection could not be performed while visually confirming the surface of the copper piece. In Comparative Example 6, emissivity was inferior due to the use of polyvinyl acetate.

An example of non-destructive inspection using a transparent black body film in Example 9 is shown. As the object to be inspected, select a stainless plate (SUS304, thickness 9 mm) with a flat-bottomed hole defect, diameter (40 mm) and depth (7 mm) that does not penetrate in the center of the back side, and the hole defect is not on the surface. A sample of the transparent blackbody film of Example 9 was attached to the right half of the measurement surface. This inspection object was heated with a halogen lamp (500 W) for 10 seconds, and an infrared thermographic image was taken to detect defects. FIG. 1 shows the appearance of the test piece in the visible light, and FIG. 2 shows the results of infrared thermography measurement in the long wavelength range (8 to 14 μm). FIG. 1 shows the appearance of the test piece, with the results of Example 9 on the left and without film on the right. FIG. 2 shows the results of infrared thermography measurement, with the left showing the results without film and the right showing the results of Example 9. FIG.
Although the surface condition of the inspected object could be confirmed visually at the portion where the sample was attached, defects could not be confirmed. On the other hand, non-destructive detection of defects was possible by infrared thermography measurement in the long wavelength range (8 to 14 μm).

Claims (4)

A water-soluble transparent black body film containing a polyvinyl alcohol resin and used for infrared thermography inspection of the surface of an object to be inspected (provided that it contains 0.5 to 25 mol% of vinyl piperate units and has a block character exceeding 0.6 (excluding water-soluble films made of polyvinyl alcohol-based polymers) . 2. The water-soluble transparent black body film according to claim 1, wherein an adhesive layer is laminated on the layer containing the polyvinyl alcohol-based resin. 3. The water-soluble transparent black body film according to claim 1, wherein a substrate layer is provided on the side of the layer containing the polyvinyl alcohol-based resin. A water-soluble transparent black body paint containing a polyvinyl alcohol-based resin and used for infrared thermography inspection of the surface of an object to be inspected .

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