JP2022144653A - Etchant and etching method for thermoplastic resin - Google Patents

Abstract

To form a pattern which is difficult to manufacture a mold and has a narrow pitch into a thermoplastic resin.SOLUTION: An etchant for a thermoplastic resin contains 5-40 mass% of alkanolamine and 15-45 mass% of an alkali metal hydroxide, wherein the alkanolamine compound is at least one compound selected from the group consisting of ethanolamine, N-(β-aminoethyl)ethanolamine, N-methyl ethanolamine, N-ethyl ethanolamine, triethanolamine, N-methyl diethanolamine and N- ethyl diethanolamine, and the alkali metal hydroxide is at least one compound selected from the group consisting of potassium hydroxide, sodium hydroxide and lithium hydroxide.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to an etchant for thermoplastic resin and an etching method.

When observing cells using microchemical devices, conventional technology can provide devices with hundreds of thousands of microwells with a minimum diameter of 10 μm, which are suitable for the cells to be observed. In order to fabricate a microchemical device in , the minimum distance between wells was required to be at least twice the well diameter (2 wells). Under such circumstances, although the number of wells accumulated in one device is several hundred thousand, there is a limit to the number of wells in one field of view in observations such as fluorescence microscopy and laser microscopy. Depending on the conditions, valuable cells sometimes did not enter the wells and existed between the wells.

In order to fabricate a microchemical device by injection molding using synthetic resin, it is necessary to fabricate a mold insert that is the reverse of the pattern shape of the device (the well shape in the case of a well device). Synthetic resins used in injection molding are generally thermoplastic resins. With current mold manufacturing technology, due to limitations imposed by processing tools, processing machines, and device shapes, it is possible to reduce the radius of the wells from 10 μm to several tens of micrometers by eliminating the radius that occurs at the corners that are not desired during well shape fabrication. It was not possible to arrange wells within a distance of one well in a well-shaped device of 100 μm.

In the optical field of imprinting, especially microlenses and diffusion sheets, there are examples of arranging nano-pattern concave shapes at a distance of one pattern or less. In some cases, it is possible to manufacture mold inserts, but in bio-related fields that handle cells and proteins, pattern sizes of 10 μm or more and several hundred μm or less cannot be manufactured using similar mold inserts. is difficult to fabricate. Furthermore, pattern arrangement is also important. Even if the well shape and the distance between wells are the same, if the pattern arrangement is staggered, it cannot be processed with the current mold processing technology. In addition, in the fields of chemistry, medicine, the environment, food, and the like, devices are becoming more miniaturized and complicated, and it is sometimes difficult to manufacture molds.

In Patent Document 1, it is described that screening from a large amount of library is recently required for screening microorganisms, cells, proteins, etc. The well size is 50 μm in diameter and the distance between adjacent wells is 80 μm. Furthermore, the cross-sectional shape of the wells is hemispherical, and the distance between the wells cannot be reduced to within one well at the conventional technical level.

JP 2006-061023 A

In the method of manufacturing microchemical devices by injection molding using synthetic resin, which is a thermoplastic resin, it was sometimes difficult to create molds for fine patterns and complicated patterns due to the limitations of mold processing technology. . In addition, it is not suitable for manufacturing small lots of devices due to the time required to manufacture the mold and the cost.

An object of the present invention is to provide a thermoplastic resin etchant and an etching method capable of forming a fine pattern on a thermoplastic resin without being restricted by mold processing technology.

(1) 5 to 40% by mass of alkanolamine and 15 to 45% by mass of alkali metal hydroxide, wherein the alkanolamine compound is ethanolamine, N-(β-aminoethyl)ethanolamine, N-methylethanolamine; , N-ethylethanolamine, triethanolamine, N-methyldiethanolamine and N-ethyldiethanolamine, and the alkali metal hydroxide is potassium hydroxide, sodium hydroxide and water. An etching solution for a thermoplastic resin, which is at least one compound selected from the group consisting of lithium oxide.
(2) The thermoplastic resin is polycarbonate, acrylonitrile-butadiene-styrene copolymer resin, cycloolefin copolymer, cycloolefin polymer, acrylic resin, polyvinyl chloride, polystyrene, polyethylene, polypropylene, polyvinyl acetate, polyethylene terephthalate, polyethylene naphthalate The etching liquid for thermoplastic resin according to the above (1), which is selected from at least one resin selected from the group consisting of:
(3) An etching method comprising a step of etching a thermoplastic resin using the thermoplastic resin etching liquid according to (1) or (2) above.

The etching liquid for thermoplastic resin of the present invention enables the formation of a fine pattern on the thermoplastic resin without being restricted by the mold processing technology.

EMBODIMENT OF THE INVENTION Below, the form for implementing this invention is demonstrated.

In this specification, "etching liquid for thermoplastic resin" may be abbreviated as "etching liquid". The etching solution of the present invention is an aqueous solution containing 5 to 40% by mass of alkanolamine and 15 to 45% by mass of alkali metal hydroxide. Thermoplastic resins sometimes have the property of swelling in a high-concentration alkaline aqueous solution, but due to their low dispersibility, it is inherently impossible to form a fine pattern with an alkaline aqueous solution. However, by using the etching solution of the present invention, a fine pattern can be produced on the thermoplastic resin. This is because the alkali metal hydroxide causes the thermoplastic resin to swell, and the alkanolamine promotes the dispersion of the thermoplastic resin.

When the alkali metal hydroxide content is less than 15% by mass, the thermoplastic resin has poor swelling properties, and when the alkali metal hydroxide content exceeds 45% by mass, precipitation of the alkali metal hydroxide occurs. The liquid is less stable over time. The content of alkali metal hydroxide is more preferably 20 to 45% by mass, more preferably 25 to 40% by mass. If the content of the alkanolamine compound is less than 5% by mass, the dispersibility of the thermoplastic resin is poor. When the content of the alkanolamine compound exceeds 40% by mass, the compatibility with water is lowered, and phase separation is likely to occur, resulting in poor stability over time of the etching solution. The alkanolamine compound content is more preferably 20 to 40% by mass, and even more preferably 25 to 35% by mass.

Alkali metal hydroxide is at least one compound selected from the group consisting of potassium hydroxide, sodium hydroxide and lithium hydroxide. Alkali metal hydroxides may be used alone or in combination of two or more.

Examples of the alkanolamine compounds include ethanolamine, which is a primary amine; a mixture of a primary amine and a secondary amine (that is, a compound having a primary amino group and a secondary amino group in one molecule); ), the secondary amines N-methylethanolamine, N-ethylethanolamine, the tertiary amines triethanolamine, N-ethyldiethanolamine and N-methyl It is at least one compound selected from the group consisting of diethanolamine. The ethanolamine compound may be used alone or in combination of two or more.

The etching solution of the present invention is an alkaline aqueous solution. Tap water, industrial water, pure water and the like can be used as the water used in the etching solution of the present invention. Of these, it is preferable to use pure water. In the present invention, pure water that is generally used for industrial purposes can be used.

A coupling agent, a leveling agent, a coloring agent, a surfactant, an antifoaming agent, an organic solvent, and the like may be appropriately added to the etching solution of the present invention, if necessary. Examples of organic solvents include ketones such as acetone, methyl ethyl ketone (MEK) and cyclohexanone; acetic acid esters such as ethyl acetate, butyl acetate, cellosolve acetate, propylene glycol monomethyl ether acetate and carbitol acetate; Tolls; aromatic hydrocarbons such as toluene and xylene; amide solvents such as dimethylformamide, dimethylacetamide (DMAc) and N-methylpyrrolidone;

The etching solution of the present invention may contain 1 to 60% by mass of at least one compound selected from alcohol compounds and carboxylic acid compounds. As the alcohol compound and the carboxylic acid compound, at least one compound selected from the group consisting of polyol compounds, polyvalent carboxylic acid compounds and hydroxy acid compounds is preferably used.

During continuous etching, carbon dioxide gas in the air may be absorbed to form precipitates insoluble in the etching solution. The precipitate may adhere to the thermoplastic resin and cause a problem that prevents a uniform etching process. However, it is believed that the alcohol compound and the carboxylic acid compound have the effect of dissolving the insoluble precipitates without adversely affecting the etchability, enabling uniform etching treatment and improving the running performance. If the content of the alcohol compound and the carboxylic acid compound is less than 1% by mass, the uniformity improving effect may be the same as that of the etching solution that does not contain the alcohol compound and the carboxylic acid compound. If it exceeds, the etchability may become insufficient. The content of alcohol compound and carboxylic acid compound is more preferably 10 to 40% by mass.

The etching solution of the present invention is preferably used within a temperature range of 50-90°C. The optimum temperature varies depending on the type of thermoplastic resin, the thickness of the thermoplastic resin, the shape of the hole or pattern to be etched, etc., but the temperature of the etchant is more preferably 60 to 85°C, more preferably 70 to 85°C. .

Examples of thermoplastic resins include polycarbonate, acrylonitrile-butadiene-styrene copolymer resin, cycloolefin copolymer, cycloolefin polymer, acrylic resin, polyvinyl chloride, polystyrene, polyethylene, polypropylene, polyvinyl acetate, polyethylene terephthalate, polyethylenena It is preferably one or more selected from the group consisting of phthalates. Commercially available thermoplastic resins can be used.

In the present invention, the thermoplastic resin can further contain a filler. Examples of fillers include inorganic fillers and organic fillers, and inorganic fillers are preferably included.

Examples of inorganic fillers include silicates such as silica, glass, clay and mica; oxides such as alumina, magnesium oxide, titanium oxide and silica; carbonates such as magnesium carbonate and calcium carbonate; Hydroxides such as magnesium oxide and calcium hydroxide; sulfates such as barium sulfate and calcium sulfate; molybdenum compounds such as molybdenum oxide and zinc molybdate; Further, aluminum borate, aluminum nitride, boron nitride, strontium titanate, barium titanate, zinc borate, zinc stannate, talc, mica, short glass fibers, hollow glass, whiskers, and the like can be used. Organic fillers such as styrene-, butadiene-, and acrylic-type rubber powders, core-shell-type rubber powders, silicone resin powders, silicone rubber powders, silicone composite powders, and fluororesin powders can also be used. As a filler, one of these may be used alone, or two or more of them may be used in combination.

The etching method of the present invention will be explained. The etching method of the present invention includes (step 1) a step of forming an alkali-developable photosensitive resin composition layer on at least one side of a substrate containing a thermoplastic resin, (step 2) exposing and It includes a step of developing to form a resist pattern, and (Step 3) a step of etching the substrate with the etching solution of the present invention.

(Step 1)
The step of forming an alkali-developable photosensitive resin composition layer on at least one side of a substrate will be described. Any substrate may be used as long as it contains a thermoplastic resin that can be etched by the etching solution of the present invention.

In the etching method of the present invention, as a method of forming a photosensitive resin composition layer, a coating liquid containing a photosensitive resin composition is applied to a substrate and dried to form a photosensitive resin composition layer. method. Alternatively, a coating liquid containing the photosensitive resin composition of the present invention is applied to a carrier film to form a photosensitive resin composition layer containing the photosensitive resin composition, and a dry film resist (DFR) is formed. ) and transfer the photosensitive resin composition layer to the substrate.

(Step 2)
A process of exposing and developing a photosensitive resin composition layer to form a resist pattern will be described. In (Step 2), first, the photosensitive resin composition layer is exposed in a pattern to cure the exposed portion. Specific examples of exposure include contact exposure using a photomask. Reflective image exposure using a xenon lamp, a high-pressure mercury lamp, a low-pressure mercury lamp, an ultra-high-pressure mercury lamp, or a UV fluorescent lamp as a light source, a proximity method, a projection method, and scanning exposure can also be used. For scanning exposure, laser light sources such as UV laser, He--Ne laser, He--Cd laser, argon laser, krypton ion laser, ruby laser, YAG laser, nitrogen laser, dye laser, excimer laser, etc. are used according to the emission wavelength. Wavelength-converted scanning exposure, scanning exposure using a liquid crystal shutter, micromirror array shutter, or the like can be mentioned.

After patternwise exposure, development is carried out to remove the photosensitive resin composition layer in the non-exposed portions, which are unnecessary portions as the resist pattern, to form a resist pattern including the cured photosensitive resin composition layer. As an alkaline developer used for development, for example, an aqueous solution of an inorganic alkaline compound can be used. Examples of inorganic alkaline compounds include carbonates and hydroxides of lithium, sodium, potassium, and the like. As an alkaline developer, a 0.1 to 3% by mass sodium carbonate aqueous solution can be preferably used. A small amount of a surfactant, an antifoaming agent, a solvent, or the like can be appropriately mixed in the developer. As a development processing method, there are a dip method, a paddle method, a spray method, a brushing method, a scraping method, and the like, and the spray method is most suitable for removal speed. The treatment temperature is preferably 15-35° C., and the spray pressure is preferably 0.02-0.3 MPa.

(Step 3)
A process of etching a substrate with the etching solution of the present invention will be described.

As an etching method, methods such as immersion treatment, puddle treatment, spray treatment, brushing, and scraping can be used. Among these, immersion treatment is preferable. A method other than the immersion treatment tends to generate bubbles in the etchant, and the bubbles may adhere to the surface of the base material, resulting in poor etching. Also, in methods other than the immersion treatment, the temperature of the etchant tends to change greatly, and the etching rate of the substrate may vary.

The treatment temperature of the etchant is preferably 60 to 90° C., and the optimum treatment temperature varies depending on the type and thickness of the substrate, the type and thickness of the photosensitive resin composition, and the pattern shape. The treatment temperature is more preferably 60 to 85°C, more preferably 70 to 85°C.

After the etching treatment, the thermoplastic resin that has not been completely removed and the etchant remaining on the surface of the thermoplastic resin are washed with water. As a method of washing with water, a spray method is preferable from the viewpoint of diffusion rate and uniformity of liquid supply. Tap water, industrial water, pure water, or the like can be used as washing water. Of these, it is preferable to use pure water. Pure water that is generally used for industrial purposes can be used.

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these Examples.

Each component shown in Table 1 was mixed to obtain a coating liquid of a photosensitive resin composition. In addition, the unit of content of each component in Table 1 is [parts by mass]. Using an applicator, the obtained coating solution is applied onto a polyethylene terephthalate (PET) film (carrier film, trade name: R310, 16 μm thick, manufactured by Mitsubishi Chemical Corporation), dried at 80° C. for 5 minutes, and solvent The components were removed to obtain a photosensitive resin composition layer (15 μm thick) containing the photosensitive resin composition on one side of the PET film. A polyethylene film (protective film, trade name: GF1, 30 µm thick, manufactured by Tamapoly Co., Ltd.) was attached to the surface of the photosensitive resin composition layer to prepare a DFR.

In Table 1, each component is as follows.

(A) Alkali-soluble resin (A-1): copolymer resin obtained by copolymerizing methyl methacrylate/n-butyl acrylate/methacrylic acid at a mass ratio of 64/15/21 (acid value: 137, mass average molecular weight: 20,000)

(B) Photopolymerization initiator (B-1): 2-(o-chlorophenyl)-4,5-diphenylimidazole dimer (B-2): 4,4′-bis(diethylamino)benzophenone

(C) Polymerizable monomer (C-1): NK Ester BPE-200 (trade name, manufactured by Shin-Nakamura Chemical Co., Ltd.)
(C-2): NK Ester BPE-500 (trade name, manufactured by Shin-Nakamura Chemical Co., Ltd.)

Next, the above DFR was attached to both sides of a 300 μm-thick polycarbonate after peeling off the polyethylene film to form a photosensitive resin composition layer (step 1). Subsequently, using a double-sided exposure machine equipped with a 5 kW ultra-high pressure mercury lamp light source, the DFR formed on the polycarbonate was passed through a photomask having a test pattern in which circles with a diameter of 100 μm were arranged at intervals of 5 μm from 100 μm to 5 μm. , exposure to UV rays at an exposure amount of 30 mJ/cm ² , using a conveyor type developing machine, a 1% by weight sodium carbonate aqueous solution at a liquid temperature of 30 ° C., and a spray pressure of 0.2 MPa. for 90 seconds to obtain a circular resist pattern with a diameter of 100 μm at the bottom of the test pattern portion (step 2).

An etchant having the composition shown in Table 2 was prepared.

The polycarbonate on which the above resist pattern was formed was immersed in an etchant kept at 80° C. with stirring to etch the polycarbonate (step 3).

Etching was performed until the depth of the opening became 100 μm, and the diameter of the opening after etching and the interval between adjacent patterns were measured to evaluate the “narrow pitch property”. For the measurement, an image observation mode of a shape analysis laser microscope VK-X1000 manufactured by Keyence Corporation was used. The spacing between adjacent patterns is preferably smaller than the diameter of the openings.

The evaluation criteria for narrow pitch property are shown below.
○: The interval between adjacent patterns is smaller than the diameter of the opening.
x: The interval between adjacent patterns is larger than the diameter of the opening.

Next, the time required for etching was measured to evaluate "workability". In this example, in consideration of productivity, the etching time is preferably less than 20 minutes, more preferably less than 15 minutes, and even more preferably less than 10 minutes.

The evaluation criteria for workability are shown below.
○: Treatment time is less than 10 minutes.
Δ: Treatment time is 10 minutes or more and less than 20 minutes.
x: Treatment time is 20 minutes or longer.

In the etching treatment, the number of days the etchant can be used continuously was evaluated as "stability". In this example, considering productivity, the number of days of continuous use is preferably 20 days or more, more preferably 30 days or more. The number of days of continuous use means the number of days in which separation of the etchant does not occur and the precipitation generated during continuous use does not hinder the etching process when the operating time is 8 hours per day. The amount of etching solution that has decreased due to continuous use and evaporation shall be replenished with the same amount of etching solution as needed.

Evaluation criteria for the stability of the etchant are shown below.
◯: After 20 days of continuous use, the etchant was not separated and the generated precipitate did not remain on the insulating layer.
Δ: After 20 days of continuous use, the etchant was not separated, and the generated precipitate remained on the insulating layer, but could be removed in a post-process.
x: After 20 days of continuous use, the etchant was separated, or the generated precipitate remained on the insulating layer and was difficult to remove.

As can be seen from the results in Table 2, the use of the etching solution of the present invention enables the formation of a pattern of narrow-pitch, small-diameter openings on the thermoplastic resin surface.

The etching solution of the present invention can form a pattern of narrow-pitch, small-diameter openings on the surface of a thermoplastic resin. In addition, since a mold is not required, it can be used for manufacturing microchemical devices with small lots or complicated shapes.

Claims (3)

5 to 40% by weight of alkanolamine and 15 to 45% by weight of alkali metal hydroxide, and the alkanolamine compound is ethanolamine, N-(β-aminoethyl)ethanolamine, N-methylethanolamine, N- At least one compound selected from the group consisting of ethylethanolamine, triethanolamine, N-methyldiethanolamine and N-ethyldiethanolamine, wherein the alkali metal hydroxide is potassium hydroxide, sodium hydroxide and lithium hydroxide An etching solution for thermoplastic resins, characterized by being at least one compound selected from the group consisting of: The group consisting of polycarbonate, acrylonitrile-butadiene-styrene copolymer resin, cycloolefin copolymer, cycloolefin polymer, acrylic resin, polyvinyl chloride, polystyrene, polyethylene, polypropylene, polyvinyl acetate, polyethylene terephthalate, and polyethylene naphthalate, in which the thermoplastic resin is 2. The etching liquid for thermoplastic resin according to claim 1, characterized in that it is selected from at least one resin selected from. An etching method comprising the step of etching a thermoplastic resin using the thermoplastic resin etching solution according to claim 1 or 2.