WO2001036905A1

WO2001036905A1 - Fingerprint reader

Info

Publication number: WO2001036905A1
Application number: PCT/JP2000/008124
Authority: WO
Inventors: Atsushi Sasaki; Yoshiki Takahashi
Original assignee: Asahi Glass Company, Limited
Priority date: 1999-11-18
Filing date: 2000-11-17
Publication date: 2001-05-25

Abstract

A capacitive fingerprint reader for reading fingerprint patterns by detecting capacitance includes a dielectric layer coated with protective film of fluorine-containing polymer that fingers touch. The capacitive fingerprint reader includes a semiconductor substrate on which is formed a laminate of a two-dimensional array of electrodes and a dielectric layer. With a finger pressed against the dielectric layer, the capacitance between the dielectric layer and the electrodes is detected to read the fingerprint patterns. The protective film of fluorine-containing polymer covering the surface of the dielectric layer helps to keep the dielectric layer clean and eliminates the need of thorough cleaning. The fingerprint reader is durable and provides accurate reading constantly and resistant.

Description

Specification

Fingerprint reader Technical field

The present invention relates to a capacitance type fingerprint reading device that reads a concave and convex pattern of a fingerprint by detecting a capacitance generated between a fingertip surface and an electrode. Background art

In security check systems, personal identification by fingerprint matching is widely performed. For example, in entry / exit checks in various buildings and facilities, in banking systems, computer systems, etc., fingerprints of persons who are trying to enter or use equipment are read to prevent entry and use of equipment other than registrants. The registrant is identified by comparing it with the registrant's fingerprint image data.

In the above system, the fingerprint reader is an optical fingerprint reader that reads the uneven pattern of the fingerprint using a CCD camera or a scanner, or detects the capacitance generated between the fingertip surface and the electrode. In general, a capacitance-type fingerprint reader that reads the concave and convex shape of the fingerprint by reading the fingerprint is generally used. However, an optical fingerprint reader has a large number of components, including a light source and a lens, and requires precise adjustment of the optical system. Generally, the device is complex, large, and expensive. It is expected that capacitance type fingerprint readers will become mainstream in the future.

By the way, the capacitance type fingerprint reader is configured by laminating an electrode group arranged in a two-dimensional array on a semiconductor substrate and a dielectric layer in that order, and a finger is brought into contact with the dielectric layer. Thus, the capacitance formed between the dielectric layer and the electrode is electrically detected. Since the magnitude of the formed capacitance is proportional to the distance between the surface of the fingertip and the electrode, there is a difference in the magnitude of the capacitance between the ridge portion and the valley line portion of the fingertip. A distribution of capacitance along the pattern is formed. The distribution of the capacitance is detected by the electrodes and processed into a two-dimensional image to produce a fingerprint uneven pattern. The steps between the ridges and valleys of the fingertips are very small, and the difference in capacitance is also very small. Therefore, if oil from a fingertip that was previously collated, or floating dust accumulates or adheres to the dielectric layer, a small difference in capacitance cannot be detected, and accurate fingerprints cannot be detected. Cannot be read. In addition, security check systems may be installed outdoors, in which case the dielectric layer is constantly exposed to the open air, which requires resistance to various outdoor environments.

As described above, contamination of the dielectric layer in the capacitive fingerprint reader is an important issue for accurate fingerprint reading, and at present, the surface of the dielectric layer is periodically cleaned. No effective measures have been found other than 诤. In addition, if dust is present on the surface of the dielectric layer, the dielectric layer may be damaged when a fingertip is pressed and, in some cases, during cleaning. In addition, it must be resistant to light such as ultraviolet rays, moisture such as rain and sweat, and chemicals such as detergents and cosmetics. Disclosure of the invention

The present invention has been made in view of such a situation, and in a capacitance type fingerprint reader, contamination of a dielectric layer is prevented, complicated cleaning work is not required, and accurate fingerprint reading is always performed. It is intended to impart various resistances. In order to achieve the above object, the present invention provides an electrode group and a dielectric layer arranged in a two-dimensional array on a semiconductor substrate in this order, and a finger is brought into contact with the dielectric layer. A fingerprint reading device that detects the capacitance formed between the dielectric layer and the electrode and reads the concave and convex pattern of the fingerprint, wherein the surface of the dielectric layer that is in contact with the finger includes: A fingerprint reader, which is covered with a protective film made of a fluoropolymer.

In particular, the above-mentioned fluorine-containing polymer is preferably a solvent-soluble fluorine-containing polymer. Such a solvent-soluble fluorine-containing polymer is preferably a fluorine-containing aliphatic ring structure, a fluorine-containing triazine ring structure or a fluorine-containing aromatic ring structure. A fluorine-containing polymer having any of the above in the main chain is preferable. BRIEF DESCRIPTION OF THE FIGURES FIG. 1 is a schematic sectional view showing one embodiment of the fingerprint reading device of the present invention.

FIG. 2 is a circuit diagram showing the configuration of the electrode portion.

FIG. 3 is a schematic sectional view showing another embodiment of the fingerprint reader of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail with reference to the drawings.

As shown in FIGS. 1 and 2, a fingerprint reader 1 of the present invention includes a semiconductor substrate 10 on which a plurality of electrodes 11 (11 a,..., 11 n) are arranged in a two-dimensional array. A reading unit main body 13 formed by laminating a dielectric layer 12 made of, for example, silicon nitride, so as to cover the entire electrode group. The surface of the dielectric layer 12 of the reading unit main body 13 on the side in contact with the fingertip F is covered with a protective film 14 made of a fluoropolymer.

The reading unit main body 13 has the same configuration as a conventional capacitive fingerprint reader. The pitch of the electrodes 11 (distance between the electrodes) is set to, for example, 100 zm or less so as to be less than the distance between the ridge and the valley of the fingerprint. Further, the total number of the electrodes 11 is a unit of tens of thousands, and for example, they are arranged in a two-dimensional array of 200 rows × 300 columns at the aforementioned pitch.

The fingerprint reading method is the same as the conventional one. That is, when the fingertip F is pressed against the protective film 14, a capacitance is formed between the fingertip surface and the electrode 11, and the magnitude of the capacitance is between the fingertip surface and the electrode 11. Because it is proportional to the distance, the capacitance formed between the ridge F a of the fingertip F and the electrode 11 facing the electrode and the capacitance formed between the valley Fb of the fingertip F and the electrode 11 facing the electrode 11 A difference is generated between the measured capacitance and a capacitance distribution corresponding to the concave and convex shape of the fingerprint is formed on the reading unit body 13. Each electrode 11 is connected to a row drive circuit 20 and a detection circuit 30 via a switch element 15 (15a, '·, 15η), and is sequentially switched. The voltage corresponding to the capacitance is output to the detection circuit 30. Information of each line of the fingerprint uneven pattern is sequentially input to the detection circuit 30. The information is processed into two-dimensional image data by the image processing circuit 40 and sent to the comparison circuit 50. The comparison circuit 50 stores the data in the data storage 60 in which the concavo-convex pattern of the registrant's fingerprint is stored, and the two-dimensional image data of the read fingerprint. Then, it is determined whether or not the user is a registrant. If it is determined that the user is a registrant, for example, the locking means 70 is released.

In the reading section main body 13, the fluoropolymer forming the protective film 14 generally has water repellency and oil repellency, so that adhesion of oil and water on the fingertip surface to the protective film 14 is suppressed, and cleaning is performed. The surface of the protective film 14 is kept clean for a long time without necessity. In addition, fluoropolymers have high light resistance, water resistance, resistance to chemical substances, etc., and have high mechanical strength when formed into a film, so they are also resistant to damage. The fluorine-containing polymer forming the protective film 14 is preferably soluble in a solvent. This is because when the protective film 14 becomes thicker, when the fingertip F is pressed against the protective film 14, it becomes difficult to form a capacitance between the dielectric layer 12 and the electrode 11, and the S / N ratio is reduced. This makes it impossible to obtain a clear fingerprint uneven pattern. In order to secure a sufficient capacitance for obtaining a fingerprint uneven pattern, the thickness of the protective film 14 is 1 m or less, preferably 0.1 to 100 nm. In order to easily form such a thin film, it is preferable to form the film by dissolving a fluorine-containing polymer in a solvent and applying the solution. Although film formation by vapor deposition is conceivable, the heat resistance temperature of a general capacitance fingerprint reader, that is, the reading unit body 13 in the present invention is about 120, and it can withstand the high temperature required for vapor deposition. I can't. If there is no problem with heat resistance, a thin film can be formed by using a solvent-insoluble fluoropolymer which does not dissolve in a normal solvent, for example, a fluoropolymer such as PTF E, ETF E, PFA and FEP. Alternatively, it is also possible to form a protective layer by thinning the fluoropolymer and then attaching the fluoropolymer to the surface of the dielectric layer with an adhesive or the like.

Further, the fluorine-containing polymer may be a fluorine-containing polymer which is formed into a thin film and then made insoluble in a solvent. For example, after forming a thin film of a solvent-soluble fluoropolymer, it may be converted to a solvent-insoluble fluoropolymer by crosslinking by heat or light, and a composition containing a solvent-soluble fluoropolymer having a crosslinkable group and a crosslinking agent. The product may be made into a thin film, and a crosslinking reaction may be carried out to form a crosslinked fluoropolymer thin film. Further, a compound such as a fluorine-containing monomer or an oligomer thereof, which can be polymerized into a fluoropolymer, can be polymerized on the surface of the dielectric layer to form a fluoropolymer thin film. For example, use fluorine-containing organoalkoxysilane as a dielectric The thin film of the organopolysiloxane containing fluorine can be formed on the surface of the dielectric layer by hydrolytic condensation polymerization on the surface of the layer.

Examples of the solvent-soluble fluorine-containing polymer that can be used in the present invention include the following fluorine-containing polymers A and B.

(Fluorine-containing polymer A)

The fluorine-containing polymer A is a polyfluoroalkyl group having 4 to 21 carbon atoms or a polyfluoroalkyl group having 4 to 40 carbon atoms having an etheric oxygen atom between carbon atoms (hereinafter, both are collectively referred to as “fluorinated polymer A”). a compound having a called) _"the R _f group", organopolysiloxane in particular having _the R _f group (hereinafter referred to as "compound I"), R _f is have a group unsaturated ester homopolymer mono- or different R, A copolymer of unsaturated esters having a group (hereinafter referred to as “compound II”) or a copolymer of an unsaturated ester having an R _f group and another copolymerizable monomer (hereinafter referred to as “compound III”).

The _Rf group may contain a hydrogen atom or a chlorine atom at the terminal, but is preferably a linear perfluoroalkyl group or a perfluoro (polyoxyalkylene) group. Particularly, a linear perfluoroalkyl group having 4 to 16 carbon atoms is preferable.

As the compound I, an organopolysiloxane having a unit in which the R _f group is bonded to a gay atom via an alkylene group is preferable. The organopolysiloxane preferably further has a hydroxyl group or a hydrolyzable group bonded to a silicon atom from the viewpoint of improving the adhesion to the surface of the dielectric layer.

Compound I can also be formed on the surface of the dielectric layer. In this case, the formed compound I may not be solvent-soluble. This is because there is no problem in forming a thin film as long as the fluorine-containing monomer or its oligomer capable of forming the compound I is soluble in a solvent. For example, a solution of the fluorine-containing monomer or its oligomer is applied to the surface of the dielectric layer to remove the solvent, and the fluorine-containing monomer or its oligomer is hydrolyzed, condensed and polymerized to form a compound I thin film. As this solvent, the same solvent as that capable of dissolving Compound I (described later) can be used.

Fluorine-containing monomers capable of forming Compound I include R _f group-containing organic groups and Hydrolytically condensable silane compounds having a decomposable group bonded to a silicon atom are preferred. Examples of the organic group having an _Rf group include an organic group having a carbon atom at the bonding terminal, such as an alkyl group having an _Rf group. Examples of the hydrolyzable group include an alkoxy group, an acyl group, a halogen atom such as a chlorine atom, and an amino group. The number of the hydrolyzable groups bonded to the gay atom of the silane compound is preferably 2 to 3, and the number of the _Rf group-containing organic groups is preferably 1 or 2. One _Rf -free functional group (such as an alkyl group) may be bonded to the silicon atom of the silane compound. Preferred silane compounds are _Rf group-containing organoalkoxysilanes (the number of alkoxy groups is 2-3).

The partially hydrolyzed condensate of the silane compound can be used as an oligomer capable of forming Compound I. The above-mentioned silane compound and its oligomer can be used in combination with a hydrolyzable and condensable silane compound having no _Rf group and its oligomer. Examples of the hydrolyzable condensable silane compound having no R _f group include silane compounds having no non-hydrolyzable group such as tetraalkoxysilane, organic groups having a functional group such as an epoxy group, an amino group, and a mercapto group and an alkoxy group. And a functional group-containing alkoxysilane having the formula

The unsaturated ester having an _Rf group to form the compound II or the compound III is not particularly limited, but for example, the following acrylates or methacrylates are preferred.

CF ₃ (CF ₂ ) ₄ CH ₂ OCOC (CH ₃ ) = CH ₂ , CF ₃ (CF ₂ ) ₆ CH ₂ OC0C (CH ₃ ) = CH ₂ ,

CF ₃ (CF ₂ ) ₇ (CH ₂ ) ₂ OCOCH = CH ₂ , CF ₃ (CF ₂ ) ₇ S0 ₂ N (C ₃ H ₇ ) (CH ₂ ) ₂ OCOCH = CH ₂ ,

CF ₃ (CF ₂ ) ₇ (CH ₂ ) ₄ OCOCH = CH ₂ , CF ₃ (CF ₂ ) ₇ S0 ₂ N (CH ₃ ) (CH ₂ ) ₂ OCOCH = CH ₂ ,

CF ₃ (CF ₂ ) ₇ S0 ₂ N (C ₂ H ₅ ) (CH ₂ ) ₂ OCOCH = CH ₂ , CF ₃ (CF ₂ ) ₇ S0 ₂ NH (CH ₂ ) ₂ OCOCH = CH ₂ ,

(CF ₃ ) ₂ CF (CF ₂ ) ₆ (CH ₂ ) ₃ OCOCH = CH ₂ , (CF ₃ ) ₂ CF (CF ₂ ) ₅ (CH ₂ ) ₂ OCOCH = CH ₂ ,

(CF ₃ ) ₂ CF (CF ₂ ) ₆ CH ₂ CH (0C0CH ₃ ) OCOC (CH ₃ ) = CH ₂ ,

(CF ₃ ) ₂ CF (CF ₂ ) ₆ CH ₂ CH (OH) CH _{2 0} C0CH = CH ₂ ,

CF ₃ (CF ₂ ) 3 (CH ₂ ) ₂ OCOCH = CH ₂ , CF ₃ (CF ₂ ) ₃ (CH ₂ ) ₂ 0C0C (CH ₃ ) = CH ₂ ,

CF ₃ (CF ₂ ) ₃ C0NH (CH ₂ ) ₂₀ C0C (CH ₃ ) = CH ₂ , H (CF ₂ ) _{i 0} CH ₂ OCOCH = CH ₂ ,

_{_{_{CF 2 C1 (CF 2) 10}}} CH 2 OCOC (CH 3) = CH "(CF 3) 2 CFOCF 2 CF 2 COO (CH 2) 2 0C0CH = CH"

(CF ₃ ) ₂ CF0 (CF ₂ CF (CF ₃ ) 0) ₂ CF ₂ CF ₂ COO (CH ₂ ) ₂₀ C0CH = CH ₂ As the monomer copolymerizable with the unsaturated ester, a wide range can be selected as long as the action and effect of the present invention are not hindered. For example, ethylene, vinyl acetate, vinyl chloride, vinyl fluoride, vinylidene halide, styrene, α-methylstyrene, ρ-methylstyrene, acrylic acid and its alkyl ester, methacrylic acid and its alkyl ester, poly (oxyalkylene) ) Acrylate, poly (oxyalkylene) methacrylate, acrylamide, methyl acrylamide, diacetone acrylamide, methylolated diacetone acrylamide, Ν-methylol acrylamide, vinyl alkyl ether, halogenated alkyl vinyl ether, vinyl alkyl ketone, butadiene, Isoprene, chloroprene, glycidyl acrylate, benzyl methacrylate, benzyl acrylate, cyclohexyl acrylate, maleic anhydride, Lysine sulfonyl § chestnut rate, aziridinyl methacrylate over preparative, monomers containing no R _f group such as Ν- vinylcarbazole one or two or more, can be copolymerized as constituent units of the copolymer. The copolymerization ratio of these copolymerizable monomers to the unsaturated ester having an _Rf group is usually from 1 to 50% by weight, and preferably from 1 to 20% by weight.

In order to obtain Compounds II and III above, the starting monomers are dissolved in an appropriate organic solvent and a polymerization initiation source (such as ionizing radiation or peroxide azo compounds dissolved in the organic solvent used) is used. Due to the action of the above, a solution polymerization method is usually employed. Solvents suitable for solution polymerization include toluene, ethyl acetate, isopropyl alcohol, dichloropentafluoropropane, dichlorofluorene, and the like.

Further, the above compounds I, II, and III may be used alone or as a mixture of two or more. However, when a mixture of the three types of compounds I, II, and III is used, it is preferable to mainly use the compound II from the viewpoint of the magnitude of the effect, the availability from the market, and the like.

Solvents that can dissolve the fluoropolymer A include ketones such as acetone and methyl ethyl ketone; esters such as methyl acetate, ethyl acetate and isopentyl acetate; ethers such as getyl ether and dioxane; trichloroethylene and tetrachloroethylene. , A kind of halogenated hydrocarbons such as dichloropentafluoropropane, dichlorofluoroethane, and meta-xylenehexafluoride Or a mixture of two or more may be employed.

(Fluorine-containing polymer B)

Examples of the fluorine-containing polymer B include a fluorine-containing polymer having a fluorine-containing aliphatic ring structure (including a fluorine-containing imide ring structure), a fluorine-containing triazine ring structure or a fluorine-containing aromatic ring structure in the main chain. Of these, a fluoropolymer having a fluorinated aliphatic ring structure in the main chain is preferable, and among them, a fluorinated aliphatic oxygen-containing heterocyclic structure having a main chain is more preferable. Here, "having a fluorinated aliphatic ring structure in the main chain" means that at least one of the carbon atoms constituting the ring is a carbon atom in the carbon chain constituting the main chain, and Has a structure in which a fluorine atom or a fluorine-containing group is bonded to at least a part of the carbon atoms.

Examples of the fluoropolymer having a fluorinated alicyclic structure in the main chain include a polymer having a fluorinated alicyclic structure in the main chain obtained by polymerizing a monomer having a fluorinated alicyclic structure, and two or more polymers. A polymer having a fluorinated aliphatic ring structure in the main chain obtained by cyclizing a fluorinated monomer having a polymerizable double bond is preferable. A polymer having a fluorinated alicyclic structure in the main chain, which is obtained by polymerizing a monomer having a fluorinated alicyclic structure, is known from Japanese Patent Publication No. Sho 63-18964. That is, by homopolymerizing a monomer having a fluorinated aliphatic ring structure, such as perfluoro (2,2-dimethyl-1,3-dioxole), or by converting such a monomer into tetrafluoroethylene, By copolymerizing with a radical polymerizable monomer having no fluorinated aliphatic ring structure, such as len or perfluoro (methyl vinyl ether), a polymer having a fluorinated aliphatic ring structure in the main chain can be obtained.

Further, a polymer having a fluorinated aliphatic ring structure in the main chain, which is obtained by cyclopolymerization of a fluorinated monomer having two or more polymerizable double bonds, is disclosed in JP-A-63-23811. This is known from Japanese Unexamined Patent Application Publication No. 1 and Japanese Unexamined Patent Publication No. Sho 63-323811. That is, cyclopolymerization of a fluorinated monomer having two or more polymerizable double bonds, such as perfluoro (aryl vinyl ether) or perfluoro (butenyl vinyl ether), which is capable of cyclopolymerization. Or such monomers as tetrafluoroethylene, black trifluoroethylene, perfluoro (alkyl vinyl ether) ), A polymer having a fluorinated aliphatic ring structure in the main chain can be obtained.

In addition, monomers having a fluorine-containing aliphatic ring structure such as perfluoro (2,2-dimethyl-1,3-dioxol) and perfluoro (aryl vinyl ether) and perfluoro (butenyl vinyl ether) A polymer having a fluorine-containing aliphatic ring structure in the main chain can also be obtained by copolymerizing with a fluorine-containing monomer having two or more polymerizable double bonds and capable of undergoing cyclopolymerization.

In the polymer having a fluorinated aliphatic ring structure in the main chain, a repeating unit having a fluorinated aliphatic ring structure in the main chain is 20 mol% or more, preferably 40 mol%, based on all repeating units of the polymer. Those containing the above are preferred in terms of transparency and mechanical properties.

As the polymer having a fluorinated aliphatic ring structure in the main chain, specifically, a polymer having a repeating unit selected from the following general formulas (1) to (4) is preferable. A fluorine atom in the polymer having a fluorinated aliphatic ring structure in these main chains may be partially substituted with a chlorine atom.

(2)

In the general formulas (1) to (4), h is an integer of 0 to 5, i is an integer of 0 to 4, j is 0 or 1, h + i + j is an integer of 1 to 6, s is 0 to 5 , T is an integer from 0 to 4, u is 0 or 1, s + t + u is an integer from 1 to 6, p, q, and r are each independently an integer from 0 to 5, p + Q + r is Integers of 1 to 6, R ^{1 to} R ⁶ are each independently a fluorine atom, a chlorine atom or a perfluoroalkyl group. As the perfluoroalkyl group, a trifluoromethyl group is preferable. Further, a part of the fluorine atoms in these repeating units may be substituted with a chlorine atom.

Further, as the monomer having a fluorinated aliphatic ring structure, the following general formula (5) W 01/36905

1 1

A monomer selected from the compounds represented by (7) is preferable,

(Five)

In the general formulas (5) to (7), R ^{7 to} R ¹⁸ are each independently a fluorine atom, a chlorine atom or a perfluoroalkyl group, and R ⁹ and R ′ ^D , R ¹³ and R ′ ⁴ and R ′ ⁷ and R ¹⁸ may be linked to form a ring. As the perfluoroalkyl group, a trifluoromethyl group is preferable. Further, some of the fluorine atoms in these monomers may be substituted with chlorine atoms.

Specific examples of the compounds represented by the general formulas (5) to (7) include the compounds represented by the formulas (11) to (18).

(Π) (12) (13)

(14) (15) (16)

(17) ( ¹⁸ )

As the fluorine-containing monomer having two or more polymerizable double bonds, compounds represented by the following general formulas (8) to (10) are preferable.

CY I _Y 2 = CY ³ OCY ⁴ Y ⁵ CY ⁶ Y ⁷ CY ⁸ = CY ⁹ Y ^{1 (}} (8)

CZ ¹ Z ² = CZ ³ 0 CZ ⁴ Z ⁵ CZ ⁶ = CZ ⁷ Z ⁸ (9)

CW ^^ CW ^ CW ^^ CW ^ CW'W 8 (1 0) general formula (8) ~ (1 0) , Y 1 ~. , Ζ '~Ζ ⁸ and W'～W ⁸ are each independently a fluorine atom, a chlorine atom or per full O b alkyl group. A trifluoromethyl group is preferred as the perfluoroalkyl group.

Specific examples of the compounds represented by the general formulas (8) to (10) include the following compounds. And so on.

CF ₂ = CFOCF ₂ CF ₂ CF = CF ₂ , CF ₂ = CF0CC1 ₂ CF ₂ CF = CF ₂ , CF ₂ = CF0CF ₂ CF ₂ CC 1 = CF ₂ ,

CF ₂ = CF0CF ₂ CFC 1 CF = CF ₂ , CF ₂ = CF0CF ₂ CF ₂ CF = CFC 1, CF ₂ = CFOCF ₂ CF (CF ₃ ) CF = CF ₂ ,

_{_{CF 2 = CFOCF 2 CF (CF}} 3) CC 1 = CF 2, CF 2 = CFOCF 2 CF = CF 2, CF 2 = CF0CF (CF 3) CF = CF 2,

CF ₂ = CFOCF ₂ OCF = CF ₂ , CF ₂ = CC 10CF ₂ 0CC 1 = CF ₂ , CF ₂ = CF0CC 1 ₂ 0CF = CF ₂ ,

CF ₂ = CF0C (CF ₃ ) ₂ 0CF = CF ₂

Each of these fluorine-containing polymers B has a fluorine content of 70% by mass or more, and when the protective film 14 is used, particularly excellent water repellency, oil repellency and film strength are obtained.

As the solvent capable of dissolving the above-mentioned fluorine-containing polymer B, a fluorine-containing solvent is preferable, and examples thereof include the following fluorine-containing solvents.

Polyfluorinated aromatic compounds such as perfluorobenzene, perfluorotrippyramine, pyrsamine, perfluorotributylamine, tris (polyfluoroalkyl) amine such as perfluorotripentylamine, perfluorohexane Polyfluoroalkanes such as perfluorooctane, perfluorodecane, (perfluoro-1-n-octylile) ethane, perfluoro (2,3,5-trimethylhexane), (perfluoro-n-octyl) ethylene, hexafluoro Polyfluoroalkenes such as propylene trimer, polyfluorocycloalkanes such as perfluorocyclohexane and perfluorodecalin, polyfluorocyclic ethers such as perfluoro (2-butyltetrahydrofuran), and methyl perfluorohexyl ether Ethers, such as alkyl per full O lower Ruki ethers such as methyl perfluoro full O Roo Chi ether.

Further, a mixed solvent of the above fluorinated solvent and another solvent can also be used. In this case, as the other solvent, a solvent that cannot alone dissolve the fluoropolymer B can be used.

As other solvents, hydrocarbons such as hexane, carbons such as chloroform, and alcohols such as methanol and ethanol can be used. The mixing ratio of these other solvents is appropriately selected depending on the concentration of the fluorinated polymer B, but is preferably 0.1 to 50 parts by mass relative to 100 parts by mass of the fluorinated solvent, and 1 to 30 parts by mass. Parts by weight are more preferred.

In forming the protective film 14, the above-mentioned fluorine-containing polymer A and fluorine-containing polymer B are dissolved in a suitable solvent to form a coating liquid. At this time, as described above, since the thickness of the protective film 14 is preferably 1 m or less, particularly preferably 0.1 to 100 nm, the concentration of the fluorine-containing polymer in the coating liquid was adjusted so as to achieve this thickness. adjust. In addition, a silane-based, epoxy-based, titanium-based, or aluminum-based coupling agent may be added to the coating liquid together with the fluorinated alcohol to improve the adhesion to the dielectric layer 12. An oligomer of a coupling agent may be blended. Then, the coating liquid is applied to the surface of the dielectric layer 12 and the solvent is dried, whereby the protective film 14 is formed. The coating method is not particularly limited, and examples thereof include a roll coating method, a cast coating method, a dip coating method, a spin coating method, a water-based cast coating method, a die coating method, a Langmuir, and a projet method. In order to prevent unevenness in film thickness, it is preferable to form a thin film under a static elimination atmosphere. Note that the drying temperature of the solvent is the heat-resistant temperature of the semiconductor substrate 10, and the upper limit temperature is set to 120, preferably 10 o t :.

Various changes can be made to the fingerprint reading device of the present invention. For example, as shown in FIG. 3, a conductive film 16 connected to a metal frame 90 provided on a base material 80 for housing the reading section main body 13 is formed by a dielectric layer 12 and a protective film 14. It is preferable to intervene between them. When static electricity is charged on the surface of the protective film 14, the static electricity electrically acts on the capacitance between the fingertip surface and the electrode 11, which adversely affects fingerprint reading. Therefore, it is preferable that the conductive film 16 allows static electricity charged on the surface of the protective film 14 to escape to the substrate 80 side. The conductive film 16 needs to be formed of a material having good adhesion to both the dielectric layer 12 and the protective film 14. For example, the dielectric layer 12 is formed of silicon nitride. In this case, it is preferable to use an indium tin oxide (ITO) film. However, when the thickness of the conductive film 16 is increased, the detection of capacitance by the electrode 11 is adversely affected, so that the film thickness is preferably 1 to 100 nm.

Further, instead of the conductive film 16, a primer layer having conductivity may be provided. A primer layer is used to improve the adhesion between the fluoropolymer and the dielectric layer surface. A conductive primer layer can be formed by mixing a conductive material such as a metal fine powder, a conductive metal oxide fine powder, and carbon black into one layer of the primer. Further, the conductive material as described above may be blended with the fluoropolymer itself to make it conductive and prevent charging. An antistatic agent can be blended in place of the conductive material to prevent charging. Industrial applicability

As described above, according to the present invention, there is no contamination of the dielectric layer, no complicated cleaning work is required, the fingerprint can always be read accurately, light resistance, water resistance, resistance to chemical substances, etc. A fingerprint reader is provided that has high sensitivity and high resistance to damage.

Claims

The scope of the claims

1. A two-dimensional array of electrodes and a dielectric layer are stacked in this order on a semiconductor substrate, and a finger is brought into contact with the dielectric layer to form a shape between the dielectric layer and the electrode. A fingerprint reading device that detects the formed capacitance and reads the concave and convex pattern of the fingerprint, wherein the surface of the dielectric layer that contacts the finger is covered with a protective film made of a fluoropolymer. Characteristic fingerprint reading device.

2. The fingerprint reader according to claim 1, wherein the thickness of the protective film is 1 / im or less.

3. The fingerprint reading device according to claim 1, wherein a conductive film is interposed between the dielectric layer and the protective film.

4. The fingerprint reader according to claim 1, wherein the fluoropolymer is a solvent-soluble fluoropolymer.

5. The fingerprint according to claim 4, wherein the solvent-soluble fluoropolymer is a fluoropolymer having any of a fluorinated aliphatic ring structure, a fluorinated triazine ring structure or a fluorinated aromatic ring structure in a main chain. Reader.

6. The fingerprint reading device according to claim 1, wherein the fluorine-containing polymer is a fluorine-containing polymer having a fluorine-containing aliphatic ring structure in a main chain.

7. The fingerprint reading device according to claim 6, wherein the fluoropolymer having a fluorinated aliphatic ring structure in the main chain is a homopolymer or a copolymer of a monomer having a fluorinated ring structure.

8. The fingerprint according to claim 6, wherein the fluoropolymer having a fluorinated aliphatic ring structure in the main chain is a polymer obtained by cyclopolymerization of a fluorinated monomer having two or more polymerizable double bonds. Reader.