JP7493315B2 - Cleaning sheet and cleaning method using same - Google Patents

Description

The present invention relates to a cleaning sheet and a cleaning method using the same, and in particular to a cleaning sheet for cleaning the contact terminals of an IC card reader that performs data communication with a contact-type IC card, and a cleaning method using the same.

An IC card is an information storage device that consists of a semiconductor memory circuit and a control microcomputer molded into a plate shape, with multiple terminals on its surface for connecting to an IC card reader/writer. Contact-type IC cards are mainly used for cash cards and credit cards in the financial sector, and ETC cards in on-board devices for automatic toll collection. When a contact-type IC card is inserted into a card reader/writer, power is supplied by the metal contact between the two, making it possible to read and write information on the IC card.

Because IC cards are carried and used directly by people, they become contaminated by oily dirt from people's finger marks (sebum stains) and dust and dirt that adheres to the dirt. When an IC card becomes contaminated, the contaminants adhere to various types of card reading devices via the IC card. Also, for example, in an ETC card reading device in an on-board device for automatic toll collection, soot and dust from the vehicle's exhaust gas directly contaminates the ETC card reading device. If the card reading device becomes contaminated in this way, it may cause problems in the communication of signals for reading and writing information on the IC card in the card reading section, so it is necessary to clean the card reading device. When cleaning a card reading device, disassembling the device to clean it is cumbersome, so a method of cleaning using a cleaning card is often used.

For example, Patent Document 1 discloses a cleaning card for cleaning the reading section of a card reading device, which is made of a nonwoven fabric coated with abrasive particles attached to one or both sides of a substrate, with the aim of providing a cleaning card that easily and quickly scrapes off contaminants adhering to the card reading section and wipes it off to clean it, and is characterized in that the size and thickness of the cleaning card are approximately the same as the size and thickness of the card used in the card reading device, and at least a portion of the cleaning card is opaque.

Japanese Utility Model Application Publication No. 5-73707

However, when a card reader is cleaned using the conventional cleaning card described in Patent Document 1, the nonwoven fabric has poor adhesion and a large degree of surface irregularity, so that it does not adhere sufficiently to contaminated areas in the device, resulting in uneven wiping and poor cleaning performance. In addition, due to the poor cleaning performance, repeated cleaning operations may cause secondary contamination, such as contaminants once adsorbed to the nonwoven fabric to reattach to the nonwoven fabric or the nonwoven fabric itself to fall off. Furthermore, the abrasive particles contained in the cleaning card may damage the card reader, causing problems with communication of signals for reading and writing information in the IC card. In addition, since a cleaning liquid is dripped onto the nonwoven fabric to improve cleaning performance, if the object to be cleaned is an electronic device, it is necessary to turn off the power when cleaning, which is cumbersome. Furthermore, because nonwoven fabrics have a relatively uneven surface shape, some of the adsorbed contaminants fall off easily while other parts of the adsorbed contaminants are firmly adsorbed. Therefore, even if the nonwoven fabric is washed, it is difficult to remove sebum stains and other dirt that have soaked into the fibers. In addition, washing causes the fibers on the surface to fall off or become frayed and twisted, reducing or eliminating the surface shape suitable for removing contaminants, making it difficult to reuse the fabric.

Therefore, the present invention aims to provide a cleaning sheet that has excellent cleaning properties for card reading devices.

The inventors of the present invention have conducted extensive research to solve the problems of the conventional technology. As a result, they have discovered that a cleaning sheet having a thickness of 0.5 to 2.0 mm and a first resin layer made of a foam having a first cleaning surface for cleaning an object to be cleaned, the first resin layer having a foam structure formed inside the first cleaning surface such that a plurality of air bubbles are overlapped and evenly dispersed in the thickness direction of the first resin layer, and openings formed from some of the air bubbles in the first resin layer are formed in the first cleaning surface, the cleaning sheet having a thickness of 0.5 to 2.0 mm, provides excellent cleaning properties for card reading devices, and have completed the present invention.

That is, the present invention is as follows.
[1]
a first resin layer made of a foam having a first cleaning surface for cleaning an object to be cleaned;
the first resin layer has a foamed structure formed on an inner side of the first cleaning surface such that a plurality of bubbles are overlapped and uniformly dispersed in a thickness direction of the first resin layer,
the first cleaning surface has openings formed from some of the bubbles contained in the first resin layer;
A cleaning sheet having a thickness of 0.5 to 2.0 mm.
[2]
the average opening diameter of the openings on the first cleaning surface is 5.0 to 30 μm;
The cleaning sheet according to [1].
[3]
the ratio of openings in the foamed structure in the first resin layer to the first cleaning surface is 1,000 to 50,000 openings/ ^mm2 ;
The cleaning sheet according to [1] or [2].
[4]
a second resin layer made of a foam and having a base material and a second cleaning surface for cleaning an object to be cleaned, on the opposite side of the first cleaning surface of the first resin layer;
the second resin layer has a foamed structure formed on the inner side of the second cleaning surface such that a plurality of bubbles are overlapped and uniformly dispersed in a thickness direction of the second resin layer,
the second cleaning surface has openings formed from some of the connected cells of the second resin layer;
The cleaning sheet according to any one of [1] to [3].
[5]
The first resin layer and the second resin layer contain a polyurethane resin.
The cleaning sheet according to any one of [1] to [4].
[6]
The first resin layer and the second resin layer are obtained by a wet film formation method.
The cleaning sheet according to [5].
[7]
A cleaning method comprising a step of cleaning an object to be cleaned with the cleaning sheet according to any one of [1] to [6].
[8]
The cleaning method according to claim 7, wherein the object to be cleaned is provided with a reading unit that reads card information by contact.

The cleaning sheet of the present invention has excellent cleaning properties for card reading devices.

FIG. 2 is a partial cross-sectional view showing a schematic example of a part of the cleaning sheet of the present embodiment, in which a first resin layer, a first adhesive layer, and a substrate are provided in this order. FIG. 2 is a partial cross-sectional view showing a schematic example of a part of the cleaning sheet of the present embodiment, in which the cleaning sheet includes a first resin layer, a first adhesive layer, a substrate, a second adhesive layer, and a second resin layer in this order.

Below, a detailed description of an embodiment of the present invention (hereinafter, simply referred to as "the present embodiment") will be given with reference to the drawings as necessary, but the present invention is not limited to the present embodiment. The present invention can be modified in various ways without departing from the gist of the invention. In the drawings, the same elements are given the same reference numerals, and duplicated explanations will be omitted. Furthermore, unless otherwise specified, the positional relationships, such as up, down, left, right, etc., are based on the positional relationships shown in the drawings. Furthermore, the dimensional ratios of the drawings are not limited to those shown in the drawings.

The cleaning sheet of the present embodiment includes a first resin layer made of a foam having a first cleaning surface for cleaning an object to be cleaned. Such a cleaning sheet can be produced, for example, by attaching a substrate to the opposite side of the resin layer from the cleaning surface via an adhesive layer.
The first resin layer has a foam structure formed on the inside of the first cleaning surface such that a plurality of bubbles are overlapped and uniformly dispersed in the thickness direction of the first resin layer. Furthermore, openings formed from some of the bubbles are formed on the first cleaning surface. In addition, the thickness of the cleaning sheet of this embodiment is 0.5 to 2.0 mm.

The reasons why such a cleaning sheet has excellent cleaning properties for a card reader are considered to be as follows. However, the reasons are not limited to these. When a card reader is cleaned using a cleaning sheet made of a conventional nonwoven fabric, the nonwoven fabric does not conform to the shape inside the device sufficiently, and has poor adhesion to contaminants, resulting in poor cleaning properties. In addition, due to the poor cleaning properties, repeated cleaning operations may cause secondary contamination, such as re-adhesion of contaminants once adsorbed by the nonwoven fabric or the nonwoven fabric fibers themselves falling off. Furthermore, if the cleaning card contains abrasive particles, the card reading unit may be damaged, which may interfere with communication of signals for reading and writing information in the IC card. In addition, since a cleaning liquid is dropped onto the nonwoven fabric to improve cleaning properties, if the object to be cleaned is an electronic device, it is necessary to turn off the power when cleaning, which is complicated. Furthermore, since the surface shape of the nonwoven fabric is relatively uneven, part of the adsorbed contaminants easily falls off, while the other part of the adsorbed contaminants is firmly adsorbed, so that it is difficult to reuse the nonwoven fabric even if it is washed. On the other hand, the cleaning sheet of the present embodiment is provided with a first resin layer made of a foam having a first cleaning surface for cleaning the object to be cleaned, so that the first cleaning surface made of a resin material can easily follow the shape of the object to be cleaned and adhere to the contaminated area in the device, resulting in excellent cleaning properties. In addition, the cleaning sheet of the present embodiment can relatively increase the amount of compression deformation on the first cleaning surface side made of a resin material made of a foam due to the multiple air bubbles in the foam, so that it can easily follow the shape of the object to be cleaned and can remove contaminants of various sizes. Furthermore, the cleaning sheet of the present embodiment does not require the use of a cleaning liquid as in the case of using a conventional nonwoven fabric.
In addition, the cleaning sheet of this embodiment has openings formed from some of the bubbles in the first resin layer on the first cleaning surface, so that the bubbles can hold the contaminants through the openings removed from the object to be cleaned, and the contaminants once removed are less likely to fall off. In addition, the first cleaning surface of the cleaning sheet can be washed thereafter to easily remove the held dust and dirt, and the cleaning sheet can be reused by drying it. Furthermore, the cleaning sheet of this embodiment has a foam structure formed in the first resin layer so that a plurality of bubbles are overlapped and evenly distributed in the thickness direction, so that the first cleaning surface has fine gaps due to the fine pores, but no large gaps. As a result, the contact area of the resin is large, so that the frictional resistance against the cleaning surface is increased, and the small openings have an edge effect, making it possible to remove even stubborn contaminants. Furthermore, since a plurality of bubbles are overlapped and evenly distributed in the thickness direction, even if the product is worn down due to repeated use, the opening diameter, the amount of openings, and the distribution state of the openings do not change, and the cleaning sheet can be used for a long time.
For these reasons, the cleaning sheet of this embodiment has excellent cleaning properties for card reading devices.

Figure 1 is a partial cross-sectional view showing an example of a part of the cleaning sheet of this embodiment, in which the first resin layer, the first adhesive layer, and the substrate are provided in this order. The cleaning sheet 1A has a polyurethane resin layer 2 (hereinafter simply referred to as "resin layer 2"). The resin layer 2 has a cleaning surface P for cleaning the object to be cleaned, and the cleaning surface P is buffed or sliced on its surface (upper surface) in the process of preparing the resin layer 2 described later so that the bubbles of the foam are exposed to form openings and the thickness of the resin layer 2 (the length in the vertical direction in Figure 1) is approximately uniform. On the other hand, the back side of the cleaning surface P in the resin layer 2 is not buffed or sliced. However, it may be buffed or sliced. In addition, the cleaning sheet 1A has the back side of the cleaning surface P (the side not buffed) and one side of the substrate 8 bonded together via an adhesive 7, which is an adhesive layer.

Fig. 2 is a partial cross-sectional view showing an example of a part of the cleaning sheet of the present embodiment, in which the cleaning sheet is provided with a first resin layer, a first adhesive layer, a substrate, a second adhesive layer, and a second resin layer in this order. Cleaning sheet 1B (hereinafter, cleaning sheets 1A and 1B are also collectively referred to as "cleaning sheet 1") is provided with a first resin layer 2a having a cleaning surface P1 for cleaning an object to be cleaned, an adhesive 7a which is a first adhesive layer, and a substrate 8a (not distinguished from the substrate 8 in Fig. 2) similarly to the configuration in Fig. 1.
The cleaning sheet 1B includes a second resin layer 2b (hereinafter, the first resin layer 2a and the second resin layer 2b are collectively referred to as "resin layer 2") similar to the adhesive 7a serving as the first adhesive layer, and an adhesive 7b (hereinafter, the adhesives 7a and 7b are collectively referred to as "adhesive 7") serving as the second adhesive layer, on the side opposite to the side where the substrate 8a is bonded to the resin layer 2a via the adhesive 7a. Here, the substrate 8b (not distinguished from the substrate 8 in FIG. 2) is bonded to the resin layer 2b via the adhesive 7b. The resin layer 2b also includes a cleaning surface P2 (hereinafter, the cleaning surfaces P1 and P2 are collectively referred to as "cleaning surface P") similar to the resin layer 2a.
In the substrate 8 in Fig. 2, the substrate 8a and the substrate 8b are shown as the same substrate for convenience, but the substrate 8a and the substrate 8b may be the same substrate or may be different substrates. If the substrates are different substrates, they may be bonded to each other with an adhesive or double-sided tape. When the substrates are bonded with double-sided tape, the double-sided tape may be one in which an adhesive is provided on both sides of the substrate, or a non-support type that does not have a substrate.

In the following, unless otherwise specified, the cleaning sheets shown in Figures 1 and 2 will be collectively referred to as cleaning sheets.

The resin layer 2 is made of a resin foam that constitutes the layer, and has a foam structure formed inside the cleaning surface P such that multiple bubbles overlap and are evenly distributed in the thickness direction of the resin layer 2. The foam 3 of the resin layer 2 is connected to each other in a three-dimensional mesh shape by communicating holes larger than the diameter of the spatial volume of the micropores formed in the skin layer. However, most of the bubbles contained in the resin layer 2 are connected bubbles, but some may be independent bubbles. Since the cleaning surface P is a surface that appears by buffing or the like, the openings of the foam 3 are formed on the cleaning surface P. In addition, in Figures 1 and 2, the resin layer 2 before being subjected to buffing or slicing has a skin layer on the cleaning surface P side in which dense micropores are formed. Here, "multiple bubbles overlap and are evenly distributed" means that, for example, when multiple bubbles are observed in the resin layer in an arbitrary thickness direction, multiple bubbles can be confirmed in the resin layer, and the distance between the closest bubbles is approximately the same, as in the bubbles shown in Figures 1 and 2.

The thickness of the resin layer 2 is not particularly limited, but may be, for example, 100 to 1500 μm or 200 to 500 μm. The thickness of the resin layer 2 is measured in accordance with the measurement method described in JIS K6550:1994. In other words, it is the thickness when a load of 100 g per ^cm2 is applied (loaded) as an initial load in the thickness direction of the resin layer 2.

In this embodiment, the average opening diameter of the openings in the resin layer 2 that communicate with the cleaning surface P is preferably 1.0 μm or more, and more preferably 5.0 to 30 μm. When the average opening diameter is 1.0 μm or more, the cleaning performance is superior due to an increased ability to capture contaminants. Furthermore, when the average opening diameter is 30 μm or less, the edges of the openings easily scrape off oily stains and the like that have stuck to them, and the stains are taken in, resulting in superior cleaning performance.

The opening ratio of the foamed structure in the resin layer 2 is preferably 1000/mm2 or ^more , more preferably 1000 to 50000/ ^mm2 , relative to the cleaning surface P. By having the opening ratio of the foamed structure of ¹⁰⁰⁰ /mm2 or more, the cleaning sheet can sufficiently secure the places where the cleaning sheet can take in contaminants during cleaning, and can easily wipe off oily contaminants that are difficult to wipe off by simply spreading the dirt with a conventional cleaning sheet made of nonwoven fabric, resulting in excellent cleaning properties. By having the opening ratio of the foamed structure of 50000/ ^mm2 or less, the contact resin area during cleaning of the cleaning sheet is secured, friction resistance is increased, and excellent wiping performance (wiping performance) is obtained, resulting in excellent cleaning properties.

The average opening diameter of the resin layer 2 and the opening formation ratio of the foam structure are measured as follows. That is, first, an arbitrarily selected rectangular area of 1.0 mm x 1.4 mm on the cleaning surface P of the resin layer 2 is observed at 200 times magnification with a laser microscope (for example, "VK-X105" manufactured by KEYENCE Corporation), and an image is obtained. Next, the obtained image is binarized using image analysis software (for example, "WinRoof" manufactured by Mitani Shoji Co., Ltd.) to distinguish the openings from other parts. Then, the circle equivalent diameter, that is, the opening diameter is calculated from the area of each distinguished opening, assuming that the openings are perfect circles. Then, the opening diameters of each opening are arithmetically averaged to obtain the average opening diameter (μm). In addition, the number of the openings is regarded as the number of bubbles, and the number of the openings relative to a certain area is regarded as the opening formation ratio (pieces/mm ² ).

The resin layer 2 has a plurality of air bubbles 3 in a material constituting a matrix such as a resin (hereinafter referred to as the "matrix material"), and is formed by a so-called wet film-forming method. However, the resin layer in the cleaning sheet of the present invention may be formed by a dry molding method or other molding method, so long as openings are formed by the air bubbles on the cleaning surface P.

The matrix material constituting the resin layer 2 is, for example, a composition containing polyurethane resin in the largest amount, and the resin layer 2 may contain 80 to 100% by mass of polyurethane resin relative to the total amount of the matrix material. The resin layer 2 more preferably contains 85 to 100% by mass of polyurethane resin relative to the total amount, even more preferably contains 90 to 100% by mass, and particularly preferably contains 90 to 95% by mass.

Examples of polyurethane resins include polyester-based polyurethane resins, polyether-based polyurethane resins, and polycarbonate-based polyurethane resins, which may be used alone or in combination of two or more. Of these, polyester-based polyurethane resins are preferred from the viewpoint of achieving the object of the present invention more effectively and reliably.

The polyurethane resin may be synthesized by a conventional method, or may be a commercially available product. Examples of commercially available products include CRISBON (trade name, manufactured by DIC Corporation), SANPREN (trade name, manufactured by Sanyo Chemical Industries, Ltd.), and REZAMIN (trade name, manufactured by Dai-Nippon Seika Kogyo Co., Ltd.). The polyurethane resin may be used alone or in combination of two or more kinds.

In addition to polyurethane resin, the resin layer 2 may contain other resins such as polysulfone resin and/or polyimide resin. The polysulfone resin may be synthesized by a conventional method, or may be commercially available. For example, Udel (product name, manufactured by Solvay Advanced Polymers, Inc.) may be mentioned. The polyimide resin may be synthesized by a conventional method, or may be commercially available. For example, Aurum (product name, manufactured by Mitsui Chemicals, Inc.) may be mentioned.

The resin layer 2 is prepared by mixing N,N-dimethylformamide (hereinafter abbreviated as DMF), a water-miscible organic solvent capable of dissolving polyurethane resin, to dissolve the polyurethane resin, and then mixing an appropriate adjusting organic solvent for foaming adjustment into the resin solution to form bubbles 3. The adjusting organic solvent has a lower solubility in water than DMF and can be mixed or dispersed approximately uniformly into the mixture in which the polyurethane resin is dissolved without solidifying (gelling) the polyurethane resin dissolved in DMF. Specific examples include ethyl acetate and isopropyl alcohol. The amount of the adjusting organic solvent is set according to the opening diameter and number of openings on the cleaning surface P of the bubbles 3. In this example, in order to set the opening diameter and opening formation ratio within the above-mentioned range, it is preferable to appropriately adjust the amount of the adjusting organic solvent to be within the range of 20 to 45 parts by mass per 100 parts by mass of the polyurethane resin solution. If the amount is within the range of 20 to 45 parts by mass, the solidification speed is not extremely slow, and a resin layer 2 having the above-mentioned opening diameter and opening formation ratio can be obtained.

In addition to the resin, the resin layer 2 may contain one or more of the following materials that are typically used in resin layers, such as pigments such as carbon black, hydrophilic additives such as sodium lauryl sulfate, hydrophobic additives such as polypropylene glycol, and water repellents, to the extent that the solution to the problem of the present invention is not hindered. Furthermore, various materials such as solvents used in the manufacturing process of the resin layer 2 may remain in the resin layer 2 to the extent that the solution to the problem of the present invention is not hindered.

The pigment content in the resin layer 2 is preferably 0.1% by mass or more and 20% by mass or less, and more preferably 1.0% by mass or more and 15% by mass or less, relative to 100% by mass of the total solid content constituting the resin layer 2. By having the pigment content within the above range, the adhesion of the cleaning surface, which is thought to be caused by the disruption of the uniformity of the bubbles inside the resin layer 2, can be further improved, and the rigidity of the resin layer 2 can be improved, which tends to improve the cleaning ability and durability.

The content of the hydrophobic additive in the resin layer 2 is preferably 0.01% by mass or more and 20% by mass or less, more preferably 0.1% by mass or more and 10% by mass or less, and even more preferably 1.0% by mass or more and 5.0% by mass or less, based on 100% by mass of the total solid content constituting the resin layer 2. By having the content of the hydrophobic additive within the above range, it is possible to promote the formation of bubbles inside the resin layer and stabilize the solidification and regeneration of the polyurethane resin, which tends to contribute to stabilizing the physical properties of the cleaning sheet.

The content of the hydrophilic additive in the resin layer 2 is preferably 0.01% by mass or more and 20% by mass or less, more preferably 0.1% by mass or more and 10% by mass or less, and even more preferably 0.5% by mass or more and 3.0% by mass or less, based on 100% by mass of the total solid content constituting the resin layer 2. By having the content of the hydrophilic additive within the above range, it is possible to promote the formation of bubbles inside the resin layer and stabilize the solidification and regeneration of the polyurethane resin, which tends to contribute to stabilizing the physical properties of the cleaning sheet.

The adhesive 7 may include a double-sided tape or pressure-sensitive adhesive that is typically used to bond resin layers or plastic materials. There are no particular limitations on the adhesive or double-sided tape used, and any adhesive or double-sided tape known in the art may be selected and used.

The substrate 8 is for supporting the resin layer 2 and is not particularly limited, and may be a substrate that is typically used to support a resin layer or plastic material, such as a resin film such as a polyethylene terephthalate (hereinafter referred to as "PET") film.

The cleaning sheet has a thickness of 0.5 to 2.0 mm, preferably 0.3 to 1.0 mm. With a thickness within the above range, it adheres better to the inside of devices such as automatic ticket gates, ATMs, vending machines, and various card readers and writers, allowing for more effective cleaning.

The density of the cleaning sheet is preferably 0.5 to 1.5 g/cm ³ , more preferably 0.6 to 1.2 g/cm ³ , and even more preferably 0.7 to 1.0 g/cm ^3. If the density is within the above range, the sheet can be used repeatedly because the sheet maintains its rigidity.

The compression ratio of the cleaning sheet is preferably 3 to 20%, more preferably 5 to 18%, and even more preferably 6 to 17%. If the compression ratio is within the above range, the sheet can be compressed and deformed to conform to the shape of the cleaning surface, improving adhesion to the cleaning surface and improving cleaning performance.

The compressive elastic modulus of the cleaning sheet is preferably 80 to 100%, more preferably 85 to 99%, and even more preferably 90 to 98%. If the compressive elastic modulus is within the above range, the compressed and tightly adhered cleaning sheet exerts a high stress on the cleaning surface, improving cleaning performance.

The Shore A hardness of the cleaning sheet is preferably 50 to 95°, more preferably 60 to 90°, and even more preferably 70 to 85°. When the Shore A hardness is within the above range, the cleaning surface has compressibility and compressive elasticity modulus, and is flexible, but the sheet as a whole has a high hardness and therefore has appropriate rigidity, and can follow the complex transport path inside the cleaning device without bending, and has durability that allows it to be washed after use and used repeatedly.

Regarding the reuse of cleaning sheets after use by washing, with conventional cleaning sheets made of nonwoven fabric, the fibers on the cleaning surface fall off or fray when washed, causing the fibers to become uneven, and the unevenness for removing dust and dirt is reduced or lost. In contrast, the cleaning sheet of the present application does not lose its air bubble structure even when washed, and can be reused by washing and removing the dust and dirt adhering to the cleaning surface and drying it. Furthermore, even if the product becomes worn due to repeated use, there is no change in the opening diameter, amount of openings, or distribution of openings, so it can be used as a cleaning sheet for a long period of time by washing and drying it.

Next, an example of a method for manufacturing the cleaning sheet of this embodiment will be described. Here, a case where the resin layer 2 is manufactured by a wet film-forming method will be described, but the method for manufacturing the resin layer in the cleaning sheet of the present invention is not limited to this. This manufacturing method includes a step of preparing the resin layer 2 and a step of bonding the substrate 8 to the resin layer 2 using an adhesive 7 to obtain the cleaning sheet 1.

The process of preparing the resin layer 2 further includes a process of preparing a resin solution containing a resin, a solvent, and, if necessary, a pigment, a hydrophilic additive, and a hydrophobic additive, using a stirring device equipped with stirring blades (resin solution preparation process), and a process of molding the resin layer 2 from the resin solution (molding process).

The process of forming the resin layer 2 further includes a step of applying a resin solution to the surface of the film-forming substrate (application step), a step of solidifying and regenerating the resin in the resin solution to form a precursor sheet (solidification and regeneration step), a step of washing and drying the precursor sheet to obtain the resin layer 2 (washing and drying step), and a step of grinding and/or partially removing the resin layer 2 by buffing or slicing (grinding and removal step). Each step is described below.

First, in the resin solution preparation process, a resin such as the polyurethane resin described above is mixed with an adjusting organic solvent for adjusting foaming, a solvent capable of dissolving the resin and miscible with the coagulation liquid described below, and a pigment, hydrophilic additive, hydrophobic additive, and other materials (e.g., a pore-forming agent, a water-repellent agent, etc.) that may be included in the resin layer 2 as necessary, and the mixture is degassed under reduced pressure as necessary to prepare a resin solution. The adjusting organic solvent has a lower solubility in water than DMF, and can be uniformly mixed or dispersed in the solution in which the polyurethane resin is dissolved without coagulating (gelling) the polyurethane resin dissolved in DMF. Specific examples include ethyl acetate and isopropyl alcohol. By changing the amount of adjusting organic solvent added, the size and amount (number) of the bubbles 3 formed inside the resin layer 2 can be controlled, and the opening diameter and opening formation ratio of the cleaning surface can be adjusted. In this example, in order to set the opening diameter and opening formation ratio of the resin layer 2 to the above-mentioned range, it is preferable to set the amount of adjusting organic solvent added to the range of 20 to 45 parts by mass per 100 parts by mass of the resin solution. The solvent is not particularly limited, but examples thereof include N,N-dimethylformamide (hereinafter referred to as "DMF") and N,N-dimethylacetamide. The resin content relative to the total amount of the resin solution is not particularly limited, but may be, for example, in the range of 10 to 50% by mass, or in the range of 15 to 35% by mass.

Next, in the coating step, the resin solution is applied to the surface of the strip-shaped film-forming substrate, preferably at room temperature, using a coating device such as a knife coater to form a coating film. The thickness of the resin solution applied at this time may be appropriately adjusted so that the final resin layer 2 has the desired thickness. Examples of materials for the film-forming substrate include resin films such as PET films, fabrics, and nonwoven fabrics. Among these, resin films such as PET films are preferred because they can increase the rigidity of the entire cleaning sheet even if they are thin.

Next, in the solidification and regeneration process, the coating of the resin solution applied to the film-forming substrate is continuously guided into a solidification liquid mainly composed of a poor solvent for the resin (for example, water in the case of polyurethane resin). In order to adjust the regeneration speed of the resin, an organic solvent such as a polar solvent such as the solvent in the resin solution may be added to the solidification liquid. The temperature of the solidification liquid is not particularly limited as long as it is a temperature at which the resin can be solidified, and may be, for example, 15 to 65°C. In the solidification liquid, a film (skin layer) is first formed at the interface between the coating of the resin solution and the solidification liquid, and countless dense micropores are formed in the resin immediately adjacent to the film. After that, the replacement of the adjusting organic solvent in the resin solution with the solidification liquid slows down. For this reason, approximately spherical bubbles 3 larger than the micropores formed in the skin layer are formed approximately evenly inside the skin layer, and the regeneration of the resin, preferably having an open-cell structure, progresses due to the cooperative phenomenon of the diffusion of the solvent contained in the resin solution into the solidification liquid and the infiltration of the poor solvent into the resin. At this time, if the substrate for film formation is one that is difficult for liquids to penetrate (for example, a PET film), the solidification liquid will not penetrate the substrate, and the solvent in the resin solution will be replaced by the poor solvent preferentially near the skin layer, and larger voids will tend to form in the region inside the skin layer rather than near it. In this way, a precursor sheet is formed on the substrate for film formation.

Here, the foam structure formed on the inside of the cleaning surface P so that multiple bubbles are overlapped and evenly dispersed in the thickness direction of the resin layer 2 will be described. In the resin solution, it is considered that two-phase separation occurs because the compatibility of the adjusting organic solvent and the polyurethane resin is poor. In addition, when the polyurethane resin is solidified and regenerated, the solidification characteristics of the adjusting organic solvent and the polyurethane resin in the solidification liquid are different, so there is a difference in the amount of shrinkage, and because of the poor compatibility, the interfacial bonding force between the adjusting organic solvent and the polyurethane resin becomes small and a detachment phenomenon occurs, so it is considered that bubbles 3 are formed. For this reason, the pore diameter of the bubbles 3 is larger than the micropores of the skin layer, and approximately spherical bubbles 3 are formed approximately evenly. In addition to the above method, the bubbles 3 can also be obtained by increasing the concentration of the solvent in the solidification liquid. Specifically, by increasing the DMF concentration in the solidification liquid, the elution of DMF in the resin emulsion in the resin solution is suppressed, and the replacement speed of DMF in the resin emulsion with the solidification liquid is slowed. This slows down the regeneration and solidification of the resin, and the resulting resin has a surface layer with foam roughly evenly distributed inside the skin layer, suppressing the formation of large cells, resulting in a roughly uniform foam structure in the thickness direction.

Next, the precursor sheet obtained by the coagulation regeneration process is peeled off from the film-formed substrate, and then washed and dried. In the washing and drying process, the solvent remaining in the precursor sheet formed by the washing process is removed to obtain the resin layer 2. Water can be used as the washing liquid. The resin layer 2 after washing is then dried. The resin layer 2 may be dried by a conventional method, for example, by drying in a dryer at 80 to 150°C for about 5 to 60 minutes. The resin layer 2 after the above process may be wound into a roll.

Next, in the grinding and removal process, the surface (upper surface) and/or the back surface (lower surface) from the process of preparing the resin layer 2 are ground and/or partially removed by buffing or slicing. The buffing and slicing processes expose the connected bubbles to the cleaning surface, forming openings, so that contaminants from the object to be cleaned can be retained within the bubbles.

Next, the substrate 8 is attached to the surface of the resin layer 2 that has not been buffed or sliced via the adhesive 7 to obtain the cleaning sheet 1. In this way, the adhesive 7, which is an adhesive layer, and the substrate 8 are laminated in this order on one surface of the resin layer 2 to obtain the cleaning sheet 1A. Furthermore, the cleaning sheet 1A is joined to the surface of another resin layer 2 (second resin layer) similar to the resin layer 2 used in the cleaning sheet 1A that has not been buffed or sliced via double-sided tape to obtain the cleaning sheet 1B.

The object to be cleaned with the cleaning sheet 1 is not particularly limited as long as it has an insertion port through which a sheet-like substance is inserted and a placement section for placing the sheet-like substance inside the insertion port, and the cleaning sheet 1 can be inserted through the insertion port and the part in the placement section that comes into contact with the cleaning sheet 1 can be cleaned. Specifically, an electronic terminal device having an insertion port for carrying in and carrying out a card can be mentioned. In such an electronic terminal device, a plurality of pairs of conveying rollers for carrying in and carrying out a card inserted through the insertion port are provided in the conveying path. The card inserted through the insertion port is conveyed through the conveying path by the conveying roller pairs and placed at a predetermined position (placement section), where information on the card can be read and written by contacting or not contacting the card reading section. In such an electronic terminal device, the cleaning sheet 1 is inserted and conveyed in the same way as the card inserted through the insertion port, and comes into contact with and cleans the members (conveying roller pairs, card reading section) that become dirty by contact with the card or become dirty by dust mixed in through the insertion port.

The cleaning method of this embodiment includes a step of cleaning an object to be cleaned using the above-mentioned cleaning sheet.

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

Example 1
To 100 parts by mass of a solution in which a polyester-based polyurethane resin, which is the raw material resin for the matrix resin, is dissolved in DMF (N,N-dimethylformamide) at 30% by mass, 60 parts by mass of DMF for adjusting viscosity, 40 parts by mass of a DMF dispersion in which 16% by mass of DMF containing 12% by mass of carbon black (manufactured by Mitsubishi Chemical Corporation under the trade name "RCF44") as a pigment is dissolved, 2 parts by mass of a hydrophobic activator as a film formation stabilizer, and 45 parts of ethyl acetate as an adjustment organic solvent were added, and the mixture was mixed and stirred to prepare a resin solution.

Next, a commercially available PET film was prepared as a film-forming substrate, and the prepared resin solution was applied thereto. The clearance of the coating device was adjusted to obtain a coating film having a thickness of 350 μm. The obtained coating film was then immersed together with the film-forming substrate in a coagulation bath at 18°C consisting of water as a coagulation liquid, and the resin was coagulated and regenerated to obtain a precursor resin layer. The precursor resin layer was removed from the coagulation bath, and the film-forming substrate was peeled off from the precursor resin layer. The precursor resin layer was then washed with a room temperature cleaning solution (desolvation bath) consisting of water, dried, and then wound up. Next, the surface of the resin layer (the surface opposite to the surface from which the film-forming substrate was peeled off and the surface opposite to the surface that had been in contact with the film-forming substrate) was buffed to a thickness of 150 μm to a thickness of 200 μm, and an opening was formed in the surface after buffing.

Two sheets were prepared by bonding the surface of the obtained resin layer (the surface opposite to the buffed surface) to a commercially available PET substrate having a thickness of 0.188 mm with an adhesive, and the surfaces with the exposed PET substrate were bonded together using commercially available double-sided tape to obtain a cleaning sheet laminated in the following order: resin layer, adhesive, PET substrate, double-sided tape, PET substrate, adhesive, resin layer. The sheets were then punched out to the size of JIS type II (53.9 mm x 85.6 mm) to produce a cleaning sheet having a thickness of 0.89 mm.

(Comparative Example 1)
The material used was "S85PG" manufactured by Chikami Miltec Co., Ltd., which is 0.79 mm thick and has a nonwoven fabric made of acrylic synthetic fibers bonded to both sides of a polyethylene terephthalate substrate.

The opening diameter and opening formation rate of each cleaning sheet obtained in Example 1 and Comparative Example 1 were measured using the following method.

The average opening diameter and opening formation rate of the openings on the cleaning surface were measured as follows. An area of approximately 1.3 mm square was observed at 175 times magnification using a microscope (Keyence Corporation, product name "VH-6300"), and the resulting image was processed and calculated using image processing software (Image Analyzer V20LAB Ver. 1.3). The results are shown in Table 1 below.

The cleaning properties of each cleaning sheet obtained in Example 1 and Comparative Example 1 were evaluated under the following conditions.

Test contaminants 1 to 5 were prepared using the prepared powders 1 to 3, artificial sebum and cotton dust as described below.
Powder 1: Three types of test powders of JIS Z8901 (silica sand: standard material of sand and dust with SiO ₂ 95% or more, particle size 9 to 61 μm, high hardness, and angular particle shape)
Powder 2: 15 types of test powders according to JIS Z8901 (a mixture of 8 types of mixed powders (72%), 12 types of mixed powders (23%), and 5% cotton linters, a standardized substance simulating indoor dust containing so-called cotton dust from clothing, etc.)
Powder 3: 12 types of test powders of JIS Z8901 (carbon black, particle size 0.03 to 0.2 μm, standardized material assuming soot-like material)
Artificial sebum: A mixture of 70% by mass of oleic acid and 30% by mass of palmitic acid Cotton dust: Cotton linters (diameter 1.5 μm x length 1 mm or less)
Test contaminant 1: Powder 1
Test Contaminant 2: A mixture of Test Powder 1 and artificial sebum at a mass ratio of 1:10 Test Contaminant 3: A mixture of Test Powder 2 and artificial sebum at a mass ratio of 1:10 Test Contaminant 4: A mixture of Test Powder 3 and artificial sebum at a mass ratio of 1:10 Test Contaminant 5: Artificial sebum

Each test contaminant was prepared and applied to the IC chip reader in the card processing device to the extent that it caused a reading error in the card processing device, and then the cleaning sheet was inserted and removed five times to perform the cleaning operation. The dirt on the cleaning sheet was then visually checked, and the operation was checked to see if the reading error in the card processing device had been resolved. Cleanability was evaluated as "○" when it was confirmed that a large amount of dirt had adhered to the cleaning sheet and the reading error in the card processing device had been resolved, and "×" when no dirt had adhered to the cleaning sheet and the reading error in the card processing device had not been resolved.

Using the card processing device, the cleaning surfaces of the cleaning sheets of the Examples and Comparative Examples after the test with Powder 1 were washed with water, and the cleaning sheets were dried. When it was judged that the appearance of the cleaning sheets after washing and drying was the same as before use, it was evaluated as "○", and when it was judged that the appearance had changed, it was evaluated as "×". In addition, the cleaning performance test was conducted again for Powder 1 using the cleaning sheets of the Examples and Comparative Examples after washing and drying. When it was confirmed that a large amount of dirt was attached to the cleaning sheet and the reading error of the card processing device had been resolved, it was evaluated as "○", and when there was no dirt attached to the cleaning sheet and the reading error of the card processing device had not been resolved, it was evaluated as "×".

Comparative Example 1, whose cleaning surface is nonwoven fabric, was able to wipe off only powder, but was unable to demonstrate cleaning properties against dirt containing artificial sebum. In addition, after washing and drying, the fibers on the cleaning surface of the Comparative Example frayed and did not return to the state before use, and when Comparative Example 1 was used to clean powder after washing and drying, wiping became impossible. On the other hand, the Example products, due to the openings on the cleaning surface and the adhesion and rigidity of the cleaning sheet, demonstrated cleaning properties against powder and difficult-to-remove dirt including artificial sebum, and the appearance remained the same even after washing and drying, making it possible to reuse them.

Reference Signs List 1, 1A, 1B... cleaning sheet 2, 2a, 2b... resin layer 3... air bubbles 7, 7a, 7b... adhesive 8... substrate P, P1, P2... cleaning surface

The present invention has industrial applicability as an IC card reader that communicates data with contact-type IC cards, and as a cleaning sheet for cleaning the transport path of an IC card reader.

Claims (8)

A cleaning sheet used for cleaning an object to be cleaned, the cleaning sheet comprising an insertion opening for inserting a sheet-like material and a placement section for placing the sheet-like material inside the insertion opening,
the cleaning sheet includes a first resin layer made of a foam having a first cleaning surface for inserting the cleaning sheet through the insertion opening to clean a portion of the arrangement section that comes into contact with the cleaning sheet,
the first resin layer has a foamed structure formed on an inner side of the first cleaning surface such that a plurality of bubbles are overlapped and uniformly dispersed in a thickness direction of the first resin layer,
the first cleaning surface has openings formed from some of the bubbles contained in the first resin layer;
A cleaning sheet having a thickness of 0.5 to 2.0 mm. the average opening diameter of the openings on the first cleaning surface is 5.0 to 30 μm;
The cleaning sheet according to claim 1. the ratio of openings in the foamed structure in the first resin layer to the first cleaning surface is 1,000 to 50,000 openings/ ^mm2 ;
The cleaning sheet according to claim 1 or 2. a second resin layer made of a foam and having a base material and a second cleaning surface for cleaning an object to be cleaned, on the opposite side of the first cleaning surface of the first resin layer;
the second resin layer has a foamed structure formed on the inner side of the second cleaning surface such that a plurality of bubbles are overlapped and uniformly dispersed in a thickness direction of the second resin layer,
the second cleaning surface has openings formed from some of the bubbles contained in the second resin layer;
The cleaning sheet according to any one of claims 1 to 3. The first resin layer and the second resin layer contain a polyurethane resin.
The cleaning sheet according to claim 4 . The first resin layer and the second resin layer are obtained by a wet film-forming method.
The cleaning sheet according to claim 5. A cleaning method comprising a step of cleaning an object to be cleaned with the cleaning sheet according to any one of claims 1 to 6,
the cleaning sheet comprises a first resin layer made of a foam having a first cleaning surface;
the object to be cleaned includes an insertion opening for inserting a sheet-like material and a placement section for placing the sheet-like material inside the insertion opening,
A cleaning method, wherein in the cleaning step, the cleaning sheet is inserted through the insertion opening to clean a portion of the arrangement portion that comes into contact with the first cleaning surface of the cleaning sheet. The cleaning method according to claim 7 , wherein the object to be cleaned is provided with a reading unit that reads card information by contact.

Images