JP7471064B2 - 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 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 intensive research to solve the problems of the conventional technology described above, and as a result have found that a cleaning sheet having 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 plurality of bubbles extending in the thickness direction of the foam, at least some of the adjacent bubbles among the plurality of bubbles being connected to each other, and the first cleaning surface having openings formed from some of the plurality of bubbles in the first resin layer, 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 plurality of bubbles extending in a thickness direction of the foam, and adjacent bubbles among the plurality of bubbles are at least partially connected to each other to form connected bubbles;
A cleaning sheet, comprising: a first cleaning surface, and openings formed by some of the plurality of bubbles contained in the first resin layer.
[2]
a maximum bubble diameter of the connected bubbles in the first resin layer parallel to the first cleaning surface is present inside the first resin layer;
The cleaning sheet according to [1].
[3]
The first cleaning surface of the first resin layer is opposite to the first cleaning surface of the first resin layer.
The cleaning sheet according to [1] or [2].
[4]
the average opening diameter of the openings on the first cleaning surface is 5.0 to 300 μm;
The cleaning sheet according to any one of [1] to [3].
[5]
the opening ratio of the openings in the first cleaning surface is 10 to 60%;
The cleaning sheet according to any one of [1] to [4].
[6]
a second resin layer made of a foam having a second cleaning surface for cleaning an object to be cleaned, the second resin layer being provided on a surface opposite to the first cleaning surface of the first resin layer;
the second resin layer has a plurality of bubbles in the foam, and at least a portion of the plurality of bubbles are connected to each other;
the second cleaning surface has openings formed from some of the connected cells of the second resin layer;
[6] The cleaning sheet according to any one of [1] to [5].
[7]
Further comprising a substrate disposed on one side of the first resin layer and one side of the second resin layer,
the substrate is disposed on a side of the first resin layer opposite to the first cleaning surface and on a side of the second resin layer opposite to the second cleaning surface;
The cleaning sheet according to [6].
[8]
a maximum bubble diameter of the connected bubbles contained in the second resin layer, the maximum bubble diameter being parallel to the second cleaning surface, is present inside the second resin layer;
The cleaning sheet according to [6] or [7].
[9]
The first resin layer and the second resin layer contain a polyurethane resin.
The cleaning sheet according to any one of [1] to [8].
[10]
A cleaning method comprising a step of cleaning an object to be cleaned with the cleaning sheet according to any one of [1] to [9].
[11]
The cleaning method according to claim 10, 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. 11 is a partial cross-sectional view that illustrates an example of a part of the cleaning sheet of the present embodiment, in which the bubble diameter of connected bubbles has a maximum diameter on the inside of the cleaning surface. FIG. 11 is a partial cross-sectional view that illustrates an example of a case in which the bubble diameter of connected bubbles decreases from the cleaning surface toward the opposite surface in a part of the cleaning sheet of the present embodiment. 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. 1 is a graph showing the measurement results for the cleaning sheet pieces of Examples 1 to 3 and Comparative Examples 1 and 2, with the amount of deformation (mm) on the horizontal axis and pressure (g/cm ² ) on the vertical axis. 1 is a photograph of a cross section of the cleaning sheet of Example 1, observed at 50x using an electron microscope. 1 is a photograph of a cross section of a resin layer of the cleaning sheet of Example 1, observed at 500 times using an electron microscope. 1 is a photograph of the cleaning surface of the cleaning sheet of Example 1 observed at 50x using an electron microscope. 1 is a photograph of a cross section of the cleaning sheet of Comparative Example 1, observed at 50x using an electron microscope. 1 is a photograph of a cross section of the cleaning sheet of Comparative Example 1, observed at 500 times using an electron microscope. 1 is a photograph of the cleaning surface of the cleaning sheet of Comparative Example 1 observed at 50 times using an electron microscope.

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 with an adhesive layer (hereinafter also referred to as an "adhesive layer").
The first resin layer has a plurality of bubbles in a foam, at least some of the bubbles being connected to one another, and openings formed from some of the connected bubbles are formed on the first cleaning surface.

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 card 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 itself 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 an 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 nonuniform, some of the adsorbed contaminants easily fall 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 has a foam having a first cleaning surface for cleaning the object to be cleaned, and has a plurality of bubbles extending in the thickness direction, so that the first cleaning surface made of a resin material can easily follow the shape of the object to be cleaned and adhere closely to the contaminated parts in the device, resulting in excellent cleaning properties. Also, 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 plurality of 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 this embodiment does not require the use of a cleaning liquid as in the case of using conventional nonwoven fabric.
In addition, the cleaning sheet of the present embodiment has openings on the first cleaning surface formed from some of the multiple bubbles in the first resin layer, so that contaminants removed from the object to be cleaned can be retained inside the connected bubbles through the openings. Therefore, once removed, the contaminants can become trapped between the connected bubbles and are less likely to fall off.
As a result, the cleaning sheet of the present embodiment has excellent cleaning properties for card readers. Furthermore, by arranging the first resin layer so that the maximum diameter of the connected air bubbles parallel to the first cleaning surface is present inside the first resin layer, it is possible to prevent contaminants once taken into the air bubbles from being released again.

Figure 1 is a partial cross-sectional view showing an example of a part of the cleaning sheet of this embodiment in which the bubble diameter of the connected bubbles has a maximum diameter inside the cleaning surface. 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. The cleaning surface P is flattened by buffing or slicing the 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 (vertical length in Figure 1) of the resin layer 2 is approximately uniform. On the other hand, the back side of the cleaning surface P 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, or an adhesive 7, which is an adhesive layer.

Figure 2 is a partial cross-sectional view showing an example of a part of the cleaning sheet of this embodiment in which the bubble diameter of the connected bubbles decreases from the cleaning surface toward the opposite surface. Cleaning sheet 1B has a resin layer 2 having a cleaning surface P for cleaning the object to be cleaned, similar to the configuration of Figure 1. However, the back surface (lower surface) in the process of preparing resin layer 2 described later is buffed or sliced to form the cleaning surface P. In addition, cleaning sheet 1B has the back side (non-buffed surface) of the cleaning surface P bonded to one side of substrate 8 via adhesive 7, which is an adhesive layer, or adhesive 7, which is an adhesive layer.

Fig. 3 is a partial cross-sectional view showing an example of a part of the cleaning sheet of this 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 1C (hereinafter, cleaning sheets 1A, 1B, and 1C 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 substrate 8 in Fig. 3), similar to the configuration in Fig. 1.
The cleaning sheet 1C 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. 3) 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.
For convenience, the substrate 8 in Fig. 3 is shown with the substrate 8a and the substrate 8b being the same substrate, 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 to 3 will be collectively referred to as cleaning sheets.

The resin layer 2 is made of a resin foam that constitutes the layer, and has pot-shaped air bubbles 3 with rounded bottoms formed along the thickness direction. In the resin part between the air bubbles 3 of the resin layer 2, micro air bubbles smaller in size than the air bubbles 3 (not shown) are formed. The micro air bubbles present in the resin part that forms the air bubbles 3 are connected in a three-dimensional mesh-like manner, and are connected to each other. The connected air bubbles refer to both the case where the air bubbles 3 are connected to each other without a resin wall, and the case where they are connected by micro air bubbles present in the resin wall. By having the connected air bubbles in the resin layer 2, the micro foreign matter taken in from the openings of the cleaning surface P can be stored in a state in which it can be interposed in the three-dimensional mesh-like connected air bubbles, and it is difficult to release the micro foreign matter once taken in to the outside. However, most of the air bubbles contained in the resin layer 2 are connected air bubbles, but some may be independent air bubbles. Since the cleaning surface P is a surface that appears due to buffing or the like, the openings of the air bubbles 3 are formed on the cleaning surface P. In addition, in Figures 1 and 3, the resin layer 2 before buffing or slicing has a skin layer with dense micropores on the cleaning surface P side. However, the resin layer 2 in Figure 2 does not have a skin layer on the cleaning surface P side.

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 5.0 to 300 μm, and more preferably 10 to 150 μm. When the average opening diameter is 5.0 μm or more, the cleaning performance is superior due to the enhanced ability to capture contaminants. Furthermore, when the average opening diameter is 300 μm or less, the adhesion of the cleaning surface P can be maintained, and therefore the cleaning performance is superior.

The aperture ratio of the openings is preferably 10 to 60%. With an aperture ratio of 10% or more, the cleaning performance is superior due to an increased ability to collect contaminants. With an aperture ratio of 60% or less, the adhesion of the cleaning surface P can be maintained, resulting in superior cleaning performance.

The average opening diameter and opening ratio of the resin layer 2 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 175 times magnification with a microscope (KEYENCE Corporation, product name "VH-6300") to obtain an image. Next, the obtained image is binarized using image analysis software (for example, (Image Analyzer V20LAB Ver. 1.3)) 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. The opening diameters of each opening are then arithmetically averaged to obtain the average opening diameter (μm). The area of the above openings relative to the total area of the above openings and other resin parts is defined as the opening ratio (%).

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.

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 bubbles in the resin layer 2 are easily arranged in a vertically elongated shape, which can further improve the adhesion of the cleaning surface, 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 cleaning surface P of the resin layer 2 may have micropores that do not extend in the thickness direction and have a bubble diameter of 10 μm or less, which are distinct from the openings resulting from the air bubbles 3. The size of the micropores can be adjusted, for example, by adding an additive when compounding the resin that forms the resin layer 2.

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 thickness of the cleaning sheet is preferably 300 to 1000 μm, and more preferably 400 to 900 μm. With a thickness within the above range, adhesion to the inside of devices such as automatic ticket gates, ATMs, vending machines, and various card readers/writers is improved, 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, reducing or eliminating the unevenness that removes dust and dirt. In contrast, the cleaning sheet of the present application does not lose its air bubble structure even when washed, and since the slight adhesion of the resin surface is derived from the properties of the resin, the slight adhesion is not lost even when washed and dried, and the sheet can be reused by washing and removing the dust and dirt adhering to the cleaning surface 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 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., pore-forming agent, water repellent, etc.) that may be included in the resin layer 2 as needed, and the mixture is degassed under reduced pressure as needed to prepare a resin solution. The solvent is not particularly limited, but examples 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. Then, due to the cooperative phenomenon of the diffusion of the solvent contained in the resin solution into the solidification liquid and the penetration of the poor solvent into the resin, the regeneration of the resin, preferably having an open cell structure, progresses. At this time, if the film-forming substrate is one that is difficult for liquid to penetrate (for example, a PET film), the solidification liquid does not penetrate the substrate, so that the replacement of the solvent in the resin solution with the poor solvent occurs preferentially near the skin layer, and larger pores tend to be formed in the area inside the skin layer rather than near the skin layer. In this way, a precursor sheet is formed on the film-forming substrate.

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 front surface (upper surface) and/or 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 improve the uniformity of the thickness of the resin layer, and also expose the connected bubbles to the cleaning surface to form openings, allowing contaminants from the object to be cleaned to be retained within the bubbles.

Next, substrate 8 is attached to the surface of resin layer 2 opposite the cleaning surface via adhesive 7 to obtain cleaning sheet 1. In this way, adhesive 7, which is an adhesive layer, and substrate 8 are laminated in this order on one surface of resin layer 2 to obtain cleaning sheet 1A or 1B. Furthermore, cleaning sheet 1C is obtained by joining the substrate surfaces of cleaning sheets 1A or 1B together via double-sided tape.

When the resin layer 2 is disposed on both surfaces, the opening on the cleaning surface is not limited to being small, and the opening on the cleaning surface may be enlarged by bonding in the direction of the air bubbles with a large diameter opening on the cleaning surface, or the opening on one side of the cleaning surface may be small and the opening on the other side of the cleaning surface may be large.

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
A resin solution was prepared by mixing and stirring 100 parts by mass of a solution in which a polyester-based polyurethane resin, which was the raw material resin for the matrix resin, was dissolved in DMF (N,N-dimethylformamide) at 30% by mass, with 60 parts by mass of DMF for adjusting viscosity and 16 parts by mass of a DMF dispersion containing 12% by mass of carbon black pigment (manufactured by Mitsubishi Chemical Corporation under the trade name "RCF44").

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 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 back 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 card-shaped cleaning sheet having a thickness of 0.89 mm.

Example 2
A cleaning sheet having a thickness of 0.79 mm was produced in the same manner as in Example 1, except that the surfaces of the two PET-substrate-attached resin layers where the PET substrate was exposed were attached to each other with an acrylic adhesive.

Example 3
A cleaning sheet was obtained in the same manner as in Example 1, except that the thickness of the coating film was changed from 350 μm to 550 μm by adjusting the clearance, and the buffing treatment for a thickness of 150 μm was changed to a buffing treatment for a thickness of 350 μm.

(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.

(Comparative Example 2)
We used "C91" manufactured by Chikami Miltec Co., Ltd., which is a 0.93 mm thick sheet made of a nonwoven fabric made of acrylic synthetic fibers bonded to both sides of an olefin fiber substrate.

The physical properties of each of the cleaning sheets obtained in Examples 1 to 3 and Comparative Examples 1 and 2 were measured using the following methods.

(Average opening diameter, opening ratio)
The openings on the cleaning surface were measured as follows: A 1.0×1.4 mm square area was observed at 175 times magnification using a microscope (Keyence Corporation, product name "VH-6300"), and the obtained image was processed and calculated using image processing software (Image Analyzer V20LAB Ver. 1.3). The results are shown in Table 1 below.

(Compressibility and Compressive Elasticity)
The compressibility and compressive elastic modulus were determined in accordance with Japanese Industrial Standard JIS L 1021. Specifically, the thickness t0 was measured after applying an initial load for 30 seconds from an unloaded state at room temperature, and then the thickness t1 was measured after applying a final load for 5 minutes from the thickness t0 state. Next, all loads were removed from the thickness t1 state, and the sample was left for 5 minutes (unloaded state), after which the initial load was applied again for 30 seconds, and the thickness t0' was measured.
The compression ratio was calculated by the formula: Compression ratio (%) = 100 × (t0-t1)/t0, and the compression modulus was calculated by the formula: Compression modulus (%) = 100 × (t0'-t1)/(t0-t1). At this time, the initial load was 100 g/cm2, and the final pressure was 1120 g/ ^cm2 .

(Shore A hardness)
The Shore A hardness was measured by cutting out a cleaning sheet sample (10 cm x 10 cm), stacking a plurality of the sample pieces to a thickness of 4.5 mm or more, and using a type A hardness tester (Japanese Industrial Standards, JIS K7311).

(Thickness variation)
The thickness variation of the cleaning sheet was measured at a total of 12 locations, 4 locations at equal intervals in the horizontal direction and 3 locations at equal intervals in the vertical direction, on the surface of the cleaning sheet, and the standard deviation σ of the thicknesses at the 12 locations was divided by the average thickness to obtain the thickness variation coefficient. The thickness variation coefficient indicates the thickness variation, and a smaller value indicates a smaller thickness variation and higher adhesion.

(Compressive Stress)
The cleaning sheet pieces were cut into 25 mm x 25 mm pieces, and the compression amount and load were measured using a microautograph (Shimadzu Corporation, "MST-1") at a temperature of 25°C, a compression speed of 0.1 mm/min, and a circular pressure plate (indenter) with a diameter of 10 mm. Figure 4 is a graph showing the measurement results for the cleaning sheet pieces of Examples 1 to 3 and Comparative Examples 1 and 2, with the horizontal axis representing the deformation amount (mm) and the vertical axis representing the pressure (g/ ^cm2 ). Table 1 below shows the stresses at deformations of 20 μm and 50 μm, respectively. Note that the results of Examples 1 to 3 showed almost the same deformation amounts, with the stress-strain curves overlapping.

The cross section and cleaning surface of the cleaning sheets of Example 1 and Comparative Example 1 were observed with an electron microscope (trade name "JMS-5500LV" manufactured by JEOL Ltd.). Figures 5 and 6 are photographs of the cross section of the cleaning sheet of Example 1 observed at 50x and 500x, respectively, using an electron microscope. Also, Figure 7 is a photograph of the cleaning surface of the cleaning sheet of Example 1 observed at 50x using an electron microscope. Similarly, Figures 8 and 9 are photographs of the cross section of the cleaning sheet of Comparative Example 1 observed at 50x and 500x, respectively, using an electron microscope. Also, Figure 10 is a photograph of the cleaning surface of the cleaning sheet of Comparative Example 1 observed at 50x using an electron microscope. From the cross-sectional photographs of Example 1 (50x and 500x), it can be seen that bubbles are formed from the cleaning surface in the direction of the PET substrate surface. Also, the black dots inside the bubbles in the photograph enlarged at 500x indicate communicating holes, and it can be seen that the resin part is finely foamed. On the other hand, the cross-sectional photograph of the comparative example shows that the fibers are densely stacked, and no voids extending from the cleaning surface toward the inside are seen. As can be seen from FIG. 6, in the cleaning sheet of Example 1, the maximum diameter of the air bubbles parallel to the cleaning surface is not on the cleaning surface but exists inside the resin layer. It is presumed that the cleaning sheet having such a structure can capture many microscopic foreign objects inside the air bubbles and is difficult to release the captured microscopic foreign objects to the outside.
In the photograph of the cleaning surface of Example 1, the approximately circular black areas represent the openings. Comparing the photographs of the cleaning surfaces, it can be seen that the openings are uniformly present on the cleaning surface of the Example, compared to the cleaning surface of the Comparative Example, in which the voids are non-uniform.

The cleaning properties of each of the cleaning sheets obtained in Examples 1 to 3 and Comparative Examples 1 and 2 were evaluated under the following conditions.

Test contaminants 1 to 4 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

After each of the prepared test contaminants was applied to the IC chip reader in the card processing device to the extent that it caused an error in reading the card processing device, 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. If it was confirmed that there was a lot of dirt on the cleaning sheet and the reading error in the card processing device had been resolved, it was rated as ◎; if it was confirmed that there was dirt on the cleaning sheet and the reading error in the card processing device had been resolved, it was rated as ○; and if there was no dirt on the cleaning sheet and the reading error in the card processing device had not been resolved, it was rated as "X".

The products of Comparative Examples 1 and 2, which have a nonwoven surface, can wipe off only powder or only artificial sebum, but cannot clean dirt that is difficult to remove due to a mixture of powder and artificial sebum. On the other hand, the products of the Examples have small thickness variations and have the same hardness as the products of the Comparative Examples, but have small stress against deformation and are easily deformed. That is, the stress of the products of the Examples when deformed 20 μm is 44 g/cm ² , while the stress of the products of the Comparative Examples is 100 g/cm ² and 124 g/cm ² , and the stress of the products of the Examples when deformed 50 μm is 204 g/cm ² , while the stress of the products of the Comparative Examples is 408 g/cm ² and 811 g/cm ² . In other words, when foreign matter of 20 μm or 50 μm in size is present, the comparative example requires a greater force to be applied to the cleaning sheet than the example product in order to compress and deform to an extent that it can capture the foreign matter, whereas the example cleaning sheet can be compressed and deformed with a relatively small force, thereby improving adhesion to the cleaning surface and to foreign matter on the cleaning surface, and the frictional force enables the foreign matter to be captured and removed within the openings in the cleaning surface.

Reference Signs List 1, 1A, 1B, 1C... 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 inside an IC card reader.

Claims (10)

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 plurality of bubbles extending in a thickness direction of the foam, and adjacent bubbles among the plurality of bubbles are at least partially connected to each other to form connected bubbles;
the first cleaning surface has openings formed by some of the plurality of bubbles contained in the first resin layer;
The cleaning sheet has an opening ratio of the openings on the first cleaning surface of 22.3 to 60% . a maximum bubble diameter of the connected bubbles in the first resin layer parallel to the first cleaning surface is present inside the first resin layer;
The cleaning sheet according to claim 1. The first cleaning surface of the first resin layer is opposite to the first cleaning surface of the first resin layer.
The cleaning sheet according to claim 1 or 2. the average opening diameter of the openings on the first cleaning surface is 5.0 to 300 μm;
The cleaning sheet according to any one of claims 1 to 3. a second resin layer made of a foam having a second cleaning surface for cleaning an object to be cleaned, the second resin layer being provided on a surface opposite to the first cleaning surface of the first resin layer;
the second resin layer has a plurality of bubbles in the foam, and at least a portion of the plurality of bubbles are connected to each other;
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 claims 1 to 4 . Further comprising a substrate disposed on one side of the first resin layer and one side of the second resin layer,
the substrate is disposed on a side of the first resin layer opposite to the first cleaning surface and on a side of the second resin layer opposite to the second cleaning surface;
The cleaning sheet according to claim 5 . a maximum diameter of the connected bubbles in the second resin layer parallel to the second cleaning surface is present inside the second resin layer;
The cleaning sheet according to claim 5 or 6 . The first resin layer and the second resin layer contain a polyurethane resin.
The cleaning sheet according to any one of claims 5 to 7 . 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 8 ,
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 9 , wherein the object to be cleaned is provided with a reading unit that reads card information by contact.

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