TECHNICAL FIELD

The invention relates to a polishing pad.

BACKGROUND ART

There is a known polishing pad that includes a substrate made from a non-woven fabric. For instance, the polishing pad disclosed in Patent Document 1 is used for scouring a target object to remove dirt on the target object.

PRIOR ART DOCUMENTS

Patent Documents

Patent Document 1 : Japanese Unexamined Patent Application Publication No. 2011-

189189

SUMMARY OF THE INVENTION

Problem to be Solved by the Invention

In some cases where a worker uses a polishing pad for cleaning, the polishing pad has to be deformed (bent) to be fit to the shape of the target object. The worker scours the target object while keeping the polishing pad deformed (bent). A worker using a polishing pad of the above- described type has to apply a force to deform (bend) the polishing pad and to keep the polishing pad deformed (bent). Hence, there has been a demand for a polishing pad that is deformable (bendable) by a smaller force to make the scouring work easier.

MEANS FOR SOLVING THE PROBLEM

A polishing pad according to an aspect of the invention includes a substrate made of a piece of non-woven fabric. The substrate has a flat-plate shape extending in a first direction perpendicular to a thickness direction and in a second direction perpendicular to both the thickness direction and the first direction. The substrate is divided into a plurality of blocks arranged in the second direction and each extending in the first direction. A boundary portion extending in the first direction is formed between each pair of the blocks, and a plurality of slits are formed in the boundary portion. Each of the slits is formed through the substrate in the thickness direction and extends in first direction. The plurality of slits that exist in the boundary portion are spaced apart from each other in the first direction. A pair of the blocks that are next to each other in the second direction are connected to each other by a connection portion formed between the slits. EFFECT OF THE INVENTION

The invention provides a polishing pad that is deformable (bendable) with a smaller force.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a perspective view illustrating a polishing pad according to an embodiment.

Fig. 2A is a drawing illustrating the polishing pad viewed from an X-axis direction. Fig. 2B is a drawing illustrating the polishing pad in a deformed (bent) state viewed from the X-axis direction.

Fig. 3 is a drawing illustrating a state of slits of the deformed (bent) polishing pad viewed from a thickness direction.

Fig. 4 is a drawing illustrating a model used for determining a Y-axis-direction dimension of each block.

Fig. 5 A is a drawing illustrating a polishing pad according to a comparative example viewed from the thickness direction. Fig. 5B is a drawing illustrating the polishing pad according to the comparative example viewed from the X-axis direction. Fig. 5C is a drawing illustrating the polishing pad in a deformed (bent) state according to the comparative example viewed from the X-axis direction.

Fig. 6A and Fig. 6B are drawings illustrating polishing pads according to modified examples viewed from the thickness direction.

DESCRIPTION OF THE PREFERRED EMBODIMENT

An embodiment of the invention will be described below with reference to the attached drawings. Note that, in the following descriptions, the same reference symbols have been assigned to elements that are the same or equivalent, and that redundant descriptions thereof have been omitted.

A polishing pad 1 according to an embodiment of the invention will be described below with reference to Fig. 1. Fig. 1 is a perspective view illustrating a polishing pad. As illustrated in Fig. 1, the polishing pad 1 includes a substrate 2. In this embodiment, a direction perpendicular to a thickness direction of the substrate 2 is defined as an X-axis direction (first direction) whereas a direction perpendicular to both the thickness direction and the X-axis direction is defined as an Y- axis direction (second direction). The substrate 2 has a flat-plate shape extending in both the X- axis direction and in the Y-axis direction. The substrate 2 has principal surfaces 2c and 2d, which are opposite to each other in the thickness direction. In Fig. 1, the substrate 2 has its longer side extending in the X-axis direction and its shorter side extending in the Y-axis direction. The shape of the substrate 2 is not particularly limited. In the substrate 2, the proportion of the side in the X- axis direction to the side in the Y-axis direction may be appropriately changed if necessary. The size of the polishing pad 1 may be one that allows the worker to hold the polishing pad 1 while the worker is working with the polishing pad 1. For instance, the polishing pad 1 may have a thickness ranging from 20 to 40 mm and a dimension ranging from 100 to 150 mm both in the X- axis direction and in the Y-axis direction.

Firstly, some illustrative examples of the substrate 2 are described below. The substrate 2 of this type is one using a water-soluble binder. The substrate 2 is made of a piece of non-woven fabric. The non-woven fabric has an abrasive coat configured to hold abrasive particles. Some non-woven webs suitable for use in abrasive cleaning articles are not limited to particular ones, and are made of an air-laid, a carded, a stitch-bonded, a spun-bonded, a wet-laid, or a melt-blown structure. Some examples of the fibers suitable for use in abrasive cleaning articles are natural fibers, synthetic fibers, and mixtures thereof. Some preferred fibers are synthetic fibers made from polyester (e.g., polyethylene terephthalate), nylon (e.g., hexamethylene adipamide and polycaprolactam), polypropylene, acryl (formed from acrylonitrile polymer), rayon, cellulose acetate, polyvinylidene chloride-vinyl chloride copolymer, vinyl chloride-acrylonitrile copolymer, or the like. Some examples of the suitable natural fibers are cotton, wool, jute, and linen fibers. The fibers to be used may be new, unused fibers. Alternatively, waste fibers may be used as well, for instance, those recycled fibers obtained by cutting garments and those obtained from carpet manufacturing processes, fiber manufacturing processes, or textile fiber manufacturing processes. The fiber material may be uniform fibers, or may be composite fibers such as conjugated fibers (e.g., co-spun sheath-core fiber). Providing an article whose web contains different fibers in different portions (e.g., a first web portion, a second web portion, and an intermediate web portion) is also within the scope of the invention. The web fiber may preferably be stretched and crimped. Alternatively, the web fiber may be continuous filaments formed by an extrusion molding process and may be continuous fibers.

The abrasive coat is designed to make the substrate 2 hold the abrasive particles and to fix the abrasive particles to the substrate 2. The abrasive coat contains a water-soluble binder. When the polishing pad 1 is used, the water-soluble binder is exposed to a solvent. Until that time, the water-soluble binder is solidified so that the abrasive particles can be held by and fixed to the non-woven fabric of the substrate 2. The solvent is one that is used for cleaning. Once the solvent starts to solve the water-soluble binder, the abrasive particles are released from the polishing pad 1. The water-soluble binder may be an oligomer or a polymer, or may contain copolymers and a blend thereof. Unlimited examples of polymers and copolymers that are suitable for use as the water-soluble binder are: polyethylene glycol, polyvinyl pyrrolidone, polyvinyl pyrrolidone/vinyl acetate copolymer, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose starch, polyethylene oxide, polyacrylamide, polyacrylic acid, cellulose ether polymer,

polyethyloxazoline, polyethylene oxide ester, copolymer of polyethylene oxide ester and polypropylene oxide, polyethylene oxide urethane, and copolymer of polyethylene oxide urethane and polypropylene oxide. The water-soluble binder may be a surfactant. In addition, the water-soluble binder may include a combination of various water-soluble binders containing a surfactant as a component. In addition, the water-soluble binder may include a combination of various surfactants.

Some of the surfactants useful in the invention are those that are easily soluble in water. In addition, the surfactant provides excellent foamability, cleaning ability, oil-fat removing property in ordinary cleaning use in households. The surfactant helps remove coloring stains, grease, oil, soil, dirt, and deposits.

Some examples of the surfactants used for the abrasive cleaning article of the invention are one or more kinds of anionic surfactants, cationic surfactants, nonionic surfactants, and amphoteric surfactants, as well as combinations of such surfactants. Desirable surfactants are those gentle on the skin of the user and nontoxic. In a blend of one or more kinds of anionic surfactants, cationic surfactants, nonionic surfactants, and/or amphoteric surfactants, the use of an anionic surfactant in a higher concentration is desirable for enhanced foamability and cleaning ability. This, however, is within the scope of the invention.

The abrasive particles are releasably fixed to the non-woven fabric of the substrate 2 by the water-soluble binder. Examples of the abrasive particles used in the manufacturing of the article according to the invention include all the known abrasive materials, combinations and aggregates of such abrasive materials. Some examples of softer abrasive materials are: inorganic materials such as flint, silica, pumice, and calcium carbonate; organic polymer materials such as polyester, polyvinyl chloride, methacrylate, methyl methacrylate, polycarbonate, and polystyrene; and combinations of some of the above-mentioned materials. These, however, are not the only examples. Some examples of harder abrasive materials are: aluminum oxides such as aluminum oxide, heat-treated aluminum oxide, and white aluminum oxide; silicon carbide; alumina zirconia; diamond; ceria, cubic boron nitride; garnet; and combinations of some of the above-mentioned materials. These, however, are not the only examples.

In addition to the water-soluble binder and the abrasive particles, the abrasive coat may contain colorants, perfumes, fragrant oils, preservatives, humectants, anti-foaming agents, coupling agents, suspending agents, pigments, and antibacterial additives. Such additional components are well known to the persons in the relevant technical field.

Secondly, different illustrative examples of the substrate 2 are described below. The substrate 2 of this type is one using a thermosetting adhesive as the binder. Some preferred non- woven fabrics are those made from thermoplastic organic fibers such as polyamide (e.g., nylon 6 and nylon 6,6 made from polycaprolactam and/or polyhexamethyl adipamide), polyolefin (e.g., polypropylene and polyethylene), polyester (e.g., polyethylene terephthalate), and polycarbonate. Commonly used non-woven fabrics are those made from nylon and polyester fibers.

In general, the fiber has a thickness (diameter) ranging from 19 to 250 μπι,

approximately. In general, the non-woven fabric has a thickness ranging from 2 to 50 mm, approximately. Once arranged in place, the fibers are bonded to one another at intersections and/or contact points by frictional forces, adhesive forces, etc. The bonding of fibers may be achieved by melting the fibers or by the use of a special adhesive agent.

Adhesive agents are used for boding the fibers of the non-woven fabric to one another or for bonding the fibers of the non-woven fabric to the abrasive particles. A single adhesive agent may be used both for bonding the fibers of the non-woven fabric to one another and for bonding the fibers of the non-woven fabric to the abrasive particles. Alternatively, different adhesive agents may be used for the above-mentioned different purposes. When a single adhesive agent is used, the bonding of the fibers of the non-woven fabric to each other and the bonding of the fibers of the non-woven fabric to the abrasive particles may be carried out simultaneously in the manufacturing process.

A first adhesive agent to be used for bonding the fibers of the non-woven fabric to one another may be such thermosetting adhesive agents as aqueous suspensions and organic solvent solutions of epoxy, melamine, phenol, isocyanate and isocyanurate resins, or such rubber-based polymer solutions or suspensions as SBR, SBS, and SIS.

The non-woven fabric is formed by hardening the adhesive agents applied by a method such as a dip coating, a roll coating, and a spray coating.

The method of manufacturing the substrate 2 is not particularly limited. For instance, the substrate 2 may be formed by, firstly, stacking a plurality of fiber sheets one upon another to form a layered body and then sticking the sheets in the layered body together with an adhesive agent.

Alternatively, the substrate 2 may be formed by collecting extruded fibers together, then sticking the fibers together, and then cutting the solid layered body with a die.

The substrate 2 is divided into a plurality of blocks 3 arranged in the Y-axis direction and each extending in the X-axis direction. The blocks 3 refer to some areas of the substrate 2 located between a first end portion 2a and a second end portion 2b in the X-axis direction. The blocks 3 are the areas with no slits 6 extending in the X-axis direction (details of the slits 6 will be described later). In the substrate 2, each of the blocks 3 extends in a band shape between the end portion 2a and the end portion 2b. While the substrate 2 is in a deformed state, the blocks 3 become the main areas that are brought into contact with the target object to polish the surface of the target object. Each of the blocks 3 is defined to have a predetermined width in the Y-axis direction. How to set the pitch at which the blocks 3 are arranged will be described later.

Between a pair of the blocks 3, a boundary portion 4 extending in the X-axis direction is formed. Each of the boundary portion 4 has a plurality of slits 6 each of which is formed through the substrate 2 in the thickness direction and each of which extends in the X-axis direction. Each of the slits 6 extends in the thickness direction from the principal surface 2c to the principal surface 2d. The slits 6 are formed by: providing a tool having a plurality of plate-shaped blade members standing on a base member; and then pressing the substrate 2 against the tool to allow the blade members to penetrate the substrate 2. In each of the boundary portions 4, the plurality of slits 6 are spaced apart from one another in the X-axis direction. The portion between one slit 6 and another slit 6 serves as a connection portion 7 configured to connect one block 3 to another block 3. To put it differently, a pair of the blocks 3 that are next to each other in the Y-axis direction are connected to each other by the connection portion 7 formed between the slits 6.

In Fig. 1, some of the boundary portions 4 are indicated by imaginary lines. Each of the boundary portions 4 is a straight line extending straight in the X-axis direction. A plurality of the slits 6 and a plurality of the connection portions 7 are alternately arranged in each of the boundary portion 4. To put it differently, each of the "boundary portions" corresponds to an imaginary line drawn to overlap the slits 6 when viewed in the thickness direction and extending to the end portions 2a and 2b. Hence, each of the boundary portions 4 refers to an imaginary line configured to virtually separate a block 3 from another block 3. Each of the "slits" refers to a cut formed in the substrate 2. While the substrate 2 is in a normal state (the state illustrated in Fig. 1), edge portions 6a and 6b of each slit (see Fig. 2 and Fig. 3) are in contact with or adjacent to each other in the principal surface 2c. If a force is applied to widen each of the blocks 3 in the Y-axis direction, the distance between the edge portions 6a and 6b of each slit 6 increases to separate the edge portions 6a and 6b separated from each other in the principal surface 2c. Each of the "connection portion" refers to a portion of the imaginary line of the boundary portion 4. The portion has no slit 6. Even if a force is applied to widen each of the blocks 3 in the Y-axis direction, the connection portion 7 fixes the blocks 3 that are next to each other by preventing the blocks 3 from departing from each other and thus by leaving no such opening as the slit 6.

As such, by forming slits in some portions of the substrate 2, the deformation (bending) of the substrate 2 in the Y-axis direction by a worker leaves the substrate 2 in a state where openings appear at the positions of the slits 6 as illustrated in Fig. 2 and Fig. 3. At each slit 6, an opening is formed in the substrate 2 so that the edge portions 6a and 6b located on the outer peripheral side for the deformation (bending) can go away from each other. In contrast, if the substrate 2 is deformed (bent) in the X-axis direction, the substrate 2 is deformed (bent) without leaving any opening at the positions of the slits 6. Hence, the worker can deform (bend) the substrate 2 more easily in the Y-axis direction than in the X-axis direction. For instance, the substrate 2 may have a bending strength in the Y-axis direction that is from 10 to 80%, preferably from 15 to 50%, of the bending strength of the substrate 2 in the X-axis direction. The bending strength is obtained by measurement using a Gurley-type bending stiffness tester and following a measurement method that conforms to the bending repulsion method A of JIS L-1096 and JAPAN TAPPI NO. 40. Note that when the polishing pad 1 is deformed (bent), a spring -back force (repulsive force) is generated in the polishing pad 1 itself. The repulsive force returns the polishing pad 1 to a substantially flat state when the force bending the polishing pad 1 is released. In addition, the repulsive force has an effect to allow the polishing pad 1 to fit closely to (stick to) the palm of the worker while the worker is working with the polishing pad 1.

In this embodiment, the connection portions 7 formed in the boundary portion 4 located on a first side, in the Y-axis direction, of a block 3 are located at different positions in the X-axis direction from the positions of the connection portions 7 formed in the boundary portion 4 located on a second side, in the Y-axis direction, of the same block 3. Note that the phrase "located at different positions" only means that the position of the center, in the Y-axis direction, of one connection portion 7 is different from the corresponding position of the other connection portion 7. Hence, a portion, in the Y-axis direction, of one connection portion 7 may overlap a portion of the other connection portion 7. The slits 6 formed in the boundary portion 4 located on a first side, in the Y-axis direction, of a block 3 are located at different positions in the X-axis direction from the positions of the slits 6 formed in the boundary portion 4 located on a second side, in the Y- axis direction, of the same block 3. To put it differently, of every two adjacent boundary portions 4, one boundary portion 4 has slits 6 that form a zigzag pattern together with the slits 6 of the other boundary portion 4. A structure like the above-described one where a plurality of slits 6 are arranged in a zigzag pattern may be referred to as a skip slit structure. In this embodiment, the slits 6 in the two boundary portions 4 located at every other line are located at the identical positions to one another, and so are the boundary portions 4 in such two boundary portions 4. Hence, a zigzag pattern of the slits 6 is formed by sets of boundary portions 4, each set including a pair of the boundary portions 4.

Each block 3, each slit 6, and each connection portion 7 in the above-described configuration may have dimensions that are not particularly limited but set in the following way, for instance. The dimension, in the Y-axis direction, of each block 3 may range from 2 to 40 mm, preferably from 2 to 20 mm. The dimension, in the X-axis direction, of the each slit 6 may range from 5 to 50 mm, preferably from 10 to 30 mm. The dimension, in the X-axis direction, of each connection portion 7 may range from 5 to 50 mm, preferably from 10 to 30 mm.

Now, descriptions will be provided below concerning an exemplar method of setting the dimension, in the Y-axis direction, of each block 3. For instance, when a target object 30 having a circular cross section as illustrated in Fig. 4 is polished by the use of the polishing pad 1, the polishing pad 1 is desirably in contact with the target object 30 at least 8 positions located in the circumferential direction. The model illustrated in Fig. 4 assumes that when the substrate 2 of the polishing pad 1 is deformed (bent) to cover the target object 30, each block 3 becomes substantially straight and the substrate 2 is bent at the positions of the boundary portions 4. In this case, the substrate 2 is brought into contact with the target object 30 at predetermined points of the blocks 3. In Fig. 4, an octagon is drawn with dashed-dotted lines on the outer circumference of the target object 30 to indicate the polishing surface of the substrate 2. Here, when the target object 30 has a diameter of 50 mm, a dimension of 19.6 mm is obtained by dividing equally the outer circumference of the target object 30 into 8.

Hence, the dimension, in the Y-axis direction, of each block 3 may preferably be not greater than 20 mm, approximately.

Next, description will be provided concerning advantageous effects of the polishing pad 1 according to this embodiment.

The polishing pad 1 is including the substrate 2 made of a piece of non-woven fabric. The substrate 2 has a flat-plate shape extending in the X-axis direction perpendicular to the thickness direction and in the Y-axis direction perpendicular to both the thickness direction and the X-axis direction. The substrate 2 is divided into a plurality of the blocks 3 arranged in the Y-axis direction and each extending in the X-axis direction. The boundary portion 4 extending in the X- axis direction is formed between each pair of the blocks 3, and a plurality of the slits 6 are formed in the boundary portion 4. Each of the slits 6 is formed through the substrate 2 in the thickness direction and extends in the X-axis direction. The plurality of slits 6 that exist in the boundary portion 4 are spaced apart from each other in the X-axis direction. A pair of the blocks 3 that are next to each other in the Y-axis direction are connected to each other by the connection portion 7 formed between the slits 6.

For instance, a polishing pad 100 according to a comparative example illustrated in Fig. 5 has no such slits as those that are provided in this embodiment. In the case of the comparative example, when the worker tries to deform (bend) the polishing pad 100, a resistance force against the bending of the substrate 2 is generated. Hence, the worker needs to apply a greater force to deform (bend) the polishing pad 100. In contrast, the polishing pad 1 according to this embodiment has slits 6 formed in the boundary portions 4 between the blocks 3 of the substrate 2 and each extending in the X-axis direction. When a force is applied to bend the substrate 2 in the Y-axis direction, the substrate 2 leaves openings that easily widen at the positions of the slits 6. Hence, when the worker tries to deform (bend) the polishing pad 1, the substrate 2 can be deformed (bent) easily by allowing the slits 6 to widen. In addition, even if such slits 6 are formed, the boundary portions 4 include the connection portions 7 configured to connect the blocks 3 to each other prevent the blocks 3 from being cut off from each other. Hence, only a reduced force is needed to deform (bend) the polishing pad 1.

The connection portions 7 formed in the boundary portion 4 located on a first side, in the Y-axis direction, of a block 3 may be located at different positions in the X-axis direction from the positions of the connection portions 7 formed in the boundary portion 4 located on a second side, in the Y-axis direction, of the same block 3. For instance, if, as illustrated in Fig. 6A later, the connection portions 7 that are next to each other in the Y-axis direction are formed at the identical positions to each other in the X-axis direction, a greater resistance force against the bending of the substrate 2 is generated at positions where the connection portions 7 are contiguously formed as described above. In contrast, if the connection portions 7 that are next to each other in the Y-axis direction are located at different positions, in the X-axis direction, from each other, the connection portions 7 can be dispersed to prevent the resistance force against the bending from becoming greater.

The substrate 2 may have a bending strength in the Y-axis direction that is from 10 to

80% of the bending strength of the substrate 2 in the X-axis direction. In this case, the worker can bend easily the polishing pad 1 to work with the polishing pad 1.

The dimension, in the Y-axis direction, of the block 3 may range from 2 to 40 mm, the dimension, in the X-axis direction, of the slit 6 may range from 5 to 50 mm, and the dimension, in the X-axis direction, of the connection portion 7 may range from 5 to 50 mm. In this case, the worker can bend easily the polishing pad 1. In addition, a sufficient strength of the polishing pad is secured.

The polishing pad 1 is including the substrate 2 made of a piece of non-woven fabric. The substrate 2 has a flat-plate shape extending in the X-axis direction perpendicular to the thickness direction and in the Y-axis direction perpendicular to both the thickness direction and the X-axis direction. In the substrate 2, a slit 6 extending in the thickness direction from the first principal surface 2c in the thickness direction and extending in the X-axis direction in the principal surface 2c is formed and a plurality of slits 6 are formed in the Y-axis direction.

In the polishing pad 1, the substrate 2 has the slit 6 extending in the thickness direction from the first principal surface 2c in the thickness direction and extending in the X-axis direction in the principal surface 2c. When a force is applied to bend the substrate 2 in the Y-axis direction, the substrate 2 leaves an opening that easily widens at the position of the slit 6. In addition, a plurality of slits 6 are formed in the Y-axis direction. Hence, the slits 6 are opened at a plurality of positions in the Y-axis direction. The entire substrate 2 can thus be deformed (bent) easily.

Accordingly, only a reduced force is needed to deform (bend) the polishing pad 1.

The present invention is not intended to be limited to the embodiment described above, but allows appropriate modifications when necessary.

The arrangement of the slits 6 is not limited to those described in the above-described embodiment. For instance, in the polishing pad 1 illustrated in Fig. 6A, the connection portions 7 formed in the boundary portion 4 located on a first side, in the Y-axis direction, of a block 3 are identical positions, in the X-axis direction, to the corresponding connection portions 7 formed in the boundary portion 4 located on a second side, in the Y-axis direction, of the same block 3. As such, the slits 6 do not have to be arranged in a zigzag pattern. In addition, in the embodiment illustrated in Fig. 1, every two boundary portions 4 form a set and sets of such boundary portions 4 form a zigzag pattern of slits 6. In lieu of this way of forming a zigzag pattern, an alternative way of forming a zigzag pattern may be employed where as illustrated in Fig. 6B, even more boundary portions 4 form a set, and the sets of such boundary portions 4 form a zigzag pattern of slits 6. The arrangement pattern of the slits 6, however, may be irregular one.

In addition, the slits 6 in the above-described embodiment are formed through the substrate 2. In lieu of this configuration, the slits 6 may be formed not through the substrate 2. For instance, each slit 6 may extend in the thickness direction from the principal surface 2c of the substrate 2 to stop at a predetermined position in the substrate 2 without reaching the principal surface 2d.

In the above-described embodiment, each of the slits is formed to extend only in the X- axis direction. In addition to these, an extra slit or extra slits may be formed to extend in the Y- axis direction. In such a case, the polishing pad can be deformed (bent) easily in the X-axis direction, as well.

In the above-described embodiment, a rectangular-plate-shaped member is employed as an exemplar substrate of the polishing pad. The shape of the substrate, however, is not particularly limited. The slit structure may be applied to any type of substrate. For instance, the slit structure may be applied to a flap brush, a unitized wheel, a unitized pad, a bevel, a wheel, and the like.