JP7748274B2 - Lapping pad, manufacturing method thereof, and manufacturing method of lapped product - Google Patents

Description

The present invention relates to a lapping pad, a method for manufacturing the same, and a method for manufacturing lapped products.

Grinding, lapping, and polishing are generally performed on materials such as optical materials such as lenses, plane-parallel plates, and reflecting mirrors, semiconductor wafer materials such as SiC disks, crystals, metals, stone, wood, resin materials, and ceramics, and lapping pads are used in lapping.

As a technology related to lapping, for example, Patent Document 1 discloses a lapping system including a platen, a polymer material attached to the platen, the polymer material having a density ranging from about 0.7 g/cm ³ to about 3.0 g/cm ³ , and a slurry including abrasive particles. Patent Document 1 states that lapping using such a polymer material enables processing at a high removal rate over a long period of time, with few defects resulting from the processing.

Special Publication No. 2018-524193

Resin sheets used in lapping processes involving free abrasive grains (slurry) are subject to the following requirements. Lapping processes often use slurries containing high-hardness abrasive grains (especially superabrasive grains), such as diamond. In recent years, reducing the cost of finish polishing has led to a need to prevent excessive scratching during lapping. One way to address these requirements is to adjust the density of the resin sheet. For example, using a low-density resin sheet tends to keep the abrasive grains within the foam of the resin sheet, preventing them from coming into strong contact with the workpiece and causing scratches. On the other hand, simply lowering the density tends to result in deterioration of the surface smoothness over time due to glazing over long periods of use. Therefore, there is a need for a resin sheet that has the ability to reveal grains through dressing (so-called dressability) and/or brittleness that allows for self-regenerative properties, i.e., the surface wears without smoothing and a new surface emerges, without affecting physical properties. From this perspective, the technology described in Patent Document 1 still leaves room for improvement.

The present invention was made in consideration of the above-mentioned problems, and aims to provide a lapping pad that has excellent dressability and a surface that is less likely to become smooth, a method for manufacturing the same, and a method for manufacturing a lapped product.

As a result of extensive research into solving the above problems, the inventors discovered that the above problems could be solved by using a resin sheet with specific physical properties, leading to the completion of the present invention.

That is, the present invention includes the following aspects.
[1]
A wrapping pad comprising a resin sheet having fine holes,
In the pore distribution of the resin sheet measured by mercury intrusion porosimetry with a contact angle of 130° and a mercury surface tension of 485 dyn/cm, the cumulative pore volume V in the pore diameter range of 0.010 μm or more and 1.0 μm or less is 0.21 cm ³ /g or more and 1.00 cm ³ /g or less,
The density of the resin sheet is 0.3 g/cm ³ or more and 0.9 g/cm ³ or less.
[2]
The lapping pad according to [1], wherein in the pore distribution of the resin sheet, the ratio of the cumulative pore volume V to the cumulative pore volume V ₀ in the pore diameter range of 0.010 μm or more and 360 μm or less is 50% or more.
[3]
The wrapping pad according to [1] or [2], wherein the resin sheet has an average pore size of 50 μm or more and 200 μm or less, as measured for pores of 10 μm or more.
[4]
[1] to [3], wherein the peak position of the maximum peak in the pore diameter range of 0.010 μm or more and 360 μm or less in the pore distribution of the resin sheet is within the pore diameter range of 0.010 μm or more and 1.0 μm or less. A wrapping pad according to any one of [1] to [3].
[5]
The wrapping pad according to any one of [1] to [4], wherein the resin sheet has a microphase separation structure.
[6]
The wrapping pad according to any one of [1] to [5], wherein the resin sheet contains polyurethane.
[7]
A method for producing the lapping pad according to any one of [1] to [6],
A method for producing a lapping pad, comprising a step of curing a mixed liquid of at least one prepolymer and at least two curing agents to obtain a resin sheet having a microphase-separated structure.
[8]
The method for manufacturing a lapping pad according to [7], wherein the curing agent includes a first curing agent having an NH ₂ equivalent of 100 or more and 300 or less, and a second curing agent having an OH equivalent of 1000 or more and 2000 or less.
[9]
A method for producing a lapped product, comprising a lapping step of lapping a workpiece using the lapping pad according to any one of [1] to [6] in the presence of a slurry.

The present invention provides a lapping pad with excellent dressability and a surface that is less likely to become smooth, a method for manufacturing the same, and a method for manufacturing a lapped product.

FIG. 1 shows the results of measuring the cumulative pore volume (pore distribution) of the resin sheet of Example 1 by mercury intrusion porosimetry. FIG. 2 is an SEM image of the surface of the resin sheet of Example 1 observed with a scanning electron microscope at 500 magnifications. Fig. 3(A) is an SEM image of the surface of the resin sheet of Example 1, observed at 2000x magnification using a scanning electron microscope. Fig. 3(B) is a portion of Fig. 3(A) where a microphase-separated structure (gyroid structure) was observed, surrounded by a dashed line. FIG. 4 shows the results of measuring the cumulative pore volume (pore distribution) of the resin sheet of Example 2 by mercury porosimetry. FIG. 5 is an SEM image of the surface of the resin sheet of Example 2 observed with a scanning electron microscope at 500 magnifications. FIG. 6 shows the results of measuring the cumulative pore volume (pore distribution) of the resin sheet of Comparative Example 1 by mercury porosimetry. FIG. 7 is an SEM image of the surface of the resin sheet of Comparative Example 1 observed with a scanning electron microscope at 500 magnifications.

The following describes in detail an embodiment of the present invention (hereinafter referred to as the "present embodiment"); however, the present invention is not limited to this embodiment, and various modifications are possible without departing from the spirit of the present invention.

(wrapping pad)
The lapping pad of this embodiment is a lapping pad comprising a resin sheet having fine pores, and in the pore distribution of the resin sheet measured by mercury porosimetry with a contact angle of 130° and a mercury surface tension of 485 dyn/cm, the cumulative pore volume V in the pore diameter range of 0.010 μm to 1.0 μm is 0.21 cm ³ /g to 1.00 cm ³ /g, and the density of the resin sheet is 0.3 g/cm ³ to 0.9 g/cm ^3. Because the lapping pad of this embodiment is configured as described above, it has excellent dressability and its surface is less likely to be smoothed.

The wrapping pad of this embodiment is not particularly limited as long as it includes the resin sheet of this embodiment, and the wrapping pad may have a configuration other than a resin sheet. Examples of configurations of the wrapping pad other than the resin sheet include conventionally known wrapping layers, cushion layers, adhesive layers, etc.

The wrapping pad of this embodiment preferably has the above-mentioned resin sheet as a wrapping layer. "Having a resin sheet as a wrapping layer" means that at least one surface of the wrapping pad of this embodiment corresponds to the surface of the resin sheet of this embodiment, and that surface of the resin sheet becomes the wrapping surface that is pressed against the workpiece during the lapping process of this embodiment. Therefore, the wrapping pad of this embodiment preferably has at least one surface made of the resin sheet of this embodiment. Alternatively, the wrapping pad of this embodiment may consist solely of the resin sheet of this embodiment.

The lapping pad of this embodiment may have grooves, embossing, and/or holes (punching) on the lapping surface as needed, and may also have a light-transmitting portion. There are no particular limitations on the shape of the grooves and embossing, and examples include lattice, concentric circle, and radial shapes.

(Resin sheet)
(density)
The resin sheet in this embodiment has a density of 0.3 g/cm or ^more and 0.9 g/cm ^{or less} . When the resin sheet in this embodiment has a density of 0.3 g/cm ^{or more} , the lapping pad is less likely to deform under pressure, and therefore, during lapping, the force applied from the lapping pad to the workpiece becomes uniform in the lapping surface direction. As a result, during lapping using a lapping pad equipped with such a resin sheet, the surface of the workpiece can be made even flatter. Note that, in this specification, "the surface of the workpiece is flat" means that the lapped surface of the workpiece is flatter overall. This can also be expressed as having good global flatness. From the same perspective, the density of the resin sheet in this embodiment is preferably 0.4 g/cm ^or more, more preferably 0.45 g/cm ^{or more} .
On the other hand, when the density of the resin sheet in this embodiment is 0.9 g/cm ^or less, it is possible to prevent the abrasive grains from coming into strong contact with the workpiece and causing scratches. In addition, the hardness of the resin sheet tends to be low, and from this viewpoint, it is also possible to prevent scratches from occurring.
The density of the resin sheet in this embodiment can be measured by a conventional method. For example, the mass and volume of a resin sheet piece can be measured by a conventional method, and the density can be calculated from the obtained values. The method for controlling the density of the resin sheet is not particularly limited, but for example, a wrapping pad can be obtained by the wrapping pad manufacturing method of this embodiment described below. In particular, when the amount of foaming agent is reduced in the manufacturing process of the resin sheet in this embodiment, the density of the resin sheet tends to increase.

(Pore distribution of resin sheet)
(Cumulative pore volume V)
The resin sheet in this embodiment has pores, and in the pore distribution of the resin sheet measured by mercury intrusion porosimetry with a contact angle of 130° and a mercury surface tension of 485 dyn/cm, the cumulative pore volume V in the pore diameter range of 0.010 μm or more and 1.0 μm or less is 0.21 cm ³ /g or more and 1.00 cm ³ /g or less.
In the following description, unless otherwise specified, the term "pore distribution" refers to a pore distribution measured by mercury porosimetry with a contact angle of 130° and a mercury surface tension of 485 dyn/cm. Mercury porosimetry is a method for measuring the pore distribution on the surface of a sample by filling mercury into the pores on the surface of the sample while sweeping the applied pressure. Therefore, when measuring the pore distribution of a foamed material by mercury porosimetry, the pore distribution mainly reflects the pore distribution of interconnected cells (generally also referred to as "open cells"), and the contribution of the pore distribution of closed cells is small.

With regard to the lapping pad of this embodiment, the inventors have found that when the cumulative pore volume V in the pore diameter range of 0.010 μm to 1.0 μm is 0.21 cm ³ /g or more in the pore distribution measured by mercury intrusion porosimetry, the lapping pad has a sufficiently good affinity with the slurry. This is presumably because, when the cumulative pore volume V is 0.21 cm ³ /g or more, interconnected pores having pore diameters of 0.010 μm to 1.0 μm are distributed throughout the resin sheet, allowing the slurry to penetrate evenly into the resin sheet through these interconnected pores during lapping. However, the reason why the cumulative pore volume V of 0.21 cm ³ /g or more results in a sufficiently good affinity of the lapping pad with the slurry is not limited to the above.
From the viewpoint of further improving the affinity with the slurry, in the resin sheet of this embodiment, the cumulative pore volume V is preferably 0.30 cm ³ /g or more, and more preferably 0.40 cm ³ /g or more.
In the resin sheet of this embodiment, the cumulative pore volume V is 1.00 cm ³ /g or less. By having a cumulative pore volume V of 1.00 cm ³ /g or less, the density of the resin sheet tends to be within the above range, and in lapping using a lapping pad equipped with such a resin sheet, the surface of the workpiece can be made even flatter. From the same perspective, the cumulative pore volume V is preferably 0.90 cm ³ /g or less.
When the cumulative pore volume V is in the range of 0.21 cm ³ /g or more and 1.00 cm ³ /g or less, the resin sheet has excellent dressability. "Dressing" or "dressing treatment" refers to a process of adjusting the surface roughness and flatness of the lapping surface of the lapping pad using a dressing jig (e.g., a diamond dresser or sandpaper) to which abrasive grains or the like are fixed before lapping the workpiece. "Excellent dressability" means that sufficient dressing can be performed by treatment under relatively easy conditions. "Lapping surface" refers to the surface that the lapping pad comes into contact with the workpiece, or the surface that is expected to come into contact with the workpiece, when lapping the workpiece with the lapping pad.

(Ratio of cumulative pore volume _V to cumulative pore volume V)
In the lapping pad of this embodiment, from the viewpoint of further improving the balance between the flatness imparted to the workpiece and the affinity with the slurry, in the pore distribution of the resin sheet, the ratio of the cumulative pore volume _V in the pore diameter range of 0.010 μm to 1.0 μm to the cumulative pore volume V in the pore diameter range of 0.010 μm to 360 μm is preferably 50% or more. In other words, the ratio (V/ _V ) of the cumulative pore volume _V to the cumulative pore volume V is preferably 0.50 or more. According to this embodiment, the resin sheet has an increased proportion of pores having relatively small pore diameters, and therefore the resin sheet can have a greater number of interconnected cells while maintaining the same density as conventional products.
From the same viewpoint, the ratio of the integral pore volume _V to the integral pore volume V is more preferably 60% or more, even more preferably 65% or more, and even more preferably 70% or more. The upper limit of the ratio of the integral pore volume _V to the integral pore volume V is not particularly limited, and the ratio of the integral pore volume _V to the integral pore volume V may be 100% or less, 99% or less, 95% or less, 90% or less, 85% or less, or 80% or less.

(Peak position of the maximum peak)
In the pore distribution of the resin sheet in this embodiment, the peak position of the maximum peak in the pore diameter range of 0.010 μm to 360 μm is preferably within the pore diameter range of 0.010 μm to 1.0 μm. Generally, in mercury intrusion porosimetry, the pore distribution is measured as the cumulative pore volume from the maximum pore diameter in the measurement range. Therefore, "the peak position of the maximum peak in the pore diameter range of 0.010 μm to 360 μm" refers to the position (pore diameter) of the maximum peak of the log differential pore volume distribution (dV / d (log D)) calculated from the pore distribution obtained by mercury intrusion porosimetry. Furthermore, when there are multiple maximum points in the pore diameter range of 0.010 μm to 360 μm, the maximum peak refers to the maximum point with the largest maximum value.
When the peak position of the maximum peak in the pore diameter range of 0.010 μm to 360 μm is within the pore diameter range of 0.010 μm to 1.0 μm, the resin sheet has pores with a more uniform distribution in the range of 0.010 μm to 1.0 μm, which tends to further improve affinity with the slurry of the lapping pad and dressability. From the viewpoint of further improving affinity with the slurry of the lapping pad and dressability, the pore diameter is more preferably within the range of 0.010 μm to 0.5 μm, even more preferably within the range of 0.030 μm to 0.5 μm, and even more preferably within the range of 0.050 μm to 0.5 μm.
From the same viewpoint, the position of the maximum peak in the range of 1.0 μm or more and 360 μm or less is more preferably in the range of pore diameters of 50 μm or more and 200 μm or less.

(Number of peaks and peak height)
In the log differential pore volume distribution of the resin sheet in this embodiment, the number of peaks in the pore diameter range of 0.010 μm to 360 μm is preferably 2 to 4, more preferably 2, and even more preferably 1 in the range of 0.010 μm to 1.0 μm and 1.0 μm to 360 μm. When the number of peaks is within the above range, the pores have a more uniform distribution, which tends to further improve the affinity with the slurry of the lapping pad and the dressability.
From the same viewpoint, in the log differential pore volume distribution, the maximum peak height in the pore diameter range of 0.010 μm or more and 1.0 μm or less is preferably at least two times, more preferably at least 2.5 times, and even more preferably at least three times, the maximum peak height in the pore diameter range of 1.0 μm or more and 360 μm or less.

(Cumulative pore volume V ₀ )
In the pore distribution of the resin sheet in this embodiment, the cumulative pore volume _V0 in the pore diameter range of 0.010 μm to 360 μm is preferably 0.1 ^cm3 /g to 2.0 ^cm3 /g, more preferably 0.4 ^cm3 /g to 2.0 ^cm3 /g, even more preferably 0.5 ^cm3 /g to 1.5 ^cm3 /g, and still more preferably 0.6 ^cm3 /g to 1.2 ^cm3 /g. When the cumulative pore volume _V0 is within the above range, the balance between the flatness imparted to the workpiece and the affinity with the slurry tends to be further improved.

In this embodiment, the cumulative pore volume V and the cumulative pore volume _V are calculated from the pore distribution measured by mercury porosimetry with a contact angle of 130° and a mercury surface tension of 485 dyn/cm, but for more detailed measurement conditions for the mercury porosimetry, the method described in the Examples can be referred to. Furthermore, the method for controlling the cumulative pore volume V, the cumulative pore volume _V , the ratio of the cumulative pore volume V to the cumulative pore volume V _, the peak position of the maximum peak, the number of peaks, and the peak height are not particularly limited, but for example, a lapping pad may be obtained by the method for producing a lapping pad of this embodiment described below.

(Structure of resin sheet)
The resin sheet of this embodiment preferably has a microphase-separated structure. In this specification, the term "microphase-separated structure" refers to a phase-separated structure formed through microphase separation. Furthermore, in this specification, the term "microphase separation" refers to phase separation in which a microscopic (typically, on the order of micrometers) structural pattern is repeated with at least one-dimensional periodicity in a macroscopically homogeneous object. Microphase separation can be achieved, for example, by employing preferred manufacturing conditions in the method for manufacturing a lapping pad of this embodiment, which will be described later. Typical examples of microphase-separated structures include, but are not limited to, a spherical structure (island-in-the-sea structure), a cylindrical structure, a lamellar structure, and a three-dimensional network structure. The microphase-separated structure of this embodiment preferably includes a cylindrical structure, a lamellar structure, and a three-dimensional network structure, and more preferably a three-dimensional network structure.
In this specification, a three-dimensional network structure refers to a structure in which a mesh-like network is formed in three dimensions. The three-dimensional network structure derived from microphase separation may include a single gyroid structure and/or a double (multiple) gyroid structure. In this specification, a single gyroid structure typically refers to a network structure in which two twisted three-way branches are combined to form a pair of thin wire structures to form a unit cell, which is then periodically repeated, and a double (multiple) gyroid structure refers to a structure in which two or more single gyroid structures are combined in a nested manner.
In the cross section of a resin sheet having a continuous foam structure resulting from conventional foaming agents or injecting an inert gas, a generally spherical foam cross section and flat resin portions (i.e., a sea-island structure consisting of a sea of resin and islands of voids) tend to be observed. On the other hand, when the resin sheet of the present embodiment has a double (multiple) gyroid structure, a phase-separated structure in which two or more resins are intertwined in a mottled manner on the order of micrometers tends to be observed in the cross section. Furthermore, when the resin sheet of the present embodiment has a single gyroid structure, an amorphous void cross section and a resin skeleton/resin skeleton cross section are typically observed in the cross section. When the resin skeleton is sufficiently large compared to the voids, the resin skeleton may not be observable and the sheet may be observed as essentially a sea of resin. However, even in this case, the voids in the resin sheet of the present embodiment are formed in a three-dimensional network-like interconnection.
When a cross section of the resin sheet in this embodiment is observed, both the characteristics of a mottled pattern of two or more resins, an amorphous void cross section, and a resin skeleton/resin skeleton cross section are observed; that is, there are cases where the boundary between the double (multiple) gyroid structure and the single gyroid structure cannot be clearly distinguished, but in such cases, the resin sheet can be evaluated as including at least one of a single gyroid structure and a double (multiple) gyroid structure.
Even when the resin sheet in this embodiment has a single gyroid structure and/or a double (multiple) gyroid structure, a sharp peak (maximum value) is typically measured in the pore diameter range of 0.010 μm or more and 10.0 μm or less in the log differential pore volume distribution.

The resin sheet of this embodiment may contain two or more phases with different compositions. In this specification, the "composition" of a phase includes both the resin that is the main component of the phase and the components contained in the phase other than the main component, and also takes into consideration the blending ratio of these. Therefore, the microphase-separated structure possessed by the resin sheet of this embodiment may contain two or more phases in which at least one of the resin that is the main component of the phase and the components contained in the phase other than the main component is different from each other, and typically may contain two or more phases in which at least one or more of the structure, average molecular weight, and functional group of the resin that is the main component of the phase is different.

Examples of two phases with different compositions include cases where the types of resin that make up one phase are different from those of the other phase; cases where the amount of additives contained in one phase is different from those of the other phase; and cases where the resin sheet is made of an AB block polymer, with one phase consisting primarily of the A block and the other phase consisting primarily of the B block.

Typical examples of microphase-separated structures containing two phases with different compositions include a first phase formed by the curing of a specific prepolymer and a specific curing agent, and a second phase formed by the curing of a prepolymer different from the prepolymer in the first phase and the curing agent in the first phase; a first phase formed by the curing of a specific prepolymer and a specific curing agent, and a second phase formed by the curing of a prepolymer different from the prepolymer in the first phase and a curing agent different from the curing agent in the first phase; and a first phase formed by the curing of a specific prepolymer and a specific curing agent, and a second phase formed by the curing of a prepolymer different from the prepolymer in the first phase and a curing agent different from the curing agent in the first phase.

The resin sheet in this embodiment may have voids resulting from microphase separation. These voids may be referred to as voids that constitute a microphase-separated structure, and specific examples thereof include, but are not limited to, voids defined by the resin skeleton that gives rise to a gyroid structure. Note that, in this specification, the voids may originate from pores, or may originate from interconnected pores that connect multiple pores.

The resin sheet having the microphase separation structure of this embodiment can be obtained, for example, by the method for manufacturing a wrapping pad of this embodiment described below. Furthermore, the fact that the resin sheet has a microphase separation structure can be confirmed by observing it with a scanning electron microscope (SEM) at a magnification of approximately 300x to 3000x.

The fact that a resin sheet has a microphase-separated structure containing two or more phases with different compositions or that it has the aforementioned voids can be observed using optical methods such as optical microscopes and phase-contrast microscopes, methods using electron microscopes such as scanning electron microscopes and transmission electron microscopes, methods using particle scattering such as light scattering, small-angle neutron scattering, and small-angle X-ray scattering, X-ray diffraction methods, fluorescence methods, and pulsed NMR measurement methods.

(Average pore diameter of resin sheet)
In the resin sheet of this embodiment, the average pore size measured for pores of 10 μm or more is not particularly limited, but is preferably 50 μm or more and 300 μm or less, and more preferably 50 μm or more and 200 μm or less.
The average pore size can be measured by the method described in the Examples below. The average pore size can be adjusted to the above range by, for example, adjusting the type and/or amount of foaming agent and foam stabilizer.

(Average thickness of resin sheet)
The average thickness of the resin sheet in this embodiment is not particularly limited, but is preferably 0.5 mm or more and 10.0 mm or less, more preferably 0.6 mm or more and 8.0 mm or less, and even more preferably 0.7 mm or more and 5.0 mm or less.

(Physical properties of resin sheet)
The compressibility of the resin sheet in this embodiment is not particularly limited, but is preferably 0.1% or more and 5.0% or less, and more preferably 0.3% or more and 3.0% or less. The compressibility of the resin sheet can be determined in accordance with Japanese Industrial Standards (JIS L 1021) using a Schopper-type thickness gauge (pressure surface: circular, 1 cm diameter). Specifically, the thickness t0 is measured after applying an initial load from an unloaded state for 30 seconds, and then the thickness t1 is measured after applying a final pressure from the thickness t0 state for 30 seconds, and the compressibility can be calculated using the following formula. The initial load is 100 g/cm ² and the final pressure is 1120 g/cm ² .
Compression rate (%) = 100 × (t0 - t1) / t0

The compressive modulus of the resin sheet in this embodiment is not particularly limited, but is preferably 70% or more and 100% or less, and more preferably 75% or more and 95% or less. The compressive modulus of the resin sheet can be determined in accordance with Japanese Industrial Standards (JIS L 1021) using a Schopper-type thickness gauge (pressure surface: circular, 1 cm diameter). Specifically, the thickness t0 is measured after applying an initial load for 30 seconds from an unloaded state, then the thickness t1 is measured after applying a final pressure for 30 seconds from the unloaded state. Furthermore, all loads are removed from the unloaded state, and the sheet is left for 5 minutes (unloaded state). Then, the thickness t0' is measured after applying the initial load again for 30 seconds, and the modulus can be calculated using the following formula. The initial load is 100 g/cm ² and the final pressure is 1120 g/cm ² .
Compression rate (%) = 100 × (t0' - t1) / (t0 - t1)

The Shore D hardness of the resin sheet in this embodiment is not particularly limited, but is preferably 10 or more and 70 or less, and more preferably 20 or more and 60 or less. The Shore D hardness of the resin sheet can be determined using a D-type hardness tester in accordance with Japanese Industrial Standards (JIS K 7311).

(Resin sheet material)
The material of the resin sheet in this embodiment is not particularly limited. Examples of materials for the resin sheet include polyurethane resins. Examples of polyurethane resins include, but are not limited to, polyester-based polyurethane resins, polyether-based polyurethane resins, and polycarbonate-based polyurethane resins. These may be used alone or in combination of two or more.

Among these, the material for the resin sheet in this embodiment preferably contains at least one of a polyester-based polyurethane resin and a polyether-based polyurethane resin. In particular, it preferably contains a polyurethane resin that is a cured product of a mixed liquid containing a urethane prepolymer and at least two types of curing agents, as described below in the method for manufacturing the wrapping pad of this embodiment. Using such a resin tends to make it easier to achieve density and pore distribution within the above ranges.

In addition to the resin component, the resin sheet of this embodiment may also contain components derived from additives. Examples of such additives include antifoaming agents, catalysts, foaming agents, foam stabilizers, abrasive grains, dyes, pigments, solid fine particles, flame retardants, hydrophilizing agents, hydrophobic agents, light resistance agents, antioxidants, and antistatic agents, which will be described later in the method for manufacturing the lapping pad of this embodiment.

[Method of manufacturing wrapping pad]
The method for producing a lapping pad of this embodiment includes a step of curing a mixed solution of at least one prepolymer and at least two curing agents to obtain a resin sheet having a microphase-separated structure. This method allows the lapping pad of this embodiment to be produced easily. Each step of the method for producing a lapping pad is described in detail below.

(Mixing process)
The method for manufacturing a lapping pad according to the present embodiment may include a mixing step of preparing a mixture of at least one prepolymer and at least two curing agents. By using at least two curing agents in the mixing step, a resin sheet having a microphase-separated structure can be obtained in the molding step following the mixing step. In particular, forming a microphase-separated structure using two or more curing agents tends to make it easier to control the curing reaction and the shape of the microphase-separated structure than forming a microphase-separated structure using two or more prepolymers.

The mixing process can be carried out, for example, by placing at least one prepolymer and at least two curing agents heated to 30°C to 90°C into a temperature-adjustable jacketed mixer and stirring at 30°C to 130°C. If necessary, the mixture can be transferred to a tank with a jacket and a stirrer for aging. The stirring time can be adjusted appropriately depending on the number of mixer teeth, rotation speed, clearance, etc., but is, for example, 0.1 to 60 seconds.

(hardening agent)
The curing agent used in the mixing step is not particularly limited, but examples thereof include an amino group-containing compound and a hydroxyl group-containing compound. Examples of the amino group-containing compound include, but are not particularly limited to, 4,4'-methylenebis(2-chloroaniline) (MOCA), ethylenediamine, propylenediamine, hexamethylenediamine, isophoronediamine, dicyclohexylmethane-4,4'-diamine, 4-methyl-2,6-bis(methylthio)-1,3-benzenediamine, 2-methyl-4,6-bis(methylthio)-1,3-benzenediamine, 2,2-bis(3-amino-4-hydroxyphenyl)propane, 2,2-bis[3- Examples of the amino group-containing compound include 2,2-bis[3-(1-methylpropylamino)-4-hydroxyphenyl]propane, 2,2-bis[3-(1-methylpentylamino)-4-hydroxyphenyl]propane, 2,2-bis(3,5-diamino-4-hydroxyphenyl)propane, 2,6-diamino-4-methylphenol, trimethylethylene bis-4-aminobenzoate, and polytetramethylene oxide-di-p-aminobenzoate. The amino group-containing compound is preferably 4,4'-methylenebis(2-chloroaniline).

Hydroxyl group-containing compounds are not particularly limited, but examples include ethylene glycol, propylene glycol, diethylene glycol, trimethylene glycol, tetraethylene glycol, triethylene glycol, dipropylene glycol, 1,4-butanediol, 1,3-butanediol, 2,3-butanediol, 1,2-butanediol, 3-methyl-1,2-butanediol, 1,2-pentanediol, 1,4-pentanediol, 2,4-pentanediol, 2,3-dimethyltrimethylene glycol, and tetramethylene glycol. Examples of suitable hydroxyl group-containing compounds include glycol, 3-methyl-4,3-pentanediol, 3-methyl-4,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,6-hexanediol, 1,5-hexanediol, 1,4-hexanediol, 2,5-hexanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, glycerin, trimethylolpropane, trimethylolethane, trimethylolmethane, polytetramethylene glycol, polyethylene glycol, and polypropylene glycol. From the standpoint of reaction control, it is preferable to use a difunctional (diol) hydroxyl group-containing compound rather than a trifunctional or higher functional compound. Furthermore, polytetramethylene glycol is more preferred as the hydroxyl group-containing compound.

The above curing agents are used in combination of two or more types. There are no particular restrictions on the combination of curing agents, but the combinations described below are preferred.

The active hydrogen equivalent (e.g., _NH2 equivalent and OH equivalent) of the curing agent is not particularly limited and may be, for example, 50 to 5,000, 100 to 4,000, or 130 to 3,000. The OH equivalent of a curing agent that is a hydroxyl group-containing compound may be 100 to 5,000, 200 to 4,000, or 300 to 3,000. The _NH2 equivalent of a curing agent that is an amino group-containing compound may be 50 to 2,000, 75 to 1,000, or 100 to 300.

At least two types of curing agents are used in the mixing step. It is preferable to use a combination of curing agents that have low compatibility with each other, and/or different reactivities, and/or different active hydrogen equivalents. This tends to more reliably obtain a microphase-separated structure. Examples of combinations of curing agents with different reactivities include combinations of curing agents with different active hydrogen groups, and more specifically, combinations of amino group-containing compounds and hydroxyl group-containing compounds.

When two or more curing agents having the same active hydrogen group are used, i.e., when two or more hydroxyl group-containing compounds or two or more amino group-containing compounds are used, the two or more curing agents preferably include two curing agents whose active hydrogen equivalent difference is 500 or more and 2000 or less. More preferably, the two or more curing agents include one curing agent whose active hydrogen equivalent is 200 or more and 500 or less, and another curing agent whose active hydrogen equivalent is 1000 or more and 2000 or less.

When two or more curing agents having the same active hydrogen group are used, and the difference in active hydrogen equivalent between these two or more curing agents is between 500 and 2000, the ratio of the amount of curing agent with the smaller active hydrogen equivalent to the amount of curing agent with the larger active hydrogen equivalent, in terms of the number of active hydrogen groups, is preferably 1:1 to 1:15, and more preferably 1:1 to 1:10.

When two or more curing agents having the same active hydrogen group are used, and these two or more curing agents include one with an active hydrogen equivalent of 200 to 500 and another with an active hydrogen equivalent of 1,000 to 2,000, the ratio of the amount of curing agent with an active hydrogen equivalent of 200 to 500 used to the amount of curing agent with an active hydrogen equivalent of 1,000 to 2,000 used, in terms of the number of active hydrogen groups, is preferably 1:1 to 1:15, and more preferably 1:1 to 1:10.

As a specific preferred combination of curing agents, the at least two curing agents preferably include an amino group-containing compound and a hydroxyl group-containing compound. The at least two curing agents more preferably include one amino group-containing compound and two or more hydroxyl group-containing compounds, or two or more amino group-containing compounds and one hydroxyl group-containing compound. The at least two curing agents even more preferably include one amino group-containing compound and two or more hydroxyl group-containing compounds.

When the at least two curing agents contain an amino group-containing compound and a hydroxyl group-containing compound, the difference between the _NH2 equivalent of the amino group-containing compound and the OH equivalent of the hydroxyl group-containing compound is not particularly limited, but it is preferable that the OH equivalent of the hydroxyl group-containing compound is larger, and it is more preferable that the OH equivalent of the hydroxyl group-containing compound is larger by 100 or more and 2000 or less than the _NH2 equivalent of the amino group-containing compound.

When the at least two curing agents contain an amino group-containing compound and a hydroxyl group-containing compound, the ratio of the amount of the amino group-containing compound used to the total amount of curing agents used is preferably 35% or more and 95% or less, and more preferably 40% or more and 90% or less, in terms of functionality ratio.

An example of a preferred combination of curing agents includes at least two curing agents, a first curing agent (amino group-containing compound) having an _NH equivalent of 100 to 300 and a second curing agent (hydroxyl group-containing compound) having an OH equivalent of 1,000 to 2,000. The ratio of the amount of the first curing agent to the amount of the second curing agent used is not particularly limited, but the amount of the first curing agent used is preferably 35% to 98% in terms of the ratio of the number of functional groups, more preferably 35% to 95%, and even more preferably 40% to 90%. The amount of the second curing agent used is preferably 2% to 60% in terms of the ratio of the number of functional groups, more preferably 3% to 60%, and even more preferably 5% to 50% in terms of the ratio of the number of functional groups, relative to the total amount of curing agent used. The amount of the first curing agent used is preferably 10% to 90% by mass, and more preferably 15% to 80% by mass, relative to the total amount of curing agents used, and the amount of the second curing agent used is preferably 10% to 50% by mass, and more preferably 15% to 40% by mass, relative to the total amount of curing agents used.

Generally, the total amount of curing agent used is determined by the R value, which is the equivalent ratio of the active hydrogen groups (amino groups and hydroxyl groups) present in the curing agent when the number of functional groups in the prepolymer is taken as 1. The total amount of curing agent used is preferably adjusted so that the R value is 0.7 or more and 1.3 or less. The R value is more preferably 0.8 or more and 1.2 or less.

By using the above-mentioned preferred combination of curing agents in appropriate amounts, it is possible to more reliably obtain a resin sheet having a cumulative pore volume V of 0.21 cm ³ /g or more and 1.00 cm ³ /g or less in the pore diameter range of 0.010 μm or more and 1.0 μm or less in the pore distribution measured by mercury porosimetry with a contact angle of 130° and a mercury surface tension of 485 dyn/cm, and/or a resin sheet having a microphase-separated structure. As a combination of curing agents, two or more curing agents having low compatibility with each other, two or more curing agents having different reactivities, and/or curing agents having different active hydrogen equivalents can be used. Even if a resin sheet having a clear microphase-separated structure cannot be obtained by such a combination, a resin sheet having a microphase-separated structure tends to be obtained by adjusting the type of curing agent so that they are mutually compatible, changing the curing agents so that their reactivities are similar, and/or changing the curing agents so that their active hydrogen equivalents are close to each other.

(prepolymer)
The prepolymer used in the mixing step is not particularly limited, and examples thereof include urethane prepolymers. Examples of urethane prepolymers include an adduct of hexamethylene diisocyanate and hexanetriol; an adduct of 2,4-tolylene diisocyanate and prenzcatechol; an adduct of 2,4-tolylene diisocyanate, poly(oxytetramethylene)glycol, and diethylene glycol; an adduct of tolylene diisocyanate and hexanetriol; an adduct of tolylene diisocyanate and trimethylolpropane; an adduct of xylylene diisocyanate and trimethylolpropane; an adduct of hexamethylene diisocyanate and trimethylolpropane; and an adduct of isocyanuric acid and hexamethylene diisocyanate. Furthermore, other isocyanate group-containing compounds prepared by reacting a polyisocyanate compound with a polyol compound, as well as various commercially available urethane prepolymers, may also be used.

The polyisocyanate compound used to prepare the isocyanate group-containing compound is not particularly limited as long as it has two or more isocyanate groups in the molecule. For example, diisocyanate compounds having two isocyanate groups in the molecule include m-phenylene diisocyanate, p-phenylene diisocyanate, 2,6-tolylene diisocyanate (2,6-TDI), 2,4-tolylene diisocyanate (2,4-TDI), naphthalene-1,4-diisocyanate, diphenylmethane-4,4'-diisocyanate (MDI), 4,4'-methylene-bis(cyclohexyl isocyanate) (hydrogenated MDI), 3,3'-dimethoxy-4,4'-biphenyl diisocyanate, and 3,3'-dimethyl-4,4'-biphenyl diisocyanate. Examples include ethyldiphenylmethane-4,4'-diisocyanate, xylylene-1,4-diisocyanate, 4,4'-diphenylpropane diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, propylene-1,2-diisocyanate, butylene-1,2-diisocyanate, cyclohexylene-1,2-diisocyanate, cyclohexylene-1,4-diisocyanate, p-phenylene diisothiocyanate, xylylene-1,4-diisothiocyanate, and ethylidine diisothiocyanate.

These polyisocyanate compounds may be used alone or in combination of two or more. Diisocyanate compounds are preferred as polyisocyanate compounds, with 2,4-TDI, 2,6-TDI, and MDI being more preferred.

Examples of polyol compounds used in preparing isocyanate group-containing compounds include diol compounds and triol compounds such as ethylene glycol, diethylene glycol (DEG), and butylene glycol; polyether polyol compounds such as polypropylene glycol (PPG) and poly(oxytetramethylene) glycol (PTMG); polyester polyol compounds such as the reaction product of ethylene glycol and adipic acid or the reaction product of butylene glycol and adipic acid; polycarbonate polyol compounds, and polycaprolactone polyol compounds. Trifunctional propylene glycol with added ethylene oxide can also be used. Polyol compounds may be used alone or in combination of two or more.

The NCO equivalent of the urethane prepolymer is preferably 150 or more and 700 or less, more preferably 200 or more and 600 or less, and even more preferably 200 or more and 500 or less. "NCO equivalent" is a numerical value indicating the molecular weight of the urethane prepolymer per NCO group, calculated by the formula "(parts by mass of polyisocyanate compound + parts by mass of polyol compound) / [(number of functional groups per molecule of polyisocyanate compound × parts by mass of polyisocyanate compound / molecular weight of polyisocyanate compound) - (number of functional groups per molecule of polyol compound × parts by mass of polyol compound / molecular weight of polyol compound)]".

At least one type of prepolymer is used in the mixing step. Two or more of the above prepolymers may be used in combination, but preferably one type is used alone. This type of prepolymer tends to make it easier to control the curing reaction and the shape of the microphase-separated structure. It is preferable to use a urethane prepolymer containing tolylene diisocyanate as the main component alone as the prepolymer.

The amount of prepolymer used is not particularly limited, but is preferably 30 to 80 parts by mass, and more preferably 40 to 75 parts by mass, based on the total mixed solution.

(Additives)
In the mixing step, components other than the prepolymer and the curing agent may be mixed as additives. Examples of additives include solvents (diluents) such as polypropylene glycol; antifoaming agents such as silicone-based antifoaming agents; catalysts; foaming agents such as water and hollow fine particles; foam stabilizers such as silicone-based foam stabilizers; and fillers (abrasive grains) such as cerium oxide; dyes; pigments; solid fine particles; flame retardants; hydrophilizing agents; hydrophobic agents; light resistance agents; antioxidants; and antistatic agents. From the viewpoint of achieving a density of 0.3 g/cm ³ or more and 0.9 g/cm ³ or less, it is preferable to add a foaming agent to adjust the density, and it is more preferable to adjust the amount of foaming agent added.

By adjusting the type and amount of catalyst added during the mixing process, the reaction rate of the curing reaction can be controlled, and the microphase-separated structure formed can be controlled.

(molding process)
The molding process is a process for obtaining a resin sheet having a microphase-separated structure by curing the mixed liquid obtained as described above. For example, the molding process may involve pouring the mixed liquid obtained in the mixing process into a mold preheated to 30°C to 150°C and heating it at approximately 30°C to 150°C for 10 minutes to 5 hours. This causes the prepolymer and the curing agent to react to form a resin, thereby curing the mixed liquid. Furthermore, secondary curing may be performed by heating in an oven at approximately 50°C to 180°C for 10 minutes to 10 hours. In the method for producing a lapping pad according to this embodiment, since the mixed liquid is as described above, a resin block having a microphase-separated structure can be obtained.

The reaction temperature when curing the mixed liquid in the molding process can be adjusted appropriately depending on the types and blending ratios of the prepolymer, curing agent, and additives used. Adjusting the reaction temperature tends to control the reaction rate of the curing reaction and the microphase-separated structure that is formed.

In the molding process, a resin sheet of an appropriate thickness is cut out from the resin block obtained as described above to obtain a resin sheet having a microphase-separated structure. The obtained resin sheet may be aged at 30°C to 150°C for approximately 1 hour to 24 hours.

The resin sheet obtained in this manner is then, for example, attached with double-sided tape to one side and cut into a predetermined shape, preferably a disk, to complete the wrapping pad of this embodiment. There are no particular restrictions on the double-sided tape, and any double-sided tape known in the art can be selected and used.

The wrapping pad of this embodiment may have a single-layer structure consisting of only a resin sheet, or may have a multi-layer structure in which another layer (cushion layer or substrate layer) is bonded to one side of a resin sheet. When it has a multi-layer structure, the multiple layers can be bonded and fixed together using double-sided tape or adhesive, while applying pressure as necessary. There are no particular limitations on the double-sided tape and adhesive used, and any double-sided tape and adhesive known in the art can be selected and used.

Furthermore, the wrapping pad of this embodiment may have grooves, embossing, and/or holes (punching) on its surface, as needed. There are no particular limitations on the shape of the grooves and embossing, and examples include lattice, concentric circle, and radial shapes.

The lapping pad may also be dressed (grinded) on the front and/or back surfaces of the resin sheet. The resin sheet used in the method for manufacturing a lapping pad of this embodiment is high-density, but has interconnected pores, making it highly dressable and allowing for easy dressing. The dressing method is not particularly limited, and can be performed by a known method such as grinding with a diamond dresser.

[Method of manufacturing lapped product]
The method for producing a lapped product of this embodiment includes a lapping step in which a workpiece is lapped using the lapping pad in the presence of a slurry to obtain a lapped product.

In the method for manufacturing a lapped product of this embodiment, while slurry is being supplied, the holding platen and lapping platen are rotated relative to each other while pressing the workpiece against the lapping pad, causing the lapping pad to act on the workpiece's surface, which is then lapped. The holding platen and lapping platen may rotate in the same direction but at different rotational speeds, or they may rotate in opposite directions. Furthermore, the workpiece may be lapped while moving (rotating) inside the frame during the lapping process.

The slurry may contain liquid components such as water and oil, additives, and abrasive grains (abrasive particles; for example, diamond, SiC, B ₄ C, and Al ₂ O ₃ ), depending on the workpiece and lapping conditions.

In addition, the workpiece may be, but is not limited to, optical materials such as lenses, plane-parallel plates, and reflecting mirrors, semiconductor wafer materials such as SiC disks, crystals, metals, stone, wood, resin materials, and ceramic materials.

The present embodiment will be described in more detail below using examples and comparative examples. The present embodiment is not limited in any way by the following examples.

[Measurement of cumulative pore volume (pore distribution) by mercury intrusion method]
The cumulative pore volume (pore distribution) of the resin sheet was measured by mercury intrusion porosimetry. A 10 mm square sample piece was cut from a 2 mm thick resin sheet and used for measurement. The cumulative pore volume was measured using a Micromeritics product named "Auto Pore III" under conditions of a contact angle of 130° and a mercury surface tension of 485 dyn/cm. The cumulative pore volume from a pore diameter of 360 μm to a pore diameter of 0.005 μm was determined by sweeping the mercury pressure from 0.5 psia to 30,000 psia. The pore distribution was determined using porosimeter data processing software (Shimadzu Corporation, product name "POREPLOT-PCW"). Note that for each measurement result, the pore distribution from a pore diameter of 360 μm to a pore diameter of 0.010 μm is shown.

[Observation of Resin Sheet]
Whether or not the resin sheet had a microphase-separated structure was confirmed by observation with a scanning electron microscope (SEM) at a magnification of about 300 to 3000 times.

[Measurement of average pore diameter]
A 1.3 mm square area of the lapping pad surface was observed at 175x magnification using a microscope (VH-6300, manufactured by KEYENCE), and the resulting image was binarized using image processing software (Image Analyzer V20LAB Ver. 1.3, manufactured by Nikon) to confirm the number of bubbles. The circle-equivalent diameter was calculated from the area of each pore, and the average value was used as the average pore diameter (μm). At this time, the cutoff value (lower limit) of the pore diameter was set to 10 μm, and the average pore diameter was obtained as the average value of pore diameters of 10 μm or more.

[Example 1]
A urethane prepolymer with an NCO equivalent of 407 and primarily composed of 2,4-tolylene diisocyanate (TDI) was prepared. 61.83 parts by weight of this urethane prepolymer was mixed with 15.18 parts by weight of 4,4'-methylenebis( ₂ -chloroaniline) (MOCA) (NH equivalent: 134), and 5.65 parts by weight of polypropylene glycol (OH equivalent: 1345). To this mixture, 0.15 parts by weight of a silicone foam stabilizer (manufactured by Dow Corning Toray Co., Ltd., product name "SH193"), 0.03 parts by weight of a catalyst (manufactured by Tosoh Corporation, product name "TOYOCAT ET"), 0.16 parts by weight of water as a foaming agent, and 17 parts by weight of calcium carbonate filler as abrasive grains were further added to obtain a mixture that would serve as a precursor to the resin sheet. The R value of the mixture was 0.9.

The resulting mixture was poured into a mold preheated to 50°C and allowed to cure for 15 minutes at 50°C. The resulting block-shaped molded product was removed from the mold and allowed to cure for 8 hours in an oven at 120°C, resulting in a urethane resin block. The resulting urethane resin block was allowed to cool to 25°C and then sliced to obtain a 2.0 mm thick resin sheet.

The density was calculated from the volume and weight of a sample cut out from the resin sheet, and the density of the obtained resin sheet was 0.55 g/ ^cm3 . The measurement results of the pore distribution are shown in Figure 1. Table 1 also shows the cumulative pore volume V in the pore diameter range of 0.010 μm or more and 1.0 μm or less, the cumulative pore volume V0 in the pore diameter range of 0.010 μm or more and 360 μm or less, the ratio V/ _V0 , the average pore _diameter , and the peak position of the maximum peak in the pore diameter range of 0.010 μm or more and 360 μm or less, all of which are obtained from the pore distribution.

Furthermore, when the surface of the resin sheet was observed with a scanning electron microscope, it was confirmed to have a microphase-separated structure (three-dimensional network structure). Examples of SEM images are shown in Figure 2 (500x magnification) and Figure 3(A) (2000x magnification). As circled by the dashed line in Figure 3(B), it was confirmed that the resin sheet had an amorphous void cross section and a resin skeleton/resin skeleton cross section, particularly in the upper left part of the figure, and was therefore evaluated to have at least a single gyroid structure.

[Example 2]
A urethane prepolymer with an NCO equivalent of 382 and primarily composed of 2,4-tolylene diisocyanate (TDI) was prepared. 55.26 parts by weight of this urethane prepolymer was mixed with 15.27 parts by weight of 4,4'-methylenebis( ₂ -chloroaniline) (MOCA) (NH equivalent: 134), 7.04 parts by weight of polytetramethylene glycol (OH equivalent: 972), and 4.24 parts by weight of polypropylene glycol (OH equivalent: 1345). To this mixture, 0.11 parts by weight of a silicone foam stabilizer (manufactured by Dow Corning Toray Co., Ltd., product name "SH193"), 0.03 parts by weight of a catalyst (manufactured by Tosoh Corporation, product name "Toyocat ET"), 0.05 parts by weight of water as a foaming agent, and 18 parts by weight of calcium carbonate filler as abrasive grains were further added to obtain a mixture that would serve as a precursor to the resin sheet. The R value of the mixture was 0.9.

The resulting mixture was poured into a mold preheated to 50°C and allowed to cure for 15 minutes at 50°C. The resulting block-shaped molded product was removed from the mold and allowed to cure for 8 hours in an oven at 120°C, resulting in a urethane resin block. The resulting urethane resin block was allowed to cool to 25°C and then sliced to obtain a 2.0 mm thick resin sheet.

The density was calculated from the volume and weight of a sample cut out from the resin sheet, and the density of the obtained resin sheet was 0.89 g/ ^cm3 . The measurement results of the pore distribution are shown in Figure 4. Table 1 also shows the cumulative pore volume V in the pore diameter range of 0.010 μm to 1.0 μm, the cumulative pore volume _V0 in the pore diameter range of 0.010 μm to 360 μm, the ratio V/ _V0 , the average pore diameter, and the peak position of the maximum peak in the pore diameter range of 0.010 μm to 360 μm, all of which are determined from the pore distribution. Figure 5 also shows an example of an SEM image.

[Comparative Example 1]
61.59 parts by weight of the same urethane prepolymer as in Example 1 was mixed with 9.24 parts by weight of 4,4'-methylenebis(2-chloroaniline) (MOCA) ( _NH2 equivalent: 134) and 9.24 parts by weight of crude MOCA ( _NH2 equivalent: 189). To this mixture, 0.18 parts by weight of a silicone foam stabilizer (manufactured by Dow Corning Toray Co., Ltd., product name "SH193"), 2.58 parts by weight of a polyether (OH equivalent: 1007) as a diluent, 0.04 parts by weight of a catalyst (manufactured by Tosoh Corporation, product name "TOYOCAT ET"), 0.13 parts by weight of water as a foaming agent, and 17 parts by weight of calcium carbonate filler as abrasive grains were further added to obtain a mixed solution that would serve as a precursor to the resin sheet. The R value of the mixed solution was 0.9.

The resulting mixture was poured into a mold preheated to 50°C and allowed to cure for 15 minutes at 50°C. The resulting block-shaped molded product was removed from the mold and allowed to cure for 8 hours in an oven at 120°C, resulting in a urethane resin block. The resulting urethane resin block was allowed to cool to 25°C and then sliced to obtain a 2.0 mm thick resin sheet.

The density was calculated from the volume and weight of a sample cut out from the resin sheet, and the density of the obtained resin sheet was 0.53 g/ ^cm3 . The measurement results of the pore distribution are shown in Figure 6. Table 1 also shows the cumulative pore volume V in the pore diameter range of 0.010 μm or more and 1.0 μm or less, the cumulative pore volume V0 in the pore diameter range of 0.010 μm or more and 360 μm or less, the ratio V/ _V0 , the average pore _diameter , and the peak position of the maximum peak in the pore diameter range of 0.010 μm or more and 360 μm or less, all of which are obtained from the pore distribution.

Furthermore, when the surface of the resin sheet of Comparative Example 1 was observed with a scanning electron microscope, no microphase-separated structure was confirmed. An example of an SEM image is shown in Figure 7. In Comparative Example 1, it is believed that the desired curing reaction did not proceed and microphase separation did not occur, at least due to an insufficient amount of curing agent with an OH equivalent of 1,000 or more and 2,000 or less.

In Example 1, the position of the maximum peak in the range of 1.0 μm to 360 μm was 129 μm, and its height was 0.40 cm ³ /g. In addition, the position of the maximum peak in the range of pore diameters of 0.010 μm to 360 μm was 0.0822 μm, and its height was 1.65 cm ³ /g.
From the above measurement results, it was confirmed that the resin sheet of Example 1 contains both voids derived from the foaming agent and voids derived from the microphase separation structure, and that the latter voids are interconnected throughout the entire wrapping pad.

In Example 2, the position of the maximum peak in the range of 1.0 μm to 360 μm was 77 μm, and its height was 0.075 cm ³ /g. In addition, the position of the maximum peak in the range of pore diameters of 0.010 μm to 360 μm was 0.0411 μm, and its height was 0.447 cm ³ /g.
From the above measurement results, it was confirmed that the resin sheet of Example 2 contains both voids derived from the foaming agent and voids derived from the microphase separation structure, and that the latter voids are interconnected throughout the entire wrapping pad.

The lapping pads of Examples 1 and 2 were used to conduct a lapping test and an evaluation test of their affinity with the slurry. As a control, the lapping pad of Comparative Example 1 was used to conduct a lapping test and an evaluation test of their affinity with the slurry under the same conditions. The results showed that the lapping pads of the Examples were able to impart better flatness to the workpiece and had superior affinity with the slurry compared to the lapping pad of Comparative Example.

The lapping pad of the present invention has industrial applicability as a lapping pad used for lapping optical materials such as lenses, plane-parallel plates, and reflecting mirrors, semiconductor wafer materials such as SiC disks, crystals, metals, stone, wood, resin materials, and ceramics.

Claims (9)

A wrapping pad comprising a resin sheet having fine holes,
In the pore distribution of the resin sheet measured by mercury intrusion porosimetry with a contact angle of 130° and a mercury surface tension of 485 dyn/cm, the cumulative pore volume V in the pore diameter range of 0.010 μm or more and 1.0 μm or less is 0.21 cm ³ /g or more and 1.00 cm ³ /g or less,
The density of the resin sheet is 0.3 g/cm ³ or more and 0.9 g/cm ³ or less. 2. The lapping pad according to claim 1, wherein in the pore distribution of the resin sheet, a ratio of the cumulative pore volume V to the cumulative pore volume _V0 in the pore diameter range of 0.010 μm to 360 μm is 50% or more. The wrapping pad of claim 1 or 2, wherein the average pore diameter measured for pores of 10 μm or larger in the resin sheet is 50 μm or larger and 200 μm or smaller. The wrapping pad described in any one of claims 1 to 3, wherein the peak position of the maximum peak in the pore diameter range of 0.010 μm to 360 μm in the pore distribution of the resin sheet is within the pore diameter range of 0.010 μm to 1.0 μm. The wrapping pad described in any one of claims 1 to 4, wherein the resin sheet has a microphase separation structure. The wrapping pad according to any one of claims 1 to 5, wherein the resin sheet contains polyurethane. A method for producing the lapping pad according to any one of claims 1 to 6, comprising the steps of:
A method for producing a lapping pad, comprising a step of curing a mixed liquid of at least one prepolymer and at least two curing agents to obtain a resin sheet having a microphase-separated structure. 8. The method for manufacturing a lapping pad according to claim 7, wherein the curing agent comprises a first curing agent having an _NH2 equivalent of 100 or more and 300 or less, and a second curing agent having an OH equivalent of 1000 or more and 2000 or less. A method for producing a lapped product, comprising a lapping step of lapping a workpiece using the lapping pad described in any one of claims 1 to 6 in the presence of a slurry.