JP2011051063A - Polishing pad and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing pad which is improved in polishing quality while a risk of a usable life being shortened is suppressed, and to provide a method for simply manufacturing the polishing pad. <P>SOLUTION: The polishing pad has a foaming layer composed of a foamed polymer composition, wherein the foaming layer has an average air bubble diameter continuously changing in its thickness direction. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a polishing pad having a foam layer formed by foaming a polymer composition, and a method for producing the same.

Conventionally, surface polishing by chemical mechanical polishing (hereinafter also referred to as “CMP”) using a polishing pad has been performed when manufacturing a product that is required to have a highly planarized surface such as a semiconductor wafer. .
In this CMP, a slurry containing abrasive grains is interposed between an object to be polished and a polishing pad, and the object to be polished and the polishing pad are brought into sliding contact with each other. The thing which formed the foaming layer as the polishing layer of the outermost surface is known.
The foamed layer is formed in a foamed state by a polymer composition, and normally, when used as a polishing layer, the abrasive grains may be carried or polishing residue generated by polishing may be taken in. In addition, the polishing pad is provided with a treatment for opening the bubbles on the surface thereof.
Thus, the polishing pad using the foamed layer for polishing can perform surface polishing while preventing the occurrence of scratches on the object to be polished, and can perform excellent surface polishing.
Further, in such a polishing pad, since the foam layer usually has an appropriate cushioning property, it is easy to stabilize the contact state between the surface of the foam layer and the object to be polished. In this respect, it is possible to easily realize excellent surface polishing.

By the way, not only in the case of having such a foam layer, it is possible to form a good contact state with the object to be polished by imparting cushioning properties to the surface of the polishing pad.
However, if the polishing pad is formed to be excessively flexible from the surface to the back side portion, it may cause “sag” at the edge portion of the object to be polished. Therefore, conventionally, the polishing layer and the back side are provided. A polishing pad in which a laminated structure with an underlayer is formed and the underlayer is formed with higher hardness than the polishing layer is used (see Patent Document 1, paragraph [0043] below).
That is, by making the characteristics different in the thickness direction, according to the shape, material, or required surface flatness of the object to be polished, a polishing pad suitable for each is manufactured to improve the polishing quality. This has been studied in the past.

  Further, in Patent Document 2 below, in order to easily produce a polishing pad having different characteristics in the thickness direction, foam sheets in different foamed states are extruded and laminated by a plurality of extruders, and the foamed state in the thickness direction. Describes forming different foamed layers in multiple stages.

JP 2008-207318 A JP 2003-220550 A

  When the characteristics are changed stepwise in the thickness direction of the foam layer as in the polishing pad described in Patent Document 2, for example, frictional force generated on the surface during polishing is likely to be concentrated on the lamination interface, and excessively When stress concentration occurs, there is a risk of causing fracture at the interface.

In particular, the foam layer is entirely formed by a thin cell membrane formed by the polymer composition, and usually the individual cell membranes themselves have low rupture strength. The bubble film is ruptured and may cause delamination in the polishing pad.
Naturally, when such delamination occurs, it cannot be used as a polishing pad. Therefore, as in the invention described in Patent Document 2, the life of the polishing pad is shortened by forming a step change in the foam layer. There is a risk of causing.

  Conventionally, no polishing pad that can improve the quality of polishing while suppressing the possibility of shortening the service life has been found, and therefore, a method for easily producing such a polishing pad is also sufficient. Has not been studied.

  The present invention has been made in view of the above problems, and a polishing pad capable of improving the quality of polishing while suppressing the possibility of shortening the useful life, and such a polishing pad as simple as possible. It is an object of the present invention to provide a method for producing a polishing pad that can be produced.

  The present invention according to the polishing pad for solving the above problems has a foam layer formed by foaming a polymer composition, and the foam layer continuously changes the average cell diameter in the thickness direction. It is characterized by that.

  In addition, the present invention relating to a polishing pad manufacturing method for solving the problem is a liquid curing containing a foaming agent in order to produce a polishing pad having a foam layer formed by foaming a polymer composition. A method for producing a polishing pad in which a foamable layer is formed by foaming and curing the curable polymer composition in a mold having a flat accommodation space, wherein the curable polymer composition is averaged in the thickness direction. In order to form the foamed layer in which the bubble diameter is continuously changed, the curable polymer composition is placed in the mold while the temperature of the curable polymer composition is different from the surface temperature of the mold. It is characterized in that the foamed state of the surface portion in contact with the mold surface is made different from the foamed state inside.

In the polishing pad of the present invention, the foamed layer formed by foaming the polymer composition changes the foamed state in the thickness direction.
That is, according to the present invention, in the thickness direction of the foam layer, for example, a portion having fine bubbles and excellent cushioning properties, and a bubble film having a thicker and thicker bubble film than the portion excellent in cushioning properties are formed with high strength. Therefore, the quality of polishing can be improved.
Moreover, since the change in the foamed state is continuously changed, for example, the property in the thickness direction of the foamed layer is changed in a state in which the property change is suppressed as compared with the invention described in Patent Document 2. Stress concentration can be suppressed.
That is, according to the present invention, it is possible to provide a polishing pad capable of improving the quality of polishing while suppressing the possibility of shortening the service life.
Moreover, according to the method for producing a polishing pad of the present invention, a polishing pad having the above effects can be easily produced.

The side view which shows the usage example of the polishing pad of one Embodiment, and the fragmentary sectional view which shows the cross-section of a polishing pad (foaming layer). The top view which shows the metal mold | die used for one Embodiment of the manufacturing method of a polishing pad. Sectional drawing which shows the structure of the metal mold | die of FIG. Sectional drawing of the polishing pad (foaming layer) of other embodiment. Sectional drawing of the polishing pad (foaming layer) of other embodiment. 2 is an SEM photograph showing a cross section of the polishing pad of Example 1. FIG. 4 is an SEM photograph showing a cross section of the polishing pad of Example 2. FIG.

Embodiments of the present invention will be described below with reference to the drawings.
The polishing pad according to the present embodiment is formed in a disk shape with a diameter of several centimeters to several tens of centimeters, and the left side of FIG. The right figure is a partial sectional view showing the sectional structure of the portion of the polishing pad indicated by the broken line X in the left figure.
As shown in FIG. 1, the polishing pad 1 according to this embodiment has a foam layer 10 formed by foaming a polymer composition, and is formed only by the foam layer 10.
That is, the foamed layer 10 constitutes the entire polishing pad 1 as a polishing layer in which the back surface is in contact with a surface plate and the surface is slid in contact with the object to be polished to polish the object to be polished.
In FIG. 1, the upper side is a surface 1s of a polishing pad 1 used for polishing an object to be polished, and the lower side is a back surface 1b.
The polishing pad 1 is subjected to a treatment for removing the bubble film on the surface side of the bubbles Fs located on the outermost surface side, and has a surface state in which the bubbles Fs are opened.
On the other hand, in the back surface 1b which is the lower side in FIG. 1, the process of opening the bubbles Fb is not performed, and a flat surface is formed by the bubble film.

Moreover, although the said foaming layer 10 of the polishing pad 1 in this embodiment is the whole being formed of the same polymer composition, it is divided into several (for example, 5 divisions) in the thickness direction, and each is divided. When the average bubble diameter is obtained, the foam is expanded in a state where the value gradually increases from the front surface 1s toward the back surface 1b, and the average bubble diameter is continuously increased in the thickness direction.
Then, the bubbles are coarsened toward the back surface side, and the bubble film is also thickened accordingly, and the foaming degree on the back surface 1b side is lower than that on the front surface 1s side. The side has a higher hardness than the surface side.

The thickness of the foamed layer 10 is not limited. However, when used for CMP in which precise finishing such as a semiconductor wafer is required, it is usually within a range of 0.5 mm to 10 mm. Either thickness is used.
In such a case, the hardness of the front surface 1s is 60 to 98 degrees in Shore A hardness, and the hardness of the back surface 1b is 20 to 70 degrees in Shore A hardness. "It is preferable from the viewpoint of prevention.
More preferable values for the hardness are 80 degrees or more on the front surface side and 30 to 75 degrees on the back surface side.
In addition, the partial hardness in this polishing pad can be measured by the method described in the examples.

The hardness of each part of the foamed layer 10 can be adjusted by selecting the material of the polymer composition used for forming the foamed layer 10 and controlling the foamed state.
In addition, it is preferable to employ | adopt a polyurethane composition as a polymer composition used for formation of the foaming layer 10 in the point which can adjust | require a required characteristic easily.
That is, the polyurethane composition can form the foamed layer 10 in that mechanical properties such as hardness and tensile strength can be adjusted by selecting an active hydrogen-containing organic compound such as a polyol compound and an isocyanate group-containing compound, respectively. Suitable as a material.

When the foam layer 10 is formed of a polyurethane composition, it includes, for example, an isocyanate group-containing compound, an active hydrogen-containing organic compound, and a foaming agent. If necessary, an antioxidant, an antioxidant, and a filling A polyurethane composition containing an agent, a plasticizer, a colorant, a fungicide, an antibacterial agent, a flame retardant, an ultraviolet absorber and the like can be used.
More specifically, the foamed layer 10 can be formed by preparing a liquid uncured composition containing the above components and foam-curing the uncured composition.

  The isocyanate group-containing compound is not particularly limited as long as it is a compound having an isocyanate group in the molecule. As the isocyanate group-containing compound, a compound having a plurality of isocyanate groups in the molecule is usually used.

As said isocyanate group containing compound, aromatic diisocyanate, aliphatic diisocyanate, alicyclic diisocyanate etc. can be used, for example.
In addition, as these isocyanate group containing compounds, the thing which combined the single thing or multiple things can be used.
Moreover, what is marketed can be used for an isocyanate group containing compound.
The proportion of the isocyanate group-containing compound in the uncured composition is preferably 30 to 70% by mass.

Examples of the aromatic diisocyanate include crude diphenylmethane diisocyanate (crude MDI) obtained by, for example, reacting an amine mixture obtained by condensing aniline and formaldehyde with phosgene in an inert solvent, and purifying the crude MDI. Diphenylmethane diisocyanate (pure MDI), polymethylene polyphenylene polyisocyanate (polymeric MDI), and modified products thereof can be used, and tolylene diisocyanate (TDI), 1,5-naphthalene diisocyanate, xylylene diisocyanate, 1 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate and the like can be used.
In addition, these aromatic diisocyanates can be used alone or in combination.

  Examples of the modified product of diphenylmethane diisocyanate include a carbodiimide modified product, a urethane modified product, an allophanate modified product, a urea modified product, a burette modified product, an isocyanurate modified product, and an oxazolidone modified product. Specific examples of such modified products include carbodiimide-modified diphenylmethane diisocyanate (carbodiimide-modified MDI).

  Examples of the aliphatic diisocyanate include ethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and 1,6-hexamethylene diisocyanate.

  Examples of the alicyclic diisocyanate include 1,4-cyclohexane diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, isophorone diisocyanate, and norbornane diisocyanate.

As the isocyanate group-containing compound, it is easy to handle in a liquid state at room temperature, has a lower vapor pressure than the TDI, is not designated as a specific chemical substance, and can reduce consideration for the working environment. MDI, the pure MDI, the polymeric MDI, or a modified product thereof is preferable.
Moreover, in terms of being liquid at room temperature and easy to handle, carbodiimide-modified MDI, polymeric MDI, or a mixture of these with MDI is preferable.

  The active hydrogen-containing liquid contains an active hydrogen-containing organic compound, and may further contain the catalyst, the foam stabilizer, and the like as necessary.

The active hydrogen-containing organic compound is an organic compound having in its molecule an active hydrogen group capable of reacting with an isocyanate group. Specifically, examples of the active hydrogen group include a hydroxy group, a primary amino group, and a secondary group. Functional groups such as amino groups and thiol groups can be mentioned.
In addition, the said active hydrogen containing organic compound may have only 1 type of the said functional groups in a molecule | numerator, and may have multiple types of this functional group in a molecule | numerator.

  As the active hydrogen-containing organic compound, for example, a polyol compound having a plurality of hydroxy groups in the molecule, a polyamine compound having a plurality of primary amino groups or secondary amino groups in the molecule, and the like can be used.

  Examples of the polyol compound include polyhydric alcohols having a molecular weight of 400 or less, polyols having a molecular weight exceeding 400, and the like.

  Examples of the polyhydric alcohol having a molecular weight of 400 or less include ethylene glycol, propylene glycol 1,3-propanediol, 1,3-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, Linear fat such as 1,6-hexanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, polyethylene glycol having a molecular weight of 400 or less, 1,8-octanediol, 1,9-nonanediol Diols such as neopentyl glycol, 3-methyl-1,5-pentanediol, 2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-methyl -1,8-octanediol Branched aliphatic glycols such as 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, hydrogenated bisphenol A and the like, and glycerin, trimethylolpropane, tributyrolpropane, penta Examples thereof include polyfunctional polyols such as erythritol and sorbitol.

  As this polyhydric alcohol, ethylene glycol and diethylene glycol are preferable in that a hardened product with high strength can be easily formed, moderate rigidity can be easily imparted to the polishing pad 1, and relatively inexpensive.

  Examples of the polyol prepolymer having a molecular weight exceeding 400 include polyether polyol, polyester polyol, polyester polycarbonate polyol, and polycarbonate polyol. In addition, as a polyol prepolymer, the polyfunctional polyol prepolymer which has 3 or more of hydroxyl groups in a molecule | numerator is also mentioned.

  Specifically, examples of the polyether polyol include polytetramethylene glycol (PTMG), polypropylene glycol (PPG), polyethylene glycol (PEG), and ethylene oxide-added polypropylene polyol.

  Examples of the polyester polyol include polybutylene adipate, polyhexamethylene adipate, and polycaprolactone polyol.

  Examples of the polyester polycarbonate polyol include a reaction product of a polyester glycol such as polycaprolactone polyol and an alkylene carbonate, and a reaction mixture obtained by reacting ethylene carbonate with a polyhydric alcohol and further reacting with an organic dicarboxylic acid. Product etc. are mentioned.

  Examples of the polycarbonate polyol include diols such as 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, polyethylene glycol, polypropylene glycol, or polytetramethylene glycol, phosgene, diallyl carbonate ( For example, a reaction product with diphenyl carbonate) or cyclic carbonate (for example, propylene carbonate) can be used.

  As this polyol prepolymer, those having a number average molecular weight of 800 to 8000 are preferable in that a cured product rich in elasticity is easily obtained. Specifically, polytetramethylene glycol (PTMG), ethylene Oxide-added polypropylene polyol is preferred.

These polyol compounds may be used alone or in combination of two or more.
In addition, it is preferable that the ratio of the said polyol compound in the said uncured composition is 10-50 mass%.

  Examples of the polyamine compound include 4,4′-methylenebis (o-chloroaniline) (MOCA), 2,6-dichloro-p-phenylenediamine, 4,4′-methylenebis (2,3-dichloroaniline), 3, 5-bis (methylthio) -2,4-toluenediamine, 3,5-bis (methylthio) -2,6-toluenediamine, 3,5-diethyltoluene-2,4-diamine, 3,5-diethyltoluene- 2,6-diamine, trimethylene glycol-di-p-aminobenzoate, 1,2-bis (2-aminophenylthio) ethane and 4,4′-diamino-3,3′-diethyl-5,5′- Examples thereof include dimethyldiphenylmethane.

As these active hydrogen-containing organic compounds, the aforementioned polyol compounds are preferable in that the reaction rate with the isocyanate group can be appropriately reduced.
Although it is a general-purpose product, it is preferable to prepare an uncured composition without using the polyamine compound such as MOCA, which is designated as a specific chemical substance and contains chlorine in the molecule.

  As the foaming agent, for example, an organic chemical foaming agent that decomposes by heating to generate a gas, a low boiling point hydrocarbon having a boiling point of −5 to 70 ° C., a halogenated hydrocarbon, water, a liquefied carbon dioxide gas, or the like alone or They can be used in combination.

Examples of the organic chemical foaming agent include azo compounds (azodicarbonamide, azobisisobutyronitrile, diazoaminobenzene, barium azodicarboxylate, etc.), nitroso compounds (N, N′-dinitrosopentamethylenetetramine, N, N′-dinitroso-N, N′-dimethylterephthalamide and the like), sulfonyl hydrazide compounds [p, p′-oxybis (benzenesulfonyl hydrazide), p-toluenesulfonyl hydrazide and the like] and the like.
Examples of the low boiling point hydrocarbon include butane, pentane, cyclopentane, and mixtures thereof.
Examples of the halogenated hydrocarbon include methylene chloride and HFC (hydrofluorocarbons).

In addition, as said foaming agent, water is preferable at the point that a finer bubble can be formed in hardened | cured material.
It is preferable that 0.01 to 0.5% by mass of water as the foaming agent is blended in the uncured composition.

As said catalyst, the metal catalyst which consists of organic acid and Sn, Zn, Co, Ni, Fe, Pb etc., or an amine catalyst is mentioned, for example.
The catalyst in the uncured composition is preferably blended in an amount of 0.0001 to 0.5% by mass in the uncured composition.

  Examples of the metal catalyst include tin octoate, tin naphthenate, dibutyltin dilaurate, and zinc octoate.

  Examples of the amine catalyst include triethylamine, dimethylcyclohexylamine, bis [(2-dimethylamino) ethyl] ether, 1,4-diazabicyclo [2.2.2] octane, 1,5-diazabicyclo [4.3.0]. And tertiary amine compounds such as non-5-ene, 1,8-diazabicyclo [5.4.0] undec-7-ene, and diethylbenzylamine.

  As the foam stabilizer, a conventionally known foam stabilizer such as polyether-modified silicone can be used. The said foam stabilizer can be used individually by 1 type or in combination of 2 or more types. The foam stabilizer is preferably blended in an amount of 5.0% by mass or less in the uncured composition.

  In addition, for additives such as antioxidants, anti-aging agents, fillers, plasticizers, colorants, fungicides, antibacterial agents, flame retardants, UV absorbers, etc., the polyurethane composition for constituting the polishing pad The additives generally used can be mentioned, and these additives are usually blended in the uncured composition at a ratio of 20.0% by mass or less.

  Examples of the polymer composition other than the polyurethane composition used for forming the foam layer 10 include a foamable epoxy resin composition, a foamable unsaturated polyester resin composition, and a foamable silicone resin composition. .

Next, a method for producing a foam layer (polishing pad) using such a forming material will be described.
As a production method for producing the polishing pad of the present embodiment, the polymer composition is poured into a mold having a flat accommodation space that is substantially the same shape as the foam layer, and the average cell diameter is continuously formed in the thickness direction. A foamed layer itself that has been changed in a mold, or a cylindrical foam having a different average cell diameter in the height direction is formed once, and then the foam is made to a predetermined thickness. And a method of producing a foamed layer by slicing into two.
The shape or the like of the mold is not particularly limited, and a mold that is widely used for forming a foam can be used.

In addition, it can be said that the method of directly producing the foamed layer itself with a mold is suitable in that the adjustment of the foamed state inside is relatively easy and the slicing step and the like can be omitted.
Therefore, hereinafter, a method for manufacturing the polishing pad of this embodiment will be described while illustrating a mold suitable for adopting such a method.

That is, an example of a method for producing a polishing pad by foaming and curing the polyurethane composition in a mold will be described more specifically with reference to FIGS.
FIG. 2 is a top view of a mold used in the method for manufacturing a polishing pad according to the present embodiment, and FIG. 3 is a longitudinal sectional view passing through a substantially central portion of the mold.

In this polishing pad manufacturing method, for example, the following steps (a) to (e) are sequentially performed using the mold 100 as shown in FIGS.
(A) A liquid uncured polyurethane composition (curable polymer composition) by continuously mixing a mixed active hydrogen liquid containing the active hydrogen-containing organic compound and the foaming agent and an isocyanate-containing liquid containing the isocyanate-containing compound. Mixing process for producing
(B) a filling step of filling the uncured polyurethane composition into a mold having a flat accommodation space;
(C) taking out the foamed layer obtained by sufficiently foaming and curing the uncured polyurethane composition in a mold;
(D) An opening step of buffing the surface 1s of the taken-out foam layer 10 to open the bubbles Fs on the surface 1s.

Below, each process is demonstrated more concretely.
First, the mold 100 to be used will be described.

As shown in FIGS. 2 and 3, the foam layer molding die 100 is configured to open and close up and down, and is opposed to the lower die 4a and the lower die 4a that are substantially circular in top view. And an upper mold 4b having a substantially circular shape when viewed from above.
On the mold surface (upper surface) of the lower mold 4a, there is a recess 4a ₁ formed by recessing downward from the edge 4e ₁ along the circumferential direction with a predetermined distance inward. Is provided.
The mold surface (lower surface) of the upper mold 4b includes a protruding portion 4b ₁ formed by protruding downward from the edge 4e ₂ along the circumferential direction with a predetermined distance inward. It has been.
Further, the mold 100 is configured such that the protruding portion 4b ₁ of the upper mold 4b is fitted into the recessed portion 4a ₁ of the lower mold 4a with a slight clearance.
Further, when allowed to plunge the projecting portion 4b ₁ in the recessed portion 4a ₁ is concave join the club 4a ₁ before the front end surface of the bottom surface and the projecting portion 4b ₁ of the concave join the club 4a ₁ is in contact The lower mold 4a and the upper mold 4b are configured so that the outer area of the projection 4 and the outer area of the protrusion 4b ₁ are in contact with each other.
That is, the lower mold 4a and the upper mold 4b, together, flat receiving space between the lowermost surface of the projecting portion 4b ₁ of the bottom and upper mold 4b of recessed portion 4a ₁ in time obtained by closest 8 (cavity 8) is formed.

Furthermore, the upper mold 4b is formed with a through-hole 9 penetrating in the thickness direction at the protruding portion so that the liquid uncured polyurethane composition can flow into the cavity 8.
The upper mold 4b is in contact with a spherical surface provided at the tip of the tubular member 6 for injecting the uncured polyurethane composition into the mold 100, and the opening of the tubular member 6 is formed in the through hole. In order to align with 9, the upper surface is recessed into a spherical shape around the through hole 9 to form a spherical portion 9a.

The flow path of the uncured polyurethane composition to the cavity 8 is not limited to the through-hole 9 and penetrates the upper mold 4b, but penetrates the lower mold 4a from below the mold 100. It may be a thing.
Further, the uncured polyurethane composition is caused to flow into the cavity 8 through a path that penetrates the lower mold 4a from the side and opens to the mold surface of the lower mold 4a at a location that defines the side surface 8a of the cavity 8. It is also possible.
For introducing the uncured polyurethane composition into the mold 100, a RIM molding machine having a mixing head for mixing the mixed active hydrogen liquid and the isocyanate-containing liquid can be used.

Although the size of the mold 100 is not particularly limited, a mold having a maximum volume that can be taken by the cavity is generally about 100 mL to 300 L.
The shape of the cavity 8 formed inside the mold 100 is substantially the same as the foamed layer to be produced here.
Also, the mold can be applied to a method of forming a cylindrical foam and slicing the foam. At this time, at least the shape of the cavity in the top view is the top view of the foam layer. It is preferable to form the mold so as to be approximately the same shape as the above.

More specifically, the shape of such a cavity is preferably formed to be a disk shape having a diameter of 30 to 200 cm and a thickness of about 1.5 to 100 mm, for example.
In addition, as a material of the said metal mold | die 100, a metal, resin, etc. are mentioned, for example.

  In addition to such molds, those having a flat upper mold with no protrusion toward the lower mold, the upper mold side is also provided with a recessed portion corresponding to the recessed portion of the lower mold, The upper mold and the lower mold are configured to have a cavity formed by the recessed portions, the mold frame and a bottom plate that closes the mold frame from below, and the upper side is open. Various types of molds such as those can be used in place of the molds illustrated above.

  Next, the above-described (a) mixing step, (b) filling step, (c) taking-out step, and (d) opening step will be described.

(A) Mixing step As described above, this mixing step continuously mixes the active hydrogen-containing organic compound and the mixed active hydrogen solution containing the blowing agent with the isocyanate-containing solution containing the isocyanate-containing compound. This is a step of producing a liquid uncured polyurethane composition (curable polymer composition).

In addition, the said mixed active hydrogen liquid can further contain the said catalyst, the said foam stabilizer, etc. in the said active hydrogen containing liquid and the said foaming agent as needed.
The mixed active hydrogen liquid containing the active hydrogen-containing liquid and the foaming agent and the isocyanate-containing liquid are prepared in advance and stored separately until the two liquids are mixed. The curing reaction hardly proceeds in each of the two liquids, and the two liquids can be stored for a relatively long time, so that there is an advantage that the time management of the process in manufacturing the polishing pad is facilitated.

The mixing step is preferably performed immediately before the filling step.
By carrying out immediately before the filling step, the filling step can be carried out before the urethanization reaction in the curable polymer composition proceeds excessively, and the filling step can be easily carried out.
Specifically, as soon as the mixed active hydrogen solution and the isocyanate-containing solution are mixed, the active hydrogen group of the active hydrogen-containing organic compound contained in the mixed active hydrogen solution and the isocyanate group contained in the isocyanate-containing solution Since the reaction with the isocyanate group of the contained compound proceeds, and the viscosity of the curable polymer composition increases with the progress of this reaction, etc., the filling of the curable polymer composition in the subsequent filling step has progressed over time. Can gradually become difficult.
Therefore, by performing the mixing step immediately before the filling step, the filling step can be performed before the viscosity of the obtained curable polymer composition is excessively increased.
Further, when the foaming agent is water, by mixing the mixed active hydrogen liquid and the isocyanate-containing liquid, the curability can be achieved in a relatively short time due to the reaction between the foaming water and the isocyanate group. Since the polymer composition starts to foam, the mixing step is preferably performed immediately before the filling step in order to perform the filling step before the foaming in the curable polymer composition proceeds excessively.

In the operation of performing the mixing step immediately before the filling step, preferably, in the mixing step, the active hydrogen-containing liquid and the mixed active hydrogen liquid containing the blowing agent and the isocyanate-containing liquid continuously collide with each other. It can be carried out by preparing a liquid uncured polyurethane composition.
Such an operation can be performed by using, for example, a reaction injection molding machine (RIM molding machine) described later.
Specifically, in such an operation, the uncured polyurethane composition is prepared as a fluid by colliding the mixed active hydrogen liquid and the isocyanate-containing liquid and mixing the two liquids.

When the foaming agent is water, it is preferable to carry out the filling step before the foaming phenomenon due to the reaction between water and the isocyanate group occurs, but it affects the reaction between water and the isocyanate group. The reactivity can be adjusted by including a component in the uncured polyurethane composition.
For example, by adjusting the type and amount of the tertiary amine compound to be contained in the uncured polyurethane composition, it is possible to adjust the time from the start of the mixing step to the start of the foaming phenomenon. There are advantages.
In addition, the reaction rate between the active hydrogen of the active hydrogen-containing organic compound and the isocyanate group of the isocyanate-containing compound can be moderately reduced, and the increase in viscosity of the uncured polyurethane composition before the foaming phenomenon can be suppressed, It is preferable that the active hydrogen-containing liquid contains the polyol compound.
In this respect, the uncured polyurethane composition comprises an isocyanate-containing liquid containing an isocyanate group-containing compound, an active hydrogen-containing liquid containing the polyol compound, water, and a tertiary amine compound as the catalyst. Is preferred.

  In the mixing step, it is preferable that the viscosity of the isocyanate-containing liquid and the mixed active hydrogen liquid is 2000 mPa · s or less at 40 ° C., respectively. By setting the viscosity of the isocyanate-containing liquid and the mixed active hydrogen liquid to 2000 mPa · s or less at 40 ° C., respectively, the efficiency at the time of uniformly mixing the two liquids becomes higher. Therefore, there is an advantage that the foaming agent can be easily mixed, the distribution of the foaming agent in the uncured polyurethane composition becomes more uniform, and the foaming can be further suppressed from varying depending on the site.

  The viscosity is 40 ° C. using a B-type viscometer (manufactured by Toki Sangyo Co., Ltd.). 1 or No. 2. A value obtained by measuring for 1 minute at a rotational speed of 6, 12, 30, or 60 rpm.

The mass ratio of the isocyanate-containing liquid and the mixed active hydrogen liquid is that the isocyanate-containing liquid / mixed activity is such that when the resulting foam layer is used alone as a polishing pad, appropriate hardness and elasticity can be imparted to the polishing pad. It is preferable that it is hydrogen liquid = 15 / 85-85 / 15.
Moreover, it is preferable that the said foaming agent with respect to a total of 100 mass parts of the said isocyanate containing liquid and the said active hydrogen containing liquid is 0.01-1.0 mass part.

(B) Filling step In the filling step, if the mold 100 illustrated in FIGS. 2 and 3 is used, the liquid inside the flat internal space (cavity 8) produced in the mixing step is used. An operation of injecting the curable polymer composition to fill the cavity 8 is performed.
Specifically, the filling step is usually performed immediately after the mixing step. For example, the mixing active hydrogen solution and the isocyanate-containing solution are collided with each other using a RIM molding machine. And the method of discharging | emitting the obtained uncured polyurethane composition from this RIM molding machine and inject | pouring in the metal mold | die 100 hold | maintained in the said 1st state through the said through-hole 9 is mentioned.
In the filling step, the amount of the uncured polyurethane composition filled in the internal space depends on the extent to which the uncured polyurethane composition increases the apparent volume by foaming after filling (foaming degree). , 50-100% of the volume of the internal space (cavity).

In addition, in RIM (Reaction Injection Molding) molding method, a curable polymer composition is prepared by mixing two or more fluids that cause a curing reaction when mixed, and the curable polymer composition is in a liquid state. It is a molding method in which a molded product is obtained by pouring into a mold or the like and demolding after curing.
In the manufacturing method for manufacturing the polishing pad of this embodiment formed of a single foam layer, the mixing step, the filling step, and the like can be performed by this RIM molding method.

  In this RIM molding method, for example, at least two raw material tanks capable of adjusting the temperature, a metering pump for circulating each of the isocyanate-containing liquid and the mixed active hydrogen liquid at a predetermined flow rate, the isocyanate-containing liquid and the mixed active hydrogen A RIM molding machine provided with a mixing head as a place where the liquid is mixed by collision, a mixing head hydraulic unit for driving a shaft for controlling mixing of the isocyanate-containing liquid and the mixed active hydrogen liquid, and the like can be used. .

Then, for example, each of the isocyanate-containing liquid and the mixed active hydrogen liquid is put in a raw material tank and held at a desired temperature, and each of the isocyanate-containing liquid and the mixed active hydrogen liquid is desired by a metering pump. Circulating at a flow rate, and driving the shaft in the mixing head with a hydraulic unit for the mixing head, causing the isocyanate-containing liquid and the mixed active hydrogen liquid to flow out for a predetermined time and colliding and mixing in the mixing head. The mixed active hydrogen liquid and the isocyanate-containing liquid can be continuously mixed in a relatively short time.
Moreover, it becomes easy to advance hardening reaction of an uncured polyurethane composition at desired temperature by putting each of the said isocyanate containing liquid and said mixed active hydrogen liquid in a raw material tank, and hold | maintaining at desired temperature.

In addition, by adopting a molding method using the RIM molding machine, the filling step can be performed while the curing reaction of the uncured polyurethane composition does not proceed excessively.
That is, by circulating each of the isocyanate-containing liquid and the mixed active hydrogen liquid to a desired flow rate by a metering pump of a RIM molding machine, these are mixed in a mixing head in a relatively short time, and quickly. It can be poured into the receiving space of the mold.
In addition, the circulation as described above also has an advantage that a desired amount of the uncured polyurethane composition can be easily injected with high accuracy.

In the RIM molding method, the curable fluid obtained by continuously colliding two or more liquids usually contains each raw material in a predetermined ratio.
However, just before the filling of the mold is completed, the stirring rate of each raw material is likely to be insufficient due to a decrease in the ejection amount, and precise control of the flow rate is likely to be difficult. It is easy to generate an error.
Therefore, it is preferable to provide a liquid reservoir in the section from the RIM molding machine to the cavity of the mold to exclude the uncured polyurethane composition that may cause this problem.
Thus, by providing a liquid reservoir that can temporarily store the liquid curable polymer composition after flowing out of the RIM molding machine and before flowing into the cavity, characteristics and foaming caused by unevenness of the forming material The possibility that unexpected disturbance of the state is formed in the foamed layer can also be reduced.

  In order to form the foamed layer in which the average cell diameter is continuously reduced from any part in the thickness direction toward the back surface side, the uncured polyurethane composition (curable polymer composition) is usually used. The uncured polyurethane composition is allowed to flow into the mold in a state in which the temperature of the mold 100 is different from the surface temperature of the mold 100, so that the surface portion (outer portion of the cavity) in contact with the mold surface The foamed state can be made different from the foamed state inside the cavity, and the continuous change can be easily formed.

For example, the mold surface (surface of the recessed portion) of the lower mold 4a is set to a temperature higher than that of the uncured polyurethane composition, and the mold surface (surface of the protruding portion) of the upper mold 4b is the same as the uncured polyurethane composition, or When the uncured polyurethane composition is allowed to flow at a lower temperature, in the vicinity of the surface of the lower mold 4a having a high temperature, the curing reaction proceeds rapidly with foaming, but in the vicinity of the surface of the upper mold 4b having a lower temperature, Since the curing reaction occurs after the foaming proceeds from the lower mold 4a side, rough bubbles are formed on the lower mold 4a side, and the degree of foaming is low (apparent density is high). As the distance from the mold 4a increases, the average cell diameter gradually becomes finer, the foaming degree is high, and the state becomes rich in flexibility.
Thus, for example, the surface temperature of one of the inner wall surfaces of the mold facing to form the flat accommodation space (cavity) is higher than that of the uncured polyurethane composition, and the other surface By allowing the uncured polyurethane composition to flow in at a temperature lower than the one surface temperature, a foamed layer whose average cell diameter continuously changes in the thickness direction can be formed more easily. Can do.

The temperature of the uncured polyurethane composition, the lower mold 4a, and the upper mold 4b depends on the components of the uncured polyurethane composition, the thickness of the foamed layer, etc., but usually the uncured polyurethane composition The surface temperature of any one of the lower mold 4a and the upper mold 4b is 60 to 90 ° C, and the other surface temperature is 30 to 60 ° C, which is lower than this. The continuous change in the foamed state can be formed in the thickness direction of the foamed layer.
If the thickness of the foamed layer is about 1.5 to 10 mm, when the temperature of the uncured polyurethane composition is T1 (° C.), the one surface temperature is (T1 + 15 ° C.) to (T1 + 60 ° C.), By setting the other surface temperature to (T1-10 ° C.) to (T1 + 40 ° C.), a continuous change in the foamed state can be favorably formed in the thickness direction of the foamed layer.

In general, the polishing pad is formed in a disk shape having a thickness of 0.5 to 10 mm and a diameter of 300 to 2000 mm, and a plurality of grooves and minute recesses are formed on the surface as necessary. is there.
And when the polishing layer is constituted by a foamed layer formed by foaming a polyurethane composition, the surface side is usually a specific gravity of 0.1 to 0.9, preferably a specific gravity of 0.2 to 0.8, The specific gravity is preferably 0.4 to 0.6, and the Shore A hardness is preferably 80 degrees or more.
The hardness of the foamed layer can be controlled by the foamed state. For example, the amount of polyamine compound such as MOCA in the uncured polyurethane composition and the amount of aromatic diisocyanate such as MDI are adjusted. Adjustment is also possible.

(C) Extraction step This extraction step is a step of sufficiently foaming and curing the uncured polyurethane composition in the mold after the filling step, and then removing the formed foam layer from the mold.

  The method for curing the uncured polyurethane composition is not particularly limited, for example, a method for maintaining the mold temperature in the previous filling step, and after completion of the filling step, it is cooled to about room temperature and is directly for about 10 to 60 minutes. For example, a method of leaving the mold, and conversely, a method of increasing the mold temperature after completion of the filling step can be exemplified.

  In order to facilitate the removal of the foam layer from the mold in this removal step, a mold release agent is applied to the inner surface forming the flat accommodation space of the mold before the filling step. It is preferable to apply it.

(D) Opening Step This opening step performs a process of buffing the surface 1s of the foam layer taken out in the take-out step to open the bubbles Fs on the surface 1s.
The foamed layer taken out in the taking-out step can be used as it is for the polishing pad 1, but when the foamed layer 10 is used as a polishing layer for polishing an object to be polished, the surface thereof is used. By carrying out the opening step for opening bubbles in the process, abrasive grains used for polishing and polishing debris generated by polishing can be taken into the opened bubbles, and scratches or the like are generated on the object to be polished. It is possible to perform excellent surface polishing while preventing the above.

The polishing pad 1 having such a foamed layer 10 as a polishing layer has the average bubble diameter continuously changed in the thickness direction. In the illustration in the above embodiment, the back surface 1b is on the front surface 1s side. The average bubble diameter is larger than that.
That is, on the side in contact with the object to be polished, fine bubbles are formed with a high foaming degree, and are formed more flexibly than the back side.
Therefore, excellent polishing performance can be exhibited, for example, the occurrence of “sag” of the edge portion on the object to be polished can be prevented.
In addition, as in the polishing pad described in Japanese Patent Application Laid-Open No. 2003-220550, the bubble diameter is not changed stepwise by forming an interface, but the average bubble diameter is continuously changing. Therefore, local stress concentration in the foamed layer is suppressed, and generation of delamination and the like can be prevented.
In addition, according to the manufacturing method of the polishing pad in this embodiment, since the continuous change of the average bubble diameter in the thickness direction can be easily adjusted, the shape and material of the object to be polished, the required surface Depending on the quality and the like, it is possible to easily produce an optimum polishing pad for each.

In the above, as an embodiment of the present invention, the description of the present invention is mainly focused on the case where the polyurethane composition is water-foamed in terms of easy adjustment of the properties of the foam layer and easy formation of fine bubbles. However, in the present invention, the foaming agent is not limited to water, and the polymer composition for forming the foamed layer is not limited to the polyurethane composition.
Further, in the present embodiment, the polishing pad constituted by a single foam layer is exemplified in that the interface that affects the product life as a polishing pad is not substantially formed. The case where a foam layer having such a continuous change in average cell diameter is laminated with another underlayer or the like and used as a polishing layer is also within the intended range of the present invention.

  Furthermore, in the present embodiment, the foamed layer is a polishing layer in that the effect of the present invention that stress due to friction with an object to be polished is likely to act and that stress concentration can be prevented can be exhibited more significantly. However, the case where the foamed layer is used as a base layer and another polishing layer is formed on the surface side to form a polishing pad is also within the intended scope of the present invention.

  Further, in the present embodiment, the foam layer in which the average cell diameter is continuously expanded from the front surface side to the back surface side is illustrated, but conversely, the average cell diameter is continuously increased from the back surface side to the front surface side. Is also within the range intended by the present invention. For example, as shown in FIG. 4 (partial sectional view), the average bubble diameter is continuously increased from the surface 1s ′ to the middle portion in the thickness direction. And a foamed layer 10 ′ having a region (constant region B) in which the average cell diameter is constant between the intermediate portion and the back surface 1b ′. The polishing pad is also within the intended scope of the present invention.

Further, for example, as shown in FIG. 5 (partial cross-sectional view), after the average bubble diameter is continuously reduced from the front surface 1 s ″ to the middle portion in the thickness direction, the intermediate portion to the rear surface 1b ″. A polishing pad provided with a foamed layer 10 ″ with an average cell diameter continuously increased in between is also within the intended scope of the present invention.
In addition, it is not limited to these, Various foaming states are employable.

In this embodiment, the case where a water-foamable curable polyurethane composition is allowed to flow into a mold by a RIM molding machine is exemplified. However, the curable polymer composition that is allowed to flow into the mold is a polyurethane composition. However, the present invention is not limited to water foaming.
In addition, in the present embodiment, the polishing pad manufacturing method of the present invention is mainly described from the viewpoint of foam layer productivity and quality stability. However, a molding method other than RIM molding is described. Can also be adopted.
Furthermore, the opening step and the like can be omitted depending on the function of the foam layer required for the polishing pad.

  Regardless of the above, in the polishing pad or the manufacturing method of the polishing pad, conventionally known technical matters can be employed in the present invention as long as the effects of the present invention are not significantly impaired.

  EXAMPLES Next, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to these.

Example 1
(Mixed active hydrogen solution)
The mixed active hydrogen solution was adjusted according to the following formulation.

Actol EP-3033 (trade name PPG-based polyol, manufactured by Mitsui Chemicals) 100 parts by weight diethylene glycol 33 parts by weight DABCO-33LV (trade name, amine-based catalyst, manufactured by Air Products) 0.15 parts by weight SH-193 (product) Name, foam stabilizer, manufactured by Toray Silicon Co., Ltd., modified silicone) 2 parts by mass ADEKATAB 465E (trade name, tin-based catalyst, manufactured by ADEKA Corporation) 0.003 parts by mass pure water 0.20 parts by mass

Using a RIM molding machine (manufactured by Canon Inc.)
(A) Millionate MTL heated to 40 ° C. (polyisocyanate, functional group = 2, manufactured by Nippon Polyurethane Co., Ltd.)
(B) The above-mentioned mixed active hydrogen solution heated to 40 ° C. at a ratio of (a) :( b) = 45 parts by mass: 55 parts by mass (casting speed = 250 g / second, pressure = 150 kgf / cm ^2. ((a), (b) Both liquids are the same)) Mixing step is carried out, and the mixture is heated to 65 ° C. in a closed mold (accommodating space = square with a side of 85 cm × gap 3.4 mm) A filling step of casting 1250 g (total amount of casting) was carried out, and a taking out step was carried out after being left for 15 minutes and foamed and cured in the mold.
The demolded sheet was after-cured in an oven at 100 ° C. for 24 hours to obtain a foam sheet (foamed layer) having an overall apparent specific gravity = 0.50 and a hardness of 90 degrees (Shore A).
A cross-sectional photograph of this foam sheet is shown in FIG.

Also from this cross-sectional photograph, it can be seen that the average bubble diameter of the polishing pad of Example 1 is continuously changed in the thickness direction (vertical direction in FIG. 6).
And based on this cross-sectional photograph, when the average bubble diameter in the area | region of the thickness direction upper side and the average bubble diameter in the lower area | region were observed, it became as follows.

Upper side: average bubble diameter 44.1 μm, bubble occupancy 62.8%
Lower side: average bubble diameter 64.6 μm, bubble occupancy 47.2%

At this time, the average bubble diameter was determined as follows.
(Measurement method of average bubble diameter)
The SEM image of the cross section of the pad is separated by binarizing the color of the pore portion and the other portion by image analysis software (manufactured by Mitani Corporation, product name: WinROOF), and any 0.5 mm × 0 in the SEM image The area ratio and the number of bubbles in the pore portion within a range of 0.5 mm were obtained.
Next, the average bubble diameter was calculated by dividing the total bubble area by the number of bubbles.
In addition, correction | amendment by the bubble diameter variation by a cut surface is not carried out.

Further, the Shore A hardness and specific gravity were measured for the upper part and the lower part in FIG.
As a result, values of the upper side (hardness: 85, specific gravity 0.44) and the lower side (hardness: 96, specific gravity 0.80) were observed.
In addition, the measurement of hardness and specific gravity was implemented as follows, respectively.

(Shore hardness)
Measurement was performed based on JIS K6253.
Specifically, the upper part of the pad was measured by removing the lower part of the pad with a buff and overlapping only the upper part so that the total thickness was about 6 mm.
Similarly, on the lower side of the pad, the upper part of the pad was removed by buffing, and only this lower part was measured so that the total thickness was about 6 mm.

(specific gravity)
It measured based on JIS K7222.
Specifically, for the upper side of the pad, the lower side of the pad was removed by buffing, and the calculation was made from the thickness and weight of only this upper part.
Similarly, the upper side of the pad was also removed by buffing, and the thickness was calculated from the thickness and weight of only the lower part.

As can be seen from FIG. 6 and the like, in the lower part, the temperature rapidly rises in contact with the mold surface, so that the curing reaction occurs simultaneously with the foaming reaction, and as a result of curing with the resin rich (low foaming), the high specific gravity High hardness.
On the other hand, the upper part is formed with a low specific gravity and a low hardness because the temperature rises moderately and curing occurs after sufficient foaming.

(Example 2)
A polishing pad was produced in the same manner as in Example 1 except that the mold temperature was 40 ° C. for the upper mold and 60 ° C. for the lower mold.
FIG. 7 shows a cross-sectional photograph (SEM photograph) of the obtained polishing pad.
When the average bubble diameter and bubble occupancy were measured in the same manner as in Example 1 in (1) to (3) in FIG.

  From the above, it can be seen that according to the present invention, a polishing pad effective for improving the quality of polishing can be obtained.

  1: polishing pad, 1s: front surface, 1b: back surface, 4a: lower mold, 4b: upper mold, 10: foam layer

Claims (6)

  A polishing pad comprising a foamed layer formed by foaming a polymer composition, wherein the foamed layer continuously changes the average cell diameter in the thickness direction.   The polishing pad according to claim 1, wherein a polishing layer on which the object to be polished is slidably contacted is formed by the foam layer to polish the object to be polished.   The polishing pad according to claim 2, wherein the foamed layer forming the polishing layer continuously increases the average cell diameter from the surface side in sliding contact with the object to be polished toward the back surface side.   The polishing pad according to any one of claims 1 to 3, wherein the polymer composition is a polyurethane composition. In order to produce a polishing pad having a foam layer formed by foaming a polymer composition, a liquid curable polymer composition containing a foaming agent is produced, and the curable polymer composition is stored in a flat storage space A method for producing a polishing pad, wherein the foamed layer is formed by foaming and curing in a mold having:
The curable polymer composition in a state where the temperature of the curable polymer composition and the surface temperature of the mold are different from each other in order to form the foamed layer whose average cell diameter continuously changes in the thickness direction. Is introduced into the mold, and the foamed state of the surface portion in contact with the mold surface is made different from the foamed state inside.   One of the inner wall surfaces of the mold facing to form the flat storage space has a surface temperature higher than that of the curable polymer composition, and the other has a surface temperature of the one of the molds. The method for producing a polishing pad according to claim 5, wherein the curable polymer composition is allowed to flow into the mold in a state where the temperature is lower than the surface temperature.