JP2006231429A - Polishing pad and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure polishing stability of a temperature change and configurational or structural polishing stability by making a visco-elastic behavior stable without presenting a glass transition point in a work temperature region of a polishing pad. <P>SOLUTION: This polishing pad is formed by single polyurethane foam composed of a main raw material made of polyol and isocyanate and various kinds of auxiliary raw materials. The glass transition point of the polyurethane foam is made to exist in the range <20°C or >50°C. D hardness stipulated to the ASTM 2240 is made the range of 40 to 70. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polishing pad and a method for manufacturing the same, and more particularly, to chemical mechanical polishing (CMP) capable of polishing a member such as a semiconductor wafer that requires flatness of its surface with high accuracy. The present invention relates to a polishing pad that can be suitably used and a method for producing the same.

  The recent remarkable advancement of information technology equipment such as computers has been achieved by high performance and high integration by wiring multiplexing of VLSI devices constituting a built-in CPU (central processing unit). This multiplexing is achieved by increasing the surface flatness (hereinafter simply referred to as “flatness”) of the silicon wafer that is the source of VLSI, and is generally ultra-precision polishing such as CMP (Chemical Mechanical Polishing). The polishing pad which comprises is suitably employ | adopted. For polishing, (1) a slurry in which fine abrasive grains are suspended in a polishing pad being polished is appropriately supplied, or (2) abrasive grains are contained (fixed) in the polishing pad. A so-called fixed abrasive polishing pad is employed.

Here, in (1), the problem is that the slurry used is expensive. In (2), while it is less expensive than (1), it has a high hardness to achieve a high polishing rate. There is a problem that the fixed abrasive scratches the wafer that is the object to be polished. In order to deal with this problem, the invention “Polishing method and apparatus” disclosed in Patent Document 1 and the invention “Polishing pad” disclosed in Patent Document 2 have been devised. All of these control the glass transition point (temperature) of the polishing tool and polishing pad that are in direct contact with the object to be polished, and suppress the generation of scratches by ensuring flexibility, and in a specific temperature range. The deterioration of the polishing stability due to the temperature change is avoided.
JP 2003-220552 A JP 2004-235446 A

  The invention according to [Patent Document 1] simply sets the polishing operation temperature to be equal to or higher than the glass transition point of the polishing tool. For this reason, for example, for the purpose of increasing the polishing rate, physical properties such as hardness are prioritized, and it is impossible to apply to a slurry or a polishing pad whose glass transition point is outside the range where polishing work is possible. . In the invention according to [Patent Document 2], a polishing pad is formed from two resins having a glass transition point outside the temperature at which the polishing operation is carried out (working temperature), so that the glass transition point is expressed in the working temperature region. This allows polishing under flexible conditions. However, the polishing pad obtained by this method shows a lot of fine peaks due to the unstable behavior of the viscoelasticity between the glass transition points of the two resins due to problems such as compatibility of the resins used. The polishing rate and the like fluctuate due to changes in the working temperature, and stable polishing cannot be expected.

  Further, in order to (a) reduce scratches and (b) achieve stable polishing of an object to be polished, the structure and shape of the polishing pad are also important. Basically (a) In order to reduce scratches, a structure that increases flexibility is suitable. In addition, (b) stable polishing is substantially determined by the polishing uniformity achieved by holding a uniform slurry in a polishing pad using a slurry, and by the flatness of the surface in a fixed abrasive polishing pad. The And as a structure which improves a softness | flexibility, the foam structure which has a bubble on the surface is suitable. In this case, the achievement of a high polishing rate by improving the slurry retention and the reduction of scratches due to the discharge of polishing residue generated during polishing can be expected. And, as a method of using a polymer material capable of controlling the glass transition point as a foam, a slab foaming method by chemical foaming that can be mass-produced and has high selectivity of raw materials and can be appropriately selected. It is.

  However, the foam obtained by the slab foaming method is difficult to control the cell diameter and density for holding the slurry, and varies depending on the site, so the uniformity of holding the slurry is poor. Moreover, since the lump of the produced foam is subjected to slicing or the like to obtain a polishing pad having a required shape, the flatness is low. In particular, a polymer material is difficult to stably cut out due to its viscoelasticity, and it is difficult to increase the flatness in terms of material. Therefore, the control of the glass transition point improves the polishing stability according to the temperature change, but does not ensure the geometrical or structural polishing stability.

In order to overcome the above-mentioned problems and achieve the intended purpose, a polishing pad according to the present invention is a polishing pad formed from a single polyurethane foam composed of a main raw material consisting of polyol and isocyanate and various auxiliary raw materials. Because
The polyurethane foam has a glass transition point in a range lower than 20 ° C. or higher than 50 ° C., and has a D hardness defined in ASTM 2240 in a range of 40 to 70.

In order to overcome the above-mentioned problems and achieve the intended purpose, a polishing pad manufacturing method according to another invention of the present application is a single polyurethane foam composed of a main raw material consisting of polyol and isocyanate and various auxiliary raw materials. A method for producing a polishing pad molded from
As the polyol, those having a number average molecular weight in the range of 3,000 to 10,000 are used, and an amine compound and a glycol are used in combination as chain extenders which are various auxiliary materials, and an NCO index is set. As a range of 100-200,
After dissolving an inert gas with respect to the polyol, it is mixed with isocyanate and various auxiliary materials to form a gas-dissolved raw material,
Injecting the gas-dissolved raw material into the mold under a regulated pressure,
By returning to the normal pressure immediately after the required amount of the gas-dissolved raw material is injected into the mold,
The polyurethane foam has a glass transition point in a range of at least less than 20 ° C. or more than 50 ° C., and a polishing pad in which the size of the formed cell (20) is homogenized is produced. To do.

  According to the polishing pad and the method for producing the same according to the present invention, a single polyurethane is used as a raw material, the number average molecular weight of the raw material polyol is within a certain range, and a specific substance is used as a chain extender. By setting the NCO index within the required range, the glass transition points of the soft segment and the hard segment are made to be lower than 20 ° C. and higher than 50 ° C., respectively, and the D hardness specified in ASTM 2240 is set to 40 to 70. As a range, it is possible to manufacture a polishing pad that can achieve a reduction in scratches on an object to be polished and a high polishing stability against a temperature change while maintaining performance such as a polishing rate. In addition, a gas-dissolved raw material in which an inert gas is dissolved in each raw material is injected into a mold under pressure adjustment by a reaction injection molding method, and after completion of the injection, the pressure is returned to normal pressure to produce a polishing pad. It is possible to provide fine cells uniformly corresponding to the shape, and improve the polishing stability derived from the outer shape and structure of the polishing pad.

  Next, a polishing pad and a method for manufacturing the same according to a preferred embodiment of the present invention will be described with reference to a preferred embodiment. The inventor of the present invention uses a single polyurethane foam as a material constituting the polishing pad, sets the glass transition point of the polyurethane foam to a required value for each of the soft segment and the hard segment, and is defined in ASTM 2240. It has been found that by setting the D hardness to be in the range of 40 to 70, it is possible to improve the polishing stability against temperature change while maintaining the polishing rate and reduce the scratches generated on the polishing object. In addition, an inert gas is dissolved in the polyurethane foam, and a polishing pad is molded by a reaction injection molding method (hereinafter referred to as RIM molding method) under control adjusted to a predetermined pressure, so as to cope with complicated shapes and fine. It has been found that a polishing pad can be manufactured which can be equipped with uniform cells and can improve the polishing stability derived from the outer shape and structure of the polishing pad. In the present invention, the glass transition point is defined to indicate the peak temperature of tan δ obtained when the viscoelastic behavior measured under conditions of a frequency of 1 Hz and a heating rate of 3 ° C./min is measured.

  The polishing pad according to the present example is formed from a single polyurethane foam basically composed of polyol and isocyanate, which are main raw materials, and various auxiliary raw materials. This polyurethane foam is such that the glass transition points of the soft segment and the hard segment constituting the polyurethane foam are less than 20 ° C. and more than 50 ° C., respectively. For this reason, in the range of 20 to 50 ° C., a change in elastic loss (tan δ) that greatly affects various physical properties of the polishing pad is greatly suppressed. Note that the temperature range of 20 to 50 ° C. is a use temperature range of a polishing pad that is generally used. If there is no variation in hardness or the like with respect to a temperature change in this temperature range, polishing stability is always ensured. . In particular, the glass transition point of the soft segment that greatly affects tan δ is preferably less than −20 ° C. By setting the temperature to less than −20 ° C., the tan δ of the polishing pad becomes smoother in the temperature range of 20 to 50 ° C., which is the operating temperature range of the polishing pad.

  The soft segment is a region formed by polyol, which is one of the main raw materials for polyurethane foam. Basically, the glass segment has a glass transition point of less than 20 ° C by setting the number average molecular weight of the polyol to 3,000 or more. It is said. The hard segment is a region formed by isocyanate or the like, which is one of the main raw materials for polyurethane foam. By using together an amine compound having a number average molecular weight (described later) and glycol as a chain extender, the glass transition point of the hard segment is set to exceed 50 ° C. Further, the type of isocyanate is not particularly limited, but as will be described later ([0017]), by adopting a diphenylmethane diisocyanate (MDI) system, the moldability is improved and the glass transition point of the hard segment can be easily set to 50 ° C. It is preferable because it can be exceeded.

  As shown in FIG. 1, the glass transition point of the soft segment and the hard segment constituting the single polyurethane foam is set to a temperature range other than 20 to 50 ° C. that is the use temperature range of the polishing pad. Polishing stability against temperature change is achieved for the temperature range. On the other hand, when a polyurethane foam is mixed with two or more types that do not have a glass transition point in the temperature range to form a polishing pad material, the glass transition point is outside the temperature range, Variations in tan δ in the temperature range due to compatibility and the like are not avoided, and therefore polishing stability against temperature changes is not achieved. In particular, when the ratio of viscosity is high and tan δ is high, so-called heat stagnation occurs in the polishing pad, and the polishing stability against temperature changes further decreases. In FIG. 1, an example of tan δ of a polishing pad manufactured from a plurality of polyurethane foams is represented by an imaginary line.

About hardness, D hardness prescribed | regulated to ASTM2240 is made into the range of 40-70. The IZOD impact strength specified in JIS K 7110 is set to 9.5 kg / m ² or more. If the polishing pad is too soft, the polishing object cannot be properly polished, and if it is too hard, the polishing pad itself becomes brittle, and the polishing pad itself becomes brittle. It becomes. This D hardness and IZOD impact strength are highly dependent on the NCO index and the number average molecular weight of the polyol. The D hardness set in this numerical range ensures a polishing rate similar to that of a conventional polishing pad. The D hardness can also be expressed by a hard segment content calculated by ((crosslinking agent amount + isocyanate amount) / (total addition amount × 100)), and the value is 35 to 60%. The physical property value range of the IZOD impact strength is achieved by setting the D hardness to 70 or less, which is the upper limit.

  The NCO index is a value indicating a mixing ratio of polyol and isocyanate, and as this value increases, hard segments increase in polyurethane foam and hardness increases. In the present invention, the NCO index is in the range of 100 to 200. By making the isocyanate excessive in this way, allophanate bond, burette bond or isocyanurate bond is formed in the polyurethane foam, and a hard segment having a high heat resistance at the bonded portion is formed, thereby achieving the above-mentioned hardness. It becomes a cause. When this value is less than 100, the polyol becomes relatively excessive, the D hardness becomes less than 40, the polishing rate decreases, and the productivity deteriorates. On the other hand, if it exceeds 200, D hardness exceeds 70 and brittleness is developed, so that particles are generated and micro scratches are induced. The number average molecular weight of the polyol is in the range of 3,000 to 10,000 from the viewpoint of D hardness. Regardless of the NCO index, if it is less than 3,000, the hard segment predominates and the D hardness exceeds 70, and if it exceeds 10,000, the soft segment predominates and the D hardness is less than 40. Become.

  Examples of the polyol having a number average molecular weight in the range of 3,000 to 10,000 and suitable for the raw material of the polyurethane foam constituting the polishing pad according to the present invention include a high molecular weight polyol such as triol. Specific examples of the polyol that can be used include (1) polyester polyol, (2) polyester ether polyol, (3) polycarbonate polyol, and (4) polyether polyol. (1) Examples of the polyester polyol include aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid and azelain, aromatic dicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid and naphthalenedicarboxylic acid, such as hexahydrophthalate. An acid, an alicyclic dicarboxylic acid such as hexahydroterephthalic acid or hexahydroisophthalic acid, or an acid ester or an acid anhydride thereof, ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, 1,3 -Butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 1,8-octanediol, 1,9 -Dehydration condensation reaction with nonanediol or a mixture thereof Polyester polyols obtained by, polylactone diols obtained by ring-opening polymerization of lactones monomer such as ε- caprolactone or methyl valerolactone. (2) Polycarbonate polyols include ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6- At least one polyhydric alcohol such as hexanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 1,8-octanediol, 1,9-nonanediol or diethylene glycol, and diethylene carbonate, dimethyl carbonate or What is obtained by making it react with diethyl carbonate etc. is mentioned. (3) Polyester ether polyols include, for example, aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid or azelaic acid, for example aromatic dicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid or naphthalenedicarboxylic acid, such as hexa Dehydration condensation of alicyclic dicarboxylic acids such as hydrophthalic acid, hexahydroterephthalic acid or hexahydroisophthalic acid, or acid esters or anhydrides thereof with glycols such as diethylene glycol or propylene oxide adducts, or mixtures thereof Those obtained by the reaction are mentioned. (4) Examples of the polyether polyol include polyethylene glycol, polypropylene glycol and polytetramethylene ether glycol obtained by polymerizing cyclic ethers such as ethylene oxide, propylene oxide and tetrahydrofuran, and copolyethers thereof. Further, it can be obtained by polymerizing the aforementioned cyclic ether using a polyhydric alcohol such as glycerin, trimethylolethane, trimethylolpropane and the like. Moreover, in this invention, these polyols may be used independently and may use 2 or more types.

The isocyanate that is the other main raw material can be basically used as long as it can achieve the above-mentioned physical properties, and when a polishing pad is produced by the RIM molding method described later ([0021]). It is desirable that the reactivity is high. In order to facilitate reaction injection, the viscosity should be low, and the NCO% is preferably in the range of 20 to 30%, preferably 23 to 27%. Specifically, it is preferable to use a polymer aromatic isocyanate based on diphenylmethane diisocyanate having an average functional group number of 2.1 to 2.7. Usable isocyanates are, for example, diphenylmethane diisocyanate (MDI), crude diphenylmethane diisocyanate, tolylene diisocyanate (TDI), naphthalene diisocyanate (NDI), P-phenylene diisocyanate (PPDI), xylene diisocyanate (XDI), tetramethylene diisocyanate (TMXDI) Or an aromatic isocyanate such as tolidine diisocyanate (TODI), isophorone diisocyanate (IPDI), cyclohexyl diisocyanate (CHDI), hydrogenated XDI (H ₆ XDI) or hydrogenated MDI (H ₁₂ MDI), or Aliphatic isocyanates such as hexamethylene diisocyanate (HDI), lysine diisocyanate (LDI) or lysine triisocyanate (LTI) are listed. Is a urethane modified product of the isocyanate compound as its modified product, dimers, trimers, carbodiimide-modified products, allophanate modified products, views - let modified product, urea modified product or prepolymer - and the like. Among these organic isocyanates, aromatic substances are preferably used in consideration of reactivity and mechanical properties as a polishing pad, in particular, 4,4′-diphenylmethane diisocyanate alone or a mixture with 2,4′-diphenylmethane diisocyanate, crude Particularly preferred is one or a mixture of two or more selected from diphenylmethane diisocyanate (MDI) obtained by carbodiimide modification of a simple substance of diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate or a part of a mixture of 2,4′-diphenylmethane diisocyanate.

  As the amine compound which is a chain extender, a diamine having an amine equivalent of 138 or less, that is, a number average molecular weight of 276 or less is used. As the glycol, those having 2 to 5 functional groups and having a hydroxyl equivalent weight of 500 or less, that is, having a number average molecular weight of 2500 or less are used. If these numerical values are out of the range, the glass transition point of the hard segment will be 50 ° C. or less. And the addition amount of these chain extenders shall be the range of 10-50 weight part with respect to 100 weight part of polyols, and the mixing weight ratio shall be amine compound: glycol = 1: 1-1: 5. Here, the amine compound raises the NCO index and hard segment content by increasing the glass transition point in the hard segment and increasing the amount of puret and / or allophanate bonds with high heat resistance in the polyurethane foam. Has the effect of causing Glycol has the role of improving the formability of the polyurethane foam, which deteriorates with the use of amine compounds. Therefore, when the amount of the chain extender added is less than 10 parts by weight, the glass transition point in the hard segment does not exceed 50 ° C., or the D hardness is low and the polishing rate is insufficient, whereas it exceeds 50 parts by weight. And D hardness increases and brittleness increases. And if the amine compound: glycol and the amine compound are small, the glass transition point in the hard segment does not exceed 50 ° C., the D hardness is low and the polishing rate is insufficient, and if it is large, the moldability as a polishing pad deteriorates. .

As the amine compound, 2,4-toluenediamine, 2,6-toluenediamine, 3,5-diethyl-2,4-toluenediamine, 4,4'-di-sec-butyl-diaminodiphenylmethane, 4,4 ' -Diaminodiphenylmethane, 3,3'-dichloro-4,4'-diaminodiphenylmethane, 2,2 ', 3,3'-tetrachloro-4,4'-diaminodiphenyllemethane, 4,4'-diamino-3 3,3′-diethyl-5,5′-dimethyldiphenylmethane, 3,3′-diethyl-4,4′-diaminodiphenylmethane, 4,4′-methylene-bis-methylanthranilate, 4,4′-methylene- Bis-methylanthranic acid, 4,4′-diaminodiphenylsulfone, N, N′-sec-butyl-p-phenylenediamine, 3,3′-dichloro-4,4-diamino-5,5′-die Diamines exemplified by diphenylmethane, 1,2-bis (2-aminomethylthio) ethane, trimethylene glycol-di-P-aminobenzoate or 3,5-bis (methylthio) -2,4-toluenediamine Can be mentioned. In particular, aromatic diamines are expected to exhibit strength due to rigid aromatic rings, and due to their high reactivity, RIM molding (described later [0021]) can be easily performed. Examples of the glycol include ethylene glycol, propylene glycol or butanediol, polyhydric alcohols such as glycerin, trimethylolpropane, pentaerythritol or sorbitol, amines such as hexamethylenediamine, hydrazine, diethyltoluenediamine or diethylenetriamine, or monoethanol. Examples thereof include those obtained by adding a hydroxyl group to the terminal of amino alcohols such as amine, diethanolamine or triethanolamine.

  Known catalysts can be used, such as dimethylcyclohexylamine, N-methyldicyclohexylamine, triethylamine, tripropylamine, tributylamine, N-methylmorpholine, N-ethylmorpholine or N-dimethylbenzyl. Non-reactive monoamines such as amine, triethylenediamine, tetramethylhexamethylenediamine, bisdimethylaminoethyl ether, tetramethylpropanediamine, dimethylaminoethinoremonophorin, tetramethylethylenediamine, diazobicycloundecene or 2-methyl-1, Non-reactive diamines such as 4-diazo (2,2,2) bicyclooctane, non-reactive triamines such as pentamethyldiethylenetriamine or pentamethyldipropylenetriamine, dimethyl Reactive amines such as ethanolamine, N-trioxyethylene-N, N-dimethylamine or N, N-dimethyl-N-hexanolamine, organic acid salts thereof, 1-methylimidazole, 2-methylimidazole, 1, Imidazole compounds such as 2-dimethylimidazole, 2,4-dimethylimidazole or 1-butyl-2-methylimidazole, or organometallic compounds such as stannous octoate, stanas oleate, dibutyltin dilaurate, dibutyltin dimaleate, lead octylate Trimerization of 2,4,6-tris (dimethylaminomethyl) phenol, 2,4,6-tris (dimethylaminoalkyl) hexahydro-S-triazine, potassium acetate, potassium octylate or potassium 2-ethylhexanoate A catalyst is mentioned. As other auxiliary materials, foam stabilizer, foaming agent, flame retardant, antioxidant, ultraviolet absorber, anti-aging agent, filler, plasticizer, Coloring agents, antifungal agents, antibacterial agents, abrasives and other substances are used as necessary. Further, as a general means for increasing the hardness, there is a method using a curing agent such as an aromatic or aliphatic short chain compound, but it is not suitable because the brittleness increases while the hardness is ensured. Further, the increase in hardness can be achieved by using various fillers, but it is not suitable because the filler causes the generation of scratches.

(Example of manufacturing method)
An example of a method for suitably producing the polishing pad according to the present invention will be described below. As described above, the polishing pad according to the present example has improved polishing stability against temperature change by setting the number average molecular weight of the polyol within a predetermined range. By adopting the RIM molding method as the manufacturing method, the polishing stability derived from both the outer shape and structure of the polishing pad can be further improved. In general, after a predetermined amount of polyol and auxiliary materials are weighed and pre-stirred, the polyol component and isocyanate are rapidly impinged and mixed using a high-pressure injector using a piston pump and a plunger. After being injected into a RIM mold (hereinafter simply referred to as a mold) and clamped, the mold is removed after a predetermined time, so that a polishing pad having a required shape can be obtained at one time without post-processing such as polishing. Specifically, as shown in FIG. 2, the process includes a raw material preparation stage S1, a mixing / injection process S2, a pad forming process S3, and a final process S4. Here, the mixing / injection step S2 is a step in which polyol, isocyanate, and the like are collided and mixed under pressure to form a gas-dissolved raw material, which is injected into the mold, and the final step S4 is a process of molding the product molded in the mold This is a process in which demolding, inspection, and the like are performed, and since it is the same as the conventional RIM molding method, details are omitted. The density of the polyurethane foam that forms the polishing pad is basically adjusted by the gas loading amount of the foaming gas. That is, in the state where an inert gas is blown into the polyol component and / or isocyanate storage means and pressurized and dissolved, the above-described collision mixing is performed, and the foam is released by pressure release when injected into the mold. It is formed. Needless to say, the present invention is not limited to RIM molding.

  Moreover, the apparatus which makes a suitable manufacturing method is based on a general reaction injection molding apparatus, and has a foaming gas supply means for supplying a foaming gas while applying a predetermined pressure to a polyol storage means such as a tank. It is an added form. The polyol storage means preferably has a stirring means. In addition, the mold is provided with a vent that discharges internal air that hinders rapid injection of the gas-dissolved raw material. In this embodiment, the discharge of the internal air of the mold by the vent is controlled. (Described below [0025]).

In the raw material preparation stage S1, adjustment of polyol, isocyanate and the like (hereinafter referred to as liquid raw material) is carried out, but in the present invention, the range is 10 to 70 parts by volume with respect to 100 parts by volume of the stored polyol. The foaming gas is mixed and dissolved by gas loading. This ratio is a numerical value of the foaming gas present in the pad when each raw material is molded into a polishing pad, and does not include the amount discharged out of the mold during the manufacturing process. As a result, a density of about 600 to 1,100 kg / m ³ that achieves a polishing rate suitable for the polishing pad can be achieved. If this value is less than 10 parts by volume, the amount of dissolved (dissolved) foaming gas is small, and it becomes difficult to form a homogeneous cell 20 in the normal pressure step S32 described later ([0026]), while 70 parts by volume. If the ratio exceeds 1, the equilibrium between the liquid raw material constituting the gas-dissolved raw material and the foaming gas is lost, and a sufficiently dissolved gas-dissolved raw material cannot be obtained. As the foam-forming gas, known substances that do not affect the reaction with polyol or isocyanate, such as CO _{2 having} a large diffusion coefficient, dry air, or nitrogen, can be employed. Here, the foam-forming gas is mixed with a chemically stable polyol, but may be mixed with an isocyanate. And when carrying out gas loading of the gas for foaming 70 volume part or more, it implements by making a gas for foaming into a supercritical state suitably. In addition, even in the RIM molding method, chemical foaming occurs depending on the type of liquid raw material. Therefore, the density of the polyurethane foam forming the polishing pad is not limited to the amount of gas-loaded foaming gas but the chemical foaming. It is necessary to consider the decrease in density due to.

  The pad molding step S3 is a step of molding a polishing pad by injecting a metered required amount of gas-dissolved raw material into a mold, and comprises a pressure-regulating injection step S31, a normal pressure step S32, and a resinification step S33. . The pressure-regulating injection step S31 is a step of sequentially injecting the metered gas dissolved raw material M into the cavity 30a of the mold 30 as shown in FIG. 3 (see FIGS. 3A to 3C). Complete in a short time. In this pressure-regulating injection step S31, the internal pressure of the cavity 30a is adjusted so that the entire amount of foaming gas can be dissolved in the polyol, and is kept substantially the same as in the polyol storage means.

  When the gas-dissolved raw material M is injected, the volume of the internal air (of the mold) corresponding to the amount is continuously discharged, so that the raw material M is rapidly injected and the dissolved material is dissolved therein. Prevention of void generation due to vaporization of the foam gas is achieved. Note that the gas-dissolved raw material M at this stage has a low viscosity because the foaming gas is dissolved, and the gas dissolved raw material M is efficiently injected into the cavity 30a. The vent 32 that performs the continuous control includes a pressure regulating valve that opens at a set pressure, and a diameter that allows a pressure applied to the gas-dissolved raw material M, an injection speed, and the like, and can perform a suitable opening / closing control. Etc. are adopted. Further, several vents 32 may be provided so as to suppress partial pressure fluctuations in the cavity 30a.

  Then, the normal pressure stage S32 is started from the time when the injection of the total amount of the gas-dissolved raw material M is completed. Specifically, by opening the vent 32, the held pressure is instantaneously released, the inside of the mold 30 is brought into a normal pressure state, and the foaming gas is vaporized at once. By releasing the pressure, the injected gas-dissolved raw material M instantly foams and increases its volume, and is almost completely filled into the cavity 30a as measured in advance. In terms of time, it is preferably completed immediately after completion of the pressure-regulating injection step S31. At this moment, all the foaming gas dissolved in the gas-dissolved raw material M is vaporized to form the cells 20. At this time, a large number of so-called nuclei that are the basis of the cell 20 are generated at almost the same time (see FIG. 3D), so that the size of the formed cell 20 (cell diameter) is entirely uniform. (See FIG. 3 (e)). The variation in the average diameter of the cells 20 is about ± 10% of the average diameter, and shows high uniformity. Further, the generation mechanism of the cell 20 has an effect of making the shape substantially spherical and uniforming the pressing force of the polishing pad. That is, a polishing pad having a uniform cell 20 size and slurry holding amount and a high structural stability can be obtained regardless of the site.

  The resinification step S33 is a step in which the liquid raw material is completely reacted and cured to be resinized before the cell 20 becomes larger by unity over time, specifically at the same time when both steps S31 and S32 are completed. is there. At this stage, the resinification reaction of the gas-dissolved raw material M and the increase in the viscosity of the gas-dissolved raw material M due to vaporization of the loaded foam-forming gas proceed simultaneously, so that the internal structure of the polishing pad is fixed before it becomes heterogeneous. Completes. Further, the cell diameter can be easily controlled by the reactivity of the liquid raw material composed of polyol and isocyanate, and NCO%. The reaction of the liquid raw material in the normal RIM molding method is about 30 seconds, and the cell diameter exceeds 100 μm. In the present invention where the reaction is completed quickly, the cell diameter can be 30 to 100 μm.

  Through such steps, a polishing pad having the cavity 30a as an outer contour shape is formed and manufactured. Usually, a high-density layer called a skin layer having a thickness of about several μm is formed on the surface of the polishing pad obtained by RIM molding. Moreover, since it is RIM molding, any polishing pad with protrusions or grooves can be manufactured without requiring post-processing or the like. Further, by performing post-cure, the reaction is completed, and changes in physical properties over time and variations in physical properties between the manufacturing rods can be reduced.

  In the above-described implementation, an example has been given in which the foaming gas is mixed and dissolved in the liquid raw material in its entirety by the internal pressure of the mold, but the present invention is not limited to this. In addition, in the RIM molding method that reacts instantaneously, the viscosity of the gas-dissolved raw material M is preferably as low as possible so as not to create a lacking portion in the molding die 30. As described above, since this viscosity is reduced by the amount of NCO% or the amount of foaming gas dissolved, gas loading of the foaming gas, which is excessive for the purpose of achieving a lower viscosity, is preferable. And the quantity shall be the range of 10-2000 volume parts with respect to 100 volume parts of polyols, Preferably it is the range of 70-500 volume parts. If this value is less than 10 parts by volume, it is difficult to form a homogeneous cell 20, while if it exceeds 2000 parts by volume, it is not realistic due to problems such as pressure resistance of the mold 30 and injection molding machine. Further, in order to spread the gas-dissolved raw material M in which the foaming gas of about 10 parts by volume is preferably spread over the entire area of the mold 30, gas loading of the foaming gas of 70 parts by volume or more is preferable. On the other hand, for the gas loading of the foaming gas exceeding 500 parts by volume, the viscosity of the gas-dissolved raw material M is greatly reduced. However, even if the supercritical state is adopted, it is difficult to achieve it.

(Experimental example)
Below, the experiment example about the polishing pad which concerns on this invention is shown. Note that a test piece for measuring each physical property value of the polishing pad is produced by molding a required raw material by a RIM molding method and performing post-cure under conditions of 130 ° C. × 1 hour.

(Experiment 1) About the physical property and mixing | blending of each raw material, and the physical property of a polishing pad Using each following raw material, each raw material was mixed as a mixing | blending described in Table 1, and Examples 1-1 to 1-9 and Test pieces according to Comparative Examples 1-1 to 1-6 were prepared, and for each test piece, the peak temperature (° C.) of tan δ, the glass transition point of the soft segment (° C.), and the glass transition point of the hard segment (° C. ), D hardness, IZOD impact strength (kg / m ² ), hard segment content, and density (kg / m ³ ). As a reference example, a polishing pad having the same physical properties as a commercially available polishing pad (trade name IC1000; manufactured by Rodel Nitta) was prepared and compared.

(Each raw material used)
・ Main ingredients:
Polyol A: polyether polyol (molecular weight 700 (trade name G-700; manufactured by ADEKA))
Polyol B: Amber (Molecular weight 1,000 (trade name PTG-1000; manufactured by Hodogaya Chemical))
Polyol C: 〃 (Molecular weight 3,000 (trade name GL-3000; manufactured by Sanyo Chemical))
Polyol D: 〃 (Molecular weight 5,000 (trade name FA-703; manufactured by Sanyo Kasei))
Polyol E: Agate (Molecular weight 6,000 (trade name: Preminol 7001K; manufactured by Asahi Glass))
Polyol F: Amber (Molecular weight 10,000 (trade name: Preminol 7012; manufactured by Asahi Glass))
Isocyanate A: Isocyanate prepolymer (trade name: M393; manufactured by Sumika Bayer Urethane)
Isocyanate B: Trade name Coronate T-80; manufactured by Nippon Polyurethane Industry)
・ Sub-raw materials:
Chain extender A: amine compound (DETDA (3,5-diethyl-2,4-toluenediamine; manufactured by Sumika Bayer Urethane))
Chain extender B: Glycol (trade name Sumifene VB; manufactured by Sumika Bayer Urethane)
Chain extender C: 3,3′-dichloro-4,4′-diaminodiphenylmethane (trade name: Iharacamine MT; manufactured by Ihara Chemical Industry)
Additive A: Catalyst (DBTDL (Dibutyltin Diurarate))
Additive B: Catalyst (trade name 33LV; manufactured by Chukyo Yushi)
Additive C: Catalyst (trade name DABCO K-15; manufactured by Air Products)
-Foaming gas: dry air

(Measurement method of each physical property)
-Glass transition point: Calculated from viscoelastic behavior measured under conditions of a frequency of 1 Hz and a heating rate of 3 ° C / min.
D hardness: Measured according to ASTM 2240.
IZOD impact strength: measured according to JIS K 7110.
Density: measured in accordance with JIS K 6401.

(Result of Experiment 1)
The results obtained according to the measurement method described above are also shown in Table 1. From these results, it was confirmed that when each raw material or the like within the numerical range of the present invention is used, a polyurethane foam exhibiting physical properties suitable as a polishing pad can be produced.

(Experiment 2) About the mixing amount of foaming gas and the density of the polishing pad in the RIM molding method Based on Example 1-3 of Experiment 1, carried out by gas loading the foaming gas shown in Table 2 Test specimens according to Examples 2-1 to 2-5 and Comparative Examples 2-1 to 2-4 were prepared, and the tan δ peak temperature (° C.) and the soft segment glass transition point (° C.) for each test specimen. In addition, the glass transition point (° C.), D hardness, IZOD impact strength (kg / m ² ), hard segment content, and density (kg / m ³ ) of the hard segment were measured. In Experiment 2, “inert gas dissolved amount” refers to the amount of foaming gas dissolved in the liquid raw material formed on the polishing pad.

(Result of Experiment 2)
The results obtained according to the measurement method described above are also shown in Table 2. From this result, the density of the test piece can be set to about 600 to 1,100 kg / m ³ by setting the gas loading amount of the foaming gas to a range of 10 to 70 parts by volume with respect to 100 parts by volume of the polyol. confirmed.

It is the graph which measured the elastic loss (tan-delta) of the polishing pad which concerns on an Example. It is process drawing which shows an example of the manufacturing process of a polishing pad. It is a state figure which shows the mode in the RIM shaping | molding die in the injection step S31 under pressure regulation and the normal pressure production | generation step S32.

Explanation of symbols

20 cells, 30 molds, M gas dissolved raw material

Claims (10)

A polishing pad formed from a single polyurethane foam composed of a main raw material consisting of polyol and isocyanate and various auxiliary raw materials,
A polishing pad, wherein the polyurethane foam has a glass transition point in a range of less than 20 ° C. or more than 50 ° C., and a D hardness defined in ASTM 2240 of 40 to 70.   The polishing pad according to claim 1, wherein the glass transition point is achieved by setting the glass transition point of the soft segment in the polyurethane foam to less than 20 ° C and the glass transition point of the hard segment to exceeding 50 ° C. . The polishing pad according to claim 1 or 2, wherein the polyurethane foam has an IZOD impact strength specified in JIS K 7110 of 9.5 kg / m ² or more.   Each physical property value in the polyurethane foam is such that the number average molecular weight of the polyol is in the range of 3,000 to 10,000, an amine compound and glycol are used in combination as a chain extender, and the NCO index is in the range of 100 to 200. The polishing pad according to any one of claims 1 to 3, wherein the polishing pad is achieved.   The polishing pad according to claim 4, wherein a diamine having an amine equivalent of 138 or less is used as the amine compound, and a glycol having 2 to 5 functional groups and a hydroxyl equivalent of 500 or less is used as the glycol.   The polishing pad according to claim 4 or 5, wherein the chain extender is used in an amount of 10 to 50 parts by weight with respect to 100 parts by weight of the polyol.   The polishing pad according to any one of claims 4 to 6, wherein a mixing weight ratio of the amine compound and glycol is in a range of 1: 1 to 1: 5.   The polishing pad according to any one of claims 1 to 7, wherein a modified MDI is used as the isocyanate.   Into the mixture of the main raw material and various auxiliary raw materials, a gas-dissolved raw material (M) in which an inert gas is dissolved under pressure is injected into a molding die (30) by a reaction injection molding method, and returned to normal pressure immediately after the completion of the injection. The polishing pad according to any one of claims 1 to 8, wherein the size of the formed cell (20) is homogenized. A method for producing a polishing pad molded from a single polyurethane foam composed of a main raw material consisting of polyol and isocyanate and various auxiliary raw materials,
As the polyol, those having a number average molecular weight in the range of 3,000 to 10,000 are used, and an amine compound and a glycol are used in combination as chain extenders which are various auxiliary materials, and an NCO index is set. As a range of 100-200,
After dissolving an inert gas with respect to the polyol, mixing with isocyanate and various auxiliary materials to form a gas-dissolved raw material (M),
Injecting the gas-dissolved raw material (M) into the mold (30) under a regulated pressure,
By returning to the normal pressure immediately after the required amount of the gas-dissolved raw material (M) is injected into the mold (30),
The polyurethane foam has a glass transition point in a range of at least less than 20 ° C. or more than 50 ° C., and a polishing pad in which the size of the formed cell (20) is homogenized is produced. A method of manufacturing a polishing pad.

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