A iodine-measuring method for determining or detecting iodine concentration in a specimen, comprising a specimen-pretreating step of thermally digesting a specimen together with an oxidizing agent, and a subsequent reaction-measuring step of reacting the resultant with an arsenious acid reagent solution and an ammonium cerium sulfate reagent solution and measuring absorbance in the reaction solution, characterized in that the specimen-pretreating step is performed by heating and cooling treatment under an airtight condition.

The present invention relates to a method for measuring iodine, a specimen-pretreating reaction tool, and an airtight tool for the specimen-pretreating reaction tool.
Iodine is an indispensable trace element that becomes a raw material of the thyroid hormone for promoting metabolism of a living body, and the iodine content in the body is 15-20 mg for a healthy adult. The weight of the human thyroid hormone in any adult is about 20 g, and the thyroid gland causes iodine in blood to be selectively concentrated and generates the thyroid hormone. The intake, per day, necessary for any living body is said to be 100-150 xcexcg. If this iodine lacks and this state is left as it is, goiter is generated and further the function of the thyroid gland deteriorates. Particularly, newborn infants come to undergo a drop in intelligence, hypoplasia, neurological symptoms and the like. Pregnant women""s shortage of iodine is said to result in stillbirths and an increase in the death rate of newborn infants.
The number of people who live in regions where there is a risk of the shortage of iodine is said to be about 16 hundred million. Such people are concentrated in developing countries. It is said that this is because in inland and mountainous regions or regions where floods arise frequently or the amount of precipitation is much, by the outflow of iodine from soil the iodine content in plants that grow therein becomes insufficient so that people and animals who/that live therein have a short intake of iodine, thereby suffering from iodine deficiency disorder. For a preventive measure for the disorder, it is said that effective is a relatively simple method, such as supplementation of iodine, for example, an intake of iodized salt. In reality, in USA, European nations and the like, the measure based on this method produces an advantageous effect in iodine-shortage regions.
In such a situation, a target of the eradication of iodine deficiency disorder was adopted in the world summit for children by the United Nations in 1990, and the eradication is listed as one of important themes of International Council for Control of Iodine Deficiency Disorders (ICCIDD), UNICEF and the World Health Organization (WHO), or is listed as a state measure of a great number of nations. For this, it is important that the actual conditions of iodine deficiency disorder are precisely grasped, the disorder is diagnosed and treated, and the actual conditions are periodically being monitoring.
It is said that iodine deficiency disorder can be diagnosed by measuring iodine in urine since the intake of iodine and the excretion amount of iodine into urine have a good correlation. The normal value of iodine in urine, which is an index for this diagnosis, is said to be 100 xcexcg/L or more.
As a method for measuring iodine, E. B. Sandell et al. reports calorimetric determination using the property that iodide ion functions as a catalyst for increasing the rate of a redox reaction represented by the chemical reaction equation (I) (and abbreviated to Sandell-Kolthoff reaction hereinafter. E. B. Sandell and Kolthoff, Mikrochemica Acta, vol. 1, P9-25(1937)).
2Ce4++As3+xe2x86x922Ce3++As5+xe2x80x83xe2x80x83(I)
That is, this is a sensitive measuring method using the fact that iodine functions, as shown by the chemical reaction equations (II) and (III), as a catalyst for a reaction that by adding an arsenious acid reagent solution and an ammonium cerium sulfate reagent solution as reagents to iodide ion in a specimen, yellow ammonium cerium sulfate (quadrivalent ion) is reduced to produce colorless trivalent cerium ion.
2Ce4++2Ixe2x88x92xe2x86x922Ce3++I2xe2x80x83xe2x80x83(II)
I2+As3+xe2x86x922Ixe2x88x92+As5+xe2x80x83xe2x80x83(III)
In measurement of a specimen such as urine, however, the specimen contains a large amount of interference materials having an effect on this redox reaction, such as ion of ascorbic acid and ion of thiocyanic acid. Thus, the specimen cannot be applied, as it is, to this reaction. Actual measurements require pretreatment such as removal of the interference materials in the specimen. As the pretreatment, the following methods are suggested: a method of heating a specimen intensely and incinerate it (M. C. Sanz et al. , Clinica Chemica Acta, 1, 570-576, 1956), a wet incinerating method of adding an oxidizing agent such as perchloric acid or chloric acid, and heating the resultant to oxidize interference materials (Zak et al., Anal. Chem., 24(8), 1345-1348, 1952) , and a method of separating interference materials by dialysis, chromatography or the like (WO96/27794). Among these pretreating methods, the wet incinerating method according to Zak et al. is used as a simplest method. As a mildest and standard wet incinerating method, there is suggested and performed a method of adding 250 xcexcl of a specimen of urine and 750 xcexcl of a chloric acid reagent solution into a glass test tube 10 cm in length and 13 mm in inner diameter in a locally-exhausting provision, heating the test tube at 110-115xc2x0 C. for 1 hour with a sand bath or an aluminum block under an open condition, cooling the tube, adding 3.5 ml of an arsenious acid reagent solution that is acidified with sulfuric acid into the tube to conduct reduction reaction for 15 minutes, adding 350 xcexcl of an ammonium cerium sulfate reagent solution into the tube, and subjecting this solution to calorimetric determination at 405 nm after the reaction for a certain time (Manual of measurement of iodine in urine, edited by International Council for Control of Iodine Deficiency Disorders, 1993).
However, it is required that a vessel used in the above-mentioned chloric acid-using pretreatment of a urine specimen is made of a raw material which can endure even if the raw material is heated together with such a strong oxidizing agent as chloric acid, and it is also required that, from the vessel, materials which interfere in the Sandell-Kolthoff reaction following the pretreatment do not flow out. Therefore, no vessel made of a polymer material has been used for the chloric acid-using pretreatment of specimens. Moreover, vapor discharged in the pretreatment step is vapor containing chlorine having an irritant smell, or the like. Thus, it is necessary that the pretreatment is performed in a locally-exhausting provision having an exhaust device. For this reason, there is being performed a method of using a glass test tube resisting both heat and any oxidizing agent as a vessel in the locally-exhausting provision having the exhaust device and further heating it together with an oxidizing agent in an open state from the viewpoint of a problem about strength. Besides, in the method of heat-treating a specimen in the glass vessel in an open state, in order to decrease a change in the amount of the solution therein by evaporation and scattering of the specimen, reagent solutions and the like, it is necessary to use a long test tube having a volume scale of 1 ml or more.
The long test tube having a volume scale of 1 ml or more is used; therefore, in order to treat a great number of specimens at the same time, it is necessary to use a wider treating space and a large-scaled heating device. Furthermore, in the chloric acid-using pretreatment of a specimen, in order to discharge harmful vapor originating from chloric acid, which is generated upon heating the specimen together with chloric acid, it is necessary to use the locally-exhausting provision. In the measurement, the color fading reaction (Sandell-Kolthoff reaction) after adding the arsenious acid reagent solution and the ammonium cerium sulfate reagent solution as reagents to iodide ion in a specimen is a relatively speedy and sensitive reaction. For this reason, in measuring an absorbance when a given time passes after the start of the color fading reaction, strictness of measuring-time is required. Therefore, in the measurement wherein specimens are transferred from test tubes to cells for absorbance-measurement one tube by one tube, capability of treating specimens is restrictive, and a measuring method for treating a great number of specimens is demanded. As an automatic device for treating a great number of specimens of urine, using Sandell-Kolthoff reaction, there is an auto-analyzer made by Technicon Instrument Company, but this device cannot be said to be a device having simplicity for operation and capability of being transported.
Furthermore, recently, Pino et al. have reported that a pretreating method wherein ammonium persulfate is used as an oxidizing agent without use of chloric acid (Clinical Chemistry, 42(2), 239-243, 1996) is a safe method. However, this pretreating method is also a method of using a glass test tube in an open state to perform heating, and has the same problem as the method using chloric acid. Thus, it is difficult that a great number of specimens are treated. In this pretreating method, the safety of gas generated upon heating has not yet been verified.
In methods of measuring iodine, toxic substances or deleterious substances such as arsenic, cerium and sulfuric acid are used as reagents. Thus, if a great number of specimens are measured, a large amount of harmful waste, which results in an environmental problem, comes to be produced. Actually, according to the above-mentioned Manual of measurement of iodine in urine, 4.85 ml of a waste solution containing arsenic are produced for each specimen.
In many cases, regions where measurement of iodine is necessary are regions that are distant from cities. Thus, there are strongly demanded a measuring method that can be safely performed and a measuring tool and a measuring device that have excellent capability of being transported.
Recently, Tsuda et al. have reported an automatic device for performing pretreatment by oxidization through both potassium persulfate and irradiation of ultraviolet rays (K. Tsuda et al., Clinical Chemistry, 41(4), 581-585 (1995)), and Poluzzi et al. have also reported and suggested a measuring method using ICP/MS or HPLC (V. Poluzzi et al., J. of Anal. Anal. Atomic Spectrometry, 11(9), 731-734 (1996)). However, it is difficult to accept introduction of these devices that are expensive and lack the capability of being transported.
The invention provides a method for measuring iodine which does not require any special provision such as a locally-exhausting provision in pretreatment and which makes it possible to pretreat a specimen safely and obtain measured values with good reproducibility by suppressing scattering of harmful vapor and a change in the solution amount of a reaction solution.
The invention provides a method for measuring iodine which makes it possible to pretreat a specimen with safety and high reliability since there do not arise troubles such as damage of any vessel upon heating treatment.
The invention provides a method for measuring iodine which does not require any special provision such as a locally-exhausting provision in pretreatment and which makes it possible to pretreat a specimen with safety and high reliability and obtain measured values with good reproducibility by suppressing scattering of harmful vapor and a change in the solution amount of a reaction solution and by no occurrence of troubles such as damage of any vessel.
The invention provides a method for measuring iodine which makes it possible to pretreat a great number of specimens promptly and easily and is suitable for measuring a great number of specimens.
The invention provides a method for measuring iodine which makes it possible to pretreat a specimen with safety and high reliability by no occurrence of troubles such as damage of any vessel upon heating treatment and no outflow of such materials that have an effect on measured values.
The invention provides a method for measuring iodine which makes it possible to obtain a low-priced and highly reliable reaction tool and pretreat safely a specimen without troubles such as damage of any vessel upon heating treatment nor outflow of such materials that have an effect on measured values.
The invention provides a specimen-pretreating reaction tool that is suitable for iodine measurement which makes it possible to pretreat safely a great number of specimens without troubles such as damage of any vessel upon heating treatment nor outflow of such materials that have an effect on measured values.
The invention provides an airtight tool, for the specimenxe2x80x94pretreating reaction tool, which does not require any special provisions such as a locallyxe2x80x94exhausting provision in pretreatment of specimens for measuring iodine, does not impose any limitations on places where specimens are treated, and can suppress evaporation of harmful vapor and the generation amount of harmful waste, and which is suitable for iodine measurement that makes it possible to treat a great number of specimens easily.
(1) The present invention relates to a iodinexe2x80x94measuring method for determining or detecting iodine concentration in a specimen, comprising a specimenxe2x80x94pretreating step of thermally digesting a specimen together with an oxidizing agent, and a subsequent reactionxe2x80x94measuring step of reacting the resultant with an arsenious acid reagent solution and an ammonium cerium sulfate reagent solution and measuring absorbance in the reaction solution, characterized in that the specimenxe2x80x94pretreating step is performed by heating and cooling treatment under an airtight condition.
(2) The present invention relates to a iodine-measuring method for determining or detecting iodine concentration in a specimen, comprising a specimen-pretreating step of thermally digesting a specimen together with an oxidizing agent, and a subsequent reaction-measuring step of reacting the resultant with an arsenious acid reagent solution and an ammonium cerium sulfate reagent solution and measuring absorbance in the reaction solution, characterized in that the specimen-pretreating step is performed by using a reaction tool made of a heat-resistant organic material.
(3) The present invention relates to a iodine-measuring method for determining or detecting iodine concentration in a specimen, comprising a specimen-pretreating step of thermally digesting a specimen together with an oxidizing agent, and a subsequent reaction-measuring step of reacting the resultant with an arsenious acid reagent solution and an ammonium cerium sulfate reagent solution and measuring absorbance in the reaction solution, characterized in that the specimen-pretreating step is performed by heating and cooling treatment under an airtight condition, using a reaction tool made of a heat-resistant organic material.
(4) The present invention relates to the iodine-measuring method according to the above-mentioned (2) or (3), wherein the reaction tool made of the heat-resistant organic material is a tool having plural reaction areas.
(5) The present invention relates to the iodine-measuring method according to any one of the above-mentioned (2)-(4), wherein the heat-resistant organic material is a polypropylene resin, a polycarbonate resin, a polysulfone resin, a polyethersulfone resin, a Teflon resin, or a polymethylpentene resin.
(6) The present invention relates to the iodine-measuring method according to any one of the above-mentioned (2)-(5), wherein the reaction tool is a microtiter plate.
(7) The present invention relates to a specimen-pretreating reaction tool for measuring iodine, comprising at least one heat-resistant organic material selected from the group consisting of a polypropylene resin, a polycarbonate resin, a polysulfone resin, a polyethersulfone resin and a polymethylpentene resin, and having plural reaction areas capable of thermally digesting plural specimens together with an oxidizing agent.
(8) The present invention relates to an airtight tool composed of the specimen-pretreating reaction tool for measuring iodine recited in the above-mentioned (7), and two, upper and lower fixing supporters which can cover plural reaction areas of this reaction tool with a spacer sandwiched and fixed from upper and lower sides, and fixing assistance members capable of applying pressure to these fixing supporters so that the reaction areas of the reaction tool can be made airtight by aid of spacer.
The following will describe a reaction tool used in the step of pretreating a specimen in the method for measuring iodine according to the present invention.
It is necessary that this reaction tool withstands treatment of thermally digesting a specimen together with an oxidizing agent. In order to suppress the generation of harmful vapor which is generated by heating in the specimen-pretreating step of heating the specimen together with the oxidizing agent, such as chlorine gas originating from chloric acid, and minimize the reproducibility (dispersion) between measured values by a change in solution amount, it is also necessary that this tool withstands airtight conditions.
The above-mentioned reaction tool preferably has plural reaction areas. Examples of such a reaction tool include a tool wherein reaction plural areas, each of which is composed of a vessel such as a test tube or a test tube for centrifugation, are lined up and connected to each other, and a tool wherein plural reaction areas, each of which is composed of a well-form or columnar-form concave portion dug made in a single plate, are lined up.
The shape of each of the reaction areas may be a U-shaped form, or a flat bottom form, as is seen about test tubes, or may be a V-shaped form, as is seen about test tubes for centrifugation.
The volume of each of the reaction areas is preferably 200-1000 xcexcl. It is more preferably 300-500 xcexcl, and still more preferably 300-350 ∥l. If the volume of each of the reaction areas is more than 1000 xcexcl, a useless space increases in volume, following the enlargement of the size of the vessel. Thus, the operation of treating a great number of specimens trends to become difficult. If it is less than 300 xcexcl, there are required fine operation of fractional pour of specimens and reagent solutions and strictness of any operation so as to trend to promote a drop in fractional pour precision and a risk of erroneous operation in treatment of a great number of specimens.
Moreover, an opening of each of the reaction areas preferably has a shape or structure that can ensure airtightness by aid of a spacer for covering the reaction area to attain an airtight state. Examples of the spacer include lid-form, sheet-form and plate-form spacers. When the lid-form spacer is used, the surface shape or structure of the opening of each of the reaction areas is preferably made complementary to the lid in a concave or convex form. When the sheet-form or plate-form spacer that is flat is used, the surface shape in the vicinity of the opening of each of the reaction areas is preferably made flat. Furthermore, in order to ensure airtightness, it is preferable to make larger the area where the spacer contacts the opening of each of the reaction areas.
The raw material of the reaction tool is preferably a heat-resistant organic material. Among such heat-resistant organic materials, preferable are organic materials that are excellent in heat-resistance and chemical resistance against oxidizing agents, have a high physical strength and can easily be molded. Preferably, by heating the organic material together with an oxidizing agent, such materials that interfere in the reaction following pretreatment do not flow out from the vessel. Examples of such raw materials include polypropylene, polycarbonate, polysulfone, polyethersulfone, Teflon and polymethylpentene resins.
A specific example of the reaction tool is a microtiter plate. In general, the microtiter plate has an integration-type form in which 96 wells (reaction areas) about 8 mm in diameter and about 8 mm in depth are arranged in a single plate so as to make 8 rows in a lengthwise direction and 12 rows in a lateral direction. However, the microtiter plate that can be used in the iodine-measuring method of the present invention is not limited to the microtiter plate having the above-mentioned number of the wells, diameter and depth and the like. For example, the diameter may be made smaller, or the depth may be made larger. Moreover, there may be used a division-type microtiter plate in which arbitrary number of wells are combined, using each unit of 8 lengthwise rows or 12 lateral rows, so that 96 wells can be divided.
In the present invention, the reaction tool is not limited to the above-mentioned microtiter plate. An example thereof is an 8-series tube for PCR (Polymerase Chain Reaction) made of polypropylene. In the tube, 8 reaction areas, each of which has a diameter of about 6 mm and a depth of about 20 mm and is in the form of a test tube for centrifugation, are linearly connected to each other (imported and sold by Assist Co., Ltd.). This 8-series tube can also be used. The number of the reaction areas in the reaction tool made of such a heat-resistant organic material is not limited, and can be appropriately selected in accordance with the number of specimens to be treated, the frequency of treatment and the like.
In the iodine-measuring method of the present invention, the reaction areas in the reaction tool are preferably made into an airtight state by means of the spacer in the specimen-pretreating step of thermally digesting a specimen together with an oxidizing agent. It is necessary that the spacer can withstand the pretreatment of the specimen.
The spacer is preferably made of a material that has no permeability of gas, and has both of chemical resistance against oxidizing agents and heat-resistance that does not cause deformation at a treating temperature (for example, 120xc2x0 C.) Examples thereof include polypropylene, polycarbonate, polysulfone, polyethersulfone, Teflon, and polymethylpentene resins; and silicone, butyl and chlorobutyl rubbers. The spacer may be preferably made of a sheet-form or plate-form material having elasticity. Examples of the material of the sheet-form or plate-form spacer include silicone, butyl and chlorobutyl rubbers. As a film for preventing these covers from deteriorating, it is preferable to coat the covers with a heat-resistant film such as a polypropylene film, a polychlorovinylidene film, a fluoroethylene film, or the like.
The surface of the opening of each of the reaction areas and the spacer are manually made flat, or are made or work-molded into complementary shapes or structures having convex and concave portions, in order to keep close adhesion and airtightness.
In the case that the number of specimens to be treated is small, the spacer preferably has a lid shape from the viewpoint of economy. In the case that a great number of specimens are treated, the spacer preferably has a cover shape from the viewpoint of easiness of the operation thereof and efficiency of the multi-specimen treatment.
The airtight tool for the pretreating reaction tool is preferably made of a heat-resistant material that is not deformed at a treating temperature (for example, 120xc2x0 C.) since the airtight tool accommodates the reaction tool and the spacer and attains treatment in a thermostat or a similar constant-temperature heater. A preferable heat-resistant material of a fixing supporter or a fixing assistance member for this may be a metal, a heat-resistant hard resin, or the like. More preferably, the heat-resistant material may be a material made of carbon, or a metal having a good heat conductivity, such as aluminum, copper or stainless steel from the standpoint of efficency of heating a specimen in the pretreating step and cooling it to room temperature after the heating treatment.
If vapor of the treated solution condenses onto the spacer after the heating, a change in its solution amount arises so as to damage the reproducibility of measurement. Therefore, in such a manner that upon cooling, a lower supporting plate of the fixing supporter is cooled earlier than an upper supporting plate contacting the spacer, it is preferable that the lower supporting plate is forcibly brought into contact with water or a heat-radiating plate, that the upper supporting plate is made thicker than the lower supporting plate, or that the upper supporting plate is made of a raw material that has a lower heat conductivity than that of the lower supporting plate. For example, a raw material having a high heat conductivity, such as aluminum or copper, is preferably used for the lower supporting plate while a raw material having a lower heat conductivity than the lower supporting plate, for example, stainless steel, is preferably used for the upper supporting plate. More preferably, these are combined.
FIGS. 1-3 illustrate an example of the airtight tool, but the airtight tool is not limited to this example.
FIG. 1 illustrates a front view of the example of the airtight tool (in use). FIG. 2 illustrates a plan view thereof (in use). FIG. 3 illustrates a sectional view (in the state that any snap screw as one fixing assistance member is taken off), which is taken on a-axe2x80x2 line of FIG. 2.
The airtight tool comprises an upper supporting plate 2, a lower supporting plate 3, and a fixing assistance members 4 fitted to the lower supporting plate 3, such as snap screws made of aluminum or the like.
A reaction tool 5 such as a microtiter plate is put in a receiving space, which is made by the upper supporting plate 2 and the lower supporting plate 3, in the state that the tool 5 is sandwiched between two spacers 6 and 7 and openings of wells are directed upward. Reaction areas of the reaction tool 5 adhere closely to the spacer 6 and are made into an airtight state by fastening the lower supporting plate 3 and the upper supporting plate 2 from the upper and lower sides by means of the fixing assistance member 4 fitted to the lower supporting plate 3. In FIG. 3, the spacer 7 between the reaction tool 5 and the lower supporting plate 3 may not be used. It is necessary that the spacer 6 between the reaction tool 5 and the upper supporting plate 2 has such a thickness that can ensure the airtightness of the reaction areas of the reaction tool 5.
The following will describe the iodine-measuring method of the present invention.
The iodine-measuring method of the present invention is preferably performed as follows: in a method for determining or detecting iodine concentration in a specimen, comprising a specimen-pretreating step of thermally digesting a specimen together with an oxidizing agent, and a subsequent reaction-measuring step of reacting the resultant with an arsenious acid reagent solution and an ammonium cerium sulfate reagent solution and measuring absorbance in the reaction solution, the specimen-pretreating step is performed by heating and cooling treatment under an airtight condition.
In the pretreatment of a specimen in the iodine-measuring method of the present invention, for example, a definite amount of a iodine standard solution or a definite amount of the specimen such as urine, and a definite amount of an oxidizing agent such as a chloric acid reagent solution are added to each of the reaction areas of the reaction tool. After the addition of the oxidizing agent, the spacer or the airtight tool is used to make the each of the reaction areas airtight. A thermostat or the like is used to heat-treat the reaction tool made airtight at a constant temperature for a definite time. After this heat-treatment, the temperature of the reaction tool is returned to room temperature. By this pretreatment, interference materials upon measurement of the specimen are removed and further iodide ion and iodine are oxidized to iodate ion.
In the iodine-measuring method of the present invention, the specimen may be urine of humans or animals. The specimen may be a iodine standard solution having a known concentration. The specimen is not limited to these. If a solution seems to contain iodine or a specimen can be made up to an aqueous solution, the solution or the specimen is allowable.
In the iodine-measuring method of the present invention, the solution amount of the specimen is preferable within the range of 2-100 xcexcl, more preferably within the range of 3-80 xcexcl, and still more preferably within the range of 5-50 xcexcl. If the solution amount is less than 2 xcexcl, the sensitivity of the measurement is bad and an accidental error in fractional pour becomes large. Thus, the reproducibility of the measurement trends to deteriorate. If the solution amount is more than 100 xcexcl, the amounts of pretreating agents for coping with it and reagent solutions of the measurement increase so that quickness of operation and the capability of multi-specimen measuring treatment trend to be damaged.
The solution amount of the added oxidizing agent is preferably 2-10 times that of the specimen. If the solution amount of the added oxidizing agent is less than 2 times that of the specimen, final concentration drops so that the recovery ratio of iodine trends to drop. If the solution amount of the added oxidizing agent is more than 10 times that of the specimen, the reagent becomes fruitless and further the discharge amount of harmful waste, which comes into an environmental problem, increases. Particularly in the case of multi-specimen treatment, they come into problems that cannot be ignored. In this range, the maximum solution amount, which results from summing up the added amounts of the specimen and the oxidizing agent, is preferably 70% or less by volume of the vessel in accordance with the volume of the vessel, and more preferably 20-50% by volume of the vessel. If the maximum solution amount is more than 70% by volume of the vessel, stirring becomes difficult or it is feared that the treated solution cannot be recovered by adhesion of the treated solution to the spacer.
The oxidizing agent may be chloric acid, ammonium persulfate or the like. In the case that chloric acid is used, the final concentration thereof in the pretreating step is preferably 10-30 (W/V)%. If it is less than 10 (W/V)%, removal of interference materials from a specimen is insufficient so that the recovery ratio of iodine falls and such recoveries are largely scattered in accordance with the particular specimens. Thus, a good reproducibility of measured values trend not to be obtained. If the final concentration of chloric acid is more than 30 (W/V)%, the chloric acid reagent solution becomes fruitless and further a large amount of harmful waste is produced. If it is 40% or more, there arises such a problem that self-decomposition is caused (Kagaku Dai-Ziten, the item of chloric acid). In the case of using ammonium persulfate, the final concentration thereof is preferably 15-30 (W/V)%. If it is less than 15 (W/V)%, the recovery of iodine from iodine in a specimen becomes insufficient and such recoveries are largely scattered. Thus, a good reproducibility of measured values trends not to be obtained. If it is more than 30 (W/V)%, ammonium persulfate becomes fruitful. Moreover, ammonium persulfate whose concentration is too high trends to block, in a subsequent reaction (Sandell-Kolthoff reaction) based on the addition of an arsenious acid reagent solution and an ammonium cerium sulfate reagent solution. Therefore, the use thereof at a high concentration is not preferred.
In the pretreatment of a specimen, reaction temperature upon thermally digesting the specimen together with the oxidizing agent is preferably 50-40xc2x0 C., more preferably 80-120xc2x0 C. and especially preferably 100-110xc2x0 C. from the viewpoint of the removal of interference materials. If it is below 50xc2x0 C., the recovery of iodine in the specimen becomes insufficient and such recoveries are largely scattered. Thus, a good reproducibility of measured values trend not to be obtained. If it is over 140xc2x0 C., no problems arise in the recovery of iodine in the specimen. However, if it exceeds the limit of heat-resistance of the reaction tool made of a heat-resistant organic material, it is feared that the deformation of the reaction areas of the reaction tool makes it impossible to block evaporation of harmful vapor and the scattering of the reagent solution.
Reaction time upon thermally digesting together with the oxidizing agent is preferably 30-120 minutes, and more preferably 45-90 minutes. If it is less than 30 minutes, iodine is insufficiently recovered from iodine in a specimen and such recoveries are largely scattered. Thus, a good reproducibility of measured values trends not to be obtained. If it is more than 120 minutes, the scattering in recoveries and the reproducibility of measured values do not change. However, the capabilities of rapid measurement and multi-specimen treatment are decreased. Within the above-mentioned range, concentration, temperature and time making it possible to oxidize organic materials or the like in the specimen sufficiently and recover iodine can be appropriately selected.
As described above, in the pretreatment of a specimen, the heating reaction is preferably performed under an airtight condition in order to suppress the generation of harmful vapor generated by heating, such as chlorine gas originating from chloric acid, and minimize the reproducibility (scattering) between measured values, following a change in the solution amount by evaporation of the reaction solution. In the pretreatment, the airtight condition is more preferably such an airtight condition that makes it possible to suppress a change in the solution amount within 2% before and after the pretreatment.
In order to attain the airtight condition, it is preferable that the above-mentioned spacer is used. By attaining the airtight condition in this way, the pretreatment of a specimen can be more safely conducted. In the case of an insufficient airtight condition, the pretreatment may be conducted in a locally-exhausting provision.
In order to make the airtight condition based on the spacer more certain, or treat a great number of specimens at the same time, an airtight tool for the above-mentioned reaction tool is preferably used. In the case that the airtight tool for the reaction tool is used, the multi-specimens can be simultaneously treated, without use of a special provision such as a locally-exhausting provision, more safely than in the case that only the spacer is used.
From the viewpoint of the pretreatment-safety for avoiding harmful vapor such as chlorine gas and the shortening of cooling time, it is more preferable that after the pretreatment of a specimen the reaction temperature of the pretreatment is positively returned to room temperature or lower by cooling or the like. In view of safety, it is necessary not to open the spacer or the airtight tool for the reaction tool until the reaction temperature of the pretreatment is returned to room temperature. By this cooling treatment, harmful gas is hardly emitted even if the airtight state is cancelled.
In the step subsequent to the above-mentioned step of pretreating a specimen, an arsenious acid reagent solution is first added to the treatment solution subjected to the pretreatment and then a yellow ammonium cerium sulfate reagent solution is added thereto so as to perform a reaction in which its color is faded (Sandell-Kolthoff reaction). For example, the temperature of the pretreated solution is returned to room temperature and subsequently a definite amount of this solution is transferred to a microtiter plate made of polystyrene. A definite amount of the arsenious acid reagent solution is added thereto. In this way, iodate ion is reduced to become iodide ion.
Next, the ammonium cerium sulfate reagent solution, which is a yellow ammonium cerium sulfate solution, is added thereto so as to start a reduction reaction (color-fading reaction) of ammonium cerium sulfate by arsenious acid, using iodine as a catalyst.
Concerning final measurement of absorbance in the present invention, a change in the color fading reaction caused by the addition of the ammonium cerium sulfate reagent solution is measured as a change in absorbance or transmittance. The concentration of iodine in a specimen is determined or detected from the relationship between measured values of the absorbance or transmittance and the amounts of iodine.
The respective reagent solutions may be prepared and used in the following ways, but the compositions thereof are not limited to the following compositions.
The arsenious acid reagent solution may be prepared, for example, by adding and dissolving 10 g of arsenious acid together with 7 g of sodium hydroxide into 250 ml of purified water, adding 32 ml of concentrated sulfuric acid thereto so as to turn the solution into acidity, adding 25 g of sodium chloride thereto, and adding purified water thereto so as to make its volume up to 1 liter. The resultant solution is stored at room temperature in the state that light is blocked off.
The ammonium cerium sulfate reagent solution may be prepared by dissolving 24 g of ammonium cerium sulfate into 3.5 N sulfuric acid to make the resultant solution up to 1 liter. The resultant solution is stored at room temperature in the state that light is blocked off.
In the present invention, in any case other than the case in which a transparent tool (particular, a transparent microplate) is used as the reaction tool used in the pretreatment, it is necessary to transfer a definite amount of the treated solution to a measuring tool having such transparency that any change in absorbance can be measured before or after the addition of the arsenious acid reagent solution (for example, a microplate).
As the measuring tool having such transparency that any change in absorbance can be measured, particularly the microplate, it is allowable to use any plate making it possible to measure absorbance, which is made of, for example, polystyrene. The volume of its wells is preferably 300-500 xcexcl, more preferably 300-400 xcexcl, and still more preferably 300-350 xcexcl. If the volume is over 500 xcexcl, the size of the vessel becomes large so that a needless space is necessary. Therefore, multi-specimen treatment trends to become difficult. If the volume is below 300 xcexcl, the size of the vessel becomes fine so that fine actions, such as fractional pour of a specimen and reagent solutions, and strictness of operations are required. Thus, fractional pour precision deteriorates and the risk that erroneous operations in multi-specimen treatment are caused trends to increase.
Concerning the measurement of absorbance in the present invention, a change in the color-fading reaction of the added ammonium cerium sulfate reagent solution is measured as a change in absorbance or transmittance.
The change in absorbance or transmittance is measured after the start of the color-fading reaction of the added ammonium cerium sulfate reagent solution. The measurement of the change in absorbance or transmittance is preferably measured by endpoint assay of measuring a change in the color-fading reaction as absorbance or transmittance at the time when a certain time passes after the start of the reaction, or reaction rate assay of measuring absorbances or transmittance after the start of the reaction, in progress of the reaction, and obtaining a difference therebetween (reaction rate). In the case that they are measured 3 times or more in the progress of the reaction, the reaction rate can be obtained by a calculating method such as the least-squares method.
In these measurements, the absorbance of a single wavelength selected from the range of 400-450 nm, as a measuring wavelength, is preferably measured. Furthermore, in order to decrease a change in measured values between wells of the microtiter plate, based on their stains, injuries or the like, a difference between absorbances of two different wavelengths is preferably measured, one of which is selected from the range of 400-450 nm as a main wavelength, and the other of which is selected from the range of 450-700 nm as a secondary wavelength.
In the case that, after the start of the color-fading reaction by the addition of the ammonium cerium sulfate reagent solution, the degree of the progress of the color-fading reaction is measured as a change in absorbance or transmittance, measuring time is preferably from 30 seconds to 60 minutes and more preferably from 5 to 30 minutes after the start of the color-fading reaction. During this period, it is necessary to measure it at least one time. In order to decrease the scattering in measurements, it is preferable to measure it two times or more.
In the present invention, an absorbance-measuring device is not limited if the device can measure absorbance within the range of 400-450 nm. A preferable measuring-device that can be used is, for example, a microtiter plate reader for wide uses, which is commonly used for ELISA etc., has good capability of being transported, and makes possible automatic continuous measurement and multi-specimen treatment.
Actually, the concentration of iodine in a specimen is measured as follows: a iodine standard solution having a known concentration, instead of the specimen, is used to measure its iodine concentration under the same conditions in advance or upon measurement of the specimen, thereby preparing a calibration curve about a relationship between absorbance or transmittance and iodine concentration, and then on the basis of this, the amount of iodine in the specimen is determined or detected. The iodine standard solution having a known concentration may be appropriately selected in accordance with the range concerning which the measurement is performed. In the case that the specimen is urine, it is necessary to select plural concentrations of at least two points between which a concentration 100 xcexcg/L, which is an index of a normal value, is sandwiched.

Method for measuring iodine and reaction instrument for specimen pretreatment


A golf ball is formed with a resin composition which contains 5 to 95 weight % of a polyester block copolymer (A) and 95 to 5 weight % of an ionomer resin (B); and a (polyester-aromatic vinyl based copolymer) block copolymer (C), which is mixed with both the polyester block copolymer (A) and the ionomer resin (B) in an amount of 1 to 40 parts by weight on the basis of 100 parts by weight of the total of the polyester block copolymer (A) and the ionomer resin (B). The polyester block copolymer (A) mainly contains a high-melting point crystalline polymer segment (a1) composed of a crystalline aromatic polyester unit, and a low-melting point polymer segment (a2) composed of an aliphatic polyether unit and/or an aliphatic polyester unit. The ionomer resin (B) is produced by neutralizing a copolymer mainly containing an xcex1-olefine (b1) and an xcex1,xcex2-unsaturated carboxylic acid (b2) having 3 to 8 carbon atoms with at least one metal ion (b3) selected from univalent, divalent, and trivalent metal ions. The (polyester-aromatic vinyl based copolymer) block copolymer (C) contains a block (c1) composed of a polyester, and at least one block (c2) selected from block or random copolymers containing aromatic vinyl based monomers and conjugated dienes and/or hydrogenated products thereof.

The present invention relates to a golf ball which is capable of increasing the flying distance of the ball, improving the ball hitting feeling, and enhancing the durability of the ball.
A polyester block copolymer containing a crystalline aromatic polyester unit such as polybutylene terephthalate, as a hard segment and an aliphatic polyether unit such as poly(alkylene oxide) glycol and/or an aliphatic polyester unit such as polylactone, as a soft segment, is excellent in mechanical properties such as strength, impact resistance, elastic recovery, and flexibility and also excellent in low temperature/high temperature characteristics, and is good in thermoplasticity to be thereby easily moldable. Such a polyester block copolymer has become a focus of attention as a resin for a golf ball, for example, as disclosed in Japanese Patent Laid-open No. Hei 7-24084.
The above-described polyester block copolymer having excellent physical properties, however, is disadvantageous in that as the hardness thereof becomes higher, the mechanical properties such as impact resilience, strength, and impact resistance, and the low temperature characteristics become lower, and therefore, to increase the flying distance of a golf ball formed by using the polyester block copolymer, it has been required to further improve the physical properties of the polyester block copolymer.
On the other hand, an ionomer resin produced by neutralizing a copolymer containing xcex1-olefine and xcex1,xcex2-unsaturated carboxylic acid with univalent, divalent, or trivalent metal ions is thermoplastic and thereby easily moldable, and further significantly tough to be thereby less broken even if being largely deformed by a high speed impact. The high toughness of the ionomer resin is advantageous in improving the abrasion resistance of a golf ball formed by using the ionomer resin and in enhancing the durability of the golf ball against repeated hitting thereof. In actual, the ionomer resin having the above excellent properties has been used as a cover material for golf balls over the years.
The ionomer resin, however, is insufficient in flexibility, and gives a rigid feeling to a player upon hitting a golf ball using the ionomer resin as a cover material.
To cope with such an inconvenience, there has been proposed a softened ionomer resin suitable as a resin composition for a golf ball, wherein the ionomer resin is provided by neutralizing a copolymer containing xcex1-olefine, xcex1,xcex2-unsaturated carboxylic acid, and xcex1,xcex2-unsaturated carboxylate with univalent, divalent, or trivalent metal ions.
The softened ionomer resin, however, is poor in impact resilience and low temperature characteristic, and is therefore required to be further improved.
An attempt has been made to produce a golf ball using a resin composition obtained by mixing a polyester block copolymer with an ionomer resin for compensating the disadvantages of the polyester block copolymer and the ionomer resin with each other. These golf balls, each using a resin composition obtained by mixing a polyester block copolymer and an ionomer resin, has been proposed, for example, in Japanese Patent Laid-open Nos. Sho 56-83367 and Sho 62-275480. According to such a resin composition, since the polyester block copolymer excellent in flexibility and impact resilience is mixed with the ionomer resin poor in flexibility but excellent in toughness and impact resilience, it is possible to make effective use of the excellent performances of both the polyester block copolymer and the ionomer resin, and particularly to improve the impact resilience.
The above-described golf ball material, that is, the mixture of the polyester block copolymer and the ionomer resin, however, has a problem. Namely, since the polyester block copolymer and the ionomer resin are not excellent in compatibility so much, the golf ball material has an uneven morphology, with a result that the resin material is easy to orient upon injection molding thereof, tending to cause laminar peeling and also failing to obtain a sufficient durability of a golf ball formed by using the resin material against repeated hitting of the golf ball.
An attempt has been made to further improve the above-described resin composition. For example, a golf ball core material composed of a resin composition containing a polyester block copolymer, an ionomer resin, and an epoxy-containing compound has been proposed in WO92/12206, and a golf ball using a resin composition containing a polyester block copolymer, an ionomer resin, and an epoxidated diene based block copolymer has been proposed in Japanese Patent Laid-open No. Hei 9-176429.
Each of the resin compositions disclosed in the above-described documents is satisfactory to improve the laminar peeling by enhancing the compatibility of the polyester block copolymer with the ionomer resin, and therefore, becomes a resin composition excellent in flexibility and impact resilience suitable for a golf ball; however, such a resin composition has another problem that since it contains the epoxy-containing copolymer, the melt viscosity of the resin composition becomes higher, with a result that the resin composition is suitable for both extrusion molding and blow molding but unsuitable for injection molding generally used for molding a golf ball.
A thermoplastic polymer composition containing a polyester based resin, an addition polymerization based block copolymer, a polyester based block copolymer, and an ionomer resin, which is usable as a golf ball cover material, has been disclosed in Japanese Patent Laid-open No. Hei 10-147690.
The above-described thermoplastic polymer composition is a hard material being high in tensile strength and bending strength but is very high in stiffness modulus, and therefore, is different from a material having a high flexibility and a high impact resilience, such as rubber. Further, the thermoplastic polymer composition cannot exhibit a sufficient durability of a golf ball formed by using the resin composition against repeated hitting of the ball, which durability is required for a golf ball cover material. Accordingly, the thermoplastic polymer composition is unsuitable as the golf ball material.
A thermoplastic resin composition for a golf ball containing an ionomer resin, a polyester based thermoplastic elastomer, and a styrene based block copolymer has been disclosed in Japanese Patent Laid-open No. Hei 11-342229.
Such a thermoplastic resin composition for a golf ball is excellent in flexibility and elastic recovery; however, it is also insufficient in durability of a golf ball formed by using the thermoplastic resin composition against repeated hitting of the ball, which durability is required for a golf ball cover material.
As described above, at present, there does not exist a resin composition for a golf ball, which has a high flexibility and a high impact resilience, and also has a high toughness, particularly, a high flexural fatigue resistance and a high tear resistance, and which is good in melt flowability and thereby suitable for injection molding with less laminar peeling after molding.
An object of the present invention is to provide a golf ball which is capable of increasing the flying distance of the ball, improving the ball hitting feeling, and enhancing the durability of the ball.
To achieve the above object, the present inventors have made studies to develop a new thermoplastic resin composition for a golf ball, which is high in rupture strength and impact strength, has properties similar to those of rubber, such as a suitable flexibility and a high impact resilience, and is excellent in durability, particularly, flexural fatigue resistance and tear strength, and which is good in melt flowability and thereby suitable for injection molding with less laminar peeling after molding, by compensating the disadvantages of a polyester block copolymer and an ionomer resin used for a prior art resin composition for a golf ball with each other, and eventually found that a resin composition containing a polyester block copolymer (A), an ionomer resin (B), and a (polyester-aromatic vinyl based copolymer) block copolymer (C) at a specific mixing ratio has a high flexibility and a high impact resilience, and also has a high toughness, particularly, high flexural fatigue resistance and a high tear resistance, and is good in melt flowability and thereby suitable for injection molding with less laminar peeling after molding, wherein the polyester block copolymer (A) mainly contains a high-melting point crystalline polymer segment (a1) composed of a crystalline aromatic polyester unit, and a low-melting point polymer segment (a2) composed of an aliphatic polyether unit and/or an aliphatic polyester unit; the ionomer resin (B) is produced by neutralizing a copolymer mainly containing an xcex1-olefine (b1) and an xcex1,xcex2-unsaturated carboxylic acid (b2) having 3 to 8 carbon atoms with at least one metal ions (b3) selected from univalent, divalent, and trivalent metal ions; and the (polyester-aromatic vinyl based copolymer) block copolymer (C) contains a block (c1) composed of a polyester, and at least one block (c2) selected from block or random copolymers containing aromatic vinyl based monomers and conjugated dienes and/or hydrogenated products thereof.
The present inventors have further examined the above-described resin composition, and found that a golf ball formed by using the resin composition is capable of increasing the flying distance of the ball, improving the ball hitting feeling, and enhancing the durability of the ball.
Accordingly, the present invention provides a golf ball in which a solid core or center, an intermediate layer or a cover layer is formed with a resin composition comprising:
5 to 95 weight % of a polyester block copolymer (A) and 95 to 5 weight % of an ionomer resin (B); and
a (polyester-aromatic vinyl based copolymer) block copolymer (C), which is mixed with both the polyester block copolymer (A) and the ionomer resin (B) in an amount of 1 to 40 parts by weight on the basis of 100 parts by weight of the total of the polyester block copolymer (A) and the ionomer resin (B);
wherein the polyester block copolymer (A) mainly contains a high-melting point crystalline polymer segment (a1) composed of a crystalline aromatic polyester unit, and a low-melting point polymer segment (a2) composed of an aliphatic polyether unit and/or an aliphatic polyester unit;
the ionomer resin (B) is obtained by neutralizing a copolymer mainly containing an xcex1-olefine (b1) and an xcex1,xcex2-unsaturated carboxylic acid (b2) having 3 to 8 carbon atoms with at least one metal ion (b3) selected from univalent, divalent, and trivalent metal ions; and
the (polyester-aromatic vinyl based copolymer) block copolymer (C) contains a block (c1) composed of a polyester, and at least one block (c2) selected from block or random copolymers containing aromatic vinyl based monomers and conjugated dienes and/or hydrogenated products thereof.
The resin composition used for forming a golf ball of the present invention has a high flexibility and a high impact resilience, and also has a high toughness, particularly, a high flexural fatigue resistance and a high tear resistance, and is good in melt flowability and thereby suitable for injection molding with less laminar peeling after molding, and a golf ball of the present invention, which can be easily obtained by using the resin composition of the present invention, has a good balance between the carrying distance, feeling against ball hitting, and durability.
A resin composition used for forming a golf ball of the present invention contains a polyester block copolymer as an essential component (A). The component (A) mainly contains a high-melting point crystalline polymer segment (a1) composed of a crystalline aromatic polyester unit, and a low-melting point polymer segment (a2) composed of an aliphatic polyether unit and/or an aliphatic polyester unit.
The component (a1) is preferably polybutylene terephthalate prepared from terephthalic acid and/or dimethylterephthalate and 1,4-butanediol. Alternatively, the component (a1) may be a polyester prepared from a dicarboxylic acid component and a diol component having a molecular weight of 300 or less, or a copolymerized polyester prepared from two kinds or more of these dicarboxylic acid components and the diol components, wherein the dicarboxylic acid component may be selected from isophthalic acid, phthalic acid, naphthalene-2,6-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid, diphenyl-4,4xe2x80x2-dicarboxylic acid, diphenoxyethanedicarboxylic acid, 5-sulfoisophthalic acid, or an ester forming derivative thereof; and the diol component may be selected from an aliphatic diol such as ethyleneglycol, trimethyleneglycol, pentamethyleneglycol, hexamethyleneglycol, neopentylglycol, or decamethyleneglycol, an alicyclic diol such as 1,4-cyclohexanedimethanol or tricyclodecanedimethylol, and an aromatic diol such as xyleneglycol, bis(p-hydroxy)diphenyl, bis(p-hydroxyphenyl)propane, 2,2-bis[4-(2-hydroxyethoxy)phenyl]propane, bis[4-(2-hydroxy)phenyl]sulfone, 1,1-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane, 4-4xe2x80x2-dihydroxy-p-terphenyl, or 4-4xe2x80x2-dihydroxy-p-quarter-phenyl. Further, a polyfunctional carboxylic acid component having three or more functional groups, a polyfunctional oxyacid, and a polyfunctional hydroxy component can be copolymerized in a range of 5 mol % or less.
The component (a2) is a low-melting point polymer segment (a2) composed of an aliphatic polyether unit and/or an aliphatic polyester unit. Specific examples of the aliphatic polyether units may include poly(ethylene oxide) glycol, poly(propylene oxide) glycol, poly(tetramethylene oxide)glycol, poly(hexamethylene oxide)glycol, ethylene oxide-propylene oxide copolymer, ethylene oxide addition polymer of poly(propylene oxide)glycol, and ethylene oxide-tetrahydrofuran copolymer.
Specific examples of the aliphatic polyester units may include poly(xcex5-caprolactone), polyenanthalactone, polycaprolactone, polybutylene adipate, and polyethylene adipate.
From the viewpoint of the elastic characteristic of the polyester block copolymer (A), the component (a2) may be selected from poly(tetramethylene oxide)glycol, ethylene oxide addition polymer of poly(propylene oxide)glycol, poly(xcex5-caprolactone), polybutylene adipate, and polyethylene adipate. In particular, poly(tetramethylene oxide)glycol is preferably used as the component (a2).
The number-average molecular weight of the low-melting point polymer segment is preferably in a range of about 300 to about 6000 in a copolymerized state.
According to the present invention, the copolymerized amount of the component (a2) contained in the component (A) is preferably adjusted to be in a range of 15 to 90 weight %, preferably 50 to 90 weight %. If the copolymerized amount of the component (a2) is more than 90 weight %, the component (a2) cannot exhibit, when mixed with the component (a1) into the thermoplastic copolymer (A), a sufficient melt characteristic, and therefore, cannot be uniformly mixed with the component (a1). If it is less than 15 weight %, the copolymer (A) obtained by mixing the component (a2) with the component (a1) is poor in flexibility and impact resilience.
The component (A) mainly containing the component (a1) and the component (a2) can be produced by any one of known production processes, some of which are shown as follows:
(1) a process of subjecting diester of dicarboxylic acid and lower alcohol, glycol having a low molecular weight in an excess amount, and a low-melting point polymer segment to ester interchange reaction under catalyst, and polycondensating a reaction product thus obtained;
(2) a process of subjecting dicarboxylic acid, glycol in an excess amount, and a low-melting point polymer segment to esterification under catalyst, and polycondensating a reaction product thus obtained;
(3) a process of previously preparing a high-melting point crystalline polymer segment, adding a low-melting point polymer segment thereto, and randomizing both the segments by ester interchange reaction;
(4) a process of linking a high-melting point crystalline polymer segment to a low-melting point polymer segment with a chain-linking agent; and
(5) a process of making, in the case of using poly(xcex5-caprolactone) as a low-melting point polymer segment, xcex5-caprolactone monomers addition-react with a high-melting point crystalline polymer segment.
The polyester block copolymer as the component (A) may have a Shore D hardness, measured in accordance with ASTM D-2240, in a range of 10 or more, preferably 25 or more, and 55 or less, preferably 50 or less. It may be preferred that the polyester block copolymer as the component (A) be softer than an ionomer resin as a component (B) to be described later.
The component (A) may have a high impact resilience, measured in accordance with BS 903, in a range of 40% or more, preferably 50% or more, and 90% or less. If the impact resilience of the component (A) is less than 40%, the impact resilience of the resin composition obtained by mixing the components (A), (B) and (C) with each other becomes smaller, with a result that the carrying performance of a golf ball formed by using the resin composition may be degraded.
The component (A) may have a relatively low stiffness modulus, measured in accordance with JIS K-7106, in a range of 5 MPa or more, preferably 10 MPa or more, more preferably 15 MPa or more, and 250 MPa or less, preferably 200 MPa or less, more preferably 150 MPa or less. If the stiffness modulus of the component (A) is more than 250 MPa, the stiffness of the resin composition obtained by mixing the components (A), (B) and (C) with each other becomes higher, with a result that the feeling of hitting a golf ball formed by using the resin composition and the durability thereof may be degraded.
The resin composition used for forming a golf ball of the present invention contains an ionomer resin as an essential component (B). The ionomer resin as the component (B) is produced by neutralizing a copolymer mainly containing an xcex1-olefine (b1) and an xcex1,xcex2-unsaturated carboxylic acid (b2) having 3 to 8 carbon atoms with at least one kind of metal ions (b3) selected from univalent, divalent, and trivalent metal ions.
Specific examples of the xcex1-olefines as the components (b1) may include ethylene, propylene, and butene-1. In particular, ethylene is preferably used as the component (b1).
Specific examples of the xcex1, xcex2-unsaturated carboxylic acids having 3 to 8 carbon atoms as the components (b2) may include acrylic acid, methacrylic acid, ethacrylic acid, itaconic acid, and maleic acid. In particular, acrylic acid or methacrylic acid is preferably used as the component (b2).
The copolymer of the component (B), which mainly contains the component (b1) and the component (b2), may further contain an acrylate and/or a methacrylate as an optional component (b4).
Specific examples of the acrylates or methacrylates as the components (b4) may include methyl acrylate, ethyl acrylate, isobutyl acrylate, acrylic acid-n-butyl, acrylic acid-2-ethylhexyl, methyl methacrylate, methacrylic acid-n-butyl, and isobutyl methacrylate. In particular, methyl acrylate, ethyl acrylate, or acrylic acid-n-butyl is preferably used as the component (b4).
The copolymer of the component (B) may contain the xcex1,xcex2-unsaturated carboxylic acid in an amount of 0.2 mol % or more, preferably 5 mol % or more, and 25 mol % or less, preferably 15 mol % or less, regardless of whether or not the copolymer contains the optional component (b4). If the content of the unsaturated carboxylic acid is less than 0.2 mol %, the stiffness and impact resilience of the copolymer become small, with a result that the carrying performance of a golf ball formed by using the resin composition obtained by mixing the components (A), (B) and (C) with each other.
The ionomer resin as the component (B) is obtained by neutralizing the above-described copolymer with at least one kind of metal ions (b3) selected from univalent, divalent, and trivalent metal ions. Specific examples of the univalent, divalent, and trivalent metal ions suitable for neutralization may include sodium ions, potassium ions, lithium ions, magnesium ions, calcium ions, zinc ions, aluminum ions, ferrous ions, and ferric ions.
The introduction of such metal ions can be performed by making the copolymer mainly containing the components (b1) and (b2) and the optional component (b4) react with a hydride, methoxide, ethoxide, carbonate, nitrate, formate, acetate, or oxide of the above-described univalent, divalent, or trivalent metal. In this neutralization, at least 10 mol % or more, preferably 30 mol % or more, and 100 mol % or less, preferably 90 mol % or less of the carboxylic groups in the copolymer is preferably neutralized with the metal ions. If the neutralized amount is less than 10 mol %, the impact resilience of the ionomer resin may be degraded.
As the ionomer resin as the component (B), there may be used a commercial product. Specific examples of the commercial products may include Himilan(copyright) 1554, 1557, 1601, 1605, 1706, 1855, 1856, AM7315, AM7316, AM7317, and AM7318 (sold by Du Pont-Mitsui Polychemicals Co., Ltd.), and Surlyn(copyright) 6320, 7930, 8120, 8945, and 9945 (sold by Du Pont DE NEMOURS and COMPANY).
According to the present invention, a single ionomer resin obtained by neutralizing a copolymer with one kind of metal ions may be used as the component (B); however, two kinds or more ionomer resins obtained by neutralizing a copolymer with different kinds of metal ions are preferably used as the component (B). For example, in the case of using the above-described commercial products, it may be preferred to use two kinds or more ionomer resins of different ion types in combination. This is effective to enhance the balance between the melt flowability, flexural fatigue resistance, tear strength, and impact resilience, and hence to improve the properties of the resin composition for a golf ball.
The component (B) may have a Shore D hardness, measured in accordance with ASTM D-2240, in a range of 45 or more, preferably 55 or more, more preferably 60 or more, and 80 or less, preferably 75 or less, more preferably 70 or less. It may be preferred that the hardness of the component (B) be higher than that of the component (A).
The component (B) may have a stiffness modulus, measured in accordance with JIS K-7106, in a range of 25 MPa or more, preferably 50 MPa or more, more preferably 200 MPa or more, and 500 MPa or less, preferably 450 MPa or less, more preferably 400 MPa or less. It may be preferred that the stiffness modulus of the component (B) be higher than that of the component (A).
In the resin composition used for forming a golf ball of the present invention, from the viewpoint of enhancing the toughness, flexibility, and impact resilience of the resin composition, the content of the component (A) may be in a range of 5 to 95 weight %, preferably 10 to 90 weight %, more preferably 20 to 80 weight %, and the content of the component (B) may be in a range of 95 to 5 weight %, preferably 90 to 10 weight %, more preferably 80 to 20 weight %, on the basis of the total amount of the components (A) and (B). If either of the contents of the components (A) and (B) is out of the above-described range, there arises a problem in degrading the performances, such as the ball hitting feeling, durability, and carrying characteristic, of a golf ball formed by using the resin composition.
According to the present invention, in the case of mixing the component (A) with the component (B), from the viewpoint of enhancing the impact resilience, low temperature characteristics, and mechanical strength of the final resin composition, a polyester block copolymer being lower in stiffness modulus and surface hardness and higher in impact resilience may be selected as the component (A), and an ionomer resin being higher in stiffness modulus and surface hardness may be selected as the component (B).
In the case of mixing the component (A) with the component (B), to make effective use of the characteristics of both the components (A) and (B), a different in surface hardness measured in Shore D hardness between the components (A) and (B) [hardness of the component (B)xe2x88x92hardness of the component (A)] may be in a range of 10 or more, preferably 20 or more, more preferably 30 or more, and 50 or less.
Further, in the case of mixing the component (A) with the component (B), a difference in stiffness modulus between the components (A) and (B) [stiffness modulus of the component (B)xe2x88x92stiffness modulus of the component (A)] may be in a range of 100 MPa or more, preferably 150 MPa or more, more preferably 200 MPa or more. If the difference in stiffness modulus is less than 100 MPa, the improvement of the impact resilience of the final resin composition may become insufficient.
The resin composition used for forming a golf ball of the present invention contains a (polyester-aromatic vinyl based copolymer) block copolymer as an essential component (C). The component (C) contains a block (c1) composed of a polyester, and a block (c2) formed by a block or random copolymer containing aromatic vinyl based monomers and a conjugated diene and/or a hydrogenated product thereof.
Specific examples of the polyesters of the components (c1) may include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, poly-1,4-cyclohexanedimethylene terephthalate, polycaprolactone, and polybutylene adipate. Of these materials, an aromatic polyester, particularly, polybutylene terephthalate is preferably used as the polyester of the component (c1).
Specific examples of the aromatic vinyl based monomers of the components (c2) may include styrene, xcex1-methylstyrene, vinyltoluene, p-methylstyrene, p-t-butylstyrene, o-ethylstyrene, o-dichlorostyrene, and p-diclorostyrene.
Specific examples of the conjugated dienes may include butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, 4,5-diethyl-1,3-octadiene, 3-butyl-1,3-octadiene, and chloroprene.
In particular, a block or random copolymer obtained from styrene, butadiene or isoprene and/or a hydrogenated product thereof is preferably used as the component (c2).
The (polyester-aromatic vinyl based copolymer) block copolymer as the component (C) is obtained by copolymerizing the block (c1) composed of a polyester, and the block (c2) formed by a block or random copolymer containing aromatic vinyl based monomers and a conjugated diene and/or a hydrogenated product thereof. In particular, from the viewpoint of enhancing the compatibility with both the components (A) and (B), the block copolymer as the component (C) may be a block copolymer obtained by copolymerizing a block composed of polybutylene terephthalate as the component (c1) and a block formed by a styrene-butadiene block or random copolymer or a styrene-isoprene block or random copolymer and/or a hydrogenated product thereof as the component (c2). The block copolymer may be of any kind selected from a diblock copolymer, a triblock copolymer, and a multiblock copolymer.
From the viewpoint of the resin strength accompanied by the compatibility, the content of the component (C) may be 1 part by weight or more, preferably 2 parts by weight or more, more preferably 3 parts by weight or more, and 40 parts by weight or less, preferably 30 parts by weight or less, more preferably 20 parts by weight or less on the basis of 100 parts by weight of the total of the polyester block copolymer (A) and the ionomer resin (B). If the content of the component (C) is out of the above range, the impact resilience of a golf ball formed by the resin composition may become insufficient and the durability of the golf ball be degraded.
The resin composition used for forming a golf ball of the present invention containing the components (A), (B) and (C) as the essential components may further contain various known additives within such ranges as not to depart from the object of the present invention. Specific examples of these additives may include a hindered phenol based, phosphite based, thioester based, or aromatic amine based oxidation inhibitor; a benzophenon based, benzotriazole based, or hindered amine based light-proof agent; a coloring agent such as pigment or dye; and other additives such as an antistatic agent, a conductive agent, a flame retardant, a stiffener, a filler, plasticizer, and a mold releasing agent.
The resin composition used for forming a golf ball of the present invention containing the components (A), (B), and (C) and various additives as needed can be produced, for example, in accordance with one of the following methods (1), (2), and (3):
The method (1) involves mixing the polyester block copolymer (A), the ionomer resin (B), and the (polyester-aromatic vinyl based copolymer) block copolymer (C) to prepare a raw material, supplying the raw material to a screw type extruder, and kneading the raw material in a molten state by the extruder.
The method (2) involves supplying the polyester block copolymer (A) to a screw type extruder and melting it, supplying the ionomer resin (B) and the (polyester-aromatic vinyl based copolymer) block copolymer (C) to the extruder through another supply port, and kneading them in a molten state by the extruder.
The method (3) involves supplying the ionomer resin (B) to a screw type extruder and melting it, supplying the polyester block copolymer (A) and the (polyester-aromatic vinyl based copolymer) block copolymer (C) to the extruder through another supply port, and kneading them in a molten state by the extruder.
Since the resin composition used for forming a golf ball of the present invention can be easily molded by injection molding, it is possible to easily obtain a golf ball having a high flexibility and a high impact resilience by injection molding the resin composition.
The resin composition used for forming a golf ball of the present invention may have a Shore D hardness, measured in accordance with ASTM D-2240, in a range of 25 or more, preferably 30 or more, and 70 or less, preferably 60 or less, and more preferably 50 or less. In particular, the resin composition can be suitably used as a material having a relatively low hardness.
The resin composition used for forming a golf ball of the present invention may have an impact resilience, measured in accordance with BS 903, in a range of 40% or more, preferably 50% or more, and 90% or less. If the impact resilience of the resin composition is less than 40%, a golf ball formed by using the resin composition may be degraded.
Next, a golf ball of the present invention will be described. The golf ball has at least one ball structural portion (for example, a core, an intermediate layer, or a cover) formed by using the above-described resin composition, and it exhibits a high toughness, a high flexural fatigue resistance, and a high tear strength, and also has a high durability against ball hitting because of no laminar peeling. Such a golf ball can be easily produced by molding the resin composition because the resin composition has a high melt-flowability enough to allow molding of the resin composition in the form of a thin film.
The golf ball of the present invention can be formed as a two-piece golf ball including a core and a cover, a multi-piece golf ball including a core covered with two or more layers, a one-piece golf ball, or a thread wound golf ball by using the resin composition as various golf ball materials such as a core material, an intermediate layer material, a cover material, a one-piece golf ball material, and a solid center material (for thread wound golf ball).
The ball structural portions of the golf ball formed by the resin composition will be described in detail below.
In the case of using the above-described resin composition for a golf ball as a core material, the diameter of the core (solid core or solid center) made from the material may be in a range of 25.00 mm or more, preferably 35.0 mm or more, and 39.95 mm or less, preferably 38.90 mm or less.
In this case, to adjust the size and weight of the core in accordance with a golf rule, an inactive filler may be used for adjusting the specific gravity of the core. Specific examples of the inactive fillers may include zinc oxide, barium sulfate, silica, calcium carbonate, and zinc carbonate. In particular, barium sulfate is preferably used as the inactive filler. The content of the inactive filler is dependent on the specific gravity of each of the core and a cover, the specification on the weight of the ball, and the like and thereby not particularly limited but may be in a range of 10 parts by weight or more, preferably 15 parts by weight or more, and 60 parts by weight or less, preferably 30 parts by weight or less, on the basis of 100 parts by weight of the resin composition of the present invention.
In the case of using the resin composition for a golf ball as an intermediate layer material, the gage of an intermediate layer made from the material may be in a range of 0.5 mm or more, preferably 1.0 mm or more, more preferably 1.4 mm or more, and 3.0 mm or less, preferably 2.5 mm or less, more preferably 1.9 mm or less. If the gage of the intermediate layer is more than 3.0 mm, the impact resilience of a golf ball may be degraded and thereby the carrying distance thereof be shortened, and if it is less than 0.5 mm, the durability of the golf ball may be degraded.
In the case of using the resin composition for a golf ball as a cover material, the thickness of a cover made from the material may be in a range of 0.5 mm or more, preferably 1.0 mm or more, more preferably 1.4 mm or more, and 3.0 mm or less, preferably 2.5 mm or less, more preferably 1.9 mm or less. If the thickness of the cover is more than 3.0 mm, the impact resilience of a golf ball may be degraded and thereby the carrying distance thereof be shortened, and if it is less than 0.5 mm, the durability of the golf ball may be degraded.
In the case of using the resin composition for a golf ball as a one-piece golf ball material, the diameter of a one-piece golf ball made from the material may be in a range of 42.60 mm or more, preferably 42.65 mm or more, and 42.75 mm or less, preferably 42.70 mm or less.
Each of the above-described ball structural portions of the golf ball can be produced by compression-molding or injection-molding the resin composition for a golf ball in a mold. In particular, the injection molding process can be preferably used.
The golf ball of the present invention can be formed with its size and weight specified under the golf rules. In general, the diameter of the golf ball of the present invention may be in a range of 42.65 to 42.75 mm, and the weight of the golf ball of the present invention may be in a range of 45.0 to 45.5 g.
As described above, according to the golf ball of the present invention, at least one ball structural portion is formed by using the resin composition used for forming a golf ball of the present invention. In particular, to make effective use of the characteristic of the resin composition, an intermediate layer between a solid core and a cover of a solid golf ball may be made from the resin composition.
To obtain the above solid golf ball, there is no limitation in materials of structural portions other than the intermediate layer. For example, the core may be made from the resin composition of the present invention; however, it can be made from a general rubber based material. In the case of using the general rubber based material, the composition of the material and the vulcanization condition may be suitably adjusted. To be more specific, the rubber based material contains a base rubber, a crosslinking agent, a co-crosslinking agent, and an inactive filler. As the base rubber, natural rubber and/or synthetic rubber, which have been adopted for solid golf balls, may be used; however, according to the present invention, 1,4-polybutadiene having at least 40% of a cis-structure is preferably used. In this case, a suitable amount of natural rubber, polyisoprene rubber, and/or styrene-butadiene rubber may be added to the above 1,4-polybutadiene as needed.
As the crosslinking agent, there may be used an organic peroxide such as dicumyl peroxide or di-t-butyl peroxide. In particular, dicumyl peroxide is preferably used. The content of the crosslinking agent may be in a range of 0.5 part by weight or more, preferably 0.8 part by weight or more, and 3 parts by weight or less, preferably 1.5 parts by weight or less, on the basis of 100 parts by weight of the base rubber.
The co-crosslinking agent is not particularly limited but may be a metal salt of an unsaturated fatty acid, particularly, a zinc salt, a magnesium salt, or a calcium salt of an unsaturated fatty acid having 3 to 8 carbon atoms (for example, acrylic acid or methacrylic acid). In particular, a zinc salt of an unsaturated fatty acid, such as zinc acrylate or zinc methacrylate is preferably used. The content of the co-crosslinking agent may be in a range of 24 parts by weight or more, preferably 28 parts by weight or more, and 38 parts by weight or less, preferably 34 parts by weight or less, on the basis of 100 parts by weight of the base rubber.
As the inactive filler, there may be used zinc oxide, barium sulfate, silica, calcium carbonate, or zinc carbonate. In particular, zinc oxide is preferably used as the inactive filler. The content of the inactive filler is dependent on the specific gravity of each of a core and a cover, and the specification on weight of a ball, and the like and thereby not particularly limited, but may be in a range of 10 to 60 parts by weight on the basis of 100 parts by weight of the base rubber.
The composition for a core, containing the above-described components, is kneaded by using a general kneader, for example, a Banbury mixer/kneader/roll mill and is compression-molded or injection-molded by using a mold for a core; and a molded body is heated and hardened at a temperature being high sufficient to promote reaction of the crosslinking agent and co-crosslinking agent (for example, in a range of 130 to 170xc2x0 C. in the case of using dicumyl peroxide as the crosslinking agent and zinc acrylate as the co-crosslinking agent).
The diameter of the solid core thus obtained is generally in a range of 38.85 to 39.95 mm.
An intermediate layer is then formed around the solid core by placing the solid core in a mold used for general ball molding, compressing-molding or injection-molding the resin composition used for forming a golf ball of the present invention as the intermediate layer material in the mold.
A cover is then formed on the intermediate layer by injection-molding a cover material. As the cover material, there may be used a known ionomer resin. Specific examples of the known ionomer resins may include Himilan(copyright) 1554, 1557, 1601, 1605, 1706, 1855, 1856, AM7315, AM7316, AM7317, and AM7318 (sold by Du Pont-Mitsui Polychemicals Co., Ltd.), and Surlyn(copyright) 6320, 7930, 8120, 8945, and 9945 (sold by Du Pont DE NEMOURS and COMPANY).
After the intermediate layer is covered with the cover, the resultant ball is subjected to polishing for deburring, pre-treatment, and painting in accordance with the same manner as that of a general golf ball production process.


The present invention relates to a composition based on fatty acid diamide comprising: a) from 92% to 100% by weight of one or more fatty acid diamides, treated in situ by a neutralizing agent so as to reduce the residual amine content to a residual amine number, expressed in mg KOH/g, which remains less than 0.5, b) optionally, up to 8% by weight of at least one amorphous or semicrystalline oligomer with a Tg of greater than 60° C., with the sum of the % by weight a)+b) being equal to 100% by weight of the said diamide composition and with a) and b) being miscible as a blend.

There already exists rheology additives which are fatty acid diamides, used for mastic and adhesive compositions, in particular diamides based on 12-hydroxystearic acid. These diamides, which are provided in the form of a micronized powder having a mean particle size ranging from 5 to 20 μm, are organogelators, that is to say small organic molecules capable of gelling organic solvents of all types, even at relatively low concentrations by weight. In their medium, they are often arranged in the form of fibres, which explains their organogelating and rheology-modifying effect. The change from the form of a powder to the form of fibres in an organic medium is known as activation. This activation is obtained by high shearing at a temperature suited to the use.
These diamides make it possible to have good performances in mastics of "MS-Polymer®" type, which are hybrid polymers based on alkoxylated silane endings, or polyurethane/silanes technology, with blocked silane endings, but they are poorly suited to the technology of polyurethane compositions, in particular one-component polyurethane compositions, symbolized in abbreviation by "1K-PU", where they may generate problems of stability of these mastics, with premature crosslinking and a limited pot life in use, rendering the composition unusable.
Additives such as treated silicas and polyureas exist as alternative routes.
However, silicas present problems of health and safety during the handling thereof because of the very fine dusts emitted into the atmosphere, the problems of performance, of reproducibility and of sedimentation, in comparison with organic additives, such as amides or polyureas. There exists a known alternative among "organic" additives which are polyureas, often developed to be measured by the formulators of polyurethanes themselves. The polyureas manufactured from isocyanates and amine have, on the other hand, the disadvantage of being difficult to control as additives in terms of structure, of the performances and of reproducibility of the said performances and of manufacture, which reproducibility is related to problems of solubility and of compatibility with the manufacturing or application medium, in view of the very cohesive structure of a urea bond. Such a urea-based rheology additive is described, for example, in U.S. Pat. No. 6,548,593.
The present invention is targeted at an additive "activatable" at low temperature in a formulation which is sensitive to nucleophiles, in particular polyurethane, such as 1K-PU but also 2K-PU, more particularly 1K-PU, which additive offers an effective rheological solution and makes it possible to retain the stability of the formulations which are sensitive to nucleophiles, in particular polyurethanes, more particularly 1K-PU mastics, or other compositions which are sensitive to nucleophiles. The main technical problem to be solved is thus the search for means which make it possible to retain the stability of the said sensitive formulations during storage. Subsequently, as regards the rheological performance related essentially to the activation process, this performance will depend on the choice of the temperature and of the plasticizer used as a function of the final application medium.
The present invention is targeted more specifically at compositions with amide additives which allow them to be used as organogelators and in particular as rheology additives in compositions of formulations which are sensitive to nucleophiles, without the disadvantages mentioned of the state of the art, while preventing the deterioration in the stability of the said compositions or a premature gelling (signifying here irreversible crosslinking).

Additives made from fatty diamides for nucleophile-sensitive cross-linkable compositions


A casting adapted to carry a light emitting diode die and an anti-static die is disclosed. The casting comprises two electrodes for opposite electrodes and a wall. The light emitting diode die is mounted one of electrodes and the anti-static die is mounted on the other electrode. The wall is arranged between the light emitting diode die and the anti-static die. Further, the height of the wall is larger than that of the anti-static die to shade the anti-static die, whereby reflecting the light emitted from the light emitting diode die. Therefore, the reflection ratio of the light emitting diode die is improved, and the intensity generated by the whole light emitting diode is also improved.

1. Field of the Invention
The present invention relates to a casting for a light emitting diode (hereinafter refers to LED) module, more specifically, to a casting adapted to carry an LED die and an anti-static die, and provided with a wall formed therein, wherein the wall can shelter the anti-static die from the LED die and reflect the light emitted from the LED die more efficiency.
2. Description of the Related Art
As shown in FIG. 1, in the conventional LED module, two electrodes 11, 11′ are mounted in a casting 10. The electrode 11 is used to carry the LED die and the electrode 11′ is used to carry the anti-static die. The LED die 20 is connected with two electrodes 11, 11′ via wires 21, and the anti-static die 30 is connected with the electrode 11 via wire 31. Furthermore, an encapsulation layer 40 in the casting 10 covers the anti-static die 30. Once a voltage is applied to the electrodes 11, 11′, the LED die 20 will emit light, and meanwhile the anti-static die 30 can prevent the LED from being damaged by static charges.
However, in the conventional LED module, the LED die 20 and the anti-static die 30 respectively mounted on the electrodes 11, 11′ have certain thickness that cannot be ignored. The light emitted from the LED die 20 presents a good reflection ratio between the inner surface of the casting 10 and the electrode 11 in the casting 10. However, the light emitted from the LED decades since the anti-static die 30 shields and absorbs some of the light, causing the intensity of the whole LED module decreases.
Therefore, in view of the above drawbacks of the prior casting, the inventor proposes the present invention to overcome the above problems based on his deliberate researches and related principles.


The present invention relates to a method of manufacturing a semiconductor device including a process of removing a photoresist mask or a photosensitive polyimide mask remaining after implanting impurity ions into a semiconductor layer or the like, and has an object to prevent generation of oxides of impurities and photoresist explosion and arranging it so that no residue remains. The present invention comprises the steps of forming a mask composed of photosensitive organic matter on a layer, implanting impurity ions into the layer through the mask, and removing the mask through processing including three steps of: exposing the mask to a plasma activated gas containing hydrogen, exposing to the mask to a plasma activated gas containing oxygen, and exposing the mask to a solution containing nitric acid under conditions sufficient to dissolve alumina which had formed on the mask during exposure of the mask to oxygen.

1. Field of the Invention
The present invention relates to a method of removing a resist mask and a method of manufacturing a semiconductor device, and more particularly to a method of removing a photoresist mask or a photosensitive polyimide mask which remains after implanting impurity ions selectively into a semiconductor substrate to form a conductive layer or a steel or the like to improve hardness and persistence and a method of manufacturing a semiconductor device including a process of removing a resist mask.
In a method of manufacturing a semiconductor device, it is required to introduce impurities such as boron and phosphorus into a semiconductor substrate or the like selectively by ion implantation in order to form a pn junction such as a source/drain region and the other conductive layers in a semiconductor layer, a semiconductor substrate or the like.
In such a case, such a process is to form a mask using a photoresist or a photosensitive polyimide and to remove the mask after ion implantation is performed.
2. Description of the Prior Art
FIG. 1A to FIG. 1E are sectional views showing how to remove a photoresist mask after conducting ion implantation selectively into a semiconductor substrate for instance using a photoresist mask.
First, a photoresist mask is formed on a semiconductor substrate 1 by spin coating. Then, after exposing the photoresist film, it is soaked in a developer and a photoresist mask 2 is formed as shown in FIG. 1A.
Next, as shown in FIG. 1B, impurity ions are implanted selectively into the semiconductor substrate 1 through the photoresist mask 2.
At the same time, impurities, such as P, B and As, are bonded chemically with the remaining photoresist polymer, and the surface layer of the photoresist mask 2 changes in quality and becomes a very hard layer. This hard layer is referred to as a carbonized layer (transmuted layer) 2b. Besides, the photoresist polymer inside the photoresist mask beyond reach of impurities remains in a state as it is. This interior layer is referred to as an un-changed layer (non-transmuted layer) 2a.
Then, ashing, using an oxygen plasma, is applied to the photoresist mask 2 so as to remove it.
Now, the ashing, using oxygen plasma, demolishes the carbonized layer 2b in the surface layer of the photoresist mask 2 by utilizing bombardment by ions in oxygen plasma, and also the photoresist mask is removed by utilizing an oxidation reaction between oxygen ions and the photoresist polymer.
As shown in FIG. 1C, however, in ashing with oxygen plasma, impurities (such as P, B and As) implanted into the photoresist mask 2 and oxygen formed into plasma react with each other, and oxides of these impurities are produced. In particular, there is such a problem that those oxides of impurities formed in the ashing of the photoresist mask after ions are implanted at high dose, are difficult to volatilize. Therefore they remain on the substrate as it is.
Further, when the wafer temperature rises, because of plasma irradiation, before the carbonized layer 2b is removed completely, volatile components inside the un-changed layer 2a are gasified and expanded as shown in FIG. 1D. In such a case, since the carbonized layer 2b which covers the un-changed layer 2a has a structure which is dense and does not pass gas 2c, what is called a "photoresist explosion", in which the carbonized layer 2b explodes becasue of the pressure of the expanded gas 2c, is generated as shown in FIG. 1E. Further, there is such a problem that the pieces of the carbonized layer 2b that have scattered by the photoresist explosion form particles, which cause lowering of production yield of semiconductor devices.
Accordingly, a method of performing hydrogen plasma processing, such that the wafer temperature is maintained at a low temperature, has been developed as a process in which the photoresist explosion is not brought about, and oxides of impurities are not produced. This processing method is called a 2-step ashing process, and has been announced already by the present inventor under a title of "High Ashing Rate of Ion Implanted Resist Layer" in DRY PROCESS SYMPOSIUM OF 1992.
It has been well known that a compound of an impurity (P, B or As) and hydrogen is liable to volatilize, and it was found that the carbonized layer had been removed without leaving residues when hydrogen plasma processing was performed practically. Further, since the wafer is cooled to a low temperature of approximately 5.degree. C., the photoresist explosion has not occurred. Reactive ion etching (RIE) for removing the carbonized layer physically and chemically by hydrogen ions is suitable for the hydrogen plasma processing.
Further, after the carbonized layer is removed by the hydrogen plasma processing, the interior un-changed layer appears. In order to remove this un-changed layer, a downstream ashing process using O.sub.2 as main reaction gas is very often applied because its process has less bombardment of the substrate by ions.
By applying the 2-step ashing processing in which the plasma processing by hydrogen gas and the downstream processing by oxygen gas described above are performed in succession, generation of oxides of impurities is prevented, and photoresist explosion is also prevented, thus greatly reducing the quantity of produced particles. With this, it is possible to aim at improvement of production yield of semiconductor devices.
When an ashing process is performed using this 2-step ashing process, however, new residues 4 remain along the side wall of the removed photoresist mask 2 sometimes as shown in FIG. 2, which becomes a problem.

Method of removing resist mask and a method of manufacturing semiconductor device