TW201422531A - Magnesium hydroxide particle and resin composition comprising the same - Google Patents

Abstract

The presnt invention provides a magnesium hydroxide particle, a resin composition comprising the same and a manufacturing method thereof, which has less α -ray releasing and excellent fluidity and dispersity while formulating the resin. This invention also provides a method for manufacture of a magnesium hydroxide particle which is a hexagonal prism particle with 2 parallel upper and lower hexagonal base surfaces and 6 outer prism surfaces formed between the base surfaces, wherein the length of the c-axis of the hexagonal prism particle is 0.5 to 6.0 μ m, the length of the c-axis is 50% or more of the average particle size of the hexagonal prism particlem, the releasing of α -ray is 0.020c/cm<SP>2</SP>/h or less, and the purity is 98.0% or more.

Description

Magnesium hydroxide particles, and resin composition containing the magnesium hydroxide particles

The present invention relates to magnesium hydroxide particles and a resin composition containing the magnesium hydroxide particles.

Since magnesium hydroxide does not generate a toxic gas during sintering and is excellent in environmental properties, it is often added as a flame retardant for a semiconductor sealing resin composition. However, the current flame retardant has a high amount of α-ray emission and causes malfunction due to α rays, so that the existing flame retardant cannot be used as a flame retardant for a memory integrated circuit. Moreover, the situation in which a logic integrated circuit that does not require an α-ray corresponding strategy has been combined with a memory volume circuit has been increasing. Therefore, the use of flame retardants for logic integrated circuits has also become a corresponding strategy for alpha rays. In order to solve such a problem, there is known a magnesium hydroxide particle which is characterized by satisfying the following elements (i) to (iv): (i) an average secondary particle diameter of 5 μm or less; (ii) a BET specific surface area of 10m ² /g or less (iii) The total amount of the content of the Fe compound and the Mn compound is 0.02% by weight or less in terms of metal (iv) The total amount of the U compound and the Th compound is converted into a metal system of 10 ppb or less (Patent Document 1) .

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2001-323169

However, the method for producing magnesium hydroxide described in Patent Document 1 is a method for producing a method in which magnesium chloride or magnesium nitrate is used as a raw material, and the aqueous medium is heated under pressure. Since the magnesium hydroxide obtained by the method is in the form of a thin plate having a thin crystal shape and is easily aggregated, there is a problem that the viscosity of the resin rises and the fluidity or workability deteriorates when it is kneaded as an additive in the synthetic resin. In other words, according to the research by the inventors of the present invention, it has been found that in addition to the problem of the α-ray corresponding strategy of the magnesium hydroxide particles of Patent Document 1, the improvement in the fluidity and dispersibility at the time of blending in the resin is improved. Room for it.

Therefore, an object of the present invention is to provide a magnesium hydroxide particle and a resin composition containing the magnesium hydroxide particle, which is capable of solving the above-mentioned problem, wherein the amount of α-ray emission is small and the fluidity is adjusted in the resin. And those with good dispersion.

In order to solve the above problem, the inventors of the present invention have repeatedly conducted various reviews, and as a result, it has been found that the amount of α-ray emission is small, and the particles containing no amorphous crystal shape are hexagonal columnar and have a very large thickness compared with the conventional crystal. When magnesium hydroxide particles are used as additives for the resin composition, In other words, when the magnesium hydroxide particles having a hexagonal column shape and a uniform crystal shape which is sufficiently grown in the c-axis direction are obtained, the α-ray emission amount is small, and excellent effects in terms of fluidity and flame retardancy are obtained, and the present invention has been completed. . Further, the inventors of the present invention have found that the magnesium hydroxide particles can be produced by using magnesium hydroxide slurry containing magnesium hydroxide having a small amount of α-ray emission and a predetermined amount of iron and calcium, and hydrating the magnesium oxide. get.

The present invention relates to a magnesium hydroxide particle having a hexagonal column formed by a base surface of a hexagonal shape which is parallel to each other and a hexagonal column formed on the surface of the base surface and having a peripheral surface of 6 faces. The size of the hexagonal columnar particles in the c-axis direction is 0.5 to 6.0 μm, and the size in the c-axis direction is 50% or more of the median diameter of the hexagonal columnar particles, and the α-ray emission amount is 0.020 c/ It is less than cm ² /h, and the purity is 98.0% by mass or more.

The present invention relates to the aforementioned magnesium hydroxide particles, wherein the content of Fe is 30 to 800 ppm, and the content of Ca is 30 to 900 ppm.

The present invention relates to a method for producing magnesium hydroxide particles. The method for producing magnesium hydroxide particles comprises the steps of: (a) adding magnesium hydroxide, an iron compound, and a calcium compound to a solvent, and stirring to obtain hydrogen. a step of slurry of magnesium oxide, iron, and calcium, wherein the purity of the magnesium hydroxide is 95% by mass or more, and the amount of α-ray emission is 0.060 c/cm ² /h or less, and the amount of Fe added to the magnesium hydroxide a step of 30 to 800 ppm and a Ca addition amount of 30 to 900 ppm; (b) a step of filtering, washing and drying a slurry containing magnesium hydroxide, iron, and calcium to obtain coarse particles of magnesium hydroxide; a step of firing magnesium hydroxide coarse particles in an atmospheric gas atmosphere at 800 to 1900 ° C to obtain magnesium oxide particles; (d) pulverizing the magnesium oxide particles by sieving to obtain a median diameter of 3 The magnesium oxide powder having a crystallite diameter of 10 × 10 ^-9 m or more is added to a temperature of 100 ° C or less in which one or more acids selected from the group consisting of organic acids and inorganic acids are added. Hydration of magnesium oxide in water followed by high shear stirring To obtain a slurry of magnesium hydroxide step; and (e) magnesium hydroxide slurry was filtered, washed with water and dried, to give magnesium hydroxide particles of step.

The present invention relates to the method for producing magnesium hydroxide particles described above, wherein the step (d) further comprises: (d') the magnesium hydroxide slurry obtained in the step (d) and the magnesium oxide powder defined in the step (d) Adding to a warm water of 100 ° C or less to which one or more acids selected from the group consisting of organic acids and inorganic acids have been added, followed by high-shear stirring to carry out a hydration reaction of magnesium oxide to obtain a magnesium hydroxide slurry step.

The present invention relates to a resin composition comprising: (I) an epoxy resin, (II) a hardener, (III) an inorganic filler, and (IV) the aforementioned magnesium hydroxide particles as a flame retardant or by The magnesium hydroxide particles obtained by the above production method.

The present invention relates to the resin composition described above, wherein the amount of the magnesium hydroxide particles is from 1 to 35 mass% of the resin composition.

The present invention relates to the use of a resin composition as described above for use in the sealing of semiconductors.

The present invention relates to a semiconductor device using the aforementioned resin composition.

According to the present invention, it is possible to obtain a magnesium hydroxide particle having a small amount of α-ray emission and having good fluidity and dispersibility when formulated in a resin, and a resin composition containing the magnesium hydroxide particle.

Fig. 1 is a view showing the appearance of the magnesium hydroxide particles of the present invention.

Magnesium hydroxide particles

The magnesium hydroxide particles of the present invention are magnesium hydroxide particles having a hexagonal column shape as shown in Fig. 1 and having a size in the c-axis direction (hereinafter referred to as "Lc") of 0.5 to 6.0 μm. In the magnesium hydroxide particles of the present invention, Lc is preferably 0.9 to 6.0 μm. Further, the ratio of Lc of the present invention to the median diameter (d) of the magnesium hydroxide particles, i.e., Lc/d, is 50% or more, preferably 50 to 150%, more preferably 60 to 90%. When Lc/d is 50% or more, the fluidity of the magnesium hydroxide particles with respect to the resin is good. The larger the value of Lc/d, the larger the hexagonal columnar particle is in the c-axis direction. There are several interactions between the magnesium hydroxide particles and the resin, and the particle shape becomes the cause of the free movement of the resin. In general, this tendency is affected by the shape of the particles. That is, the greater the degree of shape anisotropy, the greater the effect. Since the magnesium hydroxide particles of the present invention are particles which are sufficiently grown in the c-axis direction, the shape anisotropy is smaller than the conventional one, and it is an obstacle to the resin. There are few reasons for the freedom movement. Further, the median diameter d of the magnesium hydroxide particles is not particularly limited as long as it satisfies the above Lc/d, and is usually preferably in the range of 0.1 to 10 μm.

Further, the Lc of the size of the magnesium hydroxide particles in the c-axis direction is a measured value of the particles having the largest length in the field of view when observed by a scanning electron microscope. Further, the median diameter is a cumulative 50% particle diameter (D ₅₀ ) of a volume basis when measured by a laser diffraction scattering type particle size distribution measuring apparatus.

The amount of α-ray emission of the magnesium hydroxide particles of the present invention is 0.020 c/cm ² /h or less. As long as it is within this range, the possibility of semiconductor IC failure is low. It is preferably 0.001 to 0.020 c/cm ² /h, more preferably 0.001 to 0.010 c/cm ² /h.

In the present invention, examples of the element for emitting α-rays contained in the magnesium hydroxide particles include uranium (U), yttrium (Th), and lanthanum (Rn). Specifically, in the case where U, Th, and Rn are converted into a total amount of metal elements, the magnesium hydroxide particles of the present invention are contained in an amount of 10 to 100 ppm, preferably 10 to 60 ppm.

The purity of the magnesium hydroxide particles of the present invention is 98.0% by mass or more. As long as it is within this range, the elution of impurities can be highly suppressed, and an additive which is a resin used for a highly functional material can be suitably used. The purity of the magnesium hydroxide particles of the present invention is preferably from 98.5 to 99.8% by mass.

In the present specification, the purity is an impurity element (Ag, Al, B, Ba, Bi, Ca, Cd, Cl, Co, Cr, Cu, Fe, Ga, In, K, Li, Mn, Mo, in the particle to be measured). Na, Ni, P, Pb, Rn, S, The content of Si, Sr, Th, Ti, Tl, U, V, Zn, and Zr) is deducted from the total content of 100% by mass. Determination of impurity elements (Ag, Al, B, Ba, Bi, Ca, Cd, Co, Cr, Cu, Fe, Ga, In, K, Li, Mn, Mo, Na, Ni, P, Pb, Rn, S, Si, Sr, Th, Ti, Tl, U, V, Zn, and Zr) are prepared by dissolving the sample in an acid, and measuring the mass using an ICP emission spectrometer. The amount of Cl is dissolved in the acid after the sample is used, and spectrophotometry is used. The value of the measured mass is measured.

The magnesium hydroxide particles of the present invention preferably have a content of iron (Fe) of 30 to 800 ppm and a content of calcium (Ca) of 30 to 900 ppm. When the content of Fe is from 30 to 800 ppm and the content of Ca is from 30 to 900 ppm, the magnesium hydroxide particles are likely to have a hexagonal column shape and uniform crystal shape, and are highly resistant to elution of metal impurities, and can be suitably used as an additive. For example, it is used as a flame retardant. More preferably, the content of Fe is 30 to 600 ppm, and the content of Ca is 30 to 800 ppm; more preferably, the content of Fe is 30 to 500 ppm, and the content of Ca is 30 to 500 ppm; and the content of Fe is 300 to 500 ppm and a content of Ca of 300 to 500 ppm; and particularly preferably a content of Fe of 400 to 500 ppm and a content of Ca of 300 to 500 ppm.

Further, the magnesium hydroxide particles of the present invention may contain an impurity element in a range in which the elution of impurities is highly suppressed. For example, the magnesium hydroxide particles of the present invention may contain zinc (Zn) in an amount of about 10 to 2,000 ppm.

2. Method for producing magnesium hydroxide particles of the present invention

The magnesium hydroxide particles of the present invention can be produced, for example, in the following manner.

First, magnesium hydroxide (purity of 95% by mass or more and α-ray emission amount of 0.060 c/cm ² /h or less), a compound of iron, and a compound of calcium are added to a solvent and stirred to obtain magnesium hydroxide. The slurry of iron, iron and calcium is filtered and washed with water, and then the resultant is dried to obtain coarse particles of magnesium hydroxide. Next, the magnesium hydroxide raw material is fired in an atmospheric gas atmosphere at a temperature of 800 to 1900 ° C to obtain a magnesium oxide raw material. Then, the magnesium oxide raw material is pulverized, and the magnesium oxide having a median diameter of 3 to 30 μm and a microcrystalline diameter of 10×10 ^-9 m or more is added to the organic acid and the inorganic acid added thereto. The hydrated reaction of magnesium oxide is carried out in warm water of 100 ° C or less of one or more kinds of acids in the group under high shear stirring, and the formed solid fraction is subjected to filtration, washing with water, and drying to obtain Magnesium hydroxide particles obtained by the production method of the present invention.

Specifically, the method for producing magnesium hydroxide particles of the present invention comprises the steps of: (a) adding magnesium hydroxide, an iron compound, and a calcium compound to a solvent, and stirring to obtain magnesium hydroxide, iron, and calcium; The step of slurry, the purity of magnesium hydroxide in this step is 95% by mass or more, and the amount of α-ray emission is 0.060 c/cm ² /h or less, and the amount of iron added to magnesium hydroxide is 30 to 800 ppm, and calcium The amount of addition is 30 to 900 ppm; (b) the step of filtering, washing and drying the slurry containing magnesium hydroxide, iron, and calcium to obtain coarse particles of magnesium hydroxide; (c) in an atmospheric gas atmosphere, a step of firing magnesium hydroxide coarse particles at 800 to 1900 ° C to obtain magnesium oxide particles; (d) pulverizing the magnesium oxide particles, and sieving to obtain a median diameter of 3 to 30 μm and a crystallite diameter Magnesium oxide powder of 10 × 10 ^-9 m or more is added to warm water of 100 ° C or less to which one or more acids selected from the group consisting of organic acids and inorganic acids have been added, and secondly, under high shear stirring a step of hydrating magnesium oxide to obtain a magnesium hydroxide slurry; and (e) a hydrogen and oxygen solution Magnesium slurry was filtered, washed with water and dried, to give magnesium hydroxide particles of step.

(1) Step (a)

Step (a) is a step of adding magnesium hydroxide, an iron compound and a calcium compound to a solvent and stirring to obtain a slurry containing magnesium hydroxide, iron, and calcium, and the purity of the magnesium hydroxide in this step is 95% by mass. As described above, the amount of α-ray emission is 0.060 c/cm ² /h or less, the amount of iron added to magnesium hydroxide is 30 to 800 ppm, and the amount of calcium added is 30 to 900 ppm.

The magnesium hydroxide used in the step (a) is not particularly limited as long as it has a purity of 95% by mass or more and an α-ray emission amount of 0.060 c/cm ² /h or less, and a commercially available product can be used. The magnesium hydroxide used in the above step (a) may be such a magnesium hydroxide having an α-ray emission amount, for example, a uranium-free compound, a ruthenium compound or a ruthenium compound is selected, or a minimum amount is selected. Moreover, for example, commercially available products manufactured by TATEHO Chemical Industries Co., Ltd., Ube Materials Co., Ltd., Kosei Chemical Industry Co., Ltd., Suga Chemical Industry Co., Ltd., and Kyowa Chemical Industry Co., Ltd. are used as raw materials. The magnesium hydroxide used in the step (a) can also be obtained by a method of removing U, Th and Rn using hydrotalcite as described in JP-A-2001-323169. The amount of α-ray emission of the magnesium hydroxide used in the step (a) is preferably 0.001 to 0.060 c/cm ² /h, more preferably 0.001 to 0.050 c/cm ² /h. Further, U, Th, and Rn of the magnesium hydroxide used in the step (a) are converted into a total amount of metal elements, preferably 10 to 100 ppm, more preferably 10 to 60 ppm.

The median diameter of the magnesium hydroxide may be, for example, 0.5 to 50 μm. The median diameter of the magnesium hydroxide can be a median diameter by using a pulverizer such as a ball mill.

Examples of the iron compound include iron oxide (iron (II) oxide and iron (III) oxide), iron hydroxide, iron carbonate, iron chloride, and iron nitrate, preferably iron oxide. The iron compound may be used singly or in combination of a plurality of iron compounds. The calcium compound may, for example, be calcium oxide, calcium hydroxide, calcium carbonate, calcium chloride or calcium nitrate, preferably calcium oxide. The calcium compound may be used singly or in combination of a plurality of calcium compounds. The median diameter of the iron compound and the calcium compound is not particularly limited and is, for example, 0.5 to 50 μm. Further, the purity of the iron compound and the calcium compound and the amount of α-ray emission are not particularly limited as long as the amounts of Fe and Ca added in the present invention are satisfied. For example, the purity of the iron compound and the calcium compound is preferably 95% by mass or more. Further, the amount of α-ray emission of the iron compound and the calcium compound is preferably 0.060 c/cm ² /h or less.

The solvent can be exemplified by ion-exchanged water. The concentration of magnesium hydroxide in the slurry containing magnesium hydroxide, iron, and calcium is not particularly limited, but is preferably 50% by weight or less, and more preferably 10 to 40% by weight.

With respect to the amount of the iron compound and the calcium compound used, the amount of iron (Fe) added is 30 to 800 ppm with respect to magnesium hydroxide, and the amount of calcium (Ca) added is 30 to 900 ppm. The amount of the iron compound and the calcium compound to be used as the amount of Fe added and the amount of Ca added can be burned by A further hydration step is carried out to obtain magnesium hydroxide particles having a uniform crystal shape. Preferably, Fe is added in an amount of 30 to 600 ppm, and Ca is added in an amount of 30 to 800 ppm, more preferably Fe is added in an amount of 30 to 500 ppm, and Ca is added in an amount of 30 to 500 ppm, particularly preferably Fe content. It is 300 to 500 ppm, and the addition amount of Ca is 300 to 500 ppm, and further, the addition amount of Fe is 400 to 500 ppm, and the addition amount of Ca is 300 to 500 ppm.

In the present invention, the magnesium hydroxide of the raw material may contain iron or calcium. In this case, after the content of iron and calcium in the magnesium hydroxide of the raw material is measured in advance, the iron compound and the calcium are added so that the amount of iron and calcium added to the magnesium hydroxide is the same amount. The compound was stirred and a slurry containing magnesium hydroxide, iron and calcium was obtained.

Further, the iron compound of the raw material and the compound of calcium are in the case of containing uranium, cerium and lanthanum. In this case, after the content of uranium, strontium and barium in the compound of the iron of the raw material and the compound of calcium is measured in advance, the amount of uranium, thorium and cerium added to the compound of iron and the compound of calcium may be as described above. In a manner, an iron compound and a calcium compound are added and stirred to obtain a slurry containing magnesium hydroxide, iron, and calcium.

Further, in the step (a), for the purpose of improving the crystallinity of the obtained magnesium hydroxide, a zinc compound may be added to a slurry containing magnesium hydroxide, iron and calcium. Examples of the zinc compound include zinc oxide, zinc hydroxide, zinc carbonate, zinc chloride, and zinc nitrate. The amount of the zinc compound used is not particularly limited. For example, the amount of zinc (Zn) added to magnesium hydroxide may be 10 to 2000 ppm.

The stirring system can be carried out, for example, at 10 to 50 ° C for 0.5 to 5 hours at a rotation speed of 100 to 800 rpm.

(2) Step (b)

In the step (b), the slurry containing magnesium hydroxide, iron and calcium obtained in the step (a) is filtered, washed with water and dried to obtain coarse magnesium hydroxide particles. Thereby, coarse particles of magnesium hydroxide containing iron and calcium before firing can be obtained. The magnesium hydroxide coarse particles before firing contain iron and calcium derived from a slurry containing magnesium hydroxide, iron and calcium. The filtration system can be carried out using a filter paper or the like, and the water washing can be carried out by adding pure water of 5 to 100 times by mass based on the mass of the magnesium hydroxide.

(3) Step (c)

The step (c) is a step of obtaining the magnesium oxide particles by firing the coarse magnesium hydroxide particles in the atmospheric gas atmosphere at 800 to 1900 ° C obtained in the step (b). The firing of the magnesium hydroxide coarse particles can be carried out, for example, by using an electric furnace or the like in an atmospheric gas atmosphere. Here, the firing system can be achieved by a firing method including a step of raising the temperature to a firing temperature at a predetermined temperature increase rate and a step of maintaining the firing temperature for a predetermined time. The temperature increase rate is preferably from 1 to 20 ° C / min, more preferably from 3 to 10 ° C / min. The firing temperature is 800 to 1900 ° C, preferably 1000 to 1500 ° C. The firing time at the time of maintaining the firing temperature is preferably from 0.1 to 5 hours, more preferably from 0.1 to 3 hours.

(4) Step (d)

In the step (d), the magnesium oxide particles obtained in the step (c) are pulverized and sieved to obtain a magnesium oxide powder having a median diameter of 3 to 30 μm and a crystallite diameter of 10×10 ^-9 m or more. Until the addition of one or more acids selected from the group consisting of organic acids and inorganic acids to warm water of 100 ° C or lower, followed by high-shear stirring, the hydration reaction of the magnesium oxide powder is carried out to obtain a magnesium hydroxide slurry. The steps.

The pulverized and sieved magnesium oxide powder used in the hydration reaction has a median diameter of from 3 to 30 μm, preferably from 5 to 20 μm, more preferably from 5 to 15 μm. When magnesium oxide in this range is used as a raw material, the hydration reaction can be sufficiently carried out, and magnesium oxide having an incomplete hydration reaction is not left, and magnesium hydroxide of a desired size is obtained. Further, the crystallite diameter is 10 × 10 ^-9 m or more, preferably 10 × 10 ^-9 to 40 × 10 ^-9 m, more preferably 10 × 10 ^-9 to 30 × 10 ^-9 m. When magnesium oxide in this range is used as a raw material, the reaction rate at the time of hydration is suppressed, and it does not become coarse aggregated particles. Further, the microcrystal diameter refers to a value calculated by the Scherrer equation using the X-ray diffraction method.

One or more acids selected from the group consisting of organic acids and inorganic acids are added to suppress the solubility of the magnesium oxide powder of the raw material.

The organic acid may, for example, be an aliphatic or aromatic organic acid having a carboxyl group or a sulfo group. Examples of the organic acid having a sulfo group include p-toluenesulfonic acid and trifluoromethanesulfonic acid. Examples of the organic acid having a carboxyl group include formic acid, acetic acid, propionic acid, butyric acid, and benzoic acid. The organic acid is preferably an aliphatic or aromatic organic acid having a carboxyl group, more preferably formic acid, acetic acid, propionic acid, butyric acid or benzoic acid. The organic acid may be used singly or in combination of a plurality of organic acids.

Examples of the inorganic acid include hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, and boric acid, and preferably nitric acid, phosphoric acid, and sulfuric acid. The inorganic acid may be used singly or in combination of a plurality of inorganic acids.

In terms of the amount of acid added, relative to step (d) The magnesium oxide powder is preferably 100 g, preferably 0.01 to 3.0 mol, more preferably 0.01 to 2.0 mol. As long as it is such an amount, the precipitation rate of the crystal is moderate, and the unevenness of the median diameter of the obtained magnesium hydroxide particles is small. When two or more types of acids (two or more types of organic acids, two or more types of inorganic acids, and a combination of one or more organic acids and one or more types of inorganic acids) are used as the acid, the amount of acid added is The total amount of two or more acids.

The hydration reaction is carried out at a temperature below 100 ° C, for example in warm water of 50 to 100 ° C under high shear agitation. The temperature of the warm water is preferably from 60 to 100 °C. The water used for warm water is preferably ion-exchanged water in order to avoid the incorporation of impurities. In the case of high shear stirring, the hydration reaction of magnesium oxide can be sufficiently performed to obtain a desired degree of stirring of the magnesium hydroxide slurry, and for example, a high speed agitator equipped with a turbine blade can be used. get on. The rotation speed of the mixer is preferably from 8 to 18 m/s, more preferably from 9 to 15 m/s. The mixing time may vary depending on the degree of hydration reaction of the magnesium oxide, and may be, for example, 0.5 to 6 hours.

In the present invention, by using the magnesium hydroxide contained in the magnesium hydroxide slurry obtained in the step (d) as a seed crystal, when the hydration reaction of the magnesium oxide particles is carried out, magnesium hydroxide particles having a higher purity and a large particle shape can be obtained. In terms of point, it is preferred. That is, the step (d) preferably further comprises the step (d') of: adding the magnesium hydroxide slurry obtained in the step (d) to the magnesium oxide powder defined in the step (d) to be added to the organic A step of obtaining a magnesium hydroxide slurry by subjecting the magnesium oxide powder to a hydration reaction under high shear stirring, in a warm water of 100 ° C or less in which one or more acids of the acid and the inorganic acid are grouped.

In the step (d'), the magnesium oxide powder defined in the step (d) is obtained by pulverizing and sieving the magnesium oxide particles obtained in the step (c) to have a median diameter of 3 to 30 μm and a crystallite diameter of Magnesium oxide powder of 10×10 ^-9 m or more.

In the step (d'), the amount of magnesium hydroxide contained in the magnesium hydroxide slurry as the seed crystal is converted into magnesium hydroxide in the magnesium hydroxide slurry obtained in the step (d'), preferably 10 to 40. weight%.

The conditions of the hydration reaction in the step (d') are also preferably included as described in the above step (d).

(5) Step (e)

In the step (e), the magnesium hydroxide slurry obtained in the step (d) is subjected to filtration, washing with water and drying to obtain magnesium hydroxide particles. Wherein, in the step (d), the magnesium hydroxide slurry of the step (e) is the magnesium hydroxide slurry obtained in the step (d').

The method described in the above step (b) can be exemplified by filtration and washing.

In the present invention, the magnesium hydroxide particles obtained in the step (e), that is, the magnesium hydroxide particles obtained by the production method of the present invention, may be used as the hydration reaction for magnesium oxide described in the step (d). crystal.

That is, the step (e) may further comprise the following steps (e') and (e"): (e') the magnesium hydroxide particles obtained in (e), and the magnesium oxide defined in the step (d) The powder is added to warm water of 100 ° C or less to which one or more acids selected from the group consisting of organic acids and inorganic acids are added, and secondly, hydration reaction of magnesium oxide powder is carried out under high shear stirring to obtain hydrogen hydroxide. a magnesium slurry step; (e") the magnesium hydroxide slurry obtained in the step (e') The steps of filtering, washing with water and drying to obtain magnesium hydroxide particles. In the steps (e') and (e"), the conditions for the hydration reaction of the magnesium oxide and the amount of the magnesium hydroxide particles to be seeded are as described above.

By the above steps, magnesium hydroxide particles produced by the production method of the present invention can be obtained. The magnesium hydroxide particles obtained by the production method of the present invention are preferably the magnesium hydroxide particles of the present invention.

The magnesium hydroxide particles of the present invention can improve the affinity for the resin, acid resistance, water repellency, ultraviolet absorbing property, and the like by performing various surface treatments. The magnesium hydroxide particles of the present invention can sufficiently exhibit their functions even when the dispersion in the above-mentioned resin is improved and the function is imparted by the surface treatment as described above.

The surface treatment agent for improving the affinity with the resin may, for example, be a higher fatty acid or an alkali metal salt thereof, a phosphate ester, a decane coupling agent, or a fatty acid ester of a polyhydric alcohol. Further, in order to improve acid resistance, water repellency, and the like, for example, silica coating by hydrolysis of methyl decanoate or ethyl citrate may be carried out, by using silicone oil, Coating by a polyfluoroalkyl phosphate salt or the like, and surface treatment by colloidal silica, alumina sol, fumed silica, or the like. Further, in order to improve the ultraviolet absorbing property, for example, titanium dioxide may be subjected to a hydrolysis reaction to carry out a titanium dioxide coating. The above surface treatment may also be carried out in combination of plural kinds. The amount of the surface treatment agent is not particularly limited and is, for example, 0.1 to 10% by weight based on the magnesium hydroxide.

3. Resin composition

The resin composition of the present invention comprises: (I) an epoxy resin, (II) a hardener, (III) an inorganic filler, and (IV) a magnesium hydroxide particle of the present invention as a flame retardant, or by the present invention The magnesium hydroxide particles obtained by the production method.

The epoxy resin of the component (I) is not particularly limited, and a known one can be used. Specific examples thereof include a bisphenol A type epoxy resin, a phenol novolak type epoxy resin, a cresol novolak type epoxy resin, a bisphenol type epoxy resin, and the like, and a cresol novolak type epoxy is preferable. Resin.

The curing agent of the component (II) is not particularly limited, and a known one may be used, and examples thereof include a phenol resin, an acid anhydride, and an amine compound, and a phenol resin is preferable.

Examples of the inorganic filler of the component (III) include quartz glass powder, talc, silica powder, alumina powder, calcium carbonate, boron nitride, tantalum nitride, and carbon black powder. Among them, a cerium oxide powder is preferable, and a spherical cerium oxide powder is preferable, and a spherical molten cerium oxide powder is further preferable.

The resin composition of the present invention is obtained by kneading the magnesium hydroxide particles of the present invention or the magnesium hydroxide particles obtained by the production method of the present invention together with an epoxy resin, a curing agent, an inorganic filler, and the like. In the resin composition, the amount of the magnesium hydroxide flame retardant is preferably from 1 to 35% by mass based on the total amount of the resin composition. In the total amount of the inorganic materials, that is, the total amount of the magnesium hydroxide flame retardant and the inorganic filler is preferably from 60 to 95% by mass based on the total of the resin composition.

The resin composition is excellent in environmental resistance such as flame retardancy, moisture resistance, and acid resistance, and is used as a semiconductor. The sealing agent can thus produce various semiconductor devices sealed with such a resin composition.

The resin composition for semiconductor encapsulation is not particularly limited as long as the various materials are uniformly dispersed and mixed. Specific examples thereof include various forms in which, after thorough mixing by a mixer or the like, the mixture is melt-kneaded by a mixing roll, an extruder, or the like, and then cooled and pulverized, and formed into pellets. The ingot is of a size and weight that meets the molding conditions; or a mixture of the components of the above resin composition is placed on a pallet, and after cooling, by pressure rolling, rolling calendering, Or a method of forming a sheet-like material by applying a method of coating a mixed solvent or the like.

The sealing method of the semiconductor element using the semiconductor sealing resin composition obtained in this manner is not particularly limited, and for example, a known molding method such as ordinary transfer molding can be used.

(Example)

The present invention will be specifically described by way of examples, but the invention is not limited to the following examples.

The crystal shape and Lc of the magnesium hydroxide particles and the magnesium oxide particles obtained in the examples, the median diameter (measurement of the laser diffraction scattering particle size distribution), the quality and purity of the impurity elements in the magnesium hydroxide, and The amount of α-ray emission was measured by the following method.

(1) Determination of crystal shape and Lc

The crystal shape was observed by a scanning electron microscope. Moreover, when viewed by a scanning electron microscope, the particles having the largest length in the field of view are measured. Lc of the child.

(2) Determination of laser diffraction scattering particle size distribution

The median diameter (volume-based cumulative 50% particle diameter (D ₅₀ )) was measured using a laser diffraction scattering type particle size distribution measuring apparatus (trade name: MT3300, manufactured by Nikkiso Co., Ltd.).

(3) Determination of the quality of impurity elements in magnesium hydroxide

Determination of impurity elements (Ag, Al, B, Ba, Bi, Ca, Cd, Co, Cr, Cu, Fe, Ga, In, K, Li, Mn, Mo, Na, Ni, P, Pb, S, Si, Sr, Ti, Tl, V, Zn, and Zr) were measured by dissolving a sample in an acid using an ICP emission spectroscopic analyzer (trade name: SPS-5100, manufactured by Seiko Instruments).

U, Th, and Rn were measured by dissolving a sample in an acid using an ICP emission spectroscopic analyzer (product name: ICP-MS SPQ9000, manufactured by SII Nano Technology).

Cl was measured by dissolving a sample in an acid using a spectrophotometer (trade name: UV-2550, manufactured by Shimadzu Corporation).

(4) Determination of purity

The purity of the magnesium hydroxide is calculated from the total value of the mass of the impurity element measured by subtracting 100% by mass of the above-mentioned "measurement of the mass of the impurity element in the magnesium hydroxide".

(5) Determination of the amount of α-ray emission

The α particle beam density (α-ray emission amount) was measured using a low-energy alpha ray measuring device (trade name: LACS-4000M). The measurement conditions are as follows. Applied voltage: 1.9 kV, counting gas: PR-10 gas (Ar90%, CH ₄ 10%) 100 mL/min, sample area: 4000 cm ² , total counting time: 99 hours, counting efficiency: 80%

[Example 1]

<Manufacture of Magnesium Hydroxide Particles>

Put in the container: magnesium hydroxide (purity of 95% by mass or more, α-ray emission amount of 0.028 c/cm ² /h, and median diameter of 4.9 μm), and addition amount of Fe to magnesium hydroxide The amount of iron oxide (the purity is 98.4% by mass or more, the amount of α-ray emission is 0.001 c/cm ² /h, and the median diameter is 0.53 μm), and the amount of Ca added is 300 ppm. Calcium (purity of 99.5 mass% or more, α-ray emission amount of 0.002 c/cm ² /h, and median diameter of 1.04 μm), and concentration of magnesium hydroxide is 30% by weight of ion-exchanged water, and Stir. Next, the obtained white precipitate was filtered, washed with water, and dried. The dried product was pulverized in a ball mill and fired at 1400 ° C for 2 hours using an electric furnace. The fired product was pulverized in a ball mill for 4 hours, and then classified to obtain a magnesium oxide powder. The obtained magnesium oxide powder had a median diameter of 9.6 μm and a crystallite diameter of 29.9×10 ^-9 m.

The obtained magnesium oxide powder was added to a container containing 20 L of an internal volume of 10 L of acetic acid having a concentration of 0.02 mol/L in an amount such that the concentration of the oxide (MgO) was 100 g/L. While maintaining the obtained mixed solution containing magnesium oxide at 90 ° C, a hydration reaction was carried out for 4 hours while stirring at a turbine blade rotation speed of 10 m/s using a high-speed stirrer. Thereafter, the slurry was used as a seed crystal, and magnesium hydroxide in an amount of 25% by weight of magnesium hydroxide finally obtained was added in the form of a slurry, and again in a container containing 10 L of an internal volume of 0.02 mol/L of acetic acid and having an internal volume of 20 L. Adding hydroxide to the seed crystal Magnesium oxide powder in an amount of 100 g/L in terms of MgO in total of magnesium and additional magnesium oxide. While maintaining the obtained mixed solution containing magnesium oxide at 90 ° C, a hydration reaction was carried out for 4 hours while stirring at a turbine blade rotation speed of 10 m/s using a high-speed stirrer. Finally, the obtained magnesium hydroxide slurry was filtered, washed with water, and dried to obtain magnesium hydroxide particles.

The obtained magnesium hydroxide particles had a purity of 99.1% by mass of magnesium hydroxide.

<evaluation test>

The magnesium hydroxide particles were kneaded in an epoxy resin at a ratio shown in Table 1, and the spiral flow and flame retardancy of the obtained resin composition were measured under the following conditions. Here, the spiral flow is a value indicating the fluidity of the thermoplastic resin and the thermosetting resin. Further, a cresol novolak type epoxy resin (epoxy equivalent 198) was used as an epoxy resin, a phenol novolak resin (hydroxyl equivalent of 105) was used as a hardener, and triphenylphosphine was used as a hardening accelerator, and a spherical molten yttrium oxide was used. As an inorganic filler. In Table 1, the ratio of the metal hydroxide is the ratio of the magnesium hydroxide flame retardant, and the ratio of the inorganic substance is the ratio of the magnesium hydroxide flame retardant and the spherical molten cerium oxide.

(1) Method for measuring flame retardancy

Using an epoxy resin composition, a flame retardancy test piece having a thickness of 1/16 ( was produced (forming conditions: temperature 175 ° C, time 120 seconds, post cure 175 ° C × 6 hours), in accordance with UL-94 The V-0 specification method evaluates flame retardancy. Also, "X" is a worse specification than V-0.

(2) Spiral flow measurement method

The spiral flow value was measured in accordance with EMMI 1-66 using a mold for spiral flow measurement at a temperature of 175 ° C and a pressure of 6 MPa.

[Embodiment 2]

The container was charged with magnesium hydroxide (purity of 95% by mass or more, α-ray emission amount of 0.049 c/cm ² /h, and median diameter of 5.0 μm), and addition amount of Fe to magnesium hydroxide. In order to obtain iron oxide in an amount of 450 ppm, the amount of Ca added is an amount of calcium oxide of 700 ppm, and the concentration of magnesium hydroxide is 30% by weight of ion-exchanged water, and is stirred. Further, the iron oxide and the calcium oxide were the same as those of the user of Example 1. Next, the resulting white precipitate was filtered, washed with water and dried. The obtained dried product was pulverized in a ball mill and fired at 1400 ° C for 2 hours using an electric furnace. The obtained fired product was pulverized in a ball mill for 8 hours, and then classified to obtain a magnesium oxide powder. The obtained magnesium oxide powder had a median diameter of 6.8 μm and a crystallite diameter of 27.6 × 10 ^-9 m.

The obtained magnesium oxide powder was added to a vessel containing 20 L of an internal volume of 10 L of acetic acid having a concentration of 0.03 mol/L in an amount of 100 g/L of the oxide (MgO). While maintaining the obtained mixed solution containing magnesium oxide at 90 ° C, a hydration reaction was carried out for 4 hours while stirring at a turbine blade rotation speed of 10 m/s using a high-speed stirrer. Thereafter, the mixture was filtered, washed with water, and dried to obtain magnesium hydroxide particles.

The purity of the obtained magnesium hydroxide particles and magnesium hydroxide was 98.7% by mass.

[Example 3]

The container was charged with the magnesium hydroxide used in Example 2 (purity of 95% by mass or more, α-ray emission amount of 0.049 c/cm ² /h, and median diameter of 5.0 μm), relative to magnesium hydroxide. The amount of addition of Fe is an amount of iron oxide of 50 ppm, and the amount of Ca added is an amount of calcium oxide of 200 ppm, and the concentration of magnesium hydroxide is 30% by weight of ion-exchanged water, and is stirred. Further, the iron oxide and the calcium oxide were the same as those of the user of Example 1. Next, the resulting white precipitate was filtered, washed with water and dried. The obtained dried product was pulverized in a ball mill and fired at 1400 ° C for 2 hours using an electric furnace. The obtained fired product was pulverized in a ball mill for 8 hours, and then classified to obtain a magnesium oxide powder. The obtained magnesium oxide powder had a median diameter of 5.8 μm and a crystallite diameter of 26.6 × 10 ^-9 m.

The obtained magnesium oxide powder was added to a container containing 20 L of an internal volume of 10 L of acetic acid having a concentration of 0.03 mol/L in an amount of 100 g/L of the oxide (MgO). While maintaining the obtained mixed solution containing magnesium oxide at 90 ° C, a hydration reaction was carried out for 4 hours while stirring at a turbine blade rotation speed of 10 m/s using a high-speed stirrer. Thereafter, the mixture was filtered, washed with water, and dried to obtain magnesium hydroxide particles.

The purity of the magnesium hydroxide of the obtained magnesium hydroxide particles was 98.9 mass%.

[Example 4]

The container was charged with the magnesium hydroxide used in Example 2 (purity of 95% by mass or more, α-ray emission amount of 0.049 c/cm ² /h, and median diameter of 5.0 μm), relative to magnesium hydroxide. The amount of Fe added is 200 ppm of iron oxide, and the amount of Ca added is an amount of 50 ppm of calcium oxide or magnesium hydroxide, and the concentration is 30% by weight of ion-exchanged water, and is stirred. Next, the resulting white precipitate was filtered, washed with water and dried. Further, the iron oxide and the calcium oxide were the same as those of the user of Example 1. The obtained dried product was pulverized in a ball mill and fired at 1400 ° C for 2 hours using an electric furnace. The obtained fired product was pulverized in a ball mill for 8 hours, and then classified to obtain a magnesium oxide powder. The obtained magnesium oxide powder had a median diameter of 6.4 μm and a crystallite diameter of 26.8 × 10 ^-9 m.

The obtained magnesium oxide powder was added in an amount of 100 g/L of the oxide (MgO) to a concentration of 0.03 mol/L in a concentration of 10 L. A container of 20 L of acetic acid. While maintaining the obtained mixed solution containing magnesium oxide at 90 ° C, a hydration reaction was carried out for 4 hours while stirring at a turbine blade rotation speed of 10 m/s using a high-speed stirrer. Thereafter, the mixture was filtered, washed with water, and dried to obtain magnesium hydroxide particles.

The obtained magnesium hydroxide particles had a purity of 99.8% by mass of magnesium hydroxide.

[Example 5]

The container was charged with the magnesium hydroxide used in Example 2 (purity of 95% by mass or more, α-ray emission amount of 0.049 c/cm ² /h, and median diameter of 5.0 μm), relative to magnesium hydroxide. The amount of Fe added is an amount of iron oxide of 400 ppm, and the amount of Ca added is an amount of calcium oxide of 600 ppm, and the concentration of magnesium hydroxide is 30% by weight of ion-exchanged water, and is stirred. Further, the iron oxide and the calcium oxide were the same as those of the user of Example 1. Next, the resulting white precipitate was filtered, washed with water and dried. The obtained dried product was pulverized in a ball mill and fired at 1400 ° C for 2 hours using an electric furnace. The obtained fired product was pulverized in a ball mill for 8 hours, and then classified to obtain a magnesium oxide powder. The obtained magnesium oxide powder had a median diameter of 6.5 μm and a crystallite diameter of 29.1 × 10 ^-9 m.

The obtained magnesium oxide powder was added to a vessel containing 20 L of an internal volume of 10 L of nitric acid having a concentration of 0.03 mol/L in an amount such that the concentration of the oxide (MgO) was 100 g/L. While maintaining the obtained mixed solution containing magnesium oxide at 90 ° C, a hydration reaction was carried out for 4 hours while stirring at a turbine blade rotation speed of 10 m/s using a high-speed stirrer. Thereafter, the mixture was filtered, washed with water, and dried to obtain magnesium hydroxide particles.

The obtained magnesium hydroxide particles had a purity of 99.0% by mass of magnesium hydroxide.

[Comparative Example 1]

The container was charged with magnesium hydroxide (purity of 95% by mass or more, α-ray emission amount of 0.082 c/cm ² /h, and median diameter of 5.1 μm), and addition amount of Fe to magnesium hydroxide. In order to obtain iron oxide in an amount of 450 ppm, the amount of Ca added is an amount of calcium oxide of 700 ppm, and the concentration of magnesium hydroxide is 30% by weight of ion-exchanged water, and is stirred. Further, the iron oxide and the calcium oxide were the same as those of the user of Example 1. Next, the resulting white precipitate was filtered, washed with water and dried. The obtained dried product was pulverized in a ball mill and fired at 1400 ° C for 2 hours using an electric furnace. The obtained fired product was pulverized in a ball mill for 8 hours, and then classified to obtain a magnesium oxide powder. The obtained magnesium oxide powder had a median diameter of 7.2 μm and a crystallite diameter of 28.4 × 10 ^-9 m.

The obtained magnesium oxide powder was added to a container containing 20 L of an internal volume of 10 L of acetic acid having a concentration of 0.03 mol/L in an amount of 100 g/L of the oxide (MgO). While maintaining the obtained mixed solution containing magnesium oxide at 90 ° C, a hydration reaction was carried out for 4 hours while stirring at a turbine blade rotation speed of 10 m/s using a high-speed stirrer. Thereafter, the mixture was filtered, washed with water, and dried to obtain magnesium hydroxide particles.

The obtained magnesium hydroxide particles had a purity of 99.8% by mass of magnesium hydroxide.

[Comparative Example 2]

The container was charged with the magnesium hydroxide used in Example 1 (purity of 95% by mass or more, α-ray emission amount of 0.028 c/cm ² /h, and median diameter of 4.9 μm), relative to magnesium hydroxide. The amount of addition of Fe is 1500 ppm of iron oxide, and the amount of Ca added is calcium oxide in an amount of 800 ppm, and the concentration of magnesium hydroxide is 30% by weight of ion-exchanged water, and is stirred. Further, the iron oxide and the calcium oxide were the same as those of the user of Example 1. Next, the resulting white precipitate was filtered, washed with water and dried. The obtained dried product was pulverized in a ball mill and fired at 1400 ° C for 2 hours using an electric furnace. The obtained fired product was pulverized in a ball mill for 8 hours, and then classified to obtain a magnesium oxide powder. The obtained magnesium oxide powder had a median diameter of 6.5 μm and a crystallite diameter of 25.4 × 10 ^-9 m.

The obtained magnesium oxide powder was added to a container containing 20 L of an internal volume of 10 L of acetic acid having a concentration of 0.03 mol/L in an amount of 100 g/L of the oxide (MgO). While maintaining the obtained mixed solution containing magnesium oxide at 90 ° C, a hydration reaction was carried out for 4 hours while stirring at a turbine blade rotation speed of 10 m/s using a high-speed stirrer. Thereafter, the mixture was filtered, washed with water, and dried to obtain magnesium hydroxide particles.

The obtained magnesium hydroxide particles had a purity of 98.2% by mass of magnesium hydroxide.

[Comparative Example 3]

The container was charged with magnesium hydroxide (purity of 95% by mass or more, α-ray emission amount of 0.028 c/cm ² /h, and median diameter of 4.9 μm) in the magnesium hydroxide. The amount of Fe added is iron oxide in an amount of 450 ppm, and the amount of Ca added is calcium oxide in an amount of 1,500 ppm, and the concentration of magnesium hydroxide is 30% by weight of ion-exchanged water, and is stirred. Further, the iron oxide and the calcium oxide were the same as those of the user of Example 1. Next, the resulting white precipitate was filtered, washed with water and dried. The obtained dried product was pulverized in a ball mill and fired at 1400 ° C for 2 hours using an electric furnace. The obtained fired product was pulverized in a ball mill for 8 hours, and then classified to obtain a magnesium oxide powder. The volume-based 50% particle diameter of the obtained magnesium oxide powder was 7.2 μm, and the crystallite diameter was 28.4 × 10 ^-9 m.

The obtained magnesium oxide powder was added to a container containing 20 L of an internal volume of 10 L of acetic acid having a concentration of 0.03 mol/L in an amount of 100 g/L of the oxide (MgO). While maintaining the obtained mixed solution containing magnesium oxide at 90 ° C, a hydration reaction was carried out for 4 hours while stirring at a turbine blade rotation speed of 10 m/s using a high-speed stirrer. Thereafter, the mixture was filtered, washed with water, and dried to obtain magnesium hydroxide particles.

The purity of the magnesium hydroxide of the obtained magnesium hydroxide particles was 98.1% by mass.

The magnesium hydroxide particles obtained in the examples and the comparative examples were obtained by combining the purity, the crystal shape, the Lc, the d (median diameter), the amount of Fe, the amount of Ca, the total amount of U, Th, and Rn, and the Lc/d. Table 2. Further, the α-ray emission amount of the magnesium hydroxide particles obtained in the examples and the comparative examples, and the resin compositions of the magnesium hydroxide particles obtained in the examples and the comparative examples were summarized in Table 3 for the spiral flow and the flame retardancy. .

From the results of Tables 2 and 3, it is also known that the magnesium hydroxide of the present invention has an Lc of 0.5 to 6.0 μm, an Lc/d of 50% or more, an α-ray emission amount of 0.020 c/cm ² /h or less, and a purity of 98.0. More than % by mass. Further, when it was confirmed that the magnesium hydroxide particles of the present invention were added as a flame retardant, the spiral flow was larger than that of the conventional magnesium hydroxide particles, and the fluidity was good. On the other hand, the magnesium hydroxide particles of the comparative example have a large amount of α-ray emission, but when they are kneaded as an additive to the resin, they are inferior in flame retardancy or fluidity.

(industrial availability)

Since the magnesium hydroxide particles of the present invention are composed of fine particles having a small amount of α-ray emission or particles which do not contain amorphous particles, and the entire system of the particles has a uniform crystal shape, the affinity for the resin is good. For the reasons described above, the magnesium hydroxide particles of the present invention are capable of responding to the problem of the corresponding strategy of α rays, and are excellent in flame retardancy and fluidity with respect to the resin. Therefore, there is a filler for use as a sealing resin composition for a semiconductor device such as a transistor, an IC, or an LSI.

The illustration in this case only indicates the shape of the magnesium hydroxide particles, which is insufficient to represent the technical characteristics of the magnesium hydroxide particles required in the first item of the patent application scope of the present application. Therefore, there is no designated representative map in this case.

Claims (8)

A magnesium hydroxide particle having a crystal outer shape consisting of hexagonal columnar particles composed of a base surface of a hexagonal shape which is parallel to each other and a surface of a prism which is formed between the base surfaces and has a peripheral surface of six sides. The size of the hexagonal columnar particles in the c-axis direction is 0.5 to 6.0 μm, and the size in the c-axis direction is 50% or more of the average particle diameter of the hexagonal columnar particles, and the amount of α-ray emission is 0.020 c/cm ² /h or less. And the purity was 98.0% by mass or more. The magnesium hydroxide particles according to claim 1, wherein the content of Fe is from 30 to 800 ppm, and the content of Ca is from 30 to 900 ppm. A method for producing magnesium hydroxide particles, comprising the steps of: (a) adding magnesium hydroxide, an iron compound, and a calcium compound to a solvent, and stirring to obtain a slurry containing magnesium hydroxide, iron, and calcium, Wherein, the purity of magnesium hydroxide is 95% by mass or more, and the amount of α-ray emission is 0.060 c/cm ² /h or less, the amount of iron added to magnesium hydroxide is 30 to 800 ppm, and the amount of calcium added is 30 to 900 ppm; (b) a step of filtering, washing and drying a slurry containing magnesium hydroxide, iron, and calcium to obtain coarse particles of magnesium hydroxide; (c) placing coarse particles of magnesium hydroxide in an atmospheric gas atmosphere, The step of firing at 800 to 1900 ° C to obtain magnesium oxide particles; (d) pulverizing the magnesium oxide particles, and sieving to obtain a median diameter of 3 to 30 μm and a crystallite diameter of 10 × 10 ^- Magnesium oxide powder of ⁹ m or more is added to warm water of 100 ° C or less to which one or more acids selected from the group consisting of organic acids and inorganic acids have been added, followed by high-shear stirring to carry out hydration reaction of magnesium oxide And obtaining the magnesium hydroxide slurry; and (e) introducing the magnesium hydroxide slurry into the slurry Filtered, washed with water and dried, to give magnesium hydroxide particles of step. The manufacturing method according to claim 3, wherein the step (d) further comprises (d') adding the magnesium hydroxide slurry obtained in the step (d) to the magnesium oxide powder defined in the step (d) to A step of obtaining a magnesium hydroxide slurry by adding a hydration reaction of magnesium oxide to warm water of 100 ° C or less selected from the group consisting of an organic acid and an inorganic acid in a group of at least 100 ° C is added. A resin composition comprising: (I) an epoxy resin, (II) a hardener, (III) an inorganic filler, and (IV) as a flame retardant as claimed in claim 1 or 2 The magnesium hydroxide particles described herein, or the magnesium hydroxide particles obtained by the production method described in claim 3 or 4. The resin composition according to claim 5, wherein the amount of the magnesium hydroxide particles is from 1 to 35 mass% of the resin composition. A use of the resin composition according to item 5 or claim 6 of the patent application, which is used for sealing a semiconductor. A semiconductor device using the resin composition described in claim 5 or 6.