X-ray shielding silicone composition, X-ray shielding silicone sheet and method for producing same

Abstract

The X-ray shielding silicone composition contains a silicone component, X-ray shielding particles, and thermally conductive particles, and contains 15 to 60 vol.% of the silicone component, 5 to 50 vol.% of the X-ray shielding particles, and 30 to 80 vol.% of the thermally conductive particles per 100 vol.% of the composition. As an example, the molded product is formed into a sheet by sheet molding or press molding, and then cured. As an example, the method for producing the sheet includes mixing the silicone composition to form a compound, and molding and curing the compound by sheet molding, extrusion molding, or press molding. As a result, a silicone composition having high X-ray shielding properties and thermal conductivity, an X-ray shielding silicone sheet, and a method for producing the same are provided.

Description

[Technical field]

[0001] The present invention relates to a silicone composition having high X-ray shielding properties, an X-ray shielding silicone sheet, and a method for producing the same. [Background technology]

[0002] In recent years, the performance of semiconductors such as CPUs has improved remarkably, and the amount of heat generated has also increased. For this reason, heat sinks are attached to electronic components that generate heat, and thermally conductive silicone sheets are used to improve the adhesion between the semiconductor and the heat sink. As devices become smaller, more powerful, and more highly integrated, thermally conductive silicone sheets are required to be soft and have high thermal conductivity. In addition, when ionizing radiation such as X-rays or gamma rays is irradiated on typical semiconductors such as MOSFETs and integrated circuits, positive charges accumulate in the silicon oxide film used as an insulating film, and negative charges are induced on the silicon surface. This causes the threshold voltage to shift in the negative direction. The change in element characteristics becomes greater as the amount of X-rays and gamma rays exposed increases, leading to malfunctions and failures of the device. For this reason, it is also necessary to reduce unnecessary X-rays leaking from X-ray generators and protect electronic components inside the irradiated body from radiation such as X-ray inspection. Patent Document 1 proposes a radiation shielding sealant using condensation type silicone and barium sulfate. Patent Document 2 proposes a radiation shielding composition using barium sulfate as an X-ray shielding material. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-234245 A [Patent Document 2] JP 2017-206645 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the silicone compositions in the above patent documents do not have sufficient X-ray shielding properties or thermal conductivity, and there is a demand for even higher X-ray shielding properties and thermal conductivity.

[0005] In order to solve the above-mentioned problems in the conventional art, the present invention provides a silicone composition having both high X-ray shielding properties and high thermal conductivity, an X-ray shielding silicone sheet, and a method for producing the same. [Means for solving the problem]

[0006] The X-ray shielding silicone composition of the present invention is an X-ray shielding silicone composition comprising a silicone component, X-ray shielding particles, and thermally conductive particles, wherein the silicone component is 15 to 60 vol.%, the X-ray shielding particles are 5 to 50 vol.%, and the thermally conductive particles are 30 to 80 vol.% per 100 vol.% of the composition, The X-ray shielding particles are at least one selected from the group consisting of precipitated barium sulfate and elutriated barium sulfate, and the thermally conductive particles are at least one inorganic particle selected from the group consisting of alumina, zinc oxide, magnesium oxide, aluminum nitride, boron nitride, aluminum hydroxide, and silicon carbide. It is characterized by:

[0007] The X-ray shielding silicone molded article of the present invention is formed into a sheet by at least one molding method selected from the group consisting of sheet molding, extrusion molding, and press molding, and then cured.

[0008] The method for producing an X-ray shielding silicone sheet of the present invention is characterized in that the silicone composition described above is mixed to form a compound, which is then molded by at least one molding method selected from the group consisting of sheet molding, extrusion molding, and press molding, and then cured. Effect of the Invention

[0009] The X-ray shielding silicone composition of the present invention contains a silicone component, X-ray shielding particles, and thermally conductive particles, and the silicone component is 15 to 60 vol.%, the X-ray shielding particles are 5 to 50 vol.%, and the thermally conductive particles are 30 to 80 vol.% per 100 vol.% of the composition, so that a silicone composition having high X-ray shielding properties and thermal conductivity, an X-ray shielding silicone sheet, and a method for producing the same can be provided. The X-ray shielding silicone composition of the present invention can reduce unnecessary X-rays leaking from an X-ray generating device, and can also protect electronic components inside an irradiated body from radiation such as in X-ray inspection. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic cross-sectional view showing a method of using an X-ray shielding silicone sheet according to one embodiment of the present invention. [Diagram 2] 2A-B are explanatory diagrams showing a method for measuring the thermal conductivity of a sample used in an embodiment of the present invention. [Diagram 3] FIG. 3 is a microscope (SEM) photograph (magnification: 2000 times) of the precipitated barium sulfate particles used in the examples of the present invention. [Figure 4] FIG. 4 is a microscope (SEM) photograph (magnification: 5000 times) of amorphous alumina used in an embodiment of the present invention. [Diagram 5] FIG. 5 is a microscope (SEM) photograph (magnification: 500 times) of spherical alumina used in an embodiment of the present invention. [Figure 6] FIG. 6 is a microscope (SEM) photograph (magnification: 1000 times) of elutriated barium sulfate used in an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention is an X-ray shielding silicone composition containing a silicone component, X-ray shielding particles, and thermally conductive particles, and the silicone component is 15 to 60 vol.%, preferably 17 to 55 vol.%, and more preferably 20 to 50 vol.%, per 100 vol.% of the composition. The X-ray shielding particles are 5 to 50 vol.%, preferably 6 to 45 vol.%, and more preferably 7 to 40 vol.%. The thermally conductive particles are 30 to 80 vol.%, preferably 32 to 78 vol.%, and more preferably 35 to 75 vol.%. This results in a composition with high X-ray shielding properties. If the X-ray shielding particles are less than 5 vol.%, the X-ray shielding properties are low, and if they exceed 50 vol.%, the proportion of the thermally conductive particles is low and the thermal conductivity cannot be maintained high, which is not preferable. Moreover, if the thermally conductive particles are less than 30 vol.%, the thermal conductivity will be low, and if they exceed 80 vol.%, the proportion of X-ray shielding particles will be low and the X-ray shielding properties will be low, which is not preferable. The silicone component is also called silicone polymer or organopolysiloxane, and is a thermosetting resin, which is preferable because it has heat resistance.

[0012] The X-ray shielding rate of the composition is preferably 30% or more, more preferably 30 to 100%, and further preferably 35 to 100%, as measured in accordance with JIS Z 4501:2011 and JIS T61331-1:2016, resulting in a composition with high X-ray shielding properties.

[0013] The thermal conductivity of the composition is preferably 0.8 W / mK or more, more preferably 0.8 to 10 W / mK, and even more preferably 1.0 to 8.0 W / mK, as measured according to the hot disk method of ISO / CD22007-2:2008. This results in a composition with high thermal conductivity, which is suitable as a heat sink (TIM) between a heat generating part and a heat dissipating part of an electronic component or the like.

[0014] The silicone composition is preferably in at least one state selected from grease, putty, gel, and elastomer. With these properties, unnecessary X-rays leaking from an X-ray generator can be reduced, and electronic components inside an irradiated body can be protected from radiation such as X-ray inspection. Since the grease-like and putty-like compositions are liquid, they are preferably filled into a dispenser for use. The grease-like and putty-like compositions may be uncured or cured. When uncured, they can efficiently follow between the heat generating part and the heat dissipating part, which have large irregularities, so that the contact thermal resistance can be reduced to the maximum extent possible, and the pot life is long and the properties are stable. The gel-like or rubber-like composition is preferably molded into a sheet by sheet molding, extrusion molding, or press molding, and then cured. In the press molding, each molded product may be press molded into a different shape. Press molding is also called mold clamping molding.

[0015] The X-ray shielding particles are preferably at least one particle selected from the group consisting of barium, tungsten, bismuth, molybdenum, tin, zirconium, tantalum, niobium, titanium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, and compounds thereof. These particles have high X-ray shielding properties. Among these, barium sulfate is preferred. Barium sulfate includes elutriated barium sulfate (baryte powder), which is a pulverized product of barite mineral, a natural barite, and precipitated barium sulfate produced by chemical reaction. In the present invention, elutriated barium sulfate, precipitated barium sulfate, or a mixture thereof can be used. Precipitated barium sulfate has a uniform particle size, and precipitated barium sulfate is preferred. The D50 (median diameter) of the cumulative particle size distribution of barium sulfate based on volume is preferably 0.1 to 30 μm, more preferably 0.5 to 25 μm, and further preferably 1 to 20 μm. The specific gravity of barium sulfate is 4.2 to 4.5, and the melting point is 1580° C. The barium sulfate is preferably in an amorphous or crushed shape.

[0016] The thermally conductive particles are made of alumina (acidIt is preferable that the inorganic particles are at least one selected from the group consisting of aluminum oxide, zinc oxide, magnesium oxide, aluminum nitride, boron nitride, aluminum hydroxide, and silicon carbide. These inorganic particles have high thermal conductivity and low electrical conductivity. Among them, alumina (aluminum oxide) is preferable because it is inexpensive and has a relatively high thermal conductivity. It is also preferable to use alumina in combination with so-called submicron particles having a D50 (median diameter) of 0.01 μm or more and less than 1 μm, small particles having a D50 (median diameter) of 1 μm or more and less than 50 μm, and large particles having a D50 of 50 μm or more. This allows for close packing. It is preferable that the inorganic particles do not contain electrically conductive particles such as copper, gold, silver, aluminum, and tungsten. If electrically conductive particles are used as a heat sink (TIM) between a heat generating part and a heat dissipating part of an electronic component, there is a risk of an accident causing an electrical short circuit.

[0017] At least one of the inorganic particles selected from the group consisting of X-ray shielding particles and thermally conductive particles is preferably surface-treated at least in part with a silane coupling agent, a titanate coupling agent, an aluminate coupling agent, or a zirconate coupling agent. Among these, a silane coupling agent is preferred, and at least a part of the inorganic particles is preferably surface-treated with R a Si(OR') 4-a(R is an unsubstituted or substituted organic group having 1 to 20 carbon atoms, R' is an alkyl group having 1 to 4 carbon atoms, and a is 0 or 3), or a silane coupling agent of a partial hydrolyzate thereof is preferably surface-treated. The silane coupling agent may be mixed with inorganic particles in advance and heat-treated for pretreatment (pretreatment method), or may be added when mixing the base polymer, the curing catalyst, and the inorganic particles (integral blend method). In the case of the pretreatment method and the integral blend method, it is preferable to add 0.01 to 10 parts by mass of the silane coupling agent to 100 parts by mass of the inorganic particles. By performing the surface treatment, it becomes easier to fill the base polymer, and it is effective in preventing the curing catalyst (e.g., platinum-based catalyst) from being adsorbed to the inorganic particles, thereby preventing curing inhibition. This is useful for storage stability. In particular, since small particles with a D50 (median diameter) of 10 μm or less have a high tendency to adsorb the curing catalyst, it is preferable to surface-treat X-ray shielding particles and thermally conductive particles with a D50 (median diameter) of 10 μm or less.

[0018] Examples of the alkoxysilane compounds (hereinafter also simply referred to as "silanes") include methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylmethoxysilane, trimethylethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, butyltrimethoxysilane, butyltriethoxysilane, pentyltrimethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, octadecyltrimethoxysilane, octadecyltriethoxysilane, etc. The silane compounds can be used alone or in combination of two or more. As the surface treatment agent, alkoxysilane and one-terminated silanol siloxane or one-terminated trimethoxysilyl polysiloxane may be used in combination. The surface treatment mentioned here includes not only covalent bonding but also adsorption.

[0019] The silicone component is preferably an organopolysiloxane having a viscosity of 10 to 1,000,000 mPa·s at 25° C. This makes it easier to obtain a composition having a uniform composition with the X-ray shielding particles and the thermally conductive particles.

[0020] When silicone polymer is cured and crosslinked to obtain a silicone sheet-shaped cured product, the curing and crosslinking method is not limited. There are a method of adding an alkenyl group and a SiH group, a method of crosslinking an alkenyl group or an alkyl group with a peroxide, a method of condensing a silanol or an alkoxy group, and a method of crosslinking and curing by combining them. Among these, a method of adding an alkenyl group and a SiH group to be cured using a catalyst such as platinum is preferred because it does not produce by-products associated with the reaction, the reaction rate can be controlled, and the curing reaction proceeds smoothly to the depths of the molded product. In addition, a peroxide curing reaction can be cured at a higher temperature, and is preferred for rubber, elastomers, etc.

[0021] In the manufacturing method of the present invention, the silicone composition is mixed to form a compound, which is then molded by sheet molding, extrusion molding, or press molding, and cured. The thickness of the sheet is preferably in the range of 0.2 to 10 mm. The curing conditions for the sheet are preferably a temperature of 70 to 250° C. and a heating time of 1 to 15 minutes.

[0022] The silicone composition of the present invention can also be molded into any shape and used as a heat sink (TIM: Thermal Interface Material) between heat generating parts and heat dissipating parts of electronic components and the like.

[0023] The at least one inorganic particle selected from the group consisting of the X-ray shielding particles and the thermally conductive particles may have a variety of shapes, such as spherical, irregular (fractured), scaly, polyhedral, etc. When the average particle size is used, it is preferably in the range of 0.01 to 150 μm. The particle size is measured by measuring the D50 (median diameter) of the cumulative particle size distribution based on the volume standard by a laser diffraction light scattering method. An example of the measuring device is the LA-950S2 laser diffraction / scattering type particle distribution measuring device manufactured by Horiba, Ltd.

[0024] At least two inorganic particles with different average particle sizes may be used in combination, because in this way, the smaller particles are filled between the larger particles, allowing for a nearly close-packed state, improving properties such as thermal conductivity, heat insulation, electromagnetic wave absorption, and material strength.

[0025] The composition of the present invention may contain other components than those mentioned above, if necessary. For example, heat resistance improvers such as red iron oxide and titanium oxide, flame retardant auxiliaries, and curing retarders may be added. Organic or inorganic particle pigments may be added for the purpose of coloring or toning. Alkoxy group-containing silicones may be added as materials added for the purpose of filler surface treatment, etc. Also, organopolysiloxanes without addition curing reactive groups may be added. From the viewpoint of workability, it is desirable for the viscosity at 25°C to be 10 to 100,000 mPa·s, and particularly 100 to 10,000 mPa·s.

[0026] The following description will be given with reference to the drawings. In the following drawings, the same reference numerals indicate the same objects. FIG. 1 is a schematic cross-sectional view of an embodiment of the present invention in which an X-ray shielding silicone sheet is incorporated into a heat dissipation structure 10, and is an example of use as a heat dissipation body (TIM: Thermal Interface Material) between a heat generating part and a heat dissipation part of an electronic component. The X-ray shielding silicone sheet dissipates heat generated by an electronic component 13 such as a semiconductor element, is fixed to a main surface 12a of a heat spreader 12 facing the electronic component 13, and is sandwiched between the electronic component 13 and the heat spreader 12. The X-ray shielding silicone sheet 11a is sandwiched between the heat spreader 12 and a heat sink 15. The X-ray shielding silicone sheets 11a and 11b, together with the heat spreader 12, dissipate heat from the electronic component 13 and shield X-rays. The heat spreader 12 is formed, for example, in a rectangular plate shape, and has a main surface 12a facing the electronic component 13 and a side wall 12b erected along the outer periphery of the main surface 12a. The heat spreader 12 has an X-ray shielding silicone sheet 11b provided on the main surface 12a surrounded by the side wall 12b, and a heat sink 15 provided on the other surface 12c opposite to the main surface 12a via the X-ray shielding silicone sheet 11a. The electronic component 13 is, for example, a semiconductor element such as a BGA, and is mounted on a wiring board 14. EXAMPLES

[0027] The present invention will be described below with reference to examples, but is not limited to these examples. Various parameters were measured by the following methods. <Thermal conductivity> The thermal conductivity of the thermally conductive silicone sheet was measured using a hot disk (compliant with ISO 22007-2:2008). As shown in Figure 2A, this thermal conductivity measuring device 1 sandwiches a polyimide film sensor 2 between two samples 3a and 3b, applies a constant power to the sensor 2, and generates a constant amount of heat, analyzing the thermal characteristics from the temperature rise of the sensor 2. The sensor 2 has a tip 4 with a diameter of 7 mm, and as shown in Figure 2B, it has a double spiral electrode structure, with an electrode 5 for applied current and an electrode 6 for resistance (electrode for temperature measurement) located at the bottom. The thermal conductivity is calculated using the following formula (Equation 1). [Number] <X-ray shielding rate, lead equivalent> The X-ray shielding rate and lead equivalent were determined by measuring the transmitted X-ray dose in accordance with JIS Z 4501:2011 (Test method for lead equivalent of X-ray protective equipment) and JIS T61331-1:2016 (Protective equipment against diagnostic X-rays - Part 1: Method for determining the attenuation characteristics of materials). X-ray apparatus: MGi-450 type manufactured by Comet Technologies Japan X-ray tube voltage and tube current: 100 kV, 12.5 mA, additional filter plate 0.25 mm Cu Distance between X-ray tube focus and sample: 1500 mm Distance between sample and measuring instrument: 50 mm Measuring instrument: Ionization chamber irradiation dose rate meter, RAMTEC-solo type manufactured by Toyo Medic Co., Ltd., using A4 type probe X-ray beam: Narrow X-ray beam [Hardness] The following two hardnesses were measured. (1) ASKER C (ASTM D2240:2021) (2) SHORE OO (JIS K 7312:1996)

[0028] (Example 1) 1. Raw material components (1) Base polymer A commercially available two-component addition-curing silicone polymer that becomes silicone gel after curing was used. One liquid (Liquid A) contains a base polymer component (Component A) and a platinum group metal catalyst (Component C), and the other liquid (Liquid B) contains a base polymer component (Component A) and an organohydrogenpolysiloxane as a crosslinking agent component (Component B). The viscosity of Liquid A at 25°C is 400 mPa·s, and the viscosity of Liquid B at 25°C is 300 mPa·s. (2) X-ray shielding inorganic particles Precipitated barium sulfate, with a cumulative particle size distribution based on volume of D50 (median diameter) of 5 μm and an irregular shape as shown in Figure 3, and surface-treated with decyltrimethoxysilane, was used at 450 g per 100 g of base polymer (25 vol.% per 100 vol.% of the composition). (3) Thermally conductive inorganic particles The following thermally conductive inorganic particles were used. Alumina: D50 (median diameter) 0.3 μm, irregular shape as shown in FIG. 4, surface-treated with octyltriethoxysilane. 160 g (10 vol.% per 100 vol.% of the composition) was used per 100 g of base polymer. Alumina: D50 (median diameter) 35 μm, spherical shape as shown in FIG. 5 was used at 320 g per 100 g of base polymer (20 vol.% per 100 vol.% of the composition). Alumina: Spherical alumina with a D50 (median diameter) of 75 μm was used at 320 g per 100 g of base polymer (20 vol.% per 100 vol.% of the composition). 2.Mixing and hardening molding The base polymer, the thermally conductive inorganic particles, and the X-ray shielding inorganic particles were uniformly mixed to form a compound (composition). This compound (composition) was sandwiched between polyester (PET) films and passed through rolls to form a sheet, which was then heated at 100°C for 10 minutes to obtain a silicone cured sheet. The resulting cured sheet had a thickness of 2 mm.

[0029] Comparative Example 1 The same procedure as in Example 1 was carried out, except that no precipitated barium sulfate was added.

[0030] Comparative Example 2 The same procedure as in Example 1 was repeated, except that precipitated barium sulfate that had been surface-treated with decyltrimethoxysilane was used at 450 g per 100 g of base polymer (50 vol.% per 100 vol.% of the composition) and no alumina was added. The above results are summarized in Table 1.

[0031] [Table 1]

[0032] As is clear from Table 1, Example 1 has a higher X-ray shielding rate and lead equivalent than Comparative Example 1, and the thermal conductivity is practically sufficient. Example 1 has a higher thermal conductivity than Comparative Example 2, and the X-ray shielding rate and lead equivalent are practically sufficient, confirming that the silicone composition has high X-ray shielding properties and thermal conductivity. It was also confirmed that the silicone composition can reduce unnecessary X-rays leaking from the X-ray generating device, and is suitable for protecting electronic components inside the irradiated body from radiation such as X-ray inspection.

[0033] Example 2 Precipitated barium sulfate was surface-treated with decyltrimethoxysilane and 90 g of the material was used per 100 g of base polymer (10 vol.% per 100 vol.% of the composition). Alumina: D50 (median diameter) 0.3 μm, irregular shape, surface-treated with octyltriethoxysilane. 64 g (8 vol.% per 100 vol.% of the composition) was used per 100 g of base polymer. Alumina: D50 (median diameter) 35 μm, spherical shape, 128 g per 100 g of base polymer (16 vol.% per 100 vol.% of the composition) was used. Alumina: D50 (median diameter) 75 μm, spherical alumina was used at 128 g per 100 g of base polymer (16 vol.% per 100 vol.% of the composition).

[0034] Example 3 Precipitated barium sulfate was surface-treated with decyltrimethoxysilane and 200 g of the material was used per 100 g of base polymer (10 vol.% per 100 vol.% of the composition). Alumina: D50 (median diameter) 0.3 μm, irregular shape, surface-treated with octyltriethoxysilane. 240 g (13.5 vol.% per 100 vol.% of the composition) was used per 100 g of base polymer. Alumina: D50 (median diameter) 35 μm, spherical shape, 480 g per 100 g of base polymer (27 vol.% per 100 vol.% of composition) was used. Alumina: D50 (median diameter) 75 μm, spherical alumina was used at 480 g per 100 g of base polymer (27 vol.% per 100 vol.% of the composition).

[0035] Example 4 Precipitated barium sulfate was surface-treated with decyltrimethoxysilane and 300 g of the material was used per 100 g of base polymer (10 vol.% per 100 vol.% of the composition). Alumina: D50 (median diameter) 0.3 μm, irregular shape, surface-treated with octyltriethoxysilane. 400 g (15 vol.% per 100 vol.% of the composition) was used for 100 g of base polymer. Alumina: D50 (median diameter) 35 μm, spherical shape, 800 g per 100 g of base polymer (30 vol.% per 100 vol.% of composition) was used. Alumina: D50 (median diameter) 75 μm, spherical alumina was used at 800 g per 100 g of base polymer (30 vol.% per 100 vol.% of the composition).

[0036] Example 5 Precipitated barium sulfate surface-treated with decyltrimethoxysilane was used in an amount of 540 g per 100 g of base polymer (28.6 vol.% per 100 vol.% of the composition). Alumina: D50 (median diameter) 0.3 μm, irregular shape, surface-treated with octyltriethoxysilane. 160 g (9.5 vol.% per 100 vol.% of the composition) was used per 100 g of base polymer. Alumina: D50 (median diameter) 35 μm, spherical shape, 320 g per 100 g of base polymer (19 vol.% per 100 vol.% of composition) was used. Alumina: D50 (median diameter) 75 μm, spherical alumina was used at 320 g per 100 g of base polymer (19 vol.% per 100 vol.% of the composition). The above results are summarized in Table 2.

[0037] [Table 2]

[0038] From Table 2, it was confirmed that all of Examples 2 to 5 had high X-ray shielding factors and lead equivalents, and thermal conductivity that was sufficient for practical use, and were silicone compositions with both high X-ray shielding properties and high thermal conductivity.

[0039] Example 6 Precipitated barium sulfate: D50 (median diameter) 0.24 μm, irregular shape as shown in FIG. 4 was used at 450 g per 100 g of base polymer (25 vol.% per 100 vol.% of the composition). Alumina: D50 (median diameter) 2.4 μm, irregular shape, surface-treated with decyltrimethoxysilane. 160 g (10 vol.% per 100 vol.% of the composition) was used for 100 g of base polymer. Alumina: D50 (median diameter) 35 μm, spherical shape, 320 g per 100 g of base polymer (20 vol.% per 100 vol.% of composition) was used. Alumina: D50 (median diameter) 75 μm, spherical alumina was used at 320 g per 100 g of base polymer (20 vol.% per 100 vol.% of the composition).

[0040] Example 7 Elutriated barium sulfate: D50 (median diameter) 9.5 μm, irregular shape as shown in FIG. 6 was used at 450 g per 100 g of base polymer (25 vol.% per 100 vol.% of the composition). Alumina: D50 (median diameter) 0.3 μm, irregular shape, surface-treated with octyltriethoxysilane. 160 g (10 vol.% per 100 vol.% of the composition) was used per 100 g of base polymer. Alumina: D50 (median diameter) 35 μm, spherical shape, 320 g per 100 g of base polymer (20 vol.% per 100 vol.% of composition) was used. Alumina: D50 (median diameter) 75 μm, spherical alumina was used at 320 g per 100 g of base polymer (20 vol.% per 100 vol.% of the composition). The above results, together with the results of Example 1 for reference, are shown in Table 3.

[0041] [Table 3]

[0042] As is clear from Table 3, Example 7 is submicron barium sulfate, and Example 8 is elutriated barium sulfate, and the X-ray shielding factor and lead equivalent are high, and the thermal conductivity is practically sufficient. It was confirmed that the particle size and type are not limited.

[0043] Example 8 Except for using a non-curable silicone polymer, the same procedure as in Example 1 was carried out. The non-curable silicone polymer had a viscosity of 300 mPa·s at 25°C.

[0044] [Table 4]

[0045] From Table 4, Example 8 uses a non-curable silicone polymer, so it has fluidity and the hardness was less than 1 and could not be measured with a hardness meter. The X-ray shielding factor and lead equivalent were the same as those of Example 1. In addition, the thermal conductivity was sufficient for practical use. [Industrial Applicability]

[0046] The X-ray shielding silicone composition and X-ray shielding silicone sheet of the present invention are capable of reducing unnecessary X-rays leaking from X-ray generating devices, and are also suitable for protecting electronic components inside an irradiated body from radiation during X-ray inspections and the like. [Explanation of symbols]

[0047] 1. Thermal conductivity measuring device 2 Sensors 3a,3b Sample 4 Sensor tip 5 Electrode for applied current 6 Resistance electrodes (temperature measurement electrodes) 10 Heat dissipation structure 11a, 11b Thermally conductive sheet 12 Heat spreader 12b Heat spreader sidewall 13. Electronic Components 14 Wiring board 15 Heat sink

Claims

1. An X-ray shielding silicone composition comprising a silicone component, X-ray shielding particles, and thermally conductive particles, 1. An X-ray shielding silicone composition, wherein the silicone component is 15 to 60 vol.%, the X-ray shielding particles are 5 to 50 vol.%, and the thermally conductive particles are 30 to 80 vol.%, per 100 vol.% of the composition.

2. The X-ray shielding silicone composition according to claim 1, wherein the X-ray shielding rate of the composition is 30% or more as measured in accordance with JIS Z4501:2011 and JIS T61331-1:2016.

3. 2. The X-ray shielding silicone composition according to claim 1, wherein the composition has a thermal conductivity of 0.8 W / mK or more as measured in accordance with the hot disk method of ISO / CD22007-2:2008.

4. 2. The X-ray shielding silicone composition according to claim 1, wherein the X-ray shielding particles are at least one particle selected from the group consisting of barium, tungsten, bismuth, molybdenum, tin, zirconium, tantalum, niobium, titanium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, and compounds thereof.

5. 2. The X-ray shielding silicone composition according to claim 1, wherein the X-ray shielding particles are at least one selected from the group consisting of precipitated barium sulfate and elutriated barium sulfate.

6. 6. The X-ray shielding silicone composition according to claim 5, wherein the precipitated barium sulfate and the elutriated barium sulfate are in at least one form selected from the group consisting of amorphous and crushed forms.

7. 2. The X-ray shielding silicone composition according to claim 1, wherein the thermally conductive particles are at least one inorganic particle selected from the group consisting of alumina, zinc oxide, magnesium oxide, aluminum nitride, boron nitride, aluminum hydroxide, and silicon carbide.

8. 2. The X-ray shielding silicone composition according to claim 1, wherein at least a portion of the at least one inorganic particle selected from the group consisting of the X-ray shielding particles and the thermally conductive particles is surface-treated with at least one coupling agent selected from the group consisting of a silane coupling agent, a titanate coupling agent, an aluminate coupling agent, and a zirconate coupling agent.

9. The X-ray shielding silicone composition according to claim 8, wherein the silane coupling agent is added in an amount of 0.01 to 10 parts by mass per 100 parts by mass of the at least one inorganic particle selected from the group consisting of the X-ray shielding particles and the thermally conductive particles.

10. 2. The X-ray shielding silicone composition according to claim 1, wherein the silicone component is an organopolysiloxane having a viscosity of 10 to 1,000,000 mPa·s at 25°C.

11. The X-ray shielding silicone composition according to claim 1 , wherein the composition is uncured.

12. 2. The X-ray shielding silicone composition according to claim 1, wherein the composition is cured by addition curing or peroxide curing.

13. An X-ray shielding silicone molded article, characterized in that the composition according to any one of claims 1 to 10 and 12 is molded into a sheet by at least one molding method selected from the group consisting of sheet molding, extrusion molding and press molding, and then cured.

14. A method for producing an X-ray shielding silicone sheet, comprising mixing the silicone composition according to any one of claims 1 to 10 and 12 to prepare a compound, molding the compound by at least one molding method selected from the group consisting of sheet molding, extrusion molding and press molding, and curing the compound.

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