Conductive polycarbonate resin sheet for heat-resistant tray product

Abstract

To provide a conductive polycarbonate (PC) resin sheet which enables provision of a heat-resistant tray product of a middle class that is applicable to vacuum molding, and secures an electrostatic countermeasure compared to a conventional product in a sufficiently stable state.SOLUTION: A conductive PC resin sheet is any one of a conductive PC resin sheet that is a formative material of a heat-resistant tray used in vacuum molding and is formed of a resin composition containing a conductive material in a PC resin, and a conductive PC resin sheet having a coating surface of a conductive coating material on front and rear sides of a base material formed of a PC resin, wherein the PC resin has a deflection temperature at a load of 0.45 MPa of 140°C or higher and a melt mass flow rate at 300°C of 8 g / 10 min or less, an attenuation time at ±1,000 V to 10 V in the conductive PC resin sheet is 0.2 second or less, and in the Gakushin type friction fastness test performed on the conductive PC resin sheet, the conductive material is prevented from being dropped and attached onto a white cloth.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a conductive polycarbonate resin sheet for heat-resistant tray products. Specifically, the present invention relates to a conductive polycarbonate resin sheet used in manufacturing a middle-class heat-resistant tray product that can withstand a thermal drying process at 125°C by vacuum molding or compressed air molding using air pressure. Here, heat-resistant trays include non-heatable trays and heat-resistant trays used in heat treatment processes, and heat-resistant trays are further divided into trays that can withstand 150°C, which are called high-end, and trays that can withstand 125°C, which are called middle class. [Background technology]

[0002] In recent years, semiconductors are used in a variety of products, including cars and mobile devices. During the heat treatment in the manufacturing process of semiconductors, heat-resistant trays (hereinafter, sometimes referred to as heat-resistant IC trays) are used. Examples of cases where heat treatment is performed include the following processes. In the manufacture of IC (integrated circuit) packages, in order to seal the inside of the package from the outside air, the lead wire extraction portion and the like are usually sealed with a sealant. This sealant is relatively prone to moisture absorption. Therefore, when heat is applied in the soldering process when mounting the IC package on a printed circuit board, there is a problem that the moisture absorbed in the sealant suddenly expands and cracks occur in the sealant. To address this problem, a process of removing moisture in the sealant is performed by performing a thermal drying process at 125°C for 20 to 40 hours or at 150°C for 5 to 10 hours before mounting the IC package on a printed circuit board. In this thermal drying process for removing moisture from the sealant, a heat-resistant tray is used to transport the IC package.

[0003] Heat-resistant trays that can withstand a heat treatment of 125° C. in this thermal drying process are called mid-class, and trays that can withstand a heat treatment of 150° C. are called high-end class. The present invention relates to a technology developed specifically for heat-resistant trays that can withstand a thermal drying process at 125° C. While the load temperature in the thermal drying process for mid-class heat-resistant trays is 125° C., in practice, heat resistance that can withstand temperatures of 135° C. to 140° C. is required, taking into account the risks.

[0004] The resins constituting the heat-resistant trays described above include both crystalline and non-crystalline resins. For example, general-purpose engineering plastics are used, and typical examples of crystalline resins include polyacetal, PBT, PET, and polyamide, while typical examples of non-crystalline resins include polycarbonate and modified polyetherphenyl. Furthermore, super engineering plastics are also used, and typical examples of crystalline resins include polyphenylene sulfide, polyether ether ketone, and liquid crystal resins, while typical examples of non-crystalline resins include polyarylate, polysulfone, polyether sulfone, and thermoplastic polyimide. The melting temperature of the general-purpose engineering plastics listed above is 100 to 150°C, while the melting temperature of the super engineering plastics is over 150°C. It should be noted that the melting temperature of general-purpose engineering plastics can be increased by blending inorganic substances, glass fibers, carbon fibers, and the like into the resin.

[0005] Generally, crystalline resins have excellent moldability during manufacturing, but tend to lack dimensional accuracy and shape stability at high temperatures. On the other hand, amorphous resins have the opposite characteristics. Among the resins listed above, the amorphous polycarbonate resin has the advantage that its glass transition point is higher than the temperature required in the thermal drying process described above, and that it has little change in dimensions due to heating and suppresses warping and distortion during annealing treatment after molding. However, it lacks fluidity, so it is inferior in moldability and is prone to problems with impact resistance. For the reasons mentioned above, as listed below, currently, polycarbonate resins are mainly used as materials for heat-resistant trays (also called IC trays) manufactured by injection molding by blending (using in combination) with crystalline resins.

[0006] For example, Patent Document 1 discloses a resin composition containing 40-100% by weight of aromatic polysulfone resin and 0-60% by weight of aromatic polycarbonate resin as a base material, 3-20% by weight of conductive carbon, and 2-20% by weight of mica powder. It is said that by obtaining a molded product by injection molding using the composition, it is possible to provide a heat-resistant IC tray that is excellent in heat resistance, fluidity, and moldability for use at 150°C. Patent Document 2 discloses a resin composition containing 20-98% by weight of polyphenylene oxide or polyphenylene ether, 1-40% by weight of at least one resin selected from the group consisting of polystyrene, polyphenylene sulfide, polyetherimide, polycarbonate, and polyethylene, and 1-40% by weight of glass fiber or inorganic filler. It is described that the composition has excellent injection moldability, and that by using the composition, an IC tray with dimensional stability, heat resistance, and reduced warping at a temperature of 150°C can be obtained. Patent Document 3 discloses a conductive resin composition containing 40-90% by weight of polycarbonate-modified polyethylene terephthalate resin, 5-30% by weight of CFRP pulverized pieces, and 5-30% of an inorganic filler. The proportion of polycarbonate resin contained in the polycarbonate-modified polyethylene terephthalate resin is 5-25% by weight. Patent Document 4 describes the problem of carbon falling off due to friction that occurs when carbon black is added to impart conductivity, and solves this problem by using CFRP pulverized pieces. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 07-242286 [Patent Document 2] Special Publication No. 2004-510870 [Patent Document 3] JP 2006-299059 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, according to the study by the present inventors, it is difficult to easily produce a resin sheet from the resin composition of the above-mentioned conventional technology, and in particular, the resin composition lacks the necessary fluidity. Therefore, in order to produce a heat-resistant tray from the resin composition of the conventional technology, it is necessary to melt the resin composition, pelletize it, and then use the pellets to produce a heat-resistant tray by injection molding or press molding, as described in the conventional technology.

[0009] In recent years, in the current state of the manufacture of heat-resistant trays using the above-mentioned conventional techniques, the thickness of the trays has been reduced in order to reduce costs and to utilize resources more effectively. In response to this, the poor fluidity of the resin composition cannot be improved, and attempts have been made to reduce the molecular weight of the resin, but in this case, there is another problem that the impact resistance of the heat-resistant trays is inevitably reduced. Even with such a problem, the current method for manufacturing heat-resistant trays is overwhelmingly injection molding. On the other hand, the form of IC trays in recent years has become diversified according to the IC items to be stored, and the manufacture of heat-resistant trays has shifted to a small lot production of a wide variety of items. In contrast, the molds used for injection molding are extremely expensive because thick steel materials are used to accommodate high-pressure molding. For this reason, if the trend toward a small lot production of a wide variety of items is followed, the depreciation cost of the molds increases, and a practical problem occurs in that the product price of the heat-resistant trays becomes expensive. Therefore, there is a strong demand for the development of a resin sheet suitable for the simple manufacture of heat-resistant trays.

[0010] Furthermore, for heat-resistant trays used to transport IC packages, anti-static measures are essential, and electrical conductivity is an extremely important property. The present inventors have found that there is a problem to be solved in this regard, as described below. Conventionally, surface resistance or surface resistivity has been used as an electrical property value of heat-resistant trays. However, in the course of their investigation, the present inventors have found that, for example, when anti-static measures for heat-resistant trays are taken using surface resistance or surface resistivity (hereinafter referred to as surface resistance), which has been conventionally used to evaluate electrical conductivity as a standard for electrostatic damage to packaging materials, device terminals of IC packages housed in the tray may be unexpectedly destroyed. This is thought to be because, as described below, conventional evaluation values ​​cannot handle electrostatic damage when static electricity is localized on the heat-resistant tray, and the present inventors have recognized that it is urgent to improve conventional evaluation methods for electrostatic damage.

[0011] First, there is no specific value that is specified as the surface resistance value required for an IC tray. For example, in JP2011-116884A, the surface resistance value of an IC tray is 10 3 ~10 10 In addition, JP-A-11-140288 states that 10 4 ~10 10 The standard for electrostatic interference, RCJS 5-1, states that the impedance should be adjusted to 10 Ω. 2 ~10 11 Ω is the surface resistance value of packaging materials in this field.

[0012] The measurement method of the electrical resistance value is described in JIS C2139 3-1 to 3-2. It is roughly said that the surface resistivity is linked to the anti-static measures. However, as described below, the above-mentioned standardized measurement method and the distribution of the conductive material on the surface of the IC tray that is the target of anti-static measures based on the value measured by this method have potential problems as described below. In the above measurement method, a sample of a predetermined circular shape is used for measurement, and the electrical resistance value of the sample is measured between circular electrodes with an insulation resistance meter to obtain the surface resistivity. However, for example, if there is a local non-conductive part on the surface of the measurement sample and the measurement is performed across this part, the current will flow around this part, so the contribution of the negative electrical characteristics of the non-conductive part will not be shown, and the electrical resistance value will be shown as an average measurement value of that state. In other words, the electrical resistance value, which is the measurement value in this case, does not accurately indicate the distribution state of the conductive material on the surface of the IC tray. This problem is also the same when the measurement location is measured with a two-point probe.

[0013] If the above-measured electrical resistance value of a sample having a localized non-conductive portion on the surface is used to take measures against static electricity, there is a concern that if static electricity is localized in the non-conductive portion and maintains a high potential, it may destroy the device terminal of the IC package that comes into contact with that portion. Furthermore, even with the same electrical resistance value, the attenuation of the static charge is greatly affected not only by the surface resistance of the IC tray, but also by the capacitance of the surface, and if a conductive material is used, the size of the particles and the proximity of the particles. In this respect, the inventors have concluded that the conventionally used electrical resistance value is not the optimal indicator to use for static electricity countermeasures for IC trays.

[0014] Furthermore, the inventors have identified the following as important issues in anti-static measures for IC trays: Even in configurations in which carbon is kneaded into the resin material forming the tray to impart conductivity, or in configurations in which a conductive paint is applied to the front and back surfaces of a resin sheet serving as a base material, if there is friction between the surface of the IC tray and the device terminals of the IC package housed in the tray, the conductive material may peel off and adhere to the device terminals. This conductive material adhering to the device terminals must be avoided, as it can short-circuit the terminal circuits and cause serious damage.

[0015] Therefore, the object of the present invention is to establish technology for conductive resin sheets that can be applied to vacuum forming or compressed air forming (hereinafter also referred to as vacuum forming, etc.) using air pressure, which requires very inexpensive molds, and which can economically provide mid-class heat-resistant tray products that, compared to conventional products, provide sufficient and stable measures against static electricity. [Means for solving the problem]

[0016] The above object can be achieved by the following conductive polycarbonate resin sheet. That is, the present invention provides the following conductive polycarbonate resin sheet. [1] A conductive polycarbonate resin sheet used as a forming material for heat-resistant tray products by vacuum forming or pressure forming using air pressure, The conductive polycarbonate resin sheet is either a product formed from a resin composition (which does not include resins other than polycarbonate resin as main raw materials) containing a conductive material in a polycarbonate resin raw material, or a conductive polycarbonate resin sheet having a laminated surface or a coated surface formed with a conductive paint on both the front and back sides of a substrate of the polycarbonate resin sheet formed from the polycarbonate resin raw material, The polycarbonate resin raw material has a deflection temperature of 140°C or higher under a load of 0.45 MPa as measured by the measurement method of ISO 75-1 and 2, and a melt mass flow rate of 8g / 10min or less at 300°C as measured by the measurement method of ISO 1133; Furthermore, the conductive polycarbonate resin sheet for heat-resistant tray products is characterized in that the decay time from ±1000 V to 10 V in the conductive polycarbonate resin sheet measured by the electrostatic charge diffusion performance measuring method of JIS C 61340-2-1 is 0.2 seconds or less, and in a Gakushin-type friction fastness test of JIS K-5701 conducted on the conductive polycarbonate resin sheet under conditions of 1000 reciprocating strokes using a white cloth with a load of 200 g at a speed of 30 strokes / min, the conductive material does not peel off and adhere to the white cloth.

[0017] Preferable forms of the above-mentioned conductive polycarbonate resin sheet are as follows. [2] The conductive polycarbonate resin sheet for heat-resistant tray products according to the above [1], further comprising a resin protective coating layer formed on the surface of the conductive polycarbonate resin sheet. [3] The conductive polycarbonate resin sheet for heat-resistant tray products according to the above [1] or [2], having a thickness of 200 μm or more and 2 mm or less. [4] The conductive polycarbonate resin sheet for a heat-resistant tray product according to the above [1] or [2], wherein the heat-resistant tray product has heat resistance capable of withstanding a thermal drying treatment at 125°C. Effect of the Invention

[0018] According to the present invention, by using the polycarbonate resin defined in the present invention, a product can be prepared by vacuum molding or compressed air molding using air pressure, which has a very fast molding cycle and an inexpensive mold using a general-purpose aluminum material that is very inexpensive compared to the conventional technology using injection molding, and the product has properties comparable to those of conventional middle-class heat-resistant trays, and furthermore, it is possible to provide a conductive polycarbonate resin sheet for heat-resistant tray products, which is a heat-resistant tray with high practical value that stably maintains these properties. One of the features of the conductive polycarbonate resin sheet for heat-resistant tray products provided by the present invention is that the decay time from ±1000V to 10V is 0.2 seconds or less. This makes it possible to provide a suitable forming material for a heat-resistant tray that has sufficiently excellent and stable electrostatic charge diffusion performance and shows stable and suitable electrical properties against electrostatic interference, for example, a material suitable for use in a thermal drying process that contains an IC package. The electrostatic charge diffusion performance defined in the present invention is a characteristic value of the attenuation of electrostatic charge diffusion necessary to prevent electrostatic damage, and according to the study by the present inventors, it is a useful index more suitably adapted to the countermeasures against electrostatic damage, which is an important technical issue for packaging materials such as heat-resistant tray products. The present inventors have found that the surface resistance value of the electrical characteristic value that has been used to evaluate the conventional conductivity as a standard for electrostatic damage of packaging materials does not accurately link with the attenuation effect of electrostatic charge diffusion, which is a problem in packaging materials, and for example, the surface resistance value does not sufficiently correspond to the case where static electricity is localized. In contrast, by using the conductive polycarbonate resin sheet of the present invention, it is possible to provide a heat-resistant tray product that can be realized in a sufficient and stable state of electrostatic countermeasures.

[0019] Furthermore, the polycarbonate resin raw material constituting the conductive polycarbonate resin sheet for heat-resistant tray products provided by the present invention must have a deflection temperature of 140° C. or higher under a load of 0.45 MPa and a melt mass flow rate of 8 g / 10 min or lower at 300° C. The conductive polycarbonate resin sheet of the present invention uses a polycarbonate resin having such characteristics as a raw material, and therefore, when applied to heat-resistant trays, the occurrence of warping is suppressed, and in addition, the conductive polycarbonate resin sheet has suitable processing characteristics, such as good fluidity in vacuum molding or pressure molding performed using air pressure.

[0020] The conductive polycarbonate resin sheet for heat-resistant tray products provided by the present invention is characterized in that, in a Gakushin-type friction fastness test using white cloth, with a load of 200 g, 30 times / min, and 1000 reciprocations, the peeling of the conductive material from the conductive polycarbonate resin sheet formed from the resin composition or the conductive polycarbonate resin sheet having a coating surface formed from a conductive paint is well suppressed. In other words, by having the above characteristics, it becomes a material for forming a heat-resistant tray with high practical value that can effectively suppress the conductive material peeling off and adhering to the device terminal, which may cause serious damage by shorting the circuit of the terminal. [Brief description of the drawings]

[0021] [Figure 1] 1 is a graph showing the relationship between the melt viscosity (apparent viscosity) and temperature of commercially available polycarbonate resin products. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] The present invention will be described in detail below with reference to preferred embodiments. The conductive polycarbonate resin sheet for heat-resistant tray products of the present invention is a forming material for heat-resistant trays applied to vacuum forming, etc., and has good electrostatic charge diffusion performance having the following configuration. That is, the conductive polycarbonate resin sheet is either a formed product from a resin composition (but does not contain resins other than polycarbonate resin as the main raw material) containing a conductive material in a raw material polycarbonate resin, or a conductive polycarbonate resin sheet having a coating surface formed with a conductive paint on both the front and back sides of a polycarbonate resin sheet that is a substrate formed from a raw material polycarbonate resin, and the first feature is that the decay time from ±1000V to 10V in the conductive polycarbonate resin sheet of any of the above configurations, measured by the method for measuring electrostatic charge diffusion performance of JIS C 61340-2-1, is 0.2 seconds or less.

[0023] The conductive polycarbonate resin sheet for heat-resistant tray products of the present invention is secondly characterized in that it uses only the following polycarbonate resin as a resin component. The polycarbonate resin, which is a raw material constituting the present invention, is produced, for example, by reacting a divalent phenol with phosgene (carbonyl chloride), a haloformate, a carbonate ester, or the like. The divalent phenol contains one or more aromatic nuclei and contains at least two hydroxyl groups directly bonded to the aromatic nuclei. Specifically, for example, there are many divalent phenols such as 2,2-bis-(4-hydroxyphenyl)propane, 2,2-bis(4-hydroxyphenyl)pentane, 2,2-bis-(4-hydroxyphenyl)trimethylcyclohexane, and the like, and any of them can be used.

[0024] The resin raw material for forming the conductive polycarbonate resin sheet of the present invention is a polycarbonate resin obtained by using the dihydric phenols listed above, and further, a polycarbonate resin having the following characteristics is used. That is, a polycarbonate resin is used that, when made into a resin sheet, has a deflection temperature of 140°C or higher under a load of 0.45 MPa and a melt mass flow rate value of 8g / 10min or less at 300°C according to the measurement method of ISO1133. Note that, the resin composition raw material for forming the conductive polycarbonate resin sheet constituting the present invention, which is formed from the resin composition kneaded with a conductive material or has a laminated surface or coated surface formed with a conductive paint on the surface of a polycarbonate resin substrate, may contain additives as necessary, in addition to the polycarbonate resin having the above characteristics, as long as they do not impair the characteristics required for the conductive polycarbonate resin sheet of the present invention. Examples of additives include anti-aging agents against heat and light, hydrolysis inhibitors that improve hydrolysis, anti-blocking agents for the sheet, release agents and lubricants that improve adhesion during processing, laser marking agents, pigments, and the like.

[0025] The polycarbonate resin used as a raw material in the present invention is a heat-resistant non-crystalline resin, and has been used in the past by blending with other non-crystalline or crystalline resins to increase the fluidity of the resin composition and improve the moldability. For this reason, as exemplified above, in the prior art, in the preparation of heat-resistant trays, polycarbonate resins are blended with various resins or used as modified components. The reasons for this are considered to be as follows. As described above, currently, heat-resistant trays are manufactured by injection molding, whereas polycarbonate resins, being non-crystalline when used alone, have a problem that even if they have good heat resistance, they solidify very slowly and are poor in productivity. In addition, a problem specific to injection molding is that in injection molding, a fluidized resin is injected into a mold at high pressure, so that molded products with precise dimensions can be obtained, but as described above, the cost of the mold is very expensive, which affects the price of the molded products.

[0026] In response to the above-mentioned current situation, the present inventors have noticed that trays for industrial products, including trays for general food products, are produced in huge quantities by vacuum forming or compressed air forming using air pressure. The mold used for vacuum forming can be made of inexpensive aluminum material because almost no pressure is applied to the mold. The problem is that the dimensional accuracy of molded products obtained by vacuum forming is inferior to that of molded products by injection molding. The reason for this is that vacuum forming is different from injection molding in that the resin sheet is not melted, but is in a softened state and is brought into close contact with the mold by air pressure such as vacuum drawing, and then cooled and solidified. In contrast, engineering plastics, which are materials suitable for heat-resistant trays, have the characteristic that a stable softened state is difficult to obtain during the transition from a solid state to a molten state, and therefore are not used for vacuum forming because it is difficult to obtain a state in which the melt tension required for vacuum forming is maintained. Furthermore, in the case of engineering plastics, for the same reason as above, it is difficult to produce the resin sheet used as the forming material, which is the premise of vacuum forming, by an extruder, and there are almost no engineering plastic resin sheets for vacuum forming on the market.

[0027] Polycarbonate resin is classified as a general-purpose engineering plastic, and should have sufficient performance as a material for heat-resistant trays by itself. However, as shown in the above-mentioned prior art documents, the current method of using polycarbonate resin is to prepare heat-resistant trays by injection molding a material blended with other engineering plastics, rather than using polycarbonate resin by itself. According to the inventors' investigation, there has been no example of using polycarbonate resin by itself as a molding material and manufacturing a heat-resistant tray by vacuum molding, as in the present invention.

[0028] Regarding the above-mentioned configuration, the inventors consider the following, although it is not clear, regarding the fact that there have been no manufacturing examples or disclosures so far. First, since the melt viscosity of polycarbonate resin is larger than that of other engineering plastics, in order to ensure sufficient adhesion to the mold during vacuum molding, it is necessary to increase the mold temperature and the plasticization temperature of the sheet. However, these mean lowering the melt tension of the sheet. For this reason, according to the study by the inventors, it is very difficult to form a heat-resistant tray by vacuum molding using polycarbonate resin alone as a material, and for example, a product with insufficient dimensional accuracy may be obtained, or conversely, if the melt tension is insufficient, the sheet may not be able to withstand the air pressure and may develop holes. It is considered that this is due to these factors, but according to the study by the inventors, there has been no report, let alone an actual example, of the stable manufacture of a heat-resistant tray by vacuum molding using a resin sheet that uses substantially only polycarbonate resin.

[0029] In view of the above-mentioned current situation, the present inventors conducted intensive research and found that a resin sheet using polycarbonate resin substantially alone can be suitably used as a material for vacuum forming, etc., when it satisfies the following requirements. Specifically, a polycarbonate resin that satisfies both of the following requirements, that is, a deflection temperature of 140° C. or higher under a load of 0.45 MPa measured according to the measurement methods of ISO 75-1 and 2, and a melt mass flow rate of 8 g / 10 min or less at 300° C. measured according to the measurement method of ISO 1133, is a suitable raw material for a sheet for preparing a tray by vacuum forming, etc.

[0030] That is, the deflection temperature measured above occurs due to softening of the resin and is constant for each resin group, so it correlates with the plasticization onset temperature of the polycarbonate resin, and the melt tension, which correlates with the ease of flow of the resin (the degree of viscosity), depends on the molecular weight, so it can be linked to the value of the melt mass-flow rate. As a result of further investigation into this point, it was found that for the polycarbonate resin used as a raw material for achieving the object of the present invention, a melt mass-flow rate, which correlates instead of the melt viscosity, is 8g / 10min or less, as measured at 300°C according to the ISO1133 method, and preferably 5g / 10min or less, which is within a suitable balance range and can realize the effects of the present invention, and thus the present invention was arrived at.

[0031] The above range was determined based on the results of an actual vacuum molding test using polycarbonate resin as the raw material, and is a range of melt mass flow rates suitable for the purpose of the present invention. In doing so, the product catalog of Mitsubishi Engineering Plastics Corporation and pages 24-26 of "Technical Information on Polycarbonate Resin: Physical Properties" published by the same company were referenced (see Figure 1). This point will be described in detail later.

[0032] Here, the heat resistance of the resin changes depending on factors such as the synthesis components and polymerization conditions of the polycarbonate resin. The melt viscosity is affected by factors such as the structure of the resin chain, for example, whether it is linear or branched, and the molecular weight. From the independent factors listed above, even if the melt viscosity is high (the melt mass flow rate value is small), there are some grades that have low heat resistance and cannot withstand drying at 125 ° C for 20 to 40 hours, which is required for a heat-resistant tray that is called a middle class and can handle 125 ° C., and conversely, there are some grades that have high heat resistance even if the melt mass flow rate value is high. In the case of injection molding used in the conventional technology, a method can be adopted in which glass fibers or inorganic fillers are added to the resin components to increase the heat resistance and rigidity of the obtained heat-resistant tray. However, in the vacuum molding and the like that is performed using air pressure, which is the object of the present invention, adding these makes molding difficult, so it is better to avoid adopting such a method. In the conductive polycarbonate resin sheet of the present invention, the polycarbonate resin component constituting the sheet does not contain any resin other than polycarbonate resin, and the polycarbonate resin sheet having the above-mentioned configuration and a grade with a deflection temperature of 140°C or higher and a specified numerical range of melt mass flow rate is used as the material, and a heat-resistant tray product exhibiting good and stable characteristics is realized by vacuum forming using air pressure.

[0033] The above-mentioned thermal behavior and mechanical behavior are characteristics derived from the polycarbonate resin used as the raw material. The heat-resistant tray formed from the conductive polycarbonate resin sheet that characterizes the present invention is used in the field of IC packages, as can be seen from the abbreviated name of IC heat-resistant tray, and therefore requires electrical properties. That is, the heat-resistant tray product provided by the present invention is used in the manufacturing process and transport process of IC packages, and there is a problem that the terminals of the IC packages are easily damaged by static electricity generated by friction or the like during these processes, so it is essential that it is compatible with electrostatic interference.

[0034] In recent years, IC packages have become increasingly dense, and the width of the circuits has become very narrow, making them susceptible to destruction by short circuits. There are three types of destruction caused by electrostatic interference, listed below, which can occur either alone or in combination. (1) Damage caused by contact with an external electrostatic insulator causing static electricity to be discharged to a device terminal, etc. (2) Destruction caused by an increase in the potential of a device terminal, which then discharges static electricity from the device terminal to an external conductor. (3) Breakdown caused by transient voltages and eddy currents that occur inside the device due to changes in the electric field around the device terminals.

[0035] For this reason, IC heat-resistant trays must have electrical properties that allow static electricity to escape, i.e., static charge diffusion attenuation properties. As described above, the conductive polycarbonate resin sheet for heat-resistant tray products of the present invention is required to have a decay time of 0.2 seconds or less from ±1000V to 10V, thereby achieving a sufficiently excellent and stable static charge diffusion performance.

[0036] The inventors of the present invention measured the attenuation of the static electricity diffusion performance using the charged plate method based on the measurement method of electrostatic charge diffusion performance of JIS C61340-2-1. On the other hand, by measuring the surface resistance value, which has been conventionally performed, using another measuring device, and comparing it, the usefulness of the evaluation using the decay time specified in the present invention was confirmed. In the charged plate method specified in the present invention, the time it takes for the potential to decay due to leakage after charging the object to be measured with a high potential, and the remaining potential are measured. The above-mentioned JIS standard specifies a standardized measurement method, but does not specify an evaluation standard for the static electricity diffusion performance of the object to be measured. In contrast, in other countries, there are various measurement conditions depending on the target characteristics of the device to be evaluated, and the applied potential often starts from ±5000V, and there are multiple standards for the pass / fail judgment range of the decay time from 0.02 seconds to 2 seconds.

[0037] In the present invention, by adopting the evaluation standard of the packaging material standard used by many hard disk manufacturers in the United States, that the decay time from ±1000V to 10V must be within 0.2 seconds, it is possible to provide a conductive polycarbonate resin sheet for heat-resistant tray products that can provide stable static electricity countermeasures.

[0038] The measurement of the decay time from ±1000V to 10V for the conductive polycarbonate resin sheet for heat-resistant tray products specified in the present invention was performed as follows, using the method for measuring electrostatic charge diffusion performance of JIS C61340-2-1. When the specimen (sample) to be measured was a conductive polycarbonate resin sheet formed from a resin composition containing a conductive material in a raw material polycarbonate resin, the measurement was performed as is. When the conductive polycarbonate resin sheet had a laminated surface or a coated surface formed with a conductive paint on both the front and back sides of the polycarbonate resin sheet substrate, the measurement was performed by conducting the front and back sides.

[0039] The decay time was measured using a charge plate monitor CPM288 (trade name, manufactured by Monroe Electronics) as a measuring device, under an environment of humidity 50% and temperature 23° C. Measurement of the surface resistance value of a conventional conductive polycarbonate resin sheet, which was carried out for comparison with the decay time used in the evaluation of the present invention, was carried out under the same environment as above, using SM-8200 (trade name, manufactured by Hioki E.E.C.).

[0040] The conductive polycarbonate resin sheet for the heat-resistant tray product of the present invention, which is used as a forming material for the heat-resistant tray product by vacuum forming using air pressure, can be produced using a single-screw extruder. Specifically, each brand of polycarbonate resin was dried at 130°C for 4 hours and then fed into an extruder to prepare the sheet. At this time, a CPS-2 type (trade name, manufactured by Mitsubishi Heavy Industries, Ltd.) was used as the single-screw extruder. The study in the present invention was carried out by melting the resin at a temperature of 290 to 300°C and passing it through a hanger-type die to prepare a resin sheet with a thickness of 1 mm. The thickness of the conductive polycarbonate resin sheet for the heat-resistant tray product of the present invention is not particularly limited, but may be determined, for example, in the range of 200 μm or more and 2 mm or less depending on the IC product to be stored.

[0041] The resin sheet obtained as described above must be one that is imparted with electrical conductivity to the entire sheet or to the surface. For example, a resin sheet made of a resin composition containing a conductive material in a raw material polycarbonate resin, or a resin sheet made of a polycarbonate resin sheet with a conductive paint applied to the front and back surfaces, can impart electrical conductivity to the surface of the polycarbonate resin sheet. To impart electrical conductivity to the entire sheet, a resin composition in which a conductive material is kneaded into polycarbonate resin in advance is put into an extruder to prepare a resin sheet, or a master batch of a conductive material is dry-blended with polycarbonate resin, and the blend is put into an extruder. The sheet prepared by the above-mentioned method has electrical conductivity on both sides, so that the sheet prepared by either method shows good results in terms of the electrostatic charge diffusion performance defined in the present invention.

[0042] Furthermore, the conductive polycarbonate resin sheet for heat-resistant tray products provided by the present invention is characterized by its performance of suppressing peeling of the conductive material, which can be confirmed by the fact that the conductive material does not peel off or adhere to the white cloth in a JIS K-5701 Gakushin-type friction fastness test conducted under conditions of 1000 reciprocations using a white cloth, a load of 200 g, a speed of 30 times / min.

[0043] <Preparation of conductive polycarbonate resin sheet-1> The following is an example of a method for preparing the conductive polycarbonate resin sheet used in the present invention from a resin composition containing a conductive material in the raw material polycarbonate resin. 15 parts by mass of conductive carbon acetylene black granules (trade name, manufactured by Denka Co., Ltd.) and 0.15 parts by mass of Licowax S (trade name, manufactured by Clariant Japan Co., Ltd.) for the purpose of improving the slipperiness when kneading the conductive material were added to 100 parts by mass of E-2000 (trade name, manufactured by Mitsubishi Engineering Plastics Co., Ltd.), which is a polycarbonate resin, were roughly mixed, and then kneaded with a kneader S-5 type machine (trade name, manufactured by Moriyama Seisakusho Co., Ltd.) to obtain a conductive polycarbonate resin composition. Next, the resin composition was pelletized with a single-screw extruder DR-65 (trade name, manufactured by Mars Seiki Co., Ltd.), and the resin was melted at a temperature of 290 to 300 ° C. by the same operation as described above, and passed through a hanger-type die to prepare a conductive polycarbonate resin sheet with a thickness of 1 mm. The resin sheet has a structure in which a conductive material is kneaded.

[0044] <Preparation of conductive polycarbonate resin sheet-2> As mentioned above, if the purpose is to diffuse static electricity, it may be a configuration in which a laminated surface or a coated surface formed with a conductive paint is formed on the front and back sides of a polycarbonate resin sheet that does not contain a conductive material, similar to the conductive polycarbonate resin sheet obtained by containing a conductive material in the polycarbonate resin described above. As the conductive paint, any of carbon-based conductive paints, aniline-based conductive paints, and thiophene-based conductive paints, each of which has a different conductive material prepared as described below, can be suitably used. In the study conducted in the present invention, the conductive paint was applied using a bar coater #4 in accordance with the knife coat method. The conductive paints used in the study examples of the present invention will be described below.

[0045] (Carbon-based conductive paint) The raw materials, conductive material, resin, solvent, etc., were blended and subjected to a coarse dispersion process, followed by passing the mixture through a Dynomill disperser KD-20C (trade name, manufactured by Nakamura Seisakusho Co., Ltd.) to obtain the original paint. The conductive material used was Ketjen Black EC-600JD (trade name, manufactured by Lion Specialty Chemicals Co., Ltd.), a conductive carbon black, and the resin used was Dianale BR80 (trade name, manufactured by Mitsubishi Chemical Co., Ltd.), a methacrylic resin in the form of solid beads. MEK was used as the solvent. The conductive material was 4% by mass in the paint, the resin was 17%, and the total solid content was 21%.

[0046] (Aniline-based conductive paint) Aniline-based paint was prepared by neutralizing the polymer obtained from aniline by the acidic water-based redox polymerization method using a persulfate catalyst with sodium hydroxide, precipitating, and washing with a large amount of purified water. Next, it was doped with dodecylbenzenesulfonic acid and mixed with Dianale BR80, the same resin used in the carbon-based conductive paint, and then dispersed with a Ring Mill-490 (product name, manufactured by Adachi Iron Works) using a 1:1 mixed solvent of IPA and toluene to prepare the aniline-based paint. The concentration of doped aniline in the paint was 2% by mass, the resin was 4%, and the solid content was 6%.

[0047] (Thiophene-based conductive paint) The thiophene-based paint used was Orgacon LBS (trade name, manufactured by Nippon Agfa Co., Ltd.). It has a solid content of 1.2% and is water-based. Details of Orgacon LBS are not disclosed.

[0048] These base paints prepared as described above were used as is or diluted with a solvent to give different surface resistance values ​​after coating. For the dilution solvent, MEK was used for the carbon-based paints, and a 1:1 mixture of IPA and toluene was used for the aniline-based paints. For the thiophene-based paints, a mixture of water and alcohol was used, but the ratio was adjusted in the wet state.

[0049] <Protective Coating> As explained above, in the case of the configuration in which carbon is kneaded into the polycarbonate resin to impart conductivity, as well as in the case in which a conductive paint is applied to the front and back surfaces of a polycarbonate resin sheet, the conductive material is partially exposed on the surface of the resin sheet, and if it rubs against the device terminal, the conductive material may peel off and adhere to the device terminal. Since the conductive material that adheres to the device terminal shorts the circuit of the terminal and causes serious damage, it is desirable to prevent the conductive material from peeling off.

[0050] Therefore, a preferred embodiment of the present invention is to provide a layer for preventing the conductive material from peeling by applying a protective coating material to the surface coated with the conductive paint or the laminated surface, or to the surface of the kneaded product in which the conductive material is kneaded into the polycarbonate resin described above. The material of the protective coating material used for this purpose is not particularly limited and may be any. The inventors have investigated the cases in which acrylic resin, polyurethane resin, and polyester resin are used as the protective coating material. As a result of the investigation, the following was found.

[0051] When a protective coating material is applied to the surface of a conductive polycarbonate resin sheet, the conductive layer is covered, so naturally the conductivity is reduced and the static charge decay time is lengthened. For this reason, it is desirable that the conductive polycarbonate resin sheet for heat-resistant tray products of the present invention is prepared so that the decay time from ±1000V to 10V is 0.2 seconds or less when the conductive polycarbonate resin sheet is affected by the charge decay due to the use of a protective coating material. However, the conductive polycarbonate resin sheet for heat-resistant tray products of the present invention does not necessarily need to be provided with a protective coating material. That is, the protective coating material is intended to prevent and suppress the peeling of the conductive material, so that, for example, when the content of the conductive material in the conductive paint is low or when the amount of the conductive material kneaded into the polycarbonate resin is relatively small, the protective coating material is not required when the conductive material does not peel off.

[0052] In the study examples (Examples and Comparative Examples) of the present invention, a 20% MEK solution of Dianale BR80 (trade name, manufactured by Mitsubishi Chemical Corporation) was used as a protective coating material using acrylic resin. A solution of Lezamin NE310 (trade name, manufactured by Dainichiseika Chemicals Co., Ltd.) diluted to 13% with a 1:1 mixed solvent of IPA and toluene was used as a protective coating material using polyurethane resin. A 20% MEK solution of Vylon 200 (trade name, manufactured by Toyobo Co., Ltd.) was used as a protective coating material using polyester resin. The above-mentioned protective coating materials were applied to both sides of each conductive polycarbonate resin sheet with the respective solutions using a #4 bar coater.

[0053] <Evaluation method - Conductive material peeling> The JIS K-5701 Gakushin-type friction fastness test method was used to test for the presence or absence of peeling of the conductive material. Specifically, the friction terminal was wrapped with a specified white cloth and tested under the following conditions: the cloth was rolled back and forth 1000 times at a load of 200g and a speed of 30 times / min. A Gakushin-type friction fastness tester manufactured by Yasuda Seiki Co., Ltd. was used as the tester. The condition of the white cloth after the test under the above conditions was visually observed and evaluated as follows. A case in which no conductive material was attached to the white cloth was deemed a pass, and was marked with an "O". On the other hand, a case in which conductive material was attached to the white cloth after the test was marked with an "X".

[0054] <Selection of polycarbonate resin suitable for vacuum molding, etc.> The present inventors conducted the following investigations into the conditions for finding a raw polycarbonate resin that can be used to prepare a conductive polycarbonate resin sheet for the heat-resistant tray product of the present invention by vacuum forming or pressure forming using air pressure. Specifically, standard vacuum forming was conducted to find an appropriate value for the melt mass flow rate as a material suitable for a resin sheet to be applied to vacuum forming or the like using air pressure.

[0055] There are various heating methods for vacuum molding machines. For example, there are heating only the top surface, heating both the top and bottom surfaces, a method using multiple heating zones, or a combination of these. In any of these methods, the relationship ultimately depends on the plasticization temperature of the resin applied to the vacuum molding machine and the melt viscosity (melt tension) at that time. Therefore, the inventors conducted an investigation focusing on these requirements, and found the requirements specified in the present invention, believing that if specific conditions for a resin that can produce good vacuum molding results can be found, the polycarbonate resin with excellent moldability will also show good results under similar conditions in other molding machines.

[0056] In carrying out the above-mentioned study, as mentioned above, we referred to pages 24-26 of "Technical Data on Polycarbonate Resin: Physical Properties" published by Mitsubishi Engineering Plastics Corporation. As shown in Figure 1, this document describes a graph showing the relationship between the melt viscosity (apparent viscosity P) and temperature of brands that are representative polycarbonate resin products of the publisher. In Figure 1, the catalog values ​​for the melt mass flow rate are added next to the name of each brand, with reference to the publisher's catalog. All brands are Iupilon (trade name) manufactured by Mitsubishi Engineering Plastics Corporation. As shown in Figure 1, for all brands, the apparent viscosity decreases with increasing temperature on the horizontal axis. The curves are almost parallel to each other. It can be determined that the melt mass flow rate depends on the molecular weight of these resins.

[0057] In the above document, the relationship between the resin flow value Q (corresponding to the melt mass flow rate value) and the resin molecular weight M is logQ=2.39-0.023M 1 / 2 , is stated. Looking at the catalog of the publisher of the above document, the deflection temperature listed for each brand is divided into two groups: 136℃~139℃ and 142℃~145℃. However, this point is not linked to the melt mass-flow rate value. In other words, it can be said that there is no correlation between the deflection temperature and the melt mass-flow rate value.

[0058] Looking at the above-mentioned relationships, the plasticization start temperature, which the present inventors believe is related to the solution of the problem of the present invention, correlates with the deflection temperature since it is the softening of the resin, and can be considered to be constant for each group. On the other hand, the melt tension, which correlates with the flowability (viscosity) of the resin, which the present inventors believe is related to the solution of the problem of the present invention, depends on the molecular weight, that is, can be linked to the value of the melt mass flow rate. Therefore, it is possible to specify suitable conditions by comparing the value of the melt mass flow rate with the results of the actual molding test. That is, as described above, by using a specific vacuum molding machine and applying polycarbonate resin sheets with different melt mass flow rate values ​​to perform detailed molding tests, and determining the optimal range of the melt mass flow rate value for the polycarbonate resin sheet to be applied to the vacuum molding machine, it is possible to determine that polycarbonate resin sheets having similar melt mass flow rate values ​​fall within the suitable range of application for other vacuum molding machines.

[0059] The present inventors believe that the reason why there are no examples of producing heat-resistant trays by vacuum forming using polycarbonate resin essentially alone, without using it in combination with other resins as in the prior art, is due to the following: First, the plasticization temperature of polycarbonate resin is high, and above all, no attempt has been made to find a melt mass-flow rate range that exhibits an appropriate melt tension for the vacuum forming specified in the present invention, which has made it difficult to set an optimal mold temperature range.

[0060] In vacuum molding, the mold temperature affects whether the resin sheet contacts the mold with the vacuum force and stretches along the mold just enough. Therefore, if the mold temperature is low, the resin will solidify before the dimensional accuracy can be achieved, while if the mold temperature is high, bridging is likely to occur.

[0061] In the present invention, the conditions for the raw material polycarbonate resin used in vacuum forming were determined as follows: Using a HU56 single-sided heating vacuum forming machine manufactured by Shenzhen Longji Machinery Co., Ltd., a resin sheet having a plasticization temperature in the range shown in Table 1 below was used, and the mold temperature conditions for the mold used in vacuum forming were within the range shown below. The quality of each vacuum formed product was evaluated in relation to the melt mass flow rate value, and the raw material polycarbonate resin usable for vacuum forming was specified.

[0062] TIFF2025066009000001.tif27170

[0063] <Evaluation of tray formability in vacuum forming> A 1 mm thick polycarbonate resin sheet was evaluated as passing (○) when it was in good contact with the mold within the range of conditions in Table 1, and a tray was obtained in which the dimensions of the mold were accurately transferred. A rectangular tray measuring 310 mm in length, 134 mm in width, and 7 mm in depth was used. As described above, if the polycarbonate resin sheet was in good contact with the mold but the dimensions were not accurately transferred, if the resin sheet was torn, or if bridges occurred, it was evaluated as failing (×).

[0064] <Evaluation of heat resistance> Using the ISO 75-1 and 2 measurement methods, the specimen was rated as passing (◯) if no deformation occurred at 140°C under a load of 0.45 MPa, and as failing (×) if deformation occurred.

[0065] As a result of the vacuum molding test using the polycarbonate resin sheet described above, it was found that the polycarbonate resin sheet applicable to vacuum molding has a melt mass flow rate value in the range of 8g / 10min or less. Furthermore, it was found that the polycarbonate resin sheet having a melt mass flow rate value in the range of 5g / 10min or less is the most suitable. Basically, it was found that if a polycarbonate resin sheet within this range is used as a raw material, there is no significant fluctuation and it is easy to set the manufacturing conditions for obtaining a conductive polycarbonate resin sheet for heat-resistant tray products in good condition. For example, even if the heater temperature, heating time, and cooling time of the vacuum molding machine change, if the plasticization temperature of the applied polycarbonate resin sheet and the mold temperature of the vacuum molding machine are considered, a conductive polycarbonate resin sheet for heat-resistant tray products in good condition can be obtained very easily compared to the conventional method. EXAMPLES

[0066] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these.

[0067] The conductive polycarbonate resin sheet prepared by the method described above from the resin composition containing a conductive material in the raw material polycarbonate resin, and the conductive polycarbonate resin sheet having a coating surface formed with a conductive paint on the front and back sides of the substrate of the polycarbonate resin sheet formed from the raw material polycarbonate resin, are shown in Table 2. The composition of the materials used, the deflection temperature and melt mass flow rate values ​​for each sheet, and the evaluation results obtained by conducting a test on the peeling of the conductive material are shown. In addition, the surface resistance value measured for reference is also shown.

[0068] The abbreviations for polycarbonate resin, conductive paint, conductive material, and protective coat listed in Table 2 respectively indicate the following: (1) Polycarbonate resin All of these are abbreviations for the trade names of polycarbonate resins manufactured by Mitsubishi Engineering Plastics Corp. The melt mass flow rate values ​​are also shown with reference to Table 2 for each resin. 27U; abbreviation for Novarex M7027U, 3.2g / 10min 26U; abbreviation for Novarex M7026U, 5.0g / 10min 25U; abbreviation for Novarex M7025U, 6.5g / 10min 22R: abbreviation for Novarex 7022R, 14.0g / 10min E20: abbreviation for Iupilon E2000, 5.3g / 10min S20: Abbreviation for Iupilon S2000, 10.0g / 10min

[0069] (2) Conductive paint The abbreviations of the conductive paints used in the examples and comparative examples and the ratios (dilution rates) of the original paint and dilution solvent indicated by the abbreviations are as follows. Each conductive paint was prepared in the same manner as described above. The ratios of paint to solution, solvent, and water are all based on mass. (Carbon-based conductive paint) C: Abbreviation for the carbon base paint using acetylene black granules described above. C20: Carbon base paint / 20% MEK solution of BR80 = 10 / 20 C35: Carbon base paint / 20% MEK solution of BR80 = 10 / 35

[0070] (Aniline-based conductive paint) ·N: Abbreviation for aniline paint N20: Abbreviation for aniline paint / mixed solvent of IPA and toluene 1:1 = 10 / 20 N40: Abbreviation for aniline paint / mixed solvent of IPA and toluene 1:1 = 10 / 40 N50: Abbreviation for aniline paint / mixed solvent of IPA and toluene 1:1 = 10 / 50

[0071] (Thiophene-based conductive paint) ·L; abbreviation for thiophene paint · L20; abbreviation for thiophene paint / water = 10 / 20

[0072] (3) Conductive material mixed into polycarbonate resin E20C: Abbreviation for polycarbonate resin E20 mixed with acetylene black granules, which are used as a conductive material.

[0073] (4) Protective Coating For the protective coating, a resin coating material prepared in the same manner as described above was used. A: Abbreviation for acrylic resin-based protective coating ·U: Abbreviation for polyurethane resin protective coating P: Abbreviation for polyester resin protective coating

[0074] TIFF2025066009000002.tif83170

[0075] TIFF2025066009000003.tif69170

[0076] TIFF2025066009000004.tif96170

[0077] TIFF2025066009000005.tif92170

[0078] TIFF2025066009000006.tif96170

[0079] As shown in Table 2, the inventors' study has revealed the following. From Example 1 and Comparative Example 1 in which a carbon-based conductive material is kneaded into a polycarbonate resin as shown in Table 2-1, it was found that even in such a form, the conductive material may peel off if a protective coat is not provided on the surface. In this case, the electrostatic charge diffusion performance did not decrease even if a protective coat was provided. This tendency was also the same in Example 2 and Comparative Example 2, in which a coated surface was formed on both sides with a conductive paint. In addition, from a comparison between Examples 2 and 3 using a carbon-based conductive material and Comparative Example 3, it was found that if the conductive paint is diluted with MEK solvent as in Comparative Example 3 to reduce the concentration of the conductive material in the conductive paint too much, the decay time becomes longer and the electrostatic charge diffusion performance decreases.

[0080] From the comparison between Example 4 and Comparative Example 4 in the form using the aniline-based conductive paint shown in Table 2-2, it was found that the peeling of the conductive material can be effectively suppressed by applying a protective coat. In addition, from Examples 4 and 5, it was confirmed that the peeling of the conductive material can be suppressed by applying a protective coat while keeping the decay time within the range specified in the present invention. From the comparison between Example 6 and Comparative Example 5, it was found that by increasing the dilution rate of the conductive paint to be applied, the decay time can be kept within the range specified in the present invention, and furthermore, a conductive polycarbonate resin sheet for a heat-resistant tray product with a more optimal balance can be obtained that can effectively suppress the peeling of the conductive material without the need for a protective coat. In contrast, as shown in Comparative Examples 7 and 8, it was confirmed that if the dilution rate of the conductive paint to be applied with the solvent is increased to reduce the amount of conductive material in the coated surface, the problem of the peeling of the conductive material is solved without providing a protective coat, but the decay time becomes significantly longer and the electrical properties become inferior. This means that these conductive polycarbonate resin sheets cannot provide a heat-resistant tray with sufficiently stable anti-static measures. Furthermore, a comparison between Comparative Example 6 and Example 6 confirmed that when a protective coating is applied when the dilution rate of the conductive paint to be applied with the solvent is increased, the decay time of the resin sheet becomes longer than the decay time specified in the present invention, the desired electrical properties cannot be obtained, and it becomes difficult to provide a heat-resistant tray with sufficiently stable anti-static measures.

[0081] Furthermore, as shown by the decay times of Comparative Examples 6 to 8, the decay times indicating the electrostatic charge diffusion performance in these examples are extremely long, and do not indicate the good electrical properties required by the present invention. On the other hand, the surface resistance values ​​conventionally used to evaluate the electrical conductivity as a standard for electrostatic damage to packaging materials are 10 6 Ohms, 10 7 Ohms, 10 8 Ω, which is considered to be within a good range. This shows that the surface resistance value that has been used conventionally as a static electricity countermeasure for heat-resistant trays does not necessarily accurately indicate the electrostatic charge diffusion performance. It can be expected that a heat-resistant tray formed from such a conductive polycarbonate resin sheet will have a very high probability of causing electrostatic damage.

[0082] As shown in Table 2-3, when thiophene-based conductive paint is used, the decay time tends to be longer when a protective coat is applied compared to when other conductive paints are used. Therefore, it was found that when using thiophene-based conductive paint to form a coating surface, it is necessary to take this point into consideration.

[0083] Table 2-4 shows an example of a conductive polycarbonate resin sheet in which the front and back are coated with the same carbon-based conductive paint and the same protective coating is applied, except that the type of polycarbonate resin is changed. As can be seen from the comparison of Examples 10 and 11 and Comparative Examples 10 to 12 in Table 2-4, if the deflection temperature and melt mass flow rate of the conductive polycarbonate resin sheet do not both satisfy the requirements specified in the present invention, when applied to vacuum molding, it is found that a tray that adheres well to the mold and has the dimensions of the mold accurately transferred cannot be obtained. Also, from Table 2-4, it is found that heat resistance can be obtained when the deflection temperature is 140°C or higher.

[0084] The examples of conductive polycarbonate resin sheets shown in Table 2-5 are examples of conductive polycarbonate resin sheets in which the deflection temperature and melt mass flow rate are both within the ranges specified in the present invention, the coated surface is formed using a conductive paint of carbon type (C), aniline type (N), or thiophene type (L), and when the conductive paint of carbon type (C) and aniline type (N) is used, a protective coat of different materials is applied. As shown in Table 2-5, all of the examples are within the decay time specified in the present invention, show good electrostatic charge diffusion performance, and can be vacuum molded to produce a heat-resistant tray in good condition, and it was confirmed that the heat-resistant tray is a good one in which the peeling of the conductive material is suppressed.

Claims

1. A conductive polycarbonate resin sheet used as a forming material for a heat-resistant tray product by vacuum forming or pressure forming using air pressure, The conductive polycarbonate resin sheet is either a product formed from a resin composition containing a conductive material in a raw material polycarbonate resin (but does not contain any resin other than polycarbonate resin as a main raw material), or a conductive polycarbonate resin sheet having a laminated surface or a coated surface formed with a conductive paint on both the front and back sides of a substrate of the polycarbonate resin sheet formed from the raw material polycarbonate resin, The polycarbonate resin raw material has a deflection temperature of 140° C. or higher at a load of 0.45 MPa as measured by the measurement method of ISO 75-1 and 2, and a melt mass flow rate of 8 g / 10 min or less at 300° C. as measured by the measurement method of ISO 1133; Furthermore, the conductive polycarbonate resin sheet for heat-resistant tray products is characterized in that the decay time from ±1000 V to 10 V in the conductive polycarbonate resin sheet measured by a method for measuring electrostatic charge diffusion performance in accordance with JIS C 61340-2-1 is 0.2 seconds or less, and in a Gakushin-type friction fastness test in accordance with JIS K-5701, which is performed on the conductive polycarbonate resin sheet using a white cloth under conditions of a load of 200 g, a speed of 30 times / min, and 1000 reciprocations, the conductive material does not peel off and adhere to the white cloth.

2. 2. The conductive polycarbonate resin sheet for heat-resistant tray products according to claim 1, further comprising a resin protective coating layer formed on a surface of the conductive polycarbonate resin sheet.

3. 3. The conductive polycarbonate resin sheet for heat-resistant tray products according to claim 1 or 2, which has a thickness of 200 μm or more and 2 mm or less.

4. 3. The conductive polycarbonate resin sheet for heat-resistant tray products according to claim 1 or 2, wherein the heat-resistant tray product has heat resistance capable of withstanding a thermal drying treatment at 125°C.

Images