JP2019108172A5 - - Google Patents

Description

Manufacturing method of microwaved food containers

  The present invention relates to a container for foodstuffs heated by a microwave oven, and more particularly, to a method for manufacturing a container capable of efficiently exhausting water vapor from a lid.

  When cooking cooked foods for sale at a retail store such as a convenience store or for cooking after bringing them home, the container that packages these foods is made up of a container body and a lid that fits into its opening. Consist of combinations. In particular, since the single-use container is used only once, such as for storing, displaying, and selling food, the lid fitting structure is as simple as possible. For this reason, molded articles of synthetic resin sheets are currently the mainstream of containers.

  A microwave oven (microwave irradiation) is usually used for cooking and reheating food. Therefore, the food container is provided after being put into a microwave oven and heated as it is. Focusing on foods that are actually sold, there are foods with a large amount of moisture such as soups and foods with a small amount of moisture per weight such as stir-fries, and the types of foods are quite frequent. The problem here is that when the food is cooked with a microwave oven, water vapor is generated from the food in the container.

  In the case of the lid-fitted container, if the fit between the container body and the lid is loosened, the water vapor generated inside can be easily exhausted. However, when the fitting on the lid side is loose, there is a concern that foreign matter may be mixed due to a problem that the lid is likely to come off at an intermediate stage of manufacturing, shipping, and display. For this reason, the reputation of food buyers is not good. In view of this, there have been proposed lids having holes for exhausting internally generated water vapor to the outside of the container (see Patent Documents 1 and 2). According to the lids of containers represented by Patent Documents 1 and 2, a tongue-shaped opening formed by a U-shaped or V-shaped cut is formed in the lid. Water vapor is discharged to the outside of the container through the tongue-shaped opening.

  The exhaust efficiency of the tongue-shaped opening due to the U-shaped or V-shaped cut is good. However, the good evacuation of water vapor increases the possibility of foreign matter entering through the tongue-shaped opening. Therefore, in this case, a sealing tape for closing the tongue-shaped opening may be attached. Furthermore, a film member for covering the tongue-shaped opening is separately provided as necessary. For example, when a film member is covered, a wall surrounding the tongue-shaped opening is provided on the lid side, and a gap is formed around the tongue-shaped opening. And the structure was complicated, for example, a passage for water vapor was formed on this wall. Further, there is also a problem that when the tongue piece is broken due to the cut and falls into the inside of the container, foreign matter itself is mixed.

  As described above, in the case of a container employing the existing structure for exhausting water vapor, materials other than those required only for the original food packaging are required, and the cost cannot be denied. In addition, the shape of the tongue-shaped opening due to the cut is uniform, and there are many restrictions on the peripheral structure.

JP 2012-50672 A Japanese Utility Model Registration No. 3056026

  From a series of circumstances, the inventor has sought a new exhaust structure that replaces the exhaust of water vapor using a tongue-shaped opening formed by a U-shaped or V-shaped cut. Among them, it has been found that a structure in which a minute long hole exhaust portion is provided in a lid portion of a container is effective. In addition, it has been found that the fine holes have good resistance to breakage and foreign matter mixing.

  The present invention has been made in view of the above points, and proposes a new exhaust structure that replaces the steam exhaust using a tongue-shaped opening formed by a conventional U-shaped or V-shaped cut. It realizes high water vapor evacuation, and at the same time, improves sealing performance and suppresses foreign matter mixing.Also, there are few restrictions on the shape of the lid, which is also advantageous for reducing material costs. Provided is a method for manufacturing a food container for a microwave-heated food having a lid portion formed with an exhaust portion formed of an elongate exhaust hole, which shortens a perforation operation time and improves operation efficiency.

In other words, the invention of claim 1 is a lid fitting comprising a container body for storing food for microwave heating, and a lid made of a synthetic resin sheet fitted to an opening of the container body. In the container, when obtaining a lid portion having an exhaust portion for exhausting water vapor generated from food stored in the container body portion to the outside, irradiation of the lid surface portion with a laser beam is turned on to prepare time (t ₃ ) A through hole is formed by the passage of time, and after elongation to a predetermined elongated hole shape by the elapse of the operation time (t ₄ ), the irradiation of the laser beam is turned off, thereby the exhaust slot having a width of 0.15 to 1.0 mm. And forming a group of evacuation slots with a plurality of holes.

The invention according to claim 2 is the container for a microwave-heated food according to claim 1, wherein the lid is formed without a member that covers or encloses the exhaust part for preventing foreign matter from entering. According to the manufacturing method.

According to the method for manufacturing a container for heating a microwave oven food according to the invention of claim 1, a container body for storing food for heating a microwave oven, and a lid made of a synthetic resin sheet fitted into an opening of the container body. In the lid fitting container having a body portion, when obtaining a lid body portion formed with an exhaust portion for exhausting water vapor generated from food stored in the container body portion to the outside, the lid surface portion is irradiated with a laser beam. After turning on, a through-hole is formed by the elapse of the preparation time (t ₃ ), and after extending to a predetermined elongated hole shape by the elapse of the operation time (t ₄ ), the laser beam irradiation is turned off. In order to form a group of evacuation slots by piercing a plurality of evacuation slots of 15 to 1.0 mm, instead of exhausting water vapor using a tongue-shaped opening formed by a conventional U-shaped or V-shaped cut, , Good water vapor discharge And sealing performance improvements, achieves contamination suppression, more efficiently can be exhausted steam, together less restriction on the shape of the lid portion, it is possible reduce material costs. In addition, a long exhaust hole can be easily and quickly formed in the lid surface, and the drilling operation time can be shortened as compared with the circular hole shape, the work efficiency can be improved, the production amount can be increased, and particularly, mass productivity is excellent. In particular, in the case of a conventional physical processing method such as a needle stick or a drill, there is a point that sufficient processing accuracy is not obtained in addition to a long time, and a problem of generation of fine powder when forming a hole. However, such a problem can be solved at once by irradiating a laser beam.

According to the method for manufacturing a microwave oven-heated food container according to the second aspect of the present invention, in the first aspect, the lid portion is formed without a member that covers or covers the exhaust portion for preventing foreign matter from entering. Therefore, there is no need for trouble such as opening the package at the time of heating or heating the microwave oven, which can contribute to reduction of the cost of packaging materials.

It is the whole perspective view of the separation state of the container for microwave oven heating foods concerning one embodiment of the present invention. It is a 1st partial sectional view of the container for foodstuffs for a microwave oven heating. It is a 2nd partial sectional view of the container for foodstuffs for microwave oven heating. 6 is a time chart showing a relationship between laser beam irradiation and penetration. It is a perspective view near the exhaust slot group of other embodiments. It is a top view of a plane figure of an exhaust slot group. It is the enlarged photograph which image | photographed the exhaust slot group of the cover part. It is an enlarged photograph of an exhaust slot group. It is a photograph of a lid part after heating with a microwave oven.

  A food container 1 according to one embodiment of the present invention is a combination of a container body 100 and a lid 10 that fits into an opening 101 of the container body 100 as shown in the entire perspective view of the separated state in FIG. Consists of In particular, food is accommodated in the container interior 103 of the container main body 100, and is heated or heated by microwave irradiation of a microwave oven with the lid 10 covered (heating cooking). Therefore, the food container 1 is a “microwave oven heated food container”.

  A long exhaust hole 21 is formed in the lid surface 11 of the lid 10. As shown in the figure, a plurality of elongate holes 21 are provided, and a plurality of these elongate holes 21 are collected to form an evacuation section composed of a group of elongate evacuation holes 20. Water vapor generated from the food C (see FIG. 3) contained in the container main body 100 when heated or heated by the microwave oven is exhausted to the outside of the food container 1 through the exhaust slot 21. Since a plurality of evacuation slots 21 are formed to form the evacuation slots 20, water vapor can be more efficiently exhausted. In the lid body portion 10 of the present embodiment, a concave surface portion 30 dug down appropriately from the lid surface portion 11 is formed on the entire or a part of the lid surface portion 11. The long exhaust hole group 20 is formed in the concave portion 30. Further, in the drawing, a lid upper peripheral wall 35 is formed so as to surround the concave surface 30.

  The provision of the concave portion 30 prevents the water droplets from accumulating in the concave portion 30 and spreading to the lid surface portion 11 when the water vapor ejected from the elongate exhaust hole 21 liquefies and becomes water droplets. Then, the wetted portion of the lid surface portion 11 can be reduced. The upper peripheral wall portion 35 serves as an enclosure and is provided for the purpose of preventing leakage of water droplets.

  The illustrated fitting of the container body 100 and the lid 10 is referred to as an inner fitting, in which the periphery of the lid 10 is fitted into the opening 101 of the container 100. Around the lid 10, there is provided a peripheral wall 15 having a U-shaped cross section when fitted inside the opening 101 of the container body 100. In the fitting form of the inner fitting, mutual close contact between the container body 100 and the lid body 10 becomes strong. Therefore, it is difficult for the lid portion 10 to be easily detached.

  In the container body 100, an opening step 107 is provided in the opening 101, and the peripheral wall 15 of the lid 10 can be received and fitted inside. The container main body 100 is constituted by an opening 101, a body 104, and a bottom 105 from above, and is a pot-shaped or bowl-shaped container having a sufficient capacity for the amount of food. The cross-sectional shapes of the container body 100 and the cover 10 are appropriate and are circular in the drawing. It is also possible to use a cross-sectional shape such as a polygon or an ellipse.

  The food container 1 (combination of the container main body 100 and the lid body 10) is mainly sold at convenience stores, supermarkets, department stores, restaurants, specialty food shops (delicatessen), coffee shops, service areas, and the like. This is a container used for packaging foods including various types of beverages such as bento, prepared dishes, noodle dishes, soup dishes, and coffee, cocoa, black tea, green tea, herbal tea, and the like. A mainly envisaged use is a single-use container (disposable container) used for one-time use, such as one-way or disposable. Use of a single-use container is convenient for food hygiene management.

  The use of the food container 1 is mainly for use as a single use container. Therefore, the lid portion 10 is formed from a synthetic resin sheet (plastic resin sheet) which can be mass-produced inexpensively and easily. Specifically, the lid 10 is made of a sheet (synthetic resin sheet) of a thermoplastic resin such as polyethylene, polypropylene, polystyrene, or polyethylene terephthalate (PET resin), or a biodegradable thermoplastic resin such as polylactic acid. It is a sheet. Although the thickness of the synthetic resin sheet is appropriate, it is generally about 1 mm or less, usually 200 to 700 μm. Then, the synthetic resin sheet is formed by vacuum forming. When a synthetic resin sheet is used as a raw material, vacuum molding is simple and optimal in consideration of mass productivity, processing accuracy, and the like at the time of molding. Further, as described later, processing by laser beam irradiation is also considered.

  In the combination of the container body 100 and the lid 10, the raw resin of the synthetic resin sheet may be the same or different. Particularly, the food container 1 can be made of expanded polystyrene or paper in consideration of heat conduction in order to cope with heating by a microwave oven. The type of the resin to be used is appropriately selected depending on the use, the contents, and the packaging object. In the embodiment disclosed in the following FIG. 2 and the like, the lid 10 is made of polystyrene, and the container body 100 is made of expanded polystyrene.

  With reference to the partial cross-sectional views of FIG. 2 and FIG. 3, a fitting portion between the container body 100 and the lid 10 and the exhaust slot group 20 (the exhaust slot 21) in the illustrated embodiment will be described. FIG. 2 shows a state in which the lid is separated, and FIG. 3 shows a state in which the lid is fitted (fitted or attached). The peripheral wall portion 15 having a U-shape in cross section of the lid body portion 10 is formed by a lid contact wall portion 16, a peripheral groove bottom portion 17, and an inner wall portion 18. A flange portion 19 is provided on an outer edge of the lid contact wall portion 16. In the opening 101 of the container body 100 corresponding to this, an outer edge flange 109, an opening peripheral wall 106, and an opening step 107 are formed at the lower end thereof.

  As further understood from the state of FIG. 3, when the peripheral wall 15 of the lid 10 is fitted into the opening 101 of the container body 100, the lid contacting wall 16 is in close contact with the opening peripheral wall 106. Wear). Thus, the airtightness inside the food container 1 is increased. However, there is no escape route for water vapor generated from the food C stored in the food container 1 accordingly. Then, the internally generated water vapor Vp is discharged to the outside of the food container 1 from the exhaust slot 21 formed in the lid surface portion 11 of the lid portion 10. In this way, the problem that the food container 1 expands abnormally and the lid body deforms or opens unnaturally is avoided.

  At the time of each exhaust slot 21 constituting the exhaust slot group 20 in the cover section 11 of the lid body section 10, a laser beam is applied to the cover section 11, and the exhaust slot 21 is formed in the cover section 11. In the case of forming a long exhaust hole 21, for example, in the case of a physical processing method such as a needle stick or a drill, a long processing time is required, and sufficient processing accuracy cannot be obtained. Further, in forming the holes, the problem of the generation of fine powder cannot be wiped out, and post-cleaning time is required. Therefore, irradiation with a laser beam is used because a long exhaust hole can be easily and quickly formed in the lid surface.

  The laser beam is not particularly limited as long as it can obtain the processing output, the processing accuracy, and the like, and various lasers such as a carbon dioxide laser, a YAG laser, a semiconductor laser, and an argon laser and their irradiation devices are used. As described above, when the material of the lid body is formed of a synthetic resin sheet, the evacuation slot is easily and quickly formed by laser beam irradiation. Particularly excellent in mass productivity.

  The shape of each of the long exhaust holes 21 is, to be precise, a rectangular shape in which both ends are semicircular (see FIG. 8). However, the shape of both ends is ignored as an error range, and the opening area is calculated simply as a rectangle. Hereinafter, the exhaust slot is described as a rectangle. Here, the exhaust slots 21 constituting the exhaust slot group 20 will be described in further detail. First, the width (short side of the rectangle) of each exhaust slot 21 is, for example, 0.15 to 1.0 mm. More preferably, the width of the exhaust slot 21 is 0.3 to 0.5 mm.

  The lower limit of the width of the exhaust slot 21 is to obtain an opening amount sufficient for exhausting water vapor generated during microwave heating. The lower limit of 0.15 mm of the width is a value in consideration of the current processing technology. When the width of the exhaust slot 21 is less than 0.15 mm, the exhaust slot is too narrow, and the exhaust efficiency of the steam from the exhaust slot 21 is considered to decrease. As a result, the lid portion 10 fitted to the container main body portion 100 is easily released by the internal pressure. It is also considered to be the lower limit on the accuracy of the laser beam irradiation device.

  In addition, when a laser beam is irradiated on the lid portion 10 formed from a synthetic resin sheet, the resin sheet is melted at the irradiated portion to open a hole. However, if the width of the setting is too narrow, there is a possibility that the resins melted by the heat of the laser beam irradiation will be joined together when they are cooled and solidified. In this case, a desired appropriate exhaust slot is not formed at the irradiation site, and sufficient steam exhaust is impaired. For this reason, the lower limit of the width is set to 0.15 mm, preferably 0.3 mm for the purpose of making it difficult to cause inadvertent rejoining.

  The upper limit of the width of the exhaust slot 21 is set to a size for effectively preventing foreign substances from entering the inside of the food container 1. For example, in the case of a small insect or the like generally recognized as a foreign substance, if the width is smaller than 1.0 mm, entry into the container is almost prevented. Therefore, the upper limit of the width is set to 1.0 mm, more preferably 0.5 mm.

  Next, the length of the exhaust slot 21 is, for example, in the range of 1 to 12 mm, and preferably in the range of 4 to 7 mm. The width of the exhaust slot 21 is fine as described above. Therefore, it is necessary to have an appropriate length in order to be effective in evacuating internally generated water vapor. The lower limit of the length is an amount that can be approximately formed as a long hole and that takes into account the evacuation of water vapor. The upper limit of the length is due to the necessity of maintaining the strength of the lid body 10 itself. When the lid portion 10 is formed of a synthetic resin sheet, the longer the length of the long exhaust hole 21, the more easily the bending deformation or the like occurs near the long exhaust hole. Then, although the width of the exhaust slot 21 is narrowed as described above, the exhaust slot 21 is easily opened in a spindle shape. Therefore, in order to suppress the opening caused by such careless deformation of the exhaust slot, the upper limit of the length of the exhaust slot is exemplified by 12 mm, and preferably 7 mm.

In addition, the sum of the opening areas of the exhaust slot group 20 (exhaust portion) formed by collecting a plurality of exhaust slots 21, that is, the opening areas of all the exhaust slots 21 on the lid surface portion 11 (ie, The sum of the width and the length of the exhaust slot is in the range of 0.3 to 100 mm ² . The minimum amount of the total opening area corresponds to the area when two minimum exhaust slots (width: 0.15 mm, length: 1 mm) are formed. Of course, the area amount is a value for a food with a very small amount of generated steam. Therefore, in consideration of the types of foods that can be handled, the lower limit of the total realistic opening area is considered to be 0.5 mm ² , and even 1 mm ² .

For example, in the case of noodle dishes, since the amount of soup (tsuyu) in addition to noodles is large, the capacity of the food container also increases. Then, the heating time by the microwave oven becomes longer, and the amount of water vapor generated in the whole container becomes relatively larger. In this case, it is necessary to increase the total opening area in order to promote good exhaustion of water vapor from the exhaust slots. However, even if the number of exhaust slots is increased beyond the required capacity, there is a concern that the labor for drilling may be increased and the strength of the lid may be reduced. Therefore, 100 mm ² as the upper limit of the total open area, 80 mm ² are derived as a more preferable upper limit. Since the total opening area of the group of exhaust holes is within the above-described range, the microwave-heated food container (lid portion) can correspond to many foods distributed on the market.

  The great advantage of adopting the shape of the long exhaust hole 21 described above is that the working time is shortened. In particular, it is effective when forming an exhaust slot group 20 composed of a plurality of exhaust slots 21. In the embodiment, a laser beam such as a carbon dioxide gas laser is applied to the lid surface portion 11 of the lid body portion 10, and the elongate exhaust hole 21 is formed. In this situation, an operation time chart (schematic diagram) in FIG. 4 is assumed. The horizontal axis in the figure is time (t).

The upper part of FIG. 4 corresponds to, for example, a case where a circular exhaust hole is formed. In the figure, the repetition of “_Π” on the irregularities indicates the irradiation of the laser beam (ON: upper side) and the stop (OFF: lower side). The figure formed by the combination of the S-shaped line and the straight line immediately below the shape is a state of a hole formed in the lid body portion upon receiving irradiation. In particular, it may be read as the amount of drilling (depth). The stretched S-shaped portion is in a state in which the resin sheet of the lid is melted by irradiation with a laser beam. This is a preparatory state in which penetration has not yet occurred immediately after so-called irradiation, and the time during this period is represented as “t ₁ ”. The flat portion is a state in which a hole is developed to a predetermined size through the flat portion. This is a so-called actual working state, and the time between these is expressed as “t ₂ ”. The time other than the above is expressed as a waiting time (t _i ) for moving to another hole, for example.

As can be seen from the graph of the ON / OFF state of laser beam irradiation and the amount of drilling, the entire time of laser beam irradiation does not become the time for actually expanding the hole, but the preparation time (t ₁ ) for digging the hole. Also occurs. In the case of a circular exhaust hole, the preparation time (t ₁ ) and the working time (t ₂ ) are frequently repeated to form a plurality of fine holes. Therefore, the preparation time (t ₁ ) is inevitably accumulated. Furthermore, since a plurality of fine holes are formed, the irradiation position is changed to another place one after another. Then, the position adjustment and the like in between waiting time (t _i), and the even accumulated inexorably that time.

On the other hand, the lower part of FIG. 4 corresponds to the case where the long exhaust hole disclosed in the present invention is formed. In the figure, the repetition of “_Π” on the irregularities indicates the irradiation of the laser beam (ON: upper side) and the stop (OFF: lower side). However, the irradiation time is set to be longer because the exhaust slot is long. The graphic consisting of the combination of the S-shaped line and the straight line directly below the hole is a state of a hole formed in the lid portion upon irradiation, and is read as the amount of drilling (depth). Similarly to the upper stage, the stretched S-shaped portion is in a ready state in which the resin sheet of the lid portion is melted by the irradiation of the laser beam, and the time during that time is expressed as “t ₃ ”. The flat part is the actual working condition in which a hole has been developed to a predetermined size (length) through it, the time of which is represented as “t ₄ ”. Also in this example, a standby time (t _j ) for position adjustment for changing the irradiation position occurs.

Even in the case of forming a long hole, the preparation time (t ₃ ) and the standby time (t _j ) cannot be eliminated. Further, extra time may be required for the length of the long hole. However, once the long hole penetrates due to the preparation time (t ₃ ), the work time (t ₄ ) for expanding the hole into a predetermined rectangular shape may be sufficient. Therefore, as can be seen from the comparison of the upper and lower stages in FIG. 4, the cumulative amount of the preparation time (t ₃ ) is relatively reduced in the formation of the long holes on the lower stage as compared with the upper stage. From this result, when obtaining the same opening area amount, the total amount of the preparation time (t ₃ ) is reduced, which leads to a reduction in time. In addition, since the irradiation position frequently changes on the upper side, the standby time (t _i ) during that time is accumulated much. On the other hand, since the lower stage is formed with a long hole, the number of times of changing the irradiation position is smaller than that of the upper stage, and the accumulated amount of the standby time (t _j ) is generally smaller. From these comparisons, it can be said that the number of processes (the number of products) per hour increases. According to the trial of the inventor, the number of production per hour increased about 1.5 times. As described above, the manufacturing method for the long hole of the present application has a great advantage that the drilling operation time can be shortened as compared with the circular hole shape, the operation efficiency is improved, and the production amount is increased.

  FIG. 5 is an overall perspective view of a lid body 10x according to another embodiment. In the illustrated lid body portion 10x, a concave surface portion 30 is formed in the lid surface portion 11x, and an exhaust slot group 20 including a plurality of exhaust slots 21 is formed in the concave surface portion 30. Unlike FIG. 1 and FIG. 2, the upper peripheral wall 35 is omitted. As can be seen from the lid surface portion 11x in FIG. 4, the shape of the lid surface portion 11x can be simplified. In other words, there are fewer restrictions on the structure of food containers, which is also effective in reducing material costs.

  Each plan view in FIG. 6 shows another example of the exhaust slot group formed in the lid body portion 10 (the lid surface portion 11). The exhaust slot group 20a in FIG. 6A has an arrangement in which the individual exhaust slots 21 are sequentially inclined. The illustrated concave portion 30a has a rectangular shape. The exhaust slot group 20b of FIG. 1B is formed so as to form a substantially circular shape by piercing the exhaust slot 21. The illustrated concave portion 30b has a circular shape. The exhaust slot group 20c of FIG. 1C is formed in a shape imitating the letter “A” of the alphabet by piercing the exhaust slot 21. The illustrated concave portion 30c has a rectangular shape. That is, the exhaust slot group is configured as a plane figure. Planar figures include not only figures but also letters and symbols.

  The shape and direction of the plane figure of the exhaust slot group can be freely controlled by setting at the time of laser beam irradiation. For this reason, the U-shaped or V-shaped shapes such as the tongue-shaped opening formed by the conventional cut are not restricted. By the plane figure of the group of exhaust slots formed by drilling the exhaust slots, various information such as manufacturer, seller, etc. trademark, mark, logo, and even the production date can be displayed through the exhaust slots. Becomes The arrangement of the exhaust slots may be one or two or more on the lid surface of the lid. This is properly defined by the design of the food container.

  As described above, considering the size of the long exhaust hole in the food container (microwave oven-heated food container) of the present invention, it is extremely fine, so that the invasion of foreign substances such as insects can be effectively suppressed. . For this reason, in the food container of the present invention, a member such as a film that covers or foreskins the hole for exhausting the lid, which is seen in the conventional container, can be omitted. Therefore, the food container of the present invention does not require any trouble such as opening in microwave oven heating or heating, and can contribute to reduction of packaging material costs. By considering the total opening area of the exhaust slots, the food container of the present invention becomes a very suitable packaging material that can cope with the amount of water vapor generated from various types of food. Furthermore, since various exhaust slots can be formed depending on the arrangement of the exhaust slots, restrictions on the shape design of the lid portion are reduced, and the degree of freedom of the shape of the exhaust slots itself is increased.

[Production of Microwave Oven Heated Food Container]
The container for a microwave-heated food was an article comprising a combination of a container body and a lid. The “preparation of the container for foods heated by microwave oven” assumed the packaging of a large amount of food. For the lid, a sheet material of heat-resistant biaxially oriented polystyrene (heat-resistant OPS) resin was used. This was processed into a disk-shaped lid by vacuum forming. The maximum diameter of the lid was about 175 mm, and the maximum diameter of the lid face was about 135 mm. The material thickness of the lid was 0.3 mm. For the container main body, a sheet material made of heat-resistant foamed polystyrene (polypropylene film-coated product) was used. This was processed into a pot-shaped (bowl-shaped or bowl-shaped) container body having a circular cross section by vacuum forming. The diameter (inner diameter) of the opening of the container body was about 160 mm, the depth was 70 mm, and the internal capacity (capacity capable of containing food) of the container body was about 800 mL.

[Formation of exhaust slots]
At the time of forming the exhaust holes, a known carbon dioxide laser irradiation device generally used in the field of resin processing is used, and nine kinds of exhausts having different sizes and numbers are applied to the central portion of the lid obtained by the molding. An elongated hole group was formed, and Examples 1 to 9 were produced (see Tables 1 and 2). In Tables 1 and 2, in order from the top, the size (measured value) of the exhaust holes {width (mm), length (mm)}, the configuration of the group of exhaust holes {array of exhaust holes (horizontal x vertical) , The number of exhaust slots (pieces)}, and the opening area {per exhaust slot (mm ² ), total opening area (mm ² )}.

  For reference, FIG. 7 is a photograph of a group of exhaust slots in the lid of Example 6. FIG. 8 is an enlarged photograph (magnification: 50 times) of each of the exhaust slots constituting the exhaust slot group. The upper part of FIG. 8 is the exhaust slot of the first embodiment, and the lower part of FIG. 8 is the exhaust slot of the sixth embodiment. As can be seen from the figure, the exhaust slot has a long rectangular shape with both ends rounded. In addition, the numerical values of the width and length of the exhaust slot were obtained as a simple average of the measured values of the exhaust slot for each example. In calculating the opening area, the shape of the rounded portion at both ends can be ignored, and is regarded as a rectangular shape, and the product of “maximum width” and “maximum length” is used.

[Microwave heating test of food]
The types of food that are actually sold vary greatly. Therefore, the inventors have selected "curry udon" as a food having a large water content and a long time required for heating in a microwave oven. The curry udon was accommodated in the same amount (approximately 620 g in total) in each of the container bodies, and the lids (Examples 1 to 9) produced as described above were appropriately fitted. Then, it was subjected to a heating test using a high-output microwave oven introduced in a convenience store or the like. The heating condition in the microwave oven was set to 1600 W in order to obtain a high heating load condition whose output was higher than 1500 W for normal use. Under the output conditions, the microwave heating time was set to 2 minutes or more, and the upper limit was 2 minutes and 30 seconds. Then, it was observed whether or not the lid portion fitted to the container body portion came off due to the internally generated steam pressure after 2 minutes.

[Results and considerations of microwave heating test]
With respect to the lids of Examples 1 to 9, the lids did not come off from the container main body at the time when the microwave oven was heated for 2 minutes. FIG. 9 is a photograph of a state where 2 minutes have passed using the lid of Example 6.

  As described above, the disclosed microwave heating test is a test in which the heating load is higher than the condition usually performed. Even under the above conditions, the exhaust hole group of each example sufficiently exhibited the exhaust performance of internally generated steam. In addition, the foods subjected to the experiment also have a large capacity and a large amount of water, and require a long heating time. Therefore, the fact that the steam exhaust was good even under these severe conditions greatly affirms the effectiveness of the exhaust slot of the present invention.

[Regarding range of exhaust slot size]
From the test results using the lids of Examples 1 to 9, a range regarding a typical exhaust slot can be derived as follows. From Tables 1 and 2 above, the minimum width of the exhaust slot is Example 7. Therefore, the lower limit of the width is set to 0.15 mm, preferably 0.3 mm in consideration of the processing accuracy and the number of the irradiation devices. Since the maximum width was Example 9, the upper limit was 1.0 mm. Although it is possible to raise the upper limit of the width, the upper limit is set to 1.0 mm from the viewpoint of preventing foreign matter from being mixed. Therefore, the range of the width of the exhaust slot is 0.15 to 1.0 mm, preferably 0.3 to 0.5 mm.

  From Tables 1 and 2, the minimum length of the exhaust slot is Example 7. Therefore, the lower limit of the length is set to 1 mm in consideration of the processing accuracy and the number of irradiation devices, and preferably 4 mm in consideration of other embodiments. The maximum length was set to 12 mm from Example 4. Of course, it is possible to make it longer. However, in consideration of securing the strength of the long slot portion of the exhaust, mixing of foreign matter, and the like, 12 mm is a practical upper limit. Therefore, the length of the exhaust slot is in the range of 1 to 12 mm, preferably 4 to 7 mm in consideration of the length of the other embodiments.

Subsequently, with respect to the sum of the opening areas of the exhaust slots (the sum of the opening areas of all the exhaust slots on the lid surface), it is possible to derive a range of approximately 35 to 65 mm ² from the test results in this example. it can. In addition to the results, the range of 0.3 to 100 mm ² , and preferably 1 to 80 mm ² , is defined in consideration of the variety of properties, volume, and the like of the food as the contents.

  As described above, the method for producing a container for foodstuffs heated by a microwave oven according to the present invention employs a good steam exhaustion and sealing instead of the conventional steam exhaustion using a tongue-shaped opening formed by a U-shaped or V-shaped cut. This improves the stopping performance and enables more efficient exhaust of water vapor.In addition, there are few restrictions on the shape of the lid, and material costs can be reduced. Holes can be formed, and a manufacturing method that is particularly excellent in mass productivity can be provided. Since the lid is provided with the exhaust slot formed under appropriate conditions, it is possible to realize good exhaustion of water vapor, which is extremely effective as a substitute for a microwave packaging container having an existing cut structure.

1 Food container (microwave oven heated food container)
10, 10x lid portion 11, 11x lid surface portion 15 peripheral wall portion 16 lid close contact wall portion 20, 20a, 20b, 20c exhaust long hole group 21 exhaust long hole 30 concave portion 35 upper peripheral wall portion of lid surface 100 container body portion 103 container interior 104 Body 105 Bottom 106 Opening peripheral wall 107 Opening step C Food Vp Steam

Claims (2)

In a lid fitting container including a container body that stores food for microwave heating and a lid made of a synthetic resin sheet that fits into an opening of the container body,
When obtaining a lid portion that forms an exhaust portion that exhausts water vapor generated from food stored in the container body portion to the outside,
After turning on the laser beam irradiation on the lid surface portion, a through hole is formed by the elapse of the preparation time (t ₃ ), and after extending to a predetermined elongated hole shape by the elapse of the operation time (t ₄ ), the irradiation of the laser beam is started. A method for producing a container for a microwave-heated food, characterized in that a plurality of evacuation slots having a width of 0.15 to 1.0 mm are formed by turning them off to form a group of evacuation slots. The method for producing a container for a microwave-heated food according to claim 1, wherein the lid portion is formed without a member for covering or encasing the exhaust portion for preventing foreign matter from entering.