Partition and its manufacturing method

Abstract

To provide a partition with improved acoustic characteristics, by which speaker's voice is easily transmitted to a listener, and a method for manufacturing the partition.SOLUTION: In a partition 1 with a substrate 10, a recess 20 is formed in a first side 12 in the thickness direction of the substrate 10, having an opening shape of a perfect circle and a curved surface 22 that deepens from the opening edge toward the center and a flat surface 24 located inside the recess, and a recess 30 is formed in a second side 14 in the thickness direction of substrate 10, having an opening shape of a perfect circle and a curved surface 32 that deepens from the opening edge toward the center and a flat surface 34 located inside the recess.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a partition and a method for manufacturing the same. [Background technology]

[0002] Conventionally, partitions have been used to divide spaces such as offices or to create personal environments at desks. Consideration has been given to soundproofing partitions for the purpose of dividing spaces (see, for example, Patent Documents 1 to 5). Meanwhile, in recent years, partitions have been installed more frequently as a measure against virus infection, and partitions made of, for example, transparent acrylic panels have been used to prevent droplet infection through conversation, particularly in places or situations where people are having face-to-face conversations. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 58-199988 [Patent Document 2] International Publication No. 2017 / 170315 [Patent Document 3] International Publication No. 2017 / 170353 [Patent Document 4] Special Publication No. 2019-512107 [Patent Document 5] Patent Publication No. 2021-055311 Summary of the Invention [Problem to be solved by the invention]

[0004] However, conventional partitions, as described above, emphasize sound insulation, but do not consider ease of conversation, making it difficult for the speaker's voice to be transmitted to the listener. Furthermore, providing holes for conversation in the partition does not adequately prevent droplet infection through conversation. The inventors have investigated ways to improve partitions based on a new technical concept of improving the acoustic characteristics of partitions to make it easier for voices to be transmitted.

[0005] More specifically, voice transmission through a partition occurs when the speaker's voice vibrates the partition, and these vibrations then become vibrations in the air around the listener, which then propagate. Conventionally, no effort has been made to increase the vibration of the partition, and the transmission of voice is dependent on the vibration of the air around the partition. One way to make it easier for the speaker's voice to be transmitted is to make the partition thinner. However, thin partitions have drawbacks, such as insufficient strength and installation stability.

[0006] In view of the above circumstances, the present invention aims to provide a partition with improved acoustic characteristics that allows the speaker's voice to be more easily transmitted to the listener, and a method for manufacturing the same. [Means for solving the problem]

[0007] The present invention includes the following aspects. [1] A partition having a recess formed on at least one surface of a substrate in the thickness direction. [2] A partition according to [1], wherein the surface of the recess has a curved surface that becomes deeper from the open end of the recess toward the center. [3] A partition according to [2], wherein the surface of the recess has a flat surface at the center of the recess. [4] The partition according to any one of [1] to [3], wherein the opening shape of the recess is a perfect circle. [5] The partition according to any one of [1] to [4], wherein recesses are formed on both surfaces of the substrate. [6] The partition according to any one of [1] to [5], wherein a plurality of the recesses are formed on the same surface of the substrate. [7] The partition according to any one of [1] to [6], wherein a plurality of the substrates on which the recesses are formed are combined together. [8] The partition according to any one of [1] to [7], wherein the material constituting the substrate is an alloy resin of vinyl chloride resin and methyl methacrylate resin. [9] A method for manufacturing a partition according to any one of [1] to [8], A method for manufacturing partitions, in which the partitions are obtained by injection molding. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a partition having improved acoustic characteristics that allows a speaker's voice to be more easily transmitted to a listener, and a method for manufacturing the partition. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a front view of a partition according to an example embodiment. [Figure 2] 2 is a cross-sectional view of the partition shown in FIG. 1 along line AA. [Figure 3] FIG. 10 is a front view showing an example of a stationary partition. [Figure 4] FIG. 10 is a front view showing an example of a stationary partition in which a plurality of substrates each having a recess formed therein are combined. [Figure 5] FIG. 10 is a front view of a partition according to another example of the embodiment. [Figure 6] FIG. 10 is a front view of a partition according to another example of the embodiment. [Figure 7] 7 is a cross-sectional view of the partition shown in FIG. 6 BB. [Figure 8] FIG. 10 is a front view of a partition according to another example of the embodiment. [Figure 9] FIG. 10 is a front view of a partition according to another example of the embodiment. [Figure 10]10 is a cross-sectional view of the partition shown in FIG. 9 along CC. [Figure 11] FIG. 10 is a cross-sectional view of a partition according to another example of the embodiment. [Figure 12] 10 is a graph showing the results of sound pressure measurements on the partitions of Examples 1 to 3. [Figure 13] 10 is a graph showing the results of vibration measurements on the partitions of Examples 1 to 3. [Figure 14] 10 is a graph showing the results of sound pressure measurements on the partitions of Examples 3 to 6. [Figure 15] FIG. 1 is a schematic diagram showing how sound pressure is measured using a reverberation chamber and a completely anechoic chamber. [Figure 16] 10 is a graph showing the results of sound pressure measurements on partitions in Examples 1 to 3 using a reverberation room and a completely anechoic room. [Figure 17] 10 is a graph showing the results of sound pressure measurements on the partitions of Examples 3 to 6, which used a reverberation room and a completely anechoic room. [Figure 18] 1 is a graph showing the acceleration of No. 14 PMMA resin and No. 15 PC resin. [Figure 19] This is a graph showing the acceleration of No. 2 PVC resin and No. 15 PC resin. [Figure 20] This is a graph showing the acceleration of No. 2 PVC-based resin and No. 14 PMMA-based resin. [Figure 21] FIG. 1 is a perspective view schematically showing a solvent resistance test. [Figure 22] FIG. 1 is a perspective view schematically illustrating a vibration experiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] The partition of the present invention is a plate-like member for separating people, and is particularly useful in places where people talk through the partition. Furthermore, the partition of the present invention is advantageous in that it can adequately prevent droplet infection compared to partitions with perforated structures for conversation. The following describes an example of a partition of the present invention based on the drawings. Note that the dimensions of the drawings shown in the following description are merely examples, and the present invention is not necessarily limited to these. Appropriate modifications can be made within the scope of the present invention.

[0011] 1 and 2, the partition 1 of this embodiment has a flat substrate 10. A recess 20 is formed on a first surface 12 in the thickness direction of the substrate 10, and a recess 30 is also formed on a second surface 14. In this way, in the partition 1, recesses are formed on both surfaces of the substrate 10. In the present invention, the recesses may be formed on only one surface of the substrate.

[0012] Generally, the frequency of voices in conversation is about 250Hz to 4kHz, and the sound pressure is about 20dB to 80dB. Compared to a flat partition without recesses, Partition 1 has recesses formed in the base, which means that the thickness of that part is thinner and the weight is lighter, making it easier for the partition 1 itself to vibrate with the speaker's voice. This increases the sound pressure transmitted from the speaker's side of Partition 1 to the listener's side, making it easier for the speaker's voice to reach the listener. In this way, the recesses improve the acoustic characteristics of Partition 1, making conversations between people on either side of Partition 1 more comfortable.

[0013] The substrate 10 is preferably transparent. "Transparent" means that the total light transmittance measured in accordance with JIS K7361 is 50% or more. The shape of the substrate 10 in front view is not particularly limited, and examples thereof include a square, a rectangle, a polygon, a perfect circle, and an ellipse. Among these, a square, a rectangle, and a polygon are preferred, and a square is more preferred, in that multiple substrates 10 can be combined side by side without forming gaps between them.

[0014] The dimensions of the substrate 10 are not particularly limited. In the case of a mobile type, the maximum vertical length of the substrate 10 when viewed from the front from the first surface 12 side is preferably 100 mm or more, more preferably 300 mm or more, and even more preferably 400 mm or more. In the case of a fixed type, the maximum vertical length of the substrate 10 is preferably 1800 mm or less, more preferably 1200 mm or less, and even more preferably 800 mm or less. The upper and lower limits of the maximum vertical length of the substrate 10 can be arbitrarily combined, and for example, 400 mm to 800 mm is preferable. Note that the term "mobile type" refers to a type that is placed on a desk or table using a fixture or the like and can be removed or moved. Furthermore, the term "fixed type" refers to a relatively large type that is fixed to the floor and installed, such as a booth partition. The preferred lower and upper limits of the maximum length in the lateral direction when the substrate 10 is viewed from the front from the first surface 12 side are the same as the preferred lower and upper limits of the maximum length in the vertical direction of the substrate 10.

[0015] The thickness of the portion of the substrate 10 where no recesses are formed is set in consideration of the relationship with the thickness of the recesses, sufficient rigidity and durability, and weight restrictions due to the above dimensions. Specifically, the thickness of the portion of the substrate 10 where no recesses are formed is preferably 3 mm or more, and more preferably 5 mm or more. There is no particular upper limit, but from a practical and moldable perspective, it is about 20 mm. It is also possible to configure the substrate 10 by combining substrates 10 of different thicknesses.

[0016] 1, the opening shape of the recess 20 when the substrate 10 is viewed from the front from the first surface 12 side is a perfect circle. The opening shape of the recess 20 is not limited to a perfect circle, and may be a polygon such as an ellipse, a square, or a rectangle. In order for vibrations of the substrate 10 to propagate toward the center of the recess when sound is emitted toward the portion of the substrate 10 where no recess is formed and the portion where a recess is formed, it is preferable that the surface 20a of the recess 20 has a curved surface that becomes deeper and thinner from the opening end of the recess 20 toward the center, as shown in FIG.

[0017] 2, the surface 20a of the recess 20 becomes deeper from the opening edge toward the center of the recess 20. In other words, it is preferable that the substrate 10 has a curved surface 22 so that the thickness of the substrate 10 becomes thinner. In other words, in a cross section of the substrate 10 cut along a plane that is parallel to the thickness direction of the substrate 10 and passes through the center of the recess 20, the linear shape formed by the surface 20a of the recess 20 preferably includes an arc that is convex on the bottom side. In this case, the shape of the curved surface is preferably such that vibration propagation from the opening shape of the recess is synchronized with the size of the flat surface 24 of the recess 20, which will be described later.

[0018] When the recess 20 has such a curved surface 22 and a thin portion, vibrations excited in the substrate 10 by the speaker's voice are easily transmitted to the thin portion of the recess 20, increasing the vibration in this portion. This vibration excites the air and is radiated as sound. That is, the vibration of the substrate 10 excited by the speaker's voice increases the vibration in the thin portion of the recess 20, thereby increasing the radiated sound (called transmitted sound). Due to the so-called elastic edge effect, the vibration of the substrate 10 is concentrated in the center of the thin recess 20. As a result, the vibration of the substrate 10 when receiving the speaker's voice is concentrated in the center of the recess 20. As a result, when the collected vibrations, i.e., structure-borne sound, become airborne sound, the transmitted sound when the speaker's voice is transmitted to the listener is higher than that of a flat plate without a recess.

[0019] Furthermore, it is more preferable that the surface 20a of the recess 20 has a flat surface 24 in the center, inside the curved surface 22. When the recess has a flat surface in the center, inside the curved surface, in this way, the vibrations concentrated in the recess, i.e., structure-borne sound, become airborne sound over a larger area, making it easier for the sound to propagate to the listener. This makes it even easier for the speaker's voice to reach the listener through the partition.

[0020] In this example, the shape of the flat surface 24 of the recess 20 in a front view is a perfect circle. The shape of the flat surface of the recess in a plan view is not limited to a perfect circle, and may be an ellipse, a rectangle, or the like. The shape of the flat surface of the recess is preferably designed to increase the sound pressure of airborne sound, taking into consideration the shape and size of the substrate 10, the curved structure, and the design of the partition. Furthermore, to achieve the above effect, the curved surface 22 of the recess 20 needs to be rigid, and the curved structure preferably has a gentle slope or a curvature radius.

[0021] The dimensions of the recess 20 can be adjusted so that it can easily pick up vibrations of the speaker's voice during conversation and easily transmit those vibrations to the listener. In the partition of the present invention, it is preferable to provide a flat surface of the recess 20 and make its thickness thinner than the thickness of the substrate 10. As described above, the thickness for increasing the vibration of the flat surface is preferably 0.5 mm to 3.0 mm, more preferably 1.0 mm to 2.5 mm, and even more preferably 1.0 mm to 2.0 mm. Within this range, the strength of the partition can also be maintained. On the other hand, when the practical strength, weight, and texture of the partition are taken into consideration, the thickness of the substrate 10 is preferably 3.0 mm to 15.0 mm, more preferably 3.0 mm to 10.0 mm, and even more preferably 3.0 mm to 7.0 mm.

[0022] The relationship between the dimensions of the recess 20 and the thickness of the flat surface relative to the size and thickness of the substrate 10 is preferably such that the thickness of the substrate 10 is 3.0 mm to 7.0 mm and the thickness of the flat surface of the recess 20 is 1.0 mm to 2.0 mm, in order to enhance the effect of amplifying the sound emitted as described above. Furthermore, regardless of the size of the substrate 10, the size of the recess 20 may be formed in a circular, elliptical, or rectangular shape within a range of preferably 150 mm x 150 mm to 600 mm x 600 mm, more preferably 250 mm x 250 mm to 350 mm x 350 mm, based on the edge where the curved portion of the substrate 10 begins. If the size of the recess 20 is equal to or less than the above-mentioned upper limit, the vibration-collecting effect is easily achieved, and the thin portions of the substrate 10 do not become too large, making it easy to ensure the strength and texture of the partition.

[0023] The recesses 20 of the substrate 10 are preferably formed in the same shape on both sides of the substrate 10 in order to ensure that vibrations are transmitted in the same way in both directions. For example, within the above-mentioned dimensional ranges, recesses 20 can be formed on both sides of substrate 10 so as to be symmetrical in a cross section in the thickness direction of substrate 10, with the thickness of the portion of substrate 10 where recesses 20 are not formed being 5.0 mm and the recesses 20 being perfect circles with a diameter of 250 mm and having a flat surface with a thickness of 1.0 mm on the inside of the curved surface. Alternatively, recesses 20 can be formed on both sides of substrate 10 in a similar manner, with an elliptical shape with a major axis diameter of 600 mm and a minor axis diameter of 400 mm and having a flat surface with a thickness of 1.0 mm on the inside of the curved surface.

[0024] When forming these recesses 20, the dimensions of the curved portions and the flat surfaces can be designed by performing simulations based on numerical analysis of vibration propagation and flow analysis of the molding process of the curved and flat surfaces. A coupled structural-acoustic analysis can be used as the numerical analysis. The partition of the present invention aims to increase the transmitted acoustic energy from the radiated acoustic energy of the speaker's voice. The structure of the recesses 20 can be designed by estimating the transmission loss [dB], which is the difference between the incident and transmitted acoustic energy, through a coupled structural-acoustic analysis. Meanwhile, the partition of the present invention can be molded by injection molding using the resin material described below. The injection moldability of the partition structure, including the recesses 20 designed using the coupled structural-acoustic analysis, can be determined through a flow analysis. If the moldability of the structure is insufficient, the partition structure is optimized in relation to the structural design.

[0025] Examples of materials constituting the substrate 10 include polyvinyl chloride resin (hereinafter referred to as "PVC resin"), polymethyl methacrylate resin (hereinafter referred to as "PMMA resin"), polycarbonate resin, and alloy resin of PVC resin and PMMA resin. Among these, materials with rigidity are preferred for the partition of the present invention in order to enhance the radiated acoustic energy due to the above-described structure. Furthermore, PVC resin and its alloy resin are preferred in terms of flame retardancy and solvent resistance. Alloy resin of PVC resin and PMMA resin is more preferred in terms of combining flame retardancy, solvent resistance, and abrasion resistance, and alloy resin of rigid PVC resin and PMMA resin is even more preferred. This alloy resin is particularly preferred because it has resistance to alcohols such as ethanol and chlorine-based disinfectants, which is not possible with PMMA alone, allowing it to be wiped or washed with these. Partition 1, with its excellent solvent resistance, is preferred from the perspective of virus infection prevention, as its surface can be disinfected with alcohol or the like. The material for forming the substrate 10 may be one type used alone or two or more types used in combination.

[0026] The mass ratio of PVC-based resin to PMMA-based resin in the alloy resin is preferably 10 to 70 parts by mass, more preferably 20 to 60 parts by mass, and even more preferably 30 to 55 parts by mass, of PMMA-based resin per 100 parts by mass of PVC-based resin. The higher the proportion of PVC-based resin, the better the flame retardancy and solvent resistance. The higher the proportion of PMMA-based resin, the higher the surface hardness and excellent abrasion resistance.

[0027] A PVC-based resin is a polymer in which the proportion of repeating units derived from vinyl chloride (hereinafter also referred to as "vinyl chloride units") exceeds 50 mass% of all repeating units. The PVC-based resin may be a homopolymer of vinyl chloride, or a copolymer of vinyl chloride and a vinyl-based monomer copolymerizable with vinyl chloride. When the PVC-based resin is a copolymer, it may be a random copolymer, a block copolymer, or a graft copolymer. The PVC-based resin contained in the alloy resin may be one type, or two or more types.

[0028] The proportion of vinyl chloride units in the PVC resin is preferably 75% by mass or more, more preferably 80% by mass or more, even more preferably 85% by mass or more, and particularly preferably 98% by mass or more, based on all repeating units.

[0029] The vinyl monomer copolymerizable with vinyl chloride is not particularly limited, and examples thereof include fatty acid vinyl esters, acrylates, methacrylates, vinyl cyanide, vinyl ethers, α-olefins, unsaturated carboxylic acids or their acid anhydrides, vinylidene chloride, vinyl bromide, and various urethanes.

[0030] Examples of fatty acid vinyl esters include vinyl acetate, vinyl propionate, and vinyl laurate. Examples of acrylates include methyl acrylate, ethyl acrylate, and butyl acrylate. Examples of methacrylates include methyl methacrylate and ethyl methacrylate. Examples of vinyl cyanides include acrylonitrile and methacrylonitrile. Examples of vinyl ethers include vinyl methyl ether, vinyl butyl ether, and vinyl octyl ether. Examples of α-olefins include ethylene, propylene, and butylene. Examples of unsaturated carboxylic acids or acid anhydrides thereof include acrylic acid, methacrylic acid, and maleic anhydride. The vinyl monomer copolymerizable with vinyl chloride may be used alone or in combination of two or more.

[0031] In terms of moldability, the average degree of polymerization of the PVC resin is preferably 400 or more, more preferably 500 or more, and even more preferably 550 or more. In terms of improving moldability, the average degree of polymerization of the PVC resin is preferably 1200 or less, more preferably 800 or less, and even more preferably 700 or less. The lower and upper limits of the average degree of polymerization of the PVC resin can be arbitrarily combined, and for example, 400 to 1200 is preferred. The average degree of polymerization is measured according to JIS K 6720-2.

[0032] The PVC resin may be either a hard vinyl chloride resin or a soft vinyl chloride resin, but a hard vinyl chloride resin is preferred because it provides a molded product with high surface hardness and excellent scratch resistance.

[0033] A PMMA-based resin is a polymer in which the proportion of repeating units derived from methyl methacrylate (MMA) (hereinafter also referred to as "MMA units") relative to all repeating units is 80% by mass or more. The MMA-based resin may be a homopolymer of MMA, or a copolymer of MMA and a (meth)acrylate other than MMA. Note that "(meth)acrylate" is a general term for methacrylate and acrylate. When the PMMA-based resin is a copolymer, it may be a random copolymer or a block copolymer. The PMMA-based resin contained in the alloy resin may be one type or two or more types.

[0034] The proportion of MMA units in the PMMA resin is preferably 80% by mass or more, more preferably 90% by mass or more, based on all repeating units. If the proportion of MMA units is equal to or greater than the lower limit of the above range, moldability is improved.

[0035] Examples of (meth)acrylates other than MMA include methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, and 2-ethylhexyl methacrylate. The (meth)acrylates other than MMA used in the PMMA-based resin may be one type or two or more types.

[0036] In terms of improving surface hardness, the weight-average molecular weight of the PMMA resin is preferably 10,000 or more, more preferably 20,000 or more. In terms of improving strength, the weight-average molecular weight of the PMMA resin is preferably 600,000 or less, more preferably 400,000 or less. The lower and upper limits of the weight-average molecular weight of the PMMA resin can be arbitrarily combined, and for example, 10,000 to 600,000 is preferred.

[0037] In terms of improving surface hardness, the number average molecular weight of the PMMA resin is preferably 5,000 or more, more preferably 10,000 or more. In terms of improving strength, the number average molecular weight of the PMMA resin is preferably 300,000 or less, more preferably 200,000 or less. The lower and upper limits of the number average molecular weight of the PMMA resin can be arbitrarily combined, and for example, 5,000 to 300,000 is preferred. The weight average molecular weight and number average molecular weight are average molecular weights measured using gel permeation chromatography in terms of polystyrene.

[0038] To increase impact resistance, PMMA resins may contain rubber components. Examples of rubber components that can be used include butadiene rubber, acrylic rubber, polyolefin rubber, silicone rubber, and fluororubber. Acrylic rubber is preferred to maintain transparency. A mixture of low-molecular-weight methacrylic resin and high-molecular-weight methacrylic resin may also be used.

[0039] Additives such as stabilizers, UV absorbers, lubricants, antioxidants, plasticizers, antifouling agents, modifiers, colorants, and fillers can be added as needed to the material constituting substrate 10, as long as they do not impair the effects of the present invention. The material constituting substrate 10 may contain one type of additive or two or more types of additives.

[0040] Specific examples of materials constituting the substrate 10 include those exemplified in Tables 2 and 3 in the Examples section described later. For these materials, the results of surface hardness, flame retardancy, and solvent resistance evaluated by the test methods described later are also shown. When used as a partition, the surface hardness is preferably F or higher, more preferably H or higher. The flame retardancy is preferably V-0, V-1 or V-2, with V-0 or V-1 being preferred. The solvent resistance is preferably 0.5% or higher in terms of the average critical strain.

[0041] The following describes an alloy resin made of a PVC-based resin and a PMMA-based resin, which is preferably used as a material for the substrate 10. The PVC-based resin is a composition made of polyvinyl chloride resin (PVC) and additives such as plasticizers, stabilizers, lubricants, modifiers, antioxidants, UV absorbers, colorants, and fillers. Examples of such compositions include those shown in Tables 2 and 3 below. The PVC-based resin is preferably a so-called hard PVC-based resin, as it does not reduce the surface hardness of the alloy resin with PMMA-based resin and enhances the propagation of vibrations in the recesses of the partition. It is more preferable that the PVC-based resin be a composition that does not contain or contains a small amount of liquid additives. The amount of liquid additive added is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, per 100 parts by mass of PVC.

[0042] Alloy resins are produced by melt-kneading PVC-based resin and PMMA-based resin. In this production process, additives are first mixed into PVC using a known mixer, blender, kneader, or the like to produce the PVC-based resin. Next, the PVC-based resin and PMMA-based resin are preferably mixed and kneaded using a twin-screw kneader to produce the alloy resin. In this twin-screw kneading process, the PMMA-based resin is preferably introduced from the kneader's hopper, and the PMMA-based resin is melted and gelled under predetermined conditions, such as temperature and screw rotation speed. A predetermined amount of PVC-based resin, based on the mixing ratio, is then added to the PMMA-based resin and mixed and dispersed using a side feeder. This method is preferred because it helps to suppress discoloration and thermal decomposition of the PVC-based resin, improves the compatibility of the alloy resin, and enhances transparency.

[0043] The partition 1 can be used in any location where conversations are expected to take place while taking measures against virus infection, such as at tables in restaurants and reception rooms, at cash registers, at counters, and between the driver's seat and the back seat of a taxi.

[0044] The manner in which the partition 1 is installed is not particularly limited. For example, as shown in Fig. 3, the partition 1 can be a stationary type that is installed upright on a table or the like with the bottom of the substrate 10 supported by two leg members 100. In this case, there may be space below the substrate 10 as in the example of Fig. 3, or long leg members that can support the entire bottom of the substrate 10 may be used to eliminate the space below the substrate 10. Alternatively, a hole may be formed in the upper part of the substrate 10 where no recess is formed, and a string may be threaded through the hole to make a hanging partition 1 that is installed in a suspended state. The partition 1 may be a sealed type that is fitted into an opening formed in a wall or door.

[0045] As a manufacturing method for the partition 1, injection molding is preferably used to form a substrate with recesses formed therein, as this facilitates obtaining a partition with excellent surface smoothness and transparency. However, the manufacturing method for the partition 1 is not limited to injection molding, and for example, a method of forming recesses by cutting or grinding a flat plate obtained by extrusion molding or calendar molding may also be used.

[0046] As explained above, when partition 1 has a curved surface with recesses that become deeper toward the center, the elastic edge effect concentrates vibrations in the recesses, allowing the speaker's voice to be transmitted to the listener more efficiently. In this way, the acoustic characteristics of partition 1 are improved by the formation of the recesses, so the speaker's voice is more easily transmitted to the listener via the vibrations of partition 1. This allows people on either side of partition 1 to have a comfortable conversation.

[0047] The partition of the present invention is not limited to the above-mentioned partition 1. If the installation space for the partition is large, it is easier for the speaker's voice to be transmitted to the listener if there are multiple recesses of appropriate sizes rather than just one large recess. For example, the partition 2 shown in Figure 4 may be used. In the partition 2, two recesses 20 are formed on the same surface of one substrate 10. The number of recesses 20 formed on the same surface of one substrate 10 may be set appropriately depending on the installation space of the partition.

[0048] The partition 3 shown in Fig. 5 may be used. In the partition 3, a support member 200 is used, which includes a frame 210 into which a plurality of substrates 10 can be fitted and foot members 220 that support the lower part of the frame 210, and a plurality of substrates 10 each having a recess 20 formed therein are arranged and combined vertically and horizontally. The partition 3 may be a combination of a plurality of substrates 10 each having a plurality of recesses 20 formed on the same surface, as in the partition 2. The sizes of the recesses 20 do not need to be uniform, and it is also possible to arrange recesses 20 of a plurality of shapes.

[0049] The number of substrates to be combined may be set appropriately depending on the installation space of the partition. The number of recesses on the same surface of a partition made up of a combination of multiple substrates may be appropriately determined depending on the installation space of the partition.

[0050] It may be the partition 4 illustrated in Figures 6 and 7. The same parts in Figures 6 and 7 as those in Figures 1 and 2 are designated by the same reference numerals and description thereof will be omitted. Partition 4 has the same configuration as Partition 1, except that recess 20A is formed on the first surface 12 of substrate 10 instead of recess 20, and recess 30A is formed on the second surface 14 of substrate 10 instead of recess 30. The entire surface of the recess of partition 4 is a curved surface that becomes deeper from the open end of the recess toward the center. In other words, in a cross section of substrate 10 cut along a plane that is parallel to the thickness direction of substrate 10 and passes through the center of the recess, the linear shape formed by the surface of the recess preferably forms an arc that is convex toward the bottom.

[0051] The opening shape of the recess formed in the substrate is not limited to a perfect circle. For example, the partition 5 may be the one illustrated in Fig. 8. In the partition 5, the shape of the substrate 10A in front view is rectangular, and the opening shape of the recess 20B formed in the first surface 12 of the substrate 10A is elliptical.

[0052] It is preferable that the surface 20a of the recess 20B, whose opening shape is elliptical, has a curved surface 22 that becomes deeper from the opening edge toward the center of the recess 20B. This concentrates vibrations in the recess 20B, so that the speaker's voice is transmitted to the listener more efficiently.

[0053] The surface 20a of the recess 20B, which has an elliptical opening, may further have a flat surface at the center inside the curved surface that deepens from the opening edge toward the center. This concentrates vibrations in the recess 20B, allowing the speaker's voice to be transmitted to the listener more efficiently. When the recess 20B has a flat surface inside the curved surface, the shape of the flat surface is preferably elliptical. The preferred ranges for the thickness of substrate 10A and the thickness of the flat surface that recess 20B may have are the same as the preferred ranges for recess 20. The dimensions of elliptical recess 20B are preferably within the preferred dimensional ranges described for recess 20. The explanation regarding the recess 20B having an elliptical opening shape also applies to the case where a recess having an elliptical opening shape is formed on the second surface of the substrate 10A.

[0054] It may be the partition 6 exemplified in Figures 9 and 10. The same parts in Figures 9 and 10 as those in Figures 1 and 2 are designated by the same reference numerals and description thereof will be omitted. Partition 6 has the same configuration as Partition 1, except that a recess 20C with a square opening and uniform depth is formed on the first surface 12 of the substrate 10, and a recess 30C with a square opening and uniform depth is formed on the second surface 14 of the substrate 10.

[0055] In the partition of the present invention, a recess may be formed on only one surface in the thickness direction of the substrate. For example, this may be the partition 7 shown in Fig. 11. In Fig. 11, the same parts as in Fig. 2 are designated by the same reference numerals, and their explanations will be omitted. The partition 7 has a recess 20 formed only on the first surface 12 of the substrate 10 .

[0056] In addition, within the scope of the spirit of the present invention, the components in the above-described embodiments may be replaced with well-known components as appropriate, and the above-described modifications may be combined as appropriate. [Example]

[0057] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following descriptions.

[0058] [material] The components were mixed to obtain the compositions shown in Tables 1 and 2 to prepare PVC resins No. 1 and No. 2, and alloy resins No. 3 to No. 13. Furthermore, polymethyl methacrylate (PMMA, trade name "VH-001," manufactured by Mitsubishi Chemical Corporation, weight-average molecular weight: 90,000, number-average molecular weight: 50,000, MFR: 2.0 g / 10 min) was used as PMMA resin No. 14, and "SD Polyca 301-10" (manufactured by Sumika Styron Co., Ltd., MFR = 10 g / min) was used as polycarbonate (PC) resin No. 15. Furthermore, a mixed resin No. 16 was prepared by mixing PMMA resin No. 14 and PC resin No. 15 at a mass ratio of 1:1.

[0059] [Surface hardness] Each resin material was used to prepare rectangular plate-shaped test pieces measuring 1.5 mm thick, 30 mm wide, and 125 mm long by injection molding, and the pencil hardness was measured in accordance with JIS K5600-5-4. The results are shown in Tables 1 and 2.

[0060] [Combustion test] Flammability was determined by a UL94V 20mm vertical flame test in accordance with ASTM D3801. Specifically, test specimens measuring 125mm long x 13mm wide x 3mm thick were molded from each resin material, and the test specimens were placed above a burner with their length aligned vertically. They were then exposed to a 20mm flame for 10 seconds twice, and their flammability was determined based on their combustion behavior. The results are shown in Tables 2 and 3.

[0061] [Solvent resistance] Each resin material was used to form a rectangular plate-shaped test piece 700 having a thickness of 1.5 mm, a width of 30 mm and a length of 125 mm by injection molding, and the test piece was stored in a desiccator for one day. As shown in Figure 21, a jig 600 having the shape of an elliptical cylinder with a major axis 2a of 254 mm and a minor axis 2b of 76.2 mm cut into 1 / 4 along the plane passing through the minor axis and the plane passing through the major axis was placed on a horizontal surface with the minor axis (b = 38.1 mm) facing vertically, the major axis (a = 127 mm) facing horizontally, and the curved surface 610 facing upward. After storage, a strip of gauze 710 containing disinfectant ethanol (76.9 to 81.4% by volume at 15°C) was placed on the center of the width direction of the upper surface of test piece 700 so as to extend in the longitudinal direction of test piece 700, and gauze 710 on test piece 700 was covered with film 720. In this state, a first edge 700a in the longitudinal direction of test piece 700 was aligned with the edge 610a on the minor axis side of curved surface 610 of jig 600, and test piece 700 was curved so that the lower surface of test piece 700 was in close contact with curved surface 610 of jig 600, and left to stand for 24 hours under conditions of 23°C and 50% RH. After standing, test piece 700 was removed from jig 600, and the distance in the longitudinal direction between the end of a crack that had occurred in test piece 700 closest to first edge 700a and first edge 700a was defined as d (mm), and the critical strain ε (%) was calculated using the following formula (1): The above measurements were performed on three molded test pieces, and the average value (%) of the critical strain ε was calculated. Note that when the crack generation distance d at a thickness of 1.5 mm was 111 mm or more, the critical strain ε was considered to be "1.00 (%) or more."

[0062]

number

[0063] In the formula (1), t is the thickness (mm) of the test piece 10. The solvent resistance was evaluated based on the calculated critical strain ε according to the following evaluation criteria. The results are shown in Tables 1 and 2. <Evaluation criteria> ○: ε is 0.75 or more △: ε is 0.5 or more and 0.75 or less ×: ε is 0.5 or less

[0064] [Total light transmittance] Using each resin material, rectangular plate-shaped test pieces 1.5 mm thick, 30 mm wide, and 125 mm long were prepared by injection molding, and the total light transmittance was measured in accordance with JIS K7361.

[0065] [Table 1]

[0066] [Table 2]

[0067] As shown in Tables 1 and 2, the PVC resins No. 1 and No. 2 had excellent flame retardancy and solvent resistance. In addition, the surface hardness was lower than that of the PMMA resin No. 14, but higher than that of the PC resin No. 15. In the alloy resins No. 3 to No. 13 of PVC-PMMA resin, the higher the PVC-resin ratio, the better the flame retardancy and solvent resistance, and the higher the PMMA-resin ratio, the higher the surface hardness. In particular, the alloy resins No. 5 to No. 8 had excellent flame retardancy, solvent resistance, and surface hardness.

[0068] [Example 1] Using alloy resin No. 7 in Table 1, a partition having the same structure as partition 1 illustrated in FIGS. 1 and 2 was manufactured by injection molding. The substrate was a square flat plate measuring 300 mm long x 300 mm wide x 4.0 mm thick, with recesses on both surfaces with circular openings and a diameter of 260 mm. The radius of curvature of the curved surface of the recess was 2757.25 mm, the diameter of the flat surface inside the curved surface was 50 mm, and the thickness of the thinnest part of the substrate (the center of the recess) was 1.0 mm.

[0069] [Example 2] A partition was manufactured in the same manner as in Example 1, except that the shape of the partition was changed to the same shape as partition 6 illustrated in FIGS. The substrate was a square flat plate measuring 300 mm long x 300 mm wide x 4.0 mm thick, and on both surfaces were formed square recesses with openings measuring 260 mm long x 260 mm wide, with a depth of 2.0 mm.

[0070] [Example 3] A partition was produced in the same manner as in Example 1, except that no recesses were formed on either surface of the substrate, and a flat partition was used.

[0071] [Evaluation test] 1. Sound pressure measurement In a simple anechoic chamber, a square opening measuring 300 mm long x 300 mm wide was made on the top surface of a box made of 50 mm thick glass wool plate, and the partition obtained in each example was installed in the opening. A volume flow source was placed as a sound source 100 mm downward inside the box from the center of the partition installed in the box. A microphone was placed 150 mm above the center of the partition installed in the box, and random sounds were generated from the sound source to measure the sound pressure. Sound pressure was also measured in the same way when no partition was installed in the box. The measurement results are shown in a graph in Figure 12, where the horizontal axis represents the frequency of the random sound generated from the sound source and the vertical axis represents the measured sound pressure level.

[0072] 2. Vibration Measurement As in "1. Sound pressure measurement," an accelerometer was placed in the center of the outer surface of the partition installed in the box to measure vibrations. The measurement results are shown in a graph in Figure 13, where the horizontal axis represents the frequency of the random sound generated from the sound source and the vertical axis represents the vibration measured by the accelerometer.

[0073] As shown in Figure 12, the partitions of Examples 1 and 2, in which recesses were formed on both sides of the substrate, had a higher transmitted sound pressure for sounds of about 250 Hz to 4 kHz, which are common conversation frequencies, compared to the partition of Example 3, in which no recesses were formed. In particular, the partition of Example 1, in which the recess opening shape was a perfect circle, had a higher transmitted sound pressure. Furthermore, as shown in Figure 13, the partitions of Examples 1 and 2, in which recesses were formed on both sides of the substrate, had greater vibration than the partition of Example 3, in which no recesses were formed.

[0074] [Example 4] A partition was manufactured in the same manner as in Example 1, except that the shape of the partition was changed to the same shape as partition 5 illustrated in FIG. The substrate was a rectangular flat plate measuring 400 mm in length, 600 mm in width, and 4.0 mm in thickness, and an elliptical recess with an opening shape of 560 mm in major axis and 360 mm in minor axis was formed on both surfaces. The radius of curvature R of the curved surface on the minor axis side of the recess was 8417.65 mm, and the thickness of the thinnest part of the substrate (the center of the recess) was 1.0 mm, and the radius of curvature R of the curved surface on the major axis side was adjusted to match this shape.

[0075] [Example 5] A partition was manufactured in the same manner as in Example 1, except that the shape of the partition was changed to the same shape as partition 2 illustrated in FIG. The substrate was a rectangular flat plate measuring 400 mm long, 600 mm wide, and 4.0 mm thick, with two circular recesses with an opening shape of 180 mm in diameter formed on each surface. The radius of curvature R of the curved surface of the recesses was 2659.85 mm, the diameter of the flat surface inside the curved surface was 50 mm, and the thickness of the thinnest part of the substrate (the center of the recesses) was 1.0 mm.

[0076] [Example 6] A partition was produced in the same manner as in Example 1, except that no recesses were formed on either surface of the substrate, and the partition was a flat plate having a thickness of 3 mm.

[0077] [Evaluation test] 3. Sound pressure measurement In a standard room, a partition was placed on a table with its bottom center supported at one point by a leg.A speaker was placed on one surface of the partition on the table, 350 mm away from the horizontal center of the partition to one surface, so that the speaker was 150 mm high from the table top.A microphone was placed on the other surface of the partition on the table, 350 mm away from the horizontal center of the partition to the other surface, so that the microphone was 250 mm high from the table top. A pre-recorded audio source saying "Good morning" was played from a speaker and the sound pressure was measured. The measurement results are shown in a graph in FIG. 14, with the frequency of the sound reproduced from the speaker on the horizontal axis and the measured sound pressure level on the vertical axis.

[0078] 4. Hearing test With the test subjects seated 300 mm behind the microphone set up in "3. Sound Pressure Measurement," the sound "Good morning" was played three times from the speaker with and without a partition. The test subjects were asked to rate the ease of hearing on a three-point scale from 1 to 3, with 3 points (the highest score) being the ease of hearing when there was no partition. The test subjects consisted of six people in total: two men in their 20s, one woman in her 40s, one man in his 50s, and two men in their 60s. The evaluation scores and their averages for each partition are shown in Table 3.

[0079] [Table 3]

[0080] As shown in FIG. 14, the partitions of Examples 4 and 5, in which recesses were formed on both sides of the substrate, had a higher transmitted sound pressure than the partitions of Examples 3 and 6, in which no recesses were formed. Furthermore, as shown in Table 3, in the listening test, the partition of Example 5, which had two recesses with circular openings, tended to make it easier to hear voices than the partition of Example 4, which had one recess with an oval opening.

[0081] [Evaluation test] 5. Sound pressure measurement As shown in Figure 15, in an adjacent reverberation chamber and a completely anechoic chamber, test specimen 500 was placed on the reverberation chamber side of the opening (a square measuring 900 mm long x 900 mm wide) connecting the reverberation chamber and the completely anechoic chamber, and microphone 300 was placed at the height of the center of test specimen 500 on the completely anechoic chamber side so that the distance between test specimen 500 and microphone 300 was 150 mm. Speaker 400 was placed 1.5 mm away from test specimen 500 in the reverberation chamber, and a random noise signal was emitted from speaker 400 to measure the sound pressure. The recording conditions were an effective frequency of 20 kHz, 16,384 data lines, and 10-second spectrum averaging. Fig. 16 shows the measurement results using the partitions of Examples 1 to 3 as test specimen 500, with the frequency of the sound reproduced from the speaker on the horizontal axis and the transmitted sound pressure ratio, P1 / P0, calculated as the ratio of the sound pressure P0 measured when there is no partition to the sound pressure P1 measured when there is a partition for each sample, on the vertical axis. Similarly, Fig. 17 shows the measurement results using the partitions of Examples 3 to 6 as test specimen 500.

[0082] As shown in Figure 16, the partitions of Examples 1 and 2, in which recesses were formed on both sides of the substrate, had a higher transmitted sound pressure ratio for sounds of around 250 Hz to 4 kHz, which are common frequencies in conversation, compared to the partition of Example 3, in which no recesses were formed. As shown in Figure 17, the partitions of Examples 4 and 5, in which recesses were formed on both sides of the substrate, had a higher transmitted sound pressure ratio for sounds of about 250 Hz to 4 kHz, which are common conversation frequencies, than the partitions of Examples 3 and 6, in which no recesses were formed. Also, the partition of Example 5, in which two recesses with circular openings were formed, had a higher transmitted sound pressure ratio than the partition of Example 4, in which one recess with an oval opening was formed.

[0083] [Frequency response characteristics] Measurement sample 800 was fabricated by injection molding 3 mm thick rectangular flat plates measuring 100 mm x 100 mm each using PVC resin No. 2 in Table 1, PMMA resin No. 14, and PC resin No. 15 in Table 2. As shown in Figure 22, measurement sample 800 was suspended by two strings 810 and left unfixed, and a microphone was placed approximately 30 mm from the center of one side of measurement sample 800. Vibration was applied with an impulse hammer at a strength of approximately 20 N, and the frequency response characteristics (acceleration) were evaluated. The accelerance of No. 14 PMMA resin and No. 15 PC resin is shown in Figure 18, the accelerance of No. 2 PVC resin and No. 15 PC resin is shown in Figure 19, and the accelerance of No. 2 PVC resin and No. 14 PMMA resin is shown in Figure 20.

[0084] As shown in Figure 18, PC resin had a large acceleration, but little vibration in the ranges of 500-1000 Hz and 2000-2500 Hz. However, when PC and PMMA, a PMMA-based resin, are used together, the response characteristics between 500-1000 Hz cannot be compensated for, but the response characteristics between 2000 Hz and 2500 Hz can be compensated for. Also, as shown in Figure 19, when PC and PVC-based resin are used together, the response characteristics between 2000 Hz and 2500 Hz cannot be compensated for, but the response characteristics between 500-1000 Hz can be compensated for. Furthermore, as shown in Figure 20, when PVC-based resin and PMMA-based resin are used together, their frequency response characteristics complement each other, making it possible to obtain vibrations over almost the entire frequency range up to 3000 Hz. Therefore, alloy resins of PVC-based resin and PMMA-based resin are particularly preferable in terms of frequency response characteristics. [Explanation of symbols]

[0085] 1-7...Partitions, 10, 10A...Substrate, 12...First surface, 14...Second surface, 20, 20A-20C...Recess, 20a...Surface, 22...Curved surface, 24...Flat surface, 30, 30A, 30C...Recess, 30a...Surface, 32...Curved surface, 34...Flat surface, 100...Foot member, 200...Support member, 210...Frame body, 220...Foot member.

Claims

1. a flat substrate, at least one surface of the substrate in a thickness direction thereof is formed with a recess where the thickness of the substrate is partially thin, the material constituting the substrate includes a vinyl chloride resin, and the surface hardness is F or more; A partition, wherein the surface of the recess has a curved surface that becomes deeper from the opening edge of the recess toward the center, and the opening shape of the recess is a perfect circle.

2. 2. The partition according to claim 1, wherein the material constituting the substrate is an alloy resin of vinyl chloride resin and methyl methacrylate resin.

3. The partition according to claim 1 or 2, wherein the surface of the recess has a flat surface at the center of the recess.

4. The partition according to any one of claims 1 to 3, wherein recesses are formed on both surfaces of the substrate.

5. The partition according to any one of claims 1 to 4, wherein a plurality of the recesses are formed on the same surface of the substrate.

6. The partition according to any one of claims 1 to 5, wherein a plurality of the substrates each having the recess formed therein are combined together.

7. A method for manufacturing a partition according to any one of claims 1 to 6, comprising the steps of: A method for manufacturing partitions, in which the partitions are obtained by injection molding.

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