JP7015221B2 - Resin plate and method for manufacturing the resin plate - Google Patents

Description

The present invention relates to a resin plate containing bubbles and a method for producing the resin plate.

A resin plate containing air bubbles may be used as a decorative plate used in applications such as optical display devices and partitions for building materials. In the case of a decorative plate made of a transparent resin, it is possible to form a state with high design by introducing light from its end face and making bubbles stand out with the light.

As the resin plate containing bubbles, a laminated board having a bubble-containing layer containing bubbles and a resin layer laminated on both sides of the bubble-containing layer has been proposed. As shown in Patent Document 1, for example, the laminated board is foamed with a non-foaming resin sheet by sandwiching a fluid adhesive containing bubbles due to air or the like and / or generating bubbles inside between transparent non-foaming resin sheets. It can be manufactured by forming a laminated structure with a layer.

Japanese Unexamined Patent Publication No. 2011-51324

In a decorative plate used in an optical display device, if a specific number of bubbles is present and the variation in the number of bubbles is small, the decorative plate can be made to have an excellent appearance. Furthermore, in order to create a highly designed state by introducing light from the end face to make the bubbles stand out, the resin plate that contains the bubbles and forms a decorative plate is used in the situation of space production using an optical display device. Therefore, it is important to have an appropriate number of bubbles. In particular, in order for the resin plate to be effectively used as a decorative plate that is easy to use and has excellent design, an appropriate number of bubbles are emitted regardless of the size of the end face that is the light introduction portion. It is important to have a structure that can be made to stand out.

In addition, if light can be applied to an appropriate number of bubbles contained in the resin plate, the space for arranging the device equipped with the light source is small in the place where the optical display device is used, and the light introduction portion from the light source. Even when the size of the end face of the decorative plate is small, it becomes easy to appropriately make the air bubbles of the decorative plate stand out with light, and the degree of freedom of space production can be improved.

In this respect, in the invention of Patent Document 1, it is not easy to obtain a resin plate in which the number of bubbles contained is controlled in a specific range, the number of bubbles is too large, or the number of bubbles becomes coarse or dense in the resin plate. There was a risk of doing so. If the number of bubbles becomes too dense, the number of collisions between the light introduced into the resin plate from the light source and the bubbles increases, and there is a problem that the transmission of light is blocked. As a result, the resin plate obtained in Patent Document 1 has a problem that it is difficult to sufficiently spread the light to the end face opposite to the end face into which the light is introduced. Therefore, in the resin plate obtained in Patent Document 1, when the area of the display surface in the optical display device is large, it becomes difficult to spread the light to the extent that an appropriate number of bubbles can be conspicuous by the light. It was a situation that would end up.

INDUSTRIAL APPLICABILITY The present invention has a specific number of bubbles and has a small variation in the number of bubbles, so that it can be used as a decorative plate having excellent designability, and it is possible to sufficiently spread light to the opposite end surface to the end surface into which light is introduced. A resin plate capable of spreading light to such an extent that an appropriate number of bubbles can be conspicuous with light even when the area of the display surface in the optical display device is large, and such a resin plate. The purpose is to provide a manufacturing method for.

In the present invention, (1) the first transparent thermoplastic resin is used as a base resin and a bubble-containing layer containing bubbles, and the second transparent thermoplastic resin is used as a base resin and laminated on both sides of the bubble-containing layer. A resin plate having a resin layer and a total basis weight of 3000 g / m ² or more and 20000 g / m ² or less.
The area of the plate surface of the resin plate is 0.25 m ² or more, the average bubble diameter in the plate surface direction is 1 mm or more, and the average value of the number of bubbles per 100 cm ² observed from the plate surface side is 5 or more. It is characterized in that the number of bubbles is 500 or less, the coefficient of variation of the number of bubbles is 30% or less, and the ratio of the area occupied by the bubbles to the area of the plate surface of the resin plate is 0.2% or more and 50% or less. Resin plate,
(2) The resin plate according to (1) above, wherein both the first transparent thermoplastic resin and the second transparent thermoplastic resin are either polystyrene resin, acrylic resin or polycarbonate resin.
(3) The resin plate according to (1) or (2) above, wherein the ratio of the area occupied by the bubbles to the area of the plate surface of the resin plate is 0.2% or more and 20% or less.
(4) The ratio of the total basis weight of the resin layer to the total basis weight of the resin plate (total basis weight of the resin layer / total basis weight of the resin plate) is 0.70 or more and 0.98 or less. The resin plate according to any one of (1) to (3) above.
(5) The bubbles in the bubble-containing layer are formed by using talc as a bubble nucleating agent and foaming the base resin with a foaming agent, and the content of talc in the bubble-containing layer is 0. The resin plate according to any one of (1) to (4), which is 1.01% by mass or more and 1.0% by mass or less.
(6) The method for producing a resin plate according to any one of (1) to (4) above, wherein a second transparent thermoplastic resin is kneaded to form a molten resin for forming a resin layer. A bubble-containing layer-forming molten resin made by kneading a first transparent thermoplastic resin, talc, and a foaming agent was merged and laminated between the resin layer-forming molten resin and the resin layer-forming molten resin. The laminate is co-extruded and the bubble-containing layer-forming molten resin is foamed to form bubbles, and the amount of the talc added to the bubble-containing layer-forming molten resin is the first transparent thermoplastic resin and the talc. The amount of the foaming agent added is 0.05 mol or more and 0.2 mol or less per 1 kg of the first transparent thermoplastic resin. The gist is a method for manufacturing a resin plate, which is characterized by the above.

The present invention can be used as a decorative plate having excellent design, and it is possible to sufficiently distribute light to the end surface opposite to the end surface into which light is introduced, even when the area of the display surface in the optical display device is large. It is possible to obtain a resin plate capable of spreading light to such an extent that an appropriate number of bubbles can be made to stand out by light, and a method for producing such a resin plate.

FIG. 1A is a schematic plan view schematically showing one of the examples of the resin plate of the present invention. FIG. 1B is a schematic cross-sectional schematic diagram for schematically showing the state of the cross section taken along line AA of FIG. 1A. FIG. 2A is a schematic plan view schematically showing one of the examples of the optical display device using the resin plate of the present invention. FIG. 2B is a schematic cross-sectional schematic diagram for schematically showing the state of the cross section taken along the line BB of FIG. 2A. FIG. 3 is an explanatory diagram for explaining the method for manufacturing the resin plate of the present invention.

The resin plate 1 of the present invention has a bubble-containing layer 2 and a resin layer 3. As shown in FIGS. 1A and 1B, the resin plate 1 has a structure in which the resin layers 3 and 3 are laminated on both surfaces of the bubble-containing layer 2.

(Shape of resin plate 1)
The shape of the resin plate 1 is such that a side end surface capable of incident light can be formed, and light incident from the side end surface can travel through the inside of the resin plate 1. The shape is selected as appropriate. Specifically, as the shape of the resin plate 1, a shape such as a square shape, a rectangular shape, a tongue piece shape, a semicircular shape, or the like can be selected from the plan view of the resin plate 1, but it may be square or square. It is preferably rectangular, and as shown in FIGS. 1A and 1B, the resin plate 1 is more preferably rectangular in the plan view of the resin plate 1. This is because when the resin plate 1 in the plan view of the resin plate 1 has a rectangular shape, it is easy to allow light to travel in a uniform optical path from one end face of the short side of the resin plate 1 to the other end face, and the resin plate 1 is formed. This is because it is easy to spread the light in 1. Hereinafter, a case where the resin plate 1 has a rectangular shape in a plan view as shown in FIGS. 1A and 1B will be described as an example. The plan view of the resin plate 1 indicates a case where the resin plate 1 is observed with the thickness direction of the resin plate 1 as the line-of-sight direction.

(Area of plate surface of resin plate 1)
In the resin plate 1, the area of the plate surface of the resin plate 1 is 0.25 m ² or more. Since the resin plate 1 of the present invention has a large area of 0.25 m ² or more, even one resin plate 1 can be effectively used as a decorative plate arranged in a store or the like as described later.

When the resin plate 1 has a rectangular shape, the length of one side of the resin plate 1 is appropriately selected so that the area of the plate surface of the resin plate 1 is 0.25 m ² or more, but it may be 10 cm or more. It is preferably 20 cm or more, and more preferably 20 cm or more. On the other hand, the length of one side of the resin plate 1 is preferably 250 cm or less, more preferably 120 cm or less. When the length of one side of the resin plate 1 is within this range, the light bubble-containing layer is emitted from the end face formed along the short side direction of the resin plate 1 (direction along the double-headed arrow S in FIGS. 1A and 1B). When incident light is incident in 2, the incident light travels in the long side direction of the resin plate 1 (direction along the double-headed arrow L in FIGS. 1A and 1B) and is on the opposite end side to the incident side end surface of the light. It will be easier to reach the end face and will be easier to use as a decorative board in various situations. The short side direction and the long side direction of the resin plate 1 are the same in FIGS. 2A and 2B.

(Total light transmittance of resin plate 1)
The total light transmittance of the resin plate 1 is preferably 70% or more, more preferably 80% or more when the direction along the thickness direction of the resin plate 1 is the line-of-sight direction. When the total light transmittance of the resin plate satisfies the above range, it is possible to obtain the effect that the light transmittance of the decorative plate can be increased when the resin plate is used as the decorative plate. As the total light transmittance, a value measured at a randomly selected location without considering the presence or absence of air bubbles in the resin plate 1 at the measurement location is adopted. Therefore, it is preferable that the total light transmittance of the resin plate 1 satisfies the above range regardless of whether the resin plate 1 contains bubbles or does not contain bubbles. The total light transmittance can be measured using a turbidity meter (for example, manufactured by Nippon Denshoku Industries Co., Ltd., product name Haze Meter NDH7000SP) according to JIS K7361-1: 1997.

(Haze of resin plate 1)
Further, the resin plate 1 preferably has a haze of 20% or less, more preferably 10% or less, and further preferably 5% or less. Since the haze of the resin plate 1 is low, it is possible to obtain the effect that the transparency of the resin plate 1 is high and the design is excellent. The haze is obtained by cutting out a test piece from the resin plate 1, forming a plate shape from which air bubbles are removed by a hot press or the like, and measuring the haze on the plate-shaped test piece. The haze can be measured based on JIS K7136: 2000.

(Range of basis weight of resin plate 1)
It is required that the total basis weight of the resin plate 1 is 3000 g / m ² or more and 20000 g / m ² or less. This is because when the total basis weight of the resin plate 1 is within the above range, the resin plate is not easily cracked, is lightweight, and is easy to handle. From the above viewpoint, it is more preferable that the total basis weight of the resin plate 1 is 4000 g / m ² or more and 15000 g / m ² or less.

(Specification of basis weight of resin plate 1)
The basis weight [g / m ² ] of the resin plate 1 is specified as follows. From the side edge of one side extending along the long side direction L of the resin plate 1, test pieces of predetermined dimensions are cut out at equal intervals along the short side direction S, and each test piece is placed on the front and back surfaces of the test piece. The basis weight of each test piece can be calculated by calculating the area of the corresponding surface, specifying the weight of the test piece, and dividing the weight by the area.

(Specification of basis weight of resin layer 3)
In the case of a resin plate manufactured by coextrusion, the basis weight [g / m ² ] of the resin layer 3 is the discharge amount X [kg / hour] of the resin layer and the width of the obtained resin plate under the extrusion foaming conditions. It is obtained by the following formula (1) from W [m] and the length L [m / hour] of the extruded resin plate per unit time of the resin plate.

(Basis weight ratio between resin plate 1 and resin layer 3)
Regarding the total basis weight of the resin plate 1, the ratio of the total basis weight of the resin layer 3 described later to the total basis weight of the resin plate 1 according to the range of the basis weight of the resin plate 1 described above (the resin layer 3). The total basis weight / total basis weight of the resin plate 1) is preferably 0.7 or more and 0.98 or less. When the value of the above (total basis weight of the resin layer 3 / total basis weight of the resin plate 1) satisfies the above range, the resin layer has a sufficient basis weight with respect to the resin plate 1, so that it depends on the bubbles in the bubble-containing layer. It is possible to suppress the possibility that the uneven shape affects the surface of the resin layer, and to obtain a resin plate having a smooth surface. Further, from the viewpoint of enhancing this effect, it is more preferable that the ratio of the total basis weight of the resin layer 3 described later to the total basis weight of the resin plate 1 is 0.8 or more and 0.98 or less. Regarding the value of the total basis weight of the resin layer 3, when the resin layer 3 is formed at two places, it is the total basis weight of those two resin layers 3.

(Bubble-containing layer 2)
The bubble-containing layer 2 is a layer formed by using the first transparent thermoplastic resin as a base resin, and has a layer structure in which a large number of bubbles are dispersed and formed inside the layer. The bubble-containing layer 2 is formed so as to spread over the entire surface of the resin plate 1 along the plate surface direction of the resin plate 1. The area of the bubble-containing layer 2 along the plate surface direction corresponds to the area of the resin plate 1 along the plate surface direction. Here, the plate surface direction indicates the direction in which the plane spreads with the direction along the thickness direction of the resin plate 1 as the normal.

(Bubble 4)
Regarding the bubbles formed in the bubble-containing layer 2, the shape of each bubble 4 is substantially spherical or elliptical spherical. Further, the bubble 4 has an average bubble diameter of 1 mm or more in the plate surface direction. When each bubble has such a size, it is possible to obtain an effect that when the bubble 4 is exposed to light and the bubble 4 shines, it is easily recognized as a bubble by the naked eye. The bubble 4 preferably has an average bubble diameter of 1.5 mm or more in the direction orthogonal to the plate surface direction. On the other hand, the upper limit of the average bubble diameter of the bubbles 4 is preferably 4 mm.

(Method of specifying average bubble diameter)
For the bubble 4, the average bubble diameter can be specified as follows. In a dark room environment, take a picture of the resin plate 1 in a plan view. Within the area of the photographed resin plate 1, a plurality of areas of a predetermined size are randomly selected and used as designated areas. In each designated area, for example, the area of each bubble is measured by using the image processing software NS2K-pro manufactured by Nanosystem Co., Ltd., and based on the area, the diameter when the bubble shown in the photograph is a circle is calculated. The value obtained by arithmetically averaging the values of each diameter obtained in each designated area was defined as the average bubble diameter (mm).

(Number of bubbles)
In the bubble-containing layer 2, the average value of the number of bubbles 4 (number of bubbles) per 100 cm ² observed when the resin plate 1 is viewed in a plan view is 5 or more and 500 or less. When the average value of the number of bubbles is 5 or more and 500 or less, the design is excellent as a decorative plate, and when used as an optical display, the light is sufficiently spread to the opposite end surface to the end surface into which light is introduced. It is possible to obtain the effect that even when the area of the display surface in the optical display device is large, the light can be spread as a whole to the extent that an appropriate number of bubbles can be made to stand out by the light. can. From the viewpoint of enhancing this effect, the average value of the number of bubbles is preferably 10 or more, more preferably 20 or more, and further preferably 30 or more. From the same viewpoint, the average value of the number of bubbles is preferably 150 or less, more preferably 120 or less, and further preferably 100 or less.

From the viewpoint of the design of the resin plate, it is preferable that the bubble diameters are uniform and there are few extremely large bubbles or small bubbles. Specifically, the total number of bubbles having a bubble diameter of less than 0.5 mm in the plate surface direction and the number of bubbles having a bubble diameter exceeding 5 mm is 10% or less as a ratio to the total number of bubbles. It is preferably 5% or less, and more preferably 5% or less.

(Specification of the number of bubbles)
The number of bubbles can be specified as follows. In a dark room environment, take a picture of the resin plate 1 in a plan view. Within the area of the photographed resin plate 1, a plurality of areas having an area of 100 cm ² such as 10 cm × 10 cm are randomly selected and designated as designated areas. In each designated area, for example, by using the image processing software NS2K-pro manufactured by Nanosystem Co., Ltd., the number of clear bubbles existing in each range is obtained, and each of these values is calculated by arithmetic mean. Be done. Although a plurality of designated areas are randomly selected, the designated areas may or may not partially overlap with each other.

(Coefficient of variation of the number of bubbles)
The bubble-containing layer 2 has a coefficient of variation of 30% or less in the number of bubbles. Since the coefficient of variation of the number of bubbles is 30% or less, the number of bubbles is not uneven in the entire resin plate and the design is excellent, and when used as an optical display, sufficient light reaches the opposite end surface to the end surface into which light is introduced. This facilitates the process, and even when the area of the display surface in the optical display device is large, it is possible to obtain the effect that light can be spread throughout. From this viewpoint, the coefficient of variation of the number of bubbles is preferably 25% or less, more preferably 20% or less. The lower limit of the coefficient of variation of the number of bubbles is about 3%.

(Specification of coefficient of variation of the number of bubbles)
The coefficient of variation (Cv) of the number of bubbles is a value obtained by [standard deviation (V) of the number of bubbles / average value of the number of bubbles] × 100 of each number of bubbles, and is an index showing the degree of variation in the number of bubbles. ..
The standard deviation (V) of the number of bubbles is obtained by the following equation (2).

In the above formula (2), DTav represents the average value of the number of bubbles, and n represents the number of measurements. Further, i indicates an integer from 1 to n, and DTi indicates a measured value (DT1, DT2 ..., DTn) of each individual bubble number measured at the time of measuring the average bubble number. Σ represents a series ((DT1-DTav) ² + (DT2-DTav) ² + (DT3-DTav) ² ... + (DTn-DTav) ² ).

The coefficient of variation (Cv) of the number of bubbles is obtained by the following formula (3) using the standard deviation (V) obtained by the above formula (2).

(Ratio of bubbles 4 in the bubble-containing layer 2)
In the bubble-containing layer 2, the ratio of the area occupied by the bubbles 4 (referred to as the bubble occupying area) to the area of the bubble-containing layer 2 along the plate surface direction is 0.2% or more and 50% or less. That is, in the plan view of the resin plate 1, the ratio of the bubble occupying area is 0.2% or more and 50% or less.

When the ratio of the bubble occupying area is 0.2% or more and 50% or less, the transparency of the resin plate 1 can be maintained, and the effect that the resin plate having excellent design can be obtained is obtained. be able to. From this viewpoint, the ratio of the bubble occupying area is preferably 0.5% or more, more preferably 0.7% or more, and further preferably 1% or more. On the other hand, from the same viewpoint, the ratio of the bubble occupying area is preferably 20% or less, more preferably 10% or less, further preferably 5% or less, and particularly preferably 3% or less. ..

(Specification of the ratio of the occupied area of bubbles)
The ratio of the bubble occupied area can be specified as follows. The total area of individual bubbles in the designated region in the above average bubble diameter is obtained. Then, the ratio of the total area of the individual bubbles in the designated area to the area of the designated area (total area of the individual bubbles in the designated area) / (area of the designated area) × 100 is calculated. This ratio (%) is the ratio of the bubble occupied area.

(First transparent thermoplastic resin)
As the first transparent thermoplastic resin to be the base resin, a resin corresponding to the "transparent plastic" known in JIS K 7361 (1997) is preferably used. Specific examples of the thermoplastic resin include polystyrene resin, polypropylene resin, acrylic resin, polycarbonate resin, thermoplastic polyester resin, and cyclic olefin resin.

Examples of the polystyrene resin include polystyrene, styrene-α-methylstyrene copolymer, styrene-p-methylstyrene copolymer, polystyrene, a styrene-acrylic acid ester copolymer containing styrene as a main component, and a styrene-methacrylate ester copolymer weight. Combined, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-maleic anhydride copolymer, styrene-polyphenylene ether copolymer, styrene-butadiene copolymer, styrene-acrylonitrile copolymer, acrylonitrile -Butadiene-styrene copolymer, acrylonitrile-styrene acrylate copolymer, styrene-methylstyrene copolymer, styrene-dimethylstyrene copolymer, styrene-ethylstyrene copolymer, styrene-diethylstyrene copolymer, high impact Examples thereof include polystyrene (impact-resistant polystyrene resin), which are used alone or in admixture of two or more. The polystyrene resin has a styrene-based unit or styrene component content of more than 50 mol%, preferably 70 mol% or more, and particularly preferably 80 mol% or more.

The acrylic resin is a homopolymer of an acrylic acid alkyl ester and / or a methacrylic acid alkyl ester (collectively referred to as (meth) acrylic acid ester below) or a combination of (meth) acrylic acid esters. Polymers or (meth) acrylic acid ester-based copolymers having 50 mol% or more of units based on (meth) acrylic acid esters and 50 mol% or less of units based on other comonomers, and two or more of these. It is a mixture or the like. In addition, (meth) acrylic acid is a concept including acrylic acid and methacrylic acid, and means one or both of them.

Examples of the homopolymer or copolymer of the above (meth) acrylic acid ester include polymethylmethacrylate, ethylpolymethacrylate, propylpolymethacrylate, butylpolymethacrylate, methylpolyacrylate, ethyl polyacrylate, and the like. Examples thereof include a methyl methacrylate-ethyl methacrylate copolymer, a methyl methacrylate-butyl methacrylate copolymer, a methyl methacrylate-ethyl acrylate copolymer, and the like. Of these, polymethyl methacrylate, methyl polyacrylate, methyl methacrylate-ethyl methacrylate copolymer, or methyl methacrylate-ethyl acrylate copolymer is preferable, and polymethyl methacrylate is more preferable.

Examples of the polycarbonate resin include bisphenol A (4,4'-dihydroxydiphenyl-2,2-propane) polycarbonate, bisphenol F (4,4'-dihydroxydiphenyl-2,2-methane) polycarbonate, and bisphenol S (4). , 4'-Dihydroxydiphenyl sulfone) polycarbonate, 2,2-bis (4-dihydroxyhexyl) propane) polycarbonate and the like are exemplified. Of these, an optical grade polycarbonate resin is particularly preferable.

The first transparent thermoplastic resin can be used alone or in admixture of two or more. When two or more kinds of thermoplastic resins are mixed and used, or when other resins and the like are mixed and used within the range that does not impair the object of the present invention, each thermoplastic resin to be used. It is preferable that the refractive indices of are close to or equal to each other. If the difference in the refractive index of each thermoplastic resin or the difference in the refractive index between the thermoplastic resin and other resins is large, the mixed resin becomes cloudy and the transparency and image sharpness deteriorate, depending on the mixing ratio. It is desirable that the difference in refractive index is small. Specifically, the difference in refractive index is preferably 0.05 or less, more preferably 0.04 or less, further preferably 0.03 or less, and the difference in refractive index is optimally 0 (zero).

The first transparent thermoplastic resin used for the base resin forming the bubble-containing layer is any one of polystyrene resin, acrylic resin, and polycarbonate resin from the viewpoint of excellent processability among the above thermoplastic resins. It is preferable, and polystyrene resin is particularly preferable. Further, among the polystyrene resins, branched polystyrene resin is preferable. The bubble-containing layer made of the branched polystyrene resin is preferable because it suppresses bubble deformation and bubble breakage.

The base resin forming the bubble-containing layer is a resin other than the above-mentioned first transparent thermoplastic resin, an elastomer, a bubble modifier, an antioxidant, a heat stabilizer, as long as the object and effect of the present invention are not impaired. It can contain one or more functional additives such as weather resistant agents, ultraviolet absorbers, flame retardants, antibacterial agents and shrinkage inhibitors, or additives such as inorganic fillers. The total amount of the additives is preferably 10 parts by mass or less with respect to 100 parts by mass of the first transparent thermoplastic resin.

(Foam nucleating agent)
The bubble-containing layer 2 is a layer formed by foaming a molten resin for forming a bubble-containing layer, which will be described later, which is obtained by melt-kneading a first transparent thermoplastic resin and a bubble nucleating agent with a foaming agent to form bubbles inside the foam-containing layer 2. It is preferable to have.

Examples of the bubble nucleating agent include polyethylene wax, talc, calcium carbonate, silica, ethylene bisstearylamide, methyl methacrylate-based copolymer, and silicone. Among the above-mentioned bubble nucleating agents, talc is preferable because it functions efficiently as a bubble nucleating agent with a low addition amount and it is easy to adjust the number of bubbles in the bubble-containing layer to an appropriate range. In particular, when talc is used, it is excellent in that the number of bubbles 4 can be adjusted without significantly changing the average bubble diameter. Further, in the bubble-containing layer 2, when talc is used as the bubble adjusting agent, the content of talc in the bubble-containing layer 2 is preferably 0.01% by mass or more, preferably 0.02% by mass or more. More preferably, it is more preferably 0.03% by mass or more. On the other hand, the content of talc is preferably 1.0% by mass or less, more preferably 0.5% by mass or less, and further preferably 0.3% by mass or less. When the content of talc is in the above range, the decrease in transparency of the bubble-containing layer can be suppressed.

Among the talc as a bubble nucleating agent, from the viewpoint that the number of bubbles in the obtained resin plate becomes uniform and the coefficient of variation of the number of bubbles becomes small, the average particle size of the talc in the primary particle size before being charged into an extruder or the like. Is preferably 0.5 to 10 μm, and more preferably 0.5 to 8 μm. The average particle size in the present invention means the particle size (volume average particle size: d50) when the cumulative volume with respect to the volume of all particles becomes 50% based on the particle size distribution measured by the laser diffraction scattering method. ..

(Specification of the content of bubble nucleating agent)
The content of the bubble nucleating agent in the present invention can be specified by a combustion residue test for quantifying a combustion residue substance derived from an inorganic substance on a resin plate. The combustion residue test for quantifying the combustion residue substance can be carried out by the following procedure. That is, first, the amount of combustion residue derived from the inorganic substance contained in the resin plate is specified by the combustion residue test. Then, the content of talc as a bubble nucleating agent in the bubble-containing layer should be calculated by considering the ratio of the amount of combustion residue to the mass of the resin plate and the thickness of the bubble-containing layer to the total thickness of the resin plate. Can be done.

The combustion residue test can be specifically carried out as follows. Weigh the crucible into a constant weight, put a test piece made of the precisely weighed resin plate into the crucible, put it in a heating furnace, and hold it under predetermined conditions such as, for example, at a furnace temperature of 600 ° C. for 60 minutes. The organic matter including the transparent thermoplastic resin is removed by incineration or thermal decomposition to obtain a constant amount of combustion residue, the mass of the crucible containing the constant amount of combustion residue is precisely weighed, and the mass of the crucible first made constant. From the difference between the above and the above, the mass of the combustion residue in the test piece can be obtained. Then, the value obtained by dividing the mass of the obtained combustion residue by the mass of the test piece placed in the crucible is multiplied by 100, and the value is further multiplied by the thickness of the bubble-containing layer with respect to the total thickness of the resin plate to be the test piece. Therefore, the content of talc in the bubble-containing layer can be obtained.

The total thickness of the resin plate and the thickness of the bubble-containing layer are obtained as follows. First, the resin plate is cut in the thickness direction with a microtome to expose the cross section of the resin plate. Then, an enlarged photograph of the cross section is taken with a microscope (for example, Digital Microcorp VHX-900 manufactured by KEYENCE CORPORATION) or the like. Based on the obtained enlarged photograph, the total thickness of the resin plate and the thickness of the bubble-containing layer were randomly measured at 10 points, and their arithmetic average values were obtained to obtain the total thickness of the resin plate and the bubble-containing layer. The thickness of. When the boundary between the bubble-containing layer and the resin layer laminated on both sides of the bubble-containing layer cannot be seen, the maximum diameter of the bubbles in the resin plate in the thickness direction is randomly measured to be 100, and the most of them is measured. A large value is taken as the thickness of the bubble-containing layer.

(Effervescent agent)
Examples of the foaming agent include physical foaming agents for aliphatic hydrocarbons such as propane, normal butane, isobutane, normal pentane, isopentane, neopentane and hexane, and alicyclic hydrocarbons such as cyclobutane, cyclopentane and cyclohexane. These foaming agents can be used alone or in admixture of two or more. Among the above foaming agents, from the viewpoint of easy handling and no residue generated during foaming, it is preferable to use one or more selected from the above aliphatic hydrocarbons and alicyclic hydrocarbons, and normal butane, It is particularly preferable to use one or more selected from isobutane and cyclohexane.

(Resin layer 3)
The resin layer 3 is a layer formed by using a second transparent thermoplastic resin as a base resin. As shown in FIGS. 1A and 1B, in the resin plate 1 of the present invention, the resin layer 3 is laminated on both surfaces of the bubble-containing layer 2. The resin layer 3 is a bubble-free layer that does not substantially contain bubbles. Here, the bubble-free layer is a layer formed without going through a step for forming bubbles, and is a layer containing no bubbles intentionally formed. Therefore, the bubble-free layer includes not only a structure having no bubbles at all but also a structure having a structure in which bubbles that are slightly not intentionally formed are contained. The resin layers 3 laminated on both sides of the bubble-containing layer 2 may have the same thickness on both sides or may have different thicknesses on both sides. When the thicknesses of both sides of the resin layer 3 are different, the ratio of the thickness of the thicker resin layer to the thickness of the thinner resin layer (thickness of the thicker resin layer / thinner resin layer). The thickness) is preferably more than 1 and 4 or less, and more preferably more than 1 and 2 or less. The thickness of the resin layer 3 is determined by the same method as for measuring the total thickness of the resin plate and the thickness of the bubble-containing layer.

(Second transparent thermoplastic resin)
As the second transparent thermoplastic resin, a resin corresponding to the "transparent plastic" known in JIS K7361 (1997) is preferably used as in the case of the first transparent thermoplastic resin. It is also possible to use a resin different from the first transparent thermoplastic resin and the second transparent thermoplastic resin. Further, it is preferable that the transparent thermoplastic resin constituting the bubble-containing layer 2 and the transparent thermoplastic resin constituting the resin layer 3 are both polystyrene resin, acrylic resin or polycarbonate resin. The second transparent thermoplastic resin is preferably formed of a resin composed of the same molecular species as the first transparent thermoplastic resin, and can enhance the adhesiveness between the resin layer 3 and the bubble-containing layer 2. , The difference in refractive index is small, and the interfacial reflection can be suppressed to give a feeling as if it is composed of one layer. From the viewpoint of recycling, the second transparent thermoplastic resin is preferably polystyrene resin, and particularly preferably linear polystyrene resin.

The base resin for forming the resin layer 3 is a resin other than the second transparent thermoplastic resin, an elastomer, a bubble modifier, an antioxidant, a heat stabilizer, as long as the object and effect of the present invention are not impaired. It can contain one or more functional additives such as weather resistant agents, ultraviolet absorbers, flame retardants, antibacterial agents and shrinkage inhibitors, or additives such as inorganic fillers. The total amount of the additives is preferably 10 parts by mass or less with respect to 100 parts by mass of the second transparent thermoplastic resin.

[Manufacturing method of resin plate 1]
The method for producing the resin plate 1 of the present invention is not particularly limited, but can be specifically produced by using, for example, the following coextrusion method.

As illustrated in FIG. 3, a coextruder 100 in which at least two extruders (first extruder 101 and second extruder 102) are connected is prepared. The first transparent thermoplastic resin 110 and talc 111 to be the base resin are charged into the first extruder 101, and the physical foaming agent 112 is further press-fitted to knead them. In this way, a molten resin for forming a bubble-containing layer is obtained. The second transparent thermoplastic resin 113, which is the base resin, is put into the second extruder 102 and further kneaded. As a result, a molten resin for forming a resin layer can be obtained. The molten resin for forming the bubble-containing layer is introduced into the feed block 103 from the first extruder. At this time, the molten resin for forming the resin layer is extruded from the second extruder 102, then divided in the feed block 103, and covers both sides of the molten resin for forming the bubble-containing layer introduced into the feed block 103. .. That is, the layer of the molten resin for forming the bubble-containing layer joins between the layer of the molten resin for forming the resin layer and the layer of the molten resin for forming the resin layer in the feed block 103. Further, in that state, the molten resin for forming the resin layer and the molten resin for forming the bubble-containing layer are discharged from the die 104 such as the T die. At this time, the laminated body 105 is formed by co-extruding the molten resin for forming the resin layer and the molten resin for forming the bubble-containing layer while spreading over the product width. In the laminate 105, when the molten resin for forming the bubble-containing layer is co-extruded from the die 104, the layer of the molten resin for forming the bubble-containing layer foams, and bubbles are generated inside the layer of the molten resin for forming the bubble-containing layer. It is formed. Further, the laminated body 105 passes between the pressing rolls 106 and 106 and is stretched to an appropriate thickness and width to be shaped. In the example of FIG. 3, the laminated body 105 is shaped through the gaps between the three pressing rolls 106, 106, and 106 that rotate side by side, and is sent out in a predetermined direction by the auxiliary roll 107. In this way, the layer of the molten resin for forming the resin layer and the layer of the molten resin for forming the bubble-containing layer in the laminated body 105 form a resin layer and a bubble-containing layer, respectively, and the resin plate 1 of the present invention is formed. In FIG. 3, the arrows in the pressing roll 106 and the auxiliary roll 107 indicate the rotation direction of the roll.

As the method for producing the resin plate 1 of the present invention, it is preferable to adopt a coextrusion method because the uniformity of the bubble diameter is excellent, the coefficient of variation of the number of bubbles is small, and the diameter of the bubbles and the number of bubbles can be easily adjusted. ..

(Amount of bubble nucleating agent added)
By adding talc as a bubble nucleating agent to the molten resin for forming a bubble-containing layer, it is possible to obtain an effect that the number of bubbles 4 contained in the bubble-containing layer 2 can be easily adjusted to an appropriate number. That is, from the viewpoint of adjusting the number of bubbles 4 to an appropriate number, the bubble-containing layer 2 has a layer structure in which talc is used as a bubble nucleating agent and the base resin is foamed with a foaming agent to form bubbles 4. It has become. From the viewpoint of further enhancing this effect, it is preferable that the amount of talc added to the total 100% by mass of the first transparent thermoplastic resin and talc is 0.01% by mass or more and 1.0% by mass or less. When the amount of talc added is in the above range, the content of talc in the bubble-containing layer 2 in the bubble-containing layer 2 can be 0.01% by mass or more and 1.0% by mass or less.

(Effervescent agent)
The bubble-containing layer 2 has a layer structure in which bubbles 4 are formed inside by foaming due to the action of a foaming agent added to the molten resin for forming the bubble-containing layer. The type of foaming agent is not particularly limited as long as this action can be realized, and aliphatic hydrocarbons such as propane, normal butane, isopentane, normal pentane, isopentane, neopentane, and hexane, and fats such as cyclobutane, cyclopentane, and cyclohexane. Examples thereof include physical foaming agents such as ring hydrocarbons. These foaming agents can be used alone or in admixture of two or more. Among the above physical foaming agents, from the viewpoint of easy handling and no residue generated during foaming, it is preferable to use one or more selected from the above aliphatic hydrocarbons and alicyclic hydrocarbons, and normal butane. It is particularly preferable to use one or more selected from isobutane, isobutane and cyclohexane.

(Amount of foaming agent added)
The amount of the foaming agent added per 1 kg of the first transparent thermoplastic resin is preferably 0.05 mol or more and 0.2 mol or less, and more preferably 0.07 mol or more and 0.17 mol or less. When the amount of the foaming agent added is within this range, the number of bubbles 4 and the average bubble diameter can be appropriately adjusted.

[Decorative board using resin board 1]
The resin plate 1 of the present invention can be used, for example, as a decorative plate 7 in an optical display device 10 using light as shown in FIGS. 2A and 2B. The optical display device 10 includes a light source unit 5 provided with a light source 6 and a resin plate 1 serving as a decorative plate 7, and light from the light source 6 is emitted from one side end surface of the resin plate 1 (FIGS. 2A and 2B). Then, it goes from the lower end surface 1b) to the opposite end side end surface (upper end surface 1a in FIGS. 2A and 2B). At that time, when the incident light passes through the bubble 4, reflection or refraction occurs, and the portion of the bubble 4 appears to shine in the plan view of the resin plate 1. As a result, the optical display device 10 realizes high aesthetics. Further, even when the area of the display surface 10a in the optical display device 10 is large, it is possible to spread the light as a whole. The display surface 10a is a surface that exerts a decorative effect due to the light of bubbles when the optical display device is turned on.

As described above, the resin plate 1 of the present invention can be used as a decorative plate having excellent design. Further, the resin plate 1 of the present invention has an average bubble diameter of 1 mm or more in the plate surface direction, and an average value of the number of bubbles per 100 cm ² observed from the plate surface side is 5 or more and 500 or less. The coefficient of variation of the number of bubbles is 30% or less, and the ratio of the area occupied by the bubbles to the area of the plate surface of the resin plate is 0.2% or more and 50% or less, so that the number and size of the bubbles are large. Now, the distribution is controlled. As a result, in the optical display device using the resin plate of the present invention, the size of the end face of the resin plate which is the light introduction portion does not depend on the size of the end face of the resin plate, and the opposite end surface of the resin plate with respect to the end face into which the light is introduced is sufficiently reached. It is possible to make the light spread. A resin plate capable of spreading light as a whole to the extent that an appropriate number of bubbles can be conspicuous with light even when the area of the display surface in the optical display device is large, and such a resin. It is a method of manufacturing a board.

Examples 1 to 8, Comparative Example 1
A coextruder in which a first extruder (shaft diameter 45 mm, single shaft) and a second extruder (shaft diameter 120 mm / 40 mm, single shaft) are connected is prepared, and the first extruder is shown in Table 1. The first transparent thermoplastic resin and talc (manufactured by Matsumura Sangyo Co., Ltd., product name Hi-Feller # 12: average particle diameter 7.6 μm) are added in the amounts shown in Table 1 and further added to Table 1. A physical foaming agent (normal butane) as shown in Table 1 was press-fitted so as to have a blending amount as shown in Table 1, and these were melted and kneaded. In this way, a molten resin for forming a bubble-containing layer was obtained. The second transparent thermoplastic resin shown in Table 1 was charged into the second extruder, and further melted and kneaded. As a result, a molten resin for forming a resin layer was obtained.

The molten resin for forming the bubble-containing layer was extruded into the T-die from the first extruder. Then, the molten resin for forming the resin layer was extruded into the T-die from the second extruder. At this time, the molten resin for forming the bubble-containing layer was extruded between the layer of the molten resin for forming the resin layer and the layer of the molten resin for forming the resin layer. As a result, coextrusion is performed so that a laminated state of the molten resin for forming the resin layer is formed on both surfaces of the layer of the molten resin for forming the bubble-containing layer. The discharge temperature of the molten resin for forming the resin layer and the molten resin for forming the bubble-containing layer from the T die at the time of coextrusion was the temperature shown in Table 1. During coextrusion, a foaming phenomenon occurred in the layer of the molten resin for forming the bubble-containing layer, and bubbles were formed inside the layer of the molten resin for forming the bubble-containing layer. In this way, a state in which resin layers are laminated on both surfaces of the bubble-containing layer is formed, and a resin plate is prepared.

In each of Examples 1 to 8 and Comparative Example 1, the dimensions of the resin plate were 1100 mm in length × 1035 mm in width × 8 mm in thickness (the area of the plate surface of the resin plate was 1.14 m ² ). In the resin plates of Examples 1 to 8 and Comparative Example 1, the vertical direction is the long side direction, and the horizontal direction is the short side direction.

Using the resin plates of Examples 1 to 8 and Comparative Example 1, the average cell diameter in the plate surface direction, the average value of the number of bubbles per 100 cm ² observed from the plate surface side, the coefficient of variation of the number of bubbles, and the resin plate. The ratio of the area occupied by bubbles to the area of the plate surface, the content of talc, the total basis weight of the resin plate, the ratio of the total basis weight of the resin layer to the total basis weight of the resin plate, the haze of the resin plate, the resin plate The total light transmittance of was identified. The results are shown in Table 2.

(Average bubble diameter in the plate surface direction)
A photo of the resin plate viewed in a plane was taken in a dark room environment. Within the area of the photographed resin plate, 54 areas of 10 cm × 10 cm were randomly selected and designated as designated areas. The designated areas were selected so that the 54 areas did not overlap with each other. In each designated area, the area of each bubble is measured by using the image processing software NS2K-pro manufactured by Nanosystem Co., Ltd., and based on the area, the diameter when the bubble in the photograph is a circle is obtained. The value obtained by arithmetically averaging the values of each diameter obtained in each designated area was taken as the average bubble diameter (mm).

(Average number of bubbles per 100 cm ² observed from the plate surface side)
A photograph of the resin plate 1 in a plan view was taken in a dark room environment. Within the area of the photographed resin plate 1, 54 areas of 10 cm × 10 cm were randomly selected and designated as designated areas. In each designated area, the number of individual bubbles was calculated by using the image processing software NS2K-pro manufactured by Nanosystem Co., Ltd., and each of these values was arithmetically averaged to obtain the average value of the number of bubbles per 100 cm ² . Was done.

(Coefficient of variation of the number of bubbles)
The coefficient of variation (Cv) (%) of the number of bubbles is specified by using the above-mentioned equation (3), that is, the equation represented by [standard deviation (V) of the number of bubbles / mean value of the number of bubbles (DTav)] × 100. rice field. The standard deviation (V) of the number of bubbles is specified by using the above-mentioned equation (2).

(Ratio of the area occupied by bubbles (air bubble occupancy area) to the area of the plate surface of the resin plate)
The ratio of the bubble occupied area can be specified as described above. That is, the total area of individual bubbles in the designated region in the above average bubble diameter is obtained. Then, the ratio of the total area of the individual bubbles in the designated area to the area of the designated area (total area of the individual bubbles in the designated area) / (area of the designated area) × 100 is calculated. This ratio (%) is the ratio of the bubble occupied area.

(Talc content)
The content of the bubble nucleating agent in the present invention was determined from the amount of combustion residue derived from the inorganic substance contained in the resin plate by the following procedure. In the combustion residue test, a constant weight crucible is precisely weighed, and a test piece composed of a precisely weighed resin plate (length 5 cm, width 5 cm, thickness is the thickness of the resin plate) is placed in the crucible and placed in a heating furnace. By holding at a furnace temperature of 600 ° C. for 60 minutes, organic substances including transparent thermoplastic resin are removed by incineration or thermal decomposition to obtain a constant amount of combustion residue, and the mass of the crucible containing the constant amount of combustion residue. Was precisely weighed, and the mass of the combustion residue was determined from the difference from the mass of the crucible that was previously homogenized.

Divide the mass of the obtained combustion residue by the mass of the test piece placed in the crucible, multiply by 100, and multiply the value by the thickness of the bubble-containing layer with respect to the total thickness of the resin plate to obtain talc in the bubble-containing layer. Content was determined. The above combustion residue test was performed three times, and the talc content was specified in each, and the arithmetic mean value thereof was taken as the talc content.

The total thickness of the resin plate forming the test piece and the thickness of the bubble-containing layer were determined as follows. First, the resin plate forming the test piece was cut in the thickness direction with a microtome to form a cross section. The cross section was magnified and photographed with a microscope (Digital Microcorp VHX-900 manufactured by KEYENCE CORPORATION) at a magnification of 50 times. Based on the obtained photographs, the total thickness of the resin plate and the thickness of the bubble-containing layer were randomly measured at 10 points, and the arithmetic mean values were obtained. I made it thick.

(Total basis weight of resin plate)
The basis weight [g / m ² ] of the resin plate is a 10 cm × 10 cm test piece at equal intervals of 10 cm along the short side from the side edge of one side extending along the long side direction of the resin plate. For each test piece, calculate the area of one surface of the test piece corresponding to the front and back surfaces of the resin plate, specify the weight, and divide the weight by the area for the test. The basis weight of each piece was calculated, and they were calculated by arithmetic mean.

(Ratio of the total basis weight of the resin layer to the total basis weight of the resin plate)
The basis weight [g / m ² ] of the resin layer is the discharge amount X [kg / hour] of the resin layer, the width W [m] of the obtained resin plate, and the unit time of the resin plate under the extrusion foaming conditions. It was specified using the above-mentioned formula (1) based on the length L [m / hour] of the extruded resin plate. Then, by dividing the total basis weight of the resin layer by the total basis weight of the resin plate, the ratio of the total basis weight of the resin layer to the total basis weight of the resin plate (total basis weight of the resin layer / total basis weight of the resin plate). ) Was requested.

(Haze of resin plate)
For Haze, three test pieces (length 20 mm x width 20 mm, thickness is the thickness of the resin plate) are randomly cut out from the resin plate, and sufficient bubbles are sufficiently removed by heat pressing so that bubbles are not visually confirmed. After removal, a plate piece with a thickness of 2 mm was made with a heating press machine heated to 200 ° C., and for each plate piece, a turbidity meter (manufactured by Nippon Denshoku Kogyo Co., Ltd., product name Haze Meter) based on JIS K7136: 2000. It was measured using NDH7000SP). The value obtained by arithmetically averaging the haze values of each of the obtained plate pieces was taken as the haze of the resin plate.

(Total light transmittance (%) of the resin plate)
The total light transmittance in the direction along the thickness direction of the resin plate was measured using a turbidity meter (for example, manufactured by Nippon Denshoku Industries Co., Ltd., product name Haze Meter NDH7000SP) according to JIS K7361-1: 1997. .. For the total light transmission rate, a value obtained by arithmetically averaging the measured values of 15 randomly selected points without considering the presence or absence of air bubbles in the resin plate at the measurement points was adopted.

Comparative Example 2
As the resin plate of Comparative Example 2, a champagne plate with a product name manufactured by Fujidenoro Co., Ltd. was prepared. Using the resin plate of Comparative Example 2, the average bubble diameter in the plate surface direction, the average value of the number of bubbles per 100 cm ² observed from the plate surface side, the coefficient of variation of the number of bubbles, and the bubbles with respect to the area of the plate surface of the resin plate. The ratio of the area occupied by the resin plate, the haze of the resin plate, and the total light transmittance of the resin plate were specified. The results are shown in Table 2.

Next, using the resin plates of Examples 1 to 8 and Comparative Examples 1 and 2, a design evaluation test was carried out on the appearance of each resin plate. The results are shown in Table 3.

(Design evaluation test)
The resin plates of Examples 1 to 8 and Comparative Examples 1 and 2 were cut out and installed in a size of 300 mm × 900 mm, and visually observed from a position 10 m away from the resin plates. Then, the quality of the design as a decorative board for partition was evaluated based on the following criteria.

○ (Good): An appropriate number of bubbles are confirmed and the appearance is excellent.
× (Defective): An appropriate number of bubbles are not confirmed and the appearance is inferior.

For the resin plates of Examples 1 to 8 and Comparative Example 2 evaluated to be excellent in design, optical display devices as shown in FIGS. 2A and 2B were prepared by using the respective resin plates as decorative plates. , A light transmission test was carried out. The results are shown in Table 3.

(Light transmission evaluation test)
The light source of the light source unit of the optical display device was turned on, and light was incident upward from the lower end surface of the resin plate. The relationship between the position of the resin plate and the brightness was measured as follows using a luminance meter (manufactured by Tohoku Electronics Co., Ltd., product name: ColorLive CLIVE-150P3-BK). Four locations 100 mm, 300 mm, 600 mm, and 900 mm apart from the light source in the direction of the upper end surface of the resin plate were selected, and each was set as the measurement position (height). Three bubbles located at the same height at each measurement position at a distance of 100 mm, 300 mm, 600 mm, and 900 mm from the light source were randomly selected, and the brightness (cd / m ² ) of each bubble was measured. At this time, the luminance meter was arranged at a position away from the plate surface of the resin plate so that the distance between the plate surface of the resin plate and the luminance meter was 1000 mm. The arithmetic mean value of the measured brightness values for the three selected bubbles was calculated and used as the brightness (cd / m ² ) at the measurement position. The light source unit in the optical display device has a structure in which 12 light sources (light sources of a Light Emitting Diode (LED)) having a brightness of 3100 cd / m ² are arranged at equal intervals of 16.6 mm.

The light transmittance was evaluated by applying the following criteria based on the brightness value for each measurement position.

⊚ (extremely good): The brightness is 2000 cd / m ² or more.
◯ (good): The brightness is 250 cd / m ² or more and less than 2000 cd / m ² .
X (defective): The brightness is less than 250 cd / m ² .

In the above criteria for evaluating light transmittance, 250 cd / m ² is used as the criterion for brightness that distinguishes good from bad for the following reasons. That is, since the surface brightness at the point where the resin plate did not contain bubbles at 100 mm from the light source was less than 250 cd / m ² , the brightness of 250 cd / m ² was adopted as the threshold value.

1 Resin plate 1a Upper end surface 1b Lower end surface 2 Bubble-containing layer 3 Resin layer 4 Bubbles 5 Light source unit 6 Light source 10 Optical display device 10a Display surface 100 Coextruder 101 First extruder 102 Second extruder 103 Feed block 104 Die 105 Laminated body 106 Pressing roll 107 Auxiliary roll 110 First transparent thermoplastic resin 111 Talk 112 Physical foaming agent 113 Second transparent thermoplastic resin

Claims (6)

It has a bubble-containing layer using a first transparent thermoplastic resin as a base resin and containing bubbles, and a resin layer using a second transparent thermoplastic resin as a base resin and laminated on both sides of the bubble-containing layer. A resin plate having a total basis weight of 3000 g / m ² or more and 20000 g / m ² or less.
The area of the plate surface of the resin plate is 0.25 m ² or more, the average bubble diameter in the plate surface direction is 1 mm or more, and the average value of the number of bubbles per 100 cm ² observed from the plate surface side is 5 or more. It is characterized in that the number of bubbles is 500 or less, the coefficient of variation of the number of bubbles is 30% or less, and the ratio of the area occupied by the bubbles to the area of the plate surface of the resin plate is 0.2% or more and 50% or less. Resin plate. The resin plate according to claim 1, wherein the first transparent thermoplastic resin and the second transparent thermoplastic resin are both polystyrene resin, acrylic resin or polycarbonate resin. The resin plate according to claim 1 or 2, wherein the ratio of the area occupied by the bubbles to the area of the plate surface of the resin plate is 0.2% or more and 20% or less. Claim 1 characterized in that the ratio of the total basis weight of the resin layer to the total basis weight of the resin plate (total basis weight of the resin layer / total basis weight of the resin plate) is 0.70 or more and 0.98 or less. The resin plate according to any one of 3 to 3. The bubbles in the bubble-containing layer are formed by using talc as a bubble nucleating agent and foaming the base resin with a foaming agent, and the content of talc in the bubble-containing layer is 0.01 mass by mass. The resin plate according to any one of claims 1 to 4, wherein the resin plate is in an amount of% or more and 1.0% by mass or less. The method for producing a resin plate according to any one of claims 1 to 4, wherein the second transparent thermoplastic resin is kneaded to form a molten resin for forming a resin layer, and the molten resin for forming the resin layer is formed. A laminated body in which a first transparent thermoplastic resin, talc, and a foaming agent are kneaded and a bubble-containing layer-forming molten resin is merged and laminated between the resin layer and the resin layer-forming molten resin is coextruded. At the same time, the molten resin for forming the bubble-containing layer is foamed to form bubbles, and the amount of the talc added to the molten resin for forming the bubble-containing layer is 100% by mass in total of the first transparent thermoplastic resin and the talc. The resin is 0.01% by mass or more and 1.0% by mass or less, and the amount of the foaming agent added is 0.05 mol or more and 0.2 mol or less per 1 kg of the first transparent thermoplastic resin. How to make a board.

Images