JP2022091450A - Resin plate - Google Patents

Abstract

To provide a resin plate for thermal processing, capable of exhibiting excellent designability and supplying a curved article.SOLUTION: A resin plate 100 comprises a bubble-containing layer 10 having a transparent thermoplastic resin as the base material, and containing a foaming agent and large bubbles 30, and resin layers 20 laminated on both surfaces thereof. Bubbles 40 finer than the large bubbles can be generated in the bubble-containing layer by heating. A basis weight per one surface of the resin layer is 500 g/m2 or more, an average bubble diameter of the large bubbles in a plate surface direction is 1 mm or more, and an average value of the number of large bubbles per 100 cm2 observed from a plate surface side is 5 or more and 500 or less. A ratio of an area occupied by the large bubbles observed from the plate surface side to an area of the plate surface is 0.2% or more and 30% or less, an amount of the foaming agent contained in the resin plate is 0.2 wt.% or more and 1 wt.% or less, and a ratio of an average bubble diameter (mm) of the large bubbles in a thickness direction to an average thickness (mm) of the bubble-containing layer is 1.1 or more.SELECTED DRAWING: Figure 1

Description

The present invention relates to a resin plate used for thermal processing, and more particularly to a resin plate which is a raw fabric for thermal processing capable of providing a secondary processed product having excellent design by thermal processing.

Patent Document 1 proposes a decorative plate which is a transparent resin member made of a transparent resin used for an optical display device, a partition for construction, or the like. Such a decorative plate is a laminated resin plate using a transparent thermoplastic resin as a base resin and having a bubble-containing layer containing bubbles as an intermediate layer.

The decorative plate has an average bubble diameter of 1 mm or more contained in the bubble-containing layer, and is configured to reduce the variation in the number of bubbles observed from the plate surface side, thereby introducing light. It is possible to sufficiently spread the light to the opposite end surface with respect to the end surface. Such a decorative plate has a higher design than a conventional transparent resin plate having no air bubbles, and is suitably used for an optical display device or a partition for construction.

Japanese Unexamined Patent Publication No. 2020-6588

The transparent resin member is expected to be used not only for optical display devices and architectural partitions but also for various processed products, and further excellent designability is desired.

The present invention is a raw fabric for thermal processing made in view of the above-mentioned problems. That is, it is an object of the present invention to provide a resin plate for heat processing, which can exhibit a design property even better than that of a conventional decorative plate.

The resin plate of the present invention uses a transparent thermoplastic resin as a base resin, a bubble-containing layer containing a foaming agent and bubbles, and a transparent thermoplastic resin as a base resin, and is laminated on both sides of the bubble-containing layer. A resin plate for thermal processing having a layer and generating fine bubbles finer than the bubbles in the bubble-containing layer by heating, and the basis weight per one side of the resin layer is 500 g / g, respectively. m ² or more, the average bubble diameter of the bubbles in the plate surface direction of the resin plate is 1 mm or more, and the average value of the number of bubbles per 100 cm ² observed from the plate surface side of the resin plate is 5 or more. The number is 500 or less, and the ratio of the area occupied by the bubbles observed from the plate surface side to the area of the plate surface of the resin plate is 0.2% or more and 30% or less, and the above is contained in the resin plate. The amount of the foaming agent is 0.2% by weight or more and 1% by weight or less, and the ratio of the average bubble diameter (mm) of the bubbles in the thickness direction to the average thickness (mm) of the bubble-containing layer is 1.1 or more. It is characterized by being.

The resin plate of the present invention is a transparent resin plate having a bubble-containing layer containing a foaming agent and bubbles in the intermediate layer, and when heated by secondary processing, the bubble-containing layer has finer bubbles finer than the above-mentioned bubbles. Occurs. Thereby, the resin plate of the present invention can provide a secondary processed product having a very excellent design.

(1A) is a cross-sectional view schematically showing a cut surface formed by cutting a resin plate according to an embodiment of the present invention in the thickness direction, and (1B) is heating using the resin plate of the present invention. It is sectional drawing which shows typically the cut surface formed by cutting the molded secondary processed product in the thickness direction. (2B) is a cross-sectional view schematically showing a cut surface formed by cutting a resin plate to be compared in the thickness direction, and (2B) is a secondary processed product heat-molded using the resin plate to be compared. It is sectional drawing which shows typically the cut surface formed by cutting in the thickness direction. It is a perspective view of a panel-shaped secondary processed product heat-molded using the resin plate of this invention.

The resin plate of the present invention will be described with reference to FIGS. 1 to 3.
FIG. 1A is a cross-sectional view schematically showing a cut surface formed by cutting a resin plate 100 according to an embodiment of the present invention in the thickness direction, and FIG. 1B is a heat-molded resin plate 100. It is sectional drawing which shows typically the cut surface formed by cutting the next processed product 110 in the thickness direction.
FIG. 2B is a cross-sectional view schematically showing a cut surface formed by cutting the comparison target resin plate 300 in the thickness direction, and FIG. 2B is a secondary processed product 350 heat-molded using the comparison target resin plate 300. It is sectional drawing which shows typically the cut surface formed by cutting in the thickness direction.
FIG. 3 is a perspective view of a panel-shaped secondary processed product 112 that has been heat-molded using the resin plate 100.
In the following description, in order to distinguish the bubbles contained in the bubble-containing layer 10 of the resin plate 100 from the fine bubbles (fine bubbles 40) generated in the production of the secondary processed product, large bubbles (large bubbles 30) are used. ) May be called.

In addition, regarding the present invention and the description of the present invention, some terms are defined as follows. The plate surface direction of the resin plate indicates the direction in which the plane spreads with the direction along the thickness direction of the resin plate as the normal.
Observing or observing from the plate surface side of the resin plate means observing or observing the resin plate with the thickness direction of the resin plate as the line-of-sight direction. On the other hand, observing or observing from the cross-sectional side of the resin plate means observing or observing the resin plate from the normal direction of the cut surface formed by cutting the resin plate in the thickness direction. The area of the plate surface of the resin plate refers to the area of the resin plate when observed from the plate surface side. In the present specification, the term "thickness direction" refers to the thickness direction of the resin plate, and the cross-sectional direction refers to the direction in which the cut surface formed by cutting the resin plate in the thickness direction spreads. The vertical direction with respect to the resin plate refers to the vertical direction when one of the resin layers of the resin plate is installed on a horizontal plane, unless otherwise specified. The above definition of the resin plate also applies to the secondary processed product formed by using the resin plate.

The resin plate 100 according to an embodiment of the present invention has a bubble-containing layer 10 and a resin layer 20 laminated on both sides of the bubble-containing layer 10. Both the bubble-containing layer 10 and the resin layer 20 are made of a transparent thermoplastic resin as a base resin, and the resin plate 100 is transparent. The bubble-containing layer 10 contains a foaming agent (not shown) together with the large bubbles 30. Therefore, by heating the resin plate 100, it is possible to generate fine bubbles 40 (see FIG. 1B) finer than the large bubbles 30 in the bubble-containing layer 10. That is, the resin plate 100 is a raw fabric for providing a secondary processed product by thermal processing.
The transparency of the resin plate 100 does not mean that the degree of light transmission of the resin plate 100 is strictly specified, and the irradiated light can pass through the resin plate 100 and is observed from the plate surface side. When this is done, the large bubbles 30 are broadly transparent enough to be visually confirmed. Further, in the present invention, "transparency" includes not only colorless and transparent but also colored and transparent.

The resin plate 100 has a basis weight of 500 g / m ² or more per surface of the resin layer. The average bubble diameter of the large bubbles 30 in the plate surface direction of the resin plate 100 is 1 mm or more, which is a dimension with a strong presence, and the number of bubbles per 100 cm ² observed from the plate surface side of the resin plate 100. The average value is 5 or more and 500 or less.
The ratio of the area occupied by the large bubbles 30 observed from the plate surface side to the area of the plate surface of the resin plate 100 is 0.2% or more and 30% or less, and the amount of the foaming agent contained in the resin plate 100 is It is adjusted to be 0.2% by weight or more and 1% by weight or less. Further, in the resin plate 100, the ratio of the average bubble diameter (mm) of the large bubbles 30 in the thickness direction to the average thickness (mm) of the bubble-containing layer 10 is 1.1 or more.

When the resin plate 100 having the above configuration (see FIG. 1A) is heated, the foaming agent contained in the bubble-containing layer 10 foams, and the fine bubbles 40, which are relatively fine with respect to the large bubbles 30, become bubbles. It can be formed on the content layer 10. As shown in FIG. 1B, the secondary processed product 110 obtained through heating (heat processing) in this way contains large bubbles 30 and fine bubbles 40 in the bubble-containing layer 10, and is excellent in design. That is, the resin plate 100 is a secondary process that exhibits extremely excellent designability due to the relatively large-diameter large bubbles 30 that are an accent on the appearance and the snow-like fine bubbles 40 that exist around the resin plate 100. Item 110 (see FIG. 1B) can be provided. When the secondary processed product 110 is irradiated with light, the fine bubbles 40 diffuse the transmitted light to reduce the glare and produce a soft light, and the bright and shining large bubbles 30 can give a star-like design. ..
Further, since the resin plate 100 is made of a thermoplastic resin as a base material, it can be softened by being heated in the secondary processing. Therefore, the resin plate 100 has an advantage that, in addition to the effect that fine bubbles 40 are generated by heating in the secondary processing, shape forming processing such as bending processing is also possible. Therefore, the resin plate 100 is excellent in design and can easily provide secondary processed products having various shapes.
Further, the resin plate 100 is excellent in recyclability because both the bubble-containing layer 10 and the resin layer 20 are made of a transparent thermoplastic resin. That is, when the resin plate 100 is recovered as a recycled raw material, it can be beneficially recycled as a transparent raw material for a wide range of purposes and has good environmental characteristics. Hereinafter, the present invention will be described in more detail by taking the resin plate 100 as an example.

[Resin plate]
The resin plate 100 is composed of a bubble-containing layer 10 and a resin layer 20. The resin plate 100 is a raw fabric for a secondary processed product, and is not limited in its shape and dimensions. The shape and dimensions of the resin plate 100 can be appropriately determined in consideration of the dimensions and shapes of the secondary processed product scheduled to be formed in the secondary processing.

(Total basis weight of resin plate)
The total basis weight of the resin plate 100 is preferably 3000 g / m ² or more and 20000 g / m ² or less, more preferably 3500 g / m ² or more and 15000 g / m ² or less, and further preferably 4000 g / m ² . It is 10000 g / m ² or less. By performing the secondary processing using the resin plate 100 whose total basis weight satisfies the above lower limit value, it is easy to generate fine bubbles 40 in the bubble-containing layer 10 which have a remarkable dimensional difference from the large bubbles 30. It is easy to obtain a secondary processed product that has a snow-like design. Although the reason for this is not clear, the thickness of the resin plate 100 can be sufficiently increased by setting the total basis weight of the resin plate 100 to the above range, and when bubbles are generated in the bubble-containing layer 10 in the secondary processing. It is presumed that the growth of the bubbles is appropriately suppressed by the resin plates 100 laminated on both sides, and the fine bubbles 40 are formed.
On the other hand, when the total basis weight of the resin plate 100 satisfies the above upper limit value, the secondary processed product 110 having excellent lightness can be obtained.

(Method of specifying the total basis weight of the resin plate)
The total basis weight [g / m ² ] of the resin plate 100 is specified as follows. A rectangular resin plate 100 for measuring the basis weight is prepared, and test pieces of predetermined dimensions are cut out at equal intervals along the short side direction from the side edge of one side extending along the long side direction of the resin plate 100. For each test piece, calculate the area of one surface corresponding to the front and back surfaces of the test piece, specify the weight of the test piece, and divide the weight by the area to obtain the basis weight of each test piece. calculate. The calculated average value of the basis weight of each test piece can be obtained, and the total basis weight [g / m ² ] of the resin plate 100 can be converted and obtained from the average value.

(Haze of resin plate (Hz))
The resin plate 100 preferably has a haze (Hz) of 20% or less, more preferably 10% or less, and even more preferably 5% or less. Since the haze of the resin plate 100 is low, the large bubbles 30 can be easily visually confirmed, and when the secondary processed product 110 is obtained by thermal processing, the fine bubbles 40 can also be easily visually confirmed, which is preferable. The haze is obtained by cutting out a test piece from the resin plate 100, removing air bubbles by a hot press or the like to form a plate, and measuring the haze on the plate-shaped test piece. The haze can be measured based on JIS K7136: 2000.

(Total light transmittance (TT) of resin plate)
The total light transmittance of the resin plate 100 is preferably 70% or more, more preferably 80% or more when the direction along the thickness direction of the resin plate 100 is the line-of-sight direction. When the total light transmittance of the resin plate 100 satisfies the above range, the light transmittance of the secondary processed product 110 secondary processed by using the resin plate 100 can be sufficiently increased. 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 100 at the measurement location is adopted. Therefore, it is preferable that the total light transmittance of the resin plate 100 satisfies the above range regardless of whether the resin plate 100 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.

[Bubble-containing layer]
The bubble-containing layer 10 uses a transparent thermoplastic resin as a base resin, and contains a foaming agent and large bubbles 30. The bubble-containing layer 10 is formed so as to spread over the entire surface of the resin plate 100 along the plate surface direction of the resin plate 100. The thickness of the bubble-containing layer 10 is not particularly limited, but is preferably in the range of 0.5 mm or more and 10 mm or less, more preferably 0.7 mm or more and 5 mm or less, and further preferably 1 mm or more and 3 mm or less.

(Specification of average thickness of bubble-containing layer)
The average thickness of the bubble-containing layer 10 can be obtained by cutting the resin plate 100 in the thickness direction to form a cut surface, magnifying the cut surface with a microscope, and actually measuring the cut surface from the obtained photograph. Specifically, for example, it is specified as follows.
The resin plate 100 is cut in the thickness direction with a band saw, and after cutting, the cut surface is polished with sandpaper or the like to form a cut surface. The cut surface is magnified and photographed with a microscope (for example, Digital Microcorp VHX-900 manufactured by KEYENCE CORPORATION). Based on the obtained photographs, the thickness of the bubble-containing layer 10 of the resin plate 100 in the thickness direction is randomly measured at 10 points, and the arithmetic average value thereof is obtained and used as the average thickness of the bubble-containing layer 10.
When the interface between the bubble-containing layer 10 and the resin layer 20 is unclear, the thickness of the bubble-containing layer 10 is determined by the following method. The total thickness A of the resin plate 100 is measured. The basis weight of the resin layers 20 on both sides is the discharge amount X [kg / hour] of the resin layer 10, the width W [m] of the resin plate 100, and the length of the resin plate 100 extruded per unit time of the resin plate 100. Calculated from L [m / hour] (the basis weight of the resin layer 20 = 1000X / (L × W)). The thickness B of the resin layer 20 is calculated by dividing the basis weight of the resin layer 20 by the density of the resin constituting the resin layer 20. The thickness of the bubble-containing layer 10 is obtained by subtracting the thickness B of the resin layer 20 from the total thickness A of the resin plate 100.

(Average bubble diameter of large bubbles in the plate surface direction)
The large bubbles 30 contained in the bubble-containing layer 10 are relatively large-diameter bubbles that are an accent in the secondary processed product obtained by secondary processing the resin plate 100. Therefore, the average bubble diameter of the large bubbles 30 in the plate surface direction of the resin plate 100 is at least 1 mm or more, preferably 2 mm or more, more preferably 2.5 mm or more, and further preferably 3 mm or more. The upper limit of the average bubble diameter of the large bubbles 30 in the plate surface direction of the resin plate 100 is not particularly specified, but may be, for example, 5 mm or less. If the size is within such a range, each of the large bubbles 30 can be easily recognized by the naked eye and can exert its presence. The large bubble 30 is generally spherical or elliptical spherical.

(Method of specifying the average bubble diameter of large bubbles in the plate surface direction)
The average bubble diameter of the large bubbles 30 in the plate surface direction can be specified as follows. A photograph of the resin plate 100 in a plan view is taken in a dark room environment. Within the region of the photographed resin plate 100, a region having a predetermined size is randomly selected at a plurality of locations and designated as a designated region. In each designated area, the area of each large bubble 30 was measured by using, for example, the image processing software NS2K-pro manufactured by Nanosystem Co., Ltd., and the large bubble 30 shown in the photograph was defined as a circle based on the area. The diameter in the case is obtained, and the value obtained by arithmetically averaging the values of each diameter obtained in each designated area is defined as the average bubble diameter (mm).

(Average bubble diameter of large bubbles in the thickness direction)
The average bubble diameter of the large bubbles 30 in the thickness direction is not particularly limited and is appropriately determined in consideration of the ratio to the average thickness of the bubble-containing layer 10 described below, but is preferably 1 mm or more, preferably 1.5 mm or more. Is more preferable.
The average bubble diameter of the large bubbles 30 in the thickness direction is specified as follows. The average bubble diameter of the large bubbles 30 in the thickness direction of the resin plate 100 is such that the resin plate 100 is cut in the thickness direction, and after cutting, the cut surface is polished with sandpaper or the like to prepare a cut surface, and the cut surface is formed. It can be magnified and projected with a microscope and actually measured from the obtained projected image. Specifically, for example, it is measured as follows.
A strip-shaped test piece having a width of 10 mm is prepared by cutting with a band saw in the thickness direction using the resin plate 100. One side surface of the cut surface of the test piece is polished with sandpaper or the like to form an observation cut surface. The cut surface for observation is magnified and projected with a microscope (for example, Digital Microcorp VHX-900 manufactured by KEYENCE CORPORATION). Based on the obtained projected image, 10 large bubbles 30 whose entire shape was confirmed on the cut surface for observation were randomly selected, and the maximum length portion in each thickness direction (relative to the plate surface direction of the resin plate 100) was selected. The diameter of the ferret in the vertical direction) is measured, and the arithmetic mean value is calculated to obtain the average bubble diameter. In addition, the bubble whose entire shape is confirmed is the one whose shape is partially missing or cut, or the bubble whose outer shape is unclear due to integration with the adjacent bubble, etc., and the entire outer shell of the bubble is observed. It is a bubble that has been created.
By obtaining the ratio between the average bubble diameter of the large bubbles 30 measured in this way and the average thickness of the bubble-containing layer 10 described above, bubbles (large) in the thickness direction with respect to the average thickness of the bubble-containing layer 10 described below. The ratio of the average bubble diameters of the bubbles 30) can be obtained.

(Ratio of the average bubble diameter of large bubbles in the thickness direction to the average thickness of the bubble-containing layer)
In the resin plate 100, the size of the large bubbles 30 in the thickness direction is specified by the ratio to the average thickness (mm) of the bubble-containing layer 10. Specifically, in the present invention, the average bubble diameter (mm) of the large bubbles 30 in the thickness direction with respect to the average thickness (mm) of the bubble-containing layer 10 (arithmetic mean value of the thickness x in FIG. 1A) (cells in FIG. 1A). The ratio of the arithmetic mean value of the diameter y) is 1.1 or more, preferably 1.2 or more, more preferably 1.5 or more, and further preferably 1.7 or more. The upper limit of the above ratio is not particularly limited, but it is preferable that the ratio is 3 or less from the viewpoint that the strength of the secondary processed product 110 is not significantly impaired and the formation region of the fine bubbles 40 is not too narrow.
When the average bubble diameter of the large bubbles 30 in the thickness direction is specified within the above ratio range, as shown in FIG. 1A, the upper and lower ends of the large bubbles 30 contained in the bubble-containing layer 10 are from the bubble-containing layer 10 to the resin layer. It tends to exist across 20. As a result, as shown in FIG. 1B, in the secondary processed product 110 manufactured by the secondary processing using the resin plate 100, the large bubbles 30 and the fine bubbles 40 are less likely to overlap in the thickness direction. When the secondary processed product 110 is observed from the plate surface side, the large bubbles 30 maintain high brightness and exhibit a presence as an accent, which contributes to the excellent design of the secondary processed product 110.

As a method for adjusting the ratio to be 1.1 or more in the resin plate 100, there is a means for adjusting the amount of the nucleating agent or the foaming agent used when forming the bubble-containing layer. Alternatively, in order to manufacture the resin plate 100, the temperature of the laminate is controlled when the laminate having the structure of the resin layer 20 / bubble-containing layer 10 / resin layer 20 is ejected from the die by coextrusion to form a plate. Therefore, it is also possible to adjust the degree of foaming of the large bubbles 30 so that the ratio is within the above range.

(About comparison target example)
The resin plate 300 shown in FIG. 2A is a comparative example of the present invention. The resin plate 300 includes a bubble-containing layer 310 containing bubbles 330 and a foaming agent, and a resin layer 320 laminated on both sides thereof. In the resin plate 300, the ratio of the average bubble diameter (mm) of the bubbles 330 in the thickness direction to the average thickness (mm) of the bubble-containing layer 310 is less than 1.1. Therefore, in the resin plate 300, there are no or few bubbles 330 whose upper ends and lower ends have entered the bubble-containing layer 310. In the secondary processed product 350 that is secondary processed using the resin plate 300, the bubbles 330 and the fine bubbles 340 overlap in the thickness direction as shown in FIG. 2B. When the secondary processed product 350 is irradiated with light, the fine bubbles 340 act as a barrier to reduce the brightness of the bubbles 330, and excellent designability is not exhibited.

(Average number of large bubbles per 100 cm ² observed from the plate surface side)
In the present invention, the average value of the number of large bubbles 30 per 100 cm ² observed from the plate surface side of the resin plate 100 is 5 or more and 500 or less, preferably 10 or more and 300 or less. More preferably, the number is 30 or more and 100 or less. When the average value of the number of large bubbles per unit area is in the above range, it is possible to provide the secondary processed product 110 in which the large bubbles 30 are a preferable accent and exhibit good design. If the average number of bubbles per unit area of the large bubbles 30 is less than 5, it is difficult for the large bubbles 30 to be recognized as a preferable accent in the secondary processed product 110, and if it exceeds 500, in the secondary processing. The area where the fine bubbles 40 are formed is reduced, and it is difficult to show sufficient designability in the secondary processed product 110.

(Method of specifying the average number of large bubbles per 100 cm ² observed from the plate surface side)
The average number of large bubbles 30 per 100 cm ² observed from the plate surface side of the resin plate 100 is specified as follows. A photograph of the resin plate 100 in a plan view is taken in a dark room environment. Within the region of the photographed resin plate 100, a region having an area of 100 cm ² such as 10 cm × 10 cm is randomly selected at a plurality of locations and designated as a designated region. 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 arithmetically averaged to be described above. The average value of the number of bubbles of the large bubbles 30 to be generated is obtained. Although the designated areas are randomly selected from a plurality of locations, the designated areas may or may not overlap with each other.

(Ratio of the area occupied by large bubbles observed from the plate surface side to the plate surface area of the resin plate)
In the present invention, the ratio of the area occupied by the large bubbles 30 observed from the plate surface side (hereinafter referred to as the bubble occupied area) to the area of the plate surface of the resin plate 100 is 0.2% or more and 30% or less. It is preferably 1% or more and 10% or less. If the bubble occupying area is within the above range, the large bubbles 30 will be an appropriate accent, and the secondary processed product 110 will have a good balance with the fine bubbles 40 formed around the large bubbles 30, resulting in an excellent design as a whole. Can be presented.

(Method of specifying the occupied area of bubbles)
The ratio of the bubble occupied area can be specified as follows. First, the total area of the individual large bubbles 30 in the designated area is obtained. Then, the ratio of the total area of the individual large bubbles 30 in the designated area to the area of the designated area (%) [(total area of the individual large bubbles 30 in the designated area) / (area of the designated area)] × 100. calculate. This ratio (%) is the ratio of the bubble occupied area.

(Coefficient of variation of the number of large bubbles)
In the bubble-containing layer 10, the coefficient of variation of the number of bubbles of the large bubbles 30 is preferably 30% or less, and more preferably 15% or less. When the coefficient of variation of the number of bubbles is within the above range, the number of bubbles 30 of the large bubbles 30 does not become coarse or dense in the entire resin plate 100, and the design is excellent. The lower limit of the coefficient of variation of the number of bubbles of the large bubbles 30 is about 3%.

(Method of specifying the coefficient of variation of the number of large bubbles)
The method for specifying the coefficient of variation of the number of bubbles of the large bubbles 30 is as follows.
In the method for specifying the average value of the number of large bubbles per 100 cm ² observed from the plate surface side described above, the coefficient of variation of the number of bubbles in each designated region to be measured is obtained.
The coefficient of variation (Cv) of the number of bubbles is a value obtained by [(standard deviation (V) of the number of bubbles) / (mean value of the number of bubbles)] × 100 of the number of bubbles in each designated region, and is a value of the number of bubbles. It is an index showing the degree of variation. The standard deviation (V) of the number of bubbles is obtained by the following equation (1).

In the above formula (1), 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 (2) using the standard deviation (V) obtained by the above formula (1).

For example, with respect to the resin plate 100 described above, the average bubble diameter of the large bubbles 30 in the plate surface direction is 2.5 mm or more, and the average value of the number of bubbles per 100 cm ² observed from the plate surface side is 10 or more and 100. The following aspects can be said to be one of the excellent aspects of the present invention. According to such an embodiment, the average bubble diameter of the large bubbles 30 is sufficiently large to be a preferable accent, and the number thereof is adjusted to an appropriate range, so that the large bubbles 30 are formed around the large bubbles 30 in the secondary processed product 110. The balance with the fine bubbles 40 is also good, and excellent designability is shown.

(Effervescent agent)
Next, the foaming agent contained in the bubble-containing layer 10 will be described. Since the bubble-containing layer 10 contains a foaming agent, the resin plate 100 can generate fine bubbles 40 finer than the large bubbles 30 in the bubble-containing layer 10 by secondary processing accompanied by heating. ..
When the resin plate 100 is manufactured, a foaming agent is added to the base resin constituting the bubble-containing layer 10, a part thereof is used for forming the large bubbles 30, and the rest is present in the resin of the bubble-containing layer 10. .. In the resin plate 100, the foaming agent contained in the bubble-containing layer 10 is a foaming agent present in the resin of the bubble-containing layer 10.

The foaming agent contained in the bubble-containing layer 10 can be appropriately selected from the physical foaming agent or the chemical foaming agent used when forming the foamed resin body.
Examples of the physical foaming agent include aliphatic hydrocarbons such as propane, normal butane, isobutane, normal pentane, isopentane, neopentane and hexane, and physical foaming agents for 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.
Examples of the chemical foaming agent include azodicarboxylic amide, hydrazodicarboxylic amide, azobisisobutyronitrile, sodium hydrogen carbonate (boso), and sodium hydrogen carbonate and citric acid monoalkali metal salt such as citric acid or monosodium citrate. Examples thereof include a sodium bicarbonate-citric acid-based chemical foaming agent, which is a mixture of the above.
When manufacturing the resin plate 100, it is easy to form large bubbles 30 having a sufficiently large size in the bubble-containing layer 10, and the average bubble diameter of the large bubbles 30 in the thickness direction with respect to the average thickness (mm) of the bubble-containing layer 10 ( From the viewpoint that the ratio of mm) can be easily adjusted to 1.1 or more, the foaming agent is preferably a physical foaming agent.

(Content of foaming agent)
The amount of the foaming agent contained in the bubble-containing layer 10 is adjusted to 0.2% by weight or more and 1% by weight or less, preferably 0.5% by weight or more and 0.8, when the resin plate 100 is 100% by weight. It is less than% by weight. When the content of the foaming agent in the resin plate 100 is 0.2% by weight or more, a plurality of fine bubbles 40 are likely to be satisfactorily formed during the secondary processing. Further, when the content of the foaming agent in the resin plate 100 is 1% by weight or less, it is possible to prevent the fine bubbles 40 from becoming excessively large bubbles during the secondary processing.

(Method of measuring the content of foaming agent contained in the resin plate)
The content of the foaming agent in the resin plate in the present specification is a value measured by an internal standard method using a gas chromatograph. Specifically, an appropriate amount of sample is cut out from the resin plate, this sample is placed in a sample bottle with a lid containing an appropriate amount of toluene and an internal standard substance, the lid is closed, and the mixture is sufficiently stirred to provide a foaming agent in the resin plate. The content of the foaming agent in the resin plate is determined by performing gas chromatograph analysis using the solution obtained by dissolving the above in toluene as a measurement sample.

(Transparent thermoplastic resin)
As the transparent thermoplastic resin which is the base resin of the bubble-containing layer 10, the 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. The transparent thermoplastic resin preferably has a total light transmittance of 85% or more, and preferably has a haze of 5% or less.

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 transparent thermoplastic resin which is the base resin of the bubble-containing layer 10 can be used alone or in combination of two or more. When two or more types 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, the thermoplastic resins to be used are used. It is preferable that the refractive electrodes are close to or equal to each other. When the difference in the refractive index of each thermoplastic resin or the difference in the refractive index between the thermoplastic resin and the other resin is small or the refractive index is the same, it is possible to prevent the mixed resin from becoming cloudy and the transparency from being lowered. Therefore, it is desirable that the difference in refractive index is small or the refractive index is equal. 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 transparent thermoplastic resin used for the base resin forming the bubble-containing layer 10 may be any of polystyrene resin, acrylic resin, and polycarbonate resin from the viewpoint of excellent processability among the above thermoplastic resins. Preferably, polystyrene resin is particularly preferable. Further, among the polystyrene resins, a styrene-methacrylic acid copolymer or a branched polystyrene resin is preferable.

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

(Foam nucleating agent)
The bubble-containing layer 10 is generally formed by adding a foaming agent to a molten resin for forming a bubble-containing layer formed by melt-kneading the above-mentioned transparent thermoplastic resin and a bubble nucleating agent.
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 large bubbles 30 can be adjusted without significantly changing the average bubble diameter. Further, in the bubble-containing layer 10, when talc is used as the bubble adjusting agent, the content of talc in the bubble-containing layer 10 is preferably 0.01% by weight or more, preferably 0.02% by weight or more. More preferably, it is more preferably 0.03% by weight or more. On the other hand, the content of talc is preferably 1.0% by weight or less, more preferably 0.5% by weight or less, and further preferably 0.3% by weight or less. When the content of talc is in the above range, the decrease in transparency of the bubble-containing layer 10 can be suppressed.

[Resin layer]
Next, the resin layer 20 will be described. The resin layer 20 is a layer formed on both sides of the bubble-containing layer 10, and is composed of a transparent thermoplastic resin as a base resin. Therefore, when the resin plate 10 and the secondary processed product 110 formed by using the resin plate 10 are observed from the plate surface side, the bubbles contained in the bubble-containing layer 10 are visually recognized as a pattern through the resin layer 20.
Further, since the bubble-containing layer 10 is a foamed layer and the resin layer 20 is a non-foamed layer, the resin plate 100 and the secondary processed product 110 formed by using the resin plate 100 have a glossy appearance.

(Transparent thermoplastic resin)
Since the transparent thermoplastic resin which is the base resin of the resin layer 20 is the same resin as the resin used as the base resin of the bubble-containing layer 10 described above, the base resin of the bubble-containing layer 10 will be appropriately described. Referenced. The base resin of the resin layer 20 and the base resin of the bubble-containing layer 10 may be the same resin or different resins. As the transparent thermoplastic resin used for the base resin forming the resin layer 20, it is preferable to use any of polystyrene resin, acrylic resin, and polycarbonate resin as in the case of the bubble-containing layer 10, and polystyrene resin is particularly preferable. Further, among the polystyrene resins, linear polystyrene resin is preferable.

The base resin for forming the resin layer 20 is a resin other than the transparent thermoplastic resin, an elastomer, a bubble modifier, an antioxidant, a heat stabilizer, a weather resistant agent, as long as the object and effect of the present invention are not impaired. It can contain one or more functional additives such as an ultraviolet absorber, a flame retardant, an antibacterial agent and a shrinkage inhibitor, or an additive such as an inorganic filler. The total amount of the additives is preferably 10 parts by weight or less with respect to 100 parts by weight of the transparent thermoplastic resin.

(Basis weight of resin layer)
In the resin plate 100, the basis weight per one side of the resin layer 20 is preferably 500 g / m ^{2 or more, preferably 1000 g / m 2 or more, and more preferably 1500 g / m 2 or more} , respectively.
By setting the basis weight per side of the resin layer 20 to 500 g / m ² or more, it is possible to satisfactorily prevent the bubbles generated in the bubble-containing layer 10 during the secondary processing from expanding too much. As a result, fine bubbles (fine bubbles 40) are formed in the bubble-containing layer 10 of the secondary processed product 110, and a fine and beautiful design like snow can be realized.
On the other hand, the basis weight per one side of the resin layer 20 is preferably 10,000 g / m ² or less, more preferably 5000 g / m ² or less, and further preferably 4000 g / m ² or less, respectively. .. By setting the upper limit of the basis weight per one side of the resin layer 20 to the above value or less, it becomes easy to sufficiently secure the number of fine bubbles 40. Therefore, in the secondary processed product 110, a large number of fine bubbles 40 make it easy to show a design such as falling powder snow or innumerable stars shining in the night sky.

(Measuring method of basis weight of resin layer)
In the case of the resin plate 100 manufactured by coextrusion, the basis weight [g / m ² ] of the resin layer 20 is the discharge amount X [kg / hour] of the resin layer 20 and the obtained resin plate under the extrusion foaming conditions. It is obtained by the following formula (3) from the width W [m] of 100 and the length L [m / hour] of the extruded resin plate 100 per unit time of the resin plate 100.

(Average thickness of resin layer)
The average thickness of the resin layer 20 is not particularly limited, and is preferably appropriately determined within a range that satisfies the above-mentioned basis weight. For example, the average thickness can be 1 mm or more and 5 mm or less. The resin layers 20 provided on both sides of the bubble-containing layer 10 may have the same thickness or different thicknesses.
The average thickness of the resin layer can be obtained by the same method as the method for measuring the thickness of the bubble-containing layer 10 described above.

(Manufacturing method of resin plate)
The method for producing the resin plate 100 is not particularly limited, but for example, a coextrusion method is preferable.
When the resin plate 100 is manufactured by the coextrusion method, the base resin for forming the bubble-containing layer 10, the molten resin for forming the bubble-containing layer containing the bubble nucleating agent, and the base resin for forming the resin layer 20. Each of the molten resins for forming a resin layer containing the above is prepared in the extruder. Additives such as a dispersant are appropriately added to the molten resin for forming the bubble-containing layer. Further, any additive may be added to the molten resin for forming the resin layer.

In the molten resin for forming a bubble-containing layer, the amount of the bubble nucleating agent added to a total of 100% by weight of the transparent thermoplastic resin and the bubble nucleating agent is preferably 0.01% by weight or more and 1.0% by weight or less. When the amount of the bubble nucleating agent added is in the above range, it is easy to adjust the number of large bubbles 30 in the bubble-containing layer 10 to a desirable range. As the bubble nucleating agent, for example, talc is preferable.
The amount of the dispersant contained in the molten resin for forming the bubble-containing layer is preferably 0.001% by weight or more and 0.01% by weight or less. Examples of the dispersant include zinc stearate, sodium stearate, potassium stearate, magnesium stearate and the like.
A foaming agent is further added to the molten resin for forming the bubble-containing layer. The amount of the foaming agent is preferably 0.6% by weight or more and 2.0% by weight or less, and more preferably 0.7% by weight or more and 1.5% by weight or less. By setting the amount of the foaming agent added in this range, preferable large bubbles 30 are formed in the bubble-containing layer 10 of the resin plate 100, and the foaming agent is added in the resin plate in the range of 0.2% by weight or more and 1% by weight or less. Easy to contain in.

In the coextrusion machine, coextruding is performed so that the layer made of the molten resin for forming the bubble-containing layer joins between one layer made of the molten resin for forming the resin layer and the other layer made of the molten resin for forming the resin layer. In that state, the resin is discharged from a die such as a T die to form a laminated body having a three-layer structure. The resin temperature at the time of ejection from the die is preferably 190 ° C to 240 ° C.
The foaming agent foams in the intermediate layer of the discharged laminate, and large bubbles 30 are formed. The laminate passes between the opposing rolls, is stretched to an appropriate thickness and width, is shaped, and is appropriately wound on an auxiliary roll.
By controlling the temperature so as to slowly cool the laminate discharged from the die, the ratio of the average bubble diameter (mm) of the large bubbles 30 in the thickness direction to the average thickness (mm) of the bubble-containing layer 10 is 1. It is easy to adjust so that it is 1. or more. By gently cooling the laminate discharged from the die, the foaming agent contained in the bubble-containing layer 10 can be foamed while delaying the curing completion time of the resin layer 20. According to such an embodiment, it is allowed that the large bubbles 30 sufficiently expand and exceed the thickness of the bubble-containing layer 10 and enter the resin layer 20.

As described above, the resin plate 100 manufactured by the coextrusion method is preferably cured for 7 days or more under the conditions of a temperature of 23 ° C. and a relative humidity of 50%. By avoiding high temperature and high humidity conditions and curing under conditions satisfying the above conditions, it is possible to effectively suppress the dissipation of the foaming agent present in the bubble-containing layer into the air.

[Secondary processed product]
Next, the secondary processed product 110 will be described. The secondary processed product 110 is formed by performing secondary processing accompanied by heating using the resin plate 100.
The specific processing method for the secondary processing is not particularly limited, but the resin plate 100 may be heated in a temperature range of 120 ° C. or higher and 160 ° C. or lower for 5 minutes or longer and 20 minutes or shorter. Thereby, the secondary processed product 110 having the bubble-containing layer 10 having the fine bubbles 40 as well as the large bubbles 30 can be manufactured. The heating method and the heating device are not particularly limited, but heating can be performed by a conventionally known device such as an oven, a hot press, or a thermoforming machine.
Further, by bending the resin plate 100 softened by heating in the secondary processing, the secondary processed product 110 having a desired shape is formed.

As a specific example of the secondary processed product according to the present invention, FIG. 3 shows a perspective view of the panel-shaped secondary processed product 112.
As shown in FIG. 3, in the secondary processed product 112, when observed from the plate surface side, a large number of fine bubbles 40 are scattered throughout, and large bubbles 30 are scattered therein. Although the planar secondary processed product 110 is shown in FIG. 3, the resin plate 100 can also provide a non-planar secondary processed product which is curved or the like, which is not shown.
The secondary processed product 112 has a very high design because the fine bubbles 40 have a snow-like design and the large bubbles 30 scattered in the large number of fine bubbles 40 are accents. Further, when the secondary processed product 112 is irradiated with light, the fine bubbles 40 diffuse the transmitted light to reduce glare and give a soft impression, and the scattered large bubbles 30 with high brightness are scattered on the star. The appearance is beautiful because it shines like this. Moreover, since the secondary processed product 112 is made of resin, it is lightweight and has excellent recyclability.
Therefore, the secondary processed product 112 can be preferably used for various purposes in a very wide range of fields. Specifically, the secondary processed product 112 can be used as a product display, a light guide lighting, a signboard, a signboard, a lighting window for fittings, a lighting cover, and the like, and is not limited thereto.

(Fine bubbles)
The foaming agent contained in the bubble-containing layer 10 of the resin plate 100 foams when heated to form fine bubbles 40. That is, by performing the secondary processing accompanied by heating using the resin plate 100, the secondary processed product 110 containing a plurality of fine bubbles 40 as shown in FIG. 1B is formed.

(Average number of fine bubbles per 10 cm observed from the cross-sectional side)
The average value of the number of fine bubbles per 10 cm observed from the cross-sectional side of the secondary processed product 110 is not particularly limited, but is preferably 1000 or more and 10000 or less, and is 2000 or more and 5000 or less. Is more preferable. If the number is within the above range, it is easy to maintain the haze and total light transmittance of the secondary processed product 110 within an appropriate range while the fine bubbles 40 exhibit a snow-like design. The average bubble diameter and the number of bubbles of the fine bubbles 40 can be adjusted by adjusting the amount of the foaming agent contained in the bubble-containing layer 10 and the heating conditions in the secondary processing.
The average value of the number of fine bubbles per 10 cm observed from the cross-sectional side can be obtained by the following method.
Using the secondary processed product 110, the product is cut in the thickness direction with a band saw to prepare a sample having a length and width of 10 cm when viewed from the plate surface side. Each of the four cross sections of the above sample is sanded to form four cut surfaces. These four cut surfaces are magnified and photographed with a microscope (for example, KEYENCE: digital microscope VHX-900 (emergence mode)). Based on the obtained photographs, the number of bubbles having a major axis of less than 1 mm is measured on all four cut surfaces. Divide the total number of obtained fine bubbles by 4 to obtain the average number of bubbles per cut surface, and use this as the average value of the number of fine bubbles per 10 cm observed from the cross-sectional side.
That is, in this paragraph, about 10 cm observed from the cross section side refers to a length region in the direction perpendicular to the thickness direction in the cross section obtained by cutting the secondary processed product 110 in the thickness direction. The size of the observed cross-sectional thickness depends on the thickness of the secondary processed product 110.

(Average bubble diameter in the thickness direction of fine bubbles observed from the cross-sectional side)
The fine bubbles 40 are bubbles having a bubble diameter that is relatively smaller than the average bubble diameter of the large bubbles 30. From the viewpoint of sufficiently increasing the dimensional difference between the large bubbles 30 and the fine bubbles 40 to exhibit excellent design, the average bubble diameter of the fine bubbles 40 observed from the cross-sectional side of the secondary processed product 110 is 0. It is preferably 8.8 mm or less, more preferably 0.7 mm or less, and even more preferably 0.6 mm or less.
The average bubble diameter of the fine bubbles 40 observed from the cross-sectional side can be obtained by the following method. Using the secondary processed product 110, cut in the thickness direction with a band saw to prepare a sample having a size of 10 cm in length and width when viewed from the plate surface side. Each of the four cross sections of the above sample is polished with sandpaper or the like, and each cut surface is magnified and photographed with a microscope (for example, KEYENCE: Digital Microscope VHX-900 (falling mode)). Based on the obtained photographs, the maximum length portion in the thickness direction of the fine bubbles confirmed on each cut surface (the diameter of the ferret in the direction perpendicular to the plate surface direction of the resin plate 100) was measured, and the arithmetic mean value was calculated. The average cell diameter is used.

(Ratio of fine bubbles of 600 μm or less)
The ratio of fine bubbles of 600 μm or less in the secondary processed product 110 can be determined as follows. The ratio of the number of fine bubbles whose maximum length in the thickness direction is 600 μm or less to the number of total bubbles counted in the measurement of the average bubble diameter in the thickness direction of the fine bubbles observed from the cross-sectional side. Can be obtained by calculating.

(Number of large bubbles overlapping with fine bubbles per 100 cm ² observed from the plate surface side)
The number of large bubbles 30 that overlap with the fine bubbles 40 per 100 cm ² observed from the plate surface side is preferably 50 or less, more preferably 30 or less, and 10 or less. Is even more preferable. The large bubbles 30 that do not overlap with the fine bubbles 40 in the thickness direction show high brightness, become a beautiful accent in the secondary processed product 110, and contribute to the improvement of design. Therefore, it is preferable that the number of large bubbles 30 overlapping with the fine bubbles 40 per 100 cm ² confirmed from the plate surface side is small.
The number of large bubbles overlapping with the fine bubbles per 100 cm ² confirmed from the plate surface side can be specified as follows. In the secondary processed product 110, a region having an area of 100 cm ² such as 10 cm × 10 cm is randomly selected at a plurality of locations and designated as a designated region. By observing each designated area with the naked eye, it is determined whether or not the large bubble 30 overlaps with the fine bubble 40 in the thickness direction, and the number of large bubbles 30 overlapping with the fine bubble 40 in each designated area is determined. Count. Then, by arithmetically averaging each of these values, the number of large bubbles (average value) overlapping with the fine bubbles per unit area is specified.

(Ratio of the number of large bubbles overlapping with the fine bubbles observed from the plate surface side)
The ratio of the number of large bubbles 30 overlapping with the fine bubbles 40 observed from the plate surface side is preferably 30% or less, more preferably 20% or less, and more preferably 10% or less. More preferred. The lower the ratio, the larger the ratio of the large bubbles 30 having high brightness, and the higher the design of the secondary processed product 110.
The ratio of the number of large bubbles 30 overlapping with the fine bubbles 40 observed from the plate surface side is obtained as follows.
First, the average number of large bubbles per unit area is calculated as follows. A photograph of the resin plate 100 in a plan view is taken in a dark room environment. Within the area of the imaged secondary processed product 110, a region having an area of 100 cm ² such as 10 cm × 10 cm is randomly selected at a plurality of locations and designated as a designated area. In each designated area, for example, by using the image processing software NS2K-pro manufactured by Nanosystem Co., Ltd., the number of bubbles having a bubble diameter of 1 mm or more existing in each range and having a clear outer shell was obtained, and those values were obtained. It is calculated by arithmetically averaging each of the above. Although the designated areas are randomly selected from a plurality of locations, the designated areas may or may not overlap with each other.
Next, in each predetermined region, the number of large bubbles 30 overlapping with the fine bubbles 40 is the same as the method for specifying the number of large bubbles overlapping with the fine bubbles per 100 cm ² confirmed from the plate surface side described above. Is calculated and arithmetically averaged to calculate the average number of large bubbles 30 overlapping with the fine bubbles 40 per unit area.
Then, by obtaining the ratio of [the average number of large bubbles 30 overlapping the fine bubbles 40 per unit area] to [the average number of large bubbles per unit area], the fine bubbles observed from the plate surface side are obtained. The ratio of the number of large bubbles 30 overlapping with 40 can be specified.

(Average value of bubble brightness of large bubbles)
The brightness (cd / m ² ) of the large bubbles 30 observed in the secondary processed product 110 is preferably 5000 cd / m ² or more, more preferably 8000 cd / m ² or more, and 10000 cd / m ² or more. Is more preferable. By showing the brightness in such a range, when the secondary processed product 110 is irradiated with light, the large bubbles 30 tend to be a bright and shining accent on the appearance. The upper limit of the above-mentioned luminance (cd / m ² ) is approximately 20000 cd / m ² .
The average value of the bubble brightness of the large bubbles 30 is obtained as follows. A first light source (white LED) is installed at a position 250 mm away from the resin layer 20 on one side in the thickness direction of the secondary processed product 110, and a second light source (brightness) is installed at a position 300 mm away from the resin layer 20 on the other side. Total) is installed. At this time, the first light source and the second light source are opposed to each other in the thickness direction of the secondary processed product 110, and the secondary processing is performed so that one randomly selected large bubble 30 is located on the straight line connecting them. Place the item 110. Then, in this state, the brightness of the large bubble 30 is measured. This measurement is performed on 10 randomly selected large bubbles 30 and the brightness measured in each large bubble 30 is arithmetically averaged to obtain the average value of the bubble brightness of the large bubbles 30. Examples of the luminance meter include Tohoku Denshi Iwaki Seisakusho Co., Ltd., trade name; Color Live CLIVE-150P3-BK and the like.

(Haze of secondary processed products (Hz))
The secondary processed product 110 preferably has a hertz (Hz) of 50% or more, more preferably 60% or more, and even more preferably 70% or more. The haze of the secondary processed product 110 is characterized by being significantly higher than the haze of the resin plate 100 used as the raw fabric, which is due to the large number of fine bubbles 40 in the bubble-containing layer 10 of the secondary processed product 110. Indicates that it was formed. The upper limit of the hertz (Hz) is approximately 99%.
The haze of the secondary processed product 110 can be measured by the same method as the method for measuring the haze of the resin plate 100 described above.

(Total light transmittance (TT) of secondary processed products)
The secondary processed product 110 preferably has a total light transmittance of 20% or more, preferably 40% or more, when the direction along the thickness direction of the secondary processed product 110 is the line-of-sight direction. It is more preferable to have. The secondary processed product 110 in which the total light transmittance satisfies the above range has desirable light transmittance even though the haze is significantly higher than that of the resin plate 100 which is the original fabric.
The total light transmittance of the secondary processed product 110 can be measured by the same method as the above-mentioned method for measuring the total light transmittance of the resin plate 100.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto.

Examples 1 to 3, Comparative Examples 1 to 3;
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. Transparent thermoplastic resin (branched polystyrene, "HP-600" manufactured by DIC Co., Ltd.), bubble nucleating agent (Tark, "High Filler # 12" manufactured by Matsumura Sangyo Co., Ltd.) and dispersion used for the molten resin for forming the bubble-containing layer shown. The agent (zinc stearate) and the physical foaming agent (normal butane) are added in the blending amounts shown in Table 1, and the physical foaming agent shown in Table 1 is press-fitted into the blending amounts shown in Table 1 to melt them. And kneaded. As a result, a molten resin for forming a bubble-containing layer was obtained.
The transparent thermoplastic resin (straight polystyrene, "679" manufactured by PS Japan Corporation) used for the molten resin for forming the resin layer shown in Table 1 was put into the second extruder, melted and kneaded. As a result, a molten resin for forming a resin layer was obtained.

The foam-containing layer-forming molten resin obtained above was extruded into the T-die from the first extruder. Further, the molten resin for forming the resin layer obtained above 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. Then, a laminate in which the molten resin for forming a resin layer was laminated on both surfaces of the layer of the molten resin for forming a bubble-containing layer was co-extruded from the T die. Table 1 shows the discharge amount X [kg / hour] of the resin layer at the time of coextrusion, the length L [m / hour] of the extruded resin plate per unit time of the resin plate, and the width of the resin plate. .. The co-extruded laminate was passed through a pressing roll to shape it, and then passed through a transfer roll to slowly cool the laminate. At the time of coextrusion, 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 (the surface temperature of the resin immediately after extrusion from the T die) is the temperature shown in Table 1. rice field. 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. The surface temperature of the resin immediately after passing through the transfer roll was the temperature shown in Table 1. In this way, a resin plate in which resin layers were laminated on both surfaces of the bubble-containing layer was obtained.

In each of the examples and the comparative examples, 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 ). All of the resin plates were manufactured so that the vertical direction was the long side direction and the horizontal direction was the short side direction.

[Measurement of resin plate]
Using the resin plate obtained as described above, the total basis weight of the resin plate, the basis weight of the resin layer (one side), the average thickness of the bubble-containing layer, the content of the foaming agent in the resin plate, and the plate surface are used by the following methods. Average number of large bubbles per 100 cm ² observed from the side, average bubble diameter of large bubbles in the plate surface direction, average bubble diameter of large bubbles in the thickness direction, average bubble diameter of large bubbles in the thickness direction / bubble-containing layer Average thickness, fluctuation coefficient of the number of large bubbles, the ratio of the area occupied by the large bubbles observed from the plate surface side to the area of the plate surface of the resin plate, the haze (Hz) of the resin plate, the total light beam of the resin plate The permeability (TT) was identified. The results are shown in Table 2.

(Total basis weight of resin plate)
A 10 cm × 10 cm test piece was cut out at equal intervals of 10 cm along the short side direction 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 corresponding to the front and back surfaces of the test piece, specify the weight of the test piece, divide this weight by the above area, and calculate the basis weight of each test piece. It was calculated and calculated by arithmetically averaging them.

(Basis weight of resin layer (one side))
Discharge amount X [kg / hour] of the resin layer per one side at the time of coextrusion shown in Table 1, length L [m / hour] of the extruded resin plate per unit time of the resin plate, and width of the resin plate [ m] was used to determine the basis weight (one side) of the resin layer by the above formula (3).

(Average thickness of bubble-containing layer)
The resin plate was cut in the thickness direction with a band saw, and after cutting, the cut surface was polished with sandpaper or the like to form a cut surface. The cut surface was photographed at a magnification of 30 times with a microscope (Digital Microcorp VHX-900 manufactured by KEYENCE CORPORATION). Based on the obtained photographs, the thickness of the bubble-containing layer of the resin plate in the thickness direction was randomly measured at 10 points, and the arithmetic average value thereof was obtained and used as the average thickness of the bubble-containing layer.

(Content of foaming agent in resin plate)
A sample weighing 1 g was cut out from a resin plate, and the sample was placed in a sample bottle with a lid containing toluene and cyclopentane used as an internal standard substance, and the lid was closed. Then, the mixture was sufficiently stirred to obtain a solution in which the foaming agent in the resin plate was dissolved in toluene. The solution was used as a measurement sample by a gas chromatograph analyzer (manufactured by Shimadzu Corporation, product name GC-14B), and the content of the foaming agent in the resin plate was measured. The measurement conditions for gas chromatograph analysis are shown below. (Measurement conditions for gas chromatograph analysis)
Column: Made by Shinwa Processing Co., Ltd. Carrier: chromosorb W, 60-80 mesh, AW-DMCS treated product Liquid phase: Silicone DC550 (liquid phase amount 20%)
Column dimensions: column length 4.1 m, column inner diameter 3.2 mm
Column material: Glass Column temperature: 40 ° C
Injection port temperature: 200 ° C
Carrier gas: Nitrogen Carrier gas rate: 50 ml / min
Detector: FID
Detector temperature: 200 ° C
Quantitative: internal standard method

(Average number of large bubbles per 100 cm ² observed from the plate surface side)
The resin plate was photographed from the plate surface side in a dark room environment. In the photograph thus obtained, 54 areas of 10 cm × 10 cm (area 100 cm ² ) were randomly selected as designated areas in the area of the resin plate photographed. In each designated area, the number of clear bubbles existing in each range was obtained by using the image processing software NS2K-pro manufactured by Nanosystem Co., Ltd., and each of these values was arithmetically averaged. The value obtained by this was taken as the average value of the number of large bubbles per 100 cm ² observed from the plate surface side.

(Average bubble diameter of large bubbles in the plate surface direction)
The resin plate was photographed from the plate surface side in a dark room environment. In the photograph thus obtained, nine areas having a size of 30 cm × 30 cm were randomly selected as designated areas within the area of the resin plate photographed. In each designated area, the area of each large 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 large bubble shown in the photograph is made into a circle. Was calculated, and the values of the diameters of the large bubbles obtained in each designated area were arithmetically averaged. The value obtained by this was taken as the average bubble diameter (mm) of the large bubbles in the plate surface direction.

(Average bubble diameter of large bubbles in the thickness direction)
Using a resin plate, it was cut with a band saw in the thickness direction to prepare 10 strip-shaped test pieces having dimensions of length 100 mm × width 10 mm width × thickness of the resin plate. One side surface of the cut surface of the test piece was polished with sandpaper or the like to form an observation cut surface. The cut surface for observation was magnified and projected with a microscope (Digital Microcorp VHX-900, manufactured by KEYENCE CORPORATION). Based on the projected image obtained by this, 10 large bubbles whose entire shape was confirmed on the cut surface for observation were randomly selected, and the maximum length portion in each thickness direction (relative to the plate surface direction of the resin plate) was selected. The diameter of the ferret in the vertical direction) was measured. The bubble diameters of large bubbles in all the measured test pieces were calculated and averaged, and the value obtained by this was taken as the average bubble diameter of large bubbles in the thickness direction.

(Average bubble diameter of large bubbles in the thickness direction / average thickness of bubble-containing layer)
Using the values of the average thickness of the bubble-containing layer obtained as described above and the average cell diameter of the large bubbles in the thickness direction obtained as described above, the average bubble diameter of the large bubbles in the thickness direction with respect to the average thickness of the bubble-containing layer. The ratio was calculated.

(Coefficient of variation of the number of large bubbles)
The coefficient of variation (Cv) (%) of the number of large bubbles is the above-mentioned equation (2), that is, the equation represented by [standard deviation (V) of the number of bubbles / average value of the number of bubbles (DTav)] × 100. Identified using. As the standard deviation (V) of the number of bubbles in the formula (2), the standard deviation Cv (%) specified by using the above formula (1) was used.

(Ratio of the area occupied by large bubbles observed from the plate surface side to the plate surface area of the resin plate)
The area of each bubble (circle) was obtained using the diameter of each bubble in each designated region measured at the time of the average bubble diameter of the large bubbles in the plate surface direction described above, and the total of the areas was obtained. In addition, the total area of each designated area was calculated. Then, (total area of individual bubbles in each designated area) / (total area of each designated area) × 100 was calculated. The obtained value was taken as the ratio of the area occupied by the large bubbles to the plate surface of the resin plate.

(Haze of resin plate (Hz))
Three test pieces (length 20 mm, width 20 mm, thickness is the thickness of the resin plate) are randomly cut out from the resin plate, and after sufficiently removing the bubbles by a hot press to the extent that no bubbles can be visually confirmed, the temperature is 200 ° C. A plate piece with a thickness of 2 mm was prepared with a heating press machine heated to the above, and each plate piece was measured using a turbidity meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name Haze Meter NDH7000SP) based on JIS K7136: 2000. .. 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 (TT) of resin plate)
The total light transmittance in the direction along the thickness direction of the resin plate was measured using a turbidity meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name: Haze Meter NDH7000SP) according to JIS K7361-1: 1997. For the total light transmittance, the 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.

[Manufacturing of secondary processed products]
Using the resin plates of each Example and each Comparative Example obtained as described above, a secondary processed product was produced as follows.
Using a heating oven, the resin plate was heated at the temperature and time shown in the secondary processing conditions in Table 1 to obtain a flat plate-shaped secondary processed product.
Then, regarding the obtained secondary processed product, the haze (Hz) of the secondary processed product, the total light transmittance (TT) of the secondary processed product, and the average value of the number of fine bubbles per 10 cm observed from the cross-sectional side, Average bubble diameter of fine bubbles observed from the cross section side, ratio of fine bubbles of 600 μm or less, number of large bubbles overlapping with fine bubbles per 100 cm ² observed from the plate surface side, fineness observed from the plate surface side The ratio of the number of large bubbles overlapping the bubbles and the average value of the bubble brightness of the large bubbles were specified. In addition, a design evaluation test for large bubbles and a design evaluation test for fine bubbles in the secondary processed product were conducted. The results are shown in Table 3.

(Hertz (Hz) of secondary processed products)
Using the secondary processed product, the haze of the secondary processed product was determined by the same method as the above-mentioned method for measuring the haze Hz of the resin plate.

(Total light transmittance (TT) of secondary processed products)
Using the secondary processed product, the bright total light transmittance of the secondary processed product was determined by the same method as the method for measuring the total light transmittance TT of the resin plate described above.

(Average number of fine bubbles per 10 cm observed from the cross-sectional side)
Using the secondary processed product, it was cut in the thickness direction with a band saw and cut to prepare a test piece having the dimensions of length 10 cm × width 10 cm × thickness of the secondary processed product. All four cut surfaces of the test piece were sanded to form a cut surface. Such a cut surface was photographed at a magnification of 30 times with a microscope (manufactured by KEYENCE: digital microscope VHX-900 (emergence mode)). Based on the obtained photographs, the number of fine bubbles was confirmed for each cut surface, and the average value (the average value of fine bubbles in all cross sections) was calculated. The obtained value was taken as the average value of the number of fine bubbles per 10 cm observed from the cross-sectional side.

(Average bubble diameter of fine bubbles observed from the cross-sectional side)
Using the secondary processed product, it was cut in the thickness direction with a band saw and cut to prepare a test piece having the dimensions of length 10 cm × width 10 cm × thickness of the secondary processed product when viewed from the plate surface side. Each of the four cut surfaces of the test piece was sanded to form a cut surface. Each cut surface was magnified 30 times with a microscope (KEYENCE: Digital Microscope VHX-900 (Episode mode)). Based on the obtained photographs, the maximum length portion in the thickness direction of the fine bubbles confirmed on each cut surface (the diameter of the ferret in the direction perpendicular to the plate surface direction of the resin plate 100) was measured and arithmetically averaged. The value obtained by this was taken as the average bubble diameter in the thickness direction of the fine bubbles observed from the cross-sectional side.

(Ratio of fine bubbles of 600 μm or less)
The ratio of the number of fine bubbles whose maximum length in the thickness direction is 600 μm or less to the number of total bubbles counted in the measurement of the average bubble diameter in the thickness direction of the fine bubbles observed from the cross-sectional side. Was obtained by calculating.

(The number of large bubbles that overlap with the fine bubbles per 100 cm ² observed from the plate surface side)
Using a secondary processed product, an area of 10 cm × 10 cm (100 cm ² ) was randomly selected at three locations and designated as a designated area. By observing each designated area with the naked eye, it was determined whether or not the large bubbles overlapped with the fine bubbles in the thickness direction, and the number of large bubbles overlapping with the fine bubbles in each designated area was measured. Then, each of these values was arithmetically averaged to obtain the number (average value) of large bubbles overlapping with fine bubbles per 100 cm ² .

(Ratio of the number of large bubbles overlapping with fine bubbles observed from the plate surface side)
First, the average number of large bubbles per unit area was calculated as follows. A photo of the resin plate viewed in a plane was taken in a dark room environment. Within the area of the secondary processed product in the photograph taken, three areas of 10 cm × 10 cm (area 100 cm ² ) were randomly selected and designated as designated areas. In each designated area, the image processing software NS2K-pro manufactured by Nanosystem Co., Ltd. was used to determine the number of air bubbles existing in each designated area with a bubble diameter of 1 mm or more and a clear outer shell, and each of these values was obtained. Was arithmetically averaged to obtain the average number of large bubbles per unit area.
Next, in each predetermined region, the number of large bubbles overlapping with the fine bubbles is obtained in the same manner as the method for specifying the number of large bubbles overlapping with the fine bubbles per 100 cm ² confirmed from the plate surface side described above. , The obtained values were arithmetically averaged, and the average number of large bubbles overlapping with the fine bubbles per unit area was calculated.
Then, by obtaining the ratio of [the average number of large bubbles overlapping the fine bubbles per unit area] to [the average number of large bubbles per unit area], it overlaps with the fine bubbles observed from the plate surface side. The percentage of the number of large bubbles in the air was identified.

(Bubble brightness of large bubbles)
The brightness (cd / m ² ) of the large bubbles observed in the secondary processed product was determined as follows. A first light source (white LED, LDA4N-G (40W) manufactured by TOSHIBA) is installed at a position 250 mm away from the resin layer on one side in the thickness direction of the secondary processed product, and 300 mm away from the resin layer on the other side. A second light source (luminance meter; manufactured by Tohoku Denshi Iwaki Seisakusho Co., Ltd., trade name; Color Live CLIV-150P3-BK) was installed at the same position. At this time, the primary light source and the secondary light source are opposed to each other in the thickness direction of the secondary processed product, and one large bubble selected at random is located on the straight line connecting them. Was placed. Then, the brightness of the large bubble was measured in this state. This measurement was performed on 10 randomly selected large bubbles, and the brightness measured for each large bubble was arithmetically averaged to obtain the average value of the bubble brightness of the large bubbles.

(Large bubble design evaluation test)
The design of large bubbles in the secondary processed product was evaluated as follows.
〇 (Good); The bubble brightness of the large bubbles was 5000 cd / m ² or more.
Δ (normal); the bubble brightness of the large bubbles was less than 5000 cd / m ² .
× (Defective); Large bubbles could not be confirmed and measurement could not be performed.

(Design evaluation test for fine bubbles)
The design of fine bubbles in the secondary processed product was evaluated as follows.
〇 (Good); The proportion of fine bubbles of 600 μm or less was 70% or more.
X (defective); the proportion of fine bubbles of 600 μm or less was less than 70%.

The above embodiment includes the following technical ideas.
(1) A bubble-containing layer containing a foaming agent and bubbles using a transparent thermoplastic resin as a base resin, and
A transparent thermoplastic resin is used as a base resin, and a resin layer laminated on both sides of the bubble-containing layer is provided.
A resin plate for heat processing in which fine bubbles finer than the bubbles are generated in the bubble-containing layer by heating.
The basis weight per one side of the resin layer is 500 g / m ² or more, respectively.
The average bubble diameter of the bubbles in the plate surface direction of the resin plate is 1 mm or more.
The average value of the number of bubbles per 100 cm ² observed from the plate surface side of the resin plate is 5 or more and 500 or less.
The ratio of the area occupied by the bubbles observed from the plate surface side to the area of the plate surface of the resin plate is 0.2% or more and 30% or less.
The amount of the foaming agent contained in the resin plate is 0.2% by weight or more and 1% by weight or less.
A resin plate characterized in that the ratio of the average bubble diameter (mm) of the bubbles in the thickness direction to the average thickness (mm) of the bubble-containing layer is 1.1 or more.
(2) The resin plate according to (1) above, wherein the amount of the foaming agent contained in the resin plate is 0.5% by weight or more and 0.8% by weight or less.
(3) The resin plate according to (1) or (2) above, wherein the total basis weight of the resin plate is 3000 g / m ² or more and 20000 g / m ² or less.
(4) The average bubble diameter of the bubbles in the plate surface direction is 2.5 mm or more.
The resin plate according to any one of (1) to (3) above, wherein the average value of the number of bubbles per 100 cm ² observed from the plate surface side is 10 or more and 100 or less.

10 ... Bubble-containing layer 20 ... Resin layer 30 ... Large bubbles 40 ... Fine bubbles 100 ... Resin plate 110, 112 ... Secondary processed product 300 ... Resin plate 350 ...・ Secondary processed product a ・ ・ ・ Plate surface direction of resin plate b ・ ・ ・ Thickness direction of resin plate x ・ ・ ・ Thickness y ・ ・ ・ Bubble diameter

Claims (4)

A bubble-containing layer containing a foaming agent and bubbles, using a transparent thermoplastic resin as a base resin,
A transparent thermoplastic resin is used as a base resin, and a resin layer laminated on both sides of the bubble-containing layer is provided.
A resin plate for heat processing in which fine bubbles finer than the bubbles are generated in the bubble-containing layer by heating.
The basis weight per one side of the resin layer is 500 g / m ² or more, respectively.
The average bubble diameter of the bubbles in the plate surface direction of the resin plate is 1 mm or more.
The average value of the number of bubbles per 100 cm ² observed from the plate surface side of the resin plate is 5 or more and 500 or less.
The ratio of the area occupied by the bubbles observed from the plate surface side to the area of the plate surface of the resin plate is 0.2% or more and 30% or less.
The amount of the foaming agent contained in the resin plate is 0.2% by weight or more and 1% by weight or less.
A resin plate characterized in that the ratio of the average bubble diameter (mm) of the bubbles in the thickness direction to the average thickness (mm) of the bubble-containing layer is 1.1 or more. The resin plate according to claim 1, wherein the amount of the foaming agent contained in the resin plate is 0.5% by weight or more and 0.8% by weight or less. The resin plate according to claim 1 or 2, wherein the total basis weight of the resin plate is 3000 g / m ² or more and 20000 g / m ² or less. The average bubble diameter of the bubbles in the plate surface direction is 2.5 mm or more.
The resin plate according to any one of claims 1 to 3, wherein the average value of the number of bubbles per 100 cm ² observed from the plate surface side is 10 or more and 100 or less.

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