JPH07102046B2 - Agricultural polyvinyl chloride film - Google Patents

Description

TECHNICAL FIELD The present invention relates to an agricultural film suitable for cultivating agricultural crops. More specifically, the present invention relates to a film having excellent transparency, spectral performance and good anisotropic light scattering.

<Prior Art> Conventionally, materials such as various films and flat plates have been widely used as coating materials for the purpose of using scattered light for cultivation of agricultural products. The reason why scattered light is said to be effective for cultivating plants is that, in the case of direct light, the amount of light that reaches the positive leaves that the light directly hits exceeds the necessary amount of light, whereas the amount of light that reaches the shade leaves that do not hit the light directly Although it will be insufficient, when scattered light is used, a large amount of light reaches the shaded part and the photosynthetic efficiency of the entire plant is improved. Further, when the direct light is replaced with the scattered light, it is possible to prevent the sun damage (leaf burn) due to the excessive direct light without substantially lowering the total light transmittance. At present, as a means to obtain scattered light, a method of embossing the surface of coating material such as film or flat plate,
A method of mixing a substance that imparts a light-scattering property to the coating material, or a method of applying embossing to the entire surface of the coating material by embossing, as proposed in Japanese Utility Model Publication No. 50-125347. It has been known.

<Problems to be Solved by the Invention> However, the surface of the covering material having a satin embossing does not have transparency because the cross-sectional shape is a random uneven shape over the entire surface, and Incident light is often diffusely reflected in the coating material in which fine particles imparting light scattering property are mixed, and since transmitted light is isotropically scattered, this also has a drawback that it has almost no transparency. is there. In addition, the above-mentioned one in which the uneven surface is embossed on the entire surface of the covering material has a drawback that the transparency cannot be ensured because the transmitted light becomes almost anisotropic scattered light.

That is, scattered light that is effective for the photosynthetic efficiency of plants is anisotropic scattered light by prism spectroscopy, anisotropic scattered light by uneven lines,
It can be obtained by isotropic scattered light by the satin embossing, but they all have the drawback that they have little transparency. If the covering material does not have transparency, it gives farmers a sense of anxiety, and in tunnel cultivation, for example, the hem of the covering material must be frequently raised and the inside must be observed, which requires a lot of labor. Become.
However, scattered light is indispensable for improving photosynthetic efficiency as described above. In the process of researching a covering material that can obtain scattered light, the anti-inventors et al. It was found that the spectrally scattered light, which is not mixed or mixed evenly even if mixed, is more effective for plant growth. In particular, it may be more effective that the light of the seven color wavelength components is not mixed, or even if mixed, it is unevenly mixed and illuminates the leaves of the plant while moving over time. I found it.

<Means for Solving Problems> The present inventors have conducted diligent research on a coating material capable of increasing the scattered light transmittance by spectroscopy, which is effective for photosynthesis of plants, while ensuring the transparency. As a result, in a film in which a large number of concavo-convex stripes are arranged in parallel on at least one surface, and a fine plane exists between adjacent stripes,
30% to 80% of the total surface area of the uneven strip is 5 ° to the film surface
The above object can be achieved by a coating material which is a slope having an inclination angle of -40 ° and 70% to 20% is a so-called horizontal surface having an inclination of 0 ° to 5 ° with respect to the film surface. I found it. The present invention will be described in detail below. An example of a perspective view of the surface shape of the film of the present invention is shown in FIG.

The coating material of the present invention, that is, the film has excellent transparency as compared with a coating material that has been subjected to a conventional satin embossing treatment, and is excellent in forming a large amount of scattered light useful for photosynthesis of plants. Moreover, it is characterized in that the scattered light is not isotropic scattered light obtained from a product that has been subjected to satin embossing or the like, but is spectrally dispersed and anisotropically scattered.

By the way, in order to obtain a film having good transparency and anisotropic scattering performance by spectroscopy, it is necessary to set the maximum inclination angle of the uneven lines to 40 ° or less. The maximum inclination angle of the uneven line is 40
If the angle exceeds 45 °, particularly 45 °, the spectroscopic performance deteriorates and the transparency deteriorates at the same time, although the reason is not clear. On the other hand, if the maximum tilt angle is less than 5 ° and the surface is extremely smooth, the anisotropic scattered light due to the spectrum, which is useful for improving the photosynthetic efficiency of plants, will decrease. Is. It is necessary that the surface of the uneven strip is smooth in order to ensure transparency. Also, 0 ° to the film surface
It is necessary that a so-called horizontal surface having an inclination of ~ 5 ° is present in an amount of 20% to 70% with respect to the total surface area of the uneven strip.
If it is less than%, the distance between the inclined surfaces is narrow, and it becomes difficult to secure the transparency and the like due to the horizontal portion. In addition, the area of the inclined portion (that is, the portion having an inclination angle of 5 to 40 °) with respect to the total surface area of the uneven lines has an upper limit of 80% in terms of transparency, and the lower limit is to secure anisotropic scattered light by spectroscopy. 30% or more is required. Therefore, it is desirable that the area of the horizontal portion is 70% or less with respect to the total surface area of the uneven lines. The inclination angle described here means a tangent line of a curve (or straight line) forming a concave portion or a convex portion at an arbitrary point on the surface of the uneven strip as shown in FIGS. It is the angle θ formed by the extended line of the film surface shown by the dotted line. In the present invention, a portion having an inclination angle of 5 ° or more is referred to as an inclined portion, and
A portion of ° to 5 ° is called a horizontal portion. It should be noted that, as shown in FIG. 3 or FIG. 4, the sloped portions and flat portions of the convex objects 1 and 1 ′ and the concave objects 2 and 2 ′, which may be secondarily generated by embossing, are the present invention. It is not considered to be a sloped part or a flat part specified in. In the film of the present invention, a horizontal surface parallel to the film surface exists between the adjacent ridges and grooves, and a horizontal portion parallel to the film surface exists in the ridges as described above. It is extremely preferable that two kinds of horizontal planes having different heights are present in order to satisfy both the transparency and the formation of anisotropic light scattering.

By the way, it has been publicly known that the light rays of seven colors separated by wavelength can be obtained by a prism or the like. When plants perform photosynthesis, not all lights are photosynthesizing at the same efficiency. Under natural conditions, light is generally white light, which exists as a mixture of light of various wavelengths. Plants utilize a wavelength effective for photosynthesis from these white mixed light wavelengths, which are 440 nm blue light and 665 nm.
It is said that it has a peak in red light of nm as shown in FIG. Plant chlorophyll receives blue or red light, converts it to chemical energy to decompose water, and produces hydrogen and carbon dioxide gas sucked from the pores to produce reducing carbon compounds. There is. That is, light rays having wavelengths other than blue light and red light are not as strongly involved in photosynthesis as blue light and red light. Normal light that has passed through coating materials such as glass plates and plastic seeds that are currently used for greenhouse cultivation and tunnel cultivation is an average mixture of all seven wavelengths of light. The photosynthesis is more efficient when the dispersed blue light, red light, or the like is concentrated and strikes more stripes than when the chloroplasts are uniformly hit. The reason for this is not clear, but the specular and concentrated striped wavelengths strongly irradiate the leaf surface, and the striped irradiation position is periodically repeated as the position of the sun moves. It seems that the photostimulation efficiency is promoted by the stimulus. In addition, in the film of the present invention, since a large number of uneven lines are arranged in parallel on at least one surface of the film, the incident light is dispersed in a direction perpendicular to the uneven lines and becomes scattered light. In other words, it is an anisotropic scattered light. On the other hand, most of the plants grow with the leaf surface facing upward and the leaves vertically stacked at intervals. From this, when the covering material is used with the uneven strips horizontal, the light is applied to the shaded part, and the photosynthetic efficiency can be improved. Furthermore, when the rising angle of the sun in the winter is small, plants cultivated in the north-south direction, such as lettuce in tunnel houses, are usually cultivated in the north-south direction in rows 3 to 4 and in the east-west direction by about 100m, but with a transparent cover. When the wood is used, the lettuce in the most south row receives a lot of sunlight, but the second to fourth rows are shaded from the south one, so that the sunshine time is short and the growth is delayed. In such a case, if a covering material that scatters anisotropic light is used, uniform transmitted scattered light can be obtained regardless of the cultivation positions in the north and south, and most of the scattered light will be used. It is possible to reduce the difference in growth between north and south.

A film proposed in Japanese Utility Model Publication No. 50-125347 is an invention that is similar to the present invention at first glance. This film is embossed with lens-shaped and prism-shaped smooth uneven lines on its entire surface. In the case of this film, most of the incident light is light that is scattered in the direction perpendicular to the uneven strips, that is, anisotropic scattered light. It is similar to the film of the present invention in that the photosynthetic efficiency is improved by irradiation, but since the uneven surface is embossed on the entire surface of the film, there is a significant difference in transparency and anisotropic scattered light It is also different in whether or not it is spectrally separated. Therefore, they are also completely different from each other in terms of whether or not the photosynthetic efficiency of plants is further promoted.

In addition, Japanese Patent Publication No. 59-192022 discloses that by alternately arranging a transparent portion that directly transmits sunlight and a scattered light transmitting portion that scatters and transmits sunlight, scattered light effective for plants can be obtained. In addition, a technique is described to increase the temperature of the spot inside the coating material and to raise the temperature of the cultivated area.However, in the case of this technology, the coating material has a transparent portion and a scattered light transmitting portion that are alternately present. Although it is similar to the film of the present invention in that it has a see-through property, the scattered light itself is basically isotropic scattered light and is basically different from the anisotropic scattered light that is spectrally dispersed in the present invention. However, it is also inferior in terms of satisfying both of them while balancing the transparency and the scattered light at a high level.

Furthermore, as a technology related to the present invention, the actual development of Shokai 50-107652
There is one described in the publication. The technology of the utility model is
On the surface of the covering material, the parts in the form of Fresnel lenses or lenticular lenses are distributed all over and evenly distributed, and the flat transparent parts remain between them, and the light is condensed at the lens part. The heat insulation is improved and the inside can be seen through in the flat part. This technique is similar to that of the present invention in that it has a structure in which the lens portion (concavo-convex portion) and the flat portion are distributed over the entire surface. As can be seen by comparing FIGS. 1 and 3 and 4 shown as an example, it has a clearly different structure. That is, as described above, the film of the present invention has a structure in which flat portions are present between the fine ridges and valleys, and further fine horizontal portions are present in each ridge, and the entire coating material is seen through. On the other hand, in the covering material described in Japanese Utility Model Publication No. 50-107652, a large number of invisible ridges and ridges exist in a block-like wide area, and between the blocks. This is a plan view in which a flat area having a large area that can be seen through is arranged. Therefore, in the film of the present invention, when the entire surface of the coating material is viewed, the areas of the uneven portion and the flat portion may be approximately the same as those of the utility model. It is quite different from the above, and the difference in the structure has a great influence on the difference in the effects described below. First of all, in the agricultural film of the present invention, it is possible to see through the entire crop inside the covering material, whereas in the covering material of the utility model, only one part of the crop can be seen, and the crop I cannot grasp the exact growth condition. Secondly, in the coating material of the utility model, since the see-through portion and the uneven portion having a relatively large area are locally present, the sunshine distribution lacks uniformity. That is, in the flat see-through part, excessive sunlight caused by the direct light causes sunlight obstruction such as leaf burning, and in addition, the scattered light formed by the concavo-convex part causes a relatively wide shadow caused by the direct light of the see-through part. It does not contribute to the increase of crop yield because the proportion of leaves is small. On the other hand, in the film of the present invention, since the distribution of the sunshine amount becomes uniform due to the combination of the fine single ridges and the fine planes, and the scattered light is anisotropic scattered light, the various problems of the prior art. Will be solved all at once, resulting in a large increase in crop yields. As mentioned above,
It can be understood that the film of the present invention has a completely different structure from any of the above-mentioned utility model coating materials, and the effects obtained accordingly are remarkably different.

The fine concavo-convex stripes in the present invention may be continuous or discontinuous in the lengthwise direction, but it is desirable that they are continuous from the viewpoints of the transparency and the distribution of the amount of scattered light, and From the perspective and the uniformity of the scattered light distribution, is preferably parallel to the adjacent strips and more preferably straight. The pitch (P) of the uneven strip is a balance between the transparency and the scattered light transmittance.
50μ to 180μ is preferable, and the width (A) of the uneven strip is 10μ to 150μ
[mu], especially 10 [mu] to 40 [mu] is preferable from the perspective of transparency. The depth or height (D) of the uneven lines is 1 μ to 15 μ, preferably 1 μ to 5 μ from the viewpoint of the stamping workability of the uneven lines, the visibility and the prevention of dirt due to the adhesion of dust, and the thickness of the film. 1/1000 to 1/10 of that is preferable. Further, the width (B) of the fine plane existing between the adjacent strips is preferably 10 μ to 170 μ.

The pitch (P), the depth or height (D), the width (B) of the fine plane, and the width (A) of the uneven line are as follows.
The same reference numerals are used in FIGS. In the present invention, in order to scatter the direction of scattered light in an arbitrary direction as required, a group of parallel uneven lines can be crossed at an arbitrary angle. However, it is preferable to limit the number of directions to two in order to utilize the transparency and the spectrum. Further, the film of the present invention is preferably a single layer in view of satisfying the transparency and the light scattering property, as well as the handling property and the economical efficiency.

In the film of the present invention, it is indispensable that one surface is provided with the above-mentioned uneven lines, but the other surface is substantially free of uneven lines, or is significantly transparent, Concavities and convexities may be provided within a range that does not impair the anisotropic scattering.

The film as an agricultural coating material used in the present invention naturally has a high total light transmittance, but it is required that the film has good processability and good heat retention and handleability. That is, as the polymer that constitutes the film, the surface of the uneven line to be marked is processed smoothly, and the infrared rays radiated to the inside of the covering material are difficult to pass through when the infrared rays are radiated at night. That is, polyvinyl chloride is most preferable because it is excellent in heat retention, is more flexible, and is easy to handle.

As a method of imprinting the uneven strip, there are a method of specializing the shape of the die by using the T-die method to obtain the uneven strip at the same time as film formation, a method of embossing with an embossing roller having the uneven strip, and the like. . For example, by heating a roller as shown in FIG. 2 and applying a transparent coating material to the roller, an uneven line can be marked, and the temperature of the roller, the processing time, the roller contact of the affixed body, and the like. By varying the pressure, the apex angle of the concavo-convex liner tip of the roller, or the clearance between the concavo-convex liner tip of the roller and the press roller, the line inclination angle, the inclined area, or the horizontal area is controlled.

In the present invention, the total light transmittance and the scattered light transmittance are JI
Measured by SK-6714 using Shimadzu spectrophotometer (W monochromator, self-spectrophotometer, UV-365).
That is, when calculating the total light transmittance and the scattered light transmittance,
Read the transmittance between 500 nm and 700 nm and use the average value. The spectral performance is determined by placing a convex lens in front of a 10,000-lux light source in a dark room, irradiating the sample with parallel light, and observing the spectral state on a white screen 1 m in front of the sample. The depth or height of the uneven line is measured from a cross-section electron microscope photograph and is represented by D shown in FIGS. 3 and 4. The area of the inclined portion and the horizontal portion are also shown by the cross-section electron microscope photograph. And the length of the horizontal portion are measured, and the area of the inclined portion = the length of the inclined portion × L The area of the horizontal portion = the length of the horizontal portion × L However, L is a fixed sample length. Therefore, the area ratio of the inclined part (S ₁ ) and the area ratio of the flat part (S ₂ ) to the total surface area of the uneven line are calculated by the following formulas.

Example Using a transparent polyvinyl chloride film (thickness 0.1 mm), the shape of a heated embossing roller as shown in FIG. 2,
By changing the clearance between the embossing roller and the pressing roller and the heating temperature, the surface morphology as shown in Table 1 was obtained.

For example, the film of Example 1 uses a roll shown in FIG. 2 with P of 100 μ, α of 60 °, and a diameter of 160 mm.
Heated embossing roll and unheated diameter 16
Place the polyvinyl chloride film above between 0 mm press rolls.
It was obtained by passing it so that the pressure was 0.7 Kg / cm.

In addition, the film of Comparative Example 5 is a case where the flat portion does not exist between the two adjacent recesses and the two recesses are in contact with each other.

Table 2 shows the results of the spectral characteristics of the obtained film, the growth state when used as a covering material for winter vegetable lettuce, and the transparency of the inside of the house during practical use. Comparative Example 6 is an unprocessed control film used in the test, and Comparative Example 7
Is a commercially available satin-finished polyvinyl chloride film having a thickness of 0.1 mm.

[Brief description of drawings]

FIG. 1 is a perspective view of an example of the film of the present invention.
FIG. 3 is a partial sectional view of an embossing roller capable of producing the film of the present invention, and FIGS. 3 and 4 are sectional views of the obtained film. FIG. 5 is a diagram showing the relationship between the spectral absorptance of chloroplasts and wavelength.

Claims (3)

[Claims] 1. A film in which a large number of concave or convex lines (hereinafter abbreviated as uneven lines) are arranged in parallel on at least one surface and a fine plane exists between adjacent lines, 30% to 80% of the total surface area is a slope having an inclination angle of 5 ° to 40 ° with respect to the film surface, and 70% to
Anisotropic light-scattering polyvinyl chloride film for agriculture, characterized in that 20% is a so-called horizontal surface having an inclination of 0 ° to 5 ° with respect to the film surface. 2. The width of the uneven strip is 10 μ to 150 μ, the depth or height of the strip is 1 μ to 15 μ, and the pitch of the uneven strip is 50 μ to 18 μ.
The film according to claim 1, which has a thickness of 0 μ. 3. The film according to claim 1 or 2, wherein the uneven lines are straight and are equally pitched, and the width, depth or height of each uneven line is constant.