JPH0510050B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an agricultural covering material that has an excellent light diffusing property while having a perspective discrimination distance (described later), which is a measure of visibility when observing plants inside from the outside through the covering material, is 1 m or more. . BACKGROUND ART Conventionally, materials such as various films and flat plates have been widely used for the purpose of imparting light scattering properties to the cultivation of agricultural crops. The reason why scattered light is particularly effective for improving the photosynthetic efficiency of plants is that the positive leaf areas that are directly irradiated with light receive more light than necessary, while the negative leaf areas receive insufficient light. Therefore, increasing the amount of scattered light increases the amount of light reaching the shaded leaves, thereby improving the photosynthetic efficiency of the plant as a whole. It is also possible to prevent sunlight damage (leaf burn) due to excessive direct light without reducing the total light transmittance. At present, as a means of obtaining scattered light, methods such as applying a satin finish to the surface of the coating material or mixing a substance that imparts light diffusivity into the coating material are being used. However, when the surface of the coating material is satin-finished, the cross-sectional shape is a random pattern of unevenness over the entire surface, and when the coating material contains fine particles that impart light diffusivity, the incident light Due to light scattering, there is a lot of diffuse reflection on the surface, and since transmitted light is isotropically scattered, the perspective discrimination distance is almost zero. If the perspective discrimination distance is a small value, farmers will feel uneasy, and, for example, in tunnel cultivation, they will have to frequently raise the hem of the covering material and take a lot of effort to observe the inside. Therefore, although there is a need for an agricultural covering material that provides a sufficient viewing distance and has light scattering properties, in reality there is no material that fully satisfies these requirements. Under these circumstances, the present inventors applied a uniform satin finish to the entire surface of a soft film, and by varying the degree of the satin finish, the inventors created a film with a scattered light transmittance of 5% to 80%. A stage dressing was obtained. In tunnel cultivation of winter vegetable lettuce, we compared the performance of these prototypes and found that those with scattered light transmittance of 15% or more, preferably 20% or more, had good growth results. On the other hand, in order to observe the growth status of plants inside the covering material, a perspective discrimination distance of 1 m or more, preferably 2 m or more is required. A satin-finished covering material that satisfies both of these requirements has a scattered light transmittance of 15% and a perspective discrimination distance of 1 m. If you try to make the perspective discrimination distance longer than that, the scattered light transmittance will decrease rapidly, and you will only be able to obtain the same effect as the transparent plant growth.If you increase the scattered light transmittance, the perspective discrimination distance will be satisfied. I can't do it. The present inventors conducted extensive research into the possibility of increasing both the perspective discrimination distance and the scattered light transmittance, which are contradictory performances as described above. It has been found that the above object can be achieved by providing uneven stripes at intervals. The present invention will be explained in detail below. In the agricultural covering material of the present invention, the scattered light transmittance is 15% or more, preferably 20% or more in terms of plant growth, and the viewing distance required to easily observe the plants inside the covering material from the outside is required. is 1m
The length is preferably 2 m or more. As mentioned above, when the perspective discrimination distance is increased, the transmitted and scattered light decreases rapidly, and the effect on plant growth is only the same as that of a transparent one. On the other hand, when the scattered light transmittance is set high, the perspective discrimination distance generally decreases extremely. The present invention solves these contradictory phenomena and provides an agricultural covering material that is both satisfactory. In other words, a large amount of transparent scattered light, which is useful for photosynthesis in plants, is obtained by applying light refraction using fine irregularities, rather than isotropically scattered light obtained from conventional covering materials with a satin finish. It is anisotropic scattered light that is diffused in a direction perpendicular to the length direction of the uneven stripes, and due to the presence of minute planes between adjacent stripes, the perspective distance necessary for internal observation can be reduced to 1 m.
It is possible to secure more than that. The scattering angle due to fine unevenness is 2 to 3 times that of isotropic scattered light from satin finish, etc., but the scattered light transmittance at the same perspective discrimination distance is more than 3 times as large, as shown in Figure 1. The reason for this existence is not clear, but it is thought that the ability of the naked eye to recognize patterns plays a major role. With the agricultural covering material according to the present invention, it is possible to secure a total light transmittance of 85% or more, which is necessary for providing heat retention to winter vegetables, etc. It is also possible to adjust the total light transmittance to a desired value for summer vegetables, etc. The cross-sectional shape of the uneven stripes to be marked may be of any shape, such as round, triangular, rectangular, polygonal, etc., and even if they are continuous in the length direction.
Further, although it may be discontinuous, it is desirable to be continuous in view of the perspective discrimination distance and the distribution of the amount of scattered light. Further, the surface of the portion where the uneven stripes are provided is preferably smooth in order to maintain the perspective discrimination distance. The stripes are parallel from the perspective of visibility and uniformity of scattered light distribution, and more preferably the stripes are straight lines. The spacing between the stripes is 30μ to 10mm, especially 50μ to 10mm, depending on the balance between perspective discrimination distance and scattered light transmittance.
1.0mm is preferred. Furthermore, these stripes are preferably equally spaced. The width of the strip is preferably 10μ to 1.5mm, particularly preferably 20μ to 100μ. Note that the width of the stripes needs to be increased as the spacing between strips increases in order to ensure the scattered light transmittance. The depth of the stripes or the height of the strips is 1μ to the thickness of the coating material x (1/10), preferably 2μ from the viewpoint of processability of providing uneven stripes, transparency discrimination, and prevention of stains due to adhesion of dust. ~10μ. Since the light scattered by these parallel uneven stripes has directionality, the parallel stripes can be made to intersect at any angle in order to scatter the light in any direction if necessary.
However, from the perspective of perspective discrimination, it is preferable to limit the number of directions to about two. Further, in consideration of satisfying the perspective discrimination distance and scattered light transmittance of the present invention, ease of handling, and economical efficiency, it is preferable to use a single layer. As the resin constituting the coating material of the present invention, polyvinyl chloride is used in terms of light transmittance, workability, and heat retention properties. Regardless of the softness or hardness of the resin, the thickness of the coating material, or the shape of the flat or corrugated plate,
It is also possible to use a material that has been subjected to antifouling treatment, or a material that has other functions bonded together within a range that does not significantly impair the transparency and scattered light transmittance. The coating material of the present invention is not limited to the above, but any material may be used as long as it satisfies the requirements of the present invention. Methods for imparting uneven stripes include a method using a T-die method to obtain uneven stripes at the same time as film formation by specializing the shape of the die, and a method in which embossing is performed using an embossing roller having uneven stripes. be. For example, by applying pressure to a roller as shown in Fig. 2 and pressing the transparent coating material into contact with the roller, uneven stripes can be provided. The width, depth, or height of the strip is controlled by pressure or the clearance between the tip of the uneven strip of the roller and the press roller. It should be noted that the agricultural covering material of the present invention does not need to satisfy the above-mentioned configuration on one side or both sides;
Naturally, this configuration is not necessary in areas where light from the sun or an artificial light source does not reach directly, unless there is a problem with the perspective discrimination distance. However, due to usage limitations and other aspects, it is preferable to apply the structure of the present invention to the entire covering material. In connection with the present invention, Japanese Utility Model Application Publication No. 10765/1983 has been proposed. The technology of the utility model is that parts with a Fresnel lens or lenticular lens shape are distributed evenly over the entire surface, and a flat transparent part remains between them, and the parts are concentrated at the lens part. It glows to increase heat retention, and the flat part allows the inside to be seen through. At first glance, it seems to be similar to the present invention in that it has a structure in which the lens part (uneven part) and the flat part are distributed throughout, but Figures 1 to 3 of the utility model and an example of the present invention As can be seen from a comparison with FIG. 5 shown in FIG. 5, it has a clearly different structure.
That is, the present invention is characterized by a structure in which a fine plane part exists between a single fine uneven stripe, and the entire covering material can be seen through, whereas the present invention has many parts that cannot be seen through. The grooves and protrusions are arranged in blocks over a wide area, and between the blocks are arranged planar parts with a wide area that can be seen through. Therefore, the present invention differs from the utility model in that when looking at the entire surface of the covering material, the areas of the uneven parts and the flat parts may be approximately the same on average, but when looking at the local parts, they are completely different. , such structural differences greatly influence the differences in effects described below. In the agricultural covering material of the first aspect of the present invention, the entire crop inside the covering material can be seen through, whereas in the covering material of the utility model, only a portion of the crop can be seen, and therefore it is possible to see the exact growth state of the crop. I can't figure it out. Second
In the covering material of the utility model, since transparent parts and uneven parts of a relatively wide area are locally present, the distribution of sunlight lacks uniformity. In other words, in the transparent part, which is a flat surface, the excessive amount of sunlight caused by direct light can cause sunlight damage such as leaf burn, and in addition, the scattered light on the uneven parts hits the relatively wide leaf shade area caused by the direct light from the transparent part. Since the proportion is small, it does not contribute much to increasing crop yields. The present invention uniformizes the distribution of sunlight through a combination of a single fine uneven strip and a fine plane, solves all the problems of the prior art at once, and brings about a significant increase in crop yield. As described above, it can be understood that the coating material of the present invention has a completely different structure from the coating material of the utility model, and therefore the effects obtained are significantly different. In the present invention, total light transmittance and scattered light transmittance are measured using a Shimadzu spectrophotometer (W monochromator, self-spectrophotometer, UV-
365). In other words, when calculating total light transmittance and scattered light transmittance, 500nm to 700nm
Read the transmittance between the two and use the average value.
In addition, the fluoroscopy discrimination distance is for people with unaided visual acuity of 1.0 or higher
See through the covering material 1m away in front of you,
This is the maximum distance that can be determined to be 1.0 mm between the recognition maps in front of the covering material. If there is a difference in the perspective discrimination distance in the length direction or width direction of the sheathing material to be seen, or if the perspective discrimination distance differs depending on the location of the sheathing material, the perspective discrimination of that sheathing material is determined using a high numerical value. Distance. The measurement method is to set the distance between the person and the covering material to 1 m, change the distance between the covering material and the recognition map, and measure the maximum distance that can determine the interval between the recognition maps (distance between the covering material and the recognition map). . However, the illuminance in the room shall be 850 lux. The recognition diagram above shows a white background with a dominant wavelength of 609 nm and a brightness of 44.
%, using a color with a purity of 52.8%, as shown in Figure 3. Incidentally, FIG. 1 shows the results of plotting the scattered light transmittance and the perspective discrimination distance at each level of the film obtained using the roller shown in FIG. 4. Fig. 1 also shows the results for a satin-finished film. Examples 1 to 3, Comparative Examples 1 to 2 Using polyvinyl chloride film with a thickness of 0.1 mm,
By varying the contact pressure of the heated roller as shown in FIG. 4, products having the surface conditions shown in Table 1 were obtained. In addition, P, A, B shown in Table 1
As shown in FIG. 5, represent the pitch of the uneven stripes, the width of the uneven stripes, and the depth of the uneven strips, respectively.

[Table] The growth conditions when the films of these and the following comparative examples are used for winter vegetable lettuce are as follows: Comparative Examples 1 to 2
In contrast, Examples 1 to 3 were all better. Comparative Example 1 is an unprocessed control film used in the test, and Comparative Example 2 is a commercially available matte polyvinyl chloride film with a thickness of 0.1 mm. Further, the physical property values of the films of these Examples and Comparative Examples are shown in Table 2.

【table】 [Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the perspective discrimination distance and the scattered light transmittance, and FIG. Figure 3 is a recognition diagram used to measure perspective discrimination distance, and Figure 4 is a recognition diagram used for measuring perspective discrimination distance.
5 is a partial cross-sectional view of the roller used in the fifth
The figure is a perspective view of a representative example of the agricultural covering material of the present invention.

Claims (1)

[Scope of Claims] 1. A light diffusion device having a scattered light transmittance of 15% or more, a perspective discrimination distance of 1 m or more when viewed through the coating material, and a single layer made of polyvinyl chloride resin or having the layer. Agricultural covering material. 2. Claim 1, in which a large number of grooved or raised lines (hereinafter abbreviated as uneven lines) are arranged in parallel on at least one side of the layer, and minute planes exist between adjacent lines. Covering material as described in section. 3. The covering material according to claim 2, wherein the uneven stripes are straight lines. 4. The covering material according to any one of claims 2 and 3, which has parallel uneven stripes that intersect the uneven stripes at an arbitrary angle in one direction or two or more directions. 5 The width of the uneven stripes is 10 μ to 1.5 mm, the depth or height of the strips is 1 μ to the thickness of the coating material x (1/10), and the pitch of the uneven strips is 30 μ to 10 mm. The coating material according to any one of Items 2, 3, and 4. 6. Any one of claims 2, 3, 4, and 5, in which the uneven stripes are of equal pitch, and the width, depth, or height of each uneven strip is constant. Covering material described in.