JP6641720B2 - Low reflection sheet - Google Patents

Description

  The present invention relates to a low reflection sheet having a large number of protrusions on a surface.

  In recent years, as a low reflection sheet for reducing light reflection, a sheet having a large number of fine irregularities on the surface has been proposed. The low-reflection sheet with fine irregularities uses the moth-eye structure principle to eliminate sudden changes in the refractive index for incident light, thereby suppressing light reflection due to discontinuous changes in the refractive index at the material interface. And has the function of reducing the reflectance.

Such a low reflection sheet is applied to various uses depending on functions such as light transmittance and light blocking properties.
By arranging the light-transmitting low-reflection sheet on, for example, a light-emitting surface of an image display device, reflection of external light such as sunlight on a screen of the display device can be reduced, and image visibility can be improved. Reference 1). In addition, a transparent conductive laminate in which a transparent conductive layer such as indium tin oxide (ITO) is provided on the surface of the low reflection sheet on which the fine irregularities are formed is used as a touch panel electrode used for a touch panel. In addition, it is possible to prevent light reflection between various adjacent members (Patent Document 2).
On the other hand, when a low-reflection sheet having a light-shielding property is used as, for example, synthetic leather, the matte feeling on the surface becomes clearer, and the appearance, texture, and design can be improved. In addition, by using the low-reflection sheet on the surface of a shutter blade for an optical device such as a digital camera, external light irradiation to the image sensor can be suppressed.

JP 2014-29366 A JP 2001-35261 A

  However, a low reflection sheet having a light shielding property has a problem that a sufficient effect of reducing the reflectance has not been obtained.

  The present invention has been made in view of the above problems, and has as its main object to provide a low reflection sheet capable of exhibiting an excellent effect of reducing reflectance.

  The present inventor has conducted intensive studies to solve the above problems, and as a result, has found that the reflectance reduction effect is improved by miniaturizing the uneven shape provided on the surface of the sheet. It has further been found that there is a problem that the effect cannot be sufficiently exhibited only by miniaturization. Then, it has been found that the above problem occurs due to the regularity of the shape and arrangement of the individual projections (projections) and depressions (grooves) provided on the surface of the low reflection sheet. The present invention is based on such knowledge.

That is, the present invention has a low-reflection resin layer having a large number of protrusions on at least one surface side of the colored base material, and the average of the maximum diameter of the bottom surface of the protrusions is within a range of 250 nm or more and 500 nm or less. The average of the distance between the centers of the other protrusions having the center of the bottom surface at the position closest to the center of the bottom of one of the protrusions and the one protrusion is 400 nm or less; The dispersion is 10,000 or more, and the length direction and the width direction in the plane of the low reflection resin layer having the protrusion are defined in the x-axis direction and the y-axis direction, and the center of the bottom surface of the protrusion in plan view. When the position of the top of the protrusion from the above is indicated by an azimuth angle φ (0 ° ≦ φ <360 °), and the number of extraction points of the protrusion is n (n ≧ 30), | Σ _{(k = 1 to n)} cosφ _k /n|≦0.25 and | Σ _{(k = 1 To n)} A low reflection sheet characterized by satisfying a relationship of sinφ _k /n|≦0.25.

According to the present invention, since a large number of projections having a desired variation in shape and arrangement position are formed on the surface of the low reflection sheet exhibiting the color of the colored base material, the projections reflect light many times. In addition, it is possible to prevent the intensity of light of a specific wavelength from increasing due to interference. Furthermore, in the above-mentioned projections, in addition to light being absorbed into the low-reflection resin layer by multiple reflections of light, light absorption into the low-reflection resin layer due to Mie scattering also occurs, thereby lowering the reflectance. Can be done.
Therefore, the low reflection sheet of the present invention can exhibit an excellent effect of reducing reflectance.

  In the above invention, it is preferable that the coloring base material and the low-reflection resin layer be a single layer integrated. By using a single layer, the manufacturing process can be simplified and the material cost can be reduced.

  The low-reflection sheet of the present invention has an effect that an excellent reflectance-reducing effect can be exerted by imparting a desired variation in the shape and arrangement position of a large number of projections on the surface.

FIG. 2 is a schematic sectional view illustrating an example of the low reflection sheet of the present invention. FIG. 3 is an enlarged schematic cross-sectional view illustrating an example of a low reflection resin layer in the present invention. It is explanatory drawing explaining the azimuth (phi) of the top part of the protrusion in this invention. It is a plane SEM image showing an example of the low reflection sheet of the present invention.

Hereinafter, the low reflection sheet of the present invention will be described in detail.
The low-reflection sheet of the present invention has a low-reflection resin layer having a large number of projections on at least one surface side of the colored base material, and the average of the maximum diameter of the bottom surface of the projections is in a range of 250 nm or more and 500 nm or less. And the center distance between the other protrusions having the center of the bottom surface closest to the center of the bottom surface of the one protrusion and the one protrusion (hereinafter referred to as the closest center distance) Is 400 nm or less, the variance of the center-to-center distance is 10,000 or more, and the length direction and width direction in the plane of the low-reflection resin layer having the protrusions are the x-axis direction and the y-axis direction. The position of the top of the protrusion from the center of the bottom surface of the protrusion in plan view is indicated by an azimuth angle φ (0 ° ≦ φ <360 °), and the number of extraction points of the protrusion is n. when (n ≧ 30) and, | Σ _{(k = 1 n) cosφ k /n|≦0.25,} and | is characterized in satisfying the Σ _{(k =} 1~n) relationship sinφ _k /n|≦0.25.

The low reflection sheet of the present invention will be described with reference to the drawings. FIG. 1 is a schematic sectional view showing an example of the low reflection sheet of the present invention, and FIG. 2 is a schematic enlarged sectional view showing an example of the low reflection resin layer. 3A and 3B are explanatory views for explaining the azimuth angle φ of the top of the projection in the present invention. FIG. 3A is a side view of the projection, and FIG. 3B is the z-axis of FIG. It is explanatory drawing explaining the position of the top part of a projection part when it sees from a direction, ie, the planar view from the top part side of a projection part.
As shown in FIG. 1, a low reflection sheet 10 of the present invention has a low reflection resin layer 2 on at least one surface of a colored substrate 1. As illustrated in FIGS. 1 and 2, among the surfaces of the low-reflection resin layer 2, many surfaces having a desired variation in shape and arrangement position are provided on a surface facing a surface in contact with the colored base material 1. A projection 3 is provided.
Here, the desired variation of a large number of protrusions is defined by quantifying three parameters. The first parameter depends on the size of the protrusion. That is, as shown in FIG. 2, the average of the maximum diameter R of the bottom surface of the projection 3 is in the range of 250 nm or more and 500 nm or less.
The second parameter is based on the positional relationship between adjacent protrusions. That is, as shown in FIG. 2, the distance L between the centers of the one projection 3A and the center of the bottom O of the one projection 3A is closest to the center O of the bottom of the other projection 3B. The average is 400 nm or less, and the dispersion of the center-to-center distance L is 10,000 or more.
The third parameter depends on the direction indicated by the vertex of the protrusion. That is, as shown in FIG. 3, the length direction and the width direction in the plane of the low reflection resin layer 2 having the protrusions 3 are defined in the x-axis direction and the y-axis direction, and the bottom surface of the protrusions 3 in plan view. When the position of the top T of the projection 3 from the center O is indicated by an azimuth angle φ (0 ° ≦ φ <360 °) and the number of extraction points of the projection 3 is n (n ≧ 30), | Σ _{( k = 1 to n)} cos φ _k /n|≦0.25 and | Σ _{(k = 1 to n)} sin φ _k /n|≦0.25.

The conventional low reflection sheet having a light-shielding property has a problem that a sufficient effect of reducing the reflectance has not been obtained. The present inventor has studied the above problem, and found that the effect of reducing the reflectance can be improved by making the irregularities formed on the surface of the sheet finer.
However, as a result of further intense study of the above problem, the present inventors have found that simply reducing the size of the concavo-convex shape does not provide a sufficient effect of reducing the reflectance for the following reasons.
That is, the fine irregularities generally provided on the surface of the low-reflection sheet have regularity in the shape and arrangement of the individual projections (projections) and depressions (grooves), and have a desired surface roughness as a whole surface. Things. However, depending on the regularity of the fine irregularities, the interference of light causes the intensity of light of a specific wavelength to increase, thereby causing problems such as generation of interference fringes. For this reason, it is inferred that the occurrence of the above-mentioned problem hinders the effect of reducing the reflectance.

According to the present invention, since the surface of the low-reflection sheet exhibiting the color of the colored base material has the low-reflection resin layer in which a large number of protrusions having a desired variation in shape and arrangement position are formed, Can be reflected many times and absorbed by the low-reflection resin layer, and the reflectance can be reduced.
In addition, since a large number of protrusions have a desired variation, it is possible to suppress an increase in intensity of light of a specific wavelength due to interference.
In addition, since a large number of projections have a desired variation, in addition to the fact that light is absorbed into the low-reflection resin layer by multiple reflections at the top of the projections, especially at the tops of the projections, the shape of the projections The Mie scattering of the light can further increase the amount of light absorbed by the low-reflection resin layer, and the reflectance can be further reduced. This is because Mie scattering has features such as "strong forward scattering" and "small wavelength dependence".
That is, since the Mie scattering has strong forward scattering, light incident on the protrusions is scattered in the low-reflection resin layer, and the scattered light can be absorbed by the low-reflection resin layer. In addition, since Mie scattering has a small wavelength dependency, light in the entire visible light region of 380 nm to 780 nm is scattered, and the scattered light can be absorbed by the low reflection resin layer.
Thereby, the low reflection sheet of the present invention can exhibit an excellent reflectance reduction effect.

  Hereinafter, each configuration of the low reflection sheet of the present invention will be described.

A. Low-reflection resin layer The low-reflection resin layer according to the invention is provided on at least one surface side of the colored base material and has a large number of projections.
Further, the projections provided in the low-reflection resin layer have a desired variation in shape and arrangement position.

1. Projection The projection has a desired variation in its shape and arrangement position, and the degree of variation of a large number of projections determines the effect of reducing the reflectance of the low reflection sheet of the present invention.
Here, the variation in the shape and the arrangement position of the protrusion is defined by quantifying three parameters of the size of the protrusion, the positional relationship between the adjacent protrusions, and the direction indicated by the vertex of the protrusion.
Hereinafter, the quantification method of each parameter and each parameter defined by the quantification method will be described.

(1) Parameter Quantification Method Variations in the shapes and arrangement positions of the protrusions in the present invention are calculated by extracting a desired number of points from a large number of protrusions provided on the low-reflection resin layer and quantified. .
The projections were extracted using a scanning electron microscope (SEM) or an atomic force microscope (AFM) at a magnification of 10,000 times and a visual field range of 4 μm × 4 μm. A method is used in which planar observation is performed from the surface side having the projections, an in-plane arrangement of the projections in the visual field range is detected by an image, and a desired score is extracted therefrom.

Each parameter in the present invention is calculated by assuming that the minimum number of extraction points of a projection per one visual field range is 30 points. It is preferable that the number of extraction points of the protrusions is large, and the number of extraction points is preferably 30 or more, and more preferably 50 or more. In addition, the number of detections of the visual field range for extracting the protrusions is 3 or more, preferably 5 or more, particularly 10 or more per desired unit area (2500 mm ² ) of the surface of the low reflection sheet provided with the protrusions. It is preferred that
By defining the number of extraction points and the number of detections of the visual field range in the above ranges, the three parameters can be quantified with higher accuracy, and the variation in the shape and arrangement position of the protrusion can be accurately defined. It is.

Each parameter is quantified by the following procedures (a) to (f).
(A) First, an in-plane arrangement of protrusions is detected using a scanning electron microscope (SEM) or an atomic force microscope (AFM). A desired number of protrusions is extracted from the detected in-plane arrangement, and the maximum point and the minimum point of the height of each protrusion are detected. Various methods such as a method of successively comparing the enlarged shape photograph of the corresponding cross-sectional shape with a plan view shape and a method of obtaining the image by processing the enlarged plan view photograph are applied as a method of finding the maximum point and the minimum point. can do. The maximum point obtained at this time is defined as “the top of the protrusion”.

(B) From the SEM image and the AFM image, a set of minimum points surrounding the maximum point is set as the root of the projection, and the root shape is approximated to a polygon or a circle in order to determine the root shape. The root shape is a planar shape (contour shape) of the root contour, and is a region surrounded by the contour. In the approximation, partially broken lines are complemented. As a complementing method, a method of creating a closed space by setting a certain threshold value is used. The contour shape of the approximated root is not particularly limited as long as each parameter can be specified.For example, a circle, a circle such as an ellipse, a pentagon, a hexagon, an octagon, a dodecagon, etc. It can be polygonal or the like.
For approximation of the root shape, a conventionally known method used when approximating a shape from an image can be applied, and the above method is not particularly limited. Specific methods include, for example, template matching, general Hough transform, Douglas-Peucker method and the like can be used.
In template matching, a template representing a shape is prepared in advance, and a shape included in the image data is determined by examining a similarity index such as a correlation coefficient while moving the template with respect to image data to be subjected to image recognition. It is a technology to recognize. For an image approximation method using template matching, see, for example, "Takayuki Nakata, Bakuro, Naofumi Fujiwara:" Figure Recognition Using Log-Polar Transformation in 3D Environment ", IEICE Transactions on Electronics (D-II), Vol. .88, No.6, pp.985-993 (2005.6), "Fumihiko Saito:" Semiconductor Chip Image Template Matching by Partial Random Search and Adaptive Search ", Journal of the Japan Society of Precision Engineering, Vol.61, No.11, pp. .1604-1608 (1995.11). "
The generalized Hough transform is a generalization of a Hough transform that determines a straight line that passes through the feature points in image data most from infinitely existing straight lines and is applied to a curve. Also, it is possible to perform shape recognition of image data using a reference table prepared in advance. The image approximation method using the generalized Hough transform is described in, for example, "Ballad, DH:" GENERALIZING THE HOUGH TRANSFORM TO DETECT ARBITRARY SHAPES ", Pattern Recognition, Vol. 13, No. 2, pp. 111-122 (1981)" , “Akio Kimura, Takashi Watanabe:“ Generalized Huff Transform extended as an arbitrary figure detection method invariant to affine transformation ”, IEICE (D-II), Vol. J84-D-II, No. 5 , pp. 789-798 (2001.5) ".
The Douglas-Peucker method is a method for performing shape recognition by broken line approximation. Regarding the image approximation method by the Douglas-Peucker method, for example, “Wu, ST, MRG:“ A non-self-intersection Douglas-Peucker Algorithm ”, Proceeding of Sixteenth Brazilian Symposium on Computer Graphics and Image Processing, IEEE, pp.60 -66 (2003) ".
The obtained approximate shape such as a polygon is defined as “the shape of the bottom surface of the projection”. Further, the length of the widest part of the bottom surface of the protrusion, which is specified by the following method, is referred to as “the maximum diameter of the bottom surface of the protrusion (hereinafter, may be simply referred to as the maximum diameter)”, and The center of the diameter is defined as "the center of the bottom surface of the protrusion (hereinafter, simply referred to as the center)."
(C) Specify the center of the bottom surface of the projection from the shape of the bottom surface of the projection. The center of the bottom surface of the protrusion can be obtained by general linear algebra calculation. For example, if the shape of the bottom surface of the projection is a perfect circle, draw a triangle that connects three points on the circumference, and set the intersection of two perpendicular bisectors of the two sides of the triangle as the center of the circle. Can be. Further, when the shape of the bottom surface of the protrusion is an ellipse, two line segments connecting two points on the outer periphery of the ellipse are drawn so as to be parallel, and each midpoint of the two parallel line segments is connected, The center of the connected line segment can be set as the center.
Further, when the shape of the bottom surface of the projection is polygonal, the center of the bottom of the projection can be calculated by the following method.
(I) First, a diagonal line is connected from one vertex of the polygon to each of the other vertices except for the two vertices adjacent to the one vertex, and the polygon is divided into a plurality of triangles.
(Ii) Find the center of gravity of each divided triangle.
(Iii) Next, the center of gravity of each triangle is connected to form a polygon.
(Iv) When the shape of the bottom surface of the protrusion is an odd-numbered polygon, the operations (i) to (iii) are repeated until the polygon formed in (iii) becomes a triangle. On the other hand, when the shape of the bottom surface of the projection is an even-numbered polygon, the operations (i) to (iii) are repeated until the polygon formed in (iii) becomes a quadrangle.
(V) When the shape formed from the center of gravity of each divided triangle becomes a triangle by the above-described operations (i) to (iv), the center of gravity of the triangle becomes the center (center of gravity) of the bottom surface of the protrusion. .
On the other hand, when the shape formed from the center of gravity of each of the divided triangles becomes a quadrangle by the above-described operations (i) to (iv), the center of gravity of the quadrangle is obtained by the following method. First, the quadrangle is divided into two triangles by one diagonal line, the respective centers of gravity of the two triangles are obtained, and the two centers of gravity are connected by a straight line. Next, the quadrangle is divided into two triangles by another diagonal line, and the respective centers of gravity of the two triangles are obtained, and the two centers of gravity are connected by a straight line. The intersection of the two straight lines is the center (center of gravity) of the bottom surface of the projection.

(D) The size of the projection is defined by the maximum diameter of the bottom surface of the projection. The length of the maximum diameter of the bottom surface of the projection is determined from the comparison between the pixel size and the number of pixels in the scale of the SEM image or the AFM image. The maximum diameter is the widest part in the shape of the bottom surface of the protrusion, and is the widest line segment among the lengths of line segments passing through the center of the bottom surface and connecting two points on the outer periphery of the shape of the bottom surface. Say. Specifically, when the shape of the bottom surface is a perfect circle, the maximum diameter refers to the diameter of the perfect circle, and when the shape of the bottom surface is an ellipse, the maximum width passes through the center of the ellipse and Means the longest line segment among the line segments connecting the two points. When the shape of the bottom surface is a polygon, the maximum diameter refers to the longest line segment among the line segments passing through the center of the polygon and connecting two points on the outer periphery of the polygon.
By performing statistical processing on the calculated maximum diameter, an average value and a variance of the maximum diameter of the bottom surface of the protrusion are obtained. The existing spreadsheet software is used for statistical processing. When calculating the average value and the variance of the maximum diameter, it is desirable to exclude outliers. The outlier means that the absolute value of the standardized score calculated by the following formula is 3 or more.
Standardized score = (maximum diameter of individual projections-average of maximum diameter) / standard deviation

(E) Next, the position of each projection is converted into coordinates. The position of the projection means “the position of the center of the bottom surface of the projection”.
First, the origin is set at a desired position in the SEM image or the AFM image. For example, the lower left in the SEM image or the AFM image is set as the origin. Next, from the origin, the sheet surface of the low-reflection sheet in the image, that is, one direction corresponding to the length direction in the surface having the protrusions of the low-reflection resin layer is defined as the x-axis, and one direction corresponding to the width direction. Defined as the y-axis. By using an image as a coordinate plane in this way, the position of each projection can be converted to coordinates.
From the coordinates of the positions of the protrusions, the distance between the protrusions of one specific protrusion and a plurality of adjacent protrusions, that is, the center-to-center distance is calculated. The center-to-center distance is calculated by the following formula, and the minimum distance among the calculated center-to-center distances is defined as “nearest center-to-center distance”.
Center-to-center distance = {(x ₁ −x ₂ ) ² + (y ₁ −y ₂ ) ² } ^1/2 }
Note that x ₁ and y ₁ in the formula are an x coordinate and ay coordinate indicating the position of a specific one protrusion. Further, x ₂ and y ₂ are the x and y coordinates indicate the position of protrusions adjacent to the protruding portion of the one particular.
The center-to-center distance is calculated from a comparison between the pixel size of the scale of the SEM image or the AFM image and the number of pixels.
The average value and the variance of the closest center distances are calculated by extracting the closest center distances of the respective protrusions by the above-described method and performing statistical processing with existing spreadsheet software. When calculating the average value and the variance of the closest center-to-center distance, it is desirable to exclude outliers. The outlier means that the absolute value of the standardized score calculated by the following formula is 3 or more.
Standardized score = (distance between closest centers of individual protrusions−average value of distance between closest centers) / standard deviation

(F) Next, the position of the top from the center of the bottom surface of the projection is indicated by an azimuth angle φ (0 ° ≦ φ <360 °), thereby defining the direction indicated by the vertex of the projection. The azimuth angle φ is defined by an angle formed by a side connecting the center and the top of the projection with respect to the x-axis in a plan view of a coordinate plane set when the position of the projection is coordinated.
The azimuth angle φ is determined for each of the extracted protrusions, the absolute value of the value obtained by dividing the sum of the cos values of the respective azimuth angles φ of the protrusions by the number of extraction points, and the sum of the sin values of the respective azimuth angles φ by the number of extraction points Calculate the absolute value of the divided value. This calculation uses existing spreadsheet software.

Since the `` center '' and `` maximum diameter '' of the bottom surface of the projection are defined by the above-described method, the `` center '' can be rephrased as `` center of gravity '' according to the approximate shape of the bottom surface, , "Maximum diameter" can be rephrased as "maximum width".
Similarly, the “distance between closest centers” of adjacent protrusions can be rephrased as “distance between closest centers of gravity”, and the azimuth φ is defined as “the top of the protrusion from the center of the bottom surface of the protrusion. The “position” can be rephrased as “the position of the top of the projection from the center of gravity of the bottom of the projection”.
That is, the bottom surface of the protrusion has an average maximum width passing through the center of gravity of the bottom within the range of 250 nm or more and 500 nm or less, and is closest to the center of gravity of the one protrusion and the bottom of the one protrusion. The surface having the center of gravity between the other protrusions having the center of gravity of the bottom surface at the position is 400 nm or less, the dispersion of the distance between the centers of gravity is 10,000 or more, and the surface of the low reflection resin layer having the protrusions. The length direction and the width direction are defined by the x-axis direction and the y-axis direction, and the position of the top of the projection from the center of gravity of the bottom surface of the projection is defined by an azimuth angle φ (0 ° ≦ φ < 360 °) and when the number of extraction points of the protrusion is n (n ≧ 30), | Σ _{(k = 1 to n)} cosφ _k /n|≦0.25 and | Σ _{(k = 1 ~} N ₎ Satisfies the relationship sinφk / _n | _≦ 0.25.

  The value of the variance calculated in the quantification of each parameter is generally calculated by dividing the value calculated from the average value, that is, the sum of the root-mean-square differences between the measured value and the average value of the measured values, by the number of extraction points. Value.

(2) Parameters Next, parameters that define variations in the shapes and arrangement positions of the protrusions in the present invention will be described.

(A) Size of Projection The size of the projection refers to the maximum diameter (maximum width) of the bottom surface of the projection, and is a portion indicated by R in FIGS. 2 and 4A. FIG. 4 is a planar SEM image of the surface of the low reflection sheet according to the present invention having a projection, and T in FIG. 4A indicates the top of the projection.

In the present invention, the average of the maximum diameters of the bottom surfaces of the protrusions may be in the range of 250 nm or more and 500 nm or less, and particularly preferably in the range of 300 nm or more and 400 nm or less. If the average of the maximum diameters of the bottom surfaces of the protrusions is larger than the above range, geometric optical scattering becomes more dominant than Mie scattering, so that forward scattering is less likely to occur, and light absorption to the low-reflection resin layer is reduced. This is because a desired reflectance reduction effect may not be obtained. This is because, in spherical particles, the diameter governed by geometrical optical scattering is several μm or more, but the scattering in the projection shape shows different behavior, and in the present invention, the bottom surface of the projection has the maximum diameter in the above range. This is because it is assumed that Mie scattering becomes dominant in the case of a shape.
Further, the number of projections per unit area of the low-reflection resin layer is reduced, so that it is difficult for reflection to occur many times, and it may be difficult to reduce the reflectance.
On the other hand, if the average of the maximum diameters of the bottom surfaces of the projections is smaller than the above range, Rayleigh scattering becomes dominant, so that forward scattering is unlikely to occur, and light absorption to the low-reflection resin layer may be reduced. Because.

When the average of the maximum diameter of the bottom surface of the projection is within the above range, the dispersion of the maximum diameter of the bottom surface of the projection is preferably 10,000 or more. This is because it is possible to suppress a problem that the intensity of light of a specific wavelength is increased by interference. The upper limit of the dispersion is not particularly limited, and can be set in a range that can be designed for manufacturing, and is preferably, for example, 18000 or less.
The unit of dispersion of the maximum diameter of the bottom surface of the protrusion is nm ² .

(B) Positional relationship between adjacent protrusions The position of the protrusion refers to the position of the center (center of gravity) of the bottom surface of the protrusion. That is, it refers to the position of the center of the maximum diameter (maximum width) of the bottom surface of the projection, and is the portion indicated by O in FIGS.
In the present invention, the positional relationship between adjacent protrusions is determined by determining the position of one protrusion and the center of the bottom (center of gravity) closest to the center (center of gravity) of the bottom of the one protrusion. It is defined by the average of the distance between the centers (centroids).

Here, the closest center-to-center distance is calculated and quantified by the method described above, and will be described with reference to the drawings. That is, as shown in FIG. 4B, a protrusion 3B having a center O at a position closest to the center O of the protrusion 3A is extracted from the protrusions adjacent to the protrusion 3A, and the distance L1 between the centers is extracted. Is calculated as the closest center-to-center distance. Next, among the protrusions adjacent to the protrusion 3B, the protrusion 3C having the center O at the position closest to the center of the protrusion 3B is extracted, and the center distance L2 is calculated as the closest center distance.
The average of the closest center-to-center distances is calculated by repeating the above operation, calculating the total sum of the closest center-to-center distances for the number of extraction points of the protrusion, and dividing the sum by the number of extraction points.

In the present invention, the average of the closest center-to-center distances may be 400 nm or less, and particularly preferably 360 nm or less, particularly preferably 350 nm or less. If the average of the closest center-to-center distances is larger than the above range, adjacent projections are not in close contact, and there are many flat areas where no projections are formed (hereinafter, sometimes referred to as non-projection areas). As a result, the reflectance reduction effect may be reduced due to the reflection of light generated in the non-projection region.
The lower limit of the average of the closest center-to-center distances is not particularly limited, and can be set within a range that can be designed for manufacturing, and is preferably, for example, 280 nm or more.

Further, when the average of the closest center-to-center distances is within the above range, the dispersion of the closest center-to-center distances may be 10,000 or more, preferably 11,000 or more, particularly preferably 12,000 or more. If the variance of the distance between the nearest centers is smaller than the above range, a large number of protrusions will be arranged at a uniform pitch width, and the intensity of light of a specific wavelength will increase due to interference, and the desired reflectance reduction effect will be obtained. This is because it may be difficult to exhibit.
The upper limit of the dispersion is not particularly limited, and can be set within a range that can be designed for manufacturing, and is preferably, for example, 14,000 or less.
The unit of dispersion of the distance between the closest centers is nm ² .

(C) The direction indicated by the apex of the protrusion The direction indicated by the apex of the protrusion refers to the direction in which the apex of the protrusion is located with respect to the center (center of gravity) of the bottom surface of the protrusion on the surface of the low-reflection resin layer. .
That is, as shown in FIG. 3, the length direction and the width direction in the plane of the low-reflection resin layer are defined in the x-axis direction and the y-axis direction, and the projection from the center O of the bottom surface of the projection in plan view. Is indicated by the azimuth angle φ (0 ° ≦ φ <360 °), the direction indicated by the apex of the protrusion is defined. The azimuth angle φ is defined by the method described above.

In the present invention, the in-plane length direction and width direction of the low-reflection resin layer are defined as the x-axis direction and the y-axis direction, and the position of the top of the projection in plan view is indicated by an azimuth angle φ. Assuming that the number of extraction points of the protrusion is n (n ≧ 30), the absolute value of the value obtained by dividing the sum of the cos values of the respective azimuth angles φ of the protrusion by the number of extraction points (that is, | Σ _{(k = 1 to n)} cos φ _k / n |) and the absolute value of the value obtained by dividing the sum of the sin values of each azimuth angle φ by the number of extraction points (that is, | Σ _{(k = 1 to n)} sinφ _k / n |), Variations can be defined.

Here, in the case where the vertices of the plurality of protrusions are arranged facing in the same fixed direction, | Σ _{(k = 1 to n)} cos φ _k / n | and | Σ _{(k = 1 to n)} sin φ _k / n The value of | increases. On the other hand, when the plurality of protrusions are randomly arranged in different directions, | Σ _{(k = 1 to n)} cosφ _k / n | and | Σ _{(k = 1 to n)} sinφ _k / n | The value decreases.
In the present invention, by satisfying the relationship of | Σ _{(k = 1 to n)} cos φ _k /n|≦0.25 and | Σ _{(k = 1 to n)} sin φ _k /n|≦0.25, The vertices of the plurality of protrusions are oriented in random directions so that the reflectance can be reduced regardless of the incident angle of light. Above all, it is preferable to satisfy the relationship of | (Σ _{(k = 1 to n)} cos φ _k ) /n|≦0.15 and | Σ _{(k = 1 to n)} sinφ _k /n|≦0.15, and in particular, | Σ _{(k = 1 to n)} cosφ _k /n|≦0.10 and | Σ _{(k = 1 to n)} sinφ _k /n|≦0.10 are preferably satisfied. When the values of | Σ _{(k = 1 to n)} cos φ _k / n | and | Σ _{(k = 1 to n)} sinφ _k / n | are larger than the above ranges, the vertices of the plurality of protrusions are constant and the same. It is oriented in the direction and is arranged with high regularity. For this reason, light incident from a specific angle is reflected at a high reflectance, and the degree of reduction in the reflectance may differ depending on the incident angle of the light.
Note that the number of extraction points n may be 30 or more, and more preferable points are the same as those already described.

(3) Others The height of the protrusion is not particularly limited as long as it is a size capable of providing the above-described parameters. For example, the height is preferably in the range of 100 nm to 10 μm, and particularly preferably in the range of 300 nm to 1 μm. preferable. If the height of the projection is smaller than the above range, the curvature of the top of the projection becomes large, so that geometric optical scattering becomes more dominant than Mie scattering, and forward scattering is less likely to occur. Light absorption may be reduced. On the other hand, if the height of the projection is larger than the above range, it may be difficult to manufacture the projection into a desired shape.
The height of the protrusion refers to a length from the surface of the low reflective resin layer protruding portion is formed to the apex of the protrusion, a portion indicated by h ₁ in FIG. The height of the protrusion is determined from a local maximum point detected by the method described in the section “(1) Parameter quantification method” at a specific reference position (for example, the root position of the protrusion is set to height = 0). , The difference between the relative heights of the respective local maximum point positions is obtained and converted into a histogram, calculated from the frequency distribution based on the histogram, and averaged.

When the height of the projection is within the above range, the desired aspect ratio reduction effect (h ₁ / R in FIG. 2) of the height with respect to the maximum diameter of the bottom surface of the projection exhibits a desired effect. Whatever is possible, for example, the range of 0.3 to 30 is preferable, and the range of 0.8 to 3 is particularly preferable. If the aspect ratio is smaller than the above range, light is less likely to be reflected at the projection, and the reflectivity reduction effect may not be sufficiently exhibited. On the other hand, if the aspect ratio is larger than the above range, shaping becomes difficult and the projection may not have a desired shape.

The protrusion has a convex conical structure. For this reason, the low reflection sheet of the present invention has a manufacturing advantage that the shape of the projection can be accurately shaped and the productivity is improved.
Generally, in a low-reflection sheet in which projections are regularly arranged, a method of increasing the surface area by changing the shape of the projections to a multi-peaked shape with a branched top in order to improve the reflectance reduction effect is used. However, such a shape may not be accurately formed. On the other hand, in the present invention, since the reflectance is reduced by giving the desired variation to the projections, the projections do not need to have a multimodal shape, and the individual projections can be accurately shaped. It is possible.
The tip of the top of the projection may be pointed or have a curvature. Above all, it is preferable that the tip is sharp because light absorption into the low-reflection resin layer by Mie scattering increases.

The shape of the bottom surface of the projection is not particularly limited as long as the above-mentioned parameters can be specified by approximation. For example, in addition to a circular shape such as a circle and an ellipse, a pentagon, a hexagon, an octagon, and a ten Examples include polygonal shapes such as a diagonal shape.
Further, the side surface shape of the projection may be linear or curved in the longitudinal section of the projection. Furthermore, the side surface shape of the protrusion may be a multi-step shape. In particular, it is preferable that the side surfaces of the protrusions have a multi-stage shape. This is because reflection and Mie scattering many times occur more easily at the projection.

2. Low Reflective Resin Layer In the present invention, in order to exhibit a desired reflectance reduction effect, it is necessary that a large number of protrusions have a variation defined by quantification of the above-described parameters. In the present invention, the projections are formed on the low-reflection resin layer made of the cured product of the resin composition, so that the accuracy of the shape of each projection is high and a desired variation can be exhibited.

  The resin composition is not particularly limited as long as it can form a large number of protrusions having the above-described variation, and includes at least a resin, and optionally includes other components such as a polymerization initiator. contains.

The resin is not particularly limited as long as it can form a protrusion having a desired shape and arrangement variation. Such resins include, for example, ionizing radiation curable resins such as acrylates, epoxies, and polyesters, thermosetting resins such as acrylates, urethanes, epoxies, and polysiloxanes, acrylates, polyesters, and polycarbonates. A variety of materials, such as thermoplastic resins such as polyethylene-based, polyethylene-based, and polypropylene-based resins, and molding resins in various cured forms can be used. In addition, ionizing radiation means an electromagnetic wave or a charged particle having energy capable of polymerizing and curing a molecule, for example, all ultraviolet rays (UV-A, UV-B, UV-C), visible light, and gamma rays. , X-rays, electron beams and the like.
Above all, when the low reflection sheet of the present invention is used as a light shielding sheet, a polyester resin is preferred from the viewpoint of excellent hardness, scratch resistance and flatness. When the low-reflection sheet of the present invention is used as a skin material such as synthetic leather or a design sheet, a polyurethane resin is preferred from the viewpoint of flexibility, tactile sensation and the like.

  The resin composition may include an optional material as needed. Optional materials include, for example, a refractive index adjuster, a polymerization initiator, a mold release agent, a photosensitizer, an antioxidant, a polymerization inhibitor, a crosslinking agent, an infrared absorber, an antistatic agent, a viscosity adjuster, and an adhesive. An enhancer and the like can be contained. As the refractive index adjuster, for example, a low refractive index material disclosed in JP-A-2013-142821 or the like can be used.

The low reflection resin layer may be transparent or opaque. Further, the low reflection resin layer may be colored. When the low reflection resin layer is colored, it may be the same color as the colored base material or may be a different color.
The colorant that can be contained in the low reflection resin layer is not particularly limited, and a colorant or the like described in the section of “B.
The average particle size of the colorant contained in the low-reflection resin layer may be any size that does not affect the reflectance reduction effect due to the unevenness of the projections.

The thickness of the low-reflection resin layer is not particularly limited, and can be appropriately set in consideration of the material to be used, the required strength, and the like. For example, the thickness is preferably in a range of 3 μm to 200 μm, and particularly preferably in a range of 5 μm to 100 μm. Is preferred.
The portion of the thickness of the low-reflecting resin layer refers to a length from the surface on which the projecting portion of the low-reflecting resin layer is not formed to the apex at the highest point of the protrusion, indicated by h ₂ 1 It is.

The low reflection resin layer preferably has a high haze value. This is because the higher the haze value, the greater the variation in the shapes and arrangement positions of the projections, so that the low-reflection sheet of the present invention can exhibit an excellent reflectance-reducing effect. Specifically, the haze value of the low reflection resin layer may be 70% or more, and particularly preferably 80% or more. The upper limit of the haze value is preferably 95% or less.
When the haze value is smaller than the above range, the projections formed on the surface of the low reflection sheet do not have a desired variation in shape and arrangement position, and the reflection to the low reflection resin layer by multiple reflection of light and Mie scattering. This is because light absorption hardly occurs, and the reflectivity reduction effect of the low reflection sheet of the present invention may not be exhibited. On the other hand, if the haze value is larger than the upper limit, it may be difficult to produce a desired projection shape.
The haze value can be measured using a haze meter (trade name: Haze Guard, manufactured by Toyo Seiki Seisaku-sho, Ltd.) by a method based on JIS K7361.

B. Colored Substrate The colored substrate in the invention has a low-reflection resin layer having a large number of projections on at least one surface side.
The color of the colored base material is not particularly limited and can be appropriately selected depending on the use of the low reflection sheet of the present invention.For example, black, achromatic color such as white, red, blue, yellow, green, gray and the like. And chromatic colors. Above all, when the low-reflection sheet of the present invention is used as a light-shielding sheet, black or a dark color similar to black is preferable from the viewpoint of further increasing the reflectance reduction effect over the entire visible light wavelength range. The dark color is, for example, dark gray, brown, dark blue, dark green, rouge, dark purple, or the like, with a low lightness and a Y value in a Yxy color system using a standard light source C by the International Commission on Illumination CIE of 10% or less. Color. On the other hand, when the low reflection sheet of the present invention is used as a skin material such as synthetic leather or a design sheet, it may be achromatic or chromatic.
The achromatic color and the chromatic color conform to the definitions in JIS Z8102: 2001.

In the present invention, the colored substrate preferably has a high optical density in order to exhibit a desired reflectance reduction effect. Specifically, the optical density of the colored base material is preferably 2 or more. In particular, when the low reflection sheet of the present invention is used as a light shielding sheet, the optical density is preferably 3 or more. The upper limit of the optical density is not particularly limited, but is preferably 6 or less from the viewpoint of material selection of the colored base material.
The optical density of the colored substrate can be measured, for example, with X-Rite 361T (V) manufactured by Sakata Inx Engineering Co., Ltd.

  The coloring substrate is not particularly limited as long as it exhibits a desired color, and examples thereof include a coloring resin substrate in which a coloring agent is mixed with a resin, a coloring paper, a coloring cloth, and the like.

The resin used for the colored resin substrate is not particularly limited, and a cured resin obtained by curing a thermoplastic resin, a thermosetting resin, an ionizing radiation-curable resin, or the like can be used.
For example, acetyl cellulose resins such as triacetyl cellulose, polyethylene terephthalate, polyester resins such as polyethylene naphthalate, olefin resins such as polyethylene and polymethylpentene, acrylic resins, polyurethane resins, polyether sulfone and polycarbonate, Examples thereof include polysulfone, polyether, polyether ketone, acronitrile, methacrylonitrile, cycloolefin polymer, cycloolefin copolymer and the like. Further, the same resin as the resin constituting the low-reflection resin layer described in the section “A. Low-reflection resin layer” may be used.

  The colorant contained in the colored resin substrate is not particularly limited as long as it can exhibit a desired color, and generally used inorganic pigments, organic pigments, and the like can be used. Specifically, inorganic pigments such as titanium white, zinc white, red iron oxide, vermilion, ultramarine blue, cobalt blue, titanium yellow, graphite, carbon black, titanium black, etc .; isoindolinone, Hansa Yellow A, quinacridone, permanent red 4R Organic pigments such as phthalocyanine blue and aniline black; dyes; metal pigments composed of foil powders such as aluminum and brass; pearlescent pigments composed of foil powders such as titanium dioxide-coated mica and basic zinc carbonate. One or more of these can be selected.

  The average particle size of the colorant is not particularly limited as long as it can exhibit a desired color. For example, it is preferably in the range of 0.01 μm or more and 1 μm or less, and more preferably in the range of 0.01 μm or more and 0.5 μm or less. . When the average particle size of the colorant is smaller than the above range, the coloring base material may not exhibit a desired optical density, while when the average size is larger than the above range, the colorant is not dispersed in the coloring resin due to aggregation. There are cases. The average particle size of the colorant is determined by a centrifugal sedimentation method (measurement device: light transmission type / centrifugal sedimentation type particle size distribution analyzer “SA-CP3 type” manufactured by Shimadzu Corporation), measurement mode: 10 μm to 0.02 μm, acceleration: 120 rpm / min).

  The content of the colorant may be an amount capable of exhibiting a desired optical density, and can be appropriately selected depending on the average particle size of the colorant.

  The coloring resin base material may include a filler, a matting agent, a foaming agent, a flame retardant, a lubricant, an antistatic agent, an antioxidant, an ultraviolet absorber, a light stabilizer, a radical scavenger, a soft component (for example, if necessary) Various additives such as rubber) may be included.

  The colored resin substrate only needs to exhibit a desired optical density, and various forms such as a plate, a sheet, and a film can be used.

Examples of the colored paper used as the colored substrate include kraft paper, woodfree paper, various coated papers, cast coated paper, synthetic paper, and the like, to which the above-mentioned coloring agent is applied or added.
Examples of the colored cloth include a cloth formed by adding the above-mentioned coloring agent to the resin used for the above-mentioned colored resin base material to form a nonwoven fabric.

  The thickness of the colored base material is not particularly limited as long as it can support the low-reflection resin layer and can exhibit a desired optical density, but is, for example, within a range of 0.025 mm to 20 mm. preferable.

C. Others The low-reflection sheet of the present invention may have the above-described low-reflection resin layer on at least one surface side of the colored base material, but has the above-described low-reflection resin layer on both surfaces of the base material. The lamination mode can be selected according to the application. For example, when the low-reflection sheet of the present invention is used as a light-shielding sheet, light-shielding properties and flatness on both sides are required, so that an embodiment having a low-reflection resin layer on both sides of the substrate is preferable. On the other hand, when the low-reflection sheet of the present invention is used as a skin material such as synthetic leather or a design sheet, the low-reflection resin layer is usually provided on one surface side of the substrate.

The low reflection sheet of the present invention may be a single layer in which the coloring base material and the low reflection resin layer are integrated. That is, the low-reflection sheet of the present invention is a colored single layer in which the colored base material and the low-reflection resin layer are formed of the same resin material, and a large number of protrusions are desired on at least one surface of the single layer. May be formed with the above-mentioned variation. By forming a single layer in which the coloring base material and the low-reflection resin layer are integrated, the manufacturing process can be simplified and the material cost can be reduced.
As the resin material in the case where the coloring base material and the low-reflection resin layer are integrated into a single layer, the resin material described in the section “A. Low-reflection resin layer” described above is used. In addition, the colorant used in the single layer and the content thereof can be the same as the colorant and the content exemplified in the section “B. Colored base material”.
When a single layer is formed by integrating the colored base and the low-reflection resin layer, the thickness of the single layer can be equal to the thickness of the above-described colored base.

  When the low-reflection sheet of the present invention is a single layer in which the colored base material and the low-reflection resin layer are integrated, a number of protrusions are formed on at least one surface of the low-reflection sheet, It may have a large number of protrusions showing variations.

  The low reflection sheet of the present invention can have an optional layer as needed. Examples of the optional layer include a primer layer (adhesion stabilizing layer) formed between the low-reflection resin layer and the colored base material, and an adhesive layer or an adhesive layer for bonding the low-reflection sheet to an adherend. Can be.

Regarding the reflectance of the low reflection sheet of the present invention, the maximum reflectance in the visible light region of 380 nm to 780 nm is preferably 2.0% or less, and particularly preferably 1.5% or less. When the maximum reflectance of the low-reflection sheet is equal to or less than the above upper limit, a low reflectance can be exhibited over the entire wavelength range of visible light, and the reflectance-reducing effect of the low-reflection sheet of the present invention is sufficient. This is because it is exhibited and its effect can be visually confirmed.
Note that the maximum reflectance can be obtained by measuring total reflection with respect to 8 ° incident light (wavelength region of 380 nm to 780 nm) using a Scanning Spectrophotometer UV-3100PC (manufactured by Shimadzu Corporation) as a measuring device.

D. Manufacturing method The method for manufacturing the low-reflection sheet of the present invention is not particularly limited as long as it is a method capable of forming a low-reflection resin layer having a projection having at least a desired variation in shape and arrangement on a colored base material. For example, it can be manufactured by the following method.
First, a transfer master having a number of convex conical structures is prepared. It is assumed that the convex conical structure has a variation in shape and arrangement position defined by quantification of the three parameters described in the section “A. Low reflection resin layer”.
Next, a composition for forming a soft mold containing a curable resin is applied to the surface of the transfer master on which the convex conical structures are formed, and the applied layer is cured to transfer and form the soft mold. At this time, on one surface of the soft mold, a concave cone-shaped structure that is an inverted shape of the convex cone-shaped structure is formed.
Subsequently, the composition for forming a low-reflection resin layer is applied on the surface of the soft mold on which the concave conical structure is formed, and the application layer is cured with the colored substrate further disposed on the application layer. . This makes it possible to obtain a low reflection sheet having a low reflection resin layer having a large number of protrusions on one surface side of the colored base material. The protrusions correspond to the convex conical structures of the transfer original plate in terms of shape and arrangement variation.

  Further, as another manufacturing method, a soft mold obtained from the above-mentioned transfer original plate is wound around a roll to prepare a transfer roll, and after applying a composition for forming a low-reflection resin layer on a colored substrate, the transfer roll is formed. It is also possible to use a method in which a desired curing method is applied and the composition is cured and molded at the same time as the application layer is pressed.

The material of the transfer master is not particularly limited as long as a convex conical structure having a desired variation can be formed, and examples thereof include metals and resins. Among them, metals are preferable.
The method of manufacturing the transfer master is not particularly limited as long as it can have a convex conical structure having a desired variation in shape and arrangement position on the surface. For example, the surface of a stainless steel plate is blasted. It can be formed by processing and subjecting the processed surface of the stainless steel plate to electrolytic plating such as electrolytic nickel plating, electrolytic chromium plating, and electrolytic tin plating while gradually reducing the current value.
At this time, by adjusting the surface roughness of the blast, variations in the distance, directionality, and the like of the convex conical structure can be adjusted. Further, by adjusting the ratio of decreasing the current value stepwise, the height of the convex conical structure can be adjusted.

The curable resin contained in the composition for forming a soft mold may be any resin capable of accurately transferring the shape of the convex conical structure of the transfer master, such as a photocurable resin or an electron beam curable resin. , A thermosetting resin, a thermoplastic resin, or the like is used. Further, if necessary, the material may include any of the materials described in the section “A. Low reflection resin layer”.
The method for applying the composition for forming a soft mold is not particularly limited, and may be the same as the method generally used for forming a resin original plate.

  When the resin contained in the composition for forming a low reflection resin layer is a photocurable or electron beam curable resin, the soft mold preferably has light transmittance. When a colored substrate is arranged on the coating layer of the composition for forming a low-reflection resin layer, or when forming a single layer containing a coloring agent in the composition for forming a low-reflection resin layer, from the soft mold side This is because it is necessary to irradiate light, an electron beam, or the like to cure the coating layer.

The composition for forming a low-reflection resin layer contains the materials described in the section “A. Low-reflection resin layer”. The method of applying the composition for forming a low-reflection resin layer is not particularly limited, and a conventionally known application method can be applied.
The curing method and curing conditions for the composition for forming a low-reflection resin layer can be appropriately selected according to the type of the contained resin. For example, when the composition for forming a low-reflection resin layer contains an ultraviolet-curable resin, the composition can be cured by irradiating ultraviolet rays through a soft mold.

E. FIG. Uses The low reflection sheet of the present invention can be used for applications in which a reduction in reflectance is required, but among others, since it has a colored base material, it is required to have high light-shielding properties, and to applications where light transmittance is not required. Use is preferred. For example, when the low-reflection sheet of the present invention is black or dark and has high optical density, shutter blades or aperture blades such as lens shutters for digital cameras and digital video cameras, lens units for camera-equipped mobile phones and on-vehicle monitors Can be used for a fixed diaphragm in the inside, a diaphragm blade of a light amount adjustment module of a projector, and the like.
In addition, the low-reflection sheet of the present invention can be used as a skin material or a design sheet of synthetic leather or the like for the purpose of improving appearance and imparting design, because the surface can be made matte by reducing the reflectance. be able to.
Furthermore, the low reflection sheet of the present invention can be used for a stray light preventing member of an analytical instrument or an optical instrument.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and has substantially the same configuration as the technical idea described in the claims of the present invention, and any device having the same function and effect can be realized by the present invention. It is included in the technical scope of the invention.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

[Example 1]
A low reflection sheet was obtained by the following method.

(Preparation of transcription master)
The stainless steel plate was blasted and finished to have an arithmetic mean surface roughness (hereinafter abbreviated as Sa) in the three-dimensional surface roughness measurement of 0.2 μm. The surface was subjected to electrolytic chromium plating under the following conditions to obtain a transfer master A having a large number of convex conical structures A on the plate surface. In addition, the shape and the variation of the conical structure A and the shape and the variation of the protrusion A in the obtained low reflection sheet were the same.

<Conditions for electrolytic chrome plating>
Using a plating bath containing the following composition and using a graphite electrode as the anode, the current density was reduced from 80 A / dm ² by 2.0 A / dm ² every minute to finally 20 A / dm ^2. Then, a black chromium plating film was formed on the stainless steel plate by electrolytic plating.
<< Plating bath composition >>
Chromium ^{chloride: 200g / dm 3 (0.75mol /} dm 3)
-Ammonium chloride: 30 g / dm ³ (0.56 mol / dm ³ )
Oxalic ^{acid: 3g / dm 3 (0.024mol /} dm 3)
Barium carbonate: 5 g / dm ³ (0.025 mol / dm ³ )
Boric ^{acid: 30g / dm 3 (0.49mol /} dm 3)
Barium fluoride: 10 g / dm ³ (0.057 mol / dm ³ )

(Production of soft mold)
A UV-curable composition for forming a soft mold having the following composition was applied to the surface of the transfer master A on which the cone-shaped structure A was formed, and a polycarbonate (PC) film (Panlite) having a thickness of 0.2 mm was applied. UV irradiation with a wavelength of 365 nm and an irradiation energy of 170 mJ / cm ² from the PC film side. After transferring the conical structure A of the transfer master A and curing the composition for forming a soft mold, the transfer master A was peeled off to obtain a soft mold.

<Composition for forming soft mold>
・ Urethane acrylate: 35% by mass
・ 1,6-hexanediol diacrylate: 35% by mass
・ Pentaerythritol triacrylate: 10% by mass
・ Vinylpyrrolidone: 15% by mass
・ 1-hydroxycyclohexyl phenyl ketone: 2% by mass
・ Benzophenone: 2% by mass
・ Polyether-modified silicone oil: 1% by mass

(Production of low reflection sheet)
On the surface of the obtained soft mold, on which the inverted shape of the cone-shaped structure A was formed, a composition for forming an ultraviolet-curable low-reflection resin layer having the following composition was applied. A 2.0 mm black acrylic plate (Acrylite L manufactured by Mitsubishi Rayon Co., Ltd.) was arranged. UV irradiation was performed from the PC film side of the soft mold at a wavelength of 365 nm and irradiation energy of 170 mJ / cm ² to cure the composition for forming a low-reflection resin layer. Thereafter, the soft mold was peeled off to obtain a low-reflection sheet having a low-reflection resin layer having a large number of protrusions A on a black acrylic plate.

<Composition for forming low reflection resin layer>
・ Urethane acrylate: 35% by mass
・ 1,6-hexanediol diacrylate: 35% by mass
・ Pentaerythritol triacrylate: 10% by mass
・ Vinylpyrrolidone: 15% by mass
・ 1-hydroxycyclohexyl phenyl ketone: 2% by mass
・ Benzophenone: 2% by mass
・ Polyether-modified silicone oil: 1% by mass

[Example 2]
The stainless steel plate was blasted to Sa = 0.3 μm. The surface was subjected to electrolytic chrome plating under the following conditions to obtain a transfer master plate B having a large number of convex cone-shaped structures B on the plate surface. In addition, the shape and the variation of the conical structure B and the shape and the variation of the protrusion B in the obtained low reflection sheet were the same.

<Conditions for electrolytic chrome plating>
Using the same plating bath and anode as in Example 1, the current density was reduced from 80 A / dm ² by 1.0 A / dm ² every minute to 20 A / dm ² finally, and electrolytic plating was performed on a stainless steel plate. A black chromium plating film was formed by the treatment.

  A low reflection sheet having a large number of protrusions B was obtained in the same manner as in Example 1 except that transfer master B was used instead of transfer master A.

[Example 3]
The stainless plate was blasted to Sa = 0.2 μm. The surface was subjected to electrolytic chrome plating under the following conditions to obtain a transfer master C having a large number of convex cone-shaped structures C on the plate surface. The shape and the variation of the conical structure C and the shape and the variation of the projection C in the obtained low reflection sheet coincided with each other.

<Conditions for electrolytic chrome plating>
Using the same plating bath and the anode as in Example 1, was reduced by 1.8A / dm ² per minute current density from 80A / dm ^2, and finally the 20A / dm ^2, electrolytic plating on stainless steel plate A black chromium plating film was formed by the treatment.

  A low-reflection sheet having a large number of protrusions C was obtained in the same manner as in Example 1 except that transfer master C was used instead of transfer master A.

[Example 4]
The stainless steel plate was blasted to Sa = 0.15 μm. The surface was subjected to electrolytic chrome plating under the following conditions to obtain a transfer master D having a large number of convex cone-shaped structures D on the plate surface. In addition, the shape and the variation of the conical structure D and the shape and the variation of the protrusion D in the obtained low reflection sheet were the same.

<Conditions for electrolytic chrome plating>
Using the same plating bath and anode as in Example 1, the current density was reduced from 80 A / dm ² by 1.6 A / dm ² every minute to 20 A / dm ² finally, and electrolytic plating was performed on a stainless steel plate. A black chromium plating film was formed by the treatment.

  A low-reflection sheet having a large number of protrusions D was obtained in the same manner as in Example 1 except that transfer master D was used instead of transfer master A.

[Example 5]
The stainless plate was blasted to Sa = 0.25 μm. The surface was subjected to electrolytic chromium plating under the following conditions to obtain a transfer master E having a large number of convex cone-shaped structures E on the plate surface. In addition, the shape and the variation of the conical structure E and the shape and the variation of the protrusion E in the obtained low reflection sheet were the same.

<Conditions for electrolytic chrome plating>
Using the same plating bath and the anode as in Example 1, was reduced by 1.4A / dm ² per minute current density from 80A / dm ^2, and finally the 20A / dm ^2, electrolytic plating on stainless steel plate A black chromium plating film was formed by the treatment.

  A low reflection sheet having a large number of projections E was obtained in the same manner as in Example 1 except that the transfer master E was used instead of the transfer master A.

[Example 6]
The stainless plate was blasted to Sa = 0.25 μm. The surface was subjected to electrolytic chrome plating under the following conditions to obtain a transfer master F having a large number of convex cone-shaped structures F on the plate surface. The shape and variation of the conical structure F and the shape and variation of the projection F in the obtained low reflection sheet were the same.

<Conditions for electrolytic chrome plating>
Using the same plating bath and the anode as in Example 1, was reduced by 5.0A / dm ² per minute current density from 80A / dm ^2, and finally the 20A / dm ^2, electrolytic plating on stainless steel plate A black chromium plating film was formed by the treatment.

  A low reflection sheet having a large number of projections F was obtained in the same manner as in Example 1 except that the transfer master F was used instead of the transfer master A.

[Example 7]
The stainless plate was blasted to Sa = 0.25 μm. The surface was subjected to electrolytic chromium plating under the following conditions to obtain a transfer master G having a large number of convex conical structures G on the plate surface. The shape and the variation of the conical structure G and the shape and the variation of the projection G in the obtained low reflection sheet coincided with each other.

<Conditions for electrolytic chrome plating>
Using the same plating bath and anode as in Example 1, the current density was reduced from 80 A / dm ² by 0.5 A / dm ² every minute to 20 A / dm ² finally, and electrolytic plating was performed on a stainless steel plate. A black chromium plating film was formed by the treatment.

  A low reflection sheet having a large number of projections G was obtained in the same manner as in Example 1, except that the transfer master G was used instead of the transfer master A.

[Comparative Example 1]
The stainless plate was blasted to Sa = 0.25 μm. The surface was subjected to electrolytic chromium plating under the following conditions to obtain a transfer master H having a large number of convex cone-shaped structures H on the plate surface. In addition, the shape and the variation of the conical structure H and the shape and the variation of the protrusion H in the obtained low reflection sheet were the same.

<Conditions for electrolytic chrome plating>
Using the same plating bath and anode as in Example 1, the current density was reduced from 80 A / dm ² by 6.0 A / dm ² every minute to 20 A / dm ² finally, and electrolytic plating was performed on a stainless steel plate. A black chromium plating film was formed by the treatment.

  A low reflection sheet having a large number of protrusions H was obtained in the same manner as in Example 1, except that the transfer master H was used instead of the transfer master A.

[Comparative Example 2]
The stainless plate was blasted to Sa = 0.25 μm. The surface was subjected to electrolytic chromium plating under the following conditions to obtain a transfer master plate I having a large number of convex cone-shaped structures I on the plate surface. The shape and the variation of the conical structure I and the shape and the variation of the projection I in the obtained low reflection sheet coincided with each other.

<Conditions for electrolytic chrome plating>
Using the same plating bath and the anode as in Example 1, was reduced by 0.4 A / dm ² per minute current density from 80A / dm ^2, and finally the 20A / dm ^2, electrolytic plating on stainless steel plate A black chromium plating film was formed by the treatment.

  A low reflection sheet having a large number of protrusions I was obtained in the same manner as in Example 1 except that transfer master I was used instead of transfer master A.

[Comparative Example 3]
The stainless plate was blasted to Sa = 0.5 μm. The surface was subjected to electrolytic chromium plating under the following conditions to obtain a transfer master J having a large number of convex conical structures J on the plate surface. In addition, the shape and the variation of the conical structure J and the shape and the variation of the protrusion J in the obtained low reflection sheet coincided with each other.

<Conditions for electrolytic chrome plating>
Using the same plating bath and the anode as in Example 1, was reduced by 1.8A / dm ² per minute current density from 80A / dm ^2, and finally the 20A / dm ^2, electrolytic plating on stainless steel plate A black chromium plating film was formed by the treatment.

  A low reflection sheet having a large number of protrusions J was obtained in the same manner as in Example 1, except that the transfer master J was used instead of the transfer master A.

[Comparative Example 4]
The stainless plate was blasted to Sa = 0.25 μm. The surface was subjected to electrolytic chrome plating under the following conditions to obtain a transfer master K having a large number of convex cone-shaped structures K on the plate surface. In addition, the shape and the variation of the conical structure K and the shape and the variation of the projection K in the obtained low reflection sheet were the same.

<Conditions for electrolytic chrome plating>
Using the same plating bath and the anode as in Example 1, was reduced by 1.4A / dm ² per minute current density from 80A / dm ^2, and finally the 10A / dm ^2, electrolytic plating on stainless steel plate A black chromium plating film was formed by the treatment.

  A low reflection sheet having a large number of protrusions K was obtained in the same manner as in Example 1, except that the transfer master K was used instead of the transfer master A.

[Evaluation 1]
The low-reflection sheets obtained in Examples 1 to 7 and Comparative Examples 1 to 4 were observed under SEM under the following conditions. The scores shown in Table 1 were extracted from a large number of protrusions on the low-reflection resin layer for each of the examples, and the average and dispersion of the maximum diameter (maximum width) of the bottom surface of the protrusion and the dispersion of the protrusion from the SEM image in plan view. mean and variance of nearest center distance (closest distance between centers of gravity), and _{| Σ (k = 1~n) cosφ} k / n | values and _{| Σ (k = 1~n) sinφ} k / n | values I asked. In addition, about the quantification of each parameter using a planar SEM image, the method explained previously was used.
The bottom surface of the protrusion in each example was approximated to an octagon.
(conditions)
・ SEM: Field emission scanning electron microscope S-4500 (manufactured by Hitachi High-Technologies Corporation)
-Observation method: Top-View (from the side with the protrusion)
-Pretreatment: Pt-Pd sputter-Observation magnification: x10k
・ Field of view: 4 μm in length × 4 μm in width

[Evaluation 2]
The maximum reflectance of the low reflection sheets obtained in Examples 1 to 7 and Comparative Examples 1 to 4 was measured under the following conditions.
(conditions)
・ Measuring device: Scanning Spectrophotometer UV-3100PC (manufactured by Shimadzu Corporation)
・ Measurement method: Total reflection for 8 ° incident light (wavelength range 380 nm to 780 nm)

[Evaluation 3]
The haze value of the low reflection resin layer in the low reflection sheets obtained in Examples 1 to 7 and Comparative Examples 1 to 4 was measured by the following method.
(Measuring method)
In Examples 1 to 7 and Comparative Examples 1 to 4, a low reflective resin layer was formed on a PC film using a PC film instead of the black acrylic plate, and an evaluation sample was prepared. The haze value of each evaluation sample was measured by a method based on JIS K-7361 using a haze meter (trade name: Haze Guard manufactured by Toyo Seiki Seisaku-sho, Ltd.).

Table 1 shows the results of the evaluations 1 to 3. In Table 1, μ represents the average, and σ ² represents the variance.

When the low-reflection sheets prepared in Examples 1 to 7 were used as a light-shielding sheet for an optical measurement device, the effects of stray light could be sufficiently removed.
On the other hand, when the low-reflection sheets of Comparative Examples 1 to 4 were used as a light-shielding sheet of an optical measuring instrument, the removal of stray light was insufficient.

DESCRIPTION OF SYMBOLS 1 ... Colored base material 2 ... Low reflection resin layer 3, 3A, 3B, 3C ... Projection part 10 ... Low reflection sheet

Claims (4)

On at least one surface side of the colored base material, a low-reflection resin layer having a large number of protrusions,
The average of the maximum diameter of the bottom surface of the protrusion is in the range of 250 nm or more and 500 nm or less,
The average of the center-to-center distances of the one protrusion and the center of the bottom of the one protrusion having the center of the bottom surface closest to the center of the bottom is 400 nm or less, and the variance of the center-to-center distance is less than 400 nm. 10,000 nm ² or more,
The length direction and the width direction in the plane of the low reflection resin layer having the protrusion are defined in the x-axis direction and the y-axis direction, and the top of the protrusion from the center of the bottom surface of the protrusion in plan view. Is indicated by an azimuth angle φ (0 ° ≦ φ <360 °), and the number of extraction points of the protrusion is n (n ≧ 30),
| Σ _{(k = 1 to n)} cosφ _k /n|≦0.25 and | Σ _{(k = 1 to n)} sinφ _k /n|≦0.25
Meet the relationship,
The low reflection sheet, wherein the colored substrate has an optical density of 2 or more .   The low-reflection sheet according to claim 1, wherein the colored base and the low-reflection resin layer are a single layer integrated.   The low reflection sheet according to claim 1 or 2, wherein the haze value of the low reflection resin layer is 80% or more.   The reflection sheet according to claim 1, wherein an average of a maximum diameter of a bottom surface of the protrusion is in a range of 300 nm or more and 400 nm or less.