JP6274102B2 - Light diffusing sheet - Google Patents

Description

The present invention relates to a light diffusing sheet.
This invention claims priority based on Japanese Patent Application No. 2012-143088 for which it applied to Japan on June 26, 2012, and uses the content here.

In illuminating devices and liquid crystal backlights, a light diffusing sheet for diffusing light from a light source is used. As the light diffusing sheet, for example, a sheet having a light diffusing layer containing particles in a binder (see Patent Document 1) and a sheet having an uneven pattern on at least one side (see Patent Document 2) are known.
2. Description of the Related Art In recent years, with increasing interest in environmental problems, light sources using light-emitting diode light sources are rapidly spreading as light sources for lighting devices and liquid crystal backlights because of their power saving and long life.

JP-A-10-269825 JP 2008-302591 A

By the way, the light emitted from the light-emitting diode light source has high straightness and becomes point-like light. Therefore, a light diffusive sheet having higher light diffusibility is required for use in a lighting device or a liquid crystal backlight. Become. However, the light diffusing sheets described in Patent Documents 1 and 2 are not necessarily sufficiently light diffusive, and the point-like light emitted from the light emitting diode light source cannot be sufficiently diffused. Therefore, it is easy to visually recognize the light source of the light emitting diode through the light diffusing sheet.
Then, an object of this invention is to provide the light diffusable sheet | seat which has the outstanding light diffusibility.

The present invention includes the following aspects.
<1> By having a first concavo-convex pattern formed by repeating wavy unevenness along one direction Y, and repeating the wavy unevenness along the direction Y on the surface of the first uneven pattern A light diffusive sheet having the formed second concavo-convex pattern, the first concavo-convex pattern meandering, wherein the first concavo-convex pattern has a mode pitch of 3 to 20 μm and an orientation degree of 0.2 or more. The aspect ratio is 0.2 to 1.0, the second concavo-convex pattern has a mode pitch of 0.3 to 2.0 μm, an orientation degree of 0.2 or more, and the orientation direction of the first concavo-convex pattern and the first 2. A light diffusive uneven pattern forming sheet, wherein the difference between the alignment direction of the uneven pattern is within 5 °.
<2> The light diffusive uneven pattern forming sheet according to <1>, wherein the wavy unevenness of the first uneven pattern is sinusoidal.

The present invention has the following aspects.
[1] A light diffusing sheet having a first concavo-convex pattern and a second concavo-convex pattern formed on the surface of the first concavo-convex pattern on at least one side of the sheet, wherein the first concavo-convex pattern is , Formed on the surface of the sheet by arranging a plurality of protrusions along the first direction,
The second concavo-convex pattern is formed by arranging a plurality of ridges on the surface of the first concavo-convex pattern with respect to the first direction;
[2] The light diffusing sheet according to [1], wherein ridge lines of the plurality of protrusions forming the first concavo-convex pattern meander as viewed from the normal direction of the sheet;
[3] The light diffusing sheet according to [1] or [2], wherein ridge lines of the plurality of protrusions forming the second uneven pattern meander as viewed from the normal direction of the sheet;
[4] In the first uneven pattern, the degree of orientation _{C 1} indicating the degree of meandering of the ridge of the ridge is a 0.20 to 0.50, according to any one of [1] to [3] Light diffusing sheet of
[5] In the second uneven patterns, the degree of orientation _{C 2} indicating the degree of meandering of the ridge of the ridge is a 0.20 to 0.50, according to any one of [1] to [4] Light diffusing sheet of
[6] The light diffusing sheet according to any one of [1] to [5], wherein a difference between an orientation direction of the first uneven pattern and an orientation direction of the second uneven pattern is within 5 °. ;
[7] In the first concavo-convex pattern, the most frequent pitch P ₁ in the first direction of the ridge is 3 to 20 μm, and the aspect ratio A _{1 of the} ridge is 0.2 to 1.0. 1] to [6] The light diffusive sheet according to any one of the above;
[8] The light diffusion according to any one of [1] to [7], wherein in the second concavo-convex pattern, the most frequent pitch P2 in the first direction of the protrusion is 0.3 to ₂ μm. Sex sheet;
[9] The light diffusing sheet according to any one of [1] to [8], wherein the first uneven pattern and the second uneven pattern are formed only on one side of the sheet, The light diffusive sheet whose 1/10 value angle of light when light injects from the surface which does not have an uneven | corrugated pattern of the said sheet | seat is 65 degrees or more.

  The light diffusive sheet of the present invention has excellent light diffusibility.

It is an expansion perspective view which shows one Embodiment of the light diffusable sheet | seat of this invention. It is sectional drawing at the time of cut | disconnecting the light diffusable sheet | seat of FIG. 1 along a 1st direction. It is an expansion perspective view which shows an example of the 1st uneven | corrugated pattern of the light diffusable sheet of this invention. It is an example of the electron micrograph which image | photographed the 1st uneven | corrugated pattern of the light diffusable sheet of this invention, and the 2nd uneven | corrugated pattern from the normal line direction. It is an example of the electron micrograph which image | photographed the 1st uneven | corrugated pattern of the light diffusable sheet of this invention from the normal line direction. 6 is an image after a Fourier transform of the gray scale image of the electron micrograph of FIG. It is an image after carrying out the Fourier transform of the gray scale image of the electron micrograph of FIG. 7 is a graph created with the frequency of the distance (pitch) between the ridges 11a obtained from the Fourier transform image of FIG. 6 as the vertical axis and the distance from the center as the horizontal axis. In the Fourier transformed image of FIG. 5, so that the maximum frequency D ₁ of the pitch of the protrusions 11a passes through the X-axis, a Fourier transform image obtained by rotating the center portion of the Fourier transformed image as an axis. FIG. 10 is a graph created with the frequency of the period on the auxiliary line M ₁ obtained from the Fourier transform image of FIG. 9 on the vertical axis and the distance from the maximum frequency D ₁ on the horizontal axis. In the Fourier transform image of FIG. 6, an angle θ ₁ formed by a position D ₁ that indicates the maximum frequency of the pitch of the protrusion 11 a other than the center portion of the Fourier transform image and a line L ₁ drawn at the center portion of the Fourier transform image. It is drawing which described. 2 is an electron micrograph of an uneven pattern of a light diffusing sheet of Example 1. FIG. 4 is an electron micrograph obtained by photographing a concavo-convex pattern of a light diffusive sheet of Comparative Example 1. FIG. It is a figure used for description of the illumination intensity curve for evaluating light diffusivity. It is the photograph which image | photographed the state when light-emitting the illuminating device using the light diffusable sheet | seat of Example 1. FIG. It is the photograph which image | photographed the state when light-emitting the illuminating device using the light diffusable sheet | seat of Example 2. FIG. It is the photograph which image | photographed the state when light-emitting the illuminating device using the light diffusable sheet | seat of the comparative example 1. FIG.

  In the following description, the shape and arrangement of the light diffusive sheet of the present invention will be described with reference to the XYZ orthogonal coordinate system shown in FIG. In this specification, in this XYZ orthogonal coordinate system, the first direction is defined as the Y-axis direction, the second direction is defined as the X-axis direction, and the third direction is defined as the Z-axis direction. The third direction may be referred to as the normal direction of the light diffusive sheet.

(Light diffusion sheet)
One embodiment of the light diffusing sheet of the present invention will be described.
1 and 2 show the light diffusing sheet of this embodiment. The light diffusing sheet 1 of the present embodiment has a concavo-convex pattern 10 on at least one surface thereof. Here, the concavo-convex pattern 10 includes a first concavo-convex pattern 11 and a second concavo-convex pattern 12 formed on the surface of the first concavo-convex pattern 11.
The first concavo-convex pattern 11 is formed by arranging a plurality of protrusions along the first direction on the surface of the light diffusing sheet 1. Hereinafter, one of the protrusions of the first concavo-convex pattern 11 will be described as “protrusion 11a”, and the valley bottom portion of the recess between any adjacent protrusions 11a will be described as “recess 11b”.
Here, the “protrusion” means an elongated protrusion extending on the sheet surface.
In addition, “adjacent ridges” refers to an arbitrary ridge 11a and a ridge 11a that is disposed immediately beside it in the first direction.
The second concavo-convex pattern 12 is formed by arranging a plurality of protrusions on the surface of the first concavo-convex pattern 11 with respect to the first direction. Hereinafter, one of the protrusions of the second concavo-convex pattern 12 will be described as a “protrusion 12a”, and a valley bottom portion of a recess between any adjacent protrusions 12a will be described as a “recess 12b”.
In the present embodiment, when the surface of the light diffusive sheet 1 having the concavo-convex pattern 10 is observed from the normal direction, it is preferable that the ridge line of the protruding portion 11a meanders. That is, each ridgeline of the protrusion 11a has a traveling axis extending in the second direction, but it is preferable that the ridgeline meanders left and right about this traveling axis. Similarly, when the surface having the concavo-convex pattern 10 of the light diffusing sheet 1 is observed from the normal direction, it is preferable that the ridge line of the protrusion 12a meanders.
Here, the “ridge line of the protrusion 11a” means a line that connects the tops of the protrusion 11a. Further, the “ridge line of the ridge portion 12a” means a line that connects the top portions of the ridge portion 12a and continues.
Moreover, the ridgeline of the protrusion part 11a points out the line which looks white in the electron micrograph of FIG. Moreover, the ridgeline of the protrusion part 12a points out the line which looks white on the surface of the protrusion part 11a of the 1st uneven | corrugated pattern 11 in the electron micrograph of FIG.

  In one aspect of the present invention, each protrusion forming the first uneven pattern 11 may have a height difference in the second direction. Moreover, each protrusion which forms the 2nd uneven | corrugated pattern 12 may have a height difference in a 2nd direction. Here, “having a height difference in the second direction” means that in the cross-sectional view (FIG. 2) in which the light diffusing sheet 1 is cut along the first direction, It means that the height of the protruding portion 12a changes in the second direction. The height of the protrusion 11a and the height of the protrusion 12a will be described later.

In one aspect of the present invention, when the light diffusing sheet 1 is cut along the first direction, the cross-sectional view has a shape as shown in FIG. That is, the cross-sectional shape of the ridge portion 11a changes irregularly in the first direction, and a plurality of wavy cross sections of the ridge portion 12a are formed along the outline of the cross-sectional shape of the ridge portion 11a. It is preferable.
As shown in FIG. 2, the cross-sectional shape of the some protrusion 11a which forms the 1st uneven | corrugated pattern 11 is different, respectively, and is not the same. Similarly, the cross-sectional shapes of the protrusions 12a forming the second uneven pattern 12 are also different from each other and are not the same. In one aspect of the present invention, when the light diffusing sheet 1 is cut along the first direction, the cross-sectional shape of the protrusion 11a that forms the first uneven pattern 11 and the second uneven pattern 12 are formed. It is preferable that the cross-sectional shape of the ridge portion 12a that forms a pleat shape, a shape having a part of a spindle shape, or a dome shape extended in one direction.
In addition, when the light diffusing sheet 1 is cut along the first direction, it is preferable that at least one of the size and shape of the cross section of the protrusion 11a is changed along the second direction. . Similarly, when the light diffusing sheet 1 is cut along the first direction, at least one of the size and shape of the cross section of the protrusion 12a may change along the second direction. preferable. Such a shape produces irregularities of the ridges of the ridges constituting the first concavo-convex pattern 11 and the second concavo-convex pattern 12, and a light diffusive sheet that is uniform and does not generate a fringe pattern is obtained.
Here, the “fringe pattern” means a striped pattern generated when light passes through a light diffusion sheet having a regular uneven pattern.

FIG. 3 is an enlarged perspective view showing an example of the first uneven pattern 11 of the light diffusing sheet 1.
As shown in FIG. 3, the intervals between the ridge lines of the plurality of protrusions 11 a are irregularly changed in the first direction. Moreover, it is preferable that the space | interval of the ridgeline of the two adjacent protrusion parts 11a is changing irregularly and continuously in a 2nd direction. However, in the 1st direction and the 2nd direction, the part which the space | interval of the ridgeline of the protrusion part 11a does not change may be included. Moreover, the ridgeline of the protrusion part 11a may be branched into the ridgeline of arbitrary other protrusion part 11a in the middle, and the ridgeline of the some protrusion part 11a may overlap. Such branching or unity of the ridges of the ridges 11a is a factor that produces irregularities in the intervals between the ridges of the ridges 11a.
Here, “the distance between the ridge lines of two adjacent ridges 11a” means the distance (distance) between the tops of the two ridges 11a adjacent in the first direction. .

FIG. 4 is an example of an electron micrograph of the light diffusing sheet 1 taken from the normal direction of the first concavo-convex pattern 11 and the second concavo-convex pattern 12.
As shown in FIG. 4, the second concavo-convex pattern 12 is formed by arranging a plurality of protrusions 12 a on the surface of the first concavo-convex pattern 11.
The intervals between the ridge lines of the plurality of ridge portions 12a change irregularly in the first direction. Moreover, it is preferable that the space | interval of the ridgeline of the two adjacent protrusion parts 12a is changing irregularly and continuously in a 2nd direction. However, in the 1st direction and the 2nd direction, the part which the space | interval of the ridgeline of the protrusion 12a does not change may be included. Moreover, the ridgeline of the ridge part 12a may be branched into the ridgeline of any other ridge part 12a in the middle, and the ridgeline of the some protrusion part 12a may overlap.

As described above, the interval between the ridge lines of the ridges 11a of the first concavo-convex pattern 11 and the interval between the ridge lines of the ridges 12a of the second concavo-convex pattern 12 are not constant. In one embodiment of the light diffusing sheet of the present invention, "pitch" representing the distance between the ridges of the two ridges 11a adjacent to each other, it can be expressed as the pitch P ₁ most frequent. Here, the “most frequent pitch P ₁ ” means a distance between ridge lines having the highest appearance frequency among ridge line intervals (distance between ridge lines) of two adjacent ridges 11a.
In one aspect of the present invention, the most frequent pitch P ₁ of the first uneven pattern 11 is preferably 3 to 20 μm, more preferably 5 to 15 μm, and still more preferably 8 to 13 μm. . Even if the most frequent pitch P ₁ is less than the lower limit, that is, less than 3 μm, or exceeds the upper limit, that is, exceeds 20 μm, the light diffusibility is impaired.

The most frequent pitch P ₁ is a value obtained from the following equation (1).
Most frequent pitch P ₁ = 1 / R ₁ (1)
Specifically, the modal pitch P ₁ can be obtained from an electron microscopic image of the light diffusing sheet. Below, the calculation method of the most frequent pitch using an electron microscope is demonstrated.
First, the surface of the light diffusing sheet 1 on which the concave / convex pattern 10 is formed is observed with an electron microscope from the normal direction. The observation conditions are preferably an acceleration voltage of 15 to 20 kV and a working distance of about 5 to 15 mm. The observation magnification in the electron microscope observation is preferably adjusted as appropriate so that the number of arrangement of the protrusions 11a of the first concavo-convex pattern 11 is 20 to 50 rows.
Next, the obtained electron micrograph (FIG. 5) is two-dimensionally Fourier transformed to obtain a Fourier transformed image (FIG. 6). Here, when the obtained electron micrograph is a compressed image such as JPEG, it is preferable to perform a two-dimensional Fourier transform after converting to a gray scale image such as a TIFF image. In the Fourier transform image of FIG. 6, the orientation from the center means the periodic structure existing in FIG. 5, that is, the direction in which the protrusions 11 a forming the first concavo-convex pattern 11 are arranged. The distance means the reciprocal of the period of the periodic structure existing in FIG.
Further, the shading of the image in FIG. 6 represents the frequency of the periodic structure, and the lighter the light, the higher the frequency of the target periodic structure in the periodic structure included in FIG.
Subsequently, the electron microscope observation of the second concavo-convex pattern 12 is performed with the observation conditions unchanged. The observation magnification is appropriately changed so that the number of arrayed protrusions 12a in the first direction is 20 to 50 rows. The obtained electron micrograph (see FIG. 4) is two-dimensionally Fourier transformed to obtain a Fourier transformed image (FIG. 7). Here, when the obtained electron micrograph is a compressed image such as JPEG, it is preferable to perform a two-dimensional Fourier transform after converting to a gray scale image such as a TIFF image.
Then, other than the center of the Fourier transform image of Figure 6, a straight line is drawn L ₁ so as to pass through the position D ₁ indicating the maximum frequency of the pitch of the protrusions 11a, the pitch of the protrusions 11a on the straight line L ₁ A graph is created with the vertical axis as the frequency and the distance from the center (reciprocal of the period) as the horizontal axis (FIG. 8). In the graph of FIG. 8, the most frequent pitch P ₁ can be obtained from the reciprocal of the distance R ₁ at which the frequency is maximum.

The first uneven patterns 11 is preferably protrusions 11a aspect ratio _{A 1} of is 0.2 to 1.0, more preferably 0.3 to 0.7, 0.35 More preferably, it is -0.45. Even be greater than the upper limit the aspect ratio A ₁ is less than the lower limit, light diffusibility is impaired.

Here, the aspect ratio _{A 1} of the protrusions 11a is a value determined by the average height _{B 1} / modal pitch _{P 1} of the ridge portion 11a.
Average height B ₁ of the ridge portion 11a is determined as follows. That is, the surface of the light diffusing sheet 1 on which the concave / convex pattern 10 is formed is observed from the normal direction with an electron microscope, and a sectional view (see FIG. 2) cut along the first direction is obtained from the observed image. . Here, the observation conditions of the electron microscope may be the same as the conditions used in determining the most frequent pitch P ₁ of the foregoing.
As shown in FIG. 2, the height of the protrusion 11a forming the first uneven pattern 11 is 1 of the sum of the distances in the third direction from the two adjacent recesses 11b to the top of the protrusion 11a. / 2. That is, the height _{b i} protrusions 11a for forming the first uneven patterns 11, the height of the ridges 11a measured from the recess 11b on one side of the ridge portion 11a _{L i,} the other side When the height measured from the bottom of the concave portion 11b is R _i , b _i = (L _i + R _i ) / 2. In this way determine the height b _i of each ridge 11a. Then, by measuring the height R _i and L _i of 50 protrusions 11a calculates the height b _i, and averaging the height by determining the average height B _1.

The first concavo-convex pattern 11 in the present embodiment is obtained by observing the light diffusing sheet 1 from the normal direction, and the ridge lines of the protrusions 11a meander. In this specification, the degree of meandering of the ridge protrusions 11a of the first uneven patterns 11 that the degree of orientation C _1. As the value of the orientation degree C ₁ is large, the ridge line of the ridge portion 11a means that meanders. Here, the “degree of orientation C ₁ ” is the degree of meandering with respect to the second direction of the ridgeline of the ridge portion 11a. In other words, the "value of the orientation degree C ₁ is large" ridge of the ridge portion 11a, means in the state in which meanders in a large swing width to the left and right about the traveling axis of the above.
The degree of orientation C ₁ of the first concavo-convex pattern 11 is preferably 0.2 or more, more preferably 0.25 or more, and further preferably 0.30 or more. Less than the degree of orientation C ₁ is the lower limit, i.e., is less than 0.2, there is the light diffusing properties are impaired.
On the other hand, the orientation degree C1 of the _first uneven pattern 11 is preferably 0.50 or less, more preferably 0.40 or less, and further preferably 0.35 or less. Orientation degree C ₁ is less than the upper limit, i.e., if 0.50 or less can be easily produced a light diffusing sheet 1. That is, the degree of orientation C ₁ of the first uneven pattern 11 is preferably 0.20 to 0.50, and more preferably 0.30 to 0.40. If the degree of orientation _{C 1} is a 0.20 to 0.50, without the light diffusion is impaired, the preferred because it can easily manufacture a light diffusing sheet.

Orientation degree C ₁ is determined by the following method.
First, by using the Fourier transform image of FIG. 6 obtained when determining the most frequent pitch P ₁ , the center portion of the Fourier transform image is such that the maximum pitch frequency D ₁ of the protrusion 11 a passes on the X axis. A Fourier transform image rotated about the axis is created (FIG. 9). Here, the “X axis” refers to a line that passes through the center of the Fourier transform image and is horizontal to the image. Next, an auxiliary line M ₁ passing through the maximum frequency D ₁ and parallel to the first direction is drawn, the frequency of the period on the auxiliary line M ₁ is plotted on the vertical axis, and the distance from the maximum frequency D ₁ is plotted on the horizontal axis. Create (FIG. 10). From the graph of FIG. 10, the half-value W ₁ of the obtained peak (the width of the peak at a position where the frequency value of the period on the auxiliary line M ₁ becomes half of the maximum frequency D ₁ ) is obtained. The obtained value by applying the following equation (2) determines the degree of orientation C _1.
Degree of orientation C ₁ = W ₁ / R ₁ (2)

In the first concavo-convex pattern 11 in the present embodiment, the top of the ridge portion 11a and the concave portion 11b are rounded, and the wavy concavo-convex shape including the ridge portion 11a and the concave portion 11b is sinusoidal. Here, “sinusoidal” is a cross-sectional view of the first concavo-convex pattern 11 cut along the first direction, and the inclination of the tangent of the cross-sectional shape of the ridge portion 11a of the first concavo-convex pattern 11; It means that the inclination of the tangent of the cross-sectional shape of the recess 11b changes continuously.
It is preferable that the wavy unevenness including the protrusions 11a and the recesses 11b of the first uneven pattern 11 is sinusoidal because a sheet having excellent light diffusibility can be obtained.

In the present embodiment, the most frequent pitch P2 of the _second uneven pattern 12 is preferably 0.3 to 2.0 μm, more preferably 0.4 to 1.0 μm, and More preferably, it is 5-0.8 micrometers. Also be a most frequent pitch P ₂ is less than the lower limit value exceeds the upper limit, light diffusion is impaired.

Modal pitch P ₂ is a value obtained from the following equation (3).
Most frequent pitch P ₂ = 1 / R ₂ (3)
Specifically, the modal pitch P _2, using the Fourier transform image of FIG. 7, by the same method as the method of calculating the most frequent pitch P ₁ of the first uneven patterns 11, it can be obtained.
That is, a straight line is drawn so as to pass through a position indicating the maximum frequency of the pitch of the ridges 12a other than the center of the Fourier transform image of FIG. 7, and the pitch frequency of the ridges 12a on the straight line is plotted on the vertical axis. Create a graph with the horizontal axis representing the distance from the center (the reciprocal of the period). In this graph, the most frequent pitch P ₂ can be obtained from the reciprocal of the distance R ₂ having the maximum frequency.

The second uneven patterns 12 is preferably the aspect ratio _{A 2} protrusions 12a is 0.25 to 0.35, further preferably 0.28 to 0.33. Even the aspect ratio A ₂ is even less than the lower limit exceeds the upper limit, there is the light diffusing properties are impaired.

Here, the aspect ratio _{A 2} protrusions 12a is a value determined by the average height _{B 2} / modal pitch _{P 2} of the protrusions 12a.
Average height B ₂ of the protrusions 12a is determined as follows. That is, the surface of the light diffusing sheet 1 on which the concave / convex pattern 10 is formed is observed from the normal direction with an electron microscope, and a sectional view (see FIG. 2) cut along the first direction is obtained from the observed image. . Here, the observation conditions of the electron microscope may be the same as the conditions used in determining the most frequent pitch P ₁ of the foregoing.
As shown in FIG. 2, the height of the protrusion 12a forming the second uneven pattern 12 is ½ of the sum of the distances from the two adjacent recesses 12b to the top of the protrusion 12a. . Here, the distance from the recess 12b to the top of the ridge 12a is parallel to the line connecting the top of the ridge 11a and the recess 11b, and the imaginary line passing through the top of the ridge 12a. The distance in the vertical direction. That is, the height of the protrusions 12a to form the second uneven patterns 12, the recess the height of the ridges 12a measured from the recess 12b on one side of the projecting portions 12a L _S, the other side When the height measured from 12b is R _S , b _S = (L _S + R _S ) / 2. In this way, the height b _S of each protrusion 12a is obtained. Then, by measuring the height R _S of 50 protrusions 12a, and the average thereof height obtaining the average height B _2.

The second concavo-convex pattern 12 in the present embodiment also has the ridge line of the ridge portion 12a meandering when the light diffusing sheet 1 is observed from the normal direction. In the present specification, the degree of meandering of the ridge line of the ridge portion 12a with respect to the second direction is referred to as “degree of orientation C ₂ ”. As the value of the orientation degree C ₂ is large, the edge line of the ridge portion 12a means that meanders.
In one aspect of the present invention, the degree of orientation _{C 2} is preferably 0.2 or more, more preferably 0.25 or more, further preferably 0.30 or more. Less than the degree of orientation C ₂ is the lower limit, i.e., is less than 0.2, there is the light diffusing properties are impaired.
The degree of orientation C2 of the _second uneven pattern 12 is preferably 0.50 or less, more preferably 0.40 or less, and further preferably 0.35 or less. Orientation degree C ₂ is less than the upper limit, i.e., if 0.50 or less can be easily produced a light diffusing sheet. That is, the degree of orientation C2 of the _second uneven pattern 12 is preferably 0.20 to 0.50, and more preferably 0.25 to 0.35. If the degree of orientation _{C 2} is a 0.20 to 0.50, without the light diffusion is impaired, the preferred because it can easily manufacture a light diffusing sheet.

The degree of orientation C ₂ of the second concavo-convex pattern 12 is the same method as the degree of orientation C _{1 of} the first concavo-convex pattern 11 using the Fourier transform image (FIG. 7) obtained when determining the most frequent pitch P ₂ . Can be obtained.

The difference between the alignment direction of the first concavo-convex pattern 11 and the alignment direction of the second concavo-convex pattern 12 (hereinafter sometimes simply referred to as “difference in alignment direction”) is that the anisotropy of light diffusion is high. Therefore, it is preferable that it is as small as possible. That is, it is preferable that the difference in the orientation direction is small because the anisotropy of light diffusion is increased and a synergistic effect of anisotropic diffusion of the first uneven pattern 11 and the second uneven pattern 12 is obtained. In the present invention, the difference in orientation direction is preferably within 5 °, more preferably within 2 °. Further, the difference in orientation direction is preferably 1 to 5 °, and more preferably 1 to 2 °.
Here, the orientation direction of the first concavo-convex pattern 11 means a direction obtained by averaging the directions at the portions of the meandering ridgeline of the first concavo-convex pattern 11. Further, the orientation direction of the second concavo-convex pattern 12 means a direction obtained by averaging the directions of the meandering ridge lines of the second concavo-convex pattern 12.
The orientation direction of the first concavo-convex pattern 11 and the orientation direction of the second concavo-convex pattern 12 can be calculated based on an electron microscope image.
First, an electron microscope image showing 4 obtained when determining the most frequent pitch P ₁ described above, and in FIG. 5, to match the ridge line direction of the ridge common to these images.
In FIG. 6 which is the Fourier transform image of FIG. 5, a line L ₁ drawn from the position D ₁ indicating the maximum frequency of the pitch of the protrusion 11 a to the center of the Fourier transform image, other than the center of the Fourier transform image, The angle θ ₁ formed from the X axis is the orientation direction of the first concave / convex pattern 11 (see FIG. 11).
Line Next, in FIG. 7 is a Fourier transform image of FIG. 4, except the central portion of the Fourier transform image, from the position D ₂ indicating the maximum frequency of the pitch of the protrusions 12a, drawn in the center of the Fourier transform image An angle θ ₂ constituted by L ₂ and the X axis is defined as the orientation direction of the second concavo-convex pattern 12.
The difference in orientation direction can be determined from the difference between the obtained θ ₁ and θ ₂ , that is, the angle represented by θ ₁ −θ ₂ .

Moreover, in one aspect of the present invention, the 1/10 value angle of light when light is incident from a surface not having the first uneven pattern 11 and the second uneven pattern 12 of the light diffusing sheet 1 is , 65 ° or more is preferable. Further, the 1/10 value angle is more preferably 65 to 95 °, and further preferably 75 to 90 °. If the 1/10 value angle of light is 65 ° or more, the light diffusibility is excellent, which is preferable.
Here, the “1/10 value angle of light” can be obtained by the following method.
First, an illuminance curve is obtained by measuring transmitted scattered light using a goniometer (model: GENESIA Gonio / FFP, manufactured by Genesia). Specifically, the relative illuminance when the illuminance of light vertically emitted from the light diffusion sheet (the light emission angle of this light is 0 °) is set to 1 is the light emitted along the second direction or the first direction. Relative illuminance from an angle of −90 ° to 90 ° is measured at 1 ° intervals to obtain an illuminance curve. Here, the illuminance curve is a curve plotted as shown in FIG. 14 with the horizontal axis as the light output angle and the vertical axis as the relative illuminance.
Then, a 1/10 value angle of light (W _{2 in} FIG. 14) is obtained from the obtained illuminance curve.

The light diffusing sheet 1 may be a sheet itself obtained by a method for producing a light diffusing sheet to be described later, or a duplicate sheet obtained by duplicating a sheet obtained by a method for producing a light diffusing sheet as an original plate. It may be.
When the light diffusive sheet 1 is a sheet itself obtained by a method for producing a light diffusive sheet described later, the hard layer and the surface that meanderly deform when viewed from the cross section usually follow the deformation of the hard layer. It is composed of two layers of the base material layer deformed. In the case of a duplication sheet, usually, a single layer made of a resin having irregularities transferred to the surface, or an irregularity forming layer having irregularities transferred to one surface and irregularities of the irregularity forming layer are transferred. It is composed of two layers of a flat base material layer laminated on the surface that is not.

  In the light diffusive sheet 1 described above, the concavo-convex pattern 10 is composed of the first concavo-convex pattern 11 and the second concavo-convex pattern 12 formed on the surface of the first concavo-convex pattern 11. It has diffusivity. Therefore, the light diffusing sheet 1 itself can be used as a light diffusing sheet, and can also be used as an original sheet for producing a light diffusing sheet.

(Method for producing light diffusive sheet)
Next, an embodiment of a method for producing the light diffusing sheet 1 will be described.
The manufacturing method of the light diffusable sheet | seat 1 of this embodiment has a laminated | multilayer film formation process and a heat contraction process.

[Laminated film forming process]
In the laminated film forming step in the present embodiment, at least one hard layer (hereinafter referred to as “surface smooth hard layer”) having a smooth surface and comprising two kinds of resins is laminated on one surface of the heat-shrinkable resin film. This is a step of obtaining a laminated film. Here, the surface smooth hard layer is a layer having a center line average roughness of 0.1 μm or less as measured by the method described in JIS B0601, and does not soften under a temperature condition for shrinking the heat-shrinkable resin film. Is a layer. Moreover, not softening means that the Young's modulus of the surface smooth layer is 100 MPa or more.

The heat-shrinkable resin film means a film that shrinks (shrinks) in a specific direction when heated at a temperature of 80 to 180 ° C. As such a film, for example, a polyethylene terephthalate shrink film, a polystyrene shrink film, a polyolefin shrink film, a polyvinyl chloride shrink film, a polyvinylidene chloride shrink film, or the like can be used. Among these, it is preferable to use a polyethylene terephthalate shrink film or a polystyrene shrink film from the viewpoint of heat resistance.
In this embodiment, it is preferable to use a uniaxially stretched film as the heat-shrinkable resin film. Uniaxial stretching may be either longitudinal stretching or lateral stretching.
Further, the heat-shrinkable resin film is preferably stretched at a stretch ratio of 1.1 to 15 times, and more preferably stretched at 1.3 to 10 times.
Moreover, as a heat-shrinkable resin film, it is preferable that a shrinkage rate is 20 to 90%, More preferably, it is a film with 35 to 75%. In this specification, the shrinkage rate is (shrinkage rate [%]) = {(film length before shrinkage) − (length of film after shrinkage)} / (length of film before shrinkage) × 100 (where “the length of the film” means the length in the shrinking direction of the heat-shrinkable resin film). If the shrinkage rate is not less than the lower limit, that is, not less than 20%, the light diffusing sheet 1 can be more easily produced. On the other hand, it is difficult to produce a heat-shrinkable resin film having a shrinkage ratio exceeding the upper limit, that is, exceeding 90%.
The surface of the heat-shrinkable resin film is preferably flat. If the surface of the heat-shrinkable resin film is flat, it is preferable because the surface smooth hard layer can be easily formed on the surface. Here, “flat” means that the center line average roughness measured by the method described in JIS B0601 is 0.1 μm or less.

The glass transition temperature Tg ₁ of the resin constituting the heat-shrinkable resin film (hereinafter referred to as “resin L”) is preferably 40 to 200 ° C., and more preferably 60 to 150 ° C. The glass transition temperature can be measured by differential thermal analysis or the like. If the glass transition temperature Tg ₁ is 40 to 200 ° C., it can be formed more easily uneven pattern 10. That is, if the glass transition temperature Tg ₁ of the resin L is 40 to 200 ° C., the heat-shrinkable resin film composed of the resin L can be heated and shrunk at a temperature of 80 to 180 ° C. Since the uneven | corrugated pattern 10 can be formed in this, it is preferable.
The Young's modulus of the resin L is preferably 0.01 to 100 MPa and more preferably 0.1 to 10 MPa in the temperature range of the heat shrinking step, that is, in the temperature range of 80 to 180 ° C. If the Young's modulus of the resin L is equal to or higher than the lower limit value, it is a hardness that can be used as a base material, and if it is equal to or lower than the upper limit value, it is soft enough to follow and deform simultaneously when the surface smooth hard layer is deformed. That's it.
The resin having the glass transition temperature Tg ₁ and the Young's modulus as described above is preferably at least one selected from, for example, a polyethylene terephthalate resin, a polystyrene resin, and a polyvinyl chloride resin.

  As the two types of resins constituting the surface smooth hard layer (hereinafter, one is described as “resin M” and the other as “resin N”), for example, polyvinyl alcohol, polystyrene, acrylic resin, and styrene-acrylic resin are used. Polymers, styrene-acrylonitrile copolymers, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyethersulfone, fluororesin, and the like can be used.

Further, since the resin M and the resin N can easily form the second concavo-convex pattern 12, it is preferable that the glass transition temperatures are different from each other. Specifically, the glass transition temperature Tg _2M of the resin _M is a glass of the resin N. It is preferable that the transition temperature is higher than Tg _2N . Furthermore, (glass transition temperature Tg _{2M of} resin _M ) − (glass transition temperature Tg _2N of resin N) is preferably 10 ° C. or higher, more preferably 15 ° C. or higher.
On the other hand, since it becomes difficult to form the second uneven pattern 12 even if Tg _2M and Tg _2N are too far apart, Tg _2M -Tg _2N is preferably 20 ° C. or less, and more preferably 19 ° C. or less. . That is, the difference between the glass transition temperature Tg _2M of the resin _M and the glass transition temperature Tg _2N of the resin N is preferably 10 to 20 ° C., and more preferably 11 to 15 ° C.
The difference (Tg _2M −) between the glass transition temperature Tg _2M of the resin _M and the glass transition temperature Tg ₁ of the resin L is that the uneven pattern 10 composed of the first uneven pattern 11 and the second uneven pattern 12 can be easily formed. Tg ₁ ), the difference (Tg _2N −Tg ₁ ) between the glass transition temperature Tg _2N of the resin _N and the glass transition temperature Tg ₁ of the resin L is preferably 10 ° C. or more, more preferably 15 ° C. or more. It is preferably 20 ° C. or higher.

The glass transition temperatures Tg _2M and Tg _2N of the resin M and the resin N are both preferably in the range of 40 to 400 ° C., and more preferably in the range of 80 to 250 ° C. If Tg _2M and Tg _2N are not less than the lower limit and not more than the upper limit, that is, in the range of 40 to 400 ° C., the uneven pattern 10 can be more easily formed.
The Young's modulus of the resin M and the resin N is preferably in the range of 0.01 to 300 GPa and in the range of 0.1 to 10 GPa in the temperature of the heat shrinking process, that is, in the temperature range of 80 to 180 ° C. It is more preferable. If the Young's modulus of the resin M and the resin N is 0.01 GPa or more, the hardness is sufficient to maintain the shape of the concavo-convex pattern 10, and if the Young's modulus is less than the upper limit value, the concavo-convex pattern is more easily obtained. 10 can be formed.
In one embodiment of the present invention, the resin M is preferably an acrylic resin, a styrene-acrylic copolymer, or a styrene-acrylic copolymer. Further, the resin N is preferably an acrylic resin, a styrene-acrylic copolymer, or a styrene-acrylic copolymer. The combination of the resin M and the resin N is preferably an acrylic resin and an acrylic resin, an acrylic resin and a styrene-acrylic copolymer, or a combination of an acrylic resin and a styrene-acrylonitrile copolymer, and a combination of an acrylic resin and an acrylic resin. It is more preferable that

The thickness of the surface smooth hard layer is preferably more than 0.05 μm and not more than 5.0 μm, and more preferably 0.5 to 3.0 μm. When the thickness of the smooth surface hard layer on the range, the modal pitch P ₁ is an appropriate range, it is possible to increase the light diffusion property.
The thickness of the surface smooth hard layer may be continuously changed. When the thickness of the surface smooth hard layer is continuously changing, the pitch and height of the protrusions 11a of the first uneven pattern 11 formed after compression, that is, after the heat shrinking step, are continuous. To change.

As a method of laminating the surface smooth hard layer composed of the above-described resin M and resin N on the surface of the heat-shrinkable resin film, a heat-shrinkable resin film is used as a hard layer-forming coating material containing resin M and resin N. And a method of coating and drying continuously.
Examples of the method for preparing the hard layer forming paint include a method of diluting with a toluene solvent. The solid content concentration (concentration of resin M and resin N) of the hard layer forming coating is preferably 1 to 15% by mass and preferably 5 to 10% by mass with respect to the total mass of the coating. Is more preferable.
Examples of paint coating methods include air knife coating, roll coating, blade coating, Mayer bar coating, gravure coating, spray coating, cast coating, curtain coating, die slot coating, gate roll coating, size press coating, spin coating, Examples include dip coating.
Examples of the drying method include a heat drying method using hot air, infrared rays, or the like.
The dry coating amount of the resin solution on the heat-shrinkable resin film is preferably 1 to 10 g / m ² . If the dry coating amount of the resin solution is 1 to 10 g / m ² , it is preferable because the thickness of the surface smooth hard layer can be within the above-mentioned preferable range, and the uneven pattern 10 is easily formed on the surface smooth hard layer. .

[Heat shrinkage process]
In the heat-shrinking step, the laminated film is heated to shrink the heat-shrinkable resin film, thereby deforming the surface smooth hard layer so as to be folded, thereby forming the uneven pattern 10 on the surface of the heat-shrinkable resin film. It is a process.
In the heat shrinking step, the laminated film is preferably shrunk at a shrinkage rate of 40% or more. If the shrinkage rate is 40% or more, the portion where shrinkage is insufficient, that is, the portion where the uneven pattern 10 is not formed or the aspect ratio of the protrusions is not sufficiently large even if formed can be reduced. On the other hand, if the shrinkage rate is increased too much, the area of the obtained light diffusable sheet 1 is reduced and the yield is lowered. Therefore, the upper limit of the shrinkage rate is preferably 80%.

Examples of the method for heating the laminated film include a method of passing it through hot air, steam, or hot water. Among them, a method of passing it through hot air is preferable because it can be uniformly shrunk.
The heating temperature at which the heat-shrinkable resin film is thermally shrunk includes the kind of heat-shrinkable resin film to be used, the most frequent pitch P ₁ of the intended first concavo-convex pattern 11, the aspect ratio A _1, and the degree of orientation C _1. It is preferable to select appropriately according to the most frequent pitch P ₂ and the degree of orientation C ₂ of the target second uneven pattern 12.
Further, the heat shrinkage temperature is preferably set to a temperature equal to or higher than the glass transition temperature Tg ₁ of the resin L constituting the heat shrinkable resin film. When the thermal contraction is performed at a temperature of Tg ₁ or more, the first uneven pattern 11 can be easily formed.
When the glass transition temperature Tg _2M of the resin _M is higher than the glass transition temperature Tg _2N of the resin N, the heat shrinkage temperature is preferably less than (glass transition temperature Tg _2M + 15 ° C. of the resin M).
That is, in one aspect of the present invention, the heat shrinking step is performed by causing the laminated film obtained in the step to pass through hot air at 80 to 180 ° C., more preferably 120 to 170 ° C. It is preferable that it is a process of obtaining the sheet | seat in which the uneven | corrugated pattern 10 was formed in the surface of a surface smooth hard layer by deforming a property film and a surface smooth hard layer. The time for heating the laminated film with hot air is preferably 1 to 3 minutes, and more preferably 1 to 2 minutes. Moreover, as a wind speed of a hot air, it is preferable that it is 1-10 m / s, and it is more preferable that it is 2-5 m / s.

[Adjustment of uneven pattern characteristics]
By adjusting the conditions of the manufacturing method, the most frequent pitch P ₁ of the first concavo-convex pattern 11, the aspect ratio A ₁ of the ridge 11 a, the orientation degree C ₁ , and the most frequent pitch of the second concavo-convex pattern 12. P _2, it is possible to adjust the difference in the orientation direction of the orientation direction and the second uneven patterns 12 of the aspect ratio a ₂ protrusions _12a, and the degree of orientation C _2, first uneven patterns 11.
To adjust the modal pitch P ₁ may be determined as the mixing ratio of the glass transition temperature is high resin M and low resin N. As the blending ratio of the resin M is higher, the most frequent pitch P ₁ tends to increase. That is, if the blending ratio of the resin M and the resin N is 1: 1 to 1: 3, the most frequent pitch P1 of the _first uneven pattern 11 can be adjusted to a range of 3 to 20 μm.
The aspect ratio A ₁ the predetermined protrusions 11a, i.e., to the range of 0.2 to 1.0 may be determined as the mixing ratio of the glass transition temperature is high resin M and low resin N. The higher the mixing ratio of the resin M, the aspect ratio A ₁ is tend to be small. That is, the mixing ratio of the resin M and resin N is 1: 1 to 1: if 3, the aspect ratio _{A 1} of the protrusions 11a, can be adjusted in a range of 0.2 to 1.0.
The orientation degree _{C 1} the predetermined, i.e., to the range of 0.20 to 0.50 may be adjusted to shrinkage of the heat shrinking process. The degree of orientation C ₁ tends to increase as the shrinkage rate increases. That is, in the heat shrinkage process, shrinkage of the laminated film is equal 40% to 60%, it is possible to adjust the degree of orientation _{C 1} in the range of 0.20 to 0.50.
To adjust the modal pitch P ₂ may be determined as the mixing ratio of the glass transition temperature is high resin M and low resin N. The higher the mixing ratio of the resin M, modal pitch P ₂ tends to increase. That is, if the mixing ratio of the resin M and the resin N is 1: 1 to 1: 3, the most frequent pitch P2 of the _second uneven pattern 12 is adjusted to a range of 0.3 to 2.0 μm. Can do.
The aspect ratio _{A 2} protrusions 12a above a predetermined, i.e., to the range of 0.25 to 0.35 may be adjusted to shrinkage of the heat shrinking process. Also, the higher the mixing ratio of the resin M, the aspect ratio A ₂ tends to increase. That is, the mixing ratio of the resin M and resin N is 1: 1 to 1: if 3, the aspect ratio _{A 2} protrusions 12a, can be adjusted in a range of 0.25 to 0.35. Further, in the heat shrinkage step, if the shrinkage ratio 40% to 60% of the laminated film, the aspect ratio _{A 2} protrusions 12a, can be adjusted in a range of 0.25 to 0.35.
Range orientation degree C ₂ of the predetermined, i.e., in order to 0.20 to 0.50, the shrinkage of the heat shrinking step may be adjusted within a certain range. The degree of orientation C ₂ tends to increase as the shrinkage rate increases. That is, in the heat shrinkage process, shrinkage of the laminated film is equal 40% to 60%, it is possible to adjust the degree of orientation _{C 2} in the range of 0.20 to 0.50.
In order to adjust the difference between the orientation direction of the first concavo-convex pattern 11 and the orientation direction of the second concavo-convex pattern 12, the shrinkage rate of the heat shrinking process is adjusted after adjusting the blending ratio of the resin M and the resin N. do it. The difference in the orientation direction tends to increase as the blending ratio of the resin M increases and the shrinkage rate increases. That is, if the blending ratio of the resin M and the resin N is 1: 1 to 1: 3 and the shrinkage rate of the laminated film in the heat shrinking process is 40 to 60%, the orientation direction of the first uneven pattern 11 And the difference in the orientation direction of the second concavo-convex pattern 12 can be within 5 °.

[Other manufacturing methods]
Moreover, as a manufacturing method of a light diffusable sheet | seat, the method of following (1)-(4) is also applicable.
(1) A method of forming a laminated sheet by providing a surface smooth hard layer composed of two kinds of resins on one side of a resin layer for a substrate, and compressing the entire laminated sheet in one direction along the surface.
When the glass transition temperature of the resin layer for the substrate is lower than room temperature, the lamination sheet is compressed at room temperature. When the glass transition temperature of the resin layer for the substrate is room temperature or higher, the lamination sheet is compressed by the resin layer for the substrate. The glass transition temperature is not lower than the glass transition temperature of the surface smooth hard layer.
(2) A surface smooth hard layer made of two types of resins is provided on one side of the resin layer for the base material to form a laminated sheet, the laminated sheet is stretched in one direction, and the direction perpendicular to the stretching direction is contracted. The surface smooth hard layer is compressed in one direction along the surface.
When the glass transition temperature of the base material resin layer is lower than room temperature, the laminated sheet is stretched at room temperature. When the glass transition temperature of the base material resin layer is equal to or higher than room temperature, the laminated sheet is stretched at the base resin layer. The glass transition temperature is not lower than the glass transition temperature of the surface smooth hard layer.
(3) A surface smooth hard layer made of two kinds of resins is laminated on a resin layer formed of an uncured active energy ray curable resin to form a laminated sheet, and the active energy rays are irradiated to form a substrate. A method of compressing a surface smooth hard layer laminated on a substrate in at least one direction along the surface by shrinking the resin layer by curing.
(4) A surface smooth hard layer composed of two kinds of resins is laminated on the base resin layer expanded by swelling the solvent to form a laminated sheet, and the solvent in the base resin layer is dried. A method of compressing in at least one direction along the surface of the surface-smoothed hard layer laminated on the base material resin layer by shrinking by removing.

  In the method (1), as a method of forming a laminated sheet, for example, a resin solution or dispersion is applied to one surface of a resin layer for a substrate using a spin coater or bar coater, and the solvent is dried. And a method of laminating a surface smooth hard layer prepared in advance on one surface of the resin layer for the substrate.

  Examples of the method for compressing the entire laminated sheet in one direction along the surface include a method of compressing the laminated sheet by sandwiching one end portion of the laminated sheet and the opposite end portion thereof with a vise or the like. Moreover, as resin which comprises the resin layer for base materials, it is preferable to use a polyethylene terephthalate resin, a polystyrene resin, or a polyvinyl chloride resin. Moreover, resin L which comprises the above-mentioned heat-shrinkable resin film may be sufficient. Moreover, it is preferable to use the above-mentioned resin M and resin N as a surface smooth hard layer. Moreover, as thickness of a surface smooth hard layer, 0.5-3.0 micrometers is preferable and 1.0-2.0 micrometers is more preferable.

In the method (2), examples of the method of stretching the resin layer for the laminated sheet base material in one direction include a method of stretching one end portion of the laminated sheet and the opposite end portion thereof. .
In the method (3), examples of the active energy ray-curable resin include an ultraviolet curable resin and an electron beam curable resin.
In the method (4), the solvent is appropriately selected according to the type of resin constituting the substrate resin layer. The drying temperature of the solvent is appropriately selected according to the type of solvent.
Also in the smooth surface hard layer in the methods (2) to (4), the same resin component as that used in the method (1) can be used, and the thickness can be the same. The method for forming the laminated sheet is the same as the method (1), in which a resin solution or dispersion is applied to one side of the base resin layer and the solvent is dried. In addition, a method of laminating a surface smooth hard layer prepared in advance can be applied.

In the above manufacturing method, the surface smooth hard layer is composed of two kinds of resins, but is not limited thereto.
The light diffusing sheet can also be produced by using the one obtained by the above production method as an original sheet and transferring it to another material by the following method.
A resin or metal support for supporting the light diffusing sheet 1 may be attached to the original sheet.

Specific methods for producing a new light diffusing sheet using the original sheet include, for example, the following methods (a) to (c).
(A) A step of applying an uncured active energy ray-curable resin to the surface of the original sheet on which the concavo-convex pattern is formed, and curing the curable resin by irradiating the active energy ray to cure the curable resin. And a step of peeling the coating film from the original sheet. Here, the active energy ray is usually an ultraviolet ray or an electron beam, but in the present invention, it includes a visible ray, an X-ray, an ion ray and the like.
(B) A step of applying an uncured liquid thermosetting resin to the surface of the original sheet on which the concavo-convex pattern is formed; and heating and curing the liquid thermosetting resin; And a step of peeling from the original sheet.
(C) A step of bringing a sheet-like thermoplastic resin into contact with the surface of the original sheet on which the concave / convex pattern is formed, and the sheet-like thermoplastic resin is heated and softened while being pressed against the original sheet, and then cooled. And a step of peeling the cooled sheet-like thermoplastic resin from the original sheet.

Moreover, a molded article for the secondary process can be produced using the original sheet, and a new light diffusable sheet can be produced using the molded article for the secondary process. Examples of the molded product for the secondary process include a secondary process sheet. In addition, as the molded product for the secondary process, there is a plating roll obtained by rolling the original sheet and attaching it to the inside of the cylinder, plating with the roll inserted inside the cylinder, and taking out the roll from the cylinder. .
Specific methods using the molded product for the secondary process include the following methods (d) to (f).

(D) A step of performing metal plating such as nickel on the surface of the original sheet on which the concave / convex pattern is formed and laminating a plating layer (material for transferring the concave / convex pattern), and peeling the plating layer from the original sheet, A step of producing a molded product for a secondary process made of metal, and a step of applying an uncured active energy ray-curable resin to the surface on the side in contact with the concave-convex pattern of the molded product for the secondary process; And a step of irradiating active energy rays to cure the curable resin and then peeling the cured coating film from the molded product for the secondary process.
(E) A step of laminating a plating layer (a material for transferring a concavo-convex pattern) on the surface of the original sheet on which the concavo-convex pattern is formed, and a metal molded product for a secondary process by peeling the plating layer from the original sheet. And a step of applying an uncured liquid thermosetting resin to the surface that was in contact with the concave-convex pattern of the molded product for the secondary process, and after curing the resin by heating, And a step of peeling the cured coating film from the molded product for the secondary process.
(F) A step of laminating a plating layer (a material for transferring the concavo-convex pattern) on the surface of the original sheet on which the concavo-convex pattern is formed, and peeling the plating layer from the original sheet to form a metal secondary process molded product. A step of bringing the sheet-like thermoplastic resin into contact with the surface on the side in contact with the concave-convex pattern of the molded article for the secondary process, and molding the sheet-like thermoplastic resin for the secondary process A method comprising a step of heating and softening while pressing against an object and then cooling, and a step of peeling the cooled sheet-like thermoplastic resin from the molded product for the secondary process.

  A specific example of the method (a) will be described. First, an uncured liquid active energy ray-curable resin is applied to the surface of the web-shaped original sheet on which the concavo-convex pattern is formed by a coater. Next, the original sheet coated with the curable resin is pressed by passing it through a roll, and the curable resin is filled into the concave-convex pattern of the original sheet. Then, an active energy ray is irradiated with an active energy ray irradiation apparatus, and curable resin is bridge | crosslinked and hardened. And a web-like light diffusable sheet | seat can be manufactured by making active energy ray curable resin after hardening peel from an original sheet.

In the method (a), the surface of the original sheet on which the concavo-convex pattern is formed is formed from a silicone resin, a fluororesin or the like before application of an uncured active energy ray-curable resin for the purpose of imparting releasability. The layer to be formed may be provided with a thickness of about 1 to 10 nm.
Examples of the coater that coats an uncured active energy ray-curable resin on the surface of the original sheet on which the uneven pattern is formed include a T-die coater, a roll coater, and a bar coater.
Uncured active energy ray-curable resins include epoxy acrylate, epoxidized oil acrylate, urethane acrylate, unsaturated polyester, polyester acrylate, polyether acrylate, vinyl / acrylate, polyene / acrylate, silicon acrylate, polybutadiene, and polystyrylmethyl. 1 selected from monomers such as prepolymers such as methacrylate, aliphatic acrylate, alicyclic acrylate, aromatic acrylate, hydroxyl group-containing acrylate, allyl group-containing acrylate, glycidyl group-containing acrylate, carboxy group-containing acrylate, halogen-containing acrylate The thing containing the component more than a kind is mentioned. The uncured active energy ray-curable resin is preferably diluted with a solvent or the like.
Moreover, you may add a fluororesin, a silicone resin, etc. to uncured active energy ray hardening resin.
When the uncured active energy ray-curable resin is cured with ultraviolet rays, it is preferable to add a photopolymerization initiator such as acetophenones and benzophenones to the uncured active energy ray-curable resin.

  After the uncured liquid active energy ray-curable resin is applied, the active energy rays may be irradiated after a substrate made of resin, glass or the like is bonded. Irradiation of active energy rays may be performed from either one of the base material and the original sheet having active energy ray permeability.

  The thickness of the cured active energy ray-curable resin sheet is preferably about 0.1 to 100 μm. If the thickness of the cured active energy ray-curable resin sheet is 0.1 μm or more, sufficient strength can be secured, and if it is 100 μm or more, sufficient flexibility can be secured.

In the method shown above, the original sheet is web-shaped, but it may be a sheet. Here, “sheet” means a sheet cut into a certain size according to a sheet of printing paper.
In the case of using a single sheet, a stamp method using a single sheet as a flat plate mold, a roll imprint method using a single sheet wound around a roll as a cylindrical mold, and the like can be applied. Moreover, you may arrange | position the sheet | seat original plate sheet inside the type | mold of an injection molding machine.
However, in the method using these single sheets, in order to mass-produce the light diffusive sheet, it is necessary to repeat the step of forming the uneven pattern many times. When the releasability between the active energy ray-curable resin and the original sheet is low, clogging of the concavo-convex pattern occurs when repeated many times, and the transfer of the concavo-convex pattern tends to be incomplete.
On the other hand, in the method (a) shown above, since the original sheet is web-like, a concave / convex pattern can be continuously formed in a large area. Therefore, even if the number of times the light diffusing sheet is repeatedly used is small, a necessary amount of the light diffusing sheet can be manufactured in a short time.

In the methods (b) and (e), examples of the liquid thermosetting resin include uncured melamine resin, urethane resin, and epoxy resin.
The curing temperature in the method (b) is preferably lower than the glass transition temperature of the original sheet. This is because if the curing temperature is equal to or higher than the glass transition temperature of the original sheet, the concavo-convex pattern of the original sheet may be deformed during curing.

In the methods (c) and (f), examples of the thermoplastic resin include acrylic resin, polyolefin, polyester, and the like.
The pressure when pressing the sheet-like thermoplastic resin against the molded product for the secondary process is preferably 1 to 100 MPa. If the pressure at the time of pressing is 1 MPa or more, the concavo-convex pattern 10 can be transferred with high accuracy, and if it is 100 MPa or less, excessive pressurization can be prevented.
Moreover, it is preferable that the heating temperature of the thermoplastic resin in the method (c) is lower than the glass transition temperature of the original sheet. This is because if the heating temperature is equal to or higher than the glass transition temperature of the original sheet, the uneven pattern 10 of the original sheet may be deformed during heating.
The cooling temperature after heating is preferably less than the glass transition temperature of the thermoplastic resin because the uneven pattern 10 can be transferred with high accuracy.

  Among the methods (a) to (c), the method (a) using an active energy ray-curable resin is preferable in that heating can be omitted and deformation of the uneven pattern of the original sheet can be prevented.

In the methods (d) to (f), it is preferable that the thickness of the metallic secondary process molded product is about 50 to 500 μm. If the thickness of the metal secondary process molded product is 50 μm or more, the secondary process molded product has sufficient strength, and if it is 500 μm or less, sufficient flexibility can be secured.
In the methods (d) to (f), since a metal sheet that is hardly deformed by heat is used as an original sheet, active energy ray curable resins, thermosetting resins, and thermoplastic resins are used as materials for light diffusing sheets. Either of these can be used.

  In addition, in (d)-(f), the uneven | corrugated pattern of the original plate sheet was transcribe | transferred to the metal, and the molding for secondary processes was obtained, However, you may transcribe | transfer to resin and may obtain the molding for secondary processes. Examples of the resin that can be used in this case include polycarbonate, polyacetal, polysulfone, and an active energy ray-curable resin used in the method (a). When the active energy ray-curable resin is used, the active energy ray-curable resin is sequentially applied, cured, and peeled in the same manner as in the method (a) to obtain a molded product for the secondary process.

  EXAMPLES Next, although an Example demonstrates this invention further more concretely, the scope of the present invention is not limited to these.

Example 1
Acrylic resin (resin N) having a glass transition temperature of 128 ° C. and an acrylic resin (resin M) having a glass transition temperature of 139 ° C. are mixed at a mass ratio of 1: 1, diluted in toluene, and hard layer forming paint (solid content concentration). 8% by mass) was obtained. This paint is dried on a single side of a heat-shrinkable resin film (polyethylene terephthalate-based shrink film, product name SC807, manufactured by Toyobo Co., Ltd., thickness 30 μm) that shrinks in a uniaxial direction with a bar coater to a thickness of 2. The coating was performed so as to be 0 μm. Next, by drying, a surface smooth hard layer was formed to obtain a laminated sheet.
Next, both ends of the laminated sheet were fixed with clamps so that tension was applied in the uniaxial contraction direction of the laminated sheet. The laminated sheet is heated at 150 ° C. for 1 minute, and the length in the uniaxial shrinkage direction of the laminated sheet after heating is 48% of the length in the uniaxial shrinkage direction of the laminated sheet before heating (that is, the shrinkage ratio is 48 %), The tension applied to the uniaxial shrinkage direction of the laminated sheet was adjusted.
Thereby, on the surface of the surface smooth hard layer, on the surface of the first concavo-convex pattern formed by arranging a plurality of protrusions along the contraction direction (first direction), and the surface of the first concavo-convex pattern, A concavo-convex pattern including a second concavo-convex pattern formed by arranging a plurality of ridges along the first direction was obtained to obtain a light diffusing sheet.

(Example 2)
A hard layer forming paint obtained by mixing acrylic resin (resin N) having a glass transition temperature of 128 ° C. and acrylic resin (resin M) having a glass transition temperature of 139 ° C. in a mass ratio of 3: 1 and diluting in toluene. A light diffusing sheet was obtained in the same manner as in Example 1 except that the above was changed.

(Example 3)
A coating material for forming a hard layer obtained by mixing acrylic resin (resin N) having a glass transition temperature of 128 ° C. and acrylic resin (resin M) having a glass transition temperature of 139 ° C. in a mass ratio of 1: 3 and diluting in toluene. A light diffusing sheet was obtained in the same manner as in Example 1 except that the above was changed.

Example 4
A light diffusing sheet was obtained in the same manner as in Example 1. However, in this example, the length of the laminated sheet after heating in the uniaxial shrinkage direction is 51% of the length of the laminated sheet before heating in the uniaxial shrinkage direction (shrinkage rate 51%). The tension applied in the uniaxial contraction direction was adjusted.

(Example 5)
A light diffusing sheet was obtained in the same manner as in Example 1. However, in this example, the length of the laminated sheet in the uniaxial shrinkage direction after heating is 43% of the length in the uniaxial shrinkage direction of the laminated sheet before heating (shrinkage ratio 43%). The tension applied in the uniaxial contraction direction was adjusted.

(Example 6)
A mass ratio of a solution in which an acrylic resin (resin N) having a glass transition temperature of 128 ° C. is dissolved in ethyl acetate and toluene and a solution in which an acrylic resin having a glass transition temperature of 139 ° C. (resin M) is dissolved in methyl ethyl ketone is 1: 1. And further diluted with toluene to obtain a hard layer forming coating material (solid content concentration 8 mass%) having a glass transition temperature difference of 11 ° C. between resin M and resin N. This coating is applied to one side of a heat-shrinkable resin film (polyethylene terephthalate-based shrink film, product name SC807, manufactured by Toyobo Co., Ltd., thickness 30 μm) that shrinks in a uniaxial direction, and the thickness after drying is reduced to 2 μm by a bar coater. Coated so that. Next, by drying, a surface smooth hard layer was formed to obtain a laminated sheet.
Next, both ends of the laminated sheet were fixed with clamps so that tension was applied in the uniaxial contraction direction of the laminated sheet. The laminated sheet is heated at 170 ° C. for 2 minutes, and the length in the uniaxial shrinkage direction of the laminated sheet after heating is 57% of the length in the uniaxial shrinkage direction of the laminated sheet before heating (shrinkage ratio 57%). The tension applied in the uniaxial shrinkage direction of the laminated sheet was adjusted so that
Thereby, on the surface of the surface smooth hard layer, on the surface of the first concavo-convex pattern formed by arranging a plurality of protrusions along the contraction direction (first direction), and the surface of the first concavo-convex pattern, A concavo-convex pattern including a second concavo-convex pattern formed by arranging a plurality of ridges along the first direction was obtained to obtain a light diffusing sheet.

(Example 7)
Mixing a hard layer forming paint with a solution in which an acrylic resin having a glass transition temperature of 128 ° C is dissolved in ethyl acetate and toluene and a solution in which an acrylic resin having a glass transition temperature of 139 ° C is dissolved in methyl ethyl ketone at a mass ratio of 3: 1. Then, a light diffusing sheet was obtained in the same manner as in Example 6 except that it was changed to one prepared by diluting with toluene.

(Example 8)
A hard layer-forming coating material is mixed at a mass ratio of 1: 3 with a solution in which an acrylic resin having a glass transition temperature of 128 ° C. is dissolved in ethyl acetate and toluene and a solution in which an acrylic resin having a glass transition temperature of 139 ° C. is dissolved in methyl ethyl ketone. Then, a light diffusing sheet was obtained in the same manner as in Example 6 except that it was changed to one prepared by diluting with toluene.

Example 9
A light diffusing sheet was obtained in the same manner as in Example 6. However, in this example, the length of the laminated sheet in the uniaxial shrinkage direction after heating is 59% of the length in the uniaxial shrinkage direction of the laminated sheet before heating (shrinkage ratio 59%). The tension applied in the uniaxial contraction direction was adjusted.

(Example 10)
A light diffusing sheet was obtained in the same manner as in Example 6. However, in this example, the length of the laminated sheet in the uniaxial shrinkage direction after heating is 50% of the length in the uniaxial shrinkage direction of the laminated sheet before heating (shrinkage ratio 50%). The tension applied in the uniaxial contraction direction was adjusted.

(Example 11)
A light diffusing sheet was obtained in the same manner as in Example 1. Thereafter, an uncured ultraviolet curable resin A (acrylate resin, manufactured by Soken Chemical Co., Ltd.) containing a release agent is applied to the uneven pattern forming surface of the light diffusing sheet to a thickness of 20 μm and irradiated with ultraviolet rays. Then, after curing, a primary transfer product having a pattern in which the concavo-convex pattern of the light diffusive sheet was reversed by peeling was obtained.
Next, an uncured UV curable resin B (acrylate resin, manufactured by Sony Chemical Co., Ltd.) was applied to one side of a transparent PET substrate (A4300 manufactured by Toyobo Co., Ltd., thickness 188 μm) to a thickness of 20 μm. The surface having the reversal pattern of the primary transfer product was pressed against the ultraviolet curable resin B and irradiated with ultraviolet rays to be cured. After curing, the primary transfer product is peeled off to obtain a secondary transfer product having the same concavo-convex pattern as the light diffusive sheet, in which a surface layer made of a cured product of an ultraviolet curable resin is formed on a transparent PET substrate. It was.

(Comparative Example 1)
A light diffusing sheet was obtained in the same manner as in Example 1, except that the hard layer forming coating material was changed to one obtained by diluting an acrylic resin having a glass transition temperature of 128 ° C. in toluene.

(Comparative Example 2)
A light diffusing sheet was obtained in the same manner as in Example 1 except that the hard layer forming coating material was changed to one obtained by diluting an acrylic resin having a glass transition temperature of 139 ° C. with toluene.

(Comparative Example 3)
A solution in which an acrylic resin having a glass transition temperature of 128 ° C. is dissolved in ethyl acetate and toluene and a solution in which an acrylic resin having a glass transition temperature of 175 ° C. is dissolved in methyl ethyl ketone are mixed at a mass ratio of 1: 1, and further diluted with toluene. A concavo-convex pattern-forming sheet was obtained in the same manner as in Example 1 except that the coating material was changed to a hard layer-forming coating material having a glass transition temperature difference of 47 ° C.

<Surface characteristics of uneven pattern>
When the light diffusive sheets of Examples 1 to 11 were observed with a microscope, it was confirmed that the second uneven pattern was formed on the surface of the first uneven pattern (see FIG. 12). The uneven | corrugated pattern of the light diffusable sheet | seat of Example 1 was image | photographed using the scanning electron microscope.)
When the light diffusive sheets of Comparative Examples 1 to 3 were observed with a microscope, it was confirmed that the second concavo-convex pattern was not formed on the surface of the first concavo-convex pattern (see FIG. 13. Note that FIG. 13 shows a comparative example. No. 1 is a photograph of the concavo-convex pattern of the light diffusing sheet using a scanning electron microscope.
In each example, the most frequent pitch P ₁ , aspect ratio A ₁ and orientation degree C ₁ of the first uneven pattern, the most frequent pitch P ₂ , aspect ratio A ₂ and orientation degree C _{2 of} the second uneven pattern, The difference between the orientation direction of the first concavo-convex pattern and the orientation direction of the second concavo-convex pattern (abbreviated as “difference in orientation direction” in the table) was measured by the method described above. The specifications of the electron microscope used and the observation conditions are as follows.
Electron microscope: Hitachi High-Technologies S-3600N
Resolution: 3.0 nm (secondary electron image), 4.5 nm (reflected electron image),
Acceleration voltage: 0.5-30 kV, magnification: 12-300,000
Observation conditions: acceleration voltage 15 kV, working distance 10 mm
Table 1 shows the measurement results of the mode pitch, the aspect ratio, the degree of orientation, and the difference in orientation direction.

[Measurement of the most frequent pitch]
In accordance with the method described above, the most frequent pitches P ₁ and P ₂ were calculated.

[Aspect ratio measurement]
Along the above method was calculated aspect ratio A ₁ and A _2.

[Measurement of degree of orientation]
The orientation degrees C ₁ and C ₂ were calculated according to the method described above.

[Difference in orientation direction]
A difference in orientation direction was calculated along the method described above.

<Visual evaluation of light diffusibility>
Ten LED light sources (SouLight irradiation angle: about 120 °, manufactured by SYK Co., Ltd.) were linearly arranged at intervals of 17 mm to form a linear light source unit. Next, this light source unit is a light diffusive sheet of each example so that the arrangement direction of the LED light source and the arrangement direction of the protrusions of the first concavo-convex pattern coincide with each other and the light from the LED light source is a light diffusive sheet It was covered so that it may enter perpendicularly. In that case, five evaluators evaluated the light diffusibility in the said illuminating device visually after having arrange | positioned the uneven | corrugated pattern of a light diffusable sheet on the opposite side of a light source unit. The evaluation was made into five stages of 1 to 5 points, and the higher the invisibility of the LED light source and the higher the light diffusibility, the higher the score. Table 1 shows the average value of the evaluation of five people.

<Measurement of half width and 1/10 width in illuminance curve>
An illuminance curve was obtained by measuring transmitted scattered light using a goniometer (model: GENESIA Gonio / FFP, manufactured by Genesia). Specifically, the relative illuminance when the illuminance of light emitted perpendicularly from the light diffusing sheet (the light emission angle of this light is 0 °) is set to 1, the light emission angle along the first direction− The relative illuminance from 90 ° to 90 ° was measured at 1 ° intervals to obtain an illuminance curve. Here, the illuminance curve is a curve plotted as shown in FIG. 14 with the horizontal axis as the light output angle and the vertical axis as the relative illuminance.
Then, the half-width of the intensity curve and 1/10 width (1/2 width, _{W 1} in FIG. 14) _{(W 2} in FIG. 14) determined. At that time, only data in an angle range where the relative illuminance was 0.5 or more was used.
The results of the half width and 1/10 width are shown in Table 1. In addition, a diffusion angle becomes large, so that the angle of the half value width of a illuminance curve and the angle of 1/10 value width are large.

The light diffusive sheets of Examples 1 to 11 showed high numerical values in both the half-value width and the 1/10 value width of the illuminance curve, in particular, the 1/10 value width was 65 ° or more, and the diffusion angle was large. Further, in Example 1, the LED light source cannot be seen at all as shown in FIG. 15, and in Example 2, the LED light source can be seen slightly from Example 1 as shown in FIG. Had. Examples 3 to 5 were the same as Example 2. Moreover, Example 6-11 became a numerical value higher than Examples 1-5 in both the half value width of a illuminance curve, and 1/10 value width, and had the further invisibility. Therefore, it was found that the light diffusive sheets of Examples 1 to 11 had excellent light diffusibility.
In contrast, the light diffusive sheet of Comparative Example 1 had a narrow 1/10 value width and a sufficiently wide diffusion angle, and the LED light source was visible as shown in FIG. Comparative examples 2 and 3 were also the same as comparative example 1. Therefore, in Comparative Examples 1 to 3, the light diffusibility was insufficient.

  Since the light diffusive sheet of the present invention has excellent light diffusibility, it can be preferably used as a light diffusive sheet for diffusing point light such as an LED light source.

DESCRIPTION OF SYMBOLS 1 Light diffusable sheet 10 Uneven | corrugated pattern 11 1st uneven | corrugated pattern 11a Projection part 11b Concave part 12 2nd uneven | corrugated pattern 12a Projection part 12b Concave part

Claims (11)

On at least one side of the sheet, the first concave-convex pattern, and a second concave-convex pattern formed on the surface of the first concave-convex pattern, a light diffusing sheet, the first concave-convex pattern, A plurality of protrusions are formed on the surface of the sheet by arranging along the first direction,
The second concavo-convex pattern is formed by arranging a plurality of ridges along the first direction on the surface of the first concavo-convex pattern,
The interval between the ridge lines of two adjacent ridges forming the first concavo-convex pattern changes irregularly and continuously in a second direction perpendicular to the first direction, and the second The light diffusive sheet characterized in that the interval between the ridge lines of two adjacent ridges forming the concavo-convex pattern changes irregularly and continuously in the second direction . 2. The light diffusing sheet according to claim 1, wherein the intervals between the ridge lines of the plurality of protrusions forming the first concavo-convex pattern change irregularly in the first direction. 3. The light diffusing sheet according to claim 1, wherein the intervals between the ridge lines of the plurality of protrusions forming the second concavo-convex pattern change irregularly in the first direction. 4. The light diffusing sheet according to claim 1, wherein ridge lines of the plurality of protrusions forming the first uneven pattern meander as viewed from a normal direction of the sheet. The ridge of the plurality of ridges that form a second uneven pattern meanders when viewed from the normal direction of the sheet, a light diffusing sheet according to any one of claims 1-4. In the first uneven pattern, the degree of orientation _{C 1} indicating the degree of meandering edges of the plurality of ridges is a 0.20 to 0.50, according to any one of claims 1 to 5 Light diffusive sheet. In the second uneven patterns, the degree of orientation _{C 2} indicating the degree of meandering edges of the plurality of ridges is a 0.20 to 0.50, according to any one of claims 1 to 6 Light diffusive sheet. Wherein the alignment direction of the first uneven patterns, the difference between the alignment direction of the second concave-convex pattern is within 5 °, light diffusing sheet according to any one of claims 1-7. In the first concavo-modal pitch _{P 1} in the first direction of the plurality of protrusions is 3 to 20 [mu] m, the aspect ratio _{A 1} of the plurality of protrusions is 0.2 to 1.0 in it, a light diffusing sheet according to any one of claims 1-8. In the second concavo-modal pitch P ₂ in the first direction of the plurality of ridges is a 0.3 to 2 [mu] m, light diffusing according to any one of claims 1-9 Sheet. A light diffusing sheet according to any one of claims 1-10, only one surface of the sheet, and the first uneven patterns are the second uneven pattern forming, the sheet The light diffusive sheet whose 1/10 value angle of light when light enters from the surface which does not have this uneven | corrugated pattern is 65 degrees or more.