WO2014148492A1 - Body having fine concavities and convexities in surface, and production method of body having fine concavities and convexities in surface - Google Patents

Abstract

The present invention relates to a body in which fine concavities and convexities are formed in at least a part of the surface, characterized in that the fine concavities and convexities consist of a wave-shape concavo-convex pattern and multiple concavities or convexities formed on said wave-shape concavo-convex pattern; the wave-shape concavo-convex pattern consists of irregularly formed convex ridges and concave furrows between the convex ridges; the convex ridges meander non-parallel to one another; the modal pitch of the convex ridges is 3-20μm; and, the apparent modal diameter of the concavities or convexities is 1-10μm. By means of the present invention, it is possible to provide an easily produced body having fine concavities and convexities in the surface and a production method thereof, wherein, when used as a light diffuser, said body has to a certain extent a diffusion angle even in the direction perpendicular to the main diffusion direction while still maintaining the diffusion angle of the primary diffusion direction.

Description

Surface fine unevenness and method for producing surface fine unevenness

The present invention relates to a light diffusing body and a surface fine concavo-convex body suitably used as a light diffusing body forming original plate and a method for producing the same.
The present invention claims priority based on Japanese Patent Application No. 2013-55722 filed in Japan on March 18, 2013 and Japanese Patent Application No. 2014-034687 filed in Japan on February 25, 2014. , The contents of which are incorporated herein.

It is known that a sheet-like surface fine uneven body on which a concave / convex pattern composed of fine wavy unevenness is formed is used as a light diffuser such as a light diffusing sheet because of its optical characteristics.
As a method for producing a light diffusive sheet, for example, in Patent Document 1, a laminated sheet provided with a resin hard layer on a resin substrate made of a heat shrinkable film is heated to shrink the heat shrinkable film. Thus, there is disclosed a method of forming a concavo-convex pattern on the surface of a hard layer by deforming the hard layer so as to be folded into a concavo-convex shape. Patent Document 1 describes that a concavo-convex pattern with small variation in orientation can be formed by stretching after shrinking a heat-shrinkable film. When such a sheet is a light diffusing sheet, the diffusion angle in the main diffusion direction is large (for example, about 25 to 30 °), and the diffusion angle in the direction orthogonal to the main diffusion direction is small (for example, about 3 °). Excellent anisotropy.

JP 2011-213051 A

However, recently, a light diffusive sheet having a certain diffusion angle (at least 4 °) in a direction orthogonal to the main diffusion direction while maintaining a wide diffusion angle (at least 18 °) in the main diffusion direction is also required. It is like that. For example, in a head-up display system that displays information such as traveling speed on the windshield of a car that is gently curved, in order to display the image clearly on the windshield while diffusing image information, On the other hand, a light diffusing sheet having a certain diffusion angle in a direction perpendicular to the surface is also required. Such a light diffusable sheet is considered to be produced by, for example, using a biaxial heat-shrinkable film that heat-shrinks in the biaxial direction as a heat-shrinkable film and shrinking it in the biaxial direction. However, in the above method, it is difficult to control the production conditions, and it is difficult to stably obtain a light diffusing sheet having a certain performance.

The present invention has been made in view of the above circumstances, and when used as a light diffuser, also in a direction orthogonal to the main diffusion direction while maintaining a wide diffusion angle (at least 18 °) in the main diffusion direction. Provided are a fine surface irregularity body having a certain diffusion angle (at least 4 °) and easy to manufacture, and a method for manufacturing the same.

The present invention has the following aspects.
<1> A surface fine concavo-convex body having fine irregularities formed on the surface, wherein the fine irregularities are:
A wavy uneven pattern having a plurality of ridges meandering non-parallel to each other and concave ridges formed between the plurality of ridges, and having a most frequent pitch of 3 to 20 μm; A fine surface irregularity having a number of hemispherical recesses or hemispherical projections formed on the pattern;
<2> The fine surface irregularities according to <1>, wherein the hemispherical concave portion or the hemispherical convex portion has a mode diameter of 1 to 10 μm;
<3> The surface fine unevenness according to <1> or <2>, wherein the average height of the ridges is 4 to 7 μm;
<4> The surface fine unevenness according to any one of <1> to <3>, wherein an occupied area ratio of the hemispherical recess or the hemispherical protrusion in the fine unevenness is 30 to 70%;
<5> Surface fine unevenness according to any one of <1> to <4>, which is a light diffuser;
<6> The surface fine unevenness according to any one of <1> to <4>, which is a light diffuser-forming original plate for transferring the fine unevenness to produce a light diffuser;
<7> A laminate in which a large number of particles are dispersed in a matrix resin on one side of a base film made of resin, and a hard layer having a thickness of more than 0.05 μm and less than 5.0 μm is provided to form a laminated sheet And a deformation step of deforming so as to fold at least the hard layer of the laminated sheet, and the matrix resin has a glass transition temperature of 10 ° C. or higher than the resin constituting the base film, The particles are made of a material whose particle shape is not changed by heat at a temperature lower than the glass transition temperature of the resin constituting the substrate film by 10 ° C., and the particle diameter of the particles is larger than the thickness of the hard layer. , Manufacturing method of fine surface irregularities;
<8> The substrate film is a uniaxial heat-shrinkable film, and the deformation step is a step of heating the laminated sheet to shrink the uniaxial heat-shrinkable film. Method for producing uneven body;
<9> Using the surface fine unevenness produced by the production method according to <7> or <8> as an original plate for forming a light diffuser, and having a transfer step of transferring the fine unevenness of the surface fine unevenness. A method for producing a light diffuser.

Moreover, this invention has the following structures.
[1] A surface fine concavo-convex body in which fine concavo-convex is formed on at least a part of the surface, wherein the fine concavo-convex is a wavy concavo-convex pattern and a plurality of concave or convex portions formed on the undulating concavo-convex pattern The wavy uneven pattern includes a plurality of irregularly formed ridges and a recess between the plurality of ridges, and the plurality of ridges meander non-parallel to each other. The fine surface irregularities according to claim 1, wherein a mode pitch of the plurality of ridges is 3 to 20 μm, and an apparent mode diameter of the recesses or projections is 1 to 10 μm.
[2] The fine surface irregularities according to [1], wherein the average height of the ridges is 4 to 7 μm.
[3] The surface fine unevenness according to [1] or [2], wherein an occupied area ratio of the concave portion or the convex portion in the fine unevenness is 30 to 70%.
[4] The surface fine unevenness according to any one of [1] to [3], which is a light diffuser.
[5] The surface fine concavo-convex body according to any one of [1] to [3], which is a light diffuser-forming original plate for transferring the fine concavo-convex to produce a light diffuser.
[6] A laminated sheet is formed by providing a hard layer having a thickness of more than 0.05 μm and less than 5.0 μm made of matrix resin and particles dispersed in the matrix resin on one side of a base film made of resin. A laminating step, and a deforming step of deforming at least the hard layer of the laminated sheet so as to be folded,
The glass transition temperature of the matrix resin is 10 ° C. or more higher than the glass transition temperature of the resin constituting the base film,
The particles are made of a material whose particle shape is not changed by heat at a temperature lower than a temperature 10 ° C. higher than the glass transition temperature of the resin constituting the base film,
The method for producing a fine surface irregularity, wherein the particle diameter is larger than the thickness of the hard layer.
[7] The surface fine film according to [6], wherein the base film is a uniaxial heat-shrinkable film, and the deformation step is a step of heating the laminated sheet to shrink the uniaxial heat-shrinkable film. Manufacturing method of uneven body.
[8] A transfer step of transferring the fine unevenness of the surface fine unevenness using the surface fine unevenness produced by the production method according to [6] or [7] as a light diffuser forming original plate, A method for producing a light diffuser.

According to the present invention, when used as a light diffuser, a certain diffusion angle (at least 4) in the direction orthogonal to the main diffusion direction while maintaining a wide diffusion angle (at least 18 °) in the main diffusion direction. And a method for producing the same can be provided.

2 is an optical micrograph obtained by observing fine irregularities of the light diffusive sheet of Example 1. FIG. 4 is another laser micrograph of the microscopic unevenness of the light diffusing sheet of Example 1 observed. FIG. 1B is an enlarged longitudinal sectional view schematically showing a portion cut along the line I-I ′ in the optical micrograph of FIG. 1A. It is the Fourier-transform image which acquired the gray scale image from the optical microscope photograph of the light diffusable sheet | seat of FIG. 1A, and Fourier-transformed the said image. It is a schematic diagram which shows typically the Fourier-transform image of FIG. FIG. 4 is a graph in which a line L1-1 is drawn from the center of FIG. 3 so as to pass through a point having the maximum frequency in A1, and the frequency distribution of the line L1-1 is plotted. FIG. 4 is a graph in which a line L1-2 is drawn from the center of FIG. 3 in a direction orthogonal to L1-1 and a frequency distribution of the line L1-2 is plotted. It is the longitudinal cross-sectional view of the principal part of the light diffusable sheet | seat obtained from the observation result which observed the fine uneven | corrugated formation surface of the light diffusable sheet | seat of FIG. 1A or B with an atomic force microscope. It is explanatory drawing of the method of calculating | requiring the average height of a convex part. It is explanatory drawing of the method of calculating | requiring the average height of a convex part. It is an image figure which shows the shape of the projection image of the emitted light at the time of using the conventional light diffusive sheet with high anisotropy. It is an image figure which shows the shape of the projection image of the emitted light at the time of using the light diffusable sheet | seat by this invention. It is a longitudinal cross-sectional view of the original plate (surface fine unevenness | corrugation body) for manufacturing the light diffusable sheet of FIG. 1A or B. It is sectional drawing explaining the manufacturing method of the original plate (surface fine unevenness | corrugation body) of FIG.

Hereinafter, the present invention will be described in detail.
<Surface fine irregularities>
FIG. 1A is an optical micrograph (plan view; vertical 0.4 mm × horizontal) of one side of a light diffusing sheet (light diffusing body) which is an embodiment of the surface fine irregularities of the present invention (Example 1 described later). FIG. 1B is a laser micrograph of the microscopic irregularities of the light diffusing sheet of Example 1 observed with a laser microscope (“VK-8510” manufactured by Keyence Corporation). A line α in FIG. 1B indicates a height profile of a cut surface obtained by cutting the light diffusing sheet along the line β in the horizontal direction in the figure. 1A and FIG. 1B have different magnifications.
FIG. 2 is an enlarged vertical cross-sectional view schematically showing a portion cut along a line II ′ (a line along a direction in which a protruding ridge and a recessed ridge described later are repeated) in the optical micrograph of FIG. 1A. FIG. Note that FIG. 2 shows a simplified view from the viewpoint of easy understanding of the longitudinal cross-sectional shape of the light diffusive sheet.
In the present specification, the “surface fine uneven body” means an article having a fine uneven structure on the surface.

As shown in FIG. 2, the light diffusing sheet 10 of this example includes a transparent base material 11 made of polyethylene terephthalate (PET) and an ionizing radiation curable resin provided on one surface of the base material 11. It has a two-layer structure with a transparent surface layer 12 made of a cured product, and a wavy uneven pattern 13 and a number of protrusions formed on the uneven pattern 13 are formed on the exposed surface of the surface layer 12. The fine unevenness | corrugation comprised from the part 14 is formed. In this example, the convex portion 14 is formed in a substantially hemispherical shape. In this example, the exposed surface of the base material 11 (the surface on the side opposite to the side on which the surface layer 12 is provided) is a smooth surface.

The wavy uneven pattern 13 in the fine unevenness extends in the vertical direction in FIGS. 1A and 1B, and in FIG. 2, a plurality of streaky protrusions 13a extending in a direction perpendicular to the paper surface, and the plurality of protrusions. The groove portions 13b between the portions 13a are alternately repeated in one direction (lateral direction in FIGS. 1A, 1B and 2).
As shown in FIG. 2, the vertical cross-sectional shape of each ridge 13 a is a tapered shape that becomes thinner from the proximal end side toward the distal end side.
As shown in FIGS. 1A and 1B, each of the plurality of ridge portions 13a meanders, is nonparallel to each other, and is irregularly formed. That is, the ridge line meanders in each protruding line part 13a, and the valley line meanders in each recessed line part 13b. Further, the interval between the ridge lines of the adjacent ridge portions 13a is not constant, and the interval between the valley lines of the adjacent ridge portions 13b is not constant.
In the present specification, the irregularity means that when the light diffusion sheet 10 is viewed from the normal direction with respect to the base material, the ridges 13a meander and are not parallel to each other. The ridge line of the part 13a meanders, the valley line of each concave line part 13b meanders, the interval of the ridge line of the adjacent convex line part 13a is not constant, and the interval of the valley line of the adjacent concave line part 13b is Means not constant.
Moreover, the height of the ridge line is not constant in each protruding line part 13a, and the height of the valley line is not fixed in each recessed line part 13b. Therefore, as shown in FIG. 2, the longitudinal cross-sectional shape of each protruding item | line part 13a is different, respectively, and is not uniform but irregular.
The fine unevenness is composed of such a wave-like uneven pattern 13 and a large number of randomly distributed convex portions 14.
Here, the ridgeline of the “ridge 13a” means a line that connects the tops of the ridges 13a.
When the convex part 14 exists in the middle of the ridgeline of the convex part 13a, it refers to the line drawn so that the top part of the convex part 14 may be passed.

As the substrate 11 shown in FIG. 2, in addition to PET having excellent mechanical strength and dimensional stability, a transparent material such as a resin such as polycarbonate, polymethyl methacrylate, polyethylene acrylate, and polystyrene, and glass can be used. . The thickness of the substrate 11 is, for example, 30 to 500 μm.
Examples of the surface layer 12 include a cured product of a thermosetting resin, a thermoplastic resin, and the like in addition to a cured product of an ionizing radiation curable resin. Examples of the ionizing radiation curable resin include an ultraviolet curable resin and an electron beam curable resin. The thickness of the surface layer 12 may be sufficient to form the wavy uneven pattern 13, and the thickness of the thickest portion is preferably about 10 to 25 μm. The thickness of the surface layer 12 means a thickness before the surface layer 12 is deformed, and can be measured using an optical non-contact film thickness measuring instrument.

In this example, the fine unevenness of the light diffusing sheet 10 is composed of a wavy uneven pattern 13 and a large number of protrusions 14. However, the fine unevenness of the surface fine unevenness of the present invention is wavy. You may be comprised from the uneven | corrugated pattern and many recessed parts.

In the light diffusing sheet 10, the repeating direction (the horizontal direction in FIGS. 1A and 1B) of the wavy uneven pattern 13 is referred to as the Y direction, and the direction orthogonal to the Y direction (the vertical direction in FIG. 1A and B) is referred to as the X direction. There is a case.
In this specification, in this XY orthogonal coordinate system, the first direction may be referred to as the Y-axis direction and the second direction may be referred to as the X-axis direction. In addition, the direction orthogonal to the XY axis may be referred to as the third direction or the normal direction of the substrate of the surface fine unevenness.

In the illustrated example of the light diffusing sheet 10, the most frequent pitch of the wavy uneven pattern 13 is 3 to 20 μm from the viewpoint of exhibiting light diffusibility. The most frequent pitch of the wavy uneven pattern 13 is preferably 7 to 15 μm, more preferably 11 to 13 μm. The pitch is the distance between the tops of adjacent ridges.
When the most frequent pitch is within the above range, a surface on which fine irregularities are formed (hereinafter may be referred to as a fine irregularity forming surface) or a smooth surface side opposite to the surface with respect to the light diffusing sheet 10 When light is incident from the side, the outgoing light from the surface opposite to the incident surface diffuses well in the Y direction (main diffusion direction), and a sufficient diffusion angle in the Y direction (for example, 18 ° or more, preferably 23 °). Above, more preferably 25 ° or more, 1/10 diffusion angle is (diffusion angle × 1.4 + 25 °) or less, preferably (diffusion angle × 1.4 + 22 °) or less, more preferably (diffusion angle × 1.4 + 20). °) Indicates the following. The upper limit value of the diffusion angle in the Y direction is not particularly limited, but is, for example, 30 °.

Further, the fine unevenness of the light diffusing sheet 10 in the illustrated example has a large number of randomly formed convex portions 14 in addition to the wavy uneven pattern 13 mainly responsible for diffusion in the main diffusion direction as described above. is doing. Therefore, the anisotropy of the wavy uneven pattern 13 is moderately weakened by the protrusions 14. As a result, when light is incident on one of the surfaces with respect to the light diffusing sheet 10, the emitted light from the opposite surface is diffused also in the X direction (direction orthogonal to the main diffusion direction), A certain diffusion angle smaller than the Y direction (for example, 4 ° or more, preferably 8 ° or more, more preferably 10 ° or more. 1/10 diffusion angle is (diffusion angle × 1.6 + 25 °) or less, preferably ( (Diffusion angle × 1.6 + 20 °) or less, more preferably (Diffusion angle × 1.6 + 18 °) or less). The upper limit value of the diffusion angle in the X direction is not particularly limited, but is 20 °, for example.

The apparent mode diameter of the convex portion 14 is preferably 1 to 10 μm, more preferably 3 to 6 μm, still more preferably 4 to 5 μm. If the apparent mode diameter of the convex portion 14 is within the above range, the anisotropy of the wavy uneven pattern 13 can be moderately weakened, and the diffusion angles in both the Y direction and the X direction are controlled within the above range. For example, the Y direction is preferably controlled at 25 to 30 °, and the X direction is preferably controlled at 10 to 15 °. Further, the 1/10 diffusion angle in both the Y direction and the X direction can be easily controlled within the above range. For example, the Y direction is preferably (diffusion angle × 1.4 + 20 °) or less, and the X direction is preferably (diffusion angle × 1.6 + 18 °) or less.

The diffusion angle in this specification (generally referred to as “FWHM”) and the 1/10 diffusion angle are measured using a light distribution characteristic measurement device (for example, GENESISIA GonioFar Field Profiler (manufactured by Genesia)). It can be measured by the following method.
First, the light diffusing sheet 10 is irradiated with light from one of the surfaces, that is, the fine unevenness forming surface or the opposite smooth surface side. At that time, the illuminance of the outgoing light (light outgoing angle = 0 °) emitted perpendicularly from the side opposite to the incident surface is used as a reference value, and the outgoing light within the range of the light outgoing angle along the Y direction of −90 ° to + 90 °. Is measured at intervals of 1 ° as a relative value with respect to the reference value. Then, the illuminance curve is obtained by plotting the illuminance value with respect to the light emission angle in each Y direction.
The half value width (full half value width) in the illuminance curve is defined as the diffusion angle in the main diffusion direction (Y direction). Further, the 1/10 value width (all 1/10 value widths) is defined as a 1/10 diffusion angle in the main diffusion direction (Y direction).
Similarly, the illuminance of the emitted light within the range of the light emission angle of −90 ° to + 90 ° along the X direction is measured every 1 ° as a relative value with respect to the reference value. Then, the illuminance curve is obtained by plotting the illuminance value with respect to the light emission angle in each X direction. The half value width (total half value width) in the illuminance curve is defined as a diffusion angle in a direction (X direction) orthogonal to the main diffusion direction. Further, the 1/10 value width (total 1/10 value width) is defined as a 1/10 diffusion angle in the direction (X direction) orthogonal to the main diffusion direction.

In the present specification, the mode pitch of the wavy uneven pattern 13 and the apparent mode diameter of the convex portion 14 are measured and defined as follows.
First, an optical micrograph as shown in FIG. 1A is obtained for the fine surface irregularities. The observation visual field at that time is 0.4 to 1.6 mm in length and 0.5 to 2 mm in width. If this image is a compressed image such as jpeg, it is converted into a grayscale Tif image. Then, Fourier transform is performed to obtain a Fourier transform image as shown in FIG.
Moreover, the schematic diagram of the Fourier-transform image of FIG. 3 is shown as FIG.
Here, the white portions denoted by reference signs A1 and A2 in FIG. 3 include information on the pitch of the wavy uneven pattern since the shape thereof has directionality. White brightness indicates frequency (except for the center point). On the other hand, the white circular ring B in FIG. 3 includes information on the diameters of a large number of convex portions because the shape thereof has no directionality.
Therefore, when the line L1-1 is drawn from the center of FIG. 3 so as to pass through the point having the maximum frequency in A1, and the frequency distribution of the line L1-1 is plotted, the graph of FIG. 5 is obtained.
Further, when the line L1-2 is drawn from the center of FIG. 3 in the direction orthogonal to L1-1 and the frequency distribution of the line L1-2 is plotted, the graph of FIG. 6 is obtained.
In FIG. 5, 1 / XA having a high frequency is the most frequent pitch of the wavy uneven pattern in the light diffusing sheet 10.
In FIGS. 5 and 6, 1 / XB and 1 / YB, which are frequently used, are the mode diameters in the L1-1 direction and the L1-2 direction of the large number of convex portions in the light diffusing sheet 10, respectively. That is, 1 / XA is the mode pitch of the wavy uneven pattern, and 1 / (XB + YB) is the apparent mode diameter of a number of convex portions.
In the Fourier transform image of FIG. 3, the orientation from the center means the direction of the periodic structure (uneven pattern 13) existing in FIG. 1A, and the distance from the center is the period of the periodic structure existing in FIG. 1A. Means the reciprocal. In this example, as shown in FIG. 1A, since the wavy uneven pattern 13 is repeated in the horizontal direction in the drawing, the most frequent pitch in the line L1-1 extending in the horizontal direction in the drawing from the center in the Fourier transform image. The luminance (frequency) of the portion corresponding to the reciprocal of is high.
In FIG. 4, XB is a position where the frequency is maximum in a portion passing through the ring of line L1-1 (not shown in FIG. 4), and in FIG. 4, YB is a line L1-2. This is the position where the frequency is maximum in the portion passing through the ring (not shown in FIG. 4).

At least five optical micrographs as shown in the figure are taken, and the average value of the mode pitches obtained as described above for each photo is defined as the “mode pitch” of the wavy uneven pattern 13. That is, the “most frequent pitch” refers to the distance between the tops having the highest appearance frequency among the distances between the tops of the adjacent ridges. Further, the average value of the apparent mode diameter obtained as described above for each photograph is defined as the “apparent mode diameter” of the convex portion 14. That is, the “apparent mode diameter” refers to a diameter having the highest appearance frequency among the diameters of the convex portions formed on the concave / convex pattern.
The fine irregularities of the surface fine irregularities may have concave portions instead of convex portions, and the “apparent mode diameter” of the concave portions is the same as the “apparent mode diameter” of the convex portions. Desired.

The average height of the ridges 13a constituting the wavy uneven pattern 13 is preferably 4 to 7 μm, more preferably 5 to 6 μm. When the average height of the ridges 13a is within the above range, sufficient light diffusibility can be obtained.

In the present specification, the average height of the ridges 13a of the wavy uneven pattern 13 is measured and defined as follows.
First, the fine unevenness forming surface of the light diffusive sheet 10 is observed with an atomic force microscope, and from the observation result, the surface obtained by cutting the wavy uneven pattern 13 along the Y direction is a longitudinal sectional view as shown in FIG. Get. And the height H of the said protruding item | line part 13 is calculated | required from sectional drawing of the protruding item | line part 13a of the part in which the protruding part 14 does not exist. Specifically, the height H of the ridge portion 13a is set to H1 as a vertical distance between the top portion T of the ridge portion 13a and the bottom portion B1 of the ridge portion 13b located on one side of the ridge portion 13a. When the vertical distance between the top portion T of the ridge portion 13a and the bottom portion B2 of the ridge portion 13b located on the other side of the ridge portion 13a is defined as H2, H = (H1 + H2) / 2.
Such measurement is performed on 50 portions of the ridge portion 13a where the ridge portion 14 does not exist, and the average value of the 50 data is defined as “average height of the ridge portion”.

On the other hand, the average height of the convex portions 14 is preferably 0.5 to 3 μm, more preferably 1 to 2 μm, and still more preferably 1.1 to 1.5 μm. When the average height of the protrusions 14 is in the above range, the anisotropy of the wavy uneven pattern 13 can be moderately weakened, and the diffusion angles in both the Y direction and the X direction can be easily controlled within the above range.

In this specification, the average height of the convex part 14 is measured and defined as follows.
First, the cross-sectional view of FIG. 7 is obtained as described above. Then, as shown in FIG. 8, the waveform is separated into a shape derived from the wavy uneven pattern 13 and a shape derived from the convex portion 14. The waveform separation is performed using a shape derived from the wavy uneven pattern 13 as a sine curve. Next, the shape derived from the wavy uneven pattern 13 is subtracted from the cross-sectional view of FIG. 8 to obtain a cross-sectional view of only the shape derived from the convex portion 14 as shown in FIG. Then, in the cross-sectional view of FIG. 9, the height H ′ of the convex portion 14 is obtained as H ′ = (H1 ′ + H2 ′) / 2. In the cross-sectional view of FIG. 9, H1 ′ is a vertical distance between the top portion T ′ of the convex portion 14 and the base line L _α on one side of the convex portion 14, and H2 ′ is the top portion T ′ of the convex portion 14. it is a vertical distance between the baseline L _beta of the other side of the convex portion 14.
Such measurement is performed on 50 convex portions 14, and the average value of 50 data is defined as "average height of convex portions".

The occupation area ratio of the convex portions 14 in the fine irregularities of the light diffusing sheet 10 is preferably 30 to 70%, more preferably 40 to 60%, and further preferably 45 to 55%. When the occupation area ratio of the convex portion 14 is in the above range, the anisotropy of the wavy uneven pattern 13 can be moderately weakened, and the diffusion angles in both the Y direction and the X direction can be easily controlled within the above range.

In this specification, the occupation area ratio γ (%) of the convex portion 14 in the light diffusive sheet 10 is measured and defined as follows.
First, an optical microscope photograph as shown in FIG. 1A is obtained, and the number n of convex portions 14 recognized in the area S2 of the entire visual field (for example, 0.4 to 1.6 mm in length and 0.5 to 2 mm in width) is counted. In the entire field of view, an area S1 = nr ² π occupied by the n convex portions 14 is obtained. The occupied area ratio γ (%) is obtained by the following formula.

Γ (%) = S1 × 100 / S2 (where r in the formula is ½ (ie, radius) of the apparent mode diameter of the convex portion)

As described above, the light diffusive sheet 10 in the illustrated example is formed on one surface of the corrugated uneven pattern 13 mainly having diffusion in the Y direction, and the corrugated uneven pattern 13. The pattern 13 has fine irregularities including a large number of convex portions 14 that moderately weaken the anisotropy of the pattern 13 and increase diffusion in the X direction. Therefore, when light is incident on the light diffusing sheet 10 from any one surface, a sufficient diffusion angle of, for example, 18 ° or more, preferably 23 ° or more, more preferably 25 ° or more is obtained in the Y direction. . Further, a sufficient 1/10 diffusion angle of (diffusion angle × 1.4 + 25 °) or less, preferably (diffusion angle × 1.4 + 22 °) or less, more preferably (diffusion angle × 1.4 + 20 °) or less is obtained. . On the other hand, a diffusion angle of, for example, 4 ° or more, preferably 8 ° or more, more preferably 10 ° or more can be obtained in the X direction. Further, a sufficient 1/10 diffusion angle of (diffusion angle × 1.6 + 25 °) or less, preferably (diffusion angle × 1.6 + 20 °) or less, more preferably (diffusion angle × 1.6 + 18 °) or less is obtained. . When a conventional light diffusive sheet having high anisotropy is used, the emitted light diffuses in the Y direction but hardly diffuses in the X direction. Therefore, the projected image of the emitted light is flat as shown in FIG. 10A. It was an elliptical shape with a large rate. On the other hand, when the light diffusive sheet 10 shown in the figure is used, the emitted light diffuses in the X direction, so that the projected image of the emitted light has an elliptical shape with a small flatness as shown in FIG. 10B. .

Further, the ridges 13a constituting the wavy uneven pattern 13 of the illustrated light diffusing sheet 10 are non-parallel to each other and meandering, and have no regularity. For this reason, the anisotropy of the uneven pattern 13 is moderately weakened, and the effect of increasing the diffusion angle in the X direction is considered to be more prominently combined with the effect of forming the convex portion 14. It is done.
As a method of increasing the diffusion angle in the X direction, a method of adding a light diffusing agent is also conceivable.
However, the addition of a light diffusing agent tends to lower the light transmittance of the light diffusing sheet. On the other hand, in the method of increasing the diffusion angle in the X direction by specifically controlling fine irregularities as in the present invention, it is not necessary to add a light diffusing agent, and even when it is added, the amount of addition Can be made in small quantities. Therefore, the light transmittance can be maintained high.

Such a light diffusing sheet 10 in the illustrated example is, for example, in a head-up display (HUD) system that clearly displays current speed information, car navigation information, and the like on a windshield of a car that is formed in a gently curved surface. It is preferably used as a diffusion member.
The light diffusing sheet 10 is also suitably used as a diffusing member for a projector; a diffusing member for a backlight of a television, a monitor, a notebook personal computer, a tablet personal computer, a smartphone, a mobile phone, or the like. The
The light diffusive sheet 10 is also preferably used as a diffusing member or the like constituting the exit surface of the light guide member in a scanner light source in which LED light sources are arranged in a line, used in a copying machine or the like.

One aspect of the present invention is the use of the above-described surface fine irregularities as a light diffusing sheet or a light diffusing member, or a method of using the same. Further, when the surface fine irregularities of the present invention are used as a light diffusing sheet or a light diffusing member, the application destination thereof is as described above for a head-up display system, a backlight for a personal computer or a mobile phone, or Examples thereof include a diffusion member such as an emission surface of the light guide member.

<Method for producing surface fine unevenness>
The light diffusing sheet 10 in the illustrated example uses a light diffusing sheet forming original plate (light diffusing material forming original plate) having fine irregularities on the surface as a mold, and the light diffusing sheet forming original plate (hereinafter referred to as “original plate”). (Also referred to as)).
One aspect of the present invention is the use of the surface fine concavo-convex body as a light diffusing sheet or an original plate for producing a diffusing member.

The light diffusing sheet 10 in the illustrated example is a secondary transfer product obtained by transferring the fine irregularities of the original plate to obtain a primary transfer product, and then further transferring the fine irregularities of the primary transfer product. The fine unevenness of the primary transfer product is a reverse pattern of the fine unevenness of the original plate, but the fine unevenness of the secondary transfer product is the same pattern as the fine unevenness of the original plate. Therefore, in this example, a surface fine uneven body having the same fine unevenness as the light diffusing sheet 10 in the illustrated example is manufactured as an original, and this is used as a transfer mold for secondary transfer, and the light diffusing sheet 10 in the illustrated example is produced. Is manufacturing.

Further, in the n-order transfer product, when n is an even number, the fine unevenness of the transfer product is the same pattern as the fine unevenness of the original plate, but when n is an odd number, the transfer product has The fine unevenness becomes a reversal pattern of the fine unevenness of the original. And, when n is an n-order transfer product having an odd number and the fine unevenness of the original used for transfer has a convex part, the fine unevenness of the n-order transfer product (n is an odd number) The convex part has a concave part that is inverted. As already described, the fine irregularities of the surface fine irregularities of the present invention may be in the form of having concave portions instead of convex portions. Therefore, the surface fine irregularities of the present invention include not only the above-mentioned original plate and the original n-order transfer product (n is an even number) but also the original n-order transfer product (n is an odd number).
Hereinafter, the manufacturing method of the light diffusable sheet 10 of the example of illustration which is a secondary transfer product is demonstrated.

[Original version]
In manufacturing the light diffusable sheet 10 of the illustrated example, first, the surface fine uneven body 20 shown in FIG. 11 is manufactured and used as an original. The original plate has a base material 21 made of resin and a hard layer 22 provided on one entire surface of the base material 21, and the exposed surface of the hard layer 22 has the light diffusing sheet 10 in the illustrated example. Are formed in the same fine irregularities.

In this example, the hard layer 22 includes a matrix resin 22a and particles 22b dispersed in the matrix resin 22a. The hard layer 22 is deformed so as to be folded, and the thickness t of the hard layer 22 (part where no particles exist). Is set smaller than the particle diameter d of the particles. Therefore, the hard layer 22 has a wavy uneven pattern 13 ′ (projection strip portion 13 a ′ and recess strip portion 13 b ′) formed by being deformed as folded, and each particle 22 b dispersed in the hard layer 22. Has a fine asperity composed of a convex portion 14 ′ formed by projecting to the surface side of the hard layer 22. The contact surface of the base material 21 with the hard layer 22 has a concavo-convex shape following the shape of the hard layer 22 deformed as if folded.

Note that the thickness t of the hard layer 22 is a portion of the hard layer 22 where the particles 22b are not present from a micrograph of a cross section (longitudinal cross section) obtained by cutting the surface fine irregularities 20 perpendicular to the surface direction. This is the average value of the numerical values obtained when randomly extracting more than one point and measuring the thickness of each part in the normal direction.

Further, the particle diameter d of the particles 22b is a mode diameter (mode) measured by a laser diffraction / scattering particle size distribution analyzer for uniformly dispersed particles.

As described in detail later, the surface fine concavo-convex body 20 shown in FIG. 11 is a lamination process in which a hard layer in which particles are dispersed in a matrix resin is provided on one side of a base film made of resin to form a laminated sheet. And a deformation step of deforming at least a hard layer of the laminated sheet so as to be folded. According to this method, it is possible to form meandering portions 13 a ′ which meander each other and are not parallel to each other and irregular. Further, the vertical cross section of each protruding line portion 13a 'is tapered from the proximal end side toward the distal end side.

11, the glass transition temperature Tg2 of the matrix resin 22a needs to be 10 ° C. or more higher than the glass transition temperature Tg1 of the resin constituting the substrate 21. Further, the particles 22b need to be made of a material whose particle shape does not change due to heat at a temperature lower than a temperature 10 ° C. higher than the glass transition temperature of the resin constituting the substrate 21.
Here, “the particle shape does not change” means that the particle shape and particle diameter do not change before and after heating.

That is, the resin constituting the base material 21 and the matrix resin 22a need to be selected so that the difference between these glass transition temperatures (Tg2−Tg1) is 10 ° C. or more. 20 degreeC or more is preferable and 30 degreeC or more is more preferable. When (Tg2−Tg1) is 10 ° C. or higher, processing such as heat shrinkage can be easily performed at a temperature between Tg2 and Tg1 in a deformation process described later. Further, if the temperature between Tg2 and Tg1 is the processing temperature, it can be processed under the condition that the Young's modulus of the base material is higher than the Young's modulus of the matrix resin 22a. As a result, in the deformation process described later, the hard layer 22 is wavy. The uneven pattern 13 ′ can be easily formed. The processing temperature is a temperature at which the hard layer 22 is deformed so as to be folded at least in the deformation process (for example, a heating temperature at the time of thermal contraction).

Further, the necessity of using a resin having a Tg2 exceeding 400 ° C. is scarce from an economic viewpoint, and since there is no resin having a Tg1 lower than −150 ° C., (Tg2−Tg1) is preferably 550 ° C. or less. More preferably, it is 200 ° C. or lower. That is, in one embodiment of the present invention, (Tg2-Tg1) is preferably 10 to 550 ° C, more preferably 30 to 200 ° C. Note that the difference in Young's modulus between the base material 21 and the matrix resin 22a at the processing temperature in the deformation process described later is preferably 0.01 to 300 GPa because the wavy uneven pattern 13 ′ can be easily formed. More preferably, it is 1 to 10 GPa.
The Young's modulus is a value measured according to JIS K 7113-1995.

Tg1 is preferably −150 to 300 ° C., more preferably −120 to 200 ° C. There is no resin having a Tg1 lower than −150 ° C., and if the Tg1 is 300 ° C. or lower, the temperature can be easily raised and heated to the above processing temperature.

The Young's modulus of the resin constituting the substrate 21 at the above processing temperature is preferably 0.01 to 100 MPa, and more preferably 0.1 to 10 MPa. If the Young's modulus of the resin constituting the base material 21 is 0.01 MPa or more, it is a hardness that can be used as the base material, and if it is 100 MPa or less, the hard layer 22 is deformed following the deformation at the same time. It is possible softness.

As the material constituting the particles 22b, at least one kind of material whose particle shape does not change by heat can be used at a temperature lower than 10 ° C. higher than the glass transition temperature of the resin constituting the substrate 21.
For example, when the material constituting the particles 22b is at least one selected from the group consisting of a resin having a glass transition temperature and an inorganic material having a glass transition temperature, the glass transition temperature Tg3 is the glass transition temperature of the matrix resin. It is necessary to satisfy the same condition as Tg2, that is, (Tg3-Tg1) should be selected so as to be 10 ° C. or higher. (Tg3-Tg1) is more preferably 20 ° C. or higher, and 30 ° C. or higher. Further preferred. When (Tg3−Tg1) is 10 ° C. or higher, at the above-described processing temperature, the particles 22b are not deformed and melted, and the convex portions 14 ′ are reliably formed.
When the material constituting the particles 22b is a material that does not have a glass transition temperature, such as an internally cross-linked resin, the Vicat softening temperature (as defined in JIS K7206) satisfies the above-described condition, that is, It is preferably higher than the glass transition temperature of the resin constituting the substrate 21 by 10 ° C. or higher, preferably higher by 20 ° C. or higher, more preferably higher by 30 ° C. or higher.
In addition, in this specification, description of the preferable temperature range etc. about glass transition temperature Tg3 corresponds also to the Vicat softening temperature, when the particle | grains 22b consist of a material which does not have a glass transition temperature but has a Vicat softening temperature. Shall.
Further, as the material constituting the particles 22b, even if the glass transition temperature and the Vicat softening temperature cannot be measured, the particles are heated by heat at a temperature lower than 10 ° C. higher than the glass transition temperature Tg1 of the resin constituting the base material 21. Any material that does not change shape can be used in the present invention.

Tg2 and Tg3 are preferably 40 to 400 ° C, and more preferably 80 to 250 ° C. If Tg2 and Tg3 are 40 ° C. or higher, the above-mentioned processing temperature can be increased to room temperature or higher, which is useful, and matrix resin 22a or Tg3 having Tg2 higher than 400 ° C. is higher than 400 ° C. Use of the particles 22b is less necessary from the viewpoint of economy.

The Young's modulus of the matrix resin 22a at the above processing temperature is preferably 0.01 to 300 GPa, more preferably 0.1 to 10 GPa. If the Young's modulus of the matrix resin 22a is 0.01 GPa or more, sufficient hardness is obtained from the Young's modulus at the processing temperature of the resin constituting the substrate 21, and after the wavy uneven pattern 13 'is formed, The hardness is sufficient to maintain the uneven pattern 13 ′. Use of a resin having a Young's modulus exceeding 300 GPa as the matrix resin 22a is less necessary from the viewpoint of economy.

Examples of the resin constituting the substrate 21 include polyesters such as polyethylene terephthalate, polyolefins such as polyethylene and polypropylene, polystyrene resins such as styrene-butadiene block copolymers, polyvinyl chloride, polyvinylidene chloride, and polydimethylsiloxane. Examples thereof include resins such as silicone resin, fluororesin, ABS resin, polyamide, acrylic resin, polycarbonate, and polycycloolefin.
Among these, polyester and polycarbonate are preferable because a desired uneven shape can be easily obtained after shrinkage.
The resin preferably has a mass average molecular weight of 1,000 to 1,000,000. More preferably 10,000 to 100,000. The mass average molecular weight refers to a value measured using gel permeation chromatography. As specific measurement conditions, as the eluent, one appropriately selected from tetrahydrofuran, chloroform, hexafluoroisopropanol and the like can be used. Further, as the molecular weight standard substance, a material appropriately selected from known molecular weight polystyrene, polymethyl methacrylate and the like can be used. The measurement temperature can be appropriately selected within the range of 35 to 50 ° C.

The matrix resin 22a is selected according to the type of the base material 21 so that the glass transition temperature Tg2 satisfies the above-mentioned conditions. For example, polyvinyl alcohol, polystyrene, acrylic resin, styrene-acrylic copolymer, styrene -Acrylonitrile copolymer, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyethersulfone, fluororesin, etc. can be used. Among these, acrylic resins are preferable in terms of transparency.
The matrix resin preferably has a mass average molecular weight of 1,000 to 10,000,000, more preferably 10,000 to 2,000,000. The mass average molecular weight refers to a value measured using gel permeation chromatography. As specific measurement conditions, as the eluent, one appropriately selected from tetrahydrofuran, chloroform, hexafluoroisopropanol and the like can be used. Further, as the molecular weight standard substance, a material appropriately selected from known molecular weight polystyrene, polymethyl methacrylate and the like can be used. The measurement temperature can be appropriately selected within the range of 35 to 50 ° C.
The matrix resin 22a may be used alone, but may be appropriately used in accordance with the purpose of adjusting the mode pitch, average height, and orientation degree of the wavy uneven pattern. For example, resins of the same type but different in glass transition temperature can be used in combination, or different types of resins can be used in combination.

The resin constituting the particles 22b is selected according to the type of the base material 21 so that the glass transition temperature Tg3 (or Vicat softening point) satisfies the above-described conditions, for example, acrylic thermoplastic resin particles, Examples thereof include polystyrene-based thermoplastic resin particles, acrylic-based crosslinked resin particles, and polystyrene-based crosslinked resin particles. Examples of the inorganic material include glass beads.

The thickness of the substrate 21 is preferably 30 to 500 μm. If the thickness of the base material is 30 μm or more, the manufactured original plate is hardly broken, and if the thickness is 500 μm or less, the original plate can be easily thinned. In addition, the thickness of the base material 21 is randomly extracted from a microphotograph of a cross section (longitudinal section) obtained by cutting the surface fine irregularities (original plate) 20 of FIG. It is an average value of the obtained numerical values when the thickness of the substrate 21 is measured.
Further, in order to support the substrate 21, a resin support having a thickness of 5 to 500 μm may be provided separately.

The thickness t of the hard layer 22 is preferably more than 0.05 μm and not more than 5 μm, and more preferably 0.1 to 2 μm. If the thickness t of the hard layer 22 is more than 0.05 μm and not more than 5 μm, a wavy uneven pattern 13 ′ suitable as a light diffuser can be formed. Moreover, you may form a primer layer between the base material 21 and the hard layer 22 for the purpose of improving adhesiveness or forming a finer structure.

The particle diameter d of the particles 22b needs to be larger than the thickness t of the hard layer 22, and is set according to the thickness t of the hard layer 22. Further, the apparent mode diameter of the convex portion 14 of the illustrated example of the light diffusing sheet 10 manufactured using the surface fine uneven body 20 of FIG. 11 as an original plate is appropriately set so as to be within the above-mentioned preferable range. Is done. A preferred particle diameter d is, for example, 5 to 10 μm, and more preferably 5 to 8 μm.

Note that the fine surface irregularities 20 in FIG. 11 can also be used as a light diffuser instead of the original. In that case, a transparent material is used for the material used for the base material 21, the matrix resin 22 a, and the particles 22 b so that the surface fine uneven body 20 sufficiently functions as a light diffuser.

[Original plate manufacturing method]
The surface fine irregularities 20 in FIG. 11 are a laminated sheet 30 as shown in FIG. 12, that is, a matrix resin on one side (flat surface) of a base film 31 made of resin, and particles 22b dispersed in the matrix resin. A laminating step of forming a laminated sheet 30 provided with a hard layer 32 having a thickness of more than 0.05 μm and not more than 5.0 μm, and a deformation step of deforming at least the hard layer 32 of the laminated sheet 30 so as to be folded. It can be manufactured by the method of having. Here, the substrate film 31 corresponds to the substrate 21 of the surface fine irregularities 20 of FIG. Here, the term “flat” refers to a surface having a center line average roughness of 0.1 μm or less as described in JIS B0601.

(Lamination process)
In the laminating step, first, a coating liquid (dispersion or solution) containing matrix resin 22a, particles 22b, and a solvent is prepared, and the coating liquid is applied to one surface of the base film 31 by a spin coater or a bar coater. As shown in FIG. 12, the hard layer 32 having a thickness t ′ of more than 0.05 μm and 5.0 μm or less is formed. The hard layer 32 at this time is not deformed so as to be folded.
Instead of providing the coating liquid directly on the base film 31 as described above, the hard layer 32 is obtained by laminating a hard layer (a film in which particles are dispersed in a matrix resin) prepared in advance on the base film. You may provide by the method to do.

The base film 31 is preferably a uniaxial heat shrinkable film made of resin. When the uniaxial heat-shrinkable film is used, by heating the laminated sheet 30 in the next deformation step, the hard layer 32 can be easily deformed so as to be folded and the wavy uneven pattern 13 ′ can be formed. Further, according to this method, it is possible to form irregular ridges 13a 'that meander each other and are not parallel to each other.

The resin constituting the uniaxial heat-shrinkable film is as already exemplified as the resin constituting the base material 21. Specifically, a shrink film such as a polyethylene terephthalate shrink film, a polystyrene shrink film, a polyolefin shrink film, or a polyvinyl chloride shrink film can be preferably used.
Among these shrink films, those that shrink 50 to 70% in the uniaxial direction are preferable. If a shrink film that shrinks by 50 to 70% is used, the deformation rate can be increased to 50% or more. As a result, it is possible to form a wavy uneven pattern 13 ′ having a preferable mode pitch and the height of the protruding portion 13a ′.
Here, the deformation rate is (length before deformation−length after deformation) × 100 / (length before deformation) (%). Alternatively, (deformed length) × 100 / (length before deformation) (%).

Further, when a uniaxial heat-shrinkable film is used as the base film 31 as described above and this is heat-shrinked in the next deformation step, the uneven pattern 13 ′ can be formed more easily. The rate is preferably 0.01 to 300 GPa, more preferably 0.1 to 10 GPa.

As the resins constituting the matrix resin 22a and the particles 22b used in the coating liquid, those already exemplified can be used. The glass transition temperature Tg2 of the matrix resin 22a and the glass transition temperature Tg3 of the particles 22b are the base materials. It is important to select and combine the materials so that the glass transition temperature Tg1 of the film 31 is 10 ° C. or higher. Thus, after selecting each material, the laminated sheet which provided the hard layer 32 whose thickness t 'exceeds 0.05 micrometer and is 5.0 micrometers or less on the single side | surface of the uniaxial heat-shrinkable film (base film 31). When 30 is used, a wavy uneven pattern 13 ′ in which the most frequent pitch is 3 to 20 μm and the average height of the protrusions 13 a ′ is 4 to 7 μm is easily formed through the following deformation process.

As a solvent used for the coating liquid, depending on the type of the matrix resin 22a, when the matrix resin 22a is, for example, an acrylic resin, one or more of methyl ethyl ketone and methyl isobutyl ketone can be used.

The concentration of the matrix resin 22a in the coating solution is preferably 5 to 10% by mass as the net amount (solid content) from the viewpoint of coating properties. Further, the amount of the particles 22b is preferably 10 to 50 parts by mass, and more preferably 20 to 30 parts by mass with respect to 100 parts by mass of the net amount of the matrix resin 22a. Within such a range, the occupation area ratio of the convex portion 14a ′ or the concave portion in the fine irregularities to be formed can be controlled within the above-described preferable range.
Here, the net amount (solid content) refers to the ratio of the mass of the solid content remaining after the solvent in the coating solution volatilizes with respect to the mass (100 mass%) of the coating solution.

Note that the thickness t ′ of the hard layer 32 formed in the laminating step may be continuously changed as long as it is in the range of more than 0.05 μm and 5.0 μm or less. In that case, the pitch and depth of the concavo-convex pattern formed by the deformation process are continuously changed. The thickness t ′ of the hard layer 32 hardly changes even after the next deformation step, and can be considered as t ′ = t.

(Deformation process)
11 is obtained by heating the laminated sheet 30 obtained as described above and causing the base film 31 of the laminated sheet 30 to be thermally contracted. In addition, as a deformation | transformation process, the well-known method disclosed by the Japan patent 4683011 etc. is employable, for example.
Examples of the heating method include a method of passing through hot air, steam, hot water, or far infrared rays. Among them, a method of passing through hot air or far infrared rays is preferable because it can be uniformly contracted.
The heating temperature (processing temperature) at the time of heat shrinking the base film 31 is preferably set to a temperature between Tg2 and Tg1, and specifically, the type of the base film 31 to be used and the intended uneven pattern. It is preferable to select appropriately according to the pitch of 13 ', the height of the protruding portion 13a', and the like.

In this manufacturing method, the thinner the thickness of the hard layer 22 and the lower the Young's modulus of the hard layer 22, the smaller the most frequent pitch of the uneven pattern 13 ′ and the higher the deformation rate of the base film 31. The height of the ridge portion 13a ′ increases as the height increases. Therefore, in order to set the most frequent pitch of the concavo-convex pattern 13 ′ and the height of the ridge 13 a ′ to desired values, it is necessary to appropriately select the above conditions.

Note that the surface fine uneven body 20 having the structure as shown in FIG. 11 can also be manufactured by the following methods (1) to (4).
(1) A method of forming a laminated sheet by providing an undeformed hard layer on one side of a flat base film, and compressing the whole laminated sheet in one direction along the surface.
When the glass transition temperature of the base film is lower than room temperature, the laminated sheet is compressed at room temperature. When the glass transition temperature of the base film is higher than the room temperature, the laminated sheet is compressed above the glass transition temperature of the base material and hard. Performed below the glass transition temperature of the layer.
(2) An undeformed hard layer is provided on one side of a flat base film to form a laminated sheet, the laminated sheet is stretched in one direction, and the direction perpendicular to the stretching direction is shrunk to form a hard layer. A method of compressing in one direction along the surface.
When the glass transition temperature of the base film is lower than room temperature, the lamination sheet is stretched at room temperature. When the glass transition temperature of the base film is room temperature or higher, the stretching of the laminated sheet is equal to or higher than the glass transition temperature of the base film. It is performed below the glass transition temperature of the hard layer.
(3) A flat base film formed of an uncured ionizing radiation curable resin is laminated with an undeformed hard layer to form a laminated sheet, and the base film is cured by irradiation with ionizing radiation. A method of compressing the hard layer laminated on the base film in at least one direction along the surface.
(4) An undeformed hard layer is laminated on a flat base film swelled by swelling a solvent to form a laminated sheet, and the solvent in the base film is dried and contracted by removing it. The method of compressing the hard layer laminated | stacked on the base film in at least one direction along the surface.

In the method of (1), as a method of forming a laminated sheet, for example, a resin solution or dispersion containing particles is applied to one side of a flat base film using a spin coater or bar coater, and a solvent is used. Examples thereof include a drying method and a method in which a hard layer prepared in advance is laminated on one side of a flat base film. 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.

In the method (2), examples of the method of stretching the laminated sheet in one direction include a method of stretching by stretching one end portion of the laminated sheet and the opposite end portion thereof.
In the method (3), examples of the ionizing radiation 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 base film. The drying temperature of the solvent is appropriately selected according to the type of solvent.

In the hard layer in the methods (2) to (4), the same components as those used in the method (1) can be used, and the thickness can be the same. Moreover, the formation method of a lamination sheet is the same as the method of (1), the method of apply | coating a coating liquid on the single side | surface of a base film, and drying the solvent, The hard layer produced beforehand on the single side | surface of a base film The method of laminating can be applied.

[Manufacturing method of surface irregularities by transfer using original plate]
When manufacturing the light diffusive sheet 10 in the illustrated example using the surface fine irregularities 20 of FIG. 11 as an original plate, a transfer step of transferring the fine irregularities of the surface fine irregularities (original plate) 20 to another material. I do. In this example, the fine irregularities formed on the surface of the hard layer 22 of the surface fine irregularities (original) 20 are transferred to another material, and a primary transfer product having a reverse pattern of the fine irregularities of the original on the surface is obtained. Then, the reverse pattern of the primary transfer product is transferred to another material to obtain the light diffusive sheet 10 of the illustrated example which is a secondary transfer product. As the transfer step, for example, a publicly known method disclosed in Japanese Patent No. 4683011 can be adopted.
One aspect of the present invention is a method for producing a surface fine unevenness using the surface fine unevenness described above as an original plate.

Specifically, an uncured ionizing radiation curable resin containing a release agent is adjusted to a thickness of, for example, 3 to 30 μm with respect to the fine unevenness of the surface fine unevenness 20 of FIG. After coating with a coater such as a die coater, roll coater, or bar coater and irradiating with ionizing radiation to cure, the original is peeled off to obtain a primary transfer product. The primary transfer product has a reversal pattern of fine irregularities of the original plate. On the other hand, a transparent substrate 11 made of PET is prepared, and an uncured ionizing radiation curable resin is applied on one surface thereof with a thickness that sufficiently covers fine irregularities. Then, the surface of the applied uncured ionizing radiation curable resin is pressed against the surface having the reversal pattern of the previously obtained primary transfer product and cured by irradiation with ionizing radiation. The next transfer product is peeled off. Irradiation with ionizing radiation may be performed from either one of the primary transfer product side and the transparent PET substrate side having ionizing radiation transparency. Thereby, it consists of the transparent base material 11 which consists of PET, and the surface layer 12 of the ionizing radiation curable resin cured material formed on the one side, and FIG. The light diffusable sheet (secondary transfer product) 10 of FIG. 2 is obtained.

Examples of the ionizing radiation curable resin include an ultraviolet curable resin and an electron beam curable resin. The type of ionizing radiation to be irradiated is appropriately selected according to the type of resin. In general, the ionizing radiation often means ultraviolet rays and electron beams, but in the present specification, visible rays, X-rays, ion rays and the like are also included.

Uncured ionizing radiation 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 methacrylate. 1 type selected from monomers such as prepolymers such as 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, etc. The thing containing the above component is mentioned. The uncured ionizing radiation curable resin is preferably diluted with a solvent or the like. A fluorine resin, a silicone resin, or the like may be added to the uncured ionizing radiation curable resin. When the uncured ionizing radiation curable resin is ultraviolet curable, it is preferable to add a photopolymerization initiator such as acetophenones and benzophenones to the uncured ionizing radiation curable resin.

Also, instead of ionizing radiation curable resin, transfer is performed using, for example, thermosetting resin such as uncured melamine resin, urethane resin or epoxy resin, or thermoplastic resin such as acrylic resin, polyolefin or polyester. As long as fine irregularities can be transferred, the specific method and material to be transferred are not limited.
In the case of using a thermosetting resin, for example, a method of applying a liquid uncured thermosetting resin to fine irregularities and curing it by heating is mentioned. When using a thermoplastic resin, a sheet of thermoplastic resin is used. There is a method of heating and softening while pressing against fine irregularities and then cooling.

In addition, as described above, in the case of producing a secondary transfer product, for example, a method using a plating roll described in Japanese Patent No. 4683011 is also exemplified. Specifically, first, a long sheet-like material is manufactured as an original plate, the original plate is rounded and attached to the inside of a cylinder, plating is performed with a roll inserted inside the cylinder, and the roll is removed from the cylinder. Take out and obtain a plating roll (primary transfer product). Next, a light diffusive sheet (secondary transfer product) is obtained by transferring the fine irregularities of the plating roll.

As the original plate, either a single wafer type or a web type can be used. If a web type master is used, a web type primary transfer product and a secondary transfer product can be obtained. In the single-wafer type, a stamp method using the single-wafer type original as a flat plate, a roll imprint method using a single-wafer type original wound around a roll as a cylindrical die, and the like can be applied. Further, a single-wafer type master may be arranged inside the mold of the injection molding machine. However, in the method using these single-wafer type masters, it is necessary to repeat the transfer many times in order to mass-produce the light spreading powder sheet as shown in the illustrated example. When the transferability (releasability) is low, clogging occurs in the fine unevenness to be transferred, and the transfer of the fine unevenness may be incomplete. On the other hand, when the original is a web type, fine irregularities can be continuously transferred in a large area, and a necessary amount of light diffusive sheet can be produced in a short time without repeating many transfers.

[Modification of manufacturing method of original plate and manufacturing method of fine surface irregularities by transfer using original plate]
In the above-described lamination process of [Original Plate Manufacturing Method], a coating liquid containing matrix resin 22a, particles 22b, and a solvent was used. However, a hard layer is formed using a coating liquid that does not contain particles and contains a matrix resin and a solvent, and is formed into a wavy uneven pattern by a deformation process, and then a large number of recesses or protrusions on the uneven pattern. May be formed. The method for forming the hard layer can be performed in the same manner as described above except that particles are not used. The deformation process can also be performed in the same manner as described above. Next, as a method of forming a large number of concave portions or convex portions on the formed concave / convex pattern, the following methods (5) to (8) can be mentioned.
(5) A method of cutting with a rotary precision cutting machine.
(6) A method of forming a recess by pressing a projection having the same size and diameter as the recess or the protrusion onto the wavy uneven pattern.
(7) A method of forming a convex portion formed of the resin or the inorganic substance by adhering a fine resin or inorganic melt to the wavy uneven pattern and then solidifying it by cooling.
(8) A method in which a liquid in which a resin or an inorganic substance is dispersed in a dispersion medium is deposited on the wavy uneven pattern, and then the dispersion medium is evaporated to form a convex portion formed of the resin or the inorganic substance.
In addition, by applying the inkjet printing method in the method (7) or (8), a large number of concave portions or convex portions can be formed on the wavy uneven pattern with high accuracy.
In addition, a hard layer is formed using a coating liquid that does not contain particles and contains a matrix resin and a solvent, and is formed into a wavy uneven pattern by a deformation process (a large number of recesses or protrusions have not yet been formed) ) As an original plate, and a plurality of concave portions or convex portions may be formed on the concavo-convex pattern by the above methods (5) to (8). And by transferring this as an original plate, it is possible to produce a surface fine unevenness.

<About other forms>
In the above description, using the surface fine unevenness produced by the laminating process and the deformation process as an original plate, a primary transfer product obtained by transferring the fine unevenness of the surface fine unevenness is obtained, and then the primary transfer product of A secondary transfer product to which fine irregularities (reverse pattern of the original plate) were transferred was used as a light diffusive sheet 10.
However, the present invention is not limited to the above form.
That is, the surface fine uneven body 20 itself as shown in FIG. 11 manufactured by the above-described lamination process and deformation process can also be used as the light diffusive sheet. Moreover, the primary transfer product obtained by using the surface fine irregularities 20 produced by the laminating process and the deformation process as an original plate and the n-order transfer product (n is an integer of 3 or more) are used as the light diffusive sheet. If it is a transfer product, it is not limited to a secondary transfer product.
Moreover, you may transfer a fine unevenness | corrugation to the said curved surface of the molded object which has a curved surface using an original plate.
Also, using the surface fine irregularities produced by the laminating process and the deformation process and the n-order transfer product as an original plate, a transparent thermoplastic resin such as an acrylic resin or a polycarbonate resin is injection-molded, and the fine irregularities are at least on the surface. You may manufacture the injection molded product formed in part.

In the n-order transfer product obtained by using the surface fine irregularities 20 produced by the laminating process and the deformation process specifically shown above as an original plate, when n is an odd number, as the fine irregularities, a specific corrugation On the concave / convex pattern, concave portions are formed instead of convex portions. This is because in the n-th order transfer product in which n is an odd number, a reverse pattern of the convex portion formed based on the particles, that is, a concave portion is formed. In this way, even if the surface fine unevenness having a concave portion with a specific wavy uneven pattern as the fine unevenness, since the anisotropy due to the wavy uneven pattern is weakened by the concave portion, a sufficient diffusion angle in the Y direction And a certain diffusion angle in the X direction. Therefore, even if it is an n-order transfer product in which n is an odd number, it exhibits the same light diffusibility as an n-order transfer product in which n is an even number.

In addition, as the particles used for forming the hard layer, resin particles and inorganic particles can be used, and any material can be used as long as it is not melted or deformed in the deformation process or the process of transferring fine irregularities. There may be. However, as described above, when the surface fine irregularities 20 having the particles themselves as shown in FIG. 11 are used as the light diffusing sheet, the particles are transparent particles, preferably acrylic cross-linked resin particles, glass It is necessary to use beads, polystyrene-based crosslinked resin particles, and the like.

Moreover, in the above example, although the sheet-like material was illustrated as a surface fine unevenness | corrugation body and a light diffusable sheet, it is not limited to a sheet-like material, A solid molded body may be sufficient.
Further, the fine unevenness may be formed in any part depending on the purpose as long as it is at least a part of the surface of the surface fine unevenness. For example, when the surface fine unevenness is a sheet-like material, it may be formed on only one surface, on both surfaces, or may be formed on only part of each surface, You may form in at least one part of the surrounding surface (end surface) of a thing. Furthermore, even when the surface fine irregularities are three-dimensional molded bodies, they may be formed on the entire surface or only on a part thereof. In addition, when a surface fine unevenness | corrugation body is a three-dimensional molded object, the said three-dimensional molded object can be used for the use similar to the use illustrated about the light diffusable sheet. A diffusion member for a HUD system; a diffusion member for a projector; a diffusion member for a backlight of a television, a monitor, a notebook personal computer, a tablet personal computer, a smartphone, a mobile phone, etc .; In a scanner light source in which LED light sources are linearly arranged, it can be suitably used as a diffusing member that constitutes at least an emission surface of a light guide member.

Moreover, it has the following side surfaces.
It is a surface fine uneven body in which fine unevenness is formed on at least a part of the surface,
The fine unevenness has a wavy uneven pattern and a recess or protrusion formed on the wavy uneven pattern,
The wavy concavo-convex pattern comprises a plurality of ridges arranged along a first direction, and a ridge between the plurality of ridges,
The ridge lines of the plurality of ridges meander non-parallel to each other when viewed from the normal direction of the substrate of the surface fine irregularities,
The most frequent pitch in the first direction of the plurality of ridges is 3 to 20 μm;
The apparent mode diameter of the concave portion or convex portion is 1 to 10 μm,
The surface fine irregularities, wherein the concave or convex shape is hemispherical.

Moreover, it has the following aspects of this invention.
It is a surface fine uneven body in which fine unevenness is formed on at least a part of the surface,
The fine unevenness has a wavy uneven pattern and a recess or protrusion formed on the wavy uneven pattern,
The wavy concavo-convex pattern comprises a plurality of ridges arranged along a first direction, and a ridge between the plurality of ridges,
The ridge lines of the plurality of ridges meander non-parallel to each other when viewed from the normal direction of the surface fine irregularities,
The most frequent pitch in the first direction of the plurality of ridges is 3 to 20 μm;
The apparent mode diameter of the concave portion or convex portion is 1 to 10 μm,
The shape of the concave portion or convex portion is hemispherical,
The surface fine concavo-convex body in which the occupying ratio of the concave portion or the convex portion is 30 to 70 mass% with respect to the total area of the surface on which the fine unevenness is formed.

The present invention has the following aspects.
On one side of a base film made of resin, a hard layer is provided by applying a coating liquid containing a matrix resin and particles so that the thickness after drying is more than 0.05 μm and 5.0 μm or less. A lamination process for forming a laminated sheet;
A deformation step of deforming so as to fold at least the hard layer of the laminated sheet,
The resin is a polyester resin,
The matrix resin is a group consisting of polyvinyl alcohol, polystyrene, acrylic resin, styrene-acrylic copolymer, styrene-acrylonitrile copolymer, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyethersulfone, and fluororesin. At least one resin more selected, having a glass transition temperature higher by 10 ° C. or more than the resin constituting the base film,
The particles are at least one particle selected from the group consisting of acrylic thermoplastic resin particles, polystyrene thermoplastic resin particles, acrylic crosslinked resin particles, polystyrene crosslinked resin particles, and glass beads, At a temperature below 10 ° C. higher than the glass transition temperature of the resin constituting the substrate film, the particle shape does not change,
The particle size is 5-10 μm,
The method for producing a fine surface irregularity, wherein the cured layer contains 10 to 50 parts by mass of the particles with respect to 100 parts by mass of the matrix resin.

Hereinafter, the present invention will be specifically described by way of examples.
[Example 1]
The following coating liquid (1) is applied to one side of a polyethylene terephthalate uniaxial heat shrinkable film (“SC807” manufactured by Toyobo Co., Ltd., thickness: 30 μm, glass transition temperature Tg1 = 80 ° C.). The laminated sheet was obtained by coating with a bar coater (Meyer bar # 14) so that the thickness t ′ was 2 μm.
(Coating fluid (1))
Acrylic resin A (glass transition temperature Tg2 = 128 ° C.) and acrylic cross-linked resin particles having a particle diameter d of 5 μm (“SSX105” manufactured by Sekisui Plastics Co., Ltd., Vicat softening temperature of 200 ° C. or higher) are solid. The mixture was mixed at a mass ratio of 70:30, and in addition to toluene, a coating liquid (1) having a solid content concentration of 7.7 mass% was obtained.
In addition, although the said acrylic resin A is solid content concentration 20 mass%, the mass ratio and density | concentration in this example are the values calculated by the net amount (solid content amount). The following examples are also calculated with the net amount.

Next, the laminated sheet is heated at 150 ° C. for 1 minute using a hot air oven to heat shrink the polyethylene terephthalate uniaxial heat shrinkable film to 49% of the length before heating in the uniaxial direction (deformation rate). 51%), the hard layer was deformed to be folded. Thereby, the surface fine uneven sheet | seat (original) in which the fine unevenness | corrugation which has a wavy uneven pattern and many convex parts formed on it was formed in the surface of the hard layer was obtained. Further, the formed ridges meander each other and are non-parallel to each other and irregularly formed.
An uncured UV curable resin A (manufactured by Soken Chemical Co., Ltd.) containing a release agent is applied to the surface of the surface fine uneven surface of the obtained surface fine uneven sheet (original) so as to have a thickness of 20 μm and irradiated with ultraviolet rays. And cured, and then peeled to obtain a primary transfer product having a reversal pattern of fine unevenness of the surface fine unevenness sheet.
Next, an uncured UV curable resin B (manufactured by Sony Chemical Co., Ltd.) was applied to one side of a transparent PET base material (“A4300” manufactured by Toyobo Co., Ltd., thickness: 188 μm) to a thickness of 20 μm. The surface of the primary transfer product having the above reversal pattern is pressed against the ultraviolet curable resin B, cured by irradiating with ultraviolet rays, and after curing, the primary transfer product is peeled off, and then on the transparent PET substrate. A light diffusive sheet (secondary transfer product) having a surface layer made of a cured product of an ultraviolet curable resin formed on the surface layer and having the same fine unevenness as the above-mentioned surface fine unevenness sheet (original) )

[Example 2]
A light diffusing sheet was obtained in the same manner as in Example 1 except that the following coating liquid (2) was used instead of the coating liquid (1) in Example 1.
(Coating fluid (2))
Acrylic resin A (glass transition temperature Tg2 = 128 ° C.) and acrylic cross-linked resin particles having a particle diameter d of 5 μm (“SSX105” manufactured by Sekisui Plastics Co., Ltd.) at a solid content mass ratio of 80:20 It mixed and added to toluene, and the coating liquid (2) with a solid content density | concentration of 7.7 mass% was obtained.

[Example 3]
A light diffusing sheet was obtained in the same manner as in Example 1 except that the following coating liquid (3) was used instead of the coating liquid (1) in Example 1.
(Coating liquid (3))
Acrylic resin A (glass transition temperature Tg2 = 128 ° C.), acrylic resin B (glass transition temperature Tg2 = 132 ° C.), and acrylic cross-linked resin particles having a particle diameter d of 5 μm (manufactured by Sekisui Plastics Co., Ltd. “ SSX105 ") was mixed at a solid content mass ratio of 35:35:30 and added to toluene to obtain a coating solution (3) having a solid content concentration of 7.7 mass%.

[Comparative Example 1]
A light diffusing sheet was obtained in the same manner as in Example 1 except that the following coating liquid (4) was used instead of the coating liquid (1) in Example 1.
(Coating fluid (4))
Acrylic resin A (glass transition temperature Tg2 = 128 ° C.) was added to toluene to obtain a coating liquid (4) having a solid content concentration of 7.7% by mass.

[Example 4]
A light diffusing sheet was obtained in the same manner as in Example 1 except that the following coating liquid (5) was used instead of the coating liquid (1) in Example 1.
(Coating liquid (5))
Acrylic resin A (glass transition temperature Tg2 = 128 ° C.) and acrylic cross-linked resin particles having a particle diameter d of 10 μm (“SSX110” manufactured by Sekisui Plastics Co., Ltd., Vicat softening temperature point of 200 ° C. or higher) The mixture was mixed at a solid content mass ratio of 70:30, and in addition to toluene, a coating solution (5) having a solid content concentration of 7.7 mass% was obtained.

[Example 5]
A light diffusing sheet was obtained in the same manner as in Example 1 except that the following coating liquid (6) was used instead of the coating liquid (1) in Example 1.
(Coating liquid (6))
Acrylic resin A (glass transition temperature Tg2 = 128 ° C.) and acrylic cross-linked resin particles having a particle diameter d of 5 μm (“SSX105” manufactured by Sekisui Plastics Co., Ltd.) are in a solid content mass ratio of 50:50. It mixed and added to toluene, and the coating liquid (6) with a solid content density | concentration of 7.7 mass% was obtained.

[Example 6]
In Example 1, coating was performed by a bar coater (Meyer bar # 20) so that the thickness t ′ of the hard layer after coating and drying was 3 μm, and a polyethylene terephthalate uniaxial heat-shrinkable film was uniaxially before heating. A light diffusing sheet was obtained in the same manner as in Example 1 except that the film was thermally shrunk to 60% of the length (40% as the deformation rate).

[Example 7]
Nickel was deposited to a thickness of 500 μm on the surface of the surface fine uneven sheet (original) obtained by the same method as in Example 1 by nickel electroforming. Subsequently, the deposited nickel was peeled from the surface fine uneven sheet (original) to obtain a nickel secondary original having the surface fine unevenness transferred on the surface. The nickel secondary original plate was incorporated into a mold of an injection molding machine, and injection molding of an acrylic resin was performed to obtain an injection molded product having fine irregularities transferred on the surface. The obtained injection-molded product is a rectangular parallelepiped of 300 mm × 10 mm × 2 mm, in which fine irregularities are transferred to one surface of a pair of 2 mm × 300 mm surfaces, and the other surface is a smooth surface.

(Evaluation)
(1) About the fine unevenness of the light diffusive sheet and the injection-molded product obtained in each of the above examples, the most frequent pitch of the wavy uneven pattern, the average height of the protruding portion of the wavy uneven pattern, and the appearance of the protruding portion The mode diameter and the average height of the projections, and the occupied area ratio of the projections in the fine irregularities were determined by the method described above. The results are shown in Table 1.
(2) Using GENESISIA GonioFar Field Profiler (manufactured by Genesia), light is incident on the light diffusing sheet and injection molded product obtained in each of the above examples from the smooth surface side, and the diffusion angle in the Y direction and 1 / Ten diffusion angles, X-direction diffusion angles and 1/10 diffusion angles were measured. The results are shown in Table 1.
(3) The light of the red laser pointer was made incident from the smooth surface side and the diffused light was emitted from the opposite surface side to the light diffusing sheet and the injection molded product obtained in each of the above examples. White paper was placed in parallel with the light diffusing sheet and the injection-molded product on the opposite side of the light diffusing sheet and the injection-molded product. The shape of the diffused light (projected image) of the red laser pointer projected on white paper was visually evaluated in four stages. The results are shown in Table 1.
(4) Light from the LED light source (irradiation angle 10 °) is incident on the light diffusable sheet and injection molded product obtained in each of the above examples from the smooth surface side, and from the opposite surface (fine unevenness forming surface) side. Transmitted light was emitted. A luminance meter SR-3 (manufactured by Topcon Co., Ltd.) was placed at a position 1 m away from the light diffusing sheet and the injection molded product on the opposite surface side in the normal direction, and the luminance was measured. The results are shown in Table 1. In addition, the brightness | luminance of Table 1 is a relative brightness | luminance when the brightness | luminance when the light diffusable sheet | seat of Example 1 is measured by the above-mentioned method is set to 100.
(5) From the light diffusive sheet and the injection molded product obtained in each of the above examples, light was incident from the side of the fine unevenness, and in accordance with JIS K 7105 “Testing methods for optical properties of plastics” The light transmittance (%) was measured. The results are shown in Table 1.
In addition, since the injection molded product manufactured in Example 7 was a rectangular parallelepiped, the surface on which fine irregularities were formed and the smooth surface were parallel. However, when an injection molded product in which the surface on which the fine irregularities are formed and the smooth surface is not parallel is manufactured, the smooth surface parallel to the surface on which the fine irregularities are formed is obtained by appropriately cutting the injection molded product. It is preferable to use the sample that has been cut out as a sample, and to use the sample in the above measurements (2) to (5).

 

From the results shown in Table 1, a wavy uneven pattern having a plurality of irregular ridges meandering non-parallel to each other and ridges between the plurality of ridges and having a most frequent pitch of 3 to 20 μm. In addition, according to the light diffusing sheet and the injection-molded product of each Example in which fine irregularities including a large number of convex portions having an apparent mode diameter of 1 to 10 μm are formed, the diffusion angle in the Y direction is sufficiently high. It was large and the diffusion angle in the X direction was 4 ° or more. In addition, according to the light diffusing sheets and injection-molded articles of Examples 1 to 5 and Example 7, the diffusion angles in the X and Y directions are moderately large, and the 1/10 diffusion angles in the Y and X directions are The respective values were (diffusion angle × 1.4 + 25 °) or less and (diffusion angle × 1.6 + 25 °) or less, and the relative luminance was sufficiently large. Therefore, it has been understood that these can be suitably used in, for example, a head-up display system in which information such as a traveling speed needs to be clearly diffused on the windshield of an automobile. In particular, the light diffusing sheets of Examples 1 to 3 and the injection-molded product of Example 7 have a large diffusion angle in the X direction while maintaining a very high diffusion angle in the Y direction, and a balance with relative luminance. Also, it had very high performance.
On the other hand, according to the light diffusing sheet of the comparative example, the diffusion angle in the Y direction is sufficiently large, but the diffusion angle in the X direction is very small and the anisotropy is too high. It was understood that it was unsuitable for use.
Moreover, the light diffusable sheet of each Example had sufficient light transmittance.
Further, it was understood that the injection molded product of Example 7 can be suitably used in a light guide member of a scanner light source in which LED light sources are arranged in a line, which is used in a copying machine or the like.

10: Light diffusive sheet, 13: Wavy uneven pattern, 13a: Convex part, 13b: Concave part, 14: Convex part, 20: Surface fine unevenness (original), 21: Base material, 22: Hard layer 22a: matrix resin, 22b: particles, 31: base film, 32: hard layer (undeformed)

Claims (8)

1. It is a surface fine uneven body in which fine unevenness is formed on at least a part of the surface,
   The fine unevenness includes a wavy uneven pattern and a plurality of concave portions or convex portions formed on the wavy uneven pattern,
   The wavy uneven pattern is composed of a plurality of irregularly formed ridges and a groove between the plurality of ridges,
   The plurality of ridges meander non-parallel to each other,
   The most frequent pitch of the plurality of ridges is 3 to 20 μm,
   The surface fine irregularities, wherein the apparent mode diameter of the concave portion or convex portion is 1 to 10 μm.
2. 2. The surface fine irregularities according to claim 1, wherein the average height of the ridges is 4 to 7 μm.
3. 3. The surface fine uneven body according to claim 1 or 2, wherein the area occupied by the concave portion or the convex portion in the fine unevenness is 30 to 70%.
4. 4. The surface fine unevenness according to any one of claims 1 to 3, which is a light diffuser.
5. The surface fine unevenness according to any one of claims 1 to 3, which is a light diffuser-forming original plate for transferring the fine unevenness to produce a light diffuser.
6. A laminating step of forming a laminated sheet by providing a hard layer having a thickness of more than 0.05 μm and not more than 5.0 μm consisting of matrix resin and particles dispersed in the matrix resin on one side of a base film made of resin When,
   A deformation step of deforming so as to fold at least the hard layer of the laminated sheet,
   The glass transition temperature of the matrix resin is 10 ° C. or more higher than the glass transition temperature of the resin constituting the base film,
   The particles are made of a material whose particle shape is not changed by heat at a temperature lower than a temperature 10 ° C. higher than the glass transition temperature of the resin constituting the base film,
   The method for producing a fine surface irregularity, wherein the particle diameter is larger than the thickness of the hard layer.
7. The base film is a uniaxial heat shrinkable film,
   The method for producing a surface fine unevenness according to claim 6, wherein the deformation step is a step of heating the laminated sheet to shrink the uniaxial heat-shrinkable film.
8. Manufacturing of a light diffuser having a transfer step of transferring the fine unevenness of the surface fine unevenness using the surface fine unevenness produced by the manufacturing method according to claim 6 or 7 as an original plate for forming a light diffuser. Method.

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