JP2009092769A - Optical sheet and light diffusion sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical sheet which is excellent in an aimed optical characteristic (light diffusion property or the like) and further which can easily make the optical characteristic uneven. <P>SOLUTION: In the optical sheet 10a, rugged regions 12 having ruggedness are dispersedly arranged on one flat surface or on both flat surfaces and preferably the rugged regions 12 are unevenly arranged. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical sheet used as a light diffusion sheet or the like and a light diffusion sheet.

As an optical sheet having light diffusibility and the like, a sheet having an uneven surface is known. For example, Patent Document 1 discloses a light diffusing sheet in which a large number of dot-shaped convex portions are formed on the substrate surface. In the optical sheet described in Patent Document 1, ink is ejected onto a substrate by ink jet, and this is fixed to form dot-like convex portions.
JP 2004-157430 A

  When it is intended to control the diffusion and reflection of light by unevenness, if the interval between the uneven portions is about the wavelength of light, coloring due to interference becomes a problem, and if the interval exceeds several tens of μm, bright lines, etc. Therefore, the interval between the concavo-convex parts is required to be 20 μm or less. However, in the optical sheet described in Patent Document 1, if the interval between the concavo-convex portions is several tens of μm to several hundreds of μm, the interval is stably formed, but if it is 20 μm or less, it is difficult to obtain a desired interval. .

In addition, in the optical sheet, optical characteristics such as light diffusibility may not be made uniform, but may be made uneven so as to be higher or lower at a predetermined position. For example, in a light guide plate used in a backlight unit of a liquid crystal display, an image of a linear light source disposed on the side end face of the light source side surface close to the linear light source is used to prevent the image of the linear light source from being projected on the surface of the light guide plate. May increase light diffusivity. In addition, when using a direct type backlight unit having a plurality of linear light sources or point light sources in a liquid crystal display, the light from the line light sources or between the point light sources approaches the light source. May increase diffusivity.
In order to adjust the optical characteristics of the optical sheet having unevenness on the surface so that the optical characteristics become nonuniform, it is conceivable to change the interval between the unevenness parts depending on the position, but in the optical sheet described in Patent Document 1, In addition, it was difficult to change the interval after setting the interval between the concave and convex portions to 20 μm or less. Therefore, in the optical sheet described in Patent Document 1, it is difficult to make the optical sheet non-uniform so that the optical characteristics are high or low at a predetermined position.

Therefore, an object of the present invention is to provide an optical sheet that is excellent in target optical characteristics (light diffusibility, etc.) and that can easily make optical characteristics non-uniform. It is another object of the present invention to provide a light diffusing sheet that is excellent in target light diffusibility and that can easily make light diffusibility nonuniform.

The present invention includes the following aspects.
[1] An optical sheet, wherein uneven regions having unevenness are dispersed and arranged on one or both sides of a flat surface.
[2] The optical sheet according to [1], wherein the uneven regions are arranged unevenly.
[3] A light diffusion sheet comprising the optical sheet according to [1] or [2].
[4] The most frequent pitch A of the irregularities in the irregularity region is more than 1 μm and not more than 20 μm, and the ratio of the average depth B of the irregularities to the most frequent pitch A (A / B) is 0.1 to 3.0. ] The light-diffusion sheet | seat as described in.
[5] The light diffusion sheet according to [4], wherein the uneven regions are dispersed in a dot shape.

The optical sheet of the present invention has excellent target optical characteristics, and can easily make the optical characteristics non-uniform.
The light diffusing sheet of the present invention has excellent target light diffusibility, and can easily make the light diffusibility nonuniform.

<First Embodiment>
A first embodiment of the optical sheet of the present invention will be described.
In FIG. 1, the optical sheet of this embodiment is shown. In FIG. 1, for easy explanation, the uneven region 12 is enlarged and its arrangement is shown sparsely.
The optical sheet 10a of the present embodiment is used as a light diffusion sheet in which the light source 20 is disposed at one end α in the longitudinal direction. The uneven surface 12 having an elliptical outer shape is formed on the flat one surface 11 and the optical sheet 10a. Are arranged in a dot pattern in a pattern that gradually becomes denser from one end α in the longitudinal direction to the other end β. In the present invention, “flat” means that the center line average roughness described in JIS B0601 is 0.1 μm or less. Moreover, the uneven | corrugated area | region has the centerline average roughness of JIS B0601 exceeding 0.1 micrometer, especially 0.5 micrometer or more.

(Uneven area)
The uneven area 12 is an area having an uneven pattern. In the present embodiment, as shown in FIG. 2, a meandering wavy uneven pattern 12 a is formed on the surface of the uneven area 12.
In the optical sheet 10a of the present embodiment used for the light diffusion sheet, the most frequent pitch A of the uneven pattern 12a is preferably more than 1 μm and less than 20 μm, and more preferably more than 1 μm and less than 10 μm. If the most frequent pitch A is less than 1 μm, the wavelength is less than the wavelength of visible light, and the visible light is not refracted by the concavo-convex pattern 12a, and light is transmitted. It tends to be low and uneven brightness tends to occur.

The ratio of the average depth B of the concavo-convex pattern to the most frequent pitch A of the concavo-convex pattern 12a (B / A, hereinafter referred to as aspect ratio) is preferably 0.1 to 3.0. If the aspect ratio is less than 0.1, desired optical characteristics may not be obtained. On the other hand, when the aspect ratio is larger than 3.0, it is difficult to form the concave / convex pattern 12a in the manufacture of the optical sheet 10a.
Here, the average depth B is the average depth of the bottom 12b of the concavo-convex pattern 12a. The bottom 12b is a minimum point of the concave portion of the concave / convex pattern 12a, and the average depth B is an optical sheet when a cross section (see FIG. 3) obtained by cutting the concave / convex region 12 along the minor axis direction is seen. The average value (B _AV ) of the lengths B ₁ , B ₂ , B ₃ ... From the reference line L ₁ parallel to the surface direction of the entire 10 a to the top of each convex part, and the reference line L ₁ It is the difference (b _AV -B _AV ) from the average value (b _AV ) of the lengths b ₁ , b ₂ , b ₃ .
As a method of measuring the average depth B, a method of measuring the depth of each bottom portion 12b using a cross-sectional image of the concavo-convex pattern 12a photographed by an atomic force microscope and obtaining an average value thereof is employed.

As in the present embodiment, meandering when the concave / convex pattern 12a is along one direction means that the degree of orientation of the concave / convex pattern obtained by the following method is 0.3 or more. This degree of orientation is an index of variation in the orientation of the concavo-convex pattern, and the larger the value, the more the orientation varies.
In order to obtain the degree of orientation, first, the top surface of the concavo-convex pattern is photographed with a surface optical microscope, and the image is converted into a grayscale file (for example, a tiff format). In the grayscale file image (see FIG. 4), the lower the whiteness, the deeper the bottom of the concave portion (the higher the whiteness, the higher the top of the convex portion). Next, the image of the grayscale file is Fourier transformed. FIG. 5 shows an image after Fourier transform. The white portion extending from the center of the image in FIG. 5 to both sides includes information on the pitch and orientation of the concavo-convex pattern 12a.
Then, pull the extension line L ₂ in the horizontal direction from the center of the image of FIG. 5, the plots the luminance of the auxiliary line (see FIG. 6). The horizontal axis of the plot in FIG. 6 represents the pitch, the vertical axis represents the frequency, and the value X at which the frequency is maximum represents the most frequent pitch of the uneven pattern 12a.
Then, in FIG. 5, the auxiliary line L ₃ perpendicular at portions of the auxiliary line L ₂ and the value X pull, its plotting the luminance on the auxiliary line L ₃ (see FIG. 7). However, the horizontal axis in FIG. 7 is a numerical value divided by the value of X in order to enable comparison with various uneven structures. The horizontal axis in FIG. 7 represents an index (orientation) indicating the degree of inclination with respect to the direction in which the concavo-convex pattern is formed (the vertical direction in FIG. 4), and the vertical axis represents the frequency. The half width W ₁ of the peak in the plot of FIG. 7 (the width of the peak at the height at which the frequency is half the maximum value) represents the degree of orientation of the uneven pattern 12a. The larger the half width W ₁ , the more meandering and the orientation varies.

When the degree of orientation is less than 0.3, variation in the orientation of the concavo-convex pattern 12a is reduced, and thus light diffusibility is reduced.
The degree of orientation is preferably 1.0 or less. When the degree of orientation exceeds 1.0, the direction of the concavo-convex pattern 12a becomes random to some extent, so that the light diffusibility increases but the anisotropy tends to decrease.
In order to make the degree of orientation 0.3 or more, for example, in the production described later, a heat-shrinkable film and an uneven region forming convex portion may be appropriately selected.
Moreover, you may employ | adopt the method of shape | molding transparent resin using the metal mold | die with which the uneven | corrugated pattern whose orientation degree is 0.3 or more was formed in one surface.

  Although the area ratio of the uneven | corrugated area | region 12 with respect to the area of the single side | surface of the optical sheet 10a is based also on the target light diffusivity, it is preferable that it is 30 to 100%. When the area ratio of the uneven region 12 is 30% or more, sufficient light diffusibility is exhibited.

(Constituent material of optical sheet)
The optical sheet 10a is made of a transparent resin having high visible light transmittance (specifically, the total light transmittance of visible light is 85% or more).
Moreover, the optical sheet 10a can contain an additive in the range which does not impair optical characteristics, such as a light transmittance, for the purpose of improving heat resistance and light resistance. Examples of the additive include a light stabilizer, an ultraviolet absorber, an antioxidant, a lubricant, and a light diffusing agent. Especially, it is preferable to add a light stabilizer, and it is preferable that the addition amount is 0.03-2.0 mass parts with respect to 100 mass parts of transparent resins. If the addition amount of the light stabilizer is 0.03 parts by mass or more, the effect of the addition can be sufficiently exerted. However, if the addition amount exceeds 2.0 parts by mass, it becomes an excessive amount and tends to cause an unnecessary cost increase. is there.

In addition, the optical sheet 10a is provided with an inorganic light diffusing agent composed of an inorganic compound and an organic light diffusing agent composed of an organic compound within a range that does not significantly impair optical characteristics such as light transmittance for the purpose of enhancing the light diffusing effect. It can be included.
Inorganic light diffusing agents include silica, white carbon, talc, magnesium oxide, zinc oxide, titanium oxide, calcium carbonate, aluminum hydroxide, barium sulfate, calcium silicate, magnesium silicate, aluminum silicate, sodium aluminosilicate, zinc silicate, Examples thereof include glass and mica.
Examples of the organic light diffusing agent include styrene polymer particles, acrylic polymer particles, siloxane polymer particles, and polyamide polymer particles. These light diffusing agents can be used alone or in combination of two or more.
These light diffusing agents can also have a porous structure such as petals or spherulites in order to obtain excellent light scattering properties.
The content of the light diffusing agent is preferably 10 parts by mass or less with respect to 100 parts by mass of the transparent resin because the light transmittance is not easily impaired.

Furthermore, in the optical sheet 10a, for the purpose of further enhancing the light diffusion effect, fine bubbles can be contained within a range that does not significantly impair optical characteristics such as light transmittance. The fine bubbles have little light absorption and are difficult to reduce the light transmittance.
As a method for forming fine bubbles, a method of mixing a foaming agent into the optical sheet 10a (for example, a method disclosed in JP-A-5-212811 and JP-A-6-107842), or foaming an acrylic foamed resin is used. A method (for example, a method disclosed in Japanese Patent Application Laid-Open No. 2004-2812) containing fine bubbles after treatment can be applied. Furthermore, a method of causing fine bubbles to foam non-uniformly at a specific position (for example, a method disclosed in Japanese Patent Application Laid-Open No. 2006-124499) is preferable in that more uniform surface irradiation is possible.
The light diffusing agent and fine foaming can be used in combination.

(Thickness of optical sheet)
The thickness of the optical sheet 10a is preferably 0.02 to 3.0 mm, more preferably 0.05 to 2.5 mm, and particularly preferably 0.1 to 2.0 mm. If the thickness of the optical sheet 10a is less than 0.02 mm, it may be less than the depth of the concavo-convex pattern 12a, which is not appropriate. If it is thicker than 3.0 mm, the optical sheet 10a has a large mass and is difficult to handle. There is a fear.
The optical sheet 10a may be composed of two or more resin layers. Also when the optical sheet 10a is composed of two or more layers, the thickness of the optical sheet 10a is preferably 0.02 to 3.0 mm.

(how to use)
The optical sheet 10a is used as a light diffusion sheet. Specifically, the optical sheet 10a is used with the light source 20 adjacent to one end α. By arranging the light source 20 at one end α of the optical sheet 10a, light can be propagated through the optical sheet 10a. Moreover, the light propagated in the optical sheet 10a can be diffused in the uneven region 12 and emitted from the surface on which the uneven region 12 is formed. Furthermore, since the uneven region 12 is arranged in a pattern that becomes gradually denser from one end α to the other end β, the amount of light emitted can be increased toward the other end β. In general, the intensity of light propagating in the optical sheet 10a becomes weaker as it moves away from the light source 20, but the intensity of light emitted from the optical sheet 10a is made uniform by increasing the amount of light emitted toward the other end β. it can.
When using the optical sheet 10 a, it is preferable to install a reflector on the surface that does not have the uneven region 12 in order to increase the light utilization efficiency of the light source 20.

  In the optical sheet 10a of the first embodiment described above, the light diffusibility is exhibited by the concave / convex pattern 12a formed on the surface of the concave / convex region 12. Moreover, the uneven | corrugated area | region 12 is arrange | positioned by the pattern which becomes dense at the other end (beta) side of the longitudinal direction of the optical sheet 10a, and light diffusibility becomes high at the other end (beta) side of a longitudinal direction. Thus, in the optical sheet 10a, since light diffusibility can be adjusted with the space | interval of the uneven | corrugated area | regions 12, desired light diffusibility can be easily obtained in a desired position.

(Production method)
An example of a method for producing the optical sheet 10a will be described.
[First manufacturing method]
A 1st manufacturing method is a method of manufacturing the optical sheet 10a using a heat-shrinkable film.
That is, the first manufacturing method is a step of forming a printed sheet by printing a resin-made convex / concave region forming convex portion having a smooth surface on one side of a heat-shrinkable film (hereinafter referred to as a first step). And a step (hereinafter referred to as a second step) of deforming the heat-shrinkable film by heat-shrinking so as to fold at least the convex portion for forming the concave-convex region of the printing sheet (hereinafter referred to as a second step). This is a method for producing a pattern forming sheet.

-1st process As shown in FIG. 8 and FIG. 9, in the 1st process, as a method of printing the convex part 14 for uneven | corrugated area | region formation on the single side | surface of the heat-shrinkable film 13, for example, screen printing and gravure Printing, offset printing, inkjet printing, and the like can be applied.

As the heat shrinkable film 13, for example, a polyethylene terephthalate shrink film, a polystyrene shrink film, a polyolefin shrink film, a polyvinyl chloride shrink film, or the like can be used.
Among the heat-shrinkable films 13, those that shrink by 50 to 70% are preferable. If a shrink film that shrinks by 50 to 70% is used, the deformation rate can be increased by 50% or more, and the concavo-convex pattern forming sheet having the most frequent pitch A of the concavo-convex pattern 12a of more than 1 μm and 20 μm or less and an aspect ratio of 0.1 or more is easily manufactured. it can.
Here, the deformation rate is (length before deformation−length after deformation) / (length before deformation) × 100 (%). Alternatively, (deformed length) / (length before deformation) × 100 (%).

Since the convex / concave portion forming convex portion 14 is easy to form a meandering wavy concave / convex pattern 12a, the resin (first resin) having a glass transition temperature higher by 10 ° C. or more than the resin constituting the heat-shrinkable film 13 (first resin). 2 resin).
Examples of the second resin include polyvinyl alcohol, polystyrene, acrylic resin, styrene-acrylic copolymer, styrene-acrylonitrile copolymer, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyethersulfone, and fluorine resin. Etc. can be used.

Since the surface of the convex / concave portion forming convex portion 14 can easily form a desired concave / convex pattern 12a, the center line average roughness described in JIS B0601 is set to 0.1 μm or less.
Further, the thickness of the convex / concave area forming convex portion 14 is preferably 0.05 to 5.0 μm, and more preferably 0.1 to 1.0 μm. If the thickness of the convex / concave area forming convex portion 14 is within the above range, the most frequent pitch A of the concave / convex pattern 12a can surely exceed 1 μm and be 20 μm or less. However, if the thickness of the convex portion 14 for forming the concavo-convex region is less than 0.05 μm, the mode pitch A may be 1 μm or less, and if it exceeds 5.0 μm, the mode pitch A may exceed 20 μm. .
Furthermore, the thickness of the convex / concave region forming convex portion 14 may not be constant, and may be, for example, continuously thicker or thinner along one direction.
Moreover, since the meandering wavy uneven pattern 12a can be more easily formed, the Young's modulus of the uneven region forming convex portion 14 is preferably 0.01 to 300 GPa, more preferably 0.1 to 10 GPa. .

Second Step In the second step, the heat-shrinkable film 13 is heat-shrinked to cause the convex-concave region forming convex portion 14 to form a wavy concave-convex pattern 12a in a direction perpendicular to the shrinking direction. Then, the uneven region 12 is obtained (see FIG. 10).
Examples of the heating method for heat-shrinking the heat-shrinkable film 13 include a method of passing it through hot air, steam, or hot water. Among them, a method of passing through hot water is preferable because it can be uniformly shrunk.

  In this manufacturing method, the thinner the thickness of the convex / concave region forming convex portion 14 and the lower the Young's modulus of the convex / concave region forming convex portion 14, the smaller the most frequent pitch A of the concave / convex pattern 12a. The higher the deformation rate, the deeper the average depth B.

  In the first manufacturing method, the Young's modulus of the convex portion 14 for forming the concavo-convex region is higher than that of the heat-shrinkable film 13 at a temperature between the glass transition temperature of the first resin and the glass transition temperature of the second resin. . Therefore, when processed at a temperature between the glass transition temperature of the first resin and the glass transition temperature of the second resin, the convex portion 14 for forming the concave / convex region is folded rather than increased in thickness. Furthermore, since the convex / concave area forming convex portion 14 is laminated on the heat-shrinkable film 13, the stress due to the shrinkage of the heat-shrinkable film 13 is uniformly applied to the whole. Therefore, the concavo-convex region 12 can be formed by contracting the heat-shrinkable film 13 and deforming the concavo-convex region forming convex portion 14 so as to be folded. Therefore, according to the said manufacturing method, the uneven | corrugated pattern formation sheet used as the optical sheet 10a can be obtained.

  The concavo-convex pattern forming sheet obtained as described above can be used as it is as the optical sheet 10a. In that case, the optical sheet 10a is formed by the heat-shrinkable film 13 and the convex / concave area forming convex portion 14.

[Second manufacturing method]
The second manufacturing method is a method for manufacturing the optical sheet 10a using the uneven pattern forming sheet obtained by the first manufacturing method as a process sheet original plate.
The process sheet precursor may be in the form of a single sheet or a continuous sheet.

Specific examples of the second production method include the following methods (a) to (c).
(A) A step of applying an uncured ionizing radiation curable resin to the surface on which the concavo-convex region of the process sheet original plate is formed; and after curing the curable resin by irradiating with ionizing radiation, the cured coating And a step of peeling the film from the process sheet original plate. Here, the ionizing radiation is usually ultraviolet rays or electron beams, but in the present invention, it includes visible rays, X-rays, ion rays and the like.
(B) A step of applying an uncured liquid thermosetting resin to the surface of the process sheet original plate on which the concavo-convex region is formed, and a coating film cured by heating and curing the liquid thermosetting resin. And a step of peeling from the process sheet original plate.
(C) A step of bringing the sheet-shaped transparent thermoplastic resin into contact with the surface of the process sheet original plate on which the concavo-convex region is formed, and the sheet-shaped transparent thermoplastic resin is heated and softened while being pressed against the process sheet original plate. And then cooling and a method of peeling the cooled sheet-like transparent thermoplastic resin from the process sheet original plate.

  Moreover, the molded article for secondary processes can be produced using a process sheet | seat original plate, and the optical sheet 10a can also be manufactured using the molded article for secondary processes. Specific methods using the molded product for the secondary process include the following methods (d) to (f).

(D) A step of performing metal plating of nickel or the like on the surface of the process sheet original plate on which the concavo-convex region is formed, and laminating a plating layer; peeling the plating layer from the process sheet original plate; Irradiating with ionizing radiation, a step of producing a molding for process, a step of coating an uncured ionizing radiation curable resin on the side of the secondary process molding that was in contact with the uneven region, and And a step of peeling the cured coating film from the molded product for the secondary process after curing the curable resin.
(E) a step of laminating a plating layer on the surface of the process sheet original plate on which the concavo-convex area is formed, and a step of peeling the plating layer from the process sheet original plate to produce a metal secondary process molded product; A step of applying an uncured liquid thermosetting resin to the surface of the secondary process molded product that has been in contact with the uneven region, and a cured coating film after curing the resin by heating. And a step of peeling from the molded product for the secondary step.
(F) a step of laminating a plating layer on the surface of the step sheet original plate on which the concavo-convex region is formed, and a step of peeling the plating layer from the step sheet original plate to produce a metal secondary process molded product; , A step of bringing a sheet-like transparent thermoplastic resin into contact with the surface on the side that is in contact with the uneven area of the molding for the secondary process, and pressing the sheet-like transparent thermoplastic resin against the molding for the secondary process A method comprising: a step of cooling after heating and softening, and a step of peeling the cooled sheet-like transparent thermoplastic resin from the molded product for the secondary step.

  A specific example of the method (a) will be described. As shown in FIG. 11, first, an uncured liquid ionizing radiation curable resin 112 c is applied by a coater 120 to the surface of the web-shaped process sheet original plate 110 on which the uneven area 112 a is formed. Next, the process sheet original plate 110 coated with the curable resin is pressed by passing through a roll 130, and the curable resin is filled into the concave and convex area 112 a of the process sheet original plate 110. Thereafter, ionizing radiation is irradiated by the ionizing radiation irradiation device 140 to crosslink and cure the curable resin. And the web-shaped optical sheet 10a can be manufactured by peeling the ionizing radiation curable resin after hardening from the process sheet | seat original plate 110. FIG.

In the method (a), for the purpose of imparting releasability to the surface of the process sheet original plate on which the concavo-convex area is formed, before coating with an uncured ionizing radiation curable resin, from a silicone resin, a fluororesin, etc. The layer to be formed may be provided with a thickness of about 1 to 10 nm.
Examples of the coater for applying an uncured ionizing radiation curable resin to the surface of the process sheet original plate on which the uneven area is formed include a T-die coater, a roll coater, and a bar coater.
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.
Moreover, you may add a fluororesin, a silicone resin, etc. to uncured ionizing radiation curable resin.
When the uncured ionizing radiation curable resin is cured by ultraviolet rays, it is preferable to add a photopolymerization initiator such as acetophenones and benzophenones to the uncured ionizing radiation curable resin.

  The specific method of (d) is the same as the method of (a) above except that the process sheet original plate in the method of (a) is changed to a molded product for the secondary process produced using the process sheet original plate. It is the same.

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

Examples of the transparent thermoplastic resin in the methods (c) and (f) include styrene-methyl methacrylate copolymer (MS), polymethyl methacrylate (PMMA), polystyrene (PS), cycloolefin polymer (COP), and polycarbonate. Examples thereof include resins such as (PC), polypropylene (PP), polyethylene terephthalate (PET), PET-G, polyethersulfone (PES), polyvinyl chloride (PVC), and polyethylene terephthalate (PET). Among these, MS, PMMA, PS, COP, and PC are preferable from the viewpoint of molding, and those having a styrene content of 30 to 90% by mass among MS are more preferable from the viewpoint of hygroscopicity and cost.
These transparent thermoplastic resins may have a single layer or a multilayer structure. For example, a transparent thermoplastic resin having a three-layer structure in which PMMA layers are provided on both sides of the PS layer can be used.
Furthermore, what provided the resin of high refractive index on the surface of the said transparent thermoplastic resin can also be used. Examples of the high refractive index resin include fluorene epoxy compounds, fluorene acrylate compounds, fluorene polyester (OKP), polymethylphenylsilane (PMPS), and polydiphenylsilane (PDPS).

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

[Third production method]
The third manufacturing method is a method for manufacturing the optical sheet 10a using a concavo-convex pattern forming sheet in which a concavo-convex region made of metal or a metal compound is provided on the surface of a resin layer as a process sheet original plate.

The concave / convex pattern forming sheet provided with a metal / metal compound concave / convex region replaces a resin convex / concave region forming convex portion with a metal / metal compound convex / concave region forming convex portion, thereby forming a convex / concave region forming convex portion. It can be obtained by the same method as the first manufacturing method except that the part is formed by vapor deposition instead of printing.
That is, the method for producing a concavo-convex pattern forming sheet provided with a concavo-convex region made of metal or a metal compound is a method of vacuum-depositing a convex portion for forming a concavo-convex region made of metal or metal compound on one side of a heat-shrinkable film. The method includes a step of forming a sheet, and a step of causing the heat-shrinkable film to be heated and shrunk to deform so as to fold at least the convex portions for forming the concave and convex regions of the vapor deposition sheet.
In this method for producing a concavo-convex pattern forming sheet, the Young's modulus of the convex portion for forming the concavo-convex region made of metal or metal compound is significantly larger than the Young's modulus of the heat-shrinkable film. Will also be folded. As a result, the uneven | corrugated pattern formation sheet provided with the uneven | corrugated area | region can be obtained. In addition, the uneven | corrugated area | region of this uneven | corrugated pattern formation sheet is the same as that of the optical sheet 10a.

As the metal constituting the convex part for forming the concavo-convex region in the third manufacturing method, since the concavo-convex pattern 12a is more easily formed, gold, aluminum, silver, carbon, copper, germanium, indium, magnesium, niobium, palladium It is preferably at least one metal selected from the group consisting of lead, platinum, silicon, tin, titanium, vanadium, zinc and bismuth. The metal here includes a semi-metal.
For the same reason, the metal compounds include titanium oxide, aluminum oxide, zinc oxide, magnesium oxide, tin oxide, copper oxide, indium oxide, cadmium oxide, lead oxide, silicon oxide, barium fluoride, calcium fluoride, fluoride. It is preferably at least one metal compound selected from the group consisting of magnesium, zinc sulfide and gallium arsenide.

Since the surface of the convex part for forming the concave / convex region can easily form a desired concave / convex pattern 12a, the center line average roughness described in JIS B0601 is set to 0.1 μm or less.
The thickness of the convex part for forming the concave and convex area made of metal or metal compound is preferably 0.01 to 0.2 μm, and more preferably 0.05 to 0.1 μm. If the thickness of the projections for forming the concavo-convex region is within the above range, the most frequent pitch A of the concavo-convex pattern 12a can be reliably exceeded 1 μm and 20 μm or less. However, if the thickness of the convex portions for forming the concavo-convex region is less than 0.01 μm, the mode pitch A may be 1 μm or less, and if it exceeds 0.2 μm, the mode pitch A may exceed 20 μm.
Furthermore, the thickness of the convex portions for forming the concavo-convex region does not have to be constant. For example, the thickness may be continuously increased or decreased along one direction.

  When vapor-depositing convex portions for forming an uneven region made of metal or metal compound is deposited on a heat-shrinkable film, a mask opened in the same pattern as the convex portions for forming an uneven region to be formed is formed on the surface of the heat-shrinkable film. Put it on.

  Examples of the heating method for heat-shrinking the heat-shrinkable film include a method of passing it through hot air, steam or hot water. Among them, a method of passing it through hot water is preferable because it can be uniformly shrunk.

  As a specific method of the third manufacturing method, in the method of (a) to (f) in the second manufacturing method, as the process sheet original plate, a concave / convex pattern formation provided with a second resin-made concave / convex region is provided. Instead of the sheet, a method of using a concavo-convex pattern forming sheet provided with a concavo-convex region made of metal or metal compound can be mentioned.

[Fourth Manufacturing Method]
The fourth manufacturing method uses an optical sheet 10a from an unmolded transparent thermoplastic resin by using a molding apparatus including a mold, a heating / cooling means for heating and cooling the mold, and a pressurizing means for pressing the mold. It is a method of manufacturing. Examples of the transparent thermoplastic resin used in the fourth production method include the same as those used in the second production method.

Specifically, in the fourth manufacturing method, first, pellets or powders of transparent thermoplastic resin are filled in a mold, the mold is heated by a heating / cooling means, and the inside of the mold is pressurized by a pressurizing means. . Next, the inside of the mold is cooled by the heating and cooling means, the pressurization is stopped, and the optical sheet 10a is obtained.
In this manufacturing method, a mold in which a wavy concavo-convex pattern formed on a surface in contact with the emission surface of the optical sheet 10a is used. For example, as the mold, one having the concave-convex pattern forming sheet in the first to third manufacturing methods attached on one surface, or one having a wavy concave-convex pattern meandering on one surface by laser irradiation or the like can be used.

  As a molding method in the fourth manufacturing method, for example, a press molding method or an injection molding method can be applied.

  The optical sheet 10a obtained by the first to fourth manufacturing methods described above may be used as it is, or bonded to a transparent resin or glass reinforcing substrate via an adhesive as a final optical sheet. Also good.

  In the manufacturing method of the optical sheet 10a described above, it is easy to arrange the uneven region 12 in a pattern that becomes dense on the other end β side in the longitudinal direction of the optical sheet 10a on a flat one surface. Therefore, it is possible to easily obtain the optical sheet 10a having high light diffusibility on the other end β side in the longitudinal direction.

<Second Embodiment>
A second embodiment of the optical sheet of the present invention will be described.
FIG. 12 shows the optical sheet of this embodiment. Also in FIG. 12, for easy explanation, the uneven region 15 is enlarged and its arrangement is shown sparsely.
The optical sheet 10b of the present embodiment is used as a light diffusion sheet in which the light source 20 is disposed at one end α in the longitudinal direction, and is formed on a flat one surface 11 along the width direction of the optical sheet 10b. The uneven regions 15 are dispersed and arranged in a pattern that gradually becomes denser from one end α to the other end β in the longitudinal direction of the optical sheet 10b.
By arranging the uneven region 15 in this way, the light diffusibility can be increased on the other end β side of the optical sheet 10b, similarly to the optical sheet 10a of the first embodiment.

The uneven pattern of the uneven region 15 of the second embodiment is the same as the uneven pattern 12a of the uneven region 12 of the first embodiment. The area ratio of the concavo-convex region 15 to the area of one side of the optical sheet 10b is the same as the area ratio in the first embodiment.
The optical sheet 10b of the second embodiment can be manufactured by a manufacturing method similar to the manufacturing method of the optical sheet 10a of the first embodiment.

<Third Embodiment>
A third embodiment of the optical sheet of the present invention will be described.
FIG. 13 shows the optical sheet of this embodiment. In FIG. 13, in order to facilitate the explanation, the uneven region 16 is enlarged and its arrangement is shown sparsely.
The optical sheet 10c of the present embodiment is used as a light diffusion sheet in which the light source 20 is disposed at one end α in the longitudinal direction. The optical sheet 10c is a strip-shaped portion 16a along the longitudinal direction of the optical sheet 10c. And a net-like concavo-convex region 16 composed of a band-like portion 16b along the width direction is arranged in a dispersed manner. A portion 16b of the concavo-convex region 16 along the width direction of the optical sheet 10c is arranged so as to become denser as it goes from one end α to the other end β in the longitudinal direction of the optical sheet 10c.

The uneven pattern of the uneven region 16 of the third embodiment is the same as the uneven pattern 12a of the uneven region 12 of the first embodiment. The area ratio of the concavo-convex area 16 with respect to the area of one side of the optical sheet 10c is the same as the area ratio in the first embodiment.
The optical sheet 10c of the third embodiment can be manufactured by a manufacturing method similar to the manufacturing method of the optical sheet 10a of the first embodiment.

<Fourth Embodiment>
A fourth embodiment of the optical sheet of the present invention will be described.
FIG. 14 shows the optical sheet of this embodiment. In FIG. 14 as well, for easy explanation, the uneven region 17 is enlarged and its arrangement is shown sparsely.
The optical sheet 10d of the present embodiment is used as a light diffusion sheet in which the linear light source 20 is arranged on the surface C on the side where the uneven region 17 is not formed. Further, in this optical sheet 10d, the elliptical uneven regions 17 are arranged so as to be denser on the flat one surface 11 as the light source 20 is closer.
In the present embodiment, the light from the light source 20 is incident non-uniformly on the optical sheet 10d, but the uneven region 17 is arranged closer to the portion where the strong light reaches, so that the light is emitted while being diffused. Can do. Therefore, the intensity of light emitted from the optical sheet 10d can be made uniform.

The concavo-convex pattern of the concavo-convex area 17 of the fourth embodiment is the same as the concavo-convex pattern 12a of the concavo-convex area 12 of the first embodiment. The area ratio of the concavo-convex region 17 to the area of one side of the optical sheet 10d is the same as the area ratio in the first embodiment.
The optical sheet 10d of the fourth embodiment can be manufactured by a manufacturing method similar to the manufacturing method of the optical sheet 10a of the first embodiment.

<Other embodiments>
In addition, the optical sheet of this invention is not limited to the thing of embodiment mentioned above.
For example, in the first embodiment and the fourth embodiment described above, the outer shape of the concavo-convex region is elliptical, but it may be circular, rectangular, or the like.
In the optical sheet of the present invention, the uneven region may be formed at random.
Further, the uneven pattern in the uneven region may not meander and may be linear.
Moreover, the uneven | corrugated area | region may be formed in both surfaces of the optical sheet.
The optical sheet may be reinforced by a reinforcing base material.

Example 1
Polystyrene source (diluted in toluene) on one side of a polyethylene terephthalate heat-shrinkable film (Mitsubishi Resin HXIPET LX-60S, glass transition temperature 70 ° C.) having a thickness of 50 μm and a Young's modulus of 3 GPa that heat shrinks uniaxially PS, glass transition temperature 100 ° C) was printed in a dot shape with a diameter of 50 µm and a thickness of 500 nm using a gravure printing machine (K printing proofer manufactured by Matsuo Sangyo Co., Ltd.) to obtain a printed sheet.
The dot pattern is a gradation pattern in which the dot area ratio is increased by 10% every 1 cm in the range of 0 to 100% from one end to the other end in the longitudinal direction in the range of width 5 cm × length 10 cm. . A dot area ratio of 0% indicates that no printing is performed, and 100% indicates that the entire surface is printed.
Next, the printed sheet was heated at 80 ° C. for 1 minute to be heat-shrinked to 40% of the length before heating (ie, deformed to a deformation rate of 60%). At 80 ° C., the Young's modulus (1 GPa) of polystyrene is higher than the Young's modulus (50 MPa) of the heat-shrinkable film made of polyethylene terephthalate. Therefore, the dots were deformed so as to be folded during the thermal contraction, and a wavy uneven pattern having a period along the direction orthogonal to the contraction direction was formed. Thereby, the uneven | corrugated pattern formation sheet in which the uneven | corrugated area | region was formed in the flat single side | surface was obtained.
The most frequent pitch of the concavo-convex pattern in the concavo-convex region in this concavo-convex pattern forming sheet was 5 μm, the aspect ratio was 1, and the degree of orientation was 0.3.

  When the light diffusibility of the obtained uneven | corrugated pattern formation sheet was investigated, it had the anisotropic diffusibility which diffuses light strongly in the direction parallel to the perpendicular | vertical direction with respect to the shrinkage | contraction direction. In addition, the light diffusivity gradually increased along the direction in which the area ratio of the uneven region was increased. Such an uneven | corrugated pattern formation sheet of Example 1 can be utilized as a light-diffusion sheet.

(Example 2)
Example except that a polyethylene terephthalate shrink film having a thickness of 25 μm and a Young's modulus of 3 GPa (Hispet PX-40S, manufactured by Mitsubishi Plastics) was used instead of Mitsubishi Plastics' HXIPET LX-60S. In the same manner as in Example 1, a concavo-convex pattern forming sheet was obtained. A wavy uneven pattern not extending along a specific direction was formed on one side of the uneven pattern forming sheet.
The most frequent pitch of the concavo-convex pattern in the concavo-convex region in this concavo-convex pattern forming sheet was 5 μm, and the aspect ratio was 1.
When the optical characteristic of the uneven | corrugated pattern formation sheet of Example 2 was investigated, it had isotropic light diffusibility. Therefore, the uneven pattern forming sheet of Example 2 can be used as a light diffusion sheet.

(Example 3)
A concavo-convex pattern forming sheet was obtained in the same manner as in Example 1 except that the dots were printed by an inkjet printer (Fuji Film Co., Ltd., Dimatics Material Printer DMP-2831). The most frequent pitch of the concavo-convex pattern in the concavo-convex region in this concavo-convex pattern forming sheet was 5 μm, the aspect ratio was 1, and the degree of orientation was 0.3.
When the optical characteristic of the obtained uneven | corrugated pattern formation sheet was investigated, it had the anisotropic diffusivity similar to Example 1. FIG. Therefore, the uneven | corrugated pattern formation sheet of Example 3 can be utilized as a light-diffusion sheet.

Example 4
Using the uneven pattern forming sheet obtained by the method of Example 1 as a process sheet original plate, a light diffusion sheet was obtained as follows.
That is, an uncured ultraviolet curable resin composition containing an epoxy acrylate prepolymer, 2-ethylhexyl acrylate, and a benzophenone photopolymerization initiator on the surface of the process sheet original plate obtained in Example 1 on which the concavo-convex pattern was formed. Coated.
Next, a 50 μm-thick triacetyl cellulose film was superimposed on the surface of the uncured ultraviolet curable resin composition coating film that was not in contact with the process sheet original plate and pressed.
Next, ultraviolet light was irradiated from above the triacetyl cellulose film to cure the uncured ultraviolet curable resin, and the cured product was peeled from the process sheet original plate to obtain a light diffusion sheet.
The obtained light diffusion sheet had the same uneven | corrugated area | region as the light diffusion sheet of Example 1, and had the same light diffusibility.

(Example 5)
Using the uneven pattern forming sheet obtained by the method of Example 1 as a process sheet original plate, a light diffusion sheet was obtained as follows.
That is, the surface of the process sheet original plate obtained in Example 1 on which the concavo-convex pattern was formed was subjected to nickel plating, and the nickel plating was peeled off to obtain a secondary process sheet having a thickness of 200 μm. An uncured ultraviolet curable resin composition containing an epoxy acrylate prepolymer, 2-ethylhexyl acrylate and a benzophenone photopolymerization initiator was applied to the surface of the secondary process sheet on which the uneven pattern was formed.
Next, a 50 μm thick triacetyl cellulose film was superimposed on the surface of the uncured ultraviolet curable resin composition coating film not in contact with the secondary process sheet and pressed.
Then, the light diffusing sheet was obtained by irradiating ultraviolet rays from above the triacetyl cellulose film, curing the uncured curable resin, and peeling the cured product from the secondary process sheet.
The obtained light diffusion sheet had the same uneven | corrugated area | region as the light diffusion sheet of Example 1, and had the same light diffusibility.

(Example 6)
A light diffusing sheet was obtained in the same manner as in Example 5 except that a thermosetting epoxy resin was used instead of the ultraviolet curable resin composition, and the thermosetting epoxy resin was cured by heating instead of irradiating ultraviolet rays. It was.
The obtained light diffusion sheet had the same uneven | corrugated area | region as the light diffusion sheet of Example 1, and had the same light diffusibility.

(Example 7)
In the same manner as in Example 5, a secondary process sheet having a thickness of 200 μm was obtained. A polymethylmethacrylate film having a thickness of 50 μm was layered on the surface of the secondary process sheet on which the concavo-convex pattern was formed, and heated. After pressing the polymethyl methacrylate film softened by heating and the secondary process sheet from both sides, cooling and solidifying, and peeling the solidified polymethyl methacrylate film from the secondary process sheet, the light diffusion sheet Obtained.
The obtained light diffusion sheet had the same uneven | corrugated area | region as the light diffusion sheet of Example 1, and had the same light diffusibility.

(Example 8)
On one side of a polyethylene terephthalate heat-shrinkable film (Mitsubishi Resin HXIPET LX-10S, glass transition temperature 70 ° C.) having a thickness of 50 μm and a Young's modulus of 3 GPa in a uniaxial direction, a dot-like opening (pore diameter 50 μm) A large number of masks formed thereon were placed.
The pattern of the opening of the mask is a gradation that increases by 10% every 1 cm in a range of 5 cm wide × 10 cm long, with the opening area ratio ranging from 0 to 100% from one end to the other end in the longitudinal direction. Pattern was used. Note that an opening area ratio of 0% indicates no opening, and 100% indicates that the entire surface is open.
Next, with a mask placed on one side of the heat-shrinkable film, aluminum having a Young's modulus of 70 GPa was vacuum-deposited to a thickness of 0.05 μm to obtain a deposition sheet.
At this time, aluminum dots are formed on one side of the heat-shrinkable film. The dot pattern is a gradation pattern in which the dot area ratio increases by 10% every 1 cm in the range of 0 to 100% from one end to the other end in the longitudinal direction within a range of 5 cm wide × 10 cm long. A dot area ratio of 0% indicates that no vapor deposition is performed, and 100% indicates that vapor deposition is performed on the entire surface.
Next, the vapor deposition sheet was heated at 100 ° C. for 1 minute to cause heat shrinkage to 40% of the length before heating (that is, the deformation rate was changed to 60%). During the heat shrinkage, the dots were deformed so as to be folded, and a wavy uneven pattern having a period along the direction perpendicular to the shrinkage direction was formed. Thereby, the uneven | corrugated pattern formation sheet which has an uneven | corrugated area | region on one side was obtained.
The most frequent pitch of the concavo-convex pattern in the concavo-convex region in this concavo-convex pattern forming sheet was 3 μm, the aspect ratio was 1, and the degree of orientation was 0.3.

Subsequently, the obtained uneven | corrugated pattern formation sheet was used as a process sheet | seat original plate, and the light-diffusion sheet was obtained as follows.
That is, an uncured ultraviolet curable resin composition containing an epoxy acrylate prepolymer, 2-ethylhexyl acrylate and a benzophenone photopolymerization initiator was applied to the surface of the process sheet original plate on which the uneven pattern was formed.
Next, a 50 μm-thick triacetyl cellulose film was superimposed on the surface of the uncured ultraviolet curable resin composition coating film that was not in contact with the process sheet original plate and pressed.
Next, ultraviolet light was irradiated from above the triacetyl cellulose film to cure the uncured ultraviolet curable resin, and the cured product was peeled from the process sheet original plate to obtain a light diffusion sheet.
When the optical properties of the obtained light diffusion sheet were examined, it had the same anisotropic diffusivity as in Example 1.

Example 9
Example except that a polyethylene terephthalate shrink film having a thickness of 25 μm and a Young's modulus of 3 GPa (Hispet PX-40S, manufactured by Mitsubishi Plastics) was used instead of Mitsubishi Plastics' HXIPET LX-60S. In the same manner as in Example 8, a concavo-convex pattern forming sheet was obtained. The most frequent pitch of the concavo-convex pattern in the concavo-convex area in this concavo-convex pattern forming sheet was 3 μm, and the aspect ratio was 1.
Subsequently, using this uneven | corrugated pattern formation sheet, it carried out similarly to Example 8, and obtained the light-diffusion sheet. When the optical characteristics of the light diffusing sheet of Example 9 were examined, it was found to have isotropic light diffusibility.

(Example 10)
Using the uneven pattern forming sheet obtained by the method of Example 8 as a process sheet original plate, a light diffusion sheet was obtained as follows.
That is, the surface of the process sheet original plate obtained in Example 8 on which the concavo-convex pattern was formed was subjected to nickel plating, and the nickel plating was peeled off to obtain a secondary process sheet having a thickness of 200 μm. An uncured ultraviolet curable resin composition containing an epoxy acrylate prepolymer, 2-ethylhexyl acrylate and a benzophenone photopolymerization initiator was applied to the surface of the secondary process sheet on which the uneven pattern was formed.
Next, a 50 μm thick triacetyl cellulose film was superimposed on the surface of the uncured ultraviolet curable resin composition coating film not in contact with the secondary process sheet and pressed.
Then, the light diffusing sheet was obtained by irradiating ultraviolet rays from above the triacetyl cellulose film, curing the uncured curable resin, and peeling the cured product from the secondary process sheet.
The obtained light-diffusion sheet had the same uneven | corrugated area | region as the light-diffusion sheet of Example 8, and had the same light-diffusion property.

(Example 11)
A light diffusing sheet was obtained in the same manner as in Example 10 except that a thermosetting epoxy resin was used instead of the ultraviolet curable resin composition, and the thermosetting epoxy resin was cured by heating instead of irradiating with ultraviolet rays. It was.
The obtained light-diffusion sheet had the same uneven | corrugated area | region as the light-diffusion sheet of Example 8, and had the same light-diffusion property.

Example 12
In the same manner as in Example 10, a secondary process sheet having a thickness of 200 μm was obtained. A polymethylmethacrylate film having a thickness of 50 μm was layered on the surface of the secondary process sheet on which the concavo-convex pattern was formed, and heated. After pressing the polymethyl methacrylate film softened by heating and the secondary process sheet from both sides, cooling and solidifying, and peeling the solidified polymethyl methacrylate film from the secondary process sheet, the light diffusion sheet Obtained.
The obtained light-diffusion sheet had the same uneven | corrugated area | region as the light-diffusion sheet of Example 8, and had the same light-diffusion property.

  In the optical sheets of Examples 1 to 12 in which the concavo-convex area is mixed on one side, light is diffused by the concavo-convex pattern in the concavo-convex area, and thus the light diffusibility is excellent. Moreover, in the said optical sheet, since the uneven | corrugated area | region was densely arrange | positioned at the other end side of a longitudinal direction, light diffusibility is high at the other end side of a longitudinal direction.

It is a perspective view which shows 1st Embodiment of the optical sheet of this invention. It is an expansion perspective view which expands and shows a part of uneven | corrugated area | region of the optical sheet shown in FIG. It is the figure which expanded the cross section at the time of cut | disconnecting the optical sheet shown in FIG. 1 in the orthogonal direction with the formation direction of an uneven | corrugated pattern. It is a gray scale conversion image of the image obtained by image | photographing the surface of an uneven | corrugated pattern with a surface optical microscope. It is the image which carried out the Fourier transform of the image of FIG. It is the graph which plotted the brightness | luminance with respect to the distance from the center of the ring in the image of FIG. Is a graph plotting the luminance on the auxiliary line L ₃ in the image of FIG. It is sectional drawing which shows the printing sheet used when manufacturing the optical sheet shown in FIG. It is a transmission electron micrograph image of the surface of a printing sheet. It is a transmission electron micrograph image of the surface of an optical sheet. It is a figure explaining an example of the method of manufacturing the light-diffusion body of this invention. It is a perspective view which shows 2nd Embodiment of the optical sheet of this invention. It is a perspective view which shows 3rd Embodiment of the optical sheet of this invention. It is a perspective view which shows 4th Embodiment of the optical sheet of this invention.

Explanation of symbols

10a, 10b, 10c, 10d, 10e Optical sheet 11 Flat single side 12, 15, 16, 17, 18 Uneven region 12a Uneven pattern 12b Bottom portion 13 Heat shrinkable film 14 Uneven region forming convex portion

Claims (5)

  An optical sheet, wherein uneven regions having unevenness are dispersed and arranged on one flat surface or both surfaces.   The optical sheet according to claim 1, wherein the uneven regions are arranged unevenly.   A light diffusion sheet comprising the optical sheet according to claim 1.   The mode (A / B) of the average depth B of the concavo-convex to the mode pitch A (A / B) is 0.1 to 3.0. Light diffusion sheet.   The light diffusion sheet according to claim 4, wherein the uneven regions are dispersed in a dot shape.

Images