JP5277842B2 - Light diffusion sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a rugged pattern formation sheet for simply manufacturing a rugged pattern formation sheet which is utilized as a light diffuser. <P>SOLUTION: The rugged pattern formation sheet includes: a substrate made of resin; and a hard layer consisting of resin provided on at least part of one side or both sides of the substrate, and of which a rugged pattern 11 is formed on the whole surface of the hard layer. The method for manufacturing the rugged pattern formation sheet includes processes of: forming a laminated sheet by continuously or gradually changing it within a range that difference (Tg<SB>2</SB>-Tg<SB>1</SB>) between average glass transfer temperature Tg<SB>2</SB>of the resin constituting the hard layer and glass transfer temperature Tg<SB>1</SB>of the resin constituting the substrate is &ge;10&deg;C and thickness of the hard layer is 0.05 &mu;m-5.0 &mu;m; and deforming the laminated sheet so as to fold at least the hard layer of the laminated sheet. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an optical sheet and a light diffusing sheet used as an uneven pattern forming sheet, a light diffusing sheet, and the like, and methods for producing them.

In general, a concavo-convex pattern forming sheet having a wave-like concavo-convex pattern formed on the surface is used as an optical sheet having light diffusibility and the like.
For example, in Patent Document 1, as a light diffuser having a concavo-convex pattern, a plurality of protrusions are formed on at least one surface of a light-transmitting substrate, the height of the protrusion is 2 to 20 μm, and the peak of the protrusion is formed. The thing of 1-10 micrometers in space | interval and the aspect-ratio of a protrusion is 1 or more is disclosed. Patent Document 1 discloses a method of processing the surface of a light-transmitting substrate by irradiation with an energy beam such as a KrF excimer laser as a method for forming a protrusion.
Patent Document 2 discloses a light diffuser in which an anisotropic diffusion pattern made of wavy irregularities is formed on one side. In Patent Document 2, as a method for forming an anisotropic diffusion pattern, a photosensitive resin film is irradiated with a laser beam to be exposed and developed to form a master hologram having unevenness formed on one side. A method for transferring the master hologram to a mold and molding a resin using the mold is disclosed.
Further, as an optical sheet having light diffusibility and the like, a sheet in which the shape of the unevenness formed on the surface differs depending on the position is known. For example, Patent Document 3 discloses a light diffusing sheet in which concave portions or convex portions having inclined surfaces or tapered surfaces are arranged on the surface serving as a light exit surface of a translucent resin sheet, and the light source corresponding position on the sheet surface A light diffusing sheet is disclosed in which a concave portion or a convex portion that is farther from the surface has a slope angle of the inclined surface with respect to the sheet surface or a slope angle of the ridge line of the tapered surface is sequentially increased.
JP-A-10-123307 Japanese Patent Application Laid-Open No. 2006-261064 JP 2007-114587 A

  When it is intended to control the diffusion and reflection of light by unevenness, if the pitch of the uneven pattern is about the wavelength of light, coloring due to interference becomes a problem, and if the pitch exceeds several tens of μm, Since there is a possibility that it may be visually recognized or moiré may occur, it is required that the pitch of the concavo-convex pattern be 20 μm or less. However, in the optical sheet described in Patent Document 3, if the pitch of the concavo-convex pattern is several tens of μm to several 100 μm, the concavo-convex is stably formed, but if it is 20 μm or less, it is difficult to obtain a desired pitch. .

In addition, in the optical sheet, optical characteristics such as light diffusibility may not be made uniform, but may be uneven by providing a height difference 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 irregularities on the surface so that the optical characteristics become non-uniform, it is conceivable to change the pitch and depth of the irregular pattern depending on the position. In the sheet, it was difficult to continuously change the pitch and depth, and to disperse and arrange the regions having different pitches and depths after setting the pitch of the concavo-convex pattern to 20 μm or less. Therefore, in the optical sheet described in Patent Document 3, the effect of making the optical characteristics uneven at predetermined positions is not sufficient.

  Accordingly, an object of the present invention is to provide an optical sheet excellent in target optical characteristics (light diffusibility and the like) and capable of easily making optical characteristics non-uniform, and a method for manufacturing the same. 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 non-uniform, and a method for producing the same.

The present invention includes the following aspects.
[1] A concavo-convex pattern comprising a resin base material and a hard layer made of a resin provided on at least a part of one or both surfaces of the base material, and a concavo-convex pattern formed on the entire surface of the hard layer A forming sheet,
The difference (Tg ₂ −Tg ₁ ) between the average glass transition temperature Tg ₂ of the resin constituting the hard layer and the glass transition temperature Tg ₁ of the resin constituting the substrate is 10 ° C. or more, and
A step of forming a laminated sheet while changing the thickness of the hard layer in a range of 0.05 μm to 5.0 μm continuously or stepwise, and a step of deforming at least the hard layer of the laminated sheet so as to be folded. The manufacturing method of the uneven | corrugated pattern formation sheet which has.
[2] A concavo-convex pattern comprising a resin base material and a hard layer made of a resin provided on at least a part of one or both surfaces of the base material, and a concavo-convex pattern formed on the entire surface of the hard layer A forming sheet,
The difference (Tg ₂ −Tg ₁ ) between the glass transition temperature Tg ₂ of at least one kind of resin constituting the hard layer and the glass transition temperature Tg ₁ of the resin constituting the substrate is 10 ° C. or more, and
A step of forming a laminated sheet in which regions having different thicknesses are dispersed in a range of 0.05 μm to 5.0 μm in thickness of the hard layer, and a step of deforming at least the hard layer of the laminated sheet so as to be folded. The manufacturing method of the uneven | corrugated pattern formation sheet which has these.
[3] An uneven pattern forming sheet obtained by the production method according to any one of [1] or [2], wherein the light diffuser has a total light transmittance of 85% or more.
[4] A light diffuser comprising the concavo-convex pattern-forming sheet according to any one of [1] or [2], wherein the concavo-convex pattern having the same mode pitch and average depth as the concavo-convex pattern-forming sheet is formed on the surface. A process sheet original plate for producing a light diffuser used as a mold for producing a sheet.
[5] A step of applying an uncured ionizing radiation curable resin to the surface on which the concave / convex pattern is formed of the light diffuser manufacturing process sheet original plate according to [4], and the ionizing radiation curable resin. A method for producing a light diffuser comprising: curing a cured coating film from the process sheet original plate after curing.
[6] A step of laminating a concavo-convex pattern transfer material on the surface on which the concavo-convex pattern is formed of the light diffuser production process sheet original plate according to [4], and a concavo-convex pattern transfer material laminated on the concavo-convex pattern. An uncured curability is formed on the surface of the molded product for the secondary process that is peeled from the process sheet master and on the side of the molded product for the secondary process that is in contact with the concave-convex pattern of the process sheet master. A method for producing a light diffuser, comprising: a step of applying a resin; and a step of peeling the cured coating film from the molded product for the secondary step after the curable resin is cured.
[7] A step of laminating a concavo-convex pattern transfer material on the surface on which the concavo-convex pattern is formed of the light diffuser production process sheet original plate according to [4], and a concavo-convex pattern transfer material laminated on the concavo-convex pattern. A process for producing a molded product for the secondary process by peeling from the process sheet original plate, and a sheet-like thermoplastic resin on the side of the molded product for the secondary process that is in contact with the concavo-convex pattern of the process sheet original plate. A step of bringing a resin into contact, a step of heating and softening the sheet-like thermoplastic resin while pressing it against a molded product for a secondary step, and a step of cooling the cooled sheet-like thermoplastic resin. The manufacturing method of the light diffusing body which has the process of peeling from the molded object.

  The optical sheet of the present invention has excellent target optical characteristics, and can easily make the optical characteristics non-uniform. In addition, the light diffusion sheet of the present invention is excellent in the desired light diffusion property and can easily make the light diffusion property non-uniform.

<First Embodiment>
A first embodiment of the optical sheet of the present invention will be described.
In FIG. 1, the cross section of the optical sheet of this embodiment is shown. In FIG. 1, the concave / convex pattern 11 is shown enlarged for easy explanation.
The optical sheet 10a of the present embodiment is used as a light diffusion sheet in which the linear light source 30 is disposed on the surface α on the side where the uneven pattern 11 is not formed. Further, in this optical sheet 10 a, the concave / convex pattern 11 is arranged such that the closer to the light source 30, the smaller the mode pitch of the concave / convex pattern, the ratio of the mode pitch to the average depth, that is, the aspect ratio. In the present invention, “flat” means that the center line average roughness described in JIS B0601 is 0.1 μm or less. The hard layer 13 has a center line average roughness of more than 0.1 μm, particularly 0.5 μm or more, as described in JIS B0601.

(Uneven pattern)
FIG. 2 shows an uneven pattern. In the present embodiment, as shown in FIG. 2, a meandering wavy uneven pattern 11 is formed on the surface of the optical sheet 10a.
In the optical sheet 10a of the present embodiment used for the light diffusion sheet, the most frequent pitch A of the concavo-convex pattern 11 is preferably more than 1 μm and not more than 20 μm, and more preferably more than 1 μm and not more than 10 μm. When the most frequent pitch A is less than 1 μm, the wavelength is less than or equal to the wavelength of visible light, and the visible light is not refracted by the concavo-convex pattern 11 and light is transmitted. Because there is.

The ratio of the average depth B of the concavo-convex pattern to the most frequent pitch A of the concavo-convex pattern 11 (B / A, hereinafter referred to as aspect ratio) is preferably 0.1 to 3.0, and 0.3 to 2. More preferably 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 tends to be difficult to form the uneven pattern 11 in the manufacture of the optical sheet 10a.
Here, the average depth B is the average depth of the bottom 11a of the concavo-convex pattern 11.
In the present embodiment, since the average depth B of the concavo-convex pattern 11 continuously changes depending on the position from the light source 30 in FIG. 1, this is the average depth of the bottom portions 11 a of 100 adjacent concavo-convex patterns 11. .
Further, the bottom 11a is a minimum point of the concave portion of the concave / convex pattern 11, and the average depth B is an optical sheet when a cross section (see FIG. 3) obtained by cutting the concave / convex pattern 11 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 surface 10 a to the top of each convex part, and the reference line L ₁ to each concave part 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 11a using a cross-sectional image of the concavo-convex pattern 11 photographed by an atomic force microscope and obtaining an average value thereof is employed.

As in this embodiment, meandering when the concavo-convex pattern 11 is along one direction means that the degree of orientation of the concavo-convex pattern obtained by the following method is 0.3 or more. The degree of orientation is an index of variation in the orientation of the uneven pattern, and the larger the value, the more the orientation is dispersed, that is, the pitch of adjacent patterns varies along the pattern direction, and the light diffusion is high. It shows that it is preferable as a light diffuser.
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 concave / convex pattern 11.
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 reciprocal of the pitch, the vertical axis represents the frequency, and the reciprocal 1 / X of the value X at which the frequency is maximum represents the most frequent pitch of the concavo-convex pattern 11.
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 a height at which the frequency is half the maximum value) represents the degree of orientation of the uneven pattern 11. The larger the half width W ₁ , the more meandering and the orientation varies.

When the degree of orientation is less than 0.3, the variation in the orientation of the concavo-convex pattern 11 is reduced, so that the 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 11 becomes random to some extent, and thus 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 a hard layer 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.

(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 smaller than the depth of the concavo-convex pattern 11, 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 linear light source 30 arranged on the surface α on the side where the uneven pattern 11 is not formed. Further, by arranging the light source 30 on the surface α side of the optical sheet 10a, the light incident from the surface α of the optical sheet 10a can be emitted from the concavo-convex pattern surface. Furthermore, the light that has passed through the optical sheet 10 a can be diffused by the concave / convex pattern 11 and emitted from the surface on which the concave / convex pattern 11 is formed.

In this embodiment, although the incident angle of light from the light source 30 to the surface α varies depending on the position, the uneven pattern 11 is arranged so that the aspect ratio increases as the incident angle increases, and thus diffuses light. In addition, the light output direction of the light can be brought close to the normal direction of the light output surface regardless of the incident angle. Therefore, the intensity in the normal direction of the light exit surface of the light emitted from the optical sheet 10a can be made uniform. Here, the incident angle is an angle when the normal direction of the surface α is 0 °.

(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, in the first manufacturing method, a resin hard layer 13 is printed on one side of a heat-shrinkable film so that the thickness of the hard layer gradually increases or decreases to form a print sheet ( Hereinafter, it is referred to as a first step) and a step (hereinafter referred to as a second step) in which the heat-shrinkable film is heated and shrunk to deform at least the hard layer 13 of the printed sheet is folded. This is a method for producing a concavo-convex pattern forming sheet to be the optical sheet 10a.

First Step In the first step, as shown in FIG. 8, as a method for printing the hard layer 13 on one side of the heat shrinkable film 12 so that the thickness gradually increases or decreases, for example, a screen Printing, gravure printing, offset printing, inkjet printing, and the like can be applied. Among these, ink jet printing is preferable because it is easy to control the thickness of the hard layer as shown in the present embodiment.

As the heat-shrinkable film 12, 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 12, 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 to 50% or more, and the concave / convex pattern-forming sheet having the most frequent pitch A of the concave / convex pattern 11 of more than 1 μm to 20 μm and an aspect ratio of 0.1 or more Can be manufactured.
Here, the deformation rate is (length before deformation−length after deformation) / (length before deformation) × 100 (%).

Since the hard layer 13 is easy to form a meandering wavy uneven pattern 11, a resin (second resin) having a glass transition temperature higher by 10 ° C. or more than the resin constituting the heat-shrinkable film 12 (first resin). Consists of.
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 hard layer 13 can easily form the desired concavo-convex pattern 11, the center line average roughness described in JIS B0601 is set to 0.1 μm or less.
The thickness of the hard layer 13 is preferably 0.05 to 5.0 μm, more preferably 0.1 to 1.0 μm. If the thickness of the hard layer 13 is within the above range, the most frequent pitch A of the concavo-convex pattern 11 can surely exceed 1 μm and be 20 μm or less. However, if the thickness of the hard layer 13 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.
Moreover, since the meandering wavy uneven pattern 11 can be formed more easily, the Young's modulus of the hard layer 13 is preferably 0.01 to 300 GPa, more preferably 0.1 to 10 GPa.

Second Step In the second step, the heat-shrinkable film 12 is thermally contracted to form the wavy uneven pattern 11 on the hard layer 13 in the direction perpendicular to the contraction direction.
Examples of the heating method for heat-shrinking the heat-shrinkable film 12 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.

In the first manufacturing method, as the thickness of the hard layer 13 is thinner and the Young's modulus of the hard layer 13 is lower, the mode pitch A and the average depth B of the concavo-convex pattern 11 become smaller, and the heat shrinkable film The higher the deformation rate of 12, the deeper the average depth B.
In the present embodiment, in order to form the hard layer 13 so that the thickness gradually increases or decreases, the concavo-convex pattern can be arranged such that the most frequent pitch and the average depth continuously increase or decrease. .

  In the first manufacturing method, the Young's modulus of the hard layer 13 is higher than that of the heat-shrinkable film 12 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 hard layer 13 is folded rather than increased in thickness. Furthermore, since the hard layer 13 is laminated on the heat-shrinkable film 12, the stress due to the shrinkage of the heat-shrinkable film 12 is uniformly applied to the whole. Therefore, the concavo-convex pattern 11 can be formed by shrinking the heat-shrinkable film 12 and deforming the hard layer 13 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 10 a is formed by the heat-shrinkable film 12 and the hard layer 13.

[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) Step of applying an uncured ionizing radiation curable resin to the surface of the process sheet original plate on which the concavo-convex pattern is formed, and curing the curable resin by irradiating with ionizing radiation and then curing the 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 on which the concave and convex pattern of the process sheet original plate 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 a sheet-shaped transparent thermoplastic resin into contact with the surface of the process sheet original plate on which the concave / convex pattern is formed, and pressing the sheet-shaped transparent thermoplastic resin against the process sheet original plate to soften it. 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 pattern 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 molded product for the process, a step of applying an uncured ionizing radiation curable resin to the surface on the side that was in contact with the uneven pattern of the molded product for the secondary process, 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 concave / convex pattern is formed, and a step of peeling the plating layer from the process sheet original plate to produce a metal secondary process molded product; The step of applying an uncured liquid thermosetting resin to the surface on the side of the molded article for the secondary process that is in contact with the concavo-convex pattern, and the 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 process sheet original plate on which the concavo-convex pattern 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 bringing a sheet-like transparent thermoplastic resin into contact with the surface of the second-step molded product that has been in contact with the concavo-convex pattern; and pressing the sheet-shaped transparent thermoplastic resin against the molded product for the second-order 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. 9, first, an uncured liquid ionizing radiation curable resin 112 is applied by a coater 120 to the surface of the web-shaped process sheet original plate 110 on which the uneven pattern 111 is formed. Next, the process sheet original plate 110 coated with the curable resin is pressed by passing it through a roll 130, and the curable resin is filled into the concavo-convex pattern 111 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 on which the uneven pattern of the process sheet original plate is formed, before coating with an uncured ionizing radiation curable resin, from a silicone resin, a fluororesin or the like. 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 pattern 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-based epoxy compounds, fluorene-based acrylate compounds, fluorene-based polyesters (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.
In addition to the press molding method, for example, an injection molding method can be applied as the molding method in the manufacturing method (f).

  The optical sheet 10a obtained by the first and second 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 method for manufacturing the optical sheet 10a described above, it is easy to dispose the concave / convex pattern 11 on a flat single surface so that the aspect ratio increases as the incident angle of light from the light source 30 to the surface α increases. . Accordingly, it is possible to easily obtain the optical sheet 10a in which the intensity of the emitted light is uniform in the normal direction of the light exit surface.

<Second Embodiment>
A second embodiment of the optical sheet of the present invention will be described.
FIG. 10 shows the optical sheet of this embodiment. In FIG. 10, the concave / convex pattern 14 is shown in an enlarged manner for easy explanation.
The optical sheet 10b of the present embodiment is also used as a light diffusion sheet in which the linear light source 30 is disposed on the surface β on the side where the uneven pattern 14 is not formed. Also, in this optical sheet 10b, the concave / convex pattern 14 is arranged so that the closer to the light source 30, the smaller the mode pitch, the average depth, and the ratio of the mode pitch to the average depth, that is, the aspect ratio. However, the mode pitch and the average depth of the concavo-convex pattern increase or decrease stepwise instead of continuously.
By arranging the concavo-convex pattern 14 in this way, the intensity in the normal direction of the light exit surface of the light emitted from the optical sheet 10b can be made uniform as in the optical sheet 10a of the first embodiment.

  As shown in FIG. 11, the optical sheet 10b of the second embodiment is the same as that of the first embodiment except that the hard layer 15 is formed on the heat-shrinkable film 12 so that the thickness increases or decreases stepwise. It can be manufactured by the same manufacturing method as the manufacturing method of the optical sheet 10a of the embodiment.

<Third Embodiment>
A third embodiment of the optical sheet of the present invention will be described.
FIG. 12 shows the optical sheet of this embodiment.
The optical sheet 10c of the present embodiment is used as a light diffusion sheet in which the linear light source 30 is disposed on the surface γ on the side where the uneven pattern 16 is not formed.
Further, in this optical sheet 10c, as the concavo-convex pattern 16 is closer to the light source 30 as the concavo-convex patterns 16a, 16b, and 16c, the ratio of the concavo-convex with the smaller mode pitch, average depth, and aspect ratio of the concavo-convex pattern is smaller. The most frequent pitch, the average depth, and the aspect ratio are arranged to be larger than the ratio of the large unevenness.
By arranging the concavo-convex pattern 16 in this manner, the intensity in the normal direction of the light exit surface of the light emitted from the optical sheet 10c can be made uniform as in the optical sheet 10a of the first embodiment.

  In the optical sheet 10c of the third embodiment, as shown in FIG. 13, except that the hard layer 17 is formed on the heat-shrinkable film 12 so as to increase or decrease the ratio of the thick part to the thin part. It can be manufactured by the same manufacturing method as 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, the concave and convex patterns 18a and 18b are shown enlarged for easy explanation.
The optical sheet 10d of the present embodiment is used as a light diffusion sheet in which the linear light source 30 is disposed on the surface δ on one side.
Moreover, in this optical sheet 10d, the uneven | corrugated pattern is formed in the light-incidence surface and the light emission surface. The concave / convex pattern 18a on the light incident surface is not formed in a portion close to the light source 30, but is formed only in a portion far from the light source, and the most frequent pitch and average depth are uniform.
Moreover, the uneven | corrugated pattern 18b of a light emission surface is formed in the part in which the uneven | corrugated pattern 18a is not formed in the light-incidence surface, and it is with respect to the mode pitch, average depth, and average depth of an uneven | corrugated pattern, so that it is near the light source 30. They are arranged so that the ratio of the most frequent pitches, that is, the aspect ratio becomes small. Further, the concave / convex pattern 18b is also partially disposed in the portion where the concave / convex pattern 18a is formed on the light incident surface.

By arranging the concavo-convex pattern 18 in this manner, the intensity in the normal direction of the light exit surface of the light emitted from the optical sheet 10d can be made uniform as in the optical sheet 10a of the first embodiment. Specifically, the portion where the concave / convex pattern 18b is formed only on the light exit surface can make the intensity in the normal direction of the light exit surface of the light 40 emitted from the optical sheet 10d uniform by the same principle as the optical sheet 10a. In the portion where the concave / convex pattern 18a is formed on the light incident surface, the incident angle to the light 41 entering the optical sheet 10d from the light source 30 is too large. It cannot be brought close to the normal direction of the light exit surface, and the intensity in the normal direction of the light exit surface of the light exiting from the optical sheet 10d cannot be made uniform. Therefore, by arranging the concave / convex pattern 18a on the light incident surface, the incident light 41a is incident on the optical sheet 10d while being refracted by one side surface 19a of the concave / convex pattern 18a. The incident light has an angle formed with the normal to the other side surface 19b that is equal to or greater than the critical angle, so that the traveling direction is brought closer to the normal direction of the light exit surface by total reflection, and further passes through the optical sheet d, Emits from the surface. The outgoing light 41b is refracted by the concave / convex pattern 18b on the light outgoing surface as necessary, and further brought closer to the normal direction of the light outgoing surface.
By arranging the concave / convex patterns 18a and 18b as described above, even when the incident angle of the incident light to the optical sheet 10d is very large, the light exit direction is brought close to the normal direction of the light exit surface regardless of the incident angle. And the intensity in the normal direction of the light exit surface of the light emitted from the optical sheet 10d can be made uniform.
According to the present embodiment, when the distance between the light sources 30 adjacent to each other increases or the distance between the light source 30 and the optical sheet 10d decreases, the incident angle of light on the optical sheet 10d becomes very large. It is particularly effective.

In the optical sheet 10d of the fourth embodiment, as shown in FIG. 15, the hard layer 20a is formed on a part of one surface of the heat-shrinkable film 12 so that the thickness is constant, and the other It can be manufactured by a manufacturing method similar to the manufacturing method of the optical sheet 10a of the first embodiment, except that the hard layer 20b is formed on a part of the surface so that the thickness gradually increases or decreases.

Further, the optical sheet 10d of the fourth embodiment has one surface by heat shrinkage instead of forming the hard layer 20a so as to have a constant thickness on a part of one surface of the heat shrinkable film 12. Alternatively, a linear prism having a triangular cross section may be formed by cutting on a part of the other surface of the sheet on which the concavo-convex pattern 18b is formed, to form the concavo-convex pattern 18a on the light incident surface. In this case, the apex angle of the linear prism is preferably 30 ° or more and 80 ° or less, and particularly preferably 50 ° or more and 65 ° or less. This is because if the apex angle of the linear prism is 80 ° or less, the condition that the incident light causes total reflection on the side surface 19b is satisfied, and if the apex angle of the linear prism is 30 ° or more, it can be easily manufactured. .

Further, when the optical sheet 10d is manufactured using the process sheet original plate, the same uneven pattern as the process sheet original plate 21a and the uneven pattern 18b on which the uneven pattern similar to the uneven pattern 18a of the optical sheet 10d is formed. First, except that the processed sheet original plate 21b is used to bring the processed sheet original plates 21a and 21b into contact with both surfaces of a curable resin, a thermoplastic resin, and the like to form the uneven patterns 18a and 18b on both surfaces of the resin. It can be manufactured by the same manufacturing method as the manufacturing method of the optical sheet 10a of the embodiment.

Even when the molded product for the secondary process is used, the molded product for the secondary process 22a and 22b is produced from the process sheets 21a and 21b on which the same concavo-convex pattern as the concavo-convex pattern 18a and 18b is formed. The manufacturing method of the optical sheet 10a of the first embodiment is similar to the method of manufacturing the optical sheet 10a of the first embodiment except that the objects 22a and 22b are brought into contact with both surfaces of a curable resin, a thermoplastic resin, and the like to form the uneven patterns 18a and 18b on both surfaces of the resin. It can be manufactured by a manufacturing method.
The concave-convex pattern of the secondary process molded product 22a may be a linear prism having a triangular cross section formed by cutting or the like. The apex angle of the linear prism in this case is also preferably 30 ° or more and 80 ° or less, and particularly preferably 50 ° or more and 65 ° or less.

<Other embodiments>
In addition, the optical sheet of this invention is not limited to the thing of embodiment mentioned above.
For example, the optical sheet of the present invention can be used not only when the light source is incident from below the sheet surface as in a direct backlight, but also when the light source is incident from the side surface of the optical sheet. Moreover, when making a light source enter from the lower side or side surface of a sheet | seat surface, it can be used also when a light source is a point light source. In such a case, the mode pitch and average depth of the concavo-convex pattern, the extent of their continuous or intermittent change, or the extent of their dispersive arrangement may be appropriately selected.
In addition, a plurality of the optical sheets of the present invention may be used in a stacked manner. In this case, the anisotropic diffusion effect may be obtained by overlapping the concave and convex directions so as to be equal, or the isotropic diffusion effect may be obtained by overlapping them in an orthogonal manner.
The uneven pattern of the uneven pattern may not be meandering and may be linear.
In addition, when a concavo-convex pattern is formed by providing a hard layer on a heat-shrinkable film and then heat-shrinking the laminated film, the concavo-convex pattern is substantially parallel when a uniaxial shrink-type heat-shrinkable film is used. A formed optical sheet is obtained, but when a biaxial shrinkable heat-shrinkable film is used, an optical sheet having no directionality in the concavo-convex pattern is obtained.
In addition, the uneven pattern may be formed on 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, manufactured by Co., Ltd., having a glass transition temperature of 100 ° C. was printed by an inkjet printer (Fuji Film Co., Ltd., Dimatics Material Printer DMP-2831) to obtain a printed sheet.
The printing pattern has a width of 4 cm × length of 5 cm, and the printing layer thickness is in the range of 0 to 0.5 μm from one end to the other in the longitudinal direction, and 0.05 μm every 0.5 cm. Increased gradation pattern.
Next, the printed sheet is heated at 80 ° C. for 1 minute to cause heat shrinkage to 40% of the length before heating (ie, deformed to a deformation rate of 60%), and at 80 ° C., heat shrinkage made of polyethylene terephthalate. The Young's modulus (1 GPa) of polystyrene is higher than the Young's modulus (50 MPa) of the conductive film. Therefore, the printed layer was deformed so as to be folded during the heat shrinkage, 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 in which the uneven | corrugated pattern was formed in the flat single side | surface was obtained.
The concavo-convex pattern in this concavo-convex pattern forming sheet had a modest pitch gradually increasing from 0 to 5 μm along the contraction direction, an average depth from 0 to 5 μm along the contraction direction, and an aspect ratio from 0 to 1. .
Further, the degree of orientation of the concavo-convex pattern in this concavo-convex pattern forming sheet 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, when light incident from the surface on which the concave / convex pattern is not formed of this concave / convex pattern forming sheet is emitted from the surface on which the concave / convex pattern is formed, the light is emitted in the normal direction of the concave / convex pattern forming sheet. The incident angle required for the increase was gradually increased to 0 to 40 ° or more along the direction in which the aspect ratio of the concavo-convex pattern was increased. Such an uneven | corrugated pattern formation sheet of Example 1 can be utilized as a light-diffusion sheet.

(Example 2)
The print pattern of the print layer is in the range of 4 cm wide × 5 cm long from one end to the other end in the longitudinal direction with a print layer thickness of 0.1 to 0.5 μm, and 0.1 mm per 1 cm. A concavo-convex pattern forming sheet was obtained in the same manner as in Example 1 except that the pattern increased stepwise by 1 μm.
The concavo-convex pattern in this concavo-convex pattern forming sheet has a modest pitch of 1, 2, 3, 4, 5 μm along the contraction direction, and an average depth of 0.3, 1.0, 2.1, along the contraction direction. It increased in steps of 3.6 and 5 μm.
Further, the degree of orientation of the concavo-convex pattern in this concavo-convex pattern forming sheet 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 pattern forming sheet of Example 2 can be used as a light diffusion sheet.

(Example 3)
The print pattern of the print layer is printed in the range of 4 cm wide by 5 cm long by printing two types of dots having a diameter of 50 μm and a thickness of 0.1 μm or 0.5 μm, from one end to the other end in the longitudinal direction. A gradation pattern in which the dot ratio with a thickness of 5 μm is increased by 10% every 0.5 cm from 0 to 100%. Here, the dot ratio of 0% indicates that the printing layer is a flat surface having a thickness of 0.1 μm, and the dot ratio of 100% indicates that the printing layer is a flat surface having a thickness of 0.5 μm. Indicates.
A concavo-convex pattern forming sheet was obtained in the same manner as in Example 1 except for the printing pattern of the printing layer.
The concavo-convex pattern in this concavo-convex pattern forming sheet has a concavo-convex pattern portion having a mode pitch of 1 μm and an average depth of 0.3 μm, and a concavo-convex pattern portion having a mode pitch of 5 μm and an average depth of 5 μm. The proportion of the concave and convex pattern portions having a mode pitch of 5 μm and an average depth of 5 μm gradually increased.
Further, the degree of orientation of the concavo-convex pattern in this concavo-convex pattern forming sheet 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
Polystyrene source diluted in toluene on both sides 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 shrinks in a uniaxial direction. PS, manufactured by Co., Ltd., having a glass transition temperature of 100 ° C. was printed by an inkjet printer (Fuji Film Co., Ltd., Dimatics Material Printer DMP-2831) to obtain a printed sheet.
In the printing pattern, one surface P has a width of 4 cm and a longitudinal direction of 20 cm, and a printing layer thickness of 0 to 0.5 μm toward the longitudinal direction of 0 to 5 cm. Increased by 0.05 μm every 5 cm, and gradually decreased by 0.05 μm every 0.35 cm in the range of 0.5 to 0 μm in the printing layer thickness toward 5 to 8.5 cm in the length direction. The three gradation patterns gradually increased by 0.01 μm every 1.15 cm in the range of the printing layer thickness from 0 to 0.1 μm toward 8.5 to 20 cm. The other surface Q was provided with a printing layer having a thickness of 0.5 μm on the surface Q side of the portion corresponding to 5 to 20 cm in the longitudinal direction among the portions provided with the printing layer of the surface P.
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%). Thereby, the uneven | corrugated pattern formation sheet in which the uneven | corrugated pattern was formed in both surfaces was obtained.
The concavo-convex pattern in this concavo-convex pattern forming sheet has a surface pitch of 0-2 cm along the shrinkage direction, a modest pitch of 0-5 μm, an average depth of 0-5 μm, and an aspect ratio of 0. Gradually increased to ˜1, and in the range of 2 to 3.4 cm, the mode pitch gradually decreased to 5 to 0 μm, the average depth to 5 to 0 μm, the aspect ratio decreased to 1 to 0, and 3.4 to 8 cm. In this range, the mode pitch gradually increased from 0 to 1 μm, the average depth from 0 to 0.2 μm, and the aspect ratio from 0 to 0.2. On the surface Q side, irregularities having a mode pitch of 5 μm, an average depth of 5 μm, and an aspect ratio of 1 were formed in a range corresponding to 2 to 8 cm of the surface P along the shrinkage direction.
Further, the degree of orientation of the concavo-convex pattern in this concavo-convex pattern forming sheet 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, when the light incident from the surface Q side of the concavo-convex pattern forming sheet is emitted from the surface P, the incident angle necessary for emitting the light in the normal direction of the concavo-convex pattern forming sheet is along the longitudinal direction. It gradually increased to 0-80 ° or more. Such an uneven | corrugated pattern formation sheet of Example 4 can be utilized as a light-diffusion sheet.

(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, 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 pattern as the light diffusion sheet of Example 1, and had the same light diffusibility.

(Example 6)
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 pattern as the light diffusion sheet of Example 1, and had the same light diffusibility.

(Example 7)
A light diffusing sheet was obtained in the same manner as in Example 6 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 pattern as the light diffusion sheet of Example 1, and had the same light diffusibility.

(Example 8)
In the same manner as in Example 6, 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 pattern as the light diffusion sheet of Example 1, and had the same light diffusibility.

(Comparative Example 1)
100 mm thick stainless steel SUS430 is entirely plated with nickel of 100 μm thickness, and using a diamond cutting tool with apex angles of 120 °, 90 ° and 60 °, width 70 μm, pitch 70 μm, apex angle 120 °, 90 The linear prisms at 60 ° and 60 ° were cut to obtain process masters. A polymethylmethacrylate sheet having a thickness of 2 mm was overlaid on the surface of the process master plate on which the prism (uneven pattern) was formed and heated. The polymethyl methacrylate sheet softened by heating and the process master were pressed from both sides, then cooled and solidified, and the solidified polymethyl methacrylate sheet was peeled from the process master to obtain a light diffusion sheet. .
The uneven pattern of the obtained light diffusion sheet has a linear prism portion with apex angles of 120 °, 90 °, and 60 ° from one end to the other end in the short direction in a range of width 4 cm × length 2 cm. They were arranged in order, and the length in which each prism part was arranged was 0.67 cm.
Further, the linear prisms were arranged so as to be orthogonal to the lateral direction, and the prisms were parallel to each other.

(Comparative Example 2)
A light diffusing sheet was obtained in the same manner as in Comparative Example 1 except that 1 part of a fine diffusing element made of a crosslinked product of a polysiloxane polymer having a particle diameter of 2 μm was mixed with polymethyl methacrylate.

A linear cold-cathode tube (manufactured by ELEVUM, outer diameter 3 mm) was installed at a position 20 mm below the light incident surface side of the optical sheets of Examples 1 to 8 and Comparative Examples 1 and 2. The optical sheets of Examples 1 to 8 were arranged so that the portion corresponding to 0 cm in the longitudinal direction when the printing layer was provided was directly above the cold cathode tube. The optical sheets of Comparative Examples 1 and 2 were arranged so that the portion with an apex angle of 120 ° was directly above the cold cathode tube. Further, the optical sheet was arranged so that the uneven pattern was parallel to the longitudinal direction of the cold cathode tube.
The suitability as a light diffuser was evaluated based on the light diffusibility and luminance when the cold cathode tube was turned on and observed through an optical sheet. The evaluation results are shown in Table 1.
○: Light diffusibility is good or brightness decrease is small. When both are ○, it is suitable as a light diffuser.
X: Insufficient light diffusibility or large decrease in luminance, and when either one is x, it is not suitable as a light diffuser.

As shown in Table 1, in Examples 1 to 8, the light diffusibility was good and the luminance was not lowered so much that it was suitable as a light diffuser.
On the other hand, in Comparative Examples 1 and 2, the light diffusibility was inferior or the luminance was greatly reduced, and it was not suitable as a light diffuser.

It is sectional drawing 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 pattern 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 figure explaining an example of the method of manufacturing the light-diffusion body of this invention. It is sectional drawing which shows 2nd Embodiment of the optical sheet of this invention. It is sectional drawing which shows the printing sheet used when manufacturing the optical sheet shown in FIG. It is sectional drawing which shows 3rd Embodiment of the optical sheet of this invention. It is sectional drawing which shows the printing sheet used when manufacturing the optical sheet shown in FIG. It is sectional drawing which shows 4th Embodiment of the optical sheet of this invention. It is sectional drawing which shows the printing sheet used when manufacturing the optical sheet shown in FIG.

Explanation of symbols

10a, 10b, 10c, 10d Optical sheet 11, 14, 16, 16a, 16b, 16c, 18a, 18b Uneven pattern 11a Bottom 12 Heat shrinkable film 13, 15, 17, 20a, b Hard layer 19a, b Uneven side 21a, b Process sheet master 22a, b Molded product for secondary process 30 Light source 40, 41b Emission light 41a Incident light 110 Web-like process sheet master 111 Uneven pattern 112 Uncured liquid ionizing radiation curable resin 120 Coater 130 Roll 140 Ionizing radiation irradiation device

Claims (6)

In the light diffusing sheet used by placing the light source on one side surface,
At least one side of the light diffusion sheet has a concavo-convex pattern,
The light diffusion sheet disposed such that the ratio of the mode pitch to the average pitch and the mode pitch of the pattern is smaller as the concavo-convex pattern is closer to the portion where the light source is disposed. The light diffusion sheet according to claim 1, wherein the uneven pattern is a wavy uneven pattern. The light diffusion sheet according to claim 1 or 2, wherein the most frequent pitch of the uneven pattern is more than 1 µm and 20 µm or less. The light diffusion sheet according to claim 1, wherein the degree of orientation of the uneven pattern is 0.3 or more. The light diffusion according to any one of claims 1 to 4, wherein the concavo-convex pattern has a shape obtained by heat-shrinking a heat-shrinkable film in which a hard layer is laminated to deform at least the hard layer. Sheet. The shape obtained by deforming the light diffusion sheet according to any one of claims 1 to 5 so that the concavo-convex pattern heat-shrinks a heat-shrinkable film in which a hard layer is laminated and at least folds the hard layer. The light diffusing sheet according to claim 1, wherein the light diffusing sheet has a shape obtained by transferring the light.

Images