JP2013003300A - Production method of microlens sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of a microlens sheet, by which air bubbles are prevented from remaining inside each independent recessed fine shape on an outer circumference of a roll die, thereby the recessed fine shape is accurately transferred, and reduction in an optical performance or mechanical performance of the obtained microlens sheet can be prevented.SOLUTION: An active energy ray-curable composition is supplied to between an outer circumferential face of a roll die and a substrate film while the substrate film is traveling. The active energy ray-curable composition is cured by irradiating with active energy rays while the active energy ray-curable composition is held between the substrate film and the outer circumferential face of the roll die. A microlens transfer part is arranged in such a manner that, in a polygonal bottom 30B of the transfer part, an apex angle α [°] at an apex P located in the rearmost with respect to a rotation direction X of the roll die, and an angle β [°] formed by a bisector d of the apex angle of the apex P with respect to the circumferential direction X of the roll die, satisfy a relational expression of β≤[85°-(α/2)].

Description

  The present invention relates to a method for producing a microlens sheet formed by forming a large number of microlenses on the surface of a substrate film. The microlens sheet is used, for example, as a brightness enhancement film in a backlight of a liquid crystal display device, and as a light extraction film in an organic EL light emitting device.

  In a backlight device used as a surface light source element in a liquid crystal display device, it is known to improve performance such as luminance and viewing angle by arranging a microlens sheet on a light emitting surface of a light guide. .

  Further, in the organic EL (electroluminescence) light emitting device, since the total reflection angle is determined by the refractive index difference between the surface glass substrate and air, about 80% of the light generated in the light emitting part is confined inside the glass substrate, or Reflected and cannot be taken out. Therefore, it is known to arrange a microlens sheet as a light extraction film on the glass substrate surface to improve external quantum efficiency.

  The microlens sheet is formed by arranging fine convex microlenses that are present independently on the surface of a base film. Examples of the microlens include convex curved surfaces such as spherical surfaces, pyramid shapes, cone shapes, truncated pyramid shapes, truncated cone shapes, and composite shapes thereof. The arrangement pitch of the microlenses is, for example, 5 μm to 500 μm.

  As a method for manufacturing such a microlens sheet, a method described in Japanese Patent Application Laid-Open No. 2002-59436 (Patent Document 1) is known. In this method, a long resin base film is wound around a roll mold having a fine shape corresponding to the microlens shape engraved on the outer peripheral surface, and UV curing is performed between the roll mold and the base film. The active energy ray-curable composition, such as an active energy composition, is interposed between the active energy ray-curable composition and the active energy ray-curable composition. The manufactured long microlens sheet is continuously manufactured.

  In this method of manufacturing a microlens sheet, when the microlens is a lens array extending in one direction parallel to the base film surface (that is, an extended type), for example, a prism array, the microlens is finely formed on the surface of the roll mold Can be formed to continuously extend in the circumferential direction. In this case, since the fine shape of the roll mold continuously extends in the circumferential direction, when transferring the fine shape of the roll mold outer periphery to the active energy ray-curable composition, ) Can be discharged along the fine shape. Therefore, the active energy ray-curable composition is smoothly replaced with the air inside the fine shape, and a microlens sheet in which the fine shape is accurately transferred can be produced.

  On the other hand, each microlens has a convex surface shape such as a spherical surface, a pyramid shape, a cone shape, a truncated pyramid shape, a truncated cone shape, and a composite shape thereof. If it is, the fine shape of the roll mold is not continuous in the circumferential direction, and the individual independent concave fine shapes are arranged. Therefore, when transferring the fine shape of the outer periphery of the roll mold to the active energy ray-curable composition, bubbles remain without being discharged from the inside of the fine shape, and a lens sheet in which the fine shape is accurately transferred is manufactured. There are things that cannot be done. Moreover, since the active energy ray-curable composition is sandwiched between the roll mold surface and the base film and compressed, even if the active energy ray-curable composition is pushed into the fine shape and replaced with air The generated bubbles become microbubbles and flow into the active energy ray-curable composition. Thus, it becomes difficult to defoam, and bubbles may remain in the microlens sheet to deteriorate the optical performance or mechanical performance.

  Therefore, in Japanese Patent No. 4305090 (Patent Document 2), after applying the active energy ray-curable composition to a roll mold, the resin is smoothed by a roll and defoamed thereby, and then a base sheet is pasted. In addition, a method for curing the resin has been proposed.

JP 2002-59436 A Japanese Patent No. 4305090

  However, it is difficult to apply the method described in Patent Document 2 to continuous production of a long microlens sheet. In addition, this method requires that the roll is brought into direct contact with the surface of the mold, so that when a foreign object enters, the surface of the mold is scratched and the life of the mold is significantly shortened. There is also a problem.

  It is an object of the present invention to provide a microlens having a non-extending type such as a pyramid shape or a truncated pyramid shape and continuously manufacturing a long microlens sheet. It is possible to prevent bubbles from remaining inside the individual independent concave fine shapes, accurately transfer the concave fine shapes, and prevent deterioration of optical performance or mechanical performance of the obtained microlens sheet. Another object is to provide a method for manufacturing a microlens sheet.

According to the present invention, the object as described above is achieved.
On one surface of a base film, a method for producing a microlens sheet formed by forming a large number of polygonal pyramid-shaped or polygonal frustum-shaped equivalent microlenses so as to have the same orientation,
A roll mold formed by forming a concave polygonal pyramid shape or a concave polygonal frustum-shaped microlens transfer portion corresponding to the shape of the microlens on the outer peripheral surface is rotated around its central axis, and the peripheral speed of the roll mold is The outer peripheral surface of the roll mold at the meeting portion between the outer peripheral surface of the roll mold and the base film while running the base film in the circumferential direction of the roll mold along the outer peripheral surface of the roll mold at the same speed. And an active energy ray-curable composition between the base film and the substrate film,
Irradiating an active energy ray in a state where the active energy ray-curable composition is sandwiched between the base film and the outer peripheral surface of the roll mold, the active energy ray-curable composition is cured,
Here, the microlens transfer portion has an apex angle at one apex located at the rearmost position with respect to the rotation direction of the roll mold on the polygonal bottom surface of the concave polygonal pyramid shape or the concave polygonal frustum shape. When the angle formed by the bisector of the apex angle at the one vertex with respect to the circumferential direction of the roll mold is β [°], the following relational expression
β ≦ [85 ° − (α / 2)]
Is arranged so that
A method for producing a microlens sheet, characterized in that
Is provided.

  In one aspect of the present invention, when the length of the longest side among the sides of the polygonal bottom surface is A and the depth of the concave polygonal pyramid shape or the concave polygonal frustum shape is D, the concave shape The aspect ratio D / A of the polygonal pyramid shape or the concave polygonal frustum shape is 0.5 or more and 1.8 or less.

  In one aspect of the present invention, the polygonal pyramid shape or the polygonal frustum shape is a regular quadrangular pyramid shape, a regular quadrangular pyramid shape, a regular hexagonal pyramid shape, or a regular hexagonal frustum shape.

  According to the method for producing a microlens sheet of the present invention, it is possible to prevent the remaining of the bubbles inside the concave microlens transfer portion formed independently on the outer peripheral surface of the roll mold, and accurately form the concave microshape. It is possible to prevent a decrease in optical performance or mechanical performance of the microlens sheet to be transferred and obtained. For this reason, a microlens sheet can be manufactured at low cost without adding a separate defoaming step. Further, since only the active energy ray-curable composition is brought into contact with the outer peripheral surface on which the roll-type microlens transfer portion is formed, the surface is not scratched.

It is typical sectional drawing which shows the specific example of the microlens sheet | seat manufactured by the manufacturing method of this invention. It is a typical perspective view which shows the micro lens of the micro lens sheet | seat of FIG. It is a typical top view which shows the micro lens sheet | seat of FIG. It is a mimetic diagram for explaining one embodiment of a manufacturing method of a micro lens sheet by the present invention. It is a typical development view showing the relation between the polygonal bottom face of the microlens transfer portion on the outer peripheral surface of the roll mold and the direction of rotation of the roll mold in the microlens sheet manufacturing method according to the present invention. It is a typical perspective view which shows the shape of a micro lens. It is a schematic diagram which shows the cross-sectional shape of the metal mold | die used by the Example and the comparative example. It is a schematic diagram for demonstrating the manufacturing method of the microlens sheet | seat in an Example and a comparative example. It is an enlarged view which shows the surface state of the microlens sheet | seat obtained in the Example and the comparative example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, a specific example of a microlens sheet manufactured by the manufacturing method of the present invention will be described with reference to FIGS.

  As shown in FIG. 1, the microlens sheet 10 has an equivalent microlens 30 having a number of polygonal pyramid shapes (regular tetragonal pyramid shape in FIG. 1) on one surface (upper surface in FIG. 1) of the base film 20. Are formed so as to have the same orientation. The direction here refers to the directionality of the shape of the bottom surface 30 </ b> A of the microlens 30 in a plane parallel to the surface of the base film 20. That is, the fact that many microlenses 30 have the same orientation corresponds to the orthogonal projection of the microlenses 30 on the surface of the base film 20 being arranged in the same direction.

  The base film 20 is preferably a transparent film such as a polyester resin, an acrylic resin, a polycarbonate resin, or a vinyl chloride resin, which is a material that transmits active energy rays such as ultraviolet rays and electron beams. The thickness of the base film 20 is, for example, about 20 μm to 500 μm.

  A large number of microlenses 30 constitute all or part of the microlens portion 40 located on the surface of the base film 20.

  FIG. 1A shows a case where the microlens portion 40 is configured by only a large number of microlenses 30. Here, a large number of microlenses 30 are formed directly on the surface of the base film 20. The bottom surface 30 </ b> A of the microlens 30 is in contact with the surface of the base film 20.

  FIG. 1B shows a case where the microlens portion 40 is configured by a large number of microlenses 30 and an intervening layer 31 positioned between the bottom surface 30A and the surface of the base film 20, and here, A large number of microlenses 30 are formed on the surface of the base film 20 via the intervening layer 31, and the bottom surface 30 </ b> A of the microlens 30 is continuous with the intervening layer 31.

  The microlens part 40 is obtained by curing an active energy ray-curable composition as will be described later.

  FIG. 1C shows a case where an adhesion layer 50 is provided between the lower surface of the intervening layer 31 of the microlens portion 40 and the surface of the base film 20. The adhesion layer 50 functions as an anchor coat layer that improves the adhesion between the microlens portion 40 and the base film 20. In this case, the microlens portion 40 may be composed only of a large number of microlenses 30 without the intervening layer 31.

  FIG. 2 shows a schematic perspective view of one microlens 30. As shown in the drawing, each microlens 30 has a regular quadrangular pyramid-shaped bottom surface 30A having a square shape, and two of the four sides 301, 302 of the bottom surface 30A have two other sides 303, 304 and are orthogonal to each other.

  As shown in FIG. 3, such a microlens 30 has a vertical direction (direction of two sides 301 and 302 of the bottom surface 30 </ b> A) and a horizontal direction so as to have the same orientation on the surface of the base film 20. They are aligned and closely packed on both sides (the direction of the other two sides 303 and 304 of the bottom surface 30A). That is, the sides of the square bottom surfaces 30A of the microlenses 30 adjacent to each other are in close contact with each other in the vertical direction and the horizontal direction.

  The active energy ray-curable composition used to form the microlens portion 40 is not particularly limited as long as it is cured by irradiation with active energy rays such as ultraviolet rays and electron beams. For example, polyester-based compositions, epoxy-based compositions, and (meth) acrylate-based compositions such as polyester (meth) acrylate and urethane (meth) acrylate are preferable. Among these, (meth) acrylate-based compositions are particularly preferable from the viewpoint of optical properties and the like. Such an active energy ray-curable composition is mainly composed of a polyvalent acrylate and polyvalent methacrylate, a monoacrylate and monomethacrylate, and a photopolymerization initiator by active energy rays in terms of handleability and curability. Things are desirable.

  FIG. 4 is a schematic diagram for explaining an embodiment of a method for producing a microlens sheet according to the present invention.

  A concave or truncated micro frustum-shaped micro corresponding to a polygonal pyramid shape (convex polygonal frustum shape) or a polygonal frustum shape (convex polygonal frustum shape) that is the shape of the microlens A roll mold 1 having a lens transfer portion formed on the outer peripheral surface is rotated around its central axis (rotating shaft 3) in the direction indicated by the arrow X. The base film 20 is caused to travel in the circumferential direction of the roll mold 1 along the outer peripheral surface of the roll mold 1 at a speed equivalent to the peripheral speed of the roll mold 1. The base film 20 is pressed toward the roll mold 1 by the nip roll 4 and the pressing roll 4 ′ arranged in parallel with the roll mold 1, and travels in the direction of arrow Y before reaching the nip roll 4. After reaching the nip roll 4 and before reaching the pressing roll 4 ′, the vehicle travels in the direction of the arrow X, and after reaching the pressing roll 4 ′, the vehicle travels in the direction of the arrow Z.

  At the position of the nip roll 4 at the position where the outer peripheral surface of the roll mold 1 and the base film 20 meet (the part where the base film 20 first meets the outer peripheral surface of the roll mold 1), that is, the outer peripheral surface of the roll mold 1 The active energy ray-curable composition 8 is supplied from the nozzle 2 to the base film 20. As a result, the supplied resin bank 5 is formed in the meeting section.

  In the region between the nip roll 4 and the pressing roll 4 ′ where the active energy ray-curable composition 8 is sandwiched between the base film 20 and the outer peripheral surface of the roll mold 1, an active energy ray source, for example, The active energy ray-curable composition 8 is cured by irradiating active energy rays from an ultraviolet lamp (UV lamp) 7.

  On the surface of the base film 20 after running as described above and passing through the pressing roll 4 ′, a microlens portion 40 having a large number of microlenses 30 made of the cured active energy ray-curable composition 8 is provided. The formed long microlens sheet 10 is obtained. When the microlens sheet 10 having the adhesion layer 50 is manufactured, the adhesion layer 50 may be formed on the surface of the base film 20 before reaching the nip roll 4.

  Here, in the roll mold 1, the microlens transfer portions are arranged as follows.

  That is, the polygonal bottom surface of the microlens transfer portion having a concave polygonal pyramid shape or a concave polygonal frustum shape (a surface corresponding to the bottom surface 30A of the microlens 30; however, a cylindrical surface shape is formed on the outer peripheral surface of the roll mold 1). ) Is specified in relation to the direction of rotation of the roll mold 1 (the direction of the arrow X).

FIG. 5 is a schematic development view showing the relationship between the polygonal bottom surface 30 </ b> B of each microlens transfer portion on the outer peripheral surface of the roll mold 1 and the rotation direction X of the roll mold 1. As shown in FIG. 5, in the polygonal bottom surface 30B, the apex angle at the apex P located at the rearmost position with respect to the rotation direction X of the roll mold 1 is α [°]. An angle formed by the bisector d of the apex angle at the apex P with respect to the circumferential direction of the roll mold 1 (that is, the rotation direction X of the roll mold 1) is β [°]. At this time, the following relational expression
β ≦ [85 ° − (α / 2)]
Make sure that

  The significance of this relational expression is as follows.

  That is, in FIG. 5, a direction W orthogonal to the rotation direction X of the roll mold 1 corresponds to the direction of the rotation axis of the nip roll 4 parallel to the rotation axis 3 of the roll mold 1. When the active energy ray-curable composition 8 is filled into the microlens transfer portion, the pressure (linear pressure) 6 is linearly uniform in the direction W with respect to the resin 8 through the base film 20 by the nip roll 4. Is applied. The position where the linear pressure is applied to the roll mold 1 moves in the direction X ′ opposite to the roll mold rotation direction X orthogonal to the direction W as the roll mold 1 rotates. The resin 8 is already covered with the base film 20 behind the linear pressure application position with respect to this direction X ′. For this reason, surplus resin out of the resin 8 pushed into the microlens transfer portion is pushed forward from the linear pressure application position with respect to the direction X ′ (ie, behind the linear pressure application position with respect to the direction X), and finally Specifically, at the apex P, the microlens transfer portion and the base film 20 are separated from the gap in the microlens transfer portion that is to be closed. As described above, the air in the microlens transfer portion and the active energy ray-curable composition 8 are replaced.

  Here, assuming that two sides sandwiching the apex P of the polygonal bottom surface 30B of the microlens transfer portion are p and q, the angle formed between the side p and the direction W, which is smaller in the angle γ with the direction W, is the above-mentioned micro Attention is paid to the influence on the substitution between the air in the lens transfer portion and the active energy ray-curable composition 8. When the angle γ is 0 °, the linear pressure application length to the microlens transfer portion suddenly becomes 0 when passing through the apex P. For this reason, there is a high possibility that air will remain in the microlens transfer portion without sufficient separation of air from the gap. On the other hand, when the angle γ increases, the linear pressure application length to the microlens transfer portion gradually decreases until it passes through the apex P, so that the air is sufficiently separated from the gap, and the microlens There is little risk of air remaining in the transfer section.

The present inventor has found that when the angle γ is set to 5 ° or more, preferably 10 ° or more, and more preferably 15 ° or more, air can be easily detached from the microlens transfer portion. In FIG. 5, the relationship among α, β and γ is
(90 ° −β) = [(α / 2) + γ]
It is. Therefore, the condition that γ is 5 ° or more is
(90 ° −β) ≧ [(α / 2) + 5 °]
That is
β ≦ [85 ° − (α / 2)]
It becomes.

  β = 0 ° is the most preferable condition.

Here, when the polygonal pyramid shape or the polygonal frustum shape of the microlens 30 is a regular quadrangular pyramid shape or a regular quadrangular pyramid shape as described above, the shape of the bottom surface 30A of the microlens is a square, so α = 90. Therefore, the above relational expression is
β ≦ 40 °
It becomes.

Further, when the microlens 30 has a regular hexagonal pyramid shape or a regular hexagonal frustum shape, since the shape of the microlens bottom surface 30A is a regular hexagon, α = 120 °, Therefore, the above relational expression is
β ≦ 25 °
It becomes.

  In these cases, the microlenses 30 can be arranged in a close-packed arrangement (dense arrangement), which is preferable from the viewpoint of improving optical performance. That is, it is desirable that the microlens filling rate, which is the area occupied by the microlens per unit area of the microlens sheet, is higher because the optical function can be exhibited better.

  However, the present invention is not limited to these, and the polygonal pyramid shape or the polygonal frustum shape is a regular triangular pyramid shape or a regular triangular frustum shape, or a regular pentagonal pyramid shape or a regular pentagonal pyramid shape, or the like. Also good.

  The length of the longest side (one side in the case of a regular polygonal bottom) among the sides of the polygonal bottom of the microlens transfer portion is A, and the depth of the concave polygonal pyramid shape or the concave polygonal frustum shape ( If the aspect ratio D / A of the concave polygonal pyramid shape or the concave polygonal frustum shape is 0.5 or more, where D corresponds to the height of the microlens), the condition of the above relational expression is not satisfied. Since bubbles remain in the microlens transfer portion at the time, the effect of improving the bubble remaining prevention by the method of the present invention is remarkable.

  The aspect ratio D / A is preferably 1.8 or less. The reason is as follows.

For example, as shown in FIG. 6, regarding the shape of the microlens, the side inclination angle θ1 and the hypotenuse angle θ2 formed by the hypotenuse and the bottom of the regular quadrangular pyramid are respectively
θ1 = tan ⁻¹ (2D / A)
θ2 = tan ⁻¹ (2 ^1/2 D / A)
It becomes. When the aspect ratio D / A is changed, the angle θ1 and the angle θ2 change as shown in Table 1 below. In Table 1, the unit of the base A and the height D is μm. Here, if θ2 is about 70 ° or more and θ1-θ2 is about 6 ° or less, the effect of the present invention is hardly exhibited.

  The roll mold 1 having a plurality of microlens transfer portions as described above formed on the outer peripheral surface can be produced by the following method.

  First, a roll-shaped material having a Cu plating or Ni plating with a thickness of 100 μm to 500 μm on the circumferential surface of a cylindrical steel material is prepared, and a polygonal pyramid shape or a polygonal frustum shape of a precision lathe and a microlens is prepared. There is a method of obtaining the roll mold 1 by performing cutting using the rotational motion of the roll and the rotational motion of the blade with a blade having a cross-sectional shape corresponding to the cross section. In addition, a roll-shaped material having a copper plating with a thickness of 100 μm to 500 μm is prepared on the circumferential surface of a cylindrical steel material, a photosensitive agent is applied to the surface, and exposure, development, etching, etc. are performed with a laser or the like. The method of obtaining the roll metal mold | die 1 using the photoresist method which performs is mentioned. In these methods, processing is performed so that the direction of the side p with respect to the circumferential direction of the roll-shaped material is appropriately inclined to form the microlens transfer portion.

  In addition, a planar lens mold produced by the above-described method and the like, and a planar electroformed lens mold obtained by duplicating them by an electroforming method using a lens film obtained by transferring them using a cylinder, The method of obtaining the roll metal mold | die 1 is mentioned by winding and fixing to the steel material of a shape. In these methods, the microlens transfer part is formed by winding the electroformed lens mold around the cylindrical material so that the direction of the side p with respect to the circumferential direction of the cylindrical material is appropriately inclined. .

[Production example of active energy ray-curable composition]
In a glass flask, 117.6 g (0.7 mol) of hexamethylene diisocyanate and 151.2 g (0.3 mol) of isocyanurate-type hexamethylene diisocyanate trimer as isocyanate compounds, and (meth) acryloyl having a hydroxyl group As compounds, 128.7 g (0.99 mol) of 2-hydroxypropyl acrylate and 693 g (1.54 mol) of pentaerythritol triacrylate, 100 ppm of dilaurate di-n-butyltin as a catalyst, and polymerization inhibitor, Hydroquinone monomethyl ether (0.55 g) was charged and reacted under the conditions of 70 to 80 ° C. until the residual isocyanate concentration became 0.1% or less to obtain a urethane acrylate compound.

  34.6% by mass of the obtained urethane acrylate compound, polybutylene glycol dimethacrylate (trade name: Acrylate PBOM, manufactured by Mitsubishi Rayon Co., Ltd.), 24.7% by mass, and EO-modified bisphenol A dimethacrylate (trade name: New Frontier BPEM) -10, Daiichi Kogyo Seiyaku Co., Ltd.) 39.5% by mass, and 1-hydroxycyclohexyl phenyl ketone (trade name Irgacure 184, Ciba Specialty Chemicals Co., Ltd.) 1.2% by mass are mixed. An active energy ray-curable composition was obtained.

[Example 1]
Copper plating was applied to the steel plate surface to form a copper plating layer having a thickness of 200 μm and a Vickers hardness of 230 Hv. The copper plating layer was mirror-finished by cutting using a single crystal diamond tool. Thereafter, visual appearance inspection was performed, and it was confirmed that there were no defects such as pinholes on the mirror surface. Next, the mirror-plated copper plating layer is cut using a diamond tool having a regular triangle shape with a vertex angle of 60 °, so that the side surface inclination angle of the cross-sectional shape as shown in FIG. A mold was produced in which convex square pyramids with a depth of 30 μm at 60 ° and a base length of 50 μm were closely arranged in a vertical and horizontal direction at a pitch of 50 μm.

  Using this mold, an electroformed flat plate mold is produced in which the concave and convex shapes are inverted by electroforming and the concave-shaped regular quadrangular pyramid-shaped microlens transfer portions are closely arranged vertically and horizontally, and this is the required dimension. Cut to a size of 130 mm × 80 mm.

  As shown in FIG. 8, a roll mold 1 was obtained by fixing an electroformed flat plate mold 16 having a required size to the center position of the outer circumference of a steel roll having an outer diameter of 200 mm and a width of 320 mm. The electroformed flat plate mold 16 was placed on the roll mold 1 so that β in the above relational expression was 0 °.

Hereafter, according to the manufacturing method demonstrated with reference to FIG. 4, the microlens sheet | seat was produced continuously. Here, the nip roll 4 having a rubber hardness of 60 ° was used, and the base film 20 was a long polyester film having a width of 340 mm and a thickness of 125 μm. The running speed of the base film 20 was 3 m / min. The heating medium (water) from the temperature controller is caused to flow inside the roll mold 1 to keep the mold surface temperature constant at 40 ° C., and the active energy ray-curable composition obtained in the above production example from the nozzle 2. 8 was supplied. The supplied active energy ray-curable composition 8 was kept constant at a temperature of 40 ° C. and had a viscosity of 150 mPa · s. UV light of 760 mJ / cm ² is applied to the active energy ray-curable composition 8 between the base film 20 (using polyester film T910T188 manufactured by Mitsubishi Plastics) and the surface of the roll mold 1 by the UV lamp 7. Irradiated.

  As shown in FIG. 9, the surface state of the obtained microlens sheet was such that no bubbles remained on the surface of all the microlenses.

[Example 2]
The arrangement of the electroformed flat plate mold 16 relative to the roll mold 1 was carried out in the same manner as in Example 1 except that β in the above relational expression was 40 °.

  As for the surface state of the obtained microlens sheet, as shown in FIG. 9, in some microlenses, fine bubbles remain on a small part of the surface, but in most microlenses, bubbles remain on the surface. Was not visible. If air bubbles of this level remain, the optical performance is hardly lowered and can be used in practice.

[Comparative Example 1]
The arrangement of the electroformed flat plate mold 16 relative to the roll mold 1 was performed in the same manner as in Example 1 except that β in the above relational expression was 45 °.

  As for the surface state of the obtained microlens sheet, as shown in FIG. 9, large bubbles remained on the surface of all the microlenses. The decrease in optical performance was so great that it could not withstand actual use.

1: Roll mold 2: Nozzle 3: Roll mold rotating shaft 4: Nip roll 4 ': Pressing roll 5: Resin bank 6: Linear pressure 7: UV lamp 8: Active energy ray curable composition 10: Microlens sheet 16: Electroformed flat plate mold 20: Base film 30: Microlens 30A: Bottom surface 30B of microlens: Bottom surface 301, 302, 303, 304 of microlens transfer part 31: Bottom side of microlens 31: Intervening layer 40: Microlens Portion 50: Adhesion layer P: Vertex X of bottom surface of microlens transfer portion X: Direction of rotation of roll mold Y, Z: Direction of travel of substrate film d: Bisecant of apex angle W: Roll mold Directions p and q orthogonal to the direction of rotation Sides that sandwich the vertex of the bottom surface of the microlens transfer part α: Apex angle β: Angle γ formed by the bisecting of the direction of travel of the base film and the apex angle γ: Roll Mold times Angle formed by one side connected to the vertex with respect to the direction perpendicular to the direction of rolling

Claims (3)

On one surface of a base film, a method for producing a microlens sheet formed by forming a large number of polygonal pyramid-shaped or polygonal frustum-shaped equivalent microlenses so as to have the same orientation,
A roll mold formed by forming a concave polygonal pyramid shape or a concave polygonal frustum-shaped microlens transfer portion corresponding to the shape of the microlens on the outer peripheral surface is rotated around its central axis, and the peripheral speed of the roll mold is The outer peripheral surface of the roll mold at the meeting portion between the outer peripheral surface of the roll mold and the base film while running the base film in the circumferential direction of the roll mold along the outer peripheral surface of the roll mold at the same speed. And an active energy ray-curable composition between the base film and the substrate film,
Irradiating an active energy ray in a state where the active energy ray-curable composition is sandwiched between the base film and the outer peripheral surface of the roll mold, the active energy ray-curable composition is cured,
Here, the microlens transfer portion has an apex angle at one apex located at the rearmost position with respect to the rotation direction of the roll mold on the polygonal bottom surface of the concave polygonal pyramid shape or the concave polygonal frustum shape. When the angle formed by the bisector of the apex angle at the one vertex with respect to the circumferential direction of the roll mold is β [°], the following relational expression
β ≦ [85 ° − (α / 2)]
Is arranged so that
A method for producing a microlens sheet, wherein   When the length of the longest side among the sides of the polygonal bottom surface is A and the depth of the concave or truncated polygonal pyramid shape is D, the concave or truncated polygonal frustum The method for producing a microlens sheet according to claim 1, wherein an aspect ratio D / A of the shape is 0.5 or more and 1.8 or less.   The microlens sheet manufacturing method according to claim 1, wherein the polygonal pyramid shape or the polygonal frustum shape is a regular quadrangular pyramid shape, a regular quadrangular pyramid shape, a regular hexagonal pyramid shape, or a regular hexagonal frustum shape. Method.