JP6354357B2 - Method for producing light transmissive film - Google Patents

Description

  The present invention relates to a method for producing a light transmissive film.

  In recent years, a light-transmitting film having a cured resin layer has been used in various fields mainly for optical applications. Among them, articles such as a light-transmitting film having a surface with a fine uneven structure having a period of less than the wavelength of visible light. It is known to exhibit an antireflection effect, a lotus effect, and the like. In particular, it is known that a fine concavo-convex structure called a moth-eye structure is an effective antireflection means by continuously increasing the refractive index from the refractive index of air to the refractive index of the material of the article. .

As a method for producing a light transmissive film having a fine concavo-convex structure on its surface, for example, a method having the following steps (i) to (iii), that is, a photo nanoimprint method is known (Patent Document 1).
(I) A step of sandwiching the active energy ray-curable composition between a mold having an inverted structure of a fine concavo-convex structure on the surface and a base material that is a main body of the light transmissive film.
(Ii) The active energy ray-curable composition is irradiated with active energy rays such as ultraviolet rays, and the active energy ray-curable composition is cured to form a cured resin layer having a fine concavo-convex structure; Obtaining step.
(Iii) A step of separating the light transmissive film and the mold.

JP 2007-076089 A JP 2002-156505 A

Since the light transmissive film is often used on the surface of an article and requires high scratch resistance, a higher hardness is required.
Therefore, a technique (second irradiation) in which the cured resin raw material is cured once and then cured again by irradiating with active energy rays is disclosed (Patent Document 2), but the photopolymerization initiator is appropriately controlled. As a result, sufficient hardness could not be obtained.

  As a result of intensive studies, the inventors have found that by leaving a certain amount of the photopolymerization initiator before the second irradiation, the second irradiation can be effectively cured to obtain a light-transmitting film with high hardness. The present invention has been completed.

That is, the manufacturing method of the light transmissive film of the present invention is as follows.
(1) A method for producing a light transmissive film comprising a base material that absorbs a predetermined wavelength of active energy rays and a cured resin layer, wherein an average interval between convex portions on the surface of the light transmissive film is 380 nm or less. A step of supplying a cured resin raw material comprising a plurality of photopolymerization initiators having a multi-functional (meth) acrylate and a plurality of photoabsorption initiators having different absorption wavelengths of active energy rays to the surface of the substrate, A step of irradiating active energy rays from the side (first irradiation) to cure the cured resin raw material, and further curing resin by irradiating active energy rays from the side of the cured resin layer (second irradiation) after the first irradiation And a step of curing the raw material, wherein the cured resin raw material contains one or more photopolymerization initiators before the second irradiation.
(2) The method for producing a light transmissive film according to the above (1), wherein the residual ratio of at least one kind of photopolymerization initiator in the cured resin raw material before the second irradiation is 1% by mass or more.
(3) The method for producing a light-transmitting film according to (1), wherein the residual ratio of at least one kind of photopolymerization initiator in the cured resin material before the second irradiation is 10% by mass or more.
( 4 ) A sandwiching step of sandwiching a cured resin raw material between a mold having a reverse structure of a fine concavo-convex structure on the surface and a substrate, and curing by irradiating active energy rays through the substrate (first irradiation) A transfer process for curing a resin raw material and obtaining a light-transmitting film in which a cured resin layer to which the reversal structure of the mold is transferred is formed on the surface of the substrate, and separation for separating the obtained light-transmitting film and the mold The light transmitting property according to ( 1 ) above, comprising a step and a step of further curing the cured resin raw material by irradiating an active energy ray (second irradiation) from the fine concavo-convex structure side of the separated light transmitting film. A method for producing a film.

  ADVANTAGE OF THE INVENTION According to this invention, the 2nd irradiation of a cured resin layer can be performed efficiently, and a light transmissive film with high surface hardness can be provided.

It is sectional drawing which shows an example of the light transmissive film of this invention. It is a block diagram which shows an example of the manufacturing apparatus of a light transmissive film.

Hereinafter, the present invention will be described in detail.
In this specification, “(meth) acrylate” means acrylate and methacrylate, and “light-transmitting” means that light having a wavelength of at least 400 to 1170 nm is transmitted. "Means visible light, ultraviolet light, electron beam, plasma, heat ray (infrared ray, etc.) and the like.

<Light transmissive film>
The light transmissive film obtained by the present invention has a cured resin layer on at least one surface of the substrate. The shape of the surface of the light transmissive film is not particularly limited, and may be smooth or a fine uneven structure. It is preferable to have a fine concavo-convex structure on the surface because an antireflection effect is exhibited.
Further, when there are a plurality of cured resin layers, the present invention can be applied not only to the surface but also to all photocured layers. For example, you may form a 2nd curable resin layer further on the surface of the light-transmitting film excellent in the hardness of the cured resin layer (1st cured resin layer) manufactured with the manufacturing method of this invention. When the raw material of the second curable resin layer is an active energy ray curable resin composition, it serves as the second irradiation of the present invention and the active energy ray irradiation for forming the second curable resin layer. You can also.

<Base material>
As the material of the base material, it is necessary to transmit light first, methyl methacrylate (co) polymer, polycarbonate, styrene (co) polymer, methyl methacrylate-styrene copolymer, cellulose diacetate, cellulose triacetate, cellulose acetate. Examples include butyrate, polyester, polyamide, polyimide, polyether sulfone, polysulfone, polypropylene, polymethylpentene, polyvinyl chloride, polyvinyl acetal, polyether ketone, polyurethane, and glass.
Furthermore, in order to make part of the photopolymerization initiator easily remain in the first irradiation, a base material containing an ultraviolet absorber capable of absorbing a predetermined wavelength region of ultraviolet rays may be used.

<Curing resin layer>
As described above, the cured resin layer is present on the surface of the light transmissive film and / or on a layer other than the surface. The shape of the surface of the cured resin layer is not particularly limited and may be smooth or have a fine uneven structure. However, it is preferable that the surface has a fine uneven structure because an antireflection effect is exhibited.

<Curing resin material>
The cured resin raw material for forming the cured resin layer includes a polyfunctional (meth) acrylate and a plurality of photopolymerization initiators. In order to cure by irradiation with active energy rays, the cured resin raw material is preferably an active energy ray-curable resin composition containing a polyfunctional (meth) acrylate and a plurality of photopolymerization initiators. An active energy ray-curable resin composition is a resin composition that cures by irradiating active energy rays to cause a polymerization reaction.
This active energy ray-curable resin composition contains a polyfunctional (meth) acrylate, a plurality of photopolymerization initiators, and other components as necessary.

Known components can be applied as the polyfunctional (meth) acrylate. For example, a monomer, oligomer, reactive polymer ethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, isocyanuric acid ethylene oxide modified di (meta) having a radical polymerizable bond and / or a cationic polymerizable bond in the molecule. ) Acrylate, triethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,5-pentanediol di (meth) Acrylate, 1,3-butylene glycol di (meth) acrylate, polybutylene glycol di (meth) acrylate, 2,2-bis (4- (meth) acryloxypolyethoxyphenyl) propane, 2,2- (4- (meth) acryloxyethoxyphenyl) propane, 2,2-bis (4- (3- (meth) acryloxy-2-hydroxypropoxy) phenyl) propane, 1,2-bis (3- (meth) Acryloxy-2-hydroxypropoxy) ethane, 1,4-bis (3- (meth) acryloxy-2-hydroxypropoxy) butane, dimethylol tricyclodecane di (meth) acrylate, bisphenol A ethylene oxide adduct di (meta ) Bifunctional monomers such as acrylate, bisphenol A propylene oxide adduct di (meth) acrylate, neopentyl glycol hydroxypivalate di (meth) acrylate, divinylbenzene, methylenebisacrylamide; pentaerythritol tri (meth) acrylate, tri Three types such as triol propane tri (meth) acrylate, trimethylol propane ethylene oxide modified tri (meth) acrylate, trimethylol propane propylene oxide modified triacrylate, trimethylol propane ethylene oxide modified triacrylate, isocyanuric acid ethylene oxide modified tri (meth) acrylate Functional monomer: Succinic acid / trimethylolethane / acrylic acid condensation reaction mixture, dipentaerystol hexa (meth) acrylate, dipentaerystol penta (meth) acrylate, ditrimethylolpropane tetraacrylate, tetramethylolmethanetetra (meth) Tetrafunctional or higher monomer such as acrylate; bifunctional or higher urethane acrylate, bifunctional or higher polyester acrylate, etc. It is done.
These may be used alone or in combination of two or more.

  The active energy ray-curable resin composition is composed of an ultraviolet absorber, an antioxidant, a mold release agent, a lubricant, a plasticizer, an antistatic agent, a light stabilizer, a flame retardant, a flame retardant aid, and a polymerization inhibitor as necessary. , Fillers, silane coupling agents, colorants, reinforcing agents, inorganic fillers, impact modifiers and other additives may be included.

<Photopolymerization initiator>
It is essential to use a plurality of types of photopolymerization initiators in the present invention, and at least one of them needs to be contained before the second irradiation. Thereby, hardening can be effectively advanced in 2nd irradiation. Whether or not the photopolymerization initiator is contained before the second irradiation mainly depends on the absorption wavelength of the photopolymerization initiator, the wavelength of the active energy ray to be irradiated, and the absorption wavelength of the substrate. Therefore, it is possible to control by these. Here, ultraviolet rays will be described as an example of active energy rays.
In general, since an ultraviolet irradiation lamp includes a wide range of wavelengths in the ultraviolet region, most photopolymerization initiators are cleaved to generate radicals, so the residual rate of the photopolymerization initiator is low. Therefore, in order to leave a part of the photopolymerization initiator, it is necessary to cut off part or all of the ultraviolet rays in the ultraviolet absorption wavelength region of the photopolymerization initiator. As this method, a method of inserting a filter that cuts a specific wavelength into the ultraviolet irradiation lamp can be considered, but in addition to increasing the work of installing the filter, it is possible that the filter will deteriorate quickly, so the specific wavelength is cut A method using a substrate is preferred.

  As described above, when the ultraviolet absorption wavelength region of the substrate overlaps with the ultraviolet absorption wavelength region of the photopolymerization initiator, the ultraviolet light in this region is absorbed by the substrate, so that the photopolymerization initiator remains without being cleaved. be able to. However, if the photopolymerization initiator is not cleaved at all, the curing does not proceed in the first irradiation, so that problems such as failure to maintain the shape of the cured resin layer occur. Therefore, it is necessary to combine the absorption wavelength of the photopolymerization initiator and the absorption wavelength of the substrate so that one of the plurality of photopolymerization initiators remains and the other is cleaved and the curing proceeds. Specifically, a plurality of photopolymerization initiators having different absorption wavelengths are used. One photopolymerization initiator is cleaved by the first irradiation to generate radicals, while the other photopolymerization initiator is left without being cleaved. .

  Examples of these photopolymerization initiators include 1-hydroxycyclohexyl-phenyl ketone ("IRGACURE 184" manufactured by BASF) having an absorption wavelength on the low wavelength side as a photopolymerization initiator that is not easily cleaved by first irradiation, [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one (manufactured by BASF, “IRGACURE2959”), 2-hydroxy-2-methyl-1-phenyl- There is propan-1-one ("BAROCUR1173" manufactured by BASF) and the like. One photopolymerization initiator having an absorption wavelength on the high wavelength side that is easily cleaved by the first irradiation is bis (2,4,6-trimethylbenzoyl). ) -Phenylphosphine oxide (manufactured by BASF, “IRGACURE819”), 2,4,6-trimethylbenzoyl -Diphenyl-phosphine oxide (manufactured by BASF, "LUCIRIN TPO").

Furthermore, the photopolymerization initiator that remains in the first irradiation has high heat resistance because the photopolymerization initiator may be thermally decomposed by the heat generated by the curing reaction without being cleaved in the first irradiation due to absorption of the base material. It is preferable to select a photopolymerization initiator.
In addition, in this application, the residual rate of a photoinitiator represents the mass (residual amount) after hardening by the 1st irradiation or the 2nd irradiation with respect to the mass (addition amount) before hardening of a photoinitiator by a percentage. It is. The residual ratio of the photopolymerization initiator is obtained by immersing the curable resin layer after the first irradiation (before the second irradiation) in an appropriate organic solvent and analyzing it by gas chromatography or high performance liquid chromatography. Can do. When immersing the curable resin layer in a solvent, it is preferable to separate the cured resin layer from the substrate and measure and immerse the mass, but if separation is difficult, measure the total mass and determine the thickness of each layer. The mass of the cured resin layer is obtained.

When the residual ratio of the photopolymerization initiator after the first irradiation is 0% by mass, the effect of the present invention cannot be obtained. Therefore, it is preferable to leave 1% by mass or more, and the second irradiation is more efficiently cured. Therefore, it is preferable to leave 10% by mass or more. In addition, since the photoinitiator which is cleaved in 2nd irradiation increases so that a residual rate is high, since the addition amount of a photoinitiator can be reduced as a result, it is preferable. Therefore, the upper limit is not particularly defined, and the residual rate may be 100% by mass.
The addition amount of the photopolymerization-containing agent is preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the polyfunctional (meth) acrylate. If it is 0.1 parts by mass or more, the curing in the first irradiation is good, and the amount of the photopolymerization initiator before the second irradiation is sufficient. On the other hand, if the content of the polymerization photopolymerization initiator is 10 parts by mass or less, the cured resin layer is not colored and the mechanical strength is not lowered.

<Fine uneven structure>
In the present invention, the average interval between the convex portions 12 of the fine concavo-convex structure is preferably not more than the wavelength of visible light. If the average interval between the convex portions 12 shown in FIG. 1 is equal to or less than the wavelength of visible light, good antireflection properties can be exhibited, and the article 10 of the present invention can be suitably used for optical applications such as antireflection articles.
Here, “visible light” refers to light having a wavelength of 380 to 780 nm. The average interval between the convex portions 12 is preferably 380 nm or less, more preferably 300 nm or less, and particularly preferably 200 nm or less.

The average interval between the convex portions 12 is preferably 25 nm or more, and more preferably 80 nm or more, from the viewpoint of easy formation of the convex portions 12.
The average interval between the convex portions 12 is measured by measuring the distance between the adjacent convex portions 12 by electron microscope observation (distance W1 from the center of the convex portion 12 to the center of the adjacent convex portion 12 in FIG. 1) at 10 points. These values are averaged.

100-400 nm is preferable and, as for the height of the convex part 12, 150-300 nm is more preferable. If the height of the convex portion 12 is 100 nm or more, the reflectance is sufficiently low, and the wavelength dependency of the reflectance is reduced. If the height of the convex part 12 is 400 nm or less, the scratch resistance of the convex part 12 will be good.
The height of the convex portion 12 is determined by electron microscope observation. The vertical distance d1 from the height of the ten convex portions 12 (in FIG. 1, from the top of the convex portion 12 to the bottom of the concave portion 13 adjacent to the convex portion 12). ) And the average of these values.

The aspect ratio of the convex portion 12 (the height of the convex portion 12 / the length of the bottom surface of the convex portion 12) is preferably 0.5 to 5, more preferably 0.7 to 4, and particularly preferably 1.0 to 3. . If the aspect ratio of the convex portion 12 is 0.5 or more, the reflectance is sufficiently low. If the aspect ratio of the convex part 12 is 5 or less, the scratch resistance of the convex part 12 will be good.
The length of the bottom surface of the convex portion 12 is the length d2 of the bottom portion in the cross section when the convex portion 12 is cut in the height direction in FIG.

  The shape of the convex portion 12 is such that the cross-sectional area of the convex portion 12 in the direction orthogonal to the height direction continuously increases from the top to the depth direction, that is, the cross-sectional shape of the convex portion 12 in the height direction is A shape such as a triangle, trapezoid, and bell shape is preferable.

<Method for producing light-transmitting film having fine uneven structure on surface>
The method for producing a light-transmitting film of the present invention includes a sandwiching step of sandwiching a cured resin raw material between a mold having a reverse structure of a fine concavo-convex structure on a surface and a substrate, and an active energy ray via the substrate. (First irradiation) to cure the cured resin raw material, and a transfer process for obtaining a light transmissive film having a cured resin layer formed by transferring the reversal structure of the mold on the substrate surface, and the obtained light A separation step of separating the transparent film and the mold, and a method of further curing the cured resin raw material by irradiating active energy rays (second irradiation) from the fine uneven structure side of the separated light transmissive film.

  Examples of the method for forming the inverted structure of the fine concavo-convex structure on the mold include an electron beam lithography method and a laser beam interference method. For example, a mold having a fine concavo-convex structure can be obtained by applying an appropriate photoresist film on the surface of an appropriate support substrate, exposing to light such as ultraviolet laser, electron beam, and X-ray, and developing. In addition, the support substrate can be selectively etched by dry etching through the photoresist layer, and the resist layer can be removed to directly form a fine concavo-convex structure on the support substrate itself.

It is also possible to use anodized porous alumina as a mold. For example, a pore structure of 20 to 200 nm formed by anodizing aluminum with oxalic acid, sulfuric acid, phosphoric acid or the like as an electrolyte at a predetermined voltage may be used as a mold. According to this method, after anodizing high-purity aluminum for a long time at a constant voltage, the oxide film is once removed and then anodized again, whereby extremely highly regular pores can be formed in a self-organized manner. Further, by combining the anodizing treatment and the pore diameter expanding treatment in the second anodizing step, it is possible to form pores having a triangular or bell-shaped cross section instead of a rectangular cross section. Further, the angle of the innermost portion of the pore can be sharpened by appropriately adjusting the time and conditions of the anodizing treatment and the pore diameter expanding treatment.
Furthermore, you may produce a replication mold by the electroforming method etc. from the mother mold which has a fine uneven structure.

  The shape of the mold itself is not particularly limited, and may be, for example, a flat plate shape, a belt shape, or a roll shape. In particular, if a belt shape or a roll shape is used, the fine concavo-convex structure can be transferred continuously and the productivity can be further increased.

  As a method of arranging the active energy ray curable resin composition between the mold and the base material, the mold and the base material are arranged with the active energy ray curable resin composition being arranged between the mold and the base material. Examples of the method include a method of injecting an active energy ray-curable resin composition into the fine uneven structure of the mold by pressing.

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.
Various measurements and evaluation methods are as follows.

(1) Measurement of mold pores A portion of the anodized alumina on the surface of the mold was shaved, platinum was deposited on the longitudinal section for 1 minute, and a field emission scanning electron microscope ("JSM-7400F" manufactured by JEOL Ltd.). ), Magnifying the image at an acceleration voltage of 3.00 kV and magnifying it 20000 times, measuring the distance between adjacent pores (the distance from the center of the pore to the center of the adjacent pore) at 50 points, The average value was defined as the average interval (period) between adjacent pores.
In addition, the longitudinal section of the mold was magnified 30000 times, and the distance between the bottom of the pores and the top of the convex portions existing between the pores was measured at 50 points, and the average value was reduced. The average depth of the holes.

(2) Measurement of unevenness of fine concavo-convex structure Platinum is vapor-deposited for 10 minutes on the longitudinal cross section of the fine concavo-convex structure on the surface of the laminate, and with the same apparatus and conditions as in (1), The height of the convex portion was measured. Specifically, 50 points were measured, and the average value was taken as the measured value.

(3) Production of mold An aluminum plate having a purity of 99.99% by mass and a thickness of 0.3 mm is cut into a size of 30 mm × 90 mm and electropolished in a perchloric acid / ethanol mixture (volume ratio = 1/4). This was used as an aluminum substrate.
(Process (a))
A 0.3 M oxalic acid aqueous solution was adjusted to 15 ° C., an aluminum substrate was immersed, and anodized under the following conditions.
While stirring the aqueous oxalic acid solution at 150 rpm with a semilunar stirring blade, the power supply of the DC stabilizing device was repeatedly turned ON / OFF to cause anodization by intermittently passing an electric current through the aluminum substrate. The applied voltage at the time of energization is 80 V, the energization time per time is 5 seconds, the applied voltage at the time of cooling is 0 V, and the cooling time per time is 30 seconds. Formed.

(Process (b))
The aluminum substrate on which the oxide film is formed is immersed in a 70 ° C. aqueous solution in which 6% by mass phosphoric acid and 1.8% by mass chromic acid are mixed for 6 hours to dissolve and remove the oxide film, and then anodized. The pit which becomes the pore generation point of was exposed.
(Process (c))
The aluminum base material in which the pore generation point was exposed was immersed in a 0.05 M oxalic acid aqueous solution adjusted to 16 ° C. and anodized at 80 V for 7 seconds to form an oxide film on the surface of the aluminum base material again. .

(Process (d))
The aluminum base material on which the oxide film was formed was immersed in a 5% by mass phosphoric acid aqueous solution adjusted to 32 ° C. for 19 minutes, and subjected to a pore diameter enlargement process for enlarging the pores of the oxide film.
(Process (e))
The aluminum base material with enlarged pores of the oxide film was immersed in a 0.05 M oxalic acid aqueous solution adjusted to 16 ° C. and anodized at 80 V for 7 seconds to further form an oxide film.
(Process (f))
The step (d) and the step (e) were alternately repeated three times, and finally the step (d) was performed.

Then, after washing with deionized water, water on the surface is removed by air blow, and the oxide film has substantially conical pores with an average interval of 180 nm and an average depth of about 190 nm between the convex portions of the fine concavo-convex structure. A mold was obtained.
The mold thus obtained was immersed for 10 minutes in a solution obtained by diluting OPTOOL DSX (manufactured by Daikin Industries) to 0.1% by mass with Durasurf HD-ZV (manufactured by Daikin Industries), and overnight. The mold was released by air drying.

(4) Preparation of cured resin raw material 25 parts by mass of dipentaerythritol (penta) hexaacrylate (manufactured by Nippon Kayaku Co., Ltd., “KAYARAD (Kayarad) DPHA”) as a polyfunctional (meth) acrylate, and pentaerythritol (tri) tetraacrylate (Daiichi Kogyo Seiyaku Neuron Tier "PET-3") 25 parts by mass, dipentaerythritol hexaacrylate modified product (Nippon Kayaku Co., Ltd., KAYARAD (Kayarad) DPHA-12) 25 parts by mass, polyethylene glycol ( # 600) 25 parts by mass of diacrylate (manufactured by Toagosei Co., Ltd., ARONIX (Aronix) M-260) was mixed to prepare a mixed solution.
To this mixed solution, 1-hydroxycyclohexyl-phenylketone (manufactured by BASF, “IRGACURE184”) and bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide (manufactured by BASF, “IRGACURE819” were used as photopolymerization initiators. )) Was added in the amount shown in Table 1, and 0.3 part by mass of polyoxyethylene alkyl phosphate ester (manufactured by Nikko Chemicals, "NIKKOL TDP-2") was added to prepare a cured resin raw material.

(5) Production of light transmissive film Using the production apparatus shown in FIG. 2, an article having a fine concavo-convex structure on the surface was produced as follows.
As the roll-shaped mold 20, the previously produced mold was used.
As the substrate 11, a triacetyl cellulose film (thickness: 80 μm) was used.
The curable composition 38 was supplied from the tank 22 between the roll-shaped mold 20 and the strip-shaped base material 11 that moved along the surface of the roll-shaped mold 20.

Next, the curable composition 38 is irradiated with ultraviolet light having an accumulated light amount of 800 mJ / cm 2 through the substrate 11 from the active energy ray irradiation device 28 installed below the roll-shaped mold 20 to cure the curable composition 38. Thereby, the cured resin layer 15 to which the fine uneven structure on the surface of the roll-shaped mold 20 was transferred was formed.
The light-transmitting film 10 was obtained by peeling the substrate 11 having the cured resin layer 15 formed on the surface thereof from the roll-shaped mold 20 together with the support film 32 by the peeling roll 30. Further, this film was taken out and further cured by irradiating it with ultraviolet rays having an integrated light quantity of 1000 mJ / cm 2 by an active energy ray irradiator. A fine concavo-convex structure was formed on the surface of the molded body thus produced, and the average interval (pitch) between the convex portions was 100 nm, and the average height of the convex portions was 180 nm.

(6) Curability evaluation (measurement of residual C = C)
After the first irradiation and the second irradiation, the surface of the light-transmitting film having a fine concavo-convex structure is respectively divided into an infrared spectroscopic analyzer (manufactured by Thermo Fisher, “Avatar 330”) and a single reflection diamond ATR accessory (ST The IR spectrum of the film surface having a fine concavo-convex structure was obtained using Japan Sales, “Endurance Module”).
The C = C value remaining in the cured resin was determined as follows for evaluating the curability of the cured resin. Ratio of peak area of absorbance of about 1730 cm ⁻¹ derived from ester C═O of cured resin layer to peak area of absorbance of about 810 cm ⁻¹ derived from C═C of cured resin layer (peak of 810 cm ⁻¹ Area / 1730 cm ⁻¹ peak area).

(7) Residual amount of photopolymerization initiator The light-transmitting film after the first irradiation was immersed in acetonitrile overnight, and the acetonitrile was separated and analyzed by high performance liquid chromatography under the following conditions. Was calculated.
Apparatus: SERIES 1100 (manufactured by HEWLETT-PACKARD)
Separation column: CAPCELLPAK C18 4.6 mmφ × 150 mm
Equipment configuration: Degasser ⇒ Pump ⇒ Column (column thermostat) ⇒ Detector (DAD)
Column temperature: 40 ° C
Flow rate: 1 ml / min
Eluent: acetonitrile / water = 30/70 (volume ratio)

(8) Hardness of cured resin layer [Indentation (100 mN / 10 sec)] → [Creep using a Vickers indenter (four-sided diamond cone) and a micro hardness meter (Fischer Instruments HM2000XYp). The hardness of the cured resin layer was measured with an evaluation program of (100 mN, 10 seconds) → [Slow load (100 mN / 10 seconds)]. The measurement was performed in a constant temperature room (temperature 23 ° C., humidity 50%).
From the obtained measurement results, the Martens hardness of the cured resin layer was calculated by analysis software (manufactured by Fisher Instruments, “WIN-HCU”).

[Example 1]
As a photopolymerization initiator, 1 part by weight of 1-hydroxycyclohexyl-phenylketone (manufactured by BASF, "IRGACURE184") is added to 100 parts by weight of polyfunctional (meth) acrylate, and bis (2,4,6-trimethylbenzoyl)- 0.5 parts by mass of phenylphosphine oxide (manufactured by BASF, IRGACURE 819) was added to 100 parts by mass of the polyfunctional (meth) acrylate to prepare a light transmissive film having a fine uneven structure on the surface.
When the produced film was evaluated, no significant difference was observed in the cured resin layer evaluation after the first irradiation compared to Comparative Example 1 in which 0.5 part by mass of IRGACURE819 was added without adding IRGACURE184. Since the residual C = C decreased and the hardness increased after the second irradiation, it was confirmed that the curing reaction was progressing. That is, it can be said that the change rate of the hardened layer after the first and second irradiations is large and the effect of the second irradiation is remarkably exhibited. Since triacetyl cellulose containing an ultraviolet absorber is used as a base material, and a wavelength of 370 nm or less is cut, the photopolymerization initiator IRGACURE 184 having an absorption wavelength remains in this region after the first irradiation. Because. The evaluation results are shown in Table 1.

[Example 2]
As a photopolymerization initiator, 1 part by weight of 1-hydroxycyclohexyl-phenylketone (manufactured by BASF, "IRGACURE184") is added to 100 parts by weight of polyfunctional (meth) acrylate, and bis (2,4,6-trimethylbenzoyl)- 1 part by mass of phenylphosphine oxide (manufactured by BASF, “IRGACURE819”) was added to 100 parts by mass of the polyfunctional (meth) acrylate to prepare a light transmissive film having a fine concavo-convex structure. Compared with Comparative Example 2 in which 1 part by mass of IRGACURE 819 was added without adding IRGACURE 184, no significant difference was observed in the cured layer evaluation after the first irradiation, but the residual C = C decreased after the second irradiation. Since the hardness was increased, it was confirmed that the curing reaction was progressing. That is, it can be said that the change rate of the hardened layer after the first and second irradiations is large and the effect of the second irradiation is remarkably exhibited. Since triacetyl cellulose containing an ultraviolet absorber is used as a base material, and a wavelength of 370 nm or less is cut, the photopolymerization initiator IRGACURE 184 having an absorption wavelength remains in this region after the first irradiation. Because. The evaluation results are shown in Table 1.

* Change rate of cured layer after first and second irradiation (%) = ((hardened layer evaluation value after second irradiation) − (hardened layer evaluation value after first irradiation)) / (curing after first irradiation) Layer evaluation value) x 100

10 goods,
11 substrate,
12 Convex,
13 recess,
14 fine relief structure,
15 cured resin layer,
20 roll mold,
22 tanks,
24 pneumatic cylinder,
26 nip rolls,
28 active energy ray irradiation apparatus,
30 peeling roll,
32 support film,
38 Active energy ray-curable resin composition.

Claims (4)

A method for producing a light-transmitting film comprising a base material that absorbs a predetermined wavelength of active energy rays and a cured resin layer, wherein fine irregularities having an average interval between protrusions of 380 nm or less on the surface of the light-transmitting film The structure is formed,
Supplying a cured resin raw material containing a polyfunctional (meth) acrylate and a plurality of photopolymerization initiators having different absorption wavelengths of active energy rays to the surface of the substrate;
A step of irradiating active energy rays from the substrate side (first irradiation) to cure the cured resin raw material,
A step of further curing the cured resin raw material by irradiating active energy rays from the cured resin layer side (second irradiation) after the first irradiation,
One or more kinds of photopolymerization initiators are contained in the cured resin material before the second irradiation,
A method for producing a light transmissive film. The method for producing a light-transmitting film according to claim 1, wherein the residual ratio of at least one kind of photopolymerization initiator in the cured resin material before the second irradiation is 1% by mass or more. The manufacturing method of the light transmissive film of Claim 1 whose residual rate of the at least 1 sort (s) of photoinitiator in the cured resin raw material before 2nd irradiation is 10 mass% or more. A sandwiching step of sandwiching a cured resin raw material between a mold having a reverse structure of a fine concavo-convex structure on the surface and a substrate;
Irradiating active energy rays through the substrate (first irradiation) to cure the cured resin material, and obtain a light-transmitting film in which the cured resin layer to which the inverted structure of the mold is transferred is formed on the substrate surface A transfer process;
A separation step of separating the obtained light transmissive film and the mold;
A step of further curing the cured resin raw material by irradiating active energy rays (second irradiation) from the fine concavo-convex structure side of the separated light-transmitting film,
The method for producing a light transmissive film according to claim 1 .