JP5833763B2 - Mold manufacturing method - Google Patents

Description

  The present invention relates to a mold manufacturing method, and more particularly to a mold having a porous alumina layer on the surface. The “mold” here includes molds used in various processing methods (stamping and casting), and is sometimes referred to as a stamper. It can also be used for printing (including nanoprinting).

  In general, an optical element such as a display device or a camera lens used in a television or a mobile phone is provided with an antireflection technique in order to reduce surface reflection and increase light transmission. For example, when light passes through the interface of a medium with a different refractive index, such as when light enters the interface between air and glass, the amount of transmitted light is reduced due to Fresnel reflection, etc., and visibility is reduced. is there.

  In recent years, attention has been paid to a method for forming a fine uneven pattern on the substrate surface, in which the period of the unevenness is controlled to a wavelength of visible light (λ = 380 nm to 780 nm) or less as an antireflection technique (see Patent Documents 1 to 4). reference). The two-dimensional size of the convex portions constituting the concavo-convex pattern expressing the antireflection function is 10 nm or more and less than 500 nm. Note that the two-dimensional size corresponds to the diameter when the shape of the convex portion when observed from a direction perpendicular to the surface on which the concave / convex pattern is formed approximates a circle.

  This method utilizes the principle of a so-called moth-eye structure, and the refractive index for light incident on the substrate is determined from the refractive index of the incident medium along the depth direction of the irregularities, to the refractive index of the substrate. The reflection in the wavelength region that is desired to be prevented from being reflected is suppressed by continuously changing the wavelength.

  The moth-eye structure has an advantage that it can exhibit an antireflection effect with a small incident angle dependency over a wide wavelength range, can be applied to many materials, and can directly form an uneven pattern on a substrate. As a result, a low-cost and high-performance antireflection film (or antireflection surface) can be provided.

  As a method for producing a moth-eye structure, a method using an anodized porous alumina layer obtained by anodizing aluminum has attracted attention (Patent Documents 2 to 4).

  Here, the anodized porous alumina layer obtained by anodizing aluminum will be briefly described. Conventionally, a method for producing a porous structure using anodization has attracted attention as a simple method capable of forming regularly ordered nano-sized cylindrical pores (fine concave portions). When an aluminum substrate is immersed in an acidic or alkaline electrolyte such as sulfuric acid, oxalic acid, or phosphoric acid, and a voltage is applied using the aluminum substrate as an anode, oxidation and dissolution proceed simultaneously on the surface of the aluminum substrate. An oxide film having pores can be formed. These cylindrical pores are oriented perpendicular to the oxide film and exhibit self-organized regularity under certain conditions (voltage, type of electrolyte, temperature, etc.). Is expected.

  The porous alumina layer formed under specific conditions has an array in which almost regular hexagonal cells are two-dimensionally filled with the highest density when viewed from the direction perpendicular to the film surface. Each cell has a pore in the center, and the arrangement of the pores has periodicity. The cell is formed as a result of local dissolution and growth of the film, and dissolution and growth of the film proceed simultaneously at the bottom of the pores called a barrier layer. At this time, it is known that the distance between adjacent pores (center-to-center distance) corresponds to approximately twice the thickness of the barrier layer and is approximately proportional to the voltage during anodization. In addition, although the diameter of the pores depends on the type, concentration, temperature, etc. of the electrolytic solution, it is usually 1/3 of the cell size (the length of the longest diagonal line when viewed from the direction perpendicular to the film surface). It is known to be a degree. The pores of such porous alumina have an arrangement with high regularity (having periodicity) under a specific condition, an arrangement with irregularity to some extent or an irregularity (having no periodicity) depending on the conditions. ).

  Patent Document 2 discloses a method of forming an antireflection film (antireflection surface) using a stamper having an anodized porous alumina film on the surface.

  Patent Document 3 discloses a technique for forming a tapered recess having a continuously changing pore diameter by repeating anodization of aluminum and a pore diameter enlargement process.

  The present applicant discloses in Patent Document 4 a technique for forming an antireflection film using an alumina layer in which fine concave portions have stepped side surfaces.

  Further, as described in Patent Documents 1, 2, and 4, an antireflection film (antireflection surface) is provided by providing a concavo-convex structure (macro structure) larger than the moth eye structure in addition to the moth eye structure (micro structure). ) Can be given an anti-glare (anti-glare) function. The two-dimensional size of the projections that form the projections and depressions that exhibit the antiglare function is 1 μm or more and less than 100 μm.

  Thus, by using the anodized porous alumina film, a mold for forming a moth-eye structure on the surface (hereinafter referred to as “moth-eye mold”) can be easily manufactured. In particular, as described in Patent Documents 2 and 4, when the surface of an anodized aluminum film is used as it is as a mold, the effect of reducing the manufacturing cost is great. The surface structure of the moth-eye mold that can form the moth-eye structure is referred to as an “inverted moth-eye structure”.

  As a method for producing an antireflection film using a moth-eye mold, a method using a photocurable resin is known. First, a photocurable resin is applied on the substrate. Subsequently, the uneven surface of the surface of the moth-eye mold is filled with the photocurable resin by pressing the uneven surface of the moth-eye mold subjected to the release treatment against the photocurable resin in a vacuum. Subsequently, the photocurable resin in the concavo-convex structure is irradiated with ultraviolet rays to cure the photocurable resin. Thereafter, by separating the moth-eye mold from the substrate, a cured product layer of a photocurable resin to which the concavo-convex structure of the moth-eye mold is transferred is formed on the surface of the substrate. A method for producing an antireflection film using a photocurable resin is described in Patent Document 4, for example.

The moth-eye mold described above is formed on an aluminum substrate represented by a substrate formed of aluminum or a cylinder formed of aluminum, or a support formed of a material other than aluminum typified by a glass substrate. It can be manufactured using an aluminum film. However, when a moth-eye mold is manufactured using an aluminum film formed on a glass substrate or plastic film, the aluminum film (partially an anodized film) is bonded to the glass substrate or plastic film. May decrease. The applicant of the present invention forms the inorganic underlayer (for example, SiO ₂ layer) and the buffer layer (for example, AlO _x layer) containing aluminum on the surface of the substrate formed of glass or plastic. It discovered that the fall of adhesiveness was suppressed and it is disclosing in patent document 5. FIG.

  The applicant has developed a method for efficiently producing an antireflection film by a roll-to-roll method using, for example, a cylindrical (roll-shaped) moth-eye mold in Patent Document 7. A cylindrical moth-eye mold is formed, for example, by forming an organic insulating layer on the outer peripheral surface of a metal cylinder and alternately repeating anodization and etching on the aluminum film formed on the organic insulating layer. Is done. Also in this case, the adhesiveness can be improved by forming the inorganic underlayer and the buffer layer disclosed in Patent Document 5.

  The entire disclosures of Patent Documents 1, 2, 4, 5 and 7 are incorporated herein by reference.

JP-T-2001-517319 Special Table 2003-531962 JP 2005-156695 A International Publication No. 2006/059686 International Publication No. 2010/116728 International Publication No. 2010/073636 International Publication No. 2011/105206

  The present inventor examined the anion electrodeposition method as a method for forming an organic insulating layer on the outer peripheral surface of a metal cylinder. As shown in an optical microscope image in FIG. 12, foreign matter may be generated. It was. FIG. 12 shows a field of view of 482 μm × 688 μm, and the linear foreign matter extends to about 370 μm × about 250 μm. This foreign matter is not particularly problematic in general anion electrodeposition coating, but becomes a problem when forming a moth-eye mold having irregularities of the above-mentioned submicron order. That is, when the moth-eye mold is formed by alternately repeating anodization and etching on the aluminum film formed on the organic insulating layer on which the above-mentioned foreign substance exists, the shape of the foreign substance is reflected on the surface of the moth-eye mold. Will be. As a result, a defect (abnormal shape) due to a foreign substance is formed on the antireflection surface formed using such a moth-eye mold, and the antireflection function may be locally degraded.

  The present invention has been made to solve the above-mentioned problems, and its main object is to form an organic insulating layer on the surface of a metal substrate for forming a moth-eye mold by an anionic electrodeposition method. It is another object of the present invention to provide a method for manufacturing a moth-eye mold that suppresses the generation of foreign matter and thereby has few defects in the moth-eye structure having an inverted surface.

  A mold manufacturing method according to an embodiment of the present invention includes a mold having an inverted moth-eye structure on the surface having a plurality of recesses having a two-dimensional size of 10 nm or more and less than 500 nm when viewed from the normal direction of the surface. And a step (a1) of preparing a metal substrate having a surface that diffusely reflects visible light, and a step of forming an organic insulating layer on the surface of the metal substrate by anion electrodeposition ( a step (a) of preparing a mold substrate, including a2) and a step (a3) of forming an aluminum alloy layer on the organic insulating layer, and partially anodizing the aluminum alloy layer The step (b) of forming a porous alumina layer having a plurality of fine recesses, and the porous alumina layer is brought into contact with an etching solution after the step (b). A step (c) of enlarging the plurality of fine recesses of the alumina layer, and a step (d) of growing the plurality of fine recesses by further anodizing after the step (c). .

  In one embodiment, the surface of the metal substrate has a diffuse reflectance of 10% to 45% for light having a wavelength of 550 nm incident on the surface at an incident angle of 8 °.

  In one embodiment, the voltage in the step (a2) is not less than 60V and not more than 120V.

  In one embodiment, the energization time in the step (a2) is 200 seconds or less.

  In one embodiment, the step (a2) is performed using a matte anionic paint.

  In one embodiment, the step (a) further includes a step (a4) of forming an inorganic underlayer on the organic insulating layer after the step (a2) and before the step (a3). Include. The inorganic underlayer is, for example, a silicon oxide layer, a tantalum oxide layer, or a titanium oxide layer. The thickness of the inorganic underlayer is, for example, not less than 50 nm and not more than 500 nm.

  In one embodiment, the step (a) includes a buffer layer containing aluminum and oxygen or nitrogen on the inorganic underlayer after the step (a4) and before the step (a3). The step (a5) of forming is further included. The buffer layer has a thickness of not less than 10 nm and not more than 500 nm, for example. The aluminum content in the buffer layer has a higher profile on the aluminum alloy layer side than on the inorganic underlayer side.

  In one embodiment, the metal substrate is cylindrical, and the surface of the metal substrate is an outer peripheral surface of a cylinder of the metal substrate.

  In one embodiment, the metal substrate is a metal sleeve. The metal sleeve is a nickel sleeve, a stainless steel sleeve, an aluminum sleeve or a copper sleeve.

  In one embodiment, the step (b) and the step (c) are further performed after the step (d). The size and shape of the fine recesses can be adjusted by the number of times that the anodic oxidation and etching are repeated alternately. In addition, it is preferable to end by anodizing.

  According to an embodiment of the present invention, it is possible to suppress the generation of foreign matters when forming an organic insulating layer by an anionic electrodeposition method on the surface of a metal substrate for forming a moth-eye mold. A method for manufacturing a moth-eye mold with few defects in the moth-eye structure formed is provided.

(A) is a schematic diagram which shows the mold base material 10 used for manufacture of the type | mold of embodiment by this invention, (b) is a schematic diagram which shows the mold 100 for moth eyes manufactured using the mold base material 10 It is. (A)-(e) is a figure which shows the process of the production method of the roll type | mold using a metal sleeve. (A)-(e) is a figure which shows the process of the manufacturing method of the type | mold which has a porous alumina layer. It is sectional drawing which shows typically the structure of type | mold 100A which has a metal sleeve. It is a schematic diagram for demonstrating the manufacturing method of the antireflection film of embodiment by this invention. (A) is a schematic diagram which shows the apparatus used for anion electrodeposition, (b) is a figure which shows the reaction in an electrode. It is a figure for demonstrating the relationship between the magnitude | size of the process voltage at the time of anion electrodeposition, the thickness of an electrodeposition film | membrane, and surface shape, (a) is the relationship between electrodeposition time (energization time) and film thickness. (B) is a graph which shows the spectral diffuse reflectance of the electrodeposition film | membrane (insulating resin layer) from which thickness differs. It is a schematic diagram for demonstrating the production | generation mechanism of the foreign material in anion electrodeposition, (a) shows the case where a process voltage is 40V, (b) shows the case where a process voltage is 80V, respectively. It is a graph which shows the spectral diffuse reflectance of the nickel sleeve used for experiment. It is a schematic diagram for demonstrating the production | generation mechanism of the foreign material in anion electrodeposition, (a) shows the case of a mirror surface, (b) shows the case of a rough surface, respectively. It is a graph which shows the spectral diffuse reflectance of the nickel sleeve used for experiment. It is a figure which shows the optical microscope image of the foreign material produced | generated by anion electrodeposition.

  Hereinafter, a method for manufacturing a mold according to an embodiment of the present invention will be described with reference to the drawings. The mold of the present embodiment is a moth-eye mold, and has an inverted moth-eye structure on the surface having a plurality of recesses having a two-dimensional size of 10 nm or more and less than 500 nm when viewed from the normal direction of the surface. .

  A mold manufacturing method according to an embodiment of the present invention includes a metal base 72m, an organic insulating layer 13 formed on the metal base 72m, and an organic insulating layer 13 as shown in FIG. Including a step of preparing a mold base 10 having the aluminum alloy layer 18 formed. The metal substrate 72m and the organic insulating layer 13 may be collectively referred to as the support 12.

  Here, the metal base material 72m has a surface that diffuses and reflects visible light, and an organic insulating layer 13 is formed on the surface by an anionic electrodeposition method, as will be described later in detail with an experimental example. Yes. As a result, the generation of linear foreign matters (see FIG. 12) on the surface of the organic insulating layer 13 is suppressed. The thickness of the organic insulating layer 13 is, for example, 4 μm or more and 10 μm or less. If the thickness of the organic insulating layer 13 is less than 4 μm, sufficient insulation may not be obtained, and if it exceeds 10 μm, the productivity is lowered.

  The aluminum alloy layer 18 is a layer containing aluminum as a main component, and includes a layer containing a metal element M other than aluminum and / or other nonmetallic elements. The aluminum alloy layer 18 only needs to have a property as a valve metal layer (typically anodizing property), and is a layer made of pure aluminum (for example, a purity of 99.99 mass% or more). including. The aluminum alloy layer 18 is formed by a known method (for example, an electron beam evaporation method or a sputtering method). The thickness of the aluminum alloy layer 18 is preferably 100 nm or more, and preferably 3000 nm or less from the viewpoint of productivity, in order to obtain an anodized alumina layer having a surface structure serving as a moth-eye mold. Typically, it is about 1000 nm (1 μm).

  Here, it is preferable that the aluminum alloy layer 18 having a thickness of about 1 μm is deposited in a plurality of times rather than in one deposition. That is, rather than continuously depositing to a desired thickness (for example, 1 μm), the process of interrupting the deposition to a certain thickness and restarting the deposition after a certain time has elapsed is repeated. It is preferable to obtain the aluminum alloy layer 18. For example, it is preferable to interrupt each time an aluminum alloy layer having a thickness of 50 nm is deposited and to obtain an aluminum alloy layer 18 having a thickness of about 1 μm by 20 aluminum alloy layers each having a thickness of 50 nm. As described above, the quality (for example, chemical resistance and adhesiveness) of the finally obtained aluminum alloy layer 18 can be improved by dividing the deposition of the aluminum alloy into a plurality of times. The continuous deposition of the aluminum alloy increases the temperature of the substrate (which has the surface on which the aluminum alloy layer is deposited), resulting in a distribution of thermal stress in the aluminum alloy layer 18 and the film This is considered to reduce the quality.

  Here, it is preferable to have the inorganic base layer 14 between the organic insulating layer 13 and the aluminum alloy layer 18 like the type | mold base material 10 shown to Fig.1 (a). The inorganic underlayer 14 is directly formed on the surface of the organic insulating layer 13 and functions to improve the adhesion between the organic insulating layer 13 and the aluminum alloy layer 18. The inorganic underlayer 14 is preferably formed of an inorganic oxide or an inorganic nitride. When an inorganic oxide is used, for example, a silicon oxide layer, a tantalum oxide layer, or a titanium oxide layer is preferable, and when an inorganic nitride is used, For example, a silicon nitride layer is preferable. Further, the thermal expansion coefficient may be adjusted by adding impurities to the inorganic oxide layer or the inorganic nitride layer. For example, when a silicon oxide layer is used, the thermal expansion coefficient can be increased by adding germanium (Ge), phosphorus (P), or boron (B).

  The thickness of the inorganic underlayer 14 is preferably 40 nm or more, and more preferably 100 nm or more. If the thickness of the inorganic underlayer 14 is less than 40 nm, the effect of providing the inorganic underlayer 14 may not be sufficiently exhibited. The thickness of the inorganic underlayer 14 is preferably 500 nm or less, and more preferably 200 nm or less. If the thickness of the inorganic underlayer 14 exceeds 500 nm, the formation time of the inorganic underlayer 14 becomes unnecessarily long. Also, the thicker the inorganic underlayer 14 formed on a curved surface or a flexible surface, the easier it is to crack.

  The mold substrate 10 preferably further includes a buffer layer 16 between the inorganic base layer 14 and the aluminum alloy layer 18. The buffer layer 16 acts to improve the adhesion between the inorganic underlayer 14 and the aluminum alloy layer 18. Here, an example in which the buffer layer 16 is directly formed on the inorganic underlayer 14 is shown, but the present invention is not limited thereto. For example, when a conductive layer (preferably a valve metal layer) is provided on the underlayer in order to uniformly anodize the aluminum alloy layer 18, it is between the inorganic underlayer 14 and the buffer layer 16, or between the buffer layer 16 and the aluminum alloy layer. A conductive layer may be provided between the two.

  The buffer layer 16 preferably contains aluminum (and metal element M) and oxygen or nitrogen. Although the oxygen or nitrogen content may be constant, it is particularly preferable that the aluminum (and metal element M) content has a higher profile on the aluminum alloy layer 18 side than on the inorganic underlayer 14 side. It is because it is excellent in matching of physical property values such as thermal expansion coefficient. The thickness of the buffer layer 16 is preferably 10 nm or more, and more preferably 20 nm or more. Further, the thickness of the buffer layer 16 is preferably 500 nm or less, and more preferably 200 nm or less. If the thickness of the buffer layer 16 is less than 10 nm, sufficient adhesion may not be obtained between the inorganic underlayer 14 and the aluminum alloy layer 18. Further, if the thickness of the buffer layer 16 exceeds 500 nm, the formation time of the buffer layer 16 becomes unnecessarily long, which is not preferable.

  The profile in the thickness direction of the aluminum content in the buffer layer 16 may change stepwise or may change continuously. For example, when the buffer layer 16 is formed of aluminum, the metal element M, and oxygen, a plurality of aluminum oxide alloy layers whose oxygen content gradually decreases are formed, and the aluminum alloy layer 18 is formed on the uppermost layer. . The oxygen content of the buffer layer 16 is preferably 60 at% or less at the highest. The same applies to the case where the buffer layer 16 containing nitrogen instead of oxygen is formed.

  A porous alumina layer 20 having a plurality of fine recesses 22 is formed by partially anodizing the aluminum alloy layer 18 using the mold base 10 shown in FIG. A step of forming the porous alumina layer 20 by contacting the etching solution with the etching solution, and a step of enlarging the plurality of fine recesses 22 of the porous alumina layer 20; The moth-eye mold 100 shown in FIG. 1 (b) can be obtained by performing the step of growing the minute recesses 22 of FIG.

The moth-eye mold 100 is suitably used for manufacturing an antireflection film (antireflection surface). The shape of the fine recesses (pores) 22 of the porous alumina layer 20 used for manufacturing the antireflection film is generally conical. As exaggeratedly shown in FIG. 1 (b), the fine recess 22 may have a stepped side surface. The two-dimensional size (opening diameter: D _p ) of the fine recess 22 is preferably 10 nm or more and less than 500 nm, and the depth (D _depth ) is preferably about 10 nm or more and less than 1000 nm (1 μm). Moreover, it is preferable that the bottom part of the fine recessed part 22 is pointed (the bottom part is a point). Furthermore, it is preferable that the fine concave portions 22 are closely packed, and assuming that the shape of the fine concave portions 22 when viewed from the normal direction of the porous alumina layer 20 is a circle, adjacent circles overlap each other, It is preferable that a brim is formed between the adjacent fine recesses 22. When the substantially conical minute concave portions 22 are adjacent so as to form a collar portion, the two-dimensional size D _p of the fine concave portions 22 is assumed to be equal to the average adjacent distance D _int . Therefore, the porous alumina layer 20 of the moth-eye mold 100 for producing the antireflection film has a fine recess 22 having D _p = D _int of 10 nm or more and less than 500 nm and D _depth of 10 nm or more and less than 1000 nm (1 μm). It is preferable to have a densely arranged structure. Since not a circle to the shape of the opening of the minute recessed portions 22 precisely, D _p is preferably determined from the SEM image of the surface. The thickness t _p of the porous alumina layer 20 is about 1 μm or less.

  Since the generation of linear foreign matters on the surface of the organic insulating layer 13 of the moth-eye mold 100 is suppressed, the inverted moth-eye structure on the surface of the moth-eye mold 100 has few defects. When this moth-eye mold 100 is used, defects (abnormal shapes) due to foreign matters are prevented from being formed in the moth-eye structure on the anti-reflection surface. It is possible to form an antireflective surface with no increase in haze.

  Below, the example of the manufacturing method of the roll type | mold using a cylindrical type | mold base material is demonstrated.

  The roll mold was produced by the method described in Patent Document 7. Here, a nickel metal sleeve (also referred to as a nickel sleeve) was used. The metal sleeve refers to a metal cylinder having a thickness of 0.02 mm to 1.0 mm. The metal sleeve is not limited to a nickel sleeve, and a metal sleeve made of stainless steel, aluminum, or copper can be used. These metal sleeves can be obtained from, for example, Dimco Corporation.

  A roll-type manufacturing method using a metal sleeve used in the experiment will be briefly described with reference to FIG.

  First, as shown in FIG. 2A, a metal sleeve 72m is prepared. The metal sleeve 72m has a surface (outer peripheral surface) that diffuses and reflects visible light. As will be described later with reference to experimental examples, the surface of the metal sleeve 72m preferably has a diffuse reflectance of 10% to 45% for light having a wavelength of 550 nm incident on the surface at an incident angle of 8 °. . The metal sleeve is generally formed by electrodeposition of metal. The surface roughness of the metal sleeve can be adjusted by controlling the electrodeposition conditions, for example, the growth rate of the metal film.

  Next, as shown in FIG. 2B, the organic insulating layer 13 is formed on the outer peripheral surface of the metal sleeve 72m by an anion electrodeposition method (see FIG. 6). As the anion electrodeposition method, a known anion electrodeposition method can be used.

  For example, first, the metal sleeve 72m is cleaned. Next, the metal sleeve 72m is immersed in an electrodeposition tank in which an electrodeposition liquid containing an anion electrodeposition resin is stored. Electrodes are installed in the electrodeposition tank. When the insulating resin layer is formed by anion electrodeposition, the metal sleeve 72m is used as an anode, the electrode installed in the electrodeposition tank is used as a cathode, a current is passed between the metal sleeve 72m and the cathode, and the metal sleeve 72m is used. An insulating resin layer is formed by depositing an electrodeposition resin on the outer peripheral surface of the film. Then, the organic insulating layer 13 is formed by performing a washing | cleaning process, a baking process, etc. As the electrodeposition resin, for example, an acrylic resin or a mixture of an acrylic resin and a melamine resin can be used.

  The organic insulating layer 13 has a high effect of flattening the surface, and it is possible to suppress the surface scratches of the metal sleeve 72 m and the like from being reflected on the surface shape of the aluminum alloy layer 18. Conversely, by using a matte anionic paint, the organic insulating layer 13 having antiglare property can be formed on the surface. When a moth-eye mold is formed using the aluminum alloy layer 18 formed on the organic insulating layer 13 having antiglare property, a moth-eye mold capable of forming an antireflection surface having antiglare property can be obtained.

Next, if necessary, an inorganic underlayer 14 is formed on the organic insulating layer 13 as shown in FIG. For example, the SiO ₂ layer 14 having a thickness of about 100 nm is formed.

  Next, as shown in FIG. 2D, the buffer layer 16 and the aluminum alloy layer 18 are formed continuously. The buffer layer 16 is formed as necessary. The same target is used to form the buffer layer 16 and the aluminum alloy layer 18. Accordingly, here, when the aluminum alloy layer 18 includes the metal element M, the ratio of aluminum to the metal element M is constant in the buffer layer 16 and the aluminum alloy layer 18. The buffer layer 16 has a thickness of, for example, about 100 nm, and the aluminum alloy layer 18 has a thickness of about 1 μm. The formation from the inorganic underlayer 14 to the formation of the aluminum alloy layer 18 is preferably performed by a thin film deposition method (for example, sputtering), and is preferably performed in the same chamber.

  Subsequently, as shown in FIG. 2 (e), the porous alumina layer 20 having a plurality of fine recesses is formed on the surface of the aluminum alloy layer 18 by alternately repeating anodic oxidation and etching. Thus, the mold 100a is obtained.

  Next, a method for forming the porous alumina layer 20 will be described with reference to FIG. In FIG. 3, the mold base 10 is shown in which the aluminum alloy layer 18 is directly formed on the support 12.

  First, as shown in FIG. 3A, a mold base 10 is prepared. The mold substrate 10 includes a metal substrate, an organic insulating layer 13 formed on the metal substrate, and an aluminum alloy layer 18 deposited on the organic insulating layer 13.

  Next, as shown in FIG. 3B, a porous alumina layer 20 having a plurality of fine recesses 22 (pores) by anodizing the surface of the mold base 10 (the surface 18s of the aluminum alloy layer 18). Form. The porous alumina layer 20 includes a porous layer having fine concave portions 22 and a barrier layer. The porous alumina layer 20 is formed, for example, by anodizing the surface 18s in an acidic electrolytic solution. The electrolytic solution used in the step of forming the porous alumina layer 20 is, for example, an aqueous solution containing an acid selected from the group consisting of oxalic acid, tartaric acid, phosphoric acid, chromic acid, citric acid, and malic acid. By adjusting the anodic oxidation conditions (for example, the type of the electrolytic solution and the applied voltage), the pore spacing, the pore depth, the pore shape, and the like can be adjusted. The thickness of the porous alumina layer can be changed as appropriate. The aluminum alloy layer 18 may be completely anodized.

  Next, as shown in FIG. 3 (c), the porous alumina layer 20 is brought into contact with an alumina etchant so as to be etched by a predetermined amount, thereby enlarging the hole diameter of the fine recess 22. Here, by employing wet etching, the pore walls and the barrier layer can be etched almost isotropically. The amount of etching (that is, the size and depth of the fine recess 22) can be controlled by adjusting the type / concentration of the etching solution and the etching time. As the etching solution, for example, an aqueous solution of 10% by mass of phosphoric acid, an organic acid such as formic acid, acetic acid or citric acid, or a mixed solution of chromium phosphoric acid can be used.

  Next, as shown in FIG. 3D, the aluminum alloy layer 18 is partially anodized again to grow the fine recesses 22 in the depth direction and to thicken the porous alumina layer 20. Here, since the growth of the fine recess 22 starts from the bottom of the already formed fine recess 22, the side surface of the fine recess 22 is stepped.

  Thereafter, if necessary, the porous alumina layer 20 is further etched by bringing it into contact with an alumina etchant to further enlarge the hole diameter of the fine recess 22. As the etchant, it is preferable to use the above-described etchant, and in practice, the same etch bath may be used.

  Thus, by repeating the anodizing step and the etching step described above, a moth-eye mold 100A having a porous alumina layer 20 having a desired concavo-convex shape is obtained as shown in FIG. By adjusting the conditions, time, and number of times of the anodizing step and the etching step, the side surface of the fine recess 22 can be stepped, or can be a smooth curved surface or a slope.

  Next, the manufacturing method of the antireflection film using the roll type moth-eye mold of the embodiment according to the present invention will be described. The roll-shaped mold has an advantage that the surface structure of the mold can be continuously transferred to a work piece (having a surface on which an antireflection film is formed) by rotating the roll-shaped mold about an axis.

  An antireflection film manufacturing method according to an embodiment of the present invention includes a step of preparing the mold, a step of preparing a workpiece, and applying a photocurable resin between the mold and the surface of the workpiece. In this state, it includes a step of curing the photocurable resin by irradiating the photocurable resin with light and a step of peeling the mold from the antireflection film formed of the cured photocurable resin.

  When a roll-shaped film is used as a workpiece, an antireflection film can be produced by a roll-to-roll method. The film preferably includes a base film and a hard coat layer formed on the base film, and the antireflection film is preferably formed on the hard coat layer. As the base film, for example, a TAC (triacetyl cellulose) film can be suitably used. As the hard coat layer, for example, an acrylic hard coat material can be used.

  Since the metal sleeve 72m of the mold 100a shown in FIG. 2 (e) is easily deformed, it is difficult to use the mold 100a as it is. Therefore, as shown in FIG. 4, by inserting the core material 50 into the metal sleeve 72m of the mold 100a, a mold 100A that can be used in a roll-to-roll antireflection film manufacturing method is obtained. A mold 100A shown in FIG. 4 has a buffer layer 16 formed on the support 12.

  Next, with reference to FIG. 5, the manufacturing method of the anti-reflective film of embodiment by this invention is demonstrated. FIG. 5 is a schematic cross-sectional view for explaining a method for producing an antireflection film by a roll-to-roll method.

  First, the roll-shaped moth-eye mold 100A shown in FIG. 4 is prepared.

  Next, as illustrated in FIG. 5, the ultraviolet curable resin 32 ′ is irradiated with ultraviolet rays (UV) in a state where the workpiece 42 having the ultraviolet curable resin 32 ′ applied to the surface thereof is pressed against the moth-eye mold 100 A. As a result, the ultraviolet curable resin 32 'is cured. As the ultraviolet curable resin 32 ′, for example, an acrylic resin can be used. The workpiece 42 is, for example, a TAC (triacetyl cellulose) film. The workpiece 42 is unwound from an unillustrated unwinding roller, and then an ultraviolet curable resin 32 ′ is applied to the surface by, for example, a slit coater. The workpiece 42 is supported by support rollers 62 and 64 as shown in FIG. The support rollers 62 and 64 have a rotation mechanism and convey the workpiece 42. Further, the roll-shaped moth-eye mold 100A is rotated in a direction indicated by an arrow in FIG. 5 at a rotation speed corresponding to the conveyance speed of the workpiece 42.

  Thereafter, by separating the moth-eye mold 100A from the workpiece 42, a cured product layer 32 to which the uneven structure (inverted moth-eye structure) of the moth-eye mold 100A is transferred is formed on the surface of the workpiece 42. . The workpiece 42 having the cured product layer 32 formed on the surface is wound up by a winding roller (not shown).

  Although the example which uses a metal sleeve as a metal base material was demonstrated above, it replaced with a metal sleeve and a bulk metal base material (for example, pipe) can also be used.

  Hereinafter, the manufacturing method of the moth-eye mold according to the embodiment of the present invention will be described with reference to experimental examples.

  In the experiment, a nickel sleeve having a thickness of about 150 μm, a diameter of 300 mm, and a length of 1510 mm was used. Nickel sleeves with different surface roughness were prepared.

  Anion electrodeposition was performed using an apparatus schematically shown in FIG. The electrodeposition tank (width 2220 mm, depth 860 mm, length 790 mm) was filled with about 1000 L of electrodeposition liquid, and the temperature of the electrodeposition liquid was adjusted to about 23 ° C. The filter is provided to remove the gelled resin particles generated when the electrodeposition solution deteriorates. If necessary, the two cocks are opened and the electrodeposition solution is circulated through the filter. Let In this study, the two cocks are closed and the electrodeposition solution is not circulated.

As described above, the cleaned metal sleeve 72m is immersed in the electrodeposition liquid in the electrodeposition tank. The electrodeposition solution contains an anion electrodeposition resin (solid content), pure water, butanol, isopropyl alcohol (IPA), a neutralizing agent (NH ₄ ⁺ ), and butyl cellosolve (film-forming aid). As the anion electrodeposition resin, a mixed system of acrylic resin and melamine resin (HEG Coat 2000 manufactured by Kansai Paint Co., Ltd.) was used. This electrodeposition liquid has 5.3 to 6.0% by mass of an acrylic resin as a main agent, 3.6 to 3.9% by mass of a melamine resin as a crosslinking agent, 0.3% by mass of a neutralizing agent, and a function. It contains 0.1% by mass of additive aids for imparting properties, 5.0-7.5% by mass of solvent, and 82.2-85.7% by mass of deionized water. When this electrodeposition liquid is used, gel particles (diameter is approximately 0.20 μm) in which an acrylic resin is crosslinked with a melamine resin are formed, and a matte resin layer is obtained. In addition, a glossy resin layer can also be formed by reducing the compounding quantity of the acrylic resin and melamine resin in the said electrodeposition liquid. The diameter of the gel particles formed at this time is approximately 0.15 μm or less. In addition, a known material such as an anion electrodeposition paint described in JP-A-2003-49112 can be used. A method of dispersing filler in the electrodeposition liquid is also known.

  Using the metal sleeve 72m as an anode and the electrode installed in the electrodeposition bath as a cathode, a direct current voltage is applied between the metal sleeve 72m and the cathode to cause a current to flow. The voltage is preferably 120 V or less in order to prevent so-called gas pins. The energization time is preferably 200 seconds or less.

When a DC voltage is applied to the electrodeposition liquid containing the anion electrodeposition resin, the anion electrodeposition resin having a negative charge (for example, the resin having a COO ⁻ group shown in FIG. 6B) moves to the anode, and the anode H ⁺ is received on the metal sleeve 72m, and the ionicity disappears and becomes insoluble, and precipitates on the metal sleeve 72m. The deposited resin is fused by Joule heat to form the organic insulating layer 13. The thickness of the organic insulating layer 13 is, for example, 4 μm or more and 10 μm or less. In the following experimental example, the organic insulating layer 13 having a thickness of about 6 μm was formed.

  With reference to FIG. 7, the relationship between the magnitude of the treatment voltage during anion electrodeposition, the thickness of the electrodeposition film, and the surface shape will be described.

  As shown in FIG. 7A, when the processing voltage is increased (the concentration of the electrodeposition liquid is constant), the film formation rate is increased. For example, when the processing voltage is 40 V, it takes about 300 seconds to obtain a 6 μm film. However, when the processing voltage is 80 V, a 6 μm film can be obtained in about 100 seconds.

  In addition, the surface shape of the electrodeposition film strongly depends on the film thickness of the electrodeposition film. Even if the processing voltage is different (even if the processing time is different), the surface shape is almost the same as long as the film thickness is the same. I found out.

  In FIG. 7B, electrodeposition films having different thicknesses are formed, the respective surface shapes are transferred to the curable resin film, and the curable resin film having the transferred surface shape is fixed on the black acrylic plate. The results of measuring the spectral diffuse reflectance are shown below. The spectral diffuse reflectance was measured by the SCE method using CM2006 manufactured by Konica Minolta. The incident angle of the light irradiating the sample is 8 °, and the intensity of the reflected light (that is, only the diffuse reflected light) is excluded from the total reflected light (including regular reflected light and diffuse reflected light). The diffuse reflectance measured with an integrating sphere and obtained for each wavelength is shown in the graph of FIG.

  As shown in FIG. 7B, the diffuse reflectance increases as the electrodeposition film formed using the above-mentioned electrodeposition resin becomes thicker. The antiglare property desired for the antireflection film varies depending on the application. FIG. 7B shows that the antiglare property can be adjusted by adjusting the thickness of the electrodeposition film. When the electrodeposition material exemplified here is used, an appropriate antiglare property is obtained when the thickness of the electrodeposition film is in the range of 6 μm to 7 μm.

  Table 1 below shows the results obtained by forming an insulating resin layer on a commercially available nickel sleeve (diameter 300 mm, length 1510 mm) having a mirror surface by the anion electrodeposition described above. The treatment voltage during electrodeposition was 40 V and 80 V, and the thickness of the insulating resin layer was 6 μm. In Table 1, the surface of the obtained insulating resin layer was observed, and the number of foreign matters as shown in FIG. 12 was obtained. The number of foreign matters was determined for each of three levels of foreign matters of 1 mm or more, 500 μm or more and less than 1 mm, or 300 μm or more and 500 μm or less. Here, the size of the foreign matter was defined as an average (biaxial average) of lengths in two orthogonal directions of a region where the linear foreign matter spreads in the microscope image. However, one of the two orthogonal directions is a direction (short axis direction) in which the length of the region is minimized. According to this definition, the size of the foreign matter shown in FIG. 12 is 320 μm. As a result of infrared spectroscopic analysis, the foreign matter was confirmed to have the same composition as the electrodeposition film, and was found to be an abnormal precipitate of resin during electrodeposition.

  As can be seen from the results in Table 1, when the treatment voltage during anion electrodeposition is 80 V, the generation of foreign matter is suppressed. The reason is considered as follows. The following description is a consideration by the inventor and does not limit the present invention.

In the anion electrodeposition, as shown in FIG. 6B, a film is formed when the anion electrodeposition resin receives H ⁺ and insolubilizes at the anode. That is, in order to form a film, the anion electrodeposition resin needs to be present near the anode. Therefore, the deposition rate depends on the deposition reaction rate (Ra) at which the anion electrodeposition resin receives H ⁺ and insolubilizes at the anode, and the rate (Re) at which the anion electrodeposition resin moves by electrophoresis near the anode.

  When the processing voltage is 40 V, a film having a thickness of 6 μm is formed in about 300 seconds, whereas when the processing voltage is 80 V, a film having a thickness of 6 μm is formed in about 100 seconds. That is, the film formation rate when the processing voltage is 80 V is about three times the film formation rate when the processing voltage is 40 V, which is very large.

  When the treatment voltage is 40 V, the moving speed (Re) is sufficiently larger than the deposition reaction speed (Ra) at the anode, and as shown in FIG. 8A, local fluctuations in the concentration of the electrodeposition resin are observed. Even after abnormal deposition occurs, the anion electrodeposition resin (R-COO-) is uniformly supplied to the anode, so that electrodeposition proceeds and the shape of abnormal deposition is maintained.

  On the other hand, when the treatment voltage is 40V, as shown in FIG. 8 (b), the deposition reaction rate (Ra) at the anode is larger than the moving rate (Re), and as a result, in the vicinity where abnormal deposition occurs. The situation where local anion electrodeposition resin is insufficient is born. At this time, the precipitation reaction proceeds at a location where no abnormal precipitation occurs. Therefore, the difference in the amount of precipitation is small between the portion where the abnormal precipitation has occurred (convex portion) and its periphery.

  Thus, the processing voltage is preferably higher than 40V, and more preferably 80V or higher. Although the experimental results are not shown here, the number of occurrences of abnormal deposition when the processing voltage is 60 V is less than half of that when the processing voltage is 40 V, and the abnormal deposition is suppressed by setting the processing voltage to 60 V or more. can do. As is well known, if the processing voltage during electrodeposition is too large, defects (gas pins) due to the generated gas may occur. Therefore, the processing voltage is preferably 120 V or less.

  Next, the results of examining the relationship between abnormal precipitation and surface roughness in anion electrodeposition using nickel sleeves having different surface roughness will be described.

  FIG. 9 shows the measurement results of the spectral diffuse reflectance of five nickel sleeves. The spectral diffuse reflectance was measured by the SCE method using CM2006 manufactured by Konica Minolta in the same manner as described above. The incident angle of the light irradiating the sample is 8 °, and the intensity of the reflected light (that is, only the diffuse reflected light) is excluded from the total reflected light (including regular reflected light and diffuse reflected light). The diffuse reflectance measured by an integrating sphere and obtained for each wavelength is shown in the graph of FIG. Samples A, B and C in FIG. 9 are samples A, B and C having the mirror surfaces shown in Table 1. Samples G and H in FIG. 9 are nickel sleeves having a rough surface and appear cloudy visually.

  As can be seen from FIG. 9, the diffuse reflectance of the samples A to C having a mirror surface is as low as about 5% or less in the measurement wavelength range (360 nm to 740 nm). On the other hand, the diffuse reflectance of samples G and H having a rough surface has a value of 10% or more in most of the measurement wavelength range. In addition, as a diffuse reflectance with respect to visible light, a diffuse reflectance with respect to 550 nm light may be used as a representative value. The diffuse reflectance with respect to light of 550 nm is 5% or less for all of the samples A to C, and 10% or more for the samples G and H.

  The results when an insulating resin layer is formed on the rough surface of each nickel sleeve by anionic electrodeposition in the same manner as described above are shown in Table 2 below. The treatment voltage was 40 V during electrodeposition. Table 2 shows the number of foreign matters obtained in the same manner as described above for Table 1. For comparison, the results of samples A to C are also shown.

  As can be seen from the results in Table 2, when the surface of the nickel sleeve, which is the base surface for anion electrodeposition, is roughened, the generation of foreign matter is suppressed. The extent to which foreign matter generation is suppressed is equivalent to setting the voltage during anion electrodeposition to 80V. The reason why the generation of foreign matter can be suppressed by roughening the base is not well understood, but is presumed as follows. The following description is a guess by the present inventor and does not limit the present invention.

  As shown in FIG. 10A, when the surface of the base is a mirror surface, abnormal precipitation occurs due to local fluctuations in the concentration of the electrodeposition resin, and as described with reference to FIG. Thereafter, electrodeposition proceeds, and the shape of abnormal precipitation is maintained.

  On the other hand, when the surface of the base is rough, as shown in FIG. 10B, local fluctuations in the concentration of the electrodeposition resin and / or local electrolysis reaction on the surface of the base Progress seems to be hindered.

  In addition, the example which measured the surface roughness of this rough surface with the stylus type surface roughness meter (The stylus type surface roughness measuring device by JIS B 0651-1976) is shown below. The reference length was 250 μm.

  As can be seen from Table 3, the values of Ra (arithmetic mean roughness), Ry (maximum height) and Rz (ten-point mean roughness) are not so large, and the two-dimensional uneven distribution influences. It is thought that there is. It is considered that the diffuse reflectance shown above can appropriately evaluate the surface roughness including the two-dimensional uneven distribution.

  Next, the result of examining the generation of foreign matter when a nickel sleeve having a roughened surface is used and the treatment voltage during electrodeposition is 80 V will be described.

  FIG. 11 shows the measurement results of the spectral diffuse reflectance of samples I, J and K having a rough surface used this time. FIG. 11 also shows the measurement results of the spectral diffuse reflectance of the samples A to H thus far.

  As can be seen from FIG. 11, the diffuse reflectances of samples I, J, and K are higher than the diffuse reflectances of the previous samples G and H and exceed 20% over the entire measurement wavelength range. . Sample K has the highest diffuse reflectance, and the diffuse reflectance at 550 nm is more than 40% and 45% or less.

  The results when an insulating resin layer is formed on the rough surface of each nickel sleeve by anionic electrodeposition in the same manner as described above are shown in Table 4 below. The processing voltage during electrodeposition was 80V. Table 4 shows the number of foreign matters obtained in the same manner as described above for Table 1. For comparison, the results of samples A to C are also shown.

  As can be seen from the results in Table 4, the generation of foreign matter is suppressed even when a nickel sleeve having a rough surface is used and the treatment voltage at the time of anion electrodeposition is 80 V. The extent to which foreign matter generation is suppressed is when the voltage during anion electrodeposition is set to 80 V using a mirror-surface nickel sleeve (Table 1), or the voltage during anion electrodeposition is 40 V and the nickel sleeve has a rough surface. Is equivalent to the case of using (Table 2).

  However, when the number of samples is increased and the voltage at the time of anion electrodeposition is set to 80V using a mirror-like nickel sleeve, and the voltage at the time of anion electrodeposition is set to 80V using a nickel sleeve having a rough surface. As a result of comparison, when a mirror-like nickel sleeve was used, foreign matter was generated at a higher rate than the results in Table 1 with a probability of about 20%. For this reason, it is preferable to use a nickel sleeve having a rough surface and set the treatment voltage at the time of anion electrodeposition to 80 V. In order to stably suppress the generation of foreign matter, the treatment voltage at the time of anion electrodeposition is set to Roughening the surface of the nickel sleeve is more effective than increasing it.

  Since the mold manufactured by the mold manufacturing method according to the embodiment of the present invention has few defects in the inverted moth-eye structure, the antireflection film (or antireflection surface) formed using this has excellent reflection. Has a prevention function. Further, when the organic insulating layer is formed using a matte anion paint, an antireflection film (or an antireflection surface) that uniformly exhibits antiglare properties can be formed.

  The present invention relates to a mold manufacturing method, and in particular, can be widely applied to a moth-eye mold manufacturing method. The moth-eye mold can be used to form an antireflection film.

10 type substrate 12 support 13 organic insulating layer 14 inorganic underlayer 16 buffer layer 18 aluminum alloy layer 18s surface 20 porous alumina layer 22 recess 32 hardened material layer 32 ′ UV curable resin 42 work piece 50 core material 62 support roller 70 Target 72m Metal sleeve (metal base)
100, 100a, 100A Moss eye mold

Claims (10)

A method for producing a mold having a reversed moth-eye structure on the surface, having a plurality of recesses having a two-dimensional size of 10 nm or more and less than 500 nm when viewed from the normal direction of the surface,
A step (a1) of preparing a metal substrate having a surface that diffusely reflects visible light, a step (a2) of forming an organic insulating layer on the surface of the metal substrate by anion electrodeposition, and the organic insulation Including a step (a3) of forming an aluminum alloy layer on the layer, a step (a) of preparing a mold substrate,
(B) forming a porous alumina layer having a plurality of fine recesses by partially anodizing the aluminum alloy layer;
After the step (b), the step (c) of enlarging the plurality of fine recesses of the porous alumina layer by bringing the porous alumina layer into contact with an etching solution;
After the step (c), the method further comprises a step (d) of growing the plurality of fine recesses by further anodizing.   The said surface of the said metal base material is a manufacturing method of the type | mold of Claim 1 whose diffuse reflectance with respect to the light with a wavelength of 550 nm incident on the said surface with the incident angle of 8 degrees is 10% or more and 45% or less.   3. The mold manufacturing method according to claim 1, wherein a voltage in the step (a2) is 60 V or more and 120 V or less.   4. The mold manufacturing method according to claim 1, wherein the energization time in the step (a2) is 200 seconds or less. 5.   The method for producing a mold according to claim 1, wherein the step (a2) is performed using a matte anion paint.   The step (a) further includes a step (a4) of forming an inorganic underlayer on the organic insulating layer after the step (a2) and before the step (a3). The manufacturing method of the type | mold in any one of 1-5.   In the step (a), after the step (a4) and before the step (a3), at least one metal element contained in the aluminum alloy layer and oxygen or The method for producing a mold according to claim 6, further comprising a step (a5) of forming a buffer layer containing nitrogen.   The said metal base material is a cylindrical form, The said surface of the said metal base material is a manufacturing method of the type | mold in any one of Claim 1 to 7 which is the outer peripheral surface of the cylinder of the said metal base material.   The mold manufacturing method according to claim 8, wherein the metal substrate is a metal sleeve.   The method for manufacturing a mold according to any one of claims 1 to 9, wherein the step (b) and the step (c) are further performed after the step (d).

Images