JP2006349829A - Manufacturing method of low refraction material and low refraction material manufactured by the method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a low refraction material by which the low refraction material can be mass-produced at a low cost and area increase can be easily attained by physically mixing air bubbles into a liquid hardenable material. <P>SOLUTION: In the manufacturing method of the low refraction material having a low refractive index, the air bubbles 1 are mixed into the liquid hardenable material 2 which is used after hardening from a liquid state to a solid state and the hardened material 2 is pulverized to physically mix minute air bubbles 1 therein. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a low-refractive material and a low-refractive material produced by the method, and more particularly to a method for producing a low-refractive material used for antireflection, relief diffraction grating, alternating multilayer film, etc. in the field of optical elements and the like. It relates to the low refractive material produced.

  Conventionally, as a means for preventing reflection of a transparent body such as glass, (1) forming a thin film of one layer of low refractive material on the surface of the transparent body to form an antireflection film, (2) including a low refractive material on the surface of the transparent body It is known to form an antireflection film by forming a plurality of thin films, and (3) to form an antireflection body (so-called moth eye) having a periodic structure with a period of a wavelength order or less on the transparent body surface.

  In addition, the relief type diffraction grating has a fine concavo-convex shape and has a periodic (or aperiodic) structure in the surface direction, and uses transmission diffraction or reflection diffraction, for example, deflection, spectroscopy, polarization, etc. Used for functions.

  The alternating multilayer film having a low refractive index and a high refractive index has a structure in which a high refractive material and a low refractive index material are alternately laminated, and is used for, for example, a polarization separation function using reflection diffraction.

  Low refractive materials used for such optical elements are difficult to produce, difficult to increase in area, are scarce and expensive. Further, the relief type diffraction grating material is unsuitable for the degree of difficulty in processing the unevenness, and it cannot be said that a general low refractive material is necessarily suitable.

By the way, conventionally, various low-refractive materials that disperse micropores in a transparent material are known (Patent Document 1, Patent Document 2, Patent Document 3, Patent Document 4, Patent Document 5, Patent Document 6, Patent Document 7, Patent Document 8, etc.).
JP-A-6-3501 Japanese Patent Laid-Open No. 10-282305 JP 2002-311210 A JP 2004-171023 A International Publication WO00 / 37359 Specification JP 2003-261797 A JP-A-7-306529 JP 2003-334548 A

  However, as a method for producing a low-refractive material in which fine pores are dispersed in a transparent material, a method that can be produced in a large amount at a low cost and can be easily increased in area has not been known.

  The present invention has been made in view of such a situation in the prior art, and the object thereof is to physically produce bubbles in a liquid curable material, which can be produced in large quantities at low cost, and has a large area. It is an object of the present invention to provide a method for producing a low refractive material that is easy to perform.

  The method for producing a low refractive index material of the present invention that achieves the above object is to reduce the refractive index by physically mixing minute bubbles when the curable material used by curing from a liquid state to a solid is in a liquid state. It is the method characterized by having performed.

  In this case, in the curable material in a liquid state, a step of crushing and reducing bubbles by a motion such as a rotational motion or a reciprocating motion, and a step of mixing bubbles before or simultaneously with the step It is desirable to include.

  In addition, before the step of crushing and reducing the bubbles, or in the step of mixing bubbles at the same time, the bubbles before pulverization are sent by continuously or intermittently sending the gas into the liquid curable material through the fine openings. Can be mixed.

  In addition, it is desirable that the average size of minute bubbles mixed in the curable material is equal to or less than the wavelength used.

  In addition, it is desirable that the average size of the minute bubbles mixed in the curable material after curing the material is equal to or less than the wavelength used.

  The curable material includes an ultraviolet curable resin and a thermosetting resin.

  The present invention includes a liquid or solidified low refractive index material produced by the method for producing a low refractive index material as described above.

  By the above method for producing a low refractive index material of the present invention, a large amount of low refractive material can be produced at low cost. Further, it is easy to increase the area of a plate-like transparent body made of a low refractive material.

  By using the low refractive material produced by the method for producing a low refractive index material of the present invention, an optical element such as an antireflection film can be realized at low cost.

  The method for producing a low refractive material of the present invention is a method for lowering the refractive index by physically mixing bubbles in a liquid curable material. The optical noise such as scattering can be almost eliminated.

  Below, based on an Example, the manufacturing method of the low refractive material of this invention and the low refractive material manufactured by the method are demonstrated.

  An object having an array of 10 μm diameter tubular holes was inserted into a liquid ultraviolet curable resin, and air was intermittently fed from the opposite side while the resin was flowing. Thereby, a bubble group of the order of 10 μm is included in the resin. The ultraviolet curable resin mixed with bubbles of the order of 10 μm was put in a foaming device, and air bubbles were finely pulverized to obtain a resin having an average diameter of the mixed bubbles of about 200 nm.

  A general nanoparticle crusher was used as the foaming device used. Specifically, it is a wet pulverization apparatus called a bead mill (for example, manufactured by Ashizawa Finetech Co., Ltd.). In this pulverization apparatus, a schematic diagram of the apparatus is shown in FIG. 1 (a), and FIG. 1 (b). As shown in a schematic diagram showing the state of pulverization, a slurry 3 in which a gas bubble 1 to be pulverized into nanoparticles is floated in an uncured ultraviolet curable resin 2 is supplied from an inlet 5 into a container 4. Then, the beads 6 are mixed in the slurry 3 in the container 4, and the slurry 3 mixed with the beads 6 is rotated in the container 4 by the rotating body 7, and the foam 1 is sandwiched between the beads 6 during the rotating movement. As a result, it is crushed into finer bubbles 1 '.

  The size of the beads 6 is about several tens to several hundreds μm, and the size of the gas bubbles 1 is desirably started from several tens to several hundreds μm in order to reduce the final size after pulverization. Note that the beads 6 are separated by a separation mechanism disposed at the outlet 8 after the gas bubbles 1 ′ have become the desired nanobubbles (nanoparticles).

  In this way, using the pulverizer as a foaming device, the beads 6 are mixed into the ultraviolet curable resin 2 containing bubbles having a size of several tens to several hundreds of μm, and the fine bubbles 1 ′ are rotated by a rotational motion. The ultraviolet curable resin 2 mixed with smaller bubbles 1 'was produced.

  Here, as the ultraviolet curable resin 2, a monomer obtained by adding several percent of a polymerization initiator was used. Its refractive index, viscosity, etc. are close to the characteristics of the monomer because there are few polymerization initiators. Specifically, monomer: SR-213 (refractive index 1.454, viscosity 8 mPaS (25 ° C.), transparent liquid) of Nippon Kayaku Co., Ltd., polymerization initiator: Dolphin Cure 907 of Ciba Specialty Chemicals Co., Ltd. Was used.

  Next, a release agent is applied to each side of the two pieces of glass, and these are kept inside with a spacer at a thickness of 3 mm, and an ultraviolet curable resin 2 mixed with bubbles 1 ′ is sandwiched between them. Cured with UV light. As a result, a plate-shaped resin transparent body was produced. The average diameter of bubbles after curing was almost the same as that before curing and was about 200 nm, and optical noise such as scattering was hardly observed at wavelengths of 400 to 700 nm in the visible light region.

  The refractive index was 1.454 when cured without mixing bubbles in (1) resin, whereas it was 1.345 for a plate-shaped transparent body cured by mixing (2). . The optical characteristics were as shown in Table 1 below with respect to normal incidence. Here, in addition to the above two methods, (3) a resin mixed with the above-mentioned bubbles is applied to one side of a substrate having a refractive index of 1.454 with a uniform film thickness (μm order) and cured on the other side. Similarly, the coated substrate is also placed as (3).

It can be seen that the transmittance is improved as (2)>(3)> (1) with respect to (1) corresponding to a normal glass plate or the like.
[Table 1]
Refractive index Transmittance [%] (considering reflection on both sides; no absorption)
(1) 1.454 93.4
(2) 1.345 95.8
(3) 1.454 (1.345 thin film on both sides) 95.1
In the present invention, in order to physically pulverize the bubbles mixed in the curable resin to a diameter less than or equal to the wavelength used, the present invention is not limited to the above bead mill, and various types of pulverization of bubbles by a motion such as a rotational motion and a reciprocating motion. Can be used.

  Further, when bubbles having a large diameter remain in the liquid curable resin taken out from the bubble foaming device (pulverization device), it is desirable to perform a filter process or the like to remove the bubbles.

  Further, the curable resin is not limited to the ultraviolet curable resin, and other curable resins such as a thermosetting resin and an electron beam curable resin can be used.

  Furthermore, as a method of mixing bubbles with a large diameter into the curable resin before the bubbles are pulverized to a diameter of the wavelength of the wavelength used or less with a foaming device (pulverization device), the gas is continuously or intermittently sent through a fine opening. In addition to the method, a method of mixing bubbles using a whisk (a device that rotates a thin U-shaped wire at high speed) used for normal food processing may be used.

  The low refractive material according to the present invention can be used as a low refractive material used for an antireflection film, a multilayer film and the like in addition to the single low refractive material for an optical element as described above. As another example, in order to solve the problem that the unevenness of the relief type diffraction grating is exposed in an atmosphere such as air and the unevenness is buried, the performance is lowered. Covering with a material can solve the problem of filling.

  As described above, the method for producing the low-refractive material of the present invention and the low-refractive material produced by the method have been described based on the examples. However, the present invention is not limited to these examples, and various modifications are possible.

It is a schematic diagram (a) of a wet pulverizing apparatus used in a method for producing a low refractive index material of one embodiment of the present invention, and a schematic diagram (b) showing how air bubbles are pulverized using the apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Gaseous bubble 1 '... Finely pulverized foam 2 ... Uncured ultraviolet curable resin 3 ... Slurry 4 ... Container 5 ... Inlet 6 ... Bead 7 ... Rotating body 8 ... Outlet

Claims (8)

A method for producing a low refractive index material, characterized in that, in a liquid state of a curable material used by curing from a liquid state to a solid, a fine bubble is physically mixed to lower the refractive index. In a curable material in a liquid state, the method includes a step of crushing and reducing bubbles by a movement such as a rotational motion or a reciprocating motion, and a step of mixing bubbles before or simultaneously with the step. The method for producing a low refractive index material according to claim 1. Before the process of crushing and reducing bubbles, or in the process of mixing bubbles at the same time, the gas before crushing is mixed by sending gas continuously or intermittently into the curable material in the liquid state through the fine openings. The method for producing a low refractive index material according to claim 1 or 2, wherein: The method for producing a low refractive index material according to any one of claims 1 to 3, wherein an average size of minute bubbles mixed in the curable material is less than or equal to a wavelength used. The method for producing a low refractive index material according to any one of claims 1 to 4, wherein an average size of the fine bubbles mixed in the curable material after curing the material is equal to or less than the wavelength used. . 6. The method for producing a low refractive index material according to claim 1, wherein the curable material is an ultraviolet curable resin. The method for producing a low refractive index material according to any one of claims 1 to 5, wherein the curable material is a thermosetting resin. A liquid or solidified low refractive index material produced by the method for producing a low refractive index material according to claim 1.

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