JP5480049B2 - Molded body and method for producing the same - Google Patents

Description

  The present invention relates to a molded article and a method for producing the same, and in particular, a molded article used as an optical sheet or an optical film used for an optical article having optical properties such as diffraction, scattering, interference, and polarization, and the production thereof. Regarding the method.

  2. Description of the Related Art In recent years, home video cameras and digital still cameras with remarkable performance improvements have used CCD area image sensors and CMOS area image sensors as imaging means. These sensors have a configuration in which photoelectric conversion is performed by a large number of light receiving elements arranged two-dimensionally on a silicon substrate, and charges generated by each light receiving element are transferred to the outside by a CCD element or a CMOS circuit. Yes.

  In these sensors, light receiving elements that are image pickup elements are arranged in a grid pattern. Further, in order to obtain color information for each light receiving element (pixel), for example, RGB color filters are arranged in a stripe pattern or four types of filters in a square mosaic pattern on each pixel.

  As described above, in the CCD area image sensor and the like described above, since the image pickup elements and the like are regularly arranged in a grid pattern, color reproduction such as generation of a pseudo signal (moire) in the generated image of the subject is performed. Inconvenience may occur.

  In order to solve such a problem, an optical low-pass filter that cuts light having a wavelength equal to or higher than a specific frequency is used. As such an optical low-pass filter, an optical low-pass filter using the birefringence of quartz is most often used.

  On the other hand, in addition to an optical low-pass filter that uses the birefringence of quartz, an optical low-pass filter that uses diffraction by a phase grating has also been proposed. Such phase gratings include a surface irregularity type and a refractive index change type.

  As a method for forming a surface uneven mold, a method such as mechanical cutting on the surface of a transparent medium, a stamper method for pressing a mold, or a method for forming a regular uneven structure by vapor deposition or ion etching, etc. Is known (see, for example, Patent Document 1).

As a method for forming the refractive index changing type, a one-dimensional or two-dimensional regular structure is formed on a plastic film or sheet, and the plastic film or sheet is used for optical applications such as a light control plate.
As a method for forming a two-dimensional regular structure, for example, a method in which block polymers are arranged in a plane perpendicular to the thickness direction of the film has been proposed (Non-Patent Document 1).

  Furthermore, it is manufactured by irradiating an uncured UV curable composition arranged in a thin plate shape with ultraviolet rays having a high degree of parallelism to form a two-dimensional regular structure, and has a refractive index in the thin plate matrix. An optical low-pass filter made of plastic, which is a molded body in which columnar structures different from the matrix are arranged, is known. In this optical low-pass filter, the columnar structures are oriented so as to extend in the thickness direction of the matrix, and are arranged in a grid pattern in a plane orthogonal to the thickness of the matrix (Patent Document 2).

  This optical low-pass filter made of plastic is inexpensive and can be used for an optical system in which the thickness is restricted and the optical length is required to be shortened.

Further, by irradiating ultraviolet rays through a photomask having holes arranged in a lattice shape, the columnar structures are arranged with high regularity in the matrix and function as a high-precision refractive index modulation type diffraction grating. It is also known to create a molded body (Patent Document 3).
The molded article described in Patent Document 3 has a feature that it has high diffraction efficiency by realizing the high regularity and high aspect ratio of the columnar structure.

JP-A-9-263932 JP2007-34260A JP2008-134630

Maclomoecules 2003, 36, 3272-3288

  However, since the molded bodies described in Patent Documents 2 and 3 have a structure in which a columnar structure having a high aspect ratio is arranged in a matrix, when used as an optical low-pass filter, an optical depending on the angle of incident light is used. There was a problem that the performance changed greatly.

  That is, when used as an optical low-pass filter arranged in front of the imaging device, incident light is extended in the direction in which the columnar structure extends (the thickness of the matrix) near the center of the imaging region (center of the optical low-pass filter). The moiré-removing ability is exhibited because it is incident on the optical low-pass filter substantially parallel to the direction), but the light extends in the columnar structure at the peripheral portion of the imaging region (peripheral portion of the optical low-pass filter). Since the light is incident obliquely with respect to (the thickness direction of the matrix), there is a problem that a desired moire removing ability is not exhibited.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a molded body that can be used as an optical low-pass filter having high moire removal capability over the entire imaging region and a method for manufacturing the same. .

  A molded body having the configuration described in Patent Documents 2 and 3, that is, a molded body having a thin plate-like matrix and a columnar structure disposed in the matrix is excellent as an optical low-pass filter. In order to realize the angle dependency, it is necessary to realize the first-order diffraction that is uniform and highly efficient in the horizontal, vertical, and oblique directions even at the peripheral portion of the molded body where the light ray is incident obliquely.

  Since the optical low-pass filter using the molded body having the above-described structure produces a diffraction behavior close to Bragg diffraction by a columnar structure having a high aspect ratio, it has less multi-order light and can realize high first-order diffraction efficiency.

  However, since a diffraction behavior close to Bragg diffraction occurs, it has a characteristic that realizes high diffraction efficiency only when a light beam is incident perpendicularly to the structure. Therefore, for incident light from an oblique direction, the first-order diffraction efficiency becomes uneven in the horizontal, vertical, and oblique directions, and the moire removal ability in a specific direction is significantly reduced.

  As a result of intensive studies on the above points, the inventor of the present application has made the cross section of the columnar structure a shape with a large flatness, that is, an elongated shape, at the peripheral edge while keeping the arrangement pitch of the columnar structures constant. Thus, it has been found that the distribution of the first-order diffracted light can be uniformly controlled in the horizontal, vertical, and oblique directions of the image and high diffraction efficiency can be realized in the entire region.

  That is, for example, in the vicinity of the center of the molded body, the cross section of the columnar structure has a shape close to a perfect circle, and as the distance from the center increases, the cross section changes continuously or intermittently so that the ellipticity increases. Thus, it was found that high diffraction efficiency was realized in all directions in the entire molded body.

The present invention has been made based on the above findings,
A molded body comprising a thin plate-like matrix made of a cured product of a photopolymerizable composition, and a plurality of columnar structures disposed in the matrix,
The plurality of columnar structures are arranged in a lattice in an orientation extending in the thickness direction of the matrix in the matrix, and have a refractive index different from that of the matrix,
Each of the columnar structures has a larger flatness of the cross-sectional shape as the distance from the center of the molded body increases.

  According to such a configuration, when used as an optical low-pass filter disposed on the front surface of the image sensor, the refractive index modulation type phase grating has excellent moire removal capability at both the central portion and the peripheral portion of the imaging region. A molded body is provided that functions as:

According to another aspect of the invention,
A method for producing a thin plate-like molded body comprising a thin plate-like matrix comprising a cured product of a photopolymerizable composition, and a plurality of columnar structures disposed in the matrix and having different refractive indexes from the matrix. ,
Disposing the uncured photopolymerizable composition in a thin plate,
The photopolymerizable composition is irradiated with light through a photomask, the photopolymerizable composition is photopolymerized and cured, and disposed in the matrix and a plurality of columnar structures having different refractive indexes from the matrix. Obtaining a thin plate-like photopolymerized cured product comprising:
The photomask includes a plurality of mask holes that have a higher flatness ratio as the distance from the center of the photomask increases.
A method for producing a light control film is provided.

  According to such a configuration, when used as an optical low-pass filter disposed on the front surface of the image sensor, the refractive index modulation type phase grating has excellent moire removal capability at both the central portion and the peripheral portion of the imaging region. There is provided a method for producing a molded body for producing a molded body that functions as a molded body.

According to another preferred embodiment of the invention,
The shape of the mask hole is set so that the ellipticity increases as the distance from the center of the photomask increases.

  ADVANTAGE OF THE INVENTION According to this invention, the molded object which can be used as an optical low-pass filter which has high moire removal ability over the whole imaging region, and its manufacturing method are provided.

It is a typical cross-sectional view which shows the internal structure of the molded object 1 of preferable embodiment of this invention. It is drawing which shows the diffraction pattern at the time of making a laser beam enter from an orthogonal | vertical direction (Z-axis direction) into the optical low-pass filter whose cross-sectional shape of a columnar structure is a perfect circle. It is a typical top view of the optical low-pass filter whose cross-sectional shape of a columnar structure is an ellipse extended in the X-axis direction. It is a typical top view of the optical low-pass filter whose cross-sectional shape of a columnar structure is an ellipse extended in the Y-axis direction. 4 shows a diffraction pattern when a laser aperture is incident on the optical low-pass filter of FIG. 3 from the vertical direction (Z-axis direction). 6 shows a diffraction pattern when a laser aperture is incident on the optical low-pass filter of FIG. 4 from the vertical direction (Z-axis direction). It is a typical top view of the optical low-pass filter arrange | positioned so that the cross-sectional shape of the ellipse of a columnar structure may incline in a 45 degree diagonal direction. It is a fragmentary top view which shows the structure of the photomask used in preferable embodiment of this invention.

  Hereinafter, the molded article of a preferred embodiment of the present invention will be described in detail. This molded body is used, for example, as an optical low-pass filter disposed on the front surface of the image sensor of the image sensor in order to remove moire. FIG. 1 is a schematic cross-sectional view showing the internal structure of a molded body 1 according to a preferred embodiment of the present invention.

  The molded body 1 of the present embodiment has a thin plate shape having a substantially uniform thickness of 20 to 1000 μm. The molded body 1 has a phase separation structure including a transparent matrix 2 that is a substrate and is a thin plate (film), and a large number of transparent columnar structures 4 arranged in the matrix 2. The matrix 2 and each columnar structure 4 are both transparent, but have different refractive indexes.

  The columnar structures 4 are oriented parallel to each other so as to extend from the front surface to the back surface of the molded body 1 in the thickness direction of the matrix 2.

  The arrangement pattern of the columnar structures 4 is preferably the same as the image sensor array pattern of the image sensor used together with the molded body 1. That is, when the image pickup device is arranged in a square lattice shape, as shown in FIG. 1, the columnar structure 4 is also arranged in a square lattice shape, and when the image pickup device is arranged in a triangular lattice shape, the columnar structure 4. Are also preferably arranged in a triangular lattice pattern.

  The size and pitch of the columnar structure 4 are not particularly limited, but when the columnar structure 4 is a cylinder, the cross-sectional diameter is preferably 80 nm to 25 μm, more preferably 1 μm to 15 μm, and the columnar structure 4 is an elliptical column. In this case, the length of the minor axis of the ellipse is preferably 10 nm to 20 μm, more preferably 125 nm to 10 μm. The pitch is preferably 120 nm to 50 μm, more preferably 2 μm to 30 μm.

As shown in FIG. 1, the columnar structure 4 has a substantially circular cross-sectional shape at the center portion of the molded body 1, but as it goes toward the peripheral edge (as it goes away from the center of the molded body). The ellipticity (ratio of the length of the ellipse to the length of the minor axis) gradually becomes an elliptical shape.
With such a configuration, when the molded body 1 is used as an optical low-pass filter disposed on the front surface of the image sensor, high moire removal capability is realized in the entire imaging region.

  This is because the ellipticity of the cross section of the columnar structure is set to be larger at the periphery of the imaging region where light rays are incident obliquely on the optical low-pass filter, so that the light incident obliquely on the periphery This is because the moire removing ability is exhibited.

  Therefore, the orientation of the major axis of the ellipse of the columnar structure 4 is also optimized according to the position of the columnar structure 4 in the molded body 1.

Hereinafter, the orientation of the columnar structure having an elliptical cross section will be described.
A major axis vector p ′ at a certain representative point P in the optical low-pass filter 1 coincides with a vector P directed from the center point 0 of the imaging region to the representative point P. In other words, setting the direction of the ellipse so that these two vectors coincide with each other makes it possible to equalize the intensity of the first-order diffracted light in the horizontal, vertical, and diagonal directions even when light rays are obliquely incident on the periphery of the imaging region. This is a necessary condition.
In the molded body 1 shown in FIG. 1, each columnar structure 4 is oriented so that the elliptical major axis vector p ′ of the cross section faces the center point 0.

  As a modification, instead of the long diameter vector, the short diameter vector may coincide with the vector P from the center point 0 of the imaging region toward the representative point P.

  Further, the ratio of the length of the ellipse to the length of the minor axis (ellipticity) is determined in the traveling direction of the light beam traveling in the optical low-pass filter (refractive index modulation type diffraction grating) with respect to the incident light beam from the oblique direction. Δn generated when the refractive index is integrated is set to be uniform in the horizontal, vertical and oblique directions.

  In the configuration shown in FIG. 1, the ellipticity of the cross section of each columnar structure is set to be proportional to the distance from the center.

Next, depending on the cross-sectional shape of the columnar structures arranged in a lattice shape, the laser beam is perpendicular to the surface of an optical low-pass filter formed of a thin plate-like molded body as described in Patent Documents 2 and 3. The influence of the diffraction pattern upon incidence will be described.
Here, the case where it is arranged in a square lattice of columnar structures will be described as an example.

  When the cross-sectional shape of the columnar structure is a perfect circle, when laser light is incident on the optical low-pass filter from a direction perpendicular to the surface (Z-axis direction), diffraction as shown in FIG. It becomes a pattern.

  That is, the laser beam intensities are diffracted equally in the X-axis and Y-axis directions, the intensities at the four points of the (0, ± 1) -order diffracted light and the (± 1,0) -order diffracted light are equal, and (+ 1, + 1) next time The intensities at the four points of the folded light, (-1, -1) order diffracted light, (+1, -1) order diffracted light, and (-1, +1) order diffracted light are equal.

Next, when the cross-sectional shape of the columnar structure 4 is an ellipse extending in the X-axis direction or the Y-axis direction as shown in FIGS. 3 and 4, Z perpendicular to the optical low-pass filter in the plane is obtained. The diffraction pattern of laser light incident from the axial direction is as shown in FIGS.
That is, the diffraction intensities are different between the X-axis direction and the Y-axis direction, the intensities at the two points of the (0, ± 1) order diffracted light are equal, and the intensities at the two points of the (± 1,0) order diffracted light are equal. , ± 1) The difference between the intensities of the diffracted light and the (± 1,0) order diffracted light occurs. In this case, the (+1, +1) order diffracted light, the (-1, -1) order diffracted light, the (+1, -1) order diffracted light, and the (-1, +1) order diffracted light are equal.

Furthermore, for example, when the columnar structures 4 having an elliptical cross section are arranged so that the major axis of the ellipse is inclined in the direction of 45 degrees obliquely (FIG. 7), the Z-axis perpendicular to the optical low-pass filter is in-plane. The diffraction pattern of the laser light incident from the direction has the same intensity at the four points of the (0, ± 1) order diffracted light and the (± 1,0) order diffracted light, and the (+ 1, + 1) order diffracted light, (−1, − 1) The intensities at the two points of the diffracted light are equal, and the intensities at the two points of the (+1, −1) order diffracted light and the (−1, +1) order diffracted light are equal.
However, there are two intensities of (+1, +1) -order diffracted light and (-1, -1) -order diffracted light and two intensities of (+1, -1) -order diffracted light and (-1, +1) -order diffracted light. There is a difference.

  Next, a description will be given of diffraction in the case where a light beam is incident obliquely on a molded body including a columnar structure having an elliptical cross section.

For example, as in the configuration shown in FIG. 3 or FIG. 4, a columnar structure having an elliptical cross section is formed on a molded body arranged such that the major axis of the ellipse is parallel to the X axis or the Y axis. When a light beam is incident at an angle θ ₁ along the XZ plane or the YZ plane, uniform first-order diffracted light is generated in the horizontal and vertical directions. This angle θ ₁ is determined by the height of the columnar structures, their arrangement pitch, and the elliptical shape.

  Therefore, in the present embodiment, the height of the columnar structures, the arrangement pitch thereof, and the elliptical shape are set so that uniform first-order diffracted light is generated in the horizontal and vertical directions from the light incident at a predetermined angle in the peripheral portion. ing.

Next, the manufacturing method of the molded object 1 of preferable embodiment of this invention is demonstrated.
Schematically, in the method for producing a molded article according to the present embodiment, an uncured photopolymerizable composition arranged in a thin plate shape on a substrate is irradiated with parallel light to be photopolymerized and cured, and then a stretching process. To obtain the molded body 1. Each process is basically the same as that of the prior art molded body manufacturing method.

  First, an uncured photopolymerizable composition is arranged in a thin plate shape. Examples of a method for arranging the photopolymerizable composition in a thin plate include a method of applying the photopolymerizable composition on a substrate, a method of sealing the photopolymerizable composition between the substrates in a liquid-tight manner, and the like. .

  In the method of coating on a substrate, for example, a bar coater, a slit die coater, or a spin coater is applied so that the photopolymerizable composition has a uniform thickness on one surface of the substrate and the coating surface is smooth. It is applied by a known method such as a circular coater, a gravure coater or a CAP coater.

  Further, in the method of liquid-tightly sealing between the base materials, a spacer is disposed around the space sandwiched between the lower base material and the upper base material to form a liquid-tight space, and the liquid-like space is formed in the liquid-tight space. Fill with uncured photopolymerizable composition.

  Since the upper substrate is on the side irradiated with parallel light, it is necessary to be made of a material that does not absorb light used when photopolymerizing the photopolymerizable composition. Examples of such a material include transparent plastic materials such as Pyrex (registered trademark) glass, quartz glass, and fluorinated (meth) acrylic resin.

The thickness of the photopolymerizable composition applied on the substrate or filled in the liquid-tight space is preferably 20 to 1000 μm, and more preferably 50 to 300 μm.
This is because it is difficult to form the columnar structure 4 when the thickness of the photopolymerizable composition is 20 μm or less, and it is difficult to grow the columnar structure 4 in the thickness direction when the thickness is 1000 μm or more. .

(Polyfunctional monomer)
It is preferable that a polyfunctional monomer is contained in the photopolymerizable composition. As such a polyfunctional monomer, a (meth) acryl monomer containing a (meth) acryloyl group, a monomer containing a vinyl group, an allyl group, or the like is particularly preferable.

  Specific examples of the polyfunctional monomer include triethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6 -Hexanediol di (meth) acrylate, hydrogenated dicyclopentadienyl di (meth) acrylate, ethylene oxide modified bisphenol A di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, Tetramethylolmethane tetra (meth) acrylate, pentaerythritol hexa (meth) acrylate, polyfunctional epoxy (meth) acrylate, polyfunctional urethane (meth) acrylate, divinylbenzene, toluene Examples include allyl cyanurate, triallyl isocyanurate, triallyl trimellitate, diallyl chlorendate, N, N′-m-phenylenebismaleimide, diallyl phthalate, and the like. These may be used alone or as a mixture of two or more. can do.

  A polyfunctional monomer having three or more polymerizable carbon-carbon double bonds in the molecule is preferable because the density of the crosslink density due to the difference in the degree of polymerization is likely to increase and a columnar structure is easily formed.

  Particularly preferred polyfunctional monomers having three or more polymerizable carbon-carbon double bonds are trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, tetramethylolmethanetetra (meth) acrylate, penta There is erythritol hexa (meth) acrylate.

  When two or more kinds of polyfunctional monomers or oligomers thereof are used as the photopolymerizable composition, it is preferable to use those having different refractive indexes when the respective homopolymers are used. It is more preferable to combine large ones.

  In order to obtain functions such as diffraction, deflection, and diffusion with high efficiency in the molded body 1, it is necessary to increase the refractive index difference between the matrix 2 and the columnar structure 4. Is preferably 0.01 or more, more preferably 0.05 or more. Further, since the difference in refractive index is increased by the diffusion of the monomer during the polymerization process, a combination having a large difference in diffusion constant is preferable.

  In addition, when using 3 or more types of polyfunctional monomers or oligomers, the refractive index difference between at least any two of the respective homopolymers may be within the above range. In addition, the two monomers or oligomers having the largest refractive index difference of the homopolymer should be used at a weight ratio of 10:90 to 90:10 in order to obtain highly efficient functions such as diffraction, deflection, and diffusion. Is preferred.

(Monofunctional monomer)
In the photopolymerizable composition, a monofunctional monomer or oligomer having one polymerizable carbon-carbon double bond in the molecule may be used together with the polyfunctional monomer or oligomer as described above.
As such a monofunctional monomer or oligomer, those containing a (meth) acryl monomer containing a (meth) acryloyl group, a vinyl group, an allyl group or the like are particularly preferable.

  Specific examples of the monofunctional monomer include, for example, methyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, ethyl carbitol (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, isobornyl (meth) acrylate, phenyl Carbitol (meth) acrylate, nonylphenoxyethyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, (meth) acryloyloxyethyl succinate, (meth) acryloyloxyethyl phthalate, phenyl (meth) acrylate , Cyanoethyl (meth) acrylate, Tribromophenyl (meth) acrylate, Phenoxyethyl (meth) acrylate, Tribromophenoxyethyl (meth) acrylate, Ben (Meth) acrylate, p-bromobenzyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, trifluoroethyl (meth) acrylate, 2,2,3,3-tetrafluoropropyl (meth) ) (Meth) acrylate compounds such as acrylate; vinyl compounds such as styrene, p-chlorostyrene, vinyl acetate, acrylonitrile, N-vinyl pyrrolidone, vinyl naphthalene; allyl compounds such as ethylene glycol bisallyl carbonate, diallyl phthalate, diallyl isophthalate Etc.

  These monofunctional monomers or oligomers are used for imparting flexibility to the molded article 1, and the amount used thereof is preferably in the range of 10 to 99% by mass of the total amount with the polyfunctional monomers or oligomers, and 10 to 50% by mass. % Range is more preferred.

(Polymer, low molecular weight compound)
The photopolymerizable composition may also be a homogeneous solution mixture containing the polyfunctional monomer or oligomer and a compound having no polymerizable carbon-carbon double bond.

  Examples of the compound having no polymerizable carbon-carbon double bond include polymers such as polystyrene, polymethyl methacrylate, polyethylene oxide, polyvinyl pyrrolidone, polyvinyl alcohol, and nylon, toluene, n-hexane, cyclohexane, acetone, and methyl ethyl ketone. , Low molecular weight compounds such as methyl alcohol, ethyl alcohol, ethyl acetate, acetonitrile, dimethylacetamide, dimethylformamide, and tetrahydrofuran, organic halogen compounds, organosilicon compounds, plasticizers, additives such as stabilizers, and the like.

  These compounds not having a polymerizable carbon-carbon double bond are used for adjusting the viscosity of the photopolymerizable composition to improve the handleability when producing a molded article, and for the ratio of monomer components in the photopolymerizable composition. The amount used is preferably in the range of 1 to 99% by mass of the total amount with the polyfunctional monomer or oligomer, and is regular while improving handleability. In order to form a columnar structure having an appropriate arrangement, the range of 1 to 50% by mass is more preferable.

(Initiator)
The photopolymerization initiator added to the photopolymerizable composition is not particularly limited as long as it is used in normal photopolymerization in which polymerization is performed by irradiating active energy rays such as ultraviolet rays. Benzophenone, benzyl, Michler's ketone, 2-chlorothioxanthone, benzoin ethyl ether, diethoxyacetophenone, pt-butyltrichloroacetophenone, benzyldimethyl ketal, 2-hydroxy-2-methylpropylphenone, 1-hydroxycyclohexyl phenyl ketone, 2- Examples include benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1, dibenzosuberone and the like.

  The amount of these photopolymerization initiators used is preferably in the range of 0.001 to 10% by mass with respect to the weight of the other photopolymerizable composition, so that the transparency of the molded product 1 is not deteriorated. More preferably, the content is 0.01 to 5% by mass.

  In the present embodiment, the arrangement pattern and the cross-sectional shape in the matrix of the columnar structures 4 are determined by texturing using a photomask. This texturing is a method in which positional information and a cross-sectional shape are input in advance, so that the arrangement of the columnar structures to be formed has a high regularity and a target cross-sectional shape.

In order to control the cross-sectional shape of the columnar structure, a photomask in which mask holes having the same or similar shape as the cross-sectional shape of the columnar structure to be formed is used.
When a columnar structure having an elliptical cross-sectional shape is formed using a photomask, for example, the shape of the mask hole of the photomask may be an ellipse, a rectangle, or a rhombus. That is, the cross-sectional shape of the columnar structure and the hole shape of the photomask do not need to be exactly the same.
In the present embodiment, the mask hole is oriented so that its long axis is directed to the center.

  In order to perform the texturing described above, a photomask 6 (FIG. 8) is disposed between the light-polymerizable composition disposed in a thin plate shape and the light source.

  The photomask 6 is disposed substantially parallel to the upper surface of the photopolymerizable composition applied on the glass substrate. In order to control the cross-sectional shape and pitch of the columnar structure more precisely, it is preferable that the gap between the upper surface of the photopolymerizable composition coated on the substrate and the photomask is 50 μm to 600 μm.

  Due to diffraction at the mask hole 8 of the photomask 6, the formation position may be defined in a pattern different from that of the photomask, or the pattern may be deteriorated so that the formation position and the cross-sectional shape cannot be defined. In order to prevent this, the distance between the photomask and the photopolymerizable composition is accurately set to be a predetermined value.

  As the photomask, those used in the photolithography method can be used. The pattern of the mask hole is not particularly limited.

  When the mask hole is circular, the hole diameter is preferably 80 nm to 25 μm, more preferably 1 μm to 15 μm. When the mask hole is ellipse, the length of the minor axis of the ellipse is preferably 10 nm to 20 μm, more preferably 125 nm to 10 μm. The pitch is preferably 120 nm to 50 μm, more preferably 2 μm to 30 μm.

  In order to arrange the columnar structures in a square lattice pattern, a photomask in which mask holes are regularly arranged in a square lattice pattern is used. In order to arrange the columnar structures in a triangular lattice pattern, a photomask in which mask holes are regularly arranged in a triangular lattice pattern is used.

  In this embodiment, texturing using a photomask is used to form a columnar structure. However, the present invention is not limited to this, and radiation such as laser light, X-rays, and γ-rays in the visible or ultraviolet wavelength band is used. The position information and the cross-sectional shape thereof may be input to the photopolymerizable composition by scanning irradiation.

(Irradiation light source)
In order to arrange the columnar structures 4 with high regularity, it is necessary to proceed the polymerization reaction uniformly in a plane perpendicular to the thickness direction of the photopolymerizable composition arranged in a thin plate shape. For this reason, the irradiation light source uses a light intensity distribution that is substantially uniform in the irradiation range.

  As the irradiation light source, one capable of irradiating parallel light such as ultraviolet rays to the photocurable polymer coated on the substrate is used. The parallelism of the irradiated light is preferably such that the spread angle is ± 0.03 rad or less, and more preferably ± 0.001 rad or less.

  In addition to being able to irradiate parallel light, an irradiation light source having a substantially constant light intensity distribution of the parallel light in a cross section perpendicular to the traveling direction of the parallel light to be irradiated is used. Specifically, light from a point light source or a rod-shaped light source is converted into parallel light having a substantially uniform light intensity distribution (hat distribution) by a mirror or lens, or a planar light source such as a VCSEL is used. Can do.

  The laser beam is a preferable light source in terms of parallelism, but the light intensity distribution has a Gaussian distribution, and therefore the light intensity distribution should be made substantially constant by using an appropriate filter or the like. Is preferred.

The irradiation light source divides the irradiation area into a plurality of areas (9 areas in the present embodiment), measures the light intensity of each area, and the value of the illuminance distribution given by equation (1) is 2.0% The following are used. More preferably, 1.0% or less is used.
Illuminance distribution = (maximum value−minimum value) / (maximum value + minimum value) × 100 (1)

(First light irradiation step)
Next, the 1st light irradiation step which irradiates the photopolymerizable composition arrange | positioned in the thin plate shape with the parallel light from an illumination light source through the photomask 6 is performed. Specifically, parallel light such as ultraviolet rays having a full wavelength half width of 100 nm or less and a substantially constant light intensity distribution in the irradiation target range is irradiated from the irradiation light source. Thereby, the light which passed the photomask 6 is irradiated to a photopolymerizable composition with a predetermined pattern.

In the first light irradiation step, it is desirable to place the photopolymerizable composition in an inert gas atmosphere. The placement under an inert gas atmosphere may be performed before the photomask is placed or after the photomask is placed.
However, under conditions where oxygen remains above a certain level, there is a high possibility that poor curing will occur on the surface of the molded body 1. Examples of the inert gas include nitrogen, argon, helium and carbon dioxide. Since the purpose of using the inert gas is to expel oxygen, any gas can be used as long as it has a composition not containing oxygen.

  In the first light irradiation step, the formation position of the columnar structure 4 inside the molded body 1 is determined by irradiating light such as ultraviolet rays until the light irradiation site of the photopolymerizable composition is cured in a gel form.

  Specifically, in the first light irradiation step, in order to achieve both the regularity and high diffraction efficiency of the columnar structure 4, until the degree of cure of the photopolymerizable composition is in the range of 10% to 80%, More preferably, the light from the illumination light source is irradiated until the range is 20% to 60%. In the present embodiment, a state in which the photopolymerizable composition completely reacts and does not generate further heat even when irradiated with light is set to a curing rate of 100% by the optical DSC method.

(Second light irradiation step)
Subsequent to the first light irradiation step, a second light irradiation step is executed. In the second light irradiation step, with the photomask removed, the photopolymerizable composition is irradiated with parallel light having a full width at half maximum of 100 nm or less and a substantially constant light intensity distribution.
As a result, a phase separation structure composed of the columnar structure 4 whose formation position is determined in the first light irradiation step and the matrix 2 which is the other part is formed, and the matrix 2 and the columnar structure 4 are formed. Curing of the photopolymerizable composition is completely completed while increasing the difference in refractive index between them, and the molded body 1 is completed.

  Since parallel light is used as irradiation light, the columnar structure 4 is formed in the matrix 2 as a clear columnar structure. As a result, the molded body 1 is formed so that the change in refractive index clearly appears at the boundary between the matrix 2 and the columnar structure 4.

  In the present embodiment, the columnar structure 4 is not completely cured in the first light irradiation step, and only the formation position is determined. In the second light irradiation step, the entire matrix 2 and the columnar structure 4 are irradiated with parallel light in an incompletely cured state where there is a certain degree of hardness difference, and the entire structure is completely cured. At this time, due to the difference in cross-linking density with the matrix 2 due to the polymerization self-promoting effect of the columnar structure 4 and the composition distribution due to reaction diffusion between the columnar structure 4 and the matrix 2, a significant difference in refractive index between them is obtained. Further, the columnar structure 4 having a high aspect ratio extending in the vertical direction can be formed.

(Diffraction efficiency calculation)
A laser beam having an intensity distribution of standard normal distribution is incident on the manufactured molded body 1 to measure the intensity of the 0th-order, 1st-order, and 2nd-order diffraction spots, and the measured intensity of the 1st-order diffraction spots is determined as incident light. The value divided by the overall intensity is calculated as the first-order diffraction efficiency of the molded body 1. When a plurality of diffraction spots appear, the total intensity is divided by the intensity of the entire incident light.
The molded body 1 of the present embodiment has a diffraction efficiency of 10% or more (10% ≦ diffraction efficiency ≦ 100%).

  The molded body 1 can be used for an optical low-pass filter. In a photographing system such as a digital camera, moire (false color) is often a problem. This is because the sensors such as CCD and CMOS are regularly arranged and interfere with the regular pattern included in the object to be photographed. As one of means for solving this problem, an optical low-pass filter is used. The optical low-pass filter has an effect of suppressing moire by suppressing the influence of interference by separating input light into a plurality of points.

  The present invention is not limited to the above embodiments, and various modifications are possible within the scope of the invention described in the claims, and these are also included in the scope of the present invention. is there.

Claims (3)

A molded body comprising a thin plate-like matrix made of a cured product of a photopolymerizable composition, and a plurality of columnar structures disposed in the matrix,
The plurality of columnar structures are arranged in a lattice in an orientation extending in the thickness direction of the matrix in the matrix, and have a refractive index different from that of the matrix,
Each of the columnar structures has a greater flatness of the cross-sectional shape as the distance from the center of the molded body increases. A method for producing a thin plate-like molded body comprising a thin plate-like matrix comprising a cured product of a photopolymerizable composition, and a plurality of columnar structures disposed in the matrix and having different refractive indexes from the matrix. ,
Disposing the uncured photopolymerizable composition in a thin plate,
The photopolymerizable composition is irradiated with light through a photomask, the photopolymerizable composition is photopolymerized and cured, and disposed in the matrix and a plurality of columnar structures having different refractive indexes from the matrix. Obtaining a thin plate-like photopolymerized cured product comprising:
The photomask includes a plurality of mask holes that have a higher flatness ratio as the distance from the center of the photomask increases.
A method for producing a light control film. The shape of the mask hole is set so that the ellipticity increases as the distance from the center of the photomask increases.
The manufacturing method of the molded object of Claim 2.

Images