JP4423200B2 - Apparatus for generating substantially collimated light and method for curing a photopolymerizable layer using the apparatus - Google Patents

Description

  The present invention relates to an apparatus for producing substantially collimated light and is particularly useful in environments where it is desired to provide a beam of substantially collimated light with a large cross-sectional area. The invention also relates to a method of manufacturing an optical diffuser.

  One area that requires a light source of light that is substantially collimated over an elongated area is the technique of exposing sheets or layers of photopolymerizable material to light for polymerization through or without an optical screen. Is a large area light diffusing screen. Various proposals for light diffusing materials suitable for projection screens have been made in the past. For example, US5837346 discloses a method of making a suitable material for a light diffusing screen. This method provides a material having a textured surface applied to a layer of light transmissive, photopolymerizable material and forms an optical feature by exposure to a light emission pattern for polymerization.

  EP0294122 discloses a method of making a light diffusing material. In this method, a sheet of photopolymerizable material is exposed to polymerization light through an optical mask having an array of transparent windows or openings in an opaque background. EP 0 768 565 discloses a similar method. In this way, the collimated light is directed at an angle to such a layer, through such a mask or variant, or without such a mask. WO 02/39184 describes the manufacture of a diffuser from a photopolymerizable material incorporating a silicone-based material, for example silicone acrylate. In this case, the photopolymerizable material is exposed to collimated UV light directly or through an aperture mask in an elongated layer.

  Thus, as shown in the above publication, light or other light used to form an optical diffuser, for example by exposing a photopolymerizable system to light for polymerization such as UV light, It is made parallel, i.e. almost parallel.

  Prior methods of producing optical diffusers according to EP0294122, EP0775953, EP076865 or WO02 / 39184 require, for example, exposing a photopolymerizable composition or system to a polymerization emission such as UV light. In this case, light or other light emission is collimated by the lens.

  It is known that honeycomb structures can be used to collimate light. EP0531045 uses a honeycomb element to collimate the light emitted from a light signal emitter assembly that is used to remotely control traffic signals with an authorized vehicle.

  An object in one form of the invention is to provide an improved light source of substantially collimated light.

  This form of the invention provides an apparatus for providing substantially collimated light. The apparatus comprises an elongate light source and a structure disposed adjacent to the elongate light source, the structure providing a plurality of parallel paths extending through the structure, and from the elongate light source. The light passes through the path and appears as a beam substantially parallel to the path. The apparatus further comprises a lens system or a light diffuser system on one side of the structure.

  Preferably, the apparatus further comprises a lens system on one side of the structure in the vicinity of the elongated light source to further collimate light emerging from the structure.

  Another object of the present invention is to provide a light-curing material for producing a light diffusing material suitable for use in, for example, an LCD display in which the directivity of the light source is extremely important by the method disclosed in WO 02/39184. It is to provide an improved method of doing so.

  This aspect of the invention provides a method of exposing a photopolymerizable material to cause its polymerization, eg, to produce an optical diffuser. This method uses a collimated light source according to the first aspect of the invention to expose a photopolymerizable material.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  Referring to the drawings, for producing an optical GRIN (graded refractive index diffuser or diffuser exhibiting refractive index modulation) by a method similar to that disclosed in European Patents EP0294122, EP0757553, EP0768565 or International Patent Publication WO02 / 39184. The device used in the above has a honeycomb element 14 arranged in front of a light source 12 (FIG. 2) (eg having a detailed structure repeated as shown in FIG. 1). This element 14 collimates the light emitted by the light source 12 into a generally parallel, non-divergent beam. The light source 12 is a strip light source, such as strip light or a tube, that provides a method for exposing a large area of a photopolymerizable sheet or layer at once at a lower cost than those previously available. It is preferable.

  This specification refers to certain materials that are photopolymerizable. It should be appreciated that proper polymerization is effective for a given material by exposing it with imaging capable radiation, whether electromagnetic radiation or electron or other particle beams. That is. Reference to polymerizable radiation in this specification is intended to cover all such forms of radiation. Photopolymers are defined as imaging compositions based on polymers / oligomers / monomers that can be selectively polymerized and / or crosslinked upon exposure to light radiation such as ultraviolet light. As used herein, the term “photopolymerizable” refers to monomers or oligomers that can be polymerized or copolymerized upon exposure to light radiation to produce high molecular weight materials, such as oligomers, polymers, or polymeric materials. And the chemical compositions or mixtures thereof.

  The collimator element 14 in the preferred embodiment of the invention is in the form of a generally flat panel formed by a honeycomb array of parallel open-ended cells. Each of the cells has a wall orthogonal to the main surface of the panel. These surfaces are in turn defined by the free edges of the cell walls. The collimator 14 can be constructed with an array of cells of a desired cross-sectional shape, for example circular or square, but the cells are preferably hexagonal cross-sections. In the apparatus shown in FIG. 2, each cell has a diagonal dimension of about 0.35 cm and a height of 3-20 cm (corresponding to the panel thickness). The entire collimator panel 14 is large enough to straddle the length and width of the strip light source. The collimator can be formed of a light absorbing material such as anodized black aluminum. The effect of the honeycomb panel 14 is to ensure that the most inclined light component (light beam) emitted from the light source is absorbed by the surface of the honeycomb wall and to be orthogonal to the main surface of the collimator 14 and thus orthogonal. It is to ensure that only light components (light rays) parallel to the center axis of the honeycomb structured cell can pass through the collimator. The angular range of the trajectory passing through the collimator 14 is determined by the collimator path or cell height, cross-sectional configuration and size.

In the arrangement shown in FIG. 2, the substantially collimated light passing through the collimator 14 illuminates a layer 16 of photopolymerizable material (referred to as a “sample”) supported on the glass plate 18. The collimator 14 can be supported from the glass plate 18 by the spacer 20. In this and other embodiments of the invention, the distance between the light source 12 and the sample should be minimized to optimize light collimation. In a preferred embodiment, the collimated illumination dose received by the sample 16 should be in the range of 750-850 mJ / cm ² to form a diffusion film.

  Due to the action of the collimator 14, most of the light rays reaching the sample are aligned approximately in parallel. Referring to FIGS. 3 (a) and 3 (b), the arrangement described with reference to FIGS. 1 and 2 illuminates the underlying sheet or layer 16 (as shown in FIG. 3 (b)). Provides a more uniform light reach when compared to an arrangement using a localized light source 13 in combination with a collimating lens 15 (as shown in FIG. 3 (a)). . This is because when the light rays reaching the sheet travel the same distance, a more uniform distribution of optical magnification results (compare FIG. 3 (b)). Thus, the light from the point light source 13 that has traveled to the edge of the sheet 16 travels a greater distance than the light that reaches the center of the sheet 16 through the center of the lens 15 due to the diffusion effect and includes less optical power. (Compare with FIG. 3A). In addition, as shown in FIG. 3B, the strip light source 12 is used when a point light source is used in conjunction with a lens to produce a collimated beam by using a honeycomb collimator 14. Can be placed closer to the sample 16 than is possible.

  The collimator 14 can be manufactured by individually drilling a plate of hard material to form a plurality of openings. Alternatively, the collimator can be manufactured by packing separate tubes or by using a series of intersecting plates to create a square or rectangular path grid. In another method of manufacturing the collimator, corrugated thin metal foil strips are attached to each other at nodes where adjacent wall portions contact each other. In a preferred method for manufacturing the collimator 14 as an embodiment of the present invention, overlapping flat strips are stacked and fixed to each other. Such fixation is in transverse parallel lines that are zigzag to each other between successive strips in the stack so that the desired honeycomb structure is produced when the stack is expanded by pulling perpendicular to the plane of the strip. Made along. Such a collimator can also be formed, for example, by molding into a suitable plastic. As indicated above, in its finished form, the cell wall of the collimator should be light-absorbing, eg matte black. In some applications, it is desirable to have a direction that is obliquely inclined at a predetermined angle with respect to the plane of the collimator panel. The emitted light that has passed through the collimator is collimated along that direction. This is accomplished by creating a collimator panel so that the cell axes are correspondingly inclined relative to those planes that are parallel to each other at the same time.

  In some embodiments of the invention, between the collimator 14 and the lamp 12, one or more of a corrugated or conventional lens or prism array (eg, similar to a BEF type film), or a combination of lens and prism There are elements. Such a lens or prism concentrates the light forward to give a more uniform light patch (homogeneity depending on the number of elements in the array and the distance between the last array and the light patch). In one embodiment of the invention shown in FIG. 4, two layers A and B of a linear corrugated lens are provided between the light source 12 and the collimator 14 such that one is above the other. The main planes of layers A and B are parallel to the main plane of the collimator 14. Layers A and B are of course made of a material that allows UV light to pass through, preferably silica quartz, but more preferably made of fused silica. The first layer A is a cylindrical lens, the center line of which is parallel to the axis of the linear lamp 12. The second layer B is an array of small cylindrical lenses whose centerline is orthogonal to the axis of the lamp 12. When two linear structures are combined (lens or prism), the longitudinal direction of linear elements in one layer, for example prism ribs or cylindrical lenses, is arranged perpendicular to such longitudinal direction of the other layer. It is preferable. Alternatively or additionally, a light diffusing sheet may be interposed between the light source and the collimator. Although only a single linear light source 12 is shown in FIG. 4 for illustrative purposes, it is actually arranged side by side in parallel to provide a two-dimensionally extended light source. A plurality of such linear light sources are used.

  In the case of a single layer lens lens disposed between the lamp 12 and the collimator 14, the layer is preferably composed of a plurality of lenses oriented in the same manner as the lens of layer B in FIG. .

  Alternatively, a single two-dimensional array of spherical lenses may be placed between the collimator and the lamp.

  In another embodiment, a prism layer of glass, preferably quartz, is disposed between the light source 12 and the collimator 14.

  In some embodiments of the invention, the gradation index (GRIN) diffuser is made by techniques similar to those disclosed in EP 0294122 or EP 0530269. In this technique, a layer of photopolymerizable material, such as an acrylamide monomer, provided in the form of a viscous fluid or sticky gel sheet or layer formed a plurality of light transmissive apertures in an opaque background. It is applied on an optical mask or an optical mask in which a plurality of opaque patches are formed in a light transmissive background. These apertures or patches are on a microscopic scale (typically about 2 microns, with a maximum dimension of about 10 microns). FIG. 5 shows, on a larger scale, a portion of such a photopolymerizable layer 30 being exposed to ultraviolet light through a single such light transmissive aperture of such a mask. (Reference numeral 32 indicates a support substrate for such a photopolymerizable layer). After polymerization in the region of the spot that is selectively exposed to ultraviolet light, the material is fully exposed to ultraviolet light to cure the remainder that was unexposed during the initial selective exposure of the material. This material may be heat treated before or after selective exposure. Monomer diffusion occurs when a selected region is exposed to light for polymerization (see FIG. 5), resulting in a high refractive index region forming a rod or tube structure in the surrounding low refractive index material. FIG. 6 is a graph of the radial position (X axis) relative to the central axis of the mask opening and the refractive index (Y axis) of the resulting polymerized structure.

  Masks such as those disclosed in EP 0801767 may take the form of photographic negatives or transparency, which are the usual forms of glass plates. In this case, a gelatin layer containing opaque silver particles is provided on one side surface of the glass plate. The photopolymerizable mixture or system is applied directly onto the gelatin side of the prepared mask.

  In another embodiment of the invention, the optical graded refractive index (GRIN) diffuser is manufactured by a process that is similar but does not use a mask. In this case, the photopolymerizable mixture or system is applied directly onto a flat and transparent sheet or film. It is possible to obtain a diffuser having a GRIN structure only with a predetermined chemical preparation without using a mask. International patent application WO 02/39184 describes the manufacture of diffusers (scattering elements) from systems containing silicone acrylates or similar compounds, with or without the use of masks.

  As described in UK Patent Application No. 03077266.3 and International Patent Publication No. WO 02/39184, silicone-based photopolymerizable systems are exposed to light for nearly collimated polymerization. It has been found that the exposed material polymerizes to form a GRIN diffuser. This GRIN diffuser acts as a normal diffuser when viewed in a direction corresponding to the direction of the initial polymerization light emission, but when viewed from a predetermined other direction, it looks like a clear transparent sheet. The same photopolymerizable material cures when exposed to non-collimating light to form a film without a GRIN structure.

  Different results using different degrees of light collimation can be used for the production of security signs. Thus, in one embodiment of the present invention, a honeycomb structure is used as a collimator to substantially parallelize the polymerization emission used to expose the photopolymerizable material through the optical mask. This mask is opaque, for example, away from transparent letters and numbers. After exposure to such collimated light, the film is directed to light emission for blanketing polymerization to polymerize previously unexposed areas. With such an arrangement, letters and numbers are substantially invisible when viewed in the collimating direction of the collimated light. However, when viewed at an appropriate tilt angle, letters and numbers are distinguished as gray letters or numbers against a clear background or as clear letters or numbers against an opaque background.

  As described above, the honeycomb structure collimator according to the present invention can be used to manufacture a graded refractive index diffuser (using a photopolymerizable material) for LCD displays and other optical devices. As described above, in the manufacture of graded refractive index elements using the apparatus of the invention, the honeycomb structure collimator comprises one or more prisms (or microlens arrays, or light diffusers) disposed between the collimator and the light source. Even). As mentioned above, an optical mask is not required, but may be placed between the collimator and the photopolymerizable material.

  Graded refractive index light diffusers manufactured as described above can be used to enhance the contrast of image display devices such as projection screens and LCD displays. Such graded index light produced by selective polymerization of a photopolymer as described above, for example by exposure through an optical mask, or by exposure to collimated light emission without the use of an optical mask. Diffusers have the property that they maintain polarization. That is, light that passes through a diffuser with a particular polarization maintains its polarization when exiting the diffuser, and light that passes through a diffuser that does not have a special polarization is similarly special when exiting the diffuser. Does not have polarized light. This polarization maintaining property enhances the efficiency and quality of display devices such as projection screens and LCD displays.

1 is a fragmentary perspective view showing a part of a honeycomb structure incorporated in an apparatus embodying the invention. 1 is a schematic elevational view showing an apparatus embodying the invention used to cure a photopolymerizable sample. FIG. The effect of the lens on the collimated light is shown in (a), and the effect of the honeycomb structure of FIG. 1 on the collimated light is shown in (b). It is a disassembled perspective view which shows the principal part of the apparatus which actualized invention. FIG. 4 is an enlarged schematic cross-sectional view showing the polymerization of a monomer layer subjected to the action of ultraviolet light directed to the photopolymerizable monomer layer through an aperture mask. FIG. 6 shows the variation of the refractive index along the diameter of the area of the photopolymer exposed through the aperture mask under the exposure posture shown in FIG.

Claims (11)

An apparatus for providing generally collimated light comprising an elongated light source and a structure disposed adjacent to the elongated light source, the structure comprising a plurality of parallel paths extending through the structure. it is those giving, also the light from the elongated light source is passed through the path, and wherein the is to appear as a generally parallel beam in the path.   The apparatus of claim 1, wherein an optical mask is disposed between the photopolymerizable material and the structure providing a plurality of parallel paths.   The apparatus of claim 1, wherein no optical mask is disposed between the photopolymerizable material and the structure providing the plurality of parallel paths.   The apparatus according to claim 1, 2 or 3, wherein the light for photopolymerization is ultraviolet light. The apparatus of claim 1 , further comprising a lens system between the structure providing a plurality of parallel paths and the elongated light source .   6. The apparatus according to claim 5, wherein the lens system comprises at least one lens lens.   The apparatus of claim 5, wherein the lens system comprises at least one spherical lens.   The apparatus of claim 5, wherein the lens system comprises at least one microlens array. 6. Apparatus according to claim 1 or 5 , wherein one or more prisms are arranged between a structure providing a plurality of parallel paths and an elongated light source . 10. The device according to claim 1, wherein the device is used for curing a photopolymerizable material forming an optical GRIN diffuser. A method for producing an optical GRIN diffuser, wherein a layer of a photopolymerizable material is cured by irradiating substantially collimated light using the apparatus according to any one of claims 1 to 10 .

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