JP2016114758A - Light diffusion material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light diffusion material capable of clearly displaying images even under a backlight or a solar radiation from the back, and capable of diffusing heat due to light using no cooling system.SOLUTION: The light diffusion material has a metal pattern layer which has plural openings which are formed on at least one side of a transparent base material. The metal pattern layer having plural openings is desirably disposed in a mesh or ellipse state, and is preferably formed by a pattern plating transfer method.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a transparent light diffusing material.

  Materials such as film materials that can be used as transmission or reflection type screens that diffuse visible light while being transparent in applications such as information display such as speed in automobiles, augmented reality (AR), projection mapping, etc. is necessary. As such a transparent light diffusing material, a material utilizing a difference in refractive index between highly refractive fine particles in a film and a transparent material is known. For example, in Patent Document 1, a light-scattering synthetic resin (light diffusion) in which a transparent material powder having a refractive index of 0.01 to 0.1 smaller than that of a transparent resin and an average particle diameter of 1 to 10 μm is dispersed. Resin).

Japanese Patent Publication No. 60-2162

For example, when the light diffusing material is used in a head-up display for an automobile, it is necessary to be able to clearly display it even when there is backlight or solar radiation from behind. However, with the conventional transparent light diffusing material, the amount of diffusion is small, and it is clearly displayed at night or when there is little incident sunlight, but it is insufficient when there is backlight or solar radiation from behind. . As a countermeasure, it is conceivable to increase the light amount of the projector, but problems such as temperature rise, thermal deterioration, and distortion of the film itself have been problems. In order to suppress the temperature rise of the film, it is necessary to blow with a fan.
An object of the present invention is to provide a light diffusing material that can clearly display even when there is backlight or solar radiation from the back, diffuses heat generated by light, and does not require a cooling device.

The present invention relates to [1] a light diffusing material provided with a metal pattern layer having a plurality of openings on at least one surface of a transparent substrate.
The present invention also relates to [2] the light diffusing material according to [1], wherein the metal pattern layer having a plurality of openings is arranged in a mesh shape.
The present invention also relates to [3] the light diffusing material according to [1] or [2] above, wherein the opening shape of the metal pattern layer having a plurality of openings is an ellipse.
[4] The light diffusion according to any one of [1] to [3], wherein the metal pattern layer having a plurality of openings is formed by a pattern plating transfer method. Regarding materials.

  Since the light diffusion material of the present invention increases the amount of reflection and diffusion, it can be clearly displayed even when there is backlight or solar radiation from behind. Moreover, transparency and the performance as a screen can be made compatible by using a metal mesh for a light-diffusion material. Moreover, since heat generated by light can be efficiently diffused through the metal layer, a cooling device such as a fan is not necessary.

It is the upper surface schematic diagram explaining the opening shape of the metal pattern layer which has several opening of the light-diffusion material of this embodiment, (a) is a form arrange | positioned in mesh shape, (b) is a honeycomb (honeycomb) shape. The form which is arrange | positioned, (c) is the figure which showed the form arrange | positioned in the perforated shape (elliptical shape) of a different diameter. It is the cross-sectional schematic diagram of the light-diffusion material of this embodiment, and the figure which showed the metal pattern layer. The figure which showed the cross-sectional schematic diagram of the light-diffusion material of this embodiment.

Examples of the metal of the metal pattern layer having a plurality of openings used for the light diffusing material of the present embodiment include copper, silver, gold, nickel, aluminum, tin, indium, and alloys thereof.
The thermal conductivity is more preferably 10 W / mK or more, and the thermal conductivity is more preferably 100 W / mK or more in that heat can be efficiently dissipated in both the vertical and horizontal directions. The metal thickness of the metal pattern layer is preferably 3 to 30 μm, more preferably 3 to 15 μm, and even more preferably 3 to 10 μm in terms of reducing the thickness of the light diffusing material. . The metal pattern layer can be produced by a method of punching a metal foil, an electroforming method, a pattern plating method, a method of removing unnecessary portions of the metal foil by etching, or the like.

  Of these, the pattern plating transfer method prepares a plate with an insulating resist so that the metal pattern is exposed from the metal plate on the metal plate (plate) to be plated, and then the underlying metal pattern is exposed by electrolytic plating. The metal pattern is formed on the transparent substrate with the adhesive layer, and the metal pattern is transferred to the transparent substrate with the adhesive layer by peeling off the metal pattern. It peels from (plate) and forms the metal pattern of a predetermined shape. The pattern plating transfer method is preferable in that a plate can be used repeatedly and a fine pattern can be formed at low cost.

  Examples of the metal plating include metals such as copper, silver, gold, nickel, aluminum, tin, and various alloys, but copper is preferable because it is inexpensive and has excellent thermal conductivity.

When the metal on the surface of the metal layer constituting the metal pattern layer is generally flat, the light diffusing material can be flattened, which is preferable in that the image can be displayed without distortion. Here, the term “substantially flat” means that the thickness of 10 portions of the metal layer is measured and the average thickness X, the thickness Y of the thin portion, and the thickness Z of the thickest portion in the size of the light diffusing material used. , (ZY) / X is 0.3 or less. A two-dimensional metal fiber structure such as a knitted or woven metal fiber is not preferable in terms of large irregularities. In addition, the metal pattern layer having a plurality of openings needs to have a structure having openings of 50 to 97% of the total area. Preferably it is 80 to 95%. If the number of openings is small, the transparency is lowered, so that it cannot be used as a transparent screen, and the transmission screen material is very dark. Further, the reflective screen material is highly reflective and very dazzling and difficult to see. When the opening exceeds 97%, the transparency is improved, but the light diffusing performance is deteriorated, so that an image is very difficult to see as a transmission type or reflection type screen. In addition, the heat dissipation property is deteriorated and is likely to be deformed. It is preferable that there are many openings with a uniform density over the light diffusing material. The shape of the opening may be any shape such as a circle, a rectangle, a polygon, or a jagged shape, and the shape of the metal pattern layer of the light diffusing material having the opening may be (a) a lattice shape, (b) a honeycomb ( Various structures such as (honeycomb) shape and (c) perforated shapes (elliptical shapes) having different diameters can be adopted.
As described above, the metal pattern layer (metal part) may be produced by any method such as etching, plating, pattern plating transfer method, punching, etc., but the pattern plating transfer method is effective in that it can be produced efficiently and continuously. preferable.
The light diffusing material is not a single metal pattern layer having a plurality of openings, but is provided on at least one surface of a transparent substrate, and is used in a state where a transparent substrate and a metal pattern layer having a plurality of openings are bonded. Examples of such a transparent substrate include a plate made of glass, plastic, and the like, and a plastic film. As the glass, glass such as soda glass, non-alkali glass, and tempered glass can be used. Examples of the plastic include thermoplastic resins and thermosetting resins such as polystyrene resin, acrylic resin, polymethyl methacrylate resin, polycarbonate resin, and polyethylene terephthalate resin.
The transparency of the transparent substrate means that it is transparent to light rays, and is preferably colorless and transparent, but may be colored and transparent.

The transparent substrate in the present invention is preferably a plastic film. Examples of the plastic film include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate, polyolefins such as polyethylene, polypropylene, polystyrene and EVA, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, polysulfone, and polyethersulfone. A film made of plastic such as phon, polycarbonate, polyamide, polyimide, acrylic resin, etc., having a total visible light transmittance of 70% or more is preferable. These can be used as a single layer, but may be used as a multilayer film in which two or more layers are combined. Among the plastic films, a polyethylene terephthalate film or a polycarbonate film is more preferable in terms of transparency, heat resistance, ease of handling, and cost.
Although there is no restriction | limiting in particular in the thickness of the said plastic film, The thing of 1 mm or less is preferable, and when it is too thick, there exists a tendency for visible light transmittance | permeability to fall easily. Further, considering that the handleability deteriorates if the film is too thin, the thickness of the plastic film is preferably 5 to 500 μm, and more preferably 50 to 200 μm.

The surface on which the metal pattern layer having a plurality of openings is provided on the substrate preferably has adhesiveness. For this purpose, the substrate itself may have the necessary adhesiveness, but it is preferable to laminate an adhesive layer.
The adhesive layer is preferably one having adhesiveness when transferring a metal pattern layer having a plurality of openings, or one exhibiting adhesiveness under heating or pressure. As the material having adhesiveness, a resin having a glass transition temperature of 20 ° C. or lower as a main component of the adhesive layer is preferable, and a resin having a glass transition temperature of 0 ° C. or lower is more preferable. As a material used for the adhesive layer, a thermoplastic resin, a thermosetting resin, a resin that is cured by irradiation with active energy rays, or the like can be used. If it shows adhesiveness when heated, if the temperature at that time is too high, the transparent base material may be deformed such as swell, sag, curl, etc., so irradiation with thermoplastic resin, thermosetting resin, active energy rays It is preferable that the glass transition point of the resin that is cured at 80 ° C. or less. The thermoplastic resin, thermosetting resin, and resin cured by irradiation with active energy rays preferably have a weight average molecular weight of 500 or more. If the molecular weight is less than 500, the cohesive strength of the resin is too low, and the adhesion to the metal may be reduced.

  For those having adhesiveness or those showing adhesiveness (hereinafter referred to as “adhesive”), a crosslinking agent, a curing agent, a diluent, a plasticizer, an antioxidant, You may mix | blend additives, such as a filler, a coloring agent, a ultraviolet absorber, and a tackifier.

If the thickness of the adhesive layer is too thin, sufficient strength cannot be obtained. Therefore, when transferring the metal pattern layer formed by plating, the metal pattern layer does not adhere to the adhesive layer, resulting in transfer failure. There is. Accordingly, the thickness of the pressure-sensitive adhesive layer is preferably 1 μm or more, and more preferably 3 μm or more in order to ensure transfer reliability during mass production. In addition, if the thickness of the adhesive layer is large, the manufacturing cost of the adhesive layer increases, and the amount of deformation of the adhesive layer increases when laminated, so the thickness of the adhesive layer is preferably 30 μm or less, more preferably 15 μm or less. preferable. When a base film with an adhesive layer formed by applying an adhesive to another base film is bonded to the surface on which the metal pattern layer is formed, it is heated if necessary, depending on the properties of the adhesive. Is done.
In addition, in order to improve light diffusibility, a high refractive index nano-sized particle may be added to a film, an adhesive, or the like as a transparent substrate. Examples of such materials include titanium oxide, cerium oxide, and zirconium oxide.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
(Example)
As a metal pattern layer having a plurality of openings as shown in FIG. 1A, a grid (mesh) copper pattern having a pattern width of 5 μm, a thickness of 5 μm, and a distance between patterns of 70 μm was formed. The variation in pattern thickness at that time was ± 1 μm. The pattern was formed by a pattern plating method (prepared with a diamond-like carbon insulating resist in the openings of the SUS plate in a lattice shape so that the underlying metal plate grid was exposed, and then the copper The metal plate was formed to have a metal thickness of 35 μm where the underlying metal plate was exposed by electrolytic plating).

This grid-like copper pattern was affixed to a polyethylene terephthalate film (film thickness 38 μm) coated with 10 μm of transparent adhesive, and the grid-like copper pattern was peeled off from the SUS plate so as to adhere to the adhesive layer side and transferred. The lattice pattern was embedded in the adhesive and the surface was flattened. And the adhesive layer side by which the grid | lattice-like copper pattern of this film was transcribe | transferred was affixed on soda glass, and the light-diffusion material was produced (FIG. 3). The transmittance of this light diffusing material was 80%. When an image was copied onto this sample with a projector and observed in the reflection direction, the image was clearly observed.
For comparison, only a soda glass, a polyethylene terephthalate film (film thickness 38 μm) coated with 10 μm of transparent adhesive, and affixed to soda glass was also copied with a projector. Was not.

Claims (4)

  A light diffusing material provided with a metal pattern layer having a plurality of openings on at least one surface of a transparent substrate.   The light diffusing material according to claim 1, wherein the metal pattern layer having a plurality of openings is arranged in a mesh shape.   The light diffusing material according to claim 1 or 2, wherein the opening shape of the metal pattern layer having a plurality of openings is an ellipse.   The light diffusing material according to claim 1, wherein the metal pattern layer having a plurality of openings is formed by a pattern plating transfer method.

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