JP7482444B2 - Light guide plate, surface light source device, lighting device, building material, and method for manufacturing light guide plate - Google Patents

Description

The present invention relates to a light guide plate, a surface light source device, a lighting device, a building component, and a method for manufacturing a light guide plate.

Various products using light guide plates have been known for some time. For example, an edge-light type lighting device is known as one product using a light guide plate. An edge-light type lighting device includes a light guide plate made of a light-transmitting substrate and a light source arranged opposite the end face of the light guide plate.

As a light guide plate used in this type of lighting device, Patent Document 1 discloses a light guide plate having a translucent resin sheet, which is a translucent substrate having a light exit surface and a back surface facing away from the light exit surface, and a plurality of convex prisms (reflective dots) provided on the back surface of the translucent resin sheet. This makes it possible to realize a lighting device in which the light guide plate emits light from its surface.

JP 2012-178345 A

In the light guide plate disclosed in Patent Document 1, convex prisms are formed by inkjet printing. However, when convex prisms are formed by inkjet printing, it is difficult to form multiple prisms at high density.

Furthermore, when convex prisms are formed by inkjet printing, the thickness of the prisms becomes thin. For example, the thickness of prisms formed by inkjet printing is 20 μm or less. In this case, it is possible to increase the thickness of the prisms by applying a thick coat of paint using inkjet printing, but forming the prisms by applying a thick coat of paint results in longer manufacturing times and higher manufacturing costs.

In this way, in the light guide plate disclosed in Patent Document 1, multiple convex prisms are formed in a dot pattern by inkjet printing, so the multiple prisms are thin and formed at a low density. For this reason, although the surface on which the prisms are formed (prism surface) has multiple convex prisms formed, there is little sense of unevenness, and it appears to be a smooth surface when viewed by a human. Therefore, the light guide plate disclosed in Patent Document 1 does not have a three-dimensional texture and does not have excellent design.

The present invention was made to solve these problems, and aims to provide a light guide plate that can emit light from a surface and has a three-dimensional texture, as well as a method for manufacturing the light guide plate.

In order to achieve the above object, one aspect of the light guide plate according to the present invention comprises a light-transmitting substrate having a first main surface and a second main surface facing away from the first main surface, and a plurality of prisms, each of which is convex, are arranged on at least the first main surface side of the light-transmitting substrate, and when the first main surface is viewed in plan, the 10-point average of maximum height roughness of a plurality of prisms included in an arbitrarily designated rectangular region among the plurality of prisms is 50 μm or more.

Another aspect of the light guide plate according to the present invention comprises a light-transmitting substrate having a first main surface and a second main surface facing away from the first main surface, a plurality of prisms are arranged on at least the first main surface side of the light-transmitting substrate, and when the first main surface is viewed in plan, the average height of a plurality of prisms included in an arbitrarily designated rectangular region of 1 mm x 1 mm among the plurality of prisms is 20 μm or more.

An aspect of the surface light source device according to the present invention includes the above-mentioned light guide plate and a light source that emits light incident on the light guide plate.

Another aspect of the lighting device according to the present invention includes the above-mentioned light guide plate and a light source that emits light that is incident on the light guide plate.

Another aspect of the building component according to the present invention includes the above-mentioned light guide plate.

In addition, one aspect of the method for manufacturing a light guide plate according to the present invention is a method for manufacturing a light guide plate in which a resin material is spray-applied as a mist toward a first main surface of a light-transmitting substrate to form prisms on the first main surface side of the light-transmitting substrate, and the average mist diameter is 100 μm or less.

It is possible to realize a light guide plate that can emit light from a surface and has a three-dimensional texture, and a surface light source device that includes this light guide plate.

FIG. 1 is a perspective view of a lighting device according to an embodiment. FIG. 2 is a cross-sectional view of the lighting device according to the embodiment. FIG. 3 is a diagram for explaining a method for manufacturing a light guide plate according to the embodiment. FIG. 4 is a diagram showing the results of an experiment carried out to examine the uneven state of the uneven surface of each of five samples of the light guide plate according to the embodiment.

The following describes embodiments of the present invention with reference to the drawings. Note that each embodiment described below shows a specific example of the present invention. Therefore, the numerical values, shapes, materials, components, the arrangement and connection of the components, and steps (processes) shown in the following embodiments are merely examples and are not intended to limit the present invention. Therefore, among the components in the following embodiments, components that are not described in the independent claims are described as optional components.

Note that each figure is a schematic diagram and is not necessarily a precise illustration. In addition, in each figure, the same reference numerals are used for substantially the same configurations, and duplicate explanations may be omitted or simplified.

(Embodiment)
First, the configuration of a lighting device 1 according to an embodiment will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is a perspective view of the lighting device 1 according to an embodiment. Fig. 2 is a cross-sectional view of the lighting device 1.

As shown in Figures 1 and 2, the lighting device 1 is an example of a surface light source device that emits light, and includes a light guide plate 10 that guides light, a light source 20 that emits light to be guided to the light guide plate 10, and a housing 30 that holds the light source 20.

The light guide plate 10 is an optical member that guides light emitted from the light source 20 and emits it to the outside of the light guide plate 10. The shape of the light guide plate 10 in a plan view is generally rectangular, but is not limited to this. In this embodiment, the light guide plate 10 has a light-transmitting substrate 11 and a liquid-repellent layer 12.

The light-transmitting substrate 11 is an optical member having light-transmitting properties at least in the visible light region. In other words, the light-transmitting substrate 11 has optical properties that transmit visible light. The transmittance of the light-transmitting substrate 11 is preferably high, and is preferably at least 50% or more. Specifically, the light-transmitting substrate 11 is preferably a transparent substrate that is transparent to visible light. The light-transmitting substrate 11, which is a transparent substrate, has a high transmittance that allows the other side to be seen through. In this case, the transmittance of the light-transmitting substrate 11, which is a transparent substrate, to visible light is 70% or more, preferably 80% or more, and more preferably 90% or more. The light-transmitting substrate 11 may have light-transmitting properties not only in the visible light region but also in the near-infrared region. In other words, the light-transmitting substrate 11 may have light-transmitting properties in the visible light region and the near-infrared region.

The light-transmitting substrate 11 is made of a material having light-transmitting properties. The light-transmitting substrate 11 is a transparent substrate that is transparent to visible light, such as a transparent resin substrate made of a transparent resin material or a glass substrate made of a transparent glass material. As the transparent resin substrate, an acrylic substrate made of an acrylic resin or a polycarbonate substrate made of a polycarbonate resin can be used. Note that the transparent resin substrate may be a rigid substrate that does not have flexibility, or a flexible substrate that has flexibility. In this embodiment, a rigid and transparent acrylic substrate is used as the light-transmitting substrate 11.

The light-transmitting substrate 11 is a plate-shaped substrate. Specifically, the light-transmitting substrate 11 is a flat substrate having a rectangular shape in a plan view. As an example, the thickness of each of the light-transmitting substrates 11 is about several mm to several cm, but is not limited to this.

The light-transmitting substrate 11 has a first end face 11a, a second end face 11b located on the opposite side to the first end face 11a, a first main surface 11c, and a second main surface 11d facing away from the first main surface 11c.

Each of the first end face 11a and the second end face 11b is one of the multiple side faces of the light-transmitting substrate 11. In this embodiment, the light-transmitting substrate 11 is a flat substrate with a rectangular shape in a plan view, so each of the first end face 11a and the second end face 11b is one of the four side faces and has a long rectangular shape. The first end face 11a and the second end face 11b face each other in a direction perpendicular to the thickness direction of the light-transmitting substrate 11. In other words, the second end face 11b faces away from the first end face 11a. As an example, the first end face 11a and the second end face 11b are each flat surfaces and are approximately parallel. Note that the first end face 11a and the second end face 11b are not limited to flat surfaces, and may be curved surfaces that are curved concavely or convexly. In addition, the first end face 11a and the second end face 11b may be inclined surfaces.

The first main surface 11c and the second main surface 11d are surfaces that are visible when the flat light-transmitting substrate 11 is viewed from above. In this embodiment, the light-transmitting substrate 11 has a substantially rectangular shape when viewed from above, and therefore the first main surface 11c and the second main surface 11d are also substantially rectangular in shape. The first main surface 11c and the second main surface 11d face each other in the thickness direction of the flat light-transmitting substrate 11. In this embodiment, the first main surface 11c and the second main surface 11d are each flat and substantially parallel to each other.

The light-transmitting substrate 11 also has a light-guiding function as the light guide plate 10. That is, light that is incident on the light-transmitting substrate 11 is guided through the inside of the light-transmitting substrate 11 and is emitted from the light-transmitting substrate 11 to the outside. Therefore, the light-transmitting substrate 11 has a light incident surface (light entrance surface) where the light is incident, and a light exit surface (light exit surface) from which the light that is incident from the light incident surface is emitted to the outside.

In this embodiment, the first end surface 11a of the light-transmitting substrate 11 is a light incident surface into which light emitted from the light source 20 is incident. Specifically, the first end surface 11a faces the light source 20. In other words, the first end surface 11a is the surface on the light source 20 side, and the second end surface 11b is the surface on the opposite side to the light source 20 side.

The second main surface 11d of the light-transmitting substrate 11 is a light exit surface through which light guided through the inside of the light-transmitting substrate 11 is emitted to the outside of the light-transmitting substrate 11. Therefore, the second main surface 11d becomes a light-emitting surface that emits light in a pseudo manner by emitting light guided through the light-transmitting substrate 11 to the outside. In other words, the second main surface 11d is a light extraction surface for extracting light from the light guide plate 10, and is the front surface (front side) of the lighting device 1. Therefore, in the lighting device 1, illumination light is emitted from the second main surface 11d. The first main surface 11c is the back surface (rear side) of the lighting device 1.

The light exit surface of the light-transmitting substrate 11 is not limited to the second main surface 11d. In other words, a surface other than the first end surface 11a may also be a light exit surface. For example, in the light-transmitting substrate 11, not only the second main surface 11d but also the first main surface 11c and the second end surface 11b may be light exit surfaces.

A liquid-repellent layer 12 having light-transmitting properties is formed on the first main surface 11c of the light-transmitting substrate 11. The liquid-repellent layer 12 is a water-repellent and oil-repellent film having water-repellent and oil-repellent properties. The liquid-repellent layer 12 is made of a transparent resin material containing a liquid-repellent material such as fluorine, for example. In this embodiment, the liquid-repellent layer 12 is made of a fluorine-based transparent resin material. As an example, the water contact angle of the liquid-repellent layer 12 is 100° or more, more preferably 110° or more, but is not limited to this.

The liquid-repellent layer 12 is formed on the entire surface of the first main surface 11c of the light-transmitting substrate 11. The liquid-repellent layer 12 does not have to be formed on the entire surface of the first main surface 11c. For example, the liquid-repellent layer 12 may be formed only on the portion of the first main surface 11c where the prisms 10a are to be provided.

As shown in FIG. 2, a plurality of prisms 10a, each of which is convex, are arranged on at least the first main surface 11c side of the light-transmitting substrate 11. In this embodiment, the plurality of prisms 10a are formed on the surface of the liquid-repellent layer 12.

The multiple prisms 10a are multiple convex prisms, each of which has a convex shape. In other words, the surface of the light guide plate 10 facing the first main surface 11c is a convex prism surface on which the multiple prisms 10a are formed. In this way, the light guide plate 10 is a convex prism light guide plate on which multiple prisms 10a, which are convex prisms, are formed.

The multiple prisms 10a have the function of reflecting light guided inside the light guide plate 10. Specifically, the multiple prisms 10a have a reflection surface (light control surface) that reflects the light that has been guided inside the light-transmitting substrate 11 and transmitted through the liquid-repellent layer 12 toward the second main surface 11d of the light-transmitting substrate 11. The reflection surface of the prism 10a is the outer surface that serves as the interface with the air layer in each prism 10a. In this way, each of the multiple prisms 10a is a reflection prism that reflects the light guided inside the light guide plate 10 and extracts it to the outside of the light guide plate 10. In other words, the multiple prisms 10a are reflection prisms for light extraction. The outer surface of the light guide plate 10 to which the multiple prisms 10a are attached is the prism-imparting surface.

Each prism 10a is dome-shaped, and the outer surface of each prism 10a is a curved surface such as a curved surface or a spherical surface. As an example, each prism 10a is approximately hemispherical or approximately semi-elliptical. Therefore, when cut by a plane parallel to the thickness direction of the light guide plate 10, the cross-sectional shape of each prism 10a is semicircular or semi-elliptical. Note that each prism 10a does not have to be strictly hemispherical or semi-elliptical, and may be a partially deformed hemispherical or elliptical shape. In other words, each prism 10a may be anything that appears to be hemispherical or semi-elliptical.

The multiple prisms 10a are made of a light-transmitting resin material. Specifically, the multiple prisms 10a are made of a transparent resin material such as acrylic resin. In this embodiment, the multiple prisms 10a are made of a hardening resin such as a transparent ultraviolet-curing resin or a transparent thermosetting resin. In this embodiment, the multiple prisms 10a are made of an ultraviolet-curing resin made of an acrylic monomer or oligomer and a photopolymerization agent. In this embodiment, the multiple prisms 10a are formed by spray coating. Details will be described later, but for example, the multiple prisms 10a can be formed by spraying a mist of liquid hardening resin and hardening it.

The multiple prisms 10a thus formed are reflective dots scattered in a dot pattern. Specifically, the multiple prisms 10a are randomly arranged close to each other. In other words, the multiple prisms 10a are densely packed in a random positional relationship with each other, and are formed over the entire surface of the liquid-repellent layer 12 with a high density distribution. In this case, it is preferable that the average distance between two adjacent prisms 10a in all prisms 10a formed on the first main surface 11c side of the light-transmitting substrate 11 is 50 μm or less. It is preferable that two adjacent prisms 10a are not connected, but the multiple prisms 10a may include two adjacent prisms 10a that are connected.

Furthermore, the multiple prisms 10a formed on the first main surface 11c side of the light-transmitting substrate 11 may include prisms that are not uniform in size and may not have uniform size (area) and height when viewed from above. In other words, the multiple prisms 10a formed on the light guide plate 10 may include an infinite number of prisms 10a of different sizes. In this embodiment, almost all of the prisms 10a are different in size from one another. In other words, almost all of the prisms 10a have different diameters and heights.

In this way, the surface of the light guide plate 10 facing the first main surface 11c is an uneven surface (prism surface) covered with countless prisms 10a. In this embodiment, the surface of the light guide plate 10 facing the second main surface 11d is a surface on which no prisms are formed (non-prism surface) and is a flat surface. Specifically, the surface of the light guide plate 10 facing the second main surface 11d is the second main surface 11d of the light-transmitting substrate 11.

The light source 20 emits light to be incident on the light guide plate 10. The light source 20 emits light toward the light guide plate 10. Specifically, the light source 20 emits light toward the first end surface 11a of the light-transmitting substrate 11. Therefore, the light emitted from the light source 20 is incident on the first end surface 11a of the light-transmitting substrate 11. In this embodiment, the optical axis of the light source 20 is perpendicular to the first end surface 11a of the light-transmitting substrate 11 and is parallel to the first main surface 11c of the light-transmitting substrate 11.

The light source 20 is disposed to the side of the light guide plate 10. In this embodiment, the light source 20 is disposed opposite the first end surface 11a of the light-transmitting substrate 11 of the light guide plate 10, and the light emission surface of the light source 20 faces the first end surface 11a of the light-transmitting substrate 11. In other words, the lighting device 1 is an edge-light type lighting device. In this embodiment, the optical axis of the light source 20 is perpendicular to the first end surface 11a of the light-transmitting substrate 11 and parallel to the first main surface 11c of the light-transmitting substrate 11.

The light source 20 is an LED module including a light emitting diode (LED). In this embodiment, the light source 20 emits white light. Therefore, the white light emitted from the light source 20 is incident on the first end surface 11a, which is the light incident surface of the light-transmitting substrate 11.

The light source 20 has a light-emitting element 21 and a mounting substrate 22 on which the light-emitting element 21 is mounted. One or more light-emitting elements 21 are mounted on the mounting substrate 22. In this embodiment, multiple light-emitting elements 21 are mounted on the mounting substrate 22. The mounting substrate 22 is a long substrate, for example a wiring substrate on which metal wiring is formed in a predetermined pattern. As the base substrate of the mounting substrate 22, a resin substrate, a ceramic substrate, a metal substrate coated with an insulating film, or the like can be used.

The light-emitting element 21 is an LED light source composed of an LED. Specifically, the light-emitting element 21 is a white LED light source that emits white light. The light-emitting element 21 is, for example, an individually packaged surface mount device (SMD) type LED element, and includes a white resin or ceramic container (package) having a recess, one or more LED chips that are primarily mounted on the bottom of the recess of the container, and a sealing member that fills the recess of the container and seals the LED chip. The sealing member is composed of a translucent resin material such as silicone resin. The sealing member may be a phosphor-containing resin that contains a wavelength conversion material such as a phosphor.

The LED chip is an example of a semiconductor light-emitting element that emits light using a specified DC power, and is a bare chip that emits monochromatic visible light. The LED chip is, for example, a blue LED chip that emits blue light when powered. In this case, in order to obtain white light, the sealing member contains a yellow phosphor such as YAG (yttrium aluminum garnet) that fluoresces using the blue light from the blue LED chip as excitation light.

In this way, the light-emitting element 21 in this embodiment is a white LED element composed of a blue LED chip and a yellow phosphor. Specifically, the yellow phosphor absorbs a portion of the blue light emitted by the blue LED chip, becomes excited, and emits yellow light, and this yellow light is mixed with the blue light that was not absorbed by the yellow phosphor to become white light. Note that the sealing member is not limited to only the yellow phosphor, and may also contain red and green phosphors.

The multiple light-emitting elements 21 are arranged in a line on the mounting substrate 22 along the longitudinal direction of the mounting substrate 22. The multiple light-emitting elements 21 arranged in a line function as a line light source that emits light in a line. In this embodiment, the multiple light-emitting elements 21 are mounted in a row at approximately equal intervals along the longitudinal direction of the mounting substrate 22. Each light-emitting element 21 is arranged on the mounting substrate 22 so that its main light-emitting surface faces the first end surface 11a (light incident surface) of the translucent substrate 11.

The light source 20 may be a COB (chip on board) type LED module instead of an SMD type LED module. When the light source 20 is a COB type LED module, the light emitting element, which is an LED chip, is directly mounted on the mounting substrate 22. In this case, for example, blue LED chips are used as the light emitting elements, and a plurality of these blue LED chips are mounted in a row on the mounting substrate 22, and the blue LED chips are individually or collectively sealed with a sealing member made of silicone resin containing a yellow phosphor.

In addition, as necessary, a light distribution variable mechanism such as a lens that changes the light distribution of the light emitted from the light source 20, a filter that controls the wavelength of the light emitted from the light source 20, or an optical member such as a diffuser plate that scatters and transmits the light emitted from the light source 20 may be provided separately from the light source 20 or as part of the light source 20.

The light source 20 is driven by power supplied from a power supply unit (not shown). The power supply unit has, for example, a power supply (power supply circuit) made up of a circuit board on which multiple circuit components are mounted, and a housing that houses the power supply. The power supply converts the power received by the power supply unit into a specified power and supplies the power to the light source 20. This drives the light source 20 to emit light. The power supply unit may be included in the lighting device 1, or may be located separately from the lighting device 1. In other words, the lighting device 1 may be of a built-in power supply type, or may be one that receives power from an external power supply.

The light source 20 is disposed in the housing 30. The housing 30 is, for example, a bottomed cylindrical box-shaped storage member having an opening. The housing 30 is made of, for example, a metal material or a resin material. The light source 20 is disposed at the bottom of the housing 30. In this case, the mounting board 22 of the light source 20 is placed on the bottom surface of the housing 30. The light source 20 and the housing 30 may be integrally configured as a light source unit. In addition, in this embodiment, the opening of the housing 30 is closed by the first end surface 11a of the light guide plate 10, but this is not limited to this.

Next, the optical action of the lighting device 1 in this embodiment will be described with reference to FIG.

In the lighting device 1 of this embodiment, the light emitted from the light source 20 enters the inside of the light guide plate 10 from the end face of the light guide plate 10 on the light source 20 side. Specifically, the light emitted from the light source 20 enters the first end face 11a of the light-transmissive substrate 11 of the light guide plate 10 and enters the inside of the light-transmissive substrate 11.

Light from the light source 20 incident on the light-transmitting substrate 11 is guided through the light-guiding plate 10 from the first end surface 11a to the second end surface 11b of the light-transmitting substrate 11 while repeatedly undergoing total reflection at the surface on the first principal surface 11c side and the surface on the second principal surface 11d side of the light-guiding plate 10.

Then, a portion of the light guided through the light guide plate 10 reaches the prism 10a from the first main surface 11c of the light-transmitting substrate 11 through the liquid-repellent layer 12. A portion or all of the light that reaches the prism 10a is totally reflected at the interface between the prism 10a and the air layer, becoming reflected light. This reflected light travels toward the second main surface 11d of the light-transmitting substrate 11, and is emitted to the outside of the light guide plate 10 from the outer surface on the second main surface 11d side of the light guide plate 10.

In this way, in the lighting device 1, the light incident on the light guide plate 10 is reflected by a plurality of dot-shaped prisms 10a formed on the first main surface 11c side of the light-transmitting substrate 11, and can be extracted to the outside of the light guide plate 10 from the light extraction surface of the light guide plate 10, which is a non-prism surface (in this embodiment, the second main surface 11d of the light-transmitting substrate 11). In other words, in the lighting device 1, the light from the light source 20 incident on the end surface of the light guide plate 10 can be extracted as planar illumination light.

Next, a method for manufacturing the light guide plate 10 used in the lighting device 1 according to the present embodiment will be described with reference to FIG. 3. FIG. 3 is a diagram for explaining the method for manufacturing the light guide plate 10 according to the embodiment.

In the method for manufacturing the light guide plate 10 according to this embodiment, first, a light-transmitting substrate 11 is prepared as shown in FIG. 3(a). As the light-transmitting substrate 11, for example, an acrylic plate having a rectangular shape in a plan view can be used.

Next, as shown in FIG. 3B, a liquid-repellent treatment is applied to the surface of the light-transmitting substrate 11. Specifically, a liquid-repellent layer 12 is formed on the surface of the first main surface 11c of the light-transmitting substrate 11. The liquid-repellent layer 12 can be formed, for example, by applying a resin material that will become the liquid-repellent layer 12 to the first main surface 11c of the light-transmitting substrate 11.

Next, as shown in FIG. 3(c), a mist 100 of resin paint for forming the prisms 10a is sprayed onto the first main surface 11c of the light-transmitting substrate 11. In other words, the mist 100 of resin paint for forming the prisms 10a is sprayed onto the first main surface 11c of the light-transmitting substrate 11. When spraying the mist 100, for example, spray equipment equipped with a mist spraying device 2 such as a spray gun can be used.

In this embodiment, since the liquid-repellent layer 12 is formed on the first main surface 11c of the light-transmitting substrate 11, the resin paint for forming the prism 10a is sprayed onto the surface of the liquid-repellent layer 12 in the form of mist 100. Note that in this embodiment, the resin paint is a solvent-free resin that has a viscosity (e.g., about 100 mPa·s or less) that can be sprayed, but this is not limited to this, and the resin paint may contain a solvent. For example, the resin paint may contain resin solids in a solvent. In other words, as long as it is a resin paint that can be sprayed, the resin paint may not contain a solvent, or may contain a solvent.

In this embodiment, the material of the prism 10a is the same resin material as that of the light-transmitting substrate 11. Specifically, since the light-transmitting substrate 11 is an acrylic substrate, the material of the prism 10a is also an acrylic resin material. In this embodiment, the material of the prism 10a is a transparent ultraviolet-curing resin made of an acrylic resin and a photopolymerization agent. Therefore, the resin paint used to form the prism 10a is an ultraviolet-curing resin paint. The material of the prism 10a and the material of the light-transmitting substrate 11 do not have to be the same. For example, the material of the prism 10a may be an acrylic resin material, and the material of the light-transmitting substrate 11 may be glass.

In this way, the resin paint for forming the prisms 10a is sprayed onto the surface of the liquid-repellent layer 12 as a mist 100, and multiple mist 100 of the resin paint are formed in the form of dots on the entire surface of the liquid-repellent layer 12, as shown in FIG. 3(d). At this time, the mist 100 is prevented from spreading due to the surface tension of the liquid-repellent layer 12, and each mist 100 is formed to a thickness of more than 20 μm, becoming approximately hemispherical. In other words, the mist 100 is applied randomly and densely to the surface of the liquid-repellent layer 12 in a state where it can be felt as if it is made of grains as a whole. In this case, in order to form multiple prisms 10a with the above-mentioned size and high density distribution, it is preferable that the average mist diameter of the mist 100 is 100 μm or less.

When spraying the mist 100 of resin paint to form the prism 10a, it is advisable to use a rotary atomization type spray applicator as the mist spraying device. This makes it easy to apply the mist of resin paint randomly and densely to the substrate surface (the surface of the liquid-repellent layer 12 in this embodiment).

Then, the mist 100 is cured. In this embodiment, the mist 100 is an ultraviolet-curing resin paint, so ultraviolet light is irradiated onto the light-transmissive substrate 11 to which the mist 100 has been applied. This causes the mist 100 to harden, completing the light guide plate 10 on which multiple prisms 10a have been formed, as shown in FIG. 2. The light guide plate 10 manufactured in this manner is a coating-type light guide plate on which the prisms 10a have been formed by spray coating.

In this way, in the light guide plate 10 of this embodiment, the dot-shaped prisms 10a are formed by spray coating, so thick prisms 10a can be easily formed in a high density and random arrangement.

For this reason, the surface on which the multiple prisms 10a are formed (prism surface) has a three-dimensional unevenness that appears to be uneven when viewed by humans. Therefore, the light guide plate 10 according to this embodiment has a unique three-dimensional texture and is excellent in design. As a result, when the light guide plate 10 is an illumination device in a form in which the light guide plate 10 is exposed on the exterior, as in this embodiment, it is excellent in design.

In addition, in this embodiment, by providing multiple prisms 10a, it is possible to form an uneven surface that gives a three-dimensional impression, and thus it is possible to realize a light guide plate 10 with a glare-free surface. As a result, in a lighting device 1 in which the light guide plate 10 is exposed on the exterior, it is also possible to realize a glare-free state.

Here, an experiment was conducted on the uneven state of the uneven surface consisting of multiple prisms 10a formed by spray coating. The experimental results are shown in FIG. 4. FIG. 4 is a diagram showing the results of an experiment conducted to examine the uneven state of the uneven surface (prism surface) of each of five samples (examples) of the light guide plate 10 according to the embodiment. For all five samples (light guide plates), an uneven surface consisting of dot-shaped prisms 10a was formed by spray coating, but the uneven state of the uneven surface was changed by changing the amount of mist 100 applied (spray amount) by spray coating. The amount of mist 100 applied (spray amount) can be changed, for example, by adjusting the amount of resin paint discharged from the spray equipment.

Figure 4 shows the appearance, arithmetic mean roughness Ra, 10-point average of maximum height roughness Rz, average height of the prism, haze, surface emission, and texture of the uneven surface (prism surface) on the first main surface 11c side of each sample. Here, in Figure 4, "surface emission" is indicated by "◯" when the sample emits surface emission when light is incident on the end face of the sample, and "×" when the sample does not emit surface emission. In addition, "texture" is indicated by "◯" when the unevenness is perceived three-dimensionally, and "×" when the unevenness is not perceived three-dimensionally.

As a result, as shown in FIG. 4, in sample 1, which has the least amount of coating, the prisms 10a are few and sparse (i.e., distributed at a low density) as can be seen in the external photograph of the prism surface. For this reason, in sample 1, there were too few prisms 10a, and much of the substrate surface (the surface of the liquid-repellent layer 12 in this embodiment) was exposed, so the prism surface was almost smooth. Therefore, in sample 1, the texture of the uneven surface was poor, and the unevenness was not felt three-dimensionally. Also, presumably because there were too few prisms 10a, the prisms 10a in sample 1 did not function as desired as reflective prisms, and sample 1 did not emit light from its surface.

In sample 1, the arithmetic mean roughness Ra of the prism surface was 1 μm, the 10-point average value of the maximum height roughness Rz of the prism 10a was 12.9 μm, the average height of the prism 10a was 7.3 μm, and the haze of the prism surface was 19.9%.

As can be seen in the external photograph of the prism surface, sample 5, which had the greatest amount of coating, had too many prisms 10a, so that adjacent pairs of prisms 10a connected to each other across the entire area of the prism surface, resulting in the prism surface approaching a smooth surface. Therefore, the texture of the uneven surface of sample 5 was poor, and the unevenness was not perceived as three-dimensional. Also, it is presumed that this is because adjacent pairs of prisms 10a connected to each other in most cases, but the prisms 10a in sample 5 also did not function as desired as reflecting prisms, and sample 5 did not emit surface light.

In sample 5, the arithmetic mean roughness Ra of the prism surface was 5 μm, the 10-point average value of the maximum height roughness Rz of the prism 10a was 19.7 μm, the average height of the prism 10a was less than 20 μm, and the haze of the prism surface was less than 30%.

As can be seen from the results of Samples 1 and 5, if too little or too much resin paint is sprayed to form the prism 10a, the unevenness of the resin-coated surface is not perceived three-dimensionally and appears smooth to the naked eye, and surface emission is not possible. In other words, the light guide plates of Samples 1 and 5 have poor design and are therefore not suitable for lighting devices in which the light guide plate is exposed, and are also not suitable for edge-light type lighting devices because they do not emit surface light even when light is incident from the edge surface.

In contrast, for sample 2, as can be seen in the external photograph of the prism surface, the prisms 10a were densely formed with good density, and the uneven surface had a good texture, giving the unevenness a three-dimensional appearance. For sample 3, the density distribution of the prisms 10a was slightly coarser than for sample 2, but the uneven surface had a good texture, giving the unevenness a three-dimensional appearance. Similarly, for sample 4, the density distribution of the prisms 10a was coarser than for sample 2, but the uneven surface had a good texture, giving the unevenness a three-dimensional appearance.

Moreover, in samples 2, 3, and 4, the prisms 10a were formed with an appropriate size and appropriate density distribution, so the prisms 10a functioned as desired as reflecting prisms, and all emitted light from the surface.

In sample 2, the arithmetic mean roughness Ra of the prism surface was 11.4 μm, the 10-point average value of the maximum height roughness Rz of the prism 10a was 90.2 μm, the average height of the prism 10a was 25.9 μm, and the haze of the prism surface was 62.6%.

In addition, in sample 3, the arithmetic mean roughness Ra of the prism surface was 20.3 μm, the 10-point average value of the maximum height roughness Rz of the prism 10a was 153.2 μm, the average height of the prism 10a was 47.1 μm, and the haze of the prism surface was 76.4%.

In addition, in sample 4, the arithmetic mean roughness Ra of the prism surface was 34.4 μm, the 10-point average value of the maximum height roughness Rz of the prism 10a was 178 μm, the average height of the prism 10a was 53.3 μm, and the haze of the prism surface was 77.7%.

The inventors of the present application further conducted experiments to examine the conditions for the prism 10a to obtain a light guide plate capable of surface emission and having a three-dimensional texture. As a result, they found that by forming the prism 10a in the following manner, a light guide plate capable of surface emission and having a three-dimensional texture can be obtained.

That is, in the uneven surface (prism surface) on which the prisms 10a of the light guide plate 10 are formed, when the first main surface 11c is viewed in plan, the 10-point average value of the maximum height roughness (Rz) of the multiple prisms 10a included in an arbitrarily designated rectangular region among the multiple prisms 10a is preferably 50 μm or more. This makes it possible to obtain a light guide plate 10 that can emit light from the surface and has a three-dimensional texture. The 10-point average value of the maximum height roughness (Rz) of the multiple prisms 10a is preferably 90 μm or more, more preferably 150 μm or more. In addition, the upper limit value of the 10-point average value of the maximum height roughness (Rz) of the multiple prisms 10a included in an arbitrarily designated rectangular region among the multiple prisms 10a is not particularly limited, but is, for example, 200 μm. In other words, the 10-point average value of the maximum height roughness (Rz) of the multiple prisms 10a included in an arbitrarily designated rectangular region among the multiple prisms 10a is preferably 200 μm or less.

In addition, when the first main surface 11c is viewed in plan on the uneven surface (prism surface) on which the prisms 10a are formed in the light guide plate 10, the average height of the prisms 10a included in an arbitrarily specified rectangular area of 1 mm x 1 mm among the prisms 10a is preferably 20 μm or more. This makes it possible to obtain a light guide plate 10 that can emit light from the surface and has a three-dimensional texture. The average height of the prisms 10a is preferably 45 μm or more, and more preferably 50 μm or more. The upper limit of the average height of the prisms 10a is not particularly limited, but is, for example, 80 μm. In other words, the average height of the prisms 10a is preferably 80 μm or less.

The arithmetic mean roughness Ra of the prisms 10a on the uneven surface (prism surface) on which the prisms 10a of the light guide plate 10 are formed is preferably 7 μm or more. This makes it possible to obtain a light guide plate 10 that is capable of surface emission and has a three-dimensional texture. The arithmetic mean roughness Ra of the prisms 10a is preferably 10 μm or more, more preferably 20 μm or more, and more preferably 30 μm or more. The upper limit of the arithmetic mean roughness Ra of the prisms 10a is not particularly limited, but is, for example, 50 μm. In other words, the arithmetic mean roughness Ra of the prisms 10a is preferably 50 μm or less.

It is sufficient to satisfy at least one of the above conditions, but satisfying multiple conditions makes it easier to obtain a light guide plate 10 that can emit light from a surface and has a three-dimensional texture.

The haze of the uneven surface (prism surface) on which the prisms 10a of the light guide plate 10 are formed is preferably 30% or more. In other words, the haze on the prism surface side of the light guide plate 10 is preferably 30% or more. This makes it easy to obtain a light guide plate 10 that is capable of surface emission and has a three-dimensional texture. The haze of the uneven surface of the light guide plate 10 is preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more. The upper limit of the haze of the uneven surface of the light guide plate 10 is not particularly limited, but is, for example, 90%.

The diffuse reflectance of the surface of the light guide plate 10 on which the prisms 10a are not formed (non-prism surface) should be 9% or more. For example, since the wavelength at which the relative luminous efficiency of humans is highest is 555 nm, the diffuse reflectance at 555 nm when the second main surface 11d (non-prism surface) of the light-transmitting substrate 11 of the light guide plate 10 is irradiated with measurement light emitted from a halogen lamp as a light source should be 9% or more. This makes it easy to obtain a light guide plate 10 that can emit light from a surface and has a three-dimensional texture.

The multiple prisms 10a provided on the light guide plate 10 should be densely packed together. In this case, the average distance between two adjacent prisms in the multiple prisms 10a should be 50 μm or less. This makes it easier to obtain a light guide plate 10 that can emit light from a surface and has a three-dimensional texture.

(Modification)
Although the lighting device according to the present invention has been described based on the embodiment, the present invention is not limited to the above embodiment.

For example, in the light guide plate 10 in the above embodiment, multiple prisms 10a are formed only on the first main surface 11c side of the light-transmitting substrate 11, but this is not limited to the above. In other words, multiple prisms 10a may be formed not only on the first main surface 11c side of the light-transmitting substrate 11, but also on the second main surface 11d side of the light-transmitting substrate 11. In other words, multiple convex prisms 10a may be formed on both the first main surface 11c side and the second main surface 11d side of the light-transmitting substrate 11.

In this case, the liquid-repellent layer 12 may be formed on both sides of the light-transmitting substrate 11 instead of on one side of the light-transmitting substrate 11. In other words, the liquid-repellent layer 12 may be formed not only on the first main surface 11c of the light-transmitting substrate 11 but also on the second main surface 11d. Even if multiple prisms 10a are formed only on the first main surface 11c side of the light-transmitting substrate 11 as in the above embodiment, the liquid-repellent layer 12 may be formed on the entire surfaces of both sides of the light-transmitting substrate 11 when the light-transmitting substrate 11 is subjected to a liquid-repellent treatment.

In addition, in the above embodiment, the light guide plate 10 has a liquid-repellent layer 12, but it is not necessary to form the liquid-repellent layer 12. In other words, the multiple prisms 10a may be formed directly on the first main surface 11c of the light-transmitting substrate 11. However, by forming the liquid-repellent layer 12, it is possible to easily form thick prisms 10a. In other words, it is possible to easily form an uneven surface that feels three-dimensional.

In the above embodiment, the light guide plate 10 is described as being used in a lighting device or a surface light source device, but the present invention is not limited to this. For example, the light guide plate 10 according to the above embodiment may be used in other products such as building components. For example, by incorporating the light guide plate 10 into a building component, a building component with a textured appearance and high design quality and light guiding function can be realized.

In the above embodiment, the light source 20 is configured to emit white light using a blue LED chip and a yellow phosphor, but this is not limited to the above. For example, instead of using a yellow phosphor, a phosphor-containing resin containing red and green phosphors may be used in combination with a blue LED chip to emit white light.

In the above embodiment, the light emitting element 21 of the light source 20 uses a blue LED chip that emits blue light, but this is not limited to this. For example, the light emitting element 21 may use an LED chip that emits a color other than blue. For example, the light emitting element 21 may use an LED chip that emits ultraviolet light. In this case, the phosphor particles may be a combination of phosphors that emit the three primary colors (red, green, and blue). Furthermore, although phosphors are used as wavelength conversion materials, wavelength conversion materials other than phosphors may be used. For example, materials containing substances that absorb light of a certain wavelength and emit light of a different wavelength from the absorbed light, such as semiconductors, metal complexes, organic dyes, and pigments, may be used as wavelength conversion materials.

In addition, in the above embodiment, the light source 20 emits white light, but this is not limited to this. For example, the light color of the light source 20 may be configured to emit color light such as red light, blue light, green light, yellow light, or purple light. Furthermore, the color temperature and brightness of the light source 20 are not particularly limited.

In the above embodiment, the light source 20 is an LED module using an LED, but this is not limited to this. For example, the light source 20 may be a solid-state light-emitting element other than an LED, such as a semiconductor laser or an organic EL (Electro Luminescence), or may be a fluorescent lamp such as a cold cathode fluorescent lamp (CCFL).

In addition, the present invention also includes forms obtained by applying various modifications to the above-described embodiments that would come to mind by a person skilled in the art, and forms realized by arbitrarily combining the components and functions of the above-described embodiments without departing from the spirit of the present invention.

REFERENCE SIGNS LIST 1 Illumination device 10 Light guide plate 10a Prism 11 Light-transmitting substrate 11c First main surface 11d Second main surface 12 Liquid-repellent layer 100 Mist

Claims (12)

a light-transmitting substrate having a first main surface and a second main surface facing away from the first main surface;
a plurality of convex prisms are disposed on at least the first main surface side of the light-transmitting substrate,
When the first main surface is viewed in plan, a ten-point average value of maximum height roughness of a plurality of prisms included in an arbitrarily designated rectangular region among the plurality of prisms is 50 μm or more.
Light guide plate. a light-transmitting substrate having a first main surface and a second main surface facing away from the first main surface;
a plurality of prisms are disposed on at least the first main surface side of the light-transmitting substrate;
When the first main surface is viewed in plan, the average height of a plurality of prisms included in an arbitrarily designated rectangular region of 1 mm x 1 mm among the plurality of prisms is 20 μm or more.
Light guide plate. The haze of the surface on which the plurality of prisms are formed is 30% or more.
The light guide plate according to claim 1 . The arithmetic mean roughness of the plurality of prisms is 7 μm or more.
The light guide plate according to any one of claims 1 to 3. In the plurality of prisms, the average distance between two adjacent prisms is 50 μm or less.
The light guide plate according to any one of claims 1 to 4. a liquid-repellent layer is formed on the first main surface;
the plurality of prisms are formed on the surface of the liquid-repellent layer;
The light guide plate according to any one of claims 1 to 5. The plurality of prisms are made of ultraviolet curable resin.
The light guide plate according to claim 6 . Furthermore, a plurality of prisms are formed on the second main surface side of the light-transmitting substrate.
The light guide plate according to any one of claims 1 to 7. A light guide plate according to any one of claims 1 to 8,
A light source that emits light incident on the light guide plate.
Surface light source device. A light guide plate according to any one of claims 1 to 8,
A light source that emits light incident on the light guide plate.
Lighting equipment. A light guide plate according to any one of claims 1 to 8.
Building materials. A method for manufacturing a light guide plate, comprising the steps of: spraying a mist of a resin material onto a first main surface of a light-transmitting substrate to form a prism on the first main surface side of the light-transmitting substrate, the method comprising the steps of:
The average mist diameter of the mist is 100 μm or less.
A method for manufacturing a light guide plate.

Images