JP2012018323A - Luminous body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a luminous body being usable even if a combination of a diffusion material and a base material is apt to cause chromaticity change in the luminous body having the light diffusion material added therein and emitting light by a light guiding method.SOLUTION: In this luminous body, a light source is provided at an end portion, diffusion particles are included in a light guiding body base material, and a plane heading straight to the end portion emits light by the light guiding method. The diffusion particles include particles having a weight-average particle size of b, and the weight-average particle size bis defined to be outside of the range where a ratio ηB(b)/ηR(b) of a blue scattering efficiency to a red scattering efficiency, which corresponds to a phase delay amount φ (rad) of the diffusion particles, is 0.75 or more and 1.25 or less, and the light source is monochromatic.

Description

  The present invention relates to a light emitter to which light is supplied using a light guide system.

  In the light guide type surface light emitter, as seen in the backlight light source device of the liquid crystal display device, the light guide plate surface is provided with a scattering function by unevenness and dot printing, etc., and the light guide plate is refracted from the base resin. There is a configuration in which a light diffusing material having a rate difference is internally added.

  In addition, the light guide type surface light emitter can be used as a light emitting ornament such as various game machines and toys.

  In recent years, LEDs (light emitting diodes) have been widely used as light sources for light guide type surface light emitters.

  In the light guide plate in which the light diffusing material is internally added, when the particle size of the light diffusing material is small or the refractive index difference between the light diffusing material and the base resin is small, the light source incident side end face of the light guide plate It has been known so far that chromaticity changes may occur between light observed in the vicinity and light observed in the vicinity of the opposite end face.

  The change in chromaticity can be grasped by calculating the scattering efficiency of the Mie scattering theory. The smaller the particle size of the light diffusing material and the smaller the difference in refractive index between the light diffusing material and the base resin, the narrower the particle size and refractive index difference range of the light diffusing material that does not cause chromaticity change. .

  As seen in Patent Document 1, in order not to cause a change in chromaticity, a diffusing material having a large particle size is used, or the scattering efficiency ratio (ηB (b) / ηR (b)) in Mie theory is used. It was necessary to use a diffusing material having a specific particle size within 0.75 to 1.25.

  According to the theory described in Patent Document 1, when a specific particle size or a particularly large particle size is used, the ratio of the early scattering efficiency is within 0.75 to 1.25. However, it is not always easy to obtain a diffusing material having a convenient particle size for the diffusing material (inorganic material, resin material) to be used. In addition, when a diffusion material having a particle size that is usually difficult to obtain is particularly desired, the acquisition cost tends to be expensive. In addition, when particles having a large particle size are used, individual particles or aggregates thereof may become conspicuous and impair quality.

  Further, according to the theory described in Patent Document 1, when the refractive index difference between the base material and the diffusing material is in a specific range or a particularly large refractive index difference, the previous scattering efficiency ratio is 0.75 to 1. Within 25. However, the base material and the material of the diffusing material (inorganic material, resin material) to be used, the ratio of the previous scattering efficiency is not more than 0.75 to 1.25 in terms of transparency, workability, price, dispersibility, etc. It is not always possible to select a combination of a base material and a diffusing material.

Japanese Patent No. 3874222

  The present invention provides an illuminant that has a light diffusing material added therein and emits light by a light guide method, and can be used even when the chrominance is likely to change even when the diffusing material is combined with a base material. With the goal.

In order to solve the above problems, one aspect of the light emitter according to the present invention is:
A light source is provided at the end of the light guide,
A diffusing particle is contained in the light guide base material, and the light emitting body emits light on a surface orthogonal to the end portion by a light guide method,
The diffusing particles include those having a weight average particle diameter b ₀ , and the weight average particle diameter b ₀ is defined as a ratio of the blue scattering efficiency and the red scattering efficiency corresponding to the phase delay amount φ (rad) of the diffusing particles. ηB (b ₀ ) / ηR (b ₀ ) is outside the range of 0.75 to 1.25,
The light source is monochromatic.

  Furthermore, the light emitter of the present invention is characterized in that the light source is an LED.

  Furthermore, the light emitter of the present invention is a backlight of a monochrome image display device.

  Furthermore, the light emitter of the present invention is for decoration.

  According to the present invention, it is possible to use an illuminant that uses diffusion particles that are conventionally noticeable when a color change occurs and the color change is not noticeable.

It is a figure which shows the definition of the amount of phase delays of the surface emitting body concerning embodiment of this invention. It is a figure which shows the definition of the scattering cross section of the surface emitting body concerning embodiment of this invention. It is a figure which shows an example of the relationship between scattering efficiency (eta) ((phi)) and phase delay amount (phi) of the surface emitting body concerning embodiment of this invention. It is a figure which shows an example of the relationship between scattering efficiency (eta) (b) and the diffusion particle diameter b of the surface-emitting body concerning embodiment of this invention. It is a figure which shows an example of scattering efficiency ratio (eta) B (b) / (eta) R (b) of the surface light-emitting body concerning embodiment of this invention.

<Embodiment 1>
Embodiments of the present invention will be described below with reference to the drawings. In this embodiment, a surface light emitter is described as an example.
In the present invention, the scattering efficiency is calculated by defining an index called a phase delay amount. When the scattering efficiency calculation is performed according to the Mie scattering theory considered in the past, two parameters affecting the color change, specifically, the particle size of the light diffusing material, the light diffusing material and the base resin (base In many cases, one of the differences in refractive index with the material) is fixed and calculated. In this case, if the particle size of the light diffusing material with the same material becomes smaller, or the scattering efficiency changes when the refractive index becomes smaller with the same particle size, the particle size of the material and the light diffusing material is easy to understand. It is not easy to understand the change in scattering efficiency when the values change simultaneously. That is, it is difficult to grasp the change in scattering efficiency or the change in effective scattering coefficient when the refractive index difference and the particle size change simultaneously. The phase delay amount considered in the present invention includes both of two parameters (particle size of the light diffusing material, difference in refractive index between the light diffusing material and the base resin) that affect the color change. Even when the material and the particle size of the material change at the same time, the change in the scattering efficiency can be easily understood by comparing the phase delay amount.

  The phase delay amount φ (rad) in the present invention is defined as follows.

b (b> 0) is the particle diameter (μm) of the light diffusing material, Δn is the difference between the refractive index of the light diffusing material and the refractive index of the substrate, and λ (μm) is the wavelength of light. Hereinafter, the “particles of the light diffusing material” are appropriately referred to as “diffusing particles”. As shown in FIG. 1, the phase delay amount φ (rad) passes through the particle center of the light diffusing material 2 existing in the base material 1 and the light diffusing material 2 in the light of the wavelength λ (μm). In this case, the optical distance difference bΔn is expressed by the phase difference of the wavelength λ (μm).
Here, as the value of the refractive index n, the air is n = 1, the substrate 1 is n = _{n 1,} the light diffusing material 2 and n = _{n 2.} Further, the refractive index difference [Delta] n, the value obtained by subtracting the refractive index _{n 1} of the substrate 1 from the refractive index _{n 2} of the light diffusing member 2 _(n 2 -n _1).

Scattering efficiency is defined as follows. The scattering efficiency η of one diffusing particle is represented by scattering cross section A / apparent circular area πa ² , and a (a> 0) is a particle radius (μm). FIG. 2 shows the definition of the scattering cross section. The scattering cross section A is defined as a weighted integral of the particle cross section πa ² by the square of the optical electric field disturbance effect caused by the particles, and it has been found that it can be approximated by equation (2). In this case, φ (r) is the phase delay amount of the particles with respect to the light incident at a distance r from the light incident optical axis passing through the center of the particles of the light diffusing material 2. Note that the phase delay amount φ (r) is calculated by the equation (1).

  FIG. 3 shows the scattering efficiency η (φ) with respect to the phase delay amount φ on the horizontal axis. If the horizontal axis of this figure is converted from the phase delay amount φ (rad) = 2πΔnb / λ to the particle diameter corresponding to each wavelength of blue, green, and red, it can be converted into the relationship of scattering efficiency often seen in the past. Conversely, by defining the phase delay amount φ, it is possible to represent the scattering efficiency of blue, green, and red on one curve.

  In the horizontal axis phase delay amount φ (rad) = 2πΔnb / λ in FIG. 3, the refractive index difference Δn = 0.1 is fixed, blue light λ = 0.45 (μm), green light λ = 0.55 (μm). ), The respective diffused particle diameters b (μm) with respect to the red light λ = 0.63 (μm) are obtained, and the result is taken on the horizontal axis to obtain FIG.

Here, the phase delay amount φ_R (rad) of the red light is obtained from the equation (1):
φ_R (rad) = 2πΔn * b / λ = 6.28 * 0.1 * b / 0.63≈b (μm). Therefore, η (φ) in FIG. 3 and ηR (b) in FIG. 4 are almost the same value.
The red / blue ratio of the scattering efficiency of a specific particle size is obtained by ηB (b) / ηR (b).

In this calculation, Δn does not take wavelength dependency into consideration, but the same calculation may be performed even in consideration thereof.
When Δn is negative, the value of the phase delay amount φ is also negative. However, as can be seen from Equation (2), the scattering efficiency η is an even function with respect to the phase delay amount φ, and the values of Δn and the phase delay amount φ are positive or negative. Regardless, the value is 0 or a positive value. In FIG. 3, the value of the scattering efficiency η is shown only when the value of the phase delay amount φ is 0 or more, but the scattering efficiency η when the value of the phase delay amount φ is negative is omitted for the above reason. Yes.

  The fact that the red / blue ratio ηB (b) / ηR (b) of the scattering efficiency of a certain light diffusing material particle size is 1, produced a light guide plate in which only the light diffusing material having this specific particle size is internally added. In this case, there is no change in the chromaticity of light observed near both end faces. In the same configuration, when ηB (b) / ηR (b) is 1 or more, the hue of light observed near the light source incident side end surface is bluish, and the blue light component is reduced near the opposite surface. It shows that it is reddish. In addition, when ηB (b) / ηR (b) is 1 or less, the color of light observed near the end surface on the light source incident side is reddish, and the red light component is reduced near the opposite surface. Shows bluish.

  In FIG. 5, those having a particle size of about 3 μm or less, about 4 to 6 μm, and about 7 to 8.5 μm have a blue-red ratio ηB (b) / ηR (b)> 1.25 or <0.75 of the scattering efficiency. It has become. For this reason, when a light guide plate including this particle size is produced, it is expected that a change in chromaticity of light observed near both end faces will occur.

Usually, since the particle size of the light diffusing material has a certain distribution, the blue-red ratio of the scattering efficiency in the present invention is ηB (b ₀ ) / ηR using the weight average particle size b ₀ as the particle size b. (B ₀ ).

The prior art is based on the premise that the light source is white light, and in Patent Document 1, the corresponding particle size is not used in order not to cause a change in the chromaticity of light observed near both end faces.
However, in the present invention, since the light source is a single color, the color change is hardly noticeable. In the present invention, the monochromatic light source means one having a spectrum half width of 100 nm or less.

  Moreover, since the light-emitting body of the present invention is hardly noticeable in color change, it can be suitably used as a backlight of a monochrome image display device.

  Further, since the color change of the light-emitting body of the present invention is hardly noticeable, it can be suitably used as a light-emitting body for decoration.

  The LED referred to in the present invention includes a laser diode (LD).

  The monochromatic LED referred to in the present invention is not limited to one having an emission spectrum that is linear, and refers to an LED having a light source spectrum with a half-value width of 100 nm or less. On the other hand, the monochromatic light source of the present invention does not include a so-called pseudo white LED in which a blue LED element and a fluorescent agent are combined, and the emission spectrum of which has two or more peaks clearly.

  In addition, for example, when a plurality of color light sources such as a blue LED and a red LED are used at the same time, and each of them is blinking, when only one color is emitted at any time, it is substantially monochromatic. Since LEDs are used, it can be considered that the present invention is used alternately. For example, a backlight that includes three types of LEDs of red, green, and blue and alternately blinks these LEDs to emit only one color at any time may be manufactured. Color unevenness was suppressed by modulating the transmittance of the transmissive liquid crystal display device according to the timing at which each color emits light, due to the uneven brightness of the surface caused by the difference in the scattered light rate of each color. A display device is obtained.

  Furthermore, for example, when a blue LED is provided on one side of the rectangular light guide plate and a red LED is provided on the opposite side, and the LED is turned on at the same time, it can be considered that the present invention is used at the same time.

  The base material of the luminescent material used in the present invention is preferably a polycarbonate-based resin, a styrene-based resin, an acrylic-based resin or the like from the viewpoints of transparency and workability. An acrylic resin is particularly preferable from the viewpoint of transparency.

  As the light diffusing material used in the present invention, for example, a crosslinked acrylic resin, a crosslinked polystyrene resin, an inorganic glass, a metal oxide, various pigments, and the like can be used.

  As for the particle size of the light diffusing material, in a backlight using a general white light source, for example, 10 μm or less, particularly 5 μm or less, color unevenness is easily noticeable, but in the present invention, a light diffusing material having such a particle size is also suitable. Can be used for

  Regarding the difference between the refractive index of the base material and the refractive index of the light diffusing material, the color unevenness tends to be noticeable when the backlight using a general white light source is, for example, 0.3 or less, particularly 0.2 or less. Then, even if there exists such a refractive index difference, it can be used conveniently.

  If the concentration of the light diffusing material is low, color unevenness is particularly unnoticeable. For example, it is preferably 0.1% by mass or less. On the other hand, if it is less than 0.00005% by mass, the brightness may be insufficient. It is preferable to set it to 0.0001 mass% or more and 0.05 mass% or less. Furthermore, it is preferable to set it as 0.0002 mass% or more and 0.01 mass% or less.

<Other embodiments>
In Embodiment 1, the surface light emitter has been described as an example, but the present invention is not limited to the surface light emitter, and can be applied to light emitters of other shapes. For example, other shapes such as a column shape having a curved cross section (end surface) such as a circle, an ellipse, and a wave shape, a column shape having a polygonal cross section (end surface), or a cylindrical shape having these outer shapes may be used.

  In addition, the average particle diameter in this invention is a weight average particle diameter, and can be measured by the light-scattering particle | grain measuring method.

<Example>
An acrylic resin (refractive index 1.49) was used as the base resin, and a sheet containing 0.003% by mass of a crosslinked polystyrene resin (refractive index 1.59) having an average particle diameter of 2 μm was extruded as a light diffusing material. The sheet thickness was 5 mm.

  The said sheet | seat was cut | disconnected to the rectangle of 100 mm x 200 mm, and blue LED was installed as a light source in the sheet | seat end surface of the short side, and the light-guide type light-emitting plate was produced.

In this example, the average particle size is 2 μm and the refractive index difference is 0.1. As can be seen from FIG. 5, the scattering efficiency blue-red ratio ηB (b ₀ ) / ηR (b ₀ )> 1.25.

<Comparative example>
A light-guiding type light emitting plate was produced in the same manner as in Example except that a cold cathode tube was installed as a light source.

    The light source of the light guide type light emitting plate of Examples and Comparative Examples was turned on and visually observed from a plane perpendicular to the sheet. As a result, the light-emitting plate of the example was bright and the color change was not noticeable, but the light-emitting plate of the comparative example was bright, but the vicinity of the light source was bluish and became yellowish as it moved away from the light source. Was conspicuous.

  Note that the present invention is not limited to the above-described embodiment, and can be changed as appropriate without departing from the spirit of the present invention.

  1 base material, 2 light diffusion material

Claims (4)

A light source is provided at the end of the light guide,
A diffusing particle is contained in the light guide base material, and a light emitting body that emits light in a direction perpendicular to the end portion by a light guide method,
The diffusing particles include those having a weight average particle diameter b ₀ , and the weight average particle diameter b ₀ is defined as a ratio of the blue scattering efficiency and the red scattering efficiency corresponding to the phase delay amount φ (rad) of the diffusing particles. ηB (b ₀ ) / ηR (b ₀ ) is outside the range of 0.75 to 1.25,
A light emitter, wherein the light source is monochromatic.   The light-emitting body according to claim 1, wherein the light source is an LED. The light-emitting body according to claim 1 or 2, wherein the light-emitting body is used as a backlight of a monochrome image display device. The light-emitting body according to claim 1 or 2, wherein the light-emitting body is used for decoration.

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