JP2017122837A - Light diffusion body and surface light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light diffusion body using a resin matrix formed from PC that obtains output light in which yellowing is suppressed.SOLUTION: Light from a white light source L is introduced into a light diffusion body 3 from a minor surface 1, advances so as to space apart from the light diffusion body, is scattered by light diffusion particles 5 in the advancing step, and is output as diffusion light in which yellowing is suppressed from a major surface 2. The light diffusion particles 5 have a predetermined particle size, and are dispersed in a PC resin matrix with a concentration of 0.01 wt.% to 1 wt.%. The most frequent particle size R1 giving a peak of particle size distribution exists per predetermined particle size. R1 is in a range where scattering efficiency of a blue light component is lower than scattering efficiency of a red light component and a green light component. A number ratio of the light diffusion particles 5 so that a deviation from the most frequent particle size is within 20% is controlled to 60% or more. A refractive index of each of scattering elements is in a range of 1.47-1.58.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a light source and a surface light source device using the same light diffuser. More specifically, the present invention relates to a light diffuser using polycarbonate (hereinafter abbreviated as “PC”) as a resin matrix, and the same light diffuser. The present invention relates to a surface light source device in which white diffused output light is obtained by combining a white light source.

  A resin matrix in which a large number of fine particles having a refractive index different from that of the resin matrix are dispersed at a predetermined concentration as a light diffuser is used as a light diffuser in backlights and various fields. PMMA (polymethyl methacrylate) is widely known as a resin used for the matrix. This PMMA is often used because of its transparency, weather resistance, and low cost. However, PMMA has a problem of insufficient heat resistance, and it is conceivable to employ polycarbonate (PC) as an alternative resin material.

  This PC has excellent heat resistance and high mechanical strength compared to PMMA. However, when this PC is employed in the resin matrix of the light diffuser, there is a problem that yellowing occurs in the output light. In particular, yellowing is likely to occur in light emitted from the light output unit on the side away from the light input unit (the far side). Such a phenomenon is sometimes called yellowing.

  The main cause of such a phenomenon seems to be the absorption of the blue light component by the benzene ring contained in the PC. That is, due to the presence of the benzene ring, a considerably clear absorption characteristic is recognized from the wavelength region of the ultraviolet light to the wavelength region of the blue light component in the visible light. The problem of yellowing of the diffused output light is not absent even in the light diffuser using PMMA as the resin matrix, and the following Patent Document 1 is an example of the solution. According to the patent document, this problem is solved by combining light diffusing particles having two types of particle sizes (average particle size). On the other hand, there is no example in which the light diffusing particles are devised to solve the above yellowing problem in the case where a light diffuser is formed using PC as a resin matrix.

JP 2004-341446 A

  As described above, when PC is used as a resin matrix and light diffusing particles are uniformly dispersed in the matrix to form a light diffuser, excellent heat resistance and mechanical strength can be obtained. The problem of yellowing of diffused light obtained as output has so far been unsolved. An object of the present invention is to provide a light diffuser that solves the yellowing problem of the output light and an improved surface light source device that uses the light diffuser as a plate-like light scattering light guide.

  The invention according to claim 1 provides basic means for solving the above-mentioned problems. That is, according to the invention, there is provided a light diffuser in which light diffusion particles having a predetermined refractive index are dispersed at a predetermined concentration in a resin matrix made of polycarbonate. Here, the light diffuser has a light input unit for inputting white light, and the light diffused from the light input unit into the light diffuser is separated from the light input unit. A planar light output unit that outputs diffused light in the process of propagating is provided, and the predetermined refractive index has a value in the range of 1.47 to 1.58. The upper limit value 1.58 of the refractive index value means a value slightly lower than the refractive index of PC (1.59). On the other hand, the lower limit value 1.47 is a value slightly lower than the refractive index 1.49 of PMMA-based particles described in an example described later and exceeding the refractive index 1.44 of silicone-based particles taken up in a reference example described later.

  The predetermined concentration is in the range of 0.01 wt% to 11 wt%. The number distribution of the light diffusing particles with respect to the particle diameter has a mode diameter R1 that gives a peak of the distribution. And the light-diffusion particle | grains which contain 60% or more in the range of the magnitude | size of 0.8R1-1.2R1 with respect to said 1st mode diameter R1 are used. Further, the R1 is one continuous current existing on the smallest particle size side in a range where the scattering efficiency of the blue light component is lower than at least one of the scattering efficiency of the red light component and the scattering efficiency of the green light component. It is selected to be within the particle size range.

  Here, with respect to the particle size range of R1, it is more preferable that the scattering efficiency of the blue light component is lower than both the scattering efficiency of the red light component and the scattering efficiency of the green light component (claim 2). Invention).

  A typical shape of the light diffuser according to the present invention is a plate shape. In the case of this plate-like light diffuser, the light input portion can be provided by the minor surface, and the light output portion can be provided by the major surface (invention according to claim 3).

  If a primary light source for supplying white light to the minor surface of the plate-like light diffuser is disposed in combination with the light diffuser, a surface light source device can be configured. invention). As the white light source, a known light source combining LEDs having blue, green, and red emission colors can be used. Further, in the present specification, 435 nm, 545 nm, and 615 nm are generally employed as the wavelengths representing the blue light component, the green light component, and the red light component.

  According to the light diffuser according to the present invention, in the particle size value range of the mode particle size R1, one continuous light scattering efficiency of the blue light component is smaller than that of the red light component and the green light component. Benzene ring through a condition that the particle size is selected to be within a range of particle sizes and a condition that the number of particles that fall within a variation in particle size within ± 20% does not fall below 60%. The effect of absorption of the blue light component by (a main cause of yellowing) can be moderated to some extent. In the case of a plate-like light diffuser, yellowing is not noticeable even at a position away from the light input portion (minor surface) for diffused light output from the major surface that provides the light output portion. If a primary light source that supplies white light is arranged on the minor surface of such a light diffuser, a surface light source device that provides illumination light with reduced yellowing can be configured.

1 is a basic configuration diagram of a surface light source device using a light diffuser according to the present invention. It is the graph which plotted the theoretical value of the scattering efficiency according to color at the time of disperse | distributing the PMMA type | system | group particle | grains which have a refractive index of 1.49 with respect to PC resin with respect to the particle size of light-diffusion particle. It is the graph which plotted the theoretical value of the scattering efficiency according to color at the time of dispersing the light-diffusion particle which has a refractive index of 1.54 with respect to PC resin with respect to the particle size of a light-diffusion particle. It is the graph which plotted the theoretical value of the scattering efficiency according to color at the time of disperse | distributing the silicone type particle | grains which have refractive index 1.44 with respect to PC resin with respect to the particle size of light-diffusion particle | grains. It is the graph obtained by actually measuring the relative spectral transmittance about the film which disperse | distributed the light scatterer which has each mode particle diameter of 2 micrometers, 5 micrometers, and 10 micrometers uniformly in the concentration of 1 wt% in PC resin matrix. A graph obtained by actually measuring the relative spectral transmittance of a film in which light scatterers having mode diameters of 2 μm, 5 μm, and 10 μm are uniformly dispersed in a PC resin matrix at a concentration of 0.5 wt%. is there. A graph obtained by actually measuring the relative spectral transmittance of a film in which light scatterers having mode diameters of 2 μm, 5 μm, and 10 μm are uniformly dispersed in a PC resin matrix at a concentration of 0.2 wt%. is there. It is a graph which shows the particle size range distinct number distribution of the product used as the light-diffusion particle | grains with the mode particle diameter of 5 micrometers in the graph of FIGS. In addition to products having a particle size distribution corresponding to the graph by particle size range shown in FIG. 8 (mode particle size = 5 μm), products having mode particle sizes (nominal particle size) of 10 μm and 15 μm are mode. The ratio of the number of particles falling within the range of the particle size R1 ± 20% is shown in a tabular form.

  First, referring to FIG. 1, there is shown a basic configuration of a surface light source device using a light diffuser according to the present invention. The entire light diffuser is denoted by reference numeral 3 and has a plate shape. One minor surface (side surface) 1 of the light diffuser 3 provides a light input portion, and one major surface (surface) 2 provides a light output portion. However, only a part of the major surface 2 may be used as the light output unit. For example, a rectangular area excluding the frame-shaped outer edge portion of the major surface 2 may be used as the light output portion of the surface light source device. The symbol L represents a primary light source arranged to supply uniform white light over almost the entire minor surface 1. As the primary light source L, a known white light LED using LEDs that emit light of three colors (blue, red, and green) can be used.

  The light diffusing body 3 is obtained by uniformly dispersing light diffusing particles 5 at a predetermined concentration in a resin matrix made of PC. White light emitted from the primary light source L is introduced into the light diffuser 3 from the minor surface 1. This light propagates in the light diffuser 3 away from the minor surface 1 (hereinafter, the light propagating in the light diffuser 3 will be referred to as internal propagation light). Internally propagated light is repeatedly subjected to the scattering action by the light diffusing particles in the propagation process. Due to this scattering action, a light component internally incident on the major surface is generated little by little, and further, a component having an internal incident angle less than the critical angle is emitted from the major surface 2 to the outside. Or a part is utilized as illumination output light of a surface light source device.

  The thickness of the plate-like light diffuser 3 is, for example, 0.3 mm, the width (length in the longitudinal direction of the minor surface 1) is 8 cm, and the depth (length in the longitudinal direction of the major surface 2) is 15 cm. However, these various sizes can be appropriately selected according to the use (for example, a backlight for a display of a smartphone). From a practical viewpoint, it can be considered that the thickness of the light diffuser is about 0.1 mm to 1 cm, and the major surface size is about 5 cm × 8 cm to 50 cm × 80 cm. In some cases, light output portions may be provided on both the front and back surfaces of the light diffuser 3, and light emitted from them may be used as output illumination light. Furthermore, you may arrange | position a reflector (for example, Al foil) along the back surface of the light diffusing body 3. In addition, prism-like irregularities may be provided on the back surface of the light diffuser 3.

  The concentration of the light diffusing particles 5 uniformly dispersed in the PC constituting the resin matrix of the light diffusing body 3 (hereinafter also simply referred to as the concentration) ranges from 0.01 wt% (wt%) to 1 wt% (weight). %). As the light diffusing particles 5, particles having a refractive index in the range of 1.47 to 1.58 are employed. Needless to say, the refractive index of the light diffusing particles 5 is different from the refractive index (1.59) of the PC constituting the matrix resin in order for the light diffusing particles 5 to exhibit the function of scattering the internal propagation light. Is the minimum requirement. In the present invention, on the assumption of this, the range of the refractive index of the light diffusing particles is set to 1.47 to 1.58 in accordance with the purpose described above.

  If the concentration of the light diffusing particles is excessively large, it is difficult to sufficiently deliver the internally propagating light to a position away from the light input portion. On the contrary, if the concentration is too small, the light diffusing ability is insufficient. Accordingly, it is sufficient to select a preferable value in consideration of the depth size of the light diffuser 3 (distance where the internally propagating light needs to be delivered) and the like. However, in the present invention, a practical range is 0.01 wt% to 1 wt%. % Range is selected.

  As a specific example of the light diffusing particles, there is “Unipowder (registered trademark)” manufactured by JX Nippon Oil & Energy Corporation, and the nominal particle size is, for example, 2 μm, 3 μm, 5 μm, 10 μm, and 15 μm. And so on. Of these products, 5 μm is an example that can be used in this embodiment.

  By the way, it is considered that the nominal particle size in an actual product substantially means the mode particle size. In other words, in an actual product, not all grains have a particle size that exactly matches the nominal particle size, but are distributed with a certain degree of particle size variation with the mode particle size (nominal particle size) as a peak. ing. For example, for 5 μm, 10 μm, and 15 μm particles in the above products, indicate the ratio of the number of particles (number fraction) that falls within the range of the mode particle size and the surrounding ± 20% particle size based on the specifications. As shown in the table of FIG.

  As can be seen from the table, as a method of aligning the particle size, the light diffusion is such that the ratio of the number within the range of ± 20% from the mode particle size (hereinafter referred to as R1) is 60% or more. Obtaining particles is generally not difficult. Incidentally, the number distribution of the light diffusing particles having a mode particle diameter of 5 μm listed in the table of FIG. 9 in units of 1 μm is shown as a bar graph in FIG. In the present specification, the mode particle size is 1 μm, 2 μm, 3 μm,..., As depicted in the example of FIG. Each scale 1μm, 2μm, 3μm, …………………………………………………………………………………………………………………………………………………. The value is referred to as the mode particle size. In light of this definition, the example shown in FIG. 8 is exactly applicable to the mode particle size of 5 μm.

  The light diffusing particle 5 scatters and redirects the internally propagating light as described above. This scattering is called Mie scattering in the range where the particle diameter is assumed in the present invention. Can be treated as a phenomenon. According to the Mie scattering theory, the scattering efficiency in each scattering changes according to the particle size of the light diffusing particles. The method of the change varies depending on the wavelength of scattered light and the relationship between the refractive index of the light diffusing particles and the resin matrix.

  Examples of changes in the efficiency of the scattering efficiency (Mie scattering) according to the particle diameter are shown in FIGS. First, the example shown in FIG. 2 shows a blue light component (435 nm), a green light component (545 nm), and a light diffusion particle having a refractive index of 1.49 dispersed in a PC resin matrix (refractive index = 1.59), It is the graph which plotted the theoretical value of the scattering efficiency of a red light component (615 nm) with respect to the particle size of a light scatterer. As can be seen from this graph, the curves representing the transition of the scattering efficiency of each of the three colors all have a repeated wave-depressing shape as the particle size increases. The shorter the wavelength, the faster the rise and fall with respect to the particle size change. It has become.

  In the present invention, for the blue light component graph, the first rising peak (corresponding to a particle size of around 2.5 μm) followed by the lower limit peak (corresponding to a particle size of around 5 μm) after the first falling peak, the second time. Note the range of the rising peak (corresponding to a particle size of around 7 μm). In this range (particle size 2.5 μm to 7 μm), when considering the relationship with the remaining two colors of light graphs, first the green light component intersects with the green light component curve near the particle size of 3 μm. Crosses with the curve again at around the particle size of 5.7 μm. That is, in the continuous range of the particle diameter of 3 μm to 5.7 μm, the scattering efficiency of the blue light component is lower than the scattering efficiency of the green light component. Such a continuous particle diameter region in which the scattering of the green light component is more dominant than the scattering of the blue light component and is on the smallest particle diameter side is referred to as a “green dominant section” for convenience. Therefore, in this example, the green dominant section is in the range of 3 μm to 5.7 μm.

  Next, from the same consideration, the scattering efficiency of the blue light component is lower than the scattering efficiency of the red light component in the continuous range of the particle size of 3.2 μm to 6.3 μm. Therefore, such a continuous particle size region in which the scattering of the red light component becomes more dominant than the scattering of the blue light component on the smallest particle diameter side will be referred to as a “red dominant section”. Therefore, the red dominant section in this case is 3.2 μm to 6.3 μm.

  Next, as another example, when light diffusion particles having a refractive index of 1.54 are dispersed in a PC resin matrix (refractive index = 1.59), a blue light component (435 nm), a green light component (545 nm), A graph in which the theoretical value of the scattering efficiency of the red light component (615 nm) is plotted against the particle size of the light diffusing particles is shown in FIG. As in the case of the graph of FIG. 2, the curves representing the transition of the scattering efficiency of each of the three colors are all wave-shaped, and the rise and fall with respect to the particle size change become steeper as the wavelength becomes shorter. In this example as well, the same consideration as in the graph of FIG. 2 is performed, and the characteristics of this graph are described using the above-mentioned convenient names. That is, in this example, the green dominant section has a particle size range of 5.5 μm to 10.5 μm. And about a red dominant area, it becomes a particle diameter range with a particle size of 6.0 micrometers-11.8 micrometers.

  In the present invention, within the merged section (sum in the set theory sense) of the green dominant section and the red dominant section as shown in the above two examples, or in the common section (product in the set theory sense) of both dominant sections. The basic concept is to use light diffusing particles having the most frequent particle size R1. By adopting this concept, the scattering of the blue light component occurs excessively at a position near the light input portion (minor surface 1 in the example of FIG. 1) of the light diffuser 3, and the light output portion (major surface in the example of FIG. 1). 2) is suppressed from being output. In other words, after the blue light component is propagated to a position far from the light input part, it is easy to be emitted from the light output part through the scattering action by the light diffusing particles. This is very significant in consideration of the effect of absorption of the blue light component by the benzene ring, which is a situation peculiar to PC.

  Incidentally, the merged section of both dominant sections in FIG. 2 is a section of 3 μm to 6.3 μm, and the common section is a section slightly narrowed on both the short wavelength side and the long wavelength side, and a section of 3.2 μm to 5.7 μm. It becomes. In the example of FIG. 3, the merged section is a section of 5.5 μm to 11.8 μm, and the common section is a section of 6.0 μm to 10.5 μm.

  In the present invention, the light diffusing particles having the mode diameter R1 are used in such a merged section, more preferably in the common section. However, the light diffusion particles that are actually used have a variation in particle diameter as described above. Therefore, at first glance, in the case where R1 exists near both ends of the merged section or the common section, it seems that the above-described basic concept of the present invention is questioned.

  2 and 3 show the behavior of each curve in the vicinity of both ends of the merged section and the common section. In the vicinity of the center of each section (in the vicinity of 5 μm in FIG. 2 and in the vicinity of 9 μm in FIG. 3). The difference between the scattering efficiency of the blue light component and the scattering efficiency of the green light component and the red light component suddenly increases toward the) side. On the other hand, when looking at the behavior of the curve of the three color components in the outer particle size region near both ends of the merged section or the common section, such a large difference is not seen (blue light component scattering efficiency and green-red each Note that the magnitude relationship with the light component scattering efficiency is reversed.

  From this, even if the mode particle size R1 is in the vicinity of either end of the merged section or the common section, the effect of the relative drop in the scattering efficiency of the blue light component is excellent and the basic concept of the present invention is maintained. Of course, in each of the examples of FIGS. 2 and 3, it is very preferable to use light diffusing particles having a mode diameter near the center of each section, that is, around 5 μm (the case in FIG. 2) or 9 μm (the case in FIG. 3). That is.

  Next, consider the relationship between the refractive index of the light scattering particles and the refractive index (1.59) of the resin matrix PC. In the example of FIG. 2 described above, the refractive index of the light diffusing particles is 1.49, and in the example of FIG. 3, the refractive index of the light diffusing particles is 1.54. That is, the refractive index difference between the light diffusion particle and the resin matrix is smaller in the case of FIG. 3 than in the case of FIG.

  Here, when comparing the undulation behavior of each curve group in FIG. 2 and FIG. 3, the undulation of the curve group in FIG. 2 occurs with a shorter particle diameter interval than the undulation of the curve group in FIG. As a result corresponding to this, the merged section and the common section described above are larger in FIG. These things suggest the following. That is, it is presumed that the larger the difference in refractive index between the resin matrix and the light diffusing particles, the shorter the period of the undulation of the curve representing the scattering efficiency transition.

  This guess is omitted here, but it also fits the conclusions obtained from the details of the Mie scattering theory. As an example of this fact, the scattering efficiency by color in the case where silicone particles having a refractive index of 1.44 are dispersed as light diffusing particles in a PC resin matrix in the same form as in FIGS. This is shown in FIG. As can be seen immediately from the behavior of the curves of the three color light components in this case, the frequency of undulations is even more intense than in the case of FIG. As a result, both the merged section and the section corresponding to the common section described above are very narrow. Speaking numerically, those corresponding to the merged section are 2.0 μm to 4.2 μm, and those corresponding to the common section are 2.2 μm to 3.7 μm. That is, when the refractive index difference from the PC resin matrix becomes large in this way, the merged section and the common section are rapidly narrowed. For this reason, the above-described basic concept of the present invention is difficult to maintain for the mode particle size R1 anywhere in such a section due to the effect of the particle size variation around the mode particle size described above.

  Based on the discussion about the graphs of FIGS. 2 to 4, the lower limit of the refractive index of the light diffusing particles that can be employed in the present invention is 1.47, which is slightly higher than the median of 1.49 and 1.44. did.

  Here, it was performed to confirm that the effect of suppressing yellowing can be obtained by bringing the mode particle size R1 to the particle size section in which the scattering efficiency of the blue light component described so far is relatively low. Simple spectral transmittance measurement will be described with reference to FIGS. 5 to 7 all show uniform diffusion of light diffusion particles having the three most frequent particle diameters R1 (2 μm, 5 μm, and 10 μm) in the order of 1 wt%, 0.5 wt%, and 0.2 wt%. Each of the light diffuser films (one form of plate-like light diffuser) dispersed in the matrix is prepared (9 types of films), and the spectral transmittance spectrum is obtained according to a known method. As the light diffusing particles, PMMA-based particles (Unipowder (registered trademark) described above) having a refractive index of 1.49 were used. In any of FIGS. 5 to 7, the vertical axis represents the relative spectral transmittance. Here, the relative spectral transmittance represents the transmittance at each light wavelength when the spectral transmittance at 500 nm is normalized to 1.

  In any case of FIGS. 5 to 7, the spectrum of the relative spectral transmittance obtained by the measurement with respect to the film having the mode diameter R1 = 2 μm shows a clear upward trend. In other words, the transmittance tends to be higher as the wavelength is longer (red light side). This clearly shows that it is relatively difficult to internally propagate the blue light component compared to the red light component. Furthermore, if you take a closer look, you can see that there is a strong upward trend in order of increasing density. This is considered to be one proof that the relative propagation ability of the blue light component is reduced due to the scattering effect of the light diffusing particles having the mode diameter of 2 μm.

  However, it goes without saying that the blue light component absorption effect of the benzene ring contained in the PC which is the resin matrix is almost the same as the base in any case of FIGS. Thus, it is obvious that the light diffusing body aimed by the present invention is difficult to obtain when the light diffusing particles of R1 = 2 μm are used. This is also natural in light of the basic concept of the present invention clarified with reference to FIGS.

  Next, in the case of using light diffusion particles with R1 = 5 μm, the relative spectral transmittance curve is almost flat at any of the concentrations in FIGS. However, in more detail, in the case of FIG. 5 (concentration: 1.0 wt%), the trend of a gradual downward slope in the wavelength range from 410 nm near the representative wavelength of 435 nm of the blue light component to the whole of the green light component and the red light component. Is shown. That is, it is shown that the blue light component is somewhat easier to propagate than the green light component and the red light component.

  In addition, in the cases of FIGS. 6 and 7, it cannot be said that the right shoulder is lowered, but it can be said that it is not flat but is almost flat. Therefore, even in the cases of FIGS. 6 and 7, it cannot be said that the internal propagation ability of the blue light component is particularly inferior to the internal propagation ability of the green light component and the red light component. These facts coincide with the fact that the mode particle diameter of 5 μm corresponds to the approximately median value of the merged section and the common section described with reference to FIG. 2 as described above.

  Next, consider the case where R1 = 10 μm light diffusing particles are used. First, what can be said about any of the cases shown in FIGS. 5 to 7 is relatively similar to the curve representing the spectral transmittance of R1 = 5 μm, but in more detail, it is 10 μm in the wavelength region of the blue light component. The curve is below the 5 μm curve. That is, it can be interpreted that 10 μm is inferior in the internal propagation ability compared to the case of 5 μm, although it is slightly for the blue light component. When considering the wavelength regions of the green light component and the red light component, in particular, the curve of R1 = 10 μm in the graph of FIG. Further, in the cases of FIG. 6 and FIG. 7, the gradient is slightly reduced, but the curve of R1 = 10 μm also represents the upward transition.

  Comprehensively interpreting these, it is consistent with the fact that the value of R1 = 10 μm corresponds to outside the merged section and the common section in the description related to FIG. Further, in the case of FIG. 5 where the density is relatively high, the relative spectral transmittance of the blue light component tends to be clearly lower than the curve of R1 = 5 μm, and this tendency is similar to the case of FIGS. As can be seen, the density decreases as the density decreases. The reason why this tendency is observed is presumed to be that the scattering opportunity per unit optical path distance decreases proportionally as the concentration of the light diffusing particles decreases.

  Finally, a method for manufacturing a light diffuser will be briefly described. No new manufacturing technique is required for manufacturing the light diffuser according to the present invention. That is, the methods generally used conventionally can be applied almost as they are. In a typical method, first, commercially available PC pellets or PC powder and a desired mode particle diameter (for example, R1 = 5 μm light diffusing particles in the above example) are prepared. Then, the PC pellets or PC powder and the light diffusing particles are put into a hopper of a biaxial extruder, and the temperature is raised to a predetermined temperature (for example, 280 ° C.). While maintaining this heating state for several tens of minutes, both are mixed evenly by kneading. This kneading is performed by operating the kneading function of the twin screw extruder. Next, the extrusion function of the molding machine is activated to produce pellets that are the raw material of the light diffuser. The raw material pellets thus produced are put into a raw material charging hopper of an injection molding machine, and a light diffuser having a desired shape (for example, a plate shape) is obtained by this injection molding machine.

  Needless to say, the amount of the light diffusing particles to be added at the time of the kneading may be selected so as to obtain a light diffuser of a desired weight%.

1 Light input part (minor side)
2 Light output section (major surface)
3 Light diffuser (light scattering light guide)
4 Resin matrix 5 Light diffusion particle L Primary light source

Claims (4)

A light diffusing material in which light diffusing particles having a predetermined refractive index are dispersed at a predetermined concentration in a resin matrix made of polycarbonate,
A light input unit for inputting white light; and diffused light is output in the process of propagating through the light diffuser so that light input from the light input unit into the light diffuser is separated from the light input unit Having a planar light output,
The predetermined refractive index has a value ranging from 1.47 to 1.58;
The predetermined concentration is in the range of 0.01 wt% to 1 wt%;
The number distribution with respect to the particle size of the light diffusing particles has a mode particle size R1 that gives a peak of the distribution, and ranges from 0.8R1 to 1.2R1 with respect to the first mode particle size R1. The R1 is the smallest particle size in the range in which the scattering efficiency of the blue light component is lower than at least one of the scattering efficiency of the red light component and the scattering efficiency of the green light component. The light diffuser is in one continuous particle size range existing in   The light diffuser according to claim 1, wherein the scattering efficiency of the blue light component is lower than both the scattering efficiency of the red light component and the scattering efficiency of the green light component.   3. The light diffuser according to claim 1, wherein the light diffuser has a plate shape and includes a major surface that provides the light output unit and a minor surface that provides the light input unit.   A surface light source device comprising: the light diffuser according to claim 3; and a primary light source that supplies white light to the minor surface of the light diffuser.

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