JP2008291074A - Light diffusible resin molded body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light diffusible resin molded body capable of easily performing control of dispersibility, a particle diameter and an addition amount of the particle corresponding to various sizes required for a display. <P>SOLUTION: The light diffusible resin molded body 1 contains a transparent resin 2 and a crushed porous metal oxide 3, and the porous metal oxide 3 has a shape that primary particles are contacted with each other and are continued in the praying bead-like shape and further has a void formed by the primary particle. At least a part is crushed to a metal oxide primary particle at mixing with the transparent resin 2 and is dispersed in the transparent resin 2. Thereby, the structure of the porous metal oxide 3 is brittle and easily crushed, coagulation is suppressed by intruding the transparent resin to the void, dispersibility and optical diffusibility are sufficient. Further, in the metal oxide, width of refractive index is wide and width can be given to the control of the light diffusibility. Therefore, the control of the dispersibility, the particle diameter and the addition amount of the particle corresponding to various sizes is easy and the light can be efficiently utilized. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a light diffusing resin molding in which minute metal oxide particles are highly dispersed in a resin.

  Conventionally, various attempts have been made to efficiently use light such as a display used in a mobile phone or a personal computer with high brightness. In a small display, there is a method called edge light type, in which light is guided from a side surface into a transparent resin that is a light guide plate, and the light is collected on the surface of the display using scattering or a reflection sheet inside. For large displays, there is a method called direct type, in which lamps are arranged on the back, and the light is guided to a transparent resin and collected on the surface. Moreover, in both types, there are also those using a light diffusion film or the like on the surface portion.

By dispersing various particles in a polymer represented by such a light guide plate and controlling the diffusion of light, light can be used efficiently and with high luminance. That is, there is one that provides a light diffusing resin film by dispersing calcium-based inorganic particles having good uniformity of about 0.1 μm to 5 μm in a transparent resin (see, for example, Patent Document 1). This can improve the light transmittance and light diffusibility, and can stabilize the optical characteristics by controlling the particle size.
JP 2004-269653 A

  However, in the conventional configuration, the dispersibility of the inorganic particles in the transparent resin must be taken into consideration, and the addition amount and particle size are limited. In addition, there is a limit to the particle size control of the calcium-based inorganic particles. Various sizes are required for displays and the like, and light diffusing resins such as a light guide plate and a light diffusing film that achieve high luminance efficiently are required. For this purpose, the dispersibility, particle diameter, and addition amount of the inorganic particles to be dispersed must be optimized.

  The present invention solves the above-mentioned conventional problems, and provides a light diffusing resin molded article in which the dispersibility, particle diameter, and addition amount of particles according to various sizes required for a display can be easily controlled. With the goal.

  In order to solve the conventional problem, the light diffusing resin molded article of the present invention includes a porous metal oxide formed from a transparent resin and metal oxide primary particles, and the porous metal oxide includes: The primary particles are in contact with each other in a bead-like shape and have voids formed with primary particles, and at the time of mixing with the transparent resin, at least a part is crushed to metal oxide primary particles, Metal oxide primary particles are dispersed in a transparent resin.

  As a result, the structure of the porous metal oxide to be mixed is formed in a bead shape with a reduced area where the metal oxide primary particles are in contact with each other to form secondary particles, which are formed by the primary particles in the secondary particles. It is very fragile because it has voids, and is easily crushed by external force applied during mixing. In addition, a transparent resin enters the particles during mixing, which suppresses agglomeration and has excellent dispersibility. It is a structure suitable for. In addition, the metal oxide has a wide range of refractive index (up to about 1.4 to 3.0), and it can have a wide range of light diffusivity control by using various materials. Therefore, it is easy to control the dispersibility, particle diameter, and addition amount of particles according to various required sizes such as a display, and it is possible to provide a light diffusing resin molding that can use light efficiently.

  The light diffusing resin molding of the present invention can easily control the dispersibility of particles, the particle diameter, and the amount added according to various required sizes such as a display, and can utilize light efficiently.

  1st invention contains the porous metal oxide formed from a transparent resin and a metal oxide primary particle, The said porous metal oxide is the shape which continued in the shape of the rosary where the primary particles contact, Light having voids formed by primary particles, at least part of which is crushed to the metal oxide primary particles when mixed with the transparent resin, and the metal oxide primary particles are dispersed in the transparent resin. This is a diffusible resin molding. As a result, the structure of the porous metal oxide to be mixed is formed in a bead shape with a reduced area where the metal oxide primary particles are in contact with each other to form secondary particles, which are formed by the primary particles in the secondary particles. It is very fragile because it has voids, and is easily crushed by external force applied during mixing. In addition, a transparent resin enters the particles during mixing, which suppresses agglomeration and has excellent dispersibility. It is a structure suitable for. In addition, the metal oxide has a wide range of refractive index (up to about 1.4 to 3.0), and it can have a wide range of light diffusivity control by using various materials. Therefore, it is easy to control the dispersibility, particle diameter, and addition amount of particles according to various required sizes such as a display, and it is possible to provide a light diffusing resin molding that can use light efficiently.

  In particular, according to a second invention, in the first invention, a gelation step of obtaining a metal oxide wet gel by a sol-gel method, a substitution removal step of substituting and removing water in the metal oxide wet gel with a solvent, By including a porous metal oxide obtained through a drying step that removes the solvent present in the wet gel by the replacement removal step, it is possible to produce a porous metal oxide that is more easily crushed by suppressing shrinkage during drying, It becomes the material of the metal oxide particles highly dispersed in the transparent resin.

  In the third invention, in particular, in the second invention, in the gelation step, an acid catalyst is used to advance a condensation polymerization reaction in a one-dimensional or two-dimensional direction, and a basic catalyst is used for condensation in a three-dimensional direction. By combining the porous metal oxide obtained by advancing the polymerization reaction, the number of bonds to the contact area between the primary particles can be reduced, and it is suitable for high dispersion by weakening the connection between the primary particles. A porous metal oxide can be produced. Further, since the gap is large, it is easily crushed. The primary particle size can be controlled by the acid treatment time and the amount of water in the acid treatment, and the primary particle size can also be controlled by the base treatment catalyst amount and the amount of water.

  In the fourth invention, in particular, in the third invention, since the metal oxide is silica, silica particles are a widely used material, and the porous body of silica is easy to synthesize and control. Therefore, a wide range of development is possible depending on the size of the light diffusion resin. Silica has a hydroxyl group on the surface, and the hydroxyl group can be substituted with various functional groups. Considering the solubility parameter of the matrix polymer, it can be further modified with a material having good dispersibility.

  In the fifth invention, in particular, in the fourth invention, alkoxysilane is used as a silica source used in the sol-gel method, and tetraalkoxysilane, trialkoxysilane, dialkoxysilane is mixed as one or two or more kinds as alkoxysilane. By compounding the resulting porous silica, tetraalkoxysilane has four alkoxy groups by using tetraalkoxysilane as the alkoxysilane, and the condensation polymerization reaction proceeds in each direction by hydrolysis. Go. It is possible to control the progress of gelation by the difference in reactivity according to the number of carbon atoms of the alkoxy group, the amount of catalyst, and the type of catalyst, control of dispersibility after mixing with a transparent resin, It becomes easy to produce porous silica capable of controlling the size. In addition, since trialkoxysilane or dialkoxysilane is used as alkoxysilane, the number of hydroxyl groups that undergo condensation polymerization is small, so the number of bonds when metal oxide primary particles are connected to each other is reduced and the connection is weakened. Suitable porous silica can be made. Further, since there are few hydroxyl groups for condensation polymerization, porous silica having a large metal oxide primary particle size and large voids can be produced. Furthermore, it is possible to control the size of the metal oxide primary particles by changing the ratio of tetraalkoxysilane, trialkoxysilane, dialkoxysilane.

  In the sixth invention, in particular, in the fourth invention, the number of bonds when the metal oxide primary particles are bonded to each other is reduced by combining porous silica obtained by using an oligomer of alkoxysilane. The bond is weakened, and porous silica suitable for high dispersion can be produced. Moreover, since the metal oxide primary particles are large and the voids are large, they are easily crushed.

  In the seventh invention, in particular, in the first invention, the transparent resin is at least one of polystyrene, polycarbonate, polyester, polyethylene, and polymethyl methacrylate, so that the resin can be melt-mixed. There are few restrictions on the molding method. In addition, since the physical properties and transparency of the resin itself are excellent, and the refractive index is close to silica (about 1.53), it is a material having high transparency and can be controlled in accordance with a wide range of purposes.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 shows a light diffusing resin molding in Embodiment 1 of the present invention.

  As shown in the figure, the light diffusable resin molded article 1 in the present embodiment includes a transparent resin 2 and a crushed porous metal oxide 3. The porous metal oxide 3 has a bead-like shape in which the metal oxide primary particles are in contact with each other, and has a very fragile structure having voids formed by the metal oxide primary particles. At the time of mixing with the resin 2, at least a part thereof is crushed to the metal oxide primary particles by the mixing stress and is dispersed in the transparent resin 2.

  As described above, the porous metal oxide 3 is crushed to the metal oxide primary particles and highly dispersed in the transparent resin 2 to obtain an efficient light diffusing resin molded body 1.

  The crushed porous metal oxide 3 is at least partially crushed to the metal oxide primary particles by mixing stress when mixed with the transparent resin 2, but the size of the metal oxide primary particles is 2 nm or less. Not crushed. Although it is possible to produce metal oxide primary particles with a size of several nanometers or several tens of nanometers, the effect of light diffusion is Rayleigh scattering below 100 nm, so that the scattering greatly depends on the wavelength of light. Therefore, there will be a bias in color. For this reason, it is desirable that the metal oxide primary particles be a porous metal oxide 3 having a thickness of 100 nm or more. When the size of the metal oxide primary particles is increased to about 100 nm, it becomes easy to receive a force by kneading, so that most of the porous metal oxides are crushed to the metal oxide primary particles.

  As for the upper limit, a porous metal oxide of 50 μm or more does not exist because it is easily crushed. Furthermore, when the size is larger than 20 μm, it is difficult for light to travel to the entire molded body. Accordingly, a metal oxide primary particle size of 10 μm or less is desirable. Furthermore, in the metal oxide primary particles of about 1 μm to 10 μm, incident light is reflected and scattered forward. For particles of about 100 nm to 1 μm, forward reflection and scattering are reduced. Therefore, in order to take advantage of these scattering, it is desirable that the metal oxide primary particles have a thickness of 100 nm to 10 μm. However, controlling the particles by narrowing the wavelength range of the light will cause a color bias in the scattered light, so the particle size is the amount of the porous material added to the transparent resin 2 and the size of the molded body. It is desirable to select an optimal particle size according to the conditions.

  The lower limit of the mixing ratio of the transparent resin 2 and the porous metal oxide 3 is not particularly limited, and may be 0.1 wt% or more where the effect appears. The upper limit is the aggregation of the crushed porous metal oxide 3. Since it is necessary to suppress, it is desirable that it is 70 wt% or less. Furthermore, when considering the permeability of the light diffusing resin molding 1, it is more desirable to be 50 wt% or less. In addition, it is desirable to adjust the relationship between the size of the metal oxide primary particles and the addition amount so that the interparticle distance between the metal oxide primary particles is 0.01 μm to 100 μm in the dispersed state.

  The transparent resin 2 is a polystyrene-based, polycarbonate-based, polyester-based, polyethylene-based, or polymethylmethacrylate-based resin that is excellent in transparency and physical properties, and may be at least one kind or a mixture of two or more kinds. What is necessary is just to have sex. Preferably, a resin having a refractive index of about 1.40 to 1.65 is desirable. It may be crystalline or non-crystalline, and it may be large or small in polarity. Furthermore, as additives, dispersants that improve dispersibility, antioxidants that suppress deterioration, radical scavengers, crystallization nucleating agents that promote crystallization, fiber fillers that improve various mechanical properties, rubber components, etc. In addition, fillers that give various properties such as conductivity, magnetism, thermal conductivity, vibration damping, heat insulation, light weight, electromagnetic wave absorption, reflection, heat radiation, and flame retardancy are included as long as the transparency is not impaired. It doesn't matter.

  FIG. 2 shows an enlarged part of the porous metal oxide before mixing with the transparent resin 2. The structure of the porous metal oxide 11 before mixing forms a secondary particle connected in a bead shape that suppresses the area where the metal oxide primary particles 13 are in contact with each other, and the metal oxide primary is contained in the secondary particles. Since it has the space | gap 12 formed with particle | grains, it is very brittle and it is easy to be crushed by the external force added in the case of mixing. In addition, since the transparent resin 2 enters between the particles during mixing, aggregation is suppressed and the structure is very dispersible and is very suitable for light diffusion. Further, the metal oxide has a wide range of refractive index of about 1.4 to 3.0, and it can have a wide range of light diffusivity control by using various types.

  The porous metal oxide 11 before being mixed with the transparent resin 2 may have a particle diameter of the metal oxide primary particles 13 of 100 nm to 10 μm, and the porous metal oxide 11 is a series of them. 1 μm or more. The upper limit is not particularly limited, but when it is crushed by its own weight with a mixer or the like, it is crushed to 100 μm or less. Moreover, the porosity of the space | gap 12 formed in the porous metal oxide 11 should just be 50%-99%, More preferably, it is a porosity of 70% or more. This is because if the porosity is low, the porous metal oxide 11 is not easily crushed, and if the porosity is high, the porous metal oxide 11 is easily crushed, but for producing the porous metal oxide 11 having a porosity of 99% or more. It is difficult to manufacture because special equipment and methods are required.

  FIG. 3 is an enlarged view of a part of the porous metal oxide mixed and crushed with the transparent resin. Part or all of the crushed porous metal oxide 21 is crushed into metal oxide primary particles 22. The metal oxide 23 in a state in which the metal oxide primary particles are connected to each other remains when the crushing force and time are insufficient, and the metal oxide primary particles 22 are too small or contraction is significant when producing the porous metal oxide. In some cases, a part of the porous metal oxide may remain without being crushed into the metal oxide primary particles 22. Since it is a porous metal oxide in which metal oxide primary particles 22 of at least about 100 nm are continuous, it can be considered that the metal oxide primary particles 22 are almost crushed during kneading. However, if the time is too long, the metal oxide primary particles 22 once dispersed may re-aggregate, so that mixing needs to be stopped in an appropriate time.

  Next, a method for mixing the porous metal oxide with the transparent resin will be described.

  In the present embodiment, as a uniform dispersion method of the porous metal oxide 11 before mixing shown in FIG. 2, a method of crushing and dispersing with a force by mixing with the transparent resin 2 is adopted. However, it is desirable for uniform dispersion that the size and the size of the pellets or powder of the transparent resin 2 are previously matched. Further, it is desirable to make the porous metal oxide 11 fine in advance with a mixer or the like before mixing with the transparent resin 2 in terms of shortening the time required for dispersion and suppressing deterioration of the resin. In addition, when pulverizing in advance, the strong pulverization method of pulverizing the voids 12 of the porous metal oxide 11 causes the porous metal oxide 11 to aggregate and stabilize. Care must be taken because this is a factor that hinders the dispersion of the crushed porous metal oxide 11. For mixing with the transparent resin 2, devices usually used for mixing resin and filler, such as tumblers, melt mixers, roll mills, kneaders, pressure kneaders, twin screw extruders, single screw extruders, Banbury A mixer may be used.

  Next, examples of the molding method of the mixture of the mixed transparent resin 2 and the porous metal oxide 11 include compression molding, extrusion molding, injection molding, thermoforming, blow molding, and calendar molding. There is no particular limitation, and any molding method that takes into account the properties of the resin and the shape of the molded product may be used.

  As described above, as shown in FIG. 1, the crushed porous metal oxide 3 is highly dispersed in the transparent resin 2 to obtain an efficient light diffusing resin molding 1.

  As described above, the light diffusing resin molding in the present embodiment is easy to control the dispersibility of particles, the particle diameter, and the amount added according to various sizes required for a display and the like, and efficiently emits light. It can be used. In addition to displays, it can be used for information indicators, lighting equipment, and internal lighting of home appliances.

(Embodiment 2)
Next, the light diffusing resin molding in Embodiment 2 of this invention is demonstrated.

  The porous metal oxide of the light diffusing resin molding in the present embodiment may be one type or a mixture of two or more types as long as an alkoxide of the metal is easily available. Further, a metal salt that can be dissolved in one kind of metal alkoxide and one or more kinds of solvents may be used.

  Examples of the metal alkoxide include aluminum, barium, boron, bismuth, calcium, iron, gallium, germanium, hafnium, indium, potassium, lanthanum, phosphorus, lead, niobium, sodium, molybdenum, magnesium, lithium, antimony, tin, strontium, Although metal alkoxides, such as tantalum, copper, nickel, titanium, vanadium, tungsten, yttrium, zinc, and zirconium, are mentioned, monovalent and divalent metals are not suitable for use with only one kind. As the metal salt, the ligand is an amino group, phosphino group, carboxyl group, thiol group, pyridine, triphenylphosphine, nitrate ion, halide ion, ammonia, carbon monoxide, carbene, ethylenediamine, bipyridine, phenanthroline, BINAP. , Catecholate, terpyridine, ethylenediaminetetraacetic acid, porphyrin, cyclam, crown ethers, cyclopentadienyl anion, and the like, and derivatives thereof are not particularly limited. The coordination atom is aluminum, barium, boron, bismuth, calcium, iron, gallium, germanium, hafnium, indium, potassium, lanthanum, phosphorus, lead, niobium, sodium, molybdenum, magnesium, lithium, antimony, tin, strontium , Tantalum, copper, nickel, titanium, vanadium, tungsten, yttrium, zinc, zirconium and the like, but there is no particular limitation. Any of them may be a metal salt that is usually easily available.

Below, the preparation method of porous silica is demonstrated on behalf of a porous metal oxide. The process for preparing porous silica mainly comprises the following three processes.
(1) Gelation step (2) Replacement removal step (3) Drying step Details of each step will be described.

(1) Gelation step Hydroxylation of metal alkoxide and subsequent polycondensation by adding alkoxysilane as wet gel raw material by sol-gel method, water and alcohol as needed as solvent, and adding catalyst as necessary. In this step, metal oxide primary particles are generated by the reaction, and the primary particles are arranged in a bead shape to form a porous skeleton, thereby obtaining a wet gel.

  As a silica source, alkoxysilane is easy to control reaction, inexpensive and widely used. Wet tetraalkoxysilane such as tetramethoxysilane and tetraethoxysilane, trialkoxysilane and dialkoxysilane As the raw material, one kind or a mixture of two or more kinds can be used as the wet gel raw material.

  Tetraalkoxysilane has four alkoxy groups and undergoes a condensation polymerization reaction in each direction by hydrolysis. It is possible to control the progress of gelation by the difference in reactivity according to the number of carbon atoms of the alkoxy group, the amount of catalyst, and the type of catalyst, control of dispersibility after mixing with a transparent resin, It becomes easy to produce porous silica capable of controlling the size. For example, an alkoxysilane having a large number of carbon atoms in the alkoxy group has a low reactivity, and the gelation rate can be controlled by selecting the type of the alkoxy group, and the amount of catalyst can control the gelation rate of the wet gel, By reducing the amount of the catalyst, the gelation rate can be delayed and porous silica having a large metal oxide primary particle size can be produced. Similarly, the gelation rate can be controlled by the strength of the catalyst such as acidity and basicity. By reducing the gelation rate, porous silica with large metal oxide primary particles can be produced. With respect to the amount of water, porous silica having large primary metal oxide particles can be produced by the presence of a large amount of water during gelation.

  The use of an acid catalyst will be described. In the acid catalyst, hydrogen ions are first added to the oxygen of the alkoxy group of alkoxysilane, then water is nucleophilic attacked, the alkoxy group is eliminated as an alcohol, and hydrolysis proceeds. This hydrolysis reaction and the condensation polymerization reaction of silanol groups generated by hydrolysis proceed simultaneously to cause gelation. However, when the amount of water is small, hydrolysis is slow, and on the other hand, the condensation polymerization reaction proceeds, so the condensation polymerization reaction proceeds in one or two dimensions. Therefore, the coupling | bonding of the particles by the polycondensation to a three-dimensional direction can be reduced. Utilizing this, acid catalyst treatment was performed under conditions with little water, and then the basic catalyst and water were added to cause the condensation polymerization reaction to proceed in the three-dimensional direction, thereby reducing the contact area between the metal oxide primary particles. Porous silica can be produced. In addition, the metal oxide primary particles also become larger, and the voids become larger accordingly.

  Since trialkoxysilane and dialkoxysilane have few hydroxyl groups for condensation polymerization, the number of bonds when metal oxide primary particles are linked to each other is reduced, and the bond is weakened, so that porous silica suitable for high dispersion can be produced. Can do. Further, since there are few hydroxyl groups for condensation polymerization, porous silica having a large metal oxide primary particle size and large voids can be produced. That is, each has three and two alkoxy groups, and the rest each have one and two alkyl groups. By hydrolysis, the condensation polymerization reaction proceeds. However, since the alkyl group does not undergo hydrolysis or condensation polymerization reaction, the direction of the condensation polymerization reaction is controlled, and a wet gel with a limited number of bonds is formed. It is formed. The porous silica produced in this way is easy to grow in one and two dimensions as in the case of using the acid catalyst described above, has a large metal oxide primary particle size, and has a weak connection between particles. . However, it does not gel with dialkoxysilane alone. Therefore, although it can be considered to be used as a mixture, the metal oxide primary particle size is determined by the ratio of the mixture, mainly the number of alkoxy groups. For example, in a wet gel made from dialkoxysilane and tetraalkoxysilane, the primary particle diameter of the metal oxide increases as the proportion of dialkoxysilane increases. Since the metal oxide primary particles are also enlarged, the voids are increased accordingly, and the metal oxide primary particles are easily crushed.

  It is also possible to use not only monomers but also oligomers, and using oligomers reduces the number of bonds when metal oxide primary particles are connected to each other, weakening the connection, and making porous silica suitable for high dispersion. Can be produced. Moreover, since the metal oxide primary particles are large and the voids are large, they are easily crushed. By using an oligomer of about tetramer or heptamer, it is easy to control production, and porous silica in which the metal oxide primary particles are weakly connected can be obtained.

  In addition, since the wet gel raw material can use water glass and can be manufactured at low cost, it is suitable for mass production.

  After the gelation process, hydrophobic groups are introduced into the wet gel surface and the surface is hydrophobized, so that the capillary force acting from the solvent during drying can be reduced. It is easy to produce porous silica, and the porous silica is suitable for high dispersion. Examples of the introduction of a hydrophobic group onto the wet gel surface include introduction of an alkyl group such as a methyl group, an ethyl group, or a propyl group, and introduction of a fluoride or fluorine.

  The drying process will be described later, but the relationship with the surface treatment will be described a little here.

  When supercritical drying is used, it is not necessary to perform surface treatment. However, when non-supercritical drying is used, it is desirable to perform surface hydrophobization treatment because capillary force cannot be ignored. In addition, even with a method using supercritical drying, hydrophobizing the surface of porous silica increases affinity with lipophilic resin and improves dispersibility, and moisture in the air during storage. Since there is an advantage such as suppressing the shrinkage of the porous silica by preventing the adsorption of the silica, it is preferably performed as necessary.

  Even when the surface is not hydrophobized, if the porous silica has a large void, the capillary force can be reduced. Therefore, by increasing the primary particle diameter of the porous silica metal oxide, the porous silica can be dried. Can be prevented from shrinking. Thus, porous silica with reduced shrinkage during drying can be produced in the same manner as in the method using supercritical drying. In addition, since the surface of the porous silica is not hydrophobized, it has an affinity with a hydrophilic resin, has good dispersibility, and improves storage stability in air.

(2) Substitution removal step This is a step of removing water in the wet gel with a solvent. This step is strongly prepared for the next drying step, and it is desirable to substitute a solvent suitable for each drying method.

  The hot air drying will be described. Capillary force from the solvent exerts a force on the porous body skeleton at the time of drying. Since the capillary force is proportional to the surface tension, a solvent having a low surface tension is preferable in order to suppress the capillary force. For example, alcohols such as methanol, ethanol and propanol, more preferably alkanes such as pentane, hexane, heptane, octane, nonane and decane, ketones such as acetone, aromatics such as toluene, xylene and benzene, etc. It is done.

  Explaining supercritical drying, those having a low critical temperature and critical pressure are suitable. For example, carbon dioxide. Carbon dioxide has a critical temperature of 31.3 ° C. and a critical pressure of 72.9 atm. In order to use carbon dioxide as the supercritical fluid, here, a method of substituting with alcohol in the substitution removing step is adopted. It is desirable to substitute with a solvent having good compatibility with supercritical carbon dioxide.

  As for lyophilization, any solvent may be used as long as it is liquid at room temperature and normal pressure and has a triple point temperature of up to about −30 ° C., and water, t-butyl alcohol, and the like are listed as examples. Further, it may not be completely substituted, and most of them may be substituted.

(3) Drying process The drying process is a process of removing the solvent present in the wet gel. Examples of the drying method include supercritical drying, hot air drying, freeze drying, vacuum drying, and natural drying.

  The hot air drying will be described. A wet gel is put in a drying container, a temperature is applied, and drying is performed by evaporation of the solvent. The drying container is a pressure-resistant container, and a method of drying while applying pressure is more preferable because the capillary force can be further reduced. When the solvent evaporates, the capillary force from the solvent exerts a force on the pores of the porous body, but it can be reduced because the solvent is replaced with a solvent having a low surface tension. Suppressing the shrinkage at the time of drying is to suppress the aggregation and stabilization of the porous silica, which leads to an improvement in dispersibility when mixed with the transparent resin.

  Supercritical drying can reduce the surface tension because no gas-liquid interface appears, and the shrinkage of the porous silica is very small, resulting in a porous silica that is more easily crushed than the porous silica dried by hot air drying. Suitable for dispersion. The method may be general supercritical drying, such as carbonate supercritical drying or alcohol supercritical drying.

  The supercritical drying using the supercritical fluid carbon dioxide will be described. The wet gel substituted with alcohol or the like is transferred into a high-pressure vessel and supercritical carbon dioxide is circulated. Carbon dioxide has a critical temperature of 31.3 ° C. and a critical pressure of 72.9 atm in the coal bed state, but the critical temperature and critical pressure rise in the presence of a solvent, for example, coexistence with alcohol. Therefore, supercritical carbon dioxide was continuously circulated at a temperature of 80 ° C. and a pressure of 160 atm sufficient for a critical state to completely remove alcohol.

  In lyophilization, the solvent becomes solid and sublimation occurs when drying under reduced pressure, so surface tension from drying from liquid does not work, and porous silica with very little shrinkage can be produced. It becomes porous silica that is more easily crushed than dried porous silica, and is suitable for high dispersion. Also, the cost can be reduced compared to supercritical drying. However, there are problems such as an increase in atmospheric pressure due to sublimation and a long time for drying because energy is lost as latent heat due to sublimation.

  As described above, the light diffusing resin molded article according to the present invention can easily control the dispersibility, particle diameter, and addition amount of particles according to various sizes required, and efficiently use light. In addition to the display, it can be applied to information indicators, lighting equipment, and interior lighting of home appliances.

Sectional schematic diagram of the light diffusable resin molding containing the crushed porous metal oxide in Embodiment 1 of this invention Schematic diagram enlarging the porous metal oxide before mixing with the transparent resin in the light diffusing resin molding The schematic diagram which expanded the crushed porous metal oxide after mixing with the transparent resin in the light diffusable resin molding

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light diffusable resin molding 3 Transparent resin 3, 21 Crushed porous metal oxide 11 Porous metal oxide 12 Void 13, 22 Metal oxide primary particle 23 Metal oxide in a state where primary particles are bound to each other

Claims (7)

The porous metal oxide includes a porous metal oxide formed from a transparent resin and metal oxide primary particles, and the porous metal oxide is formed in a bead-like shape in which primary particles are in contact with each other, and is formed of primary particles. A light-diffusing resin molded article having voids, at least partially pulverized to metal oxide primary particles when mixed with the transparent resin, and having the metal oxide primary particles dispersed in the transparent resin. A gelation step for obtaining a metal oxide wet gel by a sol-gel method, a substitution removal step for replacing and removing water in the metal oxide wet gel with a solvent, and a drying step for removing the solvent present in the wet gel by the substitution removal step. The light diffusable resin molding of Claim 1 containing the porous metal oxide obtained through a process. In the gelation step, a porous metal oxide obtained by advancing a condensation polymerization reaction in a one-dimensional or two-dimensional direction using an acid catalyst and a condensation polymerization reaction in a three-dimensional direction using a basic catalyst The light-diffusing resin molded article according to claim 2, which is composited. The light diffusing resin molding according to claim 3, wherein the metal oxide is silica. 5. The porous silica obtained by combining alkoxysilane as the silica source used in the sol-gel method and mixing one or more of tetraalkoxysilane, trialkoxysilane and dialkoxysilane as the alkoxysilane is compounded. Light diffusing resin molding. The light diffusable resin molding of Claim 4 which compounded the porous silica obtained using the oligomer of an alkoxysilane. The light-diffusing resin molded article according to claim 1, wherein the transparent resin is at least one of polystyrene, polycarbonate, polyester, polyethylene, and polymethyl methacrylate.