TWI472808B - A light diffusion element manufacturing method and a light diffusion element - Google Patents

Description

Method for manufacturing light diffusing element and light diffusing element

The present invention relates to a method of fabricating a light diffusing element and a light diffusing element.

Light diffusing elements are widely used in lighting shades, screens for projection televisions, surface emitting devices (such as liquid crystal display devices), and the like. In recent years, the use of light diffusing elements for improvement in display quality of liquid crystal display devices and the like, improvement in viewing angle characteristics, and the like has progressed. As the light-diffusing element, it has been proposed to disperse fine particles in a matrix such as a resin sheet (see, for example, Patent Document 1). In such a light diffusing element, most of the incident light is scattered on the front side (the exit surface side), and a part is scattered on the rear side (incidence surface side). The larger the difference in refractive index between the microparticles and the matrix, the larger the diffusibility (for example, the haze value). On the other hand, if the refractive index difference is large, the backscattering increases. When the backscattering is large, when the light diffusing element is used in a liquid crystal display device, when the external light is incident on the liquid crystal display device, the screen is white, and thus it is difficult to display a contrast image or image.

As a means for solving the back-scattering as described above, it is proposed to disperse the refractive index-increasing fine particles such as GRIN (gradient index) fine particles which are continuously changed from the central portion of the fine particles toward the outside. Element (for example, refer to Patent Document 2). However, the GRIN microparticles are more complicated in manufacturing process than the usual microparticles, so the productivity is insufficient and it is not practical.

Further, in the light diffusing element including the GRIN fine particles, as a means for continuously changing the refractive index, a technique of allowing a matrix resin component precursor (for example, a monomer) to permeate into the fine particles before polymerizing the matrix resin component has been proposed. (Refer to Patent Document 3). But about In such a technique, if high-haze light diffusibility is desired, it takes a long time for the matrix resin component to permeate, or it needs to be heated at a high temperature, and there is still room for improvement in terms of productivity. .

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent No. 3071538

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2002-214408

[Patent Document 3] Japanese Patent No. 4756100

The present invention has been made to solve the above problems, and an object thereof is to provide a low-cost and high-productivity (short-time) manufacturing with high haze value, strong diffusibility, and smooth surface to suppress backscattering. A method of manufacturing a light diffusing element of a light diffusing element.

The method for producing a light diffusing element of the present invention comprises the steps of: preparing a mixed liquid by mixing light-diffusing fine particles with an organic solvent, and swelling the light-diffusing fine particles; and mixing the mixed liquid with a resin-containing precursor and super Step B of mixing the matrix forming material of the fine particle component; and step C of polymerizing the resin component precursor to form a matrix containing the resin component and the ultrafine particle component.

In a preferred embodiment, the molecular weight of the resin component precursor is from 100 to 700.

In a preferred embodiment, the organic solvent has a boiling point of 70 ° C or higher.

In a preferred embodiment, the organic solvent is a mixed solvent of a first organic solvent and a second organic solvent, and the first organic solvent is more permeable to the light diffusion than the second organic solvent. Among the fine particles, the volatility is higher than that of the second organic solvent.

In a preferred embodiment, the method for producing a light diffusing element of the present invention further comprises the step of heating the dispersion obtained by mixing the mixed liquid with a matrix forming material comprising a resin component precursor and an ultrafine particle component, and heating. The temperature is below 80 °C.

In a preferred embodiment, in the step C, a substantially spherical ball having a higher concentration of the ultrafine particle component as it moves away from the light diffusing fine particles is formed in the vicinity of the interface between the substrate and the light diffusing fine particles. Shell-like concentration modulation area.

According to another aspect of the present invention, a light diffusing element is provided. The light diffusing element was obtained by the above method, and the haze value was 70% or more.

In a preferred embodiment, the ten-point average surface roughness Rz of the light diffusing element is less than 0.20 μm.

In a preferred embodiment, the light diffusing element has an average tilt angle θa of less than 0.5°.

In a preferred embodiment, the light diffusing element has an arithmetic mean surface roughness Ra of less than 0.05 mm.

According to the present invention, in the production of a light-diffusing element including a light-diffusing fine particle, an ultrafine particle component, and a resin component, first, the light-diffusing fine particle contains an organic solvent, and the light-diffusing fine particle is swollen in advance, and then the light-diffusing fine particle is used. The precursor is mixed with the matrix forming material containing the resin component precursor and the ultrafine particle component, whereby the precursor can be infiltrated into the light diffusing fine particles in a short time. Further, according to the production method of the present invention, the precursor which penetrates into the light-diffusing fine particles is polymerized with the non-permeating precursor, whereby the light-diffusing member can be produced without special treatment or operation. In the present invention, the precursor can be infiltrated into the light-diffusing fine particles in a short period of time. Therefore, it is possible to produce a light-diffusing element which is excellent in productivity and which prevents aggregation of light-diffusing fine particles and ultrafine particle components and is excellent in smoothness. Further, in the manufacturing step, the above components are included When the coating liquid is applied and dried, the swelled light-diffusing fine particles have fluidity in the coating liquid and can follow the change in the coated surface during drying, so that a light diffusing element excellent in smoothness can be produced.

The light diffusing element obtained by the manufacturing method of the present invention can form a substantially spherical shell-like concentration modulation in the vicinity of the surface of the light diffusing fine particles as the weight concentration of the ultrafine particle component becomes higher as the distance away from the light diffusing fine particles In the region, the refractive index is modulated in the concentration modulation region, so that the refractive index can be changed stepwise or substantially continuously in the vicinity of the interface between the light diffusing element and the substrate. Therefore, reflection at the interface between the substrate and the light diffusing fine particles can be satisfactorily suppressed, and backscattering can be suppressed. Further, according to the present invention, the refractive index of the substrate can be relatively easily adjusted by using an ultrafine particle component having a specific refractive index and a specific compatibility with respect to the resin component. In particular, according to the present invention, by infiltrating the resin component into the inside of the light diffusing fine particles, the concentration of the ultrafine particle component in the matrix can be increased, so that the refractive index difference between the matrix and the light diffusing fine particles can be easily changed. Big. As a result, the light diffusing element obtained by the manufacturing method of the present invention has a high haze value, a strong diffusibility, and suppresses backscattering.

10‧‧‧Material

11‧‧‧Resin composition

20‧‧‧Light diffusing microparticles

30‧‧‧Concentration zone

100‧‧‧Light diffusing elements

Fig. 1 is a schematic view for explaining a state in which a resin component of a matrix and a state in which light-diffusing fine particles are dispersed in a light-diffusing element obtained by the production method of the preferred embodiment of the present invention.

Fig. 2 is a schematic view showing the vicinity of light diffusing fine particles in the light diffusing element of the present invention.

Figure 3 is a transmission electron microscope image illustrating the area ratio of the ultrafine particle components in the matrix.

Fig. 4 is a conceptual diagram for explaining a change in refractive index from a central portion of a light diffusing fine particle to a substrate in the light diffusing element of the present invention.

Fig. 5 (a) shows the transmission type of the section of the light diffusing element obtained in Example 1. 顕 micrograph photograph, (b) shows a transmissive 顕 micrograph of the cross section of the light diffusing element obtained in Comparative Example 1, and (c) shows a transmissive 顕 micrograph of the cross section of the light diffusing element obtained in Comparative Example 4. .

A. Method of manufacturing light diffusing element

A method for producing a light diffusing element according to an embodiment of the present invention includes a step of preparing a mixed liquid by mixing light diffusing fine particles with an organic solvent, and swelling the light diffusing fine particles (refer to step A); a step of mixing with a matrix forming material comprising a resin component precursor and an ultrafine particle component (refer to step B); and a step of polymerizing the resin component precursor to form a matrix comprising a resin component and an ultrafine particle component (refer to step C).

A-1. Step A

In the step A, a light-diffusing fine particle is mixed with an organic solvent to prepare a mixed solution. By mixing the light-diffusing fine particles with the organic solvent, at least a part of the light-diffusing fine particles contains an organic solvent and swells the light-diffusing fine particles. The light-diffusing fine particles can be made to contain an organic solvent by mixing the light-diffusing fine particles with an organic solvent for a predetermined period of time. For example, the light diffusing fine particles can contain an organic solvent by elapse of 15 minutes to 90 minutes. The mixed solution can also be produced, for example, by stirring light diffusing fine particles in an organic solvent.

A-1-1. Light diffusing fine particles

The light diffusing fine particles are made of any suitable material. The light diffusing fine particles preferably have a refractive index satisfying the relationship of the following formula (1).

0<| n _P -n _A |. . . (1)

In the formula (1), n _A represents the refractive index of the resin component of the matrix, and n _P represents the refractive index of the light diffusing fine particles. | n _P -n _A | is preferably from 0.01 to 0.10, more preferably from 0.01 to 0.06, still more preferably from 0.02 to 0.06. If | n _P -n _A | is less than 0.01, there is a case where a concentration modulation region is not formed. If | n _P -n _A | exceeds 0.10, there is a tendency for backscatter to increase. In the present specification, the term "concentration modulation region" refers to a region in which the weight concentration of the ultrafine particle component is modulated in the vicinity of the interface between the substrate and the light diffusing fine particles in the light diffusing element. In the "concentration modulation region", the weight concentration of the ultrafine particle component becomes higher as it moves away from the light diffusing fine particles (the weight concentration of the resin component is inevitably lowered). Further, in the "density modulation region", the refractive index changes substantially continuously. The details are as follows.

It is preferred that the light-diffusing fine particles are composed of a compound which is the same as the resin component of the substrate to be charged in the subsequent step B. Further, it is preferable that the light-diffusing fine particles are composed of a compound having a high compatibility with a compound having the same resin component as the matrix. The reason for this is that in the subsequent step (for example, step B), the resin component precursor of the matrix is apt to penetrate into the light diffusing fine particles (details are described below). In the present specification, the term "same system" means that the chemical structure or characteristics are the same or similar, and the term "different system" means a group other than the same system. The same or not can vary depending on the method of choice of the benchmark. For example, when it is based on organic or inorganic, the organic compounds are compounds of the same type, and the organic compound and the inorganic compound are compounds of different systems. When the repeating unit of the polymer is used as a reference, for example, although the acrylic polymer and the epoxy polymer are the same as the organic compound, they are compounds of different systems, in the case of the periodicity table, although the base is used. The metal and the transition metal are both inorganic elements, but are elements of different systems.

Examples of the material constituting the light-diffusing fine particles include polymethyl methacrylate (PMMA), polymethyl acrylate (PMA), copolymers thereof, and the like. Further, as the material constituting the light-diffusing fine particles, cerium oxide-based particles can also be used. Examples of the copolymerization component with PMMA and PMA include a polyurethane, a polystyrene (PSt), and a melamine resin. The light diffusing fine particles are particularly preferably composed of PMMA. The reason for this is that the relationship between the refractive index or the thermodynamic properties of the resin component of the substrate to be charged in the subsequent step B is appropriate. Further, the light diffusing fine particles preferably have a crosslinked structure (stereoscopic network structure). The light diffusing fine particles having a crosslinked structure can be swollen. because Thus, such light-diffusing fine particles are different from dense or solid inorganic particles, and the resin component having appropriate compatibility can be well penetrated into the interior thereof. The crosslink density of the light diffusing fine particles is preferably small until the desired penetration range (described below) is obtained (rough).

The average particle diameter (particle diameter (diameter) before swelling) of the light diffusing fine particle system is preferably 1.0 μm to 5.0 μm, more preferably 1.5 μm to 4.0 μm, still more preferably 2.0 μm to 3.0 μm. The average particle diameter of the light diffusing fine particles is preferably 1/2 or less (for example, 1/2 to 1/20) of the thickness of the light diffusing element. If the average particle diameter is such a ratio with respect to the thickness of the light diffusing element, the light diffusing fine particles can be arranged in plural in the thickness direction of the light diffusing element, so that the light can be made when the incident light passes through the light diffusing element. Multiple diffusion, as a result, sufficient light diffusibility can be obtained.

The standard deviation of the weight average particle diameter distribution of the light diffusing fine particles in the mixed liquid is preferably 1.0 μm or less, more preferably 0.5 μm or less, and still more preferably 0.1 μm or less. Further, the diffusing fine particles in the mixed liquid are preferably in a monodispersed state, and for example, a coefficient of variation ((standard deviation of particle diameter) × 100 / (average particle diameter)) of the weight average particle diameter distribution is preferably 20% or less. More preferably, it is 15% or less. When a large amount of light-diffusing fine particles having a small particle diameter with respect to the weight average particle diameter is mixed, the diffusibility is excessively increased, and the back scattering cannot be satisfactorily suppressed. When a large amount of light-diffusing fine particles having a large particle diameter with respect to a weight average particle diameter is mixed, it is not possible to arrange plurally in the thickness direction of the light diffusing element, and multiple diffusion cannot be obtained. As a result, light diffusibility exists. It is not enough.

As the shape of the light diffusing fine particles, any appropriate shape can be adopted depending on the purpose. Specific examples include a spherical shape, a scaly shape, a plate shape, an ellipsoid shape, and an amorphous shape. In many cases, spherical fine particles can be used as the light diffusing fine particles.

The refractive index of the light diffusing fine particles is preferably from 1.30 to 1.70, more preferably from 1.40 to 1.60.

The amount of the light diffusing fine particles in the mixed liquid is relative to the formed amount The base is 100 parts by weight, preferably 10 parts by weight to 100 parts by weight, more preferably 15 parts by weight to 40 parts by weight. A light diffusing element having a very excellent light diffusibility can be obtained by, for example, containing light diffusing fine particles having an average particle diameter of the above-described appropriate range in the above-described compounding amount.

As described above, the light diffusing fine particles are swollen by mixing with an organic solvent. The degree of swelling of the light-diffusing fine particles before the step B, that is, immediately before the light-diffusing fine particles and the resin component are in contact with each other, is preferably 105% to 200%. Further, in the step A, the light-diffusing fine particles are preferably in a state of being maximally swollen and not excessively swollen. When the light-diffusing fine particles are sufficiently swollen, in the next step B, the resin component precursor is easily infiltrated into the light-diffusing fine particles. In the present specification, the term "swelling degree" means the ratio of the average particle diameter of the particles in the swollen state to the average particle diameter of the particles before swelling.

The organic solvent content ratio of the light diffusing fine particles before the step B is preferably from 10% to 100%, more preferably from 70% to 100%. In the present specification, the "content ratio of the organic solvent of the light-diffusing fine particles" refers to the light-diffusing fine particles of the content (maximum content) of the organic solvent in the case where the content of the organic solvent in the light-diffusing fine particles is saturated. The organic solvent contains a ratio.

A-1-2. Organic solvent

As the organic solvent, any suitable organic solvent may be used as long as the light-diffusing fine particles are swelled to a desired extent and the light-diffusing fine particles and the respective components charged in the subsequent step B are dissolved or uniformly dispersed. . Specific examples of the organic solvent include ethyl acetate, butyl acetate, isopropyl acetate, 2-butanone (methyl ethyl ketone), methyl isobutyl ketone, cyclopentanone, toluene, and isopropanol. , n-butanol, water, etc.

In one embodiment, the boiling point of the organic solvent is preferably 70 ° C or higher, more preferably 100 ° C or higher, and particularly preferably 110 ° C or higher, and most preferably 120 ° C or higher. By using an organic solvent having a relatively low volatility, it is possible to prevent rapid volatilization when the organic solvent is dried, and a light diffusing element excellent in smoothness can be obtained.

In another embodiment, a mixed solvent can be used as the organic solvent. Make For the solvent to be mixed, for example, a solvent obtained by mixing (the first organic solvent) which is easily permeated into the light-diffusing fine particles and an organic solvent having a low volatility (the second organic solvent) can be used. The first organic solvent is preferably more permeable to light diffusing fine particles than the second organic solvent and has a high volatility. It is preferable that the second organic solvent is more difficult to permeate into the light diffusing fine particles than the first organic solvent and has a low volatility. When such a mixed solvent is used, swelling of the light-diffusing fine particles can be promoted (even if the production step is shortened), and rapid evaporation of the organic solvent can be prevented to obtain a light-diffusing element which is more excellent in smoothness. The boiling point of the first organic solvent is preferably 80 ° C or lower, more preferably 70 ° C to 80 ° C. The boiling point of the second organic solvent is preferably higher than 80 ° C, more preferably 100 ° C or higher, further preferably 110 ° C or higher, and most preferably 120 ° C or higher. Further, the ease of permeation of the organic solvent can be compared, for example, by the degree of swelling of the organic solvent corresponding to the light-diffusing fine particles, and the organic solvent which swells the light-diffusing fine particles with a higher degree of swelling can be said to be easily permeable to light diffusibility. An organic solvent in the microparticles. Further, the organic solvent having a solubility parameter (SP value) close to the SP value of the light diffusing fine particles tends to be easily penetrated into the light diffusing fine particles. The difference between the SP value of the first organic solvent and the SP value of the light diffusing fine particles is preferably 0.5 or less, more preferably 0.4 or less, still more preferably 0.1 to 0.4. The difference between the SP value of the second organic solvent and the SP value of the light diffusing fine particles is preferably more than 0.5, more preferably 0.6 or more, still more preferably 0.7 to 2.0. Further, an organic solvent having a relatively low molecular weight tends to easily penetrate into the light diffusing fine particles. The molecular weight of the first organic solvent is preferably 80 or less, more preferably 75 or less, still more preferably 50 to 75. The molecular weight of the second organic solvent is preferably higher than 80, more preferably 100 or more, still more preferably 110 to 140.

The above mixture may further contain any appropriate additives as needed. Specific examples of the additive include an initiator, a dispersant, an anti-aging agent, a modifier, a surfactant, an anti-tarnishing agent, an ultraviolet absorber, a leveling agent, and an antifoaming agent.

A-2. Step B

In the step B, the mixture prepared in the above step A and the resin component are contained. The precursor (monomer) and the matrix forming material of the ultrafine particle component are mixed, and a coating liquid obtained by dissolving or dispersing the swelled light diffusing fine particles, the resin component precursor and the ultrafine particle component in the organic solvent is prepared. (Dispersions). Typically, the coating liquid is a dispersion in which an ultrafine particle component and light diffusing fine particles are dispersed in a precursor and an organic solvent. Any means suitable for dispersing the ultrafine particle component and the light diffusing fine particles may be employed (for example, a stirring treatment).

Preferably, at least a part of the resin component precursor is infiltrated into the inside of the light diffusing fine particles by the step after the step B. In one embodiment, it is conceivable that at least a part of the resin component precursor is infiltrated into the inside of the light diffusing fine particles in the step B. In the present invention, by pre-swelling the light-diffusing fine particles in the above step A, the resin component precursor can be infiltrated into the inside of the light-diffusing fine particles in a short time. For example, in the step B, the resin component precursor can be infiltrated into the inside of the light diffusing fine particles by stirring the coating liquid for 15 minutes to 30 minutes. The coating liquid prepared in this manner can be supplied to the subsequent step C immediately after stirring, that is, without standing. Therefore, it is possible to prevent the light-diffusing fine particles and the ultrafine particle components from aggregating, and it is possible to obtain a light-diffusing element which is excellent in smoothness, has no density of ultrafine-particle components, and has less back-scattering.

The permeation range of the precursor in the light diffusing fine particles is preferably 10% or more, more preferably 50% or more, still more preferably 80% to 100%. When it is in the above range, the concentration modulation region can be favorably formed to suppress backscattering. In the present invention, when the light diffusing element is produced, the light diffusing fine particles are sufficiently swollen by the organic solvent, and then the resin component in the matrix is polymerized, whereby the resin component can be sufficiently infiltrated into the light diffusing fine particles. The penetration range can be controlled by adjusting the resin component and the material of the light diffusing fine particles, the crosslinking density of the light diffusing fine particles, the type of the organic solvent used in the production, and the like.

The solid content concentration of the coating liquid can be adjusted so as to be about 10% by weight to 70% by weight. If it is the above-mentioned solid content density, the coating liquid which has the viscosity which is easy to apply can be obtained.

A-2-1. Resin composition

The above resin component is composed of any suitable material. The resin component preferably has a refractive index satisfying the relationship of the above formula (1).

The resin component is preferably composed of a compound which is homologous to the light diffusing fine particles. Further, the resin component is preferably composed of a compound having high compatibility with a compound of the same type as the light diffusing fine particles. Thereby, since the resin component is a material which is the same as the light-diffusing fine particles, the precursor thereof can penetrate into the inside of the light-diffusing fine particles. The precursor is polymerized by the following polymerization step, and as a result, a concentration-modulating region can be favorably formed in the vicinity of the interface between the substrate and the light-diffusing fine particles. For example, when the resin constituting the resin component of the matrix is an acrylate-based resin, the light-diffusing fine particles are preferably made of an acrylate-based resin.

The resin component is preferably composed of an organic compound, and more preferably composed of a free ray-curable resin. The free ray-curable resin-based coating film is excellent in hardness. Examples of the free ray include ultraviolet light, visible light, infrared light, and an electron beam. Ultraviolet rays are preferred, and therefore the resin component is preferably composed of an ultraviolet curable resin. Examples of the ultraviolet curable resin include a radical polymerizable monomer or oligomer such as an acrylate resin (epoxy acrylate, polyester acrylate, acrylic acrylate, or ether acrylate). Specific examples of the monomer component (precursor) constituting the acrylate resin include pentaerythritol triacrylate (PETA), neopentyl glycol diacrylate (NPGDA), dipentaerythritol hexaacrylate (DPHA), and dipentaerythritol. Acrylate (DPPA), Trimethylolpropane Triacrylate (TMPTA). Such a monomer component (precursor) is preferred because it has a suitable molecular weight and a three-dimensional structure suitable for penetration into the interior of the light diffusing fine particles.

The molecular weight of the resin component precursor (monomer) is preferably from 100 to 700, more preferably from 200 to 600, still more preferably from 200 to 500. When it is in the above range, the resin component precursor (monomer) easily permeates into the inside of the light diffusing fine particles, and a light diffusing element excellent in diffusibility can be obtained.

The refractive index of the above resin component is preferably from 1.40 to 1.60.

The amount of the resin component in the coating liquid is preferably from 20 parts by weight to 80 parts by weight, more preferably from 45 parts by weight to 65 parts by weight, per 100 parts by weight of the substrate to be formed.

The resin component may contain a resin component other than the above-described free ray curable resin. The other resin component may be a free ray curable resin, may be a thermosetting resin, or may be a thermoplastic resin. Representative examples of other resin components include aliphatic (for example, polyolefin) resins and urethane resins. When a resin component is used, the kind or the amount of the compound can be adjusted so that the concentration modulation region is favorably formed and the refractive index satisfies the relationship of the above formula (1).

A-2-2. Ultrafine particle component

The ultrafine particle component can be representatively functioned as a component of the refractive index of the substrate. By using the ultrafine particle component, the refractive index of the matrix can be adjusted relatively easily, and the difference in refractive index between the light diffusing fine particles and the matrix can be made large. In particular, according to the present invention, since the resin component penetrates into the inside of the light-diffusing fine particles, the concentration of the ultrafine particle component in the matrix can be increased, so that the refractive index difference between the matrix and the light-diffusing fine particles can be easily increased. . As a result, a light diffusing element which is a film and has a high haze value (strong diffusibility) can be obtained. The ultrafine particle component preferably has a refractive index nB satisfying the following formula (2): 0 < | n _{P -} n _A | < | n _{P -} n _B |. . . (2)

In the formula (2), n _A and n _{P are} as described above. | n _{P -} n _B | is preferably 0.10 to 1.50, more preferably 0.20 to 0.80. When | n _{P -} n _B | is less than 0.10, the haze value is often 90% or less. As a result, the light from the light source cannot be sufficiently diffused when incorporated into the liquid crystal display device. And there is a narrower perspective. If | n _P -n _B | exceeds 1.50, there is a tendency for backscatter to increase. Moreover, it is preferable that the refractive index of the resin component, the ultrafine particle component, and the light diffusing fine particle satisfy the following formula (3). More preferably, the refractive index of the resin component, the ultrafine particle component, and the light diffusing fine particle satisfy the above formula (2) and the following formula (3). When the refractive index of the resin component, the ultrafine particle component, and the light diffusing fine particle is such a relationship, a light diffusing element that maintains a high haze and suppresses backscattering can be obtained.

| n _P -n _A |<| n _A -n _B |. . . (3)

The ultrafine particle component is preferably composed of a compound different from the above resin component and light diffusing fine particles, and more preferably composed of an inorganic compound. As a preferable inorganic compound, a metal oxide and a metal fluoride are mentioned, for example. Specific examples of the metal oxide include zirconia (refractive index: 2.19), alumina (refractive index: 1.56 to 2.62), titanium oxide (refractive index: 2.49 to 2.74), and cerium oxide (refractive index: 1.25~1.46). Specific examples of the metal fluoride include magnesium fluoride (refractive index: 1.37) and calcium fluoride (refractive index: 1.40 to 1.43). Since the metal oxide and the metal fluoride are less absorbed by light, and the organic compound such as the free ray-curable resin or the thermoplastic resin has a refractive index which is difficult to express, the refractive index difference between the light-diffusing fine particles and the matrix can be made large. . Further, since the metal oxide and the metal fluoride are appropriately dispersed in the resin component, the concentration-modulating region can be favorably formed in the vicinity of the interface between the light-diffusing fine particles and the substrate, and backscattering can be suppressed. A particularly preferred inorganic compound is zirconia. This is because the refractive index difference with the light-diffusing fine particles is large and the dispersibility with the resin component is appropriate, so that the concentration-modulated region having the desired characteristics (or structure) can be favorably formed.

The refractive index of the ultrafine particle component is preferably 1.40 or less or 1.60 or more, more preferably 1.40 or less or 1.70 to 2.80, particularly preferably 1.40 or less or 2.00 to 2.80. When the refractive index exceeds 1.40 or does not reach 1.60, the difference in refractive index between the light diffusing fine particles and the substrate becomes insufficient, and when the obtained light diffusing element is used for a liquid crystal display device of a collimated backlight front diffusing system, There is a problem that the light from the collimated backlight cannot be sufficiently diffused and the viewing angle is narrowed.

The ultrafine particle component may also be reduced in porosity by being made porous.

The average particle diameter of the ultrafine particle component is preferably from 1 nm to 100 nm, more preferably from 10 nm to 80 nm, and further preferably from 20 nm to 70 nm. Thus, by using an ultrafine particle component having an average particle diameter smaller than the wavelength of light, it is not possible to produce between the ultrafine particle component and the resin component. The geometrical optics reflect, refract, and scatter to obtain an optically uniform matrix. As a result, a light diffusing element having uniform optical properties can be obtained.

The ultrafine particle component preferably has good dispersibility with the above resin component. In the present specification, the term "good dispersibility" means that a coating liquid obtained by mixing the resin component, the ultrafine particle component, and an organic solvent is applied, and the solvent is dried and removed.

Preferably, the ultrafine particle component is subjected to surface modification. By performing surface modification, the ultrafine particle component can be well dispersed in the resin component, and the concentration modulation region can be favorably formed in the vicinity of the interface between the light diffusing fine particle and the substrate. As the surface modification means, any appropriate means can be employed as long as the effects of the present invention are obtained. In a representative case, the surface modification is carried out by applying a surface modifier to the surface of the ultrafine particle component to form a surface modifier layer. Specific examples of the preferred surface modifier include a coupling agent such as a decane coupling agent or a titanate coupling agent, and a surfactant such as a fatty acid surfactant. By using such a surface modifier, the wettability of the resin component and the ultrafine particle component can be improved, the interface between the resin component and the ultrafine particle component can be stabilized, and the ultrafine particle component can be well dispersed in the resin component.

The amount of the ultrafine particle component in the coating liquid is preferably from 10 parts by weight to 70 parts by weight, more preferably from 30 parts by weight to 60 parts by weight, per 100 parts by weight of the substrate to be formed.

A-3. Step C

In a representative case, the coating liquid is applied onto a substrate before the step C (the step of polymerizing the precursor). As the substrate, any appropriate film can be employed as long as the effects of the present invention are obtained. Specific examples thereof include a cellulose triacetate (TAC) film, a polyethylene terephthalate (PET) film, a polypropylene (PP) film, a nylon film, an acrylic film, a lactone-modified acrylic film, and the like. The substrate may be subjected to surface modification such as easy adhesion treatment as needed, and may include additives such as a lubricant, an antistatic agent, and an ultraviolet absorber.

As a method of applying the coating liquid to the substrate, a method using any appropriate coating machine can be employed. Specific examples of the coater include a bar coater, a reverse coater, a contact coater, a gravure coater, a die coater, and a notch coater.

Then, the above precursor is polymerized. The polymerization method may be any appropriate method depending on the kind of the resin component (hence, its precursor). For example, when the resin component is a free ray-curable resin, the precursor is polymerized by irradiation with free rays. When ultraviolet rays are used as the free ray, the cumulative amount of light is preferably 200 mJ to 400 mJ. The transmittance of the free ray to the light diffusing fine particles is preferably 70% or more, and more preferably 80% or more. Further, for example, when the resin component is a thermosetting resin, the precursor is polymerized by heating. The heating temperature and the heating time can be appropriately set depending on the type of the resin component. The polymerization is preferably carried out by irradiation with free rays. When it is irradiated with a free ray, the refractive index distribution structure (concentration modulation region) can be favorably maintained and the coating film can be directly cured, so that a light diffusion element having good diffusion characteristics can be produced. Preferably, the matrix is formed by polymerizing the precursor, and at the same time, a substantially spherical shell-like concentration is formed in the vicinity of the surface of the light diffusing fine particles as the weight concentration of the ultrafine particle component becomes higher as the distance from the light diffusing fine particles is increased. Modulation area. That is, according to the production method of the present invention, the above-mentioned precursor which penetrates into the light-diffusing fine particles and the precursor which does not penetrate into the light-diffusing fine particles can be simultaneously polymerized, and the above-mentioned interface between the substrate and the light-diffusing fine particles can be formed. The matrix is formed simultaneously with the concentration modulation region.

Needless to say, the method of manufacturing the light diffusing element of the present invention may include any suitable steps, processes, and/or operations at any suitable time in addition to the above steps A to C. The type of such steps and the like and the timing at which such steps are performed may be appropriately set depending on the purpose. For example, the method for producing a light diffusing element of the present invention further includes a step of heating the coating liquid applied to the substrate as needed. In one embodiment, the coating liquid can be dried by the heating. The above heating can be carried out, for example, before the polymerization step or after the polymerization step. The heating of the coating liquid is preferably carried out before the polymerization step. The reason is The heat penetration of the resin component precursor to the light diffusing fine particles can be promoted by heating. As the heating method of the above coating liquid, any appropriate method can be employed. The heating temperature is, for example, preferably 80 ° C or lower, more preferably 50 ° C to 70 ° C, and the heating time is, for example, 30 seconds to 5 minutes. According to the production method of the present invention, even in the case of heating at a low temperature, the penetration of the resin component precursor into the light diffusing fine particles can be promoted, and a light diffusing element having high diffusibility can be obtained.

In the above manner, the light diffusing element is coated on the substrate. The light diffusing element manufactured by the manufacturing method of the present invention has strong diffusibility and is excellent in smoothness. It is presumed that the mechanism for obtaining a light diffusing element excellent in smoothness is as follows. The light-diffusing fine particles which are sufficiently swollen with the organic solvent have fluidity in the coating liquid and can follow changes in the coating liquid surface (for example, changes in the coating liquid surface caused by drying). As a result, it is possible to prevent the light-diffusing fine particles of the present invention from protruding from the coating film, and to obtain a light-diffusing element excellent in smoothness. On the other hand, in the conventional light diffusing element produced by the light diffusing fine particles which does not sufficiently contain an organic solvent, the fluidity of the light diffusing fine particles in the coating liquid is low. When the coating liquid containing such light-diffusing fine particles is supplied to the drying step, the light-diffusing fine particles cannot follow the change in the coating liquid surface. As a result, the light-diffusing fine particles protrude from the coating film, and irregularities are generated on the surface of the light diffusing element.

In addition, by pre-swelling the light-diffusing fine particles in the above manner, the resin component precursor is easily infiltrated into the inside of the light-diffusing fine particles. The light-diffusing fine particles are further swollen by the penetration of the resin component precursor, and the average particle diameter is further increased. When the average particle diameter of the light diffusing fine particles is large, the light diffusing fine particles having a small number of light diffusing fine particles can be expressed. The light diffusing element having a small number of light diffusing fine particles included can suppress backscattering. In the present invention, the resin component existing in the periphery of the light-diffusing fine particles permeates into the light-diffusing fine particles, so that the resin component precursor does not permeate into the coating liquid applied to the substrate. The portion where the coating liquid surface of the light diffusing fine particles is in contact with each other. As a result, it is possible to prevent the light diffusing fine particles from protruding and increasing from the coating film without damaging For smoothness, there may be light diffusing fine particles having a large average particle diameter.

The obtained light diffusing element can be used as a single member by peeling off from the substrate, or can be used as a light diffusing element with a substrate, or can be transferred from a substrate to a polarizing plate or the like as a composite member (for example, a light-attached member) The polarizing plate of the diffusing element can be used as a composite member (for example, a polarizing plate with a light diffusing element) by being attached to a polarizing plate or the like together with a substrate. When it is attached to a polarizing plate or the like together with a substrate and used as a composite member (for example, a polarizing plate with a light diffusing element), the substrate functions as a protective layer of a polarizing plate.

B. Light diffusing element

The light diffusing element of the present invention can be obtained by the method described in the above items A-1 to A-3. The light diffusing element of the present invention has a matrix containing a resin component and an ultrafine particle component, and light diffusing fine particles dispersed in the matrix. The light diffusing element of the present invention exhibits a light diffusing function by a difference in refractive index between the substrate and the light diffusing fine particles. Fig. 1 is a schematic view for explaining a state of dispersion of a resin component and a light diffusing fine particle of a matrix in a light diffusing element obtained by a production method according to a preferred embodiment of the present invention. The light diffusing element 100 of the present invention has a matrix 10 containing a resin component 11 and an ultrafine particle component 12, and light diffusing fine particles 20 dispersed in the matrix 10. Preferably, the resin component of the matrix and the light diffusing fine particles have a refractive index satisfying the following formula (1): 0 < | n _{P -} n _A | . . (1)

Preferably, the ultrafine particle component has a refractive index satisfying the following formulas (2) and (3): 0 < | n _{P -} n _A | < | n _{P -} n _B |. . . (2)

| n _P -n _A |<| n _A -n _B |. . . (3)

By using the resin component of the matrix having the relationship of the above formula (1) and the light diffusing fine particles and using the ultrafine particle component having the relationship of the above formulas (2) and (3), it is possible to maintain high haze and suppress back scattering. Light diffusing element.

Preferably, as shown in FIG. 1 and FIG. 2, in the vicinity of the interface between the substrate and the light diffusing fine particles, the weight concentration of the ultrafine particle component is changed as it moves away from the light diffusing fine particles. The height is substantially a spherical shell-like concentration modulation region 30. Therefore, the matrix has a concentration-modulating region 30 in the vicinity of the interface with the light-diffusing fine particles, and a concentration-fixed region on the outer side of the concentration-modulating region 30 (the side away from the light-diffusing fine particles). The portion other than the concentration-modulating region 30 of the substrate is preferably substantially a concentration-fixed region. In the concentration modulation region 30, the refractive index changes substantially continuously. In the present specification, "the vicinity of the interface between the matrix and the light diffusing fine particles" includes the surface of the light diffusing fine particles, the outer portion near the surface, and the inner portion near the surface.

The concentration modulation region 30 is preferably formed in accordance with a substantial gradient of the dispersion concentration of the ultrafine particle component 12 in the matrix 10. Specifically, in the concentration modulation region 30, the dispersion concentration of the ultrafine particle component 12 (specifically, as defined by the weight concentration) becomes higher as it moves away from the light diffusing fine particles 20 (the weight concentration of the resin component 11 is inevitable) Go low). In other words, in the closest region of the light diffusing fine particles 20 of the concentration modulation region 30, the ultrafine particle component 12 is dispersed at a relatively low concentration, and the concentration of the ultrafine particle component 12 increases as it moves away from the light diffusing fine particles 20. For example, the area ratio of the ultrafine particle component 12 in the matrix 10 obtained by the transmission electron microscope (TEM) image is smaller on the side close to the light diffusing fine particles 20 and larger on the side close to the substrate 10, which is larger. The area ratio changes from a light diffusing fine particle side to a matrix side (concentration fixed region side) to form a substantial gradient. A TEM image showing a representative dispersion state thereof is shown in Fig. 3 . In the present specification, the "area ratio of the ultrafine particle component in the matrix obtained by the transmission electron microscope image" means in the transmission electron microscope image of the section including the diameter of the light diffusing fine particle. The ratio of the area of the ultrafine particle component to the matrix of a specific range (specific area). This area ratio corresponds to the three-dimensional dispersion concentration (actual dispersion concentration) of the ultrafine particle component. The area ratio of the ultrafine particle component can be obtained by any appropriate image analysis software. Further, the above area ratio is representatively corresponding to the average shortest distance between the particles of the ultrafine particle component. Specifically, the average shortest distance between the particles of the ultrafine particle component is shortened in the concentration modulation region as it moves away from the light diffusing fine particles, and is in the concentration fixed region. The domain is fixed (for example, the average shortest distance is about 3 nm to 100 nm in the closest region of the light diffusing microparticles, and 1 nm to 20 nm in the concentration region). With respect to the average shortest distance, the TEM image in the dispersed state of FIG. 3 can be binarized and calculated using, for example, the inter-center distance method of the image analysis software "A-like" (made by Asahi Kasei Engineering Co., Ltd.). As described above, according to the manufacturing method of the present invention, the concentration modulation region 30 can be formed in the vicinity of the interface between the substrate and the light diffusing fine particles by the substantial gradient of the dispersion concentration of the ultrafine particle component 12, and thus the GRIN can be manufactured by using a complicated manufacturing method. In contrast to the case where the microparticles disperse the GRIN microparticles, the light diffusing element can be produced in a particularly simple order and at a particularly low cost. Further, by forming the concentration modulation region by the gradient of the dispersion concentration of the ultrafine particle component, the refractive index can be smoothly changed at the boundary between the concentration modulation region 30 and the concentration fixed region. Further, by using an ultrafine particle component having a large difference in refractive index from the resin component and the light diffusing fine particles, the refractive index difference between the light diffusing fine particles and the matrix (substantially a concentration-fixed region) can be made large, and the concentration can be adjusted. The refractive index gradient of the variable region becomes steep.

The concentration modulation region can be formed by appropriately selecting a resin component of the matrix, a constituent material of the ultrafine particle component and the light diffusing fine particle, and chemical and thermodynamic properties. For example, a material having a high compatibility in a homologous material constitutes a resin component and light-diffusing fine particles, whereby a concentration-modulated region can be favorably formed. Further, the concentration-modulating region 30 is formed by, for example, the subsequent polymerization of the resin component 11 precursor (monomer) into the inside of the light-diffusing fine particle 20 as described in the above items A-1 to A-3. The thickness and concentration gradient of the concentration modulation region can be controlled by adjusting the chemical and thermodynamic properties of the resin component of the matrix and the light diffusing fine particles.

In the concentration modulation region 30, the refractive index changes substantially continuously as described above. Preferably, in addition to the above, the outermost refractive index of the concentration modulation region is substantially the same as the refractive index of the concentration fixed region. In other words, in the above light diffusing element, the refractive index continuously changes from the concentration modulation region to the concentration fixed region, preferably refraction. The rate is continuously changed from the light diffusing fine particles (more preferably, the inside of the vicinity of the surface of the light diffusing fine particles) to the concentration fixed region (Fig. 4). The refractive index change is preferably as stable as shown in FIG. That is, at the boundary between the concentration modulation region and the concentration-fixed region, the shape of the tangent line changes on the refractive index change curve. Preferably, in the concentration modulation region, the gradient of the refractive index change becomes larger as it goes away from the light diffusing fine particles. According to the light diffusing element of the present invention, a substantially continuous refractive index change can be realized by appropriately selecting the light diffusing fine particles, the resin component of the matrix, and the ultrafine particle component. As a result, even if the refractive index difference between the matrix 10 (substantially the concentration-fixed region) and the light-diffusing fine particles 20 is increased, reflection at the interface between the matrix 10 and the light-diffusing fine particles 20 can be suppressed, and backscattering can be suppressed. Further, in the concentration-fixed region, since the weight concentration of the ultrafine particle component 12 having a large difference between the refractive index and the light-diffusing fine particles 20 is relatively high, the substrate 10 (substantially a concentration-fixed region) and the light-diffusing fine particles can be obtained. The refractive index difference of 20 becomes large. As a result, even if it is a film, a high haze (strong diffusibility) can be achieved. In the present specification, the term "the refractive index changes substantially continuously" means that the refractive index is substantially continuously changed from the light-diffusing fine particles to the concentration-fixed region at least in the concentration-modulating region. Therefore, for example, even at the interface between the light diffusing fine particles and the concentration modulation region, and/or the interface between the concentration modulation region and the concentration fixed region, there is a refractive index difference within a specific range (for example, a refractive index difference of 0.05 or less). This gap can also be tolerated.

The thickness of the concentration modulation region 30 (the distance from the innermost portion of the concentration modulation region to the outermost portion of the concentration modulation region) may be fixed (that is, the concentration modulation region may also expand into a concentric spherical shape around the light diffusing fine particles). Further, the thickness may be different depending on the position of the surface of the light diffusing fine particles (for example, it may be a peripheral shape of the golden sugar). The thickness of the concentration modulation region 30 is preferably different depending on the position of the surface of the light diffusing fine particles. According to this configuration, the refractive index can be continuously changed more smoothly in the concentration rate modulation region 30.

The average thickness of the concentration modulation region 30 is preferably 5 nm to 500 nm, more preferably 12 nm to 400 nm, and still more preferably 15 nm to 300 nm. If the average thickness is less than 5 nm, Then there is a case where the backscatter becomes large. If the average thickness exceeds 500 nm, there is a case where the diffusibility becomes insufficient. As described above, the light diffusing element of the present invention, although the average thickness of the concentration modulation region 30 is extremely thin, can realize a light diffusing element having a high haze value, a strong diffusibility, and a film for suppressing backscattering. The average thickness is an average thickness when the thickness of the concentration modulation region 30 differs depending on the position of the surface of the light diffusing fine particles, and is the thickness when the thickness is fixed.

The higher the haze value of the light diffusing element, the better, specifically, 70% or more, more preferably 90 to 99.5%, further preferably 92 to 99.5%, and particularly preferably 95 to 99.5%, preferably It is 97~99.5%. By using a haze value of 70% or more, it can be preferably used as a front light diffusing element in a collimated backlight front diffusion system. In addition, the collimated backlight front diffusing system refers to a collimated backlight (a backlight having a narrow half-width of brightness concentrated in a fixed direction) and a front side on the viewing side of the upper polarizing plate in the liquid crystal display device. A system of light diffusing elements.

The diffusion characteristics of the light diffusing element are preferably 10° to 150° (single side 5° to 75°), more preferably 10° to 100° (one side 5°), as indicated by the light diffusion half angle. ~50°), further preferably 30° to 80° (15° to 40° on one side).

The thickness of the above light diffusing element can be appropriately set depending on the purpose or the desired diffusion characteristics. Specifically, the thickness of the light diffusing element is preferably 4 μm to 50 μm, more preferably 4 μm to 20 μm. According to the present invention, although it is a very thin thickness as described above, a light diffusing element having a very high haze as described above can be obtained.

According to the production method of the present invention, a light diffusing element excellent in smoothness can be obtained. The light diffusing element excellent in smoothness as described above has less scattering in the back side.

The arithmetic mean surface roughness Ra of the above light diffusing element is preferably less than 0.05 mm, more preferably 0.04 mm or less, still more preferably 0.03 mm or less. The arithmetic mean surface roughness Ra of the light diffusing element is preferably as small as possible, but the practical lower limit is, for example, 0.001 mm. Furthermore, in the present specification, "arithmetic mean surface roughness Ra" is JIS B 0601 (1994) The arithmetic mean surface roughness Ra specified in the edition).

The ten-point average surface roughness Rz of the above light diffusing element is preferably less than 0.20 μm, more preferably less than 0.17 μm, and still more preferably less than 0.15 μm. The ten point average roughness Rz of the light diffusing element is preferably as small as possible, but the practical lower limit is, for example, 0.005 μm. In the present specification, the "ten-point average surface roughness Rz" is a ten-point average surface roughness Rz prescribed in JIS B 0601 (1994 edition).

The average tilt angle θa of the light diffusing element is preferably less than 0.50°, more preferably less than 0.45°, still more preferably 0.40° or less. The smaller the average inclination angle θa of the light diffusing element, the better, but the practical lower limit is, for example, 0.01°. In addition, in the present specification, the average inclination angle θa is defined by the following formula (4).

Θa=tan ^-1 △a. . . (4)

In the above formula (1), Δa is an adjacent peak as shown by the following formula (5), and the reference length L of the roughness curve defined in JIS B 0601 (1994 edition) The sum of the difference (h1+h2+h3...+hn) of the difference between the vertex and the lowest point of the trough (h1+h2+h3...+hn) is divided by the above-described reference length L. The above roughness curve is a curve obtained by removing a surface fluctuation component longer than a specific wavelength from a profile curve by a phase difference compensation type high-band filter. Further, the cross-sectional curve is a contour which is formed by the slit when the target surface is cut by a plane at right angles to the target surface.

△a=(h1+h2+h3...+hn)/L. . . (5)

In one embodiment, the light diffusing element has a ten point average surface roughness Rz of preferably less than 0.20 μm, more preferably less than 0.17 μm, still more preferably less than 0.15 μm, and the average tilt angle θa is preferably It is less than 0.5°, more preferably less than 0.45°, and still more preferably less than 0.40°.

The light diffusing element can be preferably used for a viewing side member of a liquid crystal display device, a backlight member for a liquid crystal display device, a diffusing member for a lighting fixture (for example, an organic EL, LED), and particularly preferably used as a front side diffusion of a collimated backlight. The front diffusing element of the system. Above The light diffusing element may be provided alone as a film or plate member, or may be attached to any suitable substrate or polarizing plate as a composite member. Further, an antireflection layer may be laminated on the light diffusing element.

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited by the examples. The evaluation methods in the examples are as follows. Further, the "parts" and "%" in the examples are based on weight unless otherwise specified.

(1) Thickness of light diffusing element

The total thickness of the substrate and the light diffusing element was measured by a micrometer thickness gauge (manufactured by Mitutoyo Co., Ltd.), and the thickness of the light diffusing element was calculated by subtracting the thickness of the substrate from the total thickness.

(2) Haze value

The measurement was carried out by a haze meter (manufactured by Murakami Color Research Institute Co., Ltd., trade name "HN-150") according to the method specified in JIS 7136.

(3) Backscattering rate

The laminate of the light-diffusing element and the substrate obtained in the examples and the comparative examples was bonded to a black acrylic plate (manufactured by Sumitomo Chemical Co., Ltd., trade name "SUMIPEX" (registered trademark), thickness 2 mm) via a transparent adhesive. It is used as a measurement sample. The integral reflectance of the measurement sample was measured by a spectrophotometer (manufactured by Hitachi Instruments Co., Ltd., trade name "U4100"). On the other hand, a laminate of a substrate and a transparent coating layer was prepared by using a coating liquid from which the fine particles were removed from the coating liquid for a light-diffusing element, and the integrated reflectance was measured in the same manner as above. Surface reflectance). The backscattering ratio of the light diffusing element was calculated by subtracting the integrated reflectance (surface reflectance) of the above-mentioned control sample from the integrated reflectance of the above-mentioned measurement sample.

(4) Ten point average surface roughness Rz, arithmetic mean surface roughness Ra, and average tilt angle θa

Micro-shape measuring machine (manufactured by Otaru Research Co., Ltd., trade name "Surf" Corder ET-4000") The ten point average surface roughness Rz, the arithmetic mean surface roughness Ra, and the average tilt angle θa were measured.

(5) The density of ultrafine particles

The laminate of the light-diffusing element obtained in the examples and the comparative examples and the substrate was cooled with liquid nitrogen, and cut into a thickness of 0.1 μm using a microtome as a measurement sample. A two-dimensional image was observed using a transmission electron microscope (TEM) (manufactured by Hitachi, Ltd., trade name "H-7650", acceleration voltage: 100 kV) for the cross section of the measurement sample, and the light diffusion element of the measurement sample was confirmed. The generation of sparseness. In the measurement field of direct magnification × 1,200, MAGNIFICATION × 10,000 (13.9 μm × 15.5 μm), the portion which is observed as a white spot in the absence of the ultrafine particle component in the matrix (that is, the light diffusing fine particle in the measurement field of view) The number of white points other than the white part is counted. With respect to the laminate of the light-diffusing element and the substrate obtained in the examples and the comparative examples, the number of white spots was counted at 20 points as described above, and the average value was calculated. The average value is shown in Table 1. The more the number of white spots, the more the density of the ultrafine particle components is evaluated.

(6) Contrast of the bright spot (Production of liquid crystal display device)

A commercially available liquid crystal television (manufactured by SONY, Bravia 20, trade name "KDL20J3000") having a liquid crystal cell of a multi-region type vertical alignment mode takes out liquid crystal cells, and has respective polarizers on both sides of the liquid crystal cell A polarizing plate (manufactured by Nitto Denko Corporation, trade name "NPF-SEG1423DU") manufactured by Nitto Denko Co., Ltd. is attached to the absorption axis. More specifically, the absorption axis direction of the polarizer of the backlight-side polarizing plate is perpendicular (90° with respect to the longitudinal direction of the liquid crystal panel), and the absorption axis direction of the polarizer of the viewing-side polarizing plate is horizontal (with liquid crystal) The longitudinal direction of the panel is 0°). Further, on the outside of the viewing-side polarizing plate, a light-diffusing element of the examples and the comparative examples was transferred and bonded from the substrate to produce a liquid crystal panel.

On the other hand, on the single side of the PMMA sheet, the pattern of the lenticular lens using the transfer roller is used. Melt heat transfer is performed. On the surface (smooth surface) opposite to the surface on which the lens pattern is formed, the aluminum pattern is vapor-deposited so that the light passes only through the focus of the lens, and the area ratio of the opening portion is 7% (the area ratio of the reflection portion is 93%). The reflective layer. A concentrating element is produced in this manner. A cold cathode fluorescent lamp (CCFL manufactured by Sony Corporation, BRAVIA 20J) was used as a light source of the backlight, and a light collecting element was mounted on the light source to produce a collimated light source device (backlight unit) that emits collimated light.

A liquid crystal display device in which the backlight unit is incorporated in the liquid crystal panel to form a collimated backlight front diffusion system.

(measurement of contrast)

The fluorescent lamp (200lx: measured value of the illuminometer IM-5) was placed and irradiated so that the emitted light was incident at an angle of 15° with respect to the direction perpendicular to the liquid crystal display device, and the black display was measured by ConoScope manufactured by AUTRONIC MELCHERS. And the brightness of the white display is used to evaluate the contrast.

<Example 1>

15 parts of polymethyl methacrylate (PMMA) fine particles (manufactured by Sekisui Chemicals, Inc., trade name "XX131AA", average particle diameter 2.5 μm, refractive index 1.49) as light diffusing fine particles, and acetic acid as an organic solvent 30 parts of a mixed solvent of butyl ester and MEK (weight ratio 50/50) was mixed, and stirred for 60 minutes to prepare a mixed solution.

Then, a hard coating resin (manufactured by JSR Corporation, trade name "Opstar KZ6661") containing 62% of zirconia nanoparticles as an ultrafine particle component (average particle diameter: 60 nm, refractive index: 2.19) was added to the obtained mixture. (containing MEK/MIBK)) 100 parts of pentaerythritol triacrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., trade name "Viscoat #300", refractive index 1.52, molecular weight 298) as a resin component precursor, 22 parts, photopolymerization 0.5 part of a starter (manufactured by Ciba Specialty Chemical Co., Ltd., trade name "Irgacure 907") and 0.5 part of a leveling agent (manufactured by DIC Corporation, trade name "GRANDIC PC 4100"), and a coating liquid was prepared by stirring for 15 minutes using a disperser. .

Immediately after the preparation of the coating liquid, it was applied to a TAC film (manufactured by FUJI FILM Co., Ltd., trade name "Fujitac") using a bar coater, and heated at 60 ° C for 1 minute, and then irradiated with ultraviolet light having a cumulative light amount of 300 mJ. Light diffusing element with a thickness of 10 μm. The obtained light diffusing element was subjected to the evaluation of the above (2) to (6). Further, a TEM photograph of a cross section of the light diffusing element is shown in Fig. 5(a).

Further, the white luminance in the dark portion was set to 300 cd/m ² , and as a result, the black luminance was 0.3 cd/m ² and the contrast in the dark was 1000.

<Example 2>

Instead of pentaerythritol triacrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., trade name "Viscoat #300", refractive index 1.52, molecular weight 298) as a precursor of the lipid component, dipentaerythritol hexaacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.) was used. A light diffusing element was obtained in the same manner as in Example 1 except that the trade name "NK ester", refractive index 1.52, molecular weight 632). The obtained light diffusing element was subjected to the evaluation of the above (2) to (6). The results are shown in Table 1.

<Example 3>

A light diffusing element was obtained in the same manner as in Example 1 except that 30 parts of MEK was used instead of 30 parts of a mixed solvent of butyl acetate and MEK as an organic solvent (weight ratio: 50/50). The obtained light diffusing element was subjected to the evaluation of the above (2) to (6). The results are shown in Table 1.

<Comparative Example 1>

100 parts of a hard coating resin (manufactured by JSR Corporation, trade name "Opstar KZ6661" (including MEK/MIBK)) containing 62% of zirconia nanoparticles as an ultrafine particle component (average particle diameter: 60 nm, refractive index: 2.19) Addition of a 50% MEK solution of pentaerythritol triacrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., trade name "Viscoat #300", refractive index 1.52) as a resin component precursor, and a photopolymerization initiator (Ciba Specialty) 0.5 parts manufactured by Chemical Company, trade name "Irgacure 907", a leveling agent (manufactured by DIC Corporation, trade name "GRANDIC PC 4100"), 0.5 parts, and a polymethyl methacrylate (PMMA) fine particle as a light-diffusing fine particle (manufactured by Sekisui Chemicals Co., Ltd., trade name "XX131AA", The average particle diameter is 2.5 μm and the refractive index is 1.49) 15 parts. The mixture was subjected to ultrasonic treatment for 5 minutes to prepare a coating liquid in which the above components were uniformly dispersed. The coating liquid was allowed to stand for 24 hours, and then applied to a TAC film (manufactured by FUJI FILM Co., Ltd., trade name "Fujitac") using a bar coater, and heated at 60 ° C for 1 minute, and then irradiated with a cumulative light amount of 300 mJ. Ultraviolet light to obtain a light diffusing element having a thickness of 10 μm. The obtained light diffusing element was subjected to the evaluation of the above (2) to (6). The results are shown in Table 1. Further, a TEM photograph of a cross section of the light diffusing element is shown in Fig. 5(b).

<Comparative Example 2>

100 parts of a hard coating resin (manufactured by JSR Corporation, trade name "Opstar KZ6661" (including MEK/MIBK)) containing 62% of zirconia nanoparticles as an ultrafine particle component (average particle diameter: 60 nm, refractive index: 2.19) In addition, 11 parts of a 50% butyl acetate solution of a pentaerythritol triacrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., trade name "Viscoat #300", refractive index 1.52) as a resin component precursor, and a photopolymerization initiator ( 0.5 parts manufactured by Ciba Specialty Chemical Co., Ltd., trade name "Irgacure 907"), 0.5 part of a leveling agent (manufactured by DIC Corporation, trade name "GRANDIC PC 4100"), and polymethyl methacrylate (PMMA) as light diffusing fine particles. 15 parts of fine particles (manufactured by Sekisui Chemicals Co., Ltd., trade name "XX131AA", average particle diameter 2.5 μm, refractive index 1.49). The mixture was subjected to ultrasonic treatment for 5 minutes to prepare a coating liquid in which the above components were uniformly dispersed. The coating liquid was allowed to stand for 72 hours, and then applied to a TAC film (manufactured by FUJI FILM Co., Ltd., trade name "Fujitac") using a bar coater, and heated at 60 ° C for 1 minute, and then irradiated with an accumulated light amount of 300 mJ. Ultraviolet light to obtain a light diffusing element having a thickness of 10 μm. The obtained light diffusing element was subjected to the evaluation of the above (2) to (6). The results are shown in Table 1.

<Comparative Example 3>

After the preparation of the coating liquid, the light diffusion element was obtained in the same manner as in Comparative Example 1, except that the coating liquid was applied without being allowed to stand. The obtained light diffusing element was subjected to the evaluation of the above (2) to (6). The results are shown in Table 1.

<Comparative Example 4>

After the preparation of the coating liquid, the light diffusion element was obtained in the same manner as in Comparative Example 1, except that the coating liquid was applied without being allowed to stand, and the heating temperature was changed to 100 °C. The obtained light diffusing element was subjected to the evaluation of the above (2) to (6). The results are shown in Table 1. Further, a TEM photograph of a cross section of the light diffusing element is shown in Fig. 5(c).

According to the embodiment, it is clear that the light diffusing element having a high haze value and a high diffusibility can be produced by applying the coating liquid immediately after the coating liquid is prepared by the method for producing a light diffusing element of the present invention. Further, the light diffusing element obtained by the production method of the present invention is excellent in surface smoothness and less in backscattering. It is clear from the case where the density of the ultrafine particle component is small, and the method for producing the light diffusing element of the present invention is less likely to cause aggregation of the light diffusing fine particles and the ultrafine particle component, and therefore it is considered that the excellent characteristics as described above are obtained. Light diffusing element. Further, when a low molecular weight monomer is used as a resin component precursor, a light diffusing element which is more excellent in light diffusibility can be obtained (comparison of Examples 1 and 2). When using a solvent with a higher boiling point as the organic solvent of the mixed solution, A light diffusing element having a superior surface smoothness (comparison of Examples 1 and 3) was obtained. On the other hand, when the light diffusing fine particles, the resin component precursor, and the ultrafine particle component are simultaneously mixed as shown in the comparative example, the coating liquid is not allowed to stand for a specific period of time, or the heating after coating is improved. At the temperature, a sufficient haze value could not be obtained (Comparative Example 3). Further, when the coating liquid is allowed to stand for a certain period of time and the heating temperature after coating is increased, only the light diffusing element having a large back scattering is obtained by agglomeration of the light diffusing fine particles and/or the ultrafine particle components. (Comparative Examples 1, 2 and 4).

[Industrial availability]

The light diffusing element obtained by the manufacturing method of the present invention can be preferably used for a viewing side member of a liquid crystal display device, a backlight member for a liquid crystal display device, a diffusing member for a lighting fixture (for example, an organic EL, LED), and particularly It is preferably used as a front diffusing element for a collimated backlight front diffusing system.

10‧‧‧Material

11‧‧‧Resin composition

20‧‧‧Light diffusing microparticles

30‧‧‧Concentration zone

100‧‧‧Light diffusing elements

Claims (10)

A method for producing a light diffusing element, comprising: mixing a light diffusing fine particle with an organic solvent to prepare a mixed liquid, and swelling the light diffusing fine particle in the step A; and the mixed liquid and the resin containing the precursor and the super Step B of mixing the matrix forming material of the fine particle component; and Step C of polymerizing the resin component precursor to form a matrix comprising the resin component and the ultrafine particle component. The method for producing a light diffusing element according to claim 1, wherein the molecular weight of the resin component precursor is from 100 to 700. The method for producing a light diffusing element according to claim 1 or 2, wherein the organic solvent has a boiling point of 70 ° C or higher. The method for producing a light diffusing element according to claim 1 or 2, wherein the organic solvent is a mixed solvent of the first organic solvent and the second organic solvent, and the first organic solvent is more permeable to the above than the second organic solvent Among the light diffusing fine particles, the volatility is higher than that of the second organic solvent. The method for producing a light diffusing element according to claim 1 or 2, further comprising the step of heating the dispersion obtained by mixing the mixed liquid with a matrix forming material comprising the resin component precursor and the ultrafine particle component, And the heating temperature is 80 ° C or less. The method for producing a light diffusing element according to claim 1 or 2, wherein in the step C, a weight of the ultrafine particle component is formed in the vicinity of an interface between the substrate and the light diffusing fine particle away from the light diffusing fine particle The concentration becomes high and is substantially a spherical shell-like concentration modulation region. A light diffusing element obtained by the method of any one of claims 1 to 6. The winner has a haze value of 70% or more. The light-diffusing element of claim 7 has a ten-point average surface roughness Rz of less than 0.20 μm. The light diffusing element of claim 7 or 8 has an average tilt angle θa of less than 0.50°. The light diffusing element of claim 7 or 8 has an arithmetic mean surface roughness Ra of less than 0.05 mm.