JP6163097B2 - Light scattering layer coating - Google Patents

Description

  The present invention relates to a coating material for forming a light scattering layer.

  An organic EL element has a light-emitting element having a structure in which an organic light-emitting layer is sandwiched between a pair of electrodes on a transparent substrate, has a self-light-emitting function, and has low power consumption.

  Conventionally, in order to increase the light extraction efficiency from an organic light emitting layer, an organic EL element may be provided with a fine and periodic concavo-convex structure having a wavelength of visible light or less at the interface between an electrode and a transparent substrate. And in order to form such a structure, the light-scattering layer which makes an uneven structure may be provided on a transparent substrate.

Conventionally, a layer containing fine particles has been proposed as such a light scattering layer.
For example, Patent Document 1 describes a light scattering layer containing particles having a particle size of 80 to 700 nm or 150 nm to 8 μm.
For example, Patent Document 2 describes a light scattering layer containing inorganic fine particles of 5 nm to 50 nm.

JP 2006-286616 A JP 2011-39375 A

  However, it has been difficult to form a conventional light scattering layer as described in Patent Documents 1 and 2 on a substrate without unevenness. Therefore, it has been difficult to obtain uniformity of light scattering ability.

  An object of the present invention is to solve the above problems. That is, an object of the present invention is to provide a coating material for forming a light scattering layer, which can be formed on a substrate without unevenness, and thus can obtain a light scattering layer having a highly uniform light scattering ability.

The inventor has intensively studied to solve the above-mentioned problems, and has completed the present invention.
The present invention includes the following (1) to (3).
(1) Core-shell type silica titania particles obtained by treating the surface of titania particles having an average particle diameter of 100 to 500 nm determined by a dynamic light scattering method with alkoxysilane: 100 parts by mass;
Silica oligomer consisting of hydrolysis product of alkoxysilane: 5-50 parts by mass,
A coating material for forming a light scattering layer, comprising a high boiling point solvent having a boiling point of 100 ° C. or higher: 100 to 600 parts by mass.
(2) The light according to (1), wherein the core-shell type silica titania particles contain TiO ₂ and SiO ₂ at a ratio of SiO ₂ : 0.2 to 35 parts by mass with respect to TiO ₂ : 100 parts by mass. Scatter layer forming paint.
(3) The coating material for forming a light scattering layer according to (1) or (2) above, wherein the hydrolysis product of alkoxysilane constituting the silica oligomer has a weight average molecular weight of 700 or more and less than 5000.

  According to the present invention, since the dispersibility is high and the separation and settling of the paint does not easily occur, the light scattering layer can be formed without unevenness, and a light scattering layer having a highly uniform light scattering ability can be obtained. A paint can be provided.

2 is a photograph of a glass plate to which a light scattering layer forming coating material of Example 1 is applied.

The present invention will be described.
The present invention relates to a core-shell type silica titania particle obtained by treating the surface of titania particles having an average particle diameter of 100 to 500 nm determined by a dynamic light scattering method with alkoxysilane: 100 parts by mass, hydrolysis product of alkoxysilane It is a coating material for light-scattering layer formation containing the silica oligomer which consists of: 5-50 mass parts and the high boiling point solvent whose boiling point is 100 degreeC or more: 100-600 mass parts.
Such a coating material for forming a light scattering layer is hereinafter also referred to as “the coating material of the present invention”.

The core-shell type silica titania particles contained in the paint of the present invention will be described.
The core-shell type silica titania particles are obtained by surface-treating the titania particles, which are nuclei (core), with alkoxysilane, and have a layer made of alkoxysilane as a shell (shell) on the surface of the titania particles.

Titania particles mean particles made of titanium oxide. The titanium oxide is preferably in the form of TiO ₂ , but may not be one in which titanium atoms and oxygen atoms are bonded at a molar ratio of 1: 2.

  The titania particles have an average particle size of 100 to 500 nm determined by a dynamic light scattering method. The average particle diameter is preferably 100 to 400 nm, and more preferably 150 to 300 nm.

Here, the average particle diameter obtained by the dynamic light scattering method means an average particle diameter measured and calculated by the following method.
1.5 g of titania water sol having a solid content of 20% by mass was diluted to 20 g with an aqueous solution of pH 11, and 14 drops (about 0.5 to 1.0 ml) of tetramethylammonium hydroxide (TMAH) were added, and ultrasonic waves were applied. Take 3 minutes. Thereafter, the light intensity pattern of the titania water sol is measured with a laser diffraction particle size distribution analyzer, the particle size distribution (volume basis) is determined by the dynamic light scattering method, and the average particle diameter (median diameter) is determined.

  The core-shell type silica titania particles have a layer made of alkoxysilane on the surface of the titania particles as described above.

Alkoxysilane is R _a Si (OR ′) _4-a (where R is a vinyl group, aryl group, acrylic group, alkyl group having 1 to 8 carbon atoms, hydrogen atom or halogen atom, and R ′ is a vinyl group) , An aryl group, an acrylic group, an alkyl group having 1 to 8 carbon atoms, —C ₂ H ₄ OC _n H _{2n + 1} (n = 1 to 4) or a hydrogen atom, and a is an integer of 0 to 3. ) Is preferable.

  Such alkoxysilanes include tetramethoxysilane, tetraethoxysilane (TEOS), tetraisopropoxysilane, tetrabutoxysilane, tetraoctylsilane, methyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, methyltriisoiso Examples include propoxysilane, vinyltrimethoxysilane, phenyltrimethoxysilane, and dimethyldimethoxysilane.

  A specific method for surface treatment of titania particles with alkoxysilane will be described later.

In the core-shell type silica titania particles obtained by surface-treating titania particles with alkoxysilane, the ratio of the content of titania and silica is not particularly limited, but SiO ₂ is 0.2 to 35 with respect to 100 parts by mass of TiO _2. It is preferable to include by the ratio of a mass part, It is more preferable to include by 0.2-10 mass parts, It is further more preferable to include by 0.2-5 mass parts.

Wherein the content of TiO ₂ and SiO ₂ core-shell silica titania particles comprise measures the concentration of Ti or Si contained in the core-shell silica titania particles using an ICP emission spectrophotometer, each of the total amount TiO ₂ or Assume that the oxide is in the form of SiO ₂ .

  The coating material of the present invention containing such core-shell type silica titania particles has high dispersibility and is unlikely to cause separation and settling of the coating material.

The silica oligomer contained in the coating material of the present invention will be described.
The silica oligomer consists of a hydrolysis product of alkoxysilane.
As the alkoxysilane, the same alkoxysilane as that coated on the surface of the titania particles can be used. However, the alkoxysilane that forms the core-shell type silica titania particles and the alkoxysilane that forms the silica oligomer may be different, but are preferably the same. This is because the mixed (dispersed) state can be more stable in the coating material for forming the light scattering layer.

  A silica oligomer consists of a hydrolysis product (partial hydrolysis product, hydrolysis polycondensation product, etc.) obtained by hydrolyzing at least a part of such alkoxysilane.

  It is preferable that the weight average molecular weight of the hydrolysis product of the alkoxysilane which comprises a silica oligomer is 700 or more and less than 5000, It is more preferable that it is 1000-4000, It is further more preferable that it is 2000-3500. In such a range, the separation between the core-shell type silica titania particles and the silica oligomer is less likely to occur in the coating material, and the strength can be increased during film formation.

The high boiling point solvent contained in the paint of the present invention will be described.
The high boiling point solvent is not particularly limited as long as it has a boiling point of 100 ° C. or higher. Examples of such a solvent include 1-methoxy-2-propanol, isopropyl alcohol, diacetone alcohol (DAA), and ethylene glycol.

The coating material of the present invention contains the above core-shell type silica titania particles, silica oligomer and high boiling point solvent in a specific mass ratio.
The silica oligomer is contained in an amount of 5 to 50 parts by mass, preferably 5 to 35 parts by mass, and more preferably 10 to 20 parts by mass with respect to 100 parts by mass of the core-shell type silica titania particles.
The high boiling point solvent is contained in an amount of 100 to 600 parts by mass, preferably 150 to 400 parts by mass, and more preferably 200 to 300 parts by mass with respect to 100 parts by mass of the core-shell type silica titania particles.

  The coating material of the present invention may contain methanol, ethanol, denatured alcohol, and water as other components in addition to the core-shell type silica titania particles, silica oligomer, and high boiling point solvent as described above. The other components are preferably contained in an amount of 500 parts by mass or less with respect to 100 parts by mass of the core-shell type silica titania particles.

Such a coating material of the present invention is excellent in dispersibility and hardly causes aggregation and sedimentation, so that it can be applied uniformly on a substrate. Therefore, the light scattering layer on the substrate obtained from this is excellent in the uniformity of light scattering.
Further, it is considered that the light scattering performance is high even if the film is not thickened. Specifically, the film thickness is preferably 100 to 1000 nm, and more preferably 250 to 700 nm. Moreover, it is thought that intensity | strength is high.

Next, the manufacturing method of the coating material of this invention is demonstrated.
The paint of the present invention is preferably produced by the method described below.

A method for producing titania particles will be described.
First, an aqueous solution containing a titanium compound is prepared, and an acid, a base, or water is mixed therein and hydrolyzed to obtain a gel.

  Here, examples of the titanium compound include titanium salts such as titanium chloride, titanium tetrachloride, titanium sulfate, titanium hydride, and titanyl sulfate, and titanium alkoxides such as titanium tetraalkoxide, titanium tetraethoxide, and titanium tetraisopropoxide.

  Although the density | concentration of the titanium compound in aqueous solution is not restrict | limited, It is preferable that it is generally 20 mass% or less as an oxide, and it is more preferable that it is 10 mass% or less. When the concentration is too high, the viscosity of the gel when hydrolyzed becomes high, and it becomes difficult to obtain titania particles having a desired form. In addition, the fine particles contained in the obtained paint of the present invention may aggregate, and in this case, the film formation may not be easy.

Next, the titanium compound is hydrolyzed. Hydrolysis of the titanium compound can be performed by mixing an aqueous solution with an acid or base, or water. As the base, an aqueous alkali metal solution such as NaOH, KOH, Na ₂ CO ₃ , ammonia, tetramethylammonium hydroxide or the like can be used. As the acid, hydrochloric acid, nitric acid, sulfuric acid and the like can be used.
Moreover, although the temperature at the time of mixing does not have a restriction | limiting in particular, It is preferable to carry out at 10-40 degreeC,
More preferably, it is carried out at 15 to 30 ° C.
Further, the pH at this time is preferably 8 to 11, and more preferably 8.5 to 10.

  Next, it is preferable to wash the gel obtained by hydrolysis. The salt generated by washing or alcohol can be removed. The washing method is not particularly limited as long as the generated salt, alcohol, or the like can be removed, and a conventionally known method can be adopted. For example, the produced gel dispersion can be filtered and washed with pure water or dilute ammonia water.

  After washing, the gel becomes cake-like, but it is preferable to add pure water or the like to make a slurry. In this case, the solid content concentration in the slurry is preferably 0.1 to 10% by mass, more preferably 0.5 to 8% by mass, and further preferably 1 to 5% by mass.

Next, an oxidizing agent is added and heated to dissolve the slurry gel.
The oxidizing agent is preferably hydrogen peroxide.
When hydrogen peroxide is used as the oxidizing agent, the amount of hydrogen peroxide used is not particularly limited as long as the gel can be dissolved, but the mass of hydrogen peroxide (H ₂ O ₂ ) and the oxide of the gel (TiO ₂ ). The mass ratio (H ₂ O ₂ / TiO ₂ ) is preferably 1 to 40, and more preferably 2 to 30.

  Although the heating temperature at the time of melt | dissolving a gel changes also with the usage-amount of an oxidizing agent (hydrogen peroxide is preferable), it is preferable that it is 30-100 degreeC, and it is more preferable that it is 80-99 degreeC. In addition, although melt | dissolution time changes also with temperature, it is 0.5 to 12 hours normally.

Next, it is preferable to add a quaternary alkyl ammonium compound (TAA). This is because the crystallinity of the titanium oxide is increased during the hydrothermal treatment.
Also, the moles of quaternary alkylammonium compound (TAA) (M _AR), the molar ratio of the moles of TiO ₂ of the number of moles _{(M T) ((M AR} ) / (M T)) is 0.05 It is preferable to add so that it may become the range of -5.
Examples of the quaternary alkylammonium compound include tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide, and tetrapropylammonium hydroxide.

Next, hydrothermal treatment is performed. Here, the hydrothermal treatment temperature is preferably 100 to 300 ° C, and more preferably 150 to 280 ° C. Although the hydrothermal treatment time varies depending on the temperature, it is generally 1 to 200 hours.
After hydrothermal treatment, it is preferable to cool to room temperature.

Next, the pH is adjusted to the acidic side using an acid. Specifically, the pH is preferably 0.2 to 2.5, more preferably 0.5 to 1.5.
Here, the acid may be a conventionally known acid. For example, an aqueous hydrochloric acid solution, an aqueous sulfuric acid solution, an aqueous nitric acid solution, or the like can be used.

  Thereafter, the aqueous solvent is separated and removed as necessary. Further, a non-aqueous solvent is added as necessary. The non-aqueous solvent to be added may be a conventionally known one, and for example, methanol, ethanol or the like can be used.

  In addition, it is preferable to wash the dispersion (liquid containing titania particles) obtained by adjusting the acid before or while adding the non-aqueous solvent. For example, after concentrating using a centrifuge, the dispersion can be washed by performing an operation of recovering the solid content once or more. In addition to the centrifuge, this washing can be performed using an outer membrane.

By such a method, a dispersion containing titania particles (titania particle dispersion) is obtained.
The concentration of titania particles contained in the titania particle dispersion is preferably 1 to 30% by mass, more preferably 2 to 20% by mass, and even more preferably 5 to 15% by mass.

A method for producing core-shell type silica titania particles will be described.
The titania particle dispersion obtained as described above is treated with alkoxysilane. For example, there is a method in which alkoxysilane is added to the titania particle dispersion and mixed with stirring. The stirring and mixing may be performed at room temperature, but is preferably performed by heating to 20 to 40 ° C. (preferably about 30 ° C.).

Here, it is preferable to mix so that the ratio (SiO ₂ / TiO ₂ ratio) of the mass of TiO ₂ contained in the titania particle dispersion and the mass of SiO ₂ contained in the alkoxysilane is 0.01 to 6.4. . This ratio is preferably 0.15 to 3, more preferably 0.15 to 0.5, and still more preferably about 0.02.

The SiO ₂ concentration in the core-shell type silica titania particles (present as solid content) contained in this dispersion is preferably 0.05 to 10% by mass, and 0.1 to 5% by mass with respect to TiO ₂ . Is more preferable, it is more preferable that it is 0.5-3 mass%, and it is further more preferable that it is about 0.8 mass%.
Here, SiO ₂ concentration determines the amount of Si silica titania particles includes, all of which means a value obtained by calculating the mass was assumed to be present as SiO _2.

  A method for producing a silica oligomer comprising a hydrolysis product of alkoxysilane will be described.

The silica oligomer can be obtained by hydrolyzing the alkoxysilane.
For example, it can be hydrolyzed by adding an acid or an alkali to the alkoxysilane and aging as necessary.

Next, a high boiling point solvent having a boiling point of 100 ° C. or higher is obtained.
A high boiling point solvent that can be used in the paint of the present invention can be used.

Next, the core-shell type silica titania particles, the silica oligomer, and the high boiling point solvent are mixed to obtain a coating material for forming a light scattering layer.
The method of mixing these is not particularly limited. For example, a conventionally known stirring method can be applied.

  Moreover, each mixing ratio shall be 5-50 mass parts of said silica oligomers, and 100-600 mass parts of said high boiling point solvent with respect to 100 mass parts of said core-shell type silica titania particles.

  Examples of the present invention will be described below, but the present invention is not limited to the following examples.

[Example 1]
<Preparation of titanium oxide fine particle dispersion>
183.5 g of titanium tetrachloride solution (TiO ₂ concentration: 27.8% by mass) is diluted with pure water until the TiO ₂ concentration becomes 8% by mass, and further 15% by mass so that the pH becomes 9.3. Aqueous ammonia water was added and mixed well to obtain a titanium oxide hydrate hydrogel slurry.
Next, the obtained titanium oxide hydrate hydrogel slurry was filtered and washed with pure water, and then purified water was added to the recovered cake to adjust the TiO ₂ concentration to 3% by mass.
Next, to 800 g of the obtained slurry, 400 g of a hydrogen peroxide solution having a concentration of 5% by mass is mixed, and then dissolved by heating at 95 ° C. for 2 hours, so that the concentration as TiO ₂ is 2% by mass. An acid aqueous solution was obtained.
Next, a TMAH aqueous solution having a concentration of 25% by mass was added so that the concentration of tetramethylammonium hydroxide (TMAH) was 0.1% by mass. And after aging at 240 degreeC for 96 hours using an autoclave, it cooled to normal temperature.
Next, the pH is adjusted to 1.0 using an aqueous nitric acid solution, and the supernatant is removed by solid-liquid separation using a centrifuge, and then the same amount of methanol as the removed supernatant is added to the solid content. Further, solid-liquid separation was performed using a centrifuge. Thereafter, the supernatant was removed, and methanol was added to the solid content so that the TiO ₂ concentration was 10% by mass, and this was recovered as a dispersion.
In this way, a titanium oxide fine particle dispersion was obtained.

  With respect to the titanium oxide fine particles contained in the obtained titanium oxide fine particle dispersion, the average particle size was determined by the above-described dynamic light scattering method using HORIBA LA-300 (manufactured by Horiba, Ltd.). As a result, the particle diameter was in the range of 100 to 600 nm, and the average particle diameter was 210 nm.

<Preparation of core-shell type silica titania particles>
While stirring the obtained titanium oxide fine particle dispersion, the ratio of the mass of TiO ₂ contained in the titanium oxide fine particle dispersion to the mass of SiO ₂ contained in TEOS (SiO ₂ / TiO ₂ ratio) becomes 0.02. Then, 0.8 g of tetraethoxysilane (TEOS) was added, and then the mixture was stirred at room temperature using a magnetic stirrer (manufactured by Asone, HPS-100) at a rotation speed of 500 rpm.
And after performing the centrifuge and removing a supernatant liquid, the same amount ethanol as the removed supernatant was added to solid content, and also solid-liquid separation was performed using the centrifuge. Thereafter, the supernatant was removed, and ethanol was added to the solid content so that the solid content concentration of TiO ₂ and SiO ₂ was 35 mass%, and this was recovered as a dispersion. The SiO ₂ concentration in the solid content contained in this dispersion was 0.8% by mass with respect to TiO ₂ .
In this way, a core-shell type silica titania particle dispersion was obtained.

<Preparation of silica-based binder>
1350 g of denatured alcohol (made by Nippon Alcohol Sales Co., Ltd., trade name: Solmix AP-11, composition: ethanol 85.5%, methanol 4.7%, isopropyl alcohol 9.8%) with a nitric acid concentration of 1.0% by mass After adding 300 g of nitric acid aqueous solution and stirring well, 350 g of tetraethoxysilane (TEOS) was further added and stirred for 2 hours to obtain a silica-based binder having a SiO ₂ concentration of 5 mass%.

<Preparation of coating material for forming light scattering layer>
The obtained core-shell type silica titania particle dispersion and silica-based binder were mixed. Here, mixing was performed so that the mass ratio (SiO ₂ / TiO ₂ ) of SiO ₂ contained in the silica-based binder and TiO ₂ contained in the core-shell type silica titania particle dispersion was 0.11. The total mass concentration of TiO ₂ (derived from the core-shell type silica titania particle dispersion) and SiO ₂ (derived from the core-shell type silica titania particle dispersion and the silica-based binder) in the solvent is 15% by mass. Methoxy-2-propanol (PGME), diacetone alcohol and ethanol were added. The mass ratio of ethanol, denatured alcohol, PGME, and diacetone alcohol contained in the solvent is 33.4: 33.4: 18.2: 15.
Thereafter, the solid content concentration is adjusted to 25% by mass using an evaporator, and propylene glycol and ethanol are added at a mass ratio of 7: 1, and TiO ₂ (derived from the core-shell type silica titania particle dispersion) in the solvent is added. After the total mass concentration of SiO ₂ (derived from the core-shell type silica titania particle dispersion and the silica-based binder) was 20% by mass, the light-scattering layer-forming coating material was prepared by stirring and mixing. In addition, the mass ratio of the low boiling point solvent (ethanol + denatured alcohol), PGME, diacetone alcohol, and propylene glycol which a solvent contains is 50: 25: 22: 3.

<Settling confirmation test>
10 ml of the obtained coating material for forming a light scattering layer was put in a glass bottle and allowed to stand for 2 hours. There was no water separation at the top of the paint, nor was there any sediment on the glass bottle bottom. It is conceivable that separation and sedimentation did not occur because the obtained paint was excellent in dispersibility.

<Application test>
Next, the obtained coating material for forming a light scattering layer was applied onto a glass plate with a bar coder (manufactured by Tester Sangyo Co., Ltd., ROD No. 7). The photograph of the glass plate which apply | coated the obtained coating material for light-scattering layer formation to FIG. 1 is shown.
Since the obtained coating material for forming a light scattering layer was excellent in dispersibility and hardly caused to aggregate or settle, it could be applied evenly as shown in FIG. Therefore, the film on the glass plate obtained by drying and baking this is excellent in the uniformity of light scattering.

Claims (2)

Core-shell type silica titania particles obtained by treating the surface of titania particles having an average particle diameter of 100 to 500 nm determined by a dynamic light scattering method with alkoxysilane: 100 parts by mass,
Silica oligomer consisting of hydrolysis product of alkoxysilane: 5-50 parts by mass,
A coating material for forming a light scattering layer, comprising a high boiling point solvent having a boiling point of 100 ° C. or higher: 100 to 600 parts by mass. The said core-shell type silica titania particles contain TiO ₂ and SiO ₂ at a ratio of SiO ₂ : 0.2 to 35 parts by mass with respect to TiO ₂ : 100 parts by mass. paint.