Light-colored photoluminescent material

Abstract

To provide a photoluminescent material which exhibits a beautiful light color under light and has good luminescent properties.SOLUTION: The present invention relates to a photoluminescent material comprising 19.3-54.3 wt.% of a polymer matrix, 45-80 wt.% of a photoluminescent compound, 0.5-15 wt.% of zirconium oxide, and 0.2-7 wt.% of an optical brightener, and optionally 0-5 wt.% of aluminum oxide, 0-0.3 wt.% of porous silica, a dye system, and additives, the total percentage of the dye system and additives being 0-15 wt.%. The invention also relates to an item coated with such photoluminescent material or made as a whole from such photoluminescent material.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a bright-colored photoluminescence material with optimized luminescence performance.

Background Art

[0002] In order to produce a photoluminescence material, a phosphorescent pigment of strontium aluminate doped with europium and dysprosium (Eu 2+ , Dy 3+ :SrAl2O4) is frequently used. Such pigments that emit green to blue light are often yellowish, making it difficult to obtain specific bright colors. Although the pigment can be whitened by adding a dopant such as calcium to the crystal lattice, this has a serious adverse effect on the luminescence performance.

[0003] It has been recognized that certain compounds used in photoluminescence materials containing dye pigments have properties that suppress luminescence properties. The luminescence of the energy storage material occurs as a result of the physicochemical interaction between the compounds of the photoluminescence material.

[0004] Therefore, it is difficult to optimize the coloring performance and the luminescence performance together. In order to develop a composition, the inventors of the present invention conducted tests to whiten the luminescent material using mineral compounds such as TiO2, CaCO3, ZnO, BaSO4, SiO2, and Al2O3. The mineral-based compounds were added to a type of phosphorescent pigment of strontium aluminate doped with 60% by weight of europium and dysprosium (Eu 2+ , Dy 3+ :SrAl2O4). Tests revealed that these mineral-based compounds have an adverse effect on the luminescence characteristics. Therefore, it is necessary to always find the optimum between the color perceived under light and photoluminescence.

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention consists of a novel composition for white, and more generally bright colors, which enables obtaining a beautiful bright color under light while having good light-emitting properties.

Means for Solving the Problems

[0006] Under such circumstances, the present invention proposes adding zirconium oxide (ZrO2), particularly stabilized zirconia, to the composition, and more specifically, adding 4 to 5 mol% of yttria-stabilized zirconia, a fluorescent brightening agent, and optionally aluminum oxide (Al2O3). By this combination, the best compromise point can be obtained between whiteness and light-emitting performance, and the yellowness of the pigment obtained from rare earth-doped alkaline earth aluminate can be suppressed. This color can be adjusted to a brighter shade optionally by adding a pigment system.

[0007] Specifically, the present invention relates to a photoluminescence material containing 19.3 to 54.3% by weight of a polymer matrix, 45 to 80% by weight of a photoluminescence compound, 0.5 to 15% by weight of zirconium oxide, 0.2 to 7% by weight of a fluorescent brightening agent, optionally 0 to 5% by weight of aluminum oxide, and 0 to 0.3% by weight of porous silica, a pigment system or an additive, and the total content of the pigment system and the additive is 0 to 15% by weight.

[0008] This fluorescent brightening agent is useful for achieving a glowing white color. This is because it absorbs light in the near-ultraviolet visible region and re-emits light in the blue region. In particular, this fluorescent brightening agent suppresses the yellowness of the energy storage pigment.

[0009] If Al2O3 is added, the composition can be whitened more strongly. When Al2O3 is added alone, the light emission rapidly quenches. To address this problem, it is necessary to use Al2O3 in combination with zirconia.

[0010] Optionally, the photoluminescence material further includes porous silica obtained from algae to enhance the luminescence properties. The porous silica is obtained from the skeletons of diatoms. These diatom skeletons are microalgae, which are single-celled organisms having a silica skeleton. In fact, according to the latest biological research, diatoms, which are single-celled algae that make up plankton, are composed of silica nanocells that can absorb sunlight very efficiently and perform photosynthesis efficiently even in the dark deep sea. By adding a limited proportion of porous silica of 1% by weight or less to the photoluminescence material, the luminescence properties can be improved.

[0011] The present invention further relates to an article entirely made of or coated with the photoluminescence material.

Embodiments for Carrying Out the Invention

[0012] The present invention relates to a photoluminescence material containing zirconium oxide (ZrO2). This material can be used to entirely make an article with this material and also to coat an article with this material. The article can be, for example, a component of a timepiece. In particular, the article can be an outer component selected from the group consisting of a middle part, a back part, a bezel, a crown, a push button, a bracelet link, a bracelet, a tang buckle, a clasp, a watch face, a flange, a date disk, a hand, and an index of the watch face. Note that these do not cover all of them.

[0013] The photoluminescence material includes a polymer matrix, a photoluminescence compound, zirconium oxide, a fluorescent brightening agent, and optionally includes (consists of) aluminum oxide (Al2O3), porous silica, and pigment systems and additives.

[0014] It contains 0.5 to 5% by weight of zirconium oxide in the form of stabilized zirconia, stabilized with, for example, 4 mol% or 5 mol% of yttrium oxide, based on the total weight of the photoluminescence material. Preferably, this zirconium oxide is contained in an amount of 1 to 10% by weight. Typically, the particle size of the zirconia is at the sub-micron level, with a D50 of about 500 nm.

[0015] The polymer matrix is contained in an amount of 19.3 to 54.3% by weight, preferably 28.5 to 48.5% by weight. The upper limit value of the polymer matrix is calculated for the photoluminescence material without aluminum oxide, without porous silica, and without dyes and additives. In the presence of one of these compounds, this upper limit value is reduced so that all compounds in the photoluminescence material do not exceed 100%. In the case of the polymer matrix, the polymer matrix can include any polymer that is translucent or semi-translucent in the visible region. For example, the polymer matrix can be a polymer that is one or more types of resins selected from the acrylic family, polyamide family, polyolefin family, epoxy family, polyurethane family, fluoroelastomer family, and silicone.

[0016] The photoluminescence compound is contained in an amount of 45 to 80% by weight, preferably 50 to 70% by weight. The photoluminescence compound can consist of a pigment or a pigment encapsulated within a translucent shell. The pigment is preferably a derivative of an alkaline earth aluminate doped with rare earths. In particular, the pigment is strontium aluminate doped with europium and dysprosium of the formula Sr x Al y O z :Eu 2+ 、Dy 3+ Specifically, the pigment is strontium aluminate doped with europium and dysprosium of Sr4Al 14 O 25 :Eu 2+ 、Dy 3+ 、or SrAl2O4:Eu 2+ 、Dy 3+It can be, and optionally, both can be included in the photoluminescent compound. Advantageously, the pigment can have different particle sizes so as to optimally distribute the pigment in terms of volume and avoid free space. Also, thanks to the existence of different particle sizes in terms of volume in this way, it becomes possible to combine small particles that form shallow surface traps causing high light intensity over a short period of time and large particles that form deeper traps causing light residue over a long period of time. As an example, the pigment can have a first particle size range centered around a diameter D1 of 500 nm to 10 μm, ideally 500 nm to 5 μm, and a second particle size range centered around a diameter D2 of 10 μm to 500 μm, ideally 10 μm to 20 μm. The particle size is measured by laser particle size analysis ISO 13320:2020, which is optionally supplemented by SEM analysis using secondary electron imaging. Note that it can be combined after sieving out small portions of more than two numbers of particle sizes. For example, it can have 20 wt% of a first small portion of 500 nm to 5 μm, 60 wt% of a second small portion of 5 μm to 20 μm, and 20 wt% of a third small portion of 20 μm to 50 μm.

[0017] Optionally, the pigment can be encapsulated within a light-transmissive organic or mineral shell. The organic shell can typically be selected from the polymers mentioned for the polymer matrix. The mineral shell can be, for example, a silica (SiO2) shell obtained by the sol-gel method. Other examples of the mineral shell include zirconium oxide (ZrO2) and aluminum oxide (Al2O3).

[0018] The photoluminescence material further contains a fluorescent brightening agent so as to give the material a white luster. The fluorescent brightening agent is contained in an amount of 0.2 to 7% by weight, preferably 0.5 to 5% by weight. The fluorescent brightening agent used is a synthetic organic molecule derived from stilbene containing a sulfonic acid group that absorbs light with a wavelength of 300 nm to 400 nm and re-emits it as light in the blue-violet range. These are mainly used as bleaching agents for materials. For example, distyryl biphenyl (DSBP) and diamino stilbene derivatives.

[0019] Optionally, the photoluminescence material can contain 0 to 5% by weight, preferably 0 to 2.5% by weight, of aluminum oxide (Al2O3) according to the desired whiteness. Advantageously, it contains 0.5 to 5% by weight, more advantageously 0.5 to 3% by weight, of Al2O3.

[0020] Optionally, the photoluminescence material further contains 0 to 15% by weight, preferably 0.5 to 8% by weight, of dye systems and additives. Preferably, the photoluminescence material contains 0.5 to 5% by weight of a dye system. This dye system preferably contains an organic dye that does not absorb light in the emission wavelength range of the photoluminescence pigment. This organic dye can be a fluorescent pigment or dye whose absorption is in the UV range and whose emission is in the visible spectrum. For example, organic fluorescent pigments or dyes such as those with the trade names Radiant and Aralon (registered trademark). It can also be a semi-transparent pigment or dye with a low absorption rate at the emission wavelength of the energy storage pigment. For example, it can be a semi-transparent pigment or dye by Clariant. Other additives such as metallic pigments and pigments with a pearlescent effect, UV-resistant additives for protecting the polymer matrix, dispersants such as silanes for promoting the dispersion of additives, and silica-type nanoscale fillers for adapting the viscosity parameters of the mixture can also be added.

[0021] Optionally, the photoluminescence material can include porous silica obtained from the skeletons of diatoms. Typically, the average diameter of the pores can be on the order of 500 μm. Optionally, the porous silica can be synthetic porous silica. In the case of synthetic silica, the average diameter of the pores is typically 0.1 μm to 3 μm. The porous silica is contained in an amount of 0 to 0.3% by weight, preferably 0.01 to 1% by weight, more preferably 0.07 to 0.3% by weight, and even more preferably 0.09 to 0.2% by weight.

[0022] A method of manufacturing an article made entirely from a photoluminescence material involves mixing one or more types of polymers intended to form a polymer matrix, preferably with a dispersant. This initial mixing is carried out on a photoluminescence pigment, which may optionally be pre-encapsulated. Then, zirconium dioxide and a fluorescent brightening agent are added to this second mixture, along with any dye systems, additives, aluminum oxide, and porous silica. This mixture can be made from a liquid resin using a speed mixer or a paddle mixer. The resulting mixture can then be shaped by extrusion. Also, to produce a thermoplastic mixture and convert it into reusable granules for injection molding, the mixture can be made using a twin-screw extruder or a high-speed mixer.

[0023] A method of manufacturing an article coated with a photoluminescence material involves depositing a coating on a substrate by techniques such as screen printing, pad printing, spray coating, etc.

[0024] To conduct a test for making a sample entirely from the photoluminescence material, 5% by weight of yttria-stabilized zirconia with respect to the total weight of the photoluminescence material, SrAl2O3:Eu 2+ , Dy 3+This was done by adding to an epoxy resin in which the filler content of the photoluminescent pigment was 60% by weight. The samples were observed under a D65 light booth. In parallel, using the same base material, tests were conducted with TiO2, ZnO, BaSO4, CaCO3, SiO2, and Al2O3.

[0025] Also, tests were conducted with 5% by weight of yttria-stabilized zirconia combined with 0.25%, 2.5%, and 5% by weight of Al2O3.

[0026] Also, tests were conducted with 5% by weight of yttria-stabilized zirconia combined with 0.2% by weight of porous silica.

[0027] This material was molded by vacuum casting.

[0028] These tests showed that the best compromise between the whiteness and intensity of energy storage luminescence is obtained with yttria-stabilized zirconia such that the white level increases in the presence of Al2O3, depending on the quality of the white color achieved in the visible color.

[0029] In the tests using porous silica, the luminescence characteristics increased by 20% after 10 minutes. These luminescence characteristics were measured in accordance with ISO 17514-2003.

Claims

1. Comprising 19.3 to 54.3% by weight of a polymer matrix, 45 to 80% by weight of a photoluminescence compound, 0.5 to 15% by weight of zirconium oxide, and 0.2 to 7% by weight of a fluorescent whitening agent, Optionally comprising 0 to 5% by weight of aluminum oxide, 0 to 0.3% by weight of porous silica, a pigment system or an additive, The total content of the pigment system and the additive is 0 to 15% by weight A photoluminescence material characterized by this.

2. The polymer matrix is contained in an amount of 28.5 to 48.5% by weight, The photoluminescence compound is contained in an amount of 50 to 70% by weight, Zirconium oxide is contained in an amount of 1 to 10% by weight, The fluorescent whitening agent is contained in an amount of 0.5 to 5% by weight The photoluminescence material according to Claim 1, characterized by this.

3. Aluminum oxide is contained in an amount of 0.5 to 5% by weight, preferably 0.5 to 3% by weight The photoluminescence material according to Claim 1, characterized by this.

4. The porous silica is contained in an amount of 0.01 to 1% by weight, preferably 0.07 to 0.3% by weight, more preferably 0.09 to 0.2% by weight The photoluminescence material according to Claim 1, characterized by this.

5. The porous silica is obtained from the skeleton of diatoms The photoluminescence material according to Claim 1, characterized by this.

6. The photoluminescence compound contains a pigment which is a derivative of an alkaline earth aluminate doped with rare earths The photoluminescence material according to Claim 1, characterized by this.

7. The pigment has the formula Sr x Al y O z :Eu 2+ ,Dy 3+ and is a derivative of an alkaline earth aluminate doped with europium and dysprosium The photoluminescence material according to Claim 6, characterized by this.

8. The pigment is Sr 4 Al 14 O 25 : Eu 2+ , Dy 3+ and / or SrAl 2 O 4 : Eu 2+ , Dy 3+ is The photoluminescence material according to Claim 7, characterized by this.

9. The photoluminescence compound is composed of the pigment encapsulated in an organic or mineral translucent shell The photoluminescence material according to Claim 6, characterized by this.

10. Zirconium oxide is preferably stabilized by yttria The photoluminescence material according to Claim 1, characterized by this.

11. The polymer matrix contains one or more resins selected from the acrylic family, polyamide family, polyolefin family, epoxy family, polyurethane family, fluoroelastomer family and silicone The photoluminescence material according to Claim 1, characterized by this.

12. The organic light-transmissive shell contains one or more types of resins selected from the acrylic family, polyamide family, polyolefin family, epoxy family, polyurethane family, fluoroelastomer family, and silicone, and the mineral light-transmissive shell contains silica. The photoluminescence material according to claim 9, characterized in that.

13. The photoluminescence compound contains pigments having various particle sizes. The photoluminescence material according to claim 6, characterized in that.

14. The pigment has at least a first particle size range centered on a diameter D1 of 500 nm to 10 μm and a second particle size range centered on a diameter D2 of 10 μm to 500 μm. The photoluminescence material according to claim 13, characterized in that.

15. The optical brightener is a stilbene derivative containing a sulfonic acid group. The photoluminescence material according to claim 1, characterized in that.

16. An article made or coated with the photoluminescence material according to claim 1. Characterized by that.

17. It is a component of a timepiece. The article according to claim 16, characterized by that.