JP2010009995A - Discharge liquid, discharge liquid set, thin film pattern forming method, thin film, light emitting element, image display device, and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image display device preventive of color phase irregularity, capable of displaying improved images having wide color reproductive regions, and superior in durability while reducing a load on environment, to provide an light emitting element for stably emitting light having desired color tone over a long period while reducing a load on environment, to provide electronic equipment with the image display device, and to provide discharge liquid, a discharge liquid set, a thin film pattern forming method, and a thin film suitably applicable to the image display device and the light emitting element. <P>SOLUTION: The discharge liquid is used for a liquid droplet discharge method for intermittently discharging liquid droplets from a nozzle hole. It includes particulate quantum dots, and dispersion medium for dispersing the quantum dots. The total content ratio of Cd, Pb, Cr to the quantum dots is 100 ppm or smaller. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a discharge liquid, a discharge liquid set, a thin film pattern forming method, a thin film, a light emitting element, an image display device, and an electronic apparatus.

In recent years, display devices using light-emitting (self-luminous) materials such as inorganic electroluminescence (inorganic EL) and organic electroluminescence (organic EL) have been attracting attention because they have better viewing angle characteristics than liquid crystal display devices. Collecting.
However, inorganic electroluminescence has problems in light emission luminance, light emission efficiency, color purity and the like due to material limitations, and it is difficult to ensure a sufficiently wide color reproduction range. For the purpose of solving such problems, attempts have been made to add a colored filter or search for a light emitting material (see, for example, Patent Document 1). However, when a colored filter is used, the manufacturing process is complicated. In addition, the brightness of the displayed image is significantly reduced. In addition, substances proposed in various literatures also have problems such as not sufficiently solving the above problems and poor chemical stability. For example, Patent Document 1 discloses that a blue light-emitting layer is produced by co-evaporation of a BaS: Eu material and an AlS material, but the obtained film is subjected to heat treatment at a considerably high temperature (800 ° C. or higher). If it is not applied, sufficient light emission characteristics cannot be obtained, and the chemical stability of the AlS material is very poor in performing co-evaporation, so that there is a problem in productivity in the film forming process.

Moreover, in organic electroluminescence, since an organic compound is used as a light emitting material, there is a problem in durability and the like. Moreover, in organic electroluminescence, the color reproduction range can be widened compared to inorganic electroluminescence, but it cannot be said that a sufficient color reproduction range is still secured.
Examples of a method for forming a light emitting element include a vapor phase film forming method and a method of applying a liquid containing a light emitting material. However, in such a method, in order to arrange a large number of minute film formation regions as in an image display device, it is necessary to cover with a mask corresponding to a pattern to be formed prior to film formation. Such a mask is finally completely removed, and it is difficult to reuse the light emitting material and the mask. Therefore, it is not preferable from the viewpoint of resource saving, and the load on the environment is large. Further, when the pattern to be formed (thin film pattern) is large (large area) (when applied to an image display device having a large display area), it is difficult to make the mask position accuracy sufficiently high. There is also the problem of becoming.

  Further, when the method of applying a liquid containing a light emitting material is used, there are the following problems. That is, inorganic light-emitting materials are generally poor in solubility, so when applying such a method, it is necessary to use a uniformly dispersed dispersion. However, when a dispersion is used to form a light-emitting element, Variations in the concentration of the luminescent material tend to occur between pixels or in each part within the pixel due to stability fluctuations. When such density variation occurs, problems such as color unevenness occur in the displayed image.

JP 2002-180038 A

  An object of the present invention is to provide an image display device that can prevent the occurrence of color unevenness, can display an excellent image with a wide color gamut, and is excellent in durability, and can reduce the burden on the environment. Providing a light-emitting element capable of stably emitting light of a desired color tone over a long period of time, providing an electronic apparatus including the image display device, and displaying the image An object of the present invention is to provide a discharge liquid, a discharge liquid set, a thin film pattern forming method, and a thin film that can be suitably applied to an apparatus, a light emitting element, and the like.

Such an object is achieved by the present invention described below.
The discharge liquid of the present invention is a discharge liquid used in a droplet discharge method for discharging droplets intermittently from nozzle holes,
Including fine-particle quantum dots and a dispersion medium for dispersing the quantum dots,
The total content of Cd, Pb, and Cr in the quantum dots is 100 ppm or less.
As a result, color unevenness is prevented, an excellent image with a wide color reproduction range can be displayed, and an image display device with excellent durability, and light of a desired color tone can be stably emitted over a long period of time. Accordingly, it is possible to provide a discharge liquid that can be suitably applied to manufacture a light-emitting element or the like capable of reducing the environmental load. In addition, when manufacturing an image display device, a light emitting element, and the like, it is possible to reliably prevent an adverse health effect on workers and the like.

In the discharge liquid of the present invention, the total content of Cd, Pb, and Cr in the discharge liquid is preferably 5.0 ppm or less.
Thereby, it is possible to reduce the load on the environment when manufacturing a light emitting element, an image display device, or the like. In addition, when manufacturing an image display device, a light emitting element, and the like, it is possible to more reliably prevent an adverse health effect on workers and the like.

In the ejection liquid of the present invention, it is preferable that the content of the quantum dots in the ejection liquid is 0.005 to 6.0 wt%.
Thereby, it is possible to reduce the load on the environment when manufacturing a light emitting element, an image display device, or the like. In addition, the dispersibility (uniformity of dispersion) of the quantum dots in the discharge liquid can be made sufficiently excellent, and the discharge stability and liquid breakage during discharge of the discharge liquid can be made particularly excellent. Moreover, the formation efficiency of the thin film pattern can be made particularly excellent. Further, for example, when applied to a light emitting element, an image display device, and the like, it is possible to suitably display an image having a particularly high image density while more effectively preventing the occurrence of color unevenness.

In the ejection liquid of the present invention, the dispersion medium is decalin, tetralin, butoxyethanol, ethyl octoate, 4-methyl-1,3-dioxolan-2-one, bis (2-butoxyethyl) ether, diethylene glycol monobutyl ether acetate. And one or more selected from the group consisting of dodecane, diethylene glycol monoethyl ether acetate, dipropylene glycol methyl ether acetate, triethylene glycol butyl methyl ether, and 1,3-butylene glycol diacetate Is preferred.
As a result, the quantum dots and the discharge liquid contain Cd, Pb, and Cr at a relatively high concentration (however, the total content of Cd, Pb, and Cr in the quantum dots is 100 ppm or less). However, the ratio of mist generated during discharge of the discharge liquid (discharge liquid staying in the atmosphere without adhering to the target receiving surface) can be made particularly small. As a result, the load on the environment when manufacturing a light emitting element, an image display device, and the like can be made particularly small. It is possible to more reliably prevent adverse effects on the surface. In addition, the dispersibility of the quantum dots in the ejection liquid can be made extremely excellent, and variation in the content of the quantum dots contained in each droplet ejected from the nozzle hole can be prevented. Further, when discharging the discharge liquid from the nozzle hole, separation near the interface between the quantum dots as fine particles and the dispersion medium preferably occurs, and the liquid breakage from the nozzle hole can be made particularly excellent. Further, it is possible to more reliably prevent the droplets from flying and to improve the adhesion position accuracy of the droplets on the receiving surface. For this reason, for example, when the discharge liquid is applied to a light emitting element or an image display device, unintentional variation in the density of quantum dots between pixels or in each part in the pixel is prevented and displayed. It is possible to more effectively prevent problems such as color unevenness in the image. Moreover, since the above excellent dispersed state can be maintained over a long period of time, the long-term stable ejection required for industrial applications (industrial use) can be made extremely excellent, as described above. Such excellent effects can be stably exhibited over a long period of time. Further, when the dispersion medium is composed of the above materials, the volatility (vapor pressure) of the dispersion medium can be made relatively low. For this reason, even when droplets are repeatedly ejected over a long period of time, it is possible to effectively prevent solid components (quantum dots or the like) of the ejected liquid from adhering to the vicinity of the nozzle holes.

In the discharge liquid of the present invention, the content of the dispersion medium in the discharge liquid is preferably 70 to 98 wt%.
Thereby, the dispersibility (uniformity of dispersion) of the quantum dots in the discharge liquid can be made sufficiently excellent, and the discharge stability and liquid breakage during discharge of the discharge liquid are particularly excellent. In addition, the formation efficiency of the thin film pattern can be made particularly excellent. In addition, for example, when applied to a light emitting element, an image display device, and the like, an image display device that can display an image having a particularly high image density while efficiently preventing color unevenness more efficiently is manufactured. be able to.

In the ejection liquid of the present invention, the quantum dots include Si, Ge, GaN, GaP, InN, InP, Ga ₂ O ₃ , Ga ₂ S ₃ , In ₂ O ₃ , In ₂ S ₃ , ZnO, ZnS, In, It is preferably composed of Ag or a mixture thereof.
As a result, the load on the environment can be made particularly small, and it is particularly advantageous for ensuring the safety of workers and the like. Further, since a pure spectrum can be stably obtained in the visible light region, it is advantageous for forming a light emitting element.

The discharge liquid set of the present invention is a discharge liquid set including a plurality of discharge liquids used in a droplet discharge method for discharging droplets intermittently from nozzle holes,
The ejection liquid includes fine-particle quantum dots and a dispersion medium for dispersing the quantum dots,
The quantum dot has a particle size different between the discharge liquids, and
In each of the plurality of types of ejection liquid, the total content of Cd, Pb, and Cr in the quantum dots is 100 ppm or less.
As a result, color unevenness is prevented, an excellent image with a wide color gamut can be displayed, and an image display device with excellent durability. Thus, it is possible to provide a discharge liquid set that can be suitably applied to manufacture a light emitting element or the like that can be manufactured with a low environmental load. In addition, when manufacturing an image display device, a light emitting element, and the like, it is possible to reliably prevent an adverse health effect on workers and the like.

The thin film pattern forming method of the present invention includes a dispersion medium and fine quantum dots by a droplet discharge method in which droplets are intermittently discharged from nozzle holes, and the quantum dots are dispersed in the dispersion medium. A discharge step of discharging the discharge liquid to be adhered to the receiving surface in a predetermined pattern;
A dispersion medium removing step of removing at least a part of the dispersion medium from the discharge liquid adhered to the receiving surface,
The total content of Cd, Pb, and Cr in the quantum dots is 100 ppm or less.
As a result, color unevenness is prevented, an excellent image with a wide color gamut can be displayed, and an image display device with excellent durability. Light of a desired color tone is stably emitted over a long period of time. Thus, it is possible to provide a thin film pattern forming method that can be suitably applied to manufacture a light emitting element or the like capable of reducing the environmental load. In addition, when manufacturing an image display device, a light emitting element, and the like, it is possible to reliably prevent an adverse health effect on workers and the like.

  Also, when discharging droplets of the discharge liquid (dispersion liquid) from the nozzle holes, the dispersion of quantum dots as fine particles that are uniformly dispersed without interfering with each other at a low concentration can keep viscoelasticity low. Since the separation near the interface between the quantum dots and the dispersion medium preferably occurs, the liquid from the nozzle holes can be drained well, and variations in the amount of ejected liquid droplets can be prevented. The flight bend can be reliably prevented, and the liquid droplets that have run out of the nozzle holes quickly become spherical. For this reason, a desired amount of discharge liquid can be adhered to a desired portion of the receiving surface. As a result, it is possible to prevent unintentional variation in the amount of attached quantum dots at each portion of the thin film to be formed. Therefore, when the thin film pattern forming method is applied to a light emitting element and an image display device, it is possible to suitably prevent unintentional luminance variations from occurring at each part during light emission.

In the method for forming a thin film pattern of the present invention, the droplet discharge method is preferably an inkjet method.
As a result, it is possible to make the liquid breakage from the nozzle hole particularly excellent, and it is possible to more reliably prevent the occurrence of flight bending. As a result, the amount and position of the discharged liquid (dispersed liquid) attached to the receiving surface can be controlled more accurately. Also, compared to the so-called bubble jet method (“Bubble Jet” is a registered trademark), the ratio of mist generated during discharge of discharged liquid (discharge liquid that stays in the atmosphere without adhering to the target receiving surface) Can be particularly small. As a result, the load on the environment when manufacturing a light emitting element, an image display device, and the like can be made particularly small. It is possible to more reliably prevent adverse effects on the surface.

In the thin film pattern forming method of the present invention, it is preferable to use a plurality of types of the discharge liquids including the quantum dots having different particle diameters.
Thereby, for example, a light emitting element and an image display device having a particularly wide color reproduction range and excellent durability can be suitably manufactured.
In the thin film pattern forming method of the present invention, the discharge liquid is preferably discharged such that a plurality of minute units are arranged in a matrix.
As described above, when the liquid is ejected by the droplet ejection method so that a plurality of minute units are arranged in a matrix, it is necessary to sufficiently reduce the ejection amount of the ejection liquid per droplet. In the invention, since the total amount of Cd, Pb, and Cr contained in the quantum dots is not more than a predetermined value, the discharge liquid is generated by mist that is inevitably generated when droplets are discharged. Adverse effects are effectively prevented. In addition, when a liquid is discharged by a droplet discharge method so that a plurality of minute units are arranged in a matrix, generally, a plurality of minute units are combined to form a relatively large liquid reservoir. It is easy to cause a problem such that the discharged droplets adhere to a portion where an adjacent minute unit should be formed instead of a portion where a desired minute unit is to be formed, and a desired pattern is formed. Although difficult, such a problem is hardly caused in the dispersion liquid containing the quantum dots as described above. That is, when the present invention is applied to a method of discharging a dispersion liquid so that a plurality of minute units are arranged in a matrix, the effect of the present invention is more remarkably exhibited.

The thin film of the present invention comprises a quantum dot having a total content of Cd, Pb, Cr in the quantum dots of 100 ppm or less by a droplet discharge method in which droplets are intermittently discharged from a nozzle hole, and the quantum dots It is obtained by discharging a dispersion liquid containing a dispersion medium to be dispersed and removing at least a part of the dispersion medium from the discharged dispersion liquid.
As a result, color unevenness is prevented, an excellent image with a wide color reproduction range can be displayed, and an image display device with excellent durability, and light of a desired color tone can be stably emitted over a long period of time. Thus, it is possible to provide a discharge liquid that can be suitably applied to a light-emitting element that can be used.

The light-emitting element of the present invention includes a quantum dot having a total content of Cd, Pb, and Cr in the quantum dots of 100 ppm or less by the droplet discharge method of intermittently discharging droplets from the nozzle holes, and the quantum dots And a light emitting layer obtained by discharging at least a part of the dispersion medium from the discharged dispersion liquid.
As a result, it is possible to provide a light-emitting element that can prevent the occurrence of uneven color and can stably emit light having a desired color tone over a long period of time.

The image display device of the present invention includes the light emitting element of the present invention.
As a result, it is possible to provide an image display device that can prevent color unevenness, can display an excellent image with a wide color reproduction range, and is excellent in durability.
An electronic apparatus according to the present invention includes the image display device according to the present invention.
As a result, it is possible to provide an electronic device that can prevent color unevenness and can stably display an excellent image with a wide color reproduction range over a long period of time.

Hereinafter, preferred embodiments of the present invention will be described in detail.
<Discharge liquid (dispersion liquid)>
First, the discharge liquid (dispersion liquid) used for forming the thin film pattern will be described.
In the present invention, the discharge liquid (dispersion liquid) includes a dispersion medium and fine quantum dots, and the quantum dots are dispersed in the dispersion medium. In particular, the liquid droplets are intermittently discharged from the nozzle holes. The present invention is used for a droplet discharge method.

<Quantum dots (fine particles)>
Quantum dots are fine particles made of a crystal of a semiconductor material and having a particle size of about several nanometers to several tens of nanometers (more specifically, 2 to 20 nm).
In general, the energy level E of such fine particles can be expressed by the following formula (I) where h is the Planck constant, m is the effective mass of electrons, and R is the radius of the fine particles.

E∝h ² / mR ² (I)
As shown by the above equation, the band gap of the fine particles increases in proportion to R ⁻² (so-called quantum dot effect). In this way, the value of the band gap of the fine particles (quantum dots) can be controlled by controlling and defining the particle size of the fine particles (quantum dots). In other words, by controlling and defining the particle size of the fine particles, the fine particles can function as pseudo semiconductor atoms (artificial atoms, designer atoms), and can have diversity not found in ordinary atoms. . For this reason, it is possible to emit light at a desired wavelength by applying electrical energy to quantum dots (fine particles), or to modulate incident light (for example, ultraviolet rays) into light having a desired wavelength. Can be emitted. Moreover, electric energy can be taken out by making light of a predetermined wavelength incident on the quantum dots (fine particles). Therefore, a pattern (thin film pattern) formed using a discharge liquid (dispersion liquid) containing quantum dots can be suitably applied to, for example, a light emitting element of an image display device or a solar cell.

  As described above, the quantum dots are generally fine particles having a particle size of about several nanometers to several tens of nanometers (more specifically, 2 to 20 nm), but the present inventor includes such fine particles. When a dispersion (particularly a dispersion in which quantum dots are dispersed in a dispersion medium as described later) is applied to a droplet ejection method in which droplets are intermittently ejected from nozzle holes, they interfere with each other at a low concentration. It has been found that a dispersion of quantum dots as finely dispersed fine particles without matching can keep viscoelasticity low, and that separation in the vicinity of the interface between the quantum dots and the dispersion medium occurs favorably. Further, the liquid can be discharged from the nozzle hole at the time of discharging the droplets, the variation in the amount of discharged droplets can be prevented, and the flight of the droplets can be reliably prevented. It has been found that since the liquid droplets that have run out of the nozzle holes quickly become spherical, the adhesion position accuracy on the receiving surface to which the liquid droplets adhere is excellent. Such an effect cannot be obtained when a liquid that does not contain quantum dots as described above is used. In other words, when the liquid used for the droplet discharge method is a solution that does not contain dispersoids, liquid droplets discharged from the nozzle holes are likely to be non-uniform, so the weight of each droplet And the droplet attachment position accuracy is low. On the other hand, when the liquid (discharge liquid) used for the droplet discharge method is a dispersion liquid in which a dispersoid having a size larger than the above is dispersed, there is a variation in the weight of each droplet discharged from the nozzle hole. Especially easy to grow.

  As described above, the quantum dot has a particle size of about several nanometers to several tens of nanometers. However, when the ejection liquid (dispersion liquid) is used in an image display device having a light emitting element and a display unit as described later, The particle size corresponds to the display color. For example, when the discharge liquid (dispersion) is applied to a light-emitting element that displays red and a display unit, the particle size of the quantum dots is preferably 3 to 20 nm, and the discharge liquid (dispersion) is displayed in green. When applied to a light-emitting element and a display unit, the particle size of the quantum dots is preferably 1 to 10 nm. When applied to a light-emitting element and display unit that performs blue display on a discharge liquid (dispersed liquid), The particle size is preferably 1 to 3 nm. In addition, when a quantum dot is manufactured by the method which is mentioned later, for example, the particle size distribution of the obtained quantum dot can be made very sharp. Thereby, for example, when the discharge liquid is applied to an image display device or the like, a clear image can be suitably displayed.

  As described above, in the present invention, the discharge liquid (dispersion liquid) includes a dispersion medium and fine-particle quantum dots, and the quantum dots are dispersed in the dispersion medium. In particular, it is used for a droplet discharge method for discharging droplets. In such a droplet discharge method, mist of discharge liquid (discharge liquid that stays in the atmosphere without adhering to the target receiving surface) is inevitably generated. On the other hand, conventional quantum dots include those containing Cd, Pb, and Cr as constituent components, and Cd, Pb, and Cr as impurities, considering light emission efficiency and particle stability. (It has been extremely difficult (substantially impossible) to remove Cd, Pb and Cr substantially completely with conventional quantum dots). When Cd, Pb, and Cr are contained in the quantum dots, Cd, Pb, and Cr are retained and diffused in the atmosphere when mist of the discharge liquid is generated. Cd, Pb, and Cr are elements that give a large load to the environment and are concerned about adverse effects on the human body (particularly, adverse effects on respiratory organs and the like when Cd, Pb, and Cr are inhaled).

As a result of intensive studies, the inventor found that the total content of Cd, Pb, and Cr in the quantum dots is 100 ppm or less, Cd contained in the mist generated along with droplet discharge, While the total amount of Pb and Cr is sufficiently low, when the total content of Cd, Pb and Cr in the quantum dot exceeds 100 ppm, Cd contained in the mist generated along with the droplet discharge It has been found that the total amount of Pb, Cr increases rapidly. That is, the present inventor is concerned with the total amount of Cd, Pb, and Cr contained in the quantum dots when the total amount of Cd, Pb, and Cr contained in the mist generated along with the droplet discharge increases rapidly. The criticality (critical point) was found. Therefore, by setting the total content of Cd, Pb, and Cr in the quantum dots to 100 ppm or less, it is possible to reduce the load on the environment as described above and to cause adverse effects on the human body and the like. Etc. can be reliably prevented.
The reason why such criticality is recognized is considered to be due to the following reasons.

  That is, in the case of a dispersion liquid (discharge liquid) containing quantum dots having a special particle size, unlike the general dispersion liquid and solution, the above-described quantum dots (dispersoid) and the dispersion liquid are dispersed during droplet discharge. Separation between the medium and the vicinity of the interface preferably occurs, but the amount of Cd, Pb, and Cr eluted in the dispersion medium and the average particle size variation due to the content of Cd, Pb, and Cr contained in the quantum dot The amount of the dispersant added to stabilize the dispersion is different, and this is considered to have an influence on the behavior of the discharged liquid when the liquid is discharged. Then, depending on the amount of Cd, Pb, Cr eluted in the dispersion medium, the variation in particle size, and the amount of dispersant, the size and total amount of mist inevitably generated when droplets are ejected, quantum dots contained in the mist It is considered that the ratio of the number changes. That is, a large mist settles relatively quickly in the atmosphere and has a short time to float in the atmosphere, whereas a mist of a certain size or less can float for a long time, and a large amount of minute mist is generated.

As described above, when the total amount of Cd, Pb, and Cr in the quantum dots is high, the amount of Cd, Pb, and Cr eluted in the dispersion medium is increased as compared with the case where the content is low. Since the size and total amount of mist inevitably generated at the time of discharge and the ratio of quantum dots contained in the mist also change, it seems that the above criticality appears.
As described above, in the present invention, the total content of Cd, Pb, and Cr in the quantum dots may be 100 ppm or less, preferably 70 ppm or less, and more preferably 50 ppm or less. . Thereby, the effects as described above are more remarkably exhibited.

Examples of the constituent material of the quantum dot include a simple substance of a periodic table group 14 element such as carbon, silicon, germanium, and tin, a simple substance of a periodic table group 15 element such as phosphorus (black phosphorus), and a periodicity of selenium, tellurium, and the like. Table 16 group element simple substance, compound consisting of a plurality of periodic table group 14 elements such as silicon carbide (SiC), tin oxide (IV) (SnO ₂ ), tin sulfide (II, IV) (Sn (II) Sn (IV) Periodic table of S ₃ ), tin sulfide (IV) (SnS ₂ ), tin sulfide (II) (SnS), tin selenide (II) (SnSe), tin telluride (II) (SnTe), etc. Compounds of Group 14 elements and Group 16 elements of the periodic table, boron nitride (BN), boron phosphide (BP), boron arsenide (BAs), aluminum nitride (AlN), aluminum phosphide (AlP), aluminum arsenide (AlAs) ), Aluminum antimonide (AlS) ), Gallium nitride (GaN), gallium phosphide (GaP), gallium arsenide (GaAs), gallium antimonide (GaSb), indium nitride (InN), indium phosphide (InP), indium arsenide (InAs), indium antimonide A compound (or III-V group compound semiconductor) of a periodic table group 13 element and a periodic table group 15 element such as (InSb), aluminum sulfide (Al ₂ S ₃ ), aluminum selenide (Al ₂ Se ₃ ), Gallium sulfide (Ga ₂ S ₃ ), gallium selenide (Ga ₂ Se ₃ ), gallium telluride (Ga ₂ Te ₃ ), indium oxide (In ₂ O ₃ ), indium sulfide (In ₂ S ₃ ), indium selenide _(in 2 _Se 3), the periodic table group 13 element and the period of such telluride, indium _(in 2 Te ₃₎ Compounds with group 16 elements, thallium chloride (I) (TlCl), thallium bromide (I) (TlBr), thallium iodide (I) (TlI), etc. Compounds with elements, zinc oxide (ZnO), zinc sulfide (ZnS), zinc selenide (ZnSe), zinc telluride (ZnTe), mercury sulfide (HgS), mercury selenide (HgSe), mercury telluride (HgTe) A compound of a group 12 element of the periodic table and a group 16 element of the periodic table (or II-VI compound semiconductor), arsenic sulfide (III) (As ₂ S ₃ ), arsenic selenide (III) (As ₂ Se ₃ ), arsenic telluride (III) (As ₂ Te ₃ ), antimony sulfide (III) (Sb ₂ S ₃ ), antimony selenide (III) (Sb ₂ Se ₃ ), antimony telluride (III) (Sb ₂ ) Te _3), sulfide bis Scan _{(III) (Bi 2 S 3} ), bismuth selenide _{(III) (Bi 2 Se 3} ), the periodic table group 15 element and Periodic Table Group 16, such as bismuth telluride _{(III) (Bi 2 Te 3} ) Compounds with elements, compounds of Group 11 elements of the periodic table and elements of Group 16 of the periodic table such as copper (I) (Cu ₂ O), copper selenide (Cu ₂ Se), copper chloride (I ) (CuCl), copper bromide (I) (CuBr), copper iodide (I) (CuI), silver chloride (AgCl), silver bromide (AgBr), etc. Compounds with Group elements, Periodic Table Group 11 elements such as silver sulfide (AgS) and Periodic Table Group 16 elements, Periodic Table Group 10 elements such as Nickel (II) (NiO) and Periodic Table Periodic table of compounds with group 16 elements, cobalt oxide (II) (CoO), cobalt sulfide (II) (CoS), etc. Group 9 element and the periodic table compounds of Group 16 elements, triiron tetraoxide (Fe 3 O _4), the periodic table group 8 element and Periodic Table Group 16 element such as iron sulfide (II) (FeS) Compounds, compounds of periodic table group 7 elements and periodic table group 16 elements such as manganese (II) oxide (MnO), molybdenum sulfide (IV) (MoS ₂ ), tungsten oxide (IV) (WO ₂ ), etc. Periodic table Group 6 element and Periodic Table Group 16 compound, vanadium oxide (II) (VO), vanadium oxide (IV) (VO ₂ ), tantalum oxide (V) (Ta ₂ O ₅ ), etc. Periodic table Group 4 elements such as compounds of Group 5 elements and Periodic Table Group 16 elements, titanium oxide (TiO ₂ , Ti ₂ O ₅ , Ti ₂ O ₃ , Ti ₅ O _9, etc.) Compounds with Group 16 elements, magnesium sulfide (MgS), magnesium selenide (MgS e) and the like, compounds of periodic table group 2 elements and periodic table group 16 elements, barium titanate (BaTiO ₃ ), and the like, and the periodic table group 14 elements such as SnS ₂ , SnS, SnSe, and SnTe Compounds with Group 16 elements of the periodic table, III-V compound semiconductors such as GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb, Ga ₂ O ₃ , Ga ₂ S ₃ , Ga ₂ Se ₃ , Ga ₂ Te ₃ , In ₂ O ₃ , In ₂ S ₃ , In ₂ Se ₃ , In ₂ Te _3, etc. periodic table group 13 element and periodic table group 16 element compound, ZnO, ZnS, ZnSe, ZnTe, II-VI group compound semiconductors such as HgO, HgS, HgSe, HgTe, As ₂ O ₃ , As ₂ S ₃ , As ₂ Se ₃ , As ₂ Te ₃ , Sb ₂ O ₃ , Sb ₂ S ₃ , Sb ₂ Compound of periodic table group 15 element and periodic table group 16 element such as Se ₃ , Sb ₂ Te ₃ , Bi ₂ O ₃ , Bi ₂ S ₃ , Bi ₂ Se ₃ , Bi ₂ Te ₃ , MgS, MgSe, etc. Of the periodic table group 2 element and the periodic table group 16 element are preferable, among which Si, Ge, GaN, GaP, InN, InP, Ga ₂ O ₃ , Ga ₂ S ₃ , In ₂ O ₃ , In ₂ S ₃ , ZnO, ZnS, In, and Ag are more preferable. By using the quantum dot comprised with such a substance, while being able to make the load with respect to an environment especially small, safety | security of an operator etc. can be ensured reliably. Further, since a pure spectrum can be stably obtained in the visible light region, it is advantageous for forming a light emitting element. In addition, if the quantum dots are composed of the above-described constituent materials, the content of Cd, Pb, and Cr when the quantum dots are manufactured by a method as will be described later is easily and reliably low. It can be. Of these, InP, ZnO, and ZnS are more preferable from the viewpoints of low environmental load and safety to the human body, and are excellent in terms of high refractive index, safety, economics of raw materials, and the like. Therefore, ZnS is most preferable. ZnSe is preferable in terms of light emission stability. Moreover, the material mentioned above may be used by 1 type, and may be used in combination of 2 or more type.

  Although the content rate of the quantum dot in a discharge liquid (dispersion liquid) is not specifically limited, It is preferable that it is 0.005-6.0 wt%, and it is more preferable that it is 0.05-5.0 wt%. When the content of the quantum dots is a value within the above range, the load on the environment when manufacturing a light emitting element, an image display device, and the like can be reduced. In addition, the dispersibility (dispersion uniformity) of the quantum dots in the discharge liquid can be made sufficiently excellent, and the discharge stability (liquid dispersion) during discharge of the discharge liquid (dispersion liquid) is particularly excellent. In addition, the formation efficiency of the thin film pattern can be made particularly excellent. Further, for example, when applied to a light emitting element, an image display device, etc., it is possible to suitably display an image with a particularly high image density while more effectively preventing the occurrence of color unevenness. In particular, in the case where the quantum dots are composed of the materials as described above, the content of the quantum dots in the discharge liquid (dispersion) is within the above range. Since the content of Cd, Pb, and Cr in can be made particularly low, the load on the environment as described above can be made smaller, and the occurrence of adverse effects on the human body and the like can be further reduced. It can be surely prevented.

  In addition, the quantum dots may have a uniform composition throughout the particles, or may have different compositions at each site. For example, the quantum dot may have a core region and a shell region that covers the outer periphery of the core region and has a composition different from that of the core region (has a core-shell structure). Thereby, for example, it is possible to improve the dispersion stability of the quantum dots in the discharge liquid while improving the light emission efficiency of the quantum dots, or to improve the light emission stability. it can.

<Coating>
In the discharge liquid (dispersion liquid), the surface of the quantum dots may be coated with an inert inorganic coating layer or a film made of an organic ligand. This effectively prevents aggregation of the quantum dots in the discharge liquid (dispersion liquid), improves the dispersibility of the quantum dots, and is particularly excellent in liquid breakage during droplet discharge. It becomes. Moreover, light absorption and light emission characteristics can be stably obtained by the presence of the coating layer. In addition, since the quantum dots are coated with a coating, the quantum dots contain a relatively high concentration and contain Cd, Pb, Cr (however, the total content of Cd, Pb, Cr in the quantum dots is 100 ppm. Even below, it is possible to prevent elution, diffusion, etc. of Cd, Pb, Cr from the quantum dots. Thereby, for example, even when quantum dots are taken into the human body, it is possible to more reliably prevent adverse effects on the human body due to Cd, Pb, and Cr.

In addition, when the surface of the quantum dots is covered with a coating, a dispersant as described later can be reliably supported in the vicinity of the surface of the quantum dots. On the other hand, if the quantum dots are not covered with a film, it is difficult to reliably attach the dispersant to the surface of the quantum dots.
Although the thickness of a film is not specifically limited, It is preferable that it is 0.1-10 nm, and it is more preferable that it is 0.1-5 nm. In general, the emission color can be controlled by the size of the quantum dots, and if the thickness of the coating is within the above range, the thickness of the coating is about one quantum dot, and defects (missing, etc.) occur when forming a thin film pattern. A sufficient amount of light emission can be obtained while preventing this. Further, when the thickness of the coating is within the above range, it is possible to prevent elution, diffusion, etc. of Cd, Pb, Cr from the quantum dots, and more reliably prevent the above-described problems from occurring. be able to. In addition, the presence of the coating can suppress the transfer of non-emissive electron energy due to free electrons existing on the particle surfaces of the particles, thereby suppressing a decrease in quantum efficiency.

<Dispersant>
In the discharge liquid (dispersion liquid), it is preferable that a dispersant adheres near the surface of the quantum dots. Thereby, the dispersibility of the quantum dots in the discharge liquid (dispersion liquid) can be made particularly excellent, and the liquid breakage at the time of droplet discharge becomes particularly excellent. In addition, by attaching a dispersing agent to the surface of the quantum dots during the manufacture of the quantum dots (fine particles), the shape of the formed quantum dots has a high sphericity and the particle size distribution of the quantum dots is sharp. For example, when the discharge liquid (dispersion) is applied to the formation of a light emitting element and a display element of an image display device, the image quality displayed on the image display device is particularly excellent. can do.
The dispersant may be directly attached to the surface of the quantum dot or may be attached via a coating (the dispersant is directly attached to the coating but not in contact with the quantum dot). There may be.

  Examples of the dispersant include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, and polyoxyethylene oleyl ether; triphenylphosphine, tripropylphosphine, tributylphosphine, tri-tert-butylphosphine , Trihexylphosphine such as trihexylphosphine and trioctylphosphine (TOP); polyoxyethylene alkylphenyl ethers such as polyoxyethylene n-octylphenyl ether and polyoxyethylene n-nonylphenyl ether; tri (n-hexyl) ) Tertiary amines such as amine, tri (n-octyl) amine, tri (n-decyl) amine; tripropylphosphine oxide, tributylphosphine oxide Organic phosphorus compounds such as trihexylphosphine oxide, trioctylphosphine oxide (TOPO), tridecylphosphine oxide, triphenylphosphine oxide, diphenylphosphine oxide; polyethylene glycol diesters such as polyethylene glycol dilaurate and polyethylene glycol distearate; pyridine, Organic nitrogen compounds such as nitrogen-containing aromatic compounds such as lutidine, collidine and quinolines; aminoalkanes such as hexylamine, octylamine, decylamine, dodecylamine, tetradecylamine, hexadecylamine and octadecylamine; dialkyl such as dibutyl sulfide Sulfides; Dialkyl sulfoxides such as dimethyl sulfoxide and dibutyl sulfoxide; Sulfur-containing aromatics such as thiophene Organic sulfur compounds such as compounds; higher fatty acids such as palmitic acid, stearic acid, and oleic acid; alcohols; sorbitan fatty acid esters; fatty acid-modified polyesters; tertiary amine-modified polyurethanes; polyethyleneimines, When the quantum dot is prepared by a method as described later, the dispersant is preferably a substance that is coordinated and stabilized by the fine particles in the high-temperature liquid phase, specifically, trialkylphosphines. Organic phosphorus compounds, aminoalkanes, tertiary amines, organic nitrogen compounds, dialkyl sulfides, dialkyl sulfoxides, organic sulfur compounds, higher fatty acids and alcohols are preferred. By using such a dispersant, the dispersibility of the quantum dots in the discharge liquid (dispersion) is particularly excellent, and the discharge stability of the discharge liquid (dispersion) is particularly excellent. In addition, the shape of the quantum dots formed during the manufacture of the quantum dots can be made more highly spherical, and the particle size distribution of the quantum dots can be made sharper.

<Dispersion medium>
As described above, in the discharge liquid (dispersion liquid), the quantum dots (more preferably, the quantum dots to which the dispersant is attached) are dispersed in the dispersion medium.
Usually, most of the dispersion medium is removed in the process of manufacturing a thin film as described later.

  As the dispersion medium, for example, ester compounds, ether compounds, hydroxy ketones, carbonic acid diesters, cyclic amide compounds, and the like can be used. Among them, (1) polyhydric alcohols (for example, ethylene glycol, propylene glycol, butylene glycol, glycerin) Ethers (polyhydric alcohol ethers) as condensates of polyhydric alcohols or alkyl ethers of polyhydric alcohol ethers (eg methyl ether, ethyl ether, butyl ether, hexyl ether), esters (eg, formate, acetate) , Propionate, etc.), (2) esters of polyvalent carboxylic acids (eg, succinic acid, glutaric acid, etc.) (eg, methyl esters), (3) at least one hydroxyl group and at least one carboxyl group in the molecule Yes That ether compounds (hydroxy acid), esters and the like, (4) a polyhydric alcohol and a carbonic acid diester having a chemical structure such as obtained by reaction with phosgene, (5) is preferably 12 or more hydrocarbon carbon atoms. Specific compounds that can be used as the dispersion medium include, for example, 2- (2-methoxy-1-methylethoxy) -1-methylethyl acetate, triethylene glycol dimethyl ether, triethylene glycol diacetate, diethylene glycol monoethyl ether. Acetate, 4-methyl-1,3-dioxolan-2-one, bis (2-butoxyethyl) ether, dimethyl glutarate, ethylene glycol di-n-butylate, 1,3-butylene glycol diacetate, diethylene glycol monobutyl ether acetate, Tetraethylene glycol dimethyl ether, 1,6-diacetoxyhexane, methylpropylene triglycol, butoxypropanol, dipropylene glycol dimethyl ether, diethyleneglycol Dimethyl ether, ethyl 3-ethoxypropionate, diethylene glycol ethyl methyl ether, 3-methoxybutyl acetate, diethylene glycol diethyl ether, ethyl octoate, ethylene glycol monobutyl ether acetate, cyclohexyl acetate, diethyl succinate, ethylene glycol diacetate, propylene glycol di Acetate, 4-hydroxy-4-methyl-2-pentanone, dimethyl succinate, 1-butoxy-2-propanol, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether, dipropylene glycol monomethyl ether, 3-methoxy-n-butyl acetate, Diacetin, dipropylene glycol n-propyl ether, polyethylene glycol Methyl ether, butyl glycolate, ethylene glycol monohexyl ether, dipropylene glycol n-butyl ether, N-methyl-2-pyrrolidone, dodecane, dipropylene glycol methyl ether acetate, triethylene glycol butyl methyl ether, tetradecane, cyclohexylbenzene, decalin (Decahydronaphthalene), tetralin, butoxyethanol and the like can be mentioned, and one or more selected from these can be used in combination. Among them, as a dispersion medium, tetradecane, cyclohexylbenzene, decalin, tetralin, butoxyethanol, ethyl octoate, 4-methyl-1,3-dioxolan-2-one, bis (2-butoxyethyl) ether, diethylene glycol monobutyl ether acetate , One or more selected from the group consisting of dodecane, diethylene glycol monoethyl ether acetate, dipropylene glycol methyl ether acetate, triethylene glycol butyl methyl ether, and 1,3-butylene glycol diacetate Is preferred. When the dispersion medium is made of such a material, the dispersibility of the quantum dots (particularly, the quantum dots to which the dispersant is attached) in the dispersion liquid (discharge liquid) may be very excellent. It is possible to prevent variation in the content of quantum dots contained in each droplet discharged from the nozzle hole. Further, when discharging the discharge liquid (dispersion liquid) from the nozzle hole, separation near the interface between the quantum dots as fine particles and the dispersion medium occurs suitably, and the liquid breakage from the nozzle hole is particularly excellent. In addition, the flying curve of the droplet can be prevented more reliably, and the adhesion position accuracy of the droplet on the receiving surface can be made particularly excellent. For this reason, for example, when the discharge liquid is applied to a light emitting element or an image display device, unintentional variation in the density of quantum dots between pixels or in each part in the pixel is prevented and displayed. It is possible to effectively prevent problems such as color unevenness in an image. Moreover, since the above excellent dispersed state can be maintained over a long period of time, the long-term stable ejection required for industrial applications (industrial use) can be made extremely excellent, as described above. Such excellent effects can be stably exhibited over a long period of time. In addition, when the dispersion medium is composed of the above materials, the dispersion medium can have a relatively low volatility (vapor pressure) (a dispersion medium having a relatively high boiling point). . For this reason, even when droplets are repeatedly ejected over a long period of time, it is possible to effectively prevent solid components (quantum dots or the like) of the ejected liquid from adhering to the vicinity of the nozzle holes. In addition, when the dispersion medium is made of the material as described above, the mist generation itself at the time of droplet discharge is suppressed, and even when the mist is generated, the mist is slowly dried. Since it progresses, it falls relatively quickly and does not stay in the atmosphere for a long time. For this reason, it is possible to reduce the load on the environment as described above, and it is possible to more reliably prevent the adverse effects on the human body and the like. In addition, even when the quantum dots contain Cd, Pb, and Cr at a relatively high concentration (however, the total content of Cd, Pb, and Cr in the quantum dots is 100 ppm or less) as described above The occurrence of problems can be reliably prevented.

The boiling point of the dispersion medium under atmospheric pressure (1 atm) is preferably 150 to 280 ° C, more preferably 170 to 270 ° C, and further preferably 180 to 260 ° C. When the boiling point of the dispersion medium under atmospheric pressure is within the above range, clogging or the like in the droplet discharge head that discharges the discharge liquid (dispersion liquid) can be more effectively prevented, and a thin film pattern can be formed. The efficiency can be made particularly excellent.
Further, the vapor pressure of the dispersion medium at 25 ° C. is preferably 0.1 mmHg or less, and more preferably 0.05 mmHg or less. When the vapor pressure of the dispersion medium is within the above range, clogging or the like in the droplet discharge head that discharges the discharge liquid (dispersion liquid) can be more effectively prevented, and the efficiency of thin film pattern formation can be improved. It can be particularly excellent.

  Although the content rate of the dispersion medium in a discharge liquid (dispersion liquid) is not specifically limited, It is preferable that it is 70-98 wt%, and it is more preferable that it is 80-95 wt%. When the content of the dispersion medium is within the above range, the dispersibility (uniformity of dispersion) of the quantum dots in the discharge liquid can be made sufficiently excellent, and the discharge stability during discharge of the discharge liquid In particular, it is possible to make the film and liquid run out particularly excellent, and it is possible to make the formation efficiency of the thin film pattern particularly excellent. Further, for example, when applied to a light emitting element, an image display device, etc., an image display device capable of displaying an image having a particularly high image density while effectively preventing the occurrence of color unevenness is efficiently manufactured. be able to. Further, in the case where the dispersion medium is made of the material as described above, if the content rate of the dispersion medium is a value within the above range, the generation of mist can be more effectively performed during droplet discharge. It can be suppressed, and since it is possible to effectively prevent the mist from staying in the atmosphere for a long time, the load on the environment as described above can be reduced, The occurrence of adverse effects on the human body and the like can be prevented more reliably.

<Antioxidant>
The discharge liquid (dispersion liquid) preferably contains an antioxidant as a component in order to prevent oxidation of the quantum dots having a very small particle diameter and the resulting disintegration / aggregation. Thereby, the dispersion stability of the quantum dots in the discharge liquid (dispersion liquid) can be made particularly excellent, and the liquid breakage at the time of droplet discharge is stabilized. Examples of the antioxidant include phenol-based, sulfur-based, phosphoric acid-based and hindered amine compounds, which can be used alone or in combination of two or more.

  Examples of phenolic antioxidants include 2,2-thiobis (4-methyl-6-tert-butylphenol), 2,6-di-tert-butylphenol, dibutylhydroxytoluene, butylhydroxyanisole, dl-α-tocopherol, tetrakis [Methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate] methane, tris- (3,5, -di-t-butyl-4-hydroxybenzyl) isocyanurate, N , N′-hexamethylenebis (3,5-di-tert-butyl-4-hydroxyhydrocinnamide), 4,4′-thiobis- (2-tert-butyl-5-methylphenol), 1,3, 5-trimethyl-2,4,6-tris- (3,5-di-tert-butyl-4-hydroxybenzyl) -benzene, 2- (1- (2-hydro Cis-3,5-di-t-pentylphenyl) ethyl) -4,6-di-t-pentylphenyl acrylate, 2-t-butyl-6- (3-t-butyl-2-hydroxy-5-methyl) Benzyl) -4-methylphenyl acrylate, 6- (3- (3-t-butyl-4-hydroxy-5-methylphenyl) propoxy) -2,4,8,10-tetra-t-butyldibenz (d, f ) (1, 3, 2) dioxaphosphine. These may be used singly or in combination of two or more.

  Examples of the sulfur-based antioxidant include dialkylthiodipropionates such as dilauryl thiodipropionate, dimyristyl thiodipropionate, and distearyl thiodipropionate, and pentaerythritol tetra (竈 -dodecyl mercaptopropionate).ポ リ オ ー ル -alkyl mercaptopropionic acid esters of the above polyols. These may be used singly or in combination of two or more.

  Examples of phosphorus antioxidants include trisnonylphenyl phosphite, tris [2-tert-butyl-4- (3-tert-butyl-4-hydroxy-5-methylphenylthio) -5-methylphenyl] phos. Phyto, tridecyl phosphite, octyl diphenyl phosphite, di (decyl) monophenyl phosphite, di (tridecyl) pentaerythritol diphosphite, di (nonylphenyl) pentaerythritol diphosphite Tributylphenyl) pentaerythritol diphosphite, bis (2,6-ditert-butyl-4-methylphenyl) pentaerythritol diphosphite, bis (2,4,6-tritert-butylphenyl) pentaerythritol diphosphite Phyto, bis (2,4-dicumylphenyl) pentae Thritol diphosphite, tetra (tridecyl) isopropylidene diphenol diphosphite, tetra (tridecyl) -4,4'-n-butylidenebis (2-tert-butyl-5-methylphenol) diphosphite, hexa (tridecyl)- 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane triphosphite, tetrakis (2,4-ditert-butylphenyl) biphenylene diphosphonite, 9,10-dihydro- 9-oxa-10-phosphaphenanthrene-10-oxide, 2,2′-methylenebis (4,6-tert-butylphenyl) -2-ethylhexyl phosphite, 2,2′-methylenebis (4,6- Tert-butylphenyl) -octadecyl phosphite, 2,2′-ethylidenebis (4,6 Di-tert-butylphenyl) fluorophosphite, tris (2-[(2,4,8,10-tetrakis tert-butyldibenzo [d, f] [1,3,2] dioxaphosphin-6-yl ) Oxy] ethyl) amine, phosphite of 2-ethyl-2-butylpropylene glycol and 2,4,6-tritert-butylphenol, and the like. These may be used singly or in combination of two or more.

Examples of hindered amine antioxidants include 2,2,6,6-tetramethyl-4-piperidyl stearate, 1,2,2,6,6-pentamethyl-4-piperidyl stearate, 2,2,6. , 6-tetramethyl-4-piperidylbenzoate, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, Tetrakis (2,2,6,6-tetramethyl-4-piperidylbutanetetracarboxylate, tetrakis (1,2,2,6,6-pentamethyl-4-piperidylbutanetetracarboxylate, bis (2,2,6 , 6-Tetramethyl-4-piperidyl) .di (tridecyl) -1,2,3,4-butanetetracarboxylate, bis (1,2,2 6,6-pentamethyl-4-piperidyl) .di (tridecyl) -1,2,3,4-butanetetracarboxylate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) -2- Butyl-2- (3,5-ditert-butyl-4-hydroxybenzyl) malonate, 1- (2-hydroxyethyl) -2,2,6,6-tetramethyl-4-piperidinol / diethyl succinate polycondensation 1,6-bis (2,2,6,6-tetramethyl-4-piperidylamino) hexane / dibromoethane polycondensate, 1,6-bis (2,2,6,6-tetramethyl-4 -Piperidylamino) hexane / 2,4-dichloro-6-morpholino-s-triazine polycondensate, 1,6-bis (2,2,6,6-tetramethyl-4-piperidylamino) hexane / 2,4 - Rollo-6-tert-octylamino-s-triazine polycondensate, 1,5,8,12-tetrakis [2,4-bis (N-butyl-N- (2,2,6,6-tetramethyl- 4-piperidyl) amino) -s-triazin-6-yl] -1,5,8,12-tetraazadodecane, 1,5,8,12-tetrakis [2,4-bis (N-butyl-N- (1,2,2,6,6-pentamethyl-4-piperidyl) amino) -s-triazin-6-yl] -1,5,8,12-tetraazadodecane, 1,6,11-tris [2 , 4-Bis (N-butyl-N- (2,2,6,6-tetramethyl-4-piperidyl) amino) -s-triazin-6-yl] aminoundecane, 1,6,11-tris [2 , 4-Bis (N-butyl-N- (1,2,2,6,6-pentamethyl And hindered amine compounds such as -4-piperidyl) amino) -s-triazin-6-yl] aminoundecane. These may be used alone or in combination of two or more.
The content of the antioxidant with respect to 100 parts by weight of the dispersion is preferably 10 to 20000 ppm, more preferably 20 to 15000 ppm, still more preferably 30 to 10000 ppm, and 50 to 6000 ppm. Is most preferred.

<Other ingredients>
The discharge liquid (dispersion liquid) may contain various other components as necessary. Examples of such components (other additives) include various crosslinking agents; various polymerization initiators; dispersion aids such as blue pigment derivatives such as copper phthalocyanine derivatives and yellow pigment derivatives; fillers such as glass and alumina; Polymer compounds such as polyvinyl alcohol, polyethylene glycol monoalkyl ether, polyfluoroalkyl acrylate; vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, N- (2-aminoethyl) -3-amino Propylmethyldimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2- (3,4-epoxy Chlohexyl) adhesion promoter such as ethyltrimethoxysilane, 3-chloropropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane; sodium polyacrylate, etc. Anti-agglomeration agent; Discharge performance stabilizers such as methanol, ethanol, i-propanol, n-butanol, glycerin, etc .; ), Megafuck F171, F172, F173, F178K (above, Dainippon Ink & Chemicals, Inc.), Florard FC430, FC431 (above, Sumitomo 3M Limited), Asahi Guard AG710, Surflon S -382, SC- 01, the SC-102, the SC-103, the SC-104, the SC-105, the SC-106 (manufactured by Asahi Glass Co.), (manufactured by Shin-Etsu Chemical Co.) KP341, Polyflow No. 75, no. 95 (above, manufactured by Kyoeisha Yushi Chemical Co., Ltd.) and the like.

  The total content of Cd, Pb, and Cr in the discharge liquid (dispersion liquid) as described above is preferably 5.0 ppm or less, more preferably 3.0 ppm, and 2.0 ppm or less. Is more preferable. Thereby, generation | occurrence | production of the above problems can be prevented more reliably. That is, it is possible to reduce the burden on the environment when manufacturing a light emitting element, an image display device, and the like. It is possible to more reliably prevent adverse effects on the surface.

  Moreover, the viscosity at 25 ° C. (viscosity measured using a vibration viscometer) of the discharge liquid (dispersion liquid) as described above is not particularly limited, but is preferably 3 to 15 mPa · s. More preferably, it is 10 mPa · s. When the viscosity of the discharge liquid (dispersion liquid) is a value within the above range, in the liquid droplet discharge as will be described later, the liquid droplet amount of the discharged discharge liquid (dispersion liquid) is made particularly small, The occurrence of clogging or the like in the droplet discharge head can be prevented more reliably. The viscosity of the discharge liquid (dispersion liquid) can be measured using, for example, a vibration viscometer, and can be particularly performed in accordance with JIS Z8809.

The above discharge liquid (dispersion liquid) can be prepared as follows, for example.
The discharge liquid (dispersion liquid) of the present invention as described above is stored in an environment where oxygen and moisture are removed in order to prevent the quantum dots from being deteriorated by oxygen and moisture in the atmosphere. Good.
That is, a discharge liquid (dispersion liquid) containing quantum dots composed of an XY-type compound (where X is a metal atom and Y is a nonmetal atom) can be prepared, for example, as follows.

First, a compound containing a metal atom X as a constituent atom (raw material compound) and a compound containing a non-metal atom Y as a constituent atom (raw material compound) under conditions where oxygen and moisture are prevented from entering the system And a liquid (second liquid) containing the dispersing agent (surface modifier) as described above. Thus, by using a compound (raw material compound) containing a metal atom X as a constituent atom and a compound (raw material compound) containing a non-metal atom Y as a constituent atom, prior to the synthesis of the compound XY, the raw material The compound can be suitably purified, and Cd, Pb, and Cr are reliably prevented from being mixed into the prepared discharge liquid (dispersion).
When preparing a quantum dot composed of InP (when X is In and Y is P), examples of the raw material compound include indium chloride (InCl ₃ ) and trisdimethylaminophosphine (P (NMe _{2). 3} ) can be suitably used. Moreover, as a dispersing agent (surface modifier), trioctyl phosphine, trioctyl phosphine oxide, tridecyl phosphine oxide, tri-tert-butyl phosphine, etc. can be used conveniently. In particular, it is preferable to use a combination of two or more selected from these. Thereby, the particle diameter of a quantum dot can be adjusted easily and reliably to a desired magnitude | size, and the wavelength of the emitted light from a quantum dot can be made into a desired value easily and reliably. In addition, the stability of the quantum dots in the discharge liquid can be made particularly excellent.

Next, the reaction proceeds by mixing the first liquid and the second liquid while heating.
The heating temperature at this time is not particularly limited, but is preferably 100 to 400 ° C, and more preferably 150 to 350 ° C.
Next, the above reaction solution is cooled, and an organic solvent (organic solvent) is added to precipitate the compound XY as an insoluble matter (quantum dot).

  Examples of the organic solvent used at this time include hydrocarbon solvents (solvents) such as toluene and xylene, and alcohol solvents (solvents) such as methanol, ethanol, and 1-butanol. And an alcohol solvent are preferably used in combination, and xylene, methanol and 1-butanol are preferably used in combination. Thereby, a quantum dot with a very sharp particle size distribution can be obtained easily and reliably.

Next, the quantum dot comprised with the compound XY is obtained by centrifuging and performing decantation, vacuum drying, etc.
In addition, you may wash | clean a quantum dot as needed.
Then, the target discharge liquid (dispersion liquid) can be obtained by dispersing the obtained quantum dots in a dispersion medium.

Moreover, when preparing a quantum dot as what has a core-shell structure, the particle | grains (particle | grains demonstrated as a quantum dot in said description) as mentioned above become a nucleus (core part, core area | region). Thus, an outer shell (shell region) may be formed on the surface. As a more specific example, a method for forming a shell region made of ZnS will be described below.
First, a liquid (first liquid) containing particles prepared as described above (particles to be the core region) and a dispersant (surface modifier) under conditions where oxygen and moisture are prevented from entering the system. 3 liquid) and a liquid (fourth liquid) containing diethyl zinc, bis (trimethylsilyl) sulfide and a dispersant (surface modifier) are prepared.

Next, the third liquid and the fourth liquid are mixed while being heated, then cooled, and an organic solvent (organic solvent) is further added. Although the heating temperature at this time is not specifically limited, It is preferable that it is 80-300 degreeC, and it is more preferable that it is 90-220 degreeC. Examples of the organic solvent include hydrocarbon solvents (solvents) such as toluene and xylene, and alcohol solvents (solvents) such as methanol, ethanol, and 1-butanol. Methanol is preferably used. . Thereby, a quantum dot having a very sharp particle size distribution and a small variation in the thickness of the shell region can be obtained easily and reliably.
Then, the quantum dot which has a core-shell structure is obtained by centrifuging and performing decantation, vacuum drying, etc.
In addition, you may wash | clean the quantum dot of a core-shell structure as needed.

<Discharge liquid set>
Next, a discharge liquid set (dispersion liquid set) including a plurality of discharge liquids as described above will be described. Quantum dots included in each discharge liquid (dispersion liquid) constituting the discharge liquid set have different particle sizes. More specifically, as the discharge liquid set, for example, a first discharge liquid (first dispersion liquid) including a first quantum dot having a predetermined particle diameter and a particle diameter larger than that of the first quantum dot. A second discharge liquid (second dispersion liquid) containing the second quantum dots and a third quantum dot having a particle diameter larger than the first quantum dots and smaller than the second quantum dots. 3 discharge liquids (third dispersion liquid). In such a case, for example, the first quantum dot emits blue light by application of voltage (bonding of electrons and holes) or irradiation of ultraviolet rays, and the second quantum dot applies voltage. It emits red when irradiated with (electron and hole) or ultraviolet irradiation. The third quantum dot turns green when voltage is applied (bonding between electron and hole) or ultraviolet irradiation. It emits light.

By using such a discharge liquid set, the present invention can be suitably applied to an image display apparatus that can display a high-luminance image with a particularly wide color reproduction range.
In addition, each discharge liquid (dispersion liquid) which comprises a discharge liquid set may mutually be the same as conditions other than the particle diameter of a quantum dot, and may differ. More specifically, each discharge liquid (dispersion liquid) constituting the discharge liquid set may have the same or different content ratio of quantum dots, content ratio of dispersion medium, composition, and the like. Also good.

<< Thin film pattern forming method >>
Next, a thin film pattern forming method using the above-described discharge liquid (discharge liquid set) will be described.
The thin film pattern forming method of the present invention is a step of discharging a discharge liquid (dispersion) as described above by a droplet discharge method in which droplets are intermittently discharged from a nozzle hole, and attaching it to a receiving surface in a predetermined pattern ( A discharge step) and a step of removing at least a part of the dispersion medium from the discharge liquid (dispersion) adhering to the receiving surface (dispersion medium removal step).

  The thin film pattern forming method of the present invention is desirably performed in an environment from which oxygen and moisture are removed in order to prevent the quantum dots from being deteriorated by oxygen and moisture in the atmosphere. At this time, the oxygen concentration in the atmosphere to which the discharge liquid (dispersion) is exposed is preferably 500 ppm or less, more preferably 200 ppm or less, and even more preferably 50 ppm or less. Thus, when the oxygen concentration in the atmosphere is sufficiently low, the deterioration of the quantum dots can be more effectively prevented.

<Discharge process>
In this step, the above-described discharge liquid (dispersion liquid) is discharged by a droplet discharge method. As described above, in the present invention, the discharge liquid has a total content of Cd, Pb, and Cr in the quantum dots of a predetermined value or less. For this reason, the bad influence by the mist inevitably generated at the time of droplet discharge is effectively prevented.

  The droplet discharge method is not particularly limited as long as it is a method capable of intermittently discharging droplets of the discharge liquid (dispersion liquid) from the nozzle holes. Dispersion is intermittently ejected (so-called “inkjet method”), “dispersion is intermittently ejected from the nozzle holes of the head by gas volume change (so-called“ bubble jet method ”), etc. Is mentioned. Among these, the inkjet method is preferable as the droplet discharge method. By using the inkjet method as the droplet discharge method, the effect of including the dispersion medium composed of the components as described above is remarkably exerted, and the discharge liquid from the nozzle holes during droplet discharge ( Dispersion of the dispersion liquid can be made particularly excellent, and the occurrence of flight bending can be more reliably prevented. As a result, it is possible to more accurately control the amount and position of the dispersion attached to the receiving surface. In addition, the ratio of mist (discharge liquid that stays in the atmosphere without adhering to the target receiving surface) generated at the time of discharge of the discharge liquid is particularly small as compared with the so-called bubble jet method or the like. it can. As a result, the load on the environment when manufacturing a light emitting element, an image display device, and the like can be made particularly small. It is possible to more reliably prevent adverse effects on the surface.

The droplet discharge of the discharge liquid (dispersion liquid) is preferably performed using a droplet discharge head made of a silicon material. Thereby, it is possible to suppress adhesion of the quantum dots to the inside of the head.
Further, in this step, droplet discharge of the discharge liquid (dispersion liquid) is performed in an anaerobic environment, more specifically in a dry inert gas (eg, N ₂ , He, Ne, Ar, etc.) atmosphere. It is preferred to do so. Thereby, it is possible to reliably prevent the quantum dots from being deteriorated by oxygen or moisture, and to make the formed thin film particularly excellent in reliability.
In this step, the discharge liquid (dispersion liquid) is discharged in a pattern corresponding to the thin film to be formed, but it is preferable to discharge the liquid so that a plurality of minute units are arranged in a matrix.

  As described above, when the liquid is ejected by the droplet ejection method so that a plurality of minute units are arranged in a matrix, it is necessary to sufficiently reduce the ejection amount of the ejection liquid per droplet. As described above, in the present invention, since the total amount of Cd, Pb, and Cr contained in the quantum dots is not more than a predetermined value in the present invention, the discharge liquid is unavoidable at the time of droplet discharge. Adverse effects due to mist generated automatically can be effectively prevented. In addition, when a liquid is discharged by a droplet discharge method so that a plurality of minute units are arranged in a matrix, generally, a plurality of minute units are combined to form a relatively large liquid reservoir. It is easy to cause a problem such that the discharged droplets adhere to a portion where an adjacent minute unit should be formed instead of a portion where a desired minute unit is to be formed, and a desired pattern is formed. Although difficult, such a problem is hardly caused in the dispersion liquid containing the quantum dots as described above. That is, when the present invention is applied to a method of discharging a dispersion liquid so that a plurality of minute units are arranged in a matrix, the effect of the present invention is more remarkably exhibited.

<Dispersion medium removal step>
The method for removing at least a part of the dispersion medium from the discharge liquid (dispersion medium) adhering to the receiving surface is not particularly limited. For example, a method of heating the workpiece to which the discharge liquid (dispersion liquid) is attached, A method in which the work to which the dispersion liquid is attached is placed in a reduced-pressure atmosphere, or a combination of these methods (for example, the work to which the discharge liquid (dispersion) is attached in a reduced-pressure atmosphere at the first temperature is placed in a reduced-pressure atmosphere. Thereafter, the atmosphere is returned to atmospheric pressure and heated under atmospheric pressure, etc.). At this time, it is more effective to remove the dispersion medium in a reduced-pressure atmosphere while removing oxygen and moisture in order to prevent the quantum dots having a very small particle size from being deteriorated by oxygen and moisture in the atmosphere. .

The treatment temperature (heating temperature) in this step depends on the composition of the dispersion medium and the like, but is preferably 50 to 300 ° C, more preferably 100 to 200 ° C.
The oxygen concentration in the atmosphere in this step is preferably 500 ppm or less, more preferably 200 ppm or less, and even more preferably 50 ppm or less. Thus, when the oxygen concentration in the atmosphere is sufficiently low, deterioration of the quantum dots can be more effectively prevented.
By performing the dispersion medium removing step, a target thin film pattern can be obtained. That is, in the present invention, since the droplets are discharged as described above, it is not necessary to perform post-processing such as patterning on the formed thin film after the dispersion medium removing step.

<Thin film>
Through the steps as described above, the thin film of the present invention is obtained. The thin film thus obtained has a shape corresponding to the droplet discharge pattern.
Although the thin film of this invention changes with the uses, generally the thickness is 10-700 nm, and it is more preferable that it is 20-500 nm.
The thin film of the present invention may be used for any purpose, and can be suitably applied to, for example, a light emitting element, a light emitting layer constituting an image display device, a solar cell, a lighting device, and the like.
Hereinafter, an example when the thin film and thin film pattern forming method of the present invention is applied to a light emitting element and a light emitting layer constituting an image display device will be described in more detail.

<Image display device>
Hereinafter, an active matrix display device will be described as an example of the image display device of the present invention.
FIG. 1 is a longitudinal sectional view showing an example of an active matrix display device as an image display device of the present invention. In the following description, the upper side in FIGS. 1 and 2 is referred to as “upper” and the lower side is referred to as “lower”.

An active matrix display device (hereinafter simply referred to as “display device”) 10 shown in FIG. 1 includes a TFT circuit substrate (counter substrate) 20, a light emitting element 1 provided on the TFT circuit substrate 20, and a TFT And an upper substrate 9 facing the circuit board 20.
The TFT circuit substrate 20 includes a substrate 21 and a circuit unit 22 formed on the substrate 21.

The substrate 21 serves as a support for each part constituting the display device 10, and the upper substrate 9 functions as, for example, a protective film for protecting the light emitting element 1.
Moreover, since the display device 10 of the present embodiment has a configuration (top emission type) in which light is extracted from the upper substrate 9 (anode 8 described later) side, the upper substrate 9 is substantially transparent (colorless and transparent, colored and transparent). On the other hand, the substrate 21 is not particularly required to be transparent.
As such a substrate 21, a substrate having a relatively high hardness among various glass material substrates and various resin substrates is suitably used.

  On the other hand, as the upper substrate 9, a transparent one of various glass material substrates and various resin substrates is selected. For example, glass materials such as quartz glass and soda glass, polyethylene terephthalate, polyethylene naphthalate, polypropylene, cycloolefin A substrate composed mainly of a resin material such as polymer, polyamide, polyethersulfone, polymethyl methacrylate, polycarbonate, or polyarylate can be used.

Although the average thickness of the board | substrate 21 is not specifically limited, It is preferable that it is about 1-30 mm, and it is more preferable that it is about 5-20 mm. On the other hand, the average thickness of the upper substrate 9 is not particularly limited, but is preferably about 0.1 to 30 mm, and more preferably about 0.1 to 10 mm.
The circuit unit 22 includes a base protective layer 23 formed on the substrate 21, a driving TFT (switching element) 24 formed on the base protective layer 23, a first interlayer insulating layer 25, and a second interlayer insulating layer. 26.

The driving TFT 24 includes a semiconductor layer 241, a gate insulating layer 242 formed on the semiconductor layer 241, a gate electrode 243 formed on the gate insulating layer 242, a source electrode 244, and a drain electrode 245. ing.
On such a circuit portion 22, the light emitting element 1 is provided corresponding to each driving TFT 24. Adjacent light emitting elements 1 are partitioned by a partition wall (bank) 35 including a first partition wall portion 31 and a second partition wall portion 32.

In the present embodiment, the cathode 3 of each light emitting element 1 constitutes a pixel electrode and is electrically connected to the drain electrode 245 of each driving TFT 24 by the wiring 27. Further, the electron transport layer 5, the light emitting layer 6, and the hole transport layer 7 are individually formed for each light emitting element 1, and the anode 8 is a common electrode.
The display device 10 may be a single color display or a color display. When the display device 10 includes a plurality of types of light-emitting elements 1 including quantum dots having different particle sizes, color display can be realized. In particular, by using quantum dots having a controlled particle size, each light emitting element 1 can surely exhibit a desired color tone, so that an image with a desired image quality can be displayed. The color gamut can be widened.

Hereinafter, the light emitting device 1 will be described in detail.
As shown in FIG. 1, the light-emitting element 1 includes a cathode 3 and an anode 8, and further, between the cathode 3 and the anode 8, an electron transport layer 5 and a light-emitting layer 6 in order from the cathode 3 side. And a hole transport layer 7.
The cathode 3 is an electrode that injects electrons into the electron transport layer 5.

Examples of the constituent material of the cathode 3 include Li, Mg, Ca, Sr, La, Ce, Er, Eu, Sc, Y, Yb, Ag, Cu, Al, Cs, Rb, and alloys containing these. These can be used alone or in combination of two or more thereof (for example, a multi-layer laminate).
In particular, when an alloy is used as the constituent material of the cathode 3, it is preferable to use an alloy containing a stable metal element such as Ag, Al, or Cu, specifically an alloy such as MgAg, AlLi, or CuLi. By using such an alloy as the constituent material of the cathode 3, the electron injection efficiency and stability of the cathode 3 can be improved.

Although the average thickness of such a cathode 3 is not specifically limited, It is preferable that it is about 10-10000 nm, and it is more preferable that it is about 50-500 nm. If the thickness of the cathode 3 is less than the lower limit value, the function of the cathode 3 may not be sufficiently exhibited. The characteristics such as the above may be deteriorated.
The surface resistance of the cathode 3 is preferably as low as possible. Specifically, it is preferably 50Ω / □ or less, more preferably 20Ω / □ or less. The lower limit value of the surface resistance is not particularly limited, but is usually preferably about 0.1Ω / □.

On the other hand, the anode 8 is an electrode that injects holes into the hole transport layer 7.
As a constituent material (anode material) of the anode 8, a conductive material having translucency is selected because the display device 10 has a top emission structure in which light is extracted from the anode 8 side. A material having a larger work function than the constituent material 3) and having excellent conductivity is preferably used.

Examples of the constituent material of the anode 8 include indium tin oxide (ITO), fluorine-containing indium tin oxide (FITO), antimony tin oxide (ATO), indium zinc oxide (IZO), aluminum zinc oxide (AZO), and tin oxide. Transparent conductive materials such as (SnO ₂ ), zinc oxide (ZnO), fluorine-containing tin oxide (FTO), fluorine-containing indium oxide (FIO), indium oxide (IO), and the like, at least one of these Can be used.

  The average thickness of the anode 8 is not particularly limited, but is preferably about 10 to 2000 nm, and more preferably about 50 to 1000 nm. When the thickness of the anode 8 is less than the lower limit value, the function as the anode 8 may not be sufficiently exhibited. On the other hand, when the thickness of the anode 8 exceeds the upper limit value, the constituent material of the anode 8 Depending on the above, the light transmittance may decrease, and the light emitting element 1 having a top emission type structure may not be suitable for practical use.

Further, the surface resistance of the anode 8 is preferably as low as possible. Specifically, it is preferably 100Ω / □ or less, and more preferably 50Ω / □ or less. The lower limit value of the surface resistance is not particularly limited, but is usually preferably about 0.1Ω / □.
Such an anode 8 has a light transmittance (visible light region) of preferably 60% or more, more preferably 80% or more. Thereby, light can be efficiently extracted from the anode 8 side.

The electron transport layer 5 has a function of transporting electrons injected from the cathode 3 to the light emitting layer 6.
The electron transport layer 5 can be composed of various n-type inorganic semiconductor materials and various n-type organic semiconductor materials, but is preferably composed of an inorganic semiconductor material as a main material. Since the inorganic semiconductor material is chemically stable, the durability of the light-emitting element 1 can be further improved when the electron transport layer 5 is composed of the inorganic semiconductor material as a main material.

Examples of the inorganic semiconductor material include titanium oxide (TiO ₂ ), zirconium oxide (ZrO ₂ ), zinc oxide (ZnO), aluminum oxide (Al ₂ O ₃ ), tin oxide (SnO ₂ ), ScVO ₄ , YVO ₄ , _{LaVO 4, NdVO 4, EuVO 4} , GdVO 4, ScNbO 4, ScTaO 4, YNbO 4, YTaO 4, ScPO 4, ScAsO 4, ScSbO 4, ScBiO 4, YPO 4, YSbO 4, BVO 4, AlVO 4, GaVO 4 , InVO ₄ , TlVO ₄ , InNbO ₄ , InTaO ₄ metal oxide, ZnS metal sulfide, metal selenide, TiC, SiC metal or semiconductor carbide, BN, B ₄ N Semiconductor nitrides, etc., one or more of these In combination it can be used.
Among these, as the inorganic semiconductor material, a metal oxide, particularly, a material mainly containing at least one of titanium oxide and zirconium oxide is preferable. Metal oxides (especially titanium oxide and zirconium oxide) are preferred because they are particularly excellent in electron transport ability.

Examples of organic semiconductor materials include 1,3,5-tris [(3-phenyl-6-tri-fluoromethyl) quinoxalin-2-yl] benzene (TPQ1), 1,3,5-tris [{ Benzene compounds such as 3- (4-t-butylphenyl) -6-trisfluoromethyl} quinoxalin-2-yl] benzene (TPQ2), naphthalene compounds, phenanthrene compounds, chrysene compounds, perylene compounds, Anthracene compounds, pyrene compounds, acridine compounds, stilbene compounds, thiophene compounds such as BBOT, butadiene compounds, coumarin compounds, quinoline compounds, bistyryl compounds, pyrazine compounds such as distyrylpyrazine, Quinoxaline compounds, 2,5-diphenyl-para-benzoyl Such as benzoquinone compounds, naphthoquinone compounds, anthraquinone compounds, 2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole (PBD) Oxadiazole compounds, triazole compounds such as 3,4,5-triphenyl-1,2,4-triazole, oxazole compounds, anthrone compounds, 1,3,8-trinitro-fluorenone (TNF) Such as fluorenone compound, diphenoquinone compound such as MBDQ, stilbenequinone compound such as MBSQ, anthraquinodimethane compound, thiopyran dioxide compound, fluorenylidenemethane compound, diphenyldicyanoethylene compound, Florene compounds, 8-hydroxyquinoline aluminum Um (Alq _3), various metal complexes such as complexes that benzoxazole or benzothiazole as a ligand, phthalocyanine, copper phthalocyanine (CuPc), metal or phthalocyanine compound free metals such as iron phthalocyanine, tris (8 -Hydroxyquinolinolate) Low molecular weight materials such as aluminum (Alq ₃ ), and high molecular weight materials such as oxadiazole polymers and triazole polymers.

Although the average thickness of such an electron carrying layer 5 is not specifically limited, It is preferable that it is 1-200 nm, and it is more preferable that it is 5-100 nm. Thereby, it is possible to reduce the thickness of the light emitting element 1 while preventing the mechanical strength (film strength) of the electron transport layer 5 from being lowered.
An electron injection layer that improves the efficiency of electron injection from the cathode 3 may be provided between the cathode 3 and the electron transport layer 5, for example.

Examples of the constituent material (electron injection material) of the electron injection layer include 8-hydroxyquinoline, oxadiazole, or derivatives thereof (for example, metal chelate oxinoid compounds containing 8-hydroxyquinoline). These can be used alone or in combination of two or more thereof.
The hole transport layer 7 has a function of transporting holes injected from the anode 8 to the light emitting layer 6.

  Examples of the constituent material (hole transport material) of the hole transport layer 7 include polyarylamine, fluorene-arylamine copolymer, fluorene-bithiophene copolymer, poly (N-vinylcarbazole), polyvinylpyrene, Polyvinylanthracene, polythiophene, polyalkylthiophene, polyhexylthiophene, poly (p-phenylene vinylene), polytinylene vinylene, pyrene formaldehyde resin, ethyl carbazole formaldehyde resin or derivatives thereof, and the like, one or two of these A combination of more than one species can be used.

Moreover, the said compound can also be used as a mixture with another compound. As an example, the polythiophene-containing mixture includes poly (3,4-ethylenedioxythiophene / styrene sulfonic acid) (PEDOT / PSS) and the like.
As the hole transport material, in addition to organic materials such as the above-described polymer materials and low molecular materials, for example, MoO ₃ , V ₂ O ₅ , TiO ₂ , Cu (II) O, Cu ( I) Metal oxides such as ₂ O, NiO and CoO can also be used.

Although the average thickness of such a hole transport layer 7 is not specifically limited, It is preferable that it is 1-200 nm, and it is more preferable that it is 5-100 nm. Thereby, sufficient light emission efficiency can be obtained while preventing the light-emitting element 1 from becoming large (in particular, thick).
Note that a hole injection layer that improves the hole injection efficiency from the anode 8 may be provided between the anode 8 and the hole transport layer 7, for example.

As a constituent material (hole injection material) of this hole injection layer, for example, copper phthalocyanine, 4,4 ′, 4 ″ -tris (N, N-phenyl-3-methylphenylamino) triphenylamine ( m-MTDATA) and the like.
The light emitting layer 6 is formed using the discharge liquid (dispersion liquid) as described above, and is mainly composed of quantum dots.

  When energization (voltage is applied) between the cathode 3 and the anode 8, holes are injected from the anode 8 into the light emitting layer 6 through the hole transport layer 7, and from the cathode 3 through the electron transport layer 5. Electrons are injected into the light emitting layer 6, and holes and electrons are recombined in the light emitting layer 6. And in the light emitting layer 6, an exciton (exciton) produces | generates, and when this exciton returns to a ground state, energy is discharge | released (light emission). The energy released in this way is light having a specific wavelength that depends on the type of quantum dots constituting the light emitting layer 6.

Although the average thickness of the light emitting layer 6 is not specifically limited, It is preferable that it is about 1-150 nm, and it is more preferable that it is about 2-100 nm.
The area of each light-emitting layer 6 when viewed in plan display device 10 is preferably a 1000～200000Myuemu ^2, and more preferably 10000~100000μm ^2.
In the display device 10 as described above, one or both of the electron transport layer 5 and the hole transport layer 7 may be omitted. In other words, the light emitting element 1 may not include the electron transport layer 5 and / or the hole transport layer 7.
The display device 10 as described above can be manufactured by, for example, a manufacturing method as described below (a method to which the thin film pattern forming method of the present invention is applied).

<< Method for Manufacturing Image Display Device (Method for Forming Light-Emitting Layer) >>
FIG. 2 is a view (longitudinal sectional view) for explaining the manufacturing method of the active matrix display device shown in FIG. 1, and FIG. 3 is a perspective view showing a droplet discharge device used for forming a light emitting layer (thin film). 4 is a view of the droplet discharge means in the droplet discharge apparatus shown in FIG. 3 observed from the stage side, FIG. 5 is a view showing the bottom surface of the droplet discharge head in the droplet discharge apparatus shown in FIG. FIG. 4 is a view showing a droplet discharge head in the droplet discharge apparatus shown in FIG. 3, wherein (a) is a sectional perspective view and (b) is a sectional view.

[1] First, the TFT circuit substrate 20 is prepared.
[1-A] First, a substrate 21 is prepared, and an average thickness of about 200 to 500 nm is formed on the substrate 21 by, for example, plasma CVD using TEOS (tetraethoxysilane) or oxygen gas as a source gas. A base protective layer 23 composed of silicon oxide as a main material is formed.

[1-B] Next, the driving TFT 24 is formed on the base protective layer 23.
[1-Ba] First, amorphous silicon having an average thickness of about 30 to 70 nm is mainly formed on the base protective layer 23 by the plasma CVD method or the like with the substrate 21 heated to about 350 ° C. A semiconductor film is formed.
[1-Bb] Next, the semiconductor film is crystallized by laser annealing, solid phase growth, or the like to change the amorphous silicon into polysilicon.
Here, in the laser annealing method, for example, a line beam having a beam length of 400 mm is used with an excimer laser, and the output intensity is set to about 200 mJ / cm ² , for example. As for the line beam, the line beam is scanned so that a portion corresponding to 90% of the peak value of the laser intensity in the short dimension direction overlaps each region.

[1-Bc] Next, the semiconductor film is patterned to form islands, and for example, a plasma CVD method using TEOS (tetraethoxysilane) or oxygen gas as a source gas so as to cover each island-shaped semiconductor film 241. Thus, a gate insulating layer 242 composed mainly of silicon oxide or silicon nitride having an average thickness of about 60 to 150 nm is formed.
[1-Bd] Next, a conductive film composed mainly of a metal such as aluminum, tantalum, molybdenum, titanium, or tungsten is formed on the gate insulating layer 242 by, for example, sputtering, and then patterned. A gate electrode 243 is formed.
[1-Be] Next, in this state, high concentration phosphorus ions are implanted to form source / drain regions in a self-aligned manner with respect to the gate electrode 243. Note that a portion where impurities are not introduced becomes a channel region.

[1-C] Next, the source electrode 244 and the drain electrode 245 electrically connected to the driving TFT 24 are formed.
[1-Ca] First, the first interlayer insulating layer 25 is formed so as to cover the gate electrode 243, and then a contact hole is formed.
[1-Cb] Next, the source electrode 244 and the drain electrode 245 are formed in the contact hole.

[1-D] Next, a wiring (relay electrode) 27 that electrically connects the drain electrode 245 and the anode 8 is formed.
[1-Da] First, the second interlayer insulating layer 26 is formed on the first interlayer insulating layer 25, and then contact holes are formed.
[1-Db] Next, a wiring 27 is formed in the contact hole.
As described above, the TFT circuit substrate 20 is obtained.

[2] Next, the light emitting element 1 is formed on the TFT circuit substrate 20. [2-A] First, as shown in FIG. 2A, on the second interlayer insulating layer 26 included in the TFT circuit substrate 20, The cathode (pixel electrode) 3 is formed so as to be in contact with the wiring 27.
The cathode 3 is formed on the second interlayer insulating layer 26 by forming a conductive film made of a material constituting the target cathode 3 by, for example, a vapor deposition method such as a vacuum deposition method or a sputtering method. It can be obtained by patterning.

[2-B] Next, as shown in FIG. 2B, partition walls (banks) 35 are formed on the second interlayer insulating layer 26 so as to partition the cathodes 3.
The partition wall portion 35 can be obtained by forming the first partition wall portion 31 on the second interlayer insulating film 26 and then forming the second partition wall portion 32 on the first partition wall portion 31.
The first partition wall 31 can be formed by forming an insulating film so as to cover the cathode 3 and the second interlayer insulating film 26 and then patterning using a photolithography method or the like.

Further, the second partition wall portion 32 can be formed in the same manner as the first partition wall portion 31 obtained after forming an insulating film so as to cover the cathode 3 and the first partition wall portion 31.
Here, the constituent materials of the first partition wall portion 31 and the second partition wall portion 32 are selected in consideration of heat resistance, liquid repellency, solvent resistance, adhesion to the underlayer, and the like.
Specifically, examples of the constituent material of the first partition wall 31 include organic materials such as acrylic resins and polyimide resins, and inorganic materials such as SiO ₂ .

Moreover, as a constituent material of the 2nd partition part 32, a fluorine resin etc. can be used other than what was mentioned by the 1st partition part 31, for example. By using the fluorine-based resin, the moisture absorption resistance of the second partition wall 32 can be improved.
Further, the shape of the opening of the partition wall 35 may be any shape such as, for example, a circle, an ellipse, a rectangle, a polygon such as a hexagon.
In addition, when making the shape of the opening of the partition part 35 into a polygon, it is preferable that the corner part is rounded. Thereby, when forming the electron transport layer 5, the light emitting layer 6, and the hole transport layer 7, the liquid material for forming the electron transport layer 5, the discharge liquid (dispersed liquid) described above, The liquid material can be reliably supplied to every corner of the space inside the partition wall portion 35.

[2-C] Next, as shown in FIG. 2C, the electron transport layer 5, the light emitting layer 6, and the hole transport layer 7 are formed on each cathode 3, that is, so as to cover each cathode 3. Are stacked in this order (second step).
Hereinafter, the formation method of the electron carrying layer 5, the light emitting layer 6, and the positive hole transport layer 7 is demonstrated.
[2-Ca] First, the electron transport layer 5 is formed on each cathode 3.
The electron transport layer 5 is formed by a vapor phase process using a sputtering method, a vacuum deposition method, a CVD method, a spin coating method (pyrosol method), a casting method, a micro gravure coating method, a gravure coating method, a bar coating method, a roll. Formed by a liquid phase process using a droplet discharge method such as a coating method, a wire bar coating method, a dip coating method, a spray coating method, a screen printing method, a flexographic printing method, an offset printing method, an ink jet method, a bubble jet method, etc. Among them, a droplet discharge method is preferable, and an inkjet method is more preferable. By using such a method, the electron transport layer 5 can be made thinner and the pixel size can be reduced. Further, since the liquid material for forming the electron transport layer can be selectively supplied to the inside of the partition wall 35, the waste of the liquid material can be omitted. When the electron transport layer 5 is formed by the droplet discharge method, the droplet discharge method is preferably a method similar to that described in detail in the formation method of the light emitting layer 6 described later.

When the electron transport layer 5 is formed by a liquid phase process, a liquid material for forming an electron transport layer is applied onto the cathode 3, and then a solvent or dispersion medium contained in the applied liquid material for forming an electron transport layer. Is removed (desolvent or dedispersion medium).
Examples of the solvent removal or dispersion medium include a method of leaving in a reduced pressure atmosphere, a method by heat treatment, a method by a flow of an inert gas such as nitrogen gas, and a method combining these.
The liquid material to be used is prepared by dissolving or dispersing the electron transport material as described above in a solvent or a dispersion medium.

Examples of the solvent or dispersion medium used for preparing the liquid material include various inorganic solvents such as nitric acid, sulfuric acid, ammonia, hydrogen peroxide, water, carbon disulfide, carbon tetrachloride, ethylene carbonate, and methyl ethyl ketone (MEK). , Acetone solvents, diethyl ketone, methyl isobutyl ketone (MIBK), methyl isopropyl ketone (MIPK), ketone solvents such as cyclohexanone, alcohol solvents such as methanol, ethanol, isopropanol, ethylene glycol, diethylene glycol (DEG), glycerin, diethyl ether , Diisopropyl ether, 1,2-dimethoxyethane (DME), 1,4-dioxane, tetrahydrofuran (THF), tetrahydropyran (THP), anisole, diethylene glycol dimethyl ether (di) Rim), ether solvents such as diethylene glycol ethyl ether (carbitol), cellosolve solvents such as methyl cellosolve, ethyl cellosolve, phenyl cellosolve, aliphatic hydrocarbon solvents such as hexane, pentane, heptane, cyclohexane, toluene, xylene, Aromatic hydrocarbon solvents such as benzene, aromatic heterocyclic solvents such as pyridine, pyrazine, furan, pyrrole, thiophene, methylpyrrolidone, N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMA Amide solvents such as dichloromethane, chloroform, 1,2-dichloroethane, ester solvents such as ethyl acetate, methyl acetate, ethyl formate, sulfur compound solvents such as dimethyl sulfoxide (DMSO), sulfolane, etc. , Acetonitrile, propionitrile, nitrile solvents, formic acid such as acrylonitrile, acetic acid, trichloroacetic acid, various organic solvents such as an organic acid solvents such as trifluoroacetic acid, or mixed solvents containing them.
The liquid material supplied onto the cathode 3 has high fluidity (low viscosity) and tends to spread in the horizontal direction (plane direction). However, since the cathode 3 is surrounded by the partition walls 35, the liquid material is predetermined. Spreading outside the region is prevented, and the contour shape of the electron transport layer 5 (light emitting element 1) is accurately defined.

[2-Cb] Next, the light emitting layer 6 is formed on each electron transport layer 5 (receiving surface).
The light emitting layer 6 is formed by a droplet discharge method using the above-described discharge liquid (dispersion liquid) (a droplet discharge method in which droplets are intermittently discharged from nozzle holes). As a result, the light emitting layer 6 can be made thinner and the pixel size can be reduced. Further, since the discharge liquid (dispersion) can be selectively supplied to the inside of the partition wall 35, waste of the discharge liquid (dispersion) can be omitted. In the present invention, since the total amount of Cd, Pb, and Cr contained in the quantum dots is less than a predetermined value in the discharge liquid, adverse effects due to mist that is inevitably generated at the time of droplet discharge are effective. To be prevented.
Hereinafter, a method for applying the discharge liquid (dispersion liquid) by the droplet discharge method will be described in more detail.
The discharge (dispersion process) of the discharge liquid (dispersion liquid) is performed using a droplet discharge apparatus as shown in FIGS.

  As shown in FIG. 3, a droplet discharge device 100 used in this step includes a tank 101 that holds a discharge liquid (dispersion) 2 and a tube (feed) that discharges the discharge liquid (dispersion) 2 in the tank 101. Liquid tube) 110, and a discharge scanning unit 102 to which the discharge liquid (dispersion liquid) 2 is supplied from the tank 101 via the tube 110. The ejection scanning unit 102 includes a droplet ejection unit 103 in which a plurality of droplet ejection heads (inkjet heads) 114 are mounted on a carriage 105, and a first position control device 104 (movement) that controls the position of the droplet ejection unit 103. Means), a stage 106 for holding the TFT circuit substrate 20 (hereinafter also referred to simply as “TFT circuit substrate 20”) on which the partition wall 35, the cathode 3, and the electron transport layer 5 are formed, and the position of the stage 106 is controlled. A second position control device 108 (moving means) and a control means 112 are provided. The tank 101 and a plurality of droplet discharge heads 114 in the droplet discharge means 103 are connected by a tube (liquid supply tube) 110, and a plurality of liquids are discharged from the tank 101 via the tube (liquid supply tube) 110. A discharge liquid (dispersion liquid) 2 is supplied to each of the droplet discharge heads 114 by compressed air. The tube (liquid feeding tube) 110 and the droplet discharge means 103 (droplet discharge head 114) are connected by a connection member (not shown). The connecting portion between the tube (liquid feeding tube) 110 and the droplet discharge means 103 (droplet discharge head 114) is easily subjected to vibration energy accompanying the liquid supply, and the discharged discharge liquid (dispersion liquid) 2 is conveyed. This is a place where air or the like is likely to be mixed. For this reason, butyl rubber is generally used as a constituent material of the connecting member, which has characteristics such as excellent stretchability, low gas permeability, and excellent vibration resistance, water resistance, acid resistance, alkali resistance, weather resistance, and the like. ing. Examples of the butyl rubber used as a material constituting the connecting member include butyl 065, 268, 269, 365 (EXXON MOBILE), 101-3, 301, 402 (LANXESS), JSR butyl (JSR), and the like. It is done.

  The first position control device 104 moves the droplet discharge means 103 along the X-axis direction and the Z-axis direction orthogonal to the X-axis direction in response to a signal from the control means 112. Further, the first position control device 104 also has a function of rotating the droplet discharge means 103 around an axis parallel to the Z axis. In the present embodiment, the Z-axis direction is a direction parallel to the vertical direction (that is, the direction of gravitational acceleration). The second position controller 108 moves the stage 106 along the Y-axis direction orthogonal to both the X-axis direction and the Z-axis direction in response to a signal from the control unit 112. Further, the second position control device 108 also has a function of rotating the stage 106 around an axis parallel to the Z axis.

The stage 106 has a plane parallel to both the X-axis direction and the Y-axis direction. The stage 106 is configured so that the TFT circuit substrate 20 to which the discharge liquid (dispersion liquid) 2 is to be applied can be fixed or held on the plane.
As described above, the droplet discharge means 103 is moved in the X-axis direction by the first position control device 104. On the other hand, the stage 106 is moved in the Y-axis direction by the second position control device 108. That is, the relative position of the droplet discharge head 114 with respect to the stage 106 is changed by the first position control device 104 and the second position control device 108 (the TFT circuit substrate 20 held on the stage 106 and the liquid droplet discharge means 103). Move relatively).
The control unit 112 is configured to receive discharge data representing a relative position at which the discharge liquid (dispersion) 2 is to be discharged from the external information processing apparatus.

  As shown in FIG. 4, the droplet discharge means 103 has a plurality of droplet discharge heads 114 each having substantially the same structure, and a carriage 105 that holds these droplet discharge heads 114. In the present embodiment, the number of droplet discharge heads 114 held by the droplet discharge means 103 is eight. Each droplet discharge head 114 has a bottom surface provided with a plurality of nozzles 118 described later. The shape of the bottom surface of each droplet discharge head 114 is a polygon having two long sides and two short sides. The bottom surface of the droplet discharge head 114 held by the droplet discharge means 103 faces the stage 106 side, and the long side direction and the short side direction of the droplet discharge head 114 are respectively an X-axis direction and a Y-axis direction. Parallel to the direction.

  As shown in FIG. 5, the droplet discharge head 114 has a plurality of nozzles (nozzle holes) 118 arranged in the X-axis direction. The plurality of nozzles 118 are arranged such that the nozzle pitch HXP in the X-axis direction in the droplet discharge head 114 has a predetermined value. Although the specific value of nozzle pitch HXP is not specifically limited, For example, it can be set as 50-90 micrometers. Here, the “nozzle pitch HXP in the X-axis direction of the droplet discharge head 114” is a plurality of images obtained by projecting all the nozzles 118 in the droplet discharge head 114 onto the X-axis along the Y-axis direction. This corresponds to the pitch between nozzle images.

In the present embodiment, the plurality of nozzles 118 in the droplet discharge head 114 form a nozzle row 116A and a nozzle row 116B that both extend in the X-axis direction. The nozzle row 116A and the nozzle row 116B are arranged in parallel with a space therebetween. In the present embodiment, 90 nozzles 118 are aligned in the X-axis direction at regular intervals LNP in each of the nozzle row 116A and the nozzle row 116B. Although the specific value of LNP is not specifically limited, It can be set as 100-180 micrometers.
The position of the nozzle row 116B is shifted from the position of the nozzle row 116A by a half length of the nozzle pitch LNP in the positive direction in the X-axis direction (right direction in FIG. 5). Therefore, the nozzle pitch HXP in the X-axis direction of the droplet discharge head 114 is half the nozzle pitch LNP of the nozzle row 116A (or nozzle row 116B).

  Accordingly, the nozzle line density in the X-axis direction of the droplet discharge head 114 is twice the nozzle line density of the nozzle row 116A (or nozzle row 116B). In the present specification, “nozzle line density in the X-axis direction” means the number per unit length of a plurality of nozzle images obtained by projecting a plurality of nozzles on the X-axis along the Y-axis direction. It corresponds to. Of course, the number of nozzle rows included in the droplet discharge head 114 is not limited to two. The droplet discharge head 114 may include M nozzle rows. Here, M is a natural number of 1 or more. In this case, in each of the M nozzle rows, the plurality of nozzles 118 are arranged at a pitch that is M times the nozzle pitch HXP. Further, when M is a natural number of 2 or more, the other (M−1) nozzle rows are only i times as long as the nozzle pitch HXP with respect to one of the M nozzle rows. There is no overlap in the X-axis direction. Here, i is a natural number from 1 to (M−1).

  In the present embodiment, since each of the nozzle row 116 </ b> A and the nozzle row 116 </ b> B includes 90 nozzles 118, one droplet discharge head 114 has 180 nozzles 118. However, 5 nozzles at both ends of the nozzle row 116A are set as “pause nozzles”. Similarly, 5 nozzles at both ends of the nozzle row 116B are also set as “pause nozzles”. The discharge liquid (dispersion liquid) 2 is not discharged from these 20 “pause nozzles”. Therefore, of the 180 nozzles 118 in the droplet discharge head 114, 160 nozzles 118 function as nozzles that discharge the discharge liquid (dispersion liquid) 2.

  As shown in FIG. 4, in the droplet discharge means 103, a plurality of the droplet discharge heads 114 are arranged in two rows along the X-axis direction. The droplet ejection heads 114 in one row and the droplet ejection heads 114 in the other row are arranged so as to partially overlap when viewed from the Y-axis direction in consideration of the rest nozzles. Thereby, in the droplet discharge means 103, the nozzle 118 that discharges the discharge liquid (dispersion liquid) 2 extends in the X-axis direction at the nozzle pitch HXP over the length of the dimension of the TFT circuit substrate 20 in the X-axis direction. It is configured to be continuous.

In the droplet discharge means 103 of this embodiment, the droplet discharge head 114 is arranged so as to cover the entire length of the TFT circuit substrate 20 in the X-axis direction. May cover a part of the length of the dimension of the TFT circuit substrate 20 in the X-axis direction.
The hole diameter of the nozzle (nozzle hole) 118 is preferably 5 to 100 μm, and more preferably 10 to 50 μm.

  As shown in FIGS. 6A and 6B, each droplet discharge head 114 is an inkjet head. More specifically, each droplet discharge head 114 includes a vibration plate 126 and a nozzle plate 128. Between the diaphragm 126 and the nozzle plate 128, a liquid pool 129 that is always filled with the discharge liquid (dispersion liquid) 2 supplied from the tank 101 through the hole 131 is located.

  In addition, a plurality of partition walls 122 are located between the diaphragm 126 and the nozzle plate 128. A portion surrounded by the diaphragm 126, the nozzle plate 128, and the pair of partition walls 122 is a cavity 120. Since the cavities 120 are provided corresponding to the nozzles (nozzle holes) 118, the number of the cavities 120 and the number of the nozzles 118 are the same. The discharge liquid (dispersion liquid) 2 is supplied from the liquid pool 129 to the cavity 120 through the supply port 130 positioned between the pair of partition walls 122.

  On the diaphragm 126, the vibrator 124 is positioned corresponding to each cavity 120. The vibrator 124 includes a piezoelectric element 124C and a pair of electrodes 124A and 124B that sandwich the piezoelectric element 124C. By applying a driving voltage between the pair of electrodes 124A and 124B, the discharge liquid (dispersion liquid) 2 is discharged from the corresponding nozzle 118. The shape of the nozzle 118 is adjusted so that the discharge liquid (dispersion liquid) 2 is discharged from the nozzle 118 in the Z-axis direction.

  In the droplet discharge head 114 (particularly in the vicinity of the nozzle plate 128), generally, the discharge liquid supply section (dispersion liquid supply section) and the head drive section are made of a connecting material as an elastic material. If the connection between the discharge liquid (dispersion) supply part and the head drive part is insufficient, liquid leakage of the discharge liquid (dispersion liquid) may occur, or the pressure appropriate to the discharge liquid (dispersion liquid) 2 in the cavity 120 May not be applied or gas may be mixed into the cavity 120 from the outside. In order to prevent the occurrence of such a problem, fluorosilicone rubber is usually used as the connection material. Examples of such fluorosilicone rubber include Silastic LS (Dow Corning), FE251-U, 261-U, 271-U, 273-U, 281-U (Shin-Etsu Silicone), and Fluorsilicone 614002 (ERIKS). Etc.

The control means 112 (see FIG. 3) may be configured to give a signal to each of the plurality of vibrators 124 independently of each other. That is, the volume of the discharge liquid (dispersion liquid) 2 discharged from the nozzle 118 may be controlled for each nozzle 118 in accordance with a signal from the control unit 112. The control unit 112 can also set the nozzle 118 that performs the ejection operation during the application scan and the nozzle 118 that does not perform the ejection operation.
In this specification, a portion including one nozzle 118, a cavity 120 corresponding to the nozzle 118, and a vibrator 124 corresponding to the cavity 120 may be referred to as “ejection unit 127”. According to this notation, one droplet discharge head 114 has the same number of discharge units 127 as the number of nozzles 118.

  Using the droplet discharge device 100 as described above, the discharge liquid (dispersion liquid) 2 corresponding to the light emitting layer 6 of the light emitting element 1 of the plurality of colors included in the display device 10 is applied on the electron transport layer 5 (by the partition wall portion 35). To the enclosed area (cell). By using the apparatus as described above, the discharge liquid (dispersion liquid) 2 can be efficiently and selectively applied onto the electron transport layer 5 (inside the region (cell) surrounded by the partition wall 35). . In the configuration shown in the figure, the droplet discharge device 100 has only a tank 101, a tube 110, and the like for holding the discharge liquid (dispersion liquid) 2 for one color. You may have for several types of discharge liquid (dispersion liquid) corresponding to the light emitting layer 6 of the light emitting element 1 of multiple colors to have. In manufacturing the display device 10, a plurality of droplet discharge devices 100 corresponding to a plurality of color discharge liquids (dispersions) 2 may be used.

In this step, the temperature of the discharge liquid 2 discharged from the nozzle 118 is preferably 20 to 40 ° C, and more preferably 25 to 30 ° C.
In addition, the droplet amount (volume per droplet) of the discharge liquid 2 discharged from the nozzle 118 in this step is preferably 0.5 to 100 pL, and more preferably 1 to 20 pL.
In the present invention, the droplet discharge head 114 may use an electrostatic actuator as a driving element instead of a piezoelectric element. Further, the droplet discharge head 114 has a configuration (bubble jet method) that uses an electrothermal conversion element as a drive element and discharges a discharge liquid (dispersion liquid) by utilizing thermal expansion of a material by the electrothermal conversion element. May be.

After applying the discharge liquid (dispersion liquid) 2 on the electron transport layer 5 (receiving surface), at least a part of the dispersion medium contained in the applied discharge liquid (dispersion liquid) 2 is removed (dedispersion medium) ( Dispersion medium removal step).
The method of the dedispersing medium is not particularly limited. For example, a method of heating the TFT circuit board 20 to which the discharge liquid (dispersion) 2 is attached, or a pressure reduction of the TFT circuit board 20 to which the discharge liquid (dispersion) 2 is attached. A method of placing in an atmosphere or a combination of these (for example, after placing the TFT circuit substrate 20 to which the discharge liquid (dispersion) 2 is attached in a reduced pressure atmosphere at a first temperature in a reduced pressure atmosphere, the atmosphere is increased. For example, a method of returning to atmospheric pressure and heating under atmospheric pressure).

The treatment temperature (heating temperature) in this step is preferably 60 to 280 ° C, and more preferably 110 to 190 ° C.
As described above, in the present invention, a dispersion liquid (discharge liquid) including quantum dots and the above-described dispersion medium is discharged in a predetermined pattern by a droplet discharge method in which droplets are intermittently discharged from nozzle holes. It is characterized by a point. Thereby, a thin film pattern without a defect can be formed easily and reliably. In particular, in a light-emitting element, a variation in thickness greatly affects the light emission color (luminance, etc.), and thus it is required to form a thin film pattern having a uniform thickness. Even a pattern, particularly a fine pattern with a large area, can be precisely formed. In addition, the light emitting element does not have a uniform film thickness.For example, if there is a defect such as a so-called omission, there is a problem that the life of the light emitting element is significantly reduced due to concentration of current and voltage. According to the present invention, defects such as missing can be reliably prevented. As described above, according to the present invention, it is possible to provide a light emitting element capable of stably emitting light of a desired color tone over a long period of time, an image display device having a wide color reproduction range and excellent durability. Can be provided.
In the present invention, since the total content of Cd, Pb, and Cr in the quantum dots is not more than a predetermined value, it is possible to reliably prevent an environmental load due to the generation of mist at the time of droplet discharge, an adverse effect on the human body, etc. Can be prevented.

  In addition, according to the present invention, since a desired pattern can be directly formed without using a mask or the like during film formation or removing a part of the film after film formation, the thin film has excellent productivity. In this respect, the environmental load can be reduced. Further, since the pattern can be formed in a non-contact manner with respect to the workpiece (receiving surface) on which the thin film pattern is to be formed, the thin film pattern can be suitably formed even on a curved workpiece. Moreover, even if the workpiece (receiving surface) has irregularities, a thin film pattern can be suitably formed. In addition, since a thin film pattern can be suitably formed using a plurality of types of liquids (dispersions), it can be suitably applied to the formation of a light-emitting element used for displaying a color image. In addition, since the liquid (dispersion) used for forming the thin film pattern can be used without waste (there is no need to remove a part thereof after film formation), even when an expensive dispersion is used. In addition, an increase in the production cost of the thin film pattern can be suppressed. Further, the shape (thickness distribution) of the formed film can be easily controlled by adjusting the removal rate of the dispersion medium in the dispersion medium removal step. Moreover, in this invention, when forming a thin film pattern, it can prevent reliably that an impurity mixes.

Further, in the present invention, in the dispersion medium removing step, the dispersion is caused by causing a temperature difference between the vicinity of the top of the dispersion liquid (discharge liquid) adhered to the receiving surface and the vicinity of the bottom (contact surface with the receiving surface). Convection can be generated in the liquid. Thereby, control of the thickness of the thin film pattern formed can be performed more suitably. Further, in the present invention, for example, a predetermined amount of the liquid droplet of the dispersion liquid is discharged onto the receiving surface, and then the liquid on the receiving surface is applied by removing the dispersion medium from the liquid droplet. In the part, a thin film having a film thickness near the edge part larger than the film thickness near the center part is formed, and then, the droplet of the dispersion liquid is discharged into a region (concave part) surrounded by the edge part, Thereafter, the dispersion medium may be removed from the droplets. Thereby, control of the thickness of the thin film pattern formed can be performed more suitably.
On the other hand, even when a dispersion liquid containing quantum dots is used, when the droplet discharge method is not applied, or when a conventional organic EL material is applied to the droplet discharge method, it is excellent as in the present invention. There is no effect.

  That is, even when a dispersion liquid containing quantum dots is used, when the droplet discharge method is not applied, in general, when a predetermined pattern is formed, a corresponding mask is required, and the pattern formation efficiency is extremely high. This is not preferable from the viewpoint of resource saving. In addition, when the pattern to be formed is large, it is difficult to make the mask position accuracy sufficiently high. In addition, when pattern formation is performed by a vapor deposition method such as vacuum deposition, a large apparatus is required for large-scale pattern formation, and the increase in production cost due to the large pattern is remarkable. It is also difficult to cope with the trend of increasing size. Further, when a general printing method is used, it is difficult to accurately control the shape of the pattern to be formed. In particular, in the formation of a pattern in which a large number of minute regions are regularly arranged, such as a light-emitting element included in an image display device, and further, variation in thickness at each part is required to be sufficiently small. It is very difficult to apply the conventional printing method.

In addition, when a conventional organic EL material is used, there is a problem in durability of a formed thin film pattern (light emitting element). In addition, when the conventional organic EL material or the like is applied to the droplet discharge method, the above-described effects (for example, excellent liquid drainage, droplet discharge amount stability, etc.) obtained in the present invention are obtained. I can't.
In addition, if the total amount of Cd, Pb, and Cr contained in the quantum dots is too large, there is a high risk of adversely affecting the environment, the human body, etc. due to mist generated during droplet discharge.

[2-Cc] Next, the hole transport layer 7 is formed on each light emitting layer 6 (on the side of the light emitting layer 6 opposite to the surface facing the electron transport layer 5).
The hole transport layer 7 can also be formed by a gas phase process or a liquid phase process as described in the method for forming the electron transport layer 5 as described above. For the same reason as described above, A discharge method is preferable, and an inkjet method is more preferable.
When the hole transport layer 7 is formed by such a method, the same conditions as the formation of the electron transport layer 5 and the light emitting layer 6 as described above can be used except that the composition of the liquid material is changed.

[2-D] Next, as shown in FIG. 2D, the anode 8 as a common electrode is formed on each hole transport layer 7 and each partition wall 35 (third step).
The anode 8 is formed by, for example, a vapor phase process using a sputtering method, a vacuum deposition method, a CVD method, a spin coating method (pyrosol method), a casting method, a micro gravure coating method, a gravure coating method, a bar coating method, a roll. Formed by liquid phase process using droplet discharge methods such as coating method, wire bar coating method, dip coating method, spray coating method, screen printing method, flexographic printing method, offset printing method, ink jet method, bubble jet method, etc. can do.

These methods are selected in consideration of the physical stability and / or chemical characteristics such as thermal stability of the constituent material of the anode 8 and solubility in a solvent.
In the present embodiment, since the anode 8 is formed on the entire surface of the hole transport layer 7 and the partition wall portion 35, it is not necessary to use a mask. For this formation, a sputtering method or a vacuum evaporation method is used. The gas phase process that has been used is preferably used.
The light emitting element 1 can be manufactured through such steps.

[3] Next, as shown in FIG. 2E, the upper substrate 9 is prepared, and the anode 8 and the upper substrate 9 are joined so that the anode 8 is covered with the upper substrate 9.
The anode 8 and the upper substrate 9 can be joined by drying the adhesive in a state where an epoxy adhesive is interposed between the anode 8 and the upper substrate 9.
The upper substrate 9 has a function as a protective substrate for protecting the light emitting element 1.
The display device 10 can be manufactured through the steps as described above.

<Electronic equipment>
The display device (image display device of the present invention) 10 as described above can be incorporated into various electronic devices.
FIG. 7 is a perspective view showing a configuration of a mobile (or notebook) personal computer (electronic device) to which the image display device of the present invention is applied.
In this figure, a personal computer 1100 includes a main body 1104 provided with a keyboard 1102 and a display unit 1106 provided with a display. The display unit 1106 is rotatable with respect to the main body 1104 via a hinge structure. It is supported by.

In the personal computer 1100, the display unit included in the display unit 1106 is configured by the display device 10 described above.
FIG. 8 is a perspective view showing a configuration of a mobile phone (including PHS) (electronic device) to which the image display device of the present invention is applied.
In this figure, a cellular phone 1200 includes a plurality of operation buttons 1202, an earpiece 1204 and a mouthpiece 1206, and a display unit.
In the cellular phone 1200, the display unit is configured by the display device 10 described above.

FIG. 9 is a perspective view showing a configuration of a digital still camera (electronic device) to which the image display device of the present invention is applied. In this figure, connection with an external device is also simply shown.
Here, an ordinary camera sensitizes a silver salt photographic film with a light image of a subject, whereas a digital still camera 1300 photoelectrically converts a light image of a subject with an image sensor such as a CCD (Charge Coupled Device). An imaging signal (image signal) is generated.

A display unit is provided on the back of a case (body) 1302 in the digital still camera 1300, and is configured to display based on an imaging signal from the CCD, and functions as a finder that displays an object as an electronic image.
In the digital still camera 1300, the display unit is configured by the display device 10 described above.

A circuit board 1308 is installed inside the case. The circuit board 1308 is provided with a memory that can store (store) an imaging signal.
A light receiving unit 1304 including an optical lens (imaging optical system), a CCD, and the like is provided on the front side of the case 1302 (on the back side in the illustrated configuration).
When the photographer confirms the subject image displayed on the display unit and presses the shutter button 1306, the CCD image pickup signal at that time is transferred and stored in the memory of the circuit board 1308.

  In the digital still camera 1300, a video signal output terminal 1312 and an input / output terminal 1314 for data communication are provided on the side surface of the case 1302. As shown in the figure, a television monitor 1430 is connected to the video signal output terminal 1312 and a personal computer 1440 is connected to the data communication input / output terminal 1314 as necessary. Further, the imaging signal stored in the memory of the circuit board 1308 is output to the television monitor 1430 or the personal computer 1440 by a predetermined operation.

In addition to the above-described personal computer (mobile personal computer), mobile phone (including PHS), and digital still camera, the electronic apparatus according to the present invention may be a television, a video camera, a viewfinder type, a monitor direct view, for example. Type video tape recorder, laptop personal computer, car navigation system, pager, electronic notebook (including communication function), electronic dictionary, calculator, electronic game machine, word processor, workstation, video phone, security TV monitor, Electronic binoculars, POS terminals, devices equipped with a touch panel (for example, cash dispensers and automatic ticket vending machines for financial institutions), medical devices (for example, electronic thermometers, blood pressure monitors, blood glucose meters, electrocardiographs, ultrasonic diagnostic devices, endoscopes) Display device), fish detector, various measurements Vessels, instruments (e.g., gages for vehicles, aircraft, and ships), a flight simulator, various monitors, and a projection display such as a projector. The electronic device of the present invention may have only a light emitting function that does not have a display function. Above all, the trend of enlargement of the display unit in recent years is remarkable in the television, and high resolution such as full high-definition compatibility is also penetrating. In a television having such a large display portion (for example, a display portion having a diagonal length of 80 cm or more), characteristic variations among a large number of arranged pixels are easily noticeable, and such characteristic variations are sufficiently suppressed. It was difficult to do. In addition, with the increase in the resolution of televisions, the above problems have become more prominent. In recent years, liquid crystal televisions using color filters are becoming widespread. However, televisions using color filters rather than self-luminous type tend to have a large power consumption in order to obtain sufficient luminance. In addition, there is a problem that it is difficult to secure a sufficient viewing angle. In addition, televisions and the like having self-luminous display elements that employ organic EL or inorganic EL have problems in durability, light emission efficiency, color purity, light emission luminance, and the like. On the other hand, when the present invention is applied to a television, it is possible to reliably prevent the occurrence of the above problems. That is, when applied to a television having a large display unit as described above, the effects of the present invention are more remarkably exhibited. In addition, in a television having a large display portion as described above, a large amount of liquid is used to form a light emitting element, and it is necessary to discharge liquid droplets with a fine pattern. Although the tendency to increase is remarkable, even if it is a case where it applies to such a use, the bad influence to the environment, a human body, etc. by a mist can be prevented reliably. Also from this point, it can be said that the effect of the present invention is more remarkably exhibited when applied to a television having a large display unit as described above.
As mentioned above, although this invention was demonstrated based on suitable embodiment, this invention is not limited to these.

For example, in the above-described embodiment, the top emission type light emitting element has been representatively described. However, the light emitting element of the present invention may have a bottom emission structure.
In addition, in the thin film pattern forming method of the present invention, one or two or more optional steps may be added.
In the present invention, the light emission by the quantum dots is not limited to the above-described recombination of electrons and holes (application of voltage), and may be, for example, irradiation of ultraviolet rays. As a light emitting element, an image display device, and an electronic device using light emission by ultraviolet rays, for example, one having a configuration used for light emission in a plasma display panel can be given.

In addition, the discharge liquid set of the present invention may be provided with at least two types of discharge liquids including quantum dots having different particle diameters. For example, in addition to a plurality of types of discharge liquids including quantum dots, quantum dots It may be provided with a discharge liquid that does not contain.
In addition, each unit included in the light-emitting element, the image display device, and the electronic device can be replaced with any one that exhibits a similar function, or other configurations can be added.
Further, in the above-described embodiment, the case where the ejection liquid, the ejection liquid set, the thin film pattern forming method, and the thin film of the present invention are applied to a light emitting element, an image display device, and an electronic device including the image display device is mainly described. Although described, the present invention may be applied to any application such as a solar cell or a lighting device.

[1] Production of discharge liquid set (Example 1)
<Red light emitting layer forming discharge liquid (dispersion)>
A quantum dot having a structure in which a shell region (thickness: 0.1 nm) made of ZnS is provided on the outer surface of a core region made of InP by the method described below is used in decalin as a dispersion medium. A discharge liquid (dispersion liquid) for forming a red light emitting layer dispersed in was prepared. In the discharge liquid (dispersion liquid), the quantum dots were those in which trioctyl phosphine oxide (TOPO) and trioctyl phosphine (TOP) as dispersants were attached to the surface. The particle size of the quantum dots was 10.2 nm. Moreover, the content rate of the quantum dot in a discharge liquid (dispersion liquid) was 4.7 wt%, and the content rate of the dispersion medium in a discharge liquid (dispersion liquid) was 94.9 wt%. The total content of Cd, Pb, and Cr in the quantum dots was 30 ppm.

First, 5 g of TOPO / TOP (a mixture of 1: 1.5 by volume) is put into a transparent three-necked flask equipped with an air-cooled Liebig reflux tube and a thermocouple for adjusting the reaction temperature, and vacuum is applied. After pulling for 20 minutes, Ar was purged three times to remove impurities such as oxygen in the three-necked flask. Next, this liquid (second liquid) was heated to 345 ° C. in a dry argon gas atmosphere while stirring with a magnetic stirrer.
Separately, 0.8 g of InCl ₃ , 0.5 g of P (NMe ₂ ) ₃ and 5 g of TOPO / TOP (a 1: 1 mixture by volume ratio) are wrapped with aluminum foil and shielded from light. A first liquid was prepared by mixing in a glass bottle.

Next, this 1st liquid (2.0 mL) was inject | poured into the flask containing said 2nd liquid at once with the syringe, and temperature was then maintained at 300 degreeC for 1 hour.
Next, when heating was stopped and the liquid temperature dropped to 50 ° C., purified toluene (2 mL) was added with a syringe to dilute, and further, a mixed liquid of 1-butanol and dehydrated methanol (volume ratio of 1). : 1 mixture): 10 ml was injected to produce insolubles. This insoluble matter is centrifuged (3000 rpm), the supernatant is removed by decantation and separated, and vacuum-dried at room temperature for 14 hours to obtain particles composed of InP (particles to be the core region). It was.

Next, 15 g of TOPO was placed in a brown three-necked flask equipped with an air-cooled Liebig reflux tube and a thermocouple for adjusting the reaction temperature, and heated to 150 ° C. while stirring with a magnetic stirrer. Then, the decompression and the decompression with dry Ar gas were repeated.
After performing the heat treatment with decompression and decompression as described above for 2 hours, the liquid temperature was set to 100 ° C., and particles (0.094 g) composed of InP prepared as described above and trioctyl were added thereto. A mixture with phosphine (1.5 g) was added.

Next, this liquid (third liquid) was stirred with a magnetic stirrer for 80 minutes while being heated to 100 ° C. under reduced pressure. Thereafter, the liquid temperature was set to 180 ° C., and the pressure was restored with dry Ar gas.
Next, a separately prepared fourth liquid is dropped into the flask containing the third liquid heated to 180 ° C. over 20 minutes with a syringe, and then the liquid temperature is lowered to 90 ° C. for 1 hour. The mixture was stirred and further stirred at room temperature for 14 hours, and then stirred at 90 ° C. for 3 hours. Here, as the fourth liquid, a 1N (1N) n-hexane solution (1.34 mL) of diethylzinc prepared in a glove box in a dry nitrogen atmosphere, and bis (trimethylsilyl) sulfide (0. 239 g) and trioctylphosphine (9 mL) were used.

Next, heating was stopped, n-butanol (8 mL) was added to the reaction solution, and the mixture was cooled to room temperature.
Next, the liquid cooled to the said room temperature was dripped in 16 mL methanol under dry nitrogen stream.
Thereafter, the insoluble matter contained in this liquid is centrifuged, the supernatant is removed by decantation and separated, and dried in vacuum at room temperature, so that the outer surface of the core region composed of InP is composed of ZnS. A powdery quantum dot provided with a shell region was obtained.
Thereafter, the obtained quantum dots were converted into bis (1,2,2,6,6-pentamethyl-4-piperidyl) [[3,5-bis (1,1-dimethylethyl) -4- A discharge liquid (dispersion liquid) for forming a red light emitting layer was obtained by dispersing in decalin containing hydroxyphenyl] methyl] butyl malonate.

<Green light emitting layer forming discharge liquid (dispersion)>
Other than using tridecylphosphine oxide (TDP) instead of trioctylphosphine (TOP), the use ratio ratio of TOPO and TDP is 1: 0.8 by volume, and the particle size of the quantum dots is 4.1 nm. Prepared a discharge liquid (dispersion liquid) for forming a green light-emitting layer in the same manner as the discharge liquid for forming a red light-emitting layer.

<Discharge liquid (dispersion liquid) for forming the blue light emitting layer>
In addition to trioctylphosphine oxide (TOPO) and tridecylphosphine oxide (TDP), triphenylphosphine (TPP) is used, and the ratio of the ratio of TOPO, TDP and TPP used is 1: 0.8: 0. A blue light emitting layer forming discharge liquid (dispersion liquid) was prepared in the same manner as the red light emitting layer forming discharge liquid except that the particle size of the quantum dots was 2.1 nm.
Thus, the discharge liquid set which consists of 3 types of discharge liquids (dispersion liquid) was obtained.

(Examples 2 to 10)
A discharge liquid set comprising three types of discharge liquids (dispersions) in the same manner as in Example 1 except that the composition of each discharge liquid (dispersion) constituting the discharge liquid set was changed as shown in Table 1. Was made. In addition, about what the quantum dot comprised with ZnAgInS which is a compound which doped In and Ag to ZnS, in formation of a core particle (ZnAgInS), AgCl was used as an Ag source, and diethyldithiocarbamate zinc (( C ₂ H ₅ ) ₂ NCS ₂ Zn) was used to form particles using trioctylphosphine as an S source, and then the shell region was not formed, and the resulting particles were quantum dots as they were.

(Comparative Examples 1-4)
A discharge liquid set comprising three types of discharge liquids (dispersions) in the same manner as in Example 1 except that the composition of each discharge liquid (dispersion) constituting the discharge liquid set was changed as shown in Table 1. Was made.
(Comparative Example 5)
In this comparative example, a liquid containing an organic light emitting material was used as the liquid discharge constituting the liquid discharge set. Hereinafter, each discharge liquid which comprises a discharge liquid set is demonstrated.

<Red light emitting layer forming discharge liquid>
A discharge liquid for forming a red light emitting layer was obtained by mixing Nile Red as an organic light emitting material and decalin. The Nile Red content in the obtained discharge liquid was 5.0 wt%, and the decalin content was 95.0 wt%.
<Green light emitting layer forming discharge liquid>
A discharge liquid for forming a green light emitting layer was obtained by mixing coumarin 6 as an organic light emitting material and decalin. The content of coumarin 6 in the obtained discharge liquid was 5.0 wt%, and the content of decalin was 95.0 wt%.

<Discharged liquid for forming blue light emitting layer>
A discharge liquid for forming a blue light emitting layer was obtained by mixing TPB (1,1,4,4-tetraphenyl-1,3-butadiene) as an organic light emitting material and decalin. The content of TPB in the discharge liquid thus obtained was 5.0 wt%, and the content of decalin was 95.0 wt%.
Thus, the discharge liquid set which consists of 3 types of discharge liquids was obtained.
Each of the discharge liquids constituting the discharge liquid set obtained in each of the examples and the comparative examples is temperature: 25 ° C., oxygen concentration: 10 ppm or less, humidity: 10 until it is used for the test and evaluation described later. It preserve | saved in the environment below% RH.

  Tables 1, 2 and 3 collectively show the configurations of the discharge liquids constituting the discharge liquid set for each of the examples and the comparative examples. In the table, the red light emitting layer forming discharge liquid is “R discharge liquid”, the green light emitting layer forming discharge liquid is “G discharge liquid”, the blue light emitting layer forming discharge liquid is “B discharge liquid”, and trioctylphosphine. (TOP) is “c”, tridecylphosphine oxide (TOPO) is “d”, tributylphosphine (TBP) is “e”, decalin is “A”, tetralin is “B”, butoxyethanol is “C”, octane Ethyl acid “D”, dipropylene glycol methyl ether acetate “E”, bis (2-butoxyethyl) ether “F”, diethylene glycol monobutyl ether acetate “G”, 1,3-butylene glycol diacetate “ H, propylene glycol methyl ether acetate “I”, triethylene glycol dimethyl ether “J”, Nilele "NR", coumarin 6 "C6", bis (1,2,2,6,6-pentamethyl-4-piperidyl) [[3,5-bis (1,1-dimethylethyl) -4-hydroxy Phenyl] methyl] butyl malonate as “f”, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate as “g”, and 2,6-di-t-butylphenol as “h” Indicated. In the table, the “viscosity of the discharge liquid” column shows the viscosity of the discharge liquid at 25 ° C. measured in accordance with JIS Z8809 using a vibration viscometer, and the “boiling point” column shows The boiling point of the dispersion medium at normal pressure (1 atm) is shown, and the “vapor pressure” column shows the vapor pressure of the dispersion medium at 25 ° C.

[2] Total amount of Cd, Pb and Cr contained in mist Droplet discharge apparatus as shown in FIGS. 3 to 6 installed in a chamber (thermal chamber), and discharge liquid sets of the above examples and comparative examples In the state where the drive waveform of the piezo element was optimized, 100,000 droplets (100,000 droplets) were continuously ejected from each nozzle of the droplet ejection head. The set temperature in the chamber at this time was 25 ° C., and the range was 0.5 ° C. (25 ± 0.25 ° C.).

Cd, Pb, and Cr contained in the atmosphere in the chamber were collected and the total amount was obtained by the following method at the time of droplet ejection as described above and until 2 hours after the completion of droplet ejection. .
That is, a 10 × 10 cm plate glass is horizontally installed at a position 20 cm from the outer periphery of the discharge region of the droplet discharge device installed in the chamber, and is kept in the atmosphere at the time of discharging the dispersion liquid and until 2 hours have passed after the discharge. The misted dispersion mist was supplemented. The supplemented dispersion was recovered with the same solvent as the dispersion, and the amounts of Cd, Pb, and Cr per area were measured. Further, the total amount of Cd, Pb, and Cr scattered was obtained by collecting the atmosphere in the chamber immediately after discharge, firing, and analyzing.
The amounts of Cd, Pb, and Cr contained in the atmosphere obtained as described above were evaluated according to the following five-stage criteria.

A: The total amount of Cd, Pb, and Cr contained in the atmosphere is less than 0.001 μg.
B: The total amount of Cd, Pb, and Cr contained in the atmosphere is 0.001 μg or more and less than 0.01 μg.
C: The total amount of Cd, Pb, and Cr contained in the atmosphere is 0.01 μg or more and less than 0.05 μg.
D: The total amount of Cd, Pb, and Cr contained in the atmosphere is 0.05 μg or more and less than 0.08 μg.
E: The total amount of Cd, Pb, and Cr contained in the atmosphere is 0.08 μg or more.

[3] Stability evaluation of droplet discharge (Stable discharge evaluation)
[3.1] Evaluation of landing position accuracy Prepared are a droplet discharge device as shown in FIGS. 3 to 6 installed in a chamber (thermal chamber), and discharge liquid sets of the respective examples and comparative examples, and a piezoelectric element. In the state where the drive waveform was optimized, 10000 droplets (10,000 droplets) were continuously discharged from each nozzle of the droplet discharge head for each discharge liquid. The set temperature in the chamber at this time was 25 ° C., and the range was 0.5 ° C. (25 ± 0.25 ° C.). For 10000 droplets ejected from a designated nozzle near the center of the droplet ejection head, the average value of the deviation amounts d from the center aiming position of the center position of each landed droplet is obtained, and the following three steps Evaluation was made according to the criteria of
A: The average value of the shift amounts d is less than 0.05 μm.
B: The average value of the shift amounts d is 0.05 μm or more and less than 0.10 μm.
C: The average value of the shift amount d is 0.10 μm or more.

[3.2] Stability evaluation of droplet discharge amount Prepared are a droplet discharge device as shown in FIG. 3 to FIG. Then, in a state where the drive waveform of the piezo element was optimized, 10,000 droplets (10,000 droplets) were continuously discharged from each nozzle of the droplet discharge head for each discharge liquid. The set temperature in the chamber at this time was 25 ° C., and the range was 0.5 ° C. (25 ± 0.25 ° C.). For the two specified nozzles on the left and right ends of the droplet discharge head, the total weight of the discharged droplets is obtained, and the absolute value ΔW [ng] of the difference between the average discharge amounts of the droplets discharged from the two nozzles is calculated. Asked. The ratio (ΔW / W _T ) of ΔW to the target droplet discharge amount W _T [ng] was determined and evaluated according to the following three-stage criteria. As the value of [Delta] W / W _T is small, it can be said that the greater the stability of the droplet discharge amount.
A: The value of ΔW / _{W T} is less than 0.025.
B: The value of ΔW / _{W T} is less than 0.025 or more 0.625.
C: The value of ΔW / _{W T} is 0.625 or more.

[3.3] Intermittent printing performance evaluation Prepared are a droplet discharge device as shown in FIGS. 3 to 6 installed in a chamber (thermal chamber) and discharge liquid sets of the above-mentioned examples and comparative examples, and a piezo element With the drive waveform optimized, 1000 droplets (1000 droplets) are continuously discharged from each nozzle of the droplet discharge head for each discharge liquid, and then the droplet discharge is interrupted for 30 seconds. (First sequence). Thereafter, similarly, the operation of continuously discharging the droplets and interrupting the discharge of the droplets were repeated. The set temperature in the chamber at this time was 25 ° C., and the range was 0.5 ° C. (25 ± 0.25 ° C.). For the designated nozzle near the center of the droplet discharge head, the average weight W ₁ [ng] of the droplets discharged in the first sequence and the average weight W ₁₀ [ng] of the droplets discharged in the tenth sequence And asked. Then, a ratio (| W ₁ −W ₁₀ | / W _T ) of the absolute value of the difference between W ₁ and W ₁₀ with respect to the target discharge amount W _T [ng] of the droplet is obtained, and the following three steps are used. ,evaluated. | _W 1 _-W 10 | as the value of / _{W T} is small, it can be said to be excellent in intermittent printing performance (stability of the droplet discharge quantity).
_A: | _{W 1} -W 10 | values of / _{W T} is less than 0.025.
_B: | _{W 1} -W 10 | values of / _{W T} is less than 0.025 or more 0.625.
_C: | _{W 1} -W 10 | value of / _{W T} is 0.625 or more.

[3.4] Continuous Discharge Test 50% RH using a droplet discharge apparatus as shown in FIGS. 3 to 6 installed in a chamber (thermal chamber), and the discharge liquid set of each of the examples and comparative examples. In this environment, the droplet discharge device was continuously operated for 24 hours to discharge each discharge liquid constituting the discharge liquid set. The set temperature in the chamber at this time was 25 ° C., and the range was 0.5 ° C. (25 ± 0.25 ° C.).
The nozzle clogging rate ([(number of clogged nozzles) / (total number of nozzles)] × 100) obtained after continuous operation is found and the nozzles are clogged. As for No. 1, it was examined whether or not clogging can be eliminated by a cleaning member made of a plastic material. The results were evaluated according to the following four criteria.

A: No nozzle clogging occurs.
B: The occurrence rate of nozzle clogging is less than 0.5% (excluding zero), and clogging can be eliminated by cleaning.
C: The occurrence rate of nozzle clogging is 0.5% or more and less than 1.0%, and clogging can be eliminated by cleaning.
D: The occurrence rate of nozzle clogging is 1.0% or more, or clogging cannot be eliminated by cleaning.
In addition, said evaluation was performed on the same conditions about each Example and each comparative example.

[4] Manufacture of Image Display Device Using the discharge liquid (discharge liquid set) produced in each of the above-described examples and comparative examples, the image display device as shown in FIGS. Manufactured. At this time, an image display device was manufactured under the same conditions except that the discharge liquid was changed in each example and each comparative example.
In particular, the light emitting layer was formed as follows.

That is, a TFT circuit substrate having a partition wall and an electron transport layer formed by the method described above was prepared.
Next, using a droplet discharge device as shown in FIGS. 3 to 6, three types of discharge liquids (red light emission layer formation discharge liquid, green light emission layer formation discharge liquid, and blue light emission layer formation discharge liquid). Was discharged. The diameter of the nozzle (nozzle hole) of the droplet discharge head included in the droplet discharge device was 20 μm.

The liquid temperature of the discharge liquid at the time of droplet discharge was adjusted to be 25 ° C. In addition, the droplet volume (volume per droplet) of the discharge liquid was 12 pL for the discharge liquid corresponding to each color (discharge process). At this time, one type of discharge liquid was applied to each cell so that a plurality of types of discharge liquids were not mixed in each cell.
Next, it is allowed to stand for 10 minutes in an atmosphere reduced to 50 Pa at room temperature (20 ° C.), and then the atmospheric pressure is gradually returned to atmospheric pressure, followed by heat treatment at 150 ° C. for 10 minutes under atmospheric pressure. As a result, a light emitting layer was formed on the surface of the electron transport layer. The formed light emitting layer was 20 nm in all of the red light emitting layer, the green light emitting layer, and the blue light emitting layer. The oxygen concentration in the atmosphere at this time was 10 ppm.
Using the method as described above, 1000 image display devices were manufactured using the discharge liquid (discharge liquid set) of each example and each comparative example.
The thin film pattern formation in the tests and evaluations of [2] to [4] above was performed in an environment where the oxygen concentration was 10 ppm or less and the humidity was 10% RH or less.

[5] Evaluation of image display device The following evaluation was performed using each image display device obtained as described above.
[5.1] Evaluation of heat resistance Image display manufactured on the 1st to 10th sheets among the image display apparatuses manufactured using the discharge liquids (discharge liquid sets) of the respective Examples and Comparative Examples. About the apparatus, the chromaticity at the time of performing a red single color display, a green single color display, and a blue single color display in a dark room was determined using a spectrophotometer (MCPD3000, manufactured by Otsuka Electronics Co., Ltd.).

Next, these image display devices were allowed to stand for 500 hours in an environment where the ambient temperature was 60 ° C. and the relative humidity was 90%.
Then, the chromaticity at the time of performing the monochrome display of red, the monochrome display of green, and the monochrome display of blue was calculated | required on the conditions similar to the above about the image display apparatus cooled slowly. For each image display device, the color difference before and after the heat treatment as described above (the color difference ΔE ^* ab in the L ^* a ^* b ^* display system defined by JIS Z 8729) was obtained. And the average value of the color difference about each 10 image display apparatuses of each said Example and each comparative example was evaluated in accordance with the following three steps of criteria. It can be said that the smaller the average value of the color differences, the better the heat resistance of the discharge liquid (discharge liquid set).
A: The average color difference is less than 3.
B: The average value of color differences is 3 or more and less than 5.
C: The average value of color differences is 5 or more.

[5.2] Evaluation of light resistance Image display manufactured on the 11th to 20th sheets among the image display apparatuses manufactured using the discharge liquids (discharge liquid sets) of the respective Examples and Comparative Examples. About the apparatus, the chromaticity at the time of performing red monochromatic display, green monochromatic display, and blue monochromatic display in a dark room was determined using a spectrophotometer (MCPD3000, manufactured by Otsuka Electronics Co., Ltd.).
Next, these image display devices are placed in an environment where the ambient temperature is 60 ° C. and the relative humidity is 50%, and ultraviolet rays having a wavelength of 340 nm are applied to the image display unit with an irradiance of 0.25 W / m ² and 45 kJ / Irradiation was performed for 240 hours under the condition of m ² .

Then, the chromaticity at the time of performing red single color display, green single color display, and blue single color display under the same conditions as described above was obtained. For each image display device, the color difference before and after the ultraviolet irradiation as described above (L ^* a ^* b ^* color difference ΔE ^* ab in the display system defined by JIS Z 8729) was obtained. And the average value of the color difference about each 10 image display apparatuses of each said Example and each comparative example was evaluated in accordance with the following three steps of criteria. It can be said that the light resistance of the discharge liquid (discharge liquid set) is better as the average value of the color difference is smaller.
A: The average value of the color difference is less than 3.
B: The average value of color differences is 3 or more and less than 5.
C: The average value of color differences is 5 or more.

[5.3] Color unevenness, density unevenness, light leakage Each of the image display devices manufactured using the discharge liquid (discharge liquid set) of each of the examples and comparative examples was manufactured on the 1000th sheet. Using an image display device, in the dark room, perform visual observation in the state of red single color display, green single color display, blue single color display, and the occurrence of color unevenness and density unevenness in each part are as follows. Evaluation was performed according to the five-stage criteria.

A: Color unevenness, density unevenness, and light leakage are not recognized at all.
B: Color unevenness, density unevenness, and light leakage are hardly observed.
C: Color unevenness, density unevenness, and light leakage are slightly observed.
D: Color unevenness, density unevenness, and light leakage are clearly recognized.
E: Color unevenness, density unevenness, and light leakage are remarkably recognized.
In the above evaluation, each image display device was displayed under the same conditions, and observed and measured under the same conditions.

[5.4] Characteristic Differences between Individuals Among image display devices manufactured using the discharge liquids (discharge liquid sets) of the respective Examples and Comparative Examples, the image display apparatuses were manufactured for 990 to 999 sheets, respectively. An image display device was prepared, and in a dark room, red single color display, green single color display, blue single color display, and white single color display were performed, and color measurement was performed using a spectrophotometer (MCPD3000, manufactured by Otsuka Electronics Co., Ltd.). From the results, for each example and each comparative example, the maximum color difference (color difference ΔE in the Lab display system) in the image display device manufactured in the 990th to 999th sheets is obtained, and the following five-stage criteria are obtained. And evaluated.

A: Color difference (ΔE) is less than 2.
B: Color difference (ΔE) is 2 or more and less than 3.
C: Color difference (ΔE) is 3 or more and less than 4.
D: Color difference (ΔE) is 4 or more and less than 5.
E: Color difference (ΔE) is 5 or more.
In the above evaluation, each image display device was observed and measured under the same conditions.

[5.5] Evaluation of color reproduction range Images manufactured on the 21st to 30th sheets among the image display devices manufactured using the discharge liquids (discharge liquid sets) of the respective examples and comparative examples. For the display device, the chromaticity (R (xy), G (xy), B (xy)) by the xy display system when red single color display, green single color display, and blue single color display are performed in a dark room is obtained. The NTSC ratio was calculated. The average value of the NTSC ratio was determined for each of the 10 image display devices of each of the above examples and comparative examples, and evaluated according to the following three-stage criteria. It can be said that the higher the NTSC ratio, the wider the color reproduction range.

A: NTSC ratio (average value) is 78% or more.
B: NTSC ratio (average value) is 70 or more and less than 78%.
C: NTSC ratio (average value) is less than 70%.
These results are shown in Table 4, Table 5, and Table 6. In the table, regarding “total amount of Cd, Pb, Cr contained in mist” and “evaluation of stability of droplet discharge”, the evaluation of the red light emitting layer forming discharge liquid is shown in the “red” column, Evaluation for the green light emitting layer forming discharge liquid is shown in the “green” column, and evaluation for the blue light emitting layer forming discharge liquid is shown in the “blue” column. Regarding “evaluation of the image display device”, the “red” column indicates the evaluation when displaying a single color of red, the “green” column indicates the evaluation when displaying a single color of green, and “blue” In the column “”, the evaluation for the single color display of blue is shown.

  As is apparent from Tables 4, 5, and 6, in the present invention, the amount of Cd, Pb, and Cr that diffuses (scatters) in the atmosphere as droplets are ejected is extremely small. In the present invention, it was possible to display an image having excellent durability (heat resistance, light resistance) and a wide color reproduction range. Further, in the present invention, the occurrence of uneven color, uneven density, and light leakage is suppressed, and variation in characteristics among individuals is small. On the other hand, in each comparative example, satisfactory results were not obtained. In particular, in Comparative Examples 1 to 4 in which the total content of Cd, Pb, and Cr in the quantum dots is greater than or equal to a predetermined value, the amounts of Cd, Pb, and Cr that are diffused (scattered) in the atmosphere are extreme compared to the present invention. It was a lot. Further, in Comparative Example 5, the stability of droplet discharge was low, the durability of the obtained image display device was low, and the characteristic difference between individuals was large. In addition, the image display device obtained in Comparative Example 5 had noticeable color unevenness and a narrow color reproduction range.

It is a longitudinal cross-sectional view which shows an example of the active matrix type display apparatus to which the light-emitting device of this invention is applied. It is a figure (longitudinal sectional view) for demonstrating the manufacturing method of the active matrix type display apparatus shown in FIG. It is a perspective view which shows the droplet discharge apparatus used for formation of a light emitting layer (thin film). It is the figure which observed the droplet discharge means in the droplet discharge apparatus shown in FIG. 3 from the stage side. It is a figure which shows the bottom face of the droplet discharge head in the droplet discharge apparatus shown in FIG. It is a figure which shows the droplet discharge head in the droplet discharge apparatus shown in FIG. 3, (a) is a cross-sectional perspective view, (b) is sectional drawing. 1 is a perspective view illustrating a configuration of a mobile (or notebook) personal computer (electronic device) to which an image display device of the present invention is applied. It is a perspective view which shows the structure of the mobile telephone (PHS is also included) (electronic device) to which the image display apparatus of this invention is applied. It is a perspective view which shows the structure of the digital still camera (electronic device) to which the image display apparatus of this invention is applied.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Light emitting element 2 ... Discharge liquid (dispersion liquid) 3 ... Cathode 5 ... Electron carrying layer 6 ... Light emitting layer 7 ... Hole transport layer 8 ... Anode 9 ... Upper substrate 10 ... Display apparatus 20 ... TFT circuit board 21 ... Substrate 22 ... Circuit part 23 ... Base protective layer 24 ... Driving TFT 241 ... Semiconductor layer 242 ... Gate insulating layer 243 ... Gate electrode 244 ... Source electrode 245 ... Drain electrode 25 ... First interlayer insulating layer 26 ... Second interlayer insulating layer 27 ... Wiring 31... First partition portion 32. Second partition portion 35. Partition portion 100. Droplet discharge device 101. Tank 102. Discharge scanning portion 103. Droplet discharge means 104 ... First position control device 105 ... Carriage 106. DESCRIPTION OF SYMBOLS 108 ... 2nd position control apparatus 110 ... Tube (liquid feeding tube) 112 ... Control means 114 ... Droplet discharge head (inkjet head) 116A, 116B ... Nozzle array 118 ... Nozzle (nozzle hole) 120 ... Cavity 122 ... Bulkhead 124 ... Vibrator 124A, 124B ... Electrode 124C ... Piezo element 126 ... Vibration plate 127 ... Discharge unit 128 ... Nozzle plate 129 ... Liquid pool 130 ... Supply port 131 ... Hole 1100 ... Personal computer 1102 ... Keyboard 1104 ... Main body 1106 ... Display unit 1200 ... Mobile phone 1202 ... Operation buttons 1204 ... Earpiece 1206 ... Mouthpiece 1300 ... Digital still camera 1302 ... Case (body) 1304 ... Light receiving unit 1306 ... Shutter button 1308 ... Circuit board 1312 ... Video signal output terminal 1314 ... Input / output terminal for data communication 1430 ... Television monitor 1440 ... Personal computer Yuta

Claims (15)

A discharge liquid used in a droplet discharge method for intermittently discharging droplets from nozzle holes,
Including fine-particle quantum dots and a dispersion medium for dispersing the quantum dots,
The discharge liquid, wherein the total content of Cd, Pb, and Cr in the quantum dots is 100 ppm or less.   The discharge liquid according to claim 1, wherein the total content of Cd, Pb, and Cr in the discharge liquid is 5.0 ppm or less.   The discharge liquid according to claim 1 or 2, wherein the content of the quantum dots in the discharge liquid is 0.005 to 6.0 wt%.   The dispersion medium is decalin, tetralin, butoxyethanol, ethyl octoate, 4-methyl-1,3-dioxolan-2-one, bis (2-butoxyethyl) ether, diethylene glycol monobutyl ether acetate, dodecane, diethylene glycol monoethyl ether 4. One or more selected from the group consisting of acetate, dipropylene glycol methyl ether acetate, triethylene glycol butyl methyl ether, and 1,3-butylene glycol diacetate The discharge liquid described in 1.   The discharge liquid according to any one of claims 1 to 4, wherein a content ratio of the dispersion medium in the discharge liquid is 70 to 98 wt%. The quantum dots are composed of Si, Ge, GaN, GaP, InN, InP, Ga ₂ O ₃ , Ga ₂ S ₃ , In ₂ O ₃ , In ₂ S ₃ , ZnO, ZnS, In, Ag, or a mixture thereof. The discharge liquid according to any one of claims 1 to 5, wherein A discharge liquid set comprising a plurality of discharge liquids used in a droplet discharge method for intermittently discharging liquid droplets from nozzle holes,
The ejection liquid includes fine-particle quantum dots and a dispersion medium for dispersing the quantum dots,
The quantum dot has a particle size different between the discharge liquids, and
In each of the plurality of types of discharge liquids, the total amount of Cd, Pb, and Cr contained in the quantum dots is 100 ppm or less. A droplet discharge method in which droplets are intermittently discharged from a nozzle hole to discharge a discharge liquid that includes a dispersion medium and fine quantum dots, and in which the quantum dots are dispersed in the dispersion medium. A discharge step of attaching the substrate in a predetermined pattern;
A dispersion medium removing step of removing at least a part of the dispersion medium from the discharge liquid adhered to the receiving surface,
The thin film pattern forming method, wherein the total content of Cd, Pb, and Cr in the quantum dots is 100 ppm or less.   The method for forming a thin film pattern according to claim 8, wherein the droplet discharge method is an inkjet method.   The method for forming a thin film pattern according to claim 8 or 9, wherein a plurality of types of the discharge liquid including the quantum dots having different particle diameters are used.   The thin film pattern forming method according to claim 8, wherein the discharge liquid is discharged such that a plurality of minute units are arranged in a matrix.   A quantum dot having a total content of Cd, Pb, and Cr in the quantum dots of 100 ppm or less and a dispersion medium for dispersing the quantum dots by a droplet discharge method in which droplets are intermittently discharged from a nozzle hole. A thin film obtained by discharging a dispersion liquid containing the dispersion liquid and removing at least a part of the dispersion medium from the discharged dispersion liquid.   A quantum dot having a total content of Cd, Pb, and Cr in the quantum dots of 100 ppm or less and a dispersion medium for dispersing the quantum dots by a droplet discharge method in which droplets are intermittently discharged from a nozzle hole. A light emitting element comprising: a light emitting layer obtained by discharging a dispersion liquid containing the liquid dispersion and removing at least part of the dispersion medium from the discharged dispersion liquid.   An image display device comprising the light emitting device according to claim 13.   An electronic apparatus comprising the image display device according to claim 14.

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