KR20050016975A - Method of manufacturing a diffusing reflector - Google Patents

Abstract

The present invention provides a method of manufacturing a scattering reflector comprising coating a substrate with a suspension of metal nanoparticles and annealing the coated substrate at a high temperature, wherein the suspension of the metal nanoparticles is an additive. A method of manufacturing a scattering reflector comprising a silane derivative comprising a methyl group and at least one alkoxy group. The invention also relates to a scattering reflector formed using the method and a display device comprising the scattering reflector.

Description

Scattering reflector and manufacturing method therefor, display device TECHNICAL FIELD {METHOD OF MANUFACTURING A DIFFUSING REFLECTOR}

The present invention relates to a method of manufacturing a scattering reflector structure comprising coating a substrate with a suspension of metal (nano) particles. The present invention also relates to a scattering reflector plate produced using this method and a reflection type display device comprising the scattering reflector plate.

Reflective displays utilize an electro-optical layer based on, for example, liquid crystal, electrophoretic, electrochromic, electrowetting, or switching foil effects, and are thin and lightweight to ensure low power consumption. It is formed in the shape of a flat plate. Thus, such display devices have been developed for a wide range of applications such as displays in handheld devices. Electro-optical materials, such as liquid crystals, are not of the self emissive type and display images by selectively transmitting or shielding external light beams. Such display devices may be classified into transmissive and reflective types according to lighting systems.

In a reflective display device, the display is realized using incident light from the surrounding environment. Effective use of incident light to improve brightness is an essential goal. In addition, it is basically required to realize scattered reflection of incident light on the panel in order to realize a white display called paper white. Accordingly, reflective display devices of the prior art often include a scattering reflective layer in the panel. This scattering reflective layer has a surface containing fine unevenness and also has properties close to perfect scattering to exhibit the appearance of as much paper white as possible. However, it is difficult to conclude that such reflective characteristics are sufficient for practical use, and improving the state of non-uniformity from the design and processing stages to improve the reflective characteristics has been a problem of the reflective display device of the related art.

In EP 965863 a scattering reflector is produced by a multi-stage process wherein a resin film having photosensitivity is formed on a substrate. In the next process, the resin film is patterned by photolithography to provide gathering of columnar bodies isolated from each other. Subsequently, in the next process, heat treatment is performed to properly deform each columnar body to form a layer having an uneven surface with a maximum tilt angle of 12 ° or less. As a final process, a metal film is formed on an appropriately improved nonuniform layer. This method is very labor intensive and therefore expensive and has the problem that the roughness achieved in the heat treatment is partially undone, for example by sputtering an aluminum layer onto a roughened resin layer to cover the metal layer. have. The manufacturing cost of the TFT array increases with the number of photomasks and the yield generally decreases as the number of photomasks increases. Another problem with the pattern generation method of photolithography is that interference colors may appear upon surface illumination if these patterns are not sufficiently random. Accordingly, it is an object of the present invention to provide a method of manufacturing a scattering reflector that can be easily carried out, inexpensive, and free from the above problems.

1 is a schematic diagram of a diffuse reflector of the present invention.

Such a method comprising coating a substrate with a suspension of metal particles is an additive having at least one methyl group and at least one alkoxy group in the suspension of metal nanoparticles and / or sub-micron particles. It was found by adding a silane derivative and annealing the coated substrate to high temperature.

The addition of the silane inducing agent has been found to improve the thermal stability and cause the conductive mirror to anneal at higher temperatures. Annealing at higher temperatures improves the conductivity of the mirror. Annealing temperature is higher than 350 degreeC, More preferably, it is about 500 degreeC. At these annealing temperatures, the nanoparticles form clusters having a typical size of about 1 μm wide and 100 mm high. The silane derivative is preferably methyl trialkoxysilane and the alkoxy moieties have 1 to 4 carbon atoms. More preferably the silane inducing agent is methyl trimethoxysilane, methyl triethoxysilane or mixtures thereof.

Particularly good results are obtained when the suspension of the metal nanoparticles comprises less than 20 vol.% Inducing agent, more preferably 5 to 10 vol.%.

When scattering mirrors for reflective displays are formed, the nanoparticles are preferably colloidal silver sol particles. However, gold, platinum, rhodium, iridium, palladium, chromium, copper and aluminum and mixtures thereof may be selected. In passive matrix displays, complementary metals may be used to reduce line resistance if necessary. In active matrix displays, rows and columns may be formed, for example, by standard metallization with aluminum. In an active matrix display, deposition of metal is the last step to form an active plate. Therefore, this metal layer serves to form a mirror and also to form metal connections (vias) between the TFTs.

The display formed by the present invention has a perfect paper white appearance and no interference color appears when the layers are illuminated. This method is substantially cheaper than existing methods of forming these displays. It is possible to form pixels with a spacing of 10-20 μm, and even smaller spacing can be obtained by defining a “mushroom-shaped” line between the pixels before applying the metal. This is OE magazine, vol. 1, n4.2 (Feb. 2001), p. 18 (see also http://oemagazine.com/fromTheMagazine/feb01/brightness.html), as shown in FIG. It may also be done in a separate “paddo” process.

The invention also relates to a reflective display device comprising at least one substrate, an electro-optical layer, a scattering reflector of the invention and at least one electrode.

The scattering reflector produced by the method described above may be included in the reflective display device. In this case, the reflective display device has a basic structure comprising: a first transparent substrate disposed in the incident surface, a second substrate disposed opposite the first substrate and coupled to the first substrate through a predetermined gap; An electro-optical layer located on the first substrate side in the gap, a scattering reflection layer located on the second substrate side in the gap, and an electrode for supplying voltage to the electro-optical layer formed in at least one substrate between the first and second substrates. . The scattering reflection layer is composed of a resin film forming a heaping area and a metal film formed on the heaping area.

The present invention is directed to reflective displays and other displays using metal electrodes such as LCDs, electrophoretic, electrochromic, electrowetting displays, foil displays, switching mirrors, PALC displays and poly LEDs. It can be applied to form an active or passive plate with electrical connections and scattering mirrors.

Preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. 1 shows a diffuse reflector of the present invention. As shown in Fig. 1, the substrate 1 is made of, for example, a glass material or the like. Although not essential, the photosensitive resin film 2 may be formed on the substrate. As the resin film 2, for example, a photoresist may be used. In this embodiment, the film is formed to a thickness of about 1.0 μm by spin coating or coating of the photoresist by a printing method. In the next process, gathering of the columnar body is provided as the film 3 by patterning the substrate or the resin film 2 having the nanoparticle metal suspension of the present invention using spin coating. Other processes such as photolithography may be used. In the photolithography method, the exposure process is carried out through ultraviolet irradiation followed by the development process. Suitable irradiation energy of ultraviolet rays ranges from 150 mJ to 250 mJ. If the irradiation energy is less than 150 mJ, the energy is too low. If the irradiation energy is more than 250 mJ, the energy is too high and additional etching may occur. The metal film 3 is formed by spin coating, sputtering or vacuum evaporation, for example by depositing a metal material of nanoparticles such as aluminum, silver or the like on the substrate 1 or the resin film 2.

Yes

Submicron silver particles (14.7 g, such as Mitsui) were added to 10.14 g of water and 2.587 g of 5 wt.% Polyvinyl alcohol and were wetted overnight on a roller conveyor of 45 g of glass pearl. ball) to obtain the appropriate dispersion of 53.4 wt.% Ag.

The components of A or B are mixed to form two hydrolysis mixtures.

A) 40 g methyl trimethoxy silane (MTMS)

0.87 g tetraethyl orthosilicate (TEOS)

32g water

4.5 g ethanol

B) 40g MTMS

40g water

Mix the silver dispersion with one of the hydrolysis mixtures (A or B) in the amounts shown in the table to form a coating liquid, then mix the mixture at 50 rpm for 10 seconds and then at 300 rpm for 40 seconds. The coating liquid was spin coated and spin coated onto a glass substrate. The sample was dried at 35 ° C. Curing was achieved by heating in air at 450 ° C. or 580 ° C. for 90 minutes.

Coated samples were measured for angles dependent on scattering reflection properties and reflection / transmission properties. The sample was found to exhibit good reflection in the visible region. The intensity of the reflected light was four times compared to the reference BaSO ₄ sample (at the incident angle). At an angle of incidence of 15 °, the intensity of the reflected light was 3 to 3.5 times that of purely reflecting BaSO ₄ . At an incident angle of 50 °, the intensity of the reflected light amount was about ˜0.5 times that of BaSO ₄ .

Claims (9)

A method of manufacturing a scattering reflector comprising coating a substrate with a suspension of metal nanoparticles and annealing the coated substrate at a high temperature. The suspension of the metal nanoparticles includes a silane derivative including at least one methyl group and at least one alkoxy group as an additive. Scattering reflector manufacturing method. The method of claim 1, The annealing step is performed at a temperature higher than 350 ℃ Scattering reflector manufacturing method. A scattering reflector comprising a suspension of metal nanoparticles and an annealed substrate coated with an additive, The additive comprises a silane derivative comprising at least one methyl group and at least one alkoxy group. Scattering reflector. The method of claim 3, wherein The silane inducing agent is methyl trialkoxysilane, and the alkoxy moieties have 1 to 4 carbon atoms. Scattering reflector. The method of claim 4, wherein The silane inducing agent is methyl trimethoxysilane, methyl triethoxysilane, or mixtures thereof. Scattering reflector. The method according to any one of claims 3 to 5, The suspension of the metal nanoparticles comprises less than 20 vol.% Of a silane inducing agent. Scattering reflector. The method according to any one of claims 3 to 6, The metal nanoparticles are selected from gold, silver, platinum, rhodium, iridium, palladium, chromium, copper and aluminum and mixtures thereof Scattering reflector. The method according to any one of claims 3 to 7, The metal nanoparticles are colloidal silver sol particles. Scattering reflector. A display device comprising at least one substrate, an electro-optical layer, a scattering reflector of any one of claims 3 to 8 and at least one electrode.