DE102004024022A1 - Glass ceramic material, to block the UV component of lamps, has a structured composition to give transmission of visible light and block UV light with low thermal expansion and resistance to chemical attack - Google Patents

Abstract

The glass ceramic material, to shield the UV light component of a lamp, is in a composition with P 2O 5at a level of nil to =4 wt.% and/or CaO at a level of nil to =8 wt.%. The glass ceramic is in the form of a tube, or a miniaturized tube for back lighting in flat screens. The material can withstand lamp temperatures of >=800[deg]C and, in a layer thickness of 0.3 mm, blocks UV in wavelengths of =265 nm and gives a transmission of visible light in wavelengths of >=75%.

Description

The The invention relates to the use of glass ceramics, wherein the glass ceramics in the form of glass ceramic discs.

At the materials for Lighting equipment will be demanding their thermal and mechanical stability and a targeted set thermal expansion posed. The latter is of importance to the Melting with metals and metal alloys, for example Wires, stress-free To create mergers.

Further properties such as transparency in the visible and blocking needed in the UV range and solarization resistance.

transparent Washers are used in a wide variety of lamp types, so z. B. as a cover in cold light reflectors, in halogen lamp systems and with ceilingwashers. They are intended as UV blockers and as splinter protection serve. UV blocking is especially important in backlight systems, e.g. For TFT flat panel displays. Therefor be either miniaturized tubular fluorescent lamps, so-called. Backlights, used, wherein the bulb glass is doped in such a way that UV light is blocked. In flat backlight systems are appropriate flat transparent UV blocking materials necessary. Here is the requirement of the ability to UV light to block, especially high, since existing plastic components UV light causes yellowing and embrittlement.

For the applications are so far high temperature resistant glasses such as Borosilicate glasses, alkali-free aluminosilicate glasses or also silica glass, each also doped, to UV-blocking properties to achieve.

DE 100 17 696 A1 describes the use of a floated aluminoborosilicate glass or a glass ceramic ceramized therefrom as a transparent covering of the radiation source of lamps.

Also DE 100 17 701 A1 mentions the use of floated glass ceramics to cover luminaires.

at Lamp parts that form part of the radiation space are the Requirements for temperature resistance, UV blocking and solarization resistance particularly high.

It is the object of the invention, for Lighting applications suitable materials, especially materials with high UV-blocking and high solarization resistance, to disposal to deliver.

The The object is achieved by the use described in claim 1 solved.

According to the invention Glass ceramic panes used as lamp components.

Under Components of a lamp become essential parts of the lamp understood that define the radiation space of the lamp, for example Parts of the lamp shell, or the carriers of, for example, fluorescent layers or printed conductors or the other substrates, for example, the homogeneous light distribution serve, so are diffusion plates. Additional cover or protective disks do not fall under the term.

lamp types with such ingredients can while z. As halogen lamps or gas discharge lamps such as, backlight arrangements Be (low pressure discharge lamps). Also in high pressure discharge lamps Such components are possible.

in the Difference to conventional Backlights, in which individual miniaturized fluorescent tubes in parallel be used to each other and between two glass panes There are backlights, where the light-generating Unit is located directly on a textured disk.

The structuring is such that channels with defined depth and defined width (d _channel or W _channel ) are generated by means of parallel elevations, so-called barriers, of defined width (W _rib ) in the disc, in which the discharge luminescent material is located and the together with a phosphor layer provided with the disc form the radiation space, wherein the discs are laterally sealed and provided via feedthroughs with electrodes. In this case, one speaks of a CCFL system (cold cathode fluorescent lamp). However, external contact, ie ignition of the plasma from an externally applied electric field, is also conceivable (EEFL external electrode fluorescent lamp). Here, therefore, there is a large, flat backlight. According to the invention, both the structured pane or the other pane defining the radiation space as well as both panes of glass-ceramic can exist in such a "flat baking light." For the latter pane, the high UV blocking is particularly important.

to Production of the structured disk is preferably the starting glass pane, So the so-called green glass pane, which has been produced for example by rolling, with a conventional Structuring unit, for example, a correspondingly structured Roller, structured - this happens at a viscosity of the glass in the range approx. Ig (η / dPas) = 4 to 7.6, i. between the processing point and the softening point of the glass. - and then ceramized. The ceramization is usually done with an isotropic shrinking so that it does not adversely affect the structuring. However, the structuring of the pane can also be done after ceramization respectively. The structured glass ceramic pane preferably has structures with depths and widths in the dimension less tenths of a millimeter up to a few millimeters. Such structuring can be done by common Methods for producing structures in the mm to cm range such as Shape, Scoring, cutting, chemical etching, Laser ablation etc. take place.

1 illustrates the chosen designations. p is the sum of channel and barrier width. Also, the slice thickness t are in the range of a few millimeters, where td contains _channel .

Usual disc formats are for example about 700 mm × 400 mm.

It It can be seen that the production and in particular the installation such a flat backlight compared to manufacture and installation many backlight tubes enormously are simplified.

Also with the flat backlights there are the same different backlight types as in tubular form, so the ones mentioned above CCFL and EEFL.

glass ceramics have a unitary Spectrum of properties consisting of targeted, controlled, temperature-controlled, partial crystallization result. Depending on Composition, way of making the green glass and adaptation of the temperature regime in hot post-processing, the person skilled in the art knows in a glass ceramic different crystal phase types, crystallographic Species with different crystal morphology and size as well to produce different amounts of crystals. This can be done in particular the thermal expansion, mechanical stabilities, etc. to adjust. An outstanding basic property of glass ceramic represents the high thermal stability of the material which essentially higher is more common than the one Multi-component glasses.

Ceramic discs are already being used e.g. used as chimney panes or for cooking surfaces.

conditions to the glass ceramic panes for the uses according to the invention are in addition to a high temperature stability properties such as excellent transparency.

Long Time lacked the known glass-ceramics on transparency and / or they had their own color, so that for the one Use in lighting units would have been out of the question.

What the temperature stability from for the use according to the invention As regards suitable materials, this should be higher than to be from Hartglas. common glasses, which are suitable here and the z. B. are of the aluminosilicate glass type, have transformation points (Tg) in the range of 750 to 800 ° C. at Thus, the glass is still in a solid state at such temperatures in front.

Since no so-called "Tg" can be determined for glass-ceramics, it makes sense to determine a temperature-dependent, still stable state on the basis of the viscosity of the glass ceramic as a function of the temperature A suitable glass ceramic should not flow viscously even at relatively high temperatures ßen and lamp operating temperatures of> 800 ° C, preferably of> 900 ° C, and more preferably of> 1000 ° C withstand.

Ideally, the viscous flow of a glass-ceramic according to the invention begins at higher temperatures than with silica glass, most preferably the glass-ceramic is similarly stable or even more stable than translucent ceramics, e.g. B. those based on Al ₂ O ₃ .

Next the excellent temperature stability should glass ceramics a high transmission in the visible range (between 380 nm and 780 nm) at a layer thickness of 0.3 mm, for example> 75%, preferably> 80%, particularly preferably> 90%, which property when using the glass ceramic discs as components of a Lamp is important.

Especially in the backlight application in TFT screens Good UV blocking plays an important role. Under blocking becomes a Transmission of less than 1% with a layer thickness of 0.3 mm understood. The blocking can be achieved for wavelengths ≦ 260 nm, preferably ≦ 300, ≦ 315, ≦ 365 nm.

For some uses of the invention, the glass-ceramic should be readily fusible with electrical feedthroughs which, depending on the application, consist of molybdenum, tungsten or alloys such as Vacon ^11® ("Kovar") Thus, a permanently hermetically sealed seal between an electrically and thermally conductive metal feedthrough and can be provided to the lamp material, and problems caused by different thermal expansion properties of the glass and metal materials can be avoided, ie, stresses can be avoided, so that thermal expansion coefficients α _{20/300 can be} between 0 and 7 × 10 ^-6 / K , preferably between 3 × 10 ^-6 / K and 5 × 10 ^-6 / K. For fusions with tungsten, expansion coefficients are between 3.5 × 10 ^-6 / K and 4.3 × 10 ^-6 / K and for mergers with molybdenum expansion coefficients between 4.5 × 10 ^-6 / K and 5.0 × 10 ^-6 / K particularly preferred.

For the applications according to the invention The glass-ceramic is also important in that the materials are chemical are resistant, so that z. B. processes in a lamp permanently not affected. The materials should not be of fillers be penetrable, so have a good long-term tightness. Also should be hot, pressurized fillers do not cause corrosion of the glass ceramic.

The used according to the invention Glass ceramic panes are produced by means of ceramization programs known to the person skilled in the art produced. The ceramization program has to be designed so that the obtained glass ceramic for the respective application regarding is optimized according to the required properties.

For an optimal thermal stability It may be useful to the glass content within the glass ceramic too minimize i. for example, a crystal phase content of at least 60% by volume, preferably 70% by volume, more preferably 80% by volume, and / or the composition of the residual glass phase close to the pure Set silica glass.

The Ceramization programs are re Temperature and time regime adjusted and tuned to desired crystal phases, also attuned to the relationship of residual glass phase and crystal phase fraction as well as crystallite size.

Further can by the Keramisierungsprogramm the surface chemistry or a depth profile for certain Elements are adjusted, thereby during the ceramization in near-surface Areas z. B. a desired Alkaline content can be adjusted, even in fine adjustment from "low-alkali" to "alkali-free".

During the Ceramification can also be a concentration gradient for certain Elements are built, what by their involvement in the crystal phase or their whereabouts / enrichment in the residual glass phase are effected can, in particular by the formation of a glassy surface layer, their thickness and composition by the composition of the starting glass and the ceramization atmosphere can be determined.

The The ceramization program is also, where necessary, related to nucleation or crystal development regime to the desired level of shielding from UV radiation customized.

The UV blocking properties (position / slope) of the glass-ceramic can be tailored by a number of measures: In addition to the introduction of UV-blocking additives, such as TiO ₂ , with glass ceramics compared to glasses other adjustment options are given: Particle size (adjusted for maximum UV radiation) Scattering), particle size distribution (the more homogeneous the size of the particles, the steeper the edge). The glass ceramic can also be adjusted with respect to starting glass and ceramification status such that the active dopant Ti is ideally distributed over the residual glass phase and crystal phase. The larger the crystal particles are, the greater the UV blocking properties. Preference is given to particle sizes in the range from 10 to 100 nm, preference being given to a particle size distribution which is as monomodal as possible and preferably at least 60% of the particles present in this size range, the proportion of crystal phase in the total volume preferably being at least 50% by volume and at most 90% by volume. % is.

So prevents the total transmission in the range> 400 nm from being weakened too much, and a steep UV edge in the range 360 - 400 nm is achieved.

In one embodiment of the invention, the glass ceramics suitable for the use according to the invention have the following compositions (in% by weight based on oxide) SiO ₂ 50 - 70 Al ₂ O ₃ 17 - 27 Li ₂ O > 0 - 5 Na ₂ O 0 - 5 K ₂ O 0 - 5 MgO 0 - 5 ZnO 0 - 5 TiO ₂ 0 - 5 ZrO ₂ 0 - 5 Ta ₂ O ₅ 0 - 8 BaO 0 - 5 SrO 0 - 5 P ₂ O ₅ 0-10 Fe ₂ O ₃ 0 - 5 CeO ₂ 0 - 5 Bi ₂ O ₃ 0 - 3 WO ₃ 0 - 3 MoO ₃ 0 - 3 and optionally up to 4 wt .-% of one or more conventional refining agents such. As SnO ₂ , CeO ₂ , As ₂ O ₃ , Sb ₂ O ₃ , sulfates, chlorides.

The Compositions are characterized by the main crystal phases High quartz mixed crystal (HQMK) and / or keatite.

Ceramic discs from this composition range are particularly suitable for use in flat backlight units, as a structured substrate and / or as the other disk defining the radiation space, So the cover disc.

In a further embodiment of the invention, the glass ceramics used according to the invention have the following compositions (in% by weight based on oxide) SiO ₂ 35-70, preferably 35-60 Al ₂ O ₃ 14-40, preferably 16.5-40 MgO 0-20, preferably 4-20, more preferably 6-20 ZnO 0-15, preferably 0-9, more preferably 0-4 TiO ₂ 0-10, preferably 1-10 ZrO ₂ 0-10, preferably 1-10 Ta ₂ O ₅ 0-8, preferably 0-2 BaO 0-10, preferably 0-8 CaO 0-10, preferably 0-5 SrO 0-5, preferably 0-4 B ₂ O ₃ 0-10, preferably> 4-10 P ₂ O ₅ 0-10 Fe ₂ O ₃ 0 - 5 CeO ₂ 0 - 5 Bi ₂ O ₃ 0 - 3 WO ₃ 0 - 3 MoO ₃ 0 - 3 and optionally up to 4 wt .-% of one or more conventional refining agents such. As SnO ₂ , CeO ₂ , As ₂ O ₃ , Sb ₂ O ₃ , sulfates, chlorides.

The Compositions are characterized by the main crystal phases Spinel, sapphirine, HQMK, α-quartz, Cordierite and corresponding mixed crystals, in particular Zn spinels / sapphirins, Mg / Zn HQMK.

Ceramic discs from this composition range are particularly suitable for use as shields in very hot Lamps e.g. Halogen or HID lamps.

By Variants of the ceramization conditions can target the UV blocking be set. The ceramized disc is opposite one not ceramized disc of the same composition, so their Green glass, superior in UV blocking properties. It is therefore for the uses according to the invention excellent.

Due to the presence of TiO ₂ in the glass ceramic, the good UV blocking can be further improved. Therefore, the glass ceramics used according to the invention preferably contain at least 0.1% by weight of TiO ₂ , preferably> 1% by weight of TiO ₂ and more preferably> 2% by weight of TiO ₂ .

The Glass ceramic disk also points a very high solarization resistance on. So is after 15-hour Irradiation with UV light no or only a very small one (1% absolute, preferably <0.5% absolute) Waste of high transmission in the visible, measured at 750 nm, determine.

Also this property is for the uses according to the invention essential.

Also here it is superior to the previously used glass panes.

The Invention is based on embodiments be illustrated.

2 shows the transmission curves (transmittance [%] vs. wavelength [nm]) of an embodiment A1 and a comparative example V1 for the wavelength range 300 nm - 550 nm. The measurements were carried out on 0.3 mm thick samples.

Embodiment A1 is a LAS (Li ₂ O-Al ₂ O ₃ -SiO ₂ ) glass-ceramic of the following composition: Main component Wt .-% SiO ₂ 67.1 Al ₂ O ₃ 21.3 Li ₂ O 3.8 MgO 1.1 ZnO 1.7 TiO ₂ 2.6 ZrO ₂ 1.7 As ₂ O ₃ 0.2 K ₂ O 0.1 Na ₂ O 0.4

The Ceramization takes place in a multi-stage process by heating ramps and holding times is marked. The maximum temperature exceeds not 1000 ° C, the holding times are adapted to the optimal crystallite growth.

The Crystallite size is generally of the order of magnitude from 20 to 90 nm, the crystal phase content is at least 50%.

Comparative Example C1 is a glass of the following composition: Main component Wt .-% SiO ₂ 71.65 TiO ₂ 4.0 B ₂ O ₃ 16.9 Al ₂ O ₃ 1.15 Na ₂ O 3.75 K ₂ O 1.45 CaO 0.6 MgO 0.4 As ₂ O ₃ 0.1

2 shows in spite of the low TiO ₂ content of A1 compared to the already well UV-blocking glass V1 again significantly improved UV blocking of the glass ceramic A1 with very little negligible transmission loss in the visible.

A1 is preferable to V1 in some application- _{relevant basic properties} . For example, α _30/300 at about 0 ppm / K is significantly lower than that of V1 (3.9 ppm / K), which means that the material is more resistant to temperature changes, eg in hot lamps. In addition, a better adaptation to silica glass is given, a material which is also often used in the construction of lamps. The thermal loadability of A1 is at least 850 ° C (below that the material does not deform any more) than about 550 ° C for V1 (Tg ~ 500 ° C)

Due to its better UV blocking A1 is as a lamp component, especially for lamps of devices that have plastic components that are susceptible to yellowing, z. B. for backlights, better suited as V1. Effectively, in particular, the UV-A range (around 365 nm) is blocked: Here arises how 2 shows an improvement (reduction) by 30 transmission percentage% (ie absolute) or more.

3 shows the transmission curves (250-550 nm) of the embodiment A1 and an embodiment A2, of A1 only by its reduced TiO ₂ content (2.0 wt .-% instead of 2.6) and its increased SiO ₂ - (um 0.3 wt .-%) and increased Al ₂ O ₃ -, ZnO-, ZrO ₂ - (each by 0.1 wt .-%) and two comparative examples V2 and V3, the green glasses, ie the unkeramisierten base glasses , A1 and A2, where V2 has the same composition as A1 and V3 has the same composition as A2.

The Measurements were made on 0.3 mm thick samples.

3 illustrates not only the improvement of the UV blocking by increasing the TiO ₂ content (V2 vs. V3), but in particular the great improvement of the UV blocking by the ceramization (A1 vs. V2 or A2 vs. V3).

4 shows the transmission curves of the embodiments A1a and A1b.

A1a and A1b have the same composition as A1. They contain however, due to variations in the ceramization program, crystallites the average crystallite size of approx. 30 nm (A1a) or of about 50 nm (A1b), determined by X-ray diffractometry were.

The Measurements were made on samples with a thickness of 4 mm.

4 shows that by varying the particle size, a fine tuning of the UV edge is possible. In this case, by varying the ceramization conditions, especially the maximum temperatures / hold times of the crystal growth step set the particle size.

5 Figure 3 shows the transmission curve (350-600 nm) of an embodiment A3 before (A3a) and after (A3b) a 15-hour irradiation with a HOK-4 lamp.

The Measurements were made on 0.7 mm thick samples.

Embodiment A3 is the sample of an alkali-containing LAS glass-ceramic having a composition close to that of A1, namely Main component Wt .-% SiO ₂ 67.3 Al ₂ O ₃ 21.3 Li ₂ O 3.8 MgO 1.1 ZnO 1.7 TiO ₂ 2.3 ZrO ₂ 1.7 As ₂ O ₃ 0.3 K ₂ O 0.1 Na ₂ O 0.4

The Curves show that the irradiated sample shows no solarization. The inventively used Materials are therefore extremely stable to solarization.

6 shows the transmission curve (300-600 nm) of a comparative example V4 before (V4a) and after (V4b) a 15-hour irradiation with a HOK-4 lamp.

The Measurements were made on 0.22 mm thick samples.

Comparative Example C4 is a glass of the composition (in% by weight) SiO ₂ 68.5 Na ₂ O 10.9 K ₂ O 4.7 CaO 5.0 BaO 4.0 ZnO 2.8 TiO ₂ 1.5 CeO ₂ 2.6

The curves show that unlike A3 (s. 5 ) a solarization in the area of the UV edge has occurred. This also documents the significantly poorer suitability for the uses according to the invention compared to the materials used according to the invention.

7 again shows the transmission curve of A1, this time in comparison to that of the commercially available glass V4 and also the curve (A4) of a glass ceramic of the type ZERODUR ^® , another representative of the zero-stretching LAS glass ceramics with high quartz mixed crystals as crystal phase. This glass ceramic is characterized by average crystallite sizes> 68 nm and a crystal phase content> 70% by volume.

The Measurements were made on 0.2 mm thick samples.

The Curves show that A1 and A4 also compared to the commercial for UV blocking applications, also in lamps, glass V4 used good transmission properties, namely a high transmission in the visible and a steep enough Own UV edge.

8th shows the construction of a flat backlight, namely a flat EEFL (external electrode fluorescent lamp) with glass ceramic panes according to the invention used according to A1.

1a, 1b

Ceramic glass

2

dielectric layer

3a, 3b

electrodes

4

MgO layer

5

plasma

6

light emission in the UV and in the visible

7

phosphor layer for the conversion in particular of the UV components

8th

barrier

9

glass frit

1a and 1b are glass ceramic panes, but it is possible that only 1a or 1b one glass-ceramic pane, while the other pane represents a glass pane, for example an aluminoborosilicate glass pane. For the disc 1a the good UV-blocking is particularly important, therefore, the use of a glass-ceramic disc is particularly preferred here.

Exemplary embodiment A5:

A rolled green glass pane, matched in size to future display sizes (eg of monitors (eg 17 "or 19") or even large-format 16: 9 TV systems), the composition A1 was at a viscosity of about 10 ⁵ dPas with a structured The roll was then patterned and ceramized into the high quartz mixed crystal phase so that the disk had the desired channel and barrier structure in the mm range.

The Washer was used to make a flat backlight.

9 shows as embodiment 6 a glass ceramic disk of the composition A1, which is installed as a diffusion plate, which serves the homogeneous light distribution, in a flat display with conventional tubular fluorescent lamps. If the crystal particle size is suitably adjusted, they will take over the light diffusion due to scattering effects and eventually block even the last UV-A / B / C.

1

fluorescent lamp with UV-C blocking up to 254 nm, possibly blocked to 313nm

2

reflector

3

light Guiding polymer

4

reflecting plate

5

diffusion plate

6

prism plate

7

pattern

Embodiment A7:

In a further embodiment, the glass ceramic panes of the embodiments A5 and A6 consist of a transparent glass ceramic of the composition Wt .-% component 58.5 SiO ₂ 20.3 Al ₂ O ₃ 4.2 MgO 8.4 ZnO 3.0 TiO ₂ 5.0 ZrO ₂ 0.5 As ₂ O ₃

Claims (7)

Use of a glass ceramic pane as part of a Lamp. Use according to claim 1, wherein the disc is part of a backlight arrangement is. Use according to claim 2, wherein the disc is part of a flat backlight is. Use according to claim 1, wherein the disc is a diffusion plate serves. Use according to at least one of claims 1 to 4, wherein the disc has a composition of the following composition range (in% by weight based on oxide): SiO ₂ 50-70, Al ₂ O ₃ 17-27, Li ₂ O> 0 - 5, Na ₂ O 0-5, K ₂ O 0-5, MgO 0-5, ZnO 0-5, TiO ₂ 0-5, ZrO ₂ 0-5, Ta ₂ O ₅ 0-8, BaO 0-5 , SrO 0-5, P ₂ O ₅ 0-10, Fe ₂ O ₃ 0-5, CeO ₂ 0-5, Bi ₂ O ₃ 0-3, MoO ₃ 0-3, MoO ₃ 0-3, conventional refining agents 0 - 4. Use according to any one of claims 1 to 4, wherein the disc has a composition of the following compositional range (in weight percent based on oxide): SiO ₂ 35-70, Al ₂ O ₃ 14-40, MgO 0-20, ZnO 0 - 15, TiO ₂ 0 - 10, ZrO ₂ 0 - 10, Ta ₂ O ₅ 0 - 8, BaO 0 - 10, CaO 0 - 10, SrO 0 - 5, B ₂ O ₃ 0 - 10, P ₂ O ₅ 0-10, Fe ₂ O ₃ 0-5, CeO ₂ 0-5, Bi ₂ O ₃ 0-3, WO ₃ 0-3, MoO ₃ 0-3, customary refining agents 0-4. Use according to at least one of claims 1 to 6, wherein the disc contains at least 0.1 wt .-% TiO ₂ , preferably> 1 wt .-% TiO ₂ .