Optical filtering and electromagnetic armouring structure

Translation of description of equivalent WO 2004016053 A2

FILTER AND OPTICAL STRUCTURE OF ELECTROMAGNETIC SHIELDING

The invention relates to an optical filter structure and electromagnetic shielding to be joined to at least a transparent substrate, notably of glass, the structure comprising at least two plastic sheets, and comprising or intended to be associated to the leaves a conductive element electromagnetic shielding.

The invention will be more particularly described as to the use of such an electromagnetic shield structure for a display screen such as a plasma display.

A plasma comprises a plasma gas mixture (Ne, Xe, Ar) trapped between two sheets of glass, and phosphors provided on the inner face of the back sheet of the screen. Ultraviolet light radiation emitted by the plasma gas mixture during the plasma discharge to between the two sheets of glass interacts with the phosphors of the inner face of the backsheet to produce the visible light radiation (red, green, blue). A gas particle deexcitation mechanism competes with the UV emission, which generates infrared radiation between 800 and 1250 nm whose spread, mainly through the front face of the screen may cause very annoying disturbances, especially for equipment located nearby and controlled by infrared, for example by means of remote controls.

Furthermore the infrared radiation generated by the excitation of the plasma gas, radiation in the deep orange at 590 nm is also emitted

<By the gaseous mixture when it contains neon. This radiation in orange can be unpleasant to the eye of the beholder. In addition, it interacts with the blue and green colors of the light spectrum so that it makes an image on the display screen showing blue and green colors that can be called washed or faded, and a less frank red .

Moreover, like all electronic devices, plasma displays possess addressing systems (drivers) that can generate a interfering radiation vis-à-vis other device with which they must not interfere such as microcomputers, mobile phones ...

To annihilate, and at least reduce the spread of radiation, one solution is to have against the front of the screen a structure that is both transparent and metallized to provide electromagnetic shielding.

One type of known structure consists of two sheets of thermoplastic material, in particular of the PVB, between which is disposed a metal son network as a homogeneous grid. This grid may be formed of a metal fabric son glued between two PVB sheets by heating the thermoplastic material.

Another solution is instead to etch a copper layer deposited on a transparent substrate such as PET by a conventional technique of photolithography, and assembling the substrate to the PVB, the PET substrate is inserted between the two sheets of PVB and bonded by heating the thermoplastic material.

This advantageously laminated structure with the PVB being disposed on the front of the display screen, the front of which is a glass substrate, ensures vis-a-vis the viewer protection in the event of breakage of the screen by retaining the broken glass.

The metal grid thus provides electromagnetic shielding. However, it is always desirable to improve the performance of an electromagnetic shielding filter, further reducing the transmission waves in the infrared and to find other filtering properties such as to consistently cut the orange color . In addition, it is of course desirable for the viewer's eye to have made optimum colors on the screen.

A known type of filter for automotive glass cutting in certain wavelengths is the combination of two PVB sheets of which consists of the product Solar reflective film from 3M and the other consists of the PVB film-Sekisui Lec © marketed by Sekisui. The 3M product and the PVB film of SEKISUI are clear and neutral transmission, SEKISUI movie further containing conductive particles. This filter has the advantage of transmitting only 51% of the light, but that light is Yellow dominance, the dominant wavelength is 561 nm, which significantly changes the color rendering on a display screen. The light further has a purity of 8% which is considered significant with respect to a desired level less than or equal to 7%. Remember that purity is defined in the measurement system of CIE 1931. In this system, the color of an object is represented by a point with coordinates x, y. The purity is the ratio of the length of the segments, respectively, one seal illuminant spectrum to the locus of the end and passes through the point of coordinates x, y, and the other seal at the point of illuminant x, y coordinates. In addition, if this filter provides a transmission in the 1200 nm infrared at most equal to 5%, the transmission is still 13% at 850 nm. Finally, the orange color is not sufficiently turned off, the transmission for the corresponding wavelength is 64%.

The invention therefore aims to provide an optical filter structure and electromagnetic shielding that allows one hand to sufficiently cut the orange 590 nm centered on wavelength, and secondly, to further increase the filter performance in the infrared, while obtaining adequate transmitted light not to turn the color purity and optimize the contrast of the visible image on a display screen having associated therewith such a structure.

Also, the inventors carried out an electromagnetic shielding structure which is characterized in that at least one sheet is a thermoplastic, the other sheet is a cover sheet of the conducting element or the thermoplastic sheet material, and one or two sheets incorporate at least one mineral pigment or at least one organic dye so as to provide the structure for a filter for the wavelength of orange centered on 590 nm.

According to one feature, one of the sheets at least, the thermoplastic sheet material and / or the covering sheet, incorporates at least one mineral pigment or at least one organic dye to form an infrared filter in the range of wavelengths of 800-1250 nm.

According to one embodiment, one of the two sheets is neutral while the other sheet includes at least two pigments or dyes which perform through the structure, respectively, the filter for the orange and the infrared filter.

According to another embodiment, the thermoplastic sheet includes a pigment or dye which, through the structure the filter for the orange or the infrared filter and the covering sheet includes a pigment or dye that provides the filter for the orange color or infrared filter that does not ensure the other sheet of thermoplastic material.

In a first variation, the conductive member is made of a metal son of tissue associated between the two sheets. In a second variant, the conductive member is made of a gate metal son deposited on a support sheet, made based on one of the following materials, polycarbonate, polymethyl (meth) acrylate, polyethyleneterephthalate, polyether sulfone, polyetherketone and acyronitrile- styrene. Advantageously, according to this second variant, the carrier sheet of the conductive element constitutes the covering sheet, the conducting element being arranged between the first sheet of thermoplastic material and the cover sheet. Preferably, the covering sheet bearing the conducting element is coated on the opposite side of the conductive element with a protective film (PET) or polyvinyl chloride (PVC), or polypropylene, or enco / e, high density polyethylene, and less than or equal thickness to 60 // m.

In a third variant, the conductive member is composed of a metal layer such as silver-based, deposited on a support sheet which is constituted by the cover sheet, said element being arranged between the cover sheet and the first sheet of thermoplastic material.

According to another characteristic, the support sheet of the conducting element consists of a complementary plastic sheet that is laminated between the thermoplastic first sheet and the cover sheet.

Advantageously, the first sheet of thermoplastic material, and the covering sheet when it does not constitute a support sheet for the conducting element are made of polyvinyl butyral, or of polyurethane, or ethylene vinyl acetate. The structure can be assembled to a single transparent substrate, the first sheet of thermoplastic material being joined to the substrate.

According to another variant, the structure can be assembled laminated between two transparent substrates, the thermoplastic sheet and the cover sheet being respectively joined to each of the substrates.

According to one characteristic, the transparent substrate has, on its side facing the thermoplastic sheet material such as metal layer based on silver for forming the conductive member when the latter is associated with the structure. The structure thus provides for the overall structure and substrate (s), an infrared filter with a corresponding light transmission T_IR not exceeding 17%, and a filter for the orange color with a corresponding light transmission T_BORN between 20% and 40%, the overall structure and substrate (s) having a light transmission rate in the visible of between 40% and 60%, with a purity of less than 7%.

More particularly, the infrared filter ensures transmission at 815 nm of at most 17%, transmission at 870 nm of at most 9% and transmission between 900 and 1250 nm of at most 9%.

The structure of the invention may for example be associated with the front face of a display screen, such as a plasma display. It can also be associated with any device requiring electromagnetic shielding and filters in the infrared and in orange.

For a display screen, or the glass substrates to which is associated the structure are made of tempered glass. Preferably, at least one of the glass substrates has an antireflection layer on the opposite side to the structure. Advantageously, the covering sheet has an antireflection treatment on the opposite side to the first sheet of thermoplastic material. Finally, the structure may be directly bonded to the front face of the screen.

Other advantages and characteristics of the invention appear on reading the following description with reference to the accompanying drawings in which:

- Figure 1 is a sectional view of the structure of the invention;

- Figures 2 and 5 are sectional views of variants of the structure of the invention; - Figures 3, 4 and 5 are sectional views of the structure of the invention associated with the front face of a display screen according to several embodiments.

firstly that the relative proportions of the different size is specified, including thicknesses, elements of the invention are not complied with in the drawings so that reading is facilitated.

The optical filter and electromagnetic shielding structure 1 illustrated in Figures 1 and 2 is intended to be associated with at least a transparent substrate such as a glass substrate, the substrate being more particularly intended to be mechanically assembled against a screen display so that the structure is for a filter screen in the orange color and complementary if necessary a filter in the infrared.

The display screen is, for example a plasma, the latter in particular emitting radiation in the orange due to the neon content in the gas mixture of the screen. But this use of the structure is not limited to plasma and can be used and associated with any device requiring a filter in the color orange.

The optical filter and electromagnetic shielding structure 1 comprises a first sheet 10 of thermoplastic material and a second sheet 12 of plastic material which constitutes a cover sheet for the element to which it is associated. A conductive member 11 of electromagnetic shielding is between the two sheets 10 and 12 or is intended to be associated to the sheets when not comprised in the structure.

The conductive element 11 may be in a first variant of a metal fabric son, of the type made of copper, which is inserted between the two sheets 10 and 12 and assembled by heating the two sheets. In this case, the cover sheet

12 is preferably in the same material as the first sheet 10, polyvinyl butyral, or of polyurethane, or ethylene vinyl acetate.

In a second variant, the conductive member 11 is a gate metal son, the type of copper, obtained by a usual photolithography technique on a plastic support sheet made from any of the following materials, polycarbonate, polymethyl (meth) acrylate, polyethyleneterephthalate, polyether sulfone, polyétherketone and acyronitrile- styrene. In this second variant, the carrier sheet of the conductive member 11 can advantageously be the cover sheet 12 which is then associated with the first sheet 10 so that the conductive element is arranged between the two sheets, the assembly of sheets being effected by heating the material (Figure 1). Alternatively, the carrier sheet of the conductive member 11 may instead be comprised of a cover sheet 13 which is laminated between the first and second sheets 10 and 12 which are then preferably one and the other in the one of the following thermoplastics, polyvinyl butyral or polyurethane, or ethylene vinyl acetate (Figure 2). In a third variant, the conductive member 11 is a silver-based layer deposited on a plastic support sheet made from any of the following materials, polycarbonate, polymethyl (meth) acrylate, polyethyleneterephthalate, polyether sulfone, polyetherketone, and acyronitrile- styrene. This backing sheet can advantageously be the cover sheet 12, the layer being arranged between the two sheets 10 and 12 (Figure 1).

When the conductive member 11 constituting an electromagnetic shielding member is not integrated in the structure 1, but is associated with it, the element is, for example as a metallic layer, such as silver-based, deposited on the substrate which is intended structure, layer^' located opposite the first sheet 10 which has just assemble against the substrate. This is the example of Figure 5 in which there is shown a substrate 20 having one face provided with the conductive member 11 and which is associated with the structure 1 having the first sheet of thermoplastic material 10 and the cover sheet 12. the cover sheet ensures a function other than the function or functions performed by the sheet 10, or to protect the sheet 10 if it is made of a material which can easily be scratched by example, or to facilitate assembling the sheet 10 to the element that will come opposite the substrate. For a better electromagnetic shielding, metal son of the grid is preferred as an element conductor rather than a metal layer.

The optical filter according to the invention is obtained in the following manner, one or the other of the two sheets 10 and 12, or both sheets 10 and 12 include at least one mineral pigment or at least one organic dye to form a filter for the orange color that matches the wavelength of 590 nm. The product FILTRON A178 or A193 sold by Gentex is an example of a dye that can be incorporated into a polymeric sheet to form a filter in orange. The first sheet 10 of thermoplastic material is of polyvinyl butyral, or of polyurethane, or ethylene vinyl acetate.

The second cover sheet 12 is in a plastics material which depends on the function performed by the sheet other than the filter in orange. Examples of material have been mentioned above in the variant considered for the conductive element.

According to the invention, the structure 1 may also comprise means for constituting a filter in the infrared. As for the filter in orange, at least one pigment or at least one colorant may be incorporated into the one of the sheets 10 or 12 of the structure, or in the two sheets to form the infrared filter. An example of a dye to the infrared filter is the product FILTRON A195 or A101 sold by GENTEX society.

Also, at least one of the sheets 10 or 12, or at least the cover sheet 13 when the latter is laminated between the two sheets 10 and 12, comprises at least one pigment and / or at least one dye so that the structure 1 is firstly a filter for infrared, corresponding to wavelengths ranging from 800-1250 nm, and secondly a filter for the orange color that matches the wavelength centered on 590 nm.

Several structural variants may be considered in incorporating dyes or pigments for infrared filters and orange.

The dye or pigment and the infrared filter dye or pigment for orange color filter are both incorporated into one of the sheets 10, 12, or 13, the sheet or sheets do not contain dyes or pigments being preferably light color. Alternatively, the dye or pigment to an infrared filter is built into one of the sheets 10, 12 or 13 while the pigment or dye to the orange color filter is integrated in the sheet not containing the dye or pigment of the infrared filter . Finally, according to the invention, the covering sheet 12 has on the face opposite to that provided with the conductive element 11 when the latter is supported by the sheet, a protective film 14. The film is in the form of a sheet of polyethylene terephthalate (PET) or polyvinyl chloride (PVC) or polypropylene or high density polyethylene. Its thickness is less than or equal to 60 μ. It makes it possible firstly to protect the face opposite to that carrying the conductive element so as to avoid streaks of this face by the conductive member when the sheet is presented in roll form for delivery. Moreover, this protective film is used to create a clean surface for the assembly of the covering sheet against another surface.

The structure 1 as described above may be associated with a transparent substrate 20 such as a glass substrate, or be laminated between two transparent substrates of the type glass 20 and 21 to form the front face 2 of a screen visualization E, that is to say the portion facing the viewer. An example (Example 1) of assembly embodiment of the front screen by means of a structure 1 associated with a single substrate 20 is as follows (Figure 3):

- The substrate 20 facing the viewer;

- The first thermoplastic sheet 10 which is PVB and assembled to the substrate 20;

- The conducting element electromagnetic shield 11 which is deposited on the cover sheet 12 made of PET, this sheet being associated on the one hand to the first sheet 10 and facing the other hand to the screen E.

Another example (Example 2) of front panel screen assembly embodiment using a 1 sheet structure between the two substrates 20 and 21 is as follows (Figure 4):

- The glass substrate 20 opposite the viewer

- The first thermoplastic sheet 10 of PVB, meeting the first glass substrate 20; - The conducting element electromagnetic shield 11 deposited on a cover sheet 13 made of PET;

- The second cover sheet 12 of PVB assembly by one of the faces complementary to the sheet 13 and its face opposite the second glass substrate 21. In Examples 1 and 2, the entire substrate structure (s) is mechanically fixed on the screen by means of a not shown metal frame.

The filter formed through the structure 1, associated with a single substrate (exemplel) or laminated between two glass substrates 20 and 21 (example 2) in which have been incorporated dyes of the type FILTRON A195 or A101 for the absorption of neon stripe to 590 nm and the type FILTRON A178 or A193 for absorption in the infrared, is defined by the properties of light transmission:

- A transmission T |_R at 815 nm of at most 22%, - a TIR transmission at 870 nm of at most 18%,

- A transmission T |_R between 900 and 1250 nm of at most 12%,

- A transmission T_NOTE at 590 nm between 20 and 40%. The combination of the dyes or pigments for the filters in the orange and in the infrared, optionally combined with other pigments or dyes absorbing in the visible, leads to obtain a structure 1 associated with two glass substrates whose light transmission T_L is of the order of 40 to 60% with the dominant wavelength between 480 and 520 nm and is associated with a purity of less than 3%. The purity of less than 3% with other pigments or dyes enables a gray filter, that is to say transmission in neutral color.

The property, in the infrared transmission is in terms of light transmission in the visible. A filter having a high transmission in the infrared, for example of the order of 16%, necessarily correspond to a transmission in the visible high (of the order of 47%). therefore choose a compromise between the transmissions in the infrared and visible. By cons, the transmission in the orange may be adjusted regardless of the light transmission in the visible filter.

The use of filters in the orange and infrared can lead to a structure through which the color perceived by a viewer can be in a dominant color, such as green. In order to compensate for this color to get a neutral gray color which does not weaken the color tones rendered on the screen, or is associated as stated above other pigments or dyes, or a spacer type absorbing tinted PVB the visible and conventionally used in laminated glazing. The representation given in Figure 6 (Example 3) has an alternative use of a screen to optical filter made according to Example 1 which has the distinction of being directly bonded via the cover sheet 12 after removing the protective film 14 if one is present, against the substrate of the front face of the screen by means of an adhesive or a resin, or any other means known to those skilled in the art . The advantage of this assembly method is to remove the optical interfaces and lower the level of spurious reflection.

In the three examples of the structure of association of embodiment a or respectively to two glass substrates, and preferably in the embodiment particularly that includes only one glass substrate, or the glass substrates are tempered glass. Tempered glass is highly mechanically strong and very difficult to break. Thus in the first and third embodiments, the thickness of the total filter screen, the structure 1 and the glass substrate 20, can advantageously be reduced relative to the thickness of the second embodiment filter including two glass substrates while maintaining the protective properties vis-à-vis the viewer.

In addition, in these three embodiments, or the glass substrates are preferably coated on their external face opposite the structure 1 of an antireflection layer. In the case of Example 1 or 3, the cover sheet 12 made of PET may advantageously comprise an antireflection treatment by means of a heat curable resin or ultraviolet.