WO2023073207A1 - Spacer fabric and transparent element - Google Patents

Abstract

The invention relates to a spacer fabric comprising a first flat knitted fabric layer (1), a second flat knitted fabric layer (2), and spacer threads (6A, 6B) connecting the knitted fabric layers (1, 2), wherein the first knitted fabric layer (1) has first openings (3) each delimited by a plurality of stitches, wherein the second knitted fabric layer (2) has second openings (4) each delimited by a plurality of stitches, and wherein the first openings (3) and the second openings (4) at least partially overlap when the spacer fabric is viewed from above and form free through-holes (5) in the spacer fabric. According to the invention, the spacer threads (6A, 6B) are formed at least by a first spacer thread system of monofilament yarn and a second spacer thread system of multifilament yarn.

Description

a n d r e j e w s k i • h o n k e

Patent Attorneys and Law Attorneys

spacer fabric and see-through element

Description:

The invention relates to a spacer fabric with a first flat knitted layer, a second flat knitted layer and spacer threads connecting the knitted layers, the first knitted layer having first openings delimited by a plurality of stitches, the second knitted layer having second openings delimited by a plurality of stitches and the first openings and the second openings overlap at least partially in a top view and form free openings of the spacer fabric. The invention also relates to a see-through element.

Spacer fabrics are characterized by a light, air-permeable structure, spacer fabrics being elastic in the direction of their thickness due to the spacer threads running between the two flat knitted fabric layers.

Due to their specific properties, spacer fabrics can be considered for very different applications as technical textiles. Furthermore, spacer fabrics are also used for mattresses, upholstered furniture, clothing or shoes.

In a large number of applications, spacer fabrics are concealed in a multi-layer structure in order to form an intermediate layer that is pressure-elastic and, if necessary, also well permeable to air.

DE 10 2008 020 287 C5 discloses a spacer fabric of this type which has very good air permeability due to openings in both fabric layers and can be used, for example, in motor vehicles for ventilated seats. In this context also between the

beiden Gewirkelagen im Bereich der Abstandsfäden einen geringen Strömungswiderstand zu ermöglichen, sind die Abstandsfäden in inselförmigen Verbindungsbereichen angeordnet, wobei dann dazwischen auch diagonal verlaufende Kanäle gebildet sind, welche für eine Fluidströmung einen geringen Widerstand darstellen. Insgesamt wird trotz einer guten Stützwirkung durch die Abstandsfäden eine sehr offene, durchlässige Struktur bereitgestellt.

In order to enable both knitted fabric layers in the area of the spacer threads a low flow resistance, the spacer threads are arranged in island-shaped connection areas, with diagonal channels then also being formed between them, which represent a low resistance for a fluid flow. Overall, a very open, permeable structure is provided despite the good support provided by the spacer threads.

Furthermore, it is known to visibly arrange spacer fabrics, so that the mechanical resistance and the visual appearance are of particular importance. DE 10 2018 114 566 B3, for example, discloses a spacer fabric which is particularly suitable as an interior trim part, in particular as a headliner of a passenger car. In order to achieve a particularly uniform, high-quality appearance, at least one textile layer and the spacer threads are formed exclusively from polymeric multifilament yarns, with at least the polymeric multifilament yarns of the corresponding textile layer and the spacer threads being dyed. The corresponding textile layer then forms the visible surface of an interior trim part.

For certain applications, it is also known to use monofilament yarns on the one hand and multifilament yarns on the other for the spacer threads. For example, DE 299 24 569 U1 deals with an air-conditioning spacer fabric in which a surface close to the skin has openings and improved moisture transport is additionally achieved by multifilament yarns as spacer threads. A skin-distant knitted layer is closed.

Proceeding from the state of the art, the present invention is based on the object of expanding the range of uses of knitted spacer fabrics and a knitted spacer fabric with improved optical properties

bereitzustellen. Insbesondere sollen auch hinsichtlich einer Durchsicht spezifische Verbesserungen erzielt werden, wobei auch ein aus dem Abstandsgewirke gebildetes Durchsichtelement bereitgestellt werden soll.

to provide. In particular, specific improvements are also to be achieved with regard to viewing, with a viewing element formed from the spacer fabric also being provided.

The object of the invention and the solution to the problem are a spacer fabric according to patent claim 1 and a see-through element according to patent claim 19.

Based on a generic spacer fabric with at least partially overlapping openings in both layers of fabric and the resulting free openings, the invention provides that the spacer threads are formed at least by a first spacer thread system made of monofilament yarn and a second spacer thread system made of multifilament yarn.

Since the first openings and the second openings at least partially overlap one another in the plan view of the spacer fabric along its thickness direction, the spacer fabric is transparent along the free openings present there.

The first openings and the second openings are usually provided in the respective knitted fabric layers in a uniform arrangement one above the other, so that the openings are also in a uniform arrangement when viewed from above and enable a view through. In a conventional construction of the spacer fabric, which is explained in more detail below, an observer can look through the spacer fabric according to the invention at least at a certain distance of typically about one meter or a few meters without any problems and also focus the eye on objects present behind the spacer fabric. By the

The spacer fabric itself retains some of the light that passes through, resulting in a certain degree of darkening overall. This applies in particular if the spacer fabric according to a preferred embodiment of the invention is at least partially or also particularly preferably completely dark and in particular black and is therefore designed to be absorbent with regard to visible light.

Within the scope of the invention, a view along the free openings is possible, which are each formed by the openings lying directly one above the other.

With conventional spacer fabrics according to the prior art, a clearly perceptible transparency also results from an oblique view if, along the viewing direction, a first opening of the first knitted layer is not connected to the second opening of the second knitted layer immediately below, but to a second opening of the second, offset laterally thereto The knitted layer is aligned, even if the light passing through is partially scattered by the spacer threads then present along the viewing direction.

According to the present invention, on the other hand, it is provided that the spacer threads are formed by at least one first spacer thread system made of monofilament yarn and on the other hand a second spacer thread system made of multifilament yarn. While the monofilament yarn provides a certain compressive strength, the openings formed by the openings lying exactly one above the other are laterally opaque or essentially opaque limited by the multifilament yarn. Effective shielding is achieved thanks to the large number of filaments in the multifilament yarn.

Within the scope of the invention, the shielding can be adapted and improved by the specific configuration according to the respective requirements.

According to a preferred embodiment of the invention, it is provided that the second spacer thread system is formed from textured multifilament yarn. Due to the texturing of the multifilament yarn, it does not run straight and is also puffed up to a certain extent. The shielding against light passing through can be further improved by both effects. Even if there are several spacer threads made of the multifilament yarn lying one behind the other in a viewing direction, the texturing can better prevent gaps and cracks that are still perceptible from being visible.

According to a further aspect of the invention, to improve the shielding, it can be provided that the multifilament yarn of the second spacer thread system has filaments in the form of microfilaments and preferably consists of filaments in the form of microfilaments, the microfilaments each having a fineness of less than 1.5 dtex, preferably less than 1 dtex. Due to the very fine microfilaments, a larger volume can be filled in relation to a given fineness or a larger area can be filled in a plane perpendicular to a line of sight.

If the multifilament yarn of the second spacer thread system consists of filaments in the form of microfilaments, texturing can also be provided in principle, so that the two measures described above are then combined.

However, preliminary tests show that even with only one of the two measures and in particular a texturing of the multifilament yarn

Filaments each having a fineness of more than 1.5 dtex very good results can be achieved with regard to the optical properties desired within the scope of the invention.

In the context of the invention, the spacer fabric is transparent to a certain extent in a vertical plan view and essentially only weakens the transmission. However, as soon as, taking into account the thickness of the spacer fabric, there is no longer any overlap between directly superimposed openings at an oblique viewing angle along the viewing direction, the material is at least largely opaque.

According to the usual stitch formation in the knitting process, the two flat knitted layers have rows of stitches following one another along the direction of knitting and wales running along the direction of knitting. Even if the wales do not run exactly straight due to the formation of the openings, but in a certain wave or zigzag shape, an average distance can be determined for the rows of stitches and the wales. According to a preferred embodiment of the invention, it is provided that a length of the openings determined along the knitting direction is greater than the average distance from the rows of stitches that follow one another along the knitting direction. In addition or as an alternative, it is preferably also provided that a width of the openings determined perpendicularly to the direction of action in a transverse direction is greater than an average distance between adjacent wales. The length and width of the openings can, for example, be approximately twice the average distance between the rows of stitches or the average distance between adjacent wales.

Depending on the design of the spacer fabric, the openings can have a length and width of between 1 mm and 5 mm, for example.

In order to be able to form the openings described, it is provided according to a preferred embodiment of the invention that the first and the second knitted fabric layer are each formed by a filet weave, in particular selected from the group of cloth filet weave, jersey filet weave, satin filet weave and velvet filet weave.

Within the scope of the invention, it can be provided that the two knitted fabric layers are of the same design with regard to a laying pattern and/or the threads forming the knitted fabric layers. In particular, it can be provided that the two knitted fabric layers are designed exactly the same, so that the two knitted fabric layers are identical or initially almost identical.

Precisely when the spacer fabric within the scope of the invention is arranged so that it is freely visible when it is being used, the same appearance then results from both sides. Furthermore, in particular, the first openings and the second openings are then also made the same, which is also advantageous with regard to the use of the spacer fabric as a see-through element.

The proportion of the area of the openings in the two knitted fabric layers depends in particular on the particular knitting pattern provided, the type of yarn used, the fineness of the game and possibly other factors. In order to achieve a very uniform, dense structure in the two flat knitted fabric layers even outside of the openings, it is provided according to a preferred embodiment of the invention that the knitted fabric layers are at least partially, preferably completely

Multifilament yarns are formed, which can also be textured and in particular false-twist textured.

As described, the design of the spacer threads is decisive for the angle-dependent transparency of the spacer fabric. Correspondingly, the flat knitted fabric layers can alternatively also be partially or completely formed with a smooth yarn, which can influence the mechanical properties. In particular, high-strength smooth yarns made of polyethylene terephthalate are known, which allow a particularly high tear resistance.

In the context of the invention it is preferably provided that the first and the second openings extend in the respective knitted layer over 20% to 80%, preferably 25% to 60% and in particular 30% to 50% of a total area. The total area refers to the areal extension of the spacer fabric.

As already explained above, the specified surface area refers to the openings, which are to be regarded as macroscopic in comparison to individual meshes. The openings form a coherent free area without the threads of the knitted fabric layers running through them. Small free spaces within individual meshes or between immediately adjacent meshes are not taken into account in the determination. In any case, according to a preferred embodiment, the knitted fabric layers are knitted at least largely densely outside of the openings.

According to the invention, it is provided that the first openings and the second openings at least partially overlap when viewed from above and form free openings in the entire spacer fabric.

Within the scope of the invention, the aim is preferably to achieve the greatest possible degree of overlap. To this end, it is advantageous if the openings are formed in a recurring, uniform arrangement which is predetermined by a recurring knitting pattern. Furthermore, it is advantageous if the structure of the two knitted fabric layers is at least similar or preferably identical. Furthermore, however, it must also be ensured that the two knitted fabric layers are also aligned in a suitable manner during the production of the spacer fabric. Thus, it is known to subject spacer fabrics to mechanical and thermal conditioning as part of a so-called finishing process, in which the fabric layers can also be aligned by mechanical tension.

In the context of the invention, it is preferably provided that the first openings and the second openings have an overlap of at least 60%, preferably at least 80% and in particular at least 90% in a plan view. Except for minor deviations during production, there can be a complete or almost complete overlap of the first openings and the second openings.

As already discussed in detail above, the spacer fabric has transparency or opacity depending on the angle. This is achieved in that a view through the spacer fabric is essentially only possible along the free openings, with oblique viewing through first openings and second openings that are not directly one above the other being prevented due to the at least essentially opaque second spacer thread system made of preferably textured multifilament yarn.

An oblique view then gives the impression of a closed surface, apart from a fine structure that may still be visible. Against this background, it can be advantageous if the two knitted fabric layers and at least the multifilament yarns of the second thread system are color-coordinated. In principle, a color can be selected on the basis of design specifications.

According to a particularly preferred embodiment of the invention, however, it is provided that the thread systems of the two knitted fabric layers have black threads and that the multifilament threads of the second spaced thread system are black.

Against this background, it is of particular advantage if the two knitted fabric layers and the spacer threads and thus the entire spacer knitted fabric have a uniform coloring and a black design can be particularly expedient.

According to a preferred embodiment, it is further provided that coloring pigments or other dyes are present directly in the structure of the threads. If threads made of the thermoplastic are used according to a preferred embodiment, corresponding pigments or other dyes can be incorporated into the polymer matrix. The corresponding pigments or dyes are already added during the manufacturing process and are then evenly present as an integral part. Against this background, black threads and white threads are also referred to in practice as spinning black or spinning white.

Even if the present invention is not limited to specific starting materials, the spacer fabric preferably consists primarily or exclusively of plastic. For example, polyester and in particular polyethylene terephthalate is suitable for many applications.

In principle, however, other thermoplastics based on polyolefins, polyamides or the like can also be considered, it also being possible in principle to use blends and different materials for different threads. In a preferred single-variety or largely single-variety configuration, recycling is also easier.

Within the scope of the invention, the spacer fabric typically has a thickness of between 2 mm and 15 mm, in particular between 3 mm and 9 mm, although the invention is not restricted to the specified ranges.

With regard to the functionality, it becomes clear on the basis of simple geometric considerations that the viewing angle for the transparency of the spacer fabric essentially depends on the size and shape of the openings, the overall thickness and, as a rule, the most complete possible coverage. With full coverage and constant size of the openings, the angle of view for transparency decreases with increasing total thickness. Conversely, if the size of the openings remains the same, the aspects aimed at within the scope of the invention become smaller with a decrease in the overall thickness. If a small overall thickness is provided, a finer design of the spacer fabric with a smaller size of the openings is then expedient.

Within the scope of the invention, free openings are formed at the overlap of the first openings and second openings lying directly one above the other. This means that no spacer threads or at least no spacer threads of the second thread system made of preferably textured multifilament yarn run within these openings.

A particularly simple and dense arrangement of the second spacer thread system is possible, for example, with an I-lay. In an I-lay, the individual spacer threads each run along an assigned wale. Outside the openings, i. H. However, in particular outside of the free openings, other layouts can also be provided.

For the usually provided uniform, recurring arrangement of the first openings and the second openings in the respective flat knitted layer, there are several wales, for example four or more wales, between two openings that are adjacent along the transverse direction. In such a configuration, the preferably textured multifilament yarns of the second spacer thread system can be present on all wales or only on some of the wales, for which purpose a corresponding guide bar is then not completely occupied at all positions with the preferably textured multifilament yarn. Corresponding considerations also apply in principle to the monofilament yarn of the first spacer yarn system.

Within the scope of the invention it can be provided that the ratio of the threads of the first spacer thread system made of monofilament yarn to the preferably textured threads of the second spacer thread system is 1:2 to 2:1.

In order to form openings in the two knitted fabric layers, in particular by filleting, the two knitted fabric layers are each formed with at least two guide bars, preferably exactly two guide bars.

The spacer threads can preferably be formed with three guide bars, in which case, for example, two guide bars are assigned to the first spacer thread system made of monofilament yarn and one guide bar is assigned to the second spacer thread system made of preferably textured multifilament yarn.

The multifilament yarn of the second spacer thread system can in particular have between 11 and 49 filaments, for example 36 filaments. The fineness of the multifilament yarn of the second thread system can be, for example, in a range from 50 dtex to 120 dtex and can be 76 dtex, for example.

As already mentioned above, the two knitted fabric layers can each also have textured and/or smooth multifilament yarns or, preferably, be formed entirely from them. For example, multifilament yarns with 23 to 97, in particular 48, filaments are suitable for this. The fineness is typically in a range from 100 dtex to 250 dtex, for example 167 dtex.

If, in order to achieve good opacity, it is provided in addition or as an alternative to texturing that the multifilament yarn of the second spacer thread system consists of filaments in the form of microfilaments, the microfilaments each having a fineness of less than 1.5 dtex, preferably less than 1 dtex , different values then result for the previously specified preferred parameter ranges for the number of filaments and the fineness of the multifilament yarn.

The subject matter of the invention is also a see-through element which is formed from the spacer fabric described above.

The see-through element can be provided, for example, in residential and business premises as a blackout and anti-glare element. It should be noted that with many windows in buildings, the blinding effect of direct sunlight should be avoided, for which purpose curtains or roller blinds can be used in the simplest case. However, it can be disadvantageous in this case that indirect light from the environment that can also be used for room lighting and is often perceived as pleasant is blocked or at least it is no longer possible to see through it.

Within the scope of the invention, for example, sunlight that is generally incident directly at an angle from the side and/or at an angle from above can be held back, as a result of which a direct glare effect can be avoided. Nevertheless, the see-through element remains transparent for a user in a particularly advantageous manner when viewed approximately perpendicularly, so that the environment can be perceived. The impression of complete isolation from the environment is thus avoided.

At least for an oblique viewing direction, a certain visual protection can also be achieved at building openings. In offices and business premises, lateral incidence of light is often advantageous from an ergonomic point of view, in which case monitors, screens or other possibly confidential equipment are often aligned at an angle of 90° to a window or a window front. In the case of a vertical view through a window or a window front, corresponding devices are then generally not recognizable.

Nevertheless, corresponding facilities can be seen in an unprotected state in an oblique view. Corresponding undesired viewers who are arranged diagonally offset are then also not readily visible from a building. In a suitable configuration, a certain protective function can also be provided by the see-through element according to the invention, without complete or extensive darkening being necessary.

In principle, the see-through element can also be used for other applications in which direction-dependent transparency is or can be advantageous for practical and/or aesthetic reasons.

The invention is explained below using exemplary figures.

Show it

1 a photograph of a spacer fabric according to the invention in a plan view,

Fig. 2 shows a highly schematized, fragmented partial view of the spacer fabric in an oblique view,

3A a laying pattern for an embodiment of the spacer fabric,

3B shows the assignment of laying rails for the formation of the spacer fabric according to FIG. 3A,

4A, 4B representations according to FIGS. 3A and 3B for an alternative embodiment.

1 shows a spacer fabric according to the invention in a plan view of a first flat knitted layer 1. A second flat knitted layer 2 underneath is of the same design and aligned so that the first knitted layer 1 completely covers the second knitted layer 2 arranged underneath.

The first knitted fabric layer 1 has first openings 3 delimited by a plurality of stitches in a uniform arrangement. Due to the identical configuration, the second knitted fabric layer 2 also has corresponding second openings 4 each delimited by a plurality of stitches. In the top view shown, the first openings 3 and the second openings 4 overlap completely and form free openings 5 in the entire spacer fabric.

The two knitted fabric layers 1, 2 are connected by spacer threads 6a, 6b, which, however, are not visible in the plan view according to FIG. 1 and are explained in more detail below.

At least it can be seen in FIG. 1 that the openings 5 formed by the first openings 3, the second openings 4 and the free space between them are also free of spacer threads 6a, 6b.

FIG. 2 shows a highly schematized side view of the knitted spacer fabric 1 .

It can be seen that a first part of the spacer threads 6a are monofilament yarns and are formed by a first spacer thread system. A second spacer thread system is formed from the remaining spacer threads 6b in the form of textured multifilament yarn. False-twist texturing, for example, is suitable.

The texturing and the configuration of multifilament yarn are only indicated in the highly schematic drawing of FIG. The spacer threads 6b made of textured multifilament yarn can have, for example, between 11 and 49 filaments and a fineness in the range from 50 dtex to 120 dtex. In one exemplary embodiment, a multifilament yarn with 36 filaments and a fineness of 76 dtex made of polyethylene terephthalate (PET) that is textured by false-twist texturing is provided as an example, which yarn is formed black. Alternatively, the use of multifilament yarn made from microfilaments can also be considered.

As only indicated in Fig. 2, the texturing and the design as a multifilament yarn fills the free space between the first knitted fabric layer 1 and the second knitted fabric layer 2 on a corresponding wale practically opaque, in contrast to the schematic drawing, so that an oblique view through the Spacer fabric is avoided or at least largely avoided.

The spacer threads 6a of the first spacer thread system formed from the monofilament yarn, on the other hand, ensure good elasticity of the spacer fabric when compressed in the direction of thickness due to their stability and shape. The monofilament yarn can have a fineness of between 50 dtex and 200 dtex, for example. According to a specific

Exemplary embodiment, spin-black monofilament yarn made of PET with a fineness of 108 dtex is provided.

Both knitted fabric layers 1, 2 are preferably produced by a filet weave, in particular a cloth filet weave. In order to produce a structure that is as dense and uniform as possible outside of the first openings 3 and the second openings 4 in the respective knitted fabric layers 1, 2, the knitted fabric layers 1, 2 can also be formed from multifilament yarns, these multifilament yarns having, for example, between 23 and 97 filaments and one Fineness between 100 dtex and 250 dtex can have. In a specific exemplary embodiment, spinning black multifilament yarn made of PET with 48 filaments and a fineness of 167 dtex is provided for the two knitted fabric layers 1, 2, it also being possible for this multifilament yarn to be subjected to false-twist texturing.

The thickness of the entire knitted spacer fabric is typically between 2 mm and 15 mm, in a concrete exemplary embodiment approximately 3.5 mm.

A comparison of FIGS. 1 and 2 makes it clear that the spacer fabric can be looked through in a vertical top view, with the spacer threads 6b formed from the textured multifilament yarn making the material opaque or essentially opaque when viewed at an angle.

A distance from adjacent wales averaged over the entire width including the openings 3, 4 can be, for example, in a range between 7 mm and 0.7 mm, in particular around 1.5 mm. An average distance between consecutive rows of stitches along the

Effective direction W can be, for example, in a range from 0.5 mm to 2 mm, in particular around 1 mm. The length of the openings determined along the effective direction W and the width of the openings determined perpendicular thereto along the transverse direction is typically between 1 mm and 5 mm, for example approximately 2.5 mm.

The first openings 3 and second openings 4 can extend in the respective knitted fabric layers 1, 2 for example over 25% to 60%, for example over approximately 40% of the total area.

From the explanations for the specific exemplary embodiment, it follows that the entire spacer fabric is completely black.

FIG. 3A shows a knitting pattern that is suitable as an example within the scope of the invention, in which case the threads that overlap and cross one another cannot easily be followed individually. However, at least basic properties of a possible embodiment can be seen.

First of all, it should be noted that in the illustrated knitting pattern, stitches of the first knitted fabric layer 1 and stitches of the second knitted fabric layer 2 are shown alternately along the knitting direction W, with such a representation being usual for spacer fabrics. The individual knitted fabric layers can be viewed mentally by not considering every second row of stitches (which is assigned to the other knitted fabric layer).

Under this proviso, the result is that the individual openings 3, 4 in the exemplary embodiment are each delimited by four meshes that follow one another along the direction W of action. The along the same position

entlang der Wirkrichtung zueinander benachbarten Öffnungen 3, 4 sind jeweils durch vier Maschenstäbchen voneinander getrennt.

Openings 3, 4 that are adjacent to one another along the effective direction are each separated from one another by four wales.

FIG. 3B shows a possible assignment of a total of seven guide bars GB1 to GB7 to form the knitting pattern according to FIG. 3A. The two flat knitted fabric layers 1, 2 are each formed by a cloth fillet weave of the laying rails GB1 and GB2 or GB6 and GB7. For this purpose, spinning-black multifilament yarns with a false-twist texturing and a fineness of 167 dtex and 48 filaments made of PET with a draw-in of 2 full, 2 empty are used.

A total of three guide bars GB3 to GB5 are provided for the spacer threads 6a, 6b. The spacer threads 6a of a first spacer thread system made of spinning-black PET monofilament yarn are processed with two guide bars GB4, GB5, which are also of opposite layers. A second spacer thread system made of textured, spinning-black PET multifilament yarn with a fineness of 76 dtex and 36 filaments is tied in with a further guide bar GB3 in an offset I-lay at the openings 3, 4. According to the exemplary embodiment in FIG. 3B, the corresponding guide bar GB3 is fully occupied.

FIGS. 4A and 4B show representations corresponding to FIGS. 3A and 3B, but with the guide bar GB3 for the second spacer thread system made of textured multifilament yarn 6b there is no full feed, but a feed 2 full, 2 empty. A closer look at FIG. 4A then shows that the textured multifilament threads are then only provided on the wales that directly delimit the openings 3, 4. Even such a partial collection can vary depending on the

Be sufficient embodiment and requirements to achieve a desired level of opacity of the spacer fabric.

Claims

22 patent claims: 1 . Spacer fabric with a first flat knitted layer (1), a second flat knitted layer (2) and with the spacer threads (6a, 6b) connecting the knitted layers (1, 2), wherein the first knitted layer (1) has first openings (3 ), wherein the second knitted fabric layer (2) has second openings (4) delimited by a plurality of meshes and wherein the first openings (3) and the second openings (4) overlap at least partially in a top view and free openings (5) of the Form a spacer fabric, because the spacer threads (6a, 6b) are formed by at least a first spacer thread system made of monofilament yarn and a second spacer thread system made of multifilament yarn. 2. Spacer fabric according to claim 1, characterized in that the second spacer thread system is formed from textured multifilament yarn. 3. Spacer fabric according to claim 1 or 2, characterized in that the multifilament yarn of the second spacer thread system has filaments in the form of microfilaments and preferably consists of filaments in the form of microfilaments, the microfilaments each having a fineness of less than 1.5 dtex, preferably of less than 1 dtex. 4. Spacer fabric according to one of claims 1 to 3, characterized in that the first and the second knitted layer (1, 2) are each formed by a filet weave, in particular selected from the group of cloth filet weave, jersey filet weave, satin filet weave and velvet filet weave. 5. Spacer fabric according to one of claims 1 to 4, characterized in that a length of the openings (3, 4) determined along a knitting direction (W) is greater than an average spacing of consecutive rows of stitches along the knitting direction (W) and that a width of the openings (3, 4) determined perpendicularly to the knitting direction (W) in a transverse direction is greater than an average spacing of adjacent wales. 6. Spacer fabric according to one of Claims 1 to 5, characterized in that the two fabric layers (1, 2) are of the same design with regard to a laying pattern and/or the threads forming the fabric layers (1, 2). 7. Spacer fabric according to one of claims 1 to 6, characterized in that the first and the second openings (3, 4) in the respective fabric layers (1, 2) extend over 25% to 60% of a total area. 8. Spacer fabric according to one of claims 1 to 7, characterized in that the first openings (3) and the second openings (4) have an overlap of at least 80% in plan view. 9. Spacer fabric according to one of claims 1 to 8, characterized in that the thread systems of the two knitted fabric layers (1, 2) have black threads and that the multifilament yarns of the second spacer thread system are black. 10. Spacer fabric according to claim 9, characterized in that the two knitted fabric layers (1, 2) and the spacer threads (6a, 6b) are completely black. 11. Spacer fabric according to one of claims 1 to 10, characterized in that the total thickness is between 2 mm and 15 mm. 12. Spacer fabric according to one of claims 1 to 11, characterized in that the second spacer thread system has an I-lay. 13. Spacer fabric according to one of claims 1 to 12, characterized in that the ratio of the monofilament yarns of the first spacer thread system to the multifilament yarns of the second spacer thread system is 1:2 to 2:1. 14. Spacer fabric according to one of claims 1 to 13, characterized in that the two knitted fabric layers (1, 2) are each formed with two guide bars (GB1, GB2; GB6, GB7). 15. Spacer fabric according to one of claims 1 to 14, characterized in that the spacer threads (6a, 6b) are formed with three guide bars (GB3, GB4, GB5). 16. Spacer fabric according to one of claims 1 to 15, characterized in that the multifilament threads of the second spacer thread system each have between 11 and 49 filaments. 17. Spacer fabric according to one of claims 1 to 16, characterized in that the two knitted fabric layers (1, 2) each from Multifilament yarns are formed. 18. Spacer fabric according to one of claims 1 to 17, characterized in that the multifilament threads of the second Spacer thread systems each have a fineness in a range from 50 dtex to 120 dtex. 19. See-through element formed from a spacer fabric according to one of claims 1 to 18.