KR20170031043A - Scratch resistant anti-reflective coating - Google Patents

Abstract

The present invention relates to a transparent member having an anti-reflective coating (5). The anti-reflective coating (5) includes four layers (51, 52, 53, 54), and a color location of reflected light shows reduced dependence with respect to a variation in the layer thickness.

Description

[0001] SCRATCH RESISTANT ANTI-REFLECTIVE COATING [0002]

The present invention relates generally to optical interference coatings. More specifically, the present invention relates to an anti-reflective coating having high scratch resistance.

Chemical tempered glasses for display of portable electronic devices such as smart phones or tablet PCs are known. Aluminosilicate glass is typically used as the cover glass of such a display. Such aluminosilicate glasses typically have a refractive index above 1.5 at a wavelength of 550 nm.

It is also known and commonly practiced to chemically strengthen the cover glass for image display. Because of the chemical strengthening during which Na ions in the glass are exchanged for potassium ions from the bath, potassium ions are concentrated in the area of several micrometers thick near the surface. The potassium content therein is in the range of several mass% or less. An increase in bending strength and scratch resistance is achieved by chemical strengthening. However, a scratch type surface damage is confirmed even after a short use of a general product. Scratching is not prevented even if the pre-stress compressive prevents the glass from being easily broken when the glass is exposed to the bending stress because the pre-stress prevents or slows down the cracks caused by the scratches, for example, from diffusing.

An anti-fingerprint coating (AFP) can be applied to the glass to prevent fingerprints or at least to be very easy to clean. Because today's products generally have AFP, rather than permanent immunity, the ease of cleaning and tonic effects of fingerprinting lasts only a few months. AFP is generally a partially organic layer that is applied very thinly to be optically inactive. Therefore, the reflectance of the product is mainly determined by the glass surface. Therefore, at normal incidence, about 4% of the light is reflected off the glass surface, which is especially problematic in bright conditions such as sunlight and limits the readability of display content.

The antireflective coating is known to prevent reflection on the glass surface. According to an embodiment, the antireflective coating consists of several layers, which are applied to one or both sides of the glass substrate. Depending on the intended use of the product, the design of a mechanically stable, i.e., abrasion-resistant or scratch-resistant, antireflection system is desirable. The overall purpose of optical anti-reflective coatings is primarily to evenly suppress the reflection of the visible portion of the electromagnetic spectrum, if possible, so that no color perception due to uneven residual reflection occurs. An example of such a scratch resistant antireflective coating in a color neutral is disclosed in US 2012/0212826 A1.

During the manufacturing process of the cellular phone cover, the aforementioned glass may be provided with a decorative print, generally black or white, on the side facing away from the user, that is, the back side of the cover. Often, the manufacturer's name or product name is printed with silver lettering.

An antireflective system typically consists of more than one layer, especially if it is intended to prevent reflection equally, not only at a particular wavelength, but also for most of the visible spectrum. The two continuous layers have different refractive indices. A layer having a high refractive index and a layer having a low refractive index are alternately present. The wavelength dependent reflectance profile is the result of the interaction of the individual reflectances at the interface. The uniform color neutral reflection is the product of the perfect matching sequence of the optical layer thickness, i.e., the product of the refractive index and the layer thickness. If one or more layer thicknesses are changed, the reflection conditions and hence the reflection will change, in particular, the color coordinate or color location of the reflection.

Thus, for example, process-related variations in layer thickness or deviations between production lots, such as may occur at different locations of the sample carrier, can result in large changes in color location. The intensity of the layer thickness deviation will cause a significant deviation, especially in the color position, and the production yield will be reduced.

Therefore, the present invention provides an antireflection coating which exhibits excellent adhesion to a glass substrate, high scratch resistance, provides a good basis for anti-fingerprint coatings, and in particular, exhibits only a slight change in color position even with typical process- System. ≪ / RTI > The present invention relates specifically to a transparent member comprising an antireflective coating having four layers. Such an antireflection coating is designed in such a way that the color position of the reflected light is less dependent on the layer thickness deviation, in view of the above objects.

The antireflection interference layer system according to the present invention includes a continuum in which a high refractive index layer and a low refractive index layer alternate. Thus, the refractive index alternately changes from layer to layer. The layer system comprises at least four layers. High scratch resistance is achieved by using a rigid material that is transparent to at least one high refractive index layer.

It has been found that for a four layer antireflective coating, a reduction in layer thickness dependent variation of color location can be obtained by using more than two materials. The first high refractive index layer is applied over the substrate, it should have a refractive index of the other high-refractive-index layer and _high refractive index n between the n _low in the low refractive index layer, the refractive index n _medium.

Accordingly, the present invention provides a sheet-

A transparent substrate in the visible spectrum region; And

- an antireflective coating deposited on the substrate

, Wherein the anti-reflective coating

- the refractive index is alternately increased or decreased from the layer to the layer so that the refractive indices of the respective adjacent layers are alternately arranged so that the layer having the low refractive index and the layer having the high refractive index alternate,

And a sheet-like member.

The lowest layer among the four layers is a high refractive index layer, and thus has a higher refractive index than the adjacent second lowest layer.

The four layers have three or more different refractive indices such that the refractive index of the lowest layer adjacent to the substrate and having the highest refractive index is smaller than that of the other high refractive index layers.

The lowermost layer having a high refractive index is preferably made of an oxygen-containing material. Because of these features, the sheet-like member exhibits small deviations in color coordinates, especially with a layer thickness deviation.

The lowest layer of the antireflective coating adjacent to the substrate is preferably an oxynitride layer or an oxide layer. Silicon or aluminum or an oxynitride layer comprising a mixture of the two materials is particularly suitable because these materials are both highly transparent and hard, and the refractive index can be well tuned and adapted through the oxygen content during the coating process. In general, it is also possible to use a plurality of components in the layer composition. For example, according to one embodiment of the present invention, it is contemplated that the bottom layer comprises three or more different components in oxynitride or oxide form, the amount being greater than 1 atomic% of the total composition.

The use of an oxynitride is advantageous in that a nitride or oxynitride of silicon oxynitride or aluminum nitride, aluminum oxynitride, or a mixture of aluminum and silicon can also be used in another high refractive index hard material layer, . Since the refractive index of the latter must be higher, its oxygen content is accordingly less. Therefore, according to one embodiment of the present invention, it is contemplated that the two high refractive index layers are a silicon oxynitride layer or an aluminum oxynitride layer or a mixture of silicon oxynitride and aluminum oxynitride, The oxygen content is higher than the refractive index layer.

If it is desired to produce a pure oxide layer system using the sputtering method, only oxygen can be used as the reactive gas. Mixtures of reactive gases are excluded. However, it is possible to manufacture an antireflection layer system according to the present invention by using an alloy target composed of two or more materials such that the oxide of one material has a high refractive index and the oxide of another material has a low refractive index. By carefully selecting the composition of the alloy target, mixed oxides can be produced by sputtering under an oxygen-containing processing atmosphere, which satisfies the above requirement in that the refractive index is lower than that of the other high refractive index layers. Here, a silicon target mixed with zirconium, or an aluminum target mixed with zirconium can be mentioned as an example, but other options are not excluded.

As already mentioned above, it is also possible to use more than two components in the formation of the lowermost layer. In particular, three or more different components may be included in the oxynitride or oxide form, the amount of which amounts to more than 1 atomic percent of the total composition. For example, in addition to Si and Al, one additional component may be included at a ratio of at least 1 atomic% and may be introduced in the form of an oxide or an oxynitride.

It is most preferred to apply the four layer continuum of antireflective coating directly to the substrate. Thus, the substrate surface immediately adjoins a continuum of four layers of anti-reflective coating.

According to a particularly preferred embodiment of the present invention, a fluorine-containing organic layer may be applied to the antireflection coating. Such a layer may be formed as a single layer of a fluorine-containing organic molecule, preferably a layer thickness of 1 nm to 20 nm, more preferably a layer thickness of 1 nm to 10 nm. The fluorine-containing organic layer may be, for example, an oleophobic coating.

A layer system with an additional fluorine-containing organic layer added onto an antireflective coating comprising a thicker top rigid material layer, especially with a maximum thickness of the antireflective coating, reduces fingerprint marks and provides easy cleaning, It has been found that the coated chemically tempered glass substrate and thus the inventive element are particularly helpful in preventing scratches.

This is believed to be due to the fact that the additional fluorine-containing organic layer reduces the friction coefficient of the surface, presumably reducing the damage to the surface.

In order to deposit the antireflective coating according to the invention, preferably sputtering, in particular reactive sputtering, is used.

Hereinafter, the present invention will be described using exemplary embodiments with reference to the drawings. In the drawings, the same reference numerals designate the same or similar layers. In this figure,
Figure 1 shows a substrate having a four-layer antireflective coating;
Fig. 2 shows a modification of the embodiment of Fig. 1;
Figure 3 shows an improved version of the invention with a light absorbing back coating;
Figure 4 shows the deviation of color positions for different members, depending on the structure of the antireflective coating and the presence of the light absorbing back coating;
And Figure 5 shows a variation of the color location of the anti-reflective coating system comprising a SiO ₂ / TiO ₂ layer;
6 shows the application of the present invention to an electronic device.

Fig. 1 shows an example of a sheet-like member according to the present invention. Although not limiting to the specific example illustrated, the member 1 generally comprises a transparent substrate 3 in the visible spectrum region and an antireflective coating 5 deposited on one side 30 of the substrate 1 do.

The antireflective coating 5 comprises four continuous layers 51, 52, 53, 54. The individual adjacent layers have different refractive indices. More specifically, the refractive index changes from layer to layer so that the refractive index is alternately increased or decreased. The refractive index increases from the topmost layer 54 to the second topmost layer 53 and decreases in the next layer 52 and increases again in the bottom layer 51 as it passes from top to bottom toward the substrate 3 , But is kept lower than the refractive index level of the layer (53).

The lowest layer (i.e., layer 51) of the four layers 51, 52, 53, and 54 is a high refractive index layer and therefore has a higher refractive index than the adjacent second lowest layer 52.

Although not limiting to the particular exemplary embodiment of FIG. 1, in each case in each case an antireflective coating according to the invention, a continuum of such four layers 51, 52, 53, 54 is provided . Preferably, the coating 5 comprises only these four layers as the optically active layer. However, it is not excluded that additional layers are present below and / or above, i.e. on the substrate side of this continuum.

The four layers 51, 52, 53 and 54 have three or more different refractive indices such that the lowest refractive index layer 51 adjacent to the substrate 3 is smaller than the refractive index of the other high refractive index layer 53. The lowermost high refractive index layer 51 is preferably formed of an oxygen-containing material.

The terms " lower refractive index "and" higher refractive index "are used in reference to adjacent layers. Thus, a low refractive index layer is disposed adjacent to one high refractive index layer (if the low refractive index layer is the end of the layer system) or adjacent two high refractive index layers, which are adjacent to other layers of the layer system If you have two interfaces.

The substrate 3 is most preferably an inorganic oxide substrate, particularly a glass substrate. The antireflective coating system of the present invention is particularly suitable for chemically tempered glass substrates.

The first high adhesive strength of the hard material on the substrate, the first hard material is an oxide hard material layer (e.g., ZrO _2, or a Zr-Si mixed oxide, that is a mixture of ZrO ₂ and SiO ₂ or ZrO ₂ and Al ₂ O ₃ ), or it can be obtained when the first hard material layer is an oxygen-containing nitride in the form of an oxynitride. Suitable oxynitrides include, for example, silicon oxynitride (SiO _x N _y ) or aluminum oxynitride (AlO _x N _y ) or silicon aluminum oxynitride (SiAlO _x N _y ).

Such materials, such as ZrO ₂ , or a mixture of ZrO ₂ and SiO ₂ or Al ₂ O ₃ , and an oxynitride of silicon or aluminum, or a mixture of aluminum and silicon, are particularly preferred for the lowest refractive index layer. ZrO ₂ is, for example, be combined with a TiO ₂ layer as a high refractive index layer of the additional or top. Another option is to use a titanium-containing oxide, that is, a mixed oxide containing titanium and an additional element, in the lower high refractive index layer. One possible example is a titanium / silicon mixed oxide. According to a preferred modification of the antireflection system according to the present invention, zirconium as the lower high refractive index layer 51 and a mixed oxide of silicon or zirconium and aluminum or zirconium and silicon and aluminum as the upper high refractive index layer 51 and ZrO ₂ Layer is contemplated.

Thus, according to a preferred embodiment of the present invention, the bottom layer 51 of the antireflective coating 5 following the substrate 3 is an oxynitride or oxide layer. This layer is particularly formed of an oxide or oxynitride of at least one of elemental silicon, aluminum, or a mixture thereof. The oxide layer as the lowermost high refractive index layer 51 may be formed of an oxide of titanium and / or zirconium together with aluminum and / or silicon. Thus, in general, particularly good adhesion to chemically tempered glass substrates is also obtained.

In any case, the two layers 51 and 53 are different from each other in that the refractive indices of the two layers are different, as described above, although they are high refractive index layers.

However, it is also practically possible that the two layers 51 and 53 contain the same constituents, but with different compositions. If the constituents are at least partially identical, in principle the process can be promoted since it is only necessary to deposit the two layers using the same manufacturing process and to adapt the process parameters.

The preferred embodiment of the present invention is characterized in that both high refractive index layers 51 and 53 are layers containing silicon, nitrogen and oxygen and the lowest refractive index layer 51 is higher than the other high refractive index layer 53 It has a high oxygen content.

In the case of an oxynitride layer, it has been found that sufficient adhesion of the layer is already achieved with a low oxygen content of about 5 to 10 atomic% with respect to nitrogen. In other words, according to this embodiment of the present invention, the oxygen content of the lowermost layer 51 with respect to nitrogen is 5 atomic% or more and less than 10 atomic%. According to another embodiment, the content of oxygen in the oxynitride, preferably silicon oxynitride, relative to nitrogen (content provided as atomic%) is in the range of 0.41 to 1.02.

Generally, though not limited to the exemplary embodiment, all silicon-containing layers may comprise aluminum in addition to silicon. In the upper three layers, i.e. layers 52, 53 and 54, the proportion of aluminum in each case in atomic% is preferably less than the proportion of silicon. The ratio of the amount of aluminum to the amount of silicon is preferably more than 0.05, more preferably more than 0.08, but the amount of silicon is more than that of aluminum. Preferably, the ratio of the amount of aluminum to the amount of silicon is about 0.075 to 0.5, more preferably about 0.1.

The amount ratio given above can also be applied to the lowermost high refractive index layer 51, however, any other ratio of the amounts of Al and Si is also suitable.

The scratch resistance of the antireflective coating can be further improved by applying an additional fluorine containing organic layer 6 on the antireflective coating 5 according to the invention. Such a fluorine-containing organic layer is also effective for reducing the fingerprints and for facilitating easy cleaning.

It is believed that the improved scratch resistance is due to a decrease in the surface friction due to the additional fluorine-containing organic layer, resulting in reduced surface damage.

Fig. 2 shows a modification of the embodiment of Fig. Embodiments of the present invention in which both the upper and lower high refractive index layers of the four-layer antireflection coating 5 have a thicker layer thickness than the layers 51 and 52, Fig.

However, in the exemplary embodiment of FIG. 2, the thickness of the second highest layer 53 is significantly greater than the example shown in FIG. Generally, a layer design with one of the high refractive index layers being very thick but still having excellent antireflective properties can be found. The large thickness of one of the hard, high refractive index layers, preferably the second top layer 53, results in a high scratch resistance of the layer system. However, it has been found beneficial that the thickness of the second top layer 53 is not greater than one-half of the total thickness of all four layers 51, 52, 53, 54. Also according to another embodiment embodied in the example of FIG. 2, the layer 52, which is a low refractive index layer inserted between two high refractive index layers 51 and 53, has a minimum thickness of the four layers. Indeed, it has been found desirable to select this layer as thin as possible to achieve minimum color position deviation even in the presence of layer thickness variations.

The low refractive index layers 52 and 54 may generally comprise a SiO ₂ layer, although the invention is not limited to any particular embodiment. In other words, for the four-layer antireflective coating 5, the top layer 54 and the second bottom layer 52 are in this case SiO ₂ . Due to the relatively low refractive index, silicon oxides are particularly suitable for achieving a high index of refraction at the interface of the antireflective coating. This silicon oxide layer may preferably contain a small proportion of Al ₂ O ₃ , wherein the ratio of aluminum to silicon, expressed in atomic percent, is in the range of 0.05 to 0.3, preferably in the range of about 0.1. Such a small amount of Al ₂ O ₃ in SiO ₂ only slightly increases the refractive index.

In the exemplary embodiment of FIG. 2, another embodiment of the present invention is implemented. According to this embodiment, the layer thickness of the lowest layer 51 is thicker than the layer thickness of the second lowest layer 52. With refractive index design, this general relationship of layer thickness also improves the stability of the antireflective effect even when there is a layer thickness variation associated with manufacture. This embodiment is independent of the particular layer thickness illustrated in Fig.

Figure 3 shows an improvement of the invention. According to this embodiment, a light absorbing coating 7, preferably a black coating, is applied to the side 31 of the substrate 3 opposite the side 30 on which the antireflective coating 5 is provided. This decorative coating preferably functions as an opaque decoration and generally defines a frame of the display area 32 in which a display such as an LCD or OLED display can be seen by the observer. The opaque decoration hides the connection elements arranged in the peripheral areas of the display or components such as the peripheral attachment of the substrate 3. [

An embodiment serving as a starting point for illustrating the present invention is a cover glass provided with an antireflective coating having a layer continuum of glass / Si ₃ N ₄ / SiO ₂ / Si ₃ N ₄ / SiO ₂ known in the prior art to be. The silicon nitride layer is first deposited as layer 51 on the glass sheet as substrate 3 and then the SiO ₂ layer is deposited as layer 52 and then the other silicon nitride layer 53 is deposited , above the SiO ₂ layer is deposited as the top floor (54) of the anti-reflection coating. As illustrated in FIG. 1, a fluorine-containing organic layer may be further applied to the top layer 54 of the antireflective coating 5.

4 shows the color positional deviation on the different member 1 depending on the structure of the antireflective coating 5 and on the presence of the light absorption or light blocking coating 7 on the face 31 of the substrate 3 do. Measurement values are indicated by putting reference numerals in parentheses.

For example, when an aluminosilicate glass is used in the substrate 3, an optimal case of uniform reflection is provided, and the layer thicknesses starting from the glass are as follows:

 In this case, the color positions according to CIE-Lab are measured at coordinates a and b of 1.0 and 3.7 respectively on a pure non-decorative glass, meaning that there is no light absorbing coating 7 (measured value 40).

When the layer thickness is changed by +1 nm (16 nm (layer 51), 33 nm (layer 52), 133 nm (layer 53), 88 nm (layer 54)), color position values of 1.5 and 2.8 are identified Measured value 41). When the layer thickness decreased by 1 nm (14 nm, 31 nm, 131 nm, 86 nm), a and b were found to be 0.1 and 4.7, respectively. The above-mentioned three measured values (40, 41, 42) are indicated by triangular symbols in Fig.

In a region having a black decorative coating or having a light absorbing coating 7 on the back side of the cover glass as shown in Fig. 3, the color position value shows a considerably large deviation even in the case of the same coating. The corresponding measured values (43, 44, 45) are indicated by diamond symbols. Also stronger color position deviations occur in the off state, in this case dark state, and in the dark region of the display in the on state display, for example in the case of a dark background.

In this case, the color of the best case is: a = -0.2, b = 2.1 (measured value 43);

For +1 nm layer thickness: a = 1.7 and b = -0.7 (measured value 44);

For the -1 nm layer thickness: a = -2.6 and b = 4.6 (measured value 45).

This greater deviation and dependence on layer thickness can be attributed to a lack of back reflection which is suppressed by the decorative coating. In the case of pure glass, about 4% is reflected back from the back side (uniform over the wavelength range of visible light), which contributes to total reflection at about 10 times the antireflective front (about 0.5%). The deviation of the color position caused by the layer thickness deviation is "surpassed" by the backside, becoming less noticeable. In the case of black backing, the back reflection is almost suppressed. Thus, the color position is almost entirely determined by the anti-reflection coating 5, and the color position deviation caused by the layer thickness deviation has a larger specific gravity.

For comparison, the measured values 60 to 62 (X symbols) and 63 to 65 (square symbols) are the calculated color positional deviations of the antireflective coating 5 according to the invention which exhibit the same layer thickness deviation.

In each case, the first layer of the antireflective coating 5 of the present invention is an oxygen containing silicon nitride layer in which the oxygen to nitrogen ratio, i.e., O / N, is adjusted to obtain a refractive index of about 1.71 at 550 nm. When the refractive index is higher toward the Si ₃ N ₄ side, the color position deviation increases. When there is excess oxygen in SiO _x N _y , the four-layer antireflective coating no longer exhibits good antireflective conditions. Generally, although the composition of the lowermost layer 51 is not limited, it is advantageous that the refractive index of the lowermost high refractive index layer 51 is 1.665 to 1.795. In this case, the refractive index is preferably smaller than 1.790, and most preferably smaller than 1.785.

Measurements 60-62 are for glass substrates without decorative coatings and thus can be compared to measurements 40, 41, In the layer system of the present invention having the same layer thickness deviation, the color positions are significantly closer to each other than for an antireflective coating comprising a similar high refractive index layer. For the antireflective coating 5 of the present invention comprising the high refractive index layers 51 and 53 differing in material and refractive index in the region with the light absorbing coating 7 the color positional deviation (measured values 63 to 65) Lt; / RTI > However, even in this case, the deviation of the color positions is significantly less than that for the antireflection coating having the high refractive index layers 51 and 53 having similar materials and refractive indexes.

Specific examples of antireflective systems of the present invention that exhibit less color position deviations than prior art AR systems with layer thickness variations are described in the following table:

Figure 5, shows a color location of the light reflected from the substrate having an anti-reflection coating based on TiO ₂ / SiO _2. The color position was also calculated for the sheet-like member 1 provided with the light absorbing coating 7 on its back side.

In addition, each of these antireflective coatings 5 comprises four layers. For the high refractive index layers 51 and 53, a titanium dioxide layer (TiO ₂ ) was used for the color position values 46, 47 and 48 shown in FIG. The color position values 66, 67 and 68 indicate that the four layers of the coating 51, 52, 53 and 54 correspond to the lowest refractive index layer 51 next to the substrate 3, Belongs to a coating 5 according to the invention, having at least three different refractive indices such that the refractive index is less than the refractive index, wherein the lowest refractive index 51 is formed of an oxygen-containing material.

For the present invention, an oxygen-containing silicon nitride having a refractive index of SiO _x N _y , i.e., about 1.77, was selected for the lowermost layer 51. On the other hand, pure silicon nitride has a refractive index of about n = 2. If the value is 1.77, it is between the refractive index of the layer 51 (i.e., the refractive index of the layer (52, 54)) the value of the SiO ₂ to the value of the TiO ₂ (i.e., the refractive index of the layer 53).

Possible examples of the structure of the AR system according to the invention, made of the abovementioned materials SiO _x N _y , SiO ₂ , and TiO ₂ , are given as examples in the table below.

This result is similar to the example of Fig. If only two refractive indices are used in the 4-layer AR system (color position values 46, 47 and 48), the deviation of the color position with respect to the layer thickness deviation of the layer +/- nm results in three refractive indices (color position values 66, 67, and 68 are used, and they are larger than when they are arranged in the order of n _medium , n _low , n _high , and n _low as viewed from the substrate as described above. In the example shown in Fig. 2, the relationship of the layer thickness corresponds to the value of the above table.

Excellent antireflection characteristics can be obtained even when the layer thickness described above is deviated by 10%. Therefore, according to one embodiment of the present invention, the layer thickness is 61 ± 6.1 nm for the lowest layer 51, 10 ± 1 nm for the second lowest layer 52, and 102 ± 1 nm for the uppermost high refractive index layer 53 ± 10.2 nm, and for the top layer 54 is 89 ± 8.9 nm.

It is clear from these embodiments that it is advantageous for the two high refractive index layers 51 and 53 to have a constant minimum difference in refractive index. In general, although not limited to the embodiments described with reference to the drawings, according to an improved embodiment of the present invention, the refractive index of the lowest layer 51 of the four layers 51, 52, 53, 54 of the anti- Is smaller than 1.79 and the adjacent layer 52 is to be adjusted to have a thickness of 1 to 20 nm, preferably 5 to 15 nm. It has been found that the small layer thickness of the layer 52 is particularly effective in reducing the sensitivity of the AR system to color position variations when varying the layer thickness. Therefore, according to one embodiment of the present invention, the thickness of the low refractive index layer 52 disposed between the two high refractive index layers 51 and 53 and constituting the second lowest layer is less than 20 nm, preferably less than 18 nm , More preferably less than 15 nm.

The lower limit of the refractive index difference is provided by the refractive index of the low refractive index layer. Depending on the material used in the structure of the antireflection system, the refractive index of the lowest layer 51 is preferably 1.66 or more.

Therefore, the refractive index of the layer 51 is preferably in the range of 1.66 to 1.79.

Figure 6 shows an exemplary application of the present invention. According to an embodiment of the present invention, an electronic display 21, preferably a matrix display or a pixel-controlled display, is provided in the portable electronic device 20, Comprises a sheet-like member 1 according to the invention which covers the electronic display 21 with the side 30 of the sheet-like member 1 on which the antireflective coating 5 is provided facing outwards. In this way, the antireflective coating 5 can be effective in reducing light reflection on the one hand and protecting it from scratches due to external mechanical impact on the other hand.

The illustrated embodiment is a portable device in the form of a tablet PC. The invention is also suitable for mobile phones, particularly so-called smart phones, portable navigation devices and portable media players such as music and video players in particular, as well as smartwatches.

Such a device is particularly susceptible to mechanical stresses when the device is equipped with a user interface including a touch sensitive screen so that the surface 30 with the antireflective coating 5 of the member 1 according to the invention is simultaneously exposed to the interface As shown in FIG. Particularly, in this embodiment of the present invention, an additional coating in the form of the fluorine-containing organic layer 6 mentioned above and shown in the embodiment of Fig. 1 is advantageous.

As described above with reference to Fig. 3, it is often desirable that the cover glass of the electronic display is not completely transparent, but rather hides a particular area. For this purpose, there is provided a light absorbing coating 7 which covers the periphery of the member 1 and which provides a frame of the electronic display 21. In particular, in such a periphery, illustrated in black in Fig. 6, in which a light blocking coating is provided, the deviations in color positions are particularly apparent, as evidenced by the embodiment of Figs. In fact, due to the antireflective coating 5, the light reflection itself is very weak. However, due to the light absorbing coating, the dark background will cause high contrast, and even weaker light reflection will be perceived. The design of the antireflective coating 5 according to the invention ensures that the residual visible light appears as a uniform color.

It will be apparent to those skilled in the art that the present invention is not limited to the exemplary embodiments illustrated in the drawings but may be varied within the scope of the subject matter of the claims. In particular, the features of the individual exemplary embodiments may be combined. For example, in the case of the portable electronic device 20, both the coating shown in Fig. 1 and the additional features of the embodiment of Fig. 2 can be used. The fluorinated organic coating 6 may be provided in each of the illustrated embodiments. This option is even more desirable.

Claims (17)

As the sheet-like member 1,
A transparent substrate 3 in the visible spectrum region; And
- an antireflective coating (5) deposited on the substrate (1)
, The anti-reflection coating (5) comprising:
Refractive index layers 52 and 54 and high refractive index layers 51 and 53 are alternately arranged so that the refractive indexes of the adjacent layers 51 and 52 are different from each other such that the refractive indexes of the adjacent layers 51 and 52 , 53, 54)
, ≪ / RTI >
The lowest layer 51 of the four layers 51, 52, 53 and 54 is a high refractive index layer having a higher refractive index than the adjacent second lowest layer 52;
The four layers 51, 52, 53 and 54 have three or more different refractive indices such that the refractive index of the lowermost high refractive index layer 51 adjacent to the substrate 3 is smaller than the refractive index of the other high refractive index layer 53 , The lowermost high refractive index layer 51 is made of an oxygen-containing material,
Thus, the sheet-like member 1 exhibits, in particular, a small deviation in color position even when there is a layer thickness deviation. The sheet-like member (1) according to claim 1, wherein the substrate (3) is a glass substrate, in particular a chemically tempered glass substrate. 4. The substrate according to claim 1 or 2, wherein the lowermost layer (51) adjacent to the substrate (3) of the antireflective coating (5) comprises an oxynitride layer, preferably silicon, or aluminum, Or an oxide layer, particularly a ZrO ₂ -containing layer. The sheet-like member (1) according to claim 3, wherein the two high refractive index layers (51, 53) are silicon oxynitride layers and the lowermost high refractive index layer (51) is higher in oxygen content than the other high refractive index layers (53) . 5. The sheet according to claim 3 or 4, wherein the lowermost layer (51) contains oxygen in the range of 5 to 10 atomic%, or the content of oxygen in nitrogen in the oxynitride is in the range of 0.41 to 1.02 (One). 6. A method according to any one of claims 1 to 5, wherein the upper high refractive index layer as the second highest layer of the four-layer antireflective coating (5) has a maximum thickness of the four layers (51, 52, 53, 54) (1). 7. The sheet-like member (1) according to any one of claims 1 to 6, wherein a fluorine-containing organic layer (6) is applied on the antireflection coating (5). 8. A device according to any one of the preceding claims, characterized in that a light absorbing coating (7), preferably a decorative material, is applied on the surface (31) of the substrate (3) A sheet-like member (1) to which a coating is applied. 9. The sheet-like member (1) according to any one of claims 1 to 8, wherein the low refractive index layers (52, 54) are SiO ₂ layers. The optical information recording medium according to any one of claims 1 to 9, wherein the low refractive index layer (52, 54) is a SiO ₂ layer, and the layer has an Al / Si content ratio in the range of 0.05 to 0.3, of the Al ₂ O ₃ was set at 0.1 by further comprising a sheet-like member (1). 11. The sheet-like member (1) according to any one of claims 1 to 10, wherein the lowermost high refractive index layer (51) has a refractive index of 1.665 to 1.795, preferably less than 1.790, more preferably less than 1.785. 12. A sheet according to any one of the preceding claims, wherein the second lowest layer (52) has a layer thickness of less than 20 nm, preferably less than 18 nm, more preferably less than 15 nm. ). 13. The sheet-like member (1) according to any one of claims 1 to 12, wherein the lowest layer (51) has a layer thickness that is thicker than the layer thickness of the second lowest layer (52). 14. The sheet-like member (1) according to any one of claims 1 to 13, wherein the antireflective coating (5) has a layer thickness as follows:
61 ± 6.1 nm for the lowest layer 51 among the four continuous layers,
10 < RTI ID = 0.0 > 1 < / RTI > nm for the second lowest layer 52 of the four consecutive layers,
The refractive index of the upper high refractive index layer 53 of the four consecutive layers was 102 ± 10.2 nm,
89 ± 8.9 nm for the top layer 54 of the four continuous layers. 15. A sheet-like member (1) according to any one of the preceding claims, wherein the substrate surface is immediately adjacent to the continuum of the four layers (51, 52, 53, 54) of the antireflective coating (5). A portable electronic device (20) having an electronic display (21), preferably a matrix display, wherein the electronic device (20) covers an electronic display (21) A portable electronic device (20) comprising a sheet-like member (1) as claimed in claim 1, wherein the surface (30) of the sheet-like member (1) provided with the anti-reflective coating (5) faces outward. The portable electronic device (20) according to claim 16, wherein the surface (30) of the member (1) provided with the anti-reflection coating (5) is the operating surface of the interface, including a user interface including a touch sensitive screen.

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