TWI676924B - Touch display device - Google Patents

Abstract

A touch display device includes an array substrate, a display medium layer, a filter layer, a first transparent oxide layer, a second transparent oxide layer, a transparent conductive layer, and a touch panel. The display medium layer is disposed on the array substrate. The filter layer is disposed on the display medium layer. The first light-transmitting oxide layer is disposed above the filter layer and has a first refractive index. The second transparent oxide layer is disposed on the first transparent oxide layer and has a second refractive index, and the first refractive index is greater than the second refractive index. The transparent conductive layer is disposed on the second transparent oxide layer, and the thickness of the transparent conductive layer is between 1000 Angstroms (Å) and 3000 Angstroms (Å). The touch panel is disposed on the light-transmitting conductive layer.

Description

Touch display device

This disclosure relates to a touch display device.

With the development of electronic product design, many highly functional electronic products are gradually being developed. For products that provide users with a display screen, their products tend to allow users to perform touch operations directly on the display screen, so that the operation process can be more intuitive, so the development of related products is also highly optimistic.

Specifically, such electronic products can be realized by combining a display panel and a touch panel. The touch panel can detect a user's touch position by detecting a change in an electrical signal, such as a change in resistance. Or the capacitance changes. However, as the size of electronic products changes or the need for touch accuracy increases, the degree to which these electrical signals are disturbed by other signals may also increase, making the user ’s touch experience affected. Therefore, in terms of touch, The issue of reducing interference has become one of the development directions in related fields.

An embodiment of the present disclosure provides a touch display device including an array substrate, a display medium layer, a filter layer, a first transparent oxide layer, The second transparent oxide layer, the transparent conductive layer, and the touch panel. The display medium layer is disposed on the array substrate. The filter layer is disposed on the display medium layer. The first light-transmitting oxide layer is disposed above the filter layer and has a first refractive index. The second transparent oxide layer is disposed on the first transparent oxide layer and has a second refractive index, and the first refractive index is greater than the second refractive index. The transparent conductive layer is disposed on the second transparent oxide layer, and the thickness of the transparent conductive layer is between 1000 Angstroms (Å) and 3000 Angstroms (Å). The touch panel is disposed on the light-transmitting conductive layer.

In some embodiments, the material of the transparent conductive layer includes indium tin oxide, and the thickness of the transparent conductive layer is between 1100 Angstroms (Å) and 1600 Angstroms (Å).

In some embodiments, the thickness of the first transparent oxide layer is between 80 Angstroms (Å) and 200 Angstroms (Å), and the thickness of the second transparent oxide layer is between 250 Angstroms (Å) and 400 Angstroms (Å). Å).

In some embodiments, the material of the transparent conductive layer includes indium tin oxide, and the thickness of the transparent conductive layer is between 2550 Angstroms (Å) and 2850 Angstroms (Å).

In some embodiments, the thickness of the first light-transmitting oxide layer is between 100 Å (Å) and 220 Å (Å), and the thickness of the second light-transmitting oxide layer is between 200 Å (Å) and 400 Å ( Å).

In some embodiments, the first refractive index is between 2.1 and 2.5, and the second refractive index is between 1.4 and 1.6.

In some embodiments, the material of the first light-transmitting oxide layer includes niobium pentoxide (Nb ₂ O ₅ ), and the material of the second light-transmitting oxide layer includes silicon dioxide (SiO ₂ ).

In some embodiments, a second light-transmissive oxidation layer is disposed on the first light-transmissive oxide layer and forms an interface, and a light-transmissive conductive layer is disposed on the second light-transmissive oxide layer. An interface is formed on the layer. The material of the transparent conductive layer includes indium tin oxide, and the transparent conductive layer has a third refractive index, wherein the third refractive index is between the first refractive index and the second refractive index.

In some embodiments, the touch display device further includes a first polarizing layer and a second polarizing layer. The first polarizing layer is connected to the array substrate. The second polarizing layer is disposed between the light-transmitting conductive layer and the touch panel.

An embodiment of the present disclosure provides a touch display device including an array substrate, a display medium layer, a filter layer, a first transparent oxide layer, a second transparent oxide layer, a transparent conductive layer, and a touch panel. The display medium layer is disposed on the array substrate. The filter layer is disposed on the display medium layer. The first light-transmitting oxide layer is disposed above the filter layer and has a first refractive index. The second transparent oxide layer is disposed on the first transparent oxide layer and has a second refractive index, and the first refractive index is greater than the second refractive index. The transparent conductive layer is disposed on the second transparent oxide layer and has a thickness T, and AB ≦ T ≦ A + C, where A is a thickness reference value, B is a first thickness change value, and C is a second thickness change When the thickness T of the transparent conductive layer falls between AB and A, the thickness T of the transparent conductive layer has a positive correlation with the light transmittance, and when the thickness of the transparent conductive layer falls between A and A + C In between, the thickness T of the light-transmitting conductive layer has a negative correlation with the light transmittance. The touch panel is disposed on the transparent conductive layer.

Through the above configuration, the touch display device provides image display and touch operation functions, and the transparent conductive layer disposed under the touch panel can shield electrical signals, thereby improving the signal-to-noise ratio. In the case where indium tin oxide is used to form a light-transmitting conductive layer having a thickness of more than 1000 Angstroms (Å), the sheet resistance of the light-transmitting conductive layer can be less than 60 (Ω / □) to further improve the signal-to-noise ratio effect. While making When indium tin oxide is used to form a light-transmitting conductive layer with a thickness of less than 3000 Angstroms (Å), a light-transmitting conductive layer having a light transmittance of more than 84% can be formed due to the thin film interference phenomenon, which is suitable for the display needs of touch display devices. . Therefore, a light-transmitting conductive layer having a thickness between 1000 Angstroms (Å) and 3000 Angstroms (Å) can further improve the signal-to-noise ratio under conditions suitable for display requirements.

100‧‧‧ touch display device

102‧‧‧first polarizing layer

110‧‧‧Array substrate

112‧‧‧Display media layer

114‧‧‧ Spacer

116‧‧‧ Filter

120‧‧‧Optical matching layer

122‧‧‧The first transparent oxide layer

124‧‧‧Second transparent oxide layer

126‧‧‧ Transparent conductive layer

128‧‧‧second polarizing layer

130‧‧‧ colloid layer

132‧‧‧Touch Panel

I1‧‧‧The first interval

I2‧‧‧Second Section

T, TA, TB‧‧‧thickness

FIG. 1 is a schematic side view of a touch display device according to some embodiments of the disclosure.

FIG. 2 is a graph showing the relationship between the thickness of the light-transmitting conductive layer in FIG. 1 and its light transmittance.

In the following, a plurality of embodiments of the present invention will be disclosed graphically. For the sake of clarity, many practical details will be described in the following description. It should be understood, however, that these practical details should not be used to limit the invention. That is, in some embodiments of the present invention, these practical details are unnecessary. In addition, in order to simplify the drawings, some conventional structures and components will be shown in the drawings in a simple and schematic manner. In this article, the terms first, second, third, etc. are used to identify different components, regions, layers, and not to limit the disclosure.

The touch display device disclosed in the present disclosure can provide display and touch functions through a display panel and a touch panel integrated together, wherein the touch display device It also includes a transparent conductive layer disposed between the display panel and the touch panel to shield the electrical signals from the display panel, thereby improving the signal-to-noise ratio (S / N) of the touch display device.

Please refer to FIG. 1. FIG. 1 is a schematic side view of a touch display device 100 according to some embodiments of the present disclosure. The touch display device 100 includes a first polarizing layer 102, an array substrate 110, a display medium layer 112, a spacer 114, a filter layer 116, an optical matching layer 120, a transparent conductive layer 126, a second polarizing layer 128, and a colloidal layer 130. And touch panel 132.

The first polarizing layer 102 is connected to the array substrate 110, and the touch display device 100 may further include a backlight module (not shown) configured so that the first polarizing layer 102 is located between the backlight module and the array substrate 110, and is used for Light is emitted toward the first polarizing layer 102. The array substrate 110 may include a thin film transistor and a pixel electrode (not shown), and the thin film transistor is electrically connected to the pixel electrode to apply a voltage to the pixel electrode through the thin film transistor, thereby coupling out an electric field.

The display medium layer 112 is disposed on the array substrate 110 and has a display medium such as liquid crystal molecules. The display medium of the display medium layer 112 can be controlled by the electric field coupled by the pixel electrodes of the array substrate 110, so as to control whether the light traveling upward from the first polarizing layer 102 passes through.

The filter layer 116 is disposed on the display medium layer 112, and the spacer 114 is disposed between the array substrate 110 and the filter layer 116. The spacer 114 may be configured so that there is a gap between the array substrate 110 and the filter layer 116, so as to provide sufficient space to fill the display medium between the array substrate 110 and the filter layer 116. The filter layer 116 may include color resistances of different colors, such as red color resistance, green color resistance, and blue color resistance, so that light from the display medium layer 112 passing through the filter layer 116 The lines may have corresponding colors, so that the touch display device 100 provides an image. In addition, the touch display device 100 may further include a light-shielding layer (not shown), such as a black matrix, and is disposed on the display medium layer 112 together with the filter layer 116 so as to separate the color resistance of the filter layer 116. , And obscure the visibility of the layer body or element located below the display medium layer 112.

The optical matching layer 120 is disposed on the filter layer 116, and the light-transmitting conductive layer 126 is disposed on the optical matching layer 120. The optical matching layer 120 includes a first light-transmitting oxide layer 122 and a second light-transmitting oxide layer 124. The first light-transmitting oxide layer 122 is disposed on the filter layer 116, and the second light-transmitting oxide layer 124 is disposed on the first transparent layer. On the photo-oxidation layer 122. Specifically, the filter layer 116 may include a light-transmitting substrate, such as a glass substrate, wherein the light-shielding layer and each color resist may be formed on the surface of the light-transmitting substrate, and the optical matching layer 120 may be formed on the other side of the light-transmitting substrate. on the surface.

The material of the first light-transmissive oxide layer 122 includes a metal oxide, such as niobium pentoxide (Nb ₂ O ₅ ), titanium dioxide (TiO ₂ ), or the like. The material of the second light-transmissive oxide layer 124 includes a non-metal oxide, such as silicon dioxide (SiO ₂ ) or the like. The material of the light-transmitting conductive layer 126 includes a metal oxide, such as indium tin oxide (ITO) or the like. The second polarizing layer 128 is disposed on the transparent conductive layer 126 and is connected to the touch panel 132 through the colloidal layer 130, that is, the second polarizing layer 128 is located between the transparent conductive layer 126 and the touch panel 132. In addition, the colloid layer 130 may include an optical glue.

The user can perform touch operations on the touch display device 100 through the touch panel 132. During the operation, the light-transmitting conductive layer 126 can shield the electrical signals from the layers or components below it to avoid these electrical signals. Sexual signals interfere with the touch panel 132 to resolve the user's touch position, thereby avoiding the touch panel 132 misjudges the user's touch position. In this regard, since the light-transmitting conductive layer 126 is used for shielding electrical signals, in some embodiments, the shape of the light-transmitting conductive layer 126 in a plan view may be a completely filled pattern, such as a circle, a rectangle, or Other polygons, that is, the area and surface area within the shape contour will be the same.

The shielding effect provided by the transparent conductive layer 126 is related to its impedance. For example, the impedance of the transparent conductive layer 126 is inversely related to the signal-to-noise ratio of the touch panel 132. That is, the signal-to-noise ratio of the touch panel 132 can be improved by reducing the impedance of the light-transmitting conductive layer 126, thereby improving the touch panel 132's judgment accuracy of touch operations.

The resistance of the light-transmitting conductive layer 126 is related to its thickness T. For example, the resistance of the light-transmitting conductive layer 126 is inversely related to its thickness T. Therefore, the resistance of the light-transmitting conductive layer 126 can be reduced by thickening it. In the case where the material of the light-transmitting conductive layer 126 includes indium tin oxide and its thickness T is greater than 1000 Angstroms (Å), the sheet resistance of the light-transmitting conductive layer 126 can be made less than 60 (Ω / □), which is beneficial to improving the shielding current. Effect of sexual signals. On the other hand, the thickness T of the transparent conductive layer 126 is also related to its transmittance, and the transmittance is related to the image quality presented by the touch display device 100. For this reason, when the indium tin oxide is used to form the light-transmitting conductive layer 126 with a thickness T between 1000 Angstroms (Å) and 3000 Angstroms (Å), a thin-film interference phenomenon may be used to form a light-transmitting layer suitable for display requirements. Photoconductive layer 126.

Further, please see FIG. 2, which shows the relationship between the thickness T of the light-transmitting conductive layer 126 in FIG. 1 and its light transmittance, where the horizontal axis is the thickness of the light-transmitting conductive layer, in units Is Angstrom (Å), and the vertical axis is the light transmittance of the light-transmitting conductive layer, and the unit is percentage (%). As shown in Figure 2, by oxidation When the thickness of the light-transmitting conductive layer formed by indium tin is less than 3000 Angstroms (Å), its light transmittance will fluctuate. This fluctuation is caused by the phenomenon of thin film interference. There will be maximum values at 1300 Angstroms (Å) and about 2700 Angstroms (Å).

Here, the “maximum value” means that the thickness of the light-transmitting conductive layer conforms to the interval of “AB ≦ thickness of the light-transmitting conductive layer T ≦ A + C”, where A is the thickness reference value and B is the first thickness When C is the second thickness change value, when the thickness T of the light-transmitting conductive layer falls between AB and A, the thickness T of the light-transmitting conductive layer has a positive correlation with the light transmittance. When the thickness of the conductive layer falls between A and A + C, the thickness T of the light-transmitting conductive layer has a negative correlation with the light transmittance.

Specifically, the thickness reference value A may be about 1300 Angstroms (Å), the first thickness change value B may be about 600 Angstroms (Å), and the second thickness change value C may be about 700 Angstroms (Å), so that the interval is : 700 Angstrom (Å) ≦ thickness of the transparent conductive layer T ≦ 2000 Angstrom (Å). At this time, when the thickness of the light-transmitting conductive layer is in the range of 700 Angstroms (Å) to 1300 Å (Å), the thickness and the light transmittance are approximately correlated, and when the thickness of the light-transmitting conductive layer is 1300 Angstroms (Å) To 2000 Angstroms (Å), there will be a negative correlation between thickness and light transmittance, and the transmittance near the junction of positive correlation and negative correlation may be greater than 85%. For example, when the thickness of the light-transmitting conductive layer is between 1100 Angstroms (Å) and 1600 Angstroms (Å), its transmittance is between 86% and 92%, as shown in the first interval I1.

In addition, the thickness reference value A may also be about 2700 Angstroms (Å), the first thickness change value B may be about 700 Angstroms (Å), and the second thickness change value C may be about 700 Angstroms (Å), so that the interval is: 2000 Angstrom (Å) ≦ thickness T of the transparent conductive layer ≦ 3400 Angstroms (Å). At this time, when the thickness of the light-transmitting conductive layer is 2000 Å (Å) to 2700 Å (Å), the thickness and the light transmittance are approximately positively correlated, and when the thickness of the light-transmitting conductive layer is 2700 Å (Å) When it reaches 3400 angstroms (Å), the thickness and the light transmittance are generally negatively correlated, and the transmittance near the junction of the positive and negative correlations may be greater than 84%. For example, when the thickness of the light-transmitting conductive layer is between 2550 Angstroms (Å) and 2850 Angstroms (Å), its transmittance will be between 85% and 88%, as shown in the second interval I2.

In some embodiments, the thickness T of the transparent conductive layer 126 may be between 1100 Angstroms (Å) and 1600 Angstroms (Å), and the transmittance is between 86% and 92%. It is greater than 0 (Ω / □) and less than 60 (Ω / □). In other embodiments, the thickness T of the transparent conductive layer 126 may be between 2550 Angstroms (Å) and 2850 Angstroms (Å), and the transmittance may be between 86% and 92%. The resistance is greater than 0 (Ω / □) and less than 30 (Ω / □).

On the other hand, the optical matching layer 120 located between the filter layer 116 and the light-transmitting conductive layer 126 can provide the optical correction effect of the light-transmitting conductive layer 126, thereby preventing the light-transmitting conductive layer 126 from exceeding a thickness T of 1000 angstroms ( Å), resulting in a color shift phenomenon in the image presented by the touch display device 100. Specifically, the optical matching layer 120 can achieve the effect of compensating for color shift by the refractive index difference of the layer body. Here, the term “compensating for color shift” means that the self-filtering layer 116 passes through the optics in order. As for the light of the matching layer 120 and the light-transmitting conductive layer 126, this light has a color gamut in the CIE 1976 (L *, a *, b *) color space, and can be located at the coordinate a * and the coordinate b * It is closer to 0 by the compensation effect of the optical matching layer 120.

Specifically, the first transparent oxide layer 122 has a first refractive index, and the second transparent oxide layer 124 has a second refractive index, and the first refractive index is greater than Second refractive index. In some embodiments, the first refractive index may be between 2.1 and 2.5, and the second refractive index may be between 1.4 and 1.6. In the case where the transparent conductive layer 126 is formed of indium tin oxide, The photoconductive layer 126 has a third refractive index and is between 1.7 and 2.1, that is, the third refractive index will be between the first refractive index and the second refractive index. The thickness TA of the first light-transmitting oxide layer 122 and the thickness TB of the second light-transmitting oxide layer 124 are respectively less than 1000 Angstroms (Å), and can be adjusted according to the thickness T of the light-transmitting conductive layer 126, thereby facilitating the compensation of color shift effect. For example, in the embodiment where the thickness T of the transparent conductive layer 126 is between 1100 Å (Å) and 1600 Å (Å), the thickness TA of the first transparent oxide layer 122 is between 80 Å (Å). The thickness TB of the second light-transmitting oxide layer 124 is between 250 Angstrom (Å) and 200 Angstrom (Å), and the thickness TB is between 250 Angstrom (Å) and 400 Angstrom (Å). In the embodiment where the thickness T of the transparent conductive layer 126 is between 2550 Angstroms (Å) and 2850 Angstroms (Å), the thickness TA of the first transparent oxide layer 122 is between 100 Angstroms (Å) and 220 Angstroms. (Å), the thickness TB of the second light-transmitting oxide layer 124 is between 200 Å (Å) and 400 Å (Å). Through the above configuration, when the thickness TA of the first light-transmitting oxide layer 122 and the thickness TB of the second light-transmitting oxide layer 124 are less than 1000 Angstroms (Å), the optical matching layer can be matched with the corresponding refractive index configuration. 120 pairs of transparent conductive layers 126 achieve the effect of compensating for color shift.

In addition, the transparent conductive layer 126 can be directly stacked on the optical matching layer 120 and connected to the optical matching layer 120 to further compensate for color shift. Further, the first light-transmissive oxide layer 122, the second light-transmissive oxide layer 124, and the light-transmissive conductive layer 126 may be sequentially stacked in a stacked manner, wherein the second light-transmissive oxide layer 124 may be stacked on the first light-transmissive layer. The photo-oxidized layer 122 forms an interface, and the light-transmissive conductive layer 126 can be stacked on the second light-transmissive oxide layer 124 to form an interface.

For different touch judgment accuracy requirements, the light-transmitting conductive layers 126 in different thickness ranges can be selected correspondingly. Although the thickness of the transparent conductive layer 126 between 1100 Angstroms (Å) and 1600 Angstroms (Å) and the thickness of the transparent conductive layer 126 between 2550 Angstroms (Å) and 2850 Angstroms (Å) are in the second place. The transmittance maximum values shown in the figure are different (approximately 90% and 88%, respectively). However, in the case where the second polarizing layer 128 is provided on the light-transmitting conductive layer 126, The light of the layer 126 will pass through the second polarizing layer 128 again, so the transmittance difference between the two thickness ranges will be reduced again. On the other hand, although the above-mentioned touch display device 100 uses a combination of the display medium layer 112 and the filter layer 116 to provide an image display function, the disclosure is not limited thereto. In other embodiments, the display medium layer The combination of 112 and the filter layer 116 can also be replaced with other display elements, such as an electroluminescent element, such as a microdiode light-emitting element, a quantum dot light-emitting element, or other similar elements.

In summary, the touch display device of the present disclosure provides image display and touch operation functions, wherein the touch operation function is implemented by a touch panel. In addition, the touch display device further includes a transparent conductive layer. The transparent conductive layer is disposed under the touch panel and shields the electrical signals, thereby improving the signal-to-noise ratio. In the case where indium tin oxide is used to form a light-transmitting conductive layer having a thickness of more than 1000 Angstroms (Å), the sheet resistance of the light-transmitting conductive layer can be less than 60 (Ω / □) to further improve the signal-to-noise ratio effect. In the case where indium tin oxide is used to form a light-transmitting conductive layer having a thickness of less than 3000 Angstroms (Å), a light-transmitting conductive layer having a light transmittance of more than 84% can be formed due to the thin film interference phenomenon, which is suitable for touch display devices. Show demand. In addition, the touch display device may further include an optical matching layer, wherein the optical matching layer is disposed under the light-transmitting conductive layer and includes at least two light-transmitting oxide layers, and the two layers are light-transmitting The refractive index of the oxide layer is different and also different from the refractive index of the light-transmitting conductive layer, so as to achieve the effect of compensating for the color shift of the light-transmitting conductive layer.

Although the present invention has been disclosed in various embodiments as above, it is not intended to limit the present invention. Any person skilled in the art can make various modifications and retouches without departing from the spirit and scope of the present invention. The scope of protection shall be determined by the scope of the attached patent application.

Claims (10)

A touch display device includes: an array substrate; a display medium layer disposed on the array substrate; a filter layer disposed on the display medium layer; a first light-transmitting oxide layer disposed on the display substrate; Above the filter layer and having a first refractive index; a second light-transmitting oxide layer is disposed on the first light-transmitting oxide layer and has a second refractive index, and the first refractive index is greater than the A second refractive index; a light-transmitting conductive layer disposed on the second light-transmitting oxide layer, wherein the thickness of the light-transmitting conductive layer is between 1000 Å (Å) and 3000 Å (Å); and The control panel is disposed on the light-transmitting conductive layer. The touch display device according to item 1 of the application, wherein the material of the transparent conductive layer includes indium tin oxide, and the thickness of the transparent conductive layer is between 1100 Angstroms (Å) and 1600 Angstroms (Å). between. The touch display device according to item 2 of the scope of patent application, wherein the thickness of the first transparent oxide layer is between 80 Angstroms (Å) and 200 Angstroms (Å), and the thickness of the second transparent oxide layer is The thickness is between 250 Angstroms (Å) and 400 Angstroms (Å). The touch display device according to item 1 of the scope of patent application, wherein the material of the transparent conductive layer includes indium tin oxide, and the thickness of the transparent conductive layer is between 2550 Angstroms (Å) and 2850 Angstroms (Å). between. The touch display device according to item 4 of the scope of patent application, wherein the thickness of the first light-transmitting oxide layer is between 100 Å (Å) and 220 Å (Å), and the thickness of the second light-transmitting oxide layer is The thickness is between 200 Angstroms (Å) and 400 Angstroms (Å). The touch display device according to item 1 of the scope of patent application, wherein the first refractive index is between 2.1 and 2.5, and the second refractive index is between 1.4 and 1.6. The touch display device according to item 6 of the application, wherein the material of the first light-transmitting oxide layer includes niobium pentoxide (Nb ₂ O ₅ ), and the material of the second light-transmitting oxide layer includes dioxide Silicon (SiO ₂ ). The touch display device according to item 7 of the scope of patent application, wherein the second light-transmissive oxide layer is disposed on the first light-transmissive oxide layer and forms an interface, and the light-transmissive conductive layer is disposed on the second light-transmissive layer. An interface is formed on the oxide layer. The material of the transparent conductive layer includes indium tin oxide, and the transparent conductive layer has a third refractive index, wherein the third refractive index is between the first refractive index and the second refractive index. Refractive index between. The touch display device according to item 1 of the scope of patent application, further comprising: a first polarizing layer connected to the array substrate; and a second polarizing layer disposed between the transparent conductive layer and the touch panel. . A touch display device includes: an array substrate; a display medium layer disposed on the array substrate; a filter layer disposed on the display medium layer; a first light-transmitting oxide layer disposed on the display substrate; Above the filter layer and having a first refractive index; a second light-transmitting oxide layer is disposed on the first light-transmitting oxide layer and has a second refractive index, and the first refractive index is greater than the A second refractive index; a light-transmitting conductive layer disposed on the second light-transmitting oxide layer and having a thickness T and AB ≦ T ≦ A + C, where A is a thickness reference value and B is a first thickness change Value, C is the second thickness change value. When the thickness T of the light-transmitting conductive layer falls between AB and A, the thickness T of the light-transmitting conductive layer has a positive correlation with the light transmittance. When the thickness of the conductive layer falls between A and A + C, the thickness T of the transparent conductive layer has a negative correlation with the light transmittance; and a touch panel is disposed on the transparent conductive layer.