Substrate for display

Abstract

A display substrate according to an embodiment includes a substrate including chromium and iron, wherein the substrate includes a surface portion defined as a depth region of 5 nm depth in a thickness direction from a surface of the substrate, and a central portion, and a ratio of chromium atoms to iron atoms (Cr / Fe) of the surface portion is greater than a ratio of chromium atoms to iron atoms (Cr / Fe) of the central portion.

Description

[0001] This application is a divisional application of the parent application with the application date of January 22, 2020, the priority date of January 25, 2019, the application number of 202080011003.9, and the title of "Substrate for Display". TECHNICAL FIELD

[0002] Embodiments relate to a substrate for a display. BACKGROUND

[0003] Recently, there is an increasing demand for a flexible display device capable of easily supporting various applications and displaying an image on a large screen carried on the body.

[0004] Such a flexible display is folded or partially bent when carried or stored, but can be implemented to unfold the display when displaying an image. Accordingly, an image display area can be increased, and a user can easily carry it.

[0005] Such a flexible display device can be repeatedly folded or bent, and then a recovery process of unfolding it again can be repeatedly performed.

[0006] Accordingly, a substrate of a display device needs strength and elasticity, and no cracks and deformations should occur in the substrate during folding and recovery.

[0007] To this end, in order to eliminate or reduce stress of a substrate constituting a display device, a plurality of patterned grooves or patterned holes can be formed in the entire area or one area of the substrate.

[0008] By minimizing stress generated when folding or recovering the substrate through the patterned grooves or patterned holes, cracks and deformations can be suppressed from occurring in the substrate.

[0009] Meanwhile, a surface oxidation layer due to natural oxidation can be naturally formed on the surface of the substrate. After applying a photosensitive material to the substrate on which the surface oxidation layer is formed, a pattern can be formed using a photolithography process.

[0010] At this time, in the photolithography process, the surface oxidation layer can be etched together, and the surface oxidation layer can be over-etched, so that adhesion between the photosensitive material and the surface oxidation layer can be deteriorated, and crevice corrosion can occur in an area in which the surface oxidation layer has been etched.

[0011] Accordingly, there is a need for a display substrate having a new structure capable of solving the above-described problems. SUMMARY

[0012] TECHNICAL PROBLEM

[0013] Embodiments aim to provide a display substrate that can prevent corrosion and can easily form a pattern.

[0014] Technical means

[0015] The display substrate according to an embodiment includes a substrate including chromium and iron, wherein the substrate includes a surface portion defined as a depth region of 5 nm depth in a thickness direction of the substrate from a surface of the substrate, and a central portion, and a ratio of chromium atoms to iron atoms (Cr / Fe) of the surface portion is greater than a ratio of chromium atoms to iron atoms (Cr / Fe) of the central portion.

[0016] Technical effects

[0017] In the display substrate according to an embodiment, a gap corrosion generated when the surface portion is over-etched during etching of the substrate and adhesion to the photosensitive layer can be prevented by controlling the atomic content of the surface portion of the substrate.

[0018] Specifically, the content of chromium oxide of the surface portion in contact with the photosensitive layer can be increased by modifying the surface portion.

[0019] Accordingly, the corrosion resistance of the surface portion in the surface portion can be increased by increasing the content of chromium oxide in the surface portion.

[0020] Accordingly, a phenomenon in which the surface portion is over-etched inward during etching can be minimized, and adhesion deterioration due to a decrease in a contact area between the surface portion and the photosensitive layer caused by over-etching of the surface portion can be prevented.

[0021] In addition, by reducing the atomic content of chromium and increasing the atomic content of iron in a region other than the surface portion, a desired pattern shape can be easily achieved by smoothly performing an etching process. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a view showing a perspective view of a display substrate according to an embodiment.

[0023] Figure 2 is a view showing a side view of a display substrate according to an embodiment.

[0024] Figure 3 is a view showing a top view of one surface of a display substrate according to an embodiment.

[0025] Figure 4 is a view showing a cross-sectional view of a display substrate according to an embodiment.

[0026] Figure 5 is a view showing a cross-sectional view of a display substrate on which a photosensitive material is formed according to an embodiment.

[0027] Figure 6is a view showing a cross-sectional view of a display substrate from which a photosensitive material in a pattern area is removed, according to an embodiment.

[0028] Figure 7 and Figure 8 is a graph showing atomic content of a substrate according to an exemplary embodiment and a comparative example.

[0029] Figure 9 and Figure 10 is a graph showing distribution of a bonding state of an atom of a surface layer of a substrate according to an exemplary embodiment and a comparative example.

[0030] Figure 11 and Figure 12 is a graph showing a degree of peeling of an oxidation layer of a substrate according to an exemplary embodiment and a comparative example.

[0031] Figure 13 and Figure 14 is a photograph for describing a quality of etching after pattern formation of a substrate according to an exemplary embodiment and a comparative example. DETAILED DESCRIPTION

[0032] Hereinafter, embodiments of the present application will be described in detail with reference to the accompanying drawings. However, the spirit and scope of the present application are not limited to a part of the described embodiments, and can be implemented in various other forms, and one or more elements of the embodiments can be selectively combined and replaced within the spirit and scope of the present application.

[0033] In addition, unless explicitly defined and described otherwise, the terms used in the embodiments of the present application, including technical and scientific terms, can be interpreted the same as the meanings that one of ordinary skill in the art to which the present application belongs and is commonly used, and terms such as those defined in a general dictionary can be interpreted as having meanings consistent with the meanings in the context of relevant art.

[0034] In addition, the terms used in the embodiments of the present application are used to describe the embodiments and are not intended to limit the present application. In the present specification, the singular form can also include the plural form unless specifically stated and described otherwise in the phrase, and when describing "at least one of (or a plurality of) A, B, and C," it can include at least one of all combinations that can be combined in A, B, and C.

[0035] Further, in describing elements of the embodiments of the present application, terms such as first, second, A, B, (a), and (b) can be used. These terms are used only to distinguish the elements from other elements, and the terms are not limited to the nature, order, or sequence of the elements.

[0036] In addition, when an element is described as being "connected", "coupled", or "linked" to another element, it can include not only the case where the element is directly connected, coupled, or linked to the other element, but also the case where another element is interposed between the element and the other element.

[0037] In addition, when described as being formed or disposed "on (above)" or "under (below)" each element, "on (above)" or "under (below)" can include not only the case where two elements are directly connected to each other, but also the case where one or more other elements are formed or disposed between the two elements.

[0038] In addition, when expressed as "on (above)" or "under (below)", it can include not only the upward direction based on one element but also the downward direction based on one element.

[0039] Hereinafter, a display substrate according to an embodiment will be described with reference to the accompanying drawings.

[0040] Reference Figures 1 to 3 The display substrate according to an embodiment includes a substrate 100.

[0041] The substrate 100 can include a metal, a metal alloy, a plastic, a composite material (for example, a carbon fiber reinforced plastic, a magnetic or conductive material, a glass fiber reinforced material, or the like), a ceramic, sapphire, glass, or the like. As an example, the substrate 100 can include stainless steel (SUS).

[0042] Reference Figure 1 and Figure 2 The substrate 100 can be bent in one direction. Specifically, the substrate 100 including a first surface 1S and a second surface 2S can be folded in a direction in which any one of the first surface 1S and the second surface 2S face each other with respect to a folding axis.

[0043] At this time, in the case of the substrate 100, since the substrate 100 has rigidity and ductility, a compressive stress is generated while being bent in one direction, and has a problem that a crack is generated in the substrate 100 in a region in which the compressive stress is large.

[0044] Reference Figure 3 To solve such a problem, a plurality of patterns can be formed in one region of the substrate 100. Specifically, a pattern P including a plurality of grooves or holes H can be formed in one region of the substrate 100.

[0045] Such a pattern P can be formed in at least one region of a folded portion and an unfolded portion of the substrate 100.

[0046] In addition, a plurality of hinge portions HN can be formed at both ends of the substrate 100 to easily bend the substrate 100.

[0047] The pattern P and the hinge portion HN can be formed by an exposure, development, and etching process after forming a photosensitive material on the substrate 100.

[0048] In this case, the photosensitive material can be formed on the surface portion 110 of the substrate 100, and the surface portion 110 can be etched together when the substrate 100 is etched.

[0049] The surface portion 110 can be formed on the surface of the substrate 100 to serve as a protective layer to prevent the substrate from being corroded due to external oxygen.

[0050] Meanwhile, when the surface portion 110 is over-etched during the etching process, since the surface portion in the over-etched area is not preserved, a crevice corrosion can occur between the substrate 100 and the photosensitive material.

[0051] In addition, the contact area between the surface portion and the photosensitive material can be reduced, and the adhesion between the surface portion and the photosensitive material can be lowered, and thus the photosensitive material can be peeled off.

[0052] Therefore, the reliability and durability of the display substrate can be lowered, and a pattern having an incorrect size and shape is formed, and thus stress distribution through the pattern can not be effectively performed during folding.

[0053] The display substrate according to the embodiments described below can prevent over-etching of the surface portion generated during such an etching process to prevent corrosion, thereby forming a more accurate pattern.

[0054] Hereinafter, a display substrate according to embodiments will be described with reference to the accompanying drawings. Figures 4 to 14 A display substrate according to embodiments will be described in detail.

[0055] Referring to FIG. 1, Figure 4 The display substrate 1000 can include a substrate 100.

[0056] As described above, the substrate 100 can include a material having rigidity and ductility. For example, the substrate 100 can include stainless steel (SUS).

[0057] Specifically, the substrate 100 can include at least one material among carbon (C), silicon (Si), manganese (Mn), phosphorus (P), sulfur (S), chromium (Cr), nickel (Ni), and iron (Fe).

[0058] The substrate 100 can include stainless steel (SUS) including chromium of about 10 wt% or more. More specifically, the substrate 100 can include stainless steel (SUS) including chromium of about 11 wt% to about 20 wt%.

[0059] Specifically, the base material 100 can include a stainless steel (SUS) including about 0.15 wt% or less of carbon, about 1 wt% or less of silicon, about 2 wt% or less of manganese, about 0.045 wt% or less of phosphorus, about 0.03 wt% or less of sulfur, about 6 wt% to about 8 wt% of nickel, and iron as a balance.

[0060] The base material 100 can include two regions defined by depth. In detail, the base material 100 can be defined as a region of a surface portion 110 (the surface portion 110 is defined as a region of 5 nm thickness from a surface S of the base material 100) and a region of a central portion 120 inside the surface portion.

[0061] As described above, the base material 100 includes various components, but mainly contains iron (Fe).

[0062] Accordingly, the base material 100 can combine with oxygen in the air in a natural state to form an oxide film on a surface thereof. That is, the surface portion 110 can be defined as a surface oxide film formed on a surface of the base material 100.

[0063] The surface portion 110 can be formed on the entire surface of the base material 100. That is, can be formed on the upper surface, the lower surface, and the side surface of the base material exposed to the outside.

[0064] Accordingly, the surface portion 110 can be formed in a shape surrounding the central portion 120.

[0065] Meanwhile, the surface portion 110 can be formed with a constant thickness. For example, the surface portion 110 can have a thickness of about 10 nm to about 100 nm in the thickness direction of the base material 100.

[0066] Meanwhile, referring to Figure 5 a photosensitive material 200, such as a photoresist, can be applied on the base material 100, that is, the surface portion 110, to form a pattern having a hole or groove shape in one region of the base material 100.

[0067] Subsequently, as shown in Figure 6 , the photosensitive material 200 of a region EA to be etched by an exposure and development process can be removed.

[0068] Subsequently, the region where the photosensitive material 200 is removed can be etched by an etching solution capable of etching the base material 100. In detail, the surface portion 110 and the central portion 120 can be etched together by the etching solution. In this case, when the surface portion 110 is over-etched by the etching solution, the adhesion between the surface portion 110 and the photosensitive material 200 can be deteriorated, and corrosion can occur in the gap portion.

[0069] The display substrate 1000 according to the embodiment can control the composition of the surface portion 110 to prevent adhesion between the surface portion and the photosensitive material from deteriorating and to prevent corrosion.

[0070] Specifically, the surface portion 110 can include iron oxides such as FeO and Fe2O3 and chromium oxides such as Cr2O3. The display substrate 1000 according to the embodiment can solve the above-described problems by controlling the atomic content of chromium and iron atoms of the surface portion 110.

[0071] Specifically, the ratio of chromium atoms to iron atoms (Cr / Fe) of the surface portion 110 can be higher than the ratio of chromium atoms to iron atoms of the central portion 120. In detail, the ratio of chromium atoms to iron atoms (Cr / Fe) of the surface portion 110 can be about 0.7 or more.

[0072] That is, the surface portion 110 can include a region in which the ratio of chromium atoms to iron atoms (Cr / Fe) is 0.7 or more. For example, in at least one region of the entire region of the surface portion 110, the ratio of chromium atoms to iron atoms (Cr / Fe) can be 0.7 or more.

[0073] In addition, in at least one region of the entire region of the surface portion 110, the ratio of chromium atoms to iron atoms (Cr / Fe) can be 1 or more.

[0074] In addition, in at least one region of the entire region of the surface portion 110, the ratio of chromium atoms to iron atoms (Cr / Fe) can be 0.7 to 3.2.

[0075] For example, at a depth of 3 nm in the depth direction of the substrate 100 from the surface of the substrate 100, the ratio of chromium atoms to iron atoms (Cr / Fe) of the surface portion 110 can be 1 or more.

[0076] In addition, at a depth of 3 nm to 5 nm in the depth direction of the substrate 100 from the surface of the substrate 100, the ratio of chromium atoms to iron atoms (Cr / Fe) of the surface portion 110 can be 0.7 or more.

[0077] That is, as the surface portion 110 is closer to the surface of the substrate 100, the ratio of chromium atoms to iron atoms (Cr / Fe) can be higher.

[0078] That is, as the surface portion 110 is closer to the surface of the substrate 100, the ratio of chromium atoms to iron atoms (Cr / Fe) can gradually increase.

[0079] That is, the ratio of chromium atoms to iron atoms (Cr / Fe) can be 0.7 or more in the entire region of the surface portion 110.

[0080] Accordingly, the surface portion 110 can be a chromium-rich region having a higher chromium (Cr) content than the central portion 120, and can include a chromium-rich region.

[0081] Such a chromium-rich region of the surface portion 110 can be artificially formed. That is, on the substrate 100, oxygen in the air is combined with the surface to first form an oxide layer through natural oxidation, and the oxide layer is subjected to acid treatment with a solution such as hydrochloric acid and heat treatment thereof to change one region of the surface portion 110, that is, at least one region of the surface portion 110, to a chromium-rich region.

[0082] Since the chromium (Cr) or chromium oxide film has better corrosion resistance than the iron (Fe) or iron oxide film, the surface portion 110 can be prevented from being over-etched inward by an etching solution or the like during etching.

[0083] That is, the photosensitive material 200 is adhered to the surface portion 110, and thus, the surface portion 110 can be prevented from being over-etched by an etchant or the like during etching by adjusting the composition of the surface portion 110 to a chromium-rich state. In addition, adhesion between the surface portion 110 and the photosensitive material 200 can be prevented from being deteriorated due to over-etching of the surface portion.

[0084] Meanwhile, the ratio of chromium atoms to iron atoms (Cr / Fe) at the central portion 120 can be less than the ratio of chromium atoms to iron atoms at the surface portion 110.

[0085] In detail, the ratio of chromium atoms to iron atoms (Cr / Fe) of the central portion 120 can be less than 1. In detail, the ratio of chromium atoms to iron atoms (Cr / Fe) in the central portion 120 can be 0.3 to 0.6. That is, the central portion 120 can include a region in which the ratio of chromium atoms to iron atoms (Cr / Fe) is 0.3 to 0.6.

[0086] Accordingly, unlike the surface portion 110, the central portion 120 can be in an iron-rich state. When the ratio of chromium atoms to iron atoms (Cr / Fe) in the central portion 120 exceeds 0.6, the corrosion resistance of the central portion 120 increases to thereby reduce the etching rate, and thus, the etching efficiency during the etching process can be reduced, and thus, it can be difficult to form a pattern.

[0087] That is, in the surface portion 110 adhered to the photosensitive material, the corrosion resistance of the surface portion can increase to thereby prevent over-etching, and in the central portion 120, the corrosion resistance can be relatively reduced compared to the surface portion, and thus, the composition of the substrate 100 can be controlled so that the substrate 100 is easily etched.

[0088] Meanwhile, the display substrate according to the embodiment can be defined as a region in which a bend is generated by folding the display substrate and a region in which no bend is generated without folding. The pattern can be formed in both the region in which the bend is generated and the region in which no bend is generated. Alternatively, the pattern can be formed only in the region in which the bend is generated. Accordingly, the base material 100 can be divided into a region in which the pattern is formed and a region in which the pattern is not formed.

[0089] The chromium content and the iron content of the surface portion can be controlled in both the region in which the pattern is formed and the region in which the pattern is not formed. Alternatively, the chromium content and the iron content of the surface portion can be controlled only in the region in which the pattern is formed.

[0090] That is, since over-etching of the photosensitive material occurs in the etching process of forming the pattern, the processing time according to the reforming of the surface portion is reduced by controlling the contents of chromium atoms and iron atoms only in the region in which the pattern is formed in the region of the base material.

[0091] In the above description, the case in which the display substrate 1000 is bent is mainly described, but the embodiment is not limited thereto, and the embodiment can be applied to the case in which the pattern is formed on the display substrate 1000 which is not bent, or the case in which the pattern is formed on the base material for a use other than the display substrate, for example, for a mask, and the application field thereof is not limited to the above description.

[0092] Hereinafter, the present application will be described in more detail with reference to exemplary embodiments and comparative examples. The exemplary embodiments are merely exemplary to describe the present application in more detail. Accordingly, the present application is not limited thereto.

[0093] Exemplary Embodiments

[0094] First, a stainless steel base material was prepared.

[0095] The stainless steel base material contained 17 wt% of chromium.

[0096] Subsequently, the surface of the stainless steel base material was combined with oxygen in the air and was naturally oxidized to form a surface oxidation region on the surface of the base material. Subsequently, the surface of the stainless steel base material was subjected to acid treatment using hydrochloric acid, and then was subjected to heat treatment at a temperature of about 150°C to reform the surface oxidation region of the base material.

[0097] Subsequently, after the photoresist material was applied to the surface of the stainless steel base material, the photoresist material of a region to be patterned was removed through an exposure and development process.

[0098] Meanwhile, the heat treatment process can be performed before and after the developing process. In detail, the reaction sensitivity can be improved by diffusing the photosensitive agent through the heat treatment after the exposure process, and the surface roughness can be reduced by reducing the surface roughness of the surface portion after the development through the heat treatment after the developing process.

[0099] Subsequently, the stainless steel substrate is etched using an etchant for etching a pattern formation region.

[0100] Subsequently, the atomic content according to the depth from the surface of the stainless steel substrate, the bonding state of the atom, and the etching degree of the surface portion is measured.

[0101] Comparative Example

[0102] A stainless steel substrate identical to the exemplary embodiment is prepared. Subsequently, the surface of the stainless steel substrate is naturally oxidized to form a surface oxidation region on the surface of the substrate.

[0103] Subsequently, after the photoresist material is applied to the surface of the substrate, the photoresist material in a region where a pattern is to be formed is removed through an exposure and developing process.

[0104] Subsequently, the stainless steel substrate is etched using an etchant for etching a pattern formation region.

[0105] That is, in the comparative example, unlike the exemplary embodiment, the etching process is performed without performing the acid treatment and the heat treatment.

[0106] Subsequently, the atomic content according to the depth from the surface of the stainless steel substrate, the bonding state of the atom, and the etching degree of the surface portion is measured.

[0107] Figure 7 and Figure 8 is a graph showing the atomic content according to the depth from the surface of the stainless steel substrate measured by X-ray photoelectron spectroscopy (XPS) according to each of the exemplary embodiment and the comparative example.

[0108] Referring to Figure 7 It can be seen that the substrate according to the comparative example has a higher iron content than the chromium content at a depth of from the surface (0 nm) to about 5 nm. That is, it can be seen that the substrate according to the comparative example has a high iron content in an iron-rich state at a depth of from the surface (0 nm) to about 5 nm.

[0109] Referring to Figure 8 It can be seen that the substrate according to the exemplary embodiment has a higher chromium content than the iron content at a depth of from the surface (0 nm) to about 5 nm. That is, it can be seen that the substrate according to the exemplary embodiment has a high chromium content in a chromium-rich state at a depth of from the surface (0 nm) to about 5 nm.

[0110] The atomic content based on the depth of the substrate according to the exemplary embodiment can be shown in Table 1 below.

[0111] Table 1

[0112]

[0113] refer to Figure 8 As can be seen from Table 1, the chromium-to-iron ratio (Cr / Fe) of the substrate according to the exemplary embodiment is 0.7 or higher at a depth from the surface (0 nm) to about 5 nm. Furthermore, it can be seen that from a depth of about 5 nm in the substrate, the chromium-to-iron ratio (Cr / Fe) is less than 0.7.

[0114] In other words, at a depth of approximately 5 nm from the surface (0 nm, which is the area on the surface of the substrate where the photosensitive material adheres) to the substrate, over-etching of the surface portion during the etching process can be prevented by increasing the amount of chromium, which has strong corrosion resistance. Therefore, it is possible to prevent poor adhesion between the surface portion and the photosensitive material due to over-etching, and to prevent corrosion in the areas where over-etching would occur.

[0115] In addition, the etching process can be performed smoothly by reducing the amount of highly corrosion-resistant chromium and increasing the iron content from a depth of 5 nm in the substrate, thereby forming patterns more precisely.

[0116] Figure 9 and 10 This is a graph showing the bonding state of chromium and iron atoms in an exemplary embodiment and a comparative example, measured by bond energy analysis in a region 3 nm deep from the substrate surface, i.e., at a distance of 3 nm from the substrate surface.

[0117] refer to Figure 9 As can be seen, in the substrate according to the exemplary embodiment, the ratio of chromium oxide with strong corrosion resistance on the surface portion is almost doubled compared to the comparative example.

[0118] Additionally, refer to Figure 10 As can be seen, in the substrate according to the exemplary embodiment, the ratio of iron oxide film on the surface portion is similar to the ratio of iron oxide film in the comparative example.

[0119] In other words, the substrate according to the exemplary embodiment is in a chromium-rich state, wherein the chromium content is high at a depth from the surface (0 nm) to about 5 nm. In particular, since the chromium atoms are kept in a chromium oxide state with strong corrosion resistance, over-etching of the surface oxide layer can be effectively prevented during the etching process.

[0120] Figures 11 to 14are cross-sectional views and photographs showing the degree to which the substrate is etched in the etching process of the substrate according to the exemplary embodiment and the comparative example.

[0121] Referring to Figure 11 In the display substrate according to the comparative example, it can be seen that the area FA in which the surface portion is etched inward is large during the etching process. On the other hand, referring to Figure 12 In the display substrate according to the exemplary embodiment, it can be seen that the area FA in which the surface portion is etched inward is small during the etching process.

[0122] That is, in the display substrate according to the comparative example, as shown in Figure 13 the area in which the surface portion is etched inward increases, and corrosion can occur in the area FA in which the surface portion is etched inward. In addition, it can be seen that the surface portion is over-etched inward, the contact area between the photosensitive material and the surface portion decreases, and the adhesion between the photosensitive material and the substrate deteriorates.

[0123] However, in the display substrate according to the exemplary embodiment, as shown in Figure 14 corrosion can be prevented from occurring in the area FA in which the surface portion is etched inward by minimizing the area FA in which the surface portion is etched inward. In addition, the contact area between the surface portion and the photosensitive layer can be prevented from decreasing by minimizing the area in which the surface portion is etched inward, and thus, the adhesion between the photosensitive material and the substrate can be prevented from deteriorating.

[0124] In the display substrate according to the embodiment, the crevice corrosion that occurs when the surface portion is over-etched during etching of the substrate and the deterioration of the adhesion with the photosensitive layer can be prevented by controlling the atomic content of the surface portion of the substrate.

[0125] Specifically, the content of chromium oxide of the surface portion in contact with the photosensitive layer can be increased by modifying the surface portion.

[0126] Thus, the corrosion resistance of the surface portion in the surface portion can be increased by increasing the content of chromium oxide in the surface portion.

[0127] Thus, the phenomenon in which the surface portion is over-etched inward during the etching process can be minimized, and the deterioration of the adhesion due to the decrease in the contact area between the surface portion and the photosensitive layer caused by the over-etching of the surface portion can be prevented.

[0128] In addition, by reducing the atomic content of chromium and increasing the atomic content of iron in the area other than the surface portion, a desired pattern shape can be easily achieved by smoothly performing the etching process.

[0129] The features, structures, effects, and so on described in the above-described embodiments are included in at least one embodiment of the present application, but are not limited to only one embodiment. Furthermore, a person skilled in the art can combine or modify the features, structures, and effects shown in each of the embodiments for other embodiments. Therefore, it should be understood that such combinations and modifications are included in the scope of the present application.

[0130] In addition, although the above description focuses on the embodiments, the embodiments are merely examples and do not limit the present application. It will be apparent to those skilled in the art that various modifications and applications not shown above can be made to each of the embodiments without departing from the basic characteristics of the present embodiments. For example, elements of the exemplary embodiments described herein can be modified and implemented. In addition, it should be interpreted that differences related to such modifications and applications are included in the scope of the present application defined in the appended claims.

Claims

1. A substrate for a display, the substrate comprising: a base material including chromium and iron, wherein the base material includes a surface portion and a central portion distinguished in a thickness direction of the substrate, wherein the surface portion is defined as a depth region of 5 nm in the thickness direction from a surface of the base material, wherein a ratio of chromium atoms to iron atoms, Cr / Fe, of the surface portion is greater than a ratio of chromium atoms to iron atoms, Cr / Fe, of the central portion, wherein the surface portion includes a first region in which an atomic concentration of chromium is greater than an atomic concentration of iron and a second region in which an atomic concentration of iron is greater than an atomic concentration of chromium, wherein the first region and the second region extend in the thickness direction from the surface of the base material in that order, and wherein a depth of the first region is greater than a depth of the second region.

2. The substrate for display according to claim 1, wherein, the central portion is provided as a region in which an atomic concentration of iron is greater than an atomic concentration of chromium.

3. The substrate for display according to claim 2, wherein, the first region includes a region in which an atomic concentration of chromium gradually increases.

4. The substrate for display according to claim 3, wherein, the first region includes a region in which an atomic concentration of iron gradually increases.

5. The substrate for display according to claim 4, wherein, the second region includes a region in which an atomic concentration of chromium gradually decreases.

6. The substrate for display according to claim 1, wherein, a depth of a region in which an atomic concentration of chromium gradually increases in the surface portion is closer to the surface of the base material than a depth of a region in which an atomic concentration of chromium gradually decreases in the surface portion.

7. The substrate for display according to claim 1, wherein, the base material includes a folded region that is bent in one direction and an unfolded region that is not bent, wherein a hole or a groove is formed in the folded region, wherein the folded region includes the surface portion and the central portion, wherein the hole or the groove is formed in the surface portion and the central portion, and wherein the surface portion is a region in which a ratio of chromium atoms to iron atoms, Cr / Fe, is 0.7 to 3.

2.

8. The substrate for display according to claim 7, wherein, a ratio of chromium atoms to iron atoms, Cr / Fe, at the surface portion increases toward the surface of the base material.

9. The substrate for display according to claim 7, wherein, a ratio of chromium atoms to iron atoms, Cr / Fe, of the surface portion is 1 or more at a depth of 3 nm in the thickness direction of the base material from the surface of the base material.

10. The substrate for display according to claim 7, wherein, a ratio of chromium atoms to iron atoms, Cr / Fe, is 0.7 or more at a depth of 3 nm to 5 nm in the thickness direction of the base material from the surface of the base material.

11. The substrate for display according to claim 7, wherein, a ratio of chromium atoms to iron atoms, Cr / Fe, in the central portion is 0.3 to 0.

6.

12. The substrate for display according to claim 7, wherein, the surface portion surrounds the central portion, and wherein the surface portion includes an oxide film.

13. The substrate for display according to claim 7, wherein, a hole or a groove is formed in the unfolded region, and wherein the unfolded region includes the surface portion and the central portion.

14. The substrate for display according to claim 7, wherein, the base material includes stainless steel.

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