JP2011138683A - Electronic element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic element which has a metal substrate on which an insulating layer with high heat resistance and dimension stability is formed, and which shows superior element characteristics. <P>SOLUTION: The electronic element 1 has a metal substrate 2, an insulating layer 3, formed on the metal substrate and contains polyimide, and an electronic element part 10 formed on the insulating layer 3, and the moisture absorption expansion coefficient of the insulating layer 3 is in the range of 0-15 ppm/% RH. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electronic device such as an organic electroluminescence device or a thin film transistor.

Electronic elements such as organic electroluminescence elements (hereinafter, electroluminescence may be referred to as EL) and thin film transistors (hereinafter, thin film transistors may be referred to as TFTs) have low resistance to moisture, and element characteristics due to moisture are low. descend.
As a technique for suppressing deterioration of element characteristics due to moisture, a technique for preventing moisture from entering the element from the outside, such as sealing the element with a sealing member or a sealing structure, is the mainstream. At this time, a base material having gas barrier properties is used.

As the substrate having gas barrier properties, a glass substrate, a plastic film provided with gas barrier properties, a metal substrate, or the like is used.
A glass substrate is excellent in smoothness and heat resistance, but lacks flexibility, is unsuitable for thinning and weight reduction, and has a disadvantage that it is inferior in impact resistance.
Since a plastic film is generally inferior to a glass or metal in gas barrier properties, it is necessary to impart gas barrier properties in order to prevent moisture from entering. A plastic film with gas barrier properties has the advantages of flexibility, light weight, and impact resistance, but it is not sufficient in heat resistance and has a large coefficient of linear thermal expansion. There is a disadvantage that it is inferior and has high hygroscopicity.
On the other hand, as for the metal base material, various types of metal types and thicknesses are available and can be appropriately selected, and can satisfy heat resistance, light weight, and flexibility. However, since the metal substrate tends to be inferior in surface flatness to the glass substrate and has conductivity, it is necessary to provide an insulating layer in order to produce an organic EL element or TFT on the metal substrate. is there. For example, Patent Document 1 proposes a metal substrate having an insulating layer formed on the surface.

  By the way, organic EL elements have been actively developed for use in large-sized TVs, indoor lighting, etc. In order to increase the size, organic EL elements are caused by deterioration of elements due to heat generation during light emission and in-plane temperature unevenness. It is necessary to suppress uneven brightness. Since the metal base material in which the insulating layer is formed on the surface is excellent in thermal conductivity, it is suitable as a base material for organic EL elements.

  In recent years, in a display device such as an active matrix driving organic EL display device or electronic paper, a transparent substrate having a gas barrier property is used as a sealing substrate for sealing elements from above, and an image is observed from above. Is attracting attention. In such a display device, since it is not shielded by the TFT which is an active drive element, a display device with a high aperture ratio can be obtained. In the above display device, the metal base material cannot be used as a transparent sealing base material because it does not have transparency. However, since the metal base material has the advantages described above, it is preferably used as a support base material for supporting the element. Further, in the case of the above system, a metal substrate can be used as a supporting substrate for supporting the element in the display system such as a passive matrix driving organic EL display apparatus or electronic paper, or an organic EL element for illumination. .

  In the metal substrate having an insulating layer formed on the surface, examples of the material used for the insulating layer include inorganic materials and organic materials. In the case of an inorganic insulating layer, since it is difficult to increase the thickness, it is difficult to improve the surface flatness of the metal substrate, and it is difficult to make flexible because cracks are easily generated. On the other hand, in the case of an organic insulating layer, it is possible to obtain a desired surface flatness because it can be thickened, and it is easy to follow a metal base material, and thus has excellent flexibility.

JP 2006-331694 A

However, in general, organic materials are inferior in heat resistance, have a large coefficient of linear thermal expansion, and have problems of higher hygroscopicity than glass and metal.
Since organic materials generally have low heat resistance, there is a problem that they cannot withstand high-temperature processes necessary for forming drive elements such as TFTs. Although attempts have been made to form driving elements such as TFTs at low temperatures, practical processes have not yet been developed due to lack of performance or a very long formation time.
In addition, since organic materials generally have a large linear expansion coefficient, a stress applied to a driving element such as a TFT due to a thermal history is large, so that the element is easily destroyed.
Similarly, the organic material absorbs moisture, causing a dimensional change, which causes a problem that the element is destroyed.
Therefore, a metal substrate having an organic insulating layer formed on the surface has not been put to practical use as a substrate for electronic elements.

  In addition, even in the electronic device, even if moisture can be prevented from entering the device from the outside, there is a problem that device characteristics deteriorate when moisture is contained inside the device. When a metal substrate having an organic insulating layer formed on the surface is used, the problem of moisture existing inside the device becomes significant. Various methods have been conventionally studied as a method for preventing moisture from entering the element, but little consideration has been given to reducing moisture contained in the element.

When using a metal substrate with an organic insulating layer formed on the surface, in order to reduce the moisture contained inside the element, for example, an organic material is formed by coating an organic material by a coating method and then thermally cured. Laminating insulation layer film in high temperature or vacuum atmosphere, forming organic material by vapor phase method in vacuum, or after organic film formation, dewatering treatment at high temperature and / or depressurizing atmosphere Can be considered. However, since organic materials are inferior in heat resistance, it is difficult to sufficiently remove moisture only by heat treatment. Furthermore, even if moisture is removed by heating or depressurization, the organic material absorbs moisture during the manufacturing process of the electronic device. In the case of the vapor phase method, it is very difficult to form an organic material itself having a molecular weight that exhibits sufficient film properties in the vapor phase.
Moreover, in order to prevent moisture absorption of the organic material during the manufacturing process of the electronic device, it may be possible to maintain an atmosphere from which moisture has been completely removed.

  In the case of an organic EL element, it may be possible to perform a heat treatment immediately before forming the organic light emitting layer on the insulating layer. For example, in an organic EL element for lighting use, an electrode is formed on the insulating layer, and the insulating layer is insulated. Since most of the layers are covered with electrodes, the area for removing moisture is small, and it is difficult to remove moisture sufficiently. Similarly, in the case of an organic EL display device including a TFT, heat treatment can be performed immediately before the organic light emitting layer is formed on the insulating layer on which the TFT is formed, but an electrode is formed on the insulating layer on which the TFT is formed. Since it is formed and most of the insulating layer is covered with TFTs or electrodes, the area for removing moisture is small and it is difficult to remove moisture sufficiently. In addition, since a layer having low heat resistance such as an organic light emitting layer is formed, it is difficult to perform sufficient heat treatment for dehydration.

  The present invention has been made in view of the above problems, and mainly provides an electronic device including a metal base material on which an insulating layer having high heat resistance and high dimensional stability is formed and exhibiting good device characteristics. Objective.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that in an electronic device including a metal substrate having an insulating layer formed on the surface, a special polyimide is used for the insulating layer among organic materials. In addition to increasing the heat resistance and dimensional stability of the insulating layer, the moisture content in the insulating layer is reduced to significantly reduce the moisture inside the device, and the moisture absorption of the insulating layer during the manufacturing process of the electronic device is suppressed. As a result, it was found that the lifetime and stability of the device can be improved, and the present invention has been completed.
That is, the present invention includes a metal base material, an insulating layer formed on the metal base material and containing polyimide, and an electronic element portion formed on the insulating layer, and a hygroscopic expansion coefficient of the insulating layer. Is within a range of 0 ppm /% RH to 15 ppm /% RH.

  The hygroscopic expansion coefficient is an index of water absorption, and the smaller the hygroscopic expansion coefficient, the smaller the water absorption. In addition, the smaller the hygroscopic expansion coefficient, the smaller the dimensional change during moisture absorption and the less damage to the device. Therefore, according to the present invention, when the hygroscopic expansion coefficient of the insulating layer is within a predetermined range and the water absorption is sufficiently small, it is possible to reduce the moisture inside the element and suppress the deterioration of characteristics due to moisture. At the same time, it is possible to shorten the lifetime and suppress element destruction. Moreover, according to this invention, since an insulating layer contains a polyimide, it can be set as the insulating layer excellent in insulation, heat resistance, and dimensional stability.

  In the said invention, it is preferable that the said insulating layer has a polyimide as a main component. By using polyimide as a main component, it is possible to obtain an insulating layer having further excellent insulating properties, heat resistance, and dimensional stability. In addition, by using polyimide as a main component, the insulating layer can be thinned, the thermal conductivity of the insulating layer can be improved, and the heat dissipation can be improved.

  Moreover, in this invention, it is preferable that the said polyimide has a repeating unit represented by following formula (1).

(In formula (1), R ¹ is a tetravalent organic group represented by the following formula (2), R ² is a divalent organic group, and R ¹ and R ² that are repeated are the same. And n may be different, and n is a natural number of 1 or more.)

(In Formula (2), a is 0 or a natural number of 1 or more, and A is an ester bond. The linking group is bonded to the 2, 3 or 3 or 4 position of the aromatic ring as viewed from the bonding site of the aromatic ring. To do.)
Such a polyimide can reduce a hygroscopic expansion coefficient and can reduce a linear thermal expansion coefficient. Further, since R ¹ is a tetravalent organic group represented by the above formula (2), the hygroscopic expansion coefficient can be lowered, so that the selectivity of R ² which is a structure derived from diamine is widened. There is also.

  Moreover, it is also preferable that the said polyimide has a repeating unit represented by following formula (1).

(In formula (1), R ¹ is a tetravalent organic group represented by the following formula (2), R ² is a divalent organic group represented by the following formula (3) or (4), and is repeated. R ¹ and R ² may be the same or different, and n is a natural number of 1 or more.)

(In the formula (2), a is a natural number of 0 or 1 or more, A is a single bond (biphenyl structure), an oxygen atom (ether bond), or an ester bond. (However, except for the case where all are ester bonds.) The linking group is bonded to the 2, 3 or 3 or 4 position of the aromatic ring as viewed from the bonding site of the aromatic ring.)

(In the formula (4), a is 0 or a natural number of 1 or more, and the linking group is bonded to the meta position or the para position with respect to the bonds between the aromatic rings. Alternatively, all may be substituted with a substituent selected from a fluoro group, a methyl group, a methoxy group, a trifluoromethyl group, or a trifluoromethoxy group.)
Such a polyimide can reduce a hygroscopic expansion coefficient and can reduce a linear thermal expansion coefficient.

  Furthermore, it is also preferable that the polyimide has a repeating unit represented by the following formula (1).

(In formula (1), R ¹ is a tetravalent organic group, R ² is a divalent organic group represented by the following formula (4), and repeated R ¹ and R ² are the same. And n may be different, and n is a natural number of 1 or more.)

(In the formula (4), a is 0 or a natural number of 1 or more, and the linking group is bonded to the meta position or the para position with respect to the bonds between the aromatic rings. Alternatively, all may be substituted with a substituent selected from a fluoro group, a methyl group, a methoxy group, a trifluoromethyl group, or a trifluoromethoxy group.)
Such polyimide can reduce the hygroscopic expansion coefficient. In addition, since R ² is a divalent organic group represented by the above formula (4), the hygroscopic expansion coefficient can be lowered, and thus the selectivity of R ¹ that is a structure derived from carboxylic dianhydride. There is also an advantage that spreads.

  Further, in the present invention, the surface roughness Ra of the insulating layer is preferably 25 nm or less. When the electronic element portion is a TFT, the surface roughness of the insulating layer is in the above range, so that the electrical performance of the TFT due to unevenness can be prevented from being lowered. On the other hand, when the electronic element portion is an organic EL element, the surface roughness of the insulating layer is in the above range, so that a short circuit between the electrodes can be prevented and the occurrence of luminance unevenness can be suppressed. .

  Moreover, in this invention, it is preferable that the thickness of the said insulating layer exists in the range of 0.3 micrometer-100 micrometers. This is because if the thickness of the insulating layer is too thin, the insulation cannot be maintained, or if the metal substrate surface has irregularities due to rolling streaks or the like, it is difficult to flatten the irregularities. Moreover, if the thickness of the insulating layer is too thick, flexibility is reduced, it becomes excessive, drying during film formation becomes difficult, and costs increase. Furthermore, when the electronic element part is an element that generates heat when driving an organic EL element or the like, and the heat at the time of driving the element is released through the metal substrate, if the insulating layer is thick, the polyimide is thicker than the metal. This is because the thermal conductivity is lowered due to the low thermal conductivity.

  Furthermore, in this invention, it is preferable that the linear thermal expansion coefficient of the said insulating layer exists in the range of 0 ppm / degrees C-30 ppm / degrees C. If the linear thermal expansion coefficient of the insulating layer is within the above range, the linear thermal expansion coefficients of the insulating layer and the metal base material can be made close to each other, warpage can be suppressed and adhesion between the insulating layer and the metal base material can be improved. Because it can.

  Moreover, in this invention, it is preferable that the difference of the linear thermal expansion coefficient of the said insulating layer and the linear thermal expansion coefficient of the said metal base material is 15 ppm / degrees C or less. As described above, the closer the linear thermal expansion coefficients of the insulating layer and the metal substrate are, the more the warpage can be suppressed and the higher the adhesion between the insulating layer and the metal substrate.

  Further, in the present invention, the electronic element portion is formed on the back electrode layer formed on the insulating layer, the EL layer formed on the back electrode layer and including at least the organic light emitting layer, and the EL layer. It is preferable that the organic EL device has a transparent electrode layer formed. As described above, the hygroscopic expansion coefficient of the insulating layer is within a predetermined range, and the water absorption is sufficiently small, so that the deterioration of the characteristics of the organic EL element due to moisture is suppressed while maintaining the heat resistance and insulating reliability of the insulating layer. Is possible. In addition, heat during light emission of the organic EL element can be released through the metal substrate, and it is possible to suppress deterioration of the EL layer due to heat, resulting in uneven brightness and shortening of the element life. .

  In the present invention, the electronic element part is preferably a TFT formed on the insulating layer. As described above, since the hygroscopic expansion coefficient of the insulating layer is within a predetermined range and the water absorption is sufficiently small, the deterioration of TFT characteristics due to moisture is suppressed while maintaining the heat resistance and insulating reliability of the insulating layer. Is possible.

  In the present invention, since the hygroscopic expansion coefficient of the insulating layer is in a predetermined range and the water absorption is sufficiently small, there is an effect that it is possible to suppress deterioration of the characteristics of the element due to moisture.

It is a schematic sectional drawing which shows an example of the electronic device of this invention. It is a schematic sectional drawing which shows the other example of the electronic device of this invention. It is a schematic sectional drawing which shows the other example of the electronic device of this invention. It is a schematic sectional drawing which shows the other example of the electronic device of this invention. It is the schematic sectional drawing and the top view which show the other example of the electronic device of this invention. It is a schematic sectional drawing which shows the other example of the electronic device of this invention. It is a schematic sectional drawing which shows the other example of the electronic device of this invention. It is a schematic sectional drawing which shows an example of an organic electroluminescence display provided with the electronic element of this invention. It is a schematic sectional drawing which shows an example of electronic paper provided with the electronic device of this invention. It is the photograph of the light emission state before and behind the 80 degreeC high temperature storage test of the organic EL element of Example 2 and Comparative Example 1.

Hereinafter, the electronic device of the present invention will be described in detail.
The electronic device of the present invention has a metal substrate, an insulating layer formed on the metal substrate and containing polyimide, and an electronic device part formed on the insulating layer, and the hygroscopic expansion of the insulating layer. The coefficient is in the range of 0 ppm /% RH to 15 ppm /% RH.

The electronic device of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic cross-sectional view showing an example of the electronic device of the present invention, and is an example in the case where the electronic device portion is an organic EL device. An electronic element 1 illustrated in FIG. 1 includes a metal base 2, an insulating layer 3 formed on the metal base 2, containing polyimide, having a predetermined hygroscopic expansion coefficient, and an organic formed on the insulating layer 3. EL element 10 (electronic element part). The organic EL element 10 includes a back electrode layer 11 formed on the insulating layer 3, an EL layer 12 formed on the back electrode layer 11 and including at least an organic light emitting layer, and a transparent electrode formed on the EL layer 12. Layer 13. The organic EL element 10 is a top emission type in which light L is extracted from the transparent electrode layer 13 side.

FIG. 2A to FIG. 4B are schematic cross-sectional views showing other examples of the electronic device of the present invention, and are examples where the electronic device portion is a TFT. Each of the electronic elements 1 exemplified in FIGS. 2A to 4B is a metal base 2 and an insulating layer 3 formed on the metal base 2 and containing polyimide and having a predetermined hygroscopic expansion coefficient. And a TFT 20 (electronic element portion) formed on the insulating layer 3.
The electronic element 1 illustrated in FIG. 2A includes a TFT 20 having a top gate / bottom contact structure, and the TFT 20 includes a source electrode 22S and a drain electrode 22D formed on the insulating layer 3 and a semiconductor layer 21. The gate insulating film 24 formed on the source electrode 22S and the drain electrode 22D and the semiconductor layer 21 and the gate electrode 23G formed on the gate insulating film 24 are provided.
The electronic element 1 illustrated in FIG. 2B includes a TFT 20 having a top gate / top contact structure. The TFT 20 includes a semiconductor layer 21 formed on the insulating layer 3, a source electrode 22S and a drain electrode 22D. The gate insulating film 24 formed on the semiconductor layer 21, the source electrode 22S, and the drain electrode 22D, and the gate electrode 23G formed on the gate insulating film 24.
The electronic element 1 illustrated in FIG. 3A includes a TFT 20 having a bottom gate / bottom contact structure, and the TFT 20 covers a gate electrode 23G formed on the insulating layer 3 and the gate electrode 23G. The formed gate insulating film 24, the source electrode 22S and the drain electrode 22D and the semiconductor layer 21 formed on the gate insulating film 24, and the protective film 25 formed on the source electrode 22S and the drain electrode 22D and the semiconductor layer 21. And have.
The electronic element 1 illustrated in FIG. 3B includes a TFT 20 having a bottom gate / top contact structure, and the TFT 20 covers the gate electrode 23G formed on the insulating layer 3 and the gate electrode 23G. The formed gate insulating film 24, the semiconductor layer 21, the source electrode 22S and the drain electrode 22D formed on the gate insulating film 24, and the protective film 25 formed on the semiconductor layer 21, the source electrode 22S and the drain electrode 22D. And have.
An electronic element 1 illustrated in FIG. 4A includes a TFT 20 having a coplanar structure, and the TFT 20 includes a semiconductor layer 21 formed on the insulating layer 3 and a source electrode formed on the semiconductor layer 21. 22S and drain electrode 22D, gate insulating film 24 formed on semiconductor layer 21, and gate electrode 23G formed on gate insulating film 24.
The electronic element 1 illustrated in FIG. 4B also includes a TFT 20 having a coplanar structure, and the TFT 20 includes a gate electrode 23G formed on the insulating layer 3 and a gate insulation formed on the gate electrode 23G. A film 24; a semiconductor layer 21 formed on the gate insulating film 24; a source electrode 22S and a drain electrode 22D formed on the semiconductor layer 21; and a protective film 25 formed on the semiconductor layer 21. ing.

  In this invention, an insulating layer contains a polyimide, Preferably it has a polyimide as a main component. Therefore, an insulating layer having excellent insulating properties, heat resistance, and dimensional stability can be obtained.

In general, polyimide has water absorption. Since many semiconductor materials used in electronic devices such as TFTs and organic EL devices are vulnerable to moisture, in order to reduce the moisture inside the device and achieve high reliability in the presence of moisture, the insulating layer is water-absorbing. It needs to be small. One index of water absorption is the hygroscopic expansion coefficient. The smaller the hygroscopic expansion coefficient, the smaller the water absorption. Therefore, the hygroscopic expansion coefficient of the insulating layer needs to be small.
According to the present invention, since the hygroscopic expansion coefficient of the insulating layer is in a predetermined range and the water absorption is sufficiently small, it is possible to suppress deterioration of the characteristics of the element due to moisture. Also, the smaller the hygroscopic expansion coefficient, the better the dimensional stability. If the hygroscopic expansion coefficient of the insulating layer is large, the difference between the expansion coefficient and the metal base material, which has almost zero hygroscopic expansion coefficient, causes the electronic element to warp as the humidity increases, and the adhesion between the insulating layer and the metal base material decreases. There is a case to do. Therefore, according to the present invention, it is possible to shorten the lifetime and suppress element destruction. Even when a wet process is performed in the manufacturing process, it is important that the hygroscopic expansion coefficient is small. Moreover, if the hygroscopic expansion coefficient of the insulating layer is in the above range, the water absorption of the insulating layer can be sufficiently reduced, and the manufacturing process of the electronic element is simplified.

  Further, according to the present invention, since the insulating layer is formed on the metal substrate, when the metal substrate surface has irregularities due to rolling streaks or the like, the irregularities on the metal substrate surface can be flattened. it can. Therefore, when the electronic element portion is a TFT, it is possible to prevent a decrease in the electrical performance of the TFT due to the unevenness. Moreover, when an electronic element part is an organic EL element, while being able to prevent the short circuit between the electrodes by an unevenness | corrugation, generation | occurrence | production of the brightness nonuniformity by an unevenness | corrugation can be suppressed.

  In addition, since the electronic device of the present invention has a metal substrate, it can reduce the permeation of moisture and oxygen. Therefore, deterioration of the element due to moisture or oxygen can be suppressed. Furthermore, since a metal base material is generally excellent in thermal conductivity, heat dissipation can be imparted. Therefore, when the electronic element unit is an element that generates heat when driving an organic EL element or the like, heat at the time of driving the element can be released through the metal substrate. In particular, when the electronic element portion is an organic EL element, it is possible to suppress degradation of the EL layer due to heat generated during light emission of the organic EL element, resulting in uneven brightness and shortening of the element lifetime. Moreover, since the electronic element of this invention has a metal base material, intensity | strength can be raised and durability can be improved.

  Hereinafter, each structure of the electronic device of this invention is demonstrated.

1. Insulating layer The insulating layer in the present invention is formed on a metal substrate, contains polyimide, and has a hygroscopic expansion coefficient in the range of 0 ppm /% RH to 15 ppm /% RH.

  As described above, the hygroscopic expansion coefficient of the insulating layer needs to be small. Specifically, the hygroscopic expansion coefficient is in the range of 0 ppm /% RH to 15 ppm /% RH, preferably in the range of 0 ppm /% RH to 12 ppm /% RH, and more preferably 0 ppm /% RH to 10 ppm /%. It is within the range of RH.

The hygroscopic expansion coefficient is measured as follows. First, a film having only an insulating layer is produced. The method for producing the insulating layer film is as follows. The insulating layer film is prepared on a heat-resistant film (Upilex S 50S (manufactured by Ube Industries)) or a glass substrate, and then the insulating layer film is peeled off or the insulating layer is formed on the metal substrate. There is a method of obtaining an insulating layer film by etching a metal after producing a film. Next, the obtained insulating layer film is cut into a width of 5 mm and a length of 20 mm to obtain an evaluation sample. The hygroscopic expansion coefficient is measured by a humidity variable mechanical analyzer (Thermo Plus TMA8310 (manufactured by Rigaku Corporation)). For example, the temperature is kept constant at 25 ° C., the humidity is first set to a stable state in an environment of 15% RH, the state is maintained for about 30 minutes to 2 hours, and the humidity of the measurement site is set to 20%. RH and hold for 30 minutes to 2 hours until the sample is stable. Thereafter, the humidity is changed to 50% RH, and the difference between the sample length when the humidity becomes stable and the sample length when the humidity becomes stable at 20% RH is expressed as a change in humidity (in this case, 50-20). 30) and the value divided by the sample length is the hygroscopic expansion coefficient (CHE). At the time of measurement, the tensile weight is set to 1 g / 25000 μm ² so that the weight per cross-sectional area of the evaluation sample becomes the same.

Further, the linear thermal expansion coefficient of the insulating layer is preferably 15 ppm / ° C. or less, more preferably 10 ppm / ° C. or less, more preferably from the viewpoint of dimensional stability. Is 5 ppm / ° C. or less. The closer the linear thermal expansion coefficient between the insulating layer and the metal substrate, the more the warpage is suppressed, and when the thermal environment of the electronic element changes, the stress at the interface between the insulating layer and the metal substrate decreases, and the adhesion Will improve. In addition, it is preferable that the electronic device of the present invention does not warp in a temperature environment in the range of 0 ° C. to 100 ° C. for handling, but since the insulating layer has a large linear thermal expansion coefficient, If the linear thermal expansion coefficients of the materials differ greatly, the electronic element will warp due to changes in the thermal environment.
It should be noted that no warpage occurs in the electronic element when the electronic element is cut into a strip shape having a width of 10 mm and a length of 50 mm, and one short side of the obtained sample is fixed on a horizontal and smooth table. The floating distance from the surface of the other short side of the sample is 1.0 mm or less.

  Furthermore, it is preferable that the linear thermal expansion coefficient of the insulating layer is appropriately selected according to the type of the electronic element portion formed on the insulating layer. For example, when the electronic element portion is a TFT, it is preferable that the linear thermal expansion coefficient of the insulating layer is relatively small from the linear thermal expansion coefficient of the semiconductor layer constituting the TFT. For example, when the electronic element portion is an organic EL element, it is preferable that the linear thermal expansion coefficient of the insulating layer is relatively small from the linear thermal expansion coefficient of the electrodes constituting the organic EL element.

  Specifically, the linear thermal expansion coefficient of the insulating layer is preferably in the range of 0 ppm / ° C. to 30 ppm / ° C., more preferably in the range of 0 ppm / ° C. to 25 ppm / ° C., from the viewpoint of dimensional stability. More preferably, it is in the range of 0 ppm / ° C. to 18 ppm / ° C., particularly preferably in the range of 0 ppm / ° C. to 12 ppm / ° C. Especially, when an electronic element part is TFT, it is most preferable to be in the range of 0 ppm / ° C. to 7 ppm / ° C. Moreover, when an electronic element part is an organic EL element, it is most preferable that it is about 0 ppm / degrees C-10 ppm / degrees C.

The linear thermal expansion coefficient is measured as follows. First, a film having only an insulating layer is produced. The method for producing the insulating layer film is as described above. Next, the obtained insulating layer is cut into a width of 5 mm and a length of 20 mm to obtain an evaluation sample. The linear thermal expansion coefficient is measured by a thermomechanical analyzer (for example, Thermo Plus TMA8310 (manufactured by Rigaku Corporation)). The measurement conditions were a heating rate of 10 ° C./min, a tensile load of 1 g / 25,000 μm ² so that the weight per cross-sectional area of the evaluation sample was the same, and an average linear thermal expansion within a range of 100 ° C. to 200 ° C. The coefficient is the linear thermal expansion coefficient (CTE).

The insulating layer has an insulating property. Specifically, the volume resistance of the insulating layer is preferably 1.0 × 10 ⁹ Ω · m or more, more preferably 1.0 × 10 ¹⁰ Ω · m or more, and 1.0 × 10 ^11. More preferably, it is Ω · m or more.
The volume resistance can be measured by a method based on standards such as JIS K6911, JIS C2318, and ASTM D257.

  The surface roughness Ra of the insulating layer is preferably smaller than the surface roughness Ra of the metal substrate. Specifically, the surface roughness Ra of the insulating layer is preferably 25 nm or less, and more preferably 10 nm or less. This is because if the surface roughness Ra of the insulating layer is too large, when the electronic element portion is a TFT, the electrical performance of the TFT may be deteriorated by unevenness. In addition, if the surface roughness Ra of the insulating layer is too large, when the electronic element portion is an organic EL element, there is a risk that a short circuit may occur between the electrodes due to the unevenness or luminance unevenness may occur.

  The surface roughness Ra is a value measured using an atomic force microscope (AFM) or a scanning white interferometer. For example, when measuring using AFM, using Nanoscope V multimode (Veeco), in tapping mode, cantilever: MPP11100, scanning range: 50 μm × 50 μm, scanning speed: 0.5 Hz, surface shape Ra can be obtained by taking an image and calculating an average deviation from the center line of the roughness curve calculated from the obtained image. Further, when measuring using a scanning white interferometer, using New View 5000 (manufactured by Zygo), objective lens: 100 times, zoom lens: 2 times, Scan Length: 15 μm, 50 μm × 50 μm Ra can be obtained by imaging the surface shape of the range and calculating the average deviation from the center line of the roughness curve calculated from the obtained image.

  The polyimide constituting the insulating layer is not particularly limited as long as it satisfies the above characteristics. For example, it is possible to control the hygroscopic expansion coefficient and the linear thermal expansion coefficient by appropriately selecting the structure of polyimide.

  The polyimide is preferably a polyimide containing an aromatic skeleton from the viewpoint of making the hygroscopic expansion coefficient of the insulating layer within a predetermined range and making the linear thermal expansion coefficient of the insulating layer suitable for the electronic device of the present invention. Among polyimides, the polyimide containing an aromatic skeleton is derived from the rigid and highly planar skeleton, and is excellent in heat resistance, insulation in a thin film, and has a low linear thermal expansion coefficient. The insulating layer is preferably used.

  A general polyimide has a repeating unit represented by the following formula (1).

(In formula (1), R ¹ is a tetravalent organic group, R ² is a divalent organic group, and R ¹ and R ² that are repeated may be the same or different. n is a natural number of 1 or more.)
In the formula (1), R ¹ is generally a structure derived from tetracarboxylic dianhydride, and R ² is a structure derived from diamine.

  Since the polyimide used in the present invention needs to have a hygroscopic expansion coefficient in the range of 0 ppm /% RH to 15 ppm /% RH, it is desirable to have a skeleton exhibiting low hygroscopicity. Since the hygroscopic property of polyimide is caused by the structure of tetracarboxylic dianhydride as a raw material and the structure of diamine, in order to make the hygroscopic expansion coefficient within the range of 0 ppm /% RH to 15 ppm /% RH, It is desirable to use acid dianhydride or diamine having a structure that reduces hygroscopicity. In order to further reduce the hygroscopicity of polyimide, it is desirable to use acid dianhydrides and diamines having a structure that reduces the hygroscopicity of polyimide. However, by using an acid dianhydride having particularly low hygroscopicity, the hygroscopic expansion coefficient can be in the range of 0 ppm /% RH to 15 ppm /% RH even when a diamine that is not low in hygroscopicity is selected. In particular, when a diamine having a low hygroscopic property is used, the hygroscopic expansion coefficient can be set within the range of 0 ppm /% RH to 15 ppm /% RH even if an acid dianhydride that is not low hygroscopic is selected.

Examples of tetracarboxylic dianhydrides applicable to polyimide include ethylene tetracarboxylic dianhydride, butane tetracarboxylic dianhydride, cyclobutane tetracarboxylic dianhydride, cyclopentane tetracarboxylic dianhydride, pyro Merit acid dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 2,2 ′, 3,3′-benzophenone tetracarboxylic dianhydride, 3,3 ′, 4,4 '-Biphenyltetracarboxylic dianhydride, 2,2', 3,3'-biphenyltetracarboxylic dianhydride, 2,2 ', 6,6'-biphenyltetracarboxylic dianhydride, 2,2- Bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane dianhydride, bis (3,4-dicarboxyphenyl) Ether dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, bis (2,3-dicarboxyphenyl) methane Dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane Anhydride, 2,2-bis (2,3-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride, 1,3-bis [(3,4-dicarboxy ) Benzoyl] benzene dianhydride, 1,4-bis [(3,4-dicarboxy) benzoyl] benzene dianhydride, 2,2-bis {4- [4- (1,2-dicarboxy) phenoxy] Phenyl} propane dianhydride, 2 2-bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} propane dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride, Bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride, 4,4′-bis [4- (1,2-dicarboxy) phenoxy] biphenyl dianhydride, 4, 4′-bis [3- (1,2-dicarboxy) phenoxy] biphenyl dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride, bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} sulfone dianhydride, bis {4- [3 -(1,2-dicarboxy) Phenoxy] phenyl} sulfone dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} sulfide dianhydride, bis {4- [3- (1,2-dicarboxy) phenoxy] Phenyl} sulfide dianhydride, 2,2-bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} -1,1,1,3,3,3-hexafluoropropane dianhydride, 2,2-bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} -1,1,1,3,3,3-propane dianhydride, 2,3,6,7-naphthalene Tetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,2,3,4-benzenetetracarboxylic Acid dianhydride, 3,4,9,1 -Perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,2,7,8-phenanthrenetetracarboxylic dianhydride, 9,9-bis- (tri Fluoromethyl) xanthenetetracarboxylic dianhydride, 9-phenyl-9- (trifluoromethyl) xanthenetetracarboxylic dianhydride, 12,14-diphenyl-12,14-bis (trifluoromethyl) -12H, 14H -5,7-dioxapentacene-2,3,9,10-tetracarboxylic dianhydride, 1,4-bis (3,4-dicarboxytrifluorophenoxy) tetrafluorobenzene dianhydride, 1,4 -Bis (trifluoromethyl) -2,3,5,6-benzenetetracarboxylic dianhydride, 1- (trifluoromethyl) -2,3,5,6-benzenetetra Examples thereof include tracarboxylic dianhydride, p-phenylenebistrimellitic acid monoester dianhydride, p-biphenylenebistrimellitic acid monoester dianhydride, and the like.
These may be used alone or in combination of two or more.

  As a structure of the acid dianhydride which makes polyimide low moisture absorption, what is represented by following formula (6) is mentioned.

(In Formula (6), a is a natural number of 0 or 1 or more, A is any one of a single bond (biphenyl structure), an oxygen atom (ether bond), and an ester bond. (The acid anhydride skeleton (—CO—O—CO—) is bonded to the 2, 3 or 3, 4 position of the aromatic ring as viewed from the bonding site of the adjacent aromatic ring.)
In the above formula (6), as the acid dianhydride in which A is a single bond (biphenyl structure) or an oxygen atom (ether bond), 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2 , 3,3 ′, 4′-biphenyltetracarboxylic dianhydride, 2,3,2 ′, 3′-biphenyltetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, etc. Is mentioned. These are preferable from the viewpoint of reducing the hygroscopic expansion coefficient and from the viewpoint of expanding the selectivity of the diamine.

  In the above formula (6), a phenyl ester acid dianhydride in which A is an ester bond is particularly preferable from the viewpoint of reducing moisture absorption of the polyimide. For example, an acid dianhydride represented by the following formula may be mentioned. Specific examples include p-phenylenebistrimellitic acid monoester dianhydride, p-biphenylenebistrimellitic acid monoester dianhydride, and the like. These are particularly preferable from the viewpoint of reducing the hygroscopic expansion coefficient and from the viewpoint of expanding the selectivity of the diamine.

(Wherein, a is a natural number of 0 or 1 or more. The acid anhydride skeleton (—CO—O—CO—) is a 2, 3-position or 3 of the aromatic ring as viewed from the bonding site of the adjacent aromatic ring. , Binds to position 4.)
In the case of the tetracarboxylic dianhydride having a small hygroscopic expansion coefficient as described above, a wide variety of diamines to be described later can be selected.

  As the tetracarboxylic dianhydride used in combination, a tetracarboxylic dianhydride having at least one fluorine atom as represented by the following formula can be used. When tetracarboxylic dianhydride into which fluorine is introduced is used, the hygroscopic expansion coefficient of polyimide is lowered. The tetracarboxylic dianhydride having at least one fluorine atom preferably has a fluoro group, a trifluoromethyl group, or a trifluoromethoxy group. Specific examples include 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride. However, a polyimide precursor having a fluorine-containing skeleton tends to be difficult to dissolve in a basic aqueous solution. When patterning using a resist or the like in the polyimide precursor state, an organic solvent such as alcohol is used. It may be necessary to perform development with a mixed solution of a solvent and a basic aqueous solution.

The tetracarboxylic dianhydride preferably used from the viewpoint of the heat resistance of polyimide, the coefficient of linear thermal expansion, etc. is an aromatic tetracarboxylic dianhydride. Particularly preferably used tetracarboxylic dianhydrides include pyromellitic dianhydride, merophanic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 3,3 ′, 4. , 4′-biphenyltetracarboxylic dianhydride, 2,3,3 ′, 4′-biphenyltetracarboxylic dianhydride, 2,3,2 ′, 3′-biphenyltetracarboxylic dianhydride, 2, 2 ′, 6,6′-biphenyltetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -1,1, 1,3,3,3-hexafluoropropane dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, p-phenylenebistrimellitic acid monoester dianhydride, p-biphenylenebistrimelli Dianhydride preparative acid monoester acid.
Pyromellitic dianhydride, merophanic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,3,3 ′, 4′-biphenyltetracarboxylic dianhydride, 2 , 3,2 ′, 3′-biphenyltetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride and other rigid tetracarboxylic dianhydrides, the linear heat of polyimide This is particularly preferable because the expansion coefficient is small. Among these, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 2,3,3 ′, 4′-biphenyltetracarboxylic acid are used from the viewpoint of the balance between the linear thermal expansion coefficient and the hygroscopic expansion coefficient. Particularly preferred are dianhydride, 2,3,2 ′, 3′-biphenyltetracarboxylic dianhydride, p-phenylenebistrimellitic acid monoester dianhydride, p-biphenylenebistrimellitic acid monoester dianhydride. .

  Moreover, when it has an alicyclic skeleton as tetracarboxylic dianhydride, since the transparency of a polyimide precursor improves, it becomes a highly sensitive photosensitive polyimide precursor. On the other hand, the heat resistance and insulation of polyimide tend to be inferior compared to aromatic polyimide.

When an aromatic tetracarboxylic dianhydride is used, there is a merit that it becomes a polyimide having excellent heat resistance and a low linear thermal expansion coefficient. Therefore, in the polyimide, it is preferable that 33 mol% or more of R ¹ in the formula (1) has any structure represented by the following formula.

(In the formula (2), a is a natural number of 0 or 1 or more, A is a single bond (biphenyl structure), an oxygen atom (ether bond), or an ester bond. The linking group is bonded to the 2, 3 or 3 or 4 position of the aromatic ring as viewed from the bonding site of the aromatic ring.) The structure represented by the above formula (2) is It is a structure derived from an acid dianhydride represented by (6).
Especially, when a polyimide contains the structure represented by the said Formula (2), a low hygroscopic expansion is shown. Furthermore, there is also an advantage that it is easily available on the market and is low cost.

The polyimide having the structure as described above is a polyimide that exhibits high heat resistance and a low linear thermal expansion coefficient. Therefore, the content of the structure represented by the above formula is preferably closer to 100 mol% of R ^{1 in} the above formula (1), but at least 33% of R ^{1 in} the above formula (1) is contained. do it. Among them, the content of the structure represented by the above formula is preferably 50 mol% or more, and more preferably 70 mol% or more of R ^{1 in} the above formula (1).

On the other hand, a diamine component applicable to polyimide can also be used alone or in combination of two or more diamines. The diamine component used is not particularly limited, and examples thereof include p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 3,3′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4 ′. -Diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 4, , 4′-diaminodiphenylsulfone, 3,3′-diaminobenzophenone, 4,4′-diaminobenzophenone, 3,4′-diaminobenzophenone, 3,3′-diaminodiphenylmethane, 4,4′-diaminodiphenylmethane, 3, 4'-diaminodiphenyl meta 2,2-di (3-aminophenyl) propane, 2,2-di (4-aminophenyl) propane, 2- (3-aminophenyl) -2- (4-aminophenyl) propane, 2,2- Di (3-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 2,2-di (4-aminophenyl) -1,1,1,3,3,3-hexafluoro Propane, 2- (3-aminophenyl) -2- (4-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 1,1-di (3-aminophenyl) -1- Phenylethane, 1,1-di (4-aminophenyl) -1-phenylethane, 1- (3-aminophenyl) -1- (4-aminophenyl) -1-phenylethane, 1,3-bis (3 -Aminophenoxy) benzene, 1,3-bis (4 Aminophenoxy) benzene, 1,4-bis (3-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminobenzoyl) benzene, 1,3-bis ( 4-aminobenzoyl) benzene, 1,4-bis (3-aminobenzoyl) benzene, 1,4-bis (4-aminobenzoyl) benzene, 1,3-bis (3-amino-α, α-dimethylbenzyl) Benzene, 1,3-bis (4-amino-α, α-dimethylbenzyl) benzene, 1,4-bis (3-amino-α, α-dimethylbenzyl) benzene, 1,4-bis (4-amino-) α, α-dimethylbenzyl) benzene, 1,3-bis (3-amino-α, α-ditrifluoromethylbenzyl) benzene, 1,3-bis (4-amino-α, α-ditrifluoro) Methylbenzyl) benzene, 1,4-bis (3-amino-α, α-ditrifluoromethylbenzyl) benzene, 1,4-bis (4-amino-α, α-ditrifluoromethylbenzyl) benzene, 2,6 -Bis (3-aminophenoxy) benzonitrile, 2,6-bis (3-aminophenoxy) pyridine, 4,4'-bis (3-aminophenoxy) biphenyl, 4,4'-bis (4-aminophenoxy) Biphenyl, bis [4- (3-aminophenoxy) phenyl] ketone, bis [4- (4-aminophenoxy) phenyl] ketone, bis [4- (3-aminophenoxy) phenyl] sulfide, bis [4- (4 -Aminophenoxy) phenyl] sulfide, bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (4-aminophenoxy) Cis) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-aminophenoxy) phenyl] ether, 2,2-bis [4- (3-aminophenoxy) phenyl] Propane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [3- (3-aminophenoxy) phenyl] -1,1,1,3,3,3-hexa Fluoropropane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 1,3-bis [4- (3-aminophenoxy) Benzoyl] benzene, 1,3-bis [4- (4-aminophenoxy) benzoyl] benzene, 1,4-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,4-bis [ -(4-aminophenoxy) benzoyl] benzene, 1,3-bis [4- (3-aminophenoxy) -α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-aminophenoxy)- α, α-dimethylbenzyl] benzene, 1,4-bis [4- (3-aminophenoxy) -α, α-dimethylbenzyl] benzene, 1,4-bis [4- (4-aminophenoxy) -α, α-dimethylbenzyl] benzene, 4,4′-bis [4- (4-aminophenoxy) benzoyl] diphenyl ether, 4,4′-bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy] benzophenone 4,4′-bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy] diphenylsulfone, 4,4′-bis [4- (4-aminophenoxy) phenoxy Diphenylsulfone, 3,3′-diamino-4,4′-diphenoxybenzophenone, 3,3′-diamino-4,4′-dibiphenoxybenzophenone, 3,3′-diamino-4-phenoxybenzophenone, 3,3 '-Diamino-4-biphenoxybenzophenone, 6,6'-bis (3-aminophenoxy) -3,3,3', 3'-tetramethyl-1,1'-spirobiindane, 6,6'-bis ( 4-aminophenoxy) -3,3,3 ′, 3′-tetramethyl-1,1′-spirobiindane, 1,3-bis (3-aminopropyl) tetramethyldisiloxane, 1,3-bis (4- Aminobutyl) tetramethyldisiloxane, α, ω-bis (3-aminopropyl) polydimethylsiloxane, α, ω-bis (3-aminobutyl) polydimethylsiloxane, bis (amino) Methyl) ether, bis (2-aminoethyl) ether, bis (3-aminopropyl) ether, bis (2-aminomethoxy) ethyl] ether, bis [2- (2-aminoethoxy) ethyl] ether, bis [2 -(3-aminoprotoxy) ethyl] ether, 1,2-bis (aminomethoxy) ethane, 1,2-bis (2-aminoethoxy) ethane, 1,2-bis [2- (aminomethoxy) ethoxy] Ethane, 1,2-bis [2- (2-aminoethoxy) ethoxy] ethane, ethylene glycol bis (3-aminopropyl) ether, diethylene glycol bis (3-aminopropyl) ether, triethylene glycol bis (3-aminopropyl) ) Ether, ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1 5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 1,11-diaminoundecane, 1,12- Diaminododecane, 1,2-diaminocyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, 1,2-di (2-aminoethyl) cyclohexane, 1,3-di (2-aminoethyl) cyclohexane, 1,4-di (2-aminoethyl) cyclohexane, bis (4-aminocyclohexyl) methane, 2,6-bis (aminomethyl) bicyclo [2.2.1] heptane, 2,5-bis (amino) Methyl) bicyclo [2.2.1] heptane. In addition, a diamine obtained by substituting some or all of the hydrogen atoms on the aromatic ring of the diamine with a substituent selected from a fluoro group, a methyl group, a methoxy group, a trifluoromethyl group, or a trifluoromethoxy group may be used. it can.
Furthermore, depending on the purpose, any one or two or more of the ethynyl group, benzocyclobuten-4′-yl group, vinyl group, allyl group, cyano group, isocyanate group, and isopropenyl group serving as a crosslinking point, Even if it introduce | transduces into some or all of the hydrogen atoms on the aromatic ring of diamine as a substituent, it can be used.

  Examples of the diamine structure that makes polyimide low in moisture absorption include those represented by the following formulas (3) and (4).

(In Formula (4), a is a natural number of 0 or 1 or more, and the amino group is bonded to the meta position or the para position with respect to the bond between benzene rings. In addition, some or all of the hydrogen atoms on the aromatic ring May be substituted with a substituent selected from a fluoro group, a methyl group, a methoxy group, a trifluoromethyl group, or a trifluoromethoxy group.)
The diamine represented by the above formulas (3) and (4) is preferable from the viewpoint of making the polyimide low moisture absorption. Specifically, p-phenylenediamine, m-phenylenediamine, 2,2′-dimethyl-4,4′-diaminobiphenyl, 2,2′-ditrifluoromethyl-4,4′-diaminobiphenyl, 3,3 Examples include '-dichloro-4,4'-diaminobiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, and the like. These are preferable from the viewpoint of reducing the hygroscopic expansion coefficient and from the viewpoint of expanding the selectivity of the acid dianhydride.

  The diamine represented by the above formula (4) having a biphenyl structure in the molecule is more preferable from the viewpoint of reducing the moisture absorption of the polyimide. Specifically, 2,2′-dimethyl-4,4′-diaminobiphenyl, 2,2′-ditrifluoromethyl-4,4′-diaminobiphenyl, 3,3′-dichloro-4,4′-diamino Biphenyl, 3,3′-dimethoxy-4,4′-diaminobiphenyl, 3,3′-dimethyl-4,4′-diaminobiphenyl and the like can be mentioned. These are more preferable from the viewpoint of reducing the hygroscopic expansion coefficient and from the viewpoint of expanding the selectivity of the acid dianhydride.

  In addition, when fluorine is introduced as a substituent of the aromatic ring, the hygroscopic expansion coefficient can be reduced. For example, examples of the structure in which fluorine is introduced in the diamine represented by the above formula (4) include those represented by the following formula. However, polyimide precursors containing fluorine, particularly polyamic acid, are difficult to dissolve in a basic aqueous solution. When an insulating layer is partially formed on a metal substrate, alcohol or the like may be used during processing of the insulating layer. It may be necessary to develop with a mixed solution with an organic solvent.

The diamine can be selected depending on the desired physical properties. If a rigid diamine such as p-phenylenediamine is used, the polyimide has a low expansion coefficient. Rigid diamines include p-phenylenediamine, m-phenylenediamine, 1,4-diaminonaphthalene, 1,5-diaminonaphthalene, 2, 6 as diamines in which two amino groups are bonded to the same aromatic ring. -Diaminonaphthalene, 2,7-diaminonaphthalene, 1,4-diaminoanthracene and the like can be mentioned.
In addition, diamines in which two or more aromatic rings are bonded by a single bond, and two or more amino groups are each bonded directly or as part of a substituent on a separate aromatic ring, for example, There exists what is represented by the said Formula (4). Specific examples include benzidine and the like.

  Furthermore, in the above formula (4), it is also possible to use a diamine having a substituent at a position where the amino group on the benzene ring is not substituted without being involved in the bond with another benzene ring. These substituents are monovalent organic groups, but they may be bonded to each other. Specific examples include 2,2′-dimethyl-4,4′-diaminobiphenyl, 2,2′-ditrifluoromethyl-4,4′-diaminobiphenyl, 3,3′-dichloro-4,4′-diamino. Biphenyl, 3,3′-dimethoxy-4,4′-diaminobiphenyl, 3,3′-dimethyl-4,4′-diaminobiphenyl and the like can be mentioned.

  On the other hand, when a diamine having a siloxane skeleton such as 1,3-bis (3-aminopropyl) tetramethyldisiloxane is used as the diamine, the adhesion with the metal substrate is improved or the elastic modulus of the polyimide is lowered. The glass transition temperature can be lowered.

  Here, the selected diamine is preferably an aromatic diamine from the viewpoint of heat resistance. However, depending on the desired physical properties, the diamine may be an aliphatic diamine or siloxane within a range not exceeding 60 mol%, preferably not exceeding 40 mol%. Non-aromatic diamines such as diamines may be used.

Moreover, in polyimide, it is preferable that 33 mol% or more of R ² in the formula (1) has any structure represented by the following formula.

(R ³ is a divalent organic group, an oxygen atom, a sulfur atom, or a sulfone group, and R ⁴ and R ⁵ are a monovalent organic group or a halogen atom.)
When polyimide contains any structure of the above formula, it is derived from these rigid skeletons and exhibits low linear thermal expansion and low hygroscopic expansion. Furthermore, there is also an advantage that it is easily available on the market and is low cost.
When it has the above structure, the heat resistance of a polyimide improves and a linear thermal expansion coefficient becomes small. Therefore, the closer to 100 mol% of R ^{2 in} the above formula (1), the better, but it is sufficient to contain at least 33% or more of R ^{2 in} the above formula (1). Among them, the content of the structure represented by the above formula is preferably 50 mol% or more, more preferably 70 mol% or more, of R ^{2 in} the above formula (1).

In the polyimide, preferred combinations of R ¹ (acid dianhydride) and R ² (diamine) in the above formula (1) include the following combinations (i) to (iii).
(I) When R ¹ is a structure represented by the following formula (2) and A is an ester bond, (ii) R ¹ is a structure represented by the following formula (2), and A is a single bond (Biphenyl structure), oxygen atom (ether bond), or ester bond, all may be the same or different (except when all are ester bonds), and R ² is When it is a structure represented by Formula (3) or (4), it is a case where (iii) R < ² > is a structure represented by following formula (4). Note that the symbols in each formula are as described above.

In the case of the above (ii), it is preferable that 50 mol% or more of R ^{2 in} the above formula (1) is any structure represented by the above formulas (3) and (4). Moreover, in the case of said (iii), it is preferable that 50 mol% or more is a structure represented by said Formula (4) among R < ² > in said Formula (1).

Generally, the linear thermal expansion coefficient of a metal substrate, that is, the linear thermal expansion coefficient of a metal is determined to some extent. It is preferable to select the structure appropriately.
Further, when the electronic element portion is a TFT, the linear thermal expansion coefficient of the metal substrate is determined according to the linear thermal expansion coefficient of the TFT, and the insulating layer wire is determined according to the linear thermal expansion coefficient of the metal substrate. It is preferable to determine the thermal expansion coefficient and select the polyimide structure as appropriate. Similarly, when the electronic element portion is an organic EL element, the linear thermal expansion coefficient of the metal base is determined according to the linear thermal expansion coefficient of the organic EL element, and the linear thermal expansion coefficient of the metal base is determined. It is preferable to determine the linear thermal expansion coefficient of the insulating layer and select the polyimide structure as appropriate.

  In this invention, the insulating layer should just contain the above-mentioned polyimide, and as needed, you may laminate | stack or combine this polyimide and another polyimide, and may use it as an insulating layer.

  The polyimide described above may be obtained using a photosensitive polyimide or a photosensitive polyimide precursor. The photosensitive polyimide can be obtained using a known method. For example, an ethylenic double bond may be introduced into the carboxyl group of polyamic acid by an ester bond or an ionic bond, and a photoradical initiator may be mixed into the resulting polyimide precursor to form a solvent-developed negative photosensitive polyimide precursor. it can. In addition, for example, a naphthoquinone diazide compound is added to polyamic acid or a partially esterified product thereof to obtain an alkali developing positive photosensitive polyimide precursor, or an nifedipine compound is added to polyamic acid to form an alkali developing negative photosensitive polyimide precursor. For example, a photobase generator can be added to the polyamic acid to obtain an alkali development negative photosensitive polyimide precursor.

  In these photosensitive polyimide precursors, 15% to 35% of a photosensitizing component is added to the weight of the polyimide component. Therefore, even if it heats at 300 to 400 degreeC after pattern formation, the residue derived from a photosensitivity provision component remains in a polyimide. Because these residual materials cause the linear thermal expansion coefficient and hygroscopic expansion coefficient to increase, the reliability of the device is greater when using a photosensitive polyimide precursor than when using a non-photosensitive polyimide precursor. Tend to decrease. However, a photosensitive polyimide precursor obtained by adding a photobase generator to polyamic acid can form a pattern even if the amount of photobase generator added as an additive is 15% or less. Since there are few decomposition | disassembly residues derived from an additive, there is little deterioration of characteristics, such as a linear thermal expansion coefficient and a hygroscopic expansion coefficient, and also there is little outgas, it is the most preferable as a photosensitive polyimide precursor applicable to this invention.

  The polyimide precursor used for polyimide can be developed with a basic aqueous solution, from the viewpoint of ensuring the safety of the work environment and reducing process costs when partially forming the insulating layer on the metal substrate. preferable. Since the basic aqueous solution can be obtained at a low cost and the waste liquid treatment cost and the facility cost for ensuring work safety are low, production at a lower cost is possible.

The insulating layer is not particularly limited as long as it contains polyimide, but among them, polyimide is the main component. By using polyimide as a main component, an insulating layer having excellent insulation and heat resistance can be obtained. In addition, by using polyimide as a main component, the insulating layer can be thinned, the thermal conductivity of the insulating layer is improved, and the thermal conductivity can be improved.
In addition, that an insulating layer has a polyimide as a main component means that an insulating layer contains a polyimide to the extent which satisfies the above-mentioned characteristic. Specifically, the content of the polyimide in the insulating layer is 75% by mass or more, preferably 90% by mass or more, and it is particularly preferable that the insulating layer is made of only polyimide. If the content of the polyimide in the insulating layer is in the above range, it is possible to exhibit sufficient characteristics to achieve the object of the present invention, and the higher the content of polyimide, the heat resistance and insulation inherent to the polyimide. The characteristics such as property are improved.

  The insulating layer may contain additives such as a leveling agent, a plasticizer, a surfactant, and an antifoaming agent as necessary.

  The insulating layer may be formed on the entire surface of the metal substrate, or may be partially formed on the metal substrate. That is, the metal substrate exposed region where the insulating layer is not present and the metal substrate is exposed may be provided on the surface of the metal substrate where the insulating layer is formed. In the case where such a metal substrate exposed region is provided, when the electronic element portion is an organic EL element, the sealing member and the metal substrate can be directly adhered, and moisture to the organic EL element can be obtained. It is possible to more firmly prevent the intrusion. In addition, by selectively forming the sealing portion in the exposed area of the metal base material, it becomes possible to divide the organic EL elements in a plane or to seal them in a multi-faceted state with high productivity. There is an advantage that an element can be manufactured. In addition, the metal substrate exposed region can also be a through-hole for penetrating the insulating layer and electrically connecting to the metal substrate.

  When the insulating layer is partially formed on the metal substrate, the insulating layer 3 is formed excluding at least the outer edge portion of the metal substrate 2 as illustrated in FIGS. 5 (a) and 5 (b). It may be. 5A is a cross-sectional view taken along line AA in FIG. 5B, and in the electronic device 1 illustrated in FIGS. 5A and 5B, the metal substrate 2 and the sealing member 15 are provided. The organic EL element 10 is sealed by being bonded via the adhesive portion 16. In addition, in FIG.5 (b), the organic EL element, the sealing member, and the adhesion part are abbreviate | omitted. When the electronic element is an organic EL element, an insulating layer is formed on the entire surface of the metal substrate, and when the edge of the insulating layer is exposed, polyimide generally exhibits hygroscopicity. There is a risk that moisture may enter the element from the end face of the insulating layer. This moisture deteriorates the device performance or changes the dimensions of the insulating layer. Therefore, an insulating layer is not formed on the outer edge portion of the metal substrate, and it is preferable to reduce as much as possible the portion where the insulating layer containing polyimide is directly exposed to the outside air.

In the present invention, that the insulating layer is partially formed on the metal base means that the insulating layer is not formed on the entire surface of the metal base.
The insulating layer may be formed on the entire surface of the metal substrate except for the outer edge of the metal substrate, or may be further formed in a pattern on the metal substrate except for the outer edge of the metal substrate. Good.

  The thickness of the insulating layer is not particularly limited as long as it can satisfy the above-described characteristics, but specifically, it is preferably in the range of 0.3 μm to 100 μm, more preferably 0.5 μm to 50 μm. In the range of 1 μm to 20 μm. This is because if the thickness of the insulating layer is too thin, the insulation cannot be maintained, or it is difficult to flatten the irregularities on the surface of the metal substrate. In addition, if the insulating layer is too thick, flexibility is reduced, it becomes excessively heavy, drying during film formation becomes difficult, and the amount of material used increases, resulting in an increase in cost. . Furthermore, when the heat dissipation function is imparted to the electronic device of the present invention, if the insulating layer is thick, the thermal conductivity is lowered because polyimide has lower thermal conductivity than metal.

  The method for forming the insulating layer is not particularly limited as long as an insulating layer with good smoothness can be obtained. For example, a method of applying a polyimide solution or a polyimide precursor solution on a metal substrate, metal The method of bonding a base material and a polyimide film through an adhesive agent, and the method of thermocompression bonding a metal base material and a polyimide film can be used. Among these, a method of applying a polyimide solution or a polyimide precursor solution is preferable. This is because an insulating layer having excellent smoothness can be obtained. In particular, a method of applying a polyimide precursor solution is suitable. This is because polyimide generally has poor solubility in a solvent. In addition, polyimide having high solubility in a solvent is inferior in physical properties such as heat resistance, linear thermal expansion coefficient, and hygroscopic expansion coefficient.

The coating method is not particularly limited as long as it can obtain an insulating layer with good smoothness. For example, spin coating method, die coating method, dip coating method, bar coating method, gravure printing method, A screen printing method or the like can be used.
When applying a polyimide solution or a polyimide precursor solution, the fluidity of the film can be increased and the smoothness can be improved by heating to a temperature higher than the glass transition temperature of the polyimide or polyimide precursor after application.

  Moreover, when forming an insulating layer partially on a metal base material, the method of processing directly by the printing method, the photolithographic method, a laser etc. can be used as the formation method. As a photolithography method, for example, after forming a polyamic acid, which is a polyimide precursor, on a metal substrate, a photosensitive resin film is formed on the polyamic acid film, and a photosensitive resin film pattern is formed by a photolithography method. Then, using the pattern as a mask, after removing the polyamic acid film in the pattern opening, a method of removing the photosensitive resin film pattern and imidizing the polyamic acid; simultaneously with the formation of the photosensitive resin film pattern, A method of developing the film, and then removing the photosensitive resin film pattern and imidizing the polyamic acid; forming a photosensitive resin film pattern on the insulating layer in the state of a laminate of a metal substrate and an insulating layer; After etching the insulating layer along the pattern by wet etching or dry etching, photosensitive resin Method of removing a turn; patterning one metal substrate of a laminate in which a metal substrate, an insulating layer, and a metal substrate are laminated, etching the insulating layer using the pattern as a mask, and then removing the metal pattern Method: The method of forming the pattern of an insulating layer directly on a metal base material using photosensitive polyimide or a photosensitive polyimide precursor is mentioned. Examples of the printing method include methods using known printing techniques such as gravure printing, flexographic printing, screen printing, and ink jet method.

2. Metal base material The metal base material in this invention supports an insulating layer and an electronic element part.

  The linear thermal expansion coefficient of the metal substrate is preferably in the range of 0 ppm / ° C. to 25 ppm / ° C., more preferably in the range of 0 ppm / ° C. to 18 ppm / ° C., more preferably from the viewpoint of dimensional stability. Is in the range of 0 ppm / ° C. to 12 ppm / ° C., particularly preferably in the range of 0 ppm / ° C. to 7 ppm / ° C. In addition, about the measuring method of the said linear thermal expansion coefficient, it is the same as the measuring method of the linear thermal expansion coefficient of the said insulating layer except cut | disconnecting a metal base material to width 5mm * length 20mm and making it an evaluation sample.

  Moreover, it is preferable that a metal base material has oxidation resistance. This is because when the electronic element portion is a TFT, a high temperature treatment is usually performed when the TFT is manufactured. In particular, when the TFT has an oxide semiconductor layer, the metal substrate preferably has oxidation resistance because annealing is performed at a high temperature in the presence of oxygen.

  The metal material constituting the metal substrate is not particularly limited as long as it satisfies the above-mentioned characteristics. For example, aluminum, copper, copper alloy, phosphor bronze, stainless steel (SUS), gold, gold alloy Nickel, nickel alloy, silver, silver alloy, tin, tin alloy, titanium, iron, iron alloy, zinc, molybdenum and the like. Among these, SUS is preferable when applied to a large element. SUS is excellent in oxidation resistance and heat resistance, and has a smaller coefficient of linear thermal expansion than copper and has excellent dimensional stability. Further, SUS304 has an advantage that it is particularly easy to obtain, and SUS430 has an advantage that it is easy to obtain and the linear thermal expansion coefficient is smaller than SUS304. On the other hand, when the electronic element portion is a TFT, considering the linear thermal expansion coefficient of the metal substrate and the TFT, titanium or invar having a lower linear thermal expansion coefficient than SUS430 is preferable from the viewpoint of the linear thermal expansion coefficient. However, it is desirable to select not only the linear thermal expansion coefficient but also taking into consideration the workability of the foil and the cost due to the oxidation resistance, heat resistance, malleability and ductility of the metal substrate.

  The shape of the metal substrate is not particularly limited, and may be, for example, a foil shape or a plate shape. As illustrated in FIG. 6, the shape of the metal substrate 2 is uneven on the contact surface with air. The shape which has this may be sufficient. In particular, when the electronic element portion is the organic EL element 10 as illustrated in FIG. 6, the shape of the metal base 2 is preferably a shape having irregularities on the contact surface with air. When the metal substrate has irregularities on the contact surface with air, the thermal diffusion becomes good and the heat dissipation can be improved.

  As a method for forming irregularities, for example, a method of directly embossing, etching, sandblasting, frosting, stamping or the like on the surface of a metal substrate, or a method of forming an irregular pattern using a photoresist or the like. Can be mentioned.

  The thickness of the metal substrate is not particularly limited as long as it can satisfy the above-described characteristics, and is appropriately selected according to the type of the electronic element portion. Specifically, the thickness of the metal substrate is preferably in the range of 1 μm to 1000 μm, more preferably in the range of 1 μm to 200 μm, and still more preferably in the range of 1 μm to 100 μm. If the thickness of the metal substrate is too thin, the heat dissipation function may not be sufficiently exhibited, the gas barrier property against oxygen or water vapor may be reduced, or the strength may be reduced. Moreover, when the thickness of a metal base material is too thick, flexibility will fall, it will become heavy, and cost will become high.

  As a method for producing the metal substrate, a general method can be used, which is appropriately selected according to the type of the metal material, the thickness of the metal substrate, and the like. For example, a method of obtaining a single metal substrate or a method of obtaining a laminate of a metal substrate and an insulating layer by vapor-depositing a metal material on an insulating layer made of a polyimide film may be used. Among these, from the viewpoint of gas barrier properties, a method of obtaining a metal base material alone is preferable. In the case of a method of obtaining a metal base material alone, when the metal base material is a metal foil, the metal foil may be a rolled foil or an electrolytic foil, but because of its good gas barrier properties Rolled foil is preferred.

  The surface roughness Ra of the metal substrate is larger than the surface roughness Ra of the insulating layer, and is, for example, about 50 nm to 200 nm. The method for measuring the surface roughness is the same as the method for measuring the surface roughness of the insulating layer.

3. Electronic element part The electronic element part in this invention is formed on the said insulating layer.
The electronic element part is not particularly limited as long as it is weak against moisture, and examples thereof include organic EL elements and TFTs. Hereinafter, the description will be divided into the organic EL element and the TFT.

(1) Organic EL Element The organic EL element in the present invention is a back electrode layer formed on the insulating layer, an EL layer formed on the back electrode layer and including at least an organic light emitting layer, and the EL layer. And a transparent electrode layer formed on the substrate.
In the present invention, since the hygroscopic expansion coefficient of the insulating layer is within a predetermined range and the water absorption is sufficiently small, the deterioration of the characteristics of the organic EL element due to moisture is suppressed while maintaining the heat resistance and insulating reliability of the insulating layer. be able to. Further, heat at the time of light emission of the organic EL element can be released through the metal substrate, and it is possible to suppress deterioration of the EL layer due to the heat, resulting in uneven brightness and shortening of the element life. Furthermore, since the metal substrate has a gas barrier property against water vapor and oxygen, the device performance can be maintained well. Moreover, since it is supported by the metal base material, it can be made excellent in durability.
Hereinafter, each configuration of the organic EL element will be described.

(A) Back electrode layer The back electrode layer in this invention is formed on the said insulating layer. In the organic EL element, since light is extracted from the transparent electrode layer side, the back electrode layer may or may not have transparency.

  The material of the back electrode layer is not particularly limited as long as it is a conductive material. For example, Au, Ta, W, Pt, Ni, Pd, Cr, Cu, Mo, alkali metal, alkaline earth metal, etc. Simple metals, oxides of these metals, Al alloys such as AlLi, AlCa, AlMg, Mg alloys such as MgAg, alloys such as Ni alloys, Cr alloys, alkali metal alloys, alkaline earth metal alloys, etc. Can be mentioned. These conductive materials may be used alone, in combination of two or more kinds, or may be laminated using two or more kinds. In addition, conductive oxides such as indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide, zinc oxide, indium oxide, and aluminum zinc oxide (AZO) can also be used.

The back electrode layer may have a metal electrode formed on the insulating layer and a transparent electrode formed on the metal electrode layer. That is, the back electrode layer may be a laminate of a metal electrode and a transparent electrode. For example, an organic EL device in which a metal electrode, a transparent electrode, a hole injecting and transporting layer, an organic light emitting layer, an electron injecting and transporting layer, and a transparent electrode layer are sequentially stacked on the insulating layer can be obtained. In this case, since the back electrode layer is a laminate of a metal electrode and a transparent electrode, a conductive material having a work function of about 5.0 eV such as ITO can be used for the transparent electrode. By forming the hole injecting and transporting layer thereon, it is possible to easily transport charges. Further, the optical path length can be adjusted by controlling the thickness of the transparent electrode.
As a material of the metal electrode, the above-mentioned simple metal, oxides of these metals, alloys, and the like can be used. Moreover, as a material of the transparent electrode, the above-described conductive oxide can be used.

The back electrode layer may be formed on one surface or may be formed in a pattern. When the electronic device of the present invention is used in a lighting device, the back electrode layer is formed on one surface. When the electronic element of the present invention is used for a passive matrix organic EL display device, the back electrode layer is formed in a pattern.
The formation method and thickness of the back electrode layer can be the same as those of an electrode in a general organic EL element.

(B) EL layer The EL layer in the present invention is formed on the back electrode layer, includes an organic light emitting layer, and has one or more organic layers including at least the organic light emitting layer. That is, the EL layer is a layer including at least an organic light-emitting layer, and the layer configuration is a layer having one or more organic layers. Usually, when forming an EL layer by a coating method, it is difficult to stack a large number of layers in relation to the solvent, so the EL layer often has one or two organic layers, It is possible to further increase the number of layers by devising an organic material so that the solubility in a solvent is different or by combining a vacuum deposition method.

Examples of the layer formed in the EL layer other than the organic light emitting layer include a hole injection layer, a hole transport layer, an electron injection layer, and an electron transport layer. The hole injection layer and the hole transport layer may be integrated. Similarly, the electron injection layer and the electron transport layer may be integrated. In addition, the layer formed in the EL layer can be re-used by preventing holes or electrons from penetrating like the carrier block layer, and further preventing diffusion of excitons and confining excitons in the light emitting layer. Examples thereof include a layer for increasing the coupling efficiency.
Thus, the EL layer often has a laminated structure in which various layers are laminated, and there are many types of laminated structures.

  Each layer constituting the EL layer can be the same as that used in a general organic EL display device.

(C) Transparent electrode layer The transparent electrode layer in this invention is formed on an EL layer. In the organic EL element, since light is extracted from the transparent electrode layer side, the transparent electrode layer has transparency.

  The material for the transparent electrode layer is not particularly limited as long as it is a conductive material capable of forming a transparent electrode. For example, indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide, zinc oxide, A conductive oxide such as indium oxide or zinc aluminum oxide (AZO) can be used.

The transparent electrode layer may be formed on one surface or may be formed in a pattern. When the electronic device of the present invention is used in a lighting device, the transparent electrode layer is formed on one surface. When the electronic device of the present invention is used for a passive matrix organic EL display device, the transparent electrode layer is formed in a pattern.
The formation method and thickness of the transparent electrode layer can be the same as those of an electrode in a general organic EL element.

(2) TFT
The TFT in the present invention is formed on the insulating layer.
In the present invention, since the hygroscopic expansion coefficient of the insulating layer is within a predetermined range and the water absorption is sufficiently small, it is possible to suppress deterioration of the TFT characteristics due to moisture while maintaining the heat resistance and insulating reliability of the insulating layer. it can. In addition, since the insulating layer is formed on the metal substrate, the unevenness on the surface of the metal substrate can be flattened by the insulating layer, and the deterioration of the electrical performance of the TFT due to the unevenness can be suppressed. Furthermore, since the metal substrate has a gas barrier property against oxygen and water vapor, it is possible to suppress deterioration in device performance due to moisture and oxygen. Moreover, since it is supported by the metal base material, it can be made excellent in durability.

  Examples of the TFT structure include a top gate structure (forward stagger type), a bottom gate structure (reverse stagger type), and a coplanar type structure. In the case of the top gate structure (forward stagger type) and the bottom gate structure (reverse stagger type), a top contact structure and a bottom contact structure can be further exemplified. These structures are appropriately selected according to the type of semiconductor layer constituting the TFT.

  The semiconductor layer constituting the TFT is not particularly limited as long as it can be formed on the insulating layer. For example, silicon, an oxide semiconductor, or an organic semiconductor is used.

As the silicon, polysilicon or amorphous silicon can be used.
Examples of the oxide semiconductor include zinc oxide (ZnO), titanium oxide (TiO), magnesium zinc oxide (Mg _x Zn _1-x O), cadmium zinc oxide (Cd _x Zn _1-x O), and cadmium oxide (CdO). ), Indium oxide (In ₂ O ₃ ), gallium oxide (Ga ₂ O ₃ ), tin oxide (SnO ₂ ), magnesium oxide (MgO), tungsten oxide (WO), InGaZnO-based, InGaSnO-based, InGaZnMgO-based, InAlZnO-based InFeZnO, InGaO, ZnGaO, and InZnO can be used.
Examples of organic semiconductors include π-electron conjugated aromatic compounds, chain compounds, organic pigments, and organosilicon compounds. More specifically, pentacene, tetracene, thiophen oligomer derivatives, phenylene derivatives, phthalocyanine compounds, polyacetylene derivatives, polythiophene derivatives, cyanine dyes and the like can be mentioned.

Especially, it is preferable that a semiconductor layer is an oxide semiconductor layer which consists of the above-mentioned oxide semiconductor. Although the electrical characteristics of an oxide semiconductor change due to the influence of water and oxygen, since the metal base material has a gas barrier property against water vapor, deterioration of the characteristics of the semiconductor can be suppressed.
The method for forming the semiconductor layer and the thickness thereof can be the same as those in general.

The gate electrode, source electrode, and drain electrode constituting the TFT are not particularly limited as long as they have desired conductivity, and a conductive material generally used for TFTs can be used. Examples of such materials include Ta, Ti, Al, Zr, Cr, Nb, Hf, Mo, Au, Ag, Pt, Mo-Ta alloys, W-Mo alloys, ITO, IZO and other inorganic materials, and And organic materials having conductivity such as PEDOT / PSS.
The formation method and thickness of the gate electrode, the source electrode, and the drain electrode can be the same as those in general.

As the gate insulating film constituting the TFT, the same gate insulating film as that in a general TFT can be used. For example, silicon oxide, silicon nitride, aluminum oxide, tantalum oxide, barium strontium titanate (BST), Insulating inorganic materials such as lead zirconate titanate (PZT), acrylic resins, phenolic resins, fluorine resins, epoxy resins, cardo resins, vinyl resins, imide resins, novolac resins, etc. An insulating organic material such as an insulating organic material can be used.
The formation method and thickness of the gate insulating film can be the same as a general one.

A protective film may be formed on the TFT. The protective film is provided to protect the TFT. For example, the semiconductor layer can be prevented from being exposed to moisture or the like contained in the air. By forming the protective film, deterioration of the TFT performance with time can be reduced. For example, silicon oxide or silicon nitride is used as such a protective film.
The method for forming the protective film and the thickness thereof can be the same as those in general.

4). Adhesion layer In the present invention, an adhesion layer containing an inorganic compound may be formed between the insulating layer and the electronic element portion. By forming the adhesion layer, the adhesion between the insulating layer and the electronic element part can be improved. In addition, since the electronic element portion in the present invention is weak against moisture such as an organic EL element and a TFT as described above, an adhesion layer is formed between the insulating layer and the electronic element portion, so that the insulating layer Thus, it is possible to reduce the permeation of moisture to the electronic element portion and to avoid the influence of moisture remaining slightly in the insulating layer.
In particular, when the electronic element portion is a TFT, an adhesion layer is preferably formed. It is possible to increase the adhesion between the insulating layer and the TFT and prevent the TFT from peeling or cracking.

  The adhesion layer preferably has smoothness. The surface roughness Ra of the adhesion layer only needs to be smaller than the surface roughness Ra of the metal substrate, and is specifically preferably 25 nm or less, more preferably 10 nm or less. This is because if the surface roughness Ra of the adhesion layer is too large, the electrical performance of the TFT may be deteriorated when the electronic element portion is a TFT. The method for measuring the surface roughness is the same as the method for measuring the surface roughness of the insulating layer.

The adhesion layer preferably has heat resistance. This is because when the electronic element portion is a TFT, a high temperature treatment is usually performed when the TFT is manufactured. As the heat resistance of the adhesive layer, the 5% weight reduction temperature of the adhesive layer is preferably 300 ° C. or higher.
In addition, about the measurement of 5% weight reduction | decrease temperature, using a thermal analyzer (DTG-60 (made by Shimadzu Corp.)), atmosphere: nitrogen atmosphere, temperature range: 30 degreeC-600 degreeC, temperature increase rate: Thermogravimetric / differential heat (TG-DTA) measurement was performed at 10 ° C./min, and the temperature at which the weight of the sample decreased by 5% was defined as a 5% weight reduction temperature (° C.).

  The adhesion layer usually has an insulating property. This is because the electronic element portion is formed on the adhesion layer, and thus the adhesion layer is required to have insulating properties.

  In the case where the electronic element portion is a TFT, the adhesion layer is preferably one that prevents impurity ions contained in the insulating layer from diffusing into the semiconductor layer of the TFT. Specifically, as the ion permeability of the adhesion layer, the iron (Fe) ion concentration is preferably 0.1 ppm or less, or the sodium (Na) ion concentration is preferably 50 ppb or less. In addition, as a measuring method of the density | concentration of Fe ion and Na ion, after sampling and extracting the layer formed on the contact | adherence layer, the method of analyzing by an ion chromatography method is used.

The adhesion layer preferably has a low hygroscopic property for the purpose of reducing moisture in the element.
Further, it is desirable that the adhesion layer has a low water molecule permeability. This is because the influence of moisture remaining slightly in the insulating layer can be avoided.

  The inorganic compound constituting the adhesion layer is not particularly limited as long as it satisfies the above-described characteristics. For example, silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, aluminum nitride, aluminum oxynitride, oxidation Examples thereof include chromium and titanium oxide. These may be one type or two or more types.

The adhesion layer may be a single layer or a multilayer.
When the adhesion layer is a multilayer film, a plurality of layers made of the above-described inorganic compound may be laminated, or a layer made of the above-mentioned inorganic compound and a layer made of metal may be laminated. The metal used in this case is not particularly limited as long as an adhesion layer that satisfies the above-described characteristics can be obtained, and examples thereof include chromium, titanium, aluminum, and silicon.
When the adhesion layer is a multilayer film, the outermost layer of the adhesion layer is preferably a silicon oxide film. That is, when the electronic element portion is a TFT, it is preferable that the TFT is formed on the silicon oxide film. This is because the silicon oxide film sufficiently satisfies the above characteristics. The silicon oxide in this case is preferably SiO _x (X is in the range of 1.5 to 2.0).

  Among them, the adhesion layer is formed on the insulating layer and is selected from the group consisting of chromium, titanium, aluminum, silicon, silicon nitride, silicon oxynitride, aluminum oxide, aluminum nitride, aluminum oxynitride, chromium oxide and titanium oxide. It is preferable to have a first adhesion layer composed of at least one kind and a second adhesion layer formed on the first adhesion layer and composed of silicon oxide. This is because the adhesion between the insulating layer and the second adhesion layer can be enhanced by the first adhesion layer, and the adhesion between the insulation layer and the TFT can be enhanced by the second adhesion layer. Moreover, it is because the 2nd contact | adherence layer which consists of silicon oxides fully satisfy | fills the above-mentioned characteristic.

The thickness of the adhesion layer is not particularly limited as long as it can satisfy the above-described characteristics, but specifically, it is preferably in the range of 1 nm to 500 nm. This is because if the thickness is too thin, sufficient adhesion may not be obtained, and if the thickness is too thick, cracks may occur in the adhesion layer. Further, from the viewpoint of reducing the influence of moisture on the element, the thickness is preferably 5 nm or more in the above range. This is because if the thickness of the adhesion layer is 5 nm or more, moisture permeation from the insulating layer to the electronic element portion can be reduced.
Further, when the adhesion layer has the first adhesion layer and the second adhesion layer as described above, the thickness of the second adhesion layer is larger than that of the first adhesion layer, the first adhesion layer is relatively thin, and the second adhesion layer. Is preferably relatively thick. In this case, the thickness of the first adhesion layer is preferably in the range of 0.1 nm to 50 nm, more preferably in the range of 0.5 nm to 20 nm, and still more preferably in the range of 1 nm to 10 nm. The thickness of the second adhesion layer is preferably in the range of 10 nm to 500 nm, more preferably in the range of 50 nm to 300 nm, and still more preferably in the range of 80 nm to 120 nm. As described above, if the thickness is too thin, sufficient adhesion may not be obtained, and if the thickness is too thick, cracks may occur in the adhesion layer.

  The adhesion layer may be formed on the entire surface of the metal substrate, or may be partially formed on the metal substrate. Especially, when the insulating layer is partially formed on the metal substrate, it is preferable that the adhesion layer is also partially formed on the metal substrate in the same manner as the insulating layer. This is because if the adhesion layer containing an inorganic compound is formed directly on the metal substrate, cracks or the like may occur in the adhesion layer. That is, it is preferable that the adhesion layer and the insulating layer have the same shape.

  The method for forming the adhesion layer is not particularly limited as long as it is a method capable of forming a layer made of the above-described inorganic compound or a layer made of the above-mentioned metal. For example, DC (direct current) sputtering, RF (High frequency) magnetron sputtering method, plasma CVD (chemical vapor deposition) method, etc. can be mentioned. In particular, when a layer made of the above-described inorganic compound is formed and a layer containing aluminum or silicon is formed, it is preferable to use a reactive sputtering method. This is because a film having excellent adhesion to the insulating layer can be obtained.

5. Other Configurations In the present invention, an intermediate layer may be formed between the metal substrate and the insulating layer. For example, an intermediate layer made of an oxide film in which a metal constituting the metal substrate is oxidized may be formed between the metal substrate and the insulating layer. Thereby, the adhesiveness of a metal base material and an insulating layer can be improved. This oxide film is formed by oxidizing the metal substrate surface.
Moreover, the said oxide film may be formed also in the surface on the opposite side to the surface in which the insulating layer of the metal base material is formed.

  Moreover, when an electronic element part is an organic EL element, an insulating film, a partition, a sealing member, etc. may be formed as needed other than the above-mentioned structure.

6). Use The use of the electronic device of the present invention is appropriately selected according to the type of the electronic device portion.

In the case where the electronic element portion is an organic EL element, examples of the use include lighting devices and passive matrix organic EL display devices.
When the electronic element part is the organic EL element 10 and the back electrode layer 11, the EL layer 12, and the transparent electrode layer 13 are formed on one surface like the electronic element 1 illustrated in FIG. be able to.
Further, the electronic element 1 illustrated in FIG. 7 is formed on the metal base 2, the metal base 2, the insulating layer 3 including polyimide and having a predetermined hygroscopic expansion coefficient, and the insulating layer 3. And an organic EL element 10 (electronic element part). The organic EL element 10 includes a back electrode layer 11 formed in a stripe shape (not shown) on the insulating layer 3, an insulating film 16 that is formed so as to cover an end of the back electrode layer 11, and demarcates a pixel, A partition wall 17 formed in a stripe shape on the insulating film 16 so as to intersect with the stripe pattern of the back electrode layer 11, an EL layer 12 including at least an organic light emitting layer formed from above the partition wall 17, and the EL layer 12 And a transparent electrode layer 13 formed thereon. When the electronic element portion is an organic EL element and the back electrode layer, the EL layer, and the transparent electrode layer are formed in a pattern like this electronic element, it is applied to a passive matrix organic EL display device. Can do.

  On the other hand, when the electronic element portion is a TFT, an active matrix display device can be used as an application. Examples of the active matrix display device include an organic EL display device, electronic paper, and a reflective liquid crystal display device. In particular, it is preferably used for an organic EL display device or electronic paper. Further, when the electronic element portion is a TFT, the electronic element of the present invention can be used for a circuit such as an RFID or a sensor.

FIG. 8 is a schematic cross-sectional view showing an example of an organic EL display device including the electronic element of the present invention. An organic EL display device 30 illustrated in FIG. 8 is formed on the metal substrate 2, the insulating layer 3 that is formed on the metal substrate 2, includes polyimide, and has a predetermined hygroscopic expansion coefficient, and the insulating layer 3. An electronic device having a driving TFT 20A and a switching TFT 20B (electronic element portion), a protective film 25 formed so as to cover the driving TFT 20A and the switching TFT 20B, and a protective film 25 formed on the protective film 25, A pixel electrode 31 electrically connected to the drain electrode 22D of the driving TFT 20A through the through hole, an EL layer 32 formed on the pixel electrode 31 and including a light emitting layer, and a common formed on the EL layer 32 And an electrode 33. Each of the driving TFT 20A and the switching TFT 20B has a bottom gate / top contact structure, and includes a gate electrode 23G formed on the insulating layer 3, a gate insulating film 24 formed on the gate electrode 23G, and a gate insulating film. 24 has a semiconductor layer 21 formed on 24, a source electrode 22S and a drain electrode 22D.
The layers constituting the organic EL display device can be the same as those used in a general organic EL display device.

FIG. 9 is a schematic cross-sectional view illustrating an example of electronic paper including the electronic device of the present invention. An electronic paper 40 illustrated in FIG. 9 is formed on the metal substrate 2, the metal substrate 2, the insulating layer 3 containing polyimide and having a predetermined hygroscopic expansion coefficient, and the TFT 20 formed on the insulating layer 3. An electronic device having an (electronic device portion), a protective film 25 formed so as to cover the TFT 20, and formed on the protective film 25 and electrically connected to the drain electrode 22 </ b> D of the TFT 20 through the through hole. The pixel electrode 41 is connected, the display layer 42 is formed on the pixel electrode 41, and the common electrode 43 is formed on the display layer 42. The TFT 20 has a bottom gate / top contact structure, and includes a gate electrode 23G formed on the insulating layer 3, a gate insulating film 24 formed on the gate electrode 23G, and a semiconductor layer formed on the gate insulating film 24. 21 and a source electrode 22S and a drain electrode 22D.
As a display method of electronic paper, known ones can be applied, for example, electrophoresis method, twist ball method, powder movement method (electronic powder fluid method, charged toner type method), liquid crystal display method, thermal method. (Coloring method, light scattering method), electrodeposition method, movable film method, electrochromic method, electrowetting method, magnetophoresis method and the like.
The display layer constituting the electronic paper is appropriately selected according to the display method of the electronic paper.
Moreover, as each layer which comprises electronic paper, it can be made to be the same as that used for general electronic paper.

7). Other Embodiments Another embodiment of the electronic device according to the present invention includes a metal base, an insulating layer formed on the metal base and containing polyimide, and an electronic element portion formed on the insulating layer. The insulating layer has a surface roughness Ra of 25 nm or less, the insulating layer has a thickness of 100 nm to 30 μm, and the insulating layer has a linear thermal expansion coefficient and a linear thermal expansion coefficient of the metal substrate. The difference is 15 ppm / ° C. or less.

  Electronic devices such as organic EL devices and TFTs have low resistance to moisture, and device characteristics are degraded by moisture. As a technique for suppressing deterioration of element characteristics due to moisture, a technique for preventing moisture from entering the element from the outside, such as sealing the element with a sealing member or a sealing structure, is the mainstream. At this time, a substrate having gas barrier properties is used. As the substrate having gas barrier properties, a glass substrate, a gas barrier film, a metal foil, or the like is used. For example, Patent Document 1 proposes a substrate in which an insulating layer is formed on a metal plate or metal foil. A substrate in which an insulating layer is formed on a metal plate or metal foil has an advantage of excellent gas barrier properties and flexibility. Moreover, since it is excellent also in heat conductivity, it is suitable as a board | substrate of an organic EL element.

On the other hand, even if moisture can be prevented from entering the element from the outside, element characteristics deteriorate if moisture is present inside the element.
Polyimide can be suitably used for the insulating layer because it is excellent in heat resistance, insulation, dimensional stability, and the like. However, polyimide is highly hygroscopic. For this reason, as described above, the problem of moisture inherent in the element becomes significant.
In order to reduce moisture contained in the element, for example, it is conceivable to form a film of polyimide in a vacuum by a vapor phase method.

  By the way, when the metal foil is a rolled foil, the surface has irregularities due to rolling stripes, and when the metal foil is an electrolytic foil, the surface has irregularities. Therefore, in the TFT, the electrical performance of the TFT may be reduced due to the unevenness. Moreover, in an organic EL element, there exists a possibility that a short circuit may arise between electrodes by an unevenness | corrugation. Therefore, it is desirable that the insulating layer has good surface smoothness.

  When a polyimide film is formed by a vapor phase method in a vacuum, it is difficult to increase the film thickness, and it is difficult to obtain a desired surface smoothness. On the other hand, it is possible to increase the film thickness by forming a polyimide film by a coating method and obtain desired surface smoothness. However, warping may occur due to the thick film. Therefore, it is desirable for polyimide to have a low coefficient of linear thermal expansion.

According to this embodiment, since the thickness of the insulating layer is relatively thick in the range of 100 nm to 30 μm, the surface roughness Ra of the insulating layer can be reduced to 25 nm or less, and the insulating layer having good surface smoothness can do.
In addition, according to this embodiment, since the insulating layer is relatively thick, there is a concern about warping as described above, but the difference between the linear thermal expansion coefficient of the insulating layer and the linear thermal expansion coefficient of the metal substrate is 15 ppm. Since it is below / ° C., warping can be suppressed. Furthermore, even when the thermal environment changes, the stress at the interface between the insulating layer and the metal substrate is small, and adhesion can be maintained.

  Moreover, since polyimide has high hygroscopicity as described above, when the thickness of the insulating layer is relatively thick within the range of 100 nm to 30 μm, the moisture contained in the insulating layer increases. Therefore, it is preferable that polyimide has low hygroscopicity. Here, as an index of water absorption, there is a hygroscopic expansion coefficient. Therefore, specifically, the hygroscopic expansion coefficient of the insulating layer is preferably in the range of 0 ppm /% RH to 15 ppm /% RH.

  Further, as a method for forming the insulating layer, a coating method is usually used. This is because an insulating layer with good surface smoothness can be obtained. In addition, since the film physical properties tend to be lower in the vapor phase method than in the coating method, it is desirable to use the coating method not only from the surface smoothness but also from the viewpoint of film physical properties.

  Since the other points of the electronic element are the same as those of the above-described electronic element, description thereof is omitted here.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

Hereinafter, the present invention will be specifically described using examples and comparative examples.
[Production example]
(1) Preparation of polyimide precursor solution (Production Example 1)
4.0 g (20 mmol) of 4,4′-diaminodiphenyl ether (ODA) and 8.65 g (80 mmol) of paraphenylenediamine (PPD) were put into a 500 ml separable flask, and 200 g of dehydrated N-methyl-2 was added. -It dissolved in pyrrolidone (NMP), and it stirred, heating and monitoring with a thermocouple so that liquid temperature might be 50 degreeC with an oil bath under nitrogen stream. After confirming that they were completely dissolved, 29.1 g (99 mmol) of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA) was added thereto gradually over 30 minutes. After the addition, the mixture was stirred at 50 ° C. for 5 hours. Then, it cooled to room temperature and obtained the polyimide precursor solution 1.

(Production Example 2)
The polyimide precursor solution 2 was prepared in the same manner as in Production Example 1, except that the amount of NMP was adjusted so that the reaction temperature and the solution concentration were 17% by weight to 19% by weight, with the compounding ratio shown in Table 1 below. -15 and polyimide precursor solution Z (comparative example) were synthesized.
Acid dianhydrides include 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA) or pyromellitic dianhydride (PMDA), p-phenylenebistrimellitic acid monoester dianhydride (TAHQ), p-biphenylenebistrimellitic acid monoester dianhydride (BPTME) was used. Diamines include 4,4'-diaminodiphenyl ether (ODA), paraphenylenediamine (PPD), 1,4-Bis (4-aminophenoxy) benzene (4APB), 2,2'-Dimethyl-4,4'-diaminobiphenyl. One or two of (TBHG) and 2,2′-Bis (trifluoromethyl) -4,4′-diaminobiphenyl (TFMB) were used.

(Production Example 3)
To make photosensitive polyimide, add {[(4,5-dimethoxy-2-nitrobenzyl) oxy] carbonyl} 2,6-dimethyl piperidine (DNCDP) to the polyimide precursor solution 1 at 15% by weight of the solid content of the solution. It added and it was set as the photosensitive polyimide precursor solution 1.

(Production Example 4)
In order to obtain a photosensitive polyimide, an amide compound (HMCP) synthesized from 2-hydroxy-5-methoxy-cinnamic acid and piperidine was added to the polyimide precursor solution 1 at 10% by weight of the solid content of the solution. A polyimide precursor solution 2 was obtained.

(Evaluation of linear thermal expansion coefficient and hygroscopic expansion coefficient)
The polyimide precursor solutions 1 to 15 and the polyimide precursor solution Z are applied to a heat-resistant film (Upilex S 50S: manufactured by Ube Industries, Ltd.) pasted on glass, and dried on a hot plate at 80 ° C. for 10 minutes. Then, the film was peeled from the heat resistant film to obtain a film having a film thickness of 15 μm to 20 μm. Then, the film was fixed to a metal frame, and heat-treated at 350 ° C. for 1 hour under a nitrogen atmosphere (temperature increase rate: 10 ° C./min, natural cooling), and polyimides 1 to 15 and polyimides having a film thickness of 9 μm to 15 μm A film of Z was obtained.
Moreover, the said photosensitive polyimide precursor solutions 1 and 2 were apply | coated to the heat-resistant film (Upilex S50S: Ube Industries, Ltd. product) affixed on the glass, and it was made to dry for 10 minutes on a 100 degreeC hotplate. Thereafter, after exposure to 2000 mJ / cm ^{2 in} terms of illuminance at a wavelength of 365 nm with a high-pressure mercury lamp, the film was heated on a hot plate at 170 ° C. for 10 minutes, and then peeled off from the heat-resistant film to obtain a film having a thickness of 10 μm. Thereafter, the film is fixed to a metal frame, and heat-treated in a nitrogen atmosphere at 350 ° C. for 1 hour (temperature increase rate: 10 ° C./min, natural cooling), and photosensitive polyimide 1 and photosensitive polyimide having a film thickness of 6 μm. A film of 2 was obtained.

<Linear thermal expansion coefficient>
The film produced by the above method was cut into a width of 5 mm and a length of 20 mm and used as an evaluation sample. The linear thermal expansion coefficient was measured by a thermomechanical analyzer Thermo Plus TMA8310 (manufactured by Rigaku Corporation). The measurement conditions are as follows: the observation length of the evaluation sample is 15 mm, the heating rate is 10 ° C./min, the tensile load is 1 g / 25000 μm ² so that the weight per cross-sectional area of the evaluation sample is the same, and 100 ° C. to 200 ° C. The average linear thermal expansion coefficient in the range was defined as the linear thermal expansion coefficient (CTE).

<Humidity expansion coefficient>
The film produced by the above method was cut into a width of 5 mm and a length of 20 mm and used as an evaluation sample. The humidity expansion coefficient was measured by a humidity variable mechanical analyzer Thermo Plus TMA8310 (manufactured by Rigaku Corporation). The temperature is kept constant at 25 ° C., and the sample is first stabilized in a humidity of 15% RH. After maintaining this state for approximately 30 minutes to 2 hours, the humidity of the measurement site is set to 20% RH. Further, this state was maintained for 30 minutes to 2 hours until the sample became stable. Thereafter, the humidity is changed to 50% RH, and the difference between the sample length when the humidity becomes stable and the sample length when the humidity becomes stable at 20% RH is expressed as a change in humidity (in this case, 50-20). 30), and the value divided by the sample length was defined as the humidity expansion coefficient (CHE). At this time, the tensile load was set to 1 g / 25000 μm ² so that the weight per cross-sectional area of the evaluation sample was the same.

(Substrate warpage evaluation)
Using the above polyimide precursor solutions 1 to 15 and Z and photosensitive polyimide precursor solutions 1 and 2 on a SUS304-HTA foil (manufactured by Toyo Seiki Co., Ltd.) having a thickness of 18 μm, the film thickness after imidization is 10 μm. Polyimide films of polyimides 1 to 15 and Z and photosensitive polyimides 1 and 2 and polyimide films of photosensitive polyimides 1 and 2 were formed under the same process conditions as in the preparation of samples for evaluating the linear thermal expansion coefficient so as to be ± 1 μm. Then, the laminated body of SUS304 foil and a polyimide film was cut | disconnected to width 10mm x length 50mm, and it was set as the sample for board | substrate curvature evaluation.

This sample was fixed to the SUS plate surface with only one of the short sides of the sample with Kapton tape, heated in an oven at 100 ° C. for 1 hour, and then in the oven heated to 100 ° C., the short side on the opposite side of the sample The distance from the SUS plate was measured. At that time, a sample having a distance of 0 mm or more and 0.5 mm or less was evaluated as “◯”, a sample of more than 0.5 mm and 1.0 mm or less was evaluated as Δ, and a sample of 1.0 mm or more was determined as “X”.
Similarly, when this sample is fixed to the surface of the SUS plate with only one of the short sides of the sample with Kapton tape and left in a constant temperature and humidity chamber at 23 ° C. and 85% Rh for 1 hour, The distance from the short side SUS plate was measured. At that time, a sample having a distance of 0 mm or more and 0.5 mm or less was evaluated as “◯”, a sample of more than 0.5 mm and 1.0 mm or less was evaluated as Δ, and a sample of 1.0 mm or more was determined as “X”.
The evaluation results are shown below.

Since the linear thermal expansion coefficient of SUS304 foil was 17 ppm / ° C., it was confirmed that the warpage of the laminate was large when the difference in linear thermal expansion coefficient between the polyimide film and the metal foil was large.
Table 2 shows that the smaller the hygroscopic expansion coefficient of the polyimide film, the smaller the warp of the laminate in a high humidity environment.

(2) Formation of insulating layer (Insulating layer formation 1)
The polyimide precursor solutions 1 to 10 are coated on a SUS304-HTA foil (manufactured by Toyo Seiki Co., Ltd.) having a thickness of 18 μm cut into a 15 cm square with a die coater and dried in an atmosphere at 80 ° C. for 60 minutes in the air. Then, heat treatment was performed at 350 ° C. for 1 hour in a nitrogen atmosphere (temperature increase rate: 10 ° C./min, natural cooling) to form a polyimide film of polyimides 1 to 10 having a film thickness of 6 μm to 12 μm. Got.
Among the laminates 1 to 10, the laminates 1, 2, 3, 5, 6, 8, 9, and 10 did not warp with respect to changes in temperature and humidity environment. On the other hand, the laminated bodies 4 and 7 were conspicuous.

(Insulating layer formation 2 (insulating layer pattern))
After coating the polyimide precursor solution 1 on a SUS304-HTA foil (manufactured by Toyo Seiki Co., Ltd.) having a thickness of 18 μm cut into a 15 cm square with a die coater and drying it in the atmosphere at 80 ° C. for 60 minutes. Then, on the polyimide precursor film, resist plate-making is performed and the polyimide precursor film is developed simultaneously with development so that the resist is removed with a width of 15 mm from the outer edge of the three sides of the square SUS foil, and then the resist pattern is peeled off After that, heat treatment was performed at 350 ° C. for 1 hour in a nitrogen atmosphere (temperature increase rate: 10 ° C./min, natural cooling) to obtain a laminated body 1P from which the insulating layer at the outer edge portion was removed.
The laminated body 1P did not warp against changes in temperature and humidity environment.

(Insulating layer formation 3 (insulating layer pattern))
A resist pattern was formed on the polyimide film of the laminate 10 so that the resist was removed with a width of 15 mm from the outer edge of the three sides of the square SUS foil. After removing the exposed portion of the polyimide film using polyimide etching solution TPE-3000 (manufactured by Toray Engineering), the resist pattern was peeled off to obtain a laminate 10P from which the insulating layer at the outer edge was removed.
The laminated body 10P did not warp against changes in temperature and humidity environment.

(Formation of insulating layer 4 (insulating layer pattern))
The photosensitive polyimide precursor solutions 1 and 2 were coated on a SUS304-HTA foil (manufactured by Toyo Seiki Co., Ltd.) having a thickness of 18 μm cut into a 15 cm square with a die coater, respectively, and 60 ° C. in an 80 ° C. oven under the atmosphere. Dried for minutes. Next, three sides of the square SUS foil were masked with a width of 15 mm from the outer edge (so as not to be irradiated with ultraviolet rays), exposed to 2000 mJ / cm ^{2 in} terms of illuminance at a wavelength of 365 nm with a high-pressure mercury lamp, and then 170 ° C. on a hot plate. After heating for 10 minutes, heat treatment was performed at 350 ° C. for 1 hour in a nitrogen atmosphere (temperature increase rate: 10 ° C./min, natural cooling) to form polyimide films of photosensitive polyimide 1 and photosensitive polyimide 2 having a film thickness of 3 μm. Thus, laminates 11 and 12 were obtained.
The laminates 11 and 12 did not warp even when the temperature or humidity environment changed.

(Flatness evaluation)
The surface roughness Ra of the laminate 1 and the SUS foil was measured.
First, using Nanoscope V multimode (manufactured by Veeco), in tapping mode, cantilever: MPP11100, scanning range: 50 μm × 50 μm, scanning speed: 0.5 Hz, surface shape is imaged and calculated from the obtained image The surface roughness Ra of the laminate 1 was determined by calculating the average deviation from the center line of the roughness curve. The surface roughness Ra of the laminate 1 at 50 μm × 50 μm was 6.2 nm.
Next, using a New View 5000 (manufactured by Zygo), a surface shape in the range of 50 μm × 50 μm was imaged with an objective lens: 100 ×, a zoom lens: 2 ×, and a Scan Length: 15 μm. The surface roughness Ra of the laminate 1 was determined by calculating the average deviation from the center line of the calculated roughness curve. The surface roughness Ra of the laminate 1 at 50 μm × 50 μm was 9.3 nm.

  Similarly, the surface roughness Ra at 50 μm × 50 μm of SUS304-HTA foil (manufactured by Toyo Seiki Co., Ltd.) measured using Nanoscope V multimode (manufactured by Veeco) is 128 nm, and using New View 5000 (manufactured by Zygo). The measured surface roughness Ra at 50 μm × 50 μm was 150 nm.

[Example 1]
On a SUS304-HTA plate (manufactured by Koyama Steel Co., Ltd.) having a thickness of 100 μm, the polyimide precursor solution 1 was used and coated with a spin coater so that the film thickness after imidation was 7 μm ± 1 μm. After drying in the hot plate oven for 60 minutes in the air, heat treatment was performed in a nitrogen atmosphere at 350 ° C. for 1 hour (temperature increase rate: 10 ° C./minute, natural cooling) to form an insulating layer.
Next, an aluminum film as a first adhesion layer was formed on the insulating layer with a thickness of 5 nm by a DC sputtering method (film formation pressure 0.2 Pa (argon), input power 1 kW, film formation time 10 seconds). Next, a silicon oxide film as a second adhesion layer was formed with a thickness of 100 nm by RF magnetron sputtering (deposition pressure 0.3 Pa (argon: oxygen = 3: 1), input power 2 kW, deposition time 30 minutes). . Thus, an electronic element substrate was obtained.

For the insulating layer, the surface roughness Ra at 50 μm × 50 μm measured using New View 5000 (manufactured by Zygo) was 13.2 nm.
About the adhesion layer, the surface roughness Ra at 50 μm × 50 μm measured using New View 5000 (manufactured by Zygo) was 23.5 nm. Moreover, the surface roughness Ra in 50 micrometers x 50 micrometers measured using Nanoscope Vmultimode (made by Veeco) was 15.9 nm.

A TFT having a bottom gate / bottom contact structure was fabricated on the electronic device substrate. First, an aluminum film having a thickness of 100 nm was formed as a gate electrode film, a resist pattern was formed by photolithography, and then wet etching was performed with a phosphoric acid solution, and the aluminum film was patterned into a predetermined pattern to form a gate electrode. Next, silicon oxide having a thickness of 300 nm was formed as a gate insulating film on the entire surface so as to cover the gate electrode. This gate insulating film uses an RF magnetron sputtering apparatus and is applied to a 6-inch SiO ₂ target with a power of 1.0 kW (= 3 W / cm ² ), a pressure of 1.0 Pa, and a gas of argon + O ₂ (50%). It formed on film-forming conditions. Thereafter, a resist pattern was formed by photolithography and then dry etching was performed to form a contact hole. Next, a 100 nm thick titanium film, aluminum film, and IZO film are deposited on the entire surface of the gate insulating film to form a source electrode and a drain electrode, and then a resist pattern is formed by a photolithography method, and then a hydrogen peroxide solution is formed. Then, wet etching was continuously performed with a phosphoric acid solution, and the titanium film was patterned into a predetermined pattern to form a source electrode and a drain electrode. At this time, the source electrode and the drain electrode were formed on the gate insulating film so as to have a pattern apart from a portion other than directly above the central portion of the gate electrode.

Next, an InGaZnO amorphous oxide thin film (InGaZnO ₄ ) with an In: Ga: Zn ratio of 1: 1: 1 was formed on the entire surface so as to cover the source electrode and the drain electrode so as to have a thickness of 25 nm. The amorphous oxide thin film is 4 inches of InGaZnO (In: Ga: Zn = 1: 1: 1) using an RF magnetron sputtering apparatus under conditions of room temperature (25 ° C.) and Ar: O ₂ of 30:50. It was formed using a target. Then, after forming a resist pattern on the amorphous oxide thin film by photolithography, wet etching was performed with an oxalic acid solution, and the amorphous oxide thin film was patterned to form an amorphous oxide thin film having a predetermined pattern. The amorphous oxide thin film thus obtained was formed on the gate insulating film so as to contact the source electrode and the drain electrode on both sides and straddle the source electrode and the drain electrode. Subsequently, 100 nm thick silicon oxide was formed as a protective film by RF magnetron sputtering so as to cover the whole, and then a resist pattern was formed by photolithography, followed by dry etching. After annealing in the atmosphere at 300 ° C. for 1 hour, an EL partition layer was formed using an acrylic positive resist to produce a TFT substrate.

  After depositing an EL layer to be white on the TFT substrate, an IZO film was deposited as an electrode, and an organic EL element was sealed using a barrier film. Next, a flexible color filter formed on the PEN film was bonded, and a flexible diagonal 4.7 inch, resolution 85 dpi, 320 × 240 × RGB (QVGA) active matrix drive full color EL display was produced. About the produced full color EL display, the operation | movement was confirmed with the scanning voltage 15V, the beta voltage 10V, and the power supply voltage 10V. About the produced full-color EL display, the continuous operation | movement for 24 hours and the operation | movement six months after preparation were confirmed.

[Example 2]
On a SUS304-HTA plate (manufactured by Koyama Steel Co., Ltd.) having a thickness of 100 μm, the polyimide precursor solution 1 was used and coated with a spin coater so that the film thickness after imidation was 7 μm ± 1 μm. After drying in the hot plate oven for 60 minutes in the air, heat treatment was performed in a nitrogen atmosphere at 350 ° C. for 1 hour (temperature increase rate: 10 ° C./minute, natural cooling) to form an insulating layer. Thus, an electronic element substrate was obtained.
A 150 nm thick Cr film is formed on the insulating layer of the electronic device substrate by sputtering, and then a 50 nm thick ITO film is formed by sputtering, and the ITO film is patterned into a 2 mm wide stripe to form an organic It was set as the board | substrate for EL production.

  The following materials were used for the production of the organic EL element.

The degree of vacuum is 10 so that the volume ratio of 3-tert-butyl-9,10-di (naphth-2-yl) anthracene (TBADN) and MoO ₃ is 67:33 as a hole injection layer on the ITO film. ^A 10 nm-thick hole injection layer was formed by co-evaporation at a deposition rate of 1.5 Å / sec under the condition of ⁻⁵ Pa. Subsequently, TBADN as a hole transport layer was vacuum-deposited with a film thickness of 10 nm on the hole injection layer at a vacuum rate of 10 ⁻⁵ Pa and a deposition rate of 1.0 Å / sec.
Next, on the hole transport layer, 4,4 ′, 4 ″ -tris (carbazol-9-yl) triphenylamine (TCTA) as a host material and (5,6,11,12) as a luminescent dopant -Tetraphenylnaphthacene (rubrene) was vacuum-deposited with a film thickness of 70 nm under a vacuum degree of ^10-5 Pa and a deposition rate of 1 / sec so as to be 1% by volume.
An electron transport layer having a thickness of 20 nm was formed on the light-emitting layer by vacuum deposition under the condition of TBADN at a vacuum degree of 10 ⁻⁵ Pa at a deposition rate of 1 Å / sec. Subsequently, TBADN and 8-hydroxyquinolinolatolithium (Liq) are deposited on the electron transport layer at a deposition rate of 1 Pa / sec under a vacuum degree of 10 ^-5 Pa so that the volume ratio is 1: 1. Were co-evaporated to form an electron injection layer having a thickness of 12 nm. On the electron injection layer, Al was deposited at a deposition rate of 0.1 Å / sec with a film thickness of 1.5 nm under a vacuum degree of 10 ⁻⁵ Pa, and then Mg: Ag was in a volume ratio of 9: 1. In this way, a film having a film thickness of 5 nm was formed at a deposition rate of 1 mm / sec to form an electron injection promoting layer.
Subsequently, for the purpose of reducing damage when IZO is sputtered, TBADN and MoO ₃ as a transparent protective layer have a volume ratio of 80:20 at a vacuum degree of 10 ^-5 Pa under the condition of 1.5 Å / sec. Co-evaporation was performed at a deposition rate to form a film with a thickness of 100 nm.

Subsequently, using a shadow mask formed in a stripe shape of 2 mm width so as to cross the ITO stripe pattern, an IZO film was formed on the transparent protective layer by an opposed target sputtering method, and the film thickness was 150 nm. The cathode was formed.
Finally, a 30 μm thick glass plate coated with a thermosetting epoxy resin was bonded and bonded to produce an organic EL element.

[Comparative Example 1]
An organic EL device was produced in the same manner as in Example 2 except that the polyimide precursor solution 12 was used instead of the polyimide precursor solution 1.

[Evaluation]
The organic EL elements of Example 2 and Comparative Example 1 were subjected to an 80 ° C. high temperature storage test. FIGS. 10A and 10B show photographs of the initial light emission state of the organic EL device of Example 2 and the light emission state after 200 hours at 80 ° C. high temperature storage test, respectively. FIGS. 10C and 10D show photographs of the initial light emission state of the organic EL device of Comparative Example 1 and the light emission state after 200 hours at 80 ° C. high temperature storage test, respectively. In the organic EL elements of Example 2 and Comparative Example 1, the difference in deterioration was clear. In the organic EL element of Comparative Example 1, since the hygroscopic expansion coefficient of polyimide was large, the area of the non-light emitting portion was increased due to the influence of moisture.

DESCRIPTION OF SYMBOLS 1 ... Electronic element 2 ... Metal base material 3 ... Insulating layer 10 ... Organic EL element 20 ... TFT

Claims (11)

A metal substrate;
An insulating layer formed on the metal substrate and containing polyimide;
And an electronic element portion formed on the insulating layer, wherein the hygroscopic expansion coefficient of the insulating layer is in the range of 0 ppm /% RH to 15 ppm /% RH.   The electronic device according to claim 1, wherein the insulating layer contains polyimide as a main component. The electronic device according to claim 1, wherein the polyimide has a repeating unit represented by the following formula (1).
(In formula (1), R ¹ is a tetravalent organic group represented by the following formula (2), R ² is a divalent organic group, and R ¹ and R ² that are repeated are the same. And n may be different, and n is a natural number of 1 or more.)
(In Formula (2), a is 0 or a natural number of 1 or more, and A is an ester bond. The linking group is bonded to the 2, 3 or 3 or 4 position of the aromatic ring as viewed from the bonding site of the aromatic ring. To do.) The electronic device according to claim 1, wherein the polyimide has a repeating unit represented by the following formula (1).
(In formula (1), R ¹ is a tetravalent organic group represented by the following formula (2), R ² is a divalent organic group represented by the following formula (3) or (4), and is repeated. R ¹ and R ² may be the same or different, and n is a natural number of 1 or more.)
(In the formula (2), a is a natural number of 0 or 1 or more, A is a single bond (biphenyl structure), an oxygen atom (ether bond), or an ester bond. (However, except for the case where all are ester bonds.) The linking group is bonded to the 2, 3 or 3 or 4 position of the aromatic ring as viewed from the bonding site of the aromatic ring.)
(In the formula (4), a is 0 or a natural number of 1 or more, and the linking group is bonded to the meta position or the para position with respect to the bonds between the aromatic rings. Alternatively, all may be substituted with a substituent selected from a fluoro group, a methyl group, a methoxy group, a trifluoromethyl group, or a trifluoromethoxy group.) The electronic device according to claim 1, wherein the polyimide has a repeating unit represented by the following formula (1).
(In formula (1), R ¹ is a tetravalent organic group, R ² is a divalent organic group represented by the following formula (4), and repeated R ¹ and R ² are the same. And n may be different, and n is a natural number of 1 or more.)
(In the formula (4), a is 0 or a natural number of 1 or more, and the linking group is bonded to the meta position or the para position with respect to the bonds between the aromatic rings. Alternatively, all may be substituted with a substituent selected from a fluoro group, a methyl group, a methoxy group, a trifluoromethyl group, or a trifluoromethoxy group.)   The surface roughness Ra of the said insulating layer is 25 nm or less, The electronic device in any one of Claim 1-5 characterized by the above-mentioned.   The thickness of the said insulating layer exists in the range of 0.3 micrometer-100 micrometers, The electronic device in any one of Claim 1-6 characterized by the above-mentioned.   The electronic element according to any one of claims 1 to 7, wherein a linear thermal expansion coefficient of the insulating layer is in a range of 0 ppm / ° C to 30 ppm / ° C.   9. The electronic device according to claim 1, wherein a difference between a linear thermal expansion coefficient of the insulating layer and a linear thermal expansion coefficient of the metal base material is 15 ppm / ° C. or less.   The electronic element part is formed on the insulating layer, a back electrode layer, an electroluminescence layer formed on the back electrode layer and including at least an organic light emitting layer, and a transparent electrode formed on the electroluminescence layer The electronic device according to any one of claims 1 to 9, wherein the electronic device is an organic electroluminescence device having a layer.   The electronic device according to claim 1, wherein the electronic device portion is a thin film transistor formed on the insulating layer.