POLYAMIC ACID COMPOSITION FOR MANUFACTURING DISPLAY SUBSTRATE AND METHOD FOR MANUFACTURING SUBSTRATE FOR DISPLAY BY USING SAME

Abstract

The present invention provides a polyamic acid composition, which, in a cured state on a substrate of amorphous or crystalline silicon, has an adhesion of 0.05-0.1 N/cm with the amorphous or crystalline silicon.

Claims

1. A polyamic acid composition comprising a polyamic acid polymer in which an aromatic dianhydride-based monomer and an aromatic diamine-based monomer are polymerized, wherein the aromatic dianhydride-based monomer comprises a first component having a biphenyl structure, a second component having one benzene ring and a third component having a benzophenone structure, and the polyamic acid composition has, in a cured state on a substrate of amorphous or crystalline silicon, adhesion of 0.05 to 0.1 N/cm with the amorphous or crystalline silicon, and has, in a cured state on a substrate of amorphous or crystalline silicon, adhesion of 0.01 N/cm or less as measured after irradiation with a laser having a wavelength of 308 nm at 150 mJ/cm.sup.2.

2. The polyamic acid composition according to claim 1, wherein the content of the first component is 50 mol % to 70 mol %, and the content of the second component is 20 mol % to 40 mol %, relative to the total number of moles of the aromatic dianhydride-based monomer.

3. The polyamic acid composition according to claim 1, wherein the content of the component having the benzophenone structure is more than 1 mol % to less than 7 mol % relative to the total number of moles of the aromatic dianhydride-based monomer.

4. The polyamic acid composition according to claim 1, wherein the first component is one or more selected from the group consisting of 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) and 2,3,3′,4′-biphenyltetracarboxylic dianhydride (a-BPDA).

5. The polyamic acid composition according to claim 1, wherein the second component is pyromellitic dianhydride (PMDA).

6. The polyamic acid composition according to claim 1, wherein the third component is 3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA).

7. The polyamic acid composition according to claim 1, wherein the aromatic diamine-based monomer is a diamine component having one benzene ring in an amount of more than 50 mol % relative to the total number of moles thereof.

8. The polyamic acid composition according to claim 7, wherein the diamine component having one benzene ring is one or more selected from the group consisting of 1,4-diaminobenzene (PPD), 1,3-diaminobenzene (MPD), 2,4-diaminotoluene, 2,6-diaminotoluene and 3,5-diaminobenzoic acid.

9. The polyamic acid composition according to claim 7, wherein the diamine component having one benzene ring is 1,4-diaminobenzene.

10. The polyamic acid composition according to claim 1, further comprising at least one of a silane-based coupling agent and a silicone-based surfactant.

11. The polyamic acid composition according to claim 11, wherein the silane-based coupling agent is contained in an amount of 0.01 to 0.05 wt % relative to the weight of the polyamic acid solid content of the polyamic acid composition; and comprises one or more selected from the group consisting of (3-aminopropyl)trimethoxysilane (APTMS), aminopropyltriethoxysilane, 3-(2-aminoethylamino)propyl-dimethoxymethylsilane, 3-glycidoxypropyldimethoxymethylsilane and 2-(3,4-epoxycyclohexyl)trimethoxysilane.

12. The polyamic acid composition according to claim 11, wherein the silicone-based surfactant is contained in an amount of 0.001 to 0.02 wt % relative to the weight of the polyamic acid solid content of the polyamic acid composition.

13. The polyamic acid composition according to claim 1, wherein the polyamic acid of the polyamic acid composition has a viscosity of 3,000 to 7,000 cP as measured at 23° C.

14. The polyamic acid composition according to claim 1, wherein a polyimide resin prepared from the polyamic acid composition has a glass transition temperature of 490° C. or higher, has a thermal decomposition temperature of 555° C. or higher, and has a coefficient of thermal expansion of 8 ppm/° C. or less.

15. The polyamic acid composition according to claim 14, wherein the polyimide resin has a tensile strength of 350 MPa or more, elongation of 20% or more and transmittance of 60% or more.

16. A method for manufacturing a display substrate comprising a step of applying the polyamic acid composition according to claim 1 on an amorphous or crystalline silicon substrate.

17. The method for manufacturing a display substrate according to claim 16, wherein the method comprises steps of performing first heat treatment of the polyamic acid composition at 20° C. to 40° C.; performing second heat treatment of the polyamic acid composition at 40° C. to 200° C.; and performing third heat treatment of the polyamic acid composition at 200° C. to 500° C., and wherein through the first heat treatment, second heat treatment and third heat treatment steps, the polyamic acid composition generates a polyimide resin comprising imide groups that the amic acid groups of the polyamic acid are subjected to ring-closure and dehydration reaction, which is cured by volatilizing the organic solvent, and when the third heat treatment is completed, the polyimide resin is cured and bonded on the amorphous or crystalline silicon substrate.

18. The method for manufacturing a display substrate according to claim 17, wherein the first heat treatment, second heat treatment and third heat treatment steps are each independently performed at two or more variable heating rates selected from the range of 3° C./min to 7° C./min, or one constant heating rate selected from the above range.

19. The method for manufacturing a display substrate according to claim 17, wherein the method comprises steps of: forming a thin film transistor (TFT) on the polyimide resin, and irradiating the amorphous or crystalline silicon substrate with a laser for a predetermined time to remove the amorphous or crystalline silicon substrate from the polyimide resin, and wherein the adhesion between the polyimide resin and the amorphous or crystalline silicon substrate as measured after the laser irradiation is 0.01 N/cm or less.

Description

BEST MODE

[0163] Hereinafter, the action and effect of the invention will be described in more detail through specific examples of the invention. However, these examples are only presented as examples of the invention, and the scope of the invention is not determined thereby.

Example 1

[0164] To a reactor filled with NMP at 40° C. BPDA (first component), PMDA (second component), BTDA (third component) as aromatic dianhydride-based monomers, and PPD as an aromatic diamine-based monomer were added in the molar ratios shown in Table 1 below, and stirred for about 30 minutes to polymerize a polyamic acid.

[0165] The following substances were added thereto, and the aging process was performed for about 2 hours to prepare a final polyamic acid composition. At this time, the viscosity of the polyamic acid composition was about 5,100 cP. [0166] Silane-based coupling agent: 0.02 wt % of 3-aminopropyltrimethoxysilane (based on the weight of the polyamic acid solid content) [0167] Silicone-based surfactant: 0.01 wt % of BYK's ‘BYK-378’ (based on the weight of the polyamic acid solid content) [0168] Additive: 10 wt % of isoquinoline (based on the weight of the polyamic acid solid content)

Example 2

[0169] A polyamic acid composition having a viscosity of about 5,000 cP was prepared in the same manner as in Example 1, except that the molar ratio of BPDA (first component), PMDA (second component) and BTDA (third component) was changed to the molar ratio shown in Table 1 below and the components were added thereto.

Example 3

[0170] A polyamic acid composition having a viscosity of about 5,100 cP was prepared in the same manner as in Example 1, except that the molar ratio of BPDA (first component), PMDA (second component) and BTDA (third component) was changed to the molar ratio shown in Table 1 below and the components were added thereto.

Example 4

[0171] A polyamic acid composition having a viscosity of about 4,800 cP was prepared in the same manner as in Example 1, except that the molar ratio of BPDA (first component). PMDA (second component) and BTDA (third component) was changed to the molar ratio shown in Table 1 below and the components were added thereto.

Comparative Example 1

[0172] A polyamic acid composition having a viscosity of about 4,800 cP was prepared in the same manner as in Example 1, except that and BTDA (third component) was excluded as the component of the aromatic dianhydride-based monomer, the molar ratio of BPDA (first component) and PMDA (second component) was changed to the molar ratio shown in Table 1 below and the components were added thereto.

Comparative Example 2

[0173] A polyamic acid composition having a viscosity of about 5,300 cP was prepared in the same manner as in Example 1, except that and BTDA (third component) was excluded as the component of the aromatic dianhydride-based monomer, the molar ratio of BPDA (first component) and PMDA (second component) was changed to the molar ratio shown in Table 1 below and the components were added thereto.

Comparative Example 3

[0174] A polyamic acid composition having a viscosity of about 4,750 cP was prepared in the same manner as in Example 1, except that and BTDA (third component) was excluded as the component of the aromatic dianhydride-based monomer, the molar ratio of BPDA (first component) and PMDA (second component) was changed to the molar ratio shown in Table 1 below and the components were added thereto.

Comparative Example 4

[0175] A polyamic acid composition having a viscosity of about 4,950 cP was prepared in the same manner as in Example 1, except that and BTDA (third component) was excluded as the component of the aromatic dianhydride-based monomer, the molar ratio of BPDA (first component) and PMDA (second component) was changed to the molar ratio shown in Table 1 below and the components were added thereto.

Comparative Example 5

[0176] A polyamic acid composition having a viscosity of about 5,100 cP was prepared in the same manner as in Example 1, except that the molar ratio of BPDA (first component). PMDA (second component) and BTDA (third component) was changed to the molar ratio shown in Table 1 below and the components were added thereto.

Comparative Example 6

[0177] A polyamic acid composition having a viscosity of about 5,100 cP was prepared in the same manner as in Example 1, except that the molar ratio of BPDA (first component), PMDA (second component) and BTDA (third component) was changed to the molar ratio shown in Table 1 below and the components were added thereto.

TABLE-US-00001 TABLE 1 Composition Molar ratio Dianhydride-based monomer Diamine- Dianhydride-based monomer Diamine- First Second Third based First Second Third based component component component monomer component component component monomer Example 1 BPDA PMDA BTDA PPD 60 38 7 100 2 BPDA PMDA BTDA PPD 60 35 5 100 3 BPDA PMDA BTDA PPD 55 40 5 100 4 BPDA PMDA BTDA PPD 65 32 3 100 Comparative 1 BPDA PMDA — PPD 60 40 — 100 Example 2 BPDA PMDA — PPD 70 30 — 100 3 BPDA PMDA — PPD 80 70 — 100 4 BPDA PMDA — PPD 50 50 — 100 5 BPDA PMDA BTDA PPD 60 39 1 100 6 BPDA PMDA BTDA PPD 60 33 7 100

Experimental Example 1: Adhesion Test of Polyimide Resin

[0178] The polyamic acid compositions prepared in Examples 1 to 4 and Comparative Examples 1 to 6 were each cast at 30 μm on an amorphous silicon substrate with a width of 1 cm*a length of 10 cm and dried in a temperature range of 20° C. to 460° C. to manufacture a laminate to which the polyimide resin in the form of a thin film having an average thickness of about 15 to 17 μm were bonded.

[0179] With respect to the laminate thus manufactured, the first adhesion (before laser treatment), curl test, and second adhesion (after laser treatment) of the polyimide resin were evaluated using the following methods. [0180] First adhesion: The required force is measured, while attaching a tape with a width of 1 cm to the end of the polyimide resin and peeling the polyimide resin from the substrate using this tape. [0181] Curl test: The manufactured laminate was heat-treated at a temperature of about 400° C. for about 1 hour, and then it was confirmed whether curls occurred at the edge sites of the polyimide resin on the amorphous silicon substrate. [0182] Second adhesion: After irradiating the amorphous silicon substrate with a laser having a wavelength of 308 nm at 150 mJ/cm.sup.2, the required force is measured, while attaching a tape with a width of 1 cm to the end of the polyimide resin and peeling the polyimide resin from the substrate using this tape. [0183] The adhesion was measured while peeling it at a peel rate of 20 mm/min and a peel angle of 180°, according to ASTM D 3359.

TABLE-US-00002 TABLE 2 First adhesion Curl occurrence Second adhesion (N/cm) (◯, X) (N/cm) Example 1 0.07 X 0.01 or less 2 0.08 X 0.01 or less 3 0.07 X 0.01 or less 4 0.07 X 0.01 or less Comparative 1 0.03 ◯ 0.01 or less Example 2 0.03 ◯ 0.01 or less 3 0.03 ◯ 0.01 or less 4 0.03 ◯ 0.01 or less 5 0.03 ◯ 0.01 or less 6 0.12 X 0.05

Experimental Example 2: Physical Property Test of Polyimide Resin

[0184] The polyamic acid compositions prepared in Examples 1 to 5 and Comparative Examples 1 to 6 were applied in the form of a thin film to a stainless-based support and then heat-treated in the temperature range of 20° C. to 350° C., and subsequently peeled from the support to produce polyimide resins in the form of films having average thicknesses of about 15 to 17 μm, respectively.

[0185] The polyimide resin thus produced was tested for physical properties in the following methods, and the results were shown in Table 3 below.

[0186] (1) Coefficient of Thermal Expansion (CTE)

[0187] The coefficient of thermal expansion was measured in the range of 100 to 350° C. using TMA.

[0188] (2) Glass Transition Temperature (T.sub.g)

[0189] As for the glass transition temperature, the loss elastic modulus and the storage elastic modulus of each polyimide resin were calculated using TMA, and in their tangent graphs, the inflection point was measured as the glass transition temperature.

[0190] (3) Thermal Decomposition Temperature (T.sub.d)

[0191] While increasing the temperature at a temperature increase rate of 10° C./min in nitrogen, the temperature was measured when the initial weight of the polyimide resin decreased by 1%, using a thermogravimetric analyzer (TG-DTA2000).

[0192] (4) Tensile Strength

[0193] The tensile strength was measured by the method presented in KS6518.

[0194] (5) Elongation

[0195] The elongation was measured by the method presented in ASTM D1708.

[0196] (6) Transmittance

[0197] Using the HunterLab's ColorQuesetXE model, the transmittance of a wavelength of 550 nm was measured in the visible light region by the method presented in ASTM D1003.

TABLE-US-00003 Table 3 CTE T.sub.g T.sub.d Tensile strength Elongation Transmittance (ppm/° C.) (° C.) (° C.) (MPa) (%) (%) Example 1 6.2 507 567 385 23.8 60.8 2 6.4 509 563 388 23.4 61.0 3 6.7 506 561 382 22.7 60.7 4 7.7 495 559 374 24.8 61.3 Comparative 1 6.3 508 566 382 23.8 60.7 Example 2 11.8 481 569 347 27.9 62.1 3 14.1 435 565 374 34.8 65.7 4 5.8 521 556 398 15.2 57.1 5 6.1 508 563 378 27.8 60.4 6 9.5 489 561 382 17.5 61.8

[0198] From the results of Experimental Example 1, Examples exhibited an appropriate level of adhesion to the amorphous silicon substrate, that is, first adhesion belonging to 0.05 to 0.1 N/cm. The advantage of the first adhesion belonging to the above range can be confirmed indirectly through the occurrence of curls. According to Table 2, in Examples, even when heat treatment was performed at a high temperature of 400° C. for a predetermined time, no curl occurred at all.

[0199] If the adhesion is low, the bonding state between the polyimide resin and the amorphous silicon substrate is released at a high temperature of 400° C., and curls may occur in which the ends of the polyimide resin are rolled inward. Really, most of Comparative Examples exhibited lower first adhesion than that of Examples, and curls occurred in all.

[0200] These results suggest that the adhesion of at least 0.05 N/cm is required for a TFT process performed at high temperatures, and it can be seen that Examples according to the present invention exhibits the desirable adhesion for the TFT process. In another aspect, Examples showed extremely insignificant adhesion (second adhesion) after treatment with a laser for removal of the amorphous silicon substrate, and it can be expected therefrom that when the first adhesion is satisfied, the amorphous silicon substrate can be peeled off well from the polyimide resin.

[0201] Meanwhile, in Comparative Examples 1 to 5, it can be confirmed that the first adhesion has been out of the range of 0.05 to 0.1 N/cm. In the relevant Comparative Example, curls occurred at a high temperature due to such low first adhesion, and it can be expected that they are unsuitable for manufacturing a display substrate requiring a high temperature process.

[0202] Comparative Example 6 is a case where the first adhesion is excessive, wherein in particular, it can be confirmed that the second adhesion after laser treatment is also at a very high level, and unlike Examples, it suggests therefrom that it will be difficult for the amorphous silicon substrate to peel off well from the polyimide resin after laser irradiation.

[0203] The results of Experimental Example 2 show that the polyimide resin embodied according to the present invention satisfies all of various properties required for manufacturing a display substrate, and when linked with the results of Experimental Example 1, Examples all exhibit a desirable level of adhesion together with the above properties.

[0204] On the contrary, in Comparative Examples, at least one characteristic is not satisfied with poor adhesion, whereby it can be seen that they are unreasonable to be used as a display substrate.

[0205] Therefore, it can be seen from the results of Table 3 that the monomer combination and the combination ratio of the present invention are effective for the implementation of the polyamic acid composition.

[0206] Although the foregoing has been described with reference to the examples of the present invention, those having ordinary knowledge in the field to which the present invention belongs will be able to perform various applications and modifications within the scope of the present invention based on the above contents.