Matte black ultra-thin polyimide film

Abstract

To provide a matte black ultra-thin polyimide film for application as a cover layer of a flexible substrate.SOLUTION: The present invention provides a matte black ultra-thin polyimide film, comprising: a polyimide constituting 77 to 96 wt.% of the film; carbon black constituting 2 to 8 wt.% of the film; and hollow silica powder having an average particle size of less than 1.5 μm and density of less than 0.7 g / cm3, and constituting 2 to 15 wt.% of the film.SELECTED DRAWING: None

Description

Detailed Description of the Invention

[0001] [Technical field] The present disclosure relates to a matte black ultra-thin polyimide film, particularly one having a density of 0.7 g / cm 3 The present invention relates to a matte black ultra-thin polyimide film having a gloss level of less than 30 and a tensile elongation of more than 15% by adding silica powder having an average particle size of less than 1.5 μm.

[0002] [Background technology] Polyimide films are widely used as cover layers for flexible substrates. In particular, matte black polyimide films are commonly applied to flexible substrates due to their special optical properties.

[0003] Matte black polyimide film is widely used in flexible substrates in consumer electronic products such as smartphones and smart watches because it can improve the aesthetics of the product by shielding electronic circuits.

[0004] However, in conventional matte black polyimide films, carbon black is mainly used as a pigment or colorant to reduce the transmittance and ensure the covering and protective functions. In addition, the matte black polyimide film contains a quenching agent that scatters light, reducing the discomfort caused by reflected light from the film.

[0005] Currently, the main components of the quenching agent commonly used in matte black polyimide films are silicon dioxide and polyimide microparticles. When manufacturing polyimide films with low gloss (less than 30), it is necessary to add a certain weight ratio of the quenching agent to obtain a matte effect. However, if a large amount of particles are added to the polyimide film as a quenching agent, the area ratio of the continuous surface made of polyimide material decreases, resulting in a significant decrease in tensile elongation.

[0006] In particular, when producing low-gloss, ultra-thin polyimide films with a thickness of less than 12 μm, the addition of a quenching agent reduces the tensile elongation of the polyimide film, resulting in extremely low tensile strength, which causes the film to lose ductility and become prone to breakage.

[0007] Prior art document US840315B2 discloses a matte black polyimide film using silicon dioxide as a quenching agent. Silicon dioxide has a relatively high density (2-4.5 g / cm3). 3 ), so even if it is added at the same weight ratio, the volume is relatively small. Therefore, in order to obtain the low gloss effect, it is necessary to add a certain amount or more. However, this makes the structure of the ultra-thin film more prone to defects and also has a negative effect on the tensile elongation.

[0008] In order to improve the above-mentioned problems, the present invention aims to provide a matte black ultra-thin polyimide film that has excellent tensile elongation and ensures low gloss.

[0009] Summary of the Invention The present invention relates to a matte black ultra-thin polyimide film, comprising: polyimide that accounts for 77-96 wt % of the film; carbon black that accounts for 2-8 wt % of the film; and a cellulose ester having an average particle size of less than 1.5 μm and a density of 0.7 g / cm. 3 and a hollow silica powder occupying 2 to 15 wt % of the film, the thickness of the matte black ultra-thin polyimide film being 2 to 12 μm, the polyimide being formed by subjecting a polyimide precursor in which an aromatic dianhydride and an aromatic diamine are polymerized to a cyclization reaction, and the polyimide film having a gloss at 60 degrees of less than 30 and a tensile elongation of more than 15%.

[0010] In one embodiment of the present invention, the matte black ultra-thin polyimide film has a thickness of 2 to 7 μm.

[0011] In one embodiment of the present invention, the aromatic diamine contains at least p-phenylenediamine (PDA) in a content of 7 to 40 mol % based on the total amount of the aromatic diamine, and the polyimide film has a thermal expansion coefficient of less than 30 ppm / °C. [Mode for carrying out the invention] The present invention relates to a matte black ultra-thin polyimide film, comprising: a polyimide that accounts for 77 to 96 wt % of the film; carbon black that accounts for 2 to 8 wt % of the film; Average particle size less than 1.5μm, density 0.7g / cm 3 and a hollow silica powder occupying 2 to 15 wt % of the film, the thickness of the matte black ultra-thin polyimide film being 2 to 12 μm, the polyimide being formed by subjecting a polyimide precursor in which an aromatic dianhydride and an aromatic diamine are polymerized to a cyclization reaction, and the polyimide film having a gloss at 60 degrees of less than 30 and a tensile elongation of more than 15%.

[0012] The aromatic diamine may contain at least p-phenylenediamine (PDA) in an amount of 7 to 40 mol % based on the total amount of the aromatic diamine, so that the polyimide film has a thermal expansion coefficient of less than 30 ppm / °C.

[0013] [Production of polyimide precursor] The polyimide precursor is composed of an aromatic dianhydride and an aromatic diamine.

[0014] The aromatic diamine contains at least p-phenylenediamine (PDA), and the amount of the p-phenylenediamine added is 7 to 40 mol % based on the total number of moles of the aromatic diamine.

[0015] Solvents used in the production of polyimide precursors include, but are not limited to, dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), N-ethyl-2-pyrrolidone (NEP), γ-butyrolactone (GBL), N,N-dimethylformamide (DMF), etc. In this embodiment, dimethylacetamide is used as the solvent.

[0016] [Production of black slurry] A solution of carbon black and dimethylacetamide mixed in a weight ratio of 1:7 is stirred until it becomes homogenous, and then vibrated with an ultrasonic vibrator for 1 hour to obtain a black slurry.

[0017] The carbon black in the black slurry is insulating carbon black.

[0018] The weight ratio of carbon black to dimethylacetamide in the black slurry can be adjusted as necessary. The weight ratio of carbon black is related to the transmittance. The range of the amount of carbon black added in this embodiment is 2 to 8 wt% of the black polyimide film.

[0019] [Preparation of quenching slurry] A solution in which hollow silica powder and dimethylacetamide are mixed in a weight ratio of 1:9 is stirred until it becomes homogeneous, and then the solution is vibrated for 2 hours using an ultrasonic vibrator to obtain a quenching slurry.

[0020] The density of the hollow silica powder in the quenching slurry is in the range of 0.2 to 0.7 g / cm 3 may be also possible.

[0021] The hollow silica powder in the quenching slurry may have an average particle size within the range of 0.2 to 1.5 μm.

[0022] The weight ratio of hollow silica powder to dimethylacetamide in the quenching slurry can be adjusted as necessary. The weight ratio of hollow silica powder is related to gloss and tensile elongation. If the ratio of hollow silica powder is too low, the gloss of the matte black polyimide film increases. On the other hand, if the ratio of hollow silica powder is too high, the tensile elongation deteriorates.

[0023] [Production of ultra-thin matte black polyimide film] The black slurry, the quenching slurry and the polyimide precursor are mixed and stirred until homogeneous, and then a catalyst and a dehydrating agent are added to carry out a cyclization reaction. The dehydrating agent may be acetic anhydride or benzoic anhydride, but in this embodiment, acetic anhydride is preferred as the dehydrating agent. The catalyst may be pyridine, 3-methylpyridine, 2-methylpyridine, 4-methylpyridine, isoquinoline, quinoline, or triethylamine, but pyridine, 3-methylpyridine, 2-methylpyridine, or 4-methylpyridine is preferred, but in this embodiment, 3-methylpyridine is used as the catalyst.

[0024] The catalyst and dehydrating agent may be used alone or may be mixed with a solvent to dilute and then added to the mixture. The mixture of the dehydrating agent and catalyst is stirred until homogenous, and the solution degassed with a centrifugal defoamer is applied to a glass substrate and further coated using a scraper. The coated sample is baked in an oven at 80°C for 20 minutes, heated to 170°C and baked for another 20 minutes. Then, as a final treatment, it is heated to 350°C and baked for 20 minutes. After baking is completed, the glass substrate is immersed in water and the thin film is removed to obtain a matte black polyimide film.

[0025] In addition to glass, a metal plate may be used as the substrate in the film formation process. When a metal plate is used to manufacture the matte black ultra-thin polyimide film, the film is baked in an oven at 80°C and dried, then removed from the metal plate, and the removed semi-dried film is fixed to a metal frame and heated to 170°C and baked for another 20 minutes. Then, as a final treatment, the film is heated to 350°C and baked for 20 minutes to obtain a matte black polyimide film.

[0026] The matte black ultra-thin polyimide film may have a thickness of 2 μm to 12 μm.

[0027] The matte black ultra-thin polyimide film may be used as a cover film, which includes an adhesive layer and a substrate film.

[0028] [Example] The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto. In addition, the materials indicated by the abbreviations in each example will be described in detail below.

[0029] [Polyimide materials] PMDA: Pyromellitic dianhydride · PDA: p-phenylenediamine ODA: 4,4'-diaminodiphenyl ether [Quenching slurry materials] Low density silica powder: density 0.46g / cm 3 , average particle size 1.2μm Low density silica powder: density 0.62g / cm 3 , average particle size 1.7μm Low density silica powder: density 0.67g / cm 3 , average particle size 1.4μm Low density silica powder: density 0.76g / cm 3 , average particle size 1.3μm [Carbon black slurry materials] Carbon black: SPECIAL BLACK 4A (SB4A), manufactured by Evonik [solvent] ·DMAc: Dimethylacetamide AA: Acetic anhydride AP: 3-Methylpyridine <Measurement method> The properties of the composite films obtained in the following examples were measured by the following methods.

[0030] Thermal expansion coefficient (100°C-200°C): Measured according to ASTM D696 standard using a TA Instruments Q400 TMA device. The thermal expansion coefficient of polyimide film at 100°C-200°C was measured at a heating rate of 10°C / min. To eliminate the effect of stress due to heat treatment, the residual stress was removed in the first measurement, and the value obtained in the second measurement was used as the actual value.

[0031] Glossiness: The glossiness at 60 degrees was measured using a micro-TRI-gloss glossmeter manufactured by BYK.

[0032] Tensile elongation (%): Measured according to ASTM D882 standard using a Tinius Olsen 10ST universal material testing machine.

[0033] Thickness measurement method: Using an advanced digital gauge manufactured by SYLVAC, the thickness was measured at five different areas and the average value was obtained.

[0034] Example 1 [Production of carbon black slurry] A solution containing 1 g of carbon black and 7 g of DMAc was stirred until it became homogeneous, and then vibrated for 1 hour with an ultrasonic vibrator to obtain a black slurry.

[0035] [Production of low density mat slurry] A solution containing 1 g of hollow silica powder and 9 g of dimethylacetamide was stirred until it became homogeneous, and then vibrated for 2 hours with an ultrasonic vibrator to obtain a quenching slurry. The hollow silica powder has a density of 0.46 g / cm 3 The average particle size was 1.2 μm.

[0036] [Production of polyimide precursor] 4.05g of PDA (20mol%) was added to 425g of DMAc, and after stirring and mixing to completely dissolve the PDA, 30.03g of ODA was added. When the ODA was completely dissolved, 38.9g of PMDA was slowly added. The temperature of the mixture was controlled at 25°C and the mixture was stirred for 2 hours to react. After that, a small amount of PMDA was added to adjust the viscosity, and a polyamic acid solution with a solid content of 15% and a viscosity of 161200cps was finally obtained.

[0037] [Production of black ultra-thin polyimide film] 1.92g of carbon black slurry, 1.2g of low density matte slurry, 40g of polyamic acid solution, and 20g of DMAc were mixed so that the resulting polyimide film contained 4wt% carbon black and 2wt% hollow silica powder. Then, the mixture was stirred until homogeneous, and AA and DMAc were diluted in a weight ratio of 5:1, and AP and DMAc were further diluted in a weight ratio of 1:1. Next, a solution containing 3.41ml of AA diluted solution and 2.89ml of AP diluted solution was stirred until homogeneous, and the solution degassed with a centrifugal defoamer was poured onto a glass substrate and further coated using a scraper with a 125μm slit. The coated sample was baked in an oven at 80°C for 20 minutes, then heated to 170°C at a rate of 1.8°C / min and baked for another 20 minutes. Then, as a final treatment, it was heated to 350°C at a rate of 2.0°C / min and baked for 20 minutes.

[0038] The glass substrate was immersed in water and the matte black polyimide film was peeled off from the glass substrate. The thickness of this film was 6.2 μm.

[0039] [Example 2] The carbon black slurry was prepared in the same manner as in Example 1.

[0040] The low density mat slurry was prepared in the same manner as in Example 1.

[0041] The polyimide film precursor was prepared in the same manner as in Example 1.

[0042] A matte black polyimide film was produced in the same manner as in Example 1, except that 6 g of low density matte slurry was further added so as to contain 10 wt % hollow silica powder.

[0043] The glass substrate was immersed in water and the matte black polyimide film was peeled off from the glass substrate. The thickness of this film was 6.7 μm.

[0044] [Example 3] The carbon black slurry was prepared in the same manner as in Example 1.

[0045] The low density mat slurry was prepared in the same manner as in Example 1.

[0046] The polyimide film precursor was prepared in the same manner as in Example 1.

[0047] A matte black polyimide film was produced in the same manner as in Example 1, except that 9 g of low density matte slurry was added to provide a hollow silica powder content of 15 wt %.

[0048] The glass substrate was immersed in water and the matte black polyimide film was peeled off from the glass substrate. The thickness of this film was 6.2 μm.

[0049] [Example 4] The carbon black slurry was prepared in the same manner as in Example 1.

[0050] The low density matte slurry was prepared as in Example 1, but the hollow silica powder had a density of 0.67 g / cm 3 The average particle size used was 1.4 μm.

[0051] The polyimide film precursor was prepared in the same manner as in Example 1.

[0052] A matte black polyimide film was produced in the same manner as in Example 1, except that 9 g of low density matte slurry was added to provide a hollow silica powder content of 15 wt %.

[0053] The glass substrate was immersed in water and the matte black polyimide film was peeled off from the glass substrate. The thickness of this film was 6.0 μm.

[0054] [Example 5] The carbon black slurry was prepared in the same manner as in Example 1.

[0055] The low density mat slurry was prepared in the same manner as in Example 1.

[0056] The polyimide film precursor was prepared in the same manner as in Example 1.

[0057] A matte black polyimide film was prepared in the same manner as in Example 1, except that 9 g of low density matte slurry was added to the film to give a hollow silica powder content of 15 wt %. The film was applied using a scraper with a 50 μm slit.

[0058] The glass substrate was immersed in water and the matte black polyimide film was peeled off from the glass substrate. The thickness of this film was 2.6 μm.

[0059] [Example 6] The carbon black slurry was prepared in the same manner as in Example 1.

[0060] The low density mat slurry was prepared in the same manner as in Example 1.

[0061] The polyimide film precursor was prepared in the same manner as in Example 1.

[0062] 1.98g (10mol%) of PDA was added to 425g of DMAc, and after stirring and mixing to completely dissolve the PDA, 33.023g of ODA was added. When the ODA was completely dissolved, 38g of PMDA was slowly added. The temperature of the mixture was controlled at 25°C, and the mixture was stirred for 2 hours to react. After that, a small amount of PMDA was added to adjust the viscosity, and a polyamic acid solution with a solid content of 15% and a viscosity of 155,900 cps was finally obtained.

[0063] A matte black polyimide film was produced in the same manner as in Example 1, except that 9 g of low density matte slurry was added to provide a hollow silica powder content of 15 wt %.

[0064] The glass substrate was immersed in water and the matte black polyimide film was peeled off from the glass substrate. The thickness of this film was 6.5 μm.

[0065] [Example 7] The carbon black slurry was prepared in the same manner as in Example 1.

[0066] The low density mat slurry was prepared in the same manner as in Example 1.

[0067] The polyimide film precursor was prepared in the same manner as in Example 1.

[0068] 8.036g (38mol%) of PDA was added to 425g of DMAc, and after stirring and mixing to completely dissolve the PDA, 24.279g of ODA was added. When the ODA was completely dissolved, 38.4g of PMDA was slowly added. The temperature of the mixture was controlled at 25°C and the mixture was stirred for 2 hours to react. After that, a small amount of PMDA was added to adjust the viscosity, and a polyamic acid solution with a solid content of 15% and a viscosity of 161200cps was finally obtained.

[0069] A matte black polyimide film was produced in the same manner as in Example 1, except that 9 g of low density matte slurry was added to provide a hollow silica powder content of 15 wt %.

[0070] The glass substrate was immersed in water and the matte black polyimide film was peeled off from the glass substrate. The thickness of this film was 6.3 μm.

[0071] [Comparative Example 1] The carbon black slurry was prepared in the same manner as in Example 1.

[0072] The low density mat slurry was prepared in the same manner as in Example 1.

[0073] The polyimide film precursor was prepared in the same manner as in Example 1.

[0074] A matte black polyimide film was prepared in the same manner as in Example 1, except that 0.6 g of low-density matte slurry was added to the film to give a hollow silica powder content of 1 wt %. The film was applied using a scraper with a 100 μm slit.

[0075] The glass substrate was immersed in water and the matte black polyimide film was peeled off from the glass substrate. The thickness of this film was 4.1 μm.

[0076] [Comparative Example 2] The carbon black slurry was prepared in the same manner as in Example 1.

[0077] The low density mat slurry was prepared in the same manner as in Example 1.

[0078] The polyimide film precursor was prepared in the same manner as in Example 1.

[0079] A matte black polyimide film was prepared in the same manner as in Example 1, except that 10.2 g of low density matte slurry was added to the film to give a hollow silica powder content of 17 wt %. The film was applied using a scraper with a 100 μm slit.

[0080] The glass substrate was immersed in water and the matte black polyimide film was peeled off from the glass substrate. The thickness of this film was 4.8 μm.

[0081] [Comparative Example 3] The carbon black slurry was prepared in the same manner as in Example 1.

[0082] The low-density matte slurry was produced in the same manner as in Example 1, but the hollow silica powder used had a density of 0.62 g / cm3 and an average particle size of 1.7 μm.

[0083] The polyimide film precursor was prepared in the same manner as in Example 1.

[0084] A matte black polyimide film was prepared in the same manner as in Example 1, except that 9 g of low density matte slurry was added to the film to give a hollow silica powder content of 15 wt %. The film was applied using a scraper with a 100 μm slit.

[0085] The glass substrate was immersed in water and the matte black polyimide film was peeled off from the glass substrate. The thickness of this film was 4.2 μm.

[0086] [Comparative Example 4] The carbon black slurry was prepared in the same manner as in Example 1.

[0087] The low density matte slurry was prepared as in Example 1, but the hollow silica powder had a density of 0.76 g / cm 3 The average particle size was 1.3 μm.

[0088] The polyimide film precursor was prepared in the same manner as in Example 1.

[0089] A matte black polyimide film was prepared in the same manner as in Example 1, except that 9 g of low-density matte slurry was added to the film to contain 15 wt% hollow silica powder. The film was applied using a scraper with a 125 μm slit.

[0090] The glass substrate was immersed in water and the matte black polyimide film was peeled off from the glass substrate. The thickness of this film was 6.1 μm.

[0091] [Comparative Example 5] The carbon black slurry was prepared in the same manner as in Example 1.

[0092] The low density mat slurry was prepared in the same manner as in Example 1.

[0093] The polyimide film precursor was prepared in the same manner as in Example 1.

[0094] A matte black polyimide film was prepared in the same manner as in Example 1, except that 9 g of low density matte slurry was added to the film to give a hollow silica powder content of 15 wt %. The film was applied using a scraper with a 50 μm slit.

[0095] The glass substrate was immersed in water and the matte black polyimide film was peeled off from the glass substrate. The thickness of this film was 1.3 μm.

[0096] [Comparative Example 6] The carbon black slurry was prepared in the same manner as in Example 1.

[0097] The low density mat slurry was prepared in the same manner as in Example 1.

[0098] The polyimide film precursor was prepared in the same manner as in Example 1.

[0099] 0.98g (5mol%) of PDA was added to 425g of DMAc, and after stirring and mixing to completely dissolve the PDA, 34.47g of ODA was added. When the ODA was completely dissolved, 37.6g of PMDA was slowly added. The temperature of the mixture was controlled at 25°C and the mixture was stirred for 2 hours to react. After that, a small amount of PMDA was added to adjust the viscosity, and a polyamic acid solution with a solid content of 15% and a viscosity of 161,400 cps was finally obtained.

[0100] A matte black polyimide film was prepared in the same manner as in Example 1, except that 9 g of low density matte slurry was added to the film to give a hollow silica powder content of 15 wt %. The film was applied using a scraper with a 100 μm slit.

[0101] The glass substrate was immersed in water and the matte black polyimide film was peeled off from the glass substrate. The thickness of this film was 4.2 μm.

[0102] [Comparative Example 7] The carbon black slurry was prepared in the same manner as in Example 1.

[0103] The low density mat slurry was prepared in the same manner as in Example 1.

[0104] The polyimide film precursor was prepared in the same manner as in Example 1.

[0105] 8.968g of PDA (42mol%) was added to 425g of DMAc, and after stirring and mixing to completely dissolve the PDA, 22.933g of ODA was added. When the ODA was completely dissolved, 40.9g of PMDA was slowly added. The temperature of the mixture was controlled at 25°C and the mixture was stirred for 2 hours to react. After that, a small amount of PMDA was added to adjust the viscosity, and a polyamic acid solution with a solid content of 15% and a viscosity of 169,200cps was finally obtained.

[0106] A matte black polyimide film was prepared in the same manner as in Example 1, except that 9 g of low density matte slurry was added to the film to give a hollow silica powder content of 15 wt %. The film was applied using a scraper with a 100 μm slit.

[0107] The glass substrate was immersed in water and the matte black polyimide film was peeled off from the glass substrate. The thickness of this film was 3.6 μm.

[0108] Below, a comparison between the Examples and Comparative Examples is shown in Table 1.

[0109] [Table 1]

[0110] Comparative Example 1: The amount of hollow silica used is less than 2 wt%, so the gloss of the film at 60 degrees is more than 30 GU.

[0111] Comparative Example 2: The amount of hollow silica used exceeds 15 wt %, so the tensile elongation of the film is less than 15%.

[0112] Comparative Example 3: The particle size of the hollow silica used is more than 1.5 μm, so the tensile elongation of the film is less than 15%.

[0113] Comparative Example 4: The density of the hollow silica used was 0.7 g / cm 3 Because it is exceeded, the 60 degree gloss of the film is in excess of 30 GU.

[0114] Comparative Example 5: Since the thickness of the polyimide film is less than 2 μm, the tensile elongation is less than 15%.

[0115] Comparative Example 6: Since the amount of p-phenylenediamine (PDA) used is less than 7 mol %, the thermal expansion coefficient of the film exceeds 30 ppm / °C.

[0116] Comparative Example 7: Since the amount of p-phenylenediamine (PDA) used was more than 40 mol %, the tensile elongation of the film was less than 15%.

[0117] As shown in Table 1, the matte black ultra-thin polyimide film produced according to the embodiment of the present invention exhibits excellent optical properties (glossiness at 60 degrees) and can ensure high tensile elongation.

[0118] According to the examples, the reason for the superior extinction properties is the selection of hollow silica powder with low density and small particle size. A powder with low density means that it has a large volume even with the same weight ratio. As a result, the gloss level is low. In addition, when the particle size is small, the tensile elongation of the film can be easily ensured during the manufacturing process.

[0119] The above-mentioned specific examples are merely for the purpose of explaining the present invention in detail, and are not intended to limit the present invention. Those skilled in the art will understand that various modifications are possible within the scope of the claims, and that configurations obtained by appropriately combining the technical means disclosed in the embodiments are also included in the technical scope of the present invention.

Claims

1. A matte black ultra-thin polyimide film, a polyimide constituting 77 to 96 wt % of the film; carbon black comprising 2-8 wt % of said film; Average particle size less than 1.5 μm, density 0.7 g / cm ３ a hollow silica powder having a particle size of less than 2 to 15 wt % of the film; Including, The matte black ultra-thin polyimide film has a thickness of 2 to 12 μm; The polyimide is formed by subjecting a polyimide precursor obtained by polymerizing an aromatic dianhydride and an aromatic diamine to a cyclization reaction; The polyimide film is a matte black ultra-thin polyimide film having a gloss at 60 degrees of less than 30 and a tensile elongation of more than 15%.

2. 2. The matte black ultra-thin polyimide film according to claim 1, wherein the thickness of the matte black ultra-thin polyimide film is 2 to 7 μm.

3. 2. The matte black ultra-thin polyimide film according to claim 1, wherein the aromatic diamine contains at least p-phenylenediamine (PDA) in a content of 7 to 40 mol % based on the total amount of the aromatic diamine, and the polyimide film has a thermal expansion coefficient of less than 30 ppm / °C.

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