Patent Application
20230314950
This application claims priority to Taiwan Application Serial Number 111112735, filed Apr. 01, 2022, which is herein incorporated by reference.
The present disclosure relates to a flexible substrate and a manufacturing method of the flexible substrate.
In today’s market full of a wide variety of consumer electronic products, reflective display devices, e.g. electronic papers, now have extensively utilized as display screens. A display medium layer of a reflective display device is formed of the main elements of microcapsules that have white and black charged particles. The white and black charged particles are driven to move by applying a voltage to the display medium layer, such that each pixel displays a black color, a white color or a gray level. Since the reflective display device utilizes an incident light that irradiates the display medium layer to achieve the purpose of display, the reflective display needs no backlight to reduce power consumption.
In order to make the reflective display device have bendable feature, a thin film transistor array is usually formed on a soft plastic film. However, fillers in the soft plastic film would induce black point defects, and the black point defects appear more obvious with the higher the process temperature. The fillers and the plastic material have poor heat resistance, and thermal cracking leads to the precipitation or crystallization of low molecular weight oligomers, or leads to aggregation with the filler as the core. In addition, most plastic films are generally manufactured by roll to roll, and the process may cause uneven scratches on a surface, particle defects, gel defects, etc., and it is difficult to improve the product yield.
One aspect of the present disclosure provides a flexible substrate.
According to some embodiments of the present disclosure, a flexible substrate includes a plastic film and an overcoat layer. The plastic film includes a main portion and a plurality of fillers, wherein the fillers are located in the main portion or on a surface of the main portion. The overcoat layer covers the plastic film and is in contact with the plastic film, wherein a material of the overcoat layer includes polyimide (PI), polybenzoxazole (PBO), benzocyclobutene (BCB), acrylic resin, epoxy resin, siloxane polymer, or novolak resin.
In some embodiments, the overcoat layer includes a color resist.
In some embodiments, the color resist is tan, burgundy, red, (dark) blue, green, white or black.
In some embodiments, a thickness of the overcoat layer is in a range from 1 µm to 20 µm.
In some embodiments, a thermal expansion coefficient (CTE) of the overcoat layer is smaller than 60 ppm/°C, a thermal decomposition temperature (Td) of the overcoat layer is greater than 100° C., and a dielectric constant is smaller than 5.
In some embodiments, a Young’s modulus of the overcoat layer is greater than or equal to 1.5 Gpa, a tensile stress of the overcoat layer is greater than or equal to 100 Mpa, and a elongation of the overcoat layer is greater than or equal to 10%.
In some embodiments, the flexible substrate further includes a thin film transistor (TFT) array located on the overcoat layer.
In some embodiments, the main portion of the plastic film is a polyimide (PI) film, a polyethylene naphthalate (PEN) film, a polyethylene terephthalate (PET) film, polymethyl methacrylate (PMMA), polyether sulfone (PES), or polyarylate (PAR).
In some embodiments, a material of the fillers includes silicon nitride, silicon oxide, silicon oxynitride, or aluminium oxide.
Another aspect of the present disclosure provides a manufacturing method of a flexible substrate.
According to some embodiments of the present disclosure, a manufacturing method of a flexible substrate includes disposing a plastic film on a carrier, wherein the plastic film includes a main portion and a plurality of fillers, and the fillers are located in the main portion or on a surface of the main portion; coating an overcoat layer on the plastic film such that the overcoat layer covers the plastic film and is in contact with the plastic film, wherein a material of the overcoat layer includes polyimide (PI), polybenzoxazole (PBO), benzocyclobutene (BCB), acrylic resin, epoxy resin, siloxane polymer, or novolak resin; and removing the carrier.
In some embodiments, coating the overcoat layer on the plastic film includes spin coating or slot-die coating.
In some embodiments, disposing the plastic film on the carrier includes spraying an adhesive on one of the carrier and the plastic film.
In some embodiments, the manufacturing method of the flexible substrate further includes after disposing the plastic film on the carrier, baking the adhesive.
In some embodiments, the manufacturing method of the flexible substrate further includes after baking the adhesive and before coating the overcoat layer, detecting a defect of the plastic film.
In some embodiments, baking the adhesive is at a temperature in a range from 150° C. to 400° C. for 20 minutes to 120 minutes.
In some embodiments, the manufacturing method of the flexible substrate further includes after coating the overcoat layer on the plastic film, baking the overcoat layer.
In some embodiments, baking the overcoat layer is at a temperature in a range from 150° C. to 400° C. for 60 minutes to 120 minutes.
In some embodiments, the manufacturing method of the flexible substrate further includes after baking the overcoat layer, detecting a defect of the plastic film.
In some embodiments, the manufacturing method of the flexible substrate further includes after detecting the defect of the plastic film, forming a thin film transistor array on the overcoat layer.
In some embodiments, removing the carrier is performed after forming the thin film transistor array on the overcoat layer.
In the aforementioned embodiments of the present disclosure, since the flexible substrate includes the overcoat layer that covers the plastic film, and the material of the overcoat layer includes polyimide (PI), polybenzoxazole (PBO), benzocyclobutene (BCB), acrylic resin, epoxy resin, siloxane polymer, or novolak resin, the flexible substrate may have good thermal, physical, and mechanical properties and good chemical resistance to meet subsequent process requirements, such as a thin film transistor array process. The overcoat layer of the flexible substrate can cover black point defects caused by the fillers of the plastic film, thereby having concealer effect. Moreover, the overcoat layer can planarize uneven scratches, particle defects, gel defects, etc., on the surface of the plastic film, so as to improve the surface defects of the plastic film and increase the product yield.
Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.
The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.
Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature’s relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.
The manufacturing method of the flexible substrate is not limited to the above steps S1 to S8. For example, in some embodiments, the manufacturing method can further include other steps between two of the above steps, or can further include other steps before step S1 and after step S8.
In the following description, each step of the manufacturing method of the flexible substrate will be explained.
In this embodiment, the main portion 112 of the plastic film 110 may be a polyimide (PI) film, a polyethylene naphthalate (PEN) film, a polyethylene terephthalate (PET) film, polymethyl methacrylate (PMMA), polyether sulfone (PES), or polyarylate (PAR). The aforementioned materials can make the plastic film 110 have bendable property, and thus the plastic film 110 can serve as a substrate below the thin film transistor (TFT) array of a reflective display device (e.g., an electronic paper). Moreover, the material of the fillers 114 may include silicon nitride (SiNx), silicon oxide (SiOx), silicon oxynitride (SiNxOy), or aluminium oxide (AlOx), and thus the plastic film 110 can have a rough surface.
After the plastic film 110 is disposed on the carrier 210, the adhesive A may be baked. In some embodiment, baking the adhesive A is at a temperature in a range from 150° C. to 400° C. for 20 minutes to 120 minutes. Thereafter, the defect of the plastic film 110 may be detected by automated optical inspection (AOI) equipment.
After the overcoat layer 120 is coated on the plastic film 110, the overcoat layer 120 may be baked. In some embodiments, baking the overcoat layer 120 is at a temperature in a range from 150° C. to 400° C. for 60 minutes to 120 minutes. Moreover, after baking the overcoat layer 120, the defect of the plastic film 110 may be detected by automated optical inspection (AOI) equipment.
Specifically, since the flexible substrate 100 includes the overcoat layer 120 that covers the plastic film 110, and the material of the overcoat layer 120 includes polyimide (PI), polybenzoxazole (PBO), benzocyclobutene (BCB), acrylic resin, epoxy resin, siloxane polymer, or novolak resin, the flexible substrate 100 may have good thermal, physical, and mechanical properties and good chemical resistance to meet subsequent process requirements, such as a thin film transistor array process. The overcoat layer 120 of the flexible substrate 100 can cover black point defects caused by the fillers 114 of the plastic film 110, thereby having concealer effect. Moreover, the overcoat layer 120 can planarize uneven scratches, particle defects, gel defects, etc., on the surface of the plastic film 110, so as to improve the surface defects of the plastic film 110 and increase the product yield.
In some embodiments, the thickness of the overcoat layer 120 is in a range from 1 µm to 20 µm. The thermal expansion coefficient (CTE) of the overcoat layer 120 is smaller than 60 ppm/°C. The thermal decomposition temperature (Td) of the overcoat layer 120 is greater than 100° C. (at 1% weight loss). The dielectric constant of the overcoat layer 120 is smaller than 5 (at 1 Mhz). The Young’s modulus of the overcoat layer 120 is greater than or equal to 1.5 Gpa. The tensile stress of the overcoat layer 120 is greater than or equal to 100 Mpa. The elongation of the overcoat layer 120 is greater than or equal to 10%. As a result of such a configuration, the overcoat layer 120 may have good thermal, physical, and mechanical properties and good chemical resistance.
In addition, the overcoat layer 120 includes a color resist (pigment), and the color resist may be (dark) tan or burgundy to darken the color of the overcoat layer 120, thereby improving the concealer effect of the overcoat layer 120. In some embodiments, the color resist may be also red, (dark) blue, green, white or black, as deemed necessary by designers, and the present disclosure is not limited to this regard. As a result, the overcoat layer 120 may reduce a light transmittance for a light source of a detector (e.g., AOI), thereby preventing the defect and the scratches of the plastic film 110.
In the following process, a front panel laminate (FPL) having a display medium layer (e.g., an electronic ink having microcapsules) may be bonded to the flexible substrate 100. Thereafter, the carrier 210 may be removed. In other words, the carrier 210 is removed after forming the thin film transistor array 130 on the overcoat layer 120 and bonding the front panel laminate. The carrier 210 is configured to provide the support force for the flexible substrate 100.
The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 111112735 | Apr 2022 | TW | national |
