Optical bonding process for producing LCD panel and LCD panel produced

Abstract

This invention provides a liquid crystal display (LCD) and a method for manufacturing the LCD, wherein a layered stack of elements is secured with at least one piece of adhesive tape (e.g., black polyester tape). The layered stack is bonded to a cover glass and optionally a touch panel / sensor via an optically clear adhesive (OCA). The method and apparatus include securing at least one piece of tape to the front side of the layered stack, folding the tape over to cover the periphery of the layered stack, and securing it to the rear side of the layered stack.

Description

Technical Field

[0001] This invention relates to the field of projected capacitive touch technology for flat panel displays, and more specifically, to a capacitive liquid crystal display. Prior Technology

[0002] LCD (Liquid Crystal Display) is a known type of flat-panel display that primarily operates using liquid crystals. LCDs have a wide and diverse range of applications in consumers and businesses, commonly found in smartphones, televisions, computer monitors, and dashboards. Projected Capacitive Touch Screen (PCAP) is a touchscreen display technology that uses a matrix of microelectrodes beneath a glass surface. Compared to technologies that use individual wires connected to each pixel, this technology allows for thinner displays and higher resolutions. Summary of the Invention

[0003] The manufacture of standard liquid crystal display panels (LCD panels) typically involves a process of surrounding the periphery of a plurality of internal liquid crystal display elements (LCD components) within the LCD panel with a metal frame. Using a metal frame has several disadvantages, such as reduced LCD panel lifespan, decreased visibility and light transmittance, and increased reflection count when exposed to adverse environments.

[0004] The advantage of this invention is that it provides an improved liquid crystal display panel and a method for manufacturing the improved liquid crystal display panel.

[0005] This invention provides an improved manufacturing process for a liquid crystal display panel, which manufactures a bonded projected capacitive touch panel using an optically clear adhesive (OCA) bonding process. This invention also provides a customized method for planarizing the front surface of any liquid crystal display panel, thereby enabling the bonding of the LCD to a projected capacitive touch screen using an OCA bonding process.

[0006] Traditional liquid crystal display (LCD) panel bonding processes use a metal frame to surround the internal components of the LCD panel, which can lead to air gaps between the internal components after the metal frame is used. The method and apparatus of this invention provide a bonding process for manufacturing LCD panels that uses a liquid optically clear adhesive (LOCA) for bonding, thereby obtaining an improved LCD panel. LOCA bonding involves using a liquid adhesive to bond layers of a plurality of internal liquid crystal display elements stacked together in the LCD panel.

[0007] The advantage of the method and apparatus of this invention lies in the use of an optically transparent adhesive for bonding, thereby enabling the formation of thinner bond lines and a thinner overall display stack thickness. OCA bonding uses a dry and strong pressure-sensitive adhesive to bond the layers together. As part of the bonding process, pressure is applied to laminate the OCA onto the substrate to eliminate air gaps in the liquid crystal display panel assembly. This process allows for the bonding of rigid elements to rigid or flexible elements, as well as flexible elements (e.g., overlays) to rigid elements.

[0008] The bonding process for OCA bonding of a plurality of internal liquid crystal display elements (LCDs) in a liquid crystal display panel can include rigid-to-rigid OCA bonding and flexible OCA bonding. Rigid-to-rigid OCA bonding involves using a vacuum chamber to completely remove air between the layers of the plurality of internal LCDs, thereby bonding two or more rigid elements tightly together. Flexible OCA bonding involves using rollers to completely expel air between the flexible internal LCDs and the substrate or adhesive. Here, the substrate or adhesive can be flexible or rigid, and the rollers can be manual rollers or automated in-line rotary precision converting rollers.

[0009] Removing and preventing all air bubbles and / or gaps helps maximize optical clarity, making OCA lamination ideal for applications where readability is critical. The methods and apparatus of this invention can further include handling, processing, and assembling the OCA in a Class 100 cleanroom to ensure zero foreign object debris (FOD) or contamination. Furthermore, depending on the material and application, a UV environment or a UV-sensitive environment may be involved.

[0010] A method for optically bonding a liquid crystal display panel includes: arranging a plurality of internal liquid crystal display elements into a layered stack; fixing at least one piece of adhesive tape to the front side of the layered stack; folding the at least one piece of adhesive tape over to cover the periphery of the layered stack; fixing the at least one piece of adhesive tape to the rear side of the layered stack; and bonding the layered stack with an optically transparent adhesive.

[0011] An optically bonded liquid crystal display panel includes: a plurality of internal liquid crystal display elements arranged in a layered stack and including a front side and a rear side; an optically transparent adhesive; and at least one piece of tape; wherein the at least one piece of tape is fixed to the front side and the rear side of the plurality of internal liquid crystal display elements such that the periphery of the plurality of internal liquid crystal display elements is covered by the at least one piece of tape.

[0012] The plurality of internal liquid crystal display elements may include a touch panel, a cover glass, and a layered stack, wherein the touch panel is bonded to the cover glass and the layered stack located on both sides of the touch panel by an optically transparent adhesive. Simple Explanation of the Diagram

[0013] Figure 1 shows an exploded perspective view of a standard liquid crystal display panel of the prior art, which has a metal frame surrounding the internal components of the liquid crystal display panel.

[0014] Figure 2 shows an exploded perspective view of a liquid crystal display panel using OCA bonding according to the present invention.

[0015] Figure 3A shows a front view of the liquid crystal display panel of Figure 2 according to the invention.

[0016] Figure 3B shows a rear view of the liquid crystal display panel of Figure 2 according to the present invention.

[0017] Figure 4 shows a schematic cross-sectional view of the liquid crystal display panel of Figure 2 according to the present invention.

[0018] Figure 5 shows a block diagram of the OCA bonding process of the liquid crystal display panel of Figure 2 according to the present invention. Implementation

[0019] Before further describing the various embodiments in detail, it should be understood that the present invention is not limited to the specific embodiments described. It should also be understood that the terminology used is only for describing particular embodiments and is not intended to limit the scope of the claims in this application. It should be noted that words such as "comprising," "including," or "having" should be understood to not exclude other elements or steps, and words such as "a" or "an" should be understood to not exclude the plural form of those elements or steps.

[0020] In the drawings, although some descriptions may refer only to certain symbols and elements, it should be understood that these descriptions also apply to the same symbols and elements in other drawings. Furthermore, although various features are shown in different drawings for simplicity, it should be readily understood by those skilled in the art to which this invention pertains that the aforementioned features can be combined together without departing from the scope of the invention.

[0021] Figure 1 shows an exploded perspective view of a prior art standard liquid crystal display panel 1, which has a metal frame 100 surrounding its internal components. The metal frame 100 surrounds a flexible on-board (FOB) circuit 102, making the front side of the liquid crystal display panel 1 a non-uniform surface. As part of the standard liquid crystal display panel manufacturing process, the metal frame 100 also surrounds other internal components shown as layers in the exploded perspective view of Figure 1. These layered internal components include: a flexible on-board (FOB) printed circuit 102, a housing 110, an upper diffuser film 112, a lower prism film 128, a lower diffuser film 126, an upper prism film 114, a light bar 116, a light guide element 118, a reflective film 120, a back cover 122, and an adhesive tape 103E fixed to the back cover 122. The structure and function of these internal components of the liquid crystal display panel 1 are standard technology in the field of this invention, and therefore will not be described in detail here.

[0022] It is worth noting that the metal frame 100 hinders OCA bonding because the front surface is not flat. Due to the numerous irregularities created by the metal frame 100, standard manufacturing processes for LCDs larger than 10.1 inches can only use liquid optically clear adhesive (LOCA) for bonding. Generally, OCA bonding is not used in the manufacturing of any LCD larger than 10.1 inches.

[0023] Referring to FIG2, which shows an exploded perspective view of a liquid crystal display panel 2 according to the present invention, excluding the housing or cover glass. The liquid crystal display panel 2 is optically bonded (OCA). The liquid crystal display panel 2 does not include the metal frame found in standard liquid crystal display panels, such as the metal frame 100 shown in FIG1. ​​Instead of a metal frame, the liquid crystal display panel 2 includes one or more (or one or more) adhesive tapes 203A to 203D, which secure and bond the internal components of the liquid crystal display panel 2. The assembly method of the optically bonded liquid crystal display panel 2 may include stacking a plurality of internal liquid crystal display elements in the order shown to form a layered stack.

[0024] The plurality of internal liquid crystal display elements forming a layered stack may include: a flexible circuit board (FOB) printed circuit 202, a housing 210, an upper diffuser film 212, a lower prism film 228, a lower diffuser film 226, an upper prism film 214, a light strip 216, a light guide element 218, a reflective film 220, a back cover 222, and an adhesive tape 203E fixed to the back cover 222. The liquid crystal display panel 2 may also include a cover glass (as shown in Figure 4).

[0025] After the plurality of internal components are assembled and stacked to form a layered stack, at least one piece of adhesive tape 203A to 203D is fixed to the front side of the layered stack, with the adhesive tape 203A to 203D folded over to cover the entire stack of internal components. Then, the at least one piece of adhesive tape 203A to 203D is fixed to the back cover 222 of the liquid crystal display panel 2. Then, the adhesive tape 203A to 203D is smoothed to form a seal. The adhesive tape can be single-sided or double-sided, wherein double-sided adhesive tape has release films (liners) attached to both sides.

[0026] As shown in Figures 3A and 3B, at least one piece of adhesive tape 203A to 203D is wrapped around and covers the periphery of the front side of the liquid crystal display panel 2, which constitutes part of the OCA bonding process. Multiple pieces (including two or more pieces) of adhesive tape 203A to 203D can be used for OCA bonding of a plurality of internal components of the liquid crystal display panel 2. In some embodiments, two to five pieces of tape are used. In some embodiments, a single piece of tape can be used to cover the same area as the plurality of pieces of tape 203A to 203D shown. The single piece of tape can span and adhere to the entire periphery of the liquid crystal display panel 2. As shown in Figure 3B, the rear side of the liquid crystal display panel 2 has adhesive tape 203A to 203D, which are folded over to cover the periphery of the liquid crystal display panel 2, so that the adhesive tape 203A to 203D extend to cover the plurality of internal components and are fixed to the back cover 222 on the rear side of the liquid crystal display panel 2.

[0027] Referring to FIG4, which shows a schematic cross-sectional view of a liquid crystal display panel 2 bonded using OCA, at least one piece of tape 203A to 203D is shown surrounding a layered stack 244 of internal components. In some embodiments, each tape 203A to 203D is a 0.03 mm black polyester (mylar) tape. However, other types, colors, and sizes of tapes also fall within the scope of this invention.

[0028] Each layer 246 is a cap tape, such as black cap tape, covering the control panel of the liquid crystal display panel 2. The back cover 222 may be made of metal or plastic. The liquid crystal display panel 2 includes a cover glass 243 and an optional touch panel / sensor 242, which can be bonded together using OCA 241 and silicone adhesive waxer material 240.

[0029] In some embodiments, OCA 241 is first bonded to the touch panel / sensor 242 and the cover glass 243. Next, another layer of OCA 241 is bonded to the rear side of the sensor 242, which serves to bond the sensor 242 to the liquid crystal display panel 2. The OCA 241 located between the touch panel / sensor 242 and the layered stack 244 may be of the same material or composition as the OCA 241 located between the cover glass 243 and the touch panel / sensor 242; or, in other embodiments, the material or composition of the OCA 241 may be different. In some embodiments, the OCA is located only within the visible area of ​​the liquid crystal display panel 2. Silicone adhesive wafer material 240 may be used to fill all gaps around the frame of the liquid crystal display panel 2 that are not within the visible area, but are located next to the OCA on both sides of the touch panel / sensor in the cross-sectional view of the liquid crystal display panel 2. As part of the OCA bonding process, Mitsubishi CLEARFIT® or a similar OCA may be used as the OCA.

[0030] Referring to FIG5, which shows a block diagram of an embodiment of the OCA bonding process and the liquid crystal display panel manufactured therefrom. In some embodiments, an OCA material 500 with a light release film 506 and a heavy release film 504 is subjected to a rolling step 508. Before starting the rolling step 508, the light release film 506 is removed from the OCA material 500. Here, a roller 509 (which may be a manual roller or an automated continuous rotary precision machining roller) is used to expel all the air between the first adherend 502 and the heavy release film 504, so that the OCA material can adhere to the first adherend 502.

[0031] After OCA material 500 is bonded to the first bonding compound 502, vacuum lamination 510 is used to bond OCA material 500 to the second bonding compound 503. Vacuum lamination can be performed at a pressure of 0.006 MPa (-0.095 MPa), with an applied pressure of 0.02 MPa for one minute. During vacuum lamination, the second bonding compound 503 is bonded to the OCA material 500, such that both sides of the OCA material 500 are bonded to the first bonding compound 502 and the second bonding compound 503, respectively. Vacuum lamination technology is known to those skilled in the art to which this invention pertains, and changes to the vacuum lamination conditions still fall within the scope of this invention. The first bonding compound 501 and the second bonding compound 502 can be any of the following: cover glass, touch panel / sensor, or a layered stack of internal components, but are not limited to these specific components.

[0032] Following vacuum pressing 510, the next step is autoclaving 512. Autoclaving 512 can be performed at a pressure of approximately 0.2 to 0.4 MPa and a temperature of approximately 40 to 60 degrees Celsius for approximately 10 to 20 minutes. Autoclaving is known to those skilled in the art to which this invention pertains, and modifications to the autoclaving conditions still fall within the scope of this invention. After autoclaving 512, the OCA material 500 bonded to the first laminate 502 and the second laminate 503 is subjected to UV irradiation 514. Here, the accumulated light intensity can be, for example, approximately 2,000 to 4,000 mJ / cm².

[0033] Vacuum pressing, autoclaving, and UV irradiation are known to those skilled in the art to which this invention pertains, and the specific conditions of these steps can be modified without departing from the OCA bonding process taught in this invention.

[0034] This application claims priority to U.S. Provisional Patent Application No. 63 / 703,305, filed on October 4, 2024, the entire contents of which are incorporated herein by reference.

[0035] 1: LCD display panel 100: Metal frame 102: Flexible printed circuit board 103E: Tape 110: Shell 112: Upper diffusion film 114: Superior Prism 116: Light bar 118: Light guide element 120: Reflective film 122: Back Cover 126: Lower diffusion membrane 128: Inferior prism membrane 2: LCD display panel 202: Flexible printed circuit board 203A, 203B, 203C, 203D, 203E: Adhesive Tape 210: Shell 212: Upper diffusion film 214: Superior Prismatic Membrane 216: Light bar 218: Light guide element 220: Reflective film 222: Back Cover 226: Lower diffusion membrane 228: Inferior prism membrane 240: Silicone adhesive wafer material 241:OCA 242: Touch panel / sensor 243: Cover glass 244: Layered stacking 246: Floor 500: OCA material 502: First Adhesive 503: Second Blend 504: Release film 506: Light Release Film 508: Roller pressing step 509: Rolls 510: Vacuum pressing 512: Autoclave Processing 514: UV irradiation

Claims

1. A method for manufacturing a liquid crystal display panel, comprising: Arrange the panel components in a layered stack; Secure at least one piece of tape to the front side of the layered stack; Fold the at least one piece of tape over to cover the periphery of the layered stack; secure the at least one piece of tape to the back of the layered stack.

2. The method as described in claim 1, wherein, These panel components include flexible on board (FOB) circuitry, housing, and back cover.

3. The method as described in claim 1, further comprising: The layered stack is bonded to the touch panel or sensor using an optically clear adhesive (OCA).

4. The method as described in claim 3, wherein, The bonding process further includes using rollers to press the optically clear adhesive onto the substrate.

5. The method as described in claim 3, further comprising: The touch panel or sensor is attached to the cover glass using an optically clear adhesive (OCA).

6. The method as described in claim 1, further comprising: The cover glass is bonded to the layered stack using an optically clear adhesive (OCA).

7. The method as described in claim 6, wherein, The bonding process involves applying an optically clear adhesive (OCA) to the cover glass using rollers before bonding the cover glass to the layered stack.

8. The method as described in claim 7, wherein, The joining was performed under vacuum.

9. The method as described in claim 8, further comprising: The layered stack and the cover glass were subjected to autoclave treatment.

10. The method as described in claim 1, wherein, The at least one piece of tape includes four pieces of tape.

11. A liquid crystal display panel, comprising: Elements arranged in a layered stack, the layered stack having a front side and a rear side; At least one piece of tape is attached to the front and back sides of the layered stack and covers the perimeter of the layered stack.

12. The liquid crystal display panel as described in claim 11, wherein, These components include flex-on-board (FOB) circuitry, housing, and back cover.

13. The liquid crystal display panel as described in claim 11, further comprising: The cover glass is bonded to the layered stack via an optically clear adhesive (OCA).

14. The liquid crystal display panel as described in claim 13, wherein, The optically clear adhesive (OCA) is only located within the visible area of ​​the liquid crystal display panel.

15. The liquid crystal display panel as described in claim 13, wherein, The silicone adhesive Wacker material is disposed between the cover glass and the layered stack.

16. The liquid crystal display panel as described in claim 11, further comprising: Touch panels or sensors are attached to the layered stack via optically clear adhesive (OCA).

17. The liquid crystal display panel as described in claim 16, further comprising: The cover glass is bonded to the touch panel or sensor using an optically clear adhesive (OCA).

18. The liquid crystal display panel as described in claim 13, wherein, This optically transparent adhesive is applied using manual rollers.

19. The liquid crystal display panel as described in claim 13, wherein, This optically transparent adhesive is applied using an automated in-line rotary precision converting press.

20. The liquid crystal display panel as described in claim 13, wherein, The optically transparent adhesive (OCA) is bonded using vacuum pressing.

21. The liquid crystal display panel as described in claim 11, wherein, The at least one piece of tape includes two to five pieces of tape.

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