Technology in ProductsOrganic Light Emitting Diode (OLED) Display Manufacturing Equipment
Equipment that produces next-generation displays that are thin, lightweight, vivid, and high-definition
Devices such as smartphones, televisions, and personal computers are becoming thinner and lighter, while offering higher image quality. Facilitating this advancement are OLED displays that are thin, lightweight, and produce vivid colors. OLED display manufacturing equipment is used to manufacture high-definition OLED displays through the process of layering organic materials on glass plates with precise positioning.
The images shown on the displays of smartphones and televisions that we use in our everyday lives consist of fine dots that glow red, green, or blue, as illustrated by this figure. Displays can be divided into two types depending on the way these dots are illuminated. Liquid crystal displays (LCDs) produce colors by shining light from behind a red, green, or blue color filter, and OLED displays use organic materials that emit light on their own.
Organic electro-luminescence (OEL) is a phenomenon in which organic materials emit light themselves when a voltage is applied to them.OLED displays, which utilize this phenomenon, and are made by layering organic materials onto a glass or plastic substrate.With OLED displays individual diodes light up in red, green, or blue when a current is passed through layers of different light-emitting organic materials, projecting an image onto the display.Thus far, LCDs have played a central role in the display industryr, but OLED displays are being increasingly used in familiar devices such as televisions, computers, and smartphones.
Differences between OLED and LCD displays
OLED displays do not require backlighting like LCDs, do because the organic materials themselves emit light themselves. This allows makes possible thinner and lighter displays.
The vividness of colors also differs. While LCDs produce red, green, or blue colors by shining a white backlight from behind a color filter, OLED displays can produce each color more clearly because the material itself emits light that does not pass through a color filter. Moreover, the use of plastic as a substrate allows for folding and bending. This facilitates the manufacture of innovative devices such as foldable smartphones and TVs with rollable screens. Leveraging features , such as thinness, lightness, the ability to produce vivid colors, and a high degree of variation in shape, OLED displays are expected to be used in such devices as VR headsets and, smart glasses, as well as in-vehicle applications. The field of displays has an increasingly promising future.
Products with OLED displays
How are OLED displays manufactured?
There are many processes involved in the manufacture of OLED displays, as glass substrates must be laminated with layers of organic materials. As shown in the figure below, the full process comprises a thin-film transistor (TFT) process, vapor deposition process, and sealing process. First, in the TFT process, a TFT circuit is formed to regulate the current for each pixel. Next, in the vapor deposition process, a thin film of an organic material is deposited on a glass or plastic substrate. Finally, in the sealing process, the glass substrate is sealed without any gaps, thus protecting the display from moisture. After connecting wires and attaching a filter for adjusting reflected light, the OLED display is complete.
*The surface of a transparent conductive film (the positive terminal) is treated to prepare for the deposition of each organic material in the next process.
Out of these processes, Canon's OLED display manufacturing equipment is used in the vapor deposition process, which is an important part of achieving the end goal of high image quality. Vapor deposition is performed in a vacuum, contained inside individual stainless steel boxes, known as chambers, in order to prevent the organic material from degrading. OLED display manufacturing equipment consists of clusters, which comprise multiple chambers, and transfers units between clusters.
Layout of OLED display manufacturing equipment
As shown in the following figure, an OLED display consists of multiple layers, each of which play a different role. These layers are formed through the vapor deposition process inside each chamber. A vacuum robot is installed in the central transfer chamber. Once the process in each chamber is complete, the robot removes the glass substrates from their chambers at the appropriate time and transports them to the next chamber in the process. Once the processes in all of the clusters are complete, the glass substrates on which the organic materials are layered are automatically ejected by the robot.
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Technologies in OLED display manufacturing equipment
Deposition technology
Deposition is the process of forming a very thin film on a glass substrate using organic materials. In the manufacture of OLED displays, this is done through the “vapor deposition process.” A high vacuum is maintained in the chamber. An evaporation source (a crucible) is packed with an organic material and heated to approximately 300°C, and the material is evaporated. Evaporated particles issuing from the evaporation source travel in a straight line and adhere to the glass substrate with almost no collisions between the particles.
A monitor that uses a quartz plate as a sensor (hereafter, “quartz crystal monitor”) plays a major role in this step. A quartz crystal monitor is used to control the vapor deposition rate. The speed at which evaporated particles move toward the glass substrate is detected by the quartz crystal monitor and is kept constant. Evaporation is terminated when the specified film thickness is achieved. In order to adjust the level of coloration of a light-emitting material during vapor deposition, a certain percent of a different material must be added. To maintain a constant percentage of that material, Canon uses a quartz crystal monitor to precisely control the vapor deposition rate.
In order to consistently mass-produce displays of the same quality, each organic material must be consistently deposited over a long period of time. Canon's deposition technology utilizes quartz crystal monitors, thus enabling consistent deposition over long periods of time and facilitating the manufacture of displays that can produce vivid colors.
Alignment technology
The vapor deposition process for OLEDs involves the coating (patterning) of a light-emitting materialwith each color (red, green, or blue) simultaneously with vapor deposition. Organic materials cannot be patterned by etching (surface processing) after deposition because thin films of those materials can be damaged. Therefore, patterning must be performed at the same time as vapor deposition. The method used in this process is to place a vapor deposition mask (a metal plate with holes) opposite the glass substrate to deposit a material emitting red, blue, or green light in the desired position in accordance with the mask pattern. First, a vapor deposition mask for red is used so that the color is applied only to the areas where red is to be vapor-deposited. Afterwards, a vapor deposition mask for green and then blue is used so that each color is applied in the appropriate place.
Evaporated organic material adheres to the exact location through the vapor deposition mask
Use of a vapor deposition mask for each color to coat the substrate with red, green, and blue in specific places
Positional information is acquired with a camera and highly precise alignment is performed
The manufacture of OLED displays with higher definition and resolution requires the vapor deposition of light-emitting materials in precise positions. Therefore, alignment (placement) technology is required to precisely align the vapor deposition mask with the glass substrate. Alignment is performed by acquiring positional information for the vapor deposition mask and the glass substrate by means of a camera and then precisely controlling the positional relationship between the mask and substrate.
In recent years, the resolution of smartphones and televisions has continued to increase, and there is a growing trend to increase resolution to 4K or 8K. Canon uses this alignment technology to achieve highly precise positioning and thereby meet the growing demand for higher resolution and higher definition displays.
