I'm not too worried. These displays are so cheap I don't mind wrecking one or two for the sake of progress. The first LCD was sacrificed for the knowledge of how to take it apart, and what's inside. I have two more working LCDs waiting in the wings.

 

That's the goal my friend. Make it simple. Make it affordable. Make it high resolution.

You have to crack a few eggs and all that...

 

Well, caution was just thrown to the wind. Just ordered a 15.6" 4K LCD and controller.

 

Yup.

 

Thanks for the kind words

Are you just looking to use the LCD from the Tab2, or will it still have the digitizer attached (or even just the whole tablet)? You probably don't want to use the digitizer over the LCD as it reduces the intensity from the backlight, as well as reducing accuracy as the LCD will be further away from the vat and build surface.

 

Well, some of it depends on where you are in the world. For me, being in the US, I have found Bucktown Polymers, and Photocentric3D. I'm not sure if Bucktown Polymers will ship outside of the US, but their selection is limited for the hobbyist. They have tons of options if you want to buy it by the drum though. Photocentric has distributors globally, so that's a better option. ONO is also offering daylight resins for their printer that they Kickstarted. I don't think the resins are currently for sale outside of Kickstarter, but I'm sure they will be soon.

If we can get the LCD to pass a moderate amount of shortwave blue light (400-430nm) after some modifications, then that opens things up to UV resins that would be used with DLP style printers. Resins like Makerjuice' G+ will cure at 420nm quite readily, albeit slowly. Unfortunately, we just don't know yet whether the LCD will pass reasonable amounts of shortwave blue light.

 

You may want to sit down for this.

I was poking around in the datasheet for the 15.6" 4K display that I ordered last night (link), and came across some very interesting information.

First up, the backlight is white and red. Never seen that before, but I can see where it can be useful for increasing the color gamut of the display while maintaining brightness. This isn't really a big deal for our uses. Second up is the fact that this LCD has RGBW pixels!!!! It looks like the "white" pixel (most likely just a pixel that has no color filter) is there to help increase brightness of the image without oversaturating colors. This could be very awesome. The cost of the LCD panel is unfortunately out of the realm of "**** it, I'll buy a new one" if I break it (about $115 each shipped), so I'm a little more nervous about opening it up. BUT, if this really does have a pixel with no color filter, then this might just be the secret sauce we need.

 

Me too. A coworker of mine has a pretty good USB microscope that I hope to use to peer into the pixel matrix to see if the mysterious "white" pixel actually exists. Now I just have to not lose my mind as I wait for it to get here (slow boat China Post, so 3-4 weeks if I'm lucky)

 

"White" color would only diffuse the light, not filter it, which wouldn't make sense. They also wouldn't use a phosphor conversion seeing as the primary backlight is white already. I'm pretty confident that the subpixel is transparent. The only other limitation may be in the polarizer. If the polarizers have a cutoff point above the UV limit, then that may be problematic.

 

Right, but if it's cheaper to make a polarizer that just happens to block UV, then that's what they are going to use.

Anyway, 100 365nm 3W LEDs have been ordered. This will be set up in a 7x13 array spaced 1" on center. It's a hair smaller than the active area of the panel, but with an inch or two of spacing behind the panel, it should be plenty to get decent performance at the edges. This is all dependent on whether I'm feeling ballsy enough to open it all up

 

Finding UV LEDs at a decent price is a challenge all by itself (I paid $126 on AliExpress for 100 365nm LEDs of questionable quality). Finding side emitting UV LEDs for a reasonable price is near impossible (and the cost would have been triple or quadruple the cost of the LEDs I bought with 1/4 the output). Plus, I have no idea what format the LEDs are, but they are most likely the same as the LEDs used in the iPad display seeing as both are made by LG (I had looked them up, but I don't remember what style/size they were). Opening the back up and using a higher power array will be the most practical method. This will allow for substantially higher output and better thermal management.

No reflectors or lenses here. I'd rather utilize the wider emission angle of the LEDs to create more uniform output at the LCD. I will outline the perimeter of the heatsink with a baffle that will reflect light back into the working area of the LCD. That will add to the safety of the whole printer, as well as scavenging stray light to be put to more useful purposes. The height of the baffle will also help set the distance of the LEDs to the LCD.

For those looking for high quality heatsinks, check out HeatsinkUSA. Tons of different profile options from 0.601" to 12", cut to any length you want. I've been using these guys for years for my aquarium related LED lighting projects.

 

Well, I think we can all agree that the more the merrier is applicable when it comes to reducing cure times

I wonder how much the various films degrade over time when exposed to UV? It can't be good for them long term, especially at the intensity levels I plan on throwing at them. One way to find out

 

That's a good point. Well, we shall see in due time. Hopefully it's less complicated than that

 

I've been doing some more reading today about the whole RGBW UHD situation, and I'm starting to get a little nervous about the whole situation (only a little nervous).

The datasheet states that "Each pixel is divided into White/Red, Green/Blue 2 sub-pixels or dots which are arranged in mosaic structure." On paper, that sounds great, as it makes it sound like there are four sub-pixels per pixel. Apparently, there is a bit of a to-do going on at the moment in regards to LG's M+ UHD panels for TVs that implement the RGBW setup. What they end up doing is putting a white sub-pixel every 4 sub-pixels. Each pixel is still a group of 3 sub-pixels (a pixel is defined as the minimum number of sub-pixels required to generate all colors, with a height to width ratio of 1:1). That means that the sub-pixel groupings for 4 pixels in a row would be RGB, WRG, BWR, GBW. This is apparently creating image quality issues, as well as color and brightness inconsistencies.

I'm hoping that their mobile/laptop division is doing things a little differently, but I'm not holding my breath. Will this ultimately hurt the image quality when it comes to displaying layers to print? Probably not, as we are still showing a white image for each layer, meaning that we are still utilizing all three colors to create white, but with an extra oomph from the white sub-pixel. That may end up being a slight advantage when it comes to cure time per watt used (a silly metric, but hey, I'm trying to find any silver lining at this point). Will it be the secret sauce needed when it comes to printing using shorter wavelengths? To be determined. It's possible that there may be only a slight loss of overall definition, as 3 out of the 4 pixels in each row contain a white sub-pixel, but the pixel immediately above and below will have a white sub-pixel. When we are talking 89.7 micron XY resolution, diffusion between the sub-pixels may make this issue moot.

Anyway, I'm speculating here. For all I know, the display I'm getting is actually a true RGBW sub-pixel structure. Probably not though.

 

Also, now that I've chewed this over for a bit, I think that the white sub-pixel's use for HDR may not be accurate. In my reading, it sounds like it's more of an energy saving tactic. There were some statistics thrown around in some of the articles stating that the transmittance rate of a modern LCD is only 5%. Seems a little low, but whatever. The point is that a white pixel is unfiltered and allows a lot more white light through to make the image appear brighter without needing to crank up the backlight and consuming more energy.