Seveal years ago (2008), I developed a method to get very dense transparencies with a LaserJet printer (LJ4 and LJ4101mfp). Basically, I went over the transparency with a Dry Erase marker (Expo brand), such as is used on white boards for presentations. That worked great, until I replaced the HP with a Brother HL2270DW.
As you point out, the toner is softer and comes off easily. I think that will be a problem with all of the LED-based printers. There is a "sort of" fix for that. The problem with the original method was that the felt tip was too hard for the soft toner, and it created scratches.
Here is a link to the original and to an EEVVlog description:
Description:
Images:
https://www.eevblog.com/forum/begin...nsparencies-for-uv-pcb/msg1107747/#msg1107747
EEVBlog apparently deleted the link I gave.
The Fix:
I opened the marker in a resealable plastic bag. Removed the tampon-like felt that contained ink. Expressed that ink with duck-bill pliers and poured it into a small medicine cup. Then, I used a soft camel hair brush to paint the transparency (use the softest brush you can find). Let it dry thoroughly -- a hair dryer helps. Then rub off the ink as before.
That revision was only partially effective. I still got good resolution around thermals and such, but the difference between hard enough and too hard was critical. About 1 in 3 tries worked to my satisfaction. You can also try heatig the film before adding the dry erase ink, but you will get some dimensional changes. Those changes are not huge when compared to 805 SMD devices, but they did make a difference when I did double sided boards with vias.
Final Solution:
I broke down and bought a cheap (ca. $50 USD) Canon PIXMA MG3620 inkjet, and it works great. A later post by me in that EEVBlog link describes some of the conditions. I am addicted to the Pictorico Premium OHP film. Early on (circa 2005), I tried other OHP films without the same success. I have not tried more recent products. Drafting vellum, as used for old fashioned "ink" tracings, may also work, but I have not tried it.
For me, the decision to go to the best solution (i.e., ink jet) once I saw the price was easy to make. I also now have a color printer for the occasions when I need it. I think any difference between pigment ink (i.e., the black with that printer) and dye-based inks (i.e., color with that printer) is still an open question. Some of the best transparencies I got with my older HP ink jet printer were done using the color cartridges alone. Yellow and other colors are pretty good at blocking UV light.
Regards, John
Edit: Here is an example with the Brother printer and modified dry erase method showing before and after:
Unfortunately I do not have a good macro lens on this camera.