We can never actually emit darkness, its physically impossible from the current knowledge of physics.

To elaborate upon that answer, normally when humans look with their eyes they see the visible spectrum and therefore we cannot see any more or less frequency than that, this therefore results in us either not being able to see it in its true form. Now, consider wearing an infrared camera to our eyes, then we would be able to detect any sort of black-body radiation that is too weak to detect with our eyes.

That said we can now say at temperatures (getting higher), black bodies glow with increasing intensity and colors that range from dull red to blindingly brilliant blue-white as the temperature increases. Or anything that has any temperature glow some black-body

Now, let us assume we do have such a material that can never emit light at all, then using our first statement we can say it must not have any energy of heat in side it, this would mean that the object is literally in absolute zero temperature which is impossible as Heisenberg's uncertainty principle, which says the more precisely we know a particle's speed, the less we know about its position, and vice versa. If you know your atoms are inside your experiment and their respectful masses, there must be some uncertainty in their momentum therefore now if we refer back to the equation of momentum:

$\vec{p} = mv$

we can say since we know the mass of the particles in our experiment, we must conclude it must have some velocity, but since any high-school student will learn temperature is an macroscopic feature of the average velocities of the particles in side it, we must conclude that that it cannot be absolute zero temperature and since we have said previously anything with a temperate environment must also emit black-body radiation. That said we can never reach absolute zero due to quantum mechanical effects that come into play at those temperatures.

As for black-holes, even those are hypothesized to emit very little black-body radiation dubbed hawking radiation after the world-re-known physicist Stephen Hawking, who hypothesized this effect, although not experimentally verified or any observation made pertaining to this quantum effect, its expected to leak our very small energy:

$$ P =\hbar c^2/15360\pi G^2M^2 = 9.004 * 10^{-29} $$

where $M$ which is equal to $1.98855\pm 0.00025 * 10^{30}$ (mass of a solar mass).

Not to mention, black holes are not really an material just an extreme curvature of space-time which results in an lack of light from its event horizon.

This therefore concluded that its impossible to emit darkness (black light) after all black light does not exist but its just darkness

We can never actually emit darkness, its physically impossible from the current knowledge of physics.

To elaborate upon that answer, normally when humans look with their eyes they see the visible spectrum and therefore we cannot see any more or less frequency than that, this therefore results in us either not being able to see it in its true form. Now, consider wearing an infrared camera to our eyes, then we would be able to detect any sort of black-body radiation that is too weak to detect with our eyes.

That said we can now say at temperatures (getting higher), black bodies glow with increasing intensity and colors that range from dull red to blindingly brilliant blue-white as the temperature increases. Or anything that has any temperature glow some black-body

Now, let us assume we do have such a material that can never emit light at all, then using our first statement we can say it must not have any energy of heat in side it, this would mean that the object is literally in absolute zero temperature which is impossible as Heisenberg's uncertainty principle, which says the more precisely we know a particle's speed, the less we know about its position, and vice versa. If you know your atoms are inside your experiment and their respectful masses, there must be some uncertainty in their momentum therefore now if we refer back to the equation of momentum:

$\vec{p} = mv$

we can say since we know the mass of the particles in our experiment, we must conclude it must have some velocity, but since any high-school student will learn temperature is an macroscopic feature of the average velocities of the particles in side it, we must conclude that that it cannot be absolute zero temperature and since we have said previously anything with a temperate environment must also emit black-body radiation. That said we can never reach absolute zero due to quantum mechanical effects that come into play at those temperatures.

As for black-holes, even those are hypothesized to emit very little black-body radiation dubbed hawking radiation after the world-re-known physicist Stephen Hawking, who hypothesized this effect, although not experimentally verified or any observation made pertaining to this quantum effect, its expected to leak our very small energy:

$$ P =\hbar c^2/15360\pi G^2M^2 = 9.004 * 10^{-29} $$

where $M$ which is equal to $1.98855\pm 0.00025 * 10^{30}$ (mass of a solar mass).

Not to mention, black holes are not really an material just an extreme curvature of space-time which results in an lack of light from its event horizon.

Finally, if an object even still managed to get to absolute zero (which is impossible as I have concluded in previous statements) it would then start to violate laws of thermodynamics, therefore its impossible to make such a machine.

This therefore concluded that its impossible to emit darkness (black light) after all black light does not exist but its just darkness