I'm not sure that this is exactly biology, more physics, however the answer is sometimes, though this depends on the type of microscope and how the light is impinging on it.
This answer assumes a common upright compound microscope.
The reason I say this is that microscopes used to (and some still do, such as this one. I have no affiliation with the linked site nor is this an endorsement of the site) have mirrors for reflecting the sun so that you could see your sample.
However, what you are seeing is that your samples appear dim when there is bright light in the room. What is actually happening here is that your eyes are compensating for that level of brightness in your peripheral vision, constricting your pupil so that less light enters the eye. This is called the pupillary light reflex and happens every time your eye is subjected to light. Because of the constriction of your pupil, the central (microscope) image appears dimmer.
Having said that, bright light entering the condenser, not from the (diffused) point-source of the bulb can cause loss of image definition because the light source is not linearized and condensed fully by the condenser arrangement. This results in some images being a bit less sharp. Nikon's MicroscopyU has some detail on how this works.