Light guide device and method for sequentially lighting light guide device

1. A light guide device comprising:

a light guide comprising a light-emitting surface, light-incident surfaces formed on both sides of the light-emitting surface and configured to receive light, and a light-reflecting surface formed opposite to the light-emitting surface and configured to reflect the received light to the light-emitting surface;

a first light source unit and second light source unit disposed on the light-incident surfaces, respectively, and configured to irradiate light; and

a light transmission control layer formed above the light-emitting surface and configured to control the transmittance of light emitted,

wherein the light transmission control layer has a light transmittance which decreases from a first end to a second end of the light transmission control layer,

wherein the light transmission control layer has a thickness which increases from the first end to the second end of the light transmission control layer.

2. The light guide device of claim 1 , wherein each of the first light source unit and the second light source unit comprises a substrate comprising a light source and a driving integrated circuit electrically connected to the light source and configured to supply a driving current to the light source.

3. The light guide device of claim 2 , wherein the light source comprises a flip chip-type light-emitting diode.

4. The light guide device of claim 1 , wherein the light transmission control layer is disposed to be spaced apart from the light guide.

5. The light guide device of claim 1 , wherein the light transmission control layer has a triangular or trapezoidal sectional shape.

6. The light guide device of claim 5 , wherein the light transmission control layer has a right triangular sectional shape such that an upper surface thereof is parallel to the light-emitting surface of the light guide and a lower surface thereof is formed to be inclined with respect to the light-emitting surface.

7. The light guide device of claim 6 , wherein the lower surface of the light transmission control layer has irregularities formed thereon.

8. A light guide device comprising:

a light guide comprising a light-emitting surface, light-incident surfaces formed on both sides of the light-emitting surface and configured to receive light, and a light-reflecting surface formed opposite to the light-emitting surface and configured to reflect the received light to the light-emitting surface;

a first light source unit and second light source unit disposed on the light-incident surfaces, respectively, and configured to irradiate light; and

a light transmission control layer formed above the light-emitting surface and configured to control the transmittance of light emitted,

wherein the light transmission control layer has a light transmittance which decreases from one end to the other end of the light transmission control layer,

wherein the light transmission control layer comprises a resin matrix and a light transmission control agent dispersed in the resin matrix.

9. The light guide device of claim 8 , wherein the resin matrix comprises one or more of polycarbonate, polystyrene, an acrylonitrile-butadiene-styrene copolymer, polyolefin, polyester, and polyalkyl (meth)acrylate, and the light transmission control agent comprises one or more of dyes and pigments.

10. A method for sequentially lighting the light guide device of claim 1 , the method comprising:

driving the first light source unit of the light guide device;

increasing a brightness of the first light source unit to a target value by increasing an amount of a driving current which is supplied to the first light source unit; and

driving the second light source unit at a time point when the brightness of the first light source unit reaches the target value.