1.  Field of the Invention
The present invention relates to an ink composition, an ink set, and an image forming method. 
2.  Description of the Related Art
As image recording methods in which an image is formed on a recording medium such as paper based on an image data signal, there are an electrophotographic method, a sublimation-type and fusion-type thermal transfer method, an ink jet method, and the like. 
In the ink jet method, a plate is not required at the time of printing, and an image is directly formed on a recording medium by ejecting an ink composition only to a necessary image portion.  Therefore, the ink composition can be used with excellent efficiency, and the running cost becomes low.  Furthermore, the ink jet method uses an inexpensive printing device and generates little noise.  As described above, the ink jet method has more various advantages than other image recording methods. 
As an ink composition used in the ink jet method, a radiation-curable ink composition is known.  The radiation-curable ink composition is cured when polymerizable components in the ink composition are polymerized by being irradiated with radiation such as ultraviolet rays.  Consequently, blurring of an image barely occurs compared to a case of using a non-radiation-curable ink composition (a solvent-based ink composition), and this is one of the advantageous of the radiation-curable ink composition.