Abstract:
An injection molding method includes: providing a mold core which defines a mold cavity, depositing a lubrication layer on an inner surface of the mold cavity, injecting plastic material into the mold cavity, and molding the plastic material into the plastic element.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present disclosure relates to injection molding, and particularly, to an injection molding method including depositing a lubrication layer on an inner surface of a mold core using an atomic layer deposition process. 
         [0003]    2. Description of Related Art 
         [0004]    Plastic elements having fine and complicated structure are generally manufactured by injection molding. Polyetherimide (PEI) resin, due to its excellent mechanical properties, high light-transmittance and outstanding thermal stability, has been widely used for manufacturing optical fiber connectors. However, molten PEI resin has poor fluidity. That means, in manufacturing, a mold cavity may not be completely filled with the molten PEI resin. To solve this problem, high pressure is generally applied into the mold cavity to improve the flow speed of the molten PEI resin, which can shorten the lifetime of a corresponding injection molding machine. Therefore, providing an injection molding to ensure plastic elements quality and avoid harming the injection molding machine is desired. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0005]    Many aspects of the present disclosure can be better understood with reference to the following drawing. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure. 
           [0006]      FIG. 1  is a schematic view of an exemplary embodiment of an injection molding method. 
           [0007]      FIG. 2  shows a mold core in a coating chamber according to one embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0008]    Embodiments of the present disclosure will now be described in detail and with reference to the drawing. 
         [0009]    Referring to  FIG. 1 , an exemplary embodiment of a method for injection molding a plastic element is provided. The method includes the following steps. 
         [0010]    In step  200 , a mold core is provided, wherein the mold core defines a mold cavity. Referring to  FIG. 2 , in one embodiment, a mold core  120  is provided. The mold core  120  is used for molding an optical fiber connector using polyetherimide (PEI) resin. The mold core  120  defines a mold cavity  110 . The mold cavity  110  has an inner surface  111 . 
         [0011]    In step  202 , a lubrication layer is positioned on an inner surface of the mold cavity. In one embodiment, the lubrication layer is comprised of titanium nitride (TiN) and is formed on the inner surface  111  using an atomic layer deposition process. In detail, the mold core  120  is positioned in a coating chamber  130 . The coating chamber  130  includes a gas inlet  131 , a gas outlet  132  and an exhaust opening  133 . The coating chamber  130  is exhausted to vacuum phase, and then heated to a predetermined temperature. A first reactive gas is introduced into the coating chamber  130 . In the present embodiment, an organically metallic gas containing Ti, such as TiCl 4 , Ti(N(CH 3 ) 2 ) 4 , Ti(N(C 2 H 5 ) 2 ) 4 , and Ti(N(CH 3 )(C 2 H 5 )) 4 , is employed as the first reactive gas. The predetermined temperature is equal to the thermal decomposition temperature of the first reactive gas. As such, the first reactive gas thermally decomposes, generating an ion layer containing Ti 4+  absorbed on the inner surface  111 . For improving uniformity, prior to decomposing the first reactive gas, an activation process is applied to the inner surface  111  to enhance adhesive force between the inner surface  111  and the ion layer. In one embodiment, the inner surface  111  is finely corroded with an etchant such that pluralities of pores are formed in the inner surface  111 . In other embodiments, the inner surface  111  is corroded using an electrochemical process. 
         [0012]    A small amount of the first reactive gas might remain. Under this situation, the remaining first reactive gas is exhausted out of the coating chamber  130 . Then, a second reactive gas, such as nitrogen gas (N 2 ) or ammonia gas (NH 3 ), is introduced into the coating chamber  130 . The second reactive gas reacts with the ion layer, thereby forming the lubrication layer on the inner surface  111 . 
         [0013]    In step  204 , plastic material is injected into the mold cavity and molded into a plastic element. The PEI resin is fed into the mold cavity  110  and molded into the optical fiber connector. 
         [0014]    In the present embodiment, molten PEI resin flows quicker on the lubrication layer than on the inner surface  111 . Therefore, the mold cavity  110  can be completely filled. Additionally, the lubrication layer formed with the atomic layer deposition process is atomic-class thick, avoiding diminishing the size of the plastic element. Furthermore, the atomic layer deposition process is adapted for forming a coating layer on any mold core even having complicated and fine structure, ensuring plastic element quality. 
         [0015]    The described embodiments are intended to illustrate rather than limit the disclosure. Variations may be made to the embodiments and methods without departing from the spirit of the disclosure. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the disclosure.